US2833237A - Thread tension release and presser bar lifter - Google Patents

Description

K. KLEEMANN THREAD TENSION RELEASE AND PRESSER BAR LIFTER Filed Aug. 15, 1955 May 6, 1958 2 Sheets-Sheet 1 INVENTOR. Km Km mam BY aka-MAE i Woo- RMLLQ K. KLEEMANN THREAD TENSION RELEASE AND PRESSER BAR LIFTER Filed Aug. 15, 1955 2 Sheets-Sheet 2 INVENTOR. Karl Kleemunn BY (Am ATTORNEYS erator. actuated by a series of levers, and a cam shaft or a quadrantshaftwith guide curves. In such sewing machines "thread tensions are notprematurely loosened even when THREAD TENSION RELEASE AND PRESSER BAR LIFTER Karl Kleemnnn, Kaiserslautem, Germany, assignor to G. M. Pfaif A. G., Kaiserslauteru, West Germany, a corporation of West Germany Application August 15, 1955, Serial No. 528,401 Claims priority, application Germany August 16, 1954 laims. (Cl. 112238) tension can be released bythe use of a pin passing through the arm of the sewing machine which supports the sewmg head and which pin, directly or indirectly, is operative to compress the spring which forces the thread tension disks together. Such a pin is commonly operated by the manual lifting device forthe presser bar so that as the presser bar and foot are lifted to clear the material on the work table the release pin is simultaneously operated to loosen the compressive force exerted upon the tension disks through which the thread passes between the spool and needle. Heretofore with thread tension releases of this type it has been common practice to position a block fixed on the presser bar, against which the cam surface of a manual presser lifter bears upwardly to lift the presser bar and foot. When the presser bar is so lifted to raise'the presser foot from the material, the block afixed to the presser bar directly or indirectly engages the thread tension release pin and thus simultaneously releases tension on the thread passing to the needle. Such a device, however, is subject to the disadvantage that the thickness of the material reaches a maximum clearance between presser foot and throat plate at which undesirable slackening of thread tension occurs. It has heretofore also been found that this problem can be avoided by constructing the block which lifts the presser bar in two pieces, such that'one piece is aflixed to the presser bar and the other is loosely mounted on'the presser bar but positioned between the cam surface of the presser lifter and the part of the block afiixed to the presser bar. Tension is released in this arrangernent by engagement of the loose part of the block with therelease pin. In this manner upward movement of the presser bar caused. by the thickness of the material has no effect upon the release pin and thread tension can be loosened only when the presser bar lifter forces the loose part of the block upwardly into engagement with the fixed part of the block.

In many machines, however, such as those employing a pair ofalternating presser bars, the two-piece presser bar block arrangement cannot be employed without substantial change in the design of the machines. For this reason in such machines a two-piece presser bar block has not been used and thread tensions have heretofore been released simply by separate manual control.

Anotherproblem arises in many commercial machines I .which employ secondary presser bar lifter systems for operation, for example, by the knee or foot of the op- In such systems the tension releasing pin is vice or by a manual presser bar lifter.

2,833,237 Patented May 6, 1958 ice thicker material is used. The construction of such releasing devices and the limited possibility of incorporating them in the sewing machine renders it impossible, however, to provide for release of thread tension also by means of a manual presser lifter.

It is an important object of this invention to provide an apparatus for releasing thread tensions by providing for engagement with a conventional thread tension release pin so that it will not release the thread tension when thicker material is employed and yet so that it can be actuated either by a secondary presser bar lifting de- It is a further object of this invention to provide such an apparatus for releasing thread tensions which can readily be incorporated in existing machines Without changing the design of such machines.

This invention contemplates employment of a mechanism for actuating a thread tension release pin which is independent of the position of the presser bar but which is actuated to release the thread tension by engaging the thread tension release pin when either the secondary or manual presser bar lifter is operated. In particular it is preferred to employ a two-armed lever pivoted at its center to the machine, one arm of which is actuated by the manual presser bar lifter and the other arm of which is actuated by a secondary presser bar lifter, both such actuations causing the two-arm lever to rotate about the central pivot in the same direction to cause the two-arm lever to drive a spring-loaded, sliding, tapered, bar to engage and actuate the tension releasing pin. In this preferred arrangement it is advantageous to construct the two-arm lever such that one arm engages the manual presser bar lifter while the other arm both presses against the sliding member to actuate the tension release pin and is actuated by the secondary presser bar lifter. These and other objects of the invention which will become more apparent hereinafter are illustrated in the accompanying drawings with reference to aspecific construction embodying the principles of this invention for releasing thread tensions in a sewing machine. In the accompanying drawings:

Fig. 1 is a fragmentary perspective view of the head of a sewing machine employing compound feed and alternating pressers which is provided with a tension release device in accordance with this'invention;

Fig. 2 is'an-exploded view of the essential parts for actuating the tension release pin which are employed in the machine shown in Fig. 1;

Fig. 3 is a perspective view of the assembled operating parts for producing thread tension release in the machine shown in Fig. l; and

Fig. 4 is an end elevation of the machine shown in Figure 1, shown partly in section to illustrate in particular the operative connection between the presser bar lifters and tension disks. i

In the drawings the reference numeral 10 designates a sewing machine having compound feed and alternating pressers. This general type of sewing machine is conventional and its operation will be described more fully hereinafter. Sewing machine 10 includes a work table 11 for supporting the material to be sewn, and an overhanging arm 12 supported above work table 11 and carrying a sewing head 13 at its end.

Arranged in sewing head 13 are a needle bar 14 which is vertically reciprocable in and depends at its lower end from a rocking double guide sleeve 15 pivotally connected at its upper end to sewing head 13 to permit its movement through an arc in a plane extending transversely across work table 11 and aligned with the direction of feed. Needle bar 14 is connected to a crank shaft (not shown) of conventional construction which causes to the rear of arm 23a as seen in Fig. 1.

needle bar 14 .to reciprocate vertically and to drive a needle 16, secured in the lower end of needle bar 14, into and out of an opening in throat plate 17. Throat plate 17 is embedded in and secured on the surface of work table 11 and so positioned such that needle 16 cooperates with a rotary hooktnot shown) in orderto produce a conventional lock stitch. A power take-01f (not shown) from the crank shaft having an eccentric movement is connected to sleeve to cause it to oscillate about its top pivot.

An inside presser bar 18 is'also mounted in and depends at its lower end from sleeve 15 for vertical reciprocating movement. The lower end of inside presser bar 18 carries .an inside presser foot 19, sometimes known as a walking foot, which bears downwardly against thefeed dog (not shown) to cooperate with the feed dog in pullingmateiial across work table 11. Inside presser foot.19 is provided with an aperture through which needle 16 passes in its downward stroke to cooperate with the hook.

i To the rear of needle bar 14and inside presser bar 18 is the outsidepresser. bar. 20 which is mounted for vertical sliding movement in anddepends at its lower end from head 13. The lower end of outside presser bar 20 carries, an outside presser foot 21 which cooperates with throat plate 17 to hold the material being sewn in fixed position. A heavy helical. spring is positioned about the upper end ,of outside presser bar 20 andbears at its lower end against, a presser bar block 23 which is affixed to outside. presser bar. 20.

Presser bar block 23 carries an arm 23:: which extends laterally from presser bar 20 towards therear. of the machine. Presser bar block 23 also carries a guide arm 24 extendinglaterally from presser bar 20 and at right angles toarm 23a more or less parallel to the length of supporting arm 12. Guide arm 24 is provided with a tapped opening 25 which threadedly engages, a screw 26 serving to affix an upright post 27 to guide arm 24. The upper end of upright post 27 carries a small stud 28 projecting toward the rear of the head which on its underside is aligned to engage the upper edge of presser bar lifting arm 29.

Lifting arm 29 is pivotally secured at its center (beyond thefragmentary views shown) to sewing machine arm 12 in a conventional manner and at its'remote end is pivotally connected to.a vertical link extending through work table 11 for vertical reciprocation by means ofa treadle actuatable by the footofthe operatoror by means of a knee-operated lever. This actuation of lifting arm 29 causes ,it to ride upwardly at its end adjacent head 13 to engage stud 28 andlift outside presser bar:20 upwardly against biasing of spring 22.

.Presser bar block arm 23:: in its lowermost position is closely adjacent to the end of manual presser bar lifter 30 in the proximity of the pivotal connection 31 by which presser bar lifter 30 is connected to head 13. In the vicinity of pivot 31'presser bar lifter 30is provided with a pair of cam surfaces, one cam surfaoe32 disposed forward of arm 23a, and the other cam surface 33 disposed When presser bar lifter 30 is actuated by lifting its outer end remote from head 13, cam surface 33 engages the underside of arm 23a and thereby lifts outside presser bar 20 to remove outside presser foot 21 from throat plate 17.

On arm 23a. of outside presser bar block 22 there is affixed a bearing bolt 34-which extends horizontally and lengthwise of sewing machine arm 12 toward the outer end of head 13. Bearing bolt 34 rotatably carries the center of bell cranklever 35, one'arm, 36, of which is pivotally connected by link 37, to crank arm 38 of shaft 39 supported. on sewing arm 12 in journals 40.

The remote end of shaft 39 (beyond fragmentary views shown) is provided with a similar crank arm and link which engage an eccentric on the main crank shaft and wobble through a small arc. .to the inside face of plate 56 prevents lever 64 from thus an oscillating movement is imparted to shaft 39 during operation of sewing machine 10.

The other arm of bell crank lever 35 (not visible) terimnates in a pivotal link connection to the upper end of inside presser bar 18. Bell crank lever 35 is .held in position on hearing bolt 34 by means of a guide disk 42. The outer end of bearing bolt 34 carries a small bearing cylinder 43 which rests in a vertical guide slot on the inside face of guide plate 44 affixed on the end of head 13.

The oscillating movement of shaft 39 produced during operation of sewing machine 10 causes a similar oscillating movement of hell crank lever 35. As this movement of bell crank lever 35 approaches its clockwise limit, as seen in Fig. 1, the arm of hell crank lever 35 extending forward in head 13 bears down against the upper end of inside presser bar 18, the foot 19 of which is resting firmly on the feed dog. Thus, further movement of bell crank lever 35in a clockwise direction lifts outside presserbar20 and its foot 21 above throat plate 17 As .the same oscillating movement of bell crank lever 35. is reversed and approaches its counter-clockwise limit, as seen in Fig. 1, thecentral pivoted part of bell crank lever 35 forces down. against outside presser bar'20 to cause. outside. presser. foot 21 to bear against throat plate 17. Further. counterclockwise movement thereby lifts the forward arm of lever 35 carrying withit inside presser ,bar 18 to remove foot 19 from the feed dog, clear of. table 11. It isapparent therefore that the vertical movement of the inside and outside presser bars is alternating.

The timing of the vertical reciprocation of needle bar 14,and of the transversemovement of the feed dog cooperates with this alternating movement such that, as the needle 16 is plunged through the openings in inside presser fOOt 19 and throat plate17 to cooperate with the hook, sleeve 15 carrying both needle bar 14 and inside presser bar 18 is oscillated toward the rear as seen from the operators side of the machine. Simultaneously, the feed dog is in its upper position and moves toward the rear of the machine. At the same time outside presser bar 20 is raised and holds foot 21 above throat plate 17. As sleeve 15 reaches its rearward limitof movement, outside presser bar 20 and presser foot 21 drop. At the same time the feed dog is lowered and removed to the forward position,

and inside presser bar 18 and presser foot 19, and needle bar 14 and needle 16 are raised and moved forward. In

this action the material is alternately pulled and held firm,

and the: stitchis taken during the pulling movement.

Thread tension itself is maintained by a conventional device shown most clearly in Fig. 4, which includes a plate 50, .afiixed to the forward. face of sewing arm 12 of machine 10, which carries a forwardly projecting threaded stud 51 having a central bore 52and along slot 53 at On the outer face of plate 50 are positioned slot 53. These membersare held under tension by spring 58 and nut 59, the desired tension during sewing being set by the relative compression exerted upon spring 58 by nut 59.

. 0n the inside face of plate 50 there is loosely positioned by means of a pair of screws 60 a triangular plate 61, the lower end ofwhich is freely movable through a small arc and which carries aprojection 62. A small pin 63 extends through the bore 5210f stud 51 abutting at its innerend the outside s'urfaceof triangular plate 61 and abutting at its outer end web 57 of cup 56.

A lever 64 is pivotallyv secured at its center 65 to the inside ofplate 50 with sufficient freedom to permit it to A guide .pin 66 attached rotating .through an appreciable angle. One end of lever 64 .is..provided with a projection 67 which engages the inside face of projection 62. oftriangular plate 61. Thus,

wobbling movement of lever 64 forces plate 61 against plate 50 and thus causes pin 63 outwardly in bore 52 to push web 57 and cup 56' from tension disk 55, carrying with them spring 58 and thereby releasing the tension on the thread which ultimately passes through an appropriate take-up mechanism to the eye of the needle.

-A long pin 68 passing through the body of arm 12 projects outwardly on the forward face of'arm 12' into engagement with the inside face of projection 67 on lever 64 and also projects from the rear face of arm 12 slightly above the outer, end of .guide arm 24. This rearward projection of pin 68 is commonly employed in many domestic and commercial machines in direct engagement with the presser bar block to produce release of tension on disks 53,and .54.. Inmachines of the type illustrated, however, where it is desired to effect release of tension only ,when the. presser bar is deliberately lifted, as opposed to lifting that occurs in ordinaryfeeding of material between presser bar and throat plate, pin 68 cannot be positioned for actuation by any usual means.

Insofar as sewing machine has been described above, with the exception of cam 32, its construction is conventional and the description has necessarily been limited to such details as are necessary for a complete understanding of the operation of the tension release device of this invention. In the present invention pin 68 is actuated by upward vertical movement of a sliding member 70 which is on three of its sides surrounded and guided by guide piece 71 aflixed to arm 12. .As is shown most clearly in Fig. 2 the flanged extension 71a of guide piece 71 which serves as a guide for two sides of slide 70 also serves in part as a guide for the outer end of guide arm 24. The fourth side of slide 70 is guided by a plate 72 aflixed over the outer side of guide piece 71 by means of screws 73 which :also serve to aflix guide piece 71 to arm 12.

The upper end of slide 70 is provided with a vertical fiat 74 on its inside face against which pin 68 rests. The lower end of fiat 74 merges into a taper 75 which is engageable with the rearward projection of pin 68 when slide 70 is urged upwardly in guide piece 71.

The lower end of slide 70 is provided with a rearwardly angled piece 76, the upper face of which bears against the lower end of a pin 77 which is vertically reciprocable within a small vertical bore 78 in a boss 79 on plate 72. A small coil spring 80 is positioned within bore 78 to bias pin 77 into contact with angle 76.

A two-armed lever 81 is pivotally secured at its center by means of bolt 82 to sewing arm 12. One end, 83, of lever 81 is positioned immediately below cam surface 32 of the manual presser bar lifter 30, such that upward movement of the outer end of lifter 30 causes cam surface 32 to bear downwardly against end 83 and rotate lever 81 clockwise as seen in Figs. 1 and 2. The other arm 84 of two-arm lever 81 carries at its outer end the impact plate 85 which is positioned with its upper face abutting the lower end of the angle portion 76 on slide 70. Clockwise movement of lever arm 81 thus raises slide 70 to cause the end of pin 68 to move from its engagement with flat 74 on to taper 75 and thereby reciprocates pin 68 to cause it to bear against projection 67 and ultimately to release the tension of disks 53 and 54.

Toward the outer end of lifting arm 29 there is aflixed a downwardly depending hook arm 86 provided with a hook 87 at its lower end which is located beneath impact plate 85. Thus, upward movement of the outer end or upward movement of the outer end of lifting arm 29 produces a clockwise rotation of lever 81 and'thus'depresses pin 68, as seen from the rearof machine 10, torelease thread tension. In the particular machine illustrated the same upward movement not only carries the outside presser bar 20 upwardly, but also carries inside presser bar 18 upwardly by producing a movement of bell crank lever 35 equivalent to that utilized to lift inside presser bar 18 during operation of the machine.

While this invention has been described in a specific application to a machine employing a compound feed and alternating pressers and is particularly advantageous in such a machine, devices constructed in accordance with the invention can similarly be employed to coordinate intentional lifting of the presser bar with simultaneous release of thread tension in any conventional machine employing one or more presser'bars which hold the material in position on the work table or cooperate with the feed dog.

I claim:

1. A device for a sewing machine having a reciprocable presser bar, a presser bar lifter movably mounted on said sewing machine operably engageable with said presser bar to lift said bar upon movement of said lifter and thread tension release means including a reciprocable release pin, which device comprises a lever pivotally mounted on said sewing machine, said presser bar lifter being operably engageable with said lever separately of said presser bar to rotate said lever upon actuation of said presser bar lifter to lift said presser bar, a block having a tapered end slidably mounted on said machine with its tapered end extendable past an end of said release pin in sliding engagement therewith to reciprocate said release pin, and means biasing the other end of said block into engagement with said lever opposing said rotation of said lever and biasing said tapered end of said block out of engagement with said pin.

2. A device according to claim 1 in which said sewing machine further includes a second presser bar lifter movably mounted on said machine operably engageable with said presser bar to lift said presser bar and operably engageable with said lever separately of said presser bar to rotate said lever opposing the biasing of said block.

3. A device for a sewing machine having a vertically reciprocable presser bar, a presser bar lifter pivotally mounted on said sewing machine and operably engageable with said presser bar to lift said bar upon pivotal movement of said lifter and thread tension release means in cluding a reciprocable release pin, which device comprises a lever pivotally mounted on said sewing machine, said presser bar lifter being operably engageable withsaid lever separately of said presser bar to rotate said lever upon actuation of said presser bar lifter to lift said presser bar, an arm affixed to said presser bar, a block having a tapered end slidably mounted in said arm with its tapered end extendable past an end of said release pin in sliding engagement therewith to reciprocate said release pin, and means biasing the other end of said block into engagement with said lever opposing said rotation of said lever and biasing said tapered end of said block out of engagement with said pin.

4. A device according to claim 4 in which said sewing machine further includes a second presser bar lifter pivotally mounted on said machine operably engageable with said presser bar to lift said presser bar upon pivotal movement of said second lifter and operably engageable with said lever separately of said presser bar to rotate said lever opposing the biasing of said block.

5. A device for a sewing machine having a vertically reciprocable presser bar, a first presser bar lifter pivotally mounted on said sewing machine and operably engageable with said presser bar to lift said bar upon pivotal movement of said first lifter, a second presser bar lifter pivotally mounted on said sewing machine and operably engageable with said presser bar to lift said bar upon pivotal movement of said second lifter, and thread tension release means including a reciprocable release pin, which device comprises a lever pivotally mounted intermediate at its ends on said sewing machine, a cam surface on said first presser bar lifter operably engageable at one end of said lever separately of said presser bar torotate said lever upon actuation of said first presser bar lifter to lift said presser bar, a hook on said second presser bar lifter operably engageable at the other end of said lever separately of said presser bar similarly to rotate said lever upon actuation of said second presser bar lifter to lift said presser bar, an arm afiixed to said presser bar, a block having a tapered end slidably mounted in said arm with its tapered end extendable past an end of said release pin in sliding engagement therewith to reciprocate said release pin, and means biasingthe other end of said block into engagement with said other end of said lever 8 opposing said rotation of said lever and biasing said tapered end 'of said block out of engagement with said pin.

References Cited in the file of this .patent UNITEDSTATES PATENTS 433,971 Wheeler Aug. 12, 1890 434,037 Wheeler Aug. 12, 1890 1,518,494 Elcock Dec. 9,1924 1,534,264 Hanson Apr; 21, 1925 2,701,694 Hamlett Feb. 8, 1955 2,760,458 Ayres Aug. 28, 1956 FOREIGN PATENTS 33,402 Germany Oct. 22, 18 85 44,473 Austria Oct. 25, 1910 Italy Ian. 4, 1939 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nou 2,833,237 May 6, 1958 Karl Kleemalm It is hereby certified that error appears in the printed specification of the above numbered. patent requiring correction and that the said Letters Patent should read as corrected belowo Column 6, line 62, for the elaim reference numeral "4" read 3 Signed and sealed this 29th day of July 1958.

(SEAL) Attest:

KARL H. AXLINE I ROBERT c. WATSON Attesting Officer @onmissioner of Patents

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