US2322232A - Tension device - Google Patents

Description

June'zz, 1943."

J. GOULDBOURN TENSION DEVICE 'F'iled Sept. 20,;1959

2 SheetS -Sheet 1 Jun 22, 1943. J, soQLpBoURN TENSION' DEVICE Filed Sept 20, 1959 2 Sheets-Sheet 2 Patented June 22; 1943 TENSION DEVICE Joseph Goul'dbourn, Leicester, England, assignor to United Shoe Machinery Corporation, Borough of Flemington, N. 1., a corporation of New Jersey Application September 20, 1939, Serial No. 295,780 In Great Britain November 3, 1938 '17 Claims.

This invention is concerned with improvements in or relating to tension devices or to machines making use of the same. I

The invention will hereinafter be explained by way of illustration, and not of limitation, in connection with sewing machines and, in particular, in connection with a curved hooked needle chainstitch sewing machine organized for use in the manufacture of boots or shoes. An example of such a machine as last mentioned is that illustrated in the patent to Eppler No. 1,076,201, dated October 21, 1913.

Curved hooked needle chainstitch sewing machines for sewing the inseams of boots or shoes commonly include a thread tension device comprising a pair of thin discs providing between them a peripheral V-shaped groove which receives the thread passing around the discs and, in order to prevent too free rotation of the discs as the thread is drawn round them, a braking action is exerted on the discs by means of a relatively stationary brake-shoe thrust by a spring against the periphery of a brake drum secured to the discs. Suitable means is provided in such machines for automatically varying the pressure of the brake-shoe against the drum at different times in each stitch-forming cycle so that the thread may run more freely through the machine at some stages in the formation of the stitches than at others.

The brake-shoe, being relatively stationary, applies a dead pressure against the periphery of the brake drum and at certain times in the operation of the machine (for example either at the commencement of the formation of each stitch or during the thread pulling-off action of the usual take-up or during the thread pulling action of the needle as it retreats after having penetrated the between-substance), the operation of the various thread-handling instrumentalities causes thread to be drawn relatively rapidly around the tension discs and thus causes the tension discs either to start into actual rotation or to move with an accelerated motion if they are already rotating. However I have found that the force necessary either to set the discs into rtation from rest or to cause them to rotate with an accelerated motion while they are actually rotating is considerably greater, in such a tension device as above referred to, than the force necessary to keep the discs rotating at a uniform speed. This fact not only causes the tension applied by the device on the thread at different times in the machine cycle to vary considerably from that which would produce the best results in the formation of the successive stitches but also, by making it necessary when initially adjusting the tension device prior to the commencement of a sewing operation to allow for such unwanted but unavoidable increases in the tension on e thread, often makes it impossible so to set the machine as to cause the stitches to be drawn as tightly against the work as desired.

The above-mentioned tendency of the tension device to exert a considerably increased tension on the thread when it is attempted to draw thread more rapidly around the discs or when the stationary thread is initially pulled around them on the commencement of the formation of each stitch arises, so it is believed, not so much from the actual inertia due to the weight of the discs themselves as from the dead-weight nature of the braking action exerted on the discs which has to be overcome.

It is one of the several objects of the present invention to provide an improved form of tension device of such a nature that it will be able to exert a more nearly uniform degree of tension on thread passing around it in spite of variations in the speed at which the thread is pulled around itthus not only contributing to a more uniform setting of the successive stitches against the work but also making it possible, by initial adjustment of the, device, to make sure that the stitches will be uniformly pulled as hard against the work as is justified by the quality of the work and/or the strength of the thread.

To this end a particular illustrative 'embodi ment hereinafter described, of the present invention embodies a pair of thread tension discsof somewhat conventional form which, instead of having a dead-weight braking action exerted on them by a relatively stationary brake shoe as hitherto, hav a braking action exerted on them by a friction disc which bears against a member secured to the tension discs and, is rotated at a constant low speed (e. g. about 60 R. P. M. assuming. the machine to be making some 600 stitches per minute) and in a direction opposite to that in which the discs are rotated by the passage of'the thread therearound. The said friction disc commences to rotate in this direction, and thus exerts, a live backward drag on the tension discs, immediately the machine is started into operation after the presentation of work to it and continues uniformly so to rotate until the machine is actually brought to rest. In spite however of the constant backward rotation of the friction disc and of the fact that it bears against a member secured to the tension discs, the latter discs are not allowed to rotate backwafdly with it but, on the contrary, are held from so doing by a pawl and ratchet device and this fact brings about the result that a slippage,

' bringing about a predetermined degree of live frictional torque, takes place between the friction disc and the tension discs.

The application to the tension discs of such a constantly backwardly exerted frictional effort has, during tests of such a tension device as above Ltd indicated, shown itself to be of considerable benefit both in allowing the tension discs to apply a substantially even tension to the thread throughout the various desired stages of each stitch forming cycle and in allowing the discs to rotate forwardly from rest, when the thread is initially pulled around the discs at the commencement of each stitch forming operation of the machine, without exerting on the thread (by reason of undue resistance to such forward rotation) a degree of tension substantially higher than that needed to maintain the discs in forward movement once they have started from rest.

However it is desirable that the tension device should exert a reduced tension on the thread at that time in the machine cycle when the neede is retiring through the work, after having penetrated it, and is drawing a loop of thread therethrough. For this purpose the device of said illustrative embodiment includes a pair of compression springs which serve to thrust the said rearwardly moving friction disc into bearing contact with the member which is secured to the tension discs and automatically acting means is provided for causing both said springs to cooperate in thrusting the friction disc and the member together during the greater part of each sewing cycle but to cause one of them to become inoperative (thus reducing the pressure between the friction disc and the member) during the retiring movement of the needle. Moreover said means acts automatically to render both said springs inoperative to thrust the friction disc and member together when the machine comes to rest at the end of a sewing operation thus allowing the tension disc to be rotated freely while the machine is idle, preparatory to the commencement of another sewing operation, and thus allowing the operator to draw thread easily through the machine ready for the recommen-cement of the machine into operation on another boot or shoe.

It will be understood that the present invention in its broader aspects is not limited in its application to an inseam chainstitch shoe sewing machine of the type described, but may well be applied to other types of machines for operating upon heavy work such as leather, having thread handling devices including means for intermittently drawing off thread from the supply wherein it will be of advantage to provide applicants improved thread tension embodying therein a thread engaging member such as a tension wheel, and a friction device acting thereon having means to maintain a continuously live frictional resistance to the movement of the thread engaging member which will eliminate uncertainties or variations in the thread tension due to added frictional resistance ordinarily encountered in starting or in accelerating the drawoff movement of the thread engaging member.

With the above noted and other objects in view, as may hereinafter appear, the several features of the invention consist also in the devices, combinations and arrangement of parts hereinafter shown and described, which together with the advantages to be obtained thereby, will be readily understood by one skilled in the art from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a view in left side elevation of the sewing head of a chain-stitch inseam shoe sewing machine illustrating a preferred embodiment of the invention, only so much of the machine having been illustrated as is necessary to show the connection of the invention therewith; Fig. 2 is an enlarged detail view of applicants improved thread tension shown in Fig. 1; and Fig. 3 is a sectional view taken on the line 3--3 of Fig. 2.

The shoe machine illustrated in the drawings as embodying in a preferred form the several features of the present invention, is adapted for sewing the upper and insole of a welt shoe, and

1 tension, and is again drawn in against a thread tension during the thread drawing stroke of the take-up, which acts to tighten the previous loop against the shank of the needle after the needle has entered the work, and to draw oif additional thread from the supply against the tension. In the preferred embodiment illustrated in the drawings, a tensioning device is employed which is capable of applying a relatively light tensioning strain on the thread during the needle loop drawing stroke, and of applying on the thread a considerably heavier tensioning strain during the loop drawing stroke of the take-up. in order to tighten the previous stitch. In each instance, it is desirable to adjust the tensioning strain on the thread as accurately as possible in accordance with such factors as the quality and nature of the work and the strength of the thread employed.

With the thread tensioning devices of the prior art in which the cooperating friction surfaces are normally stationary and are moved relatively to one another only upon starting the tension wheel, it has been necessary in adjusting these tensions, to take into account the additional ten sioning strain on the thread and on the work required to start the tension wheel both at the limit of the loop drawing stroke of the needle, and again as the take-up approaches the limit of its loop drawing stroke, to draw off additional thread from the supply. Correct adjustments of such thread tensioning devices of the prior art are made still more difiicult by the fact that the amount of force required to start the friction surfaces from a relatively stationary position is not directly dependent upon the frictional engaging pressure, but may vary considerably as the surfaces become more or less firmly set in a stationary position.

Referring specifically to the drawings, the illustrative embodiment comprises a bracket 2 8 which is secured on the rear of the head 22 of the sewing machine and which has a bearing for a horizontal tension shaft 25 extending laterally of the machine. Secured on the left end of the said shaft 26 is a thread wheel 26 around which the thread passes from its source of supply to the stitch forming devices of the machine. The thread wheel 2:: is formed of two discs secured together. The outer margin of each disc is notched and the projecting portions of the discs between adjacent notches are bent away from each other so as to form a V-shaped groove in hich the thread lies. The tension shaft 24 has formed on its right hand end a ratchet wheel 28, the teeth ofwhich are engaged by two pawls 30 and 32 which are pivoted on the bracket and are urged towards the ratchet wheel by spring plunger 34 and 36. The pawls 30 and 32 are so arranged that when one is in engagement with a tooth on the ratchet wheel 28 the other engages the ratchet wheel about half-way between two adjacent ratchet teeth on the wheel. Said pawls cooperate with the teeth on the ratchet wheel to prevent rotation of the thread wheel 26 in a direction opposite to that in which it is moved by the passage of the thread therearound.

The tension shaft 24 is rotatably mounted in a sleeve 38 which is rotatably mounted in the said bearing and the sleeve 38 has formed on its righthand end a flange 49 in which is secured a friction ring 42 which engage the left-hand face of the ratchet disc28. Between the flange 40 and the end of the bearing is an anti-friction ball bearing 4.4. The flange 46 has formed on its outer peripheral face gear teeth 46 which mesh with a worm gear 43 on a worm gear shaft 50 which is rotatably mounted in bearings in the bracket 20 below the tension shaft 24. The worm gear shaft 50 has secured on its forward end a grooved pulley 52 around which passes a belt and the belt also passes around a second pulley which is driven whenever the machine is being operated. The flange 40 is driven in the opposite direction to that in which the aforesaid thread wheel 25 is rotated when the thread is being drawn from the supply during the operation of the machine. The engagement of one of the aforesaid pawls 39 or 32 with a tooth on the ratchet Wheel 28 prevents the thread wheel 25 from being rotated with the flange 40 in spite of its frictional engagement with the friction ring 42. The fact that the thread wheel 26 is prevented from rotating backwardly with the friction ring 42 brings about the result that a constant, slippage occurs between the thread wheel 26 and the friction ring 42 and this slippage has the effect of exerting a constant torque on the thread wheel 26 which can be overcome by a smooth and predetermined, but not excessive, amount of tension exerted on the thread when the latter tends to rotate the thread wheel 26 forwardly.

The'ratchet wheel 28 is pressed against the aforesaid friction ring 42, which may be of cork or a composition of cork and other material, by two compression springs 54, 58 arranged one within the other which are in axial alignment with the axis of the tension shaft 24, the pressure of the springs against the ratchet wheel being controlled through means new about to be described.

The left-hand end of the inner spring 54 engages a collar 58 which i supported in the lower forked end of one arm 6 of a bell-crank lever 52 which is pivoted on a horizontal forwardly and'rearwardly extending shaft 64 secured to the bracket 20. The arms of the fork have extending through them horizontal screws, the inner ends of which enter recesses in the opposite sides of the collar 58.

Between the left-hand end of the collar '58and the aforesaid ratchet wheel 28 is a ball thrustbearing 66. The right-hand end of the inner spring 3 ls engaged by a flanged plug 68 which is engaged by a horizontal adjusting screw is rotatably mounted in an arm 12 extending to the right from the bracket 20 and secured thereto. The screw if! has a comparatively large head which has indicating marks around its periphcry and the arm 12 has secured to it a scale 14 parallel to the screw and close to it, which also has indicating marks on it. The indicating marks assist the operator in adjusting the spring 54 by means of the screw and enable the operator to readily return the spring to a previous adjustment thereof if desired. The screw 10 is held securely in its adjusted position by means of a locking screw 15 mounted on the arm 12 at right angles to the screw Ill for locking engagement therewith.

The outer spring 55 engages a second collar 16 which normally engages the first collar 58. The second collar 16 is supported on the ends of horizontal pins l8, 18 extending inwardly from the arms of a fork at the lower end of an arm 82 of a second bell-crank lever 84 pivoted on the same shaft 64 as the first mentioned bellcrank lever 62. The other end of the second spring 56 is received in a recess in an adjustable collar 85 which surrounds the screw 19 and spring 54 and which is adjustably mounted in the aforesaid arm 12 on the bracket Zll. The adjustable collar 85 has formed thereon a flange 81 by which it may be rotated to adjust the spring 56 and the peripheral face of the flange has on it indicating marks. The peripheral face of the flange of the collar 86 is close to the aforesaid scale 14 and the marks on the face and marks on the scale assist the operator in adjusting the collar or returning it to previous adjustment.

The aforesaid thread wheel 26, Worm gear 48 and flange 40 are housed within the bracket 20, the thread wheel being in a recess 88 which is closed by a cover plate 90 pivoted on the bracket. The flange and worm gear are housed within a second recess in the bracket and the friction ring lies just within this recess.

The aforesaid bell-crank levers 62, 84 have more or less horizontal arms 92, 54 extending towards the left from their pivot 64. The horizontal arm 94 of the second bell-crank lever 84 is arranged to be engaged by a screw 95 in a rearwardly extending arm 98 of a cam actuated l bell-crank lever which is pivoted on a horizontal shaft I00 extending laterally of the machine. An upwardly extending arm I02 of the latter bell-crank lever carries a cam roll I04 at its upper end which is held against a cam on the cam shaft of the machine by a spring I06.

During the operation of the machine both springs 54, 56 act to cause the ratchet wheel 28 to be pressed against the friction ring 42 on the aforesaid flange 40 (which is being comparatively slowly rotated, i. e., at about 60 revolutions per minute, in the opposite direction to that in which the thread wheel 26 is rotated by a pull on the thread passing around it) during the whole of the machine cycle except during that portion when the needle is moving rearwardly and drawing a' loop of thread through the work and is also drawing thread from the supply. Just before the needle commences to move rearwardly and while the looper is laying the thread in the needle barb the bell-crank lever 84 is actuated by its cam to relieve the pressure of the second spring 56 on the ratchet wheel 28 and 'just before the needle commences to move forwardly again the pressure of the second spring 56 against the ratchet wheel 28 is again applied and is continued until just before the needle commences to move rearwardly again.

U The thread therefore is under a lighter tension (due to the partialQrelief in the pressure with which the ratchet wheel and friction ring are pressed together) when the needle is moving back than at other times in the machine cycle.

The horizontal arm 92 of the first bell-crank lever 62 is arranged to be depressed by stopping mechanism of the machine as the machine comes to rest, to release the thread tension. As best shown in Figs. 1 and 3, the arm 92 is arranged to be acted upon by an adjustable stop screw 5 IE on one arm of abell-crank lever I I2 mounted to turn on a pivot stud H4. The other arm of the bell-crank H2 is connected by links H5, H! to a lever H8 supported to turn on the shaft IEO. A shifter lever in connected to an upwardly extending arm of the lever H8 is rendered operative by the rotation of the main cam shaft 224 in a reverse direction in stopping the machine to rock the lever H8, causing the bellcrank H2 to be rocked in a direction to depress the arm 52. When this arm of the bell-crank lever 62 is depressed, its other arm 63 which carries the first collar 58 is swung towards the right and moves both collars 58, 76 away from the ratchet wheel 28 against the pressure of both springs 54, 5'3, and thus releases the pressure of the ratchet wheel 28 against the rotating friction ring 42 so that the thread wheel 26 can rotate freely and allow thread to be drawn freely by the operator from the supply.

It will be apparent that the illustrative embodiment comprises a tension device for a chainstitch shoe sewing machine in which the drawing of thread from the supply is resisted by the relative movement of friction faces pressed together by springs and in which one of the friction faces is continuously rotated, while the machine is in operation, in the opposite direction to that in which the other face is rotated by the drawing of the thread from the supply by the stitch forming devices of the machine, the device also including means for preventing the latter face from being rotated backwardly by the first mentioned face at all times when the thread is not tending to rotate it forwardly. Such relative movement of the friction faces provides a live tension which enables the thread to be readily drawn from the supply at the commencement of such drawing of thread and provides at all times when the machine is being operated a substantially uniform tension enabling the thread to be drawn smoothly from the supply.

The invention having been described, what is claimed is:

1. In a machine having thread handling devices including means for intermittently drawing off thread from a supply, a thread tension including a thread engaging member movable intermittently with the thread, and a friction device acting upon said thread engaging member, said friction device comprising cooperating friction surfaces, and means for relatively moving said friction surfaces to provide a live frictional resistance effective to reduce the resistance to the starting of said member.

2. In a machine having thread handling devices including means for intermittentl drawing off thread from a supply, a thread tension'including a thread engaging member movable intermittently with the thread, and a friction device acting upon said thread engaging member comprising cooperating friction surfaces, and means for relatively moving said friction surfaces continuously to maintain a live frictional engagement therebetween.

'3. In a machine having thread handling devices including means for intermittently drawing oif thread from a supply, a thread tension including a thread engaging member movable intermittently with the thread, and a friction device acting upon said thread engaging member comprising cooperating friction surfaces arranged for continuous relative movement to maintain a live frictional engagement therebetween.

4. In a machine having thread handling devices including means for intermittently drawing off thread from a supply, a thread tension including a thread engaging member movable intermittently with the thread, and a friction device acting upon said thread engaging member comprising cooperating friction surfaces, tensioning means for exerting a frictional engaging pressure between said surfaces, and means for relatively moving said friction surfaces continuously to maintain a live frictional engagement therebetween.

5. In a machine having thread handling devices including means for intermittently drawing oif thread from a supply, a thread tension including a thread engaging membermovable intermittently with the thread, and a friction device acting upon said thread engaging member comprising cooperating friction surfaces, tensioning means for exerting a frictional engaging pressure between said surfaces, adjusting means for adjusting the pressure exerted by said tensioning means to any one of a plurality of predetermined values, and means for relatively moving said friction surfaces continuously to maintain a live frictional engagement therebetween.

6. In a machine having thread handling devices including means for intermittently drawing off thread from a supply, a thread tension including a thread engaging member movable intermittently with the thread, and a friction device comprising a friction member frictionally acting on said thread engaging member, and means for continuously moving said friction member relatively to the thread engaging member to maintain a live frictional engagement of the friction member with the thread engaging member.

7. In a machine having thread handling devices including means for intermittently drawing off thread from a supply, a thread tension including a thread engaging member movable intermittently with the thread, and a friction device comprising a friction member frictionally acting upon said thread engaging member, means for continuously moving the friction member in a direction opposite to the draw-off movement of the thread engaging member with the thread, and means to prevent movement of the thread engaging member with the friction member.

8. In a machine having thread handling devices including means for intermittently drawing off thread from a supply, a thread tension including a tension wheel over which the thread passes from the supply, a friction surface associated with the tension wheel, a friction member frictionally engaging with and rotatable with relation to said friction surface, tensioning means for maintaining a frictional engaging pressure between said surface and friction member, means to prevent rotation of the tension wheel in a reverse direction, and means for continuously rotating the friction member in said reverse direction to maintain a live frictional engagement beif;ween the friction member and the friction surace.

9. A chainstitch shoe sewin machine having,

in combination, thread handling devices including a needle, a looper, a take-up, and a thread. tension comprising a tension wheel from which thread is intermittently drawn off from the supply by the thread handling devices, and a friction device acting upon said tension wheel, said friction device comprising cooperating friction surfaces, and means for relatively moving said friction surfaces to provide a live frictional resistance effective to reduce the resistance to the starting of the tension wheel.

10. A chainstitch shoe sewing machine having, in combination, thread handling devices including a needle, a looper, a take-up, and a thread tension comprising a tension wheel over which thread is intermittently drawn off from the supply by the thread handling devices, a friction device acting upon said tension wheel comprising cooperating friction surfaces, and means for relatively moving said friction surfaces continuously to maintain a live frictional engagement therebetween to resist the starting of the tension wheel.

11. A chainstitch shoe sewing machine having, in combination, thread handling devices including a needle, a looper, a take-up acting to pull the thread tightly around the needle while the needle is in the work, and to draw off additional thread from the supply, and a thread tension against which the take-up acts comprising a thread engaging member movable with the thread, a friction member frictionally acting upon said thread engaging member to tension the thread, and means for continuously moving said friction member to maintain a continuously live frictional resistance to the starting of said thread engaging member.

12. A chainstitch shoe sewing machine having, in combination, thread handling devices including a needle movable to draw in a loop of needle thread, a looper, a thread finger, and a take-up movable to give up thread and thereafter to pull the thread tightly around the needle while the needle is in the work, a thread tension including a tension wheel, a friction surface associated therewith, a friction member engaging said surface and rotatable relatively thereto, tensioning means for maintaining frictional engagement between said surface and friction member, means to prevent rotation of the tension wheel in a reverse direction, and means for continuously rotating said friction member in said reverse direction to maintain a live frictional resistance to the starting of the tension wheel.

13. A chainstitch shoe sewing machine having, in combination, thread handling devices including a needle movable to draw in a loop of needle thread, a looper, a thread finger, and a take-up movable to give up thread and thereafter to pull the thread tightly around the needle While the needle is in the work, a thread tension including a tension wheel, a friction surface associated therewith, a friction member engaging said surface and rotatable relatively thereto, tensioning means for maintaining frictional engagement between said surface and friction member, means to prevent rotation of the tension wheel in a reverse direction, means for continuously rotating said friction member in said reverse direction to maintain a live frictional resistance to the starting of the tension wheel, and means operative in stopping the machine to relieve the tension between the surface and friction member.

14. A chainstitch shoe sewing machine having, in combination, thread handling devices including a needle movable to draw in a loop of needle thread, a looper, a thread finger, and a take-up movable to pull the thread tightly around the needle while the needle is in the work and to draw off additional thread from the supply, a thread tension including a tension Wheel, a friction surface associated therewith, a friction member engaging said surface and rotatable relatively thereto, tensioning means constructed and arranged to apply a frictioning tension of a predetermined value between said surface and friction member during the loop drawing stroke of the needle and a frictioning tension of a predetermined greater value between said surface and friction member during the tightening of the thread by the take-up, means to prevent reverse movement of the tension wheel, and means for continuously rotating said friction member in said reverse direction to maintain a live frictional resistance to the starting of the tension wheel.

15. A chainstitch shoe sewing machine having, in combination, thread handling devices including a needle movable to draw in a loop of needle thread, a looper, a thread finger, and a take-up movable to pull the thread tightly around the needle while the needle is in the work and to draw off additional thread from the supply, a thread tension including a tension wheel, a friction surface associated therewith, a friction member engaging said surface, means for continuously rotating the friction member in a direction reverse to the draw-off movement of the tension wheel, means to prevent movement of the tension wheel in said reverse direction, a normally operative tension mechanism for exerting a constant frictionally engaging pressure between said sur face and friction member during operation of the machine, a supplementary tension mechanism operative durin the loop tightening movement of the take-up, and means operative in stopping the machine to relieve both tension mechanisms.

16. A thread tension of the character described which comprises a tension wheel over which the thread is drawn off, a friction surface associated with the tension Wheel, a friction member engaging said surface, means for continuously rotating the friction member in a direction reverse to the draw-off movement of the tension wheel, means to prevent rotation of the tension wheel in said reverse direction, and tensioning means for exerting a predetermined frictional engaging gressure between said surface and friction mem- 17. A thread tension of the character described which comprises a tension wheel over which thread isdrawn off, a friction surface associated with the tension wheel, a friction member engaging said surface, a worm and worm wheel driving connectionfor continuously rotating the friction member in a direction reverse to the draw-off movement of the tension Wheel, a pawl and ratchet connection to prevent rotation of the tension wheel in said reverse direction, and tensioning means comprising a spring and adjusting means therefor for exerting a predetermined frictional engaging pressure between said surface and friction member.

JOSEPH GOULDBOURN.

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