FR2865782A1 - Mobile body driving device for e.g. displaying goods, has friction coupling unit with pressure unit, between motor plate and driving plate and/or counter plate, to apply friction force, adjusted by adjusting unit, to motor plate - Google Patents

Abstract

The device has a driving plate (2) movable in rotation with respect to a supporting frame (3) along an axis. A friction coupling unit (7) couples a motor plate (9) of an electrical gear motor (6) with the plate (2). The unit (7) has a pressure unit (11) between the motor plate and the driving plate and/or a counter plate (12) integrated with the plate (2), to apply friction force, adjusted by an adjusting unit (20), to the plate (9).

Description

The present invention relates to the field of devices used for

  the rotation of a mobile. In one application, preferred but not exclusive, the invention relates to devices used for the presentation, in rotation, merchandise or billboards or other.

  A device for rotating a mobile generally comprises a carrier frame which can be either placed or fixed on a support or, on the contrary, suspended. The carrier chassis is then completed with a drive plate, movable in rotation, with axis 0 relative to the chassis and provided with means for adapting and / or receiving the mobile which can be, for example, constituted by a display stand or, for example, a poster board.

  To ensure a rotation of the drive plate, it has been proposed to involve a friction drive system, comprising a roller, rotated by an electric motor and bearing on a drive track offered by the training plate or by a counter-plate secured to the latter.

  Such a device makes it possible, in fact, to ensure the drive in rotation of the plate and has, however, the disadvantage of being relatively bulky, so that it increases the total volume of the drive device and to allow only a couple of training weak enough. In addition, if the friction drive device according to the prior art actually allows a slip and therefore a disengagement of the plate relative to the drive roller it does not adjust the value of the torque from which the disengagement will occur. However, in the case of driving relatively large loads, this lack of adjustment of the disengagement torque can be prohibitive.

  Thus, it appears the need to have a new type of mobile drive device comprising friction coupling means which, on the one hand, has a smaller footprint than the trainings proposed according to the art prior art and which, on the other hand, offers a great possibility of adjustment of the stall torque of the friction drive means, making it possible to take into account different configurations of use and, in particular, to overcome construction of appliances, imperfections or dispersions likely to affect the surface conditions of the different rooms or the dimensions of the latter.

  In order to achieve this object, the invention relates to a device for driving a mobile in rotation, comprising: a carrier frame, a drive member, rotatable, with axis A relative to the frame and provided with means for adapting or receiving the mobile, ^ an electric geared motor which is integral with the frame and which comprises a drive member, ^ and friction coupling means of the motor member to the body d 'training.

  According to the invention, the device for rotating a mobile is characterized in that the friction coupling means comprise adjustable pressure means interposed between the driving member and the driving member and / or, possibly, a drive counter-drive integral in rotation with the drive member, so as to apply at least one adjustable friction force to the drive member.

  The implementation of an adjustment of the friction force, applied by the pressure means, thus makes it possible to adjust the value of the stall torque of the coupling means, as a function of the load to be rotated, as well as than the power of the electric motor.

  This adjustment capability then offers the possibility of implementing a geared motor including a synchronous electric motor, which has the advantage of having a low cost compared to an asynchronous electric motor but which does not allow, on the other hand, any possibility of slipping, so that it is absolutely necessary for the friction drive means to be adjusted so as to have a lower stall torque than the stall torque of the synchronous motor. However, the pressure adjustment means, offered by the invention, allow, precisely, an adjustment and a possible readjustment which guarantees the reliability of the device according to the invention, as well as a complete use of the engine torque for different ratios reduction.

  According to the invention, the adjustable pressure means can be made in any suitable way. In a first embodiment, the pressure and adjustment functions are dissociated and the adjustable pressure means then comprise pressure means and adjustment means. Thus, preferably but not strictly necessary, the pressure means comprise at least one spring element which operates in compression axis A ', parallel to the axis A of rotation of the drive member or coincides with this axis of rotation. In a preferred manner but not strictly necessary, in order to reduce the size of the device, the spring element or elements used are chosen to have an axial height, of the order of a few millimeters.

  Furthermore, the adjustment means can be made in various appropriate ways, depending on the configuration adopted for the coupling means and / or the nature of the pressure means used.

  According to another characteristic of the invention, the adjustment means are adapted to allow a modification of the distance between the motor member, the drive member and the drive against-member.

  According to one characteristic of the invention, the spring element or elements press the motor member against the drive member. It is then possible to provide either a friction piece interposed between the spring element and the motor member, or, on the contrary, a direct contact between the spring element and the motor member. This solution will preferably, but not necessarily, be retained, in order to reduce, as far as possible, the manufacturing costs of the device according to the invention.

  In one embodiment, the following configuration is adopted: the motor member rubs directly on the drive member and / or an element integral with the drive plate, and the spring element is interposed between the motor member and the drive member opposite the drive member with respect to the drive member.

  The means for adjusting the pressure are then, preferably but not necessarily, interposed between the drive member and the drive member and the pressure adjustment means can be made in different ways.

  According to a characteristic of the invention, the adjustment means comprise at least one pressure screw engaged in a bore of the drive member so as to be accessible from above the drive member and to come into position. support on the motor unit.

  According to another characteristic of the invention, the adjustment means comprise: a counter-plate integral in rotation with the drive member and provided with an inclined ramp, and at least one pressure screw engaged in a bore radial of the drive member, so as to be accessible from the side of the drive member and abut on the inclined ramp to change the distance between the plate against and against the drive member.

  As has been said above, the pressure means can be made in any suitable manner and, according to one embodiment, the pressure means comprise at least one spring element, of the Belleville washer type, of axis coinciding with the axis of rotation of the drive member.

  According to another embodiment, the pressure means comprise a series of helical springs which are each arranged in an axis A housing "parallel to the axis A of rotation of the drive member. strictly necessary, the helical springs will have at least one ground flat end in direct contact with the drive member.

  According to the invention, the helical springs may be arranged in housings provided in the drive member or in the driving member.

  According to another characteristic of the invention, the compression means comprise two sets of helical springs, one of which is arranged in bores of the drive member, while the other is disposed in bores of the counter-member of the invention. training.

  In the case of use as helical spring series pressure means, the pressure adjusting means can be made in different ways.

  Thus, according to one characteristic of the invention, the adjusting means comprise at least one pressure screw disposed in the bottom of a bore receiving a coil spring, so as to allow an adjustment of its compression. It can thus be provided a screw for each spring or, for some only springs.

  According to another characteristic of the invention, the device comprises, as adjustment means, at least one spring of the series of helical springs which is removably arranged in its bore, in order to allow, by its withdrawal, a reduction the total pressure force exerted by the series of coil springs.

  According to yet another feature of the invention, the device comprises rolling balls which are interposed between the drive member and the drive member, and which are in simultaneous contact with the drive and drive members. According to another embodiment of the invention, the adjustment and pressure functions are not dissociated and are, for example, filled by a single element, such as, for example, a pressure screw, integral with the plate of by being engaged in a bore of the latter and rubbing on the drive member which can then be embodied in the form of a drive shaft engaged in the drive plate or in the form of a plateau motor substantially parallel to the drive plate, the elasticity necessary for the proper operation of the friction drive being provided by at least one of the elements, such as screw, or motor member or member or against / drive member.

  Various other features of the invention emerge from the description below, made with reference to the accompanying drawings which illustrate various forms, non-limiting, embodiment of a drive device according to the invention.

  Fig. 1 is an axial section illustrating a first embodiment of a drive device according to the invention.

  Figs. 2 to 5 illustrate, in axial section, other embodiments of the driving device 1, as illustrated in FIG. 1.

  Fig. 6 illustrates, in schematic axial section, a drive device according to the invention, more particularly adapted for driving in rotation of suspended mobiles.

  Fig. 7 is a partial section along the line VII-VII of FIG. 6.

  Fig. 8 is a section similar to FIG. 7, showing an alternative embodiment of the device according to FIG. 6.

  Fig. 9 illustrates another embodiment of a device according to the invention.

  Fig. 10 is a top view along line X-X of FIG. 9.

  Figs. 11 to 13 and 13B illustrate other embodiments of the device according to the invention.

  The driving device according to the invention, as illustrated in FIG. 1 and designated as a whole by the reference 1, is intended to allow the driving in rotation of a mobile, not shown, which will be placed, fixed on a drive member formed, according to the illustrated example, by a tray 2 of the device or still suspended from this drive plate according to the embodiment of the device 1.

  Thus, the drive device 1 comprises a carrier frame 3, with respect to which the drive member or plate 2 is rotatable along an axis A. According to the illustrated example, the rotation guide of the drive plate 2 relative to the frame 3 is formed by means of balls 4 flowing in two facing grooves 5, arranged respectively in the drive plate 2 and the chassis 3. It should be noted that any other known means of the Those skilled in the art can be used to provide a guide in rotation of the drive plate 2 relative to the frame 3, such means not specifically falling within the scope of the present invention.

  In order to be able to ensure the rotation of the plate 2, the device 1 further comprises an electric geared motor 6 which is integral with the frame 3 and which is associated with friction coupling means 7. According to the illustrated example, the geared motor 6 comprises a drive shaft 8 which is associated with a drive member 9 formed here by a motor plate 9, movable in rotation, with axis 0 relative to the frame 3 and rotated by the drive shaft 8, via a pinion 10 integral with the drive shaft 8 and a toothing, arranged at the periphery of the motor plate 9.

  It should be noted that, according to the invention, the driving of the motor plate 9 by the shaft 8 could be carried out in a completely different way, such as, for example, by means of a belt or, still, of a chain. However, for reasons of space and cost, it will be preferred a gear drive and peripheral teeth, as shown in FIG. 1.

  According to the illustrated example, the friction coupling means 7 comprise, pressure means 11 working in compression and being interposed between the motor plate 9 and a drive against-member formed, according to the illustrated example, by a counter-plate 12, integral in rotation with the drive plate 2.

  Still according to the illustrated example, the counter plate 12 is located opposite the drive plate 2 relative to the motor plate 9 being disposed in a bore 13 of the frame 3, with the interposition of guide balls 14. Against the plate 12 is further secured to the drive plate 2 by a screw 15.

  Given the previously described configuration, the pressure means 11 then come to press the motor plate 9 against the drive plate 2 which will then be frictionally driven when the geared motor 6 is started up.

  According to the invention, the pressure means 11 may be made in different ways and, according to the illustrated example, the pressure means 11 comprise a spring washer, Belleville washer type 16, interposed between the counter-plate 12 and the tray engine 9.

  It is therefore the axial directional pressure A, exerted by the Belleville washer 16, which will determine the friction forces between the motor plate 9 and the drive plate 2 and thus the maximum driving torque of the motor plate 9.

  In order to be able to adjust this torque to take into account the power of the geared motor 6 or even the load to take away, as well as the possible fatigue that the washer Belleville is likely to know in the time, the friction drive means 7 comprise, according to another essential feature of the invention, means 20 for adjusting the friction force applied by the pressure means 11 and, here, the Belleville washer 16.

  According to the illustrated example, the adjustment means 20 comprise at least one pressure screw 21, engaged in a bore 22 of the drive plate 2, so as to be accessible from above the latter and to bear , directly or via one or more parts, on the motor plate 9, to allow a distance adjustment, between said motor plate 9 and the contreplateau 12, to compress more or less the Belleville washer 16. Thus, by screwing or unscrewing the pressure screw 21, it is possible to modify the driving torque of the plate 2.

  In addition, it should be noted that the accessibility of the pressure screw 21 by the top of the plate 2 makes the adjustment operation of the drive torque particularly easy.

  Fig. 2, illustrates an alternative embodiment of the drive device 1, as illustrated in FIG. According to this variant embodiment, the adjustment means comprise a counter-plate 31, integral in rotation with the drive plate 2 and provided with an inclined peripheral ramp. The adjustment means comprise, in addition, a 33, disposed in a radial bore 34 of the drive plate 2, so as to be accessible from the side of said plate 2. The support screw 33 then has a bearing end which acts on the ramp 32, more or less distance away against the plate 31 of the drive plate 2. However, insofar as the motor plate 9 is supported on the plate against 31, it is possible to adjust the distance between said 9 and the counter platter 12, so that the action on the pressure screw 33 to adjust the pressure exerted by the Belleville washer 7.

  Furthermore, it should be noted that the position of the pressure screw 33, arranged in the radial bore allowing its access from the side of the drive plate 2, allows, very advantageously, an adjustment of the pressure exerted by the Belleville washer 16 and therefore the driving torque, even when a mobile is fixed on the upper part of the drive plate 2.

  It should be noted that, according to the illustrated example, the screw 33 is, in addition, completed by a pressure screw 38 disposed in a bore 39 of the drive plate 2, so as to be accessible from above the latter .

  According to the examples, illustrated in FIG. 1 and 2 and described above, the pressure means comprise a Belleville washer 16. However, in accordance with the invention, the pressure means could also include a stack of Belleville washers - or, again, comprise another type of washer. spring elements working in axial compression.

  Thus, according to another embodiment of a drive device according to the invention, more particularly illustrated in FIG. 3, the pressure means 11 comprise a series of helical springs 40 each arranged in a housing 41, arranged in the counter-plate 12. Each housing 41 then has an axis A "parallel to the axis A of rotation and located at a distance of the axis A. In addition, each housing 41 opens opposite the motor plate 9, so that the spring 40, which is arranged, rubs directly on the plate 9. Preferably, the coil springs 40 then have a rectified end which is placed in contact with the motor plate 9.

  According to the invention, in the case of an implementation of a series of helical springs, the means for adjusting the pressure exerted by the latter can be made in different ways.

  Thus, it may be envisaged to implement the adjustment means 20 mentioned above in relation to FIGS. 2 and 3, for adjusting the distance between the motor plate 9 and the drive plate 2 or the counter plate 12 in which the springs are arranged.

  According to another alternative embodiment, the pressure control means 20 comprise at least one helical spring 40 which is removably disposed in its corresponding bore 41. Thus, it is possible, by removing one or more helical springs 40, ensure a modulation of the friction forces and the pressure exerted by the latter on the engine plate 9.

  According to the embodiment more particularly illustrated in FIG. 3, the pressure adjustment means 20 are constituted by support screws 45, arranged at the bottom of the bores 41 and pressing, on the springs 40, so as to adjust their compression and therefore the effort they exert on the engine plate 9.

  Fig. 4 illustrates another embodiment of a drive device implementing two series of springs 40, a first 46 is disposed in bores 41 formed in the contreplateau 12, as described above, while the second series 47 is arranged in bores 48 arranged in the drive plate 2, so as to be located at a distance from the axis of rotation A by having an axis A "parallel to the axis A. Preferably, the two series of springs 46 , 47 are arranged to exert a different pressure on the motor plate 9. This pressure difference can then be ensured by means of the bearing screws 49 arranged in the bores 41 for receiving the coil springs on the counter plate 12 or again by a combination of two series 46, 47 having a different number of springs 40 or springs 40 of distinct stiffness.

  In the examples described above, the springs rub directly on the motor member formed by the motor plate 9. However, according to a variant of the invention, not shown, the springs each bear on a ball and the motor plate includes bowls into which the balls come to engage.

  This feature of the invention provides a stall frank when exceeding the limit torque drive.

  Fig. 5 illustrates a simplified embodiment of a device 1 for driving a mobile according to the invention. According to this other embodiment, the friction coupling device 7 is directly integrated into the geared motor and the pressure means used 11 comprise a series of helical springs 50 arranged in bores arranged in the drive plate 2 which found, according to the illustrated example, secured to an axis 52 to which the mobile to be driven will be coupled. The springs 50 are in direct abutment on the engine plate 9.

  Thus, this embodiment differs from the examples described above in relation to FIGS. 1 to 4, only in that the coupling with the driven mobile is not performed at the drive plate 2, but at the axis 52 outside the latter. On the other hand, it should be noted that this training device operates on the same principle as those described above. Furthermore, according to this example, the adjustment of the pressure results from the removable nature of certain springs 50. However, the adjustment of the pressure could be carried out by means of a support screw arranged in one or more of the receiving bores 51. springs 50.

  In the examples described above, in relation with FIGS. 1 to 5, the driving member 2 and the driving member 9 are, each, constituted respectively by a drive plate and a motor plate, and the spring elements work in compression along an axis parallel to the axis A of rotation of the driving member 2 and the driving member 9.

  However, such an embodiment of a drive device according to the invention is not strictly necessary. Thus, according to another embodiment, more particularly illustrated in FIGS. 6 to 8, the spring elements 60 work in compression along an axis A 'perpendicular to the axis A of rotation of the drive member 9 and the drive member 2.

  The drive device, particularly illustrated in FIG. 6, allows the rotational drive of a suspended mobile.

  According to this embodiment, the drive member 9 is engaged in a central bore of the drive member 2. Thus, the drive member 9 and the drive member 2 have facing coaxial surfaces and the springs 60 are arranged in bores at level 61 of the drive member, so as to bear against a substantially cylindrical bearing surface 62 of the drive member 9. According to the invention, the cylindrical term defining the cylindrical bearing surface of the motor member 9, must be understood in the broad sense. Thus, this scope 62 may have one or more facets, as shown in FIG. 7, for which the scope 62 has an octagonal transverse cross section. The bearing 62 may also have a cylindrical shape of revolution, as shown in FIG. 8. According to the illustrated example, the device comprises, as adjustment means, a screw disposed in the bottom of each bore 61, so as to allow adjustment of the compressive stress of each spring element constituted, according to the for example, by a coil spring.

  According to the illustrated example, the driving member 2 is equipped with eight springs arranged in eight bores 61. However, within the meaning of the invention, the driving element 2 could, of course, comprise only one single spring 60.

  According to the examples described above, the adjustable pressure means comprise, as pressure means, one or more spring elements working in compression. However, it is also possible, according to the invention, to implement one or more spring elements working in tension, as illustrated in FIGS. 9 and 10.

  Thus, according to this example, the geared motor 6 comprises, as the driving member 9, a drive shaft 65 engaged in an axial bore of the drive plate 2.

  The friction coupling means then comprise a pivoting arm 66, integral with the drive plate being connected to the drive plate, at one of its ends, on the one hand, by a pivot 67 and, d on the other hand, by a tension spring whose one end is connected to the shaft 66 and the other to an eccentric 69 for adjusting the tension exerted by the spring 68 on the arm 66. Thus, it is possible to adjust, by the eccentric 69, the friction force of the arm 66 on the shaft 65 and thus the clutch torque together.

  It should be noted that, according to the invention, the adjustable pressure means do not necessarily implement spring pressure means.

  Thus, according to another embodiment illustrated in FIG. 11, the pressure means comprise a screw 70, engaged in a radial bore 71 of the drive plate 2, to bear on the drive shaft 9 which, by its deformation capacity, provides the necessary elasticity. Thus, it is possible to modulate, on the one hand, the friction force of the screw 70 against the drive shaft 9 and, on the other hand, the friction of the shaft 9 in the bore of the plate 2 and therefore the clutch release torque of the friction drive system, thus created.

  Figs. 12 and 13 illustrate alternative embodiments according to which the adjustable pressure means comprise a ball pushed by means of a screw or a spring to bear directly on the driving shaft 9.

  According to the example illustrated in FIG. 12, the adjustable pressure means comprise two balls 73, 74, a first 73 comes into direct contact against the drive shaft 9, 65, while a second 74 bears on the first ball to transmit the pressure exerted by a screw 75.

  In figs. 13 and 13A are implemented, as adjustable pressure means, on the one hand, a ball 76 in direct abutment against the drive shaft 9 and pressed against the latter by means of a screw 77 and, on the other hand, a ball 78 in direct abutment against the drive shaft 65 and pressed against the latter by a ball 79 biased by pressure by a spring 80 whose compression is adjusted by means of a screw 81. It should be noted that, according to this example and according to the inclination of the axis passing through the center of the two balls, the configuration, here at right angle, adopted allows a reduction of the force exerted by the spring 80 at the screw 78 directly to the contact of the motor shaft 65. The elasticity of the motor shaft is then used to the extent that the two ends of the shaft are supported, while the central region of the shaft, where the ball acts support, is located in a recess allowing an arching of the tree. It should be noted that the pressure or the radial force is applied to the shaft 65, either by the ball 78 (FIG 13), or by the ball 76 (FIG.

13A).

Claims (21)

  1 - Device for driving a mobile in rotation, comprising: a carrier frame (3), a drive member (2), movable in rotation, with axis A relative to the frame (3) and provided with means for adapting or receiving the mobile, ^ an electric geared motor (6) which is integral with the frame (3) and which comprises a drive member (9), ^ and friction coupling means (7). ) of the drive member (9) to the drive member (2), characterized in that the friction coupling means (7) comprise adjustable pressure means (11) interposed between the drive member (9) and the drive member (2) and / or, optionally, a drive member (12) rotatably connected to the drive member (2), so as to apply at least one adjustable friction force to the motor unit.   2 - Device according to claim 1, characterized in that the pressure means (11) comprise at least one spring element (16, 40, 50) which operates in axial compression axis parallel to the axis A of rotation of the driving member.   3 - Device according to claim 2, characterized in that the pressure means comprise adjusting means (20) adapted to allow a change in the distance between the drive member (9) and the drive member (2) and / or the drive counter-member (12).   4 - Device according to claim 2, characterized in that the spring element (16, 40) presses the drive member (9) against the drive member (2).   - Device according to claim 4, characterized in that the spring element (16, 40) rubs directly on the motor member (9).   6 - Device according to claim 4 or 5, characterized in that: the motor member (9) rubs directly on the drive member (2) and / or a member (31) integral with the drive plate ( 2), ^ and the spring element (16, 40) is interposed between the drive member (9) and the drive member (12) located opposite the driving plate (2) relative to to the engine plate (9).   7 - Device according to claim 6, characterized in that the adjustment means (20) of the pressure are interposed between the drive member (2) and the motor member (9).   8 - Device according to claim 7, characterized in that the adjusting means (20) comprise at least one pressure screw (38) engaged in a bore (39) of the drive member (2), so as to can be accessible from above the drive member (2) and come to bear on the motor member (9).   9 - Device according to claim 7, characterized in that the adjusting means (20) comprise: a counter plate (31) integral in rotation with the drive member (2) and provided with an inclined ramp ( 32), ^ and at least one pressure screw (33) engaged in a radial bore (34) of the drive member (2), so as to be accessible from the side of the drive member (2). ) and resting on the inclined ramp (32) to modify the distance between the counter-plate (31) and the drive-against member (12) - Device according to one of claims 2 to 9, characterized in that the pressure means (11) comprise at least one spring element, of the Belleville washer type (16), whose axis coincides with the axis A of rotation of the drive member (2).   11 - Device according to one of claims 2 to 9, characterized in that the pressure means (11) comprise a series of helical springs (40, 50) which are each arranged in a housing A "axis parallel to the axis A and located at a distance from the axis A. 12 - Device according to claim 11, characterized in that each helical spring (40, 50) has, at least, a ground flat end in contact with the drive member (9).   13 - Device according to claim 11 or 12, characterized in that at least one series (47) of springs is disposed in bores (48) of the drive member (2).   14 - Device according to one of claims 11 to 13, characterized in that at least one series (46) of springs is disposed in bores (40) against the drive member (12).   - Device according to one of claims 1 to 14, characterized in that the adjusting means (20) comprise at least one pressure screw (45) disposed in the bottom of a bore (41) receiving a coil spring ( 40), so as to allow an adjustment of its compression.   16 - Device according to one of claims 11 to 14, characterized in that it comprises, as adjustment means (20), at least one spring (40) of the series of coil springs which is arranged, removable, in its bore (41), so as to allow, by its withdrawal, a decrease in the total pressure force exerted by the series of helical springs (40).   17 - Device according to claim 1, characterized in that it comprises: a counter-drive member (12) integral in rotation with axis A of the drive plate (2) and located opposite the driving member (2) relative to the driving member (9), ^ at least one spring element (47) working in compression, axis A "parallel to the axis A, interposed between the body the drive (2) and the driving member (9), and at least one compression spring member, of axis A "parallel to the axis A interposed between the drive member (12) and the motor member (9).   18 - Device according to claim 17, characterized in that the value of the friction force, exerted on the drive member (9) by the spring element or elements, interposed between the drive against-member (12) and the motor member (9), is different from the value of the force exerted on the drive member (9) by the spring element or elements interposed between the drive member (12) and the motor member (9).   19 - Device according to claim 1, characterized in that the drive member and the drive member have facing coaxial surfaces and in that the pressure means (11) comprise at least one spring element which works in compression axis perpendicular to the axis A of rotation of the drive member.   20 - Device according to claim 19, characterized in that the drive member has a central bore of axis A in which is placed the drive member and comprises at least one radial bore in which is disposed a spring element which a end bears against a substantially cylindrical bearing provided by the motor member.   21 - Device according to claim 20, characterized in that the scope of the motor member comprises at least one substantially flat facet.   22 - Device according to claim 20 or 21, characterized in that it comprises, as adjustment means, at least one screw disposed in a radial bore, so as to exert a compression stress of adjustable value on the element spring.   23 - Device according to one of claims 20 to 22, characterized in that the spring element is formed by a helical spring.   24 - Device according to one of claims 1 to 23, characterized in that it comprises rolling balls which are interposed between the drive member and the drive member and which are in simultaneous contact with the motor and drive.   25 - Device according to claim 1, characterized in that the drive member is constituted by a drive shaft (9) disposed in a bore of the drive member (2) and in that the pressure means (70) , 76, 78) exert their radial force on the motor shaft (9).