Hand-held hammer tool

A hand-held hammer drill comprising:

• a housing (13);
• a drill (16) projecting into said housing (13);
• a single rotor-type electromotor (17) in said housing (13) incorporating a stator (19) and a rotor (18);
• a reciprocating hammer mechanism (14) and a rotary mechanism (15) in said housing (13) driven by a common rotor shaft (24) of said rotor (18), said hammer mechanism (14) including a connecting rod (43) connected to a drive piston (40) reciprocably movable in a cylinder (42) for driving a hammer piston (41) towards and away from said drill (16) via an air cushion (44) in a working chamber (45) located between said pistons (40,41) in said cylinder (42), said rotor (18) continuously driving crank means (34) mounted eccentrically on said rotor shaft (24) to rotate therewith and connected to said connecting rod (43) to move said drive piston (40) in a reciprocating manner within said cylinder (42) without any intermediate gear means, said rotary mechanism (15) including drill engaging means (46,47) for imparting a rotary motion to said drill (16) during the reciprocating movement of said drive piston (40);
• a drive shaft (37) in said rotary mechanism (15) drivingly connected to said drill engaging means (46,47) at one end thereof, the other end thereof being connected to a driving gear (36) on said rotor shaft (24) for transmitting a rotary movement to said drive shaft (37) a bowl-shaped inertial body (25) surrounding said electromotor (17), fixedly from the bottom of which said rotor shaft (24) extends centrally into and through said bowl-shaped body (25), said bowl-shaped body (25) while continuously rotating, being adapted to counterbalance by its flywheel momentun the load variations of said hammer mechanism (14) acting on said rotor shaft (24), the interior wall (27) of said bowl-shaped body (25) supporting the electromagnetically active parts (23,49) of said rotor (18) so as to rotatably surround the electromagnetically active parts (21,22) of said stator (19);
• and a tubular structure (20) of said housing (13) extending centrally into the bowl of said bowl-shaped body (25) for fixedly supporting on said structure (20), said active stator parts (21,22) and rotatably supporting said rotor shaft (24) in said structure (20).