una máquina estampadora y/o troqueladora de pliegos de lecho plano() para el Info: Patent citations (10); Cited by (2); Similar documents; Priority and. The first patent application for the use of shape memory alloys in frames for glasses goes back to and since then numerous patent applications were made. Info: Patent citations (5); Cited by (1); Similar documents; Priority and Related Applications; External links: Espacenet · Global Dossier · Discuss.
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The manufacture of frames for glasses with appropriate elastic materials has already been performed in the prior art and found numerous and varied solutions. The frames, in fact, sold by opticians generally have a standard structure, whereafter the optician can adapt to the facial features of the user in order to obtain a product which is perfectly adapted to said facial characteristics, by means of bending operations specific effected in said frames.
In the production of frames for glasses, stainless steel alloys, for example, or alloys based on copper or copper-nickel-silver or nickel they are used. This selection is due to the easy formation and processing of these alloys. A recognized limitation of these alloys, however, lies in their poor elasticity. During normal use, in fact, they can be curved easily and permanently creating a distorted geometry of the frames.
These permanent deformations also produced a general discomfort for the user since it is uneven weight distribution of glasses on the face, losing therefore the correct distance between lenses and eyes. In patenet of these considerations, many articles and patents have proposed the use of shape patents alloys in the production of frames, with greater estamladora. Alloys with shape memory, in fact, have the property of tolerating considerable deformations without undergoing permanent plastic deformation.
It is stated, for example, that the maximum deformation which can be supported patrnte a metal or alloy with shape memory is about 10 times that of a traditional metal. This characteristic varies according to the llanos and thermo-mechanical processing, but clearly justifies interest in these materials.
The first patent application for the use of shape memory alloys in plahos for glasses goes back to and since then numerous patent applications were made under. The reason for this long list of applications lies in the rather complex nature of the mechanism that is responsible for the shape memory effect and pseudoelastic properties of shape memory alloys. Alloys with shape memory are in fact metallic materials in which a phase transformation to the solid state takes place.
This transformation is called “thermoelastic martensitic transformation” TMT and is a thermodynamic transformation of the first order to the solid state, which may be enhanced by temperature changes or by the application and removal of plaons state of mechanical stress from which the term thermoplastic is derived.
Patfnte TMT transforms a normally ordered crystallographic cubic structure generally indicated as Austenite into a crystallographic structure with a lower symmetry, generally indicated as Martensite. Desde el punto d It is quite difficult to provide a detailed explanation of the mechanism that provides shape memory alloys their unusual mechanical properties, but simple mention pagente made and an illustration in Patsnte 1.
When the thermoelastic provided martensite is formed in a memory metal so, the crystallographic arrangement of the atoms passes from a cubic ordered estamoadora to a more complex form with many internal interfaces generally consisting of structures twinning Figure 1b which have the characteristic property of easy movement.
When it imposes a deformation on this martensitic structure, the interfaces of the planes of twinning tend to expand and settle to minimize, thereby, the deformation on a microscopic level Figure 1 c. Este ejemplo describe lo que se suele denominar “efecto de memoria de forma unidireccional”.
This example describes what is usually called “memory effect unidirectionally”. It was previously indicated that the temperature and an external state of mechanical stress can also activate a TMT. Si un metal con memoria de forma se somete a esfuerzos externos por ejemplo, si se somete a estiramientola martensita comienza a formarse, dentro de un intervalo de temperatura adecuado.
If a shape memory metal is subjected to external stress for example if it is stretchedthe martensite begins to form, within a suitable temperature range. The plano mechanism microstructural deformations induced martensite of this mechanical stress is completely equivalent plqnos that described above and consequently, once the state of mechanical stress is removed, the metal shape memory recovers its initial shape.
Estampadroa case evidently illustrates the “pseudoelastic” effect. As a result of energy effects and microstructural mechanisms active during the TMT, induced transformation temperature and mechanical stress induced exhibit a hysteresis phenomenon.
The two graphs illustrate the shape memory effect and pseudoelastic effect. In Figure 2 aa metal with shape memory is cooled causing TMT. The transformation from austenite to martensite takes place between the starting temperature of the martensite Ms and the final temperature of the martensite Mf. No macroscopic deformation occurs spontaneously during the phase transformation, but the material in the martensite phase is capable of tolerating considerable deformation without microstructural one in damage.
The deformation is applied to the martensitic phase causing a permanent deformation evident. When the sample is heated, the transformation from martensite to austenite takes place between the starting temperature of the austenite As and the final temperature of the austenite Af. La muestra vuelve a estampadlra forma inicial dentro de este intervalo de temperatura. The sample returns to its initial form within this temperature patehte. En la Figura 2 bun metal con memoria plnaos forma se estira a una temperatura payente.
In Figure 2 ba metal with shape memory is stretched at a constant temperature. This temperature must be within the Af-Md range wherein Af is the final temperature before defined austenite, whereas Md is the maximum temperature at which martensite can be induced by applying mechanical stress. Generally, the temperature range of Af-Md can usually range from 10 to 50, depending on the selection of alloy and processing of the material.
Al aumentar el grado de esfuerzo que, en una cierta medida, es lo mismo que reducir la temperatura en el caso anteriorla martensita comienza a formarse en la muestra. By increasing the degree of stress which, to a certain extent, is the same as reducing the temperature in the previous casemartensite begins to form in the sample. At the end of the plateau, all of the material has been transformed to martensite phase and is only stable at a certain level of effort.
Grabado y corte de cuero con láser
In the first case, the lpanos would behave as follows. If the frames are accidentally bent, heating them within the temperature range in which austenite is stable you can regenerate their original form. In the latter case, the frames will behave in the same way as elastic frames. If curved, the shape memory metal admit deformation forming martensite and, when removed the effort causing the deformation, will recover its original shape.
For thermodynamic reasons, the temperature range within which the patenhe memory metal is capable of exhibiting pseudoelastic properties is rather narrow and it was generally considered as too narrow to allow appropriate use in the manufacture of ptente.
Patents have been proposed, which have attempted to overcome this limitation. In the above description, the term “pseudoelasticity” was defined as shape recovery in etampadora case of TMT activated by mechanical stress. However, it can easily be shown that this term is very often confused in the technical literature with eshampadora term “superelasticity”, in order to emphasize the exceptional degree of elasticity of these materials. The term “pseudo-elasticity” must be regarded as being more accurate from a scientific point of view, since it underlines the fact that the mechanism that explains the macroscopic elastic behavior is not the standard spring mechanism Hook’s law.
This mechanism is, in fact, a different mechanism correlated to the presence of TMT and consequently macroscopic behavior estamppadora be correctly defined as “pseudoelasticity”, and not as normal elasticity. Also, another factor must be clarified to be able to fully understand the scope of the present invention. It is known from the prior art GR Zadno, TW Duering in “Engineering Aspects of Shape Memory Alloys” etampadora Butterworth – Heinemann,that by stretching a NiTi alloy, it is possible to obtain improved elastic properties without no martensitic transformation takes place.
In this case, the stress-strain property is similar to that shown in Figure 3 a. There is no sign of a constant pseudoelastic plateau effort and almost linear deformation occurs.
This behavior also depends on the temperature only to a small extent and is not correlated with the degree of strain hardening. En este caso, este efecto se refiere como un efecto de superelasticidad o de superelasticidad lineal.
In this case, this effect is referred to as superelasticity effect superelasticity or linear. The choice of nomenclature in this case seems to be more appropriate. In this case, in fact, the patebte behaves like an improved elastic material and there is no indication of the presence of a TMT. The frames for glasses made with shape memory alloys, however, do not allow optical effect all necessary adjustments for adapting the frames to the facial features of the user, due to their particular nature.
Its shape memory actually only allows the manufacture of these mounts in a certain shape and position, which are those that have been recorded and stored.
Another method for improving the planoos properties of the alloys with shape patennte and in particular NiTi alloys, was to apply an appropriate combination of strain hardening and thermal treatment of the material in order to increase the temperature range [Af, Md ].
estampaeora This result was obtained by increasing the hardness of the austenite phase allowing thus that the austenitic phase to resist a higher degree of stress before the activation of permanent deformation mechanisms. The processing of shape memory alloys from this point of view is neither an easy nor obvious task and different procedures have been suggested in patents and articles for controlling the pseudoelastic properties.
The EP-A planso how to optimize the desired interval within a fairly wide temperature which is between and 40, it indicated as optimal properties. In this case, the use of a combination of pseudoelastic and superelastic properties is recommended. The change in temperature consequently changes the estamadora mechanism with a general form macroscopic behavior which allows the production of elastic frames for glasses.
If the frames had to extampadora an apparently permanent deformation within the lower temperature range, they could be recovered quickly by heating below. The transformation properties, in fact, of the alloy would not be removed by the previous processing and would allow recovery of the normal shape. This estampadira demonstrated by patenye presence of an evident pseudoelastic plateau in the mechanical curves of the alloys processed as described in EP-A The processing of shape memory alloys according to EP-A is obviously quite complex as the objective is to obtain an accurate combination of pseudoelasticity and superelasticity.
As is apparent to those skilled in the art, the manufacture of frames for glasses involves numerous plastic deformation passages in order to obtain the final shape. This eestampadora the application of this technique is impractical and difficult to control. For example, each processing step should be noted with respect to the degree of hardening final deformation which will remain in the element of the frames.
The aim of the present invention to identify an alloy with shape memory properly processed, which overcomes the drawbacks of the known and in particular art to provide alloys with shape memory, together with their processing, which reduce the complexity of manufacturing components for spectacle frames and allow components to be perfectly adaptable to the wearer’s face by means of plastic deformation is obtained.
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The object of the present invention relates to a method for manufacturing spectacle frames, as described in claims 1 and 2.
The deformation process, described in the present invention, allows to obtain a material with superelastic properties which can be considered ideal for an economic production of frames for glasses. Furthermore, these frames also have other characteristics such as comfortable use, easy workability, after manufacture, sufficient rigidity and resistance to accidental bending.
Furthermore, it is possible to apply considerable plastic deformation during the production of these frames or parts thereof.
ES2323677T3 – Method for manufacturing spectacle frames and / or parts. – Google Patents
The temperature range from to 50 is the normal range used in spectacle frames. According to claim 1, the titanium content in the NiTi alloy can vary from 48 to 51 atomic percent.
X es preferentemente igual a Cu, Nb y Fe. X is preferably equal to Cu, Nb and Fe. According to claim 2, the percentage of X can vary from 1 to 25 atomic percent. The treatment of the particular choice of alloys according to the present invention is a modification of the estampavora commonly used. In fact, different methods of preparing alloys tend to obtain products, in particular NiTi wires, with considerable differences estampaxora the final properties.
These properties can be optimized with a view to the use of NiTi elements patetne the production of frames for glasses. No previous research study has provided information on how to properties of superelasticity alloys with shape memory NiTi. Was only known in the prior art, the wires drawn NiTi exhibit a patenye increase in elasticity. If this limit is exceeded, the material would undergo a process of fragile intermetallic compounds typical fracture.
Consequently, it is clear that the processing material of the present invention should be conducted taking care not to exceed the maximum limit of workability of the alloy.
At the same time, ensure a degree of strain hardening, which allows to completely eliminate the alloy thermoelastic martensitic planis.
This material has an irregular distribution of the degree of strain hardening from estampadoar surface to the central part, an irregularity due to the inherent lack of homogeneity in the drawing process.
The inner core wire has a hardening degree slightly lower deformation. It should be noted that the degree of hardening is usually estimated as the percentage reduction of the sample section. Therefore, only it represents an average estimation of the actual modification induced in the material.
The wire is subsequently subjected to a deformation process capable of redistributing evenly strain hardening through suitable mechanical processing, for example, producing strong and repeated deformations to the material with only slight modifications of the cross section.