FI58759C - PLASTBEHAOLLARE - Google Patents

Description

RÄF ^ l M (11) PUBLICATION ROncq ffiTjft l J '' UTLÄGGNINGSSKRIFT 00 / Ό7 C Patent granted 10 04 1981 ^ Patent meddelat ^ v ^ (51) Kv.ik? /Int.a.3 B 65 D 90 / 02 ENGLISH - Fl N LAN D (21) P * MnUlh »k« mu «- Pit # nt» n * <> knlnx 753069 (22) Hak «ml> fUvl - An * eknlng« dif 03 · 11 · 75 (23) Alkuptlvt — Gllti (h «t * dt | 03.11.75 (41) Tullut JulklMkal - Bllvle offentilf 05.05.76 reki * t« rlhallitue (44) Nttittvikslp «non |« kuul | ultul * un pvm. -

Patent- och ragftterstyralaan '' AntOten utl «| d och utl.ikrlft.n publicarmd 31.12.60 (32) (33) (31) Pyydetty atuoikau * —Bejlrd priori t * t 0¾ .11 .jh 25.02.75, 19.03. 75 Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 2k ^ 22k9.k G 7505698.3, G 7508728.¾ (71) SULO Eisenwerk Streuber & Lohmann, Waltgeristrasse 29-37 »1 * 9 Herford,

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (72) Heinrich Osteraeier, Herford, Klaus Peter Gusch, Herford, Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (7¾) Oy Kolster Ab (5¾) Plastic container - Plastbeh & llare

The invention relates to a rectangular or spherical or oval-shaped, thermoplastic-blown tank of the order of magnitude for fuel oil tanks, in which opposite indentations are formed in each of the opposite side walls, the indentations colliding in the middle of the tank and welded in a blow molding.

Such tanks are used as individual or combination tanks, for example as honeycomb tanks for storing fuel oil. The connection and support of the individual tanks to the honeycomb takes place only with connecting lines and not, as in other known tanks, with hoops and spacers.

Fuel oil tanks known from German Offenlegungsschrift 21 15 507 are manufactured by an extrusion-blow process. In it, a soft-shaped, tubular blank is inserted between the halves of the two molds, compressed from above and below, and compressed air is blown into it, whereby the hose conforms to the contour of the wall of the blow mold.

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The wall of the hose also surrounds the protrusions in the mold cavity, causing the material to stretch. The otherwise uniform wall of the hose thins at these points.

In addition to the known stretch ratio observed in blow molding between the surfaces of the hose and the mold cavity, the ratio of the wall thickness and height of the respective protrusions of the mold cavity, or rather the wall thickness and the depth of the container indentation, must also be taken into account. In the above-mentioned fuel oil tanks with a volume of 1000 to 2000 liters and an average wall thickness of 6 mm and a tank width of 720 mm, the ratio of wall thickness to depth at the indentation is 1:60, since the depth of each indentation in the side wall is about 36Ο mm. Such a large indentation depth causes problems, especially with respect to the wall thickness of the indentation peaks and also with the breaking strength of the butt weld.

Of course, when the hose is extruded, a more favorable ratio can be obtained by suitable wall thickness adjustment, although this operation significantly increases the proportion of material and thus the cost of the container. For this reason alone, it is necessary to make the wall thicknesses of the border areas sufficient.

All thermoplastic tanks have a certain resilience, which causes the side walls of the tanks to bulge more or less depending on the wall thickness and the degree of filling. Even traditional tanks would not be able to withstand the loads that occur and are therefore equipped with rims that roughly prevent bulging and distribute it evenly on the tank wall. Thus, by means of these rims, the installation dimensions are also given to the tank cell lift at the same time.

Although the tanks according to German publication 21 15 507 do not require a rim, because the specific stiffness of the tanks absorbs the load, even if they have a slight bulging effect, it is inevitable. It must be assumed that the lower area of such containers bulges more in the filled state than the upper area. It follows that the installation dimensions of the tank cell always depend on the largest dimension of the lower part of the individual tanks, which, however, only becomes clear after filling. Therefore, rimless tanks must also be placed at a suitable distance from each other. However, this is already difficult in basement spaces due to installation dimensions. It is therefore desirable that the bulging of the side walls of the container be prevented in rimless containers as much as possible or leveled. Then, firstly, the distance from the center of the tank to the center of the tank can be kept as small as possible. Secondly, the minimum and uniform bulging possible has a favorable effect on the above-mentioned load on the indentation point.

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As already mentioned above, the containers according to German advertisement 21 15 507 do not need to be strapped due to their special design. This rim had several functions in previous tanks. The rims surround either the individual tank or, in the cell tank grouping, also the entire tank cell. Separately sealed tanks use spacers that connect the rims and then the individual tanks as a tank cell. The rims can also be used to surround the entire tank cell. The rims and their spacers are used not only to dampen the bulging of the filled containers but also to ensure transport so that the stacked containers do not slip during transport. Since the rims are omitted from the known tanks according to German announcement 21 15 506, an attempt must be made to replace the functions of the rims with appropriate shaping of the tanks. Because there is a certain, albeit low, bulging tendency in rimless containers, it seems advisable not to rimlessly group the rimless containers, but to leave so much space in between that the side walls of the filled containers do not apply any pressure to each other. In order to be able to fulfill this condition in practice when installing a tank cell, care should be taken to ensure that the required distance between the rimless individual tanks is maintained.

The object of the invention is to develop known rimless containers in such a way that the liquid with which the rimless container is filled increases the stability of the containers with respect to the pressure load and that, taking this severity into account, the bulging of the containers is reduced to a minimum or even. It must further be ensured that the functions performed by the hoops and spacers of the known strapped containers are also carried out in rimless containers.

In its first embodiment, the rimless container according to the invention is characterized in that at least one buffer surface is pressed by a circumferential recess or a plurality of recesses extending to the circumferential parts, which extend or extend outwards in the vicinity of the buffer edge.

When the recess or recesses are compressed during the welding of the butt points, which occurs simultaneously with the blow molding, a corresponding amount of material flows radially outwards and further into the areas inside the walls of the indentations. By placing the recess or recesses, this results in a strengthening of the area of the weld and also of the indentation walls adjacent to the welds. This displacement of the material is achieved by compressing the piece of wood in the vicinity of the buffer edge more strongly than other parts of the buffer surface during welding.

4,5759 The effect obtained with this embodiment of the containers according to the invention can be further improved by making the wall thickness of the butt point smaller than the sum of the wall thicknesses of the two indents before welding. The described extrusion and blow molding technique provides this measure of wall thickness such that the corresponding frustoconical mold cavity protrusions are at a suitable distance from each other in a closed mold. If this distance is chosen so as to obtain the desired wall thickness, too much material is also compressed radially outwards from the butt points and increases the reinforcement of the walls of the butt edge or indentations.

The recesses are formed in a segmental manner, leaving a step between the segmental recesses. Thanks to this arrangement of the recesses, the material which, when welded, is inside the recesses and therefore under increased pressure, can penetrate radially outwards between the parts of the projections of the mold, the parts which form the recesses.

Furthermore, the desired protrusion of the material from the butt point into the walls of the indentations is advantageous when the recesses are arranged symmetrically on both butt surfaces.

Furthermore, it has surprisingly been found that the controlled reinforcement of the welding point, or rather the indentation walls, can be further improved by giving the slope of the indentation walls in the vicinity of the butt point a value of 28 °. To this end, the inclination near the end face of the protrusion of the mold cavity must be chosen appropriately. It must also be borne in mind that this measure does not depend on whether there are indentations or protrusions in the mold cavity, i.e. the side walls of the tank are based on a circular, oval or approximately rectangular cross-section.

It has proven advantageous for the tensile strength of the weld that the radius of the transition between the inner surface of the indentation and the associated butt surface is 3 to 7 mm. If the radius is larger than this, there is a high risk of cracks in the bevel of the weld, but if the radius is too small, there is a risk of cracks in the neck of the butt spot.

According to another embodiment, a rimless container according to the invention is known in that the center of the container indentations is moved downwards relative to the actual center of the container, closer to the hydrostatic center of gravity. Free surfaces refer to the surfaces of the side wall of the Tank adjacent to the indentation. Only deformation caused by their internal pressure must be prevented.

The displacement of the center of the indentation results in the most favorable distribution of the load on the free surfaces of the side wall of the container, as the stiffening effect of the indentation becomes closer to the hydrostatic center of gravity.

A preferred embodiment of the rimless containers according to the invention is characterized in that the indentation is based on a rectangular shape in the side wall of the container, which extends in the form of a truncated cone up to the weld in the center of the container. The indentation with respect to the regular frustoconical structure is given by the starting point of the indentation, i. the rectangular shape in the wall has the advantage of reducing the free surfaces of the side walls of the container.

In view of the above requirements, it is advantageous when the containers are erected and transported if the side walls of the containers are provided with locking elements formed in one piece. The locking elements are mainly cams and notches in the lower part of each side wall, which are formed by blowing and arranged vertically in succession. When the tank cell is erected, these cams protrude and keep the tanks spaced apart. The height of the cams from the side wall is chosen so that when the tank is full, contact with the side walls is still avoided or that only light contact takes place. The cams and notches are arranged on each side wall of the tank twice and the positions of the cam and notch alternately. So. as seen from the grip side of the container, there is a spout at the front of the side wall at the top and a notch at the bottom and vice versa at the back of the side wall. With this arrangement, the cams grip the container 180 degrees at a time when the container is rotated and prevent the containers from slipping against each other during transport, e.g. in trucks.

In this last-described embodiment of the rimless containers according to the invention, it is advantageous that, when the container cell is erected, the predetermined distance between the containers is maintained without force and without additional devices. When transporting containers, eg in a truck, the stacked containers are prevented from sliding against each other with the same spacers.

An exemplary embodiment of the invention will be described with reference to the accompanying drawings, in which: Fig. 1 is a vertical section of a first embodiment of a container according to the invention; Fig. 58759 is a side view of a rimless container according to Fig. 4, Fig. 6 is a side view of an embodiment of a container according to the invention similar to Fig. 5, with further details of containers according to the invention and a partial section along the line A-B in Fig. 6;

Figure 1 shows a container 2 according to the invention with indentations 4, 4 '. The inclination of the inner walls of the indentations is 28 °. The indentations 4, 4 'are pushed against each other in the center of the container, whereby the welding of the fabric points 6 is performed during blow molding.

The top view of the dozer point 6 is shown in Fig. 2. Symmetrical segment-shaped recesses 10, 10 'are pressed into the dozer surfaces 8, 8' so that a step 12, 12 'always remains between the two recesses 10, 10'. The recesses 10 are in the vicinity of the buffer edge, the edge shown by the broken line 14 »depicting the center of the rounding R (Fig. 3). · In a simplified embodiment, the recesses 10, 10 'can be replaced by a circumferential annular recess. Finally, Fig. 2 shows a bore 16 and a side wall 18 running obliquely from the buffer surface to the bore.

Figure 3 shows a cross-section of the butt point taken along line III-III of Figure 2. Arrow F indicates the way in which the substance flows during the blow molding from the part inside the butt point to the butt edge, i. into the walls of the indentations 4, 4 '. As already mentioned, the radius R is 3 to 7 m®.

If the radius is chosen to be larger than this, there is a high risk that the fabric point, as shown by the broken lines 20, will be incompletely welded and the beginning of such a part 20 'will tear, as shown by the broken line 22.

If the radius R is chosen too small, there is also a risk of cracking, and in particular in the neck 24 of the butt point, at a point which is then approximately at the point of intersection of the two dashed lines 26, 26 '.

Figures 4 and 5 show another embodiment of a rimless container 30 according to the invention. The container 30, like the container described above, is provided with indentations 32, 32 ', the center 34 of which is offset downwards from the actual center line 35 of the container. The indentations 32, 32 ', i.e. the starting side walls 36 of the container are based on a rectangular basic shape 37 projecting into the container in the form of a truncated cone. The indentations are reconnected by welds 38 ·

It can be seen from Figure 4 that the indentations 32, 32 'of the side walls 36 of the container are made symmetrical. By moving the indentations 32, 32 'downwards by a distance a from the center line 35 of the container, a lower space 39 is formed below the weld 38 and an enlarged upper space 40 above the weld 3®, the side surfaces of which are larger than the side surfaces of the lower space 39. The distance a (Fig. 5) is chosen so that the bulge 7 58759 of the lower space 39 of the container 30 is approximately equal to the bulge of the upper space 40. The distance a can be determined by taking into account the hydrostatic pressure of the tank. The distance shown in Figure 5 is about 1/10 of the total height of the tank 50.

Although only one indentation on each side of the container is shown in the figures at a time, the indents being based on either a round or rectangular shape, the design of the side surfaces of the container can be adapted to the size of the sides of the container. Long elongate indentations can be fitted with either elongate indentations or two or more small indentations to avoid losing too much container space. Fig. 6 shows a rimless container 50 formed in the same manner as the container 30 (Fig. 5). Locking elements 53 »formed by a cam 54 and a notch 55 in the structure of Figs. when forming with the containers in one piece so that when two containers rotated 180 ° relative to each other are superimposed, the locking elements adhere to each other. This provides transport protection for the containers 50 against displacement. Conversely, when the containers are assembled into a tank cell, the spout 54 of the second container abuts the spout 54 of the second container placed adjacent to it so that a predetermined distance is maintained and the bulging of the side walls of the container can be taken into account.