Positioning device using negative spring-rate tensioning means
First Claim
1. Positioning apparatus of the type comprising:
- an element at least one spatial dimension of which is variable with temperature, said element being connected to a spring arranged to develop a force tending to oppose such temperature-induced dimensional change of said element;
means to controllably change the temperature of said element in response to changes in an applied signal;
that improvement in such apparatus wherein said spring means has a negative spring rate.
1 Assignment
0 Petitions
Accused Products
Abstract
A positioning device for controlling a member such as a pen of a chart recorder, wherein the positioning motion is produced by a wire formed of temperature-responsive material (Nitinol) exhibiting a martensitic transformation which contracts the wire when its temperature is increased within a predetermined temperature range, and relaxes the wire when cooled within that range. The wire is maintained under tension by a spring having a negative spring-rate. This spring cooperates with internally-generated forces and the elasticity of the wire material to produce contraction/expansion length changes of the wire in response to changes in its temperature. Electrical circuitry for controlling the wire temperature is disclosed, and includes means for inductively developing a frequency-modulated pulse-current through the wire.
48 Citations
17 Claims
-
1. Positioning apparatus of the type comprising:
- an element at least one spatial dimension of which is variable with temperature, said element being connected to a spring arranged to develop a force tending to oppose such temperature-induced dimensional change of said element;
means to controllably change the temperature of said element in response to changes in an applied signal; that improvement in such apparatus wherein said spring means has a negative spring rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- an element at least one spatial dimension of which is variable with temperature, said element being connected to a spring arranged to develop a force tending to oppose such temperature-induced dimensional change of said element;
-
14. In positioning apparatus of the type having a temperature-responsive wire means adapted to be contracted and expanded to actuate a motion member to produce movement of an output member in accordance with the contraction/expansion of the wire means;
- said apparatus comprising;
spring means coupled between said motion member and said output member normally providing corresponding movement of said two members but permitting relative movement therebetween in the event movement of said output member is prevented, thereby limiting the stress in said wire means. - View Dependent Claims (15, 16, 17)
- said apparatus comprising;
Specification