This application claims priority to Provisional Application No. 60/774,168, filed Feb. 16, 2006 and incorporated herein by reference in its entirety.
This invention relates to containers and more particularly to containers suitable for hot filling with perishable foods or beverages.
Perishable foods, such as juices and soup, are often filled at an elevated temperature in a process generally referred to as “hot-fill.” In a typical hot-fill process, a perishable food or beverage is introduced into a plastic container at approximately 185° F. and a cap is applied to seal the container. Upon subsequent cooling of the contents, a negative pressure (that is, below atmospheric pressure) is formed within the container due to shrinkage of the contents. The container may also shrink upon being subjected to hot-filling temperatures, but the product contents generally shrink by a greater volumetric amount upon cooling than the decrease in container volume.
In order to withstand the temperatures common to hot-filling, containers typically are formed of a thermoplastic having a relatively high intrinsic viscosity and typically are heat treated. For example, a container may be formed in a heated blow mold, which is maintained at approximately 250° F. to 290° F. A container that is held in a heated blow mold undergoes a decrease in the orientation of the polymer and an increase in its crystallinity, which diminishes the distortion of the container when subjected to hot-fill temperatures.
Containers suitable for hot-filling applications typically are designed with vacuum panels formed in the container sidewall that flex in response to a decrease in internal pressure. For example, some plastic containers have several, equidistantly spaced vacuum panels that are configured to enable a circular label to be wrapped around the container. Land areas between the panels provide surfaces around which the label may be applied. Inward flexing of the vacuum panels in response to vacuum pressure prevent severe distortion of the land areas. Other plastic containers are configured to have opposing hand-grips that flex to absorb the internal vacuum. Flexing of the hand-grips in response to internal negative pressure prevents severe distortion of the surfaces to the front and to the rear of the hand-grips, which can receive labels.
Even though hot-fill containers are configured to function under internal vacuum conditions, the containers are sometimes subjected to positive internal pressure during the filling process. For example, some filling equipment subjects the container to internal positive pressure for a brief period. Containers having long stiffening ribs or other long stiff structures (such as structures having a large moment of inertia, in transverse cross section relative to the horizontal axis) may, in response to positive internal pressure, locally bulge outwardly in a kink. And the kink might remain even after the container encounters internal vacuum or the kink may disappear but leave a wrinkle in the plastic wall. Even a wrinkle makes the container unappealing and is considered to be commercially detrimental.
Typically, the specifications for such processes require the containers to withstand internal positive pressures of up to 3 psi. It is possible, however, for a pressure filling line to stop during the filling process, for example under unexpected or alarm conditions, and subject the container being filled to a filling pressure of greater than 3 psi.
Provided is a container capable of being hot filled with a product, sealed while the product is hot, and allowed to cool, thereby creating an internal vacuum. The container has improved positive pressure resistance during pressure filling and yet has sufficient vacuum absorption capabilities. The container has an enclosed base, a body having a sidewall that extends upwardly from the base, and an upper portion extending upwardly from the body to a finish on which a closure may be applied. The container also includes a pair of opposing vacuum panels disposed between front and rear portions of the sidewall of the body. The container has relatively smooth transitions between its vacuum panels and the front and rear portions of the sidewall and the container does not have vertical reinforcing ribs such that the radial dimension is small for each portion of the front and rear edges of the panel.
The vacuum panels have a generally flat field that transitions smoothly into the front and rear portions of the sidewall. Also, the vacuum panels each include a handgrip and a pair of inwardly extending windows formed at least partly in the field generally below the handgrip. The handgrip includes a gripping surface and at least a proximal wall and a distal wall. The gripping surface is adapted to receive a user's fingers on one of the vacuum panel handgrips and a user's thumb on the opposing one of the vacuum panel handgrips.
The proximal wall of the handgrip preferably merges smoothly with the rear portion of the sidewall The distal wall forms an oblique long wall angle A1 with a vertical line in elevational view and a short wall angle A2 with the field in transverse cross section. The long wall angle Al is preferably between approximately 10 degrees and approximately 25 degrees. The short wall angle A2 is preferably between approximately 85 degrees and approximately 115 degrees. Further, where structure having a substantially radial orientation is included, such as in the distal wall of the gripping surface, the radial component preferably has a relatively short vertical length in elevational view and is nearly radially oriented in transverse cross section. The container is designed to preferably achieve a failure mode in the form of a bulge in the handgrip distal wall when the container is subjected to a positive internal pressure. Preferably, the container can withstand and internal positive pressure of between 3.5 and 7.5 psi.
Also, provided is a method of hot-filling a bottle. According to the method, a bottle that is designed in accordance with the above description of the container is filled with contents at an elevated temperature and at a positive pressure of up to 9.0 psi. Then, the bottle is capped while the contents are still at an elevated temperature and the contents of the capped bottle are allowed to cool, which causes the vacuum panels to deflect inwardly in response to the cooling and shrinking of the contents.
FIG. 1 is a side elevational view of a bottle illustrating features of the present invention;
FIG. 2 is a front elevational view of the bottle of FIG. 1;
FIG. 3 is a transverse cross sectional view of the bottle of FIG. 1 taken through lines III-III in FIG. 1;
FIG. 4 is an enlarged view of a portion of the bottle shown in FIG. 1;
FIG. 5A is a transverse cross sectional view of the container taken through lines V-V in FIG. 1 and illustrating the bottle bulging in response to positive internal pressure;
FIG. 5B is a transverse cross sectional view of the bottle taken through lines V-V in FIG. 1 and showing the bottle after hot filling;
FIG. 6 is a graphical representation of a finite element analysis of deflection of the bottle of FIG. 1 illustrating the bottle bulging in response to positive internal pressure; FIG. 6 shows the same condition as shown in FIG. 5A; and
FIG. 7 is a graphical representation of a finite element analysis of stress of the bottle of FIG. 1 illustrating the bottle's response to internal vacuum.
A bottle 10 includes an enclosed base 12, an upper portion 14, and a body 16 extending between base 12 and upper portion 14, as best shown in FIGS. 1, 2, 6, and 7. Bottle 10 is generally suitable for use in a hot-filling process, in which bottle 10 is filled with a product at an elevated temperature, capped, and allowed to cool. Typically, bottle 10 is formed by an injection blow molding process, but the present invention is not limited by the method of forming the bottle.
Base 12 preferably is conventional and includes a reentrant portion 20 (shown only in dashed lines in FIG. 2), a standing ring 22, and a heel 24. Base 12 terminates in a shoulder 26. Upper portion 14 includes an upper shoulder 28, a waist 30, a dome 32, and a finish 34. Finish 34 includes threads for receiving corresponding threads of a closure 36 (shown FIGS. 6 and 7). Upper shoulder 28 is located at the boundary between upper portion 14 and body 16. Waist 30 is a portion of reduced diameter located above shoulder 28 and below dome 32. Dome 32 diminishes in diameter as it upwardly extends toward finish 34. In the figures, dome 32 is illustrated with structural elements, but neither these structural elements nor any other aspect of upper portion 14 is intended to be limiting unless expressly recited in the claims.
Body 16 includes a sidewall 38 and a pair of opposing vacuum panels 56. Sidewall 38 generally extends between shoulders 26 and 28 and preferably includes a front portion 42 and a rear portion 44. Front portion 42 and rear portion 44 preferably include horizontal stiffening ribs 46a and 46b, respectively. Preferably, neither front portion 42 nor rear portion 44 have horizontal stiffening ribs. Front portion 42 preferably a surface capable of receiving a label. The label surface of front panel 42 is generally straight in longitudinal cross section, but it is expected and acceptable for the longitudinal cross section of front portion 42 to deflect slightly in response to internal pressures within bottle 10. The desired magnitude of the deflection of front panel 42 is governed by label considerations, as will be understood by persons familiar with labeling technology for hot fill containers.
Stiffening ribs 46a and 48b are curved to match the curvatures of panels 42 and 44, respectively, and terminate at ends 48a and 48b, respectively. Preferably, sidewall 38 extends, rearward and arcuately, past ribs ends 48a of front portion 42; and sidewall 38 extends, frontward and arcuately, past rib ends 48b of rear portion 42; which portions of the sidewall are referred to a sidewall intermediate portions 50a and 50b, respectively. Preferably, sidewall intermediate portions 50a and 50b (i) do not have vertical stiffening ribs, or (ii) have ribs that have only a small vertical component (such as curved ribs or ribs forming an oblique angle with a vertical line), or (iii) have only horizontal ribs, or (iv) have stiffening structure that is part of a three dimensional window (described more fully below) and that has a small vertical dimension.
Each vacuum panel 40 includes a field 56 that is defined by the panel's front edge 58a and its opposing rear edge 58b. FIG. 1 and FIG. 4 show panel edges 58a and 58b in dashed lines to schematically show the boundaries of the vacuum panel, as the boundary in the physical version of bottle 10 is not pronounced, which is evident in FIG. 3. Field 56 is generally planar in its as-molded state, but may also be curved.
Each panel 40 also includes a handgrip 60 and a pair of inwardly directed first window 90 and second window 96. Handgrip 60 includes a gripping surface 62 that preferably includes a pair of ribs 64. Handgrip 60 is defined by a proximal wall 66, a distal wall 68, an upper wall 70, and a lower wall 72. Walls 66, 68, 70, and 72 are joined by transitions 74a, 74b, 74c, and 74d as shown in FIG. 4.
Gripping surface 60 preferably is flat except for a pair of ribs 64 that protrude outward from the remainder of the surface. Proximal wall 66 preferably is curved in transverse cross section, such as illustrated in FIGS. 5A and 5B, and preferably is located at the boundary of panel 40 and sidewall rear intermediate portion 50b. The smooth transition between the surfaces of gripping surface 60 and sidewall 50b may comfortably receive a user's hand and, as described above, forgoes a vertical rib.
Distal wall 68 is on the opposite side of gripping surface 60 from proximal wall 66 and preferably is inclined at an angle from a vertical line by and angle A1, which will be referred to herein as the long wall angle. Preferably, angle A1 preferably is not 0° (that is, not vertical), preferably is between approximately 10 degrees and approximately 20 degrees, and more preferably, as illustrated in FIG. 4, approximately 15 degrees for the particular bottle shown. The upper ends of proximal wall 66 and distal wall 68 are connected by upper wall 70 that, for ease of hand placement, is oriented at an oblique angle to a horizontal reference line, as shown in FIG. 4. The lower ends of proximal wall 66 and distal wall 68 are connected by lower wall 72, which also is oriented at an oblique angle.
As shown in FIG. 3, distal wall 68 is formed by a main wall surface 76 and a pair of curved wall transitions 78a and 78b. An inner wall transition 78a merges the inner edge of main wall 76 and gripping surface 62 and; an outer wall transition 78b merges the outer edge of main wall 76 and panel field 56. As shown in FIG. 3, main wall surface 76 is oriented relative to gripping surface 60 by an angle A2 that preferably is approximately 90 degrees. The inventors surmise that angle A2 may be (preferably) as large as 115 degrees while maintaining the advantage of resisting kinking during position pressure. Angle A2 may be as small as 85 degrees, as angles smaller than 90 degrees may provide an undercut surface that diminishes local wall thickness upon blowing. As will be clear to persons familiar with container development and design, angle A2 may vary according to container dimensions, wall thickness, positive pressure design point, and like parameters. Accordingly, the present invention may encompass wall angles A2 outside of the above range.
Also, the depth of gripping surface 64 (measured radially from the deepest point of surface 64 to the hypothetical extension of the panel field 46), which is shown schematically as dimension D in FIG. 3 preferably is greater than approximately 0.050 inches, and more preferably greater than approximately 0.100 inches. The depth most preferably is approximately 0.200 inches. Depth D has an inverse relationship with the variables of distal wall length L, such that the preferred length L preferably diminishes with increasing depth D.
All angle magnitudes provided herein are based on the bottle prior to filling. The wall angles may be chosen according to the overall container and panel size, wall thickness, blow molding parameters, and the like, as will be understood by persons familiar with blow molded bottle engineering.
Preferably, a first window 90 and a second window 96 are provided in the panel field 56. First window 90 has substantially straight edges 92 that merge panel field 56 with a window bottom surface 94. Preferably window bottom surface 94 is substantially flat. Second window 96 has substantially straight edges 98 that merge panel field 56 with a window bottom surface 100. The window edges 92 may be parallel to form a rectangle or square in elevational view, such as is illustrated by window 90. As illustrated by second window 96, the windows are not required to have a rectangular shape, as window 96 includes an extended portion 102 that extends upward to diminish the area of unreinforced field 56. As shown in the Figures, window 102 may extend outside of boundaries of panel 40.
Preferably, the vertical dimension of any radial structure in the panel 40 and vertical components of structure in the intermediate sidewalls 50a and 50b, such as the walls of window 102, have relatively small dimensions. The overall length L of distal main surface 76 is shown in FIG. 4. Preferably, the overall length L is less than 3.5 inches, and more preferably less than 3.0 inches. The lower magnitude of the preferred range of length L is dictated by ergonomic factors, and may be as low as approximately 1.25 inches. Further, the container vertical component L′ of the length L is preferably less than about 3.0 inches, and more preferably less than 2.5 inches. Preferably, the vertical component of all other structures in the panel 40 or sidewall intermediate portions 50a and 50b is less than length L.
The dimensions herein are provided for the container shown having a sidewall diameter of approximately 4.5 inches and sidewall height (that it, between shoulders 26 and 28) of approximately 5.6 inches such that the container volume is 64 ounces. The dimensions and angles provided are not intended to limit the scope of the invention unless expressly set forth in the claims.
FIG. 5 graphically shows calculated deformation of the bottle 10 upon internal pressurization, assuming a constant wall thickness and wall temperature of 185 degrees ° F. The bulge or kink forms at or near the gripping surface distal wall 68 at 6.6 psi for a 64 ounce container having the dimensions stated above and weighing approximately 80 to 85 grams. The deformation graphic of FIG. 5 shows the effectiveness of bottle 10 in deforming relatively uniformly throughout its body except for the grip.
FIG. 6 graphically shows calculated deformation of the bottle 10 upon vacuum filling at 185 degrees ° F. after the container has cooled to room temperature. As shown, the maximum magnitude of deformation is in field 56.
The present invention is illustrated by structure and function disclosed herein, and is not limited to the particular structure and function, but rather is limited according the claims. Further, advantages of the bottle 10 are provided in the context of pressure filling, and the present invention is not limited to any pressure filling process, but rather to any hot fill container having the claimed structure.