Critical torque detector

An apparatus for detecting the critical torque imposed on a rotating drill, comprising:

• a rotating input member,
• an output member for supporting said drill and connected in a flexible driving connection with said rotating input member, and
• means for detecting the difference in rotational speed between said input and output members, when said drill is subjected to a torque greater than the predetermined critical torque,
• said rotating input member including:
• a rotating tubular member having therein a tapered bore and a plug member with sloped cam surfaces fixed coaxially with said bore,
• a cap member adjustably mounted on said tubular member, and
• a coil spring connecting said cap member in flexible driving connection with the output member,
• said output member including:
• an intermediate sleeve fitted over said tubular member and connected by said coil spring with said cap member, and
• a cup shaped member secured to said intermediate sleeve and surrounding the forward end of said tubular member to permit limitedly relative rotation between them, said cup shaped member having an integral tapered portion projecting forwardly for mounting a drill,
• a central bore formed within said cup shaped member and said integral tapered portion coaxially with said plug member, and
• said detecting means including:
• a rod member longitudinally slidably disposed within said central bore of said cup shaped member and tapered portion and having sloped cam surfaces in opposite relation to the sloped cam surfaces of said plug member,
• balls disposed between opposite cam surfaces of said rod and plug members, respectively,
• a collar member fitted around said integral tapered portion so as to be movable limitedly in the longitudinal direction with said rod member, and
• switch means located adjacent to said collar member and connected to an electrical circuit for controlling the movement of the drill.