Pallet container with plastics inner container

Abstract

A pallet container having a thin-walled rigid inner container including thermoplastic plastics material, having a tubular grid frame, which tightly encloses the plastics inner container as a support covering and includes horizontal and vertical tubular rods, is disclosed. At least one member selected from the group consisting of at least one of the vertical tubular rods and at least one of the horizontal tubular rods has a square-shaped or round hollow profile as the original basic profile and a tube profile that has been changed by mechanical shaping. The original basic profile of at least one member selected from the group consisting of at least one of the horizontal tubular rods and at least one of the vertical tubular rods is constructed so as to be increased by a predeterminable amount via an intersection region of the horizontal tubular rods and vertical tubular rods, which are welded to each other.

Claims

1. Pallet container for storing and for transporting flowable filling materials having a thin-walled rigid inner container comprising thermoplastic plastics material, having a tubular grid frame which tightly encloses the plastics inner container as a support covering and which comprises horizontal and vertical tubular rods which are welded to each other in intersection regions, and having a rectangular base pallet on which the plastics inner container is positioned and to which the tubular grid frame is securely connected, wherein at least one member selected from the group consisting of at least one of the vertical tubular rods and at least one of the horizontal tubular rods has, when considered in the longitudinal direction, a square-shaped or round hollow profile as the original basic profile and have, in certain regions, a tube profile that has been changed by mechanical shaping, characterised in that the original basic profile of at least one member selected from the group consisting of at least one of the horizontal tubular rods and at least one of the vertical tubular rods is constructed so as to be increased by a predeterminable amount via an intersection region of the horizontal tubular rods and the vertical tubular rods which are welded to each other or, the original basic profile of at least one member selected from the group consisting of at least one of the horizontal tubular rods and at least one of the vertical tubular rods is provided with an increased rear region wherein the original basic profile is shaped in the region of the increased rear region and has a practically triangular hollow profile, wherein the increased rear region is constructed by mechanical shaping from the original basic profile by means of a lateral pressing pressure action and has a narrow rear which extends in the longitudinal direction of the tubular rods.

2. Pallet container according to claim 1, characterised in that the increased rear region is arranged at an outwardly or inwardly directed side of the tubular rod with respect to the tubular grid frame.

3. Pallet container according to claim 1, characterised in that the increased rear region is one or more of constructed in a vertically extending tubular rod at an inwardly directed side and is arranged in a horizontally extending tubular rod at an outwardly directed side with respect to the tubular grid frame.

4. Pallet container according to claim 1, characterised in that the increased rear region has a definitively delimited extent in the longitudinal direction of the tubular rods.

5. Pallet container according to claim 1, characterised in that the extent of the increased rear region in the longitudinal direction of the tubular rods is between twice and ten times, the width of the tubular rods or a diameter of the tubular rods.

6. Pallet container according to claim 1, characterised in that the basic profile is constructed as a square tubular profile.

7. Pallet container according to claim 6, characterised in that the square profile of the tubular rods has a wall thickness of from 0.8 mm to 1.0 mm.

8. Pallet container according to claim 6, characterised in that the square profile of the vertical tubular rods has a wall thickness of 0.8 mm and the square profile of the horizontal tubular rods has a wall thickness of 0.9 mm.

9. Pallet container according to claim 6, characterised in that the square profile has two opposing parallel straight side walls and two opposing parallel, slightly curved side walls, wherein one curved side wall is constructed to be slightly concave inwards and the other curved side wall is constructed to be slightly convex outwards.

10. Pallet container according to claim 1, characterised in that the increased rear region f is constructed in the intersection regions only in the vertical tubular rods.

11. Pallet container according to claim 1, characterised in that the original basic profile is constructed as a round tubular profile.

12. Pallet container according to claim 1, characterised in that the triangular hollow profile has a profile height of at least 20 mm in the region of the increased rear region.

13. Pallet container according to claim 1, characterised in that the increased rear region is produced in the intersection regions preferably in the region of the side walls of the tubular grid frame with maximum convexity, that is in the central region of the second and third horizontal tubular rod from the bottom in the tubular grid frame.

14. Method for producing a triangular hollow profile from a square basic profile in a tubular grid rod of a tubular grid frame for a pallet container according to claim 6, characterised in that, in order to form the central rear piece for the intersection regions of the tubular rods by means of correspondingly formed pressing tools, a pressing pressure is applied to the provided region of the tubular basic profile in a direction parallel with the plane of the grid walls at the same time from two opposing parallel side walls.

15. Method according to claim 14, characterised in that the pressing pressure on the two opposing side walls which extend linearly in a parallel manner is applied substantially only in the region or portion of the square basic profile which adjoins or is adjacent to the slightly convexly outwardly curved side wall.

16. Method according to claim 14, characterised in that the pressing pressure on the two opposite side walls which extend parallel is produced in such a manner that the tips, chamfered at the front, of the pressing tools which are moved towards each other produce in the end position a V-shaped gap between the tips of the pressing tools and a triangular tube cross-section with an increased tubular profile height is formed in the shaped region of the tubular rod.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained and described in greater detail below with reference to drawings of schematically illustrated embodiments, in which:

(2) FIG. 1 is a front view of an IBC according to the invention,

(3) FIG. 2 is a cross-sectional view of a preferred embodiment of a tubular rod basic profile BP with a substantially square cross-section,

(4) FIG. 3 is a cross-sectional view of the tubular rod profile according to FIG. 1 after shaping with a substantially triangular cross-section,

(5) FIG. 4 is a cross-sectional view of another embodiment of a tubular rod basic profile with a circular cross-section,

(6) FIG. 5 is a cross-sectional view of the tubular rod profile according to FIG. 4 after a first shaping step to form a weldable cross-section with a 4-point support of the intersecting tubular rods,

(7) FIG. 6 is a cross-sectional view of the tubular rod profile according to FIG. 4 after further shaping to form a triangular cross-section,

(8) FIG. 7 is a partial side view of a vertical tubular rod with a square cross-section and

(9) FIG. 8 is a partial plan view of a vertical tubular rod with a square cross-section from the inner side from the tubular grid frame.

DETAILED DESCRIPTION

(10) In FIG. 1, there is generally designated 10 a pallet container according to the invention for storing and transporting in particular hazardous fluid or flowable filling materials. For use for storing and/or transporting hazardous filling materials, the pallet container 10 complies with particular test criteria and is provided with a corresponding official hazardous goods permit. In an embodiment for a filling material volume of approximately 1000 l, the pallet container 10 has standardised dimensions having a length of approximately 1200 mm, a width of approximately 1000 mm and a height of approximately 1150 mm. The main elements of the pallet container 10 comprise a thin-walled rigid inner container 12 which is produced from a thermoplastic plastics material using the blow-moulding method, a steel tube grid frame 14 which tightly encloses the plastics inner container 12 as a support covering and a base pallet 16, on which the plastics inner container 12 is positioned and to which the steel tube grid frame 14 is securely connected. The outer tubular grid frame 14 comprises horizontal and vertical steel tubular rods 18, 20 which are welded to each other. The closed basic profile BP of the horizontal and vertical tubular rods 18, 20 has no formations or dents which reduce the profile height transversely relative to the longitudinal direction of the tubular rods.

(11) The base pallet 16 is constructed as a composite pallet in the version illustrated. An identification panel 22 comprising thin sheet steel for identifying the respective fluid filling material is fixed to the front side of the tubular grid frame 14. A removal fitting 24 is connected at the centre of the base of the plastics inner container 12 for removing the fluid filling material.

(12) The horizontal tubular rods 18 are securely welded in intersection regions 26 with the vertical tubular rods 20 of the tubular grid frame 14 via a 4-point support by means of conventional resistance pressure welding. In the present case, the steel tube grid frame 14 comprises eighteen vertical tubular rods 20 each with a length of approximately 1000 mm and six circumferential horizontal tubular rods 18 which are constructed by means of four 90° bends with a total length of approximately 4400 mm and a connection location of the two pipe ends to form a rectangular tubular ring. Inside the tubular grid frame 14, there are seventy-two (72) pure intersection locations 26 and eighteen (18) upper and eighteen (18) lower intersection joint locations 28. At the intersection joint locations 28, the upper and lower ends of the vertical tubular rods 20 are securely welded to the uppermost and the lowermost horizontally extending tubular rod 18. The pallet container 10 can also be constructed as a large container with different volume sizes between 500 I and 1300 I.

(13) In FIG. 2, a tubular rod basic profile BP with a practically square tubular cross-section is illustrated as a cross-sectional view as a preferred embodiment. This original basic profile BP as a square profile—here, of a vertical tubular rod 20—does not have any formations or dents transversely relative to the longitudinal direction of the tubular rods. The outer dimensions are approximately 16×16 mm and consequently the height H.sub.(Q) as a side length of the square profile is also 16 mm. As a result of the increase of the rigidity of the steel tube grid frame according to the invention, the previous wall thickness of the tubular rods of 1.0 mm can be reduced, wherein the square profile then has a reduced wall thickness of from 0.7 mm to 1.0 mm, preferably 0.9 mm.

(14) In a preferred embodiment, there is provision for the square profile of the vertical tubular rods 20 to have a wall thickness of 0.8 mm and the square profile of the horizontal tubular rods 18 to have a wall thickness of 0.9 mm. The weight and the material costs of the pallet container can thereby be reduced while retaining a high wall rigidity level.

(15) Preferably, the basic square profile BP has two opposing parallel straight side walls 32 and two opposing practically parallel, slightly curved side walls 34, 36, wherein one curved side wall 34 is constructed to be slightly concave inwards and the other curved side wall 36 is constructed to be slightly convex outwards. The slightly concavely inwardly curved side walls of the tubular rods 18, 20 have at the two lateral outer edges thereof a planar rear line 40 which extends in the longitudinal direction of the tubular rods.

(16) At the intersection locations 26, the horizontal tubular rods 18 and the vertical tubular rods 20 are located on each other with the slightly concavely inwardly curved side walls 34 or with the two outer, longitudinally extending rear lines 40 thereof and form the necessary 4-point supports for welding the tubular rods 18, 20. The slightly convexly outwardly formed side wall 36 of the square basic profile is, in the region of the intersection locations 26 in which it is desirable and provided for, easier to shape as a result of pressing pressure applied at both sides into a triangular shaping profile with a centrally formed rear piece 30. The rear-like increased portions are produced from the basic profile square tube as a result of cold-forming by means of simple hydraulic pressing tongs.

(17) A tubular rod profile which is processed and shaped in such a manner in the region of the intersection locations 26 and which has a substantially triangular cross-section and a centrally formed rear piece 30 according to the present invention can be seen in FIG. 3 as a cross-sectional view.

(18) In a square basic profile having a side length or height H.sub.(Q) of 16 mm there results a height H.sub.(D) of the triangular tubular rod profile of approximately 20.5 mm in the region of the triangular cross-section from the slightly concavely inwardly curved side wall equal to the basic wall for the 4-point contact locations for welding the intersecting tubular rods as far as the tip of the central rear piece 30, depending on the size of the radius at the rear tip. In this case, the two opposing side walls 32 which extend linearly and in a parallel manner and the slightly convexly outwardly curved side wall 36 are each shaped by half into two equal-sided triangle side walls 38.

(19) During the shaping operation, two outwardly directed humps 48 are produced—as a cross-sectional view—from the two 90° bends between the two opposing side walls 32 which extend linearly in a parallel manner and the slightly convexly outwardly curved side wall 36 in the two shaped triangle side walls 38. The square basic profile BP was originally shaped in a roller type roll stand from a round steel tube to form a square profile. In this case, the four 90° bends between two adjacent side walls were formed by cold-forming. During cold-forming, a local increase in strength is produced as a result of structure changes in the steel material. In the region of the shaped triangular cross-section, the two 90° bends which are adjacent to the slightly convexly outwardly curved side wall 36 are bent open again. As a result of the increase in strength in the two 90° bends, the bending back is not carried out completely and there remain the two humps 48 in the two equal-sided triangle side walls 38.

(20) The processing and shaping of the basic profile tubular rods is not carried out here in contrast to the previously known solutions in a direction perpendicular to the plane of the grid walls but instead in a direction parallel with the plane of the grid walls, wherein in order to form the central rear piece 30 a pressing pressure is applied by means of correspondingly formed pressing tools at the same time by two opposite side walls to the provided region of the tubular rod. In this case, this pressing pressure is applied to the two opposite side walls 32 which extend linearly in a parallel manner, beginning in a region or portion of the square basic profile which adjoins or is adjacent to the slightly convexly outwardly curved side wall 36. This can, for example, be brought about by means of a pressing tool having two pressing stamps which move towards each other and the tips of which are chamfered accordingly at the front so that in the end position a V-shaped gap between the tips of the pressing stamps and a practically triangular or triangle-like tube cross-section with an increased tube profile height of the shaped region of the tubular rod are produced. This shaping operation can also be carried out accordingly by means of a pressing tongs type tool, wherein two tong jaws act via a pivot point on the two opposite side walls 32 which extend linearly in a parallel manner. In this case, only the slightly concavely inwardly bent side wall 34 remains unshaped for the 4 welding spots in the intersection region 26 of the horizontal and vertical tubular rods 18, 20.

(21) The basic profile square tube has a basic side wall which is curved slightly inwardly, whereby outer-side longitudinal ribs for the 4-point resistance welding are produced. During the cold-forming, the two 90° bends which are opposite the basic side wall are bent open and brought to the greatest possible degree to a rectilinear extent while the straight side wall which is opposite the basic side wall is shaped at the centre to form a comparatively narrow bend with a small radius.

(22) Another embodiment of a known tubular rod basic profile is illustrated in FIG. 4 as a cross-section. This original tubular bar basic profile is constructed as a round tube profile 42 and has a circular cross-section with an outer diameter D.sub.(AR) of approximately 18 mm and a wall thickness of 1.0 mm. In order to obtain a corresponding mutual support of the tubular rods in the intersection regions for a 4-point weld, in a first shaping step—as illustrated in the following FIG. 5—a side of the round tubular profile is shaped radially by a small amount so that a slightly concave or slightly inwardly curved wall piece 44 is formed with outer-side longitudinal ribs or longitudinal humps which form a 4-point support in the case of intersecting tubular rods. As a result of the denting of the round tubes in order to form the four weld contact points, the round tube of known pallet containers is subjected to a powerful loss of rigidity or bending resistance moment. This loss of rigidity can again be compensated for well by shaping in an additional shaping step to form a practically triangular cross-sectional profile with the introduction of increased rear regions 30, as can be seen in FIG. 6. This embodiment with a triangular hollow profile also has in the region of the increased rear region 30 a profile height H.sub.D of at least 20 mm.

(23) FIG. 7 illustrates in an intersection region 26 a lateral part-view of a vertical tubular rod 20 with a square cross-section. The horizontal tubular rod 18 has the same square cross-section of the basic profile BP. In the intersection region 26, the original square basic profile BP of the vertical tubular rod 20 was shaped to form a practically triangular hollow profile with a central increased rear region 30. The central increased rear region 30 which is constructed by mechanical shaping by means of a lateral pressing pressure action from the original basic profile has a narrow rear which extends in the longitudinal direction of the tubular rods, wherein the increased rear region 30 is limited to a defined extent in the longitudinal direction of the tubular rods. This extent of the increased rear region 30 in the longitudinal direction of the tubular rods is intended to be between two times and ten times, preferably five times, the width of the tubular rod or diameter of the tubular rod (in the case of a round tube).

(24) There is produced at both sides between the original non-shaped basic profile and the central increased rear region 30 which is constructed by shaping a transition region 46 which extends obliquely. These obliquely extending transition regions 46 are produced in that, in order to form the increased rear region for the intersection regions of the tubular rods by means of correspondingly formed pressing tools, a pressing pressure is applied to the provided region of the basic tubular profile in a direction parallel with the plane of the grid walls at the same time by two opposing parallel side walls. In this case, the pressing pressure is applied to the two opposite side walls which extend linearly in a parallel manner substantially only in the region or portion of the square basic profile which adjoins or is adjacent to the slightly convexly outwardly bent side wall.

(25) The shaping operation is carried out in this instance in such a manner that the pressing pressure is applied to the two opposite side walls which extend parallel, for example, by two tips, chamfered at the front, of two pressing stamps of a pressing tool which are moved towards each other or the pivotable jaws of a set of pressing tongs, wherein in the end position a V-shaped gap is produced between the tips of the pressing stamps or the jaws of the set of pressing tongs and thereby a practically triangular tube cross-section with an increased tubular profile height is formed in the shaped region of the tubular rod.

(26) To this end, FIG. 8 shows as a partial plan view of a vertical tubular rod 20 with a square basic cross-section from the inner side out of the tubular grid frame the shaped triangular cross-sectional region of the vertical tubular rod 20 with the central increased rear region 30 which is formed by shaping and transition regions 46 which adjoin at two sides. The longitudinal extent of the oblique transition regions 46 should be approximately once to twice the height of a side wall of the square basic profile, that is to say, between 15 and 35 mm, preferably approximately 20 mm.

(27) If the specific case of an IBC which is filled with a fluid filling material and in which the filling material surges back and forth as a result of transport loads and thereby acts on the side walls of the tubular grid frame with changing pressure forces is considered, this brings about dynamic permanent loads with constantly swelling and subsiding tensile and pressure stresses in the tubular profile, which can lead in the long term to cracks in the tubular profile regions which are most greatly stressed and the breakage of the weld spots in the intersection locations. In this case, the outward bulging of the side walls of the tubular grid frame is, as a result of the inner pressure in the plastics inner container, approximately twice as large as the inward “indentation” or rebound of the tubular grid frame as a result of the resilient restoring forces. In this case, therefore, flexural loads of different magnitudes in the radial direction occur on the tubular rods (=bending bars) of the tubular grid frame.

(28) The magnitude for a resistance against bending is referred to as an axial resistance moment W or bending resistance moment. The resistance moment constitutes in the technical mechanism a variable which is derived only from the geometry (form and dimensions) of a bar cross-section and which is a measurement for the resistance which a bending bar applies during loading counter to the occurrence of inner stresses. In this case, the largest stresses σ.sub.max in terms of value always occur in the peripheral fibres of the bending bar which have the greatest spacing from the neutral fibres. The resistance moment W of a bar cross-section is in a simple geometric relationship with the geometrical moment of inertia I, by means of which the shaping is calculated during the cross-section measurement in order to establish the bending rigidity of a bar during loading. The resistance moment W is defined as the quotient comprising the geometrical moment of inertia I, and the greatest stress σ.sub.max. The unit for the resistance moment is m.sup.3.

(29) During comparison measurements relating to the bending rigidity of the square basic profile and the shaped triangular tube cross-section with an increased rear region, the following was found: the square basic profile has a geometrical moment of inertia I.sub.x in the order of approximately 1610 mm.sup.4 while a geometrical moment of inertia I.sub.x of approximately 2000 mm.sup.4 results for the triangular cross-sectional profile. This results in a substantial increase of approximately 24%.

(30) In corresponding comparison measurements, a geometrical moment of inertia I.sub.x of approximately 1770 mm.sup.4, which is further substantially reduced in the previously carried out formations and cross-sectional reductions in the intersection regions, resulted for an unshaped round tube profile of a known pallet container. In comparison, a high power increase could also be brought about here with a shaping of the round tube cross-section to form the triangular profile with an increased rear region and an increase of the geometrical moment of inertia I.sub.x to over 2000 mm.sup.4.

(31) Consequently, the present invention provides a cost-effective solution which is easy to apply and which functions correctly for an advantageous increase of the rigidity of the tubular grid frames of pallet containers. No additional material is required, but instead only a special and partial shaping of the tubular rod basic profile is applied, and, conversely, a material and cost saving can even be achieved by reducing the wall thickness of the tubular rods.

(32) As a result, an increased level of security against the occurrence of damage resulting from excessive transport loads is ensured when using such large containers in particular for hazardous fluid filling materials.