EP1883499A1

EP1883499A1 - Method and device for working on the periphery of an ophthalmic lens pertaining to a pair of glasses

Info

Publication number: EP1883499A1
Application number: EP06726123A
Authority: EP
Inventors: Michel Nauche; Gaël MAZOYER
Original assignee: Essilor International Compagnie Generale dOptique SA
Current assignee: EssilorLuxottica SA
Priority date: 2005-04-29
Filing date: 2006-03-22
Publication date: 2008-02-06
Anticipated expiration: 2026-03-22
Also published as: FR2885063B1; US7803035B2; DE602006015047D1; WO2006117443A1; FR2885063A1; EP1883499B1; US20090305614A1

Abstract

The invention relates to a method for working on the periphery of an ophthalmic lens (L) with an edge (C), whereby the edge of the lens is ground using a first grinder (31) which is mounted in such a way that it can rotate about a rotational axis (A4). According to the invention, during the edge grinding, the first grinder, in addition to rotating about the rotational axis, has a tilting mobility with two degrees of freedom about two separate pivoting directions which are essentially transversal to the rotational axis.

Description

METHOD AND DEVICE FOR WORKING THE PERIPHERY OF A LENS

OPHTHALMIC GLASSES

TECHNICAL FIELD TO WHICH THE INVENTION RELATES 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 tool for working the periphery of an ophthalmic lens. a pair of spectacles, as well as a device for trimming an ophthalmic lens incorporating such a working tool.

The invention finds a particularly advantageous application for a recovery of edging of the edge of a lens after a first machining.

BACKGROUND TECHNOLOGY 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 includes the edging for the shaping of the periphery of the lens and, depending on whether the mounting is of the type circled (the frame then comprising circles having an inner bezel forming a groove), pierced (with a frame without circles with occasional pinching through a fixing hole formed in the lens) or grooved (with a frame having on the one hand two semicircles having a bevel or a bezel rimmed frames and on the other hand a nylon thread completing the strapping the lenses over the rest of their periphery), beveling or proper creasing of the lens and / or drilling. In the case of a pierced type mounting, it is also carried out after the trimming at the piercing of the lens at the points of attachment of the nasal bridge, on the trimming device or on a separate apparatus.

The edging, (or trimming itself) consists in eliminating the superfluous peripheral part of the ophthalmic lens concerned, to bring back the contour, which is usually initially circular, to that desired of the circle or surrounding of the spectacle frame concerned or simply to the desired aesthetic shape when the frame 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.

When the assembly is of the type circled, this chamfering is accompanied or preceded by a beveling consisting in ensuring the formation of a rib usually called bevel, usually of triangular cross section, on the edge of the ophthalmic lens. 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 mount is of the type without a circle, the trimming of the lens and, possibly, the reduction of sharp edges (chamfering) are followed by the appropriate drilling of the lenses to allow the attachment of the branches and the nose bridge of the frame without a circle. Finally, when the assembly is of the Nylon-wire strapping type, the chamfering is accompanied by a groove consisting in providing a groove in the edge of the lens, this groove being intended to receive the nylon wire of the frame intended to press the lens against the rigid part of the frame.

Conventionally, these clipping means are constituted by a grinding machine, called a grinder which has a main wheel set and means for locking and rotational driving of the lens constituted by two rotary shafts coaxial mounted movable relative to one another. to the other axially to tighten the lens along the axis thereof in the manner of a clamp. To allow the approximation or spacing of the lens relative to the grinding wheels during machining, the clamping shafts and drive are carried by a mobile rocker (pivoting or translation) transversely to the shafts.

Most often, the operations of edging, chamfering and beveling are successively conducted on the same grinder, equipped with a train of appropriate main wheels. Drilling, when necessary, can be performed on the grinder which is then equipped with the corresponding tooling or on a separate drilling machine.

The optician must also carry out a certain number of measuring and / or marking operations on the lens itself, before trimming, to identify some of its characteristics such as for example the optical center in the case of a unifocal lens or the cross mounting in the case of a progressive lens, or the direction of the axis of progression and the position of the centering point for a progressive lens.

In practice, each lens is usually delivered by the manufacturer with marks on its convex front, some of which are representations of a centering reference of the lens. If these marks are not sufficiently visible, the optician defers certain characteristic points with a sharp point on the ophthalmic lens itself. These marks are used to position and fix on the lens an adapter or acorn centering and drive to properly position the ophthalmic lens in the grinding machine to give it the desired contour, corresponding to the shape of the frame chosen. The operation of positioning and depositing the glans, can be performed manually or automatically, with a device called centering-blocker. Anyway, this glans is most often stuck temporarily on the lens with a double-sided adhesive. This operation is usually called the centering of the lens, or by blocking extension of the lens since the glans can then block, that is to say immobilize, the lens on the means of its trimming in a known geometric configuration thanks to this acorn.

After placing the centering glue, the lens thus equipped is then placed in the clipping machine where it is given the shape corresponding to that of the chosen frame. The centering glide makes it possible to define and physically materialize on the lens a geometric reference frame in which the points and the characteristic directions of the lens, necessary for the coherence of this lens with the position of the pupil, and the values are identified. of clipping so that these points and characteristic directions are properly positioned in the frame.

When the trimming of the lens does not result in a first fitting in the mount, the operator resumes machining. To do this, it puts the lens in the machine and blocks it with the same tassel, which allows to recover the initial clipping repository.

However, the use of a glued acorn is a disadvantage in that it must be removed after mounting the lens, which is time consuming and labor intensive. In addition, the lens is secured to the glans by gluing which can lead to intensive cleaning of the lens surface after treatment, resulting in a risk of scratching. Finally, these operations of laying and removal of the glans being relatively complex and delicate, they require a qualified and careful workmanship and are revealed in practice time consuming and therefore expensive; and for the same reasons, it is difficult to automate them.

Thus, in the context of this research work, the applicant wishes to overcome the centering by glans because of the aforementioned constraints.

However, in this hypothesis, where the pose of the glans no longer exists, prior to the first machining, the lens is centered and blocked using optical measuring means and / or mechanical manipulation means on the clamping shafts and drive. Optical measurements provide a theoretical reference for centering the ophthalmic lens in the clamping shafts. The inaccuracies of centering and locking of the lens by the measurement and manipulation means that we obtain a first real centering reference of the lens relative to the clamping shafts slightly different from the theoretical one calculated by optical measurement. It is in this first real reference that the first machining is performed.

The lens is then cut by machining by means of cylindrical roughing and finishing grinding wheels whose edging faces are parallel to the axes of rotation of the clamping and driving shafts, belonging to the main wheels and rotatably mounted around the wheel. axis of rotation of the wheel train.

After this first machining, the lens is unlocked and is thus detached from the locking noses of the clamping shafts. It results from this release a loss of the first real centering repository.

In the case where the trimming of the lens previously performed by means of the first machining is not in accordance with the desired result, the optician must resume trimming by means of a second machining.

To properly resume machining, it would be necessary to replace the lens in the real center of reference of the first machining step so that the edging face of the grinding wheel is well parallel to the edge of the lens to resume.

Before the second machining, we recalculate by optical measurements the theoretical centering reference of the lens. The inaccuracies of these optical measurements mean that the centering reference obtained in this second machining step differs slightly from the first theoretical reference used during the first machining step. Moreover, in addition to these optical measurement inaccuracies, inaccuracies of locking of the lens by the locking noses of the clamping shafts. The second centering reference obtained is therefore different from the first in which it is desirable to return to the recovery. This results in a positioning error of the lens relative to the grinding wheel during this second machining. In particular, the lens being off-center with respect to its centering position of the first machining, the edge of the lens is inclined relative to the edge of the work wheel. Thus machining in this configuration, can not achieve the desired radii of curvature at the edge of the lens.

In addition, for a lens having a bevel, the positioning error of the lens relative to the grinding wheel that, when resuming machining, the flange face of the wheel grinds the bevel unsymmetrically. The problem therefore lies in the implementation of a recovery of the overhang in the new centering reference of the ophthalmic lens of glasses, in order to properly re-make the edge of this lens.

Document FR 2 811 599 describes a chamfering tool for improving the accuracy of a chamfering operation applied to a spectacle lens. But this invention neither poses nor solves the technical problem of resuming the edging in the new reference centering glass.

It is indeed proposed to insert compensation means having an elastic deformation capacity between, on the one hand, the periphery concerned of any of the elements that constitute the chamfering tool used and the spectacle lens worked and on the other hand, the support shaft of this same element.

But it is not specified to use such a tool for the recovery of edging of the edge of an ophthalmic lens. The structural features of the proposed tool would not lend themselves to such a transposition. The chamfering tool does not have any edge face of the edge of the lens.

In addition, the tool does not meet the accuracy requirements of the recovery of edging of the edge of the lens and can not respond to it, the means of compensation inserted leaving the chamfering tool free to deform radially.

OBJECT OF THE INVENTION

The purpose of the present invention is to successfully remake the edge of this lens despite the fault of positioning of the lens relative to the machining wheel because of the parasitic tilting occurring during a second blocking, after loss of centering reference of the lens, by the shafts of the clipping device.

For this purpose, it is proposed according to the invention a working method of the periphery of an ophthalmic lens, the periphery of the lens having a edge, comprising the edge of the edge of the lens by machining by means of a first grinding wheel mounted rotatable about an axis of rotation, wherein it is provided that, during the edging, the first grinding wheel has, in addition to its rotation about said axis of rotation, a tilting mobility with two degrees of freedom around two distinct pivoting directions substantially transverse to its axis of rotation.

The invention also relates to a working tool of the periphery of an ophthalmic lens for implementing the working method of the periphery of the lens which comprises a support and a first grinding wheel mounted on the support, the first grinding wheel presenting a face of revolution overflow around an axis of revolution, wherein the mounting of the first grinding wheel on the support is made in favor of mechanical tilting connection means for pivoting of the first grinding wheel relative to the support around two distinct pivotal directions substantially transverse to the axis of revolution of the edging face of the grinding wheel.

The invention finally relates to a device for trimming an ophthalmic lens for implementing the working method of the periphery of the lens comprising shafts for rotating and driving the ophthalmic lens, and roughing wheels. , and a working tool as aforesaid. Thus, during the edging of the edge of the periphery of the lens, the first grinding wheel can, thanks to its two degrees of freedom around two distinct pivoting directions according to the invention, tilt to adapt to the local orientation of the song of the lens. This adaptability of orientation of the grinding wheel makes it possible to compensate for the parasitic tilting of the lens appearing during its re-locking in the tightening shafts of the lens, and thus correctly machining the edge of the lens.

According to a first advantageous characteristic of the invention, the tilting mobility of the grinding wheel is spherical, rigid radially. Thus, the edging always takes place at the right dimension and allows to reproduce the different rays describing the contour of the desired shape of the lens, with precision.

According to a second advantageous characteristic of the invention, the tool is disposed on a module of the device for trimming the ophthalmic lens, retractable in a plane substantially transverse to the axis of the shafts and rotating drive of the lens ophthalmic.

According to a third advantageous characteristic of the invention, the first grinding wheel is recalled, in its pivoting about its pivoting directions, in a return position. Thus, the edge face of the first grinding wheel remains in abutment against the edge of the lens to be machined and the edge face and the edge are correctly positioned relative to each other.

According to a fourth advantageous characteristic of the invention, the support constitutes a driving shaft of the first grinding wheel having an axis of rotation substantially coinciding with the axis of revolution of the edge face of the first grinding wheel, driving means being provided to ensure torque transmission from the shaft to the first grinding wheel. The drive means are then merged with the mechanical tilt connection means and are arranged to make a spherical finger mechanical connection. Thus, the drive system and tilting of the first grinding wheel is compact.

According to a fifth advantageous characteristic of the invention, the drive means of the first grinding wheel are separate from the mechanical tilting connection means. Thus, the rotational driving and tilting functions of the first grinding wheel are decoupled. According to a sixth advantageous characteristic of the invention, the method is adapted to a recovery of the edging of the edge of the lens after a first machining. It then advantageously comprises the following preliminary steps: prior to the first machining, the lens is centered and locked according to a first centering reference, after the first machining, the lens is unlocked with loss of centering reference, before the second machining, the lens is centered and locked again. It is then possible to resume trimming the edge of the lens with the first wheel despite the positioning error of the lens relative to the wheel.

Thus, the method is well applicable following the clipping steps performed by the optician and in particular when, after the first machining, the mounting of the ophthalmic lens in the frame is not satisfactory and it is necessary to resume the edging of the song of the lens.

According to a seventh advantageous characteristic of the invention, the first grinding wheel has on its flange face a beveling groove. Thus, the method is applied to the resumption of edging of the edge of the ophthalmic lenses having a bevel. According to an eighth advantageous characteristic of the invention, the first grinding wheel comprises a chamfering face whose generator forms an angle with the edge face. Thus, the first grinding wheel makes it possible to perform the step of chamfering the sharp edges of the edges of the lens.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description with reference to the accompanying drawings of the various embodiments, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: FIG. 1 is a general schematic perspective view of a trimming device equipped with a working tool of the periphery of an ophthalmic lens in accordance with the invention; FIG. 2 shows, from another angle and on a larger scale, the detail of FIG. 1 indicated by an inset II in this FIG. 1, showing the working tool of the periphery of the ophthalmic lens according to the invention with the first grinding wheel and other grinding wheels and working discs of the periphery of the lens; Figure 3 is a schematic view of the ophthalmic lens and its clamping shafts ideally positioned relative to the first grinding wheel; Figure 4 is a schematic view of the ophthalmic lens and its clamping shafts having a positioning drift, with parasitic tilting relative to the first grinding wheel; Figure 5 shows, on a larger scale, the detail of Figure 4 indicated by an inset V in this Figure 4 showing the positioning drift of the lens relative to the grinding wheel; Figure 6 is a block diagram of the first wheel mounted with a spherical mechanical connection according to the invention; Figure 7 is an axial sectional view of Figure 2, showing the working tool of the periphery of the ophthalmic lens according to a first embodiment according to the invention; Figure 8 is an axial sectional view of Figure 2, showing the working tool of the periphery of the ophthalmic lens according to a second embodiment according to the invention; - Figure 9 is an axial sectional view of Figure 2, showing the working tool of the periphery of the ophthalmic lens according to a third embodiment according to the invention; Figure 10 is an axial sectional view of Figure 2, showing the working tool of the periphery of the ophthalmic lens according to a fourth embodiment according to the invention.

In Figure 1 there is shown a device 10 for trimming for the implementation of a working method of the periphery of a lens L ophthalmic spectacle.

The trimming device 10 according to the invention can be made in the form of any cutting or material removal machine adapted to modify the contour of the ophthalmic lens L to adapt to that of the frame or

"circle" of a selected mount. Such a machine may consist for example of a grinder, as in the example described below, but also in a milling machine or cutting laser or jet water, etc.

In the example shown diagrammatically in FIG. 1, the trimming device 10 comprises, in a manner known per se, an automatic grinder, commonly known as a digital grinder. This grinder comprises, in this case, a rocker 11, which is mounted freely pivoting about a first axis A1, in practice a horizontal axis, on a frame 1.

For the immobilization and rotational drive of an ophthalmic lens such as L to be machined, the grinder is equipped with two clamping shafts 12, 13. These two shafts are aligned one with the other. another along a second axis A2, called the blocking axis, parallel to the first axis A1. The two shafts 12, 13 are rotated synchronously by a motor (not shown), via a common drive mechanism (not shown) embedded on the rocker 11. This common synchronous rotation drive mechanism is of type current, known in itself.

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

The rotation ROT of the shafts 12, 13 is controlled by a central electronic and computer system (not shown) such as an integrated microcomputer or a set of dedicated integrated circuits.

Each of the shafts 12, 13 has a free end which faces the other and which is equipped with a locking nose 62, 63. The two locking noses 62,

63 are generally of revolution about the axis A2 and each have an application face (not shown) generally transverse, arranged to bear against the corresponding face of the ophthalmic lens L.

In the example shown, the nose 62 is integral and is fixed without any degree of mobility, neither sliding nor rotating, on the free end of the shaft 12. The nose 63 comprises two parts: a pellet application 66 intended to cooperate with the lens L and carrying for this purpose a useful face (not shown) and a tail (not shown) arranged to cooperate with the free end of the shaft 13, as we shall see more in detail thereafter. The pellet 66 is attached to the tail 67 by a cardan link 68 transmitting rotation about the axis A2 but allowing the orientation of the pellet 66 about any axis perpendicular to the axis A2. The useful faces (not shown) of the noses are preferably covered with a thin plastic or elastomeric material gasket. The thickness of this lining is of the order of 1 to 2 mm. This is for example a flexible PV or a neoprene.

The shaft 13 is movable in translation along the blocking axis A2, opposite the other shaft 12, to effect the compression in axial compression of the L lens between the two locking nose 62, 63. The shaft 13 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 12 is fixed in translation along the blocking axis A2. The trimming device 10 comprises, on the other hand, a set of wheels

14, which is locked in rotation on a third axis A3 parallel to the first axis A1, and which is also properly driven in rotation by a motor 20.

In practice, the device 10 comprises a train of several grinding wheels 14 mounted coaxially on the third axis A3, for a roughing and finish of the edging of the ophthalmic lens L to be machined. These different grinding wheels are each adapted to the material of the cut lens L and the type of operation performed (roughing, finishing, mineral or synthetic material, etc.).

The train of main wheels 14 is attached to a common shaft axis A3 ensuring their rotation in the operation of edging. This common shaft, which is not visible in the figures, is controlled in rotation by the electric motor 20 controlled by the electronic and computer system.

The train of main wheels 14 is also movable in translation along the axis A3 and is controlled in this translation by a drive motor. Specifically, the entire main wheel train 14, its shaft and its motor is carried by a carriage 21 which is itself mounted on slides 22 integral with the frame 1 to slide along the third axis A3. The translational movement of the grinding carriage 21 is called "transfer" and is denoted TRA. 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 14 and the axis A2 of the lens L during the edging, the pivoting capacity of the rocker 11 is used around the axis A1. This pivoting causes in fact a displacement, here substantially vertical, of the lens L sandwiched between the shafts 12, 13 which brings the lens L closer to the grinding wheels 14. This mobility, which makes it possible to restore the shape of the desired and planned edging in the electronic and computer system, is called restitution and is noted RES in the figures. This RES restitution mobility is controlled by the central electronic and computer system. As illustrated in Figure 1, the rocker 11 is directly articulated to the nut 17 mounted movably along the axis of restitution A5. A strain gauge is associated with the rocker to measure the machining advance force applied to the lens L. Thus, during the machining, the grinding force force applied to the lens L is constantly measured. and piloting the progression of the nut 17, and therefore of the rocker 11, so that this effort remains below a maximum setpoint value. This set value is, for each lens L, adapted to the material and to the shape of this lens L.

For machining the ophthalmic lens L according to a given contour, it suffices, therefore, firstly to move the nut 17 accordingly along the fifth axis A5, under the control of the motor 19, to control the movement of restitution and, secondly, to jointly rotate the support shafts 12, 13 around the second axis A2, in practice under the control of the motor that controls them. The transverse restitution movement RES of the rocker 11 and the rotational movement ROT of the shafts 12, 13 of the lens L are controlled in coordination by an electronic and computer system (not shown), duly programmed for this purpose, so that all points of the contour of the ophthalmic lens are successively brought back to the correct diameter. At the same time, the transfer TRA is controlled by the electronic system for the axial tracking of the bevel, the groove or the chamfer by the grinding wheels.

The grinder further comprises a finishing module 25 which is movable according to a degree of mobility, in a direction substantially transverse to the axis A2 of the shafts 12, 13 for holding the lens L and to 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 finishing module 25 around the axis A3. Concretely, the module 25 is carried by a lever 26 secured to a tubular sleeve 27 mounted on the carriage 21 to pivot about the axis A3. For the control of its pivoting, the sleeve 27 is provided, at its end opposite the lever 26, a toothed wheel 28 which meshes with a pinion (not visible in the figures) fitted to the shaft of an electric motor 29 integral with the trolley 21.

In summary, it can be observed that the degrees of mobility available on such a trimming machine are: the rotation of the lens L to rotate the lens about its holding axis, which is generally normal to the general plane of the lens, the restitution, consisting of a transverse relative mobility of the lens L (ie 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 L, the transfer, consisting of an axial relative mobility of the lens L

(That is to say, perpendicular to the general plane of the lens) with respect to the grinding wheels 14, allowing the lens L and the chosen cutting wheel to be positioned opposite one another and, during machining, to follow the path of the bevel, groove or chamfer. the retraction, consisting of a transverse relative mobility, in a direction different from that of the restitution, of the finishing module 25 with respect to the lens L, making it possible to put the finishing module 25 in the position of use and to store it.

In this context, the general object of the invention is to integrate in this grinder a work recovery function of the periphery of an ophthalmic lens L previously cut out.

FIG. 3 shows the ophthalmic lens L blocked by its clamping shafts 12, 13 opposite a first grinding wheel intended to resume the edging of the edge C of the lens, called the grinding wheel 31. In this figure 3 the lens L is ideally centered so that its edge C is parallel to the edge face 99 of the grinding wheel.

In practice, after the first machining, the lens L is unlocked with loss of the centering reference. Then, before the second machining, the lens L is centered and locked again. However, because of the loss of the centering reference of the first machining there is always a centering gap between the first and the second machining. This gap generates a tilting of the lens L at the origin of a positioning error of the edge C of the lens L with respect to the edging face 99 of the grinding wheel 31 (FIGS. 4 and 5).

As shown in the block diagram of FIG. 6, the general principle of the solution provided by the invention consists in mounting the grinding wheel 31 on a support 38 for driving in rotation by means of a spherical mechanical connection. ; As schematized in FIG. 1, the finishing module 25 of the grinder 10 comprises a tool 30 for working around the periphery of the ophthalmic lens L. This tool is mounted on the finishing module 25 of the device 10 for trimming the ophthalmic lens L. In addition, the finishing module 25 accommodating the working tool 30 is retractable in a plane substantially transverse to the axis A2 of the clamping shafts 12, 13 and for rotating the ophthalmic lens L.

Thus, the work tool 30 also has a degree of ESC retraction mobility. The working tool 30 is rotated about its axis of rotation A4 by a motor (not shown).

The axis A4 of the work tool 30, mounted on the finisher 25, is inclined with respect to the axis A3.

For the resumption of the edging after a first machining, the working tool 30 comprises the grinding wheel 31 of overflow, having an edge face 99 of revolution about an axis of revolution, a second grinding wheel already known per se called grinding wheel crease 35, and a third grinding wheel referred to as a finishing grinding wheel 34.

It is obvious that if the edging face 99 of the grinding wheel 31 is cylindrical as well as the edging faces of the main grinding wheels 14, the inclination of the tool causes the inclination of the edging face 99 of the grinding wheel. of recovery 31 with respect to the edge C of the lens L. The error of positioning grinding wheel relative to the lens is then very important.

Consequently, to have an edging face 99 as parallel as possible to the edge C of the lens L, the edging face 99 of the grinding wheel 31 is conical. More specifically, the cone angle substantially corresponds to the angle of inclination of the tool 30.

In addition, as shown in FIG. 2, the grinding wheel 31 comprises two chamfering faces 33, 98 whose generatrices form an angle with the edging face 99. These chamfering faces are intended for chamfering the two edges B1, B2. vivid edge of the lens O ophthalmic overflowing. In particular, the grinding wheel 31 also includes on its flange face 99 a groove 32 beveling. This groove is intended for resumption of edging of the edge of the lens comprising a bevel.

In FIGS. 1 and 2 presenting the trimming device 10 and the tool 30, the comparison of the grinding wheel 31 mounted on the tool 30 with the main grinding wheels mounted on the grinding wheel 14, shows that the diameter of the grinding wheel 31 is less than that of the main grinding wheels of the grinding wheel 14. The use of the grinding wheel 31 characterized by a smaller diameter than that of the main grinding wheels of the grinding wheel 14 reduces the shear of the grinding wheel. bevel of the lens L appearing when working on the periphery of a lens L with one of the main grinding wheels.

The mounting of the grinding wheel 31 on the support 38 is achieved by means of mechanical tilting connection means for pivoting of the grinding wheel 31 relative to the support 38 around two distinct pivotal directions substantially transverse to the axis of revolution of the edging face 99 of the grinding wheel.

The grinding wheel 31 comprises a spherical connection, radially rigid. When the grinding wheel 31 is subjected to a bearing force on its edging face 99, the rigid spherical connection radially prevents the grinding wheel 31 from translating radially relative to the support 38 drive.

In addition, the working tool 30 comprises return means of the grinding wheel 31 in a return position around its pivoting directions.

This return position of the grinding wheel 31 is such that the axis of revolution of its edging face 99 coincides with the axis of rotation A4 of the grinding wheel.

Preferably, the support 38 constitutes a drive shaft of the grinding wheel 31 having an axis of rotation substantially coincident with the axis of revolution of the edging face 99 of the grinding wheel 31. For the rotary drive of the grinding wheel 31, drive means are provided to ensure a torque transmission of the support 38 to the grinding wheel 31. These drive means are merged with the mechanical tilting connection means and are arranged to achieve a spherical mechanical link finger, blocking the rotation of the grinding wheel 31 around its axis of revolution A4 relative to the support 38.

FIG. 7 represents a first embodiment according to the invention of a tool 3OA. In particular, the mechanical spherical finger connection comprises, on the one hand, a grooved ball 40 secured to the support 38 by means of a locking pin 50 in rotation, having a plurality of curved sections, and, on the other hand, on the other hand, a splined housing 70 associated with the grinding wheel 31A, having a plurality of panels, and arranged to cooperate with said spline 40.

More specifically, the ball 40 and the housing comprise panels oriented in the direction of the axis of rotation A4 of the grinding wheel 31 A. These flaps block the grinding wheel 31A rotating about the axis A4 relative to the support 38 on which it is mounted. This blocking rotation of the grinding wheel relative to the support then makes it possible to transmit the torque of the support 38 to the grinding wheel 31 A. The transmission of torque causes the rotation of the grinding wheel around the axis of rotation A4. Advantageously, the curved sections of the ball 40 leaves the free grinding wheel 31A free following the other two degrees of freedom in rotation which allows it to always adapt well to the edge C of the ophthalmic lens L to resume.

In particular, in this embodiment, the grinding wheel 31A comprises a ring 45 having an outer face constituting the edge face 99A. The ring 45 of the grinding wheel 31A is mounted on another ring in two parts 41, 42 whose inner face has grooves for cooperating with the fluted ball 40.

The two parts of the ring are interconnected by two screws 43,44. The two-part assembly of the ring using the two screws makes it possible to overcome the problem of mounting the grinding wheel 31A on the ball 40.

In order to stop axially the grinding wheel 31A with respect to the ball 40, the grooved housing 70 of the grinding wheel 31A is narrowed at its ends to form shoulders 71, 72 for stopping the grinding wheel 31 A relative to the ball 40. The shoulders 71, 72 of the housing have a plurality of curved sections whose shapes follow those of the curved sections of the ball 40 allowing pivoting of the grinding wheel 31A around its pivot axes until at a certain pivot angle. In this embodiment, the grinding wheel 31A has a free angular deflection around its two pivoting directions. As a result, the angular return of the grinding wheel 31A in its return position is exclusively generated by the rotation of the grinding wheel around its axis of rotation A4, under the effect of its inertial centripetal force.

For mounting considerations, there is disposed between the grinding wheel 31A and the shaft 37 for rotating a spacer 51 to the right of the ball 40 in the drawing of Figure 7, to stop the various elements that could opposing the tilting of the grinding wheel 31A around its pivot axes.

Indeed, after having arranged all the components of the tool 3OA working on the drive shaft 37, it is tighten all the various elements arranged on the work tool 30A with a screw 36 and a washer 23.

This screw cooperates with a tapped hole arranged at the end of the shaft 37 of the working tool 30A.

It is interesting to note that the restoring force being solely due to the inertial force of rotation, it is preferable to have a well balanced regrind wheel 31A.

Figure 8 shows a second embodiment of a work tool 3OC. This embodiment is a variant of the previous embodiment. For the sake of consistency from one embodiment to another, the identical or similar elements of the different embodiments of the invention are referenced by the same reference signs. We thus find the creasing wheel 35 mounted on the support 38 in favor of the ball 40 and the locking pin 50, the rotating drive shaft 37, the screw 36 and its washer 23.

This tool 3OC comprises a recovery wheel 31 C made differently from the previous embodiment. For mounting considerations, there is provided between each seal 47,48 elastic and drive shaft 37 a spacer 55,56. The spacers 55,56 then serve as shoulder to the various elements distributed on either side of the grinding wheel 31 C on the tool 3OC.

The return means of the grinding wheel are elastic. More precisely, these return means comprise two axially and / or radially compressible elastic joints 47, 48 mounted on the axis of rotation A4. The seals each have an edge bearing against the corresponding side of the grinding wheel 31 C and an opposite edge bearing against a stop associated with the spacers 55,56. The two seals 47.48 elastic are for example elastomer. The return force due to these elastic return means is then added to the restoring force due to the centripetal inertial force resulting from the rotation of the grinding wheel around its axis of rotation.

Here, unlike the first embodiment, the grooved housing 75 of the grinding wheel 31 C does not have parts closing around the ball 40. Indeed in the first embodiment the closed parts of the housing serve as a shoulder for the axial stops of the grinding wheel with respect to the patella. Here, the grinding wheel 31 C is stopped in axial translation by the joints 47,48.

Figure 9 shows a third embodiment of a working tool 30B. This embodiment is a variant of the previous embodiment. For the sake of consistency from one embodiment to another, the identical or similar elements of the different embodiments of the invention are referenced by the same reference signs. We thus find the creasing wheel 35 mounted on the support 38 in favor of the ball 40 and the locking pin 50, the rotating drive shaft 37, the screw 36 and its washer 23.

This tool 3OB comprises a recovery wheel 31 B made differently from the previous embodiment. The bulk around the grinding wheel 31 B is optimized by mounting an elastic return seal 46 on one side of the ball 40. As in the previous embodiment, for mounting considerations, it is disposed between the grinding wheel of recovery 31 B and the shaft 37 for rotating a spacer 53 to the right of the ball 40 in the drawing of Figure 9, to stop in stop the various elements that could oppose the tilting of the grinding wheel 31 B around its pivot axes.

As in the previous embodiment, the elastic seal 46 is axially and / or radially compressible. This seal is mounted along the axis of rotation A4 and has an edge bearing against the corresponding side of the grinding wheel 31 B and an opposite edge bearing against an abutment associated with the spacer 53. This seal 46 is elastic by example elastomer. The grinding wheel 31 B is stopped axially in one direction by the elastic seal, placed on one side of the ball joint. This elastic seal forms an axial abutment in one direction (to the right in FIG. 9). To stop the grinding wheel 31 B in axial translation in the other direction, the grooved housing 74 of the grinding wheel 31 B is narrowed at the end of the side of the elastic seal 46 to form a stop shoulder 73 of the grinding wheel 31 B relative to the ball 40. The shoulder 73 has a plurality of curved sections whose shapes follow those of the curved sections of the ball 40 allowing the pivoting of the grinding wheel 31 B around its pivot axes up to a certain pivot angle.

Note that it will be necessary to use an elastic seal having an elastic resistance twice as large compared to the previous embodiment since this seal must perform the same work as two elastic joints distributed on either side of the patella. Figure 10 shows a fourth embodiment of a 3OD work tool. This embodiment is a variant of the previous embodiment. For the sake of consistency from one embodiment to another, the identical or similar elements of the different embodiments of the invention are referenced by the same reference signs. We thus find the creasing wheel 35 mounted on the support 38 in favor of the ball 40, the rotary drive shaft 37, the screw 36 and its washer 23.

This tool 3OD comprises a recovery wheel 31 D made differently from the previous embodiments. The grinding wheel 31 D is made in the form of a ring 49. The mechanical spherical finger connection means comprise an inner flange 39. This flange 39 is integral with the grinding wheel 31 D. The flange is located in the plane perpendicular to the axis of revolution of the grinding wheel 31 D, centered on the axis of revolution and substantially in the center of the width of the grinding wheel.

The inner flange 39 cooperates by substantially multi-point or linear contact with the support. This type of contact between the drive support 38 and the collar 39 of the grinding wheel 31 D makes it possible to obtain a double pivot connection. This double pivot connection allows the grinding wheel 31 D to rotate along the axes perpendicular to its axis of rotation A4. In addition, the The rigidity of the flange 39 disposed in the center of the grinding wheel 31 D gives the latter a radial rigidity.

According to this embodiment, the return means of the grinding wheel 31 D in its return position comprise at least two elastic bodies 91, 92 mounted on either side of the collar 39 of the central grinding wheel. These bodies 91, 92 cooperate on the one hand with the support 38 and on the other hand with the ring 49.

To ensure this cooperation, the support 38 and the ring 49 forming the grinding wheel 31 D are provided with arrangements 80,81, 82,83, for example notches, trapping a portion of the elastic bodies in the support 38 and the ring 49 of the grinding wheel. These arrangements 80, 81, 82, 83 make the elastic bodies 91, 92 integral with the ring 49 and the support 38. Thus, the arrangements 91, 92 prevent the rotation of the ring 49 and the central flange 39 which is secured to it , in relation to the support. The elastic bodies then ensure the transmission of the torque of the support 38 to the grinding wheel 31 D.

The establishment of the elastic bodies 91, 92 on either side of the central flange 39 can be performed by casting these elastic bodies. These elastic bodies are for example elastomer.

Thus, the edging face 99D of the grinding wheel 31 D can be seated by bearing on the elastic bodies 91, 92, on either side of the collar 39. This possibility of elastic depression at its level. edges, associated with the double pivot connection flange 39, gives the grinding wheel 31 D tilt mobility sought to adapt to the edge C of the lens L to overflow. Alternatively (not shown) to the previous embodiments, it is conceivable to take an anisotropic elastomer having elastic deformation properties on its edges and almost zero elastic deformation in a central plane of the elastomer. This almost zero elastic deformation along a central plane makes it possible to ensure a radially rigid spherical connection.

According to another variant of the envisaged invention (not shown), the drive means of the grinding wheel are separate mechanical tilting connection means. The side face on each side of the grinding wheel takes the form of a tank. The grinding wheel is maintained by holding arms arranged on either side of its lateral faces. These arms hold the grinding wheel like a pliers. They use for this point pointed tips arranged at the ends of the support arms. These tips are applied to the center of the side faces in the form of a tank. In this configuration, elastic bodies are arranged between the support arms and the lateral faces of the grinding wheel to provide an elastic return. The grinding wheel is thus free along its three axes of rotation. The rotation of the grinding wheel can then be carried out by means of driving cooperating, by means of a clutch for example, with one of the outer faces of the grinding wheel.

The trimming device 10 and its working tool 30 (or one of its variants 30A; 30B; 30C; 30D) according to the invention are advantageously used for the implementation of a working method of the periphery of the L ophthalmic lens. Advantageously, the method of recovering the protrusion of the periphery of the ophthalmic lens L is applied to the resumption of the edging of the edge C of the ophthalmic lens L by machining after a first machining.

Before each recovery of the ophthalmic lens L, the lens is probed. This feeling of the lens L makes it possible to position the grinding wheel vis-à-vis the lens to be cut.

Prior to the first machining, the lens L is centered and locked according to a first centering reference by means of the two locking noses 62, 63. Optical measurements provide a theoretical reference for centering the ophthalmic lens L in the clamping shafts 12, 13. The locking inaccuracies of the lens L make it possible to obtain a first real centering reference of the lens L with respect to the clamping shafts 12, 13 slightly different from the theoretical one calculated by optical measurement. It is in this first real reference that the first machining is performed.

The lens L is then cut off by machining by means of the main roughing and finishing grinding wheels of the grinding wheel set 14. the edge faces of these main grinding wheels are parallel to the axis A2 of rotation of the clamping shafts 12, 13 of the L lens. After this first machining, the lens L is unlocked and thus is disengaged from the locking faces of the clamping shafts 12, 13. It results from this release a loss of the first real centering repository.

In the case where the trimming of the lens L previously performed by means of the first machining is not in accordance with the desired result, the optician resumes the trimming of the edge C of the lens L by means of a second machining.

To properly resume machining, it would be necessary to replace the lens L in the real center of reference of the first machining step so that the edging face 99 (or one of its variants 99A; 99B; 99C; 99D) of the wheel used is well parallel to the edge C of the lens L to resume.

Before the second machining, the theoretical centering reference of the lens L is recalculated by optical measurement. The inaccuracies of these optical measurements mean that the centering reference obtained in this second machining step differs slightly from the first theoretical reference used during the analysis. first machining step. In addition, in addition to these optical measurement inaccuracies, the locking inaccuracies of the lens L. The second centering reference obtained is therefore different from the first in which it is desirable to replace for recovery. This results in a positioning error of the lens L relative to the grinding wheel during this second machining. In particular, the lens L being off-center with respect to its centering position of the first machining, the edge C of the lens L is inclined relative to the edging face 99 (or one of its variants 99A; 99B; 99C; 99D) of the working wheel. Thus, machining in this configuration can not achieve the desired radii of curvature at the edge of the lens. The second machining is then performed with the grinding wheel 31 (or one of its variants 31A; 31 B; 31C; 31 D) edging. The grinding wheel is then positioned at the edge C of the lens L to overflow thanks to the degree of retraction mobility ESC of the finishing module 25, in a plane transverse to the clamping shafts 12, 13 of the lens L. During this recovery of the edging, the tilting mobility of the grinding wheel 31 (or one of its variants 31A, 31B, 31C, 31D) around its two pivoting directions is used.

With this tilting mobility, when the lens L is brought into contact with the edging face 99 (or one of its variants 99A; 99B; 99C; 99D) of the grinding wheel 31 (or one of its variants 31A; 31B; 31C; 31D), this face tilts itself to adapt to the local orientation of the edge C of the lens L.

The tilting mobility of the grinding wheel 31 (or one of its variants 31 A, 31 B, 31 C, 31 D) is of spherical type, rigid radially. When a pressing force is exerted from the lens L on the grinding wheel, this radial rigidity allows the grinding wheel does not move radially relative to the support 38. A radial displacement of the grinding wheel relative to the support 38 would change the machining dimension of the lens. However, the machining dimension must be respected as precisely as possible to obtain the desired radius at the C song considered that is taken again.

During this second machining of the edge C of the lens L, the grinding wheel 31 (or one of its variants 31A, 31B, 31C, 31D) is recalled, in its pivoting about its pivoting directions, in its return position so that the edging face 99 (or one of its variants 99A; 99B; 99C; 99D) of the grinding wheel is always parallel to the edge C of the lens L to overflow. This booster can result from the inertial force driving in rotation of the grinding wheel. Thanks to this inertial force, the grinding wheel naturally tends to recover in a plane perpendicular to its axis of rotation A4 while following the edge C of the lens by using its two degrees of freedom of tilting around the axis of rotation. A4 rotation.

This reminder of the grinding wheel 31 (or one of its variants 31A, 31B, 31C, 31D) in its return position can also be achieved by means of elastic means. In the latter case, the inertial force of rotation drive is added to the elastic restoring force.

In addition, the groove 32 (or one of its variants 32A; 32B; 32C; 32D) beveling the edging face 99 (or one of its variants 99A; 99B; 99C; 99D) of the grinding wheel Fig. 31 (or one of its variants 31A, 31B, 31C, 31D) makes the working process of the periphery of the lens L applicable to the edging of the edge C of the ophthalmic lenses L having a bevel.

In addition, the chamfering face 33, 98 (or one of its variants 33A, 98A, 33B, 98B, 33C, 98C, 33D, 98D) of the grinding wheel 31 (or one of its variants 31A; 31B; 31C; 31D) makes it possible to carry out a step of chamfering the sharp edges B1, B2 of the edges of the lens L by means of said grinding wheel.

The mounting of the grinding wheel 31 (or one of its variants 31A; 31B; 31C; 31D) mounted on its support 38 by means of a spherical connection, optimizes this chamfering step. To make a correct chamfering it must be taken into account that the width of the chamfer is proportional to the machining force and thus to avoid the variations of machining force.

The rotational mounting of the grinding wheel 31 (or one of its variants 31A; 31B; 31C; 31D) makes it flexible. However, it is known that the flexibility of the working wheel makes it possible to absorb the variations of bearing pressure during the chamfering step. The flexibility of the wheel thus makes it possible to exert a regular support of the lens on the grinding wheel and to have a regular chamfer width.

Finally, the creasing wheel 35 of the tool 30 (or one of its variants 30A; 30B; 30C; 30D) for working the periphery according to the invention makes it possible to perform a step of creasing the lens L. in particular, when a groove is made with the creasing wheel in the edge C of the lens L, the groove must follow a certain axial curvature desired on the edge C of this lens L, depending on the shape of the frame. Ideally, the outer portion of the creasing wheel 35 for creasing the edge C of the lens is tangent to the desired curvature. That is, a creasing wheel 35 would be required whose inclination would be adaptive to the curvature of the desired groove of the lens L. Or the orientation of the creasing wheel 35 with respect to the lens L Ophthalmic is fixed. Consequently, assuming that the axis of rotation A4 of the creasing wheel is parallel to that of the lens L, the creasing wheel is on at least a portion of the periphery of the lens, at an angle to the desired groove shape. It results from this bias a groove whose width varies according to the angle that makes the grinding wheel with respect to its trajectory. Indeed, this groove results from the accumulation of bias grooves at each groove of the edge C of the lens L, like a snowplow.

In order to at least partially overcome this machining problem, the creasing of the lens L is advantageously carried out with an inclination of the order of fifteen degrees of the tool 30 (or one of its variants 30A, 30B, 30C ; 30D) and so of the axis of rotation A4 in the plane considered. This makes it possible to improve the regularity of the thickness of the groove along the edge C of the lens L.

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.

The working tool comprising the grinding wheel can also be used for resuming the trimming of a lens on which is applied a tassel maintenance. Indeed, the grinding wheel allows to resume the trimming of the lens despite the repositioning dispersions of the glans attached to the lens on the shafts and rotation drive.

Claims

1. Working method of the periphery of an ophthalmic lens (L), the periphery of the lens (L) having a edge (C), comprising the edge of the edge (C) of the lens (L) by means of machining a first grinding wheel (31; 31A; 31B; 31C; 31D) rotatably mounted about an axis of rotation (A4), characterized in that, during the edging, the first grinding wheel (31; 31A; B; 31 C; 31 D) has, besides its rotation about said axis of rotation (A4), a tilting mobility with two degrees of freedom around two distinct pivotal directions substantially transverse to its axis of rotation (A4).

2. Method according to claim 1, characterized in that the tilting mobility of the first grinding wheel (31; 31A; 31B; 31C; 31D) is of spherical type, radially rigid.

3. Method according to one of the preceding claims, characterized in that the first grinding wheel (31; 31A; 31B; 31C; 31D) is recalled, in its pivoting about its pivoting directions, in a return position.

4. Method according to one of the preceding claims, characterized in that it is adapted to a recovery of the edging of the edge (C) of the lens (L) after a first machining.

5. Method according to the preceding claim, characterized in that it comprises the following preliminary steps: prior to the first machining, the lens (L) is centered and blocked according to a first centering reference, after the first machining, the lens (L ) is unlocked with loss of the centering reference, before the second machining, the lens (L) is centered and locked again.

6. Method according to one of the two preceding claims, characterized in that the first grinding wheel (31; 31A; 31B; 31C; 31D) having on its edge face (99; 99A; 99B; 99C; 99D; ) a beveling groove (32; 32A; 32B; 32C; 32D), said method is applied to the resumption of the edging of the edge (C) of the ophthalmic lenses (L) having a bevel.

7. Tool (30) for working around the periphery of an ophthalmic lens (L) comprising a support (38) and a first grinding wheel (31; 31A; 31B; 31C; 31D) mounted on the support (38). ), the first grinding wheel (31; 31A; 31B; 31C; 31D) having an edge face (99; 99A; 99B; 99C; 99D) of revolution about an axis of revolution, characterized in that the mounting the first grinding wheel (31; 31A; 31B; 31C; 31D) on the support (38) is made with the aid of mechanical tilting connection means enabling pivoting of the first grinding wheel (31; 31A; 31B; 31C; 31 D) relative to the support (38) about two distinct pivotal directions substantially transverse to the axis of revolution of the edging face (99; 99A; 99B; 99C; 99D) of the first grinding wheel (31; 31A; 31B; 31C; 31D).

8. Tool (30) according to the preceding claim, characterized in that the first grinding wheel (31; 31A; 31B; 31C; 31D) comprises a spherical connection, radially rigid.

9. Tool (30) according to one of the two preceding claims, characterized in that the first grinding wheel (31; 31A; 31B; 31C; 31D) comprises on its edge face (99; 99A; 99B; 99C; 99D) a beveling groove (32; 32A; 32B; 32C; 32D).

10. Tool (30) according to one of the three preceding claims, characterized in that it comprises return means of the first grinding wheel

(31; 31A; 31B; 31C; 31D) in a return position about its pivoting directions.

11. Tool (30) according to the preceding claim, characterized in that the return means comprise at least one axially and / or radially compressible elastic return gasket (46, 47, 48) mounted along the axis of rotation (A4). and having an edge bearing against the corresponding side of the first grinding wheel (31; 31A; 31B; 31C; 31D) and an opposite edge bearing against an abutment associated with the support (38).

12. Tool (30) according to one of claims 7 to 11, characterized in that the support (38) constitutes a drive shaft of the first grinding wheel

(31; 31A; 31B; 31C; 31D) having an axis of rotation (A4) substantially coinciding with the axis of revolution of the edging face (99; 99A; 99B; 99C; 99D) of the first grinding wheel (31; 31A; 31B; 31C; 31D), drive means being provided for ensuring torque transmission from the support (38) to the first grinding wheel (31; 31A; 31B; 31C; 31D).

13. Tool (30) according to one of claims 7 to 12, characterized in that the drive means are merged with the mechanical tilting connection means and are arranged to achieve a spherical finger mechanical connection.

14. Tool (30) according to the preceding claim, characterized in that the spherical finger mechanical connection comprise, firstly, a grooved ball (40) associated with the support (38) and, secondly, a grooved housing (70; 74; 75) associated with the first grinding wheel (31; 31A; 31B; 31C; 31D) and arranged to cooperate with said fluted ball joint (40).

15. Tool (30) according to claim 13, characterized in that, the first grinding wheel (31; 31A; 31B; 31C; 31D) being formed in the form of a ring (49), the mechanical connection means spherical finger include an inner collar (39) cooperating by substantially multi-point or linear contact with the support (38).

16. Tool (30) according to the preceding claim, characterized in that the return means comprise at least one elastic body (91, 92) mounted on one side at least of the collar (39) central of the first grinding wheel (31). 31A; 31B; 31C; 31D), this body (91, 92) cooperating on the one hand with the support (38) and on the other hand with the ring (49) for transmitting the torque of the support (38) at the first grinding wheel (31; 31A; 31B; 31C; 31D).

17. Tool (30) according to one of claims 7 to 12, characterized in that the drive means of the first grinding wheel (31; 31A; 31 B; 31 C; 31 D) are distinct from the mechanical connection means. tipping.

18. Tool (30) according to one of claims 7 to 17, characterized in that the first grinding wheel (31; 31A; 31B; 31C; 31D) comprises at least one chamfering face (33,98; 33A , 98A; 33B, 98B; 33C, 98C; 33D, 98D) whose generator forms an angle with the overflow face (99; 99A; 99B; 99C; 99D).

19. Tool (30) according to one of claims 7 to 18, characterized in that the flange face (99A; 99B; 99C; 99D) of the first grinding wheel (31; 31A; 31B; 31C; 31D; ) is conical.

20. Apparatus (10) for trimming an ophthalmic lens (L) comprising clamping shafts (12, 13) and rotating the lens (L) ophthalmic lens, main grinding wheels (14), and a working tool (30) according to one of claims 7 to 19.

21. Apparatus (10) for trimming according to the preceding claim, characterized in that the tool (30) is disposed on a module (25) of the device (10) for trimming the ophthalmic lens (L), retractable in a plane substantially transverse to the axis of the clamping shafts (12, 13) and driving in rotation of the ophthalmic lens (L).