(19)
(11)EP 3 259 121 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
24.06.2020 Bulletin 2020/26

(21)Application number: 16759844.0

(22)Date of filing:  25.08.2016
(51)International Patent Classification (IPC): 
B29D 11/00(2006.01)
B24B 13/00(2006.01)
B23B 31/30(2006.01)
(86)International application number:
PCT/GB2016/052644
(87)International publication number:
WO 2017/037428 (09.03.2017 Gazette  2017/10)

(54)

METHOD AND APPARATUS FOR MANUFACTURING CONTACT LENS MOULDS

VERFAHREN UND VORRICHTUNG ZUR HERSTELLUNG VON KONTAKTLINSENFORMEN

PROCÉDÉ ET APPAREIL DE FABRICATION DE MOULES DE LENTILLES DE CONTACT


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 28.08.2015 GB 201515399

(43)Date of publication of application:
27.12.2017 Bulletin 2017/52

(73)Proprietor: CooperVision International Holding Company, LP
St. Michael (BB)

(72)Inventors:
  • BALL, Colin
    Eastleigh Hampshire SO53 4LY (GB)
  • DEAN, Gregg A.
    Deceased (GB)

(74)Representative: Abel & Imray 
Westpoint Building James Street West
Bath BA1 2DA
Bath BA1 2DA (GB)


(56)References cited: : 
WO-A2-2010/062520
US-A1- 2007 007 733
GB-A- 2 503 037
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD



    [0001] This invention relates to the field of contact lens manufacture. In particular, the invention provides a contact lens mold half and a collet for holding the contact lens mold half during machining of a surface of the mold according to claim 1 and a method of machining a surface of a contact lens mold according to claim 11.

    BACKGROUND



    [0002] Various methods of manufacturing contact lenses are known, including spin casting, machining (for example by diamond turning), and cast molding (for example, using injection molded mold halves). Cast molding of contact lenses involves forming a pair of mold halves (i.e., a first mold half and a second mold half), placing a volume of a contact lens formulation on an optical quality surface of one of the two mold halves, and placing the two mold halves in contact with each other to form a contact lens mold assembly that has a contact lens-shaped cavity containing the contact lens formulation. The contact lens mold assembly is then exposed to conditions to cause the contact lens formulation to polymerize or cure in the contact lens mold assembly.

    [0003] Contact lenses providing common prescriptions, for example to correct myopia, hyperopia or astigmatism, are mass-produced in very large numbers, at least for low to moderate lens powers. However, it is not economical to produce very large numbers of contact lenses for prescriptions that are less common; contact lenses have only a limited shelf life, so large numbers cannot be produced and stored until they are needed. A preferred approach is to provide such lenses on a "made-to-order" basis.

    [0004] One approach to producing a made-to-order lens is to cast-mold the lens in a contact lens mold assembly in which at least one of the mold halves includes a surface that has been machined to provide a shape suitable for a desired prescription. For example, WO2010062520A2, describes injection-molded ophthalmic lens mold halves that are subsequently machined to have customized optical quality lens-defining surfaces for producing customized ophthalmic lenses.

    [0005] GB2503037 describes a kit for forming a contact lens and a method of using the kit; the kit comprises a male mould portion 10 and a female mould portion 5, the male and female mould portions each having a contact surface for, in use, contacting the surface of a moulded contact lens 15, and wherein the polarity of the contact surfaces of the male and female mould portions differ.

    [0006] US 2007/0036878 A1 is an example of a document describing contact lens mold halves having a "pan-handle" shape; that is, mold halves having a circular head portion and an elongate tail (or "handle") portion. The circular head portion includes a concave or convex surface which co-operates with a corresponding convex or concave surface of another mold half to form a contact-lens-shaped cavity in which a contact lens is to be cast. The elongate tail portion is useful for handling the mold half and can be used for other purposes, for example to receive a label in order to identify the mold half The pan-handle contact lens mold halves described in US 2007/0036878 A1 each have both a concave and a convex lens-forming surface, both of which can form contact-lens-shaped cavities in co-operation with adjacent mold halves, but pan-handle contact lens mold halves are envisaged in which only one such lens-forming surface is provided.

    [0007] During machining, the mold half is rotated at high speed and a cutting tool is brought into contact with the surface of the mold half, with the high-speed rotation resulting in material being cut away by the tool. The optical surface is provided with a customized shape by moving the cutting tool relative to the surface whilst the mold half is rotating. The cut-away material, referred to as "swarf' typically falls away from the cut surface, or is sucked and/or blown away.

    [0008] However, when attempting to machine a pan-handle contact lens mold half, problems can arise. In particular, the elongate tail portion (i.e. the handle of the pan handle), being part of the mold half, rotates at high speed, in a propeller-like manner. Swarf can readily become entangled with the elongate tail portion, and can then interfere with the cutting process, causing damage to the mold half.

    SUMMARY



    [0009] Briefly and in general terms, the present invention provides apparatus directed towards improving lens manufacturing in approaches employing machining a surface of a contact lens mold half.

    [0010] A first aspect of the invention provides a contact lens mold half and a collet for holding the contact lens mold half during machining of a surface of the mold half, the collet comprising a disc having a face and defining:

    a central structure, at the centre of the face, for receiving a head portion of the mold half, and

    an elongate recess, in the face, for receiving a tail portion of the mold half, the elongate recess extending from the central structure along a radius of the disc.



    [0011] A second aspect of the invention provides a lathe for machining a surface of a contact lens mold half according to the first aspect, the lathe comprising a headstock and a carriage, wherein the headstock carries a collet according to the first aspect and the collet holds the contact lens mold half.

    [0012] A third aspect of the invention provides a method of manufacturing a contact lens, the method comprising machining a surface of a contact lens mold half of the first aspect whilst the contact lens mold half is retained in the collet of the first aspect.

    [0013] It will be appreciated that features described in relation to one aspect of the present invention can be incorporated into other aspects of the present invention. For example, an apparatus of the invention can incorporate any of the features described in this disclosure with reference to a method, and vice versa. Moreover, additional embodiments and aspects will be apparent from the following description, drawings, and claims. As can be appreciated from the foregoing and following description, each and every feature described herein, and each and every combination of two or more of such features, and each and every combination of one or more values defining a range, are included within the present disclosure provided that the features included in such a combination are not mutually inconsistent. In addition, any feature or combination of features or any value(s) defining a range may be specifically excluded from any embodiment of the present disclosure.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0014] An embodiment will now be described, by way of example only, with references to the accompany drawings.

    FIG. 1 is a lathe including a headstock carrying a collet.

    FIG. 2 is the headstock of Fig. 1 in more detail.

    FIG. 3a is a front perspective view and

    FIG. 3b is a rear perspective view of another example collet.


    DETAILED DESCRIPTION



    [0015] Embodiments are described herein in the context of improving lens manufacturing in approaches employing machining a surface of a contact lens mold half.

    [0016] Those of ordinary skill in the art will realize that the following detailed description is illustrative only and is not intended to be in any way limiting. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will be made in detail to implementations as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts.

    [0017] As previously stated, the first aspect is directed to a contact lens mold half and a collet for holding a contact lens mold half during machining of a surface of the mold half. The collet comprises a disc having a face. The collet defines a central structure, at the centre of the face, for receiving a head portion of the mold half, and an elongate recess, in the face, for receiving a tail portion of the mold half The elongate recess extends from the central structure along a radius of the disc.

    [0018] Optionally, the central structure is a recess. Optionally, the central structure is a protrusion.

    [0019] The elongate recess is shaped and sized to receive the entire length, of the tail portion of the mold half.

    [0020] Optionally, the disc defines a void sized and positioned to balance the elongate recess when the disc is rotated. Optionally, the balancing void is aligned with, but on the opposite side of the central structure from, the elongate recess.

    [0021] Optionally, the balancing void is a recess on the front or rear the surface of the disc.

    [0022] Optionally, the balancing void is a cylinder, for example a cylinder of circular cross-section. Optionally, the balancing void is a slot or groove extending circumferentially around part of the disc.

    [0023] Optionally, the disc also defines a peripheral slot to facilitate removal the contact lens mold half from the recesses.

    [0024] Optionally, the disc also defines a hole in, for example a hole at the centre of, the central structure.

    [0025] Optionally, the collet includes a tubular stock for insertion into a chuck of a lathe and for application of a vacuum to the hole.

    [0026] As previously stated, the second aspect is directed to a lathe for machining a surface of a contact lens mold half according to the first aspect, the lathe comprising a headstock and a carriage, wherein the headstock carries a collet according to the first aspect and the collet holds the contact lens mold half.

    [0027] Optionally, the collet carries a panhandle contact lens mold half having a circular head portion and an elongate tail portion.

    [0028] Optionally, the elongate recess has a depth less than the depth of the mold half.

    [0029] Optionally, the panhandle mold is retained in the collet by application of a vacuum. Optionally, the collet comprises a stock and the vacuum is applied via the stock, for example via a passage in the stock to a central hole in the collet. Optionally, the headstock comprises a chuck and the vacuum is applied through the chuck.

    [0030] Alternatively or additionally, the panhandle mold may be retained in the collet using wax.

    [0031] Optionally, the carriage carries a first translation stage providing lateral movement relative to the longitudinal axis of the headstock a second translation stage providing longitudinal movement, along or parallel to the longitudinal axis of the headstock, and a cutting tool carried on the first or second translation stage.

    [0032] Optionally, the carriage carries a blowing nozzle, which blows air to clear away swarf during cutting. Optionally, the carriage carries a sucking nozzle, which sucks away swarf during cutting.

    [0033] Optionally, the headstock includes a rotationally driven chuck which carries the collet.

    [0034] As previously stated, the third aspect is directed to method of manufacturing a contact lens, the method comprising machining the surface of a contact lens mold half of the first aspect whilst the contact lens mold half is retained in the collet of the first aspect.

    [0035] The machining will typically be lathing.

    [0036] Optionally, the surface being machined is a surface that will form an optical surface of a contact lens to be cast using the mold half. Optionally, the optical surface is an aspheric surface.

    [0037] With reference to the drawings, an example machining apparatus 10 (Fig. 1) comprises a headstock 20, having a rotating internal spindle (not visible in Fig. 1), and a carriage 30. The headstock 20 carries a collet 230. The carriage carries a Y-translation stage 40, providing horizontal lateral movement relative to the longitudinal axis of the headstock 20, which in turn carries an X-translation stage 50, providing longitudinal movement, along or parallel to the axis of the headstock 20. The X-translation stage 50 carries a cutting tool 60. Thus, the cutting tool 60 can be moved backwards and forwards towards the headstock 20, using the X-translation stage 50, and side-to-side in front of it, using the Y-translation stage 40. The cutting tool 60 is mounted so that it cuts at the height of the spindle of the headstock 20.

    [0038] The carriage 30 also carries a blowing nozzle 70, which blows air to clear away swarf during cutting, and a sucking nozzle 80, which simultaneously sucks away swarf. The carriage 30 also carries a proximity sensor 90, calibrated to identify the position of the collet 230 and a laser 100 for precision etching of contact lens mold halves.

    [0039] The headstock 20 (Fig. 2) includes a housing 210 surrounding the spindle (not shown), a chuck 220, which is rotationally driven by the spindle and which carries the collet 230. The collet 230 carries a panhandle contact lens mold half 240 having a circular head portion 240a and an elongate tail portion 240b. (The circular head portion 240a is configured to mate with a complementary circular head portion (not shown) to form a cavity in which a contact lens is formed by curing, as described above.)

    [0040] The structure of the collet 230 will now be described in more detail with reference to the embodiment of Fig. 3(a) and (b).

    [0041] The collet 230 includes a disc 235 that defines a mold-half-shaped recess 250 (Fig. 3(a)) having approximately the shape of a panhandle contact lens mold half 240. The mold-half-shaped recess 250 has a depth slightly less than the corresponding depth of the mold half 240: it is sufficiently deep to retain the mold half, but is as shallow as is otherwise possible, to minimize its unbalancing effect on the collet 230. The mold-half-shaped recess 250 has a circular recess 250a for receiving the head portion 240a of the contact lens mold half 240 and an elongate recess 250b for receiving the tail portion 240b of the mold half 240. (The elongate recess 250b also includes a slot 255, which receives a protruding element of the mold half 240, which is provided on the mold half 240 to improve stacking of mold halves.) The disc 235 also defines a central hole 250c, at the centre of the circular recess 250a and a peripheral slot 270 to facilitate removal the contact lens mold half 240 from the recess 250.

    [0042] The disc 235 also defines a circular balancing recess 260, aligned with, but on the opposite side of the central hole 250c from, the tail portion 250b. (The embodiment of Figs. 1 and 2 does not include the circular balancing recess 260. The embodiment of Figs. 1 and 2 does include four assembly screws 241 which are not required in the collet of Fig. 3.)

    [0043] At its rear Fig. 3(b), the collet 230 includes a stock 300 for insertion into the chuck 220, by means of which the collet 230 is carried and rotated in the headstock 20. The stock 300 consists of three sleeve portions 310, 320, 330, located at the centre of the disc 235, each of substantially circular cross section. The sleeve portion 330 extends farthest from the disc 235 and has an outer diameter smaller than that of the next sleeve portion 320, which in turn has an outer diameter smaller than that of the sleeve portion 310 extending least far from the disc 235. The sleeve portion 310 is truncated to form a flat portion 315.

    [0044] The three sleeve portions 310, 320, 330 define a passage from the central hole 250c to the chuck 22. The mold half 240 is retained in the mold-shaped recess 250 by a vacuum applied through the chuck 22 via the passage to the central hole 250c.

    [0045] While the present disclosure has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the disclosure lends itself to many different variations not specifically illustrated herein.

    [0046] For example, whilst the mold half 240 is held in the collet 230 by a vacuum in the example of Fig. 3, in alternative embodiments the mold half 240 may be held in the collet 230 by a different mating approach, for example using wax.

    [0047] Where, in the foregoing description, integers or elements are mentioned that have known, obvious, or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, while of possible benefit in some embodiments of the disclosure, may not be desirable, and can therefore be absent, in other embodiments.


    Claims

    1. A contact lens mold half (240) and a collet (230) for holding the contact lens mold half (240) during machining of a surface of the mold half (240), the collet comprising a disc (235) having a face and defining:

    a central structure (250a), at the centre of the face, for receiving a head portion (240a) of the mold half (240), and

    a recess (250b), in the face, for receiving a tail portion (240b) of the mold half (240), the recess (250b) extending from the central structure (250a) along a radius of the disc (235);

    CHARACTERISED IN THAT:
    the recess (250b) is elongate and shaped and sized to receive the entire length of the tail portion (240b) of the mold half (240).
     
    2. The contact lens mold half and the collet of claim 1, wherein the disc defines a void sized and positioned to balance the elongate recess when the disc is rotated.
     
    3. The contact lens mold half and the collet of claim 2, wherein the balancing void is a recess in the surface of the disc.
     
    4. The contact lens mold half and the collet of any preceding claim, wherein the central structure is a recess.
     
    5. The contact lens mold half and the collet of any preceding claim, wherein the central structure is a protrusion.
     
    6. The contact lens mold half and the collet of any preceding claim, wherein the disc defines a hole in the central structure and the collet includes a tubular stock for insertion into a chuck of a lathe and for application of a vacuum to the hole.
     
    7. A lathe for machining a surface of a contact lens mold half according to any preceding claim, the lathe comprising a headstock and a carriage, wherein the headstock carries a collet according to any preceding claim and the collet holds the contact lens mold half.
     
    8. A lathe as claimed in claim 7, wherein the contact lens mold half is a panhandle contact lens mold half having a circular head portion and an elongate tail portion.
     
    9. A lathe as claimed in claim 8, wherein the elongate recess has a depth less than the depth of the mold half.
     
    10. A lathe as claimed in any of claims 8 to 9, in which the panhandle mold is retained in the collet by application of a vacuum.
     
    11. A method of manufacturing a contact lens, the method comprising machining a surface of the contact lens mold half of any of claims 1 to 6 whilst the contact lens mold half is retained in the collet of any of claims 1 to 6.
     
    12. A method as claimed in claim 11, in which the surface being machined is a surface that will form an optical surface of a contact lens to be cast using the mold half.
     
    13. A method as claimed in claim 12, in which the optical surface is an aspheric surface.
     


    Ansprüche

    1. Kontaktlinsen - Formhälfte (240) und Halterung (230) zum Halten der Kontaktlinsen - Formhälfte (240) während der Bearbeitung einer Fläche der Formhälfte (240), wobei die Halterung eine Scheibe (235) umfasst, die eine Fläche aufweist und folgendes definiert:

    eine zentrale Struktur (250a), an der Mitte der Fläche zur Aufnahme eines Kopfabschnitts (240a) der Formhälfte (240), und

    eine Aussparung (250b) in der Fläche zur Aufnahme eines Endabschnitts (240b) der Formhälfte (240), wobei sich die Aussparung (250b) von der zentralen Struktur (250a) entlang eines Radius der Scheibe (235) erstreckt;
    dadurch gekennzeichnet, dass

    die Aussparung (250b) länglich und so dimensioniert ist, dass sie die gesamte Länge des Endabschnitts (240b) der Formhälfte (240) aufnehmen kann.


     
    2. Kontaktlinsen - Formhälfte und Halterung nach Anspruch 1, wobei die Scheibe einen Hohlraum definiert, der so bemessen und positioniert ist, dass er die längliche Aussparung ausgleicht, wenn die Scheibe gedreht wird.
     
    3. Kontaktlinsen - Formhälfte und Halterung nach Anspruch 2, wobei der Ausgleichshohlraum eine Vertiefung in der Oberfläche der Scheibe ist.
     
    4. Kontaktlinsenformhälfte und Halterung nach einem der vorhergehenden Ansprüche, wobei die zentrale Struktur eine Aussparung ist.
     
    5. Kontaktlinsenformhälfte und Halterung nach einem der vorhergehenden Ansprüche, wobei die zentrale Struktur ein Vorsprung ist.
     
    6. Kontaktlinsenformhälfte und die Halterung nach einem der vorhergehenden Ansprüche, wobei die Scheibe ein Loch in der zentralen Struktur definiert und die Halterung einen rohrförmigen Schaft zum Einsetzen in ein Spannfutter einer Drehmaschine und zum Anlegen eines Vakuums an das Loch umfasst.
     
    7. Drehmaschine zum Bearbeiten einer Oberfläche einer Kontaktlinsen - Formhälfte nach einem der vorhergehenden Ansprüche, wobei die Drehmaschine einen Spindelstock und einen Schlitten umfasst, wobei der Spindelstock eine Halterung nach einem der vorhergehenden Ansprüche aufweist und die Halterung die Kontaktlinsen - Formhälfte hält.
     
    8. Drehmaschine nach Anspruch 7, wobei die Kontaktlinsen - Formhälfte eine Pfannenstil - Kontaktlinsen - Formhälfte mit einem kreisförmigen Kopfabschnitt und einem länglichen Endabschnitt ist.
     
    9. Drehmaschine nach Anspruch 8, wobei die Tiefe der länglichen Aussparung geringer als die Tiefe der Formhälfte.
     
    10. Drehmaschine nach einem der Ansprüche 8 bis 9, wobei die Pfannenstil Form in der Halterung durch Anlegen eines Vakuums gehalten wird.
     
    11. Verfahren zur Herstellung einer Kontaktlinse, wobei das Verfahren das Bearbeiten einer Oberfläche der Kontaktlinsen - Formhälfte nach einem der Ansprüche 1 bis 6 umfasst, während die Kontaktlinsen - Formhälfte in der Halterung nach einem der Ansprüche 1 bis 6 gehalten wird.
     
    12. Verfahren nach Anspruch 11, wobei die bearbeitete Oberfläche eine Oberfläche ist, die eine optische Oberfläche einer Kontaktlinse bilden wird, die unter Verwendung der Formhälfte gegossen werden soll.
     
    13. Verfahren nach Anspruch 12, bei dem die optische Oberfläche eine asphärische Oberfläche ist.
     


    Revendications

    1. Demi-moule (240) de lentille de contact et pince de serrage (230) pour maintenir le demi-moule (240) de lentille de contact pendant l'usinage d'une surface du demi-moule (240), la pince de serrage comprenant un disque (235) ayant une face et définissant :

    une structure centrale (250a), au centre de la face, pour recevoir une partie de tête (240a) du demi-moule (240) et

    un évidement (250b), dans la face, pour recevoir une partie de queue (240b) du demi-moule (240),

    l'évidement (250b) s'étendant à partir de la structure centrale (250a) le long d'un rayon du disque (235),

    caractérisés en ce que :
    l'évidement (250b) est allongé et façonné et dimensionné pour recevoir toute la longueur de la partie de queue (240b) du demi-moule (240).


     
    2. Demi-moule de lentille de contact et pince de serrage selon la revendication 1, dans lesquels le disque définit un vide dimensionné et positionné pour équilibrer le creux allongé lorsque le disque est tourné.
     
    3. Demi-moule de lentille de contact et pince de serrage selon la revendication 2, dans lesquels le vide d'équilibrage est un évidement dans la surface du disque.
     
    4. Demi-moule de lentille de contact et pince de serrage selon l'une quelconque des revendications précédentes, dans lesquels la structure centrale est un évidement.
     
    5. Demi-moule de lentille de contact et pince de serrage selon l'une quelconque des revendications précédentes, dans lesquels la structure centrale est une saillie.
     
    6. Demi-moule de lentille de contact et pince de serrage selon l'une quelconque des revendications précédentes, dans lesquels le disque définit un trou dans la structure centrale et la pince de serrage comporte une poupée tubulaire pour insertion dans un mandrin d'un tour et pour application d'un vide au trou.
     
    7. Tour pour usiner une surface d'un demi-moule de lentille de contact selon l'une quelconque des revendications précédentes, le tour comprenant une poupée fixe et un chariot, dans lequel la poupée fixe porte une pince de serrage selon l'une quelconque des revendications précédentes et la pince de serrage maintient le demi-moule de lentille de contact.
     
    8. Tour selon la revendication 7, dans lequel le demi-moule de lentille de contact est un demi-moule de lentille de contact à manche ayant une partie de tête circulaire et une partie de queue allongée.
     
    9. Tour selon la revendication 8, dans lequel l'évidement allongé a une profondeur inférieure à la profondeur du demi-moule.
     
    10. Tour selon l'une quelconque des revendications 8 et 9, dans lequel le moule à manche est retenu dans la pince de serrage par application d'un vide.
     
    11. Procédé de fabrication d'une lentille de contact, le procédé comprenant l'usinage d'une surface du demi-moule de lentille de contact de l'une quelconque des revendications 1 à 6, tandis que le demi-moule de lentille de contact est retenu dans la pince de serrage de l'une quelconque des revendications 1 à 6.
     
    12. Procédé selon la revendication 11, dans lequel la surface en cours d'usinage est une surface qui formera une surface optique d'une lentille de contact à couler en utilisant le demi-moule.
     
    13. Procédé selon la revendication 12, dans lequel la surface optique est une surface asphérique.
     




    Drawing














    Cited references

    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 European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description