Molded ophthalmic lens housing and method for manufacturing such molded housing

Abstract

An ophthalmic lens molded housing (30) has two main faces (31, 32) and an edge face (33) surrounding the main faces, a first of the main faces being adapted to face the other molded housing during molding of an ophthalmic lens. The ophthalmic lens molded housing further comprises:-a flat facet (34) extending along an outer edge of the first major face, and-a first chamfer (36) extending along an outer edge of the flat facet between the flat facet and the edge face.

Description

Technical Field

[0001] The present invention relates generally to the field of eyewear.

[0002] The invention more particularly relates to a molded shell suitable for molding an ophthalmic lens, for which purpose the molded shell has two main faces and edge faces surrounding the main faces, a first of the main faces being adapted to face another molded shell when molding an ophthalmic lens. Background Art

[0003] A conventional mold for molding an ophthalmic lens includes two molding shells at the peripheries of which an annular closing member is provided, which defines a molding cavity together with the shells.

[0004] The two molded shells are usually made of a transparent material, while the closing member is made of an adhesive tape.

[0005] The main function of the tape is to close the spaces between the molded shells in order to hold the monomer to be polymerized between these shells when the mold assembly is filled with the monomer.

[0006] The molded housing is usually manufactured by a computer numerical control machine and polished in a polishing machine.

[0007] Each molded shell has two main faces, a first main face being designed as the face for producing a lens. Each shell also comprises an edge face surrounding these main faces.

[0008] The edge line of the first main face at the junction between the first main face and the edge face is rounded or sharp around the main axis. However, due to the polishing tool, its cross section (taken by a plane including the main axis) may be rounded, thereby producing a chamfer.

[0009] The rounded or sharp shape of the chamfer is not intentional, and its size is difficult to control, especially in a small size.

[0010] The applicant has observed that such rounded or sharp shapes can generate chips along the edges of the major faces, thereby shortening the life of the molded housing.

[0011] The Applicant has also observed that, in order to facilitate the disassembly of the lens during polymerization of the monomers, it is important to provide the chamfer with very specific dimensions.

[0012] In practice, however, controlling such chamfer dimensions is a difficult goal to achieve and may render the molded housing very brittle. Summary of the invention

[0013] In this context, the present invention provides a solution for the durability of the molded housing while improving the lens removal performance.

[0014] More specifically, the invention relates to an ophthalmic lens molded shell as defined in the introduction, comprising:

[0015] - a flat facet extending along the outer edge of the first main face, and

[0016] - a first chamfer extending along an outer edge of the planar facet between the planar facet and the edge facet.

[0017] In other words, the applicants have discovered a specific shape that can be machined about the first major face to improve the durability of the molded housing without affecting its lens removal performance (ie, without increasing the time required to mold and remove the lens).

[0018] The applicant has also developed a machining method to produce this specific shape that allows for better chamfer dimensional consistency and better mold edge quality, thus enabling low lens scrap rates and good casting yield performance.

[0019] The molded housings obtained by this method are indeed more durable (and can last twice as long as the molded housings currently in use) and have less debris, thus reducing the number of discarded lenses.

[0020] Other preferred features of the present invention are as follows:

[0021] - The width of the flat facet is equal to 0.5 mm with a tolerance of plus or minus 0.1 mm.

[0022] The edge surface extends around the central axis.

[0023] - In each cross section of the first chamfer taken in a plane passing through the central axis, the first chamfer is inclined at an angle of 40° relative to the flat facet, with a tolerance of plus or minus 5°.

[0024] The width of the first chamfer, measured radially relative to said central axis, is equal to 0.08 mm, with a tolerance of plus or minus 0.05 mm.

[0025] The ophthalmic lens molded shell comprises a second chamfer between the edge face and the other main face.

[0026] - In each cross section of the second chamfer taken in a plane passing through the central axis, the second chamfer is inclined at an angle of 45° relative to the edge face, with a tolerance of plus or minus 5°.

[0027] The width of the second chamfer, measured radially relative to said central axis, is equal to 0.5 mm, with a tolerance of plus 0.2 mm or minus 0.1 mm.

[0028] The present invention also relates to a method for manufacturing a molded shell for an ophthalmic lens, the method comprising the following steps:

[0029] - machining the blank piece to obtain a semi-finished molded shell having two main faces and edge faces surrounding the main faces, a first of the main faces being adapted to face another molded shell during the molding of the ophthalmic lens, the preliminary chamfer being located between the edge face and the first main face,

[0030] - polishing the preliminary chamfer and the edge face to produce:

[0031] ¤ a flat facet extending along an outer edge of the first major face, and

[0032] ¤ A first chamfer extending between the flat facet and the edge facet along an outer edge of the flat facet.

[0033] Preferably, during the polishing step, a material thickness of at least 0.03 mm is removed from the edge face and / or from the preliminary chamfer.

[0034] Preferably, the polishing step comprises a first sub-step during which the preliminary chamfer is reduced and a flat facet appears, and a second sub-step during which the first chamfer is completed.

[0035] Preferably, at the end of the first sub-step, the width of the flat facet measured radially with respect to the central axis of the edge face is between 0.5 mm and 0.6 mm, and the width of the first chamfer is equal to 0.13 mm, with a tolerance of plus or minus 0.02 mm.

[0036] Preferably, at the end of the machining step, the preliminary chamfer is inclined at an angle of 40 degrees relative to the edge face, with a tolerance of plus or minus 5 degrees.

[0037] Preferably, at the end of the machining step, the preliminary chamfer has a width measured radially relative to the central axis of 0.8 mm with a tolerance of plus or minus 0.05 mm. DETAILED DESCRIPTION

[0038] The following description, given by way of non-limiting examples with reference to the accompanying drawings, makes clear what the invention consists of and the manner in which it can be put into practice.

[0039] In the attached picture:

[0040] - Figure 1 is a schematic diagram of a mold assembly according to the present invention,

[0041] - Figure 2 yes Figure 1 A cross-sectional view of a molded housing of a mold assembly,

[0042] - Figure 3 yes Figure 2 A detailed view of Region III,

[0043] - Figure 4 yes Figure 3 A detailed view of Region IV,

[0044] - Figure 5 Is manufacturing Figure 2 a cross-sectional view of a portion of the molded housing after a first step of molding the housing, and

[0045] - Figure 6 is Figure 5 The same cross-sectional view of the portion of the molded housing at the end of manufacturing the molded housing.

[0046] Figure 1 A mold assembly 10 is shown.

[0047] The mold assembly 10 includes two molding shells 20, 30 and an annular closure member 40 located at the outer periphery of these shells.

[0048] Each molded shell 20 , 30 has the shape of a transparent thick disk having two main faces 21 , 22 , 31 , 32 and a peripheral edge face 23 , 33 .

[0049] The first main faces of the molded shells 20, 30 facing each other are called "inner faces 21, 31". These inner faces are shaped to produce the main faces of an ophthalmic lens. One of these inner faces is convex and the other is concave.

[0050] The other major surface of the molded housing 20, 30 (referred to as the outer surface 22, 32) may be a flat surface (such as Figure 1 ) or may show different shapes (such as Figure 2 shown).

[0051] The peripheral edge faces 23 , 33 of the molded housings 20 , 30 have here a cylindrical shape of revolution about the main axis A1 .

[0052] The thickness of the peripheral edge surfaces 23 , 33 is typically between 3 mm and 6 mm.

[0053] Both edges of each peripheral edge surface 23 , 33 have a circular shape.

[0054] During the moulding process, the two moulded shells 20 , 30 are positioned relative to each other so that their inner faces 21 , 31 face each other and so that their main axes A1 remain coincident.

[0055] The closing member 40 has the shape of a band that is wound around at least a portion of the outer peripheral edges of the two molded shells 20 , 30 and glued.

[0056] The closure member holds one molded shell at a distance from the other molded shell. Thus, the two molded shells 20, 30 and the closure member 40 together define a mold cavity 11 to be filled with molding material (hereinafter referred to as "monomer"), which is (negative) lens-shaped.

[0057] The inner face of the closing member 40 therefore has two lateral portions to be glued on the peripheral edge faces 23 , 33 of the two moulding shells 20 , 30 and a central portion adapted to close the moulding cavity.

[0058] Here, the length of the closing member 40 is longer than the circumference of the outer peripheral edge surface 23, 33 of each mold shell 20, 30, so as to completely close the molding cavity 11 after the molding cavity 11 is filled with the monomer.

[0059] The two molded shells 20, 30 are manufactured in the same way so as to have similar characteristics. For clarity of description, only one of these molded shells 20, 30 will be described below and will be shown in the drawings.

[0060] The molded housing 30 is a molded housing whose inner main surface 31 is a concave surface.

[0061] The exact shape of the inner and outer faces can vary greatly and will not be described here. Figure 2 As shown, only the molded housing 30 having a constant thickness will be considered here.

[0062] The invention more particularly relates to the shape of the area located at the interface between the inner main face 31 and the outer peripheral edge face 33 of the molded housing 30 .

[0063] The shape of this area is indeed important to ensure good demoulding of the lens and to increase the durability of the molded shell (this area is subject to high stress and it is usually this area that affects the replacement of the molded shell).

[0064] According to the present invention, Figure 3 and Figure 4 As shown, the molded housing 30 comprises in this area:

[0065] a flat facet 34 , one side of which coincides with the outer edge line of the inner main face 31 , and

[0066] A first chamfer 36 , one side of which coincides with the outer edge line of the flat facet 34 , and the other side of which coincides with the inner edge line of the peripheral edge face 33 .

[0067] It may be noted here that if the terms "inner" and "outer" refer to directions parallel to the main axis A1, the term "outer" refers to a direction radially relative to the axis (the outer side is located in a direction opposite to the axis).

[0068] The flat facet 34 has a flat ring shape, the first chamfer 36 has a truncated cone shape, and the flat facet and the first chamfer extend between the inner main face 31 and the peripheral edge face 33 , the first chamfer being located outside the flat facet 34 relative to the main axis A1 .

[0069] like Figure 3 As shown, the flat facet 34 extends on a plane orthogonal to the main axis A1 and has an annular shape of a constant width W3 around the main axis A1. Therefore, both sides of the flat facet have a circular shape.

[0070] The width W3 measured radially with respect to the main axis A1 is preferably equal to 0.5 mm, with a tolerance of plus or minus 0.1 mm.

[0071] like Figure 4 As shown, in a cross section taken in an undifferentiated plane containing the main axis A1 , the first chamfer 36 is inclined at an angle α1 relative to the flat facet 34 , which angle remains constant around the main axis A1 .

[0072] The angle α1 is not zero. The angle is preferably 40°, with a tolerance of plus or minus 5°.

[0073] The width W1 of the first chamfer 36 is also not zero and remains constant around the main axis.

[0074] This width W1 , measured radially with respect to the central axis A1 , is preferably equal to 0.08 mm, with a tolerance of plus or minus 0.05 mm.

[0075] In other words, the width W3 is three times or more the width W1 , and preferably five times or more the width W1 .

[0076] like Figure 3 As shown, on the other side of the peripheral edge face 33 , the molded housing 30 includes a second chamfer 35 between the edge face 33 and the outer main face 32 .

[0077] In each cross section taken in a plane containing the main axis A1 , the second chamfer 35 is inclined relative to the peripheral edge face 33 at a non-zero angle α2 , which is preferably 45° with a tolerance of plus or minus 5°.

[0078] The width W2 of this second chamfer 35 is also non-zero and remains constant around the main axis. This width W2 measured radially with respect to the central axis A1 is preferably equal to 0.5 mm, with a tolerance of plus 0.2 mm or minus 0.1 mm.

[0079] The method used to manufacture the molded housing 30 is quite unique because machining the precise flat facets 34 and first chamfer 36 is quite difficult.

[0080] To this end, the method includes two main steps.

[0081] The first major step involves machining the blank to obtain a semi-finished molded shell 30' having only a preliminary chamfer 39, such as Figure 5 shown.

[0082] The second step involves polishing at least a portion of the semi-finished molded housing 30 ′ to obtain the molded housing 30 described above.

[0083] The method may be described in more detail.

[0084] The blank piece may be of any shape, but its dimensions must be larger than the dimensions of the semi-finished molded shell 30' to be machined.

[0085] For example, the stock piece may be in the shape of a thick disk of constant thickness.

[0086] However, in a preferred embodiment, the blank piece already has two main faces and an edge face, presenting a shape similar to that of the molded housing 30 described above. The main difference is that, instead of having a flat facet and a first chamfer, the blank piece has a rounded edge connecting each main face and edge face. The rounded edge has the shape of an arc with a radius of 2 mm in the cross-sectional plane.

[0087] The first step is preferably performed by a CNC machine to remove some material from the blank piece, thereby obtaining a semi-finished molded shell 30'. The CNC machine is preferably a lathe.

[0088] For example, the lathe is a Schaublin lathe (eg, a 302 Schaublin machine).

[0089] During this first step, the edge face is ground in order to reduce its diameter and produce a preliminary chamfer 39 .

[0090] Therefore, if Figure 5 As shown, at the end of the first step, the semi-finished molded housing 30 ′ has:

[0091] - two main faces 31 , 32 (referenced 31 , 32 because their shape is similar to that of the main faces of the finished molded shell 30 ) and an edge face 33 ′ surrounding these main faces 31 , 32 , and

[0092] A preliminary chamfer 39 between the edge face 33 ′ and the first main face 31 .

[0093] The preliminary chamfer 39 has a frustoconical shape (with rotational symmetry about the main axis A1 ) and extends between the outer edge of the inner main face 31 and the peripheral edge face 33 ′.

[0094] In each cross section taken in a plane containing the main axis A1 , the preliminary chamfer 39 is inclined relative to the peripheral edge face 33 ′ at a non-zero and constant angle α4 , which is preferably 40° with a tolerance of plus or minus 5°.

[0095] The width W4 of the preliminary chamfer 39 is also non-zero and remains constant around the main axis A1. The width W4 measured radially relative to the central axis A1 is greater than 0.1 mm. In this step, the width W4 is between 0.2 mm and 0.3 mm.

[0096] The second step involves polishing the first main face 31, the preliminary chamfer 39 and the peripheral edge face 33 of the semi-finished molded shell 30' in order to remove material (along the Figure 5 38), thereby producing a flat face 34 and a first chamfer 36 (see Figure 6 ).

[0097] For this purpose, a material thickness of at least 0.03 mm is removed from the peripheral edge face 33 and the preliminary chamfer 39 .

[0098] In practice, this polishing step comprises a first sub-step, during which the preliminary chamfer 39 is reduced, producing a flat facet 34 , and a second sub-step, during which the first chamfer 36 is completed.

[0099] The first sub-step is performed by a polishing machine (for example, a machine sold under the brand name "Kwangjin KJ-4 Spherical Polishing Machine").

[0100] During this first sub-step, the semi-finished molded shell 30' is blocked on a support and its first main face 31 is pressed against the polishing pad and then rubbed against it in counter-rotation. In other words, grinding is performed along an axis substantially parallel to the main axis A1.

[0101] In this process, the flat face 34 is enlarged until it reaches a target size. At the same time, the preliminary chamfer 39 is partially removed until it reaches another target size.

[0102] At the end of this first sub-step, the semi-finished molded shell 30 ′ is polished so that:

[0103] the width of the flat facet 34 is non-zero and constant around the main axis and is preferably comprised between 0.5 mm and 0.6 mm when measured radially relative to the central axis A1 , and

[0104] The width of the remainder of the preliminary chamfer 39 (which forms the first chamfer 36 ) is also non-zero and constant around the main axis and is preferably equal to 0.13 mm when measured radially relative to the central axis A1 , with a tolerance of plus or minus 0.02 mm.

[0105] No further finishing process is performed on the flat facet 34 .

[0106] The second sub-step is performed by another polishing machine, here a machine sold under the brand name "CP-8 Automatic Lens Polisher".

[0107] This machine differs from the previous one in that the molded housing is held in a different way. During the first sub-step, the first main face 31 is simply pressed down onto the polishing tool or polishing pad. In contrast, during this second sub-step, the molded housing is held by clamping its main faces 31, 32 between two cylinders in order to press the edge face 33 onto the polishing wheel below.

[0108] During this sub-step, only the edge face 33 of the molded housing is pressed against the polishing pad and rubbed against it in the reverse direction. In other words, grinding is performed along an axis substantially radial to the main axis A1 (or more radial than during the previous sub-step).

[0109] Therefore, the edge face 33 is polished and its diameter is reduced until it reaches the target size. At the same time, the first chamfer 36 is partially removed until it reaches its target size (0.08 mm).

[0110] At the end of this second sub-step, the molded housing 30 is achieved and has the shape described above.

[0111] The invention is in no way limited to the described and shown embodiments. In particular, the widths and angles given may differ slightly.

Claims

1. An ophthalmic lens molded shell (30) having two main faces (31, 32) and edge faces (33) surrounding the main faces (31, 32), wherein a first main face (31) of the main faces is adapted to face another molded shell (20) during the molding process of the ophthalmic lens, It is characterized in that The ophthalmic lens molded shell further comprises: - a flat facet (34) extending along the outer edge of the first main face (31), and - a first chamfer (36) extending between the flat facet (34) and the edge face (33) along the outer edge of the flat facet (34).

2. The ophthalmic lens molded shell (30) according to claim 1, wherein: The width (W3) of the flat face (34) is equal to 0.5 mm, with a tolerance of plus or minus 0.1 mm.

3. An ophthalmic lens molded shell (30) according to any one of claims 1 and 2, wherein: The edge surface (33) extends around the central axis (A1), and in each cross-section of the first chamfer (36) taken by a plane passing through the central axis (A1), the first chamfer (36) is inclined at an angle (α1) of 40° relative to the flat face (34), with a tolerance of plus or minus 5°.

4. The ophthalmic lens molded shell (30) according to any one of claims 1 to 3, wherein: The edge surface (33) extends around the central axis (A1), and the width (W1) of the first chamfer (36) measured radially relative to the central axis (A1) is equal to 0.08 mm, with a tolerance of plus or minus 0.05 mm.

5. The ophthalmic lens molded shell (30) according to any one of claims 1 to 4, comprising a second chamfer (35) located between the edge face (33) and the other main face (32).

6. The ophthalmic lens molded shell (30) according to claim 5, wherein: The edge surface (33) extends around the central axis (A1), and in each cross-section of the second chamfer (35) taken by a plane passing through the central axis (A1), the second chamfer (35) is inclined at an angle (α2) of 45° relative to the edge surface (33), with a tolerance of plus or minus 5°.

7. An ophthalmic lens molded shell (30) according to any one of claims 5 and 6, wherein: The edge surface (33) extends around the central axis (A1), and the width (W2) of the second chamfer (35) measured radially relative to the central axis (A1) is equal to 0.5 mm, with a tolerance of plus 0.2 mm or minus 0.1 mm.

8. A method of manufacturing an ophthalmic lens molded shell (30), the method comprising the steps of: - machining the blank piece to obtain a semi-finished molded shell (30') having two main faces (31, 32) and an edge face (33) surrounding the main faces (31, 32), a first main face (31) of the main faces being adapted to face another molded shell (20) during the molding of the ophthalmic lens, a preliminary chamfer (39) being located between the edge face (33) and the first main face (31), - polishing the preliminary chamfer (39) and the edge face (33) to produce: a flat facet (34) extending along the outer edge of the first main face (31), and A first chamfer (36) extending between the flat face (34) and the edge face (33) along the outer edge of the flat face (34).

9. The method according to claim 8, wherein: During the polishing step, a material thickness of at least 0.03 mm is removed from the edge face (33) and / or from the preliminary chamfer (39).

10. The method according to any one of claims 8 and 9, wherein: The polishing step comprises a first sub-step, during which the preliminary chamfer (39) is reduced and the flat facet (34) appears, and a second sub-step, during which the first chamfer (36) is completed.

11. The method according to claim 10, wherein: At the end of the first sub-step, the width of the flat face (34) measured radially relative to the central axis (A1) of the edge face (33) is between 0.5 mm and 0.6 mm, and the width of the first chamfer (36) is equal to 0.13 mm, with a tolerance of plus or minus 0.02 mm.

12. The method according to any one of claims 8 to 11, wherein: The edge surface (33) extends around the central axis (A1) and at the end of the machining step, the preliminary chamfer (39): - an angle (α4) of 40 degrees relative to the edge surface (33), with a tolerance of plus or minus 5 degrees, - The width (W4) measured radially relative to said central axis (A1) is 0.8 mm with a tolerance of plus or minus 0.05 mm.

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