Jewelry – Body member encircling ornament
Reexamination Certificate
2000-12-23
2004-01-13
Chop, Andrea (Department: 3677)
Jewelry
Body member encircling ornament
Reexamination Certificate
active
06675610
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to jewelry composed of metallic components and methods of manufacturing such components, and in particular relates to jewelry, such as necklaces, bracelets, earrings, gem stone settings, and the like, which comprise a metallic component consisting of a shape memory metal alloy in the form of a wire, rod or cable, and in particular a shape memory metal alloy composed of a near stoichiometric alloy of nickel and titanium, such as the alloy known as Nitinol.
A shape memory alloy is an alloy which upon being thermally treated at a very high temperature (typically at least about 500 degrees C. or above) becomes fixed in a given shape due to crystalline alignment, yet when cooled below a transition temperature is relatively easily deformable. Often the alloy is shaped on mandrels or forms to create the desired memory shape. Cooling after forming is preferably performed in a rapid manner through a water quench or rapid air cool. The particular temperatures and treatment times are dependent on the particular alloy being treated and the shape and thickness of the alloy. Superelastic characteristics are inherent in the alloys after particular treatments. Alloys subjected to extreme plastic deformation, such that the wire or rod is bent or kinked, can be returned to the pre-deformation configuration upon reheating to a temperature above the transition temperature, the alloy automatically recovers its pre-deformation fixed shape due to realignment of the crystalline phase.
Nitinol is the name given to a family of intermetallic alloys of nickel and titanium which show unique properties of shape memory and superelasticity. These properties were discovered in near equiatomic Ni—ti alloys at the Naval Ordinance Laboratory. Nitinol comprises from about 50 to 60 percent Ni and about 40 to 50 percent Ti, with less than about 5 percent other elements. A very common alloy is Nitinol-55, which contains approximately 55 percent Ni. The temperature for the shape memory reaction can be varied from below zero degrees C. to about 100 degrees C. go by changing the Ni content of the alloy.
Shape memory is physical phenomenon by which a plastically deformed metal is restored to its original shape by a solid state phase change caused by heating. The explanation of the shape memory response is found in the strong crystallographic relationship between the phase stable at low temperature, called martensite (a close packed monoclinic crystalline structure), and the phase stable at high temperature, called austenite (an ordered body centered cubic phase crystalline structure). A wire or rod to be formed into a particular memory shape is formed, usually on a mandrel or other fixture, and heated to a temperature through the austenite start temperature, A(s), and above the austenite finish temperature, A(f), and held for a suitable time period at temperature. The wire is then rapidly cooled, through the martensite start temperature, M(s), and below the martensite finish temperature, M(f). The stress due to the constrained shape produces twins in the martensite phase which are reversible realignments of the crystal lattice. This phase structure is easily deformed into other shapes by continued realignment and preferential growth of favorably oriented twins. To recover the imparted memory shape, the wire is reheated to above A(f), which reverses the alignment of the twins and reforms the austenite crystalline structure, the wire automatically resuming the memory shape.
Superelasticity, reversible non-linear elastic deformation, is imparted to Nitinol by a particular treatment during the austenite phase. The Nitinol wire is stained, cold-worked, drawn, formed or the like, at a temperature above A(s) but below the maximum temperature at which superelasticity is obtained.
Typical representative properties of Nitinol alloys, which will vary somewhat dependent on composition, are as follows:
Melting point
1310 degrees C.
Density
6.5 gm/cc
Young‘s modulus
120 Gpa (austenite)
50 Gpa (martensite)
Yield strength
379 Mpa (austenite)
138 Mpa (martensite)
Ultimate tensile strength
690 to 1380 Mpa
Elongation
up to 20% or more
Shape memory
transformation temp.
−50 to 100 Degrees C.
recoverable strain
6.5 to 8.5%
superelastic recoverable strain
up to 8%
transformation fatigue life
several hundred cycles at 6% strain
10,000 cycles at 2% strain
1,000,000 cycles at 0.5% strain
The following examples illustrate the different characteristics which can be imparted to Nitinol alloys by varying composition and treatment.
Alloy #1 (superelastic):
55.8 ± 0.5 wt % Ni, balance of Ti,
≦0.5 C, O, Fe
A(s) = −10 degrees C. ± 5
A(f) = +5 degrees C. ± 5
typical tensile properties of cold-drawn and tempered material:
Upper superelastic plateau stress:
55 ksi
Lower superelastic plateau stress:
20 ksi
Permanent set after 6% strain:
0.1%
Yield strength of the martensite
after transition:
118 ksi
Ultimate tensile strength:
155 ksi
Elongation to failure:
17.5%
Maximum strain recovery:
8%
Alloy #2 (high-strength, superelastic):
55.9 ± 0.5 wt % Ni, balance of Ti,
≦0.5 C, O, Fe
A(s) = −20 degrees C. ± 5
A(f) = −5 degrees C. ± 5
typical tensile properties of cold-drawn and tempered material:
Upper superelastic plateau stress:
70 ksi
Lower superelastic plateau stress:
30 ksi
Permanent set after 6% strain:
0.1%
Yield strength of the martensite after
transition:
185 ksi
Ultimate tensile strength:
210 ksi
Elongation to failure:
12.5%
Maximum strain recovery:
8%
Alloy #3 (high-temperature, shape
memory):
55.5 ± 0.5 wt % Ni, balance of Ti,
≦0.05 C, O, Fe, ≦0.005 H,
≦0.01 other trace elements
A(s) = 95 degrees C. ± 5
A(f) = 115 degrees C. ± 5
typical tensile properties of cold-drawn and tempered material:
Ultimate tensile strength:
180 ksi
Elongation to failure:
12% min.
Maximum strain recovery:
8%
Alloy #4 (body-temperature):
55.5 ± 0.5 wt % Ni, balance of Ti,
≦0.05 C, O, Fe, ≦0.005 H,
≦0.01 other trace elements
A(s) = 15 degrees C. ± 5
A(f) = 35 degrees C. ± 5
typical tensile properties of cold-drawn and tempered material at
36-38 degrees C.:
Upper superelastic plateau stress:
50 ksi
Lower superelastic plateau stress:
2 ksi
Permanent set after 6% strain:
0.5%
Ultimate tensile strength:
180 ksi
Elongation to failure:
12% min.
Maximum strain recovery:
8%
Alloy #5 (chrome-doped,
superelastic):
55.8 ± 0.5 wt % Ni, balance of Ti,
0.2-0.3 Cr, ≦0.05 C, O, Fe,
≦0.005 H, ≦0.01 other trace
elements
A(s) = −30 degrees C. ± 5
A(f) = −10 degrees C. ± 5
typical tensile properties of cold-drawn and tempered material:
Upper superelastic plateau stress:
80 ksi
Lower superelastic plateau stress:
35 ksi
Permanent set after 6% strain:
0.1%
Ultimate tensile strength:
225 ksi
Elongation to failure:
10% min.
Maximum strain recovery:
8%
Alloy #6 (high-strength, superelastic,
Ni—Ti—Fe):
53.5 ± 1.0 wt % Ni, balance of Ti,
1.0-2.0 Fe, ≦0.05 C, O,
≦0.005 H, ≦0.01 other trace
elements
A(s) = −30 degrees C. ± 5
A(f) = −10 degrees C. ± 5
typical tensile properties of cold-drawn and tempered material:
Upper superelastic plateau stress:
100 ksi
Lower superelastic plateau stress:
65 ksi
Permanent set after 6% strain:
0.5%
Ultimate tensile strength:
210 ksi
Elongation to failure:
10%
Maximum strain recovery:
8%
In comparison to other metals typically used in the manufacture of jewelry, and in particular in comparison to metals having structural properties considered as good, such as for example stainless steel, Nitinol exhibits dramatically increased tensile strength, at least an order of magnitude greater than stainless, and greater flexibility, at least 50 percent greater than stainless, and much greater superelasticity characteristics. Individual wire strands or thin rods may be intertwined to create bundles of
Chop Andrea
Saitta Thomas C.
LandOfFree
Jewelry including shape memory alloy elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Jewelry including shape memory alloy elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Jewelry including shape memory alloy elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3250173