Patent GB-794979-A (GB)
Title: Improvements in or relating to presses suitable for use in performing cutting operations of sheet materials
IPC: C14B5/00
Filed: 1955-07-12
Abstract: 794,979. Clicking presses. BRITISH UNITED SHOE MACHINERY CO., Ltd. (United Shoe Machinery Corporation). July 11, 1956 [July 12, 1955], No. 20078/55. Addition to 764,634. Class 31 (1). [Also in Group XXIX] In a press comprising a bed 10 and a presser member, e.g. a beam 16, having oppositelydisposed portions 40, 124 of electrically-conductive material between which sheet material 20 and a cutting-die 18 are positioned, and an electric circuit arrangement effective to cause power-operated means to bring about a relative movement of separation between the bed and presser member (after it has brought about a relative movement of approach between the bed and presser member) when a cutting edge portion of the die has completely penetrated the sheet material, all as set forth in the parent Specification, which is referred to, the electric circuit arrangement comprises a first thyratron 460 having an input circuit including a source 468 of direct current bias voltage and a resistance 470 to maintain the thyratron normally non-conductive, the source 468 being connected across the conductive portions 124, 40 whereby the bridging of the gap between the portions 124, 40 by the cutting die 18 is effective, to render the thyratron conductive, a time delay device comprising a resistor 478 and a variable capacitance element 480 associated with the output of the thyratron, and a second thyratron 462 normally biased so as to be non-conductive and having an input circuit connected with the time-delay device, the arrangement being such that the thyratron 462 is rendered conductive to initiate a relative movement of separation between the bed and presser member at a predetermined time after the thyratron 460 is rendered conductive. The thyratron 460 is associated with electrode means (e.g. a handle 132) adapted to be electrically connected with the operator and with the bed, or presser member, so that, if, during the relative movement of approach between the bed and presser member, the operator contacts the presser member, or bed, a relative movement of separation between the bed and presser member will be initiated automatically. The press is further provided with a mechanically-operated switch device 216, alternative to the electronic control means, for causing the power-operated means to bring about a relative movement of separation between the bed and presser member after it has brought about a relative movement of approach between the bed and presser member to a predetermined extent. The output circuit for the thyratron 460 comprises a resistor 476 connected in series with a direct current supply source 306. The thyratron 462 has an output circuit including a normally-closed relay 272 which is operative, when the thyratron is rendered conductive, to initiate a relative movement of separation between the bed and presser member. The power-operated means comprises a piston-and-cylinder device 50, 52 connected with a spindle 14 supporting the post 12 and associated beam 16. Pressure fluid is supplied through passages 138, 152, 154 to the ends of the cylinder 52 from a sump 136 by means of a motor-driven pump 134 and a valve casing 140 in which is slidable a spring-influenced valve element 146 controlled by a solenoid 196 which is electrically connected to the conductive portions 124, 40 through a switch 208 or 210 which is operable by means of the spring-influenced handle 132. The electric circuit arrangement includes an alternating current supply source, a normally-closed auxiliary relay 266, a normallyopen starting relay 268 and the relay 272. When the handle 132 is depressed, the solenoid 196 is energized and pressure-fluid is supplied to the upper end of the cylinder 52 to move the beam towards the bed. A high-pressure relief valve 176 is provided which is operable, should the pressure of the pump 134 build up to a peak point while the beam is being forced downwardly, to trip a switch 184 which causes the valve element 146 to be moved upwardly to arrest downward movement of the beam. The valve casing is provided with low-pressure relief mechanism in the form of a spring-influenced slotted sleeve 156 to avoid the building up of excess pressure by the action of the pump 134 when the valve element 146 is in its uppermost position and with high-pressure relief means in the form of a spring-influenced needle valve 170 which is operative when pressure has been built up to a predetermined point during the operation of forcing the beam downwardly. Movement of the beam to its uppermost position is cushioned by means of a valve in the passage 154. When a switch 312 is in the closed position shown, the switch device 216 is used to terminate downward movement of the beam. In this case, the direct current source 306 for the electronic stroke-terminating means is isolated by means of a switch 310 rendering the electronic control means inoperative. The switch device 216 is operated automatically when a split collar 74 on the spindle 14 engages a roller 256 on an arm carried by one end of a pivotallymounted spring-influenced rocking lever 218 provided at its other end with a rod 234 on which is adjustably mounted a sleeve 236. When it is desired to use the electronic stroke-terminating means, the switch 310 will be closed and switch 312 may be opened, thus disconnecting the switch device 216. If the switch 312 is left closed, however, the switch device 216 acts as a safety device to reverse the movement of the beam after a predetermined stroke should the electronic means fail to operate for any reason. Use may be made of a two-hand safety control by which the operator is required to depress the handle 132 with one hand and to press one or other of two buttons 212 to close a switch 214, in series with the switch 208, in order to initiate operation of the stroke-starting means. The control by the push-buttons can be eliminated when desired, by moving a switch 282 to a contact 314. The heightwise position of the beam is adjustable by means of a hand wheel 86 (not shown) and the swinging movement of the beam is arrested by means of the engagement of stops 100, Fig. 4 (not shown), with rubber buffers 102 (not shown). The fluid-pressure operated means may be replaced by mechanical means. In a modification, Fig. 7 (not shown), the portion of electrically conductive material is insulated from its associated bed while the oppositelydisposed portion of electrically-conductive material is electrically connected to the beam. Specification 794,980 also is referred to.