GB625711A - Improvements in or relating to fluid pressure operated ram-and-cylinder devices - Google Patents

Abstract

625,711. Hydraulic apparatus. AUTOMOTIVE PRODUCTS CO., Ltd., and HARRISS, J. H. May 8, 1947, Nos. 12514 and 24980. [Class 69 (ii)] [Also in Group XXVIII] In a ram-and-cylinder device of the kind which can be automatically set by suitable selection of the position of a control valve, to either of two extreme positions defined by the limits of the ram stroke, or to a predetermined intermediate position, a floating piston 18, Fig. 1, is provided in the cylinder 10, and the interior of the cylinder is divided into three pressure spaces by the ram head 15 and the piston 18, fluid pressure supplied to two of the spaces acting on the ram head 15 to move the ram 14 towards one or other end of its stroke respectively, and fluid pressure supplied to the third space urging the floating piston 18 against an abutment 17, intermediate the ends of the cylinder 10, to form a stop defining the intermediate position of the ram 14; the cylinder may have a larger bore for part of its length and the ram 54, Fig. 3, has a head 45 fitting slidably in the smaller bore of the cylinder, whilst a floating piston 46, which is annular and surrounds the ram 54, fits slidably in the larger bore, a shoulder at the change of diameter of the cylinder bore acting as a stop to define the intermediate position of the ram 54. The cylinder 10, Fig. 1, has a hollow centrallypositioned tube 16 projecting into its left-hand end, which tube has the abutment 17 formed on its inner extremity and acts as a guide for the floating piston 18. The ram 14, which is hollow and can pass over the abutment 17, is slidingly supported by and protrudes from the right-hand end of the cylinder 14. A valve 31 with a sliding-valve member 39, inlet port 32 from a pump 27 and exhaust port 33 has three outlet connections to the ram-and-cylinder device which, dependent upon the position of the sliding valve member 39, enables the ram 14 to be either retracted, by applying pressure to the right of the piston head 15, partially extended, by applying pressure to the left of the floating piston 18 or completely extended by maintaining the latter pressure and directing pressure fluid down the hollow tube 16 so that it acts between the opposing faces of the piston 18 and the piston head 15. In a modification, the pressure connection to the right of the piston head is taken directly to the pump, but the action of the apparatus remains unaltered since the area of the right-hand end of the piston head is less than the other active areas. In another modification, Fig. 3, the valve 31 is identical with that of Fig. 1, and the ram 54 is in two parts. One part of the ram 54 extends from each end of the stepped cylinder, the two parts being joined by a universal joint 56. Upon the left-hand portion of the ram is fixed the head 45 co-operating with a bore 43, whilst on the other ram portion is slidably mounted the floating piston 46, this latter ram portion being provided with a shoulder 47 to engage the floating piston. When pressure fluid is directed to the left of the piston head 45 and to the right of floating piston 46, the ram is held in the mid-position shown. If the pressure is only applied to the left end of the piston head 45 the ram is moved to the extreme right-hand position. When pressure is admitted between piston head 45 and piston 46, as well as to the right of the latter piston, the ram moves to the extreme left-hand position. An accumulator may be used to supply pressure liquid in place of the pump.