EP0820837B1 - Optical glasses grinding machine - Google Patents

Description

The present invention relates to a optical lens grinding machine, of the type described in the preamble to claim 1. Such a machine is known, for example, from EP-A-0 350 216.

When an optical glass blank has been ground to the contour corresponding to the spectacle frame who will receive it, it must undergo on each side a anti-bevel operation which cuts down the two edges vivid of its outline. In addition, when the frame includes, on at least part of the periphery of each circle, a glass retaining wire, you must make a corresponding groove, i.e. a groove, on the slice of the draft.

The invention aims to integrate on a grinding machine one and / or the other of the operations abovementioned bevelling and creasing so economical and efficient.

To this end, the subject of the invention is a grinding machine of the aforementioned type, characterized by the characterizing part of claim 1.

The machine according to the invention may include one or more of the characteristics described in the claims 2 to 15.

• la Figure 1 est une vue partielle de dessus, suivant la ligne I-I de la Figure 2, d'une machine de meulage conforme à l'invention;
• la Figure 2 est une vue en bout de la machine, prise suivant la flèche II de la Figure 1, avec la meule additionnelle en position escamotée;
• la Figure 3 est une vue analogue à la Figure 2, mais avec la meule additionnelle en position active;
• la Figure 4 est une vue partielle prise en coupe suivant la ligne IV-IV de la Figure 3, mais à plus grande échelle, qui illustre le fonctionnement de la meule additionnelle;
• la Figure 5 est une vue analogue à la Figure 4, mais à encore plus grande échelle, illustrant une variante;
• la Figure 6 est une vue analogue à la Figure 4, illustrant une autre variante; et
• la Figure 7 est une vue analogue à la Figure 1, correspondant à la variante de la Figure 6.

Examples of embodiments of the invention will now be described with reference to the appended drawings, in which:

• Figure 1 is a partial top view, along line II of Figure 2, of a grinding machine according to the invention;
• Figure 2 is an end view of the machine, taken along arrow II of Figure 1, with the additional wheel in the retracted position;
• Figure 3 is a view similar to Figure 2, but with the additional grinding wheel in the active position;
• Figure 4 is a partial view taken in section along the line IV-IV of Figure 3, but on a larger scale, which illustrates the operation of the additional grinding wheel;
• Figure 5 is a view similar to Figure 4, but on an even larger scale, illustrating a variant;
• Figure 6 is a view similar to Figure 4, illustrating another variant; and
• FIG. 7 is a view similar to FIG. 1, corresponding to the variant of FIG. 6.

The grinding machine shown in the Figures 1 to 3 is intended to make an optical glass beveled and counter-beveled from a blank generally circular. It basically includes a frame 1 in which two shafts are rotatably mounted parallel, namely a grinding wheel shaft 2 of axis X-X and an arm-shaft 3 of axis X'-X '. The X-X and X'-X 'axes are horizontal. A carriage 5 is also mounted sliding on the frame 1 parallel to the two shafts. This carriage is also mounted tilting on the frame and, for this purpose, it is articulated by a longitudinal edge around a tree 6 parallel to trees 2 and 3. The carriage 5 door, along its other longitudinal edge, two half-shafts 7 adapted to grip the blank, which is shown ground in 8 in Figure 2. The machine also includes an additional 9 diamond sintered metal mounted freely rotatable at the end of an arm 10 fixed on the shaft 3. The tilting of arm 10 is controlled by a mechanism 11 of the type crank rod.

The machine also has a unit of electronic control 12 with programming keyboard, shown schematically in Figure 1. This unit is suitable for carry out the commands which will be described later in order to perform a fully automated machining cycle optical glass.

The grinding wheel shaft 2 is driven in rotation around the X-X axis by an electric motor not visible in the drawings, via a transmission belt 13. Several juxtaposed grinding stones are placed on this tree forming a main train of grinders T, one of which grinding wheel 14A for roughing mineral glasses, a grinding wheel 14B for roughing synthetic glasses, a grinding wheel 15 finishing (ice grinding or beveling) and a grinding wheel 16 polishing. The grinding wheel 16 has the same profile as the wheel 15, but with a finer grain. Between these two last grinding wheels is wedged a friction disc 17 having a cylindrical peripheral surface constituted by a plastic or elastomer coating. Stacking 14A, 14B, 15, 16 is fixed in place by means of members 18 screwed at the end of the shaft.

The arm 10 forms a crank whose crankpin 19 has a Y-Y axis parallel to the X-X axes and X'-X 'and carries the grinding wheel 9, freely rotating, to its free end.

This grinding wheel 9, of diameter much less than that of the wheels 14A to 16, externally present (Figure 4) a cylindrical central surface 20 framed by two frustoconical surfaces which converge away of this surface 20. It is a surface 21 having a relatively small apex half angle, by example of the order of 45 °, and of an opposite surface 22 having a relatively large apex half angle, by example 60 °.

The axial position of the following grinding wheel 9 the Y-Y axis is adjustable and can be locked using a radial screw 23. The adjustment is such that the plane median of the cylindrical surface 20 of the grinding wheel 9 located in the vicinity of that of the friction disc 17.

The mechanism 11 comprises a disc 24 with an axis vertical, motorized, on the periphery of which is articulated by a ball 25 a connecting rod 26 of adjustable length. AT its other end, the connecting rod 26 is connected via a second ball joint 27 at the end of a crank 28, which is wedged on the shaft 3. We have also shown in Figures 1 to 3 a switch limit switch 29 cooperating with the periphery of the disc 24, as well as a helical tension spring 30 which constantly requests the crank 28, and therefore the arm 10, in the direction of the X-X axis.

The electronic control unit 12 contains in memory the data relating to the spectacle frame to equip and the patient's morphology. From these data, it controls the translation and the position angle of carriage 5 as a function of position angular of the blank 8 on the half-shafts 7, during grinding, finishing / polishing and roughing the blank, as described below.

At the start (Figures 1 and 2), the arm 10 is tilted outward relative to the grinding wheel train T and completely clears the space above these grindstones. As known, the blank is wedged between the half-shafts 7 by a suitably centered adapter, then is brought successively on the grinding wheels 14A or 14B, 15 and possibly 16.

The blank then has its final outline and has on its edge a bevel 31 visible on the Figure 4.

The stem 5 being reassembled, the unit 12 causes the disc 24 to rotate and, as a result, the tilting of the arm 10 towards the axis X-X. This movement brings the cylindrical surface 20 of the grinding wheel 9 in contact with the disc 17, so that this grinding wheel is driven to high speed rotating around its Y-Y axis, which is parallel to axes X-X and X'-X '.

Under the control of unit 12, the translation of the carriage 4 and the inclination of the stem 5 are controlled so as to bring an edge of the contour of the blank on the frustoconical surface 21 of the grinding wheel 9 for at least one turn of the blank on itself, then to bring the other edge of the outline of the blank onto the other frustoconical surface 22. In this way, the two glass bevels are produced without moving roughing, without additional equipment and without operator intervention other than programming of this operation on the control keyboard of the machine.

Note that the steepest slope, with respect to the radial direction, from the surface 21 by relative to the surface 22, makes it possible to produce the counter-bevel on the convex side of the glass, as illustrated on Figure 4.

Figure 4 also shows a variant possible from the machine, according to which the hub 32 of the grinding wheel 9, which is rotatably mounted in the crankpin 19 of the arm 10 by means of a bearing 33, extends beyond of the grinding wheel 9. On this extension is wedged a disc of creasing 34, of diameter significantly smaller than that from the grinding wheel 9, kept at a predetermined distance of the latter by a spacer 35, the assembly being fixed in position by an end screw 36.

So when the counter bevel is made, or before this operation, we can bring the blank in line with the creasing wheel 34, to dig on its slice a groove extending over a predetermined part around the glass.

Alternatively, as shown in Figure 5, the grinding wheel 9 can be modified to also form a grinding wheel creasing. For this, provision is made on the cylindrical surface 20 a radial projection 37 whose profile is conjugate of that of the groove groove 38 to be produced.

In the case where, according to Figure 4 or according to Figure 5, the arm 10 carries a creasing wheel, the translation of the carriage 4 is controlled, during the creasing operation, so as to position the groove 38 as desired on the edge of the glass, for example at e / 3 of the front face, where e denotes the thickness of the edge of the glass.

When, as in the variant of Figure 5, the grinding wheel 9 is equipped with the projection 37, provision is made in the friction disc 17 a groove 39 adapted for receive this projection, as shown.

In the variant of Figure 6, the arm 10 is equipped with a freely rotating triple assembly counter-beveling, creasing and drilling function.

Thus, the end of the arm 10 carries a male crank pin 40 on which a sleeve 41 is mounted rotation by means of two bearings 42 and 43. The end of this sleeve opposite the arm 10 has a countersink outside on which a creasing ring 44 is threaded, held by a ring 45.

The sleeve 41 is extended by a shaft end 46 on which is threaded the grinding wheel 9 against beveling. A nut 47, screwed onto the threaded end of the end shaft 46, axially presses the assembly consisting of the grinding wheel 9, the ring 45 and the ring 44.

In addition, the base of a drill bit 48 is introduced into an axial channel of the shaft end 46 and fixed in place by a radial screw 49.

So, by controlling the axial position of the carriage 5, the blank 8 can be brought into position chosen creasing. Two different positions are illustrated in FIG. 6, one 8A in solid lines, the other 8B in phantom.

It should be noted that the position of the ring 44 set back from the grinding wheel 9 reduces the size of the finishing device carried by the arm 10.

The blank 8 can also be bevelled as previously described, or even breakthrough. For this, it is brought before wick 48, in the desired angular position, as shown in phantom in 8C, then the carriage is moved to the drill bit and the blank is perforated therewith. The displacement of carriage ends when wick has slightly emerged of the blank, the latter then being in the position 8D shown in phantom.

To be able to drill not only holes circular, but also oblong lights, the wick 48 is preferably a cutting end cutter and on its flanks. We can then, after drilling a hole, move the blank in its general plane to realize the oblong light.

For each of the beveling operations and creasing, precise control of the carriage position, for each angular position of the blank, can be obtained from two probes brought respectively into contact with the two faces of the glass. These probes take the plots of these two faces, and the control unit 12 deduces therefrom the control of the carriage.

For example, unit 12 contains in memory a series of predetermined trajectories and chooses, among these, a trajectory that fits between the two traces noted by the probes, as described in FR-A-2 499 442.

In another embodiment, the control of the carriage can result from a calculation law, applied to the two plots noted. For example, creasing can be carried out at e / 3 from the front face, where e denotes the thickness of the glass at its periphery.

Similarly, the positioning of the carriage and its stroke, for the drilling operation, can be determined from the probing of the two sides of the blank in its angular position of drilling, and a pre-established calculation law. The race, during drilling, can thus be equal to e + ε, ε being the distance emergence of the drill bit after drilling (for example ε = 0.5 to 1 mm) and the stroke being calculated from drill bit contact. Such contact can be obtained, in a manner known per se in machine tools with numerical control, by a procedure called "offset" zero ", that is to say learning the carriage vis-à-vis an adjustment template.

Thanks to the command described above, the active length L of drill bit 48, which is a piece of very small diameter (typically 1 mm) attacking curved surfaces, can be limited to E + ε, where E denotes the thickest glass that we plan to drill. For example, you can choose L = 5 mm approximately.

Figure 7 schematically shows, from similar to Figure 1, a two-way arrangement probes suitable for implementing the variant of the Figure 6.

For this, we added to the machine two S 50 levers, articulated on two vertical axes parallel 51 secured to the machine frame. To his free end, each lever carries a caster 52, also with vertical axis, forming a feeler. The other end of each arm is biased by a spring 53, via a cable 54, in the direction which separates the two feelers of each other. This movement is limited by the coming from a vertical pin 55 carried by each arm in abutment against a control plate 56.

The plate 56 carries a horizontal threaded rod 57 actuated by a gear motor. In the illustrated extension position of the rod 57, the plate 56 maintains the two feelers in the position of maximum separation. When the rod 57 is retracted (arrow f 1), the arms 50 are released, so that the springs 53 bring the two feelers closer to one another (arrows f 2), until contact with the blank 8 previously positioned axially and angularly in a predetermined manner. The angular displacement of the two arms 50 thus provides, via the unit 12, the thickness e of the blank at the location of the drilling to be made.

We also schematized in Figure 7 limit switches 59 (sensors fully discarded) and 60 (rod 57 fully retracted).

For a beveling operation or creasing, it is possible, by means of the two probes, to produce a series of double probes on the front-back side of the blank, in a number of angular positions predetermined from the latter, and deduce the axial movement of the carriage 5 as a function of the angular position of the blank during counter-beveling or creasing.

Claims (15)

1. Machine for grinding lenses, of the type comprising a main set of grinding wheels (T) keyed on a shaft (2), an additional grinding wheel and a blank holder assembly (5, 7) adapted to bring the blank (8) in contact with the grinding wheels, characterised in that the additional grinding wheel (9) is mounted so as to be freely rotatable on a support (10, 19), means (11) for actuating the support being adapted to move the additional grinding wheel (9) between a retracted position and an active position in which the rotation axis (Y-Y) of the additional grinding wheel is parallel to the axis (X-X) of said shaft and wherein the additional grinding wheel is in driving contact with a driving disc (17) fixedly connected to the set of grinding wheels (T), and in that it comprises means (12) for bringing the blank into contact with the additional grinding wheel (9) when the latter is in the active position.
2. Machine according to claim 1, characterised in that the additional grinding wheel (9) has an external diameter significantly smaller than that of the grinding wheels (14A, 14B, 15, 16) of the set of grinding wheels (T).
3. Machine according to claim 1 or 2, characterised in that the driving disc (17) is an additional disc having an outer surface of frictional material, added to the stack of grinding wheels (14A, 14B, 15, 16) of the set of grinding wheels (T).
4. Machine according to claim 3, characterised in that the frictional material is a plastic or elastomeric material.
5. Machine according to any one of claims 1 to 4, characterised in that the support (10, 19) comprises a crank handle (10) pivotably mounted about an axis (X'-X') parallel to the axis (X-X) of said shaft (2).
6. Machine according to any one of claims 1 to 5, characterised in that the additional grinding wheel (9) is a counter-bevelling grinding wheel which has two opposing active sides (21, 22) which are generally frustum-shaped.
7. Machine according to claim 6, characterised in that the two active sides (21, 22) have different vertex angles.
8. Machine according to claim 6 or 7, characterised in that, between the two opposing surfaces (21, 22), the additional grinding wheel (9) has a radial scoring projection (37).
9. Machine according to claim 8, characterised in that the driving disc (17) comprises a peripheral groove (39) adapted to receive the radial projection (37).
10. Machine according to claim 6 or 7, characterised in that the support (10, 19) also carries a second additional grinding wheel (34, 43) forming a scoring grinding wheel, which is axially spaced from and fixedly connected to the first additional grinding wheel (9), and the outer radius of which is smaller than that of said latter grinding wheel (9).
11. Machine according to claim 10, characterised in that the second additional grinding wheel (43) is recessed relative to said counter-bevelling grinding wheel (9).
12. Machine according to any one of claims 1 to 11, characterised in that the support (10, 19) also carries a drilling tool (47) coaxial with the additional grinding wheel (9) and connected for rotation therewith.
13. Machine according to claim 12, characterised in that the drilling tool (47) is a cutter adapted to produce oblong openings.
14. Machine according to any one of claims 1 to 13, characterised in that it comprises means (50 to 54) for probing (sensing? feeling?) the two sides of the lens, and guide means (12) for controlling the movements of the blank holder assembly (5, 7) in response to the results of the probing.
15. Machine according to claim 14, taken together with claim 12 or 13, characterised in that the guide means (12) are adapted to calculate a drilling course as a function of the thickness of the blank (8) obtained from the results of the probing.

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