SERVO-DRIVE POSITIONING DEVICE
United States Patent 3828893
A linkage connects an off-center point of a motordriven assembly to a pivot point on a reference or frame member and is used for holding a movable member in a fixed position relative to the reference member. The linkage includes a double-locking clutch with two sets of springloaded washers carried on a shaft in canted manner, and a pair of opposed plungers positioned between the sets of washers to maintain position of the washers on the shaft. A small force applied to a trigger sleeve, which encloses the clutch, unlocks one set of the washers to release a locking sleeve to move in the direction of the applied force and thereby adjust the position of the locking sleeve in relation to the reference member, and when the force is removed, the locking sleeve is locked on the shaft in a self-centering position.
US Patent References:
Cable tension regulator
Cade - November 1944 - 2363229
Position-adjusting mechanism
Cushman - December 1951 - 2579305
Portable drill press
Hart - February 1953 - 2629267
One-directional clutch
Owen - November 1964 - 3156963
Manipulator motion lock
Haaker - October 1966 - 3277980
Cable tension regulator
Cade - November 1944 - 2363229
Position-adjusting mechanism
Cushman - December 1951 - 2579305
Portable drill press
Hart - February 1953 - 2629267
One-directional clutch
Owen - November 1964 - 3156963
Manipulator motion lock
Haaker - October 1966 - 3277980
Application Number:
05/308652
Publication Date:
08/13/1974
Filing Date:
11/22/1972
View Patent Images:
Export Citation:
Assignee:
The National Cash Register Company (Dayton, OH)
Primary Class:
Other Classes:
74/531, 248/354.100
International Classes:
B41J15/02; B65H59/10
Field of Search:
188/67 248/355 74/531 254/105,106 403/104
Primary Examiner:
Halvosa, George E. A.
Attorney, Agent or Firm:
Cavender Jr., Hawk Wilbert Muckenthaler George J. T. J.
Claims:
What is claimed is
1. A positioning device comprising a shaft and journal means therefor, said shaft being connected to a reference member, locking means including a sleeve slidable on the shaft and a
2. The device of claim 1 wherein said lost-motion connection includes elongated apertures in said actuating sleeve for permitting said opposing resilient means to move said actuating sleeve to its centered position.
3. A positioning device for a servo-assembly, said device comprising a
4. The device of claim 3 wherein said lost-motion connection includes elongated apertures in said actuating sleeve for permitting said plungers to move said actuating sleeve to its centered position.
5. Means for adjusting and retaining position of a servo-assembly in relation to a reference member on a business machine, said means comprising a shaft pivotally connected to said reference member,
6. The subject matter of claim 5 wherein said lost-motion connection includes elongated apertures in said actuating sleeve permitting said pair of spring loaded plungers to move said trigger sleeve to its centered position.
1. A positioning device comprising a shaft and journal means therefor, said shaft being connected to a reference member, locking means including a sleeve slidable on the shaft and a
2. The device of claim 1 wherein said lost-motion connection includes elongated apertures in said actuating sleeve for permitting said opposing resilient means to move said actuating sleeve to its centered position.
3. A positioning device for a servo-assembly, said device comprising a
4. The device of claim 3 wherein said lost-motion connection includes elongated apertures in said actuating sleeve for permitting said plungers to move said actuating sleeve to its centered position.
5. Means for adjusting and retaining position of a servo-assembly in relation to a reference member on a business machine, said means comprising a shaft pivotally connected to said reference member,
6. The subject matter of claim 5 wherein said lost-motion connection includes elongated apertures in said actuating sleeve permitting said pair of spring loaded plungers to move said trigger sleeve to its centered position.
Description:
BACKGROUND OF THE INVENTION
In the matter of positioning and retaining the position of mechanical devices, which are subject to forces not contemplated within a system, there have been ways and means for controlling the position of one member relative to another member. In this respect, the use of springs, plungers, and like devices have been used for maintaining various elements in adjustment where such devices can be used in an assembly. The spring loading feature and associated structure, as well as hydraulic or dash-pot devices, may also be utilized in similar circumstances to control or to adjust one element in relation to another. Normally, such structure takes on the concept of providing means for maintaining position of a movable member relative to a fixed member, while permitting adjustment of the movable member under certain conditions.
Closer to the present invention is the concept of a rod carrying a slidable member abutting a cylinder wherein the slidable member assumes a canted position to retain the cylinder along the rod, such as is commonly used in door closers.
SUMMARY OF THE INVENTION
The present invention relates to positioning devices and more particularly to a linkage mechanism connected to a reference member and to an assembly for adjusting certain parts of the assembly in relation to the reference member. The linkage mechanism incorporates a double-locking clutch with two sets of spring-loaded washers carried on a shaft in canted manner and a pair of opposed plungers positioned between the sets of washers to maintain position thereof. A slidable locking sleeve encircles the washers and a portion of the shaft, and the washers, when in the canted position, prevent relative motion between the locking sleeve and the shaft, except when it is desired to make an adjustment.
A small force is applied in one direction to a trigger or actuating sleeve and thereby releases one set of the locking washers from the shaft to permit movement of the locking sleeve along the shaft to a new position. The locking sleeve follows the motion of the trigger sleeve in the direction of the applied force and when once the force is stopped, the locking sleeve will be locked on the shaft with the trigger sleeve recentering itself in relation to the locking sleeve. The construction of the present invention and the action obtained therefrom permit a self-centering of the trigger sleeve when the new adjustment position is reached.
In line with the above discussion, the principal object of the present invention is to provide a positioning device which performs fine-tuning adjustment.
Another object of the present invention is to provide a linkage mechanism for connecting a servo assembly to a reference member for remote control of adjustment.
An additional object of the present invention is to provide a positioning device for adjusting printing mechanism along a print line.
A further object of the present invention is to provide spring loaded plungers and sets of washers for locking of a cylinder along a shaft.
Another object of the present invention is to provide resilient means between the several members for recentering of the actuating member after adjustment of the positioning device.
Additional features and advantages will become apparent from a reading of the following specification taken together with the annexed drawings, in which:
FIG. 1 is a side elevational view of a portion of servo mechanism incorporating the subject matter of the present invention;
FIG. 2 is a sectional view taken on the line 2--2 of FIG. 1;
FIG. 3 is an enlarged sectional view of a portion of FIG. 2;
FIG. 4 is an end view of the positioning device;
FIG. 5 is a sectional view taken on the line 5--5 of FIG. 4;
FIG. 6 is a sectional view taken on the line 6--6 of FIG. 4;
FIG. 7 is a sectional view taken on the line 7--7 of FIG. 4;
FIG. 8 is a sectional view similar to FIG. 6 and showing a slightly different position of the parts thereof; and
FIG. 9 is an enlarged view taken on the line 9--9 of FIG. 3.
Referring now to FIGS. 1 and 2 of the drawings, there is shown certain structure including a motor shaft for a servo assembly which assembly has one application for positioning and controlling the position of printing mechanism when printing on form paper or the like. As is well known, continuous form paper is used in high speed printing apparatus, the form paper being driven by tractor mechanism past a print station wherein character or other indicia printing may be accomplished in line manner. As is also well know, it is extremely important that the printing position on the paper be controlled to the extent that, because of pre-printed lines on the paper, the printed characters or other indicia are maintained evenly spaced and in a straight format across the paper. Additionally, after certain periods of operation, there may be a tendency for the paper to inch ahead or fall behind during the travel thereof in relation to the printing mechanism. This becomes even more important when the paper includes such pre-printed lines thereon and it is desired to print in precise manner between the lines. Of course, should the paper have the tendency to become slightly displaced in relation to the printing mechanism, there must be provided means for adjusting the line of print so as to maintain an exact format of line printing.
The present invention is considered important as a part of a drive assembly which performs a stepping operation by driving the paper a line at a time. In this respect a servo mechanism drives the paper forward in stepping manner so that the paper is successively positioned for printing on each succeeding line.
The present invention is directed to means for re-positioning or adjusting the drive mechanism in those instances when the drive line veers from a correct position and such drive mechanism includes a motor shaft 10 driven by a servo motor 12 supported from machine framework in the nature of a flange, the major portion of surrounding framework being omitted from the drawing for reason of clarity. Shaft 10 is carried in bearings located inside the motor in conventional manner, and the shaft carries a pivotable casting 40 upon bearings 16 and 18, and within such casting carries a gear cluster 20 for meshing with a second gear cluster 22 on a shaft 24 parallel to shaft 10, the shaft 24 being supported in suitable bearings in the casting 40. In other words, the casting 40 is solely supported from the shaft 10, which extends from and is supported from the motor 12, which, in turn, is flange mounted to the machine frame. The purpose of the gear clusters 20 and 22 is to provide for the printing of either 6 lines or 8 lines per inch, with the gears shown in the 6 lines per inch position. One end of a bowden wire 26 is for the purpose of changing the line spacing from 6 to 8 lines. Gear cluster 22 has connected thereto an optical disk 28 used in the control system, which is not a part of the present invention.
The shaft-supported casting 40 furthermore has legs 42 and 44 (FIG. 2) extending downwardly and connected to a positioning device 50 carried on a rod or shaft 52 pivotally supported at one end thereof to a clutch anchor pivot 54 connected to a framework 56 so as to provide a reference member for the device 50. The device 50 is constructed to be slidable along the rod 52 in relation to the reference member 56 in operation of which will be further described. Sliding movement of the device 50 along the rod 52 is accomplished by means of a link or arm 58 connected to the device 50 and extending to a control lever (not shown).
In FIG. 3 is shown an enlarged sectional view of the positioning device 50 with the rod or shaft 52 in the center thereof, and the legs 42 and 44 connected to the device by means of studs or shoulder screws 60 and 62 threaded into the body of the device midway between the ends thereof. It is thus seen that the location of device 50 on shaft 52 determines the angular position of casting 40 about its support shaft 10, within desired adjustment limits. FIG. 4 shows an end view of the positioning device with certain parts similar as FIG. 3. The link 58 connects to a shoulder 70 on the device 50 and the other end connects to the manually positionable control lever, not shown. A washer 71 is disposed between the leg 42 and the exterior surface of the device 50.
Referring now to FIG. 5, the positioning device 50 is carried by the shaft 52 and includes a locking sleeve 72 adjacent the shaft, the sleeve assuming the shape of a "T" in cross-section thereof and providing a recess 74 in the vicinity of each end for reception of a set of washers 76 and a set 78. The two sets of washers are positioned on the rod 52 in such manner as to be capable of being slightly canted thereon for purposes to be described. The support for the shaft 52 in the device 50 is derived from a pair of hubs 80 and 82 over the ends of which are cover plates 84 and 86, respectively, the plates being retained in position by means of coil springs 90 attached to the cover plate at each end of a cylinder 92 and stretched along the periphery thereof. The cylinder 92, which generally comprises a sleeve, encloses the parts in compact manner with screws 94 securing the shaft support hubs 80 and 82 with the locking sleeve 72. Additionally, a pair of adjusting screws 98 and 100 (FIG. 6) are threaded into the respective cover plates 84 and 86 and through respective openings 101 and 102 in the hubs 80 and 82 to position the ends of the screws adjacent the sets of washers 76 and 78. A nut 103 is carried by the screw 98 to be disposed against the cover plate 84 and a similar nut 104 is on screw 100 and against plate 86 to provide for the adjusting action of the ends of the screws in relation to the sets of washers.
The two sets of washers 76 and 78 are position controlled along the shaft 52 by means of four spring-loaded locking plungers 110, (FIGS. 6 and 8) a pair of which are axially aligned and diametrically opposite from a second pair, also axially aligned, and engaging the sets of washers on one side thereof in opposing manner by a pair of springs 109. A pair of stop pins 111 and 112 are secured in the support hubs 80 and 82 in position directly opposite the adjusting screws 98 and 100.
An additional feature of the present invention provides for self-centering of the trigger sleeve 92 in relation to the locking sleeve 72 after the adjusting action is completed. This is accomplished by means of a pair of centering plungers 115 and 116 loaded by a spring 117 and having stems 118 and 119 engageable with the cover plates 84 and 86, respectively (see FIGS. 6 and 8). This structure, in effect, provides a self-centering concept in the design to bring the trigger sleeve 92 to a new home position in relation to the locking sleeve 72. This is an important feature in that it maintains, while the device is in a holding condition, a finite gap between screw 100 and washers 78 and between screw 98 and washers 76 so that minute machine vibrations will not cause gradual loss of position due to "creep" (see FIG. 6). As seen in FIG. 9, the trigger sleeve 92 includes an elongated slot 125 through which extends the shank 126 of stud or screw 60. A similar slot 127 on the opposite side of the sleeve 92 from the slot 125 accommodates the shank 128 of stud 62 (FIG. 7) so as to permit clearance for the self-centering featured parts. The screws 126 and 128 fit tightly in the locking sleeve 72 but freely pivot in the casting bosses 42, 44, as shown.
In the operation of the device, wherein a typical application is in a line printer wherein it is desired to maintain registration of the line of print hammers with the pre-printed lines on continuous form paper or the like, the normal stepping action of the paper advancing mechanism can be position adjusted at any point in time. Once the paper has started through the printer, it is extremely difficult to advance or retard the continuous form, so it is necessary to pivot the movable assembly in relation to the machine frame. Since, as mentioned above, the servo-drive assembly is supported by bearings 16 and 18 on the motor shaft 10 or an extension thereof, te assembly must be restrained against rotation during advancement of and stopping of the motor because of the torque and counter torque action. Additionally, the motor is prevented from a reversing or backing action against a one-way clutch (not shown) to maintain position of the drive mechanism. In the present instance, it may be necessary to pivot the servo-drive assembly up to 22° in either direction by means of the remote control handle, in order to adjust the line of character or other indicia printing to register with the pre-printed lines on the paper. The positioning device 50 is intended to hold the movable servo-assembly at a fixed position in relation to the machine frame, and therefore the relative paper stopping point, and to resist any forces tending toward relative motion of the movable assembly; however, when so desired, the assembly may be moved to a new "fixed" position and thereheld in the new position against all forces tending to act thereon.
The device acts as a link connecting the off-center point on the movable assembly to the pivot point on the machine frame, and therefore the locking sleeve 72 must not slide on the shaft 52. It must resist forces tending to make the link longer or shorter, except when an adjustment is required. When a small force is applied to the trigger sleeve 92, a slight relative lost motion occurs between the trigger sleeve 92 and the locking sleeve 72, by reason of the elongated slots 125 and 127 in the trigger sleeve, which motion permits the locking sleeve 72 to be unlocked and to move freely along the shaft 52. This establishes a new length for the link and a new annular position for the movable assembly. When the small force is removed from the link by stopping movement of the control handle, the locking sleeve is bi-directionally locked in the new position.
The principle is based upon the sets of wasers being canted on the shaft and retained in position by the spring loaded plungers, the stop pins and the adjusting screws. In FIG. 6 is shown the locked position of the device with the sets of washers 76 and 78 being held in the canted position on the shaft 52. A small force on the arm or link 58, say to the right in FIG. 6, acts on the hub 70 to move the locking sleeve 72 to the right. This movement straightens the washers 78 on the shaft and permits such washers to be moved therealong, while at the same time the movement of the locking sleeve 72, along with the action of the plungers 110, straightens the washers 76 by reason of the frictional effect of the washers 76 against the shaft 52. When the new position is reached, the control handle is released and the locking sleeve 72 is again locked on the shaft 52 and the washers 76, 78 are urged to the canted position. The self-centering plungers 115, 116 then return the trigger sleeve 92 to the new home position so that no forces can prevail against the locking sleeve 72 until the next adjustment is made.
It is therefore seen that herein shown and described is a positioning device which utilizes canted washers on a shaft, and is controlled by spring-loaded plungers to effect adjustment of position of the locking sleeve along the shaft. The trigger sleeve centers itself in the new position so that the locking sleeve is not affected by forces derived from operation of the drive means for the stepping action, and so that vibrations of the trigger sleeve related linkage are not communicated to the locking washers. The apparatus enables the accomplishment of the objects and advantages mentioned above, and while only one embodiment of the invention has been disclosed herein, certain variations may occur to those skilled in the art. It is contemplated that all such variations, not departing from the spirit and scope of the invention, are to be construed in accordance with the following claims.
In the matter of positioning and retaining the position of mechanical devices, which are subject to forces not contemplated within a system, there have been ways and means for controlling the position of one member relative to another member. In this respect, the use of springs, plungers, and like devices have been used for maintaining various elements in adjustment where such devices can be used in an assembly. The spring loading feature and associated structure, as well as hydraulic or dash-pot devices, may also be utilized in similar circumstances to control or to adjust one element in relation to another. Normally, such structure takes on the concept of providing means for maintaining position of a movable member relative to a fixed member, while permitting adjustment of the movable member under certain conditions.
Closer to the present invention is the concept of a rod carrying a slidable member abutting a cylinder wherein the slidable member assumes a canted position to retain the cylinder along the rod, such as is commonly used in door closers.
SUMMARY OF THE INVENTION
The present invention relates to positioning devices and more particularly to a linkage mechanism connected to a reference member and to an assembly for adjusting certain parts of the assembly in relation to the reference member. The linkage mechanism incorporates a double-locking clutch with two sets of spring-loaded washers carried on a shaft in canted manner and a pair of opposed plungers positioned between the sets of washers to maintain position thereof. A slidable locking sleeve encircles the washers and a portion of the shaft, and the washers, when in the canted position, prevent relative motion between the locking sleeve and the shaft, except when it is desired to make an adjustment.
A small force is applied in one direction to a trigger or actuating sleeve and thereby releases one set of the locking washers from the shaft to permit movement of the locking sleeve along the shaft to a new position. The locking sleeve follows the motion of the trigger sleeve in the direction of the applied force and when once the force is stopped, the locking sleeve will be locked on the shaft with the trigger sleeve recentering itself in relation to the locking sleeve. The construction of the present invention and the action obtained therefrom permit a self-centering of the trigger sleeve when the new adjustment position is reached.
In line with the above discussion, the principal object of the present invention is to provide a positioning device which performs fine-tuning adjustment.
Another object of the present invention is to provide a linkage mechanism for connecting a servo assembly to a reference member for remote control of adjustment.
An additional object of the present invention is to provide a positioning device for adjusting printing mechanism along a print line.
A further object of the present invention is to provide spring loaded plungers and sets of washers for locking of a cylinder along a shaft.
Another object of the present invention is to provide resilient means between the several members for recentering of the actuating member after adjustment of the positioning device.
Additional features and advantages will become apparent from a reading of the following specification taken together with the annexed drawings, in which:
FIG. 1 is a side elevational view of a portion of servo mechanism incorporating the subject matter of the present invention;
FIG. 2 is a sectional view taken on the line 2--2 of FIG. 1;
FIG. 3 is an enlarged sectional view of a portion of FIG. 2;
FIG. 4 is an end view of the positioning device;
FIG. 5 is a sectional view taken on the line 5--5 of FIG. 4;
FIG. 6 is a sectional view taken on the line 6--6 of FIG. 4;
FIG. 7 is a sectional view taken on the line 7--7 of FIG. 4;
FIG. 8 is a sectional view similar to FIG. 6 and showing a slightly different position of the parts thereof; and
FIG. 9 is an enlarged view taken on the line 9--9 of FIG. 3.
Referring now to FIGS. 1 and 2 of the drawings, there is shown certain structure including a motor shaft for a servo assembly which assembly has one application for positioning and controlling the position of printing mechanism when printing on form paper or the like. As is well known, continuous form paper is used in high speed printing apparatus, the form paper being driven by tractor mechanism past a print station wherein character or other indicia printing may be accomplished in line manner. As is also well know, it is extremely important that the printing position on the paper be controlled to the extent that, because of pre-printed lines on the paper, the printed characters or other indicia are maintained evenly spaced and in a straight format across the paper. Additionally, after certain periods of operation, there may be a tendency for the paper to inch ahead or fall behind during the travel thereof in relation to the printing mechanism. This becomes even more important when the paper includes such pre-printed lines thereon and it is desired to print in precise manner between the lines. Of course, should the paper have the tendency to become slightly displaced in relation to the printing mechanism, there must be provided means for adjusting the line of print so as to maintain an exact format of line printing.
The present invention is considered important as a part of a drive assembly which performs a stepping operation by driving the paper a line at a time. In this respect a servo mechanism drives the paper forward in stepping manner so that the paper is successively positioned for printing on each succeeding line.
The present invention is directed to means for re-positioning or adjusting the drive mechanism in those instances when the drive line veers from a correct position and such drive mechanism includes a motor shaft 10 driven by a servo motor 12 supported from machine framework in the nature of a flange, the major portion of surrounding framework being omitted from the drawing for reason of clarity. Shaft 10 is carried in bearings located inside the motor in conventional manner, and the shaft carries a pivotable casting 40 upon bearings 16 and 18, and within such casting carries a gear cluster 20 for meshing with a second gear cluster 22 on a shaft 24 parallel to shaft 10, the shaft 24 being supported in suitable bearings in the casting 40. In other words, the casting 40 is solely supported from the shaft 10, which extends from and is supported from the motor 12, which, in turn, is flange mounted to the machine frame. The purpose of the gear clusters 20 and 22 is to provide for the printing of either 6 lines or 8 lines per inch, with the gears shown in the 6 lines per inch position. One end of a bowden wire 26 is for the purpose of changing the line spacing from 6 to 8 lines. Gear cluster 22 has connected thereto an optical disk 28 used in the control system, which is not a part of the present invention.
The shaft-supported casting 40 furthermore has legs 42 and 44 (FIG. 2) extending downwardly and connected to a positioning device 50 carried on a rod or shaft 52 pivotally supported at one end thereof to a clutch anchor pivot 54 connected to a framework 56 so as to provide a reference member for the device 50. The device 50 is constructed to be slidable along the rod 52 in relation to the reference member 56 in operation of which will be further described. Sliding movement of the device 50 along the rod 52 is accomplished by means of a link or arm 58 connected to the device 50 and extending to a control lever (not shown).
In FIG. 3 is shown an enlarged sectional view of the positioning device 50 with the rod or shaft 52 in the center thereof, and the legs 42 and 44 connected to the device by means of studs or shoulder screws 60 and 62 threaded into the body of the device midway between the ends thereof. It is thus seen that the location of device 50 on shaft 52 determines the angular position of casting 40 about its support shaft 10, within desired adjustment limits. FIG. 4 shows an end view of the positioning device with certain parts similar as FIG. 3. The link 58 connects to a shoulder 70 on the device 50 and the other end connects to the manually positionable control lever, not shown. A washer 71 is disposed between the leg 42 and the exterior surface of the device 50.
Referring now to FIG. 5, the positioning device 50 is carried by the shaft 52 and includes a locking sleeve 72 adjacent the shaft, the sleeve assuming the shape of a "T" in cross-section thereof and providing a recess 74 in the vicinity of each end for reception of a set of washers 76 and a set 78. The two sets of washers are positioned on the rod 52 in such manner as to be capable of being slightly canted thereon for purposes to be described. The support for the shaft 52 in the device 50 is derived from a pair of hubs 80 and 82 over the ends of which are cover plates 84 and 86, respectively, the plates being retained in position by means of coil springs 90 attached to the cover plate at each end of a cylinder 92 and stretched along the periphery thereof. The cylinder 92, which generally comprises a sleeve, encloses the parts in compact manner with screws 94 securing the shaft support hubs 80 and 82 with the locking sleeve 72. Additionally, a pair of adjusting screws 98 and 100 (FIG. 6) are threaded into the respective cover plates 84 and 86 and through respective openings 101 and 102 in the hubs 80 and 82 to position the ends of the screws adjacent the sets of washers 76 and 78. A nut 103 is carried by the screw 98 to be disposed against the cover plate 84 and a similar nut 104 is on screw 100 and against plate 86 to provide for the adjusting action of the ends of the screws in relation to the sets of washers.
The two sets of washers 76 and 78 are position controlled along the shaft 52 by means of four spring-loaded locking plungers 110, (FIGS. 6 and 8) a pair of which are axially aligned and diametrically opposite from a second pair, also axially aligned, and engaging the sets of washers on one side thereof in opposing manner by a pair of springs 109. A pair of stop pins 111 and 112 are secured in the support hubs 80 and 82 in position directly opposite the adjusting screws 98 and 100.
An additional feature of the present invention provides for self-centering of the trigger sleeve 92 in relation to the locking sleeve 72 after the adjusting action is completed. This is accomplished by means of a pair of centering plungers 115 and 116 loaded by a spring 117 and having stems 118 and 119 engageable with the cover plates 84 and 86, respectively (see FIGS. 6 and 8). This structure, in effect, provides a self-centering concept in the design to bring the trigger sleeve 92 to a new home position in relation to the locking sleeve 72. This is an important feature in that it maintains, while the device is in a holding condition, a finite gap between screw 100 and washers 78 and between screw 98 and washers 76 so that minute machine vibrations will not cause gradual loss of position due to "creep" (see FIG. 6). As seen in FIG. 9, the trigger sleeve 92 includes an elongated slot 125 through which extends the shank 126 of stud or screw 60. A similar slot 127 on the opposite side of the sleeve 92 from the slot 125 accommodates the shank 128 of stud 62 (FIG. 7) so as to permit clearance for the self-centering featured parts. The screws 126 and 128 fit tightly in the locking sleeve 72 but freely pivot in the casting bosses 42, 44, as shown.
In the operation of the device, wherein a typical application is in a line printer wherein it is desired to maintain registration of the line of print hammers with the pre-printed lines on continuous form paper or the like, the normal stepping action of the paper advancing mechanism can be position adjusted at any point in time. Once the paper has started through the printer, it is extremely difficult to advance or retard the continuous form, so it is necessary to pivot the movable assembly in relation to the machine frame. Since, as mentioned above, the servo-drive assembly is supported by bearings 16 and 18 on the motor shaft 10 or an extension thereof, te assembly must be restrained against rotation during advancement of and stopping of the motor because of the torque and counter torque action. Additionally, the motor is prevented from a reversing or backing action against a one-way clutch (not shown) to maintain position of the drive mechanism. In the present instance, it may be necessary to pivot the servo-drive assembly up to 22° in either direction by means of the remote control handle, in order to adjust the line of character or other indicia printing to register with the pre-printed lines on the paper. The positioning device 50 is intended to hold the movable servo-assembly at a fixed position in relation to the machine frame, and therefore the relative paper stopping point, and to resist any forces tending toward relative motion of the movable assembly; however, when so desired, the assembly may be moved to a new "fixed" position and thereheld in the new position against all forces tending to act thereon.
The device acts as a link connecting the off-center point on the movable assembly to the pivot point on the machine frame, and therefore the locking sleeve 72 must not slide on the shaft 52. It must resist forces tending to make the link longer or shorter, except when an adjustment is required. When a small force is applied to the trigger sleeve 92, a slight relative lost motion occurs between the trigger sleeve 92 and the locking sleeve 72, by reason of the elongated slots 125 and 127 in the trigger sleeve, which motion permits the locking sleeve 72 to be unlocked and to move freely along the shaft 52. This establishes a new length for the link and a new annular position for the movable assembly. When the small force is removed from the link by stopping movement of the control handle, the locking sleeve is bi-directionally locked in the new position.
The principle is based upon the sets of wasers being canted on the shaft and retained in position by the spring loaded plungers, the stop pins and the adjusting screws. In FIG. 6 is shown the locked position of the device with the sets of washers 76 and 78 being held in the canted position on the shaft 52. A small force on the arm or link 58, say to the right in FIG. 6, acts on the hub 70 to move the locking sleeve 72 to the right. This movement straightens the washers 78 on the shaft and permits such washers to be moved therealong, while at the same time the movement of the locking sleeve 72, along with the action of the plungers 110, straightens the washers 76 by reason of the frictional effect of the washers 76 against the shaft 52. When the new position is reached, the control handle is released and the locking sleeve 72 is again locked on the shaft 52 and the washers 76, 78 are urged to the canted position. The self-centering plungers 115, 116 then return the trigger sleeve 92 to the new home position so that no forces can prevail against the locking sleeve 72 until the next adjustment is made.
It is therefore seen that herein shown and described is a positioning device which utilizes canted washers on a shaft, and is controlled by spring-loaded plungers to effect adjustment of position of the locking sleeve along the shaft. The trigger sleeve centers itself in the new position so that the locking sleeve is not affected by forces derived from operation of the drive means for the stepping action, and so that vibrations of the trigger sleeve related linkage are not communicated to the locking washers. The apparatus enables the accomplishment of the objects and advantages mentioned above, and while only one embodiment of the invention has been disclosed herein, certain variations may occur to those skilled in the art. It is contemplated that all such variations, not departing from the spirit and scope of the invention, are to be construed in accordance with the following claims.