U.S. patent application number 11/306230 was filed with the patent office on 2007-06-21 for method and apparatus for the dry release of a compliant opthalmic article from a mold surface.
This patent application is currently assigned to BAUSCH AND LOMB INCORPORATED. Invention is credited to Kevin Beebe, Wen Jin, Mahendra P. Nandu, Sanjay Rastogi, William J. Seyboth, James Vermeire, Raymond Walker.
Application Number | 20070138670 11/306230 |
Document ID | / |
Family ID | 38172531 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070138670 |
Kind Code |
A1 |
Beebe; Kevin ; et
al. |
June 21, 2007 |
Method and Apparatus for the Dry Release of a Compliant Opthalmic
Article from a Mold Surface
Abstract
An apparatus for releasing a molded lens from a deformable mold
includes a shear ring for temporarily retaining an annular portion
of the deformable mold outside a periphery of the lens and a
plunger for deforming an annular section of the deformable mold
within the periphery of the lens. The apparatus can be employed to
release a non-hydrated hydrogel lens from a deformable mold
section.
Inventors: |
Beebe; Kevin; (Spencerport,
NY) ; Seyboth; William J.; (Rochester, NY) ;
Walker; Raymond; (Rochester, NY) ; Rastogi;
Sanjay; (Rochester, NY) ; Nandu; Mahendra P.;
(Pittsford, NY) ; Vermeire; James; (Rochester,
NY) ; Jin; Wen; (Victor, NY) |
Correspondence
Address: |
Bausch & Lomb Incorporated
One Bausch & Lomb Place
Rochester
NY
14604-2701
US
|
Assignee: |
BAUSCH AND LOMB
INCORPORATED
One Bausch and Lomb Place
Rochester
NY
|
Family ID: |
38172531 |
Appl. No.: |
11/306230 |
Filed: |
December 20, 2005 |
Current U.S.
Class: |
264/2.6 ;
264/334; 425/289; 425/808 |
Current CPC
Class: |
Y10S 425/808 20130101;
B29D 11/00221 20130101; B29D 11/00432 20130101 |
Class at
Publication: |
264/002.6 ;
264/334; 425/289; 425/808 |
International
Class: |
B29D 11/00 20060101
B29D011/00 |
Claims
1. A method for releasing an ophthalmic molded lens from a mold
cavity of a deformable mold, the deformable mold having an anterior
molding surface and an opposite curved posterior surface, the
method comprising: a) distorting the anterior molding surface by i)
pressing against the curved posterior surface along a first
annulus; and ii) pressing against the anterior molding surface
along a second annulus comprising a shear ring; b) the first and
second annuli being generally concentric with the molded lens with
the first annulus being within a perimeter of the molded lens and
the second annulus being radially spaced from the perimeter of the
molded lens; and c) the distorting of the molding surface creating
sufficient shear between the molded lens and the molding surface to
effect a peeling of the molded lens from the molding surface.
2. The method of claim 1, wherein the peeling progresses radially
inward from the perimeter of the molded lens.
3. The method of claim 1, wherein pressing against the curved
posterior surface is continuous along the first annulus.
4. The method of claim 1, further comprising forming the first
annulus of a rounded surface.
5. The method of claim 1, wherein pressing against the curved
posterior surface is intermittent along the first annulus.
6. The method of claim 1, wherein pressing against the anterior
molding surface is continuous along the second annulus.
7. The method of claim 1, wherein pressing against the anterior
molding surface is intermittent along the second annulus.
8. The method of claim 1, further comprising forming the shear ring
to include a knife edge.
9. The method of claim 8, further comprising forming the knife edge
from facets intersecting at an acute included angle.
10. The method of claim 8, further comprising forming the knife
edge from facets intersecting at an obtuse included angle.
11. The method of claim 1, further comprising hydrating the molded
lens after peeling of the molded lens from the molding surface.
12. The method of claim 1, further comprising releasing an
ophthalmic molded lens having a hydrated modulus less than 70
gm/mm.sup.2.
13. A method for releasing a compliant hydrogel molded lens from a
concave mold surface of a deformable mold comprising deforming the
mold in a manner that creates a shear force between the concave
surface and the molded lens sufficient to effect the peeling of the
molded lens from the concave mold surface wherein the peeling
starts at an outer periphery of the molded lens and propagates to a
center of the molded lens.
14. The method of claim 13, further comprising hydrating the molded
lens after peeling.
15. The method of claim 13, further comprising releasing the molded
lens from the concave mold surface prior to initially hydrating the
lens.
16. The method of claim 13, further comprising deforming the mold
by fixing a portion of the deformable mold spaced radially beyond a
periphery of the molded lens and deforming the concave mold surface
to peel a portion of the molded lens from the deformable mold.
17. The method of claim 13, further comprising continuously
propagating the peeling from the outer periphery of the molded lens
to the center of the molded lens.
18. A method of releasing a molded ophthalmic lens having a
periphery from a deformable mold section, the deformable mold
section having concave anterior mold surface and a corresponding
curved posterior surface, the method comprising confining a portion
of the deformable mold section radially spaced beyond the periphery
of the molded ophthalmic lens and deforming the deformable mold
inside the periphery of the molded ophthalmic lens to induce
separation of the molded ophthalmic lens from the deformable mold
section.
19. The method of claim 18, further comprising hydrating the molded
ophthalmic lens after separation from the deformable mold
section.
20. The method of claim 18, wherein confining a portion of the
deformable mold section includes contacting an exposed surface of
the portion of the deformable mold section with a shear ring.
21. The method of claim 18, wherein confining the portion of the
deformable mold section includes contacting the exposed surface of
the portion of the deformable mold section with a knife edge.
22. Apparatus for releasing a molded ophthalmic lens from a mold
cavity of a deformable mold having an anterior molding surface and
an opposite curved posterior surface, the apparatus comprising: a)
a plunger having an end face and rounded surface raised from the
end face for pressing against the curved posterior surface in an
annulus smaller in diameter than the lens; and b) a female section
having a recess for receiving the deformable mold, the female
section including a shear ring edge extending into the recess for
pressing against the anterior surface in an annulus greater in
diameter than the lens.
23. The apparatus of claim 22, wherein the molded ophthalmic lens
has a hydrated modulus less than 70 gm/mm.sup.2.
24. The apparatus of claim 22, wherein the shear ring is a knife
edge.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the releasing of a molded
ophthalmic lens from a mold surface and in particular to the dry
release of a lens formed of a compliant material from a mold.
DESCRIPTION OF RELATED ART
[0002] The molding of contact lenses is known in the art and
reference in this regard is made to U.S. Pat. No. 5,466,147 the
disclosure of which is incorporated by reference. Briefly stated, a
contact lens generally is formed in a single use mold unit
comprising a female mold section having a concave optical surface
and a male mold section having a convex optical surface. The male
and female mold sections are formed of a single use deformable
material and are complementary shaped. The mold sections are
brought together to form a lens-molding cavity between the facing
convex and concave mold surfaces.
[0003] To form the lens, a quantity of lens forming material first
is dispensed into the concave optical surface of the female mold
section. In the context of the present invention the lens forming
material is a mixture for producing a silicone-containing hydrogel
lens. An appropriate mixture for making a silicone hydrogel lens is
known in the art and reference is made to U.S. Pat. No. 5,260,000
the disclosure of which is incorporated herein by reference for a
description of the process.
[0004] Briefly, and as disclosed in U.S. Pat. No. 5,269,000, the
process involves preparing a monomeric mixture comprising a
silicone-containing monomer, a hydrophilic monomer and an organic
diluent. This mixture is charged into the mold and then the male
mold section is seated upon the female mold section such that a
lens forming mold cavity is formed therebetween. The joined male
and female mold sections form a single mold unit that under goes a
curing cycle to polymerize the lens material in the mold cavity.
Once the lens material is cured, the mold sections are separated to
retrieve the cured lens.
[0005] Upon mold separation the cured lens generally adheres to the
concave optical surface of the female mold section. The problem
then is to effect the release of the cured lens from the female
mold section without damaging the lens. In most cases a dry release
of the cured lens can be accomplished by a method as disclosed US
Publication No. 2004/0061246.
[0006] In this respect the method as disclosed in US Publication
No. 2004/0061246 uses an plunger that that has an annular ridge on
an end surface. This annular ridge has a flat end face, which is
pressed against the anterior surface of the female mold section.
Since the anterior surface of the female mold section is curved
(convex) the flat end face of the raised ridge has a relatively
sharp edge that first contacts the curved anterior surface of the
female mold section. The force exerted by the plunger against the
anterior surface of the female mold section is concentrated by this
shape edge at a location radially outward of the center of this
surface. In most cases this application of force will sufficiently
deform the mold section so that the entire lens will release from
the mold. If the lens continues to adhere to the mold a second
force applied by the flat face of an axial plunger to the center of
the non-optical surface will result in the release of the lens.
[0007] However, in the case of a silicone hydrogel lens, this has
been found not to be the case in that the application of forces as
noted above will not cause the lens to release form the mold. The
problem presented by a silicone hydrogel lens is that it is
relatively compliant. For example, when fully hydrated, the lens
may have a modulus of 70 gm/mm.sup.2 or less. While the cured lens
still attached to the female mold section is not hydrated, even in
its dry state the cured lens still is so compliant that the lens
lacks sufficient rigidity to peel or release from the mold as the
shape of the mold is distorted first by the flat face of the
annular plunger and then by the axial plunger. Instead the silicone
hydrogel lens contorts so as to conform along with the mold surface
and remains adhered to the optical surface of the mold section even
after the mold is distorted.
[0008] Accordingly, an object of the present invention is to
provide an improved method and apparatus for releasing a compliant
ophthalmic article from a concave mold surface.
[0009] Another object of the present invention to provide a method
and apparatus for releasing a mold compliant ophthalmic article
such as a dry silicone hydrogel lens or the like from a concave
optical mold surface.
[0010] A further object is to effect the release of a mold
compliant ophthalmic article such as a silicone hydrogel contact
lens or the like from a concave mold surface by causing a
continuous peeling separation of the article from the mold surface.
An additional object includes releasing a non-hydrated molded
ophthalmic lens from a mold by peeling the lens from the mold from
a radially spaced location to a central or axial location.
[0011] Yet another object is to effect the peeling separation of a
compliant silicone hydrogel contact lens from a concave mold
surface wherein the peeling starts at the outer edge of the lens
and progresses radially towards the lens center.
BRIEF SUMMARY OF THE INVENTION
[0012] In the present invention, molded contact lens, preferably a
compliant lens such as a silicone hydrogel contact lens, is
released from the surface of a female mold section, while the lens
remains in a dry state. By a dry state, it is meant the lens is not
yet hydrated after formation of the lens. The female mold section
has an anterior surface that includes a concave optical surface
portion or mold cavity from which the molded lens must be released
and a posterior surface.
[0013] The release of the molded lens is accomplished by locating a
circular shear ring against the anterior surface of the mold at a
location radially spaced from and surrounding the optical surface
portion of the mold cavity. A plunger, having a raised annular lip
on an end surface then is pressed against the posterior surface of
the mold so the mold is pressed between the shear ring and the
plunger lip. The outside diameter of the raised lip is just less
than the diameter of the circular shear ring so the plunger exerts
a force on the anterior surface of the mold along an annulus that
has a slightly smaller diameter than the diameter of the shear
ring.
[0014] The edge of the shear ring pressed against the anterior
surface of the mold approximates a knife edge. In contrast, the
surface of the raised lip of the plunger that contacts and presses
against the posterior surface of the mold is rounded. As the shear
ring and plunger move one towards the other and as each press
against the mold, the portion of the mold immediately above the
raised lip begins to bulge upwardly. The shear ring prevents the
bulge from propagating radially outward so the mold begins to roll
radially inward over the rounded surface of the lip. This creates
mechanical shear between the lens and the surface of the mold
cavity sufficient to cause the compliant lens to peel and release
from the mold surface. The peeling action begins at the periphery
of the lens and as the plunger continues to press into the mold and
the mold material rolls over the rounded surface, there is a
continuous propagation of the peeling that progresses radially
inward from the outer edge (periphery) of the lens to its
center.
[0015] In another embodiment, the raised lip and its rounded
surface are replaced with a plurality of axially extending pins
arranged about the longitudinal axis of the plunger. The operative
end of each pin is rounded and in one alternative embodiment the
pins are mounted for rotation about the longitudinal axis of the
plunger so that in effect, a surface of revolution is created
comparable to the rounded surface of the raised lip as described
above. The net result is a comparable application of force causing
the lens to peel from the mold with the peeling beginning at the
periphery of the lens and propagating radially inward to the center
of the lens. Thus, the peeling, or line of separation, initiates at
a perimeter of the molded lens and propagates radially inward.
[0016] In a still further embodiment the pins are mounted for axial
movement. In this case the axial movement of the pins either with
or with out rotation about the longitudinal axis of the plunger
generates the force for peeling the lens from the mold.
[0017] After the lens is released from the mold, the lens is
removed and transported to a separate workstation for further
operations. In a preferred embodiment a suction cup is employed to
grab the lens and remove it from the mold. In particular the
suction cup has a flared, generally conical wall formed of a
compliant material. As the suction cup picks up the lens, the
compliant nature of the suction cup wall allows the suction cup to
conform to the lens shape so there is a greater surface area of
contact between the suction cup and the lens. The resulting
increase in surface tension between the two acts to hold the lens
to the suction cup with minimal differential pressure.
[0018] Accordingly, the present invention may be characterized in
one aspect thereof releasing a molded compliant hydrogel lens from
a concave mold surface of a deformable mold by deforming the mold
in a manner that creates a shear force between the concave mold
surface and the molded lens to effect the peeling of the lens from
the mold surface, wherein the peeling starts at the outer periphery
of the lens and progresses radially inwardly along the lens
surface.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0019] FIG. 1 is a schematic exploded view of a representative mold
assembly for forming a silicone hydrogel lens or other ophthalmic
article;
[0020] FIG. 2 is a cross-sectional view of the mold assembly in a
nested position;
[0021] FIG. 3 is a schematic view of an anterior section of the
mold assembly showing the molded lens in the mold cavity;
[0022] FIG. 4 is a cross-sectional view of the release apparatus
prior to the capturing of the anterior mold section;
[0023] FIG. 5 is a view similar to FIG. 4 only showing the
apparatus after the lens has been released form the mold
cavity;
[0024] FIGS. 6-8 are views on an enlarged scale showing a portion
showing a portion of the apparatus at various stages in the process
for separating the molded lens from the mold cavity;
[0025] FIG. 9 is a perspective view showing another arrangement for
effecting the release of the lens form the mold surface; and
[0026] FIGS. 10 and 11 show an arrangement for plucking a molded
lens from the mold after the molded lens is released from the mold
surface.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Referring to the drawings, FIGS. 1 and 2 show a mold
assembly 10 as may be used to make a silicone hydrogel contact lens
or the like. The mold assembly 10 includes an anterior mold section
12 and a posterior mold section 14. The mold sections 12, 14 are
individually made from a plastic resin by injection molding; at
least the anterior mold section 12 is deformable.
[0028] The anterior mold section 12 includes a mold cavity 16
including a concave optical surface 18 that forms the convex
anterior surface 20 of a molded lens 22. The anterior mold section
12 further includes a generally convex, non-optical surface 24
(FIG. 2), a land 19 that surrounds the mold cavity 16 and an
annular wall 26 that extends generally perpendicular from about the
periphery of the land.
[0029] The posterior mold section 14 includes a convex optical
surface 28 (best seen in FIG. 2) that forms the concave posterior
surface 30 of the molded lens. The posterior mold section 14 has a
concave non-optical surface 32 located opposite the convex optical
surface 28 and an annular wall 33 that defines the outer periphery
of the posterior mold section.
[0030] In an assembled position as shown in FIG. 2 the mold
sections 12, 14 nest together with the anterior section 12 being
disposed within the posterior section 14. In this position, a mold
cavity is formed between the optical surfaces 18, 28 that receives
and molds a curable material for making the molded lens 22.
[0031] To form a molded lens, a curable liquid is cast into the
mold cavity 16 in the anterior mold section 12. Then the anterior
and posterior mold sections 12, 14 are nested as shown in FIG. 2 so
the liquid conforms to the shape of the mold cavity formed between
the mold sections. After a time sufficient to allow the liquid to
polymerize, the mold sections 12, 14 are separated leaving the
molded lens 22 in the mold cavity 16 of the anterior mold section
12 as shown in FIG. 3.
[0032] Separation of the mold sections 12, 14 leaves the molded
lens 22 adhered to the optical surface 18 of the anterior mold
section 12. The problem now is to effect the separation of the lens
22 from the optical mold surface 18 without doing damage to the
lens.
[0033] One prior art method for separating the lens from the mold
is disclosed in US Publication No. US 2004/0061246. As described in
this publication, the lens is released from the mold surface by
applying a force to the generally convex, non-optical surface of
the anterior mold section. This distorts the optical surface
opposite the non-optical surface so as to effect a separation of
the lens from the mold surface.
[0034] While this prior art method is effective for most types of
molded contact lenses, it is not effective in cases where the
molded lens is highly compliant. As noted above, a highly compliant
lens tends to deform with the optical surface of the mold so there
is no relative shear developed between the lens and the optical
surface sufficient to effect the separation of the lens.
Accordingly, the method as disclosed in US 2004/0061246 is
ineffective for separating a compliant lens and in particular a
silicone hydrogel lens, from the anterior mold section.
[0035] In accordance with the present invention, FIG. 4 shows that
the lens release apparatus includes a female section 34 having a
circular recess 36 configured to receive therein the anterior mold
section 12 with the attached molded lens 22. The female section 34
includes an annular shear ring, such as knife edge 38 that extends
into the recess 36. The diameter of the shear ring, such as knife
edge 38, is slightly greater than the diameter of the mold cavity
16 for purposes set out hereinbelow. It is contemplated the shear
ring 38 can be formed by an acute or obtuse transition between two
faces or facets. Therefore, while the knife edge 38 configuration
of the shear ring is shown with an acute included angle, the knife
edge can be defined by an included angle greater than an acute
angle. It is further contemplated that the shear ring 38 can
include a radius, however it is believed advantageous to employ a
relatively abrupt edge, such as the knife edge, and particularly
along the radially inner face of the shear ring. That is, beyond
the radially innermost contact between the shear ring 38 and the
upper surface of the anterior mold section 12, the contact
configuration is not believed to be critical.
[0036] The release apparatus also includes male section comprising
an axially movable plunger 40. The longitudinal axis of the plunger
40 is aligned with the axis of the female section 34 so the plunger
can move axially into the circular recess 36. Located on an end
face of the plunger 40 is an annular raised lip 42. The raised lip
42 has a radial cross section defined by a rounded surface 44 and
the diameter of the annular raised lip is less than the diameter of
the shear ring or knife edge 38 so the entire lip lies within the
annulus of the knife edge. It is understood an interchangeable
center pin may be utilized for increased robustness and versatility
of dry release with different mold/monomer families.
[0037] The outside diameter of the plunger 40 is slightly smaller
than the inside diameter of the anterior mold section 12. This
allows the plunger 40 to receive the anterior mold section 12 over
the end face of the plunger so the raised lip 42 rests against the
convex posterior surface 24 of the mold section 12 in a position
that is generally concentric with the molded lens 22. When the mold
section 12 is positioned over the end of the plunger 40, the
plunger is moved axially to introduce the anterior mold section 12
into the circular recess 36 of the female section 34. The plunger
40 continues to push the anterior mold section 12 into the recess
36 until the annular knife edge 38 presses against the land 19 in a
position that is generally concentric with the molded lens 22.
[0038] When the anterior mold section 12 is firmly seated within
the recess 36 and against the shear ring 38 any further travel of
the plunger 40 towards the knife edge acts to distort the anterior
mold section 12 so as to effect the separation of the molded lens
22 from the optical surface 18 of the mold section as shown in FIG.
5. In this respect FIGS. 6-8 show in schematic fashion the sequence
whereby the molded lens 22 separates from the optical surface 18 of
the mold section 12.
[0039] FIG. 6 shows the rounded surface 44 of the annular raised
lip 42 as the lip starts to press against the convex, non-optical
surface 24 of the anterior mold section 12 and to move the land 19
of the mold section against the annular knife edge configuration of
the shear ring 38. As the plunger 40 continues to move, the rounded
surface 44 begins to press into the non-optical surface 24 and
causes the mold section 12 to distort an annulus that is just
radially inward of the outer edge or periphery of the lens 22 as
shown in FIG. 7.
[0040] The knife edge 38 likewise presses into the land 19 along an
annulus that is just radially outward of the outer edge or
periphery of the lens 22. The two members pressing against opposite
sides of the anterior mold section 12 and the resulting distortion
of the mold cavity produces shear between the optical surface 18 of
the mold cavity and the convex surface 20 of the molded lens 22
sufficient to effect a separation of the outer edge of the lens
from the optical surface as shown at 46 in FIG. 7.
[0041] FIG. 8 shows that as the plunger 40 continues to move, the
plunger causes the mold cavity to bulge upwardly. The shear ring as
a knife edge 38 pressing against the land 19 prevents the bulge
from propagating outwardly in a radial direction so the bulge is
confined to the annulus defined by the knife edge. Accordingly, as
the plunger 40 continues to move, the non-optical surface 28 rolls
over up and over the raised lip 42. The rounded surface 44 of the
raised lip 42 facilitates this rolling action. The result is that
the shear created between the optical surface 18 and the convex
surface 20 of the molded lens 22 continuously progresses inward
from the outer edge of the lens so the separation 46 that begins at
the outer periphery of the molded lens propagates inwardly so the
convex lens 20 peels from the optical surface 18. The anterior mold
section 12 takes a permanent set when distorted allowing the easy
removal of the molded lens 22 from the mold.
[0042] The rounded surface 44 of the raised lip 42 is important for
the development of a shear force sufficient to effect the
separation of the lens 22 from the mold cavity (mold section 12)
and for the correct propagation of the shear force. In this respect
the rounded surface of the raised lip 42 allows the mold material,
such as lens 22, to roll up and over the raised lip so there is a
smooth continuous propagation of the shear force radially inward
from the outer edge of the molded lens.
[0043] The shear ring 38 can contact the anterior mold 12 outside
the periphery of the molded lens 22, either along the convex
portion of the anterior mold as seen in FIG. 5, or along the land
area 19 of the anterior mold, as shown in FIGS. 6-8. The critical
aspects include the contact of the shear ring 38 with the anterior
mold 12 radially outward of the periphery of the molded lens 22 and
contact of the raised lip 42 radially inward of the shear ring.
[0044] As described hereinabove, the raised lip 42 and rounded
surface is a continuous member that presents an unbroken surface
(the rounded surface 44) for pressing against the convex,
non-optical surface 24 of the anterior mold section 12. In the
embodiment as shown in FIG. 9, the plunger 24' includes an outer
shell 48 and a rotatable core 50. The end face of the core 50 has a
plurality of rounded projections 52. When the core 50 is rotated
about the longitudinal axis of the plunger 24', a surface of
revolution is created that approximates the continuous rounded
surface 44 of the raised lip 42. Accordingly, advancing the
rotating plunger core 50 against the convex, non-optical surface 28
of the anterior mold section 12 mimics the action of the raised lip
42. In addition the rotation of the rounded projections against the
convex, non-optical surface of the mold section "ripples" the mold
cavity so peeling occurs at multiple points about the perimeter of
the molded lens 22. The rippling adds another component of force
that aids in the separation of the molded lens 22 from the optical
surface of the mold.
[0045] After the molded lens 22 is separated from the optical
surface of the mold section 12, a picker can be used to pluck the
lens from the mold. In this respect, FIG. 10 shows a picker 54
including a generally conical suction cup 56. A line 58 that
includes a flexible portion connects the suction cup to a suction
pump (not shown).
[0046] In operation, the picker 54 moves over the anterior mold
section 12. As noted above the mold section 12 takes a permanent
set after distortion by the plunger 40 and the shear ring 38 so the
molded lens 22, now separated from the concave optical surface,
sits in the distorted cavity 16 of the anterior mold section 12.
The picker 54 is moved over the mold section 12 as shown in FIG. 10
and is lowered close to or against the mold section over the molded
lens 22.
[0047] When suction is applied, the lens 22 is picked from the
mold. Both the suction cup 56 and the molded lens 22 are compliant
so the lens inverts as shown in FIG. 11 and the two members
generally conform one to the other. This conformity increases the
surface area of contact between the suction cup 56 and the molded
lens 22 so a surface tension is created between the conical
interior surface 60 of the picker 54 and the molded lens. This
surface tension allows the lens 22 to remain captured by the picker
even if suction is stopped so there is less likelihood of damage to
the lens during the removal. After removal from the mold, the lens
22 either is manually removed from the picker 54 or an air pulse
applied through the line 58 to expel the molded lens.
[0048] It is also understood the either or both of the lip 42 and
the knife edge 38 can be continuous or substantially continuous
surface. That is, one or both of the lip 42 and the shear ring such
as knife edge 38 can have a discontinuity and still effect peeling
of the lens 22 from the mold surface 18.
[0049] Accordingly, having the described the invention in detail it
should be appreciated that the present invention accomplishes its
intended objects in providing an improved method and apparatus for
releasing a compliant ophthalmic article from a concave mold
surface and in particular a method and apparatus for releasing a
molded compliant ophthalmic article such as a silicone hydrogel
lens or the like from a concave optical mold surface.
[0050] The method and apparatus of the present invention provides
for the release of a molded compliant ophthalmic article such as a
silicone hydrogel contact lens or the like from a concave mold
surface by causing a peeling separation of the article from the
mold surface, wherein the peeling separation starts at the outer
edge of the lens and progresses radially towards the lens
center.
[0051] Although the invention has been described with respect to
certain exemplary embodiments, other modifications will be readily
apparent to skilled practitioners of this art in accordance with
the overall teaching of this invention. For example, although the
invention is primarily directed to improvements in contact lenses,
other ophthalmic biomedical optics could also benefit from the
invention.
* * * * *