Envelopes – wrappers – and paperboard boxes – Paperboard box – Box material includes a coating or a nonpaperboard...
Patent
1983-10-26
1985-12-03
Moy, Joseph Man-Fu
Envelopes, wrappers, and paperboard boxes
Paperboard box
Box material includes a coating or a nonpaperboard...
229 45, 229 55, 220457, 220458, B65D 540
Patent
active
045561664
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid-tight cardboard barrel having a plastic film on the inner surface of the wall portion and bottom plate, whereby the plastic film on the wall portion forms a coating fastened substantially over the entire area of said wall portion. The invention also relates to a method and a device for manufacturing such a cardboard barrel.
BACKGROUND ART
A plurality of methods are previously known for making a cardboard barrel liquid-tight. One method is to provide the inner surface of the wall and bottom plate of the barrel with a plastic coating before joining the bottom plate to the wall portion. The bottom plate is hereafter mechanically joined to the cylindrical wall portion. This solutions suffers from the disadvantage of an unreliable liquid-tightness at the joint between the bottom plate and the wall because if the barrel during transport is subjected to bumps, a slit may be formed in the joint through which liquid is able to flow out of the barrel. The strength of the joint can be improved by welding the coatings the each other at the joint but because the thin plastic film is easily torn in connection with the deformation of the joint, is this sealing method neither very reliable. In this connection it is also to be noted that the upper and lower edge of the barrel are in general mostly subjected to bumps.
In addition to the above described barrel, barrels are known inside which a plastic bag is arranged which is secured to the barrel at its mouth only. The liquid-tightness of such a barrel in general remains satisfactory inspite of bumps because the deformations of the barrel do not directly affect the bag. However, barrels provided with a loose inner bag suffer from a plurality of disadvantages, wherefore they are not very commonly used. They are particularly difficult to fill and empty.
DISCLOSURE OF INVENTION
The object of the present invention is to provide a liquid-tight cardboard barrel, which is not sensitive to bumps. The cardboard barrel according to the invention is characterized in that the plastic film located at the bottom plate and abutting against it is loose with respect to the bottom plate and joins the plastic coating of the wall portion. Because the plastic film at the bottom plate is loose with respect to said plate, deformations at the lower edge of the barrel and relative movements between the wall and the bottom do not directly affect the sealing film, which thus in all likelihood will remain intact when the barrel is subjected to bumps. However, because the sealing plastic film is fastened to the wall of the barrel, the same problems do not arise in use of the barrel as in connection with barrels comprising a loose inner bag. In addition, it is to be noted that the connection point between the loose plastic film and the wall coating can be located inside the junction between the wall portion and the bottom plate at a short distance from said junction, due to which the tendency of the film to break is further reduced.
The invention also relates to a method for manufacturing a liquid-tight cardboard barrel, according to which method the inner surface of the wall portion and the bottom plate of the barrel is provided with a continuous plastic film. The method according to the invention is characterized in that, in order to provide the inner surface of the bottom plate with the plastic film, a plastic film disc having a diameter somewhat larger than the inner diameter of the barrel is pressed against the inner surface of the bottom plate, whereafter the edge of the disc is secured to the plastic coating of the wall portion of the barrel by welding. In a cardboard barrel so manufactured the film does not extend to the joint between the wall and the bottom plate, which is easily subjected to bumps, so that deformations of the lower edge of the barrel are not able to break it. The strength of the liquid-tight film is improved by the fact that the plastic film disc is not secured to the inner surface of the bottom plate so that the
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patent: 4061782 (1977-12-01), Baxter
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