US3173391A

US3173391A - Chain stitch device for lock stitch sewing machines

Info

Publication number: US3173391A
Application number: US300561A
Authority: US
Inventors: Ernest H Doerner
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1963-08-07
Filing date: 1963-08-07
Publication date: 1965-03-16
Anticipated expiration: 1982-03-16
Also published as: GB1007698A

Description

March 16, 1965 E. H. DOERNER CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES 3 Sheets-Sheet 1 Filed Aug. 7, 1963 R m E V W.

ERNEST H. DOERNER WITNESS TTORNE Y March 16, 1965 E. H. DOERNER CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES Filed Aug. '7, 1963 3 Sheets-Sheet 2 Fig.4

INVENTOR. ERNEST H. DOERNER I (fa-M ATTORNEY March 16, 1965 E. H. DOERNER CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES 3 Sheets-Sheet 3 Filed Aug. 7, 1963 I N VENTOR. ERNEST H. DOERNER WITNESS ATTORNEY United States Patent Ofitice 3,173,391 CHAIN STITCH DEVICE FQR LOCK STITCH SEWING MACHINES Ernest H. Doerner, Morris Plains, N.J., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Aug. 7, 1963, Ser. No. 300,561 4 Claims. (Cl. 112-468) This invention relates to sewing machines, and more particularly, to devices for converting a lock stitch sewing machine into a chain stitch sewing machine.

It is an object of this invention to provide devices attachable to a lock stitch sewing machine for converting the machine to chain stitch formation.

A further object of this invention is to provide chain stitch conversion devices comprising stationary elements fixedly secured relatively to the sewing machine frame and adapted to cooperate with the regular lock stitch forming instrumentalities of the sewing machine including needle, loop taker, needle thread take-up and work feeding mechanism unaltered in structure or cooperative relation from that required for the formation of lock stitches.

A still further object of this invention is to provide chain stitch conversion device-s of the above character supported on a throat plate exchangeable on a lock stich sewing machine to elfect the conversion to chain stitch formation.

The accompanying drawings illustrate a preferred embodiment of this invention in which:

FIG. 1 represents a head end elevational view of a lockstitch sewing machine with the bracket arm cover plate removed and portions of the bed broken away to illustrate the stitch forming instrumentalities having the chain stitch conversion device of this invention applied thereto,

FIG. 2 represents an enlarged top plan view of a portion of the work supporting bed of the sewing machine of FIG. 1 with the throat plate removed and the bed slide withdrawn to expose the stitch forming instru mentalities within the bed.

FIG. 3 is a detached perspective view of the elements carried on the throat plate which comprise the chain stitch conversion fittings of this invention,

FIG. 4 is a bottom plan view of the throat plate with the chain stitch fittings of this invention applied thereto,

FIG. 5 is an elevational view taken substantially along line 5-5 of the throat plate assembly of FIG. 4,

FIG. 6 represents a perspective view of fragments of the stitch forming instrumentalities of the sewing machine of FIG. 1 with the chain stitch conversion device of this invention including the needle thread and illustrating the position of parts and thread at needle penetration during the formation of chain stitches,

FIG. 6A represents a vertical cross sectional view taken substantially along line 6A6A of FIG. 6,

FIG. 7 represents a perspective view of fragments of the stitch forming instrumental-ides of the sewing machine similar to that of FIG. 4 but with the position of parts and thread illustrated shortly after needle loop seizure during the formation of chain stitches,

FIG. 7A is a vertical cross sectional view taken substantially along line 7A7A of FIG. 7,

FIG. 8 represents a perspective view of fragments of the stitch forming instrumentalities of the sewing machine similar to that of FIG. 4 but with the position of parts and thread illustrated at the upstroke of the needle and after the seized needle thread loop has been cast off the loop taker beak, and

FIG. 8A is a vertical cross sectional view taken substantially along line 8A8A of FIG. 8.

Patented Mar. 16, 1965 This invention provides for the conversion to single thread chain stitch sewing of a conventional lock stitch sewing machine. FIG. 1 illustrates a head end elevational view of a conventional household lock stitch sewing machine to which this invention may be applied.

The sewing machine frame includes a bed 11 from which rises a standard 12 supporting a bracket arm 13 overhanging the bed. A main shaft 14 journaled lengthwise in the bracket arm drives all of the moving parts of the sewing machine and may be actuated by an electric motor (not shown), by foot treadle or the like.

A counterbalanced crank 15 on the mainshaft 14 is operatively connected by means of a drive link 16 to a needle bar 17 endwise slidable in a bearing 18 in the bracket arm and carrying at its lower extremity an eye pointed needle 19. The crank 15 also actuates .a needle thread take-up lever 20 of which the motion is constrained by an anchor link 21. The path of a needle thread passes from a supply (not shown) to a thread tensioning device 22, through an eyelet 23 in the take up lever 20, and then through appropriate guides such as the thread guide 24 on the needle bar 17 and to the needle eye. This needle thread control arrangement is typical of that which is required for lock stitch formation. The use of the chain stitch conversion devices of this invention will operate successfully, however, with such lock stitch type needle thread controls.

Journaled in the bed on a loop taker shaft 30 is a loop taker indicated generally at 31. The loop taker illustrated in the drawings is a vertical axis rotary hook adapted to partake of two revolutions for each reciprocation of the needle. The loop taker is formed with a cup shaped body portion 32 formed with an inwardly extending loop seizing beak 33 adapted to engage and manipulate loops of thread from the needle 19 which as illustrated in FIG. 2 rcciprocates in a path which passes inwardly of the cup shaped loop taker body portion.

A bobbin case 34 is journaled within the loop taker body portion 32 and constrained against rotation therewith by means of a rotation restraining assembly 35 including a spring 36 which engages an abutment 37 on the bobbin case 34-. A bobbin accommodating cavity 38 is formed in the bobbin case within which a conventional thread carrying bobbin (notshown) may be placed with freedom to rotate.

The needle and loop taker thus far described are capable of producing lock stitches in a conventional manner. The loop seizing beak 33 of the loop taker will engage and carry loops of needle thread completely about the bobbin case and thus if a threaded bobbin is in place in the bobbin case the needle and bobbin threads will be concatenated into true lock stitches (Federal type #301) following each needle penetration. The loop taker may be driven at two revolutions for each needle reciprocation by means of a shaft 40 in the standard 12 driven by bevel gears 41 from the mainshaft and con nected in turn by bevel gears 42 to a bed shaft 43 which drives the loop taker shaft 30 by a set of bevel gears 44.

Illustrated in FIG. 1 is a work feeding mechanism of the drop feed variety. A feed dog 49 formed with a transverse web 50 operates through slots 51 in a throat plate 52 and is secured by screws 53 to a feed bar 54 beneath the bed. Feed advance and return movements are imparted to the feed bar from an oscillating feed advance rock shaft 55 connected to the feed bar by means of a rock arm 56. The feed advance rock shaft 55 is oscillated by means of conventional connections 57 in the standard from a feed cam 58 on the mainshaft 14. The connections 57 may include conventional regulating means 59 for varying the stitch length. Rising and falling motion is imparted to the feed bar from an oscillating feed lift rock shaft 60 in the bed. The feed lift rock shaft 60 is provided with a rock arm 61 connected by means of a link 62 to the feed bar 54. The feed lift rock shaft is oscillated by means of conventional connections 63 in the standard from a feed lift eccentric 64 on the mainshaft 14. It will be appreciated that as is conventional in the art the work feeding mechanism is timed relatively to the needle reciprocation so that the feed dog is lifted and advanced while the needle is raised out of any work on the throat plate, and the feed dog is lowered beneath the throat plate and returned while the needle descends.

Referring to FIGS. 2-5, the conversion device for rendering the above described lock stitch sewing machine suitable for sewing chain stitches includes a rigid metal bracket 70 secured beneath the throat plate 52 by screws 71. The bracket 76* extends transversely across the throat plate in front of the feed dog slots 51 in a shallow recess 72 formed beneath the throat plate. Bent downwardly therefrom so as to depend from the bracket '76 in front of a needle aperture 73 in the throat plate is a thread loop engaging finger 74. The side edges 75 of the thread loop engaging finger preferably diverge slightly from the bracket 70 downwardly so as to deter inadvertent dropping of a thread loop therefrom as will be explained hereinbelow.

Also secured beneath the throat plate 52 by the screws 71 is a leaf spring 76 which extends parallel to the bracket 70 and is bowed downwardly therefrom. At the extremity opposite the securing screws 71, the leaf spring is formed with an inturned portion 77 adapted slidably to embrace the bracket 70 in a notch 78 formed in the bracket. The leaf spring 76 forwardly of the thread loop engaging finger 74 is formed with a downwardly extending protrusion 79 which is preferably arranged slightly toward the right hand side of the thread loop engaging finger 74 as viewed in FIGS. 2 and 5.

Referring to FIGS. 2, 6 and 6A, a leaf spring 8t) is secured by a screw 81 to the bobbin case 34 on that side of the bobbin accommodating cavity 38 which faces the path of needle reciprocation. The leaf spring 8%) extends generally parallel to the bracket 70 and the leaf spring 76 associated with the bracket when the bobbin case is properly restrained within the loop taker. An abutment projection 82 formed on the bobbin case extends over a portion of the leaf spring 80 as illustrated in FIGS. 6 and 6A, thus providing a stop limiting the upward position of the free extremity of the leaf spring 80. When the throat plate 52 is secured on the sewing machine bed the protrusion 79 on the leaf spring 76 engages the projection 82 and the. thread loop engaging finger 74 engages and shifts the leaf spring 80 downwardly away from the stop projection 82.

Referring to FIGS. 6, 7 and 8 and the companion FIGS. 6A, 7A and 8A, the operation of a sewing machine fitted with the chain stitch conversion device of this invention will now be described.

FIGS. 6 and 6A illustrate the position of the parts of the sewing instrumentalities during the formation of chain stitches and particularly during that portion of a stitch forming cycle when the needle is penetrating the work at S. The feed dog 49 will occupy a rearward position toward the left as viewed in FIG. 6A, having just completed a feed stroke, and will be starting to drop out of engagement with the work. The needle 19 will have carried through the work at S and through a needle aperture 73 in the throat plate a loop of thread of which a supply limb T leads to the thread guide 24, take up eyelet 23, tension device 22 and thence to the supply, and a work limb T leads to the previous needle penetration 8-1 in the work. Tracing the work limb T of the new needle thread loop T T beyond the previous needle penetration S4 in the work it will form a thread loop T which extends under the feed dog web 59 and around the thread loop engaging finger 74-. The new needle thread loop T T will be carried by the needle feed dog upon being lowered and moved toward the thread loop engaging finger 74 during the return stroke of the feed dog will have forced the thread lop T downwardly on the thread loop engaging finger 74, the loop T being held only by the constraining influence of the spring 3% FIGS. 8 and 8A illustrate the positions as the needle nears the top of its stroke. The new needle thread loop T T will have been carried by the loop taker beak completely about the bobbin case 34 and in so doing will have applied sufficient tension to the thread loop T as to draw the loop T between the finger 74 and the leaf spring 86. The take up lever 20 will act to draw the loop T T taut but while any slack remains the new needle thread loop T T will be constrained by the protrusion 79 on the interengaging leaf spring 76 and the abutment 82, as illustrated in FIGS. 8 and 8A, and will not fall between the bobbin case 34 and the thread loop engaging finger 74. The feed dog 49 will be raised into engagement with the work and partaking of a feed advance stroke.

As the sewing machine take-up lever 20 sets the stitch, the new needle thread loop T T will be drawn taut and pulled between the abutment 82 and the protrusion 79 on the leaf spring 76. The thread loop T T will then snap onto the thread loop engaging finger 74. The thread loop once taut on the finger 74- will remain thereon until it is forced downwardly and off the finger by the thread stripping action of the feed dog web 50.

When the needle again penetrates the work, what had been the new needle thread loop T T becomes the detained thread loop T as illustrated in M65. 6 and 6A thus completing a cycle of chain stitch forming operation.

Since the lop taker 31 will carry needle thread loops completely about the bobbin case 34 during chain stitch formation using the conversion fittings of this invention, just as in lock stitch formation, a thread carrying bobbin if placed in the bobbin case cavity 38 will deliver a locking thread to the chain stitch seam. When chain stitching, however, the bobbin or locking thread will not be drawn tightly into the work as in lock stitching because in chain stitching the stitches are set during each succeeding needle penetration. In chain stitching therefore, the bobbin or locking thread will reeve through the chain stitch loops on the underside of the work and may be severed and drawn out conveniently to permit the chain stitch seam to ravel if desired.

To convert the lock stitch sewing machine for chain stitching with the conversion fittings of this invention, it is only required that the conventional throat plate used for lock stitch formation be exchanged for the throat plate as illustrated in FIGS. 4 and 5 having the

elements

70 and 76 secured thereto. The spring on the bobbin case is compatible with both lock and chain stitch formation and thus the same bobbin case 34 may be used for either lock or chain stitch formation.

In lock stitch formation, a round needle aperture in the throat plate is conventional. In chain stitch formation, an elongate needle aperture 73 as illustrated in the drawings is preferable to provide clearance for thread movement in the delayed setting of the stitches.

Having thus set forth the nature of this invention what is claimed herein is:

1. In a sewing machine having lock stitch forming instrumentalities including a frame having a work support formed with a needle aperture, a thread-carrying eyepointed needle supported above the work support for endwise reciprocation through said needle aperture, a circularly moving loop taker disposed below said work support, means for driving said needle and loop taker in timed relation for the seizure of a loop of thread from the eye of the needle by said loop taker during each stroke of the eedle downwardly through said needle aperture and the release of said seized loop by the loop taker during each succeeding upward stroke of the needle, a bobbin supporting case journaled in said loop taker, stop means sustained on said frame for constraining said bobbin supporting case from circular movement with said loop taker, and a linear Work feeding mechanism effective to advance work fabric on said work support in one direction from said needle aperture between each needle penetration thereof, means for sewing chain stitches using thread carried by said needle comprising a stationary thread loop engaging finger carried by said frame and having a free extremity extending in a direction from said work support substantially parallel to said path of endwise needle reciprocation and arranged at that side of said path of needle reciprocation which is opposite the direction of advancement of work fabric by said work feeding mechanism, needle thread take-up mechanism effective alternately to draw tight and slacken said needle thread, opposed spring means and spring abutment means arranged between said frame and said bobbin case on that side of said thread loop engaging finger which is opposite to said needle aperture for resiliently constraining passage of thread loops from said loop taker onto said thread loop engaging finger until said thread loops are drawn taut by said needle thread take-up mechanism, a stripping element disposed between said thread loop engaging finger and the path of endwise reciprocation of said needle, and means for reciprocating said stripping element in timed relation with said endwise reciprocation of said needle and toward the free end of said thread loop engaging finger as said needle penetrates said needle aperture.

2. In a device as set forth in claim 1, in which said spring abutment means is carried by said bobbin case and said spring means comprises a leaf spring secured relatively to said sewing machine frame bearing resiliently against said abutment means.

3. A device as set forth in claim 1 in which the sewing machine frame is fitted with a removable throat plate formed with said needle aperture and in which said stationary thread loop engaging finger is fixed beneath said throat plate.

4. In a sewing machine having lock stitch forming instrumentalities including a frame having a work support formed with a needle aperture, a thread-carrying eyepointed needle supported above the work support for endwise reciprocation through said needle aperture, a circularly moving loop taker carried below said work support on an axis substantially parallel to the path of end- Wise reciprocation of said needle, means for driving said needle and loop taker in timed relation for the seizure of a loop of thread from the eye of the needle by said loop taker during each stroke of the needle downwardly through said needle aperture and the release of said seized loop by the loop taker during each succeeding upward stroke of the needle, a bobbin supporting case journaled in said loop taker, stop means sustained on said frame for constraining said bobbin supporting case from circular movement with said loop taker, and a linear work feeding mechanism effective to advance work fabric on said work support in one direction from said needle aperture between each needle penetration, means for sewing chain stitches using thread carried by said needle comprising a stationary thread loop engaging finger carried by said frame and having a free extremity extending in a direction from said work support substantially parallel to said path of endwise needle reciprocation and arranged at that side of said path of needle reciprocation which is opposite the direction of advancement of work fabric by said work feeding mechanism, needle thread take-up mechanism effective alternately to draw tight and slacken said needle thread, a projection on said bobbin case, a first leaf spring secured relatively to said frame adjacent to said thread loop engaging finger, said first leaf spring being bowed into resilient engagement with said bobbin case projection on that side of said thread loop engaging finger which is opposite to said needle aperture for constraining passage of thread loops from said loop takeronto said thread loop engaging finger until said thread loops are drawn taut by said needle thread take-up mechanism, a second leaf spring secured on said bobbin case and extending therefrom into abutting relation beneath said thread loop engaging finger, a thread stripping element disposed between said thread loop engaging finger and the path of endwise reciprocation of said needle, and means for reciprocating said stripping element in timed relation with said endwise reciprocation of said needle and toward the free end of said thread loop engaging finger as said needle penetrates said needle aperture.

References Cited by the Examiner UNITED STATES PATENTS 1,014,033 1/12 Baker 112197 2,999,472 9/61 Yamano 112-168 FOREIGN PATENTS 58,545 1/ 91 Germany. 809,217 2/59 Great Britain.

JORDAN FRANKLIN, Primary Examiner.

Claims

1. IN A SEWING MACHINE HAVING LOCK STITCH FORMING INSTRUMENTALITIES INCLUDING A FRAME HAVING A WORK SUPPORT FORMED WITH A NEEDLE APERTURE, A THREAD-CARRYING EYE-RT POINTED NEEDLE SUPPORTED ABOVE THE WORK SUPPORT FOR ENDWISE RECIPROCATION THROUGH SAID NEEDLE APERTURE, A CIRCULARLY MOVING LOOP TAKER DISPOSED BELOW SAID WORK SUPPORT, MEANS FOR DRIVING SAID NEEDLE AND LOOP TAKER IN TIMED RELATION FOR THE SEIZURE OF A LOOP OF THREAD FROM THE EYE OF THE NEEDLE BY SAID LOOP TAKER DURING EACH STROKE OF THE NEEDLE DOWNWARDLY THROUGH SAID NEEDLE APERTURE AND THE RELEASE OF SAID SEIZED LOOP BY THE LOOP TAKER DURING EACH SUCCEEDING UPWARD STROKE OF THE NEEDLE, A BOBBIN SUPPORTING CASE JOURNALED IN SAID LOOP TAKER, STOP MEANS SUSTAINED ON SAID FRAME FOR CONSTRAINING SAID BOBBIN SUPPORTING CASE FROM CIRCULAR MOVEMENT WITH SAID LOOP TAKER, AND A LINEAR WORK FEEDING MECHANISM EFFECTIVE TO ADVANCE WORK FABRIC ON SAID WORK SUPPORT IN ONE DIRECTION FROM SAID NEEDLE APERTURE BETWEEN EACH NEEDLE PENETRATION THEREOF, MEANS FOR SEWING CHAIN STITCHES USING THREAD CARRIED BY SAID NEEDLE COMPRISING A STATIONARY THREAD LOOP ENGAGING FINGER CARRIED BY SAID FRAME AND HAVING A FREE EXTREMITY EXTENDING IN A DIRECTION FROM SAID WORK SUPPORT SUBSTANTIALLY PARALLEL TO SAID PATH OF ENDWISE NEEDLE RECIPROCATION AND ARRANGED AT THAT SIDE OF SAID PATH OF NEEDLE RECIPROCATION WHICH IS OPPOSITE THE DIRECTION OF ADVANCEMENT OF WORK FABRIC BY SAID WORK FEEDING MECHANISM, NEEDLE THREAD TAKE-UP MECHAMISM EFFECTIVE ALTERNATELY TO DRAW TIGHT AND SLACKEN SAID NEEDLE THREAD, OPPOSED SPRING MEANS AND SPRING ABUTMENT MEANS ARRANGED BETWEEN SAID FRAME AND SAID BOBBIN CASE ON THAT SIDE OF SAID THREAD LOOP ENGAGING FINGER WHICH IS OPPOSITE TO SAID NEEDLE APERTURE FOR RESILIENTLY CONSTRAINING PASSAGE OF THREAD LOOPS FROM SAID LOOP TAKER ONTO SAID THREAD LOOP ENGAGING FINGER UNTIL SAID THREAD LOOPS ARE DRAWN TAUT BY SAID NEEDLE THREAD TAKE-UP MECHANISM, A STRIPPING ELEMENT DISPOSED BETWEEN SAID THREAD LOOP ENGAGING FINGER AND THE PATH OF ENDWISE RECIPROCATION OF SAID NEEDLE, AND MEANS FOR RECIPROCATING SAID STRIPPING ELEMENT IN TIMED RELATION WITH SAID ENDWISE RECIPROCATION OF SAID NEELDE AND TOWARD THE FREE END OF SAID THREAD LOOP ENGAGING FINGER AS SAID NEEDLE PENETRATES SAID NEEDLE APERTURE.