Double check valve having floating function

Abstract

A double check valve having a floating function is disclosed, whereby a working device that is operated by a hydraulic cylinder having a double check valve (e.g., a dozer blade) can perform a floating function when the working device performs land readjustment of a work surface. The double check valve having a floating function includes a hydraulic pump, a hydraulic cylinder operating a working device, a control valve controlling a start, a stop, and a direction change of the hydraulic cylinder, and a double check valve installed to open/close flow paths between the control valve and the hydraulic cylinder, and having a pair of plungers dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied thereto, and a pair of check valves being pressed to remove their check functions through a shifting of the plungers. When the control valve is shifted to a neutral state and a floating function mode is selected, a large chamber and a small chamber of the hydraulic cylinder are connected to each other by the double check valve.

1 . A double check valve having a floating function, comprising:
 a hydraulic pump;   a hydraulic cylinder connected to the hydraulic pump to operate a working device;   a control valve installed in flow paths between the hydraulic pump and the hydraulic cylinder and shifted to control a start, a stop, and a direction change of the hydraulic cylinder; and   a double check valve installed in flow paths between the control valve and the hydraulic cylinder, and having a pair of plungers dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied from an outside, and a pair of check valves being pressed to remove their check functions through a shifting of the plungers;   wherein in the case where the control valve is shifted to a neutral state and a floating function mode of the working device is selected, a large chamber and a small chamber of the hydraulic cylinder are connected to each other by the double check valve.   
   
   
       2 . The double check valve of  claim 1 , wherein the double check valve further comprises:
 a housing in which first flow paths connecting the control valve to the small chamber of the hydraulic cylinder and second flow paths connecting the control valve to the large chamber of the hydraulic cylinder are formed;   a signal pressure flow path to which a signal pressure for shifting the plungers is supplied;   a pressing member pressing the check valve for opening/closing the first flow paths;   a first elastic member elastically supporting the pressing member so as to elastically bias the first flow paths, which have been blocked by the check valve, to their initial states,   a pressing member pressing the check valve for opening/closing the second flow paths; and   a second elastic member elastically supporting the pressing member so as to elastically bias the second flow paths, which have been blocked by the check valve, to their initial states.   
   
   
       3 . The double check valve of  claim 1 , wherein a pilot signal pressure, which is supplied from the hydraulic pump to the signal pressure flow path, is used as a signal pressure for shifting the plungers. 
   
   
       4 . The double check valve of  claim 1 , wherein a ball type or poppet valve is used as the check valve. 
   
   
       5 . The double check valve of  claim 2 , wherein a ball type or poppet valve is used as the check valve.