Patent Description:
It is known that spring hinges, also called "elastic hinges" or "flex hinges", allow extra opening of the side arms without damage to the frame. These usually comprise two elements which are pivotably mounted together and associated respectively with the front piece and one of the two side arms of the frame.

The flex hinge generally comprises an element or swivel piece which is slidable against the action of a spring and is located inside a seat associated with one end of the side arm or one end of the front piece.

Recently, for mainly aesthetic reasons, a type of flex hinge defined as "hidden" or "concealable" has been developed where the seat for the swivel piece is formed directly inside the body of the side arm or the front piece. In this case, the seat consists, in fact, of a cavity provided inside the side arm or the front piece which are preferably made of polymer material.

In order to prevent the swivel piece from rotating with respect to the cavity in which it is slidably fixed, the cavity and the swivel piece have respective cross-sections designed to provide a form-fitting connection with each other.

Such a type of hinge is described for example in Italian patent <CIT>.

This patent describes a swivel piece provided with a longitudinal through-hole inside which, via an opening formed in the hinging portion of the said swivel piece, a fixing screw is inserted.

A helical spring is fitted onto the fixing screw so as to be locked between the head of the screw and a bearing portion formed in the end part of the swivel piece.

The end portion of the fixing screw is threaded and designed to project from a hole formed in the terminal end of the swivel piece, in a position opposite to the front opening, so as to be fixed inside the side arm. Once the screw has been fixed in the side arm, the swivel piece is able to slide inside the cavity formed in the side arm against the action of the spring.

Firstly, the hinge may not be supplied in a preassembled condition. The fixing screw, in fact, before being fixed to the side arm, may not be locked in position inside the swivel piece.

The manufacturer of the spectacles is not only required to provide in the body of the side arm a longitudinal cavity with specific dimensions and shape, but is also required to assemble the various parts of the hinge at the time of mounting.

Such assembly, considering the increasingly small dimensions of the parts to be handled, requires a not insignificant amount of time, with obvious disadvantages in terms of cost and productivity.

Moreover, the need to insert the fixing screw, with the spring fitted thereon, through a front opening provided in the hinging portion of the swivel piece, means that there are dimensional constraints. In order to ensure the necessary strength of the hinging portion of the swivel piece, in fact, the transverse dimensions of the latter may not be smaller than a certain value and this means that the hinge may be used solely in combination with side arms which have larger transverse dimensions.

A spring hinge of the "hidden" flex type is also described in <CIT> in the name of the same Applicant.

In this solution, the fixing screw of the swivel piece is fixed to the side arm by means of a stop element provided with gripping means suitable for securing the stop element, and therefore the fixing screw, to the side arm.

The provision of the stop element allows the hinge to be provided already in the preassembled condition, with the fixing screw inserted inside the swivel piece and locked in position by means of the stop element.

The manufacturer of the spectacles, in order to lock the swivel piece in position, must no longer screw the fixing screw into the side arm. Fixing, in fact, may be performed by exerting an axial compressive force at the front end of the fixing screw so that the stop element and the associated gripping means engage inside the seat provided in the cavity of the side arm. This solution is therefore advantageous compared to <CIT>. However, although the stop element may be fixed on the outside of the swivel piece, it is also envisaged that the fixing screw on which the spring is fitted is inserted inside the swivel piece by means of a through-hole formed in the hinging portion of the swivel piece.

This solution, therefore, in order to ensure the necessary strength of the hinging portion of the swivel piece, also does not allow the transverse dimensions thereof to be reduced by more than a certain amount.

An alternative solution, finally, is described in the United States patent <CIT>.

The swivel piece, which is intended to be seated inside a cavity provided in the side arm of the spectacles, has the form of a cuboid and has a lateral opening for insertion, inside it, of a fixing screw on which a helical spring is fitted.

The screw projects at the rear through a hole provided in the end wall of the swivel piece, so that it may be fixed in the side arm.

This hinge may be supplied in a preassembled condition since the swivel piece is not provided with a through-hole in its hinging portion. Once the fixing screw has been inserted in position, the head of the screw comes into contact against the front end wall of the swivel piece, therefore remaining locked inside the opening formed therein.

At the time of fixing of the swivel piece inside the cavity of the side arm, the presence of the front end wall, without through-openings, allows the fixing screw to be pushed inside the side arm, allowing fixing thereof.

Owing to the absence of a through-hole in the hinging portion, it is possible moreover to obtain hinges with hinging portions which are smaller than those of the solutions described above, with obvious aesthetic advantages.

However, this hinge is also not without defects.

Insertion of the screw inside the swivel piece is not easy to perform since the screw must be inclined in order to be inserted inside the rear through-hole. This insertion, moreover, is made difficult by the presence of the spring.

In order to facilitate insertion of the screw the usual procedure adopted is to widen the transverse dimensions of the swivel piece, thus partly losing the advantage which can be obtained by the absence of the through-hole in the front end portion.

Moreover, again in order to facilitate the insertion of the fixing screw inside the swivel piece, the usual procedure is to provide a rear hole with bigger dimensions than those which would be sufficient for inserting the shank of the fixing screw.

This larger hole may create problems during fixing of the screw in the side arm. The screw, in fact, owing to the play existing between its terminal end portion and the rear hole could become inclined following the compressive force acting on its front end portion, making fixing of the hinge less precise.

In the worst case, owing to the friction between swivel piece and cavity, the hinge could get stuck during the opening and closing movements of the side arm.

Finally, once the swivel piece is fixed inside the side arm, the absence of a through-opening in the hinging portion prevents the possibility of accessing the fixing screw. It is therefore not possible to adjust the travel of the swivel piece or to replace the hinge.

The object of the present invention is therefore to overcome the aforementioned drawbacks. In particular, a task of the present invention is to provide a spring hinge for spectacles which may be applied to the frame in a simple and low-cost manner.

Moreover, a task of the present invention is to provide a spring hinge for spectacles which has small dimensions and which may also be applied to side arms and front pieces with small cross-sections, without adversely affecting the mechanical strength.

Furthermore, a task of the present invention is to provide a spring hinge for spectacles which may be fixed in the side arm or in the front piece in a safe and simple manner and which is precise and reliable.

Moreover, a task of the present invention is to provide a spring hinge for spectacles which, after being fixed to the side arm or to the front piece of a frame, may be adjusted and if necessary replaced.

Furthermore, a task of the present invention is to provide a frame for spectacles, which may be easily assembled.

Finally a task of the present invention is to provide a method for assembling the hinge which is simple and may be easily automated.

These and other objects and tasks are achieved with a spring hinge according to claim <NUM>, with a frame for spectacles according to claim <NUM> and with a method according to claim <NUM>.

In order to explain more clearly the innovative principles of the present invention and its advantages compared to the prior art, a number of examples of embodiment applying these principles will be described below with the aid of the attached drawings. In the drawings:.

The spring hinge <NUM> is intended to hinge together a side arm <NUM> and a front piece <NUM> of a spectacles frame <NUM> about a pivoting axis X (see <FIG> and <FIG>).

In the description below, with reference to the attached figures, "front" will define the part of the hinge, or of its single elements, which during use is relatively closer to pivoting axis X. "Rear" will indicate the part of the hinge, or its single elements, which during use is relatively further from the pivoting axis X.

With reference to <FIG>, <FIG>, <FIG> and <FIG>, the spring hinge <NUM> comprises a swivel piece <NUM> having a front pivoting end <NUM>, advantageously provided with a hole or eyelet <NUM> for pivotably mounting the hinge <NUM>, for example by means of the screw <NUM> (see <FIG> and <FIG>).

The swivel piece <NUM> also has a rear wall <NUM> opposite to the front pivoting end <NUM>.

As is clearly visible in <FIG>, <FIG>, <FIG> and <FIG>, the swivel piece <NUM> has an open cavity <NUM>, preferably positioned along a side wall of the swivel piece <NUM>.

The cavity <NUM> receives, seated inside it, an anchoring element <NUM> which has, fitted thereon, elastic means <NUM>, preferably a helical spring, acting between a front end portion <NUM> of the anchoring element <NUM> and the rear wall <NUM> of the swivel piece <NUM> (see for example <FIG>).

In particular, the elastic means <NUM> may advantageously act with their first thrusting end on the front end portion <NUM> of the element <NUM>, which forms a bearing projection, and react with an opposite second end against the rear wall <NUM>, which acts as an abutment.

<FIG> show, by way of example, a configuration of the hinge <NUM> in which, following a pulling force acting on the hinging portion <NUM> of the swivel piece <NUM>, the spring <NUM> is compressed between the front end portion <NUM> of the anchoring element <NUM> and the rear wall <NUM> of the swivel piece <NUM>. The pulling force in <FIG> is schematically indicated by the arrow F.

In accordance with the invention the anchoring element <NUM> is seated inside the cavity <NUM> so that a rear portion thereof <NUM> projects from the swivel piece <NUM> through a recess <NUM> formed in the rear wall <NUM> of the said swivel piece <NUM>.

For the purposes of the present invention "recess" is understood as meaning an open concavity; said open concavity is provided in the rear wall <NUM> of the swivel piece <NUM>.

Unlike a hole, the recess does not define a closed surface.

The recess <NUM> is therefore open on one of its sides. Preferably, the cavity <NUM> and the recess <NUM> are open in a same side wall of the swivel piece <NUM>.

The recess <NUM> preferably has a U or V shaped cross-section, but different shapes are possible in order to satisfy different requirements.

Owing to the provision of the recess <NUM>, it is possible to insert the anchoring element <NUM>, already provided with the spring <NUM>, inside the swivel piece <NUM> by moving it laterally close to the side of the cavity <NUM>, without having to incline it.

In other words, as will become clear below, during assembly of the hinge <NUM>, the anchoring element <NUM> with the spring <NUM> may be rested on the bottom of the cavity <NUM> and the recess <NUM>, remaining in a position substantially parallel to the longitudinal axis L of the swivel piece <NUM>, thus simplifying significantly the operations for assembly of the hinge <NUM>.

Moreover, the groove of the recess <NUM> may act as a support for the rear portion <NUM> of the anchoring element <NUM> and act as a guide for the movements of the swivel piece <NUM> during opening and closing of the side arm.

As is clearly visible, for example in <FIG>, it is possible in fact to provide a minimum amount of play between the inner surfaces of the recess <NUM> and the rear portion <NUM> of the anchoring element <NUM> since the recess <NUM> is not required to have dimensions larger than those of the rear portion <NUM> in order to allow the anchoring element <NUM> to be seated inside the cavity <NUM>.

In a first embodiment of the hinge <NUM>, as shown in <FIG>, the rear portion <NUM> of the anchoring element <NUM> may be lengthened so that it may be provided with a threading or knurling and thus be directly fixed, hot or cold, to the side arm <NUM> or the front piece <NUM>.

Alternatively, as shown in the attached figures, a stop element <NUM>, provided with gripping means <NUM>, may be fixed to the rear portion <NUM> of the anchoring element <NUM> projecting from the swivel piece <NUM>. Advantageously, the stop element <NUM> has transverse dimensions greater than those of the recess <NUM> and smaller than those of the swivel piece <NUM> and is intended, when the swivel piece <NUM> is located in its rest position, to bear against the outer surface of the rear wall <NUM> (see for example <FIG>).

The stop element <NUM> provides a greater gripping surface and therefore allows a more secure fixing of the element <NUM> to the side arm <NUM> or to the front piece <NUM>.

The stop element <NUM> may have a tapered shape, while the gripping means <NUM> preferably consist of ratchet gripping means shaped so as to facilitate insertion of the stop element <NUM> in the side arm <NUM>.

The gripping means <NUM> are preferably arranged on a side surface of the stop element <NUM>.

The stop element <NUM> may be provided with a threaded hole <NUM> inside which the rear portion <NUM> of the anchoring element <NUM> may be fixed, for example screwed.

In a different embodiment, the stop element <NUM> may be provided with a through-hole in which the rear portion <NUM> of the anchoring element <NUM> is intended to be inserted and then riveted there, so as to allow fixing together of the element <NUM> and stop element <NUM>.

Once the anchoring element <NUM> with the spring <NUM> is seated inside the cavity <NUM>, the front end portion <NUM> of the anchoring element <NUM> by means of the action of the spring is intended to bear against a front wall <NUM> of the cavity <NUM> (see <FIG>, <FIG>, <FIG> and <FIG>). This allows the hinge <NUM> to be supplied in a preassembled condition to the spectacles manufacturer, thus simplifying the operations for fixing the hinge to the side arm or the front piece of the frame.

As is known, the front end portion <NUM> remains in abutment against the front wall <NUM> when the hinge is in the rest condition, i.e. with the spring <NUM> not compressed. Once fixed to the side arm, the opening and closing movements of the side arm cause the relative sliding of the swivel piece <NUM> and the anchoring element <NUM>, with the consequence that in some operating conditions the front end portion <NUM> is spaced from the front wall <NUM> (see for example <FIG>, <FIG> and <FIG>).

With reference to the embodiment shown in <FIG>, the front end portion <NUM> of the anchoring element <NUM> may be flat so as to bear against a flat front wall <NUM> of the cavity <NUM>.

This front wall <NUM> is situated opposite the rear wall <NUM>.

In this embodiment, the anchoring element <NUM> is preferably a screw and the front end portion <NUM> consists of the head of the screw. Advantageously the head of the screw may be provided with a transverse slit <NUM>. Once the screw <NUM> has been arranged inside the swivel piece <NUM>, by acting transversely on the slit <NUM> of the screw head, on the open side of the cavity <NUM>, it is possible to screw or unscrew with a suitable tool the screw <NUM> with respect to the stop element <NUM>, thus varying the compression of the spring <NUM> and consequently adjusting the travel of the swivel piece <NUM>.

As is clearly visible in <FIG> and <FIG>, in this embodiment, the provision of a flat front end portion <NUM> and a flat front wall <NUM>, together with the absence of a transverse through-hole, allows the transverse thickness of the hinging portion <NUM> to be reduced. In this way, advantageously, the hinge <NUM> may be mounted on side arms and front pieces having smaller transverse thicknesses.

The anchoring element <NUM> is retained firmly inside the cavity <NUM> owing to the action exerted by the elastic means <NUM>. There is no risk, therefore, that during the handling of the hinge <NUM>, the anchoring element <NUM> may come out of the swivel piece. However, along the side walls of the swivel piece <NUM>, once the anchoring element <NUM> has been inserted with the elastic means <NUM> inside the cavity, fastening means may be provided, for example a band which surrounds the side walls of the swivel piece <NUM>, so as to be able to provide a further system for preventing the anchoring element <NUM> from coming out of the cavity <NUM>.

According to the invention, the embodiment shown in <FIG> and the embodiment shown in <FIG>, the front end portion <NUM> of the anchoring element <NUM> has a prismatic form, so as to be able to be slidably inserted inside a seat <NUM> formed in the front wall <NUM> of the cavity <NUM>.

Advantageously in the embodiment shown in <FIG>, the seat <NUM> and the front end portion <NUM> of the anchoring element <NUM> create a form-fitting connection having respective cross-sections with a matching shape.

Advantageously, in the embodiment shown in <FIG>, the front end portion <NUM> has a square cross-section with chamfered edges. In this way, there is not a single direction for insertion of the front end portion <NUM> inside the seat <NUM>.

Advantageously, when the hinge <NUM> is in use, following sliding of the swivel piece <NUM> inside the cavity formed in the side piece, the front end portion <NUM> of the anchoring element <NUM> may slide inside the seat <NUM> (see <FIG>).

Advantageously, the seat <NUM>, in combination with the recess <NUM>, ensures more precise movements of the swivel piece <NUM> with respect to the anchoring element <NUM>, ensuring that the anchoring element <NUM> is unable to flex or bend during the hinge opening and closing movements.

Moreover, the seat <NUM>, since it may be formed in a solid portion of the swivel piece <NUM>, does not adversely affect the mechanical strength of the hinging portion <NUM> and does not result in an increase in the transverse dimensions of the swivel piece.

Furthermore, as will be clarified below, the provision of the seat <NUM> also allows the operations for assembly of the hinge <NUM> to be simplified.

With reference to the embodiment shown in <FIG>, the front end portion <NUM> of the anchoring element <NUM> may be provided with a plurality of radial projections <NUM> designed to define a plurality of longitudinal grooves <NUM> (see <FIG>).

In this embodiment, as can be clearly seen in <FIG> and <FIG>, the cavity <NUM> of the swivel piece <NUM> is provided with a transverse opening <NUM> in the vicinity of the front wall <NUM>.

Once the hinge <NUM> is assembled, according to the procedures which will be described below, the radial projections <NUM> of the front end portion <NUM> are accessible via the transverse opening <NUM> (see for example <FIG>).

In this way, once the hinge <NUM> has been assembled, with a suitably shaped tool able to engage inside the longitudinal grooves <NUM> defined by the projections <NUM> it is possible to operate the anchoring element <NUM>, screwing it into the stop element <NUM> so as to compress the spring <NUM> and vary the travel of the swivel piece <NUM>, depending on the different requirements. Moreover, the radial projections <NUM> are accessible also once the hinge <NUM> has been fixed in the side arm <NUM> or in the front piece <NUM> of the frame <NUM>, allowing if necessary also the removal of the hinge from the side arm or front piece.

As can be clearly seen in <FIG>, in order to access the projections <NUM> of the anchoring element <NUM>, it is sufficient to incline the side arm <NUM> with respect to the front piece <NUM> by about <NUM>°-<NUM>°, bringing it into a semi-open position.

In this position, the hinging portion <NUM> of the swivel piece <NUM> owing to the pulling force F acting on it is located spaced from the terminal end 11A of the side arm <NUM> so as to make the opening <NUM> and consequently the projections <NUM> accessible.

The operator by means of a suitable tool able to engage inside the grooves <NUM> may therefore adjust the anchoring screw <NUM> and if necessary unscrew it from the stop element <NUM>, allowing the removal of the swivel piece <NUM> from the side arm <NUM>. The stop element <NUM>, in turn, remains fixed to the side arm.

The swivel piece may therefore be replaced by one which is the same and which will be locked inside the seat by screwing using the methods described above the terminal end portion of the anchoring screw <NUM> inside the stop element <NUM> which is fixed to the side arm.

As already mentioned, with reference now to <FIG> and <FIG>, the present application also relates to a frame <NUM> comprising the hinge <NUM>.

In particular, the frame <NUM> comprises a front piece <NUM> and two side arms <NUM>, each side arm <NUM> being hinged together with the front piece <NUM> by means of the hinge <NUM> about a pivoting axis X.

Preferably, the front piece <NUM> and the side arms <NUM> of the frame <NUM> are formed by means of injection-moulding of polymer material. Advantageously, the front piece <NUM> and the side arms <NUM> may be made of nylon. Advantageously, the front piece <NUM> and the side arms <NUM> may be made of cellulose acetate.

The swivel piece <NUM> is intended to be inserted inside a cavity <NUM> which may be formed at one end of the side arm or the front piece.

The swivel piece <NUM> of the hinge <NUM> and the cavity <NUM> have respective cross-sections which are designed to create a mutual form-fitting connection. This form-fitting connection prevents the swivel piece <NUM> from rotating, about its longitudinal axis L, with respect to the side arm <NUM> or the front piece <NUM>.

<FIG> and <FIG> show an embodiment in which the cavity <NUM> is provided in the side arm <NUM>. The embodiment in which the cavity <NUM> is provided in the front piece <NUM> is similar and may be easily imagined by the person skilled in the art.

The swivel piece <NUM> is locked slidably inside the cavity <NUM> by means of the anchoring element <NUM>, the projecting rear portion <NUM> of which is intended to be fixed directly (see <FIG>), or by means of the stop element <NUM> (see <FIG>), in the material forming the side arm or the front piece.

Said fixing is performed hot, after heating slightly the side arm or the front piece, so as to reduce the resistance of the polymer material of the frame to insertion of the stop element <NUM> or the rear portion of the anchoring element.

Alternatively, in the case of the embodiment shown in <FIG>, fixing of the rear portion <NUM> of the anchoring element <NUM> may be performed in cold conditions.

Advantageously, the stop element <NUM> may be inserted inside a seat <NUM> which is provided in the side arm or in the front piece and is adjacent to and communicates with the cavity <NUM>.

The seat <NUM> preferably has dimensions compatible with those of the stop element <NUM> so as to ensure that the gripping means <NUM> grip the inner surfaces of the seat <NUM>.

<FIG> show a seat <NUM> which is advantageously formed by two adjacent portions <NUM> and <NUM> having different transverse dimensions so as to engage better with the stop element <NUM>.

In <FIG>, the seat <NUM> has dimensions compatible with those of the rear portion <NUM>. In particular the dimensions of the seat <NUM> are defined so as to provide a form-fit with interference between the rear portion <NUM> and the seat <NUM>.

The insertion of the hinge <NUM> inside the cavity <NUM> is performed by exerting a longitudinal compressive force, i.e. a force directed along the longitudinal axis L, on the hinging portion <NUM> of the swivel piece <NUM>.

This insertion is facilitated by the fact that, once the anchoring element <NUM>, together with the spring <NUM>, has been inserted inside the cavity <NUM>, the front end portion <NUM> of the anchoring element <NUM> is intended to bear against the flat front wall <NUM> of the cavity <NUM> or be inserted inside the seat <NUM>.

A compression exerted on the hinging portion of the swivel piece <NUM> therefore results in a thrust against the front end portion of the anchoring element <NUM>, allowing pushing and blocking of the rear portion <NUM> of the anchoring element <NUM> in the polymer material of the side arm or the front piece.

The present application relates, moreover, to a method for assembly of the hinge <NUM>.

With reference firstly to <FIG>, <FIG>, <FIG> and <FIG>, relating respectively to the hinges shown in <FIG>, <FIG>, <FIG> and <FIG>, the assembly method comprises the steps of:.

Advantageously, the provision of the recess <NUM> facilitates the insertion of the anchoring element <NUM> and the elastic means <NUM> inside the cavity <NUM>.

In order to insert the anchoring element <NUM> into the cavity <NUM> it is sufficient, in fact, to compress slightly the elastic means <NUM> fitted onto the anchoring element <NUM> against the front end portion <NUM> of the anchoring element <NUM>, by passing the rear portion <NUM> of the anchoring element <NUM> through the recess <NUM>.

Once the anchoring element <NUM> has been inserted in the cavity <NUM> and in the recess <NUM>, with the rear portion <NUM> projecting from the swivel piece <NUM>, releasing of the spring <NUM> causes the front end portion <NUM> of the anchoring element <NUM> to bear against the front wall <NUM> of the cavity, locking in position the anchoring element <NUM> and the spring <NUM>.

Advantageously, in order to facilitate the fixing of the hinge <NUM> to the side arm <NUM> or to the front piece <NUM> of the frame <NUM>, assembly of the hinge <NUM> may be completed by fixing a stop element <NUM> on the rear portion <NUM> of the anchoring element <NUM> (see <FIG>, <FIG> and <FIG>).

With reference to the method illustrated in <FIG> and <FIG>, in order to prevent the front end portion <NUM> of the screw <NUM> from rotating during fixing of the stop element <NUM>, therefore preventing fixing of the rear portion <NUM> inside the stop element <NUM>, advantageously it is possible to use a tool suitably shaped so as to engage transversely with the slit <NUM> (see <FIG>) or the grooves <NUM> (see <FIG>) provided on the front end portion <NUM>. By means of the tool it is possible to prevent rotation of the screw during the operation involving screwing of the stop element <NUM>.

In the embodiment shown in <FIG>, advantageously it is not necessary to use this tool, because of the form-fit which is provided between the front end portion <NUM> of the anchoring screw <NUM> and the seat <NUM>. This form-fit prevents the head of the anchoring screw <NUM> from rotating during fixing of the stop element <NUM>.

The stop element <NUM> is intended to bear against the outer rear wall <NUM>, thus ensuring secure fixing of the element <NUM> inside the cavity <NUM>. The rear portion <NUM> of the anchoring element <NUM> is in fact prevented from coming out of the recess <NUM>.

In an alternative embodiment (see <FIG> and <FIG>), fixing of the stop element <NUM> on the rear portion <NUM> of the anchoring element <NUM> is performed before inserting the anchoring element <NUM> inside the cavity <NUM> (see <FIG> and <FIG>).

Fixing of the stop element <NUM> is performed after the elastic means <NUM> have been fitted onto the anchoring element <NUM>. In this way it is easy to lock the front end portion of the anchoring element <NUM> so as to allow fixing of the stop element <NUM>, without there being the risk of the front end portion <NUM> of the anchoring element <NUM> being able to rotate.

It is also possible to act longitudinally on the front end portion of the screw, this being accessible.

Once the stop element has been fixed, the anchoring element <NUM> may be inserted inside the cavity <NUM> compressing slightly the elastic means <NUM>. These means will then be released so as to be able to bear on one side against the rear wall <NUM> of the swivel piece <NUM> and on the other side against the front end portion <NUM> of the screw <NUM>, ensuring that the latter is securely inserted inside the cavity <NUM>.

The assembly method illustrated in <FIG> and <FIG> may be used also with the hinge shown in <FIG>.

At this point it is clear how the predefined objects have been achieved.

The hinge <NUM>, in fact, since it does not have a transverse through-hole in the pivoting portion <NUM> of the swivel piece <NUM>, has smaller dimensions which allow it to be mounted also on side arms or front pieces having smaller cross-sections, while ensuring in any case the necessary mechanical strength.

The provision of the recess <NUM> allows easy assembly of the various parts of the hinge <NUM> and allows the latter to be supplied to the manufacturer of the spectacles in a preassembled condition.

Once the anchoring element <NUM> has been inserted in the cavity <NUM> so that the rear portion <NUM> projects form the swivel piece, the action exerted by the elastic means between the front end portion <NUM> and the rear wall <NUM> ensures that the anchoring element remains in position.

The recess <NUM>, provided in the rear wall <NUM>, and the seat <NUM>, formed in the front wall of the cavity <NUM>, ensure that the swivel piece <NUM> is guided by the anchoring element <NUM> during its movements in a precise and reliable manner.

The transverse slit <NUM> or the radial projections <NUM> provided on the anchoring screw <NUM> allow adjustment of the travel of the swivel piece once the hinge has been assembled.

The radial projections <NUM> of the anchoring screw and the transverse opening <NUM>, which is formed in the vicinity of the hinging portion of the swivel piece, allow, even in the absence of a transverse through-hole, the head of the anchoring screw to be operated, even when the hinge has been fixed to the side arm or the front piece. In this way, if necessary, it is possible to replace the hinge <NUM> alone, without having to replace the entire front piece or the entire side arm of the frame.

Moreover, the hinge assembly method described above may be easily automated, with obvious advantages in terms of costs and productivity.

It is clear that the elastic hinge for spectacles described hitherto may be subject to modifications and/or the addition of parts, without thereby departing from the scope of the present invention.

Claim 1:
Spring hinge (<NUM>) intended to hinge together a side arm (<NUM>) and a front piece (<NUM>) of a frame for spectacles (<NUM>), comprising a swivel piece (<NUM>) having a front pivoting end (<NUM>) and a rear wall (<NUM>); said swivel piece (<NUM>) is provided with an open cavity (<NUM>) which receives, seated inside it, an anchoring element (<NUM>) which has, fitted thereon, elastic means (<NUM>) acting between a front end portion (<NUM>) of the anchoring element (<NUM>) and said rear wall (<NUM>);
said spring hinge (<NUM>) being characterized in that the anchoring element (<NUM>) is seated inside said cavity (<NUM>) so that a rear portion (<NUM>) thereof projects from the swivel piece (<NUM>) through a recess (<NUM>) formed in the rear wall (<NUM>) of the swivel piece (<NUM>); the recess (<NUM>) being open on one of its side, wherein the front end portion (<NUM>) of the anchoring element (<NUM>) is intended to bear, through the action of the elastic means (<NUM>), against a front wall (<NUM>) of the cavity (<NUM>) when the hinge (<NUM>) is in a rest condition; the front end portion (<NUM>) of the anchoring element (<NUM>) having a prismatic shape and being intended to be inserted slidably inside a seat (<NUM>) formed in the front wall (<NUM>) of the cavity (<NUM>).