HK1174305B - Block piece for holding an optical workpiece, in particular a spectacle lens, for processing thereof, and method for manufacturing spectacle lenses according to a prescription - Google Patents

Description

Blocking element for holding an optical workpiece, in particular a lens, during a machining process and method for producing a lens according to specifications

The present patent application is a divisional application of an invention patent application having an international application number of PCT/EP2009/001310, an international application date of 2009, 24/2, and an application number of 200980105414.8, entitled "a block for holding an optical workpiece, particularly a lens, during machining and a method of manufacturing a lens according to regulations", which enter the chinese national phase.

Technical Field

The present invention relates generally to a block piece for supporting an optical workpiece during machining. In particular, the invention relates to a block piece according to the preamble of claim 1 for large-scale use in a prescription workroom (prescription workroom), i.e. a production workroom for manufacturing individual lenses according to specifications, using common materials (inorganic glass, polycarbonate, PMMA, CR 39 and materials known as "high index"), which block piece holds the lenses during the processing of the lenses. The invention also relates to a method for manufacturing a lens according to the prescription as described in the preamble of claim 11.

Background

Ophthalmic lens blanks generally include a first face having a predetermined curvature and a second face opposite the first face on which a desired surface profile is produced by a machining process. The overall process is commonly referred to as "lens surfacing" and the overall goal is to produce a finished ophthalmic lens in which the curvatures of the first and second faces cooperate to produce the desired optical properties. Furthermore, the first and second faces of the lenses are generally coated to give the finished lenses a high scratch resistance (achieved by "hardening the coating"), to obtain a low residual reflection and a desired colour (achieved by "anti-reflection coating"), and/or to have certain surface properties such as hydrophobicity, oleophobicity, dust-excluding properties (achieved by so-called "top-coating"). Generally, there is also another process (so-called "edging") which aims at finely machining the edge of the lens so that it can be inserted into the frame. In all these steps, the lens (blank) must be held in some way on the processing machine and the coating machine, respectively.

In more detail, the following main processing steps have hitherto generally been carried out in a prescription workroom (prescription workshop): first, the appropriate right and/or left ophthalmic lens blanks are removed from the semi-finished product library. The term "semi-finished product" is used to indicate an ophthalmic lens blank, which is generally circular or oval in plan view and not yet edged, which has been molded, machined or otherwise contoured on only one of their two optically active surfaces. The lens blank is then ready for a blocking operation, i.e. the application of a suitable protective film or a suitable protective lacquer, to protect the already machined or profiled optically active, i.e. first or blocking, face.

The lens blank is then subjected to a so-called "blocking". During this time, the lens blank is connected to a suitable blocking element, for example a lens blocking element manufactured according to german standard DIN58766 or EP 1593458 a2 (which form the preamble of the claims). To this end, the block piece is first placed in a predetermined position with respect to the protected first face of the lens blank, and then the space between the block piece and the lens blank is filled in this position with a molten material (generally a metal alloy or wax) or with an adhesive composition which can be cured by UV or visible light (see for example document EP2011604a1 by the same applicant). Once the material has cured, the block piece forms a holder or a stand for machining the second side of the lens blank. The block piece is gripped by chucks or other suitable coupling means during the lens production process to provide a particularly secure mounting of the profiling machine while avoiding damage to the lens.

The lens surfacing is then carried out using a profilometer, which typically has some type of cutting machine that moves across the second face of the lens blank to bring the macroscopic geometry (macrogeometry) of the second face into compliance with the prescription requirements. The lens blank may be stationary or rotating during the cutting operation described above, depending on the particular profiling machine used. Typical machining processes for surfacing lenses include single point diamond turning (which is the presently preferred fine cutting process for plastic materials as described in the applicant's earlier patent application EP 1719585 a 2), diamond tool fly cutting, milling (which is the presently preferred rough cutting process for plastic materials as described in the applicant's earlier patent application EP 0758571 Al), and grinding processes, the use of which depends on the lens material.

The ophthalmic lenses are then usually subjected to a fine machining in which the pre-machined second face of the respective lens blank is brought into the desired micro-geometry (microgeometry), see for example the earlier patent applications EP 1473116 Al and EP 1698432 a2 of the same applicant. In addition to this, the fine machining process is divided into a fine grinding operation and a subsequent polishing operation, or only a polishing operation if a polishable second face has been produced in a pre-machining stage, depending on the material of the lens.

Before the cleaning step is carried out, the ophthalmic lens blank is separated from the lens block only after the polishing operation ("deblocking"). The coating process is then carried out depending on, among other factors, the material of the lens blank, which may include applying a spin coating (or dip coating) to the deblocked lens blank to coat the lens blank with a hardened or similar coating on at least the second side, as described, for example, in document US 20080035053 a1, wherein the lens blank is held on the spin coating device by a lens holder having suction cups.

In any case, the coating comprises vacuum coating the deblocked lens blank such that said lens blank is coated on at least the second side with an anti-reflection coating and optionally with a top coating, for the purposes described above. During vacuum coating, the lens blanks are clamped to a base carrier of a rotary turret apparatus, which is located under a vacuum chamber and is vertically spaced from an evaporation source, so that the vapor is injected into the lens blanks mounted on the base carrier, see for example the description of european patent application EP 0806492 Al.

After the coating step, the lens blank is typically edged so that the lens can be inserted into the frame. For this purpose, the lens blank, to which the coating has been applied, is blocked again, but this time by partially blocking the lens with, for example, an adhesive film onto a different smaller blocking piece, see, for example, the description of european patent application EP 1243381 a2 in the name of the same applicant. The edging process also comprises the formation of apertures, grooves, recesses and/or bevels corresponding to the respective mounting requirements on the edge zone of the lens, see for example the description of european patent application EP 1243380 a2 in the name of the same applicant.

Finally, after edging and another deblocking step, the lenses are washed again, ready to be inserted or mounted on the frame after inspection.

One disadvantage of the conventional process described above is that the lens needs to be deblocked after surfacing prior to the coating process and resealed after the coating process prior to edging, which requires manual handling, is time consuming and labor intensive.

One problem with conventional methods in the prescription studio is particularly related to the single point diamond turning process, which is currently the preferred fine-cut process for lens blanks made of plastic. Thus, such surfacing is liable to generate small but unacceptable errors in the centre of rotation of the lens blank, which are generally caused by machine errors and by tool calibration, a detailed explanation of which can be found in european patent application EP 1719584 Al of the same applicant. This, together with certain limitations of the subsequent (elastic) polishing process, where it is difficult to completely "eliminate" or remove these center errors, results in certain limitations in the amount of prism that can be cut or polished (i.e., tilting or shifting of the surface relative to the axis of rotation) during the integrated surfacing process. Experiments have shown that it is easier to cut and polish a surface containing 2 to 3 degrees of prism at the center to maintain an accurate center, but the higher degree of prism at the center can be problematic.

A method is known (see for example US 6913356B 2) for fitting a block piece to a semi-finished blank for an ophthalmic lens having a specific prism power, said method essentially consisting of the following steps: the method comprises the steps of fixing a lens blank to a fixed base in a centrally aligned and angularly defined manner, such that the finished face of the lens blank is supported in succession on a plurality of support points of the base, defining the orientation of the blocking piece relative to the lens blank, orienting the blocking piece in a defined manner, and fixing the blocking piece to the finished face by means of a castable low-melting-point metal alloy as blocking material, while maintaining the defined orientation.

Once the lens blank is blocked on the block piece with a predetermined prism power (the prism power is generated after the lens is subjected to surface machining), there is no need to generate, i.e. cut, any prisms during the surface machining. However, a disadvantage of this known method is that if a lens blank having a large prism power (for example 7 or 8 prism powers) is to be blocked, the thickness of the wedge-shaped layer of blocking material between the lens blank and the blocking piece may vary greatly along the prism axis. This results in varying degrees of shrinkage of the blocking material in the thickness direction along the prism axis upon curing (or if hardening using an adhesive composition), which shrinkage in turn may cause the blocked lens blank to bend/deform (or even shift relative to the block piece) such that the curve of the surface of the lens blank to be cut may deform and resume its natural shape when the lens blank is unblocked from the block piece, see document EP2011604a1 by the same applicant. This approach, in turn, limits the amount of prism that can be blocked.

Object of the Invention

The object of the present invention is to provide a block piece for holding an optical workpiece, in particular a lens, during machining, which block piece can solve the above-mentioned drawbacks of the known art in the field, enabling a lens, in particular of high optical quality, to be obtained more quickly and at a lower cost, without being subject to the lens geometry usually machined in a fitting studio. The object of the present invention consists in providing a method for manufacturing a lens according to the regulations which achieves the above mentioned objects.

Disclosure of Invention

The above object is solved by the features stated in claims 1 and 11. Further developments of the advantages or functions of the invention can be derived from claims 2 to 10, 12 and 13.

According to the present invention there is provided a block piece for holding an optical workpiece, in particular a lens, during machining, the block piece comprising a base body having a central axis and a workpiece mounting face portion on which the workpiece can be blocked by a blocking material; and a clamping portion by which a workpiece to be plugged on the base body can be fixed to a machine or apparatus for machining the workpiece, wherein the workpiece mounting face portion is substantially spherical and is inclined or displaced by a predetermined amount with respect to a central axis of the base body so as to provide a prescribed prism power in the plugging member.

For example, by tilting the workpiece mounting face portion of the block by 2 degrees of prism relative to the central axis of the base, 2 degrees of prism can be provided in the block. Thus, all lens blanks subsequently blocked on these "pre-blocked prism" (PBP) blocks start with 2 degrees of prism (assuming that the lens blanks are blocked on the respective PBP block in such an orientation that the prism axis of the lens manufactured according to the prescription is aligned with the prism direction of the PBP block). Knowing the positioning of the prism orientation of the PBP block piece relative to the block mounting feature (datum) typically defined by the geometry of the clamped portion of the block piece, one can calculate by adding or subtracting the prism power of the PBP block piece to increase or decrease the prism power of the finished lens cut. This can be used to substantially effectively reduce the total prism power produced by the prism angle surfacing of a PBP block, and can address the above-mentioned limitations of the integrated surfacing process in which a lens blank made of plastic is finely cut in a single point diamond turning process and then polished with a flexible polishing tool.

For example, if the maximum prism that can be cut safely and without causing excessive center defects during the integrated surfacing process is 3, and the maximum prism that should be supported during the surfacing process is 5.5, then a PBP block having 2.5 prisms should be provided. Thus, all lens blanks blocked on these PBP blocks are tilted 2.5 degrees of prism in a known direction. Then the 2.5 prism degrees can be compensated by cutting-2.5 prism degrees resulting in a lens with 0 prism degrees, or the prism degrees can be added to the 2.5 pre-blocked prism degrees by cutting a maximum of 3 prism degrees resulting in a total of 5.5 prism degrees, i.e. without cutting an upper limit of more than 3 prism degrees. As a result, any prism between ± 3 can be safely cut, so that the finished lens obtains 0 to 5.5 prisms. In the fitting studio, the lens layout program (layout calculation program) needs to keep track of the arrangement according to the prescribed cylinder axis relative to the prism axis, because the PBP block has a fixed prism orientation, but its cylinder axis orientation is variable relative to the block reference geometry (this is different from the conventional surfacing process, in which the cylinder axis is aligned in a fixed orientation relative to the block reference geometry, while the prism alignment is variable). This implies that such PBP block is mainly used for "flexible" polishing, unlike conventional hard disk polishing which requires a fixed cylinder axis direction.

In addition, such PBP block pieces also solve the above-mentioned problems associated with large variations in the thickness of any wedge layer of blocking material between the lens blank and the block piece. Obviously, even if the finished lens contains a large prism power, for example, 5.5 or more prism powers, the PBP block is such that the thickness of the block material layer along the prism axis does not vary much as in the case of using a block having a workpiece mounting face portion without prism power. In one example, the wedge angle between the lens blank and the block piece can only have 3 degrees of prism, with the workpiece mounting face portion of the PBP block piece having 2.5 degrees of prism, and in the case where the workpiece mounting face portion of the block piece does not contain degrees of prism, it can contain 5.5 degrees of prism. Therefore, the use of PBP blocks minimizes the risk that the blocking material, after hardening or curing, will shrink causing the blocked lens blank to deform and/or change the desired prism.

In this respect, a second advantageous effect is that it contributes to reducing the costs of the fitting studio, since the use of PBP block pieces minimizes the gap between the lens blank and the block piece, which must be filled with blocking material, and also minimizes the amount of blocking material that needs to be used.

In a preferred embodiment of the closure element, the clamping portion is adapted to be clamped by a clamping force exerted substantially in a circumferential direction with respect to a central axis of the base body or by a clamping force exerted remotely in a substantially tangential direction with respect to the central axis of the base body.

The main effect of this block piece design is that, even if the block piece is made of a non-flexible plastic, the clamping forces exerted on the block piece in the circumferential or tangential direction by a corresponding suitable clamping disk in the surfacing or edging machine do not "move" or pass through the entire block piece as is the case conventionally (in which radial pressure is applied to the clamping portion of the block piece), thereby avoiding excessive deformations of the block piece which in turn may be transferred to the work piece being blocked on the block piece, leading to undesired deformations of the geometry of the finished work piece. Also, this facilitates the production of high optical quality lenses in the fitting studio.

In an embodiment, the clamping portion of the base body may comprise at least one radially extending clamping bead for applying the clamping force, said clamping bead having two opposite sides each facing in the circumferential direction. Preferably, the clamping portion of the base body comprises three circumferentially distributed radially extending clamping protrusions. This may be a uniform distribution; however, it is preferred that the clamping protrusions are not distributed uniformly along the circumference, so that the clamping protrusions can also be used to rotationally orient the block piece in the processing machine.

Furthermore, the clamping protrusions of the clamping portion are preferably each provided with a radial outer surface inclined with respect to the central axis of the basic body, which outer surfaces together define an outer conical central portion of the basic body, corresponding to german standard DIN58766, so that the block piece is centered on the assigned chuck of the respective processing machine.

In addition, the clamping protrusions preferably each have an axial end facing away from the workpiece mounting face portion, wherein said axial ends each have a V-shaped cross-section, viewed in radial direction, also serving to facilitate mounting of the block piece in a given chuck of the respective machining machine.

In a preferred embodiment of the block piece, the basic body comprises, on the side facing away from the workpiece mounting face portion, two annular portions of different diameter which are arranged concentrically about a central axis of the basic body and between which the clamping projection extends, and the radially inner annular portion projects axially beyond the radially outer annular portion. Such a design is particularly advantageous if the closure is injection molded from plastic, since it serves to provide a substantially uniform wall thickness throughout the base body, thereby avoiding problems associated with shrinkage during injection molding. In this embodiment, the clamping bead extends between the two annular portions or bridges the annular gap between the two, advantageously serving to reinforce or stiffen the base body of the closure. A further advantage of this embodiment is that, since the block piece is already of a "honeycomb" structure, the block piece is lighter in weight and less in mass to move along one side of the workpiece during machining of the blocked workpiece than conventional block pieces, such as those according to german standard DIN 58766.

In this case, the radially inner annular portion of the basic body may be provided with two notches for aligning the cylinder axis of the block piece with the spindle of the machining machine, corresponding to german standard DIN58766, said notches being arranged on diametrically opposite sides with respect to the central axis of the basic body.

In this embodiment, the radially inner annular portion of the base may further define a central cylindrical blind bore having a flat bottom, wherein a plurality of reinforcing ribs extend between the flat bottom and an inner circumference of the radially inner annular portion. In this case, the stiffening ribs preferably each have a radial inner surface which is inclined with respect to the central axis of the basic body, wherein these radial inner surfaces together define an inner conical central portion of the basic body, corresponding to german standard DIN58766, so that the block piece as a whole is compatible with various standard chuck conditions, including being accommodated in handling devices and in working trays (see, for example, german standard DIN 58763).

The invention also provides a method of manufacturing a lens according to prescription, the method comprising the steps of: (i) blocking a lens blank with a blocking material, wherein a blocking face is placed on the part of the workpiece mounting surface, said lens blank having a second face opposite to said blocking face and an edge between said blocking face and said second face, (ii) processing the second face of the blocked lens blank, if necessary also processing said edge, to obtain a processed lens, and (iii) deblocking said processed lens from said block, wherein the same block is used throughout step (ii) and the blocked lens blank is left on this block.

Since the lens blank remains on the blocking piece throughout the processing step, the processing step reduces the operating procedures relative to conventional methods requiring blocking and unblocking of the lens blank at the processing stage, and thus the processing step is shorter and more efficient. This reduces production costs and even allows more automation in the fitting room. The method of the invention also ensures that lenses of high optical quality are produced, since the lens blank and the block piece are maintained in the same geometric relationship throughout the processing phase, thus avoiding errors that can be derived in conventional re-blocking methods in which the orientation of the lens blank relative to a given different block piece may unintentionally change after re-blocking. Furthermore, since the lens blank remains on the block piece as a standardized interface and handling mechanism at all times during the processing, the risk of: any operator inadvertently touches the lens blank and may create problems in the application substep. A further advantage is that all production information can be retained on the closure element, for example by means of a "transponder" integrated or fixed to the closure element, as described in european patent application EP 1593458 a2, which offers the possibility of a complete tracking of the entire process.

Continuing the concept of the present invention, the above processing step (ii) may comprise the following sub-steps: processing the blocked lens to obtain a second face according to a specified macroscopic geometry; finely processing the blocked lens to enable the second surface to obtain a required microscopic geometrical shape; cleaning the blocked lens blank that has been machined and fine machined; applying a spin or dip coating to the blocked lens blank, if necessary, to coat the second side with a hard coat, or a primer, or both a primer and a hard coat; applying a vacuum coating to the second side of the blocked lens blank to provide an anti-reflective coating, if desired, applying a top coating such as a hydrophobic and/or oleophobic and/or dust repellent coating; and, if necessary, edging the blocked lens blank to obtain the desired geometry of the edge so that the finished lens is ready for insertion into a frame or frame. Since there are no more deblocking steps in the process stage, some process substeps can be carried out in a different order than is required in conventional methods, and if desired or required, a fixed order is not necessary from a product point of view, and in particular all process operations including edging can be carried out before the coating process.

Finally, the blocking surface of the lens blank, before the blocking step described above, including the hard coating, the anti-reflection coating and, if desired, the top coating, such as a hydrophobic and/or oleophobic and/or dust-repellent coating, is preferably completely finished. In this case, the blocked lens blank is advantageously sent from the lens manufacturer to a fitting studio where only the second side of the lens blank, if required, and the edge machining are needed to obtain a lens ready for insertion/mounting into a frame, wherein the first side of the lens blank is protected by the blocking piece until the finished lens is unblocked. This method also minimizes the labor involved in the production of the prescription studio.

Other effects and benefits of the block-out piece and the method of manufacturing a lens according to the prescription proposed by the present invention will be apparent to those skilled in the art in view of the following description of the currently preferred embodiments of the invention.

Drawings

The invention will be explained in detail below on the basis of preferred embodiments of the embodiments and with reference to the accompanying partial schematic drawings. In the drawings:

fig. 1 is a perspective view, on an enlarged scale with respect to the actual dimensions, of a closure not according to the invention, viewed obliquely from the front and above;

fig. 2 is a perspective view of the closure of fig. 1 obliquely from behind and below;

FIG. 3 is a bottom view of the closure of FIG. 1;

FIG. 4 is a cross-sectional view of the closure of FIG. 1 taken along line IV-IV of FIG. 3;

FIG. 5 is a cross-sectional view of the closure of FIG. 1 taken along line V-V of FIG. 3;

FIG. 6 is a cross-sectional view of the closure of FIG. 1 taken along section lines VI-VI in FIG. 3;

FIG. 7 is a bottom view, on a reduced scale relative to the previous figures, of the block piece of FIG. 1 on which a lens blank is blocked as an optical work piece by an adhesive composition;

FIG. 8 is a cross-sectional view of the block piece and a lens blank blocked thereon taken along line VIII-VIII of FIG. 7;

fig. 9 is an enlarged partial view of part IX of fig. 8 showing a cross-section of a coating that may be applied to the closure to seal the closure;

FIG. 10 is an enlarged partial view of portion X of FIG. 8, showing one example of a coating that may be applied to the concave and/or convex surfaces of a lens precursor;

fig. 11 is a perspective view of a closure according to the invention viewed obliquely from the front and above, with dimensions substantially close to the actual dimensions;

figure 12 is a perspective view of the closure of figure 11 viewed obliquely from behind/below;

figure 13 is a side view of the closure of figure 11;

fig. 14 is a bottom view of the closure of fig. 11;

FIG. 15 is a cross-sectional view of the block piece of FIG. 11 taken along section line XV-XV in FIG. 14, showing the substantially spherical workpiece mounting face portion of the block piece tilted with respect to the central axis of the block piece, providing a predetermined degree of prism on the block piece;

FIG. 16 is a plan view of a lens blank showing the horizontal and vertical mounting axes, prescribed prism axis and prescribed cylinder axis of the lens blank; and

FIG. 17 is a flow chart of the main steps in a method of manufacturing a lens according to the present invention.

Detailed Description

Fig. 1 to 6 show a block piece 10 for holding an optical workpiece, in particular a lens, during processing (see fig. 7 and 8). The block piece 10 comprises a base body 12, said base body 12 having a workpiece mounting face portion 14, on which workpiece mounting face portion 14 a lens blank B can be blocked (see fig. 8) by means of a blocking material 16, preferably an adhesive blocking composition curable by UV and/or visible light, see document EP2011604a1 of the same applicant. The base body 12 of the block piece 10 further comprises a clamping portion 18, by means of which clamping portion 18 a lens blank B blocked on said base body 12 can be fixed in a machine or device for processing said lens blank B (i.e. surfacing, coating, edging, tinting, cleaning, etc., as the case may be).

In the present example, the base body 12 is injection-molded in one piece from a plastic which is capable of transmitting UV and visible light for curing the blocking material 16 and which has a water absorption of less than 1% by weight when saturated, the water absorption being measured according to DIN EN ISO 62: 1999-08 method 1 (measuring the amount of water absorbed after immersion in water at 23 ℃). As shown in fig. 8 and 9, the substrate 12 may be sealed by a sealing coating 20 (or tape, as the case may be) that at least partially covers the outer surface of the substrate 12, thereby preventing or at least reducing the escape of any moisture forming moisture that may build up within the material of the substrate 12 under vacuum conditions. Obviously, the seal coat 20, if present, should cover those surface portions of the substrate 12 that are exposed to the "environment" of the vacuum chamber in the lens precursor B coating apparatus.

As shown in particular in fig. 4 to 6 and 8, the workpiece mounting face portion 14 on the front side of the blocking piece 10 is substantially spherical, without any cut-outs, completely supporting the blocked lens blank B almost close to the edge E between the first or blocking face cx (which is convex) and the second face cc (which is concave) of the blocked lens blank B. It can also be seen from these figures that substrate 12 is entirely free of depressions and narrow grooves that could trap liquid.

Adjoining the workpiece mounting face portion 14 of the basic body 12 on the outer circumferential side is a substantially conical transition face 22 which adjoins a substantially flat rear face 24 on the rear side of the closure 10. Starting from the rear face 24 of the base body 12, the base body 12 is provided with two annular portions 26, 28 of different diameter, which are arranged concentrically about the central axis a of the base body 12, and the radially inner annular portion 28 projects axially beyond the radially outer annular portion 26, as is particularly apparent from fig. 1, 4 to 6 and 8.

A particular feature of the closure 10 is that the clamping portion 18 of the base body 12 is adapted to be clamped by a clamping force applied in a substantially circumferential direction relative to the central axis a of the base body 12, or by a clamping force applied remotely in a substantially tangential direction relative to the central axis a of the base body 12. To this end, the clamping portion 18 of the base body 12 comprises at least one, in the present embodiment three, radially extending clamping protrusions 30 which, starting from the rear face 24 of the base body 12, are distributed unevenly along the circumference and bridge the annular gap between the radially outer annular portion 6 and the radially inner annular portion 28. Each clamping lug 30 has two opposite side faces 32, each facing in the circumferential direction, for exerting the clamping force described above, which is indicated by the arrow F in fig. 1 to 3 and 7. Obviously, these clamping forces F cancel each other out at the respective clamping protrusions 30, not over the entire substrate 12. Thus, the clamping force F does not bend the block piece 10, i.e. does not deform the workpiece mounting surface portion 14 and the lens blank B blocked thereon.

Furthermore, the clamping protrusions 30 are each provided with a radial outer surface 34 inclined with respect to the central axis a of the base body 12, these radial outer surfaces 34 together defining an outer conical central portion of the base body 12 which adjoins the outer circumference of the radial outer annular portion 26. Finally, the clamping lobes 30 each have an axial end 36 facing away from the workpiece mounting face portion 14, wherein the axial ends 36 each have a V-shaped cross-section as viewed radially, forming a "roof" shaped end, also serving the purpose of being centrally located within a designated chuck (not shown) of each machining machine.

As can be seen most clearly in fig. 1, 2, 4 and 6, the radially inner annular portion 28 of the base body 12, starting from its free end, is provided with two cutouts 38 for aligning the cylinder axis of the block piece 10 with the main axis of the respective machining machine, said cutouts 38 being arranged on diametrically opposite sides relative to the central axis a of the base body 12, which tapers substantially in a V-shape, viewed in side view, towards the rear face 24 of the base body 12, ending axially in front of the radially outer annular portion 26 (see fig. 4 to 6).

Furthermore, the radially inner annular portion 28 of the basic body 12 defines a central cylindrical blind hole 40 having a substantially flat bottom 42, wherein a plurality of reinforcing ribs 44 extend between said bottom 42 and an inner circumference 46 of said radially inner annular portion 28. The stiffening ribs 44 each have a radial inner surface 48 inclined with respect to the central axis a of the basic body 12, these radial inner surfaces 48 together defining an inner conical central portion of the basic body 12. As a result, when the basic body 12 is rotated about the central axis a, the outer circumference of the radially outer annular portion 26, the radially outer surfaces 34 and the axial ends 36 of the clamping protrusions 30, the back of the radially inner annular portion 28 and the radially inner surfaces 48 of the reinforcing ribs 44 together define an "encapsulated" body whose geometry substantially corresponds to that of the block piece according to german standard DIN58766, but the block piece 10 of the present invention is much lighter than a standard block piece due to its material and "honeycomb" structure. This geometry of the base body 12, together with the cut-outs 38 of the radially inner annular portion 28, makes the closure 10 compatible with the various conditions of a standard chuck 12.

As regards the actual plugging operation, the results can be seen in fig. 7 and 8, and also in document EP2011604a1 of the same applicant, which discloses a plugging device that can be used and a currently preferred plugging method.

The closure 10 according to the present invention will be described below with reference to fig. 11 to 16, in which like reference numerals designate like or equivalent components or parts, only with respect to its differences from the above-described closures.

The back side of the base body 12 of the closure 10 differs from the back side of the base body 12 of the closure only in that: the conical transition surface 22 is provided with a plurality of slots 50 evenly distributed circumferentially, the slots 50 serving to provide substantially the same wall thickness throughout the base 12, avoiding shrinkage-related problems that occur during preferred plastic injection molding. Basically, however, the rear side of the closure element 10 can be made different, for example, as disclosed in patent application EP 1593458 a 2.

The most important difference is the front side of the substrate 12. As shown in fig. 13 and 15, the generally spherical workpiece mounting face portion 14 is tilted or displaced relative to the central axis a of the base 12 by a predetermined amount to provide a defined degree of prism in the block piece 10. In this embodiment, the workpiece mounting face portion 14 is inclined by 2 degrees of prism with respect to the central axis a. This degree of prism in the geometry of the closure element 10 is described in more detail in the context of the present description and is hereby incorporated by reference.

With regard to the actual blocking operation, which is carried out essentially according to the method described in document EP2011604a1 of the same applicant, it should be noted here that the blocking piece 10 with inherent prism ("pre-blocking prism" (PBP) blocking piece) needs to be oriented differently with respect to the lens blank B compared to the conventional method, as will be explained in connection with fig. 16.

Fig. 16 shows a plan view of the lens blank B, showing the vertical axis 52 and the horizontal axis 54 of the lens blank B, which correspond to the mounting axes of the finished lens in the frame, respectively. Assuming that the second face cc of the lens blank B must be made to contain a predetermined amount of prismatic power (measured in prism diopters) relative to the blocking face cx, the prism axis 56 is oriented in a predetermined direction relative to, for example, the horizontal axis 54. Further, assuming that the lens must be curved, the cylinder axis 58 is oriented in a predetermined direction relative to, for example, the horizontal axis 54, which is generally different from the predetermined direction of the prism axis 56. At this point, in conventional occlusion methods, the cylindrical axis 58 is generally aligned with the cutout 38 of the occluding member 10. This is clearly not possible with the PBP plugs of the present invention. Specifically, if a defined prism power is to be produced in the lens, the lens blank B must be blocked with its prism axis 56 aligned with the prism direction of the PBP block piece 10. In this embodiment, the prisms of the workpiece mounting face portion 14 are oriented along line XV-XV of FIG. 14 and run at right angles to the cut-outs 38 of the substrate 12 (see FIG. 15). However, this may be difficult to do as long as there is a definite relationship between the prism direction of the workpiece mounting face portion 14 and the block mounting feature on the back side of the block 10.

Finally, fig. 17 shows in a flow chart the main steps of a method for manufacturing a lens according to the prescription using the above-described block piece 10.

Basically, the method comprises the steps of: (i) blocking a lens blank B with a blocking material 16, wherein a blocking surface cx is placed on the workpiece mounting surface portion 14 of the block piece 10, (ii) processing a second side cc of the blocked lens blank B, optionally processing the edge E, resulting in a processed lens, and (iii) deblocking the processed lens from the block piece 10, characterized in that the lens blank B remains on the block piece 10 throughout the processing stage or step (ii). According to fig. 17, the processing stage or step (ii) generally comprises the following sub-steps: "producing" i.e. processing the blocked lens blank B such that the macroscopic geometry of the second face cc meets the specified requirements; "polishing" i.e. fine machining the blocked lens blank B to form the second face cc into the desired microscopic geometry; cleaning the blocked lens blank B which has been machined and fine machined; (optionally) applying a spin (or dip) coating to the blocked lens blank B to coat the second side cc with a hard coat HC (see fig. 10), or a primer layer, or both a primer layer and a hard coat; applying a vacuum coating to the second side cc of the blocked lens blank B to provide an anti-reflection coating AR (typically consisting of 4 to 7 layers of two to four materials of different refractive index, as shown in fig. 10), and (optionally) applying a top coating TC (see again fig. 10) such as a hydrophobic and/or oleophobic and/or dust-repellent coating; and (optionally) edging the blocked lens blank B to obtain the desired geometry of the edge E, so that the finished lens is ready for insertion into a frame or frame after deblocking and final inspection. Since these process substeps and the equipment used are known to those skilled in the art, they will not be described in detail here.

It can also be seen from fig. 17 that, for the reasons stated in the introductory part of the present description, the blocking surface cx of the lens blank B, which preferably comprises the hard coating HC, the anti-reflection coating AR and optionally the ground coating TC, such as a hydrophobic and/or oleophobic and/or dust-repellent coating, before the blocking step (i) described above, is preferably completely finished, i.e. the blocking surface cx of the lens blank B is provided with a multilayer system before the blocking operation, as shown in fig. 10.

The invention provides a plugging piece for holding a workpiece, in particular a lens, and a use method thereof, wherein the plugging piece comprises a base body, a first sealing ring and a second sealing ring, wherein the base body is provided with a workpiece mounting surface part, and the workpiece can be plugged on the workpiece mounting surface part through a plugging material; and a clamping portion by which the blocked workpiece can be fixed to a machine or apparatus that processes the workpiece. The base body is composed of a material with a defined low water absorption and/or is sealed in such a way that at least the moisture forming moisture evacuation under vacuum conditions is reduced, making the closure suitable for use in a vacuum coating process. In addition, the clamping portion is adapted to be clamped by forces substantially perpendicular to the radial direction, which forces cancel each other out and thus do not deform the base body, and/or the workpiece mounting surface portion is provided with a predetermined degree of prism.

List of reference numerals

10 plugging piece

12 base body

14 workpiece mounting face portion

16 plugging material

18 clamping part

20 sealing coating

22 conical transition surface

24 back side

26 radially outer annular portion

28 radially inner annular portion

30 clamping lug

32 side surface

34 radially outer surface

36 axial end portion

38 cuts

40 blind hole

42 bottom part

44 reinforcing rib

46 inner circumference

48 radially inner surface

50 slot

52 vertical axis

54 horizontal axis

56 prism axis

58 cylinder axis

Central axis of A

B lens blank

Edge of E lens blank

F clamping force

Second side of cc lens blank

Blocking surface of cx lens blank

AR antireflective coatings

HC hard coating

TC topcoat

Claims (23)

1. A block piece for holding an optical workpiece during processing, the block piece comprising:

an integrally formed base body (12) having

A central axis (A);

a workpiece mounting surface portion (14) on which the workpiece can be plugged by a plugging material (16); and

a clamping part (18) by means of which a workpiece plugged onto the base body (12) can be fixed on a machine or a device for machining the workpiece;

characterized in that the workpiece mounting face portion (14) is substantially spherical without any cut-out to fully support the workpiece once plugged and is inclined or displaced by a predetermined amount relative to the central axis (A) of the base body (12) to provide a defined degree of prism in the plug (10).

2. The block piece (10) according to claim 1, characterized in that the optical work piece is a lens.

3. The closure (10) according to claim 1, wherein the clamping portion (18) is adapted to be clamped by a clamping force (F) exerted in a substantially circumferential direction with respect to the central axis (a) of the base body (12) or by a clamping force (F) exerted in a substantially tangential direction at a distance with respect to the central axis (a) of the base body (12).

4. The closure (10) according to claim 3, wherein the clamping portion (18) of the base body (12) comprises at least one radially extending clamping protrusion (30) for applying the clamping force (F), the clamping protrusion (30) having two opposite sides (32) each facing in the circumferential direction.

5. The closure (10) according to claim 4, wherein said gripping portion (18) of said base body (12) comprises three radially extending gripping protrusions (30) distributed along the circumference.

6. The closure (10) according to claim 5, wherein said clamping protrusions (30) are each provided with a radially outer surface (34) inclined with respect to the central axis (A) of said base body (12), these radially outer surfaces (34) together defining an outer conical central portion of said base body (12).

7. The block piece (10) of claim 5, wherein the clamping protrusions (30) each have an axial end (36) facing away from the workpiece mounting face portion (14), wherein the axial ends (36) each have a V-shaped cross-section as viewed radially.

8. The block piece (10) according to claim 6, wherein the clamping protrusions (30) each have an axial end portion (36) facing away from the workpiece mounting face portion (14), wherein the axial end portions (36) each have a V-shaped cross-section as viewed radially.

9. The block piece (10) according to any one of claims 5 to 8, characterized in that the base body (12) comprises, on a side facing and away from the workpiece mounting face portion (14), a radially outer annular portion (26) and a radially inner annular portion (28) of different diameters, the radially outer annular portion (26) and the radially inner annular portion (28) being concentrically arranged about a central axis (A) of the base body (12), the radially inner annular portion (28) projecting axially beyond the radially outer annular portion (26), wherein the clamping protrusion (30) extends between the radially outer annular portion (26) and the radially inner annular portion (28).

10. The block piece (10) according to claim 9, characterized in that the radially inner annular portion (28) of the base body (12) is provided with two notches (38) for aligning the cylinder axis of the block piece (10) with the main axis of a machining machine, the two notches being arranged on diametrically opposite sides with respect to the central axis (a) of the base body (12).

11. The closure (10) according to claim 9, wherein the radially inner annular portion (28) of the base body (12) defines a central cylindrical blind bore (40) having a flat bottom (42), wherein a plurality of reinforcing ribs (44) extend between the flat bottom (42) and an inner circumference (46) of the radially inner annular portion (28).

12. The closure (10) according to claim 10, wherein the radially inner annular portion (28) of the base body (12) defines a central cylindrical blind bore (40) having a flat bottom (42), wherein a plurality of reinforcing ribs (44) extend between the flat bottom (42) and an inner circumference (46) of the radially inner annular portion (28).

13. The closure (10) according to claim 11, wherein the reinforcing ribs (44) each have a radial inner surface (48) which is inclined with respect to the central axis (a) of the basic body (12), wherein these radial inner surfaces (48) together define an inner conical central portion of the basic body (12).

14. The closure (10) according to claim 12, wherein the reinforcing ribs (44) each have a radial inner surface (48) which is inclined with respect to the central axis (a) of the basic body (12), wherein these radial inner surfaces (48) together define an inner conical central portion of the basic body (12).

15. A method of manufacturing a lens according to prescription, the method comprising the steps of:

(i) blocking a lens blank (B) with a blocking material (16), wherein a blocking face (cx) is placed on a workpiece mounting face portion (14) of a block piece (10), the lens blank (B) having a second face (cc) opposite to the blocking face (cx), and an edge (E) between the blocking face (cx) and the second face (cc),

(ii) processing said second face (cc) of the blocked lens blank to obtain a processed lens, an

(iii) Deblocking the machined lens from the blocking piece (10),

characterized in that, using a block piece (10) according to any of the preceding claims, the lens blank (B) blocked in the entire step (ii) remains on the block piece (10).

16. The method of claim 15, wherein step (ii) further comprises machining the edge (E).

17. The method of claim 15, wherein step (ii) comprises the sub-steps of:

(a) processing the blocked lens blank (B) so that said second face (cc) acquires a macroscopic geometry according to specifications;

(b) fine machining the blocked lens blank (B) to obtain the desired microscopic geometry of said second face (cc);

(c) cleaning the blocked lens blank (B) which has been machined and fine machined; and

(d) applying a vacuum coating to the second face (cc) of the blocked lens blank (B) to provide an anti-reflection coating.

18. A method according to claim 17, further comprising the substep of applying a spin or dip coating to the blocked lens blank (B) between substeps (c) and (d) to coat the second side (cc) with a hard coating, or a primer coating and a hard coating.

19. The method according to claim 17, wherein said substep (d) further comprises applying a vacuum coating to said second side (cc) of the blocked lens blank (B) to provide a top coating.

20. A method according to claim 17, further comprising, after sub-step (d), a sub-step of edging the blocked lens blank (B) to obtain the desired geometry of said edge (E) so that the finished lens is ready for insertion into a frame or frame.

21. The method according to claim 15 or 17, wherein the blocking surface (cx) of the lens precursor (B) is completely finished before step (i) is carried out, comprising a hard coating and an anti-reflection coating.

22. The method according to claim 21, wherein the fully finished blocking surface (cx) of the lens precursor (B) further comprises a topcoat.

23. A method according to claim 19 or 22, wherein the top coat is a hydrophobic and/or oleophobic and/or dust repellent coating.