EP2846969B1 - Method for cutting-out a multi-layer ophthalmic lens - Google Patents

Description

TECHNICAL FIELD TO WHICH THE INVENTION REFERS

The present invention generally relates to the preparation of multilayer ophthalmic lenses (i.e. comprising a substrate and at least one coating film which is made of a material distinct from that of the substrate and which covers a main surface of the substrate ) for mounting in spectacle frames.

• une étape de pré-ébauche de la lentille ophtalmique au moyen d'un outil préliminaire, selon un contour préliminaire distinct et déduit dudit contour souhaité,
• une étape d'ébauche de la lentille ophtalmique au moyen d'une meule d'ébauche, suivant un contour d'ébauche confondu avec ou élargi par rapport au contour souhaité, et
• une étape de finition de la lentille ophtalmique au moyen d'un outil de finition.

It relates more particularly to a method of trimming an ophthalmic lens according to a desired contour, comprising:

• a step of pre-roughing the ophthalmic lens by means of a preliminary tool, according to a distinct preliminary contour and deduced from said desired contour,
• a step of roughing the ophthalmic lens by means of a roughing wheel, according to a rough outline coincident with or widened with respect to the desired contour, and
• a finishing step of the ophthalmic lens by means of a finishing tool.

BACKGROUND

It is common to affix to the substrate of an ophthalmic lens one or more coating layers in the form of films.

Such a film can be used for various reasons, in particular to improve the optical comfort of the ophthalmic lens or to increase the optical performance thereof.

It may for example be a micro-cell film which makes it possible to confer on the ophthalmic lens properties of photochromism or index variation.

The disadvantage of such a multilayer ophthalmic lens is that its trimming is in practice difficult to achieve.

The use of a conventional grinding wheel, in normal trimming conditions and in the presence of a lubricant, has the effect of weakening the ophthalmic lens, or even causing delamination and / or delamination, that is to say to say a separation of the different layers of the ophthalmic lens.

We then know of the document FR 2 962 676 a clipping method as defined in the introduction, which is especially intended for the trimming of multilayer ophthalmic lenses.

The pre-roughing step of the trimming process which is exposed to it consists in cutting the lens by means of a cutter, on the thickness of the film only and in a preliminary outline narrowed relative to the desired contour. The roughing and finishing steps are conventionally operated using form grinding wheels.

It will be understood that the cutting of the film prevents the useful part of this film (situated inside the preliminary outline) from being subjected to stresses during the roughing and finishing operations of the ophthalmic lens.

Cutting the film unfortunately reveals the end of the trimming of the lens a sidewalk running along the edge of this lens.

This sidewalk is particularly unattractive. It is also more unsightly that the film has a different color than the substrate. It can even generate unpleasant optical effects for the wearer of glasses.

The cutting of the film by the cutter also generates waves along the edge of the film, which creates an effect of lace also unattractive.

OBJECT OF THE INVENTION

In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a method of careful trimming of a multilayer ophthalmic lens.

More particularly, it is proposed according to the invention a method of trimming as defined in the introduction, wherein said preliminary contour is widened relative to the desired contour and wherein it is expected that the blank wheel used has a particle size included between 0.1 and 0.5 mm and that it is controlled relative to the ophthalmic lens so as to apply during said roughing step a radial force on the ophthalmic lens between 0.1 and 5 Newton.

Thus, the preliminary contour being widened with respect to the desired contour, the roughing and finishing steps make it possible to erase the traces that the pre-roughing step might possibly have left on the ophthalmic lens.

Moreover, the Applicant has experienced said combination of particle size and radial force used to rough the lens, and thus observed that it makes it possible to reduce as much as possible the stresses exerted on the useful part of the film of the lens and that it thus concur (with the pre-roughing step) to avoid any detachment and / or delamination of the film.

• ledit outil de finition utilisé est une meule présentant une granulométrie comprise entre 0,02 et 0,1 mm, pilotée relativement à ladite lentille ophtalmique suivant le contour souhaité, de manière à appliquer au cours de ladite étape de finition une force radiale sur la lentille ophtalmique comprise entre 5 et 18 Newton ;
• au cours de ladite étape de finition, ledit outil de finition est piloté relativement à ladite lentille ophtalmique pour usiner ladite lentille ophtalmique en au moins trois passes ;
• après ladite étape de finition, il est prévu une étape de polissage de ladite lentille ophtalmique au moyen d'un outil de polissage ;
• ledit outil de polissage utilisé est une meule présentant une granulométrie comprise entre 0,0005 et 0,02 mm, pilotée relativement à ladite lentille ophtalmique de manière à appliquer au cours de ladite étape de polissage une force radiale sur la lentille ophtalmique comprise entre 10 et 35 Newton ;
• au cours de ladite étape de polissage, ledit outil de polissage est piloté relativement à ladite lentille ophtalmique pour usiner ladite lentille ophtalmique en au moins trois passes ;
• ledit outil préliminaire étant une fraise, ladite étape de pré-ébauche consiste à découper la lentille ophtalmique sur toute l'épaisseur du film de revêtement et sur une partie seulement de l'épaisseur du substrat, selon le contour préliminaire ;
• le contour d'ébauche est élargi par rapport au contour préliminaire ;
• ladite étape d'ébauche est opérée en présence d'un lubrifiant ;
• ledit outil préliminaire étant la meule d'ébauche, ladite étape de pré-ébauche est opérée en présence d'un lubrifiant, selon le contour préliminaire ;
• ladite étape d'ébauche est opérée à sec, en l'absence de lubrifiant, suivant le contour souhaité.

Other advantageous and non-limiting features of the trimming method according to the invention are the following:

• said finishing tool used is a grinding wheel having a particle size of between 0.02 and 0.1 mm, driven relative to said ophthalmic lens according to the desired contour, so as to apply during said finishing step a radial force on the lens ophthalmic between 5 and 18 Newton;
• during said finishing step, said finishing tool is driven relative to said ophthalmic lens for machining said ophthalmic lens in at least three passes;
• after said finishing step, there is provided a step of polishing said ophthalmic lens by means of a polishing tool;
• said polishing tool used is a grinding wheel having a particle size of between 0.0005 and 0.02 mm, controlled relative to said ophthalmic lens so as to apply during said polishing step a radial force on the ophthalmic lens of between 10 and 35 Newton;
• during said polishing step, said polishing tool is driven relative to said ophthalmic lens to machine said ophthalmic lens in at least three passes;
• said preliminary tool being a milling cutter, said pre-roughing step comprises cutting the ophthalmic lens over the entire thickness of the coating film and only a portion of the thickness of the substrate, according to the preliminary outline;
• the rough outline is enlarged relative to the preliminary outline;
• said roughing step is carried out in the presence of a lubricant;
• said preliminary tool being the roughing wheel, said pre-roughing step is operated in the presence of a lubricant, according to the preliminary outline;
• said roughing step is operated dry, in the absence of lubricant, according to the desired contour.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The following description with reference to the accompanying drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be achieved.

In the accompanying drawings:

• the figures 1 and 2 are schematic views of two embodiments of an ophthalmic lens trimming apparatus;
• the Figures 3A and 3B are schematic views, side and front, of an ophthalmic lens before trimming;
• the Figures 4A and 4B are diagrammatic views, from the side and from the front, of the ophthalmic lens represented on the Figures 3A and 3B , as it appears at the end of a pre-roughing step operated according to a trimming method according to a first embodiment of the invention;
• the Figures 5A and 5B are diagrammatic views, from the side and from the front, of the ophthalmic lens represented on the Figures 4A and 4B , as it appears at the end of a roughing step operated according to the first embodiment of the trimming method according to the invention;
• the Figures 6A and 6B are diagrammatic views, from the side and from the front, of the ophthalmic lens represented on the Figures 5A and 5B as it appears at the end of a finishing step;
• the Figures 7A and 7B are diagrammatic views, from the side and from the front, of the ophthalmic lens represented on the Figures 3A and 3B , as it appears at the end of a pre-roughing step operated according to a trimming method according to a second embodiment of the invention; and
• the Figures 8A and 8B are diagrammatic views, from the side and from the front, of the ophthalmic lens represented on the Figures 7A and 7B , as it appears at the end of a roughing step operated according to the second embodiment of the trimming method according to the invention.

Clipping device

On the figures 1 and 2 two embodiments of a trimming apparatus adapted to detach an ophthalmic lens are shown schematically. These embodiments are for illustrative purposes and other commercially available trimmers may be used for the practice of the present invention.

Such a trimming apparatus can be made in the form of any cutting or removal machine capable of modifying the contour of the ophthalmic lens to adapt it to a frame selected by the future wearer of the pair of spectacles.

• une bascule 201 qui est montée librement pivotante autour d'un axe de référence A5, en pratique un axe horizontal, sur un châssis non représenté, et qui supporte la lentille ophtalmique 100 à usiner ;
• un train de meules 214, qui est calé en rotation sur un axe de meule A6 parallèle à l'axe de référence A5, et qui est lui aussi dûment entraîné en rotation par un moteur non représenté ;
• un module de finition 220 qui est monté à rotation autour de l'axe de meule A6, et qui embarque notamment des outils de finition de la lentille ophtalmique 100.

As schematized on the figure 1 , the trimming apparatus is constituted, in known manner, by an automatic grinder 200, commonly called digital. This grinder includes in this case:

• a latch 201 which is mounted freely pivotally about a reference axis A5, in practice a horizontal axis, on a frame not shown, and which supports the ophthalmic lens 100 to be machined;
• a wheel set 214, which is set in rotation on a grinding wheel axis A6 parallel to the reference axis A5, and which is also properly rotated by a motor not shown;
• a finishing module 220 which is rotatably mounted around the wheel axis A6, and which includes the finishing tools of the ophthalmic lens 100.

The latch 201 is equipped with a lens support here formed by two shafts and rotation drive 202, 203 of the ophthalmic lens 100 to be machined.

These two shafts 202, 203 are aligned with each other along a blocking axis A7 parallel to the axis A5. Each of the shafts 202, 203 has a free end which faces the other and is equipped with a locking nose of the ophthalmic lens 100.

A first of the two shafts 202 is fixed in translation along the blocking axis A7. The second of the two shafts 203 is instead movable in translation along the blocking axis A7 to effect the compression in axial compression of the ophthalmic lens 100 between the two locking noses.

The wheel set 214 here comprises four wheels 210, 211, 212, 213 mounted coaxially on the wheel axis A6, each designed for a specific machining operation of the ophthalmic lens 100.

The grinding wheel 214 comprises in particular a grinding wheel 210 cylindrical in revolution around the wheel axis A6. This roughing wheel 210 comprises diamonds whose particle size is between 0.1 and 0.5 mm and is here equal to 0.3 mm.

The wheel train 214 also comprises a beveling wheel 211, said shape. This beveling grinding wheel 211 has a generally cylindrical shape of revolution around the wheel axis A6, with however a central groove (not visible in the figures), V-section and revolution around the wheel axis A6. This central groove thus makes it possible to machine a rib on the field of the ophthalmic lens 100 to be machined. This beveling grinding wheel 211 comprises diamonds whose particle size is between 0.02 and 0.1 mm and is here equal to 0.06 mm.

Finally, the set of wheels 214 comprises two polishing grinding wheels whose shapes are respectively identical to those of the roughing grinding wheel 210 and beveling wheel 211, but whose diamonds have particle sizes of between 0.0005 and 0.02 mm, here equal to 0.005mm.

The set of wheels 214 is carried by a carriage, not shown, mounted to move in translation along the grinding wheel axis A6. The translational movement of the trolley is called "transfer" TRA.

It is understood that it is a matter here of making a relative movement of the grinding wheels with respect to the lens and that it will be possible, in a variant, to provide an axial mobility of the lens, the grinding wheels remaining fixed.

The grinder 200 further comprises a connecting rod 230, one end of which is articulated relative to the frame for pivoting about the reference axis A5, and the other end of which is articulated with respect to a nut 231 for pivoting around an axis A8 parallel to the reference axis A5.

The nut 231 is itself mounted to move in translation along a restitution axis A9 perpendicular to the reference axis A5. As schematized on the figure 1 , the nut 231 is a threaded nut threaded with a threaded rod 232 which, aligned along the restitution axis A9, is rotated by a motor 233.

The link 230 further includes a force sensor 234 which interacts with a corresponding element of the latch 201. The pivot angle of the link 230 about the reference axis A5 is then linearly associated with the vertical translation, noted RES (for "restitution"), of the nut 231 along the axis of restitution A9.

When, duly sandwiched between the two shafts 202, 203, the ophthalmic lens 100 to be machined is brought into contact with one of the wheels of the train of mills 214, it is subject to an effective removal of material. The radial force applied by the grinding wheel on the ophthalmic lens can then be controlled precisely, thanks to the force sensor 234.

For the machining of the ophthalmic lens 20 according to a given contour, it suffices, therefore, firstly to move accordingly the nut 231 along the restitution axis A9, under the control of the motor 233, to control the restitution movement RES and, secondly, to jointly rotate the support shafts 202, 203 around the locking axis A7. The restitution movement of the rocker 201 and the rotational movement of the shafts 202, 203 are controlled in coordination by a control unit 251, duly programmed for this purpose, so that all the points of the contour of the ophthalmic lens 20 are successively brought back at the right radius.

The finisher 220 has a pivotal mobility around the wheel axis A6, called pivot mobility PIV. Specifically, the finisher 220 is provided with a toothed wheel (not shown) which meshes with a pinion equipping the shaft of an electric motor integral with the wheel carriage. This mobility allows it to move closer to or away from the ophthalmic lens 100. This electric motor is controlled in position and effort, so as to precisely control the force applied by the finishing tools on the ophthalmic lens 100.

The finisher 220 here embeds a stud 224 which supports the finishing tools and which is adapted to pivot about a finishing axis A10 orthogonal to the wheel axis A6. This mobility, referred to as FIN finishing mobility, makes it possible to orient the finishing tools with respect to the lens 100. This stud 224 more precisely supports here a disc-shaped creasing wheel 222 and a milling cutter 223, both driven in rotation. around the same axis perpendicular to said finishing axis A10.

When, duly sandwiched between the two shafts 202, 203, the ophthalmic lens 100 is brought into contact with the milling cutter 223 or the creasing wheel 222, it is also effectively removed from the material.

For this, the pivoting movements of the pad 224, pivoting of the finishing module 220, restitution of the latch 201 and rotation of the shafts 202, 203 are then controlled in coordination by the control unit 251.

• le moteur d'entraînement en translation du deuxième arbre 203 ;
• le moteur d'entraînement en rotation des deux arbres 202, 203 ;
• le moteur d'entraînement en translation du chariot porte-meules suivant la mobilité de transfert TRA ;
• le moteur 233 d'entraînement en translation de la noix 231 suivant la mobilité de restitution RES ;
• le moteur d'entraînement en rotation du module de finition 220 suivant la mobilité d'escamotage ESC ;
• le moteur d'entraînement en rotation du plot suivant la mobilité de finition FIN.

This control unit 251 is of electronic and / or computer and allows in particular to measure the radial force applied by the grinding wheels and finishing tools on the ophthalmic lens and to control:

• the drive motor in translation of the second shaft 203;
• the drive motor in rotation of the two shafts 202, 203;
• the drive motor in translation of the grinding carriage according to the transfer mobility TRA;
• the motor 233 driving in translation of the nut 231 according to the restitution mobility RES;
• the drive motor in rotation of the finishing module 220 according to ESC retraction mobility;
• the driving motor in rotation of the stud following FIN finish mobility.

The grinder 200 finally comprises a human-machine interface 252 which here comprises a display screen 253, a keyboard 254 and a mouse 255 adapted to communicate with the control unit 251. This interface HMI 252 allows the user to enter numeric values or to acquire various data in the form of electronic files, in order to control accordingly the grinder 200.

On the figure 2 there is shown a second embodiment of this grinder 200.

In this embodiment, the grinder 200 has an architecture identical to that of the grinder shown in FIG. figure 1 , with the difference that it has no finishing module 200.

Ophthalmic lens

On the Figures 3A and 3B , there is shown an ophthalmic lens 100 not yet cut off, of an indifferent type (convergent, divergent, non-corrective ...).

As the figure 3A , this ophthalmic lens 100 is a multilayer lens, in that it comprises a substrate 101 and a coating film 102 which covers the substrate 101.

The substrate 101 is made of a first material, for example mineral glass or organic glass, that is to say polymer.

It has two main faces 104, 106, including a rear face 104 intended to be turned towards the eye of the wearer, and a front face 106 opposite.

The coating film 102 is designed to present specific physico-chemical or optical properties, such as, for example, reflection, hydrophobicity, birefringence, polarization, absorption in certain wavelength ranges such as ultra-violet or certain wavelengths that are visible to give a particular color to the lenses, or anti-shock, anti-scratch, anti-reflective or anti-fouling properties.

The film 102 may be composed of a single layer, or several layers of coating having distinct properties.

Anyway, it is made of a material distinct from that of the substrate 101. This material is preferably plastic and transparent.

The film 102 also has two main faces 103, 107, including a rear face 107 intended to be turned towards the eye of the wearer, and an opposite front face 103.

This film 102 is fixed by its rear face 107 on the front face 106 of the substrate 101, for example by gluing.

The rear face 104 of the substrate 101 thus forms the rear face of the ophthalmic lens 100, while the front face 103 of the film 102 forms the front face of the ophthalmic lens 100. The wafers of the substrate 101 and the film 102 together form the wafer. 105 of the ophthalmic lens 100.

An average plane P1 is defined with respect to the ophthalmic lens 100 as being the plane passing through the peripheral edge of the rear face 104 of the ophthalmic lens 100. A central axis A1 is also defined as being the axis orthogonal to the mean plane P1, which passes through the center of the rear face 104 of the ophthalmic lens 100.

Finally, we define an orthonormal cylindrical coordinate system (O, p, θ, Z) attached to the ophthalmic lens 100, whose origin O corresponds to the intersection of the mean plane P1 and the central axis A1, and whose third dimension Z quantifies the height of the points of the lens relative to the average plane P1.

Eyeglass frame

This ophthalmic lens 100 is intended to be cut off so that its contour adapts to the shape of the eyeglass frame selected by the wearer.

There are three main categories of spectacle frames that can be selected by the wearer. Among these, there are rimmed eyeglass frames, semi-rimmed eyeglass frames (also called snap frames). arcades) and eyeglass frames without a circle (also called pierced frames).

The rimmed eyeglass frames conventionally comprise two surrounds which are intended to each accommodate a cut-away ophthalmic lens. These two surrounds are connected to each other by a trigger guard and each carry a branch. Each surround has a groove, commonly called a bezel, running along its inner face.

When the selected spectacle frame is a rimmed frame, the ophthalmic lens 100 must be cut off so as to present along its edge 105 a nesting rib 109 (see FIG. Figure 6A ), commonly called bevel, whose section here has a V-shaped. The bevel 109 thus formed on the edge 105 of the lens 100 is then adapted to fit into the bezel of the circled frame.

The semi-rimmed spectacle frames have two arches on the inner faces of which ribs extend, and two holding wires which are connected to the ends of the arches to form with them closed contours.

When the selected spectacle frame is a semi-rimmed frame, the ophthalmic lens 100 must be cut off so as to have a circumferential groove along its edge 105. The lens is then held in place in the eyeglass frame by fitting the upper portion of its wafer in the rib provided along the inner face of the corresponding arch, and engaging the holding wire in the groove.

Finally, the frames of glasses without circle have two branches and a trigger guard, but are devoid of entourage or arcade. These branches and this bridge are, on the other hand, provided with lugs adapted to be inserted into drill holes previously made in the ophthalmic lenses.

When the selected eyeglass frame is a semi-rimmed frame, the ophthalmic lens 100 must be cut off so as to present a wafer 105 whose section is straight, then pierced so that the bridge can be fixed therein and the corresponding branch of the spectacle frame.

Clipping process

As the figure 2 , before clipping, the lens Ophthalmic 100 has an initial contour Co of circular shape.

To adapt to the shape of the eyeglass frame chosen by the future wearer of glasses, the ophthalmic lens 100 must then be cut to a desired contour C3.

In the case shown in the figures, in which the selected spectacle frame is of the rimmed type, this desired contour C3 corresponds to the closed curve according to which it is desired to cut the apex of the bevel 109 of the ophthalmic lens 100 so that the latter fits perfectly into the corresponding environment of the eyeglass frame.

In the case where the eyeglass frame is semi-circled or without a circle, this desired contour would correspond to the closed curve according to which it would be desirable to cut the edge of the lens.

1. i) de lecture, au cours de laquelle on détermine sur la monture de lunettes ou sur l'un des verres de présentation de cette monture, la géométrie du contour que doit présenter la lentille ophtalmique 100 pour être assemblée à la monture de lunettes sélectionnée, et
2. ii) de centrage, au cours de laquelle on positionne et on oriente convenablement ce contour souhaité C3 dans le référentiel de la lentille de manière qu'une fois montée dans sa monture, cette lentille soit correctement positionnée par rapport à l'oeil correspondant du porteur afin qu'elle puisse exercer au mieux la fonction optique pour laquelle elle a été conçue.

Whatever the case may be, the geometry and the position of this desired contour C3 with respect to the ophthalmic lens are generally obtained in two operations called:

1. i) reading, during which is determined on the eyeglass frame or on one of the presentation glasses of this frame, the contour geometry that must present the ophthalmic lens 100 to be assembled to the selected spectacle frame, and
2. ii) of centering, during which this desired contour C3 is properly positioned and oriented in the reference frame of the lens so that once mounted in its mount, this lens is correctly positioned relative to the corresponding eye of the wearer so that it can best perform the optical function for which it was designed.

These two operations being well known to those skilled in the art, they will not be described here in more detail.

They make it possible to obtain a set of N triplets corresponding to the coordinates of a set of points P _i characterizing the shape of the desired contour, expressed in the reference frame of the ophthalmic lens.

The coordinates of each of these points P _i in the cylindrical coordinate system (O, p, θ, Z) are here denoted ρ _i , θ _i , Z _i , with i lying between 1 and N (N being for example equal to 360) .

In the following, for the sake of clarity, it will be considered that the desired contour C3 is centered on the central axis A1.

We will also focus more specifically on the case where the ophthalmic lens must be cut out so as to fit into a circle surrounded by a rimmed eyeglass frame.

Prior to the trimming of the ophthalmic lens 100, the latter is placed between the shafts 202, 203 of the grinder, such that its central axis A1 coincides with the axis of these shafts.

• une étape de pré-ébauche de la lentille ophtalmique 100 selon un contour préliminaire C1, C1' distinct du contour initial Co et du contour souhaité C3, et qui est déduit du contour souhaité C3 au moyen d'une opération d'élargissement de ce dernier,
• une étape d'ébauche de la lentille ophtalmique 100, suivant un contour C2, C3 confondu avec ou élargi par rapport au contour souhaité C3, en pilotant la meule d'ébauche 210 de telle manière qu'elle exerce un effort radial (par rapport à l'axe de blocage A7) sur la tranche 105 de lentille compris entre 0,1 et 5 Newton, et
• une étape de finition de la lentille ophtalmique 100.

According to the invention, the clipping of the ophthalmic lens 100 is then operated in at least three steps, including:

• a step of pre-roughing the ophthalmic lens 100 according to a preliminary outline C1, C1 'distinct from the initial contour Co and from the desired contour C3, which is deduced from the desired contour C3 by means of a widening operation of the latter ,
• a step of roughing the ophthalmic lens 100 along a contour C2, C3 coincides with or widened with respect to the desired contour C3, by driving the roughing wheel 210 in such a way that it exerts a radial force (with respect to the locking pin A7) on the lens wafer 105 between 0.1 and 5 Newton, and
• a finishing step of the ophthalmic lens 100.

Preferably, the clipping method also comprises a subsequent polishing step.

1 ^st embodiment

There are different ways to implement these four machining steps.

It will first be considered, in a first embodiment of this method, that the optician has a grinder 200 of the type of that shown in FIG. figure 1 .

It will also be considered that it has obtained, for example in the form of an electronic file, the geometrical characteristics of the ophthalmic lens, so that the control unit 251 has in memory the thickness at the center of the lens, the thickness of the film 102, and a mapping of the front faces 103 and rear 104 of the lens.

Then, during the pre-roughing step, the control unit 251 co-ordinates the pivoting movements of the pad 224, the pivoting of the finishing module 220, the restitution of the rocker 201 and the rotation of the shafts. 202, 203 so that the cutter 223 cuts through its free end the ophthalmic lens 100 over the entire thickness of the coating film 102 and only a part of the thickness of the substrate 101, according to the preliminary outline C1 (see FIG. Figures 4A and 4B ).

Here, the cutter is more particularly controlled to machine the substrate to a depth of 0.2 millimeters, which ensures a complete cutting of the film 102 over its entire thickness. The film 102 is thus cut into two distinct parts, including a central portion 102A and a peripheral portion 102B.

The preliminary contour C1 (which corresponds to the contour of the central portion 102A of the film 102) according to which the cutter 223 is driven is in turn deduced from a mathematical operation for widening the desired contour C3. Various mathematical enlargement operations can be used, such as, for example, a homothety operation with a ratio strictly greater than 1.

Here, the widening operation simply consists in defining the preliminary outline C1 by a plurality of points P _{1, i} whose coordinates are noted (ρ _{1, i} , θ _{1, i} , Z _{1, i} ) and are calculated from the following way:

k étant une constante prédéterminée comprise entre 0,1 et 0,9 millimètre, ici égale à 0,3 millimètre ; $${\mathrm{\theta }}_{\mathrm{1},\mathrm{i}}={\mathrm{\theta }}_{\mathrm{i}},$$

$${\mathrm{Z}}_{\mathrm{1},\mathrm{i}}={\mathrm{Z}}_{\mathrm{i}}\mathrm{.}$$

For all i between 1 and N, $${\mathrm{<figure-callout\; id="1"\; label="\rho "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\rho </figure-callout>}}_{\mathrm{1},\mathrm{i}}={\mathrm{\rho }}_{\mathrm{i}}+\mathrm{k},\mathrm{k\; being\; a\; predetermined\; constant\; between}\mathrm{0},\mathrm{1}\mathrm{and}$$

k being a predetermined constant of between 0.1 and 0.9 millimeters, here equal to 0.3 millimeters; $${\mathrm{<figure-callout\; id="1"\; label="\theta "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\theta </figure-callout>}}_{\mathrm{1},\mathrm{i}}={\mathrm{\theta }}_{\mathrm{i}},$$

$${\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="imgf0003.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{1},\mathrm{i}}={\mathrm{Z}}_{\mathrm{i}}\mathrm{.}$$

For the roughing of the ophthalmic lens 100, the roughing wheel 210 (whose particle size is equal to 300 micrometers) is used in order to return the initially circular contour Co of the lens to the shape of an intermediate contour C2 close to the desired contour C3 (see Figures 5A and 5B ).

This intermediate contour C2 is derived from a desired contour widening mathematical operation C3, which is such that the intermediate contour C2 is distinct and surrounds the preliminary outline C1.

Here again, the widening operation simply consists in defining the intermediate contour C2 by a plurality of points P _{2, i} whose coordinates are noted (ρ _{2, i} , θ _{2, i} , Z _{2, i} ) and are calculated as follows :

s étant une constante prédéterminée supérieur à k, ici égale à 0,6 millimètre ; $${\mathrm{\theta }}_{\mathrm{2},\mathrm{i}}={\mathrm{\theta }}_{\mathrm{i}},$$

$${\mathrm{Z}}_{\mathrm{2},\mathrm{i}}={\mathrm{Z}}_{\mathrm{i}}\mathrm{.}$$

For all i between 1 and N, $${\mathrm{\rho }}_{\mathrm{2},\mathrm{i}}={\mathrm{\rho }}_{\mathrm{i}}+\mathrm{s},\mathrm{s\; being\; a\; predetermined\; constant\; greater\; than\; k},\mathrm{here\; equal}$$

s being a predetermined constant greater than k, here equal at 0.6 millimeters; $${\mathrm{\theta }}_{\mathrm{2},\mathrm{i}}={\mathrm{\theta }}_{\mathrm{i}},$$

$${\mathrm{Z}}_{\mathrm{2},\mathrm{i}}={\mathrm{Z}}_{\mathrm{i}}\mathrm{.}$$

In practice, the roughing wheel 210 and the rocker 201 are then driven relative to each other so as to reduce, for each angular position of the lens around the locking axis A7, the radius of the lens at a length equal to the radius ρ _{2, i} , which is strictly greater than the radius ρ _{1, i} .

Thus, during the roughing step, the stresses applied by the roughing wheel 210 on the ophthalmic lens 100 propagate in the film 102 to the groove machined by the cutter and do not reach the central portion 102A. of the film 102, which then makes it possible to avoid any delamination of the central portion 102A of the film 102.

A single pass of the roughing wheel 210 around the ophthalmic lens 100 is here performed during this roughing step.

This roughing operation is carried out here in the presence of a lubricant, for example in the presence of water, so as to reduce the amount of dust generated by the machining of the lens, to prevent the roughing wheel 210 from clogs, and to limit the smells emitted.

For the finishing of the ophthalmic lens 100, the beveling grinding wheel 211 (whose particle size is equal to 60 micrometers) is used in order to bring the intermediate contour C2 of the ophthalmic lens to the desired contour C3, by showing the bevel 109 on the 105 field of the lens (see Figures 6A and 6B ). During this step, the grinder 200 is then controlled so that the radial force applied by the beveling grinding wheel 211 on the ophthalmic lens 100 remains invariably equal to a constant between 5 and 18 Newton, here equal to 10 Newton.

The combination of grain size and radial force used during this step then makes it possible to avoid any delamination of the ophthalmic lens 100.

In practice, the beveling grinding wheel 211 and the rocker 201 are then driven relative to each other so as to reduce, for each angular position of the lens around the locking axis A7, the radius of the apex of the bevel 109 of the lens to a length equal to the radius ρ _i .

Here, this finishing step is performed in three passes of the grinding wheel. bevel 211 around the ophthalmic lens 100, in the presence of water.

It is understood that this step makes it possible to erase the traces left by the pre-roughing operation, and in particular the groove machined by the cutter.

For polishing the field 105 of the ophthalmic lens 100, the polishing wheel 213 (whose shape is identical to that of the beveling wheel 211 and whose particle size is equal to 5 micrometers) is used. The grinder 200 is then controlled so that the radial force applied by the polishing wheel 213 on the ophthalmic lens 100 remains here invariably equal to a constant between 10 and 35 Newton, here equal to 20 Newton.

The combination of particle size and radial force used during this step here also makes it possible to avoid any delamination of the ophthalmic lens 100.

Here, this finishing step is performed in three passes of the beveling wheel 211 around the ophthalmic lens 100, in the presence of water.

Once polished, the lens 100 is then extracted from the grinder 200 by means of the translational mobility of the second shaft 203, and is then fitted into the corresponding surround of the selected spectacle frame.

2 ^nd embodiment

It will now be considered, in a second embodiment of the method according to the invention, that the optician has a grinder 200 of the type of that shown on the drawing. figure 2 .

It is then understood that it will not be able to implement the pre-roughing step in the same manner as mentioned above since this grinder is devoid of strawberries.

For the pre-roughing of the ophthalmic lens 100, the roughing wheel 210 (whose particle size is equal to 300 micrometers) is then used in order to bring the initially circular contour Co of the lens to a contour close to the desired contour C3. which is called preliminary outline C1 'and which is widened with respect to the desired contour C3 (see Figures 7A and 7B ). The grinder 200 is then controlled so that the radial force applied by the roughing wheel 210 on the ophthalmic lens 100 remains invariably equal to a value between 0.1 and 5 Newton, here equal to 2.5 Newton .

Here again, the operation of widening the desired contour C3 to obtain the preliminary contour C1 'consists in calculating the coordinates (ρ _{3, i} , θ _{3, i} , Z _i ) of a plurality of points P _{3, i} as follows:

t étant une constante prédéterminée comprise entre 1 et 2 millimètres, ici égale à 1,5 millimètre ; $${\mathrm{\theta }}_{\mathrm{3},\mathrm{i}}={\mathrm{\theta }}_{\mathrm{i}};$$

$${\mathrm{Z}}_{\mathrm{3},\mathrm{i}}={\mathrm{Z}}_{\mathrm{i}}\mathrm{.}$$

For all i between 1 and N, $${\mathrm{\rho }}_{\mathrm{3},\mathrm{i}}={\mathrm{\rho }}_{\mathrm{i}}+\mathrm{t},\mathrm{t\; being\; a\; predetermined\; constant\; between}\mathrm{1}\mathrm{and}\mathrm{2}$$

t being a predetermined constant of between 1 and 2 millimeters, here equal to 1.5 millimeters; $${\mathrm{\theta }}_{\mathrm{3},\mathrm{i}}={\mathrm{\theta }}_{\mathrm{i}};$$

$${\mathrm{Z}}_{\mathrm{3},\mathrm{i}}={\mathrm{Z}}_{\mathrm{i}}\mathrm{.}$$

In practice, the roughing wheel 210 and the rocker 201 are then driven relative to each other so as to reduce, for each angular position of the lens around the locking axis A7, the radius of the lens at a length equal to radius ρ _{3, i} .

Here, this pre-roughing step is performed in a single pass of the rough grinding wheel 210 around the ophthalmic lens 100, in the presence of water.

The combination of grain size and radial force used during this step makes it possible to best reduce the delamination phenomenon of the ophthalmic lens 100.

This combination, however, does not completely prevent the appearance of delamination along the preliminary outline C1 '. This is the reason why this pre-roughing step is not extended to the desired contour C3, and it stops at a distance from the latter so that the delamination does not reach the desired contour C3 .

The presence of water here also makes it possible to reduce the amount of dust generated by machining the lens, to prevent the roughing wheel 210 from becoming clogged, and to limit the odors emitted.

For the roughing of the ophthalmic lens 100, the blank wheel 210 (whose particle size is equal to 300 micrometers) is still used in order to bring the contour of the lens to the desired contour C3 (see FIG. Figures 8A and 8B ). The grinder 200 is then controlled so that the radial force applied by the roughing wheel 210 on the ophthalmic lens 100 remains invariably equal to a value between 0.1 and 5 Newton, here equal to 2.5 Newton .

In practice, the roughing wheel 210 and the rocker 201 are then driven relative to each other so as to reduce, for each angular position of the lens around the locking axis A7, the radius of the lens at a length equal to radius ρ _i .

Here, this roughing step is performed in a single pass of the roughing wheel 210 around the ophthalmic lens 100, in the absence of lubricant.

As seen during the pre-roughing step, the combination of grain size and radial force used during this step makes it possible to reduce the delamination phenomenon of the ophthalmic lens 100 at best. The absence of lubricant then allows to totally prevent the appearance of this phenomenon.

The quantity of dust generated and the odors emitted by the machining of the lens are then very small, since the quantity of material to be machined between the preliminary outline C1 'and the desired contour C3 is reduced.

The finishing and polishing steps are then performed in the same manner as in the first embodiment of the invention mentioned above.

The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind.

• une première opération d'usinage de la lentille selon le contour souhaité au moyen de la meule d'ébauche, en l'absence de lubrifiant (pour que la lentille présente la forme représentée sur la figure 8A), puis
• une seconde opération de rainage, consistant à pratiquer le long du champ de la lentille ophtalmique une rainure au moyen de la meulette de rainage embarquée sur le module de finition de la meuleuse.

In particular, in the case where the eyeglass frame is semi-circled and where the grinder is of the type of that shown in FIG. figure 1 , the finishing step will include:

• a first machining operation of the lens according to the desired contour by means of the roughing wheel, in the absence of lubricant (so that the lens has the shape shown on the drawing); figure 8A ) and then
• a second creasing operation, consisting in making a groove along the field of the ophthalmic lens by means of the creasing grinding wheel on the finisher of the grinder.

• une première opération d'usinage de la lentille selon le contour souhaité au moyen de la meule d'ébauche, en l'absence de lubrifiant (pour que la lentille présente la forme représentée sur la figure 8A), puis
• une seconde opération de perçage, consistant à pratiquer des trous de perçage au travers de la lentille, au moyen de la fraise, de manière à pouvoir y fixer les ergots des branches et du pontet de la monture de lunettes.

In the case where the spectacle frame is without a circle and the grinder is of the type shown on the figure 1 , the finishing step will include:

• a first machining operation of the lens according to the desired contour by means of the roughing wheel, in the absence of lubricant (so that the lens has the shape shown on the drawing); figure 8A ) and then
• a second drilling operation, consisting of drilling holes through the lens, by means of the cutter, so as to fix the lugs of the branches and the bridge of the spectacle frame.

• au cours des étapes de pré-ébauche et/ou d'ébauche à l'aide de la meule d'ébauche, on pourra ainsi prévoir que l'effort radial appliqué par cette meule sur la lentille ophtalmique varie entre 0,1 et 5 Newton ;
• au cours de l'étape de finition à l'aide de la meule de biseautage, on pourra prévoir que l'effort radial appliqué par cette meule sur la lentille ophtalmique varie entre 5 et 18 Newton ;
• au cours de l'étape de polissage à l'aide de la meule de polissage, on pourra prévoir que l'effort radial appliqué par cette meule sur la lentille ophtalmique varie entre 10 et 35 Newton.

According to another variant of the invention, one and / or the other of the pre-roughing, roughing, finishing and polishing steps can be carried out by vary the force applied by the grinding wheel on the ophthalmic lens in a reduced range of values. So :

• during the pre-roughing and / or roughing steps using the roughing wheel, it will thus be possible to provide that the radial force applied by this grinding wheel on the ophthalmic lens varies between 0.1 and 5 Newton. ;
• during the finishing step using the beveling wheel, it can be provided that the radial force applied by the wheel on the ophthalmic lens varies between 5 and 18 Newton;
• during the polishing step using the polishing wheel, it can be provided that the radial force applied by the wheel on the ophthalmic lens varies between 10 and 35 Newton.

Claims (11)

1. A process for trimming an ophthalmic lens (100) along a desired outline (C3), said ophthalmic lens (100) comprising a substrate (101) and at least one coating film (102) that is made of a different material to that of the substrate (101) and that covers a main face (106) of the substrate (101), comprising:

   - a step of pre-roughing the ophthalmic lens (100) by means of a preliminary tool (210; 223), along a preliminary outline (C1, C1') separate and deduced from said desired outline (C3);

   - a step of roughing the ophthalmic lens (100) by means of a roughing abrasive wheel (210), along a roughing outline (C2, C3) coincident with or enlarged relative to the desired outline (C3); and

   - a step of finishing the ophthalmic lens (100) by means of a finishing tool (212),

   characterized in that said preliminary outline (C1, C1') is enlarged relative to the desired outline (C3) and in that the roughing abrasive wheel (210) used has a grain size comprised between 0.1 and 0.5 mm and is steered relatively to said ophthalmic lens (100) so as to apply in said roughing step a radial force to the ophthalmic lens (100) comprised between 0.1 and 5 newtons.
2. The trimming process as claimed in the preceding claim, in which said finishing tool (212) used is an abrasive wheel having a grain size comprised between 0.02 and 0.1 mm, steered relatively to said ophthalmic lens (100) along the desired outline (C3), so as to apply in said finishing step a radial force to the ophthalmic lens (100) comprised between 5 and 18 newtons.
3. The trimming process as claimed in one of the preceding claims, in which, in said finishing step, said finishing tool (212) is steered relatively to said ophthalmic lens (100) in order to machine said ophthalmic lens (100) in at least three passes.
4. The trimming process as claimed in one of the preceding claims, in which, after said finishing step, a step of polishing said ophthalmic lens by means of a polishing tool (211; 213) is provided.
5. The trimming process as claimed in the preceding claim, in which said polishing tool (211; 213) used is an abrasive wheel having a grain size comprised between 0.0005 and 0.02 mm, steered relatively to said ophthalmic lens (100) so as to apply in said polishing step a radial force to the ophthalmic lens (100) comprised between 10 and 35 newtons.
6. The trimming process as claimed in one of the two preceding claims, in which, in said polishing step, said polishing tool (211; 213) is steered relatively to said ophthalmic lens (100) in order to machine said ophthalmic lens (100) in at least three passes.
7. The trimming process as claimed in one of claims 1 to 6, in which, said preliminary tool (223) being a cutter, said pre-roughing step consists in cutting the ophthalmic lens (100) right through the thickness of the coating film (102) and through only some of the thickness of the substrate (101), along the preliminary outline (C1).
8. The trimming process as claimed in the preceding claim, in which the roughing outline (C2) is enlarged relative to the preliminary outline (C1).
9. The trimming process as claimed in one of the two preceding claims, in which said roughing step is carried out in the presence of a lubricant.
10. The trimming process as claimed in one of claims 1 to 6, in which, said preliminary tool consisting of said roughing abrasive wheel, said pre-roughing step is carried out in the presence of a lubricant, along the preliminary outline (C1).
11. The trimming process as claimed in the preceding claim, in which said roughing step is carried out dry, in the absence of lubricant, along the desired outline (C3).

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