A pressure operating device includes several valves disposed at fluid channels of a base such that high pressure fluid compels the valves to a closed position; a pressure disk disposed above the base and several swing arms extending from a swing seat; a guide member having an axial hole and several guide channels surrounding the axial hole, and an operating rod unit extending through the axial hole for coupling with the swing seat in such a manner that movement of the operating rod unit into one guide channel results in swinging of the swing seat into the guide channel, thereby swinging a respective one of the swing arms above and pressing a corresponding valve downward and opening the corresponding valve to permit entry of the high pressure fluid into the pressure operating device while remaining the swing arms are spaced apart from and maintaining remaining valves in the closed position.

A hydraulic tool including a tank, which is filled with oil, a hand pump connected to the tank in fluid communication, having a spring-loaded lever mechanism, which is in operative connection with a pump piston, with a piston cylinder system as actuator, which is connected to the pump in fluid communication with a non-return valve, wherein the piston surface of the actuator is a multiple of the piston surface of the hand pump.

In a method of controlling a main control valve of an excavator, when speeds of a boom cylinder and an arm cylinder is increased by handling a boom joystick and an arm joystick, a second arm control spool between a first hydraulic pump and the arm cylinder may be closed. A first boom control spool between the first hydraulic pump and the boom cylinder may be opened to supply a first flux generated from the first hydraulic pump to the boom cylinder. A second boom control spool between a second hydraulic pump and the boom cylinder may be closed. A first arm control spool between the second hydraulic pump and the arm cylinder may be opened to supply a second flux generated from the second hydraulic pump to the arm cylinder.

A pneumatic gauge/pressure control device includes a first body, a pneumatic gauge that is fixed to the first body, and a second body that is rotatable relative to the first body and gauge to: (i) a fill position in which compressed air is communicated into a system; (ii) a vent position in which compressed air is vented from the system. The second body activates a first switch when rotated in the first direction and activates a second switch when rotated in the second angular direction. A method for controlling the flow of compressed air relative to a pneumatic system includes rotating a second body in a first or second directions relative to a pneumatic pressure gauge to fill or vent positions to cause compressed air to be introduced into or vented from the pneumatic system, respectively.

A hydraulic excavator 1 includes an engine 16, a main hydraulic pump 17 driven by the engine 16, a plurality of hydraulic actuators driven with pressure oil discharged from the main hydraulic pump 17, a plurality of flow rate control valves adapted to control the flow rate of pressure oil to be supplied from the main hydraulic pump 17 to the respective hydraulic actuators, a pilot hydraulic pump 18 adapted to supply pressure oil for driving the flow rate control valves, and a controller 15 configured to control the discharge flow rate of the pilot hydraulic pump 18. The controller 15 controls the discharge flow rate of the pilot hydraulic pump 18 such that it becomes equal to the sum of requested pilot flow rates determined in accordance with control commands for the respective flow rate control valves and a preset standby flow rate.

A hydraulic pump includes a housing including a work port, a bladder that stores hydraulic fluid, and a pump assembly that pumps hydraulic fluid from the bladder to the work port. The bladder includes a bladder relief assembly with a control element that is moveable between a first position that seals the bladder to the atmosphere and a second position that opens the bladder to the atmosphere to relieve a pressure within the bladder. The control element moves from the first position to the second position when the pressure in the bladder reaches a set pressure.