IES67006B2 - An apparatus and method for manufacturing lenses - Google Patents

Abstract

An apparatus for manufacturing lenses comprises a support member 10 bearing a plurality of lens mould holders 11 for mounting respective lens moulds 17, Fig. 5, one above the other on a substantially common vertical axis. A UV source 29 is provided for directly irradiating a lens material in the lens moulds to cure the lens material, and a motor 26 is provided for spinning the support member 10 about the common vertical axis during such irradiation.

Description

AN APPARATUS AND METHOD FOR MANUFACTURING LENSES This invention relates to an apparatus for manufacturing lenses, for *> example contact lenses.

According to the present invention an apparatus for manufacturing lenses comprises a support means, a plurality of lens mould holders on the support means for mounting respective lens moulds one above the other on a substantially common vertical axis, means for directly irradiating a lens material in the lens moulds to cure the lens material, and means for spinning the support means about said common axis during irradiation.

The invention further provides a method for manufacturing lenses comprising loading a curable lens material into a plurality of lens moulds supported by a support means one above the other on a substantially common vertical axis, directly irradiating a lens material in the lens moulds to cure the lens material, and spinning the support means about said common axis during irradiation.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an apparatus for manufacturing contact lenses, Figure 2 is an enlarged perspective view of a portion of the stand of figure 1, Figure 3 is a cross-section through the stand of figure 2, Figure 4 is an enlarged perspective view of one of the lens mould holders of figure 2, Figure 5 is a cross-section through the lens mould holder of figure 4 with a lens mould supported therein, and -2Figure 6 shows a number of vertical arrays of lens moulds being driven by a common motor for mass production of lenses.

Referring initially io figures 1 to 3, an apparatus for manufacturing contact lenses comprises a substantially vertical support means or stand 10 having a plurality of lens mould holders 11 for mounting respective lens moulds one above the other on the stand 10.

The stand 10 comprises a member 12 (figure 3) of L-shaped cross-section which extends the vertical height of the stand. The holders 11, which are essentially thick square plates with circular apertures 13, fit into the right angle formed by the two limbs of the member 12 and are spaced apart by spacers 14 which alternate with the holders 11 along the vertical height of the L-shaped member 12.

The rear surface of each spacer 14 is right angled to fit into the right angle of the L-shaped member 12 and the front surface is curved, as seen in figure 3. The centres of the circular apertures 13 in the lens mould holders 11 lie on a substantially common vertical axis.

Referring now also to figures 4 and 5, each lens mould holder 11 has a groove 15 on the inside periphery of its aperture 13 and a coil spring 16 is set into the groove 15 and extends around the inside periphery of the aperture 13.

Each holder 11 is adapted to releasably hold a respective lens mould 17, as seen in figure 5. The lens mould 17 is circularly symmetrical and has an upper body portion 18 and a dependent skirt 19. The diameter of the body portion 18 is less than that of the skirt 19 to define a shoulder 20 between them. The body portion 18, which constitutes the mould proper, has a recess 21 in its upper surface, the recess 21 having a concave surface 22.

The lens mould 17 is inserted into the mould holder 11 from below, and the external diameter of the body portion 18 is such as to be firmly and resiliency gripped by the spring 16 when the body portion is pushed into the aperture 13. The hollow skirt 19 facilitates manual manipulation of the -3 mould 17, and the shoulder 20 provides a stop which comes to abut against the undersurface of the holder 11 when the body portion 18 is properly located in the aperture 13.

When the lens moulds 17 are properly located in the respective lens mould holders 11 as described above, the centres of the lens moulds 17 lie on the same substantially common vertical axis as the centres of the apertures 13 with the upper surface of each body portion 18 being exposed in the respective apertures 13.

The stand 10 is mounted in top and bottom bearings 23 and 24 respectively, which are fixed to a vertical post 25, for rotation about the aforesaid substantially common vertical axis. Such rotation is effected by a motor 26 which drives the stand. 10 by a belt and pulley drive 27. The motor 26 is electric powered from the mains by a power supply unit 28. The stand 10 may be spun at a rate of for example approximately 470 r.p.m., and the stand 10 is suitably balanced to permit this without undue vibration.

A means is provided for irradiating the lens moulds 17 during rotation of the stand 10, in order to directly cure a curable lens material contained in the lens moulds. In the present case this is indicated by the U.V. lamp 29, but may of course be carried out by an ultra violet laser beam. The important aspect is that the curable lens material contained in the lens moulds receives the radiation directly, I.e. without the irradiation having to pass through the lens moulds first. It is clear therefore that the U.V. irradiation whether from a U.V. laser or the lamp 29 is directed into the recesses 21 of the lens moulds 17 so that the curable lens material in the recesses 21 of the moulds 17 is directly exposed to the U.V. radiation. This direct exposure of the curable lens material is highly advantageous and results in rapid curing of the lens material and uses much less energy than if the lens material was irradiated through the lens moulds. Also in general alpha, gamma, U.V. or other radiation may be used, depending upon the nature of the curable lens material used, and the apparatus would use multiple radiation sources and/or reflectors such that the moulds are more evenly exposed to radiation during the exposure thereof. -4In use of the above described apparatus, the lexis moulds 17 are first loaded into the respective holders 11 and then the mould surfaces 22 are pretreated as required for example by sterilisation, deactivation and/or ultracleaning. The recess 21 in each mould 17 is then filled with a pre-determined amount of a liquid monomer which may be of a kind conventionally used for contact lens manufacture.

The filled moulds 17 are then spun in an inert atmosphere, for example nitrogen, while being irradiated by U.V. from the source 29. This causes the monomer to cross-link and solidify, while at the same time the spinning imparts a concave upper surface to the lens material. Of course, the lower surface of each lens takes the form of the shape of the surface 22 of the mould 17, in this case convex.

If necessary or desirable the top surface of the solidified lenses may be machined, in a conventional manner. The lenses are removed from the moulds in a bath of hot water as is well known.

The advantage of the apparatus described above is that many lenses may be processed and irradiated simultaneously, providing substantially increased throughput. Further, there is a significant saving of resources because, for example, the volume of the irradiation chamber is small, and is a closed system producing significant savings in the usage of inert gases. The system and method of the invention produces the maximum throughput at the irradiation stage resulting in a much lower cycle time per lens.

As shown in figure ό, to further increase throughput in a commercial production line a single motor 26 may drive a plurality of vertical stands 10 each containing a plurality of lens moulds as described above.

Claims (5)

1. An apparatus for manufacturing lenses comprising a support means, a plurality of lens mould holders on the support means for mounting respective lens moulds one above the other on a substantially common vertical axis, means for directly irradiating a lens material in the lens moulds to cure the lens material, and means for spinning the support means about said common axis during irradiation.

2. An apparatus as claimed in claim 1, wherein each lens mould holder has an aperture into which a lens mould is inserted from below so as to expose the upper surface of the lens mould, the upper surface of the lens mould having a recess to accommodate the lens material.

3. An apparatus as claimed in claim 2, wherein the lens mould holder has a resilient means in the aperture for retaining the lens mould therein.

4. An apparatus as claimed in claim 2, wherein the aperture in the lens mould holder is substantially circular, wherein at least an upper portion of the lens mould is also substantially circular, and wherein the resilient means comprises a coil spring set into a groove on the inside periphery of the aperture for gripping the upper portion of the lens mould.

5. A method for manufacturing lenses comprising loading a curable lens material into a plurality of lens moulds supported by a support means one above the other on a substantially common vertical axis, directly irradiating a lens material in the lens moulds to cure the lens material, and spinning the support means about said common axis during irradiation.