Abstract: An engine tappet of high abrasion resistance, whose surface is coated with a sintered layer. This sintered layer is prepared from a binder comprising about 50-100 wt % of nickel powder, about 0-45 wt % of Cr, about 0-35 wt % of Mo, about 0-10 wt % of Al, about 0-25 wt % of Co, about 0-10 wt % of Cu and inevitably mixed impurities; and from hard particles selected from the group consisting of carbides, nitrides, borides and the mixtures thereof. Also, there is provided an engine tappet which is coated with an alloy powder composition comprising about 44-88 wt % of WC, about 4-10 wt % of Co, about 15-50 wt % of Ni, about 5-20 wt % of Cr, about 0.5-4 wt % of B, about 2-4 wt % of Fe, about 0.5-4 wt % of Si, about up to 1.0 wt % of C and inevitably mixed impurities.

Abstract: Disclosed is automatic fluid pressure-intensifying apparatus and method of a hydraulic traveling device for increasing a traveling capability or a pulling capability of a heavy equipment by changing a relief pressure in a hydraulic circuit under the state that a working device of the heavy equipment does not operate and a traveling device only operates. In the automatic fluid pressure-intensifying apparatus of the hydraulic traveling device, a first control valve selectively changes a flow direction of a hydraulic fluid being supplied by a hydraulic pump toward a traveling motor of the heavy equipment. Further, a second control valve selectively changes the flow direction of the hydraulic fluid being supplied by the hydraulic pump toward a working device of the heavy equipment. A relief valve restricts an allowable maximum pressure in a hydraulic circuit.

Abstract: A tandem-type pump assembly having a first housing and a second housing. A first main pump and a second main pump are coaxially aligned and disposed in the first housing. A first driving shaft having a first end and a second end is rotatably supported in the first housing and coaxially interconnects the first main pump and the second main pump. A driving gear is fixed to the first end of the first driving shaft for rotation therewith. A second driving shaft is rotatably supported in the second housing for driving an auxiliary pump. A driven gear is fixed to the second driving shaft for rotation therewith and directly engages the driving gear.

Abstract: A hydraulic system for working cylinders of construction equipment is disclosed. The system allows oil to be smoothly drained from a chamber of a working cylinder into an oil tank through a first passage or/and a second passage without being resisted during an operation of the cylinder. The system thus effectively and smoothly moves the working cylinder while improving operational efficiency and operational speed of the cylinder. When the system is used with a boom cylinder of a power excavator, the system effectively performs a boom-up or boom-down action without losing pressure.

Abstract: Disclosed is an apparatus for increasing the operating capability of a construction machine during a fine operation mode and a method for the same. The apparatus being capable of preventing a merged hydraulic fluid from being supplied into a hydraulic actuator and increasing the pressure of the hydraulic fluid being supplied into the hydraulic actuator during the fine operation mode. The apparatus includes a detector that detects the RPM count of the engine of the construction machine and determines whether the engine is switched into the fine operation mode. A first anti-confluence valve and a second anti-confluence valve prevent a first hydraulic fluid supplied into the first actuator and a second hydraulic fluid supplied into the second actuator from merging while either the first actuator or the second actuator is operating. An anti-confluence relay turns the first anti-confluence valve and the second anti-confluence valve on/off.

Abstract: A power steering system for construction equipment is disclosed. In the steering system, a plurality of internal passages are selectively formed in the directional control valve for left and right steering cylinders. The internal passages thus selectively allow pressurized oil to be fed from an oil pump into both the large chamber of the right cylinder and the small chamber of the left cylinder with a reversible motor starting by pressurized oil discharged from the other chambers of the two cylinders in the event of rotating the steering wheel to the left. The internal passages also allow the pressurized oil to be fed into both the small chamber of the right cylinder and the large chamber of the left cylinder so that the motor is started by pressurized oil discharged from the other chambers of the two cylinders when the steering wheel rotates to the right.

Abstract: A work brake apparatus for a wheel type excavator having a travelling device, a suspension device, and a service brake device. The work brake apparatus comprises: a first means, which is connected to the forward/backward lever of the travelling device, for unlocking the suspension device as the suspension locking solenoid valve switches over in response to a predetermined signal when the forward/backward lever switches over to its forward or backward position, and a second means, which is connected to the forward/backward lever of the travelling device, for keeping the service brake applied as the service brake valve switches over in response to a predetermined pilot pressure when the forward/backward lever switches over to its neutral position.

Abstract: An improved absolute position detection method is provided for a stroke sensing cylinder which includes a magnetic scale detecting step for obtaining a plurality of sine wave form voltages having different phases using a magnetic sensor unit in accordance with a driving operation of the cylinder. A wave form generation step is also provided for converting the sine wave form voltage obtained in the magnetic scale detection step into a square wave form and generating a triangle wave form having the same period as the thusly converted square wave form. A first absolute position value detection and stroke direction judging step is then provided for judging a first absolute position value and stroke direction of the cylinder using a pair of square and triangle wave forms generated in the wave form generation step.

Abstract: A method for detecting the direction and displacement of a rod member of a hydraulic cylinder assembly is provided. The hydraulic cylinder assembly includes a plurality of magnetic sensors for outputting a magnetic field variation signal disposed adjacent a hydraulic cylinder. The plurality of magnetic sensors cooperate with a plurality of magnetic projections equally spaced along a rod member for producing the magnetic field variation signal. The signal is converted from a sine wave into a square wave by using a microprocessor. The edges of the converted square wave are counted to accurately detect a direction and displacement amount. The method further includes the steps of ignoring a square wave edge caused by disturbance, if the square wave edge occurs prior to a pre-set time, wherein the pre-set time is based on the average time interval for previous edges. The method further includes the step of generating a correction edge when no edge is detected during the pre-set time interval.

Abstract: A device for matching the operation of a travelling unit in a construction vehicle is disclosed. The device reduces the required levering force of a travelling control pedal, easily controls the rotating force of an engine, and safely changes the engine output torque in accordance with both the levering stroke of the travelling control pedal and a travelling resistance. The device has a pressure reduction valve which is synchronized with a levering motion of a travelling control pedal in order to feed pilot fluid from a pilot pump to a direction select valve. A branch line is branched from a fluid line extending between the pressure reduction valve and the direction select valve. A hydraulic cylinder is connected to the branch line and selectively receives the pilot fluid through the branch line when the travelling control pedal is levered.

Abstract: Disclosed is a device for mounting an attachment to a heavy equipment or for detaching the attachment from the heavy equipment. The device can mount an attachment such as a bucket, and the like, to a working device of the heavy equipment, or can detach the attachment from the working device in accordance with an object to be processed. A circular bar is detachably mounted to a hook portion formed at a rear upper side of the bucket. A cover having a predetermined shape is fixed to a side plate which is formed downwards at the both sides of the circular bar. A housing receives a fixing pin which is installed in the both sides of the cover and is detachably mounted to the bucket. A hydraulic cylinder is supported by the fixing pin at its both ends. The hydraulic cylinder can mount the fixing pin to the bucket or can detach the fixing pin from the bucket.

Abstract: A variable-regeneration directional control valve for construction vehicles is disclosed. The control valve has a pressure control means for controlling the opposite pressure caused by elasticity of a valve spring. The opposite pressure acts on one end of a regeneration switching spool, while a self pressure (hydraulic pressure of pressurized fluid output from a pump) acts on the other end of the regeneration switching spool and thereby moves the spool. In the preferred embodiment, the means is a pressure control piston, which is provided on the end of the valve spring. The pressure control piston receives an outside control signal through an electronic proportional control valve and thereby continuously moves. The electronic proportional control valve outputs pressurized fluid in proportion to a current amount of the outside control signal.