Patent ID: 7055801

Claim:
A no-load quick rise hydraulic lifting mechanism comprising: a) a hydraulic actuator, the hydraulic actuator comprising: a hydraulic cylinder having an extendible piston rod; an oil reservoir; a drive pump operably connected to the hydraulic cylinder, the drive pump comprising a drive cylinder and a drive piston; a suction-discharge valve operably connecting the oil reservoir, the drive pump, and the hydraulic cylinder during hydraulic-actuated lifting; a drive pump over-pressure relief valve operably connecting the drive pump and the oil reservoir; and, an oil vacuum relief valve operably connecting the oil reservoir and the hydraulic cylinder, the oil vacuum relief valve allowing oil to flow from the oil reservoir into the hydraulic cylinder during mechanically-actuated lifting; b) a lift arm operably connected to the piston rod by a pin, the lift arm being pivotable about an axis; and c) a mechanical actuator, the mechanical actuator comprising: a ratchet mechanism; and, an articulated linkage connecting the ratchet mechanism to the lift arm, wherein, the articulated linkage is connected to the lift arm by the same pin that connects the piston rod to the lift arm.