Method and device for switching hydraulic fluid supplies, such as for a hydraulic pump/motor

A valve, comprising:

• a valve body having first and second input ports and first and second output ports;
• a valve bore positioned within the valve body;
• a spool positioned within the bore;
• means for establishing fluid communication between the first and second input ports and the first and second output ports, respectively;
• means for establishing fluid communication between the first and second input ports and the second and first output ports, respectively;
• means for establishing fluid communication between the second input port and the first and second output ports, simultaneously;
• and
• means for preventing fluid from flowing outward from the valve via the second output port.

A system, comprising:

• a hydraulic motor having first and second input ports, configured to apply torque to an output shaft of the motor in a first direction when a fluid pressure at the first input port exceeds a fluid pressure at the second input port, and configured to apply torque to the output shaft in a second direction when the fluid pressure at the second input port exceeds the fluid pressure at the first input port;
• a spool valve having first and second output ports coupled to the first and second input ports, respectively, and a high-pressure input port and a low-pressure input port, the valve configured to selectively couple the high-pressure and low-pressure input ports to the first and second input ports, respectively, or to the second and first input ports, respectively, according to a selected position of a spool of the valve;
• and
• a check valve positioned and configured to prevent fluid flow into the hydraulic motor from the second input port at least while the high-pressure input port is coupled to the second input port.

A valve for controlling a hydraulic device, comprising:

• a valve body having an interior bore;
• a first valve port configured to be coupled to a fluid source pressurized to a first pressure range;
• a second valve port configured to be coupled to a fluid source pressurized to a second pressure range, lower than the first pressure range;
• an output port configured to carry fluid to a hydraulic device;
• an input port configured to receive fluid from the hydraulic device;
• a valve spool axially movable within the bore and configured to selectively channel fluid from the first and second valve ports to the output and input ports, respectively, while in a first position, from the second valve port to both the output and input ports while in a second position, and from the second and first valve ports to the output and input ports respectively, while in a third position;
• and
• a check valve configured to permit one-way fluid passage from the input port to the first valve port.

A method of operating a hydraulic pump/motor, comprising:

• placing a spool of a spool valve in a first position, such that a first fluid port of the pump/motor is in fluid communication with a first pressurized fluid source and a second fluid port of the pump/motor is in fluid communication with a second pressurized fluid source, and such that a torque in a first direction is applied to an output shaft of the pump/motor;
• placing the spool in a second position, such that the first and second fluid ports of the pump/motor are in fluid communication with each other and with the second pressurized fluid source, and such that substantially no torque is applied to the output shaft;
• placing the spool in a third position, such that the first fluid port of the pump/motor is in fluid communication with the second pressurized fluid source and the second fluid port of the pump/motor is in fluid communication with the first pressurized fluid source, and such that a torque in a second direction is applied to the output shaft of the pump/motor;
• and
• preventing, while the spool is in the third position, the output shaft of the pump/motor from rotating in the second direction.

A system, comprising:

• a hydraulic motor having first and second input ports, configured to apply torque to an output shaft of the motor in a first direction when a fluid pressure at the first input port exceeds a fluid pressure at the second input port, and configured to apply torque to the output shaft in a second direction when the fluid pressure at the second input port exceeds the fluid pressure at the first input port;
• a spool valve having first and second output ports coupled to the first and second input ports, respectively, and a high-pressure input port and a low-pressure input port, the valve configured to selectively couple the high-pressure and low-pressure input ports to the first and second input ports, respectively, or to the second and first input ports, respectively, according to a selected position of a spool of the valve;
• and
• a check valve configured to permit fluid passage from the second input port to the high-pressure input port, regardless of a position of the spool.