GB1587297A

GB1587297A - Hydraulically damped buffer for railway vehicles

Info

Publication number: GB1587297A
Application number: GB2266/78A
Authority: GB
Original assignee: Rheinmetall GmbH
Current assignee: Rheinmetall Industrie AG
Priority date: 1977-01-28
Filing date: 1978-01-19
Publication date: 1981-04-01
Also published as: NL7713334A; NL182950C; FR2378662A1; DE2703530A1; IT1091843B; DE2703530C2; FR2378662B1; IT7819236A0; NL182950B; BE863369A

Description

(54) AN HYDRAULICALLY DAMPED BUFFER FOR RAILWAY VEHICLES (71) We, RHEINMETALL GESELLS CHAFF MIT BESCHRANKTER HAFTUNG, of U1menstrasse 125, 4 Dusseldorf, German Federal Republic, a Company organised and existing under the laws of the German Federal Republic, 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 an improved, hydraulically-damped buffer for railway vehicles.

An hydraulically-damped buffer has been proposed in which the reservoir into which incompressible fluid is displaced when a horizontally moving piston enters a cylinder in response to telescoping of the buffer is disposed at the free end of the cylinder presented toward the piston, so that the piston rod moves through and is surrounded by the reservoir. The reservoir must be large enough to provide enough free internal space to accept all the displaced hydraulic fluid, bearing in mind that the volume occupied by the fluid varies with the considerable temperature variations which occur in use, as well as a pocket of a compressible gas, such as air, above the level of the hydraulic fluid.

If the reservoir is provided by a cylindrical bore of adequate diameter which is coaxial with the cylinder the reservoir is a relatively wide and bulky component, and difficulty is experienced in accommodating this is in the limited interior space of a preferred buffer, especially of the type incorporating an annular spring which surrounds the piston and cylinder assembly within the two telescopic parts of the buffer.

A principal object of the invention is to provide a reservoir of acceptably small dimensions without detriment to its function.

In accordance with the present invention there is provided an hydraulically-damped buffer for railway vehicles comprising a piston assembly and a cylinder and reservoir assembly fixed to respective, relatively movable parts of the buffer whereby when the buffer is compressed, in use, the piston will move generally horizontally into the cylinder to displace an incompressible fluid therefrom to the reservoir, the piston assembly comprising a piston rod fixed at one end to one said respective part and having a piston head at its free end and the cylinder and reservoir assembly comprising a casing fixed at one end to the other said respective part, the cylinder and reservoir being provided by a continuous bore in the casing of which the cylinder portion is in the region of said fixed end of the casing and the reservoir portion is in the region of the free end of the casing so that the reservoir surrounds the piston assembly and is dimensioned to receive incompressible fluid displaced by the piston head from the cylinder portion and to provide space above the piston assembly and above the level of incompressible fluid in the reservoir for a compressible gas, means being provided to form a sliding seal between the free end of the casing and the piston rod, wherein the continuous bore which defines the cylinder and reservoir is so shaped throughout the greater part of the length of its reservoir-defining portion that the volume of that part of the reservoir above a horizontal plane containing the longitudinal axis of the piston assembly is substantially greater than the volume of that part of the reservoir below said plane, the radial gap between the piston assembly and the wall of the bore defining the reservoir being substantially uniform, in cross-section of the reservoir, below said plane and increasing above said plane from said uniform size to a maximum size above the piston assembly.

Preferably an aperture for replenishing the cylinder and reservoir with incompressible fluid is provided in the casing on one side of the reservoir above the piston assembly.

A preferred embodiment of the invention will now be described with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side sectional elevation of a railway buffer in accordance with the invention, and Figure 2 is a cross-section taken on the line Il-Il of Figure 1.

The railway buffer illustrated comprises an outer buffer casing 2 with a flange 2a, to which a buffer plate 6 has been fastened by means of a fixing screw 38. The outer buffer casing 2 surrounds an inner buffer casing 4, which is screwed to a railway vehicle by means of flange 4a. Inside the buffer casing 4 an annular spring 8 is located, which is supported at its ends on thrust washers 10,12.

The front thrust washer 10 is fastened to a piston rod 20a by means of a fixing screw 14, while the rear thrust washer 12 is fastened to a casing 18 by means of a fixing screw 14.

The front thrust washer 10 has an outwardly extending area 10a which rests in an appropriate indentation 6a of the buffer plate 6 and prevents angular movement of the buffer plate 6 applying lateral forces to the piston rod 20a. The same applies to the contacting areas 12a and 18d of the rear thrust washer 12 and the casing 18. A retaining ring 16 prevents the outer buffer casing 2 from slipping off the inner buffer casing 4.

The casing 18 has an internal bore, which includes an asymmetrically designed reservoir 1 8b for receiving hydraulic fluid displaced as a result of movement of the piston rod and expansion due to rise in temperature.

The piston head 20 with a piston ring 20B is movable into an inner portion of the bore of the casing 18 defining a cylinder 1 8a when the inner buffer casing is telescopically received in the outer buffer casing. The cylinder 1 8a is connected with the reservoir 1 8b via overflow apertures 1 8c arranged around the bore circumference. The casing 18 is sealed by means of a packing holder 26, which contains a packing 28 for the piston rod and which contains a guide bush 22 between the piston rod and the piston head 20. The packing holder 26 is supported by a support plate 24 on the casing 18 and is secured against falling out by a circlip 34.

Furthermore a skimmer 30 is located in the packing holder 26, which surrounds piston rod 20a and helps protect the highly sensitive packing device 28 against penetration of foreign bodies. Sealing of packing holder 26 against the casing 18 is effected by means of O-ring 32. Inside the casing 18-in a lateral position-an oil filler screw 36 is positioned at the oil level to be maintained. An easy check of the oil level is possible by means of this screw.

The reservoir 18b is an extension of the bore of the casing 18 and contains air above piston 20 and piston rod 20a. The reservoir extends from the piston rod guide bush 22, support disc 24, packing holder 26 and seal 28 to just in front of the cylinder 18a.

It will be seen from Figure 2 that the continuous bore in the casing 18 which defines both the cylinder 18a and the reservoir 1 8b is coaxial with the piston assembly except for its assymetrical enlargement above the piston assembly 20, 20a. Therefore the volume of that part of the reservoir above a horizontal plane containing the longitudinal axis of the piston assembly is substantially greater than the volume of that part of the reservoir below said plane, the radial gap between the piston assembly and the wall of the bore defining the reservoir being substantially uniform, in cross-section of the reservoir, below said plane and increasing above said plane from said uniform size to a maximum size above the piston assembly. A consequence of this is that a relatively small quantity of hydraulic fluid is adequate to achieve the necessary oil level inside the casing 18. This oil level must not be below the upper edge of the fully retracted piston head 20, while with the piston head 20 fully received into the cylinder 1 8a sufficient space must remain inside the reservoir to allow for expansion of the hydraulic fluid into this chamber under increased temperature conditions. Furthermore the air pressure must increase in such a way that the packing 28 is not overloaded, in order to avoid difficulties in achieving a perfect seal. The described design of the reservoir 1 8b can be achieved by appropriate modification of the bore formed in the casing 18. Initially a bore concentric to the external contour of the casing 18 may be produced, so that the wall strength of the casing is adequate, and subsequently the reservoir may be given the form shown in Figure 2. This may be done by asymmetrically enlarging the bore in the region of the reservoir or by opening the top of the casing 18 in the region of the bore and then reclosing it with a suitably shaped cover e.g. of a synthetic plastics material.

WHAT WE CLAIM IS: 1. An hydraulically-damped buffer for railway vehicles comprising a piston assembly and a cylinder and reservoir assembly fixed to respective, relatively movable parts of the buffer whereby when the buffer is compressed, in use, the piston will move generally horizontally into the cylinder to displace an incompressible fluid therefrom to the reservoir, the piston assembly comprising a piston rod fixed at one end to one said respective part and having a piston head at its free end and the cylinder and reservoir assembly comprising a casing fixed at one end to the other said respective part, the cylinder and reservoir being provided by a continuous bore in the casing of which the cylinder portion is in the region of said fixed end of the casing and the reservoir portion is in the region of the free end of the casing so that the reservoir surrounds the piston assembly and is dimensioned to receive incompressible fluid displaced by the piston head from the cylinder portion and to provide space above the piston assembly and above

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The railway buffer illustrated comprises an outer buffer casing 2 with a flange 2a, to which a buffer plate 6 has been fastened by means of a fixing screw 38. The outer buffer casing 2 surrounds an inner buffer casing 4, which is screwed to a railway vehicle by means of flange 4a. Inside the buffer casing 4 an annular spring 8 is located, which is supported at its ends on thrust washers 10,12. The front thrust washer 10 is fastened to a piston rod 20a by means of a fixing screw 14, while the rear thrust washer 12 is fastened to a casing 18 by means of a fixing screw 14. The front thrust washer 10 has an outwardly extending area 10a which rests in an appropriate indentation 6a of the buffer plate 6 and prevents angular movement of the buffer plate 6 applying lateral forces to the piston rod 20a. The same applies to the contacting areas 12a and 18d of the rear thrust washer 12 and the casing 18. A retaining ring 16 prevents the outer buffer casing 2 from slipping off the inner buffer casing 4. The casing 18 has an internal bore, which includes an asymmetrically designed reservoir 1 8b for receiving hydraulic fluid displaced as a result of movement of the piston rod and expansion due to rise in temperature. The piston head 20 with a piston ring 20B is movable into an inner portion of the bore of the casing 18 defining a cylinder 1 8a when the inner buffer casing is telescopically received in the outer buffer casing. The cylinder 1 8a is connected with the reservoir 1 8b via overflow apertures 1 8c arranged around the bore circumference. The casing 18 is sealed by means of a packing holder 26, which contains a packing 28 for the piston rod and which contains a guide bush 22 between the piston rod and the piston head 20. The packing holder 26 is supported by a support plate 24 on the casing 18 and is secured against falling out by a circlip 34. Furthermore a skimmer 30 is located in the packing holder 26, which surrounds piston rod 20a and helps protect the highly sensitive packing device 28 against penetration of foreign bodies. Sealing of packing holder 26 against the casing 18 is effected by means of O-ring 32. Inside the casing 18-in a lateral position-an oil filler screw 36 is positioned at the oil level to be maintained. An easy check of the oil level is possible by means of this screw. The reservoir 18b is an extension of the bore of the casing 18 and contains air above piston 20 and piston rod 20a. The reservoir extends from the piston rod guide bush 22, support disc 24, packing holder 26 and seal 28 to just in front of the cylinder 18a. It will be seen from Figure 2 that the continuous bore in the casing 18 which defines both the cylinder 18a and the reservoir 1 8b is coaxial with the piston assembly except for its assymetrical enlargement above the piston assembly 20, 20a. Therefore the volume of that part of the reservoir above a horizontal plane containing the longitudinal axis of the piston assembly is substantially greater than the volume of that part of the reservoir below said plane, the radial gap between the piston assembly and the wall of the bore defining the reservoir being substantially uniform, in cross-section of the reservoir, below said plane and increasing above said plane from said uniform size to a maximum size above the piston assembly. A consequence of this is that a relatively small quantity of hydraulic fluid is adequate to achieve the necessary oil level inside the casing 18. This oil level must not be below the upper edge of the fully retracted piston head 20, while with the piston head 20 fully received into the cylinder 1 8a sufficient space must remain inside the reservoir to allow for expansion of the hydraulic fluid into this chamber under increased temperature conditions. Furthermore the air pressure must increase in such a way that the packing 28 is not overloaded, in order to avoid difficulties in achieving a perfect seal. The described design of the reservoir 1 8b can be achieved by appropriate modification of the bore formed in the casing 18. Initially a bore concentric to the external contour of the casing 18 may be produced, so that the wall strength of the casing is adequate, and subsequently the reservoir may be given the form shown in Figure 2. This may be done by asymmetrically enlarging the bore in the region of the reservoir or by opening the top of the casing 18 in the region of the bore and then reclosing it with a suitably shaped cover e.g. of a synthetic plastics material. WHAT WE CLAIM IS:

1. An hydraulically-damped buffer for railway vehicles comprising a piston assembly and a cylinder and reservoir assembly fixed to respective, relatively movable parts of the buffer whereby when the buffer is compressed, in use, the piston will move generally horizontally into the cylinder to displace an incompressible fluid therefrom to the reservoir, the piston assembly comprising a piston rod fixed at one end to one said respective part and having a piston head at its free end and the cylinder and reservoir assembly comprising a casing fixed at one end to the other said respective part, the cylinder and reservoir being provided by a continuous bore in the casing of which the cylinder portion is in the region of said fixed end of the casing and the reservoir portion is in the region of the free end of the casing so that the reservoir surrounds the piston assembly and is dimensioned to receive incompressible fluid displaced by the piston head from the cylinder portion and to provide space above the piston assembly and above

the level of incompressible fluid in the reservoir for a compressible gas, means being provided to form a sliding seal between the free end of the casing and the piston rod, wherein the continuous bore which defines the cylinder and reservoir is so shaped throughout the greater part of the length of its reservoir-defining portion that the volume of that part of the reservoir above a horizontal plane containing the longitudinal axis of the piston assembly is substantially greater than the volume of that part of the reservoir below said plane, the radial gap between the piston assembly and the wall of the bore defining the reservoir being substantially uniform, in cross-section of the reservoir, below said plane and increasing above said plane from said uniform size to a maximum size above the piston assembly.

2. A buffer as claimed in claim 1, wherein an aperture for replenishing the cylinder and reservoir with incompressible fluid is provided in the casing on one side of the reservoir above the piston assembly.

3. An hydraulically-damped buffer for railway vehicles constructed and arranged substantially as herein described and as shown in the accompanying drawings.