EP3206837A1 - Polishing disc for a tool for finely machining optically active surfaces on spectacle lenses - Google Patents

Abstract

The invention relates to a polishing disc (10) for a tool (12) for finely machining optically active surfaces on spectacle lenses, having a main part (14) which has a central axis (M) and to which an intermediate layer (16) that is softer than the main part and is made of an elastic material is secured, a polishing means support (18) resting on said intermediate layer. The intermediate layer has at least two regions (20, 22) with different degrees of hardness, said regions being arranged one behind the other in the direction of the central axis of the main part. The intermediate layer region adjoining the main part is softer than the intermediate layer region on which the polishing means support rests. The simply constructed polishing disc can cover a large enough range of spectacle lens curvatures so as to allow a high prescription productivity.

Description

 POLISHING MACHINE FOR A TOOL FOR FINISHING OPTICALLY EFFECTIVE SURFACES ON GLASS GLASSES

TECHNICAL AREA

The present invention relates to a polishing plate for a tool for fine machining of optically effective surfaces on workpieces, according to the preamble of claim 1. Such polishing plates are used in particular in the production of prescription eyeglass lenses in bulk.

When we talk about "spectacle lenses" below, not only spectacle lenses made of mineral glass, but also

Eyeglass lenses from all other common materials, such as polycarbonate, CR 39, HI index, etc., so also plastic are understood.

STATE OF THE ART

The machining of the optically effective surfaces of spectacle lenses can be roughly subdivided into two processing phases, namely first the pre-processing of the optically effective surface to produce the macrographic recipe and then the fine machining of the optically effective surface to eliminate pre-processing traces and the desired micro-geometry To maintain form loyalty. While the pre-processing of the optically effective surfaces of spectacle lenses u.a. Depending on the material of the lenses by grinding, milling and / or turning done, the optically effective surfaces of spectacle lenses are usually subjected to a fine grinding, lapping and / or polishing during the finishing.

For this finishing operation in the prior art (see, for example, the publications DE 10 2005 010 583 AI, EP 2 464 493 Bl or the preamble of claim 1 forming document EP 2 014 412 AI) increases adaptive - in contrast to rigid, form-matched tools - used polishing plate. These polishing plates have a substantially three-part or -lagigen structure, with (1) one of the tool spindle facing, in solid or rigid carrier or base body, on the (2.) a softer contrast

Layer of elastic material, e.g. a foam layer is attached, which (3.) rests a grinding or polishing film (polishing medium carrier) facing the workpiece as a processing-active tool component. Due to the elastic deformability of the foam layer, the polishing film can be adjusted within certain limits in situ to the geometry of the surface to be machined. This in both "static" terms, i. from spectacle lens to spectacle lens, which is to be processed and which differ in their geometry, in particular the surface curvature, as a rule, as well as in "dynamic" terms, i. during the actual processing of a particular spectacle lens, in which a relative movement between the polishing plate and the spectacle lens takes place. The

In addition, the elasticity of the foam layer has a significant influence on the removal behavior of the polishing plate during the polishing process. Now, in the production of prescription lenses to be polished to the most diverse geometries. Macrogeometrically, the radii of curvature of the optically effective surfaces (sphere or cylinder in the case of approximately toric surfaces) of the spectacle lenses range from infinity (flat surface) to approx. 35 mm even in the standard effective range (0 to approx. 14 dioptre). In the case of, for example, free-form surfaces, additional, rather microgeometric, influencing factors, such as addition or asphericity, are added here. In order to cover the standard area of effect, geometry-different types of beater are therefore required in the above prior art. which differ in particular in the (pre) curvature of the machining-active tool surface.

Thus, known polishing tool concepts in the formulation manufacture include e.g. seven geometry-different types of beater. Of course, during the production of spectacle lenses, this necessitates a tool change when successive spectacle lenses are to be machined which differ in their geometry from one another so that they can not be polished with one and the same pole element. Each tool change, however, comes at the expense of productivity in the recipe production.

Also known in the prior art are polishing tool concepts for spectacle lens manufacturing that manage with up to at least three different polishing tool types to cover the standard range of effectiveness. Such polishing tools are e.g. shown in the document US 7,559,829 B2. Here, between a foam layer, on which a polishing foil rests, and a rigid body, via which the polishing tool can be held in or on a tool holder, an elastically resilient support structure is inserted, which has a star-shaped part with a plurality of leaf spring-like acting spring arms and a elastic ring for supporting the spring arms relative to the base body comprises. In this prior art, however, a tool change is also required if successively to be polished lenses vary greatly in geometry from each other. In addition, these polishing tools have a relatively complex structure.

TASK

The invention is based on the object starting from the prior art, as it is represented by the document EP 2 014 412 AI, as simple as possible polished polishing To create a plate for a tool for fine machining of optically effective surfaces of spectacle lenses, which allows an increase in productivity in the production of prescriptions.

PRESENTATION OF THE INVENTION

This object is achieved by the features specified in claim 1. Advantageous or expedient developments of the invention are subject matter of the claims 2 to 15.

According to the invention, in a polishing plate for a tool for fine machining of optically effective surfaces of spectacle lenses, which has a central axis having base body to which a softer relative to the base body intermediate layer of an elastic material is fixed, on which rests a polishing agent, the intermediate layer at least two regions of different hardness, which are arranged one behind the other in the direction of the central axis, wherein the region of the intermediate layer adjacent to the base body is softer than the region of the intermediate layer on which the polishing agent carrier rests.

A key idea here is to provide the necessary to cover the required range of action (eg 0 to 14 diopters) adaptability of the polishing plate to the macrogeometry of the lenses to be polished by the - treatment or remote from intervention - lower hardness of the intermediate layer and thereby also large differences in the cusp of spectacle lens to "bridge" to spectacle lens. The adaptability of the polishing plate to the microgeometry of the lenses to be polished, which is necessary to achieve the required surface fidelity on, for example, free-form surfaces and the desired smoothing, is provided by the area of greater hardness of the intermediate layer, which is close to the machining or engagement. It is hereby accepted that in the polishing processing from spectacle lens to spectacle lens depending on the respective geometry of the spectacle lens, the actual polishing or engagement surface between polishing plate and spectacle lens can change - for example, from almost punctiform with plane spectacle lens surfaces to more (circular or ring) planar with curved spectacle lens surfaces - because this can be compensated in the polishing process in particular by suitable change in the amplitude and / or frequency of the relative movement between the polishing plate and spectacle lens (Oszilla- tionhub of the tool transverse to the workpiece).

As a result, in the ideal case, only one type of polishing pad is needed, but in any case significantly less polishing pad types than in the generic state of the art, in order to cover the usual areas of curvature of the lenses to be polished in the preparation. On the one hand, such a universally applicable polishing plate type reduces the expense associated with having a plurality of geometry-different polishing plates. On the other hand, which is even more important, the tool changes which are customary in the state of the art and are caused by various geometries of the lenses to be polished can ideally be eliminated, or at least significantly reduced. The time savings achieved here lead, even with constant polishing time, to a considerable increase in productivity in the production of prescriptions. Downtime of the polishing machines - even those that were caused by re Werkzeugjustage in the art - are also reduced or eliminated. All this requires according to the invention, moreover, no costly measures or new parts on - so still very simple design - polishing plate; it is only local targeted influence on the properties of the elastic material of the intermediate layer.

With regard to a simple and cost-effective production of the polishing plates, it is preferred if the at least two rich of the intermediate layer by different from each other

Foam layers are formed, namely at least one softer foam layer on the body and at least one harder foam layer under the polish carrier. However, other suitably elastic materials for the intermediate layer are also conceivable, in particular for the harder region of the intermediate layer, which is e.g. could consist of a rubber material. Preferably, the mutually different foam layers are glued together, which only requires a cost-effective, well manageable in mass production process step in which commercially available foam and adhesive materials can be used. Alternatively, a suitable foam composite or sandwich could alternatively be made by foaming different types of foams together.

As far as the shape of the individual foam layers of the intermediate layer before their attachment to the base body is concerned, the individual foam bodies for influencing the elastic properties of the polishing plate may in principle be deviating from a planar surface, for example convex or concave on one or both end faces - as well as on the edge, for example cylindrical, conical, spherical or ring-shaped - for which, however, special casting molds would have to be provided. In this respect, it is particularly preferred for reasons of cost if the various foam layers of the intermediate layer each have a substantially constant thickness, measured along or parallel to the central axis of the base body, which opens up the possibility of producing large quantities of plate-shaped materials in the production of the polishing plates use. Investigations carried out by the present inventors have shown that a specific relation of the thicknesses of both foam layers optimally adapts to a large curvature. mung radius range while maintaining and smoothing the micro-geometries on the lenses to be polished allows. Thus, it has been found that the ratio of the substantially constant thickness of the harder foam layer to the substantially constant thickness of the softer foam layer should preferably be between 1 to 2 and 1 to 4, more preferably about 1 to 3.

The inventors have also carried out practical tests with various foam materials, in which on the one hand it has been checked. the extent to which the geometry of the pre-processed spectacle lens was preserved or changed during polishing; and on the other hand it was investigated with which foamed material the removal of polishing per unit time was as high as possible without significant microstructures or unsoundness on the polished surface. It has been found that, determined in the case of a full-surface compression, the static modulus of elasticity of the harder foam layer is preferably between 0.40 and 1.50 N / mm ² , more preferably between 0.80 and 1.00 N / should be ² mm, while the static elastic modulus of the softer foam layer should preferably be between 0.25 and 0.45 N / mm ² , more preferably between 0.35 and 0.45 N / mm ² . With regard to the foam material of the individual constituents of the intermediate layer, it has also proved to be advantageous in the tests carried out if the softer foam layer consists of an at least partially oxy-porous polyether urethane elastomer, while the harder foam layer consists of a closed-cell polyether urethane elastomer - mer exists. On the one hand, with this combination of materials, there is no danger of the intermediate layer becoming too saturated with the polishing agent during polishing and then becoming excessively hardened during drying; on the other hand, the partial opacity of the intermediate layer is advantageous for the removal evaluate the frictional heat generated during the polishing process on the polishing agent and favors the bonding of the individual layers in the preferred production of the intermediate layer.

In the considerations and investigations carried out by the inventors, the following geometric features for a universally applicable polishing plate for the polishing treatment of spectacle lenses in the curvature range customary today have emerged or proven: Preferably, the main body of the polishing plate should be substantially facing the intermediate layer have spherical end face, on which the intermediate layer attached, is suitably glued, this end face should have a radius of curvature, which is preferably between 35 and 42 mm, more preferably between 36 and 40 mm. Furthermore, the base body in the region of its end face should preferably have a diameter between 35 and 60 mm, wherein the substantially constant thickness of the intermediate layer along or parallel to the central axis measured should preferably be between 15 and 22 mm - expedient with the smaller

Thickness values for the smaller diameters and the larger thickness values for the larger diameters. With regard to the polishing agent carrier, it is furthermore advantageous if, in relation to the central axis of the main body, it protrudes on all sides over the intermediate layer of the polishing plate. This protruding region of the polishing agent carrier can exert no pressure on the spectacle lens during polishing, so that there is no danger that the outer edge of the polishing agent carrier will be imaged on the spectacle lens in the form of microstructures or preferred directions.

The polishing plates according to the invention can advantageously on a tool for fine machining of optically active surfaces Eyeglass lenses are used, comprising an axially and rotationally engageable on a spindle shaft of a tool spindle fastened tool holder head, wherein the polishing plate is replaceably held on the tool holder head, including the base body of the polishing plate and the tool holder head with complementary structures for axial locking and for rotational drive of the polishing plate with the Tool receiving head are provided. This causes on the one hand a simple interchangeability of the polishing plate and a secure hold of the polishing plate on the tool spindle, on the other hand, a defined, positive torque transmission from the tool spindle to the polishing plate during polishing.

Here, the tool holder head may have a ball joint, with a ball socket received in a ball socket, which is formed on a fastened to the spindle shaft of the tool spindle ball pin, while the ball socket is formed in a receiving plate, with which the polishing plate can be locked. This makes it possible in a simple manner to tilt the polishing plate relative to the spindle shaft of the tool spindle during the polishing process so that the polishing plate can easily follow the most varied spectacle lens geometries, even, for example, cylindrical surfaces or progressive surfaces with high additions. In addition, the tiltability of the polishing plate advantageously allows the carrying out of polishing processes with so-called "tangential polishing kinematics", in which the polishing disc, which is in machining engagement with the spectacle lens, which is driven in rotation by means of a workpiece spindle about a workpiece axis of rotation, either rotates by friction taken along or self-rotating, while a linear drive ensures that the angularly defined with respect to the workpiece axis of rotation employed tool spindle is alternately moved back and forth in the polishing machine, so that the polishing plate with a relatively small path continuously across the lens before and strikes back. In a preferred embodiment of the ball head can have a receiving hole for a transverse pin which ^■ extending through the ball head through it and engages on both sides of the ball head with associated recesses in the ball socket to connect the receiving plate can rotate therewith with the ball pin. Such a configuration of the ball head as a universal joint makes it possible in a simple manner to drive the polishing plate in a rotating manner, which, compared with a likewise conceivable, merely friction-induced rotational drive of the polishing plate with the spectacle lens, allows significantly shorter polishing times. With regard to tiltability and rotary drive possibility Although similar could basically be realized by means of a homokinetic joint, but this would be associated with a much greater effort and higher costs.

Furthermore, it is preferred if the receiving plate is resiliently supported by an elastic ring element on a ball pin-side support flange such that the polishing plate latched to the take-up plate endeavors to align with its central axis with the ball pin and thus with the spindle shaft of the tool spindle. As a result, the polishing plate is prevented from excessive tilting movements, which has a favorable effect, in particular during the reversal of motion in the mentioned oscillation of the polishing plate over the spectacle lens, since the polishing plate does not buckle and can jam in consequence on the spectacle lens. On the other hand, such an elastic support of the receiving plate of the tool when mounting or placing the polishing plate is advantageous because the receiving plate here assumes a defined position with slight compulsion by the elastic ring member. The bringing together of polishing plate and spectacle lens can also take place as a result of the elastic (Vor) orientation of the receiving plate so that the polishing plate touches down substantially axially oriented on the lens, and not tilted about what in particu- thick or high-pile polishing plates could lead to problems. In principle, it would also be possible to make such a (pre) orientation of the polishing plate by means of a pneumatically actuated rubber bellows on the receiving plate, but this would be much more complex.

In further pursuit of the inventive concept, the base body of the polishing plate and the tool holder head may be provided with a radially projecting collar, the frets in the mounted on the tool holder head state of the polishing plate face each other and are positively overlapped by means of a locking ring with a substantially U-shaped cross-section , Such a circlip reliably prevents the polishing plate from inadvertently releasing from the tool receiving head when forces occur, e.g. when, during the polishing process, the polishing pad is lifted off the lens (or vice versa) to change the relative tool rotation direction and / or bring fresh polishing agent to the point of intervention, or at the end of the polishing process, always with a at the

Spectacle lens "sucked" polishing plate must be expected. Accordingly, due to the above backup, the polishing plate and the lens can be safely moved apart at any time in the polishing process. Although the problem of unintentional release of the polishing plate from the tool holder head could also be remedied procedurally with a sufficiently wide transverse method of the polishing plate with respect to the spectacle lens before picking up, this procedure would lengthen the process times in an undesired manner.

Finally, the locking ring is preferably formed by two half-rings, which are pivotally connected to one another by means of a hinge and on the other side via a snap connection releasably locked together, which is not only a simple and inexpensive producible This solution is also easy to clean, but also ensures an uncomplicated (because tool-free), easy and quick handling.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be explained in more detail by means of a preferred embodiment with reference to the attached, partially schematic and not to scale drawings. In the drawings show:

Fig. 1 is a longitudinal sectional view of a partially

 broken illustrated yoke of a polishing machine recorded tool spindle with a tool according to the invention for fine machining of optically active surfaces of spectacle lenses, on the tool holder head a polishing plate is releasably held, which is in machining engagement with a surface to be machined, wherein the tool is extended in a relation to the tool spindle , lower position;

Fig. 2 is a half section of the tool spindle with tool according to

 Fig. 1 in the unmounted state, without bellows between the tool and tool spindle, the here for a better view. It has been omitted, wherein the tool is located with the polishing plate in a relation to the tool spindle retracted, upper position in which the Werkzeugaufrtahmekopf the tool is locked to the tool spindle;

Fig. 3 is an aborted sectional view of the at

Tool spindle attached tool of Figure 1 according to the section line III-III in Fig. 2. Fig. 4 is a sectional view of the mounted on the tool spindle shown only partially tool of Figure 1 in the retracted, upper position of FIG. 2, with the. the tool spindle latched tool receiving head and one of them removed polishing plate;

Fig. 5 is an exploded perspective view of the tool shown in FIG. 1, broken away here, obliquely from below, with the tool receiving head, an opened locking ring and the polished ^' ller, to illustrate the interfaces between the tool spindle, tool holder head, retaining ring and polishing plate;

Fig. 6 is a view corresponding to the parts shown in FIG. 5, corresponding perspective exploded view of the opposite shown again broken tool spindle tool of FIG. 1 obliquely from above, with the tool holder head, the locking ring in the closed position and the polishing plate, for further illustration the interfaces between tool spindle, tool holder head, circlip and polishing plate; and

Fig. 7 is a sketch of a spectacle lens and a erfindungsge MAESSEN polishing plate to illustrate the essential geometric data for the dimensioning of a universally applicable polishing plate as a function of spectacle lens curvatures and spectacle lens diameter DETAILED DESCRIPTION OF THE EMBODIMENT

According to particular FIGS. 1 to 6 has a polishing plate 10 for a tool 12 for. Fine machining of optically effective surfaces cc, cx on spectacle lenses L (see FIGS. 1 and 7) has a base body 14 having a central axis M, to which a softer intermediate layer 16 made of an elastic material is fastened relative to the base body 14 a polishing medium carrier 18 rests, the actual, outer processing area 19 of the polishing plate 10 forms. It is essential that the intermediate layer 16 has at least two areas of different hardness, which are arranged one behind the other in the direction of the center axis M, wherein the area of the intermediate layer 16 adjoining the base body 14 is softer than the area of the intermediate layer 16 on which the polishing agent carrier 18 rests , as will be explained in more detail below.

In the exemplary embodiment illustrated here, the two regions of the intermediate layer 16 are formed by mutually different foam layers 20, 22 of constant thickness, namely a softer foam layer 20 on the base body 14, more precisely its end face 21, and a harder foam layer, viewed along the center axis M. 22 under the polish carrier 18. The mutually different foam layers 20 and 22 are glued together at 23.

Similarly, the polish carrier 18 is adhered to the harder foam layer 22 and the softer foam layer 20 on the end face 21 of the body 14. In order to prevent the edge of the polishing plate 10 from forming on the machined surface cc of the spectacle lens L in the form of very fine, scratch-like microstructures, the polishing agent carrier 18 protrudes on all sides, relative to the central axis M, via the intermediate layer 16. The substantially rigid base body 14 serves on the one hand with its preformed end face 21 for shaping and for supporting or supporting the above-described elastic

Layer structure of the polishing plate 10, on the other hand, it forms the connector to the rest of the tool 12, as will be described below. In the illustrated embodiment, the end face 21 of the base body 14 is substantially spherically preformed and bulges virtually the intermediate layer 16 against. The end face of the main body can, however, in principle but also differently, for example in accordance with the macrogeometry of the surfaces cc or cx to be machined, e.g. be aspheric preformed.

As can be seen in Figs. 1 to 6, the tool 12 has a tool holder head 24 with a receiving plate 25 which is axially and rotationally capable - yet releasably - attached to a spindle shaft 26 of a tool spindle 28. On the tool holder head 24 of the polishing plate 10 is held interchangeable, including the main body 14 of the polishing plate 10 and the tool holder head 24, more precisely its receiving plate 25 with complementary structures 29 (see in particular FIGS. 5 and 6) for axial locking and rotational driving of the polishing plate 10th are provided with the tool receiving head 24. The interface formed by the complementary structures 29 between polishing plate 10 and tool holder head 24 is the subject of the above-mentioned document EP 2 464 493 B1, to which reference is first expressly made at this point with regard to structure and function of the interface to avoid repetition. In short, as best seen in FIGS. 4 to 6, the main body 14 of the polishing pad 10 has on its inside a limited by a wall surface 30 and a base 31 interior 32, which for pushing the polishing pad 10 and latching a complementary formed receiving shoulder 33 at the receiving plate 25 of the tool holder head -24 is provided and has at its Grundfläche.31 driver elements 34 for torque transmission, which are assigned corresponding Mitnehmergegenelemente 35 on the receiving shoulder 33. Further, between the wall surface 30 and the receiving shoulder 33 in a

 Ring groove 36 fixed elastic retaining ring 37 is provided, which provides the latching with a corresponding counter-groove 38 and a seal of the interior 32. The latching occurs during the sliding of the polishing plate 10 before the driver elements 34 engage with the Mitnehmergegenelementen 35 ,. the only on further pushing the polishing plate 10 under sealing between the wall surface 30 and the receiving shoulder 33 can be achieved. On the side facing away from the interior 32 side of the receiving plate 25 of the tool holder head 24 has a ball joint 40, with a ball socket 42 received in a ball head 44 which is formed on a screw shaft 26 of the tool spindle 28 fastened, screwed in more detail ball pin 46. The ball socket 42, however, is formed in the receiving plate 25, with which the polishing plate 10 can be latched. Referring in particular to FIGS. 3 and 4, the ball head 44 has a receiving bore 48 for a transverse pin 50. The cross pin 50 extends through the ball head 44 with rounded ends and engages on both sides of the ball head 44 with associated recesses 52 in the ball socket 42 to the receiving plate 25 rotationally engageable with the ball pin 46 and thus with the spindle shaft 26 of the tool spindle 28 connect.

As further best seen in Figs. 3 and 4, between the ball pin 46 and the free end of the spindle ^¬ shaft 26 an annular Abstützflansch 54 is inserted and fixed by means of the ball pin 46 to the spindle shaft 26. On the Abstützflansch 54 is an elastic ring member 56th For example, from a suitable foam over which the receiving plate 25 of the tool holder head 24 on the ball pin side Abstützflansch 54 resiliently supported so that the latched with the receiving plate 25 polishing plate 10 strives to be with its central axis M with the ball pin 46 and so that the spindle shaft 26 of the tool spindle 28 auszufluchten.

Finally, to detachably connect the polishing plate 10 and the tool receiving head 24, according to FIGS. 3, 5 and 6 both the base body 14 of the polishing plate 10 and the tool holder head 24 on the receiving plate 25 are provided with a radially projecting collar 58 or 59 is provided. These collars .58, 59 lie in the mounted on the tool holder head 24 state of the polishing pad 10 opposite each other and are positively overlapped by means of a locking ring 60 having a substantially U-shaped cross-section (see Fig. 3) to unintentional release of the polishing pad 10 from the tool holder head 24 to prevent. The expediently made of a suitable plastic circlip 60 is, as clearly shown in Figs. 3, 5 and 6, formed by two half-rings 62, 63 pivotally connected to one another by means of a hinge 64 and on the other side over a per se known resilient snap connection 66 with undercuts are releasably locked together.

In order to show the possibilities of movement of the tool 12 relative to the lens L to be polished, particular details of the tool spindle 28 and its installation situation in a polishing apparatus are shown in particular in FIGS. These tool spindle 28 as well as the preferred for the use of the tool 12 described herein polishing device are the subject of parallel, ie filed with the same filing date German patent application DE 10 2014 XXX XXX. X, at this point in terms of more detailed construction and the Function of the tool spindle 28 and the polishing device to avoid repetition is expressly made.

Only the following is to be mentioned with regard to the possibilities of movement of the spectacle lens L and the tool 12 to be machined: The tool spindle 28 is arranged opposite in a working space a workpiece spindle 68, indicated by dashed lines in FIG. 1, by means of which the spectacle lens L to be polished is inserted into a a recording of the workpiece spindle 68 held block piece 69 can be driven to rotate about a workpiece axis of rotation C. Also, the spindle shaft 26 of the tool spindle 28 is rotatably driven via an electric servo motor 70 by means of a belt drive 71 about a tool axis of rotation A. The tool spindle 28 further includes a pneumatically actuated piston-cylinder arrangement 72, by means of which the tool 12 can be delivered axially via the spindle shaft 26 along an alignment axis Z aligned with the tool rotation axis A. In this case, the tool 12 can be locked to the tool spindle 28 in a position close to the tool spindle by means of a latching device 74 (compare FIGS. 2 to 4).

The tool spindle 28 itself is flanged with servo motor 70 and belt drive 71 on a pivot yoke 76, which is pivotable about a pivoting adjustment axis B which is substantially perpendicular to the workpiece rotation axis C. In addition, the pivot yoke 76 with tool spindle 28 and its drive along a - in Fig. 1 perpendicular to the plane extending - linear axis X can be moved axially, in the

Aligned substantially perpendicular to both the pivot axis B and the workpiece axis of rotation C.

In that regard, it can be seen that the polishing plate 10 and the lens L rotating - the same or opposite directions, with the same or different speeds - can be driven

(Rotary axes A, C). At the same time, the polishing plate 10 can be used in tion of the lens L are delivered axially (Z delivery axis). Furthermore, the axes of rotation A, C relative to each other angularly preset or dynamically pivoted (pivoting adjusting axis B) and transversely to each other (linear axis X) are. The various polishing processes that can be carried out with this kinematics are well known to the person skilled in the art and will therefore not be described in detail here.

Below will be explained with reference to FIG. 7, how the polishing pad 10 described above can be dimensioned.

In this case, the range of spectacle lens curvatures which it is at the. optically effective surface cc to be polished, with Runax as the maximum radius of curvature on the "thinnest" to be processed lens L and R _Lm in as the minimum radius of curvature at the most "curved" to be processed lens L, and the diameter D _{L of} the polished Spectacle lenses L.

Based on experience of the present inventors, the diameter D _{w of} the polishing plate 10 should be slightly smaller than the diameter

Diameter D _L to be polished lenses L are selected, but not too small. Suitably, the diameter ratio D _W / D _{L should be} in the following range:

Thus, about 50 mm would be a standard diameter D _w for the polishing plate 10. For very small spectacle lens diameters of up to 40 mm - and very strong spectacle lens curvatures - a diameter D _{w of} the polishing plate 10 of about 35 mm would be suitable. For a basically also possible convex-side spectacle lens processing tion, however, a larger diameter Dw of the polishing plate 10 could be provided by about 60 mm.

For the diameter Dw of the polishing plate 10 thus selected, the (smallest) arrow height P _min on the "thinnest" lens L and the (largest) arrow height Ρ _max on the most "curved" lens L can be determined from the following range of spectacle lens curvatures Calculate relationships:

with the (smallest) opening angle <pmin for the selected diameter Dw of the polishing disc 10 on the "thinnest" lens L and the (largest) aperture angle qw for the selected diameter Dw of the polishing pad 10 on the most "curved" lens L from the following formulas :

From the thus obtained arrow heights Pmin and Ρ _max , a mean arrow height P _{m can be determined} : and from this determine a mean radius of curvature Rm of the spectacle lens L, to which the radius of curvature R _{w of} the polishing plate 10 at its working surface 19 on the polishing agent carrier 18 should correspond:

In principle, it would also be possible to still weight the average radius of curvature R _{Lm of} the spectacle lens L and thus the radius of curvature R _{w of} the. Make polishing pad 10 based on statistical frequency of the spectacle lens curvatures, or to determine the radius of curvature of a universally applicable polishing plate alone from a statistical distribution of the spectacle lens curvatures, which depends on the particular mode. At present, the maximum of a - regionally different - statistical distribution is about ± 5 dioptres. If, for example, the current trend towards strongly curved sports glasses continues in the case of prescription spectacles, a "shift" towards more crooked curves, ie a reduction of the radius of curvature R _{w of} the polishing plate 10, could be expedient.

Now, the total thickness S _{s of} the intermediate layer 16 and the individual thicknesses of the foam layers 20, 22 with S _w as the thickness of the softer foam layer 20 and S _H as the thickness of the harder foam layer 22 are respectively along and parallel to the central axis M, as well as the radius of curvature R _{G of} the end face 21 of the main body 14 to calculate, wherein the thickness S _{P of} the - commercial - polish carrier 18 is known. For the thickness calculation, it is assumed that the polishing plate 10 during the polishing process must be able to bridge the mean arrow height P _M while deforming the intermediate layer 16. Here, investigations carried out by the inventors have shown that to achieve reproducible polishing results this "bridging" should take place in the purely elastic deformation area of the foam, the factor 4 being found to be a good value, ie the maximum deformation of the foam should not increase than 25% of the total thickness S _{s of} the intermediate layer 16, ie:

In order to determine the individual thicknesses S _H , S _{w of} the foam layers 20, 22, the inventors carried out further experiments in order to achieve a good compromise between adaptability (primarily macrogeometry) and polishing performance (microgeometry), the following range for the thickness ratio

was found:

with a preferred thickness ratio of about 1 (S _H ) to 3 (S "). Finally, the calculation of the radius of curvature R _{G of} the end face 21 of the main body 14 remains via the following simple subtraction:

For a conventional geometrical range of up to 14 diopters to be polished in the manufacture of spectacle lenses, radii of curvature R _{G of} the end face 21 between 35 and 42 mm were found, with a preferred range between 36 and 40 mm. With tool diameters D _w of 35 to 60 mm, layer thicknesses S _{s were} between 15 and 22 mm.

In the experiments conducted by the inventors, various foam materials were further tested. Here, the hardness or "softness" of the individual foam materials has shown that, determined in the case of a full-surface compression (form factor q = 6), the static modulus of elasticity of the softer foam layer 20 between 0.25 and 0.45 N / mm ² , forward should be between 0.35 and 0.45 N / mm ² , while the static Young's modulus of the harder foam layer 22 should be between 0.40 and 1.50 N / mm ² , preferably between 0.80 and 1.00 N / mm ² should be.

In the tests, by the way, good experiences - also with regard to tool life - were made with foams of polyetherurethane elastomers, in particular with an at least partially open-pore polyetherurethane elastomer foam for the softer foam layer 20, as used, for example, by Getzner Werkstoffe GmbH, Bürs, Austria, under the trade name "Sylomer ^® SR28" or "Sylomer ^® SR42" is commercially available, and a closed-cell polyether urethane elastomer foam for the harder foam layer 22, as he, for example, from Getzner under the trade designation "Sylodyn ^® NC" is to be referred.

The polishing agent carrier 18 which forms the processing-active tool component, also called "polishing film" or "polishing pad", can be a commercially available, elastic and abrasion-resistant fine grinding or polishing agent carrier, such as, for example, a PUR (polyurethane) film containing a Thickness of 0.5 to 1.4 mm and a hardness between 12 and 45 to Shore D. In this case, the polishing agent carrier 18 is rather thicker if, by means of the polishing plate 10, a pre-polishing is to take place, but rather thinner in the case of a fine polishing. It is also possible to use polishing felts or heat and pressure-treated foams, with or without support material, as polishing agent carrier 18, as are obtainable, for example, from Delamar, Mantes La Jolie, France. In this connection, it should be mentioned that the upper side of the harder foam layer 22 facing the polish carrier 18 can be provided with a final "casting skin" (release layer to the casting mold, not shown) which is produced by production technology, but need not, that of the intermediate layer 16 on the outside gives extra rigidity; if necessary, such a "cast skin" can even form the polish carrier 18 itself.

The base body 14 of the polishing plate 10 is preferably made of a plastic, "35 Terluran ^® GP" injection molded from BASF SE, Ludwigshafen, Germany, such as an ABS (acrylonitrile-butadiene-styrene polymers rol-polymer), for example.

Finally ^{, it} is suitable, for example ^, for the individual components of the polishing plate 10 (base body 14, softer foam layer 20, harder foam layer 22, polish carrier 18) to be fastened to one another ^. a commercial adhesive brand "Pattex ^®" by the company Henkel AG & Co. KGaA, Dusseldorf,

Germany. In particular, however, the polish carrier 18 may also be otherwise more or less permanently bonded to the intermediate layer 16, e.g. by vulcanization or Aufkletten. In any case, the connection between the individual constituents of the polishing plate 10 must be so strong that, at any time during processing, a movement drive, in particular rotational drive, is ensured.

A polishing plate for a tool for fine machining of optically effective surfaces of spectacle lenses has a central body having a base body to which a softer relative to the base body intermediate layer is attached from an elastic material on which a polishing agent carrier rests. The intermediate layer has at least two regions of different hardness, which are arranged one behind the other in the direction of the central axis of the base body. In this case, the area of the intermediate layer adjoining the basic body is softer than the area of the intermediate layer on which the polishing agent carrier rests. The simply constructed polishing plate can thus cover a large range of spectacle lens curvatures, which in particular enables high productivity in recipe production. REFERENCE LIST Polishing plate

Tool

body

interlayer

Polisher carrier

working surface

softer foam layer face

harder foam layer adhesive

Werkzeugaufnahmeköpf

mounting plate

spindle shaft

tool spindle

complementary structures wall surface

Floor space

inner space

seating shoulder

entrainment

Mitnehmergegenelemente

ring groove

retaining ring

counter-groove

ball joint

ball socket

Kugelköpf

Kugelstift

location hole

cross pin

recess

support flange

elastic ring element 58 fret

 59 fret

 60 circlip

 62 half ring

 63 half ring

 64 hinge

 66 snap connection

 68 workpiece spindle

 69 block piece

 70 servomotor

 71 belt drive

 72 piston-cylinder arrangement

74 latching device

 76 swing yoke

A tool rotation axis

 B swivel adjusting axle

 C workpiece axis of rotation

cc second optically effective area

cx first optically effective surface

D _L Diameter of the spectacle lens

 Dw Diameter of the polishing plate

 L spectacle lens

 M central axis of the main body

 Rmax maximum arrow height

 Pm mean arrow height

 Pmin minimum arrow height

 RG Radius of curvature of the face of the base body

Rlimax maximum radius of curvature of the spectacle lens

Run mean radius of curvature of the spectacle lens

RLmin minimum radius of curvature of the spectacle lens

Rw radius of curvature of the polishing plate

S _H thickness of the harder foam layer

S _P thickness of the polishing agent carrier

S _s total thickness of the intermediate layer S _w thickness of the softer foam layer X linear axis

Z infeed axis ⁽ Pmax maximum opening angle

cpmin minimum opening angle

Claims

PATENT CLAIMS: 1. polishing plate (10) for a tool (12) for fine machining of optically active surfaces (cc, cx) on spectacle lenses (L), with a central axis (M) having base body (14) on which a relative to the main body ( 14) softer intermediate layer (16) is fastened from an elastic material, on which a polish carrier (lg), rests, characterized in that the intermediate layer (16) has at least two regions (20, 22) of different hardness, which in the direction Center axis (M) are arranged one behind the other, wherein the region (20) of the intermediate layer (16) adjoining the main body (14) is softer than the region (22) of the intermediate layer (16) on which the polish carrier (18) rises; lies . 2. polishing plate (10) according to claim 1, characterized in that the at least two regions of the intermediate layer (16) by mutually different foam layers (20, 22) are formed, namely at least one softer foam layer (20) on the base body (14) and at least one harder foam layer (22) under the polish carrier (18). 3. polishing plate (10) according to claim 2, characterized in that the mutually different foam layers (20, 22) are glued together. 4. polishing plate (10) according to claim 2 or 3, characterized in that the ratio of the substantially constant thickness (S _H ) of the harder foam layer (22) to the substantially constant thickness (S _w ) of the softer foam layer (20) between 1 to 2 and 1 to 4, preferably at about 1 to 3 wherein the thicknesses (S _H , S _w ) are measured along or parallel to the central axis (M). 5. polishing plate (10) according to one of claims 2 to 4, character- ized in that, determined in the case of a full-surface compression, the static modulus of elasticity of the harder Foam layer (22) is between 0.40 and 1.50 N / mm ² , preferably between 0.80 and 1.00 N / mm ² , while the static E modulus of the softer foam layer (20) is between 0.25 and 0 , 45 N / mm ² , preferably between 0.35 and 0.45 N / mm ² . 6. polishing plate (10) according to any one of claims 2 to 5, characterized in that the softer foam layer (20) consists of an at least partially open-pore polyetherurethane elastomer, while the harder foam layer (22) consists of a closed-cell polyetherurethane elastomer. 7. polishing plate (10) according to any one of the preceding claims, characterized in that the base body (14) one of the intermediate layer (16) facing, substantially spherical end face (21) to which the intermediate layer (16) attached, in particular is glued wherein the end face (21) has a radius of curvature (R _G ) which is between 35 and 42 mm, preferably between 36 and 40 mm. 8. polishing plate (10) according to claim 7, characterized in that the base body (14) in the region of its end face (21) has a diameter between 35 and 60 mm, wherein the substantially constant thickness (S _s ) of the intermediate layer (16) along or parallel to the central axis (M) measured between 15 and 22 mm. 9. polishing plate (10) according to any one of the preceding claims, characterized in that the polishing agent carrier (18) projects in relation to the central axis (M) radial direction on all sides via the intermediate layer (16). 10. Tool (12) for fine machining of optically active surfaces (cc, cx) of spectacle lenses (L), with an axially and rotationally engageable on a spindle shaft (26) of a tool spindle (28) attachable tool holder head (24), characterized in that a polishing plate (10) according to one of the preceding claims on the tool holder head (24) is held interchangeable, to which the main body (14) of the polishing plate (10) and the tool holder head (24) with complementary structures (29). axial locking and for rotational drive of the polishing plate (10) with the tool holder head (24) are provided. 11. Tool (12) according to claim 10, characterized in that the tool holder head (24) has a ball joint (40), with a ball socket (42) received ball head (44) which on one of the spindle shaft (26 ) of the tool spindle (28) can be fastened ball pin (46) is formed while the ball socket (42) in a receiving plate (25) is formed, with which the polishing plate (10) can be latched. 12. Tool (12) according to claim 11, characterized in that the ball head (44) has a receiving bore (48) for a transverse pin (50) which extends through the ball head (44) and on both sides of the ball head (44 ) with associated recesses (52) in the ball socket (42) engages / to connect the receiving plate (25) rotatable with the ball pin (46). 13. tool (12) according to claim 11 or 12, characterized in that the receiving plate (25) via an elastic beautiful ring element (56) on a ball pin-side Abstützflansch (54) so resiliently supported, that with the receiving plate (25) latched polishing plate (10) strives with its central axis (M) with the ball pin (46) and thus the spindle shaft ( 26) of the tool spindle (28) auszufluchten. 14. Tool (12) according to any one of claims 10 to 13, characterized in that the base body (14) of the polishing plate (10) and the tool holder head (24) are each provided with a radially projecting collar (58, 59), wherein the Frets (58, 59) mounted in the tool receiving head (24) state of the polishing plate (10) face each other and are positively overlapped by means of a locking ring (60) having a substantially U-shaped cross-section. 15. Tool (12) according to claim 14, characterized in that the securing ring (60) by two half rings (62, 63) is formed, which on one side by means of a hinge (64) pivotally connected to each other and on the other side via a Schnappverbindüng (66) are releasably locked together.