Improvements in or relating to impulse senders of the finger disc type

摘要

297,388. Telefonaktiebalaget L. M. Ericsson. Sept. 20, 1927, [Convention date]. Impulse transmitters for automatic exchange systems. In an instrument of the finger-dial type the contact springs 11 - - 13 are located between the circumference of the impulse wheel 9 and the dial shaft 2 and are actuated by a spring arm 16 which moves in a plane parallel to that of the impulse wheel. The arm 16 carries a pivoted pawl 18 having a sloped projecting end 19 which engages with sloping teeth on the impulse wheel, the pawl being held normally in the position shown in Fig. 4 by a spring 20. In the normal position of the impulse wheel the projection 19 rests on a reduced portion of the wheel so that off-normal contacts 12, 13 are held open. During the setting operation the pawl 18 oscillates in its own plane and the spring 16 only moves sufficiently to close contacts 12, 13. During the return movement, however, the oscillation of the pawl in the opposite direction is prevented by a stop 22 formed by a projection on the spring 16 so that the pawl and spring 16 are lifted to the top of each tooth and the spring 11, 12 are separated to send impulses. The return movement is controlled by a governor 27 geared to a toothed wheel which is connected to the shaft 2 by a oneway friction clutch consisting of a spiral spring.