US3750972A - Automatic tension regulation of yarn and wire winding devices - Google Patents

Abstract

A device for regulating the tension of a yarn or an assembly of yarns, or wires, between a pulling capstan and a winding bobbin. The device is intended for avoiding the inconveniences resulting from sudden stoppages of the winding machine, the winding rate being controlled automatically by the yarn or wire tension through means adapted to modify accordingly the pressure of a friction coupling disposed between the pulling capstan and the winding bobbin.

Description

United States Patent [1 1 Bonnabaud et al.

1 Aug. 7, 1973 AUTOMATIC TENSION REGULATION OF YARN AND WIRE WINDING DEVICES [76] lnventors: Joannes Francis Marcel Bonnabaud, 23 rue Noelas, Roanne; Claude Brat, 119 route de Vichy, Riorges, both of France [22] Filed: Feb. 23, 1971 [21] Appl.No.: 118,111

[52] US. Cl. 242/45 [51] Int. Cl B6Sh 58/38 [58] Field of Search 242/45, 75, 75.5

[56] References Cited UNITED STATES PATENTS 5/1934 Livingston 242/45 10/1944 Goodwin 242/45 2,814,332 12/1957 Molla 242/755 X 3,035,784 5/1962 Defontenay .i 242/45 3,233,397 2/1966 Bonikowski 242/45 X Primary ExaminerStanley N. Gilreath Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT A device for regulating the tension of a yarn or an assembly of yarns, or wires, between a pulling capstan and a winding bobbin 'ljhe device is intended for avoiding the inconveniences resulting from sudden stoppages of the winding machine, the winding rate being controlled automatically by the yarn or wire tension through means adapted to modify accordingly the pressure of a friction coupling disposed between the pulling capstan and the winding bobbin.

8 Claims, 5 Drawing Figures PATENIEB 7973 SHEET 1 If 3 AUTOMATIC TENSION REGULATION OF YARN AND WIRE WINDING DEVICES FIELD OF THE INVENTION The present invention relates to an improved device for regulating the tension of a yarn or wire, or an assembly of yarns or wires, between a pulling capstan and a winding bobbin.

DESCRIPTION OF THE PRIOR ART In most present applications, to wind one or more yarns on a bobbin at a constant linear speed the yarn or yarns are pulled directly by the bobbin. However, due to the gradual increment in the diameter of the turns being wound this bobbin must be driven at a variable speed, and therefore generally costly and cumbersome devices are used to this end.

This conventional winding system was improved by pulling the yarn or yarns by means of a capstan providing a constant speed and driving said bobbin through friction means.

Although this device is considerably simpler and more compact it is not entirely satisfactory. In fact, during the starting period the yarn'tends to become slack between the capstan and the bobbin, due to the slower speed increment of the bobbin. Moreover, in case of sudden stoppage of the machine, the bobbin tends to continue its rotational movement by inertia and is stopped by the yarn, the latter being thus exposed to considerable tension forces likely to break or at least elongate the yarn, so that its properties are impaired or modified.

SUMMARY OF THE INVENTION It is an essential object of the present invention to avoid the inconveniences set forth hereinabove by providing a device for regulating the tension of a yarn or wire, or an assembly of yarns or wires, between a pulling capstan and a winding bobbin, notably of the type used in yarn-assembling machines, and comprising between said capstan and said bobbin a friction-type transmission means, this device being characterized in that the shaft supporting said capstan has mounted thereon for free rotation a predetermined but variable number of pulleys adapted to deflect the yarn or yarns to be wound towards other'pulleys equal in number to said variable number and also mounted for free rotation on a second shaft parallel to said capstan supporting shaft, said yarn or yarns being partially wound over said other pulleys, said second shaft being rigid with one end of an arm having its otherend rigidwith a third shaft parallel to said first and second shafts and mounted for free rotation in the frame structure of the machine equipped with this device and supporting the friction means provided for transmitting the rotational movement of said capstan to said winding bobbin, said third shaft comprising means adapted, as a consequence of the angular movements of said arm which are due to an overstretch or a slackness in the yarn or yarns to be wound, to increase or reduce the contact pressure of said friction means according to the direction of said angular movements,other means being also provided for quickly stopping the bobbin rotation in case of sudden stoppage of the machine.

Thus, the pulleys carried byoneend of said arm are held in a position subordinate to thetension of the yarn or yarns wound on said pulleys, and any change occuring in this tension involves necessarily a movement of said pulleys towards or away from said capstan, and therefore an angular movement of said arms which modifies accordingly the force of application of said means, whereby the winding bobbin is caused to rotate more or less rapidly so as to restore the yarn tension to a normal, predetermined value.

According to a specific form of embodiment of this invention the means provided for transmitting the capstan rotational motion to the boblbin comprises a motion input pinion mounted for loose rotation on the shaft supporting said arm, a socket mounted for free rotational and axial translation movement on said shaft, said socket carrying at one end a friction disk disposed with its friction lining registering with said pinion, and at the opposite end a motion output pinion, said shaft further comprising a screw-threaded portion engaging a tapped bore formed in said frame structure, whereby the angular movements of said arm are attended by an axial movement of its supporting shaft and consequently by the compressionor release of resilient washers interposed between the end of said socket opposite to that comprising said friction disk and a nut screwed on the corresponding end of said shaft.

On the other hand, the means contemplated for quickly stopping the bobbin rotation in case of sudden excessive yarn tension comprise mainly a ratchet wheel mounted for loose rotation on said friction disk supporting socket, said friction disk being provided with a lining on its face registering with the adjacent side of said ratchet wheel, resilient whashers constantly urging with a relatively strong pressure said ratchet wheel against said lining, a pawl carrying at one end a catch adapted to engage theteeth of said ratchet wheel, pivoted intermediate its ends to a fixed fulcrum pin and provided at the end opposite to said catch with a roller follower constantly urged by spring means against a cam carried by said shaft and formed with two are sec tions of different radii centered to the fulcrum axis of said arm so as to provide an upper cam face and a lower cam face, whereby, during the angular movements of said arm either of said cam sections will engage said roller andthus, by actuating said pawl, lock or release said ratchet wheeland cause said ratchet wheel to stop or not the friction disk associated therewith and consequently the socket supporting same, the motion output pinion and the winding bobbin.

Advantageously, the cam mounting allows a certain degree of axial movement of the cam which is constantly urged by spring means to a predetemined position so that in case the pawl catch were retained by the tip of a tooth of said ratchetwheel the cam movement will enable said catch to clear the "tooth.

According to a preferred and simpler form of embodimentof the present invention the means provided for causing, an consequenceof the movements of said arm, the necessary increment or reduction in the contact pressure of said friction means comprise, in addition to the shaft formed with a screw-threaded portion engaging the aforesaid tapped bore of thcframe structure of the machine, a platc provided with a friction lining onits face registering with said motion input pinion, said plate being rigidly connected to the motion output pinion and free to reveolve on, but held againstaxial translation along, said shaft, a nut screwedon the free end of said shaft permittingthe initial adjustment of the frictional contact pressure between said plate and said input pinion.

According to a complementary feature of the preferred form of embodiment of this invention the means contemplated for quickly stopping the bobbin rotation in case of sudden yarn overstretch include a disk rigid with the assembly comprising said plate and said output pinion, and a device incorporating a strap pivotally mounted about an axis perpendicular to the shaft carrying said assembly, said strap being provided with a stud carrying through the medium of a swivel or ball-joint a flat friction button held in contact with said disk, said strap further receiving therethrough a rod adapted to move freely in translation therein and provided at one end with a stack of spring washers disposed between one face of said strap and a mushroom-shaped or contoured head screwed to the corresponding end of said rod, a roller carried by an extension of the arm rigid with said shaft being adapted to roll on said mushroomshaped head so as to compress said spring washers and increase the force of application of said flat friction button against said disk, suitable adjustment means being provided for constantly braking said disk and, consequently, the bobbin.

Advantageously, the strap stud swivel or ball-joint carries two such flat friction buttons disposed at diametrally opposed positions so that when one button is worn the other can be put into service by simply pivoting same about said swivel joint.

BRIEF DESCRIPTION OF THE DRAWINGS In order to afford a clearer understanding of this invention the same will now be described more in detail with reference to the attached drawings illustrating diagrammatically byway of example a typical form of embodiment of the invention. In the drawings FIG. 1 is a simplified side elevational view showing the path followed by the yarn or yarns to be wound FIG. 2 is a developed front view of the device shown in section taken along the irregular line 22 of FIG. 1

FIG. 3 is a side elevational view showing more in detail the function and mode of operation of the arm, and

FIGS. 4 and 5 are a vertical front and sectional view and a side elevational view with parts broken away of a modified form of embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description and also in the claims attached hereto, it is understood that the term yarn is used to simplify the disclosure and could be replaced as well by the term wire" since the tension control device constituting the object of this invention is applicable to any machine in which it is desired to control the tension of a yarn, wire or other similar filament, whether of synthetic, natural, metallic or compound nature.

In this device, the yarn or yarn assembly 2 (FIGS. 1 and 2) is led to a point 3a of a pulling capstan 3 keyed on a power or driven shaft 4. Then the yarn 2 passes over an inclined capstan 5 mounted for loose rotation on a shaft 6, the yarn 2 emerging form this other capstan 5 at a point 5a before engaging a groove 3b of the first capstan 3, and so forth until the yarn engages the groove 3e.

From this groove 3e the yarn 2 is directed to a pulley 7 mounted for free rotation on a shaft 8 carried in turn by an arm 9. Then the yarn 2 engages a pulley 10 revolving freely on shaft 4 and subsequently a pulley 12 adjacent to pulley 7, another pulley 13 adjacent to pulley 10, a further pulley 14 adjacent to pulley l2, and finally a pulley 15 adjacent to pulley 13.

As it emerges from pulley 15 the yarn engages a pulley 16 having a fixed axis and then another pulley 17 supported by conventional support means so as to be adapted to pivot angularly about a point 18 the yarn is eventually received by a winding bobbin 19, on which its turns are regularly distributed as a consequence of rectilinear reciprocating movements imparted to the support means of pulley 17 in conventional manner parallel to the axis of rotation of said bobbin 19.

The bobbin 19 is carried by a horizontal shaft 20 to which it is adapted to be rotatably and releasably connected by means ofa stud 22 carried by a plate 23 rigid with and extending radially from, the shaft 20.

As clearly shown in FIG. 2 the movement of rotation of capstan 3 is transmitted to the bobbin 19 through a power pinion 24 keyed on shaft 4, a pair of intermediate pinions 25, 26 and a pair of parallel, coaxial pinions 27, 28 mounted for loose rotation on a shaft 29, and finally a driven pinion 30 keyed on said shaft 20 supporting the bobbin l9 suitable friction coupling means are provided between the parallel pinions 27 and 28.

These friction coupling means comprise essentially a cylindrical socket 32 mounted for free rotation on said shaft 29 and having one end provided with an axially offset and projecting plate-forming flange 32a of which the face registering with the pinion 27 is covered by a friction lining 33. The other end of socket 32 carries said pinion 28 secured thereto by means of set screws 34. A plurality of dished spring washers 35 are interposed between the free face of pinion 28 and a nut 36 screwed on the correspondingly screw-threaded end portion of shaft 29, whereby the socket 32 and its friction lining 33 are pressed against the pinion 27, and the bobbin 19 can thus be driven through the resulting friction coupling.

According to an essential feature characterizing this invention, the shaft 29 is mounted for free rotation and axial translation in another socket 37 carried by the frame structure 38 of the machine equipped with this device. This shaft 29 comprises at its end opposite to that carrying nut 36 a screw-threaded portion 29a of greater diameter engaging a tapped bore of socket 37. This screw-threaded shaft portion has a plain cylindrical extension 29b to which the end of arm 9 remote from the pulleys 7, l2 and 14 is rigidly secured so that the shaft 29 and arm 9 can rotate bodily with each other.

As a result, if for any reason the tension of yarn 2 decreases, the coaxial pulleys 7, 12 and 14 (normally held in a predetermined position by the yarn turns) move away from capstan 3 as a consequence of the gravity force acting upon these pulleys. FIG. 1 clearly illustrates this feature. Consequently, the arm 9 is moved angularly in the direction of the arrow 39 of FIG. 1, the shaft 29 rotating in the same direction. The pitch of the screw-threaded portion 29a of shaft 29 is so directed that it effects, in conjunction with this rotation, axial movement of said shaft in the direction of the arrow 40 of FIG. 2, thereby causing compression of the resilient dished washers 35 whereby these washers will urge the friction lining 33 with a greater force against the pinion 27.

Thus, any slack occuring in the travelling yarn 2 is attended by a proportional angular movement of the arm 9 and by an increment likewise porportional of the pressure with which the lining 33 engages the pinion 27, so that the relative slip between these members is reduced and the bobbin 19 is driven at a higher rotational speed in order to restore the initial tension of yarn 2.

Similarly, in case the yarn turns 2 are overstretched, the pulleys 7, 12 and 14 move towards the capstan 3 and the arm is moved radially in the direction of the arrow 42 of FIG. 1, thus causing axial movement of translation of shaft 29 in the direction of the arrow 43 of FIG. 2. Under these conditions, the washers 35 are allowed to expand and the pressure with which the friction lining 33 engages the pinion 27 is decreased until the yarn tension has resumed its normal value.

It may also be noted that the permissible angular movements of arm 9 are limited by stop means 44 and 45.

This device is completed by another device adapted to quickly stop the bobbin rotation in case of sudden stoppage of the machine. In fact, if the traction exerted on the yarn 2 were suddenly removed or, otherwise stated, if the -capstan 3 were suddenly stopped, the bobbin would continue its rotation by inertia, thus causing during a very short time period an increment in the yarn tension between the capstan and the bobbin, and therefore an upward movement of arm 9 in the direc tion of the arrow 42 of FIG. 1 and a considerable reduction in teh friction pressure between lining 33 and pinion 27. Thus, no braking effort is exerted on the bobbin l9.

The device contemplated for avoiding this serious inconvenience constitutes another essential feature of this invention and comprises mainly a ratchet wheel 46, a pawl 47 and a cam 48.

The ratchet wheel 46 is mounted for free rotation and translation on the socket 32 and urged by resilient washers 49, with a relatively strong pressure against the outer face of the plate-forming flange 32a of this socket, i.e. the face opposite to that carrying the lining 33. Said outer face of flange 32a is also covered by a friction lining 50.

The ratchet wheel 46 co-acts with a pawl lever 47,.as illustrated in FIG. 3, pivoted to a fixed fulcrum pin 52 carried by the frame structure 38 of themachine. The pawl 47 engages the teeth of ratchet wheel 46 with a catch 47a and carries at its opposite end a roller 53 urged against the cam 48 by a tension spring 54.

The cam 48 is carried by the arm 9 and is formed with two are sectionscentered on the axis of shaft 29. These are sections48a and 48b have however different radii in order to constitute an upper cam face 48b and a lower cam face 48a, respectively.

This device operates as follows Assuming that the pawl lever 47 is in its lower or mean position, i.e. under normaloperating conditions, the roller 53 engages the upper portion or cam face 48b of cam 48, whereby the pawl 47 urged by spring54 releases its catch 470 from the teeth of ratchet wheel 46.

When the arm 9 is moved towards the stop member 44 as a consequence of an increase in the yarn tension,

it carries along the cam 48 so that the lower cam face 480 engages the roller 53.

As a result, the catch 47a engages the wheel 46 and the latter is locked against rotation, so as to ensure an efficient braking of bobbin 19.

Advantageously, the cam 48 is so mounted on arm 9 that it can move longitudinally thereon and is urged to an end position by a return spring 55.

This possibility of moving the cam 48 permits the clearing of the tip of a tooth of wheel 46 in case the catch 47a of pawl 47 were urged against, and retained by said tip.

Moreover, it will be seen that at. an average machine braking rate the pawl catch 47a can be caused to alternatively lock the wheel 46 and travel away several times during this braking action.

The modified embodiment illustrated in FIGS. 4 and 5 permits avoiding this hunting in the pawl and ratchet operation of the device. Moreover, this modified arrangement provides a device considerably simpler, and therefore more economical and reliable than the one described hereinabove.

According to this modified construction the shaft 29 is simply provided with a plate 32-32a having a single friction lining on its face registering with the motion input pinion 27. This plate 32 is rigidly connected to the motion output pinion 28 meshing with the pinion 30 rotatably driving the bobbin 19.

This modified device is therefore: substantially similar to that of the preceding form of embodiment, the essential difference residing in the elimination of the re silient dished washers 35. A nut engaging the screwthreaded free end of shaft 29 permits the adjustment of the initial friction. I v

However, the device according to this modified form of embodiment operates in. conjunction with particularly simple means adapted to rapidly stop the bobbin rotation in case of sudden stoppage of the machine.

This device includes essentially a disk 62 rigid with the assembly comprising the plate 32, 32a and pinion 28, and a braking system incorporating a strap 63 pivotally mounted on a fulcrum 64 extending at right angles to the shaft 29. This strap is provided with a stud 65 carrying by means of a swivel or ball-joint66 a pair of opposed parallel buttons 67 having their outer faces lined with a suitable friction material 68.

One of these linings is urged against the inner face of disk 62 as illustrated in FIG. 4.

On the other hand the strap 63 has mounted for axial sliding movement therethrough a rod 69 parallel to shaft 29and formed with screw-threaded ends adapted to be engaged at oneend by a nut and lock-nut 70, and at the other end by a mushroom-shaped or like convex head 72. A plurality of resilient dished washers 76 carried by the rod 69 are interposed between the mushroom-shaped head 72 and the registering face of strap 63. I

A roller 73 carried by another strap 74 rigid with an extension 9a of arm 9 is adapted to roll on mushroom head 72. Under these conditions it is clear thatany angular movement of arm 9 will be attended by achange in the pressure exerted by the button 67 against the disk 62. Thus, for instance, in caseof sudden stoppage of the machine,i.e. of the pulling capstan 3, the bobbin 19 by continuing its rotation by inertia will introduce an overstretch in the yarn 2 and consequently anangular movement of arm 9 in the direction of the arrow 75 of FIG. 5. As a consequence of this angular movement, the roller 73 is caused to move towards the center of mushroom head 72, thus increasing considerably the pressure exerted by the button 67 against the disk 62 and causing a rapid stoppage of this disk and therefore of the bobbin 19.

It is also apparent that an adequate adjustment permits advantageously exerting a permanent light braking action on the bobbin 19 during the normal operation of the machine.

Furthermore, the button 68 not contacting the disk 62 is kept in reserve and can at any time replace the other button, for instance in case of wear, by simply rotating the support constituted by the swivelor balljoint 66.

With the device of this invention it is therefore possible, within relatively reduced over-all dimensions, to keep the yarn 2 under a substantially constant tension between a pulling capstan 3 and a winding bobbin l9, irrespective of the winding diameter of the yarn, the speed of capstan 3 and the values of its accelerations and decelerations.

However, it will readily occur to those skilled in the art that this invention should not be considered as being strictly limited by the specific examples and illustrations given herein,-since many modifications and variations and many applicaitons, may be contemplated in the practical embodiment of the invention without departing from the basic principles thereof as set forth in the appended claims.

What is claimed as new is 1. A device for regulating the tension of a yarn between a pulling capstan and a winding bobbin in a yarnassembling machine, the machine having a frame and a capstan supporting shaft rotatably mounted on the frame, said device comprising transmission means including a variable friction coupling between the capstan and bobbin for transmitting drive therebetween, control means for regulating said transmission comprising a plurality of first pulleys'mounted for free rotation on the capstan supporting shaft, a second shaft extending parallel to the capstan supporting shaft, a plurality of second pulleys equal in number to the first pulleys and mounted for free rotation on the second shaft, the yarn passing from the pulling capstan to the winding bobbin via said first and second pulleys, a third shaft rotatably mounted on said frame and extending parallel to said first and second shafts, an arm having one end rigidly connected with the third shaft and supporting the second shaft at its other end so that variation in tension in the yarn will act on said second pulleys and cause said arm to pivot with said third shaft on said frame, said friction coupling being mounted on said third shaft and including means for increasing and decreasing the degree of frictional engagement and consequent drive connection between the capstan and bobbin in response to rotation of the said third shaft caused by angular movement of said arm in one direction or the other due to variation in tension in the yarn, and braking means coupled with said arm for quickly stopping rotation of the bobbin upon sudden stoppage of rotation of the pulling capstan.

2. A device as claimed in claim 1 wherein the transmission means further comprises an input pinion driven from the capstan and mounted for loose rotation on the third shaft, a socket mounted for free rotation and axial translation on said third shaft, an output pinion for driving the bobbin mounted on said socket at one end thereof, and a nut threaded on said third shaft, the friction coupling comprising a friction disk disposed on said socket at the other end thereof and including a friction lining which registers with said input pinion, and resilient washers interposed between said socket and said nut, said third shaft further comprising a screw-threaded portion threadably engaged in the frame so that angular movements of said arm causes axial movement of said third shaft and consequently compression or release of the resilient washers.

3. A device as claimed in claim 2 wherein said braking means comprises a ratchet wheel mounted for loose rotation on said socket, said friction disk including a second lining facing said ratchet wheel, second resilient washers strongly urging said ratchet wheel against said second lining, a pawl carrying at one end a catch adapted to co-act with teeth of said ratchet wheel, said pawl being pivoted intermediate its ends to a fixed fulcrum and including at its end opposite to said catch a roller follower, a cam carried by said arm and including two are sections of different radii centered on the fulcrum axis of said arm so as to provide an upper cam face and a lower cam face, and spring means urging the roller follower against the cam such that during angular movements of said arm one or the other of said cam sections will engage said roller follower and thus, by actuating said pawl, lock or release said ratchet wheel and cause said ratchet wheel to selectively stop the friction disk associated therewith and consequently the socket, the output pinion and the winding bobbin.

4. A device as claimed in claim 3 comprising means supporting said cam on said arm to allow a degree of axial movement of the cam so that in case the pawl catch were retained by the tip of a tooth of said ratchet wheel the cam can move to enable said catch to clear the tooth.

5. A device as claimed in claim I wherein said means for increasing and decreasing the frictional engagement as a consequence of the angularmovements of said arm comprises a plate including a friction lining facing said input pinion, said plate being rigidly connected to the output pinion and free to revolve on, but held against axial translation along said third shaft, said nut screwed on said shaft permitting initial adjustment of frictional contact pressure between said plate and said input pinion.

6. A device as claimed in claim 5 wherein said braking means includes a disk rigid with said plate and said output pinion, and a means incorporating a strap pivotally mounted about an axis perpendicular to said third shaft, said strap including a stud, and a flat friction button pivotably mounted on said stud and held in contact with said disk, a rod supported in said strap for free translation movement, a contoured head secured to one end of the rod, a stack of spring washers disposed on said rod between said strap and said contoured head, and a roller carried on said arm to roll on said contoured head to compress said spring washers and increase the force of application of said friction button adainst said disk.

7. A device as claimed in claim 6 comprising adjustment means coupled to said rod for constantly braking said disk and thereby the winding bobbin.

8. A device as claimed in claim 6 comprising a second friction button disposed in opposition to the first button so that in case of wear of one button, the other button can be put into service by simply pivoting the buttons i i 1 i

Claims (8)

1. A device for regulating the tension of a yarn between a pulling capstan and a winding bobbin in a yarn-assembling machine, the machine having a frame and a capstan supporting shaft rotatably mounted on the frame, said device comprising transmission means including a variable friction coupling between the capstan and bobbin for transmitting drive therebetween, control means for regulating said transmission comprising a plurality of first pulleys mounted for free rotation on the capstan supporting shaft, a second shaft extending parallel to the capstan supporting shaft, a plurality of second pulleys equal in number to the first pulleys and mounted for free rotation on the second shaft, the yarn passing from the pulling capstan to the winding bobbin via said first and second pulleys, a third shaft rotatably mounted on said frame and extending parallel to said first and second shafts, an arm having one end rigidly connected with the third shaft and supporting the second shaft at its other end so that variation in tension in the yarn will act on said second pulleys and cause said arm to pivot with said third shaft on said frame, said friction coupling being mounted on said third shaft and including means for increasing and decreasing the degree of frictional engagement and consequent drive connection between the capstan and bobbin In response to rotation of the said third shaft caused by angular movement of said arm in one direction or the other due to variation in tension in the yarn, and braking means coupled with said arm for quickly stopping rotation of the bobbin upon sudden stoppage of rotation of the pulling capstan.

2. A device as claimed in claim 1 wherein the transmission means further comprises an input pinion driven from the capstan and mounted for loose rotation on the third shaft, a socket mounted for free rotation and axial translation on said third shaft, an output pinion for driving the bobbin mounted on said socket at one end thereof, and a nut threaded on said third shaft, the friction coupling comprising a friction disk disposed on said socket at the other end thereof and including a friction lining which registers with said input pinion, and resilient washers interposed between said socket and said nut, said third shaft further comprising a screw-threaded portion threadably engaged in the frame so that angular movements of said arm causes axial movement of said third shaft and consequently compression or release of the resilient washers.

3. A device as claimed in claim 2 wherein said braking means comprises a ratchet wheel mounted for loose rotation on said socket, said friction disk including a second lining facing said ratchet wheel, second resilient washers strongly urging said ratchet wheel against said second lining, a pawl carrying at one end a catch adapted to co-act with teeth of said ratchet wheel, said pawl being pivoted intermediate its ends to a fixed fulcrum and including at its end opposite to said catch a roller follower, a cam carried by said arm and including two arc sections of different radii centered on the fulcrum axis of said arm so as to provide an upper cam face and a lower cam face, and spring means urging the roller follower against the cam such that during angular movements of said arm one or the other of said cam sections will engage said roller follower and thus, by actuating said pawl, lock or release said ratchet wheel and cause said ratchet wheel to selectively stop the friction disk associated therewith and consequently the socket, the output pinion and the winding bobbin.

4. A device as claimed in claim 3 comprising means supporting said cam on said arm to allow a degree of axial movement of the cam so that in case the pawl catch were retained by the tip of a tooth of said ratchet wheel the cam can move to enable said catch to clear the tooth.

5. A device as claimed in claim 1 wherein said means for increasing and decreasing the frictional engagement as a consequence of the angular movements of said arm comprises a plate including a friction lining facing said input pinion, said plate being rigidly connected to the output pinion and free to revolve on, but held against axial translation along said third shaft, said nut screwed on said shaft permitting initial adjustment of frictional contact pressure between said plate and said input pinion.

6. A device as claimed in claim 5 wherein said braking means includes a disk rigid with said plate and said output pinion, and a means incorporating a strap pivotally mounted about an axis perpendicular to said third shaft, said strap including a stud, and a flat friction button pivotably mounted on said stud and held in contact with said disk, a rod supported in said strap for free translation movement, a contoured head secured to one end of the rod, a stack of spring washers disposed on said rod between said strap and said contoured head, and a roller carried on said arm to roll on said contoured head to compress said spring washers and increase the force of application of said friction button adainst said disk.

7. A device as claimed in claim 6 comprising adjustment means coupled to said rod for constantly braking said disk and thereby the winding bobbin.

8. A device as claimed in claim 6 comprising a second friction button disposed in opposition to the first button so that in caSe of wear of one button, the other button can be put into service by simply pivoting the buttons 180*.

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