WO2002087842A1

WO2002087842A1 - Method and device for demolding molded lenses

Info

Publication number: WO2002087842A1
Application number: PCT/IB2001/000733
Authority: WO
Inventors: Jean-François Magne
Original assignee: Concepcionlicence Ag
Priority date: 2001-05-02
Filing date: 2001-05-02
Publication date: 2002-11-07

Abstract

Described is a demolding method and device suitable for demolding formed bodies (3), in particular ophthalmic lenses (3). Said method encompasses the simultaneous application of transverse or essentially radial forces (F₁; F₂₁, F₂₂) by means (8, 9, 13) suitable to apply essentially radial forces (F₁; F₂₁, F₂₂) to essentially opposite sides of the edge of the formed body (3) and simultaneously to essentially opposite sides of at least one molding shell (1, 2).

Description

Method and Device for Demolding Molded Lenses

Technical Field

The present invention concerns a method and device for demolding formed bodies, in particular ophthalmic lenses.

Background Art

In usual lens production methods two molding shells having the same diameter as the lens or two molding shells having a larger diameter than the lens are used. In both cases, an automatic demolding is not possible, or only with great difficulties. Usual demolding methods are performed by applying mechanical force by a mechanical means, e.g. a screw or a spatula, on the lens close to the interface lens/molding shell in order to separate the parts . This demolding method has the drawback that in the case of lenses with differing thicknesses and molding shells without overhang, the screw or spatula or the interface, respectively, must exactly be positioned, and that in the case of two molding shells with a diameter larger than the diameter of the lens said screw or spatula must be very small to allow entering into the gap between the two molding shells. In the case of blanks said gap is usually sufficiently large. However, in the case of a lens with a thickness of only 2 mm, the gap is so small that only little force can be applied without damaging the fine tool . Said state of the art methods are therefore primarily suitable for blanks, i.e. lenses with constant and larger thicknesses.

It is therefore desirable to have an easier applicable demolding method, in particular for ophthalmic lenses and not only blanks . Brief Disclosure of the Invention

Hence, it is an object of the present inven- tion to provide a demolding method that is very generally applicable to a broad variety of formed bodies, in particular ophthalmic lenses .

It is a further object of the present invention to provide a demolding apparatus suitable for demolding formed bodies, in particular ophthalmic lenses.

Such a demolding method refers to demolding formed bodies from at least one molding shell, wherein a first mechanical force Fi is applied in a transverse direction of the formed body to essentially opposite sides of an edge of the formed body and close to an edge of at least one interface between the formed body and the molding shell by a formed-body-force-applying-means, and wherein simultaneously a second mechanical force F_2i, F₂₂ is applied in a transverse direction of the at least one molding shell to essentially opposite sides of the molding shell by a molding-shell-force-applying-means, such that demolding of the at least one molding shell is obtained.

The formed body may be any precision-molded article, such as an optical lens and in particular an ophthalmic lens . For the purpose of the present description, transverse direction refers to a direction of lateral extension of the formed body or molding shells and in particular of optical faces of the formed boy or molding shells. The transverse directions are essentially perpendicular to an axial direction or optical axis of the formed body or molding shells, respectively. Application of a force in transverse direction means that a main part, i. e. at least 50%, preferably 75%, more preferred all of said force acts in the transverse direction. It has surprisingly been found that application of transverse forces Fi and F₂ to essentially opposite sides of an edge of the formed body close to an edge of at least one interface formed body/molding shell and simultaneously to two essentially opposite sides of at least one of the molding shells leads to a rupture of the molding shell/formed body adhesion and therefore to a demolding. The demolding occurs with rather little force and without damaging optical surfaces, neither of the formed body nor of the molding shells. The method is specifically suitable to demolding ophthalmic lenses that do not require subsequent fine-machining.

Further aspects, embodiments and advantages of the invention become apparent from the claims in connection with the specification and drawings.

Brief Description of the Drawings

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:

Figure 1A shows a schematic cross-sectional view of a mold especially suitable for preparing formed bodies to be demolded by the method of the present invention. The mold is shown in a disassembled state with a one-piece gasket having an aperture which is large enough in an opened state to receive the back molding shell due to a suitable gasket shape or a radial gasket expansion;

Figure IB shows a schematic cross-sectional view of a mold of the present invention with a divisible gasket in a disassembled state; Figure 1C shows a schematic cross-sectional view of the mold of Figure 1A and Figure IB in a partially assembled state with the gasket already pressed to the back molding shell;

Figure ID shows a schematic cross-sectional view of the same molds as Figures 1A to 1C in a fully assembled state;

Figure 2 shows a schematic cross-sectional view of a molding shell-formed body assembly in a demolding device suitable to apply pressure force to one molding shell and the formed body, wherein the force- applying-means is in one piece acting both on the front molding shell and the formed body;

Figure 3 shows a variant of Figure 2 , wherein the force-applying-means is in two parts acting separately onto the front molding shell and, via spring- loading, onto the formed body;

Figure 4 shows a modification of the force- applying-means of Figure 2 with a demolding finger projecting into the formed body;

Figure 5 shows a cross-sectional view of a molding shell-formed body assembly in a demolding device of Figures 2 or 3 , but rotated by 90°about a vertical axis such that the force-applying-means acting onto the back molding shell are visible;

Figure 6 shows a schematic bottom view of a demolding device in operating position, wherein one active means for applying pressure force to the formed body, a therewith coupled active means for applying pressure force to the front molding shell, one means for actively applying pressure force to the back molding shell, as well as a holder for holding the formed body and holding means for keeping the molding shells in position are provided;

Figure 7 shows a cross-sectional view of a molding shell-formed body assembly before demolding wherein the front molding shell is in an off-center position. Modes for Carrying Out the Invention

In the method of the present invention for demolding formed bodies 3, a first mechanical pressure force Fi is applied in a transverse, in particular essentially radial, direction of the formed body 3 to essentially opposite sides of an edge of the formed body 3 close to an edge 31, 32 of at least one interface between the formed body 3 and a molding shell 1, 2 by a formed-body-force-applying-means 13, and a second mechanical pressure force F₂ is applied in a transverse, in particular essentially radial, direction of the at least one molding shell 1, 2 to essentially opposite sides of the at least one molding shell 1, 2 at a time by a molding-shell-force-applying-means 8, 9, such that demolding of the at least one molding shell 1, 2 is achieved.

Synonyms used for some terms within the scope of the present description are - demolding, disassembling,

- interface between formed body 3 and molding shell 1, 2, interface formed body/molding shell, formed body/molding shell interface.

Although the disassembling method of the present invention is generally applicable, in view of the easy positioning, it is peferably applied to an assembly comprising a front and a back molding shell 1, 2 and a formed body 3 , preferably an ophthalmic lens 3 , wherein said front molding shell 1 is larger than said formed body 3 and said second or back molding shell 2. Such a molding shell-formed body assembly 1, 2, 3 or a corresponding molding device, respectively, is preferably obtained as described in PCT/IB99/01776, the disclosure of which is herewith incorporated in its entirety by reference.

Such a mold 1, 2, 3 for producing optical lenses 3 is shown in Figure 1. It allows, as described in PCT/IB 99/01776, that various lens prescriptions can be embodied with a greatly reduced number of molding shells 1, 2. Said mold 1, 2, 3 comprises: a gasket 4 enclosing an aperture 5, which extends along an axis 6, said gasket 4 further providing a contact surface 7 radially extending from said aperture 5 and preferably extending over a front molding shell 1 abutting against said contact surface 7, preferably a front molding shell 1 with a transverse extension or projected area (projected on a plane perpendicular to the axial direction 6) that is larger than a transverse extension or projected area of a back molding shell 2 (see Figures 1A to ID), the back molding shell 2 arranged within said aperture 5 at an axial distance from said front molding shell 1, at least one means 10 for pressing said front molding shell 1 against said contact surface 7, at least one means 11 for radially expanding said gasket 4 or for radially pressing said gasket 4 against said back molding shell 2 or for radially expanding and radially pressing said gasket 4 against said back molding shell 2, and at least one filling opening (not shown) . Said front molding shell 1, said back molding shell 2 and said gasket 4 are arranged such as to form a molding cavity for molding a formed body 3 which molding cavity can be filled with molding material.

Such a mold for producing optical lenses 3 is primarily suitable for lenses 3 made from a polymerizable synthetic material, and a broad variety of lens types with a minimum of molding shells 1, 2. While, namely, the molding shells 1, 2 must be shaped for specific corrections (such as monofocal, multifocal, progressive, toric etc. corrections or combinations thereof), lenses 3 of different thickness, torus orientation, decentering and prism (e. g. for right/left eye corrections) can be formed with one and the same pair of molding shells 1, 2.

The use of such a mold for the manufacturing of an optical lens 3 from a polymerizable synthetic material comprises the steps of: a) providing a gasket 4 with an aperture 5 wherein a cross sectional area of said aperture 5 perpendicular to said axis 6 (further on also referred to as perpendicular area) is larger than the projected area of said back molding shell 2 projected in the direction of the axis 6 (further on also referred to as projected area) (see Figure IB) , thereby allowing easy positioning of said back molding shell 2 within said aperture 5, b) positioning said back molding shell 2 in said aperture 5 enclosed by said gasket 4 (see Figure

IB), c) radially clamping said back molding shell 2 in position by releasing a forced radial expansion of said gasket 4 or by radially pressing said gasket 4 against said back molding shell 2 by means of said at least one radially pressing means 10 or by releasing said forced radial expansion of said gasket 4 and by radially pressing said gasket 4 against said back molding shell by means of said at least one radially pressing means 10 (see Figure 1C) , d) forming a molding cavity by pressing said front molding shell 1 against said contact surface 7 of said gasket 4 by means of said at least one pressing means 11 for said front molding shell 1 (see Figure ID) . The steps a) to d) can be performed in the following sequences a) prior b) prior c) prior d) , or a) prior d) prior b) prior c) , or a) prior b) prior d) prior c) , or d) prior a) prior b) prior c) .

For the production of a lens 3 , the such formed molding cavity is filled through a filling opening (not shown) in said molding cavity with molding material, followed by at least partial polymerization of said molding material inside said molding cavity to form the lens 3, disassembling the mold and separating the formed body 3. During the steps of disassembling the mold and separating the formed body 3, the molding shells 1, 2 have to be removed. Such removal of the molding shells 1, 2, due to the great variety of formed bodies 3 producible by the specific mold, is preferably performed by the method of the present invention.

The removal is started by first removing both pressing means and the gasket 4 such that the formed body 3 remains in exclusive contact to the molding shells 1, 2. Such assembly 1, 2, 3 can then be positioned in a specific demolding device, optionally after an additional curing step to ensure that no lasting deformation of an insufficiently cured formed body 3 occurs during demolding.

Such a further curing step may be necessary if within the fully assembled mold, the polymerization is only performed to the level of pre-polymerization which is often the case. This pre-polymerization level is at least up to the gel point and allows the removal of the gasket 4. Most often, the pre-polymerization is performed to a higher degree, allowing not only the removal of the gasket 4 but the full disassembling of the mold, i.e. the removal of the gasket 4 and the molding shells 1, 2.

In view of the different dimensions of the front molding shell 1 and the back molding shell 2 and the formed body 3 producible according to the above described method, said front molding shell 1, prior to the application of force Fi, F₂ι, F₂₂, can easily be placed on a holder 16 such that said back molding shell 2 and said formed body 3 extend from said holder 16 to one side and said front molding shell 1 extends from said holder 16 to the opposite side of the holder 16. By such a positioning, an edge position 31 of the interface front molding shell 1/formed body 3 is clearly defined. Any holder 16 with an opening larger than the diameter of the back molding shell 2 and the formed body 3 but smaller than the diameter of the front molding shell 1 is suitable. Said opening may be formed by several moveable ring segments, preferably by three or more ring segments, that in closed position need not be circular or clearly shaped. Such a holder 16 will - as soon as the lens/molding shell assembly 1, 2, 3 is positioned - reduce the opening and also apply some force to the formed body 3 in order to ensure that the formed body 3 is kept in place after removal of the molding shell 1, 2. Usually the force applied by the holder 16 is in the range of 10 kg to 18 kg, preferably about 15 kg. To further improve the holding capacity, one or more of the ring segments can be provided with a thin plate of about 0.2 mm thickness or a respective projection that can penetrate the formed body 3 and such can position the holder 16 on the formed body 3 even after demolding and prevent the formed body 3 from falling down.

By placing the larger molding shell 1 on said holder 16 such that the upper edge of said holder 16 is placed at the interface 31 of molding shell 1/formed body 3, the front molding shell 1 and the interface 31 of molding shell 1/formed body 3 are unambiguously positioned. Due to said unambiguous positioning, the force Fi can easily be applied to the formed body 3 close to an edge 31 of the interface molding shell 1/formed body 3. Due to the thickness of the molding shells 1, 2, it is also easy to "find" or locate the molding shell 2, if the force F₂χ shall be applied thereto as well.

The molding shells 1, 2 can be made of a variety of materials, provided that, in the case of application of transverse or radial force or pressure F₂₁, F₂₂, respectively, to at least one molding shell 1, 2, said molding shell 1, 2 is deformable, and that the adhesion of the formed body 3 to the molding shell 1, 2 is weaker than the force that causes a lasting deformation or even damage of the formed body 3.

Suitable materials for the molding shells 1, 2 are known to the skilled person. They encompass glass, ceramics, plastics and metals, provided that such material is suitable in the curing process of the used polymerizable material. For UV curing, molding shells of glass are preferred. However also compatible and sufficiently UV transmissible polymeric materials can be used. The use of expensive quartz is not needed since most materials cure in a UV range that is sufficiently transmitted by glass. For ecologic and economic reasons, it is of course preferred that the material is suitable for several applications. In the case of thermal curing metal molding shells 1, 2 are preferred due to their higher heat transfer rate.

In order to weaken the adhesion between the molding shell 1, 2 and the formed body 3, the molding shell 1, 2 can be covered by an anti-adhesion coating. Suitable anti-adhesion coatings are e.g. silicon based coatings .

The molded body 3 , in particular the formed body 3, can be of any suitable material known to the skilled person. Such materials, in particular, encompass any optically suitable polymerizable or thermoplastic material or combinations thereof, or materials with simultaneously thermoplastic and polymerizable features. Not limiting examples of such materials are methacrylates or derivatives thereof, in particular sulfur comprising derivatives, allyl/vinyl polymers, thiol/ene polymers, polycarbonates, polyurethanes, and derivatives thereof, such as polythiourethanes, etc.

Demolding by application of a first pressure force Fi to at least the formed body 3 close to at least one interface 31, 32 between molding shell 1, 2 and formed body 3 and of a second force F₂ι, F₂₂ to at least one of the molding shells 1, 2, after removal of a molding-shells-sealing part 4, such as a gasket 4, can be achieved in various ways .

The forces Fi; Fι, F₂₂ can be applied to one side of the formed body 3 or molding shell 1, 2 (further on referred to as active force or actively applied force) while one or more other sides of the formed body 3 and an essentially opposite side of the at least one molding shell 1, 2 are fixed. The essentially opposite side provide essentially opposite reactive forces acting on the molding shell 1, 2 or formed body 3, respectively (passive force) . Such a passive or reactive forces are provided in the case of the formed body 3 by the holder 16, in the case of the front molding shell 1 by the holding means 18, and in the case of the back molding shell 2 by the holding means 19.

The force Fi to the formed body 3 e. g. is preferably applied to at least one area on one side of the edge of the formed body 3 while the opposite side of the edge of the formed body 3 is kept unmovable e. g. by the holder 16 or ring segments 17 of said holder 16 that are positioned on a semicircle opposing the area of active force application and in symmetric positions with respect to a line through the force application area and the center of the formed body 3 or molding shell/formed body assembly 1, 2, 3, respectively. Besides of such two ring segments 17, it is also possible to use only one ring segment (not shown) opposite to the force application area or force-applying-means 13, respectively. However, if the reactive force to F₂ι shall be applied to the front molding shell 1 at the same circumferential position by the holding means 18, or respectively the reactive force to F₂₂ to the back molding shell 2 by the holding means 19, the ring segment (not shown) and the holding means 18 or 19 shall be designed thin enough to allow their simultaneous application to the assembly 1, 2, 3 in close vertical proximity to each other. In an alternative embodiment, the first and/or second forces Fi; F₂ι, F₂₂ can be actively applied to both essentially opposing edge sides of the formed body 3 and/or at least one molding shell 1, 2 by providing the required pressing or force-applying means 13 and/or 8, 9, respectively.

The force application F₂ι, F₂₂ to the molding shells 1, 2 results in an elastic deformation, possibly a plastic deformation and in shear and mostly tensile forces, possibly also local pressure forces, acting on the interfaces 31, 32 between the molding shells 1, 2 and the formed body 3, which further result in a displacement of at least one molding shell 1, 2 relative to the therebetween located formed body 3 and to a separation of the adhesion layer between the molding shells 1, 2 and the formed body 3. This process is supported by the application of force Fi to the formed body 3. Due to the lower elasticity of the formed body 3, temporary elastic deformations and possibly - dependent on the shape of the formed-body-force-applying-means 13 - lasting plastic deformations may occur. According to invention, such deformations occur only in the optically not used edge regions of the formed body 3, and furthermore are kept small enough to remain invisible and undeterminably small. The above comments on the possible force and deformation effects are explanatory only and are not intended to limit the scope of the present invention. Furthermore, the first force Fi applied to the formed body 3, in view of the relative softness of plastic formed bodies 3, should be applied to a sufficiently large areas or regions on the body edge, whereas the second force F_2i, F₂₂ to the molding shells 1, 2 can be applied to very small areas (punctual application) or to more extended regions (regional application) . The regional force application may also comprise several punctual or regional symmetrically or asymmetrically distributed application positions within essentially opposite regions, or the application can be a mixture of punctual and regional application, e. g. a punctual application to one side and a regional application to an opposite side. Essentially opposite in the scope of the present invention means that the reactive forces can balance the active forces Fi; F₂ι, F₂₂ such that the resulting forces act, in particular press, on the assembly 1, 2, 3 without moving it out of its mounting position. Geometrically speaking, essentially opposite means that a line through the center of the region of applied force on the first side and the center of the region of applied or reactive force on the opposing side may include an angle with a line through the center of the first region of applied force and the center of the formed body 3, wherein a vanishing angle is preferred. Thus, preferred in this respect is opposite application of force F₂ι, F₂₂ to the molding shells 1, 2, as provided by the molding-shell-force-applying means 8, 9 and possibly the respective holding means 18, 19, and the opposite application of force Fi to the formed body 3 by the formed-body-force-applicaing means 13 and possibly the ring segments 17 (see Figures 2, 3, 5 and 6) .

Active force Fi to the formed body 3 is applied by two different means. Great force is applied with the formed-body-force-applying-means 13, while little force is applied by the holder 16 and in particular ring segments 17. While great force is actively applied to one or both sides, little force is usually applied via several ring segments 17 to at least two areas of the edge of the formed body 3. Thus, the opposite application of force Fi to the formed body 3 is effected by the formed-body-force-applying means 13 and possibly the ring segments 17 (see Figures 2, 3 and 6). While it is not necessary that the transverse first and second forces Fi, F₂χ, F₂₂ are exactly radially applied, such application is preferred, whereby "exactly" means within the technically reasonable margins.

A preferred application of forces Fi, F_2i, F₂₂ to essentially opposite sides is an application to exactly opposite sides, wherein also here "exactly" means within technically reasonable margins and includes several part means the center of which is opposite to a one-part means or the center of a several-part means. Several-part means are primarily holding means 18, 19 that do not themselves apply active forces.

It is much preferred that the first force Fi is applied to the formed body at the interface 31 of front molding shell 1/formed body 3, since said interface 31 is positioned unambiguously. It is also preferred that force is simultaneously applied to the formed body 3 and the front molding shell 1, more preferred to the formed body 3 and both molding shells 1, 2.

If second forces F₂ι, F₂₂ are applied to both molding shells 1, 2, the second force F₂ι applied to said front molding shell 1 is essentially perpendicular, and preferably "exactly" perpendicular, to the second force F₂ applied to said back molding shell 2.

In a much preferred embodiment, the first force Fi is applied to the formed body 3 to essentially opposite sides of said formed body 3, the second force F_2i applied to the front molding shell 1 is in parallel with said first force Fi, and the second force F₂₂ applied to opposite sides of the edge of the back molding shell 2 is essentially perpendicular to the forces Fi, F_2i applied to the front molding shell 1 and the formed body 3, respectively. Simultaneously little force, also referred to as holding force, is applied to the formed body 3 by the holder 16. Said holding force is usually applied by four ring segments 16 at rotated positions with regard to the application of the above discussed forces, preferably at positions rotated by a n angle of about 45°. As already mentioned above, the application of force to the formed body 3 should be as a regional force, i.e. by means of a tool providing a sufficiently large transfer or contacting area 15. In view of a usual circular shape of the formed body 3, said contacting area 15 contacting the circular edge of said formed body 3 should have the form of a ring segment matching said edge or should comprise such a segment. Said contacting area 15 should have an extent of at least 15 mm², preferably between 15 mm² and 30 mm², preferably about 25 mm². A presently preferred shape of the lens-force-applying- means 13 is a ring segment with a thickness of about 1.5 mm and a circumferential width W of about 16.5 mm. It is furthermore preferred that the contact area 15 is provided with a treated surface, e.g. a riffled surface, to increase friction and thus force transfer to the assembly 1, 2, 3. The same shape and dimension can also be applied for the legs 16 of the holder 16, while the actual shape and dimensions in view of the reduced force applied are not so critical.

A suitable first force Fi applied to the formed body 3 is e. g. smaller than the second force F₂ι applied to the molding shell 1. In one embodiment the formed-body-force-applying-means 13 comprises a finger 13a fixed on the molding-shell-force-applying-means 8 for applying force to the front molding shell 1. The finger 13a extends over a position that would abut against the formed body 3 and penetrates into the formed body 3 , when the first force Fi is applied. The forces F_2i applied to the front molding shell 1 are usually in the range of 100 kg-400 kg (-1000 N-4000 N) , preferably about 200 kg (-2000 N) . By a rigidly mounted finger 13a the same force F₂ι is applied and transferred to the formed body 3. In view of the softness of e. g. the lens 3, part of said force F₂ι may be lost due to plastic deformation of the lens 3 in the optically not used region. The such lost force is dependent on the shape of the finger 13a. For usual acrylic lenses 3 of edge thickness T, a finger 13a with a thickness t < T, usually t < 2 mm, preferably 1 mm ≤ t ≤ 2 mm, much preferably about t=l .5 mm, and/or with a circumferential width W of 10 mm to 20 mm, preferably about W=16.5 mm, and/or an overhang or projecting length 1 of about 1.5 mm proved to be very suitable for forces F₂₁ of 100 kg to 400 kg, preferably about 200 kg. Note that projecting length or overhang signifies the length exceeding the difference between the radius of the molding shell 1 and the formed body 3. If a too little force is applied to the front molding shell 1 and the formed body 3, demolding will only occur with regard to part of the formed bodies 3 or interfaces 31, 32, respectively. For example, with 50 kg applied to the front molding shell 1 and formed body 3 no demolding occurs, with 100 kg some demolding was obtained, with 150 kg only some assemblies remained intact, and with 200 kg all assemblies hitherto examined could be demolded. While each molding shell 1, 2 could be removed separately by the same or different methods, it is possible and preferred to remove both shells 1, 2 simultaneously by the inventive method. In the case of simultaneous removal of both shells 1, 2, and in order to minimize the stress in the formed body 3, it is preferred to apply the deformation forces F_2i, F₂₂ to the molding shells 1, 2 such that they act in different directions, prefe'rably in directions perpendicular to one another. For simultaneous pressure forces Fi, F₂ι, F₂₂ to the molding shell 1, the formed body 3 and the back molding shell 2, the second force F₂₂ applied to the back molding shell 2 is usually in the range of about 100 kg-200 kg (1000 N to 2000 N) , peferably about 140 kg.

The holding force applied to the formed body 3 by each leg 16 of the holder 16 is usually in the range of 10 kg to 18 kg (about 100 N to 180 N) , preferably about 15 kg. Usually the simultaneous application of the above defined forces leads to a full and damage-free disassembling within a force-application time of 5 s (seconds) to 20 s, preferably 10 s to 15 s. The demolding by application of pressure force may be supported by reducing in advance the adhesion between the molding shells 1, 2 and the formed body 3. In particular, in the case of different thermal expansion coefficients of the molding shells 1, 2 and the formed body 3 material, such adhesion reduction can be obtained e. g. by heating at least part or the whole of one or both molding shells 1, 2. Such heating, however, in order to avoid lasting deformation of the formed body 3 has to be performed at temperatures below the glass transition temperature T_g of the formed body 3. Preferred is a demolding temperature in the range of 20 to 50°C, much preferred ambient temperature.

The demolding can also be assisted by application of an airstream. Said airstream is positioned such that it is focused to the interface 31 or 32 of molding shell 1, 2/formed body 3. In view of positioning requirements, the airstream is applied radially on the interface 32 between the smaller molding shell 2 and the formed body 3 with sufficient focussing. Said airstream or airstreams are assumed to hinder a once formed gap to close again and to support the further gap growth. Said focused airstream is usually focused or redirected to the interface 31, 32 by a deflection element, e. g. a metal sheet. If airstreams are used, care must be taken to avoid pollution of the formed body 3 by particles blown onto optical surfaces of the formed body 3 or molding shells 1, 2 that may causes scratches.

Besides of air, it is of course also possible to use other gases, such as inert gases etc., whereby inert gases, in view of their higher cost, are only applied where needed. A suitable air or gas pressure is in the range of about 6 bar or more. In the method of the present invention, when only one formed-body-force-applying-means 13 and only one molding-shell-force-applying-means 8, 9 is used, said molding-shell-force-applying-means 8 is usually a means 8 applying a transverse or radial force to the front molding shell 1. In the case of application of force to only one molding shell 1, it may happen that only one of the molding shells 1 is removed. In this case the back molding shell 2 can be removed by mechanical and/or thermal shock, or by mechanical force.

It has been proven that - even if no force is directly applied to the back molding shell 2, the force applied to the formed body 3 is sufficient to weaken the adhesion of the back molding shell 2 to the formed body 3 thereby rendering the mechanical and/or thermal shock more efficient than it was found by immediate shock application. Thermal shock is usually performed in a liquid or in air, e.g. by cooling to about 15°C. Mechanical methods comprise e. g. the separation of a second shell 2 by mechanical means if an at least partial overhang or insert, respectively, exists with regard to the back molding shell 2. Such a mechanical means is e. g. a spatula.

A further object of the present invention is a demolding device comprising at least one formed-body- force-applying-means 13 for the application of a first transverse or essentially radial force Fi to a formed body 3 and at least one molding-shell-force-applying- means 8, 9 for the application of a second transverse or essentially radial force F_2i, F₂₂ to at least one of a front and/or a back molding shell 1, 2, wherein the presence of at least a molding-shell-force-applying-means 8 for applying force F_2i to the front molding shell 1 is preferred, and preferably also at least one holder 16 for holding the formed body 3 after disassembling. Much preferred is the simultaneous presence of two means 8, 9 for the application of a transverse or essentially radial force F_2i, F₂₂ to said front and said back molding shell 1, 2, said means 8, 9 being designed to apply transverse or essentially radially second forces F_2i, F₂₂ to said front and back molding shells 1, 2, wherein said force F₂ι applied to said front molding shell 1 is preferably perpendicular to said force F₂ applied to said back molding shell 2.

For the application of force to the formed body 3, it is preferred that said formed-body-force- applying-means 13 is in parallel with one of the molding- shell-force-applying-means 8, 9. The holder 16 applying holding force to the formed body 3 and optionally simultaneously acting as fixation of the opposite side of the formed body 3 for the application of an at least partial reactive force to the formed-body-force-applying- means 13 is usually designed to apply force to three or more areas or legs 16 evenly distributed on the edge of the formed body 3, much preferably to four legs 16, said four legs 16 including a rotational angle with the essentially opposite sides of said at least one molding shell 1, 2 of about 45°.

Said formed-body-force-applying-means 13 and/or said molding-shell-force-applying-means 8, 9 usually have an edge abutting said formed body 3 and/or said at least one molding shell 1, 2, said edge preferably being riffled, in particular the one abutting the formed body 3

It has been found that, in order to avoid damages to the formed body 3, the force-applying-means 13 has to transfer force F_x to a circumferential part 15 of width W about 10 mm to 20 mm, preferably about W=16.5 mm extension (see Figure 6) . Said force-applying-means 13 is preferably thin at the formed body contacting end over the projecting length 1 and then extends to a greater thickness such that its stability is encreased. The contacting face 15 has to be thinner than the thinnest formed body 3 intended to be demolded, usually t < 2 mm, preferably 1 mm ≤ t ≤ 2 mm, much preferably about t=1.5 mm. The thickness of the formed body distant part is not critical as long as the thickness is sufficient to ensure stable transfer of the applied force. The overhang is the length 1 exceeding the difference between the lateral extension of the molding shell 1 and the formed body 3.

Said means 13 applying force to the formed body 3 can be an integral part of means 8 applying force to the molding shell 1 and may e. g. have the shape of an overhanging portion 13. Such embodiment (with formed body penetration not shown) is represented in Figure 1, 2, 4 and 6. The means 13 applying force to the formed body 3 can be fully or partially independent of force applying means 8, e.g. in that it is spring-loaded. An embodiment where the means 13 or the spring 14, respectively, are supported by means 8 is represented in Figures 3 and 6, again with the formed body penetration by the overhanding portion 13 not shown. Also in this embodiment, means 13 could simultaneously act as a holder or part of a holder (e. g. no gap between means 13 and molding shell 1) .

It is also possible and preferred that the holder 16 is places at a position rotated by an angle of about 45° with respect to the force applying means 8 and preferably has four force applying legs 16, each suitable for applying a holding force.

Furthermore, the demolding device of the present invention may comprise at least one heat source, e.g. an IR source and/or an airstream source. Although an assembly 1, 2, 3 with both molding shells 1, 2 larger than the formed body 3 can easily be positioned, application of a first force Fi to the formed body 3 close to an interface 31, 32 molding shell 1, 2/formed body 3 would be more difficult, since the means 13 applying said force Fi - in view of the back molding shell 2 - on a rather long distance has to be very thin, thereby limiting the force Fi that can be applied to the formed body 3.

In the preferred embodiment of the mold, the larger front molding shell 1 enables easy decentering of its optical axis (see Figure 7), namely by a lateral movement of the front molding shell 1 in a direction about perpendicular to the axis 6 such that the center of molding shell 1, that in centered position is on the axis 6, moves to the axis 61. Due to the larger size of said front molding shell 1 compared to said back molding shell 2, such decentering movement is possible without loosing the sealing contact to the contact surface 7 of the gasket 4. Dependent on the actual positioning of the front molding shell 1 relative to the gasket 4 or back molding shell 2, respectively, one side of the formed body 3 and the front molding shell 1 may be favored for the application of active force or the deformation or displacement, respectively. Depending on the shape of the molding shell 1, 2 namely, on the one side of the formed body 3 an edge 12 is formed in the formed body 3 that might affect the desired effect of actively applied force and therewith the deformation. Thus, in this case one side might be favored for the application of active force, might it be the side of increased or decreased overhang of the front molding shell 1 due to its decentering or might it be a direction perpendicular to its decentering displacement.

While there are shown and described presently preferred embodiments of the invention, it is to be dis- tinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

Claims

1. A method for demolding formed bodies (3) from at least one molding shell (1, 2), wherein a first mechanical force (Fi) is applied in a transverse direction of the formed body (3) to essentially opposite sides of an edge of the formed body (3) and close to an edge (31, 32) of at least one interface between the formed body (3) and the molding shell (1, 2) by a formed- body-force-applying-means (13), and wherein simultaneously a second mechanical force (F₂ι, F₂₂) is applied in a transverse direction of the at least one molding shell (1, 2) to essentially opposite sides of the molding shell (1,2) by a molding-shell-force-applying- means (8,9), such that demolding of the at least one molding shell (1, 2) is obtained.

2. The method of claim 1 wherein said formed body (3) is held in a holder (16) by a holding force applied thereto, preferably by a holder (16) having three or more legs (16), much preferred four legs (16) .

3. The method of claim 1 or 2 , wherein said first (Fi) is actively applied to one side of said formed body (3) with the essentially opposing side of said formed body (3) being fixed, and/or said second force (F₂) is actively applied to one side of said molding shell (1, 2) with the essentially opposing side of said molding shell (1, 2) being fixed.

4. The method of anyone of the claims 2-3, wherein said first force (Fi) is actively applied to one side of said formed body (3) while the opposing side is fixed by the holder (16) .

5. The method of anyone of the preceding claims, wherein said first and/or second force (Fi; F₂ι, F₂₂) is applied to opposite sides of said formed body (3) and/or said at least one molding shell (1, 2).

6. The method of anyone of the preceding claims, wherein the first and/or second force (Fi; F_2i, F₂₂) is or are a force (F₁₍- F_2i, F₂₂) in a radial direction of said formed body (3) or molding shell (1, 2), respectively .

7. The method of anyone of the preceding claims, wherein said holder (16) comprises four legs

(16), each of them applying active holding force.

8. The method of anyone of the preceding claims, wherein said second force (F₂ι) comprises a force (F_2i) applied to a front molding shell (1) .

9. The method of anyone of the preceding claims, wherein said second force (F₂ι, F₂ ) comprises a force (F_2i) applied to a front molding shell (1) and a force (F₂₂) applied to a back molding shell (2) .

10. The method of claim 9, wherein the force (F₂ι) applied to said front molding shell (1) is essentially perpendicular, preferably perpendicular, to the force (F₂₂) applied to said back molding shell (2) .

11. The method of anyone of claims 2 to 10, wherein said holding force applied to said holder (16) is at a rotational angle of about 45° from said second force (F₂ι) applied to said at least one molding shell (1, 2) .

12. The method of anyone of the preceding claims wherein said first force (Fi) is a regional force (Fi) , preferably a regional force (Fi) applied to an area of at least 15 mm², preferred 15 to 30 mm², most preferred about 25 mm², at the edge of said formed body (3) .

13. The method of anyone of the preceding claims wherein the second force (F₂χ, F₂₂) applied to one side of said molding shell (1, 2) is a punctual force (F₂ι, F₂₂) or a circumferential force (F₂ι, F₂ ) applied to a thin circumferential segment of said molding shell (1, 2).

14. The method of anyone of the preceding claims, wherein the second force (F_2i, F₂₂) applied to one side of said molding shell (1, 2) is a regional force (F₂ι, F₂₂) .

15. The method of anyone of the preceding claims, wherein the second force (F₂χ, F₂₂) applied to one side of said molding shell (1, 2) is a punctual or circumferential force (F₂ι, F₂₂) and the force (F_2i, F₂₂) applied to the opposing side is a regional force (F₂ι, F₂₂) .

16. The method of anyone of claims 1 to 15, wherein the first force (Fi) is applied by a finger (13a) provided on the formed-body-force-applying-means (13).

17. The method of claim 16, wherein the finger (13a) has a projecting length (1) of about 1.5 mm, and/or a thickness (t) smaller than a thickness (T) of the formed body (3), preferably a thickness t ≤ 2 mm, more preferred 1 mm < t ≤ 2 mm, most preferred t=1.5 mm, and/or and a circumferential width (W) of at least 10 mm, preferably 10 mm ≤ W ≤ 20 mm, more preferred W=16.5 mm.

18. The method of anyone of the preceding claims wherein the second force (F_2i) applied to a front molding shell (1) is in a range of 100 kg to 400 kg, preferably about 200 kg, and/or the second force (F₂₂) applied to a back molding shell (2) is in a range of 100 kg to 200 kg, preferably about 140 kg, and/or a holding force applied to the formed body (3) is between 10 kg and 18 kg, preferably about 15 kg.

19. The method of anyone of the preceding claims wherein the time of force application is in the range of 5 s to 20 s, preferably in the range of 10 s to 15 s.

20. The method of anyone of the preceding claims wherein the formed body (3) is an ophthalmic lens (3) .

21. The method of anyone of the preceding claims wherein a front molding shell (1) is larger than said formed body (3) and a back molding shell (2), and wherein said front molding shell (1) prior to an application of force is placed on a holder (16) such that said back molding shell (2) and formed body (3) project onto one side and said front molding shell (1) onto an opposite side of said holder (16) .

22. The method of claim 20, wherein a part (17) of said holder (16) assists in generating force to opposing sides of said formed body (3) .

23. The method of anyone of the preceding claims wherein said force-applying-means (13; 8, 9) is riffled at the edge contacting the formed body (3) and/or the molding shell (1, 2) .

24. The method of anyone of the preceding claims wherein prior to an application of force a heating step is performed during which heat is applied to at least part of at least one molding shell (1, 2) .

25. The method of anyone of the preceding claims wherein the demolding is assisted by simultaneous application of an air stream, preferably an air stream of about 6 bar, directed onto the edge of the formed body (3) and preferably onto the edge (31, 32) of the at least one interface between the formed body (3) and the molding shell (1, 2) .

26. A demolding device comprising at least one formed-body-force-applying-means (13) for an application of a first mechanical force (Fi) in a transverse direction to a formed body (3) and at least one molding-shell-force-applying-means (8, 9) for an application of a second mechanical force (F_2i, F₂₂) in a transverse direction to at least one of a front molding shell (1) and/or a back molding shell (2) .

27. The demolding device of claim 26 comprising at least one means (8) for applying the second force (F₂₁, F₂₂) in an essentially radial direction to said front and/or back molding shell (1, 2).

28. The demolding device of claim 26 or 27 comprising two means (8, 9) for applying the second force (F₂ι, F₂₂) in a radial direction to said front and back molding shell (1, 2), wherein said means (8, 9) are designed for applying the second force (F₂ι) to the front molding shell (1) in a perpendicular direction to the second force (F₂ ) to the back molding shell (1) .

29. The demolding device of one of claims 26 to 28, wherein said demolding device comprises a holder (16) suitable to apply a holding force to the formed body (3), said holder (16) preferably comprising three of more, much preferred four regularly distributed legs (16), most preferred four legs (16) at a rotational angle of about 45° relative to essentially opposite sides of said at least one molding shell (1, 2).

30. The method of anyone of claims 24 to 29, wherein said formed-body-force-applying-means (13) and/or said molding-shell-force-applying-means (8, 9) have a contact area (15) abutting said formed body (3) and/or said at least one molding shell (1, 2), said contact area (15) preferably being riffled.

31. The demolding device of claim 30, wherein said formed-body-force-applying-means (13) has a contact area (15) abutting the formed body (3) over a circumferential length or width (W) of at least 10 mm, preferably 10 mm ≤ W ≤ 20 mm, more preferred W=16.5 mm, and/or over a thickness (t) smaller than a thickness (T) of the formed body (3), preferably a thickness t ≤ 2 mm, more preferred 1 mm < t ≤ 2 mm, most preferred t=1.5 mm, and/or with an excess or projecting length (1) of about 1.5 mm, preferably of constant thickness.

32. The demolding device of claim 31, wherein said formed-body-force-applying-means (13) at the formed body distant end is extending, preferably continuously, to a larger thickness than the thickness (t) of the contact area (15) .

33. The demolding device of one of claims 26 to 32 comprising at least one heat source, e.g. an IR source, and/or an air stream source.