Abstract:
This invention relates to a container consisting of a thermoplastic material, with side walls, flat top and bottom panels of which the top panel is provided with at least one fill/drain opening, and with a continuous circumferential carrying and transport rim. For better utilization of pallet space, the container body has an approximately square cross-section with slightly convex lateral surfaces and slightly radiused corners. In order to counteract the inherent tendency of the flat container walls to bulge and buckle, the container body is provided with vertical and/or horizontal reinforcement elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of copending PCT International Patent Application PCT/EP00/03643, filed Apr. 20, 2000, and a continuation-in-part of copending U.S. patent application Ser. No. 09/525,526, filed Mar. 15, 2000, now pending, the contents of both of which is expressly incorporated herein by reference thereto. 

   TECHNICAL FIELD OF INVENTION 
   The present invention relates to large-volume containers and, in particular, large-volume containers made from a thermoplastic material. 
   BACKGROUND OF THE INVENTION 
   Large-volume containers of the type discussed are typically in the form of a cylindrical drum having a capacity (volumetric net content) of about 16 to 80 gallons. These containers are commonly used for the storage and transportation of liquid contents or solid, particle-shaped and pasty contents. 
   A commonly employed container design is the bung-type drum with a net capacity of about 58 gallons. When these cylindrical drums or barrels are stored or shipped in ISO containers, there remains wasted space between the round wall surfaces of neighboring drums. Also, conventional drums of this type exhibit a tendency to buckle at their sides when multiple drums are stacked upon one another. 
   Therefore, it is desirable to provide a drum that avoids wasted space between adjacent drums, and at the same time does not tend to buckle when other drums are stacked upon it. The present invention provides such a drum. 
   SUMMARY OF THE INVENTION 
   According to the invention, this is accomplished by means of an approximately square cross-sectional shape of the drum body with slightly convex lateral surfaces and slightly radiused corners. Such a design results in a substantially improved utilization of pallet space. Compared to conventional, round drums, the essentially square drums according to this invention, when stacked side-by-side, leave significantly smaller gaps between them, thus permitting enhanced utilization of previously wasted carrier space (for instance in ISO containers). In a practical implementation of this invention, the lateral walls of the drum are provided with reinforcing vertical and/or horizontal ribs which will substantially reduce the tendency of the flat lateral wall panels to bulge or buckle. This buckling tendency increases as a function of the internal pressure, building up due to the hydrostatic pressure of the liquid contents, the weight of stacked drums, or the like. The reinforcing ribs may be in the form of molded-in U- or V-channels facing and protruding inward and/or outward. 
   In one embodiment of this invention, a sturdy drum body is obtained by means of continuous circumferential reinforcing elements in the form of enlarged annular wall protrusions. These reinforcing annular wall protrusions are preferably produced by an upset-stamping process during the blow molding of the drum body. In order for the upset-stamping-produced reinforcing rings to retain roughly the same outer diameter as the remaining drum wall, they are configured as a continuous, circumferential, fairly flat V-shaped outward-facing indentation. 
   In another preferred embodiment, the corners of the drum body are provided with deep angular indentations in such fashion that in the appropriate horizontal plane the drum has a nearly circular cross-section. This embodiment as well results in a considerable reduction of the buckling tendency especially in the lower half of the drum, thus permitting high stacking loads. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further explained and described below in the drawings of the embodiments that are presented. The following is shown: 
       FIG. 1  is a top view of a square drum-type container according to the present invention; 
       FIG. 2  is a side view of a square drum-type container according to the present invention, with the right side showing a partially cross-sectional representation of the upper and lower segments taken along line A—A of  FIG. 1 , and the left side showing a partially cross-sectional representation of a different embodiment according to the present invention; 
       FIG. 3  is a cross-section through the body of a square drum-type container according to the present invention, showing a circular footprint for comparison; 
       FIG. 4A  is a side view of one embodiment of a drum according to this invention, with a partially cross-sectional representation of the upper and lower segments; 
       FIG. 4B  is a side view of another embodiment of a drum according to this invention, with a partially cross-sectional representation of the upper and lower segments; 
       FIG. 5  is a top view of the preferred embodiment of the drum  10 . This embodiment of drum  10  has a first portion with a generally square cross-section, and a second portion with a generally round cross-section defined by four angular corner indentations  24  formed in the drum. The angular corner indentations  24  are outlined by the round dashed line. The indentations  24  may be deeper at the corner areas than they are on the side wall sections in between. In addition, as shown in  FIG. 6 . the indentations  24  define a vertical thickness that varies around the circumference of the side wall, e.g., is greatest in the corner areas and transitions into the flat surfaces of the side wall sections in between. 
       FIG. 6  is a side view of the container of  FIG. 5 , with a partially cross-sectional representation of the upper and lower segments; 
       FIG. 7  shows a diagonal cross-section of the drum of  FIG. 5  taken along line B—B; 
       FIG. 8  illustrates the handling of a drum according to the present invention, lying sideways; 
       FIG. 9  illustrates the handling of a tipped drum according to the present invention; and 
       FIG. 10  is a top view of four palletized drums according to the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference number  10  shows a large-volume blow molded bung container made of thermoplastic material in  FIG. 1  with a capacity of approximately 66 gallons, which is equipped on the upper wall of the container with a carrying and transport rim, or L-ring  12 , that runs around the circumference of the container. L-ring  12  serves as a handling ring for lifting the drum with typical drum handling equipment. In the first end wall of the drum  10  are located two side bungs  14  in die-sunk, recessed bung wells  16 . In this top view, the square cross-section becomes clear, namely that the drum bottom exhibits a sectional surface that approximates the shape of a square with side surfaces or side wall sections that are slightly embossed and rounded corner sections. 
     FIG. 2  shows an embodiment with a bung  14  centrally located in a bung well  16 . In an alternate configuration, the drum  10  can have a larger, screw cap-equipped fill/drain opening with a larger diameter of, for instance, 6 inches or 10 inches. A screw cap-equipped drum  10  of that type is ideally suited as a reusable container for viscous, pasty or granular bulk material. According to one embodiment, the fill/drain opening may be centrally located on the top surface, or first end wall, of the drum  10 . In the left half of the picture, the drum  10  is equipped with a reinforcing ring, or rolling ring  18 , that runs around the circumference of the drum and allows it to be rolled over the floor, while in the right half of the picture, another embodiment without a rolling ring is shown. 
     FIG. 3  shows a cross-section through the wall of a drum body according to this invention, which drum can be designed with a loose lid. For comparison to the cross-section, a circle with the same circumferential length is superimposed over it. This circle is intended to show the usual bulging-out tendency of a drum filled with content. The internal pressure that builds up inside the drum  10  would cause the flat walls to bulge outwards while pulling in the corners, taking on the shape of the least structural stress, that being a circle. To work against this disadvantageous tendency, the drum body is provided with a continuous horizontal reinforcing element, as shown in  FIG. 4 . 
   To resist buckling of the side walls and to increase stackability, drum  10  is configured with at least one reinforcing element disposed about its circumference. In the left half of the illustration in  FIG. 4 , the reinforcing element is an annular protrusion  22  that runs around the drum&#39;s circumference. In the right half of the illustration, the reinforcing element is in the form of inward corner indentations  24 . In either configuration, the reinforcing element (annular protrusion  22  or corner indentation  24 ) is measured at a height of about 43% from the drum  10  bottom, i.e., at the point where the square drum  10  is exposed to maximum buckling pressure. The annular protrusion  22  is configured as a shallow V-shaped, continuous indentation in such a fashion that the diameter of the annular protrusion  22  is roughly the same as that of the remaining drum body. Alternatively, the annular protrusion  22  can stick out slightly so that drums standing next to one another touch each other by way of the annular protrusion  22 . In an alternate embodiment, drum  10  can be configured with any number of reinforcing elements disposed about its circumference. 
     FIG. 5  is a top view of the preferred embodiment of the drum  10 . This embodiment of drum  10  has a first portion with a substantially rectangular or substantially square cross-section, and a second portion with a substantially circular cross-section defined by four angular corner indentations  24  formed in the drum. The angular corner indentations  24  are outlined by the round dashed line. The indentations  24  may be deeper at the corner areas than they are on the side wall sections in between. In addition, as shown in  FIG. 6 , the indentations  24  define a vertical thickness that varies around the circumference of the side wall, e.g., is greatest in the corner areas and transitions into the flat surfaces of the side wall sections in between. 
   In the preferred embodiment of  FIG. 5 , the second portion of the drum  10  has a substantially circular cross-section in the horizontal plane of maximum continuous indentation. Referring to the outline of the substantially square drum  10 , the ratio between the long radius  36 , which is measured toward the corners, and the short radius  38 , which is measured toward the midpoint of the side walls, is between 1.05 and 1.34 and preferably about 1.22. 
   As also shown in  FIG. 5 , drum  10  has on its top surface, or first end wall, two molded-in, mutually parallel reinforcing ribs  28 . Reinforcing ribs  28  act to reinforce the upper surface of drum  10 . In an alternate embodiment, any number of reinforcing ribs could be added to the top surface in varying orientations with respect to one another. 
     FIG. 6  shows the axial indentations  26  (axial reinforcing ribs) in the middle of the side wall sections of the square drum  10 , serving to reinforce and stabilize the filled drum  10  against any buckling or bulging when subjected to stacked loads or internal pressures. In this particular embodiment, in contrast to a conventional square container such as a thin-walled canister, it is the flat side wall sections that support the axial load while the corner indentations  24  prevent any excessive radial bulging. The indentations  26  as well as reinforcing ribs  28  can be in the form of molded-in U- or V-shaped indentations or protrusions that face inward and/or outward. 
     FIG. 7  shows a diagonal cross-section of drum  10 . In this case, the container with the angled indentations  24  and smaller corners has the largest overall cross-section. It is evident from this illustration how much more volumetric capacity (10%) is obtainable when compared to a cylindrical drum. 
     FIG. 8  shows a drum  10  according to this invention firmly lying in a sideways position  30 . Without an external force, the drum  10  will not roll away in an uncontrolled fashion, yet the rounded corners allow it to be rolled and moved. 
     FIG. 9  shows how the drum  10 , when tipped, can be rolled in its slanted position  32 . In this slanted position even manual manipulation and rolling of the drum  10  using the rolling ring  18  is entirely possible without much of an effort. 
     FIG. 10  shows four square drums set on a standard-34 pallet (45 inches×45 inches), with maximum utilization of the space between the drums. Thus, when drums according to this invention are stacked in an ISO container, for instance when shipped by truck, about 10% more bulk material can be shipped in the same space and at the same cost of transportation. 
   While it is apparent that the invention herein disclosed is well calculated to fulfill the objects above stated, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art, and it is intended that the appended claims cover all such modifications and embodiments as fall within the true spirit and scope of the present invention.