FR2745348A3 - Engagement device between two shafts, especially on drive train - Google Patents

Abstract

The device is fitted especially between a driving (13) and a driven (30) shaft. A helical spring (21) is coiled around two roughly similar, opposing cylindrical bushes (11,28). Each bush is connected to a shaft, and is matched to the size of the spring in order to allow torque transmission between the shafts, due to friction between the spring and the bush.The device has a tubular element (14) with a curved outer surface, and which has two internal notches set against the direction of coiling, in order to fix an end part of the spring. A sleeve (24) is arranged around the tubular element, and has an internal axial groove, in order to accept the other end of the spring. The sleeve has curved inner surfaces which complement the tubular element, which combine with them under the effect of an axial force, in order to guide the device between engaged and disengaged positions

Description

The present invention relates to a clutch device between shafts

  mechanical and, in particular, a friction type clutch device, having a cylindrical helical spring wound around two cylindrical elements axially opposite one another, made in one piece with two aligned mechanical shafts , one motor and the other driven, and adapted so as to transmit a torque between the two shafts, together with the possibility of declutching

  also during engine operation.

  Devices of the aforementioned type are already known.

  For example, American patents 1,968,155 and 3,493,088 describe friction type clutch devices, in which a cylindrical helical spring, wound around two cylindrical elements, has radial ends respectively attached to two rings which surround them . When the two rings are rotated relative to each other in a direction opposite to that of the winding of the spring, the inside diameter of this spring increases, causing mutual freedom between the two cylindrical bodies and therefore the connection interruption

  between the motor shaft and the driven shaft.

  When the two rings are not subjected to any action, the spring is rewound by adhering to the two cylindrical bodies and causing the friction transmission of a torque between the motor shaft and the driven shaft, when

  the motor shaft rotates in the winding direction of the spring.

  In the aforementioned embodiments, the rotation of the two rings with respect to each other takes place by means of transverse action. However, such mechanisms for rotating the rings are bulky and imprecise, in addition to the fact that they are subject to rapid wear. In another form of the clutch device, the rotation of the two rings with respect to each other, to which the spring is hooked, takes place by means of a third control ring provided with triangular radial fins which s '' are inserted and removed between reliefs on the first ring and teeth on the second ring, determining the unwinding and winding of the spring arranged around two cylindrical bodies made in one piece with the trees, and

  therefore the adhesion, more or less strong, to such cylinders.

  These clutch devices, although acting satisfactorily, have a rather

  complex and are therefore relatively expensive.

  The object of the present invention is to avoid the complexity of the known devices by producing a simplified and therefore more economical clutch device, while

offering the same results.

  More particularly, the clutch device between two mechanical shafts, among which a motor shaft and a driven shaft, by means of a cylindrical helical spring wound around two cylindrical sleeves, substantially identical and opposite one with respect to the other, each of them being made in one piece with one of the mechanical shafts and intended to transmit the torque from the motor shaft to the shaft driven by friction exerted on the sleeves, is characterized, according to the present invention, by the fact of comprising: - a tubular element enclosing the cylindrical helical spring, externally having cam surfaces and internally a couple of notches, each of them being adapted so as to engage against one end of the spring helical cylindrical, in the direction of winding of the spring, - a control ring, arranged around the tubular element and provided with an axial groove e interior serving to slide the other end of the spring and having within it cam surfaces adapted to those of the tubular element and intended to cooperate with the latter, under the action of an axial force, in order to determine the "clutch" condition and

"disengaging" of the device.

  The characteristics and advantages of the device according to the present invention will become apparent on

  reading the following detailed description of its form of

  preferred embodiment, compared with the accompanying drawings, in which: FIG. 1 illustrates an exploded perspective view of the device according to the present invention; FIG. 2A is a front view of the tubular element of the device according to the present invention; Figure 2B is a sectional view along line II-II of Figure 2A; FIG. 3A is a front view of the control ring of the device according to the present invention; Figure 3B is a sectional view along line III-III of Figure 3A; Figure 4 is a longitudinal sectional view of the device according to the present invention, during a first assembly phase; Figure 5 is a longitudinal sectional view of the device according to the present invention, during a second assembly phase; Figure 6 is a longitudinal sectional view of the device according to the present invention, in the "clutch" state; Figure 7 is a longitudinal sectional view of the device according to the present invention, in the state of "disengagement"; and Figure 8 is a top view of the fork

  for controlling the device according to the present invention.

  Referring to the figures, the latter illustrate a clutch device according to the present invention, generally designated by the number 10 and comprising the following elements: - a cylindrical sheath 11 produced integrally with a toothed wheel 12 wedged on a drive shaft 13 of a transmission (see in particular Figure 1); - A tubular element 14 having, on the outer surface, two axial trapezoidal flanges 15 and 16 having shoulders 17 and 18, substantially identical and diametrically opposite and, on the outer edges, two pairs of aligned notches, a small one 19, 19 'and a large 20, 20' (Figures 1 and 2A, 2B); - A cylindrical helical spring 21 whose radial ends 22 and 23 project outwards (see in particular Figure 1); - A cylindrical control ring 24 having, on the inner surface, two trapezoidal flanges 25 and 26 axial, substantially identical and diametrically opposite, the flange 25 being provided with an axial groove 27 of a length identical to the axial length of the cylindrical ring 24 (Figures 1, 3A, 3B); - A cylindrical sheath 28, made in one piece with the driven shaft 30 and substantially identical to the cylindrical sleeve 11, but turned in the opposite direction, the sheath 28 being provided with a shoulder 29 (see in particular Figure 1 ); a control fork 31 having legs 32 and 33, intended to press against the dorsal part of the control ring 24, causing, by a simple contact, the sliding of the ring 24 when the control fork 31 is driven in rotation around pivot 34, being actuated by a control lever (not shown)

  articulated at the end 35 of the fork 31 (Figure 8).

  FIG. 4 shows in particular the device according to the present invention partially assembled, the cylindrical sleeves 11 and 28 being opposite one with respect to the other and brought into contact with one another so as to have a coincident geometric surface S. Around such sleeves is wound the cylindrical helical spring 21, the inside diameter of which is slightly less than the outside diameter of the sleeves 11 and 28, so that, at rest, the spring 21, free from any constraint, adheres to the cylindrical sleeves 11 and 28, the spring 21 having a length equal to twice the length

  cylindrical sleeves 11 and 28.

  FIG. 5 shows in particular the device according to the present invention still partially assembled with the tubular element 14 disposed around the cylindrical helical spring 21 and delimited at the ends of the central body of the toothed wheel 12 and the shoulder 29 of the cylindrical sheath 28 The projecting radial ends 22 and 23 of the spring 21 are housed in the notch 19 or 19 ', respectively 20, 20', arranged on the outer edges of the tubular element 14, depending on whether the spring 21 is wound

to the left or to the right.

  Figure 6 shows in particular the clutch device 10 according to the present invention, completely assembled. In this configuration, the projecting radial end 23 of the cylindrical helical spring 21, housed in the notch 20 or 20 ′, is folded along the axis of the tubular element 14 so as to form a guide pivot, engages against the axial groove 27 of the trapezoidal rim 25 of the control ring 24, forcing the ring 24 to be placed around the tubular element 14, so that one of the sides of each axial trapezoidal rim 25 and 26 and the control ring 24 is respectively in partial contact with one of the sides of each axial trapezoidal flange 15 and 16 of the tubular element 14, the sides being intended to come into contact

  between them according to corresponding inclinations.

  When the control ring 24 is in the configuration illustrated in FIG. 6, the device 10 is in a "clutch" state. The cylindrical helical spring 21, being free of any constraint, adheres to the cylindrical sleeves 11 and 28 by causing the friction of the cylindrical sleeve 28 from a part of the cylindrical sleeve 11, when the motor shaft 13 rotates in the direction of winding of the cylindrical helical spring 21, the adhesion of the spring 21 around the sleeves 11 and 28 increasing as the

transmitted torque increases.

  When the control ring 24 is in the position illustrated in FIG. 7, the device 10 is in a "disengaging" state. This state is obtained by actuating the control fork 31 (FIG. 8) by means of the control lever. The legs 32 and 33 of the control fork 31 exert pressure on the dorsal part of the control ring 24, by determining the displacement along the axis of the tubular element 14. The displacement of the control ring 24 is of roto-translatory type, by virtue of the relative sliding of one of the flanks of each of the trapezoidal flanges 25 and 26 axial of the control ring 24, along axial inclined planes, each of which is formed by one of the flanks of each of the axial trapezoidal flanges 15 and 16 of the tubular element 14, the sides in contact with the flanges 15 and 16 of the tubular element 14 and of the trapezoidal flanges 25 and 26 of the control ring 24 having corresponding inclinations so to facilitate the

  reciprocal sliding. Under the effect of the rotational displacement

  translation of the control ring 24, the axial groove 27 of the ring 24, engaging against the protruding radial end 23 of the cylindrical helical spring 21, thus determines the rotation in the opposite direction of its winding, the other end radial 22 projecting from the spring being however anchored in the notch 19 or 19 'of the tubular element 14. Such rotation, taking place in the opposite direction of winding of the coil spring 21, determines one of its "unwinds" , that is to say an increase in its internal diameter, sufficient to eliminate the adhesion between the spring 21 and the cylindrical sleeves 11 and 28, the sleeve 28 being consequently free to rotate in the two directions of rotation jointly with the driven shaft 30 which is integral therewith, independently of the direction of rotation of the motor shaft 13. The stroke of the control ring 24 ends against the shoulders 17 and 18 of the axial trapezoidal flanges, respec 15 and 16, from

the tubular element 14.

  By acting on the control fork 31, when the action of the legs 32 and 33 of the fork 31 on the dorsal part of the control ring 24 is eliminated, the cylindrical helical spring 21 contracts in order to present the equilibrium configuration static and the radial end 23 protruding from the spring 21, by engaging, in the form of a guide pivot, in the axial groove 27 of the control ring 24 determines the automatic return of the ring 24 in the position " clutch ". The return stroke of the control ring 24 always takes the form of a roto-translatory movement, but in the opposite direction to that executed by the ring 24 during the phase of

"disengaging" of the device 10.

  This is why, by actuating the control fork 31 by means of a control lever, it is possible to control at will, also during operation, the declutching and the clutching between the motor shaft 13 and

the driven shaft 30.

  As can be noted from the description

  given above, the clutch device according to the present invention has a very simple structure owing to the fact that it consists of only two tubular elements, intended to cooperate with one another, with a view to causing the clutch and the disengaging. A higher ease and speed of assembly and disassembly is therefore obtained, which thus provides the device of the invention with an economic advantage, both from the point of view of construction and from the point of view of maintenance. Although the present invention has been described and illustrated only with respect to one of its preferred embodiments, it is obvious that all the possible variants and modifications can be made to those skilled in the art, without get out of the spirit of protection. In particular, the edges of the tubular element and those of the control ring, although they have been illustrated here in trapezoidal form, can have any other shape as long as they each have at least one surface.

inclined adapted.

Claims (9)

  1. Clutch device between two mechanical shafts, one of which comes from a motor and the other is a driven shaft, by means of a cylindrical helical spring wound around two cylindrical sleeves, substantially identical and opposite the one with respect to the other, each of them being made in one piece with one of said mechanical shafts and being intended to transmit the torque from the drive shaft to the driven shaft, by friction exerted on said sleeves, characterized by comprising: - a tubular element (14) enclosing the cylindrical helical spring (21), having cam surfaces on the outside and internally a pair of notches (19, 19 ', 20, 20'), each of them being adapted so as to engage against one end (22) of the cylindrical helical spring (21), in the winding direction of the spring, - a control ring (24), arranged around the tubular element (14) and provided with a internal axial groove (27) serving to slide the other end (23) of the spring and having therein cam surfaces adapted to those of the tubular element (14) and intended to cooperate with the latter, under the action of an axial force, to determine the state   "clutch" and "disengage" of the device.   2. Device according to claim 1, characterized in that the end (23) of the cylindrical helical spring (21), intended to be inserted in the axial groove (27) inside the control ring (24), protrudes and is folded parallel to the axis of the spring.   3. Device according to one of claims 1   and 2, characterized in that the inside diameter of the cylindrical helical spring (21) is slightly smaller than the outside diameter of the cylindrical sleeves (11, 28), so as to cause adhesion between said spring (21) and said sleeves (11, 28).   4. Device according to at least one of   previous claims, characterized in that the   external cam surfaces of the tubular element (14) form a trapezoidal flange, together with the lower base,   facing the control ring (24).   5. Device according to at least one of   previous claims, characterized in that the   outer cam surfaces of the tubular element (14) form a triangular rim, together with the top,   facing the control ring (24).   6. Device according to claim 1, characterized in that the cam surfaces of the control ring (24) form an inner rim of trapezoidal shape, together with the lower turned base towards the tubular element (14).   7. Device according to claim 1, characterized in that the cam surfaces of the control ring (24) form an inner rim of triangular shape, together with the vertex facing the tubular element (14).   8. Device according to claim 1, characterized in that the groove (27), formed in the control ring (24) to accommodate the cylindrical helical spring (21), extends over the entire axial length of the ring control (24), so as to allow the   free sliding of such a spring end.   9. Device according to claim 1, characterized in that the axial force necessary in order   actuating the clutch device is exerted by a fork (31) capable of performing a rectilinear5 or rotary movement.