The shipment of fragile and delicate products and articles mandates the use of packaging which gives sufficient protection against shock, thermal changes, electric fields, moisture, abusive handling and other external influences. The use of plastic foam in a shipping container or carton to partially or wholly surround the packaged article has become widespread. Commercial and practical success has been found when the foamed plastics, such as polyurethane, wholly surrounds a packaged article, and various techniques have been used to position and form the foamed plastics within the carton. However, many of these methods have been found to be inadequate both in cost and time.
Early foam packaging developments suspended the article to be protected within a container in spaced relation to the walls. A foamable plastic was then introduced into the spaces between the container walls and object. The foamable plastic expanded, taking up the spaces between the container walls and articles. A variation of this method included the use of plastic bags, filled with foamable plastic which were then placed within the shipping container. The foamable plastic expanded within the bags and the expanding bags encompassed the object. The plastic bags formed a separation line which permitted removing the encapsulated object with ease.
These systems of packaging proved disadvantageous since the article to be encased had to be suspended within the container prior to encapsulation. To overcome the hinderance of suspending an article before encapsulation, a method, known as carton molding, was developed which formed the molded foamable plastic in the carton or container before the article was placed therein. U.S. Pat. No. 4,390,337 to Gately discloses the current, conventional process of producing synthetic foamed material into predetermined shapes at preselected locations inside a container or carton.
In the current and conventional method, a male mold is provided with an image conforming to the size and shape or sizes and shapes of the desired articles to be placed therein. A horizontal flap area consisting of two horizontal channels is incorporated into the mold to allow the formation of foam panels on two of the carton flaps to form a protective top covering once the carton is closed. A plastic sheet is placed over the mold to provide a surface on which the packaged object will rest once the foam is formed. A vacuum internal to the mold is applied to assist the placement of the plastic sheet and to secure the sheet to the mold. An open-ended carton is then placed over the mold with two of the lower end flaps in a horizontal position. The plastic sheet is folded back over the horizontal flaps to close the ends of the channels; the horizontal flaps are clamped securely to the mold; foam precursors are dispensed within the carton, and the top of the carton is closed and secured. When the precursors have foamed, the clamps are released and the finished box ejected from the mold.
This current and conventional process has achieved significant commercial usage and is decidedly advantageous over previously available methods. However, this process does have several disadvantages, foremost of which is the necessity of manually placing the plastic sheet in areas of the mold that are difficult to reach and then folding the plastic back over the horizontal flaps. Since the horizontal mold also requires a large amount of floor space, mounting such a mold on automated molding equipment is difficult. These disadvantages make full automation impractical. Further disadvantages of this horizontal molding include the requirement of a complex mold with restrictive channeling techniques designed to force the foam into the horizontal flap areas of the mold, the lack of control over foam densities in the flap areas and the impracticability of using poly tube materials.
The present invention overcomes these disadvantages and provides an even more advantageous process and apparatus which use a fully vertical mold where all carton flaps can be placed in a vertical position. The plastic sheet does not have to be doubled-up over the vertical flaps, and the lack of a horizontal channel also permits ease in the placing and tucking of a plastic sheet or a poly tube material over the mold by either manual or mechanized techniques. The fully vertical mold provides for gravity flow of foam into the flap areas of the mold with a better control of foam densities in flap areas. In addition, the overall mold is simpler and requires smaller mold construction techniques and less floor space making mounting on automated molding equipment practical with a better control of foam densities in flap areas. These advantages of the present invention lend this process to a greater degree of automation.
With the foregoing in mind, it is an object of the present invention to provide an efficient foam molding process and apparatus for the molding of foam inside a carton for the cushioning of an article to be placed therein which overcome the disadvantages of the currently used process.
A more specific object of the present invention is to provide a method of and an apparatus for foam carton molding using a fully vertical mold which provide full automation when placing the plastic sheet routinely over the mold and which simplifies the channeling requirements of the mold design.