Jack assembly with integrated pressure relief assembly

A jack assembly, comprising:

• a cylinder defining an interior;
• a piston having a piston head that is slideably engaged with the interior of the cylinder;
• an extension chamber defined between the piston head and the interior of the cylinder;
• and a pressure relief assembly in the piston head and defining a relief passageway in selective fluid communication with the extension chamber;
• the pressure relief assembly being responsive to fluid pressure in the extension chamber so that when the fluid pressure in the extension chamber exceeds a certain level the pressure relief assembly causes fluid to flow through the relief passageway, wherein the pressure relief assembly comprises a one-way valve assembly coupled to the piston for selectively permitting the fluid to flow from the extension chamber toward the relief cavity, the one-way valve assembly further comprising a valve body engaged with the piston and defining the relief passageway;
• a valve seat defined by the valve body;
• and a plug biased toward the valve seat to inhibit flow of the fluid through the relief passageway.