Patent GB-502486-A (GB)
Title: Improvements in or relating to hydraulically operated reciprocating mechanism
IPC: B23Q5/033
Filed: 1937-09-17
Abstract: 502,486. Liquid - pressure engines ; hydraulically - operated machine tools. KAPELLA, Ltd., and COOKE, E. A. Sept. 17, 1937, No. 25285. [Class 69 (ii)] Hydraulically operated reciprocating mechanism comprises two pistons mounted on a common piston rod and operating in separate cylinders, a supply of high pressure liquid from a high pressure circuit being alternately admitted to one under piston face and one upper piston face of the same effective area to cause reciprocation of the pistons, and a supply of low pressure liquid from an independent low pressure circuit being admitted to the other under piston face as the pistons move upwards. The space 7 below the upper piston 3 and the space 8 above the lower piston 2 form the high pressure working chambers, and the space 9 below the lower piston 2 forms the low pressure chamber; low pressure liquid from the pump 11 is admitted to chamber 9 through line 12 and non-return valve 13, and can exhaust therefrom through port 8b and line 22 containing a pre-set throttle valve to the tank A, under the control of a valve X which also controls the supply to, and exhaust from, the chambers 8, 9 of the high pressure liquid supplied by pump 17 through line 18. The valve X is hydraulically operated under the control of'a pilot valve 16 operated by tappets 6 on the reciprocated member 5. For the up stroke, high pressure liquid enters the chamber 7 through inlet port 7a, the outlet port 7b being at that time closed ; high pressure liquid passes from chamber 8 through port 8a, passage 21, throttle valve 20b and line 20 to the tank; low pressure liquid enters the chamber 9 through the non-return valve 13, the outlet port 8b being at that time closed. For the down stroke, high pressure liquid enters the chamber 8 through port 8a; high pressure liquid passes from chamber 7 through outlet port 7b, passage 19, throttle valve 20b and line 20 to the tank ; low pressure liquid passes from the chamber 9 through the port 8b. The throttle valve 20b is adjustable to vary the speed of operation. Movement of the valve X is cushioned at the ends of its stroke by liquid trapped in its actuating spaces by projections on the ends of the valve. The pistons 2, 3 are provided with annular spaces which are at all times in communication with the chambers 7, 9 respectively through ports and passages 2a, 3a in the pistons, the said annular spaces serving to establish communication at all times between said chambers 7, 9 and the corresponding ports 7b, 8b. In a modification, Fig. 2 (not shown), the chambers below the pistons and the annular spaces in the pistons which are in constant communication with the corresponding outlet ports for the chambers, communicate through ports controlled by spring-loaded valves mounted in the pistons, these valves opening only when exhaust from the chambers is taking place. In a further modification, Fig. 4, the main valve Y is actuated electromagnetically under the control of a reversing switch 41 actuated by tappets 40. The valve Y controls the high pressure chambers 36 and 38 only. The low pressure is that due to the gravity head from the tank A, the low pressure pump being dispensed with. Exhaust from the low pressure chamber 37 through line 22b to the tank is controlled only by a spring-loaded sleeve valve provided in the lower piston as described above with reference to Fig. 2. A similar valve is also provided in the upper piston. The invention is stated to be applicable to machine tools as, e.g. abrading machines.