US4899543A — Pre-tensioned shape memory actuator

Claim 1

Independent Claim 85 words

A shape memory actuator capable of reliable functioning after long periods of inactivity for providing remote actuation at relatively high loads to clamping mecahnisms comprising a two-way shape memory alloy formed into an actuator having an original position, said alloy being pre-tensioned to a pre-tensioned position, means for partially compressing said alloy actuator to a position intermediate said original position and said pre-tensioned position whereby said alloy actuator fore-shortens back to its original position when heated and expands back to the intermediate position when cooled.

Claim 2

Dependent Claim 85 words

A shape memory actuator capable of reliable functioning after long periods of inactivity for providing remote actuation at relatively high loads to clamping mecahnisms comprising a two-way shape memory alloy formed into an actuator having an original position, said alloy being pre-tensioned to a pre-tensioned position, means for partially compressing said alloy actuator to a position intermediate said original position and said pre-tensioned position whereby said alloy actuator fore-shortens back to its original position when heated and expands back to the intermediate position when cooled.

Claim 3

Dependent Claim 20 words

An actuator in accordance with claim 1 wherein the alloy is selected from the group consisting of CuZnAl and NiTi.

Claim 4

Dependent Claim 112 words

An actuator in accordance with claim 2 wherein the alloy possesses the following properties: ______________________________________ Transition Temperature Range (T.sub.z) -200° C. to 80° C. Service Temperature Range -200° C. to 100° C. Beta Mechanicals Yield Strength (psi × 10.sup.3) 40 Young's Modulus (psi × 10.sup.6) 15 Tangent Modulus (psi × 10.sup.6) 3.0 Martensite Mechanicals Yield Strength (psi × 10.sup.3) 15 to 30 Young's Modulus (psi × 10.sup.6) 10 Tangent Modulus (psi × 10.sup.6) 0.06 Recoverable Strain - One Time Device Tension (%) 2 Shear (%) 4 Cyclic Device Tension (%) 1 Shear (%) 2 Density (lb/in.sup.3) 0.29 Electrical Resistivity (ohm - in × 10.sup.-6) 3 Thermal conductivity (BTU/ ft- hr-F.°) 60 ______________________________________

Claim 5

Dependent Claim 116 words

An actuator in accordance with claim 2 wherein the alloy possesses the following properties: ______________________________________ Transition Temperature Range (T.sub.z) -200° C. to 100° C. Service Temperature Range -200° C. to 300° C. Beta Mechanicals Yield Strength (psi × 10.sup.3) 60 to 80 Young's Modulus (psi × 10.sup.6) 10 to 15 Tangent Modulus (psi × 10.sup.6) -- Martensite Mechanicals Yield Strength (psi × 10.sup.3) 10 to 15 Young's Modulus (psi × 10.sup.6) 5 Tangent Modulus (psi × 10.sup.6) -- Recoverable Strain - One Time Device Tension (%) 4 Shear (%) 8 Cyclic Device Tension (%) 2 Shear (%) 4 Density (lb/in.sup.3) 0.23 Electrical Resistivity (ohm - in × 10.sup.-6) 30 Thermal conductivity (BTU/ ft- hr-F.°) 10 ______________________________________

Claim 6

Dependent Claim 148 words

A clamping device comprising a shape memory actuator capable of reliable functioning after long periods of inactivity for providing remote actuation at relatively high loads to mechanisms, a two-way shape memory alloy formed into said actuator and having an original position, said alloy being pre-tensioned to a pre-tensioned position, means for partially compressing said alloy actuator to a position intermediate said original position and said pre-tensioned position whereby said alloy actuator fore-shortens back to its original position when heated and expands back to the intermediate position when cooled, means for applying force to a work object, said actuator being in contact with the applying means whereby said actuator supplies the force to said applying means at its intermediate position under normal temperatures and releases the force to said applying means when heated, the force being supplied again when said actuator is cooled and reverts to its intermediate position.

Claim 7

Dependent Claim 148 words

A clamping device comprising a shape memory actuator capable of reliable functioning after long periods of inactivity for providing remote actuation at relatively high loads to mechanisms, a two-way shape memory alloy formed into said actuator and having an original position, said alloy being pre-tensioned to a pre-tensioned position, means for partially compressing said alloy actuator to a position intermediate said original position and said pre-tensioned position whereby said alloy actuator fore-shortens back to its original position when heated and expands back to the intermediate position when cooled, means for applying force to a work object, said actuator being in contact with the applying means whereby said actuator supplies the force to said applying means at its intermediate position under normal temperatures and releases the force to said applying means when heated, the force being supplied again when said actuator is cooled and reverts to its intermediate position.

Claim 8

Dependent Claim 21 words

A clamping device in accordance with claim 5 wherein the alloy is selected from the group consisting of CuZnAl and NiTi.

Claim 9

Dependent Claim 113 words

A clamping device in accordance with claim 6 wherein the alloy possesses the following properties: ______________________________________ Transition Temperature Range (T.sub.z) -200° C. to 80° C. Service Temperature Range -200° C. to 100° C. Beta Mechanicals Yield Strength (psi × 10.sup.3) 40 Young's Modulus (psi × 10.sup.6) 15 Tangent Modulus (psi × 10.sup.6) 3.0 Martensite Mechanicals Yield Strength (psi × 10.sup.3) 15 to 30 Young's Modulus (psi × 10.sup.6) 10 Tangent Modulus (psi × 10.sup.6) 0.06 Recoverable Strain - One Time Device Tension (%) 2 Shear (%) 4 Cyclic Device Tension (%) 1 Shear (%) 2 Density (lb/in.sup.3) 0.29 Electrical Resistivity (ohm - in × 10.sup.-6) 3 Thermal conductivity (BTU/ ft- hr-F.°) 60 ______________________________________

Claim 10

Dependent Claim 117 words

A clamping device in accordance with claim 6 wherein the alloy possesses the following properties: ______________________________________ Transition Temperature Range (T.sub.z) -200° C. to 100° C. Service Temperature Range -200° C. to 300° C. Beta Mechanicals Yield Strength (psi × 10.sup.3) 60 to 80 Young's Modulus (psi × 10.sup.6) 10 to 15 Tangent Modulus (psi × 10.sup.6) -- Martensite Mechanicals Yield Strength (psi × 10.sup.3) 10 to 15 Young's Modulus (psi × 10.sup.6) 5 Tangent Modulus (psi × 10.sup.6) -- Recoverable Strain - One Time Device Tension (%) 4 Shear (%) 8 Cyclic Device Tension (%) 2 Shear (%) 4 Density (lb/in.sup.3) 0.23 Electrical Resistivity (ohm - in × 10.sup.-6) 30 Thermal conductivity (BTU/ ft- hr-F.°) 10 ______________________________________

Claim 11

Dependent Claim 32 words

A clamping device in accordance with claim 5 wherein the force applying means constitutes a pair of spaced apart platens, said actuator being in contact with at least one of said platens.

Claim 12

Independent Claim 84 words

The method of making a two-way shape memory alloy article comprising the steps of fabricating the article from a shape memory alloy having a predetermined initial length l o , stretching the article to a length l s greater than its initial length l o , compressing the article to a length l c , heating the article until its length returns to the initial length l o , and cooling the article until its length expands to the compressed length l c .

Claim 13

Independent Claim 84 words

The method of making a two-way shape memory alloy article comprising the steps of fabricating the article from a shape memory alloy having a predetermined initial length l o , stretching the article to a length l s greater than its initial length l o , compressing the article to a length l c , heating the article until its length returns to the initial length l o , and cooling the article until its length expands to the compressed length l c .

Claim 14

Independent Claim 120 words

The method of applying a compressive force to a work object comprising the steps of utilizing as part of a clamping device a two-way shape memory alloy actuator, pre-tensioning said alloy actuator to a pre-tensioned position, partially compressing said actuator to a position intermediate its original position and said pre-tensioned position, heating said actuator and allowing said actuator to fore-shorten back to its original position, cooling said actuator to cause it to expand again to its intermediate position, arranging said actuator in the clamping device in order to apply compressive forces to the work object under normal temperatures, heating the actuator to release the compressive forces, and cooling the actuator to again apply the compressive forces to the work object.

Claim 15

Independent Claim 120 words

The method of applying a compressive force to a work object comprising the steps of utilizing as part of a clamping device a two-way shape memory alloy actuator, pre-tensioning said alloy actuator to a pre-tensioned position, partially compressing said actuator to a position intermediate its original position and said pre-tensioned position, heating said actuator and allowing said actuator to fore-shorten back to its original position, cooling said actuator to cause it to expand again to its intermediate position, arranging said actuator in the clamping device in order to apply compressive forces to the work object under normal temperatures, heating the actuator to release the compressive forces, and cooling the actuator to again apply the compressive forces to the work object.

Claim 16

Independent Claim 88 words

The method of treating an alloy in order to impart to its pretensioned properties comprising the steps of fabricating an article from a shape memory alloy having a predetermined initial length l o , stretching the article to a length l s greater than its initial length l o , compressing the article to a length l c , heating the article until its length returns to the initial length l o , and cooling the article until its length expands to the compressed length l c .

Claim 17

Independent Claim 88 words

The method of treating an alloy in order to impart to its pretensioned properties comprising the steps of fabricating an article from a shape memory alloy having a predetermined initial length l o , stretching the article to a length l s greater than its initial length l o , compressing the article to a length l c , heating the article until its length returns to the initial length l o , and cooling the article until its length expands to the compressed length l c .

Claim 18

Independent Claim 19 words

A method as in one of the claims 10-12 wherein the alloy is in the shape of a tube.

Claim 19

Independent Claim 22 words

A method as in one of the claims 10-12 wherein the alloy is selected from the group consisting of CuZnAl and NiTi.

Claim 20

Dependent Claim 114 words

A method as in one of the claim 10-12 wherein the alloy possesses the following properties: ______________________________________ Transition Temperature Range (T.sub.z) -200° C. to 80° C. Service Temperature Range -200° C. to 100° C. Beta Mechanicals Yield Strength (psi × 10.sup.3) 40 Young's Modulus (psi × 10.sup.6) 15 Tangent Modulus (psi × 10.sup.6) 3.0 Martensite Mechanicals Yield Strength (psi × 10.sup.3) 15 to 30 Young's Modulus (psi × 10.sup.6) 10 Tangent Modulus (psi × 10.sup.6) 0.06 Recoverable Strain - One Time Device Tension (%) 2 Shear (%) 4 Cyclic Device Tension (%) 1 Shear (%) 2 Density (lb/in.sup.3) 0.29 Electrical Resistivity (ohm - in × 10.sup.-6) 3 Thermal conductivity (BTU/ ft-hr-F.° ) 60 ______________________________________

Claim 21

Independent Claim 118 words

A method as in one of the claims 10-12 wherein the alloy possesses the following properties: ______________________________________ Transition Temperature Range (T.sub.z) -200° C. to 100° C. Service Temperature Range -200° C. to 300° C. Beta Mechanicals Yield Strength (psi × 10.sup.3) 60 to 80 Young's Modulus (psi × 10.sup.6) 10 to 15 Tangent Modulus (psi × 10.sup.6) -- Martensite Mechanicals Yield Strength (psi × 10.sup.3) 10 to 15 Young's Modulus (psi × 10.sup.6) 5 Tangent Modulus (psi × 10.sup.6) -- Recoverable Strain - One Time Device Tension (%) 4 Shear (%) 8 Cyclic Device Tension (%) 2 Shear (%) 4 Density (lb/in.sup.3) 0.23 Electrical Resistivity (ohm - in × 10.sup.-6) 30 Thermal conductivity (BTU/ ft- hr-F.°) 10 ______________________________________

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-02-12	1993-08-14	1994-02-13	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-02-12	1997-08-14	1998-02-13	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-02-12	2001-08-14	2002-02-13	$7700.00	Window Closed / Lapsed

Pre-tensioned shape memory actuator

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