Abstract:
A handgrip formed in a wall of a plastics container, the wall having an interior, an interior surface, an exterior surface and a wall thickness and suitable for containing a carbonated beverage, including an integral structure formed of a central dome having a convex surface facing toward the adjacent said exterior surface and at least two concentric annular troughs, each having an annular concave surface facing the adjacent said exterior surface, an outer frustum interconnected with each trough and connecting rings, each of curved cross-section having an annular concave surface facing toward the interior, to join, integrally, the frustums to the next outer trough and the outermost frustum to the container wall surrounding the handgrip, the handgrip having a thickness approximately equal to the wall thickness, wherein the handgrip does not extend radially outwardly of the wall. An associated container, blow mold and method are also included.

Description:
FIELD OF THE INVENTION 
     This invention relates to recessed handgrip features for liquid under pressure e.g. carbonated beverage containers, including bottles, made of a plastics and to methods and apparatus for producing such containers. 
     DEFINITIONS 
     “Plastics” are polymerizable materials that can be bi-axially oriented, e.g. polyethylene terephthalate (PET), polypropylene (PP) and acrylonitrile (AN) for use in containers for liquid under pressure, e.g. carbonated beverages. 
     “PET” as used herein shall be construed as including all materials defined hereinbefore as “Plastics”. 
     “Handgrip” as used herein is a circular feature formed by a deformation of the wall, which includes a shoulder, of a plastics container which does not extend outwardly (relative to the axis of the container) from the outer surface of the container even when the container contains liquid under pressure, e.g. a carbonated beverage, and is exposed to industry defined test procedures for such containers including exposure to stresses resulting from pressure and elevated temperatures during filling, packaging, distribution, sale and the end user actions. 
     “Circular” as used herein with respect to handgrips shall be construed to include ovals, ellipses, teardrops, circular segments and other rounded shapes as well as circular shapes 
     “Container” as used herein shall be construed to include plastics bottles. 
     “Frustum” as used herein shall be construed as a truncated hollow right circular cone in which the apex is replaced by a plane section parallel to the cone base and which has parallel inner and outer surfaces and shall be construed to include a hollow cylinder which has parallel inner and outer surfaces. 
     BACKGROUND OF THE INVENTION 
     In the past, different designs have been used to make a bottle meet specifications. The typical failure for a bottle is in the grip area or deep contour which will expand (creep) upon pressurization (carbonation) and/or higher than room temperatures. Typical bottle tests call for PET bottles to be pressurized to 4.0 volumes of CO 2  (˜55 psi at room temperature) and then placed in an oven for 24 hours at 100° F. At this temperature, the gas pressure rises to ˜95 psi. In addition to the higher forces applied to the plastic walls, the elastic modulus of the plastic is also slightly lower due to the higher temperature. Due to geometry, the bottles will creep in such a way distorting to the point of eliminating any grip or contour design elements in the sidewall of the bottle. 
     Some geometric designs will resist the creep and try to retain their original shape, but generally a good percentage of the shape is lost. U.S. Pat. No. 5,803,290 shows one design that claims to hold a significant portion of the shape. 
     PET for carbonated beverage containers has been used for many years. Many different shapes have been suggested to provide handgrips to easy user handling of these containers. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide a plastics container for liquids under pressure, e.g carbonated liquid beverages having stable handgrip features, in a wall thereof, which do not extend outwardly from that wall. 
     A further object of the present invention is to provide a blow mold design for producing a blow molded plastics container having stable handgrip features, in a wall thereof, which do not extend outwardly from that wall. 
     Another object of the present invention to provide a method of producing a plastics container having stable handgrip features, in a wall thereof, which do not extend outwardly from that wall. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a handgrip formed in a wall of a plastics container, the wall defining an interior of the container, an interior surface, an exterior surface and a wall thickness and being suitable for containing a carbonated beverage, comprising an integral structure formed of a central dome having a convex surface facing an adjacent portion of the exterior surface, at least two concentric rings each having an annular concave surface facing the interior, at least two annular troughs, disposed between the concentric rings, each having an annular concave surface facing an adjacent portion of the exterior surface; a frustum interconnecting one of the dome to the innermost trough and the innermost trough to the innermost ring; and further frustum(s) each interconnecting one of the rings to the next outer trough and next outer trough to the next outer ring, the outermost ring joining integrally the container wall surrounding the handgrip, the handgrip having a thickness approximately equal to the wall thickness wherein the handgrip does not extend radially outwardly from the wall. 
     Additionally frustums may be provided to interconnect domes, rings and troughs not otherwise so provided. 
     The troughs preferably increase in diameter from the dome to the wall of the container and the troughs and frustums increasingly extend further into the container relative to the wall, from the outermost trough and frustum to the dome. 
     Also according to the invention there is provided a plastics container for liquids under pressure having at least one handgrip, formed in a wall of the plastics container, the wall defining an interior of the container, an interior surface, an exterior surface and a wall thickness, the handgrip comprising an integral structure formed of a central dome having a convex surface facing an adjacent portion of the exterior surface, at least two concentric rings each having an annular concave surface facing the interior, at least two annular troughs, disposed between the concentric rings, each having an annular concave surface facing an adjacent portion of the exterior surface; a frustum interconnecting one of the dome to the innermost trough and the innermost trough to the innermost ring; and further frustum(s) each interconnecting one of the rings to the next outer trough and next outer trough to the next outer ring, the outermost ring joining integrally the container wall surrounding the handgrip, the handgrip having a thickness approximately equal to the wall thickness wherein the handgrip does not extend radially outwardly from the wall. 
     In addition, according to the invention there is provided a blow mold for blow molding a plastics container for liquids under pressure having at least one handgrip formed in a wall defining an interior of the plastics container and having, an interior surface, exterior surface and a wall thickness, the handgrip comprising an integral structure formed of a central dome having a convex surface facing an adjacent portion of the exterior surface, at least two concentric rings each having an annular concave surface facing the interior, at least two annular troughs, disposed between the concentric rings, each having an annular concave surface facing an adjacent portion of the exterior surface; a frustum interconnecting one of the dome to the innermost trough and the innermost trough to the innermost ring; and further frustum(s) each interconnecting one of the rings to the next outer trough and next outer trough to the next outer ring, the outermost ring joining integrally the container wall surrounding the handgrip, the handgrip having a thickness approximately equal to the wall thickness wherein the handgrip does not extend radially outwardly from the wall. 
     The invention also provides a method of producing a handgrip, in a plastics container for pressurized liquids, which does not, in use, extend outwardly from the outer surface of the container, comprises: 
     a) providing a blow mold having an axis and handgrip forming features in the form of at least two concentric annular projections, to form a handgrip, extending toward the axis of the mold cavity and container to be formed, each annular projection having an outer extremity and adjacent side surface complimentary to a trough and a frustum; 
     b) pre-heating a preform to facilitate blow molding to form the container and the handgrip; 
     c) introducing the preform into the blow mold; 
     d) applying a gas at a pressure sufficient to inflate and deform the preform into contact with the mold cavity to form the container and into contact with handgrip forming features to produce the handgrip in a wall of the container, the handgrip being formed failing to contact the mold cavity in the region of a central dome and a substantial portion of trough connecting rings of the handgrip; 
     e) cooling the container; and 
     f) removing the container with the handgrip(s) formed therein from the blow mold cavity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a cross-section of a handgrip of a first embodiment of the present invention; 
     FIG. 1A is a large cross-section of the fourth outer frustum; 
     FIG. 1B is an enlarge cross-section of the first outer frustum; 
     FIG. 2 is a fragmentary elevation of the handgrip of FIG. 1 with solid lines used to clarify the boundaries of structural elements of the handgrip; 
     FIG. 3 is a cross-section of the handgrip of FIG.  1  and of a portion of a blow mold for producing this handgrip; 
     FIG. 4 is a partial elevation of a plastics container for carbonated beverages having handgrips of the present invention; 
     FIG. 5 is a cross-section of a plastics container incorporating two handgrips taken on section  5 — 5  of FIG. 4; 
     FIG. 6 is an angled cross-section similar to that of FIG. 5 showing a fragmentary portion of the plastics container; 
     FIG. 7 is a longitudinal cross-section of a blow mold for producing the container of FIG. 4; 
     FIG. 8 is a fragmentary cross-section of a handgrip of a second embodiment of the present invention and a portion of a blow mold for producing this handgrip; 
     FIGS. 9 and 10 illustrate alternative designs of handgrips to that shown in FIG. 4; and 
     FIG. 11 is a block diagram illustrating the method of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIGS. 1 and 2, a handgrip  6  of the first embodiment, formed in the wall  8  of a container, the wall  8  having an interior  14 , an interior wall, and a exterior wall and a wall thickness  9 A and a radius  11 . The container is blow molded from a conventional preform of PET, and the handgrip  6  is an integral structure with wall  8  and is composed of a circular central dome  10  having a wall thickness  9 B and that is smoothly connected to a first inner frustum  16  increasing in diameter to a first annular trough  18 . 
     Trough  18  is, in turn, smoothly connected to a first outer frustum  20  that is generally the same as wall thickness  9 A increasing in diameter to a connecting ring  22  smoothly interconnecting the first outer frustum  20  to a second annular trough  19  by way of a second inner frustum  21  increasing in diameter to trough  19 . 
     Trough  19  is, in turn, smoothly connected to a second outer frustum  23  increasing in diameter to a connecting ring  22  smoothly interconnecting the second annular trough  19  to a third annular trough  25  by way of a third inner frustum  27  increasing in diameter to trough  25 . 
     Trough  25  is, in turn, smoothly connected to a third outer frustum  29  increasing in diameter to a connecting ring  22  smoothly interconnecting the third annular trough  25  to a fourth annular trough  31  by way of a fourth inner frustum  33  increasing in diameter to trough  31 . 
     Trough  31  is, in turn, smoothly connected to a fourth outer frustum  35  increasing diameter to an annular outer connecting ring  22  smoothly interconnecting the fourth outer frustum  35  to the wall  8  of the container. 
     The troughs  18 ,  19 ,  25 ,  31  and frustums  16 ,  20 ,  21 ,  23 ,  27 ,  29 ,  33 ,  35  increase in diameter from the dome  10  starting with the trough  18  and frustum  16 . In addition, the troughs and frustums increasingly extend further into the container, relative to the wall  8 , from the outermost trough  31  and frustum  35  to the dome  10 . 
     The central dome  10  has a convex outer surface extending toward the adjacent outer surface  12  of the container wall  8  and a concave surface parallel to the convex surface and facing the interior  14  of the container. 
     The following dimensions are without a pressurized interior of the container and without the container being exposed to an elevated temperature substantially above ambient room temperature. In addition, the following dimensions relate to a handgrip formed in a container having a radius in the range of about 1.1 inches to about 1.6 inches, preferably about 1.3 inches. A typical central dome  10  has a radius  24  of the concave surface in a range of from about 0.19 inch to about 0.32 inch, preferably about 0.23 inch, a diameter of about 0.25 of an inch, a radial spacing  26  from the outer extremity of the convex surface to the outer surface of the wall  8  of the container in a range of about 0.01 of an inch to about 0.03 of an inch, preferably about 0.013 of an inch and a thickness  9 B approximately equal to the wall  8  thickness  9 A of the container, for example, of about 0.013 inch. Wall thicknesses are preferably in a range from about 0.010 of an inch to about 0.015 of an inch, but should not be construed as being limited to this range. 
     A typical inner frustum  16 ,  21 ,  27 ,  33  has a length  30  in cross-section in a range of about 0.003 of an inch to about 0.05 of an inch and preferably has a length of at least 0.005 of an inch and a thickness approximately equal to the thickness  9 A of the wall  8 . Although the presence of the inner frustum  16  is preferred and enhances the stability of the handgrip  6 , this feature may be omitted, with the central dome then directly and smoothly joining trough  18 , without departing from the concepts of the present invention. 
     The annular troughs  18 ,  19 ,  25 ,  31  typically have diameters of about 1, 1.6, 2.2 and 3 inches respectively and an internal radius  34  in cross-section in a range of from about 0.005 of an inch to about 0.05 of an inch with a preferred radius of about 0.015 of an inch. The thickness  36  of the trough walls in cross-section is approximately equal to the thickness  9 A of the wall  8 . The radial spacing of the inner surface (the surface facing the exterior surface of the container) of the troughs  18 ,  19 ,  25 ,  31  from the outer surface of wall  8  are about ¼, ½, ¾ and 1 of an inch each step of an increase in this dimension being variable by +/−⅛ inch. 
     A typical connecting ring  22  has a radius  40  in cross-section in a range of from about 0.09 of an inch to about 0.13 of an inch, preferably about 0.11 of an inch and a wall thickness in cross-section approximately equal to the wall thickness  9 A of wall  8 . 
     The diameter  42  of the handgrip  6  is preferably in a range of from about 1.5 inches to about 4 inches preferably about 2.750 inches. The above dimensions are chosen to allow formation of a handgrip  6  having a diameter at or close to the maximum diameter of 4 inches. 
     It will be appreciated that the choice of actual dimensions for the features of the handgrip  6  will be chosen to produce smooth transitions to between the various elements (dome, troughs, frustums, connecting rings and container wall) making up the handgrip  6  and to the wall  8 . 
     Now referring to FIG. 3 a fragmentary portion of a blow mold  44  illustrates the blow mold features which form a handgrip  6  during a blow molding of a convention PET preform into a container. The fragmentary portion of the blow mold is a cross-section taken normal to the longitudinal axis  46  of the blow mold and the container. The blow mold features include an annular projections  48  (one for each trough) (two only being shown) each terminating at its outer extremity  50  in a radius in cross-section to form the internal radius of the associated trough and providing side surfaces  52  to form the inner and outer frustums associated with that trough. The annular projections decrease in diameter toward the outer extremities  50  with an included angle  53  of approximately 10°. 
     The provision of this inwardly decreasing diameter of the projections  48  facilitates the formation of the troughs and frustums and eases removal of the container with formed handgrip(s) from the blow mold. 
     It is to be noted that the blow molding is achieved by applying a pressure sufficient (about 600 p.s.i. or greater) to the interior of a conventionally pre-heated preform to inflate and deform the preform into engagement with the blow mold and its handgrip forming features. However, it should also be noted that while the cylindrical wall  8  of the container intimately contacts the wall forming portion of the blow mold the handgrip  6 , being formed, contacts only the outer extremities  50  and the side surfaces  52  adjacent these outer extremities. 
     FIGS. 4 and 5 illustrates two handgrips disposed offset (see FIG. 5) relative to the axis  46  of the container to facilitate the gripping of larger (e.g. 3 liter) containers of liquids under pressure. 
     In FIG. 6 the container illustrated in FIGS. 4 and 8 has be sectioned at an angle to clearly illustrate a cross-section of the handgrips thereof. 
     As previously mentioned the handgrips do not extend outwardly of the container and are preferable recessed relative to the outer surface of the wall  8  (and shoulder  56 ) even when the container filled with a carbonated beverage or other pressurized liquid is subjected to elevated temperatures and mechanical stresses in accordance with industry standards. 
     FIG. 7 is a cross-section of a blow mold  58  having a blow mold cavity  60  defining handgrip forming features  62 , as illustrated in FIG. 4, for producing the container of FIGS. 4,  5  and  6  with two handgrips  6 . 
     FIG. 8 illustrates a second embodiment of a trough, of the present invention, when replaced by a trough  66  having a very small radius or a nonexistent internal surface joining the frustums  16  and  20 . The portion  44  of the blow mold shown in FIG. 8 has an annular projection  68  having an outer extremity which is complimentary to the form of the trough  66 . Only one projection  68  is shown in FIG. 8 although it will be appreciated that as with FIG. 3 the number of projections will be equal to the number of troughs. 
     FIG. 9 illustrates a variation of handgrips according to the present invention in which each handgrip is of a teardrop shape (see definition of circular above). 
     FIG. 10 illustrates a further variation of handgrips according to the present invention in which the central dome has a plurality of parallel deformations or ridges and valleys to provide additional rigidity to the dome and thus the handgrip. 
     FIG. 11 illustrates the method of the present invention to produce a handgrips, in the wall of a container for pressurized liquids (e.g. a carbonated beverage), which does/do not, even under acceptable elevated temperatures and mechanical stresses acceptable to the industry (i.e. the carbonated beverage industry), does not distort or extend outwardly from the outer surface of the container, comprises: 
     a) providing a blow mold having handgrip forming features (to form at least two handgrips) in the form of at least two annular projections extending toward the axis  46  of the mold cavity and container to be formed, the annular projection(s) having an outer extremity and adjacent side surfaces complimentary to the troughs and frustums respectively of the handgrips; 
     b) pre-heating a preform to facilitate blow molding to form the container and handgrips; 
     c) introducing the preform into the blow mold; 
     d) applying a gas at a pressure sufficient to inflate and deform the preform into contact with the mold cavity to form the container and into contact with the complimentary features to produce the handgrips in the wall thereof, the handgrips being formed-failing to contact the mold cavity in the region of the/their central dome(s)  10  and a substantial portion of the connecting rings  22 ; 
     e) cooling the container; and handgrips; and 
     f) removing the container with handgrips formed therein from the blow mold cavity. 
     It will be appreciated that in some circumstances a single handgrip may be utilized. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Reference numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 6 
                 handgrip 
               
               
                 8 
                 wall 
               
               
                 9A 
                 wall thickness 
               
               
                 9B 
                 central dome thickness 
               
               
                 10 
                 dome 
               
               
                 11 
                 container radius 
               
               
                 12 
                 outer surface 
               
               
                 14 
                 interior 
               
               
                 16 
                 first inner frustum 
               
               
                 18 
                 first annular trough 
               
               
                 19 
                 second annular trough 
               
               
                 20 
                 first outer frustum 
               
               
                 21 
                 second inner frustum 
               
               
                 22 
                 connecting ring 
               
               
                 23 
                 second outer frustum 
               
               
                 24 
                 radius of central dome 
               
               
                 25 
                 third annular trough 
               
               
                 26 
                 radial spacing 
               
               
                 27 
                 third inner frustum 
               
               
                 29 
                 third outer frustum 
               
               
                 30 
                 inner and outer frustum length 
               
               
                 31 
                 fourth annular trough 
               
               
                 33 
                 fourth inner frustum 
               
               
                 34 
                 trough internal radius 
               
               
                 35 
                 fourth outer frustum 
               
               
                 36 
                 trough thickness 
               
               
                 38 
                 included angle of straight portions 
               
               
                 40 
                 connecting ring radius 
               
               
                 42 
                 handgrip diameter 
               
               
                 44 
                 blow mold 
               
               
                 46 
                 axis 
               
               
                 48 
                 annular projection 
               
               
                 50 
                 outer extremity 
               
               
                 52 
                 side surfaces 
               
               
                 53 
                 including angle 
               
               
                 54 
                 container 
               
               
                 56 
                 shoulder 
               
               
                 58 
                 blow mold 
               
               
                 59 
                 preform 
               
               
                 60 
                 cavity 
               
               
                 62 
                 handgrip forming features 
               
               
                 64 
                 handgrip 
               
               
                 66 
                 trough 
               
               
                 68 
                 annular projection