Reciprocator for use with rotary drills

A device for driving a tool with a reciprocating motion and adapted to be operated from a rotary power source comprising:

• a stationary frame having a shaft bearing therein;
• a hand grip attached to said frame for holding of said device by a user;
• a cylindrical sleeve-like eccentric member having an angular forward surface, said forward surface cut at a selected acute angle with respect to the longitudinal axis of said eccentric member with the periphery, formed by the junction of said cylindrical eccentric member and the face formed by said forward surface cut, being rounded to form a broad contact area, said eccentric member disposed on and concentric with said shaft and rigidly attached thereto, said shaft and said eccentric disposed in said shaft bearing and rotatable with respect thereto, said front end of said shaft projecting from said angular forward surface;
• a cylindrical sleeve-like tool driving member having an angular rear surface thereof cut at said selected acute angle, and a forward end having internal threads therein for accepting a tool holding chuck, said driving member slidably disposed on and concentric with said front end of said shaft, said driving member having a diameter greater than the diameter of said eccentric member;
• a downward projecting slide block attached to said cylindrical driving member, said slide block having a rod bearing therethrough;
• a guide rod attached to said frame and slidably engaged with said rod bearing of said slide block;
• and
• an external, adjustable compression spring, connected to said guide rod and said slide block, and adapted to urge said angular rear surface of said driving member into contact with said broad contact area of said eccentric member, said spring adjustable to vary the length of the reciprocating stroke of said tool;
• whereby rotation of said shaft causes said broad contact area of said eccentric member to rotate against said angular rear surface of said driving member so as to slide said driving member alternately forward on said shaft against the compression of said spring and rearward on said shaft in response to the tension in said spring, thereby resulting in a longitudinally reciprocating motion of said driving member.