US2420643A - Sewing machine - Google Patents

Description

y F. AsHwoRTH 2,420,643

SEWING MACHINE 5 Sheets-Sheet l y 1947- F. AsHwoRfi-l 2,420,643

SEWING MACHINE Filed April 17, 1945 5 Sheets-Sheet 2 'F.' ASHWORTH 2,420,643

SEWING MACHINE May 20, 1947 Filed April 17, 1945 5 Sheets-Sheet 5 May 20, 1947. F ASHWORTH 2,420,643 SEWIING MACHINE Filed April 17, 1945 5 Sheets-Sheet 4 $5015 wafin/ May 20, 1947.

F. .ASHWORTH SEWING MACHINE I "IIIIIIIIII IIA Patented May 20, 1941 SEWING MACHINE Fred Ashworth, Wenham, Mass, assignor to United Shoe Machinery Corporation, Flemington, N. J a corporation of New Jersey Application April 17, 1945, Serial No. 588,821

17 Claims. 1

The present invention relates to improvements in sewing machines and more particularly to lockstitch shoe sewing machines, the stitch forming devices of which comprise a curved hook needle and a loop taker in the form of a rotary hook which acts to cast loops of needle thread over a locking thread case without itself passing bodily through the loops and in so doing imparts a twist of 180 to each needle loop as it is carried about the thread case. Examples of such machines are disclosed in United States Letters Patent No, 1,169,909, granted February 1, 1916, upon application filed in the name of the present inventor; No. 2,271,611, granted February 3, 1942, upon application filed in the names of the present inventor and Carl F. Whitaker, jointly; and No. 2.350395, granted June 13, 1944, upon application filed in the name of the present inventor.

As illustrated and described in the patents above referred to, the loop taker of the machine is provided with a loop entering beak forming a hook to carry a leg of each loop drawn through the work by the needle and which leads to the inner surface of the beak (termed for convenience in the present application the n r leg of the thread loop) across the exposed front end of the thread case while the other leg of the loop which leads from the work to the outer surface of the beak (termed for convenience the outer leg of the loop) is carried across the back end of the thread case. During this operation, the inner leg of the needle loop is lifted from the needle hook and the outer leg is swung across and in front of the point of the needle, the inner leg of the loop remaining without substantial movement until the loop reaches its position of maximum extension about the thread case where it is ready to be contracted and pulled back toward the Work together with the locking thread in the formation of a lockstitch. Due to the lack of movement in the inner leg of the loop as the outer leg swings from one side to the other across the back end of the thread case, there is a tendency for the inner leg to retain its position on the thread case longer than it should, the frictional engagement of the thread with the thread case not being overcome in a uniform manner:

reached a position. of maximum extension, no movement occurring in the inner leg of the loop on the thread case to enable its release, there is an opportunity for an excessive strain to be imparted to the thread and possible breakage to result therefrom if the loop is not free to contract. Where frictional engagement of the inner leg of the loop retains that leg in position longer than usual, in the type of machine referred to, the tendency for thread breakage, par- Thus, if a continued pull is' applied to the thread after the needle loop has i til) ticularly during operations at relatively high speeds and close timing, is especially troublesome. Furthermore, with high speeds and close timing of the stitch forming devices in a machine of this type, it is highly desirable to make provision for convenient adjustments, particularly where a frictional tension device is employed to control the thread while being laid in the hook of the needle before being drawn through the work and after being drawn through the work and while being transferred from the needle to the loop taker.

Accordingly, the present invention has for its objects, among others, the "provision of means for insuring uniform and reliable release of each needle loop in a lockstitch machine having a loop taker of the type referred to and, generally, to obviate the difficulties above noted. With these objects in view, an important feature of the present invention relates to the provision of a tension reducing step located alon those Surfaces of the loop taker engaged by the needle loop as it reaches a position of maximum extension about the thread case, so that a pull on the thread at a critical time during movement of the loop about the thread case will cause sufficient lengthwise movement of the inner leg of the loop along the surface of the thread case engaged thereby to cause the loop to be released with certainty. By employing a tension reducing step arranged to act in this way, the inner leg of the loop is momentarily slackened at a time when the loop is rapidly changing its position and, sincethe slackening occurs uniformly at a time in the rotation of the loop taker which is readily controllable, the use of the step isof advantage not only to enable easy release of the loop but also to produce uniformly a momentary application of tension of unvarying degree in the loop just before its release from the thread case to ensure proper tightening of the needle thread extending between stitches and withdrawal of all the measured thread past a thread lock against which each stitch is set.

After release of the needle loopfrom the thread case during each sewing cycle in the machines of the patents above referred to, the needle loop is free to contract and move in an irregular manner toward the work, sometimes twisting itself about the locking thread and at other times engaging moving surfaces of the loop taker in such a way as to vary the tension in the contracting loop from one sewing cycle to another.

To avoid irregular movement of and tension in the needle loop so far as is possible after the loop is released from the thread case, according to a further feature of the present invention, a loop retaining hook is provided on the loop taker for maintaining the needle loop out of contact with the Work and other parts of the loop taker after operation of the loop retaining hook is suchoas,

to retard movement of theneedle loop toward the work until the hook has approached so close to the surface of the work that there is little if any opportunity for the thread in the loop to wrap itself excessively around the lockingthread.

or to engage further with any part of the loop taker. Thus, the contraction of the needle loop after being released from the thread case is maintained substantially under control at all times.

As a still further feature of the invention, which is useful in machines employing a loop taker of the type referred to and particularly when a tension reducing step acts uniformly at a predetermined point in each sewing cycle to cause the loop to be released from the thread case and a predetermined tension to be applied to the thread in the loop prior to its release, the machine is equipped with needle thread measuring means acting between a. front thread lock and a rear thread lockto pull off from the supply during each sewing cycle-an amount of thread corresponding to that employed. in each stitch, in. which the front thread lock remains open until after theloop-taker imparts a-uniform tension to the-needle loop to draw from the measured supply all the available'thread and to lay the thread snugly against the work without im-- parting such a strain to the thread as would be likel to disturb the position'in the work of the previously formed and set stitch. The application-of tension by the loop taker in this way-is substantially less than that required to draw the interengaged needle and locking threads into the work so that excessive tension will not be applied to the thread in each sewing cycle before a stitch is set;

According to a still further feature of the in vention, therefore, it is desirable to close thefront thread look before a stitch setting tension is applied to the thread and so avoid the necessity of applying to the thread between the front and rear thread locks such a degree of tension as wouldinterfere with measurement of thread. In the embodiment of this feature in the illustrated machine, each stitch is set by a'rotary take-up while'both thread locks are'closed, thus giving an assurance of a secure grip on the thread and avoiding any possibility of variation in the amount of thread measured.

The several features of the present invention will .be clearly understood from an inspection of the. accompanyingdrawings; in which Fig; 1 is a view in side elevation: and, partly in section, looking from the left, of so much of a lockstitch sewing machine as is necessary to illustrate the embodiment of the'present invention therein;

Fig.2 is a sectional view of the thread tension wheel. in the machine illustrated in Fig. 1 taken along the line IIT-II;

Fig. 3 is a View in front elevationand partial section of. the portions of the machineillustrated inFig.v 1;

Fig. 4 is a, detailview in side elevation, on a somewhat enlarged scale; of certain of the stitch:

forming devices in the machine illustrated in Figs. 1 and 2;

Fig. 5 is a sectional view taken along the line V-V of Fig. 4 on a still further enlarged scale;

Fig. 6 is an enlarged detail view of the rear thread lock illustrated in Fig. 4;

Fig. '7. is an enlarged detail plan view of the rear thread lock;

Fig. 8 is a detail view on a similarly enlarged scale of the rear side of the loop taker and thread case of'the machine, illustrating the movement of each needle loop about the thread case at a position before the maximum extension of the loop is reached;

Fig. 9 is a similar view with the needle loop substantially at a position of maximum extension after the tension reducing step has acted;

Fig. 10 is a sectional view taken along the line XX ofFig. 8;

Fig. 11 is a sectional View taken along the line XI-XI of Fig. 9;

Fig. 12 is a detail View of the stitch forming devices in the machine, illustrating the position of the parts after each needle loop has been freed from the thread case and drawn substantially down to the surface of the work before the stitch is set;

Fig. 13 is a similar view illustrating the positions of the parts while setting each stitch;

Fig. 14 is a side detail view on an enlarged scale, partly broken away and in section, of the loop taker, thread case and presser foot looking from the right side of the machine and indicating the relationship with the work, with a needle loop indicated in a position after being released from the thread case;

Fig. 15 is a'front sectional view of the loop taker I and thread case taken along the line XV-XV of Fig. 14;

Fig. 16 is a similar sectional view of the same parts, with the loop taker about to release a needle loop as the loop is being pulled toward the work;

Fig. 17 is a perspective view of a portion of the work, with the stitch set;

Fig. 18is a detail viewof the thread case and thread tension adjusting device thereon;

Fig. 19 is a sectional 'view ofthe thread case, taken along the line XIXXIX of Fig. 18;

Fig. 20 is a further sectional view of the thread case, taken along the line XX-XX of Fig. 18;

Fig. 21 is a side detail view, on a still further enlarged scale, of the tension controlling spring for the thread case; and

Fig. 22 is a plan view, on the same scale, of the tension controlling spring.

The machine illustrated in the drawings is a lockstitch shoe outsole sewing machine having a work support 0, a presser foot I, a curved hook needle 2, a continuously rotating take-up 4, a needle looper 6-, a thread finger 8, a loop taker or shuttle iii enclosing a locking thread case i2, a pull-off M, a thread measuring arm I 6, a front threadlock IS, a rear thread lock 20,,a tension wheel 30 and other stitch forming devices similar in construction and mode of operation except as hereinafter pointed out to those disclosed in Patents No. 2,271,611 and No. 2,350,995 above referred to.

As in the machine of the patents, the stitch forming devices are so operated that th take-up gives up thread while passing each needle loop about the thread case and acts to pull the needle loop from the thread case into the work to set each stitch. To control the needle thread while each loop is being formed and carried about the thread case, in the machine of the patents, a frictional tension device comprising a spring-pressed plate 23 is provided past which the thread moves between the take-up and the looper, In pulling the loop of needle thread from the thread case, sufficient tension is exerted on the thread to cause the thread measured by the pull-off to be drawn past the front lock, where it is available for the formation of a succeeding stitch.

In the machine of the patents, the take-up, in pulling the needle loop from the thread case, may act on the thread in some instances before the needle loop is fully released from the thread case, due to slight inaccuracies of timing and irregu: larities in the formation of successive stitches. Furthermore, the loop taker, in passing each loop about the thread case, moves the outer leg 25 (see Figs. 8, 9, 14 and 15) of the loop across the back of the thread case much more rapidly than the inner leg 24 is moved across the exposed front end of the thread case, the inner leg of the loop moving most rapidly after the outer leg has completed its movement, The inner leg 24 of the loop is the one which is connected to the lastformed stitch, so that there is little if any lengthwise movement of this part of the loop, whereas the outer leg is being pulled directly through the work, so that it slides lengthwise as well as transversely of its length along the surfaces of the thread case and loop taker. Accordingly, when the surfaces of the thread case and the loop taker are somewhat obstructed by accumulations of wax or other foreign materials, there may be a tendency for the inner leg of the loop to be retained in place, thus delaying somewhat the release of the loop from the thread case.

To avoid excessive tension in a needle loop as the take-up acts to pull the loop from the thread case before complete release of the loop occurs, in the embodiment of the present invention, the loop taker is formed with a tension releasing step or shoulder 25 located to pass the position of the inner leg 24 of the needle loop as it extends from the loop taker to the work exactly at the instant of maximum extension in the needle loop. Be-

yond the step 25, the edge portion of the loop taker has a reduced area or is relieved to cause the tension on the thread to remain reduced for a susbtantial portion of the loop taker rotation. The tension releasing step is arranged to act just after the take-up has exerted a slight tension on the thread and enables that portion of the inner leg of the needle loop which engages the thread case to move slightly in a lengthwise directionafter the step has passed, thus facilitating freeing of the needle loop from the thread case. The slack produced in the thread by movement of the step beyond the inner leg of the loop releases the tension which has been applied by the takeup at a definite instant in the rotation of the loop taker, and the step is of sufiicient depth to insure that there is no possibiilty for the take-up to exert or apply further tension to the thread in the needle loop before the loop taker has carried the loop with certainty to a position which is entirely free of the thread case.

In the machine of the prior patents, after each needle loop is freed from the thread case, it is contracted by the take-up 4 acting to draw thread through the work at a relatively high rate of speed. The loop of needle thread at th time it is freed from the thread case is of sufficient length to reach nearly to the highest part of the thread case as in Fig. 9.

In order to maintain an adequate control in the movements of each needle. loop after being freed from the thread case, according to a feature of the present invention, the loop taker ID has formed at the outer side of its beak a loop retaining hook 2B directed oppositely from the point of the beak and so arranged as to prevent formation of excessive slack in the needle loop while it is being drawn toward the work by the take-up. The action of the loop retaining hook 28 is illustrated in Figs. 9 and 14 to 16, inclusive.

After reaching a position of maximum extension about the thread case (Fig. 9), the needle loop begins to move toward the extreme end of the loop taker beak and, unless prevented otherwise, would drop clear of the loop taker shortly thereafter. With the use of the loop retaining hook, the position of the needle loop on the loop taker is maintained as shown in Figs. 15 and 16, the loop being contracted nearly as fast as slack is provided by rotation of the loop taker. When the needle loop has been contracted sufficiently and the loop taker rotated to a position with its beak portion close to the surface of the work, as in Fig. 16, a condition is reached in which the loop is no longer retained by the hook 2B and, between the solid and dot-dash line positions of the loop taker illustrated in Fig. 16, it drops clear of the hook and is drawn rapidly to the surface of the work together with the encircled portion of the looking thread extending from the last-formed stitch in the work to the thread case. At this time, the length of the needle loop is so short that there is little opportunity for excessive or erratic action. If there is a tendency for the needle loop to wrap itself around the locking thread, the shortened length of the loop so restricts the wrapping action as to avoid excessive resistance to continued downward pull on the thread by the takeup, as frequently occurs in machines of the prior art. Thus, extremely uniform stitches result and the full advantage of accurate thread measurement is rendered possible.

Fromthe use of the tension releasing step 25 on the loop taker, the tension imparted to the thread by the take-up, before the step passes the inner leg of each needle loop being carried about the thread case, is controlled more accurately than with the machine of the prior patents. Thus, the tension imparted to the thread by the take-up as each needle loop reaches a position of maximum extension about the thread case may be regulated to a relatively light uniform intensity as compared with that of the tension employed to set each stitch. Accordingly, it is possible to utilize the tension imparted to the needle thread at this time in each sewing cycle by the take-up to pull the measured supply of thread from between the thread locks l8 and 23 and to retime the operation of the thread locks in the patented machine so that a particularly effective and advantageous method of handling the thread results.

strained and stretched by the take-up in settingeach stitch. Thus, the full stitch setting tension is applied to the thread between the locks and is retained in the thread between the locks until the rear thread lock is opened in preparation for measuring thread for the succeeding stitch.

On account of, the amount of stretch in. the thread and elasticity of the thread, when the rear thread lock'is opened before the pull-off acts, elastic contraction of the thread may be sufficient to draw thread past the rear lock to such an extent as to cause inaccuracy in the thread measurement. When the machine is operating at high speeds, an amount of thread which is greater than that drawn from the supply by the pull-off may be drawn by contraction of the thread in this way past the rear lock. Thus, an improper thread measurement will occur. To avoid this difficulty, the thread locks in the illustrated machine have been retimed and a tension Wheel has been employed in the illustrated machine to operate in a novel and effective manner to be described.

The retiming of the thread locks rendered possible by this feature of the invention comprises closing the front thread lock I8 against the thread to clamp it between the time at which each needle loop reaches a position .of maximum extension on the thread case and the time at which each stitch is set in the substance of the work. In this way, a uniform tension imparted by the take-up to the needle thread before the inner leg of the needle loop is released by the step on the loop taker causes the thread measured between the thread locks to be drawn past the front thread lock without causing excessive tension or stretch in the thread. After the front thread lock is closed, the stitch is set by the ap plication of a much greater tension, the rear thread lock remaining closed while the stitch is being set. After the stitch setting tension has substantially been released, the rear thread lock is opened and the pull-off i4 acts with the measuring arm I3 to cause withdrawal from the supply of a length of thread in the usual way in accordance with the thickness of the work, the tension wheel indicated at 30 acting to prevent movement of the thread past the rear lock in excess of that required by the measuring operation.

The construction of the tension wheel 39 corresponds to a common form with alternately bent tangs on a radially slotted disk forming thread guiding crevices within which the thread is gripped. The wheel is mounted for rotation upon a flanged sleeve 32 (see Fig. 2) slidably mounted within an inclined opening through a block as having an angularly disposed extension clamped to the frame of the machine. At opposite sides of the tension wheel on the sleeve 32 are a pair of friction washers 36 pressed against the tension wheel by the force of a coiled spring 33 surrounding a bolt 45 passing through the sleeve 32 and a shouldered nut 452 received within an Enlargement of the opening in which the sleeve is supported. The outer end of the bolt 48 has a suitable knurled head 44 for obtaining the desired adjustment of friction pressure, a pin 36 which passes through a slot in the block 3 3 from the nut 42 preventing rotation of the nut with the bolt. The spring 38 is proportioned to provide a comparatively light tension in the thread drawn past the wheel within the range of the tensions impartedto the thread by the take-up at those times in each sewing cycle when the needle loop is at its position of maximum extension about the thread case. Thus, the strain and stretch in the thread produced by the tension wheel 39 may be regulated to counterbalance those in the thread imparted by the take-up before each stitch is set, so that no movement in the thread past the rear thread lock will occur before the pull-ofi acts. Accordingly, the amount of thread drawn past the rear thread 8 lock will conform accurately with the amount required for each stitch in accordance with the operation of the thread measuring arm in a desirable manner.

The mechanism for actuating the thread locks 58 and 2c, the pull-01f I4 and the thread measuring arm 16, except for retiming, is substantially the same as that disclosed in Patent No. 2,271,611 and in United States Letters Patent No. 2,354,731, granted August 1, 1944, on application of the present inventor and Carl F. Whitaker. Briefly, the pull-off and lock actuating mechanism comprises cam members 48 and 50 on a stationary cross shaft 52 mounted in the machine frame and suitably connected yoke members spaced along the shaft with their arms connected to actuating links one of which is indicated at 54 and another of which is indicated at 58. The links 56 and 55 are controlled by cams secured to a sewing shaft of the machine, indicated at 58.

To provide an extremely effective and durable thread lock construction in the machine of the present invention, both locks l9 and 20 are in the form of rolls 60 having substantially cylindrical surfaces about which the thread is wrapped, and a stationary guide lug 62 extends axially across the cylindrical surface of each roll With a radial thread guiding face 6 disposed between the ends of the roll to prevent displacement of the thread along the roll. As in the machine of the prior patents, the thread lock proper comprises a shoe 66 shaped to fit the surface of the thread lock roll but, in the patented machine, each thread lock roll is formed with side flanges to prevent the escape of thread along the roll from the grasp of the shoe. As a consequence of wrapping the thread about the roll in the thread lock construction of the patents, the thread has a tendency to creep along the roll until it engages one of the flanges on the roll. The thread will remain in a position engaging the fianges and become clamped by the shoe throughout continued operation of the machine so that, eventually, as a result of wear, the roll and the shoe will become grooved. After excessive wear, the groove will become of sumcient depth to prevent further clamping. action on the thread, after which slippage and inaccurate thread measurement occur.

The use of a stationary lug having a thread guiding face disposed between the ends of each roll in the thread locks of the present illustrated machine prevents the formation of grooves at the ends of the cylindrical roll surfaces and insures that the wear of the thread clamping parts will take place centrally of the thread engaging surfaces of both the roll and the shoe. On this account, the thread engaging surfaces: may be rendered more resistant to wear, particularly in case the roll is heat treated to harden it, the shapes of the roll surfaces being more accessible for uniform treatment than where side flanges are used. For convenience in construction, the lug 62 is formed as a part of a thread guide ring surrounding a stud on which each roll is mounted at one end of the roll with a portion of the lug projecting part way across the cylindrical surface of the roll.

To adjust the locking thread tension, in the illustrated machine, the locking thread case I2 supports a curved, resilient thread engaging member 68 maintained in thread engaging position within a peripheral grOOVe in the cylindrical side wall of the thread case by a tension adjusting member provided with laterally projecting lugs 12 fitting within undercut grooves within the peripheral groove of the thread case side wall, as in the thread case disclosed in United States Letters Patent No. 1,128,651, granted February 16, 1915, on application of the present inventor.

To hold the tension adjusting member securely locked in adjusted position, one end of the member is slotted and has a projection 14 arranged to engage any of a series of holes formed in the adjacent side wall of the peripheral groove 5. In the patented thread case, these holes pass through the side wall of the thread case parallel to the axis thereof, and the outer ends of the holes form perforations in an edge at the open, exposed end of the thread case. When the inner 10 in Fig. 1 before the needle loop for-the succeeds ing stitch is opened by the loop taker to a position of its greatest extension.

As in the patented machines, the illustrated machine is provided with a driving and stopping mechanism for bringing the machine to rest with the stitch forming devices disengaged from the work, the thread locks opened, and the tension wheel released from frictional engagement with leg of each needle loop is being carried across the open front end of the thread case, it encounters the edges of the perforations formed by these holes which frequently intersect the edges of the thread case so close to the outer circumference of the thread case that sharpened knifelike irregularities are formed. On this account, in some instances the thread in the needle loop is injured by engagement with such sharpened irregularities.

To avoid formation of knife-like irregularities in the edge of the thread case, in the present machine, the series of holes for locking the tension adjusting member in position are bored in a radial direction through the circumferential side wall of the thread case, as best illustrated at 16 in Figs. 18 to 20, inclusive. By so boring the tension member locking holes, there is no possibility for the needle loop, in being carried about the thread case, to'come into contact with the surfaces cn the thread case perforated by the holes and accordingly there is no chance for injury to the needle thread from this cause.

In order to avoid displacing the stitch previously formed and set in the work as the take-up contracts each needle loop against the loop retaining hook 28 on the loop taker, a needle thread controller 13 is provided, located between the thread lock l8 and a guide roll 80, to maintain a more nearly uniform tension on the needle thread while the take-up acts. The controller 18 is of the same construction and general mode of operation as that described in Patent No. 2,271,- 611. The use of the thread controller also avoids slack thread in the needle loop as the take-up is pulling the needle loop from the retaining book 28 toward the work.

The novel timing of the thread locks l8 and is of advantage not only with the type of loop taker illustrated and described but also is useful with other forms of loop takers or shuttles where uniform and accurate release of each needle loop therefrom in each sewing cycle is assured. After the measured thread has been drawn past the front thread lock l8 and the take-up has pulled the needle loop together with the encircled looking thread substantially to the surface of the work, as illustrated in Fig. 12, the front lock is closed and the remainder of the retracting stroke of the takeup pulls the locking thread into the work to set the stitch. As has been explained, while a stitch setting strain is applied to the thread, both front and rear thread locks are held closed so that there is no possibility of movement in the thread past the locks. The rear lock, therefore, is kept closed until the stitch setting strain has been relieved in the thread and the take-up has reached a position indicated at 82 the washers 36. The thread locks are opened by mechanism of the same construction and mode of operation as that described in Patent No. 2,271,- 611, and the pressure of the friction washers on the tension wheel is released through connections to the same mechanism. The driving and stopping mechanism is controlled by a foot actuated treadle rod 84 pivotally connected to one arm of a lever 86 rotatable on a shaft 88 carried in a bracket 90 at the rear of the machine frame. Another arm of the lever 86 is forked and rotatably supports a transversely perforated pin 92, through the perforation of which passes a horizontal connecting rod. 94 pivotally connected at its forward end to one arm of a tension releasin lever 96 rotatable on a shaft 98 secured in the machine frame. The lever 96 has a yoke portion extending along the shaft 98 and a vertical tension releasing arm arranged to engage the lower end of the tension bolt 40, the arrangement being such that, when the treadle rod 84 is released to bring the machine to rest, the connecting rod 94 is moved rearwardly and the tension bolt 40 forwardly to relieve the pressure of the friction washers on the tension wheel. In order to insure a free action of the treadle rod, the rearward end of the connecting rod 94 has coiled about it a spring Hill compressed between the pin 92 and a collar l0| pinned to the rod.

The spring-pressed plate 23 of the frictional tensioning device is mounted on a stationary housing I02 for the take-up and is actuated to impart a light tension to the thread while the needle is being looped in each sewing cycle, and to release the tension for a short interval thereafter, as in the machine of inventors copending application for United States Letters Patent Serial No. 529,465, filed April 4, 1944, now Patent No. 2,389,124, granted November 20, 1945. Instead of actuating the tension plate directly by the take-up, as in the machine of that patent, however, the plate 23 of the present machine is actuated by mechanism, best illustrated in Fig. 5, including a cam I03 clamped to the continuously rotating take-up shaft, indicated at I04, between a shoulder I06 on the shaft and the take-up arm, indicated at I08. The hub of the arm I08 of the take-up is keyed to the take-up shaft and is clamped in place by a nut H0 threaded on the reduced end of the shaft. The cam I03 is cupshaped to receive the hub of the take-up arm and is retained in position on the take-up shaft by the clamping pressure of the nut H0 acting through the hub of the take-up arm I08.

The take-up cam I03 is flanged with a radially disposed cam surface arranged to engage the lower arm of a friction plate actuating lever H2 within a recess of the take-up housing fulcrumed on a pin- H4 secured to a U-shaped bracket H6 embracing the lever. The bracket H6 is secured by screws H8 to the take-up housing I02. The upper arm of the lever I I2 is T-shaped and enters slots formed in pins slidably mounted in the take-up housing and is actuated againstthe friction plate 23 by a compression spring I22 disposed in a recess of the housing I02 with its outer end engaging the upper arm-of the lever H2. 'The friction plate-23 is secured to the frame of the take-up housing in the'same manner asthat in the above-mentionedapplication and the lever and enclosing recess within the housing is protected from engagementwith the thread and from the entrance of fibers bya circular shield I24 surrounding thehub of the take-up arm.

In certain instances, it may be desirable to change the time in each sewing cycle at which the tensioning device is rendered inoperative. For adjusting the tension device in this way, it is only necessary to loosen the nut HE! and to turn the cam I83 to the desired relationship with the shaft I M. In other respects, the manner of operation of the take-up and frictional tensioning device remains the same as in the machine of the application.

'From the construction and arrangement of the frictional tension actuating mechanism thus described, it is apparent that the parts are-readily accessible and conveniently disposed for effective adjustments.

The nature and scope of the invention having been indicated and an embodiment thereof-having been specifically described, what is claimed is:

1. Ailockstitch shoe sewing machine having stitch forming devices including a curved hook needle, a locking thread case, and a loop taker actingto pass each loop of needle thread about the thread case without itself passing through the needle loop, in combination with a tension reducingstep on one of the thread engaging surfaces of the loop taker acting at a time in the movement of the needle loop about the thread case when the loop is in a position of maximum extension,

' to insure certain release of'the loop from the thread case at a uniform time in each sewing cycle.

-A lockstitch sewing-machine having stitch forming devices including a hook needle, a lockingthread case having an exposed front end directedtoward the needle, anda rotary loop taker acting to twist each-loop of-needle thread and-open it"fer passage about the thread case, said loop taker being-provided with a loop entering-beak-acting-to carrya leg of the loop extending from the needle to-the inner surface of the beak -in-front-of the thread case and to carry-the etherleg of theleop extending from the work to --the o uter surface ofthe-beal across the back end ofthe-thread case, in combination with a tensien-reducing step on the looptaker located at a -position-to-pass the inner leg of each needle loop as the locp reachesa position of maximum exten- --sion about the thread case, to insure certain releaseof the loop when the take-up pulls the thread.

3. A lockstitch sewing machine having stitch forming devices comprising a needle, a loop taker, -atake-up, a pull-01f, afront thread lock between the'take-up and pull-off, a rear thread lock between the pull-off and the thread supply, and mechanism fOr actuating the parts timed to cause the take-up to set each stitch while both thread locks are closed and to close the front thread lock before a stitch setting strain is applied to the threadby the take-up.

4. A lockstitch sewingmachine having stitch forming devices comprising a needle, a loop taker,

a-take-up,-a pull off, a front thread lock between the take-up and pull-off, a rear thread lock between-the pull-off and the thread supply, and

; mechanism for -actuating the parts timed to cause the take-upto set each stitch while both'thread 12 looks are closed, to close the front lock before a stitch setting strain is applied to the thread by the take-up, and to open the'front lock onl after substantially all of the stitchsetting strainhas been relieved from the thread.

5. A lockstitch sewing machine havingstitch forming devices comprising a needle, a loop taker, a take-up, a pull off, a front thread lock between the take-up and pull-01f, a rear thread lock between the pull-off and the thread supply, and mechanism for actuating the parts timed to'cause the take up to set each stitch while both thread locks are closed, to close the front lock before a stitch setting'strain is applied-to the thread by the take-up, and to retain the rear thread lock closed until the stitch setting strainis substantially relieved.

6. A lockstitch sewing machine having stitch forming devices comprising a needle, a loop taker for opening each loop of needle thread, a thread case about which the loop taker passes each needle loop, a take-up, a pull-01f, afront thread lock between the take-up and the pull-01f to provide a measured length of thread for each stitch, and a rear thread lockbetween the pulloif and the thread supply, in combination with mechanisms for actuating the parts timed to close the front threadlock before astitoh'setting strain is applied to the thread by the take-up, to cause the take-up to set each stitch while both thread locks are closed, and to open the rear thread look only after substantially all strain has been'relieved from the thread before the needle loop for the succeeding stitch is opened by the loop taker to a position of greatest extension.

'7. A lockstitch sewing machine having stitch forming devices comprising a needle, a loop taker, a take-up, a pull-off, a front thread lock between the take-up and pull-off, a'rear'thread lock between the pull-off and the-thread supply, mechanism for actuating the parts to cause the take-up to set each stitch while both thread locks are closed, to close the front thread lock before a stitch setting strain is applied to the thread by the take-up, and to retain the rear thread lock closed until thestitch setting strain is substantially relieved, and an adjustable thread tension acting between the rear thread lock and the thread supply to enable measurement of thread by the pull-off under substantially the same strain as that applied to the thread between the looks at the time the front thread lock is closed.

8. A sewing machine having stitch forming devices including a needle, a pull-off, and a thread lock between the pull-ofi and the work, comprising a roll having a substantially cylindrical surface about which the thread is wrapped, a thread gripping shoe acting to clamp the thread against the cylindrical surface of the roll, and a stationary guide lug extending axially across the cylindrical surface of the roll with a radial thread guiding face disposed between the ends of the roll to-prevent displacement of the thread lengthwise of the roll.

-9. A sewing machine having stitch forming devices including a needle, a pull-off, and a thread lock between the pull-01f and the work, comprising a roll having a substantially cylindrical surface about which the thread is wrapped, a thread gripping shoe acting to clamp the thread against the cylindrical surface of the roll,a stud on which the roll is mounted, and a replaceable thread guide ring surrounding the stud at one end ofithe roll formed with a .portion'projecting across the cylindrical surface ofthe'roll withia 115 thread guiding face disposed between the ends of the roll to prevent displacement of thread lengthwise of the roll.

10. A lockstitch sewing machine having stitch forming devices comprising a needle, a loop taker for opening each loop of needle thread, a thread case about which the loop taker passes each needle loop, a take-up, a pull-off, a front thread lock between the take-up and the pull-off to provide a measured length of thread for each stitch, and a rear thread lock between the pullbefore each stitch is set, and means for counterbalancing the tension on the thread between the off and the thread supply, in combination with means for imparting a momentary uniform tension to the thread in the needle loop while each loop is reaching a position of maximum extension about the thread case, to insure withdrawal of the measured thread from between the thread looks through the work.

11. A lockstitch sewing machine having stitch forming devices comprising a needle, a loop taker for opening each loop of needle thread, a thread case about which the loop taker passes each needle loop, a take-up, a pull-off, a front thread lock between the take-up and the pull-off to provide a measured length of thread for each stitch, and a rear thread lock between the pull-off and the thread supply, in combination with means for imparting a momentary uniform tension to the thread in the needle loop while each loop is reaching a position of maximum extension about the thread case, to insure withdrawal of the measured thread from between the thread looks through the work, comprising a step surface on the loop taker acting with the take-up to reduce the tension with certainty while the take-up continues to pull the thread.

12. A lockstitch sewing machine having stitch forming devices comprising a needle, a loop taker for opening each loop of needle thread, a thread case about which the loop taker passes each needle loop, a take-up, a pull-off, a front thread lock between the take-up and the pull-off to provide a measured length of thread for each stitch, and a rear thread lock between the pull-off and the thread supply, mechanism for actuating the parts to cause the front thread lock to be closed before a stitch setting strain is applied to the thread to cause the take-up to set each stitch while both thread locks are closed and to open the rear thread look only after substantially all strain has been relieved from the thread, in combination with means for imparting a momentary uniform tension to the thread between the thread locks before each stitch is set, and means for counter-balancing the tension on the thread between the looks when the rear lock is opened.

13. A lockstitch sewing machine having stitch forming devices comprising a needle, a loop taker for opening each loop of needle thread, a thread case about which the loop taker passes each needle loop, a take-up, a pull-off, a front thread lock between the take-up and the pull-off to provide a measured length of. thread for each stitch, and a rear thread lock between the pull-off and the thread supply, mechanism for actuating the parts to cause the front thread lock to be closed before a stitch setting strain is applied to the thread to cause the take-up to set each stitch while both thread locks are closed and to open the rear thread look only after substantially all strain has been relieved from the thread, in combination with means for imparting a momentary uniform tension to the thread between the thread locks looks when the rear lock is opened comprising a tension wheel adjusted to prevent movement of the thread through the rear look before the pulloff acts:

14. A lockstitch shoe sewing machine having stitch forming devices including a curved hook needle, a locking thread case, a loop taker acting to pass each loop of needle thread about the thread case and to free the needle loop from the thread case with a substantial length remaining outside the work, a take-up for pulling the freed loop from the thread case, and a loop retaining hook on the loop taker for maintaining the needle loop out of contact with the work for a substantial portion of the movement of the loop taker after the loop is disengaged from the thread case.

15. A lockstitch sewing machine having stitch forming devices including a curved hook needle,

a locking thread case having an exposed end directed toward the needle and a rotary loop taker acting to twist each loop of needle thread and open it for passage about the thread case, said loop taker being provided with a loop entering beak and acting to carry a leg of the loop extending from the needle to the inner surface of the beak behind the thread case and the leg of the loop extending from the work to the outer surface of the beak across the exposed end of the thread case, in combination with a loop'retaining hook on the outer surface of the loop taker beak for maintaining the needle loop out of contact with the work for a substantial portion of the movement of the loop taker after the loop is disengaged from the thread case.

16. In a sewing machine having stitch forming devices including a hook needle, a needle looper and a take-up, a rotary shaft on which said take-up is mounted, means for securing the take-up to the shaft, and a frictional tensioning device acting with a yielding pressure on the thread between the looper and the take-up, in combination with connections for rendering the tensioning device inoperative during a portion of each sewing cycle comprising a cam retained adjustably in position on the shaft by the act of securing the take-up to the shaft.

17. In a sewing machine having stitch forming devices including a hook needle, a needle looper, and a take-up, an arm for the take-up, a shaft to which the take-up arm is keyed, a clamping nut on the take-up shaft for securing the take' up arm to the shaft, a frictional tensioning device acting with a yielding pressure on the thread between the looper and the take-up, in combination with connections for rendering the tensioning device inoperative during a portion of each sewing cycle, comprising a cam retained adjustably in position on the take-up shaft by the clamping force of the nut in securing the takeup to the shaft.

FRED ASHWORTH.

REFERENCES CITED UNITED STATES PATENTS Name Date Ashworth et al. Feb. 3, 1942 Number

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