Note: Within nine months of the publication of the mention of the grant of the European patent in the European PatentBulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with theImplementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has beenpaid. (Art. 99(1) European Patent Convention).

Printed by Jouve, 75001 PARIS (FR)

(19)E

P0

890

414

B1

TEPZZZ89Z4_4B_T(11) EP 0 890 414 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention of the grant of the patent: 10.12.2014 Bulletin 2014/50

(21) Application number: 98112667.5

(22) Date of filing: 08.07.1998

(51) Int Cl.:B24B 9/14 (2006.01) B24B 17/10 (2006.01)

B24B 49/00 (2012.01) B24B 49/02 (2006.01)

(54) Lens grinding apparatus

Linsenschleifvorrichtung

Dispositif de meulage de lentilles

(84) Designated Contracting States: DE ES FR GB

(30) Priority: 08.07.1997 JP 19922797

(43) Date of publication of application: 13.01.1999 Bulletin 1999/02

(73) Proprietor: Nidek Co., Ltd.GamagoriAichi (JP)

(72) Inventors: • Obayashi, Hirokatsu

Hoi-gun,Aichi (JP)

• Shibata, RyojiToyokawa-shi,Aichi (JP)

(74) Representative: Weber, JoachimHoefer & Partner Patentanwälte Pilgersheimer Strasse 2081543 München (DE)

(56) References cited: EP-A- 0 379 426 EP-A- 0 510 462EP-A- 0 798 076 EP-A- 0 798 077GB-A- 2 117 287 US-A- 5 347 762

• PATENT ABSTRACTS OF JAPAN vol. 016, no. 498 (M-1325), 15 October 1992 (1992-10-15) -& JP 04 183566 A (NIDEK CO LTD), 30 June 1992 (1992-06-30)

EP 0 890 414 B1

2

5

10

15

20

25

30

35

40

45

50

55

Description

[0001] The present invention relates to a lens grindingapparatus which grinds the periphery of an eyeglass lens(see for example GB-A-2117287).[0002] An apparatus is known which grinds an eye-glass lens so that it fits into an eyeglass frame. In anoptician’s shop, an optician processes the periphery ofeach eyeglass lens so as to make the periphery coinci-dent with the shape of an eyeglass frame selected by thecustomer, to form a bevel or a groove, and then mountsthe processed lens into the frame. The thus groundedlens has an angular portion at front and rear ends of theedge. If such angular portions are left intact, they maypossibly hurt the user or become a cause of crack orbreakage of the lens. Therefore, it is common practicefor lens processors to chamfer edge portions.[0003] Conventionally, such chamfering is performedwith a hand grinder having a rotating grinding wheelbounded by conical slope, and the optician who holds alens urges its edge into contact with the chamfering grind-ing wheel and chamfers edge portions to give a desiredshape under visual checking.[0004] However, such a chamfering operation with ahand grinder requires skill and is not easy to perform.For an unskilled optician, the operation is time-consum-ing and does not guarantee grinding to the intendedshape. Furthermore, chamfering constitutes an impor-tant factor in appearance.

SUMMARY OF THE INVENTION

[0005] In view of the problems, it is an object of theinvention to provide a lens grinding apparatus with whicha chamfering process can be easily performed to a de-sired shape and particularly chamfering can be uniformlyperformed.[0006] The object is solved by the features of claim 1.The dependent claims contain further preferred develop-ments.[0007] The present disclosure relates to the subjectmater contained in Japanese patent application No. Hei.9-199227 (filed on July 8, 1997).

BRIEF DESCRIPTION OF THE DRAWING

[0008]

Fig. 1 is a diagram illustrating the general configu-ration of the apparatus.Fig. 2 is a diagram illustrating the configuration ofgrinding wheels in the apparatus of the embodiment.Fig. 3 is a view illustrating upper and lower parts ofa lens chuck.Fig. 4 is a view illustrating the mechanism for movinga lens grinding part 300R.Fig. 5 is a sectional side view illustrating the config-uration of the lens grinding part 300R.

Fig. 6 is a diagram illustrating a lens thickness meas-uring section.Fig. 7 is a schematic block diagram showing a controlsystem of the apparatus of the embodiment.Fig. 8 is a flowchart illustrating a method of calculat-ing a chamfering process locus.Fig. 9 is a diagram illustrating the calculation of ameasurement locus in a second measurement.Fig. 10 is a diagram illustrating the calculation of acorrection angle σ of a rear surface inclination angleρ in a finishing grinding wheel.Fig. 11 is a diagram illustrating the calculation of anedge position P3 after a finishing process.Fig. 12 is a diagram illustrating a change due to aperipheral length change and the calculation of a cor-rection amount ω in the direction of a reference lineL3.Fig. 13 is a diagram illustrating the calculation of theedge position after a finishing process in the casewhere a peripheral length correction is performed.Fig. 14 is a diagram illustrating the calculation of thechamfering process locus.Fig. 15 is a diagram illustrating the calculation of avalue of a bevel bottom position in a radial directionof the lens.Fig. 16 is a side view for explanation about a rearsurface inclination angle ρ of a finishing grindingwheel.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0009] A lens grinding apparatus according to an em-bodiment of the present invention will be hereinafter de-scribed with reference to the accompanying drawings.

Configuration of Whole Apparatus

[0010] In Fig. 1, reference numeral 1 denotes a mainbase, and 2 denotes a sub-base that is fixed to the mainbase 1. A lens chuck upper part 100 and a lens chucklower part 150 hold a lens to be processed by means oftheir respective chuck shafts during processing it. A lensthickness measuring section 400 is accommodated be-low the lens chuck upper part 100 in the depth of the sub-base 2.[0011] Reference symbols 300R and 300L respective-ly represent right and left lens grinding parts each havinggrinding wheels for lens grinding on its rotary shaft. Eachof the lens grinding parts 300R and 300L is held by amoving mechanism (described later) so as to be movablein the vertical and horizontal directions with respect tothe sub-base 2. As shown in Fig. 2, a rough grindingwheel 30 and a finishing grinding wheel 31 having a bevelgroove are mounted on the rotary shaft of the lens grind-ing part 300L. Further, a front surface chamfering grind-ing wheel 32 having a conical surface is coaxially at-tached to the upper end surface of the finishing grindingwheel 31, while a rear surface chamfering grinding wheel

1 2

EP 0 890 414 B1

3

5

10

15

20

25

30

35

40

45

50

55

33 having a conical surface is coaxially attached to thelower end surface of the rough grinding wheel 30. On theother hand, a rough grinding wheel 30, a mirror-finishing(polishing) grinding wheel 34 having a bevel groove, afront surface mirror-chamfering grinding wheel 35 havinga conical surface, and a rear surface mirror-chamferinggrinding wheel 36 having a conical surface are mountedon the rotary shaft of the lens grinding part 300R coaxi-ally. The diameter of these grinding wheels are relativelysmall, that is, about 60 mm. The chamfering surface ofeach of the chamfering grinding wheels 32, 33, 35 and36 is 4mm in height and 45° in inclination.[0012] A display unit 10 for displaying processing dataand other information and an input unit 11 for allowing auser to input data or an instruction to the lens grindingapparatus are provided in the front surface of a body ofthe apparatus. Reference numeral 12 denotes a closabledoor.

Structures of Main Parts

<Lens Chuck Part>

[0013] Fig. 3 illustrates the lens chuck upper part 100and the lens chuck lower part 150. A fixing block 101 isfixed to the sub-base 2. A DC motor 103 is mounted ontop of the fixing block 101 by means of a mounting plate102. The rotational force of the DC motor 103 is trans-mitted through a pulley 104, a timing belt 108 and a pulley107 to a feed screw 105. As the feed screw 105 is rotated,a chuck shaft holder 120 is vertically moved while beingguided by a guide rail 109 fixed to the fixing block 101.A pulse motor 130 is fixed to the top portion of the chuckshaft holder 120, so that the rotational force of the pulsemotor 130 is transmitted via a gear 131 and a relay gear132 to a gear 133 to rotate the chuck shaft 121.[0014] A lower chuck shaft 152 is rotatably held by achuck shaft holder 151 fixed to the main base 1. Therotational force of a pulse motor 156 is transmitted to thechuck shaft 152 to rotate the chuck shaft 152.

<Moving Mechanism for Lens Grinding Part>

[0015] Fig. 4 illustrates a mechanism for moving theright lens grinding part 300R. (Since a moving mecha-nism for the left lens grinding part 300L is symmetricalwith that for the right lens grinding part 300R, it will notbe described.) A vertical slide base 201 is vertically sli-dable along two guide rails 202 that are fixed to the frontsurface of the sub-base 2. A nut block 206 is fixed to thevertical slide base 201. When a ball screw 205 coupledto the rotating shaft of the pulse motor 204R is rotated,the vertical slide base 201 is moved in the vertical direc-tion together with the nut block 206.[0016] Reference numeral 210 denotes a horizontalslide base to which the lens grinding part 300R is fixed.The horizontal slide base 210 is slidable in the horizontaldirection along two slide guide rails 211 that are fixed to

the front surface of the vertical slide base 201. A mech-anism for moving the horizontal slide base 210 is basi-cally the same as the above-described moving mecha-nism for the vertical slide base 201. The pulse motor214R rotates the ball screw 213, so that the horizontalslide base 210 fixed to the nut block 215 is moved ac-cordingly in the horizontal direction along the guide rails211.

<Lens Grinding Part>

[0017] Fig. 5 is a side sectional view showing the struc-ture of the right lens grinding part 300R. A shaft supportbase 301 is fixed to the horizontal slide base 210. A hous-ing 305 is fixed to the front portion of the shaft supportbase 301, and rotatably holds therein a vertically extend-ing rotary shaft 304. A group of grinding wheels includinga rough grinding wheel 30 and so on are mounted on thelower portion of the rotary shaft 304. A servo motor 310Ris fixed to the top surface of the shaft support base 301through a mounting plate 311, so that the rotational forceof the servo motor 310R is transmitted via a pulley 312,a belt 313 and a pulley 306 to the rotary shaft 304, therebyrotating the group of the grinding wheels.[0018] Since the left lens grinding part 300L is sym-metrical with the right lens grinding part 300R, its struc-ture will not be described.

<Lens Thickness Measuring Section>

[0019] Fig. 6 illustrates the lens thickness measuringsection 400 (Fig. 1). The lens thickness measuring sec-tion 400 includes a measuring arm 527 having two feelers523 and 524, a rotation mechanism such as a DC motor(not shown) for rotating the measuring arm 527, a sensorplate 510 and photo-switches 504 and 505 for detectingthe rotation of the measuring arm 527 to thereby allowcontrol of the rotation of the DC motor, a detection mech-anism such as a potentiometer 506 for detecting theamount of rotation of the measuring arm 527 to therebyobtain the shapes of the front and rear surfaces of thelens. The configuration of the lens thickness measuringsection 400 is basically the same as that disclosed inJapanese Unexamined Patent Publication No. Hei.3-20603 and U.S. Patent No. 5,333,412 filed by or as-signed to the present assignee, which are referred to fordetails of the lens thickness measuring section 400. Adifference from that disclosed in Japanese publication3-20603 is that the lens thickness measuring section 400of Fig. 6 is so controlled as to move in front-rear direction(indicated by arrows in Fig. 6) relative to the lens grindingapparatus by a front-rear moving means 630 based onedge processing data.[0020] In addition, the lens thickness (edge thickness)measurement is performed in the following manner. Themeasuring arm 527 is rotated, that is elevated, so thatthe feeler 523 is brought into contact with the lens frontrefraction surface. While keeping the feeler 523 in contact

3 4

EP 0 890 414 B1

4

5

10

15

20

25

30

35

40

45

50

55

with the lens front refraction surface, the lens is rotatedas well as the lens thickness measuring section 400 iscontrolled to move forward or backward by the front-rearmoving means 630, so that the shape of the lens frontrefraction surface (on the edge of the lens to be formed)is obtained. Then, the shape of the lens rear refractionsurface (on the edge of the lens to be formed) is obtainedsimilarly by rotating the lens and by moving the lens thick-ness measurement section 400 while keeping the feeler524 in contact with the lens rear refraction surface. Basedon the shapes of the lens front and rear refraction sur-faces, the lens thickness (edge thickness) is obtained.The lens thickness is measured such that the measuringarm 527 is rotated upward from its lower initial positionand the feelers 523 and 524 are respectively brought intocontact with the front and rear refraction surfaces of thelens. Therefore, it is preferable that the rotary shaft of themeasuring arm 527 be equipped with a coil spring or thelike which cancels out the downward load of the meas-uring arm 527.

<Control System>

[0021] Fig. 7 is a block diagram showing a general con-figuration of a control system of the lens grinding appa-ratus. Reference character 600 denotes a control unitwhich controls the whole apparatus. The display unit 10,input unit 11, micro switch 110, and photosensors areconnected to the control unit 600. The motors for movingor rotating the respective parts are connected to the con-trol unit 600 via drivers 620-628. The drivers 622 and625, which are respectively connected to the servo motor310R for the right lens grinding part 300R and the servomotor 310L for the left lens grinding part 300L, detect thetorque of the servo motors 310R and 310L during theprocessing and feed back the detected torque to the con-trol unit 600. The control unit 600 uses the torque infor-mation to control the movement of the lens grinding parts300R and 300L as well as the rotation of the lens.[0022] Reference numeral 601 denotes an interfacecircuit which serves to transmit and receive data. An eye-glass frame shape measuring apparatus 650 (see USP5,333,412), a host computer 651 for managing lensprocessing data, a bar code scanner 652, etc. may beconnected to the interface circuit 601. A main programmemory 602 stores a program for operating the lensgrinding apparatus. A data memory 603 stores data thatare supplied through the interface circuit 601, lens thick-ness measurement data, and other data.

Operation

[0023] Next, a method of calculating the process locusin the chamfering process will be described (see the flow-chart of Fig. 8). First, an edge position locus after thefinishing process is obtained, and the chamfering proc-ess locus is then calculated on the basis of the edgeposition locus.

(I) Calculation of edge position locus

[0024] When a chamfering process is to be performedon each of the rear and front refraction surfaces of thelens, the edge position locus is obtained in each of thesurfaces. Hereinafter, the case where the process is per-formed on the rear surface of the lens will be described.[0025] When the edge position locus is to be calculat-ed, two-dimensional process data with respect to the ro-tation center of the lens are obtained on the basis of theframe shape data obtained by the eyeglass frame shapemeasuring apparatus 650 and the layout data inputthrough the input unit 11 (processes such as correctionof warpage of the frame may be added). By using thelens thickness measuring section 400, the lens shape ismeasured two times on the basis of the process data andin accordance with different measurement loci.[0026] In the first measurement of the lens shape, themeasurement is performed in accordance with the locusof the position of the bevel apex (in the specification, thisis referred to as the reference shape) to be formed in thelens. This measurement locus can be obtained from thetwo-dimensional process data based on the frame shapedata and the layout data.[0027] The second measurement is performed in ac-cordance with the shape (the locus) of the bevel bottom(the portion where the bevel slope and the bevel shoulderintersect each other). This measurement locus in thiscase can be obtained in the following manner.[0028] As shown in Fig. 9, when a point a at the bevelapex (reference shape) is to be processed, the line con-necting the rotation center of the lens and that of thegrinding wheel is indicated as an axis L1, the line con-necting the process point a and the rotation center of thegrinding wheel is indicated as a normal L2, the line con-necting the process point a and the rotation center of thelens is indicated as a reference line L3, and the followingsare defined:

δ = height of the bevel (the line segment ac) in thedirection of the reference line L3,θ = angle between the normal L2 and the referenceline L3,γ = reference height of the bevel (the line segmentab, and already known from the shape of the bevelgroove), andτ = angle formed by the normal L2 and the axis L1.The position of the process point a can be obtainedby a process correction calculation (basically identi-cal with that described in U.S. Patent No. 5,347,762)which calculates the axis-to-axis distance betweenthe lens rotation center and the wheel rotation centerduring a process, from information indicative of theradius vector-angle and length of the lens on the ba-sis of the frame shape data and the layout data, andin correspondence with the radius vector angle (thelens rotation angle during a process). When the po-sition of the process point a is once obtained, θ and

5 6

EP 0 890 414 B1

5

5

10

15

20

25

30

35

40

45

50

55

τ are known.

[0029] Assuming that the angle formed by the line seg-ments ab and bc of Δabc of Fig. 9 is approximately rec-tangular, the following is held:

By subtracting the bevel height δ from the referenceshape in the direction of the reference line L3, the dis-tance of the bevel bottom at the process point a can beobtained. When the distance is calculated at each placesin correspondence with the radius vector angle, themeasurement locus in the second measurement can beobtained.[0030] When the lens shape is once measured, it ispossible to obtain three-dimensional bevel curve locusdata which are to be applied to the lens edge, on thebasis of information indicative of the lens shape and inaccordance with a predetermined program. As for thiscalculation, there have been proposed several methodssuch as that a curve is determined from front and rearsurface curves, that the edge thickness is divided, andthat the two methods are combinedly performed (themovement or the selection may be performed in re-sponse to an input operation by the optician). For detailsof this calculation, reference may be had to commonlyassigned U.S. Patent No. 5,347,762, etc.[0031] When the bevel curve locus data are obtained,the edge locus after the beveling process is obtained onthe basis of the data and the edge position information(the edge position locus) obtained by the two lens shapemeasurements described above. When the edge locusis to be obtained, deviation of the edge position is cor-rected with respect to the inclination angle which is pro-vided to the finishing grinding wheel in order to form abevel shoulder.[0032] First, a correction angle for the lens rear surfaceinclination with respect to the rear surface inclination an-gle ρ (this value is previously known and stored in themain program memory 602) of the finishing grindingwheel (as shown in Fig. 16) is calculated. When a lensis processed at the rear surface inclination angle ρ of thefinishing grinding wheel, the inclination angle of the lensbevel shoulder in the direction of the normal L2 becomesas it is to the inclination angle ρ. In order to obtain theedge locus in the direction of the reference line L3, how-ever, a correction angle must be considered for the sec-tion shape in the direction of the reference line L3. FromFig. 10, the correction angle σ for this purpose is obtainedas:

This correction angle σ is obtained for each place in ac-

cordance with the radius vector angle.[0033] Next, as shown in Fig. 11, the section shape inthe direction of the reference line L3 is considered in ac-cordance with the correction angle σ of the rear surfaceinclination, and the edge position P3 of the lens rear sur-face after the beveling process is obtained. In Fig. 11,P1 denotes the edge position obtained in the first meas-urement of the lens edge position, and P2 denotes theedge position obtained in the second measurement. Inthis case, h of Fig. 11 is obtained from the result of themeasurement of the lens edge position, and E from theresult of the second measurement (the measurement re-sult at the bevel bottom) and the bevel calculation result.When the rear surface is approximately considered as astraight line, therefore, a correction amount m in the op-tical axis direction of the lens, and a correction amountξ in the radial direction of the lens are expressed as fol-lows:

Optical axis direction

Radial direction

[0034] When the correction amounts are obtained foreach place in accordance with the radius vector angle,information of the edge locus on the side of the rear sur-face after the beveling process is obtained.[0035] As described in U.S. Patent No. 5,347,762,when a lens which has undergone a beveling process isto be mounted to an eyeglass frame, it is preferable tocorrect the position of the bevel apex so that the curvelocus of the eyeglass frame substantially coincides in pe-ripheral length with the bevel curve locus. In the correc-tion (hereinafter, referred to as peripheral length correc-tion), the peripheral length of the bevel curve locus isapproximately obtained by calculating distances amongthe bevel curve locus data obtained in the bevel calcu-lation on the basis of the data, and summing the distanc-es. The correction amount can be obtained from the thusobtained peripheral length, and the peripheral length of

7 8

EP 0 890 414 B1

6

5

10

15

20

25

30

35

40

45

50

55

the eyeglass frame shape which is similarly obtainedfrom the radius vector information of the frame shape.The calculation of the edge locus after the beveling proc-ess in the case where the peripheral length correction isperformed will be described. In the above, all the correc-tion calculations are performed on the reference line L3.The shape change due to the peripheral length correctionoccurs in the direction of the axis L1 (see Fig. 12(a)).Consideration will be made with substituting the shapechange due to the peripheral length correction for that inthe reference line L3. It is assumed that, as shown in Fig.12(b), a point b of the bevel bottom before the peripherallength correction is corrected in the direction of the axisL1 by a peripheral length correction amount λ, and a pointc also is corrected in the direction of the axis L1 at thepoint b. In this case, a correction amount ω in the directionof the reference line L3 can be approximately obtainedby:[0036]

[0037] In order to obtain the edge locus after the bev-eling process due to the peripheral length correction, thesection shape shown in Fig. 13 and in the direction of thereference line L3 will be considered in the same manneras described above. Assuming that the edge position P3is shifted to P4 as a result of the peripheral length cor-rection, when the correction amount in the radial directionof the lens is indicated by κ and that in the optical axisdirection of the lens is indicated by η, these correctionamounts are as follows:[0038]

[0039] In the case where the peripheral length correc-tion is performed, therefore, the correction amounts ofthe edge position after the final beveling process are ex-pressed as follows:

Radial direction

Optical Axis direction

[0040] When the correction amounts are obtained foreach place in accordance with the radius vector angle,information of the edge locus on the side of the lens rearsurface in the case where the peripheral length correctionis performed is obtained.

(II) Calculation of chamfering process locus

[0041] Next, the calculation of the chamfering processlocus which is performed during the chamfering processin order to visually uniformalize the chamfer shape willbe described with reference to Fig. 14. Even when theedge locus is obtained as described above and a fixedchamfering amount from the edge end (P4) in the beveldirection is designated (an offset of a fixed amount isapplied), the length of the chamfered slope after cham-fering (hereinafter, the length is referred to as chamferingwidth) is changed by influence of the rear surface curve,with the result that the chamfering is visually recognizednot to be uniformly performed. In order to visually unifor-malize the chamfering width in the case where a fixedchamfering amount is designated, therefore, the cham-fering process locus is obtained so that the length of theslope after chamfering is uniform irrespective of the ra-dius vector angle.[0042] In Fig. 14, g denotes an offset component of thechamfering amount, j denotes an-offset amount after cor-rection, f denotes a correction angle of the inclinationangle F of the chamfering grinding wheel (a previouslyknown value, and, in the embodiment, 45 degrees) in thedirection of the reference line L3, and e denotes a cham-fering width in the case where the rear surface of the lensis flat. The chamfering width becomes equal in size tothe chamfering width d because of the rear surface curve.In a method of uniformalizing the chamfering width, anoffset correction amount k is obtained so as to attain thechamfering width which is equal to that in the case wherethe rear surface of the lens is flat. In order to perform themethod, the correction angle f is first obtained. In thesame manner as that of obtaining the correction angle σin Fig. 10, the correction angle is obtained by:

9 10

EP 0 890 414 B1

7

5

10

15

20

25

30

35

40

45

50

55

From the figure, the offset correction amount k is obtainedas follows:

This method is based on the approximation expression.When the offset component g is largely increased, there-fore, the error is increased. From the view point of visualuniformalization, when the offset component g is greaterthan 1 mm, it is preferable to obtain the offset correctionamount k while setting g to be 1 (g = 1). When the cor-rection angle σ is sufficiently small, the offset correctionamount may be expressed as follows:

(in the correction on the side of the front surface of thelens, particularly, the influence is very small).[0043] From the above, it will be seen that the positionof a chamfering process point Q in the optical axis direc-tion with respect to the edge position P4 shown in Fig.14 can be obtained by an addition of g + k. For the positionof the chamfering process point Q in the radial directionof the lens with respect to the edge position P4, a cor-rection amount m can be obtained by:

[0044] The thus obtained position of the chamferingprocess point Q is information which is obtained withoutconsidering the position of the bevel bottom. In the caseof a beveling process, the chamfering process must beperformed so as not to interfere with the bevel. To complywith this, a process is performed in which the position ofthe bevel bottom is obtained, the position is comparedwith the chamfering process point, and, if the chamferingprocess point Q in the optical axis direction is in the innerside with respect to the position of the bevel bottom, thebevel bottom position is substituted for the chamferingprocess point.[0045] As shown in Fig. 15, the value of the bevel bot-tom position in the radial direction of the lens can beobtained by subtracting t = δ + ω from the reference shape

(this is equal to that obtained by subtracting ω from thelocus of the second measurement). The value of the bev-el bottom position in the optical axis direction of the lensis obtained by using q and q’ obtained by splitting thebevel apex. The q and q’ are obtained from the shape ofthe bevel groove of the finishing grinding wheel.[0046] In this way, the chamfering process point Q andthe position of the bevel bottom are obtained for the wholeperiphery in accordance with the radius vector angle, andthe chamfering process locus in which the chamferingprocess does not interfere with the bevel can be obtained.The chamfering process locus on the side of the frontsurface of the lens can be obtained in the same method.[0047] Also in a plane process in which a beveling proc-ess is not performed, the chamfering process locus canbe obtained in a basically same concept.[0048] Next, an actual processing operation will bebriefly described. The optician measures the shape of aneyeglass frame (template) by using the eyeglass frameshape measuring apparatus 650, and inputs the meas-ured shape. Thereafter, the optician inputs layout datasuch as the PD value of the user and the height of theoptical center are input with respect to the lens shapebased on the eyeglass frame data. Furthermore, a proc-ess mode such as the beveling process, the plane proc-ess, or a mirror-polish process is input, and instructionsrelating to the chamfering amount is input. The input ofthe chamfering amount can be performed by means ofa ratio (referred to as a chamfering ratio) which is usedfor splitting the width (the width in the optical axis direc-tion) of the bevel shoulder extending from the bevel bot-tom to the edge position, in the whole periphery, and theoffset amount g shown in Fig. 14. When both the instruc-tions of the chamfering ratio and offset amount are con-currently used, the chamfering process position obtainedby splitting the width of the bevel shoulder on the basisof the input ratio is shifted by the amount correspondingto the instructions of the offset amount. When the wholeperiphery of the edge is to be uniformly chamfered, onlythe offset amount g is input. Hereinafter, the case wherethe beveling process and the chamfering process areperformed will be described.[0049] The optician performs predetermined process-es on the lens to be processed and places the lens onthe chuck shaft 152. When preparation for the processis completed, the START switch of the input unit 11 isdepressed to start the operation of the apparatus. -[0050] In response to START signal, the control unit600 controls the operations of the front-rear movingmeans 630 and lens thickness measuring section 400,and the rotation of the chucked lens to be processed.Two measurements, i.e., the first and second measure-ments are performed on each of the rear and front re-fracting surfaces of the lens on the basis of the layoutinformation and the lens frame shape. On the basis ofthe measurement results, the apparatus performs calcu-lations of the edge and peripheral length correction, sothat the edge locus information and the chamfering proc-

11 12

EP 0 890 414 B1

8

5

10

15

20

25

30

35

40

45

50

55

ess locus information are obtained as described above.[0051] When the calculations are completed, a rough-grinding process, the beveling process, and the cham-fering process are automatically performed in a sequen-tial manner. In the rough-grinding process, both the rightand left rough grinding wheels 30 are moved to the levelof the lens to be processed, and the lens grinding parts300R and 300L are then slid toward the lens to be proc-essed. The lens is gradually ground in two directions bymoving the right and left lens grinding parts 300R and300L which are rotating, toward the lens to be processed.The movement amounts of the right and left rough grind-ing wheels 30 toward the lens are independently control-led on the basis of the process data.[0052] When the rough-grinding process is ended, theprocess advances to the beveling process-. The controlunit 600 controls the movements of the finishing grindingwheel 31 (or the finishing grinding wheel 34) in the heightof the bevel groove and the lens direction on the basisof beveling process data stored in the data memory 603,thereby performing the beveling process.[0053] When the beveling process is ended, the proc-ess advances to the chamfering process. The control unit600 controls the movements of the front surface cham-fering grinding wheel 32 and the rear surface chamferinggrinding wheel 33 (or the chamfering grinding wheels 35and 36 are used) in the vertical directions and the radialdirection of the lens on the basis of the chamfering proc-ess data stored in the data memory 603. When only theoffset amount g is designated, the correction is performedso that the length of the chamfered slope is uniform irre-spective of the radius vector angle, and hence the cham-fering is visually recognized not to be uniformly per-formed, thereby improving the appearance.[0054] In the embodiment described above, the edgeof a lens is measured by two measurements, i.e., the firstand second measurement on the whole periphery. Sincethe inclination angle of a lens is not abruptly changed,the edge may be measured at intervals of, for example,15 degrees, and the measurement results may besmoothly interpolated. If the lens data can be obtainedfrom other means, the data may be used. That is to say,lens data of the eyeglass lens or edge position informa-tion obtained by measuring different positions with re-spect to the radius vector may be used as a positionvariation information to calculate edge positions after afinishing process.[0055] As described above, according to the invention,a chamfering process can be easily performed and thechamfered shape can be finished to a satisfactory one.

Claims

1. A lens grinding apparatus for grinding the peripheryof an eyeglass lens, comprising:

data inputting means (11, 601, 650) for inputting

shape data of an eyeglass frame and layout dataof the eyeglass lens to the eyeglass frame;edge position measuring means (400) for meas-uring first edge positions of front and rear sur-faces of the eyeglass lens on the basis of theinput data;storing means (602) for storing an inclination an-gle of a processing surface of a finishing grindingwheel (31, 34);chamfering means which has a chamferinggrinding wheel (32, 33, 35, 36), for chamferingedge corner portions of the front and rear sur-faces of the finish-processed eyeglass lens byrelatively moving a shaft (300R, 300L) of thechamfering grinding wheel with respect to ashaft (121, 152) holding the eyeglass lens;characterized byposition variation information inputting means(400) for inputting position variation informationof the front and rear surfaces of the eyeglasslens with respect to a radius vector;calculating means (600) for calculating a cham-fering process locus of the front and rear surfac-es of the eyeglass lens so that a length of achamfered slope of the eyeglass lens after achamfering process becomes substantially con-stant regardless of a radius vector angle, on thebasis of the measured first edge positions, thestored inclination angle, and the input positionvariation information; andchamfering process controlling means (600) forcontrolling an operation of said chamferingmeans on the basis of the calculated chamferingprocess locus.

2. A lens grinding apparatus according to claim 1,wherein said position variation information inputtingmeans is arranged to input, as the position variationinformation, second edge positions of the front andrear surfaces of the eyeglass lens different from andnear the measured first edge positions with respectto the radius vector.

3. A lens grinding apparatus according to claim 1 or 2,further comprising:

inclination angle correcting means (600) for cor-recting the stored inclination angle on the basisof a positional relationship between a processpoint of the finishing grinding wheel and a rota-tion center of the eyeglass lens, andwherein said calculating means calculates thechamfering process locus on the basis of thecorrected inclination angle.

4. A lens grinding apparatus according to any one ofclaims 1 to 3, further comprising:

13 14

EP 0 890 414 B1

9

5

10

15

20

25

30

35

40

45

50

55

chamfering amount instructing means (11) forinstructing a chamfering amount, andwherein said calculating means calculates thechamfering process locus on the basis of theinstructed chamfering amount.

5. A lens grinding apparatus according to any one ofclaims 1 to 4, further comprising:

roughing means which has a roughing grindingwheel (30), for roughing the peripheral edge ofthe eyeglass lens by relatively moving a shaft(300R, 300L) of the roughing grinding wheel withrespect to the shaft (121, 152) holding the eye-glass lens; andfinishing means which has the finishing grindingwheel (31, 34), for finishing the peripheral edgeof the rough-processed eyeglass lens by rela-tively moving a shaft (300R, 300L) of the finish-ing grinding wheel with respect to the shaft (121,152) holding the eyeglass lens.

Patentansprüche

1. Linsenschleifvorrichtung zum Schleifen des Um-fangs einer Brillenlinse, umfassend:

- eine Dateneingabeeinrichtung (11, 601, 650)zum Eingeben von Formdaten eines Brillenrah-mens und Layout-Daten der Brillenlinse für denBrillenrahmen;- eine Kantenposition-Messeinrichtung (400)zum Messen erster Kantenpositionen der Vor-der- und Rückflächen der Brillenlinse auf der Ba-sis der eingegebenen Daten;- eine Speichereinrichtung (602) zum Speicherneines Neigungswinkels einer Bearbeitungsflä-che einer Endbearbeitungs-Schleifscheibe (31,34);- eine Abfasungseinrichtung, die eine Abfa-sungs-Schleifscheibe (32, 33, 35, 36) zum Ab-fasen von Kanteneckbereichen der Vorder- undRückflächen der endbearbeiteten Brillenlinsedurch relatives Bewegen einer Welle (300R,300L) der Abfasungs-Schleifscheibe bezüglicheiner Welle (121, 152), die die Brillenlinse hält,aufweist;- gekennzeichnet durch- eine Positionsänderungsinformations-Einga-beeinrichtung (400) zum Eingeben einer Positi-onsänderungsinformation der Vorder- undRückflächen der Brillenlinse bezüglich einesRadiusvektors;- eine Berechnungseinrichtung (600) zum Be-rechnen einer Abfasungsbearbeitungs-Ortskur-ve der Vorder- und Rückflächen der Brillenlinse,sodass eine Länge einer abgefasten Flanke der

Brillenlinse nach einer Abfasungsbearbeitung,ungeachtet eines Radiusvektorwinkels, auf derBasis der gemessenen ersten Kantenpositio-nen, des gespeicherten Neigungswinkels undder Positionsänderungsinformationseingabe imWesentlichen konstant ist; und- eine Abfasungsbearbeitungs-Steuerungsein-richtung (600) zum Steuern eines Ablaufs derAbfasungseinrichtung auf der Basis der berech-neten Abfasungsbearbeitungs-Ortskurve.

2. Linsenschleifvorrichtung gemäß Anspruch 1, wobeidie Positonsänderungsinformations-Eingabeein-richtung angeordnet ist, um zweite Kantenpositionender Vorder- und Rückflächen der Brillenlinse, die na-he der gemessenen ersten Kantenpositionen liegenund sich von den gemessenen ersten Kantenpositi-onen bezüglich des Radiusvektors unterscheiden,als Positionsänderungsinformation einzugeben.

3. Linsenschleifvorrichtung gemäß Anspruch 1 oder 2,ferner umfassend:

- eine Neigungswinkel-Korrektureinrichtung(600) zum Korrigieren des gespeicherten Nei-gungswinkels auf der Basis eines Positionsver-hältnisses zwischen einem Bearbeitungspunktder Endbearbeitungs-Schleifscheibe und einesDrehzentrums der Brillenlinse, und- wobei die Berechnungseinrichtung die Abfa-sungsbearbeitungs-Ortskurve auf der Basis deskorrigierten Neigungswinkels berechnet.

4. Linsenschleifvorrichtung gemäß einem der Ansprü-che 1 bis 3, ferner umfassend:

- eine Abfasungsbetrags-Ausführungseinrich-tung (11) zum Ausführen eines Abfasungsbe-trags, und- wobei die Berechnungseinrichtung die Abfa-sungsbearbeitungs-Ortskurve auf der Basis desausgeführten Abfasungsbetrags berechnet.

5. Linsenschleifvorrichtung gemäß einem der Ansprü-che 1 bis 4, ferner umfassend:

- eine Schruppeinrichtung, die eine Schrupp-Schleifscheibe (30) zum Schruppen der Um-fangskante der Brillenlinse durch relatives Be-wegen einer Welle (300R, 300L) der Schrupp-Schleifscheibe bezüglich der Welle (121, 152),die die Brillenlinse hält, aufweist; und- eine Endbearbeitungseinrichtung, die die End-bearbeitungs-Schleifscheibe (31, 34) zum End-bearbeiten der Umfangskante der geschrupp-ten Brillenlinse durch relatives Bewegen einerWelle (300R, 300L) der Endbearbeitungs-Schleifscheibe bezüglich der Welle (121, 152),

15 16

EP 0 890 414 B1

10

5

10

15

20

25

30

35

40

45

50

55

die die Brillenlinse hält, aufweist.

Revendications

1. Appareil de meulage de verre pour meuler la péri-phérie d’un verre de lunettes, comprenant :

des moyens d’entrée de données (11, 601, 650)pour entrer des données de forme d’une mon-ture de lunettes et des données de dispositiondu verre de lunettes par rapport à la monture delunettes ;des moyens de mesure de position de bord(400) pour mesurer les premières positions debord des surfaces avant et arrière du verre delunettes sur la base des données d’entrée ;des moyens de stockage (602) pour stocker unangle d’inclinaison d’une surface de traitementd’une meule de finition (31, 34) ;des moyens de chanfreinage qui ont une meulede chanfreinage (32, 33, 35, 36), pour chanfrei-ner des parties de coin de bord des surfacesavant et arrière du verre de lunettes traité enfinition en déplaçant relativement un arbre(300R, 300L) de la meule de chanfreinage parrapport à un arbre (121, 152) maintenant le verrede lunettes ;caractérisé par :

des moyens d’entrée d’information de va-riation de position (400) pour entrer l’infor-mation de variation de position des surfacesavant et arrière du verre de lunettes par rap-port à un vecteur de rayon ;des moyens de calcul (600) pour calculerun lieu de procédé de chanfreinage des sur-faces avant et arrière du verre de lunettesde sorte qu’une longueur d’une inclinaisonchanfreinée du verre de lunettes après unprocédé de chanfreinage devient sensible-ment constante indépendamment de l’an-gle de vecteur de rayon, sur la base despremières positions de bord mesurées, del’angle d’inclinaison mémorisé et de l’infor-mation de variation de position d’entrée ; etdes moyens de contrôle de procédé dechanfreinage (600) pour contrôler un fonc-tionnement desdits moyens de chanfreina-ge sur la base du lieu de procédé de chan-freinage calculé.

2. Appareil de meulage de verre selon la revendication1, dans lequel lesdits moyens d’entrée d’informationde variation de position sont agencés pour entrer,en tant qu’information de variation de position, dessecondes positions de bord des surfaces avant etarrière du verre de lunettes différentes de et proche

des premières positions de bord mesurées par rap-port au vecteur de rayon.

3. Appareil de meulage de verre selon la revendication1 ou 2, comprenant en outre :

des moyens de correction d’angle d’inclinaison(600) pour corriger l’angle d’inclinaison mémo-risé sur la base d’une relation de position entreun point de procédé de la meule de finition et uncentre de rotation du verre de lunettes, etdans lequel lesdits moyens de calcul calculentle lieu de procédé de chanfreinage sur la basede l’angle d’inclinaison corrigé.

4. Appareil de meulage de verre selon l’une quelcon-que des revendications 1 à 3, comprenant en outre :

des moyens d’instruction de quantité de chan-freinage (11) pour donner l’instruction d’unequantité de chanfreinage, etdans lequel lesdits moyens de calcul calculentle lieu de procédé de chanfreinage sur la basede la quantité de chanfreinage instruite.

5. Appareil de meulage de verre selon l’une quelcon-que des revendications 1 à 4, comprenant en outre :

des moyens de dégrossissage qui ont une meu-le de dégrossissage (30), pour dégrossir le bordpériphérique du verre de lunettes en déplaçantrelativement un arbre (300R, 300L) de la meulede dégrossissage par rapport à l’arbre (121,152) maintenant le verre de lunettes ; etdes moyens de finition qui ont la meule de finition(31, 34) pour finir le bord périphérique du verrede lunettes dégrossi en déplaçant relativementun arbre (300R, 300L) de la meule de finitionpar rapport à l’arbre (121, 152) maintenant leverre de lunettes.

17 18

EP 0 890 414 B1

11

EP 0 890 414 B1

12

EP 0 890 414 B1

13

EP 0 890 414 B1

14

EP 0 890 414 B1

15

EP 0 890 414 B1

16

EP 0 890 414 B1

17

EP 0 890 414 B1

18

EP 0 890 414 B1

19

EP 0 890 414 B1

20

EP 0 890 414 B1

21

EP 0 890 414 B1

22

EP 0 890 414 B1

23

EP 0 890 414 B1

24

EP 0 890 414 B1

25

REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the Europeanpatent document. Even though great care has been taken in compiling the references, errors or omissions cannot beexcluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• GB 2117287 A [0001]• JP HEI9199227 B [0007]• JP HEI320603 B [0019]• US 5333412 A [0019]

• JP 3020603 A [0019]• US P5333412 A [0022]• US 5347762 A [0028] [0030] [0035]