JPS6248563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In the production of double-walled lunch boxes made of thermoplastic resin, the present invention involves housing an inner box and an outer box in a mating mold consisting of an upper mold and a lower mold. The present invention relates to a method for manufacturing a double-walled lunch box in which resin is polymerized and injected into the gap between the joint between an inner box and an outer box and a mold, and the joint is fused and bonded.

Conventionally, double-walled lunch boxes for keeping stored food warm have been made by injection molding the inner and outer boxes of thermoplastic resins such as polyethylene and polypropylene, and then bonding the two with adhesive and applying ultrasonic waves. Alternatively, they are joined by welding using hot wire, etc.
In bonding methods using adhesives, surface treatment is performed before bonding to remove organic matter from the surface of the bonded part, either mechanically by polishing and degreasing, or chemically by chemical treatment, etc., to ensure an appropriate surface. In addition to requiring manufacturing work, the bonding process is mainly performed by hand, which requires skill, is extremely time-consuming, and has the disadvantages of a large amount of product variation.

Furthermore, it is difficult to achieve complete adhesion with adhesive methods that utilize ultrasound or skill, and it is difficult to ensure airtightness between double walls, making it difficult to use for food containers such as lunch boxes that are repeatedly washed and sterilized by boiling. I couldn't do it.

The present invention relates to a method for manufacturing a double-walled lunch box that eliminates these drawbacks.The method will be explained using an example of a school lunch box shown in the figure. The outer box 1 of the container main body is formed integrally by injection molding so that the upper end periphery 2 has a flange 3 that projects slightly outward, and the inner side forms an outer wall 4 of a heat insulating material storage space that is concave downward. . The inner box 5 of the container body has a flange 7 that protrudes outward so that the outer peripheral edge 6 coincides with and contacts the upper surface of the flange 3 of the outer box 1, and has an inverted U shape upward from the inside of the flange 7. An inner box upper wall section 8 having a similar shape is formed, and an inner box lower wall section 9 is formed as a concave portion by extending downward, and is formed integrally with the outer box 1 by injection molding from the same material. The space formed by the inner wall 10 of the upper wall 8 and the lower wall 9 is used as a container storage tank 11, and as shown in FIG. 3, the inner box 5 is inserted into the outer box 1 and the flanges 3 and 7 are overlapped. A space in the upper wall of the inner box and a communicating space formed between the outer wall 4 and the lower wall 9 of the inner box are defined as a heat insulating material storage chamber 12.

Next, the outer circumferential surfaces of the outer box 1 and the inner box 5 are in contact with each other except for the opening side, and the outer circumferential surfaces 13 of the flanges 3 and 7,
13' is inserted into the upper mold 14 and lower mold 15 which are fitted with a slight interval t, t', and the molds 14 and 15 are overlapped and pressed together as shown in FIG. Sprues 17, 17, . . . are provided at appropriate positions of the mold 14 or 15 within the joint space 16 formed by the gaps t, t'.
Then, a resin made of the same material as the inner and outer boxes 5, 1 and slightly higher temperature (approximately 80°C to 40°C) than the molding temperature of the boxes 5, 1 is injected to form the outer circumferential surfaces 13', 13 of the flanges 7, 3.
The double-walled bento box container body is produced by injection molding and demolding to form a double-walled lunch box container body, which is removably covered with a lid body 19.

In addition, there is a heat insulating material 2 such as urethane in the heat insulating material storage chamber 12.
0, the heat insulating material 20 is stored in the storage chamber 12 before welding the inner and outer boxes 5 and 1, or after welding, an injection port is provided at a suitable location on the bottom wall of the outer box 1 to fill the resin material. is injected, foamed and filled in the storage chamber 12, the injection port is closed, and the surface of the part is finished.

Next, to explain the effect of the present invention, as the standard of living has improved, the double-walled lunch boxes for school lunches that are entirely the same color are no longer popular.
Multi-colored containers with color variations have become required, but it is not easy to bond the individually manufactured parts of the container (for example, the inner box, outer box, etc.) and the cost is high. At the same time, it is difficult to join completely, and in containers that are repeatedly washed, boiled, and sterilized, such as lunch boxes, there are drawbacks such as water seeping into the insulation storage chamber from the joint or separation from the joint. Improvements were requested.

The present invention is a method for manufacturing a double-walled lunch box that eliminates these drawbacks, and involves injecting a resin material into the gap between the joint surfaces of the mold and the inner and outer boxes by injection molding, and fusing and bonding the joints. This makes it possible to bond the two together reliably and easily, and by using different colored resin materials for the inner and outer boxes and the adhesive parts, it is possible to produce multi-colored double-walled bento boxes. This invention has excellent practical effects.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views of an inner box and an outer box, respectively, according to an embodiment of the present invention, FIG. 3 is a longitudinal sectional view of the inner box and outer box stacked together, and FIG. 4 is a longitudinal sectional view of the inner box and outer box, respectively. FIG. 5 is an operational view showing the box and outer box inserted into the upper and lower molds and stacked one on top of the other; FIG. be. 1... Outer box, 3... Flange, 5... Inner box, 7... Flange, 1
3...Outer periphery of flange 3, 13'...Outer periphery of flange 7, 14...Upper mold, 15...Lower mold, 16...Joining space, 17...Gate, 18...Adhesion.

Claims (1)

[Claims] 1. In the production of a lunch box made of double-walled thermoplastic resin, an inner box and an outer box that have been molded separately are inserted into an upper mold and a lower mold, and the flanges of both are overlapped and pressure-welded, The bento box is formed through a sprue placed at an appropriate location in the mold in the joint space formed by the gap between the outer peripheral surfaces of the flanges of the inner and outer boxes and the corresponding walls of the upper and lower molds. Injecting thermoplastic resin at a temperature of 30 to 40 degrees Celsius higher than the temperature to fuse the joints of the outer and inner boxes, as well as inserting insulation into the insulation storage chamber formed between the outer and inner boxes. A method for manufacturing a double-walled lunch box made of thermoplastic resin, characterized by filling.