Abstract: Straight travelling apparatus for construction vehicles capable of keeping the construction vehicle travelling straight even when a work implement of the construction vehicle is manipulated during travelling. The apparatus includes hydraulic circuitry for making the hydraulic oil of first and second pumps be supplied to left and right travelling motors respectively when only the left and right travelling motors are operated, and making the oils be confluent together and equally distributed and supplied to the left and right travelling motors when even one work implement is to be manipulated at the same time as operating the left and right travelling motors. The hydraulic circuitry includes left and right directional selecting valves and a confluent line extending between the directional selecting valves for selectively making the hydraulic oil confluent together.

Abstract: An improved implement attaching device for construction equipment is disclosed. The device has an implement mount link hinged to the arm of the construction equipment. A first bracket is provided on the rear wall of the implement and supports the link. A pair of key holes are provided on opposite sides of the first bracket. A pair of keys are provided on the link such that the keys are horizontally movable relative to the link to be inserted into or taken out of the key holes and thereby detachably attaching the implement to the implement mount link. The device also has a lever and a linkage for linearly moving the keys horizontally. The linkage achieves a pantographic motion in accordance with a turning motion of the lever and detachably attaches the implement to the link.

Abstract: An apparatus for and a method of controlling the engine RPM in hydraulic construction equipment, being capable of detecting a neutral valve position corresponding to the idle state of the construction equipment and controlling the engine to drive at a low RPM while the construction equipment is in its idle state, thereby achieving a reduced noise generation and reduced fuel consumption.

Abstract: An improved mono-block control valve having a side bypass passage substituting for a typical center bypass passage is disclosed. The side bypass passage simplifies the passage structure of the valve body into a two-dimensional structure, thereby remarkably reducing the valve body size and improving the space efficiency and cutting down the cost. The left and right return passes are connected together by a connection passage at every section of the valve body. Due to the connections passages, the control valve prevents passage resistance and pressure loss in the return passages and makes both the negative pressures in the right and left actuator ports and the negative pressures in the sections uniform. The control valve thus improves the operational stability and reliability.

Abstract: A priority control valve used in a hydraulic apparatus for supplying fluid delivered from a single pump to at least two actuators respectively via parallel fluid lines, the actuators operating independently or in combination with each other. The variable priority device includes a priority control valve installed in the parallel fluid line associated with one of the actuators and adapted to be switched between an orifice state and an orifice release state, the priority control valve being initially maintained at the orifice release state by resilience means while being switched from the orifice release state to the orifice state against a resilience of the resilience means in response to a pilot pressure for moving the spool of a control valve for the other actuator.

Abstract: A device for sensing actuator operating signal in a hydraulic system is disclosed. The device has auxiliary valves directly coupled to the directional control valves respectively, the internal lines of which auxiliary valves are opened or become orifices in accordance with positions of spools of their associated directional control valves. A fluid line extends from a hydraulic pump to a return tank after passing the auxiliary valves in a series. The device also has two elements for detecting fluid pressure at two given points along the fluid line. An additional orifice is formed in the hydraulic line between the auxiliary valves and the pressure detecting elements is provided in the hydraulic line before and after the additional orifice.

Abstract: A straight travelling apparatus for heavy construction equipment such as excavator or crane, including a straight travel valve disposed in both lines respectively branching from first and second hydraulic pumps and switched between a first state at which a fluid delivered from the first hydraulic pump is supplied to a right travel motor and a part of the actuators of a working system while a fluid delivered from second hydraulic pump is supplied to a left travel motor and the remaining part of the actuators of the working system and a second state at which the fluid delivered from the first hydraulic pump is supplied to both the right and left travel motors while the fluid delivered from the second hydraulic pump is supplied to all actuators of the working system, first and second pilot fluid lines both branching from the pilot pump, a connecting fluid line adapted to communicate the first and second pilot fluid lines with each other, a fluid line branching from the connecting fluid line, and a relief check v

Abstract: An engine cooling system with a blade angle controllable cooling fan. The system has a water temperature sensor, a controller and a pitch actuator. The sensor senses a cooling water temperature and outputs a temperature signal. The controller generates a blade angle control signal on the basis of the temperature signal. The pitch actuator is placed in the interior of a hub of the cooling fan and adjusts a blade angle of the cooling fan in response to the blade angle control signal of the controller.

Abstract: Disclosed is an automatic transmission system in which an ECU calculates change of the running speed to automatically shift the gears under optimal conditions. The automatic transmission system used for heavy construction equipment for variably changing a rotative speed of an output shaft by selectively engaging any one of a plurality of change gears according to the selection of oil passages of a solenoid valve includes a speed sensor for sensing the rotative speed of the output shaft or a running speed of the heavy construction equipment, a converter connected to the speed sensor, for converting a value sensed by the speed sensor into an electrical signal and a controller for receiving the electrical signal output from the converter and comparing the electrical signal with a pre-stored value, to apply a driving signal to the solenoid valve if the electrical signal is within a predetermined range, so as to shift gears.

Abstract: A holding check control valve including a main valve, an assistant valve, a check valve installed in an actuator fluid passage provided at the main valve and provided with a spring chamber, the check valve being adapted to be switched between an opened state for opening the actuator fluid passage and a closed state for closing the actuator fluid passage in response to a pressure difference between the actuator fluid passage and the spring chamber so that the return oil in the actuator fluid passage is returned via a return fluid line provided at the main valve at the opened state, a pair of spaced seat members fixedly disposed in the assistant valve, a hydraulic chamber defined between the seat members, the hydraulic chamber communicating with the spring chamber of the check valve, a plunger extending through the seat members, the plunger being slidable along the seat members between a position closing the hydraulic chamber and a position opening the hydraulic chamber, a pressure setting spring for exerting i

Abstract: Disclosed is a hydraulic turning joint which has substantially reduced longitudinal length with an equal number of oil passages therein and can reduce the mounting space in the equipment and which improves the work efficiency, accuracy and reliance of the product. The hydraulic turning joint includes a shaft, a housing for rotatably and closely accommodating the shaft, at least one oil supply passage formed in the shaft, said oil supply passage longitudinally passing through the shaft, and at least one oil discharge passage formed on the top of the the housing, said oil discharge passage being correspondingly communicated with at least one oil supply passage, wherein each of said oil supply passages are transversely communicated with each of said oil discharge passages on the same plane. The hydraulic turning joint further includes sealing means installed between the oil discharge passages within the housing.

Abstract: An apparatus for and a method of controlling the engine and pumps of hydraulic construction equipment capable of achieving automation of the hydraulic construction equipment by controlling the oil quantity fed to solenoid controlled proportional valves such that it is proportional to the manipulation amount of a manipulation command unit through a computation performed by a controller on the basis of engine RPM data from an engine RPM detection unit and pump delivery pressure variation data from a pump delivery pressure detection units so that the suction horse power of each of the pumps corresponds to the maximum output horse power of the engine and by controlling the oil quantity fed to the hydraulic cylinders 105a and 105b by oil quantity control valves such that it corresponds to the manipulation amount and manipulation ratio from the manipulation command unit.

Abstract: The present invention is concerned about high toughness and high strength untempered steel having the mechanical properties equivalent to or better than those of tempered steel and processing method thereof, more particularly, the high toughness and high strength untempered steel having the tensile strength higher than 90 kgf/mm.sup.2 with the impact toughness higher than 5 kgf-m/cm.sup.2 in the KS 3 specimen, and processing method thereof.

Abstract: An apparatus for generating a noise sound, which is equipped in industrial electric cars with little or no driving sound and generates an appropriate amount of noise sound so that the nearby cars or pedestrians can notice their approch in a narrow pathway or stock room. The apparatus has a cornical air collector installed in the car, a shutter installed rotatably in the air collector and controls the flow amount of air passing through the air collector, and a U-shaped tube installed apart by a predetermined distance from a small diameter portion of the air collector and generates the noise sound by the air discharged from the air collector.

Abstract: Disclosed is a shock prevention apparatus and method for hydraulic construction equipment such as excavators, loaders, dozers and cranes, which use hydraulic cylinders and motors as actuators. The shock prevention apparatus of the present invention low pass filters an original actuator driving command signal of the rectangular wave in accordance with displacement data of the piston stroke in the actuator, to generate a smooth actuator driving command signal, so that the shocks due to rapid opening and closing of the oil passages of the hydraulic actuator and the shocks at the stroke ends of the piston of the hydraulic actuator are prevented.

Abstract: Disclosed is a a time delay valve, which has a reduced number of components so that the manufacture thereof is easy and the number of manufacturing processes is reduced, and by which the delay time thereof is easily reset and changed. The time delay valve is disposed incorporated in a casted-housing of the hydraulic motor to be prevented from being damaged. The time delay valve has a spool movably disposed therein in such a manner to be elastically supported by a spring and be moved by a signal pressure applied to a signal pressure port, and an orifice spool movably disposed therein with being elastically supported by another spring. The constant pressure port and the pressure receiving chamber is interconnected with each other through an oil flowing path in the course of an alternating stroke of the spool. The orifice spool is moved by the elastic force of the spring and the pressure difference between a spring chamber of the orifice spool and an oil flowing path.

Abstract: A speed control device automatically controlling the travelling speed of overspeeding electric automobiles so as to allow the automobile to travel safely.

Abstract: A transmission for a heavy construction equipment such as a wheel type excavator adopting the hydrostatic drive system for transmitting travelling power. The transmission applied to a heavy construction equipment having an upper turning body, a lower travelling body and a turning joint for coupling the upper turning body to the lower travelling body so as to turn the upper turning body with respect to the lower travelling body and having a gear box disposed in the lower travelling body and provided with clutches for at least two speed change stages, and a control unit disposed in the upper turning body, a charging pump disposed in the upper turning body, a power shift motor disposed in the lower travelling body and adapted to be actuated by an oil fed from the charging pump, and a power shift pump disposed in the lower travelling body and adapted to be actuated by the power shift motor, with the gear box performing a speed change operation by oil fed from the power shift pump.

Abstract: A variable priority device for a swing motor in heavy construction equipment including a variable orifice device installed in an arm cylinder-side parallel oil passage of an parallel oil passage for supplying oil pumped by a single pump to a swing motor and an arm cylinder, the variable orifice device serving to perform a switching operation between an orifice state and an orifice release state in response to a pilot pressure for moving the spool of a swing motor control switching valve.

Abstract: The present invention relates to a method for automatically controlling the speed ratio of swing and boom operation of the excavator, which makes the operator perform the dig-up task in a easy and precise manner by adapting an electronic control using micro-module and sensors and so forth. The controlling method according to the present invention utilizes the angular velocity for the swing and the boom operation which is dependent on the position of the truck and is preset by the operator in the input/output board of the controller. When the dig-up task is performed, the operator will operate the joy sticks for the swing and the boom as much as possible and the controller enables the swing operation to move to the desired position without dropping a lump of earth. Again, when the operator operates the joy sticks for the dipper and the bucket in the same manner, the dipper and the bucket will move to the position in which the truck is placed.