GB539406A - Improvements in and relating to electric impulse counters - Google Patents

Abstract

539,406. Counting-apparatus. BOULTON PAUL AIRCRAFT, Ltd., and COX, J. H. April 26, 1940, No. 7495. [Class 106 (i)] An electric impulse counter comprises a spring controlled toothed drum held a gainst a stop and engaged by an actuating pawl and a retaining pawl, the actuating pawl being actuated by the armature of an electric motor when the armature is displaced in one direction from a normal position in response to each of the impulses to be counted, and tripping means for both pawls, effective upon the reversed displacement of the armature to trip the pawls and allow the counter to return to zero position. As shown in Figs. 1 and 2, a counter wheel 1 is loosely mounted on a shaft 13 and is normally held by a spring 23 with an abutment 24 engaging a stop 25. The shaft 13 supports the laminated armature 6 of an electric motor with two armature windings. 2, 3 and associated field windings 4, 5. Two field magnets 7, 8 of arcuate form and laminated have pole pieces 9 ... 12 projecting radially towards the armature. To the armature is secured an arm 14 carrying an actuating pawl 15 and, at its opposite end, an abutment 16 disposed against the tail end of a retaining pawl 17. The normal position of the armature is maintained by a spring 20. The windings 2 and 4 are electrically connected to a pair of input terminals for the impulses to be counted and drive the counter anti-clockwise in Fig. 1. The movement being limited to one step by a suitable stop 22. The windings 3 and 5 are electrically connected to a second pair of terminals in a resetting circuit whereby the armature is actuated in the reverse direction to retract the actuating and retaining pawls whereupon the spring 23 returns the counter wheel to zero position. A mutilated portion of the teeth of the wheel permits the actuating pawl to oscillate if for any reason the pawl continues to operate after the wheel has reached the limit of its travel. The device may be applied to a machine gun for counting the number of rounds fired and the re-setting circuit may be completed on the application of a loaded magazine to the gun. The re-setting circuit may be completed manually by the operation of a push button or lever. According to the Provisional Specification the indicator drum may carry an abutment to actuate the switch and complete the re-setting circuit when the drum reaches the end of its travel.