Abstract
This disclosure relates generally to a release device utilizing at least two load bearing elements joined by a thermally degradable structural adhesive with an integral heating element to cause thermal degradation of the mechanical properties of the adhesive resulting in separation of the elements under load. The apparatus of the invention is particularly useful for spacecraft and other vehicular separation mechanisms.
Claims
1. A Thermally Actuated Release Device comprising: a first element, a second element, a thermally degradable bond element, and a thermal source; where said first element and said second element are connected by said thermally degradable bond element and, where said thermal source causes said thermally degradable bond element to release connection between said first and second elements.
2. A method of providing a Thermally Actuated Release function, said method comprising: a connecting means utilizing a thermally degradable bond and, removing said connecting means by heating said thermally degradable bond.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] A more complete understanding of the invention and the many attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings wherein:
[0025] FIG. 1a is a section view of the first embodiment before release.
[0026] FIG. 1B is a detail view of the first embodiment before release.
[0027] FIG. 1c is a detail view of the first embodiment after release.
[0028] FIG. 2a is a cutaway view of the second embodiment before release.
[0029] FIG. 2b is a cutaway view of the second embodiment after release.
[0030] FIG. 3a is a section view of the third embodiment before release.
[0031] FIG. 3b is a section view of the third embodiment after release.
[0032] FIG. 4 is a graph showing a typical strength to temperature curve for a typical adhesive used for the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] In FIG. 1a the inventive device utilizes two printed circuit boards 100 and 101 joined by adhesive layer 102 in tension mode (the “Must Hold” state). Printed circuit board 100 contains 30 resistive heating element traces 103. Printed circuit board 101 contains solid conductive layer 104. Disc springs 106 are applying a tension preload between printed circuit board 100 and 101. Dowel pins 105 are constraining disc springs 106 and controlling relative location of printed circuit boards 100 and 101 to each other. Holes in printed circuit boards can be utilized to fasten to other elements or printed circuit boards can be bonded directly to other elements.
[0034] In FIG. 1b the inventive device utilizes two printed circuit boards 100 and 101 joined by adhesive layer 102 in tension mode (the “Must Hold” state). Printed circuit board 100 contains resistive heating element traces 103. Printed circuit board 101 contains solid conductive layer 104. Disc springs 106 are applying a tension preload between printed circuit board 100 and 101. Dowel pins 105 are constraining disc springs 106 and controlling relative location of printed circuit boards 100 and 101.
[0035] In FIG. 1c the resistive heating element traces 103 have been heated by applying electrical current transferring heat flux into and through adhesive layer 102 to conductive layer 104 which reflects and distributes heat flux evenly across adhesive layer 102 to the point of causing the adhesive layer 102 to reduce in tensile strength to permit separation of printed circuit boards 100 and 101 at the intersection of adhesive layer 102 and conductive layer 104 under the tension load applied by disc springs 106 to printed circuit boards 100 and 101 (the “Must Release” state).
[0036] In FIG. 2a the inventive device utilizes resistive film heating element 204 to heat external body 201 and adhesive layer 202 bonding external body 201 and internal body 200 together in shear mode (the “Must Hold” state). Disc springs 203 are providing a shear load between external body 201 and internal body 200. The threaded element in 200 and threaded elements in 201 can be utilized to hold together any other elements by means well known in the arts.
[0037] In FIG. 2b the resistive film heating element 204 has been heated by applying electrical current causing external body 201 and adhesive layer 202 to also be heated by direct transfer of heat flux to the to the point of causing adhesive layer 202 to reduce shear strength to permit separation of threaded elements 200 and 201 under shear load applied to elements 200 and 201 (the “Must Release” state) by disc springs 203.
[0038] In FIG. 3a the inventive device utilizes resistive film heating element 303 to heat external body 301 and adhesive layer 302 bonding external body 301 and internal body 300 together in shear mode (the “Must Hold” state). Hoist rings 304 provide a means to hang an external mass in a gravity environment or to attach to an external tension load providing a shear load between external body 301 and internal body 300. The threaded element in 300 and threaded element in 301 can be utilized to attach directly to any other elements other than hoist rings 304 by means well known in the arts.
[0039] In FIG. 3b the resistive film heating element 303 has been heated by applying electrical current causing external body 301 and adhesive layer 302 to also be heated by direct transfer of heat flux to the to the point of causing adhesive layer 302 to reduce shear strength to permit separation of threaded elements 300 and 301 under shear load applied to elements 300 and 301 (the “Must Release” state) by hoist rings 304 interfacing with an external load.
[0040] FIG. 4 illustrates the strength to temperature curve for a typical adhesive (e.g., 2216 epoxy). It is apparent that at lower temperatures 400 the adhesive provides maximum strength to perform the “Must Hold” state of the invention but, as the temperature rises by applying heat through any means, preferably concentrated heat flux as in resistive heating elements 103/204/303, the strength of the adhesive is reduced over zone 401 to the point of permitting a relatively small force to separate the connecting elements 100/101 or 200/201 or 300/301.
[0041] The invention is preferably electrically actuated via a resistive heating element capable of operating in a liquid, high 5 pressure, low or zero pressure (vacuum) environment but can be of any heating means deemed convenient for the application (e.g., hot fluid pumped through the separable element, an ultrasonic element, frictional element, radio wave or microwave diathermic heating element, chemical reaction element, etc.). The heating means may 10 also consist of a redundant heating system (two or more resistive heating elements connected in series or parallel) to provide increased reliability for the assured separation (the “Must Release” state) of at least two elements 100 and 101/200 and 201/300 and 301.
[0042] The inventive device permits the maximum strength of the bonded joint (100 to 101/200 to 201/300 to 301) to be utilized in an evenly distributed manner reducing the need for additional structure and larger quantities of lower performance separation devices. This has the effect of minimizing the total mass required for the holding/release mechanism of the overall system.
[0043] It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
