Safeguard coupling for power driven flexible shafts

Claim 1

In a coupling device for transmitting power from a rotating flexible shaft to a spindle of a worktool, said device having a handpiece for manually holding said worktool by an operator, a coupling shaft axially rotatably mounted within said handpiece for axially interconnecting said flexible shaft and said worktool spindle, said flexible shaft having a casing within which said flexible shaft rotates, a ferrule for tightly gripping one end of said casing and maintaining said flexible shaft in operable alignment with said coupling shaft and handpiece, the improvement therewith comprising ball bearing members disposed within said handpiece for operably axially rotatably mounting said coupling shaft, said ball bearing members comprising a ball bearing member at an input end of said coupling device and another ball bearing member at an output end of said coupling device, a washer disposed between said ferrule and said input end bearing member, an annular recess disposed at an input end of said handpiece, and retaining means engaged within said recess for retaining at least a portion of said ferrule within said handpiece whereby said handpiece and said retaining means will rotate together on a longitudinal axis about said portion of said ferrule within said handpiece in a direction to relieve twisting stresses introduced into said casing when said operator moves said worktool by said handpiece with respect to a workpiece.