US Patent 7331496 Hammer drill

A hammer drill (2) includes a clockwise and counterclockwise driven tool spindle (28), a drive pinion (70) operatively connectable with the tool spindle (28) for transmitting a torque thereto, a separate control handle (6) for selecting one of the hammer drill functions including a pure drilling operation, a pure percussion operation, and a rotary-percussion operation), and a switching device (8) which is adjustable in accordance with a position of the control handle (6) and which is shiftable by the control handle (6) in a clockwise rotation position for effecting a pure drilling operation in a clockwise direction and in a counterclockwise rotation position for effecting a pure drilling operation in a counterclockwise direction.