EP1963066B1 - Method for calibrating an optical glass drilling machine - Google Patents

Description

• un support de lentille ;
• un ensemble porte-outil portant un outil de perçage rotatif comprenant une fraise de perçage ;
• des moyens de déplacement relatif de l'ensemble porte-outil par rapport au support de lentille ; et
• des moyens de commande de la position de l'outil de perçage par rapport au support de lentille comprenant des moyens de détermination de la position relative de l'ensemble porte-outil par rapport au support de lentille et au moins un actionneur de mise en position relative de l'ensemble porte-outil par rapport au support de lentille.

The present invention relates to a method of calibrating an optical lens piercing machine comprising:

• a lens holder;
• a toolholder assembly carrying a rotary drilling tool comprising a piercing cutter;
• relative movement means of the tool holder assembly relative to the lens holder; and
• means for controlling the position of the piercing tool with respect to the lens support comprising means for determining the relative position of the tool-holder assembly relative to the lens support and at least one positioning actuator relative to the tool holder assembly relative to the lens holder.

We know EP-A-1,310,327 a drilling machine of the aforementioned type. In this machine, a drill bit is wedged into a tool holder assembly to make through holes through an ophthalmic lens. The end position of the drill cutter is calibrated according to the position of this cutter in the tool holder, and the nominal length of the milling cutter supplied by the manufacturer. The accuracy on this position is for example of the order of 0.5 mm.

The document WO 00/67974 describes a calibration method according to the preamble of claim 1.

Such a calibration of the machine is satisfactory for making through holes in ophthalmic lenses. Indeed, the machine is programmed to move the drilling tool relative to the lens on a displacement greater than the sum of the thickness of the lens and the maximum tolerance of length of the cutter.

However, this calibration method is not entirely satisfactory for the production of blind holes and / or counterbores in ophthalmic lenses.

Indeed, given the small thickness of the ophthalmic lenses, the precision on the position of the end of the drill bit provided by the manufacturer is not sufficient to control the position of the bottom of the blind hole in the lens with sufficient precision.

In an attempt to more accurately determine the position of the end of the piercing cutter, it is known to place a lens in the holder and then move the piercing cutter toward the lens to determine the position of the door assembly. tool relative to the support when the assembly can no longer move towards the lens, after contact between the cutter and the lens.

However, the accuracy of this process is limited, and the risk of breakage of the drill bit, which is very thin, is high.

An object of the invention is therefore to obtain a calibration method of an optical glass drilling machine of improved precision and reliability.

For this purpose, the subject of the invention is a method according to claim 1.

The method according to the invention may comprise one or more of the features which are the subject of claims 2 to 7.

• la Figure 1 est une vue schématique partielle en élévation des parties pertinentes d'une machine de perçage pour la mise en oeuvre du procédé selon l'invention ;
• la Figure 2 est une vue agrandie d'un détail marqué II sur la Figure 1;
• la Figure 3 est une vue partielle en perspective d'une ébauche de lentille utilisée dans le procédé selon l'invention, lors d'une première étape de ce procédé ;
• la Figure 4 est une vue analogue à la Figure 3 lors d'une deuxième étape de ce procédé ; et
• la Figure 5 est une vue en section verticale suivant un plan V-V d'un détail de la Figure 4.

The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which:

• the Figure 1 is a partial schematic view in elevation of the relevant parts of a drilling machine for carrying out the method according to the invention;
• the Figure 2 is an enlarged view of a detail marked II on the Figure 1 ;
• the Figure 3 is a partial perspective view of a lens blank used in the method according to the invention, in a first step of this method;
• the Figure 4 is a view similar to the Figure 3 during a second step of this process; and
• the Figure 5 is a view in vertical section along a VV plane of a detail of the Figure 4 .

The drilling machine 11 shown on the Figure 1 is intended to make holes in ophthalmic lenses, these lenses having been previously roughed by peripheral grinding.

The machine 11 shown on the Figure 1 is adapted to drill blind holes or countersinks in a lens, these blind holes being used to immobilize a mechanical part, for example by pressing a pin.

In the example shown on the Figure 1 , a calibration blank 13 is placed in the machine 11. The blank 13 is a substantially planar disk having a constant thickness.

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 with respect to the support 19, a probe assembly 24 and a control unit. order 25.

The lens holder 19 comprises a carriage 27 pivotally mounted on the frame 17, provided with two half-shafts 29A, 29B adapted to grip the blank 13, and a motor 31 for slowly rotating the blank 13.

The carriage 27 is hinged relative to the frame 17, by a rear longitudinal edge 28, about an axis X-X '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 substantially horizontal first axis AA 'parallel to the X-X axis .

The half-shafts 29A, 29B are provided with respective free ends 33A, 33B arranged opposite one another, adapted to grip the blank 13.

The drive motor 31 of the blank 13 rotates the half-shafts 29A, 29B around the first axis A-A 'by a transmission mechanism (not shown).

In the machine 11 illustrated by the Figure 1 , the tool holder assembly 21 comprises a support 35, a linkage arm 37 projecting from the support 35, a drilling tool 39, a rotation drive motor 41 the tool 39, and means 43 for tilting the tool 39 relative to the support 35.

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

As illustrated by Figure 2 , the tool 39 is mounted in a guide housing formed at the free end 47 of the connecting arm. The tool 39 is rotatably mounted about a second axis CC 'substantially orthogonal to the linkage arm 37.

The tool 39 comprises, from left to right on the Figure 2 , a substantially cylindrical drive portion 49 axially wedged against an inner surface 50 of the linkage arm 37, and a piercing cutter 51 integral with a free end 52 of the actuating portion 49.

The inner surface extends along an axis of the arm 37 perpendicular to the axis C-C '.

The piercing cutter 51 protrudes outwardly from the arm 37 along the axis C-C '. It has a free end 53 of drilling.

The drilling cutter 51 has a theoretical or nominal length L _T of between 12 mm and 40 mm and a diameter of between 0.8 mm and 3.0 mm.

The arm 37, and consequently the tool 39, is rotatable about the axis BB 'on an angular displacement of at least 30 ° and preferably 180 °, in particular being able to take an upper vertical position in which the second axis CC 'is substantially parallel to the first axis A-A', and a plurality of inclination positions in which the second axis CC 'is inclined with respect to the first axis A-A'.

In the example illustrated by the Figure 1 , the tool 39 remains substantially in the vertical plane passing through the first axis A-A ', regardless of its position around the axis B-B'.

The motor 41 for rotating the tool 39 is fixed on the link arm 37. It is connected to the tool 39 by transmission means 55 arranged in the arm 37.

The adjusting means 43 of the inclination angle of the tool 39 comprise a motor 61 for actuating a worm 63, and a toothed wheel 65 tangent; mounted to the link arm 37. The worm 63 extends in a direction substantially parallel to the first axis A-A '.

The toothed wheel 65 is fixed on the arm 37 at its end 45. It extends in a vertical plane.

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

The tilting means 71 of the carriage 27 and the axial translation means 73 of the tool-holder assembly are respectively connected to an actuator 75A for placing the carriage 27 in relative position with respect to the tool-holder assembly 21 along the an axis perpendicular to the axis A-A ', and an actuator 75B relative positioning of the tool holder assembly 21 relative to the carriage 27 along the axis A-A'. These actuators 75A, 75B are constituted, for example, by respective drive-stepper motors of the tilting means 71 and translation means 73. The actuators 75A and 75B are controlled by the control unit 25.

The control unit 25 comprises a computer 77 which determines the relative position of the tool-holder assembly 21 with respect to the carriage 27, with reference to their positions on the frame 17, as a function of the respective control signals transmitted to the actuators 75A. , 75B.

The calculator 77 also calculates the relative position that must be occupied by the free end 53 of the cutter 51 with respect to the blank 13 during drilling, as a function of the depth of penetration and the type of blind hole or countersink. realize in the sketch 13.

The control unit 25 controls, on the one hand, the displacement of the tool-holder assembly 21 along the axis DD 'and, on the other hand, the displacement of the carriage 19 around the axis X-X' . This last movement is likeable to a pseudo-translation movement along an axis perpendicular to the first axis A-A '.

The control unit 25 also slaved the axial and radial positioning means 23 to position the cutter 51 of the tool 39 in contact with the blank 13 of the lens 15 and make it penetrate into it.

The control unit 25 is connected to the actuating motor 61 of the tilting means 43 for controlling the rotation of the worm 63 in a first direction or in the opposite direction to the first direction, so as to adjust the inclination of the second axis CC 'relative to the first axis A-A'.

The probe assembly 24 comprises two arms 79A, 79B carried by the frame 17, each arm 79A, 79B being provided with a respective feeler finger 81A, 81B.

Each arm 79A, 79B is thus movable in translation along a substantially horizontal axis E-E ', between a retracted retracted position in the frame 17 and an active measuring position.

In the active measuring position, the fingers 81A, 81B extend substantially parallel to the axis A-A ', facing each other, on either side of the blank 13. in the measuring position, the front finger 81A is applied against a front surface 83A of the blank 13 and the rear finger 81B is applied against a rear surface 83B of the blank 13.

The probe assembly 24 further comprises a sensor 85 for measuring the linear position of the feeler fingers 81A, 81B along the axis E-E '. The sensor 85 is connected to the computer 77. The linear positions obtained by the sensor 85 are converted by the computer 77 into a distance between the feeler fingers 81A, 81B.

A calibration method according to the invention will now be described.

This method comprises a step of placing the blank 13 in the support 19, a step of drilling a blind bore of a desired depth into the front surface 83A of the blank, a step of measuring the actual depth of the blank. the blind bore using the probe assembly 24, which comprises a probing phase before the drilling step and a probing phase after the piercing step. The method according to the invention further comprises a step of calibrating the control means 25.

Initially, the blank 13 is wedged between the two ends 33A, 33B of the half-shafts 29A, 29B by an adapter suitably positioned on this blank. In this position, the front surface 83A of the blank 13 is substantially perpendicular to the axis A-A '.

In the first probing phase, the probe assembly 24 is activated. As illustrated by Figure 3 , the feeler arms 79A, 79B are brought from their retracted position to their active measuring position in which the fingers 81A, 81B are respectively in contact with the front surface 83A and the rear surface 83B of the blank.

The measurement taken by the position sensor 85 is transmitted to the computer 77, which determines the thickness E _AV of the blank 13, before drilling, at the desired drilling point 87 located on the front surface 83A.

At the beginning of the drilling step, the inclination adjusting means 43 are activated so that the link arm 37 is arranged perpendicularly to the axis A-A '. The axis CC 'of the drilling cutter 51 is then substantially parallel to the axis A-A'. The computer 77 then determines the relative position of the inner surface 50 of the arm 37 relative to the position of the front surface 83A of the blank 13. The position of the free end 53 of the drilling cutter is then calculated by the calculator, based on the relative position of the surface 50 and the theoretical length L _T of the drilling tool 39, provided by the manufacturer.

The control means 25 are then activated to move the free end 53 and bring it substantially in contact with the surface 83A, at the point 87.

The control unit 25 activates the actuators 75A, 75B to mill a blind bore 91 of axis CC 'and a desired depth P _D into the front surface 83A of the blank 13, based on the relative position of the free end 53 of the cutter 51 with respect to the blank calculated by the computer 77.

When the computer 77 determines that the desired depth P _D is reached, the axial displacement of the cutter 51 is stopped. The cutter 51 is then moved radially relative to the axis CC 'to make the bore 91 visible on the Figure 4 . This bore therefore has a cross section greater than the cross section of the cutter 51.

Then, the cutter 51 is extracted from the bore 91 and the tool-holder assembly 21 is moved away from the blank 13.

In the second probing phase, the probe assembly 24 is activated again. The probe arms 79A, 79B are brought into their active measuring position, so that the front finger 81A contacts the bottom of the blind bore 91, and the rear finger 81B comes into contact with the rear surface 83B , opposite the background. The thickness E _AP of the blank 13 in the blind bore 91 is thus determined and transmitted to the computer 77.

où L_R est la longueur réelle de l'outil de perçage 39, L_T est la longueur théorique de l'outil de perçage donnée par le fabricant, P_D est la profondeur désirée de l'alésage borgne, E_AV est l'épaisseur mesurée par l'ensemble de palpage 24 avant le perçage de l'alésage borgne 91, et E_AP est l'épaisseur mesurée par l'ensemble 24 dans l'alésage borgne 91 après son perçage.With reference to Figures 2 and 5 the calculator 77 then determines the actual length of the piercing tool 39 by the following formula: $${\mathrm{The}}_{\mathrm{R}}={\mathrm{The}}_{\mathrm{T}}-\left[{\mathrm{P}}_{\mathrm{D}}-\left({\mathrm{E}}_{\mathrm{AV}}-{\mathrm{E}}_{\mathrm{AP}}\right)\right],$$

where L _R is the actual length of the drilling tool 39, L _T is the theoretical length of the drilling tool given by the manufacturer, P _D is the desired depth of the blind bore, E _AV is the thickness measured by the feeler assembly 24 before the drilling of the blind bore 91, and E _AP is the thickness measured by the assembly 24 in the blind bore 91 after drilling.

The actual length L _R of the drilling tool 39 is then introduced into the computer 77, to replace the theoretical length L _T to control the tool 39 during the subsequent drilling of blind holes and counterbores in ophthalmic lenses.

Thanks to the invention which has just been described, it is possible to have a simple and accurate method of calibrating a drilling machine 11 of optical glasses, without the use of specific tools that could deteriorate the 51. The calibration is thus achieved without contact of the cutter 51 with an additional calibration tool.

This method is used to overcome the manufacturing tolerances of drilling drills 51 used to make blind holes or counterbores in ophthalmic lenses.

By simply drilling a blind bore 91 in a blank 13, and by measuring the actual depth of the blind bore 91 by a separate probing sensor of each positioning actuator 75A, 75B which feels at least the 83A front surface of the blank 13, before and after drilling, it is possible to significantly improve the accuracy of the calculation of the position of the drilling cutter 51 on the machine 11.

Alternatively, the two probing phases are performed after drilling the blind bore 91, by measuring the thickness of the lens in the blind bore 91, and at a point in the vicinity of this bore 91.

In another variant (not shown), the grinding machine 11 further comprises a wheel set comprising, for example, a roughing wheel, a beveling finishing wheel and a beveling polishing wheel. Such a machine is described for example in the French application no. 03 03 792 .

In another variant, the probe assembly 24 comprises a single probe finger 81A for sensing the front surface 83A. In this variant, the actual depth of the blind bore 91 is determined by the difference between the measurement of the linear position of the finger 81A in contact with the piercing point 87, before the piercing, and the measurement of the linear position of the finger 81A at contact of the bottom of the bore 91, after drilling.

Claims (7)

1. Method for calibrating a machine (1) for drilling optical glasses comprising:

   • a lens support (19);

   • a tool holder assembly (21) holding a rotary drilling tool (39) having a drill cutter (51);

   • means (23) for relative displacement of the tool holder assembly (21) in relation to the lens support (19); and

   • means (25) for controlling the position of the drilling tool (39) in relation to the lens support (19) comprising means (77) for determining the relative position of the tool holder assembly (21) in relation to the lens support (19), and at least one actuator (75A, 75B) for relative positioning of the tool holder (21) in relation to the lens support (19);

   comprising the following steps:

   (a) placing a blank (13) in the support (19);

   (b) drilling a blind bore (91) on the basis of a desired depth (P_D) into a first surface (83A) of the blank (13),

   characterised in that the drilling is controlled by the control means (25) on the basis of the relative position of the drilling tool (39) in relation to the blank (13) determined as a function of the desired depth (P_D) and the theoretical length (L_T) of the drilling tool (39) by the determination means (77), wherein the method comprises the following steps:

   (c) measuring the real depth (E_AV - E_AP) of the blind bore (91); and

   (d) calibrating the control means (25) as a function of the desired depth (P_D) and the measured real depth (E_AV - E_AP).
2. Method according to claim 1, characterised in that step (c) is conducted by means of at least one position sensor (85) connected to a front feeler (81A) intended to be positioned to face the first surface of step (c) comprising at least two phases of sensing the first surface (83A), wherein at least one sensing phase is performed in the base of the bore (91) after the blind bore (91) has been drilled.
3. Method according to claim 2, characterised in that at least one phase of sensing the first surface (83A) is performed at the level of the drilling point (87) of the blind bore (91) before the blind bore (91) is drilled.
4. Method according to claim 2 or 3, characterised in that the position sensor (85) is additionally connected to a rear feeler (81B), wherein for each sensing phase of the first surface (83A), step (c) comprises sensing a second surface (83B) of the blank located opposite the first surface (83A) in order to determine a measured thickness of the blank (13).
5. Method according to claim 4, characterised in that the calibration step comprises calculating a real length (L_R) of the drilling tool (39) on the basis of the theoretical length (L_T) of the drilling tool (39) corrected by the difference between the thickness (E_AV) of the blank (13) measured before the blind bore (91) is drilled and the thickness(E_AP) of the blank measured after this blind bore has been drilled.
6. Method according to any one of the preceding claims, characterised in that the drilling step comprises the formation of a blind bore (91) with a cross-section larger than the cross-section of a drill cutter (51) of the tool (39).
7. Method according to any one of the preceding claims, characterised in that step (a) comprises arranging a plane blank (13) of substantially constant thickness in the lens support (19).

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