US2207957A - Sewing machine - Google Patents

Description

y 1940- L. E. TOPHAM SEWING MACHINE Filed Feb. 28, 1938 7 Sheets-Sheet 1 July 16, 1940. 1.. E. TOPHAM 2,207,957

SEWING MACHINE Filed Feb. 28, 1938 7 Shets-Sheet 2 L. E. TOPHAM July 16, 1940.

SEWING MACHINE Filed Feb. 28, 3.938

7 Sheets-Sheet 5 July 16, 1940. L. E. TOPHAM SEWING MACHINE Filed Feb. 28, 1938 7 Sheets-Sheet 4 Wimass July16,1940. L. E. TOPHAM 2,207,957

' SEWING MACHINE 4 Fiied Feb. 28, 1938' '7 Sheets-Sheet 5 Witness 10 ean/25m f 1 m zzpfw w L. E. TOPHAM July 16, 1940.

SEWING MACHINE Filed Feb. 28, 1938 7 Sheets-Sheet 6 was #6. mm

July 16, 1940. E. TOPHAM SEWING MACHINE Filed Feb. 28, 1938 7 Sheets-Sheet 7 Patented July 1 6, 1 940 PATENT OFFICE SEWING MACHINE Laurence E. Topham, Wenham, Mass, assignor to United Shoe Machinery Corporation, Borough of Flemington, N. J., a corporation of New Jersey Application February28, 1938, Serial No. 193,035 I 24 Claims. (01. 11258) The present invention relates to sewing machines, and more particularly to thread measuring devices for supplying the stitch formingdevices with measured amounts of needle thread 5 during the formation of each stitch. I

The present invention is designed primarily for use in a lock'stitch machine of the type in. which the position of the interlockingportions of the needle and shuttle threads in the work is determined by devices which draw thread from the shuttle during the formation of each stitch and act to prevent further withdrawal of shuttle thread while the stitch is being set. While, however, the invention is of special value when embodied i'i'a lockstitch machine of thetype referred to, it is also applicable to'other types of lockstitch sewing machines and in its broader aspects is applicable to any type of sewing machine, lockstitch or otherwise, in which is de- 29 sirable to draw from the supply of needle thread measured amounts of thread for use by the stitch forming devices. 1

The objects f I the present invention are to provide a sewing machine of improved construction and operation so arranged that stitches may be set at high speeds with greater uniformity in tension and location of interlocking portions of thread in the work than heretofore, and particularly to maintain uniformly a predetermined tension in the sewing thread while setting stitches without regard to the tension on the thread required to overcome the inertia of the thread engaging parts of the thread supply.

In the sewing machine disclosed in the application for U. S. Letters Patent of O. R. Haas, Serial No. 118,622, filed December 81, 1936, each stitch is set by imparting to the thread a predetermined tension acting against a friction controlled device in the form of a thread engaging 4O tension wheel and thereafter an amount of sewthread for the next stitch is drawn, by means of the tension on the thread, past the tension wheel roan the wound mass or other supply package in which the thread is contained. The tension on the thread which draws the thread from the supply is caused by the pull' exerted by the stitch-forming devices comprisinga hook needle, a shuttle or loop taker, and a take-up. Due to the oscillating movements of the stitch forming devices, and principally to the movement of the take-up, an irregular pull is exerted on the thread corresponding to the movementsof the stitch forming devices. -As a result of the irregular pull on the thread, whensewing at even .55 moderately high speeds, the inertia in the tension ventors U. S. Letters Patent No. 1,165,817, dated December 28, 1915, there is a needle thread feeding device arranged to deliver during each sewing cycle the proper quantity of thread for the succeeding stitch without depending upon the pull exerted by the stitch forming devices. The thread feeding device of this machine, however, comprises a continuously rotating thread engaging wheeL'the speed of rotation of which is 'controlled'by theposition of the p-resser-foot on the work. While this arrangement is conducive locking threads in the work at speeds somewhat higher than with the useof a friction controlled wheel, theamount of thread measured for each stitch is independent of the thread tension and,

consequently, Where soft materials are being sewed, the stitches "may not be set with the same tension and at the same location as with harder or stiffer materials. The quality of the thread employed also may change the resulting stitches I to an undesirable extent. The control of the thread feeding device from the presser-foot alsosometimes results in irregularities in the location of the interlocking threads and in the tension due to failure of the pressure-foot to accurately measure the thickness of the work or to improper handling of the work, a fault common to all machines which utilize the presser-foot to control the thread measuring devices.

An important feature of the present invention, therefore, contemplates the provision in a sewing machine of means for feeding thread from the supply to the stitch forming devices, under the control of the tension on the thread when a stitch is set, so that an accurate measurement of the thread will be obtained, equal tothe amount of thread used in the stitch being set, and unvaried by the undesirable effects of intension wheel. At the same time, control of the thread feeding operation indirectly by the position of the presser-foot on the work, as in the machine of. inventors Patent No. 1,165,817, is

,avoided.

to uniformity in tension and location of interis set, so that irregular pull on the thread by the stitch forming devices will have no tendency-to" cause overthrow of the feeding means. To measure threadfrom the supply in the manner outlined not only improves the uniformity of stitching, but is effective during the first two or three stitches of a seam to prevent undesirable looseness in the stitches by insuring that no more than the exact amount of thread required for.

each stitch will be measured.

Other features of theinvention will be readily understood from an inspection of the accompanying drawings and following description of the construction illustrated therein.

In the drawings, Fig. 1 is a view in front elevation of a portion of a sewing machine embodying the present invention; Fig. 2 is a detail View of certain parts of the operating mechanism in the machine, as viewed from the right side; Fig. 3 is a view in front elevation on an enlarged scale of the lower portionof the machine, shown partly in section; Fig, 4 is a view in right side elevation of the lower portion of the machine, on an enlarged scale, with the parts shown in positions assumed while setting a stitch; Fig. 5 is a detail view of some of the operating connections illustrated in Figs. 3 and 4, looking from the front of the machine; Fig. 6 is a view of the same parts looking from the right side of the machine; Fig. 7 is an enlarged sectional detail view illustrating the operating mechanism for an auxiliary thread tensioning device of the machine; Fig. 8 is a detail view, on an enlarged scale, partly in section, of parts cooperating with the needle thread feed wheel of the machine; and Figs. 9 and 10 are detail views of the stitch forming devices in positions assumed while the locking thread is being measured, and while the under or needle thread is being fed, respectively.

Except as hereinafter described, the machine illustrated in the drawings is a lockstitch shoe sewing machine of the same construction, arrangement, and mode of operation of its various parts as the machine disclosed in the application of Haas, Serial No. 118,622, above referred to. In this machine, a measured amount of locking thread is provided for each stitch so that the interlocked portions of the locking and needle threads will be pulled to a regular depth beneath the surface of the work by the tension applied to the needle thread.

Referring to the drawings, the work feeding and stitch forming devices of the illustrated machine are actuated by the main sewing cam shaft, indicated at 2, and comprise a curved hook needle 4, a curved awl 6, a work support 8, a presser foot in, a looper H, a rotary loop taker or shuttle i2 and a stitch setting take-up I l. The stitch forming devices operate in the usual way to draw a loop of needle thread, indicated at It, through the work and by rotation of the shuttle, to pass it about a thread case l'l mounted within the shuttle. Thereafter, the loop of nee- "dle thread is drawn from the thread case and pulled into the work, together with a portion of the locking thread, during the downward stroke of the take-up, the take-up being secured to a rock shaft l8 and oscillated uniformly in each sewing cycle by a link I9 (Fig. 2) and a lever engaging a cam onthe cam shaft 2,

The means for drawing off looking thread and for preventing further withdrawal while the stitch is set, as shown in Figs. 2 and 9, includes,

from a supply, arranged in the manner described in the U. S. Letters Patent to Ashworth No. 1,923,563, dated August 22, 1933, consisting of a cop or other suitable package 26 (see Fig. 9) mounted on a spindle 28.. From the package 26' the thread passes through a wax pct 30 and a tension wheel 32 before entering the machine.

The machine embodying the present invention is so constructed and arranged that a measured quantity of needle thread is delivered to the stitch forming devices in each sewing cycle, and the needle thread is held against movement from the supply until a predetermined stitch setting tension is applied to the thread in the machine. After this tension has been applied to the needle thread, a quantity of thread equal to that used in the stitch just set is withdrawn from the supply by the feeding means, and delivered to the stitch forming devices, the ten sion on the needle thread in the machine acting merely to initiate the thread feeding operation which is completed thereafter without requiring the thread to overcome the inertia of the tension wheel or the resistance offered by the supply.-

The feeding means comprises a thread engag-= ing device in the form of a wheel 34 (see Fig. 8) the thread engaging portions of which are provided with oppositely bent tongues similar to those of the usual tension wheel, and measuring mechanism, hereinafter described, is arrangedto drive the tension wheel and hold itfrom rotation alternately at the proper times. After reaching the thread Wheel 34, the thread passes over a small pulley 36 downwardly around one of a pair of pulleys 38 (see Fig. 4) on the main takeup I l, upwardly over a pulley 40 on a tension control arm 42, to be more fully described hereinafter, downwardly under the other pulley 38 on the take-up and upwardly to the work. The arrangement is such thatduring the downward stroke of the take-up, the thread wheel 34 is held locked in position until the tension on the needle thread is sufiicient to move the control arm 42 downwardly, at which time the thread measuring mechanism is tripped into operation in a manner hereinafter described, to rotate the thread wheel 34 a predetermined amount.

Thereafter, the wheel is again held immovable so that no further movement of the needle thread towards the work is possible. By this arrangement, any irregular resistance met in feeding needle thread from the supply towards the stitch The needle thread for each stitch is drawn forming devices has no effect in setting the stitches because the needle thread is fed only after each stitch is set.

To hold the tension control arm 42 in raised position a yielding force sufliciently strong is applied to the control arm to prevent the control arm from being lowered by the needle thread during the greater part of each sewing cycle. The yielding force applied to the control arm is heavy enough to maintain the arm in raised position, except when a tension of suflicient predetermined intensity to set a stitch is applied by the takeup. When each stitch is set, the measured amount of locking thread is drawn tight by pulling the locking thread to a fixed depth in the work, so that the interlocking portions of threads are set at a uniform location.

The thread measuring mechanism comprises a hollow cylindrical support member 44 (see Fig. 8) having a conical inner surface. The thread wheel 34 is secured to the support member. The support member 44 is rotatable about a fixed horizontal stud or shaft 46 secured at its rearward end in the machine frame. Also rotatable on the shaft 46 is an oscillating cone clutch member 48 which is shaped to fit within the conical surface of the support member and is shiftable towards and from driving relation with the supheaded pivot pin 50 connected with one end of a link 52 shown in Figures 5 and 6. The other end of the link 52 is connected to a similar pin 54 at the end of a vertical arm. 56, which is formed with a sleeve-like hub portion rotatable within a suitable stationary bearing. To the sleeve portion of the vertical arm 56 is clamped a horizontal arm 58 pivotally connected with the lower end of a link 68' having its upper end similarly connected to a cam actuated lever 62 (see Fig. 2). The movements of the lever 62 are timed with relation to the movements of the take-up so that, during the latter part of each downward stroke of the take-up I4, the clutch member 48 will be rotated in a direction to feed thread towards the stitch forming devices at the exact rate required by the take-up. When the take-up has reached the end of its stitch setting stroke, the clutch member also reaches the end of its oscillatory movement in a direction to feed the thread. To engage the clutch member 48 with the thread wheel support member 44 when the control arm is lowered, a spring 64 surrounds the shaft 46, one end of the spring being engaged with the frame, and the other end with a thrust bearing Bil acting against the clutch member, 48.

To hold the clutch member in inoperative position against the pressure of the spring 64 during the first part of the downward stroke of the take-up, and to release the clutch at the proper time, suitable connections are provided, arranged to be tripped when the tension on the thread is sufficient to lower the control arm 42. The clutch connections include a clutch actuating yoke 69 having diametrically extending pins I0 cooperating with recesses formed in a pair of upwardly extending arms I2. The arms 12 are formed integrally with a horizontal shaft I4 mounted on the conical ends of a pair of oppositely disposed set screws I6 (see Fig. 3) cooperating with concavities at the end of the shaft I4. Extending upwardly from the shaft 84 is an arm I8 pivotally connected at one end of a toggle, best shown in Figs. 5 and 6, comprising a link and a downwardly curved forwardly extending arm. of a three-armed lever 82 rotatabiy mounted on a stub shaft 34 secured in the frame of the machine. When the curvedarm of lever 82 is in itsraised position (Fig. 6), it engages an adjustable set screw 83 secured in the frame to hold the toggle in set position, and the connections are arranged to hold the clutch member 48 out of engagement with the support member 44 to which the thread feed Wheel is attached. When the toggle is broken (Fig. 4) the connections described establish a driving relation between the clutch member and the thread wheel support member.

The tension control arm 42 is secured to the right end of a short horizontal shaft 85 (see Figs. 3, 5 and 6) rotatable in bearings in the frame of the machine. Fixed to the left end of the shaft is a forwardly extending forked arm, 86 which surrounds an inclined threaded rod 88, shown most clearly in Figures 3 and 4. Surrounding the rod 88 is a coil spring 90 and the lower end of therod passes through a threaded block 92 engaged by the lower end of the spring. The upper end of the spring 90 is engaged by a shouldered sleeve 94 which is forced by the spring against the forked terminal of arm 86. The rod 88-is rotatably supported in bearings at its upper and lower ends in the frame of themachine, and the block 92 is held from rotation with the rod by an upwardly extending forked portion of the block which surrounds a pin 96 mounted in the frame. To prevent lengthwise movement of the rod 88, a collar 98 is secured to the rod below the upper bearing for the rod and an adjusting wheel me is secured to the upper end of the rod. When the adjusting wheel is rotated, the block 92 is moved lengthwise of the rod to cause the spring 90 to act with greater or less force against the arm 86 so that the tension on the thread required to lower the control arm may be regulated-as desired.

To trip the clutch connections when the control arm 42 is pulled downwardly, the arm 86 is 1 provided with a lug I62 (see Fig. 6) arranged to engage a lug I03 on a downwardly extending arm of lever 82. The lever 82 is rocked in a counterclockwise direction by engagement of lugs 92,

I03 when the control arm v42 moves downwardly To lock the thread feed wheel, the shaft 46 is provided with an enlargement forming a brake I04 having a frusto-conical surface to fit the inner surface of the thread wheel support member 44. When the clutch member 48 is disengaged from the support member 44, the support memher is forced against the brake I 94 by a compres sion spring H15 coiled about the outer end of shaft 46. The outer end of the shaft is provided with a nut I06 which holds the spring IE5 in place, forcing it against a thrust bearing I08 engaging a disk IIti closing the end of the support member 44. When the clutch connections are tripped, the spring 64 which is stronger than the spring I65 forces the clutch member 48 into driving relation with the support member 44' and the support member is moved away from the surface of brake H14, rendering the brake ineffective.

Rotation of the thread wheel 34 is thus started at the instant the tension control arm 42 is actu- Since the connections for oscillating the clutch member t8 are arranged to feed thread at the same rate as required by the downward stroke of the take-up, no increase in tension will be imparted to the thread after setting the stitch. Also, when starting a new seam, the first few stitches will be set with the required tension since no thread will be withdrawn from the supply until a properly set stitch is formed.

To enable the rotary clutch member 48 to be disengaged, the brake I04 engaged with the thread wheel support member M, and the control arm 42 to be raised with certainty when the clutch member is rotated in a direction reverse to the thread feeding rotation, connections operated by the main sewing shaft 2 are provided. These connections comprise a bifurcated upwardly extending arm of the three-armed lever 82 which embraces the forward end of a reciprocating rod II 2 slidingly mounted within the sleeve-like hub portion of the arm 56. Surrounding the outer end of the rod I I2 is a yoke II4 having diametrical pins engaged by recesses in the bifurcated portions of the upwardly extending arm of lever 32. The rearward end of the rod H2 is slidingly mounted within a bore H6 (see Figs. 2 and 6) in the main frame, and the central part of the rod is formed with a groove to receive a yoke II8 secured by alined screws, l2!) mounted in the forked downwardly extending arm of a bell crank I22 fulcrumed at I24 on the machine. A horizontal arm of the bell crank H2 is pivotally connected to the lower end of a link I26, the upper end of which is connected with the cam actuated lever 25 (see Fig. 2). When the rod H2 is moved rearwardly, an adjustable nut I28 on the rod engages the yoke I I4 and rocks the lever 82 to the position shown in Figures 2 and 6, thus moving the toggle formed in part by the lever 82 upwardly past centers to its set position. This movement forces the clutch member rearwardly to disengage the clutch member 48 from the thread wheel support member 44 after the clutch member reaches the end of its thread feeding movement and the requisite amount of needle thread has been fed. At the same time the tension control arm 42 is raised by the lug I03 of lever 82 to insure proper control of the thread feeding operation in the succeeding stitching cycle.

During the setting of the stitch and the thread feeding operation, the tension on the thread is maintained by the tension control arm 42. Since this arm is depressed to trip the thread feed into action only when the tension on the thread reaches a certain amount, the thread feed may be started into action at varying times during a stitch forming cycle and thus the feed of the thread varied for different thicknesses of work. The thread feed, however, is always thrown out of action at a predetermined time in the stitch forming cycle and the arrangement is such that the amount of thread measured from the supply during each operation of the thread feeding devices is equal to the amount used up by the stitch forming devices in making a stitch.

As a convenient means for preventing slack thread during the looping operation, a light auxiliary frictional tension device similar to that of the machine disclosed in'the Haas application above identified, acts on the thread between the take-up and the looper when the thread feed wheel is locked. After leaving the take-up, the thread passes between a cover portion I30 (see Figs. 1 and '7) of a protecting casing in the machine anda spring pressed plate I32 secured to one end of a horizontal sliding pin I34. After the looping operation is completed, and just before the take-up sets a stitch, the plate I32 is retracted from frictional engagement with the thread by the engagement of an inclined surface in a slotted portion of the rod I34 and the forward end of a sliding bar I36 operated by a cam I38 on the shaft l8 which carries the take-up.

The bar I 36 is held yieldingly against the cam 438 by a spring I 40 surrounding the bar I36 between a portion of the frame and a collar I42 secured to the bar.

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

1. A sewing machine having, in combination, stitch forming devices including means for tightening the stitch, means for feeding thread to the stitch forming devices, and means responsive to the increase in tensionon the thread created by the operation of the stitch forming devices in tightening the stitch to cause the thread feeding means in each stitch forming cycle to feed thread in an amount suificient for the-succeeding stitch forming operation.

2. A sewing machine having, in combination,

stitch forming devices including means for tightening the stitch, means for feeding thread to the stitch forming devices, and means responsive to the increase in tension on the thread created by the operation of the stitch forming devices in tightening the stitch to start said thread feeding means in operation, and means acting at a predetermined point in the stitch forming cycle to arrest said thread feeding means whereby an amount of thread regulated in accordance with the thickness of the work is fed to the stitch forming devices during each stitch forming cycle.

3. A sewing machine having, in combination, stitch forming devices including means for tightening the stitch, athread engaging device, mechanism for actuating the thread engaging device to feed thread to the stitch forming devices and thereafter for holding the thread from further movement toward the stitch forming devices, and means responsive to the increase in tension on the thread created by operation of the stitch forming devices in tightening the stitch for rendering said mechanism operative to feed including means for further movement toward the stitch forming devices, a yielding thread take-up tension engaging the thread between said thread engaging device and the work, and means responsive to the increase in tension on the thread created by the operation of the stitch forming devices in tightening the stitch for rendering said mechanism operative to feed thread in an amount sufiicient for the succeeding stitch forming operation.

5. A sewing machine having, in combination, stitch forming devices comprising a work piercing needle and a stitch setting take-up, a thread engaging device arranged to prevent the needle thread from being withdrawn from the supply as each stitch is being set, andmechanism rendered operative by the thread during each stitchmember is oscillated the other direction to,

forming cycle while a stitch is being set to cause thethread engaging device to feedthread from the supply to the stitch forming devices.

6. A sewing machine having,in combination,

stitch forming devices comprising a work piercing needle and a take-up having a uniform stitch setting stroke, a thread engaging device for preventing. the needle threadfrom being withdrawn from the supply as each stitch is being set, mechanism for actuating the thread engaging device to feed thread to the stitch forming devices during the stitch setting stroke of the take-up at substantially the same rate as the thread is taken up by the take-up, and means controlled by the thread for preventing said mechanism from actuating the thread engaging device until a stitch setting tension is applied to the thread during each stitch-forming cycle.

8. A sewing machine having, in combination, stitch forming devices comprising awork piercing needle and a take-up having a uniform stitch setting stroke, a rotary thread engaging device,

a clutch member for rotating the thread engaging device to feed thread to the stitch forming devices during each stitch setting stroke of the take-up and for stopping rotation of thethread engaging device when said take-up stroke is completed, and means controlled by the thread for holding the clutch member inoperative during each stitch-forming cycle until a'stitch setting tension is applied to the thread. I

9. A sewing machine having; incombination, a main sewing shaft, stitch forming devices actuated thereby comprising a work piercing needle and a take-up having a uniform' stitch setting stroke, a rotarythread-engaging device, a clutch member for rotating the thread engaging device to feed thread towards the stitch forming devices during the stitch-setting stroke of the take-up and for stopping rotation ofthe thread engaging device when said take-up stroke is completed,

stroke, a rotary thread engaging device, an os- I cillating clutch member for rotating the thread engaging device to feed thread towards the stitch forming devices during the stitch setting stroke of the take-up, a brake controlled by the thread for preventing rotation of the thread engaging device by the clutch member when oscillated in a direction to feed thread until a stitch setting tension is applied to the thread, andconnections actuated by the Sewing shaft when the clutch cause the brake to lock the thread engaging device.

11. A sewing machine having, in combination,

stitch forming devices comprising a work piercing needle and a take-up having a uniform stitch setting stroke during each sewing cycle, a rotary device for feeding thread, a clutch member for driving the rotary device during the stitch setting stroke of the take-up, a brake, yielding means for rendering the brake effective to lock the rotary device, a second yielding means of greater strength than said yielding means first mentioned for rendering the brake ineffective and for; causing the clutchmember to rotate the rotary device to feed thread towards the stitch forming devices, and a toggle arranged to be controlled by the thread for preventing the second'yielding I means from; rendering the brake ineffective until a stitch setting tension is applied to the thread."

12. A sewing machine having, in combination, a main sewing shaft, stitch forming devices actuated thereby comprising a work piercing needle and a take-up having a uniform stitch setting stroke, a rotary thread engaging wheel, a clutch I member for driving the wheel during the take-up devices, atoggle arranged to be controlled by'the 7 thread for preventing the second yielding means from rendering the brake ineffective until a stitch setting tension is applied to the thread, and connections actuated by the sewing shaft for setting the toggle after the stitch setting stroke of the take-up iscompleted. i v

13. A sewing machine having, in combination, stitch formin devices including a work piercing needle, a rotary thread engaging wheel, a stationary brake, yielding means for rendering the brake effective to lock the thread wheel, a clutch member for driving the thread wheel to feed thread towards the stitch forming devices, and means controlled by the thread for rendering the clutch member operative and for rendering the brake ineffective when the tension on the thread exceeds a definite value.

14. A sewing machine having, in combination,

stitch forming devices comprising a work piercing needle, and a take-up having a uniform stitch setting stroke during each cycle of the machine, a tension control arm, a rotary device for feeding the'thread, a stationary brake, means for rendering the brake effective to lock the rotary device, a clutch member. for drivingthe rotary deviceto feed thread at. a predetermined rate towards the stitch forming devices, and connections actuated by the tension control arm for causing the clutch member to be rendered operative and the brake member to be rendered ineffective when the take-up applies a stitch setting tension to the, thread.

15. A lockstitch sewing machine having, in"

combination, stitch'iforming devices comprising needle threadtowards the stitch forming devices during each stitch forming cycle and for thereafter holding the thread from further movement towards the stitch forming devices, and yielding means for exerting tension on the needle thread during the loop drawing movement of the takeup.

16. A lockstitch sewing machine having, in combination, stitch forming devices comprising a work piercing needle, a thread case containing a supply of locking'thread, a loop taker for passing a loop of needle thread about the thread case, and a take-up for drawing the needle loop from the thread case into the'work, means for measuring an amount of locking thread from the thread case for each stitch, and means for feeding the needle thread towards the stitch forming devices when the resistance offered by the locking threadto the needle loop as it pulls the locking thread into the work is sufiicient to set the stitch.

17. A sewing machine having, in combination, stitch forming devices comprising a work piercing needle and a take-up having a pair of thread guiding members, a thread engaging device for holding the thread from being withdrawn from the supply before each stitch is set, driving mechanism for the thread engaging device, a control arm having a single thread guiding member engaging the thread between the'pair of thread guiding members on the take-up, and connections between the control'arm and the driving mechanism for causing the thread engaging device to feed thread towards thestitch forming devices'when a stitch setting tension is applied to the thread. r

18. A sewing machine having, in combination, stitch forming devices comprising a work piercing needle, a needle looper, and a take-up,'a thread engaging device for preventing the needle thread from being withdrawn from the supply as each stitch is being set, a tension control arm over which the thread passes, mechanism arranged to be renderedoperative when the control arm is actuated by a stitch setting tension on the thread to cause the thread engaging device to feed thread towards the stitch forming devices, and means acting on the thread between the take-up and the looper to impart a tension to the thread during the operation of the looper. Y

19. A sewing machine having, in combination, stitch forming devices comprising a work piercing needle, a needle looper, and a take-up, a thread engaging device for preventing the needle thread acting on the thread between the take-up and the looper to impart a tension to the thread during the operation of the looper, and mechanism for actuating the friction means to release the thread before the take-up acts to set each stitch.

20; A sewing machine having, in combination, stitch forming devices comprising a work piercing needle,a needle lodperyanda takeup, a thread engaging device for; preventing the needle thread from being withdrawn from the supply as each stitch is being set, a tension control'arm over which the thread passes, mechanism arranged to be rendered operative when the control arm is actuated by a stitch setting tension on the thread to cause the thread engaging device tofeed thread towards the stitch forming devices,

and connections operated in timed relation to the take-up for returning the control arm to its original position'after the thread has been withdrawn from the supply; v

21. A lockstitch sewing" machine having, in combination, amain swin'gshaft, stitch forming devices operated therebycomprising a work piercing needle and'a take-up having a uniform stitch setting stroke, a rotary thread engaging device, a brake acting to preventthe thread from being drawn from the thread engaging device during the stitch setting stroke of the take-up,

means actuated by the application of a stitch setting tension to the thread to render the brake ineffective, and connections operated bythe sewing shaft to render the brakeagain eifective before the succeeding stitch settingstrokeof the take-up. w

22. A lockstitch sewing machine having,

tension of 'the' threadand the brake again to be rendered effective.'

23. A sewingmachine having, in combination, stitch forming devices comprising a work piercing needle and a take-up, having a uniform stitch setting stroke during each sewing cycle, a thread engaging device, mechanism for actuating the thread engaging device to feed a quantity of thread to the stitch forming devices at Substantially thesame rate as thethread is taken up by the take-up,'and means for causing said mechanism to actuate the thread'engaging device at a time in each cycle in which the quantity of thread last fed is used up.

24. A sewing machine having, in combination, stitch forming devices including means for tightening the stitch, a thread engaging device, mechanism for feeding measured amounts of thread to the stitch forming devices, means responsive to a variation in tension on the thread created by the operation of the stitchforming devices for throwing said'mechanism into operation at a time predetermined by said variation in tension on the thread, and means forthereafter throw-.

ing said mechanism out of operation at a predetermined time during each stitch forming cycle.

' LAURENCE E. TOPHAM.

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