Barrel spring

A hinge for connecting a first portion and a second portion, the hinge including a device for applying an axial force, the device comprising:

• a longitudinal axis having a first end and a second end;
• a first compression surface positioned at the first end of the longitudinal axis;
• a second compression surface positioned at the second end of the longitudinal axis;
• a plurality of resilient members positioned between the first compression surface and second compression surface, the plurality of resilient members including:
• a first resilient member being oriented with a first end of the first resilient member proximate the first compression surface and a second end of the first resilient member proximate the second compression surface, and
• a second resilient member being oriented with a first end of the second resilient member proximate the first compression surface and a second end of the second resilient member proximate the second compression surface;
• and
• the device having a compressed state and an expanded state, the first compression surface and second compression surface configured to move in a direction of the longitudinal axis between the compressed state and the expanded state, the device having a spring constant between the compressed state and the expanded state of at least 150 Newtons per millimeter, and the device having a displacement of the first compression surface and second compression surface between the compressed state and the expanded state being less than 500 microns.

A system for movably coupling two structures, the system comprising:

• a shaft having a rotational axis;
• a protrusion extending from the shaft in a radial direction perpendicular to the rotational axis;
• a link in contact with the protrusion, the link being positioned to contact a side surface of the protrusion and apply a torque to the shaft;
• a barrel spring contacting the link and configured to apply a force to the link toward the shaft, the barrel spring comprising:
• a longitudinal axis having a first end and a second end;
• a first compression surface positioned at the first end of the longitudinal axis;
• a second compression surface positioned at the second end of the longitudinal axis;
• a plurality of resilient members positioned between the first compression surface and second compression surface, the plurality of resilient members including:
• a first resilient member being oriented with a first end of the first resilient member proximate the first compression surface and a second end of the first resilient member proximate the second compression surface, and
• a second resilient member being oriented with a first end of the second resilient member proximate the first compression surface and a second end of the second resilient member proximate the second compression surface;
• and
• the barrel spring having a compressed state and an expanded state, the first compression surface and second compression surface configured to move in the direction of the longitudinal axis between the compressed state and the expanded state, a displacement of the first compression surface and second compression surface between the compressed state and the expanded state being less than 500 microns, a spring constant between the compressed state and the expanded state being at least 150 Newtons per millimeter.