Patent ID: 7076896

Claim:
A hydraulic system for an earthmoving vehicle having an operating arm movable between a raised position and a lowered position, the hydraulic system causing the operating arm to move between the raised position and the lowered position, the hydraulic system comprising: at least one hydraulic atuator connected to the operating arm and defining a first variable-volume chamber; a fluid drain line for draining hydraulic fluid from the first variable-volume chamber so as to lower the operating arm; a first fluid flow control means positioned between the first chamber and the drain line, the first fluid flow control means being operable to shift in a first respective direction that is associated with lowering the operating arm so as to drain the fluid from the first chamber, the first control means having a free flow opening permitting free flow of fluid to the fluid drain line when the first control means is shifted in the first respective direction; a second fluid flwo control means positioned in fluid flow series between the first control means and the first chamber, the second control means being operable to shift in a second respective direction that is associated with lowering the operating arm so as to drain the fluid from the first chamber, the second control means having a variable flow section; a pilot pressure having a variable value for shifting the first and second control means in their respective directions; and the free flow opening of the first control means being larger than the flow section of the second control means for each variable value of the pilot pressure.