Hydraulic system with energy regeneration

Abstract

A hydraulic system includes a tank for hydraulic fluid, a supply line connected to the tank and a plurality of hydraulic functions connected to the supply line. Each hydraulic function includes an actuator that is connectable to a load and that has a first side and a second side. Each function includes a first control valve connected to the first side and a second control valve connected to the second side. Each function also has an independent tank line, and the first and second control valves are connected to both the supply line and the independent tank line. A third control valve is connected between the independent tank line and the tank, and a check valve is connected between the supply line and the independent tank line.

What is claimed is: 
     
         1 . A hydraulic system, comprising:
 a tank for hydraulic fluid;   a supply line connected to the tank;   a plurality of hydraulic functions connected to the supply line, each hydraulic function including
 an actuator that is connectable to a load, wherein the actuator has a first side and a second side; 
 a first control valve connected to the first side, 
 a second control valve connected to the second side, 
 an independent tank line, wherein the first and second control valves are connected to the supply line and the independent tank line, 
 a third control valve connected between the independent tank line and the tank, and 
 a check valve connected between the supply line and the independent tank line. 
   
     
     
         2 . The hydraulic system of  claim 1 , wherein the actuator is a cylinder, the first side is a rod side and the second side is a head side, and wherein the system further comprises a piston disposed within the cylinder and separating the rod side and the head side. 
     
     
         3 . The hydraulic system of  claim 1 , further comprising a controller, and wherein at least one of the first and second control valves are controlled by the controller. 
     
     
         4 . The hydraulic system of  claim 4 , wherein the first and second control valves are solenoid-operated valves. 
     
     
         5 . The hydraulic system of  claim 4 , wherein the third control valve is a solenoid-operated valve controlled by the controller. 
     
     
         6 . The hydraulic system of  claim 4 , wherein the third control valve is a pressure-controlled valve. 
     
     
         7 . The hydraulic system of  claim 1 , wherein the check valve is a pressure-operated valve. 
     
     
         8 . The system of  claim 1 , further comprising a pump connected between the tank and the supply line. 
     
     
         9 . The system of  claim 1 , further comprising a first pressure sensor that monitors pressure at the first side of the actuator and a second pressure sensor that monitors pressure at the second side of the actuator. 
     
     
         10 . A hydraulic system, comprising:
 a tank for hydraulic fluid;   a controller;   a supply line connected to the tank;   a pump connected between the tank and the supply line;   a plurality of loads; and   a plurality of hydraulic functions, each hydraulic function connected to one of said plurality of loads and connected to the supply line, wherein each hydraulic function includes
 a cylinder and a piston disposed within the cylinder, wherein the piston is connected to the load and divides the piston into a rod side and a head side, 
 a first operated control valve connected to the rod side and responsive to a first signal from the controller, 
 a second control valve connected to the head side and responsive to a second signal from the controller, 
 an independent tank line, wherein the first and second control valves are connected to the supply line and the independent tank line, 
 a third control valve connected between the independent tank line and the tank, 
 a pressure-operated check valve connected between the supply line and the independent tank line, 
 a first pressure sensor that monitors pressure at the rod side of the cylinder, 
 a second pressure sensor that monitors pressure at the head side of the cylinder, and 
 a third pressure sensor that monitors pressure in the independent tank line. 
   
     
     
         11 . The hydraulic system of  claim 10 , further comprising a controller, and wherein at the first and second control valves are solenoid-operated valves. 
     
     
         12 . The hydraulic system of  claim 10 , wherein the third control valve is a solenoid-operated valve controlled by the controller. 
     
     
         13 . The hydraulic system of  claim 10 , wherein the third control valve is a pressure-operated valve.