Hammer drill with a mechanism for preventing inadvertent hammer blows

A hammer drill comprising:

• a bit;
• a housing;
• a piston member disposed rear of the bit for making reciprocating motion;
• a motor capable of rotation;
• an intermediate shaft capable of being rotated by the rotation of the motor transmitted thereto;
• a rotation mechanism for transmitting rotation of the motor to rotate the bit;
• a conversion mechanism for converting the rotation of the intermediate shaft into reciprocating motion of the piston member;
• a striking mechanism including a striker interlocked with the piston member for causing the striker to deliver hammer blows to the bit;
• a switch member for selectively preventing the rotation of the motor from being transmitted to the conversion mechanism, the switch member being operable from outside of the housing to select one of at least two operating modes, a drill mode, in which only the rotation of the motor is transmitted to the bit, and a hammer drill mode, in which the rotation of the motor and the hammer blows are transmitted to the bit;
• and
• a lock mechanism interlocked with the. switch member such that the lock mechanism can prohibit the reciprocating motion of the piston member only in the drill mode.