Patent ID: 7036796

Claim:
A hydraulic lifting mechanism comprising: a frame of horizontally spaced side plates, each side plate having a plurality of first mounting holes therein; a plurality of wheels attached to the frame; a monolithic hydraulic power block attached to the frame, the hydraulic power block having an oil reservoir therein, the oil reservoir having at least one open end, a plurality of valve ports extending from an upper surface of the hydraulic power block, one valve port having an intake check valve and a discharge check valve therein, another valve port having a pressure relief valve therein, the hydraulic power block having a laterally extending octagonal shape, a plurality of mounting flanges extending from the upper surface thereof, two sets of second mounting holes therein, each set of second mounting holes being oriented on a vertical line, each set of second mounting holes being aligned with the first mounting holes on a side plate, each mounting flange having one second mounting hole therein; a removable threaded end plug sealing the open end of the oil reservoir; a removable vent plug in fluid communication with the oil reservoir, the removable vent plug having: a valve body having a cavity therein, an exterior vent hole in communication with the cavity, and an interior vent hole in communication with the cavity, and a vent valve body within the valve body cavity, the vent plug having two venting mechanisms, one venting mechanism operating to allow air to flow from a first side of the vent valve body to a second side of the vent valve body when air pressure is higher on the first side of the vent valve body than on the second side of the vent valve body, the other mechanism operating to allow air to flow from the second side of the vent valve body to the first side of the vent valve body when air pressure is higher on the second side of the vent valve body than on the first side of the vent valve body; one of the venting mechanisms comprising: a spring biasing the vent valve body into contact with a valve seat within the valve body cavity, when air pressure on the first side of the vent valve body is higher than air pressure on the second side of the vent valve body, the vent valve body moves out of contact with the valve seat permitting air to flow between the vent valve body and the valve seat, the other of the venting mechanisms comprising: the vent valve body having a flexible flange at one end thereof, the flexible flange being in sealing contact with a valve seat within the valve body cavity, when air pressure on the second side of the vent valve body is higher than air pressure on the first side of the vent valve body, the flexible flange flexes out of contact with the valve seat permitting air to flow between the vent valve body and the valve seat; a hydraulic cylinder having an extensible piston, the hydraulic cylinder being attached to the hydraulic power block; and a lifting arm attached to the frame, the lifting arm being operatively connected to the extensible piston.