GB2067262A

GB2067262A - Suspension strut with safety end-closure

Info

Publication number: GB2067262A
Application number: GB8000504A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1980-01-08
Filing date: 1980-01-08
Publication date: 1981-07-22
Also published as: DE3048556A1; FR2474968A1; JPS56103605A

Abstract

A monotube suspension strut for a vehicle comprises a cylinder 1 which is closed at one end and which has at its other end a closure 4 through which a piston rod 2, carrying a damper piston, passes. In order to permit removal of the closure 4 to service the strut, without a sudden damaging surge of pressure as the closure is fully released, there is provided a fluid leak path 11 which communicates the interior of the cylinder 1 with the exterior before the closure 4 is fully released. Instead of being formed in the closure 4 the leak path may be formed in the cylinder wall. <IMAGE>

Description

SPECIFICATION Suspension struts This invention relates to suspension struts for vehicles.

Suspension struts are known which comprise a single cylinder which is closed at one end and within which works a damper piston having a piston rod which extends sealingly through a rod guide and closure at the other, open end of the cylinder. The cylinder is usually filled with liquid and gas under pressure. An example of a suspension strut is the well-known McPherson strut which has a wheel spindle attached to the lower, closed end of the cylinder for supporting a steerable road wheel, the piston rod being adapted for attachment to the vehicle body. The strut may conveniently use a "monotube" construction.

Monotube struts are expensive to produce and when they require servicing, for example for replacement of worn seals, the whole strut has to be replaced by a fresh one, the old strut being returned to the factory for reconditioning. To reduce the cost of servicing the struts, it has been proposed simply to remove the piston and piston rod, and accompanying seals, from the cylinder and insert into the cylinder a carriage comprising an auxiliary cylinder, piston and piston rod supplied as a replacement unit and locating the unit by a closure secured to the open end of the cylinder.

However, when the cylinder is removed from the cylinder to permit removal of the original piston and rod, and insertion of the cartridge, there is a danger of accidents occurring because of the sudden release of pressure from the cylinder.

When the closure is fully released, the pressure within the cylinder may force the closure out at high speed, in the manner of a cork from a Champagne bottle, and also cause liquid to spurt from the open end of the cylinder.

The present invention aims to obviate or at least reduce, such danger.

In accordance with the present invention, there is provided a suspension strut for vehicles, comprising a cylinder which is closed at one end and in which works a piston secured to a piston rod which extends sealingly through a closure removably attached to the other end of the cylinder, wherein removal of the closure establishes a fluid leak path between the interior of the cylinder and the exterior thereof before the closure is fully released from the end of the cylinder.

The closure preferably carries a seal which normally seals the interior of the cylinder from the exterior thereof, the leak path being established when the seal passes an opening during removal of the closure.

The opening may be the extreme open end of the closure or may be one or more apertures in the cylinder spaced from the extreme end.

As an example, the leak path may comprise an annular recess or one or more axial recesses or grooves formed in the closure, the or each recess extending from the inner end of the closure to the seal.

A form of suspension strut in accordance with the invention, and a modification thereof, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevational view of the strut, Figure 2 is a cross-sectional detail of the strut in the region marked A in Figure 1, and Figure 3 is a view similar to Figure 2 of the modification.

Referring to Figure 1, the illustrated strut is a monotube strut of the McPherson type comprising a cylinder 1 which contains pressurised liquid and gas and which is closed at its lower end. Within the cylinder a damping piston (not shown) works and is carried by a piston rod 2 which extends sealingly from the upper end of the cylinder 1. The lower end of the cylinder has fixed thereto a spindle 3 for attachment of a steerable road wheel (not shown). At its upper end the piston rod 2 is adapted for attachment to a vehicle body.

With reference to Figure 2, the rod 2 passes sealingly through a closure 4 comprising a locking ring 5 and locates a rod guide 6. The rod guide 6 carries a dynamic seal 7 and seats against a stop 8 in the form of a spring clip located in an annular recess 9 in the cylinder 1. The locking ring 5 is screwed into the upper end of the cylinder 1 and holds the rod guide 6 in position.

A fluid leak path 11 comprises axial recesses 1 1A, 1 B formed respectively in the locking ring 5 and the rod guide 6 and extending to a static seal 12 between the locking ring 5 and the cylinder 1.

A further static seal 1 3 is provided to prevent leakage between the guide 6 and ring 5.

To remove the piston and rod 2 for service, the ring 5 is unscrewed and when the seal 12 passes the end of the cylinder 1, that is before the ring 5 is fully released, the pressurised fluid leaks from within the cylinder, along leak path 11, and out from the cylinder open end. In order to prevent fluid from spurting out too suddenly and injuring the service operative, a protector plate 14 is preferably attached to the locking ring 5 and has a depending portion 1 5 adjacent the leak path exit.

The modification of Figure 3 is similar to Figure 2 and the same reference numerals are used to denote corresponding parts. In Figure 3 the locking ring and rod guide are formed as a unitary closure 4 and the stop 8 for the closure is provided by the engagement of the bottom of the screw thread of the closure 4 with a shoulder 1 6 on the internal surface of the cylinder 1. The seal 12 is located inwardly of the stop 8 and one or more radial passages 1 7 are provided which extend through the cylinder 1. As the closure 4 is unscrewed the leak path 11, 1 7 is opened from the inside of the cylinder to the outside thereof when the seal 12 passes the stop 8, thereby permitting release of the pressure within the cylinder before the closure is fully released.

Other modifications of the above-described strut are possible. For example, the connection of the closure 4 to the cylinder 1 may be other than a screw thread, for example a bayonet connection.

Furthermore, the leak path 11 may comprise an annular recess in the closure or rod guide, or may comprise one or more axial passages.

It will be appreciated that once the piston and rod 2 are removed a cartridge comprising a pressurised cylinder having a fresh piston and rod may be inserted within the cylinder t and held in position by the closure 4. In this way, the strut need not be replaced completely and the old unit reconditioned at the factory, but normal service outlets can service the struts simply by inserting into the cylinder 1 a factory-prepared replacement cartridge.

Although the described strut is a monotube strut it will be appreciated that the invention is also applicable to pressurised twin tube struts.

Claims

1. A suspension strut for a vehicle, comprising a cylinder which is closed at one end and in which works a piston secured to a piston rod extending sealingly through a closure removably attached to the other end of the cylinder, wherein removal of the closure establishes a fluid leak path between the interior of the cylinder and the exterior thereof before the closure is fully released from the end of the cylinder.

2. A suspension strut according to claim 1, wherein the closure carries a seal which normally seals the interior of the cylinder from the exterior thereof, the leak path being established when the seal passes an opening during removal of the closure.

3. A suspension strut according to claim 2, wherein the opening is the extreme open end of the cylinder.

4. A suspension strut according to claim 2, wherein the opening comprises one or more apertures in the cylinder spaced from the extreme end of the cylinder.

5. A suspension strut for a vehicle constructed and arranged substantially as herein described with reference to Figures 1 and 2 or to Figures 1 and 3.