| 摘要 |
<p>1,114,721. Press brake; shearing. PACIFIC PRESS & SHEAR CORPORATION. 18 Oct., 1966 [20 April, 1966], No. 46557/66. Headings B3E and B3W. A device to control the attitude of a ram 1 of a press brake, shear &c. which includes an hydraulic motor 7 at each end of the ram and a pump 13 for each of the motors comprises means responsive to deviation of the ram from a desired attitude which continuously and non- proportionally unbalances the hydraulic flow to the motors to restore the ram to its desired attitude. The ram 1 has a tape 45 fixed at one end to the frame 43 of the machine and at its other end to a servo-valve assembly 41 which comprises a housing 51, housing inlets 53, 55 and an outlet 57 with a spool 61 slidable therein to restrict the flow of fluid at one inlet and increase the flow at the other when the ram deviates from the desired attitude. The inlets 53, 55 are connected to the discharge line 19, 17 respectively of each pump 13. A restriction 75, 77 is placed in each of the flow connections 65, 67 for the servo-valve 41 so that the line 65, 67 which has its flow increased by the valve has a large pressure drop across the restriction. This pressure drop is used to control a relief valve 71, 73, Fig. 2 (not shown), which permits the associated pump to discharge directly to the tank when it is open. In each pump discharge line 17, 19 there is a blocking valve 33 which is normally open, but each valve is controlled by a flow connection 35 to the discharge line of the other pump so as to maintain equal loading on the pumps.</p> |
