Rotary hammer driving mechanism

A rotary hammer, comprising:

• a pneumatic impact mechanism having a beat piece driven by a reciprocating piston;
• a rotatably driven drive shaft for driving said impact mechanism;
• a coupling element fixed non-rotatably on said drive shaft for rotation therewith;
• a drive element rotatably mounted on said drive shaft and optionally engageable with said coupling element by axial displacement relative to said drive shaft;
• means, drivingly connecting said drive element to said piston, for reciprocating said piston upon rotation of said drive element, said piston being driven in a forward direction to generate percussive blows and returning in a rearward direction;
• said drive element and said coupling element having interengageable tapered coupling surfaces;
• and
• said coupling element being rearward of said drive element with the coupling surface of said coupling element facing in said forward direction and the coupling surface of said drive element facing in said rearward direction, the relative disposition of said drive element and said coupling element causing reaction force on said piston consequential upon generation of said percussive blows to urge said drive element into intensified engagement with said coupling element.

A rotary hammer, comprising:

• a rotatable tool spindle for holding a tool for operating upon a workpiece, said tool spindle being rearwardly displaceable along an axis about which it is rotatable when, in use, the tool is pressed in a forward direction against the workpiece;
• a drive shaft disposed parallel to said axis and geared to said tool spindle for rotatably driving the latter;
• an armature shaft geared to said drive shaft for rotatably driving the drive shaft;
• a coupling element rigidly secured on a rear end of said drive shaft and having a conical engagement surface facing forwardly at a forward end of said coupling element;
• a drive element mounted on said drive shaft and being rotatably and axially displaceable relative thereto;
• said drive element being disposed on said drive shaft forwardly of said coupling element, and said drive element having a conical engagement surface facing rearwardly at a rearward end of said drive element;
• a spring mounted on said drive shaft between said drive element and said coupling element and biasing said drive element forwardly away from said coupling element to space said engagement surfaces apart;
• rearward displacement of said drive element along said drive shaft towards said coupling element effecting driving engagement of said conical engagement surfaces;
• a pneumatic impact mechanism for imparting percussive blows to said tool, and including a piston mounted for reciprocation along said axis for generating said percussive blows;
• means for drivingly connecting said drive element to said piston and for causing rotation of said drive element to effect said reciprocation of said piston;
• and
• said drivingly connecting means also functioning to transmit recoil force on said piston, consequential upon said piston generating said percussive blows, to said drive element as a rearward force enhancing driving engagement of said engagement surfaces.