Patent GB-635501-A (GB)
Title: Improvements in and relating to hydraulic presses
IPC: B30B15/16
Filed: 1947-07-17
Abstract: 635,501. Hydraulic presses. HARE, P. J. July 17, 1947, No. 19123. [Class 69 (ii)] In an hydraulic press the motive liquid is delivered to a ram 10 by a reciprocating pump 26 which is actuated by a hand lever 62 having an amplitude of movement such that the pump crank can be moved through at least 90 degrees out of its outer deadcentre position and a release valve 51 is arranged so as to open a return circuit for the liquid when the lever is moved into one of its extreme positions. The rain 10 has a piston 12 at one end sliding in a cylinder 14 which communicates through holes 20 with a sump 22, overflowing into a sump 24 in which the pump 26 is positioned. The ram 10 is lowered against the action of a spring 18 when liquid from the pump 26 is admitted through pipes 32 and 30 to a bore 28 in the top of the ram. A pipe 34 leads from the pipe 32 to a control valve 36 which is in the form of a spring-loaded piston 38 and a rod 41 guided by a block 42. In the raised position and the idle stage of the downward stroke the cylinder 14 is not connected to the pipe 34 but connected to the sump 22 by means of a passage 40, a reduction 43 around the piston 38, a passage 44 and a pipe 46. When the ram encounters resistance the pressure build up acts on the rod 41 lifting the piston 38 and closing the passage 44 whereby the pump delivery is passed from the pipe 34 into the space above the ram by means of a bore 48 and a passage 49 in the block 42, a pipe 50, (see Fig. 4, not shown), the reduction 43 and the passage 40. The raising of the piston also cuts off communication between the pipe 46 and the reduction 43. After the working stroke the relief valve 51, Fig. 5, permits communication between the upper and lower parts of the cylinder 14 allowing the spring 18 to raise the ram. The valve 51 is arranged between a pipe 52 connected to the pressure pipe 32 and an exhaust pipe 53 leading to the sump 22, and consists of a spring actuated ball 54, and is operated by a lever 62, Fig. 1. The pump 26 has a piston 57 connected by a rod 58 to a crank 59 on a shaft 60, Fig. 5, to which is fixed a crank 61 carrying the lever 62. With a light load the lever 62 is oscillated so that the crank and connecting rod make a small angle (approximately 90 degrees) with each other, whereby a long stroke is obtained for a given amplitude of oscillations of the lever 62. With a heavy load, the lever is oscillatedinto and out of an extreme position so that the crank and connecting rod make a large angle (up to 180 degrees) with each other enabling a short stroke to be obtained for the same amplitude of oscillation. The valve 51 has a tappet 66, Fig. 5, projecting from a block 68 and is forced inwards by the crank 59 when the lever 62 is moved beyond the upper dead-centre position of the pump. The tappet 66 then unseats-the ball 54 which permits communication between the pipes 52 and 53 past the valve seat 55 and a passage 69 formed by a flat on the tappet 66. A safety valve 70 is connected to the pressure pipe 52 and is regulated by a screw 71 to operate at any desired pressure. The Provisional Specification states that a releasable stop may be arranged to prevent accidental operation of the valve 51 during pumping, the stop being controlled by a trigger on the lever 62.