CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is filed as a continuation-in-part of the US national part of International Application No. PCT/AU2010/000624 filed May 24, 2010 and claims priority under 35 USC 119 of Australian Patent Application No. 2009100522 filed May 28, 2009. This application is also filed as a continuation-in-part of the US national part of International Application No. PCT/AU2010/000623 filed May 24, 2010 and claims priority under 35 USC 119 of Australian Patent Application No. 2009202203 filed May 28, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The subject matter of this application relates to blister package stiffening and, more particularly, relates to enhancing the stiffness of a blister package and is more specifically concerned with stiffening a blister package having sealed blisters between which air can pass by way of ducts extending between them. 
         [0003]    Patients required to take prescribed medication doses at pre-determined times of the day are often provided with a blister package containing the doses. The package is constructed from a transparent blister sheet having blisters which individually contain the medication which the patient is required to take at a particular time on a particular day. The medication doses are held in the blisters by a frangible backing sheet, such as a thin metal foil. The blisters are transparent and have a relatively flexible front face so that finger pressure applied to the front face of a selected blister presses the doses inside it downwardly and against the backing sheet with sufficient force to cause the backing sheet to rupture. Such rupturing allows the doses to be released from the blister so that they can be collected for subsequent administration to the patient. 
         [0004]    German published patent specification No. DE 3607012 A1 discloses in FIG. 9 a combination of bonded-together layers for altering the outline shape of a rectangular blister package so that it will fit within a holder side-by-side with other blister packages of the same rectangular outline. The combination is created by several superimposed layers. 
         [0005]    The first layer (designated 1′ in FIG. 9 of the German publication) comprises a blister sheet formed with as line of blisters (2) each of which has a separate tablet sealed within it. The first layer has a rectangular outline but it is different from that required to fit side-by-side with other blister packages inside the holder. 
         [0006]    The second layer (designated 11) comprises a preformed, rigid PVC deep-drawing foil formed with depressions which individually accommodate the blisters of the first layer. It also has the same rectangular outline shape as the first layer and is bonded to it. 
         [0007]    The third layer is a carrier strip (designated 5) formed with a line of holes or cut-outs (7) through which the depressions of the second layer protrude. The third layer is of the same rectangular outline as other blister packages which are to fit alongside it within the holder. The surfaces of the third layer which are contiguous with the second layer are bonded to it and it is also formed with fingers arranged in opposed pairs and located between the holes. The purpose of these fingers are said to prevent the removal of one tablet from inadvertently rupturing the integrity of the neighboring sealed blister. 
         [0008]    A fourth layer (not shown in FIG. 9) is a covering foil through which a tablet located in a depression may be pressed out by hand. 
         [0009]    Elderly patients and those having relatively weak fingers sometimes have difficulty in exerting enough thrust on the front face of the blister to push the medication dose within the blister against the frangible backing sheet to rupture the backing sheet. This problem is partially caused by compression of a cushion of air held inside the blister resisting the downward movement of the front face of the blister. To overcome this difficulty we have created a new form of blister sheet which has pairs of parallel, narrow ducts communicating at their pairs of ends with respective blisters. An increase in air pressure inside one of the blisters is then dissipated by air flowing through the duct or ducts into one or more neighboring blisters which are preferably designed to expand slightly to absorb the additional air. This new form of blister sheet is described and claimed in our co-pending Australian patent-of-addition application No. 2009202203 filed on May 28, 2009 and in the corresponding International Application No. PCT/AU2010/000623, the entire disclosure of which is hereby incorporated by reference herein for all purposes. 
         [0010]    It is customary practice to stiffen and protect a blister package loaded with medication doses. This may be achieved by covering the exposed surface of the package from which the blisters protrude, with a stiff panel made of plastics, card or some other material which will enhance the stiffness of the package and which may also protect it from subsequent damage. The panel may also be marked with legend to denote the times of day and the days of the week in which particular blisters are to be opened. Such marking cannot be easily carried out on the blister sheet itself. 
         [0011]    In some situations, such as in nursing homes, it is preferable to trap a loaded blister package inside a stiff plastic folder so that it can be easily accessed by authorized personnel entrusted with the responsibility of administering the medication doses to a particular patient. However, if the patient is mobile it is usually more convenient to provide the patient with a light, cheap and easily-portable blister package which only has to be used once and is still strong enough to withstand normal day-to-day handling by the patient. 
       SUMMARY OF THE INVENTION 
       [0012]    In accordance with a first aspect of the subject matter disclosed herein there is provided an article of manufacture comprising a stiff planar sheet-form member for forming a stiffening panel, the sheet-form member being formed with cuts extending through its thickness and framing portions that, when removed, form an array of windows, whereby the stiffening panel that remains after removing said portions may be placed against lands on one face of a blister sheet with the windows receiving respective blisters of the blister sheet, and wherein the cuts extending through the thickness of the sheet-form member also form openings that communicate at opposite respective ends with respective windows, the openings being wider than they are long. 
         [0013]    In accordance with a second aspect of the subject matter disclosed herein there is provided a planar stiffening panel for placing against lands on one face of a blister sheet from which blisters protrude, the panel being formed with an array of windows for receiving respective blisters of the blister sheet, and openings communicating at opposite respective ends with respective windows, and wherein the openings are wider than they are long. 
         [0014]    In accordance with a third aspect of the subject matter disclosed herein there is provided blister package comprising a planar stiffening panel formed with cuts extending through its thickness and framing an array of windows, and a blister sheet having a major portion with first and second opposite faces and also having blisters protruding from the first face of the major portion, the major portion of the blister sheet having lands between adjacent blisters, wherein the blister sheet is positioned against the planar stiffening panel with the windows receiving the blisters and with portions of the stiffening panel in face-to-face contact with the lands of the blister sheet, the blister sheet includes at least one duct interconnecting two adjacent blisters, the stiffening panel has an opening that communicates at opposite respective ends with two adjacent windows that receive the two adjacent blisters respectively, and said opening accommodates the duct or ducts that interconnect said two adjacent blisters. 
         [0015]    In the illustrated embodiment of the invention the windows are arranged in perpendicular columns and rows to provide a rectangular array of windows. The windows are rectangular and the openings are formed between the shorter sides of the blisters flanking the two sides of the strip. 
         [0016]    Suitably the face of the panel destined to lie flush against said one face of the blister package, is covered with an adhesive layer protected by a flexible cover slip which can be manually peeled off the panel prior to panel being placed in its operating position against the blister package. The cuts extending through the panel do not pass through the cover slip so that when it is peeled off, portions of the panel remain adhering to the cover slip to expose the windows and openings in the panel. 
         [0017]    The panel may be made from stiff card or board or even plastic. Being planar it allows legend or other markings to be provided on its exposed face. As the panel can now lie flush against the sheet it can be firmly secured to it throughout its area. Contact between the panel and the sheet is thus uniform and not impaired in any way by the existence of the ducts extending between the blisters. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: 
           [0019]      FIG. 1  shows in plan a rectangular stiff card providing a panel having one side covered by a pressure adhesive layer protected by a manually-removable flexible cover slip which can be peeled off to expose the adhesive layer, the card being formed with thin lines of severance provided by cuts which extend through the thickness of the card but do not extend through the slip; 
           [0020]      FIG. 2  is a plan view of a stiffening panel as seen after the adhesive layer has been exposed by removal of the cover slip which takes with it adhering portions of the panel to expose the windows and openings; 
           [0021]      FIG. 3  shows an unloaded blister sheet having a rectilinear array of blisters and formed with pairs of parallel ducts which open at their ends into the cavities of respective blisters; 
           [0022]      FIG. 3A  is a vertical section through part of  FIG. 3  as indicated by, and in the direction of the arrows  3 A- 3 A in that figure; 
           [0023]      FIG. 4  shows the combination of panel and blister sheet which is formed when the panel is pressed down to adhere onto coplanar lands of the blister sheet which extends around and between the blisters; and 
           [0024]      FIG. 4A  is a vertical section through part of  FIG. 4  as indicated by, and in the direction of the arrows  4 A- 4 A in that figure. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  shows a rectangular stiff card  1  backed by a layer of a pressure-sensitive adhesive (not shown) which is covered by a protective cover slip (also not shown). The adhesive layer is pressure sensitive in the sense that when it is exposed to air by peeling off the slip, it will adhere to virtually any surface onto which it is pressed without being heated. 
         [0026]    The card  1  is cut by slits extending through its thickness and defining closed outlines  3  which define separate portions  4  of the card which are not required. When the cover slip is peeled off the back of the card to expose the adhesive layer, the unwanted portions  4  of the card remain adhering to the cover slip and are removed with it. The card then has the shape of the panel shown in  FIG. 2 . 
         [0027]    The removal of the separate portions  4  of the card leaves the panel with a rectangular array of windows  7  as shown in  FIGS. 2 and 4 . These windows are approximately rectangular and are arranged in seven horizontal rows and four vertical columns. 
         [0028]    Adjacent rows are mutually separated by strips  8  and the windows  7  in each row are partially separated from one another by pairs of opposed fingers  9  extending from the strips  8  to leave gaps  10  between their opposed ends. 
         [0029]    One end portion of the panel (the lower end portion seen in  FIGS. 1 and 2 ) has no windows  7  and provides a dedicated area for displaying personal details of a patient together with details of medication doses which a doctor has prescribed and which are to be contained in blisters  21  of a blister sheet  20 , shown in  FIG. 3 . The personal details and details of medication doses may be recorded on a self-adhesive label that is attached to the lower end portion of the panel. The blister sheet  20  has its lands between the blisters attached to the panel by the adhesive layer on the back of the card. The blisters protrude individually through the windows  7  of the array as shown in  FIG. 4 . 
         [0030]    The opposite end portion  11  of the panel  16  (the upper end portion seen in  FIGS. 1 and 2 ) is marked with a line  14  of small slits shown in  FIG. 2  to facilitate its folding into two parts  15  and  16  which can be folded together beyond the end of the blister sheet  20  to bring two holes  13  on the parts into registration with one another. Slits extending between the registering holes enable the panel with an adhering blister sheet  20  to be easily suspended from hooks when not required. 
         [0031]    The blister sheet  20  is shown in  FIG. 3  prior to being loaded with prescribed medication doses. It will be apparent that the four blisters  21  of each row communicate with one another through a pair of narrow ducts  22  as shown in  FIGS. 3 ,  3 A,  4 , and  4 A. The function of these ducts is to allow air to pass through them when one of the blisters is depressed by finger pressure so that its contents can be ejected through a frangible foil backing strip which adheres to the back of the panel. The foil backing strip seals the cavities of the blisters after they have been loaded with medication doses. 
         [0032]    It is important to observe certain parameters in the design of the card. The gap  10  should not have a length measured between two neighboring windows  7  greater than the distance separating a pair of opposed fingers  9 . If the length of the gap is greater than this distance, the resistance to air flow passing between neighboring blisters by way of the ducts will oppose the depression of a blister by finger pressure. It is also important that the duct wall is not salient with respect to the exposed surface of the card. The reason for this is that the pressure which must be applied to the surface of the lands of the card extending around and between the blisters must not result in the pressure also being applied to the external walls of the ducts. The effect of applying such pressure to the duct walls could be to reduce their internal cross-sectional area and thus impede the air flow through them during depression of a blister. 
         [0033]    It has been found empirically that the optimum number of ducts is two extending in parallel to one another between neighboring blisters. To have more than two increases costs of tooling and increases the risk of damage to the ducts during the cold sealing process when pressure is applied to the card. Also the resistance to air flow through the ducts can increase rather than decrease, when a given cross-sectional area for air flow is provided by more than two ducts each of a smaller internal cross-sectional area than the ducts of a two-duct arrangement. 
         [0034]    It has been found that the best results are obtained when the distance between neighboring windows is three millimeters, the width of the gap between a pair of opposed fingers is six millimeters, and the card thickness is slightly less than one millimeter. 
         [0035]    It will be appreciated that the invention is not restricted to the particular embodiment that has been described, and that variations may be made therein without departing from the scope of the invention as defined in the appended claims, as interpreted in accordance with principles of prevailing law, including the doctrine of equivalents or any other principle that enlarges the enforceable scope of a claim beyond its literal scope. Unless the context indicates otherwise, a reference in a claim to the number of instances of an element, be it a reference to one instance or more than one instance, requires at least the stated number of instances of the element but is not intended to exclude from the scope of the claim a structure or method having more instances of that element than stated. The word “comprise” or a derivative thereof, when used in a claim, is used in a nonexclusive sense that is not intended to exclude the presence of other elements or steps in a claimed structure or method.
A stiff planar sheet-form member is formed with cuts extending through its thickness and framing portions that, when removed, form an array of windows, whereby the panel that remains after removing the portions may be placed against lands on one face of a blister sheet with the windows receiving respective blisters of the blister sheet for stiffening the blister sheet. The cuts extending through the thickness of the sheet-form member also form openings that communicate at opposite respective ends with respective windows.