JPS60143925A - Process for molding vessel with formed sheet and it mold - Google Patents

Abstract

PURPOSE:To uniformize the total thickness distribution of a avessel, causing the thickness of the vessel-bottom not to be reduced by stretching and deforming the foamed sheet with which a knurl part is in contact, while having applied knurl machining to the part of a male mold corresponding to the adjacency of the vessel-bottom surface. CONSTITUTION:The tip surface 10 (corresponding to a vessel bottom) and the partial width adjacent to the tip surface 10-side of a male mold 1 are knurl-machined 20, thereby increasing the friction resistance between said knurl part and a foamed sheet, and causing tis sliding not to occur. Accordingly, at the process where the made molde 1 is pushed into, the being in contact with the tip surface of the male mold 1 at the center of the foamed sheet 4, is not stretched and its wall thickness is not reduced. The peripheral portion of the foamed sheet 1 is mainly stretched and drawn into a female mold 3. When the male mold 1 is further pushed into the female mold 3, the foamed sheet 4 is stretched and deformed, causing said sheet to be in contact with the male mold 1 orderly from the tip surface 10 to the base side of the male mold by way of the tip side of a side surface 11. Because the part of the foamed sheet 4 with which the knurl part 20 is in contact has large friction resistance, the sheet is not stretched any more and its thickness is not reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and a mold for molding a container using a foamed sheet, and relates to a molding method that can improve the wall thickness distribution of a container to be molded, and a mold used in the molding method.

Conventionally, a method for forming a cup-shaped or bowl-shaped container from a foamed sheet such as expanded polystyrene sheet is to stretch and deform a heated foamed sheet along a mold corresponding to the shape of the container. Molding the container.

In particular, when molding is performed using only a male mold or a male mold and a female mold, the center tip of the male mold contacts the foam sheet first during molding, and the male mold is directly attached to the foam sheet. The foam sheet is stretched and deformed by pushing it to the side.

However, with the above dimensions, the part of the foam sheet where the center tip of the male mold is in contact is constantly stretched toward the periphery, and the wall thickness of that part, which becomes the bottom of the container, is thinner than other parts. turn into.

As a result, the strength of the container decreases, and the bottom surface may become dented due to the pressing force applied to the bottom surface of the container by the knots used to take out the product during trimming after molding, and the bottom surface may become deformed by pouring hot water during use of the container. , regarding the molding of containers, especially deep containers, we have developed a molding method and a mold that can improve the overall thickness distribution without reducing the thickness of the bottom of the container. , a method of molding a deep container by heating a thermoplastic resin foam sheet and causing it to expand and contract in a mold having at least a male die, and knurling at least a portion of the male die corresponding to the vicinity of the bottom of the container. The method is characterized in that the knurling portions are processed and the foamed sheet is brought into contact with the foamed sheet to cause the foamed sheet to expand and contract, thereby performing molding.

Next, embodiments of the present invention will be illustrated below with reference to the drawings.

First, the molding method to which the present invention is applied can be freely applied to known vacuum forming and other various sheet molding methods as long as it uses at least a male mold as a molding die.

In the illustrated embodiment, a pair of male and female molds are used to mold a beverage cup container.

The male mold 111 shown in FIG. 1 basically has the same structure as a normal molding die, and is formed into an elongated truncated conical shape corresponding to the inner surface shape of the cup container to be molded. There is.

The shape and dimensions of the male mold +11 can be freely changed depending on the container to be molded, but in this invention, the container (5) is one with a steep side drawing angle A of 15° or less as shown in FIG. applied, and the ratio H/D of depth H to opening diameter is 0.
It is preferable to apply it to deep containers of 7 or more, so the male type (
1) The side aperture angle A' is also within 15° and the height HJ
(corresponding to the depth H of the container) to the base diameter D' (corresponding to the diameter of the opening of the container) H'/D' put.

However, due to shrinkage after molding and other effects, the container (5
) and the dimensions of the male fi+ may not completely match.

And the tip of the male mold (1) (corresponding to the bottom of the container) QO
I and a part of the width of the side surface (11) near the tip surface (10) is knurled (A). The shape of this knurling part 0) can be any shape as long as fine irregularities are formed on one side. For example, the shape specified by JIS-BO951 (knurling) can be used. In the case of the figure, the knurled portion σl is formed at a knurling angle of 30° as defined in the above-mentioned JIS standard. However, the knurling angle may be 30 to 9 degrees, and either cross-cut or flat-cut knurling can be used. In addition, in the case of a flat sheet, it is preferable to form the side surface so that the direction of the knurling grooves is perpendicular to the generatrix direction in order to reduce the frictional resistance with the foam sheet, which will be described later. Become.

Further, although the module varies depending on the shape and dimensions of the container to be molded, a module of 0.2 to 0.5 is appropriate, and in fact, the smaller the module is, the better the result will be.

The side surface (11) of the male type il+ of the knurled part (A)
) is preferably 1/3 to 1/4 of the total height H' of the side surface (11), but it is preferable to form the knurled portion (a) over a wider width or over the entire height of the side surface. You can also do it.

In addition, in the bottom surface (lO) part, in addition to forming a low left part (2 hammers) on the entire bottom surface (lO), a knurling part (a) is formed only near the outer periphery of the bottom surface (lO),
), even if the central part is not formed with a knurling part, the practical effect can be sufficiently exhibited (see Fig. 6 a). As shown in Fig. 2, the female mold (3) used for Inserting the foam sheet in between is done in the same way as conventional molding equipment, but
Illustration is omitted.

A method for molding a container using the above molding mold +I+ +31 will be explained step by step.

First, the foamed sheet (4) used for molding is polystyrene, crosslinked polyethylene, or polypropylene.

Foamed sheets made of various other thermoplastic resins can be used, and in addition to a single foamed sheet, a foamed sheet laminated with a non-foamed thermoplastic resin film on one or both sides can also be used.

The foam sheet (4) is heated in advance to a predetermined temperature suitable for molding, and then held in the center of the male mold (1) and female mold (3) (see Figure 2), - not shown. However, the ends of the foam sheet (4) shall be fixed and held using an appropriate clamp mechanism.

Next, when the male type Fi+ is moved to the female type (3) side, the male type i
The tip surface (10) of l+ comes into contact with the foam sheet (4), and when the male mold (1) is pushed into the female mold (3),
The foam sheet (4) is stretched and deformed while being drawn toward the female mold (3) (see Figure 3).

At this time, since the tip surface (10j) of the female mold (1) is a knurled part (20), the frictional resistance between it and the foam sheet (4) is large, causing it to slip and curl. In the process of pushing the mold (1), the central part of the foam sheet (4) that contacts the tip surface (10) of the male mold il+ does not expand and its thickness does not decrease, and the foam sheet (4)
The peripheral part of is mainly stretched and drawn into the female mold (3).

Furthermore, when the male mold flll is pushed into the female mold (3),
The foam sheet (4) is subjected to elongation deformation while successively contacting the male die (from the tip surface (10) of I+ to the side surface Qt) from the tip side to the base side. At the point where the knurling part (20) contacts the foamed sheet (4), the friction j4 resistance becomes large, so that there is no further elongation and deformation, and the thickness P does not decrease.

When the male mold (Otori) is completely pushed into the female mold (3) side, the foam sheet (4) is molded into a predetermined container shape whose inner and outer mL are in line with the male mold (1) and female mold (3). (See Figure 4).

Thereafter, the mold is opened and the molded foam sheet (4) is taken out and trimmed to produce a cup container (5) (see FIG. 5).

On the inner surface of the cup container (clear) manufactured as described above, an uneven shape of the knurling may be formed at the place where the knurling part of the male mold (1) was in contact, but usually If the knurling is fine, it is hardly noticeable in appearance.

The shape of the container to be molded in the present invention may be, in addition to the illustrated cup shape, a bowl shape or an outer shape, and in addition to a cylindrical shape, a rectangular tube shape or other irregularly shaped tube shapes may be used.

However, the conditions regarding the aperture angle A of the side surface and the ratio H/D between the depth H and the opening diameter are applied in the same manner as those for the illustrated shape.

The method of this invention can also be applied to a molding method using the male mold il+ alone; however, in this case, the male mold (1
) It is necessary to form a vacuum suction hole in advance and adopt a so-called vacuum forming method.

According to the molding method of the present invention configured as above,
Among the foam sheets (4), the container (5) is the one that has undergone the largest elongation deformation and whose wall thickness is easily discernible. [A male mold (1
), it is possible to increase the frictional resistance between the tip end surface (10) of the male die (1) and its neighboring surfaces and the foamed sheet (4), and prevent the foamed sheet (4) from being excessively stretched. It is possible to prevent a decrease in the wall thickness around the bottom of the container (5) that would otherwise occur due to the lowering of the container (5).

If the bottom surface of the container (5) is sufficiently thick, the strength of the bottom surface and the strength of the entire container will increase, and the stability when loading the container will also improve. Furthermore, even when hot water is poured into the container, there is no need to worry about it deforming due to heat, as the wall is thick enough. Furthermore, when trimming the shaped container,
Even if the bottom of the container is pressed with a knotker, the bottom will not be dented or deformed because the bottom is strong.

Next, the central part of the foam sheet (4) that is in contact with the knurling part (4) is not stretched much, and the peripheral part is pulled in to improve the so-called pull-in rate, so it is molded from a raw rebound foam sheet of the same basis weight. However, the overall wall thickness or weight of the container increases, and the container performance, such as strength and heat insulation, improves.

The above-mentioned improvement in the drawing rate has a great effect on improving the elongation and shrinkage of the original fabric, that is, speeding up the molding cycle.

Therefore, it is an excellent molding method that can successfully mold deep containers, which have conventionally been difficult to manufacture and have many problems in finished quality.

In addition, as a mold for molding, the male mold fl+ has a knurled part -
Since only the forming process is performed, processing costs and equipment costs do not increase, and conventional molding equipment can be used as is, which is convenient.

Example 1, mold shape (male mold) Base diameter D' = 76 tx 1g Tip diameter = 46 wm d Height H' = 84g H'/D'-1,1 Aperture angle A' = 8635' Number of holes in 1 shot: 25 Knurling position Tip surface and side knurling of h = 25 wx from the tip direction mO, 2, cross stitch, 30°2, raw rebound foam sheet expanded polystyrene sheet width 640 m, Tsubo nail 350 f/, ! Thickness 2.0 m, foaming ratio 6x3, molding conditions Molding shot length 640, bait heating furnace temperature (atmosphere) 110°C, heating time 8.0 seconds Molding time 6.5 seconds Vacuum suction time 4.0 seconds Molding mold Setting temperature: 70°C Molding timing: Male mold advance 4, molding results Various tests were conducted on the container of the example molded under the above conditions, together with the container of the comparative example molded using the male mold without knurling. Shown in the table below.

/ In the table, the dent on the bottom surface during trimming was measured by pressing the bottom surface of the container with a knob and trimming.

The draw rate is a percentage of the basis weight of the original fabric. The lip strength is the strength in the circumferential direction at the container opening, and the top and bottom strength is the strength when the container is pressed in the vertical direction.

From the above table, it is clear that the performance of the containers manufactured according to the present invention is much better than the conventional ones.

[Brief explanation of the drawing]

The figures illustrate embodiments of the present invention; FIG. 1 is a perspective view of a male mold, FIGS. 2 to 4 are sectional views showing the sequential molding process, and FIG. 5 is a sectional view of a manufactured container. FIG. 6 is a perspective view of a modified example. fl+...Male type, (10)...Tip surface, ('')...
・Side surface, 0)...knurling part, (3)...female mold, (4)...foam sheet, (5)...container. Figure 2 Figure 4 0 Figure 5

Claims (1)

[Claims] 1. In a method of molding a container by heating a thermoplastic resin foam sheet and expanding and deforming it in a mold having a male mold, at least a portion of the male mold near the bottom of the container. A method for molding a container using a foamed sheet, characterized in that knurling is applied to a portion corresponding to the number, and the knurling portion is brought into contact with the foamed sheet to expand and contract the foamed sheet to perform molding. 2. Molding. 3. The method for forming a container according to claim 1, wherein the squeezing angle is within 15'. 3. The above patent for forming a deep container in which the ratio of the depth of the container to the opening diameter is 0.7 or more. Foamed seaweed according to claim 1.
A method of forming containers using 4. A mold for molding a container using a foamed sheet, which is a male mold for molding a container, and is knurled at least in a portion corresponding to the vicinity of the bottom of the container. 5. The mold for forming a deep container according to claim 4, wherein the constriction angle of the side surface of the container is within 15 degrees. 6. The foam sheet according to claim 4, wherein the ratio of the diameter of the male mold corresponding to the depth of the container to the diameter of the base of the male mold corresponding to the opening diameter of the container is 0.7 or more. mold for molding containers.