US3051110A - Power control unit for sewing machines - Google Patents

Description

Aug. 28, 1962 R. P. GRAHAM ETAL 3,051,110

POWER CONTROL UNIT FOR SEWING MACHINES Filed March 10, 1959 4 Sheets-Sheet 1 INVENTORS. Richard P. Graham, William L.Herran and Stanley J. KeiIerer.

Big 6 7 ATTORNEY WITNESS Aug. 28, 1962 R. P. GRAHAM EI'AL 3,051,110

POWER CONTROL UNIT FOR SEWING MACHINES Filed March 10, 1959 4 Sheets-Sheet 2 Aug. 28, 1962 R. P. GRAHAM ETAL 3,051,110

POWER CONTROL UNIT FOR SEWING MACHINES 4 Sheets-Sheet :5

Filed March 10, 1959 VHTNESS INVENTORS.

Richard P. Graham, William L. Herron and Stanley J. Keflerer.

Fig. 5. wa 44 BY 2 1 H 6 ATTORNEY Aug. 28, 1962 R. P. GRAHAM ETAL ,1

POWER CONTROL UNIT FOR SEWING MACHINES Filed March 10, 1959 4 Sheets-Sheet 4 INVENTORS. Richard P. Graham, William L. Herron and Stanley J. Keflerer.

ATTOMY ilnzited ra es hatent POWER CGNTRGL UNlT FER SEWIN G MAQIMQES Richard P. Graham, Stratfoid, Wiiiiam L. Herron,

Bridgeport, and Stanley J. Ketterer, Stratford, Conn,

assignors to The Singer Manufacturing Company, Elizabeth, Ni, a corporation of New Jersey Filed Mar. 10, 1959, Ser. No. 798,491 13 Claims. ((1 112-239) This invention relates to sewing machines and, more particularly, .to a power operated device for assisting a sewing machine operator in the manipulation of the sewing machine or any of the various mechanism appurtenant to a sewing machine. The device of this invention may thus be utilized to control the operation of the sewing machine, to open a work clamp, to raise a presser foot, or to operate a thread or work cutting device and the like. I

It is an object of this invention to provide a simple and efficient power assisting device for a sewing machine operator which is dependable and foolproof in operation.

Another object of this invention is to provide a power assisting device for a sewing machine operator capable of controlling not only the operative motion of a sewing machine appurtenance, but also the returnmotion thereof.

Still another object of this invention is to provide a power control unit adapted for use with a wide variety of different types of sewing machines without alteration of the sewing machine.

With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

sewing machine and may be operatively connected in any known manner to effect opening and closing of the work clamp. Also fulcrumed on the sewingmachine is a starting lever 22, rocking of which serves to initiate a cycle of stitch forming operations of the sewing machine. The levers 21 and'ZZ in FIG. 1 have been illustrated in positions turned bodily at right angles to the positions actually occupied in the sewing machine of the referenced United States Patent No. 2,822,771, in order to clarify the understanding of this invention.

It will be understood that, as is commonly known in the art, the starting lever 22 when rocked to start the machine will be constrained in the running position by a latch means (not shown) which is released automatically PEG. 1 represents an elevational view of the power control unit of this invention as applied beneath the supporting table of a sewing machine, I

FIG. 2 represents a bottom plan View of the power control unit installation of FIG. 1,

FIG. 3 is an enlarged cross-sectional View of one form of the power control unit taken substantially along line 33 of FIG. 2,

FIG. 4 is across-sectional view taken substantially along line 44 of FlG. 3,

FIG. 5 is a bottom plan view of a portion of the power control unit of FIG. 3,

FIG. 6 is an enlarged elevational view of the throw out device illustrated in the position holding the power control mechanism out of operation,

FIG. 7 represents a bottom plan view of a portion of the power control unit illustrating a modified form thereof,

PEG. 8 is a cross-sectional View taken substantially along ine 33 of FIG. 7, and 7 FIGS. 9 and 10 are enlarged cross-sectional views taken substantially along line 9-9 of FIG. 7 illustrating the control member of the power control unit in opposite extreme positions. 7

In the drawings, the power control device of this invention is illustrated as applied to .a sewing machine supporting table 2i and arranged to open and close the work clamp of a cyclically operated sewing machine. The sewing machine may be of any known variety, as for instance, that disclosed in the United States patent of Hale et al., No. 2,822,771, February 11, 1958, to which reference may be had for description of its operation.

The sewing machine work clamp (not illustrated) is preferably of the type which is biased toward its closed position as is well known in the art. As illustrated in FIG. 1, a clamp opening lever 21 is fulcrumed on the after a predetermined number of stitches have been formed.

Secured beneath the supporting table is a cradle 23 adapted to accommodate a sewing machine and formed with a drip pan 24 underlying the sewing machine. lournaled in bearing lugs 25 at one side of the cradle is a sewing machine starting rock shaft 26. A rock arm 2'7 fast on the starting rock shaft is connected by means of a chain 28 to a foot treadle or the like (not shown), and a rock arm 2% fast on the starting rock shaft is joined by means of a connecting rod 3% to the sewing machine starting lever 22. The rock arm 2% is formed at the free extremity with a vertical slot 31 into which the connecting rod 3t] protrudes, providing a lost motion connection between the rock shaft 2s and the sewing machine starting lever. A coil spring 32 biases the rock shaft 26 in a clockwise direction, as viewed in FIG. 1, to take up the slack in the lost motion connection between the rock arm 29 and the connecting rod 30.

' Journaled in bearing lugs 33 at the opposite side of the cradle from the starting rock shaft 26 is a clamp lifting rock shaft 34. A rock arm 35 fast on the rock a shaft 34 is connected by means of a cable 36 to the clamp opening lever 21 on the sewing machine. A rook arm 37 fast on the clamp opening rock shaft 34 is connected, as will be hereinafter described, to the power operated device of this invention.

As illustrated in FIGS. 1 and 2, an electric motor 40 is fitted with a belt pulley 41 for driving a sewing machine actuating belt 42. The motor 4%? is secured on a frame 43 pivoted on a bracket 44 secured beneath the sewing machine supporting table and adjustably secured by means of a threaded bolt 45 to a bracket 46 also secured beneath the table. By means of lock nuts 47 on the bolt 45, the position of the electric motor 40 may be adjusted to regulate the tension in the belt 42.

The electric motor 40 is also fitted with an adjustable diameter belt pulley 48 engaging a belt 49 for driving the power operated device of this invention. The variable diameter pulley may be of any known construction for maintaining a substantially constant tension in the belt 49 by decreasing its efiective diameter inresponse to increase in belt tension, The variable diameter pulley 48 permits adjustments of the position'of the electric motor without interference with the belt drive 49.

The power control unit of this invention comprises a bracket 68 secured beneath the table 2e, in which bracket a shaft 51 is journaled for turning and axial siding movement. .lourn-aled on a bearing 62 for turning movement relatively to' the shaft 61 is a pulley 63 engaging the belt 49. The pulley 63, which is thus driven continuously by the'electric motor 46, is formed with a clutch surface 64 cooperating with'a clutch disk 65 carried fast on the shaft 61 Axial movement of the shaft serves to engage and disengage the clutch parts 64 and 65. A coil spring 66 confined between a collar 67 fast on the shaft and a thrust bearing 68 abutting the bracket 6%), serves to bias the shaft axially toward the engaged position of the clutch parts 64 and 65.

FIGS. 3, 4 and 5 illustrate one form of the power con-.

trol unit of this invention, in which the collar -67 carries a single stop finger 69 rotatable in 'a circular path with the shaft 61.- Cooperatingwith the stop finger 69 is a control'member 70 mounted for swinging movement on a ametrically opposite sides of the circular path of motion of the stop finger 69. As illustrated in FIGS. '4 and 5, the space between the stop lugs 73-73 is less than the maximum diameter of the trace'of the path of motion of the stop finger 69 so that in any position of the control mem- 7: bet, at least one of the stop lugs will always be disposed in the path of thestop finger. As illustrated in FIGS. 3

and 4, the control member is formed with cam surfaces 7474,one adjacent to each of the stop' lugs 73-73 for urging the stop finger 69 and the shaft 61 axially in a direction to disengage the clutch parts 64 and 65.

' 11 formed on the control member .70. A rod 91 (FIG. 2) pivotally connected-to'the depending arm 96 has secured thereto a block 92 in which a rod 93 is lengthwise slidable, rods 91and 93 being substantially parallel. A stop collar '94 fast on the rod 93 abuts the block 92 on the rod 91 to limit movement'of -the rods together and a spring 95 confinedbetween the block 92 and a collar 96 on the rod 93 resists movement of the rods apart. The rod 93 is pivotally connected to a rock arm. 97 carried on the sewing machine starting rock shaft 26.

FIG. 1 illustrates the position whichthe parts occupy when the sewing machine is at rest and the power control unit constrains the sewing machine work clamp in opened position. During the initial turning movement of the'sewing machine starting rock shaft 26 and While the lost motion provided by the slot 31 is being taken up and thus-before the-rod St is depressed to actuate the sewing machine starting' -lever 22, the rock arm 97 acts through rods 93 and 91 to turn the-control member 70 to theopposite side, thus causing the shaft 61 of the power control unit to turn one half revolution to close the Work clamp. Continued'motion of the sewingma- Referring to FIGS. 4 and 5, the control member 70 is 7 illustrated in' oneextreme position and the stop finger 69 shifted intoclutch disengaged position by the cam surface 74 and held in that position by the stop lug 73 'at' one side of the control member. When the controlrmernber 70 is' shifted into the other extreme position, as illustrated in dashed lines in FIG. 4, the stop lug 7'3 and 'the cam surface 74'. at the oppositeside' of the control 'me'mber will be shiftedinto the path of motion of the stop finger, and the stop finger will be released from the stop lug together with the cam surface by which it had been constrained. The spring 66 will thus urge the shaft 61 axially into engaged position of the clutch to drive the shaft and the stop finger until the stop finger turns one half-revolution and is then stopped in the disengaged clutch position by the cam surface 74." and stop lug 73'...

Fast on the power controlshaft 61'is a rotary actuator j 'preferablyin the form of'a crank 8i) including 'a crank pin 81 entering a slot 82 formed in a connecting link 83.

A clevis 84 formed on the connecting link embraces the clamp opening rock arm 37 and is pivotally connected thereon by a pin 85.

As illustrated in FIG. 1, the crank 86 is preferably arranged to' occupy a position corresponding to clamp openposition of the rock arms 35 and '37 in one stopped position of the stop finger 69, and to occupy -a position corresponding to closed position of'the clamp in the other stopped position of the stop finger 69. The power control mechanism may be adjusted to provide such turning of the crank 80 by an angular adjustment of the collar 67 relatively to the shaft 61, the collar being 'securedin selected position of adjustment by the set screw 86 (FIGJS).

chine starting rock shaft 26 depresses therod-Stl and turns the sewing machinestarting lever to start the. machine. The spring 95 between rods 91 and 93 permits the rodsto move apart after the control member 71 has reached the limit of its movement The mechanism of the sewing. machine, which may be of any well known type for locking the starting lever in running position during a cycle of machine operation, will by virtue of the rod 30 and'the rock arm 29, hold the starting rock shaft 26 in a counterclockwise position in opposition to the spring 32, thuszholding the power control unitin apposition in which the work clamp is closed. When the startinglever is released at the end of acycle of sewing, the parts will return to the position illustrated in FIG. 1

V and the power control unit will be operated to open the work clamp.' r r :As illustrated inthedrawings'the power control unit may be enclosedby a cover plate 98 secured inplace on'the bracket 66 by screws 99. V

FIGS. 7, 8, 9 and 10 illustrate'a modified form of the power control unit of this invention which differs from the form illustrated in FIGS. 3, 4 and '5 in that a plurality of stop fingers are carried for rotation with the shaft 61 and cooperate with a single stop lug and cam surface 7 on the control member 711' Referring to FIGS. 7, 8, :9 andjlO, the collar '67 is formed with two stopffingers 169 and 169' each extending from the collar in a direction axially of the shaft 61. Thestop finger 169' is offset radially outward from the axis of the shaft 61 with respect to the stop finger 169 so as to describe a path of' motion outwardly beyond that described by the stop finger 169 uponirotation of Thus, when the control member is reciprocated in one 1 direction to the position illustrated in FIG. 1, the shaft 61 will be released and will be driven one half revolution to a stopped position in which the crank 80 will hold the work clamp open. When the control member 70 is re-. ciprocated in the opposite direction, the shaft 61 will be released and will be driven the other half revolution into a'stopped position in which the workiclamp is closed. The work clamp will be opened and closed at a speed dependent upon the speed of rotation of the constantly running drive pulley 63 and thus, thework clamp will not slam closed in response to its own biasing spring, but V will be closed at a predetermined deliberate rate which will materially reduce the impact, shock and vibration heretofore experienced in automatic work clamp opening and closing devices.

The :position of the control member 70, which as described above determines opening and closing of the work clamp, is regulated by means of a depending arm 90 the shaft 61. The control member 71 is formed with a single stop lug 173 and with a cam surface 174 adjacent thereto. The control member may be swung into a position as shown in FIG. 9, in which the stop lug 173 and cam surface 174 are disposed in the path of motion ofthe stop finger 169' or the control member may be turned in the other direction into a position as shown in FIG. 10in which the stop lug 173 and cam surface are disposed in the path of motion of the stop finger There are several distinct advantages which may be ascribed to the modified form of construction illustrated in FIGS. 7, 8, 9 and 10. The stop fingers 169 and 169' may be arranged in any desired angular relation about the periphery of the collar 67' limited only by the fact that sufficient spacing must be preserved to accommodate would not be available for movement of the stop lugs into and out of the path of motion of the stop finger. Whereas the increments of shaft movement available with the form of construction of FIGS. 3, 4 and 5, will be 180 plus or minus but a few degrees, the increments available with the version illustrated in FIGS. 7-10, include the range from approximately to 340. I

Furthermore, the form of construction illustrated in FIGS. 35 is inherently limited to two stop positions,

' while in the form illustrated in FIGS. 7-10, more than two stop fingers may be included. With an even number of stop fingers, more than two alternate fingers could share a common path of motion and thus mechanism for positioning the control member 7% into either of two positions as disclosed in the drawings would sufiice. If an odd number of stop fingers is used more than two, a third position for the control member would be required.

If it should occur that automatic opening of the clamp by the power control unit is not desired and a pull chain 160 or the like is to be used to open and close the work clamp, provision is made for rendering the power control unit ineffective. Referring to FIGS. 1 and .6, it will be apparent that the power control unit is operated during the traverse of the rod 36 along the slot 31, that is, during the period of lost motion between the starting lever and the starting rock arm 29. A sliding keeper 101 slidably embracing the rod 29 is formed with a hooked extremity 192 which may be moved by the upturned finger grip 103 to embrace the rod 30 and to constrain the rod in the upper extremity of the lost motion slot 31, as illustrated in FIG. 6. With the keeper 101 in the position shown in FIG. 6, complete return of the starting rock shaft 26 is prevented and the spring 95, in the connections to the power control unit, is not relaxed to the point where the control memberiil may be shifted to open the work clamp. The keeper 191 thus locks the power control unit in the clamp closed position so that the machine may be operated but the work clamp must be opened and closed manually by the pull chain 180 or by a manually operable rock arm (not shown) on the clamp lifting rock shaft 34. 7

Having thus described the nature of the invention, what we claim herein is:

1. For use with a sewing machine having stitch forming ins-trumentalities, means for driving said stitch forrning instrumentalities intermittently, and an operable appurtenance such as a work clamp or the like associated with said stitch forming instrumentalities, a power assist mechanism for operating said appurtenance to a sewing machine, comprising a rotary actuator, means for operatively connecting said rotary actuator to said sewing machine appurtenance for operation of said appurtenance during turning movement of said rotary actuator, continuously operating means for turning said rotary actuator independently of said intermittently operated driving means for said stitch forming instrumentalities, a stop finger carried for rotation with said rotary actuator in a circular path, a control member, a plurality of stop means carried on said control member and disposed in spaced relation angularly about the circular path of said stop finger, and means shiftably supporting said control member for movement relatively to the circular path of said stop finger to position any selected one of said plurality of stop means into the path of motion of said stop finger.

2. Mechanism for opening and closing a sewing machine work clamp or the like, comprising a shaft, frame means for supporting said shaft in turning and axial movements, rotary actuating means fast on said shaft and adapted to be operably connected to open and close a sewing machine work clamp or the like, a drive member journaled in said frame means, means for imparting con tinuous rotary motion to said drive member, interengaging clutch means carried on said shaft and on Said drive member engageable and disengageable upon the shifting of said shaft, means biasing said shaft axially in one direction into the engaged position of said clutch means, a cam follower finger fast on said shaft to describe a circular path upon rotation of said shaft, a cam member embracing said shaft at one side of said cam follower finger, means for supporting said cam memberon said frame means for shifting movement substantially perpendicularly to said shaft, said cam member formedwith a pair of inclined cam surfaces disposed at diametrically opposite sides of said shaft and spaced apart a distance less than the diameter of the circular path described by said cam follower finger, and operator influenced means for shifting said cam member transversely of said shaft to position a selected one of said pair of cam surfaces out of the path of motion of said cam follower finger.

. ing rotation of said shaft in half revolution increments,

3. Mechanism for opening and closing a sewing machinework clamp or the like, comprising a rotary actuator, means adapted to operatively connect said rotary actuator to a work clamp for opening said work clamp on one half of each revolution of said rotary actuator and for closingsaid work clamp on the other half of each revolution of said rotary actuator, means for turning said rotary actuator, a stop finger carried for rotation with said rotary actuator in a circular path, a control member, a pair of stop means carried on said control member and disposed on diametrically opposite sides of the circular path of said stop finger, and means shiftably supporting said control member for movement relatively to the circular path of said stop finger to position said pair of stop means alternately into the path of motion of said stop finger.

4. Mechanism for'opening and closing a sewing machine work clamp or the like, comprising a shaft, means for supporting said shaft in turning and axial shifting movement, a constantly rotating drive member, clutch means associated with said shaft and efiective on axial movement of said shaft drivingly to connect and disconnect said shaft with said constantly rotating drive member, a rotary actuator fast on said shaft, means adapted to operatively connect said rotary actuator to a work clamp for opening said work clamp on one half of each revolution 'of said rotary actuator and for closing said work clamp on the other half revolution of said rotary actuator, a stop finger carried fast on said shaft for rotation in a circular path, a control member, a pair of stop means carried on said control member and disposed on diametrically opposite sides of the circular path of said stop finger, cam means associated with each of said pair of stop means for shifting said stop finger and said shaft axially to disconnect said clutch means, and means supporting said control member for reciprocation transversely of said shaft to position said pair of stop means alternately into the path of motion of said stop finger.

5. Mechanism for opening and closing a sewing machine work clamp or the like, comprising a shaft, means for supporting said shaft in turning and axial shifting movement, a constantly rotating drive member, clutch means associated with said shaft and effective on axial movement of said shaft drivingly to connect said shaft with said constantly rotating drive member, a rotary actuator fast on said shaft, means adapted to operatively connect said rotary actuator to a sewing machine work clamp to open said clamp in one half of each revolution and to close said work clamp on the other half of each revolution of said rotary actuator, and means for elfectsaid means including a finger carried fast on said shaft for rotation in a circular path, a pair of cam members, means for locating said cam members in fixed relation relatively to each other and on diametrically opposite sides of the circular path of rotation of said finger, means for supporting said cam members for movement alternately one into and the other out of the path of said finger, said cam members each being formed with an 7 V inclined camming, surface for engagement with said finger to shift said shaft 'ally into disengaged position of-said clutch means, and stop means associated with each, of said cam members determining an angular stopped position of said finger and of said shaft;

' 6. Mechanism for opening and closing a sewing machine work clamp or the like which is biased toward a closed position, comprising a rotary actuator, work clamp opening and closing linkage, means operatively connecting said rotary actuator to said linkage for opening said work clamp during one half of each revolution of saidrotary actuator, and closing said work clamp during'alternate half revolutions of said rotary actuator, a constantly rotating drive means for said rotary actuator, clutch means Y after each half revolution or an rotary actuator by said i drive means.

7. Mechanism for opening and closing a sewing'machine work clampor the like which is biased toward a closed position, comprising a rotary actuator, work clamp opening and closing linkage, meansoperatively connecting said rotary actuator to said linkage for successivelyv opening clamp'during each complete cycle 7 and closing said work of rotation of said' actuator, a constantly rotating drive means for said rotary actuator, clutch means for drivingly interconnecting said drive means with said rotary actuator, a control member, means shiftably supporting said control member for movement into a selected one of two i extreme-positions, means carried on such control member and effective in one extreme position of said control mem- J her for disengaging said clutch means and stopping said rotary actuator in the opened position of said Work clamp opening linkage, means carried on said control member and eifective in the other; extreme position of said control 7 member for disengaging said clutch means and stopping said rotaryactuator in the closed position o-f'said work clamp opening linkage, and means effective during each to the oflier for engaging said clutch means.

8. Mechanism for opening and closing a sewing machine work clamp or the like, comprising a shaft, means for sup-V porting said shaft in turning and axial shifting movement, a constantly rotating drive member, clutch means associated with said shaft and efiective on axial movement of said shaft drivingly to connect and disconnect said shaft with'said constantly rotating drive member, a rotary actuator'fast on said shaft, means adapted to operatively 1 connect said rotary actuator to a work clamp for open! ing said work clamp on one half of each revolution of said rotary actuator and for closing said work clamp on the other half revolution of said rotary actuator, a stop finger carried fast on said shaft for'rotation in a circular path, a' control me'mber,-a pair of stop means carried onsaid shift of said control member'from'one extreme position control member and disposed 'on diametrically opposite sides of the circular path of said stop finger, cam means associated with-each of said pair of stop means for shifting said stop finger and said shaft axially to disconnect said clutch means, and means pivotally supporting said controlmember for oscillation transversely of said shaft to position saidpair of stop means alternately into the path of motion of said stop finger.

9. For use with a sewing having a stop motion mechanism and a work clamp, an operator actuated sewing ma- 1 chine starting member, means operatively connecting said operator influenced member with said sewing machine stop motion-mechanism, a rotary actuator, means operatively connecting said rotary actuator to said work clamp for openingsaid work clamp on one half of each revolution of said rotary actuator and for closing said work clamp on the other half of each revolution of said rotary actuator, continuously operating means capable of turning said 7 8 a rotary actuator, a stop finger carried for rotation with said rotary actuator in a circular path, 'a control member, a pair of stop means carried on said control member and disposed on diametrically, opposite sides ofthe circular path of said stop finger, said pair of stop means corresponding one to the open position of the sewing machine work clamp and the other to the closed position thereof, means shiftably supporting said control member for movement relatively to the circular path of said stop finger to position said pair of stop 'means alternately into the path of motion of said stop finger, and means operatively connecting said sewing machine starting member with said control member to position the stop means corresponding to the open position of the work clamp into the path of motion of the stop finger when the sewing machine is stopped and to shift the stop means corresponding to tor, means adapted to operatively connect said rotary actuator to a work clamp for opening said work clamp on oneposition of each revolution of said rotary actuator and for closing said work clamp during the other position ofeach revolution of said rotary actuator, means for turning said rotary actuator, a pair of stop fingers carried for rotation with said rotary actuator, said stop fingers being disposed at different distances from the axis of rotation of said rotary actuator'for movement in separate circular paths, a control member a stoprmeans carried on said control member, and means shiftably supporting said control-member formovement relatively to thecircular paths of said stop fingers to position said stop means alternately into the circular paths of motion of saidstop fingers.

11. A power assist'mechanism for operating an appurtenance to'a sewing machine, comprising a rotary actuator, means adapted to operatively connect said rotary actuator to a sewing: machine appurtenance for operation of said appurtenance during increments of turning move- 7 ment of said rotaryiactuator, means for turning saidrotary actuator, a plurality of stop fingers carried for tothe axis of said rotary actuator, said'stop fingers being disposed each at a ditferent'distance from the axis of rotation of said rotary actuator with respect to adjacent stop fingers for movement in separate circular paths, a control member, a stop means carried on said control member, and meansshiftably supporting said control member for movement relatively to the circular paths of said stop fingers to position said sto-p means into the path of motion of a selected one ofsaid stop fingers.

12. Mechanism for opening and closing a sewing machine'work clamp or the like, comprising a shaft, means for supporting said shaft in turning'and axial shift movement, a constantly rotating drive member, clutch means associated with said shaft and effective on axial movement of said shaft drivingly' to connect and disconnect said shaft with said constantly rotating drive member, a rotary actuator fast on said shaft, means adapted to op eratively connect said rotary actuator to a work clamp for opening said work clamp during one portion of each revolution of said rotary actuator and for closing said Work clamp on the other portion of each revolution of said rotary actuator, a pair of stop fingers carried fast on said shaft and disposed at different distances from the axis in separate circular paths, a control member, a stop means carried on said control member, cam means associated with said stop means for shifting said stop fingers and said shaft axially to disconnect said clutch means, and means supporting said control member for reciprocation transversely of said shaft to'position said stop means and said cam means alternately into the paths of motion of said pair of stop fingers.

13. For use with a sewing machine having stitch forming instrumentalities, means for driving said stitch forming instrumentalitics intermittently, and an operable appurtenance such as a Work clamp or the like associated with said stitch forming instrumentalities, a power assist mechanism for operating said appurtenance, comprising a rotatable actuating means, means for operatively connecting said actuating means to said sewing machine appurteuance for operation of said appurtenance during turning movement of said actuating means, a rotatable drive member, means for supporting said actuating means and said drive member for relative turning movement, means for imparting continuous rotary motion to said drive member independently of said intermittently operated driving means for said stitch forming instrumentalities, operator influenced stop means effective to engage and lock said rotatable actuating means against rotation, means for shifting said stop means from one to another of a plurality of positions each effective to engage and lock said rotatable actuating means in a different position of rotation, means efiective upon each shift of said stop means from one to another of said positions for establishing a driving connection between said drive member and said rotary actuating means, and means automatically efiective upon engagement of said rotary actuating means with said stop means in any of said plurality of different positions of said stop means for disengaging said driving connection between said drive member and said actuating means.

References Cited in the file of this patent UNITED STATES PATENTS 117,708 West Aug. 1, 1871 676,817 Hall June 18, 1901 809,160 Wingo Jan. 2, 1906 1,273,348 Fifield July 23, 1918 2,540,987 McCann Feb. 6, 1951 2,730,058 McCann Jan. 10, 1956 FOREIGN PATENTS 491,040 Germany Feb. 8, 1930

Images