Overspeed safeguards in hydraulically controlled fuel boost pump

A hydraulic system comprising:

• a pump including an inlet and an outlet;
• a hydraulic motor for driving the pump;
• a control valve including a valve body defining a spool bore, the valve body defining a fluid supply port and a fluid outlet port both in fluid communication with the spool bore, the fluid supply port being adapted to be connected to a fluid supply, and the fluid outlet port being fluidly connected to the hydraulic motor to provide fluid for driving rotation of a rotating group of the hydraulic motor, the control valve including a spool positioned within the spool bore, the spool having a first end and an opposite second end, the spool being linearly moveable within the spool bore along an axis of the spool bore to move the control valve between a first operating state and a second operating state, the spool being configured to open a non-restrictive flow path within the spool bore between the fluid supply port and the fluid outlet port when the control valve is in the first operating state, the control valve defining a restrictive flow area through which hydraulic fluid from the fluid supply port is required to pass to reach the fluid outlet port when the control valve is in the second operating state, the control valve including a piston chamber at the first end of the spool and an outlet pressure piston within the piston chamber that is acted on by an outlet pressure from the pump to move the spool along the axis of the spool bore in a first direction away from the piston chamber, the control valve including a spring at the second end of the spool to apply a bias to the spool along the axis of the spool bore in a second direction that is opposite from the first direction, the spring providing a spring force that corresponds to a normal operating pressure desired at the outlet of the pump, wherein, when the outlet pressure of the pump is at the normal operating pressure or above the normal operating pressure, the outlet pressure piston moves the spool in the first direction along the axis of the spool bore against the bias of the spring to a first position or positions corresponding to the first operating state, and wherein when the outlet pressure of the pump is below the normal operating pressure the spring moves the spool in the second direction along the axis of the spool bore to a second position corresponding to the second operating state;
• wherein the valve body defines a motor control port for providing pressure to a control piston for moving a swash plate to destroke the hydraulic motor, wherein, when the outlet pressure of the pump exceeds the normal operating pressure, the outlet pressure piston moves the spool in the first direction towards a position in which the motor control port is in fluid communication with the fluid supply port.

A hydraulic system comprising:

• a pump including an inlet and an outlet;
• a hydraulic motor for driving the pump;
• a control valve including a valve body defining a spool bore, the valve body defining a fluid supply port and a fluid outlet port both in fluid communication with the spool bore, the fluid supply port being adapted to be connected to a fluid supply, and the fluid outlet port being fluidly connected to the hydraulic motor to provide fluid for driving rotation of a rotating group of the hydraulic motor, the control valve including a spool positioned within the spool bore, the spool having a first end and an opposite second end, the spool being linearly moveable within the spool bore along an axis of the spool bore to transition the control valve between a first operating state and a second operating state, the control valve defining a flow path between the fluid supply port and the fluid outlet port, the flow path being non-restrictive when the control valve is in the first operating state, the flow path being restrictive when the control valve is in the second operating state, the control valve including a spool actuation piston that is operatively coupled to the first end of the spool for forcing the spool in a first direction along the axis of the spool bore in response to a pressure that corresponds to the outlet of the pump and that is being applied to the spool actuation piston, the control valve also including a spring operatively coupled to the second end of the spool for biasing the spool along the axis of the spool bore in a second direction opposite from the first direction, wherein the control valve transitions between the first and second operating states based on a direction of a net force applied to the spool by the spool actuation piston and the spring;
• wherein when the control valve is in the second operating state, the flow path defines a flow restriction area that is small enough to provide a restriction of flow to the hydraulic motor to prevent the hydraulic motor from an unsafe speed when the pump is spinning dry, and is large enough such that at start-up under non-dry pump conditions enough pressure and flow are provided to the hydraulic motor from the control valve to drive the pump at a speed which causes sufficient outlet pressure at the pump to cause the control valve to transition from the second operating state toward the first operating state.

A hydraulic system comprising:

• a pump including an inlet and an outlet;
• a hydraulic motor for driving the pump;
• a control valve including a valve body defining a spool bore, the valve body defining a fluid supply port and a fluid outlet port both in fluid communication with the spool bore, the fluid supply port being adapted to be connected to a fluid supply, and the fluid outlet port being fluidly connected to the hydraulic motor to provide fluid for driving rotation of a rotating group of the hydraulic motor, the control valve including a spool positioned within the spool bore, the spool having a first end and an opposite second end, the spool being linearly moveable within the spool bore along an axis of the spool bore to transition the control valve between a first operating state and a second operating state, the control valve defining a flow path between the fluid supply port and the fluid outlet port, the flow path being non-restrictive when the control valve is in the first operating state, the flow path being restrictive when the control valve is in the second operating state, the control valve including a spool actuation piston that is operatively coupled to the first end of the spool for forcing the spool in a first direction along the axis of the spool bore in response to a pressure that corresponds to the outlet of the pump and that is being applied to the spool actuation piston, the control valve also including a spring operatively coupled to the second end of the spool for biasing the spool along the axis of the spool bore in a second direction opposite from the first direction, wherein the control valve transitions between the first and second operating states based on a direction of a net force applied to the spool by the spool actuation piston and the spring;
• and
• a flow limiting valve integrated into the valve body at the fluid supply port, wherein a flow restriction of the flow path when the control valve is in the second operating state is less restrictive than the flow limiting valve when operating at comparable flows and pressures.