Override arrangement and actuating knob for a shifting mechanism in portable tools

Claim 1

In a power-driven drill and screwdriver including: a housing; a drive motor mounted in the housing; a case attached to the housing; a first clutch member rotatably mounted in the case and operatively connected to the drive motor; a second clutch member rotatably mounted in the case and slideably movable relative to the first clutch member between a first location whereat the second clutch member firmly engages the first clutch member and a second location whereat the second clutch member is disengaged from the first clutch member; means biasing the second clutch member into the second location; an eccentric member rotatably mounted on the case so as to be rotatable from one position thereon corresponding to the screwdriving mode of the tool to another position thereon corresponding to the drill mode of the tool; the eccentric member being arranged in the case with respect to the second clutch member to counteract the urging force of the biasing means and to displace the second clutch member into the first location when the eccentric member is rotated from the one position to the other position, said eccentric member including a shaft portion penetrating said case; a manually-adjustable handle attached to said shaft portion for rotating the eccentric member between the two positions; first limit means and second limit means coacting with the handle for defining said positions, respectively; the improvement which comprises: said case defining a smooth uninterrupted outside wall surface in the immediate vicinity of said handle, said handle being contoured so as to abut against said outside wall surface when the handle is rotated past one of said first limit means and said second limit means whereby the operator of the power-driven drill and screwdriver is prevented from overriding said one limit means; said case having a substantially flat outer wall surface adjacent said handle, said handle having a mid portion connected to said shaft and an end portion extending outwardly away from said mid portion, said end portion being in the form of a cam-like lobe having a surface contoured so as to cause said handle to abuttingly engage said wall surface when said handle is rotated beyond said one limit means in one angular direction and to clear said wall surface when said handle is rotated away from said one limit means to the other one of said first limit means and said second limit means in an angular direction opposite to said one angular direction.