EP1698432A2 - Polishing disc for a finishing tool for finishing optical surfaces especially eyeglass lenses - Google Patents

Abstract

A polishing foil (18) has an aperture (20) in a center area. During processing, the aperture causes balanced pressure and supplies a liquid polishing agent from inside a layer of foam material. This produces better washing and cooling of polishing disk areas that are otherwise put at a disadvantage. An independent claim is also included for a tool for fine machining of optically active surfaces on spectacle lenses.

Description

TECHNICAL AREA

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

If the following example of workpieces with optically active surfaces of "lenses" is mentioned, including not only eyeglass lenses made of mineral glass, but also eyeglass lenses from all other common materials, such as polycarbonate, CR 39, HI index, etc., including plastic be 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 recipe macrogeometry and then the fine processing of the optically effective surface to eliminate Vorbearbeitungsspuren and obtain the desired microgeometry. 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, the prior art (eg EP 1 249 307 A2, DE 102 48 104 A1, DE 102 50 856 A1, DE 103 19 945 A1) increasingly used polishing plates, which have an at least three-layer or -lagigen structure, with (1) one of the tool spindle facing, solid or rigid support body to which (2) a foam layer is attached, the (3.) rests a grinding or polishing foil facing the workpiece as a processing-active tool component. Due to the elastic deformability of the foam layer, the polishing film can be adapted within certain limits to the geometry of the surface to be machined, both from "spectacle" to spectacle glass, which is to be processed, as well as in "dynamic" terms, ie during the processing of a specific spectacle lens, in which a relative movement between the polishing plate and the spectacle lens takes place. In addition, the elasticity of the foam layer significantly influences the removal behavior of the polishing plate during the polishing process.

An essential prerequisite for a trouble-free polishing process and durable tools as well as for obtaining high-quality machining results is a good supply of liquid polishing agent during processing. The latter has abrasive components which are to be transported by means of the liquid to the point of engagement between the tool and the workpiece, and further serves for cooling and flushing at the point of engagement between the tool and the workpiece. In the prior art, the polishing agent supply takes place from the radially outside via flexibly adjustable hoses whose outlet openings are positioned as close as possible to the working gap between the polishing foil and the surface of the spectacle lens to be machined.

With the use of the above-described, adaptable polishing plate has now been shown under conventional polishing supply, that in particular in areas of the polishing plate, which during the processing kinematically due to leaving the working surface of the lens, comes to a relatively poor wetting of the polishing film with the liquid polishing agent. In the addressed areas of the polishing plate, this can lead to the polishing-active surface structures of the polishing film not being sufficiently flushed away and the high frictional heat being dissipated only insufficiently. As a result, it can come in these areas of the polishing plate to a proper drying and thus undesirable solidification of the polishing film, which leads to the machined surface to a deterioration of the surface quality achieved and thus makes an exchange of the polishing plate required.

The invention is based on the object, starting from the prior art, as he e.g. represented by the DE 102 50 856 Al, to provide a simply constructed polishing plate for a tool for fine machining of optically active surfaces on particular eyeglass lenses, which is used as long as possible in achieving high surface qualities.

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

PRESENTATION OF THE INVENTION

According to the invention, in a polishing plate for a tool for fine machining of optically effective surfaces on in particular spectacle lenses, which has a carrier body, to which a foam layer is fixed, which rests on a polishing film, the polishing film is provided in a central region with at least one opening.

The opening according to the invention in the polishing foil provides a fluid connection between an inner region of the spongy foam layer soaked with polishing agent during processing and the outer surface of the polishing foil in machining engagement with the surface of the workpiece to be machined. Thus, the liquid polishing agent can circulate better and also pass from the interior of the polishing pad to the engagement areas between the polishing film and the surface to be machined of the workpiece, whereby at these engagement areas due to increased wetting of the polishing film or a more uniform polishing agent on this better rinsing and Cooling is ensured. Accordingly, it no longer results in partial solidification of the polishing film which is detrimental to the surface quality produced, so that the polishing plate can be used longer as compared with the above prior art.

In addition, the opening according to the invention virtually performs a valve function: In order to polish as form-retaining as possible, the polishing-active surface of the polishing plate, and therefore the polishing film must have a relatively high flexibility. As a result of this flexibility, the polishing film is relatively strongly deformed in particular during the passage of the polishing plate on the edge of the lens to be processed but also in the processing of, for example, toric surfaces during rotation of the tool and workpiece. Along with this deformation of the polishing film, the underlying foam layer, which is saturated with the liquid polishing agent, is forced to flex; The result is a pumping effect between different areas of the top and bottom covered foam layer.

In the prior art, if the liquid polishing agent could not emerge laterally from an edge region of the foam layer, then it could be found particularly in the interior lying areas of the foam layer to pressure jam. In the prior art, these pressure jams could cause the pores of the foam layer to be partially torn and / or the foam layer to be at least partially torn off at its connection points to the carrier body and / or the polishing foil from the respective mating surface, so that the polishing plate had to be replaced.

With the opening according to the invention in the polishing film, a faster pressure equalization is now possible, it is no longer dangerous to high pressure jam, especially in the more interior areas of the foam layer, so that there no longer tears the foam or no longer from the mating surfaces on carrier body and / or polishing foil.

In addition, the described described, caused by the opening in the polishing film inner circulation / ventilation on the polishing plate according to the invention to an improved exchange of the liquid polishing agent in the foam layer, along with an advantageous "internal cooling" of the polishing plate.

As a result, a conceivable simple and inexpensive constructed polishing plate is proposed, which is significantly more durable compared to the prior art in achieving high surface qualities, which makes it predestined for the industrial production of spectacle lenses by prescription.

For the at least one opening in the polishing foil different geometries are conceivable. Thus, the opening can be cross-shaped, star-shaped, curved or S-shaped, elliptical or the like. be educated. Also, a plurality of openings may be provided, in shape and distribution, for example as the mounting holes on a button. However, it is preferred if the at least an opening in the polishing film is round, thus having a simple and easy to produce geometry.

Investigations by the Applicant have shown that a particularly good circulation and ventilation of the liquid polishing agent on the at least one opening in the polishing results, without that the opening substantially reduces the polishing-active surface of the polishing film when the at least one opening in the polishing film Surface area of 0.25 to 2% of the total face of the polishing film occupies.

It is further preferred if a recess in the foam layer adjoins the at least one opening in the polishing film in the direction of the carrier body. This recess can advantageously serve as a reservoir for the liquid polishing agent. But it is also conceivable that no recess is provided here, but the foam layer ends directly and openly pores on the at least one opening in the polishing film.

If a recess is provided in the foam layer, it may extend as far as the carrier body. Such a continuous recess is not only particularly easy to produce, but also advantageously maximizes the uptake volume of the reservoir formed by the recess for the liquid polishing agent.

Furthermore, the polishing film can project beyond an outer circumference of the recess in the foam layer inwards. As a result of the missing of the protruding region of the polishing film support of the polishing film through the foam layer, the polishing film in the direction of the carrier body can yield more easily; it comes to a rounding or to a natural radius of the polishing film. As a result, can be so undesirable on the surface processed by means of the polishing pad Can be avoided, which could otherwise be caused by a more or less sharp edge of the polishing film, which is formed when the at least one opening in the polishing film is made by cutting or punching.

Also, the polishing film can project beyond an outer periphery of the foam layer to the outside. The fact that the polishing foil is intentionally kept larger in its radial dimensions than the underlying foam layer, that is, has a certain overhang with respect to the foam layer, the polishing foil spreads slightly in this area of the surface to be machined. As a result, on the one hand unwanted impressions are avoided, as already described above; In this case no significant polishing pressure can be exerted on the surface to be machined over the outer edge of the polishing film. On the other hand, the overhang of the polishing film with respect to the foam layer also leads to a further improvement of the polishing agent supply: Between the surface of the spectacle lens just worked and the overhanging part of the polishing foil which is slightly folded away, a capillary gap which opens radially outwards forms, even at high temperatures Speeds always carries a certain amount of polish with it. The thus created additional polishing agent reservoir is not thrown off, but carried along with each movement and is thus constantly available.

Furthermore, the carrier body can be provided with a depression for orientation of the foam layer, which in particular simplifies the attachment of the foam layer to the carrier body. On the one hand, the edge delimiting this depression clearly defines the mounting location for the foam layer and thus also serves as an aid in the application of an adhesive for fastening the foam layer to the carrier body. On the other hand, the edge defining the depression provides also for a certain positive fit of the foam layer on the carrier body.

With regard to a polishing surface of the polishing foil which is as large as possible even at low polishing pressures, an embodiment of the polishing plate is furthermore preferred in which the carrier body for fixing the foam layer has a carrier surface preformed in accordance with the macrogeometry of the surface to be processed, e.g. in the case of processing a toric surface has a corresponding toric preform.

Further, in order to improve the adaptability of the polishing plate to the macrogeometry of the surface to be processed beyond the elasticity of the foam layer, the carrier body may be made of a rubber elastic material having a hardness of Shore A in a range of preferably 60 to 80.

The polishing plate according to the invention can advantageously be used on a tool for fine machining of optically effective surfaces on, in particular, spectacle lenses, comprising a base body which can be attached to a tool spindle of a processing machine, a joint part which has a tilting and longitudinally movably guided receiving section with respect to the base body, to which in the direction of the main body is connected a bellows portion, by means of which the joint part is rotationally fixed on the base body, and a limited by the main body and the joint part pressure medium chamber which is selectively acted upon by a pressure medium, wherein the polishing plate interchangeable held on the receiving portion of the joint part is.

With a simple interchangeability of the polishing plate a secure hold of the. Poliertellers on and a rotational drive of To ensure polishing plate with the receiving portion of the joint part, complementary shaped structures may be formed on the mutually facing surfaces of the receiving portion and the carrier body of the polishing plate, which engage in a form-fitting manner. Here, the complementary shaped structures may be formed by a projection on the carrier body of the polishing plate and an associated recess in the receiving portion of the joint part. In particular, with regard to a simple handling of the polishing plate, however, it is preferred if the complementary shaped structures are formed by a projection on the receiving portion and an associated recess in the carrier body.

In a particularly simple manufacturing design, finally, the projection on the receiving portion and the recess in the carrier body may have the shape of a truncated pyramid, which has a rectangular, non-square base with a longer edge pair and a shorter edge pair. With regard to a good tilting stability of the polishing plate during processing, in the case of a polishing plate in which the carrier surface of the carrier body is toroidally preformed, with a base axis and a cylinder axis, it is preferred if the truncated pyramid-shaped recess in the carrier body is aligned with respect to the carrier surface in that the longer edge pair runs parallel to the base axis.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

eine abgebrochene Längsschnittansicht eines Werkzeugs zur Feinbearbeitung von optisch wirksamen Flächen an Brillengläsern, an dem ein Polierteller nach einem ersten Ausführungsbeispiel der Erfindung lösbar gehalten ist, der sich mit einer zu bearbeitenden Fläche in Bearbeitungseingriff befindet, in einem gegenüber der Realität vergrößerten Maßstab,

Fig. 2

eine Draufsicht auf den vom Werkzeug abgenommenen Polierteller gemäß Fig. 1 von oben in Fig. 1, in einem gegenüber der Darstellung in Fig. 1 etwas verkleinerten Maßstab,

Fig. 3

eine Unteransicht des vom Werkzeug abgenommenen Poliertellers gemäß Fig. 1 von unten in Fig. 1, im Maßstab von Fig. 1,

Fig. 4

eine abgebrochene Längsschnittansicht eines Werkzeugs zur Feinbearbeitung von optisch wirksamen Flächen an Brillengläsern, an dem ein Polierteller nach einem zweiten Ausführungsbeispiel der Erfindung lösbar gehalten ist, der sich mit einer zu bearbeitenden Fläche in Bearbeitungseingriff befindet, in einem gegenüber der Realität vergrößerten Maßstab, und

Fig. 5 bis 9

Draufsichten auf vom Werkzeug abgenommene, erfindungsgemäße Polierteller, die sich von den Poliertellern gemäß den Fig. 1, 2 und 4 hinsichtlich der Form bzw. Anzahl von Öffnungen in einer oberen Polierfolie des Poliertellers unterscheiden, im Maßstab von Fig. 2.

In the following the invention with reference to preferred embodiments with reference to the accompanying drawings is explained in more detail, wherein the same or corresponding parts are provided with the same reference numerals. In the drawings show:

Fig. 1

a broken longitudinal sectional view of a tool for fine machining of optically effective surfaces of spectacle lenses, on which a polishing plate is releasably held according to a first embodiment of the invention, which is in machining engagement with a surface to be machined, in an enlarged scale compared to reality,

Fig. 2

1 is a top view of the polishing plate removed from the tool according to FIG. 1 from the top in FIG. 1, in a comparison with the illustration in FIG. 1 somewhat reduced scale,

Fig. 3

1 is a bottom view of the polishing plate removed from the tool according to FIG. 1 from below in FIG. 1, in the scale of FIG. 1,

Fig. 4

a broken longitudinal sectional view of a tool for fine machining of optically effective surfaces of spectacle lenses, on which a polishing plate is releasably held according to a second embodiment of the invention, which is in machining engagement with a surface to be machined, in a relation to reality enlarged scale, and

Fig. 5 to 9

Top views of removed from the tool, inventive polishing plate, which differ from the polishing plates according to FIGS. 1, 2 and 4 with respect to the shape or number of openings in an upper polishing foil of the polishing plate, in the scale of Fig. 2nd

DETAILED DESCRIPTION OF THE EMBODIMENTS

According to FIG. 1, a polishing plate 10 for a tool 12 for fine machining of optically active surfaces F on, in particular, spectacle lenses L has a carrier body 14 to which a foam layer 16, which rests a polishing foil 18, is fastened. It is essential that the polishing film 18 is provided in a central region with at least one opening 20, as will be described in more detail below.

In the polishing film 18, also called "polishing pad", which forms the machining-active tool component according to FIG. 1, is a commercially available, elastic and abrasion-resistant fine abrasive or polishing agent carrier, such as a PUR (polyurethane) film, the has a thickness of 0.5 to 1.4 mm and a hardness between 12 and 45 Shore D. In this case, the polishing film 18 is rather thicker, if by means of the polishing plate 10 is a pre-polishing to take place, but rather thinner in the case of a fine polishing.

The radial dimensions of the polishing foil 18 are preferably selected such that the polishing foil 18, seen in the plan view according to FIG. 2, protrudes outwards with an outer edge region 22 over an outer circumference 24 of the foam layer 16 cut to size cylindrically in this exemplary embodiment (see FIG. 1). , The outer diameter of the polishing film 18 may be, for example, so dimensioned that the outer diameter of the foam layer 16 is about 85 to 95% of the outer diameter of the polishing film 18. As a result of this supernatant of the flexible polishing film 18 on the supporting foam layer 16, there is a natural radius or a "Kantenabrundung", which is indicated in Fig. 1 with 26 and by avoiding a sharp edge for a clean surface structure and thus a high cosmetic quality of the machined surface F provides. In addition, results during processing at the outer edge region 22 of the polishing sheet 18 between the machined surface F and the polishing sheet 18, a wedge-shaped gap 28, which always carries a certain amount of liquid polishing agent due to its capillary action and thus also serves as an annular polishing agent reservoir.

At a central location of the polishing film 18, the through opening 20 is made by cutting or punching, which has a circular shape in the embodiment shown in FIGS. 1 to 3. Preferably, the opening 20 in the polishing film 18 occupies a surface area of 0.25 to 2% of the entire face of the polishing film 18 facing the surface F to be processed.

In the illustrated embodiment, the polishing sheet 18 is attached to the foam layer 16 by means of a suitable adhesive. However, the polishing sheet 18 may also be connected to the foam layer 16 more or less permanently in some other way, e.g. by vulcanization or Aufkletten. In any case, the connection between the polishing sheet 18 and the foam layer 16 must be so strong that at any time during processing Bewegungsmitnahme, in particular rotational drive of the polishing sheet 18 is ensured with the foam layer 16.

The foam layer 16 may be, for example, an open-celled PUR (polyurethane) foam, as it is available, for example, under the trade name Sylomer® R from Getzner Werkstoffe GmbH, Berlin, Germany. This has a hardness of about 60 to Shore A. The top of the foam layer 16 facing the polishing sheet 18 may, but need not be provided with a final, manufacturing technology-related "casting" (release layer to the mold, not shown), the foam layer 16 an additional Stiffness gives. The thickness of the foam layer 16 may be the respective Processing requirements, for example, between 2 and 10 mm. It will be apparent to those skilled in the art that the size and distribution of the pores in the foam layer 16 should be selected so as to provide the desired rinse and cooling previously discussed by means of the liquid polishing agent through the opening 20 in the polishing sheet 18.

In the embodiment shown in FIG. 1, a recess 30 in the foam layer 16 adjoins the opening 20 in the polishing film 18 in the direction of the carrier body 14, which extends to the carrier body 14. The preferably formed by punching recess 30 has a cylindrical outer peripheral surface 32, whose diameter corresponds to the diameter of the opening 20 in the polishing sheet 18. The recess 30 also serves as a reservoir for the liquid polishing agent during processing.

The foam layer 16, in turn, for example, by means of a suitable adhesive firmly attached to the support body 14, which preferably consists of a rubber-elastic material, such as NBR (elastomer based on acrylonitrile-butadiene-styrene rubber), EPDM (elastomer based on ethylene-propylene-diene rubber ) or a PUR (polyurethane) elastomer, having a hardness to Shore A in a range of 60 to 80. Here, the support body 14 is provided in the embodiment of FIG. 1 with a recess 34, the edge 36 of the orientation of the foam layer 16th serves. The bottom of the recess 34 forms the actual support surface 38 to which the foam layer 16 is attached. In the exemplary embodiment according to FIG. 1, the carrier surface 38 is preformed in accordance with the macrogeometry of the surface F to be machined, in this case a toric surface.

On the outer circumference, the carrier body 14 has a cross-sectionally V-shaped annular groove 40, which serves as a handle for a gripper (not shown) of an automatic polishing plate changing device (also not shown). On a level bottom 42 of the carrier body 14 of the polishing plate 10 is held in a manner to be described interchangeable on the tool 12.

According to FIG. 1, the tool 12 has a base body 44 which can be attached to a tool spindle 46 of a processing machine (not shown) indicated by dashed lines in FIG. 1. Furthermore, the tool 12 has a generally numbered 48 with a hinge part having a respect to the body 44 tilt and longitudinally movably guided receiving portion 50 to which the polishing plate 10 is held interchangeable. Adjoining the receiving portion 50 in the direction of the main body 44 is a bellows portion 52, by means of which the joint part 48 is fastened on the main body 44 so as to be capable of rotation. The main body 44 and the hinge part 48 define a pressure medium chamber 54, which can be acted upon via a channel 56 optionally with a suitable liquid or gaseous pressure medium (eg oil or compressed air), during the processing of the optically active surface F on the receiving portion 50 and resting thereon polishing plate 10 to apply a processing pressure. Guided longitudinally displaceable on the base body 44 is a guide member 58, which is operatively connected to the receiving portion 50 of the joint part 48, so that the receiving portion 50 in the longitudinal direction of the guide member 58 and held movable in the transverse direction to the guide member 58, but under an elastic deformation of the Faltenbalgabschnitts 52 of Joint part 48 is tiltable with respect to the guide member 58 is.

The preferably metallic base body 44 has a fixing portion 60, by means of which the tool 12 releasably attached to the Tool spindle 46 can be mounted, and a subsequent to the mounting portion 60 head portion 62 to which the hinge part 48 is mounted interchangeable by means of the Faltenbalgabschnitts 52. In the illustrated embodiment, the attachment portion 60 in a very simple embodiment, a cylindrical outer peripheral surface. For an automatic tool change the mounting portion but can also be designed as a steep taper, with eg a hollow shaft cone according to the German standard DIN 69893. According to the respective handling requirements, it is also conceivable to form the mounting portion as a block connector, as is customary in the production of prescription lenses L and standardized in the German standard DIN 58766. If necessary, this connection can also be provided with a gripping groove for any handling systems.

The head section 62 of the main body 44 has a cylindrical shoulder 64, which is provided with a radial groove 66 for the positive fastening of the bellows section 52 of the joint part 48 on the main body 44. In this case, the Faltenbalgabschnitt 52 of the joint part 48 has a substantially hollow cylindrical mounting end portion 68 which is provided on the inner peripheral side with a radially inwardly projecting, circumferential nose 70 which engages positively into the radial groove 66 of the shoulder 64 on the head portion 62. On the outer circumference of the fastening end portion 68 in turn is provided with a radial groove 72 which serves the positive reception of a known, metallic ring clamp 74. The ring clamp 74 clamps the fastening end section 68 against the shoulder 64. As a result, the joint part 48 is positively locked by means of the bellows section 52 in the tensioning and pressure direction and in the circumferential direction by friction, thus rotationally fixed to the base body 44.

In an analogous manner, the receiving portion 50 of the joint part 48 is positively secured to the Faltenbalgabschnitt 52 in the tensile and compressive direction and in the circumferential direction frictionally. In this case, the substantially plate-shaped receiving portion 50 on a cylindrical outer peripheral surface 76 has a radial groove 78 into which engages on a hollow cylindrical mounting end 80 of the Faltenbalgabschnitts 52 on the inner circumference circumferentially mounted, radially inwardly projecting nose 82 positively. Also, the mounting end portion 80 is provided on the outer peripheral side with a radial groove 84 for receiving a ring clamp 86, which braces the mounting end 80 with the receiving portion 50.

The in the illustrated embodiment of a plastic receiving portion 50 of the joint part 48 is seen in a plan view from above in Fig. 1 is circular and has on its the pressure medium chamber 54 facing inside substantially centrally an undercut receiving chamber 88 for articulation of the receiving portion 50 on the guide member 58. The latter is formed by a pin which is longitudinally displaceably and rotatably guided in a central receiving bore 90 in the main body 44, which extends in the longitudinal direction through the entire base body 44 therethrough. At its end facing the receiving portion 50 of the joint part 48, the guide member 58 has a ball head 92, which is connected via a conical transition section with a cylindrical main part 94 of the guide member 58 guided in the receiving bore 90. The ball head 92 of the guide member 58 is knotted in the undercut receiving chamber 88 of the receiving portion 50 in the manner of a ball joint, so that the receiving portion 50 can pivot relative to the guide member 58 and perform gimbal compensating movements.

1, the channel 56 is formed for pressurizing the pressure medium chamber 54 in the guide member 58, wherein the channel 56 in the guide member 58 has a longitudinal bore 96, which has a transverse bore 98 near the ball head 92 with the pressure medium chamber 54 communicates. Furthermore, the guide member 58 is biased in the direction of the surface F to be processed by means of a helical compression spring 100, which is received in Fig. 1 below the guide member 58 in the receiving bore 90 and is supported on a grub screw 102. The grub screw 102 is finally screwed into an internally threaded portion 104 of the receiving bore 90 in the base body 44 and provided with a through hole 106 for the pressure medium.

It can be seen that the receiving portion 50 of the joint part 48 by means of the guide member 58 in the transverse direction relative to the base body 44 is supported. At the same time, the guide member 58 can follow the receiving portion 50 in the axial direction and vice versa, when the pressure medium chamber 54 is acted upon by the channel 56 with the pressure medium or the receiving portion 50 is pressed by external action against the force of the helical compression spring 100 in the direction of the main body 44. In addition, the receiving portion 50 of the hinge portion 48 due to the hinge connection to the guide member 58 on the ball head 92 of the guide member 58 tilt, wherein the Faltenbalgabschnitt 52 of the joint part 48 is deformed accordingly.

In order to ensure a secure hold of the polishing pad 10 and a rotational drive of the polishing pad 10 with the receiving portion 50 of the tool 12, are on the facing surfaces of the receiving portion 50 of the joint part 48 and the support body 14 of the polishing pad 10, ie 1 formed on the upper end surface 108 of the receiving portion 50 and the bottom 42 of the support body 14 complementary shaped structures which engage in a form-fitting manner. These Structures are formed in the illustrated embodiment by a projection 110 on the receiving portion 50 of the joint part 48 and an associated recess 112 in the carrier body 14 of the polishing pad 10.

1 and 3, both the projection 110 on the receiving portion 50 and the recess 112 in the carrier body 14 in the form of a truncated pyramid, which has a rectangular, non-square base with a longer edge pair 114 and a shorter edge pair 116. In the case of a toric preformed support surface 38 on the support body 14, which has a base axis BA and a cylinder axis ZA (see Fig. 3), the truncated pyramidal recess 112 in the support body 14 is aligned with respect to the support surface 38, that the longer edge pair 114 parallel to the base axis BA runs, which increases the tilt stability of the polishing pad 10 during processing. A high tilting stability of the polishing pad 10 is also conducive to the fact that the formed by the undercut receiving chamber 88 in the receiving portion 50 of the joint part 48 and the ball head 92 of the guide member 58 ball joint at least partially located in the region of the projection 110, whereby the point to the the receiving portion 50 can tilt, the location of the machining engagement between the polishing plate 10 and the lens L is relatively close.

In the fine machining of the optically active surface F of the spectacle lens L to be processed, which takes place in a known manner by means of unbound grain, which is supplied by a suitable liquid to the point of contact between the polishing plate 10 and lens L, both from radially outside by means of initially mentioned flexibly adjustable hoses (not shown) as well as from radially inwardly over the foam layer 16, the recess 30 in the foam layer 16 and the at least one opening 20 in the polishing film 18, the tool 12 and the lens L are also in a conventional manner substantially synchronously, that is driven in the same direction and at substantially the same speed. Here, the tool 12 and the lens L are simultaneously pivoted relative to each other, so that the engagement area between the polishing plate 10 and lens L changes continuously. These fine machining processes, in which, for example, in the case of the machining of free-form surfaces, the pivotal movement takes place in a fixed setting about the center of a "best fit radius", ie an approximated center of the surface F to be machined L of the spectacle lens L or the relative movement between the tool 10 and spectacle lens L. is generated by a path-controlled method in two CNC linear axes and a CNC pivot axis are well known to those skilled in the art and are therefore not described in detail here.

As a result of the relative movement of the tool 12 and lens L, as already mentioned, the foam layer 16 of the polishing pad 10 imposed on the polishing film 18 a flexing, ie the foam layer 16 is also locally compressed and relieved elsewhere, whereby the liquid polishing agent in the Foam layer 16 migrates or is displaced from one area to another area of the foam layer 16 when expressing a sponge. Excess polishing agent is in this case, as indicated in Fig. 1 with arrows in the foam layer 16, displaced both radially outward and radially inward from where it can over the opening 20 in the polishing film 18 to wet the surface to be processed F of the lens L , It comes - radially outward or radially inward - to a pressure relief, which prevents the pores in the foam layer 16 rupture or the (adhesive) connection between the foam layer 16 and the polishing film 18 and between the foam layer 16 and the support surface 38 of the carrier body 14 triggers.

4 shows a second embodiment of a polishing plate 10, which is mounted on a tool 12 for fine machining of optically active surfaces F in particular spectacle lenses L. Since the latter does not differ from the tool 12 according to FIG. 1, the drawing was aborted downwards. The polishing plate 10 according to the second embodiment differs from the polishing plate 10 according to the first embodiment only in that the polishing film 18 projects beyond the outer peripheral surface 32 of the recess 30 in the foam layer 16 with an inner edge portion 118 radially inward. Here, too, a natural radius or an "edge rounding" arises at 120, which leaves no undesirable machining marks during the machining of the optically effective surface F.

5 to 9 illustrate finally still that the opening 20 / openings 20 in a central region of the polishing sheet 18 of the polishing pad 10 according to the respective processing requirements, for example, depending on the polishing pressure, the size and / or the position of the surface area on the working surface F, which is constantly covered by the polishing plate 10 during processing, may have a different position, size, shape and / or number. Illustrated by way of example are a cross-shaped (FIG. 5), star-shaped (FIG. 6), curved or S-shaped (FIG. 7) and elongated or elliptical (FIG. 8) opening 20 in the polishing foil 18 and a plurality of openings 20 (FIG. Fig. 9) similar in shape and distribution to the mounting holes on a button.

Disclosed is a polishing plate for a tool for fine machining of optically effective surfaces on, in particular, spectacle lenses, which has a carrier body to which a foam layer is attached, which rests on a polishing foil. According to the invention, the polishing film is in a central region provided with at least one opening. The opening provides pressure equalization during processing and provides liquid polishing agent from inside the foam layer, thereby providing better rinsing and cooling of otherwise less favored beater areas. As a result, a conceivable simple and inexpensive constructed polishing plate is proposed, which is significantly more durable compared to the prior art in achieving high surface qualities.

LIST OF REFERENCE NUMBERS

10

polishing plate

12

Tool

14

support body

16

foam layer

18

polishing film

20

opening

22

Outer edge region

24

outer periphery

26

rounding off

28

gap

30

recess

32

Outer circumferential surface

34

deepening

36

edge

38

support surface

40

ring groove

42

bottom

44

body

46

tool spindle

48

joint part

50

receiving portion

52

bellows

54

Fluid chamber

56

channel

58

guide member

60

attachment section

62

header

64

paragraph

66

radial groove

68

Fixing end portion

70

nose

72

radial groove

74

ring clamp

76

Outer circumferential surface

78

radial groove

80

Fixing end portion

82

nose

84

radial groove

86

ring clamp

88

receiving chamber

90

location hole

92

ball head

94

Bulk

96

longitudinal bore

98

cross hole

100

Helical compression spring

102

grub screw

104

Internally threaded portion

106

Through Hole

108

face

110

head Start

112

recess

114

edge pair

116

edge pair

118

Inner edge area

120

rounding off

F

optically effective surface

L

lens

BA

base axis

ZA

cylinder axis

Claims (15)

Polishing disc (10) for a tool (12) for fine machining of optically active surfaces (F) on, in particular, spectacle lenses (L), with a carrier body (14) to which is attached a foam layer (16) which rests on a polishing foil (18) , characterized in that the polishing film (18) is provided in a central region with at least one opening (20). The polishing plate (10) according to claim 1, characterized in that the at least one opening (20) in the polishing foil (18) is round. The polishing plate (10) according to claim 1 or 2, characterized in that the at least one opening (20) in the polishing foil (18) occupies a surface area of 0.25 to 2% of the entire end face of the polishing foil (18). The polishing plate (10) according to one of the preceding claims, characterized in that a recess (30) in the foam layer (16) adjoins the at least one opening (20) in the polishing foil (18) in the direction of the carrier body (14). Polishing disc (10) according to claim 4, characterized in that the recess (30) extends to the carrier body (14). The polishing plate (10) according to claim 4 or 5, characterized in that the polishing foil (18) protrudes inwardly over an outer periphery (32) of the recess (30) in the foam layer (16). Polishing disc (10) according to one of the preceding claims, characterized in that the polishing foil (18) projects beyond an outer periphery (24) of the foam layer (16) to the outside. Polishing disc (10) according to one of the preceding claims, characterized in that the carrier body (14) is provided with a recess (34) for orientation of the foam layer (16). The polishing plate (10) according to one of the preceding claims, characterized in that the carrier body (14) has a carrier surface (38) to which the foam layer (16) is attached, wherein the carrier surface (38) in accordance with the macrogeometry of the surface to be machined (F) is preformed. The polishing plate (10) according to one of the preceding claims, characterized in that the carrier body (14) consists of a rubber-elastic material having a Shore A hardness in a range of preferably 60 to 80. Tool (12) for fine machining of optically active surfaces (F) in particular spectacle lenses (L), with
a base body (44) which can be attached to a tool spindle (46) of a processing machine,
a joint part (48) which has a relative to the base body (44) tilted and longitudinally movable receiving portion (50) to which in the direction of the base body (44) a bellows portion (52) connects, by means of which the hinge part (48) rotatable attached to the base body (44),
one of the base body (44) and the hinge part (48) limited pressure medium chamber (54) which is optionally acted upon by a pressure medium, and
a polishing plate (10) according to one of the preceding claims, which is replaceably held on the receiving portion (50) of the joint part (48). Tool (12) according to claim 11, wherein on the mutually facing surfaces (108, 42) of the receiving portion (50) of the joint part (48) and the carrier body (14) of the polishing plate (10) complementary shaped structures (110, 112) are formed , which engage in a form-fitting manner, in order to ensure a secure hold of the polishing plate (10) and a rotational drive of the polishing plate (10) with the receiving portion (50). The tool (12) of claim 12, wherein the complementarily shaped structures are formed by a projection (110) on the receiving portion (50) and an associated recess (112) in the carrier body (14). The tool (12) according to claim 13, wherein the projection (110) on the receiving portion (50) and the recess (112) in the carrier body (14) have the shape of a truncated pyramid having a rectangular, non-square base with a longer edge pair (114 ) and a shorter edge pair (116). The tool (12) of claim 14 further comprising a polishing plate (10) according to at least claim 9, wherein the carrier surface (38) of the carrier body (14) is toroidally preformed, having a base axis (BA) and a cylinder axis (ZA), and wherein truncated pyramidal recess (112) in the carrier body (14) is aligned with respect to the support surface (38), that the longer edge pair (114) parallel to the base axis (BA).

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