EP0191689B1 - Supporting ring for fixing a mounting block on the progressively variable finished face of a disc such as an ophthalmic lens or a mould - Google Patents

Description

The present invention relates generally to commonly called progressive ophthalmic lenses.

As is known, these are ophthalmic lenses of which at least one of the faces has a progressively variable curvature over at least part of at least one meridian line, in order to obtain a progressive addition of power along it.

In practice, this is the case for the only convex front face of such an ophthalmic lens, and the latter is usually characterized, on the one hand, by its basic curvature, to which a far vision zone corresponds. for the patient concerned, and, on the other hand, by its addition of power, to which corresponds a near vision zone for the latter.

At the same time, the concave rear face of progressive ophthalmic lenses is assigned to any special prescriptions to be satisfied, moreover, for the vision correction of such a patient.

Taking into account, on the one hand, the difficulties of producing surfaces with progressively variable curvature, and, on the other hand, the diversity, in nature and in intensity, of the other possible vision corrections, it is more economical to produce a reduced number of semi-finished blanks, covering by their front face, which then constitutes a finished face, a determined range, considered sufficient to correspond to all the conceivable cases, basic curvatures and power additions, and then adapt these blanks, by machining their rear face, to the various requirements to be met.

For the resumption of machining which it is therefore necessary to apply to the rear face of such semi-finished blanks, it is usual to attach a gripping block to their front face, according to a process commonly called "gliding", commonly known as a mounting block, suitable for then allowing proper maintenance on a surfacing machine.

For the production of such a mounting block, a casting process is usually carried out within a blocking device of a material with a low melting point between the face concerned of the semi-finished blank to be treat and a mold, commonly called a support ring, open in a bell towards it.

The difficulty in this case is twofold.

First of all, to guarantee the precision of the subsequent surfacing operations, and thus allow the obtaining of a finished opthalmic lens having the required optical characteristics, it is essential to ensure a precise positioning of the finished face of the 'semi-finished blank to be treated vis-à-vis the support ring used.

However, as indicated above, this finished face is of gradually variable curvature, which, without other, can make its support on the support ring random.

This can in particular result in obtaining, in an uncontrolled manner, a more or less large prism for the near vision zone to which this progressively variable curvature corresponds, and therefore difficulties in pairing ophthalmic lenses for the same patient. .

In addition, it is desirable that the same blocking device can be used for all the semi-finished blanks to be processed.

Most often, an adapter ring is used to do this, one of the faces or bearing face of which is annularly shaped so as to be able to match the finished face of a semi-finished blank to be treated. , while the other is adapted to cooperate with the mold, or support ring, used.

Such a solution requires having a large fleet of adapter rings with different characteristics, each corresponding respectively to the entire range of semi-finished blanks to be processed.

In practice, an adapter ring is therefore required by basic curvature and by addition of power, that is, most frequently, a total of about thirty adapter rings for each type of progressive ophthalmic lens.

In addition to the storage space to which it leads, this solution is all the more expensive since each of the adapter rings thus to be implemented is usually a metal ring produced by machining and therefore expensive.

To minimize this drawback, it has been proposed to use, as a replacement for these adapter rings, mounting reinforcements that can be produced in synthetic material, these mounting reinforcements constituting lost parts which, at the time of the casting of the block of mounting, are at least partially overmolded by such a mounting block.

Although such a solution, which is the subject of patent application FR-A-2 186441, has given and can still give satisfaction, it also leads to the need for having a large fleet of mounting fittings. corresponding to the different basic curvatures and power additions to be observed for each type of progressive ophthalmic lens.

Another solution already proposed consists, moreover, of using rings or reinforcements suitable for obtaining a circularly continuous support zone for the finished face of the semi-finished blanks to be treated, but simple studs, which, locally applied to this finished face, define for the latter a limited number of support zones suitably distributed circularly around the axis of the assembly.

Depending on the basic curvature and the addition of power, two of these pads, or compensating pads, are thus applied to the periphery of this finished face, each being

respectively arranged at the ends of the horizontal diameter thereof, so that the support of the whole of this finished face is done at three points, and therefore in a plane, the third point, which intervenes on a circular half-crown passing through the other two, not involving the implementation of any compensating stud.

If it is economical, this solution has the drawback of only ensuring the support of a semi-finished blank to be processed in a semicircle, which can be the source of errors which irretrievably lead to the rejection of the lenses. finished ophthalmic subsequently obtained.

The present invention generally relates to a provision which, while satisfying the conditions to be observed, advantageously makes it possible to avoid these drawbacks.

More specifically, it relates to a support ring for semi-finished blank of a puck, which may be an ophthalmic lens, but which may as well be a mold intended for molding such an ophthalmic lens, type comprising, for contact with said semi-finished blank, a limited number of bearing zones, which, suitably distributed circularly about an axis, are all generally inclined relative to a reference plane perpendicular to such an axis, in each extending between two ends offset both radially and axially with respect to each other, this support ring being characterized in that the planes tangent to the ends of each of the support zones, one and the other orthogonal to the same axial plane of the assembly passing through the median radius of such a support zone, make a dihedral between them.

The present invention is in fact based on the observation, not revealed to date for a support ring, that due to the very topography of the surfaces with progressively variable curvature, a limited number of support zones, arranged on the same circle, the diameter of which depends on the base curvature of this surface, may suffice.

In practice, three support zones may thus suffice, without two of them necessarily being arranged at the ends of the same diameter.

On the contrary, they are advantageously distributed at the top of an isosceles triangle, each side of which is away from the center of the corresponding circle, surrounding it.

According to the invention, the planes tangent to the ends of each of the support zones used form a dihedral between them.

In other words, the inclination of such a support zone is not the same at both of its ends.

According to a first possible embodiment, this inclination varies discontinuously from one end to the other of a support zone.

In such a case, each of the support zones implemented comprises in practice a plurality of support facets, which, all generally inclined relative to the reference plane and all orthogonal to the axial plane of the assembly passing through the radius median of such a support zone, are of different inclinations with respect to said reference plane, said support facets succeeding each other radially on circumferences of different diameters according to their inclination, and those extreme merge with the tangent planes d 'corresponding ends.

In practice, to cover all of the possible basic curvatures, it suffices, then for each of the support zones used, a limited number of such support facets, each of these support facets being able to indifferently suit one or more of such basic curvatures.

Taken together, these multiple support facets form a globally convex whole.

However, it even turns out that, according to a second possible embodiment of the invention, a single support facet is sufficient for each of the support zones used.

This single support facet is then continuously curved from one to the other of the ends of such a support area.

In other words, the inclination of such a support zone then varies continuously from one of its ends to the other.

Its unique support facet is in practice a convex facet.

In all cases, multiple facets or single curved facet, where it was customary to date to provide, for the support of the finished face of a semi-finished blank to be treated, a ring or a reinforcement of complementary shape that of this face and therefore conforming to it, it suffices, according to the invention, to facet (s) suitably produced (s) and generally convex (s).

It turns out, as a corollary, that, for the same basic curvature, the length of the main median of the triangle along which the support is made, on a support ring according to the invention of the finished face d '' a semi-finished blank to be treated is substantially constant, whatever the addition of power thereof, the point of contact with each of the corresponding bearing facets simply moving, both radially and circumferentially, along of such a facet of support, according to the addition of power.

It follows overall from the above that, for a determined topography of surface with progressively variable curvature, that is to say for a determined type of progressive ophthalmic lens, a single support ring, with number of support zones limited, can advantageously and economically satisfy the processing of the whole range of semi-finished blanks, with basic curvature and different power additions, to be taken into consideration for the production of such progressive ophthalmic lenses.

Indeed, according to the base curvature of the finished face of such a semi-finished blank, its support on the support ring is made on such or such support facets that each of the support areas of that includes -ci, if they are support zones with multiple support facets, or at such or such point of the support facet of these support zones, if they are support with single support facet, and, according to the addition of power of this semi-finished blank, the corresponding contact point simply moves radially and circumferentially.

In all cases, the contact is made tangentially in an appropriate manner, and, having regard, moreover, to compliance with benchmarks provided for this purpose, the installation, on a support ring according to the invention, of a semi-blank -finished to be treated can be done, in a systematic way, with all the desirable precision.

In particular, it is possible, if desired, to orient this blank so that the plane tangent to the top of its finished face makes, with respect to a fixed reference plane, a determined angle proportional to its addition of power.

However, regardless of this angle, the precision of the positioning thus ensured guarantees that of the optical characteristics finally obtained after the machining of such a blank.

Similarly, with an off-center semi-finished blank, that is to say with a semi-finished blank whose optical axis is offset transversely to the geometric axis, it suffices, with the following support ring the invention, to place such a semi-finished blank on such a support ring by orienting it suitably with respect thereto.

It is then simply observed that the supports of this off-center semi-finished blank on the support ring are no longer made along the vertices of an isosceles triangle, as is on the contrary in practice the case with a semi-finished blank whose the optical axis coincides with the geometric axis.

However, no particular adjustment is then advantageously to be carried out on the surfacing machine subsequently implemented.

In other words, when the support ring used for producing a mounting block on a semi-finished blank is a support ring according to the invention, the adjustment of such a surfacing machine remains the same as it is a semi-finished blank with optical and geometrical axes combined or it is a semi-finished blank offset.

Furthermore, generally using only a few support facets, and these being in practice only simple, flat, spherical or toric surfaces for example, the support ring according to the invention is advantageously relatively easy and economical to make.

Certainly, in the English patent GB-A-1 155 719, a holding block for an ophthalmic lens is described, which, for contact with such an ophthalmic lens, has, suitably distributed circularly, a plurality of insulated support zones, each of which extends between two ends offset both radially and axially with respect to each other.

However, in addition to the fact that such a retaining block does not constitute a support ring within the meaning of the present application, since it is not a part to be used for the production of a mounting block. , but of a part capable of ensuring directly by itself the maintenance of the ophthalmic lens during its surfacing, only its support is provided on a cylindrical or toric surface, and not its support on an aspherical surface such as the constitutes a surface with progressively variable curvature, and, therefore, if it only has one support facet per support area, it is in practice a flat support face, the problem of its adaptation to a range of different basic curvatures and / or to different power additions which do not arise.

It is not the same with the support ring according to the invention.

Likewise, in patent US-A-3 140 568 these are support zones which are suitable for marrying a spherical surface and, moreover, this spherical surface being convex, the support facet which they form is a concave facet.

• la figure 1 est une vue en coupe axiale d'une ébauche semi-finie d'une lentille ophtalmique progressive;
• la figure 2 est une vue en coupe axiale, qui, analogue à celle de la figure 1, illustre la mise en place d'un bloc de montage sur une telle ébauche semi-finie;
• la figure 3 est, avec un arrachement, une vue en perspective d'une bague d'appui propre à la coulée d'un tel bloc de montage;
• la figure 4 est une vue en plan de cette bague d'appui, suivant la flèche IV de la figure 3;
• la figure 5 en est une vue en coupe axiale, suivant la ligne brisée V-V de la figure 4;
• la figure 6 reprend, à échelle supérieure, le détail de la figure 5 repéré par un encart VI sur celle-ci;
• les figures 7, 8 sont des vues en plan illustrant schématiquement l'appui, sur une telle bague d'appui, d'une ébauche semi-finie à traiter.
• Tel qu'illustré par la figure 1, l'ébauche semi- finie 10 d'une lentille ophtalmique progressive se présente en général sous la forme d'un palet dont la face avant 11, qui en est en pratique la face convexe, est celle présentant, le long d'une des parties au moins d'un au moins de ses méridiens, supposé être celui dans le plan de la figure, une courbure progressivement variable.

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 semi-finished blank of a progressive ophthalmic lens;
• Figure 2 is an axial sectional view, which, similar to that of Figure 1, illustrates the establishment of a mounting block on such a semi-finished blank;
• Figure 3 is, with a cutaway, a perspective view of a bearing ring suitable for casting such a mounting block;
• Figure 4 is a plan view of this support ring, along arrow IV of Figure 3;
• Figure 5 is an axial sectional view along the broken line VV of Figure 4;
• Figure 6 shows, on a larger scale, the detail of Figure 5 identified by a VI insert thereon;
• Figures 7, 8 are plan views schematically illustrating the support, on such a support ring, of a semi-finished blank to be treated.
• As illustrated in FIG. 1, the semi-finished blank 10 of a progressive ophthalmic lens is generally in the form of a puck whose front face 11, which in practice is the convex face, is that having, along at least one of the parts of at least one of its meridians, assumed to be that in the plane of the figure, a gradually variable curvature.

For example, and as shown, the face 11 of this semi-finished blank 10 may be globally spherical over a portion VL of its surface, supposed to correspond to the distant vision of the patient concerned, while for the other VP portion of this surface, supposed, it, to correspond to the near vision of this one, it presents, along at least along its meridian main, a gradually variable curvature.

Thus, and as shown diagrammatically in broken lines in FIG. 1, along its central meridian, the portion VP of the surface of the front face 11 of the semi-finished blank 10 progressively deviates from the spherical surface constituting moreover the other portion VL of this surface.

Be that as it may, the front face thus with gradually variable curvature 11 of this semi-finished blank 10 constitutes the finished face.

It is therefore its rear, convex face 12 which is to be machined for any prescriptions to be observed.

As shown, this rear face 12 can be a spherical face, of radius R equal to that of the far vision portion VL of the front face 11.

But such a provision is of course not imperative.

It also has no impact on the present invention.

In any event, the outline of the puck forming the semi-finished blank 10 thus formed is usually circular, and the corresponding edge 13 of this puck is usually cylindrical, along generatrices parallel to the optical axis A of the assembly.

This optical axis A, which is shown diagrammatically in broken lines in FIGS. 1, 2, usually passes through the optical center of each of the faces 11, 12.

For machining the rear face 12, it is necessary to attach, to the front face 11, by casting a metal with a low melting point, a mounting block 15, as shown diagrammatically in broken lines in FIG. 2 , this mounting block 15 being intended to ensure the establishment of the semifinished blank 10 concerned on an appropriate surfacing machine.

For good control of this positioning, it is important that the tangent plane T at the top of the front face 11, that is to say the tangent plane, which, perpendicular to the optical axis A, contains the optical center of this face 11, occupies, with respect to a reference plane P, a determined orientation.

In FIG. 2, in which the tangent plane T and the reference plane P have been shown diagrammatically by their traces, in solid lines for the first, and in broken lines for the second, the tangent plane T has been assumed to be parallel to the plane reference P.

As a result, the optical axis A is then itself perpendicular to this reference plane P.

But this is not necessarily so, any other desired orientation may be possible.

For casting the mounting block 15, it is necessary to place the semi-finished blank 10 on a support ring 16.

In a manner known per se, the support ring 16 implemented for this purpose according to the invention comprises, annularly, around an axis A ', a crown 17.

This axis A 'is shown diagrammatically in broken lines in FIG. 5, and it appears by its trace in FIG. 4.

On the side opposite that on which the semi-finished blank 10 to be treated must come to bear, that is to say downwards, the crown 17 is extended axially by a skirt 18.

Inside the skirt 18, the crown 17 comprises transversely a planar bearing surface 19, which extends perpendicular to the axis A 'of the assembly.

This surface 19 constitutes a reference plane P 'making it possible to control the position of the assembly of the support ring 16, and therefore that of the semi-finished blank 10 to be treated, in the blocking device used for casting the mounting block 15.

To check the angular orientation of the support ring 16 around its axis A 'in this blocking device, the skirt 18 has at least one notch 20 on its edge 21.

In the embodiment shown, two notches 20 are thus provided on the edge 21 of this skirt 18, in diametrically opposite positions relative to each other.

In addition, in this embodiment, the outer surface of the skirt 18 is in continuity with that of the crown 17 of which it forms an extension, and, radially, its thickness is less than that of the latter, for example approximately of half.

On the side opposite the skirt 18, that is to say upwards, there is provided, for contact with the semi-finished blank 10 to be treated, a limited number of support zones Z; in practice, three support zones Z1, Z2, Z'2 are thus provided.

These support zones Z are suitably distributed circularly around the axis A '.

For example, and as shown, with respect to one of them, the support zone Z1, supposed to constitute a central support zone, the two support zones Z2, Z'2, supposed to constitute zones lateral support, can be arranged symmetrically with respect to one another with respect to an axial plane of the assembly passing through the median radius of the central support zone Z1.

In practice, the bearing zones Z each respectively form the upper face of studs 25 radially projecting towards the axis A 'of the assembly relative to the crown 17 common to said assembly.

At their base, they are connected to each other by a collar 26, which, like them, also extends radially projecting from the crown 17, in the direction of the axis A 'of the assembly.

This collar 26, which is substantially perpendicular to said axis, extends in practice at the base of the crown 17, at the connection of the latter with its skirt 18.

It is in practice its lower surface which forms the bearing surface 19 constituting the plane of reference P '.

With regard to the crown 17 and the flange 26, the studs 25 carrying the support zones Z are separated from each other by recesses 27 whose axial profile, substantially square, with however a draft, is turned towards the top, in direction opposite to skirt 18.

Axially, projecting upwards relative to the studs 25 carrying the support zones Z, the crown 17 comprises, in the embodiment shown, an extension 28, which extends substantially annularly around the axis of the together, in alignment with the skirt 18, and which, like the latter, has radially a thickness substantially half relative to that of the crown 17, with its outer surface in continuity with that of the latter.

When connected to this extension 28, the crown 17 forms, inside the volume delimited by it, an annular area 29, which is connected continuously with the upper face of each of the studs 25 carrying the bearing zones Z, and which is generally inclined with respect to the reference plane P ', approaching this reference plane P' at the same time as the axis A 'of the assembly.

This annular area 29 is used for the establishment of markers 30.

In practice, these are simple lines, etched radially on the surface of the annular area 29.

Three lines 30 are thus provided.

One is established at the right of the meridian radius of the central support zone Z1, and the other two are each respectively arranged at 90 ° relative to the previous one, on either side of it, in alignment one of the other.

Locally, there is provided in the support ring 16 thus constituted, at least one notch 32, which, practiced generally radially, not only cuts, in the embodiment shown, the crown 17 and its axial extension upwards 28, but still, fairly broadly, the collar 26 presents internally at the base of this ring 17, thereby transversely cutting the corresponding clearance 27.

In the embodiment shown, only such a notch 32 is provided, being substantially radially opposite the central support zone Z1.

The support zones Z are all generally inclined with respect to the reference plane P ', each extending between two ends E _B , E _H , offset both radially and axially with respect to each other.

The end E _H , or upper end, is located radially on a circumference of diameter greater than that of the circumference on which the end E _B , or lower end is located, and, axially, it is located, relative to the plane reference P ', at a level higher than this.

In practice, the end E _H of a support zone Z is at the connection of the corresponding stud 25 with the crown 17, and its end E _B forms the free edge of this stud 25.

According to the invention, the tangent planes T _B , T _H at the ends of each of the support zones Z, both orthogonal to the same axial plane of the assembly passing through a median radius of such a support zone Z, make a dihedral D between them.

These tangent planes T _B , T _H are shown diagrammatically by their trace in FIG. 6 (so as not to overload it with hatching, the corresponding cutting plane passes away from the stud 25 concerned; in reality it must be considered as passing through the middle area of it).

They do not necessarily contain in their entire length the corresponding ends E _B , E _H , these not necessarily being plane, and / or not necessarily extending in their plane; they are in fact simply planes, which, therefore tangent to the bearing zone Z considered, are at least in contact with the latter at the intersection of its ends E _B , E _H with the axial plane of l 'set passing through its median zone, or, in other words, through its median radius.

In practice, the concavity of the dihedral D formed by these tangent planes T _B T _H is turned towards the reference plane P ', and therefore, in practice in the axial direction going from the end E _H radially outermost to the radially innermost end E _B.

In the embodiment shown in solid lines in the figures, each of the support zones Z comprises a plurality of support facets P 'which all generally inclined relative to the reference plane P' and all orthogonal to the axial plane of l 'assembly passing through the median radius of such a support zone Z, extending symmetrically on either side of this axial plane, are of different inclinations with respect to the reference plane P', said facets of support F successively radially on circumferences of different diameters according to their inclination.

In practice, each of these support facets F forms a simple surface.

In the embodiment shown, it forms a flat surface.

As a variant, it may form a spherical or toric surface whose axis, which is in the axial plane of the assembly passing through its median zone, is or is not inclined relative to the axis A 'of the ring d '' support 16.

In practice, in the embodiment shown, three flat support facets FI, Fil, FIII are thus provided for each support area Z, and, from one support area Z to another, the facets of support F of the same rank are on circumferences of the same diameter.

All these support facets F are inclined in the same direction relative to the reference plane P '.

In practice, they approach this reference plane P 'at the same time as the axis A' of the assembly.

For each support zone Z, the most inclined support facet, the support facet FI, is the one that is located on the circumference of the smallest diameter, and therefore ends at the end E _B , and the least inclined support facet, the Fil! support facet, is the one which is located on the largest circumference diameter, and therefore ends at the end E _H , the intermediate support facet, the support facet FII, having an intermediate inclination between that of the previous two.

It follows from the above that the support surface offered by each of the support zones Z by these support facets F is generally convex, with its concavity facing the reference plane P '.

It also follows from the above that the least inclined support facet F, the support facet FIII, is located as close as possible to the crown 17.

In practice, in the embodiment shown, it is an extension of the annular area 29 formed by the latter at its connection to its axial extension 28.

In practice, also, the extreme support facets FI, FIII being planar in this embodiment, they form by themselves, for each support zone Z, the tangent end planes T _B , T _H corresponding d 'such a support zone Z.

In other words, they merge with these tangent end planes T _B , T _H.

The angle at the center 0 of each support zone Z thus formed can be quite reduced.

For example, it can be of the order of 10 °.

Each of the support facets F that such a support area Z comprises circularly extends over the entire width of the latter.

In practice, their respective inclinations depend on the type of progressive ophthalmic lens to be considered, that is to say on the particular topography of the portion with progressively variable curvature of the semi-finished blanks 10 to be treated, as well as on the range of possible basic curvatures for these.

They therefore do not need to be specified here.

In practice, too, the internal diameter of the axial extension 28 of the crown 17 is substantially equal to the external diameter of the puck that constitutes such a semi-finished blank 10, being slightly greater than the latter.

When it is engaged therein by its finished face 11, as shown diagrammatically in broken lines in FIG. 5, a semi-finished blank 10 to be treated is therefore substantially adjusted in this axial extension 28 of the crown 17, without however being there tight.

Preferably, and as shown, the height of the axial extension 28 of the crown 17 is less than the thickness of the semi-finished blank 10, to facilitate handling of the latter.

In practice, the semi-finished blank 10 to be treated carries markers, not visible in the figures.

It is sufficient, for its correct implantation in the support ring 16 to make these pins coincide with the pins 30 carried by the latter.

As illustrated diagrammatically in FIG. 7, the semi-finished blank 10 thus put in place by its finished face 11 in the support ring 16 comes to bear punctually by the latter on each of the support zones Z provided at this effect on this support ring 16, and, more precisely, on a support facet F of the same rank of these support zones Z.

In practice, taking into account the benchmarks used, these having been provided for this purpose, it is by its portion of near vision VP, and, more precisely, by a point thereof located on its main meridian that the semi-finished blank 10 to be treated thus comes to bear on the central support zone Z1 of the support ring 16, while it is by its far vision portion VL, and, more precisely, by two points of the latter each situated respectively on either side of this main meridian, that it comes jointly to carry on lateral support zones Z2, Z'2; of this support ring 16.

Let P be the corresponding contact points, P1 for the support area Z1, P2 for the support area Z2, and P'2 for the support area Z'2.

These points P1, P2, P'2 are all on the same circumference C, centered on the axis A 'of the assembly.

They form the vertices of an isosceles triangle.

Let h be the length of the main median of this isosceles triangle, i.e. that which, coming from point P1 corresponding to the central support zone Z1, is perpendicular to the side connecting to each other the points P2, P'2 corresponding to the lateral support zones Z2, Z'2, and therefore jointly formed the corresponding height.

If, for the same basic curvature, the addition of power to the finished face 11 of the semi-finished blank 10 to be treated varies, the contact points P move radially, and circumferentially, on the support facet F corresponding, but, as shown diagrammatically in FIG. 8, the length of the main median of the isosceles triangle that they form remains substantially constant despite the deformation of which the object is this isosceles triangle.

In FIG. 8, and for the visibility thereof, the displacements of the contact points P have been greatly exaggerated.

As indicated above, they are each supposed to remain respectively on the same facet of support P.

Next, now, the base curvature of the finished face 11 of the semi-finished blank 10 to be treated, it is this or that of the support facets F which, for each support zone Z, and according to the provisions described above, is concerned.

However, in practice, the same support facet F may be suitable for a whole reduced range of different basic curvatures.

This is the reason why a limited number of support facets F suffices to cover the assembly from the ranges of basic curvatures usually used.

Thus for a given topography of the finished face 11 of the semi-finished blanks 10 to be treated, a single support ring 16 is sufficient.

In other words, a support ring 16 is sufficient for each type of progressive ophthalmic lens.

When, according to the arrangements described above, the corresponding semi-finished blank 10 is engaged by its finished face 11 in this support ring 16, the assembly is attached to a blocking device, where, thanks to the notch 32 provided for this purpose, a metal with a low melting point is poured into the internal volume delimited by this semi-finished blank 10 and this support ring 16.

The desired mounting block 15 is thus formed, with an implantation and an orientation determined with respect to the semi-finished blank 10 to which it adheres, the reference plane P 'formed by its inner face 19 the crown 17 of the support ring 16 coming to merge with the reference plane P with respect to which the orientation of the optical axis A of this semi-finished blank 10 is estimated.

The axis A 'of the support ring 16 can then itself merge with this optical axis A.

But this is not necessarily so.

On the contrary, this optical axis A can be inclined relative to the reference plane P ', and therefore relative to the reference plane P, if desired.

As already indicated above, if, in the embodiment shown, the support facets F used are planar, they can also be curved, for example spherical or toric, as already indicated, to compensate for the effect due certain nonlinear progression laws; in the case of spherical or toric bearing facets, the radius of the sphere or of the meridian of the torus has in practice a value between that of the radius of the far vision zone and that of the radius of the near vision zone .

In the variant embodiment shown schematically in broken lines in FIG. 6, each of the support zones Z has a single support facet F, and this is continuously curved from one of its ends E _B , E _H to l 'other.

For the convenience of the layout, it has been assumed, in FIG. 6, that the corresponding outline of this single support facet F fits into the polygonal outline defined by the previous planar support facets FI, Fil, FIII (in being in practice tangent as well to the intermediate support facet Wire as to the extreme support facets FI, FIII).

But this is obviously not necessarily so, this contour can for example be at least locally more or less raised, or lowered (as shown for the intermediate support facet FII), compared to the previous one.

The single curved support facet F _c thus implemented by each support zone Z can, for example, but not necessarily, be spherical or toric.

Anyway, the concavity that it presents is generally turned towards the reference plane P ', the tangent planes T _B , T _H at its ends E _B , E _H , forming as before a dihedral D enters aux.

In other words, it is generally convex, like the assembly formed by the planar support facets FI, FII, Flll above.

Of course, the present invention is not limited to the embodiments described and shown, but encompasses any variant, in particular as regards the number of support zones used.

However, in all cases, the support surface offered by each of these support zones is generally convex.

Furthermore, if, in the above, it has been assumed that the progressive surface concerned is symmetrical with respect to the main meridian of the treated puck, this is not necessarily so, the invention applying as well to the case of asymmetrical progressive surfaces.

Likewise, this surface is not necessarily a convex surface, but may as well be a concave surface.

Finally, instead of forming directly by itself the semi-finished blank of a progressive ophthalmic lens, the treated puck can for example constitute the semi-finished blank of a mold suitable for molding such a progressive ophthalmic lens.

Claims (13)

1. Bearing ring for semi-finished blank an ophthalmic lens or mold, of the kind comprising, for contact with said semi-finished blank, a limited number of bearing areas (Z) which, appropriately distributed circumferentially around an axis (A'), are all generally inclined relative to a reference plane (P') perpendicular to said axis, each extending between two ends (E_B, E_H) offset radially and axially relative to each other, characterised in that the planes (T_B, T_H), tangential to the ends (E_B, E_H ) of each of the bearing areas (Z) both orthogonal to the same axial plane of the assembly passing through the median radius of such a bearing area (Z) form between them a dihedron (D).

2. Bearing ring according to claim 1, characterised in that the concave side of said dihedron (D) faces towards the reference plane (P').

3. Bearing ring according to claim 1, characterised in that each of the bearing areas (Z) comprises a plurality of bearing facets (F), which, all generally inclined relative to the reference plane (P'), and all orthogonal to the axial plane of the assembly passing through the median radius of a bearing area (Z) of this kind, are differently inclined relative to said reference plane (P'), said bearing facets being in radial succession on circumferences of different diameter according to their inclination and those at the ends (Fl, Fill) being coincident with the corresponding end tangential planes (T_B, T_H).

4. Bearing ring according to claim 3, characterised in that in each bearing area (Z), the most inclined bearing facet (FI) is that situated on the smallest diameter circumference and the least inclined bearing facet (FIII) is that situated on the largest diameter circumference.

5. Bearing ring according to anyone of claims 2, 3, characterised in that each of the bearing facets (F) forms a simple surface that is plane spherical or toroidal, for example.

6. Bearing ring according to claim 1, characterised in that each of the areas (Z) comprising a single bearing facet (F_c), the latter is continously curved from one of its ends (E_B, E_H) to the other.

7. Bearing ring according to claim 6, characterised in that the curved single bearing facet (F_c) is a convex facet.

8. Bearing ring according to anyone of claims 1 to 7, characterised in that the bearing areas (Z) form the upper face of studs (25) projecting radially towards the axis (A') of the assembly from a ring (17) common to said assembly.

9. Bearing ring according to claim 8, characterised in that said studs (25) are separated from each other by notches (27).

10. Bearing ring according to claim 8, characterised in that said studs (25) are linked at their base by a collar (26) common to the assembly.

11. Bearing ring according to anyone of claims 8 to 10, characterised in that the ring (17) comprises an extension (28) projecting axially relative to said studs (25) and extending annularly around the axis (A') of the assembly.

12. Bearing ring according to anyone of claims 8 to 11, characterised in that the ring (17) comprises internally a plane bearing surface (19) perpendicular to the axis (A') of the assembly and constituting the reference plane (P').

13. Bearing ring according to anyone of claims 1 to 12, characterised in that bearing surface offered by each of the bearing areas (Z) is generally convex.

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