Patent Application
20240416476
The present invention relates generally to a device for retaining an optical workpiece at a first one of two opposite workpiece surfaces for processing or treatment of the optical workpiece at a second one of the workpiece surfaces, according to the preamble portion of claim 1. In addition, the invention generally relates to a method for retaining an optical workpiece by a first one of two opposite workpiece surfaces at a retaining device for processing or treatment of the optical workpiece at a second one of the workpiece surfaces, according to claim 14. In particular the invention relates to a device for retaining and a method for retaining a spectacle lens for surface processing or treatment thereof such as takes place on a large scale in so-called “RX workshops”, i.e. production facilities for production of individual spectacle lenses in accordance with ophthalmic prescription. The surface processing can be here, for example, “polishing” and the surface treatment can be, for example, “marking”, such as described in more detail in the following.
In document DE 10 2021 004 831 A1 there has already been description in detail of those process steps which conventionally are usually performed in RX workshops in the industrial production of spectacle lenses. For that reason the usual procedure shall be only briefly outlined at this point, express reference otherwise being made to the aforesaid document with respect to the conventional procedure and further documented prior art. The starting product in industrial production of spectacle lenses is a semi-finished spectacle lens blank, also termed “blank”, which has one already preshaped optically effective surface and which is to be processed at its other optically effective surface and at the edge between the optically effective surfaces to form a finished spectacle lens.
After protection of the pre-shaped optically effective surface by a protective film or protective lacquer so-called “blocking” of the respective spectacle lens blank is carried out, which in that case is connected with a suitable so-called “blocking member”. For the blocking, the spectacle lens blank and blocking member each with a previously known or measured geometry are positioned relative to one another so that the blocking member adopts a predetermined position relative to the protected, preshaped surface of the spectacle lens blank. Fixing of this set position takes place subsequently by filling the space between the blocking member and spectacle lens blank with a conventional molten material (metallic alloy or wax) or alternatively by a suitable plastic or adhesive. After solidifying or hardening of this filler material the blocking member represents a mount or machine interface for processing of the spectacle lens blank, which subsequently remains at the spectacle lens for several processing procedures in different machines so as to then be able to, in particular, rotationally drive the spectacle lens and reliably hold it in an always defined position.
In the next process step, i.e. the so-called “generation”, the formerly not yet processed optically effective surface of the respective spectacle lens blank gains its macrogeometry, i.e. optically active shape in accordance with prescription, in a special processing machine, also called “generator”, by (preliminary) processing by machining; in the case of, for example, plastic as lens material this is usually milling and/or turning with a geometrically defined cutting edge and in the case of, for example, mineral glass as lens material usually grinding with a geometrically undefined cutting edge. In that case the blocked spectacle lens blank is held by the blocking member at a rotationally driven workpiece spindle, while initially preliminary edge processing and then surface processing are carried out.
Fine processing by (micro) machining, which is broadly termed “polishing”, of the spectacle lenses is then carried out, in which the pre-processed optically effective surface of the respective semi-finished product gains the desired microgeometry (surface quality), in particular by a geometrically undefined cutting edge. For that purpose the blocked semi-finished product, which has been pre-processed by machining, is removed from the generator and further processed in a fine-processing or polishing machine. In that case, positioning and fixing of the semi-finished product as well as optionally rotational drive of the semi-finished product in the polishing machine also take place by the blocking member. During the polishing treatment there is movement—with addition of a liquid polishing agent provided with abrasive particles—by a usually flexible polishing tool or polishing plate in defined tracks over the pre-processed surface so as to reduce surface roughness.
“Marking” of the semi-finished product takes place as a next, optional process step, wherein, for example, two small circles are generated on the rear surface of the semi-finished product by, for example, a laser beam or mechanically by an engraving graver. This is necessary for, for example, freeform surfaces so as to reliably find, by way of the applied markings, the position of the semi-finished product in later processing steps. Since a comparatively high degree of accuracy in positioning is required here, positioning and fixing during marking also take place by way of the blocking member.
The semi-finished product is separated from the blocking member only after this processing. The so-called “deblocking” takes place, for example, in the case of the afore-mentioned adhesive connection by a high-pressure water jet which is delivered by a nozzle and which impinges on an edge location between blocking member and semi-finished product in order to detach the semi-finished product from the blocking member by application of hydraulic forces. As a consequence, the processed semi-finished product is now present as a single item and the separated blocking member is cleaned and returned to the process step of blocking.
In further processing, the semi-finished product after cleaning is optionally coated at its front side and/or rear side in order to achieve additional effects: increase in scratch resistance by hard-coating, anti-reflection properties, coloration, metallization, hydrophobic properties, etc.
In conclusion, so-called “edging” is performed as a final process step, in which the semi-finished product is processed again at the edge for fitting into a desired spectacles frame, so that it receives the shape of the respective spectacles rim. Since the semi-finished product is now no longer fixed on the blocking member, the position has to be re-established here (for example by way of the afore-mentioned markings) before the semi-finished product can be suitably fixed and finally processed in a so-called “edger” as an edge processing device with respect to its edge shape and fastening in the spectacles frame.
In the case of spectacle lenses, special demands on the processing and treatment steps described in that respect additionally result from the circumstance that there can be a requirement—for example the ophthalmic prescription for the individual spectacle lens—for the front and the rear surfaces of the spectacle lens to be set at a specific angle relative to one another, thus tilted relative to one another so as to provide compensation for specific eye defects. It is usual for production of such spectacle lenses with a predetermined so-called “prism” for the spectacle lens blank to be “prismatically” blocked, i.e. with, for example, its front surface to be secured to the associated retaining surface at the blocking member tilted in defined manner or laterally offset or rotated with respect to the blocking member axis in defined manner. In the case of tilting, the filling material then quasi forms a wedge—optionally together with a wedge-shaped intermediate member (see, for example, document U.S. Pat. No. 6,382,790 B1, FIGS. 4 and 8A)—between spectacle lens blank and blocking member.
The prismatic blocking has the consequence, for example, that—during generation—the geometry, which is to be formed, of the rear surface of the rotationally driven spectacle lens blank or—during polishing—the previously generated rear surface, which is then to be finely processed, of the rotating semi-finished product executes in the course of rotation thereof at most comparatively small wobble movements with respect to a notional plane extending perpendicularly to the workpiece rotational axis. As a consequence of that the requirements of the respective workpiece adjusting movement parallel to the workpiece rotational axis with respect to movement stroke and movement dynamics are quite low, which enables surface processing with a high degree of processing quality.
The process chain from the prior art outlined in that regard now includes by the steps of “blocking” and “deblocking” two sequences which represent necessary auxiliary processes, but which themselves do not increase the value of the produced spectacle lens. A process chain managing without these auxiliary processes and specifically the auxiliary and operating materials used therein would thus be desirable. In particular, in order to increase efficiency and also for ecological considerations it has already been proposed in the prior art to operate “blocklessly” in the production of optically effective surfaces of spectacle lenses, wherein the spectacle lenses are held during the processing by special holding devices or retainers.
By way of example, mention may be made of sub-atmospheric-pressure lens holders for that purpose, such as are known from documents DE 39 24 078 C2 (FIGS. 1 to 3), US 2008/0299881 A1 (FIGS. 3 to 5) or U.S. Pat. No. 7,500,908 B2 (FIGS. 1 to 5). In all of these cases there is provided at a lens retaining surface of the lens holder at least one sealing element extending around the center axis of the lens retaining surface, thus an annular sealing element. This sealing element is capable of confining a vacuum, which is applied through the lens holder or from outside and is between the lens retaining surface and the spectacle lens placed on the sealing element, to radially within the sealing element so as to detachably secure the spectacle lens to the lens holder.
In this connection, with an eye on the subject of production of spectacle lenses with a predetermined prism, document EP 3 608 055 A1 discloses a method for producing an optical surface of an optical lens, which comprises the following steps: a lens blank preparation step, in which a lens blank, which is blocked on the lens blocking member, is provided; a step of clamping in place, in which the lens blocking member holding the lens blank is clamped in place in a lens processing device; a tilting step, in which the lens blank and the lens blocking member are tilted relative to the rotational axis of the lens processing device; a step of determining surface position, in which the position of the surface to be processed is determined on the basis of the tilt angle of the lens blank and the lens blocking member relative to the rotational axis of the lens processing device; a step of configuring the processing tool, in which the work parameters of the lens processing tool are configured so as to produce the surface, which is to be processed, in correspondence with the determined surface position so that there is adherence to the desired optical properties of the optical lens. In other words, in the context of production of a spectacle lens with a predetermined prism the proposal here is to block the spectacle lens blank not prismatically, but without a prism, for example on a sub-atmospheric-pressure lens holder (cf. paragraph [0037] of this document) and to then address the desired prismatic effect solely during the actual processing step and in the processing device by defined tilting of the workpiece. Such a procedure is obviously accompanied by a certain degree of outlay on device and regulation technology, which is not desired for many applications.
Finally, with respect to the subject of prismatic blocking document EP 3 116 684 B1 (FIGS. 1 to 4), which defines the preamble portion of claim 1, discloses a device for blocking a spectacle lens blank having a finished surface and a processing surface, which is opposite the finished surface, for processing in a processing device. The device, which is proposed here, for blocking is of two-part construction, comprising a retaining component and a clamping block.
The retaining component has a convex, planar or concave retaining surface for blocking the finished surface of the spectacle lens blank with the assistance of a usual blocking material (see paragraphs [0025] and [0026]) and a substantially planar opposing surface arranged opposite the retaining surface, wherein the normal of the opposing surface is inclined by 1° to 10° relative to the normal at the center point of the retaining surface. In that case, the retaining surface is configured so that the spectacle lens blank during blocking is placeable on the retaining surface over substantially the whole area so as to fully support the spectacle lens blank during processing.
On the other hand, the clamping block has a substantially planar and inclined bearing surface on which the retaining component is rotatably mounted by its opposing surface and is constructed for being clamped in place in a processing device. Thus, not only does the retaining component itself have an inclined opposing surface, but also the mounting component (clamping block) on which the retaining component is mounted. The final inclination of the retaining surface for the spectacle lens blank thus depends not only on the inclination of the opposing surface, but also on the inclination of the mounting surface. As a result the inclination of the retaining surface is individually adjustable to the prism, which is to be created, for the spectacle lens by the respective rotational positioning of the opposing surface relative to the mounting surface. Finally, the retaining component and the mounting component are mechanically positively and/or frictionally connectible together in the respective relative position.
Such a design of the device thus advantageously enables adjustment of the prism in accordance with, for example, the ophthalmic prescription so that the blocking material does not have to form a correspondingly thick wedge, as a consequence of which the mass thereof can be reduced and other blocking materials can be used (cf. again paragraphs [0025] and [0026] of this document). However, simplification of the adjustment of a defined prism for use of such a device in RX workshops on an industrial scale and as far as possible in a production sequence managing without conventional blocking materials would be desirable.
By contrast with the prior art outlined in that respect the invention has the object of providing a device, particularly for a production process chain ideally managing entirely without conventional blocking aids (blocking member, blocking material), for retaining an optical workpiece, namely a spectacle lens, at a first one of two opposite workpiece surfaces for processing or treatment of the optical workpiece at a second one of the workpiece surfaces, which device generally addresses the problems described above with respect to the prior art and specifically enables simplified setting of a clearly defined prismatic tilt of the optical workpiece, particularly for use in an at least partly automated production environment. The object of the invention further comprises statement of a corresponding method for retaining an optical workpiece, particularly a spectacle lens, with a first one of two opposite workpiece surfaces at a retaining device for processing or treatment of the optical workpiece at a second one of the workpiece surfaces, by which prismatic tilting of the optical workpiece can also be set and maintained in simplest possible manner.
The above objects are fulfilled by a device for retaining an optical workpiece, particularly a spectacle lens, with the features of claim 1 and a method for retaining an optical workpiece, particularly a spectacle lens, by the method steps according to claim 14. Advantageous or expedient embodiments and developments of the invention are the subject of the dependent claims.
According to a first aspect of the invention a device for retaining an optical workpiece, particularly a spectacle lens, at a first one of two opposite workpiece surfaces for processing or treating the optical workpiece at a second one of the workpiece surfaces comprises a lower part with a base, which has a central base axis and which comprises an interface for three-dimensionally defined securing to a holder and a lower wedge section adjoining the base along the base axis and extending transversely to the base axis, and an upper part with a retaining section, which has a central retention axis, for the optical workpiece and an upper wedge section adjoining the retaining section along the retention axis and extending transversely to the retention axis, wherein the lower part and the upper part by the mutually facing lower and upper wedge sections are rotatable relative to one another about a common rotational axis inclined with respect to the base axis and the retention axis so that a relative rotation of the upper part and lower part about the rotational axis produces relative tilting of the retaining section with respect to the base; the device having a wedge orientation arrangement with, at the upper part, an orientation aid by way of which a rotational angle position of the upper part about the base axis can be determined and/or the upper part is fixable in a rotational angle position about the base axis, and/or with an abutment between the upper part and the lower part which defines at least one rotational angle end position of the upper part about the rotational axis with respect to the lower part, in which the retaining section at the upper part has minimum or maximum tilt relative to the base of the lower part.
The provision of a wedge orientation arrangement according to the invention at a retaining device configured for adaptive, i.e. adjustable, prismatic retention—which within limits is as desired—of a workpiece simplifies presetting of the retaining device with respect to a prism predetermined for the workpiece to be retained, particularly in an (at least partly) automated processing sequence such as is desirable in, for example, an industrial production process of spectacle lenses. In that case the invention exploits the circumstance that in the case of the retaining device according to the invention, in which two wedges lying one on or above the other at the upper part and lower part are rotated relative to one another about the common rotational axis, the relative rotational setting of the upper part and lower part is decisive for prismatic tilting of the retaining section at the upper part with respect to the base of the lower part. The three-dimensional position of the lower part of the retaining device is in that regard clearly defined by way of the interface provided at the base of the lower part, which also includes, in particular, the rotational setting of the lower part about the base axis.
The orientation aid at the upper part now allows the rotational angle position of the upper part about the base axis to be established and/or fixed in simple manner and thus to directly ensure, i.e. check or set, the prismatic tilt of the retaining section with respect to the base. If a retaining device according to the invention is inserted into an associated holder with, for example, a preselected relative rotational setting of the lower part and upper part with the interface at the base of the lower part, whereby the lower part has a clearly defined and known position in three dimensions, it is possible by way of the orientation aid at the upper part to detect the relative rotational setting thereof with respect to the lower part and thus readily draw a conclusion about the tilt of the retaining section with respect to the base. This can, for example, be used for the purpose in the processing sequence of undertaking matching of an actual tilt of the retaining section with respect to the base with a target tilt of the retaining section with respect to the base so as to, for example, verify the actual tilt of the retaining section in relation to the base before the workpiece is retained at the retaining device.
If, in addition, the orientation aid is optionally adapted for the purpose of allowing fixing of the rotational angle position of the upper part about the base axis a desired or required tilt of the retaining section with respect to the base can be set or corrected in simple manner in the further processing sequence. It is then possible, for example, to rotate the lower part together with the interface, which is received in the associated holder, of the base by way of the holder in defined manner about the base axis while the upper part is fixed at the orientation aid of the wedge orientation arrangement against (co-)rotation about the base axis. Due to the afore-described wedge action the relative tilt of retaining section and base then changes in accordance with the relative rotation of the upper part and lower part in a predetermined and known manner.
If the wedge orientation arrangement comprises—alternatively or in addition to the afore-described orientation aid—the claimed abutment between the upper part and lower part, which fixes at least one rotational angle end position of the upper part and lower part with minimum or maximum tilting of the retaining section with respect to the base, it is advantageously possible, for example, in an (partly) automated processing sequence to rotate the lower part and upper part of the retaining device relative to one another about the rotational axis and into abutment without further control—whether by rotation only of the upper part or only of the lower part or an opposite rotation of the upper part and lower part—in order to achieve a minimum or maximum tilting of the retaining section with respect to the base. If one part (upper part or lower part) is then secured against rotation a desired tilt of the retaining section with respect to the base can be set by defined (return) rotation of the other part (lower part or upper part) out of the abutment position. The respective amount of tilt is then dependent on the wedge angle of the wedge sections at the lower part and upper part as well as on the angle amount of the relative rotation between the lower part and upper part.
In a preferred embodiment of the retaining device the orientation aid of the wedge orientation arrangement can have a projection which extends substantially radially outwardly away from the upper wedge section of the upper part with respect to the rotational axis. By contrast with, for example, a mere notch or marking externally on the upper part, which in principle would be sufficient for rotational position detection of the upper part, such a projection can also advantageously serve as a handle by which the upper part can be fixed in its rotational angle position about the basis axis, for example by a suitable counter-bearing secure against rotation. However, as an alternative to such a “raised” geometry at the upper part, the upper part can also have a cut-out which extends substantially radially inwardly with respect to the rotational axis. Such a cut-out can then, for example, co-operate with a slide of complementary configuration so as to fix the upper part in its rotational angle position about the base axis. There are obviously also other possibilities of temporarily securing the upper part of the retaining device against rotation about the base axis, for example by circumferential clamping at the retaining section or at the upper wedge section of the upper part.
If the wedge orientation arrangement (also) comprises the afore-mentioned (rotation) abutment between the upper part and the lower part then this abutment in an advantageous embodiment can have dedicated abutment sections preferably formed in the interior of the retaining device, namely a first abutment section at the lower part which co-operates with a second abutment section at the upper part. In that case the arrangement can be preferably such that the first abutment section and the second abutment section of the abutment as seen in plan view along the rotational axis each have the configuration of a ring segment of 90° and as seen in a circumferential direction about the axis or rotation each have two end-face abutment surfaces, wherein one of the abutment surfaces of the first abutment section co-operates with one of the abutment surfaces of the second abutment section so as to fix maximum tilting of the retaining section at the upper part relative to the base of the lower part, while another one of the abutment surfaces of the first abutment section co-operates with another abutment surface of the second abutment section so as to fix minimum tilting of the retaining section at the upper part relative to the base of the lower part. A rotational abutment of that design between the upper part and lower part of the retaining device thus advantageously defines two extreme positions of tilting of the retaining section. The configuration of the abutment sections as ring segments additionally offers the advantage that by comparison with, for example, an equally conceivable four discrete abutment points instead of the end-face abutment surfaces at the ring segments an inverted mounting of the retaining device in the relative rotational position of upper part and lower part is excluded.
Fundamentally, an adjusted relative rotational angle position of the upper part and lower part of the retaining device can be steplessly secured in rotational angle by, for example, a friction couple between upper part and lower part, optionally with the intermediation of a rubber ring or the like between the upper part and the lower part, if a sufficient normal force acts between upper part and lower part. However, with respect to, in particular, reliable maintenance of the set relative rotational angle position of the upper part and lower part—and thus the desired tilt of the retaining section with respect to the base—even under, for example, torques acting about the rotational axis on the upper part or lower part as a consequence of processing or handling of the workpiece held at the retaining device and/or as a consequence of the rotational drive of the retaining device it is preferred if a set relative rotational angle position of the upper part and lower part is mechanically positively securable in steps about the rotational axis.
A possibility, which is preferred here, of stepped mechanically positive securing of the set relative rotational angle position of the upper part and lower part includes providing between the upper part and the lower part a Hirth toothing as a mechanically positive connection, with a first toothing section on an upper side of the lower part and a second toothing section, which is formed to be complementary with the first toothing section, on a lower side of the upper part. An advantage of such a Hirth toothing is that the Hirth toothing—such as in use, for example, as a slip clutch in a torque-limited battery drill/driver—in the case of comparatively low normal forces between the toothing sections allows selective “slipping over” of the toothing sections, which is conducive to sensitive setting of a defined relative rotational angle position of the upper part and lower part. When the relative rotational angle position of the upper part and lower part required for the desired tilting of the retaining section is achieved the attained mechanically positive connection can be secured in simple manner by increase in the normal force. A further advantage of such a Hirth toothing additionally arises in that case from the self-centering characteristics thereof, which is due to the conical shape of the individual teeth as seen in cross-section and which seeks to center the upper part and the lower part of the retaining device equally with respect to the rotational axis.
In tests carried out by the inventors a Hirth toothing, which preferably has a tooth count between 28 and 36 teeth and/or in which the individual teeth have a tooth height between 1 millimeter and 3 millimeters at the radially outer edge of the teeth referred to the rotational axis and/or in which the individual teeth lie within a circle about the rotational axis having a radius of between 15 millimeters and 20 millimeters with respect to the rotational axis, has proved advantageous here with respect to a small need for installation space and moderate necessary axial holding forces.
As far as the actual retention of the optical workpiece at the retaining section of the upper part is concerned this can in principle be designed in such a way that the workpiece is rigidly and detachably fastened by, for example, a conventional (blocking) adhesive to the retaining section of the upper part, which can have advantages for specific applications due to the comparatively firm whole-area support of the workpiece at the retaining section. However, on the other hand an embodiment of the retaining device is preferred here in which a flexible retaining ring on which the optical workpiece can be placed by its first workpiece surface is mounted on the retaining section of the upper part. In particular, this advantageously enables—with avoidance of use of conventional blocking materials—holding of the workpiece at the retaining section of the upper part by way of the principle of “vacuum”. Prior investigations of the inventors had in this connection shown that in the case of, for example, production of spectacle lenses in, for example, the polishing process with flexible tools the demands with respect to positioning accuracy and area support are substantially less than in the case of upstream generation of the optically active form, which in the case of, for example, spectacle lenses of plastic usually comprises force-intensive processing by milling and turning. In such a polishing process a positioning accuracy in the millimeter range has proved sufficient and with respect to support it has proved adequate to secure the spectacle lens against tipping, which the flexible retaining ring is entirely capable of performing.
In the tests carried out by the inventors it has in addition proved particularly advantageous, especially with respect to a best possible capability of adaptation of the flexible retaining ring to the surface geometry of the optical workpiece which is to be retained, without the risk of a too “soft” supporting of the workpiece for, for example, a polishing process as well as with respect to a good level of resistance to the liquid additives which might be used in the respective production step, if the flexible retaining ring is made of NBR or EPDM and/or has a hardness according to Shore A of between 15 and 80, preferably between 20 and 50, and/or a material thickness of between 1.0 millimeter and 8.0 millimeters, preferably between 2.0 millimeters and 5.0 millimeters. The mentioned material thickness can—but does not have to—be uniform over the area dimension of the retaining ring, but may increase or decrease within the claimed limits particularly in radial direction depending on the respective retaining requirements. Moreover, in this connection, “retaining ring” does not necessarily mean a ring with a circularly annular shape, but also includes rings which have a different closed annular shape, for example with an external outline which as seen in plan view has a cushion shape or the like.
As already indicated further above the retaining device in an embodiment preferred for, for example, a polishing process for spectacle lenses can comprise at the upper part an outer vacuum chamber which is bounded at least by an end surface of the retaining section at the upper part and an inner circumferential surface of the flexible retaining ring and can be evacuated for releasable holding of the optical workpiece, which is placed on the flexible retaining ring, at the first workpiece surface. Thus, for example, the use of conventional blocking materials for releasable fastening of the workpiece to or on the retaining section can advantageously be avoided.
As far as the releasable coupling or securing of the lower part and upper part to one another are concerned, when these are in their desired or required relative rotational setting with respect to one another different approaches to a solution are also possible. Thus, for example, a releasable connection can be provided by spring force or a combined frictional and mechanically positive securing with the assistance of screws or the like. However, with respect to, especially, a good capability of automation of production and cancellation of the connection of the lower part and upper part, an efficiency which in that case is as high as possible—even in terms of time—and a smallest possible outlay with respect to the device it is preferred for those purposes if the lower part and upper part bound an inner vacuum chamber which is sealed relative to the environment by a sealing ring and which can be evacuated in order to releasably hold the upper part at the lower part in a predetermined rotational angle setting about the rotational axis. The sealing ring can be, for example, a commercially available O-ring or, however, a so-called “quad-ring”, i.e. a toroidal sealing ring with an approximately square cross-section.
In that regard it is particularly preferred if the inner vacuum chamber is pneumatically connectible or connected with the outer vacuum chamber, the latter preferably by way of a connecting hole in the retaining section of the upper part. It is thus advantageously possible to use, in particular, one and the same vacuum for the purpose of releasably holding together the assembly of lower part, upper part and workpiece in a predetermined relative setting. An advantage of the optional connecting hole is that a permanent connection of the inner and outer vacuum chamber promotes release of the workpiece from the retaining device after processing or treatment of the workpiece, since the vacuum is thus present at two separation points with respect to the environment, namely inwardly at the sealing ring and outwardly at the retaining ring, and the presence of these two separation points increases the probability of at least one of them being released.
In a development of the retaining device it can be further provided that a spring element is arranged between the lower part and the upper part so as to produce between the lower part and the upper part a biasing force which urges the lower part and the upper part apart. Such a spring element can advantageously assist release of the lower part and upper part from one another, serving—in the case of use of sub-atmospheric pressure for holding the lower part and upper part together—particularly for cancellation of the vacuum in a time-efficient manner.
With respect to a highest possible processing reliability in, for example, use of the retaining device in an (at least partly) automated production environment it is, in addition, preferred if there is formed between the lower part and the upper part of the retaining device a detent connection which secures the upper part, with play, to the lower part against loss, preferably comprising a plurality of flexible detent hooks at one part, the hooks co-operating with an undercut at the other part.
Finally, in a preferred embodiment of the retaining device a centering aid which aligns the upper part and the lower part with respect to the common rotational axis can be formed between the lower part and the upper part, preferably comprising a substantially hollow-cylindrical sleeve section at one part, the sleeve section co-operating with a substantially cylindrical collar at the other part. Such a centering aid advantageously simplifies mounting of the retaining device.
According to a second aspect of the invention, a method for retaining an optical workpiece, particularly a spectacle lens, by a first one of two opposite workpiece surfaces at a retaining device for processing or treating the optical workpiece at a second one of the workpiece surfaces, comprises the following steps: a) providing the optical workpiece to be processed or treated; b) providing the retaining device for the optical workpiece, comprising a lower part with a base, which has a central base axis and which comprises an interface for three-dimensionally defined securing to a holder, and a lower wedge section adjoining the base along the base axis and extending transversely to the base axis, as well as an upper part with a retaining section, which has a central retention axis, for the optical workpiece, and an upper wedge section adjoining the retaining section along the retention axis and extending transversely to the retention axis, wherein the lower part and the upper part by the mutually facing lower and upper wedge sections are rotatable relative to one another about a common rotational axis inclined with respect to the base axis and the retention axis so that a relative rotation of the upper part and lower part about the rotational axis produces a relative tilting of the retaining section with respect to the base, wherein the retaining device additionally comprises a flexible retaining ring at the retaining section, an outer vacuum chamber bounded at least by an end surface of the retaining section and an inner circumferential surface of the flexible retaining ring, and an inner vacuum chamber, which is sealed relative to the environment by a sealing ring, between the lower part and the upper part; c) ensuring that the desired relative tilting of the retaining section at the upper part with respect to the base of the lower part is present; d) placing, with alignment with the retention axis of the retaining device, the optical workpiece by its first workpiece surface on the flexible retaining ring at the retaining section of the upper part of the retaining device; and e) evacuating the inner vacuum chamber and the outer vacuum chamber together in order at the same time to secure the upper part and lower part of the retaining device to one another in the relative rotational setting thereof about the rotational axis and the optical workpiece to the retaining section of the retaining device.
Thus, in a manner which is also particularly efficient in terms of time use can advantageously be made in this procedure of one and the same vacuum not only to temporarily, i.e. releasably, fix the workpiece to the retaining device, but at the same time to also releasably secure the relative rotational setting of the lower part and upper part of the retaining device with respect to one another and the tilt setting, which is thus achieved, of the retaining section at the upper part with respect to the base of the lower part.
In a preferred embodiment of this method at least the step e) can be performed in an evacuable container into which the retaining device and the optical workpiece are inserted. Thus, in particular, there is no requirement for the inner vacuum chamber and the outer vacuum chamber to have any pneumatic connection within the retaining device. This has at the outset the advantage that, for example, in the case of loss of the workpiece during, for example, a polishing process no abrasive polishing medium can pass into the interior of the retaining device and contaminate any mechanism (for example the afore-mentioned Hirth toothing) present therein. Considered in the opposite direction there is also no risk of abraded material, which arises, for example, at the mechanism of the retaining device, from passing from the inner vacuum chamber into the outer vacuum chamber and possibly leading to damage of the held surface of the workpiece therein. Thus, cleaning of the retaining device without the workpiece held thereat is also advantageous since the inner vacuum chamber even without a workpiece is closed towards the outside.
If the step e) is carried out in an evacuable container, a step f) of removal of the retaining device and optical workpiece retained thereat from the evacuable container can follow, with the specific feature that at the start of this step the evacuable container is ventilated while the optical workpiece is urged substantially along the retention axis against the flexible retaining ring. This is in turn conducive to a high level of process reliability, because it is ensured that during ventilation of the evacuable container the inner vacuum chamber and the outer vacuum chamber are not unintentionally ventilated at the same time.
Moreover, the step c) of securing the desired relative tilt of the retaining section with respect to the base can comprise relative rotation of the upper part and lower part of the retaining device about the rotational axis. On the other hand, if the retaining device at the time of its provision in step b) already has a relative rotational setting of the lower part and upper part which produces the desired or required tilt of the retaining section of the upper part with respect to the base of the lower part a relative rotation of upper part and lower part in step c) is redundant. The step c) then comprises merely a check whether the actual tilt of the retaining section corresponds with the target tilt of the retaining section. Such a check can obviously also be carried out directly by way of a comparison between a relative actual rotation of the upper part and lower part and a relative target rotation of the upper part and lower part.
Finally, the step d) of aligned placement of the optical workpiece with respect to the retention axis of the retaining device can comprise centering of the optical workpiece with respect to the retention axis of the retaining device and/or a rotational angle orientation of the optical workpiece about the retention axis of the retaining device. In every case it must be ensured in step d) that the optical workpiece is positioned in a relative setting on the retaining section of the retaining device in which the desired or required prismatic tilting of the workpiece results—thus usually a relative setting in which the prism set at the retaining device substantially compensates for the prism of the workpiece. In that regard, a division of movement between workpiece and retaining device can also take place, for example in such a way that the retaining device itself is rotated only about the base axis, while the workpiece is, with knowledge of its rotational position, positioned in the remaining three translational and two rotational degrees of freedom of movement with respect to the retaining device.
Further features, characteristics and advantages of the device according to the invention and the method according to the invention for retaining or receiving an optical workpiece will be evident to the person ordinarily skilled in the art from the following description of a preferred embodiment.
The invention is explained in more detail in the following by way of a preferred embodiment with reference to the accompanying partly schematic drawings, in which:
In general it is be noted at this point with respect to the drawings that in
A device for retaining an optical workpiece—also called retaining device for short in the present application—is denoted generally by the reference numeral 10 in
A special feature of the spectacle lens 12 illustrated herein is that, as
As can be readily recognized in
The upper part 22, which is shown separately in
The lower wedge section 28 of the lower part 20 and the upper wedge section 32 of the upper part 22 have a common rotational axis DA, which is inclined not only with respect to the base axis BA, but also to the retention axis AA, as indicated in
As also explained in detail in the following, different measures i), ii) and iii) which improve, especially simplify and accelerate, the setting and holding of a defined prismatic tilting of the spectacle lens 12 at the retaining device 10 in an at least partly automated production environment are undertaken at the retaining device 10. These measures i) to iii) are, in fact, realized together in the illustrated embodiment for the retaining device 10, but this is not obligatory, i.e. they can also each be used individually.
Thus, the retaining device 10 at the outset is provided with a wedge orientation arrangement which in the illustrated embodiment comprises (inter alia) not only i) an orientation aid 34 at the upper part 22, as can be readily seen, for example, in
Moreover, iii) an outer vacuum chamber 38 is provided at the upper part 22 of the retaining device 10 (cf., for example,
According to, in particular,
It is at the outset obvious particularly from
The wedge orientation arrangement further comprises externally visible—indeed even when a retaining device 10 is inserted by the base 24 into a holder—marking slots 52, 53 in the lower wedge section 28 of the lower part 20 and the upper wedge section 32 of the upper part 22, which indicate in which relative rotational setting the lower part 20 and upper part 22 are disposed. If these marking slots 52, 53 are congruent, as shown in
Moreover, in the transition region from the lower part 20 and upper part 22 it can be seen at the outside that formed between the lower part 20 and the upper 22 is a centering aid 54 which aligns the upper part 22 and the lower part 20 with respect to the common rotational axis DA. In the illustrated embodiment the centering aid 54 comprises a substantially hollow-cylindrical sleeve section 55 at the upper part 22, which co-operates with a substantially cylindrical collar 56 at the lower part 20, as can be best seen in the sectional views according to
The retaining section 30 of the upper part 22 has an end surface 58, which faces away from the lower part 20 and which is formed to be concave. A flexible retaining ring 60 on which the spectacle lens 12 can be placed by its first workpiece surface 14 is mounted on the retaining section 30 of the upper part 22 in the region of the end surface 58 or surrounding this. As already mentioned in the introduction, the flexible retaining ring 60 can be made of, for example, NBR (nitrile butadiene rubber) or EPDM (ethylene-propylene-diene; M group) and preferably has a hardness according to Shore A of between 15 and 80, more preferably between 20 and 50. However, as an alternative thereto a foam ring of, for example PUR (polyurethane elastomer) is conceivable, which is provided with a cover of natural rubber and has a similar hardness range. A suitable, in a given case uniform, material thickness for such a flexible retaining ring 60 is preferably between 1.0 millimeter and 8.0 millimeters, more preferably between 2.0 millimeters and 5.0 millimeters. The concave form of the end surface 58 makes it possible, by its comparatively strong curvature as well as the flexible, adaptable retaining ring 60, to hold spectacle lenses 12 with widely different front curvatures at its respective workpiece surface 14.
As far as the operating principle of the holding is concerned, provided at the upper part 22 of the retaining device 10 in accordance with, in particular,
The interior of the retaining device 10 can be best seen in the perspective views according to
Moreover, the abutment 36, which was already briefly described further above, of the wedge orientation arrangement is formed in the interior of the retaining device 10. According to, in particular,
A further special feature of the retaining device 10 is that a relative rotational angle position of the lower part 20 and upper part 22 about the rotational axis DA can be mechanically positively secured in steps. A Hirth toothing 74 is in turn formed for this purpose in the interior of the retaining device 10 between the lower part 20 and the upper part 22. The Hirth toothing 74 comprises a first toothing section 75 on an upper side of the lower part 20 and a second toothing section 76, which is formed to be complementary to the first toothing section 75, on a lower side of the upper part 22. In the mounted state of the retaining device 10 the two toothing sections 75, 76 interengage mechanically positively and with self-centering in a manner known per se for a Hirth toothing 74 when the inner vacuum chamber 40 is evacuated and in that case the sealing ring 64 between the lower part 20 and upper part 22 is compressed under axial approach of the upper part 22 and lower part 20. As a result, an undesired relative rotation of the lower part 20 and upper part 22 is then prevented by interlock.
For a concrete case of use, investigations by the inventors have shown that the Hirth toothing 74 should have a tooth count of between 28 and 36 teeth. The individual teeth of the Hirth toothing 74 at the radially outer edge of the teeth as referred to the rotational axis DA should, in addition, have a tooth height of between 1 millimeter and 3 millimeters. Moreover, the individual teeth of the Hirth toothing 74 should lie within a circle about the rotational axis DA which has a radius of between 15 millimeters and 20 millimeters with respect to the rotational axis DA. Resulting therefrom is a comparatively steep radial course of the individual teeth of the Hirth toothing 74 referred to a notional plane transverse to the rotational axis DA. In other words, as considered in a projection onto a plane containing the center axis(=rotational axis DA) of the Hirth toothing 74 the tooth root and tooth crown of a tooth of the Hirth toothing 74 include an angle of inclination which is relatively large for a Hirth toothing.
Moreover, in order to secure the upper part 22 of the retaining device 10 to the lower part 20, with play, against loss or unintended separation from the lower part 20 there is formed—again in the interior of the retaining device 10—a detent connection 78 between the lower part 20 and the upper part 22. As can be best seen in the perspective view according to
In terms of structure it is additionally to be noted with respect to the retaining device 10 that, as indicated in
Finally, as far as the wedge configuration of the wedge sections 28, 32 at the lower part 20 and upper part 22 are concerned
Depending on the division of the Hirth toothing 74 different tiltings of the retaining section 30 at the upper part 22 with respect to the base 24 of the lower part 20 are settable therebetween in steps, wherein the deformation capability of the flexible retaining ring 60 allows a spectacle lens 12 with a prism between 0° and, for example 10° to be respectively retained at the suitably set retaining device 10 in such a way that its workpiece surface 16, which is to be processed or treated, ultimately has substantially no tilt with respect to the base 24 of the retaining device 10.
In conclusion, the method for retaining the spectacle lens 12 by its first workpiece surface 14 at the retaining device 10 for processing or treatment of the spectacle lens 12 at its second workpiece surface 16 shall be briefly described with reference to the different method stages according to 1)
In general the method comprises the following steps: a) providing the spectacle lens 12 which is to be processed or treated and which has or is to have a predetermined prism; b) providing the afore-described “adaptively” constructed retaining device 10 for the spectacle lens 12; c) ensuring that the desired relative tilt of the retaining section 30 at the upper part 22 of the retaining device 10 with respect to the base 24 of the lower part 20 is present; d) placing—aligned with respect to the retention axis AA of the retaining device 10—of the spectacle lens 12 by its first workpiece surface 14 on the flexible retaining ring 60 at the retaining section 30 of the upper part 22 of the retaining device 10; and e) evacuating in common the inner vacuum chamber 40 and the outer vacuum chamber 38 so as to simultaneously secure the upper part 22 and the lower part 20 of the retaining device 10 to one another in the relative rotational setting thereof about the rotational axis DA as well as the spectacle lens 12 to the retaining section 30 of the retaining device 10.
The steps a) and b) of “providing” the workpiece (spectacle lens 12) and workpiece retainer (retaining device 10) obviously assume in an (partly) automated process sequence the presence of appropriate handling devices for positioning the workpiece and workpiece retainer in three dimensions, but these are not explained in more detail at this point since they are sufficiently known to the person ordinarily skilled in the art. In particular, provision of the retaining device 10 in an (partly) automated process sequence comprises loading the retaining device 10 into a joining unit FE, which is illustrated in
The joining unit FE in this example comprises a container BH which can be tightly closed by a cover DE and evacuated by way of a vacuum connection VA. A holder HA for retaining the base 24 of the retaining device 10 at the interface 26 thereof is arranged in the container BH. The holder HA is rotatable in defined manner, i.e. controlled in rotational angle, as indicated by the rotary arrow in
In principle, at the time of providing the retaining device 10 in accordance with step b) the retaining section 30 thereof can already have a known tilt with respect to the base 24. In such a case it merely has to be verified in step c) of ensuring the tilting that the desired or required tilt of the retaining section 30 at the retaining device 10 is present. This can be carried out in the joining unit FE, for example, by measuring with the assistance of the marking slots 52, 53 at the lower part 20 and upper part 22, their relative rotational angle position being representative of a specific tilt of the retaining section 30 with respect to the base 24 of the retaining device 10.
If, however, the lower part 20 and the upper part 22 of the retaining device 10 are in an arbitrary relative rotational setting with respect to one another about the rotational axis DA the tilt of the retaining section 30 with respect to the base 24 is correspondingly arbitrary. In this case the step c) of ensuring the desired relative tilt of the retaining section 30 with respect to the base 24 comprises a relative rotation of the upper part 22 and lower part 20 of the retaining device 10 about the rotational axis DA.
Since the upper part 22 of the retaining device 10 is now secured by the fixed abutment FA against further rotation, the lower part 20 of the retaining device 10 is, in the case of further rotation of the holder HA about the base axis BA relative to the upper part 22 of the retaining device 10, rotated until—as illustrated in
When this rotational setting is achieved, fixing of the desired relative rotational setting and thus the desired tilt of the retaining section 30 with respect to the base 24 can be carried out with knowledge of the relative rotational setting between the upper part 22 and lower part 20 of the retaining device 10. For that purpose, in correspondence with the illustrations in
Placing—aligned with respect to the retention axis AA of the retaining device 10—of the spectacle lens 12 by its first workpiece surface 14 on the flexible retaining ring 60 at the retaining section 30 of the upper part 22 of the retaining device 10 is subsequently carried out in accordance with step d), wherein this step includes centering of the spectacle lens 12 with respect to the retention axis AA of the retaining device 10 and/or rotational angle orientation of the spectacle lens 12 about the retention axis AA of the retaining device 10. In an (partly) automated process sequence the handling system associated with the spectacle lens 12 must thus have appropriate degrees of freedom of movement.
The inner vacuum chamber 40 and the outer vacuum chamber 38 of the retaining device 10 are then evacuated together in step e) so as to simultaneously secure the upper part 22 and lower part 20 of the retaining device 10 to one another in the relative rotational setting thereof about the rotational axis DA as well as the spectacle lens 12 to the retaining section 30 of the retaining device 10. In the illustrated embodiment this takes place by application of a vacuum to the evacuable container BH—which in that case is tightly closed by the cover DE according to
In the embodiment described herein this step is followed by a step f) of removal of the retaining device 10 and spectacle lens 12 retained thereat from the evacuable container BH, in which initially the evacuable container BH is ventilated and, in particular, by way of the vacuum connection VA and/or by opening the cover DE, while the spectacle lens 12 is urged substantially along the retention axis AA against the flexible retaining ring 60 (not shown in the figures). The urging during ventilation of the evacuable container BH prevents the inner vacuum chamber 40 or the outer vacuum chamber 38 of the retaining device 10 from being erroneously ventilated therewith. The reasons for that would be an undesired contact of one of the sealing front surfaces or a compression spring (spring element 82) which might be arranged between the lower part 20 and the upper part 22, as illustrated in
The spectacle lens 12 held—in a given case prismatically—at the retaining device 10 can, if desired, now be processed or treated at the free workpiece surface 16. If after the processing or treatment the spectacle lens 12 is to be separated again from the retaining device 10, it is possible to re-insert the retaining device 10 together with the spectacle lens 12 into the evacuable container BH and to evacuate this more strongly than in the case of the preceding joining. This has the effect that the higher pressure then prevailing in the vacuum chambers 38, 40 endeavors to drive the individual parts apart.
The above-described retaining device 10 and the method illustrated here make it possible, for example in the production process of spectacle lenses 12, to retain—in a given case also prismatically—the respective spectacle lens 12, for example after generation of the optically active shape, in simple manner specifically for a downstream polishing process so that the spectacle lens 12 does not in the process sequence have to be conventionally “blocked” for the downstream polishing process. The same applies to further treatment steps such as, for example, laser engraving. To that extent the retaining device 10 and the described retaining method are particularly tailored to use in a “blockless” production process for spectacle lenses, such as is the subject of documents DE 10 2021 004 831 A1, DE 10 2021 005 202 A1 and DE 10 2021 005 399 A1, to which express reference may be made at this point with respect to further process details.
A device for retaining, in particular, a prismatic spectacle lens at one workpiece surface for processing or treatment of the other workpiece surface comprises lower and upper parts. The lower part has a base with a holding interface and a wedge section transverse to the basis axis. The upper part comprises a spectacle lens retaining section and a wedge section transverse to the retention axis. The lower part and upper part are rotatable relative to one another by their mutually facing wedge sections about an rotational axis inclined with respect to the base axis and retention axis so as to tilt the retaining section and base relative to one another. A wedge orientation arrangement comprises, for determining or fixing an upper part rotational angle position about the base axis, an orientation aid at the upper part and/or an abutment between the upper part and lower part, which defines a relative rotational angle end position of the upper part and lower part corresponding with a minimal or maximal tilt of the retaining section with respect to the base. Outer and inner vacuum chambers of the device can be evacuated in common so as to couple the lower part, upper part and spectacle lens.
Other variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2023 115 420.6 | Jun 2023 | DE | national |
