Patent ID: 7913491
Filing Date: 2011-03-29
Classification: E02F,F15B

Abstract:
1. Apparatus for controlling a double-acting hydraulic cylinder during a load-induced rod-extending operation, the cylinder being activated by fluid supplied from a reservoir by a pump, the cylinder having a rod end, a head end, a piston connected to a rod for engaging the load, the cylinder piston being urged toward the rod end by the load during the operation, the apparatus comprising: a cylinder activation circuit including an activation valve for providing a flow path from the pump to the cylinder head end; a flow regeneration circuit fluidly connecting the cylinder rod end and the cylinder head end and configured for providing flow from the cylinder rod end to the cylinder head end during rod extension, the regeneration circuit including a regeneration flow valve controllable independently from the activation valve; a rod position sensor configured and positioned to generate rod position signals; a controller responsive to the rod position signals and operatively connected to the regeneration flow valve and the activation valve, the controller being responsive to rod-extending rate demands from an operator to control the activation valve to provide flow from the pump to the head end and to control the regeneration valve to provide flow from the rod end to the head end; and wherein the cylinder activation circuit also includes a return flow path between the cylinder rod end and the fluid reservoir, and a return valve positioned in the return flow path and configured to control flow from the cylinder rod end to the fluid reservoir, wherein both the activation valve and the return valve are controllable by the controller independently from the regeneration flow valve wherein the activation valve comprises a directional control valve configured to selectively fluidly interconnect the pump with the cylinder head end or the cylinder rod end, and wherein the return valve is configured as part of the directional control valve.