Flushing circuit for hydraulic cylinder drive circuit

A flushing circuit for a hydraulic cylinder drive circuit, comprising:

• a hydraulic pump connected to a tank of hydraulic oil to generate pressurized hydraulic oil;
• a hydraulic cylinder including a piston which slidably enters a cylinder main body and to which a piston rod is fixed and a head-side pressure chamber and a rod-side pressure chamber which are formed by the piston and the cylinder main body;
• a multifunction valve including:
• a head-side in-valve supply/discharge circuit provided in the hydraulic cylinder, connected to the head-side pressure chamber, and having a head-side on-off valve;
• a rod-side in-valve supply/discharge circuit connected to the rod-side pressure chamber and having a rod-side on-off valve;
• and a bypassing circuit having a bypass on-off valve connecting the head-side in-valve supply/discharge circuit with the rod-side in-valve supply/discharge circuit on the upstream of the head-side on-off valve and the rod-side on-off valve;
• a control valve unit including:
• an in-valve head-side supply/discharge circuit to which a head-side supply/discharge circuit which is connected to the head-side in-valve supply/discharge circuit of the multifunction valve is connected via a head-side lowermost circuit;
• an in-valve rod-side supply/discharge circuit to which a rod-side supply/discharge circuit which is connected to the rod-side in-valve supply/discharge circuit of the multifunction valve is connected via a rod-side lowermost circuit;
• and a direction switching valve which switchably connects the in-valve head-side supply/discharge circuit and the in-valve rod-side supply/discharge circuit with the hydraulic pump and the tank;
• a pump-side bypass circuit in which a head-side branch circuit, which branches from the head-side lowermost circuit or the head-side supply/discharge circuit of the control valve unit, or a rod-side branch circuit, which branches from the rod-side lowermost circuit or the rod-side supply/discharge circuit of the control valve unit, is connected to a pump-side branch circuit branching from the discharge side of the hydraulic pump, the pump-side bypass circuit including a pump-side stop valve;
• and
• a tank-side bypass circuit in which a head-side branch circuit, which branches from the head-side lowermost circuit or the head-side supply/discharge circuit of the control valve unit, or a rod-side branch circuit, which branches from the rod-side lowermost circuit or the rod-side supply/discharge circuit of the control valve unit, is connected to a tank-side branch circuit branching from a tank circuit connected to the tank, the tank-side bypass circuit including a tank-side stop valve, wherein, a flushing circuit bypasses the control valve unit being constituted by the pump-side bypass circuit, the bypass circuit of the multifunction valve, and the tank-side bypass circuit.

A flushing circuit for a hydraulic cylinder drive circuit, comprising:

• a hydraulic pump connected to a tank of hydraulic oil to generate pressurized hydraulic oil;
• a hydraulic cylinder including a piston which slidably enters a cylinder main body and to which a piston rod is fixed and a head-side pressure chamber and a rod-side pressure chamber which are formed by the piston and the cylinder main body;
• a multifunction valve including:
• a head-side in-valve supply/discharge circuit provided in the hydraulic cylinder, connected to the head-side pressure chamber, and having a head-side on-off valve;
• a rod-side in-valve supply/discharge circuit connected to the rod-side pressure chamber and having a rod-side on-off valve;
• and a bypassing circuit having a bypass on-off valve connecting the head-side in-valve supply/discharge circuit with the rod-side in-valve supply/discharge circuit on the upstream of the head-side stop valve and the rod-side stop valve;
• a control valve unit including:
• an in-valve head-side supply/discharge circuit to which a head-side supply/discharge circuit which is connected to the head-side in-valve supply/discharge circuit of the multifunction valve is connected via a head-side lowermost circuit;
• an in-valve rod-side supply/discharge circuit to which a rod-side supply/discharge circuit which is connected to the rod-side in-valve supply/discharge circuit of the multifunction valve is connected via a rod-side lowermost circuit;
• and a direction switching valve which switchably connects the in-valve head-side supply/discharge circuit and the in-valve rod-side supply/discharge circuit with the hydraulic pump and the tank;
• a head-side bypass circuit including a head-side valve connected to a head-side branch circuit branching from the head-side lowermost circuit or the head-side supply/discharge circuit of the control valve unit, a pump-side branch circuit branching from the discharge side of the hydraulic pump, and a tank-side branch circuit branching from a tank circuit of the hydraulic oil, the head-side valve being constituted by a head-side pump bypass circuit connecting the head-side branch circuit with the pump-side branch circuit and a head-side tank bypass circuit connecting the head branch circuit with the tank-side branch circuit;
• and
• a rod-side bypass circuit including a rod-side valve connected to a rod-side branch circuit branching from the rod-side lowermost circuit or the rod-side supply/discharge circuit of the control valve unit, a pump-side branch circuit branching from the discharge side of the hydraulic pump, and a tank-side branch circuit branching from the tank circuit of the hydraulic oil, the rod-side valve being constituted by a rod-side pump bypass circuit connecting the rod-side branch circuit with the pump-side branch circuit and a rod-side tank bypass circuit connecting the rod-side branch circuit with the tank-side branch circuit,
• wherein, either a clockwise flushing circuit constituted by the head-side pump bypass circuit of the head-side bypass circuit, the rod-side tank circuit of the rod-side bypass circuit, and the bypassing circuit of the multifunction valve or a counterclockwise flushing circuit constituted by the rod-side pump bypass circuit of the rod-side bypass circuit, the hear-side tank bypass circuit of the head-side bypass circuit is selectively constructed.