GB2076503A - End bearing for fluid suspension unit - Google Patents

Abstract

A fluid pressure device, particularly a telescopic unit for a vehicle springing system, has mounting means 23, 35 with part spherical bearing surfaces 33, 34 permitting universal angular movement, the bearing surfaces being accessible to fluid from the device and sealed at 49 to prevent escape of the fluid. <IMAGE>

Description

SPECIFICATION Mounting of fluid pressure devices This invention relates to the mounting of fluid pressure operating devices. The invention has been developed in relation to a telescopic liquid displacement unit intended to form part of the springing means of a vehicle suspension system.

When such a unit is utilized in a vehicle suspension system, it is unlikely that it will be arranged to operate between components which move relative to one another in a straight line.

More typically it will be arranged between components which move relative to one another in such a way that some pivotal or universal angular movement is required at one or both ends of the unit. Hitherto this requirement has generally been met either by the provision of a pivotal mounting or by the use of resilient elements in the mounting. It is the object of the present invention to provide an improved provision for universal movement.

According to the broadest aspect of the present invention, we provide a fluid pressure operating device incorporating a mounting means with cooperating part spherical bearing surfaces permitting universal angular movement, said surfaces being accessible to fluid from the device and there being sealing means for preventing escape of fluid from said surfaces.

By virtue of this, the necesssity for resilient mountings or external bearings is avoided, and the fluid provides for lubricating of the bearing surfaces to facilitate relative movement thereof.

As applied to a device which is a telescopic liquid displacement unit for vehicle suspension systems, the unit may incorporate first and second telescopically assembled tubular elements each having an end cap, and the bearing surfaces may be provided respectively on one of said end caps and on a mounting member adapted to be secured to the vehicle structure.

Preferably the end cap is provided with concentric inner and outer part spherical surfaces, the outer surface cooperating with the mounting member and the inner surface with a further part spherical surface provided on an internal member secured to the mounting member and extending through an aperture in the end cap. The amount of movement permitted by such an arrangement is of course limited by the dimensions of the aperture in the end cap through which the part fixed to the mounting member extends, but sufficient freedom of movement for practical applications can be obtained.

These and other features of the invention will now be described by way of example with reference to the accompanying drawing, which is a vertical section through a unit embodying the invention.

The illustrated unit is shown in the vertical orientation as it is intended to form part of the springing means of a vehicle suspension system, and thus in service will usually be in the vertical or inclined orientation.

The unit comprises a lower end cap 10 which is provided with a formation not shown for attachment to, e.g., an axle part of a motor vehicle or other component which is movable with a vehicle wheel or wheels. Screwed to the end cap 10 is an upstanding tubular element 11 which carries at its upper end two sliding angular seals 12, 13. The interior surface of the tubular element 11 forms a bearing surface. A sealing ring 14 is compressed in an annular space between the bottom of the tubular element 11 and the end cap, to form a liquid tight seal.

There is also attached to the lower end cap 10 a central column 1 5 which extends upwardly within the element 11. At its base, a column 1 5 has an increased diameter portion 1 6 with a cylindrical outer surface. At its head the column 1 5 carries a piston 1 7 with a cylindrical circumferential surface part 1 8 and a frustoconical part 1 9. Opposite the portion 1 6 of the column, the end cap is formed to define a cylindrical internal surface 20, and a frusto-conical surface 21.

Telescopically slidable within the tubular element 11 is an inner tubular element 22, secured to an upper end cap 23. The element 22 carries a sliding bearing 24 at its lower end working within the bearing surface of element 11, and a bearing 25 between the seals 12, 13 in element 11 guides the element 22 accurately within the element 11. At its lower end the inner tubular element 22 has an internal cylindrical surface 26 and frusto-conical surface 27, the cylindrical surface 18 of the piston 1 7 being a close sliding fit within the cylindrical surface 26.

Secured to the lower end of element 22 is a component 28 which affords an internal cylindrical surface 29 and frusto-conical surface 30. An enlarged diameter portion 31 below the piston 1 7 on central column 1 5 has a cylindrical external surface which is a close sliding fit within the internal cylindrical surface 29 of component 28. The component 28 also carries an annular piston 32 with piston rings which engage the internal cylindrical surface 20 of end cap 10 and the external cylindrical surface of the portion 1 6 of column 15.

The upper end cap 23 has an outer part spherical surface 33 and an inner part spherical surface 34 concentric with the surface 33. The surface 33 fits against a complementary part spherical surface in a mounting member 35, which has a spigot 36 receiving a threaded collar 37 which is used to attach the mounting member 35, with the intermediary of resilient elements 38, 39, to an element 40 of a vehicle structure.

The upper end cap 23 carries a tubular dust shield 41 with a dust seal 42 at its lower end, and a flexible gaiter 43 connects the end cap 23 and mounting member 35.

The spigot 36 of mounting member 35 is hollow, and adapted to be connected to a source of liquid under pressure which gives a springing action to the unit. A tubular member 44 is fitted within the spigot 36, and extends downwardly through a frusto-conical opening 45 in the end cap 23. At its lower end the member 44 carries a stiff nut 46 supporting a collar 47 with a part spherical upper surface which mates with the surface 34 in the end cap 23. The concentric part spherical surfaces 33, 34 of the upper end cap 23 thus by co-operation with the complementary surfaces on mounting member 35 and collar 47 constrain the main part of the unit to limited universal movement, about a point which is actually at the common centre of the part spherical surfaces. This eliminates the need to provide for such movement in the mounting of the unit to the vehicle structure.

The member 44 has laterally extending apertures 48 which provide for venting of any gas from the interior of the unit when it is filled with liquid to the connection to the liquid springing means. It will be noted that the part spherical bearing surfaces which permit the angular movement of the unit are exposed to the liquid pressure within the unit, and thus are, in effect, hydrostatic bearings. The mounting member 35 carries two annular seals 49 to prevent escape of liquid.

The unit is illustrated in the position of maximum compression., i.e. with its internal volume at a minimum. In this state, the annular piston 32 has contacted the end cap 10. Just before such contact is reached, however, the piston 32 enters the space between the internal surface 20 of the end cap and the external surface of the portion 16 of column 15, and traps liquid in this space, the liquid escaping at a limited rate back to the main part of the unit. This acts as a bump cushion preventing the sudden shock caused by mechanical contact within the unit.

Before the hydraulic cushion condition is established, the piston 32 traverses the frustoconical portion 21 within the end cap, providing a lead in for the piston ring seals on the piston 32.

As the permitted limit of maximum extension of the unit is reached, the enlarged diameter portion 31 at the head of column 15 enters, as a piston in a cylinder, the frusto-conical surface 30 and parallel surface 29 within the member 28.

Simultaneously, the piston 1 7 enters the cylindrical surface 26 within the inner tubular element 22, trapping a quantity of liquid in the annular space beneath the piston 1 7 and above the member 28. This provides a rebound cushion in manner analogous to the bump cushion above described. Again, a degree of damping is provided by frusto-conical surfaces 19, 27, and 30 and by leakage of liquid back to the main part of the unit, so that there is no sudden shock as the unit reaches its condition of extreme extension. Thus there is provided a liquid displacement unit incorporating an effective system for limiting its extension and compression without mechanical engagement of parts, and capable of accommodating universal movement internally of the unit rather than relying on resilient or pivoted external mountings.

It will be noted that the diameter at which the innermost of the annular seals 49 is effective is substantially equal to the operating diameter of the telescopically engaged parts 11,22. Thus there is a substantial hydrostatic balance between the forces exerted in opposite directions on the end cap 23, which means that the unit can undergo its universal pivotal movement relatively freely. The part-spherical surfaces be substantially equal in area, or slightly smaller than, the effective operating diameter of the piston-cylinder unit.

Claims (7)

1. A fluid pressure operating device including a mounting means with cooperating part spherical bearing surfaces permitting universal angular movement, said surfaces being accessible to fluid from the device and there being sealing means for preventing escape of fluid from said surfaces.

2. A device according to Claim 1 which is a telescopic liquid displacement unit adapted to form part of the springing means of a vehicle suspension system.

3. A unit according to Claim 2 incorporating first and second telescopically assembled tubular elements, each having an end cap, said bearing surfaces being provided respectively on one of said end caps and on a mounting member adapted to be secured to a vehicle structure.

4. A unit according to Claim 3 wherein said end cap is provided with concentric inner and outer part spherical surfaces, the outer surface cooperating with said mounting member surface and the inner surface co-operating with a further part spherical surface provided on an internal member secured to the mounting member and extending through the end cap.

5. A unit according to Claim 4 wherein there is provided means for adjustment of the position of said further part spherical surface which cooperates with the inner surface of the end cap.

6. A unit according to any one of claims 2 to 5 wherein the area of said bearing surfaces is substantially equal to or less than the effective operating area of the unit.

7. A unit substantially as hereinbefore described with reference to and as shown in the accompanying drawings.