Abstract:
A method for molding an optical lens by using two moulding shells and a closing element acting in the periphery thereof. The moulding shells are placed in holding elements. If necessary, one of the holding elements is made to rotate around a centering axis which is common to the unit. The moulding shells are removed from the holding elements using removing elements. The possible inclination of the moulding shells is verified in relation to a reference plane. If necessary, their position is adjusted in relation to the removing elements which bear them. Both of the moulding shells are moved towards each other using the removing elements while maintaining their position in relation thereto. The closing element is placed around the moulding shells and the moulding cavity thus formed is filled. The invention can be used with optical lenses which are made of a polymerizable material.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is the 35 USC 371 national stage of International Application PCT/FR00/01024 filed on 19 Apr. 2000, which designated the United States of America. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to molding optical lenses, more particularly, although not necessarily exclusively, ophthalmic lenses, i.e. spectacle lenses, in particular when the corresponding molding material is a synthetic material that can be polymerized by irradiation. 
     BACKGROUND OF THE INVENTION 
     As is known in the art, two molding shells are usually employed to mold an optical lens and adapted to define between them, in conjunction with a closure member operative at their periphery, the necessary molding cavity, and the latter is filled with molding material. 
     At present, in mass production, some or all of the corresponding operations are usually carried out manually. 
     However, nowadays, to meet the expectations of interested parties, who wish to take delivery as quickly as possible, and nevertheless to satisfy a large number of envisagable prescriptions, which can be highly varied, there is a requirement for unitary production. 
     As a corollary to this it is desirable for at least some of the diverse operations required to be fully or partly automated. 
     In this instance, the particular problem is that, to satisfy any particular prescription, it is necessary to ensure rigorous control of the position of the two molding shells relative to each other. 
     In the case of prescriptions requiring a torus, for example, the torus of the molded optical lens depends on the angular position of the two molding shells relative to each other, independently of the thickness at the center, which depends on the corresponding distance at the center between two molding shells, and the prism of the lens depends on any inclination of one or both of the molding shells relative to any transverse plane taken as a reference plane. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and an installation for surmounting these difficulties and in particular authorizing very fast fabrication of any ophthalmic lens responding to a given prescription, as soon as an order is received, and preferably in less than one hour. 
     The method according to the invention is generally characterized by the execution of the following operations: each of the two molding shells is placed in one of two respective individual holding means adapted to rotate about a common centering axis, if necessary, at least one of these holding means is turned about that centering axis, until the angular position is reached corresponding to the required torus, if any, each of the two molding shells is extracted from its holding means with the aid of picking means, the inclination, if any, of each of the molding shells with respect to a reference plane is checked with the molding shell engaged in this way with its picking means, if necessary, until the inclination corresponding to the required prism is reached, the position of at least one of the molding shells on its picking means is adjusted, the two molding shells are moved one toward the other with the aid of their picking means, preserving their position with respect to this picking means, the closure member is placed around the two molding shells, and the molding cavity formed in this way is filled with molding material. 
     If the molding material is a synthetic material that can be polymerized by irradiation, the combination consisting of two molding shells, the closure member and the mass of molding material filling the corresponding molding cavity is then exposed to irradiation means. 
     As a corollary of this, and ignoring any initial placing of each of the molding shells in holding means, the installation according to the invention includes the means for automatically executing the above various operations. 
     To be more precise, it includes, in addition to the necessary two holding means and two picking means, at least two separate workstations for executing the required operations and transfer means for relative movement of each molding shell with respect to each workstation. 
     The two molding shells are preferably treated at the same time. 
     To control their inclination, if any, relative to a reference plane, and therefore to obtain any required prism, the front face, and thus the active face, of each molding shell, i.e. its face which defines the molding cavity, is preferably pressed against feelers for assessing the distance of a chosen number of points on that active face relative to the reference plane adopted. 
     The use of such feelers is undoubtedly disclosed in French patent No. 1 316 497. 
     However, in French patent No. 1 316 497 the feelers are operative on the rear face of the molding shells, and thus on the opposite face of the molding shells to the molding cavity, and the molding shells are brought into contact with the feelers by injecting compressed air between them. 
     Under these conditions, it is not possible to ensure that the molding shells are not subjected to any unintentional movement, to the detriment of their relative position with respect to each other, when the compressed air supply is disconnected. 
     This does not apply when, in accordance with the invention, the feelers are operative directly on the active face of the molding shells, while each is being held correctly by its picking means. 
     As a corollary of this, the various transfer means operative from one workstation to another in the molding installation according to the invention advantageously guarantee conservation of the centering axis common to the two molding shells. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the invention will emerge further from the following description, which is given by way of example and with reference to the accompanying diagrammatic drawing, the single FIGURE in which is a block diagram of a molding installation according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in the FIGURE, the overall aim is to assemble two molding shells  10 A,  10 B, one concave, the other convex, for molding an optical lens, for example an ophthalmic lens, i.e. a spectacle lens, respecting the prescription which this kind of ophthalmic lens must satisfy. 
     As is known in the art, the two molding shells  10 A,  10 B take the form of circular contour disks and, for the required molding operation, they are used conjointly with a closure member  11  operative at their periphery and with which they define the necessary molding cavity  12 . 
     The molding shells  10 A,  10 B are made of glass, for example. 
     The closure member  11  can be a simple sleeve, made in one piece or in the form of a strip appropriately wound around the molding shells  10 A,  10 B. 
     However, instead of this, it can equally well, and preferably, be a device of the type that is the subject matter of French patent application No. 94 14927 filed 12 Dec. 1994, publication No. 2 727 895. 
     According to the invention, to carry out the molding operation, the following operations are executed: the two molding shells  10 A,  10 B are placed in the respective two individual holding means  13 A,  13 B adapted to rotate about a common centering axis A, if necessary, at least one of the holding means  13 A,  13 B is turned about the centering axis A, to obtain the required angular position for the two molding shells  10 A,  10 B with respect to each other, i.e. the angular position corresponding to the required torus, if any, each of the two molding shells  10 A,  10 B is extracted from its holding means  13 A,  13 B by the picking means  14 A,  14 B, the inclination, if any, of each of the molding shells  10 A,  10 B with respect to a reference plane is checked with the molding shell  10 A,  10 B interengaged in this way with its picking means  14 A,  14 B, if necessary, the position of at least one of the molding shells  10 A,  10 B on its picking means  14 A,  14 B is adjusted to obtain the inclination corresponding to the required prism, the two molding shells  10 A,  10 B are moved toward each other by their picking means  14 A,  14 B, preserving their position with respect to said picking means  14 A,  14 B, the closure member  11  is disposed around the two molding shells  10 A,  10 B, and the molding cavity  12  formed in this way is filled with molding material. 
     If the molding material is a synthetic material that can be polymerized by irradiation, which is usually the case in practice, the combination  16  consisting of two molding shells  10 A,  10 B, the closure member  11  and the mass  18  of molding material then filling the corresponding molding cavity  12  is exposed to irradiation means  15 . 
     Apart from the two holding means  13 A,  13 B each adapted to grasp a molding shell  10 A,  10 B and adapted to rotate about a common centering axis A and the two picking means  14 A,  14 B each adapted to extract a molding shell  10 A,  10 B from its holding means  13 A,  13 B, the molding installation  19  in accordance with the invention includes, globally, on the one hand, at least two separate workstations P 1 , P 2 , P 3 , P 4  for executing the necessary operations and, on the other hand, and as described in more detail later, transfer means  20  adapted to move each of the molding shells  10 A,  10 B with respect to each of the workstations P 1 , P 2 , P 3 , P 4 . 
     As is the case in the molding installation  19  shown, the two molding shells  10 A,  10 B are preferably treated at the same time. 
     The molding installation  19  is not described in complete detail here. 
     Only its essential components are succinctly described hereinafter. 
     In the embodiment shown, the molding installation  19  in accordance with the invention includes, firstly, a first workstation P 1  which, by virtue of its equipment, and as will become more comprehensively apparent hereinafter, is adapted to place each of the molding shells  10 A,  10 B in its holding means  13 A,  13 B, center the molding shell  10 A,  10 B with respect to the centering axis A, and, if necessary, rotate at least one of the holding means  13 A,  13 B about the centering axis A to adjust the torus, if any, required for the optical lens to be molded. 
     For example, and as shown diagrammatically in the FIGURE, the holding means  13 A,  13 B are part of the equipment of the first workstation P 1 , and each of the holding means  13 A,  13 B includes three jaws  22 , by mean$ of which it is adapted to grasp a molding shell  10 A,  10 B by its edge, thereby operating at the periphery of the molding shell  10 A,  10 B, and which are movably mounted on a base  23  which is itself rotatably mounted on a plinth  24  around the centering axis A common to the whole system. 
     The jaws  22  are preferably also operative on the rear face  21 A,  21 B of the molding shell  10 A,  10 B concerned, i.e. on the opposite face thereof to the molding cavity  12 . 
     Accordingly, during a first step, the holding means  13 A,  13 B advantageously ensure, simultaneously, the centering, by its edge, that is to say by its edge surface, of a molding shell  10 A,  10 B, and its placement, by its rear face  21 A,  21 B, on three reference points, in this instance the corresponding three jaws  22 . 
     In the embodiment shown, the bases  23  of the two holding means  13 A,  13 B are back-to-back on the same plinth  24  so that, from one of the holding means  13 A,  13 B to the other, the jaws  22  are directed in opposite directions with respect to each other. 
     For example, for the required centering, the jaws  22  are mounted to move in a radial direction on the base  23  that carries them. 
     As a corollary of this, in this embodiment, each of the picking means  14 A,  14 B intended to enable extraction of the molding shells  10 A,  10 B from their holding means  13 A,  13 B includes a sucker  25  mounted like a ball-and-socket joint on a support  26 . 
     In accordance with dispositions that are not shown in the FIGURE, the ball-and-socket joint operative in this way between the sucker  25  and the support  26  can preferably be locked at will. 
     For example, and as shown diagrammatically in the FIGURE, each picking means  14 A,  14 B is under the control of a motor  27  adapted to drive reciprocating movement thereof along the centering axis A. 
     In the embodiment shown, the molding installation  19  according to the invention includes a second workstation P 2 , which, by virtue of its equipment, and as will become more comprehensively apparent hereinafter, is adapted to control the inclination, if any, of each of the molding shells  10 A,  10 B with respect to a reference plane, to adjust the required prism of the optical lens to be molded. 
     For the purposes of this control, and as shown diagrammatically in dashed outline in the FIGURE, the active face  28 A,  28 B, that is to say the front face, of each of the molding shells  10 A,  10 B is preferably pressed against at least three feelers  29 , the active face  28 A,  28 B being the face of the molding shell  10 A,  10 B that contributes to defining the molding cavity  12 , and which is a concave face for the molding shell  10 A and a convex face for the molding shell  10 B. 
     For each of the molding shells  10 A,  10 B, the equipment of the second workstation P 2  of the molding installation  19  according to the invention therefore includes a set of at least three feelers  29 , of which at least two are mobile parallel to the centering axis A. 
     For example, four feelers  29  are provided, in a cruciform arrangement with respect to each other. 
     In the embodiment shown, the equipment of the second workstation P 2  includes two sets of feelers  29  back-to-back on a common support  30 , one for each molding shell  10 A,  10 B. 
     Clearly, the reference plane taken into account at the time of the intervention of the feelers  29  is a plane transverse to the centering axis A. 
     When checking the inclination, if any, of the molding shells  10 A,  10 B with respect to this reference plane, the distance at the center of each of the molding shells  10 A,  10 B with respect to the reference plane is preferably also taken into account, by means of the feelers  29 . 
     Be this as it may, defining the reference in this way in the workstation P 2  and on the active faces  28 A,  28 B of the molding shells  10 A,  10 B advantageously compensates any prism errors between the faces of each of the molding shells  10 A,  10 B during a second step. 
     In the embodiment shown, the molding installation  19  according to the invention includes a third workstation P 3  which, by virtue of its equipment, and as will become more completely apparent hereinafter, is adapted to move the two molding shells  10 A,  10 B, one toward the other, taking account of the distance at the center previously measured, which adjusts the required thickness at the center of the optical lens to be molded, and, equally, is adapted to dispose the closure member  11  around the two molding shells  10 A,  10 B and to fill the molding cavity  12  then formed in this way with molding material. 
     In this embodiment, the molding installation  19  according to the invention further includes a fourth workstation P 4  which, by virtue of its equipment, is adapted to irradiate the combination  16  previously obtained as required. 
     In practice, the equipment of the fourth workstation P 4  is reduced to the irradiation means  15   
     For example, and as shown diagrammatically in the FIGURE, the irradiation means  15  include two ultraviolet radiation lamps  31 A,  31 B, which are disposed facing each other, at a distance from each other, and between which the combination  16  to be irradiated is inserted. 
     As a corollary of this, the transfer means  20  of the molding installation  19  according to the invention include, firstly, in the embodiment shown, a table  32  which is adapted to reciprocate between the first workstation P 1  and the second workstation P 2 , in a direction substantially perpendicular to the centering axis A, and carries the equipment of each of these workstations P 1 , P 2 . 
     The transfer means  20  then include a second table  33  which is adapted to reciprocate between the first workstation P 1  and the third workstation P 3  and on which the picking means  14 A,  14 B and the motor  27  thereof operate. 
     For example, and as shown diagrammatically in the FIGURE, the second table  33 , which is globally orthogonal to the first table  32 , moves on rails  34 . 
     In the embodiment shown, the transfer means  20  finally include a third table  35  which is adapted to reciprocate between the third workstation P 3  and the fourth workstation P 4 , in a direction substantially perpendicular to the centering axis A, and on which the closure member  11  operates, in particular when, as envisaged hereinabove, that closure member  11  is a device of the type described in French patent No. 94 14927. 
     Of course, the various tables  32 ,  33  and  35  used in this way are motorized. 
     In service, the molding shells  10 A,  10 B are first loaded onto the holding means  13 A,  13 B, i.e. the molding shells  10 A,  10 B are placed between the jaws  22  of the holding means  13 A,  13 B, then the molding shells  10 A,  10 B are centered by the action of the jaws  22  that grip them, and, finally, the required torus, if any, is adjusted. 
     The suckers  25  of the picking means  14 A,  14 B are then applied to the molding shells  10 A,  10 B and the molding shells  10 A,  10 B are extracted from the holding means  13 A,  13 B by the picking means  14 A,  14 B. 
     As will be noted, the picking means  14 A,  14 B operate on the rear face  21 A,  21 B of the molding shells  10 A,  10 B. 
     After the necessary movement of the table  32 , the picking means  14 A,  14 B press the molding shells  10 A,  10 B against the feelers  29  of the second workstation P 2  and the required prism is adjusted, if necessary, by modifying, for this purpose, the position of the suckers  25  with respect to the support  26  that carries them. 
     The picking means  14 A,  14 B with which they remain engaged then disengage the molding shells  10 A,  10 B from the feelers  29  and the table  33  carrying the picking means  14 A,  14 B transfers them to the third workstation P 3 , for assembling them with the closure member  11  and filling the molding cavity  12  then formed in this way. 
     The table  35  thereafter transfers the corresponding combination  16  to the fourth workstation P 4 . 
     As will be noted, the molding installation  19  in accordance with the invention advantageously executes all of the required operations with no discontinuity. 
     Also, all the required operations can advantageously be effected mechanically, and therefore automatically, with the possible exception of those concerning the placing of the molding shells  10 A,  10 B in the holding means  13 A,  13 B, the centering of these molding shells  10 A,  10 B on the holding means  13 A,  13 B, any adjustment of their angular position, and any adjustment of their inclination. 
     Of course, the present invention is not limited to the embodiments described and shown, but encompasses any variant execution thereof.