APPARATUS FOR FORMING PATTERNED SEAMS IN FABRIC WORKPIECES
United States Patent 3810436
A cyclical workpiece control apparatus operatively associated with a sewing machine for holding a workpiece while moving the same through the stitch forming area of the machine and which is movable transversely with and while advancing the workpiece to form seams of stitches in accordance with the dictates of a predetermined pattern.
US Patent References:
APPARATUS FOR MANIPULATING A WORKPIECE ALONG AN IRREGULAR CONTOURED PATH THROUGH A WORKSTATION
Noiles - October 1969 - 3474747
Transmission mechanism
Bartelt - February 1949 - 2462060
Railway sewing machine in combination with a pin-type work holder
Briggs - January 1965 - 3167041
/1197112.html
Eberley - September 1916 - 1197112
Work supporting and guiding means
Sommer - January 1934 - 1942128
APPARATUS FOR MANIPULATING A WORKPIECE ALONG AN IRREGULAR CONTOURED PATH THROUGH A WORKSTATION
Noiles - October 1969 - 3474747
Transmission mechanism
Bartelt - February 1949 - 2462060
Railway sewing machine in combination with a pin-type work holder
Briggs - January 1965 - 3167041
/1197112.html
Eberley - September 1916 - 1197112
Work supporting and guiding means
Sommer - January 1934 - 1942128
Application Number:
05/253973
Publication Date:
05/14/1974
Filing Date:
05/17/1972
View Patent Images:
Export Citation:
Assignee:
S.p.A. Virginio Rimoldi & Co. (Milan, IT)
Primary Class:
Other Classes:
74/37
International Classes:
D05B21/00; D05B65/00; D05B21/00
Field of Search:
112/121.12,121.15,121.11,121.29,2,121.14 74/37,27 198/110
US Patent References:
Other References:
Sommer, Apparatus For Automatic Quilting, May 11, 1943 A.P.C. Serial No. 311,428..
Primary Examiner:
Boler, James R.
Claims:
I claim
1. For a sewing machine of the type having a work supporting surface operatively associated therewith and a workpiece clamping member movable by a carriage on the supporting surface for advancing a workpiece along the latter and through a stitch forming area of the machine, a mechanism for cyclically forming patterned stitched seams in a workpiece as it is moved through the stitching area of the machine comprising:
1. For a sewing machine of the type having a work supporting surface operatively associated therewith and a workpiece clamping member movable by a carriage on the supporting surface for advancing a workpiece along the latter and through a stitch forming area of the machine, a mechanism for cyclically forming patterned stitched seams in a workpiece as it is moved through the stitching area of the machine comprising:
Description:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for forming (cyclically) seams of predetermined configuration and length on a sewing machine. There are several types of industrial sewing machines in which the work is guided towards the sewing zone in an automatic manner by a clamping element which follows a predetermined trajectory and not necessarily a straight trajectory. These machines, even in cases where the clamping element opens automatically at the end of each sewing cycle, must be started again manually when starting each successive cycle, especially when positioning the clamping element for receiving the workpiece in the starting position.
Also well known is the fact that the sewing units presently used in the industry of ready-to-wear garments have a much higher degree of automation when the sewing profiles to be obtained with the same unit do not vary much among themselves as far as shape is concerned. However, until now it was impossible to have automatic sewing units with such a degree of versatility that they could be used to make seams having different profiles or shapes such as in the manufacture of various garments. With the technique used until now, it was impossible to perform sewing cycles on long and differently shaped stretches of fabric and impossible to repeat said cycles automatically.
An apparatus, which forms a part of this invention, is capable of automatically producing seams of a predetermined configuration. This is achieved by the unit by following the working method of working cycle which also forms a part of the invention. It is the object of the invention to provide a method for obtaining (cyclically) long and variously shaped seams, said method consists of a series of operations which are better defined below, and of an apparatus which permits the automatic performance of said operations with a great degree of versatility as far as the shapes of the seams are concerned. Another object of this invention is to provide an automatic sewing unit which is highly versatile and which requires only the minimum amount of manual intervention during the entire cycle of operations, as all security features and the relative drive controls are automated.
The automatic unit of the invention presents also the advantage of performance speed being that the complete series of operations are performed automatically with the minimum amount of idle time or waiting period between one operation and the next. Other objectives, advantages and characteristics of the sewing method and of the automatic sewing unit of the present invention are described below in detail and are illustrated on the attached drawings.
FIG. 1 -- is a perspective view of the automatic unit according to the invention;
FIG. 2 -- is a plan view of the unit of FIG. 1;
FIG. 3 -- is a sectional view along the line III--III of FIG. 2;
FIG. 4 -- is a side view showing further detail the transversal system of the work clamp;
FIG. 5 -- is a schematic plan view of the unit of the invention, illustrating particularly the suction system;
FIG. 6 -- is a view in side elevation of the working surface with the suction system of FIG. 5;
FIG. 7 -- is a side view showing a portion of FIG. 6 on an enlarged scale;
FIG. 8 -- is a schematic view of a portion of the unit's drive electrical system;
FIG. 9 -- is a schematic view of the electrical circuitry for the mechanism of FIG. 6, and;
FIG. 10 -- shows schematically the pneumatic drive circuit of the present invention.
With reference to FIGS. 1, 2, and 3, the automatic sewing unit consists essentially of a support frame 1, a working surface 2, a sliding support means 3, represented by a movable carriage capable of shifting the unfinished work on the working surface so that it can be sewn by a fixed sewing machine 4. The sewing cycle in accordance with the present invention consists of a series of operations which can be described as follows:
a. Move the carriage at medium speed in order to draw the work up to the sewing machine;
b. sew a small section in very short stitches, by moving the carriage at low speed;
c. continue sewing at medium speed, similar to the speed used in drawing the work up to the sewing machine;
d. reduce speed when the end of the sewing approaches so that a second small piece can be sewn in short stitches, as in b);
e. resume change of position at medium speed until the run is finished;
f. stop to allow work clamp to open in the rejecting zone and position same in relation to the sewing axis;
g. return to starting point of the carriage at high speed and;
h. reduce speed to extremely low level in order to position the carriage, during the last part of the return run.
Three different speeds are provided and preferably not less than four. These speeds are obtained through a motor 5 equipped of an electro-magnetic brake unit (not illustrated) which can be inserted gradually and which at the proper time affects the run between the armature and the inductor of the motor itself in order to vary the electro-magnetic force. The carriage is moved through a belt or transmission chain 6 activated by the motor 5 always in the same direction. The movement in one direction or the other is achieved by connecting the carriage 3 to the upper part or the lower part of the chain 6 through a coupling 7 activated at the proper time by an opposite drive consisting, for example, of a pneumatic cylinder 8 whose piston carries said coupling 7 equipped with teeth 9, on the free extremity (FIG. 3). Based on which tooth 9 is used in the chain 6, the carriage 3 moves in one direction or the other. The carriage 3 includes all the machine elements which move and slide lengthwise along the working surface 2.
The carriage itself is mounted for sliding and rotary movement on a guide shaft 10 by supporting brackets 11, supported on the side of the working surface 2 and includes; a work clamp 12 capable of locking the work into place and letting it slide on the working surface 2; and of transversal guiding units (illustrated in detail in FIG. 4) consisting of a support rod 13 mounted telescopically in supporting tubes 14 of the carriage 3. The work clamp 12 includes a contoured edge 15 shaped in such a way that it can reproduce the same profile of the seam to be made and to avoid interference with the needle 16 of the machine 4 during operation of the subject unit. Parallel to the contoured edge 15, the work clamp 12 carries a guide 17 in the form of a cam track which reproduces exactly the profile of said edge and of the seam to be made. Such guide 17 serves to determine the transversal movements of the work clamp 12 during the longitudinal movements of the carriage 3. To obtain transversal movements, the guide 17 becomes engaged by a fixed locator, or guide pin 18, mounted on the machine near the needle 16, thus the work clamp 12 is forced to move from one side and/or the other transversally of the working surface 2 in order to keep the edge 15 constantly at the same distance from the needle 16. In this way the needle 16 penetrates freely only in the part of the material carried by work clamp 12. In order to produce the seam parallel to the border of the work, the latter is inserted under the work clamp with the help of a template 19. The amount of free space between the work clamp 12 and the template 19 is occupied by the protruding portion of the work on which the seam is to be made. When the work clamp 12 comes into contact with the sewing machine 4, the fixed locator or pin 18 enters into the guide 17 in order to give to the work clamp 12 a transversal movement with relative movement of the work and thus obtain the variation of the seam's trajectory. For what concerns the moving speed of the carriage 3 which speed is obtained with the motor 5, we point out that the so-called high speed is obtained through the complete coupling of the electro-magnetic brake-clutch assembly which is not adjustable. The lower speeds, instead, can be adjusted by means of suitable potentiometers. The minimum amount of each speed is fixed, and it is possible to increase the amount of one or more speeds, except the highest speed, affecting thus the higher ones, whereas by working with higher speeds, the lower ones are not affected. For example, by regulating the potentiometer relative to the lowest speed in a way to obtain the maximum of said speed, and the potentiometer of the second speed in such a way as to obtain its maximum speed, it is possible to achieve the maximum speed, without passing through the medium of third speed.
The maximum speed has a set amount since it corresponds to the maximum level of magnetization.
The transversal positioning of guide 17 with the relation to the pin 18 is assured the means consisting of a single pneumatic cylinder 20 FIG. 4, divided into two chambers 21 and 22 separated by a partition 23 in which chambers slide the pistons 24 and 25 respectively. The piston 25 is connected to the work clamp 12 by means of a cross-bar 26 fixed on the actuating rod 13, while the piston 24 is connected with the carriage 3 by means of a cross-bar 27 fixed on tubes 14. During the positioning of the work clamp 12 each chamber 21 and 22 is put in communication with a pneumatic circuit, which will be explained later, through tubes 28 and 29 respectively, which tubes are situated in opposite sides of the relative pistons. The reason for such position of these compressed-air feeding tubes (28 and 29) is that when both chambers 21 and 22 are filled with compressed air, the positioning of the work clamp 12 unequivocally determined, corresponds to a central position of the work clamp itself and consequently to the work placed under it, in relation to the transversal movement from one side or the other of the needle 16, which includes the maximum movement of the straight line required by the profile of the seam. Once the exact initial position has been determined, the work clamp can move inside the transversal positioning strip, following the trajectory determined by the pin 18 with the guide 17 after the discharge of compressed air contained in chambers 21 and 22. (FIGS. 3 and 4) show also a cylinder 30 which serves to open the work clamp 12 and which is hinged on carriage 3 on the upper side and on a bracket 31 on the lower side. The work clamp 12 can be opened to insert a new piece of work at the start of the cycle, or also at the end of the cycle to remove the piece of work after it has been sewn. This is possible because the work clamp 12 is directly hinged on the guideshaft 10 of cylindrical section. For the above-mentioned reason, the pivot around which the work clamp 12 moves, is connected with the carriage 3 which pivots upwardly during the changes of work. The work clamp 12 could also be opened in another way and that is by lifting the work clamp itself or in any other manner capable of freeing the work underneath the work clamp without any interference between the work clamp and the fixed elements, particularly the sewing machine 4, during the return-run of the carriage 3. FIGS. 2 and 3, also show a mutual control 32 which permits the opening of the work clamp before the cycle starts, independently from the function of the element which activates automatically cylinder 30 and which will be described in more detail later. Said mutual control 32 is shown in FIGS. 2 and 3 as a foot pedal control.
Referring to FIG. 5, the working surface 2 presents the loading zone having a plurality of holes 33 connected by a tube 34 to a depression unit, which, as indicated in FIG. 6 can consist of a suction fan driven by a motor 35. This suction serves to straighten and smoothly spread the material on the working surface in order to permit position adjustment of the material itself with relation to the work clamp, or with relation to the template 19 in its lowered position. In fact, by itself the material normally does not have a consistency sufficient to insure an even spread on the support surface before the work clamp 12, which at the start of the working cycle is open, can engage it and then move it toward the sewing machine 4. To prevent clinging of the material to the working surface 2 and permit the work clamp to move said material along said working surface the force of air entering holes 33 is sufficient only for the purpose of positioning the material to be sewn. Underneath the working surface 2, the suction zone is divided into separate chambers 36, 37, and 38, (FIG. 6) the longest of which, indicated as "36" connects with the tube 34 through an opening 40 and a chamber 39, while the other chambers 37 and 38 are connected with chamber 39 and with the suction conduit 34 by means of valves 41 and 42 respectively. The closing of valves 41 and 42 causes the rejection of the suction from the corresponding chamber. This is because the workpieces can have various dimensions, for example, they may vary from trousers to the neck or the cuffs of a shirt and therefore it would be useless to supply suction in zones not touched by the material. During the sewing cycle the depression unit is not stopped, that is to say the motor 35 is left running and by means of a damper 43 activated, for example, by a cylinder 44 (FIG. 7) the connection between the suction tube 34 and the chamber 39 is blocked which connects the depression unit directly with the outside so that it may function freely without creating a condition such as over-heating or other problems and at the same time without stopping it completely, which would be useless since once the ventilator is separated from the circuit, it would continue to function by inertia for a while thus interferring with the free movement of the work. As soon as the work clamp is lifted by emission of air in cylinder 30, the suction is restored immediately as the cylinder is also driven to open the damper 43, thus connecting the chamber 39 with the conduit 34. As mentioned above, the carriage 3 is a structure consisting of a coupling element 7 (FIGS. 1 and 3) driven by a cylinder 8 capable of being inserted alternatively in one or the other (the upper or lower) part of the belt or carrying chain 6 so that, by inserting it in the first part, the carriage moves in one direction and by inserting it in the second part, the carriage moves in the opposite direction. This method permits the change or the inversion of the carriage's running direction and to adjust the speed of the run. In fact to drive the carriage in a certain position it is only necessary to insert in the drive circuit a contact which controls the movement of the cylinder 8 which will thus cause the movement of the coupling element 7 to the other part of the chain 6. In the same way, in order to regulate the forward movement of the carriage 3 with respect to its maximum speed, which is fixed, it is only necessary to insert a time contact in the electric control circuit so that in a certain position of the carriage, the relative contacts become closed and affect the brake-clutch assembly and rate of travel of the carriage by restricting the motor 5 to a predetermined speed. Naturally it is not necessary only to let the carriage run back and forth to obtain the complete working cycle, but it is also necessary to lift and lower the work clamp 12 in relation to the working surface in order to have room available to insert a workpiece at the beginning of the sewing cycle and to be able to remove it at the end and let the carriage return to the initial starting position.
With regard to FIGS. 8, 9 and 10, the first cycle is started by pressing button PM which prepares the apparatus for its function and determines the temperature of the amplification circuit 45 of a sensitive element 46, consisting of a photocell mounted on the machine 4 to put it into operation when the work reaches it. By pushing button PA, which is normally closed, a remote control-switch TEL becomes thus activated. Said switch closes its contact TEL 1 on the feeding circuit of the motor 47 of the sewing machine 4, of the motor 5, of the chain and of the suction fan driven by motor 35. The other contact TEL 2, also normally open, by closing itself keeps the same remote control switch activated and permits the release of the button PM. At this point all that has to be done is to press the button 48 to start the operation cycle as described above.
FIG. 10, which is the sketch of a pneumatic drive circuit, shows that the circuit is activated by the electrical circuit of FIGS. 8 and 9 and that at the beginning of the cycle the cylinder 30 which opens the work clamp is full of air, therefore the work clamp 12 is lifted to the position shown by dotted lines in FIG. 3. In a like manner the cylinder 8 is also filled with air to provide for the coupling of the carriage 3 to the chain. The coupling of the carriage to that part of the chain for the return run requires that the cylinder 8 be filled with air and the work clamp in lifted position. Compressed air from any suitable source 49 passes, through a distributor valve 50 and a three-way valve 51, into the feeding line of the cylinders 8 and 30. At the same time, the contact A/R3 is in a position indicated in FIG. 9, and the element A2 of the electric valve 52 becomes energized through the secondary of the transformer T and the rectifier bridge P. When the electric valve 52 is activated, the air passes from the main line to the upper part of cylinder 44 relative to the position of template 19 (see also FIG. 3). This means that template 19 is lowered in operating position being that its drive element, consisting of cylinder 53, is filled with air, while the damper 43 is open and for this reason there is suction in the chamber 39 and in the chamber 36 and eventually in the other chambers 37, 38 having the relative valves 41, 42 open. In this case the lower parts of cylinders 44 and 53 are connected with the atmosphere and at the same time both chambers 21 and 22 of the positioning cylinder 20 are fed through an electric valve 6 which is activated, reason for which the work clamp 12, besides being lifted is already positioned in a fixed manner by the activation of said pneumatic cylinder 20.
Before pushing the starting button 48, it is necessary that the work clamp be closed in its operating position and that the coupling 7 connected to the piston of cylinder 8 be lowered to enable the coupling of the carriage to the driving devices in order to prepare for the advancement of the working clamp toward the sewing machine 4. This is achieved by pressing and then releasing the control 32 of the work clamp, which after said maneauver permits the passage of air through a one-way valve 54 with which it is connected and which directs a flow of air on a distributing valve 50 causing the discharge into the atmosphere of the air contained in cylinders 8 and 30. By keeping the control 32 depressed, the air passing through valve 54 reverses valve 51, so that the line for cylinders 8 and 30 is still fed with air. As soon as the control 32 is released and the valve 54 is returned to the position indicated in FIG. 10, the air contained in cylinders 8 and 30 is discharged into the atmosphere. In the meantime, the first activity of control 32 does not cause any variation in the position of work clamp 12, but when the control 32 is released the work clamp closes and successively, every time the control 32 is activated and then released, the work clamp is lifted and then lowered, while valve 50 is always in a different position with respect to the one illustrated in FIG. 10. At the same time, the piston of cylinder 8 which couples the carriage to the chain, becomes subject to movements, but has no effect since the carriage is idle. The important thing is that before the carriage is started it is necessary to close the work clamp which movement causes a discharge of air from cylinder 8, for which reason the piston thereof is lowered and as mentioned before, when this piston is lowered the carriage becomes coupled to that part of the chain which effects movement of the carriage toward the sewing machine. After having pushed and released control 32 of the work clamp 12, it is necessary to push the starting button 48. If the sewing threads, which are controlled by micro-switches 57 (not visible in FIGS. 1 and 2) are found intact, and consequently their contacts in the circuit are closed, a relay A/R becomes energized, causing movement of its contacts A/R1 which close determining its own activity. Even after the release of the starting button 48, A/R2 closes causing the energization of the low speed control S1 and at the same time the medium speed control S2 through contacts B/1 and D/1. This is possible because the photocell 46 (FIGS. 1 and 2) at the beginning of the cycle becomes activated and after having reached operating temperature has the function of an activated relay with its contact 58 moved so as to close the activity circuit of a relay B which, when also energized, reverses its contact B/1 while D/1 remains in the same position as indicated in FIG. 8 and permits the flow of current necessary to energize S2.
The other contact 59 of the photocell 46 also closes causing the energizing of a relay C, whose function is that of "annuling" the parallax distance existing between the photocell 46 which senses the presence of the work approaching the machine 4 and the position of the needle 16 of the machine. At the same time the relay A/R is energized contact A/R 3 reverses its position, de-energizing A2 and closing the activity circuit of unit A1 of the electric valve 52. Thus we obtain a movement which causes the air contained in the upper part of the cylinder 53 and 54 to be discharged into the atmosphere, and the air coming from the main line is introduced in the lower part of said two cylinders whose pistons are pushed upwardly causing the lifting of template 19 and the closing of the damper 43 respectively, which removes the suction from the working surface. At this point the work clamp is in operating position and the positioning cylinder 20 of the work clamp has its chambers filled with air, template 19 has been in the meantime lifted, the suction has been closed and the carriage 3 moves towards the sewing machine at a medium speed S2 which prevails over the lower speed S1. At the beginning of the run it is necessary to activate in sequence the two micro-switches 60 and 61 to complete the backward run, the contact of the micro-switch is closed on the activity circuit S3, arranging thus the energization of the control at high speed. Then there is the closing of the contact of the micro-switch 61 on the activity circuit of S4 without effect because the latter in the meantime is energized by the closing of contact S1/1. After the relay C has been energized, its contact C/1, (normally closed), becomes open to prevent the relay A/M which controls the coupling of motor 47 for the drive of the sewing machine 4 from being immediately energized. In fact, even if the contact D/2 is closed due to relay D being de-energized, the auxiliary contact A/M2 of A/M stops the relay on said auxiliary contact from becoming energized. By continuing its forward movement, the carriage 3 brings the front edge of the work clamp 12 in relation to a micro-switch 62 which causes the chambers 21 and 22 of cylinder 20 in discharge themselves immediately. This causes the work clamp 12 to free itself from the rigid position in which it was at the start of the cycle so that it is free to make any predetermined transversal movement from the moment the fixed pin 18 is engaged by the guide 17 and reproduces exactly the desired profile of the seam to be made. This rigid positioning by means of compressed air is necessary to obtain the perfect positioning and alignment of the guide with the sewing machine. As soon as these two elements come into engagement it is necessary to free the work clamp by release of the compressed air in order to permit the transversal movements required by the seam's profiles. For this reason the micro-switch must be positioned on the working surface 2 so that it can be reached by the leading edge of the work clamp 12, just prior to guide 17 engaging pin 18. Shortly after the micro-switch is activated, the forward portion of the workpiece (which protrudes from under the work clamp) reaches the photocell 46, obscuring it, thus causing it to become inactive causing its contacts 58 and 59 to return to the position shown in FIG. 8 thus activating the relay D. The relay D reverses its contact D/1 thus interrupting the activity circuit of S2 which becomes immediately inactive due to the fact that contact B/1 does not reverse immediately its position since relay B, which should become inactive when photocell 46 becomes obscured, continues to be activated by its timer T1. C also remains energized for a predetermined period after the photocell is obscured, which energization is due to its timer T3, that keeps it contact C/1 open.
As mentioned above, this is required due to the fact that the photocell is disposed in spaced relation to the needle 16, and is effective in preventing the sewing machine from starting and forming stitches before the workpiece reaches the needle. This is what we have referred to as "Annulment" of the distance between the photocell and the needle of the machine 4, which is performed by the timer T3.
The length of time S2 remains de-energized depends on the timing of relay B so that the movement at low speed, controlled only by S1 is more or less ample depending on the delay anticipated by the timer T1. This delay provides a so-called thickening of the stitches during the initial sewing of the seam.
C controls, with its timer, the delay of the starting of operation of the machine, which for example forms not more than two stitches before the workpiece is engaged by the needle which is descending to form the next stitch.
It is advised that not more than two stitches be formed before engagement by the workpiece because by so doing the threads cannot come apart especially during the formation of the small chain stitch. In fact, while the work clamp continues its advance the timing of T3 which is less than the timing of T1, becomes inoperative and the contact C/1 closes energizing the relay A/M that closes its contact A/M2 which keeps it active being that contact D/2 is also closed owing to the activity of D. The contact A/M1 also closes causing activation of the unit F (FIG. 9) of the electric valve 63 connected with a cylinder 64 and the relay A/TS which reverses its contact A/TS1, causing the condenser T4 to be charged. After F has been activated, the valve 63 normally closed, becomes opened causing compressed air to activate the cylinder 64 connected mechanically with the coupling of motor 47 which starts the sewing machine and the sewing operation. During this initial phase of sewing, low speed is needed to produce a series of short stitches for the purpose of providing increased resistance to the seams.
When the timing set by T1 is completed, B also de-energizes and consequently its contact B/1 returns to the position indicated in FIG. 8, causing the energizing of S2 since contact D/1 moves from the same side when D becomes energized. In this manner we achieve the phase of seams at high speed with normal stitches. The closing of 62 has no consequence being that the micro-switch is connected in series with a second micro-switch 65, which was open without consequences when the leading edge of the work clamp 12 came in contact with it. When the photocell 46 becomes activated, the contacts 58 and 59 change from the position indicated in FIG. 8, and contact 58 in particular causes the immediate energizing of relay B, which through the movement of its contact B/1 de-energizes S2 and introduces another reduction of speed, which is controlled only by S1.
At the time contact 58 closes, relay D will de-energize so that contact D/1 will close and maintain energization of S2. However, D remains energized for a certain period of time due to a timer T2 which assures for a certain period of time the exclusion of S2 and consequently a second group of stitches is formed of reduced length. At the same time relay C becomes energized, the opening of contact C/1 produces no effect on the activity of A/M being that it is kept between A/M2 and D/2, with relay D energized. In this manner even the final portion of the workpiece is sewn in very short stitches due to the combination of the high speed of the machine 4, which is constant, and the moving speed of the work clamp which is reduced.
As soon as the timer of T2 completes its function, contact D/1 moves towards the same part of contact B/1, causing the energization of S2 and consequently, the removal at medium speed of the work clamp and of the work from the needle to the end of the run. Contact D/2 also opens but the operation of A/M continues for some time, due to its timer T5 which allows the machine to produce a certain amount of chain-type stitches beyond the material workpiece, where they can be safely cut. At the end of the time controlled by T5, A/M de-energizes and A/M2 opens without effect as does contact A/M1 which causes the de-energizing of F which controls cylinder 64 and determines the stopping point of the machine. The de-energizing of A/TS occurs with a slight delay by a timer T6 and is connected to an electrical control of the thread-cutting device. The delay is given to permit the machine to stop completely, to eliminate powers of inertia and delays, so that the chain of stitches to be cut is subjected to a certain tension at the moment of the cut which is accomplished by work clamp 12 continuing to move when the thread is stopped or pinched on the working surface by the thread-cutting device, before the actual cut occurs. Referring again to the circuitry in FIGS. 8 and 9, the de-energizing of A/TS causes the change of its contact A/TS1 on a relay A/TT which becomes energized at the same time as a result of the current discharge of condensor T4. The energizing of A/TT causes contact A/TT1 to close in the circuitry of the electric valve H which activates the cylinder 67 whose piston is connected mechanically with the thread cutter 68 mounted on the machine 4. Once the discharge current of T4 is exhausted the contact A/TT1 opens again and the electric valve H is again energized causing the thread-cutter 68 to return to its initial position.
At this point the micro-switch 65 is deactivated by the rear side of the work clamp 12 closing its contact which activates the electric valve G that determines the passage between chambers 21 and 22 of the pneumatic cylinder 20 of the work clamp and at the same time, by means of a regulating valve 69, the passage into 56 and through 55 the passage to a micro-switch 70 and to the distributor valve 50 bringing thus to the position indicated in FIG. 10. The function of valve 59 causes the passage of compressed air, through the three-way valve 51 disposed within the cylinder 8 shown in FIG. 10, coupling to the chain 6 and in cylinder 30 for the opening of the work clamp. The work clamp is thus lifted and held in the transversal position when both pistons 24 and 25 of the chambers 21 and 22 are pushed to the end of their run, while the raising of the piston of cylinder 8 causes the coupling of the carriage 3 to the part of the chain 6 for effecting the return movement of the carriage. In the meantime, the opening of the contact of the micro-switch 70 causes immediate de-energizing of relay A/R and opens its contact A/R1 and its contact A/R2 which caused the de-energizing of S1 and S2 and by the opening of contact S1/1, the relay S4 controls the complete cessation of the motor 5 and of the work clamp 12. After G has been energized, container 56 (FIG. 10) is filled with air and valve 55 which is moved toward the right closes the passage of the air toward the micro-switch 70 and toward distributor valve 50, as mentioned above, arranging for the latter to be moved by the flow of air sent by distributing valve 54 of the manual control 32 which serves for the opening of the work clamp.
The micro-switch 70 recloses its contact, but without effect being that in the meantime relay A/R is de-energized and therefore contact A/R1 is open.
Through valve 50 and valve 51, the compressed air continues to be present in cylinder 8 and 30. Once the opening of the work clamp by means of the piston of cylinder 30 has been completed at the end of the run, a micro-switch 71 is activated by the flow of air from a valve 72. The microswitch reverses its contact on the activity or encitement circuit of S3 through the contact of the micro-switch 60 which is already closed on S3. Motor 5 is then operated at maximum speed being that the control S3 introduces the maximum amount of magnetization and due to the position of the piston of cylinder 8, the carriage is returned to its starting position at this maximum speed.
At the end of the run the micro-switch 60 is opened by the carriage itself and its contact in the circuit is closed on the active circuit of S4 through the closed micro-switch 61, thus the high speed is cut out by the de-energizing of S3 and the exact position is made at very low speed determined by assembly S4. Once the positioning has been completed, the carriage at the end of the run opens the contact of the micro-switch 61 causing a cessation of the motor 5 and the carriage. By returning to the initial position, a new cycle of operations can be started by closing the work clamp as indicated above, after having inserted a new workpiece beneath it.
It is to be noted that some of the construction particulars have been described only because they are evident to those conversant in the art and because they are subject to modifications, as they are not essential to the aims of the invention. For example, it is preferable, even if it is not part of this invention, to place the potentiometer, which regulates the medium speed of the sewing speed, in such a way that it becomes accessible from the outside, for the length of the stitch and the sewing time of the workpiece depend by its adjustment or regulation.
Additional changes and/or modifications could be made by those familiar with automatic sewing units according to the present invention as described above and to the working cycle which is an object of this invention. A different working cycle with similar characteristics can be used, for instance having the characteristic of being able to increase the number of stitches in one part of the work only, or having a different level of speed, for example having an approaching speed to the sewing machine different than the one relative to the seaming phase. Also, regarding the construction of the automatic unit, modifications can be made to the type of sewing guide, which besides having any type of shape as mentioned before, can also be built differently, for example it could consist of an inverted T-bar clasped by two small rollers with fixed axis, etc. Furthermore, the work clamp could consist of two elements which clasp the work and which can be opened and closed as a book, or also a different type of guide for the transversal movements of the work clamp itself could be proposed. Also, the pneumatic cylinders for activating the various parts above-mentioned, could be substituted by actuating devices with different drives, for example electro-magnetic.
The present invention relates to a method and apparatus for forming (cyclically) seams of predetermined configuration and length on a sewing machine. There are several types of industrial sewing machines in which the work is guided towards the sewing zone in an automatic manner by a clamping element which follows a predetermined trajectory and not necessarily a straight trajectory. These machines, even in cases where the clamping element opens automatically at the end of each sewing cycle, must be started again manually when starting each successive cycle, especially when positioning the clamping element for receiving the workpiece in the starting position.
Also well known is the fact that the sewing units presently used in the industry of ready-to-wear garments have a much higher degree of automation when the sewing profiles to be obtained with the same unit do not vary much among themselves as far as shape is concerned. However, until now it was impossible to have automatic sewing units with such a degree of versatility that they could be used to make seams having different profiles or shapes such as in the manufacture of various garments. With the technique used until now, it was impossible to perform sewing cycles on long and differently shaped stretches of fabric and impossible to repeat said cycles automatically.
An apparatus, which forms a part of this invention, is capable of automatically producing seams of a predetermined configuration. This is achieved by the unit by following the working method of working cycle which also forms a part of the invention. It is the object of the invention to provide a method for obtaining (cyclically) long and variously shaped seams, said method consists of a series of operations which are better defined below, and of an apparatus which permits the automatic performance of said operations with a great degree of versatility as far as the shapes of the seams are concerned. Another object of this invention is to provide an automatic sewing unit which is highly versatile and which requires only the minimum amount of manual intervention during the entire cycle of operations, as all security features and the relative drive controls are automated.
The automatic unit of the invention presents also the advantage of performance speed being that the complete series of operations are performed automatically with the minimum amount of idle time or waiting period between one operation and the next. Other objectives, advantages and characteristics of the sewing method and of the automatic sewing unit of the present invention are described below in detail and are illustrated on the attached drawings.
FIG. 1 -- is a perspective view of the automatic unit according to the invention;
FIG. 2 -- is a plan view of the unit of FIG. 1;
FIG. 3 -- is a sectional view along the line III--III of FIG. 2;
FIG. 4 -- is a side view showing further detail the transversal system of the work clamp;
FIG. 5 -- is a schematic plan view of the unit of the invention, illustrating particularly the suction system;
FIG. 6 -- is a view in side elevation of the working surface with the suction system of FIG. 5;
FIG. 7 -- is a side view showing a portion of FIG. 6 on an enlarged scale;
FIG. 8 -- is a schematic view of a portion of the unit's drive electrical system;
FIG. 9 -- is a schematic view of the electrical circuitry for the mechanism of FIG. 6, and;
FIG. 10 -- shows schematically the pneumatic drive circuit of the present invention.
With reference to FIGS. 1, 2, and 3, the automatic sewing unit consists essentially of a support frame 1, a working surface 2, a sliding support means 3, represented by a movable carriage capable of shifting the unfinished work on the working surface so that it can be sewn by a fixed sewing machine 4. The sewing cycle in accordance with the present invention consists of a series of operations which can be described as follows:
a. Move the carriage at medium speed in order to draw the work up to the sewing machine;
b. sew a small section in very short stitches, by moving the carriage at low speed;
c. continue sewing at medium speed, similar to the speed used in drawing the work up to the sewing machine;
d. reduce speed when the end of the sewing approaches so that a second small piece can be sewn in short stitches, as in b);
e. resume change of position at medium speed until the run is finished;
f. stop to allow work clamp to open in the rejecting zone and position same in relation to the sewing axis;
g. return to starting point of the carriage at high speed and;
h. reduce speed to extremely low level in order to position the carriage, during the last part of the return run.
Three different speeds are provided and preferably not less than four. These speeds are obtained through a motor 5 equipped of an electro-magnetic brake unit (not illustrated) which can be inserted gradually and which at the proper time affects the run between the armature and the inductor of the motor itself in order to vary the electro-magnetic force. The carriage is moved through a belt or transmission chain 6 activated by the motor 5 always in the same direction. The movement in one direction or the other is achieved by connecting the carriage 3 to the upper part or the lower part of the chain 6 through a coupling 7 activated at the proper time by an opposite drive consisting, for example, of a pneumatic cylinder 8 whose piston carries said coupling 7 equipped with teeth 9, on the free extremity (FIG. 3). Based on which tooth 9 is used in the chain 6, the carriage 3 moves in one direction or the other. The carriage 3 includes all the machine elements which move and slide lengthwise along the working surface 2.
The carriage itself is mounted for sliding and rotary movement on a guide shaft 10 by supporting brackets 11, supported on the side of the working surface 2 and includes; a work clamp 12 capable of locking the work into place and letting it slide on the working surface 2; and of transversal guiding units (illustrated in detail in FIG. 4) consisting of a support rod 13 mounted telescopically in supporting tubes 14 of the carriage 3. The work clamp 12 includes a contoured edge 15 shaped in such a way that it can reproduce the same profile of the seam to be made and to avoid interference with the needle 16 of the machine 4 during operation of the subject unit. Parallel to the contoured edge 15, the work clamp 12 carries a guide 17 in the form of a cam track which reproduces exactly the profile of said edge and of the seam to be made. Such guide 17 serves to determine the transversal movements of the work clamp 12 during the longitudinal movements of the carriage 3. To obtain transversal movements, the guide 17 becomes engaged by a fixed locator, or guide pin 18, mounted on the machine near the needle 16, thus the work clamp 12 is forced to move from one side and/or the other transversally of the working surface 2 in order to keep the edge 15 constantly at the same distance from the needle 16. In this way the needle 16 penetrates freely only in the part of the material carried by work clamp 12. In order to produce the seam parallel to the border of the work, the latter is inserted under the work clamp with the help of a template 19. The amount of free space between the work clamp 12 and the template 19 is occupied by the protruding portion of the work on which the seam is to be made. When the work clamp 12 comes into contact with the sewing machine 4, the fixed locator or pin 18 enters into the guide 17 in order to give to the work clamp 12 a transversal movement with relative movement of the work and thus obtain the variation of the seam's trajectory. For what concerns the moving speed of the carriage 3 which speed is obtained with the motor 5, we point out that the so-called high speed is obtained through the complete coupling of the electro-magnetic brake-clutch assembly which is not adjustable. The lower speeds, instead, can be adjusted by means of suitable potentiometers. The minimum amount of each speed is fixed, and it is possible to increase the amount of one or more speeds, except the highest speed, affecting thus the higher ones, whereas by working with higher speeds, the lower ones are not affected. For example, by regulating the potentiometer relative to the lowest speed in a way to obtain the maximum of said speed, and the potentiometer of the second speed in such a way as to obtain its maximum speed, it is possible to achieve the maximum speed, without passing through the medium of third speed.
The maximum speed has a set amount since it corresponds to the maximum level of magnetization.
The transversal positioning of guide 17 with the relation to the pin 18 is assured the means consisting of a single pneumatic cylinder 20 FIG. 4, divided into two chambers 21 and 22 separated by a partition 23 in which chambers slide the pistons 24 and 25 respectively. The piston 25 is connected to the work clamp 12 by means of a cross-bar 26 fixed on the actuating rod 13, while the piston 24 is connected with the carriage 3 by means of a cross-bar 27 fixed on tubes 14. During the positioning of the work clamp 12 each chamber 21 and 22 is put in communication with a pneumatic circuit, which will be explained later, through tubes 28 and 29 respectively, which tubes are situated in opposite sides of the relative pistons. The reason for such position of these compressed-air feeding tubes (28 and 29) is that when both chambers 21 and 22 are filled with compressed air, the positioning of the work clamp 12 unequivocally determined, corresponds to a central position of the work clamp itself and consequently to the work placed under it, in relation to the transversal movement from one side or the other of the needle 16, which includes the maximum movement of the straight line required by the profile of the seam. Once the exact initial position has been determined, the work clamp can move inside the transversal positioning strip, following the trajectory determined by the pin 18 with the guide 17 after the discharge of compressed air contained in chambers 21 and 22. (FIGS. 3 and 4) show also a cylinder 30 which serves to open the work clamp 12 and which is hinged on carriage 3 on the upper side and on a bracket 31 on the lower side. The work clamp 12 can be opened to insert a new piece of work at the start of the cycle, or also at the end of the cycle to remove the piece of work after it has been sewn. This is possible because the work clamp 12 is directly hinged on the guideshaft 10 of cylindrical section. For the above-mentioned reason, the pivot around which the work clamp 12 moves, is connected with the carriage 3 which pivots upwardly during the changes of work. The work clamp 12 could also be opened in another way and that is by lifting the work clamp itself or in any other manner capable of freeing the work underneath the work clamp without any interference between the work clamp and the fixed elements, particularly the sewing machine 4, during the return-run of the carriage 3. FIGS. 2 and 3, also show a mutual control 32 which permits the opening of the work clamp before the cycle starts, independently from the function of the element which activates automatically cylinder 30 and which will be described in more detail later. Said mutual control 32 is shown in FIGS. 2 and 3 as a foot pedal control.
Referring to FIG. 5, the working surface 2 presents the loading zone having a plurality of holes 33 connected by a tube 34 to a depression unit, which, as indicated in FIG. 6 can consist of a suction fan driven by a motor 35. This suction serves to straighten and smoothly spread the material on the working surface in order to permit position adjustment of the material itself with relation to the work clamp, or with relation to the template 19 in its lowered position. In fact, by itself the material normally does not have a consistency sufficient to insure an even spread on the support surface before the work clamp 12, which at the start of the working cycle is open, can engage it and then move it toward the sewing machine 4. To prevent clinging of the material to the working surface 2 and permit the work clamp to move said material along said working surface the force of air entering holes 33 is sufficient only for the purpose of positioning the material to be sewn. Underneath the working surface 2, the suction zone is divided into separate chambers 36, 37, and 38, (FIG. 6) the longest of which, indicated as "36" connects with the tube 34 through an opening 40 and a chamber 39, while the other chambers 37 and 38 are connected with chamber 39 and with the suction conduit 34 by means of valves 41 and 42 respectively. The closing of valves 41 and 42 causes the rejection of the suction from the corresponding chamber. This is because the workpieces can have various dimensions, for example, they may vary from trousers to the neck or the cuffs of a shirt and therefore it would be useless to supply suction in zones not touched by the material. During the sewing cycle the depression unit is not stopped, that is to say the motor 35 is left running and by means of a damper 43 activated, for example, by a cylinder 44 (FIG. 7) the connection between the suction tube 34 and the chamber 39 is blocked which connects the depression unit directly with the outside so that it may function freely without creating a condition such as over-heating or other problems and at the same time without stopping it completely, which would be useless since once the ventilator is separated from the circuit, it would continue to function by inertia for a while thus interferring with the free movement of the work. As soon as the work clamp is lifted by emission of air in cylinder 30, the suction is restored immediately as the cylinder is also driven to open the damper 43, thus connecting the chamber 39 with the conduit 34. As mentioned above, the carriage 3 is a structure consisting of a coupling element 7 (FIGS. 1 and 3) driven by a cylinder 8 capable of being inserted alternatively in one or the other (the upper or lower) part of the belt or carrying chain 6 so that, by inserting it in the first part, the carriage moves in one direction and by inserting it in the second part, the carriage moves in the opposite direction. This method permits the change or the inversion of the carriage's running direction and to adjust the speed of the run. In fact to drive the carriage in a certain position it is only necessary to insert in the drive circuit a contact which controls the movement of the cylinder 8 which will thus cause the movement of the coupling element 7 to the other part of the chain 6. In the same way, in order to regulate the forward movement of the carriage 3 with respect to its maximum speed, which is fixed, it is only necessary to insert a time contact in the electric control circuit so that in a certain position of the carriage, the relative contacts become closed and affect the brake-clutch assembly and rate of travel of the carriage by restricting the motor 5 to a predetermined speed. Naturally it is not necessary only to let the carriage run back and forth to obtain the complete working cycle, but it is also necessary to lift and lower the work clamp 12 in relation to the working surface in order to have room available to insert a workpiece at the beginning of the sewing cycle and to be able to remove it at the end and let the carriage return to the initial starting position.
With regard to FIGS. 8, 9 and 10, the first cycle is started by pressing button PM which prepares the apparatus for its function and determines the temperature of the amplification circuit 45 of a sensitive element 46, consisting of a photocell mounted on the machine 4 to put it into operation when the work reaches it. By pushing button PA, which is normally closed, a remote control-switch TEL becomes thus activated. Said switch closes its contact TEL 1 on the feeding circuit of the motor 47 of the sewing machine 4, of the motor 5, of the chain and of the suction fan driven by motor 35. The other contact TEL 2, also normally open, by closing itself keeps the same remote control switch activated and permits the release of the button PM. At this point all that has to be done is to press the button 48 to start the operation cycle as described above.
FIG. 10, which is the sketch of a pneumatic drive circuit, shows that the circuit is activated by the electrical circuit of FIGS. 8 and 9 and that at the beginning of the cycle the cylinder 30 which opens the work clamp is full of air, therefore the work clamp 12 is lifted to the position shown by dotted lines in FIG. 3. In a like manner the cylinder 8 is also filled with air to provide for the coupling of the carriage 3 to the chain. The coupling of the carriage to that part of the chain for the return run requires that the cylinder 8 be filled with air and the work clamp in lifted position. Compressed air from any suitable source 49 passes, through a distributor valve 50 and a three-way valve 51, into the feeding line of the cylinders 8 and 30. At the same time, the contact A/R3 is in a position indicated in FIG. 9, and the element A2 of the electric valve 52 becomes energized through the secondary of the transformer T and the rectifier bridge P. When the electric valve 52 is activated, the air passes from the main line to the upper part of cylinder 44 relative to the position of template 19 (see also FIG. 3). This means that template 19 is lowered in operating position being that its drive element, consisting of cylinder 53, is filled with air, while the damper 43 is open and for this reason there is suction in the chamber 39 and in the chamber 36 and eventually in the other chambers 37, 38 having the relative valves 41, 42 open. In this case the lower parts of cylinders 44 and 53 are connected with the atmosphere and at the same time both chambers 21 and 22 of the positioning cylinder 20 are fed through an electric valve 6 which is activated, reason for which the work clamp 12, besides being lifted is already positioned in a fixed manner by the activation of said pneumatic cylinder 20.
Before pushing the starting button 48, it is necessary that the work clamp be closed in its operating position and that the coupling 7 connected to the piston of cylinder 8 be lowered to enable the coupling of the carriage to the driving devices in order to prepare for the advancement of the working clamp toward the sewing machine 4. This is achieved by pressing and then releasing the control 32 of the work clamp, which after said maneauver permits the passage of air through a one-way valve 54 with which it is connected and which directs a flow of air on a distributing valve 50 causing the discharge into the atmosphere of the air contained in cylinders 8 and 30. By keeping the control 32 depressed, the air passing through valve 54 reverses valve 51, so that the line for cylinders 8 and 30 is still fed with air. As soon as the control 32 is released and the valve 54 is returned to the position indicated in FIG. 10, the air contained in cylinders 8 and 30 is discharged into the atmosphere. In the meantime, the first activity of control 32 does not cause any variation in the position of work clamp 12, but when the control 32 is released the work clamp closes and successively, every time the control 32 is activated and then released, the work clamp is lifted and then lowered, while valve 50 is always in a different position with respect to the one illustrated in FIG. 10. At the same time, the piston of cylinder 8 which couples the carriage to the chain, becomes subject to movements, but has no effect since the carriage is idle. The important thing is that before the carriage is started it is necessary to close the work clamp which movement causes a discharge of air from cylinder 8, for which reason the piston thereof is lowered and as mentioned before, when this piston is lowered the carriage becomes coupled to that part of the chain which effects movement of the carriage toward the sewing machine. After having pushed and released control 32 of the work clamp 12, it is necessary to push the starting button 48. If the sewing threads, which are controlled by micro-switches 57 (not visible in FIGS. 1 and 2) are found intact, and consequently their contacts in the circuit are closed, a relay A/R becomes energized, causing movement of its contacts A/R1 which close determining its own activity. Even after the release of the starting button 48, A/R2 closes causing the energization of the low speed control S1 and at the same time the medium speed control S2 through contacts B/1 and D/1. This is possible because the photocell 46 (FIGS. 1 and 2) at the beginning of the cycle becomes activated and after having reached operating temperature has the function of an activated relay with its contact 58 moved so as to close the activity circuit of a relay B which, when also energized, reverses its contact B/1 while D/1 remains in the same position as indicated in FIG. 8 and permits the flow of current necessary to energize S2.
The other contact 59 of the photocell 46 also closes causing the energizing of a relay C, whose function is that of "annuling" the parallax distance existing between the photocell 46 which senses the presence of the work approaching the machine 4 and the position of the needle 16 of the machine. At the same time the relay A/R is energized contact A/R 3 reverses its position, de-energizing A2 and closing the activity circuit of unit A1 of the electric valve 52. Thus we obtain a movement which causes the air contained in the upper part of the cylinder 53 and 54 to be discharged into the atmosphere, and the air coming from the main line is introduced in the lower part of said two cylinders whose pistons are pushed upwardly causing the lifting of template 19 and the closing of the damper 43 respectively, which removes the suction from the working surface. At this point the work clamp is in operating position and the positioning cylinder 20 of the work clamp has its chambers filled with air, template 19 has been in the meantime lifted, the suction has been closed and the carriage 3 moves towards the sewing machine at a medium speed S2 which prevails over the lower speed S1. At the beginning of the run it is necessary to activate in sequence the two micro-switches 60 and 61 to complete the backward run, the contact of the micro-switch is closed on the activity circuit S3, arranging thus the energization of the control at high speed. Then there is the closing of the contact of the micro-switch 61 on the activity circuit of S4 without effect because the latter in the meantime is energized by the closing of contact S1/1. After the relay C has been energized, its contact C/1, (normally closed), becomes open to prevent the relay A/M which controls the coupling of motor 47 for the drive of the sewing machine 4 from being immediately energized. In fact, even if the contact D/2 is closed due to relay D being de-energized, the auxiliary contact A/M2 of A/M stops the relay on said auxiliary contact from becoming energized. By continuing its forward movement, the carriage 3 brings the front edge of the work clamp 12 in relation to a micro-switch 62 which causes the chambers 21 and 22 of cylinder 20 in discharge themselves immediately. This causes the work clamp 12 to free itself from the rigid position in which it was at the start of the cycle so that it is free to make any predetermined transversal movement from the moment the fixed pin 18 is engaged by the guide 17 and reproduces exactly the desired profile of the seam to be made. This rigid positioning by means of compressed air is necessary to obtain the perfect positioning and alignment of the guide with the sewing machine. As soon as these two elements come into engagement it is necessary to free the work clamp by release of the compressed air in order to permit the transversal movements required by the seam's profiles. For this reason the micro-switch must be positioned on the working surface 2 so that it can be reached by the leading edge of the work clamp 12, just prior to guide 17 engaging pin 18. Shortly after the micro-switch is activated, the forward portion of the workpiece (which protrudes from under the work clamp) reaches the photocell 46, obscuring it, thus causing it to become inactive causing its contacts 58 and 59 to return to the position shown in FIG. 8 thus activating the relay D. The relay D reverses its contact D/1 thus interrupting the activity circuit of S2 which becomes immediately inactive due to the fact that contact B/1 does not reverse immediately its position since relay B, which should become inactive when photocell 46 becomes obscured, continues to be activated by its timer T1. C also remains energized for a predetermined period after the photocell is obscured, which energization is due to its timer T3, that keeps it contact C/1 open.
As mentioned above, this is required due to the fact that the photocell is disposed in spaced relation to the needle 16, and is effective in preventing the sewing machine from starting and forming stitches before the workpiece reaches the needle. This is what we have referred to as "Annulment" of the distance between the photocell and the needle of the machine 4, which is performed by the timer T3.
The length of time S2 remains de-energized depends on the timing of relay B so that the movement at low speed, controlled only by S1 is more or less ample depending on the delay anticipated by the timer T1. This delay provides a so-called thickening of the stitches during the initial sewing of the seam.
C controls, with its timer, the delay of the starting of operation of the machine, which for example forms not more than two stitches before the workpiece is engaged by the needle which is descending to form the next stitch.
It is advised that not more than two stitches be formed before engagement by the workpiece because by so doing the threads cannot come apart especially during the formation of the small chain stitch. In fact, while the work clamp continues its advance the timing of T3 which is less than the timing of T1, becomes inoperative and the contact C/1 closes energizing the relay A/M that closes its contact A/M2 which keeps it active being that contact D/2 is also closed owing to the activity of D. The contact A/M1 also closes causing activation of the unit F (FIG. 9) of the electric valve 63 connected with a cylinder 64 and the relay A/TS which reverses its contact A/TS1, causing the condenser T4 to be charged. After F has been activated, the valve 63 normally closed, becomes opened causing compressed air to activate the cylinder 64 connected mechanically with the coupling of motor 47 which starts the sewing machine and the sewing operation. During this initial phase of sewing, low speed is needed to produce a series of short stitches for the purpose of providing increased resistance to the seams.
When the timing set by T1 is completed, B also de-energizes and consequently its contact B/1 returns to the position indicated in FIG. 8, causing the energizing of S2 since contact D/1 moves from the same side when D becomes energized. In this manner we achieve the phase of seams at high speed with normal stitches. The closing of 62 has no consequence being that the micro-switch is connected in series with a second micro-switch 65, which was open without consequences when the leading edge of the work clamp 12 came in contact with it. When the photocell 46 becomes activated, the contacts 58 and 59 change from the position indicated in FIG. 8, and contact 58 in particular causes the immediate energizing of relay B, which through the movement of its contact B/1 de-energizes S2 and introduces another reduction of speed, which is controlled only by S1.
At the time contact 58 closes, relay D will de-energize so that contact D/1 will close and maintain energization of S2. However, D remains energized for a certain period of time due to a timer T2 which assures for a certain period of time the exclusion of S2 and consequently a second group of stitches is formed of reduced length. At the same time relay C becomes energized, the opening of contact C/1 produces no effect on the activity of A/M being that it is kept between A/M2 and D/2, with relay D energized. In this manner even the final portion of the workpiece is sewn in very short stitches due to the combination of the high speed of the machine 4, which is constant, and the moving speed of the work clamp which is reduced.
As soon as the timer of T2 completes its function, contact D/1 moves towards the same part of contact B/1, causing the energization of S2 and consequently, the removal at medium speed of the work clamp and of the work from the needle to the end of the run. Contact D/2 also opens but the operation of A/M continues for some time, due to its timer T5 which allows the machine to produce a certain amount of chain-type stitches beyond the material workpiece, where they can be safely cut. At the end of the time controlled by T5, A/M de-energizes and A/M2 opens without effect as does contact A/M1 which causes the de-energizing of F which controls cylinder 64 and determines the stopping point of the machine. The de-energizing of A/TS occurs with a slight delay by a timer T6 and is connected to an electrical control of the thread-cutting device. The delay is given to permit the machine to stop completely, to eliminate powers of inertia and delays, so that the chain of stitches to be cut is subjected to a certain tension at the moment of the cut which is accomplished by work clamp 12 continuing to move when the thread is stopped or pinched on the working surface by the thread-cutting device, before the actual cut occurs. Referring again to the circuitry in FIGS. 8 and 9, the de-energizing of A/TS causes the change of its contact A/TS1 on a relay A/TT which becomes energized at the same time as a result of the current discharge of condensor T4. The energizing of A/TT causes contact A/TT1 to close in the circuitry of the electric valve H which activates the cylinder 67 whose piston is connected mechanically with the thread cutter 68 mounted on the machine 4. Once the discharge current of T4 is exhausted the contact A/TT1 opens again and the electric valve H is again energized causing the thread-cutter 68 to return to its initial position.
At this point the micro-switch 65 is deactivated by the rear side of the work clamp 12 closing its contact which activates the electric valve G that determines the passage between chambers 21 and 22 of the pneumatic cylinder 20 of the work clamp and at the same time, by means of a regulating valve 69, the passage into 56 and through 55 the passage to a micro-switch 70 and to the distributor valve 50 bringing thus to the position indicated in FIG. 10. The function of valve 59 causes the passage of compressed air, through the three-way valve 51 disposed within the cylinder 8 shown in FIG. 10, coupling to the chain 6 and in cylinder 30 for the opening of the work clamp. The work clamp is thus lifted and held in the transversal position when both pistons 24 and 25 of the chambers 21 and 22 are pushed to the end of their run, while the raising of the piston of cylinder 8 causes the coupling of the carriage 3 to the part of the chain 6 for effecting the return movement of the carriage. In the meantime, the opening of the contact of the micro-switch 70 causes immediate de-energizing of relay A/R and opens its contact A/R1 and its contact A/R2 which caused the de-energizing of S1 and S2 and by the opening of contact S1/1, the relay S4 controls the complete cessation of the motor 5 and of the work clamp 12. After G has been energized, container 56 (FIG. 10) is filled with air and valve 55 which is moved toward the right closes the passage of the air toward the micro-switch 70 and toward distributor valve 50, as mentioned above, arranging for the latter to be moved by the flow of air sent by distributing valve 54 of the manual control 32 which serves for the opening of the work clamp.
The micro-switch 70 recloses its contact, but without effect being that in the meantime relay A/R is de-energized and therefore contact A/R1 is open.
Through valve 50 and valve 51, the compressed air continues to be present in cylinder 8 and 30. Once the opening of the work clamp by means of the piston of cylinder 30 has been completed at the end of the run, a micro-switch 71 is activated by the flow of air from a valve 72. The microswitch reverses its contact on the activity or encitement circuit of S3 through the contact of the micro-switch 60 which is already closed on S3. Motor 5 is then operated at maximum speed being that the control S3 introduces the maximum amount of magnetization and due to the position of the piston of cylinder 8, the carriage is returned to its starting position at this maximum speed.
At the end of the run the micro-switch 60 is opened by the carriage itself and its contact in the circuit is closed on the active circuit of S4 through the closed micro-switch 61, thus the high speed is cut out by the de-energizing of S3 and the exact position is made at very low speed determined by assembly S4. Once the positioning has been completed, the carriage at the end of the run opens the contact of the micro-switch 61 causing a cessation of the motor 5 and the carriage. By returning to the initial position, a new cycle of operations can be started by closing the work clamp as indicated above, after having inserted a new workpiece beneath it.
It is to be noted that some of the construction particulars have been described only because they are evident to those conversant in the art and because they are subject to modifications, as they are not essential to the aims of the invention. For example, it is preferable, even if it is not part of this invention, to place the potentiometer, which regulates the medium speed of the sewing speed, in such a way that it becomes accessible from the outside, for the length of the stitch and the sewing time of the workpiece depend by its adjustment or regulation.
Additional changes and/or modifications could be made by those familiar with automatic sewing units according to the present invention as described above and to the working cycle which is an object of this invention. A different working cycle with similar characteristics can be used, for instance having the characteristic of being able to increase the number of stitches in one part of the work only, or having a different level of speed, for example having an approaching speed to the sewing machine different than the one relative to the seaming phase. Also, regarding the construction of the automatic unit, modifications can be made to the type of sewing guide, which besides having any type of shape as mentioned before, can also be built differently, for example it could consist of an inverted T-bar clasped by two small rollers with fixed axis, etc. Furthermore, the work clamp could consist of two elements which clasp the work and which can be opened and closed as a book, or also a different type of guide for the transversal movements of the work clamp itself could be proposed. Also, the pneumatic cylinders for activating the various parts above-mentioned, could be substituted by actuating devices with different drives, for example electro-magnetic.