EP1172176A1 - Method to improve the accuracy of spectacle glasses bevelling and bevelling tool therefore - Google Patents

Abstract

The procedure, using a rotary tool (14) to grind a spectacle lens (10) to produce a bevelled edge, employs a compensator (22, 22') to provide an elastic deformation capacity between the tool and its supporting shaft (16). The compensator, located between the tool's working rim (18, 18') and hub (15), is made from a material such as an elastomer with a Shore A hardness of 40 - 80.

Description

The present invention relates generally to chamfering glasses.

As we know, the overflowing of a glass of glasses necessary for the bringing its contour into conformity with that desired, usually produced by grinding, leads to the formation of a sharp and sharp edge on the periphery of each of its front and rear faces, with, possibly, the presence of possible burrs related to the surface treatment of these faces.

It is therefore customary, if only for security reasons, to proceed to a chamfering of such an edge to deburr it and break the angle, and, thus, limit its aggressiveness.

First insured by means of a manual recovery operation, it is now provided that this chamfering occurs automatically, at less on some grinders, especially those on order digital.

During such a chamfer, a determined position setpoint is applied between the chamfering tool used and the spectacle lens worked, or, more precisely, between, on the one hand, the support shaft of this tool chamfering, and, on the other hand, that of the spectacle lens formed, in practice, of two pins enclosing this glass.

But, having regard, on the one hand, to the inevitable random distortions most common spectacle lenses than, on the other hand, inaccuracies equally unavoidable hardware and software available grinders, for example example regarding the relative position of the support shafts and pins in question, it is difficult, to date, if not impossible, to achieve reliably the desired chamfer with all the desired precision.

On the contrary, it is not uncommon to observe an untimely dispersion of the flat value of this chamfer all along the worked edges, i.e. the width of this chamfer.

The present invention generally relates to an arrangement allowing this difficulty to be overcome in a simple and effective manner and further leading to other benefits.

More specifically, it firstly relates to a process for improve the precision of a chamfering operation applied to a glass of glasses; it also relates to a chamfering tool specific to the setting work of this process.

In general, the invention is characterized by the insertion of means of compensation between, on the one hand, the relevant periphery of one any of the elements that constitute the chamfering tool used and the glasses of glasses worked, and, on the other hand, the support shaft of this same element.

By compensation means is meant here means having a elastic deformation capacity, i.e. means allowing the intervention of such a deformation capacity.

According to a particular embodiment, these means of compensation intervene, for example, within the tool of chamfering.

By the capacity of elastic deformation which they present, they allow then to this chamfering tool to deform under too much effort, and, so that the relevant periphery of this tool takes a position in space allowing it to best apply to the glass of glasses worked, ensuring the engagement of the chamfering tool with respect to this spectacle lens while systematically absorbing possible position dispersions of these two elements relative to each other.

As a result, this results in an advantageous regularization of the flat value of the chamfer obtained, for the benefit of the quality and reliability of the corresponding chamfering operation.

But it also follows that, the other conditions being equal by elsewhere, it is possible, if desired, to be satisfied with a less calibrated rigorous position of the chamfering tool in relation to the glass glasses worked, for the benefit of a simplification of the manufacture of the corresponding grinder.

Furthermore, the compensation means thus implemented within the chamfering tool also make it possible to advantageously reduce its inertia, to the benefit of the dynamics of the whole.

Finally, a chamfering tool comprising such means of compensation can if desired be placed on a support shaft concurrently with another rigid chamfering tool, the grinder as well equipped then being able to choose, either to ensure faithful and rigorous respect of a given position setpoint, or to be satisfied with a certain modulation of this position setpoint, to the benefit, depending on the applications, its flexibility of use.

• la figure 1 est une vue en coupe axiale d'un outil de chanfreinage suivant l'invention ;
• la figure 2 reprend, à échelle supérieure, le détail de la figure 1 repéré par un encart II sur cette figure 1 ;
• la figure 3 est une vue en coupe axiale qui, déduite de celle de la figure 1, illustre le fonctionnement de l'outil de chanfreinage suivant l'invention ;
• la figure 4 reprend, à échelle supérieure, le détail de la figure 3 repéré par un encart IV sur cette figure 3 ;
• la figure 5 est une vue en coupe axiale analogue à celle de la figure 1, pour une première variante de réalisation de l'outil de chanfreinage suivant l'invention ;
• la figure 6 est une autre vue en coupe axiale analogue à celle de la figure 1, pour une deuxième variante de réalisation de cet outil de chanfreinage ;
• la figure 7 est, suivant la flèche VII de la figure 6, une vue en élévation de cette deuxième variante de réalisation ;
• la figure 8 est une autre vue en coupe axiale analogue à celle de la figure 1, pour une troisième variante de réalisation de l'outil de chanfreinage suivant l'invention ;
• la figure 9 est la vue en élévation-coupe repérée par IX-IX sur la figure 8 ; et
• la figure 10 est une autre vue en coupe axiale analogue à celle de la figure 1, pour une quatrième variante de l'outil de chanfreinage selon l'invention.

The characteristics and advantages of the invention will become apparent from the description which follows, by way of example, with reference to the appended schematic drawings in which:

• Figure 1 is an axial sectional view of a chamfering tool according to the invention;
• Figure 2 shows, on a larger scale, the detail of Figure 1 identified by an insert II in this Figure 1;
• Figure 3 is an axial sectional view which, deduced from that of Figure 1, illustrates the operation of the chamfering tool according to the invention;
• Figure 4 shows, on a larger scale, the detail of Figure 3 identified by an insert IV in this Figure 3;
• Figure 5 is an axial sectional view similar to that of Figure 1, for a first alternative embodiment of the chamfering tool according to the invention;
• Figure 6 is another view in axial section similar to that of Figure 1, for a second alternative embodiment of this chamfering tool;
• Figure 7 is, according to arrow VII of Figure 6, an elevational view of this second embodiment;
• Figure 8 is another view in axial section similar to that of Figure 1, for a third alternative embodiment of the chamfering tool according to the invention;
• Figure 9 is the elevation-sectional view identified by IX-IX in Figure 8; and
• Figure 10 is another view in axial section similar to that of Figure 1, for a fourth variant of the chamfering tool according to the invention.

As illustrated in Figure 3, it is, overall, to cut down by a chamfers the edges presented by a spectacle lens 10 along its contour, and, for example, as shown, the front edge 11 of this spectacle lens 10, that is to say that of these edges which intervenes at the intersection of its front face 12 and its peripheral outline 13.

Usually, the corresponding chamfering operation is provided by means of a chamfering tool 14 comprising, overall, a hub 15, tubular, suitable for fitting onto a support shaft 16 shown in broken lines in the figures, and at least one working rim 18 integral in rotation with this hub 15.

In a manner known per se, also, this working rim 18 comprises an active periphery 19 abrasive.

For example, and as shown, this active periphery 19 extends following a frustoconical facet of the working rim 18.

Let R be its mean radius.

In a manner known per se, finally, the support shaft 16 of the tool chamfer 14 is rotatably mounted, and the same applies to the support shaft as a corollary maintaining the spectacle lens 10 to work, this shaft support being in practice usually constituted by two pins support suitable for enclosing this spectacle lens 10.

The corresponding provisions being well known in themselves and not coming under the present invention, they will not be described in more detail here.

According to the invention, the insertion of compensation means is ensured, that is to say means having an elastic deformation capacity, between, on the one hand, the relevant periphery of any of the elements that constitute the chamfering tool 14 used and the spectacle lens 10 worked, and, on the other hand, the support tree of this same element.

In the embodiments shown, these means of compensation occur within the chamfering tool 14.

More specifically, this chamfering tool 14 comprises, between the active periphery 19 of its working rim 18 and its hub 15, or, more again precisely, between the active periphery 19 of its working rim 18 and the internal periphery 21 of its hub 15, such compensation means.

In the embodiment more particularly represented on the Figures 1 to 4, the working rim 18 comprises a binder of rigid material in which are disseminated abrasive grains of average diameter between 4 and 20 micrometers, these grains being in diamond, silica, boron nitride or in all other abrasive material, and the compensating means having a capacity of elastic deformation comprise an intermediate piece 22 which, interposed, radially, between the working rim 18 and the hub 15, is itself made of material flexible, for example made of elastomer.

This intermediate piece 22, which, for example, and as shown, is circularly continuous, is duly secured in rotation both to the hub 15 than at the working rim 18.

In the embodiment shown in Figures 1 to 4, according to which the outer periphery of the hub 15 and the inner periphery of the rim of work 18 are cylindrical, being in practice coaxial with each other, the The corresponding connection is made, for example, by gluing.

Preferably, the compensation means thus implemented according to the invention have an elasticity corresponding to a shore hardness of between 40 and 80 ShA according to standard NF T 46052, a breaking strength of between 4 and 10 MPa as well as a elongation at break greater than 200% according to standard NF T 46002, and, according to standard NF T 46007C, a tear limit greater than 4 DaN / cm ² .

As a corollary, the cutting power of the working rim 18 along the active periphery 19 is preferably limited.

Preferably, and this is the case in all of the forms of shown embodiment, at the working rim 18 of the chamfering tool 14 are associated with abutment means 23 from which it is separated by a clearance J at rest.

For example, and as shown, these stop means 23 comprise a disc 24, which, coaxial and integral with the hub 15, extends transversely by compared to this one.

In practice, the face 25 of the working rim 18 which, opposite its active periphery 19, faces the disc 24, is parallel to it, and it therefore extends itself transversely relative to the hub 15.

In practice, also, the stop means 23 are reduced to the disc 24.

In the embodiments shown in Figures 1 to 9, the tool chamfering 14 according to the invention comprises two working rims 18, 18 ' each arranged respectively on either side of the disc 24.

In practice, these two working rims 18, 18 'have constitutions identical.

In the embodiments more particularly represented on the Figures 1 to 5 as well as 8 and 9, they are even identical to each other.

In particular, they have active peripheries 19, 19 'whose radii means R, R 'are equal, and each part is associated with a part intermediate 22, 22 '.

In service, that is to say when the chamfering tool 14 is applied to the spectacle lens 10 to be worked, for example by its working rim 18, and, more specifically, by the active periphery 19 of this working rim 18, this rim working 18 tilts more or less relative to the axis of the next hub 15 the corresponding application force, thanks to an elastic deformation of the compensation means used for this purpose, as shown in the figure 3.

At the corresponding point of contact, this generally results in a more or less accentuated from this working rim 18 compared to the spectacle lens 10.

Thus, and as shown schematically in Figure 4, in which the original position of the working rim 18 is shown in dashed lines while its retracted position is shown in solid lines, the value on flat I, or width, of the chamfer 26 formed is less than the flat value L which would have prevailed in the absence of such a step back.

Overall, this results in a regularization of this flat value.

Of course, the retraction of the working rim 18 relative to the glass of glasses 10 worked only intervenes within the limits authorized by the means stop 23, that is to say by the disc 24, this working rim 18 being likely to ultimately come into abutment against the latter.

It should be noted that the possibility of the rim receding is favorable to the sustainability of the chamfering function insofar as it allows a some wear.

According to the variant embodiment shown in FIG. 5, the rim of work 18 is at least partly made of flexible material and thus constitutes by itself the compensation means having a deformation capacity elastic, and, for example, the same is true for the 18 'working rim.

More specifically, in the alternative embodiment shown in the figure 5, the working rim 18 comprises a binder of flexible material, for example in elastomer, in which grains are disseminated, at least on the surface abrasives made of suitable material such as one of the materials mentioned above, and the same is true for the 18 'working rim.

But, for the rest, the provisions are of the same type as the above, in particular with regard to the elasticity characteristics and the cutting power.

Note that the choice of these two parameters must be made jointly.

Thus, when the cutting power is reduced, the elasticity must be increased by in order to apply a tool / glass bearing force large enough to compensate for the low cutting power.

Conversely, when the cutting power is important, the elasticity must be reduced so as to generate a low tool / glass bearing force.

In the alternative embodiment shown in Figures 6 and 7, which is of the same type, with intermediate part 22, 22 ', as that shown on the Figures 1 to 4, the two working rims 18, 18 'have active peripheries 19, 19' whose mean radii R, R 'are different.

It is thus possible, depending on the spectacle lenses 10 to be worked, and / or depending on whether the machining of these concerns their edge before 11 or their edge rear, to machine such a spectacle lens 10 using one or the other of the two working rims 18, 18 ', and therefore on different spokes, which allows apply separate efforts to it.

For example, the machining of such a spectacle lens 10 along a small radius of the chamfering tool 14 makes it possible to increase the stiffness of the means of compensation thereof, and, on the contrary, machining along a large radius reduces this stiffness.

In either case, it is possible to intervene in this way on the effort transmitted, and, therefore, on the resulting pressure.

More precisely, in the case, for example, of a simple deburring, it is preferably the working rim 18 'having the largest average radius R' which is implemented.

As a corollary, in the case where, on the contrary, a relatively chamfer important is desired, it is the working rim 18 with the smallest radius means R which is preferably used.

Furthermore, in the embodiment shown in Figures 6 and 7, between the working rim 18, 18 'and the intermediate piece 22, 22' forming the corresponding compensation means intervene, preferably, and such as shown, mechanical anchoring means 27, to consolidate the secured in rotation between this working rim 18, 18 'and this part intermediate 22, 22 '.

Similarly, and for the same reasons, between the intermediate piece 22, 22 ' and the hub 15 intervenes mechanical anchoring means 28.

For example, the mechanical anchoring means 27, 28 are constituted by teeth, respectively 29, 30, which extend annularly so regular, and in a complementary manner, between the parts in question.

In the alternative embodiment shown in Figures 8 and 9, there is no hub 15 common to the working rims 18 and 18 'and to the disc 24, but three individual hubs.

In addition, between the rim 18 and its hub 15, and likewise between the rim 18 ' and its hub 15, the intermediate piece 22, 22 'is not constituted by a continuous monobloc element, but by several distinct elements, which are here in radius shape. The elasticity characteristics of these elements are chosen so that they are equivalent to the above mentioned of an element continuous monoblock.

Finally, the disc 24 has on the periphery, beyond the working rims 18 and 18 ', a flange 31 for machining a groove on the contour peripheral 13 of the spectacle lens 10.

In the variant embodiment shown in FIG. 10, the tool 14 does not has only one working rim 18, but the active periphery 19 of this working rim has a frustoconical facet on each side, so that the same working rim 18 allows both to make the chamfer between the face front 12 and the peripheral contour 13 of the spectacle lens 10 and the chamfer between the peripheral contour 13 and the rear face.

The stop means 23 of the tool 14 shown in FIG. 10 are not constituted by a single disc 24, but by two discs 24 located respectively on either side of the working rim 18, one of the discs 24 used for the machining of the chamfer located on the side of the front face of the glass glasses 10 and the other disc for the chamfer located on the side of the rear face.

It will be observed that having two discs 24 located respectively on either side of the rim 18 ensures the maintenance in position of this rim in case of accidental separation between the part intermediate 22 and the working rim 18 or between the intermediate piece 22 and the hub 15.

For reasons of mounting convenience, the disc 24 that we see on the left in Figure 10 is integral with the hub 15 while the disc 24 that we see on the right is secured to a hub against an annular part being in abutment at the end of the hub 15 and comprising a tubular part is housed inside the hub 15 and bearing at the end of the shaft of support 16.

In this embodiment, the flange 31 used to machine the groove of the peripheral contour 13 of the spectacle lens 10 is not located on a disc 24 forming part of the stop means 23, but at the periphery of a disc 32 mounted, like tool 14, on the support shaft 16.

Note that the diameter of the discs 24, because in this mode of realization it is less than the smallest diameter of the abrasive periphery 19, allows the chamfering of small diameter spectacle lenses.

In variants not illustrated, the connections made respectively by the mechanical anchoring means 27 and 28 in the embodiment of the Figures 6 and 7 are replaced by a connection of the same type as in the other illustrated examples, i.e. by adhesion and, conversely, the connections by adhesion of the other illustrated embodiments are replaced by connections with mechanical anchoring means of the kind identified by 27 and 28 in Figures 6 and 7.

In other variants not illustrated, exemplary embodiments which have just been described in support of Figures 1 to 7 and 10, the intermediate piece continuous monobloc is replaced by a part in several distinct elements, in the form of a radius as in the example of FIGS. 8 and 9 or in another appropriate form; and the intermediate piece into several separate elements of the example of FIGS. 8 and 9 is replaced by a one-piece intermediate piece keep on going.

In still other alternative embodiments, not illustrated, of the embodiment of FIGS. 1 to 7, the disc 24 is completed at the periphery by a tool grooving like the flange 31 of the examples illustrated in Figures 8 to 10.

In still other alternative embodiments not illustrated, the chamfering 14 has two rims of separate constitution, for example one with a continuous monobloc intermediate piece and the other with a piece intermediary in several elements, in order to best adapt to the work at achieve.

Of course, the present invention is not limited to the forms of realization described and represented, but includes any variant and / or a combination of their various elements.

In particular, the hub of the chamfering tool could be directly formed by the internal periphery of its working rim or that of the intermediate part possibly implemented, without being otherwise more individualized.

In addition, instead of intervening within this chamfering tool, the compensation means used according to the invention can equally intervene well in the mounting of the spectacle lens on its support shaft.

Claims (20)

Method for improving the precision of a chamfering operation applied to a spectacle lens, characterized by the insertion of compensation means (22, 22 '; 18, 18') having an elastic deformation capacity between, on the one hand , the periphery concerned of any of the elements that constitute the chamfering tool (14) used and the spectacle lens (10) worked, and, on the other hand, the support shaft of this same element . Chamfering tool for spectacle lenses, of the type comprising a hub (15) suitable for being placed on a support shaft (16), and at least one working rim (18, 18 ') integral in rotation with this hub (15), characterized in that it comprises, between the active periphery (19, 19 ') of its working rim (18, 18') and its hub (15), compensation means (22, 22 ') having an elastic deformation capacity. Chamfering tool according to claim 2, characterized in that the working rim (18, 18 ') is made of rigid material, and the compensation means comprise an intermediate piece (22, 22') which, interposed between the working rim (18, 18 ') and the hub (15), is made of flexible material. Chamfering tool according to claim 3, characterized in that , between the working rim (18, 18 ') and the intermediate piece (22, 22') intervene mechanical anchoring means (27). Chamfering tool according to any one of claims 3, 4, characterized in that , between the intermediate piece (22, 22 ') and the hub (15), there are mechanical anchoring means (28). Chamfering tool according to any one of claims 4, 5, characterized in that the mechanical anchoring means (27, 28) consist of teeth (29, 30). Chamfering tool according to claim 2, characterized in that the working rim (18, 18 ') is at least partly made of flexible material and thus constitutes by itself the compensation means. Chamfering tool according to claim 7, characterized in that the working rim (18, 18 ') comprises a binder of flexible material in which the necessary abrasive means are disseminated, at least on the surface. Chamfering tool according to any one of Claims 2 to 8, characterized in that the compensation means (22, 22 '; 18, 18') have an elasticity corresponding to a breaking strength of between 4 and 10 Mpa as well an elongation at break greater than 200% according to standard NF T 46002. Chamfering tool according to any one of Claims 2 to 9, characterized in that the compensation means (22, 22 '; 18, 18') have an elasticity corresponding to a shore hardness of between 40 and 80 ShA according to the standard NF T 46052 and / or a tear limit greater than 4 DaN / cm ² according to standard NF T 46007C. Chamfering tool according to any one of Claims 2 to 10, characterized in that , to the working rim (18, 18 '), there are associated stop means (23) from which it is separated by a clearance (J) resting. Chamfering tool according to claim 11, characterized in that the stop means (23) associated with the working rim (18, 18 ') comprise a disc (24) which, coaxial and integral with the hub (15), s' extends transversely with respect thereto. Chamfering tool according to claim 12, characterized in that the face (25) of the working rim (18, 18 ') facing the disc (24) is parallel to the latter. Chamfering tool according to any one of Claims 12, 13, characterized in that it comprises two working rims (18, 18 ') each arranged respectively on either side of the disc (24), and the hub ( 15) is common to the whole. Chamfering tool according to claim 14, characterized in that the two working rims (18, 18 ') have active peripheries (19, 19') whose mean radii (R, R ') are different. Chamfering tool according to claim 3, characterized in that the intermediate piece (22, 22 ') is in one piece and continuous. Chamfering tool according to claim 3, characterized in that the intermediate piece (22, 22 ') is formed from several distinct elements. Chamfering tool according to claim 17, characterized in that said separate elements are formed in radius. Chamfering tool according to any one of Claims 1 to 13 and 16 to 18, characterized in that it comprises a working rim (18) whose active periphery (19) has two opposite frustoconical facets. Chamfering tool according to any one of Claims 2 to 19, characterized in that it comprises two discs (24) situated respectively on either side of the working rim.

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