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 being coupled by welding to the working cylinder and comprising a solid metal body defining a plurality of intersecting drilled bores sealed by caps, 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, and wherein the valve body is integral with the working cylinder such that all hydraulic connections between the locking valve and the working cylinder are internal to the valve body;
- and
- a housing wherein the working cylinder body and the valve body are installed within the housing and further wherein the housing is coupled to the trailer by welding or bolting for stabilizing the trailer;
- a mounting pin for attaching the working cylinder to the housing of the jack, and wherein the valve body includes a fourth cavity configured to receive the mounting pin to secure the valve body to the housing of the jack;
- an outer and inner mechanical tube to substantially contain and shield the working cylinder and facilitate attachment to the trailer.