US2465356A - Tension device for thread handling machines - Google Patents

Description

March 29-, 1949. 1 F. :E. COLE TENSION DEVICE FOR THREAD HANDLING MACHINES Filed Sept. 13, 1946 Z'Sheets-Sheet 1 Inventor Ff'ank E Cole B his Aitorney March 29, 1949. F. E. COLE 2 4 5,

TENSION DEVICE EOR THREAD HANDLING MACHINES Filed Sept. 15, 1946 2 Sheets-Sheet 2 Z3 24 LAW/103% lnvenior Frank E. Cole Patented Mar. 29, 1949 TENSION DEVICE FOR THREAD HANDLING MACHINES Frank E. Cole, Manchester, Mass, assi'gnor "to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application September 13, 1946, Serial No.'B9'6,786

25 Claims. 1

The present invention relates to improvements in thread handling devices and particularly tensioning devices intended for use with shoe sewing machines and is hereinafter illustrated as applied to a curved hook needle chain-stitch sewing machine sirnilar to that illustrated in United States Letters Patent No. 2,359,662, granted October 3, 1944', upon an application filed in the name of Alfred R. Morrill.

The sewing machine illustrated in the patent is intended for automatic operation to attach a welt and upper to the insole of a lasted shoe and, in machines of this type, the stitch forming devices include an oscillating take-up acting successively during each sewing cycle to give up thread for the formation of each stitch, to set the stitch by exerting a predetermined tension on the thread andthereafter to draw from the supply sufficient thread for the formation of the succeeding stitch. While each stitch is being set, the resistance ofiered by the tensioning device reaches a maximum and the thread moves past the tensioning dvice. The time allotted for the movement of thread past the tensioning device from the suppiy is extremely short with the result that effects of inertia and irregular resistance to movement under some circumstances may cause difliculties in theformation and setting of successive stitches.

The tensioning device of the patented machine as shown comprises a thread traction member in the form of a pair of toothed disks providing between them a peripheral V-shaped groove within which the thread passes and a friction brake connected to the traction member. The brake is in the form of a drum secured to a shaft on which the disks are mounted and arelatively stationary braking shoe thrust by a spring against the periphery of the drum. Suitable means is provided in the patented machine for automatically varying the pressure of the braking shoe against the drum at difierent times in each sew-- ing cycle so that the thread may be drawn more freely from the supply at some stages in the formation of stitches than at others.

The tensioning devices in both the patented machine and other machines of the prior art cause a heavy tension to be applied to the thread while the inertia of the thread engaging disks and brake drum are being overcome at the instant of stitch setting. Also, the frictional retardation of the braking shoe on the brake drum is highest in starting rotation of the disks and drum.

At the instant of stitch setting, the brake drum and shoe are in firm, definite contact witheach other. If there is oil on the engaging surfaces of the drum and shoe, 2. continuous film of oil will immediately be built up as soon .asrelative movement takes place, thus reducing the frictional force necessary to continue movement of the thread. The action of a tensioning device constructed with a conventional braking shoe, therefore, will apply an extremely heavy tension upon setting each stitch in the machine and, as soon as thread is drawn from the supply, the tension on the thread may be substantially reduced, with the result that considerable overthrow of the disks may occur. Unless the machine is provided with an auxiliary take-up capable of absorbing the surplus thread drawn past the tensioning device as a result of overthrow, the thread will become slack and stitches will be improperly formed or the thread will be broken. Further than this, the amount of overthrow is difficult to control uniformly from one cycle to another, particularly when the sewing speed changes during insertion of a seam, and, consequently, successive stitches maybe set with irregular tensions.

One of the several-objects of the present inventionis to provide an improved form of tensioning device of such nature that it will not only cause a more nearly uniform degree of tension to be applied to the thread from one sewing cycle ;to another but that a substantial reduction will be made in the amount of overthrow of thread taking place past the tensioning device from the supply after each :stitch is set. These results are obtained by reducing the mass of the parts moving with the thread traction member and by providing a brake which does not reduce its frictional action after thread drawing movement has started or under an intermittent .or jerky thread action from anycause.

To this end, the illustrated embodiment of the invention resides in .a thread tensioning device in which the diameter of the brake drum is re duced substantially to the size of the shaft to which the thread traction disks are secured for rotation and, instead of utilizing a braking shoe of ordinary construction, the present tensioning device is controlled 'frictionally by an elongated braking band having a series of turns engaging the drum. The advantage of such ac-onstruction is that successive portions of the braking band apply a progressively decreasing pressure along the'length of the band from the trailing to the leading end thereonxthe frictional retardation being less subject to variation and irregularities 3 than with the use of the conventional form of braking shoe.

Preferably, the braking band comprises a round wire coil spring wrapped a plurality of times around the drum. With this construction, it is possible to impart a retarding action to the drum, the variation of which will be less than ten per cent when the coefficient of friction between the drum and the coil spring varies more than 400 per cent. According to the present invention, it is also possible to provide means for changing the lengthwise force applied to the braking band during each sewing cycle to vary the tension on the thread as in the machine of the prior patent, and this is accomplished in the illustrated form of the tensioning device by securing the trailing end of the spring in a fixture attached to the machine frame to prevent rotation of the spring with the drum and by providing mechanism for applying a changing force to the leading end of the spring durin each sewing cycle.

While the tensioning device of the invention is particularly adapted for use with an inseam chain-stitch shoe sewing machine of the type described, it is to be understood that in its broader aspects the invention is not limited in application to such machine but may well be utilized with machines of other types in which thread handling devices including means for intermittently drawing thread from a supply are employed or wherein it is of advantage to maintain uniform unvarying tension in the thread without uncertainties resulting from overthrow and increased frictional resistance ordinarily encountered in starting, or resulting from inertia or other effects.

The several features of the invention consist in the devices, combinations and arrangements of parts hereinafter shown and described which together with the advantages to be obtained thereby will readily be understood from the following description and pointed out in the appended claims, taken in connection with the accompanying drawings, in which Fig. 1 is a view in left side elevation of the upper portion of a chain-stitch inseam shoe sewing machine, illustrating a preferred embodiment of the invention;

Fig. 2 is a sectional plan view of the tensioning device, looking in the direction of the arrow II of Fig. 1;

Fig. 3 is a. detail View on an enlarged scale of the tension brake drum in section and the braking band of the machine, illustrating the positions assumed while the machine is stopped with the band essentially disengaged from the drum;

Fig. 4 is a similar view of the same parts taken during normal sewing operations;

Fig. 5 is a detail view on a. reduced scale of the coil spring which forms the band before being applied to the drum; and

Fig. 6 is a detail view on a much larger scale, illustrating the action of the braking band when oil is present on the drum.

The shoe sewing machine illustrated in the drawings is provided with the usual stitch forming devices of a welt or inseam sewing machine comprising a curved hook needle 4, a looper 6, a take-up 8, an auxiliary take-up It], a welt guide l2, and a channel guide [4. During the operation of the machine, the needle enters the work, the thread is laid in its hook by the looper, and the take-up gives up thread to the needle during its retracting stroke. Thereafter, the work is fed a Stitch length and the needle again enters the work, passing through the loop formed during its first work entering movement, and the take-up sets the stitch by tightening the loop about the shank of the needle. After setting each stitch, the take-up draws a length of thread past a tensioning device suflicient to form the succeeding stitch. These operations are repeated during each sewing cycle. The parts thus referred to together with the operating mechanism therefor are the same and operate in the same manner, except as hereinafter described, as in the machine of the Morrill patent above referred to.

The thread tensioning device of the present machine has a thread traction member similar to that of the patent, comprising a pair of toothed disks l6 secured together and to a rotatable shaft l8 to provide a tension wheel about which the thread passes from the supply (not shown) to the stitch forming devices. The stitch forming devices and take-up act intermittently to draw thread past the tension wheel, imparting a tension to the thread equal to the resistance offered by the tension wheel against rotation in the direction of the arrow (Fig. 1). In the patented machine, the tension wheel is frictionally retarded by a braking shoe acting on a rell atively heavy brake drum secured to a shaft corresponding to the shaft l8. The inertia efiect of the brake drum adds materially to the resistance offered to the thread in starting the tension wheel in rotation, and the characteristics of the braking shoe engaging the tension wheel are such that the static friction required to start rotation is substantially greater than the dynamic friction offered after rotation is started.

The tension wheel is stationary during the 7 major portion of each stitch forming cycle and,

in the patented machine, the braking shoe firmly grips the brake drum, offering a relatively heavy static resistance to rotation. As soon as the tension wheel begins to rotate, however, the braking shoe is forced outwardly somewhat from the shaft I8 and the dynamic friction resisting rotation is reduced. Furthermore, if oil is present on the drum, a continuous film will be built up after the drum is started so as to prevent intimate contact between the shoe and the drum. Thus, the resistance to rotation of the tension wheel will be modified by the characteristics of the oil film which ordinarily results in friction reduction. The reduced friction during rotation reacts on the thread to reduce its tension and increase the tendency of the wheel to continue rotating non-uniformly from one cycle to another beyond the point where the tension on the thread reaches a practical minimum value. In many instances, the tension wheel will so rotate, providing such a surplus of thread that it becomes slack for a short interval during each sewing cycle. Ordinarily, moderate amounts of slack in the thread cause no difiiculty in the operation of the machine but, if the slack becomes excessive, the needle will not be looped properly and the thread will become entangled with some of the operating devices in the machine.

To avoid these undesirable results and to reduce the slack and non-uniformity of tension in the thread from one sewing cycle to another. in the machine embodying the present invention, the tensioning device hereinafter described is equipped with frictional retarding means peculiarly well fitted for the purpose intended. The

brake drum of the illustrated machine, indicated at 1'9, also is reduced in size approximately to the diameter of the shaft 1 8 and comprises a' slight enlargement at the left end of the shaft sufiicient in diameter only to form a shoulder beyond the journal portion of the shaft received in a bearing 22 in the machine frame. The enlargement in diameter of the shaft l8 beyond the bearing 22 is so small that its inertia adds a negligible amount to the total inertia of the tensioning device, reducing the tendency toward overthrow of the tensioning device far below that in the patented machine.

For imparting frictional retardation to the shaft l8 of the illustrated tensioning device, the enlarged end of the shaft which forms the brake drum 19 has engaging it a braking member arranged positively to grip the drum and thereafter to reduce its grip on the drum while maintaining sufficient frictional drag on the drum to insure a more nearly constant tension on the thread than has been possible heretofore. The tension applied to the thread is controlled by causing that portion of the braking member which surrounds the drum to move bodily with the drum and to grip the drum with increasing pressure as the tension on the thread increases, thus positively preventing slippage of the drum beneath the braking member. When the tension on the thread reaches a predetermined intensity, the braking member is actuated to reduce its grip in a manner to be more fully explained hereinafter. The braking member engaging the drum [9 comprises an elongated band wrapped about the drum a plurality of times and is composed vof an expanded round wire coil spring 23, the normal internal diameter of which is somewhat less than the outside of the brake drum IS. The direction of rotation of the shaft under tension of the thread is such that the spring is wound more tightly as it moves with the drum positively preventing slippage. At the end of the free bodily movement of the spring with the drum, the coils of the spring are unwound, partially releasing them from the drum so that the maximum frictional force is applied by the coils at the leading end of the spring on the drum, and the force of successive coils in the direction of the trailing end of the spring is progressively reduced. It thus appears that the first few coils at the leading end of the spring apply most of the retarding effect to the drum, producing an unwinding effect on the trailing coils suificient to reduce their frictional engagement with the drum. For this reason, the static friction of the spring on the drum is equal only to the retardation of a few coils of the spring, the unwinding movement of these coils as the shaft begins to move with relation to the spring causing the braking pressures of the remainder of the coils on the drum to become reduced. In this way, the braking pressure of the braking band after relative rotation of the shaft is started is always eoual to the force required to expand the spring forming the band.

The retarding action of the spring 23 on the shaft is not subject to wide variations as a result of changes in coefficient of friction between the spring and the shaft. With the engaging surfaces of the spring and the drum in clean, dry condition, the coefficient of friction between these surfaces may be assumed to be at a maximum. Under these conditions, most of the frictional retardation of the spring on the drum is applied by the first few coils of'the spring at the leading 6 end thereof. As the shaft rotates, the frictional retardation of the spring tends to unwind the remaining coils of the spring with a force which is proportional to that used in expanding the spring to the size of the drum, thus reducing their respective pressures on said drum. If, however, oil is applied to the spring, as indicated in Fig. 6, it fills the spaces between the coils and collects at 24 between the engaging surfaces. Under these conditions, the pressure of the first few coils at the leading end of the spring is reduced and is insufficient to produce enough friction to unwind the remaining. coils of the spring, so that several additional coils near the leading end of the spring continue to grip the drum before frictional force is exerted to unwind the other coils. In this way, the spring automatically compensates for variations in coeiiicient of friction caused by changing operatingconditions of the surfaces on the drum and braking band formed by the coil spring 23. Also, the use of a round or other shaped wire coil spring having approximately a line contact with the drum instead of a spring formed of Wire having a rectangular or other fiat-sided section is of advantage since the round wire tends to force the oil outwardly from the line of contact between the spring and the drum.

It has been found that a spring having ten coils on a tension wheel drum i9 is sufficient for all practical purposes in maintaining the frictional retardation of a tension wheel uniformly under the worst operating conditions met in shoe factory practice. With the use of ten turns, the

' retardation of the tension wheel and the tension on the thread will not change more than ten per cent while the coefficient of friction between the drum and th spring varies more than four hundred per cent. Variation in coeflicient of friction of approximately four hundred per cent is the limit capable of being caused by the applica. tion of a lubricant to a clean, dry brake drum about which the coil spring is wrapped. Greater variation than this is unlikely to occur in ordinary usage. Since there is unlikely to be a change in strength of thread employed for Welt or inseam shoe sewing operations of as much as ten per cent, a greater refinement and uniformiy in frictional retarding action on a sewing thread 'ension wheel is unnecessary. With an arrangement having a retarding action which is maintained uniformly wihin ten per cent under all operating conditions, extremely beneficial results are obta ned in the formation and setting of stitches in the work. Thread breakage as a result of variations in friction is thereby reduced to a minimum and the necessity for constant adjustment of the tensioning device, as with the usual braking shoe construction. is avoided. These resuls are particularly noticeable when the speed of sewing is changed substantially throughout the insertion of a single seam. With the use of the usual braking shoe retarding device, the stiches inserted by a machine at higher speeds are much tighter than at lower speeds. With the use of a coil spring braking band, variation in sewing speed appears not to affect the tightness of the stitches to any perceptible degree.

In the machine of the prior patent, tension on th thread is varied by increasing and decreasing the braking pressure on the tension wheel brake drum during each sewing cycle while the take-up is taking'up thread. To increase and decrease the braking force of a tensioning device employing a coil spring braking band ac-' cording to the present invention, the trailing end of the coil spring is secured in a releasable clamp fixture 26 at a substantial distance radially from the drum l9 (Fig. 2) to enable relative yielding movement between that portion of the spring engaging the drum and that portion secured by the fixture. The leading end of the coil spring is controlled through connections to the take-up 8 in a manner similar to those for controlling the braking shoe in the machine of the patent referred to. For this purpose, the leading end of the coil spring is also connected at a distance from the brake drum to a clamp fixture 28 pivotally connected at 30 to a link 32 through the lower end of which passes loosely a bolt 34 clamped within a lengthwise slot 36 in a lever 38. The lever 38 is rotatably mounted on the hub of the take-up 8 so that it oscillates with the take-up about a fixed stud 40 forming the fulcrum for the take-up. The lever 38 is adjustably secured to the take-up by a clamp screw 42 passing through an arcuate slot in one arm of the lever and entering a threaded opening in the take-up. During operation of the machine, oscillating movements of th take-up are transferred to th clamp fixture 28 through the connections thus described, adding and substracting from the force of the coil spring which causes it to contract and expand more or less on the shaft l8. By these connections, the leading end of the spring 23 is moved during the taking-up stroke of the take-up in a direction in opposition to the movement of the tension wheel by the thread.

To enable the action of the spring 23 to be increased and decreased smoothly during each sewing cycle and the entire spring to be freed from frictional engagement with the tension wheel shaft l8 at the end of each sewing operation so that thread may be drawn freely past the tension wheel in removing the work from the machine, the flexibility of the trailing end of the spring is augmented by a reverse curvature having at its outer extremity an arcuate portion 44, engaging the fixture 26, substantially concentric with the coils surrounding the drum and with an angular portion 46 closer to the coils. The arcuate. portion 44 when unclamped is slidable in the clamp fixture 26 without deforming or straining the trailing end of the spring. The angular portion 46 of the spring is arranged to engage the upper end of an abutment 48 during each sewing cycle to limit its flexing movement and the bodily movement of the main portion of the spring with the tension wheel drum. The abutment 48 is engaged by the spring close to one of the angles in the portion 46 and the spring is moved slightly from the dot-dash position of Fig. 4 in engagement with the abu ment 48 to the solid position as the fixture 28 is oscillated through connections with the take-up. Th movement of the angular portion provides an eifective means for enabling the grip of the spring to be built up to a maximum on the tension wheel drum and causes a limited yielding movement of the shaft with the braking spring under tension of the thread before the angular portion engages the abutment 48. This yielding movement is so short that it does not affect the formation or setting of a stitch and, in fact, may react beneficially to apply a yielding tension to the thread for some time after the stitch is set.

By securing the leading end of the braking spring in the clamp fixture 28 at a distance from the brake drum advantage is taken of the flexibility of the leading end of the spring to improve the retarding action of the braking band. Thus, when the braking band begins to move bodily with the drum as the tension is first applied to the thread during each sewing cycle, the leading end of the spring is flexed until the abutment 48 is engaged by the trailing end of the spring to releas the grip of the spring on the drum. In this way, an accurate and reliable retarding force is applied to the drum and the tension wheel, even before slippage occurs between the spring and the drum.

When the machine is brought to rest at the end of each sewing operation, a stopping mechanism, similar to that disclosed in the Morrlll patent, becomes operative to release the coils of the spring 23 from frictional engagement with the drum IS on the tension wheel shaft. Briefly, this stopping mechanism includes a lock bolt 50 cooperating with a clutch shifting lever 52 supported on a vertical pivot and arranged to oscillate idly during sewing. When the lock bolt engages the clutch shifting lever 52, the lock bolt is moved bodily to the right, in Fig. 1, together with a carrier or slide 54 in which the lock bolt is mounted for vertical sl'ding movement. The slide 54 has along its upper side an abutment engaging a downwardly extending arm 56, which arm is connected to a substantially horizontal arm 58 rotatable on a pivot shaft 60. To the upper surface of the arm 58 is screwed the abutment 48, the arrangement being such that, in bringing the machine to rest, the stopping mechanism moves the abutment from the dot-dash position of Fig. 3 into the solid position, carrying it beneath the angular portion 46 of the spring and camming this portion upwardly. This upward movement of the angular portion 46 of the spring serves to uncoil the spring and disengage it frictionally from the drum IS. The abutment 48 is retained in spring-releasing position by a latch 62 supported on a fixed pivot 64 and held yieldingly in operative pos'tion with relation to the arm 58. The latch thus holds the arm 58 and abutment 48 in tension releasing position while the machine is stopped. As soon as the machine is started, a second latch 66 pivotally mounted on the first latch 62 engages a notch in the hub of the take-up 8 and draws the latch 62 away from the arm 58. As soon as the arm 58 is freed from the latch 62, the abutment 48 moves from the solid position of Fig. 3 to the dot-dash position and the coils are again allowed to come into frictional engagement with the brake drum IS.

The nature and scope of the invention having been pointed out and a particular embodiment having been described, what is cla med is:

1. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a traction member moved by the thread, and a brake drum connected to the traction member, in combination with an elongated braking band having a series of turns frictionally engaging the drum.

2. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a traction member moved by the thread, and a brake drum connected to the traction member, in combination with an elongated braking band wrapped a plurality of times about the drum.

3. In a machine for handling thread having devices acting intermittently to draw thread from a supply. a traction member moved by the thread,

and a brake drum connected to the traction member, in combination withanelongatedbraking band comprising a round wire coil spring wrapped a plurality of times about the drum.

4. In a machine. for handling thread having devices acting intermittently to draw thread from a-s-upply, a traction member moved by the thread, and a brake drum connected to the traction member, in combination with an elongated braking band having a sufi'icient number of turns-frictionally engaging the drum to prevent change in tension on the thread of. morethan ten per cent as a resultv of variat on in coefficient of friction between thedrum and the brakingband of more than four hundred per cent.

5. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a traction member moved by the thread, and a brake drum connected to the traction member, in combination with an elongated braking band having a series of turns frictionally engaging the'd'rum, and means forchanging the force applied to the braking band during each sewing cycle tovary the tension. on the thread.

6. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a tractionmember moved by the thread, and a brake. drum connected to the traction member, in combination with an elongated braking band having a series of turns frictionally engaging the drum, means for changing the force applied to one end. of the braking hand during each sewing cycle to vary the tension on; the thread, and a fixture for securing the other end of the band at a substantial distance radially from the drum to enable-relative yielding movement between the portionv ofthe band engaging the drum and the portion secured to thefixture.

7.. In a machine for handling thread having devices acting intermittently to draw off thread from a supply, a thread tract on member and a brake drum connected to the traction member, in combination with a friction spring having a plurality of turnsof normally smaller internal diameter than the outside of the brake drum expanded about said drum and arranged to be unwound by the rotation of the brake drum.

8. In a machine for handling thread having devices acting intermittently to draw off thread from a supply, a thread traction member and a brake drum connected to the traction member, in combination with a friction spring having a plurality of turns of normally smaller internal diameter than the outside of the brake drum expanded about said drum and arranged to be unwound by the rotation of the brake drum, and a fixture for securing the trailng end of the spring against rotation with the brake drrm.

9. In a machine for handling thread having devices acting intermittently to draw off thread from a supply, a thread traction member and a brake drum connected to the traction member, in combination with a friction spring having a plurality of turns of normally smaller internal diameter than the outside of the brake drum expanded about said drum and arranged to be unwound by the rotation of the brake drum, a fixture for securing the trailing end of the spring against rotation with the brake drum, and mechanism connected to one of said thread drawing devices for applying a changing force to the leading end of the spring during each sewing cycle.

10. In a machine for handling thread having devices acting intermittently to draw ofi thread from a supply, a thread traction member and a 1 0 brake drum connected to the traction! member, in combination with afriction: spring-having. alplurality of turns of normally smaller. internal: diameter than the outside. or the brake drum. expanded about said. drum and arranged to be unwound by the rotation of the brake drum, the trailing endof thespring being reverselycurved, a fixture for securing said; trailing end against rotation with. the brake. drum, means for controlling the position of; the. leading end of the spring, and mechanism acting against the reversely' curved. portion of the spring; when the machine is being brought to rest to free the spring from frictional engagement with thedrum.

11. In a machine for handling threadv having devices acting intermittently to draw offthread from a supply, a thread. traction member: and a brake drum connected to the traction member, in combination with a friction spring. having a plurality of turns of normally smaller internal diameter than the outside of the. brakev drum expandedv about said drum and arranged to be unwound by the rotation of the brake drum, a fixture for securing the trailing end of the spring against rotation-with the brakedrum, and mechanism acting when the machine is being brought torest to free the spring from frictional. engagement with the drum.

12. In a machine for handling. thread having devices acting intermittently todraw oiT thread from a supply, a rotary thread traction member, a brakev drum connected to the traction member, in combination with a coil spring of normal internal diameter less. than the outside diameter of the brake drum expanded to the diameter of the drum to produce a braking pressure on the drum substantially equal to" the force required to'expand the spring.

13. In a sewing machine havingstitch forming devices including a take-up acting intermittently to draw off thread from a supply, a movable thread tractionmember, abrake drum connected to the traction member, in combination with a braking band wrapped about the drumandconnected at one end to the take-up for increasing the force applied to-thebraking hand: during the taking-up stroke of the take-cpl 14'. In a sewing machine having. stitch forming devices. including a take-upacting. intermittenty to draw oif thread from a; supply. a movable thread traction member, a brake drum connected to the traction member, in combination with a brak ng band on the drum comprising a coil spring, the trailing end of which is yieldingly connected with a fixed part of the machine and the leading end of which is connected to the takeup to cause movement of the leading end in a direction in opposition to the movement of the traction member by the thread to change the force apolied to the braking band during the taking-up stroke of the take-up.

15. A thread tension having a tension wheel over which the thread is drawn. and a brake drum connected to the tension wheel. in combination with a braking band surrounding the drum, comprising a spring coiled about the brake drum a plurality of times.

16. A thread tension having a tension wheel over which the thread is drawn. and a brake drum c nnected to the tension wheel, in combination with a braking band surrounding the drum, comprising a coil spring of normally smaller internal diameter than the outside of the brake drum expanded to surround the brake drum for applying a, frictional retardation to the drum pro- 11 portional to the force used in expanding the spring to the size of the brake drum.

17. A thread tension having a tension wheel over which the thread is drawn, and a brake drum connected to the tension wheel, in combination with a braking band surrounding the drum, comprising a spring coiled about the brake drum a plurality of times, and means acting periodically at one end of the spring to increase and decrease the frictional retardation exerted by the spring.

18. A thread tension having a tension wheel over which the thread is drawn, and a brake drum connected to the tension wheel, in combination with a braking band surrounding the drum, comprising a spring coiled about the brake drum having at one end a reversely curved portion secured to a fixed part of the machine, and an abutment cooperating with the reversely curved portion of the spring to limit the movement of the spring with the drum as the tension wheel is rotated with the thread.

19. A thread tension having a tension wheel over which the thread is drawn, and a brake drum connected to the tension wheel, in combination with a braking band surrounding the drum, comprising a spring coiled about the brake drum having at one end a reversely curved portion secured to a fixed part of the machine, an abutment cooperating with the reversely curved portion of the spring to limit the movement of the spring with the drum as the tension wheel is rotated with the thread, and stopping mechanism for actuating the abutment to release the spring from frictional engagement with the drum at the end of a sewing operation.

20. In a machine for handling thread having devices for drawing thread from a supply, a traction member moved by the thread and a drum having a friction surface connected to the traction member, in combination with an elongated braking member tensioned against the friction surface of the drum and constructed to apply to successive portions of the friction surface a progressively varying pressure along the length of the braking member during movement of said surface, with the leading ,end of the braking member first engaging said surface acting to decrease the pressure of the trailing end of the braking member as the coefficient of friction between the friction surface and said member increases.

21. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a traction member moved by the thread, and a brake drum connected to the traction member, in combination with a brakin band engaging the drum arranged for yielding bodily movement with the drum, and an abutment arranged to disengage the braking band from the drum when the band moves a predetermined distance with the drum.

22. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a traction member moved by the thread and a brake drum connected to the traction mem-- ber, in combination with an elongated braking band surrounding the drum, comprisin a coil of wire having line contact only with the drum.

23. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a traction member moved by the thread, and a brake drum connected to the traction member, in combination with an elongated spring having a series of turns frictionally engaging the drum, means engaging one end of the spring at a substantial distance radially from the drum to provide relative yielding movement between the portion of the spring on the drum and the portion engaged by said means, and an abutment acting on the other end of the spring to release the grip of the spring on the drum when the tension on the thread reaches a predetermined value.

24. In a machine for handling thread having devices acting intermittently to draw thread from a supply, a traction member moved by the thread, and a brake drum connected to the traction member, in combination with an elongated braking b-and having a series of turns frictionally engaging the drum, and means for securing the leading end of the braking band including yielding means to enable the band to move bodily through a limited distance with the drum as the tension is applied to the thread during each sewing cycle.

25. A thread tension havin a tension wheel over which the thread is drawn, and a brake drum connected to the tension wheel, in combination with a braking band surrounding the drum, comprising a spring coiled about the brake drum ten times.

' FRANK E. COLE.

No references cited.

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