Cylinder with automatic hydraulic fluid circulation

A hydraulic cylinder comprising a rod end cap and a blind end cap and a piston that allows for hydraulic fluid to pass through the piston at the end of every stroke at the blind end cap side of the hydraulic cylinder, the hydraulic cylinder comprising:

• a barrel having the rod end cap at one end and the blind end cap at the other end;
• the piston slidingly disposed within the barrel, the piston comprising an aperture therethrough;
• the piston dividing the barrel into a rod end hydraulic fluid chamber and a blind end hydraulic fluid chamber wherein the piston is operable to move toward the rod end cap by increasing the pressure of the hydraulic fluid in the blind end hydraulic fluid chamber and to move toward the blind end cap by increasing the pressure of a hydraulic fluid in the rod end hydraulic fluid chamber;
• a piston rod connected to the piston, the piston rod being reciprocatingly received within the barrel, and
• a valve assembly situated within the aperture in the piston, the valve assembly comprising a plug valve and a poppet valve
• wherein the plug valve is located on the rod end side and is operable to be opened by the pressure of the hydraulic fluid from the rod end hydraulic fluid chamber to permit the flow of hydraulic fluid through the plug valve and is operable to close by increasing the pressure of the hydraulic fluid from the blind end hydraulic fluid chamber;
• wherein the poppet valve is located on the blind end side and is operable to be opened by the pressure of the hydraulic fluid from the blind end hydraulic chamber to permit the flow of hydraulic fluid through the poppet valve and is operable to close by increasing the pressure of the hydraulic fluid from the rod end hydraulic fluid chamber and wherein the poppet valve is operable to open each time the poppet valve contacts the blind end cap;
• to permit the passage of hydraulic fluid through the open plug valve and the poppet valve of the valve assembly;
• wherein the plug valve and the poppet valve are never both closed at the same time;
• and
• wherein the plug valve is always open when the pressure in the rod end side hydraulic chamber increases and the poppet valve is always open when the pressure in the blind end side hydraulic chamber increases.