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FIELD OF INVENTION
This invention relates to a spring seat for torsion beam type of rear
suspension of vehicle.
BACKGROUND/PRIOR ART
Spring seat for torsion beam type of rear suspension is known to
have been available in the market, for which reference may be
made to fig. 1. The seat is provided at one end of the spring so as
to avoid metallic contact between the spring and torsion beam and
also at other end preventing contact between the spring and
vehicle body. Same seat is used at both ends. Therefore seat at any
end can be considered to describe.
The spring seat is a circular piece, top part of which receives
spring and bottom part of which remains in contact with the
torsion beam. Thus, the seat acts as an isolator preventing metal
to metal contact.
The upper side comprises a top surface (1) and a bottom surface
(2) with a connecting wall (3) therebetween. There is a stopper (4)
as shown in Fig 2a.
Lower side of the seat comprises a top surface(l) and a lip(2) with
an annular space therebetween. The top surface is mounted with a
lug (3) for tight fitment/snap fitting into the torsion beam as
shown in fig 2b.
All of the above are integrated into one single piece to constitute
the spring seat with a hole at its centre.
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A typical standard material for spring seat is vulcanized rubber
with low heat and oil resistance. Hence, the material undergoes
wear and tear after certain cycles.
Due to less stress resistance cracks are developed with usage,
thereby rendering it unfit for further use. This results in reduction
in its useful life span.
Further, it involves ejection (slip) of seat due to non linear
movement of the coil spring. This leads to uneven wear and tear of
the seat. The rubber material also contributes to weight of seat,
which adds to cost.
Now, reference may be made to the following:
JP 2011069446A: The spring seat is formed of an elastic member
and arranged between a coil spring which constitutes the vehicular
suspension and a seat bracket to which the spring seat is
attached. The coil end close-contact part thereof, which the coil
end of the coil spring contacts closely when the coil spring is
compressed and deformed, is formed of a high hardness elastic
member whose hardness is higher than that of the elastic member
other than the coil end close-contact part.
It is made of rubber with variable hardness, which is mounted on
any mounting member of a suspension of vehicle. Here, spring seat
with high hardness elastic material (natural rubber) is provided at
one region and lower hardness on rest of spring seat. Thus, it
involves two different hardness rubber.
Disadvantages
Rubber is heavy in weight
No provision of anti slip means.
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Another prior art teaches a suspension assembling structure,
wherein a suspension link has an engagement hole formed in a
mounting face for a spring seat. The spring seat has a protrusion
formed on the lower face of a seat body and configured to be
brought into engagement with the suspension link by insertion
into the engagement hole. Also, the spring seat has a flange formed
on the outer peripheral surface of a cylindrical portion in a manner
so as to radially protrude through a clearance space defined
between adjacent wires of a coil spring, and configured to hold the
wire of a first turn at the lower end of the coil spring.
It consists of spring seat with cylindrical protrusion on its top
surface for fitment of coil spring lower end. The material used for it
is synthetic resin containing polyethylene. It does not involve any
means to resist slip of spring seat.
US 8414004 B2: A spring seat is mounted to a suspension arm to
receive a coil spring of a suspension, a spring seat body is provided
with a receiving part for receiving the coil spring and a locking
protrusion, which projects from the spring seat body to the side
opposite to the receiving part so as to be locked in a locking hole
formed in the suspension arm, are formed integrally using an
elastic member, and a core material harder than the elastic
member is incorporated in the spring seat body and the locking
protrusion.
It consists of rubber spring seat with metal insert together with a
plurality of locking protrusion of different diameters on its bottom
surface for self stabilization. There is bonding of metallic spring
seat with natural rubber. It is mounted on trailing arm type of rear
suspension.
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Disadvantages
- Rubber is heavy in weight
- No provision of anti slip means.
None of the above can serve the purpose for which the invention
has been designed. Therefore, there is a requirement to develop
novel spring seat of light weight and low cost with the provision of
anti slip means which can efficiently function and at the same time
address various issues of known spring seats.
OBJECTS OF THE INVENTION
The principal object of the present invention is to provide a spring
seat for torsion beam type of rear suspension of vehicle which
obviates limitations of the prior arts.
Another object of the present invention is to provide a spring seat
for torsion beam type of rear suspension of vehicle to prevent
ejection of spring seat during spring operation by providing anti
slip means.
Yet another object of the present invention is to provide a spring
seat for torsion beam type of rear suspension of vehicle which
constitutes simplified design of spring seat with reduction in
weight.
Still another object of the present invention is to provide a spring
seat for torsion beam type of rear suspension of vehicle which is
cost effective and light in weight.
Another object of the present invention is to provide a spring seat
for torsion beam type of rear suspension of vehicle which is
efficient with more durability and improved performance.
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SUMMARY OF THE INVENTION
The present invention provides a spring seat for torsion beam type
of rear suspension of vehicle comprising a upper side having a
stopper on its outer peripheral spring resting surface and lower
side having outer peripheral top surface mounted with a lug and a
lip with an annular space therebetween wherein an improved
spring resting surface is provided on its top part and a plurality of
anti slip ribs in the annular space of its bottom part to prevent
seat ejection.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more
apparent from the ensuing description when read in conjunction
with the accompanying drawings and wherein:
Figure 1 shows: mounting of spring seat between coil spring and
torsion beam in a vehicle;
Figure 2a shows: Upper side of conventional rubber spring seat;
Figure 2b shows: Lower side of conventional rubber spring seat;
Figure 3A shows: Upper side of spring seat according to present
invention;
Figure 3B shows: Enlarged view of depression;
Figure 3C shows: Lower side of spring seat in accordance with
present invention;
Figure 4A shows: Tendency of ejection of spring seat while being
subjected to spring force;
Figure 4B shows: Direction of application of spring force during
wheel articulation;
Figure 5 shows: Wedge shaped anti slip ribs of present invention;
Figure 6 shows: Exemplary embodiment of lug with slit according
to present invention.
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DETAILED DESCRIPTION OF INVENTION WITH REFERENCE
TO THE ACCOMPANYING DRAWINGS
The invention discloses a novel spring seat for rear coil spring in
torsion beam type of rear (RR) suspension of a vehicle.
The spring seat (S) is placed between metallic coil spring (1) and
torsion beam (2) as indicated in fig 1. Now, reference may be made
to fig. 3A for Upper side of the seat, which is having a top surface
(1) and an outer peripheral bottom surface (2) connected by means
of a side wall (4) with the provision of a stopper (3) integrated to
each other as already available in the art.
The improvement in the existing design is discussed hereinbelow.
There is provision of a depression (5) in the bottom surface (2)
(spring resting surface) adjacent to the stopper (3).
Said depression (fig.3B) is provided, so that the spring edge
remains in the depressed space during spring operation i.e. in
dynamic condition of vehicle to counter act hit marks of spring
edge. This leaves no marks on the surface of top part of spring
seat.
The improvement further comprises an annular groove (6) along
the spring resting surface (2) as shown in figure 3A. The groove is
disposed from the end of the depression and preferably upto 300°
as the spring comes in contact with the lower surface maximum
upto 300°.
The annular groove acts as spring resting surface, thereby
reducing stress by proper distribution of load on contact surface
and hence avoiding failure of spring seat.
In contrast to the above feature, currently available spring seat
offers a resting line for spring, which causes more stress leading
to failure of the seat.
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Actually in the present invention, the spring resting surface
distributes the load to reduce stress, which avoids seat's failure.
Again as observed in the fig. 3A, there is partial removal of
material from outer periphery of the seat. Removal of material is
carried out on the opposite side of the depression, which
constitutes low load bearing area. This leads to reduction in
weight and therefore reduction in the cost as well.
Now reference may be made to fig. 3C for Lower side of spring
seat, which comprises an outer peripheral top surface (7) and a
lip (8) with an annular space (9) therebetween integrally provided
as already discussed.
In accordance with present invention, a multitude of anti slip ribs
(10) are accommodated in the annular space and mounted
radially on its inner surface (11) as shown in fig. 3C. In this
exemplary embodiment, the anti slip ribs are directing towards
lip. Alternatively, said ribs can be mounted on the lip itself
directing towards the inner surface i.e. ribs can protrude radially
in opposite direction.
The ribs counteract nonlinear movement of coil spring resulting in
ejection of seat during operation of spring while the vehicle is in
motion as in fig. 4A and resulting in uneven wear and tear. Fig.4A
indicating direction of resultant force (D) and rotational tendency
of spring seat due to application of spring force (R). Therefore,
plastic seat of invention has been optimized relying on actual
force direction from coil spring and rotation pattern of the spring
seat by providing anti slip ribs.
The ribs are preferably wedge shaped as shown in fig. 5 so as to
facilitate ejection of the part from moulds and for
manufacturability.
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During shock loadings in the form of side twisting and bending
forces were previously transferred directly into the spring seat
causing distortion and/or excessive wear of the spring seat. By
adopting the construction of this invention, shock loading can be
at least in part absorbed by the plastics seat and in particular by
the ribs which resiliency transfer twisting/bending loads to the
torsion beam mating area whilst keeping the spring seat under
compression as in fig. 4A and Fig. 4B indicating direction of
application of spring force (D) of spring (P) on the seat (S) during
wheel articulation.
Furthermore, by varying the geometry of the spring seat (S) (fig.
4B) it is possible to develop different degrees of resilience in the
assembly, so that performance can be optimized. Because of the
built-in resilience (variable thickness of seat) by keeping a>b
(thickness of sidewall is more than outer peripheral part) the
instantaneous stresses on the parts are reduced, thereby
minimizing the risk that the part will be broken by shock loading,
as is the case with current designs. These are being confirmed by
CAE results.
The top flat surface (7) of Lower side is having a lug (L) for snap in
fitment for proper seating of the seat in the torsion beam. For
enlarged view of lug, reference may be made to fig. 6.
As the seat is made of plastic material, therefore it is not flexible
like rubber seat. For proper fitment of the plastic seat in torsion
beam, the snap-fit region of the lug is having a slit (T) bifurcating
the region into two ribs (R) preferably semi-circumferential in
shape that the ribs are spaced apart axially.
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This construction provides the lug with an ability to deflect
resiliently in response to the insertion loading which is
encountered during assembly and at the same time flat contact
between upper surface of the ribs & mating surface of the torsion
beam ensuring high pull out force throughout the service load.
Considering severe fatigue load carrying application, a special
grade of engineering plastics being selected which has
considerable better stress and crack resistance compared with
other alternatives available.
A special variant of plastic raw material in spring seat is selected
which can meet durability & performance of equivalent rubber
spring seat. Linear low density polyethylene plastic can be
considered which has high stress crack resistance, heat
resistance, low temp characteristics, stress crack resistance & is
suitable for fatigue load application of the order ~ 5000 N.
Chemical resistance of the plastic material is better than rubber.
The plastic material is mere an example without restricting scope
of the invention to the same. Thus other suitable materials readily
apparent to a person skilled in the art are understood to be within
scope of this invention.
Spring seat of invention is a single piece manufactured preferably
by moulding such as injection moulding, extrusion blow
moulding.
It is to be noted that the present invention is susceptible to
modifications, adaptations and changes by those skilled in the art.
Such variant embodiments employing the concepts and features of
this invention are intended to be within the scope of the present
invention, which is further set forth under the following claims:-

Af\\~
WE CLAIM: ' C% ':' " V->-. r ** ' v
/ • • '••' * i i AUG
1. A spring seat for torsion beam type of rear suspension of vehicle
comprising a upper side having a stopper on its outer
peripheral spring resting surface and lower side having outer
peripheral top surface mounted with a lug and a lip with an
annular space therebetween wherein an improved spring resting
surface is provided on its top part and a plurality of anti slip
ribs in the annular space of its lower side to prevent seat
ejection.
2. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in claim 1, wherein the spring resting surface
comprises a depression (depressed region) adjacent to said
. stopper so as to counteract hit marks of spring edge.
3. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in claim 1 or 2, wherein an annular groove is
disposed from the end of said depression along the spring
resting surface.
4. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in any of the preceding claims, wherein the anti slip
ribs are mounted on inner surface of the annular space
directing radially towards lip.
5. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in any of the preceding claims, wherein the anti slip
ribs are mounted on the lip directing radially towards inner
surface of annular space.
v rA
. • * • * " H
F&t^
6. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in any of the preceding claims, wherein the ribs are
preferably wedge shaped to facilitate manufacturing.
7. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in any of the preceding claims, wherein the lug is
having a slit axially in snap fit region bifurcating the region into
two ribs preferably semi-circumferential in shape that the ribs
are spaced apart axially for proper fitment of the seat in torsion
beam.
8. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in any of the preceding claims is made of suitable
grade engineering plastic such as herein described.
9. A spring seat for torsion beam type of rear suspension of vehicle
as claimed in any of the preceding claims, wherein the seat has
variable thickness.
10. A spring seat for torsion beam type of rear suspension of
vehicle as claimed in any of the preceding claims comprises
outer periphery with a cut section on opposite side of the
depression to eliminate low load bearing area for weight
reduction.
Dated this 8th day of August, V / 2014
\ & ^
(SOMA RANI MISHRA)
OF L.S.DAVAR & CO.,
APPLICANT'S AGENT