Image Number 2 for United States Patent #5511267.
A dock leveler having a deck assembly, a first hydraulic cylinder to power said deck assembly to a raised position, lip mounted to said deck assembly, and a second hydraulic cylinder for powering said lip into an extended position. An hydraulic power circuit is coupled to the first and second hydraulic cylinders to control movement of said deck and lip. The hydraulic power circuit includes a pump to deliver fluid under pressure, a first valve operatively coupled to the pump to control fluid flow to the first hydraulic cylinder. A second valve is operatively coupled to the second hydraulic cylinder. An adjustable relief valve is coupled to the second valve to prevent a reduction of fluid pressure to the second hydraulic cylinder after the pump has supplied fluid under pressure through the second valve to extend the lip.