JPS5924672Y2 - free standing bag - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-supporting bag formed by folding a single film or sheet into a bag shape and thermally welding the periphery.

Usually, the film or sheet used as the material for this type of bag is made of synthetic resin film or metal foil, and one side, which is to become the outer surface of the bag, is heat-welded with paper, metal foil, polyester, or nylon. A layer of a neutral substance is attached to the bag, and a layer of a synthetic resin such as polyethylene, which has good thermal weldability, is attached to the other surface which is to become the inner surface of the bag.

A pair of opposing sidewall sheets made of such a film or sheet has a bottom wall sheet integrally folded into a W-shape at the bottom, and both side edges of the sidewall sheet are part of the bottom wall sheet. Self-supporting bags constructed by heat welding together are known.

In such a self-supporting bag, the heat-welded parts on both sides have the same width as described below, and therefore, in the finished bag, the inner fold line of the bottom wall sheet and the inner border of the side-edge heat-welded parts If the lines intersect at a point and something is put into the bag and left to stand on its own or dropped, the bag has the disadvantage that stress due to the force exerted by the contents of the bag is concentrated at that point, causing the bag to easily break.

In order to eliminate this drawback, a bag has been proposed in which the inner boundary line of the heat-welded portion on both sides is recessed in an arc toward the outside of the bag in the area where it intersects with the inner fold line of the bottom wall sheet. (Refer to Utility Model Application Publication No. 52-101622).

In this bag, the presence of the arcuate recessed portion prevents excessive stress from concentrating at that portion, making the bag less likely to be damaged.

However, there is still a certain degree of stress concentration in the vicinity of such an arcuate recess, and the formation of the arcuate recess narrows the width of the heat weld in the vicinity, resulting in the problem that the heat weld itself becomes weaker. There is.

Therefore, the present invention aims to provide a self-supporting bag free from such problems.

According to the present invention, the width of the heat welded portion above the inner fold line of the bottom wall sheet is gradually reduced over a relatively long range from above to the position of the inner fold line, and The edges of the cutout at both longitudinal ends of the sheet,
The above-mentioned problem is solved by creating a shape that gradually approaches both side edges of the side wall sheet in the region close to the arcuate recess.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a self-supporting bag according to the present invention.

The bag, generally indicated by the numeral 10, is comprised of a pair of opposing sidewall sheets 11 and a bottom wall sheet 12, and has an opening 13 at the top end.

Both side edges 14 of the side wall sheet 11 are heat welded to each other with both ends 12a of the bottom wall sheet 12 sandwiched therebetween, as will be described in detail later, to form a side edge heat welded portion.

In a portion 14a where the bottom wall sheet 12 does not exist at the lower end of the both side edge welded portions 14, the side wall sheets 11 are directly welded to each other.

Furthermore, the lower edge of the side wall sheet [1] and the lower edge of the bottom wall sheet 12 are heat-welded to each other with a width defined by the portion 15, so that the bottom wall sheet 12 is always positioned above the lower edge of the side wall sheet 11. However, even when the contents are stored in the bag 10, the bottom wall sheet 12 does not come into contact with surfaces such as the floor or stand on which the bag 10 is placed.

The more detailed structure of the self-supporting bag 10, which has been outlined above with reference to FIG. 1, will be explained with reference to FIGS. 2 to 7.

The self-supporting bag 10 is made of material (see Fig. 2)
made from.

Material sheet) B is a pair of side wall sheets 11 and a bottom wall sheet 12.
It is a single sheet that is integrally connected.

The bottom wall sheet 12 has cutout portions 17 at both ends in the longitudinal direction (left-right direction in the figure), and the cutout portions 17 gradually become higher toward the center, and the highest portion 17
The point a reaches the extension line of the side edge of the side wall sheet 11.

One side of the material B is coated with a well-known heat-fusible material, such as polyethylene, and the other side is coated with a non-heat-fusible material.

The material sheet B shown in FIG. 2 is then folded as shown in FIG.

That is, the bottom wall sheet 12 is folded upward between the side wall sheets 11 along its center line 18, so that the material sheet hB has a W-shaped cross section, and the center line 18 becomes an inward fold line.

In this case, the heat-weldable surface is on the inside, and the non-thermal-weldable side is on the outside.

This folding is continued until the side wall sheets 11 are in close contact with each other as shown in FIG.

Next, as shown in FIG. 5, the lower end edge 15 of the side wall sheet 11 is subjected to a thermal welding process between a pair of hot platens at the dotted portion.

As a result, the lower end edge 15 of the inner surface of the side wall sheet 11 and both longitudinal edges of the inner surface of the bottom wall sheet 12 are welded to each other, but the outer surfaces of the bottom wall sheet 12 are not welded to each other.

Next, as shown in FIG. 6, the both side edges 14 of the side wall sheet 11 are subjected to heat welding treatment to form a special shape.

As a result, the inner surfaces of the side edge portions 14 of the side wall sheet 11 are welded to each other at the dotted portions and are integrated.

This thermal welding process is also performed by compressing the side edge portion 14 between a pair of hot platens, and at this time, the end portion 12a of the bottom wall sheet 12 located between the hot platens is also subjected to the pinching pressure. Same end part 1
Only the side of 2a facing the side wall sheet 11 has heat weldability, so it is welded to the side wall sheet 11, and the outer surfaces of the bottom wall sheet 12, which will be on the lower side when formed into a bag, do not have heat weldability, so they are welded to each other. There is no.

Details of the specially shaped heat welded portions 14 on both side edges of the bag are shown in an enlarged scale in FIG.

This heat welded portion 14 has a uniform width G in the vertical direction range shown by C and F in the figure.

However, in a relatively long range, the width gradually decreases, for example, almost linearly from G to H from the top to the bottom.

The position where the width becomes the minimum value H is the bottom wall sheet 12.
It coincides with the center line of the fold, that is, the position of the inward fold line 18.

In the lower range E, the width of the heat welded portion gradually increases from H to G.

The angle θ that the boundary line of the gradually increasing portion makes with the inward fold line 18 is preferably about 45° to 60°, preferably about 56°.

Note that the boundary between the range and E is configured to have a small radius of curvature R (for example, about 3.7 mm).

On the other hand, as described with reference to FIG. 2, the cutout portion 17 gradually becomes higher toward the central portion 17a, so that the edge of the cutout portion 17 extends from the bottom to the top as shown in FIG. As it goes, it gradually approaches the side edge of the bag and reaches part 17.
Matches the side edge of the bag at H.

This portion 17a is located directly below the inward fold line 18.

As already mentioned, the present invention employs a side edge heat-welded part 14 having a special shape in which the width gradually decreases and gradually increases toward the bottom at range and E, but this shape of the heat-welded part The heat welded part of the conventional shape, that is, the 8th
The reason why this is superior to the thermally welded portion 14A in which the width G is uniform over the entire length in the vertical direction as shown in the figure will be explained.

A bag having a conventionally shaped heat welded portion 14A shown in FIG.
When in use, it assumes the form shown in Figure 9 and stands on its own with the contents accommodated.

In this case, the bottom wall sheet 1-12 of the bag has a boat-like shape, and the weight of the contents on it is entirely at the bottom welded part of the bag, especially at the inward fold line 18 of the bottom wall sheet 12 folded inwardly and on both sides. The damage is concentrated at the point P where the inner boundary lines of the edge heat welded parts 14A and 14A intersect, and this part is likely to be damaged.

This tendency becomes especially noticeable when a large external force or severe shock is applied.

Such drawbacks are overcome by the specially shaped side edge heat welded portion 14 of the present invention.

As can be seen from FIG. 10, which shows the state in which the self-supporting bag 10 of the present invention is made to stand on its own with contents stored therein, the bag of the present invention has the following features:
At the part corresponding to point P in FIG.
Due to the special shape of No. 4, a recessed portion Pa that is not welded and curves outward in a substantially arc shape is formed, and a certain space is formed at both left and right corners of the bottom. The entire area around becomes the welded part.

Therefore, compared to the conventional case where the inward fold line 18 and the boundary line of the side heat-fused lid part intensively intersect at point P, the force applied to the bottom of the bag is not received at a point with no area. , since it is received by a long support surface, the force due to the contents is dispersed and the portion Pa is not easily damaged.

In addition, in the present invention, in particular, the inner boundary line 20 of the heat welded portion 14
(FIG. 7) descends toward the portion Pa in the area immediately above the inward fold line 18 of the bottom wall sheet 12 with the radius of curvature hardly changing, so that the contents of the bag are There is no place where stress is concentrated due to the force exerted downwardly toward the bottom of the structure.

Since there is a portion with a small radius of curvature R from the lower end of this relatively long inner boundary line 20 toward the inner boundary line 21 of the range E, here as well, compared to the conventional example, Stress concentration at the recessed portion Pa can be avoided.

This stress concentration can be avoided by making the recess Pa not a narrow recess at the entrance, but a recess with a wide opening over a large angle on the entrance side, creating a spacious space at both left and right ends of the bottom. It becomes certain.

On the other hand, in the present invention, the recessed portion Pa of the cutout portion 17
By shaping the closer portion to a shape that gradually approaches the side edge of the side wall sheet 11, the side wall sheet 11
It is possible to prevent the width of the inner surface of the side wall sheet 11 and the inner surface of the bottom wall sheet 12 from being directly welded at the side edges from becoming narrower in the region of the gripping part Pa, thereby increasing the strength of the welded portion of the side wall sheet 11 and the bottom wall sheet 12. can prevent a decline in

The self-supporting bag of the present invention described above can be manufactured continuously by the method shown in FIGS. 13 to 15.

First, as shown in FIG. 11, a continuous strip S is folded in half in its longitudinal direction and sent in the direction of arrow T, and slots 31 are punched at regular intervals along the fold line 30.

Next, the fold line 30 of the stonop is inserted by the folding member 32.
Reverse it to make the inner fold line 33, and create two new fold lines 3.
4 so that the strip S forms a W half cross section.

Next, as shown in FIG. 12, the hot platen 36 is applied along the fold line 34 to thermally weld the dotted portions, and then (i) the hot platen 37 in the direction across the IJ tube is used to seal the slot 31. Heat weld the dotted parts at the positions.

In this case, the shape of the hot platen 37 is the same as that of the heat welded part 1 shown in FIG.
It has a shape that is a symmetrical combination of two shapes of 4 on the left and right, and has recesses Pa on both sides.

Next, as shown in FIG. 13, the strip is cut as indicated at 39 at the center of the slot 31, resulting in a bag indicated at 10.

This bag is the same as the bag shown in FIG.

In addition, in the embodiment of the present invention described above, the recessed portion Pa
By forming the inner surface of the side wall sheet 11 and the bottom wall sheet 1
Since the width of the inner surface of the sheet 2 that is directly welded at the side edge may become too narrow in the area of the recess Pa, in order to prevent this, the cutout 17 of the bottom wall sheet 12 is cut out as shown in FIG. It is also possible to make the shape as shown in FIG. 16 so that the width of the welded portion in the portion 12C is increased.

As described above, according to the present invention, the shape of the side edge heat welded portion is recessed near the inward fold line of the bottom wall sheet, and the length at the upper part of the recessed portion is approximately the same. By making the width of the side edge heat-welded part gradually decrease toward the bottom, there is no concentration of stress near the recessed part, making it difficult to break. Furthermore, the welded part of the side wall sheet and bottom wall sheet due to the formation of the recessed part A self-supporting bag is obtained that can prevent a decrease in strength due to a decrease in the width of the bag.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an example of the self-supporting bag of the present invention, Fig. 2 is a developed view of the material sheet of the bag, Fig. 3 is a perspective view of the bag in the middle of folding, and Fig. 4 is a perspective view of the bag in the middle of folding. 5 and 6 are explanatory diagrams showing the position where heat welding is applied to the bag material sheet in the state shown in FIG. 4. FIG. 7 is an explanatory diagram of the shape of the side edge heat welded part, Figure 8 is a diagram showing the shape of the conventional side edge heat welded part, Figure 9 is an explanatory diagram when the conventional self-supporting bag is used, and Figure 10 is
The figure is an explanatory view of the use of the self-supporting bag of the present invention, and FIGS. 11 to 13 are sequential views showing the process of continuously manufacturing the bag of FIG. 1. 10... Self-supporting bag, 11... Side wall sheet, 12... Bottom wall sheet, 14... Side edge heat welded part, 15...・・Lower edge heat welded part, 17・
. . . Cutout portion, 18 . . . Center line (inward fold line) of bottom wall sheet 12, Pa . . . Recessed portion, 20.
21... Boundary line of heat welded part 14.

Claims (1)

[Claims for Utility Model Registration] 1. Two side wall sheets 11 facing each other, and a bottom whose both side edges are connected to the lower edges of these side wall sheets and folded between the both side wall sheets in an inverted V-shaped cross section. At both ends of the bottom wall sheet 12 in the longitudinal direction, a cutout 17 is formed inward from both side edges of the sidewall sheet 11, and over a width wider than the cutout width of this cutout, the sidewall Heat welding parts 14 are formed on both side edges of the sheet 11 so that the inner walls of the side wall sheets are directly welded to each other at the cutout part,
The inner boundary lines 20° 21 of the heat welded portions 14 on both sides are recessed in an arc shape towards the outside of the bag in the area where they intersect with the inner fold line 18 of the bottom wall sheet 12. In the upper part of the heat-welded part, the width of the heat-welded part 14 extends over a relatively long range from the top to the inward fold line 1.
8, so that the edges of the cutout portions 17 at both longitudinal ends of the bottom wall sheet 12 gradually approach both side edges of the side wall sheet 11 in a region close to the recessed portion Pa of the inner boundary line. A self-supporting bag characterized by having a shape like that. 2. Utility model registration claim 1, in which the portion of the heat-welded part 14 above the inner folding line 18 has an inner boundary line 20 that slopes almost linearly from above toward the inner folding line.
Free-standing bag as described in section.