EP0627906B1

EP0627906B1 - Improvements in blister packs

Info

Publication number: EP0627906B1
Application number: EP93903726A
Authority: EP
Inventors: Thomas Toren
Original assignee: Toren Consulting Pty Ltd
Current assignee: Toren Consulting Pty Ltd
Priority date: 1992-02-26
Filing date: 1993-02-12
Publication date: 2000-05-24
Anticipated expiration: 2013-02-12
Also published as: EP0627906A4; DE69328718D1; EP0627906A1; AU671979B2; DE69328718T2; AU3486693A; WO1993016673A1

Description

Field of Invention

Blister packs are now widely used for medicinal and food supplement tablets and capsules, whereby these tablets or capsules are contained between a normally transparent, flexible plastic sheet, thermoformed so as to define a plurality of pockets, with each pocket being just large enough to receive the shape of the individual tablet or capsule, and a flat aluminium foil, heat sealed to said plastic sheet.
The main advantage of this type of packaging is the extended shelf life, due to protection against oxygen and humidity, that it provides for these medicinal tablets and capsules, compared to conventional packaging in bottles and containers. With blister packaging, the tablet or capsule does not get exposed to external air and humidity until such time that the aluminium foil is broken. The aluminium foil is not supposed to be broken until just prior to the user ingesting the tablet or capsule.
In the case of conventional bottles and containers, all of the tablets or capsules inside that bottle or container are exposed to external air and humidity every time that the cap is taken off in order to take out just one of these tablets or capsules.
The second advantage of blister packs is the convenience to the user of being able to carry around in his or her pocket or handbag just one flat and light blister card of tablets instead of having to carry the whole bulky and heavy bottle. The need to carry tablets on one's person applies to many tablets, such as headache, anti-histamine, contraceptive, antacid, anti-inflammatory and heart tablets etc.
Whilst such blister packs provide a level of convenience and security to the user over loose tablets or capsules, in presenting a controlled dosage regime to encourage patient compliance, conventional pack formats have generally proved somewhat inflexible in adapting to variations in dosages between patients and have remained vulnerable to accidental damage and contents discharge. There have been pack proposals addressing these issues individually.
Thus, GB-A-2 223 741 is concerned with a tablet pack for dispensing variable dosages, by employing a matrix of tablet receptacles on a carrier, with markings dividing the receptacles into different daily dosage groups - enabling selectively variable tablet dosage dispensation from a common pack format.
US Serial No: 4,120,400 teaches a pill package with certain child-proof features, using a standard blister card mounting for pills. A plastic shield is slidably mated with the blister card to enable selective interlocking of card and shield. However, pill accessibility is not wholly precluded by shield locking.

Statement of Invention

The present invention provides a blister pack for tablets or capsules, impervious to humidity and oxygen, the pack comprising a flexible plastic sheet thermoformed to define a plurality of open faced pockets each pocket being shaped to receive an individual tablet or capsule, the open faces of the pockets being closed by a sheet of aluminium foil heat sealed to the plastic sheet, hinge means provided across the pack on a line about which the pack is substantially symmetrical, the two halves of the pack movable about the hinge between an open configuration in which a tablet or capsule can be removed from the pack and a closed configuration in which the area of aluminium foil of each of said halves faces the other whereby the aluminium foil is protected from accidental damage, removal of a tablet or capsule being possible only when the pack is in the open configuration, and resealable integrally formed fastening means provided to maintain the pack in the closed configuration, and the hinge means and releasable integrally formed fastening means being constructed and arranged to allow repeated opening and closing of the pack, characterised in that the hinge means consists of a thermoformed hinge groove with cuts extending parallel and directly adjacent to both sides of the groove, the depth of the groove and the lengths of the cuts being selected in relation to the characteristics of the sheet so that when the sheet is folded about the hinge, parts thereof on either side of the hinge will fold through 90° to lie flat against one another.
This configuration of pack inhibits accidental damage of pack contents, whether tablets, pills or capsules, when individual blister cards are being carried around in pockets, handbags, briefcases, glove compartments etc. Such damage occurs frequently with conventional known blister cards, when other hard objects such as keys, coins, lipstick, pen, comb, spectacles etc., come into contact with the individual blister card, punctures the frangible aluminium foil and thereby exposes the tablet or capsule to the external air, humidity and other contaminants.
Without restricting the full scope of this invention various features will now be described with reference to the accompanying drawings, not all of which have all the features of the invention, but in which:
Figure 1 is a plan view of a blister card with one creased or perforated hinge line which is not a feature of the invention but with two pairs of press studs.
Figure 2 is a cross-sectional view of the blister card and aluminium foil of Figure 1 before being folded.
Figure 3 is an end elevational view of the blister card and aluminium foil of Figure 1.
Figure 4 is a part cross-sectional view and part side elevational view of the blister card of Figure 1 after being folded.
Figure 5 is a plan view of a blister card with a thermoformed hinge which is not a feature of the invention, but with two pairs of inter-locking cuts.
Figure 6 is a side elevational view of the blister card and aluminium foil of Figure 5 before being folded.
Figure 7 is an end elevational view of the blister card and aluminium foil of Figure 5, not showing the thermoformed hinge.
Figure 8 is a side elevational view of the blister card of Figure 5 after being folded.
Figure 9 is a plan view of a blister card with one hinge line and two pairs of alternative inter-locking cuts. Blister pockets are not shown.
Figure 10 is a plan view of a blister card with one hinge line and one pair of alternative inter-locking cuts. Blister pockets are not shown.
Figure 15 is a plan view of a blister card with a thermoformed hinge which is also not a feature of the invention, but with key and groove fastening means.
Figure 16 is a side elevational view of the blister card and aluminium foil of Figure 15 before being folded.
Figure 17 is an end elevational view of the blister card and aluminium foil of Figure 15.
Figure 18 is a side elevational view of the blister card of Figure 15 after being folded.
Figure 19a is a plan view of a blister card with a thermoformed hinge, which is also not a feature of the invention, but with two key and groove fastening means, two pairs of opening tabs and four rows of blisters for tablets, each row holding seven tablets, one tablet for each day of the week.
Figure 19b is an end elevational view of the blister card of Figure 19a.
Figure 19c is a side elevational view of the blister card of Figure 19a before being folded.
Figure 19d is a side elevational view of the blister card of Figure 19a after being folded.
Figure 20a is a plan view of a blister card with tongue and cut-out fastening means.
Figure 20b is an end elevational view of the blister card of Figure 20a.
Figure 21a is a plan view of a blister card with a thermoformed hinge, which is also not a feature of the invention but with two key and groove fastening means, one pair of opening tabs and stiffening ribs along the straight edges and rounded corners.
Figure 21b is an end elevational view of the blister card of Figure 21a.
Figure 21c is a side elevational view of the blister card of Figure 21a before being folded.
Figure 21d is a side elevational view of the blister card of Figure 21a after being folded.
Figure 22 is a cross-sectional view through a thermoformed hinge where the hinge groove depth equals R, before folding.
Figure 23 is a cross-sectional view through the hinge of Figure 22, after folding.
Figure 24 is a cross-sectional view through a thermoformed hinge where the hinge groove depth equals R+H, before folding.
Figure 25 is a cross-sectional view through the hinge of Figure 24 after folding.
Figure 26 is a cross-sectional view through a hinge similar to hinge of Figure 24, but incorporating cuts on either side of the thermoformed groove, before folding and embodying the invention.
Figure 27 is a cross-sectional view through the hinge of Figure 26 after folding.
Figure 28 is a plan view of the hinge of Figure 26.
Figure 29 is a cross-sectional view through a thermoformed hinge where the hinge groove depth equals R+T before folding.
Figure 30 is a cross-sectional view through the hinge of Figure 29, after folding.
The blister card 1 shown in Figures 1, 2, 3 and 4 comprises a sheet of flexible plastic material with a plurality of thermoformed blisters or pockets 2, suitably shaped to receive either round tablets and pills or - elongate capsules of medication 3. The tablets, pills or capsules are placed into these pockets and then covered with the aluminium foil 4 which is heat-sealed to the plastic sheet, in order to hermetically seal the medication inside the pockets.
The creased or perforated hinge line 5, is not a feature of the invention but divides the blister card into two equal halves and enables the blister card to be folded, as shown in Figure 4. Two pairs of press studs 6 or 7 engage and thereby secure the blister card in its folded state. When the blister card is folded, the frangible aluminium foil is protected against any accidental puncturing by other objects.
Ribs 8 and 9 along the edges of the blister card can be thermoformed into the plastic sheet in order to give the blister card some additional stiffness and flatness.
Figures 5, 6, 7 and 8 show a blister card where instead of the above mentioned press studs there are a pair of inter-locking cuts 10 and 11 in the edges of the blister card parallel to the hinge line 12. The distance between the two cuts 10 is somewhat greater than the distance between the two cuts 11, so that when the blister card is folded and the edge between cuts 10 is pressed against the edge between cuts 11, the pliable edges will deform and inter-lock, thereby securing the blister card in its folded state, as shown in Figure 8.
The hinge 12 shown in Figure 5 is thermoformed into a slightly thinned out U-shape, not according to the invention, to facilitate the folding action.
One or more ribs 13 at right angles to the hinge line can be thermoformed into the plastic sheet in order to keep the blister card flatter before and after folding.
Figures 9 and 10 show two further examples of similar inter-locking cuts. There exist many different shapes of inter-locking cuts that will perform the same basic function of fastening the folded blister card.
Figures 15, 16, 17 and 18 show a channel shaped hinge 17 which is thermoformed and has thinned out walls to facilitate the folding action, again not a feature of the invention. A continuous groove 19 is formed along the three edges of one half of the blister card. Two keys 18, formed in the other half of the blister card, engage groove 19 with a light friction fit when the blister card is folded. Grooves 19 and 20 and keys 18 give the two halves of the blister card added stiffness and flatness. Tabs 21 facilitate opening of the folded card.
Figures 19a, 19b, 19c and 19d show a blister card where in order to secure the folded blister card, the two thermoformed keys 22 in one half of the blister card press into the two thermoformed grooves 23 in the other half of the blister card. When opening the folded blister card, it is necessary to overcome the frictional resistance of the engaged keys 22 and grooves 23. The two pairs of tabs 24 and 25 are located close to the keys 22 and grooves 23 in order to help overcome said frictional resistance with minimum distortion caused to the rest of the blister card. The ribs formed into the tabs 24 and 25 improve the finger gripping action of the tabs. Ribs 26 and 27 along the edges of the blister card are thermoformed into the plastic sheet in order to give the blister card additional stiffness and flatness. The blister card has four rows of blisters for tablets, each row holding seven tablets, one tablet intended for each day of the week. The days of the week are printed adjacent to the corresponding blisters on the aluminium foil that seals the blister card.
Figures 20a, 20b show a blister card where one half of the blister card incorporates a tongue 28 which engages the cut-out 29 in the other half of the blister card in order to secure the blister card in its folded state. Ribs 30 formed along the edges of the blister card give it additional stiffness and flatness.
Figures 21a, 21b, 21c and 21d show a blister card where two thermoformed keys 34 in one half of the blister card press into the two thermoformed grooves 35 in the other half of the blister card. The thermoformed ribs 36 and 37 along the straight edges and rounded corners provide additional stiffness and flatness to the blister card.
The basic function of folding the individual blister card and fastening it in its folded state, in order to protect the frangible aluminium foil against damage, in all these preferred forms of the invention, is identical.
It may be necessary for the end-user to open and close the blister pack many times. Therefore the hinge must be durable and, at the same time, it must not be too stiff, so as not to distort the blister pack during folding.
Thermoformed groove hinges can be formed into any plastic sheet, whatever the plastic polymer, e.g. polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET) etc. or any co-extruded combination of layers of these polymers. However, unless the blister pack itself is very rigid as a result of a deep blister or blisters and/or stiffening ribs, these thermoformed groove hinges could be much too stiff and cause unacceptable distortion of the blister pack when it is folded through 180°.
The geometry and function of a thermoformed hinge as developed in the invention are explained below:
The hinge groove 101 in Figure 22 has a depth that equals the radius R of the groove profile, before folding. The same hinge 102 in Figure 23, after folding through 180°, has reduced the radius of the groove profile from R to 1/2R, as a result of the folding. Provided the two sides of this blister pack are rigid enough, as a result of deep blisters 103 and/or stiffening ribs, the folded blister pack will not be distorted and the two folded sides 104 will be parallel and will make contact along their full length, with no gap between them. However, if the two sides of the blister pack cannot be made rigid enough, due to the shallow configuration of the packaged product, then this hinge will be much too rigid and the blister pack will distort during and after folding.
In order to weaken the hinge's resistance to folding, the depth of the hinge groove 105 can be increased from R to R+H, as shown in Figure 24. The hinge resistance to folding is weakened primarily because the plastic sheet is thinned out further in the deeper groove during thermoforming. However, as a result of the geometrical change in groove profile, when this blister pack is being folded, the corners 106 will touch before the 180° folding angle is being completed and before the two folded sides 107 have become parallel. When attempting to fold the blister pack by force beyond this touching point the blister pack will distort.
It is desirable to weaken the resistance to folding of the thermoformed groove hinge in order to prevent distortion of the folded blister pack and, at the same time, allow the two folded sides to be parallel and to make contact along their full length, substantially without gaps.
This is achieved by the incorporation of cuts 108, parallel and adjacent to the hinge groove 109, on either side of the groove, as shown in Figure 26 and Figure 28. These cuts weaken the hinge's resistance to folding and, at the same time, prevent the premature contact of the corners 106 at a folding angle less than 180°, as was shown in Figure 25. The two folded sides 110 will be parallel and will make contact along their full length, substantially with no gap between them as shown in Figure 27.
Should, however, the combined lengths of these cuts 108, L=L1 +L2 + L3, be too great, thereby weakening the hinge's resistance to folding by too much, then the contact of the two sides 111 of the folded blister pack will be delayed past the 180° and the blister pack will develop a gap 112, as shown in Figure 30 and the two folded sides 111 will, once again, not be parallel and will not make contact along their full length.
Increasing the combined lengths of cuts L and/or increasing the depth of the hinge groove will weaken the hinge's resistance to folding and vice versa.
Increasing the combined lengths of cuts L and/or reducing the depth of the hinge groove, as shown in Figure 29, where R+T<R+H, will delay the contact of the two sides of the blister pack beyond the folding angle of 180° and they will not be parallel and will not make contact along their full length, as shown in Figure 30.
Consequently, in an embodiment of the invention correct balance between the increased hinge groove depth and the combined lengths of cuts L, will result in the hinge not being too stiff and therefore will not distort the blister pack and, at the same time, the two sides of the blister pack will fold to 180° and be parallel and make contact along their full length.
To achieve the above mentioned balance, the type of plastic polymer and the sheet thickness must be taken into consideration. E.g. for 0,37 mm thick PVC sheet, groove radius R = 2, 75 mm, groove depth R+H = 4 mm and a hinge length of 82 mm, the combined cut lengths L = 22 mm, or L= 27 mm per 100 mm of hinge length.
The individual cut lengths L1, L2, ... Ln do not have to be equal. They can be varied in length to suit the size and location of the blisters on the blister pack, as shown in Figure 28, so as to improve flatness of the folded blister pack in its direction of length and width.
Any one of the various forms of hinge may be used in conjunction with any one of the forms of fastening means described above, and where a thermoformed hinge groove is used with cuts extending parallel and directly adjacent to both sides of the groove instead of the arrangements shown in Figures 1 to 21 then an embodiment of the invention is created.

Claims

A blister pack (1) for tablets or capsules, impervious to humidity and oxygen, the pack comprising a flexible plastic sheet thermoformed to define a plurality of open faced pockets (2) each pocket being shaped to receive an individual tablet or capsule (3), the open faces of the pockets being closed by a sheet of aluminium foil (4) heat sealed to the plastic sheet, hinge means (5) provided across the pack on a line about which the pack is substantially symmetrical, the two halves of the pack movable about the hinge between an open configuration in which a tablet or capsule (3) can be removed from the pack and a closed configuration in which the area of aluminium foil (4) of each of said halves faces the other whereby the aluminium foil (4) is protected from accidental damage, removal of a tablet or capsule (3) being possible only when the pack is in the open configuration, and resealable integrally formed fastening means provided to maintain the pack in the closed configuration, and the hinge means and releasable integrally formed fastening means are constructed and arranged to allow repeated opening and closing of the pack characterised in that the hinge means (5) consists of a thermoformed hinge groove with cuts extending parallel and directly adjacent to both sides of the groove, the depth of the groove and the lengths of the cuts being selected in relation to the characteristics of the sheet so that when the sheet is folded about the hinge, parts thereof on either side of the hinge will fold through 90° to lie flat against one another.
A blister pack as claimed in claim 1 wherein the said resealable integrally formed fastening means (6 and 7) consists in protrusion from one half of the sheet arranged to engage frictionally within cavities formed in the other half when the card is folded to maintain the card in a folded condition.
A blister pack as claimed in claim 1 wherein the said resealable fastening means (10 and 11) consists in cuts formed in the card constructed and arranged so that the edges thereof interlock when the card is folded to maintain the card in a folded condition.
A blister pack as claimed in claim 1 wherein the said resealable means is not an integral part of said plastic sheet.