Patent GB-652103-A (GB)
Title: Improvements in or relating to fluid pressure operated control systems
Inventor: HACKNEY STANLEY
IPC: F15B20/00
Filed: 1947-12-22
Abstract: 652,103. Single stroke apparatus. ELECTRO-HYDRAULICS, Ltd. Dec. 22, 1947, No. 33872. [Class 8(ii)] [Also in Group XXIX] A fluid pressure-operated control system comprises a cylinder, a piston or piston assembly slidable therein, a floating piston within the cylinder and two different sources of fluid pressure, the arrangement being such that the sliding piston or piston assembly is capable of controlling, as selected in one or other or both directions, the system to be operated whilst the floating piston is capable on selection of controlling in one direction only the same operation of the system as that controlled by the piston or piston assembly. Fig. 4 shows one embodiment of the invention comprising a double-acting jack which can be extended and retracted alternatively by two different sources of fluid under pressure. The two sources of fluid pressure, may be operated by different fluids, e.g. one oil and one air. If fluid is supplied to a connection 15 an annular floating piston 29 is moved to the right to retract the jack. Retraction can also be obtained by allowing fluid pressure to pass through a connection 10 and through the interior of a hollow piston rod 2. Extension can be obtained by applying fluid pressure either to a connection 16 where it acts on a floating piston 13 or to a connection 30 from which it passes through a tube 28 to the space between the piston 4 and the piston 13. Various other embodiments are described. In one the provision for alternative retraction and in another the provision for alternative extension are deleted by dispensing respectively with the floating pistons 29 and 13 and modifying the design accordingly. In another embodiment a single floating piston is employed at the end of the cylinder opposite that at which the piston rod passes through the cylinder end and this piston slides over a tube through which fluid can pass to the interior of the cylinder between the main piston and the floating piston for extension. In another embodiment which is double-acting and in which the jack can be operated both ways by an alternative source of fluid under pressure the piston rod extends on each side of the piston through the ends of the cylinder and carries at each end an attachment member. There is an annular floating piston at each end of the cylinder and fluid pressure connections carried by each attachment member. It is stated that where a double-acting jack has been described a single-acting jack could be provided which could be biassed into one position by a spring or by the weight of the part being moved. In the embodiment shown in Fig. 6 for operation of an aircraft undercarriage retraction is effected by supplying fluid under pressure through an inlet 15. When it is desired to lower the undercarriage fluid pressure is admitted through an inlet 22. Alternative lowering is effected by supplying fluid under pressure through an inlet 10. The fluid acts on a floating piston 13 to extend the jack. Fig. 9 shows a fluid pressure operated system for operating a jack 64 with pistons 86, 99 and 104 in both directions by normal and alternative sources of fluid pressure supply. Fluid pressure applied at an inlet 59 for normal operation is directed to one or other side of the jack by a control valve 48 which can apparently be operated either manually, electrically, or by pressure from an alternative system to be described later. When employing electrical operation solenoids 76, 77 control valves 73, 74 which control the supply of fluid from the inlet 59 to one or other side of a valve member 68 to move this valve member to the desired position. When employing the alternative system fluid pressure is applied at an inlet 96 and a selector valve 98 controlled by electrically-operated valves 97, 100 directs fluid to act on one or other of pistons 86, 104 and one or other side of the selector valve 48. Floating pistons 90, 92 in the casing of the valve 48 move the valve member if it is not already in the desired position so that it connects the appropriate side of the jack to exhaust. An arrangement including a valve similar to the valve 48 but with provision for moving it in one direction only by the alternative source of fluid pressure is described. The jack may have incorporated therein a mechanical lock for example of the type described in Specification 527,225 or a load limiting device of the type described in Specification 652,094. When a jack is singleacting one of the fluid connections in the jack is open to atmosphere.