US20020031993A1

US20020031993A1 - Receiving chuck for optical components for the purpose of precision-grinding and/or polishing

Info

Publication number: US20020031993A1
Application number: US09/961,408
Authority: US
Inventors: Eginhard Jung; Guenther Boehm; Michael Thomas; Helmut Lotz
Original assignee: Leica Camera AG
Current assignee: Leica Camera AG
Priority date: 2000-01-27
Filing date: 2001-09-25
Publication date: 2002-03-14
Also published as: CZ20013364A3; DE10003291C2; WO2001054861A1; EP1165286B1; ATE256528T1; JP2003520694A; CZ294053B6; DE50101171D1; EP1165286A1; DE10003291A1

Abstract

A chuck for optical components for fine grinding and/or polishing, has a plurality of supporting elements (9) of elastic material for the components and an arrangement for feeding or discharging air relative to the rear side of each supporting element. The chuck has a basic body (1) with a spindle shank (2) having a central bore (3) and a cover part (6) for accommodating the supporting elements. The basic body (1) is designed in a pot shape (5) with an encircling rim (4), and the cover part (6), provided with a flat base area, is put onto the rim (4) in an airtight manner. The cover top side (15) has cylindrical recesses (8) which lie symmetrically to the axis (17) of the spindle shank (2) and are designed for the insertion of the elastic supporting elements (9). Each of the recesses (8) is fluidly connected to the common pot space (5) of the basic body (1) via at least one bore (13). The elastic supporting element is designed as a hat-shaped diaphragm part (9), with an outwardly pointing hat brim (10) which rests on the base of the recess (8) and is held in a groove (11) of the recess (8) in an airtight manner via an O-ring (12). The elastic supporting element can also be inserted into a cylindrical holder (19) which is supported in the recess via a rotary bearing (21).

Description

This application is a continuing application of pending PCT application PCT/DE01/00241, filed on Jan. 19, 2001, and published in German on Aug. 2, 2001 as WO 01/54861. The applicants hereby claim the benefit under 35 U.S.C. 120 of this PCT application, and under 35 U.S.C. 119 of German application 100 03 291.5, filed Jan. 27, 2000. The entire contents of this PCT application and this German application are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a chuck for optical components for fine grinding and/or polishing, having a plurality of supporting elements of elastic material for the components and an arrangement for feeding or discharging air relative to the rear side of the supporting element, the chuck having a basic body with a spindle shank having a central bore and a cover part for accommodating the supporting elements. The optical components provided are preferably spherical convexly or concavely curved lenses.

German Publication DE 198 12 186 A1 discloses a chuck of this type for machining individual lenses. The lens holder consists of a rotationally symmetrical basic body with a recess, into which a lens to be machined is inserted and which is closed off toward the other side by a rubber diaphragm. Compressed air can be admitted to the rubber diaphragm at its rear side via a central bore in the shank of the chuck. When the rubber diaphragm then extends, it bears against the lens and presses the latter uniformly against the polishing tool. Surface contact occurs in the process, since both parts have the same radius of curvature. By producing a vacuum at the diaphragm surface, the lens can be drawn against the diaphragm surface and put into a suspended position.

Different bearing pressures by the diaphragm surface may occur on account of the dead weight of the lens. Since, during polishing, not only is the surface quality improved but corrections in the lens geometry within a fine range are also carried out. A varying bearing pressure leads to inaccuracies in the lens surface. The suspended mounting of the lens is therefore preferably selected, so that its dead weight assists the bearing pressure relative to the polishing tool after the diaphragm has been vented for the polishing operation. In the case of a horizontal mounting, the uniformity of the bearing pressure can be assisted, for example, by different thicknesses in the diaphragm. The centrally supplied compressed-air quantity can be adapted individually to the lens to be machined.

In the case of thinner lenses, in which the ratio between lens diameter and average thickness is high, aspherical deformation of the lens body may occur to an increased extent on account of different bearing pressures, this deformation likewise having a considerable adverse affect on the quality of the polishing result.

To avoid such effects, European Publication EP 0 169 931 A1 discloses a chuck with which supporting zones having different bearing pressure can be produced in the diaphragm surface by the supply of differently controlled air pressures. For the chuck described, an embodiment for the simultaneous mounting of a plurality of lenses is also described.

Such a chuck has a basic body and a supporting body connected to it. The supporting body is provided with a cap-shaped covering, which is held by an enclosing ring on the basic body. A plurality of recessed portions are provided in the supporting body symmetrically to the rotational axis of the supporting body. In the region of these recessed portions, the cap-shaped covering forms an elastic diaphragm, on which the lenses to be machined rest with their central region. The mounting of the lens as a whole is formed by a shaped portion in the cap-shaped covering, this shaped portion being adapted to the lens diameter.

The basic body has a shank for holding the chuck in a machine tool. In the region of the shank, the basic body contains a central aperture for the air feed. Each of the recessed portions in the supporting body is connected to the central aperture in the basic body by a separate air passage, and the respective diaphragm parts of the covering are fixed in the recessed portion and close off the latter in an airtight manner. Via a passage inside the central aperture and through the supporting body, this passage is separate from the other air passages, and compressed air can be admitted to the remaining bottom surface of the covering. In this way, supporting zones with different pressure can be produced inside each lens seating. The covering has a complex shape and requires complicated assembly on the supporting body. Although the air feed can also be controlled individually in the diaphragm parts, the local pressure build-up under the remaining surface of the covering cannot be influenced via the central air feed.

U.S. Pat. No. 2,509,211 discloses a device with which a plurality of lenses can be mounted on a convex cup. To this end, the cup contains a plurality of recesses in which adjustable knife-edge seatings of metal can be inserted as essential functional elements. The cup is designed as a hemispherical shell which is closed with a base plate. A bore leads from the recesses into the cup interior space. A hollow shank is fastened centrally to the base plate, this hollow shank likewise being connected via a bore to the cup interior space. The hollow shank is connected to a vacuum line, so that the lenses placed on the knife-edge seatings are held by the vacuum. The device serves to feed the lenses, preadjusted on the cup via the knife-edge seatings, into the bed of a concave grinding or polishing cup in such a way as to be oriented in position.

SUMMARY OF THE INVENTION

An object of the invention is to provide a chuck which permits multiple mounting having the advantages of single mounting through the use of mass-produced diaphragm elements and is of simple design.

Systematic tests with direct air feed to individual supporting elements in a multiple mounting have shown that the machining qualities of the simultaneously machined lenses are markedly different from one another. However, it surprisingly transpires that, by means of a common air reservoir in the chuck, to which the individual recesses are connected to the supporting elements via one or more short air passages, the machining quality of the lenses machined together turns out to be markedly more uniform. The requisite pot volume for the air reservoir can be adapted in a simple manner to the different lens diameters and lens weights via the rim height of the basic body. The cover parts are screwed to the basic body and form a reliable closure of the air reservoir by means of an O-ring seal. In this way, the cover parts can be quickly exchanged.

The recesses in the cover part can be prepared for commercially available elastic supporting elements having different dimensions. The fastening and sealing via an O-ring pressed into a groove permits simple assembly and also acts as a pressure relief device. If air pressure reaches the diaphragm unintentionally without a lens being properly seated and a polishing tool being brought up to the lens, the supporting element is pushed out of the holder without being destroyed.

In addition to a uniform bearing pressure between a lens surface and the polishing tool, their relative movements are also of importance for the machining quality of the lens surface and the machining time. By the arrangement of the supporting elements in a cylindrical holder which is mounted so as to be rotatable in the recess of the cover part, an additional relative movement of the individual lenses on the common chuck can be realized. In an advantageous manner, the holder can be provided with a drive spindle which extends into the space of the basic body and is connected here to the drive for the spindle shank via gearing means.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the chuck are schematically shown in the drawings and are described in more detail below with reference to the figures. In the drawings: [0014]
FIG. 1 shows a chuck with supporting elements firmly inserted into the cover part, and [0015]
FIG. 2 shows a chuck with supporting elements inserted into the cover part in a rotatable manner.[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The chuck according to FIG. 1 contains a [0017] basic body 1 with a spindle shank 2 which is inserted into a machine spindle (not shown in any more detail) for rotating the chuck. The spindle shank 2 is provided with a central bore 3 which is connected to a compressor vacuum system (likewise not shown) for the air supply. The basic body 1 has an encircling rim 4 which forms a pot-shaped space 5 in the basic body 1, this pot-shaped space 5 extending over the entire base area of the basic body 1.
Lying on the [0018] rim 4 of the basic body 1 is a cover part 6, which is screwed to the basic body 1 and closes the pot (that is, cylindrical) space 5 via an O-ring seal 7. The cover part 6 has a cylindrical recess 8. An elastomeric supporting element, which in this case is designed as a hat-shaped diaphragm part 9 with a hat brim 10 pointing outward, lies on the base of the recess 8. Such diaphragm parts 9 are available as mass-produced parts for individual lens receptacles. The hat brim 10 engages in a groove 11 in the recess 8 and is firmly pressed here onto the base of the recess 8 by an O-ring 12. That spatial region of the recess 8 which lies below the diaphragm part 9 is fluidically connected to the pot space 5 via a bore 13. Of course, further bores, also of different diameter, may be provided for more rapid air supply if required. A lens 14 to be machined is placed with its convex lens side onto the diaphragm part 9. Here, the lens surface to be machined is slightly concave. The top side 15 of the cover part 6 is adapted to the concave lens surface in a conventional manner with a slightly larger radius, so that the schematically indicated polishing cup 16 can machine the lens surface without hindrance. To this end, a positive pressure is produced in the space below the diaphragm part 9 via the air reservoir built up in the pot space 5 and via the bore 13, and this positive pressure elastically deforms the diaphragm part 9 until it bears against the surface of the lens 14 in a positive-locking manner.
Further recesses [0019] 8 with diaphragm parts 9 inserted in the same way are provided in the cover part 6 symmetrically to the axis 17 of the spindle shank 2. Three lenses 14 are preferably machined simultaneously.
An exemplary embodiment shown in FIG. 2 is based on the same basic construction as in FIG. 1. The same parts are provided with the same reference numerals. In this case, however, the [0020] cylindrical recess 8 is designed as a cylindrical bore 18, into which a cylindrical holder 19 is inserted, this holder 19 having the same holding elements for the diaphragm part 9 as in FIG. 1. The holder 19 is provided with a drive spindle 20 which is provided with a bore 13 for the fluid connection to the pot space 5 and extends into the pot space 5. The drive spindle 20 is held in the base of the cylindrical bore 18 by a rotary bearing 21, so that the holder 19 is rotatable about its axis 22. The drive spindle 20 is provided with gearing means 23 (not shown in any more detail), which are coupled, for example, to the drive for the spindle shank 2 via a bevel gear 24.
A convex lens surface is provided here for the machining, so that the [0021] top side 15 of the cover part 6 is of corresponding convex shape. In this case, the axis 22 is inclined with respect to the axis 17 of the spindle shank 2. For machining a concave lens surface, the axis 22 would be directed away from the axis 17. The different direction of the rotational axes relative to the central drive means can be compensated for by appropriately shaped bevel gears 24 as part of the gearing means 23.
The invention is not limited to the embodiments described above. Variations and modifications of the invention will occur to those skilled in the field, after receiving the above teachings. The invention is thus defined with reference to the following claims. [0022]
List of Designations [0023]
[0024] 1 Basic body
[0025] 2 Spindle shank
[0026] 3 Central bore
[0027] 4 Rim
[0028] 5 Pot space
[0029] 6 Cover part
[0030] 7 O-ring seal
[0031] 8 Recess
[0032] 9 Diaphragm part
[0033] 10 Brim
[0034] 11 Groove
[0035] 12 O-ring
[0036] 13 Bore
[0037] 14 Lens
[0038] 15 Cover part, top side
[0039] 16 Polishing cup
[0040] 17 Spindle shank axis
[0041] 18 Cylindrical bore
[0042] 19 Holder
[0043] 20 Drive spindle
[0044] 21 Rotary bearing
[0045] 22 Holder axis
[0046] 23 Gearing means
[0047] 24 Bevel gear

Claims

What is claimed is:

1. A chuck for optical components for fine grinding and/or polishing, comprising:

a plurality of supporting elements of elastic material for the components and an arrangement for feeding or discharging gas relative to a rear side of a supporting element, the chuck comprising a basic body with a spindle shank having a central bore and a cover part for accommodating the supporting elements, wherein

a) the basic body has a pot shaped space and an encircling rim,

b) the cover part includes a flat base area which is jointed to the rim in a gas-tight manner, and

c) a cover part top side has cylindrical recesses which lie symmetrically to an axis of the spindle shank and elastic supporting elements inserted in the cylindrical recesses, each of the recesses being fluidly connected to the common pot shaped space of the basic body via at least one bore.

2. A chuck for optical components for fine grinding and/or polishing, comprising:

a) the basic body has a pot shaped space and an encircling rim,

c) a cover part top side has cylindrical recesses which lie symmetrically to an axis of the spindle shank and elastic supporting elements inserted in the cylindrical recesses, each of the recesses being fluidly connected to the common pot shaped space of the basic body via at least one bore, and wherein an elastic supporting element is inserted into a cylindrical holder which is supported in at least one of said recesses via a rotary bearing.

3. A chuck as claimed in claim 2, wherein an elastic supporting element has a hat-shaped diaphragm part, and an outwardly pointing brim which rests on a base of the cylindrical holder and is held in a groove of the cylindrical holder in a gas-tight manner via an O-ring.

4. A chuck as claimed in claim 2, wherein the cylindrical holder has a drive spindle leading into the pot shaped space.

5. A chuck as claimed in claim 4, wherein the drive spindle is coupled to a drive of the spindle shank via a gear assembly.

6. A chuck as set forth in claim 1, wherein an elastic supporting element has a hat-shaped diaphragm part, and an outwardly pointing brim which rests on a base of a cylindrical recess and is held in a groove of the recess in a gas-tight manner via an O-ring.

7. A chuck as claimed in claim 1, wherein an elastic supporting element has a hat-shaped diaphragm part, and an outwardly pointing brim which rests on a base of a cylindrical recess and is held in a groove of the cylindrical recess in a gas-tight manner via an O-ring.

8. A chuck as claimed in claim 3, wherein the cylindrical holder has a drive spindle leading into the pot shaped space.