05/426605

11/12/1974

12/20/1973

Download PDF 3847101       PDF help

Click for automatic bibliography generation

112/294

112/70, 112/260

D05B65/00; D05B73/02; D05B73/00; D05B65/02

112/65,66,68,70,76,129,130,252,259,260

Schroeder, Werner H.

Mcglew, And Tuttle

What is claimed is

1. A sewing machine comprising a machine frame having a workpiece support, a bracket mounted on said frame for pivotal movement upwardly to a rest position and downwardly to an operative position, a needle mounted on said frame for upward and downward reciprocation below said support, a rotatable shuttle mounted on said bracket overlying said needle for cooperative engagement therewith, a clamping arm connected to said bracket for movement therewith and pivoted on said frame over said support and having an end adapted to clamp the workpiece on the support, a thread cutter carried by said bracket and connected to said clamping arm, said clamping arm being movable by upward movement of said bracket to actuate said cutter to sever the thread.

2. A sewing machine, according to claim 1, wherein said cutter comprises a cutter lever mechanism, a pressure plate supported on said racket, said lever mechanism being pivoted on said pressure plate and being connected to said clamping arm and being pivotal thereby to effect the cutting operation.

3. A sewing machine, according to claim 1, including a press plate, a vertically movable member carrying said press plate and having a pin portion, a guide carried on said bracket in which said member is movable upwardly and downwardly and including a slot in which said pin portion is engageable and confined for movement within defined limits of said slot, and spring means urging said pressure plate downwardly away from said bracket, said pressure plate being engageable with the workpiece and carrying said cutter.

4. A sewing machine, according to claim 3, wherein the connection between said clamping arm and said bracket includes a crank pivotally mounted on said clamping arm and having an end pivotally connected to an actuating member connected to said cutter, said crank having a pawl engagement surface, and a ratchet lever pivoted on said bracket and engageable with said pawl to rotate said crank to move said actuating member to actuate said cutter when said bracket is moved upwardly by a predetermined amount.

5. A sewing machine, according to claim 4, wherein said cutter is connected by four-bar linkage comprising said actuating member, said crank with said pawl, and said cutter, said cutter including a pivotal lever portion included in said four-bar linkage.

6. A sewing machine, according to claim 4, including a bridge pivotally mounted on said bracket, said ratchet lever being pivoted on said bridge and adjustment means connected to said bridge for adjusting in the position thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to the construction of sewing machines and, in particular, to a new and useful sewing machine which includes a rotatable shuttle mounted on a bracket which is pivotally mounted on a frame carrying the needle which reciprocates upwardly and downwardly in the frame from below the workpiece support in cooperation with the shuttle and which includes means for severing the thread when the sewing machine is stopped and the arm is moved to a non-operative or rest position.

2. Description of the Prior Art

The present invention relates to sewing machines of a type having a rotating shuttle provided above the table for the sewn material and received in a bracket which is movable from a working position into a rest position; a needle cooperating with the shuttle, and adapted to pass through the sewn material from beneath upwardly, and a material clamping arm movable from a clamping position into a rest position.

To sew so-called purl stitched buttonholes, it is known to use sewing machines in which the shuttle is located above the table receiving the sewn material and the needle penetrates the material from beneath upwards. Since in machines of this type, the bracket receiving the shuttle requires much more space than a usual bracket receiving the needle and must be positioned during the stitching very close above the material to ensure a faultless stitch, it is a common practice that after the stitching cycle, the bracket is brought back from its working position into a rest position which is distant from the stitching area. Before removing the bracket, however, it is necessary to draw off and cut the thread extending between the upper surface of the sewn material and the thread bobbin of the shuttle.

SUMMARY OF THE INVENTION

The invention provides a thread cutting mechanism for sewing machines of the mentioned type, which comes automatically into effect at the end of the sewing operation while the bracket is moving from its working into its rest position, assuring a very short end portion of the thread remaining with the sewn material and avoiding the necessity of using both a special thread puller and a particular drive and control means for the cutting tool.

In accordance with the invention, the sewing machine includes a drive connection operating with an idle stroke and interconnecting the bracket receiving the shuttle with the clamping arm for the sewn material and a drive mechanism for a cutting tool which, in a well-known manner, is carried on the clamping arm and actuated by the motion of the bracket. The idle stroke of the drive connection between the bracket and the clamping arm has the effect that at the end of the sewing operation, the bracket is first lifted from the material and the clamping arm up to a certain distance, while the clamping arm remains applied against the material, whereby the thread is pulled off the shuttle in a length corresponding to the length of the idle stroke. At the end of the idle stroke, while the bracket continues to move towards its rest position, the bracket motion is transmitted to the cutting tool which is mounted on the clamping arm. Thus, both the beginning and the execution of the cutting operation proper is automatically derived from the necessary movement of the bracket and the thread is cut off close to the surface of the material. Still another advantage results therefrom, namely, that both the pulling off and the cutting of the thread is effected during the motion of the bracket from its working into its rest position so that the operational cycle of the sewing machine can be considerably reduced.

Advantageously, to obtain an idle stroke between the bracket and the clamping arm and coordinate the cutting operation with the bracket motion, there is provided a claw engaging the clamping arm from beneath and movable relative thereto within limits and against the action of a spring and, as the drive means for the cutting tool, a ratchet lever mounted on the bracket for cooperation with a crank having the shape of a pawl and forming part of a four-bar linkage hinged on the clamping arm and including a swinging member carrying the cutting blades is provided.

To be able to adjust the time of the thread cutting and thereby the thread length to be pulled off within certain limits in respect to the motion of the bracket, there is provided in accordance with a development of the invention, the mounting of a ratchet lever on a bridge, which is supported on the bracket and whose relative position thereto is adjustable.

Accordingly, it is an object of the invention to provide an improved sewing machine of a type which includes a bracket or arm which is mounted on a machine frame for pivotal movement upwardly to a rest position and downwardly into pressing engagement with the material on a support of the frame and which includes a rotatable shuttle mounted over a reciprocating needle which is carried in the frame below the workpiece support and which includes a clamping arm which engages the workpiece and which is moved by movement of the bracket to actuate a cutting mechanism to cut away the thread when the bracket is moved to a rest position.

A further object of the invention is to provide a sewing machine which includes a rotatable bobbin mounted above the reciprocating needle of a sewing machine frame and which includes a clamping arm arranged below a movable bracket carrying the bobbin which holds the workpiece as the thread is drawn upwardly therethrough during the time in which the bracket is moved to a rest position and thereafter actuates a cutting mechanism to cut the thread close to the material and to leave a length of thread remaining in the bobbin for the formation of a new loop when the machine is again operated.

A further object of the invention is to provide a sewing machine construction which is simple in design, rugged in construction, and economical to manufacture.

For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side elevational view of a stitch-group sewing machine constructed in accordance with the invention;

FIG. 2 is a partial elevational view of the mechanism shown in FIG. 1 with the bracket in a lifted position;

FIG. 3 is a view similar to FIG. 2 with the bracket in a complete rest position;

FIG. 4 is a section taken along the line IV--IV of FIG. 1;

FIG. 5 is a partial top plan view of the pressure plate indicating the cutting mechanism; and

FIG. 6 is a view similar to FIG. 5 showing the cutting mechanism in the operative position.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in particular, the invention as embodied therein, comprises a sewing machine, which for example, may be a stitch-group buttonhole sewing machine, comprising a stationary substructure or frame 1, with a bracket or arm 2 pivotally mounted thereon at the location of a pivot pin 3. To move the bracket from a working position into a rest position, a double-action electromagnet 4 is provided in the substructure 1, whose armature is connected to a portion of the bracket 2 lateral to the pivot 3. Both the working and the rest position is fixed by corresponding non-represented stops.

A main shaft 5 is mounted in the substructure 1 of the sewing machine, and carries a pulley 6, driven by a stop motor (not shown). A crank 7, mounted on the free end of shaft 5, drives a needle bar 11, carrying a thread guiding needle 10, through a link 8 and an intermediate member 9. Needle 10 pierces the sewn material from beneath upwards and cooperates with a rotating shuttle 12 which is mounted on the end surface of bracket 2.

A pulley 13 on the main shaft 5 transmitting motion through a toothed belt 14 and another pulley 15 drives a shaft 16 mounted in the bracket 2 and, therefrom, through a pair of bevel gears 17, a vertical shaft 18, and another pair of bevel gears 19 to the shaft 20 of the shuttle 12. By means of this drive train, shuttle 12 is driven at a double speed with respect to the reciprocating motion of the needle.

In the present example, the sewing machine is provided with a support 21 for the material to be sewn. The support 21 is pivotally mounted at 22 and backed up, in the stitching area, by a slidable rest 23, both the pivot 22 and the rest 23 being supported by the substructure 1. The rest 23 comprises a bolt 24 which is biased by an adjustable spring 25 and movable within a distance predetermined by a stop 26. On the support 21 is a plate 28 provided, which is shiftable in the direction of the longitudinal axis of the machine by means of a worm gear 29 and in a manner not specifically shown. The material to be sewn is placed on surface 27 of plate 28. The worm gear 29 is driven by a toothed belt 32 passed around two pulleys 30, 31 and receives its motion from a stepping mechanism 33. Stepping mechanism 33 comprises two eccentrics 34, 35 which are mounted on main shaft 5 and impart an advance, spreading, and clamping motion to belt tongs 36.

A clamping arm 38 is pivotally mounted on support 21 at 37. On its free end, the clamping arm 38 carries a pressure piece 39 (FIG. 4) with a tenter or presser plate 40 mounted thereon and serving to press the material to be sewn against surface 27. The tenter 40 is provided with a slot 41 to permit the passage of the needle 10 and of a buttonhole gauge. Pressure piece 39 carries a rail 42, as particularly seen in FIG. 4, which extends in the advance direction of the clamping arm. A pressure roller 43 mounted for free rotation in a a carrier 44 is adapted to ride on rail 42. Carrier 44 is rigidly connected to rod 45 which is slidably received in guide hole 47 of lug 46 provided on bracket 2. Spring 48 is mounted between the lug 46 and carrier 44 urging the pressure roller 43 permanently downwards, the traveling distance of the carrier 44 being limited by a pin 50 projecting from sliding rod 45 and guided in an oblong slot 49 of lug 46. Carrier 44 is further provided with a claw 51 engaging the pressure piece or the rail from beneath and with an angle stop for engaging bracket 2.

The cutting mechanism or the thread comprises a swinging member 54 (see FIGS. 4, 5 and 6), pivoted on a pin 53 which is provided on the tenter 40. The free end of the swing member 54 is formed with a cutting blade 55. Counterblade 56 cooperating therewith is a piece which is pivotally mounted on a pin 57 provided on swinging member 54 and which is formed with two toes 58, 59 cooperating with a stop piece 60 secured to tenter 40, in a manner described hereinafter. To improve the cutting reliability, a flat spring 62 applying against the counterblade 56 is secured to a pin 61 provided on the swinging member 54.

The cutting tool comprising the blades 55, 56 is actuated by means of a connection lever 63 whose other end is hinged to crank 64 (FIGS. 1 to 3) which is pivotally mounted on pin 65 provided on the clamping arm 38 and retained in its initial position by worm spring 66. Crank 64, connection lever 63, swinging member 54 and the two pins 53 and 65 form a four-bar linkage. As may be seen in FIGS. 1 to 3, crank 64 is formed with a nose 67, and serves simultaneously as a pawl for ratchet lever 68 which is pivotally mounted on pin 69 provided on bridge 70. Ratchet lever 68 is held in the position shown in FIG. 1 by means of a worm spring 71 and is formed with an arm 72 adapted to apply against stop pin 73 which is provided on bridge 70 for limiting the pivotal motion of ratchet lever 68. Bridge 70, which has an angular cross-section, is mounted tiltable about pin 74 provided on bracket 2, and can be adjusted in a desired position by means of two set screws 75, 75 which are received in support 76 secured to bracket 2 and apply against the upper surface of bridge 70, the position of the latter being given by the length of engagement of the screws.

The sewing machine operates as follows:

During the sewing operation, the bracket 2 is fixed in its working position (FIG. 1); the sewn material is placed between the surface 27 and the tenter 40 of clamping arm 38. By the action of spring 25 provided in substructure 1, support 21, and thereby surface plate 27 of plate 28, is pressed against tenter 40. Angle stop 52, provided on carrier 44, applies against the bottom surface of bracket 2; and spring 48, having a flatter characteristic than spring 25, is compressed. At the end of the sewing operation, the machine is stopped in the lowermost position of needle 10 and the electromagnet 4 is energized.

The needle thread extends between the bottom side of the sewn material and the needle and the shuttle thread extends between the upper side of the sewn material and the shuttle or the shuttle bobbin.

As soon as bracket 2 begins to execute its motion about pivot 3, from the working into the rest position, spring 25 expands first. Therefore, the angle stop 52 remains applied against the bottom side of bracket 2 and support 21 along with the surface 27 as well as the clamping arm 38 mounted thereon execute a pivotal movement about the pivot 22. During this motion, the relative position of the sewn material and the shuttle 12 and of the clamping arm 38 and shuttle 12 is not changed. Once the support 21 has reached its end position, as determined by stop 26, bracket 2 begins to move away from the surface 27 while continuing its pivotal movement about pivot 3. At this moment, spring 48 begins to expand and the sliding rod 45 is shifted in lug 46 of bracket 2 relative to the latter. Since the pressure roller 43 applies against rail 42, the sewn material is still clamped during this relative motion and, because shuttle 12 is moved away from the material, a length of thread corresponding to the increased distance is drawn off the shuttle bobbin (FIG. 2). Meanwhile, the ratchet lever 68 engages from beneath the nose 67 of crank 64 and imparts to the latter a pivotal motion about pin 65 and against the action of worm spring 66. This pivotal motion is transmitted by connection lever 63 to swinging member 54 which, consequently, swivels about pin 53 (FIGS. 5 and 6) and brings cutting blade 55, formed at its extremity, into the cutting position. During the further relative motion between bracket 2 and clamping arm 38, swinging member 54 continues to turn about pin 53. Toe 58 of counterblade 56 comes then to apply against the stop piece 60 and executes a pivotal movement relative to swinging member 54, about the pin 57 fixed to the latter. Thereby, cutting blade 55 and counterblade 56 move against each other and cut the thread extending between the sewn material and the shuttle bobbin close above the upper surface of the material (FIG. 6). This cutting operation takes place at the end of the relative movement of bracket 2 and clamping arm 38 so that the thread portion remaining, attached to the shuttle after the cutting, is sufficiently long to permit the formation of the initial stitches in the next sewing cycle. Also, because clamping arm 38 is still resting upon the sewn material, favorable conditions for the cutting operation are ensured.

During the following continuing pivotal movement of bracket 2, the clamping arm 38 is taken along upwards by claw 51 engaging from beneath rail 42; thus, the arm 38 turns about pivot 37. Thereby, ratchet lever 68 and pawl 67 are disengaged, and arm 72 of lever 68 abuts against pin 73 (FIG. 3). As soon as crank 64 and lever 68 are disengaged, the worm spring 66 is released and returns the four-bar linkage formed by crank 64, the connection lever 63 and swinging member 54 into the initial position. Toe 59 of counterblade 56 applies against stop piece 60 fixed to tenter 40 so that counterblade 56 is pivoted about pin 57 in the counterclockwise direction and swing member 54, under the action of worm spring 66, is pivoted about pin 53 and returns into its initial position.

To bring the bracket 2 from its rest position back into its working position, the electromagnet is energized again. Bracket 2 takes clamping arm 38 along in the downward direction until tenter 40 comes to rest upon the sewn material. Since the characteristic of spring 48 is flatter than that of spring 25, during the continuing downward movement of bracket 2, spring 48 is compressed first and angle stop 52 applies against the bottom surface of bracket 2. Pressure roller 43, resting upon rail 42, presses tenter 40 against surface 27 of plate 28, and support 21 is thereby urged to pivot about 22 and overcome the force of spring 25. The downward movement of bracket 2 continues until it reaches and is fixed in its working position predetermined by a stop.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.