GB846109A - Fluid-pressure control system - Google Patents

Abstract

846,109. Pneumatic jacks. DUNLOP RUBBER CO. Ltd. March 15 1957 [March 29, 1956], No. 9791/56. Class 8(2). [Also in Group XXIX] A pneumatic control system for fluid pressure operated mechanisms and as aircraft undercarriages comprises a source of pneumatic pressure 7a which can be connected to a double acting ram 2 through an "up " line 3 or a "down "line 6 by means of a four-way cock 4 the other line being connected to expand, and a damper valve mechanism comprising a tubular valve member 24 with a stepped end 25 arranged in the "up" line between the cock and the ram to allow free flow of air to the ram when the cock is set to connect the source to the "up" line 2 and to check the flow to exhaust through the "up" line when the cock is set to connect the source to the "down" line. The damper valve mechanism 12 comprises a pressure chamber 13 adopted to be connected to a source of air pressure, a supply chamber 15 adapted to be connected to the ram 2. The tubular valve member 24 is slidable in a fluid-tight manner through a wall 23 between the chambers and its stepped end 25 of reduced diameter is resiliently urged into closing contact with a valve seat itself spring urged against a stop member. Fluid pressure in the chamber 13 acting on the shoulder 26 of the valve member 24 moves the latter away from its seat and permits a substantially free flow from the chamber 13 to the chamber 15. Flow in the reverse direction however is impeded by the valve seat 28 which has to be raised from the tubular valve member 24 against the pressure of an adjustable spring 34. The stop member is in the form of a series of fixed fins in the base of the chamber 13. The valve seat which may be of rubber or the like is supported on a slidably carrier member 31 having a recess 35 to receive the spring 34. The valve member 24 is held against the seat 28 by a light spring 50 engaging a flange 48. The chamber 13 is supplied through ports 65 from a supply connection 14. The valve housing has a base portion such as 20 having a connection 21 enabling it to be screwed into a ram cylinder, or a base portion having a boss fitting a corresponding recess in a ram cylinder. A shuttle valve 5 is mounted in the "down" line 6 and enables a second source of pressure 10, normally cut off by a valve 11, to be applied to lower the undercarriage in an emergency.