Patent Application
20080045392
The present invention relates to a method of manufacturing food containers or covers formed of vegetable fiber material, more specifically, to a method of manufacturing the food container or covers formed of the vegetable fiber material commercially at low cost.
Conventional food containers for containing food, such as lunch boxes or trays, are made of plastic materials like foamed polyurethane and so on. However, since the plastic materials have a problem in disposing them after use, vegetable-fiber-made food containers are strongly required in view of environmental conservation.
However, there has been a problem in manufacturing the vegetable-fiber-made food containers by die molding process in that only shallow containers with insufficient strength could be manufactured. Further, in the case of the containers made from pulp board, there has been a problem of costly manufacturing, since the containers are so manufactured that cuts are formed at four corners, sidewall pieces are erected, edges of the sidewall pieces are brought into superposition to each other to apply bonding agent, and the bonded portions are manually fixed. As a consequence thereof, the vegetable-fiber-made food containers are not widely distributed comparing to the other food containers, e.g., cheap trays as presently sold in supermarkets.
In addition, paper-made containers that have a number of bellows-like wrinkles formed at the corner portions and the surface is coated with film have also been known. However there has been a problem of extremely expensive cost.
Meanwhile, with regard to paper as vegetable-fiber-made material, the natural forest including the virgin forest is to be deforested for raw material of paper. However, it is a current issue to deforest the natural or virgin forest not only from view point of natural ecosystem where various animals inhabit but also from local environmental disruption view point.
An object of the present invention is to provide a method of manufacturing a vegetable-fiber-material made food container which has a practical strength and can be manufactured commercially at low cost.
Another object of the present invention is to provide a method, considering a problem as to a global environment, of manufacturing the vegetable-fiber-material made food container at low cost, capable of reducing an amount of pulp to be used therefor.
The above stated objects can be achieved with the present invention by employing the steps of: forming a board of a predetermined size from at least one kind of material selected from the group of pulp and vegetable fiber material other than pulp; coating either of front surface or back surface of the paperboard article with thermoplastic resin having a heat sealing property;forming foldout pieces for connecting adjacent sidewall pieces at four corners of the paperboard article; and forming the food container or cover by hot-pressing the paperboard article thus obtained between a pair of male and female press dies; wherein one pair of the sidewall pieces opposed to each other is configured to be erected ahead of the other pair of the sidewall pieces opposed to each other; the V-shaped foldout pieces include a V-shaped foldout piece shorter than portions that are adjacent to both side portions on the foldout piece, and the V-shaped foldout piece is overlapped or stuck to an adjacent one side of the foldout piece or sidewall piece.
It is preferable to form the foldout portions for connecting so as to be bonded with the sidewalls in a state that the foldout portions are folded uprightly. It is also preferable to form the foldout portions to be substantially V-shaped to bond in overlapping manner with the sidewalls after folding at the center of the V-shape to form a pyramidal shape which collapses to put the both sides together.
In this case, a notch is formed at the top end of the foldout portion on the abutting side of the same against the one sidewall in overlapping manner for bonding, after the substantially V-shaped foldout portion is folded at the center thereof in a pyramidal shape, so that the rear surface of the other side of the foldout portion is directly abutted for bonding against the front surface of aforementioned one sidewall.
Moreover, especially in the case where to fold up the foldout portion in a smaller angle below 90 degrees, it is preferable to form the foldout portion for connecting in substantially V-shape and fold it as V-shape to bond in overlapping manner with the sidewall. In this case, a notch is formed at the top end of the substantially V-shaped foldout portion so that the front surface of the sidewall with which the foldout portion is bonded in overlapping manner and the rear surface of the other sidewall interposing the notch therebetween are abutted to be bonded together. In the present invention, coating of thermoplastic resin having heat sealing property on the front or rear surface only can perform bonding the corner portion effectively.
Such an arrangement that a protruded portion is formed at one of the opposing sections of an recess perimeter of the female die so that the pair of opposing sidewall pieces placed on the protruded portion is erected earlier than the other pair of the opposing sidewall pieces can make it possible to manufacture food containers commercially at low cost, four corners of containers being attached together through the hot press process using dies.
In a case of manufacturing the container with lip sections, the opposing protruded portions are configured so as to be away from the concaved periphery of the female die at least by a distance corresponding to the lip sections of the container to be formed.
Before the pressing process, if one pair of the opposing sidewall pieces, which are arranged to be erected prior to the other pair of the opposing sidewall pieces, is bent, conventional dies can be employed to manufacture the container. However, when considering productivity of the manufacturing method, the above stated arrangement will be more preferable to produce the container.
It is preferable that the pulp and at least one kind of the vegetable fiber material other than the pulp are made of mixture of the pulp and the vegetable fiber material other than the pulp in order to minimize global environment destruction due to deforestation. To minimize cost, it is preferable to use wastepaper(pulp) alone.
It is preferable that the vegetable fiber material other than the pulp be made of reed, sugar cane or kanaf.
It is preferable to employ polyethylene or polypropylene as the thermoplastic resin having the heat sealing property according to the present invention.
Next an embodiment of the present invention is described.
The present invention is composed of the following processes.
(1) The paperboard of the predetermined size is formed from one or more kinds of pulp and vegetable fiber materials other than the pulp.
(2) Thermoplastic resin having the heat sealing property is applied to the paperboard.
(3) Folding lines are formed on the aforementioned board.
(4) Thus obtained paperboard is subjected to the hot press process using a pair of press dies, male and female in order to form the food container.
The process (1) can be performed by a known method of manufacturing the paperboard from pulp. More specifically, the paperboard is obtainable through the processes that pulp suspended in water is subjected to a sheet-forming process, followed by a water-squeezing process and drying process. The paperboard thus obtained is cut into developed shape of a container or a cover thereof to be formed. It is preferable that the paperboard contain water proof agent.
As the vegetable-fiber-made material other than the pulp used in the present invention, it is preferable to use reed, sugar cane or kenaf. More specifically, using the reed is preferred since it imparts excellent strength to the resultant container.
In the present invention, it is preferable to use a mixture of the pulp and the vegetable fiber material other than the pulp in order to minimize destruction of the global environment due to the deforestation.
As to the proportions of the pulp and the vegetable fiber material other than the pulp, it is preferable that the vegetable fiber material other than the pulp be between 20 and 80 wt %, more preferably between 30 and 60 wt %. The less addition of the vegetable fiber material, the less effect in protection of the global environment, while the more addition of the vegetable fiber material, the less strength and the more tendency of abruption of the bonding section.
The process (2) in which the thermoplastic resin having the heat sealing property is coated onto the paperboard may be done after a formation of the cuts or may be done before the formation of the cuts; however, the coating process is done before the formation of the cuts in the present embodiment. The thermoplastic resin is applied to either surface, front or rear, of the paperboard. If the thermoplastic resin is applied to both surfaces, paperboard sticks to a die. In addition, the thermoplastic resin is preferred to be applied to the surface on which the food is placed. The reason for applying coating on the surface on which the food is placed is that the coating prevents juice or the like from infiltrating into the container. As the thermoplastic resin, it is preferable to use especially polyethylene or polypropylene. Still, when you complete a film on the container surface, you had better coat it on the container back side.
A content of the thermoplastic resin differs depending on the kinds of the thermoplastic resin. In particular, that content is a range between 2 and 10% with respect to a mass of the paperboard, more preferably, between 3 and 6% with respect to the mass of the paperboard. Here, the “content” is represented by a percentage of the “mass of the heat sealing agent to be applied to the paperboard” with respect to the entire mass of the paperboard of which one surface is applied with the thermoplastic resin.
The foldout line in the process (3) is preferably formed by a blanking die. That is, the folding lines between the bottom and the side, the side and the foldout portion, and the like are formed by pressing a paperboard placed on a blanking die having projected lines thereon, whereby the folding lines are formed. As a matter of course, other means may be applicable to form the folding lines.
The sidewalls (side plane pieces) 3a, 3b, 3c and 3d are provided consecutively with the bottom plate 1 via the folding lines 2a, 2b, 2c and 2d. The adjacent sidewalls 3a/3b, 3b/3c, and 3c/3d are connected with the foldout portions 4a, 4b, 4c and 4d via the folding lines 5 and 6.
The foldout portions 4a to 4d are formed in substantially V-shape and a folding line 7 is formed at the center of the V-shape so that the folding line can be folded towards inside of the container in a pyramidal shape. The foldout portions 4a to 4d are composed of a long substantially V-shaped foldout portion 8 and a short substantially V-shaped foldout portion 10 having a notch 9 formed at the upper top thereof.
Since the above mentioned food container is coated with the thermoplastic resin having the heat sealing property only on the front surface, the long substantially V-shaped foldout portion 8 and the short substantially V-shaped foldout portion 10 are not bonded to fix unless the notch 9 is formed. In the above embodiment, since the notch 9 is formed, the top of the long substantially V-shaped foldout portion 8 and the sidewall 3c are bonded, and consequently the long substantially V-shaped folding portion 8 and the short substantially V-shaped folding portion 10 are fixed.
The lip portions 13a, 13b and 13c are provided on the top end of the sidewalls 3a, 3b and 3c via the folding lines 11a, 11b and 11c, and the sidewall 3d is provided with a cover 14 via the folding line 11d.
In
As described above, the short V-shaped piece 10 is bonded to the front surface of the sidewall 3c, and the rear surface of the long V-shaped piece 8 is bonded to the front surface of the sidewall 3c. If the notch 9 is not provided, pieces 8 and 10 are not bonded to any part because the rear surfaces of pieces 8 and 10 are not coated with polymer.
In
At the top end of the substantially V-shaped foldout portions 4a′ and 4b′, the notches 15a and 15b are formed. The long front surface part than foldout portion of the sidewall on which the folding portion is overlapped for bonding thereto and the rear surface of the other sidewall interposing the aforementioned notch are arranged to be abutted for bonding.
In order to form the food container by means of a pair of hot press dies consisted of the male die and the female die in accordance with the process (4), one of the pairs of the opposing sidewall pieces of the paperboard on which cuts are formed as illustrated in FIGS. 1 to 2 is erected prior to the other pair of the opposing sidewall pieces and the paperboard thus formed is placed in the female die to be subjected to a hot pressing process by the upper male die in order to form the container, and simultaneously, the paperboard is subjected to the heat sealing process If the sidewall pieces are preliminary erected by means of a paper foldout machine, conventional press dies can also be utilized to form the container.
In
In the above-mentioned embodiment, thermoplastic resin having a heat sealing property is coated only on the front surface or rear surface of the paperboard. In the case the face is coated, the female die is heated, whereas in the case the rear surface is coated, the male die is heated. Such process helps to avoid the paperboard from adhering to the die.
If upper parts than the short V-shaped piece 10′ are folded back by pressing the container with outwardly spread opening portion formed as described above by means of the female and male dies, the lip portion 13 can be easily formed. If the V-shaped piece 10′ is made longer, and the upper parts are folded back together with V-shaped piece 10′, there occur the cases where many wrinkles may be produced, or they may be broken, with the result that a fine lip portion 13 can not be formed.
In the above-mentioned embodiment, the lip portion 13 has semicircular cross-sections. This is because ring-shaped protruding lines with semicircular cross-sections are provided around the perimeter of the recess at the top level of the female die.
The paperboard illustrated in
Accordingly, the pair of the opposing sidewall pieces 3b, 3d (not shown) is erected prior to the other pair of the opposing sidewall pieces 3a, 3c, and then the container can be manufactured in a single step by a complete fitting and the hot pressing process. Note that, as shown in
In order to form the lips 12c′-13d′ on the upper edge of the container, as shown in
Manufacturing of containers shown in
A cover 14 can be formed with the container of the present invention. In the case of forming the cover, the cover may be formed with the sidewall piece (preferably with either one of the sidewall pieces 3, 3′) as shown in
As shown in
The food containers manufactured by the method according to the present invention are not limited to, but are suitable for use as lunch boxes, fermented soybeans containers, trays, covers of the lunch boxes, and the like.
According to the present invention, the food container formed of the vegetable-fiber-made material and having practical strength can be produced commercially at low cost; therefore the container according to the present invention is sufficient enough as an alternative to the food container made of plastic, resulting in remarkably contributing to the environment protection.
Moreover overlapped bonding after cutting the material and coating the thermoplastic resin having heat sealing property only on the front surface causes liquid penetration from the cut surface of bonding portion at the corner, resulting in leakage and seeping. On the contrary, the container according to the present invention does not have such concern since there is no cut surface at the corners.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-183903 | Jun 2005 | JP | national |
This is a continuation-in-part of Ser. No. 11/472,682 filed Jun. 22, 2006.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11472682 | Jun 2006 | US |
| Child | 11823282 | Jun 2007 | US |
