Manually operable rotary pulse generating apparatus for pulse counting and similar applications

In electrical apparatus having control means responsive to the number of pulses fed to the input thereof, a manually operable pulse generating apparatus whose output is to be coupled to the input of said control means and comprising a manually operable dial knob member movable in at least a first operating direction, a cam member having sawtooth ratchet teeth-forming lobes, means coupling said dial knob member to said cam member when said dial knob member is moved in said operating direction, said coupling means comprising a spring force-urged detenting and force-transmitting pawl member formed by a spring having at one end a pawl-forming end, each of said lobes having a gradually rising leading side over which said pawl-forming end of the spring rides when said knob member is moved in said operating direction and a sharply dropping trailing side, the spring being stressed at least when the pawl-forming end member of said spring leaves said crotch and rides on any point of the gradually rising side of a lobe of said cam member, such stress in the absence of an external force causing the cam member to rotate to a position where said pawl-forming end of the spring is in the crotch between said gradually rising side of a lobe and the trailing side of the adjacent lobe, to detent the movement of said dial knob member and cam member, so that the dial knob member has discrete positions which it assumes as it is advanced in said operating direction, a stationary piezoelectric element with output terminals across which an appreciable damped waveform appears when the stress on the same is suddenly changed, said pawl-forming end of said spring joining a curved spring portion extending part way around a cylindrical pivot-forming member and terminating in a flat spring end bearing against a side of said piezoelectric element, said pawl-forming end of said spring being urged toward the opposite end of the spring bearing against said piezoelectric element to progressively compress the same as the dial knob member is advanced from one detented position toward the next detented position thereof, said pawl-forming end of the spring applying an initial stress to said piezoelectric element as said pawl member starts to ride up the leading side of a lobe of said cam member, which stress reaches a maximum value and is suddenly relieved to generate a damped waveform at said output terminals when said pawl-forming end of the spring falls off the high point of one of said lobes.