Asselin, Robert Raymond Maurice (Elbenf, FR)
Asselin, Pierre Henri Leon (Elbenf, FR)

05/372996

08/19/1975

06/25/1973

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451/240

B24B9/14; B24B17/10; C03B33/04; B24B9/06; B24B17/00; C03B33/00; B24B9/14

51/127,165.71,11R,11LG

3807098

PLURAL GRINDING STATIONS WITH MASTER CONTROLLER

April 1974

Schaller

Simpson, Othell M.

Schaffer, Murray

We claim

1. Apparatus for bevelling the edges of a lens in conformance with a predetermined bezel contour comprising a support for holding a member having a bezel contour, means for rotating said bezel support about an axis perpendicular to the mean plane of the bezel member, means for following the contour of said bezel member to sense the shape thereof, a grinding machine having a grinding wheel, a support for holding a lens, means for rotating said lens support, each of the bezel member support and lens support being carried on an individually pivotable arm, said means for rotating the corresponding support being mounted on the respective arm and means for copying the shape of said bezel on said lens comprising means interconnecting said means for rotating said lens support and said means for rotating said bezel support rotating said lens synchronously with the rotation of said bezel member, means for simultaneously moving said lens support and said grinding wheel relatively toward each other in response to the sensing of the shape of said contour to cause said grinding wheel to grind said lens into the shape of said bezel and means for controlling the relative pressure between said lens and said grinding wheel independently of the means for following said bezel.

2. The apparatus according to claim 1 in which the arm carrying said bezel member support is movable in a plane parallel to the plane of said bezel and includes means for exerting a restoring force on said arm in opposition to the position of the bezel follower, said copying means controlling, in response to the movement of the arm carrying said bezel member support, the position of said arm carrying said lens support in relation to said grinding wheel.

3. The apparatus according to claim 2 including an auxiliary arm associated with the arm carrying said lens support and including adjustable stop means causing said lens support arm and said auxiliary arm to be in at least intermittent mutual contact.

4. The apparatus according to claim 3 including means for exerting on said lens support arm a substantially constant force urging the lens against the grinding wheel.

5. The apparatus according to claim 1 wherein the arms carrying said supports are pivotable about a pin journaled in a machine frame and extending through the end of said arm remote from the corresponding support.

6. The apparatus according to claim 1 including means for removably attaching said bezel member support on its associated arm comprising a rotatable shaft connected to said means for rotating said support and having resilient latching means for axially restraining said support on said shaft.

7. The apparatus according to claim 6 in which said bezel member support is so shaped as to be capable of being laid flat on a flat surface.

8. The apparatus according to claim 1 in which the work surface for the bezel member support, on which the latter is placed, is horizontal.

9. The apparatus according to claim 1 wherein said bezel member comprises a spectacle frame for which the lens is intended and said means for following the contour of said bezel comprises a feeler adapted to engage the surface of said bezel.

10. The apparatus according to claim 9 in which the bezel member support carries the frame and comprises two independently rotatable parts, means for separately adjusting the position of each part to rotate in succession about two axes corresponding to the two eyes of the spectacle frame.

11. The apparatus according to claim 1 wherein said bezel member comprises a template having a shape conforming to the grinding dimensions for a spectacle lens, and said bezel follower comprises means for sensing the edge of said template.

12. The apparatus according to claim 11 in which said template comprises a thin rigid sheet having a peripheral edge and said follower means comprises a feeler adapted to be in physical contact with said edge.

13. The apparatus according to claim 11 in which said template comprises a sheet on which the contour of said lens is inscribed and said follower is adapted to sense said inscription optically and includes a servomotor responsive thereto for controlling the movement of said bezel member support and said follower.

14. The apparatus according to claim 11 in which the template comprises a sheet on which the contour of said lens is inscribed and said follower is adapted to sense said inscription photoelectrically and which includes a servomotor responsive thereto for controlling the relative motions of the bezel member support and said follower.

15. The apparatus according to claim 11 in which the template comprises a sheet on which the contour of said lens is inscribed and said follower is adapted to sense said inscription magnetically and including a servomotor in response thereto for controlling the relative motion of the bezel member support and said follower.

16. The apparatus according to claim 2 including sensing means for measuring the movements of the bezel member support arm, said copying means including circuit means for remotely slaving said lens support arm thereto.

17. The apparatus according to claim 16 including means for recording the information issuing from the sensing means, said copying means circuit including playback means for said recording.

18. The apparatus according to claim 1 in which the bezel follower is movable and is provided with means for slaving its position so as to constrain the point at which said follower senses the bezel surface so as to be homologous with the grinding point comprising the point of contact of the grinding wheel against the lens being so contoured.

19. The apparatus according to claim 18 in which the means for slaving the bezel follower defines the point homologous with the grinding point as being that point on the bezel at which the tangent thereto is perpendicular to the straight line homologous with the straight line joining the center of the grinding wheel to the grinding point.

20. The apparatus according to claim 19 in which the follower means includes a feeler adapted to engage the bezel surface, said feeler being mounted on the end of an arm having a length substantially equal to the radius of the grinding wheel and being pivotable about the point homologous with the center of the grinding wheel, said feeler being flanked by two adjacent auxiliary feelers movable in the direction of said arm, a detector for detecting the respective positions of said feelers and slaving means adapted to rotate said arm until the straight line which joins the end of the auxiliary feelers and virtually merges with the tangent to the bezel is perpendicular to the direction of the arm.

21. The apparatus according to claim 20 including a rocking beam lever interconnecting the auxiliary feelers with the supporting arm, and wherein said detector is an angular position detector which measures the angle formed by said rocking beam lever and the direction of movement of said arm.

22. The apparatus according to claim 20 in which the detector detects the relative position of the feelers in a direction parallel to that of the arm.

23. The apparatus according to claim 22 in which the follower means includes a feeler adapted to engage the edge of said bezel, said feeler being carried by an arm having a length substantially equal to the grinding wheel radius, said arm being pivotable in response to said slaving means and a computer responsive to the angular motion of the arm carrying the bezel member support for determining the derivative of the curve of the bezel contour.

24. The apparatus according to claim 19 in which said follower means is provided with means for imparting low amplitude, high frequency vibration thereto.

25. The apparatus according to claim 18 in which said slaving means defines the homologous point as the extreme point on the bezel in a fixed direction homologous with the line joining the rotation centers of the lens and the grinding wheel.

26. The apparatus according to claim 25 in which the follower means includes a mechanical feeler having a point, said mechanical feeler being mounted on the end of an arm having a length substantially equal to the grinding wheel radius, means for continuously vibrating said arm at its other end, said other end being movable linearly with respect to the center of the bezel and including a detector sensing the position of said other end farthest from the bezel and transmitting a signal in response thereto to the copying means.

27. The apparatus according to claim 25 in which the follower means comprises a series of proximity sensors capable of exploring the interior of the bezel, a sliding support for said proximity sensors, said sensors being positioned in succession along a circular arc homologous with the grinding wheel periphery, said sliding support being movably translationally along a straight line homologous with the center line in response to slaving means until said support is brought into that position farthest from the bezel in which only one follower explores the inside of the bezel.

28. The apparatus according to claim 16 in which the means for slaving the arm carrying the bezel member and the arm carrying the lens support includes means for adjusting the initial position of the lens support arm with respect to said grinding wheel.

29. The apparatus according to claim 28 including means for adjusting the position of said arm continuously.

30. The apparatus according to claim 28 including means for intermittently adjusting the position of said arm.

31. The apparatus according to claim 30 including means for automatically activating said intermittent adjustment means in accordance with a predefined lens grinding program.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for manufacturing optical lenses and in particular to apparatus for contouring lenses to match the bezel of the spectacle frames.

Devices for machining the edges of spectacle lenses, not from a conventional template but according to the spectacle frame for which the lenses are intended, have disadvantages such that no machine of this kind proposed heretofore has given real satisfaction in practice. The reason for this is to be found in their inherent drawbacks.

In all prior art systems for grinding spectacle lenses according to the shape of the spectacle frame, the lens grinding pressure against the grinding wheel is provided directly by the pressure of a mechanical feeler on the frame bezel. But because bezels, especially metal ones, are fragile and deformable, the grinding pressure has to be low and cannot exceed a few hundred grams, thereby resulting in very long grinding times and frequent deformation of the frame bezel under the pressure of the feeler.

In such prior art systems, moreover, the frame is mounted on the grinding machine in a plane perpendicular to the rotation axis of the lens. This results in a number of disadvantages:

a. positioning the frame support on the machine is a delicate and by no means easy operation; it is usually necessary to remove the sides of the spectacle frame as they would otherwise tend to swing about as the frame rotates about its horizontal axis;

b. the fact that the copying assembly is mounted off-centre at the end of the lens supporting carriage generates out-of-balance forces detrimental to accuracy;

c. in certain special cases the operator may wish to have the option of producing a lens according to a template, in which case he is compelled to remove the copying assembly and fit a template support in its place;

d. lastly, the main disadvantage of such prior art machines is that, because the copying assembly is secured to the lens supporting carriage, free transverse motion of the latter is compromised by the lateral resistance offered by the feeler positioned in the bezel's groove; this makes it difficult to perform the bevelling operations, which require the carriage to be free, i.e., to be able to move laterally relative to the groove in the bevelling wheel responsively to variations in the curvature of the lens as it rotates.

In prior art systems furthermore, the frame support provides only one connection for imparting rotation, so that only one eye of the frame -- chosen arbitrarily -- can be properly positioned on the support.

This has several drawbacks:

In order to make the second lens (corresponding to the other eye of the spectacle frame) it is necessary either to turn the frame round in its support, thus entailing a dual manipulation and a dual centering of the frame, or to turn the lens round, which then makes certain grinding operations impossible, such as guided bevelling or the cutting of facets.

Further, it frequently happens that, in the same frame, the two eyes have bezels which are not of exactly the same size, in which case the second lens produced will be too small and have to be rejected, or be too large and require reworking.

In addition, it is not usually possible either to make accurate offsettings of the frame or to adjust the offsets of each frame eye separately. It consequently becomes mandatory to make the offsets on the lens, in which case the latter will no longer be positioned on the grinding machine in a plane perpendicular to its rotation axis, making it impossible to bevel it properly. Moreover, the operator must wait until the lens has finished being ground before removing the frame from its support and fitting a new frame for the next job. This results in considerable non-productive loss of time in operation of the lens grinding machine.

It has been found moreover that in all automatic spectacle lens grinding machines the point of contact between the grinding wheel and the lens shifts continually on either side of the line joining the centres of the grinding wheel and the lens, responsively to successive variations in the radius of the lens being ground. Hence in the case of machines for copy-grinding the lens according to the frame, the bezel feeler device must assume successive corresponding positions along the frame bezel.

In accordance with a known principle, the feeler is supported by a hinged lever the radius of which is equal to the grinding wheel radius and the hinge point of which corresponds substantially with the centre of the grinding wheel and is pulled downwardly by a spring or counterweight in such manner that the feeler be always returned to the lowermost point of the frame corresponding with the point of contact of the lens with the grinding wheel.

In practice, this arrangement has several drawbacks:

-- In the case of plastic spectacles, the interior of the bezel often reveals irregularities, corrugations, snag marks, and so on, that cuase the feeler or sensing point to move unevenly.

-- In the case of metal spectacles, the two ends of the bezel are not always perfectly aligned; flash is frequently present at the weld spot, so that when the bezel joint arrives beneath the feeler the latter is accidently entrained.

-- Lastly, the rotation of the frame tends to shift the feeler in the direction of rotation, so that there is invariably a certain amount of drift in the sensing point that varies according to the coefficient of friction between the bezel and the feeler.

This results in frequent distortions in the lens because the position of the sensing point in relation to the axis of the centres does not always correspond with the position of the contact point between the lens and the grinding wheel in relation to said axis.

It is the object of the present invention to overcome all the above-mentioned drawbacks and accordingly to provide a machine for grinding spectacle lenses according to the spectacle frame, in which the grinding pressure is independent of the bezel feeler pressure and can be adjusted to as high a value as required, it being possible for the feeler pressure to be very low.

A further object provides for the spectacle frame to be mounted horizontally on its support, which support is mechanically independent of the grinding machine lensholder allowing grinding of the two lenses without reversing either the frame or the lenses.

In addition, it is an object to provide a device for installing the frame support very quickly and easily making possible to use two frame supports in order that the one can be readied while the other is being worked upon. A machine according to a further object of this invention will allow grinding lenses according to a template substituted for the frame.

SUMMARY OF THE INVENTION

A lens grinding machine according to the present invention comprises two sections which are independent mechanically. The first portion includes a horizontal frame support which is rotated by a motor through one of two quickly engageable parts which are independently adjustable and correspond to the two frame eyes respectively. A fixed feeler follows the bezel of each eye in succession. The frame support is provided on the end of an arm movable in a horizontal plane, and the position of this arm is measured by a sensor which, subsequent to transmission to a second machine section with power amplification, mechanically controls the position of a further similar arm carrying a motor for rotating the lens to be ground, said motor being caused to rotate synchronously with the frame support motor by suitable synchronization means.

In the case of rimless spectacles, the frame can be replaced by a template consisting of a thin sheet mounted on a suitable support similar to the frame support, the contour of this sheet being followed by a mechanical feeler; alternatively, said sheet may merely bear a contour tracing which can be followed by a preferably optical or magnetic contactless sensor.

Further, in order to constrain the feeling point on the bezel so that it is homologous with the lens grinding point in order to ensure greater grinding accuracy, the bezel feeler means according to this invention may be movable and comprise means for so slaving its position that the sensing point be at all times homologous with the grinding point on the corresponding lens. The sensing point to be determined by the slaving means can be defined either as the extreme point on the bezel in a direction homologous with the grinding-wheel and lens centerline or as the point on the bezel at which the tangent thereto is perpendicular to the straight line homologous with the straight line joining the centre of the grinding-wheel to the contact point thereof with the lens being ground.

In the latter event, the direction of the tangent can be determined by a sensor for measuring the position of auxiliary feelers which feel the bezel on either side of the main feeler and define a bezel secant very close to the tangent sensing or feeling point. Alternatively, the direction of said tangent can be determined mathematically by differentiating the successively varying radii of the bezel in polar coordinates, preferably with respect to the centre of the bezel, and this with the help of an auxiliary computer.

The feeling arm of a feeler device according to this invention is preferably possessed of continuous transverse or orthogonal low-amplitude high-frequency vibration with respect to the bezel of the spectacle frame. Such vibration allows the feeler arm to pass more readily over bezel surface irregularities and helps to obtain the desired position of the sensing point. It can be used with advantage, moreover, to so control the copying chain of the machine as to cause copying to be effected only at the lowermost point on the bezel.

It is a further object of the invention to overcome another disadvantage which stems from the fact that the different finishing grinding-wheels used on automatic grinding machines are not all of the same height and that the feeler must be calibrated differently according to the type of finish required. In accordance with the invention, such calibration is accomplished through the agency of means which adjust the system for slaving the motions of the arm supporting the lens-carrier by copying the motions of the arm supporting the frame carrier. This adjusting means permits the initial setting of one of the arms with respect to the other to be selectively adjusted. In accordance with the invention, the adjusting means are preferably electrically operating means such as resistors or potentiometers affecting the copying chain. These latter means can provide either intermittent adjustment to allow adapting to grinding-wheels of different heights or radii, or continuous adjustment to provide compensation for variable differences resulting, say, from wear on the grinding-wheels. Preferably, the intermittent adjusting means are controlled by a machine operation program determined according to the type of finish required for the lenses.

The description which follows with reference to the accompanying non-limitative exemplary drawings will give a clear understanding of how the invention can be carried into practice.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings:

FIG. 1 schematically illustrates the two sections A and B of a lens grinding machine according to the invention;

FIG. 2 is a section through the line II--II in FIG. 1, showing the spectacle-frame support of the machine and its driving means;

FIG. 3 is a section through the line III--III of FIG. 1, showing the same frame support;

FIG. 4 shows the frame support of FIG. 2 removed from the machine and placed on a flat surface;

FIG. 5 schematically portrays a section A in which the frame is replaced by a mechanical template;

FIG. 6 schematically portrays a section A in which the frame is replaced by a sheet bearing a tracing of the desired contour;

FIG. 7 collectively illustrates in diagrammatic form a spectacle frame, the associated feeler, a lens and a grinding-wheel forming part of a machine for trimming the edges of spectacle lenses;

FIG. 8 shows a first embodiment of movable feeler means according to the invention;

FIG. 9 shows a second embodiment of movable feeler means according to the invention;

FIG. 10 shows a third embodiment of movable feeler means according to the invention;

FIG. 11 shows a fourth embodiment of movable feeler means according to the invention;

FIG. 12 shows a fifth embodiment of movable feeler means according to the invention;

FIGS. 13A and 13B show detail XIII of FIG. 10 on an enlarged scale, in two different positions;

FIG. 14 is a top view of a position sensor suitable for the subject of FIGS. 13A and 13B;

FIG. 15 is a sectional view through the line XV--XV of the subject of FIG. 14; and

FIG. 16 portrays detail XVI of FIG. 11 on an enlarged scale.

DESCRIPTION OF THE INVENTION

A machine according to this invention consists of two sections: a section A in which the shape of the spectacle-frame bezels is analysed and a section B in which the lenses are ground accordingly. In FIG. 1, these sections are separated by a dot-dash line. Section A is shown as a top view and section B as a side elevation view. A frame support 1 comprises a horizontal baseplate 3 on which a spectacle frame 2 is fixed in the flat position and beneath which are mounted, substantially underneath each eye of the frame, two similar driving parts 4 and 5. One of these parts, for instance the part 5, engages with and is elastically latched to a sleeve 6 with which it is made angularly rigid by studs 7 on sleeve 6 engaging into corresponding recesses 8 in part 5. Sleeve 6 is rotatable in a bearing supporting ball-bearings 10, 11 on the end of a horizontal arm 9 pivotally mounted about a fixed vertical pin 12 extending through its other end. An electric motor 13 fixed to arm 9 rotates sleeve 6, part 5 and frame support 1 relatively to said arm through a drive pinion 14 meshing with a gearwheel 15 of large diameter secured fast with said sleeve. Said motor may be a stepwise motor or a synchronous motor.

A frame feeler point 16 is carried on the end of a vertical rod 17 extending through sleeve 6 and through an opening 18 formed in part 5. The point 16 is applied against the bottom of the bezel 19 of the frame eye corresponding to part 5. Rod 17 is extended by a horizontal rod 20 which may be caused to slide in a fixed support 21 by means of a hand lever 22 hingedly connected to the end of rod 20. Lever 22 controls the setting in the work position of feeler 16 in bezel 19 by pulling on rod 20 until an annular stop 23 on said rod contacts the support 21. Arm 9 of frame support 1, which is subjected to the restoring force of a spring 24, then assumes an angular position which is adjustable by means of micrometer adjustment means 25 of the position of stop 23 on rod 20.

The spectacle lens to be ground 26 is held in the vertical plane of grinding-wheel 28 by a support 120 on the end of an arm 29 which is pivotable about a horizontal pin 30 extending through its other end. This arm is similar to the arm 9 of frame support 1, being of equal length thereto and likewise comprising an electric motor 31 similar to motor 13 whereby to rotate the support 120 of lens 26 through reduction gears 32, 33. Alternatively, the lens can be rotated directly by motor 13 through suitable bevel gearing. Arm 29 further carries a weight 34 which provides the force needed to apply lens 26 against grinding-wheel 28.

The angular travel of arm 29 is limited downwardly by an adjustable stop 35 positioned at the end of an auxiliary arm 36 pivoting about a horizontal pin 37, the angular position of which arm is dependent on a rod 39 driven by any convenient means 38 such as an electric, magnetic or hydraulic servomotor for imparting linear or rotary motion. Alternatively, the motor 38 could provide the required grinding pressure itself.

The machine functions in the following manner: the spectacle frame 2 is first secured flat on its support 1 and the feeler 16 is applied by means of the lever 22 against the bottom of the bezel 19 to which the lens to be ground 26 must be matched, the appropriate initial position of arm 9 being obtained by adjustment of the micrometer device 25. When the stop 23, associated with the micrometer device, contacts the support 21 of rod 20, it closes an electric contact switch 40, energizing the motor 13. As the latter rotates it rotates the frame 2 (via its support 1) about the axis of sleeve 6. Thereafter the angular position of arm 9, which is urged back by the spring 24, varies with the varying radius of bezel 19. This angular position is measured by a displacement detector 41 connected through a rod 42 to arm 9. This detector is part of a remote transmission system 43 comprising at least one power amplifier which feeds the drive means 38 for auxiliary arm 36 in such manner that the angular shifting of arm 36 is invariably equal to those of arm 9.

Further, motor 31, which is energized at the same time as motor 13, is caused to rotate synchronously therewith by synthronization means 44 setting the lens 26 in identical rotation with the frame 2. As the lens shares the angular motions of arm 29, controlled by stop 35 on arm 36, with the cooperation of the weight 34, the motions copying those of arm 9, the lens is ground by grindingwheel 28 in strict conformity with the contour of the bezel 19 for which it is intended.

Thus it will be seen that the desired result is obtained, in accordance with this invention, by means of two distinct units, to wit, a unit A which explores the spectacle frame and a unit B which reproduces on the grinding machine the data issuing from unit A via remote transmission means. The grinding pressure is thus made independent of the feeling pressure, thereby eliminating the usual drawbacks. Further, this arrangement allows the lens holder device to be relieved of all supplementary accessories. Hence by designing this device to have minimum inertia, it is possible to obtain perfectly even bevels irrespective of variations in the curvature of the lens as it rotates.

Additionally, the work is facilitated through the use of a frame support which is independent of the grinding machine. Such an arrangement can be adapted to existing spectacle lens grinding machines more readily and more cheaply. Moreover, it allows template jobs to be performed without any dismantling operations.

The copying chain interconnecting unit A and unit B can be devised with the most appropriate transmission and amplification components, the latter being preferably mechanical, hydraulic, optical, magnetic, electric, photoelectric or electronic.

A machine according to this invention possesses countless features and adjustment possibilities that endow it with great functional flexibility. As already stated, the frame support 1 comprises two rotation imparting parts 4, 5, each corresponding to one of the spectacle-frame eyes. The two lenses are ground by simply engaging the parts 4 and 5 into the sleeve 6 in succession, without manipulating the frame or reversing one of the lenses, each lens being ground to match the bezel for which it is intended. In addition, the position of each of the two parts 4, 5 is laterally adjustable by independent micrometer-screw controls 45, 46, and is identified by means of pointers 47, 48 fixed to parts 4 and 5 respectively and graduated scales 49, 50 carried on a member 51 of support 1. These scales can be so graduated that the sum of the two readings corresponds with the sum of the geometrical centre distances it is required to obtain between the two lenses to be ground, the distance being determined by the operator according to the distance between the pupils of the eyes of the person for whom the spectacles are intended.

The transverse position of frame 2 on plate 3 is determined by an abutment strip 52 slidable along guides 53, 54 and positionally adjustable by means of micrometer screw means 55 with locating graduation marks 62. The frame 2 is applied against strip 52, then secured by means of horizontally and vertically acting means 56 and 57 respectively.

Thus, since the adjustment means 45, 46 and 55 allow all desired offsets, it is possible, in the case of each frameeye, to fetch the rotation centre of the frame into the appropriate position in relation to the bezel, which position corresponds to the optical centre of the lens to be ground.

Furthermore, the fact that the spectacle frame can be offset in any desired degree relative to its rotation axis makes it possible to position the centre of the lens to be ground on the rotation axis of the lens about itself, in such manner that, regardless of its curvature, the lens remain in a plane perpendicular to its rotation axis, thereby enabling it to be correctly bevelled.

The means enabling each of the two parts 4, 5 to be engaged with drive sleeve 6 allows the operator to rapidly fit or remove the support 1; moreover, the frame support is devised so that it can be properly positioned flat on a table. Thus, by making two identical spectacle-frame supports available to the operator, it is possible to mount one frame on one of the supports placed flat on a table (FIG. 4) while the second support is used on the machine to reproduce a lens according to the frame.

The angular setting of arms 9 and 36 can be verified by means of indiator means 58 and 59, and that of motors 13 and 31 by indicator means 60 and 61. Examples of such indicator means are angle encoders or devices which deliver a signal that becomes null when synchronism is achieved.

A machine according to this invention is likewise capable of grinding spectacle lenses, not on the basis of the frame but of a template replacing either the frame or the customary template. Whereas the latter is designed to withstand the grinding pressure, the substitute template can in this case be made of a thin sheet of metal or rigid plastic by reason of the low feeler pressure being greatly below the grinding pressure. FIG. 5 shows such a template 63 fixed to an appropriate support 121 carried on the end of an arm 9 devised and actuated as heretofore described (FIG. 1), like parts bearing like reference numerals. Template 63 is convex, and a point on its outer contour contacts a feeler head 64 replacing the bezel feeler 16 and likewise convex, its radius of curvature being preferably equal to that of the grinding-wheel. This head 64 is mounted on the end of a rod 20 which can be moved longitudinally by a lever 22 identical to the lever in FIG. 1, with the same associated parts 21, 23, 25 and 40. Template 63 is applied against the head 64 by a spring 24a corresponding to spring 24 but exerting an oppositely directed force on arm 9. The manner of operation of a machine section A devised as above is similar to that of the machine section A previously described (FIG. 1).

Alternatively, template 63 can be replaced by a thin sheet 65, such as a sheet of paper, on which is inscribed the desired lens contour 66 (FIG. 6). Sheet 65 is fixed to a support 122 likewise carried on the end of an arm 9 as hereinbefore described but devoid of a return spring 24 or 24a. The lower part 67 of contour 66 is distinguished from the rest of sheet 65 by a simple physical property, being for instance black on a white background, or vice versa; alternatively it may have magnetic properties different from those of the remainder of the sheet. The feeler is an appropriate detector 68, such as an optical or magnetic detector. Its position is fixed and it is coupled to a slaving circuit 69 which energizes a linear servo-motor 70 that actuates arm 9 mechanicaly through a rod 71 in such manner that the edge of the detector head 68 be invariably positioned exactly opposite a point on the contour 66. This being so, arm 9 is possessed of the same motions as in the previous embodiments (FIGS. 1 and 5), and the remainder of the machine is unchanged. Alternatively, arm 9 may remain stationary, in which case the head 68 is movable and its motions impart identical motions to the lens support.

The two sections A and B of a machine according to this invention, in the different embodiments hereinbefore described, may, by virtue of their indirect interconnection via a remote copying chain, be dissociated and not used concurrently, in which case the data issuing from section A and defining the shape of a spectacle-frame bezel are stored in a memory such as a punched-tape or magnetic-tape recorder. The recording obtained is then applied to section B in such manner that the lens support be actuated in the way hereinbefore described. Further, an A-section can be associated to two or more B-sections and drive the same synchronously. This makes 14 possible in particular to produce the two spectacle lenses simultaneously on the basis of only one of the frame bezels, by means of two symmetrically operating sections B and B' (FIG. 1) which are copy-referenced to one and the same section A bearing the spectacle frame. Manifestly, this solution is viable provided only that the contours of the two spectacle-frame bezels are mirror-images of each other.

FIG. 7 shows that, in order to ensure that the lens 26 is ground in exact conformity with the bezel 19 for which it is intended, the feeler point 70 on bezel 19 must at all times be homologously positioned with the grinding point 71 on lens 26. But because, as the grinding operation proceeds, the grinding point 71 recedes in variable manner from the centerline 72 joining the centre 73 of grinding-wheel 28 to the centre 74 of lens 26, the feeler point 70 on bezel 19 must shift correspondingly in relation to the line 75 joining the centre 76 of bezel 19 to the point 77 homologous with the grinding-wheel centre 73. If the feeler point 16 is carried on an arm 78 substantially equal in length to the radius of grinding-wheel 28 and capable of pivoting about the point 77, then this means that the angle α which arm 78 forms with the line 75 must at all times be maintained equal to the angle β which the radius line of grinding-wheel 28 to the grinding point 71 forms with the line 72, and this irrespective of friction between feeler 16 and bezel 19 or of unevenness in the latter.

In the specific embodiment shown in FIG. 8, the arm 78 carrying the feeler 16 is made to continuously vibrate about its end 77 by convenient drive means such as an electromechanical generator with rotating weights, an electromagnetic vibrator, an ultrasonics generator, or any other convenient means. This vibration is of high frequency and low amplitude and can be adjusted according to the type of spectacle frame. The mean position of the feeling point is thereby made independent of the surface condition of the bezel or of unevennesses thereon. It is to be understood that this vibratory motion can be applied to all the slaved feeler devices with mechanical feeling points to be described hereinbelow with reference to FIGS. 10 through 12.

FIG. 8 further shows that the end 77 of arm 78 is guided linearly along the axis 75, within appropriate means 79 for detecting the position of the point 77. This position detector is so coordinated with the copying-chain for controlling the position of the lens before the grinding-wheel that the copying data is transmitted to the lens supporting arm only when the position of point 77 is farthest from the bezel in the course of a complete excursion of feeler 16, the latter being then located at the extreme point on the bezel in the direction of axis 75, i.e., at the point homologous with grinding point 71 (FIG. 7).

The feeler point homologous with the grinding point 71 is defined in similar manner in the feeler system shown in FIG. 9. This system comprises a series of suitable contacts or proximity detectors 80 which ara capable of exploring the interior of bezel 19 and are positioned one after the other along a circular arc 81 homologous with the periphery of grinding-wheel 28, on a support 82 which is provided with an arm 83 sliding along the axis 75 responsively to drive means 84. The latter acts on the overall position of the detectors 80 under servo control means in such manner that, in that particular position, only one of the detectors 80A may lie facing the interior of bezel 19.

The feeler devices of FIGS. 10 and 11 differ little from each other. They comprise a mechanical feeler point 16, closely flanked on either side by two auxiliary feeler points 85 capable of sliding parallel to the axis of supporting arm 78 and continuously applied by elastic means against the inside of bezel 19. Supporting arm 78 is pivotable about its end 77 and its position is governed by rotation imparting means 86 controlled by slaving means on the basis of position sensors associated to the auxiliary feeler points 85, thereby causing the straight line joining the ends thereof (which virtually merges with the tangent 87 to the bezel) to remain perpendicular to the axis of arm 78. When this is the case, the position of the feeling point is homologous with the grinding point 71 (FIG. 7). Two corresponding exemplary embodiments will be described in greater detail hereinbelow.

FIG. 12 shows an alternative embodiment in which a single feeler point 16 is carried on the end of arm 78 which is capable of pivoting about its end 77 responsively to drive means 86. The tangent 87 to bezel 19 is defined mathematically by a computer on the basis of the variations in the angular position of arm 9 carrying the support for frame 2, in the course of rotation of the latter about the centre 76 if bezel 19, which variations depend on the successive changes in the length of the vector radius 88 joining centre 76 to feeling point 70. Through the agency of slaving means, the computer so controls the means 86 for driving the arm 78 that the tangent 87 at sensing point 70 remain perpendicular to the axis of arm 78.

FIGS. 13A and 13B illustrate an exemplary embodiment of the arrangement used for the feeler in FIG. 10. The main feeler 16 is provided with two lateral sleeves 89 through which are slidable, parallel to the axis of arm 78, two rods 90 carrying the auxiliary feelers 85 and applied by springs 91 against a common beam-lever 92 capable of rocking motion about a central pivot 93 fast with feeler 16. The angle 94 formed by beam-lever 92 with arm axis 78 is measured by an angle sensor, and means for slaving the position of the arm operate on the basis of this sensor to maintain said angle at 90°. An angle sensor usable in this particular application is shown in FIGS. 14 and 15. Beam-lever 92 rotates a disc 95 embodying a hole 96 which is illuminated by a light source 97 beamed in the direction of two photoelectric cells 98 which are positioned so as to receive equal light intensity when the beam-lever defines an angle 94 equal to a right angle. The cells 98 are electrically connected in a differential configuration whereby to drive the means for slaving arm 78.

An exemplary embodiment of the feeler arrangement of FIG. 11 is shown in FIG. 16. The auxiliary feelers are supported as before by sliding rods 90 which are urged towards the bezel by springs 99 and carry photoelectric cells 100 illuminated by a common light source 101 fast with feeler 16, through holes 102. Here also the cells 100 are connected in a differential configuration in order to drive the means for slaving the arm 78, the components 100, 101, and 102 jointly forming a linear position detector for measuring the respective positions of the pair of auxiliary feelers 85 in relation to main feeler 16.

The various position detectors or proximity sensors utilized can be electric, magnetic, optical or electronic devices, or devices sensitive to other kinds of waves.

The present invention further relates to means for calibrating the feeler device, in order notably to initially set the position of lens 26 before grinding-wheel 28 and that of the feeler 16 which feels the bezel 19 of frame 2. This initial setting must allow for the height or radius of the grinding-wheel and for the different types of grinding surface and shapes of the grinding-wheel, the dimensions of which may differ. Allowance must also be made for gradual wear on the grinding-wheels, which reduces their radius.

It is a teaching of this invention that the machine is provided with relevant adjustment means 110 (FIG. 1) for operating on the copying chain, which chain is preferably controlled automatically by the machine program which selects the desired type of finish and controls the manner in which the lens to be ground is offered up the appropriate grinding-wheel. In an electric or electronic copying chain, such adjustment means employ switchable resistors 111 which provide intermittent adjustment according to the different grinding-wheel radii, and potentiometers 112 which provide continuous fine adjustment to compensate for grinding-wheel wear. Such adjustment means likewise provide compensation for other similar parameters affecting the calibration and may provide any desired initial settings.