Hydraulic actuator with shock absorbing capability

A hydraulic actuator, comprising:

• a cylinder;
• a first piston slidably disposed within said cylinder;
• an actuator shaft attached to said first piston and extending through a first end of said cylinder;
• a second piston slidably disposed within said cylinder, said first and second pistons being movable relative to each other to define the volumes of a first chamber between said first piston and a first end of said cylinder, a second chamber between said second piston and a second end of said cylinder, and an intermediate chamber between said first and second pistons;
• a fluid passage through said first piston;
• and
• a poppet supported by said first piston, said poppet being movable relative to said first piston between a closed position blocking said fluid passage and an open position which connects said first chamber and said intermediate chamber in fluid communication with each other, said poppet being movable into said open position in response to an increase of pressure within said first chamber beyond a predetermined magnitude, said poppet having first and second effective areas against which pressure within said fluid passage can act, said pressure within said fluid passage acting against said first effective area causing a force on said poppet toward said open position, said pressure within said fluid passage acting against said second effective area causing a force on said poppet toward said closed position.

A hydraulic actuator, comprising:

• a cylinder;
• a first piston slidably disposed within said cylinder;
• an actuator shaft attached to said first piston and extending through a first end of said cylinder;
• a second piston slidably disposed within said cylinder, said first and second pistons being movable relative to each other to define the volumes of a first chamber between said first piston and a first end of said cylinder, a second chamber between said second piston and a second end of said cylinder, and an intermediate chamber between said first and second pistons;
• a fluid passage through said first piston;
• a poppet supported by said first piston, said poppet being movable relative to said first piston between a closed position blocking said fluid passage and an open position which connects said first chamber and said intermediate chamber in fluid communication with each other, said poppet being movable into said open position in response to an increase of pressure within said first chamber beyond a predetermined magnitude, said poppet having first and second effective areas against which pressure within said fluid passage can act, said pressure within said fluid passage acting against said first effective area causing a force on said poppet toward said open position, said pressure within said fluid passage acting against said second effective area causing a force on said poppet toward said closed position, said first effective area being larger than said second effective area, said first and second effective areas being sized to cause said poppet to move from said closed position to said open position in response to the pressure within said first chamber exceeding a predetermined magnitude;
• and
• a bleed passage formed through said first piston to allow fluid to flow from said intermediate chamber to said first chamber in response to a force on said shaft urging said first piston toward said second piston.