Note: Descriptions are shown in the official language in which they were submitted.
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Package Drying Apparatus and Method
The present invention relates to the manufacture and packaging of ophthalmic
lenses, and more particularly relates to an apparatus and method for drying
the seal area
of a blister package immediately prior to sealing (e.g., by heat) a cover
(also known as
lidstock) to the seal area of the package.
Ophthalinic lenses such as contact lenses, for example, are typically packaged
in a
disposable plastic container known generally as a "blister package". The
blister package
has a well in which the lens and a packaging solution are deposited. The
packaging
solution is necessary to keep the lens in a hydrated state during shipping and
storage. A
cover such as a foil lidstock is applied and heat sealed to the area
surrounding the well.
The user peels away the lidstock to access and remove the lens from the well
(usually
with a finger), at which time the blister package, solution and cover may be
disposed of.
It is very important that the cover is securely sealed to the blister package
so as to
prevent leakage of solution from the blister package during shipping and
storage thereof.
Should solution leakage occur, the sterility and hydrated state of the lens is
breached,
thereby requiring rejection of the entire lens and blister package.
A typical molded, soft lens manufacturing environment incorporates the
following
basic process operations (not necessarily in this order):
a) Making of the female and male mold halves;
b) Depositing monomer into the female mold half;
c) Capping the male mold half onto the female mold half;
d) Curing the monomer;
e) Removing the male mold half from the female mold half;
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f) Removing the lens from the mold;
g) Hydrating and extracting volatiles (if needed) from the molded lens
(sometimes
this is done directly in the lens package);
h) Depositing the lens into the well of a blister package (the blister package
may
be the male mold - see, e.g., U.S. Patent No. 5,573,108);
i) Depositing a solution in the well with the lens; and
j) Applying a cover to the well to seal the lens and solution in the blister
package.
The cover is thus applied to the blister package with the lens and solution
located
in the well thereof. The cover is typically a flexible lidstock (e.g., a foil)
with printing
thereon to identify the manufacturing lot and other lens information as
desired. The
lidstock is affixed to the blister package with a liquid-tight seal being made
in about the
entire periphery of the well to prevent leakage and preserve lens sterility as
discussed
above. One manner of affixing the lidstock to the blister package is with a
heating
element to cause a heat seal between the cover and blister package in the area
surrounding the well, although other methods are also used in the art. The
portion of the
lidstock located outwardly of the seal area is typically left~un-affixed to
the blister
package to permit easy peeling away of the lidstock from the blister package
when
opening the package to retrieve the lens. Since the lens is housed within the
package well
with a storage solution, the solution may wet the area surrounding the well
where the
lidstock is to be affixed. Needless to say, any moisture on the seal area will
impede a
secure seal between the lidstock and blister package which is highly
undesirable as
explained above. It is thus necessary to dry the seal area prior to affixing
the lidstock
thereto. This may be accomplished with a vacuum head that vacuums any moisture
from
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the seal area such that the lidstock may be reliably affixed to a dry seal
area. In a lens
manufacturing process which is a batch process, an array of lens packages are
typically
processed simultaneously.
Iri a broad aspect, the invention comprises a vacuum block having an array of
vacuum heads to dry a respective array of blister packages at the same time.
The array of
vacuum heads are aligned with respective packages of a like array of blister
packages and
are moved in a circular pattern to circumscribe the entire seal area which is
at the
periphery of the well. Each vacuum head circumscribes a respective blister
package seal
area removing any moisture therefrom and thereby providing a dry seal area for
affixing
the lidstock thereto. In a particularly advantageous aspect of the invention,
the vacuum
heads are individual components which are individually mounted and removable
from the
vacuum block. The vacuum block is bored to provide the vacuum channels to
which the
individual vacuum heads are interconnected. The vacuum heads themselves each
include
a longitudinal bore which aligns with the vacuum channels of the vacuum block
when in
the fully inserted position. The provision of the vacuum heads being
individually
mounted and removable from the vacuum block allows for a damaged vacuum head
to be
quickly replaced on the vacuum block without requiring replacement of the
entire
vacuum block and without substantial down-time of the machine.
The present invention will be described, by way of example, with reference to
the
accompanying drawings, in which:
Figure 1 is a perspective view of one embodiment of contact lens blister
package;
Figure 2 is a partial cross-sectional view of the blister package with a
lidstock
affixed thereto;
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Figure 3 is the view of Figure 1 showing a lidstock affixed thereto;
Figure 4 is another embodiment of contact lens blister package;
Figure 5 is another embodiment of contact lens blister package;
Figure 6a is a fragmented, cross-sectional view of the vacuum block and vacuum
head of the present invention;
Figure 6b is a fragmented, perspective view of the vacuum block and vacuum
head engaging the seal area of a blister package in the intended manner; and,
Figure 6c is an end view of the vacuum tip.
Refernng to the drawing, Figure 1 shows an embodiment of one type of
disposable plastic blister package used for packaging a contact lens. More
specifically,
as seen in FIG. 1, package 10 generally comprises support base 12 with concave
recessed
well area 14 for receiving and holding contact lens 5 therein. Generally, the
contact lens
will be packaged along with an aqueous storage fluid, such as buffered saline
solution, in
well area 14. Package 10 may be molded from a material such as polypropylene.
Base 12
includes a substantially planar top surface 16 and a seal area 20 encircling
the periphery
of well area 14. Seal area 20 may be raised relative to the remainder of top
surface 16 if
desired. Also, while raised surface 20 is shown to be ring-shaped, other
shapes are may
be used, for example, a chevron-shaped raised surface surrounding the well.
Figure 4 shows another embodiment of blister package 200 having a generally
circular seal area 210 surrounding well area 212 in which a lens 214 is
deposited with an
aqueous storage solution 216. Seal area 210 requires drying prior to affixing
the lidstock
thereto to ensure a liquid-tight seal as stated above.
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Figure 5 shows yet another embodiment of blister package 300 which is actually
the male mold half used in molding the lens 310 deposited in well area 312
with solution
314. Blister package 300 includes a seal area 316 surrounding well area 312 to
which a
lidstock 318 is affixed. Seal area 316 requires drying prior to affixing the
lidstock thereto
to ensure a liquid-tight seal as stated above.
While several embodiments of blister packages have been shown herein, it is
understood that other package styles may be used and benefit from the
advantages of the
present invention which particularly provides a dry seal area for securely and
reliably
affixing a lidstock to the blister package.
As seen in FIG. 2, in the embodiment where seal area 20 is raised, outer wall
22
forms a substantially right degree angle with respect to raised surface 20. A
contact lens
is been deposited in well area 14 with a quantity of aqueous storage solution
7.
Lidstock 30 is applied, so as to cover substantially the entire top surface
16, for example
by heat-sealing the lidstock about annular surface 20, and thereby
hermetically sealing
lens 5 in well 14 of package 10 (see also Fig. 3). It is noted that raised
surface 20 is a
generally flat annular surface as illustrated in Figure 2. As such, moisture
may collect on
surface 20 (e.g., during solution fill) which, if not dried, would interfere
with a proper
seal of lidstock 30 thereto.
Referring now to Figs. 6a and 6b, an embodiment of the invention is shown
which
is an apparatus useful for drying the seal area of a blister package prior to
affixing a
lidstock thereto. The invention includes one or more vacuum heads 50 which
have a
vacuum tip 52 at one end thereof and a vacuum channel V 1 extending
longitudinally
therethrough. Vacuum head 50 is mounted to a vacuum block 54 which includes
one or
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more vacuum channels V2 connected to a vacuum source Vs. The vacuum block 54
and
vacuum heads 50 may be formed of any suitable material, one example being
acetal.
Vacuum block 54 is moved such that the vacuum head and more particularly, the
vacuum
tip 52, is moved into engagement with the seal area 316 of a respective
package 300.
With a vacuum applied, the vacuum block 54 is moved to cause the vacuum tip 52
to
circumscribe the entire seal area, thereby removing any moisture therefrom.
Once dry,
the vacuum block 54 and vacuum heads 50 are moved away and the blister package
is
ready for the lidstock to be affixed thereto. In the preferred embodiment, the
lidstock is
affixed by the application of heat, although other affixing methods may be
used if desired
(e.g., with an adhesive). The seal between the lidstock and blister package is
hermetic to
prevent leakage of solution therefrom and also to prevent a breach of the
sterility in the
well area. The lidstock portions located outside the seal area may be left un-
affixed so as
to permit easy peeling of the lidstock from the package when opening the
package for
retrieval of the lens.
In high speed manufacturing processes, lenses are typically processed in
batches
and are placed in ordered arrays as they travel from one process station to
another. As an
example, an array of 15 lenses are arranged in a 3x5 array. It is understood,
however, that
the present invention is not limited to any particular number or array of
lenses. In this
type of array, the blister packages are held on a suitable support in the
array. ~nce a lens
and storage solution has been deposited into each of the blister packages in
the array, the
vacuum block and lens package array are placed in vertical alignment with the
vacuum
block located above the array. The vacuum block and array are moved toward one
another until a respective vacuum tip comes into engagement with the seal area
of a
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respective blister package. With the vacuum source activated, the vacuum tips
are moved
to circumscribe the entire seal area, thereby drawing off any moisture on the
seal area.
One full revolution of the vacuum tip about the seal area is usually
sufficient to remove
all the moisture from the seal area, although this step may be repeated if
necessary. The
vacuum block together with the vacuum heads are then cleared from the blister
packages,
at which time the array of blister packages are ready for affixing a lidstock
thereto.
The vacuum heads of the present invention are made to be easily removable and
replaceable upon the vacuum block. As such, should one or more of the vacuum
tips
become damaged, only the vacuum heads) which is damaged needs to be removed
and
replaced upon the vacuum block. This saves time and money over a vacuum block
which
incorporates integral vacuum heads. In case where the vacuum heads are
integrally
formed with the vacuum block (e.g., by CNC machining), the entire vacuum block
would
require replacing, an expensive and time-consuming job.
Thus, as seen best in to Fig. 6a, vacuum head 50 is a separate piece which is
mounted to the vacuum block 54 by a screw 55 which is secured into the end of
vacuum
head 50 located opposite vacuum tip 52. An annular locating flange 57 is
formed adjacent
vacuum tip 52 to secure vacuum head 50 within a respective vacuum head bore 59
formed in vacuum block 56. A pair of rubber O-rings 61 a, 61b are attached
about vacuum
head 50 both above and below vacuum channel V1 to ensure a good vacuum seal.
When
using an array manufacturing format, the vacuum head bores are formed in
vacuum block
56 in the same spacing and array as the blister packages are presented to the
vacuum
block so that proper alignment between the vacuum heads 50 and blister
packages is
maintained.
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In the preferred embodiment, as shown in Fig. 6c, each vacuum tip 52 includes
castellations formed by two perpendicular slots S1 and S2 which are provided
to draw an
effective drying vacuum when the vacuum tip is engaged with and is
circumscribing the
seal area of a respective blister package. The castellations are prone to
damage as
compared to other portions of the vacuum head. By providing vacuum heads which
are
individually removable and replaceable upon vacuum block 56, the damaged
vacuum
heads 50 may be quickly and easily replaced on vacuum block 56.
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