Abstract:
A plastic container is provided for containing a fluid. The container has a base; a sidewall attached to the base and extending upward from the base; a top receiving portion for receiving a top for sealing the container; and at least one protrusion protruding upward from the base, the protrusion forming a mixing surface that is for promoting movement of the fluid when the container is shaken.

Description:
[0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/646,997 filed Jan. 27, 2005, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a base for a plastic container. The base having a shape that promotes the agitation of a material in the container.  
       SUMMARY OF THE INVENTION  
       [0003]     An embodiment of the invention provides a plastic container for containing a fluid. The container has a base; a sidewall attached to the base and extending upward from the base; a top receiving portion for receiving a top for sealing the container; and at least one protrusion protruding upward from the base, the protrusion forming a mixing surface that is for promoting movement of the fluid when the container is shaken. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]     Further advantages and details of the invention follow from the exemplary embodiments and are explained in the following with the aid of the Figures, in which:  
         [0005]      FIG. 1  is a perspective view of the bottom of a container in accordance with the invention; and  
         [0006]      FIG. 2  is a top perspective view of the container shown in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0007]     The invention will be described using the example of a one gallon paint container. It is noted that although a one gallon paint container is being used to describe the invention, the invention can be applied to containers having different sizes and uses. In addition, the example shown in the drawings is a substantially square container having a round base. However, the invention can be applied to containers having different shapes.  
         [0008]      FIGS. 1 and 2  show a container  100  having a base  200  and a sidewall  300  connected to base  200 . In this example, container  100  is a blow molded plastic container. However, containers in accordance with the invention can be made from other materials and by other methods.  
         [0009]     Containers having a base in accordance with the invention enhance the mixing of viscous fluids within the container when the container is rotated or shaken. In the example shown in the drawings, the invention is applied to the base of a paint can that enhances the mixing of paint inside the can when the can is shaken with a shaking machine or when shaken by hand. By configuring the base of the container with one or more lobes or protrusions that protrude into the interior surface of the container, mixing is enhanced due to a wave effect caused within the fluid by the fluid being forced into contact with the protrusions. The protrusions are preferably shaped so that the container can be removed easily from a mold for making the container. Particular embodiments of the invention provide a shape with an extreme angle on one side and a lesser angle on the opposite side. This shape, when the container is rotated or reciprocated about a vertical central axis, will generate a wave effect within the fluid, thus causing enhanced mixing of the fluid. The wave or turbulence created by the container movement creates substantially more fluid motion within the container than a smooth bottom or base, resulting in more thorough and efficient mixing. The most motion is created near the bottom of the container, which is where heavy solids tend to settle in fluids. While the protrusions are shaped to promote mixing as discussed above, their shapes still allows the use of stirring sticks or paddles. This configuration is appropriate for at least quart, gallon and multi-gallon sizes as well as round, modified round, square and rectangular shaped containers.  
         [0010]     Although two protrusions are shown in the figures, one, three or any number of protrusions can be used. Also, the shape of the protrusions can be other than the shapes shown as long as the protrusions promote mixing and demold easily. In particular embodiments, the face of the protrusion created by the more extreme angle relative to the base extends radially substantially the entire length from a central portion of the base to an outer periphery of the base.  
         [0011]     In the example shown in the drawings, base  200  has two protrusions  220 . Each protrusion  220  has a mixing surface  225  located between a lower edge  230  of the mixing surface and an upper edge  240  of the mixing surface. A sloping surface  250  extends from upper edge  240  and slopes down to an intersection  260  where sloping surface  250  intersects base  200 . In this example, intersection  260  is a curved line.  
         [0012]     In this example, base  200  has a support ring  210  that provides a flat surface on which the container rests when the container is placed on, for example, a table or floor. In particular embodiments, support ring  210  is shaped to interact with a top (not shown) of the container so that multiple containers can be securely stacked on top of each other.  
         [0013]     In the example shown in the drawings, a handle  500  is provided to facilitate carrying container  100  and to facilitate rotational mixing by hand. Depending on the design and removability of handle  500 , multiple containers can be stacked on top of each other as described above.  
         [0014]     In the example shown in the figures, base  200  has a center  270  and protrusions  220  extend substantially the entire distance between center  270  and an outer limit of base  200 . However, it is noted that protrusions  220  can be longer or shorter than the example shown in the figures.  
         [0015]     The invention is not limited to the above-described exemplary embodiments. It will be apparent, based on this disclosure, to one of ordinary skill in the art that many changes and modifications can be made to the invention without departing from the spirit and scope thereof.