Jack with hydraulic lock

A hydraulic jack for use with a trailer, the hydraulic jack configured to be attached to the trailer and operable for extending and retracting to an adjustable height, the hydraulic jack comprising:

• a hydraulic power unit having an extend line and a retract line, the hydraulic power unit capable of producing a hydraulic pressure to provide hydraulic fluid flow through the extend line and the retract line;
• a working cylinder defining a body, an extend port and a retract port;
• an internal portion comprising a cylinder rod, the internal portion coupled to the working cylinder, and the internal portion further comprising a foot coupled to the cylinder rod, the internal portion, cylinder rod, and foot operable to extend and retract relative to the working cylinder body to provide the adjustable height for stabilizing the trailer;
• a valve body coupled to the working cylinder, the valve body comprising an extend coupler and a retract coupler configured for respective connection to the extend and retract lines of the hydraulic power unit, the valve body further comprising:
• a first port coupled to the extend port of the working cylinder and a first internal cavity interconnecting the extend coupler and the first port;
• a second port coupled to the retract port of the working cylinder and a second internal cavity interconnecting the retract coupler and the second port, and
• a third internal cavity interconnecting the second internal cavity and the first internal cavity,
• a locking valve installed in the first internal cavity of the valve body, the locking valve comprising a pilot port coupled to the third internal cavity of the valve body and therethrough to the second internal cavity and the retract coupler of the valve body, the locking valve operable to allow substantially free hydraulic fluid flow through the first internal cavity in a first direction from the extend coupler to the first port, the locking valve further operable, under control of the pilot port:
• to allow substantially free hydraulic fluid flow in a second direction from the first port to the extend coupler when hydraulic pressure is present at the pilot port;
• and
• to substantially prevent hydraulic fluid flow in the second direction from the first port to the extend coupler when hydraulic pressure is not present at the pilot port.