DE10332673A1 - Production of optical lenses, for spectacles, uses plastics blanks for machining and polishing to the required geometry and surface quality, leaving a thicker edge zone around the circumference for clamping and stabilizing during working - Google Patents

Abstract

For production of ophthalmic lenses (32), plastics blanks are used structured to a general or specific prescription. Outer edge of blank is clamped for front (19) and rear (27) surfaces to be machined to give final surface geometry and quality, using grinder and/or lathe followed by smoothing and polishing. During machining, a ring zone (30) is retained with an increased thickness (33) at outer circumference of workpiece (16). The thicker ring zone is for clamping the workpiece during machining and movements, and stabilize the ophthalmic lens for further machining. Shapers are fitted to the ring zone to identify the working axes. Fine marking lines are applied to the lens for lens identification. The finished lens is finally separated from the thicker ring zone.

Description

The The invention relates to a method and to carrying out the Method suitable apparatus for the production of spectacle lenses and other moldings with optically effective surfaces corresponding to those mentioned in the preamble of claim 1 and claim 16 Features. It is preferably the production of spectacle lenses.

The here mentioned lenses and shaped bodies consist predominantly of plastics, which at high refractive index over a have a low specific weight and are easy to machine. The But it can also be for lenses and shaped bodies made of silicate glass.

to Linguistic simplification will be described below instead of "spectacle lenses and lenses other moldings "only spoken of eyeglass lenses, but always meant "others moldings with similar ones Properties". Although the text below only refers to "plastic lenses", so are always meant those made of mineral glass.

The following requirements apply to the manufacturing processes of modern spectacle lenses:
A so-called thickness optimization must be possible, with which the weight of the lenses is minimized to increase the wearing comfort.

at Plus glasses (Lens center is thicker than the lens edge) and neutral lenses (lens center is the same thickness as the lens edge) is in the thickness optimization the Thickness of the lenses is reduced as much as this with regard to remaining edge thickness (= thickness at the peripheral edge of the finished spectacle lens) is possible. The edge thickness must be kept, so that the lens in the spectacle frame can be properly mounted, d. H. this thickness must be about the same Width of the frame correspond to the spectacle frame.

at Minus lenses (Lens center is thinner than Lens edge) is in the context of thickness optimization, the thickness of the lenses reduced as far as this in view of the remaining residual thickness possible in lens center is. A certain minimum thickness in the center of the lens is required thus the mechanical stability of the, spectacle lens guaranteed is.

at The following description of the method according to the invention is essentially on Plus lenses Referenced, since the benefits of the process here emerge particularly concise. The procedure leaves analog, but also for neutral and minus glasses. To the linguistic Simplification is spoken in the following text only of eyeglass lenses.

There the two optically active surfaces of Plus glasses (front and back) are not plane-parallel to each other, but in different places have different angles to each other, plays in the thickness optimization the size of the lens a crucial role. The shape and size of the spectacle frame must therefore be known before the thickness optimization.

outgoing of the given thickness at the edge (eyeglass frame) is then the greater thickness determined in the middle of the lens.

• 1. Die Brillengläser lassen sich während der Herstellungsprozesse (Flächenbearbeitung und Randbearbeitung) nach dem Stand der Technik nur mit besonders großem Aufwand für die verschiedenen Bearbeitungsschritte Festspannen, da bei der Flächenbearbeitung der Randbereich angeschnitten wird und der Rand außerdem bearbeitet werden muss. Der Rand ist daher als Spannfläche nur geeignet, wenn besondere Verfahren angewandt werden. Nach der Randbearbeitung sind die Brillengläser am Umfang nicht mehr kreisrund, sondern entsprechen den verschiedenen Formen und Größen der Brillenfassungen (entweder exakt oder mit einer Bearbeitungszugabe für den Optiker). Diese nahezu beliebigen Formen und Größen machten es erforderlich, spezielle Spann- und Fertigungsverfahren zu entwickeln und eine Vielzahl von unterschiedlichen Werkzeugen vorzuhalten.
• 2. Durch die Dickenoptimierung (Brillenglas so dünn wie möglich) und die verwendeten Kunststoffe als Linsenmaterial (geringe Festigkeit) werden die erzeugten Brillengläser während der spannehmenden Fertigung zunehmend instabiler. In dem Maße wie sie durch den Materialabtrag dünner werden, verlieren sie an Stabilität und weichen dem Druck der Bearbeitungswerkzeuge aus, was zu unerwünschten Veränderungen der Oberflächengeometrie führt. Auch in diesem Zusammenhang mussten Verfahren gefunden werden, die der genannten Instabilität entgegen wirken.

In the production of spectacle lenses in compliance with the aforementioned requirement (thickness optimization), the following problems arise:

• 1. The lenses can be during the manufacturing processes (surface processing and edge processing) according to the prior art only with great effort for the different processing steps clamping, since in the surface treatment of the edge region is cut and the edge also has to be edited. The edge is therefore suitable as a clamping surface only if special procedures are used. After edge processing, the lenses on the circumference are no longer circular, but correspond to the different shapes and sizes of the spectacle frames (either exactly or with a machining allowance for the optician). These virtually any shapes and sizes made it necessary to develop special clamping and manufacturing processes and to provide a variety of different tools.
• 2. Through the thickness optimization (spectacle lens as thin as possible) and the plastics used as lens material (low strength), the spectacle lenses produced become increasingly unstable during the exciting manufacturing. As they become thinner due to the removal of material, they lose stability and give way to the pressure of the processing tools, which leads to undesirable changes in the surface geometry. Also in this context, procedures had to be found that counteract the instability mentioned.

method which avoids the problems mentioned under 1. and 2. above can, and device for carrying out the methods are known per se.

So z. B. in the DE 40 03 002 A1 a method for the production of spectacle lenses described in which the lenses are blocked before processing. By this one understands the Be consolidation of the cast or pressed plastic blank on a so-called block piece using Woodchem metal.

The block piece is designed so that it on the one hand easily on the workpiece spindles the processing machines can be attached and on the other hand Has structures to which the Woodche metal adheres well.

Preferably Plastic blanks are used, one side (preferably the convex front) during of the casting or pressing process is already completed. That is the surface geometry and the surface quality already meets the final one Requirements and are not changed anymore. The surface geometry is usually bifocal with sliding transitions (progressive) executed. This side is blocked so that the concave back (Raw state) and the scope can be edited.

make the surface geometry is corresponding Specification, with simultaneous thickness optimization. Since the blank already has a finished page that does not need to be edited, just a single Block process. After blocking, the lens may be attached to the workpiece spindle be clamped the processing machine. Through the connection with the Woodchen metal (supporting action) is also given the required mechanical stability for the subsequent machining operations.

The procedure according to the mentioned prior art method is then as follows:
The semi-finished plastic blank is coated on the already finished page with a protective varnish and then brought into connection with the block piece. In this case, the axis position of the already finished lens surface (eg bifocal) must be aligned very precisely with the axis position (angle of rotation) of the block piece.

This is important so later the surface geometries match the lens front and back sides. The space between the two parts (plastic blank and Block pieces) is then poured out with Woodchem metal. The metal connects it is with the protective coating, so that a firm adhesion arises.

Of the Plastic blank is made by means of the block piece on the workpiece spindle attached to a machine tool and the desired surface geometry on the previously rough surface the second lens side (usually concave lens backside) mill or turning produced. Here also the edge is processed and the thickness is optimized.

Further mechanical machining operations like fine grinding by means of forming tools (with grinding pad) on fine grinding machines and polishing also by means of molds (with polishing foil) on Close polishing machines on.

It follows the blocking in hot Water and removing the protective varnish.

The lenses are then coated with a so-called coating layer, which is for improvement the optical properties (eg anti-reflection) and the scratch resistance serves.

in this connection have to the lenses be placed on masks whose neckline is approximately the outer circumference the glasses equivalent.

In order to prevents the coating material supplied from above during the coating process on the lenses passed down and create unwanted impurities.

Because of the adaptation of the masks to the outer contour of the lenses has to be a big one Stock kept on masks. This results in considerable Costs.

The final Edging and adjustment to the eyeglass frame is then later by Eyewear optician performed.

• – Das Aufblocken mit Woodschem-Metall ist ein aufwändiger, teurer Arbeitsschritt und eignet sich nur bedingt für automatische Fertigungsverfahren.
• – Das Woodsche-Metall enthält gesundheitsschädliche Bestandteile (z. B. 12,5 % Cadmium) und ist daher nur unter Einhaltung besonderer Schutzmaßnahmen zu verarbeiten.
• – Beim Auf- und Abblocken gehen ca. 10 % des Metalls verloren. Bei einer jährlichen Fertigungsmenge von weltweit einigen 100 Millionen Brillengläsern stellt dies nicht nur einen erheblichen Kostenfaktor dar, sondern ist auch ein großes Umweltproblem.
• – Das Vorhalten der vielen unterschiedlichen Masken für das Coating verursacht hohe Kosten.

The method described above, as in DE 40 03 002 A1 has a number of significant disadvantages:

• - The blocking with Woodschem metal is a complex, expensive operation and is only partially suitable for automated manufacturing processes.
• - The Woodsche metal contains harmful components (eg 12.5% cadmium) and must therefore only be processed in compliance with special protective measures.
• - When blocking and blocking, about 10% of the metal is lost. With an annual production of some 100 million spectacle lenses worldwide, this not only represents a significant cost factor, but is also a major environmental problem.
• - The provision of the many different masks for the coating causes high costs.

Another method is used in the DE 100 36 158 C1 proposed, which works without blocking, but provides that the lenses must be cut in the course of processing and welded together again.

Again, there are the same problems associated with thickness optimization as previously described (the lens must be tensioned and mechanically stabilized). Plastic blanks are used in the form of round, flat disks whose diameter is significantly greater than that of the spectacle lenses to be produced. The plastic blanks are either completely raw or roughly preformed. Basically, semi-finished plastic blanks could be used, but this increases the inventory.

If These disadvantages should be avoided, so have both sides of the lens to be edited.

Since blocking is avoided here, the following production sequence is provided:
The plastic blank is stretched at its edge and first processed the convex front of the lens. This page is chosen because it can be easily reached by the tools used because of its convex shape.

To the mechanical processing of the front is followed by polishing and the coating of the finished surface with protective varnish. At the half-finished lens then the back to be edited. If so, using thickness optimization done so would because of the contact angle between the front and back of the outer, yet circular edge of the half-finished lens from the tool trimmed before the desired edge thickness on the outer contour of the spectacle lens would be achieved. This step is therefore not possible because the lens his Clamping edge and lose its mechanical strength.

Out For this reason, it is provided, the half-finished spectacle glass along its final outer contour Cut out (circumference) from the edge area, using a laser shall be.

To an axial displacement of the half-finished spectacle lens relative to the left outer ring of the plastic blank by a few millimeters, it will be in this position with the outer ring re-welded by laser.

There the half-finished lens projected clearly beyond the outer ring, it can be used to create the second side (concave back) be machined without the outer ring thereby cut becomes. The half-finished spectacle lens remains so with it tension on the outer circumference and is through the outer ring mechanically stabilized.

The Eyeglass lenses finished on both sides are subsequently used Coating layers coated, the outer ring the mentioned mask replaced to prevent contamination.

The finished spectacle lens is then, also by laser, in the field the weld from the outer ring cut out and made ready for despatch.

• – Das Ausschneiden der halbfertigen Linse aus dem äußeren Rand mit axialem Verschieben und anschließendem Verschweißen der beiden Teile, erfordert eine aufwändige Spezialmaschine mit Lasereinrichtungen, die entsprechend teuer ist. Das Fertigungsverfahren wird durch die zusätzlichen Arbeitsschritte auf der Spezialmaschine erheblich verteuert.
• – Das zweimalige Ausschneiden und das Verschweißen der beiden Teile mittels Laser führt zu erheblichen, bleibenden Wärmespannungen in den fertigen Linsen. Viele der benutzten Kunststoffe sind jedoch sehr anfällig gegen solche Wärmespannungen und reagieren nach einiger Zeit mit Rissbildung im Randbereich. Dies ist jedoch nicht akzeptabel und stellt einen erheblichen Nachteil des Verfahrens dar.
• – Das zweimalige Ausschneiden und das Verschweißen der beiden Teile mittels Laser führt zu erheblichen, bleibenden Wärmespannungen in den fertigen Linsen. Viele der benutzten Kunststoffe sind jedoch sehr anfällig gegen solche Wärmespannungen und reagieren nach einiger Zeit mit Rissbildung im Randbereich. Dies ist jedoch nicht akzeptabel und stellt einen erheblichen Nachteil des Verfahrens dar.

Although that in the DE 100 36 158 C1 described method some disadvantages of the in DE 40 03 002 A1 does not have the proposed method, however, there are other disadvantages:

• - The cutting of the semi-finished lens from the outer edge with axial displacement and subsequent welding of the two parts, requires a complex special machine with laser devices, which is correspondingly expensive. The manufacturing process is considerably more expensive due to the additional work steps on the special machine.
• - The two-time cutting and welding of the two parts by laser leads to significant, lasting thermal stresses in the finished lenses. However, many of the plastics used are very susceptible to such thermal stresses and, after some time, react with marginal cracking. However, this is unacceptable and represents a significant disadvantage of the method.
• - The two-time cutting and welding of the two parts by laser leads to significant, lasting thermal stresses in the finished lenses. However, many of the plastics used are very susceptible to such thermal stresses and, after some time, react with marginal cracking. However, this is unacceptable and represents a significant disadvantage of the method.

The Cut out the semi-finished lens with mechanical tools (to avoid thermal stress) can not, because the gap would be too big and not the lens with the outer ring could fit more accurately.

In another, under the file number DE 103 10 561.1 proposed methods are also used as starting material for the glasses to be produced plastic blanks, which have the shape of flat, round discs. The shape of the two surfaces (front and back) is arbitrary. The diameter of the plastic blanks is selected 5 to 7 mm larger than is usual in other methods.

at The plastic blanks used can be blanks where both sides are unprocessed or it will be semi-finished parts used in which a page already has optical quality.

The The basic principle of this method is that the plastic blanks while All processing steps on the outer circumference be tense and the exciting process is conducted, that a ring-shaped Area on the outer circumference is maintained, whose thickness is approximately that of the plastic blank equivalent.

First if all operations (Milling, Turning, fine grinding, if necessary polishing, marking and coating) finished are, the actual lens from the outer, annular area separated. This can be z. B. done mechanically by means of milling cutters. It can however, other methods such as e.g. a waterjet can be used.

These Type of production of spectacle lenses is possible, because the plastic blanks have a slightly larger diameter than otherwise usual and also Manufacturing devices are used, with which the desired geometry on the surface of the spectacle lens without having the annular one Area on the outer circumference of the workpiece is cut.

Thereby, that on the outer circumference of the workpiece said annular Range in approximate full thickness of the plastic blank is preserved during the entire machining suitable clamping surfaces available. In addition, can the workpiece on the annular Area are filed.

The Presence of these clamping or storage surfaces in ever more uniform Size and shape is for all further processing and transport processes an advantage since the tools and devices are standardized (standardized) can be.

Of the annular Area is because of its large Thickness and also very stable due to its circular ring shape and therefore able to be stuck in his inner realm with him to support connected spectacle lenses. This one gets thereby the mechanical stability, which for further processing is required. This naturally applies in particular for the Edge region of the spectacle lens.

If required, are used to identify the optical axes the annular Area markings attached, showing the shape of flats, Notches or millings (Indexing).

The mechanical machining to produce the desired surface geometry takes place on special milling / turning machines. With these machines will be first rough processing of one or both lens pages for production the surface geometry by milling carried out, to which the finishing of the surface by means of a turning process followed.

To the production of the predetermined surface geometry by means of the aforementioned Machining process is carried out on subsequent machines the Feinstschleifen and polishing, followed by the coating. The workpiece is clamped at all operations again at the outer, annular area.

The workpiece will follow for separating spectacle lens and annular area on a milling machine by means of the annular Spanned area and with a suitable cutter (eg small end miller Diameter) the spectacle lens is separated from the annular area.

adversely in the method described here it is that the annular area produced by mechanical processing and usually about the same Height has like the lens center at the convex lens front.

By this supernatant of the annular area at the convex lens front side further processing is through Fine grinding or polishing especially in the edge area difficult because the tool with the annular Area may collide or not beyond the edge of the workpiece may be moved.

One Further disadvantages is that for producing the annular region relatively much material has to be cut on the front of the lens. this leads to to higher Material costs and a little longer Processing times during milling the front of the lens.

At another, under the file number DE 103 15 008.0 proposed method, semi-finished parts are used as starting material for the spectacle lenses to be produced, which are preferably produced by means of chipless shaping method of plastic.

The concave lens back already has optical quality, with the non-cutting shaping process will be produced. New in these material-optimized semi-finished parts is that they are in the edge area of the concave lens back (with optically effective area) have a mold edge, which in the manufacture of the semi-finished part is formed by means of non-cutting shaping process with.

Of the Form edge has, based on the concave lens back, a clear supernatant and is used in the following processing steps to tension the workpiece used.

There the mold edge on the concave back of the semi-finished part located and thus clamped in the various processing machines is, the front of the lens can be edited freely.

Of the Form edge is retained in all processing steps and serves for depositing and clamping the workpiece. Due to its width, height and ring shape he is very stable and supports in all processing steps, the resulting in its interior and the lens connected to it.

There the workpiece keeps the mold edge to the last operation, all clamping tools can be standardized can and the workpiece can tensioned and processed without blocking. A deformation of the lens part by the cutting forces takes place because of the support function the form edge does not take place.

adversely In this method, the convex lens front is mechanical must be edited. Because here are complicated surface geometries (bifocal surfaces, progressive surfaces) have to be generated This processing can only be done with complex and therefore expensive CNC machines carried out become. Added to the tooling costs for these machines.

at many manufacturers of eyeglass lenses (especially in countries the third world) are such machines and the associated tools but not available. There is therefore a need for methods the without consuming Technology and still offer the benefits of this process.

Of the The invention described below was based on the object To find a method by which the production costs of the produced lenses lower.

These Task is solved according to the invention, with a method and a device of the type mentioned, according to the characterizing features of claim 1 and 16. Advantageous Embodiments result from the features of the subclaims.

The method proposed here corresponds essentially to the method with the file number DE 103 15 008.0 , but avoids its disadvantages. These consist of the fact that complex machines (eg CNC machines) are required and that the tools available at the manufacturers can for the most part no longer be used. Above all in third world countries, processes are needed that can be produced without complex technology.

at the method according to the invention are used as blanks semi-finished parts by means of chipless Shaping process are generated. Preference is given to semi-finished parts made of plastic, in a casting or injection molding process getting produced. However, there are also pressing methods and semi-finished parts made of mineral glass.

The convex lens front already has this optical quality, with the non-cutting shaping process is produced. This front has a spherical or aspherical surface with diopter jumps from Z. B. ¼ dpt. However, they are basically also other surface forms possible. Also bifocal surfaces and progressive surfaces are provided.

New with these material-optimized semi-finished parts is that they are in the Border area of the convex lens front side (with optically more effective Surface) have a mold edge, which in the manufacture of the semi-finished part is formed by means of non-cutting shaping process with.

Of the Form edge has, based on the convex lens front side, a clear supernatant. This form edge is used in the following processing steps for Clamping the workpiece (Semi-finished part) in the clamping tools of the processing machines and stabilizes the resulting lens in the edge area as he remains until the last processing step.

There in the method according to the invention the mold edge is located at the convex front of the semi-finished part and this is thus tightened in the various processing machines, can the lens back be edited freely, without a disturbing edge is present. This is a significant advantage.

It Costs can be, in particular, the finest grinding and polishing save as effective tools can be used. Besides, because of the unobstructed accessibility the lens surface Polishing produces a good surface quality become.

The supernumerary Form edge on the convex lens front side does not bother, because there is no editing More takes place, because the optical quality of the surface is already produced there during the non-cutting shaping of the semi-finished part. There are plans for this prefers casting and injection molding as well Pressing process.

For reasons of linguistic simplification, only semi-finished parts made of plastic, which are produced by means of casting or injection molding, will be discussed below. Meant however, all other methods for chipless shaping are also always suitable, as far as they are suitable (eg pressing method) and also semi-finished parts made of mineral glass.

at The non-cutting shaping can the concave back of the semi-finished part the lens geometry to be generated are already roughly adjusted. This results in a material savings and less machining costs. However, this increases the number of semi-finished parts to be kept and thus also the storage costs.

Of the Form edge is retained in all processing steps and serves for depositing and clamping the workpiece. Due to its width, height and ring shape he is very stable and supports in all processing steps, the resulting in its interior and the lens connected to it.

There the workpiece the form edge retains until the last operation, there is the great advantage that all clamping tools can be standardized (unified) and the workpiece without blocking or consuming Laser treatment can be stretched and processed. A deformation of the lens part by the cutting forces takes place because of the support function the form edge does not take place.

At the mold edge is, if necessary, also a cast Recess (marking), with which the axis of the casting process finished lens front side is defined. For manufacturing of plastic semi-finished parts are preferred glass molds (glass molds) used according to the invention designed in this way are that a simple demolding is possible. For the production of semi-finished parts made of mineral glass, steel molds are used.

The used machines and tools correspond to the state of the art. CNC-controlled machines and the corresponding special tools are not needed. It can Rather, all machines and tools that are used continue to be used in connection with the usual Blocking processes were used and available from manufacturers are.

Also those with manufacturers in connection with the blocking process introduced Recipes and machine settings for processing the concave Lens back can continue to be used. Since the workpieces are stretched on the edge of the mold be omitted but in any case the expensive and environmentally harmful blocking.

to execution the method according to the invention become with the manufacturers of the spectacle glasses or with their Unterlieferanten only the new casting tools needed for the production of semi-finished parts. These can be on the existing casting machines to be used.

The casting tool consists of a back mold and a front mold and a sealing ring on the perimeter, both halves of the mold connects with each other. New in this casting tool is the design of the Front shape, which is not, as usual from a simple, arched inwards Disc exists, but has a paragraph in the edge region, with the said mold edge is formed on the semi-finished part.

This Paragraph is preferably carried out with a slope, which facilitates the molding. in the Area of this slope can also be a "nose" exist with which the above-mentioned mark is produced.

The surface the back mold can be flat or the back of the lens to be produced coarse, but without creating an optically effective surface can be.

The during the casting process effective surface of the Front shape is designed to give the required surface geometries can generate. The surface of the front surface of the lens produced by the casting process is optically effective and in the usual execution with spherical or aspherical or toric or atoric geometry z. b. graded in 0.25 dpt. This by pouring The lens front side produced may also have bifocal surfaces or progressive surfaces. The further adaptation of the lens to be produced to the prescription takes place by a corresponding processing of the lens back.

The procedure is then as follows:
On known production facilities, the semi-finished parts are produced by means of the novel casting tool. These are preferably made of plastic, but it can also be semi-finished parts made of mineral glass.

The Semi-finished parts then become more conventional in the workpiece holders Machine tools tightened by means of their edge form and the concave back by means of these machines by milling, turning, grinding, superfinishing and polished.

Although complicated multi-axis CNC machines can be used, but are not prerequisite for carrying out the method according to the invention, since only relatively simple geometries must be produced, such. As spherical or aspherical or toric or atoric surfaces without bifocal surface elements. The compli A more complex geometry with bifocal surfaces or progressive surfaces is in this case on the convex lens front side, which was produced by chipless forming processes.

If the lens to be produced is a spectacle lens, so at the first stages of this mechanical machining becomes a Thickness optimization of the lens performed.

The is called, the spectacle frame is known and the lens is with respect to his Thickness matched to this version. Spectacle lenses thicker in the middle as are on the edge (plus glasses), are processed so that they only have one thickness in the later version which corresponds approximately to the edge of the socket. Eyeglass lenses, the thinner in the middle as are on the edge (minus glasses), are machined so that the middle with regard to their strength so thin as possible is designed. This produces lenses that are the least possible Identify weight.

The Geometry of the concave lens back is designed in the manufacture of eyeglass lenses that they in combination with the available convex lens front the desired optical Results according to the recipe that the production too Reason lies.

At the mechanical machining operations close the coating and the Mark the optical axis. The form edge remains with all mentioned operations obtained and used for clamping or placing the workpiece in the different machines and standardized devices.

First after the coating and the marking becomes the actual spectacle lens separated from the mold edge. For this purpose, the workpiece with its shape edge on the workpiece spindle a milling machine strained and the inner contour of the spectacle lens by means of a small end miller Diameter cut out. For however, other methods are provided for this cutting. Thus, e.g. a waterjet can be used.

The inventive method and the apparatus for carrying out the method will be described below by way of example and the 1a u. 1b , such as 2a u. 2 B explained in more detail. However, other embodiments are provided.

1a shows the casting tool in a sectional view.

1b shows the front shape in a sectional view and in plan view.

2a shows the semi-finished part before machining in a sectional view, clamped in a workpiece holder.

2 B shows the workpiece after processing the concave lens back in section and in plan view.

To 1a Casting tool ( 13 ) in section: and
To 1b Front shape ( 14 ) in sectional view and in plan view:
The casting tool shown here ( 13 ) consists of a front form ( 14 ), a sealing ring ( 15 ) and a back form ( 16 ). The mentioned 3 components close an inner cavity ( 17 ) into which the liquid mass for producing the semi-finished part ( 1 ) is poured.

These Mass can be one for optical purposes suitable liquid Be plastic, then cures. Provided, however, mineral glasses, by heat be melted and then shed as well.

The in the semi-finished part ( 1 ) facing mold surface ( 18 ) of the front form ( 14 ) is provided with a very finely polished surface, which is a negative impression of the convex lens front side ( 5 ). So that the number of required front shapes ( 14 ) remains small for cost savings, diopter jumps of 0.25 or greater are provided.

The optical effect of the finished spectacle lens ( 7 ), according to the recipe to be carried out, by the interaction of the convex lens front side ( 5 ) and the machined, concave lens backside ( 6 ) reached.

The concave lens back ( 6 ) is calculated and processed accordingly.

The semi-finished part ( 1 ) facing mold surface ( 19 ) of the posterior form ( 16 ) does not produce an optically effective surface. It is slightly concave in the illustrated case, so that in the subsequent operations Zerspanungsaufwand is saved. The molding surface ( 19 ) can also be flat.

The molding surface ( 18 ) of the front form ( 14 ) is according to the invention with a paragraph ( 20 ), which is used for molding the mold edge ( 3 ) on the semi-finished part ( 1 ) serves. This paragraph ( 20 ) has an oblique annular surface ( 21 ), with which the shaping is relieved.

This paragraph ( 20 ) on the front form ( 14 ) is new. He has not been described in the hitherto known methods and apparatus for producing raw or semi-finished parts by means of casting or injection molding in connection with the lens production.

It is also particularly advantageous that this paragraph ( 20 ) on the numerous, already existing in the production, front forms ( 14 ) can be added later. This saves considerable costs.

In the area of the ring surface ( 21 ) is also a nose ( 22 ) for molding the marking ( 4 ) on the semi-finished part ( 1 ). This nose ( 22 ) is therefore very exactly along the axis of the molding surface ( 18 ).

For connecting the front form ( 14 ) and the Hinterform ( 16 ) is a sealing ring ( 15 ) provided on its inside via a bevel ( 23 ). This bevel ( 23 ) also serves to facilitate shaping of the semi-finished part ( 1 ) from the casting tool ( 13 ).

By varying the height (dimension in the axial direction) of the sealing ring ( 15 ), the thickness of the semi-finished part ( 1 ) are selected so that in the thickness optimization of the spectacle lens ( 7 ) only a minimal machining effort arises.

For the production of semi-finished parts ( 1 ) are preferably made of plastic casting tools ( 13 ), in which the front shape ( 14 ) and the back form ( 16 ) consist of mineral glass. This has the advantage that glass can be processed on the known optical machines (lens processing) with the highest precision and is also easy to polish.

Another advantage is the corrosion resistance of glass, which is the storage of the casting tools ( 13 ) much easier. Also the molding of the semi-finished part ( 1 ) from the casting tool ( 13 ) is particularly easy if the front shape ( 14 ) and the back form ( 16 ) consist of mineral glass, since the plastics do not adhere firmly to the mineral glass.

The casting tool ( 13 ) is used for the actual casting process in a corresponding device or machine, where the casting takes place.

Such Devices and machines are state of the art and therefore become not shown and described.

After hardening of the semi-finished part ( 1 ) is the shaping by pulling the front shape ( 14 ) and the Hinterform ( 16 ), as well as by stripping the sealing ring ( 15 ). Subsequently, the machining can take place, wherein the edge of the mold ( 3 ) for clamping the workpiece ( 9 ) in the various processing machines.

To 2a Semi-finished part ( 1 ) before processing in a sectional view, in a workpiece holder ( 24 ) clamped:
At the semi-finished part ( 1 ) is the convex lens front side ( 5 ) produced by the casting process already in optically effective quality. A processing on this convex lens front side ( 5 ) does not take place. In the edge area of the semi-finished part ( 1 ) is a form edge ( 3 ), which was cast with and over the convex lens front side ( 5 protrudes). This shape border ( 3 ) remains throughout the subsequent processing and is used to clamp the workpiece in a workpiece holder ( 24 ).

The form edge ( 3 ) is annular and has on its inner or outer side via an inner bevel ( 11 ) or an outer bevel ( 12 ). These chamfers serve the easier formation of the semi-finished part ( 1 ) after pouring.

At the right side of the form edge ( 3 ) is a cast-on mark ( 4 ) used to identify the axis of the optically active lens front side ( 5 ) serves.

The slightly concave back ( 2 ) of the semi-finished part ( 1 ) has no optical properties and needs to be edited. For this purpose, the semi-finished part ( 1 ) in the workpiece holder ( 24 ) clamped a known processing machine.

For clamping the form edge ( 3 ), which is sufficiently high, so that the concave back ( 2 ) of the semi-finished part ( 1 ) far enough above the workpiece holder ( 24 protrudes). This allows the concave back ( 2 ) can also be machined on its edge area, without the machining tool being connected to the workpiece holder ( 24 ) collides The processing machine with the various tools and also the processing method will not be further described, since they are already known.

To 2 B Workpiece ( 9 ) after processing the concave lens backside ( 6 ) in sectional view and in plan view:
The concave lens back ( 6 ) is finished and has received its optically effective surface. Both lens sides are finer by subsequent coating and marking the optical axis Engravings completed.

As part of the production, thickness optimization was also carried out. The actual spectacle lens ( 7 ) is located in the interior of the workpiece ( 9 ) and is defined by the geometric boundary line ( 8th ) from the edge area ( 10 ). To the edge area ( 10 ) also belongs to the form edge ( 3 ).

The boundary line ( 8th ) marks in plan view the outline of the finished spectacle lens, possibly with a small machining allowance for the optician. Because the spectacle lens ( 7 ) in the illustrated example thicker in the middle than at the edge (plus glass), was in the context of thickness optimization of the edge of the lens ( 7 ) along the boundary line ( 8th ) processed until it was about the width of the spectacle frame.

As the last operation, after the coating and marking of the axis, the spectacle lens ( 7 ) then from the workpiece ( 9 ) separated. For this purpose, the machining tool (eg thin end mill) along the boundary line ( 8th ) and the spectacle lens ( 7 ) cut out by it. The processing is done in such a way that the outline of the boundary line ( 8th ) preserved.

It is also envisaged that the workpiece ( 9 ), as in 2 B shown is delivered to the optician who is the edge area ( 10 ) and the contour along the boundary line ( 8th ) produces itself.

1

Semi-finished part

2

concave back

3

shaped rim

4

mark

5

convex Front of the lens

6

concave Lens back

7

lens

8th

boundary line

9

workpiece

10

border area

11

inner bevel

12

outer bevel

13

casting tool

14

front form

15

seal

16

background form

17

internal cavity

18

form surface

19

form surface

20

paragraph

21

ring surface

22

nose

23

bevel

24

Workpiece holder

Claims (22)

Process for the production of spectacle lenses and other optical moldings, using semi-finished parts, which are produced by chipless forming processes such as casting, injection molding or pressing by means of casting tools or pressing tools, followed by mechanical production steps such as milling, turning, grinding and polishing characterized in that semi-finished parts ( 1 ) are produced by means of chipless shaping method and thereby the convex lens front side ( 5 ) as optically effective surface and a form edge ( 3 ) and then that the semi-finished parts ( 1 ) by means of its shape edge ( 3 ) are clamped in processing machines and there the desired surface geometry and quality of the concave lens backside ( 6 ) are produced by machining and superfine grinding and possibly by polishing, wherein the edge of the mold ( 3 ) and during all further processing and transport operations for clamping or depositing the workpiece ( 9 ) and also the actual spectacle lens ( 7 ) or the shaped body for further processing and mechanically stabilized and that the spectacle lens ( 7 ) or the shaped body at the end of the processing of the edge region ( 10 ) with associated form edge ( 3 ) are separated. A method according to claim 1, characterized in that in the manufacture of spectacle lenses ( 7 ) the concave lens back ( 6 ) receives a visually effective geometry by the mechanical processing, which coincides with that of the convex lens front side ( 5 ) supplemented so that the spectacle lens ( 7 ) has an optical effect that corresponds to the prescribed recipe. A method according to claim 1 and 2, characterized in that on the semi-finished part ( 1 ) a mark ( 4 ) by means of non-cutting shaping processes in the region of the mold edge ( 3 ), which shows the axis position of the surface geometry at the optically effective, convex lens front side (FIG. 5 ). A method according to claim 1 to 3, characterized in that in the non-cutting production of the geometry on the convex lens front side ( 5 ) a superposition of different curves or geometries is performed and in particular spherical or aspheric or toric or atorische shapes are optionally superimposed with bifocal surfaces or progressive lenses. A method according to claim 1 to 4, characterized in that during clamping of the semi-finished part ( 1 ) in the processing machines the position of the mark ( 4 ) is taken into account. A method according to claim 1 to 5, characterized in that on the surfaces of the spectacle lens ( 7 ) or of the shaped body, a coating is applied before it is removed from the edge area ( 10 ) with associated form edge ( 3 ) are separated. A method according to claim 1 to 6, characterized in that on the surface of the spectacle lens ( 7 ) very fine engravings for marking the optical axis are attached before the spectacle lens ( 7 ) from the edge area ( 10 ) with associated form edge ( 3 ) is separated. A method according to claim 1 to 7, characterized in that the semi-finished part ( 1 ) is made slightly larger in diameter than the diameter of the actual spectacle lens ( 7 ) would require. A method according to claim 1 to 8, characterized in that the semi-finished part ( 1 ) consists of plastic. A method according to claim 1 to 8, characterized in that the semi-finished part ( 1 ) consists of mineral glass. A method according to claim 1 to 10, characterized in that in producing the concave lens backside ( 6 ), a thickness optimization is carried out by means of mechanical processing methods. A method according to claim 1 to 11, characterized in that for separating the actual spectacle lens ( 7 ) from the edge area ( 10 ) with associated form edge ( 3 ) a mechanical tool is used. A method according to claim 1 to 12, characterized in that for separating the actual spectacle lens ( 7 ) from the edge area ( 10 ) with associated form edge ( 3 ) a small diameter end mill is used. A method according to claim 1 to 11, characterized in that for separating the actual spectacle lens ( 7 ) from the edge area ( 10 ) with associated form edge ( 3 ) a waterjet is used. A method according to claim 1 to 14, characterized in that the actual spectacle lens ( 7 ) when separating from the edge area ( 10 ) with associated form edge ( 3 ) receives an outer contour which is adapted to the intended spectacle frame. Device for carrying out the method according to claim 1, comprising a casting tool which is composed of a front mold, a back mold and a sealing ring, wherein said three parts are releasably and sealingly connected to each other, characterized in that the front mold ( 14 ) via a paragraph ( 20 ) and that the front shape ( 14 ) a molding surface ( 18 ), can be produced with the optically effective surfaces and that the Hinterform ( 16 ) a molding surface ( 19 ), with which no optically effective surfaces can be produced. Apparatus according to claim 16, characterized in that in the area of the paragraph ( 20 ) a nose ( 22 ), which correspond to the geometric axis of the molding surface ( 18 ) on the front form ( 14 ) is aligned with great precision. Device according to claim 16 and 17, characterized in that the shoulder ( 20 ) an oblique annular surface ( 21 ) having. Apparatus according to claim 16 to 18, characterized in that the sealing ring ( 15 ) on its inside a bevel ( 23 ) having. Device according to claims 16 to 19, characterized in that between the front form ( 14 ), the posterior form ( 16 ) as well as the sealing ring ( 15 ) an inner cavity ( 17 ) is available. Apparatus according to claim 16 to 20, characterized in that the front form ( 14 ) and the back form ( 16 ) consist of mineral glass. Apparatus according to claim 16 to 20, characterized in that the front form ( 14 ) and the back form ( 16 ) consist of steel.