U.S. patent application number 10/117545 was filed with the patent office on 2002-12-12 for ir-emitter heating device and method for demolding lenses.
Invention is credited to Bingaman, Thomas P., Darabi, H. Anthony, Hood, Charles R., Kernick, Edward R., Kimble, Allan W., Pegram, Stephen C., Ricard, Joseph W., Voss, Leslie A..
Application Number | 20020185763 10/117545 |
Document ID | / |
Family ID | 25250660 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020185763 |
Kind Code |
A1 |
Pegram, Stephen C. ; et
al. |
December 12, 2002 |
Ir-emitter heating device and method for demolding lenses
Abstract
A method and a device for removing molded soft contact lenses,
high-precision intraocular lenses and the like, from the individual
molds in which they are produced. Provided is an infra-red
radiation or heater device preferably constituted of silicon
carbide IR-emitters, and which employs an individual infra-red
emitter for each individual mold, to impart a desired thermal
gradient. Also provided are infra-red emitters having improved
reflectors.
Inventors: |
Pegram, Stephen C.;
(Jacksonville, FL) ; Kimble, Allan W.;
(Jacksonville, FL) ; Voss, Leslie A.;
(Jacksonville, FL) ; Bingaman, Thomas P.; (Ponte
Vedra Beach, FL) ; Ricard, Joseph W.; (Jacksonville,
FL) ; Kernick, Edward R.; (Jacksonville, FL) ;
Hood, Charles R.; (Jacksonville, FL) ; Darabi, H.
Anthony; (Ponte Vedra Beach, FL) |
Correspondence
Address: |
AUDLEY A. CIAMPORCERO JR.
JOHNSON & JOHNSON
ONE JOHNSON & JOHNSON PLAZA
NEW BRUNSWICK
NJ
08933-7003
US
|
Family ID: |
25250660 |
Appl. No.: |
10/117545 |
Filed: |
April 5, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10117545 |
Apr 5, 2002 |
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09827995 |
Apr 6, 2001 |
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Current U.S.
Class: |
264/2.3 ;
264/334; 264/402; 425/174.4; 425/436RM; 425/808 |
Current CPC
Class: |
B29K 2105/0002 20130101;
Y10S 425/808 20130101; B29C 43/50 20130101; B29C 37/0003 20130101;
B29C 43/021 20130101; B29D 11/00221 20130101; B29L 2011/0016
20130101; B29L 2011/0041 20130101; B29D 11/00211 20130101; B29C
2035/0822 20130101 |
Class at
Publication: |
264/2.3 ;
264/402; 264/334; 425/808; 425/174.4; 425/436.0RM |
International
Class: |
B29D 011/00 |
Claims
What is claimed is:
1. An apparatus for demolding a lens formed between front and back
mold halves, said apparatus comprising: means for directing a
predetermined amount of infra-red energy at one of said mold halves
to thereby provide a controlled thermal gradient between said mold
halves.
2. An apparatus as claimed in claim 1, wherein each said infra-red
energy means comprises a silicon carbide (SiC) IR-emitter.
3. An apparatus as claimed in claim 2, wherein each said silicon
carbide IR-emitters is arranged within a cylindrical sleeve, and a
cooling housing collectively encompasses said cylindrical sleeves
to inhibit excessive heating of said silicon carbide
IR-emitters.
4. An apparatus as claimed in claim 3, wherein reflector means are
arranged in each said sleeve extending about head portions of said
silicon carbide IR-emitters so as to direct the infra-red energy
towards the back curve mold halves for controlled heating
thereof.
5. An apparatus as claimed in claim 4, wherein said reflector means
comprises a mirror-like reflecting surface for directing said
infra-red energy.
6. An apparatus as claimed in claim 5, wherein said reflecting
surface possesses a frusto-conical configuration.
7. An apparatus as claimed in claim 5, wherein said reflecting
surface forms a parabolic reflector.
8. An apparatus as claimed in claim 2, wherein each said silicon
carbide IR-emitter is connected to a source of electrical current
to facilitate varying the heat being conveyed to each respective
therewith associated back curve mold half so as to impart the
required thermal gradient to each said respective back curve mold
half.
9. An apparatus as claimed in claim 2, wherein means for sensing
the temperatures at each back curve mold half form a feedback of
each said temperatures to a preheater for preheating said back
curve mold halves to a predetermined temperature prior to said
silicon carbide IR-emitter imparting said thermal gradients to each
of said back curve mold halves.
10. An apparatus as claimed in claim 9, wherein said curve mold
halves are each preheated to a temperature of between about
57-65.degree. C. prior to being subjected to infra-red energy from
said silicon carbide IR-emitter.
11. An apparatus as claimed in claim 9, wherein said temperature
feedback measures voltage and current for each said silicon carbide
IR-emitters, and regulates the voltage and current to provide the
required thermal gradient for each said back curve mold half.
12. An apparatus as claimed in claim 11, wherein said voltage and
current is regulated by a PID controller.
13. An apparatus as claimed in claim 1, further comprising means
for separating each of said associated front and back curve mold
halves subsequent to the application of the thermal gradient
thereto by said infra-red energy means.
14. A method of demolding a lens formed between corresponding front
and back curve mold halves, said method comprising: separately
having a source directing predetermined amounts of infra-red energy
at one of said mold halves to thereby provide a controlled thermal
gradient between said mold halves.
15. A method as claimed in claim 14, wherein said infra-red energy
is provided by silicon carbide (SiC) IR-emitters.
16. A method as claimed in claim 15, wherein each of said silicon
carbide IR-emitters is arranged within a cylindrical sleeve, and a
cooling housing collectively encompasses said cylindrical sleeves
to inhibit excessive heating of said silicon carbide
IR-emitters.
17. A method as claimed in claim 16, wherein reflector means are
arranged in each said sleeve extending about head portions of said
silicon carbide IR-emitters so as to direct the infra-red energy
towards the back curve mold halves for controlled heating
thereof.
18. A method as claimed in claim 17, wherein said reflector means
comprises a mirror-like reflecting surface for directing said
infra-red energy.
19. A method as claimed in claim 18, wherein said reflecting
surface possesses a frusto-conical configuration.
20. A method as claimed in claim 18, wherein said reflecting
surface forms a parabolic reflector.
21. A method as claimed in claim 15, wherein each said silicon
carbide IR-emitter is connected to a source of electrical current
to facilitate varying the heat being conveyed to each respective
therewith associated back curve mold half so as to impart the
required thermal gradient to each said respective back curve mold
half.
22. A method as claimed in claim 15, wherein sensing the
temperatures at each back curve mold half provides a feedback of
each said temperatures to a preheater for preheating said back
curve mold halves to a predetermined temperature prior to said
silicon carbide IR-emitter imparting said thermal gradients to each
of said back curve mold halves.
23. A method as claimed in claim 22, wherein said curve mold halves
are each preheated to a temperature of between about 57-65.degree.
C. prior to being subjected to infra-red energy from said silicon
carbide IR-emitter.
24. A method as claimed in claim 22, wherein said temperature
feedback measures voltage and current for each said silicon carbide
IR-emitters, and regulates the voltage and current to provide the
required thermal gradient for each said back curve mold half.
25. A method as claimed in claim 24, wherein said voltage and
current is regulated by a PID controller.
26. A method as claimed in claim 14, further comprising
mechanically separating each of said associated front and back
curve mold halves subsequent to the application of the thermal
gradient thereto by said infra-red energy means.
27. An apparatus for demolding a plurality of lenses formed between
corresponding front and back mold halves, said apparatus
comprising: a plurality of means each directing a predetermined
amount of infra-red energy at a respective associated one of said
mold halves to thereby provide a controlled thermal gradient
between said mold halves.
28. An apparatus for demolding a plurality of contact lenses formed
between corresponding front and back curve mold halves which are
positioned in a regular array on a pallet, after formation and
curing of said lenses, each of said mold halves having an arcuate
central portion and an annular flange portion, said apparatus
comprising: a plurality of means each directing a predetermined
amount of infra-red energy at a respective associated one of said
back mold halves to thereby provide a controlled thermal gradient
between each of said back mold halves and the therewith associated
infra-red energy means.
29. A method of demolding a plurality of contact lenses formed
between corresponding front and back curve mold halves which are
positioned in a regular array on a pallet, after formation and
curing of said lenses, each of said mold halves having an arcuate
central portion and an annular flange portion, said method
comprising: separately having sources directing predetermined
amounts of infra-red energy at a respective associated one of said
back mold halves to thereby provide a controlled thermal gradient
between each of said back mold halves and the therewith associated
infra-red energy.
30. An apparatus for demolding a lens formed within a mold
assembly, said apparatus comprising: an infra-red emitter and a
reflector, wherein said reflector reflects radiation at said mold
assembly.
31. The apparatus of claim 30 wherein said reflector comprises an
upper portion having a conical, circular elliptical or circular
parabolic shape.
32. The apparatus of claim 31 wherein said reflector further
comprises a second portion connected to said first portion wherein
said second portion has a conical shape.
33. The apparatus of claim 32, wherein said reflector further
comprises a nozzle connected to said second portion.
34. The apparatus of claim 31 wherein said reflector further
comprises a nozzle connected to said first portion.
35. An apparatus for demolding a lens formed within a mold
assembly, said apparatus comprising: an infra-red emitter and a
reflector, wherein said reflector comprises a reflector having a
surface roughness less than 0.3 micrometers RMS.
36. The apparatus of claim 35 wherein said surface roughness is
less than 0.2 micrometers RMS.
37. The apparatus of claim 35 wherein said surface roughness is
less than 0.1 micrometers RMS.
38. An apparatus for demolding a lens formed within a mold
assembly, said apparatus comprising: an infra-red emitter and a
reflector, wherein said reflector comprises a gold coating of
between from 1.3 to 2.9 micrometers.
39. The apparatus of claim 38 wherein said reflector further
comprises a primer layer between from 7 to 25 micrometers thick.
Description
[0001] This is a continuation-in-part application of U.S. Ser. No.
09/827,995 filed Apr. 6, 2001 titled Silicon Carbide IR-Emitter
Heating Device and Method for Demolding Lenses, which is entirely
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the invention
[0003] The present invention relates generally to the production of
ophthalmic lenses, and, in particular pertains to a method and a
device for removing molded soft contact lenses, high-precision
intraocular lenses and the like, from the individual molds in which
they are produced.
[0004] 2. Discussion of the Prior Art
[0005] In view of the intense growth of the ophthalmic contact lens
industry, it has become desirable and even necessary to be able to
supply contact lenses which are periodically and frequently
replaced in order to minimize the possibility of user induced
contamination. This has created an opportunity for manufacturers to
strive for automated methods and apparatuses that are able to
automatically produce high quality ophthalmic lenses in a
cost-effective and highly efficient manner.
[0006] It is currently the practice in the manufacturing technology
for ophthalmic lenses, such as soft contact lenses of the hydrogel
type, to form a monomer or monomer mixture that may be polymerized
in a plastic mold. Details of typical direct mold processes for
forming soft hydrogel contact lenses are described in U.S. Pat.
Nos. 5,080,839, 5,039,459, 4,889,664, and 4,495,313. The process
for forming soft contact lenses as generally described in the
above-mentioned patents includes the steps of dissolving a monomer
mixture in a non-aqueous, water-displaceable solvent and placing
the monomer/solvent mixture in a mold having the shape of the final
desired hydrogel lens. Thereafter, the monomer/solvent mixture is
subjected to conditions whereby the monomer(s) polymerize, to
thereby produce a polymer/solvent mixture in the shape of the final
desired hydrogel lens. After the polymerization is complete, the
solvent is displaced with water to produce a hydrated lens whose
final size and shape are similar to the shape of the original
molded polymer/solvent article.
[0007] Examples of typical plastic molds used for carrying the
polymerizable feed material are disclosed in U.S. Pat. Nos.
5,094,609, 4,565,348 and 4,640,489. The mold disclosed in U.S. Pat.
No. 4,640,489 is a two-piece mold with a female mold portion having
a generally concave lens surface, and a male mold portion having a
generally convex lens surface, both mold portions preferably made
of a thermoplastic material such as polystyrene. As discussed in
U.S. Pat. No. 4,640,489, polystyrene and copolymers thereof are
preferred mold materials because they do not crystallize during
cooling from the melt, and exhibit little or no shrinkage when
subject to the processing conditions required during the direct
molding process discussed above. Alternatively, it is also possible
to employ molds made of polypropylene or polyethylene, such as
described in U.S. Pat. No. 4,121,896.
[0008] During the molding process, the monomer and monomer mixture
is supplied in excess to the female concave mold portion prior to
the mating of the molds. After the mold portions are placed
together, defining the lens and forming a lens edge, the excess
monomer or monomer mixture is expelled from the mold cavity and
rests on or between flanges that surround one or both mold
portions. Upon polymerization this excess material forms an annular
(HEMA) ring around the formed lens between the flange portions of
the molds.
[0009] As discussed in the above-mentioned U.S. Pat. Nos.
5,039,459, 4,889,664, and 4,565,348, there is the requirement that
the materials, chemistry, and processes be controlled so that the
mold portions may be separated without having to apply an undue
force, which may be necessary when the lens sticks to one or more
of the lens mold or when the lens mold portions are adhered to each
other by the excess HEMA ring after polymerization.
[0010] The prior art process for separating the mold portions and
removing the lens therefrom consists of a heating stage, a mold
half separation stage, and a lens removal stage. The heating stage
of the prior art lens removal process is to apply heated air to the
back mold portion thereby causing a differential expansion between
the heated mold polymer and the cooler lens polymer. This
differential expansion provides a shearing impetus which weakens
the adhesion forces between the mold surface and the lens formed
thereon. The mold half separation stage, which follows the heating
stage is characterized by removal of the previously heated mold
half. With respect to prior art systems for removing the back curve
mold halves, inefficient means and damaging forces associated
therewith have rendered such devices less desirable for producing
high quality lenses, inasmuch as the steps of heating and
separation that break the polymerized lens/polymer mold adhesion
and provide access to the nearly formed lens occasionally damage
the lens, and thereby decreasing the yield rate of the process.
[0011] With respect to the temperature gradient between the mold
halves and the lens, the larger the thermal gradient, the more
reduced will be the residual adhesion forces present between the
lens and the mold halves, and correspondingly, the more reduced
will be the force required to separate the mold portions.
Conversely, the lower the thermal gradients created between the
mold halves and the lens, the greater will be the required force to
separate the mold portions. The greater the forces which may be
required in separating the mold from the lens, the greater becomes
the possibility of fracturing a mold portion and/or damaging the
lens. Furthermore, it is to be understood that a process in which a
thermal gradient must be applied on a repeated basis must be such
whereby the environment does not heat appreciably, therein reducing
the effectiveness of the process.
[0012] With respect to the separation of the mold halves, and
thereby, the separation of the top mold half from the lens, it is
understood that devices must be employed which do not damage, or
apply undue stress on the contact lenses. When front and back curve
mold parts, which are designed to form an integral frame such as
are illustrated in U.S. Pat. No. 4,640,489, are placed together to
form a lens shaped volume therebetween, the resultant combined
structure provides limited accessible space for a separating means
to engage and displace one mold from the other. Even minimal
warpage of either mold half can adversely affect both accessibility
to the space as well as the accuracy of the displacing forces. The
same requirements apply to the removal of the lens from the mold
section in which it remains after separation.
[0013] Presently, as widely employed in the technology and as
described in European Patent 0 775 571 A2 "Infra-red Heat Source
for Demolding Contact Lenses" which is commonly assigned to the
assignee of the present application, in order to assist in the
demolding of the lens from the mold section there is employed
infra-red heat source providing a thermal gradient wherein the
infra-red energy is directed against the back curve of the mold
through the intermediary of reflective tubes or buffers. In that
instance, the structure as described that publication employs
quartz or sapphire windows on the infra-red heater which filters
out some of the infra-red radiation. This necessitates a longer
period of heating and consequently lengthier demold times are
required for demolding the lenses. Furthermore, pursuant to the
foregoing construction, the infra-red heater employs one heater for
multiple molds, in effect one heater for four molds, which in
essence does not take into consideration potential variations in
heat distribution among the various molds due to the presence of
only a single infra-red heat output across the current sources for
a plurality of molds.
[0014] Pursuant to another embodiment of the prior art, the thermal
gradient which assists in the demolding of the lenses comprises the
employment of a plurality of steam injection tubes each of which
directs a jet of steam onto the concave surfaces of a back curve
section. Pursuant to further variation described in the European
patent publication, the thermal gradient is provided by a laser
wherein a selected amount of concentrated, coherent light energy is
directed at the back curve mold section, with the absorption
thereof by the back curve providing the necessary thermal
gradient.
[0015] In general, the process of providing the necessary thermal
gradient, as indicated with the use of quartz or sapphire windows
on the infra-red heater, filters out a portion of the infra-red
radiation, and requires lengthier demolding times. In effect, the
quartz glass surrounding the infra-red heating element is subject
to breakage and causes an efficacy problem. Consequently, in order
to protect the product from this problem, an additional hard
protective window was required, in the nature of a sapphire
protective window. However, the combination of the quartz element
tube employed in the prior art and the sapphire protective window
effectively attenuates the infra-red energy associated with these
materials, thereby reducing the available output of the heat source
and limiting the use of longer wavelength infra-red energy to
excite the lens molds in order to derive the desired temperature
gradients.
SUMMARY OF THE INVENTION
[0016] Accordingly, in order to further improve on the foregoing
infra-red heat, or steam and laser devices employed to provide the
necessary thermal gradient which assists in the demolding of the
lenses, pursuant to the invention there is contemplated the
provision of a novel infrared radiation or heater device
constituted of resistance IR-emitters, preferably silicon carbide
IR-emitters, and which employs an individual infra-red emitter for
each individual mold, as opposed to the foregoing prior art
construction which employ one infra-red heater for multiple molds.
Resistance IR-emitters are IR-emitters that convert electrical
energy to radiation via the resistance of the material through
which the electricity flows. Such IR-emitters comprise ceramic
materials and wires, such as, silicon carbide materials, silicone
nitrate materials, electrofused magnesium oxide, inconel, nickel
chrome and ferro chrome, incoloy, and other nickel and chrome
alloys as the resistance or emittance material and the like.
[0017] The foregoing improvement also enables the use of an
unfiltered infra-red emitter heating device whereby it is possible
to achieve precise control over the heating temperature for each
individual mold rather than for conjointly a plurality of
molds.
[0018] The elimination of the quartz and/or sapphire window on the
infra-red heater which is utilized in the prior art also eliminates
the filtering out of portions of the infra-red radiation, thereby
providing a greater degree of efficiency by reducing the time of
demolding required due to a greater portion of the generated
infra-red radiation being received by the molds. Pursuant to the
present invention, the independent control of the infra-red energy
being emitted to each individual lens assembly facilitates the
varying of the input wattage to each element or set of elements,
whereby the magnitude in infra-red spectra profile can be readily
adjusted in conformance with the requirements of each mold. In
effect, higher wattages respond with high output in full wave
distribution, whereas lower wattages respond with lower total
output in a spectral shift away from short-wave infra-red
emittance. Medium and long wave spectrum are more desirable for the
demolding process. The higher the wattage to the IR emitter, the
higher the IR energy, the higher the frequency, and the shorter the
wavelengths.
[0019] In addition to the foregoing, pursuant to the invention
there is also contemplated the provision of a preheating step in
the production sequence prior to demolding of the lenses, in which
a slight amount of heat in the process cycle preceding the
demolding step utilizes any suitable heating source, such as an
infra-red lamp. In an embodiment there could be a feedback control
loop sensing the temperature at the demolding device, which enables
thermal control over the molds to be within a specified temperature
range upon entering the demolding station of the manufacturing
system, thereby further enhancing the efficiency of and reduction
in demolding time.
[0020] Accordingly, it is a primary object of the present invention
to provide an efficient and reliable means for applying a
controlled thermal gradient to the unseparated mold sections,
thereby providing a sufficient relative shear force to break the
adhesion between the contact lens and the mold section.
[0021] It is another object of the present invention to provide a
silicon carbide (SiC) IR-emitter heating device for demolding
ophthalmic lenses that can easily and consistently separate the
contact lens mold portions having a contact lens formed
therebetween without damaging the lens.
[0022] Another object of the instant invention is to reduce contact
lens manufacture process time by separating the greatest number of
back curves from front curves in a rapid manufacturing line thereby
permitting the fast and efficient production of hydrophilic contact
lenses.
[0023] Pursuant to a more specific object of the present invention,
a thermal gradient is provided at the demolding station through the
provision of an infra-red emitter for demolding the lenses, wherein
a ceramic infra-red emitter has a head portion constituted of
silicon carbide enabling the emitting of unfiltered infra-red
radiation without the need for a further quartz or sapphire window
on the infra-red heater as required in the current technology.
[0024] Moreover, pursuant to a further aspect of the invention, it
is an object to preheat the molds prior to entering the demold
station. In one embodiment the temperature at the demolding station
may be measured and relayed through a feedback loop to a preheater
so as to ensure that the mold enters the demolding station while
preheated to a specified temperature, thereby further decreasing
the amount of time required for demolding.
[0025] Pursuant to another aspect of the invention, the inventive
silicon carbide infra-red emitter which is utilized in the heating
device for demolding the lenses employs a separate infrared emitter
for each separate lens mold, thereby enabling each mold to be
thermally controlled so as to be within a specified thermal
gradient required for the highly efficient and rapid demolding of
the lenses.
[0026] In another aspect of the invention, the invention provides a
reflector positioned to encompass at least a portion of each
infra-red emitter to optimize the reflection of heat in the
direction of the lens assembly such that the efficiency of the
infra-red emitter is increased. The surface of the reflector
preferably has a surface roughness of less than 0.3 micrometers
RMS. The surface of the reflector preferably comprises a thinner
layer of gold than was used in the prior art; however, preferably
it comprises a thicker primer layer under the gold layer. The
reflector preferably is shaped to reflect the heat towards the
curves. The reflector shape is such that it is angled or otherwise
shaped to focus the heat at the lens curves or lens mold assembly.
At least a portion of the reflector is preferably elliptically or
parabolically shaped to provide that the radiation is directed at
the lens mold assembly. The optimum elliptical or parabolic shaped
reflector can be determined by doing a ray trace analysis
considering the shape of the infra-red emitter, and the portion of
the infra-red emitter that produces the radiation.
[0027] The foregoing and other objects are attained by an apparatus
for separating a back mold half from a front mold half of a contact
lens mold assembly useful in the production of contact lens. Each
of the front and back mold halves has a central curved section
defining opposing concave and convex surfaces, and also has a
circular circumferential flange which extends outward from the
central portion. The concave surface of the front curve provides
the shape defining surface of the front portion of the contact
lens. Conversely, the convex surface of the back curve mold half
provides the shape defining surface of the back portion of the
contact lens. The fabrication of the contact lens, as set forth
conceptually hereinabove, is carried out by placing a predetermined
amount of monomer in the concave portion of the front curve,
positioning the convex surface of the back curve mold section into
the concave portion of the front curve mold section, and
subsequently subjecting the monomer to curing or crosslinking,
therein providing the lens shape to the hydrophilic material. The
term "cured" will be used herein to cover any reaction mechanism,
including crosslinking, used to form the contact lens. The paired
front and back curve mold sections may be transported through much
of the fabrication line on pallets, each pallet containing a
plurality of paired curve molds. Alternatively, the mold sections
may be transported via another means, such as a conveyor or pusher
rods, and may be transported individually or in plurals by such
means. In the preferred embodiment the back curve rests on top of
the front curve; however, the opposite is contemplated by this
invention.
[0028] The mold separating and lens removal apparatus, which is
positioned in the manufacturing line at a position downstream from
the station wherein the lens material is cured, comprises a device
for applying a thermal gradient to the concave surface of the back
mold half, thereby providing a differential expansion which causes
an adhesion breaking shearing force between the convex surface of
the back mold half and the contact lens. As stated above, it is
understood that the greater the thermal gradient, the greater the
effectiveness of the adhesion breaking. Temperature gradient ranges
from about 2.5.degree. C. to 12.degree. C. are desirable.
[0029] Pursuant to the invention as described in further detail
hereinbelow, the required thermal gradient for assisting in the
demolding of the lenses is provided by an infra-red heat source,
this heat energy being directed at one of the mold curves through
the intermediary of a silicon carbide (SiC) emitter heating device,
whereby the device is constructed such that an individual silicon
carbide infra-red emitter is associated with respectively each one
of a separate mold of a plurality of molds which are transported to
the demolding station on a pallet. In the preferred embodiment as
described herein, the heat energy is directed at the back curve
mold half, although the de-mold process would be as effective if
the heat energy were directed at the front mold half instead of at
the back mold half. This invention is therefore not limited to the
application of heat to only the back mold half, and the front mold
half could be substituted for the back mold half in the demold
apparatus and method described below. However, the lens will remain
adhered to the mold half that is not heated.
[0030] Pursuant to a further aspect, associated with the silicon
carbide infra-red emitter which provides for the thermal gradient
in the heating of the mold, there is provided a preheating step in
the process, which may incorporate a feedback control loop
measuring the temperature sensed at the demolding station so as to
raise each mold to within a specified temperature range upon
entering the demolding station, such as within 57-65.degree. C.,
prior to the application of the demolding temperature gradient by
the silicon carbide infra-red emitters.
[0031] Once the temperature gradient, supplied by the above device,
has weakened the adhesion forces between the back curve mold
sections and the corresponding lenses, an apparatus which is
directed to complete the separation of the mold sections by
mechanical means is introduced in the form of pry fingers between
the front and back curve mold sections.
[0032] In one such embodiment, as described in EP 0775 571 Al, the
separation apparatus comprises two pairs of opposing thin shims,
oriented parallel to the direction of the advancing pallet, which
are initially disposed on top of one another, and which together
slide between the lateral extending flanges of corresponding front
and back curves. Once so positioned, the upper ones of each pair
shims is raised, therein lifting the back curve molds upward and
away from the secured front curves and the lenses thereon. The
removed back curves may be transported to a waste disposal area by
a variety of devices, such as a plurality of suction cups or
stripper fingers. In a second variant, the separation device
comprises an eccentric cam driven prying means mounted transverse
to the direction of the advancing pallets as disclosed in U.S. Pat.
No. 5,770,119 assigned to the assignee of the present invention,
and incorporated herein by reference. This prying means includes a
first set of securing fingers which engage the front curve mold
sections and hold them stationary as a second set of pry fingers,
translated eccentrically, first pivotally and then substantially
upwardly, engage the corresponding back curve mold halves. These
prying fingers bias the back curve molds at a predetermined force
with respect to the associated front mold halves, thereby
effectively removing the back mold halves therefrom, and exposing
the lenses. In a third variant, the separation device comprises a
dual linkage, lifting device, mounted parallel to the direction of
motion of the pallet stream that demolds the mold sections in
pairs. This device includes thin retainer elements which slide
between the flanges of the front and back curves as a pallet
carrying the molds advances. The retainer elements secures the
front curve mold sections to the pallet and prevents them from
translating upward. As the front curve halves are secured by the
retainer elements, a set of separation fingers, shaped for fitted
engagement with the flanges of the back curve mold sections
translates upward via a dual motion linkage system. The upward
translation of the separation fingers lifts the back curves away
from the stationary front curves and the pallet, thereby exposing
the lenses, one pair of lenses at a time.
BRIEF DESCRIPTION OF DRAWINGS
[0033] Further benefits and advantages of the present invention
will become apparent from a consideration of the following detailed
description in conjunction with the accompanying drawings,
illustrative of preferred embodiments and variations of the
invention:
[0034] FIG. 1 is a top plan view of a production line pallet, used
to transport a plurality of contact lens molds throughout a contact
lens production facility;
[0035] FIG. 2 is a side elevational view of the production line
pallet; and
[0036] FIG. 3 is a front view of two lens molds situated in
respective cavities of the lens mold pallet;
[0037] FIG. 4 is a diagrammatic front elevational view of an
infra-red demolding device for imparting a thermal gradient across
a back curve mold and the lens formed thereunder pursuant to the
prior art;
[0038] FIG. 5 is a diagrammatic front elevational view of the
inventive infra-red demolding heater device for imparting a thermal
gradient across the back curve mold and the lens formed
thereunder;
[0039] FIG. 6 is a side elevational view of the infra-red demolding
heater device illustrated in FIG. 5;
[0040] FIG. 7 is a top plan view of the infra-red demolding heater
device of FIG. 5 for imparting a thermal gradient across the back
curve mold and lens formed thereunder;
[0041] FIG. 8 is a detail view of the silicon carbide IR-emitter of
the device of FIG. 5;
[0042] FIG. 9 is a side view of a separating mold section,
illustrative of the operation of the mechanical separation
means;
[0043] FIG. 10 is a graphical representation of the advantages of
the silicon carbide IR-emitter of the heater device compared with
prior IR-heaters for attaining the desired thermal gradient.
[0044] FIG. 11 is a cross-sectional view of an alternate embodiment
of the infra-red demolding heater device of this invention.
[0045] FIG. 12 is a cross-sectional view of an alternate embodiment
of the infra-red demolding heater device of this invention.
[0046] FIG. 13 is a detail view of the silicon carbide IR-emitter
of the device of FIG. 11.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0047] The ophthalmic lens to be demolded in the practice of the
present invention is preferably formed in a volume defined between
front and back contact lens mold portions, each of which are formed
by the processes set forth in U.S. Pat. No. 5,540,410, assigned to
the assignee of the present invention, and the disclosure of which
is incorporated by reference herein.
[0048] More particularly, the front and back curve mold portions
are preferably transported through the manufacturing line on
pallets 10, one of which is shown in FIGS. 1 and 2. Referring also
to FIG. 3, it is understood that the front curve portion 12 of the
mold is carried within one of the plurality of recesses 14 defined
by the pallet 10. In the presently illustrated embodiment of the
pallet 10, the pallet 10 has the capacity to carry up to eight
front curve molds in its recesses 14. During the process by which
the lens is formed, the concave portion 16 of the front curve mold
12 is partially filled with a reactive mixture or monomer solution
18 (which becomes the contact lens), and then receives the convex
portion of back curve mold 20 therein. The back curve mold 20 is
seated within the concave portion 16 of the front mold half 12
under a vacuum to avoid the possibility of trapping an air bubble
in the monomer. The mold halves 12,20 are then clamped squeezed
together to displace excess monomer 22. The excess monomer 22
collects in a ring around the periphery of the curved portions of
the mold halves 12,20. In as much as each mold half 12,20 includes
circumferential flange portions 24,26 respectively, the excess
monomer collects in a space therebetween. The pallet 10 travels
along a process path while guided by along tracks 28,30 having each
inwardly directed transverse ribs or projections 32 engaged in side
recesses or grooves 34 formed in the pallet 10.
[0049] The assembled mold halves 12,20 may then be clamped again
and precured which may occur in a low oxygen environment. Following
precure, the lenses are fully cured with heat and UV radiation
which causes the complete polymerization of the monomer matrix of
the contact lens.
[0050] The annular flanges 24,26, formed at the circumferential
periphery of each lens mold portion 12,20, has the additional
purpose of providing a site at which an external apparatus may be
employed to facilitate the separation of the lens molds 12,20 to
access the newly formed lens. This separation step, however, is
preceded by the application of a thermal pulse to the back curve
mold 20. The purpose of this thermal pulse is to establish a
thermal gradient between the interface of the back curve 20 and the
newly formed lens L. This gradient causes a differential expansion
of the back curve with respect to the lens therein reducing the
adhesion of the lens L to the back curve 20. The device for
establishing the thermal gradient comprise the novel aspects of the
present invention, and is described in detail below.
[0051] First, however, referring specifically to FIG. 2, in which a
side view of the pallet 10 is shown, it is necessary to set forth
the important features of the mold carrier. In order to insure that
the continuous stream of pallets 10, which characterize a fully
functional automated fabrication line, travels smoothly and
consistently, each pallet includes the groove 34 formed in the side
thereof. These grooves 34 are designed to engage the transverse
ribs 32 which thereby minimize possible vertical motion of the
pallet 10 during fabrication steps, such as the demolding and
separation stage which is the subject of the present invention.
[0052] More particularly, with respect to FIG. 3, which is a front
view of a pallet 10 carrying a pair of assembled molds 38 (each
comprising a front curve 12 and a back curve 20, having a newly
formed contact lens L disposed therein), the engagement of the side
grooves 34 of the pallet 10 and the set of transverse ribs 32 which
extend along the inner surfaces 40 of a conveyor line is
demonstrated. A suitable registration means (not shown) may also be
included for locating the pallets along the conveyor path, therein
holding the pallet absolutely fixed for fabrication stages, such as
the demolding station.
[0053] THE DEVICE FOR APPLYING THE THERMAL GRADIENT
[0054] As illustrated in FIG. 4 of the drawings, there is
diagrammatically represented an infrared heating apparatus for
generating a thermal gradient pursuant to the prior art,
particularly as represented in European Patent EPO 775 1 A2, US
535996, incorporated herein by reference.
[0055] In that instance, a vertically reciprocating housing 40
containing infra-red heating elements 42 and reflected tubes 44 are
adapted to have the heating heads 46 of each of the heating
elements come into close contact with the back half mold portion
20. In this particular apparatus each of the heating elements is
provided from a single current source, so as to prohibit any
adjustment of variations in the temperatures of the respective
heating elements which are adapted to contact the respective mold
halves, of which 8 are present in each pallet 10. The preferred
embodiment does not include the prior art constructions which are
extensively discussed in the European patent which discloses
heating elements that incorporate quartz windows and protective
sapphire windows which reduce the amount of heat being conveyed to
the mold half portions by the heating elements, consequently
reducing the efficacy and the efficiency of the apparatus due to a
more extensive heating period required to provide the desired
thermal gradient.
[0056] Referring now to FIGS. 5 through 8, each of which illustrate
different views and details of an inventive infra-red heating
device 50 for generating a thermal gradient across the back curve
mold portion (or other mold portion) and the lens formed
therebelow.
[0057] The infra-red heating device 50 pursuant to the present
invention which provides the desired thermal gradient in the
implementation of the separation between the mold halves 12, 20
between which the lens is formed, includes a housing structure 52
comprising an upper housing portion 54 which is equipped with
terminal strips 56 that are connected to an electronic control
system and related power source equipment (not shown). The lower
portion 58 of the housing structure 52 comprises a water-cooled
housing through which there pass a plurality of upwardly or
vertically extending infra-red emitters 60, preferably silicon
carbide (SiC) infra-red emitters The infra-red emitters 60 are
adapted to impart a predetermined amount of heat to the molds in
the pallets 10 which are positioned therebeneath at this demolding
station. Around each of the infra-red emitters 60 is an outer
sleeve 62 of essentially cylindrical configuration, which sealingly
extend through the water cooled housing 58, and the lower ends of
which sleeves 62 are adapted to be in contact with the upper or
back mold half 20 during the heating thereof, based on the downward
displacement of the housing structure 52 during operation. The
sleeves are preferably tapered at their bottoms to have a diameter
sized to fit into the concave shape of the back curves to avoid
heating the reactive material that may have overflowed the lens
curves during the assembly of the lens curves. Contained within
each of the sleeves, as shown in more specific detail in FIG. 8 of
the drawings, is an igniter assembly 70 which includes a ceramic
bushing 72 sealingly positioned at the upper portion of the water
cooled housing 58, so as to seal the sleeves 62 against the ingress
of cooling water. Extending downwardly from the ceramic bushing 72
is an igniter portion 73 which at the lower end thereof emits
radiation that heats the back curve mold half 20. This igniter
portion 73 includes a spirally grooved portion 74 adapted to
receive electrical wire leads 76 extending upwardly into electrical
engagement with the terminal strips 56 for each of the infra-red
emitters 60.
[0058] Within each of the sleeves 62, there is positioned,
surrounding at least the radiation emitting portion of IR emitter,
that is, the spirally-grooved portion 74, a reflector 78 which may
contain either a frusto conical or parabolic reflector adapted to
project the desired amount of heat onto the surface of the back
curve 20 of the mold located therebeneath. The reflector 78 will be
described in more detail in reference to FIGS. 11 and 12. Note the
terms mirror and reflector will be used interchangeably herein. The
use of one of the terms mirror or reflector includes both
terms.
[0059] Each of the infra-red emitters 60 is controlled by a
separate source of electrical current so as to be able to adjust
the amount of heat generated upon contact with the back half mold
portion 20 in order to provide the desired thermal gradient at
maximum efficiency and minimum amount of time.
[0060] In the preferred embodiment, each silicon carbide emitter 60
is unfiltered, by being quartz-free and sapphire-free, by
eliminating the windows and resultant IR filtering, as in the
previous instances known from the prior art as represented by the
European Patent 775 571 A2, the infra-red radiation is unfiltered
and consequently the heat losses are considerable reduced in
comparison with the prior art heaters, thereby considerably
shortening the heating time required for the demolding of the
lenses. Furthermore, by being unfiltered, the present silicon
carbide infra-red emitter requires less energy in order to generate
a greater amount of heat, and enables a longer wavelength of the
infra-red radiation to be employed for heating the mold.
[0061] Pursuant to the invention, each infra-red emitter 60
representing a individual irradiating heat lamp irradiates only a
single mold, unlike the prior art wherein four molds are serviced
by a single IR-heat lamp. The present construction facilitates the
utilization of individual temperature regulation for each mold so
as to optimize the thermal gradient for each respective mold while
concurrently reducing the heating and demolding time.
[0062] In order to achieve a maximum efficiency both as to required
heating time and reduction in energy, it is advantageous to be able
to preheat the molds prior to the applying of the demolding thermal
gradient, preferably as shown by means of the silicon carbide
infra-red emitters 60. To that effect, suitable sensors (not shown)
may be positioned proximate each of the molds, and connected to a
preceding processing station (not shown) wherein suitable heating
means may provide for preheating of the molds located in the
pallets 10 prior to the latter being advanced into the demolding
station represented by the present silicon carbide IR-emitter
heating device 50. Thus, there may be temperature feedback
information provided by the sensors to the preceding preheating
station so as to afford preheating of the molds to a temperature
range of approximately within 57-65.degree. C. at their entering
the demolding station. This can be implemented by an infra-red
lamp, forced air heater, or any other type of convection or radiant
heat source in the preheating station, as may be required. The
feedback provided by the sensor may measure voltage and current and
can employ a PID controller (proportional, integral and derivative
controller) to regulate the required length in time of infra-red
radiation heat produced by each respective infra-red emitter in
connection with its associated mold on the pallet, thereby assuring
a uniformity of thermal gradients and separation between the mold
halves not at all attainable in the previous constructions.
[0063] As shown in FIG. 10 of the drawings in a graphical
representation, the left hand portion of the graph essentially
represents the peaks which are attained during heating with the
prior art systems utilizing quartz and sapphire windows, wherein
the mold is constituted of polystryene mold. To the contrary, by
removing the quartz and sapphire windows, there was achieved a peak
representation, as shown at the right hand portion of the graph,
demonstrating that these peaks enable a more rapid heating of the
molds for the separation of the halves thereof. Presently, by using
the apparatus and method of this invention, the mold halves require
approximately one and one half seconds or less to reach demold
temperature, as compared to four seconds or more required by the
prior art system and method.
[0064] The foregoing device for applying the thermal gradient
pursuant to the invention may be utilized in conjunction with
mechanical separating means, which are not the subject of this
invention, of which one optional embodiment of the various known
embodiments utilizing pry fingers as illustrated in European Patent
0 775 571 A2, the details of which are incorporated herein by
reference, and the description set forth hereinbelow is merely for
purpose of providing a more comprehensive understanding of the
overall aspects of the mold separating arrangement.
[0065] An unexpected result of this inventive SiC heater device 50
is a major reduction in the "center pull" defect. This defect is
associated with the excessive heat that the target mold receives at
the center of the heating area with previous methods. The SiC
heating element used in this device is shaped as a hollow cylinder
with the base end facing the target mold. The direct IR energy that
the mold receives is shaped symmetrically to the mold assembly with
the center receiving a proportionally reduced amount of energy
compared to other methods. This shaping of the IR energy
distribution results in a reduction of defects that can be
introduced during the demold process. The IR energy from the side
of the silicon carbide cylindrical emitter is reflected down toward
the mold using a cone mirror or parabolic mirror. This results in a
more desirable and symmetrical heating pattern.
[0066] FIGS. 11 and 13 show an alternative embodiment of this
invention. Like elements are labeled the same as the embodiment
shown in FIGS. 5-8. The difference between the embodiments is the
shape of the reflector 78 and the shape of the IR emitter 60. The
reflector 78 shown in FIG. 11 encompasses the radiation emitting
portion of the IR emitter 60, that is the spirally grooved portion
of the IR emitter 60. FIG. 13 shows in detail the IR emitter 60
that is used in the embodiment shown in FIG. 11. As shown in FIG.
13 the spirally grooved portion 74 of the IR emitter 60 begins a
shorter distance from the ceramic bushing 72, relative to the IR
emitter shown in FIG. 8. For this reason the reflector in FIG. 11
is located closer to the ceramic bushing 72; and the reflector
flares out from a collar portion 801 which preferably is reflective
around (preferably spaced from) the IR emitter 60 above the
spirally grooved portion 74. As shown the reflector comprises an
upper section 802, and a lower section 803. The upper section 802
and lower section 803 are preferably conical shaped. The upper
section 802 which is conical shaped is preferably sized to extend
from the collar 801 to approximately match the length of the IR
emitter, preferably to a length that is approximately or at least
parallel with the bottom of the spirally grooved portion 74. The
lower section 803 which is also preferably of conical shape meets
the widest part of the upper section 802. The lower section 803
tapers to a diameter D that is approximately equal to the diameter
of the concave portion of the back curve, or as shown is
approximately equal to a diameter less than five percent larger
than the portion of the lens curve desired to be heated. As shown
in FIG. 11, the reflector further comprises a nozzle 804. The
nozzle is preferably has a cylindrical shape or a tapered cylinder
shape. As shown the nozzle 804 further comprises a diameter step
805 that reduces the diameter of the nozzle to that of the concave
portion of the back curve. The diameter step 805 is optional in the
nozzle 804, and is not present in the embodiment shown in FIG. 12.
The reflector 78 is shaped so that it reflects the radiation toward
the lens curves. The size and shapes of the upper and lower
sections are determined by factors such as space, the IR emitter
length, particularly the length of the spirally grooved portion,
and the results of ray tracing analysis, which can be performed by
several commercially available computer programs, e.g., ASAP
Optical Software from Breault Research Organization, and BEAM FOUR
by Stellar Software, and others.
[0067] FIG. 12 shows an alternative embodiment of the invention in
which the shape of the reflector 78 is maximized. The labeling is
the same as in the earlier Figures. Any IR emitter shape may be
used with the reflector shape shown in this embodiment; however,
the IR emitter shown in detail FIG. 8 is preferred and is shown in
FIG. 11. The most preferred upper section 802 of the reflector
comprises a circular partial ellipsoid or circular paraboloid
shape. Again, the size and shapes of the upper and lower sections
are determined by factors such as space, the IR emitter length,
particularly the length of the spirally grooved portion, and the
results of ray tracing analysis. In the preferred embodiment the
reflector also comprises a lower section 803 which comprises a
partial conical. Also in the preferred embodiment the reflector
also comprises a nozzle 804 which is sized to direct the radiation
to the lens assembly; however, the nozzle could be eliminated if
the diameter D of the lower section 803 were sized as desired to
contact the lens assembly. Further, the lower section 803 could
also be eliminated, and the upper section 802 with or without the
presence of the nozzle 804 could be used as the reflector 78 if the
circular partial ellipsoid or circular paraboloid shape was
designed so that sufficient radiation was focused at the lens
assembly for demold. Preferably, the nozzle 804 would be used with
the upper portion 802, so that the proper contact could be made
with the lens assembly; however, if sufficient radiation were
directed at the lens assembly, a nozzle and contact with the lens
assembly would not be necessary. Further, the upper portion 802
could be shaped to provide a tapered bottom that could be used to
contact the lens assembly, if desired.
[0068] To increase the efficiency of the IR emitter device, the
surfaces of the reflectors that reflect the radiation were modified
to provide a very smooth surface, preferably a surface having a
surface roughness less than 0.3 micrometers RMS, more preferably
less than 0.2 micrometers RMS, and most preferably less than or
equal to 0.1 micrometers RMS. The preferred reflectors are specular
reflectors. Additionally the reflective coating on the reflectors
was modified to provide a gold coating having a thickness of
approximately between from 1.3 to 2.9 micrometers, more preferably
between from 1.5 to 2.5 micrometers, most preferably between from
1.7 to 2.2 micrometers. The presently preferred embodiment has a
gold coating approximately 1.9 micrometers thick. The gold coating
is preferably applied on a primer coating. The preferred primer
coating is an electroless nickel coating. The primer coating is
preferably between from 7 to 25 micrometers, more preferably
between from 10 to 20, micrometers, and most preferably between
from 12 to 18 micrometers thick on the reflector support or sleeve.
The primer coating is preferably applied to a copper, brass or the
like, more preferably a brass reflector support structure, which
may be used to form the outermost layer of the sleeve, or another
layer such as a ceramic layer may be added over the brass. It was
found that the earlier gold coated reflectors used in the prior art
were not as durable, not as efficient, and difficult to clean.
Because the earlier gold coated reflectors were not as efficient
the IR emitters had to produce higher radiation which resulted in
charred materials building up on the surface of the reflectors
which reduced the efficiency of the reflectors. Feedback controls
caused the IR emitters to produce even higher radiation, which
produced and caused the build up of more charred material, and this
process continued until the IR emitters would break down. Modifying
the reflectors to provide the reflectors comprising the primer and
gold coatings just described and having a surface smoothness of
less than 0.1 micrometers RMS, increased the efficiency of the
reflectors by 10%, translating into a 10% decrease in power to the
IR emitter, which significantly increased their useful life. The
preferred reflectors used in the invention provided a 98%
reflectivity for 1,000 to 4,000 nm infra-red range. However, the IR
emitters can produce radiation anywhere in the IR range, most
preferably radiation comprising radiation or consisting of bands of
radiation between 1,000 and 15,000 nm.
[0069] MEANS FOR SEPARATING THE THERMALLY LOOSENED MOLD
SECTIONS
[0070] The mechanical demolding assemblies or devices of the mold
separation apparatus may comprise a variety of different
variations, one of which is illustrated hereinbelow. It shall be
understood, that while variations may be described in conjunction
with the above described means for applying a thermal gradient,
various other types of separation means may be equivalently
utilized with the disclosed means for loosening the back curve
molds from the lenses.
[0071] Basically, as shown in FIG. 9, the separation means function
by mechanically prying the back curve mold half 20 from the front
curve half 12 of each contact lens mold assembly 38. The prying
process occurs under carefully controlled conditions, with somewhat
different force vectors, so that the back curve half will be
separated from the front curve half without destroying the
integrity of the lens formed in the lens mold.
[0072] The separation device 80 includes two pairs of separating
shims 82, 84 on either side of the molds for each conveyor line.
Each of the pairs of shims 82, 84 are introduced between the
flanges 24, 26 of corresponding front and back curves 12, 20. When
separated, one 84 of each of the pairs of shims hold the front
curves 12 down on the pallet 10, and the second 82 of each pairs of
shims is raised, lifting the back curve 20 off the pallet,
separating it from the lens beneath. This operation is described in
detail in conjunction with the infrared thermal gradient
application as set forth hereinabove.
[0073] It is understood that each set of shims 82, 84 is inserted
in a manner such that the finger portions of the shims anchor the
annular flange portion 26 of the front curve 12 of the lens mold to
the surface of the pallet 10, and that the finger portions of the
top shims 82, by action of a vertical drive means (not shown) lift
and vertically separate the back curve mold portions 20 from the
front curve mold portions without destroying the integrity of the
contact lens or either of the mold portions.
[0074] It has been found that by properly controlling the lift rate
of the top shim 82, so as to mimic a constant force (in contrast to
a constant linear motion) lift, a higher effective yield may be
achieved. The specific profile of the pseudo-constant force lift
may be determined empirically off-line and then applied uniformly
to all mold pairs with considerable effectiveness.
[0075] In the illustrated embodiment, a 2 mm space exists between
the mold flanges 24, 26, and the combined thickness of the upper
and lower separation shims is approximately 1.5 mm. After
insertion, the shims are separated at a velocity of 10 mm/sec for a
distance of 1 mm, thus providing a small preload to the mold
halves. The separation velocity is 0.6 mm/sec for a separation
distance of approximately 1.3 mm, and then a high velocity lift off
at the maximum velocity of the device motor.
[0076] In an alternate embodiment, each pair of laterally disposed
shims separates slightly after insertion in order to preload the
front and back curves, thereby providing a small bias apart prior
to the application of a thermal gradient.
[0077] After the preload is established, the infra-red emitters 60
are energized and the back curve 20 heated under preload. This
provides essentially a mold release from thermal energy, assisted
by mechanical energy.
[0078] It may be understood that such above-described mechanical
assistance is best supplied just after heating, although no adverse
effects would be contemplated if there was less time between the
application of a thermal gradient to break adhesion and mechanical
removal.
[0079] In practicable manufacturing terms, the time between thermal
exposure and mold separation is between about 0.2 and about 1.5
seconds.
[0080] The present invention, which comprises an apparatus and
method of manufacturing contact lenses including the loosening and
separating of mold pairs used in the fabrication of the lenses,
after the lenses have been formed therebetween, has been set forth
hereinabove with reference to a preferred embodiment.
[0081] While the invention has been particularly shown and
described with respect to a preferred embodiment thereof, it will
be understood by those skilled in the art that the foregoing and
other changes in form and details may be made therein without
departing from the spirit and scope of the invention.
* * * * *