Abstract:
A container for a material, wherein the container has a body, a base, and a lid is presented. The base may be with or without a tamper-evident feature, depending on requirements, while the lid is made preferably of a clear, transparent plastic. The body has a bottom and a tubular element defining sides of the body and extending upwardly from a periphery of the bottom. An upper portion of the tubular element forms an aperture of the body. The base has an externally directed annular protrusion which engages a recess in the aperture-forming portion of the tubular element of the body. In this way, a permanent seal is made at the top of the body after filling with the material. A lid is adapted to removably engage a top portion of the base.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of priority to U.S. provisional patent application Ser. No. 61/257,118 filed Nov. 2, 2009, now pending, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to the field of containers, and more particularly to thermoplastic cans for shipping and storing materials. 
       BACKGROUND OF THE INVENTION 
       [0003]    The current application incorporates by reference the Thermoplastic Can presented by U.S. Pat. No. 7,419,068, hereinafter referred to as the &#39;068 patent, granted on Sep. 2, 2008 to Maxwell Bushby; international publication no. WO/2003/055754 (info enclosed). International counterparts are as follows: Australian Patent No. 2002351876 (info enclosed); South African Patent No. 2004/5794; Australian Design Registration No. 152397 (info enclosed); New Zealand Patent No. 533257 (info enclosed); Indian Patent No. 208441 (info enclosed); Philippines Patent Appl. No. 12004450967; and Malaysian Patent No. 20042500. The Abstract of patent &#39;068 specifies: “A thermoplastic can ( 1 ) comprising a thermoplastic body ( 2 ) having a disc like top ( 3 ) molded as one with a tubular element ( 5 ) defining the sides of the body ( 2 ) and extending downwardly from the peripheral portions of the top ( 3 ); an openable portion associated with the top to facilitate use of the can contents by an end user, a thermoplastic base member ( 7 ) having an externally directed protrusion ( 8 ) engaged in a relatively thin walled recess ( 9 ) in the radially internally facing lower peripheral portion of the body thereby effecting a permanent seal at the base of the container after filling thereof; the resistance to permanent inward deformation of the externally directed protrusion exceeding the resistance to permanent outward deformation of the thin walled recess; the wall thickness of the lower peripheral portion of the body below the thin walled recess exceeding that of the thin walled recess.” 
         [0004]    The majority of paints on the market are supplied in tin cans with tin covers, either lacking tamper-evident features or having tamper-evident features constructed of a different material, such as plastic, the combination of materials not only requiring a complicated manufacturing and installation process, but rendering such containers un-recyclable in facilities where separation cannot be achieved by use of machinery. 
         [0005]    The present invention relates to a thermoplastic can of a three piece design comprising a paint can (container), a base, and a lid, wherein a permanent base to container seal is effected between a peripheral portion of the base and an internally facing surface adjacent the aperture of the can (similar with the seal of the &#39;068 patent), further presenting an openable attachment of lid to base, the lid being made of preferably transparent plastic to allow visibility to the contents of the can package. Paint can, base and lid are made of thermoplastic material, hence being recyclable as a unit. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present application builds on the design of the &#39;068 thermoplastic can, presenting a can-to-base closure with three circumferential seals similar in principle to the seal of the &#39;068 patent, and further adding a lid-to-base closure with another set of three circumferential seals. The base may be with or without tamper-evident feature, depending on requirements, while the lid is made preferably of a clear, transparent plastic that allows instant color verification (i.e. a re-opening of the lid for color verification is not necessary). While the object of the present invention is intended for use as paint can package, it may be used for any applications where it is desired for the contents of the can to be visible without opening the lid. No particular comments are made regarding the size of the paint can package, other than to specify it is envisioned for a comprehensive range of sizes as to be commercially useful. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1  (prior art) presents the thermoplastic can of patent &#39;068 (copy of Sheet 1 of 4 of &#39;068 patent, showing  FIGS. 1 and 3 ). 
           [0009]      FIG. 2  is a perspective view of the paint can, base and lid in accordance with the present invention, shown before installation. 
           [0010]      FIG. 3  is a perspective view of the paint can, base and lid in accordance with the present invention, shown after installation. 
           [0011]      FIG. 4  is a cross-section through the opening of the paint can, showing its key features. 
           [0012]      FIG. 5  is a cross-section through the periphery of the base according to a preferred embodiment of the invention, showing its key features. 
           [0013]      FIG. 6  is a cross-section through the periphery of the lid, showing its key features. 
           [0014]      FIG. 7  is a cross-section through the closure of the paint can, base and lid of a preferred embodiment of the invention, showing the three circumferential seals between lid and base, and the three circumferential seals between base and body of paint can, the base having tamper-evident feature. 
           [0015]      FIG. 8  is a cross-section through the closure of the paint can, base and lid of a second embodiment of the invention, presenting a base without tamper-evident feature. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    A detailed description of the preferred embodiment of the invention follows with reference to  FIGS. 2-7 . 
         [0017]    As can be seen in  FIG. 7 , the easy-mix paint can package is formed by a paint can  10 , a base  12 , and a lid  14 . 
         [0018]    With reference to  FIG. 4 , paint can  10  has an aperture  16  presenting an annular protrusion  18  having an angular surface  20  projecting upwardly and radially inwardly from the paint can wall, with an angle between 0° and 45° measured from the horizontal, but preferably 15°-25°. A periphery  22  of paint can further presents sloped surfaces  24  and  26 , followed by a thickened rim  28 . Sloped surfaces  24  and  26  form a thin walled recess or undercut  25 , the thickness of the membrane  25   a  between corner of undercut  25  and outer surface of paint can  10  being substantially thinner than the thickness of rim  28 . 
         [0019]    As can be seen in  FIG. 5 , base  12  has a somewhat U-shaped periphery, with a bottom portion  30  having a bottom surface  32  sloped to match surface  20  of the paint can. An externally directed annular protrusion  36  of base  12  extends upwardly and outwardly, having sloped surfaces  38  and  40  matching sloped surfaces  24  and  26  of the paint can. 
         [0020]    As base  12  is installed in paint can  10  at the aperture  16 , protrusion  36  flexes inwardly to ride over the inner surface of rim  28 , flexing outwardly again to bite into recess  25  while its sloped bottom surface  32  comes into contact with sloped surface  20  of paint can. The thickness differential between membrane  25   a  and rim  28  allows the membrane to flex radially outwardly as base  12  is installed. Once protrusion  36  comes to rest in recess  25 , the superior ‘memory’ of the thickened rim  28  returns it to its original diameter. Similar to the behavior explained in the &#39;068 patent, this succession of motions is possible due to the fact that the thin membrane  25   a  undergoes some plastic deformation, while the thickened rim  28  undergoes an elastic deformation during installation of base into paint can. A membrane thickness of 0.006″ to 0.032″ is recommended in order for the thin walled recess to deform outwardly during installation of the base and thereafter. 
         [0021]    Once installation has thus been achieved, base  12  and paint can  10  form a first seal  34  at surfaces  20  and  32 , a second seal  42  at surfaces  24  and  38 , and a third seal  44  at surfaces  26  and  40 . 
         [0022]    The thickness of annular projection  36  is such that its resistance to permanent inward deformation exceeds the resistance to permanent outward deformation of thin walled recess  25  due to the fact that protrusion  36  has a 30-35% thicker cross-section than that of thin walled recess  25 . It is obvious that once the base is installed in the paint can, it cannot be disengaged without permanently damaging these two components. 
         [0023]    The outermost edge  39  of protrusion  36  (which bites into thin walled recess  25 ) should preferably be rounded. While a larger radius would ease installation of base into paint can, it should however be sufficiently small to not overly reduce the surface area coverage of seals  42  and  44 , values of R0-0.030″ being a suitable compromise. 
         [0024]    Similar to the design of the &#39;068 patent, the paint can and base should preferably have a slight interference or friction fit, such that when the base is secured between surfaces  20  and  26  of paint can, there is an interference of 0.000″-0.002″. With reference to the embodiment presented here, surfaces  26  and  40  should have an angle between 15° and 45° with the horizontal, but preferably 24°-32°. Further similar with the &#39;068 patent, the angle of protrusion  36  is recommended to be between 20° and 45° with the vertical. 
         [0025]    Furthermore, the maximum diameter of protrusion  36  is larger than the maximum diameter of recess  25  into which it is fitted. This interference fit is critical to the seal of the paint can, and, while dependent on capacity and size of paint can, it is preferably in the range of 0.004″ to 0.028″. 
         [0026]    Further with reference to  FIGS. 2 and 5 , base  12  has an inner annular projection  46  extending upwardly into a thickened rim  48 . Rim  48  has outer sloped surfaces  50  and  52 , a flat top surface  54 , and an inner sloped surface  56  meeting the predominantly vertical inner surface of annular projection  46 . A preferred embodiment of the invention presents base  12  with a horizontal continuous panel  58 , connected to the inner surface of annular projection  46  by a thin tear-tab membrane  60 . On the top surface of panel  58 , an easy-pull tear-tab handle  62  projects towards the aperture side of the paint can. When color mixing is desired, panel  58  is removed from base  12  by pulling on tear-tab handle  62  and breaking the tear-tab membrane  60  all around its circumference. 
         [0027]    As can be seen in  FIG. 6 , lid  14 , preferably made of transparent plastic, has a continuous central panel  64  and a substantially reinforced periphery  66 . Periphery  66  presents two downwardly-projecting portions, a first portion in the shape of a ridge  68  with a tapered surface  70  matching that of surface  56  of base  12 , followed by a flat portion  72 , and a second downwardly-projecting portion  74  having sloped surfaces  76  and  78 , surface  78  with an angle matching that of surface  50  of base. Lid  14  further has two downwardly projecting ridges  80  and  82 , and an external, substantially horizontal projection  84 . As lid  14  is installed on base  12  (itself installed on paint can  10 ), lid and base form a first seal  86  at surfaces  50  and  78 , a second seal  88  at surfaces  54  and  72 , and a third seal  90  at surfaces  56  and  70 . Therefore, and with reference to  FIG. 7 , when the paint can, base and lid are fully assembled, no fewer than six circumferential seals protect the contents of the can. 
         [0028]    In order for the thickened rim  48  to snap into its seat in the lid, surface  52  rides along the tip and inner surface of ridge  80 , slightly flexing radially inwardly while forcing ridge  80  to flex radially outwardly. As rim  48  reaches up and into contact with ridge  68  of lid, it is guided along both sides into its seat. As can be seen in  FIG. 6 , to allow such installation, all edges involved in contact and guiding should preferably be rounded. Edge  51  of thickened rim  48  should preferably be rounded to help it ride against inner surface  79  of ridge  80 . The bottom of ridge  80  should preferably be fully rounded, while inner surface  79  should preferably be sloped at an angle of 5°-15°, preferably 7°-10° to the vertical. Furthermore, inner edge  77  (formed between sloped surfaces  79  and  78 ) should be rounded. 
         [0029]    As rim  48  snaps into its seat in the lid, it is held snugly between surfaces  78 ,  72 , and  70 , forming the three circumferential seals described above. 
         [0030]    As can be seen in  FIGS. 5 ,  6 , and  7 , surfaces  52  and  76  are designed with clearance, and while parallel to each other in the embodiments presented here, they need not necessarily be so. The only requirement is that they not interfere with each other, the angle of surface  52  being selected mainly with the purpose of easing installation in the manner described above, while keeping the thickness of rim  48  sufficiently substantial for long term performance of the closure, a value of 15°-45° from the vertical being recommended. The angle of surface  76  should derive accordingly, to allow sufficient clearance, ideally 0.020″-0.040″. A similar clearance should be achieved in the space between seals  34  and  42  of container to base, as can be seen in  FIG. 7 . 
         [0031]    The overwhelming majority of paint cans on the market are tin cans with tin lids, having no tamper-evident feature. White paint is supplied, with the tint being added upon sale of the paint. After color blending, the seller typically opens the lid to reveal the color to the customer, and may smear a smidge of paint on the lid as further visual proof of the content. 
         [0032]    The invention presented here brings considerable improvement over existing art. Firstly, panel  58 , molded integrally with base  12 , provides a tamper-evident feature over current designs. The three circumferential seals of base  12  to paint can  10 , together with the three circumferential seals of base  12  to lid  14 , protect the paint while preventing leaks. 
         [0033]    Another major improvement of the present invention is that by using a transparent lid, the color is visible without necessitating a re-opening of the paint can for color verification. This provides not only for faster service, but also prolongs the life of the paint by preventing air or contaminants from entering the paint can cavity until the end user accesses the paint. 
         [0034]    As can be seen in  FIG. 6 , lid  14  is provided with an annular bump  92  on its top surface, near the periphery, the purpose of this bump being to center paint cans for stacking purposes, as is common procedure in the field of plastic containers and lids. 
         [0035]    A second embodiment of the invention is presented with reference to  FIG. 8 . The base  12 ′ is similar with base  12  of the preferred embodiment, less the central panel  58 . This is an alternative for applications not requiring a tamper-evident feature, also allowing for a more economical option by reducing the amount of plastic injected in the base. 
         [0036]    The closure of the &#39;068 design presented in  FIG. 1  (prior art) is at the bottom of the container. The embodiments presented here have the closure at the top end of the container, allowing installation, capping and filling in the same orientation, hence simplifying the filling process, which ultimately results in financial savings. 
         [0037]    As can be noticed in  FIG. 7 , the paint can is shaped with a neck-like portion  94  below seal  34 , to minimize wall thickness while allowing a sufficiently sturdy construction of annular protrusion  18  to support the base without buckling during installation or usage. The wall outline projects along the same line above and below the neck-like portion. This feature minimizes the overall diameter of the paint can, reducing spatial requirements with regards to transportation and storage. 
         [0038]    As shown in  FIGS. 2 and 3 , the paint can is provided with a handle of a suitable construction for safely lifting and carrying the weight of the filled can. 
         [0039]    Furthermore, while the embodiments presented here are of circular design, it should be understood that rectangular, square, oval and oblong cross-sections are also considered. 
         [0040]    Although the present invention has been described with respect to one or more particular embodiments, it will be understood that other embodiments of the present invention may be made without departing from the spirit and scope of the present invention. Hence, the present invention is deemed limited only by the appended claims and the reasonable interpretation thereof.