US2846967A - Thread severing device for sewing machines - Google Patents

Description

s- 2, 1958 .1. DOERR EIAL 2,846,967

THREAD SEVERING DEVICE FOR SEWING MACHINES Filed Dec. 9, 1955 3 She'ets-Shee't 1 Wyn/r025 Aug. 12,195 3. Dom- ETAL may: 'SEVERING DEVICE FOR SEWING MACHINES Filed Dec. 9, 1955 5 Sheets-Sheet 2 M Q m a w. p Q. 5%.. mm qw y MN: l g R Q M w .i a 4 J h s flOEPP Mlbe/m pen/ER 1953 J. DOERR ETAL 2,846,967

THREAD SEVERING DEVICE FOR SEWING MACHINES s sheets-sheet 3 Filed D60. 9, 1955 INVENTORS: Jo6ann?s 8 and lA/rlfi'elm Drake, BY [J a THREADSEVERING DEVICE FOR SEWING 'MAICHINES Johannes Doerrand Wilhelm Dreher, Kaiserslautern,

Germanyaassignors to Gt M.:Pfaff A.-G., Kaiser- .slautern; Germany, a corporation of Germany ApplicationDecember 9; 1955,'"Serial No. 552,085

Claims priority, application Germany December '10, 1954 12Claims. (Cl; 1l2252) The-.invention relates .to. sewing-machines, and relates more. particularly to athreadsevering device for-use in connection with a sewing machine.

Still more particularlyythe invention-relates -to a-thread severing device .fon-cuttingthe upper-thread as well-as the lower thread on a-sewingamachine.

. The invention has among its objects to provide for the severance-cf the upper land'rlower'threads of asewing .machine, characterized' by simple means of actuation and subsequent automatic thread release.

.. his a further'objectof the. invention to provide'such .a. device which-will cut the upper and lower threads adjacent the uppernandtlower surfaces of the work-piece. It is a stillsfurther objected-the invention to provide such a device which .will. first clamp the threads,-thereafter cutithem, vanclsubsequently release them.

The foregoing andother-= objects of the invention-will be. best understood. from, i the following description of .exemplification"thereof, referencebeing had to-the accornpanying.drawings,- wherein:

Fig. 1 isaa fragmentary perspective view'ofasewing machineswith: a built-in thread-severing device in accordance with-theinventiomthe needle plate has been removed in the illustrationof Fig. 1 to expose theparts below the needle plate;

Fig.2 is an. underside perspective view of the needle plate including-the.parts'ofthe devicefor'use in severing .the. lower. thread;

\Eig. .3:is.an=extended perspective view-=01? the needle severing .device;

"Fig-4. isaa sectional viewofthe needle. plate, taken :01]. line. IV-.-IV of Fig. 2;

Fig 5. is :a large scale fragmentary vertical sectional view, .taken .on line VF-Vcf Fig. 1, showingthe parts inv position during the first step of the severingoperation;

Fig.- 6 .is... a: fragmentary plan view, partly in'section,

taken. on line- VI-VI of vFig.

Fig. 7 is a fragmentary large scale vertical sectional view similarto Fig. 5; butshowingthe'parts :positioned as duringthe second step of the-severingoperation, when thethread is. actually cm;

Fig. 8'..is1.a.. fragmentary; plan view, partly 'in'section taken. on line-.VlIL-VIII of :Fig. 7;

'Fig. 9 is a fragmentary :l'arge-scale vertical sectional view similar to. Big. 1,= buthshowing'ftheparts released after thread 1 cutting;

Fig/1011s .a fragmentary plan view," partly in" section taken on line X-1X"ofEig. 9;

Eig..11-.is:.an elevational view ofasewing machine :with-a thread 'severing device in accordance withfthe invention.

:In" carrying 'the'invention' into effect? in one of the embodiments which has been selected for illustration mithe accompanying :drawings and for description in "this-specification, and: referring now particularlyto Figs.

1-3, there is provided a sewing machine that isrsupported one work table 1, and comprises an arm-Zandahead 3.

United States PatentO facing recesses 24anda rearwardtfacing groove25. The

351 in alignment-with, the recesses -24 of'theh-'flange 23:0f

2,846,967 Patented Aug-- 12,

A' needle'bar 4,-and a presserbar- 5 for a sewing foot, are journalled for reciprocal movement the head 3.

Thecpresser bar 5 operates a'thread- 'tensioner 6-as well with a sectional s1ot16 whichincludesa needle-hole '17.

In thebottom surface of the body -11. there is=-formed a guide recess in which there is guidedifor reciprocating sliding movement a slide19 (Figs. 3 and 5). Fheslide 19 carries on its=front endon outer-visefijaw-l0athat has a rear'edgezl. Adjacenttherear edge-21 there is formed onthe slide 19a slot-22 (Figs: 3 and 6:) which -extends from a-lateral-edge of the slide-19 inwardly to a point mid-way-of thewidth ofthew' slide: 19-. The

rearedge 21 as :well---as'-the:slot"22 are inclinedrelative to i the direction of reciprocation 0f the slide 19; as :best :shown inFig. -6. On'therearend; theslide 19 carries a flange v23; (Figs. 3, 5, and-.7) which has two-forward vise jaw 20 carries a pin 26 (Figs; 3-.a-nd 6), whichvcan abut against the lower front surface ofthebody 11*(Fig.

' 8) .to limit the rearward movement oftheslide-19.

A plate 27 is-mounted tothe underside of the body 11; it is formed on-its front as va-c-utter-ZS,- andthecon- -necti0n to the-body.11-ma ybe-madei'by screws, for-instance byscrews 27a (Fig. 3). The body-11-has -two recesses 29 (Fig. 7) whieh aredisposed opposite to,and

the slide 19. Compression springs 30 (Figs. 3 and7) are disposed in the opposite recesses-24 and 29 and normally urge :the slide 19 into "-the rearwardmost position (Fig. 7)- wherein-the, pin 26 abuts against the body- 11.

An inner vise jaw-31 (Figs.- 3 and 5) is? carried'at'the forward end of a.rod-32, ands-the rod--32-=is--guided for reciprocation in the body 11. The-innervise' jaw e31 is in sliding engagement with- 1 the top=v surfaceof the slide 19, rearwardly of theouter'viseijaw20,-- and-:co- 'operates with'the saidouter-vise jaw 20 .fOF'I-6183S3blY clamping the upper -thread. The rod32 extends to-"the hollow interior ofthe body and has onrthe'rear end portion an-annular. groove 33 (Fig-3). -A' leaf' spring 34 (Figs. 3 and 7) has on its lower-end a bifurcation which engages the groove 33 of the rod 32. The spring 34 'isidis'posed uprightly, and'is connected with its upper "end to the'body 11 by means ofa-screw 35. The 'rod 32'and the inner vise jaw 31 are movable between: a forwardmost position (Fig. 5)--andta rearwardmost'positron (Fig. 9-).

'The body-11 has a vertical-hollow chamber, into.

which there extend therear portions of the-slidew 19 and of" the'rod 32. The spring- 34 is disposed in 'the chamber 36. In this chamber 36- thejrewis furthermore tiltably movable a reciprocable lever-38; (Figs.- 3:and"5) which is pivoted at37. The reciprocable 1ev'er"38 is tiltable'between two extreme positions.namely an active position (Fig. 5) whereinits..-1ower end-is disposed torwardmost, and an inactiveposition (Fig. 9 )"wherein its lowermost end is disposed rearmost. The lower part 39- ('Figs. 3 and 5) ofthelever 38 engages-the groove '25 of the flange 23. The upper part of the lever-38 -is curved and forms a cam follower 40 for acarn roll 43.

The roll 43 is carried on a tiltable retractable actuating lever 42 (Figs. 3 and 5) which'is pivoted with its .forward 'end'about 'a'pin 45 -'in a recess 44 to the body 11.

The lever 42 base slot- 41*th1'0ugh'" which'there extends the cam follower 40 of the lever 38. The actuating lever 42 to the set position (Fig. 5) is controlled by a lifting mechanism'49 that includes a rope or cable 48 that engages with a loop 47 (Fig. 3) the free end of the lever 42. The lifting mechanism 49 may be controlled from electromagnetic actuating means 87 (Fig. 11). When the lifting mechanism is released, the springs 30 will turn the lever 38 in the opposite direction, thereby returning the lever 38 as well as the tiltable lever 42 to their inactive positions. The lifting mechanism 49 includes a tube 51 seated in a tubular extension 50 of the body 11.

A tiltable member 52 is hinged to the body 11 and has its major portion disposed frontwardly of the face of the body 11. The tiltable member 52 includes two parallel lugs 53 that extend into the frontal recess 44 of the body 11 and are pivoted to the body 11 about a pin 54. The pin 54 is disposed lower than the pin 45 of the lever 42. The tiltable member 52 is provided with a central upright slot 55 and has a horizontal groove 56 formed in the front face above the slot 55. The lower part of the tiltable member 52 is provided with lateral flanges 57 (Fig. 3) against which there abut from the rear two pressure rods 59 which are slidably guided in horizontal bores 58 of the body 11. The pressure rods 59 extend rearwardly into the hollow chamber 36 of the body 11, and their rear ends extend into the path of lateral flanges 60 which are formed on the lower end portion of the lever 38. A rod 61 is provided which is guided in a horizontal bore 62 of the body 11, and disposed mid-way between the pressure rods 59 and located below the same. The front end of the rod 61 is disposed for abutment with a bridge portion of the tiltable member 52 that is formed below the slot 55 thereof, and the rear end of the rod 61 extends to the chamber 36 and is adapted to abut against the front face of the upright leaf spring 34.

A compression spring 63 (Fig. 5) extends from a recess that is formed in the front surface of the body 11, and exerts pressure with its front end against the top portion of the tiltable member 52, urging the latter into a rest position (Fig. 9) wherein the tiltable member 52 presses rearwardly the pressure rods 59 and the rod 61, whereby the rods 59 will press rearwardly the lower portion of the lever 38, and the rod 61 will press rearwardly the lower end of the leaf spring 34.

A latch member 65 (Figs. 3 and 5) extends through the slot 55 of the tiltable member 52, and has an extension 66 which is pivoted about the pin 45 to the body .11. The upper end of the latch member 65 forms a rearwardly projecting finger 67 which is adapted, when in the active position (Figs. 5 and 7), to engage the groove 56 of the front face of the tiltable member 52. The lower forward end of the latch member 65 is pointed frontwardly and forms a nose 68 which is adapted to cooperate with the needle bar 4; the nose 68 projects in the active position of the latch member 65 (Figs. 5 and 7) into the path of the needle bar 4, and may be engaged by the needle bar 4 to tilt the latch member 65 into the rest position (Fig. 9) thereof.

A spiral spring 69 (Fig. 5) surrounds the pivot pin 54, and exerts pressure with one arm 70 against the lower edge 71 of the slot 44 of the body 11, and with its other arm 72 exerts pressure from the rear against the latch member 65. The spring 69 tends to turn the latch member 69 into the active position (Figs. 5 and 7).

On the underside of the needle plate 8 (Figs. 2 and 4 there is mounted a thread severance device, of conventional construction, for the lower thread 84. It comprises a guiding groove 72 that extends at right angle to the work feeding direction A (Fig. 1). A cuttlng knife 73 (Fig. 4) is secured to the needle plate by means of a counter-sunk screw 74. A slide 76 18 m a sliding engagement with the cutting knife 73, and is guided in the groove 72, and includes a hook 75. A spring 77 presses the slide 76 towards the cutting knife 73. A pin 78 extends downwardly from the slide 76, and projects into a slot 79 of one arm of a lever 80 that is jonrnalled on the underside of the needle plate 8. The other arm of the lever 80 is connected to a pulling device 81 and to a retraction spring 87.

The operation of the above described device is as follows:

A work piece 85 (Figs. 5, 7) is provided with a seam 86. The needle thread or upper thread 83, and the lower thread 84, are to be cut off. As a first step, the operator will move the needle bar 4 approximately to the topmost position (see Fig. 5) and thereafter will cause the cable 48 to be pulled upwardly to lift the lever 42 into its horizontal upper position (Fig. 5). The lifting of the cable 48 of the lifting mechanism 49 may be accomplished by the actuation of the electromagnetic actuating means 87 to which the cable 48 is connected. The lifting of the cable 48 causes turning of the tiltable lever 42 from the rest position (Fig. 9) to the set position (Fig. 5).

During the upward tilting movement of the actuating lever 42, the roll 43 thereof will push to the rear the cam follower portion 40 of the reciprocable lever 38, thereby tilting the lever 38 about the pivot 37, from the inactive position (Fig. 9) to the active position thereof (Fig. 5). The lower part 39 of the lever 38 engages the groove 25 of the flange 23 of the slide 19, and during the tiltingto the active position will push the slide 19 together with the outer vise jaw 20 forwardly towards the upper thread 83. In the raised position of the needle bar 4 (Fig. 5) the upper thread 83 is tensioned vertically and, when the slide 19 is pushed forwardly, the upper thread 83 will be engaged by the inclined slot 22 of the slide 19 (Figs. 5 and 6).

During the tilting movement of the lever 38 to the active position, the lateral flanges 60 thereof will push forwardly the pressure rods 59, causing rotation of the tiltable member 52 from the rest position (Fig. 7) into the active position (Fig. 5). This turning of the tiltable member 52 is about the pivot 54, and against the pressure of the spring 63. During this turning of the tiltable member 52 to the active position, the latch member 65 will, under the pressure of the spring 69, be tilted about the pivot pin 45, and will engage with its finger 67 the horizontal groove 54 of the tiltable member 52, coming to rest in the active position in which the nose 68 projects into the vertical path of the needle bar 4 (Fig. 5).

By the forward movement of the lower part of the tiltable member 52, the rearward pressure that had been exercised against the rod 61 will be released, thereby releasing the leaf spring 34 which will push forwardly the rod 32 and thereby place the inner vise jaw 31 in the forwardrnost position (Fig. 5).

Upon release of the pedal (not shown) of the lifting mechanism 49, the lever 42 will be released and will rotate downwardly about the pivot pin 45 to its rest position (Fig. 7 Thereupon the springs 30 will retract the slide 19, and the latter will return the lever 38 from the active position (Fig. 5) into the inactive position (Fig. 7).

The upper thread 83 which passes through the slot 22 (Fig. 6) will by the rearward movement of the slide 19 first be pressed by the outer vise jaw 20 against the inner vise jaw 31 which is pressed forwardly by the leaf spring 34. Both vise jaws 20 and 31, which form clamping means for the upper thread 83, thereafter will slide together rearwardly for a distance while still gripping the thread 83, until the outer vise jaw 20 is arrested in its rearward estless? :zmovement byttheabutment. impact1 between the'pin 26 atmtlzthelower front surface of the body' 11,-(Figr8).' During this a-tied rearward: movmnent of the two :jaws, the

28 to sever the upper thread 83.

After the lever, 3& has been returned to the inactive position (Fig. 7), the ;latch member-:65 will-'stillsremain in the upwardly tilted position 'wherein its nose .68'projects' t forwardly. into the I, path \ofzthexneedle .bar.

Simultaneously with-the .cuttingiof thenpper thread. 83 there will be cut the lower thread 84. The electromagnetic actuating means 87 which actuatesthe pulling mechanism 49, also. pulls at .thesame time the, pulling devicev 81 (Fig. 2),-to'tilt' the lever '80 to move thereby the hook 75 ofithe'1slide v76.tovvards..t-he.needle path until the slot behindzthe hook.75 is positioned in registry with the stitching hole ofzthe needle. plate..8. .The hook 75 will engage ;the lowerzthread .84 and, uponrelease ofthe pulling device .81, the spring .87 willretract .the slide 76 and the thread 84 will be cut by the knife 73. The end of the lower thread 84 will be engaged between the spring 77 and the underside of the slide 76.

The pressure foot 10 may be lifted in a conventional manner for the removal of the work piece 85, and work may be resumed thereafter at any desired place of the Work piece 85 following lowering of the pressure foot 10.

When the work on the sewing machine is resumed by the needle 82, the upper thread 83 will remain gripped between the jaws 20 and 31 (Fig. 7) until the needle bar 4 by impact actuation with the nose 68 returns the latch member 65 to the rest position (Fig. 9). Upon such impact, the finger 67 will be moved out of the groove 56 and will be positioned as shown in Fig. 9. At the same time, the movable member 52 will be tilted by the force of the spring 63, whereby the rod 61 will again tension the leaf spring 34 causing a further rearward movement of the inner jaw 31 (Figs. 9 and 10). By this further rearward movement of the inner jaw 31, the vise grip of the upper thread 83 will be released, and the thread 83 thereafter be moved by the needle 82 into the work piece 85 almost to its severed end, rendering possible the forming of a new seam after picking up the lower thread 84.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Having thus described the invention, what we claim as'new and desire to be secured by Letters Patent, is as follows:

1. In a thread severing device for sewing machines having a pressure foot and a needle plate and a needle bar carrying a needle, in combination, a first mechanism disposed below said needle plate for severing the lower thread, and a second mechanism operable for severing the upper thread and comprising a body connected to said pressure foot a cutter connected to said body and a releasable vise including jaws guided in said body for movement adjacent said cutter reciprocably in opposite directions towards and from the path of said needle and engaging and being settable for gripping said upper thread, said vise and cutter cooperating for severing said thread, means operable for moving said jaws from a rest position towards said needle path, and resilient means urging said jaws to return to said rest position, vise release means connected to said body and being movable between an active position wherein it projects into the path of said needle bar and blocks the return of one jaw and, respectively, an inactive position wherein it is spaced from said path and unblocks said one jaw, and means moving said release means into said active position during movement of said vise towards the needle path, said needle bar actuating said release means by impact during the last phase of the next succeeding downward stroke to return the release means to'the inactive position thereby to releaseusaid vise.

' 2; In a thread severing device for-sewing machines having a pressure footand a needle plate and a vertically movable needle bar carrying a needle, in combination, a

first mechanism disposedbelowsaid needle plate for severing the lower thread, and a second mechanism connected tosaid pressure foot andoperable' for severing the upper thread-and comprising a body connected to said pressure foot, avcutter connected to said body, and releasably 'actuatable thread clamp means guidedin said bodyand being adjacent: said cutter movable towards, and retract- ..able from, thepathwof said needle for first clamping said thread, said clamp. means cooperating-with'said ..means urging.said-jawsJto'returnto said rest position,

vise .release'means :connected. to said body and: being mov- 1 ablev between. an: active position'wherein it projectsinto the path of said needle bar and blocks the return of one jaw and respectively, an inactive position wherein it is spaced from said path and unblocks said one jaw, and means moving said release means into said active position during movement of said vise towards the needle path, said needle bar actuating said release means by impact during the last phase of the next succeeding downward stroke to return the release means to the inactive position thereby to release said vise.

3. In a device as claimed in claim 2, together with, means for actuating said clamping meam comprising a retractable first lever pivoted to said body and including a cam, a reciprocably movable second lever movable to and from a position of engagement with said clamping means and operable to actuate the same upon engagement and including a cam follower for said cam and operable to be moved by said first lever to said position to actuate said clamping means to engage said thread, and resilient means operable to return said second lever and to close and to retract said clamping means following retraction of said lever.

4. -In a device, as claimed in claim 2, the underside of one of said vise jaws forming a shearing head cooperating with said cutter to sever said upper thread.

5. In a device, as claimed in claim 2, said vise release means including a tiltable member pivoted to said body for tilting about a horizontal axis, and a latch member pivoted to said body and operable to be tilted for setting together with said control member and having a nose projecting in the set position into the path of said needle bar.

6. In a device, as claimed in claim 5, said tiltable member having parallel of its tilting axis a groove, said latch member being pivoted at a point below the pivot of said tiltable member andincluding a finger engaging in the set position said groove to latch said tiltable member in said position.

7. In a device, as claimed in claim 5, together with, resilient means urging said latching member towards the set position and urging said tiltable member from the set position.

8. In a thread severing device for sewing machines having a pressure foot and a needle plate and a needle bar carrying a needle, in combination, a first mechanism disposed below said needle plate for severing the lower thread, and a second mechanism operable for severing the upper thread comprising a body connected to said pressure foot, a cutter connected to said body, and thread clamp means guided in said body for movement adjacent said cutter towards and from the path of said needle and being operable for clamping the upper thread and subsequently cooperating with said cutting means for thread severing and thereafter releasing the upper thread, said clamp means including two jaws, resilient means urging said jaws to close, means for moving one jaw to engage said thread and subsequently releasing it for gripping the thread between said jaws, resilient means operable for moving said clamp means with closed jaws past said cutter for thread severance and means for moving the other jaw away from the first to release the thread thereafter, said means for moving said other jaw including a tiltable member pivoted to said pressure foot and tiltable between a set position and a clamp releasing position, a spring connected to said other jaw and normally urging said other jaw towards said one jaw, and a rod guided in said pressure foot and operable to be moved by said tiltable member upon release thereof into abutment with said spring to move the same against its tension to move said other jaw away from said one jaw thereby breaking the grip of said clamp means.

9. In a device, asclaimed in claim 8, together with, means for setting said tiltable member comprising at least one pressure rod guided for shifting in said body and operable to abut against said tiltable member for tilting it into the set position, said means for moving said one jaw including a movable lever, an extension formed on said lever, said pressure rod extending into the path of said extension, whereby said extension of said lever will shift said pressure rod to set said tiltable member.

10. In a device, as claimed in claim 8, together with, abutment means between said one jaw and said body for limiting the movement thereof in the direction from said needle path.

11. 'In a device, as claimed in claim 8, together with, pulling devices for said mechanisms operable from the exterior of said sewing machine.

12. In a device, as claimed in claim 11, said pulling devices comprising electromagnetic pulling means.

References Cited in the file of this patent UNITED STATES PATENTS 952,010 Kiewicz Mar. 15, 1910 1,816,308 Allen July 28, 1931 1,962,905 Miller June 12, 1934 2,077,531 Pudelko Apr. 20, 1937 2,707,927 Artzt et al. May 10, 1955

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