Patent GB-878902-A (GB)
Title: Improvements in or relating to control apparatus
IPC: G05B19/04
Filed: 1956-10-12
Abstract: 878,902. Switching systems. JENSEN, H. B. F. Oct. 9, 1957 [Oct. 12, 1956], No. 31087/56. Class 38 (4). [Also in Group XXII] A control unit as shown in Figs. 2 and 4 includes two stepping switches each of which is connected to a multi-terminal plug u and h, the switches of each group being included respectively in a plurality of check or conditionsensing circuits and in a plurality of control circuits. An actuator S advances the fingers R1, R2 of the switches simultaneously. The condition-sensing circuits contain switches U1- U5 located in a machine to indicate the completion of various operations, the switches being connected to a multi-terminal plug u<SP>1</SP>. The control circuits include electrically-controlled members H1-H3 which may be pneumatic or hydraulic means actuated by solenoid valves, the members being connected to a multiterminal plug h<SP>1</SP>. In a particular instance, the switch U1, may be a manual starting switch, the member H1 may be a work clamp with correct clamping indicated by the switch U2 or a valve in a chemical plant with full opening or closing indicated by the switch U2. The switch U3 may indicate when a certain temperature has been reached or a particular fluid flow has occurred. The member H2 may be for working on the workpiece or for controlling heating of the fluid. The member H3 may remove the workpiece or open a valve. In a modification, several selector switches may be connected in series or an assembly line may be controlled by two control units in parallel. In a drilling- machine, a magazine 102, Fig. 7, contains striking plates for locks, the plates having two holes to be counter-sunk. The plates are fed by a fluid-pressure device H 2  which can be stopped in two positions by a stop 112 and a stop 114 movable by means H 1 . Each plate is clamped in two positions successively by clamps 116, 118 for counter-sinking the holes by the single drill 106. A control member H6 moves a finger 120 to check correct drilling of every other hole. If a hole has not been countersunk or is not deep enough, the gauge 120 causes a switch u14 to actuate a solenoid H 7  to advance a ratchet 134 thus turning a screw 136 and adjusting the position of the lower limit of the drill-moving arm 140. A gauge may also be fitted to check if a hole is too deep. Initially, a feeler 124 checks that there are workpieces in the feed-channel. Checks are also made to ensure that the drill reaches its upper and lower positions, that the stops are correctly positioned and that the workpiece is clamped. A programme chart may be prepared to assist in wiring the plugs connecting the machine with the control unit. A feeler 103 may indicate when the magazine 102 has emptied to cause a signal to be sent to a second control unit which rotates a table and brings a full magazine into position and may also refill the empty magazine. Alternatively, a regular check could be made in the number of workpieces in the magazine, such a check being made after a certain number of drilling operations. A device 105 measures the time taken to countersink a hole. If the time is too long, due to a blunt drill, a switch u<SP>1</SP>5 is opened to raise the drill, shut-off the drill-motor, clamp the drill spindle, position a tray beneath the drill and rotate the chuck to drop the drill, the falling drill closing a switch to move away the drill. Furthermore, a magazine arm is moved to supply a new drill which is inserted and clamped, and the machine is then re-started with the control unit in its initial position. A test apparatus may be used to check correct setting- up, the apparatus consisting of a manuallyadvanceable switch and indicator lamps. In another application, a welding-machine is automatically controlled to rotate a table to bring a work-holder to the electrodes, to withdraw the electrodes when welding is complete and again to rotate the table. Additionally, the work-holder may be opened to allow a workpiece to be blown clear, there being a check to prevent incorrectly held workpieces from passing to the electrodes. A worn drill may be detected by measuring the temperature of the cutting fluid and causing a new drill to be supplied. A check may be in the form of photo-cells in a Wheatstone bridge. Specification 878,903 is referred to.