Title:
Bottom structure for plastic containers
United States Patent 3871541
Abstract:
A bottom structure for containers particularly suited for carbonated beverage bottles. The bottom end is formed with a domed center portion and an intersecting downwardly convexed semi-torus portion which is interrupted by a plurality of radially arranged rib configurations extending from the side wall of the bottle inwardly to the juncture of the aforesaid portions and form a plurality of downwardly bulged legs arranged in a rosette pattern and adapted to be loaded in bend in opposition to a compression loading on the dome portion when subjected to internal fluid pressure and heat to provide a novel creep resistant structure.
US Patent References:
High-pressure container safety means
Daley - June 1962 - 3038627
BOTTOM END STRUCTURE FOR PLASTIC CONTAINERS
Adomaitis - August 1971 - 3598270
High-pressure container safety means
Daley - June 1962 - 3038627
BOTTOM END STRUCTURE FOR PLASTIC CONTAINERS
Adomaitis - August 1971 - 3598270
Application Number:
05/335974
Publication Date:
03/18/1975
Filing Date:
02/26/1973
View Patent Images:
Export Citation:
Assignee:
Continental Can Company, Inc. (New York, NY)
Primary Class:
Other Classes:
220/606, 220/608
International Classes:
B65D1/02; B65D23/00
Field of Search:
215/1C 220/66,70,72
Primary Examiner:
Price, William I.
Assistant Examiner:
Pollard, Steven M.
Attorney, Agent or Firm:
Kowalik, John Kerwin Joseph Dittmann William J. E. A.
Claims:
What is claimed is
1. A blow molded pressure resistant plastic container having a body comprising a generally cylindrical side wall and a bottom structure, said bottom structure comprising:
2. The invention according to claim 1 and said dome portion disposed for loading in compression and said ribs disposed for loading in bend.
3. The invention according to claim 2 and said ribs having maximum width in the area of juncture of the rim to the side wall and narrowing and shallowing at their outer and inner extremities.
4. The invention according to claim 3 and said by portions having narrow inner sections and broadening from said inner sections to relatively wide outer sections in the area of juncture with the side wall.
5. The invention according to claim 1 and said bottom structure having a diametric seam centered on diametrically disposed ribs.
6. In a plastic container formed of material adapted to deform when subjected to predetermined pressure loads, said container having a cylindrical lower side wall portion, an integral bottom defined by a wall comprising an inwardly convexed sperical center portion, a reversely convexed rim portion extending between said inwardly convexed center portion and said side wall and projective axially of the container below the lowermost edge of said center portion, and a plurality of reinforcing elements formed as an integral part of said rim portion and extending radially of the container and having inner ends merging into said center portion and flaring therefrom outwardly and beyond the juncture of the bottom wall with the side wall narrowing circumferentially of the container and flaring into said side wall, and said reinforcing elements defining a plurality of legs oriented radially of the container and having wide circumferential sections adjacent to said side wall and narrow inner end sections at said center portion, and said reinforcing elements having lateral side segments of relatively thin cross section in their regions of merger with respective legs and forming the sides thereof and progressively being thicker axially inwardly of the container and merging into a relatively thick arcuate inner crest portion.
7. The invention according to claim 6 and said elements blending at their ends into the side wall portion and said spherical portion respectively.
8. The invention according to claim 7 and said legs being essentially U-shaped in radial cross-section.
1. A blow molded pressure resistant plastic container having a body comprising a generally cylindrical side wall and a bottom structure, said bottom structure comprising:
2. The invention according to claim 1 and said dome portion disposed for loading in compression and said ribs disposed for loading in bend.
3. The invention according to claim 2 and said ribs having maximum width in the area of juncture of the rim to the side wall and narrowing and shallowing at their outer and inner extremities.
4. The invention according to claim 3 and said by portions having narrow inner sections and broadening from said inner sections to relatively wide outer sections in the area of juncture with the side wall.
5. The invention according to claim 1 and said bottom structure having a diametric seam centered on diametrically disposed ribs.
6. In a plastic container formed of material adapted to deform when subjected to predetermined pressure loads, said container having a cylindrical lower side wall portion, an integral bottom defined by a wall comprising an inwardly convexed sperical center portion, a reversely convexed rim portion extending between said inwardly convexed center portion and said side wall and projective axially of the container below the lowermost edge of said center portion, and a plurality of reinforcing elements formed as an integral part of said rim portion and extending radially of the container and having inner ends merging into said center portion and flaring therefrom outwardly and beyond the juncture of the bottom wall with the side wall narrowing circumferentially of the container and flaring into said side wall, and said reinforcing elements defining a plurality of legs oriented radially of the container and having wide circumferential sections adjacent to said side wall and narrow inner end sections at said center portion, and said reinforcing elements having lateral side segments of relatively thin cross section in their regions of merger with respective legs and forming the sides thereof and progressively being thicker axially inwardly of the container and merging into a relatively thick arcuate inner crest portion.
7. The invention according to claim 6 and said elements blending at their ends into the side wall portion and said spherical portion respectively.
8. The invention according to claim 7 and said legs being essentially U-shaped in radial cross-section.
Description:
DISCUSSION OF THE PRIOR ART
The best art known is previous U.S. Pat. No. 3,598,270. The structure therein shown is satisfactory from a functional standpoint, but it has been found too expensive to manufacture necessitating an expensive mold. Also the bottom is loaded solely in tension which requires deep rib conformations and required excessive use of material. This provides a rigid structure with deep grooves in the side wall at the bottom end.
As stated in the prior art the duplication in plastic of glass bottles is not feasible since plastic economically suitable for such bottles is subject to distortion and creep particularly when subjected to temperatures of 120° to 140°F. as during pasteurization or on a hot summer day in enclosed vehicles or the like. Such plastic bottles must withstand pressures of 40 p.s.i. to in excess of 100 p.s.i. As heretofore noted, the bottom end of the bottle is normally the weakest part necessitated by manufacturing techniques and simply thickening the section will not solve the problems enumerated particularly since the plastic bottle must be a substitute in general shape and capacity for currently used glass bottles, that is it must of necessity be of substantially the same size not only to accept the same quantity of beverage but also to be handled by equipment currently in use.
Furthermore, the bottle must be aesthetically pleasing to the customer as well as being satisfactory functionally.
SUMMARY OF THE INVENTION
Bottom bulging of a pressurized plastic container is a serious problem. Such a container becomes a "rocker" or may loose completely its footing and tip over. Because of bottom bulging volume of the container increases and the fill line drops to unacceptable level.
It has been known for along time, that the strongest pressure vessel is one of a spherical shape. Its excellent performance is based on a uniform distribution of stresses: tensile stresses in case of internal pressure and compressive stresses in case of external pressure. Since spherical containers or those with hemispherical bottoms require extra stands or footing they are impractical for application such as beverage bottle.
Next to the hemispherical there is the domed bottom, which has a built-in up-side-down hemisphere, a cone or construction between the two. However, under pressure domed bottoms bulge, too. Despite its rigidity, the dome looses some of its depth and the base diameter decreases. After these changes the bottle becomes also taller and not as stable.
The usual approach to solve the problem is to make the bottom heavy.
The approach of this invention is to use material where it is needed.
In looking for reasons of domed bottom bulging and instability the forces and stresses applied to the bottom in service, was analyzed. The external pressure on a cone or hemisphere cannot decrease height of these constructions unless compressive strength of the wall would be exceeded and the walls would be compressed or the diameter and circumference of its base would be increased.
At the lowermost wall of the bottom dome there is an area where compressive stresses are changing to flexural (bending) and tensile stresses. That critical area usually is the bottom rim or the adjacent bottom section. Since plastic material is weakest in tension, the critical tensile stresses in this area are reached first and they are followed by critical flexural stresses before the critical compressive stresses can be expected. With this in mind the mechanism of the bottom bulging, which is manifested mainly by a decreased dome height and base diameter, can be described.
The domed bottom is strong as long and/or where it is exposed to compressive stresses only. However, at the area where the dome blends with the bottom rim it is exposed to the most damaging tensile stresses. When these stresses become critical the area involved yields and elongates, thus giving a chance for bending stresses and partial inversion of the dome. Depth of the cone or dome can decrease only if the base diameter and circumference of the dome at these points elongate to allow bending of the lower section of the dome outwardly.
From the above analysis and description of bottom bulging mechanism it can be concluded that in order to improve performance of the dome bottom, reinforcement of its critical base section is needed. This finding constitutes the core of my invention.
The purpose of the invention is to eliminate domed bottom bulging by providing an integral reinforcing rim at its base in order:
1. to expose the bottom dome to compressive stresses only;
2. to arrest the tensile and bending stresses at the base of the dome;
3. to cut excessive material from the dome and to produce a more economical plastic container.
The present invention is directed to a bottle particularly adapted for use with carbonated beverages.
A general object of the invention is to provide a novel bottom end portion for a plastic bottle wherein the end portion is contoured to place certain sections in compression and others in bend in a unified construction which utilizes the least amount of material, obtains a stable product, aesthetically is acceptable and pleasing and is capable of either blow molding or injection blow molding.
A further object is to provide a novel bottom conformation for a container easy to manufacture and provides the necessary strength developed by a novel arrangement of wall components including a domed center portion and an encompassing rim portion with which it is integrated and at its outer edge merges with the outer side wall, the rim portion being formed with a plurality of rib formations which extend from the juncture of the rim with the dome portion to and beyond the juncture of the rim portion with the side wall.
These and other objects and advantages inherent in and encompassed by the invention will become more readily apparent from the specifications and drawings, wherein:
FIG. 1 is a side elevational view of a bottle incorporating the invention;
FIG. 2 is an end view of the bottom;
FIG. 3 is a transverse longitudinal sectional view taken substantially on line 3--3 of FIG. 1;
FIG. 4 is a partial sectional view taken essentially on line 4--4 of FIG. 2; and
FIG. 5 is a sectional view taken substantially on line 5--5 of FIG. 1.
DESCRIPTION OF THE INVENTION
Describing the invention in detail there is shown a plastic bottle generally designated 2 suitable for carbonated beverages. The material used may be of the type identified as DuPont NR-16 or Barex 210 sold by Vistron Corporation located in Ohio or any other like suitable material. Although such bottles represent a principal application of the invention, it will be understood that the invention is applicable to containers generally.
The bottle comprises an upper end neck portion 3 which blends into a body comprising a side wall portion 4 having at least a bottom section 5 of cylindrical configuration. The lower edge of the cylindrical section blends into a bottom wall structure 7 which essentially extends transaxially of the bottle.
The bottom section comprises a center dome portion 8 which has a convex upper side 9 internally of the body and a concave underside 10.
The dome portion 8 merges at its lower edge into the inner edge of a rim section 11 which is in the form of semitorus or half a donut, the outer edge of which merges into the lower section of the cylindrical wall portion 5.
The rim section is generally U-shaped in cross-section and has a concave inner side 12 and a convex outer or bottom side 13.
A series of regularly spaced ribs or reinforcing elements 14,14 are provided between legs 15,15 in the rim portion.
Each rib 14 is U-shaped in transverse cross-section and comprises side webs 16,16 which grow thicker inwardly and merge into a crest or ridge portion 17 of relatively thicker section. The side edges 18,18 of the ribs diverge slightly radially outwardly and define the margins of an intervening groove 19.
The inner and outer ends 20 and 21 of the grooves converge toward their extremities and shallow out and blend into the dome wall and the side wall respectively.
It will be noted that the ribs are of widest formation circumferentially of the container at 22 in the corner 23 formed by the juncture of the bottom and side walls of the container.
Thus strength is imparted at a critical area to resist bending moments imposed by the compressive loading of the dome portion.
The ribs are convexed inwardly of the container and have concave bottom sides forming the grooves.
Each leg portion 15 has a base pad section 25 which extends laterally, that is, circumferentially of the container side webs of adjacent rib structures and merges therewith in inturned rounded surface configurations. In longitudinal section, that is, radially of the container, the legs are of U-shaped convexed outwardly and provide at said pad sections 25 coplanar seating areas for the bottle.
The instant structure has been tested at 140°F. for two hours and has performed satisfactorily.
The best art known is previous U.S. Pat. No. 3,598,270. The structure therein shown is satisfactory from a functional standpoint, but it has been found too expensive to manufacture necessitating an expensive mold. Also the bottom is loaded solely in tension which requires deep rib conformations and required excessive use of material. This provides a rigid structure with deep grooves in the side wall at the bottom end.
As stated in the prior art the duplication in plastic of glass bottles is not feasible since plastic economically suitable for such bottles is subject to distortion and creep particularly when subjected to temperatures of 120° to 140°F. as during pasteurization or on a hot summer day in enclosed vehicles or the like. Such plastic bottles must withstand pressures of 40 p.s.i. to in excess of 100 p.s.i. As heretofore noted, the bottom end of the bottle is normally the weakest part necessitated by manufacturing techniques and simply thickening the section will not solve the problems enumerated particularly since the plastic bottle must be a substitute in general shape and capacity for currently used glass bottles, that is it must of necessity be of substantially the same size not only to accept the same quantity of beverage but also to be handled by equipment currently in use.
Furthermore, the bottle must be aesthetically pleasing to the customer as well as being satisfactory functionally.
SUMMARY OF THE INVENTION
Bottom bulging of a pressurized plastic container is a serious problem. Such a container becomes a "rocker" or may loose completely its footing and tip over. Because of bottom bulging volume of the container increases and the fill line drops to unacceptable level.
It has been known for along time, that the strongest pressure vessel is one of a spherical shape. Its excellent performance is based on a uniform distribution of stresses: tensile stresses in case of internal pressure and compressive stresses in case of external pressure. Since spherical containers or those with hemispherical bottoms require extra stands or footing they are impractical for application such as beverage bottle.
Next to the hemispherical there is the domed bottom, which has a built-in up-side-down hemisphere, a cone or construction between the two. However, under pressure domed bottoms bulge, too. Despite its rigidity, the dome looses some of its depth and the base diameter decreases. After these changes the bottle becomes also taller and not as stable.
The usual approach to solve the problem is to make the bottom heavy.
The approach of this invention is to use material where it is needed.
In looking for reasons of domed bottom bulging and instability the forces and stresses applied to the bottom in service, was analyzed. The external pressure on a cone or hemisphere cannot decrease height of these constructions unless compressive strength of the wall would be exceeded and the walls would be compressed or the diameter and circumference of its base would be increased.
At the lowermost wall of the bottom dome there is an area where compressive stresses are changing to flexural (bending) and tensile stresses. That critical area usually is the bottom rim or the adjacent bottom section. Since plastic material is weakest in tension, the critical tensile stresses in this area are reached first and they are followed by critical flexural stresses before the critical compressive stresses can be expected. With this in mind the mechanism of the bottom bulging, which is manifested mainly by a decreased dome height and base diameter, can be described.
The domed bottom is strong as long and/or where it is exposed to compressive stresses only. However, at the area where the dome blends with the bottom rim it is exposed to the most damaging tensile stresses. When these stresses become critical the area involved yields and elongates, thus giving a chance for bending stresses and partial inversion of the dome. Depth of the cone or dome can decrease only if the base diameter and circumference of the dome at these points elongate to allow bending of the lower section of the dome outwardly.
From the above analysis and description of bottom bulging mechanism it can be concluded that in order to improve performance of the dome bottom, reinforcement of its critical base section is needed. This finding constitutes the core of my invention.
The purpose of the invention is to eliminate domed bottom bulging by providing an integral reinforcing rim at its base in order:
1. to expose the bottom dome to compressive stresses only;
2. to arrest the tensile and bending stresses at the base of the dome;
3. to cut excessive material from the dome and to produce a more economical plastic container.
The present invention is directed to a bottle particularly adapted for use with carbonated beverages.
A general object of the invention is to provide a novel bottom end portion for a plastic bottle wherein the end portion is contoured to place certain sections in compression and others in bend in a unified construction which utilizes the least amount of material, obtains a stable product, aesthetically is acceptable and pleasing and is capable of either blow molding or injection blow molding.
A further object is to provide a novel bottom conformation for a container easy to manufacture and provides the necessary strength developed by a novel arrangement of wall components including a domed center portion and an encompassing rim portion with which it is integrated and at its outer edge merges with the outer side wall, the rim portion being formed with a plurality of rib formations which extend from the juncture of the rim with the dome portion to and beyond the juncture of the rim portion with the side wall.
These and other objects and advantages inherent in and encompassed by the invention will become more readily apparent from the specifications and drawings, wherein:
FIG. 1 is a side elevational view of a bottle incorporating the invention;
FIG. 2 is an end view of the bottom;
FIG. 3 is a transverse longitudinal sectional view taken substantially on line 3--3 of FIG. 1;
FIG. 4 is a partial sectional view taken essentially on line 4--4 of FIG. 2; and
FIG. 5 is a sectional view taken substantially on line 5--5 of FIG. 1.
DESCRIPTION OF THE INVENTION
Describing the invention in detail there is shown a plastic bottle generally designated 2 suitable for carbonated beverages. The material used may be of the type identified as DuPont NR-16 or Barex 210 sold by Vistron Corporation located in Ohio or any other like suitable material. Although such bottles represent a principal application of the invention, it will be understood that the invention is applicable to containers generally.
The bottle comprises an upper end neck portion 3 which blends into a body comprising a side wall portion 4 having at least a bottom section 5 of cylindrical configuration. The lower edge of the cylindrical section blends into a bottom wall structure 7 which essentially extends transaxially of the bottle.
The bottom section comprises a center dome portion 8 which has a convex upper side 9 internally of the body and a concave underside 10.
The dome portion 8 merges at its lower edge into the inner edge of a rim section 11 which is in the form of semitorus or half a donut, the outer edge of which merges into the lower section of the cylindrical wall portion 5.
The rim section is generally U-shaped in cross-section and has a concave inner side 12 and a convex outer or bottom side 13.
A series of regularly spaced ribs or reinforcing elements 14,14 are provided between legs 15,15 in the rim portion.
Each rib 14 is U-shaped in transverse cross-section and comprises side webs 16,16 which grow thicker inwardly and merge into a crest or ridge portion 17 of relatively thicker section. The side edges 18,18 of the ribs diverge slightly radially outwardly and define the margins of an intervening groove 19.
The inner and outer ends 20 and 21 of the grooves converge toward their extremities and shallow out and blend into the dome wall and the side wall respectively.
It will be noted that the ribs are of widest formation circumferentially of the container at 22 in the corner 23 formed by the juncture of the bottom and side walls of the container.
Thus strength is imparted at a critical area to resist bending moments imposed by the compressive loading of the dome portion.
The ribs are convexed inwardly of the container and have concave bottom sides forming the grooves.
Each leg portion 15 has a base pad section 25 which extends laterally, that is, circumferentially of the container side webs of adjacent rib structures and merges therewith in inturned rounded surface configurations. In longitudinal section, that is, radially of the container, the legs are of U-shaped convexed outwardly and provide at said pad sections 25 coplanar seating areas for the bottle.
The instant structure has been tested at 140°F. for two hours and has performed satisfactorily.