Method for Manufacturing a Spectacle Frame

The present invention relates to a spectacle frame, in particular made of sheet metal, and to a method for manufacturing such a spectacle frame. Spectacle frames of that kind, for example, are known from European Patent No. 0 863 424. This patent describes a spectacle frame which is assembled from stamped pieces of metal sheet, a rim and two spectacle temples, in which a joint mechanism is formed in that free ends of leaf springs of the spectacle temples do pass through corresponding recesses being provided in a connecting element of the rim during the folding-in and folding-out motion.

Due to the configuration of such a screwless spring-type joint mechanism, as it is disclosed in the afore-mentioned patent and to which it is explicitly referred to herein, several sliding surfaces do exist in the region of the joint mechanism, which sliding surfaces are subjected to an increased wear. This wear, in particular, will be increased in that sections of the spectacle temples, which are relatively thin, do move over or along sections of the connecting element, which are relatively thin either, since these both components of the spectacle frame are cut from corresponding thin metal sheet.

In principle, coatings could be possibly applied for such spectacles made from metal, which reduce the friction resistance in the area of the sliding surfaces of the joint mechanism and thereby reduce the wear. Independent from the type of their application, such coatings, however, comprise the disadvantage that these will stand in the way for a corresponding machining of the metal surfaces of the spectacle frame for the purpose of enhancing its optical appearance.

However, spectacle frames always are considered to be fashion accessory which shall exhibit a desired fashionable effect in the eye of the user.

In case the metal surfaces will be furnished with lacquering or similar coatings, for metal frames having a joint mechanism as described above, always the drawbacks appear that the lacquering in the area of the sliding surfaces proves to be not substantially wear-resistant.

Therefore, there exists the need for such spectacles made from metal to provide a coating which takes account of the requirements both with respect to a desired optical appearance and with respect to a wear-resistant and thus long-lasting joint mechanism.

Such objective is solved by a spectacle frame according to claim 1 and by a method for manufacturing such a spectacle frame according to claim 4.

According to the invention, a spectacle frame is suggested which comprises a rim or front end and two spectacle temples being arranged on the left and on the right side of the rim by means of a joint mechanism in a swiveling manner, respectively, in which the rim and the spectacle temples are made from metal, the main component of which is ferric, and in which the joint mechanism is configured such that during folding-in and folding-out of the spectacle temples at least one section of the spectacle temples slideably moves along at least one section of the rim under the presence of a frictional contact.

The surfaces made from metal of the rim and of the spectacle temples are each provided with a metallic oxide layer which comprises such a layer thickness that in the region of the sections of the rim and of the spectacle temples, which section are moving relatively to each other, the friction is reduced and at the same time a refraction of light in the metallic oxide layer (i.e. inside the metallic oxide layer over the entire thickness of it) is generated, which allows the reflection of one specific wavelength of the light only.

In this respect, the entire layer thickness does not exceed 1 ym (micrometer) , in which preferably the coating can be separated into and combined by several layers with exactly defined layer thicknesses in the range of some nm (nanometers), i.e. as a composite layered structure. Depending on the exact layer configuration in nanometers, light radiating onto the surfaces of the spectacle frame, which are coated in such a way, will be refracted or split into the corresponding single wavelengths. The radiating light will be refracted within the metallic oxide coating, basically by the small crystal particles of it, and only one specific wavelength will be reflected from the surfaces of the spectacle frame depending on the layer thickness and on the material used for the metallic oxide layer.

This effect results from interference of light, which occurs at the very thin, plane-parallel and at least partly transparent layers of the metallic oxide coating. A plane wave front of radiating (white) light will be separated both at the front layer of the coating (i.e. the externally visible surface of the oxide coating) and at the rear layer (i.e. the transition from the oxide coating to the metallic surface of the spectacle frame) into one part, which passes the coating, and into another part, which will be reflected. The passing part will be refracted corresponding to the thickness of the coating and reflected at the rear layer again. Since both reflecting parts (as well as the passing parts) do interfere, this leads to the effect that, depending on the thickness of the coating, only one defined wave length will be irradiated from the spectacle frame and thus only one single colour will become visible.

Moreover, in that according to the invention a metal is utilized for the oxide layer, metals can be selected which also comprise corresponding characteristics with respect to hardness, so that the sliding surfaces of the joint mechanism can be provided with a friction reducing coating at the same time, which renders the joint mechanism to be more smooth- running.

Furthermore, the invention suggests a method for manufacturing a spectacle frame from a metal, which main component is ferric, and which comprises the steps:

- cutting of single pieces or components for the spectacle frame from metal sheet,

applying a metallic coating onto the pieces by means of physical vapour deposition, and

- creating a metallic oxide layer from the metal coating by means of anodic oxidation of the pieces.

The pieces being cut or stamped from metal sheet, preferably from spring sheet made of steel or stainless steel, which pieces consist of the rim and both spectacle temples, will be subjected to the process of physical vapour deposition in a vacuum chamber, in which preferably sputtering will be utilized for that.

For the purpose of providing a better optical effect the surfaces can be subjected to matting by means of blasting in advance. For that, for example, blasting using glass beads is suitable. Moreover, to enable a corresponding better adhesion of the metallic coating on the surfaces of the pieces, these can be further subjected to scrubbing in advance. If applicable, cleaning and drying phases can follow.

The advantage in connection with the physical vapour deposition inter alia is to be seen in that an uniform, covering application or deposition can be realized for a layer thickness of only one ym, whereas the pieces could already be bent into their final shape. The coating uniformly reaches the still smallest surface region, as in particular also the sliding surfaces of the joint mechanism. After the pieces have been provided with the metallic coating from a defined material, according to the invention, the step of the anodic oxidation follows.

In this respect, the coated pieces will be subjected to a suitable acid electrolyte and connected as an anode. In that the pieces are serving and functioning as an anode no further layers will be added to or coated onto the already coated surfaces, but rather the oxide layer results from the transformation of the existing base material, namely from the metallic coating as previously applied.

In particular, metals from the group of the transition metals are suitable as metal for the metallic coating and the metallic oxide layer, respectively. By means of the method according to the invention, the spectral characteristics of the metals can selectively and specifically be influenced and altered. Finally, a coating for a spectacle frame with defined spectral characteristics results therefrom. Further advantages and features of the invention do become apparent from the description of the embodiments as explained in connection with the accompanying drawings.

Fig. 1 schematically shows a spectacle made of metal and having a screwless joint mechanism in perspective view;

Fig. 2a, b schematically show the functioning principle of the joint mechanism; and

Fig. 3 schematically shows a cross section of a layer configuration for any piece of the metal spectacle .

Fig. 1 shows a spectacle frame which consists of a metal, the main component of which is ferric, as, for example, steel.

The metal spectacle comprises a rim 1 and a spectacle temple 2 on the left and on the right, respectively. In the direction towards the spectacle temples 2 the rim 1 comprises a connecting element 3 at corresponding positions, at which the spectacle temples 2 are supported in a swiveling manner.

The rim-side end of each spectacle temple 2 is divided into three leaf springs 4, 5 and 6. As can be seen from Figures 2a and b, the connecting element 3 comprises two vertical recesses 7 and 8, which form a vertical joint axis. With their free ends the outer leaf springs 4 and 5 do pass these recesses 7 and 8, whereas the central leaf spring 6 is supported against the surface of the connecting element 3, facing away from the face of the spectacle wearer in the folded-out condition. It becomes apparent that the inner surfaces and edges, respectively, of the recesses 7 and 8 on one hand and the sections of the free ends of the outer leaf springs 4 and 5 passing there through on the other hand do form corresponding sliding surfaces, which are subjected to an increased friction .

Fig. 3 shows a section of a component or piece 9 of the spectacle frame according to the invention in a substantially enlarged view.

All pieces or components, the rim 1 with the connecting elements 3 at both sides and the spectacle temples 2 with the leaf springs 4, 5, 6, do comprise an uniform material thickness, which is relatively thin and is in the region of approximately 0.5 mm.

A metal coating 10 will be applied onto the component 9 made from sheet metal by means of the method of physical vapour deposition, in which for that metal is selected, which qualifies for the desired tribological requirements for the joint mechanism. In doing so, the components 9 will be coated entirely, i.e. finally then all surfaces of the components 9 are provided with a corresponding coating 10, which does not exceed a thickness of 1 ym. In the following, the components 9 coated as such will be immersed in an acid electrolyte and connected as an anode, so that the metal coating 10 will be anodized at its surface and by that an oxide layer 11 of the metal will be formed, which has been selected for the coating. For that purpose metals for the component 9 having a high ferric rate prove to be very good conductors .

The oxide layer 11 comprises defined refraction characteristics for light. According to the invention, the layer thickness of the oxide layer 11 shall be selected such that finally only one specific wavelength of the radiating light will be reflected from the surface of the components 9 of the spectacle frame, which surface is being manufactured in such a way.

Therefore, the spectacle frame appears in one colour, which results from the refraction and reflection of light, and not from the application of an additional coloured coating.