Positioning device using negative spring-rate tensioning means
US3940935A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 22, 1974 |
| Grant date | Mar 2, 1976 |
| Priority date | — |
| Expiry date | Feb 22, 1994 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF03G7/066
- WIPO fieldEngines, pumps, turbines
- WIPO sectorMechanical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.