A DEVICE FOR NEUTRALIZING METAL CHIPS IN A PRESSURE LIQUID ACCUMULATOR

Abstract: The invention refers to a device for rendering metal chips harmless which during operation occurs at a scraper ring (8) to a piston (4) in a cylinder (2) of a pressure liquid accumulator (1). In order to catch and maintain such metal chips present in the pressure liquid and prevent same from being carried away with the pressure liquid it is suggested according to the invention that radially inwardly of the scraper ring (8) is located an annular strip (9) of magnetic material adapted to collect the metal chips thereon.

Description: The present invention refers to a device for neutraliz­ ing or rendering metal chips harmless, which occur at a scraper ring of a piston in a cylinder of a pressure liquid accumulator. In hydraulic drive and control systems it is often used pressure accumulators in the form of a cylindrical chamber, in which a pressurized liquid, conventionally hydraulic oil, is confined by means of a piston under counter-pressure from a gas body. When the accumulator is emptied, the piston is moved in the emptying direction under the action of the gas body pressure, while when the accumulator is loaded, said piston moves in the opposite direction in the cylinder and compresses the gas body. During the piston movement and moreover during operation of e.g. hydrostatic transmissions metal chips arise which accompany the pressure liquid. Particularly in a pressure accumulator such metal chips might cause great harm since the piston at its pressure liquid side often is provided with a scraper ring where the metal chips might be clamped between said ring and the cylinder wall. By this, the cylinder wall might be scratched as the piston and its associated scraper ring moves. Such scratch damages might occur not only in the cylinder wall but also on the scraper ring and the piston. Sometimes oil filters are included in hydraulic systems but since the oil often has to travel a long distance to such a filter in which metal chips present might be removed, they still manage many times to cause great harm prior thereto. Thus, there is a great need of an improved device to render such metal chips harmless and particularly in connection with the most vital portion of the system, namely the pressure accumulator. The object of the present invention now is to remedy said problem and this object is reached substantially in that radially inwardly of said scraper ring is mounted an annular strip of magnetic material for collecting the metal chips thereon. If, according to a preferred embodiment of the invention a free space is formed in the piston at the side of the scraper ring and strip closest to the head of the piston, the metal chips might be collected and retained there in a very advantageous manner. By way of example, the invention will be further de­ scribed below with reference to the accompanying drawing, in which is illustrated a partial longitudinal section of a pressure accumulator having a scraper ring-provided piston ac­ cording to the invention. A hydraulic pressure accumulator 1 has a cylindrical casing 2, which at one end is closed by means of an end plate 3. In the cylindrical casing 2 is axially movably mounted a piston 4, which defines between itself and the end plate 3 a pressure liquid chamber 5. At its opposite side, the piston 4 defines a gas-filled space 6 within the cylindrical casing 2. At its peripheral surface the piston 4 is sealed against the cylinder wall of the casing 2 by means of conven­ tional piston rings 7 located in ring grooves. At the portion of the peripheral surface located closest to the head of the piston a scraper ring 8 is located in a groove in a similar manner. Preferably said scraper ring is formed with a front edge, which is inclined obliquely forwardly-outwardly as il­ lustrated. In order to render metal chips, i.e. of steel and similar materials which might be attracted by magnetic forces, harmless and prevent them from penetrating into the space between the scraper ring 8 and the cylinder wall of the casing 2 and cause damages of the aforementioned kind, which chips possibly occur in the pressure liquid, there is according to the invention radially inwardly of the scraper ring 8 arranged an annular strip 9 of magnetic material. Preferably, said magnetic strip 9 might be made in the form of a plastic-pressed elastic ring of e.g. samarium and cobalt. When the piston 4 moves within the cylindrical casing 2 metal chips possibly existing in the pressure liquid and located in the vicinity of the scraper ring 8 will be pulled towards the magnetic strip 9 by the magnetic forces therefrom and hence carried away from the cylinder wall of the casing 2 and the scraper ring 8. The chips get stuck onto the magnetic strip 9 and can then no longer hurt the cylinder wall and the scraper ring and/or the piston 4. It is also advantageous to provide at the side of the scraper ring 8 and the strip 9 closest adjacent the head of the piston a free space 10 in the piston 4 for housing the metal chips collected. Said space then also remains when the piston 4 reaches its end position into abutment against the end plate 3 such that the metal chips collected onto the magnetic strip 9 will not be dislodged and again discharged into the hydraulic liquid.

Claims: 1. A device for neutralizing metal chips occurring at a scraper ring of a piston in a cylinder of a pressure liquid accumulator, characterized in that radially inwardly of said scraper ring is mounted an annular strip (9) of magnetic material for collecting the metal chips thereon. 2. A device according to claim 1, characteriz­ ed in that at the side of the scraper ring and band located closest to the piston head is formed a free space in the piston for housing metal chips collected.

Inventors: ALUND, OLOF, Älund, Olof
Applicants: VOLVO FLYGMOTOR AB
Application year: 1988
Main classification: F15B1
IPC codes: F15B21, F15B1