Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses
Utility Patent
1999-11-19
2001-01-02
Dang, Hung Xuan (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
C351S111000, C351S114000
Utility Patent
active
06168272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spectacle frame whereof certain elements, notably the temples, the connecting piece(s) between the lens rim (eyewire), or the supports for the nasal pads, are made of a so-called “shape-memory” material having a superelasticity (or pseudo-elasticity).
2. Description of the Prior Art
By material with a shape-memory is meant any metallic alloy able to adopt a first shape while in a first martenisite phase at high temperature and a second shape while in a second austenitic crystalline phase at low temperature. To be able to pass from one state to the other, the material has a great elasticity, or superelasticity, namely its minimum elastic deformation without irreversible plastic transformation can reach 6% or even 11%, compared to the usual value of only 0.2% for common metals.
This superelasticity property is of interest for the production of elements of spectacle frames. For instance, if the connecting bridge for the lens rims is made of such material, the frame can be crushed without breaking. If a temple is made of such material, it can be twisted and folded without risk of rupture, so that one may even envisage dispensing with the hinge connecting it to the front-piece consisting of the lens rims assembled by a bridge.
U.S. Pat. Nos. 4,772,112 and 4,896,955 describe spectacle frames comprising elements of superelastic material based on a Nickel—Titanium (Ni—Ti) alloy. However, nickel can cause allergies to a person wearing such spectacles. Moreover, it is very difficult to assemble these elements in Ti—Ni alloy to elements of other metals commonly used in spectacle frames (Monel, nickel—silver, bronze, copper—beryllium, stainless steels or titanium alloys) and joining with such materials is unreliable over time.
WO 96/24086 describes the use of a monocrystalline resilient memory alloy selected from Cu based alloys: Cu—Zn—Al, Cu—Al—Ni or Cu—Al—Be to make elements of spectacle frames, notably the temples and bridges. By virtue of their monocrystalline structure, these alloys possess a capacity for superelastic deformation greater than 11% between −40° C. and +80° C. However, with this superelasticity it is impossible to shape the elements by the usual bending or hammering (shrinking) operations such as are used in the optical trade, the only possible shaping being under stress at high temperature, which is very costly. Moreover, such spectacle frames become rubbery to such an extent that they are no longer able to properly hold correcting lenses exactly in position relative to the eyes. As a result, there is a risk that the wearer suffers from aberrations of the view, particularly in the case of bifocal lenses.
BRIEF SUMMARY OF THE INVENTION
The present invention aims to provide a spectacle frame with superelastic elements that can be repetitively bent and folded at given locations, or even temporarily crushed, without breaking or becoming permanently deformed, but which can also firmly hold correcting lenses exactly in position relative to the eyes.
These aims are achieved by a spectacle frame having at least one element made of a polycrystalline Copper—Aluminum—Beryllium (Cu—Al—Be) alloy of elasticity limit comprised between 3 and 6%, preferably of the order of 4%.
Advantageously, the composition of the polycrystalline alloy is from 0.5% to 1%, preferably 0.63% by weight Beryllium, and from 11% to 12%, preferably 11.8% by weight Aluminum, with the remainder of Copper.
Advantageously, the mean grain size of the polycrystalline alloy does not exceed 0.12 mm.
The alloy composition is such that there is practically no risk of allergy with the wearers' skin. By voluntarily restricting to a particular composition in polycrystalline form with predefined grain size, the elasticity is established with a value sufficient to support accidental bending without however undergoing permanent deformation and while being able to hold the lenses correctly relative to the eyes.
Advantageously, therefore, the Cu—Al—Be element is shaped by one or more hammering or cold forming operations not exceeding {fraction (5/100)} mm of deformation per passage, namely 40% shrinkage for a wire.
Usefully, after a hammering operation the Cu—Al—Be element undergoes a so-called thermal beta treatment at a temperature exceeding the allotopic transformation temperature of the alloy, of the order of 650° C., followed by rapid cooling to relax the internal stresses created during hammering or cold forming.
Thanks to the specific chosen composition of the alloy, shaping by shrinkage remains possible even if several passages are required. Apart from the ability to be able to shape the superelastic element, it is observed that this operation also improves its surface state, transforming it from an “orange peel” state after degreasing following drawing, into a perfectly smooth state.
Alternatively, shaping of the Cu—Al—Be element may be carried out hot, in particular at a temperature above 650° C. during a heating time less than 15 seconds/gram of material to be heated, preferably of the order of 1 second if the element has been preheated, or between 10 and 15 seconds if the element has not been preheated. This shaping is then followed by rapid cooling to ambient temperature.
Advantageously then, the Cu—Al—Be element may for example be assembled with a part of Monel by brasing with a silver-based solder in paste or wire form, at a temperature of the order of 700° C. using induction or resistance heating, which is particularly well adapted to optical applications due to the fact that it allows well-controlled local heating.
After extensive workshop testing, it has been observed that this welding/brasing permits the ends of bridges to be assembled parallel and arched against the lens rims, and also to be assembled end-on orthogonal to these rims.
Advantageously, the Cu—Al—Be element is plated with a surface layer of Copper or Nickel by a galvanic treatment independent of the galvanic treatment of other parts of the frame, such that a subsequent coating on this underlayer of gold, or any other final coating (gold or palladium) conventionally used in the optical trade, is perfectly smooth.
REFERENCES:
patent: 4976529 (1990-12-01), Segoshi et al.
patent: 4983029 (1991-01-01), Sato
patent: 5452028 (1995-09-01), Iijima
patent: 33 09 365 (1983-12-01), None
patent: 33 07 442 (1984-09-01), None
patent: 0 187 937 (1986-07-01), None
patent: 0 648 856 (1995-04-01), None
patent: 2 504 284 (1982-10-01), None
patent: 87 07961 (1987-12-01), None
patent: 96 24086 (1996-10-01), None
A. Lu. Tec. Association Lunetiere Technologique
Dang Hung Xuan
Henderson & Sturm LLP
LandOfFree
Spectacle frame with elements of superelastic alloy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Spectacle frame with elements of superelastic alloy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spectacle frame with elements of superelastic alloy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2555415