Construction equipment machine with improved boom suspension

Abstract

A construction equipment machine of the loader type is provided and has at least a chassis, a traction arrangement and a loader arrangement. The loader arrangement includes a loader boom structure which is controlled through a two way boom hydraulic cylinder system, and a boom suspension system through which a lift-side of the boom cylinder system may be connected to a hydraulic pressurized accumulator while the drop-side of the boom cylinder system is connected to a tank return line. The tank return line has a flow limiter for limiting the flow of hydraulic oil in the direction from the drop-side of the boom cylinder system to the tank.

1 . Construction equipment machine of the loader type, of the type having at least:
 a chassis and   a traction arrangement and   a loader arrangement,   
       wherein the loader arrangement comprises a loader boom structure which is moveable with respect to the chassis and which holds a tool assembly, wherein the position of the boom structure with respect to the chassis is controlled through a two way boom hydraulic cylinder system, and wherein the loader arrangement has a boom suspension system through which a lift-side of the boom cylinder system is adapted to be connected to a hydraulic pressurized accumulator while the drop-side of the boom cylinder system is connected to a tank return line, wherein the tank return line has a flow limiter for limiting the flow of hydraulic oil in the direction from the drop-side of the boom cylinder system to the tank. 
     
     
         2 . Construction equipment machine according to  claim 1 , wherein the flow limiter limits the flow of hydraulic oil in the direction from the drop-side of the boom cylinder to the tank at a rate lower than the possible flow rate in the reverse direction. 
     
     
         3 . Construction equipment machine according to  claim 1 , wherein the flow of oil in the tank return line is not substantially limited in the direction from the tank to the drop-side of the boom cylinder. 
     
     
         4 . Construction equipment machine according to  claim 1 , wherein the flow limiter is a unidirectional flow limiter comprising a check valve hydraulically in parallel with a throttle. 
     
     
         5 . Construction equipment machine according to  claim 1 , wherein the tank return line is a dedicated return line for the boom suspension system which may be shut off when the boom suspension system is not operative. 
     
     
         6 . Construction equipment machine according to  claim 1 , wherein the loader boom structure is articulated with respect to the chassis around a boom axis. 
     
     
         7 . Construction equipment machine according to  claim 1 , wherein the tool assembly is articulated with respect to the loader boom at a distal end thereof around a tool axis, and in that the angular position of the tool assembly with respect to the boom is controlled through a two way tool hydraulic cylinder system. 
     
     
         8 . Construction equipment machine according to  claim 7 , wherein the loader arrangement has a self level system through which the drop-side of the boom cylinder system is adapted to be connected to the drop-side of the tool cylinder system. 
     
     
         9 . Construction equipment machine according to  claim 1 , wherein at least one of the hydraulic cylinder systems comprises two two-way-cylinders arranged in parallel. 
     
     
         10 . Method for operating a construction equipment machine of the loader type having at least:
 a chassis,   a traction arrangement and   a loader arrangement, wherein the loader arrangement comprises a loader boom structure which is moveable with respect to the chassis and which holds a tool assembly, wherein the position of the boom structure with respect to the chassis is controlled through a two way boom hydraulic cylinder system, and wherein the loader arrangement has a boom suspension system through which a lift-side of the boom cylinder system is adapted to be connected to a hydraulic pressurized accumulator while the drop-side of the boom cylinder system is connected to a dedicated tank return line which is adapted to be shut off when the boom suspension system is not operative,   wherein the method comprises:   connecting the drop side of the boom cylinder system to a source of pressurized fluid through a directional boom control valve,   simultaneously maintaining the drop side of the boom cylinder connected to the tank by the dedicated return line and limiting the flow of oil to the tank in that the tank return line thanks to a flow limiter for limiting the flow of hydraulic oil in the direction from the drop-side of the boom cylinder system to the tank.   
     
     
         11 . The method as set forth in  claim 10 , wherein the flow limiter limits the flow of hydraulic oil in the direction from the drop-side of the boom cylinder to the tank at a rate lower than the possible flow rate in the reverse direction. 
     
     
         12 . The method as set forth in  claim 10 , wherein the flow of oil in the tank return line is not substantially limited in the direction from the tank to the drop-side of the boom cylinder. 
     
     
         13 . The method as set forth in  claim 10 , wherein the flow limiter is a unidirectional flow limiter comprising a check valve hydraulically in parallel with a throttle. 
     
     
         14 . The method as set forth in  claim 10 , wherein the dedicated return line for the boom suspension system is shut off when the boom suspension system is not operative. 
     
     
         15 . The method as set forth in  claim 10 , wherein the tool assembly is articulated with respect to the loader boom at a distal end thereof around a tool axis, and in that the angular position of the tool assembly with respect to the boom is controlled through a two way tool hydraulic cylinder system. wherein the loader arrangement has a self level system through which the drop-side of the boom cylinder system is adapted to be connected to the drop-side of the tool cylinder system. and wherein the method includes operating simultaneously both the boom suspension system and self leveling system by maintaining the drop side of the boom cylinder connected to the tank by the dedicated return line and limiting the flow of oil to the tank in the tank return line thanks to the flow limiter for limiting the flow of hydraulic oil in the direction from the drop-side of the boom cylinder system to the tank.