This invention relates to a method and apparatus for packaging a material between upper and lower films by vacuumizing a space about the material therebetween.
Some of the known methods and apparatus of this type are shown in Japanese patent applications laid-open under Nos. 49-95782 and 49-111786 and Japanese utility model publication No. 48-3022. In any one of these methods and apparatus, a material or materials to be packaged are placed on a lower film or paper on a pedestal which is provided inside of a lower chamber to be movable upwardly and downwardly. The lower chamber has an upper open end which is adapted to be closed by a lower open end of an upper chamber with an upper film interposing between the open ends of the upper and lower chambers. The upper chamber has a heating means therein for softening the upper film by heat to make it expansible.
In such structure, after softening the upper film by heating, the pedestal is moved up while the interior of the upper and lower chambers are being vacuumized. Due to the upward movement of the pedestal, the material thereon contacts the lower surface of the upper film and then expands it upwardly until the peripheral portion of the upper film encloses the material and attaches to the lower film or paper on the pedestal by vacuum suction. After enclosing the material by the upper and lower films, the packaged material is taken out by lifting the upper chamber upwardly to separate from the lower chamber.
In these methods and apparatus set forth above, it has usually been required to place the material or materials to be packaged on the pedestal and also to remove the packaged material or materials from the pedestal by manual operations. Accordingly, it was quite difficult to put the above known packaging methods and apparatus into an automatic production line which automatically conveys the material to be packaged on the lower film and finally discharges the packaged materials as final products.
Another serious problem has been experienced in such known methods and apparatus when it was intended to package a frozen or refrigerated material. Because, when the frozen material is moved up against the upper film to expand the latter, the upper film is cooled immediately at the surface thereof contacted by the frozen material, so that small wrinkles are formed on the upper film of the packaged material to deteriorate the appearance thereof.
As an automatic vacuum packaging method and apparatus, it is known, as shown in U.S. Pat. No. 3,189,505, to provide a number of upper and lower molding members connected to upper and lower endless belts, respectively, in order that each of the upper and lower molding members can be moved synchronously with each other. When upper and lower films are supplied continuously into the packaging process or device with a material to be packaged being on the lower film at predetermined intervals, the upper and lower molding members contact the upper and lower films, respectively, and enclose the material between the upper and lower films and also between the upper and lower molding members. Thus, the materials placed on the lower film are enclosed by the upper and lower molding members successively in turn and conveyed forwardly by the movement of the endless belts, during which a vacuumizing process is carried out in each of the enclosed molding members in synchronization with a rotary valve connected to a vacuum source.
Such a known method and apparatus set forth directly above has an advantage that vacuum packaging can be made by continuously supplying the upper and lower films with the materials to be packaged being on the lower film at predetermined intervals.
However, due to the continuous operation, this method is very complicated, and also the apparatus for carrying out the method is vary large and expensive.