Patent ID: 6644418
Filing Date: 2003-11-11
Classification: B25D

Abstract:
A hammer drill comprising:a crank shaft driven by a motor; a piston engaged with said crank shaft and slidably accommodated in a cylinder to reciprocate in an axial direction of said cylinder; a striking member axially offset from said piston via an air chamber and slidably accommodated in said cylinder to reciprocate in the axial direction of said cylinder so that a reciprocative motion of said piston is transmitted via said air chamber to said striking member; a tool holder disposed coaxially with said cylinder for detachably holding a working tool; an intermediate member slidably accommodated in said tool holder or in said cylinder to reciprocate in the axial direction of said cylinder in response to a reciprocative motion of said striking member to strike said working tool; a rotational motion transmitting mechanism for transmitting a rotational motion of said motor to said working tool, wherein said cylinder has a ventilation hole for allowing said air chamber to communicate with the outside, a slide sleeve is slidable in the axial direction of said cylinder and always urges said intermediate member in a direction opposed to said piston, so that said slide sleeve closes said ventilation hole when said intermediate member is positioned close to said piston while said slide sleeve opens said ventilation hole when said intermediate member is positioned far from said piston; an engaging portion is formed at an axial end of said intermediate member and engageable with said slide sleeve; said cylinder has an elongated hole with an axial length longer than a shifting distance of said intermediate member; and said slide sleeve comprises an annular member and a slide member, wherein said annular member has an inner cylindrical wall engageable with said engaging portion of said intermediate member and a projection extending in a radially outward direction passing through said elongated hole beyond an outer surface of said cylinder, and said slide member is coupled around the outer surface of said cylinder and slidable in the axial direction of said cylinder, with one axial end of said slide member positioned closer to said working tool being engaged with said projection of said annular member and the other axial end of said slide member being urged toward said working tool by an urging member.