Abstract: A switch includes an actuating element movable against a biasing force from a rest into a working position. The element is engageable with a member movable under a force of a predetermined magnitude applied thereto between a first position corresponding to the rest position of the element and a second position in which it displaces the element into the working position. The member is provided with a spring for urging the member against the applied force into the first position so as to release the actuating element. The member tends to prematurely move into the first position in response to a slight decrease of the applied force to a lever below the predetermined magnitude. The switch is further provided with an arrangement for preventing the premature movement of the member into the first position until after the applied force decreases below the above-mentioned level.

Abstract: The spindle neck of a manually held power drill is to be releasably secured in a slotted sleeve of an auxiliary tool unit. For this purpose a tensioning band is provided which surrounds the sleeve and tensions the same about the spindle neck, and a manually operable tensioning-lever arrangement is provided which requires no use of tools and which serves for rapidly engaging and disengaging the tensioning band.

Abstract: A chuck for hammerdrills and the like is provided with a chuck body; a plurality of jaws on said chuck body for engaging and holding a tool bit; and means connected to said jaws for adjusting the engagement of said jaws with the tool bit, said means comprising a guide sleeve having a main portion with an outer and inner surface, said main portion defining a central axis therethrough, a toothed gear encircled by said sleeve and having a circumferentially extending groove having a roughened surface facing the inner surface of said sleeve, said sleeve including at least one inwardly offset locking portion having an outer and inner surface which are inwardly offset with respect to the main portion of said sleeve, said inwardly offset portion projecting into said groove.

Abstract: In a hand-held electric power tool, a combination including an electromotor, and an electric circuit for controlling the speed of the motor, including a pressure switch for controlling the motor speed, a first control potentiometer operatively associated with said pressure switch for adjusting the motor speed from zero up to a predetermined motor operating speed.

Abstract: A drill chuck having a body adapted for connection to a spindle and a clamping member rotatable on the body and operable to actuate clamping jaws. Cooperating and selectively releasable elements of a spring loaded pawl and ratchet device are carried by the body and clamping member and lock the clamping member to the body in clamping position.

Abstract: An output shaft is rotatably journalled in a housing, as is a motor, and motion is transmitted from the motor to the output shaft via a variable gear transmission which has at least two selectable gear ratios.

Abstract: A chuck body has one end for connection to a power tool, and another end from which a plurality of jaws project. A sleeve turnably surrounds the body and jaws and is operative, when turned in one direction, for moving the jaws inwardly towards one another into engagement with a tool bit that is located between them. A plate spring is mounted at the one end of the body and has a circumferential marginal portion which engages and frictionally locks the sleeve when the latter is turned in the aforementioned one direction.