US1850611A - Tension device for sewing machines - Google Patents

Description

March 22, 1932. E, E, w Y 1,850,611

TENSION DEVICE FOR SEWING MACHINES Filed May 7, 1930 2 Sheets-Sheet 1 ili'z'rzeaa' V jvengaj/ Patented Mar. 22, 1932 lTE-D STATES PArENrFor-FicIE ERASTUS E. WINKLEY, 0F LYNN, MASSACHUSETTS; .ASSIGNOR TO UNITED SHOE .MA-

GHINERY COBIPGBATION, OF PAT ERSON, NEW JERSEY, A COEPORATIONOF NEW.

JERSEY TENSION DEVICE FOR SEWING MACHINES Application filed May 7, 1930. Serial No. 450,420.

The present invention has relation to sewing machines, and in particular to the tension devices which are applied to such machines to control the thread during the setting of ,5; the stitch, and at other times in the operation of the sewing machine.

Devices of many sorts have been employed to put tension upon the thread in such machines, the commonest forms of tension delo; vices employing friction to hold back the travel of the thread as drawn from the supply by the stitch forming'devices or otherwise, until the desired degree of tension has been attained in the thread. lhe friction has been applied in general through two different arrangements. In the -one,-the thread'has been drawn between or around surfaces in such manner that the thread slips or slides rela-' in the common form of tension device in 2 .1 which a movable presser squeezes the thread against a stationary abutment under a strong pressure, and the thread is drawn from between the two, it is commonly found that the rubbing of these opposed surfaces against op the twist in the thread in the direction of the supply, until such' twist accumulates to the extent and degree where it forces its way through the tension devices. The thread. thickened and rendered harder by this accumulated twist, meets with more resistance in being drawn through the tension device, and hence is moved forward with increased effort by the thread handling and stitch forming devices, resulting in uneven setting of the stitches and unsatisfactorw appearance of the finished seam. As to the other class of device, in which the friction is applied to a member whose surface moves'with Q1the thread, as in the case of the familiar .posite sides of the thread tends to run back rotating tension wheel having a brake resisting its rotation, there is not the tendency to run back the twist, but the vperformance of such devices leaves room for improvement in that they are i incapable of retrieving any slack momentarily and incidentally occurring in the thread between such tension device and the work.

It is one object of the present invention to improve the operation of tension devices in these respects, so as to provide a novel device of this class capable of handling twisted thread with-out any tendency to-run back the twist and also adapted to retrieve any slack occurring betweenit and the work during its plariod of operation in the cycle of the mac me.

It is a further object of the present invention to provide novel and improved mechanism for tensioning-the thread leading from the supply during the operation of the stitch-forming devices adapted to maintain a constant tension of a predetermined amount on the thread leading to the stitch-forming devices which will be independent of any variations in the resistance offered to the passage of the thread fromthe supply to the ten-' sioning mechanism.

NVith the above objects in view, one feature of the invention consists'in the provision of tension devices for sewing machines having thread'clampin-g means which are adapted to engage the thread and travel along with it as it is drawn from the supply, such thread clamping means being adapted to resist yieldingly the forward movement of the thread and adapted to release the thread at the.

proper point in the cycle of the machine and reengage the thread at afmore remote point knots, variations in the thickness of the thread, or variation in the consistency and distribution of the wax which must be stripped off by the stripper.

In order to eliminate more completely the variations in the tension and the consequent irregularities and defects in the finished stitching, the present invention further contemplates the provision of a thread pull-off cooperating with the thread clamping devices herein disclosed to pull off the requisite amount of thread from the supply through the wax pot and stripper prior to the movement of the clamping means with the thread during the needle loop drawing stroke.

An embodiment of the invention in its preferred form is shown in the drawings, applied merely for purposes of'illustration to a well-known type of sewing machine. In the drawings Fig. 1 is a side elevation of a McKay type of sewing machine, with the invention applied thereto; Fig. 2 is a view of certain parts shown in Fig. 1, also in side elevation and on a large scale; Fig. 3 is a front sectional view, of the parts of Fig. 2.

-Having reference to the drawings, the machine indicated in Fig. 1 is a typical McKay type chain stitch shoe sewing machine such as is shown and described in U. S. Letters Patent No. 1,177,581 granted on March 28, 1916 to W. C. Meyer, to which patent reference may be had for a full and complete deseri tion of the construction and operation of t e machine, and of such parts as are not dealt with in the present specification.

The tension device is shown applied to the machine to engage the thread just as it emerges from the wax pot 2 and just prior to its entry into the end of the hollow shaft 4 comprising one of the series of shafts transmitting power from the cam shaft of the machine to rotate the usual whirl 5 located in the tip of the horn 6 which serves to place the thread in the hook or barb of the needle 7.

j The novel tension device comprises threadclamping jaws adapted to grip the thread and to travel along with it without relative motion with respect to the thread while acting to create tension. The jaws are constituted by-the cooperating end-portions of a pair of arms 8 and 28, pivoted together at 26 and swinging as a unit about a pivot pin 10 rotating in the hub 12 of a bracket 14 that is fixed to the bracket 16 which is applied to the side of the column 18 and supports the horn 6 and other parts. The arms are adapted to swing through an arc of considerable amplitude in the vertical plane of the thread as the latter stretches from the stripper 20 of the wax pot to the hollow shaft 4. The end of the'arm 8 is provided at its opposite edges with lugs 22 provided with guide holes through which the thread passes. Lugs 24 on the arm 8 support the pivot 26 upon which is mounted the second arm 28, the extremity of which enters between the thread guiding lugs 22 to engage the thread in its passage across the intervening surface of the arm 8. An axial bore 80 in the end of the ivot 10 of arm 8 contains a plunger 32 presse outwardly by a spring 34 and bearing against the under surface of one end of the arm 28 to force the latters opposite end against the thread guiding extremity of the arm 8, so as to seize and clamp the thread firmly where it extends across the surface of the arm 8.

The hub 12 of bracket 14 is provided with a projecting hollow stud through which the pin 10 extends and about which is coiled a spring 38 having one of its ends fixed in the hub 12 and its other secured in a collar 40 adj ustably fixed on the pivot pin 10 on which the arm 8 is mounted. This spring acts to hold the two arms swung downwardly with the side of arm 8 resting against a sto pin 42 in an extension of the bracket 14. rom this depressed position the tension drive is adapted to be swung upward through its grip upon the thread for a distance determined by the amount of thread drawn from the supply by the stitch-forming devices of the machine during each cycle of operation.

The thread clamping jaws are released to free the thread from tension, as the needle reaches its farthest retracted position in drawing a loop of thread through the work. To effect this release, the end of arm 28 is pressed inwardly against the resistance of its spring plunger 32 to spread the clamping jaws and release the thread, and this operation is effected at the proper moment in the cycle of the machine by means of a rocker lever 44 carried on a stud 46 mounted in the bracket 16, one of its arms having a cam roll 48 engaging with a cam 50 on the horizontal shaft 52 of the whirl-actuating connections. The shaft in the machine illustrated is geared to make one revolution for each revolution of the cam shaft in the head of the machine and, therefore, makes one complete revolution during each stitch-forming cycle. A spring 54 holds the rocker lever so that its cam roll follows the cam surface.

In order to eliminate any possibility of variation in the amount of tension exerted on the thread which may be occasioned by variations in the resistance which must be overcome in drawing the thread from the supply through the wax pot and stripper, mechanism is provided to cooperate with the clamping jaws to pull off the requisite amount of thread from the supply through the wax pot and the stripper 20 so that during each upward movement of the clamping jaws with the thread during the loop drawing stroke of the needle, a sufiicient amount of slack thread will be provided for this operation. The pull-off mechanism herein disclosed for drawing oi the requisite amount of thread from the supply through the wax stripper comprises a bell crank lever 56 which is mounted to swing on a pivot 58 on the machine frame and is provided at its lower end with a pulley 60 which is adapted to engage with the thread between an idler roll 61 above the thread stripper 20 and the clamping jaws 8 and 28. The thread pull-off is actuated in timed relation to the clamping jaws and other parts of the machine by means of a face cam 62 formed on the shaft 52 which engages with a roll 64 on the upper end of a bell cranklever 66 loosely mounted to turn on a pivot 68 on the bracket 14. The other arm of the bell crank lever 66 is connected by means of a link 70 to a pin 72 on the pulloff lever 56. A spring 74 coiled about the pivot shaft 68 and secured at one end to the lever 66 and at its other end to the bracket 14 tends to rotate the lever in a direction'to hold the roll 64 at all times in engagement with the cam 62.

In the operation of the machine starting with the parts in substantially the positions shown in Fig. 2 the arm 8 is in its depressed position against thestop 42 with the thread tightly clamped between the jaws 8 and 28. The pulley 60 is now moved to the right as shown in dotted lines in Fig. 2 to draw ofi thread from the supply through the wax pot and wax stripper and is then returned to the full line position at the left, giving up its thread as the thread is drawn upwardly through the hollow shaft 4 during the loop drawing stroke of the needle 7. Due to the clamping action of the jaws 8 and 28 the arm is moved upwardly with the thread against the pressure of the spring 38 to provide a constant tensioning strain of predetermined amount on the thread throughout its travel. This tension may be modified by adjusting the angular position of the collar upon the pivot 10 to wind up or unwind the spring 38. When the rocker 44 causes the aws to be separated and to release the thread, the tension is released and the arms 8 and 28 swinging downwardly into contact with stop 42 through the recoil of spring 38, and assume a position in readiness to take a new grip upon the thread at a point more remote from the stitch forming devices for the repetition of the tension applying function. Since there is no relative movement of the thread with respect to the clamping jaws to run back t action of the spring 38, the tension is mainface, and no slack can develop between the tension device and the stitch forming devices.

lVhat is claimed as the invention is: 1. Tension devices for sewing machines having, in combination, thread-clamping means adapted to travel with the thread,

means acting to resistsuch travel, and means acting to disengage and reengage the clamp ing means with the thread.

2. Tension devices for sewing machines having, in combination, thread-clamping means adapted to engage and be carried along with the thread when the latter 1s pulled upon by the stitch-forming devices, means yieldingly acting to move the clamping means reversely to such pull of the thread, and means acting periodically to disengage and reengage the clamping means with the thread.

3. Tension devices for sewing machines having, in combination, an arm mounted to swing along the path of travel of the thread, clamping jaws upon the arm to engage the thread, means tending to move the arm reverse'ly to the direction of travel of the thread and yielding to the pull of the thread when the latter is engaged by the jaws, and means for periodically disengaging and reengaging the jaws with the thread.

4. Tension devices for sewing machines having, in combination, a pair of threadclamping jaws movable along the line of travel of the thread, means yieldingly urging the clamping jaws to move in a direction opposed to the travel of the thread, and means alternately freeing the jaws to permit them to move oppositely to the thread under their yielding actuating means, and then effecting the clamping of the jaws upon the thread at the end of such movement so that ensuing movement of the thread will carry the jaws alongtherewith against the resistance of the yielding actuating means.

5. Tension devices for sewing machines having, in combination with stitch-forming devices including a hook needle, threadclamping means movable back and forth along the path of travel of the thread from its supply to the work, means yieldingly resisting the travel of the clamping means in the direction toward the work, and means for engaging the clamping .means with the thread to hold back on the thread as the needle is drawing the latter through the work, and for releasing the clamping means from the thread as the needle completes its thread-drawing movement.

6. Tension devices for sewing machines having, in combination with stitch-forming devices including a hook needle, of threadclamping means movable in the direction of travel of the thread as drawn forward by the needle, adapted to grip the thread tightly to prevent relative movement, means urging the clamping means reversely of the direction of travel of the thread to cause it to exert a tensioning pull upon the thread and to take up any slack, and means adapted to disengage and reengage the clamping means with the thread.

7. Tension devices for sewing machines having, in combination with the stitch-forming devices including a hook needle, of thread-clamping means adapted to be moved in one direction by the thread as drawn forward by the stitch-forming devices, spring means adapted to resist such movement of the clamping means and to move it reversely when disengaged from the thread, a cam, and

" means operably combined with the cam and the thread-clamping means for disengaging and reengaging the latter with the thread in timed relation with the movements of the stitch-forming devices.

8. Tension devices forsewingmachineshaving, in combination, thread clamping means adapted to engage with and move with the thread, means acting to resist the movement of the clamping means with the thread, and a thread pull-ofi' to supply slack thread to the thread clamping means in advance of the movement of the said clamping means with the thread.

9. Tension devices for sewing machines having, in combination, with the stitch forming devices including a hook needle, of thread clamping means movable back and forth along the path of travel of the thread from its supply to the work, means yieldingly resisting the travel of the clamping means toward the work, means for engaging the clamping means with the thread to hold back on the thread as the needle is drawing the latter through the work, and for releasing the clamping means from the thread as the needle completes its thread drawing movement, and a thread pull-ofi to supply slack thread to the thread clamping means in advance of the movement of the said clampl ing means with the thread.

10. Tension devices for sewing machines having, in combination with the stitch forming devices including a hook needle, and a whirl containing horn for supplying the 'thread to the needle and a wax stripper through which the thread is drawn from the supply, of thread clamping means interposed between the thread stripper and the work movable back and forth along the travel of the thread from its supply to the work, means yieldingly resisting the travel of the clamping means in the direction toward the work, means acting to disengage and re-engage the clamping means with the ithread, and a thread pull-off interposed between the thread clamping means and the thread stripper to supply slack thread to the thread clamping means in advance of the movement of the said clamping means with the thread.

In testimony whereof I have signed my name to this specification.

ERASTUS E. WINKLEY.

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