DE3047091A1 - Injection moulded plastic canister - where side extensions of open preform are remoulded and bent inwards to form base - Google Patents

Abstract

A standard capacity plastic canister preform, with four sides and their extensions which are bent over through 90 deg. to form the base, has a projecting rib on the outer faces of each injection moulded side; this rib is roughly triangular in section, its one face extends the outer face of the side after bending through 90 deg., the corner of the triangle forms the outer edge and the remaining area of the triangle forms a further part of the final base. Low cost, minimal internal and external radii at base corners and hence (1) minimal loss of capacity and (2) max. stability (esp. important with standard higher capacity canisters), no diminution in thickness at base corners.

Description

PLASTIC CONTAINERS, IN PARTICULAR CANISTERS

The invention relates to a container blank according to the preamble of the main claim.

Containers of this type have - as is usual with canisters - a very specific volume. They also have a very specific shape, most of the time is right flat. They are either made of sheet metal as deep-drawn ones Parts or in the injection molding process or in the blow molding process or in the centrifugal casting process etc.

The known containers have the following disadvantages: a) Even sheet metal canisters have transition radii between the side walls and the bottom wall. The transition radius - Which is even larger in containers made of plastic, especially if they are made by blow molding or centrifugal casting - given away Volume that is no longer available to the container. This brings the designer in difficulty, because the gross volume, which the container including any existing Handles and pouring spout occupies should, if possible, be equal to that Be net volume.

b) If e.g. an L-canister or 10 L-canister falls over, then will moving relatively small masses. But if a 20L or 30 L canister falls over, this can have significant consequences. These containers have a significant Height, a not so great width and a very much smaller depth. if they fall over, then they fall sideways because they are the most unstable in this direction are. This falling over is favored by the radii mentioned above because they the outermost area by about 20% of the canister depth inwards laid, whereby the canister depth dimension is the smallest anyway.

c) When deep drawing the sheet metal, but even more so with plastic blow molding, in centrifugal casting, etc., these radii are the places with the smallest Material thickness. This is bad in many ways: In the area of the floor it will the container is the most stressed. But it is precisely there that the material is the thinnest. If the containers are used as petrol cans, certain minimum wall thicknesses must be met must be observed so that the diffusion density of the container is maintained. Many Test regulations in different countries prescribe a minimum wall thickness. You can help yourself by overdimensioning other walls according to their thickness, which means Material is consumed and the container also becomes heavier.

The object of the invention is to provide a way by which the above Disadvantages can be avoided cheaply and practically.

This problem is solved according to the characterizing part of the Main claim.

One can refer to the technique according to the German patent application P 30 08 737.7 (U.S. patent application, my file 51 754, Canadian patent application , my file 51 755). According to this process, the blank is initially injection molded with its side walls including the upper part and the bottom is then made by turning an area that protrudes beyond the side walls.

The measures according to claim 2 are particularly important because straight with canisters, the question of the optimal floor space plays a major role. For example they must not start to slide if they are on an inclined plane specific inclination. In addition, this is the case with these canisters Diffusion tightness problem if they are used as a petrol can.

Due to the features of claim 3, the Kpp risk is set straight down in the direction in which such a container such. B. a canister on most likely to tip over.

The features of claim 4 achieve that the triangular surfaces after turning the wall areas protruding over the side walls are flat and lie in the alignment of the side walls or that part of the floor on which the canister is standing.

The features of claim 5 achieve those mentioned above Advantages along the entire length of the side walls.

The features of claim 6 create one in advance intended accumulation of material the amount of material which ißung for bottom seam welding is provided. The containers are sometimes also at this bottom seam weld Thinnest after their production, thus the weakest material and susceptible to it the diffusion of gasoline, etc.

The invention will now be described on the basis of preferred exemplary embodiments described.

In the drawing: FIG. 1 shows the lower area of the blank with Section through the side walls in a first processing phase, FIG. 2 is a view similar to FIG. 1, but after a second processing phase, FIG. 3 shows the bottom view to Fig. 2, Fig. 4 is a significantly enlarged area around the strip of material after a first step and, in dashed lines, after a second step.

A 20 L Knnisicr hat 1001 it # in Figure 1 urld 2 not shown above The usual handles and the pouring spout. Such a canister is for example 47 cm high, 34 cm wide and 16 cm deep. The blank shown in Fig. 1 accordingly Side walls 11, 12 of corresponding length, transverse walls 13, 14 and over these side walls protruding wall areas, the wall area 16 being the side wall 11, the wall area 17 the side wall 12, the wall area 18, the transverse wall 13 and another not wall area shown extend the transverse wall 14. The wall areas be the straight continuations of the side walls or transverse walls, as shown in Fig. 1 shows, or it can also be funnel-shaped something after run outside, as the older application shows. After injection molding or else can also be used simultaneously with it on the side walls, transverse walls and wall areas additional layers 19 on the outside 6nd / or additional layers 21 are applied.

In the transition area between the side walls and the transverse walls on the one hand and the wall areas on the other hand is a strip of material protruding outward 22, 23, 24 are provided. Dr & iecks-Quersc, for example, have all of these material bars hnitt with an upper concave triangular surface 26, which after a point 27 in a lower concave triangular surface 28 merges. The triangular surface 26 is wider than the triangular surface 28. As Figure 1 shows in conjunction with Figure 3, the range Material do 22, 23, 24 not up to the radii 29, under which the side walls 11, 12 and the transverse walls 13, 14 meet. Rather, they stop before the radii 29.

Just in front of the lower edge 31, 32 of the wall areas 161 17 is one outwardly protruding accumulation of material 33, 34 is provided, which has the shape of a has protruding semicircular bar.

In the further processing of the blank according to FIG. 1, it becomes - as sometimes happens with blow-molded blanks - into another heated processing mold set after the plastic of the injection molded Blank has been brought to plasticizing temperature. Be in this form then the lower wall areas 16, 17, 18 (and also the one parallel to the wall area 18, wall area not shown in Fig. 1) folded inwards to the floor to shape.

The wrapping and squeezing in the blow molding process usual way happens in the invention in the area of the material bars 22, 23, 24, so that this after bending in with its tip 27 the outer standing edge of the canister, which is on the outside. The wall areas 16, 17, 18 (and the wall area not shown) in the area of the accumulation of material 33, 34 pinched off, so that only a slight thickening 35 remains.

Depending on the shape of the triangular surfaces 26, 28 and the tip 27 is obtained one under different contact areas in the edge area. Since the triangular surfaces 26, 28 have unequal widths, a design according to FIG. 4 is pronounced form sharp, non-slip edge 36. How concave the triangular surfaces 26, 28 be must be found in the experiment. If they are concave, they will pull out after bending definitely right now.

If the width of the triangular flaps 26, 28 is the same, then one obtains instead of the pronounced edge 36, a slightly larger footprint.

It should be noted that the bottom of the canister is overall after is curved on the inside, as shown in FIG. 2, so that, if possible, only the very outer ones Areas contribute to the stand space.

It is not necessary for the material strips 22, 23, 24 to be continuous to train.

Rather, it is sufficient if these are provided in sub-areas, so that more or less numerous feet 37 are formed, the surface of which is shown in FIG 3 is dotted.

Claims (6)

Patent claims: 1. The container blank made from plastic with four side walls and over ½ the side walls protruding wall areas that later use an approximately right-angled bend to form the floor, characterized in that in the transition area from side wall to floor-wall area beyond the outer surface of the injection molded side wall and floor-wall area a plastic material strip protrudes, the approximately triangular cross-section of a shape has, in which the one triangular surface after a right-angled turn in continuation the outer surface of the side wall, the triangle tip an outer edge and the other triangular surface forms part of the floor standing area. 2. Blank according to claim 1, characterized in that it is a canister blank is. 3. Blank according to claim 1, characterized in that the material are provided on the two long sides of the blank. 4. Blank according to claim 1, characterized in that the triangular surfaces are concave surfaces. 5. Blank according to claim 1, characterized in that the material strip is provided continuously along the entire length of the long sides. 6. Blank according to claim 1, characterized in that close to the free Edge of the bottom edge area in the case of two opposing bottom edge areas an accumulation of material is provided for the later welding of the bottom seam.