US 5,320,177 AGranted

Power driven hammer drill

AssigneeMakita Corporation

InventorsMitsuyoshi Shibata, Masao Miwa

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Abstract

The invention provides an improved intermediate housing incorporated in a power driven hammer drill, which is light in weight, easily and safely handled, and uncostly manufactured. The intermediate housing of the invention includes a bearing member and a cylindrical piston housing member which are integrally composed of a synthetic resin having high tenacity and excellent heat resistance and wear resistance. The intermediate housing further includes a plurality of ribs radially extending from the piston housing member to give a sufficient strength durable to a stress applied onto the piston housing member. In the intermediate housing thus constructed, the bearing member has at least one opening for feeding an air flow generated by a fan while the piston housing member includes at least one air conduit for circulating the air flow. This structure efficiently prevents overheat and thermal deformation of the piston housing member and the bearing member in continuous operation of the hammer drill.

Claims9

Dependent claims

A power driven hammer drill comprising an electric motor, a tool holder for supporting a tool bit and for transmitting a rotation of said electric motor to said tool bit by way of a driving mechanism, said driving mechanism including an intermediate shaft, a piston cylinder slidably movable along an axis of said power driven hammer drill, an air cushion percussive mechanism for converting said rotation of said electric motor to a reciprocating movement of said piston cylinder and for transmitting said reciprocating movement to said tool bit as an axial impact force, and an externally accessible switching mechanism for switching off said air cushion percussive mechanism,

said power driven hammer drill further including an intermediate housing disposed between a gear housing and a motor housing and having a bearing member for supporting an armature shaft of said electric motor and said intermediate shaft, and a piston housing member for holding said tool holder and said piston cylinder, said bearing member and said piston housing member being integrally composed of a synthetic resin,
said intermediate housing including a plurality of ribs radially extending from an outer face of said piston housing member and being integrally formed thereon, said plurality of radially extending ribs facing an inner wall of said gear housing and being selectively radially spaced from said inner wall.

A power driven hammer drill comprising an electric motor, a fan for cooling said electric motor, a tool holder for supporting a tool bit and for transmitting a rotation of said electric motor to said tool bit by way of a driving mechanism, said driving mechanism includes an intermediate shaft, a piston cylinder slidably movable along an axis of said power driven hammer drill, an air cushion percussive mechanism for converting said rotation of said electric motor to a reciprocating movement of said piston cylinder and for transmitting said reciprocating movement to said tool bit as an axial impact force, and an externally accessible switching mechanism for switching off said air cushion percussive mechanism,

said power driven hammer drill further including an intermediate housing disposed between a gear housing and a motor housing,
said intermediate housing including a bearing member for separating said gear housing from said motor housing and for supporting an armature shaft of said electric motor and said intermediate shaft, and a piston housing member extending from said bearing member for holding said tool holder and said piston cylinder,
said bearing member having at least one opening for feeding an air flow generated by said fan to said piston housing member, and said piston housing member having at least one air conduit for circulating said air flow through said opening.

Dependencies are inferred from the claim text.