DESC:Field of the invention:
The present invention relates to a shock absorber and more particularly relates to shock absorber with controlled damping force.
Background of the invention:
Normally in automotive suspension systems, the shock absorbers are employed to absorb the vibration energy that causes vibrations in the vehicle body in order to provide for a better riding comfort of the vehicle. This achieved by the tension and compression damping functions of the shock absorber to suppress the relative displacement between the vehicle body and a suspension member so as to suppress attitude change for driving stability. The driving comfort and the driving stability are achieved by absorbing a high frequency vibration and damping the low frequency vibrations.
The major functionalities of shock absorber, the tension and the compression damping are depending upon certain preset values. These values are one time set while manufacturing/ assembling and there is no provision of adjustments. During movement of the piston in the damper, oil flows through piston holes. Resistance to the oil flow is experienced as the damping force. Damping force or resistance to oil flow path is the key function of the shock absorber, which is mainly controlled by
a) Number of holes and its size on piston
b) Number of plate valves, its thickness, number of holes and size.
c) Piston differential height and flatness affecting oil flow path
One of the major contributions to damping force / oil flow path at low velocities is piston differential height and flatness, which is controlled by gap between piston face and plate valve seating face. Piston manufactured through sintering process has its own limitations in maintaining consistent geometrical accuracies on face and will affect achieving slot consistency.
Accordingly, there exists a need to simplify the design of piston head and the piston rod so as to reduce the time required for damper assembly.
Summary of the invention
The invention provides a shock absorber with controlled damping force. The shock absorber comprising an outer tube, an inner tube slidable in the outer tube, and a piston assembly having a piston with plurality of piston holes, a piston rod having one end connected to the piston at other end extending through the inner tube and a slotted plate valve. The slotted plate valve comprises a plurality of semicircular cuts at the outer diameter thereof and a plurality of circular cavities alongside the centre opening thereof, is fitted between the piston and a retainer valve; wherein, the piston oil flows through the gap between piston face and slotted plate valve at low velocities and at high velocities, the piston oil passes through a piston holes and the slotted plate valve, causing deflection of the slotted plate valve and providing a resistance to the piston oil flow, thereby adjusting the damping force.
Objects of the invention:
An object of the present invention is to provide consistent damping force at low velocities through predesigned slotted plate valve of the shock absorber.
Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows a cross sectional view of a shock absorber piston assembly in accordance with the present invention,
Figure 2 shows a cross sectional view of a shock absorber piston with slotted plate valve in accordance with the present invention.
Figure 3 shows a perspective view of a slotted plate valve in accordance with the present invention.
Detailed description of the embodiments:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The invention provides a shock absorber with an inner tube, outer tube and a piston assembly. The piston assembly controls the damping force by employing a specially designed plate valve. Thus the damping force can be predesigned and predicted for low velocity functioning.
The present invention is illustrated with reference to the accompanying drawings, wherein numbers indicated in the bracket represent the components of the invention throughout the description.
Table:
Component No: Component name:
100 shock absorber
1 Lock nut
2 Piston
3 Piston ring
4 Retainer valve
5 Piston rod
10 Slotted valve
20 Gap
30 Piston face
50 piston assembly

Referring to Figure 1 a cross sectional view of shock absorber (100) and a piston assembly (50) in accordance with the present invention is shown. A shock absorber (100) includes an outer tube (not numbered); an inner tube (not numbered) and a piston assembly (50). The inner tube is slidable in the outer tube and a piston rod (5) is connected to the piston assembly (50) and extending through the inner tube.
Referring to the figure 1, a piston assembly (50) consists of a piston (2), a retainer valve (4), a piston oil (not shown) and a slotted plate valve (10). The piston rod (5) is configured with a plurality of piston holes. The piston rod (5) having one end connected to the piston (2) and the other end extends through the inner tube. During movement of the piston (2), piston oil flows through piston holes. Resistance to the piston oil flow in the shock absorber (100) is experienced as damping force.
Referring to Figure 3, a slotted plate valve (10) in accordance with the present invention is shown. The slotted plate valve (10) is a flat metallic disc with an opening at the centre. The slotted plate valve (10) comprises a plurality of semicircular cuts at the outer diameter and a plurality of cavities made in a circular fashion alongside the centre opening thereof. The cavities are of identical in shape and size. The slotted plate valve (10) is inserted into the piston rod (5) through the centre opening and is placed in between the piston (2) and the retainer valve (4). The retainer valve (4) holds the slotted plate valve (10) at the inner circumference and provides a gap (20) between the piston face (5) and slotted plate valve (10). This gap (20) facilitates a controlled piston oil flow at lower velocities. Also the semicircular cuts and cavities of the slotted plate valve ensure a fixed oil flow at lower velocities.
Again referring to the figures 1 to 3 in an operation of the slotted valve, at low velocities, the piston oil passes through the gap (20) between piston face (30) and slotted plate valve (10). At higher velocities the piston oil passes through piston holes and the slotted plate valve (10). This causes deflection of the slotted plate valve (10) and provides a resistance to the piston oil flow.
The resistance to the piston oil flow through the holes in piston (2) and slotted plate valve (10) combination is a resultant of required damping force that contributes to the ride comfort. Thus the piston assembly (50) provides a damping force that can be predesigned and predicted for low velocity functioning.
Any changes in the design of the piston oil flow path or volume of piston oil transfer affects the damping force. Piston face (30) flatness and evenness is one of the most critical parameter for achieving required damping force. Hence the piston face (30) is kept constant and the gap (20) is maintained through the pressed part of the slotted plate valve (10).
Advantages of the invention:
• Slot size is precisely controlled while slot preparation in slotted plate valve (10), independent of piston process limitations.
• Damping force at low velocities is consistent and can be preset while designing.
• The gap (20) maintained by adjusting the slotted plate valve gives a much easier, accurate and economic may of achieving the piston oil flow through the slotted plate valve (10).
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.
,CLAIMS:We claim:
1. A shock absorber (100) with controlled damping force, the shock absorber comprising:
an outer tube;
an inner tube slidable in the outer tube; and
a piston assembly (50) having a piston (2) with plurality of piston holes, a piston rod (5) having one end connected to the piston (2) at other end extending through the inner tube, and a retainer valve (4);
characterized in that a slotted plate valve (10) comprising a plurality of semicircular cuts at the outer diameter thereof and a plurality of circular holes alongside the centre opening thereof, is fitted between the piston (2) and a retainer valve (4);
wherein, at low velocities, the piston oil flows through the gap (20) between piston face (30) and slotted plate valve (10) and at high velocities, the piston oil passes through the piston holes and slotted plate valve (10), causing deflection of the slotted plate valve (10) and providing a resistance to the piston oil flow, thereby adjusting the damping force.

Dated this 23 February 2018

Prafulla Wange
(Agent for Applicant)
IN/PA-2058