Friction unit and a method of making it, and a torsion damper including such a friction unit

A torsion damper, especially for a motor vehicle friction clutch, includes a friction unit, or unitary friction assembly, that comprises a guide ring, at least one drive ring, and axially acting resilient members in biassing relationship on the drive ring. The drive ring and these resilient members are mounted in a cavity which is bounded by the guide ring and by a closure ring which is secured to the guide ring. The closure ring is formed at its inner periphery with at least two axial stop lugs for preventing rotation. The stop lug penetrates into an associated aperture which is formed in the guide ring.

FIELD OF THE INVENTION 
The present invention relates to a unitary friction assembly (or friction 
unit) for a torsion damper, and in particular for a torsion damper of or 
comprising a friction clutch for a motor vehicle, the torsion damper being 
of the kind comprising a guide ring for receiving circumferentially acting 
resilient means, at least one drive ring adapted for engagement with a 
damper plate of the damper, and axially acting resilient means in biassing 
relationship with the drive ring. 
The invention is also concerned with a method of fitting such a friction 
unit, and a torsion damper which includes such a friction unit or unitary 
assembly. 
BACKGROUND OF THE INVENTION 
Arrangements as described above are further described for example in U.S. 
Pat. No. 4,222,475 and the corresponding French published patent 
application No. FR 2 370 902A. In those documents, the friction unit is 
mounted axially between the damper plate and the guide ring of the torsion 
damper. The assembly includes leaf spring elements which are part of the 
axially acting resilient means, such that, before final assembly on to the 
other components of the torsion damper, the leaf spring elements run the 
risk of being damaged, especially during the various handling and 
transport operations involved, because they are exposed. In addition, 
these leaf spring elements are sensitive to the effects of circumferential 
forces. In addition, problems of control and optimisation of the elastic 
load exerted by the leaf spring elements are found to arise. 
In order to overcome these various drawbacks, it may be thought that 
recourse could be had to the arrangement described in U.S. Pat. No. 
4,573,562, in which the resilient means are mounted within a cavity which 
is delimited by the guide ring and by a closure ring which is secured to 
the guide ring. A thrust ring is interposed between the axially acting 
resilient means and the drive ring. This thrust ring has at its inner 
periphery axially oriented portions such that it is not of simple form. In 
addition, the friction unit is not as rigid as is desirable at its inner 
periphery. 
DISCUSSION OF THE INVENTION 
An object of the present invention is to overcome the above mentioned 
drawbacks by providing, in a simple and inexpensive manner, a novel 
friction unit which is of increased stiffness or rigidity, in which the 
thrust ring is of simple form, with a guide ring and protected axially 
acting resilient means. 
According to the invention in a first aspect, a unitary friction 
sub-assembly for a torsion damper, in particular for a motor vehicle 
friction clutch, of the kind comprising a guide ring for receiving 
circumferentially acting resilient members, and at least one drive ring 
adapted to make contact with a damper plate, the guide ring being acted on 
by axially acting resilient means, wherein the said drive ring and the 
said resilient means are mounted within a cavity which is delimited by the 
guide ring and by a closure ring secured to the guide ring, is 
characterised in that a first one of the elements comprising the closure 
ring and the guide ring has at its inner periphery at least two stop lugs 
for preventing rotation, the said stop lugs being directed axially towards 
the second one of the said elements comprising the guide ring and the 
closure ring, so as, by mating cooperation, to prevent the rotation of a 
thrust ring which is interposed between the said resilient means and the 
drive ring. 
Thanks to the invention, the axially acting resilient means are protected 
by the closure ring, and the force exerted by these resilient means depend 
on the axial distance by which the guide ring and the closure ring are 
separated. This distance is generally invariable, because the stop lugs 
stiffen the friction unit that comprises the guide ring and the closure 
ring, so that this assembly is robust. 
It will also be appreciated that the stop lugs which are provided in 
accordance with the invention facilitate the positioning in advance of the 
components which are mounted within the friction unit or unitary friction 
assembly, and that the inner periphery of these said components is 
protected thereby. 
In addition, the stop lugs make it possible to fit the thrust ring in a 
simple axial movement, the thrust ring being of simple form. The same is 
true of the axially acting resilient means themselves, which can be simply 
fitted over the stop lug. 
The stop lugs make it possible to provide a large number of different 
embodiments. Thus, it is possible to interpose the drive ring between two 
friction rings, each of which has a slot at its inner periphery, or a 
window, for meshing with the stop lug. 
The friction rings do not need to be adhesively attached on the drive ring, 
and one of the said friction rings may constitute the above mentioned 
thrust ring. 
It is of course possible to provide an arrangement with two drive rings, 
mounted for rotational movement with respect to the stop lugs, and three 
friction rings, one of which is interposed between the two drive rings, 
while another constitutes the thrust ring, and the third one constitutes a 
ring which is interposed between the closure ring and the drive ring 
concerned. 
All of the foregoing considerations depend on the particular application 
and on the axial dimensioning of the cavity. 
Preferably, each stop lug penetrates into an aperture in the element 
concerned comprising the closure ring or guide ring. The stop lugs are 
then elongated, which facilitates fitting of the various rings of the 
friction unit. 
One feature of the invention is that the (or each) aperture which receives 
a stop lug or lugs enables an axially oriented annular flange to be formed 
at the inner periphery of the element having the aperture, this flange 
being adapted to cooperate (in centring relationship which may be local) 
with the bearing of a spacing ring which is interposed axially between the 
damper plate of the damper and the closure ring. 
In this connection, this flange may be long enough to provide such centring 
without unduly increasing the size of the torsion damper, because such a 
flange is directed axially either towards the damper plate, that is to say 
in the direction away from the stop lugs, when it is fixed with respect to 
the guide ring, or else towards the guide ring when it is fixed with 
respect to the closure ring. In this last case, advantage can be taken of 
the space which is available between the damper plate and the guide ring. 
The flange therefore protects the stop lugs, especially during handling 
operations of the friction unit before it has been finally fitted. 
Preferably there is a radial clearance between the said flanges and stop 
lugs. This facilitates manufacture, because manufacturing tolerances which 
have to be observed for the guide ring do not need to be very precise, due 
to the radial clearance. 
According to the invention in a further aspect, a torsion damper includes a 
friction unit according to the invention. 
In one embodiment, the closure ring has at its outer periphery at least one 
radial fastening lug for securing it to the guide ring. It is this lug 
that determines geometrically the axial distance between the guide ring 
and the closure ring. In certain applications, this lug enables the 
closure ring to be secured by riveting to the guide ring. 
In a modification, the fastening of the closure ring to the guide ring may 
be achieved by virtue of a plurality of the said stop lugs, which are bent 
back radially away from the axis of the assembly after having passed 
through the above mentioned apertures. These stop lugs may be arranged 
alternately with shorter axial lugs, which also serve to prevent rotation 
of the thrust ring and which are adapted to engage on the guide ring. The 
axial distance between the guide ring and the closure ring is thus 
determined geometrically by the shorter lugs. The gripping action which is 
exerted by the axially acting resilient means on the drive ring is then 
also determined by these shorter lugs. 
In one procedure, this gripping action may be calibrated during the 
assembly operation. In this connection, in one modification, the closure 
ring only has stop lugs which pass through their associated apertures, and 
the closure ring is deformed so as to compress the resilient means until 
the desired gripping action is obtained, after which the ends of the lugs 
are bent back radially away from the axis of the assembly and into contact 
with the guide ring, so as to lock the closure ring into position. In this 
way, a unit is obtained which has an axial thickness determined by the 
resilient means, which within a torsion damper are stiffer than the other 
axially acting resilient means which work between the damper plate of the 
damper and a further guide ring. 
In all of the foregoing arrangements, it is of course possible to reverse 
the structures, with the guide ring having the shorter lugs and/or the 
stop lugs then being bent back radially away from the axis of the 
assembly. 
In one embodiment, the closure ring is arranged to make contact with plate 
elements, which are preferably of plastics material and which constitute 
spacing rings between the closure ring and the damper plate of the damper 
which includes the friction unit according to the invention. Two of these 
plate elements may be provided, on either side of the damper plate, the 
said plate elements having at their inner periphery a bearing in the form 
of a sleeve, which is fitted over a hub to which the damper plate is 
joined. These plate elements serve for the mounting of the low stiffness 
resilient members which work circumferentially between these latter and 
the damper plate. 
According to another feature of the invention, each of these bearings of 
the plate elements is formed with a projection, which is preferably 
divided, and which is directed towards the axis of the assembly for 
fitting, with a clearance, in an associated groove which is formed for 
this purpose in the hub at its outer periphery. In this way it is possible 
to provide a sub-assembly comprising the two plate elements, the hub with 
its damper plate, and the low stiffness resilient means, with the plate 
elements being snap-fitted on to the hub by virtue of the above mentioned 
projections being snapped into the grooves in the hub. This represents a 
considerable simplification in the method of assembling the torsion 
damper, because the latter then comprises two unitary assemblies, namely 
the unitary assembly mentioned above having the plate elements, and the 
friction unit. 
During the assembly operation, the resilient members of higher stiffness 
are fitted on to the drive ring or rings of the friction unit, and the 
other unitary assembly or sub-assembly, including the plate elements, is 
then fitted. Finally, a guide ring is fitted, with a further friction 
means being interposed. In this way the assembly operation is considerably 
simplified. 
Various preferred embodiments of the invention will be described below, by 
way of example only and with reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
The drawings show a friction clutch 1 for a motor vehicle, incorporating a 
torsion damper with a unitary friction sub-assembly, or friction unit 35. 
The friction clutch 1 in these examples, and as shown in particular in 
FIG. 1, comprises a clutch disc 2 having, secured on each of its faces, 
friction liners 18 which are arranged to be gripped in the usual way 
between a pressure plate 104 and a reaction plate 100 of the clutch, so as 
to transmit engine torque from the crankshaft 111 of the internal 
combustion engine of the motor vehicle to the input shaft 110 of the 
gearbox. To this end, the reaction plate 100 is secured by means of screw 
fasteners 112 on to the crankshaft 111, while the friction clutch 1 has a 
central hub 13 which is internally splined so as to couple it in rotation 
on the input shaft 110 of the gearbox. 
The pressure plate 104 is part of a unitary clutch mechanism 101, which 
also includes a cover plate 102 in the form of a dished plate, together 
with a diaphragm 103 which is mounted on the cover plate 102 by means of 
spigot members 108, in such a way that it can tilt or deflect. The clutch 
mechanism 101 is carried on the reaction plate 100 through screw fasteners 
(not shown) inserted through the radial flange of the cover plate 102 of 
the clutch mechanism. 
The diaphragm 103, constituting an axially acting resilient means, bears on 
the base of the cover plate 102, which has a central aperture, so as to 
urge the pressure plate 104 towards the reaction plate 100 and so to grip 
the liners 18 between the reaction and pressure plates, so that the engine 
torque is transmitted from the crankshaft 111 to the gearbox input shaft 
110 through the friction clutch 1, in such a way as to damp out 
vibrations. 
This clutch is of the kind which is disengaged by exerting an axial thrust 
on the diaphragm, i.e. it is a clutch of the "push off" type. This is 
achieved by means of a clutch release bearing 109, which exerts a thrust 
on the ends of the fingers of the diaphragm 103, so as to deflect the 
diaphragm 103 and cause it to cease acting on the pressure plate 104. 
A set of tangentially oriented resilient tongues 106 then urge the pressure 
plate 104 towards the base of the cover plate 102, so as to release the 
friction liners 18. In the known way, each of the tongues 106 is for this 
purpose secured by riveting at one of its ends to a radial lug 107 of the 
pressure plate 104, being secured at its other end to the radial flange of 
the cover plate 102. The pressure plate 104 is thus fixed to the cover 
plate 102, for rotation with the latter, while being movable in axial 
linear movement with respect to the latter. 
The torsion damper is here an integral part of the friction clutch 1, so 
that the assembly as a whole can be regarded as consisting of a clutch and 
consisting of a torsion damper, so that these two expressions may be used 
interchangeably. Referring to FIGS. 1, 3 and 9 in particular, the torsion 
damper comprises two coaxial parts which are mounted for angular 
(circumferential) movement of one with respect to the other against the 
action of circumferentially acting resilient means 9, 10, and axially 
acting resilient means 25, 35. It should be noted that elements that are 
identical or substantially identical in all the embodiments shown in the 
drawings are given the same reference numerals throughout the drawings. 
More precisely, one of the two coaxial parts of the torsion damper 
comprises the clutch disc 2 mentioned above, constituting the input 
element of the torsion damper, together with two guide rings 3 and 5 
(which are here of metal), these guide rings having apertures for 
receiving the resilient members 9. The other coaxial part of the torsion 
damper comprises the hub 13, which constitutes the output element of the 
torsion damper, together with a damper plate 4, which is of generally 
transverse orientation and which is secured to the hub 13. 
In this example the damper plate 4, which is again of metal, is integral 
with the metal hub 13, but in a modification it may be a separate 
component secured on the latter by seaming. The transversely oriented 
guide rings 3 and 5 surround the hub 13 and lie on either side of the 
damper plate 4, the guide rings and damper plate being parallel to each 
other. The clutch disc 2 is secured to the first guide ring 3 by means of 
rivets 6, while spacer elements in the form of spigot members 7, which are 
fitted radially inwardly of the rivets 6, join the two guide rings 3 and 5 
together. For this purpose, the spigot members 7 extend through the damper 
plate 4, via windows 41 and 42 (see FIGS. 2 and 3) which are formed in the 
latter and in which a first series of the resilient members 9 are fitted. 
Further resilient members 10 are fitted radially inwardly of the members 
9. 
In this example, the members 9 and 10 consist of two series of coil springs 
working circumferentially, though at least some of these, and in 
particular the springs 10, may be in the form of blocks of elastic 
material such as rubber. More precisely, the members 9 are stiffer than 
the members 10, which are adapted to absorb vibrations in the general 
speed range associated with the slow running mode of the internal 
combustion engine; while the springs 9 are adapted for absorbing 
vibrations when the engine is running under load. 
In the present example the springs 9 are spaced apart circumferentially at 
regular intervals on a common pitch circle, and are mounted in pairs 91, 
92 (FIG. 2), with a circumferential clearance, in the windows 41 and 42 of 
the damper plate 4. These springs 9 are also received, but without any 
circumferential clearance here, in windows 31 which are formed in the 
metallic guide rings 3 and 5. The various windows therefore constitute 
housings for the springs 9. In a modification, these housings may consist 
of pressed out portions formed in the guide rings 3 and 5. 
The windows 31 in the guide rings are arranged in facing relationship with 
the windows 41 and 42 of the damper plate. The window 41 has a 
circumferential width which is greater than that of the window 42, so as 
to enable the pairs of springs 91, 92 to act in a differential way. In 
this example there are four pairs of springs 91 and 92. The number of 
these pairs does of course depend on the particular application, and it 
will be understood that a single spring 92 may be mounted in a window 41, 
42. 
The springs 10 are mounted without any clearance in windows 14 formed in 
the damper plate 4, and in recesses 24 (FIG. 3) or 124 (FIG. 9) formed in 
motion transmission plates, or spacing rings, 11 and 12 in facing 
relationship with the windows 14 (FIG. 3) or 14, 114 in FIG. 12. The 
springs 10 are spaced apart at regular intervals on a common pitch circle 
around the axis of the assembly. In this example there are four springs 
10. Here again, the number of these springs does of course depend on the 
particular application, and some of the springs 10 may be mounted with a 
clearance in the recesses 24 or in the windows 124, of the motion 
transmission plates, so that the springs 10 can be enabled to work in a 
differential manner. 
In the embodiment shown in FIG. 3, the recesses 24 are in the form of 
pockets flanking the springs 10, which are mounted without any clearance 
in the windows 14 of the damper plate 4, but with a clearance in the 
recesses 24 of the plates 11 and 12. In the embodiment shown in FIGS. 8 to 
14, the springs 10 are all mounted without any clearance in the windows 
124 (see especially FIG. 10) of the motion transmission plates 11 and 12, 
with two of them being mounted without clearance in two windows 14 of the 
damper plate 4, and the other two with a clearance in two windows 114 of 
the damper plate 4, the windows 114 being larger than the windows 14. 
The springs 10 thus work in a stepped or sequential way. However, all 
combinations are of course possible, so that for example the springs 10 
can be fitted, in the general arrangement shown in FIG. 3, without any 
clearance in the windows 14 and in two of the recesses 24 (which can be in 
the form of windows themselves), and with a clearance in two further 
recesses 24. 
The motion transmission plates 11 and 12 are made of a suitable plastics 
material, preferably reinforced with fibres, for example glass fibres, 
while the components 2, 3, 4, 5 and 13 are of metal. 
The motion transmission plates 11 and 12 constitute spacing rings in a 
manner described below. The plates 11 and 12 are arranged on either side 
of the damper plate 4, being in frictional contact with the latter under 
the action of the friction means 25 and 35. In this example, the plates 11 
and 12 are identical to each other and include at their outer periphery a 
sleeve portion 17 (see FIG. 3) which constitutes a centring bearing. The 
plates 11 and 12 thus have an L-shaped cross section, and they are fitted 
around the hub 13, being centred by their sleeve portions 17. At its outer 
periphery, each of the plates 11 and 12 is formed with at least one fork 
15 (see FIGS. 2 and 4), for engagement with the circumferential ends of 
the pairs of springs 91 and 92 mounted in the window 42. This fork 15 has 
accordingly two radial arms which delimit slots 16 through which the 
metallic spigot members 7 pass. In this example there are two 
diametrically opposed forks 15, for balancing reasons (see FIGS. 2, 8 and 
10). These forks are in engagement with the springs 91 and 92, which are 
mounted with a clearance in the windows 42, these latter being generally 
diametrically opposed to each other. 
The friction means 25, 35 consist of a first friction device 25 together 
with the friction unit 35. The first friction device 25 is arranged 
between the second guide ring 5 and the motion transmission plate 12. The 
friction device 25 comprises a resilient ring 26, which is here in the 
form of a diaphragm, with a peripheral Belleville ring portion and radial 
fingers, together with a thrust ring 27 in contact with the motion 
transmission plate 12. The resilient ring 26 bears on the guide ring 5 so 
as to act on the thrust ring 27 and to urge the motion transmission plate 
12 into contact with the damper plate 4 (see FIGS. 4 and 9). 
The friction device 25 surrounds the bearing 17 of the motion transmission 
plate 12. The thrust ring 27 is mounted on the guide ring 5, for rotation 
with the latter, by means of axial lugs 28 which are received, with a 
radial clearance, in circumferentially complementary notches 29 which are 
formed in the inner periphery of the guide ring 5. In the embodiment shown 
in FIG. 4, the lugs 28 are centred by the bearing 17, and pass through the 
ring 26 via apertures formed in two consecutive internal fingers of the 
ring 26. There is a radial clearance between the lugs 28 and the base of 
the notches 29. 
The friction unit 35, constituting a second friction device, is fitted 
between the other motion transmitting plate 11 and the guide ring 3. The 
friction unit 35 is so arranged that the spring (or diaphragm) 26 of the 
friction device 25, through the spigot members 7, causes the motion 
transmitting plate 11 to be gripped between the damper plate 4 and the 
friction unit 35. 
With reference to FIGS. 3 and 4, the unit 35 comprises a metallic drive 
ring 40 which projects radially outwardly. The ring 40 includes forks 44, 
which are the mirror image of the forks 15 described above, but here the 
arms of the forks 44 have end portions 45, defining with the remainder of 
the arm an L-shaped or angle-iron cross section in the axial direction. 
These end portions 45 engage with the circumferential ends of the springs 
91 and 92 mounted with a clearance in the windows 41. The end portions 45 
extend lengthwise in the axial direction as shown in FIG. 3, and penetrate 
into the windows 41. These end portions 41 are arranged to interfere with 
the lateral edges of the windows 41, and are configured for this purpose 
as is best seen in FIG. 2. 
The drive ring 40 therefore has two diametrically opposed forks 44, for 
engagement with the springs 91 and 92 in the windows 41, these latter 
being generally also diametrically opposed to each other. However, a 
single fork 44 could of course also be provided. In every case, one spigot 
member 7 passes through the fork 44 between the arms of the latter. 
The torsion damper works in the following way. 
(1) In a first phase of relative angular displacement between the clutch 
disc 2 and the hub 13, the guide rings 3 and 5 drive the motion 
transmitting plates 11 and 12, through the springs 91 and 92 mounted 
without circumferential clearance on the forks 15, in such a way that the 
low stiffness springs 10 are compressed, and that friction, loaded by the 
diaphragm ring 26 (which is configured accordingly) occurs between the 
motion transmission plates 11 and 12 on the one hand, and the damper plate 
4 on the other, and also between the bearings 17 and the hub 13. 
(2) In a second phase of the relative angular displacement, after the 
mounting clearance has been taken up, the pairs of springs 91 and 92, 
mounted in the appropriate windows 42, are compressed in such a way that 
the motion transmission plates 11 and 12 are immobilised with respect to 
the damper plate 4, with the springs 10 remaining in their compressed 
state. Friction then occurs between the friction unit 35 and the motion 
transmitting plate 11, and also between the plate 12 and the thrust ring 
27. The diaphragm ring 26 is so designed that this will take place. 
(3) In a third phase of the relative angular displacement, after the 
mounting clearance of the springs 91 and 92 has been taken up in the 
windows 41, these springs are compressed, and the end portions 45 of the 
arms 44 make contact with the corresponding lateral edges of the windows 
41, so as to produce additional friction in a manner described below. 
More precisely, the second friction device, i.e. the friction unit 35, 
constitutes a unitary friction assembly with the first guide ring 3, at 
the inner periphery of the latter. The unit 35, which is of the kind 
usually referred to as a hysteresis cassette, also includes a closure ring 
36. As is best seen in FIG. 3, this closure ring 36 and the guide ring 3 
together define a cavity 34. 
The closure ring 36 in this example is arranged to cooperate frictionally 
with the motion transmitting plate 11 which, like the other similar plate 
12, constitutes a spacing ring. The closure ring 36, which in this example 
is of metal, is provided at its inner periphery with at least two axially 
oriented stop lugs 51 for preventing rotation. These lugs 51 are directed 
axially towards the guide ring 3 and away from the damper plate 4 and 
plate 11. There are preferably at least three of these lugs 51. However, 
if only two lugs 51 are present, these are arranged in generally 
diametrically opposed relationship to each other. 
In this example, each stop lug 51 penetrates into an associated aperture 50 
which is formed for this purpose in the guide ring 3 at the inner 
periphery of the latter and radially outwardly of the spigot members. A 
radial and circumferential clearance exists between each stop lug 51 and 
the aperture 50. Each lug 51, by mating cooperation, prevents rotation of 
at least one thrust ring 38 (see FIG. 4) which is interposed between the 
drive ring 40 and at least one axially acting resilient ring 37, which 
will be described below. It will be appreciated that the stop lugs 51 in 
this example enhance the rigidity of the closure ring 36, and that the 
thrust ring 38 is of simple form. 
At its inner periphery, the guide ring 3 has an axially oriented annular 
flange 33, which is directed towards the damper plate 4 and which is 
mounted coaxially on the bearing 17 of the motion transmission plate 11. 
It is this flange 33 which enables the guide rings 3 and 5 to be centred 
with respect to the hub 13, and this is why there is a radial clearance 
between the lugs 28 and the base of the notches 29. The flange 33 extends 
axially in the opposite direction from the stop lugs 51 of the closure 
ring 36. The annular flange 33 increases the rigidity of the guide ring 3, 
so that the unitary friction assembly mentioned above, comprising the 
friction unit 35, the guide ring 3, and the closure ring 36, is very rigid 
and is in no danger of opening up. 
The aperture 50 for the stop lugs 51 of the closure ring 36 is formed in 
the bend which joins the centring flange 33 to the main part of the guide 
ring 3. The centring flange 33 is of substantial length, and is made 
inexpensively because it is formed in a portion which would normally 
constitute discarded material. In addition, the apertures 50 facilitate 
the bending of the flange 33, which protects the stop lugs 51 and the 
various components which are fitted within the cavity 34. However, the 
axial length of the flange 33 is smaller than the axial length of the stop 
lugs 51, which in this example pass right through the apertures 50. These 
lugs 51 are thinner than the guide ring 3, as is the closure ring 36 as a 
whole. In particular, this is made possible due to the flange 33 which 
masks the lugs 51. However, according to the particular application, it is 
possible to increase the thickness of the closure ring 36. 
In addition, in a modification, it is possible to reverse the structures, 
with the closure ring 36 then having the flange 33 and the apertures 50, 
while the guide ring 3 has the lugs 51, which in this case, do not project 
with respect to the closure ring 36 or penetrate into a groove of the 
motion transmitting plate 11. 
In this example a plurality of stop lugs 51, and therefore a plurality of 
apertures 50, are spaced apart at regular intervals. The closure ring 36 
has at its outer periphery at least one radial fastening lug 53 for 
securing it to the guide ring 3 by means of the spigot members 7. In this 
example, one fastening lug 53 is provided for each spigot member 7 passing 
through the forks 44 of the drive ring 40. This again does of course 
depend on the particular application, as does the number of stop lugs 51 
and apertures 50. In this embodiment, there are four radial lugs 53 (i.e. 
one for each spigot member 7), and eight axial stop lugs 51. 
The closure ring 36 accordingly has at its inner periphery the form of an 
annular comb, with a bend 52 joining the comb portion to the remainder of 
the ring 36. At its outer periphery, the latter has the fastening lugs 53 
projecting radially. In more general terms, the component comprising the 
guide ring 3 and closure ring 36, having the lugs 51, has the form of a 
comb with the junction bend 52, which is continuous circumferentially, 
joining it to the main portion of this component 3, 5. 
The lugs 51 and 53 are of rectangular cross section, and are flat and thin. 
In a modification, it is the guide ring 3 that has the form of a comb, 
with the closure ring 36 having the flange 33. 
The drive ring 40 is mounted in the cavity 34, together with the axially 
acting resilient ring 37 and the two friction rings 38 and 39, which are 
arranged on either side of the drive ring 40. The ring 37 is the mirror 
image of the resilient ring 26 (FIG. 4), and in this example the ring 37 
is in the form of a diaphragm having a peripheral portion in the form of a 
Belleville ring, which is extended radially inwardly by fingers, some of 
which are slotted in facing relationship with the stop lugs 51, so that 
the latter can pass through them, the stop lugs 51 being arranged 
circumferentially in a complementary way. This provides rotational 
coupling of the ring 37 with the lugs 51. The ring 37 then has at least 
one finger which meshes with a corresponding lug 51. 
The rings 38 and 39 have at their inner periphery slots 61 through which 
the stop lugs 51 pass, again in a complementary manner circumferentially, 
and for rotational coupling of the rings 38, 39 with the stop lugs 51 and 
the closure ring 36. Each lug 51 meshes with a slot 61 of the ring 38, 39 
concerned, for preventing rotation of the latter. The drive ring 40 
surrounds the stop lugs 51 with a radial clearance, being centred by the 
pairs of springs 91 and 92 via its forks 44. It is mounted for movement in 
relation with respect to the stop lugs 51. 
In general terms, it will be appreciated that the stop lugs 51 facilitate 
the positioning, in advance, of the rings 37 to 40 in the cavity 34. 
In this example, the resilient ring 37 bears on the guide ring 3 and on the 
thrust ring 38, so as to provide an axial gripping force for gripping of 
the drive ring 40 between the two rings 38 and 39, the ring 39 being in 
contact with the closure ring 36. The ring 38 then acts as a thrust ring, 
prevented from rotating by the stop lugs 51. The drive ring 40 is 
interposed between the rings 38 and 39, and fitting is carried out by 
threading the components 37, 38, 39 and 40 axially on to the stop lugs 51 
before the fastening lugs 53 are secured. 
In this way, gripping of the drive ring 40 is well controlled by the 
distance between the closure ring 36 and the guide ring 3, and no relative 
movement that might give rise to wear and/or noise can occur in the 
circumferential direction between the rings 38 and 37, so that the rings 
38 and 39 are not of metal in this example. 
It will be appreciated that this gripping action is very well controlled 
because the components 3 and 36 are stiffened at their inner peripheries, 
respectively by the flange 33 and by the stop lugs 51 and junction bend 
52. Accordingly the danger of the cavity 34 opening out is minimised. 
In all cases there is a radial clearance between the stop lugs 51 and the 
flange 33 parallel to the latter, in order to avoid any interference 
between this flange and the rings 37, 38 and 39, and to facilitate 
manufacture, especially as regards conformity with manufacturing 
tolerances. 
The structures can of course be reversed, with the ring 37 bearing on the 
closure ring 36 and the ring 39 on the guide ring 3. It is even possible 
to increase the number of friction rings 38, 39 and the number of drive 
rings 40, as is for example described below with respect to the embodiment 
shown in FIGS. 8 to 14. 
One drive ring 40 may be associated with each pair of springs 91 or 92 
mounted in the windows 41. In that case, there are three friction rings 
and two drive rings arranged in axial succession. 
As will have been understood from the foregoing, the arrangement shown in 
the drawings is of advantage because it prevents any metal to metal 
friction between the rings 36 and 40, and it leads to the least possible 
deformation of the sinuous forks 44 of the drive ring 40. The forks 44 in 
this example are offset axially with respect to the main friction part of 
the thrust ring 40, i.e. that which is arranged to make frictional contact 
against the rings 38 and 39. 
Although the ring 40 is arranged to induce friction in contact with the 
rings 38 and 39, it may of course be arranged to do so directly against 
the closure ring 36. 
The guide ring 3 is deformed at its inner periphery and has a portion 32 
which contains the apertures 50, and which is offset axially away from the 
damper plate 4 and closure plate 36. Similarly, the fastening lugs 53 are 
offset axially towards the guide ring 3, with respect to the main part of 
the closure ring 36. 
The fastening lugs 53 and the offset portion 32 are joined by sinuous 
portions to the main part of the closure ring 36 and to the main part of 
the guide ring 3 respectively, the lugs 53 being abutted to the ring 3. 
The sinuous portions of the lug 53 are robust enough to resist the 
gripping force which is exerted by the resilient diaphragm 26. These 
portions stiffen the ring 36, as does the bend 52. 
It is thus possible to control the volume of the cavity 34. It will be 
appreciated that the closure ring 36 is made easily by press-forming 
(blanking and bending), as is the guide ring 3, which differs from the 
other guide ring 5 in regard to its inner periphery. The inner periphery 
of the guide ring 5 is also offset axially away from the damper plate 4, 
in order to accommodate the friction device 25. Thus, in the second phase 
of the relative angular displacement between the two parts of the torsion 
damper, i.e. between the clutch disc 2 and the hub 13, the flange 33 is 
brought into frictional engagement against the bearing 17, and the closure 
ring 36 undergoes friction against the motion transmitting plate 11, the 
latter being thicker than the drive ring 40, so that it can come into 
engagement with the springs 91 and 92. The same applies during the third 
phase of the angular displacement, during which relative movement, in 
which friction is controlled by the ring 37, takes place between the drive 
ring 40 (acting differentially) and the rings 38 and 39. 
The present invention is of course not limited to the embodiments described 
up to this point. In particular, as mentioned above, it is possible to 
reverse the structures, with the guide ring 3 having the stop lugs and the 
closure ring having the flange 33 surrounded by the stop lugs 51. In all 
cases, however, the stop lugs 51 and the flange 33 extend axially in 
opposite directions. 
The present invention is applicable to a friction clutch of the kind which 
is described in French patent specification FR 2 370 902A and the 
corresponding U.S. Pat. No. 4,222,475, having six springs which are spaced 
apart circumferentially. In that case, the spacing ring associated with 
the friction unit 35 (or hysteresis cassette) does not have any fork at 
its outer periphery, and the inner springs 10 are omitted, some of the 
outer springs 9 being in engagement with windows formed in the damper 
plate 4. The friction device 25 is in this case modified, being then of 
the type shown in FIG. 8 of the documents just mentioned, with one single 
spacing ring, constituting a bearing, being then provided. In this case, 
specific rivets are provided for the purpose of securing the closure ring 
36, the spacer elements being fitted at the outer periphery for fastening 
the clutch disc 2. 
Instead of the end portions 45 arranged at right angles on the arms of the 
forks 44, it is possible to make use of axial lugs like the lugs 42 in 
FIG. 5 of U.S. Pat. No. 4,222,475, with these lugs meshing, with a 
clearance, with apertures in the damper plate 4 (i.e. the internal edge of 
the windows). Forks and axial lugs, meshing with a clearance with slots in 
the damper plate 4 so as to engage with the latter, are thus arranged 
alternately. In all cases, the drive ring 40 has drive means for 
engagement with the damper plate 4. 
The pockets 24 may of course be replaced by windows 124 as shown in FIG. 9, 
with the springs 10 having in all cases a diameter which is smaller than 
the axial distance between the outer faces, opposed to the damper plate 4, 
of the motion transmitting plates 11 and 12. 
The damper plate 4 could also mesh, with a clearance, with the hub 13, with 
the springs 10 working between the components 4 and 13, while the plates 
11 and 12 are then without any arms. 
The clutch disc 2 of the torsion damper may be secured directly on the 
reaction plate 100, and the hub 13 may mesh with the input shaft of a 
transmission unit, for example of the variable pulley type. In that case, 
there is no longer any clutch mechanism. 
The ring 37 may be in the form of a resiliently deformable corrugated ring, 
having at its inner periphery fingers which mesh with the stop lugs 51 of 
the closure ring 36. It is of course possible to provide a plurality of 
resilient rings mounted in series. In particular, two Belleville rings 
with fingers inclined in opposite directions may be provided. In that 
case, these rings are in contact with each other through their outer 
peripheries, and the elastic load is well controlled. 
The fastening lugs 53 may be secured to the guide ring 3 by welding. Also, 
at the level of the stop lugs 51, it is possible to provide, alternately 
with each other, long lugs 51 which penetrate into the apertures 51, and 
shorter axially oriented lugs (which can be seen at 151 in FIG. 7), which 
project from the inner periphery of the closure ring 36 and which bear on 
the guide ring 3, or vice versa. 
Thus, with reference to FIG. 7, four long lugs penetrate into four 
apertures, and these alternate circumferentially with short lugs 151 which 
bear on the guide ring 3. In that case the resilient ring 26 may be 
arranged to exert a higher load. 
In a modification, the ends of the lugs 51 may be formed with shoulders. In 
that case, the lugs 51 may have a T-shaped end portion, the central 
portion of which penetrates into the aperture 50 while its wings bear on 
the guide ring 3. 
In a further modification, shown in FIG. 5, a clearance is provided between 
the spigot members and the fastening holes 154 which are provided in the 
fastening lugs 53 for accommodating the shanks of the spigot members 7. In 
this case the stop lugs 51 penetrate circumferentially in a complementary 
manner, in this example with a fitting clearance, into the apertures 50, 
so as to prevent the closure ring 36 from rotating. As a result, the stop 
lugs 51 mesh with the apertures. In this case, it is possible to apply 
seaming to the stop lugs 51. To this end, the axial end portion 152 of 
each lug 51 is bent back radially away from the axis of the assembly. 
The presence of the fastening lugs 53 is not mandatory. In this connection 
(see FIGS. 6 and 7), it is sufficient to arrange, in circumferential 
alternation, short lugs 151 as mentioned above, bearing on the guide ring 
3, and long lugs 51 which are bent back radially away from the axis of the 
assembly. 
In a further modification the lugs 51 are shouldered. In the preceding 
cases, the lugs 51 or 151 secure the closure ring 36 to the guide ring 3. 
When the structures are reversed, a groove can be arranged in the spacer 
ring 11, into which the bent-back ends 152 of the guide ring 3 penetrate, 
so reducing axial size. 
The drive ring 40 may be fixed with respect to the friction rings 38 and 
39, these being without the slots 61. The rings 38 and 39 then surround 
the lugs 51 with a radial clearance, while an additional thrust ring, 
meshing with the stop lugs 51 through the above mentioned slots 61, is 
then interposed axially between the rings 37 and 38. 
Having regard to the presence of this thrust ring, it is possible to 
provide a single friction ring which is interposed between the closure 
ring 36 and the thrust ring, this single ring carrying at its outer 
periphery (for example applied by moulding on to the ring itself) the 
metallic forks 44 and 45. In the drawings, it is of course possible to 
secure the ring 39, thus not having the slot 61, on the ring 36 
adhesively, as illustrated in FIG. 7. 
The slots 61 may be replaced by windows in the case in which the radial 
clearance between the flange and the lugs 51 permits it. 
In all cases, rotation is prevented by a mating cooperation between the 
axial stop lugs 51 and the appropriate ring or rings 37 to 39. 
In a further modification, the closure ring 36 of FIG. 6 does not have the 
lugs 151 of FIG. 7. In this case, the end portions 152 of the lugs 51 are 
no longer bent back, and a tool is used to apply pressure on the closure 
ring 36 so as to compress the various components contained within the 
cavity 34, against the load exerted by the resilient ring 37, which 
adjusts the calibration of the ring 40. Once this load has reached the 
value which is desired in order to exert the suitable force on the drive 
ring 40, and to regulate hysteresis in the desired manner, the movement of 
the tool is stopped, and the end portion 152 of the lugs 51 is bent back 
radially away from the axis of the assembly and into contact with the 
guide ring 3. In this way a unitary friction sub-assembly is obtained, in 
which the gripping force exerted on the drive ring is set at a desired 
value. 
It will be noted that in operation, the ring 37 is not deflected by the 
ring 26 of FIG. 4, because the ring 26 is so calibrated that it does not 
obliterate the action of the low stiffness resilient means 10, while it 
does enable the motion transmitting plates 11 and 12 to be immobilised by 
friction during the second and third phases of the relative angular 
displacement between the clutch disc 2 and the hub 13. The force exerted 
by the ring 26 is accordingly lower than the force exerted by the ring 37. 
It will also be noted that in FIG. 7, the calibration of the ring 37 is 
determined geometrically by means of the lugs 151. In FIGS. 4 and 5, the 
calibration of the ring 37 is determined by means of the radial fastening 
lugs 53, which in all cases are engaged on the spigot members 7, with or 
without a clearance. The closure ring 36 is thus attached to the guide 
ring 3 through its radial fastening lugs, which, it should be noted, may 
be welded on to the guide ring. 
With reference to FIG. 2, it should be noted that the axis of symmetry 
passes through two diametrically opposed spigot members 7 which are offset 
circumferentially with respect to the axis of symmetry that passes through 
two pairs of diametrically opposed springs 91 and 92, in order to increase 
the material which is present between two consecutive windows 41, and so 
to stiffen the damper plate 4. 
It is not mandatory to provide the deformation 32: whether or not it is 
provided depends on particular applications. 
With reference now to FIGS. 8 to 14, in this embodiment there is a 
sub-assembly which cannot be lost, and which can be handled and 
transported easily, and which comprises the motion transmitting plate 12, 
the damper plate 4 with its hub 13, and the low stiffness springs 10. To 
this end, each motion transmitting plate 11, 12 has at the free axial end 
of its bearing 17, at least one pointed projection 211 (see FIG. 11), 
which is arranged to penetrate into an associated groove 311 (see FIG. 
13), which is formed in one of the ends of the hub 13, at the outer 
periphery of the latter. 
In this example the projection 211 is in its preferred form, in that it is 
divided into a plurality of annular sectors which are separated by grooves 
213 formed in the internal bore of the bearing 17. These grooves 213 
reduce the thickness of the bearing 17 locally, and extend over the whole 
axial length of the latter, as shown in FIG. 11. The grooves 213 are 
formed with slots 212 which are shorter axially than the bearing 17, with 
each of these slots 212 having an open end at the free end of the bearing 
17, the other end of each slot being closed, as can again be seen in FIG. 
11 which shows the oblong shape of these slots 212. 
The projections 211 extend radially towards the axis of the assembly, and, 
as can be seen in FIG. 11, they are delimited by a transverse edge which 
extends towards the axis of the assembly the terminal face 214 (i.e. the 
face which is furthest away from the transverse portion of the plate 11 or 
12 concerned), and by an inclined portion which projects into the bore of 
the bearing 17. 
As can be seen in FIGS. 13 and 14, the hub 13 has an annular groove 311 at 
each of its ends, for receiving the projections 211 of the plate 11 and 
plate 12 respectively. The axial ends of the hub 13 are chamfered in the 
known way. During fitting of the plates 11 and 12 on the hub 13, by 
threading them on to the latter, the inclined portions of the projections 
211 accordingly cooperate with the appropriate chamfer, so that the 
projections are lifted and then penetrate into the associated grooves 311. 
In this way the plates 11 and 12 are snap-fitted on to the hub 13. This 
fitting operation is facilitated by the flexibility of the projections 211 
due to the presence of the grooves 213 and their slots 212. 
The projections 211 penetrate into their associated annular grooves 311 
with radial and axial clearance. Thus, parasitic friction effects due to 
the presence of the projections 211 are minimised during operation of the 
torsion damper. More precisely, the grooves 311 are of matching shape to 
the projections 211. As seen in FIGS. 13 and 14, the grooves 311 have in 
cross section a transverse edge 314 which is joined through a rounded base 
312 to an inclined edge 313. In this example, the angle between the edges 
313 and 314 is 45 degrees, but the actual value of this angle will of 
course depend on the particular application. Accordingly, the transverse 
edge of the projection 211 is enabled to cooperate with the transverse 
edge 314 of the associated groove 311 after an axial clearance has been 
taken up. 
It will be appreciated that it is easy to disconnect the plates 11 and 12 
from the hub by reversing the snap-fitting operation, due in particular to 
the flexibility of the projections 211. 
The above mentioned assembly, or sub-assembly, which cannot be lost and 
which can be handled and transported easily, and which comprises the 
damper plate 4, hub 13, plates 11 and 12 and springs 10, is able to be 
created due to the projections 211 directed towards the axis of the 
assembly and formed at the inner periphery of the bearings 17. 
The presence of this sub-assembly, and the presence of the unitary friction 
sub-assembly comprising the friction unit 35 with the components 3 and 36, 
greatly facilitate the manufacture of the torsion damper. In this 
connection, both of these sub-assemblies can be manufactured in separate 
manufacturing locations, with the resilient members 91, 92 being 
subsequently fitted on the forks 44, 45 of the drive rings 40 and 140 
described below. The sub-assembly that includes the plates 11 and 12 is 
subsequently fitted, and finally, the friction means 25 and the guide ring 
5 are fitted, and the spigot members 7 can then be secured by a seaming or 
upsetting operation. The number of components to be handled during the 
final assembly operation is considerably reduced. 
In this example, an operating clearance exists between the flange 33 and 
the bearing 17 of the plate 11. This operating clearance takes account of 
the misalignment that exists (as is well known) between the crankshaft 111 
and the gearbox input shaft 110 shown in FIG. 1. By virtue of this 
clearance, the bearing 17 will come into local contact with the flange 33 
in such a way that risks of jamming are minimised, and good local centring 
is obtained without any danger of jamming. The friction effects between 
the flange 37 and the bearing 17 are minimised. The guide rings 3 and 5 
are centred by means of the flange 33. 
It will also be noted that there is a radial clearance between the lugs 28 
of the ring 27 and the bearing of the plate 12, with the guide rings 3 and 
5 adopting the correct position with respect to the plates 11 and 12. 
In this example, in the way already described above, the friction unit 35 
has three friction rings 138, 38, 39, and two drive rings 40 and 140 which 
are mirror images of each other. The resilient means 37 bear on the ring 
138 which constitutes the thrust ring and which meshes with the stop lug 
51 as in FIGS. 1 to 7, as do the rings 38 and 39, with the ring 38 being 
interposed axially between the two drive rings 140 and 40, while the ring 
39 is interposed axially between the drive ring 40 and the closure plate 
36. 
The stop lugs 51 here have their free ends shouldered in the way described 
below, with that portion of the lugs 51 that is of reduced width 
penetrating into the hole 50. These lugs 51 thus determine the spacing 
between the two rings 3 and 36, in such a way that the fastening lugs 53 
are spaced away from the guide ring 3, being in contact with the larger 
diameter portions of the spigot members 7 (see FIG. 9). 
The fitting of the sub-assembly 35 is facilitated due to the fact that the 
rings 138, 38 and 39, together with the ring 37, mesh with the stop lugs 
51, so stiffening the closure ring 36. 
It will be noted that the drive ring 140 is superimposed on the forks 15 of 
the motion transmitting plate 11, with this ring 140 engaging, through its 
forks 44 with their angled ends defining the axial end portions 45 
directed towards the damper plate 4 and penetrating into the windows 42, 
with the springs 91 and 92 that are mounted in these windows 42. 
The drive ring 40 is mounted, as in FIG. 2, in the windows 41. The windows 
41 and 42 are best seen in FIG. 12. Each window 42 has a lateral edge 142 
for cooperation, after a circumferential clearance has been taken up, with 
the end portions 45 of the ring 140. 
The windows 41 also have lateral edges, and in the embodiment shown in FIG. 
12, these edges are notched at 141, i.e. at their radially inner ends, so 
as to cooperate with the end portions 45 of the drive ring 40 after a 
circumferential clearance has been taken up. The two drive rings 40 and 
140 are the mirror image of each other and have two forks 44 with 
diametrically opposed end portions 45. 
Thus, in FIG. 8 the drive rings 40 and 140 operate differentially. To this 
end, the springs 41 and 42 which are mounted without any clearance in the 
windows 31 of the guide rings 3 and 5, are mounted in an asymmetrical 
manner in the windows 41 and 42 in the rest position of the torsion 
damper. 
If, with reference to FIG. 8, it is assumed that in the direct sense (i.e. 
the mode of operation in which the engine drives the gearbox input shaft 
110 and the road wheels of the vehicle), the friction liners 18 and the 
guide rings 3 and 5 rotate in the anti-clockwise direction with respect to 
the damper plate 4, then the end portions or lugs 45 of the drive rings 40 
and 140 will come into contact at the same time with the edges 142 and 141 
of the windows 42 and 41 respectively, in such a way that the drive ring 
40 rubs frictionally between the ring 138 and the ring 38, and the drive 
ring 140 rubs frictionally between the ring 38 and the ring 39, in 
relative rotation with high friction. 
In the opposite sense, or regenerative sense (in which the road wheels in 
effect drive the engine), the guide rings 3 and 5 will rotate in the 
clockwise direction in FIG. 8, so that the end portions 45 of the guide 
ring 40 make contact first with the edges 142, and the end portions 45 of 
the drive ring 140 will then make contact with the edges 141 of the 
windows 41. In this way, the drive rings work in a differential manner 
according to the direction of rotation, in such a way that it is possible 
to optimise the characteristic curve of the torsion damper so as to give 
the best possible absorption of vibrations. 
The flanges 33 may of course be fitted on the bearing 17 without any 
clearance, and the bearing is accordingly elastic in the radial direction 
as is described, for example, in French patent specification FR 2 576 
985A. Thus, in FIG. 15, some of the projections 211 have labyrinth slots 
430 which enable the projections 211 to deform radially. 
In FIG. 16, the projections 211 are slotted in the region of their grooves, 
and a recess 431 is formed in each motion transmitting ring 11 or 12 at 
the adjacent ends of two consecutive projections 211. These projections 
are thus radially elastic. 
In all cases it is possible to take up the radial offsets between the 
crankshaft 111 and the gearbox input shaft 110, without any risk of 
jamming. 
In FIGS. 15 and 16, there can of course be an optional clearance, 
subsequently taken up locally, between the flange and the bearings of 
FIGS. 15 and 16. 
In FIG. 12, it will be noted that the damper plate 4 has, in the known way, 
a telltale hole 400, which corresponds with holes (not shown) which are 
formed in the guide rings so that the damper plate 4 can be fitted in an 
indexed manner with respect to the rings 35.