US3712256A

US3712256A - Device on sewing machines for guiding the thread chain

Info

Publication number: US3712256A
Application number: US00118764A
Authority: US
Inventors: W Striegler; E Angele
Original assignee: Pfaff Industriemaschinen GmbH
Current assignee: Pfaff Industriemaschinen GmbH
Priority date: 1970-05-29
Filing date: 1971-02-25
Publication date: 1973-01-23
Anticipated expiration: 1990-01-23
Also published as: DE7020068U

Abstract

Guiding means for the thread chain between successive work blanks on sewing machines having a work clamp that is displaceable on the work plate relative to the reciprocating needle, a cutting device and a clamp for the thread chain, where a thread chain engaging member is provided which is movably disposed and driven between an initial position proximate the stitch hole and a final guiding position located at a distance therefrom. The thread chain engaging member by its movement toward the final guiding position is in thread chain tensioning engagement with the part of the thread chain disposed between the stitch hole and the clamping location.

Description

ilnited States Patent [191 Striegler et a1.

[ 51 Jan. 23, 1973 I541 DEVICE ON SEWING MACHINES FOR GUIDING THE THREAD CHAIN [73] Assignee: Firrna Ptat'f G.M.B.H., Germany [22] Filed: Feb. 25, 1971 211 App1.N0.: 118,764

., lndi r ew hi Kaiserslautem/ Pfalz,

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS Sommer ..112/121.l5

3,118,405 1/1964 Schenkengel ..112/252 3,256,845 6/1966 Eguchi ..112/252 3,379,151 4/1968 Tiemann ..112/252 Primary Examiner-James R. Boler Att0meyRobert H. Jacob [57] ABSTRACT Guiding means for the thread chain between successive work blanks on sewing machines having a work clamp that is displaceable on the work plate relative to the reciprocating needle, a cutting device and a clamp for the thread chain, where a thread chain engaging member is provided which is movably disposed and driven between an initial position proximate the stitch hole and a final guiding position located at a distance therefrom. The thread chain engaging member by its movement toward the final guiding position is in thread chain tensioning engagement with the part of the thread chain disposed between the stitch hole and the clamping location 6 Claims, 5 Drawing Figures DEVICE ON SEWING MACHINES FOR GUIDING THE THREAD CHAIN BACKGROUND OF THE INVENTION The invention relates to a guiding arrangement for the thread chain between successive work blanks on sewing machines having a work-clamp displaceable relative to the reciprocating needle on the material work plate, a cutting device and a clamp for the thread chain.

In cutting devices for the thread chain, it is known to conduct the leading end or the trailing end of the thread chain for severing in a suction tube and between cutters that operate in the manner of shears. The suction air causes continuous noise that is frequently found to be disturbing. Besides, a relatively large quantity of air is required in order to guide or conduct the thread chain faultlessly. These devices were used heretofore only particularly in overedge-sewing machines where the thread chain is formed by means of a stitch forming tongue provided at the end of the stitch plate, a bridge of the material feed dog and of the presser foot and where, owing to its voluminous structure, the thread chain is especially well adapted to be guided by suction air.

In order to ensure proper stitch formation between successive work blanks, i.e., forming a thread chain by running the sewing machine in absence of material blanks on sewing machines having a lower feed dog chainingpresser feet are known which in cooperation with a part of the feed dog advance the thread chain in the direction of sewing. In automatically operating sewing devices where angles, curves, narrow bows and acute angular corner seams are made, it is necessary to dispense with the otherwise conventional material feeding device and use a guiding or clamping frame for displacing the material, by means of which the sewing material is held and is suitably moved on the supporting plate for the material in accordance with the configuration of the seam that is predetermined usually by control cams. Prior to the start of sewing it is necessary with such machines to clamp the leading ends of the threads either manually or by means of a controllable thread clamp that can be placed upon the material supporting plate until the first stitches of a new seam have been formed. With such machines the material to be sewn has to be placed with its edge so accurately below the needle that for setting the first stitch the needle pierces the work as close as possible to the marginal edge of the material being sewn. This exact positioning of the work blank, however, introduces in the first place an undesirable loss of time and, on the other hand, certain indefiniteness in the stitch forma tion at the edge of the material being sewn. With seams that are at an acute angle with respect to the edge of the work blank, for example with so-called dart seams where the seam is started at the terminating point of a dart on the inside of the work blank within the visible area of the finished product, it frequently occurs that the material in the area of the terminal where ordinarily the seam is locked by barring stitches the seam and material is partly drawn into the stitch hole and is thereby crimped or twisted. Since sewing edges or tucks are usually located at prominent and exposed visible locations of the garment, it is necessary to take care that they are flawlessly executed.

SUMMARY OF THE INVENTION It is an object of the invention to so influence the thread chain clamped for cutting between successive work blanks after severing, while avoiding the shortcomings mentioned in machines having a work clamp, that the formation of the thread chain and the feeding of the thread chain being newly formed are ensured so that the sewing machine can already start before the edge of the work blank is located under the needle.

In accordance with the invention this problem is solved by a thread chain engaging element movably disposed and driven between an initial position proximate the stitch hole and a final guiding position located at a distance therefrom, which in its movement directed into the final guiding position is held between the stitch hole and the clamping position of the thread chain in a contact engagement that tensions the thread chain. In this manner the thread chain which is normally clamped and cut off at the end of a seam during the start of the machine, also in sewing machines without the conventional four-motion feed dog is withdrawn from the stitch forming location. The feeding of the edge of the work blank to the stitch forming location is supported, the exact formation of the stitches in the area of the edge of the blank is ensured and the drawing in of the material into the stitch hole by the needle is counteracted, so that the seam is smoothly and evenly formed along the entire length of the work blank.

Preferably the thread chain engaging member is in the form of a pin for that purpose and extends on both sides of the path of needle movement transversely to the direction of feed movement.

An embodiment which structurally is particularly simple is obtained in that as a support for the thread chain engaging member a slide is provided below the stitch plate laterally spaced from the needle in a guide channel of the stitch plate, which is movable parallel to the direction of feed.

In order that the thread lead member becomes effective without delay after each severing of the thread chain, the support means with the thread chain engaging member is held during the sewing operation by means of air under pressure against the effect of a ten.- sioning element in the starting position between the stitch hole and the clamping location and can be released at the end of the seam.

In accordance with a further feature of the invention a weight is used as the tensioning element, whose lateral distance relative to the axis of rotation of a lever connecting the slide with the piston rod of a compressed air cylinder is adjustable in order to accomplish that the thread chain is tensioned substantially with equal force along the relatively short path that the thread chain engaging element covers while the thread chain is withdrawn.

In order that the operation of the thread chain engaging element is not adversely affected in a sewing machine having a movable thread chain cutter and a stationary counter cutter, the thread chain cutter is arranged in a manner that it is movable about the thread chain along a path corresponding .to a rectangle. Furthermore it has an edge which, together with a stationary leaf spring, constitutes the clam-p forcthe thread chain.

Thus, the thread chain cutter can be removed from the area of the stitch formation and the withdrawing area of the thread chain and moved into inoperative position of rest, and moved forwardly and above the stitch plate only for severing the thread chain. Accordingly it impedes neither the thread chain engaging member which extends transversely of the withdrawing path of the thread chain, nor the displacement of the sewing material.

BRIEF DESCRIPTION OF THE DRAWINGS Further details and advantages of the invention will become apparent from the embodiment illustrated in the accompanying drawings, in which FIG. 1 is a perspective illustration of a sewing machine equipped with the device in accordance with the invention provided with a material guiding frame,

FIG. 2 is a perspective view of the stitch plate insert of the sewing machine with the guiding device, a cutting and clamping device for the thread chain as well as of the drive means for the individual devices, and

FIGS. 3, 4 and 5 illustrate in sections of enlarged scale taken along the line III-III in FIG. 2 the manner of operation of the thread chain guiding member, the thread chain cutter and the thread chain clamp.

DESCRIPTION OF THE INVENTION A sewing machine 2 is seated in a cut-out portion of the table top 1 in such a manner that the top of the work plate 3 is in the same plane with the upper surface of the two-thread chainstitch sewing machine, where the needle 4 works with the thread guiding looper 5, which is partly shown (FIG. 2), in order to form twothread chainstitches. However, the invention is not limited to the use of such a machine; it can also be used on other sewing machines.

A known feeding device 6 that is driven independently of the machine serves for holding and displacing or feeding the material being sewn. The feeding device 6 has a slide 7 that is movable parallel to the table top 1 and perpendicularly to the longitudinal axis of the sewing machine, and which is driven in any desired manner, for example, by way of a motor driven pinion which rolls on a toothed bar, likewise not illustrated, below the table top 1. The slide 7 which extends through a longitudinal slot 8 of the table top carries a guiding sleeve 9, (FIG. 1) in which a stud 10 is longitudinally slidable and which is pressed downwardly by spring action. An intermediate member 11 is disposed at the lower end of the stud 10 which at one end supports a presser bar 13 that serves as a work clamp extends parallel to the table top 1 and which is guided between rollers 12 mounted on the machine head 2, and to the other end of which the piston bar 14 of a compressed air cylinder 15 is secured.

A mounting plate 16 (FIGS. 1, 2) seated in the work plate 3 of the machine serves as a stitch plate and a mounting plate to accommodate the guiding device, the cutting device and the clamping device for the thread chain as well as the drive means for these devices. In a guide channel of the mounting plate 16 a slide 17 displaceable in the feed direction V is slidably received and secured in the guiding channel by a cover plate 19 that is fastened to the plate 16 by means of screws 18. At one end of the slide 17, a pin 22 is secured, which pin extends transversely of the direction of feed, as engaging member for the thread chain 20 that is disposed in a vertical plane that passes through the stitch hole 21 for the needle 4. The pin 22 secured to slide 17 is movable for guiding the thread chain 20 within the recess 23 of an insert 25 secured to the mounting plate 16 by means of screws 24. The insert 25 has a cutting edge 26 which constitutes the counter cutter for the thread chain cutter 27. The thread cutter 27 has a blade portion with an edge 26 that cooperates in the manner of shears with the cutting edge 28, as well as a rounded edge 29 which, together with a leaf spring 31 fastened to a bridge member 30, serves for clamping down the thread chain 20.

The blade portion of the thread chain cutter 27 extends into an elongated slot 32 in the plate 16, while the lower guide portion of the thread chain cutter 27 is guided in a slide member 33 which is mounted on two slide rods 36 secured by means of screws in a bridge member 34 on the plate 16.

A lug 37 is provided on the guide portion of the cutter 27 to which the piston rod 38 of a double action compressed air cylinder 39 is fastened, which has an upper and a lower compressed

air conduit

40 and 41, respectively. The compressed air cylinder 39 serves for the vertical movement of the thread chain cutter 27. A further compressed air cylinder 42 having a supply conduit 43 is provided for the horizontal movement, whose piston rod 44 is passed through a bore 45 of the bridge 34 and secured to the slide member 33 of the thread chain cutter 27. Guidance and drive of the thread chain cutter 27 are designed in a manner that the blade portion executes a movement about the thread chain 20 that corresponds substantially to a rectangle, clamps the thread chain 20 between the edge 29 and the leaf spring 31 and then severs the thread chain 20 by means of

cutting edges

26 and 28.

A compressed air cylinder 46 having a supply conduit 47 is mounted on a stationary angularly offset member 48 and serves for operating the slide member 17 with the thread chain engaging member 22. The piston rod 49 of the compressed air cylinder 46 has a bifurcated head 50, which is pivotally connected by means of pin 53 with the lower end of a double armed lever 52 pivotally supported for movement about a pin 51. The upper end of the double armed lever 52 has an elongated slot 54 into which projects a stud 56 that is secured to a lug on the slide 17. Below the bearing pin 51 a supporting arm 58 is adjustably mounted on a stud 57 that is rigidly fastened to the lever 52, which arm has a weight 59 adjustably secured thereto.

In operation, before the sewing starts, the operator slides the material to be sewn, for example a blank W, below the raised pressing bar 13, and aligns it. Thereupon the operator allows the air to escape from the compressed air cylinder 15 by actuating a known valve (not shown), as a result of which the pressure spring in the guiding sleeve 9 presses the pressing bar 13 down onto the work blank W by means of the stud 10 and intermediate member 11. The pressing bar 13 seizes the work blank W by frictional contact and moves it over the smooth table top 1 in the direction of the stitch forming location, while the vertical bridge at the free end of the pressing bar 13 which is tapered down on both sides arrives between the guiding rollers 12 that are secured to the head of the sewing machine.

During this operation the thread chain cutter 27 and the thread chain engaging member 22 assume a position about as indicated in FIG. 4, i.e., the thread chain leading to the previously sewn work blank is severed and the thread chain piece at the side proximate the needle is clamped in between the edge 29 of the thread chain cutter 27 and the leaf spring 31. The thread chain engaging member 22 is held between stitch hole 21 and the clamping location below the clamped in thread chain 20 by the compressed air cylinder 46 charged with air under pressure by way of a valve, lever 52 with weight 59, elongated slot 54, stud 56 and slide 17. Simultaneously with turning on the sewing machine the compressed air cylinder 46 is discharged by way of a valve. As a result lever 52 is turned clockwise by the gravity effect of the weight 59 fastened to the support 58, and thus the slide 17 with the thread chain engaging member 22 is displaced by the

connection

54, 56 in the direction of feed V, so that the thread chain engaging member 22 tensions the thread chain 20 between the clamping location and stitch hole 21 and moves away the thread chain newly formed in the direction of feed V as the machine is running. This ensures the so-called chaining, i.e., the stitch formation on two-thread chainstitch sewing machines in the absence of the material to be sewn. Furthermore, by moving away the thread chain 20 in the advancing direction of (arrow V) the feeding of the blanks by the feeding device 6 to the stitch forming location is supported, in particular drawing in of the forward edge of the blank by the needle into the stitch hole 21 is counteracted by moving away the thread chain. Thus pulling together and crimping of the edge of the blank can no longer occur.

It would, of course, also be possible to use a spring instead of weight 59 for moving the slide 17 with the thread chain engaging member 22. For this, however, it would be necessary due to the changing spring characteristic along the chain guiding stretch to take into account that the thread chain 20 is tensioned differently at different locations of this chain guiding stretch, while when using a weight the thread chain 20 is tensioned by relatively equal forces along the relatively short chain guiding stretch.

If several starting stitches have been sewn the number of which can be predetermined by a known retarding circuit, then the air of compression is permitted to escape from the compressed air cylinder 42 by way of the delaying circuit, whereupon under the spring action the piston rod 44 displaces the slide guide 33 with the thread chain cutter 27 upon the slide bars 36 toward the bearing bridge 34. The clamp 29/31 is thereby opened, and thus the thread chain 20 is released.

The compressed air cylinder 46 is again supplied with air under pressure so that by way of the piston rod 49, forked head 50, lever 52, slot 54 and the stud 56, the slide 17 with the thread chain engaging member 22 is moved from the position at the end of the chain guiding stretch FIG. 5 toward the stitch hole 21 into the position in accordance with FIG. 3. The sewing of the seam is thereupon continued. When the rearward edge of the blank has left the stitch forming location, then the sewing machine is stopped and the pressure bar 13 is raised from the sewing material by the compressed air cylinder 15 which is controlled by a valve. The feeding device 6 returns to its starting position that is illustrated in FIG. 1.

The compressed air cylinder 39 is then first supplied with air under pressure through the supply conduit 40 under control of valves. The piston bar 38 in this connection presses the thread chain cutter 27 upwardly with its cutting edge 28 over the thread chain 20 (as illustrated in FIG. 3). By supplying air under pressure to the compressed air cylinder 42 by way of the conduit 43, the thread chain cutter 27 together with the slide guide 33 is moved toward the needle with the cutting edge 28 until it is above the thread chain 20. Thereupon the compressed air cylinder 39 is supplied with air under pressure by way of conduit 41, whereby the thread chain cutter 27 is moved downwardly into the position illustrated in FIG. 4. Thus, the thread chain 20 is first clamped between the rounded edge 29 and the leaf spring 31, and then during the course of further downward movement of the thread chain cutter 27 the thread chain 20 is severed by means of the cutting edges 26 and 28. At the end of the downward movement of the thread chain cutter 27 the thread chain engaging member 22 is freely movable over the top of the edge portion of the thread chain cutter 27 as shown in FIG. 5. After a further blank has been placed and aligned below the pressure bar 13, the described course of operations starts anew.

Having described the invention with reference to the embodiment illustrated what is desired to protect by letters patent is set forth in the appended claims.

We claim:

1. In a sewing machine having a work plate, a mounting plate in said work plate having a stitch hole, a reciprocable thread carrying needle in alignment with said stitch hole adapted to cooperate with a thread carrying looper below said work plate to form a row of stitches by concatination of said needle thread and said looper thread, a work clamp disposed on said work plate in front of said needle, means operative to move said work clamp relative to said needle, a guiding device for a thread chain being formed between two successive workblanks, a cutting device and a thread chain clamp disposed behind said needle, means to actuate said cutting device, a thread chain engaging.

member movably disposed between a starting position proximate said stitch hole and a thread chain guiding end position, means for moving said thread chain engaging member from said starting position to said end position, said thread chain engaging member being in engagement with the part of the thread chain between said stitch hole and the clamping location defined between said cutting device and said thread chain clamp for tensioning said thread during movement into the thread chain guiding end position.

2. Guiding device in accordance with claim 1, characterized in that said thread chain engaging member is a pin extending on both sides of the path of needle movement transversely of the direction of feed of the material being sewn.

3. Guiding'device in accordance with claim 1, includ ing a guide means in said stitch plate, a slide movable parallel to the direction of feed in said guide means and supporting said thread chain engaging member.

4. Guiding device in accordance with claim 3, where said slide having said thread chain engaging member is held during the sewing operation in the starting position between said stitch hole and said clamping location by means including a tensioning element with a weight under control of a compressed air cylinder.

5. Guiding device in accordance with claim 4, comprising a compressed air cylinder having a piston rod, a lever having one end connected to said slide and its other end to said piston rod, and said weight being supported at a variable distance from a pivot axis on said

Claims

1. In a sewing machine having a work plate, a mounting plate in said work plate having a stitch hole, a reciprocable thread carrying needle in alignment with said stitch hole adapted to cooperate with a thread carrying looper below said work plate to form a row of stitches by concatination of said needle thread and said looper thread, a work clamp disposed on said work plate in front of said needle, means operative to move said work clamp relative to said needle, a guiding device for a thread chain beinG formed between two successive workblanks, a cutting device and a thread chain clamp disposed behind said needle, means to actuate said cutting device, a thread chain engaging member movably disposed between a starting position proximate said stitch hole and a thread chain guiding end position, means for moving said thread chain engaging member from said starting position to said end position, said thread chain engaging member being in engagement with the part of the thread chain between said stitch hole and the clamping location defined between said cutting device and said thread chain clamp for tensioning said thread during movement into the thread chain guiding end position.

3. Guiding device in accordance with claim 1, including a guide means in said stitch plate, a slide movable parallel to the direction of feed in said guide means and supporting said thread chain engaging member.

5. Guiding device in accordance with claim 4, comprising a compressed air cylinder having a piston rod, a lever having one end connected to said slide and its other end to said piston rod, and said weight being supported at a variable distance from a pivot axis on said lever.

6. Guiding device in accordance with claim 5, including a stationary clamp member proximate said needle and said cutting device comprising a movable cutter, and a stationary cutting edge cooperating therewith for cutting said thread chain, said movable cutter being disposed for movement along a path defining substantially a rectangle about the thread chain, said cutter having an edge operative to cooperate with said clamp member to define a clamp for the thread chain.