GB2312659A - Buffers - Google Patents

Abstract

A railway side buffer comprises a telescopic casing consisting of a cylinder (11) which is closed at its outer end by a buffer plate (10) and which slides within a closed ended cylindrical casing part (12). The end of the cylinder (11) within the casing part (12) is closed by a ring (14). A plunger comprises a rod (15) which abuts the end wall of the casing part (12) and slides within the bore of the ring (14), and a piston head (18) which slides within the bore (17) of the cylinder (11). The cylinder space (26) between the piston head (18) and the buffer plate (10) is a compression chamber. The annular cylinder space (25) between the piston head (18) and the ring (14) is a reservoir within an annular gas-filled space (32). The liquid in the reservoir and the gas are in direct contact. A spring closed ring valve (21) on the piston rod (15) allows flow from the compression chamber (26) to the reservoir (25), damping that flow, and prevents flow in the reverse direction.

Description

"BUFFERS" This invention relates to buffers of the kind that comprises a telescopic casing having external abutment means mounted at one end of a cylindrical part of the casing which is constrained for rectilinear sliding movement within another part of the casing, that other casing part being for mounting on support structure, the telescopic casing enclosing a telescopic hydraulic buffer capsule which acts between the two parts of the casing.

More particular, although not exclusively a buffer of the kind referred to is a railway side buffer.

The telescopic buffer capsule enclosed within conventional buffers of the kind referred to is a separate structural element inside the casing which serves to shield the buffer capsule from dirt and the elements, and which protects it from side loads. The buffer capsule comprises a plunger slidable within a cylinder which is for mounting on support structure such as part of a railway vehicle, the plunger abutting the inner face of the casing in the region of the external abutment means.

Although the construction of such a railway side buffer would be simplified if the external abutment means were to be mounted directly upon the buffer capsule, so that the number of component parts and thus the Cost of the railway side buffer would be reduced, the buffer capsule would be directly exposed to the elements with the consequent risk of dirt being carried into its interior on compression which is undesirable for various reasons. Also the buffer capsule would be subjected directly to any side loads.

According to this invention there is provided a buffer of the kind referred to wherein the cylindrical part of the casing is slidable on a piston head which is mounted coaxially in the other casing part, the piston head dividing the interior of the cylindrical part into a reservoir and a compression chamber which is between the piston head and said one end of the cylindrical part, there being liquid damping means comprising a normally closed valve operable to be opened against the action of biasing means by the pressure of liquid in the compression chamber as the cylindrical part is urged into the other part of the casing by an impact on said external abutment means whereby liquid is displaced from the compression chamber into the reservoir through said damping means and energy is absorbed, such displacement of liquid in the reservoir increasing the volume of liquid in the reservoir with a consequent compression of gas within a gas containing space in the reservoir, there being a direct interface between gas and liquid in the reservoir.

A railway side buffer in which this invention is embodied will be described by way of example with reference to the accompanying drawing which is a longitudinal section of the buffer, the section being in a plane which includes the longitudinal axis of the buffer.

The drawing shows the railway side buffer comprises abutment means in the form of a buffer plate 10 mounted at one end of a cylinder 11 which slides within a cylindrical portion of a component 12 so that the cylinder 11 and the component 12 together comprise a telescopic casing. The end of the component or casing part 12 remote from the buffer plate 10 is closed and is formed as an integral base portion which is for mounting on structure of a railway vehicle.

The cylinder 11 comprises a tube 13 which is closed at one end by the buffer plate 10 and at the other end by a ring 14 which is slidably fitted onto a cylindrical rod 15 which projects from the cylinder 11 and is substantially coaxial with the cylindrical portion of the casing part 12. The buffer plate 10 has an integral tubular boss portion 16 which is spigotted into the tube 13 to which it is welded. The boss portion 16 and the tube 13 together comprise the cylinder 11. The interior of the tubular boss portion 16 is formed as a cylindrical bore 17. A piston head 18, which is mounted at the end of the rod 15 remote from the closed end of the casing part 12, is slidably engaged within the bore 17. The diameter of the bore 17 is greater than that of the rod 15 but less than the inside diameter of the tube 13.

That portion of the piston head 18 that projects radially from the rod 15 is formed with an array of through holes 19 at circumferentially spaced intervals on a common pitched circle diameter. A ring valve 21 is urged by a stack 22 of spring washers to engage the annular face of the piston head 18 remote from the buffer plate 10 so as to close the adjacent ends of the through holes 19. The stack 22 of spring washers reacts against an annular shoulder 23 formed on the rod 15.

A one-way valve 24 in the piston head 18 is operable to allow liquid flow from the annular chamber 25 within the tube 13 and around the rod 15 to the compression chamber 26 that is formed within the bore 17 between the piston head 18 and the closed end of the buffer plate 10, but to prevent such liquid flow in the opposite direction.

The casing part 12 is formed with a diametrically opposed pair of axially extending inwardly opening grooves 27 which extend over approximately half the actual length of the casing part 12 from its open end to a substantially radially extending shoulder. A stop 28 is spigotted into the open end of each of the grooves 27.

The cylinder 11 has a diametrically opposed pair of radially outwardly extending lugs or keys 29 which each project into a respective one of the grooves 27 which serve as a key-way.

A fluid charging valve 31 is fitted into the ring 14 to enable the compression chamber 26 and a major part of the annular chamber 25 to be charged with hydraulic fluid. The remainder of the interior of the annular chamber 25, namely the space 32, is charged with air or nitrogen under pressure, there being an air/fluid interface at the boundary of the air space 32, whereby the air or gas on the one hand and the hydraulic fluid on the other hand are in direct contact.

The pressure of that volume of air or nitrogen acts through the hydraulic fluid to displace as much of the hydraulic fluid from the annular space 25 as possible, that displaced hydraulic fluid being displaced through the non-return valve 24 into the compression chamber 26.

Hence the buffer plate 10 and the cylinder 11 are urged to the maximum extended position in the casing part 12 that is determined by engagement of the keys 29 with the respective stops 28.

On high speed impact which causes compression of the buffer, liquid in the compression chamber 26 is displaced therefrom through the through holes 19 displacing the ring valve 21 against the resilient loading of the stack 23 of spring washers so that the liquid displaced from the compression chamber 26 enters the annular chamber 25.

Hence the volume of hydraulic fluid in the chamber 25 increases further compressing the compressed air or nitrogen in the gas container space 32.

The compressed air or nitrogen provides a recoil force which urges the buffer capsule to expand when the impact force that caused contraction is removed.

The arrangement of the buffer in which this invention is embodied is such that the casing part 12 serves as the cylinder within which the buffer plunger that comprises the buffer plate 10 and the cylinder 11, slides. That casing part 12 protects the dynamic seal between the buffer plunger and the rod 15 on which it slides. By this arrangement, the buffer part of the plunger on which the buffer plate is mounted is part of the externally exposed structure of the buffer.

Claims (8)

1. A buffer comprising a casing, a telescopic hydraulic buffer capsule and external abutment means mounted on one end of a cylindrical part which is constrained for rectilinear sliding movement within a part of the casing, that casing part being for mounting on support structure, wherein the capsule comprises a plunger slidable within a cylinder and dividing the interior of the cylinder into a reservoir and a compression chamber, resilient means which act to oppose displacement of liquid from the compress ion chamber to the reservoir by movement of the plunger into the cylinder in reaction to an impact on the external abutment means and thereby to provide a restoring force, and liquid damping means operable to absorb energy from liquid so displaced from the compression chamber to the reservoir, characterised in that the cylinder of the buffer capsule is formed by said cylindrical part, the plunger comprising a piston head and a piston rod, the piston head being slidably engaged in a bore which is formed by said cylindrical part and the piston rod being slidably engaged in an aperture formed in an end wall of the cylinder which is remote from said one end and which is within said casing part, the piston rod extending coaxially towards an end wall of said casing part towards which it is urged by the action of liquid pressure in said compression chamber.

2. A buffer according to claim 1, wherein said resilient means comprise gas in a gas containing space, there being a direct interface between gas and liquid in the reservoir.

3. A buffer according to claim 1 or claim 2, wherein said liquid damping means comprise a normally closed valve operable to be opened against the action of biassing means by the pressure of liquid in the compression chamber as said cylindrical part is urged into said casing part by an impact on said external abutment means whereby liquid is displaced from the compression chamber into the reservoir through said damping means and energy is absorbed.

4. A buffer according to claim 3, wherein the piston head is formed with an array of through holes at circumferentially spaced intervals and said normally closed valve comprises a ring valve which is urged by said biassing means to close the adjacent ends of the through holes.

5. A buffer according to claim 4, wherein the biassing means comprise a stack of spring washers, which react against an abutment formed by the piston rod.

6. A buffer according to any one of claims 1 to 5, wherein said casing part is formed with a diametrically opposed pair of axially extending inwardly opening grooves which extend over part of the axial length of the casing part and which are closed at each axially spaced end and the cylindrical part has a diametrically opposed pair of radially outwardly extending protruberences which each project into a respective one of the grooves which serve as a keyway.

7. A buffer according to any one of claims 1 to 6 wherein said external abutment means comprise a buffer plate and said cylindrical part comprises a tubular boss portion which is integral with the buffer plate and a tube into which the tubular boss portion is spigotted, the boss portion and the tube being bonded together and the interior of said boss portion forming said bore.

8. A railway side buffer substantially as described hereinbefore with reference to and as illustrated in the accompanying drawings.