Rectangular plastic container

Abstract

The invention relates to a rectangular plastic container (1, 2) for storing, transporting and mixing liquids or liquid-solid mixtures, having a base (1) and four container walls (2) arranged vertically and each at a right angle to one another and stiffened by way of reinforcing elements. In order to develop a plastic container (1, 2) of this kind in such a manner that the production costs are significantly reduced while at least the same stability is achieved, and thus also such that during its use as a mixing vessel, energy costs for mixing the container contents can be saved, the invention proposes that the reinforcement elements of the container walls (2) consist exclusively of one or more reinforcement ribs (3) which extend helically about the circumference of the plastic container (1, 2) and rise upwards from the bottom and which are formed from thickened wall portions of the container walls (2) projecting inwards into the interior of the plastic container (1, 2).

Description

[0001] Rectangular plastic container

[0002] The invention relates to a rectangular plastic container for the storage, transport and mixing of liquids or liquid-solid mixtures, with a bottom and four vertically arranged container walls each at right angles to each other and stiffened by reinforcing elements.

[0003] Plastic containers of this type typically have a capacity of 500 to 1500 liters and are used in commercial applications for the storage and transport of liquids or liquid-solid mixtures. Furthermore, such plastic containers often also serve as mixing containers for the liquids or liquid-solid mixtures they contain. For all of these applications, it is also important to be able to easily clean the plastic containers after each use and remove any residue from the contents.

[0004] The rectangular shape (cubic or cuboid) of the plastic containers has the advantage of requiring less space during transport and / or storage compared to cylindrical containers, but has the disadvantage that the container walls deform uncontrollably outwards under the pressure of the container contents and form bulges across the surface.

[0005] To prevent these undesirable deformations, it is common practice and known in the art to stiffen the walls of such rectangular plastic containers using horizontal and / or vertical reinforcement elements that are applied externally to the container walls, e.g., in the form of a metal mesh basket (cf. DE 2004 039 482 B4) or in the form of horizontal plastic bandages applied to the outside of the container walls (cf. DE 32 48 068 C2). However, such stiffening measures involve considerable material and labor expenditure and are accordingly expensive. Such external reinforcement elements are particularly problematic when used on containers containing aggressive substances that attack the material from which the external reinforcement elements are manufactured, for example, through corrosion. In this case, additional, costly corrosion protection measures are generally necessary.

[0006] Furthermore, EP 0661 220 A1 discloses a rectangular container for the storage, transport, and mixing of liquids or liquid-solid mixtures. The container comprises a thin-walled inner container made of thermoplastic material and an outer container made of packaging cardboard, which serves as an additional reinforcement element and supports the walls of the inner container. The vertical walls forming the inner container shell are provided with horizontally or helically extending beads extending into the interior of the container, allowing the emptied inner container to be compressed like a bellows.

[0007] The object of the invention is to further develop the rectangular plastic container of the type mentioned at the outset, without additional reinforcing materials, in such a way that the manufacturing costs are significantly reduced while at least maintaining the same stability.

[0008] To achieve this object, the invention proposes, starting from a rectangular plastic container of the type mentioned at the outset, that the reinforcing elements of the container walls consist exclusively of one or more stiffening ribs running helically around the circumference of the plastic container, rising from bottom to top, which are formed by thickened wall sections of the container walls projecting inwards into the interior of the plastic container.

[0009] The rectangular plastic container according to the invention is characterized first of all by the fact that the stiffening ribs used for wall reinforcement, consisting of appropriately shaped wall sections, require neither additional material nor additional labor for their production. Because the stiffening ribs run continuously helically from bottom to top around the entire circumference and across the entire height of the rectangular plastic container, the increased stability of the plastic container is achieved with minimal material expenditure, not only against horizontally acting forces but also against vertically directed forces. This increased stability was verified by means of FEM calculations.

[0010] Additionally, particular advantages arise when the rectangular plastic container is used as a mixing container for the liquids or liquid-solid mixtures it contains. This is because, during all stirring movements around a vertical axis, the helically arranged stiffening ribs projecting into the interior of the plastic container impose an additional vertical movement component on the material being mixed, resulting in faster and more intensive mixing. Furthermore, considerable energy is saved on the drive energy required for the mixing tools (circulation pumps or agitators).

[0011] It is particularly advantageous if the wall sections of the container walls that form the stiffening are curved towards the interior of the plastic container. These curvatures have the advantage that, on the one hand, the stresses that occur in the material under load are better distributed and, on the other hand, the inner walls of the plastic container can be cleaned more easily because there are no acute angles or dead spaces in the area of ​​the stiffening ribs. Another advantage is that the rounded stiffening elements ensure a particularly gentle stirring effect. This gentle stirring effect is necessary, for example, when mixing fibers or flakes into a liquid because these could get caught on sharp edges and / or be damaged.

[0012] A particularly preferred embodiment of the plastic container according to the invention provides that the wall sections forming the stiffening ribs protrude into the interior of the plastic container by 1.2 to 1.5 times their wall thickness, and that the radius of curvature of the curvature of these wall sections corresponds to 1.6 to 1.9 times their wall thickness. With these dimensional ratios, the best results in terms of stability and mixing have been achieved.

[0013] A suitable development of the rectangular plastic container according to the invention provides a circulating device arranged at the upper edge of the plastic container, engaging into the interior of the plastic container, which sets the contents of the plastic container in a rotating circular motion around a vertical axis. This makes the aforementioned circulating device, which can be designed as a stirring device or a circulating pump, virtually an integral part of the rectangular plastic container.

[0014] For attaching the circulation device, a lid that can be secured to the upper edge of the container walls is advantageously provided. This lid is provided with mounting interfaces for the circulation device and / or other auxiliary equipment. These other auxiliary equipment can be, for example, cleaning tools or the like.

[0015] Furthermore, at least one closable opening is advantageously arranged in the lower region of a tank wall, directly above the base, which can serve as a connection port for a circulation pump and / or as an outlet port. This closable opening directly above the base has the advantage that a particularly simple, non-self-priming pump connected to this opening can be used as a circulation device to mix the tank contents.

[0016] An embodiment of the invention is explained below with reference to the accompanying drawings. They show:

[0017] Figure 1: schematically shows a transparent view of a rectangular plastic container according to the invention;

[0018] Figure 2: a section through the stiffening rib of the container walls;

[0019] Figure 3: schematically shows a perspective view of a rectangular plastic container according to the invention with a lid having mounting interfaces for a circulation device and auxiliary devices.

[0020] In the embodiment shown in the drawing, the base of the rectangular plastic container is designated by the reference numeral 1. This base 1 consists of a rectangular plate resting horizontally on a support surface, which is connected at its four edges to four vertically running side walls 2, which together with the base form the cuboid body of the container. The base 1 and the side walls 2 are connected to one another in one piece, are made of a suitable plastic (e.g., polyethylene with sufficient UV and chemical resistance), and have a wall thickness that meets the requirements. All angles defining the interior space between the base and the side walls, as well as between the side walls, are rounded so that there are no bottlenecks or dead spaces that are difficult to access for cleaning.

[0021] In order to prevent the container walls 2 from bulging outwards due to the pressure of the liquids or liquid-solid mixtures contained in the container, the side walls 2 are provided with a stiffening rib 3 which runs helically around the circumference of the plastic container 1, 2 and rises from bottom to top, which projects inwards into the interior of the plastic container 1, 2 and is formed by inwardly curved wall sections 2a (cf. Figure 3) of the container walls 2.

[0022] As can also be seen from Figure 2, the container walls 2 are slightly thickened in the area of ​​the stiffening rib 3. This thickening results in a wall thickness in the area of ​​the stiffening rib 3 that corresponds to 1.2 to 1.5 times the wall thickness of the container walls 2. Furthermore, the radius of curvature R of the curvature is approximately 1.6 to 1.9 times the wall thickness of the container walls 2. These thickenings and the radius of curvature ensure improved stability and better cleaning options for the interior of the container.

[0023] As can also be seen from Figure 1, the rectangular plastic container 1, 2 shown there is covered at the top by a lid 4. This lid 4 has a closable filling opening 5 and also an access opening 6 for a circulating device engaging in the interior of the plastic container, which, when used as a mixing container, imparts a circular motion to the contents of the plastic container 1, 2, rotating around a vertical axis. This circulating device can be designed, for example, as an agitator or a circulating pump.

[0024] When using the plastic container 1, 2 as a mixing container, an advantageous synergistic effect arises between this circulation device on the one hand and the helically extending stiffening rib 3 projecting into the interior of the plastic container 1, 2 on the other hand, because the helically extending stiffening rib 3 imposes a movement component in the vertical direction on the mixed material, which leads to faster and more intensive mixing. Long-term tests with such circulation devices in rectangular plastic containers 1, 2 according to the invention have shown that energy savings of more than 20% can be achieved during mixing through the interaction of the circularly operating circulation device on the one hand and the helical stiffening ribs 3 on the other.

[0025] In the embodiment according to Figure 3, the lid 4 of the plastic container 1, 2 is additionally provided with mounting interfaces 7 and 8 for the circulation device and other auxiliary devices.

[0026] In addition, a closable opening 9 is provided in a container wall 2 in its lower area immediately above the base 2, which opening can be used as a connection for a non-self-priming pump as a circulation device or can also be used as a simple drain opening.

[0027] List of reference symbols Underbody Container wall, 2a Wall section Reinforcing rib Cover Filling opening Access opening Mounting interface Mounting interface Lockable opening

[0028] - Patent claims -

Claims

Patent claims 1. Rectangular plastic container (1, 2) for the storage, transport and mixing of liquids or liquid-solid mixtures, with a bottom (1) and four vertically arranged container walls (2) each at right angles to one another, stiffened by reinforcing elements, characterized in that the reinforcing elements of the container walls (2) consist exclusively of one or more stiffening ribs (3) extending helically around the circumference of the plastic container (1, 2), rising from bottom to top, which are formed by thickened wall sections of the container walls (2) projecting inwards into the interior of the plastic container (1, 2).

2. Plastic container (1, 2) according to claim 1, characterized in that the container walls (2) are thickened by 1.2 times to 1.5 times in the region of the stiffening ribs (3).

3. Plastic container (1, 2) according to claims 1 or 2, characterized in that the wall sections (2a) of the container walls forming the stiffening ribs (3) are curved in the direction of the interior of the plastic container (1, 2).

4. Plastic container (1, 2) according to claim 3, characterized in that the wall sections (2a) forming the stiffening ribs (3) protrude into the interior of the plastic container (1, 2) by 1.2 times to 1.5 times their wall thickness and that the radius of curvature (R) of the curvature of these wall sections corresponds to 1.6 times to 1.9 times their wall thickness.

5. Plastic container (1, 2) according to one or more of the claims 1-4, characterized by a circulation device arranged on the upper edge of the plastic container (1, 2), engaging in the interior of the plastic container, which sets the contents of the plastic container (1, 2) in motion in a circular movement rotating about a vertical axis.

6. Plastic container (1, 2) according to claim 5, characterized in that the circulation device is designed as a stirring device.

7. Plastic container (1,2) according to claim 5, characterized in that the circulation device is designed as a circulation pump.

8. Plastic container (1, 2) according to one of the claims 5-7, characterized by a lid (4) which can be fixed to the upper edge of the container walls and which is provided with mounting interfaces (7, 8) for the circulation device and / or for other auxiliary devices.

9. Plastic container (1, 2) according to one or more of claims 1-4, characterized in that in at least one container wall (2), in the lower region thereof above the base (1), at least one closable opening (9) is arranged, which serves as a connection opening for a circulation pump and / or as an outlet opening. - Summary -

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