Abstract: An electric switch for a power tool, comprising: a slider slidably received in a switch casing along a longitudinal direction, a handle provided in the grip of the power tool for manually actuating the slider along the longitudinal direction; a plurality of fixed contact pieces arranged in an internal bottom surface of the switch casing and provided with contact surfaces located substantially in a same plane; and a plurality of moveable contact pieces arranged in the bottom surface of the slider and urged toward the fixed contact pieces by spring members so as to selectively contact at least some of the contact surfaces of the fixed contact pieces. The contact portions of this switch achieve various conductive states by planar arrangement and movement of the contact pieces, the component parts can be fitted into a small switch casing, particularly having a small height.

Abstract: A motor control circuit for controlling supply of electric power from a power source to an electric motor, in particular for use in electric power tools, comprising: an output power device for controlling supply of current to the motor according to a duty ratio of a control input signal supplied thereto; current detecting means for detecting an amplitude of an electric current supplied to the electric motor; and feedback means for supplying the control input signal to the output power device, the duty ratio of the input control signal being increased with an increase in the electric current supplied to the electric motor as detected by the current detecting means. Since the torque otuput of the motor is increased when such a need arises, the need for more a complex and expensive continually variable speed control system is eliminated.

Abstract: A switch mechanism for an electric power tool, comprising: a linear slider received in a switch case so as to be moved manually in a first direction against the biasing force of a return spring; an actuating pin carried by the linear slider so as to be moveable along a second direction perpendicular to the first direction; a pair of direction converting levers crossed in the manner of a pair of scissors by a pivot pin mounted on the switch case, the actuating pin being located adjacent to first ends of the direction converting levers; a pair of lateral sliders engaged by second ends of the direction converting levers and allowed to move in the second direction; a first contact set including contacts carried by the linear slider and the wall surface of the switch case for mutual cooperation as the linear slider is moved in the first direction; and a second contact set including contacts carried by the lateral sliders and the wall surface of the switch case for mutual cooperation as the lateral sliders are move

Abstract: A switching circuit for varying rotational speed of a motor includes a power supply line for connecting the motor to a power source so as to supply driving power to the motor. A parallel connecting circuit of an on-off switch and a short circuiting switch is provided in the power supply line, in such a manner that the driving power is continuously supplied to the motor when the short circuiting switch is on, while in the case that the short circuiting switch is off, the driving power is supplied to the motor during on of the on-off switch but is not supplied during off of the on-off switch. A control member is provided for operation by an operator for varying rotational speed of the motor. The control member is operative for turning on the short circuiting switch at the maximum amount of its operation.

Abstract: An electric switch system for a DC motor powered power tool, comprising: a moveable block which is adapted to be manually displaced between a first position and a second position for speed control of the motor; a fixed block arranged adjacent to the first moveable block; a manual selection lever pivotally attached to the fixed block and adapted to be manually rotated from a neutral middle position to either side for the selection of the rotational direction of the motor; a cam structure for permitting the manual rotation of the manual selection lever in either direction away from the middle neutral position only when the moveable block is at the first position and keeping the angularly displaced state of the manual selection lever when the moveable block is displaced away from the first position. Thus, the selection of the rotational direction of the motor and the speed control of the motor can be accomplished as a continuous single operation, and the convenience of the power tool is improved.

Abstract: An electric power tool includes an electric motor. A switch assembly for this power tool includes a device for controlling the on/off operation of the motor, actuated to and fro along a first actuation line, and a device for controlling the forward/reverse operation of the motor, actuated to and fro along a second actuation line. The first and the second actuation line do not intersect one another. This confers good operability upon the switch and upon the power tool as a whole. More particularly, the first actuation line should be skew to the second actuation line, even more particularly substantially skew perpendicular to it; or, alternatively, the first actuation line may be substantially parallel to the second actuation line and somewhat displaced therefrom.

Abstract: An electrical switch which includes a casing, a pair of fixed contacts each formed by cutting a rod member into a predetermined length, and disposed in the casing to confront each other, a plunger slidably accommodated in the casing for movement in an axial direction, bearing members slidably supporting the plunger, a movable contact formed by cutting a rod member into a predetermined length and mounted to an intermediate portion of the plunger in a direction intersecting with the fixed contacts, and a return spring directed around the outer periphery of the plunger. The movable contact is restored together with the plunger to close the pair of fixed contacts in a free state.

Abstract: A variable speed control switch for an electric tool including a DC motor having an armature circuit, includes: a device for turning off and on the armature circuit; an upper heat dissipation cover for covering the top of the turning off and on device; a lower heat dissipation cover for covering the bottom of the turning off and on device; a printed circuit board located at the lower surface of the lower cover for controlling motor speed; a resistor element is provided on the lower surface of the board; a movable contact assembly, including a first contact member for short circuiting the motor terminals, a second contact member for turning ON the power source, a third contact member for short circuiting the turning off and on device, and a brush for providing variable resistance by sliding over the resistor element; a device for biasing the movable contact assembly to the position of short-circuiting the motor terminals; a box like casing which receives the above-mentioned components, the power source termina

Abstract: A high precision and compact contact switch which comprises a housing, a pair of fixed contact elements fixedly supported within the housing, a plunger axially slidably extending into the housing, a generally cylindrical movable contact member, a support piece for the support of the fixed contact elements and a biasing spring. The generally cylindrical movable contact member is tiltably carried by the plunger so as to extend transversely in relation to the plunger. The support piece is preferably made out of synthetic resin. The biasing spring is used for urging the opposite end portions of the movable contact member in order to contact the respective fixed contact elements.

Abstract: An electrical switch which includes a casing, a pair of fixed contacts each formed by cutting a rod member into a predetermined length, and disposed in the casing to confront each other, a plunger slidably accommodated in the casing for movement in an axial direction, bearing members slidably supporting the plunger, a movable contact formed by cutting a rod member into a predetermined length and mounted to an intermediate portion of the plunger in a direction intersecting with the fixed contacts, and a return spring directed around the outer periphery of the plunger. The movable contact is restored together with the plunger to close the pair of fixed contacts in a free state.

Abstract: A temperature detecting device which comprises an electrical bridge circuit including four arms, a temperature responsive resistance contained in one of the arms, a resistance type potential divider having at least one intermediate terminal which represents an output terminal of the network, and switching means connected across two power source terminals thereof for inverting the connection of the potential divider in accordance with a temperature state, positive or negative, which is detected by said device, the respective divided portion divided by the intermediate terminal forming two arms of the network.