EP2015896B1 - Method for trimming a lens by cutting said lens - Google Patents

Description

TECHNICAL FIELD TO WHICH THE INVENTION REFERS

The present invention relates generally to the mounting of ophthalmic lenses of a pair of corrective eyeglasses on a frame and more particularly to a method and a device for trimming an ophthalmic lens of a pair of spectacles for mounting on a frame.

TECHNOLOGICAL BACKGROUND

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

• le centrage de chaque lentille qui consiste à positionner et orienter convenablement la lentille en regard de l'oeil du futur porteur, puis
• le détourage de chaque lentille qui consiste à usiner ou découper son contour à la forme souhaitée, compte tenu des paramètres de centrage définis.

This assembly is broken down into two main operations:

• the centering of each lens which consists of positioning and orienting the lens properly facing the eye of the future wearer, then
• the trimming of each lens which consists in machining or cutting its contour to the desired shape, taking into account the defined centering parameters.

In the context of the present invention, we are interested in the second operation called clipping. The trimming of a lens for mounting in or on the frame chosen by the future carrier is to change the contour of the lens to adapt to the frame and / or the desired lens shape. The trimming conventionally breaks down into two main operations, with an edging operation (often called "roughing") and a finishing operation adapted to the type of assembly. The edging consists in eliminating the superfluous peripheral part of the ophthalmic lens concerned, in order to reduce the contour, which is most often initially circular, to that whichever of the circle or surround of the spectacle frame concerned or simply to the desired aesthetic shape when the mount is of the type without circles. This edging operation is usually followed by a chamfering operation which consists of cutting or chamfering the two sharp edges of the edge of the overflow lens. The finishing operation depends on the assembly to be performed. When the assembly is of the type rimmed, this chamfering is accompanied by a beveling consisting in ensuring the formation of a rib usually called bevel. This bevel is intended to be engaged in a corresponding groove, commonly called bezel, formed in the circle or surround of the eyeglass frame in which the lens is to be mounted. When the frame is of the type without circles, the trimming of the lens and, possibly, the reduction of the sharp edges (chamfering) are followed by the appropriate drilling of the lenses to allow the fixation of the branches and the nasal bridge of the mount without circle. Finally, when the assembly is of the Nylon wire strapping type, the chamfering is accompanied by a grooving consisting of a groove in the edge of the lens, this groove being intended to receive the nylon wire of the frame for pressing the lens against the rigid part of the frame.

Most often, these operations are successively conducted on the same grinding machine, called grinder, equipped with a train of appropriate wheels. The drilling can be performed on the grinder which is then equipped with the corresponding tooling or on a separate drilling machine.

The edging and finishing operations can themselves be divided into several sub-operations, for example: roughing, finishing, polishing.

Usually, the trimming of the lens is performed on a numerically controlled grinder which has means for holding and rotating the lens and several wheels suitable for the various operations to be performed. The lens is first locked on the holding and driving means in a known configuration so that its optical reference is known and operations can be performed accurately with reference to this reference. It is understood that this blocking, accompanied by the storage of the optical reference system, makes it possible to define and physically materialize on the lens a geometric reference system in which the points and directions characteristic of the lens, necessary for the coherence of this with the position of the pupil, as well as the clipping values so that these points and characteristic directions are properly positioned in the frame.

Recently, a new type of lens has been introduced to the market for which maintenance and training difficulties have appeared. In order to limit the staining of the faces of the ophthalmic lenses, in particular for the anti-reflection lenses, it is in fact known to apply a specific coating, said to be of low surface energy, on one or both sides of the lens. These specific coatings have the particularity of not letting water adhere (hydrophobic coating) or greases (oleophobic coating).

However, such coatings make the surfaces of the lens, on which they are deposited, very slippery. The adhesive used for the placement of the glans then adheres weakly on the slippery surface of the lens. The same problem arises for the application of the locking noses which adhere weakly on the faces of the lens. However, during the trimming of the lens, the grinding wheel (s) exerts orthoradial (rubbing) forces on the edge of the lens during the removal of material, which generate a large torque on the lens, in particular when the roughing blank of the lens for which a large amount of material is ground. It follows that, during the trimming, and in particular the roughing blank, the lens slides relative to the holding means and rotational drive (the glans or locking nose) of the lens. The centering of the lens, in particular the axis (that is to say, the angular orientation of the lens in the reference frame of the grinder) is then modified and the resulting contour of the lens is different, compared to its optical reference, the desired final contour after clipping.

One solution is to reduce the amount of material removed at each grinding pass so as to reduce the torque exerted on the edge of the lens. However, this solution is unsatisfactory and in any case significantly increases cycle times.

For locking the lens with an acorn, it is also known to apply on the sliding coating an interface increasing the adhesion with the adhesive used for the installation of the glans. This solution also does not give full satisfaction and increases overall production rates.

A similar problem arises for the trimming of lenses whose thickness and material weakens them and exposes their coatings to a risk of cracking. It is understood that a lens having a reduced thickness and made of a deformable material such as polycarbonate deforms in bending during its clamping between the shafts of support and rotary drive of the trimming machine. This deformation of the lens can reach excessive proportions that cause cracking of the lens coatings, which is not acceptable and leads to the disposal of the lens. To avoid this phenomenon, it is necessary to reduce the deformation of the lens and, for this purpose, to reduce the intensity of the tightening force of the lens between the shafts of support and rotary drive of the trimming machine.

On the other hand, certain organic materials used in the composition of the lenses give off malodorous substances when machined. It is in particular medium organic materials and high indices, typically index greater than 1.6. However, it is easy to understand that the release of such odors is detrimental not only to the working conditions of the operators working on or in the vicinity of the clipping machines, but also to the satisfaction of the customers when the lens preparation workshop. adjoins the sales area or is simply visited.

The document DE 197 38 668 A1 discloses a method of trimming an optical lens comprising at least one edging operation in a desired contour, wherein the trimming operation comprises cutting out the lens material by means of a cutting tool.

OBJECT OF THE INVENTION

An object of the present invention is to provide a method clipping device allowing an efficient, accurate and reliable clipping of lenses having various properties exposing them or not to a risk of slipping or deformation during their machining.

Another object of the present invention is to provide a method of trimming capable of reducing the release of smelly or harmful substances when trimming certain lenses.

In order to achieve at least one of these objects, it is proposed according to the invention a method of trimming an optical lens comprising at least one edging operation according to a desired contour, in which process the edging operation comprises a cutting in full material of the lens by means of a cutting tool, this cutting having several cutting passes each made according to the desired contour with a reduced axial depth of depth, that is to say less than the thickness of the lens.

For a lens whose properties expose it to a risk of slipping, deformation or emission of uncomfortable substance during its machining, the cutting tool is selected and then makes it possible to restore the desired radius at each point of the contour of the lens by machining a small amount of material. Indeed, the amount of material machined by cutting corresponds to the length of the path followed by the cutting tool (mainly the desired contour of the lens) over a width corresponding to the diameter of the cutting tool. Unlike machining the edge of the lens, it is not necessary to machine all the material between the periphery, or gross outline, of the lens and the desired contour of the lens. In addition, the realization of the cutting in several passes of reduced depth of pass (lower for each pass to the thickness of the lens) allows to cut the lens by further limiting, at will, the amount of material removed each pass and therefore to reduce the torque exerted by the cutting tool on the lens.

• de limiter l'énergie globale transmise à la lentille par frottement et donc de limiter le glissement de la lentille par rapport à ses moyens de maintien, et/ou
• de réduire la quantité de substance malodorante dégagée au cours de l'opération d'usinage.

The small amount of material to be machined during cutting allows

• to limit the overall energy transmitted to the lens by friction and therefore to limit the sliding of the lens relative to its holding means, and / or
• to reduce the amount of smelly substance released during the machining operation.

For the sake of clarity, it is estimated that the volume of material machined by cutting in full material by means of a milling cutter with a diameter of 1.5 mm is approximately 10 times smaller than the volume of material machined by grinding by means of a grinding wheel. 155 mm in diameter.

For the machining of a lens with a sliding coating, this makes it possible to avoid with a normal tightening, the sliding of the lens during machining, thus allowing the precise trimming of the glasses with sliding coating. For the machining of a fragile lens, this makes it possible to limit, on the one hand, the clamping force of the lens during machining, without causing slippage, and, on the other hand, the exerted force by the cutting tool (which is smaller than the force exerted by a large diameter wheel), which prevents the lens from bending excessively. For a lens whose material contains smelly substances, reducing the overall volume of machined material reduces the amount of malodorous substances released by machining.

On the other hand, for a lens that does not tend to slip or that does not have a particular fragility or whose material contains little or no smelly substances that may be released during machining or whose desired final contour does not has no point of inflection, a tool of machining of the edge of the classic lens, of the grinding wheel type, can be selected so as to obtain more quickly the desired contour and to avoid a too fast wear of the cutting tool.

Thus, the selection of the working tool makes it possible to choose either the cutting tool (with which the risk of sliding of the given tightening lens and / or release of troublesome substances is limited during the trimming), or tool for machining the edge of the lens if the lens is neither slippery nor fragile and contains no smelly substances. The clipping of the lenses is then efficient, precise and reliable and it does not inconvenience the operator or his neighborhood.

The selection between the machining of the edge of the lens and the cutting in full material of the lens is performed according to criteria relating to one and / or the other of the risks incurred by the specific flushing operation to be performed. : sliding of the lens, cracking of the lens, release of uncomfortable substances.

According to another advantageous characteristic of the invention, the edging operation is a blank followed by a finishing performed on another tool for machining the edge of the grinding-type lens.

The cut-out roughing blank (often referred to as flanging) makes it possible to limit the slippage of the lens without significantly increasing the cycle times of the lens. And carrying out the finish of the trimming of the lens with a grinding wheel makes it possible to precisely machine the periphery of the lens that has been roughed out to obtain a desired contour of precise dimension. The amount of material to be machined, remaining between the blank outline and the desired contour, is low and therefore limits the friction and torque exerted by the finishing wheel on the lens. In addition, the radius of the lens is substantially reduced after roughing, which mechanically reduces the torque transmitted by the wheel to the lens.

According to another advantageous characteristic of the invention, the diameter of the cutting tool in full material of the lens is substantially less than the radius of the lens. The small diameter of the cutting tool makes it possible to cut the material in full material of the lens. The smaller the diameter of the cutting tool, the lower the frictional forces and the torque exerted on the lens. The sliding of the lens is then reduced and the trimming is more precise.

Prior to cutting, at least one face of the lens is palpated along the desired contour and, during at least one cutting pass, the cutting tool is driven axially according to the sensing data thus collected.

Advantageously, the steps of the axial depths of cutting passes are adjustable.

The adjustment of the axial depth pitch between two passes makes it possible to vary the quantity of material to be removed with each pass and thus to adapt the torque exerted by the cutting tool on the lens to limit the sliding of the lens.

According to another advantageous characteristic of the invention, the lens being driven in rotation with respect to the cutting tool around an axis of the lens, the direction of rotation is reversed between two cutting passes.

The reversal of the direction of rotation between two cutting passes makes it possible to reverse the direction of the torque exerted by the cutting tool on the lens and therefore the direction of sliding of the lens relative to the holding means. The sliding of the lens in one direction is then compensated by the sliding of the lens in the other direction, which limits the sliding resulting from the lens relative to the holding means.

According to another advantageous characteristic of the invention, the lens being driven in rotation with respect to the cutting tool around an axis of the lens, at least part of a cutting pass is made with a first direction of rotation and the complementary portion of said pass is made with a second direction of rotation opposite the first direction of rotation.

The reversal of the direction of rotation during the same cutting pass also limits the overall sliding of the lens during this pass.

According to another advantageous characteristic of the invention, the cutting of the lens comprises, in addition to the cutting of the lens along the desired contour, the cutting along the radial sectoring lines separating a plurality of peripheral sectors.

The cutting of the lens by making several parts of the drop makes it possible to limit the stresses exerted on the lens by the part of the lens situated between the periphery of the lens and the desired contour which has just been cut off and which remains attached to the lens. .

Advantageously, the cutting of the radial lines precedes the cutting according to the desired contour. In practice, prior to cutting, at least one face of the lens is palpated along the radial sectoring lines. During cutting, the cutting tool is driven axially according to the sensing data thus collected.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The following description with reference to the accompanying drawings of an embodiment, 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 en perspective d'un dispositif de détourage d'une lentille optique équipé d'un module de découpage ;
• la figure 2 est une vue de face d'une lentille optique débordée par découpage, dans un plan moyen de cette lentille.

In the accompanying drawings:

• the figure 1 is a perspective view of a device for trimming an optical lens equipped with a cutting module;
• the figure 2 is a front view of an optical lens overcut by cutting, in a medium plane of this lens.

Clipping device

To the figure 1 there is shown a trimming device 6 equipped with a cutting module 636 of an optical lens 100. The trimming device 6 is adapted to modify the contour of the ophthalmic lens to fit that of the frame or "circle" of a selected mount.

The trimming device comprises a flip-flop 611, which is freely pivotally mounted about a first axis A1, in practice a horizontal axis, on a frame.

For the immobilization and rotational drive of an ophthalmic lens to be machined, the shaping device is equipped with support means able to clamp and rotate an ophthalmic lens. These support means, or holding means, comprise two shafts and rotation drive 612, 613. These two shafts 612, 613 are aligned with each other along a second axis A2, called locking pin , parallel to the first axis A1. The two shafts 612, 613 are rotated so that they synchronous by a motor (not shown), via a common drive mechanism (not shown) embedded on the flip-flop 611. This common synchronous rotation drive mechanism is of the current type, known in itself.

Alternatively, it will also be possible to drive the two shafts by two separate motors synchronized mechanically or electronically.

The ROT rotation of the shafts 612, 613 can be controlled by the central electronic and computer system such as an integrated microcomputer or a set of dedicated integrated circuits.

Each of the shafts 612, 613 has a free end which faces the other and is equipped with a locking nose (not shown). These locking noses are not always fixed on the shafts 612, 613. They are in fact previously used by gripping means (not shown) to lock the lens before being transferred to the present clipping device 6 while remaining in position. contact with the transferred lens.

The shaft 613 is movable in translation along the blocking axis A2, facing the other shaft 612, to effect the compression in axial compression of the lens between the two locking noses. The shaft 613 is controlled for this axial translation by a drive motor via an actuating mechanism (not shown) controlled by the central electronic and computer system. The other shaft 612 is fixed in translation along the blocking axis A2.

In practice, the trimming device comprises a machining tool train 614 which firstly comprises a first machining tool 50 intended to produce a blank of the trimming of the edge of the lens 100. This first machining tool 50 is here a grinding wheel, but alternatively, one can provide to use a roughing cutter. The grain size of the roughing wheel is of the order of 150 to 500 microns.

It is also expected that the machining tool train 614 comprises a second machining tool 55 of the edge of the lens 100 distinct from the first machining tool 50 of the edge of the lens 100 intended to perform a finishing of the trimming of the This second machining tool 55 of the edge of the lens 100 is here a finishing wheel which comprises a beveling groove and grains whose size is of the order of 55 microns. The roughing and finishing wheels are cylindrical and have a diameter of the order of 155 mm. There is also provided a polishing wheel on this machining tool string 614 (or wheel train).

The machining tool train 614 is attached to a common shaft of axis A3 ensuring their rotational drive during the edging operation. This common shaft, which is not visible in the figures shown, is controlled in rotation by an electric motor 620 driven by the electronic and computer system.

The machining tool train 614 is also movable in translation along the axis A3 and is controlled in this translation by a drive motor. Concretely, the entire machining tool train 614, its shaft and its motor is carried by a carriage 621 which is itself mounted on slides 622 secured to the frame for sliding along the third axis A3. The translational movement of the wheel trolley 621 is called transfer and is noted TRA on the figure 1 . This transfer is controlled by a motorized drive mechanism (not shown), such as a screw and nut or rack system, controlled by the central electronic and computer system.

To allow a dynamic adjustment of the distance between the axis A3 of the grinding wheels 614 and the axis A2 of the lens during the edging, the pivoting capacity of the lever 611 about the axis A1 is used. This pivoting causes indeed a displacement, here substantially vertical, of the lens sandwiched between the shafts 612, 613 which brings the lens closer to or away from the wheels 614. This mobility, which makes it possible to restore the desired shape of edging and programmed in the electronic system and computer science, is called restitution and is noted RES in the figures. This RES restitution mobility is controlled by the central electronic and computer system.

For the machining of the ophthalmic lens according to a given contour, it is necessary to move accordingly a nut 617 along the fifth axis A5, under the control of the motor 619, to control the restitution movement and, on the other hand, to rotate together the support shafts 612, 613 about the second axis A2, in practice under the control of the motor that controls them. The transverse restitution movement RES of the flip-flop 611 and the rotational movement ROT of the shafts 612, 613 of the lens are controlled in coordination by an electronic and computer system, duly programmed for this purpose, so that all the points of the contour of the ophthalmic lens are successively brought back to the correct diameter.

The clipping device illustrated by the figure 1 further comprises a working module 625 which embeds chamfering and grooving grinders 630, 631 mounted on a common axis 632 and which is movable with a degree of mobility, in a direction substantially transverse to the axis A2 of the shafts 612, 613 maintaining the lens and the axis A5 of the restitution RES. This degree of mobility is called retraction and is noted ESC in the figures.

In this case, this retraction consists of a pivoting of the working module 625 around the axis A3. Specifically, the module 625 is carried by a lever 626 integral with a tubular sleeve 627 mounted on the carriage 621 to rotate about the axis A3. For the control of its pivoting, the sleeve 627 is provided, at its end opposite the lever 626, a toothed wheel 628 which meshes with a pinion (not visible in the figures) fitted to the shaft of an electric motor 629 integral with the trolley 621.

• la rotation de la lentille permettant de faire tourner la lentille autour de son axe de maintien, qui est globalement normal au plan général de la lentille,
• la restitution, consistant en une mobilité relative transversale de la lentille (c'est-à-dire dans le plan général de la lentille) par rapport aux meules, permettant de reproduire les différents rayons décrivant le contour de la forme souhaitée de la lentille,
• le transfert, consistant en une mobilité relative axiale de la lentille (c'est-à-dire perpendiculairement au plan général de la lentille) par rapport aux outils de travail, permettant de positionner en vis-à-vis la lentille et l'outil de travail choisi.
• l'escamotage, consistant en une mobilité relative transversale, suivant une direction distincte de celle de la restitution, du module de travail par rapport à la lentille, permettant de mettre en position d'utilisation et de ranger le module de finition.

In summary, it can be observed that the degrees of mobility available on such a clipping device are:

• the rotation of the lens making it possible to rotate the lens around its holding axis, which is generally normal to the general plane of the lens,
• restitution, consisting of a transverse relative mobility of the lens (that is to say in the general plane of the lens) with respect to the grinding wheels, making it possible to reproduce the different rays describing the contour of the desired shape of the lens,
• the transfer, consisting of an axial relative mobility of the lens (that is to say, perpendicular to the general plane of the lens) relative to the working tools, to position the vis-à-vis the lens and the tool selected work.
• the retraction, consisting of a transverse relative mobility, in a direction different from that of the restitution, of the working module relative to the lens, to put in position of use and store the finishing module.

The working module 625 is provided with a cutting module 636 equipped with a cutting tool 637 for roughing out the blanking of the lens 100 (see FIG. figure 1 ). Cutting 637 in full material consists of making penetrate all the diameter of the tool in the lens and move the tool in the lens along a cutting path to obtain the desired cut 110. The desired cutout 110 is an outline desired blank 110 of the same shape as the desired final contour but of larger size.

The cutting in full matter is distinguished from the machining of the edge of the lens in the sense that, according to the latter, only a small part of the diameter of the machining tool is engaged in the material of the edge of the lens and the whole material, located between the periphery (or edge) raw lens and the outline of draft to be machined.

The cutting tool is here a milling cutter, or cutter, axis A6 substantially parallel to the axis A2 of the shafts 612, 613 (that is to say to the axis of the lens). Alternatively, this cutting tool may consist of a grinding spindle, of smaller diameter than the grinding wheel or roughing cutter, or a laser beam.

For example, the cutting bit has a length of 12 mm and is made of tungsten carbide. In order to be able to cut the lens according to a blank in full material, the diameter of the cutting tool 637 is much smaller than the diameter of the lens. The diameter of the cutter 637 in full material of the lens 100 is preferably less than 4 mm and is typically between 1 and 2 mm. The diameter of the first machining tool or grinding wheel 50 is for example about 155 mm. Otherwise formulated, it can also be considered that the diameter of the cutter 637 is on average from 1 to 6% of the radius of the lens 100 (which is typically of the order of 70 mm).

The positioning of the cutting cutter is achieved by means of two pre-existing degrees of mobility which are the retraction ESC on the one hand and the transfer TRA on the other hand.

The trimming device 6 comprises an electronic processing unit 130, also called an electronic and computer control system, here consisting of an electronic card designed to coordinate the coordination of the different mobilities of the working tools and the clamping and driving means. rotation of the lens (the holding means) in accordance with the automated trimming method which will be explained later.

The electronic and computer system 130 comprises for example conventionally a motherboard, a microprocessor, a random access memory and a permanent mass memory. The mass memory contains a program for executing the clipping process which will be described later. This mass memory is preferably rewritable and is advantageously removable to allow its rapid replacement or programming on a remote computer via a standard standard interface. There is also provided means for storing the desired final contour 120 of the lens. These storage means may consist of a rewritable memory and an interface (for example a keyboard and a screen) for writing in this memory.

The electronic and computer system 130 finally comprises selection means for selecting either the first machining tool 50 of the edge of the lens 100, or the cutting tool 637 of the lens 100, for at least one given clipping operation . The selection means comprise means determining means for determining which of the first machining tool 50 of the edge of the lens 100 or of the cutting tool 637 of the lens 100 is to be selected. For this, the determination means comprise means for calculating the value of a parameter relating to the lens and / or to the machining and cutting tools and / or relative to the means for holding the lens 100. The means of determination also comprises means for comparing this value with a reference value and are designed to determine which of the first machining tool 50 of the edge or of the cutting tool 637 of the lens 100 is to be selected according to the result of the comparison.

Clipping process

The characteristics relating to the optical lens 100 to be trimmed such as the desired final contour 120 and the surface energy of the lens are stored in the electronic processing unit. The surface energy of the lens can be quantified by the wettability angle. By considering a drop of water present on the face of the lens concerned, this wettability angle is defined as the angle formed between the plane tangent to the surface of the drop of water at a point of contact with this surface. with the lens and the plane tangential to the surface of the lens face at said point of contact with the surface of the drop of water. The larger this angle is, the lower the surface energy and therefore the slippery the lens.

A selection is made between either the first machining tool 50 of the edge of the lens 100, or the cutting tool 637 in full material of the lens 100, to perform at least one given clipping operation. The given clipping operation for which said selection is made is in this case a roughing-out of the lens followed by a finishing performed on the second machining tool 55 of the edge of the lens 100.

This selection is made as a function of one or more parameters relating to the lens, such as the friction capacities of one or both faces held by the holding means, and / or the thickness and / or the material of the lens. . The selection can also be made as a function of parameters relating to the means for holding the lens, such as the frictional capacities of the holding means.

• une première catégorie de paramètres relatifs au caractère glissant ou non de la surface de la lentille,
• une seconde catégorie de paramètres relatifs à la rigidité de la lentille,
• une troisième catégorie de paramètres relatifs à la présence ou l'absence, dans la composition du matériau constitutif de la lentille, de substances malodorantes susceptibles d'être libérées lors de l'usinage,
• une quatrième catégorie de paramètres relatifs à la forme du contour souhaité de la lentille après débordage.

The tool selection can be performed according to four categories of parameters, combined or not:

• a first category of parameters relating to the slipperiness or otherwise of the surface of the lens,
• a second category of parameters relating to the rigidity of the lens,
• a third category of parameters relating to the presence or absence, in the composition of the constituent material of the lens, of malodorous substances that may be released during machining,
• a fourth category of parameters relating to the shape of the desired outline of the lens after edging.

The first category of parameters comprises, for example, the maximum value of the torque that can be applied to the lens 100 without it sliding relative to the holding means 612, 613. This admissible torque value depends both on the means of maintaining, the force with which they are applied against the lens and the surface of the lens. The comparison means compare this calculated maximum value with a reference value. This reference value is, for example, 2 Nm. If this calculated maximum value is greater than the reference value, the first machining tool 50 is selected to proceed with the blanking of the trimming and if this calculated maximum value is lower or equal to the reference value, the cutting tool 637 is selected to proceed with the blanking of the blank cutting clipping. In the latter case, it is said that the optical lens has a low surface energy.

Another parameter relating to the slipperiness or otherwise of the surface of the lens that can be taken into account for tool selection is the wettability angle. If the wettability angle is greater than 100 degrees, it is considered that the optical lens has a low surface energy and the cutting tool is selected.

For example, it can be assumed that the lens has a hydrophobic and / or oleophobic coating which gives each of its surfaces a slipperiness. It follows that the maximum value of the torque that can be applied to the lens 100 without it sliding relative to the holding means 612, 613 is here of the order of 0.3 Nm. in this case you have to select the cutting tool.

The selection of the machining tool can be further made depending on the rigidity of the lens. If the thickness and / or the material of the lens may cause deformation of the lens, the tightening of the lens on its support means is reduced and, to prevent slippage of the lens, the tool is selected. cutting to make the clipping blank. The selection can then be made according to a combination of the thickness and the material of the lens.

The selection of the machining tool can be done again according to the presence or absence, in the composition of the constituent material of the lens, of malodorous substances that may be released during machining. This criterion depends primarily on the nature of the constituent material (s) of the lens. For example, most lenses made of a material of medium or high index, that is to say typically of index greater than 1.6, currently contain substances releasing, during machining, smelly substances . In order to take this criterion into account, the electronic processing unit has or accesses a local or remote register whose registration relates to a material or a category of material and contains, in addition to an identifier of this material or the category of materials, an indicator of the presence, in the composition of the material or the category of materials, of smelly substances that may be released during machining.

Another criterion for selecting the machining tool is the desired shape of the final contour of the lens. Indeed, if this shape has one or more portions of concave shape, that is to say that the projection of this contour in a mean plane of the lens has one or more points of inflection, this shape will probably not be obtained by means of a machining tool of the periphery of the conventional lens, such as a grinding wheel or a cutter, the diameter of which is too large to respect the points of inflection.

In any case, if the lens is detected by the electronic processing unit as slippery or fragile, or if the lens material contains smelly substances, or if the shape of the desired contour of the lens has one or more several concave portions, in application of the criteria mentioned above, the processing unit proposes to the operator, via an appropriate interface such as a screen associated with a keyboard or other, to select the cutter to realize the roughing out the lens. As a variant, the electronic processing unit can also operate this tool selection and the corresponding overflow mode automatically, without resorting to a dialogue with the operator.

As explained above, this mode of edging by cutting in full material reduces the risk of sliding of the lens relative to the means of its maintenance and / or the amount of smelly substances released. It also allows the lens to be unfolded in a contour of complex shape, such as a shape having one or more concave-shaped portions with points of inflection, which can not be formed by a conventional grinding wheel or cutter working around the periphery of the lens. .

During cutting, the electronic processing system 130 appropriately co-ordinates the transfer mobilities TRA of the working module 625 carrying the cutting tool 637, restitution RES of the tightening and rotation shafts 612, 613, d ESC retraction of the working module 625 and ROT rotation of the lens to obtain the mobilities of the cutting tool with respect to the lens necessary to achieve the cutting of the lens.

According to a first embodiment; in order to proceed to cutting in full material, the cutting bit, is rotated about its axis A6 and positioned along an axis parallel to the lens so as to enter the material of the lens by a transverse displacement. The cutter 637 is also positioned axially so that, during the transverse displacement, it passes through the lens on both sides of its face. The cutter 637 is then moved transversely to the axis of the lens 100 to obtain the desired blank outline 110. The rough outline 110 has the shape of the desired final outline 120 with a slightly larger dimension.

In a variant that is not shown, the blank outline 110 and the final outline 120 have one or more concave-shaped portions, that is to say the projection of this contour in an average plane of the lens (as illustrated by FIG. figure 2 ) presents (unlike the example illustrated by the figure 2 ) one or more inflection points. As we saw previously, the cutting tool in full matter is then selected or, at least, proposed.

As shown on the figure 2 , the blank cutting of the lens comprises cutting following radial sectoring lines 105, 106, 107, 108 separating a plurality of peripheral sectors of the lens into several parts.

The cut out peripheral sectors of the lens are drop portions 101, 102, 103, 104 which are discarded and the remaining central portion of the lens held by the holding means 612, 613 has the desired blank outline 110. Each falling part is obtained by an input displacement of the cutting tool 637 substantially along a radius of the lens 100 and directed towards the lens center 100, up to the blank outline 110 to be produced, and then by a moving along a portion of the blank contour 110 to be made, and finally by an output displacement of the cutting tool 637 substantially along another radius of the lens 100 and directed in the opposite direction to the lens center 100 until to the disengagement of the cutting tool of the lens.

As a variant, provision can be made for the cutting of the radial sectoring lines to precede the cutting along the desired contour 110.

Alternatively, to further reduce the risk of sliding of the lens (when the lens is fragile or slippery) can also be provided to cut the lens 100 by performing several cutting passes. In this case, prior to cutting, the two faces of the lens are palpated, on the one hand, according to the desired contour and, on the other hand, along the radial sectoring lines. The blank of the lens is then cut into several successive axial passes. The lens is first cut along the radial sectoring lines, each radial sectoring line being subjected to several passes each having a reduced axial depth of pass. Then, after the lens has been cut along the radial sectoring lines, the lens is cut according to the desired lens contour. This cut is subjected to several passes each having a reduced axial depth of pass. The axial depths of the cutting passes are adjustable and the depths of the pass may typically be greater for cutting along the radial sectoring lines than for cutting according to the desired final contour. The axial depth of passage of each pass is of course less than the maximum thickness of the lens along the desired contour. The depths and the number of the different passes can advantageously be defined according to the geometric data of lens thickness provided by the probing of the two faces of the lens according to the final contour.

During each cutting pass, the cutting tool 637 is driven axially, that is to say in transfer, according to the previously collected probing data. The control of the transfer for the division along the radial sectoring lines is carried out according to the probing data along these sectorization lines. The control of the transfer for the cutting according to the desired final contour is carried out according to the probing along this desired contour.

The direction of rotation of the lens 100 (which constitutes the machining advance) is reversed between two cutting passes. It is thus avoided that, in the event that slight sliding in rotation of the lens relative to the means of its maintenance occur, these slips do not accumulate in the same direction.

It can even be provided that part of a cutting pass is made by rotating the lens relative to the cutting tool in a first direction of rotation and that the complementary portion of the pass is performed with a second direction of rotation opposite the first direction of rotation.

Whatever the embodiment envisaged, it is possible, instead of initially entering the lens through the peripheral edge of the lens, to preposition the cutting tool by piercing the lens, by means of its transfer mobility with respect to the lens. the lens, over a portion or all of its thickness and then move transversely the cutting tool according to the desired cut during rotation of the lens.

Finishing of trimming by grinding

The finish is then finished by grinding on the finishing wheel 55. The bevelling groove makes it possible, if necessary, to make a bevel on the edge of the lens. The transfer mobilities TRA of the finishing wheel and the restitution mobilities RES and rotation ROT of the lens are controlled so as to reach the desired final contour 120 by removing the small quantity of material situated between the contour of blank 110 obtained by cutting in full material and the desired final contour 120. The grain of the finishing wheel 55 being thin, the desired final contour 120 is reached accurately.

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.

In a variant, it is possible to use an apparatus which has neither a tool for machining the edge of the lens nor selection means, but which comprises a cutting tool made of the full material of the lens. This apparatus is then used to cut optically coated optical lenses coated with a low surface energy treatment.

Alternatively, the cutter, can be steerable. The orientation can be achieved for example by rotation about an axis transverse to the axis of the cutting bit. This cutting bit can also be used for drilling the lens. It can also be replaced by a drill used, on the one hand, for drilling the lens and, on the other hand, in the manner of a cutting cutter to perform the cutting function of the lens as described herein. -before.

Other finishing steps, after finishing the trimming on the finishing wheel, can be envisaged such as grooving, drilling and chamfering. Alternatively the roughing blank wheel can be replaced by a water jet cutting device.

Regarding the selection means, it can be provided, in a variant, that these are only partly automated. We can thus predict that selection means comprise a program and an interface with the operator designed to provide a choice of working tool to perform the roughing blank. The operator then only has to choose manually, by means of the communication interface, the cutting tool or the machining tool that must be used for the roughing blank.

Claims (10)

1. A method of shaping an optical lens (100), the method including at least one operation of edging along a desired outline, which includes cutting through the material of the lens (100) by means of a cutting-out tool (637), the method being characterized in that the cutting out comprises a plurality of cutting-out passes, each performed along the desired outline as a pass that is axially shallow.
2. A shaping method according to the preceding claim, applied to lenses having at least one surface provided with a slippery coating, the lens being held while being cut out at least via said surface.
3. A shaping method according to the preceding claim, applied to lenses constituted of material containing smelly substances that will be released during machining.
4. A shaping method according to any preceding claim, in which the diameter of the cutting-out tool (637) for cutting through the material of the lens (100) is substantially smaller than the radius of the lens (100).
5. A shaping method according to any preceding claim, in which, prior to cutting out, at least one face of the lens is felt around the desired outline, and in which, during at least one cutting-out pass, the cutting-out tool (637) is controlled axially as a function of the feeler data as obtained in this way.
6. A shaping method according to any preceding claim, in which, for the lens (100) being turned relative to the cutting-out tool (637) about an axis of the lens, the turning direction is reversed between two cutting-out passes.
7. A shaping method according to any preceding claim, in which, for the lens (100) being turned relative to the cutting-out tool (637) about an axis of the lens (100), at least a portion of a cutting-out pass is performed while turning in a first direction, and the remaining portion of said pass is performed while turning in a second direction opposite to the first.
8. A shaping method according to any preceding claim, in which cutting the lens (100) comprises, in addition to cutting out the lens around the desired outline, cutting out along radial sector lines that separate a plurality of peripheral sectors (101, 102, 103, 104).
9. A shaping method according to the preceding claim, in which the radial lines are cut out prior to cutting out along the desired outline.
10. A shaping method according to claim 8 or claim 9 as dependent on claim 5, in which, prior to cutting out, at least one face of the lens is felt along the radial sector lines, and in which, during cutting, the cutting-out tool (637) is controlled axially as a function of the feeler data as obtained thereby.

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