WO1999055522A1

WO1999055522A1 - Process for making molded eyeglasses and eyeglasses made by said process

Info

Publication number: WO1999055522A1
Application number: PCT/IL1998/000191
Authority: WO
Inventors: Michael Wolman
Original assignee: Michael Wolman
Priority date: 1998-04-23
Filing date: 1998-04-23
Publication date: 1999-11-04
Also published as: CA2329361A1

Abstract

Process for making Oxford type eyeglasses, which comprises the steps of: providing an elastic bridge, intended to connect the two lenses of the Oxford eyeglasses; inserting the ends of said bridge into a mold comprising two symmetrical halves, each of which is so shaped as to define a lens frame constituting the periphery of one of the lenses of the eyeglasses that it is intended to produce; injecting plastic matter into said mold, whereby to generate two symmetrical lens frames, the end portions of the bridge being enclosed in said lens frames, thus joining them together to generate an eyeglass frame; introducing said eyeglass frame into a mold defining the two lenses of the Oxford eyeglasses, and injecting plastic matter into said mold to mold said lenses, each within the corresponding lens frame, whereby to generate the finished eyeglasses.

Description

PROCESS FOR MAKING MOLDED EYEGLASSES AND EYEGLASSES MADE BY SAID PROCESS

Field of the Invention

This invention relates to molded eyeglasses, particularly eyeglasses of the "Oxford" type or pince-nez, and more specifically, to a process for making them by injection molding in order to obtain simple, inexpensive and yet optically efficient eyeglasses of said type. This invention further relates to the eyeglasses obtained by the said method.

Background of the Invention

Oxford eyeglasses, or pince-nez, are known in the art and have been used for many years. They consist essentially of two lenses and a bridge between them, in particular a spring-like bridge which, drawing the lenses toward one another, applies a pressure on the user's nose and keeps the eyeglasses in place.

In modern days, Oxford eyeglasses have been largely abandoned because their advantages do not offset their disadvantages, which are mainly that they are less stable than standard glasses and, in order that nevertheless sufficiently stability may be achieved, they tend to apply a possibly irritating pressure on the nose. However, recently, the market has developed a demand for ready-made glasses that are not made to prescriptions, but are sold in stores, including drugstores, in a series of standard graduations, each user selecting the glasses - 2 -

which best suit his eyesight. Such ready-made eyeglasses are much less expensive than those made to prescription, and yet are efficient from the optical viewpoint, so that they are extremely attractive to the wide public.

The structure of Oxford eyeglasses, being particularly simple, would suggest that they are particularly adapted for mass production at low cost. For instance, it could be considered to provide an elastic bridge, e.g., a metal bridge, insert it into a mold, and mold the lenses about the ends of the bridge. However, I have found that eyeglasses made in this way are found to be optically defective. No matter how accurately the molds for the lenses are designed, to provide certain optical parameters, I have found that the finished eyeglass lenses deviate from the planned optical parameters and therefore from the required optical behavior.

It is a purpose of this invention to overcome the aforesaid problem and to provide a process for making Oxford eyeglasses that are optically efficient and have the planned optical parameters and the desired optical properties.

It is another purpose of this invention to provide such a method which is based on known injection molding procedures.

It is a further purpose of this invention to provide such a method which minimizes the pressure on the user's nose of the resulting eyeglasses. - 3 -

It is a still further purpose of this invention to provide Oxford eyeglasses that are optically perfect and yet extremely cheap, as well as simple and light.

It is a still further purpose of this invention to provide a process that results in the production of such eyeglasses.

Other purposes and advantages of the invention will appear as the description proceeds.

Summary of the Invention

The method according to the invention comprises a two-stage injection molding. In the first stage, an elastic bridge, intended to connect the two lenses of the Oxford eyeglasses, is provided and is inserted into a mold comprising two symmetrical halves, each of which is so shaped as to define a lens frame constituting the periphery of one of the lenses of the eyeglass that it is intended to produce. Plastic matter is injected into said mold, in such a way that two symmetrical lens frames are generated and the end portions of the bridge become inserts in said lens frames, thus joining said lens frames together to generate an eyeglass frame comprising said elastic bridge and two symmetrical lens frames. In a second stage of the molding process, the eyeglass frame is introduced into a mold defining the two lenses of the Oxford eyeglasses, and plastic matter is injected into said mold to mold said lenses each within the corresponding lens frame, whereby to generate the finished eyeglasses. - 4 -

Preferably, each of the lens frames comprises a lug in which an end of the bridge is inserted, which lug is thick enough to hold therein the ends of the bridge as inserts, and is in general thicker than the lenses themselves.

Preferably, the lens frames are also provided with ridges at the location where they are expected to bear on the user's nose, so as to provide nesting surfaces for the two halves of the eyeglasses, as is customary in eyeglasses.

Preferably, but not necessarily, the lens frames are made of the same transparent thermoplastic material which constitutes the lenses. Thus the lens frames will not be distinguishable as separate elements from the lenses in the finished eyeglasses. An example of a suitable lens and lens frame material is polymethylmethacrylate, commercially known as Perspex. However, any plastic material that can be injection-molded, and is sufficiently transparent and sufficiently hard, can be used for making the lenses of the eyeglasses according to this invention.

The bridge is preferably made of elastic metal material, such as spring steel, although it could be made of plastic, as well. It is preferably shaped as a leaf of arcuate configuration, more preferably having two substantially straight ends, inserted into the lens frame lugs. It is resistant to bending about an axis that is the intersection of said plane with a plane that contains the center line of the bridge - 5 -

with the plane of symmetry of the eyeglasses, and it is easily flexible about an axis contained in said plane of symmetry, perpendicular to said first mentioned axis and passing through said center line of the bridge.

Brief Description of the Drawings

In the drawings:

- Fig. 1 is a vertical view of a pair of Oxford eyeglasses according to an embodiment of the invention;

- Fig. 2 is a plan view of the same, seen from below;

- Fig. 3 is a vertical view of the structure obtained from the first molding, comprising the bridge and the frames, one of the frames being broken off;

- Fig. 4 is a plan view of the structure of Fig. 3, seen from the top; and

- Fig. 5 is a cross-section at an enlarged scale, partially broken off, of the eyeglasses of Figs. 1 and 2, taken along plane N-N of Fig. 1, looking in the direction of the arrows.

Detailed Description of Preferred Embodiments

In the embodiment of the invention, illustrated in Figs. 1 and 2, the Oxford eyeglasses, generally indicated at 10, comprise a bridge 11 and two symmetrical lenses 12 and 13. The bridge has an arcuate central portion and two substantially straight ends 18-19. It is preferably made of a metal leaf, e.g. spring steel, but could be made of plastic material as well. The lenses, as seen in the finished eyeglasses, appear to be of one piece. They have a curved, moderately - 6 -

concave shape as seen from the side of the user wearing the glasses, which is the viewpoint of Fig. 1. The curvature of their surface is the optically relevant factor, determining the desired eyesight correction, but they are also provided with two pairs of elements which are mechanically and not optically relevant, and precisely lugs 14-15 and ridges 16-17. These latter serve to provide a greater area of contact between the lenses and the nose of the user, as is customary in eyeglasses. The lugs, on the other hand, house, as inserts, the ends 18-19 of the bridge 11.

As better seen in the cross-section of Fig. 5, the lugs have a thickness that is greater than that of any other point of the lens, and therefore they project from the concave surface of the lens and form a shoulder, as shown at 20-21. The ends 18-19 of the bridge 11, as seen in Fig. 5, are trapeze-shaped and taper down towards the lenses, so that the surface of the lugs has a correspondingly slanted surface at 22-23. Said ends are illustrated as provided, in this embodiment, with holes 24-25, through which the plastic matter of the lugs passes, better to anchor the bridge to the lugs. The central part of the bridge 11 may have any desired width, but in general its width is only slightly smaller than the maximum thickness of the lugs and is only slightly larger, if at all, than the thickness of the body of the lenses.

In this embodiment, the bridge is preferably made of stainless spring steel and has a thickness from 0.2 to 0.6 mm and a width from 3 to 5 mm. Considering the plane of symmetry of the eyeglasses and a first axis that is the intersection of said plane with a second plane that - 7 -

contains the center line of the bridge, it is seen that the bridge is highly resistant to bending about said first axis, but is highly flexible about a second axis, contained in said plane of symmetry, perpendicular to said first axis and passing through said center line of the bridge. Because of this high flexibility, the pressure of the eyeglasses on the user's nose is minimized.

In the first stage of the manufacture of the glasses, the assembly of Figs. 3 and 4, which is the eyeglass frame, generally indicated at 29, is created. A mold is provided, which is constituted by two symmetrical halves, each having the shape of one of the lens frames 30-31, shown in Figs. 3 and 4. The mold has cavities, defining the lugs 14-15 and the ridges 16-17. The thickness of the frames, at points other than the lugs and ridges, does not have rigid limits, but in general may be comprised between 0.45 and 0.6 mm. The width of the frame, at points other than the lugs and ridges, is equal to or slightly higher than the thickness of the lenses of the eyeglasses to be made, which depends on the number of diopters, but, in most cases, may vary between 3 and 4 mm.

In the second stage of the manufacture of the glasses, the eyeglass frame 29 is introduced into a mold, comprising two symmetrical halves, each of which defines the shape of one of the lenses. It will be appreciated that this stage is critical for the optical properties of the eyeglasses, and that in order for those properties to be satisfactory, it is necessary, and it would seem to be sufficient, that the mold halves have the exact shape that will confer to the lenses, at any point - 8 -

thereof, the required curvature. However, I have surprisingly found that this is not sufficient: if it is attempted to mold the lenses directly about the bridge, without generating firstly the lens frames, the resulting eyeglasses do not have the optical properties that should have resulted from the shape of the mold, and that do result from that shape if the molding is effected within the lens frames. Why this occurs, I cannot say with certainty, but experience has taught me that it does occur.

The two molding operations herein described are carried out by conventional injection molding techniques, adapted in each case to the thermoplastic material used, e.g. Perspex. Any person skilled in the injection molding art knows how to carry them out, and no particular instruction need be given, either as to the shape of the molds or to the injection parameters.

While an embodiment of the invention has been described for the purpose of illustration, it will be apparent that the invention may be carried out by persons skilled in the art with many modifications, variations and adaptations, without departing from its spirit or exceeding the scope of the claims.

Claims

- 9 -CLAIMS

1. Process for making Oxford type eyeglasses, which comprises the steps of: providing an elastic bridge, intended to connect the two lenses of the Oxford eyeglasses; inserting the ends of said bridge into a mold comprising two symmetrical halves, each of which is so shaped as to define a lens frame constituting the periphery of one of the lenses of the eyeglass that it is intended to produce; injecting plastic matter into said mold, whereby to generate two symmetrical lens frames, the end portions of the bridge being enclosed in said lens frames, thus joining them together to generate an eyeglass frame; introducing said eyeglass frame into a mold defining the two lenses of the Oxford eyeglasses; and injecting plastic matter into said mold to mold said lenses, each within the corresponding lens frame, whereby to generate the finished eyeglasses.

2. Process according to claim 1, wherein each of the lens frames comprises a lug thick enough to hold therein the ends of the elastic bridge as inserts.

3. Process according to claim 1, wherein the lens frames are provided with ridges at the location where they are expected to bear on the user's nose, so as to provide nesting surfaces for the two halves of the eyeglasses. - 10 -

4. Process according to claim 1, wherein the lens frames are made of the same material which constitutes the lenses.

5. Process according to claim 1, wherein the lenses are made of a transparent thermoplastic material.

6. Process according to claim 1, wherein the lens frames and the lenses are made of a transparent thermoplastic material.

7. Process according to claim 5 or 6, wherein the transparent thermoplastic material is polymethylmethacrylate.

8. Process according to claim 1, wherein the bridge is made of elastic metal material.

9. Process according to claim 8, wherein the bridge is made of spring steel.

10. Oxford type eyeglasses, comprising an elastic bridge, intended to connect the two lenses of the Oxford eyeglasses, two symmetrical lens frames in which the ends of said bridge are inserted, and two lenses solid with said lens frames.

11. Eyeglasses according to claim 10, wherein each of the lens frames comprises a lug which holds therein the ends of the bridge as inserts. - 11 -

12. Eyeglasses according to claim 10, wherein the lens frames are provided with ridges at the location where they are expected to bear on the user's nose, so as to provide nesting surfaces for the two halves of the eyeglasses.

13. Eyeglasses according to claim 10, wherein the lens frames and the lenses are made of a transparent thermoplastic material.

14. Eyeglasses according to claim 13, wherein the lens frames and the lenses are made of polymethylmethacrylate.

15. Eyeglasses according to claim 10, wherein the bridge is made of elastic metal material.

16. Eyeglasses according to claim 15, wherein the bridge is made of spring steel.

17. Eyeglasses according to claim 11, wherein the bridge comprises an arcuate central portion and two substantially straight ends, inserted into the lens frame lugs.

18. Process for making Oxford type eyeglasses, substantially as described and illustrated.

19. Eyeglasses, substantially as described and illustrated.