DESC:Field of the invention
The present invention relates to a shock absorber of a vehicle, and more particularly, the present invention relates to improvement of the structure of a shock absorber piston rod assembly.
Background of the invention
Currently, pistons are retained on a piston rod either by (A) Torqueing, (B) Torqueing and riveting, or (C) by Riveting. Specifically, the pistons are located on the piston rod with a designed clearance. The piston rod and piston has run-out to the degree of clearance between hole and shaft while retaining the piston assembly. This process constraint leads to rubbing on one side of piston assembly and deteriorates the performance of the piston functioning. Also, torque values for tightening the nut onto piston rod plays a major role of excess and low fastening, resulting in damping force rejections.
Since this method is associated with threading on piston rod and an additional part piston nut, the cost associated is high for obtaining the designed retaining and centering function of piston holding to piston rod.
Accordingly, there exists a need to provide a method for retaining a piston on a piston rod that overcomes the drawbacks of the prior art.
Objects of the invention
An object of the present is to provide a method of retaining piston on a piston rod with self-centering effect, in a shock absorber piston assembly.
Another object of the present invention is to reduce friction of the piston within the assembly thereby improving the durability and performance of the shock absorber.
Still another object of the present invention is to provide an economic method of assembling shock absorber piston.
Summary of the invention
The present invention provides a method of retaining piston on a piston rod with self-centering effect; in a shock absorber piston assembly. In this method, piston is modified to have a chamfer on riveting side. The piston rod is also modified accordingly. Piston rod is then riveted into the piston cavity with defined tool and pressure. This method of retaining piston on a piston rod with self-centering effect increases performance of the piston. With this, a uniform wear on piston and inner tube is observed across the circumference which in turn, helps in enhancing the life of shock absorber.
Brief description of the drawings
The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
Figure 1 shows a shock absorber piston rod assembly in accordance with the present invention.
Figure 2 shows the flowchart for the method of retaining piston on a piston rod with self-centering effect, in a shock absorber piston assembly, in accordance with the present invention.
Detailed description of the invention
The foregoing objects of the present invention are accomplished, 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 present invention provides a method of retaining piston on a piston rod with self-centering effect, in a shock absorber piston assembly. The invented method provides an assembly of piston onto piston rod concentric to each-other thereby minimizing the friction and enhancing the performance of the shock absorber. With this, a uniform wear on piston and inner tube is observed across the circumference.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to figure 1, there is shown a shock absorber piston assembly (100) in accordance with the present invention. The shock absorber piston assembly (100) comprises of a piston rod (10), having piston rod end (10A) riveted concentrically onto a piston (20) having modified chamfer (20A) on the riveting side, at least one model specific plate valve (30) and a retainer (40).
Referring to figure 2, there is shown a method (200) for retaining piston (20) on a piston rod (10) with self-centering effect, in a shock absorber piston assembly, in accordance with the present invention.
At step (110), the method (200) includes configuring the piston (20) to have chamfer (20A) on the riveting side.
At step (120), the piston rod end (10A) is configured to allow the flow of piston rod material into piston chamfer (20A) during the riveting operation.
At step (130), piston sub-assembly is prepared by arranging retainer (40), plate valves (30) and piston (20) concentrically, the plate valve (30) in between the retainer (40), and the piston (20) and the piston chamfer (20A) at the outer side. Number of plate valves (30) is decided based on the damping force requirements.
At step (140), the piston sub-assembly is inserted into the piston rod (10) guide diameter with the piston chamfer (20A) at the piston rod end (10A) side; and

At step (150), the assembly is loaded on a special purpose machine designed to rivet the exposed piston rod end (10A) into the piston cavity with defined tool and pressure. Riveting process is established to obtain required flow of material and piston (20) retaining strength. The riveting operation is done to retain the piston sub-assembly into the piston rod (10). During the operation with modified piston chamfer (20A), the material of piston rod (10) starts self-centering the piston (20) and fills the cavity of the chamfer (20A) uniformly. Once set value of riveting height and width is achieved on the piston rod (10) by spreading the piston rod material, the sub-assembly is unloaded.
Advantages of the invention
• The present invention avoids piston rubbing on one side in assembly because of run-out leading to premature failure of shox or strut.
• With the present invention with modified piston chamfer and riveting method, functioning is improved without affecting the safety requirement.
• The present invention also reduces the machining activity of thread making on Piston rod and Piston Nut is eliminated with this process.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.

,CLAIMS:
We claim:

1. A shock absorber piston assembly (100) comprising:
a piston rod (10), a piston (20), at least one plate valve (30) and a retainer (40), characterized in that,
the piston (20) being configured to have a chamfer (20A) on one side thereof;
a piston rod end (20A) being configured to allow flow of a piston rod material into the piston chamfer (20A) during a riveting operation;
a piston sub-assembly having at least one plate valve (30) arranged concentrically between the retainer (40), and the piston (20), with the piston chamfer (20A) at the outer side, and the said piston sub-assembly inserted into the piston rod (10) guide diameter, with the piston chamfer (20A) at the piston rod end (10A) side and
the piston rod end (10A) riveted into the piston cavity such that the material of piston rod (10) self centers the piston (20) and fills the cavity of the chamfer (20A) uniformly during riveting.
2. The shock absorber piston assembly (100) as claimed in claim 1, wherein the number and pattern of the plate valve (30) is decided depending upon the damping force requirements.
3. A shock absorber piston assembly method (200) for retaining piston (20) on a piston rod (10), the method comprising:
configuring the piston (20) to have a chamfer (20A) on one side thereof;
configuring the piston rod end (10A) to allow flow of a piston rod material into the piston chamfer (20A) during a riveting operation;
forming a piston sub-assembly by concentrically arranging at least one plate valve (30) in between a retainer (40), and the piston (20), with the piston chamfer (20A) at the outer side,
inserting the piston sub-assembly into the piston rod (10) guide diameter, with the piston chamfer (20A) at the piston rod end (10A) side; and
riveting the exposed piston rod end (10A) into the piston cavity with defined tool and pressure to achieve the set value of riveting height and width on the piston rod (10);
characterized in that, the material of piston rod (10) self centers the piston (20) and fills the cavity of the chamfer (20A) uniformly during riveting.
4. The method (200) as claimed in claim 3 wherein the number and pattern of plate valve (30) is decided depending upon the damping force requirements.