Constant force spring actuator
OwnerWeyman Weemsinventor
Life of this patent
Estimating the term…
Abstract
A constant force actuator transforms applied heat to an applied force on an output device. Strips of shape memory alloy are coiled into spirals and trained to have this configuration as a static state. The shape memory alloy springs are attached to the output device to apply a directional force. When one of the springs is heated, the modulus of elasticity within the spring material changes. This change in modulus increases the force which the spring exerts in returning to its static state, which in turn increases the force applied to the output device, upsetting the balance of forces and resulting in a rotation.
Claims15
An apparatus for applying rotational forces on a rotatable device comprising:
- first shape memory alloy spring means connected to said rotatable device which exerts a first force on the rotatable device in a first rotational direction, the first shape memory alloy spring means has a first modulus of elasticity and upon application of heat to a selected area of the first spring means effects a austenite state in the selected area of the first spring means that creates a second modulus of elasticity and changes the first force;
- and
- second shape memory alloy spring means connected to said rotatable device which exerts a second force on the rotatable device in a second rotational direction which is opposite the first rotational direction, the second shape memory spring means has a first modulus of elasticity and upon the application of the heat to a selected area of the second shape memory alloy spring means effects the austenite state in the selected area that creates a second modulus of elasticity which changes the second force.
A constant force spring actuator for applying a force to an output device, comprising:
- a first rotatable connection device;
- and
- a first shape memory alloy spring, with a first end connectable to the first rotatable connection device and a second end connectable to the output device in such a way that a first force is applied to the output device, wherein said first shape memory alloy spring has a first modulus of elasticity and upon application of heat to a selected area of the first shape memory alloy spring, a austenite change is effected in the selected area which creates a second modulus of elasticity in the selected area which increases the first force.
Dependencies are inferred from the claim text.