Source: http://www.google.com/patents/US7066794?dq=6,123,819
Timestamp: 2017-06-24 10:06:24
Document Index: 388324956

Matched Legal Cases: ['in fine', 'art 34', 'art 34', 'art 34', 'art 86', 'In fine']

Patent US7066794 - Tool for fine machining of optically active surfaces - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA tool (10) is disclosed for fine machining of optically active surfaces (F), with a base body (12) that can be attached to a tool spindle of a machine tool, and an elastic membrane (14) that has a machining section (16) to which connects a gaiter section (18) by means of which the membrane is attached...http://www.google.com/patents/US7066794?utm_source=gb-gplus-sharePatent US7066794 - Tool for fine machining of optically active surfacesAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7066794 B2Publication typeGrantApplication numberUS 10/834,720Publication dateJun 27, 2006Filing dateApr 29, 2004Priority dateMay 2, 2003Fee statusPaidAlso published asDE10319945A1, DE502004000096D1, EP1473116A1, EP1473116B1, US20040224619Publication number10834720, 834720, US 7066794 B2, US 7066794B2, US-B2-7066794, US7066794 B2, US7066794B2InventorsGilles Granziera, Reiner Herold, Peter Philipps, Karl-Heinz TroβOriginal AssigneeSatisloh GmbhExport CitationBiBTeX, EndNote, RefManPatent Citations (9), Referenced by (23), Classifications (9), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetTool for fine machining of optically active surfaces
US 7066794 B2Abstract
A tool (10) is disclosed for fine machining of optically active surfaces (F), with a base body (12) that can be attached to a tool spindle of a machine tool, and an elastic membrane (14) that has a machining section (16) to which connects a gaiter section (18) by means of which the membrane is attached to the base body such that it can be rotated therewith. The base body and the membrane delimit a pressure medium chamber (20) which via a channel (22) can be optionally pressurized with a pressure medium in order to apply a machining pressure via the machining section during machining of the optically active surface. A guide element (24) guided longitudinally mobile on the base body is actively connected with the machining section so that the machining section can be moved in the longitudinal direction of the guide element and held in the transverse direction to the guide element, although under an elastic deformation of the gaiter section it is tilt-mobile in relation to the guide element. The result is a tool of simple design and reliable function which has an excellent adaptability to a wide range of geometries to be machined.
10. Tool (10) according to claim 9, wherein the reinforcement (88) in cross-like arrangement has four sets of slots (90, 92) essentially parallel in each set, which extend inwards from the edge (94) of the reinforcement (88) and there end at a slot-free area (96) of the reinforcement (88) which essentially has the form of an “X” curved inwards on both sides.
The present invention relates to a tool for fine machining of optically active surfaces such as is used for example in lens production in fine machining of optical lenses. In particular the invention relates to a tool for fine machining of free form surfaces and toric surfaces on spectacle lenses.
When the description below uses the term “spectacle lenses” as an example of optical workpieces, these refer not only to spectacle lenses of mineral glass but also to spectacle lenses of all other conventional materials e.g. polycarbonate, CR 39, HI index, etc. i.e. also plastics.
The invention consequently is based on the object of creating a tool designed as simply as possible with reliable function for fine machining of optically active surfaces, in particular free form surfaces and toric surfaces on spectacle lenses, which has good adaptability to a wide range of geometries to be machined.
Because of the pressurisability of the elastic membrane via the pressure medium chamber, the axial mobility of the machining section of the membrane guided by the guide element, its tilt-mobility in relation to the guide element and the elastic deformability of the gaiter section of the membrane, the tool according to the invention can be adapted excellently to the geometry of the surface to be fine machined. At the same time the guide element of the tool according to the invention, by holding the machining section of the membrane in the transverse direction, ensures excellent guidance of the machining section close to the surface to be fine machined as the guide element is actively connected with the machining section so that the torsional and transverse forces necessary for machining can be reliably transferred to the surface to be fine machined while undesirable tilting forces are avoided. This excellent adaptability of the tool and very good guidance of the machining section of the membrane are not reduced by the torque transfer—necessary in any case—from the base body of the tool to its membrane as this torque transfer takes place via the gaiter section of the membrane i.e. functionally separately from the guide element. Also finally no complex construction of the tool is required. As a result of the design of the tool according to the invention, the tool can firstly adapt to virtually arbitrary geometries or curvatures of the surfaces to be fine machined and secondly reliably transfer the process forces necessary for machining for example to a fine grinding or polishing film. Also the tool is able to eliminate kinematic roughness of the pre-machined surface e.g. turning or milling grooves, by smoothing the structure.
In an advantageous embodiment of the invention it can be provided that the machining section of the membrane is stiffened by means of an areal reinforcement. This measure compensates in particular for the long wave unevenness which can result from the pre-machining structures (kinematic roughness in the form of turning or milling grooves), due to the greater removal of the raised parts of the turning or milling structure, whereby the fine machined surface is smoothed. Also the reinforcement ensures a better pressure distribution during fine machining. The reinforcement can essentially be preformed spherical which—compared with a flat form of the reinforcement which is also possible—ensures better deformability of the reinforcement and hence better adaptability of the machining section of the membrane to the surface to be machined.
For better adaptation to non-rotationally symmetrical, especially toric surfaces, in particular those with high cylinder power i.e. great discrepancy between the base and cylinder curves, the reinforcement of the machining section can also have different flexional rigidities in two planes running perpendicular to each other or in the directions of the base and cylinder axes of the torus. This can for example be achieved if the reinforcement in a cross-like arrangement has four sets of slots essentially parallel in each set, which extend from the edge of the reinforcement towards the inside and there end at a slot-free area of the reinforcement which essentially has the form of a “X” curved inwards on both sides, whereby the slots in the one direction on average have a different length from the slots in the direction perpendicular to this.
The invention is now explained below with reference to preferred embodiments using the enclosed drawings, where the same or corresponding parts carry the same reference signs. The drawings show:
According to FIG. 1 a tool 10 for fine machining of optically active surfaces F, in particular for free form surfaces and toric surfaces on spectacle lenses L, has a base body 12, which can be attached to a tool spindle (not shown) of a machine tool known in itself (also not shown). Furthermore the tool 10 has an elastic membrane 14 that has a machining section 16 attached to which is a gaiter section 18, by means of which the membrane 14 is attached to the base body 12 so that it can rotate therewith. The base body 12 and the membrane 14 delimit a pressure medium chamber 20 of the tool 10 which via a channel 22 can be pressurized optionally with a suitable liquid or gaseous pressure medium (e.g. oil or compressed air with a pressure of around 0.2 to 0.6 bar), in order during machining of the optically active surface F to exert a machining pressure via the machining section 16. Guided longitudinally mobile on the base body 12 is a guide element 24, which as will be described in more detail below, is actively connected with the machining section 16 of the membrane 14 so that the machining section 16 is held mobile in the longitudinal direction of the guide element 24 and fixed in the transverse direction to the guide element 24, although under an elastic deformation of the gaiter section 18 of the membrane 14 it is tilt-mobile in relation to the guide element 24.
In the direction of membrane 14, after the step 30 of the head section 28 via a further ring shoulder 40 is a further cylindrical step 42 of smaller diameter which is fitted with a radial groove 44 for a form fit fixing of the membrane 14 to the base body 12. An area protruding in the axial direction over the ring shoulder 40 of a cylindrical inner peripheral surface of the ring part 34, the ring shoulder 40 and the step 42 with the radial groove 44 of the head section 28, delimit an annular receiving chamber for a slotted ring 46 and an annular fixing end section 48 of the gaiter section 18 of the membrane 14. By means of the ring 46 preferably made of POM (polyoxymethylene, e.g. Delrin® by Dupont), the membrane 14 is attached, by form fit in the tension and pressure direction and by friction fit in the peripheral direction, i.e. rotationally fixed to the base body 12. More precisely the fixing end section 48 of the membrane 14 on the inner periphery side has a radially inwardly protruding peripheral lug 50 which engages form fit in the radial groove 44 of the step 42 on the head section 28. On the outer periphery side the fixing end section 48 is itself fitted with a radial groove 52 which engages with form fit in a peripheral lug 54 protruding radially inwards and formed on the inner periphery of the ring 46. The ring 46 itself lies with a cylindrical outer peripheral surface flat on the inner peripheral surface of the ring part 34. It is clear that the membrane 14 is thus held firmly on the base body 12 by means of the ring part 34 and the ring 46.
The membrane 14 is comprised of an elastomer material such as NBR (elastomer based on acrylonitrile-butadiene-styrene rubber), EPDM (elastomer based on ethylene-propylene-diene rubber), or PUR (polyurethane) elastomer (e.g. Vulkollan® by Bayer), with a Shore A hardness of 45 to 70, preferably 55 to 60. In the area between the fixing end section 48 and the machining section 16, the membrane 14 according to the embodiment shown has three folds 56, where the last i.e. the upper fold 56 starting from the base body 12 transforms directly into the machining section 16 of the membrane 14. The machining section 16 of the membrane 14 in the embodiment shown is circular viewed in a top view from above in FIG. 1 and, as the section view shows, has an essentially spherical preformation so that the machining section 16 curves away from the base body 12.
On the outside of the machining section 16 of the membrane 14 facing away from the pressure medium chamber 20 is glued an elastic, abrasion-resistant fine grinding or polishing compound carrier 58 also called a “polishing pad”, as available commercially. On the inside of the machining section 16 of the membrane 14 facing the pressure medium chamber 20, the machining section 16 has a hollow cylindrical extension 60 formed essentially centrally of one piece with the membrane 14, which on its free end has a collar 62 protruding radially inwards so that the extension 60 together with the collar 62 delimits an undercut receiving chamber 64.
These movement possibilities of the machining section 16 of the membrane 14 are shown in FIGS. 2 and 3. Here the tool 10 with the machining section 16 of the membrane 14 is in contact with the optically active surface F to be machined of a spectacle lens L which has a toric geometry. The spectacle lens L is blocked onto a block piece 86 as known from German standard DIN 58766. In FIG. 3 in comparison with FIG. 2, the block part 86 with the spectacle lens L and the tool 10 are merely rotated further in the same direction by 90° about their respective axes without this leading to movement of the entire tool 10 or the block piece 86 in the vertical or horizontal direction and without a swivel movement between the spectacle lens L and the tool 10.
In fine machining of the optically active surface F to be machined of the spectacle lens L which takes place in the known manner by means of non-bonded grains that are supplied by means of a suitable fluid to the contact point between the tool 10 and the spectacle lens L, the tool 10 and the spectacle lens L are driven in a known manner, essentially in synchrony i.e. in the same direction and at essentially the same speed (approximately 800 to 1000 revolutions per minute), the tool 10 and the spectacle lens L being at the same time swiveled relative to each other so that the area of contact between the tool 10 and the spectacle lens L continuously changes. This fine machining process in which, in the case of machining of free form surfaces, the swivel movement takes place in a fixed setting about the center point of a “best fit radius” i.e. an approximate center point of the surface F to be machined of the spectacle glass L, or the relative movement between the tool 10 and the spectacle lens L is generated by a track-controlled process in two CNC linear axes and one CNC swivel axis, has been known to the person skilled in the art for some time and will not therefore be described in more detail at this point.
This reinforcement 88 achieves two main effects: firstly the reinforcement 88 stiffens the machining section 16 of the membrane 14 such that the machining section 16 is not so flexible that it can adapt to the long wave kinematic roughness which can occur if the premachining of the spectacle lens L takes place by means of turning or milling, rather it is sufficiently rigid to smooth out these roughnesses. Secondly the reinforcement 88 because of its plastic deformability is able to give the machining section 16 a preselectable geometry corresponding to the machining requirements, where the reinforcement 88 again because of its inherent rigidity prevents the machining section 16 from specifying its own geometry thanks to its shape “memory” due to its formation from an elastomer.
In the embodiment shown here the reinforcement 88 is furthermore formed especially for the fine machining of non-rotationally symmetrical, in particular toric surfaces F, as it has been given different flexional rigidities in two planes running perpendicular to each other. This as shown in FIG. 5 would be achieved by a cross-shaped arrangement of four sets of slots 90, 92 essentially parallel in each set which extend inwards from the edge 94 of the reinforcement 88 and there end on a slot-free area 96 of the reinforcement 88 which essentially has the form of an “X” curved inwards at both sides. In other words, in the embodiment shown, the slots 90 of each set of slots 90 at their inner end are delimited by an imaginary circle arc K90 (in FIG. 5 shown only for the left-hand side) drawn about a center point M lying on the axis BK. An imaginary circle arc K92 drawn about the same center point M with a larger radius and running through the center Z of the reinforcement 88 limits the adjacent outer slots 92 of the two other sets of slots 92. In FIG. 5 figures BK and ZK also indicate the alignment of the reinforcement 88 in relation to the base curve or cylinder curve of the toric surface F to be fine machined.
In the embodiment according to FIG. 6 a reinforcement 88 is also provided. Also the membrane 14 in this embodiment has an elastic intermediate layer 98 which is applied to the side of the machining section 16 facing away from the pressure medium chamber 40 above the reinforcement 88 on the machining section 16 of the membrane 14 by means of a suitable adhesive and has the same outer diameter as the machining section 16. The intermediate layer 98 here is comprised of a PUR (polyurethane) foam (e.g. Aclacell® by Aclawerken) and has a Shore A hardness of 35 to 60, preferably 45 to 50. This intermediate layer 98 is primarily intended for the fine machining of free form surfaces so that here transitions between surface areas of different geometry can be polished out cleanly.
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