US2486531A

US2486531A - Thread seam and method and machine for inserting the same

Info

Publication number: US2486531A
Application number: US602854A
Authority: US
Inventors: Clyde L Knott
Original assignee: United Shoe Machinery Corp
Current assignee: United Shoe Machinery Corp
Priority date: 1945-07-02
Filing date: 1945-07-02
Publication date: 1949-11-01
Anticipated expiration: 1966-11-01

Description

L. KNOTT -THREAD SEAM AND METHOD AND MACHINE Nov. 1, 1949.

FOR INSERTING THE SAME 5 Sheets-SheetI 1 Filed July 2, 1945 riUJ lmlmn n n 6K2 ULA! im w Filed July 2, 1945 THREAD SEAM AND METHOD AD-.MAGHINE FOR INSERTING THE SAMEV Nov. l, 1949; c. KNo'r-r 2,486,531

3 Sheets-Sheet 2 Nov. l, 1949. c. L. KNOTT THREAD SEAM AND METHOD AND MACHINE FOR INSERTING THE SAME 3 Sheets-Sheet 3 l Filed July 2, 1945 Patented Nov. 1, 1949 THREAD 'sEAM' AND METHoD AND MACHINE FOR INSERTING THE SAME Clyde L. Knott, Beverly, Mass., assignor to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application July 2, 1945, Serial No. 602,854

23 Claims.

The present invention relates to thread seams and methods and a machine for inserting the same, more particularly intended for use in uniting relatively heavy pieces of work, such as those employed for shoe soles, in which the substance of the work is more or less compressible and the thickness is several times greater than the diameterof the thread employed in the seam as distinguished from cloth or fabric sewing in which the thickness of the work is Ycomparatively negligible.' v

The use of wax or other similar materials on sewing threads where heavy sole leather is being operated upon is as old as the shoemaking industry. These materials act principally to lubricate and to serve as a preservative agent on sewing threads. Incidentally, some cementing action takes place inhardening they wax or other material to assist in securing a seam against unraveling or loosening as a result of thread slippage. The cementing action in hardened Wax and similar materials is slight, however, as compared to especially prepared adhesives, particularly those compounded with modern synthetic plastics or resins. However, when synthetic plastics designed primarily to maintain their eifective strength are employed in an activated or softened condition, their tenacity may be so great and their setting time so short that proper stitch formation is extremely difficult' in threads treated With or containing them, the threads becoming jammed Within perforation's of the' Work substance before it is possible to tighten the stitches securely. Furthermore, when attempts are made to utilize threads treated with such highly adhesive materials in sewing machines of the usual design, excessive amounts of adhesive material on the thread are thrown off against the moving parts of the machine and the work being operated upon, frequently clogging the machine and damaging or otherwise giving the work an unsightly appearance.

When adhesive material having accentuated cementing action applied to sewing thread is utilized in a seam to lock the threads in place, the tendency is not only to secure the threads against slippage within the substance of the work operated upon but also to harden the threads between stitches and cement them to the exposed surfaces of the work in such a way as to stiffen the work substantially. With the use of such materials, if the work is flexed after hardening, the threads themselves may be subjected to excessive strains as the result of the increasing stiffness or the Work itself may be damaged.

It is an object of the present invention to pro- `vide a novel and improved seam, method of inserting the seam, and machine in which the method may be practiced in sewing with stitches .which are securely locked in place entirely within the perforations in the work preferably by cement forming materials having a strong adhesive aihnity for the substance of the Work without the difiiculties ordinarily encountered when such materials are applied to the sewing thread and carried with the thread vinto the perforations in the work while in an activated or softened condition and more generally the object of the invention is to provide a novel and improved plug locked :seam and also a method and machine for in.

sorting such a seam which are useful whether an adhesive material isemployed or not' and in which greater uniformity between successive stitches' and greater security are obtainable than heretofore considered possible with this type of seam.

Another object of the invention is to provide a thread seam for uniting heavy pieces of Work, such as sole leather, the threads in which are formed into loops and cemented to the substance of the work only in the bights of the loops, the remaining portions of the sewing thread being substantially free from cementing material so that the parts secured by the seam will remain exible and the threads in the seam will not be subject to injury when the parts are flexed.

A further object of the invention is to provide a method for inserting such a seam, in which the cementing material is introduced Within a perforation in the work separately from the thread so as to avoid difficulty in drawing the thread a substantial distance through the perforation in the presencey ofA the cementing material.

A still further object is to providek a machine for inserting a seam of the type referred to and for practicing the method, having a needle for carrying loops of' thread through the work in the usual manner of sewing without the inconvenience or resistance ordinarily onered by strongly adhesive materials acting within a perforation to resist movement of the thread therethrough and for introducing within the perforation the cementing material to enable the seam ,to be tightened in the usual way while insuring a firm bond between each loop of thread and the substance of the work.

In accordance with these and other objects', an important feature of the invention contemplates the provision of a seam for uniting heavy pieces of work, in which loops of thread extend into the work with their bights surrounding hardcned plugs containing a suitable plastic material shaped with constrictions to conform with the bights of the loops, preferably adhesively bonded to the substance of the work. As a means for reinforcing the seam and preventing the plugs from being cut through by the bights of thread, the plugs are preferably formed with bers runningcrosswise of the perforations within the thread bights.

In the feature of the invention relating to the method of inserting the seam, the plugs of the material which support the bights of the loops are introduced within the perforations through which the thread loops pass while the loops are in a position withdrawn from the work, so that no substantial strain will be applied to the plugs before the loops are contracted into the positions in which they are locked in place by the plugs. To enable plugs of synthetic material to be inserted and softened, in the present form of this feature of the invention, the material of each plug includes a thermoplastic carried through a heated portion of the machine before being introduced within the perforation of the work. Thus, the material of the plugs is activated or softened while being inserted within the perforations so that they will conform readily with the inner surfaces of the perforations and of the bights of the loops when the loops are contracted to set the stitches. Any tendency for the bights to cut through the plugs while the plugs are in activated condition is resisted, in the illustrated form of this feature, by the reinforcing fibers within the plugs. Thus, the bights of thread and the surrounded plugs may be drawn entirely beneath the adjacent surface of the work while the cement bond between the threads and the work securely locks the thread within the perforations.

The machine, as illustrated, includes the usual stitch forming devices for carrying loops of thread from one side of the work through and withdrawing them from the opposite side of the work, one of the stitch forming devices acting to form suitable perforations in the work and in the embodiment of the invention there is provided means for introducing a plug of material between the sides of the withdrawn loop within each perforation formed in the work by the perforating instrument to lock the bight of the loop in place when contracted. For simple and eiective operation a needle of the usual construction and mode of operation is employed for carrying the loops of thread through and withdrawing them successively from the work together with a loop spreader and a take-up for opening and contracting the loops and, as hereinafter described, the means for inserting the stitch locking plug acts while the withdrawn needle loop is held in opened position by the loop spreader.

The machine comprising this feature of the invention is so arranged that the locking plugs are formed during sewing operations from a length of strip material which is passed between a pair of toothed forming wheels, and a presser is provided for inserting each plug after being formed within a perforation. The presser, after inserting each plug within a perforation, is retracted so that the bight of the thread in the loop surrounding the plug may be tightened against the plug to set the stitch. In its preferred form, the presser acts within a chute movable toward and from the work to avoid the needle while engaging the work and to enter the loop after being withdrawn and opened by the loop spreader. By this construction, each plug is conned within the chute and introduced Within a perforation in the work without the possibility of escaping or of having its position twisted while being transferred from the plug forming devices.

Although the features of the invention are illustrated and described in connection with a sewing machine of the plug-lock type, the invention, in certain of its aspects, particularly with relation to the form of loop spreader herein disclosed, is readily applicable to lock stitch machines employing a shuttle or other form of stitch locking device.

These and other features of the invention consist in the novel and improved devices, combinations and arrangements of parts and elementary steps of the method and in the seam, the construction and practice of which are described and claimed hereinafter and the advantages to be obtained thereby will readily be understood from the following description taken in connection with the accompanying drawings illustrating one embodiment of the invention.

In the drawings,

Fig. 1 is a view in right-side elevation, partly broken away and shown in section, of a portion of a machine surrounding the stitch forming devices and embodying the features of the present invention;

Fig. 2 is a detail perspective view on a somewhat enlarged scale of a portion of the stitch locking plug introducing mechanism;

Fig. 3 is a detail sectional view taken along the line III-III of Fig. l;

Fig. 4 is a partial sectional view of the actuating mechanism of Fig. 2 on an enlarged scale, taken along the line IV-IV of that figure;

Fig. 5 is a sectional detail on an enlarged scale, illustrating the operation of the loop spreader as viewed along the line V-V of Fig. 6;

Fig. 6 is a view in front elevation and partly in section, of portions of the stitch forming devices of the machine and work surrounding the point f operation of said devices;

Fig. 7 is a sectional detail view, looking from the front of the machine as indicated by the line VI-VII of Fig. 10, of the plug forming devices;

Fig. 8 is a sectional View, taken along the line VIII-VIII of Fig. 7;

Fig. 9 is a detail view on a further enlarged scale of the plug inserting chute and presser;

Fig. 10 is a sectional view, taken along the line X-X of Fig. 7;

Fig. 11 is a sectional view on an enlarged scale, taken along a plane passing through the plug of a stitch inserted by the present machine;

Fig. 12 is a sectional view on an enlarged scale of the plug forming devices taken along the line XII-XII of Fig. 10;

Fig. 13 is a detail view of a portion of actuating mechanism for the plug forming devices;

Fig. 14 is a sectional view of a rotary shoe supporting horn employed in the present machine as a work support; and

Fig. 15 is a sectional view. of a seam in a modified form inserted kaccording to the features of the present invention.

As illustrated in the drawings a seam is provided to secure together parts of a McKay type shoe, the thread in the stitches of which is formed into a series of loops passing through the substance of the shoe parts locked in place by preliminarily shaped hard plugs of relatively dense thread supporting material disposed within the perforations through which the loops pass either with the plugs partly exposed or entirely embedded beneath the surface of the work within the substance of the shoe parts. A section of such seam is illustrated in Fig. 6 of the drawings and comprises a series of loops of sewing thread 2 carried through an insole 4, an upper 6 and an outsole 8 of a McKay type shoe. Locking plugs are indicated at ID surrounded by thread loops and disposed in close proximity to the tread surface of the outsole 8 within the outer ends `of perforations through which the loops are carried, the stitches being tightened and set to form sharp bights in the loops about the plugs so as to hold the plugs in place and to locate the bights substantially below the tread surface of the outsole 8. Thus the bights of thread are protected from Wear and locked in place while the other portions of thread connecting the bights remain free to flex when the shoe is worn.

In order to prevent escape of the plugs from the thread loops while the stitches are being contracted and set, according to an important feature of the invention, each plug is introduced into a perforation in the work between the sides of a loop while the loop is in a withdrawn position and the plugs are shaped to conform with the bights of the loops, there being central constricted sections in the plugs and enlargements at their ends filling the spaces of each perforation in the outsole at the sides of the loops, as illustrated in Fig. 11. To accomplish these results, the plugs I!! are composed of a thermoplastic material of a type commonly identified as Vinyl resin, nylon, cellulose acetate or nitrate or other similar dense material suitably compounded with a plasticizing agent for the purpose of accentuating the adhesive nature of the material. The plugs are subjected to an activating action directly before being incorporated into the seam to soften at least their outer layers. When a plug is introduced into a perforation in the outsole it conforms itself with the space in the perforation not already occupied by the thread. While each loop of thread is being contracted and a stitch set, the bight ofthe loop causes' a constriction in the central section of the plug and the ends of the plug are forced into close conformity with the inner surfaces of the perforation through which the loop passes. Activation of the outer surfaces of the plug also causes the material of the plug to adhere to the inner surfaces of the perforation as well as to the thread in the bight, thus forming a secure bond to seal the bights of the loops to the substance of the outsole. Close conformity of the plugs with the shapes of the perforations in the outsole not occupied by the thread assists materially in lling the void spaces, particularly adjacent to the tread surface of the outsole, against entry of deteriorating elements such as moisture or chemically reactive agents. The use of plugs composed of such materials provides also an opportunity for effective ornamental design resulting from contrasting colors at the to the thread, the plastic material of the plug may become forced to the sides of the bight in. the loop until the short length of reinforcing thread I2 takes up the pressure of the contracting loop. Still further application` of tension.- on. the sewing thread 2 may deform a plug still more but necessarily will react upon the reinforcing. thread length even if the. bight of sewing thread 2 is drawn substantially below the tread surface of the outsole. So long as the reinforcing thread length remains within the bight of the loop, a substantial proportion of the plastic material in the plug will be retained in contact with the bight, thus affording an opportunity for the plastic material to lock the loop in place as soon as hardening occurs.

In another form of seam which may be sewn by the illustrated machine with relatively simple modification, two threads I3 and I 4, instead of the single thread 2, are employed, both of which are formed into loops extending from opposite surfaces of the work with the plug I0 of plastic material acting as a lock to connect a loop in one thread t'o a corresponding loop in the other within the substance of the work, as shown in Fig. 15. This type of seam is particularly useful for exceptionally heavy work having an outsole 8 of extreme thickness. By inserting a plug to connect the loops of thread extending from opposite surfaces of the work in this way, relatively heavy thread may be employed. The plugs will be introduced into the perforations together with one set of surrounding loops while the other set of loops are withdrawn and held open. As each plug is introduced into a perforation it engages the upper thread and draws it along with it.

With either type of seam, the plugs are softened somewhat before being introduced into the perforations to enable them readily to conform with the shape of the bights in both sets of loops while being inserted within the perforations. By softening them, formation of irregular edges, and thus irregular movement of the plugs while being inserted within the perforations, is avoided.

To sew a seam with two threads in the manner shown in Fig. 15, it is necessary to ,carry a thread I3 across the perforation into which each plug Il) is introduced in such manner that it will be carried beneath the surface of the work into the perforation when the plug is pressed in to form a second loop surrounding the plug. A simple thread guide of any suitable construction for the second thread I3 is, for this purpose, located in line with the stitches. When a plug is introduced into the perforation between the sides of the open first loop of thread I4 it draws with it the thread I3 lying in line with the perforation, foron ing the thread into the perforation before the surrounding loop of thread is tightened. A thread lock may be employed in the machine, if desired, acting on the thread I3 at the proper time in each sewing cycle to prevent its movement when the lower thread I4 is tightened. Thus the plug acts against the second loop in the work to maintain its position until after the thread I4 is tightened.

Referring more particularly to the drawings illustrating the machine, the construction and mode of operation of the actuating parts, except as hereinafter described, is the same as that disclosed in an application for United States Letters Patent Serial No. 572,119, filed January l0, 1945, in the name of the present inventor. The stitch forming devices of the machine comprise work perforating instruments in the form of a curved awl I5 and a straight hook needle I6, a rOtating and reciprocating looper I8 (see Fig. 14) a thread finger 20 and a take-up 22, the latter three of which are mounted within a work support cornprising a rotary horn 24 similar to that disclosed in the application noted. The shuttle and driving mechanism therefor have been eliminated in the illustrated machine and as a result the length of the take-up may be substantially reduced. Cooperating with the work support is a presser foot 26 engaging the upper tread surface of a shoe sole being operated upon a short distance behind the point of operation of the needle I6. Duiing sewing, the needle reciprocates through each perforation in the Work toward and from an opening 28 at the tip of the horn and receives a loop of thread from the looper at the end of each down stroke. As the threaded needle is retracted from the tip of the horn in the work with a loop of thread, the loop is withdrawn and opened by a suitable loop spreader. While each loop of thread is held open a preliminarily shaped plug of plastic material is introduced within the needle perforation between the sides oi the opened loop.

The loop spreader comprises a pair of oppositely actuated notched arms 30, one disposed at the forward side of the needle and the other at the rearward side to open a loop into a triangular form, illustrated in Figs. and 6. The loop spreader arms 3i) extend downwardly and toward each other from shank portions extending rearwardly into eccentric split bushings 32 (Fig. l) clamped within the slotted forward ends of a pair of rockshafts 34. The rockshafts 34 are rotatably supported in suitable bearings in the machine frame and at their rearward ends are connected with interengaging gear segments 36 for causing the shafts to rock in opposite directions by equal amounts. For actuating the rockshafts, the shaft 34 at the right side of the needle has a laterally extending arm 3S pivotally connected to a downwardly extending actuating link 40 corresponding to the thread lifter actuating link 466 of the machine in inventors prior application. By this mechanism the loop spreader arms are given suitable movements to enter and open each needle loop at the proper time as the needle reaches the highest point in its travel. In opening the needle loop, the loop is entirely disengaged from the needle hook so that, as soon as a plug is introduced within the loop, it may be released by the spreader and contracted to tighten the stitch.

To introduce the preliminary shaped plugs into the perforations between the sides of the loops while the spreader holds the loops open, the machine is provided with an arcuate presser .42 in a correspondingly shaped chute 44 surrounding the presser, both of which are movable toward and from the point of needle operation in the work. The presser and chute are actuated during each sewing cycle while the needle is disengaged from the work and the loop of needle thread is held in open position to carry a plug into the loop and force the plug within a perforation formed by the needle through which the threads of the loop pass between the threads at the opposite sides of the loop. When the takeup 2i. acts to contract the loop and the loop becomes disengaged from the spreader, a sharp bight is formed in the loop surrounding the plug to lock the loop in place, the plug having been suitably activated before being introduced within the perforation in the work to receive a shape conforming accurately with` the thread in the bight of the loop and with the inner surfaces of 8 the perforation at the loop side of the work not occupied by the thread.

The plug presser 42 and chute 44 are mounted within a block 46 to the lower end surface of which the presser foot 26 is secured. The block 46 is mounted at the lower end of a reciprocating presser foot bar 46 (see Fig. 1) and is constructed with a curved guideway 50 to receive the outer edges of the chute 44. The presser 42 is similarly shaped and formed with side anges fitting grooves within opposite edges of the chute 44, as illustrated in Fig. 3. The lower ends of the chute and presser are cut away to reduce the size and Weight at theA operating ends of their parts and to enable convenient handling of the plugs individually, the plugs being of the proper diameter to enter the perforations formed by the needle. The chute and the presser ride along the outer arcuate surface of the presser foot 26, as illustrated in Fig. 9, and the presser foot is disposed to act with the work supporting horn 24 downwardly against the upper surface of the work just behind the point of needle operation.

To actuate the presser 42 and the chute 44, their rearward ends are pivotally connected to a pair of

links

52 and 54 extending horizontally at either side of the presser and chute and having pivotal connections with a pair of

arms

56 and 58 secured respectively to a sleeve 60 and a shaft 62 passing through the sleeve 60. The shaft 62 is supported directly in a bearing within the machine frame beside the arm 58. Beside the arm 56, the sleeve 60 is mounted within a similar bearing. The sleeve 60 has an arm 64 keyed thereto, and a roll B6 on the arm enters a suitably shaped cam slot in a helical gear 68. The shaft 62 has xed upon it an arm 10 carrying a roll 'l2 entering another slot in the opposite side of the gear 68. The gear 68 is fastened to a shaft 14 rotatable in the frame of the machine and is so located that its teeth mesh with the teeth of a helical gear 'I6 rotating with the main sewing shaft 18 of the machine, the helical gear 'I6 corresponding substantially with the gear 316 of the machine disclosed in inventors prior application and acting to drive the cam gear 68 a single rotation during a single sewing cycle.

To bring a preliminarily shaped plug into the space within the sides of the chute 44 beneath the operating end of the presser 42 in proper timed relation during each sewing cycle, the illustrated machine is equipped with plug forming and strip severing means constructed and arranged to cooperate effectively with the plug introducing chute and presser. The plug forming and strip severing means comprises a pair of simultaneously rotating toothed wheels and 82 spaced sufficiently close together to enable an eX- truded strip 63 of plastic material to pass between them while giving shape to the plugs. The wheels are so spaced that the teeth on the wheels form deep indentations in opposite sides of the strip of plastic material without severing the material entirely between the plugs. The shape of the teeth on the wheels is such that the end surfaces of the plugs are given a slight radius to conform more readily to the spaces in the perforations while the sides of the plugs are somewhat fiattened. The sides of the thread loops engage the fiatened sides of the plugs so that less opportunity will be given for displacement of the plugs while the loops are being tightened.

To sever the individual plugs completely from the strip of plastic material after passing the forming wheels, the lower, active end of the presser has a sharp right-angle edge 84 which' cooperates with an opposed edge 88 on the presser foot beneath the length of plastic material to teeth on the wheels, final shearing of the thread taking place at the outlet of the guide groove 81 only when the presser acts.

For actuating the

plug forming wheels

80 and 82 to give them the proper angular rotation required in forming a single plug during each sewing cycle and in advancing the plug into the plug introducing chute 44, the

wheels

80 and 82 are splined to fit the lower ends of a pair of parallel

grooved shafts

88 and 90 having keyed to their upper ends a pair of intermeshing spur gears 92, 94 to cause simultaneous rotation. The

shafts

88 and 90 are rotatably mounted within bearings in the block 46 and the shaft 88 extends above the block to support a ratchet wheel 98 pinned to the shaft 88 and engaged by a spring actuated pawl 98 rotatable on a bolt IDD. The bolt |80 passes through and is secured within an arm |02 rotating on the upper end of the shaft 88 and is formed with a spherical projection l04 surrounded by a socket in one end of a link |86. The link |86 `extends rearwardly from the bolt |00 and is pivotally connected to the lower end of a lever (08 fulcrumed on a stud IlD threaded in the frame of the machine. The lever |08 is also connected to an arm of an eccentric strap H2 surrounding an eccentric portion of the shaft 14, the movement of the eccentric strap being sufficient to carry the ratchet wheel 9B through the space of a single tooth and the wheels 8|] and 82 through the desired angular movement.

I'o activate the plugs as they are introduced within the perforations and to enable easy formation of the plugs from the plastic strip, the block 4'6 is drilled to receive an electrical heating unit H4 disposed horizontally just above the plug forming wheels. 'The location of the heating unit is such that the heat is carried down the length of the presser foot so that, as the presser foot engages the work, some of the heat is transferred to the work. Thus a continued softening action occurs in the plugs from the time of formation until the presser `foot is lifted after the complete setting of each stitch. The use of a heated presser in this way not only activates the material of the plugs but compresses the work in close proximity to the perforations in which the plugs are introduced so as to force the substance of the work firmly against the softened plugs, with the .result that a secure bond will be established between the work, the plugs and the thread,

The nature of the invention having been indicated and a particular embodiment having been described, what is claimed is:

il. 4A thread seam for uniting heavy pieces of work, comprising loops f thread extending into the work with their bights engaging centrally constricted plastic plugs of hard dense material shaped to conform with said bights and adhesively bonded to the substance of the work.

'2. A thread kseam for uniting heavy pieces of work, comprising loops of thread extending into perforations in the work with their bights sur- 10 rounding plugs containing a plastic material hardened within the perforations and provided with lengths of fibrous reinforcement running crosswise of the perforations.

3. A thread seam for uniting heavy pieces of work, comprising a series of loops of thread extending through the work from one side thereof with the bight of each loop surrounding a plug of thread supporting material also surrounded by a bight of each in a series of loops extending into the work from the -other side. 1

4. A thread seam for uniting heavy pieces of work, comprising a 'series of loops of thread extending through the work from one side thereof with the bight of each loop surrounding a plug of plastic material having a marked adhesive afnity for the work pieces and hardened within the substance of the work, said plugs also being surrounded by bights vof a `series of loops extending into the work from the other side thereof.

5. That improvement in methods of inserting a thread seam having a series of loops extending into a work piece, which comprises the steps of withdrawing each loop from a perforation in the work piece and introducing a plug of thread supporting material within the perforation while the loop is in withdrawn position to cause the loop to be locked in place when contracted.

6. That improvement in methods of inserting a thread seam having a series of loops extending into a work piece, which comprises the steps of withdrawing each loop from a perforation in the work piece and introducing a plug of softenable thread supporting material within the perforation while the loop is in withdrawn position and softening the plug to cause each loop of thread to be sealed within its perforation.

7. That improvement in methods of inserting a thread seam having a series of loops extending into a work piece, which comprises the steps of withdrawing each loop from a perforation in the work piece and introducing a plug of softenable thread supporting material within the perforation while the loop is in withdrawn position, softening the plug to cause it to conform with the shape of the space in the perforation not occupied by the thread, and contracting the loop tightly against the plug.

8. That improvement in methods of inserting a thread seam having a series of loops extending into a work piece, which comprises the steps of withdrawing each loop'from a perforation in the work piece and introducing a plug of thread supporting material already surrounded by a second loop of thread into the perforation while the rst mentioned loop is withdrawn from the work and contracting the iirst mentioned loop to secur-e the plug and second loop in position when the second loop is tightened.

9.` That improvement in methods of inserting a thread seam having a series of loops extending into a work piece, which comprises the steps of withdrawing each loop from a perforation in the work piece and introducing a preliminarily shaped plug of softenable thread supporting man terial within the perforation, softening the plug to `cause it to conform partially with the shape of the space in the perforation not occupied by the thread while the loop is withdrawn and contract.

ing the loop tightly against the plug to cause the plug to become conformed more closely --to the shape of the bight portion of the loop.

l0. A sewing machine having stitch forming devices for carrying loops of thread through and withdrawing them from the work, including a 11 perforatingv instrument, in combination with means for introducing within a perforation in the work a plug of thread supporting material between the sides of a withdrawn loop to lock the loop in place when the loop is contracted in setting each stitch.

11. A sewing machine having, together with other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work, a loop spreader, and a take-up for contracting the withdrawn needle loops and for setting each stitch, in combination with means for introducing a plug of thread supporting material within each needle perforation between the sides of the withdrawn needle loop while held by the loop spreader to lock said loop in place when the loop is contracted in setting each stitch.

12. A sewing machine having, together with other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work, and a take-up for contracting the needle loops and for setting each stitch, in combination with means for introducing a plug of softened plastic material within each needle perforation through which a loop passes to lock the loop in place.

13. A sewing machine having, together with other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work, and a take-up for contracting the needle loops and for setting each stitch, in combination with a device for forming plugs to conform with the shape of a needle perforation in the work, a presser for introducing the plugs within the perforations through which the loops pass to lock the loops in place, and means for activating the plugs while being inserted to seal the loops within the perforations.

14. A sewing machine having, together with other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work, and a take-up for contracting the needle loops and for setting each stitch, in combination with a guide for a strip of plastic material reinforced in a lengthwise direction by textile fibers, a device for forming plugs to conform with needle perforations in the work, severing means for cutting off the plugs successively crosswise of the reinforcing fbers, a presser for introducing the cut-off plugs with the fibers running crosswise of the perforations through which the loops pass, and means for activating the plastic material surrounding the fibers while being introduced to seal the loops of thread within the per-forations.

15. A sewing [machine having, together with other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work,` a loop spreader, and a take-up for icontracting the withdrawn needle loops and for setting each stitch, in combination with a guide for a strip of plastic material, a pair of toothed wheels between which the plastic strip passes to form plugs for the needle perforations in the work, and a presser for introducing each plug within a perforation loetween the sides of a needle loop while held by the loop spreader to lock said loop in place when the loop is contracted.

16. A sewing machine having, together with other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work, a loop spreader,

and a take-up for contracting the withdrawn needle loops and fior setting each stitch, in combination with a guide for a strip of plastic material, a pair of toothed wheels between which the plastic strip passes to form plugs for the needle perforations in the work, a presser for introducing each plug within a perforation loetween the sides of a needle loop while held by the loop spreader to lock said loop in place when the loop yis contracted, and means for activating the plastic material of the plug while being inserted to seal the loops of thread within the perforations.

17. A sewing machine having, together with :other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work, a loop spreader, and a take-up for contracting the withdrawn needle loops and for setting each stitch, in comfbination with a guide for a strip of plastic material, a pair of toothed wheels between which the plastic strip passes to form plugs for the needle periorations in the work, a presser for introducing each plug within a perforation between the sides of a needle loop while held lby the loop spreader to lock said loop in place when the loop is contracted, and a heater for the plug forming wheels to cause the plugs to be softened sufliciently to conform with the shapes of the perforations and the sides of the needle loops while being inserted.

18. A sewing machine having, together with other stitch forming devices, a needle for carrying loops of thread throughand withdrawing them successively from the work, in combination with means for introducing a plug of thread supporting material within each needle perforation through which a loop passes, comprising a chute movable toward and from the work to avoid the needle while withdrawing its loop and to enter the needle loop in line with the needle perforation after the loop is withdrawn.

19. A sewing machine having, together with other stitch forming devices, a needle for carrying loops. of thread through and withdrawing theun successively from the work, a loop spreader, and a take-up for contracting the withdrawn needle loops and for setting each stitch, in .oombination with a presser for introducing a plug of thread supporting material within each needle perforation between the sides of a needle loop while held .by the loop spreader to lock said loop in place when the loop is contracted, and mechanism for actuating the presser towards and from the work while the needle is disengaged from the work.

20. A sewing machine having, together with other stitch forming devices, a needle for carrying loops of thread through and withdrawing them successively from the work, in combination with means for introducing a plug of thread supporting material within ea'ch needle perforation through which a loop passes, comprising a chute movable toward and from the work to avoid the needle while withdrawing its loop and to enter the needle loop in line with the needle perforation after the loop is withdrawn, and a presser acting within the chute to move toward and from the work while the needle is disengaged from the work.

21. A sewing machine having, together with other stitch forming devices, a needle for carryi'ng loops of thread through and withdrawing them successively from the work, a loop spreader,

and a take-up for contracting the withdrawn needle loops and for setting each stitch, in comloination with a guide for a strip of plastic material, a pair of toothed wheels between which the plastic, strip passes to form plugs for the needle perforations in the work, and means for severing each plug from the strip and introducing the plug within each needle perforation through which a loop passes, comprising a presser actuated toward and from the work, and a cutting edge cooperating with the presser to cause each plug to be sheared from the strip during movement of the presser toward the work.

22. A sewing machine having stitch forming devices for carrying loops of thread through and withdrawing them from the work including a hook needle, in combination with a loop spreader comprising oppositely acting arms disposed at opposite sides of the needle to open each loop.

23. A sewing machine having stitch forming devices for carrying loops of thread through and 14 withdrawing them from the work including a hook needle, in combination with a loop spreader comprising arms disposed at opposite sides of the needle, and connections between the arms for actuating them in opposite directions to `open and to dsengage each loop from the needle.

CLYDE L. KNOTT.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 43,236 Sturtevant June 21, 1864 85,891 Reed Jan. 12, 1869 431,192 Pierce July 1, 1890 857,465 Iwory June 18, 1907 1,368,059 Schick Feile, 8, 1921 2,189,067 Hlavaty Feb. 6, 1940