Single actuation pushing device driven by a material with form m

Details Single actuation pushing device driven by a material with form m Single actuation pushing device driven by a material with form m

1997-03-26

1998-11-03

Kamen, Noah P.

Power plants

Motor operated by expansion and/or contraction of a unit of...

Mass is a solid

411909, F01B 2910

Patent

active

058292535

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a pushing device driven by a material with form memory, in such a way that it can only be actuated once.
Such a pushing device can be used in numerous industrial fields whenever one wishes to be able to command a single and irreversible relative movement between two components, of limited amplitude, in a sure and effective fashion and without causing any impact.
One important application relates to the space industry and notably the carrying out of operations such as the locking of a hinged coupling, without any play, after deployment of an appendage such as an antenna reflector, or a solar generator panel. Furthermore, the present invention can prevent the disengaging of components immobilized with respect to one another during the launch of the spacecraft, and the possible separation of surfaces of these components that are in contact.
2. State of the Art
It has already been suggested that materials with form memory be used to command the disengaging of an appendage. Hence, document FR-A-2 667 842 describes a rotational mechanism in which an initial load is applied between two components connected to one another by ball bearings, during the launch of a spacecraft, so that the bearings are not damaged by the high mechanical stresses which occur at that time. This mechanism includes a component made of a material with form memory which, when heated above its transition temperature, brings about elongation. This elongation has the effect of separating the surfaces held in contact during the launch and of removing the initial load applied to the bearings in a way that allows relative rotation of the two components.
A mechanism of this type has numerous advantages. These advantages notably include reliability, the high level of the force supplied, the absence of impact and the nonpolluting property.
When one wishes to integrate a device made of a material with form memory into any mechanism of the kind such as that described in document FR-A-2 667 842, it is currently necessary to adapt adjacent components so as to protect the device made of material with form memory during handling, and to link to it an electric heater and its power supply conductors, as well as thermal insulation means when this is necessary. This need for adaptation constitutes a drawback which hinders the use of such devices made of material with form memory, compared with more traditional concurrent techniques, such as pyrotechnic compounds, which can be used directly without any adaptation at all.
Furthermore, the only materials with form memory that are currently usable are irreversible materials, that is to say materials which cannot return to their initial state when they have once passed through their phase transition temperature. In itself this does not constitute a disadvantage when one wishes to produce an irreversible single actuation pushing device. However it could become one, notably in the application to a spacecraft, if there is a danger of passing through the phase transition temperature before the launch of the spacecraft. In effect the assembly of a device made of material with form memory which has already been used previously could have very serious consequences, possibly going so far as to prevent the carrying out of the mission initially planned.


SUMMARY OF THE INVENTION

The principal subject of the invention is a single actuation pushing device, driven by a material with form memory, also known as shape memory alloy, designed in such a way that it can be used, without particular adaptation, in the manner of a pyrotechnic compound. This pushing device is produced in such a way that it can only be assembled with the condition that the phase transition temperature of the material with form memory has not been previously passed through.
According to the invention, this result is obtained by means of a single actuation pushing device, characterized by the fact that it includes two annular components forming bosses, an annular device, made

REFERENCES:
patent: 5160233 (1992-11-01), McKinnis
patent: 5248233 (1993-09-01), Webster
patent: 5312152 (1994-05-01), Woebkenberg, Jr. et al.

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