Patent GB-536143-A (GB)
Title: Automatic hydraulic control valve mechanism
IPC: B30B15/26
Filed: 1939-11-08
Abstract: 536,143. Hydraulic presses: electric motor control systems. HARTFORD-EMPIRE CO. Nov. 8, 1939, No. 29679. Convention date, Nov. 12, 1938. [Class 69 (ii)] [Also in Group XXXVII] A hydraulic press such as is used for moulding plastic materials is fitted with an automatic valve controlling mechanism which comprises a release valve R, Fig. 1, a low pressure valve L, and a high pressure valve H separated from the valve L by a check valve 74, the valves R, L, H being operated in the desired sequence by electric motors M which are controlled by switches operated by mechanism driven by reduction gearing from the motor shafts, and under the control of timing clocks adapted to control the periods of operation of the low and high pressure devices and to cut off the pressure when the moulding operation is completed. Standard valves of the screw stem or needle type are used, and these are moved for opening or closing by fixed nuts N in which the threads S of the valves engage. The circuits for operating the motors M, which are of the reversing type, are controlled by a master starting button and a cycle starting button, the latter being operated after a series of blanks are placed in the moulds. On pressing the starting button the sequence of operations is as follows. The motor M of the release valve R is rotated in a direction to close the valve, and when the valve is nearly closed a closing limit switch cuts out the release motor and it coasts to completely shut position. A transfer switch then starts the motor of the valve L in a direction to open the valve, and also starts a low pressure timing clock. When the low pressure valve is open its motor is stopped by the opening of the open limit switch. The press then closes and the time of closing is allowed for in the setting of the low pressure time switch. At the expiration of the time of low pressure treatment the low pressure clock starts the opening of the high pressure valve, the setting of the high pressure clock and the closing of the low pressure valve which takes place at a small interval after the starting of the opening of the high pressure valve. When the high pressure valve is nearly open its open limit switch stops the motor, and a closing limit switch stops the closing movement of the low pressure motor. Finally the high pressure clock starts the high pressure motor in closing direction, and its limit switch cuts off its motor so that the valve coasts to closing position. A transfer switch of the high pressure valve then starts the release valve motor in the opening direction and its motor is stopped by an open limit switch. The press then opens to its full extent and when stripped and reloaded is ready for a further cycle of operations. In addition to the automatic cycle of operations described the various operations can be controlled also by a series of hand-operated switches. An electrical indicating system is used in connection with the motors which give red signals to indicate the opening of the valves and green signals for the closing. The position and method of operation of the switches are shown in Figs. 1 and 2 in which 32 represents the open limit switch, 34 the transfer switch, and 36 the closing limit switch. The contacts 106, Fig. 2, are pushed in front by levers 22 which are controlled by notched discs driven by worm reduction gearing from the motors. The arrangement is such that circuits are opened when the tipped ends 24 of the levers bear against the reduced parts 102 of the discs. These parts 102 are made long enough to permit the coasting of the motors referred to above, or the levers may be formed with spring-controlled tips which are moved aside if they run on to a raised part of the disc after moving into a depressed part. The transfer disc Fig. 7, is formed of two discs which are relatively adjustable to bring into register apertures 128, 130 which when in register permit operation of the switch, but prevent operation when the apertures are out of register, which occurs when the driving-disc is moving counter clockwise.