FORM 2
THE PATENT ACT, 1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(Section 10; rule 13)
“AN IMPROVED CLUTCH RELEASE BEARING”
APPLICANT NATIONALITY ADDRESS
DELUX
BEARINGS PVT.
LTD.
INDIAN Shop No.31/A, 32,
Ideal Industrial Estate, Mathuradas
Mill Compound, 124, Delisie
Road, Mumbai, Maharashtra
400013
THE FOLLOWING COMPLETE SPECIFICATION PARTICULARLY DESCRIBES
THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
TITLE:
An Improved Clutch Release Bearing
FIELD OF THE INVENTION:
The present invention mainly discloses an improved form of clutch release bearing which
incorporates novel features viz. vibration pads between the hub and the bearing, a
polyamide hub, a fork resting plate, bearing cover and sleeve to be moulded in polyamide
material, a grease reservoir in hub for lubricating sleeve, a wax/heat plug for temperature
indication, grooves in inner ring to entrap dust particles, sealing paste to trap contaminants
and cool down bearing, rubber seals at both ends with sheet metal cover over the entire
bearing and a built in locking clip with self-centring mechanism, the said features,
collectively enhancing the performance and life of the said clutch release bearing.
BACKGROUND & PRIOR ART:
Majority of automobiles are equipped with clutches which is used to disconnect the
transmission from the engine with the help of mechanical linkages, hydraulic or pneumatic
systems. Hence, by pressing the clutch pedal, the clutch is disengaged cutting off the
power from the engine to transmission. To disengage the clutch, a clutch release bearing or
throw out bearing is used. The release bearing is the most important aspect of clutch
operation. When the clutch pedal is depressed, the release bearing moves toward the
flywheel, pushing in the pressure plate's release fingers and moving the pressure plate
fingers or levers against pressure plate spring force. This action moves the pressure plate
away from the clutch disc, thus interrupting power flow. Mounted on an iron casting called
a hub, the throw-out bearing slides on a hollow shaft at the front of the transmission
housing. It decreases the friction between the release fork and the clutch pressure plate
levers, preventing them from wearing out. To do this efficiently, the bearing should be
finely lubricated. For a smooth ride, it is essential that clutch and its adjacent parts operate
smoothly hence many of the parts such as mechanical linkages and the release bearings are
lubricated. Release bearings are subjected to extensive wear and tear due to which the
temperature increases, thereby leading to an early failure of clutch bearings. Overheating
of the bearing causes the grease to escape due to which there is dry sliding of the hub. It is
difficult to determine the heating of the bearing because as such economic indicator is not
present which can help in avoiding further damage to bearing and clutch. Non-lubricated
operation of the hub creates friction and excessive wear of the hub. This causes eccentric
loading of the release bearing leading to premature failure. The hub of the existing release
bearings is made of cast iron which weighs more, contributing to imbalanced load on the
bearing thereby increasing wear. These casting hubs are prone to blow holes. The weight
of the hub plays a crucial role in performance of bearing especially in case of Heavy
Commercial Vehicles (HCV). It is not possible to observe the bearings once they are
assembled as the performance of the bearing is evaluated by the noise when they are
rotating. Noise is usually generated owing to vibrations caused directly or indirectly by the
bearing on surrounding structure. These vibrations can travel to other systems and hamper
the functions of other components such as mechanical linkages, hydraulic, pneumatic
actuators, clutch pedal, bolts, etc. creating unpleasant noise. One of the reasons for
vibrations is also contaminants. The said clutch release bearings are subjected to operate in
contaminated conditions due to which dirt particles may enter the bearing and can be over
rolled by the rolling elements. Also, contaminants affect the quality and performance of the
grease; these contaminants are retained in the grease and damage the balls, the cage, the
ring raceways any many other components owing to which bearing fails. Though seals are
provided to avoid the contaminants from entering the bearing and retain good quality
grease, contaminants still enter the bearing thereby leading to deterioration of the clutch
bearing.
Pertaining to prior art documents, US Patent mainly discloses US4529075 a clutch release
bearing which comprises an actuator member whereby it is adapted to act on a clutch
release device of a clutch mechanism and an operating member whereby it is adapted to be
acted on by a control member. The actuator member is axially coupled to the operating
member by a cover. Snap-action engagement means between the cover and the operating
member comprise at least one elastically deformable lug on the operating member and at
least one retaining shoulder on the cover adapted to cooperate with the elastically
deformable lug on the operating member. The clutch release bearing is suitable for
"traction" type applications, in automotive vehicles.
However, the said prior art uses a regular ball bearing whereas the present invention
mainly uses a bearing the bearing has an Angular contact in nature wherein the ring
profiles of the bearing are modified Further, the said prior art does not include any
mechanism by which entire actuation is lubricated to ensure smooth actuation and also any
mechanism to absorb high shocks and impacts onto the release bearings to increase the life
and reduce the damage on the bearing is absent.
Further, Patent No. US4555190 discloses an improved self-centring bearing assembly for
clutch release mechanism which includes a radial bearing with a rotatable inner and
nonrotatable outer race. The outer race is resiliently held for radial self-centring movement
by an attachment member which mounts the bearing assembly to a plastic carrier of the
clutch release mechanism. The resilient element that allows self-centring is compressed
between a radial flange of the attachment and a face of the outer race. When removed from
the carrier, the resilient element expands sufficiently to bias the radial flange into a radially
extending portion of a declutching finger contacting member rigid to the inner race. This
retains the attachment member to the bearing as a separately handled, rattle-free unit. The
spacing between that portion of the contact member and the face of the outer race against
which the resilient element bears is small enough not only to allow unitization, but also
small enough that when the resilient element of the mounted bearing assembly is
compressed, the resulting gap between that portion of the contact member and the radial
flange is just sufficient to allow relative rotation of the races, so that the bearing is
shielded. Therefore, the extension of the contact member has both, a retention and a
shielding function in cooperation with structure already present for other purposes.
However, even though the said prior art comprises of a similar shielding via cover, it does
not contain a light weight hub, vibration damping pads, grease reservoir, sealing paste,
thermal indicator and grooves in ID of inner ring.
Patent No. JPH10176724A is mainly oriented towards decreasing weight and compact a
device as a cost is reduced. An out-flange part is integrally moulded at a sleeve made of
resin which axially slides over the front cover of a transmission through operation of a
release fork. The inner ring of a ball bearing is inserted externally of the outer periphery of
the sleeve with a radial gap there between. A side plate made through press of a steel plate
is partially arranged in a position of contact of the flange part with the release fork and the
side plate is moulded integrally with the flange part. An elastic means is located between
the sleeve and the outer ring flange part of the ball bearing and the outer ring flange part is
resiliently pressed against the flange part of the sleeve and the ball bearing is held in an
aligning manner. However, in the said prior art, the mechanism through which bearing is
fastened to the body is done via Belleville spring clip, while in the present invention it is
through a sheet metal that is crimped cover Further, the bearing raceways are made of
sheet metal which are suited for smaller vehicles whereas the present invention is mainly
suited for bearing which are used in larger vehicles. Further, the present invention consists
of vibration damping pads, grease reservoir, sealing paste, thermal indicator, grooves in ID
of inner ring which is absent in the said prior art.
Also, Patent No. US3604545 is concerned with improved ball bearings for clutch
mechanism, wherein the bearing races engaged by the balls are impressed in annular
members consisting of rolled steel sheet to which a suitable contour is given, members
being provided for incorporating the bearings in the clutch mechanism and possibly
imparting a self-centring characteristic thereto, means being also provided for making said
bearing self-lubricating and noiseless in actual service. The said prior art consists of races
made of two rolled steel sheets without any claims on hub whereas the present invention
consists of a polyamide hub with groove to trap contaminants. Also, the said prior art
depicts a radial ball bearing whereas in the present invention, an angular contact bearing is
used. Further, in the prior art, baffles are provided to protect the bearing but in the present
invention, seals and sealing paste is provided to entrap the dust particles. Also, in the prior
art, a self-lubricating, synthetic elastomeric vibration damping material is provided
whereas, in the present invention, grease reservoirs are provided with different damping
pads and also comprises of a thermal indicator which indicates the overheating of the
bearing.
Patent No. US4566578 mainly discloses a clutch release bearing and a bearing carrier
assembly comprising a support flange proximate an end of the carrier member and a pair of
resiliently flexible lugs on the bearing housing face in engagement with the carrier flange
disposed each in a pocket formed in the peripheral surface of the carrier proximate to the
flange such as to retain the bearing in assembly with the carrier while permitting limited
radial motion of the bearing relative to the carrier for self-alignment and preventing
rotational motion of the bearing housing relative to the carrier. An elastomeric cushion is
preferably disposed on the surface of the carrier flange for permitting limited angular axial
alignment of the bearing with the axis of rotation of the clutch. Lugs are provided for
abutment and are engaged in pockets. Lugs laterally engages a lateral wall of said pocket
whereby said bearing housing rear wall is held against rotation relative to said carrier
member However, in the present invention, there are no lugs provided. Further, in the
prior art, elastomeric cushions are provided to allow limited angular alignment of axis of
rotation whereas in the present invention there are no cushions used. Also, damping pads
are used to damp vibrations in the present invention along with grease reservoir, thermal
indicator, sealing paste and plastic hub are present. Further, in the prior art, longitudinal
grooves are provided on the bearing for guiding lugs whereas in the present invention there
are circumferential grooves on inner ring ID.
OBJECT OF THE INVENTION:
It is the object of the present invention, to provide an improved form of clutch bearing
which enhances the performance of the said clutch release bearing.
It is also the object of the present invention, to provide an improved form of clutch bearing
which increases the life duration of the said clutch bearing.
It is also the object of the present invention, to impart novel features to the said clutch
bearing such as vibration pads between the hub and the bearing, a polyamide hub, a fork
resting plate bearing cover and sleeve to be moulded in polyamide material, a grease
reservoir in hub for lubricating sleeve, a wax/heat plug for temperature indication, grooves
in inner ring to entrap dust particles, sealing paste to trap contaminants and cool down
bearing, rubber seals at both ends with sheet metal cover over the entire bearing and a built
in locking clip with self-centring mechanism, the said features collectively are not present
in any of the prior arts as discussed above.
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 shows a cross sectional view of the entire clutch bearing assembly
Figure 2 shows a perspective view of the polyamide hub
Figure 3 and Figure 4 show a perspective view of the grease reservoirs
Figure 5 and Figure 6 show a perspective view of the thermal indicator
Figure 7 shows the blown up view of the four layer contaminant protection.
DETAILED DESCRIPTION OF THE INVENTION:
The present invention will now be described with the help of the accompanying drawings
wherein the same numerals are used to denote the same part. However, the drawings only
illustrate the invention and in no way limit the invention.
In a preferable embodiment of the said invention, the improved clutch release bearing
comprises a light weight polyamide hub (1) provided with grease pockets (6) from which
grease oozes out at high temperatures and lubricates the transmission input shaft thereby
reducing the friction generated at high temperatures as bearing slides. The grease seeps
through grease vent (10) and helps in cooling the bearing. This grease is retained within the
hub (1) by shield cover (7) for grease reservoir. The hub (1) consists of a sheet metal insert
which serves as a fork resting pad (11). The fingers of the fork are in contact with hub (1)
at this point and move along a pivot pushing or pulling the bearing and thus engaging or
disengaging the clutch. Fork can be mechanically or hydraulically actuated. The housing
comprises of a splined bore from which the transmission input shaft passes. The bearing
along with housing slides over this input shaft. Shaft is provided with splines to guide the
hub (1). Housing consists of a thermal indicator at the bottom, a plastic heat plug is
inserted in a hole which melts when the bearing is subjected to abnormal temperatures. A
groove is provided on the hub (1) where a circlip (8) is used for locking. A vibration
damping pad (5) is inserted in a recess provided on the hub (1). A sheet metal cover (12)
houses the vibration damping pad (5) with sheet mentioned as spacer (13) at the top on
which the angular contact ball bearing rests. The angular contact bearing consists of inner
ring (2), outer ring (18), cage (14), balls (16), seals (3), steel inserts, Belleville spring and
grease designed considering temperature, load, fit and function, speed, etc. One of the rings
is fixed while other rotates and Belleville spring is used to achieve self-centring of the
bearing. The inner ring (2) is provided with grooves (17) to trap the dust particles. A
sealing paste (9) is provided between inner ring (2) and hub (1) to trap the contaminants
escaped from the inner ring (2) grooves (17). Bearing is protected from environment with
the help of a cover (4) which is crimped over the outer ring (18) and sits in the recess of
hub (1). When the clutch pedal is pressed, the force is transferred hydraulically,
pneumatically or mechanically to the slave cylinder or through cables to the fork which
moves along a pivot. This movement of the fork pushes or pulls the clutch release bearing
owing to which the clutch engages or disengages. Herein below, the components of the
said clutch bearing are described along with its assembly.
POLYAMIDE HUB:
A Cast iron hub is replaced by a polyamide hub thereby achieving 30% weight reduction.
The hub weight is balanced to ensure symmetric load on the CRB. Hence, the bearing
weight is estimated to reduce from 2 kg to 1.25 kg. Also, it prevents the slippage of bearing
due to integrated moulding of sheet metal cover and Hub OD. Also, reduction in weight
minimises unbalancing thereby increasing bearing life by around 0.05% as the radial
weight acting on the bearing is greatly reduced because bearing weight and hub weight is
taken by the bearing. The polyamide will be moulded with sheet metal cover forming a
single unit. The fork resting plate is made of hardened steel strip and moulded with the
hub. There is no relative motion between the cover and the hub hence 100% motion
transfer is achieved while declutching. The hub bore is coated with solid lubricants to
reduce friction. The solid lubricant endures the elevated temperatures, dust particles and
uneven duration of loading unloading cycles. Effective lubrication reduces wear of the hub
thereby imparting prolonged life to the bearing. Hub manufacturing cost can be reduced for
mass production. Also, moulding process ensures uniformity of hub structure.
GREASE RESERVOIR:
A covered grease reservoir is provided to store more grease for lubrication of carrier sleeve
and sleeve to ensure that there is no dry sliding of hub. Further, the pocket shaped grease
reservoir provided in hub enables autonomous maintenance as grease will ooze out of the
passage provided at the grease pockets as the temperature increases. This grease then will
flow to hub bore and lubricate sleeve. Hence, the temperature rise leading to overheating
and failure of bearing can be controlled. Further, frequent greasing on the release bearing
for every short interval can be minimised. Also, due to reduced servicing of vehicle, the
downtime is decreased thereby leading to cost savings for the owner.
THERMAL INDICATOR:
A coloured heat sensing plug is inserted in at the bottom of the hub at a position which is
accessible to mechanics. These plugs indicate excessive heat generation of the bearing.
This indicator can be melted off or discolouration can be observed. The Thermal indicator
will indicate the highest operating temperature thus, signalling the rise in temperature that
the bearing has reached. Therefore, with the evidence from the indicator, the bearing can
be replaced. The said thermal indicator indicates that the Clutch Release Bearing has
undergone abnormal working conditions as the temperature has crossed the predetermined
value. This indicates that the Clutch Release Bearing is to be replaced to avoid
malfunctioning of the clutch. Due to thermal indicator, mechanics can judge whether to
replace or service the said part. Therefore, this leads to minimisation of costs of the repairs.
FOUR LAYER CONTAMINANT PROTECTION:
For the said protection, grooves are provided in Inner race ID which will accumulate the
contaminants from the clutch wear and surroundings and reduce the contamination layer. A
sealing paste is applied between the sleeve OD and the Inner ring ID to obstruct the dust
particles from entering the bearing. This paste also helps in cooling down the bearing. The
rubber seals are provided at both ends ensuring positive sealing at both ends which will not
allow the dust to enter the bearing. A sheet metal cover is also provided for entire bearing
thus protecting the bearing from environmental dust.

We claim:
1. An improved clutch release bearing compromising of a hub with an inner ring and
an outer ring wherein the bearing is mounted on a transmission input shaft that slides over
it for clutch actuation, wherein the said bearing further comprises of vibration pads, a fork
resting plate, a grease reservoir, a wax or heat plug and grooves in the said inner ring.
2. A hub as claimed in claim 1 which is made of polyamide and integrated with
sheet metal, the fork resting plate is made of hardened steel strip and molded with the said
hub and wherein the said hub consists of a bore through which an input shaft passes.
3. The bore of the hub as claimed in claim 2 is coated with molybdenum disulphide
to reduce the friction and improve the sliding of bearing over the said input shaft.
4. The grease reservoir as claimed in claim 1 wherein grease or solid lubricant is
stored and comprises of a cover and a vent from where the greases comes out and spreads
over the input shaft.
5. A wax or heat plug as claimed in claim 1 which comprises of thermal indicator
wherein the said indicator melts or alternatively discoloration takes place in the indicator
assembly to indicate the degree of deterioration of the said part.
6. The vibration pad as claimed in claim 1 which comprises of Hydrogenated
Acrylonitrile Butadiene Rubber with Cold Rolled Close Annealed steel sheet which is
placed between the hub and the bearing resting face to absorb vibrations, compensate axial
misalignment and absorb shocks.
7. The vibration damping pad mentioned in claim 5 is placed in a sheet metal cover
between hub and bearing.
8. The clutch release bearing as claimed in claim 1 wherein the said bearing is
provided with a sealing paste between the outer diameter of the hub sleeve and inner
diameter of the bearing inner ring to entrap contaminants.
9. The clutch release bearing as claimed in claim 1 wherein the said bearing consists
of a sealing means at both ends of bearing and the said bearing is covered with sheet metal
cover for protection