EP2380701B1 - Konturfräsverfahren einer ophtalmischen Linse für Brillen - Google Patents

Description

The present invention relates to a method of trimming an ophthalmic lens to a desired contour, for mounting in a spectacle frame.

It relates more specifically to the determination of a locking position of the lens on a locking medium on which the lens is maintained during its trimming.

This method is particularly suitable for trimming ophthalmic lenses whose contour has a complex shape, including negative curvature zones.

BACKGROUND

The preparation of an ophthalmic lens for mounting on a circled, semi-rimless or no-circle (or "pierced") spectacle frame is achieved by acquiring the desired contour according to which the ophthalmic lens is to be cut off to fit to the shape of this eyeglass frame. This contour is positioned on the lens according to the optical reference of the lens so that the latter is, when worn, properly positioned in front of the eyes of the wearer. The lens is then cut off following this desired contour.

This operation is for example described in the document US2004 / 097168 .

When trimming, it may happen that some parts of the desired contour can not be machined without the tool holder or tool conflicting with another element of the machining device, for example the locking bracket of the lens in the machining device. This is typically so when the relevant portion of the desired contour is located near the lens support and / or when the tool diameter is substantially smaller than that of the tool holder.

Ophthalmic lenses intended to be cut in contours of low heights and large widths, usually rectangular contours, often generate this type of interference.

The same is true of ophthalmic lenses intended to be cut off according to contours of complex shapes including, for example, curved zones towards the center of the lens, called zones of negative curvature. These negative curvature zones generally correspond to decorative details of the contour of the lens and need to be machined by a tool of diameter less than the diameter of the grinding wheel commonly used to cut the lens. We for example, uses a milling tool of a few millimeters in diameter.

OBJECT OF THE INVENTION

In order to solve this problem, it is proposed according to the invention a trimming method according to claim 1.

The internal cutting limit is defined around the blocking support and corresponds to the zone around this support in which the machining tool in question can not access, because of the risk of interference between the tool (or the door tool) and the locking bracket.

Thus, thanks to the invention, it is possible to detect, even before the setting of the blocking support on the lens (generally at the optical center or at the boxing center of the lens), the risks of interference between the tool of machining and blocking bracket.

If such a risk is detected, it is then possible to modify the position at which the locking support must be fixed on the lens, so that during the machining of the lens, the tool considered has not to access the interior of the inner cut limit.

Other advantageous and non-limiting features of the process according to the invention are defined in claims 2 and following.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The description which follows, with reference to the accompanying drawings, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved.

• la figure 1 est une vue schématique en perspective d'un dispositif de détourage utilisé pour mettre en oeuvre le procédé selon l'invention ;
• la figure 2 est une vue schématique en coupe d'une lentille ophtalmique maintenue par un support de lentille et prête à être détourée par une fraise ;
• la figure 3 est une vue schématique d'un contour souhaité suivant lequel il convient de détourer la lentille ophtalmique ; et
• la figure 4 est un organigramme illustrant l'algorithme de mise en oeuvre du procédé selon l'invention.

In the accompanying drawings:

• the figure 1 is a schematic perspective view of a trimming device used to implement the method according to the invention;
• the figure 2 is a diagrammatic sectional view of an ophthalmic lens held by a lens holder and ready to be cut by a cutter;
• the figure 3 is a schematic view of a desired contour according to which the ophthalmic lens should be trimmed; and
• the figure 4 is a flowchart illustrating the algorithm for implementing the method according to the invention.

In the following description, the term envelope will be used to designate the surface that delimits a volume considered. The envelope of an object in motion will in particular designate the surface in which is circumscribed all the positions of the object when it moves according to the movement considered.

The technical part of the optician's profession is to mount a pair of ophthalmic lenses on a frame selected by the future wearer of the pair of glasses.

• l'acquisition d'un contour souhaité selon lequel devra être détourée chaque lentille ophtalmique ;
• le centrage du contour souhaité dans le référentiel de la lentille correspondante, qui consiste à déterminer la position qu'occupera chaque lentille sur la monture afin d'être convenablement centrée en regard de la pupille de l'oeil du porteur de manière à ce qu'elle exerce convenablement la fonction optique pour laquelle elle a été conçue ;
• le blocage de chaque lentille qui consiste à fixer sur chaque lentille un accessoire de blocage permettant au dispositif d'usinage de saisir la lentille et de mémoriser la position du référentiel de cette lentille ; et
• le détourage de chaque lentille qui consiste à l'usiner ou à la découper selon le contour souhaité, compte tenu des paramètres de centrage définis.

This assembly is broken down into four main operations:

• acquiring a desired contour according to which each ophthalmic lens must be cut off;
• the centering of the desired contour in the reference frame of the corresponding lens, which consists in determining the position that each lens will occupy on the frame so as to be properly centered facing the pupil of the wearer's eye so that it properly performs the optical function for which it was designed;
• blocking each lens which consists in fixing on each lens a locking accessory enabling the machining device to grasp the lens and to memorize the position of the reference frame of this lens; and
• the trimming of each lens which consists of machining or cutting according to the desired contour, taking into account the defined centering parameters.

This clipping operation is generally performed in three successive stages of roughing, finishing and finishing. The roughing step consists of bringing the initial contour of the lens back to a near or identical contour of the desired contour. The finishing operation consists of beveling the edge of the lens if it is intended to be mounted on a circled spectacle frame, or to groove the edge of the lens if it is intended to be mounted on a frame of semi-rimmed glasses. The finishing step consists of polishing and chamfering as necessary the sharp edges of the edge of the lens. The clipping method according to the invention applies here to all of these steps.

The ophthalmic lens

On the figure 2 an ophthalmic lens 10 has two front 14 and rear 15 optical faces, and an initially circular wafer 16 which should be returned to the shape of the desired contour, so that the ophthalmic lens can then be attached to the selected eyeglass frame.

On the figure 3 there is shown a particular example of desired contour 11. Of course, the method according to the present invention applies to any type of contour, regular or not. However, it applies particularly advantageously to ophthalmic lenses to be cut on desired contours of irregular shapes, and to assemble with frames of pierced type spectacles (In which the branches and the bridge of the frame have means for fixing to drilling holes made in the lenses).

On the figure 3 , the desired contour 11, considered in projection in a general mean plane of the ophthalmic lens not yet cut-off, comprises a regular lower sector and an irregular upper sector AD. This upper sector is formed of several complex regions delimited respectively by the points A, B, C and D.

Each complex region A-B, B-C, C-D has one or more zones of negative curvature. These areas of negative curvature are areas in which the desired contour 11 is concave.

On this figure 3 the boxing frame of this desired contour 11, which corresponds to the rectangle in which the desired contour 11 is inscribed and whose two sides define the horizon axis of this contour, has also been represented. The center of this rectangle, called boxing center, then forms the origin of the benchmark of the reference of the ophthalmic lens.

In addition, the average plane of the ophthalmic lens is defined as the plane which contains the circular rear edge of the lens which has not yet been cut off. The desired contour 11 then corresponds to the projection in this mean plane of the three-dimensional contour along which the lens must be cut off.

The machining device

To cut off this ophthalmic lens 10, it is placed in a machining device 200 known in itself, such as that described in the document W02008 / 043910 .

• une bascule 204 qui est montée pivotante autour d'un axe de bascule A1, en pratique un axe horizontal, sur un châssis 203, et qui comporte des moyens de support 210 de la lentille ophtalmique 10 permettant une mise en rotation motorisée de cette lentille autour d'un axe de blocage A2 sensiblement perpendiculaire au plan moyen de la lentille et parallèle à l'axe A1 ;
• un train de meules de grand diamètre, comportant notamment une grande meule 220, montées sur le châssis 203 pour tourner, par entraînement motorisé, autour d'un axe de meule A3 parallèle à l'axe de bascule A1 ;
• un module de finition 235 qui embarque plusieurs outils de finition, dont une meulette 231 et une fraise 230 montées rotatives autour d'axes A5, A6 parallèles aux axes de bascule A1, de blocage A2 et de meule A3, et qui est monté à pivotement autour de l'axe de meule A3 pour la commande de la position de ses outils de finition par rapport à la lentille ; et
• un dispositif de calcul et de pilotage 100, permettant en particulier de piloter les différents degrés de liberté du dispositif de meulage 200, qui comporte ici un clavier 101 et un écran 102 adapté à l'affichage d'une interface graphique.

Such a device, as illustrated on the figures 1 and 2 , is a grinder that features:

• a rocker 204 which is pivotally mounted about a rocker axis A1, in practice a horizontal axis, on a frame 203, and which comprises means 210 for supporting the ophthalmic lens 10 allowing motorized rotation of this lens around a blocking pin A2 substantially perpendicular to the average plane of the lens and parallel to the axis A1;
• a set of large-diameter grinding wheels, including in particular a large grinding wheel 220, mounted on the frame 203 to rotate, by motorized drive, around a grinding wheel axis A3 parallel to the flip-flop axis A1;
• a finishing module 235 which embeds several finishing tools, including a grinder 231 and a milling cutter 230 rotatably mounted about axes A5, A6 parallel to the rocking axes A1, blocking A2 and grinding wheel A3, and which is pivotally mounted about the grinding wheel axis A3 for controlling the position of its finishing tools relative to the lens; and
• a calculation and control device 100, in particular enabling the different degrees of freedom of the grinding device 200 to be controlled, which here comprises a keyboard 101 and a screen 102 suitable for displaying a graphic interface.

Typically, this computing and control device 100 is integrated in the electronic and / or computer system of the grinder 200.

The support means 210 of the ophthalmic lens 10 here more specifically comprise two shafts and rotation drive 211 of the ophthalmic lens 10 to be cut. These two shafts 211 are aligned with each other along the blocking axis A2.

Each of these shafts 211 has a free end which faces the other, one of which is equipped with a locking nose 214 of the ophthalmic lens 10 and the other of which is equipped with a receiving means 213. a locking accessory 215 of the lens (prepositioned on the lens at the time of its blocking).

This locking accessory is conventionally positioned on the ophthalmic lens at a given point and with a given orientation, which makes it possible to locate the position of the reference frame of the ophthalmic lens relative to the reference frame of the frame 203 of the machining device 200. Conventionally, this blocking accessory 215 comprises a body arranged to cooperate with the corresponding shaft 211 of the grinder 200, and an adhesive patch arranged to stick to the front optical face 14 of the ophthalmic lens.

As shown in figure 2 during the machining of the ophthalmic lens 10, a central portion of its front and rear optical faces 14, 15 are covered by the nose and the locking accessory 214, 215. It is then possible to define around the axis of blocking A2 a surface, called inaccessibility envelope B1, in which it is not possible to machine the ophthalmic lens 10. Since the nose and locking accessory 214, 215 here have the same contour of known transverse dimension (typically, a circular contour of known or rectangular diameter of known sides), the inaccessibility envelope B1 is defined as the cylinder of revolution about the locking pin A2, which has a diameter equal to that of the nose and locking accessory 214 215 (or slightly greater than this diameter, given the possible deformations of these nose and locking accessory).

A first of the two shafts 211 is fixed in translation along the blocking axis A2. The second of the two shafts 211 is conversely mobile in translation along the blocking axis A2 to achieve the compression in axial compression of the ophthalmic lens 10 between the two shafts.

The large grinding wheel 220 is a conventional grinding wheel, which comprises a cutting surface defining, in its rotation about the axis A3, a cutting envelope of revolution about this axis A3, having a diameter greater than or equal to 80 millimeters, for example equal to 155 millimeters.

The grinder 231 is a wheel of smaller diameter than the grinding wheel 220, which comprises a cutting surface defining, in its rotation about the axis A5, a revolution cutting envelope about this axis A5, preferably having a smaller diameter. at 80 millimeters, for example equal to 11 millimeters.

The cutter 230 comprises a cutting edge defining, in its rotation about the axis A6, a cutting envelope of revolution about this axis A6, which has a diameter less than 10 millimeters and preferably less than 5 millimeters, for example equal at 1.4 millimeters.

These three tools 220, 230, 231 are carried by tool holders.

The large grinding wheel 220 and the grinder 231 are respectively carried by an axis and a mandrel. They have diameters much greater than those of this axis and this mandrel. During machining of the lens, these tool holders are therefore not likely to interfere with the 211 locking shafts of the ophthalmic lens.

As shown in figure 2 , the cutter 230 is however supported by a mandrel 240, itself supported by the finisher 235, whose dimensions (transverse to the axis A6) are greater than those of the cutter. More specifically here, the cutter 230 is positioned in such a way on the finishing module 235 that the latter may interfere with the locking shafts 211 of the ophthalmic lens.

It is therefore possible to define around this finishing module 235 a surface, called the security envelope B2, in which are included the mandrel 240 and the finisher 235.

In comparison, the safety shells of the large grinding wheel 220 and the grinder 231 are formed by their cutting shells since their tool holders are not likely to interfere with the shafts 211 for blocking the ophthalmic lens.

It is then understood that, during the machining of the ophthalmic lens, the security envelope B2 must never intersect the envelope of inaccessibility B1 in order to avoid, on the one hand, any risk of machining of the nose and locking accessory 214, 215, and, on the other hand, any risk of interference between the tool in question (or the door tool) and the locking shafts 211 of the ophthalmic lens.

Given these two envelopes B1, B2, it is possible to define a limit around the blocking axis A2, referred to as the inside cutting limit 12, 13 (see FIG. figure 3 ), which delimits the volume in which the tool in question can not come to machine the wafer 16 of the ophthalmic lens 10. Otherwise formulated, this internal cutting limit 12, 13 corresponds to the envelope in which the cutting surface moves. of the tool considered during its movement around the locking shafts 211 of the lens in a permitted functional displacement range.

Since the security envelopes B2 of the tools are different, it is understood that each tool is associated with an inner cutting limit 12, 13 which is specific to it.

As represented on the figure 3 , that is to say in projection on the mean plane of the ophthalmic lens 10, the internal cutting limits 12 associated with the grinding wheel 220 and the grinding wheel 231 are combined. They have cylindrical shapes of revolution around the blocking axis A2, of diameter equal to that of the inaccessibility envelope B1.

The internal cutting limit 13 associated with the cutter 230 also has a cylindrical shape of revolution about the blocking axis A2, but it has a diameter greater than that of the inaccessibility envelope B1.

Since these internal cutting limits 12, 13 are of constant shapes, it is possible to store their characteristics in a register of the calculation and control device 100, so that at the start of the grinder 200, the calculation and control device 100 can acquire these characteristics.

More generally, in the case where the lens can be blocked with locking accessories of different shapes (larger or smaller depending on the sliding nature of the lens), each inner cutting limit will then not only associated with a tool, but also to a type of locking accessory.

Tool selection method

The desired contour 11 of the ophthalmic lens 10 to be cut out comprising, as shown in FIG. figure 3 , AB complex regions, BC, CD, the clipping of the lens can be achieved using the only grinding wheel 220. It is indeed in the case where the diameter of the grinding wheel 220 is too large to respect the geometry of the desired contour 11 in its negative curvature areas having a too pronounced concavity.

The trimming could then be performed using the single mill 231. However, the use of a small diameter tool is more expensive than that of a large diameter tool. Several tools will therefore be used here for machining the ophthalmic lens 10 according to the desired contour 11.

Thus, before starting the machining of said lens, the calculation and control device 100 determines which regions of the desired contour 11 of the ophthalmic lens 20 will be machined by which tool 220, 230, 231, depending on the geometrical characteristics of the lens. this desired contour 11 and as a function of the diameters of the cutting envelopes of the tools 220, 230, 231.

For this, the computing and control device 100 begins by acquiring, in one way or another, the desired contour 11.

This desired contour 11 can for example be obtained by simply searching, in a register of a database, a record which is associated with the reference of the selected eyeglass frame and which stores the desired contour. A regularly updated database register is however necessary.

More conventionally, this desired contour 11 can be obtained by capturing a digital snapshot of the presentation eyeglass frame that the optician has at its disposal, and by processing this snapshot to determine the two-dimensional coordinates of a set of points characterizing the shape. slices of the lenses of this presentation frame.

The desired contour 11 can also be obtained by palpating the edge of the lenses of this presentation frame with a conventional reader, such as that described in the patent. EP 0 750 172 or marketed by Essilor International under the trademark Kappa or under the trademark Kappa CT. At the end of this probing operation, the calculation and control device 100 will thus have acquired the two-dimensional coordinates of a plurality of points characterizing the geometry of the desired contour 11.

Whatever the method of acquisition of the desired contour used, the calculation and control device 100 then executes a desired contour analysis algorithm 11 in order to determine a first region of the desired contour 11 comprising the points of this contour for which the use of the grinding wheel 220 is possible to cut the ophthalmic lens without damaging the shape of the desired contour.

More precisely, it is a matter of isolating the points of the desired contour 11 at which the machining of the lens with the large grinding wheel 220 to reach the desired lens radius dimension at the point in question is achieved without cutting other parts of the lens 10 located within the desired contour 11.

As shown in figure 3 for each point of the set of points modeling the desired contour 11, the algorithm calculates for this purpose the position of the cutting envelope 30 of the grinding wheel 220 when it is tangent to the contour at this point. This position corresponds to the position of the grinding wheel 220 when it is in position to machine the lens 10 according to the desired contour 11 at this point. The algorithm then searches for the points of the desired contour 11 that are inside this first cutting envelope, that is to say located on the side of the arc corresponding to the wheel 220, if exists. These points correspond to the additional points trimmed by the grinding wheel 220 when it is machining the lens 10 at the considered point of the desired contour 11. The algorithm can thus determine the complex sectors of the contour in which the use of the grinding wheel 220 is not necessary. possible. In the case of the desired contour 11 shown on the figure 3 this sector corresponds to the upper sector of the desired contour 11, between the points A and D.

The algorithm then checks whether the whole of this upper sector can be machined using the grinder 231.

For this, the algorithm proceeds in the same manner as with the grinding wheel 220, this time considering only the points of the upper sector of the desired contour 11. The algorithm can thus determine the complex regions of the desired contour 11 in which the use of the grinder 231 is not possible. In the case of the desired contour 11 shown on the figure 3 these complex regions are between the points A and B on the one hand, and C and D on the other hand.

The algorithm finally verifies whether these two complex regions AB and CD can be machined using the mill 230. If this is not the case, it displays an error message on the screen 102, meaning that optician that the trimming of the ophthalmic lens is not possible.

• le secteur inférieur de la lentille ophtalmique 10 doit être détouré à l'aide de la meule 220,
• les régions complexes A-B et C-D doivent être détourées à l'aide de la fraise 231, et
• la région complexe B-C doit être détourée à l'aide de la meulette 230.

On the contrary, if the two complex regions AB and CD can be machined using the cutter 230, the calculation and control device 100 memorizes that:

• the lower sector of the ophthalmic lens 10 must be cut off using the grinding wheel 220,
• the complex regions AB and CD must be cut with the aid of the strawberry 231, and
• the complex region BC must be cut off using the millstone 230.

Determination of the blocking point

It is then necessary to determine whether, by blocking the lens at its boxing center P ₁ , it is possible to cut the ophthalmic lens 10 according to its desired contour 11 using the tools provided, and, if such is not the case, to shift the blocking point of the lens relative to the boxing center P ₁ , until finding a position, called final blocking P _F , in which the clipping is possible.

The algorithm for carrying out this method of searching for a final blocking position P _F is decomposed into successive steps illustrated on FIG. figure 4 .

During a first step E1, the computing and control device 100 resets a counter. The value N stored in this counter is then equal to 1.

During a second step E2, the computing and control device 100 looks in the database register to which it has access, on the one hand, the internal cutting limit 12 associated with the grinding wheel 220 and on the other hand. grinder 231, and, on the other hand, the internal cutting limit 13 associated with the cutter 230.

During a third step E3 detailed above, the calculation and control device 100 acquires the two-dimensional coordinates of the points characterizing the desired contour 11, then calculates the position of the boxing center P ₁ .

During a fourth step E4, the calculation and control device 100 determines whether at least a portion of the desired contour 11 intended to be machined using the grinding wheel 220 or the grinder 231 has a non-zero intersection with the inner cutting limit 12 and if at least a portion of the desired contour 11 intended to be machined using the cutter 230 has a non-zero intersection with the inner cutting limit 13.

The calculation and control device 100 superimposes for this purpose the internal cutting limits 12, 13 and the desired contour 11, so that the centers of the circles representative of these inner cutting limits 12, 13 are merged with the boxing center. P ₁ . It simulates the blocking of the ophthalmic lens 10 at its boxing center P ₁ .

Then he solves two systems of equations to find possible points of intersection between the desired contour 11 and these circles. In these two systems of equations, the first equation will correspond to that of the desired contour 11. In the first system, however, the second equation corresponds to the equation of the circle representative of the inner cutting limit 12, while in the second system it corresponds to the equation of the circle representative of the inner cutting limit 13.

On the figure 3 it can be seen that a part Q ₁₁ - Q ₁₂ of the complex portion AB intended to be cut by the cutter 230 is situated inside the internal cutting limit 13. It can also be seen that part Q ₂₁ - Q ₂₂ of the complex portion BC intended to be cut by the grinder 231 is located within the inner limit of section 12. It is therefore understood that by placing the locking accessory 215 on the ophthalmic lens 10 in such a way that it is centered on the boxing center P ₁ , it will appear during the machining of the lens a problem of interference between the shafts 211 of locking the lens and the tools or tool holders of the grinder 200.

The calculation and control device 100 therefore suspends the blocking of the ophthalmic lens 10 to find a new blocking position P _N modified with respect to the boxing center P ₁ , in the hope that in this position, the desired contour 11 does not present more intersection with inner cutting boundaries 12, 13.

During a fifth step E5, the computing and control device 100 calculates an offset vector V1 which will make it possible to shift the blocking point in a position likely to solve the aforementioned interference problems.

The calculation and control device 100 locates, for each intersection zone Q ₁₁ - Q ₁₂ , Q ₂₁ - Q ₂₂ , the segment of radius S 1, S 2 of the circle representative of the inner cutting limit 12, 13 associated with this intersection zone, which is located between the desired contour 11 and this circle, and which has the greatest length.

He then determines the coordinates of two shift vectors V2, V3 which are oriented opposite these radius segments S1, S2 and which have lengths identical to those of these radius segments S1, S2. It thus deduces the coordinates of the offset vector V1, which is equal to the sum of the two shift vectors V2, V3.

During a sixth step E6, the calculation and control device 100 then proceeds to shift the position of the blocking point from the boxing center P ₁ to the new blocking point P _N , according to this offset vector V1.

This offset of the locking point thus makes it possible to ensure that no intersection remains between the zones considered Q ₁₁ - Q ₁₂ , Q ₂₁ - Q ₂₂ of the desired contour 11 and the inner cutting limits 12, 13.

Of course, it will also be possible to provide a predetermined safety margin, which will consist in shifting the locking point according to a vector of identical direction but slightly higher standard than the offset vector V1.

Alternatively, the offset vector can be calculated differently. It may for example be provided that it has a length identical to that of the vector V1, but that it is oriented otherwise. Its orientation can for example be determined by calculating the direction of the average normal to the desired contour at the intersection areas Q ₁₁ - Q ₁₂ , Q ₂₁ - Q ₂₂ , that is to say the direction of the combination of two normal vectors, on average, to the two intersection zones.

At this point, as it appears on the figure 3 However, it may appear a new interference zone Q ₁₁ - Q ₁₂ that should be detected before blocking the ophthalmic lens.

For this purpose, during a seventh and eighth step E7, E8, the calculation and control device 100 increments the value N stored in the counter by one unit, and then verifies that the new value N is less than a predetermined threshold N ₀ .

The purpose of these two steps is to control that the iterative method of determining a locking point of the lens does not rotate indefinitely in a loop. Here, past one hundred tests (N ₀ = 100), it will be estimated that no locking position of the lens is suitable and that the grinder 200 is therefore not able to cut the ophthalmic lens 100 according to the desired contour 11.

Here, since the value stored in the counter N is equal to 2, the calculation and control device 100 again implements the steps E4 to E8 mentioned above, to determine whether the contouring of the ophthalmic lens according to the desired contour 11, as positioned in its new locking position P _N , and with the tools 220, 230, 231 provided, is possible.

As shown on the figure 3 This clipping is again not possible since it appears a region of intersection Q ₁₁ - Q _'12 between the desired contour 11 and the inner edge 12 cutting associated with the large wheel 220.

Consequently, the calculation and control device 100 repeats the aforementioned steps E4 to E8.

If, after one hundred iterations, no final blocking position P _F is found, the calculation and control device 100 displays on the screen 102 an error message indicating to the optician that the trimming of the ophthalmic lens to using the grinder 200 is not possible. It also displays an image of the desired contour 11 with, in red, the part (s) of this contour which is likely to pose problems of interference. In this case, the optician can possibly intervene by modifying on the screen the displayed shape of the desired contour in order to enlarge it at the level of the red zone. Thus, the computing and control device 100 can again try to find a final locking point P _F which is suitable.

On the contrary, if the calculation and control device 100 finds a final blocking position P _F in which the areas of the desired contour 11 to be cut with the grinding wheel 220 or the grinder 231 do not intersect the inner limit 12 and in which the areas AB and CD of the desired contour 11 to be cut using the cutter 230 does not intersect the internal cutting limit 13, the optician proceeds to block the ophthalmic lens 10 at the level of this final blocking position P _F. Otherwise formulated, the position of the desired contour 11 in the reference frame of the ophthalmic lens 10 being determined, the locking accessory 215 is bonded to the front optical face 14 of the ophthalmic lens 10 at the final locking point P _F identified by ratio to desired contour 11.

The ophthalmic lens 10 equipped with its locking accessory 215 is then locked between the two shafts 211 of the grinder 200 to be cut along the desired contour 11.

At the end of these various operations, the ophthalmic lens 10 cut away according to the desired contour 11 is therefore able to be attached to the selected spectacle frame if it is of the rimmed or semi-rimmed type.

On the other hand, if the spectacle frame is of the type without a circle, it is necessary to make drilling holes or notches in the lens so that the bridge and the corresponding branch of the spectacle frame can be hooked to it.

The drilling holes are generally made in the lens in full material, by a drill bit provided on the grinder 200, along a determined axis. The position of this axis is marked with respect to the desired contour 11 and its orientation relative to the lens is chosen so that it is orthogonal to the front face of the lens at the piercing point.

Notches form nicks in the edge of the lens Ophthalmic 10. As a result, they can be made both by the milling cutter 230 and by the drill bit. They could even be made directly during the trimming of the lens, which however is not the subject of this presentation. On the contrary, here, these notches and drilling holes will be made after trimming the ophthalmic lens, even though the lens is still locked between the shafts 211 of the grinder 200.

1. i) acquérir les positions des bords des crans ou des trous de perçage par rapport au contour souhaité 11.
2. ii) contrôler que les bords des crans ou des trous de perçage, lorsque le contour souhaité est repositionné à la position de blocage finale P_F, ne présente pas d'intersection avec la limite intérieure de coupe associée au foret de perçage (ou à la fraise), et, si une intersection est détectée,
3. iii) déterminer une nouvelle position de blocage finale P_F', décalée par rapport à la position de blocage finale P_F initialement trouvée et qui est telle que, d'une part, le contour souhaité 11, repositionné à la nouvelle position de blocage finale P_F', ne présente pas d'intersection avec la limite intérieure de coupe associée au foret de perçage (ou à la fraise), et que, d'autre part, les bords des crans ou trous de perçage ne présentent pas d'intersection avec cette limite intérieure de coupe.

To prevent any interference between the tool holder of the cutter or the drill bit and the shafts 211 during drilling or notching of the lens, advantageously, the calculation and control device 100 then implements additional steps consisting in :

1. i) acquiring the positions of the edges of the notches or the drilling holes relative to the desired contour 11.
2. ii) checking that the edges of the notches or drill holes, when the desired contour is repositioned to the final locking position P _F , does not intersect with the inner cutting limit associated with the drill bit (or the strawberry), and, if an intersection is detected,
3. iii) determining a new final locking position P _F ', offset from the final locking position P _F initially found and which is such that, on the one hand, the desired contour 11, repositioned to the new final locking position P _F ', does not intersect with the internal cutting limit associated with the drill bit (or mill), and that, on the other hand, the edges of the notches or drill holes do not intersect with this inner cut limit.

Thus, the new final locking position P _F 'will be chosen so as to avoid any interference between the tool holder and the shafts 211 as well during the trimming as during the drilling or the notching of the ophthalmic lens.

In step i), the positions of the edges of the notches or the drilling holes are acquired in projection in the middle plane of the ophthalmic lens (shown in FIG. figure 3 ). It will be noted here that in this projection, the edges of the front and rear mouths of each piercing hole will generally be slightly offset, since the drilling axis is generally not parallel to the axis of the projection used. The edge considered will then preferentially correspond to the overall contour which envelops the projections of the front and rear mouths of the piercing hole in the middle plane of the ophthalmic lens.

Steps ii) and iii) will be implemented following a method identical to that described supra, of shifting the final locking point P _F to find a new final locking point P _F 'which satisfies the conditions required.

At the end of these various operations, it may happen that the ophthalmic lens is subjected to other machining operations by the grinder 200. By way of example, it may be provided an engraving operation of areas of interest specific to the lens, such as the periphery of its front face, by means of the free end of the cutter 230 or a diamond tip provided for this purpose.

In such a case, and in the same way as for the drilling holes, it will then be possible, when calculating the position of the final blocking point P _F , to carry out additional steps to check that no interference between the Tool holder of the milling cutter and the locking shafts 211 of the lens will not appear when engraving this lens.

The present invention is not limited to the embodiment described and shown, but the art can apply any variant within his mind.

In particular, it can be provided that the method for determining the final locking position P _F is not iterative, but instead consists in considering a plurality of alternative locking positions, for example in the number of one hundred, then in determining for each of these alternative blocking positions whether the areas of the desired contour 11 to be cut with the aid of the grinding wheel 220 or the grinder 231 intersect the inside cutting limit 12 and whether the areas AB and CD of the desired contour 11 to detour using the cutter 230 intersects the inner cutting limit 13.

Then, if none of the alternative blocking positions satisfies these two conditions, the calculation and control device displays an error message on the screen.

On the other hand, if only one of the alternative locking positions satisfies these two conditions, this locking position is selected as being the final locking position at which the locking accessory will be fixed on the lens.

Finally, if at least two of the alternative blocking positions satisfy these two conditions, the blocking position selected as the final blocking position is the one which, among these alternative blocking positions, is the closest to the boxing center.

We understand that the translation performed by each point of the lens when the locking shafts 211 of the lens rotate one degree is not the same when the lens is blocked at the boxing center or remote thereof. Therefore, selecting the blocking point closest to the boxing center makes it possible to maintain lens machining conditions close to conventional machining conditions.

Alternatively, the selected blocking point could be the one closest to the center of gravity (or "barycenter") of the desired contour 11 (or, alternatively, the center of the circular initial contour of the ophthalmic lens).

It is understood that during trimming, the more the machined point is away from the locking point of the lens, the greater the locking torque between the lens and the locking accessory is important. Therefore, selecting the locking point closest to the center of gravity of the desired contour 11 reduces the risk of sliding of the lens relative to its locking accessory, and hence the risk of loss of the reference frame of the lens ophthalmic. In this way, it is not necessary to use a locking device of large diameter, adapted to prevent such slippage.

According to another variant, it can be provided that the internal cutting limits are acquired not in the form of three-dimensional surface envelopes, but on the contrary in the form of two-dimensional linear envelopes, for example in the form of simple circles such as those represented on the figure 3 .

In another variant, it will be possible to provide that all the calculations exposed are made, not by the calculation and control device 100 of the grinder 200, but on the contrary by the calculation unit of the centering device and the blocking the lens used by the optician.

In this variant, before the lens is machined to the desired contour 11, the calculation unit will then transmit to the grinder 200 the final locking position P _F , so that the grinder 200 takes into account the information that the ophthalmic lens 10 is blocked not at the boxing center P ₁ , but at another point distinct from this boxing center.

According to another embodiment of the method according to the invention, provision may be made for the ophthalmic lens to be cut off using a machining tool having a given axis of rotation and a variable diameter along this axis of rotation. . In particular, provision may be made to use a cutter having a first end portion held by the tool holder, a substantially cylindrical central portion intended to cut the ophthalmic lens, and a second free end portion, of greater diameter than that of the central portion, designed to chamfer the ophthalmic lens.

In this embodiment, it is understood that the free end portion of the cutter may then interfere with the locking shafts 211 during operations of trimming the lens by the central portion of the cutter. The two parts of the cutter then behave in the manner of two separate tools that would be attached to one another. We can then define for this single strawberry two internal cutting limits, each associated with the two parts of this strawberry.

According to another embodiment of the invention, it may be provided that the initial blocking point of the ophthalmic lens is not the boxing center of the desired contour, but rather the optical center of the ophthalmic lens or its center of gravity.

Claims (14)

1. A method of shaping an ophthalmic lens (10) for eyeglasses to have a desired outline (11) by means of a machining device (200) including a blocking support (210) for the ophthalmic lens (10) and at least one first machining tool (220) that is rotatable about a first axis (A3) that is movable relative to the blocking support (210), the method comprising the steps of:

   a) obtaining an inner cutting limit (12) of said first machining tool (220), defined in a frame of reference of the machining device (200);

   b) defining an initial blocking position (P₁) for the ophthalmic lens (10) and its desired outline (11) on the blocking support (210) in the frame of reference of the machining device (200);

   c) calculating whether at least a fraction of the desired outline (11), when positioned using the initial blocking position (P₁), presents a non-zero intersection (Q₂₁ - Q₂₂) with said inner cutting limit (12);

   d) defining as a final blocking position (P_F), either the initial blocking position (P₁) without change if the intersection calculated in step c) is zero, or else, a blocking position that is modified relative to the initial blocking position (P₁) so that the desired outline (11) as repositioned to the modified blocking position does not present any intersection with the inner cutting limit (12) associated with the first tool;

   e) blocking the ophthalmic lens (10) on the blocking support (210) in the final blocking position (P_F); and

   f) shaping the ophthalmic lens (10) with the desired outline (11) using at least the first machining tool (220) .
2. A method according to claim 1, wherein:

   • the machining device (200) has a plurality of machining tools (220, 230, 231), and at least two distinct machining tools (220, 230) are selected, including said first tool (220) and at least one other tool (230) rotatable about an axis (A6) that is movable relative to the blocking support (210), each tool (220, 230) being for machining a portion associated therewith of the desired outline (11);

   • in step a), obtaining, for each machining tool (220, 230), an inner cutting limit (12, 13) defined in a frame of reference of the machining device (200), the inner cutting limit (12) of the first tool (220) being distinct from the inner cutting limit (13) of the other tool;

   • in step c), calculating, for each machining tool (220, 230), whether the portion that is associated therewith of the desired outline (11), as positioned using the initial blocking position (P₁), presents any non-zero intersection (Q₁₁ - Q₁₂₁ Q₂₁ - Q₂₂) with the inner cutting limit (12, 13) associated with the machining tool (220, 230) under consideration;

   • in step d), defining as the final blocking position (P_F), either the unchanged initial blocking position (P₁) if the intersections calculated in step c) are zero, or else a blocking position that is modified relative to the initial blocking position (P₁) so that the desired outline (11) as repositioned using the modified blocking position does not present any intersection with the inner cutting limits (12, 13) that are associated respectively with the different machining tools (220, 230); and

   • in step f), shaping the lens with the desired outline (11) using the different machining tools (220, 230), a first portion of the desired outline (11) being shaped with said first machining tool (220), and the other portion of the desired outline (11) being shaped with said other machining tool (230).
3. A method according to claim 1 or claim 2, wherein, if the intersection (Q₁₁ - Q₁₂, Q₂₁. - Q₂₂) calculated in step c) is non-zero, step d) comprises the following substeps:

   d1) determining an alternative blocking position (P_N) different from the initial blocking position (P₁);

   d2) calculating, for each machining tool (220, 230) and for said alternative blocking position (P_N), whether at least a portion of the desired outline (11) as repositioned using said alternative blocking position (P_N) presents a non-zero intersection (Q'₁₁ - Q'₁₂) with the inner cutting limit (12, 13) associated with the machining tool (220, 230) under consideration; and

   d3) repeating steps d1) and d2) so long as step d2) gives a non-zero intersection result (Q'₁₁ - Q'₁₂).
4. A method according to claim 1 or claim 2, wherein, if the intersection (Q₁₁ - Q₁₂, Q₂₁ - Q₂₂) calculated in step c) is non-zero, step d) comprises the following substeps:

   d'1) determining a plurality of alternative blocking positions different from the initial blocking position (P₁) ;

   d'2) calculating, for each tool and for each alternative blocking position, whether at least a portion of the desired outline as positioned using the alternative blocking position under consideration presents a non-zero intersection with the inner cutting limit associated with the tool under consideration; and

   d'3) selecting the modified blocking position from said alternative blocking position.
5. A method according to claim 4, wherein, in step d), the modified blocking position is defined from amongst the alternative blocking positions as the blocking position of the lens on the blocking support that is the closest to the initial blocking position.
6. A method according to claim 4, wherein, in step d), the modified blocking position is defined from amongst the alternative blocking positions as the blocking position of the lens on the blocking support that is the closest to the position of the center of gravity of the desired outline (11).
7. A method according to any preceding claim, wherein, in step c), the radius segment (S1, S2) is calculated around the initial blocking position (P₁) that is situated inside said intersection (Q₁₁ - Q₁₂₁ Q₂₁ - Q₂₂) and that presents the greatest length, and wherein, in step d), the modified blocking position (P_N) is the result of shifting the position of the initial blocking position (P₁) in the direction of said radius segment (S1, S2).
8. A method according to claim 7, wherein said shift is through a distance equal to the length of said radius segment.
9. A method according to claim 7 or claim 8, wherein, for step c) giving as its result at least two non-zero intersections (Q₁₁ - Q₁₂' Q₂₁ - Q₂₂) between the desired outline (11) and each inner cutting limit (12, 13), there is calculated, for each intersection (Q₁₁ - Q₁₂ Q₂₁ - Q₂₂), the radius segment (S1, S2) about the initial blocking position (P₁) that is situated inside the intersection (Q₁₁ - Q₁₂, Q₂₁ - Q₂₂) under consideration and that presents the greatest length, and wherein, in step d), the modified blocking position (P_N) results from at least one combination of shifts of the initial blocking position (P₁) along the directions of said radius segments (S1, S2) respectively associated with said at least two intersections (Q₁₁ - Q₁₂, Q₂₁ - Q₂₂)
10. A method according to any preceding claim applied to an ophthalmic lens for being drilled or notched by means of a second machining tool in order to be mounted on a rimless frame, the method comprising:

    • a step of obtaining an inner cutting limit of said second machining tool defined in the frame of reference of the machining device;

    • a step of acquiring the positions of the edges of the notches or of the drill holes in a frame of reference associated with the desired outline;

    • between steps d) and e), a calculation step of detecting whether, when the desired outline is repositioned at the final blocking position, the edges of the notches or drill holes present a non-zero intersection with the inner cutting limit associated with said second tool; and

    • if an intersection is detected, a step of determining a new final blocking position distinct from said final blocking position and such that firstly the desired outline, when repositioned using the new final blocking position, does not present any intersection with the inner cutting limit associated with the second tool, and secondly the edges of the notches or drill holes do not present any intersection with said inner cutting limit.
11. A method according to any preceding claim, wherein the inner cutting limit (12, 13) of each machining tool (220, 230) depends on the shape of the machining tool (220, 230) and/or of a tool carrier (240) carrying said machining tool (220, 230), and also on the shape of the blocking support (210) of the ophthalmic lens (10).
12. A method according to any preceding claim, wherein the inner cutting limit (12, 13) of each machining tool (220, 230) depends on the angle formed between the axis of rotation (A6) of the tool under consideration and a blocking axis (A2) about which the ophthalmic lens (10) turns relative to the machining tools (220, 230) while it is being shaped in step f).
13. A method according to any preceding claim, wherein the inner cutting limit (12, 13) of each machining tool (220, 230) is obtained from a registry in which each record contains an identifier of a machining tool (220, 230) and an inner cutting limit (12, 13) associated with said machining tool (220, 230).
14. A method according to any preceding claim, wherein steps a) to d) are implemented by a calculation device distinct from said machining device (200), and includes, between steps d) and f), a step of transmitting the final blocking position (P_F) from the calculation device to the machining device (200).

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