Screed cushioning system and method

Abstract

A paver including a screed and a hydraulic actuator coupled to the screed. The hydraulic actuator is configured to raise the screed to a transport position by pressurizing a raise end of the hydraulic actuator. An accumulator is selectively connected to the hydraulic actuator. A control valve configured to switch the screed in the transport position between a non-cushioned state and a cushioned state by connecting the accumulator to the raise end of the hydraulic actuator in the cushioned state. The hydraulic pressure of the accumulator is equalized to a hydraulic pressure of the hydraulic actuator before the control valve switches the screed from the non-cushioned state to the cushioned state.

What is claimed is: 
     
         1 . A paver comprising:
 a screed;   an actuator coupled to the screed and configured to raise the screed to a transport position by pressurizing a raise end of the actuator;   an accumulator selectively connected to the actuator;   a control valve configured to switch the screed in the transport position between a non-cushioned state and a cushioned state by connecting the accumulator to the raise end in the cushioned state;   wherein an accumulator hydraulic pressure is equalized to an actuator hydraulic pressure before the control valve switches the screed from the non-cushioned state to the cushioned state.   
     
     
         2 . The paver of  claim 1 , further comprising a pressure equalization passage connecting the actuator and the accumulator for equalizing the accumulator hydraulic pressure with the actuator hydraulic pressure. 
     
     
         3 . The paver of  claim 1 , further comprising a damping orifice between the raise end and the accumulator. 
     
     
         4 . The paver of  claim 1 , further comprising a one way check valve between the raise end and the accumulator. 
     
     
         5 . The paver of  claim 1 , further comprising a controller operatively coupled to the actuator and the control valve, and wherein the controller configured to switch the screed to the cushioned state when the screed is in the transport position. 
     
     
         6 . The paver of  claim 5 , further comprising a stop member, and wherein the controller is configured to move the stop member to restrict travel of the screed out of the transport position when the screed is in the cushioned state. 
     
     
         7 . The paver of  claim 1 , wherein the actuator includes a first actuator connected to a first end of the screed and a second actuator connected to a second end of the screed. 
     
     
         8 . The paver of  claim 7 , wherein the control valve is configured to connect the accumulator to the raise end of the first actuator and to the raise end of the second actuator in the cushioned state. 
     
     
         9 . A paver comprising:
 a screed;   an actuator coupled to the screed and configured to move the screed between a raised position and a lowered position;   a control valve configured to switch the screed between a non-cushioned state and a cushioned state in the raised position; and   a controller operatively coupled to the actuator and the control valve, the controller configured to raise the screed to the raised position and switch the screed to the cushioned state when the screed is in the raised position.   
     
     
         10 . The paver of  claim 9 , further comprising an accumulator, wherein an accumulator hydraulic pressure is equalized to an actuator hydraulic pressure before the screed is switched to the cushioned state. 
     
     
         11 . The paver of  claim 10 , further comprising a pressure equalization passage connecting the actuator and the accumulator. 
     
     
         12 . The paver of  claim 9 , further comprising a stop member configured to block movement of the screed out of the raised position. 
     
     
         13 . The paver of  claim 10 , further comprising a damping orifice between a raise end of the actuator and the accumulator. 
     
     
         14 . The paver of  claim 12 , wherein the controller is configured to control movement of the stop member based on an operator input. 
     
     
         15 . A method of cushioning a screed comprising:
 raising the screed from a lowered position to a raised position;   equalizing an actuator pressure to an accumulator pressure; and   placing the screed in a cushioned state by connecting the actuator to the accumulator.   
     
     
         16 . The method of  claim 15 , further comprising determining whether the screed is in the raised position. 
     
     
         17 . The method of  claim 16 , further comprising extending a stop member to lock the screed in the raised position when the screed is in the raised position. 
     
     
         18 . The method of  claim 17 , further comprising determining an operator request to move the screed to the lowered position. 
     
     
         19 . The method of  claim 18 , further comprising retracting the stop member after receiving the operator request to move the screed to the lowered position. 
     
     
         20 . The method of  claim 19 , further comprising moving the screed from the raised position to the lowered position.