Abstract:
A shipping container for liquids is described. This consists of an outer corrugated paperboard container containing an inner corrugated liner forming corner posts. A flexible or semi-flexible bladder or jug generally conforming in cross section to the inside of the corrugated container contains the liquid. It is desirable for the inner corrugated liner to be bonded to the outer container, especially along the margins of the corner posts. It has been found to be critical that the ratio of the length of the outside face of the outer container to the corner post length should be no greater than about 8:1. This is essential to prevent face bulging, especially when the inner plastic container is filled with a high density material such as a paint. Where the inner plastic container has an upstanding handle or spout it is useful to have filler pieces that bear between the plastic container and upper flaps of the outer corrugated container. This prevents any up and down motion of the inner container during normal handling or under the severe stresses that might be imposed on a paint shaker.

Description:
[0001]    The present invention is directed to a shipping container for liquids. This is of the type in which a thin plastic inner container for the liquid is placed within a corrugated outer container for structural rigidity and protection. The container is particularly suitable for products such as paints that must be severely agitated in the container to disperse and homogenize the contents before use.  
         BACKGROUND OF THE INVENTION  
         [0002]    It has been common practice for many years to ship liquid materials contained within plastic bags enclosed in a rigid outer container. One might note U.S. Pat. No. 4,174,051 to Edwards et al. as an example. This patent shows a corrugated box containing a flexible plastic inner container with a pull-up spout for filling and dispersing the liquid contents.  
           [0003]    Rutter, U.S. Pat. No. 4,322,018, is primarily directed to a valve with means to pierce an otherwise imperforate bag at the time of use. The patent shows a liquid filled bag within a corrugated paperboard container having a keyhole-shaped portion that can be opened for access to the valve.  
           [0004]    Cox, Jr., in U.S. Pat. No. 3,100,587 shows a liquid container having a plastic bag within a containerboard box. The bag has a capped pouring tube affixed by a wire tie to a tab on one of the inner upper flaps of the container. When the overlying outer flap is opened the tab with its affixed tube is exposed.  
           [0005]    Nichols, in U.S. Pat. No. 5,029,734, shows a reusable pallet mounted molded plastic container enclosed within a reinforcing containerboard shell. Similarly, Perkins, in U.S. Pat. No. 5,813,562, is another pallet mounted container having an interior collapsible plastic bag within exterior multiwalled containerboard in the form of a regular octagon. This particular construction enables the bag, with a lower drain, to be conveniently installed from the bottom of the exterior container.  
           [0006]    Containers having a bag within a box and permanently mounted exterior spouts have also been used for many years. Exemplary among these might be noted the following U.S. patents: Parker, U.S. Pat. No. 2,973,119; McCullough et al., U.S. Pat. No. 4,696,840; Gordon et al., U.S. Pat. No. 5,156,295; and Voorhies Jr., U.S. Pat. Nos. 4,793,519 and 4,930,661.  
           [0007]    Baker, in U.S. Pat. Nos. 5,348,186 and 5,474,203, shows a bag within a multipiece octagonal exterior corrugated container. These patents are especially directed to a construction that maintains an upper spout locked in place to accept a hand pump. Openings at the top of the container allow it to be handled by a conventional barrel hand truck. A similar plastic bag within an octagonal corrugated outer container is shown in Benner et al., U.S. Pat. No. 5,749,489, although in this case the inner container has a bottom drain.  
           [0008]    More commonly, liquid materials in larger quantities have been shipped within metal drums or in metal or plastic buckets of various sizes. Buckets are frequently of about 5 gallon (˜20 L) capacity so that they can be readily handled. When shipping paints and other compositions that may contain a significant percentage of suspended solid materials, these buckets typically have removable heads covering the entire top. Again using paints as an example, the buckets are palletized for shipping and at the point of use individual buckets may be placed on a shaker to disperse the pigment and/or other solid components. The action of the shaker is quite violent, as anybody who has observed a smaller shaker in a paint store can testify.  
           [0009]    Containers must be capable of withstanding severe forces during shipping and use. There are significant disadvantages to shipping palletized buckets. Foremost among these are the inefficient use of space on the pallet and the hazard of the outermost buckets inadvertently slipping off the edges. Depending on the particular bucket size and configuration on the pallet, as much as half of the pallet surface may be underutilized. Another disadvantage is that the upper surface of the buckets provides an unstable and irregular bearing surface for stacking additional pallets. One proposed solution to the above problems has been to ship the paint within a plastic bag contained in a corrugated paperboard shipping container. This has had only limited success for a number of reasons. The entire inner and outer container must be strong enough to withstand stacking and the action of the shaker. Many times the material shipped is a tint base and various customized pigments are added at the point of use and the inner container must be able to accommodate this added material. If the inner container is not completely filled the contained liquid can slosh violently back and forth during shaking. For this reason, and to exclude air from leftover contents, the inner container is usually flexible enough so that it can be partially collapsed after partial removal of the contents.  
           [0010]    It is highly undesirable to have to open the top flaps of the container for access to the spout; e.g., to add pigment. The container then loses much of the strength needed on the shaker and during subsequent handling, as when the container is picked up to pour paint into a smaller working container. Cartons may be designed with an opening for the spout, as in the aforenoted Edwards et al. patent, but these are effective only if the spout is always located exactly under the opening. During shipping, and especially during shaking, there is a strong tendency for the filled bags to rotate within the container so that an originally properly located spout is then nowhere to be found without tearing open the top flaps. Rotation during shaking can also result in abrasion and failure of the inner bag.  
           [0011]    The present invention overcomes the deficiencies just noted and provides an effective plastic container-within-a-box for paints and many other liquid materials.  
         SUMMARY OF THE INVENTION  
         [0012]    The invention is a shipping container for liquid materials comprising the combination of a relatively lightweight liquid tight flexible or semi-flexible bladder or jug within a corrugated paperboard outer carton. An upper access spout with a removable cap is normally integral with the jug. The construction is designed to minimize relative motion between the inner plastic portion and the outer corrugated container during use. This use may vary from low energy routine handling to high energy shaking. By minimizing relative motion between the inner plastic container and outer corrugated paperboard, any tendency to create stress points and form leaks in the plastic inner container is controlled.  
           [0013]    In the past with bag-in-a-box construction, the inner plastic containers have usually been a simple rectangular flat bag within a conventional corrugated container. Alternatively, a blow-molded jug having a rectangular cross section with rounded corners has been used. When such a container is used for paint it must be able to withstand severe shaking at the time of use to uniformly disperse the pigments. This is an extreme requirement for a container. Not only must it have sufficient strength to permit stacking multiple heavy units, it be strong enough to withstand rough handling on the shaker. Further, it must retain sufficient strength even the extreme humidity of a Southeastern summer. It is well established that at 90% relative humidity the edge compression strength of most corrugated board drops to about half that at 50% R.H.  
           [0014]    When attempts have been made to package paint in a bag-in-a-box-type container, the bags or jugs have been subject to failure during shaking. This failure might be as minor as pin hole leaks or as major as catastrophic tears. Neither is acceptable. A significant part of the problem appears to be due to movement of the plastic container within the outer box during shaking. In one attempt to make a more satisfactory paint container, a conventional blow molded bladder or jug was placed in a corrugated container having corner posts. This construction initially failed. As the plastic container attempted to conform to the corner posts, the resulting wrinkles or folds created stress points that led to pinhole failures. Further, bulging of the corrugated box sidewalls permitted excessive movement of the paint filled bladder within the container. Bulging, in effect, increases the volume of the corrugated container and allows the inner plastic container to rotate and/or bounce up and down. In addition to causing leaks, this bouncing or rotation can occur at a frequency that will significantly increase the load on the shaker to the point that the motor will overload and shut down.  
           [0015]    A major solution to the above problems has been the use of corner posts in the corrugated outer container that are sufficiently long to prevent face bulging during shaking. A second part of the solution is to use an inner plastic container that will closely conform in cross section to the inside of the outer corrugated container in order to eliminate the wrinkling or creasing and subsequent leak formation.  
           [0016]    The shipping container overall is configured as a rectangular parallelepiped which may be square or rectangular when seen in plan view. An outer corrugated portion will be of sufficiently heavy one-piece construction as could be easily determined by a skilled packaging engineer. The outer portion has a conventional side wall section and top and bottom sections comprising overlapping flaps. This is fitted with a snugly fitting interior insert comprising a corrugated secondary sidewall with truncated corners so that it is octagonal in plan view. The secondary sidewall provides reinforcement of the outer sidewalls while the truncated corners act as vertically oriented corner posts. Most preferably, the secondary sidewall is adhesively bonded to the outer container, at least along the margins of the corner posts. As seen in plan view, the ratio of the length of the sidewalls of the outer container to the length of the corner sections of the interior insert had been found to be critical. This should be no greater than about 8:1 and will fall within the range of about 3.3:1 to 8:1. Construction within this ratio is essential to prevent bulging of the face portions that might be caused by the high stresses experienced during shaking of container filled with a heavy material such as paint. The length of the corner posts must be sufficient, within the 3.3:1 to 8:1 range, to prevent sidewall bulging, but preferably the length is held to the minimum necessary to reduce lost space within the container.  
           [0017]    The inner liquid tight plastic container will normally have an integral spout for filling and accessing the contents and may, optionally, have an integrally molded handle. Both spout and handle, if present, may be permanently upstanding or they may be conventionally formed or telescoped down below the top surface of the container. In the case where the spout and handle are upstanding, there will normally be a space between the inner plastic container and the upper flaps of the outer corrugated container. This space is necessary so that the spout and handle do not protrude above the top surface where they would interfere with stacking. The area of this space should be wholly or in part filled with a filler piece or pad to reduce or prevent vertical displacement of the plastic container during handling or shaking. It is also desirable to have some means within this space to restrain rotation of the jug or bladder. The filler pieces may be as simple as several thickness of containerboard. Material for their construction is not critical and there are many options besides containerboard. These may be separate from the main outer container or may be integrally formed on opposing upper flaps. Preferably they are located symmetrically on either side of the spout, the spout normally being located centrally along one edge of the top surface of the jug. Normally the filler pieces would be bonded into place to prevent movement during handling or shaking. If the spout and the handle, if one is present, are recessed below the upper surface of the plastic container the filler pieces are unnecessary and the top flaps of the outer corrugated container can be located directly against the upper surface of the plastic container.  
           [0018]    The plastic jug or bladder would normally be blow molded from polyethylene or a similar material. Preferably it should have sufficient flexibility so that it can be at least partially collapsed prior to filling or following withdrawal of some of the contents. This flexibility is desirable to minimize the amount of space required to inventory the containers prior to filling and for ultimate disposal.  
           [0019]    The invention thus consists of an outer corrugated container, an inner octagonal secondary corrugated sidewall forming corner posts, and a space conforming octagonal liquid-tight plastic inner container. The ratio of the lengths of the face portion of the outer container sidewall to the corner sections should be no greater than about 8:1.  
           [0020]    It is an object of the invention to provide a container for liquids that is lightweight, disposable, and which will withstand severe external forces during shipping and downstream handling.  
           [0021]    It is another object to provide a container for liquids having an inner plastic container within a corrugated outer shipping container.  
           [0022]    It is a further object to provide a container for paints that is resistant to developing leaks when the contents are dispersed on a shaker.  
           [0023]    It is yet an object to provide a paint container that will withstand the forces delivered by a paint shaker yet will not induce an excessive load on the shaker motor or mechanism.  
           [0024]    It is an additional object to provide a container for liquids that is collapsible when empty to minimize storage space for the containers before and after use.  
           [0025]    These and many other objects will become readily apparent upon reading the following detailed description taken in conjunction with the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is an exploded view of the container of the present invention.  
         [0027]    [0027]FIG. 2 is a perspective view showing the assembly steps of the container of FIG. 1.  
         [0028]    [0028]FIGS. 3 and 4 show alternative top spacer units for the FIG. 1 container.  
         [0029]    [0029]FIG. 5 is an exploded view of an alternative configuration in which the interior container handles are depressed so that they are flush with the upper surface.  
         [0030]    [0030]FIGS. 6 and 7 show the assembled package using the interior container of FIG. 5.  
         [0031]    [0031]FIG. 8 shows an additional design for the spacer units for the FIG. 1 container.  
         [0032]    [0032]FIG. 9 illustrates an alternative construction for the bladder rotation means. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    Referring now to the drawings, FIG. 1 shows the container of the present invention. This comprises an outer corrugated box  2  having face panels  4  and upper flaps  6 ,  6 ′, and  8 ,  8 ′. Similar flaps, not shown, are present to form a bottom closure. An insert portion  10 , also of corrugated board, fits snugly within outer box  2 . The insert has face panels  12  and truncated corners  14  that serve as top-to-bottom corner posts. The insert can be formed from one or more individual pieces and is most preferably adhesively bonded to the outer box, especially along the edges of the corner posts. A blow molded or similarly formed semi-flexible octagonal plastic bladder or jug  16  fits snugly within the corrugated insert  10 . The jug has face portions  18  and corner sections  20  that correspond to and are closely configured to the interior of insert  10 . A spout and cap  22  are located on the upper surface of the jug, as is an optional handle  24 . Above the jug is an optional sheet of corrugated board  26  having cutouts  28  and  30  to pass through the spout and handle of the jug. This piece is useful to restrain rotational movement of the jug during shaking. Finally filler pieces or pads  32 , which may be formed of corrugated board or any other material, are located on each side of the spout and handle and preferably bonded to sheet  26 . These correspond in thickness to the height of the spout and handle and bear against the upper flaps  6 ,  6 ′,  8 ,  8 ′ when closed. The filler pieces serve to prevent upward movement of the jug when the package is closed or during agitation on a shaker.  
         [0034]    Referring now to FIG. 2, assembly steps of the container are shown. Insert  10  is first placed within the outer box  2  then jug  16  is slid inside the insert. The upper sheet of corrugated board  26  is placed on top of jug  16  then the pads  32  are laid along each side of the spout  22 . Side flaps  6 ,  6 ′ are first closed to retain pads  32  the front and rear flaps  8 ,  8 ′ are closed and glued to flaps  6 ,  6 ′ to complete the container  40 .  
         [0035]    [0035]FIG. 3 shows one of several possible alternative configurations of the container. Here the separate upper insert  26  and filler pieces  32  shown in FIGS. 1 and 2 are replaced by a piece generally seen at  42  in which the insert  44  and filler pieces  46  are formed from a single piece of corrugated board. Another alternative is seen in FIG. 4 in which side flaps  6  of the outer container  2  are modified and the filler pieces are formed integrally from extended side flaps  50  by bending along score lines  52 .  
         [0036]    Another alternative construction, shown in FIG. 5, would employ a bladder or jug  50  in which the spout  52  and handle  54 , if present, would be placed below the upper surface of bladder or jug  50 . A handle can be conveniently be located within a depressed portion of the upper surface and a well known telescoping or popup-type spout used in place of the one shown in the earlier figures. In this case the filler pieces shown earlier would not normally be required since the upper surface of the inner plastic bladder or jug could be flush and in contact with the top flaps  6 ,  6 ′,  8 ,  8 ′ of the outer corrugated container. In FIGS. 6 and 7 the bladder  50  is shown inserted into the corrugated container at  56  and the completed container with the upper flaps sealed at  58 .  
         [0037]    Where the container must withstand very severe handling forces, such as a paint shaker, it is desirable to fill the space above the rotation prevention sheet  26  and the upper flaps  6 ,  6 ′,  8 ,  8 ′ to the maximum extent reasonable. FIG. 8 shows a construction  60  for the filler pieces that serves this purpose. It is also desirable that the filler pieces, whether of construction  32 ,  46 , or  60 , be relatively rigid so that they do not deform by racking or in other ways when subject to the forces of a paint shaker. Preferably, if corrugated paperboard is used, they will have a minimum of interior void space, other than that within the interior of corrugations. In addition to the constructions shown, fan-folded corrugated board, rigid foam materials, honeycomb, wood, etc. are all suitable. The rotation prevention sheet  26  may also be formed somewhat differently to assist in reducing tendency of the interior bladder or jug to rotate during shaking. Rather than the simple slot  30  seen in the earlier figures, FIG. 9 shows a preferred construction. The jug or bladder handle  24  is in the form of an inverted U having upstanding legs and a connecting crosspiece. Two holes  62 , large enough to pass the legs of the handle, are punched in the sheet. These are connected by a slit  64 , embraced by score lines  66 , that permit the handle to be pushed through. After the handle  24 , shown here in phantom view, is inserted the containerboard on both sides of the slit closes and the two adjoining sides bear against each other to provide extra strength.  
       EXAMPLE 1  
       [0038]    A shipping container approximately 14 inches (35.6 cm) high and of 10×12 inch (25.4×30.5 cm) square cross section was formed from corrugated board having 56 pound liners and 36 pound corrugated medium (274-176-274 kg/m 2 ). A snugly fitting insert formed from two pieces of the same board was used to double the sidewall thickness. A generally rectangular-shaped plastic jug having an integral handle and spout and having an approximate 10×12 inch (25.4×30.5 cm) cross section was placed within the corrugated container. The jug had a wall thickness in the range of 0.04-0.06 inches (1.0-1.5 mm) with each edge being rounded on an approximate ¾ inch (19 mm) radius. Filler pieces were placed between the upper surface of the jug and the top of the outer container, the top flaps of the outer container were closed and sealed, and the jug was then filled with paint. The filled jug was then placed on a Harbil 5G model paint shaker supplied by Fluid Management, Inc. Wheeling, Ill. Paint shakers are available from a number of manufacturers and this should not be considered as an endorsement of this particular piece of equipment over others that are available. The shaker has a pair of separated platens that squeeze together to hold the paint container during shaking. These platens place a force of about 800-1200 pounds (3600-5400 N) on the container to hold it in place. The shaker vibrates via a belt driven offset cam mechanism at about 600 cycles/minute and is powered by a ¾ hp (0.56 kW) motor equipped with a current overload. The shaking time can be adjusted up to a maximum of 3 minutes.  
         [0039]    For this and all subsequent tests the containers were conditioned to equilibrium at 90% relative humidity prior to testing. The motor was started with the paint filled container on the shaker but after about 1 minute the motor overloaded and kicked out due to overheating. Apparently, sidewall bulging of the corrugated container had allowed the interior plastic container to move at a different vibration rate than the shaker. The movement of the paint-filled plastic interior container evidently began increasing resistance to the motion of the vibrating platens so that a motor overload occurred. No leaks were observed in the plastic inner container. However, agitation time to achieve good paint mixing was regarded as insufficient.  
       EXAMPLE 2  
       [0040]    A second container was formed in all ways similar to that of Example 1 with the exception that the inner liner of the corrugated container was formed to provide 1 inch (25 mm) corner posts, this measurement being the length of the truncated corner portions. Again, the paint shaker motor overloaded and shaking could not proceed beyond about 1-1½ minutes. Some wrinkling was noted in the interior plastic container where it contacted the corner posts. This wrinkling created stress points that caused pinholes to develop during shaking and paint leaks to occur.  
         [0041]    A similar container was formed except that the length of the corner posts was increased from 1 inch to 2 inches (from 2.5 to 5.1 cm). This time the motor did not overload for the full 3 minute shaking period. However, upon examination, pinhole leaks were again noted where the corners of the jug had become deformed and wrinkled from contact with the corner posts in the corrugated container. Similar results were noted when the corner post length was extended to 3 inches (7.6 cm).  
       EXAMPLE 3  
       [0042]    While not in any way limiting of the invention, an outer container size is 10×12 inches (254×305 mm) in cross section and 14 inches (356 mm) high is convenient. This enables 16 containers each holding 5 gallons (18.9 L) or 20 L to be placed on a standard 40×48 inch (1.02×1.22 m) Grocery Manufacturers Association (GMA) pallet. In this example the outer container was constructed from a corrugated board having a 69 pound liners and a 36 pound corrugated interior construction (336-176-336 kg/m 2 ). The secondary sidewall or inner liner was formed in two pieces and used to provide corner posts having a 1.5 inch (38 mm) length. This was conveniently formed from a corrugated board of similar weight to the outer box and was spot bonded to the outer container. It is especially important that the area along the edges of the corner posts be bonded to the outer container. The inner liner may be made in either one or two piece construction. While other constructions of the corrugated components are possible, those just described use a minimum of fiber to accomplish the required result. For a box having a major face 12 inches (305 mm) long, extensive experimentation has shown that the length of the corner post section of the secondary sidewall should be at least 1.5 inches (38 mm) and preferably less than 3 inches (76 mm). With a 1.5 inch corner post the ratio of face length to corner post length is 8:1 for the 12 inch dimension of the outer container and 6.7:1 for the 10 inch dimension. It appears critical that this ratio should not exceed about 8:1 if sidewall bulging is to be prevented. For other sizes of outer containers these lengths may be adjusted somewhat as long as the maximum ratio of length face length to corner post is not exceeded. It is desirable from the point of minimizing unused space within the container to reduce corner post length to the minimum necessary to provide adequate top-to-bottom stiffness, prevent bulging, and prevent inner container movement. Shorter corner post lengths; e.g. those greater than about 8:1 ratio of face to corner post length have been found to permit considerable movement of the interior container within the outer container. This usually results in breaker kick-out of the paint shaker and/or leak formation within the inner plastic container.  
         [0043]    A new design bladder or jug having an octagonal cross section was used. The corners were about 2 inches (50.8 mm) wide so that the jug conformed closely to the interior dimensions of the corrugated container. This design permits the container filled with paint and conditioned to equilibrium at 90% relative humidity to shake a full 3 minutes without motor overload. Movement of the plastic container within the corrugated container was minimized during shaking and no wrinkling or pinhole leaks occurred.  
         [0044]    Having described the best mode of construction of the container, it will be evident to those skilled in the art that there may be other possible variations in the design that are not described herein. These should be considered within the purview of the invention if encompassed within the following claims.