Patent GB-828103-A (GB)
Title: An impulse sending device, more particularly a telephone dial
IPC: H04M1/34
Filed: 1957-04-16
Abstract: 828,103. Impulse transmitters. KRONE, G. April 16, 1957 [April 17, 1956], No. 12370/57. Class 40 (4). In an impulse transmitter a ball or roller is positioned between an impulse cam and impulse springs and is mounted in a carriage such that as a finger wheel is rotated to set the transmitter the ball or roller is moved away from between the cam and the impulse springs through a predetermined arc and when the transmitter is released to return under the control of a governor the carriage returns the ball or roller to its initial position in which it follows the contours of the cam and operates the impulse springs. In the embodiment shown in Figs. 3, 5 and 7, a shaft 9 driven by the finger wheel is fast with a cam disc 12 the periphery of which is surrounded by the cylindrical flange 15 of the carriage 14. At opposite sides of the flange 15 holes are bored to accommodate balls 18 and 19 which are retained between the cam edge and leaf-springs 20. The carriage 14 is frictionally coupled to the shaft 9 by means of a hairpin spring 25 and has stops 22, 23, which with an abutment 24 permits the carriage to move between the two positions shown in Figs. 3 and 5. When being set by the finger plate the carriage moves to the position of Fig. 3 and the balls 18, 19 are oscillated idly by the cam. When the cam returns the carriage is taken back to the position of Fig. 5 and the balls 18, 19 are then oscillated to break the contacts 27, 28, which are connected in parallel. Contacts 28 are hard wearing and of high contact resistance and make after and break before contacts 27 which are of softer material and -low contact resistance. The contour of the cam may be such as to give the balls a sinusoidal oscillation and the cam and balls may be coated with graphite or molybdenum sulphite. In place of the integral leaf spring 20, separate springs may be provided to hold the balls in place at each rest position, fixed rails being provided to contain the balls during movement from one position to the other (see Figs. 11 and 12, not shown). In the embodiment shown in Fig. 18 the balls may be caged by the cam 12 which has a flange 12a extending beyond its cam edge to form a thickened lip at its periphery to hold the balls within slots in the rim of the carriage disc 14. Circular ridges 49, 50 on each side of the carriage 14 bear on friction discs 45 and 46 pressed together by a spring washer 48. Arms 44 on the outer limbs of impulse contacts 27, 28 project inwardly to engage the balls when these are in the impulsing position. In this embodiment a flat spiral driving spring is used, the governor is driven through a one-way ball clutch, and off normal contacts are made when a projection from the periphery of the cam releases a spring- set. To check the number dialled a visible register may be operated by additional impulsing contacts when the balls are in the displaced position of Fig. 3. Additional sets of balls may be provided on the carriage to operate additional impulsing contacts, for instance, contacts having different make-to-break ratios which can be selected for use as required. To protect the contacts from dust and abraded particles the contacts are contained in a sealed compartment while a separate compartment contains the gears for the governor mechanism.