| 摘要 |
1283986 Valves; fluid pressure brakes ROBERT BOSCH GmbH 9 Dec 1969 [10 Dec 1968] 59993/69 Headings F2F and F2V In a pressure relief valve having an inlet 4 and an outlet 10, the closure member 7 is formed from a sheet metal part 15 and a rubber part 21, with the rubber part having an axially directed annular extension 11, a portion 20 of which is sealingly slidable along a housing extension 19. With the above construction, communication between the fluid flow path and the valve spring- chamber 12 is inhibited and, as a result of appropriate dimensioning of the seat 6 and the extension 19, the effective valve area does not vary after opening of the valve. In modifications (Figs. 2 and 3, not shown), the annular extension 11 may take the form of a bellows (29), and the inlet port 5 may contain a T-shaped throttling member (32) which is arranged to be in operative communication with the closure member by means of an additional spring (34) and which itself can act as a relief valve. The valve is stated to be primarily suitable for use in brake systems where it serves to maintain a residual pressure in the part of the system connected upstream of the valve. When so applied, the valve is adjusted to open at a threshold pressure lower than that which is still sufficient for braking. If a leak occurs in the brake system downstream of the relief valve whilst that upstream of the relief valve is intact, pressure will drop not only downstream of the valve but also upstream. When the pressure upstream of the valve has dropped below the threshold pressure, the relief valve will close and cut off the defective part from the intact part which will continue to function provided that there is sufficient pressure upstream. |
