Hydraulic lock and method for a hydraulic system

A hydraulic lock for a hydraulic system, the hydraulic lock comprising:

• a flow control valve having a first inlet, a first outlet, a first check valve and a flow restrictor, each of the first check valve and the flow restrictor being communicably coupled to the first inlet and the first outlet and being arranged in parallel between the first inlet and the first outlet;
• and
• a second check valve having a second inlet and a second outlet, the second inlet being communicably coupled to the first outlet, the second check valve further having:
• a second ball seating surface having an aperture there through,
• a second ball, and
• a second resilient member biasing the second ball towards the second ball seating surface to seal the aperture, the aperture being communicably coupled to the second inlet and the second outlet;
• wherein the second ball of the second check valve includes a stem that extends from the second ball in a direction substantially opposite the second ball seating surface so as to extend, through a second check valve housing of the second check valve, to an ambient pressure surrounding the second check valve housing.

A hydraulic system comprising:

• a hydraulic fluid reservoir;
• an actuation cylinder;
• and
• a hydraulic lock disposed between the hydraulic fluid reservoir and the actuation cylinder so as to fluidly couple the hydraulic fluid reservoir to the actuation cylinder, the hydraulic lock including
• a flow control valve having a first inlet, a first outlet, a first check valve and a flow restrictor, each of the first check valve and the flow restrictor being communicably coupled to the first inlet and the first outlet and being arranged in parallel between the first inlet and the first outlet;
• and
• a second check valve having a second inlet and a second outlet, the second inlet being communicably coupled to the first outlet, the second check valve further having:
• a ball seating surface having an aperture there through,
• a ball having a hydraulic fluid reservoir side with a reservoir side hydraulic area and an actuation cylinder side with an actuator side hydraulic area, where the reservoir side hydraulic area is greater than the actuator side hydraulic area,
• and a resilient member biasing the ball towards the ball seating surface to seal the aperture, the aperture being communicably coupled to the second inlet and the second outlet.

A hydraulic system comprising:

• a hydraulic fluid reservoir;
• an actuation cylinder;
• a hydraulic lock disposed between the hydraulic fluid reservoir and the actuation cylinder so as to fluidly couple the hydraulic fluid reservoir to the actuation cylinder, the hydraulic lock including
• a flow control valve having a first inlet, a first outlet, a first check valve and a flow restrictor, each of the first check valve and the flow restrictor being communicably coupled to the first inlet and the first outlet and being arranged in parallel between the first inlet and the first outlet;
• and
• a second check valve having a second inlet and a second outlet, the second inlet being communicably coupled to the first outlet, the second check valve further having a ball seating surface having an aperture there through, a ball, and a resilient member biasing the ball towards the ball seating surface to seal the aperture, the aperture being communicably coupled to the second inlet and the second outlet;
• and
• a passive mechanical lock coupled to the actuation cylinder, where the passive mechanical lock and the hydraulic lock are arranged in parallel to provide two distinct load paths for maintaining the actuation cylinder in a predetermined extended or retracted position.

A method for operating a hydraulic lock in a hydraulic system, the method comprising:

• blocking a return hydraulic fluid flow through a flow control valve with a first check valve of the flow control valve where the first check valve directs the return hydraulic fluid flow through a flow restrictor, of the flow control valve, the first check valve and the flow restrictor being arranged in parallel between a first inlet and a first outlet of the flow control valve;
• holding a second ball of a second check valve away from a second ball seating surface of the second check valve, against a biasing force of a second resilient member biasing the second ball towards the second ball seating surface, with at least a hydraulic fluid gauge pressure, in a second manifold of the second check valve, effected by the flow restrictor;
• and
• seating the second ball against the second ball seating surface to close a second inlet of the second check valve when a differential pressure based force exerted on the second ball of the second check valve is substantially zero or less than a biasing force of the second resilient member, where the differential pressure based force is effected by the flow control valve and a differential hydraulic surface area on opposite sides of the second ball where the second ball has an inlet side with an inlet side hydraulic area and an outlet side with an outlet side hydraulic area and the inlet side hydraulic area is greater than the outlet side hydraulic area.