Sandwich blister package for tablets and similar articles

There is disclosed a novel sandwich blister package for tablets and similar articles which generally comprises a plastic film having a plurality of heat-formed cavities which contain tablets or similar articles; and, a plastic film/aluminum foil laminate sheet superimposed upon and heat sealed to the plastic film to form a blister card of pre-set size, each blister card being bonded to another blister card so that the aluminum foil forms the outer protective cover with the plastic film sandwiched between them.

BACKGROUND OF THE INVENTION 
Many consumer articles such as prescription medicines are provided in the 
form of tablets or pills. It is desirable to prolong the shelf life of 
these articles by protecting them from exposure to air, gas and moisture. 
Some of these articles are hygroscopic making it necessary to protect them 
from moisture degradation so that they retain their usefulness over 
prolonged periods; i.e. shelf life stability, until they are consumed. 
In order to accomplish these desirable ends, these tablets and pills are 
typically contained in what are commonly referred to as blister packages; 
that is, relatively flat packages having a plurality cavities formed in 
them from suitable moisture/vapor/gas impervious materials which are 
sealed to each other. The tablets or pills are carried in the cavities and 
are protected from moisture/vapor/gas degradation until the protective 
materials are unsealed to remove the pills or tablets to be consumed. 
A typical moisture/vapor/gas impervious blister package currently in 
commercial use comprises two sheets of protective material, one sheet 
being a three ply laminate consisting of a flexible plastic film, aluminum 
foil and a resilient plastic film such as nylon. The aluminum foil ply 
imparts the desired moisture/vapor/gas barrier protection and is the 
middle ply of the laminate with the flexible plastic film bonded to one 
surface of the aluminum foil ply and the resilient plastic film ply bonded 
to the other surface of the aluminum foil ply. The flexible plastic film, 
typically a polyvinyl chloride (PVC film, is the innermost ply of the 
package and serves primarily as a sealant, although it also protects the 
tablets or pills by preventing them from contacting the aluminum foil ply. 
Since the aluminum foil ply used is relatively thin, it can be easily 
punctured and has a tendancy to tear. Consequently, the resilient plastic 
film is used to protect the aluminum foil ply and prevent it from being 
torn or punctured as cavities are cold formed in the laminate. After the 
cavities are formed, tablets or pills can be placed in them and the other 
sheet, which is typically a two ply aluminum foil/plastic sheet laminate, 
is overlaid onto and sealed to the tablet carrying sheet as a cover to 
complete the blister package. 
The aluminum foil ply in the cover sheet is typically somewhat thinner 
(e.g., about 0.02 millimeters) and therefore not as strong as the aluminum 
foil ply in the tablet carrying sheet which typically has a thickness of 
about 0.04 millimeters. This enables the pills or tablets to be removed by 
manually pushing them through and rupturing the cover sheet. 
These types of blister packages are uneconomical to produce due to the high 
cost of the three ply laminate sheet. In addition, cold forming the 
cavities in the three ply laminate sheet must be done slowly and carefully 
to avoid tearing or puncturing the aluminum ply thereby decreasing 
production line output. 
SUMMARY OF THE INVENTION 
It has now been found that the shortcomings of these all aluminum-type 
blister packages can be overcome by the novel sandwich blister package of 
the invention. In general, the sandwich blister package of this invention 
comprises a sheet of plastic film having a plurality of heat-formed 
cavities; a two-ply plastic film/aluminum foil laminate sheet superimposed 
upon and sealed to the plastic film to form a first blister card of 
pre-set size; and, a second blister card bonded to said first blister card 
to complete the sandwich blister package with the aluminum foil forming 
the outer protective cover of said sandwich blister package. 
Use of the heat-formable plastic film in the sandwich blister package of 
the invention reduces the cost of materials, eliminates the need for 
additional aluminum foil lamination, and permits faster package production 
since the cavities can be quickly heat formed in the plastic film. In 
addition, since only one ply of aluminum foil is used, the materials costs 
to produce the sandwich blister package of the invention are substantially 
reduced. 
The plastic materials that can be used for the plastic film portion of the 
blister package of the invention are those which are resilient, heat 
formable and heat sealable such as polyvinyl chloride (PVC) polyvinylidine 
chloride, fluoro plastics, and the like, preferably PVC. PVC films having 
a thickness of from about 0.2 to about 0.25 millimeters provide the 
desired packaging and processing properties for use in the sandwich 
blister package of the invention and are commercially available. The PVC 
films can be readily heated to form the cavities for tablets or pills, 
retain the integrity of the formed cavities after cooling and are heat 
sealable. 
The aluminum foil used in the two-ply laminate sheet of the invention 
sandwich blister package generally has a thickness of from about 20 to 25 
microns, and is also commercially available. These types of aluminum foils 
are typically referred to as "lid" foils as they are generally used as 
temporary covers on bowls or pans to protect foods. 
The PVC film laminated to the aluminum foil is typically about 0.02 
millimeters thick. 
Conventional packaging apparatus can be used to produce the sandwich 
blister package of the invention which generally comprises feeding a sheet 
of PVC plastic film over a heating plate having a plurality of spaced 
apertures formed therein; concurrently applying heat and vacuum to the PVC 
plastic sheet while it is held over the heating plate to vacuum form a 
plurality of spaced cavities in the PVC plastic sheet; advancing the PVC 
plastic sheet and filling the cavities with pills or tablets; 
superimposing a two ply plastic film/aluminum foil laminate sheet over the 
filled cavities; bonding the plastic film/aluminum foil laminate to the 
PVC plastic sheet; cutting the thusly bonded members to obtain separate 
blister cards of pre-set sizes, each containing a pre-determined quantity 
of tablets or pills; and, superimposing pairs of said blister cards on 
each other and bonding them to each other by heat sealing them together so 
that the aluminum foil portion of the two ply laminate forms the outer 
protective cover with the plastic films and tablets sandwiched 
therebetween.

As shown in FIG. 1, one blister card of the sandwich blister package of the 
invention is generally identified by reference letter A and comprises a 
PVC plastic sheet 10 having a plurality of cavities 11 heat formed therein 
and in which have been placed a pill or tablet 12. Superimposed upon and 
bonded to PVC sheet 10 is two ply laminate 13 consisting of an inner ply 
of PVC plastic film 14 and an outer ply of aluminum foil 15. 
In FIG. 2, an assembled sandwich blister package of the invention, is shown 
comprising blister card A of FIG. 1 and a second blister card generally 
identified by reference letter B. Blister card B is a duplicate of blister 
card A as indicated by like reference numerals identifying like parts. 
Blister card A is overlaid onto blister card B and they are bonded; i.e., 
heat sealed, to each other in the area of their common overlapping edges 
as indicated at 16 and 17. 
The sandwich blister package thus formed consists of the tablets or pills 
12 contained in the cavities 11 of PVC plastic sheet 10 sandwiched between 
and enveloped by the outer plies of aluminum foil 15 which serves as the 
moisture/vapor/gas impervious material. Thus, the pills or tablets 12 are 
maintained in a stable condition for prolonged periods retaining their 
full potency until they are removed for consumption. 
To remove a pill or tablet 12 from the assembled package shown in FIG. 2, 
finger pressure can be applied against a pill or tablet on either side of 
the package as shown by the blocked arrows until the pill opposite the 
point of applied pressure is pushed through its adjacent two ply laminate. 
In the assembled sandwich blister package shown in FIG. 3, blister card A 
is overlaid onto blister card B so that the cavities 11 of blister card A 
are off-set from those of blister card B in an intermeshing fashion. To 
remove a pill or tablet from this package configuration, finger pressure 
can be applied directly against the pill or tablet to be removed as shown 
by the blocked arrows until the pill or tablet is pushed through its 
adjacent two ply laminate. 
In the sandwich blister package shown in Fig 4, the common, overlapping 
edges of the two blister cards are heat sealed to each other as shown by 
peripheral cross-hatching 17 so that the two ply laminate 13 can be 
peelably removed from the underlying PVC plastic sheet 10 until a pill or 
tablet 12 is exposed for removal. 
FIG. 5 illustrates an assembly line method that can be used to continuously 
produce completed blister packages of the invention. As can be seen in 
FIG. 5, PVC film 10 can be continuously supplied in sheet form from a roll 
of PVC film 18 and led over a hot plate 19 having a plurality of spaced 
apertures 20. Hot plate 19 is kept at a temperature sufficient to heat the 
PVC sheet 10 so that it becomes softened and heat formable. When PVC sheet 
10 has reached a softened, heat formable state (usually within about 2 
seconds to about 6 seconds) vacuum is applied by conventional means (not 
shown) to draw the softened PVC sheet film 10 down into apertures 20 to 
thereby form the cavities 11 in the PVC sheet 10. The PVC sheet 10 is then 
fed beneath a pill or tablet supply means such as hopper 21 where a pill 
or tablet is deposited in each cavity. Sufficient distance from the cavity 
forming operation and the hopper 21 should be provided so that the 
cavities formed have time to cool, set and become integral. Usually, the 
cavities are set and cooled to maintain an integral self-supporting shape 
within about 2 seconds to about 6 seconds. 
Downstream from hopper 21, two ply laminate 13 consisting of the aluminum 
foil ply and the PVC film ply is fed from laminate supply roll 22 to be 
superimposed upon the PVC sheet 10 carrying the pills or tablets in its 
cavities. Two-ply laminate 13 is then heat sealed to the PVC sheet 10 such 
as by means of heat sealing platen 23 to obtain an elongated blister 
package assemblage. Conventional knife blades, such as those respectively 
shown at 25 and 26, can then be used to cut the elongated blister package 
assemblage 24 into individual blister cards A and B of pre-set sizes so 
that each blister card is the same size and contains a pre-determined 
number of pills or tablets. Blister cards A and B are then fed to 
downstream stations (not shown) where one blister card is first overlaid 
upon another blister card and the common overlapping edges of the blister 
cards are heat sealed to each other to produce the sandwich blister 
package of the invention.