GB2153483A

GB2153483A - Fluid-pressure springs

Info

Publication number: GB2153483A
Application number: GB08401900A
Authority: GB
Inventors: Robert Howell Marjoram
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1984-01-25
Filing date: 1984-01-25
Publication date: 1985-08-21
Also published as: GB2153483B; GB8401900D0

Abstract

A fluid pressure spring, e.g. for a motor car suspension incorporates a pair of liquid-filled chambers 30,31 communicating with one another through a damper valve 27, and a gas-filled chamber 23 separated from one 30 of the liquid-filled chambers by a diaphragm 22. The liquid-filled chamber 31 remote from the gas-filled chamber is formed within an elastomeric container 41 having an end wall 40 with a coupling connection and a tapering convoluted elastomeric sidewall 47. No external support is provided for the sidewall 47, but a coil spring may be moulded into its inwardly-turned portions 46. <IMAGE>

Description

SPECIFICATION Fluid-pressure springs This invention relates to fluid-pressure springs, such as may be employed in the suspension of a motor car.

In conventional fluid-pressure springs of the kind which incorporate a gas-filled chamber separated by a diaphragm from a pair of liquid-filled chambers which inter-communicate through a damper valve, the liquid-filled chambers are normally closed at one end by a diaphragm which has an end wall attached to a connecting shaft through which loads are imposed on the spring. The chambers of the spring are normally enclosed by metal containers, and the end wall of the diaphragm through which loads are transmitted to the spring is normally provided with a rolling-lobe portion which is retained by the metal container against radial expansion under pressure.

Such conventional springs tend to be of complex construction, involving the securing together of a number of metal pressings, and one object of the present invention is to provide a simplified structure.

According to the invention, a fluid-pressure spring comprises a gas-filled chamber, a diaphragm bounding one side of the gas-filled chamber, a first liquid-filled chamber separated from the gas-filled chamber by the said diaphragm, a wall enclosing one side of the first liquid-filled chamber, a second liquid-filled chamber, a damper valve providing restricted communication between the first and second liquid-filled chambers, and an elastomeric container forming a closure for the second liquidfilled chamber, the elastomeric container having an end wall comprising coupling means to enable the end wall to be moved axially of the spring and having an elastomeric side wall surrounding the second liquid-filled chamber without external support to retain and pressurise fluid in the second liquid-filled chamber during axial movement of the end wall.

In a preferred construction, the elastomeric side wall is of convoluted form, and may be of tapered shape, the narrower portion being adjacent the end wall of the container. Reinforcing means may be provided within the corrugated side wall, such as a metal spring.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a plan view, partly in axial crosssection, showing a spring assembly incorporating a spring in accordance with the invention, and Figure 2 is an end view, partly sectioned as indicated by the line II toll in Figure 1, of the spring assembly.

The spring assembly 10 shown in the drawings comprises a pressed metal housing 11 in which a roller bearing 12 is mounted for connection to a member (not shown) forming part of a vehicle suspension. A coupling shaft 14 is arranged to be coupled by means of a roller bearing 15 to another member (not shown) of the suspension which is relatively movable, on deflection of the suspension, to the member associated with the bearing 12.

Deflection of the suspension therefore causes relative movement between the housing 11 and the coupling shaft 14, and this movement is controlled by a spring 20.

The spring 20 comprises a plastic end member 21 and an elastomeric diaphragm 22 which enclose a gas-filled chamber 23.

A metal carrier 25 having a flange 26 supports a damper valve mechanism 27 and provides a wall 28 which separates a first liquid-filled chamber 30 from a second liquid-filled chamber 31, restricted communication between the two liquid-filled chambers being provided by the valve 27.

The damper valve 27 will not be described in detail since it is of generally known form, incorporating ports 34, 35, which are normally closed by metal spring closure members 36,37 which open under "bump" conditions to permit flow of fluid from the chamber 31, through the ports 34, 35 and a port 38 in the metal carrier to the chamber 30. Under "rebound" conditions, pressure in the chamber 23 moves the diaphragm 22 to return fluid from the chamber 30 to the chamber 31 through other spring-closed ports (not shown) of the valve 27.

Thus in operation, fluid contained in the second chamber 31 is subjected to varying pressure loads imposed by movement of the end wall 40 of an elastomeric container 41, opposed by pressure generated in the gas-filled chamber 23 and governed by the flow of liquid between the two chambers 30, 31.

The elastomeric container 41 is of a material such as "Hytrel" (Registered Trade Mark) having sufficient flexibility and fatigue resistance to permit the axial movement of the end wall 40, whilst also having sufficient circumferential strength to contain the pressure generated in the chamber 31 and to ensure that upon axial movement of the end wall of the container the container remains stable, to retain the pressure without buckling. To this end, the container is made in convoluted shape as illustrated, and may be reinforced by means, for example, of a metal coil spring 45 moulded into inwardly turned portions 46 of the container side wall 47.

The end wall 40 of the container 41 is moulded around a flange 48 of a boss 49 having a screwed connection to the coupling shaft 14. As its other end, the container 41 comprises a flange 55 which may be secured, for example by ultrasonic welding, to a flange 56 formed on the plastic end member 21.This provides a fluid tight joint into which the flange 26 of the metal carrier 25 and the outer edge of the diaphragm 22 are secured, and for additional strength the portion of the housing 11 surrounding the joint may be compressed around it to provide a permanent assembly.

The spring assembly described above has the advantage that it is compact and contains fewer components than conventional fluid pressure springs of this kind, particularly since it eliminates the need for a complicated assembly of metal pressings. This enables the spring to be assembled more cheaply.

The elastomeric container in the spring in accordance with the invention provides a dual function in that it contains the hydraulic fluid, taking the place of a metal casing, and also provides means to enable the fluid to be compressed by an axially directed force. The material and wall thickness of the container may be selected to provide an additional stiffness in the axial direction which takes part of the spring load and thus enables lower fluid pressures to be used.

Claims

1. A fluid-pressure spring comprising a gas-filled chamber, a diaphragm bounding one side of the gas-filled chamber, a first liquid-filled chamber separated from the gas-filled chamber by the said diaphragm, a wall enclosing one side of the first liquid-filled chamber, a second liquid-filled chamber, a damper valve providing restricted communication between the first and second liquid-filled chambers, and an elastomeric containerforming a closure for the second liquid-filled chamber, the elastomeric container having an end wall comprising coupling means to enable the end wall to be moved axially of the spring and having an elastomeric side wall surrounding the second liquid-filled chamber without external support to retain and pressurise fluid in the second liquid-filled chamber during axial movement ofthe end wall.

2. A fluid-pressure spring according to Claim 1 wherein the side wall of the elastomeric container is of convoluted form.

3. A fluid-pressure spring according to Claim 1 or Claim 2 wherein the elastomeric container is of tapered shape, the narrower portion being adjacent the said end wall.

4. A fluid-pressure spring according to any of Claims 1 - 3 wherein the elastomeric container comprises a reinforcement.

5. A fluid-pressure spring according to Claim 4 wherein the container is of convoluted form and the reinforcement comprises a coil spring moulded into inwardly turned portions of the container side wall.

6. A fluid-pressure spring according to any of the preceding claims wherein an end member of the gas-filled chamber and a flange formed on the elastomeric container are welded together.

7. Afluid-pressure spring according to Claim 6 wherein a carrier, providing the said wall enclosing one side of the first liquid-filled chamber, comprises a flange interposed between the diaphragm and the flange formed on the elastomeric container.

8. A fluid-pressure spring according to Claim 7 wherein a metal housing is arranged to surround and compress the flange region to provide a permanent spring and housing assembly.

9. A fluid-pressure spring constructed and arranged substantially as described herein and illustrated in the accompanying drawings.