Abstract:
Le procédé consiste notamment à :- déterminer une caractéristique de fonctionnement de la source de fluide,- maintenir, tant que la caractéristique de fonctionnement possède une valeur inférieure à une valeur dite seuil, le débit (Q1) du flux prioritaire (S1) sensiblement égal au débit (QE) du flux d'entrée (E) et le débit du flux secondaire (S2) à une valeur nulle,- répartir le flux d'entrée (E) entre le flux prioritaire (S1) et le flux secondaire (S2), lorsque la caractéristique de fonctionnement possède une valeur supérieure à la valeur seuil (V1), en faisant varier le débit (Q1) du flux prioritaire (S1) en fonction de la valeur de la caractéristique de fonctionnement de la source de fluide (2).
Abstract:
A hydraulic controller improved to prevent a hunching from occurring and reduce a size and used for a multiple hydraulic control system (1) having a load sensing function, comprising a PLS port allowing the maximum negative pressure in the system to be supplied therein, wherein a restriction is provided in a compensator, and a function equivalent to a check valve is provided to the restriction, the function of a shuttle valve (selector valve) is provided to the compensator, and the shuttle valve is operated independently of the compensator to always regulate a PLS.
Abstract:
A regeneration hydraulic circuit which increases the speed of one action of a double action cylinder. The hydraulic circuit includes first hydraulic line in fluid communication with one end of the double action cylinder, and a second hydraulic line in fluid communication with an opposing end of the double action cylinder. A third hyraulic line connects the first hydraulic line and the second hydraulic line. A pilot check valve is disposed in the third hydraulic line, and has a pilot line. The pilot line is connected to the first hydraulic line, wherein the pilot check valve is open when hydraulic fluid flows through the first hydraulic line and into the one end of the double action cylinder The pilot check valve is closed when hydraulic fluid flows out of the end of the double action cylinder and through the first hydraulic line. A check valve is disposed in the second hydraulic line, wherein hydraulic fluid flowing out of the opposing end of the double action cylinder is diverted into the third hydraulic line.
Abstract:
A hydraulic drive device of working machine, comprising a merge valve (2) connected to a directional control valve (1) of a first directional control valve group through a center bypass passage (3), a merge circuit (5) communicating the merge valve (2) with the supply port of a directional control valve for merge (4), an actuator for merge (20) controlled by the directional control valve for merge (4), and a release valve (10) releasing the merge by the merge valve (2) when the load pressure of the actuator for merge (20) exceeds a specified value, wherein a total horse power is controlled so that the total value of the input torques of two hydraulic pumps (15) and (18) does not exceed the output torque of an engine (30), whereby a merge is stopped forcibly when the load pressure of the actuator for merge where the pressure oils from two hydraulic pumps are merged with each other becomes higher than a specified pressure and the actuator for merge is driven only by the pressure oil from one hydraulic pump.
Abstract:
An oil passage slit (20) that is formed in the valve disc (50) of a flow dividing valve (5-1), a control chamber (70) and oil passage (31-1) are connected to a signal transmission oil passage (9), the oil passage slit (20) being formed with a lap portion (32) having a check valve function with a lap quantity X at the shut-off position of the valve disc (50), the oil passage (31-1) having a 2-position 3-way valve (11) installed therein. The valve (11) connects the control chamber (70) of the flow dividing valve (5-1) to the signal transmission oil passage (9) alone when there is no external signal (F), while when the external signal (F) is applied, it connects the control chamber (70) both to the signal transmission oil passage (9) and to a low pressure detection oil passage (35) connected to the outlet passage (5b) of a flow dividing valve (5-2) on the side of a hydraulic actuator (3-2). This ensures that during composite operation driving an inertial body, the pressure on the low load pressure side is detected as a signal pressure without shutting off a load pressure detection oil passage on the high load pressure side and that the portion for detecting the load pressure is simplified and the flow dividing function is not impaired.
Abstract:
When a boom cylinder (11) and an arm cylinder (18) are to be actuated simultaneously, the arm cylinder (18) is actuated after the boom cylinder (11) is actuated. A pressure reducing valve (30) is provided on a circuit which connects a hydraulic pilot valve (13) for an arm and a first pressure receiving section (16) of an arm operating valve (4) to each other. A throttle (40) and an accumulator (41) are provided on a circuit (23) connected to an output circuit of a hydraulic pilot valve (5) for a boom. The pressure reducing valve (30) is reduced in pressure by a pressure difference across the throttle (40). Thus a pressure oil flows to the accumulator (41) to produce a pressure difference across the throttle (40), so that the pressure reducing valve (30) is reduced in pressure until the pressure oil fills up the accumulator (41), and the arm operating valve (4) is switchingly actuated after a boom operating valve (3) has been switched.
Abstract:
The invention concerns a positioning drive which is used in particular for machine tools and which comprises a hydraulic motor (10). The hydraulic motor comprises: a control disc (17) which is rotatable with a motor shaft (18) and is provided with a radial cam (19); a control valve (12) which, with the hydraulic motor (10), forms a unit with a preferably multi-part housing (37, 46) and comprises a valve piston (15) which can be displaced between a plurality of settings; a control component (16) by means of which the valve piston (15) can be supported on the control disc (17); and an adjusting component (65) which is operatively disposed between the control component (16) and the valve piston (15) and is coaxial to the latter. The relative position between the valve piston (15) and control component (16) can be varied by the relative adjustment of the adjusting component (65) to the valve piston (15). The position of the adjusting component (65) relative to the valve piston (15) can be secured by a releasable securing component. In order to be able to adjust the position between the valve piston (15) and the control component (16) very simply, the outer of the two parts, valve piston (15) and adjusting component (65), is guided outwards through the housing and the securing component (72, 80) is accessible externally of the housing.
Abstract:
A travelling hydraulic device characterized in that a spool hole having a pump port, an actuator port and a return port is formed in a first valve block, that a spool for establishing and blocking communication between the respective ports is fittingly inserted into the spool hole so as to constitute a leftward switching valve, that a spool hole having a pump port, an actuator port and a return port is formed in a second valve block, that a spool for establishing and blocking communication between the respective ports is fittingly inserted into the spool hole so as to constitute a rightward switching valve, that a spool hole having a main port and a drain port is formed in a third valve block, that a spool for establishing and blocking communication between the respective ports is fittingly inserted into the spool hole so as to constitute a switching valve and that the first and second blocks are connected to the third valve block, respectively, so as to establish communication between the return ports and drain port, respectively.
Abstract:
This invention relates to a hydraulic circuit for working machines, provided with a hydraulic fluid source (1), at least one hydraulic actuator (3 or 13) adapted to be driven by the hydraulic fluid supplied from the hydraulic fluid source, flow rate control valves (4; 4A or 14; 14A) adapted to control a flow of the hydraulic fluid supplied to the actuator, and pressure control means (5; 5A or 15; 15A) for maintaining the pressure differences across the flow rate control valves on predetermined levels. The apparatus according to this invention has a first means (20; 23; 35, 36) for selectively producing one of a pressure equal to a load pressure and an intermediate pressure higher than the load pressure but lower than a supply pressure, on the basis of a load pressure on the actuator (3 or 13) and a supply pressure in the hydraulic fluid source (1), and outputting the resultant pressure as a control pressure; a second means (21; 27; 29; 34, 36) for operating the first means to specify a pressure to be selected as a control pressure, i.e. one of the pressure equal to the load pressure and the intermediate pressure; and a communication means (22) for introducing the control pressure to the pressure control means (5; 5A or 15; 15A). The pressure control means is adapted to maintain the above-mentioned pressure difference on the above-mentioned predetermined level when the control pressure is equal to the load pressure, and set the pressure difference to one lower than the predetermined level when the control pressure is the intermediate pressure.
Abstract:
An improvement in a hydraulic system (10) having a variable displacement pump (12) and being capable of delivering pressurized fluid from the pump (12) to selectively engage at least three work circuits (18) with a first (20) of the circuits (18) being normally operable up to a first pressure and a second (22) of the circuits (18) being normally operable up to a second and lower pressure. The improvement comprises circuitry (80, 92, 94, 98, 108, 120, 122, 124, 126) for selectively operating a third (24) of the circuits (18) atone of the first or second pressures or at an upstaged pressure which exceeds the first pressure and circuitry (128) for reducing the displacement of the pump (12) in response to the third circuit (24) being operated at the upstaged pressure. Such upstaged pressure is available in a controlled manner for working against particularly heavy loads. Thus, a third and higher operating level is added to a system which already operates at at least two pressure levels.