POLISHING FILM FOR PLASTIC SPECTACLE LENSES

Abstract

A polishing film for a polishing head for plastic spectacle lenses, for polishing zones on a front side or rear side of the spectacle lens, having a polishing surface which can be positioned against the spectacle lens and is bounded by a peripheral surface, wherein an edge is provided between the polishing surface and the peripheral surface, wherein the edge either has a radius r of at least 0.5 mm to 10 mm or has a chamfer f with an extent f1×f2, where the extent f1 or f2 is at least 0.5 mm to 10 mm, or the polishing film, when not in use, has a basic curvature G with a radius RG≧75 mm and, in addition to this, a peripheral curvature G with a radius Rg≦0.5 G, wherein the peripheral curvature g is limited to the peripheral zone, or the polishing film is formed without any basic curvature G and has a peripheral curvature g with a radius Rg≦35 mm, wherein the peripheral curvature g is limited to the peripheral zone.

Description

FIELD OF THE INVENTION

The invention pertains to a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is formed between the polishing surface and the peripheral surface.

Moreover, the invention pertains to a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, the polishing surface having a peripheral surface with a width b of at most 0.1 D to 0.3 D or at most 0.2 D.

The invention also pertains to a method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is provided between the polishing surface and the peripheral surface, wherein the polishing film at the start of the method is carved out from a web of material, such as punched out or cut out.

The invention furthermore pertains to a method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, having a basic diameter D, wherein the polishing film in a first step is carved out from a web of material, such as punched out or cut out, and the polishing surface has a peripheral zone with a width b of at most 0.1 D to 0.3 D.

BACKGROUND OF THE INVENTION

A polishing head with a polishing film is already known from DE 10 2005 010 583 A1. The polishing film is arranged on a foam carrier body and has a convex basic curvature. In the radial direction, it projects above the foam carrier body. According to paragraph [0036], a gap is formed during the machining of a spectacle lens between the lens and the polishing film, serving as an annular reservoir of polishing agent.

A polishing head with a polishing film, a carrier layer, and a basic body is already known from DE 10 2007 026 841 A1. The carrier layer of the basic body has a chamfer or recess at the outer circumference so that the polishing film after being glued fast to the carrier layer is set back in the axial direction on the outer circumference.

SUMMARY OF THE INVENTION

The problem of the invention is to configure and arrange a polishing film so that an improved polishing result is assured.

Polishing films, also known as a polishing pad, are punched out or cut out from corresponding webs of material during the manufacture. In this process, a peripheral surface of the polishing film which bounds the polishing surface is formed, one edge making an angle of around 90° with the polishing surface itself. In the case of both flat or evenly configured polishing films and convex configured polishing films with a basic curvature G, the polishing film can be positioned against the lens surface being machined with the entire polishing surface, i.e., up to the margin or edge. This is especially due to the fact that the elastic carrier layer which carries the polishing film is fitted to the lens surface, so that the polishing film lies with its entire surface against the spectacle glass. The basic curvature G of the polishing film secured to the polishing head is generally somewhat larger than the curvature of the side of the spectacle glass being worked. Therefore, the concave lens surface will at first make contact with the peripheral zone before the polishing film is placed fully against the lens surface.

To avoid unwanted polishing effects due to this edge, especially when using rather thick polishing films, it is advantageous for the edge to have a radius r of at least 0.2 mm to 10 mm or 0.5 mm to 3 mm. The radius r forms a transitional zone z between the polishing surface and the peripheral surface, preferably passing tangentially into the polishing surface. Depending on the size of the radius r on the one hand and the thickness d of the polishing film on the other hand, different values result for the remaining height h of the peripheral surface. If the radius r runs out to a support surface of the polishing film arranged opposite the polishing surface, the height h is reduced to zero. A common feature of all designs is that there is no unbroken edge at the start of the polishing process which might adversely affect the polishing result.

The radius r or the chamfer f should be chosen so that on the one hand the edge is sufficiently broken and on the other hand the polishing film does not become too thin, or else it will tear more easily.

Polishing films are generally at most 0.5 mm to 3 mm thick. The thickness d most often used is between 0.8 mm and 2 mm.

The problem is also solved in that the edge has a chamfer f with a dimension of f1×f2, where the dimension f1 or f2 is at least 0.2 mm to 10 mm or 0.5 mm to 3 mm. The closer the angle which the chamfer f makes with the polishing surface to the 180° limit, the more constant the transition between the chamfer f and the polishing surface. In addition to the chamfer f, of course, a radius r can also be worked into said transition, so that no edge remains behind at the transition between the chamfer f and the polishing surface. The influence of the chamfer f on the height h results accordingly.

Moreover, it can be advantageous for the radius r or the chamfer f to be worked into the polishing film by a cutting process or a grinding process. The radius r or the chamfer f form a rounding or flattening of the edge remaining between the polishing surface and the peripheral surface after the fabrication process. A cutting process using a milling cutter or a cutting process using a grinding tool can be used for this.

The problem is also solved in that the diameter D1 is: D1=D−2b or D1<D−2b and the polishing film in the unused state prior to being placed against a spectacle lens a1) has a basic curvature G with a radius RG>=70 mm and in addition to this it has a peripheral curvature g with a radius Rg<=0.5 G, Rg<=0.4 G, Rg<=0.3 G, Rg<=0.2 G or Rg<=0.1 G, the peripheral curvature g being confined to the peripheral zone, or a2) the polishing film is formed with no basic curvature G and it has a peripheral curvature g with a radius Rg<=25 mm, Rg<=15 mm or Rg<=7 mm, the peripheral curvature g being confined to the peripheral zone.

The basic curvature G of the polishing film secured to the polishing head can be determined by the curvature of a coupling surface of the basic body of the polishing head, since the curvature of the basic body is transferred to the elastic carrier layer. But the elastic carrier layer only partly transfers this curvature to the polishing film, so that the basic curvature G of the fastened polishing film is somewhat larger, i.e., it has a somewhat larger radius than the curvature of the basic body. The polishing film can also itself have the basic curvature G thanks to a corresponding manufacturing or machining process. In the case without basic curvature G, neither the polishing film nor the basic body or the carrier layer has a curvature.

Thanks to the use of a peripheral curvature g, the edge between the polishing surface and the peripheral surface is sufficiently distanced from the lens surface being polished. A detrimental influence on the polishing results is prevented. Especially when the polishing film is unused, said edge is relatively stiff, so that detrimental influences might be produced.

The elastic carrier layer is generally made of foam material and forms the connecting element to the coupling surface of a basic body G of a polishing head. If the elastic carrier layer is secured to the basic body, the polishing head so formed can be used with the polishing film secured to the carrier layer. The fastening of the polishing film generally occurs via a glue connection or by vulcanization or a hook and eye closure.

It can be advantageous for the peripheral curvature g to be limited to a maximum of 10% or 50% of the peripheral zone. Hence, the polishing film projects radially beyond the carrier layer by more than the peripheral zone. This projection U has no curvature, or only the basic curvature G.

The problem is also solved by a polishing head with a polishing film, as described above, which is suitable for zone polishing of a plastic spectacle lens. This suitability is due to the fact that the carrier layer is elastically configured and the polishing head or the carrier layer with the polishing film is smaller by a diameter of around 45 mm than a spectacle lens or semifinished product being machined. The diameter of a spectacle lens being machined is on average 60 mm to 85 mm. In this case, an edge machining has not yet been done for the spectacle lens being polished.

The method according to the invention involves feeding the polishing film to a cutting tool, such as a cup-shaped grinding tool or a milling head, and breaking the edge by the cutting tool. The edge after this preferably has a radius r and/or a chamfer f of at least 0.2 mm to 10 mm or 0.5 mm to 5 mm. This occurs independently of a basic curvature G of the polishing film.

The additional method according to the invention involves providing the polishing film with a basic curvature G with a radius RG>=70 mm and in addition to this providing an extra peripheral curvature g in a shaping process, i.e., by application of a shaping tool in the peripheral zone , prior to the use for a spectacle lens being manufactured, with Rg<=0.5 G, Rg<=0.4 G, Rg<=0.3 G, Rg<=0.2 G, or Rg<=0.1 G, or configuring the polishing film without a basic curvature G, i.e., flat or level, and providing a peripheral curvature g located exclusively in the peripheral zone in a shaping process prior to the use for a spectacle lens being manufactured. Preferably, a peripheral curvature g is used with a radius Rg<=35 mm, Rg<=25 mm, Rg<=15 mm or Rg<=7 mm. The peripheral curvature produces a peripheral region of the polishing film at a distance from the lens surface. The peripheral curvature g can also be chosen to be very small with increasing distance from the peripheral surface, since the transition between the projecting peripheral region of the polishing film and the polishing surface of the polishing film making contact with it is sufficiently constant.

The basic curvature G is accomplished by fastening the naturally flat or level polishing film to an elastic carrier layer partly reflecting the convex shape of the basic body. The carrier layer itself is a hollow cylinder, with no curvature at the contact zone or at the top or bottom side. Alternatively, the basic curvature G can also be an intrinsic part of the polishing film, i.e., generated in a corresponding manufacturing or machining process of the polishing film.

Furthermore, it can be advantageous for the breaking of the edge or the molding of the peripheral curvature g to occur after the fastening on the carrier layer, wherein the polishing film is guided or supported indirectly by the carrier layer when machining the edge. The carrier layer can generally be secured already to a basic body of a polishing head, serving to hold the polishing head in a tool spindle for the machining of the polishing film.

The polishing film can also be machined basically before the fastening onto the carrier layer and for this it is placed in a separate workpiece holder.

The molding of the peripheral curvature g can also be done by a molding process with the use of heat and/or pressure. This depends primarily on the material properties of the polishing film.

The problem is also solved in that a structurized material web is produced before carving out the polishing film, which has several formations whose shape corresponds to a polishing film with a peripheral curvature g arranged in the peripheral zone, and in that the carving out of the respective formation produces a polishing film with a peripheral curvature g situated in the peripheral zone. Since it is not easily possible to mold the peripheral curvature g, especially in the case of materials like duopolistic, a molding of the peripheral curvature g during the generic manufacturing process of the corresponding film or material web is advantageous. The material web is provided with corresponding troughlike formations or indentations during the fabrication, having the geometry of the ultimately desired polishing film with peripheral curvature g. The formations or indentations are cut out or punched out from the material web produced in this way.

BRIEF DESCRIPTION OF THE DRAWINGS

Further benefits and features of the invention are explained in the patent claims and in the specification and represented in the figures. There are shown:

FIG. 1, a sectional representation of a polishing head with various detail views;

FIG. 1a, another detail view,

FIG. 2a, 2b, a perspective diagram of a material web of the film.

DETAILED DESCRIPTION OF THE INVENTION

According to FIG. 1, the polishing head 2 has a basic body 2.2 for seating in a polishing spindle (not shown), an elastic carrier layer 2.1 fastened on the basic body 2.2 and a polishing film 1 fastened on the elastic carrier layer 2.1. The basic body 2.2 has a concavely shaped coupling surface 2.3, on which the carrier layer 2.1 is secured. The elastic carrier layer 2.1 has a contact zone 2.4, on which the polishing film 1 is secured. The contact zone 2.4 and therefore the polishing film 1 are likewise concavely shaped, according to the coupling surface 2.3. The polishing film 1 has a basic diameter D, which is around 15% larger by a width b than a basic diameter D′ of the carrier layer 2.1. Therefore, a radial projection of the polishing film 1 results, whose configuration shall be described hereafter by means of the detail views D1, D2 and D3, as well as FIG. 1b. The elastic carrier layer 2.1 has a convex top side, following the shape of the coupling surface 2.3 of the basic body 2.2, with a basic curvature G, whose radius of curvature thanks to the elasticity of the carrier layer 2.1 is somewhat larger than that of the coupling surface 2.3.

According to detail view D1, the polishing film 1 has a peripheral zone 1.4, which extends for a width b, which corresponds to 5% of the diameter D of the polishing film 1. Within this peripheral zone 1.4, a peripheral curvature g is formed on the polishing film 1, which differs in size from the basic curvature G.

The peripheral curvature g is superimposed on the basic curvature G. The polishing film 1 has a polishing surface 1.1 which can be placed against the spectacle lens 3, which according to detail view D1 runs radially outward across the peripheral zone 1.4 as far as one edge 1.3. The edge 1.3 constitutes the boundary between the polishing surface 1.1 and a peripheral surface 1.2 adjoining the polishing surface 1.1. Thanks to the shaping of the peripheral curvature g, the edge 1.3 is given a sufficiently large distance from a rear side 3.2 of a plastic spectacle lens 3 which can be placed against the polishing surface 1.1 according to the basic curvature G. Thus, the plastic spectacle lens 3 does not come into contact with the edge 1.3 and at least a part of the peripheral zone 1.4.

The peripheral surface 1.2 in the region of the edge 1.3 makes an angle of around 90° with the polishing surface 1.1. This geometry results from the punching out process of the polishing film 1 from a material web forming the polishing film 1 by means of a cup-shaped punching tool.

According to detail view D2, the polishing film 1 has a radius r in the region of the edge 1.3 so that the former edge 1.3 is broken. Thanks to the radius r, a transitional zone z is formed between the peripheral surface 1.2 and the polishing surface 1.1, which runs tangentially into the polishing surface 1.1. Depending on a thickness d of the polishing film 1 on the one hand and the chosen radius r on the other hand, a remaining height h is produced for the peripheral surface 1.2, which is preferably not larger than 50% of the thickness d. Thanks to the forming of the radius r, it is not necessary to form a peripheral curvature g, as shown in detail view D1. Even so, both the peripheral curvature g and the radius r can also be provided.

According to detail view D3, as an alternative to the radius r described in detail view D2 there is provided a chamfer f on the edge 1.3. The chamfer f has the dimensions f1, f2. The two dimensions f1, f2 are chosen such that a transition between the chamfer f and the polishing surface 1.1 is as smooth as possible. In keeping with the remarks on the radius r, a remaining height h of the peripheral surface 1.2 results, depending on the particular dimensions f1, f2 for the chamfer f on the one hand and the thickness d of the polishing film 1 on the other hand.

The polishing head 2 can be positioned with the polishing film 1 against a plastic spectacle lens 3 or a rear side of the spectacle lens 3 for the purpose of polishing the rear side 3.2. Depending on the plastic spectacle lens 3 or plastic spectacle lens semifinished product used, the polishing head 2 will in addition or alternatively to the rear side 3.2 of the spectacle lens 3 also polish a front side 3.1 of the spectacle lens 3.

For the purpose of forming the radius r or the chamfer f, the use of a cutting tool is provided, such as a grinding tool or a milling cutter. The forming of the peripheral curvature g is done by the use of an appropriate mold.

According to FIG. 1a, the radius r is chosen such that the polishing film 1 runs out to a point at the edge 1.6. The radius r makes an angle α of around 40° with a supporting surface 1.5 lying opposite the polishing surface 1.1. At the edge 1.6, the angle α subtended between the radius r or the chamfer f and the supporting surface 1.5 should not be less than 30°, so that the polishing film 1 does not tear.

According to FIG. 2a, 2b, the structurized material web 4 of the polishing film 1 has several formations 4.1, 4.1′, whose shape corresponds to a polishing film 1 with a peripheral curvature g situated in the peripheral zone 1.4. According to FIG. 2a, the formation 4.1 is configured to be upwardly projecting, while according to FIG. 2b the formation 4.1 is downward projecting. By cutting or punching along the peripheral line, the respective formation 4.1 is carved out and thus one obtains a polishing film 1 with a peripheral curvature g situated in the peripheral zone 1.4, such as is secured on the carrier layer according to detail view D1. The polishing film 1 shown here has no basic curvature G. It is given such curvature by being fastened to the convex shaped elastic carrier layer 2.1.

LIST OF REFERENCE SYMBOLS

• 1 polishing film
• 1.1 polishing surface
• 1.2 peripheral surface
• 1.3 edge
• 1.4 peripheral zone
• 1.5 support surface
• 1.6 edge
• 2 polishing head
• 2.1 elastic carrier layer, carrier layer
• 2.2 basic body
• 2.3 coupling surface
• 2.4 contact zone
• 3 plastic spectacle lens, spectacle lens
• 3.1 front side
• 3.2 rear side
• 4 material web
• 4.1 formations
• 4.1′ formations
• b width
• D basic diameter
• D′ basic diameter
• d diameter of 1
• f chamfer
• f1 dimension
• f2 dimension
• G basic curvature
• g peripheral curvature
• h height of 1.2
• r radius of 1.3
• RG radius of the basic curvature
• Fg radius of the peripheral curvature
• U projection
• z transition zone
• α angle

Claims

1. A polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, comprising: a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is formed between the polishing surface and the peripheral surface, wherein the edge has a radius r of at least 0.2 mm to 10 mm.

2. A polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, comprising: a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is formed between the polishing surface and the peripheral surface, wherein the edge has a chamfer f with a dimension of f1×f2, where the dimension f1 or f2 is at least 0.2 mm to 10 mm.

3. The polishing film according to claim 1, wherein the radius r is worked into the polishing film by a cutting process or a grinding process.

4. A polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, comprising: a polishing surface which can be positioned against the spectacle lens, having a basic diameter D, wherein the polishing film is secured to an elastic carrier layer with a diameter D1 and the polishing surface has a peripheral zone with a width b of at most 0.1 D to 0.3 D, wherein the diameter D1 is: D1=D−2b or D1<D−2b and

the polishing film in the unused state prior to being placed against a spectacle lens

a1) has a basic curvature G with a radius RG>=70 mm and in addition to this it has a peripheral curvature g with a radius Rg<=0.5 G, the peripheral curvature g being confined to the peripheral zone, or

a2) the polishing film is formed with no basic curvature G and it has a peripheral curvature g with a radius Rg<=35 mm, the peripheral curvature g being confined to the peripheral zone.

5. The polishing film according to claim 4, wherein the peripheral curvature g is limited to a maximum of 10% of the peripheral zone.

6. A polishing head with a polishing film according to claim 1 for zone polishing of a spectacle lens.

7. A method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, being bounded by a peripheral surface, while an edge is formed between the polishing surface and the peripheral surface, comprising the steps of:

a) carving the polishing film out from a web of material,

b) bringing the polishing film up to a cutting tool and the edge is broken off by the cutting tool.

8. A method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, having a basic diameter D, comprising the steps of:

a) carving the polishing film out from a web of material, wherein the polishing surface has a peripheral zone with a width of at most 0.3 D,

b1) providing the polishing film with a basic curvature G, with G>=70 mm, and in addition to this it is provided with an extra peripheral curvature g in a shaping process in the peripheral zone, prior to the use for a spectacle lens being manufactured, with a radius Rg<=0.5 G, or

b2) configuring the polishing film without a basic curvature G, and it is provided with a peripheral curvature g located exclusively in the peripheral zone in a shaping process prior to the use for a spectacle lens being manufactured.

9. The method for producing a polishing head with a polishing film according to claim 7, wherein the polishing film is secured to an elastic carrier layer of a polishing head, wherein the breaking of the edge occurs after the fastening on the carrier layer, wherein the polishing film is guided or supported indirectly by the carrier layer when machining the edge.

10. A method for producing a polishing film for a polishing head for plastic spectacle lenses for zone polishing of a front side or rear side of the spectacle lens, with a polishing surface which can be positioned against the spectacle lens, having a basic diameter D, wherein the polishing surface has a peripheral zone with a width of at most 0.3 D, comprising the steps of:

a) carving several polishing films out from a material web,

producing a structurized material web before step a), which has several formations whose shape corresponds to a polishing film with a peripheral curvature g arranged in the peripheral zone, and wherein the carving out of the polishing film from the structurized material web at the periphery of the respective formation produces a polishing film with a peripheral curvature g situated in the peripheral zone.

11. The polishing film according to claim 2, wherein the chamfer f is worked into the polishing film by a cutting process or a grinding process.

12. A polishing head with a polishing film according to claim 2 for zone polishing of a spectacle lens.

13. A polishing head with a polishing film according to claim 4 for zone polishing of a spectacle lens.

14. The method for producing a polishing head with a polishing film according to claim 8, wherein the polishing film is secured to an elastic carrier layer of a polishing head, wherein the molding of the peripheral curvature g occurs after the fastening on the carrier layer, wherein the polishing film is guided or supported indirectly by the carrier layer when machining the edge.