Threaded load transferring attachment
First Claim
1. A threaded load transferring device comprising:
- a Nitinol element having threads therein for threaded attachment to another member;
said threads in said Nitinol element being formed by forcing threads of a forming tool into said Nitinol element when said Nitinol element was at a temperature higher than the lowest temperature at which the ultimate yield strength of said Nitinol element is less than the yield strength of the material of which said forming tool was made;
said Nitinol element is formed from a blank, said element having two end portions, each threaded for attachment between two relatively movable members; and
an elongated integral intermediate portion between said end portions;
whereby said intermediate portion can be heated to its transition temperature and undergoes a phase transformation and a shortening of the length of said intermediate portion, such that said threaded end portions, attached to said relatively movable members, exert a tensile force on said members to produce a desired motion.
1 Assignment
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Accused Products
Abstract
A Nitinol element is threaded by first heating it to a temperature of about 800° C., and then applying a threading tool, such as a tap or die, to form the threads. Nitinol has a unique property of increasing yield strength as cold work is applied, but this property ceases to exist above a temperature of about 800° C. The strength of the material at this temperature, however, is sufficient to resist the torque applied by a threading die being screwed onto a Nitinol blank even though it is low enough to permit the Nitinol to flow when the cutting threads of the threading die are forced into the material. At this temperature, the Nitinol is not actually cut by the cutting threads of the tap, die or other threading tool, but instead, the material flows around the cutting threads to form threads in the Nitinol. Since the metal flows into spaces between the threads of the “cutting” or forming tool, it is necessary to use slightly undersized rod or slightly oversized holes when using conventional dies and taps since no chips are removed.
124 Citations
4 Claims
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1. A threaded load transferring device comprising:
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a Nitinol element having threads therein for threaded attachment to another member;
said threads in said Nitinol element being formed by forcing threads of a forming tool into said Nitinol element when said Nitinol element was at a temperature higher than the lowest temperature at which the ultimate yield strength of said Nitinol element is less than the yield strength of the material of which said forming tool was made;
said Nitinol element is formed from a blank, said element having two end portions, each threaded for attachment between two relatively movable members; and
an elongated integral intermediate portion between said end portions;
whereby said intermediate portion can be heated to its transition temperature and undergoes a phase transformation and a shortening of the length of said intermediate portion, such that said threaded end portions, attached to said relatively movable members, exert a tensile force on said members to produce a desired motion. - View Dependent Claims (2, 3, 4)
said threaded end portions were formed by applying a forming tool having forming threads made of a hard, heat resistant material at a temperature above the temperature at which the ultimate yield strength of said Nitinol is below the yield strength of said material, but below the temperature at which Nitinol sags under the influence of gravity.
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3. A threaded load transferring device as defined in claim 1, wherein:
said end portions include externally threaded rods, and said intermediate portion has a wide and thin aspect for rapid heating and cooling.
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4. A threaded load transferring device as defined in claim 3, wherein:
said intermediate portion is formed by heating to a temperature between about 800°
C. and 1200°
C. and is rolled while within said temperature range to said wide and thin aspect.
Specification