GB2117287A

GB2117287A - Lens edge grinding machine

Info

Publication number: GB2117287A
Application number: GB08228723A
Authority: GB
Inventors: Victor Freeman
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-10-07
Filing date: 1982-10-07
Publication date: 1983-10-12
Also published as: GB2117287B

Abstract

An ophthalmic optical lens edge grinding machine has an uncut spectacle lens 20 profiled to the peripheral shape required to fit a required frame, using the empty frame as a former, and providing for decentration and orientation of the cylinder axis. <IMAGE>

Description

SPECIFICATION Lens glazing machine The invention relates to an ophthalmic optical lens glazing machine whereby an uncut spectacle lens, precisely formed to the curvatures required by optical considerations but normally in circular shape, may be profiled to the peripheral shape required by other considerations, and particularly to fit a required frame.

According to one aspect of the invention there is provided an ophthalmic optical lens glazing machine comprising means for mounting one or each of a pair of uncut lenses, means for supporting an empty spectacle frame as a former defining a required lens shape, feeler means arranged to move relative to, and about the inner periphery of, the frame when so supported, and means for forming the peripheral shape of the or each lens in accordance with said movement.

One of the characteristics of an ophthalmic lens is that it commonly has a precisely defined cylinder axis, and it is recognised in ophthalmic practice that an individual's eye may require that his spectacle lens should have its cylinder axis at a particular orientation which may or more likely may not correspond with the geometrical axis of the spectacle frame on which the lens is to be mounted in use. Moreover, the lens normally has a specific optical centre which lies on any cylinder axis there may be and the location of an individual's eye in relation to the lens when mounted in a particular frame frequently requires that the optical centre be displaced from the geometrical centre of the spectacle frame or, as it is commonly termed, "decentered".The angular positioning of the cylinder axis and the linear decentration required are commonly factors in the practitioner's prescription for the spectacles.

In the conventional method of profiling lenses to the shape of the required frame by use of a glazing machine, the lens is mounted on a spindle the axis of which will correspond to the position of the geometrical centre of the lens when profiled.

The method frequently involves the timeconsuming and delicate steps of first locating the optical centre and cylinder axis of the uncut lens and then marking the lens with the desired decentered position of the geometrical centre along the cylinder axis before mounting the lens with the decentred position on the spindle axis.

According to another aspect of the invention therefore there is provided an ophthalmic optical lens glazing machine comprising means for mounting one or each of a pair of uncut lenses with one or both of its optical centre and cylinder axis at a predetermined position or as it may be orientation, means for supporting a former defining a required lens shape, feeler means arranged to move relative to, and about the periphery of, the former when so supported, means for forming the peripheral shape of the or each lens in accordance with said movements, and adjustment means whereby the said optical centre or the said cylinder axis or both may be located in the formed lens independently of the shape thereof.

The adjustment means may comprise angular adjustment means whereby the lens mounting means may be turned through a required angle prior to the shaping of the lens.

The adjustment means comprise decentring means for linearly displacing one or other of the feeler means and former.

Preferably the former support means is adapted to support a spectacle frame as the former and the feeler means are arranged to follow the inner periphery of the frame.

The lens support means may be capable of turning the or each lens about an axis substantially normal to the surfaces thereof, and this axis may be vertica!. The forming means preferably comprises rotary cutting means arranged to approach or depart from the said axis under control of the feeler means. As the cutting means approach more closely to the axis, they may be displaced axially to an extent required to compensate for concavity of the lens.

The lens support means may comprise co-axially arranged upper and lower mounting elements movable relative to one another in the axial direction so as to grip the lens therebetween, and may also comprise means for releasably holding the lens at its edges from which the lens may be released by the said relative movement of the said elements. The lens support means may further comprise means whereby the cylinder axis of the lens may be; located in predetermined orientation, and the said inclination of the cylinder axis may be determined.

The lens forming means may be of a milling type for cutting plastics lenses or a grinding type for glass lenses.

According to a further aspect of the invention, there is provided an ophthalmic optical lens for forming to a desired peripheral shape and provided with at least one projection or depression indicative of the position of the cylinder axis of the lens. Preferably the lens is provided with a projection or a depression in the form of a groove at each end of the cylinder axis.

Embodiments of the invention will now be described by way of example and with reference to the accompanying diagrammatic drawings, of which:~ Fig. 1 is a perspective view of an ophthalmic optical lens glazing machine; Fig. 2 is a plan view of the machine of Fig. 1; Fig. 3 is a section on lines Ill-Ill of the machine of Fig 1; Fig. 4 is a diagram showing relative position or lens to frame; Fig. 5 shows in plan a lens holder; and Fig. 6 is a section on lines VI-VI of Fig. 5.

As shown in Fig. 1, the machine has two spindles, 2, 4, each associated with other elements, and only one of the spindles and its associated elements will be described in detail, the other spindle and its associated elements being identical in all respects but one which will be referred to below. Spindle 2 terminates at its lower end in pad 6. Below the pad and coaxially with spindle 2 is shaft 10, which terminates at upwardly facing surface 14.

The spindle 2 and shaft 10 are arranged to be displaceable axially relative to one another so that the pad 6 may be separated from and close upon the surface 14 to enable a lens 20 to be inserted between and then gripped by the pad 6 and the surface 14. To this end the pad and the surface 14 are of material which will grip a lens without damaging it and may for example be of rubber or soft plastics material.

The arrangement whereby the lens 20 is held prior to being gripped between the pads 6 and the surface 14, and the means by which the precise position at which the lens is so gripped is determined will be described later.

The purpose of the machine is to grind or otherwise shape the peripheral edge 1 8 of the lens 20 to the shape of the frame of a pair of spectacles. In practice, lenses for ophthalmic purposes are supplied to an optician with their convex and/or concave surfaces formed to curvatures required by the person for whom the spectacles are to be used, but are normally circular in shape and in most cases require to be shaped peripherally to the size and shape required to fit into a spectacle frame.

Moreover, the lens supplied will commonly have precisely defined optical centre and cylinder axis which may but commonly will not be required to coincide with respectively the nominal centre and nominal horizontal of the spectacle frame.

The shaping of the periphery is effected by cutting away some of the material of the lens, and this is effected by means of a rotary cutting tool 24 having cutting surfaces 26. As shown, the tool 24 is mounted for rotation about vertical axis in bearings carried in upper and lower horizontal bars 28, 30 which project from a housing 32.

The housing 32 is arranged for horizontal movement in the direction of the line joining the axes of spindle 2 and cutting tool 24. The distance travelled by the housing 32 in that direction and thus the depth of cut created by the cutting tool 24 into the lens 20 is at each position around its periphery 18 controlled according to an arrangement now to be described.

As shown in Fig. 2 an empty frame of a pair of spectacles is mounted in a horizontal plane so as to surround an elongate feeler 34 which lies in the same plane. The frame is arranged for rotation about a circular track 36, the axis of which lies on the line of the longitudinal axis of the feeler 34, by means to be described below. The feeler is arranged for movement in the direction of its longitudinal axis and is outwardly urged so that its tip engages the inner periphery of the frame.

Means such as a mechanical linkage or a servo motor are provided to move the housing 32 according to the inward displacement of the feeler from a nominal start position outside the frame, at any orientation of the feeler relative to the frame.

In an alternative embodiment, not shown, the feeler 34 may be arranged to rotate within a fixed spectacle frame. It is to be understood that the horizontal movement of the housing 32 is proportional to the movement of the feeler 34 so that if the spectacle frame is wide in the direction of horizontal linear movement of the feeler 34 so that the feeler 34 moves a relatively short distance from its start position, which corresponds with the periphery 18 of lens 20, the housing 32 moves a correspondingly smaller distance and the cutting tool 24 cuts into the lens 20 to a relatively small depth at that position around the periphery 18.

In a further alternative arrangement, particularly suitable for repetitive work but not shown, a former in the form of a flat plate shaped according to the required shape of the lens is mounted in place of the spectacle frame as shown in Fig. 2. The feeler 34 is arranged to move horizontally and linearly to contact the shaped outer edge of the former from the outside.

In the embodiment in which the feeler is arranged to rotate, the feeler may be replaced by a former mount displaceable linearly to bring the former into contact with a fixed peg.

When the lens 20 has been cut at the one position about the periphery 18 to the depth required by the shape of the frame at the corresponding position about its periphery, the lens 20 is turned through a small angle by a turning movement of the spindle 2 and shaft 10 whilst at the same time the frame is moved about the track 36 by a similar angle by means to be described below.

According to the shape of the frame, the feeler 34 will move further outwardly from the centre of track 36 or be moved inwardly and the mounting 32 will accordingly move backwardly from or forwardly towards the axis of the spindle 2 so that a further portion of the periphery 1 8 of the lens 20 is cut to the shape of the corresponding portion of the periphery of the spectacle frame.

In practice the angular movement of the lens 20 by reason of the angular movement of the spindle 2 and shaft 10 may be substantially continuous particularly if little of the lens material is to be cut away, and when the lens 20 has made one complete revolution, its peripheral shape has been formed to that of the spectacle frame. The cutting edge 26 provides a bevelled edge by which it may be securely located within a normal spectacle frame.

If the lens 20 were substantially flat, the movement of the cutting edge 26 of the tool 24 in a horizontal direction would result in the bevelled edge being formed in the same position relative to the thickness of the lens irrespective of the depth of cut. However, in most cases, the lenses used in spectacles are concavo-convex or have what is known as a third dimensional variation as shown in Fig. 3. From this it will be clear that if the cutting edge 26 had to cut deeply into the lens 20 it would eventually run off the edge of the lens. To avoid this, the horizontal bars 28, 30 are mounted on a slide 38 arranged for vertical movement within housing 32 so that the cutting edge may be raised or lowered as required by the curvature of the lens.In order to raise the cutting edge 26 as the axis of the tool 24 moves towards the axis of the spindle 2, the lower bar 30 is arranged to engage upon an inclined plate 40, the inclination of which can be varied according to the curvature of the lens. This inclination is effected by tilting the plate 40 about a pivot 42 and securing it in the required angle by means of a wing nut or the like on a threaded rod attached to the plate 40 at the end 44, the rod passing through an arcuate guide slot 46.

As has already been mentioned, the spindle 2 and its associated elements are duplicated by spindle 4 and associated elements. Among these elements are a pad 8 and a shaft 12 terminating in a surface 16, the pad 8 and the surface 16 being for supporting another lens 22 which with the lens 20 constitute a pair of lenses for a pair of spectacles. The cutting tool 24 is also duplicated by cutting tool 48 which is rotated, moved backwardly and forwardly with the housing 32 and raised and lowered on a slide 38 as described above in connection with the cutting means for the lens 20. The angular displacement of the lens 22 is effected by a rotation of the spindle 4 and shaft 12 in synchronisation with but, and this is the distinction referred to above, in opposite direction to that of lens 20 so that a matching pair of lenses is produced simultaneously.

Drives to the spindles 2, 4 and shafts 1 0, 12 and the corresponding rotary drive to the frame are effected by conventional means shown diagrammatically in Fig. 4 as chains or belts 48, 50 but other convenient drive means may be used and preferably may include a servocontrolled motor. The cutting tools 24 may more simply be continuously rotated by conventional means shown in Fig. 4 as a belt or chain 52.

Reference was made above to the relative positioning of the optical centre and the cylinder axis of the lens within the spectacle frame and this is illustrated by reference to Fig. 5. If point A represents the nominal centre of the spectacle frame F and H the nominal horizontal line of the frame, it may be that the so-called cylinder axis C of the lens requires to be displaced from the horizontal axis H of the frame by an angle h and the optical centre A' of the lens required to be displaced ("decentred") from the nominal axis A of the frame. With a machine according to the invention, the necessary adjustments are readily made, and indeed decentration can be carried out on a lens which has no cylinder axis or of which the cylinder axis needs no angular adjustment.

The mounting of the lens 20 between the pad 4 and the surface 14 is effected by firstly mounting the lens in a temporary holder 54 shown only in Fig. 5. The holder 54 comprises a flat plate having upturned flanges 56 at its ends and a central opening 58 which is a tight but sliding fit on the upper end of the shaft 10. When the lens 20 is of plastics material it is formed, according to one aspect of the invention, with diametrically opposed notches 58 at the edges of the lens on the line of the cylinder axis thereof, and these notches engage upon corresponding projections on the holder 54 so that the lens may always be supported on the support 54 with its cylinder axis in a defined position.

In an alternative arrangement the lens 20 may be provided with aligned projections which correspond with holes in the holder 54. When the lens is of glass which cannot readily be provided with notches or projections, the cylinder axis is indicated by surface markings which may be aligned with a guide line on the holder 54.

With the lens so held, the holder is rotated either manually or by power means through the angle h, which angle may be determined by a scale fixed relative to the shaft 10. The scale for example may be inscribed on the upper face 14 of the shaft 10 about which the holder 54 may be turned by the appropriate angle. The spindle 2 is then lowered as previously described so that the pad 6 engages against the upper surface of the lens 20. The pad 6 may have a convex lower surface and impart a suction action against the lens. The shaft 10 is then raised through the opening 58 until the upper face 14 engages the underside of the lens and grips it against the lens 6 after which the holder 54 can fall away. A narrowing of the shaft 10 facilitates the release of the holder from the shaft.

In an alternative arrangement, the uncut lens may be mounted on the spindle 2 with the cylinder axis in a predetermined position, and the spindle turned through an adjustment angle h with the link to the rotary drive to the former temporarily disconnected.

The linear displacement or decentration of the optical centre of the lens is effected by the displacement by the necessary distance AA' of the means by which the former or spectacle frame is mounted relative to the guide track 36 or otherwise relative to the feeler 34. This is accomplished by arranging for a former-holding and/or frame-holding jig to be slidable horizontally by a distance indicated by reference to a scale, and clamped at the required decentred position.

Claims

1. An ophthalmic optical lens glazing machine comprising means for mounting one or each of a pair of uncut lenses, means for supporting an empty spectacle frame as a former defining a required lens shape, feeler means arranged to move relative to, and about the inner periphery of, the frame when so supported, and means for forming the peripheral shape of the or each lens in accordance with said movement.

2. A lens glazing machine according to Claim 1 wherein the lens support means are capable of turning the or each lens about an axis substantially normal to the surfaces thereof.

3. A lens glazing machine according to Claim 2 wherein the said axis is vertical.

4. An ophthalmic optical lens glazing machine comprising means for mounting one or each of a pair of uncut lenses with one or both of its optical centre and cylinder axis at a predetermined position or as it may be orientation, means for supporting a former defining a required lens shape, feeler means arranged to move relative to, and about the periphery of, the former when so supported, means for forming the peripheral shape of the or each lens in accordance with said movement, and adjustment means whereby the said optical centre or the said cylinder axis or both may be located in the formed lens independently of the shape thereof;

5. A lens glazing machine according to Claim 4 wherein the adjustment means comprises angular adjustment means whereby the lens mounting means may be turned through a required angle relative to the former prior to the shaping of the lens.

6. A lens glazing machine according to Claim 4 or Claim 5 wherein the adjustment means comprises decentring means for linearly displacing one or other of the feeler means and former.

7. A lens glazing machine according to any one of Claims 4 to 6 wherein the former support means is adapted to support a spectacle frame as the former and the feeler means are arranged to follow the inner periphery of the frame.

8. A lens glazing machine according to any one of Claims 4 to 7 wherein the lens support means are capable of turning the or each lens about an axis substantially normal to the surfaces thereof.

9. A lens glazing machine according to Claim 8 wherein the said axis is vertical.

10. A lens glazing machine according to any of Claims 2, 3, 8 or 9 wherein the forming means comprise rotary cutting means arranged to approach or depart from the said axis under control of the feeler means.

11. A lens glazing machine according to Claim 10 wherein as the cutting means approach more closely to the axis, they are displaced axially to an extent required to compensate for concavity of the lens.

12. A lens glazing machine according to any preceding Claim wherein the lens mounting means comprise co-axially arranged upper and lower mounting elements movable relative to one another in the axial direction so as to grip the lens therebetween.

13. A lens glazing machine according to Claim 12 wherein the lens mounting means further comprises means for releasably holding the lens at its edges from which the lens may be released by the said relative movement of the said elements.

14. A lens glazing machine according to any preceding Claim wherein the lens mounting means further comprises means whereby the cylinder axis of the lens may be located in said predetermined orientation.

15. A lens glazing machine according to any preceding Claim wherein the lens forming means are of a milling type for cutting plastics lenses or a grinding type for glass lenses.

16. An ophthalmic optical lens for forming to a desired peripheral shape and provided with at least one projection or depression indicative of the position of the cylinder axis of the lens.

17. A lens according to Claim 16 wherein the lens is provided with a projection or a depression in the form of a groove at each end of the cylinder axis.

1 8. An ophthalmic optical lens glazing machine comprising means for mounting one or each of a pair of uncut lenses with its surfaces normal to a vertical axis, means for supporting a former defining a required lens shape, feeler means arranged to move relative to, and about the periphery of, the former when so supported, and means for forming the peripheral shape of the or each lens in accordance with said movement.

19. A lens glazing machine according to Claim 18 wherein the lens mounting means comprise co-axially arranged upper and lower mounting elements movable relative to one another in the axial direction so as to grip the lens therebetween.

20. A lens glazing machine according to Claim 18 or Claim 19 wherein the lens mounting means comprises means for releasably holding the lens at its edges from which the lens may be released by the said relative movement of the said elements.

21. A lens glazing machine according to one of Claims 18 to 20 wherein the lens mounting means further comprises locating means whereby the cylinder axis of the lens may be located in said predetermined position.

22. An ophthalmic optical lens glazing machine comprising means for mounting one or each of a pair of uncut lenses comprising co-axially arranged upper and lower mounting elements movable relative to one another in the axial direction so as to grip the lens therebetween, means for supporting a former defining a required lens shape, feeler means arranged to move relative to, and about the periphery of, the former when so supported, and means for forming the peripheral shape of the or each lens in accordance with said movement.

23. A lens glazing machine according to Claim 14 when mounting a lens according to Claim 16 or Claim 17.

24. An ophthalmic optical lens glazing machine substantially as described with reference to the drawings.

25. An ophthalmic optical lens for forming to a desired peripheral shape substantially as described with reference to the drawings.