Abstract: The present invention provides a chip breaker for reliably breaking chips produced during a cutting operation by an annular cutter. Disclosed is a chip breaker having a surface (26) facing the upstream side of the rotational direction of an annular cutter and extending outward relative to the radius of the annular cutter from an edge (24) adjacent to the outer peripheral surface of the annular cutter. The edge (24) is inclined from a first end (27) positioned at a small distance from the outer peripheral surface of the annular cutter toward a second end (28) positioned closer to the surface of a workpiece than the first end and spaced at a greater distance from the outer peripheral surface of the annular cutter than the first end.

Abstract: When a start SW 3 is pressed, a one-shot multivibrator circuit 15 turns on and releases a pulse. The pulse is transmitted to a self-hold circuit 16 which in turn stays in self-hold mode and releases an H level output continuously until it is reset. This cause a transistor 17 to turn on and actuate a ram downward movement relay R1. When the ram arrives at the lower limit of its movement, a lower LS 4 is opened causing a self-hold circuit 21 to produce an H level signal in accordance with an output of a one-shot multivibrator 18. The H level signal from the self-hold circuit 21 is delayed by a delay circuit 22 and turns on a transistor 23. As the result, a ram upward movement relay R2 is actuated. Because of the function of the one-shot multivibrator circuit 15, the ram will not restart when the start SW 3 is continuously depressed. The delay circuit 22 contributes to the longer operational life of a directional valve switching mechanism.

Abstract: The operation of an electric drill is inhibited when it is interrupted by an abrupt fault such as power failure and then the fault is recovered, or when the coil of an electromagnet has a trouble such as disconnection.After the fault is eliminated with a power switch 50 remaining closed for energizing the electromagnet and the electric drill, a photocoupler 38 turns on a thyristor 31 to disable the conduction of a transistor 35. As the result, a drill motor 16 will not start before the magnetization of the electromagnet. The trouble in the coil 27 is detected by a potential examining circuit 30 measuring a potential difference across a resistor 31. The detection of the trouble causes the thyristor 31 to interrupt the conduction of the transistor 35. Accordingly, the electric drill will not start again unless it is securely anchored by the electromagnet.

Abstract: When a start SW 3 is pressed, a one-shot multivibrator circuit 15 turns on and releases a pulse. The pulse is transmitted to a self-hold circuit 16 which in turn stays in self-hold mode and releases an H level output continuously until it is reset. This cause a transistor 17 to turn on and actuate a ram downward movement relay R1. When the ram arrives at the lower limit of its movement, a lower LS 4 is opened causing a self-hold circuit 21 to produce an H level signal in accordance with an output of a one-shot multivibrator 18. The H level signal from the self-hold circuit 21 is delayed by a delay circuit 22 and turns on a transistor 23. As the result, a ram upward movement relay R2 is actuated. Because of the function of the one-shot multivibrator circuit 15, the ram will not restart when the start SW 3 is continuously depressed. The delay circuit 22 contributes to the longer operational life of a directional valve switching mechanism.

Abstract: When a start SW 3 is pressed, a one-shot multivibrator circuit 15 turns on and releases a pulse. The pulse is transmitted to a self-hold circuit 16 which in turn stays in self-hold mode and releases an H level output continuously until it is reset. This cause a transistor 17 to turn on and actuate a ram downward movement relay R1. When the ram arrives at the lower limit of its movement, a lower LS 4 is opened causing a self-hold circuit 21 to produce an H level signal in accordance with an output of a one-shot multivibrator 18. The H level signal from the self-hold circuit 21 is delayed by a delay circuit 22 and turns on a transistor 23. As the result, a ram upward movement relay R2 is actuated. Because of the function of the one-shot multivibrator circuit 15, the ram will not restart when the start SW 3 is continuously depressed. The delay circuit 22 contributes to the longer operational life of a directional valve switching mechanism.

Abstract: A hand tool driven by a DC battery comprises a tool driving section having a motor, a DC source connected to the tool driving section, a plurality of LEDs connected to the DC source, an LED turning-off section for sequentially turning off the LEDs in accordance with the power remaining in the DC source, and an LED flickering section for causing flickering of at least one illuminated LED, when the driving section is overloaded.

Abstract: A quick return mechanism for a drilling machine comprises an input shaft, an output shaft, an overdrive gear train and a speed-reduction gear train, each disposed between the input and output shafts, a first clutch for connecting the output shaft to the input shaft through the over-drive gear train when a motor for driving the input shaft rotates in the quick-return direction and disconnecting the output shaft from the input shaft when the motor rotates in the feed direction, a second clutch selectively set at a first position and a second position, for connecting the output shaft to the input shaft through the speed-reduction gear train at the first position when the motor is rotated in the feed direction, and disconnecting the output shaft from the input shaft through the speed-reduction gear train at the second position, when the motor rotates in the quick-return direction, and a rotation=linear-movement converting unit for setting the second clutch at the first position when the motor rotates in the feed

Abstract: A drill apparatus with an electromagnet base, which has an electric drill directed downwards, is provided with an electromagnet base having an electromagnet for attaching the apparatus to a to-be-worked object by magnetic force. The electric drill is rotated by a drill motor and moved by a feed motor towards the object. A Hall element is situated on the electromagnet base. Two comparators detects whether or not a Hall voltage output from the Hall element falls in a predetermined range of voltage values. When the Hall voltage does not fall in this range, a transistor is turned on. Consequently, a relay is operated, a contact is opened, and power supply to the drill motor and the feed motor is stopped.

Abstract: The states of contact switches are switched when a mode switch is turned on. If the drilling operation is effected by means of a drill motor in this state, an oscillation signal which is repeatedly set to "H" and "L" in a preset period corresponding to an output of an oscillator is supplied to the control terminal of a firing pulse generator. The firing pulse generator interrupts supply of the control signal to the control terminal of a triac in the above preset period based on the oscillation signal supplied to the control terminal thereof to interrupt supply of an AC power source from a commercial AC power source to a bridge-type rectifier so as to intermittently drive a feed motor which is energized by an output of the rectifier in the above preset period. As a result, the drill motor can be intermittently fed towards a to-be-worked object by means of the feed motor, and, when the feeding operation is interrupted, a cutting operation can be instantaneously stopped and swarf can be cut apart.

Abstract: A boring apparatus wherein the size in the axial direction of the shaft of the manual handle horizontally supported can be made small-sized. A clutch is composed of spherical bodies, a cylindrical body having formed therein hole portions for receiving the spherical bodies, spherical body pressing means for pressing the spherical bodies to the outside or inside of the cylindrical body, and an engagement member having recessed portions engaging with the spherical bodies which are projected to the outside or inside of the cylindrical body, and the boring apparatus is constructed by using the clutch.

Abstract: A magnet base drill unit in which the driving of the drill motor and the feed motor of the magnet base drill unit is stopped by operation of the switch which operates on the instant when sliding has been produced in the magnet base drill unit, and the stopping thereof is maintained electrically or electronically. A mercury switch comprising a cylindrical body in which mercury is sealed, and a pair of contacts provided so as to project into the cavity of the cylindrical body, or a vibration switch comprising a fixed contact, and a vibration responsive contact placed by a spring means in proximity to the fixed contact is preferably used.

Abstract: A controller for a magnetic base drill unit provided with a safety circuit which is constructed by connecting in series a relay provided with contacts for cutting the power supply to the drill motor and feed motor, a resistor and a diode. The relay is actuated when a voltage higher than the predetermined voltage to be applied to the feed motor in the hole cutting mode is applied to the feed motor during the hole cutting, thereby cutting the power supply to the drill and feed motors. The controller has a means for confirming the operation of the safety circuit which apply a test voltage higher than the maximum predetermined voltage to be applied during the hole cutting to the feed motor in the fall mode of the electric drill.

Abstract: A chip breaking device for annular cutters has a comb-shaped member fixed to the front wall of a boring machine. The comb-shaped member includes a stem extending in parallel with the annular cutter rotated by the boring machine and three or more elongated chip breaking elements extending perpendicularly from the stem and into proximity to the outer periphery of the annular cutter. Chips formed by the annular cutter hit against the chip breaking elements and their tip portions are caught by the elements. Then, intermediate portions pass through the spacings between the adjacent chip breaking elements. Thereafter the chips are pulled and broken into pieces.

Abstract: A boring apparatus has a rotary member rotated by a motor, a transmission shaft transmitting its rotation to an electric drill by means of a rotation transmission mechanism for reciprocally moving the electric drill on the frame of the apparatus. The transmission shaft is selectively connected directly to the rotary member and connected operatively thereto through a coupling which is rotated reversely to the rotary member through a reduction mechanism and is designed to be disengaged from the transmission shaft when the shaft is directly connected to the rotary member and to be engaged with the shaft when the shaft is not directly connected to the roatary member. The apparatus has a selecting member which directly connects the shaft to the rotary member and disengages the coupling from the sahft.

Abstract: A drilling machine comprises an electric drill having a drill motor for rotating an annular drilling tool and a feed control motor for moving the annular drilling tool forward and backward with respect to a workpiece, both connected to an AC power source, and an electromagnetic base for fixing the electric drill on an object to be drilled.

Abstract: An annular hole cutter is disclosed which has a plurality of cutting teeth disposed about a lower end of a cylindrical annular wall, each tooth having intersecting back-off surfaces, a first back-off surface inclining inwardly and a second back-off surface inclining outwardly. Teeth with high and wide cutting edges alternate with teeth having a low and narrow cutting edge, thereby reducing stress on the teeth, dissipating heat more effectively and preventing the blockage of the hole cutter by the cut chips.

Abstract: A drilling machine including an electric drill being selectively fixed at a desired angle with respect to a workpiece and a manual feed handle for moving the electric drill toward and away from the workpiece. A control circuit for the electric drill is provided having a sensor member being operatively connected in said control circuit for detecting a load applied on the electric drill. An alarm member is operatively connected in the control circuit for sending out a signal when a load signal exceeding a first reference level is detected. A switch is operatively connected in the control circuit for deenergizing said control circuit for the electric drill when a load signal exceeding a second reference level is detected.