GB1306364A - - Google Patents

Abstract

1306364 Timed control operations in electric circuits D H GREENHILL 13 Aug 1970 [15 May 1969] 24722/69 Heading G3T [Also in Division B3] A timed control arrangement for a machine cutting coiled springs or metal strips into predetermined lengths, modifies the machine operation - e.g. stops a material feed motor - in the event of faulty operation. The arrangement includes timers T1, T2, Fig.1. T2 is energized via a normally closed relay switch 5a and begins its timing cycle immediately a supply switch S is closed. The period of its cycle is just longer than the time normally required for a given length of spring 8 Fig.2, to be fed from a mandrel 9 to reach a probe 6. If no contact is made with the probe within the said period the timer through contacts therein (not shown) interrupts the spring feed motor supply and actuates an audible or visual alarm. If the spring contacts the probe 6 then terminals X Y are bridged thereby so that a transistor conducts energizing a relay coil 4 which closes contacts 4a. This in turn energizes a relay coil 15, thereby opening contacts 5a and tripping and resetting the timer T2, and simultaneously starts a timer T1. The period of T1 is just greater than the time normally necessary for a cutter 10 to sever the spring. If the spring is cut and severed then the link across X Y is broken and the transistor cuts off stopping timer T1. If the spring is not severed then T1 continues timing and stops the machine also actuates an alarm at the end of its period. Relay 4 and the transistor may be omitted, the timer T1 being started directly on contact of the spring with the probe 6.