GB1604244A

GB1604244A - Telescopic suspension units

Info

Publication number: GB1604244A
Application number: GB2096477A
Authority: GB
Original assignee: Girling Ltd
Current assignee: Girling Ltd
Priority date: 1977-05-18
Filing date: 1977-05-18
Publication date: 1981-12-02
Also published as: NL7805198A; DE2821545A1; JPS53142724A; AU3582178A; YU119778A; BR7803041A; HU178549B

Description

(54) TELESCOPIC SUSPENSION UNITS (71) We, GIRLING LIMITED, a British Company, of Kings Road, Tyseley, Birmingham 11, 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 telescopic suspension units.

The present invention provides a telescopic suspension strut comprising an outer tube having a seat for a suspension spring attached to the exterior thereof, an inner cylinder located within the tube, the strut being filled with a pressurised mixture of gas and liquid and the inner cylinders being in fluid flow communication with a space between the inner cylinder and the outer tube, a piston axially movable in the inner cylinder and having a piston rod which extends sealingly through one end of the outer tube, and a stop intermediate and a substantial distance from the ends of the outer tube and engageable by the piston to limit movement thereof.

The seat may be a flange for supporting an external coil compression spring and may be secured to the tube at any desired axial position.

Preferably, the length of the inner cylinder is substantially the same as the stroke of the piston in which case one end of the cylinder is preferably axially and radially located by a retainer intermediate the ends of the tube, the retainer providing the stop for limiting movement of the piston.

The retainer may, for example, be welded to the inner surface of the tube or secured thereto in some other suitable manner.

The other end of the cylinder is preferably located by an end closure of the tube, which end closure provides another stop limiting movement of the piston.

A suspension unit 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 part axial cross-sectional view of the unit, and Figure 2 is a detail view showing the modification of the unit of Figure 1.

The illustrated suspension unit is a McPherson strut which is intended for use as a spring damper unit for a steerable road wheel of a vehicle. It will be appreciated, however, that the invention is applicable to suspension units other than McPherson struts.

Referring to Figure 1, the unit comprises a valved piston 1 secured to a piston rod 2 which extends sealingly through a rod guide 3 mounted at one end of a tube 4. The unit is usually mounted in use with the rod 2 secured to the vehicle body and the lower end of the tube 4 secured to a stub axle 5.

The piston 1 is axially slidable in an inner cylinder 6 which is separate from the tube 4.

The cylinder 6 is located at its lower end by a closure or cap 7 which seals the lower end of the tube 4. The upper end of the cylinder 6 is located by an annular retainer 8 secured within the tube 4 intermediate the ends thereof. The retainer 8 is held in place by indentations 9 formed in the tube 4 and protruding into the outer periphery of the retainer 8.

Figure 2 illustrates a modified form of retainer 8 which is welded or otherwise secured to the inner surface of the tube 4.

Attached to the exterior of the tube 4, for example by welding or other suitable means, is an attachment in the form of a flange 10 which is intended to support an exterior coil compression spring (not shown).

The length of the cylinder 6 is preferably, as illustrated, substantially equal to the desired maximum stroke of the piston 1. The retainer 8 can provide an upper stop which is a substantial distance from the ends of the outer tube 4 and which limits upward movement, or "rebound" of the piston and end cap 7 provides a lower stop to limit downward movement, or "bump" of the piston.

It will be seen that the inner cylinder 6 is not subjected to any substantial loading and can be made more thinly and out of lower quality material than the load-bearing tube 4.

The tube 4 is in use filled with a pressurised liquid/gas mixture, commonly referred to as an "emulsion" the minimum liquid level being at the stop formed by the bottom of the retainer 8, so that the piston is always immersed in liquid. Thus, the space 11 between the cylinder 6 and tube 4 is usually filled with liquid so that heat dissipation efficiency is not substantially different from known units in which there is no such space.

To accommodate expansion of the liquid in the space 11 caused by heating, one or more overflow passageways 12 are provided in the retainer 8, the passageways 12 permitting liquid to pass from the space 11.

The inner cylinder may be of such a diameter to accept a piston 1 of a common size.

It will be appreciated that the above described unit is relatively simple and cheap to manufacture and the attachment of the flange in no way damages or deforms the cylinder 6 in which the piston slides.

WHAT WE CLAIM IS: 1. A telescopic suspension strut comprising an outer tube having a seat for a suspension spring attached to the exterior thereof, an inner cylinder located within the tube, the strut being filled with a pressurised mixture of gas and liquid and the inner cylinder being in fluid ow communication with a space between the inner cylinder and the outer tube, a piston axially movable in the inner cylinder and having a piston rod which extends sealingly through one end of the outer tube, and a stop intermediate and a substantial distance from the ends of the outer tube and engageable by the piston to limit movement thereof.

2. A telescopic suspension unit according to claim 1, wherein the length of the inner cylinder is substantially equal to the maximum stroke of the piston.

3. A telescopic suspension unit according to claim 2, wherein the stop is one of two stops which are provided respectively at the ends of the inner cylinder to limit piston movement.

4. A telescopic suspension unit according to claim 3, wherein said one stop is provided by a retainer which is secured to the tube intermediate the ends thereof and which locates one end of the inner cylinder.

5. A telescopic suspension unit according to claim 4, wherein the retainer is an annular member which locates said one end of the inner cylinder both axially and radially.

6. A telescopic suspension unit according to any one of claims 3 to 5, wherein the other of the stops is an end closure of the tube.

7. A telescopic suspension unit according to claim 6 as appendant to claim 4 or 5, wherein the closure locates the other end of the inner cylinder both axially and radially.

8. A telescopic suspension unit according to any preceding claim, wherein the minimum level of liquid is at the stop intermediate the ends of the outer tube.

9. A telescopic suspension unit constructed and arranged substantially as herein described with reference to Figure 1, or to Figure 1 as modified by Figure 2, of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. downward movement, or "bump" of the piston. It will be seen that the inner cylinder 6 is not subjected to any substantial loading and can be made more thinly and out of lower quality material than the load-bearing tube 4. The tube 4 is in use filled with a pressurised liquid/gas mixture, commonly referred to as an "emulsion" the minimum liquid level being at the stop formed by the bottom of the retainer 8, so that the piston is always immersed in liquid. Thus, the space 11 between the cylinder 6 and tube 4 is usually filled with liquid so that heat dissipation efficiency is not substantially different from known units in which there is no such space. To accommodate expansion of the liquid in the space 11 caused by heating, one or more overflow passageways 12 are provided in the retainer 8, the passageways 12 permitting liquid to pass from the space 11. The inner cylinder may be of such a diameter to accept a piston 1 of a common size. It will be appreciated that the above described unit is relatively simple and cheap to manufacture and the attachment of the flange in no way damages or deforms the cylinder 6 in which the piston slides. WHAT WE CLAIM IS:

1. A telescopic suspension strut comprising an outer tube having a seat for a suspension spring attached to the exterior thereof, an inner cylinder located within the tube, the strut being filled with a pressurised mixture of gas and liquid and the inner cylinder being in fluid ow communication with a space between the inner cylinder and the outer tube, a piston axially movable in the inner cylinder and having a piston rod which extends sealingly through one end of the outer tube, and a stop intermediate and a substantial distance from the ends of the outer tube and engageable by the piston to limit movement thereof.