US3599588A

US3599588A - Thread-carrying looptaker for chain stitch sewing machines with thread catcher and clamping device

Info

Publication number: US3599588A
Application number: US25680A
Authority: US
Inventors: Eugen Angele
Original assignee: GM Pfaff AG
Current assignee: GM Pfaff AG
Priority date: 1969-04-26
Filing date: 1970-04-06
Publication date: 1971-08-17
Anticipated expiration: 1988-08-17
Also published as: DE6916929U; GB1263205A

Abstract

A combined thread-carrying looptaker and cutting device for chain stitch sewing machines including a thread catcher is fitted with means to clamp, during initiation of a sewing operation, the free cut length of the thread comprising a spring-loaded clamping plate rotatively mounted upon the looptaker body about a pivot axis spaced from and parallel to the axis of a guide bore in the looptaker through which is passed the looptaker thread. The clamping plate has a further guide bore normally registering with the guide bore in the looptaker body and is deflected from its normal position by an abutment thereof camming with the edge of a thread catcher during the latter''s displacement from its rest position to the thread-cutting position, resulting in clamping of the thread between the plate and looptaker body. The pull on the thread upon formation of the initial stitches of a subsequent sewing operation causes the automatic return of the clamping plate to its normal operating position.

Description

United States Patent [54] THREAD-CARRYING LOOPTAKER FOR CHAIN STITCH SEWING MACHINES WITH THREAD CATCHER AND CLAMPING DEVICE 7 Claims, 3 Drawing Figs.

[52] U.S. Cl 1 12/252, 1 12/253 [51] Int. Cl D05b 65/00 [50] Field of Search 112/252, 253

[56] References Cited UNITED STATES PATENTS 3,371,633 3/1968 Hedegaard .1. 112/252 3,354,852 11/1967 Kennedyetal.... 3,532,065 9/1968 Marforio Primary Examiner.lames R. Boler AttorneyGreene & Durr ABSTRACT: A combined thread-carrying looptaker and 1 upon the looptaker body about a pivot axis spaced from and parallel to the axis of a guide bore in the looptaker through which is passed the looptaker thread. The clamping plate has a further guide bore normally registering with the guide bore in the looptaker body and is deflected from its normal position by an abutment thereof camming with the edge of a thread catcher during the latters displacement from its rest position to the thread-cutting position, resulting in clamping of the thread between the plate and looptaker body. The pull on the thread upon formation of the initial stitches of a subsequent sewing operation causes the automatic return of the clamping plate to its normal operating position.

PATENTED AUG] 7 Ian Fig.3

Fig.2

INVENTOR EU rE V Ali/4'55 mael- B477! 4 r/OA'NEY THREAD-CARRYING LQOPTAKER FOR CHAIN STITCH SEWING MACHINES WITH THREAD CATCHER AND CLAMPING DEVICE I The present invention relates to double chain stitch sewing machines, more particularly of the type including a threadcarrying oscillating looptaker, a thread catcher to seize the looptaker threadat the end of a sewing operatiomto draw out the thread to a length sufficient for the sewing of the starting stitches during a subsequent sewing operation, and operate the thread into engagement with a thread-cutting knife, and a clamping ,device to'lock the free cut length of the thread during formation of the starting stitches.

ln order to prevent the looptaker thread, drawn out prior to cutting by the thread catcher of a conventional thread cutting device to a length sufficient to enable formation of the next starting stitches, from being withdrawn from the thread guide of the looptaker by the action of the thread takeup withdrawing definite lengths of thread from the supply spool required for stitch formation, and furthermore, in order to ensure a safe initiation of the starting stitches, it has already become known to clamp the end of the thread portion emerging from the egress guide bore of the looptaker between the thread catcher of the cutting device and a stationary abutment disposed upon the frame of the sewing machine and exteriorly of the stitchforming tools, until such time as to ensure a safe formation of the starting stitches and to subsequently return the thread catcher to its inoperative or rest position, to thereby release the looptaker thread. A relatively complex operating and control mechanism for the thread catcher is required in a thread: clamping device of this type.

According to another proposal, a clamping spring for the free end of the looptaker thread is disposed in the space underneath the stitching plate and within the operating path of the thread catcher of the cutting device, to clamp the free end ofthe thread, cut after been drawn out to a sufficient length by the thread catcher plate," between said clampingspring and stitching plate. A drawback of such a thread clamping arrangement is the fact that the clamping force produced by the spring varies widely for threads of different diameters and that adaptation of the clamping pressure to the thread diameter is extremely difficult to achieve in practice for the reasons, among others, that the clamping pressure must have a sufficient value to enable the thread takeup to withdraw thread from the supply spool without withdrawing the free end of the thread from the clamp, on the one hand, and that a'substantial pull on the thread is required during the work feed or advance stroke to withdraw the thread from the clamp, on the other handl Among other drawbacks, this may result in a contraction of the fabric near the start of a seam, especially during sewing of relatively thin and light materials, due to the locking of the free end of the thread by the clamp and lack of sufficient loose thread for the sewing of the starting stitches of the seam, as well as due to the action on the thread by the thread takeup.

Accordingly, an important object of the present invention is the provision of a looptaker thread-clamping device for chain stitch sewing machines of the referred to type which, while being of relatively simple construction, is substantially devoid of the foregoing and related defects and drawbacks.

A more specific object of the invention is the provision of a ,threadclamp of this type which is closed by the thread catcher of acutting-device and opened automatically after the sewing of the starting stitches of the new seam.

I The invention, both as to the foregoing and ancillary objects as well as novel aspects thereof, will be better understood from the following detailed description, taken in conjunction with the accompanying drawing forming part of this disclosure and in which: 1

FIG, 1 is a perspective view of a conventional thread-carrying chain stitch looptaker and thread catcher, embodying an automatic thread-clamping device constructed in accordance with the principles of the invention;

seizure of the looptaker thread and of its camming edge in initial engagement with said clamping plate; and

FIG. 3, being similar to FIG. 2, shows the device in the clamping position at the end of the forward operating stroke of the thread catcher.

Like reference numerals denote like parts in the different views of the drawing.

With the foregoing objects in view, the invention, according to one aspect, involves generally the provision of a springloaded clamping plate rotatively mounted upon the looptaker body between a normal and a clamping position, with the pivot axis of said plate being parallel to and spaced a sufficient distance from the axis of the ingress guide bore of the looptaker passing the looptaker thread and with said plate having a guide bore registering with said ingress guide bore during its normal operating (sewing) position, in such a manner as to clamp the thread in the deflected or clamping position of said plate by the resilient pressure between the plate and the adjoining surface of the looptaker body. Operation of the clamping plate from its normal to its clamping position is effected by an abutment thereof camming with an edge of the thread catcher of the cutting device during the forward operating stroke of the thread catcher plate towards the cutting position.

The rotatable mounting of the clamping plate upon the looptaker body and relative positions of the guide bores disposed in said plate and body and passing the looptaker thread has the effect that the pull on the thread by the takeup between the supply spool and looptaker and the tension upon the thread after completion of the starting stitches are substantially at right angle to the direction of the thread within the deflecting range between the guide bores, whereby to require a relatively slight deflecting force to automatically return the clamping plate to its normal operating position after formation of a safe number of starting stitches of a new seam being sewn, due to the substantial leverage effect as a result of the distance between the pivot axis and thread guide bore of the plate.

In order to adapt the clamping device for use with threads of different materials and thread diameter, the clamping pressure upon the plate is adjustable, such as by the provision of a clamping spring and setscrew or the like, in the manner as will become further apparent as the description proceeds in reference to the drawing.

The latter shows, by way of example, a thread-carrying chain stitch looptaker comprising an oscillating bar 1, a looptaker foot 2 extending transversely from said bar and a neck or support 3 extending from said foot substantially parallel to the bar 1 and terminating in the needle thread loop-seizing looptaker beak 4, all of conventional construction. Beak 4 is provided with an egress guide bore 5 near its pointed end and a longitudinal guide groove 6 for passage and guidance in a known manner, of the looptaker thread 20 taken from a supply spool (not shown).

During operation, the point of the beak 4 moves along an either straight oscillating path 4a or an elliptical oscillating path 4b, depending on the type of chain stitch sewing machine, for cooperation, in a known manner, with the needle thread (not shown) in the formation of double chain stitches in the work operated on.

Provided in the neck 3 near the inner end of the beak 4 is an ingress thread guide bore 7 through which is passed the supply limb of the thread 20 supplied by the thread takeup (not shown) which is interposed between the supply spool and and the looptaker in accordance with known sewing machine construction.

Affixed to the underside of the foot 2, by means of a securing screw 9 and in accordance with the improvement of the present invention, is a bracket or carrier 8 fitted with a pivot pin 10, the axis of which is spaced from and parallel to the axis about the pin 10 is a clamping plate 17 which is provided with a further thread guide bore 1 l, registering with the guide bore 7 in the normal position of the plate, as shown in FIGS. 1 and 2, during operation of the sewing machine. Plate 17 is furthermore provided with a slot 12 and has an upper extension 13, forming an abutment 14 for cooperation with the oblique camming edge 15 of a thread catcher plate 16 forming part of a conventional thread-cutting device. The thread catcher l6 functionsin a known manner by seizing and'drawing out the work limb of the looptaker thread on its way to the'cutting knife, as indicated by the arrow in the drawing, in such a manner as to provide a length of free thread upon cutting sufficient to enable the safe initiation of the starting stitches during a'subsequent sewing operation.

The clamping plate 17 frictionally engages the outer surface of the neck or support 3 by the action of a flat spring 18 overlying the outer surface of the plate 17 and being secured by the aid of an adjustable setscrew 19 passing through a bore in the'spring 18 and the slot 12 in the plate 17, and threadedly engaging'th'e neck 3. The clamping pressure between the plate 17 and neck 3 may thus be adjusted, to suit existing operating conditions and requirements and to define two fixed limit positions of the clamping plate by the slot 12, viz. an operative position of registry of the guide bores 7 and 1 1, FIGS. 1 and 2, and a temporary deflected or clamping position after-cutting of the thread, as shown in FIG. 3.

As previously described,.the looptaker thread is passed, in the manner shown, from the supply spool and via the thread takeup (not shown) through the guide bore 11 of the clamping plate 17, the ingress guide bore 7 of the looptaker neck 3, along the guide groove 6, through the guide bore of the beak 4, and on to the work being operated on. The part of the thread between the bore 5 and the work is ordinarily known as the work limb of the thread to be cutupon completion of the sewing operationby the thread-cutting device. During operation of the sewing machine, with the axes of the guide bores 7 and 11 being in registry, as shown in FIGS. 1 and 2, thethread may be drawn freely through the looptaker, as required for the stitching operation.

In operation, if, upon stoppage, at the end of a seam-sewing operation, of a sewing machine equipped with a clamping device according to the invention, the thread catcher 16 of the cutting device is displaced, either manually or automatically, in thedirection opposite to the point of the looptaker beak 4, as indicated by the arrow in FIG. 1, to seize the work limb of the thread 20 above said beak, to draw out the thread to a length sufficient to ensure the safe formation of starting stitches during the next sewing operation, and to operate the threadinto. engagement with a stationary cutting knife (not shown) of known construction, the edge 15 of the thread catcher 16 engages the abutment 14 of the clamping plate 17, as shown in FIGS. 1 and 2, whereby to deflect said plate about the pivot to its thread-clamping position, as shown in FIG. 3. In the latter, the thread 20 is clamped between the springloaded plate 17 and the outer surface of the neck 3. Subsequently, the thread catcher 16 is displaced to its rest or starting position (not shown) in the direction opposite to the arrow, whereby to retain plate 17 in the clamping position by the pressure exerted by the spring 18.

During starting of the next sewing operation or cycle, the clamping device remains in the closed or clamping position, FIG. 3, until the free starting length of the thread 20 has become safely interlocked with the needle thread during the formation of the first chain stitch or stitches of the new seam being sewn. There is ensured thereby that the free end of the looptaker thread is utilized in its full previously drawnout length for the formation of the starting stitches, preventing thereby distortion or tightening of the fabric on the one hand, and withdrawal of the thread'20 from its guide bores 5, 7 and 11 by the action of the thread takeup interposed between the clamping point and supply spool, on the other hand.

After the starting stitches of the new seam have been sewn and the free drawnout end of the looptaker thread has been fully consumed, continuation of the stitch formation will result in tensioning of the limb of the thread between the clamping point and the work accompanied by the simultaneous pull on the thread limb between the clamping point and thread takeup by the action of the latter. Both forces act substantially at right angle to the thread between the guide bores 7 and with a leverage determined by the distance between the pivot 10 and guide bore 11 of the plate 17, in such a manner as to safely and automatically deflect or return the latter by a relatively slight force from the clamping position, FIG. 3, to the normal or sewing position, FIG. 2, and to enable the looptaker thread 20 to be withdrawn freely from the supply spool via the thread takeup and thread guide bores 11, 7 and 5, during continued sewing operation. The limit operating positions of the plate 17 (sewing and clamping positions) are determined by the slot 12 in the plate 17, while the clamping pressure may be adjusted by the aid of the setscrew 19, to suit different types of thread and thread diameters.

In the foregoing, the invention has been described in reference to a specific exemplary or illustrative device. It will be evident that variations and modifications, as well as the substitution of equivalent parts for those shown, may be made without departing from the broader spirit and purview of the invention.

I claim:

1. In a chain stitch sewing machine, the combination comprising:

l. a thread-carrying oscillating looptaker including a support having a first thread guide bore and a looptaker beak extending from said support,

2. a thread catcher forming part of a cutting device and operable from a rest position to a cutting position, for the drawing out of the looptaker thread, and back to said rest position upon cutting of the thread,

3. a spring-urged thread-clamping plate in resilient frictional engagement with and rotatively mounted upon said support about a pivot axis spaced from and parallel to the axis of said first guide thread bore, said plate having a second thread guide bore registering with said first guide bore in its inoperative position during operation of the sewing machine, and

4. means to deflect said plate to an operative position by displacement of said thread catcher from said rest position to said cutting positions,

5. whereby to relatively displace said first and second guide bores and to clamp said thread between said plate and said support.

2 In a chain stitch sewing machine as claimed in claim 1, wherein said thread catcher has the form of a plate and said clamping plate has an abutment camming with said thread catcher plate, to deflect said clamping plate during operation of said thread catcher from its rest position to its cutting posi- Hon.

3. In a chain stitch sewing machine as claimed in claim 1, including means to fix the inoperative and operative positions of said clamping plate.

4. In a chain stitch sewing machine as claimed in claim 1, including an adjustable clamping spring urging said plate against said support.

5. In a chain stitch sewing machine as claimed in claim 1, including a flat spring having a perforation and overlying said clamping plate, and a setscrew passing through said perforation and a slot in said plate and threadedly engaging said support, for adjusting the clamping pressure between said plate and said support and to fix the inoperative and operative position of said plate by said slot.

6. In a chain stitch sewing machine as claimed in claim 1, including adjusting means to vary the clamping pressure between said plate and said support, to automatically return said plate from its operative position to its inoperative position by the pull on the thread after sewing of a predetermined number of starting stitches.

7. In a chain stitch sewing machine, the combination comprising:

2. a thread catcher plate forming part of a cutting device and operable from a rest position to a cutting position, for the drawing out of the looptaker thread, and back to said rest position upon cutting of the thread,

3. a spring-urged thread-clamping plate in resilient frictional engagement with and rotatively mounted upon said support about a pivot axis spaced from and parallel to the axis of said first guide bore, said clamping plate having a third guide bore registering with said first guide bore in its inoperative position during operation of the sewing machine,

. means to deflect said clamping plate to an operative position by camming with said thread catcher plate during displacement of the latter from its rest position to its cutting position,

. whereby to relatively displace said first and third guide bores and to clamp said thread between said clamping plate and said support,

. the pressure between said clamping plate and said support being such as to cause an automatic return of said plate from its operative position to its inoperative position by the pull on the thread after sewing of the predetermined number of starting stitches.

Claims

1. In a chain stitch sewing machine, the combination comprising: 1. a thread-carrying oscillating looptaker including a support having a first thread guide bore and a looptaker beak extending from said support, 2. a thread catcher forming part of a cutting device and operable from a rest position to a cutting position, for the drawing out of the looptaker thread, and back to said rest position upon cutting of the thread, 3. a spring-urged thread-clamping plate in resilienT frictional engagement with and rotatively mounted upon said support about a pivot axis spaced from and parallel to the axis of said first guide thread bore, said plate having a second thread guide bore registering with said first guide bore in its inoperative position during operation of the sewing machine, and 4. means to deflect said plate to an operative position by displacement of said thread catcher from said rest position to said cutting positions, 5. whereby to relatively displace said first and second guide bores and to clamp said thread between said plate and said support.

2. In a chain stitch sewing machine as claimed in claim 1, wherein said thread catcher has the form of a plate and said clamping plate has an abutment camming with said thread catcher plate, to deflect said clamping plate during operation of said thread catcher from its rest position to its cutting position.

4. means to deflect said clamping plate to an operative position by camming with said thread catcher plate during displacement of the latter from its rest position to its cutting position,

5. whereby to relatively displace said first and third guide bores and to clamp said thread between said clamping plate and said support,

6. the pressure between said clamping plate and said support being such as to cause an automatic return of said plate from its operative position to its inoperative position by the pull on the thread after sewing of the predetermined number of starting stitches.

7. In a chain stitch sewing machine, the combination comprising: