IL136346A - Device for centring and positioning a spectacle lens blank - Google Patents

Abstract

Device for centring and positioning a spectacle lens blank in order to place a grinding adapter on that blank, of the type including a support turntable (5) provided with means (32, 38, 39) for holding the blank, characterized in that the holding means include retractable support members (32) on which the blank can be placed and members (38,39) for holding the periphery of the blank which are retractable independently of the support members. 1460 א' בתמוז התשס" ד - June 20, 2004 1461 א' בתמוז התשס" ד - June 20, 2004

Description

ii Nii7 WW mittb )pnn Device for centring and positioning a spectacle lens blank Briot International C. 125439 The present invention relates to a device for centring and positioning a spectacle lens blank in order to fit a grinding adapter to the blank. It applies in particular to systems in which the blank is exposed to radiation picked up by a video camera, as described in FR-A-2 762 247, for example.' The object of the invention is to provide a device for centring and positioning the blank relative to the adapter without encroaching on the field of view of the video camera and, in order to prevent any risk of deterioration, without sliding contact between the periphery of the blank and a plane glass surface.

To this end, the invention provides a centring and positioning device of the aforementioned type characterized in' that the holding means include retractable support members on which the blank can be placed and members for holding the periphery of the blank which are retractable independently of the support members.

One embodiment of 'the invention will now be described with reference to the accompanying drawings, in which: - Figure 1 is a diagrammatic general perspective view of a centring and positioning device according to the invention; - Figure 2 is an exploded perspective view of the support turntable of that device; - Figure 3 is .a view corresponding to Figure 2, after assembly, showing the members in a first position; - Figure 4 is an analogous perspective view from below, omitting the bottom ring; and - Figure 5 is a view analogous to Figure 3, after taking hold of a blank. .

The device 1 shown in Figure 1 for centring and positioning a spectacle lens blank essentially includes a fixed chassis 2 which carries a first plate 3 which can move in a straight line in a direction X. On this is mounted a second plate 4 which can move in a straight line in a direction Y perpendicular to the direction X. A turntable. 5 is mounted on the plate 4.

The chassis 2 carries a drive motor 6 for the plate 3 whose output gear meshes with a rack 7 on the plate. The plate 3 carries a drive motor 8 for the plate 4 whose output gear 9 meshes with a rack 10 on the plate. The plate 4 carries a drive motor 11 for rotating the turntable 5 and whose output gear 12 meshes with peripheral teeth 13 on the turntable.

A video camera 14 has a fixed vertical reference aiming axis Z-Z which passes through the central region of large openings in the two plates and the turntable. The video camera is above the turntable 5 and there is a light source, not shown, on the axis Z-Z under the turntable. The video camera is connected to an image analyser 15.

A post 16 with a vertical axis Z'-Z' offset from the axis Z-Z carries a horizontal arm 17 at the end of which can be mounted a grinding adapter 18 for mounting the lens blank in a grinding machine. The arm 17 can take up an active position 17A in which the axis Z-Z and the axis of the adapter coincide. The post 16 can then be lowered to place the adapter on a spectacle lens blank, under conditions described below. While the video camera is operating, the arm 17 is pivoted to a laterally retracted position 17B.

The device 1 further includes an electronic control unit 19 which controls the motors 6, 9 and 11 on the basis of information received from the analyser 15 to centre the blank relative to the axis Z-Z and possibly to orient it as required about that axis.

The structure of the turntable 5 will now be described with reference to Figures 2 to 5.

The turntable 5 has ternary symmetry about its vertical axis Y-Y and includes a main ring 21 consisting of a cup-shaped bottom ring 22 and a top ring 23 which has the teeth 13 at its periphery. The two rings have substantially the same inside diameter. The bottom of the ring 22 is flat and incorporates three arcuate openings 24, each of which incorporates a circumferential ramp 25, and six assembly holes 26. The generally plane ring 23 also incorporates six assembly holes 27 and has an arcuate opening 28 near the rack 13.

An actuator ring 29 with six upwardly projecting studs 30 and an external radial lug 31 is centred on the top face of the ring 23. The actuator ring actuates six plane horizontal support sectors 32 articulated to the ring 23 by respective assembly screws 33. Each screw passes through a pair of holes 26, 27 and a spacer 34 and is screwed into a nut 35 (only one spacer and one nut are shown) . Each sector 32 has an external appendix 36 incorporating an oblong groove 37 receiving a stud 30.

The ring 29 can therefore be turned relative to the ring 23 by means of the lug 31 and the studs 30 then cause the six sectors 32 to oscillate simultaneously about the axes of the six screws 33, like the blades of an iris diaphragm. The sectors can therefore take up either an active position close to the axis Y-Y (Figures 1, 3 and 4) or a retracted position (Figure 5) in which they do not encroach on the central opening of the two rings 22 and 23.

Three horizontal holding arms 38 each of which has a rubber cylindrical finger 39 whose axis is vertical at its free end are articulated between the two rings 22 and 23 on three spacers 34. Each arm 38 has an appendix 40 with an oblong . opening 41 at the end of the finger 39 opposite the spacer 34. The three arms are jointly actuated by two rotational assemblies that will now be described.

The first assembly is a ring 42 under which are fixed three arcuate parts 43. Each of these parts has a thick fixing portion which has a cam 44 at the bottom and a thin guide portion 45 which has an arcuate opening 46 through which a spacer 34 passes freely. Each part 43 is fixed to the ring 42 by two screws 47.

The bottom face of the ring 42 carries a stud 48 and an L-shaped lug 49 projects from the periphery of this ring.

The second of the rotary assemblies referred to above is a ring 50 forming a satellite sandwiched between the ring 42 and the bottom of the ring 22. The satellite has a number of cut-outs to prevent interference with the other moving parts. On the bottom face of the satellite are three studs 51 each received in an oblong opening 41 of an arm 38 and three spring-attachment projections 52. A substantially circumferential coil spring 53 is tensioned between each projection 52 and a point on the fixed ring 22 to spring-load the satellite rotationally in the anticlockwise direction (only one spring is shown in Figure 2) . The satellite also incorporates an arcuate opening 54 which receives the stud 48.

In the assembled state, each arm 38 is guided in a horizontal plane between the portion 45 of a part 43 and the bottom face of the satellite 50. At rest, the springs 53 urge the satellite in the anticlockwise direction. This pivots the arms 38 towards an active •position in which a circle whose diameter is smaller than that of the smallest blanks to be held is inscribed within the holding fingers 39. This pivoting movement is stopped by the stud 48 abutting on the left-hand end of the opening 54.

The lug 49 projects upwards through the opening 28 in the top ring 23 (see Figure 3) and the lug 31 is at a small circumferential distance from this opening.

Referring to Figure 1, the ring 21 is centred on the plate 4 by means of rollers 55 whose axis is vertical; it is also carried by other rollers whose axis is horizontal and which roll on its bottom peripheral area. The chassis 2 also carries a C-shaped finger whose top branch 56 is slightly above the plate 4 and directed towards the axis Z-Z.

Operation is as follows.

With the turntable 5 in the rest position described above and the sectors 32 in the active position the motors 6, 9 and 11 are energized to bring the finger 56 alongside and to the right of the lug 49. The turntable 5 is then turned in the anticlockwise direction Fl (Figure 1) which causes the stud 48 to rotate the satellite 50 against the springs 53. The co-operation of the pegs 51 and the openings 41 then pivots the arms 38 to their totally retracted position in which, the fingers 39 abut against the inside periphery of the satellite and locate in recesses 57 in the inside periphery of the ring 23.

During this pivoting the fingers pas's freely through gaps 58 between the sectors 32.

The turntable 5 is then in the Figure 3 configuration with the sectors 32 close together and the fingers 39 spread apart. A circular spectacle lens blank 59 is then, placed and approximately centred on the inner portions of the set of sectors, as shown in chain-dotted outline in Figure 3.

The turntable 5 is then turned in the clockwise direction F2 so that the lug 49 moves towards the right in the opening 28.

During " a first portion of this . relative movement the springs 53 rotate the satellite 50 whose pegs 51 cause the three arras 38 to pivot inwards.

When the three fingers 39 are in contact with the periphery of the blank the satellite 50 is immobilized and there is some lost motion of the peg 48 in the opening 54. At the end of this lost motion the cams 44 come into contact with the ramps 25 on the ring 22.

Completion of the movement of the lug 49 in the opening 28 forces the cams 44 to rise up the ramps 25, which raises the assembly 42-43-50, and therefore the three arms 38, slightly, a distance in the order of one millimetre. The blank 59, held by the three fingers 39, is therefore raised slightly relative to the sectors- 32.

By appropriate movement of the turntable 5 the fixed finger 56 is then brought alongside and to the right of the lug 31, after which the turntable 5 is again rotated in the direction Fl . This actuates the ring 29 and simultaneously opens the six sectors 32.

The situation is then that shown in Figure 5: the blank is held at three points on its periphery by the fingers 39 alone and with 'a radial force determined by the springs 53, and the sectors 32 do not encroach on the central opening of the turntable 5.

Because this situation is stable, the turntable ' 5 can be disengaged from the finger 56 and returned to the position centred on the axis Z-Z. The video camera 14 then has an unimpeded view of the blank and transmits an image to the analyser 15. On the basis of signals received from the analyser and. other information relating to the spectacle frame, obtained from elsewhere and symbolized by an arrow in Figure 1, the unit 19 commands movements in the X and Y directions, and possibly rotation, of. the turntable 5 to centre and position the blank correctly relative to the axis Z-Z. The adapter 18, which until now has been in the retracted position, is finally aligned with the axis Z-Z and then lowered along that axis to place it on the blank. r

Claims (11)

1. Device for centring and positioning a spectacle lens blank in order to place a grinding adapter on that blank, of the type including a support turntable (-57 provided with means 3-9^ for holding the blank , characterized in that the holding means include retractable support members {2r2?) on which the blank can be placed and members (3θ*, 2 ) for holding the periphery of the blank which are retractable independently of the support members.

2. Device according to claim 1 characterized in that the holding members C3#*, are adapted to raise the blank J&T) after engaging with its periphery.

3. Device according to claim 1 or claim 2 characterized in that the holding members V?) are spring-loaded towards a position for radially clamping a blank having a minimum diameter and in that the device includes means 5&) for simultaneously opening all the holding members against this spring-loading and simultaneously releasing all the holding members, the connection Off, between the opening and releasing means 02", and the holding members (-3^, Ί&) including lost motion.

4. Device according to claim 3 characterized in that the opening and releasing means 2", 5&) include a first ring &G) which has raised portions (¾T) for actuating the holding members ^fif, 2r% and is spring-loaded in rotation and a second ring <

5. Device according to anyone of claims 1 to 4 characterized in that the support members form sectors which, in an active position, delimit between them . gaps enabling the holding members (-9=8", 3&) to move between their active and retracted positions.

6. Device according to claim 5 characterized in that it includes an actuator ring ^9 which has an actuator raised portion and is adapted to open and close all the sectors simultaneously.

7. Device according to claim 4 in conjunction with claim 6 characterized in that it includes a single member (5-6 for selectively operating the opening and releasing means LAS, 5-Θ or the actuator ring .

8. Device according to claim 7 characterized in that the support turntable includes drive means (j&i 97 A-f) for displacement in two perpendicular axes and in rotation.

9. Device according to claim 8 characterized in that the actuator member (Jȣr) is fixed and in that said raised portions i^i, 4-9") are adapted to engage with the actuator member by movement of the support turntable (-5T in translation and in rotation.

10. Device according to anyone of claims 1 to 9 characterized in that it includes emission/reception means for emitting/receiving radiation for analysing the. blank, means. for acquiring characteristics of the blank by analysing signals delivered by the emission/reception means and means for commanding displacements of the support turntable according to the characteristics of the blank determined in this way and other information.

11. Device according to anyone of claims 1 to 10 characterized in. that it includes a device (A-67 Ψ) for moving a grinding adapter onto a predetermined vertical axis (Z-Z) and lowering that adapter until it comes into contact with the blank fir?) held by the holding members 2% . For the Applicants REIMHOLD COHN AND PA TNBS