| 摘要 |
<p>1275838 Valves ROBERT BOSCH GmbH 6 July 1970 [28 Aug 1969] 32574/70 Heading F2V Flow from port 11 to port 12 of the valve assembly shown, takes place when the supply pressure exceeds the loading of a spring 9 acting upon a main member 3, such loading being applied to the main valve member through to intermediary of a second valve member 7. However, when it is desired to control flow from port 12 to port 11, a pilot-pressure is supplied to the left-hand end of a piston 17 which then acts, through the intermediary of a stem 14, to first move the second valve member 7 off its seating on the main valve member 3, and then to move valve member 3 off its seating 4 formed within a cylindrical sleeve 2. Pilot pressure supplied to an annular channel 19 is communicated to the piston end initially through radial and axial piston passages 20 and 21. Subsequently, as the piston 17 moves to the right, radial passages 20 are moved out of communication with channel 19 and further radial passages 23, of a diameter less than that of passages 20, are brought into communication with channel 19. The arrangement permits the pilot pressure to be supplied to the piston end in a manner such that the pressure force acting on the piston end is decreased as the piston moves towards the end of its actuating stroke.</p> |
