GB1603420A

GB1603420A - Hydraulic shock absorbers

Info

Publication number: GB1603420A
Application number: GB3220077A
Authority: GB
Original assignee: Jonas Woodhead Ltd
Current assignee: Jonas Woodhead Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-11-25

Description

(54) HYDRAULIC SHOCK ABSORBERS (71) We, JONAS WOODHEAD LIMITE, a Company registered under the laws of England, of 177 Kirkstall Road, Leeds, LS4 2AQ, Yorkshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :- This invention relates to hydraulic shock absorbers comprising a working cylinder, a piston reciprocatable in the working cylinder, a piston rod to one end of which the piston is attached and the other end of which extends out of one end of the working cylinder through a piston rod seal, and valve means carried by the piston and controlling flow through the piston in both directions.

In the most common construction, the piston has two rings of axially extending passages flow through which is controlled by annular discs which are themselves of springy material or which are controlled by back-up spring discs. It has also been proposed to provide a single ring of axially extending passages alternate ones of which are controlled by spring-loaded poppets at one end to control flow in one direction and the remaining ones of which are controlled by spring-loaded poppets at the other end to control flow in the opposite direction.

In each of these prior constructions, the valving is located in the annular zone be tween the piston rod and the working cylinder or the annular zone between the working cylinder and the imaginary cylinder produced by projecting the cross-section of the piston rod. These zones are narrow and accordingly to obtain the necessary flow a plurality of passages and valves for each direction is required, leading to complexity and expense.

According to the present invention, a hydraulic shock absorber comprises a working cylinder, a piston reciprocatable in the working cylinder, a piston rod to one end of which the piston is attached and the other end of which extends out of one end of the working cylinder through a piston rod seal, and valve means carried by the piston and controlling flow through the piston in both directions, the valve means being located on the side of the piston remote from the piston rod seal and comprising two passageways, each passageway being in communication with port means through the piston and each passageway containing a valve closure member cooperating with a valve seat which faces substantially axially of the piston, and the width of each passageway at the point where the valve closure member engages the seat being such that it extends inwardly in a direction radial of the piston into the imaginary cylindrical space formed by projecting in a direction axial of the piston rod the cross section of the portion of the piston rod adjacent the side of the piston rod seal.

In a preferred construction, the end of the piston rod which is attached to the piston has a portion of reduced cross section to which the piston is attached and the width of each passageway at the point where the valve closure member engages the seat is such that it extends inwardly in a direction radial of the piston into the imaginary cylindrical space formed by projecting in a direction axial of the piston rod the cross section of the portion of the piston rod of reduced cross section.

The invention may be carried into practice in various ways but one hydraulic shock absorber embodying the invention will now be described by way of example with reference to the accompanying drawings, in which : Figure 1 is a longitudinal section of the part of the shock absorber in the region of the piston; and Figure 2 is a view on the line A-A of Figure 1.

The shock absorber comprises a working cylinder 1 closed at the right-hand end by the usual end fitting and closed at the left-hand end by a piston rod seal through which passes a piston rod 2 having a reduced threaded shank 3 on to which is screwed a piston 4 having a circumferential groove containing an O-ring 5.

Secured to the right-hand end of the piston of the piston as seen in Figure 1 is a valve housing 6 which is wholly located beyond the end of the reduced shank 3.

The housing contains a first axially extending passage 7 having a reduced portion 8 forming a valve seat 9 which cooperates with the head 11 of a poppet 12 a flange 13 on which is engaged by one end of a valve spring 14 the other end of which engages on a shoulder 15 on the valve housing.

The valve housing 6 has a second axially extending passage 16 comprising a first cylindrical portion 17 (of non-circular crosssection as can be seen in Figure 2) and a second cylindrical portion 18 of smaller cross-sectional area. A stud 19 extends through the portion 18 and has a reduced shank 21 which is staked to a plate 22 which is of generally rectangular shape but the ends are arcuate as can be seen in Figure 2 so that the plate is located in the cylindrical portion 17 of the passage 16. Sliding on the stud 19 is an annular valve disc 23 which engages on a seat 24 formed on the valve housing around the mouth of the cylindrical portion 18 of the passage 16.

The valve disc 23 is held against the seat by a compression spring 25 one end of which bears against the valve disc and the other end of which bears against a head 26 on the stud 19.

A port 27, which may be circular or arcuate in cross-section, extends through the piston 4 and communicates with the passage 7 and a port 28, which may also be of circular or arcuate cross-section, extending through the piston 4 and leads into the cylindrical portion 17 of the passage 16.

It will be noted that part of each of the passages 7 and 18 lies within the projection of the reduced shank 3 of the piston rod.

The shock absorber operates as follows.

On compression, the loading of the spring 14 is overcome and the head 11 of the poppet 12 moves away from the seat 9 to allow flow from the right-hand side of the piston through the passage 7,8 and the port 27 to the left-hand side of the piston.

During this time the valve disc 23 is held on the seat 24. On rebound, the poppet 12 is held on the seat 9 while the valve disc 23 moves away from the seat 24 against the force of the spring 25 and flow occurs through the port 28, the cylindrical chamber 17 and around the sides of the plate 22, through the passage 18 and past the seat 24 to the right-hand side of the piston.

Claims

WHAT WE CLAIM IS :-

1. A hydraulic shock absorber comprising a working cylinder, a piston reciprocatable in the working cylinder, a piston rod to one end of which the piston is attached and the other end of which extends out of one end of the working cylinder through a piston rod seal, and valve means carried by the piston and controlling flow through the piston in both directions, the valve means being located on the side of the piston remote from the piston rod seal and comprising two passageways, each passageway being in communication with port means through the piston and each passageway containing a valve closure member cooperating with a valve seat which faces substantially axially of the piston, and the width of each passageway at the point where the valve closure member engages the seat being such that it extends inwardly in a direction radial of the piston into the imaginary cylindrical space formed by projecting in a direction axial of the piston rod the cross section of the portion of the piston rod adjacent the side of the piston adjacent the piston rod seal.

2. A hydraulic shock absorber as claimed in Claim 1 in which the end of the piston rod which is attached to the piston has a portion of reduced cross section to which the piston is attached and the width of each passageway at the point where valve closure member engages the seat is such that it extends inwardly in a direction radial of the piston into the imaginary cylindrical space formed by projecting in a direction axial of the piston rod the cross section of the portion of the piston rod of reduced cross section.

3. A hydraulic shock absorber as claimed in Claim 1 or Claim 2 in which the passageways extend parallel to the axis of the piston.

4. A hydraulic shock absorber as claimed in Claim 1, 2 or 3 in which the valve closure members are spring-loaded.

5. A hydraulic shock absorber as claimed in Claim 4 in which one of the valve means is a poppet valve.

6. A hydraulic shock absorber as claimed in any of the preceding claims in which one of the valve means comprises: a stud which extends axially of the piston and is stationary with respect to the piston and extends through the seat of the valve ; an annular valve disc which is movable axially on the stud toward and away from the seat; and a spring extending between the stud and the disc and biassing the disc against the seat.

7. A hydraulic shock absorber substantially as described herein with reference to the accompanying drawings.