Mechanical spring actuator

A linear actuator, comprising:

• a housing comprising a first end and a second end, and defining a central cavity extending axially through the housing;
• a tube having a first portion and a second portion, the first portion arranged to slide within the central cavity of the housing, and the second portion extending outwardly from the second end of the housing;
• a first elongated rotatable screw positioned axially within the central cavity of the housing and connected to the tube, wherein the first elongated rotatable screw is coaxial with the tube;
• a first cylindrical nut positioned within the central cavity of the housing and mounted about the first elongated rotatable screw, wherein the first cylindrical nut is configured to move axially within the central cavity of the housing as the first elongated rotatable screw rotates;
• a second elongated rotatable screw positioned axially within the central cavity of the housing;
• a second cylindrical nut positioned within the central cavity of the housing and mounted about the second elongated rotatable screw, wherein the second cylindrical nut is configured to move axially within the central cavity of the housing as the second elongated rotatable screw rotates;
• and
• a spring positioned within the central cavity of the housing and around the second elongated rotatable screw between the second cylindrical nut and the second end of the housing, wherein the spring is configured to bias the second cylindrical nut away from the second end of the housing.