Cylinder driving apparatus

1. A cylinder driving apparatus for driving a cylinder, comprising:

a cylinder having a first chamber and a second chamber that are partitioned by a piston provided on a piston rod;

a pump including a first port and a second port, the pump being configured to be capable of discharging a working fluid from each of the first port and the second port, respectively;

a tank configured to store the working fluid;

a first passage connecting the first chamber to the first port;

a second passage connecting the second chamber to the tank;

a third passage connecting the second port to the tank;

a throttle located along the third passage to apply resistance to the working fluid flowing through the third passage;

an operated check valve provided in the first passage to allow the working fluid to flow from the pump into the first chamber, the operated check valve being configured to allow the working fluid to flow from the first chamber into the pump according to a fluid pressure of the working fluid in the third passage between the pump and the throttle;

a bypass passage connected to the third passage and having a first end connected to the third passage on one side of the throttle and having an opposite end connected to the third passage on an opposite side of the throttle from the one side, so as to bypass the throttle; and

a check valve provided in the bypass passage to allow the working fluid flowing through the bypass passage to flow only in a flow direction toward the pump,

wherein one end of the second passage is connected to the third passage at a junction, such that the throttle is connected between the junction and the pump, and

the cylinder is configured such that when the pump discharges the working fluid from the first port, the discharged working fluid is supplied to the first chamber via the operated check valve, thereby causing the piston rod to move in an expansion direction, and

when the pump discharges the working fluid from the second port, the throttle generates an increase in working fluid pressure to operate the operated check valve, and the working fluid in the first chamber is discharged from the first chamber via the operated check valve, thereby causing the piston rod to move in a contraction direction.

2. The cylinder driving apparatus as defined in claim 1 , wherein the cylinder is configured such that the piston rod is moved in the expansion direction by a fluid pressure of the working fluid in the first chamber, and the piston rod is moved in the contraction direction by a piston rod side own weight.

3. The cylinder driving apparatus as defined in claim 1 , wherein a connecting passage for operating the operated check valve in the first passage is connected to the third passage on an opposite side of the throttle from the junction of the second passage and the third passage.

4. The cylinder driving apparatus as defined in claim 1 , wherein, when the pump discharges the working fluid from the first port:

the pump is configured to intake working fluid from both the second chamber and the tank,

the working fluid from the tank is configured to combine with the working fluid from the second chamber at the junction, and

the working fluid from the tank and the second chamber are configured to be received at the second port from the junction via both the throttle in the third passage and the check valve in the bypass passage.