EP1866124A1

EP1866124A1 - Optical lens grinding machine provided with an inclined finishing grinding wheel and a corresponding optical lens

Info

Publication number: EP1866124A1
Application number: EP06726126A
Authority: EP
Inventors: Jean Meunier; Jean-Jacques Videcoq; Bruno Bizet
Original assignee: Briot International SA
Current assignee: Briot International SA
Priority date: 2005-04-07
Filing date: 2006-03-22
Publication date: 2007-12-19
Also published as: KR20080002930A; FR2884163A1; FR2884163B1; CN100558509C; CN101155664A; WO2006106200A1

Abstract

The inventive machine (11) comprises a lens holder (19) provided with means (31) for rotationally driving a lens (15) around a first axis (A-A') and a finishing grinding wheel (49) provided with a peripheral groove (55) for forming a bevel edge (16) on the peripheral surface (13) of the lens (15). The finishing grinding wheel (49) is mounted in such a way that it is rotatable around a second axis (C-C'). The machine (11) comprises means (23) for displacing the finishing grinding wheel (49) with respect to the lens holder (19) in such a way that said finishing grinding wheel (49) is brought into active bevelling position. The displacing means (23) comprise inclination means (43) for inclining the second axis (C-C') with respect to the first axis (A-A').

Description

Optical lens grinding machine with an inclined finishing wheel and corresponding optical glass.

The present invention relates to a machine for grinding optical glasses, of the type comprising:

- an optical lens support, provided with means for driving a lens in rotation about a first axis; - a finishing wheel having a peripheral groove intended to form a bevel on a peripheral surface of the glass, the finishing wheel being rotatably mounted around a second axis; and

- Means for relative movement of the finishing wheel relative to the glass support to bring the finishing wheel in an active beveling position.

EP-A-1 310 326 discloses a grinding machine of the aforementioned type, comprising a train of grinding wheels which has a roughing grinding wheel and a finishing grinding wheel provided with a circular groove. This machine makes it possible to produce optical lenses or glasses comprising a bevel on a peripheral surface. This bevel is received in a corresponding groove, called a "bezel", provided in the spectacle frame.

To grind such a lens, a blank is machined along its periphery on the roughing wheel to give it the shape of the frame. Then, the rough lens is brought to the finishing wheel to make the bevel.

Such a machine is not entirely satisfactory, in particular for grinding lenses of large curvature and having angular shapes, for example square or rectangular.

In fact, due to the strong curvature of the lens in these angular parts, the lens comes into contact with distinct regions of the finishing wheel during the passage of the latter in the angular parts. The shape and profile of the bevel in these angular parts is thus altered.

An object of the invention is to obtain a bevelling machine which, even with an ophthalmic lens of high curvature and angular shape, makes it possible to obtain a peripheral bevel of satisfactory aesthetic appearance, with a sectional profile suitable for being precisely received in a throat corresponding provided in the frame, this bevel does not weaken the mechanical strength of the lens.

To this end, the invention relates to a machine of the aforementioned type, characterized in that the relative displacement means comprise tilting means adapted to tilt the second axis relative to the first axis.

The machine according to the invention may include one or more of the following characteristics, taken in isolation or in any technically possible combination: - the means for relative displacement comprise means for adjusting the angle of inclination of the second axis with respect to the first axis;

the adjustment means comprise means for calculating the angle of inclination as a function of the curvature and / or of the radius of the glass along its periphery; - The finishing wheel has a substantially cylindrical peripheral finishing surface into which the groove opens, the width of this peripheral surface being greater than the maximum width of the peripheral surface of the glass;

- The finishing wheel has at least one chamfered end intended to perform a beveling of the glass;

the machine comprises a train of grinding wheels mounted to rotate about a grinding wheel axis substantially parallel to the first axis, and an additional tool holder assembly, the finishing grinding wheel being rotatably mounted on the additional tool holder assembly; and - the additional tool holder assembly comprises a creasing disc.

The invention also relates to an optical glass produced by means of the above machine. This optical glass, provided with a bevel on its periphery, is characterized in that, in at least one meridian half-section of the glass, the peripheral surface, on either side of the bevel, is inclined relative to the optical axis of the glass.

In one embodiment, said peripheral surface is inclined relative to the optical axis over substantially the entire periphery of the glass. The invention will be better understood on reading the description which follows, given solely by way of example, and made with reference to the appended drawings, in which:

- Figure 1 is a partial schematic view in elevation of the relevant parts of a first grinding machine according to the invention;

- Figure 2 is an enlarged view of a detail marked II in Figure 1;

- Figure 3 is a perspective view of an angular lens intended to be ground in the first machine according to the invention; and - Figure 4 is a partial perspective view of a second grinding machine according to the invention comprising a train of grinding wheels.

The first grinding machine 11 according to the invention, shown in Figures 1 and 2, is intended to produce a finish on the peripheral surface

13 of an ophthalmic lens or glass 15 by polishing and beveling operations, this lens 15 having been previously roughed by peripheral grinding.

The lens 15 has, after treatment, a bevel 16 projecting radially extending in a middle region of the peripheral surface 13. The profile of the bevel 16 is for example in V. The machine 11 comprises a frame 17, a lens support 19, a tool holder assembly 21, means 23 for axial and radial relative positioning of the assembly 21 relative to the support 19, and a control unit 25.

The lens support 19 comprises a carriage 27 pivotally mounted on the frame 17, provided with two half-shafts 29A, 29B adapted to grip the lens 15, and a motor 31 for driving the lens 15 in rotation.

The carriage 27 is articulated relative to the frame 17, by a rear longitudinal edge 28, around an axis XX ′ of substantially horizontal tilting.

The two half-shafts 29A, 29B are mounted along the front longitudinal edge 32 of the carriage 27. These half-shafts 29A, 29B extend along a first axis AA ′ substantially horizontal parallel to the axis X-X '. The half-shafts 29A, 29B are provided with respective free ends 33A, 33B arranged opposite one another, adapted to grip the lens 15.

The drive motor 31 of the lens 15 drives the half-shafts 29A, 29B in slow rotation around the first axis A-A 'by a transmission mechanism (not shown).

As illustrated in FIG. 1, the tool holder assembly 21 comprises a support 35, a link arm 37 projecting from the support 35, a tool holder shaft 39, a motor 41 for driving in rapid rotation of the tool shaft

39, and means 43 for tilting the tool-holder shaft 39 relative to the support 35.

The link arm 37 is articulated by a first end 45 on the support 21, around a horizontal pivot axis B-B 'substantially orthogonal to the first axis A-A'.

The tool-holder shaft 39 is rotatably mounted at the free end 47 of the link arm, around a second axis C-C substantially orthogonal to the link arm 37.

The shaft 39 carries a finishing wheel 49 and a creasing disc 51. It also carries at its free end a drilling tool 53. The members 49, 51 and 53 have as axis C-C. As illustrated in FIG. 2, the finishing wheel 49 comprises a peripheral cylindrical surface 54 for finishing or polishing, in which a circular groove 55 is formed. The groove 55 has a profile of shape complementary to the profile of the bevel 16 to be produced on lens 15

The width ei of the cylindrical part of the grinding wheel 49, taken parallel to the axis C-C, is greater than the maximum width β2 of the peripheral surface 13 of the lens 15, taken along its edge.

In the example illustrated in Figure 1, the width ei is substantially constant and between 4 and 18 mm.

The creasing disc 51 is thin. In the example illustrated in Figure 1, the thickness of this disc 51 is substantially constant and between 0.5 and 1.6 mm. The presence of the creasing disc 51 and the finishing wheel 49 on the tool holder assembly 21 makes it possible to produce, with the same machine 11, a lens 15 having a bevel 16 or, on the contrary, having a groove in its surface. peripheral 13. As a variant, as indicated in phantom in Figure 2, each end of the grinding wheel 49 can be chamfered, so as to also be able to perform counter-beveling operations on the front and rear edges of the lens.

With reference to FIG. 1, the arm 37, and consequently the tool-holder shaft 39, is movable in rotation about the axis BB 'on an angular displacement of at least 30 ° and preferably 180 °, in can in particular take an upper vertical position in which the second axis CC is substantially parallel to the first axis A-A ', and a plurality of tilt positions in which the second axis CC is inclined relative to the first axis A-A'.

In the example illustrated in Figure 1, the tool shaft 39 remains substantially in the vertical plane which passes through the first axis A-A ', whatever its position around the axis B-B'.

The motor 41 for driving the tool-holder shaft in rotation 39 is fixed to the link arm 37. It is connected to the shaft 39 by transmission means 59 arranged in the arm 37.

The means 43 for adjusting the angle of inclination of the tool-holder shaft 39 comprise a motor 61 for actuating an endless screw 63, and a tangent gear 65, mounted integral with the link arm 37. The worm 63 extends in a direction substantially parallel to the first axis AA ′.

The toothed wheel 65 is fixed on the arm 37 at its free end 45. It extends in a plane substantially parallel to the plane defined by the first axis A- A 'and the second axis C-C.

The means 23 for axial and radial relative positioning of the tool holder assembly 21 relative to the lens support 19 for example comprise means 71 for tilting the carriage 27 about its tilt axis X- X ', and means 73 for axial translation of the tool holder assembly 21 along an axis DD' parallel to the first axis A-A '.

The control unit 25 controls on the one hand the movement of the tool holder assembly 21 along the axis D-D ', and on the other hand the movement of the carriage 19 around the axis X-X '. This latter movement is comparable to a pseudo-translation movement along an axis perpendicular to the first axis AA ′.

The control unit 25 also controls the axial and radial positioning means 23 for selectively positioning the grinding wheels 49 and 51, and the drilling tool 53 in contact with the periphery 13 of the lens 15.

The control unit 25 is connected to the actuation motor 61 of the tilting means 43 for controlling the rotation of the worm screw 63 in a first direction or in the direction opposite to the first direction, in order to adjust the tilt of the second axis CC relative to the first axis A-A '. The control unit 25 is connected to a computer 77 which makes it possible to calculate one or each angle of inclination of the finishing wheel 49, as described below.

An example of a beveling method according to the invention will now be described with reference to Figures 2 and 3. This method comprises a step of choosing the bevel contour, a step of calculating one or each processing angle corresponding to this bevel contour, a step of adjusting the angle of inclination of the finishing wheel 49 relative to the rough lens 15, and a step of grinding the bevel 16. Initially (Figure 1), the rough lens 15, which has its final outline, is wedged between the two ends 33A, 33B of the half-shafts 29A, 29B by an adapter suitably positioned on this lens 15. The axis AA 'coincides for example with the optical axis of the lens.

Referring to Figure 3, in the step of choosing the contour, the optician chooses a contour 109 of bevel determined by selecting the position of the bevel on the periphery 13, for a number of points 111 chosen around the axis AA '' of the lens 15. Each point 111 corresponds to an angular position of the lens 15 around the first axis AA ′.

This number of points 111 is for example between 128 and 1024 and in particular equal to 512. The contour 109 of the bevel depends in particular on the shape of the lens and on the frame chosen for this lens.

In the calculation step, the computer 77 calculates a processing angle as a function of the curvature and / or the radius of the glass along the contour 109.

This processing angle can vary for each point 111 corresponding to an angular position of the lens 15 around the first axis AA ', or can be maintained at a constant value, as described in French application No. 04 05427.

Then, in the adjustment step, the actuation motor 61 is actuated to drive the endless screw 63 in rotation and consequently, the support arm 37 until the angle α formed by the first axis AA 'and the second axis CC corresponds to the processing angle corresponding to the first beveling point 111.

In the grinding step, the finishing wheel 49 is brought into contact with the periphery 13 of the lens 15 by the displacement means 23. The motor 31 for driving the lens 15 in rotation is then actuated, and the bevel 16 is formed on the periphery 13 of the lens 15, along the contour 109, by varying or not varying the inclination α of the second axis CC relative to the first axis AA 'for each angular position of the lens 15 around the first axis A-A '. The machine 11 according to the invention makes it possible to obtain, for each lens

15 considered, a bevel 16 which has an aesthetic appearance and a sectional profile satisfactory for being received with precision in a groove of corresponding shape provided in a corresponding spectacle frame.

The bevel 16 produced has a substantially constant transverse profile, even in the angular parts of the lens 13. In addition, being in the extension of the edge of the glass, it does not harm the mechanical strength of the latter. The peripheral surface of the lens 13 is inclined relative to the axis AA ′, which allows the lens to be held securely in a wide variety of frame shapes, in particular with large curvature.

In a variant shown in FIG. 4, the grinding machine 11 also comprises a train of grinding wheels 201 comprising for example a roughing grinding wheel 203, a finishing grinding wheel 205 and a polishing wheel 207. The grinding wheel train 201 is mounted integral in translation with the support 35 and the tool holder assembly 21 is retractable under the grinding wheel assembly 201 by rotation about the axis B-B '. The grinding wheels 203, 205 and 207 are rotatably mounted relative to the support 35 around an axis of grinding wheels E-E 'parallel to the first axis A-A'. The axis E-E 'extends in a vertical plane passing substantially through the first axis A-A'.

The method then comprises a step of roughing out the lens 13, before the step of grinding the bevel 16.

Claims

1. Machine (11) for grinding optical glasses, of the type comprising:

- an optical glass support (19), provided with means (31) for driving in rotation a glass (15) about a first axis (A-A '); - a finishing wheel (49) having a peripheral groove (55) intended to form a bevel (16) on a peripheral surface (13) of the glass (15), the finishing wheel (49) being rotatably mounted around a second axis (CC); and

- Means (23) for relative movement of the finishing wheel (49) relative to the glass support (19) to bring the finishing wheel (49) into an active beveling position; characterized in that the relative displacement means (23) comprise tilting means (43) adapted to tilt the second axis (C-C) relative to the first axis (A-A ').

2. Machine (11) according to claim 1, characterized in that the relative displacement means (23) comprise means (43) for adjusting the angle of inclination of the second axis (CC) relative to the first axis ( A-A ').

3. Machine (11) according to claim 2, characterized in that the adjustment means (43) comprise means (77) for calculating the angle of inclination as a function of the curvature and / or the radius of the glass ( 15) along its periphery.

4. Machine (11) according to any one of the preceding claims, characterized in that the finishing wheel (49) has a substantially cylindrical finishing surface (54) into which the groove (55) opens, the width (ei ) of this peripheral surface (54) being greater than the maximum width (e ₂ ) of the peripheral surface (13) of the glass (15).

5. Machine (11) according to any one of claims 1 to 4, characterized in that the finishing wheel (49) has at least one chamfered end intended to perform a beveling of the glass.

6. Machine (11) according to any one of the preceding claims, characterized in that it comprises a train of grinding wheels (201) rotatably mounted around a grinding wheel axis (EE ¹ ) substantially parallel to the first axis (A-A '), and an additional tool holder assembly (21), the finishing grinding wheel (49) being rotatably mounted on the assembly additional tool holder (21).

7. Machine (11) according to claim 6, characterized in that the additional tool holder assembly (21) comprises a creasing disc (51).

8. Optical glass (15) provided with a bevel (16) on its periphery, characterized in that, in at least one meridian half-section of the glass, the peripheral surface (13), on either side of the bevel , is inclined relative to the optical axis (A-A ') of the glass.

9. Optical glass according to claim 8, characterized in that said peripheral surface (13) is inclined relative to the optical axis over substantially the entire periphery of the glass.