IMPROVED ELASTIC HINGE FOR SPECTACLES

The present invention relates to an improved elastic hinge for spectacles.

Elastic hinges are known for insertion between the frontpiece and each arm of the spectacles. They generally comprise a box casing which is fixed to the end of an arm and internally houses a slidable carriage provided with a portion emerging from an end of said box casing and forming one of the two elements of the hinge. The other hinge element is directly secured to the frontpiece of the frame and is hinged to that carriage portion emerging from the box casing.

A spring is associated with the carriage of this hinge element to act in the sense of pulling the element towards the interior of the box casing to cause the hinge element fixed to the frontpiece to cooperate with the box casing, to hence define the two stable open and closed positions of the corresponding arm.

Two different types of box casings exist, namely open box casings and closed box casings. In the first case their internal cavity is accessible during assembly via the lacking bottom of the box casing, while in the second case their internal cavity is accessible via an aperture provided in the end wall of the box casing, from this aperture there emerging the carriage portion to be hinged to that hinge element fixed to the frontpiece of the spectacles.

Generally the carriage spring is preloaded under compression and is interposed between a first stop applied to or formed at the end of a pin fixed to the carriage, and a second stop which is then fixed to the box casing. As the unit formed by the pin, the preloaded spring and its end stops has to be inserted into the cavity of the box casing and maintained in its seat until the

operations involved in fixing the box casing to the arm have been completed, it is already known to form this second stop as an elastic stop, generally consisting of a metal ring, which is urged to contract on inserting the unit into the box casing, such that when stressing ceases it is able to elastically resume its rest configuration and in this manner retain the unit in its seat.

This operation is effected by utilizing the particular shape of said elastic stop and in particular by providing it with an elastically yieldable portion which is stressed during insertion of the box casing and is released on termination of said insertion. In this manner the elastic reaction on termination of the insertion step causes stable engagement of said elastic stop in a corresponding groove (bored or milled) provided in the box casing and enables said element to counteract the axial stresses which arise in the elastic element of the hinge during normal use of the spectacles. Given the very small dimensions which the elastic hinge must have in order to be as hidden from view as possible and not to alter the overall line of the frame, the elements contained within the box casing must be of very small dimensions resulting in considerable rigidity of the elastic element, which not only makes it very difficult to assemble and fix the hinge, especially if effected by traditional automatic machines, but also subjects the elastic stop to high stress and deformation, hence requiring the use of quality materials of high cost.

Small elastic hinge dimensions and low stresses on the elastic stop during assembly hence constitute opposing requirements, to which a satisfactory solution has so far not been found.

An object of the invention is therefore to reconcile these opposing requirements by providing an elastic hinge for spectacles, in which small dimensions can be achieved even though a high elasticity spring stop is present, hence requiring only small force during assembly. This and other objects which will be apparent from the ensuing description are attained, according to the invention, by an improved elastic hinge as described in claim 1.

Three preferred embodiments of the present invention together with some variants thereof are described hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a partial perspective view of an improved elastic hinge according to the invention, with the box casing shown in longitudinal section, Figure 2 shows a different perspective view thereof with the box casing sectioned longitudinally on a plane perpendicular to the preceding, Figure 3 is an exploded perspective view thereof,

Figure 4 is a perspective view thereof during insertion of the preassembled unit, formed from the second hinge element, the pin, the spring and its two stops, into the box casing,

Figure 5 is a side view of a variant with the box casing without a bottom and sectioned longitudinally, and with the preassembled unit not yet inserted into the box casing, Figure 6 is a plan view thereof from below in the direction Vl-Vl of Figure 5, with the preassembled unit inserted into the box casing, Figure 7 is a cross-section through the box casing on the line VI I-VII of Figure 6,

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Figure 8 is an exploded perspective view of a second embodiment of an improved elastic hinge according to the invention,

Figure 9 is a side view thereof with the box casing lacking the bottom and shown in longitudinal section, with the preassembled unit not yet inserted into the box casing,

Figure 10 is an exploded perspective view of a third embodiment thereof, and Figure 11 is a different partially sectioned perspective view of this third embodiment thereof shown in the assembled condition, Figure 12 shows it in the same view as Figure 8 but with a fork element of different shape, and Figure 13 shows the same embodiment thereof as Figure 12, but with the fork element rotated axially through 180°.

As can be seen from the figures, the improved elastic hinge for spectacles according to the invention comprises, in a first embodiment, a box casing 2 provided with a longitudinal internal cavity, which in the embodiment shown in Figures 1 -4 is closed on all sides and open at a base, while in the variant shown in Figures 5-7 it is open both at a base and also on the bottom, i.e. on that side on which the arm (not shown) of the spectacles is applied. In a like manner to traditional hinges, the improved hinge of the invention also comprises a first hinge element, which is applied to the frontpiece of the spectacles and is not shown herein for simplicity, being of traditional type and not forming part of the invention.

The hinge also comprises a second hinge element 4, formed from a substantially parallelepiped portion 6 intended to slide within the box casing 2,

and a portion 8 emerging from said box casing 2 to be pivoted to the first hinge element.

A pin 10 is fixed in traditional manner to the parallelepiped portion 6 of the second hinge element 4 to support a solenoid spring 12 maintained in a precompressed condition between a stop ring 14, applied to the free end of the pin 10, and a second stop 16, provided at the opposite end of said pin 10.

Specifically, this second stop 16 consists of a fork element formed with a flat blade defining two prongs 20 and a portion 18 joining them together. A part of these prongs 20 and their joining portion 18 lie in the same plane, and when the hinge is mounted they lie interposed between the parallelepiped portion 6 and the upper wall of the cavity of the box casing 2.

The two ends of the prongs 20 are bent at 90° to their remaining part, to give the stop an L-shape. The outer edge of each bent part of the prongs 20 is profiled to project from the overall outline of the stop 16 and of the parallelepiped portion 6 of the second hinge element 4.

The two prongs 20 present a certain elasticity which enables them, when suitably forced, to elastically approach each other; in addition their shape, and in particular the shape of their bent part, is such that when they have approached each other, the overall lateral dimension of the stop 6 is reduced to a width less than the width of the cavity of the box casing 2.

At a distance from the open end of the box casing 2 substantially equal to the length of the straight parts of the prongs 20, the side walls of the box casing 2 comprise a perimetral groove (bore) 22, complementary to the projecting edge of the bent part of the prongs 20, to enable them to be elastically engaged by these when external forces are absent.

To assemble the hinge, the pin 10 already provided with the terminal stop 14 is inserted into the solenoid spring 12 between the two bent parts of the prongs 20 of the second stop 16, and is fixed with this to the second hinge element 4, such as to maintain the spring 12 in a slightly precompressed condition.

Having formed the preassembled unit, it can be inserted into the box casing 2. This is achieved by exerting opposing forces at the edge of the bent parts of the prongs 20 to cause said prongs to approach each other and reduce the lateral dimension of the elastic stop 16, to enable the preassembled unit to then be inserted axially into the cavity of the box casing 2 (see Figure 4).

On termination of insertion, the outer edge 24 of the two ends of the two prongs 20 encounters the perimetral groove 22 and can snap-engage it to securely lock the stop 16 to the box casing 2. The box casing 2 with the preassembled unit inserted can then be fixed to the corresponding arm of the spectacles, to enable the second hinge element 4 to be fixed to the first, which is already fixed to the frontpiece of the spectacles.

The variant shown in Figures 5-7 uses the same principle, but applied to an open box casing 2, i.e. without the bottom on the side at which it is applied to the arm of the spectacles.

In this case the preassembled unit is inserted into the cavity of the box casing perpendicularly to the axis of the pin 10 and of the solenoid spring 12, in this case the stability of the connection being ensured by the friction engagement of the outer edge 24 of the two prongs 20 of the second stop 16

in the two grooves 22 provided in the two side walls of the cavity of the box casing 2.

The aforedescribed improved hinge of the invention is particularly advantageous in that: - because of the particular shape of the elastic stop 16 with the two prongs 20 it enables the elastic deflection of each prong to be distributed over a large length portion, even though of very small dimensions. On the one hand this enables the overall length of the box casing 2 and hence of the hinge to be limited, and on the other hand it enables the force previously applied to the elastic stop on inserting the preassembled unit into the box casing to be reduced,

- the same automatic machines used to assemble traditional hinges can be used to assemble the hinge of the invention.

In the embodiment shown in Figure 8, in which corresponding elements are indicated by the same reference numerals, the second stop 16' presents an inversion between the position of its prongs 20' and their joining piece 18' in the sense that this latter forms the part which embraces the pin

10, while the two prongs extend parallel to the parallelepiped portion 6 of the second hinge element 4. In this case the connection between the second stop 16' and the box casing 2 is obtained by the snap-engagement of two appendices 24' provided at the free end of the prongs 20' in corresponding seats 22' provided in the walls of the box casing 2.

To form this hinge, the unit comprising the hinge element 2, the pin 10, the solenoid spring 12 and the two stops 14 and 16' is firstly preassembled, this unit then being inserted axially into the cavity in the box casing 2. For this purpose the appendices 24' of the prongs 20' usefully present a flared portion

26', which facilitates elastic approach of the prongs during insertion, on termination of which the prongs reopen elastically as soon as the appendices

24' reach their seats 22', engaging therein to stabilize the preassembled unit within the box casing 2. In this embodiment the base of the parallelepiped portion 6 is provided with a cylindrical peg 28 which during hinge assembly is inserted between and in contact with the prongs 20'.

The function of this peg is to maintain the ends 24' of the prongs 20' always engaged in the seats 22' of the box casing 2, even when the hinge is under maximum stress, i.e. when the spring is compressed to its maximum extent. In this manner accidental disengagement of the second hinge element

4 from the box casing 2 is prevented.

In addition to presenting all the advantages of the first embodiment, the second embodiment presents the further advantage of simplifying the insertion of the preassembled unit into the box casing 2 by traditional automatic techniques.

In the variant shown in Figure 9, although the shape of the second stop 16' and the method of connecting this to the box casing 2 remain the same, this latter is of open type, i.e. is without a bottom, to enable the preassembled unit to be inserted into the cavity of the box casing 2 by translation perpendicular to the axis of the pin 10. Again in this case, stabilized fixing of the preassembled unit to the box casing 2 is achieved by engagement of the appendices 24' on the prongs 20' in the seats 22' provided in the side walls of the box casing. In the embodiment shown in Figures 10 and 11 , in which corresponding elements are indicated by the same reference numerals, the

second stop 16" consists, as in the case of the preceding embodiment, of a fork element with two straight prongs 20" joined together by a part 18" which embraces the pin 10. However in this case, instead of being interposed between the parallelepiped portion 6 of the second hinge element 4 and the upper wall of the box casing 2, the prongs 20" are housed in a bottomless portion of said box casing (see Figure 11 ).

As in the previous case the free end of each prong 20" is provided with an appendix 24" projecting to the outside and housable in a corresponding seat 22" provided in the side wall of the box casing 2. This appendix 24" also presents a flared portion 26" which facilitates insertion of the preassembled unit into the box casing 2.

This third embodiment, in addition to presenting all the already described advantages relative to the first and second embodiment, also presents the further advantage of utilizing the thickness of the bottom of the box casing 2 to house that portion of the fork element 16" parallel to the axis of the pin 10, requiring in this manner a minimum height for that part of the box casing which guides the parallelepiped portion 6 of the second hinge element 4, without on this account losing guiding effectiveness.

In the embodiment shown in Figures 12 and 13, the fork element 16'" has its prongs 20'" joined together at the portion 18'" by a portion 30 the purpose of which is to increase its rigidity

Again in this embodiment, the 90° bent portion of the prongs extends into a block 32 to prevent tilting of the fork element 16"'

During assembly, this block rests against the base or bottom of the box casing, if this is closed, or directly against the arm of the frame, if the box casing is open.