Counterbalance Valve with Two Setting Springs in Parallel

A hydraulic system comprising:

• a source of fluid;
• a fluid reservoir;
• an actuator having a first actuator chamber and a second actuator chamber;
• a directional control valve configured to direct fluid flow from the source of fluid to the second actuator chamber via a fluid line;
• and
• a counterbalance valve having a first port fluidly coupled to the second actuator chamber, a second port fluidly coupled to the fluid reservoir, and a pilot port fluidly coupled to the fluid line and configured to receive a pilot pressure fluid signal therethrough, wherein the counterbalance valve comprises:
• a poppet configured to be subjected to (i) a first fluid force by fluid received at the first port acting on the poppet in a proximal direction, (ii) a second fluid force by the pilot pressure fluid signal received at the pilot port acting on the poppet in the proximal direction, and (iii) a third fluid force by fluid of the second port acting on the poppet in a distal direction,
• a first setting spring disposed in a first chamber and applying a first biasing force on the poppet in the distal direction, and
• a second setting spring disposed in a second chamber and applying a second biasing force on the poppet in the distal direction, wherein the first chamber and the second chamber are fluidly coupled to the second port of the counterbalance valve, wherein the second setting spring is in parallel with the first setting spring such that an equivalent biasing force acting on the poppet in the distal direction comprises substantially a sum of the first biasing force and the second biasing force, and wherein the poppet is configured to move to an axial position based on a substantial force equilibrium between the first fluid force, the second fluid force, the third fluid force, and the equivalent biasing force to allow fluid flow received at the first port from the second actuator chamber to the second port that is fluidly coupled to the fluid reservoir.

A method comprising:

• applying a first fluid force on a poppet of a counterbalance valve in a proximal direction, wherein the counterbalance valve comprises a first port fluidly coupled to a chamber of an actuator, a second port, and a pilot port, and wherein the first fluid force is applied by fluid received at the first port from the chamber of the actuator;
• applying a second fluid force on the poppet of the counterbalance valve in the proximal direction by a pilot pressure fluid signal received at the pilot port;
• applying a third fluid force on the poppet of the counterbalance valve in a distal direction by fluid of the second port;
• applying a first biasing force on the poppet in the distal direction by a first setting spring disposed in a first chamber within a housing of the counterbalance valve;
• and
• applying a second biasing force on the poppet in the distal direction by a second setting spring disposed in a second chamber within the housing of the counterbalance valve, wherein the first chamber and the second chamber are fluidly coupled to the second port of the counterbalance valve, wherein the second setting spring is in parallel with the first setting spring such that an equivalent biasing force acting on the poppet in the distal direction comprises substantially a sum of the first biasing force and the second biasing force, and wherein an axial position of the poppet is based on a substantial force equilibrium between the first fluid force, the second fluid force, the third fluid force, and the equivalent biasing force.