Patent GB-762420-A (GB)
Title: Precision control system for press brakes or the like
IPC: B30B15/24
Filed: 1954-06-29
Abstract: 762,420. Hydraulic presses. PACIFIC INDUSTRIAL MANUFACTURING CO. June 29, 1954 [Dec. 14, 1953], No. 19003/54. Class 69 (2). The moving platen of a press is moved quickly until the work stroke is nearly completed and then is moved slowly to complete the stroke and either end of the platen can be halted, independently of the other end, in completing the stroke. Pistons 11 in cylinders 13 move the upper platen 9, each cylinder being supplied with oil from a separate pump 15 and having supply and return pipes, the pipes for both cylinders being connected to a distributing valve 21 actuated by solenoids 24, 26. Both pumps may be driven by the same electric motor and are connected to separate, or a common, reservoir 17. The pressure of the fluid supplied to the two cylinders is equalized by blocking valves 27 and by a connection 35. A relief valve 37 is provided adjacent each pump. The press is controlled by a starting relay 185, a foot-operated switch 193, and a switch 189 for inching. When the switch 193 is released, the platen 9 moves to its "up" position and stops. Maintaining platen level.-A vertical rod 57 pivoted near its centre and mounted on the left-hand side of the platen 9 engages one of two micro-switches 51, 55 when one end of the platen advances with respect to the other end. The switches operate solenoid controlled valves 39 which supply extra oil to the cylinder that is lagging. Further micro-switches 61, 65 are provided on either side of the rod 57 and actuate solenoid-controlled "maximum out-of-level" valves 43 which direct the flow from the adjacent pump directly into the reservoir 17. Below the switches 61, 65 are two further switches 67, 69 termed "emergency" switches which, when opened, cut off the electrical supply to the press. Unequal movement of one end of the platen swings the rod 57 by a cord 73 attached at 79 to a bracket on one side of the press and passing over a pulley 77 and under a second pulley 75 on the platen and connected to a spring-loaded arm 71 on the rod 57. Limiting stroke.-Switches 83, 93 are mounted at both sides of the press and co-operate with stops 107, 111 respectively to limit the depth of stroke. The stops are connected by a cord 115 so that the stops will move together during adjustment. A micrometer adjustment 109 is provided on the stop 107. A switch 85 is engaged by a stop 123 to determine the uppermost position of the platen, fine adjustment of this position is not necessary. Initiating up-stroke.-When both the left and right depth switches have closed, a relay 215 closes contacts 217 and a circuit is made through a delay relay 199. A relay 223 is then energized and a solenoid 26 moves the main valve 21 and the platen 9 is raised. When the stop 123 engages the switch 85, the circuit through the relay 199 is broken, the relay 223 is deenergized and the valve 21 returns to its neutral position. Slow-speed movement of the platen.-Slowspeed movement is brought into operation when a switch 163 is actuated by the left-hand depth stop 107. The slow-speed system includes a pair of low capacity flow control valves 127, 129, check valves 131, 133, and solenoidcontrolled valves 135, 139 which are closed when the machine is running at normal speed. The platen is maintained level by the left flow valve being of slightly higher capacity than the right flow valve and by providing a third valve 142, which is solenoid operated, and supplements the flow of the right flow valve.