Abstract: Energy of returning pressurized fluid of an actuator is recovered and reused as energy for operating other accumulators. A first pump motor (16) and a second pump motor (17) are mechanically connected to form a pressure converter (18), and a first circuit (22), to which the returning pressurized fluid is supplied, is connected to the first pump motor (16). A pressure accumulator (27) is provided to a second circuit (25) connected to the second pump motor (17). The first circuit (22) is connected to a discharge passage (11) of a primary hydraulic pump (10) by a third circuit (29) and the pressure of a high pressure pressurized fluid is supplied to the discharge passage (11) by the pressure of the high pressure pressurized fluid, and is reused.

Abstract: Air blower apparatus (20) in which a fan boss (41) at the rotational center portion of a fan (29) has a recessed form. Meanwhile, the central part of the body portion (21) of the air blower apparatus (20), i.e., a boss portion (38), has a projecting form to be housed within the recessed fan boss (41). The central part of the body potion (21), i.e., the boss portion (38), is housed within the recessed fan boss (41) at the rotational center portion of the fan (29), and the rotary shaft (39) of the body portion (21) of the air blower apparatus (20) is mounted on the fan (29).

Abstract: A discharged pressurized fluid of a primary hydraulic pump 2 driven by an engine 1 is supplied to an actuator 5 through an operating valve 4. A first hydraulic rotary machine 8 for rotating a cooling fan 7 is driven to rotate by a returning pressurized fluid of the actuator 5. A second hydraulic rotary machine 9 for rotating the cooling fan 7 is driven to rotate by the discharged pressurized fluid of an auxiliary hydraulic pump 3 which is driven by the engine 1. By utilizing the returning pressurized fluid of the actuator 5, the air blowing ability of the cooling fan is made high and the wasting of engine horse power is prevented.

Abstract: An improved pressure fluid supply and delivery apparatus is disclosed that has a pressure compensating function and yet a reduced loss in pressure. The apparatus includes a variable displacement hydraulic pump unit(10; 60, 61) having a plurality of fluid discharge ports(10a, 10b; 60a, 61a) independent each other and a common drive shaft. A plurality of fluid circuits (11, 12) are connected to the plural discharge ports (10a, 10b; 60a, 61a), respectively, and a plurality of fluid operated actuators (14, 16; 14, 14′, 16, 16′) are connected via respective operating valves (13, 15; 13, 13′, 15, 15′) to the plural fluid circuits (11, 12), respectively. Also included in the apparatus is a displacement control means (19, 20; 64, 64) operable in response to discharge pressures in the fluid discharge ports (10a, 10b; 60a. 61a) and load pressures in the actuators (14, 16; 14, 14′, 16, 16′) for controlling discharge fluid pressure of the variable displacement pump unit (10; 60, 61).

Abstract: The present invention has an object to enable to supply a discharged pressurized fluid of a hydraulic pump without any energy loss with an arbitrary flow rate distribution ratio to a plurality of actuators. A discharged pressurized fluid of the hydraulic pump 11 is supplied to the first and second actuators 15 and 16 via the first and second variable displacement type hydraulic pump/motors 13 and 14. The first variable displacement type hydraulic pump/motor 13 and the second variable displacement type hydraulic pump/motor 14 are mechanically connected to rotate at the same revolution speed. By this, the pressurized fluid is supplied to the first and second actuators 15 and 16 depending upon displacements of the first and second variable displacement type hydraulic pump/motors.

Abstract: A directional control valve system is provided in conjunction with a hydraulic actuator, using a meter-in flow control valve that is simple in structure to permit pressure fluid to be fed into a first and a second chamber of the hydraulic actuator. The directional control valve system includes a meter-in flow control valve 1 for establishing and blocking fluid communication of a pump port with an outlet port 12, a first and a second load checking valve 2 and 3 that is in fluid communication with the outlet port 12, and a meter-out flow control valve 4 for establishing fluid communication of one of a first and a second actuator port 72 and 74 at an output side of the first and second load checking valves 2 and 3 with a tank port 71, and has an arrangement that permits the first and second load checking valves 2 and 3 to be held in a closed state with pressure fluid.

Abstract: A pressurized hydraulic fluid supply apparatus capable of merging or separating a plurality of hydraulic pump lines according to the driving states of a plurality of actuators. The pressurized hydraulic fluid supply apparatus has a merge/separation valve 40 that merges or separates the hydraulic fluids delivered under pressure by the first hydraulic pump 1 and the second hydraulic pump 11. The merge/separation valve 40 is set to a flow separation state upon driving of the second hydraulic actuator 16 and is preferentially shifted to a flow merging state when the third hydraulic actuator 21 is driven. Hence, even when a manually driven operation valve is used, the merge/separation valve 40 is automatically switched between the flow separation state and the flow merging state according to the operation of the operation valve. This apparatus prevents an unintended flow rate difference between the first and second actuators from being produced upon driving of the third actuator.

Abstract: A meter-out flow control valve is provided that is compact and possesses a regenerative function. A poppet valve 70 for establishing and blocking fluid communication between a first actuator port 73-1 and a tank port 74 is urged by a spring 71 into a pressure contact with a seat 72. The poppet valve 70 is moved away from the seat 72 under pressure in a first pressure receiving chamber 80-1. A cylindrical valve 103 is fitted with the poppet valve 70 to provide a regenerative switching valve 101 that may establish and block fluid communication between the first actuator port 73-1 and a first regenerative port 100. A meter-out flow control valve having a poppet valve 70 and a cylindrical valve 103 fitted together is thus provided that is compact in form and yet capable of regenerating pressure fluid in a first actuator port 73-1 into a first regenerative port 100.

Abstract: A system that can recover flows of a hydraulic pressure fluid returned from a plurality of hydraulic actuators is disclosed which includes a plurality of fluid recovery circuits (15, 19, 25 and 27) into which flows of a hydraulic pressure fluid returned from such a plurality of actuators are admitted, and a main fluid recovery circuit (36). There is provided a selector means (30, 31, 32, 33, 34, 35, 37) for permitting at least one of the plural fluid recovery circuits (15, 19, 25 and 27) selectively to communicate with the main fluid recovery circuit (36). The system, by permitting at least one of a plurality of fluid recovery circuits to communicate with a main fluid recovery circuit, enables a hydraulic return pressure fluid from at least one of a plurality of actuators to be recovered and hence is applicable to a working machine involving a plurality of hydraulic actuators.

Abstract: For supplying a large volumetric flow into a particular hydraulic actuator without requiring a directional control valve to be large-sized and without making large a pressure difference between a pump discharge pressure and a load pressure or reducing the pressure loss when a large volumetric flow is flushed out into a tank, a flow control apparatus in a hydraulic circuit is designed to supply a pressurized discharge fluid from the hydraulic pump (10) via a directional control valve (15) and a pressure compensation valve (18) to a plurality of hydraulic actuators (16) which are arranged in parallel to one another, the apparatus in its construction including an auxiliary control valve (30) for supplying the pressurized fluid to a particular one of the hydraulic actuators (16), which is supplied with the pressurized discharge fluid from the hydraulic pump (10) via the said auxiliary directional control valve (30) and the directional control valve (15), or whose return fluid out of that particular hydraulic actu

Abstract: A hydraulic circuit for a boom cylinder in a hydraulic shovel has a pressurized discharge fluid from a hydraulic pump that is driven by an engine, the pressurized discharge fluid supplied via a directional control valve for a boom into a retraction pressure chamber and an extension pressure chamber of a boom cylinder for swinging the boom upwards and downwards. A relief valve is included in a circuit for connecting the retraction pressure chamber of the boom cylinder to the boom directional control valve, the relief valve having a relief set pressure. A switching device is included for switching the relief set pressure to a low pressure as well as to a high pressure if the directional control valve is set at a position that is other than a neutral position thereof, when the engine is driven, the switching device being adapted to switch the relief set pressure to a high pressure when the engine is halted.

Abstract: A flow reinforcement directional control valve that is capable of reinforcing a pressure fluid to two actuators, can be formed as compact and yet is capable of flowing a return fluid out of a single actuator into a tank is provided, wherein a valve block 20 has a spool bore 21 in which a first spool (22) and a second spool (23) are slidably inserted; in which the first spool (22) is adapted to be held at a neutral position thereof by a first spring (36) and to be displaced by a pressure fluid in a second pressure receiving chamber (47) to a position thereof for supplying the fluid to an actuator; and in which the above mentioned second spool (23) is adapted to be held at a neutral position thereof by a second spring (41) and to be displaced by a pressure fluid in a first pressure receiving chamber (42) to a position thereof for flowing a return fluid into a tank and to be displaced by a pressure fluid in a third pressure receiving chamber (52) to a position thereof for supplying a pressure fluid to an actuato

Abstract: In a displacement control system for a variable displacement type hydraulic pump for supplying a discharge pressurized fluid of the variable displacement type hydraulic pump to an actuator via a direction control valve and then controlling a displacement of said variable displacement type hydraulic pump for maintaining a pressure difference between a discharge pressure of said variable displacement type hydraulic pump 1 and a load pressure at a portion between a direction control valve and an actuator, wherein an inlet side pressure of said direction control valve is detected as said discharge pressure.

Abstract: A hydraulic circuit including a pressure compensating valve, which aims at preventing the delay in operation of the valve due to the time required for the inflow of fluid in amount corresponding to stroke volume thereof, thereby improving the response of thereof. This hydraulic circuit includes a pressure compensating valve (3) provided between the delivery side of a hydraulic pump (1) and the inlet of a directional control valve (4), the pressure compensating valve (3) being arranged to be urged by the pressure applied to first pressure receiving portion (6) to position (D) where the area of opening thereof is kept maximum, and also urged by the pressure applied to second pressure receiving portion (8) to position (E) where the area of opening thereof is kept minimum, the portions (6) and (8) being connected with the outlet and inlet sides of the valve (4).