The prior art The present invention relates to a blister pack comprising a lower web in which cavities are provided, and an upper web which is tearably welded to the lower web, and which is punched-through at a distance from each cavity, said punching-through following a line which surrounds the cavity completely or partly.

Blister packs consist of a lower web in a relatively thick material which is configured with cavities or hollow spaces, and an upper web which is welded to the configured lower web, after a product has been filled into the cavities or hollow spaces.

Most frequently, the lower web is of PVC (polyvinyl chloride), but now and then also of APET (amorph polyester) or PP (polypropylene), and sometimes also with a layer of aluminium sheet laminated to the polymer material - this solution is frequently used if there are very high barrier require- ments.

On most upper webs, there is today a relatively hard aluminium sheet, e.g. in a 20 μ thickness, where the product (pill, chewing gum, etc.) may be pushed through. This solution, however, cannot readily be approved as child resistant.

There are also types with pure aluminium, which may be approved as child resistant, typically by providing an opening or snip where the upper web is not welded to the lower web.

The child resistance is ensured by using a somewhat tougher and option- ally thicker aluminium sheet which cannot be pushed through, for which reason the upper web has to be peeled off instead.

The child resistance is then provided by making a preform of the lower web on a sheet, centrally between four cavities, where the upper web is not welded, and through which a perforation line extends. As a result, a snip is produced, which may be pulled, whereby the material of the upper web may be pulled or peeled off the lower web, thereby giving access to the product in the cavity.

US 5,360,116 discloses a blister pack made of plastics material, where an upper web sheet is welded to a lower web in which cavities are provided. To facilitate tearing, weakened lines may be configured in the upper web, or sheets of various thicknesses may be used.

These means, however, have been found not to be sufficient to satisfy the requirements of child resistance.

The object of the invention

The object of the invention is to make a blister pack which may be approved as being child resistant (both according to the DIN standard and the ASTM standard), which also makes it possible to manufacture a blister pack which may be opened easily, e.g. for rheumatic individuals.

Thus, the invention relates to a blister pack comprising an upper web which is welded to the lower web by a lacquer or a polymer layer with a peel effect in a rim around the cavity. An area of the upper web therefore covers each cavity or hollow space and is welded firmly to the lower web in a rim around the cavity. The rim is de- fined by the circumference of the cavity and the line where the punching- through has been made. The width of the rim, together with the nature of the welded layer, decides the force which is necessary to remove or push the punched-through part of the upper web away from the cavity.

Preferably, the welded layer is a lacquer or a polymer layer. The welded layer must have peel effect, that is that the welded layer must allow the welded upper web to be pushed or pulled off the lower web and/or loosen itself continuously when the upper web is affected by a sufficiently great force.

The invention makes it possible to adjust this force in a surprisingly simple manner, thereby allowing blister packs to be manufactured where the application of force must be relatively great for child resistant blister packs. Con- versely, it is also possible to manufacture blister packs where the application of force must be relatively small for use by e.g. elderly people and/or rheumatic individuals.

In terms of production and owing to the strength of the blister pack, it is preferred, as stated in claim 2, that the upper web is fully welded to the lower web in the areas where no cavities are provided.

When, as stated in claim 3, the rim area around the cavity has a width of between 0.1 and 3.5 mm, the force to be applied to separate the layers and thereby to give access to the contents in the cavity may be adapted as needed.

A wider rim area will thus require more force than a narrow one. Finally, it is expedient, as stated in claim 4, to pass the punching-through or the perforations at the same distance from the cavity, viz. between 0.1 and 3.5 mm.

Blister packs may be provided where the punching-through is not performed all the way round the cavity, whereby the upper layer may remain more easily on the blister pack when it is opened. It is also possible to provide blister packs where the upper web is punched-through along a line which surrounds the cavity completely. Hereby, the entire upper web above the cavity may easily be removed. Typically, the upper web is made of PVC (polyvinyl chloride), PET (polyester), APET (amorph polyester), PP (polypropylene), PE (polyethylene) coated aluminium or PE coated APET. Typically, the lower web is made of PVC (polyvinyl chloride), APET (amorph polyester) or PP (polypropylene), and sometimes also with a layer of aluminium sheet laminated to the poly- mer material - in the event that the barrier requirements are very high.

The upper web may be made of a transparent material and/or with print, if so desired. The upper web may be of such a strong material that it cannot readily be pierced, but has to be peeled off the lower web.

The drawing

The invention will now be described more fully with reference to the drawing, in which

Fig. 1 shows a lower web,

Fig. 2 shows a sketch of a blister pack according to the invention, Fig. 3 shows an alternative blister pack according to the invention, and Fig. 4 shows the blister pack of fig. 3 with an open cavity.

Description of exemplary embodiments Figure 1 shows a lower web 1 configured with hollow spaces or cavities 2. The cavities 2 in the lower web have a circumference 3, as shown in the figure. In principle, the lower web 1 may be a lower web of the type which is used in the known blister packs. Figure 2 shows the lower web where it has applied thereto an upper web 4 according to the invention. Around the circumference 3 of the cavities 2, the upper web 4 has been subjected to a punching-through 5 of the upper web, so that a rim 6 is created between the circumference 3 and the punching- through 5. The rim 6 has applied thereto a welded layer, which holds the part of the upper web which is disposed within the punching-through 5 to the lower web, until it is subjected to a force which is sufficiently great to break the holding force of the welded layer, so that the upper web peels off, and the cavity 2 is opened. The width of the rim 6, together with the properties of the welded layer, decides how great a force is necessary to open the cavity 2.

Figure 3 shows an alternative embodiment of the blister pack according to the invention. The blister pack 10, too, consists of a lower web 11 with cavities 12. The lower web 11 has welded thereto an upper web 14, in which a punching-through 13 has been performed through part of the upper web 14 around the cavities 12. This means that the upper web 14 may more easily remain attached to the lower web 11 when the cavity 12 is opened. This is shown in figure 4, where the one cavity 12 in the blister pack 10 has been opened. The released piece of the upper web 17, which has peeled off the lower web 11 , remains attached to the lower web 11 along the edge 18. Hereby, it is easier to discard all the material from the blister pack, which can therefore be more environmentally friendly. As will be seen, there is a rim 16 around the cavity, along which rim 16 the punched-through part of the upper web 17 has been welded, until it has been peeled off by the opening of the cavity 12. The width of the rim 16 may be varied, whereby the force required to open the cavity may also be varied. By making the rim 16 sufficiently wide, the blister pack may be made child resistant, since a greater force is required in order to open the cavities in the blister pack when a relatively wide rim is used.