Abstract: An electric-discharge machining apparatus for machining a workpiece by an electric discharge generated between a machining electrode and the workpiece, includes a correcting unit that corrects a machining amount input for machining the workpiece, based on a usage history of the machining electrode; and a control unit that controls a machining processing on the workpiece based on the machining amount corrected.

Abstract: An electric-discharge machining apparatus for machining a workpiece by an electric discharge generated between a machining electrode and the workpiece, includes a correcting unit that corrects a machining amount input for machining the workpiece, based on a usage history of the machining electrode; and a control unit that controls a machining processing on the workpiece based on the machining amount corrected.

Abstract: An electrical discharge machine for applying a pulsed voltage to a machining gap between an electrode and a workpiece disposed opposite thereto. An insulating dielectric fluid, such as oil or water mixed with a compound additive, is disposed in the gap. A positive polarity voltage and an opposite polarity voltage are applied via switches and respective impedances to the machining gap in order to generate a discharge for machining the workpiece. A pulse having a first polarity is applied to machine the workpiece and a pulse having a second polarity is applied when the first polarity pulse is not applied. A misfire pulse detector detects an undesired drop in the machining voltage by determining whether the first polarity voltage is in a range between two voltages, the first of which has a magnitude greater than the magnitude of the machining gap during discharge and the second of which has a magnitude greater than the magnitude of the first voltage.

Abstract: An electrical discharge machine for applying a pulsed voltage to a machining gap between an electrode and a workpiece disposed opposite thereto. An insulating dielectric fluid, such as oil or water mixed with a compound additive, is disposed in the gap. A positive polarity voltage and an opposite polarity voltage are applied via switches and respective impedances to the machining gap in order to generate a discharge for machining the workpiece. A pulse having a first polarity is applied to machine the workpiece and a pulse having a second polarity is applied when the first polarity pulse is not applied. The time of application of the second polarity pulse is increased depending upon the number of short-circuits detected between the electrode and the workpiece.

Abstract: A machining operation end position detecting unit detects the end position for a machining operation at a (k-1)-th step. A machining operation starting position detecting unit detects the starting position for the machining operation at a k-th step. A machining position comparison unit compares them with each other. If the difference between them is less than a predetermined value, a signal is output to a machining condition changing unit and a control valve. As a result, the machining condition is changed, and a powdered substance is fed into a working fluid.

Abstract: A method and apparatus for detecting the build up of tar on the electrode or workpiece in an electric discharge machine is achieved by determining the difference between a machining gap impedance found from dielectric fluid resistivity and an electrode area and a machining gap impedance actually measured.

Abstract: An electrical discharge machine for applying a pulsed voltage to a machining gap between an electrode and a workpiece disposed opposite thereto. An insulating dielectric fluid, comprising an oil or water with compound additive, is disposed in the gap. A positive polarity voltage and an opposite polarity voltage are applied via switches and respective impedances to the machining gap in order to generate a discharge for machining the workpiece. The impedance values may be selectively set and the switching of the voltages controlled such as to apply a positive polarity voltage at the stop time of an opposite polarity pulsed voltage, whereby the average voltage approximates a predetermined value, preferably zero, during the stop time. Voltage control during the stop time will result in high speed and finish, especially for control in connection with a jump operation.

Abstract: An electrical discharge machine for applying a pulsed voltage to a machining gap between an electrode and a workpiece disposed opposite thereto. An insulating dielectric fluid, comprising an oil or water with compound additive, is disposed in the gap. A positive polarity voltage and an opposite polarity voltage are applied via switches and respective impedances to the machining gap in order to generate a discharge for machining the workpiece. A high frequency alternating current voltage is applied between the electrode and the workpiece when the first polarity and second polarity voltages are not being applied.

Abstract: An electrical discharge machine for applying a pulsed voltage to a machining gap between an electrode and a workpiece disposed opposite thereto. An insulating dielectric fluid, including either oil or water with a compound additive, is disposed in the gap. A first voltage is applied to the machining gap. If a predetermined period of time passes and a discharge has not occurred at the machining gap, then a second voltage, opposite in polarity to the first voltage, is applied to the machining gap.

Abstract: A machining pulse control apparatus applies a first polarity pulse voltage during a machining operation and a second opposite polarity voltage in a machining stop period in which the electrode is moved away from and toward the workpiece during a jump operation. Preferably, the second opposite polarity is applied for a period of time sufficient to maintain the voltage across the machining gap at zero voltage. The amount of direct current voltage applied during the jump operation is adaptively controlled.

Abstract: An electric discharge machine having a machining solution tank for storing a machining solution containing machining particles, a machining vessel filled with the machining solution to machine a workpiece, and a machining solution circulating system for circulating the machining solution between the machining solution tank and the machining vessel. The vessel has a pair of machining solution jetting devices arranged in the machining vessel in opposition to each other, the machining solution jetting means jets the machining solution delivered thereto, through the machining solution circulating system from the machining solution tank, towards the workpiece in the machining vessel in a predetermined order.

Abstract: An apparatus for actuating an operating valve unit for winch comprising a casing, a first shaft fixedly supported within said casing, second and third shafts rotatably supported within said casing, said second and third shafts being operatively connected with a hook lever and a boom lever, respectively. Said valve unit includes six valves for operating a hook clutch, a hook brake, a boom clutch, a boom brake, a lifting clutch, and a lower clutch, respectively.First and second cams are slidably and rotatably mounted on said first shaft and a third cam is rotatably but not slidably mounted on said first shaft. Said first shaft is operatively connected with said second and third shafts, respectively, so as to selectively actuate said valves in response to operations of said hook lever and said boom lever.

Abstract: A paving material agitation apparatus for use in water channel forming machines comprising a hopper adapted to accommodate therein paving materials to be laid, a plurality of first screws spaced apart with each other in said hopper, a plurality of rotary drives each being secured to one end of said first screws, respectively, an agitation impeller rotatably engaged with one of said first screws, a rotary shaft rotatably supported by said hopper, said agitation impeller being fixedly secured to said rotary shaft so as to be rotated therewith, and a second screw formed on said rotary shaft.

Abstract: An operating device for winch control valves, featuring that, in a construction wherein a valve of a clutch for winding up a winch, a valve of a clutch for winding down the winch, and a valve of a brake can be operated by a single control lever to thus simplify the operation of the winch, the boss section of the primary lever linked with a spool of the valve for winding up the winch and the boss section of the secondary lever linked with a spool of the valve of the brake are put to interlocking rotation only at the time of rotation in the unitary direction, the boss section of the said secondary lever and the boss section of the tertiary lever linked with a spool of the valve for winding down the clutch are properly interlocked with each other only at the time of rotation in the unitary direction, a couple of positions as are confronted with each other on the both sides of the center of rotation of a rotator to be put to rotation either forward or backward by the operating lever are properly linked with the s