Proportional valve for fluid flow control

A hydraulic system comprising:

• a source of fluid;
• a tank;
• an actuator;
• and
• a valve having a first port fluidly coupled to the tank, a second port fluidly coupled to the actuator, and a third port fluidly coupled to the source of fluid, wherein the third port comprises a pilot cross-hole and an inlet flow cross-hole, and wherein the valve comprises:
• a piston that is axially movable between a neutral position and an actuated position, wherein in the neutral position:
• (i) the second port is fluidly coupled to the first port, and (ii) the inlet flow cross-hole of the third port is fluidly decoupled from the second port,
• a solenoid actuator sleeve that is axially movable between an unactuated state and an actuated state, wherein in the unactuated state, the solenoid actuator sleeve blocks the pilot cross-hole of the third port, and in the actuated state, the solenoid actuator sleeve is configured to allow the pilot cross-hole to be fluidly coupled to the first port and allow pilot fluid to apply a fluid force on the piston in a distal direction,
• a first feedback spring, and
• a second feedback spring disposed in series with the first feedback spring, wherein the first feedback spring and the second feedback spring cooperate to apply a biasing force in a proximal direction on the piston against the fluid force, wherein the piston is configured to move axially to the actuated position based on a relationship between the fluid force and the biasing force, and wherein in the actuated position, the inlet flow cross-hole is fluidly coupled to the second port whereas the second port is fluidly decoupled from the first port.

A method comprising:

• operating a valve in a first state, wherein a first port of the valve is fluidly coupled to a second port of the valve such that fluid is allowed to flow from the second port to the first port;
• receiving an electric signal energizing a solenoid coil of a solenoid actuator of the valve to operate the valve in a second state;
• responsively, causing an armature and a solenoid actuator sleeve coupled thereto to move, thereby (i) compressing a first feedback spring and a second feedback spring disposed in series with the first feedback spring to increase a biasing force applied by the first feedback spring and the second feedback spring on a piston of the valve in a proximal direction, and (ii) opening a pilot flow path to allow pilot fluid to flow from a third port of the valve to the first port, wherein the pilot fluid applies a fluid force on the piston in a distal direction, and wherein the piston moves to a particular axial position determined by a relationship between the fluid force and the biasing force;
• and
• in response to motion of the piston to the particular axial position, opening a main flow path from the third port to the second port while blocking fluid path from the second port to the first port.