The present invention pertains to an air cylinder (10) in which flow rate controllers (24, 24A) are built into a head cover (14) and a rod cover (16), said flow rate controllers (24, 24A) being provided with a first flow rate adjustment part (28) connected between a port (14a, 16a) and a cylinder chamber (12c), a second flow rate adjustment part (32) provided adjacent to the first flow rate adjustment part (28), and a pilot check valve (38) connected in series to the second flow rate adjustment part (32). In response to the pressure of pilot air, the pilot check valve (38) switches between a state in which the passage of exhaust air from the cylinder chamber (12c) is permitted and a state in which the passage of exhaust air is prevented.

An example valve includes: a first port, a second port, and a load-sense port; a valve piston configured to block fluid flow from the first port to the second port when the valve piston is in a neutral position; a reverse flow spring applying a first biasing force on the valve piston in a proximal direction; and a pressure compensation spring disposed in a spring chamber and applying a second biasing force on the valve piston in a distal direction, wherein when pressure level of fluid at the second port is higher than pressure level of fluid at the load-sense port, fluid flows from the second port to the spring chamber and the load-sense port, and wherein when pressure level of fluid at the load-sense port is higher than pressure level of fluid at the second port, fluid of the load-sense port is provided to the spring chamber.

A flow rate controller and a drive device are provided with a cylinder flow passage connected to an air cylinder; a main flow passage for supplying air to and discharging air from the air cylinder; an auxiliary flow passage that has a first throttle valve and through which exhaust air discharged from the air cylinder passes with a smaller flow rate than that of the main flow passage; a switch valve that switches between a first position in which the cylinder flow passage communicates with the main flow passage and a second position in which the cylinder flow passage communicates with the auxiliary flow passage; and a pilot air adjustment part that guides a portion of the exhaust air from the air cylinder as pilot air to the switch valve.

A flow rate controller and a drive device are provided with a first flow passage connected between an operation switching valve and an air cylinder, and that supplies air to and discharges air from a cylinder chamber of the air cylinder; a first flow rate adjustment part provided in the first flow passage; a second flow passage adjacent to the first flow passage; a pilot check valve provided at a point along the second flow passage; a second flow rate adjustment part connected in series to the pilot check valve at a point along the second flow passage; a pilot air flow passage, one end of which communicates with the operation switching valve and the other end of which is connected to a pilot port of the pilot check valve; and a third flow rate adjustment part provided in the pilot air flow passage.

In a flow rate controller and a drive device, a housing is provided therein with a first flow passage, a second flow passage adjacent to the first flow passage, a first throttle valve provided to the first flow passage, and a second throttle valve provided to the second flow passage. A pilot check valve is provided to the second flow passage and is connected in series to the second throttle valve. A pilot air flow passage communicates with a pilot port of the pilot check valve for supplying and discharging pilot air, and a third throttle valve is provided to the pilot air flow passage. In response to the pressure of the pilot air, the pilot check valve switches between a state in which the passage of exhaust air discharged from an air cylinder is permitted and a state in which passage of the exhaust air is prevented.

A valve system, for use with a cylinder having an extensible rod, includes a first valve assembly having a first inlet/outlet port, a check valve biased toward a closed state, the check valve having a check valve body at least partially receivable within a first port of the cylinder, a flow control valve positioned in series between the first inlet/outlet port and the check valve, and a first pilot port selectively communicable with a source of pressurized gas for opening the check valve. The valve system further includes a second valve assembly having a second inlet/outlet port, a second pilot port through which the pressurized gas must flow before being introduced to the first pilot port, and a valve body at least partially receivable within a second port of the cylinder.

An example valve includes a valve piston configured to block fluid flow from a first port of the valve to a second port of the valve when the valve is in a closed position; a forward flow spring applying a first biasing force on the valve piston in a distal direction; a reverse flow spring applying a second biasing force on the valve piston in a proximal direction; and a pressure setting spring applying a third biasing force on a check element in the distal direction, wherein fluid from the first port applies a fluid force on the check element in the proximal direction, and fluid from a pilot port applies a respective fluid force on the check element in the distal direction.

In a hydraulic system which is biased to a minimum system pressure using a bias valve or other flow obstruction disposed in a tank line, there is provided in a bypass line to the bias valve an evacuating and filling valve through which the hydraulic system is first evacuatable and subsequently fillable with a hydraulic fluid. The valve closes the bypass when a differential pressure overcomes a preadjusted force of a spring element. For this purpose, the valve possesses a displaceably mounted valve body with an integrated throttle and a seal face which closes a through opening when the valve body is shifted against the bias force of the spring element due to the pressure difference.

Disclosed is a tower lifting device for a rotary blasthole drill, comprising a hydraulic cylinder (5), an extending oil path (7), a retracting oil path (6), a speed control oil path (14) and a proximity switch (3), wherein the extending oil path (7) is connected to a non-rod-end chamber of the hydraulic cylinder (5), and an extension control unit is provided on the extending oil path (7); the retracting oil path (6) is connected to a rod-end chamber of the hydraulic cylinder (5), and a retraction control unit is provided on the retracting oil path (6); the speed control oil path (14) is connected to the retracting oil path (6), the speed control oil path (14) is connected to a speed control valve block (15) in series and the tail end thereof is connected to an oil tank (16); the proximity switch (3) is arranged on a tower supporting frame (2) for controlling the switching on and off of the speed control valve block (15), and when the tower (4) is approximately in a horizontal state, the speed control valve block (15) is on. By using such a tower lifting device in the present invention, the speed at which the tower is laid down to a horizontal state can be conveniently controlled.

A speed controller capable of controlling an action speed of an external cylinder in one stroke in a step-wise manner. The speed controller includes a first flow path and a second flow path that allow a first port and a second port to be in communication with each other. The first flow path is provided with a first check valve for allowing flow from the first port to the second port. The second flow path is provided with a first needle valve, and an opening hole of the first check valve is constituted as a part of a flow path. The first needle valve adjusts the flow rate by changing an opening area of the opening hole with a tip portion fixed on a piston in the cylinder chamber. The speed controller further includes a third flow path allowing the first port and the cylinder chamber to be in communication with each other. The third flow path is provided with a second check valve for allowing flow from the first port to the cylinder chamber.