Patent GB-502969-A (GB)
Title: Improvements in hydraulic systems
IPC: B21J15/20
Filed: 1937-09-27
Abstract: 502,969. Hydraulic presses; hydraulic intensifiers; hydraulic apparatus. BURGESS, A. F. (Hannifin Manufacturing Co.) Sept. 27, 1937, No. 26132. [Class 69 (ii)] A hydraulic system includes a hydraulic machine such as a press having a tool which is operated by a piston moving in a cylinder, a source of pressure fluid, an intensifier and a control unit for regulating the connection between said source, said intensifier and both ends of the cylinder of said hydraulic machine, said control unit including a manually controlled means and an automatically acting means, the manually controlled means serving to initiate the forward stroke of the piston of the hydraulic machine and the automatically acting means to effect the change from low to high pressure when the tool contacts the work, the initiation of the return stroke at the completion of the forward stroke and the cessation of movement at the end of the return stroke, the manually controlled means being also effective at any point in the advance stroke of the piston to stop such advance stroke and to initiate the return stroke of the piston. The manually controlled means may also be operable at any point in the return stroke of the piston of the hydraulic machine to stop such stroke and to initiate the advance stroke of the piston. A riveting press comprises a yoke 10 carrying a cylinder 12 connected by flexible pipes 15, 16 with a control unit 14; pressure liquid is supplied by a pump 17, and the control unit comprises a main distributing valve 33 and a valve 78 controlling the operation of an intensifier 23. To initiate a cycle, a push-button switch 51 on the riveter is depressed and held down ; this energises a solenoid 45 and causes depression of the valve 33 to " Forward " position, the fulcrum 53 of the link 47 being fixed since the pin 54 is held down by a latch 58 urged to the right by a spring 61. Depression of the valve 33 partly compresses a spring 67. Pressure liquid passes to the cylinder 12 via 36, 63, 62, 27, 15. The pressure acts on member 69 and raises pin 68 to an elevated position in which it is locked by latch 73 pressed to the left by a spring 74 ; the spring 67 is thus further compressed. When the tool contacts the work; pressure rises in conduit 36 and acts through 82, 84, 83 to raise the valve 78 against spring resistance ; pressure liquid now passes via valve 78 and line 26 to the underside of the intensifier piston 24, the plunger 25 cutting off the line 62 and subjecting the liquid 26, 27, 15, 12 to high pressure. When the pressure reaches a sufficient value it acts through line 96 on member 94 and raises a pin 28, a cam surface 99 on the latter withdrawing the latch 58 against the spring 61 to release the fulcrum pin 54 ; the spring 67 expands, moving the valve 33 upwards to the " Return " position. At the end of the return stroke, the rise in pressure acts through 104 on member 103 to elevate pin 30, a cam surface 108 on the latter withdrawing the latch 73 against the spring 74 ; spring 77 then depresses pin 68, and spring 56 then depresses pin 54, causing the valve 33 to move down to the " Inoperative " position in which the pump is byepassed. On release of the button 51 the solenoid 45 is de-energized, and pin 54 moves down under the action of the spring 56 and is re-engaged by the latch 58. The system is thus re-set for a new cycle initiated by again depressing the push-button. If, during the cycle the button 51 is released, forward travel is'interrupted and return travel initiated, and if the button be again depressed, forward travel is resumed. The valve 78 is loaded by a spring 86 acting through a liquid column 81; when the valve 78 rises, some liquid escapes through line 87 so that the liquid column is shortened, and the spring 86 cannot return the valve 78 to its initial position. During the return part of the cycle, line 37 is under pressure and liquid passes from the line 87, pushes back a plunger 100 loaded by a spring 109 and makes up the liquid column to its original length so that the valve 78 is returned to its initial position. A spring-loaded pressure relief valve 113 is provided; the pump 17 is immersed in a reservoir to which liquid returns through a filter screen.