BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention concerns torsional damper devices of the type used in the construction of a motor vehicle friction clutch, for example. 
     2. Description of Related Art 
     Torsional damper devices of the above kind usually include, between an input member and an output member rotatable relative to each other, two dampers which, in kinematic terms, come into action successively upon relative angular movement between the input member and the output member, namely, in the reverse order to that in which they come into action, a main damper and a pre-damper, each of these dampers including two guide washers which, disposed on respective opposite axial sides of a web, are rotatable relative to the web, circumferentially acting spring means disposed circumferentially between the guide washers and the web, and friction means which, operative between the guide washers and the web or parts constrained to rotate therewith, are acted on by axially acting spring means. 
     In the construction of a friction clutch the input member is for example a disc which carries friction linings at its periphery which are clamped between the pressure plate and the reaction plate of the clutch and the output member is for example a hub adapted to be constrained to rotate with the input shaft of a gearbox. 
     The function of the dampers is to filter out vibrations caused by the engine, when idling in the case of the pre-damper and in normal operation in the case of the main damper. 
     To satisfy particular operating conditions document FR-A-2 735 548, to which this patent application explicitly refers, proposes the provision of a third or intermediate damper which comes into action after the pre-damper and before the main damper. 
     SUMMARY OF THE INVENTION 
     An aim of the invention is to reduce the overall axial size of a torsional damper device including an intermediate damper of the above kind. 
     To be more precise, it consists in a torsional damper device of the kind briefly described hereinabove and which includes an intermediate damper, the torsional damper device being generally characterised in that the axially acting spring means of the intermediate damper are disposed radially between its circumferentially acting spring means and those of the pre-damper. 
     Accordingly, these axially acting spring means do not require any particular axial space to fit them, which advantageously has the benefit of reducing the overall axial size of the clutch. 
     The pre-damper and the intermediate damper both being on the same axial side of the web of the main damper, with first friction means operative on the other side of the web, forming part of the friction means of the main damper, and third friction means forming part of the friction means of the pre-damper and offset radially relative to the first friction means, in accordance with the invention the corresponding guide washer of the main damper preferably and advantageously has an annular portion between said first friction means and said third friction means which is offset axially towards the web of the main damper. 
     This advantageously forms a recess on the surface of the guide washer concerned of the main damper facilitating the operation at its location of any other member external to the torsional damper device, for example the control device usually associated with a clutch for engaging and disengaging the clutch. 
     This advantageously facilitates installing the torsional damper device in accordance with the invention in an increasingly congested environment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the invention will emerge from the following description given by way of example and with reference to the accompanying diagrammatic drawings, in which: 
     FIG. 1 is a view in axial section of a torsional damper device; and 
     FIG. 2 shows the detail II from FIG. 1 to a larger scale. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The figures show a torsional damper device  10  of the type described in the previously mentioned document FR-A-2 735 548. 
     Accordingly the torsional damper device  10  does not need to be described in complete detail here and, as and when required, the description of document FR-A-2 735 548 must be deemed to constitute an integral part of the present description. 
     The torsional damper device  10  includes three dampers A, B, C between an input member  11  and an output member  12  that are rotatable relative to each other. In kinematic terms the three dampers come into action successively upon relative angular movement between the input member  11  and the output member  12 , namely, and in the reverse order to that in which they come into action, a main damper A, an intermediate damper B and a pre-damper C. 
     Because the present example refers to a motor vehicle friction clutch, here the input member  11  is a disc  13  carrying annular friction linings  14  at its periphery and on both faces. 
     Here the output member  12  is a hub with internal splines  15 , a reduced height external portion  16  at one end and an external frustoconical bearing surface  17  at the other end, with splines  18  between them. 
     At the same end as the reduced height portion  16  the output member  12  has a transverse shoulder  19  continuous with the corresponding end edge of the splines  18 . 
     The dampers A, B, C each comprise respective pairs of guide washers  20 A- 21 A,  20 B- 21 B,  20 C- 21 C which, on respective opposite axial sides of a respective web  22 A,  22 B,  22 C, can rotate relative to the web within particular relative angular movement limits, respective circumferentially acting spring means  23 A,  23 B,  23 C disposed circumferentially between the guide washers  20 A- 21 A,  20 B- 21 B,  20 C- 21 C and the web  22 A,  22 B,  22 C and respective friction means  25 A,  25 B,  25 C operative between the guide washers  20 A- 21 A,  20 B- 21 B,  20 C- 21 C and the web  22 A,  22 B,  22 C or parts constrained to rotate therewith, are acted on by respective axially acting spring means  26 A,  26 B,  26 C. The spring members  26 A,  26 B,  26 C are preferably pre-stressed to reduce noise. 
     Here the guide washers  20 A,  21 A of the main damper A are fastened together and held a particular distance apart by spacers  27  at their periphery and by which the disc  13  carrying the friction linings  14  is fastened to the guide washer  20 A. 
     The spacers  27  pass with circumferential clearance through notches  28  provided for this purpose at the outside periphery of the web  22 A and co-operate with the ends of the notches  28  to define the limits of angular movement of the guide washers  20 A,  21 A relative to the web  22 A. 
     The web  22 A also has notches  29  at its inside periphery, through which it meshes with circumferential clearance with the splines  18  of the output member  12 . 
     The circumferentially acting spring means  23 A of the main damper A are partly located inside windows  30  in the guide washers  20 A,  21 A and partly inside facing windows  31  in the web  22 A. 
     Here each comprises two elongate coaxial coil springs substantially tangential to a circumference of the assembly. 
     Here the intermediate damper B and the pre-damper C are both on the same axial side of the web  22 A of the main damper A, between that web  22 A and the guide washer  20 A. 
     They are therefore both axially between the guide washers  20 A,  21 A of the main damper A. 
     The intermediate damper B, which surrounds the pre-damper C, is for the most part radially under, i.e. short of, the circumferentially acting spring means  23 A of the main damper A. 
     Its guide washer  21 B is formed by the web  22 A of the main damper A, to be more precise by the radially innermost portion of that web  22 A. 
     Its guide washer  20 B is a synthetic material confinement member disposed axially in contact with the guide washer  20 A of the main damper A. 
     The guide washer  20 B, which is the guide washer of the intermediate damper B at the greater axial distance from the web  22 A of the main damper A, has axial tenons  33  constraining it to rotate with the web  22 A, the tenons  33  engaging with notches  34  provided for this purpose in the edges of the windows  31  in the web  22 A. 
     The tenons  33  advantageously pass completely through the web  22 A, are shaped to form elastically deformable hooks  35  beyond the web  22 A and are adapted to clip onto the web to form a sub-assembly with it. 
     As this sub-assembly is not in itself relevant to the present invention it will not be described in more detail here. 
     At its inside periphery the web  22 B has notches  36  which mesh with circumferential clearance with the splines  18  on the output member  12 , but the clearance here is less than that of the web  22 A of the main damper A. 
     The circumferentially acting spring means  23 B of the intermediate damper B are engaged partly in recesses  37  in the guide washer  20 B and in windows  38  in the guide washer  21 B and partly in facing windows  39  in the web  22 B. 
     Here each comprises two elongate coaxial coil springs substantially tangential to a circumference of the assembly. 
     Here the limits of relative angular movement between the guide washers  20 B,  21 B of the intermediate damper B and the web  22 B thereof are defined by the circumferential ends of the notches  29  in the web  22 A of the main damper A abutting on the splines  18  of the output member  12 . 
     Here one of the guide washers  20 C,  21 C of the pre-damper C is formed by the web  22 B of the intermediate damper B, to be more precise by the radially innermost portion of that web  22 B. 
     Here it is the guide washer  21 C at the shorter axial distance from the web  22 A of the main damper A. 
     For constraining them to rotate together one of the guide washers  20 C,  21 C (here the guide washer  21 C) has axial lugs  40  circumferentially spaced from the circumferentially acting spring means  23 B of the intermediate damper B and radially beyond the web  22 C. These lugs engage with notches  41  on the other guide washer  20 C,  21 C (here the guide washer  20 C). 
     Here the axial lugs  40  on the guide washer  21 C extend towards the guide washer  20 A of the main damper A and the notches  41  in the guide washer  20 C are at its outside periphery. 
     Here the web  22 C of the pre-damper C is constrained to rotate with the output member  12 , its inside periphery being engaged with and crimped to a reduced height portion of the splines  18  of the output member  12 . 
     The circumferentially acting spring members  23 C of the pre-damper C are partly engaged in windows  43  in the guide washers  20 C,  21 C and partly in facing windows  44  in the web  22 C. 
     Here each comprises an elongate coil spring substantially tangential to a circumference of the assembly. 
     Here the limits of relative angular movement between the guide washers  20 C,  21 C of the pre-damper C and its web  22 C are defined by circumferential ends of the notches  36  in the web  22 B of the intermediate damper B abutting against the splines  18  of the output member  12 . 
     The friction means  25 A of the main damper A include, in addition to the guide washer  20 B of the intermediate damper B, a friction washer  45  on the opposite side of the web  22 A to the guide washer  20 B and in contact with the web  22 A. 
     The associated axially acting spring means  26 A are here in the form of a Belleville washer that bears on the guide washer  21 A. 
     Here the friction washer  45  is substantially level with the guide washer  20 B and therefore at a distance from the output member  12 . 
     Here the friction washer  45  has axial tenons  46  which are offset radially away from the output member  12  and constrain it to rotate with the guide washer  21 A, the tenons  46  engaging with openings  48  provided for this purpose in the guide washer  21 A. 
     The tenons  46  advantageously pass completely through the guide washer  21 A, are shaped as elastically deformable hooks  49  beyond the guide washer  21 A and are adapted to clip onto the guide washer to form a sub-assembly with it. 
     As this sub-assembly is not in itself relevant to the present invention it will not be described in more detail here. 
     The tenons  46  are also used to centre the Belleville washer constituting the axially acting spring means  26 A. 
     Here the friction means  25 C of the pre-damper C include, on the one hand, a bearing  50  operative between the output member  12  and the guide washer  20 A of the main damper A, to centre the guide washer  20 A, and which has a frustoconical bearing surface  51  through which it bears on the frustoconical bearing surface  17  of the output member  12  and, on the other hand, a friction washer  52  at the other end of the output member  12  which bears on the transverse shoulder  19  of the output member  12 , possibly through an intermediate washer, not shown. 
     The friction washer  52  has axial tenons  53  along its inside periphery constraining it to rotate with the guide washer  21 A of the main damper A, the tenons  53  engaging with notches  54  provided for this purpose at the inside periphery of the guide washer  21 A. 
     Similarly, the bearing  50  is constrained to rotate with the guide washer  20 C of the pre-damper C by tenons that cannot be seen in the figures. 
     Here the associated axially acting spring means  26 C are formed by a Belleville washer which is centred by the tenons  53  with which it is engaged via notches  55 . 
     In accordance with the invention the axially acting spring means  26 B of the intermediate damper B are disposed radially between the circumferentially acting spring members  23 B of the intermediate damper B and those  23 C of the pre-damper C. 
     Here the guide washers  20 C,  21 C of the pre-damper C are mobile relative to each other in the axial direction and the axially acting spring means  26 B of the intermediate damper B are disposed axially between them. 
     The axially acting spring means  26 B therefore urge the guide washers  20 C,  21 C of the pre-damper C axially away from each other. 
     The friction means  25 B of the intermediate damper B include a first friction washer  57  disposed axially between its web  22 B and one of the guide washers  20 B,  21 B, here the guide washer  21 B formed by the web  22 A of the main damper A, and a second friction washer  58  disposed axially between the guide washer  20 C of the pre-damper C at the greater distance from the web  22 A of the main damper A and the guide washer  20 A of the main damper A at the shorter distance from the guide washer  20 C. 
     Here the second friction washer  58  is in one piece with the bearing  50  and includes windows  59  in which the circumferentially acting spring members  23 C are axially engaged, which has the benefit of reducing the overall axial size of the assembly. 
     Similarly, the first friction washer  57  includes windows  60  in which the circumferentially acting spring members  23 C are axially engaged, which has the benefit of reducing the overall axial size of the assembly. 
     Here the axially acting spring means  26 B of the intermediate damper B are disposed radially between the web  22 C of the pre-damper C and the circumferentially acting spring members  23 B of the intermediate damper B. 
     One of the guide washers  20 C,  21 C of the pre-damper C advantageously has an annular portion  61  offset axially towards the other one and the axially acting spring means  26 B of the intermediate damper B are advantageously level with this offset annular portion  61 . 
     Here the guide washer  20 C,  21 C including the offset annular portion  61  is the guide washer  20 C, i.e. that at the greater distance from the web  22 A of the main damper A. 
     The offset annular portion  61  is advantageously operative at the outside periphery of the guide washer  20 C and it is therefore this annular portion that has the notches  41  which engage with the axial lugs  40  of the guide washer  21 C. 
     By virtue of its being offset, the annular portion  61  of the guide washer  20 C advantageously reduces the length of the axial lugs  40  of the guide washer  21 C. 
     Here the axially acting spring means  26 B of the intermediate damper B are formed by a Belleville washer which is centred on the axial lugs  40  of the guide washer  21 C and which includes notches  62  constraining it to rotate with the axial lugs  40 . 
     Consequently there are operative on the other side of the web  22 A of the main damper A first friction means that form part of the friction means  25 A of the main damper A and which here comprise the friction washer  45  and third friction means which form part of the friction means  25 C of the pre-damper C and which are offset radially relative to the first friction means, here the third friction means comprising the friction washer  52 . 
     In accordance with the invention, the corresponding guide washer  21 A of the main damper A has an annular portion  63  offset axially towards the web  22 A of the main damper A between the first friction means consisting of the friction washer  45  and the third friction means consisting of the friction washer  52 . 
     The stiffness of the circumferentially acting spring members  23 C of the pre-damper C is less than that of the circumferentially acting spring members  23 B of the intermediate damper B which is in turn less than that of the circumferentially acting spring members  23 A of the main damper A. 
     At the beginning of their intervention the members  23 B advantageously apply a lower torque than that applied by the members  23 C at the end of their intervention. Similarly, at the beginning of their intervention the members  23 A apply a torque which is lower than that applied by the members  23 B at the end of their intervention. 
     The stiffness of the axially acting spring means  26 C of the pre-damper C is lower than that of the axially acting spring means  26 B of the intermediate damper B which is in turn less than that of the axially acting spring means  26 A of the main damper A. 
     When the input member  11  and the output member  12  rotate relative to each other in operation only the circumferentially acting spring members  23 C of the pre-damper C are initially compressed. 
     At this time only the friction means  25 C of the pre-damper C are operative. 
     The circumferentially acting spring members  23 B of the intermediate damper B and the members  23 A of the main damper A constrain the guide washers  20 C,  21 C of the pre-damper C to rotate with the guide washers  20 A,  21 A of the damper A with which the friction washer  52  constituting the friction means  25 C is constrained to rotate, and likewise the bearing  50  through the intermediary of the guide washer  20 C of the pre-damper C. 
     The circumferentially acting spring members  23 B of the intermediate damper B are then compressed but the circumferentially acting spring members  23 C of the pre-damper C remain compressed. 
     At the same time the friction means  25 B of the intermediate damper B add their effects to those of the friction means  25 C of the pre-damper C. 
     The guide washers  20 B,  21 B of the intermediate damper B then turn relative to the guide washers  20 A,  21 A and to the web  22 A of the main damper A and the friction washers  57 ,  58  constituting the friction means  25  are operative between them and the latter. 
     Finally, the circumferentially acting spring members  23 A of the main damper A are compressed but the circumferentially acting spring members  23 B of the intermediate damper B and those  23 C of the pre-damper C remain compressed. 
     At the same time, the friction means  25 A of the main damper A come into action, adding their effects to those of the friction means  25 C of the pre-damper C, but only some of the friction means  25 B of the intermediate damper B, namely the friction washer  58 , continue to be operative. 
     The circumferentially acting spring members  23 C of the pre-damper C and those  23 B of the intermediate damper B then constrain the output member  12  to rotate with the guide washers  20 C,  21 C,  20 B,  21 B and therefore the web  22 A, only the guide washers  20 A,  21 A of the main damper A of the input member  11  then moving relative to the previously assembly. 
     Consequently, on relative angular movement between the input member  11  and the output member  12 , the pre-damper C directly upstream of the output member  12  is the first to come into action, the intermediate damper B is the second to come into action and the main damper A, which in kinematic terms is driven directly by the input member  11 , is the third and last to come into action. 
     It follows from the aforegoing description that the three dampers A, B, C are disposed in series. 
     If required their circumferentially acting spring members  23 A,  23 B,  23 C can be pre-stressed in their respective housings (windows  30 ,  38 ,  43  or recesses  37 ). 
     To prevent discontinuous operation the final torque of the pre-damper C can be greater than the pre-stressing of the circumferentially acting spring member  23 B of the intermediate damper B and the final torque of the intermediate damper B can be greater than the pre-stressing of the circumferentially acting spring members  23 A of the main damper A. 
     The offset annular portion  63  of the guide washer  21 A of the main damper A of the torsional damper device  10  in accordance with the invention, which is whichever of the guide washers  20 A,  21 A is at the greater distance from the input member  11 , includes a recess  64  which can receive the actuator device  65  for engaging or disengaging the clutch concerned, as shown diagrammatically in chain-dotted outline in FIG.  1 . 
     As shown diagrammatically in FIG. 1, the actuator device  65  comprises the fingers of a diaphragm, for example. 
     As already indicated, the hooks  35  and  49  enable the assembly of sub-assemblies. 
     The hooks  35 ,  49  are advantageously in one piece with the corresponding tenons  33 ,  46  and are preferably narrower than the tenons in the circumferential direction so as not to contribute to the transmission of torque, which reduces the stresses on them. 
     If required, the friction washer  57  can have male teeth on its inside periphery meshing with the splines  18  on the output member  12 , as described in document EP-A-0 732 525, to which reference may be had for more information, in particular with regard to the width of the windows  60  that the friction washer  57  includes. 
     Rotational coupling with the facility for axial movement of the guide washers  20 C,  21 C, and therefore friction, are obtained by virtue of the axial lugs  40  on the guide washer  21 C and the notches  41  on the guide washer  20 C. 
     The invention is not limited to the embodiment described and shown but encompasses any variant execution within the scope of the claims. 
     For example the axially acting spring means employed can consist at least in part in a corrugated washer. 
     Also, all the embodiments disclosed in document FR-A-2 735 548 can be envisaged.
A torsion damper for a motor vehicle clutch comprising, between an entrance component ( 11) and an exit component ( 12), a pre-damper (C), an intermediate damper (B) and a main damper (A). The axially operating elastic means ( 26 B) included in the intermediate damper (B) are radially arranged between the elastic members with said intermediate damper (B) circumferentially operating elastic members ( 23 B) and those of pre-damper (C).