| 摘要 |
<p>1,172,008. Pressure-reducing valves. SOC. ANON. D.B.A. 21 July, 1967 [4 Aug., 1966; 29 June, 1967], No. 33691/67. Headings F2F and F2V. An hydraulic pressure modifying device for a vehicle braking system comprises a normally open valve between inlet and outlet chambers controlled by the pressure in the outlet chamber to close the valve when the inlet pressure is above a predetermined value, the valve seat being movable towards the outlet chamber against the force of resilient means, means being provided to oppose the displacement of the pressure-responsive element which is connected to the valve control member by retractable means. In the device of Fig. 1, a through path is normally open from the master cylinder 12 to the brake cylinders 14 via inlet chamber 44, orifice 30 and outlet chamber 46. When the pressure in the latter reaches a predetermined value a piston 32 is driven back against a spring 42 until it reaches an abutment 52. A U- shaped piece 60 bears against the piston and is driven with it by a spring 64, carrying with it a head 56, valve stem 54 and valve closure member 50, thereby closing the orifice 30. Further increase of inlet pressure drives the piston 28 backwards against a spring 38, the valve 50 remaining closed, the decrease in volume of chamber 46 causing the outlet pressure to rise, but at a lower rate than the inlet pressure. The relationship between the two (preferably linear) depends on the characteristics of spring 38. In a modification (Fig. 2, not shown) the piston 32 and spring 42 are replaced by an elastomeric diaphragm, to the other side of which a modifying pressure can be introduced, e.g. representing axle loading. The piston 28 and spring 38 are also replaced by an elastomeric washer. In another modification (Fig. 3, not shown) both piston-spring assemblies 28/38/64 and 32/42 are replaced by elastomeric rings of circular cross-section as in Specification 1,148,557. The spring 62 is replaced by a further spring (78) between the head 56 and a plate (76) bearing on the right-hand ring. In both these modifications the abutment 52 is omitted. The different features of the various modifications shown may be combined in any way.</p> |
