The present invention relates to an elastic hinge device for spectacles having the characteristics stated in the preamble to Claim 1, which is the principal claim. Prior art

In the technical field to which the present invention relates, there are known elastic hinge devices for pivoting arms on the front of a spectacle frame, including a spring mechanism which causes the arms to return elastically to preferred angular positions. In known types of these devices, the spring means is formed with one or more helical springs made from metallic material such as spring steel. In this case, these solutions make the arm rather bulky, and require rather complicated assembly operations. This type of solution, in the many versions provided by the prior art, also results in a considerable overall weight of the components used in the device for the mounting of the aforesaid springs, making it unsuitable for use in lightweight frames and/or those made from plastics material. Description of the invention The object of the invention is to provide an elastic hinge device for spectacles which is structurally and functionally designed to overcome the limitations of the prior art, and which, in particular, has a simplified structure which is easily and rapidly fitted to the frame and is particularly light and with small overall dimensions, making it suitable for use in particularly slender and lightweight frames. The objects stated above, together with others which will be made clear below, are achieved by a spectacle frame made in accordance with the appended claims.

Brief description of the drawings

Other features and advantages of the invention will be made clear by the following detailed description of some preferred examples of embodiment thereof, illustrated, for the purposes of guidance and in a non-limiting way, with reference to the appended drawings, in which:

Figure 1 is a perspective view of spectacles including elastic hinge devices according to the present invention, - Figure 2 is an exploded perspective view on an enlarged scale of the device of Figure 1;

Figure 3 is a perspective view of the device of Figure 2 in the partially assembled state,

- Figure 4 is a view in longitudinal section of the device of the preceding figures,

Figure 5 is a perspective view of a variant embodiment of the device according to the invention,

- Figure 6 is a partially exploded perspective view of another variant embodiment of the device according to the invention, - Figure 7 is a partial exploded perspective view of another variant embodiment of the device according to the invention,

- Figure 8 is a partially exploded perspective view on an enlarged scale of another variant embodiment of the device according to the invention,

- Figures 9 and 10 are cross-sectional views of the device of Figure 8, in separate stages of the assembly operation, - Figures 11, 12 and 13 are views, in exploded perspective form, in longitudinal section and in plan from above respectively, of another variant embodiment of the invention. Preferred embodiments of the invention With reference to the cited drawings, the number 1 indicates the whole of a pair of spectacles, shown schematically in Figure 1, comprising a front piece 2 of the frame, a pair of side arms 3 and, for each arm, a corresponding elastic hinge device 4, made according to the present invention, for pivoting the corresponding arm on the front piece. Only one of the hinge devices will be described, as they are structurally identical.

Each elastic hinge device 4 comprises a first and second hinge element, connected to the front piece 4 of the frame and to the arm 3 respectively, which can swing with respect to each other about a hinge axis indicated by X in the drawings. The first hinge element comprises a pair of eyelet formations 7 provided on a block 8 fixed to the front piece, while the second hinge element comprises an eyelet formation 9 provided in a bar element, indicated as a whole by 10, which is slidably associated with the arm, as described more fully below. More specifically, the bar 10 is shaped with a first portion 10a on the free end of which the eyelet formation 9 is provided, and a second portion 10b, forming an extension of the first portion, in which a through hole 11 of rectangular cross section is formed, the function of this hole being made clear by the text below. The bar 10 is pivoted on the block 8 by means of a screw or pin 12 coaxial with the axis X, passing through the eyelet 9 and the eyelet formations, which are coaxial with each other, provided in the block. The hinge device 4 also comprises a box-like support 13 in which the bar 10 is slidably housed. The support contains a longitudinally extending housing 14 having opposing sides between which the bar 10 is slidably located, forming a coupling with a limited amount of play. By means of this coupling, the bar 10 is slidably guided in the support. The housing 14 can conveniently be formed by milling if the arm is made from metallic material, the support being an integral part of the arm. Alternatively, for example in the case of an arm made from plastics material, the box-like support 13 can be made in one piece with the arm by the injection moulding of the arm. An appendage 15 also projects into the cavity of the housing 14, this appendage passing through the hole 11 of the bar and having a surface 16 which is formed on it and which faces one of the opposing end surfaces of the hole 11, identified by the number 17. This end surface is formed on one of the shorter sides of the rectangular cross section of the through hole 11 in the bar. An elastic return means is located between the surfaces 16 and 17, and, according to one of the principal features of the invention, this means is formed by a parallelepipedal body 18 made from a suitable elastomeric material. Preferably, this elastomeric body 18 is made from a polyester-based copolymer thermoplastic material. It has characteristics of flexibility and elasticity which are maintained over a wide temperature range, and by means of which the body 18 tends to cause the elastic return of the bar 10 in its sliding movement with respect to the support 13.

The body 18 is shaped in such a way as to be housed in the cavity formed by the hole 11 passing through the portion 10b of the bar, this portion being slidably guided in the housing 14 of the support. The numbers 19a and 19b indicate surface stops formed in the corresponding sides of the housing 14, these stops serving to limit the travel of the bar 10 by interference with corresponding shoulders 20a and 20b formed between the portions 10a and 10b of the bar. It should also be noted that the preloading of the elastic return body 18 can be carried out during the assembly of the device in the support associated with the arm. This preloading is carried out in the body 18 at the time when it is fitted, in combination with the support, in the housing of the arm support, by contrast with the conventional solutions in which the elastic preloading is carried out in the stage at which the bar is fitted pivotably on the block. According to the invention, the preloading is carried out to a greater extent during the assembly of the arm, although further preloading, to a smaller extent, can also be carried out during the stage of fitting pivotably on the block. Conveniently, it is possible to carry out preloading up to values of about 0.7 mm for example, expressed in terms of axial deformation of the body 18, during the assembly of the arm. Further preloading, of about 0.3 mm in this case, can be added to this principal preloading when the bar is fitted pivotably on the block. Preferably, the bar 10 is made from a polyether imide resin which can impart high mechanical strength and a high modulus of elasticity. This resin also imparts high chemical resistance and high heat-resistance.

If made from plastics material, both the arm 3 and the box-like support 13 are formed from a thermoplastic material, preferably belonging to the polyamide group. These materials impart good characteristics in terms of robustness, mechanical strength, chemical resistance, heat-resistance, transparency and ease of processing. The device also comprises a cover element, indicated by 21, for closing the box-like support 13 and thus retaining the bar 10 inside the support housing 14.

The cover 21 is conveniently made from the same material as the arm, preferably polyamide.

In a first embodiment, the cover 21 is fixed to the box-like support 13 by welding. This fixing is preferable if the arm is made from plastics material. To facilitate assembly, the cover 21 is provided, before welding, with a projecting pin 22 which can engage in a corresponding housing 23 (made in the form of a blind hole for example) in the appendage 15 of the support 13. The aforesaid pin serves to hold the assembled components in place before welding, in opposition to the elastic action of the body 18 due to the effect of preloading, an effect which tends to push the bar back into the housing 14 of the support, thus possibly causing the displacement of the cover from its position in the support.

The welding system is preferably based on the use of laser or ultrasonic welding.

As a further alternative, it is possible to provide a removable fixing using screw means 24a, as shown in Figure 6. This fixing system is preferable in the case of an arm whose body is made from metallic material.

In yet another alternative, a coupling of the elastic snap-fitting type can be provided for fixing the cover 21 to the box-like support 13. In this case, a plurality of pin-like appendages 26 are provided on the cover 21, for engagement by fitting into corresponding housings 27 (in the form of blind holes, for example) provided in the support 13, as shown in Figure 7. In a further variant, shown in Figures 8 to 10, the snap-fitting of the cover 21 on the box-like body 13 is obtained by providing opposing longitudinal edges 21a and 21b on the cover which can engage, by deformation with elastic return, in corresponding housings 13a and 13b provided in the support on the arm. Each edge is conveniently provided with a terminal projection running along the edge and designed to be fastened in the corresponding housing so as to retain the cover on the support when it has been snap-fitted into the housing. In this case, the cover 21 is made from a plastics material having sufficient flexibility, at least in the areas of fastening, to be deformed elastically along the edges for the corresponding snap-fitting into the housing.

In a further variant embodiment, shown in Figures 11 to 13, which can be used conveniently when the body of the arm is made from metal, the screw fixing means of the cover 21 comprise a single screw, indicated by 28, designed to be engaged by screwing in the threaded blind hole provided in the appendage 15. A projection 29, projecting from the cover and designed to engage in a housing 30 formed in the arm, also helps to fix the cover, as Figure 12 clearly shows. Regardless of the fixing system, the cover 21 can be made from a material having characteristics of transparency, in order to make at least part of the elastomeric body 18 and of the bar 10 visible from outside the support 13. This enables an attractive appearance to be provided, particularly if the bar, the support together with the arm, and the elastomeric body are made from materials of different colours.

It is also possible to provide one or more surfaces on the elastomeric body 18 for the application of decorative patterns or distinctive signs (such as trademarks), so that these are visible through the transparent cover. In a further variant, the support and the body of the arm are also made from materials having characteristics of transparency, in order to maximize the effect of the visibility of the components of the elastic hinge device (the support and the elastomeric return means) from the outside. In a further embodiment, the device comprises a stop element, indicated by 25, provided at the end of the arm designed to contact the block 8 in the pivoting movement. The element 25 is provided, in particular, if the arm is assembled on to a front frame piece made from metallic material (in other words, if it has a metal block). This is because, in this case, the friction between the contact surfaces of the plastic arm and the metal block would create a degree of wear of the former which would adversely affect the operation of the arm pivot. The stop element 25 is therefore highly abrasion-resistant, and for this purpose is preferably made from an acetal resin, which can be filled subsequently with Teflon (PTFE) fibres or with any particles of lubricant and/or reinforcing material.

As shown in Figure 2, the element 25 is plate-shaped and can be applied to the arm by a process of overmoulding the body of the arm on to the element. The bar, the elastomeric elastic return body and the cover are made in advance and independently in the manufacturing process. If necessary, the stop element is also formed by overmoulding on the body of the arm. In the next stage of assembly, the bar and the elastic return means are first housed in the support housing, which is then closed by means of the cover.

Thus the invention achieves the proposed objects while yielding the stated advantages by comparison with the known solutions. In addition to the advantages described above, particular mention should be made of the fact that the device according to the invention advantageously offers a significant reduction in the production costs of both the device itself and the arm associated with it. This advantage is seen, in particular, in the forming of the bar and of the elastic return element, compared with the conventional embodiments and the typical materials used.