True index gear tooth space checking machine

In an apparatus for recording in succession the deviation of a predetermined point of each of a series of teeth on a gear from a constant radius reference line comprising probe means for sensing said deviation of each of said gear teeth, sensing means mounted on said probe means and being movable with respect to said probe means upon contact with said teeth to provide an electrical signal that varies with said deviation of each of said teeth from said reference line, recording means responsive to said sensing means for recording each of said deviations, rotatable support means for said gear, support drive means for rotating said support means and said gear and endocer means driven by said drive means for providing electrical pulse signals representative of the amount of rotation of said support means and said gear between each successive predetermined point;

• the improvement comprising control circuity coupled to said encoder means for converting said electrical pulse signals to a repetitive succession of "forward" command signals and "backward" command signals that are precisely spaced in accordance with the number of teeth on said gear, probe drive means coupled to said digital processing means constructed to drive said probe means forward toward each of said gear teeth at said predetermined points upon the generation of a "forward" command signal and backward away from each of said gear teeth upon the generation of "backward" command signal, said probe drive means comprising a continuously rotating motor, an output shaft for said motor, a brake means coupled to said output shaft, a clutch means coupled to said output shaft, an eccentric coupled to said output shaft, an arm member connected between said eccentric and said probe means for driving of said probe means towards said gear during one-half revolution of said output shaft and said eccentric and for driving of said probe means away from said gear during the next one-half revolution of said output shaft and said eccentric, brake energization means and clutch energization means coupled to said control circuitry and constructed to respectively de-energize said brake means and to energize said clutch means in response to said "forward" and said "backward" command signals in order to achieve synchronization of said probe drive means with the rotation of said support means, forward limit switch means accuated by said probe drive means when said probe means is adjacent one of said predetermined points of said gear teeth for terminating the drive of said probe means toward said gear following the generation of "forward" command signal and prior to the generation of the next "backward" command signal and backward limit switch means accuated by a said probe drive means upon withdrawal of said probe means from the last contacted gear tooth by a predetermined amount following the generation of a "backward" command signal and prior to the generation of the next "forward" command signal wherein the actuation of one of said forward or of said backward limit switch means terminates each one-half revolution of said eccentric, wherein said probe drive means comprises a housing, a frame, stop means and a coiled spring wherein said housing is slideable in said frame and has a first cavity therein which receives said probe means and a second cavity therein adjacent to said first cavity which receives said coiled spring, said coiled spring being compressed when said probe means contacts said stop means such that said probe means stops at approximately the same position upon the contact of each gear tooth and such that the forward drive impact of said probe means is cushioned thereby.