GB2094416A - Gaseous fluid spring devices - Google Patents

Abstract

A gaseous fluid spring device 10, including a casing 11 and a member 13 extending through an aperture 14 from the interior of the casing to the exterior thereof, in which a chamber 19, defined by a recess 20 formed in the surface 21 of the aperture and by that portion of the surface 22 of the member 13 adjacent the recess, is in part occupied by lubricating liquid 23. Two sealing devices 27, 28 are disposed in respective grooves 25 and 26 also formed in the surface 21 of the aperture 14 and are spaced apart axially thereof, one on one side of the chamber 19 and the other on the other side thereof. <IMAGE>

Description

SPECIFiCATION Gaseous fluid spring devices This invention relates to gaseous fluid spring devices.

Such devices usually comprise a casing, which may be in the form of a cylinder, charged with gas under pressure and having a member, for example a piston rod, extending from the interior of the casing the exterior thereof.

Hitherto difficulty has been experienced in providing reliable sealing means in association with the member and the wall of the casing through which the member passes, particularly where the gaseous pressures within the casing are relatively high. Also, difficulty has been experienced in providing a reliable means for effecting lubrication of the member upon its movement with respect to said wall during operation of the spring device.

The invention as claimed is intended to provide a remedy. It solves the problem of how to design a gaseous fluid spring device in which reliable sealing and adequate lubrication of a said member thereof are provided.

According to the invention there is provided a gaseous fluid spring device, including a casing and a member extending through an aperture from the interior of the casing to the exterior thereof, in which a chamber, defined by a recess formed in the surface of said aperture and by that portion of the surface of said member adjacent the recess, is in part occupied by lubricating liquid, and in which two sealing devices are disposed in respective grooves also formed in the surface of said aperture and spaced apart axially thereof, one on one side of said chamber and the other on the other side thereof.

The said casing may comprise a cylinder which houses a piston reciprocable therein in which case said member comprises a piston rod of circular cross-section connected to said piston, said aperture being also of circular cross-section and formed in one of the two end walls of the cylinder.

The chamber may then be of annular form and said sealing devices may each comprise a sealing ring which may be of circular cross-sectional shape.

The cylinder may be charged with gas to a predetermined pressure through a charging valve fitted to the other of said two end walls of said cylinder.

The advantages offered by the invention are mainly that adequate lubrication of said member is provided as during operation of the spring device that member reciprocates in said aperture and reliable sealing against the leakage of gas from the interior of the casing is afforded, even when the pressures therein are relatively high.

One way of carrying out the invention is described in detail below with reference to drawings which illustrate only one specific embodiment, in which, Figure 1 is a cross-sectional side elevation of a gaseous fluid spring device in accordance with the invention, and Figure 2 is a cross-section taken along the line Il-Il on Figure 1.

The figures show a gaseous fluid spring device 10 comprising a casing in the form of a cylinder 11, and a piston 1 2 of circular cross-section which is reciprocable within the cylinder and which has a member connected thereto in the form of a piston rod 13 also of circular cross-section. The piston rod extends to the exterior of the device through an aperture 14 of circular cross-section formed in the left-hand end wall 15, as viewed in Figure 1, of the cylinder. The end wall 1 5 is screw-threadedly engaged at 1 6 with the main part 1 7 of the cylinder 11 and at its right-hand end this main part is closed by an end wall 1 8 formed integrally therewith.

An annular chamber 1 9 is provided in the end wall 15, being defined by an annular recess 20 formed in the cylindrical surface 21 of the aperture 14and by that portion of the cylindrical surface 22 of the piston rod 13 which, depending on the position of the piston 1 2 in the cylinder 11, is adjacent the recess. The chamber 1 9, which forms a reservoir, is in part occupied by lubricating liquid in the form of a predetermined quantity of oil 23.

In this embodiment, and as can be seen by the lines 24, the volume of the chamber is a little more than half-occupied by oil and the remaining space is occupied by air.

Two annular grooves 25, 26 are formed in the cylindrical surface 21 of the aperture 14, being spaced apart axially thereof on one side of the chamber 19 and the other on the other side thereof. A respective sealing ring 27, 28 of circular cross-section is disposed in each of these grooves and is in sealing engagement with the cylindrical surface 22 of the piston rod 13.

A further sealing ring 29 of circular crosssection is disposed in an annular groove 30 formed in the outer cylindrical surface of the end wall 1 5 and is in sealing engagement with the adjacent inner cylindrical surface of the main part 17 of the cylinder 11.

The piston 12 is provided with an annular groove 31 in which a sealing ring 32 of square cross-section, which is also in sealing engagement with the inner cylindrical surface of the main part 17, is disposed.

Damping orifices 33 are provided in the piston 12, certain of which are each provided with a nonreturn valve as at 34.

The right-hand end wall 1 8 of the cylinder 11 is provided with a charging valve 35 screwthreadedly engaged therewith at 36 through which the gaseous fluid spring device 10 can be charged with gas, for example compressed nitrogen, to a predetermined pressure which in this embodiment is 1 500 p.s.i. It is intended that such charging of the device with gas and the introduction of oil into the annular chamber 1 9 is effected at a final stage of manufacture so that the device can be despatched for sale in complete readiness for use. The device may be used in substitution for a mechanical coil spring, for example such as associated with a large fluid valve as used in chemical plant for urging the valve to its closed position.

During compression of the gaseous fluid spring device 10 flow of compressed nitrogen takes place through all the damping orifices 33 from the right-hand side of the piston to the left-hand side thereof. Since non-return valves 34 are provided in association with certain of the orifices, during subsequent extension of the device those orifices are automatically closed by these valves and flow of compressed nitrogen from the left-hand side of the piston 12 to the right-hand side thereof takes place only through the remaining damping orifices so that greater damping is afforded during such extension.

As the piston 12 reciprocates in the cylinder 11 and the piston rod 1 3 reciprocates in the aperture 14, oil in the annular chamber 19 reaches the sealing rings 27, 28 by capillary action, thereby moistening and thus lubricating them whatever the attitude of the device.

Since the annular chamber 1 9 is only partly occupied by oil, high pressures due to thermal expansion and/or hydro-dynamic viscous effects, which might otherwise unduly load the sealing rings 27, 28, are unlikely to be generated in that chamber.

During operation of the device the sealing ring 28 forms the first sealing barrier to the escape of compressed nitrogen from within the cylinder, and the sealing ring 27 prevents leakage of the oil from the annular chamber 1 9 to the exterior. In the event however that some leakage does inadvertently take place past the sealing ring 28, the pressure in the annular chamber 1 9 will rise, possibly, in the extreme, even to the full pressure within the cylinder, in which case the sealing ring 27, which effectively forms a back-up to the sealing ring 28, is capable of taking over the sealing function completely.

Pre-charged gaseous fluid spring devices hitherto proposed have suffered from gradual loss of charging pressure during their use in service, while undue friction has been set up between the piston rod and its sealing gland. By the trapping of a relatively small volume of oil in the annular chamber 19 and between the two dynamic sealing rings 27, 28 the present invention is intended to reduce the likelihood of the occurrence of such pressure loss and the generation of excessive friction.

The gaseous fluid spring device of this invention is intended to replace conventional mechanical or rubber springs and has the advantages of less bulk and weight and of a builtin preload which can be altered by adjustment of the charging pressure.

In contrast for example to a mechanical coil spring the volume occupied by a device in accordance with this invention can be between a tenth and a twentieth of that occupied by a coil spring having similar characteristics, and the weight can be less than half that of a coil spring.

The need for a coil spring container is also avoided, as well as means for pre-compressing the coil spring.

By the construction since reliable gas sealing and adequate seal and piston rod lubrication are provided, a relatively long life of the device both in storage and in service can be expected.

Although in the embodiment above described with reference to the drawings one end wall of the cylinder is screw-threadedly secured to the main part thereof while the other end wall is formed integrally therewith, in alternative embodiments of the invention both end walls are screw-threadedly secured to the main part of the cylinder.

Further, although in the embodiment above described with reference to the drawings the gaseous fluid spring device is of piston-andcylinder type, in alternative embodiments of the invention the device may be of other suitable type having a casing which is of a shape other than cylindrical.

Claims (7)

1. A gaseous fluid spring device, including a casing and a member extending through an aperture from the interior of the casing to the exterior thereof, in which a chamber, defined by a recess formed in the surface of said aperture and by that portion of the surface of said member adjacent the recess, is in part occupied by lubricating liquid, and in which two sealing devices are disposed in respective grooves also formed in the surface of said aperture and spaced apart axially thereof, one on one side of said chamber and the other on the other side thereof.

2. A device as claimed in Claim 1, wherein said casing comprises a cylinder which houses a piston reciprocable therein.

3. A device as claimed in Claim 2, wherein said member comprises a piston rod of circular crosssection connected to said piston, said aperture being also of circular cross-section and formed in one of the two end walls of the cylinder.

4. A device as claimed in Claim 3, wherein said chamber is of annular form.

5. A device as claimed in either Claim 3 or Claim 4, wherein said sealing devices each comprise a sealing ring which is of circular crosssectional shape.

6. A device as claimed in any one of Claims 3 to 5, wherein said cylinder is charged with gas to a predetermined pressure through a charging valve fitted to the other of said two end walls of said cylinder.

7. A gaseous fluid spring device substantially as hereinbefore described with reference to the accompanying drawings.