Non-explosive separation device

• US 5,119,555 A
• Filed: 10/02/1990
• Issued: 06/09/1992
• Est. Priority Date: 09/19/1988
• Status: Expired due to Term

• Current Assignee: TiNi Alloy Company
• Original Assignee: TiNi Alloy Company
• Inventors: Johnson, Alfred D.
• Primary Examiner(s): Gorski, Joseph M.
• Assistant Examiner(s): VO, PETER DUNG BA
• Application Number:
  US07/591,628
• Time in Patent Office: 616 Days
• Field of Search: 29/412-416, 29/446, 29/447, 29/452, 29/254, 29/426.4, 29/566.1, 337/140, 337/296, 403/28, 403/29, 411/1-5, 411/390, 411/392, 411/396, 411/411, 411/424, 411/909, 425/405.2
• US Class Current: 29/254
• CPC Class Codes: B23P 11/025 by using heat or cold
• CPC Class Codes: B23P 19/04 for assembling or disassembling parts
• CPC Class Codes: F16B 31/007 Break-bolts loosening at high temperature
• CPC Class Codes: Y10T 29/4979 Breaking through weakened portion
• CPC Class Codes: Y10T 29/49821 by altering or destroying work part or connector
• CPC Class Codes: Y10T 29/5148 including severing means
• CPC Class Codes: Y10T 29/53839 having percussion or explosive operator
• CPC Class Codes: Y10T 403/21 Utilizing thermal characteristic, e.g. , expansion or contraction, etc.

Abstract

A non-explosive separation device for releasably holding together components of equipment or apparatus which are to be separated under controlled conditions. The separation device and method of operation includes a retaining element having a strain concentrated portion which completely cleaves when strained at a predetermined magnitude. Strain is applied to the retaining element by an actuating element which is comprised of a solid state phase change material having a shape memory. The actuating element is deformed to an armed shape at a temperature below the phase-change transition temperature. The device is activated by heating the actuating element through its transition temperature so that it recovers toward its memory shape. The retaining element is strained beyond its ultimate strength so that it cleaves at the strain concentrated portion. One embodiment of the invention provides a method for the non-destructive testing of the integrity and readiness of the separation device as well as a method of calibrating the release point of the device.

Claims

1. A non-explosive separation device which rapidly separates through the use of an electrical power source, the separation device including the combination of first and second lever arms, means for mounting the lever arms to pivot about a fulcrum, said fulcrum being positioned offset from the midspan of the arms to provide a first-order lever with the fulcrum at a distance from the first common ends of the arms which is greater than the distance of the fulcrum from the second common ends whereby a force applied between the first common ends for pivoting the arms about the fulcrum produces a multiplied force at the second common ends, a retaining element mounted to hold the second common ends of the lever arm in a predetermined orientation, said retaining element formed with a strain concentrated portion which completely cleaves when the strain concentrated portion is strained at a predetermined magnitude, a thin, elongate actuating element comprised of a solid state phase-change material having a shape memory which contracts from an armed shape to a memory shape when heated through the material'"'"'s phase-change transition temperature, means for connecting one end of the actuating element with the first end of the first lever arm and for connecting the other end of the actuating element with the first end of the second lever arm, and means for selectively directing electric current from the power source through the actuating element to resistively heat the phase-change material through said transition temperature whereby contraction of the actuating element to its memory shape applies a force between the first ends of the arms which pivots the lever arms about the fulcrum with the second ends of the arms multiplying and applying the force to strain the retaining element to said predetermined magnitude to cause the same to cleave the retaining element and release the arms.

2. A non-explosive, integral separation device for releasably holding multiple components together and for selectively separating the components, said device comprising the combination of a retaining element for engaging portions of the components to hold the same together, means providing a strain concentrated portion on the retaining element which completely cleaves when the strain concentrated portion is strained at a predetermined magnitude, said strain concentrated portion including means forming a zone of reduced cross-sectional area in the retaining element at which strain is concentrated when said tension force is applied to the retaining element, said reduced cross-sectional area being less than said first cross-section by which tension forces applied along the axis of the shank concentrates the strain at said reduced cross-section whereby when the strain at the reduced cross-section reaches said predetermined magnitude the retaining element is completely severed at the reduced cross-section for releasing the components, an actuating element comprised of a sold state phase change material having a shape memory which recovers from an armed shape to a memory shape when heated through the material'"'"'s phase-change transition temperature, said actuating means including a portion which recovers by elongating from said armed shape to said memory shape, said actuating element being comprised of a hollow cylinder axially mounted about the shank of said retaining element with said hollow cylinder undergoing said phase change by elongating in a direction along its axis for applying said tension force along the axis of the shank, and means for coupling said actuating element with said retaining element for applying a tension force on the retaining element for applying said stress thereto responsive to said recovery of the actuating element when the actuating element is heated through its phase-change transition temperature.

3. A non-explosive, integral separation device for releasably holding multiple components together and for selectively separating the components, said device comprising the combination of a retaining element for engaging portions of the components to hold the same together, means providing a strain concentrated portion on the retaining element which completely cleaves when the strain concentrated portion is strained at a predetermined magnitude, an actuating element comprised of an elongate strand of solid state phase change material having a shape memory which recovers from an armed shape to a memory shape when heated through the material'"'"'s phase-change transition temperature, said element being formed into a helical coil in which adjacent turns of said coil are in juxtaposed relationship and said recovery from the armed shape to the memory shape is in a direction axially of the coil, means for coupling said actuating element with said retaining element for applying said stress thereto when the actuating element is heated through its phase-change transition temperature, and means for transferring heat energy into the actuating element including means for directing an electrical current through the coil for causing resistance heating of the coil through its phase-change transition temperature.

4. The device as in claim 3 which includes means forming an electrical insulation barrier between adjacent turns of the coil.

5. A non-explosive, integral separation device for releasably holding multiple components together and for selectively separating the components, said device comprising the combination of a retaining element for engaging portions of the components to hold the same together, said retaining element comprising a fastener having a cylindrical shank sized for mounting through aligned openings formed in said components, said fastener having a distal end and a proximal end formed with a head which is normally in engagement with at least one of the components, means providing a strain concentrated portion on the retaining element which completely cleaves when the strain concentrated portion is strained at a predetermined magnitude, said means forming the strain concentrated portion comprising means forming an annular groove at a portion of the shank between the proximal and distal ends, said groove having a predetermined depth which concentrates stress at the portion of the shank circumscribed by the groove whereby the retaining element is cleaved at the groove responsive to said strain reaching the predetermined magnitude, an actuating element comprised of a solid state phase change material having a shape memory which recovers from an armed shape to a memory shape when heated through the material'"'"' s phase-change transition temperature, said actuating element being comprised of a hollow cylinder mounted about a portion of the shank distal end, and means for coupling said actuating element with said retaining element for applying said stress thereto when the actuating element is heated through its phase-change transition temperature, said means for coupling the actuating element including a nut together with means for threadably mounting the nut on the shank distal end for axial movement along the shank for applying a force along the length of the fastener which normally holds the cylinder of the actuating element and the components in compression against the fastener head.

6. The device as in claim 5 which includes means for heating the actuating element through its transition temperature.

7. The device as in claim 6 in which said heating means comprises an annular cylinder mounted about the cylinder of the actuating element, said cylinder being comprised of an exothermic compound which chemically reacts to release thermal energy when activated, said cylinder being in close-spaced heat exchange relationship about the outer surface of the activating element for transferring said thermal energy thereto.

8. The device as in claim 6 which includes at least one cap formed of a resilient material, said cap being cup-shaped and of a size sufficient to substantially envelope a side of the retaining element, and means for mounting the cap about said side of the retaining element whereby the cap absorbs kinetic energy of at least one part of the retaining element which is severed after the retaining element is cleaved with the cap capturing said part of the retaining element to prevent further movement of such part.

9. A non-explosive, integral separation device for releasably holding multiple components together and for selectively separating the components, said device comprising the combination of a retaining element for engaging portions of the components to hold the same together, means providing a strain concentrated portion on the retaining element which completely cleaves when the strain concentrated portion is strained at a predetermined magnitude, said means providing the strain concentrated portion including means forming a zone of reduced cross-sectional area in the retaining element at which strain is concentrated when said tension force is applied to the retaining element, an actuating element comprised of a solid state phase change material having a shape memory which recovers from an armed shape to a memory shape when heated through the materials'"'"' phase-change transition temperature, said actuating element including a portion which recovers by elongating from said armed shape to said memory shape, and means for coupling said actuating element with said retaining element for applying said stress thereto when the actuating element is heated through its phase-change transition temperature, said means forming the strain concentrated portion including means forming a zone of reduced cross-sectional area in the retaining element at which strain is concentrated when said tension force is applied to the retaining element, the maximum length of the strain concentrated portion is sized in accordance with:

##EQU3## where;

L_A is the length of the SMA actuator;

L_c is the length of the strain concentrated portion of the retaining element;

S_c is the percent strain elongation of the strain concentrated portion to failure;

S_A is the percent shape recovery of the actuator; and

S_R is the percent elongation of the retaining element.

10. The device as in claim 9 in which the material of the actuating element has a percent shape recovery S_A ≃

3 percent, and the percent strain elongation of the strain concentrated portion to failure is S_c ≃

30 percent.