FIELD OF THE INVENTION
The present invention relates to clutches with a damper disc assembly, and more particularly to an improved damper disc assembly.
BACKGROUND OF THE INVENTION
In general, a clutch used in an automotive provides a means of selectively engage gears of the gearbox and provide means for disconnecting and connecting power transmission. Clutch comprises of a clutch cover assembly mounted of the flywheel and a clutch disc assembly placed between flywheel and clutch cover assembly and from the center it is connected to the input shaft of the gearbox. A general clutch disc includes an outer disc with friction lining on both sides, which is selectively coupled to a flywheel of an engine for transmission of torque. Such a clutch disc assembly has a spline hub connected to the outer disc via a damper mechanism. A damper mechanism is an arrangement used in clutch disc assembly for smooth transmission of torque and for absorbing and dampening torsional vibrations transmitted from the engine in the driveline. The damper mechanism is basically formed of a first rotary member, a second rotary member and plurality of coil springs, which are arranged between the first and second rotary members. The springs are compressed between the first and second rotary members when these members rotate relatively to each other while transmitting torque. Two retainer plates, one on each sides are generally used to hold these springs in position and allow them to compress while torque transmission.
The outer disc is constructed with a pair of friction facings mounted on the both sides of a metallic plate generally called as front plate of clutch disc. This set of friction facings and front plate is compressed between the flywheel and pressure plate of clutch

cover assembly while transmitting torque. The front plate extends through damper mechanism. A spline hub is usually configured to connect to an input shaft extending from a transmission for rotation therewith.
An opening is generally provided in the retainer plates such that coil springs are disposed in them. There have been several arrangements for locating the coil springs in these openings in retainer plates. While some uses an extra piece generally called 'catcher' with protruding lugs which locates and guides the coil spring, the other uses a formed lip on overall or a part of the opening in the retainer plate.
Different design poses different problems and also because of recent trend of increased torque capacity of the engine, there has been a demand of arresting the coil springs more securely into the clutch disc. This need is pronounced further in case of overloading in a vehicle and poor road conditions where there is a shock load applied to the coil springs and the entire clutch disc core.
During clutch use, coil springs of clutch disc gets compressed and relaxed and follow the path defined by the openings provided in retainer plates and front plate. The path of rotation of coil springs is very critical and can not be precisely predicted under dynamic clutch working conditions. Various forces like centrifugal, centripetal, lateral, axial, engine cyclic forces and forces due to coils springs resonating frequency during clutch operation makes this path of rotation so complex to determine. This path if not predicted properly and means are not provided in front plate and retainer plates to properly arrest and guide coil spring movement can cause premature wear of these plates.
Hence, there is a well-felt need for a clutch assembly having a proper coil spring guide.

SUMMARY OF THE INVENTION
It is an object of the present invention to provide a damper disc assembly that can effectively hold damper springs in their position under all conditions of clutch working and even in abuse conditions to minimise wear.
It is yet another object of the present invention to arrest the damper springs so that they cannot come out its position and location during service life of clutch disc.
It is another object of the present invention to minimize working stresses in coil spring so that they lasts longer.
According to the invention, these objectives are achieved by providing retainer plates having coil spring openings such that the coil springs after assembly of the clutch disc are always covered in an enclosure provided by the precise forming in the retainer plate. The windows are provided with a formed cover from one edge to the other edge in radial direction and having slits on either side in the circumferential direction so required for forming and separating formed window from flat surface of retainer plate. One side face of slit forms the face of formed cover, while other face of this slit is on the flat portion of retainer plate and comes into contact with the coil spring.
According to an embodiment of the present invention an enclosed window clutch disc assembly having a damper mechanism is disclosed. The disclosed clutch disc assembly has a central hub, a first rotary member, a second rotary member and a plurality of resilient members. The central hub is connected to an input shaft of a gearbox. The first rotary member is secured to the central hub using rivets and has a plurality of windows, wherein the windows are partially covered by a projection formed in the first

rotary member. The second rotary member have a front plate and spacer plate riveted together using rivets, containing one or more friction facings, the second rotary member have a plurality of windows corresponding to the windows provided in the first rotary member. The pluralities of resilient members are arranged in the windows. The resilient members provide a dampening mechanism between the first and second rotary members, such that the projection formed in the first rotary member securely holds the resilient members in the windows.
According to another embodiment of the present invention a clutch disc assembly having an enclosed window damper system is disclosed. The damper system have a plurality of windows, such that each window have at least one coil spring arranged therein, wherein each window is covered with a cover formed in first rotary member and have a slit at each side of the formed window such that the said cover retains the coil spring in position within the window and the slit allow effective movement of one or more coil spring during torque transmission.
BRIEF DESRIPTION OF THE DRAWINGS
To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings in which:

Fig. 1 illustrates a clutch disc according to an embodiment of the present invention;
Fig. 2 illustrates an isometric view of a clutch disc according to an embodiment of the present invention;
Fig. 3 illustrates an isometric view of a clutch disc according to another embodiment of the present invention; and
Fig.3 illustrates a cross-sectional view of a clutch disc showing the said damper mechanism according to an embodiment of the present invention.
DETAILED DESRIPTION OF THE DRAWINGS
According to embodiment of the present inventions the coil springs in the retainer plates of the clutch disc are always covered in an enclosure provided by the forming in the retainer plate. The windows are provided with a formed cover from one edge to the other edge in radial direction and having slits on either side in the circumferential direction so required for forming and separating formed window from flat surface of retainer plate. One side face of slit forms the face of formed cover, while other face of this slit is on the flat portion of retainer plate and comes into contact with the coil spring.
The pair of retainer plates is formed with openings that extend in axial direction. These windows are typically formed by making circumferentially extending slits in the retainer plates and then forming the material area in between two slits in axial direction.
The outer disc having a pair of friction facings attached to a front plate. The front plate extends through damper mechanism. The coil springs are disposed in the metallic plate and covered by retainer plates on each side. The retainer plates are connected

securely to a central hub carrying splines which unions with the input shaft of the gearbox.
This way the connection between the central hub and the pair of friction facings becomes elastic and they can be rotated with respect to one another by compressing and relaxing coil springs disposed between them.
In accordance with the present invention, when the pair of friction facings and central hub is rotated relative to each other, as happens during clutch working, the coil springs repeat compression and expansion in the circumferential direction. Since a centrifugal force caused by the rotation of the clutch disc assembly is also applied to the coil springs, the coil springs are urged to move to the outer circumferential portions of the windows. Also because of vehicle shock loads the coil springs also tends to come out in radial direction. This phenomenon causes severe wear and tear on the mating plates and sometimes causes coil spring to come out of the clutch disc.
To overcome this problem raised portions extending in the axial direction are formed in the retainer plate at the both sides of each of the coil springs. The raised portions are used to limit the radially outward movement of the coil springs and to limit the movement of the coil springs in the axial direction. These raised portions in the retainer plates also help in guiding the movement of coil springs during use.
Referring to the figures 1-4 that illustrates the clutch disc according to embodiments of present invention. The enclosed window clutch disc assembly 100 has a damper mechanism 101. The clutch assembly comprises a central hub 102, a first rotary member 104, a second rotary member 111 and a plurality of resilient members 103. The clutch disc assembly 100 has the central spline hub 102 connected to an input shaft (not

shown) of a gearbox (not shown) and to a pair of friction facings 110 via the damper mechanism 101.
The first rotary member 104 is secured to the central hub 102 using rivets 113 and have a plurality of windows 105, wherein the windows 105 are partially covered by a projection 106 formed in the first rotary member 104. The projections 106 are formed in the first rotary member 104 from one edge to the other edge in radial direction and have a slit 107 at either side of the formed projection 106. According to an embodiment the first rotary member 104 is retainer plate of the clutch assembly.
The second rotary member 111 has a front plate 113 and a spacer plate 112 riveted together using rivets 114, containing one or more friction facings 110, the second rotary member 111 have a plurality of windows 105 corresponding to the windows provided in the first rotary member 104. According to an embodiment the second rotary member 111 is a metallic plate attached to friction facings 110
The plurality of resilient members 103 is arranged in the windows 105. The resilient member 103 provides a dampening mechanism between the first 104 and second 111 rotary members, such that the projection 106 formed in the first rotary member 104 securely holds the resilient members 103 in the windows. According to an embodiment the resilient members 103 are coil springs.
The resilient members 103 are compressed between the first 104 and second 111 rotary members when the members rotate relatively to each other. The central hub 102 is provided with internal keyways called splines and engages with the gearbox input shaft (not shown). The central splined hub 102 is securely fixed to the first rotary member 104.

According to yet another embodiment a clutch disc assembly having an enclosed window damper system is disclosed. The damper system comprising a plurality of windows 105, such that each window 105 has at least one coil spring 103 arranged therein. Wherein each window 103 is covered with a cover 106 formed in a first rotary member 104 and have a slit 107 at each side of the formed window 103 such that the said cover retains the coil spring 103 in position within the window 103 and the slit 107 allow effective movement of one or more coil spring 103 during torque transmission.
It is to be appreciated that the subject matter of the claims are not limited to the various examples and language used to recite the principle of the invention, and variants can be contemplated for implementing the claims without deviating from the scope. Rather, the embodiments of the invention encompass both structural and functional equivalents thereof.
While certain present preferred embodiments of the invention and certain present preferred methods of practicing the same have been illustrated and described herein, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

We Claim:
1. An enclosed window clutch disc assembly (100) having a damper mechanism
(101) comprising:
a central hub (102) connected to an input shaft of a gearbox;
a first rotary member (104) secured to the central hub (102) using rivets (113) and having a plurality of windows (105), wherein the windows are partially covered by a projection (106) formed in the first rotary member (104),
a second rotary member (111) having a front plate (113) and spacer plate (112) riveted together using rivets (114), containing one or more friction facings (110), the second rotary member (111) having a plurality of windows (105) corresponding to the windows provided in the first rotary member (104); and
a plurality of resilient members (103) arranged in the windows (105), the resilient members (103) providing a dampening mechanism between the first (104) and second (111) rotary members; such that the projection (106) formed in the first rotary member (104) securely holds the resilient members (103) in the windows.
2. The enclosed window damper system (101) as claimed in claim 1, wherein the projections (106) are formed in the first rotary member (104) from one edge to the other edge in radial direction and have a slit (107) at either side of the projection (106).
3. The enclosed window damper system (101) as claimed in claim 1, wherein the resilient members (103) are coil springs.
4. A clutch disc assembly having a enclosed window damper system, the damper system comprising a plurality of windows (105), such that each window (105) have at least one coil spring (103) arranged therein, characterized in that each window (105) is covered with a cover (106) formed in first rotary member (104) and have a slit (107) at each side of the formed window (105) such that the said cover (106) retains the coil spring (103) in position within the window (105) and the slit (107) allow effective movement of one or more coil spring (103) during torque transmission..