Patent GB-744053-A (GB)
Title: Improvements in control of automatic machines
IPC: G05B19/08
Filed: 1952-10-09
Abstract: 744,053. Switching systems. NORTHERN ALUMINIUM CO., Ltd., and HOWITT, F. Jan. 8, 1954 [Oct. 9, 1952], No. 25300/52. Class 38 (4). [Also in Group XXIII] A control system for an automatic machine such as a casting machine, comprises a multipole, multi-way uni-selector switch wherein the operating coil 4, Fig. 1, is energized by a circuit between two contacts N1, N2 in each way 1 ... 25, other contacts N3, L4, L5, L6 in some or all of the ways being connected to operating circuits in the machine to energize the circuits when the poles of the switch engage the respective contacts and de-energize the circuits when the poles advance to the next way. The control system may control a machine for casting aluminium pistons in which the opening of the mould dies takes place in several stages, each being switched in by the closure of a limit switch or micro-switch or operation of a photo-electric relay at the end of the preceding stage. Photo-electric relays may also give warning of the absence of components such as sand cores, mould linings or steel inserts. The casing operation is started by pressing a button 14 to energize the coil 4 and advance the switch poles from the first bank of contacts to the second bank in which a pair of contacts are connected to a single pole, two-way limit switch 9. If the switch is functioning correctly, i.e. capable of being opened by a projection 11 on one of the mould operating jacks 3, 7 when the mould member has reached the correct position, it will complete the circuit through the contacts and transmit a pulse to the coil 4 which then advances the poles to way 3. The contacts of this bank are connected to the switch 9 and to a gas-filled valve or an operating coil 6 for controlling a valve 2 to supply air to the jack. Operation of the latter, which is terminated by the projection 11 closing the switch 9 to transmit a pulse to the coil and again advance the poles, opens a switch 10 for limiting movement of the jack in the return direction. Preferably the limit switch for each operation is checked in the above way, the poles of the selector switch remaining against the bank of contacts connected to any faulty switch. When several parts of the mould are moved together the limit switches are series connected in the manner shown in Fig. 3 to prevent transmission of a pulse to the coil 4 until all the contact switches have the same setting, either C or D. The automatic cycle is arranged to start with the closing of the mould, and the limit switch closed at the end of the mould closure is arranged to switch in an operator circuit including a pyrometer located in one of the outer dies of the mould. The pyrometer controls a capacity relay which switches in an electronic timer when the mould temperature has reached a certain level following the pouring operation which is effected by hand. At the end of the time interval, the coil 4 is energized to advance the poles and switch in the first of the operator circuits controlling opening of the mould dies. The side dies and gudgeon-pin bore dies of the piston mould are moved apart simultaneously, the central core die then being withdrawn followed by the moving together of the outer core-dies. In order to prevent the dies from becoming too cool during the interval between successive casting cycles, a second electronic timer may be switched in when the outer core-dies complete their movements, this timer sounding an alarm bell if the dies are not closed and a further casting poured during the set time interval. The capacity relay of the pyrometer normally de-energizes the circuit of the warning timer through advancement of the selector switch. Up to twelve uni-selector switches may be controlled by a single uniselector switch to provide more operating contacts. Electronic timing relays may be used to time the interval between successive operations in a cycle of operations or between successive cycles, and hydraulic cylinders or electric motors may be used to effect the movements in the cycle. The Provisional Specification refers also to the use of relays and warning lights in the test circuits of the limit switches and to testing all the circuits before the machine cycle proper commences.