WO2007134036A2

WO2007134036A2 - Blow molded plastic bottle with reinforced base and method

Info

Publication number: WO2007134036A2
Application number: PCT/US2007/068448
Authority: WO
Inventors: Kristopher J. Ivie
Original assignee: Graham Engineering Corporation
Priority date: 2006-05-11
Filing date: 2007-05-08
Publication date: 2007-11-22
Also published as: WO2007134036A3

Abstract

The dome base of a blow molded plastic bottle includes a number of circumferential pads spaced below the dome by vertical and angled walls. The walls strengthen the dome and prevent bowing of the dome.

Description

Attorney's Case No. 3-2628-PCT

BLOW MOLDED PLASTIC BOTTLE WITH REINFORCED BASE AND

METHOD Field of the Invention

The invention relates to blow molded plastic bottles which are filled and pressurized, and to methods for making the blow molded bottles . Description of the Prior Art

Blow molded plastic bottles are manufactured by blowing air into and expanding molten plastic tubes or parisons against a mold cavity. The bottles have bases sealed by pinching together the sidewalls of the parison at pinch seal beams. When the contents of the bottles are under pressure, blow molded bottles have thick, strong dome bases to withstand internal pressure without bowing .

Bottles of this type may be filled, sealed and then heated to sterilize and cure the contents. Heating expands the air in the top of the bottle, increasing the pressure in the bottle. Thick, strong dome bases are required to withstand internal pressure without deforming or bowing the base. Pressure deformation of the base pushes the dome out so that the bottle will not stand vertically on a surface. Bowing is unacceptable. Thick, strong domes are expensive and increase the cost and weight of the bottle.

If the thickness of the plastic in the base dome is decreased to reduce the cost of the bottle the strength of the dome is undesirably decreased. The depth of the dome may be increased to increase resistance to pressure deformation. However, increasing the depth of the dome increases the amount of plastic required, increases the cost of the bottle, and decreases the interior volume of the bottle. Shrinkage of the plastic forming the dome base during stabilization normally decreases the height of the dome and weakens the dome.

Accordingly, there is a need for a blow molded bottle with an improved and strong dome base capable of withstanding increased internal pressure without bowing. The base dome should use a minimum of plastic resin in order to minimize the cost and weight of the bottle. It should be readily manufacturable by blow molding and be highly reliable. Summary of the Invention

The invention is an improved blow molded plastic bottle having a strong, lightweight dome base for supporting the bottle vertically without bowing and method for making the bottle. A number of circumferentially spaced reinforcing pads are formed in the dome to either side of a pinch seal beam. The pads include bottom walls below the dome and

U-shaped side and end walls extending between the dome and the bottom walls. The side and end walls stiffen the dome during stabilization and prevent bowing caused by increased internal pressure.

The pad sidewalls facing the pinch seal are angled at about 45 degrees from the vertical to facilitate disengagement of the molded bottle from the bottom of the mold cavity as the mold opens. The corresponding surfaces on the mold halves move the bottle upwardly and out of engagement from the mold. The sidewalls of the pads facing away from the pinch seal are vertical for maximum strength against bowing.

The thickness of the improved base dome is greater than the thickness of the bottle body but considerably thinner than a conventional base dome. The strong base dome prevents bowing, requires less plastic and is cheaper and lighter. Description of the Drawings

Figure 1 is a side view of a first embodiment bottle according to the invention;

Figure 2 is a sectional view taken along line 2--2 of Figure 1 ;

Figure 3 is an enlarged view taken along line 3--3 of Figure 2;

Figure 4 is a sectional view taken along line 4--4 of Figure 3 ;

Figure 5 is a sectional view taken along line 5--5 of Figure 3 ;

Figure 6 is a sectional view showing the lower portion of the bottle as blown in a mold;

Figure 7 is a view like Figure 6 with the mold partially open;

Figure 8 is a view like Figure 3 of a second embodiment bottle; and

Figure 9 is a sectional view taken along line 9--9 of Figure 8. Description of the Preferred Embodiments

Figures 1-7 disclose a first embodiment blow molded bottle 10. Bottle 10 has an integral plastic body 12 with mouth 14 at the top of the body and sealed closed base 16 at the bottom of the body. The body 12 has a circular horizontal cross section. Different cross section bodies are contemplated within the scope of the invention. The body is formed from plastic resin of the type used for extrusion blow molding, including polyethylene, high-density polyethylene, or polypropylene. The bottle may be formed from a monolayer or multilayer parison.

The bottle can be about 10.2cm high, 4.2cm in maximum diameter and have a fill capacity of 95ml. The bottle has a thin body wall thickness of about 0.5 mm. The base has a thickness of about 1.5 mm. Other sizes are contemplated .

Blow molded bottle base 16 is shown in Figures 3, 4, and 5 and includes a circular rim or heel 18 surrounding concave dome 20. Diametral parison pinch seal beam 22 extends diametrically across the base below the dome. The pinch seal beam has a high point 24 at the center of the dome and angles downwardly from the high point along the dome to dome edge 19. The seal beam 22 is above the bottom of the bottle. Recesses 26 are formed in rim 18 at the ends of the pinch seal beam to accommodate mold tooling forming the pinch seal. Beam 22 helps support the dome 20. Four shallow feet 28 are spaced 90 degrees apart on the bottom of rim 18. Each foot is located 45 degrees to one side of the beam 22 with the two feet on each side of the beam and spaced apart 90 degrees. Feet 28 project below the rim a short distance to support the bottle vertically. Four 45 degree-spaced reinforcing pads 30 are formed downwardly from dome 20. The width of the pads is greatest adjacent dome edge 19 and decreases inwardly to a blunt end at end wall 36. Each pad includes a generally flat bottom wall 32, which extends radially inwardly from dome edge 19 toward the center of the dome to the blunt end. The bottom wall is separated from the top of dome 20 by vertical sidewall 34, 45 degree tapered front wall 36 at the blunt end and 45 degree tapered sidewall 38. The walls 34, 36, and 38 are U-shaped and extend around the sides of each pad 30 away from dome edge 19. See Figure 3.

Vertical sidewalls 34 face away from the pinch seal beam 22. Tapered front walls 36 and sidewalls 38 face the pinch seal beam 22. The bottom walls 32 joins edge 19 at upward step 40 so that pad 30 is recessed above the rim 18 and is located within the concavity of dome 20. Recessing of the reinforcement pad above rim 18 assures that the bottle is not supported by the pads.

The four reinforcement pads 30 are 90 degree spaced apart around the base 16 with each pad having a circumferential width of about 45 degrees. The top of the dome 20 has four top walls 42 spaced apart 90 degrees around the base and located between the sidewalls of the pads. Each dome top wall 42 extends circumferentially about 45 degrees. The top 42 walls are the same shape as the bottom walls 32. Pinch seal beam 22 extends below and angles downwardly from two opposed dome top walls 42. Walls 42 are domed upwardly as shown in Figure 4.

The reinforcing pads 30 formed in dome 20 strengthen the dome against outward bowing at rim 18 during stabilization of plastic and during increased pressure in the bottle. The sidewalls 34, 36 and 38, resist outward deformation of the dome 20. Vertical sidewalls 34, facing away from the pinch seal 22, are particularly strong. The tapered sidewalls 36 and 38 are also strong and resist outward bowing of the base. Walls 36 and 38 are tapered in order to facilitate upward movement of the bottle and ejection of the bottle from the bottom of the blow mold as the blow mold opens, as illustrated in Figure 7. The strong dome 20 is shallower than conventional domes and requires less plastic.

The thickness of plastic in dome 20 is less than the thickness of the plastic in the dome of a conventional bottle. The amount of plastic needed to make bottle 10 with a strong base which prevents outward bowing is less than the amount of plastic required in a bottle with a thicker conventional base which prevents bowing. Plastic is saved and cost and weight are reduced. For instance, in the described bottle, the weight of the disclosed dome base is about 20 percent less than the weight of a conventional dome base. The disclosed bottle uses 8 percent less plastic than a like bottle with a conventional base.

Figure 6 illustrates the lower portion of the bottle 10 blow molded in cavity 44 between blow mold halves 46 and 48.

The bottle is blow molded from a tubular parison captured between the mold halves. The surfaces at the bottom of cavity 44 define the shape of the exterior of bottle base 16 and include 45 degree-sloped surfaces 50 facing away from the parting line 52 between the mold halves. The portion of the parison blown against surfaces 50 form angled walls 36 and 38 of reinforcing pads 30. The bottom of the mold also includes vertical surfaces facing away from the parting line 52 (not illustrated) , which form vertical sidewalls 34 in reinforcing pads 30 facing away from the parting line. Following blow molding of a bottle, the mold halves open as shown in Figure 7. Opening of the mold halves moves surfaces 50 against walls 36 and 38 in the reinforcing pads in the dome to raise the bottle above the bottom of the mold in position for ejection from between the fully opened mold halves. The bottle is raised above the vertical surfaces in the mold forming sidewalls 34 to prevent injury to the bottle during opening of the mold.

The bottle is ejected from the mold immediately following blow molding when the plastic in the bottle has set but has not stabilized. As the ejected bottle stabilizes, the bottle shrinks and the plastic forming the dome shrinks tending to reduce the height of the dome and the strength of the dome. Height reduction of the dome is resisted by the reinforcing pad walls 34, 36 and 38 which extend transversely to the shrink direction and strengthen the dome. Walls 34 are perpendicular to the vertical shrink direction and strongly resist shrinkage. Walls 36 and 38 are angled to the shrink direction and resist shrinkage. Walls 34, 36 and 38 effectively resist shrinkage of the dome so that when the bottle is fully stabilized the height of the dome has not been decreased appreciably from the height when molded and the dome resists outward bowing during heat processing of the contents placed in a sealed bottle.

Bottle 10 may be filled with a food product, sealed with an air space at the top of the bottle and then placed in a hot water bath at a temperature as high as 90⁰C in production and as high as 100⁰C for testing purposes. The bottles are immersed in the hot water bath for a period of time sufficiently long to heat and process the ingredients sealed in the bottles, which may be water and solids used to make a food product such as yogurt, and to sterilize the bottles and contents.

During immersion in the hot water bath the contents of the bottles, including the air in the headspace is heated and the pressure in the sealed bottles is increased. The pads 30 with walls 34, 36 and 38 support the domes against outward bowing due to the increased pressure in the bottles during sterilization and curing of the sealed product. The base is not distorted and supports the bottle vertically. Figure 9 and 10 illustrate a second embodiment blow molded bottle 58 having a reinforced base similar to the first embodiment blow molded bottle 10.

Bottle 58 includes a body 60 of a circular cross section, a mouth (Not illustrated) and a base 62. The base has a rim or heel 64 at the bottom of body 60 surrounding concave dome 66. Pinch seal beam 68 extends diametrically the base below the dome. The pinch seal beam does not extend to the outer edge 70 of the dome. Circular flex hinge 72 joins the outer edge 70 of dome 66 to base rim or heel 64. The pinch seal beam has a high point 74 at the center of the dome and extends downwardly from the high point along the dome to pinch seal beam ends 76 spaced inwardly from edge 70. Four shallow supports or feet 78 are spaced 90 degrees apart on the bottom of rim or heel 64. Each foot is located 45 degrees to one side of beam 68 with two feet on each side of the beam and spaced apart 90 degrees. The feet 78 project below the rim a short distance to support the bottle vertically.

Four 45 degree-spaced reinforcing pads 8, like pads 30, are formed downwardly from the top of dome 66. The width of the pads is greatest adjacent edge 70 and decreases inwardly to a blunt end at narrow end wall 82. Each pad includes a generally flat bottom wall 84 extending inwardly from dome edge 70 toward the center of the dome to the end wall 82. Each bottom wall 84 is separated from the top of the dome 66 by vertical side wall 86, 45 degree tapered front wall 82 at the blunt end and 45 degree tapered side wall 88. The vertical side wall 86 faces away from the pinch seal beam 68. The tapered front walls 76 and side walls 88 face the pinch seal beam. The bottom walls join the dome slightly inwardly from edge 70 so that the pad is recessed above rim or heel 64. Walls 86, 82, and 88 extend around the edges of walls 80 away from edge 70 and U-shaped.

The pads 80 in dome 66 strengthen the dome against shrinking during stabilization of the plastic forming the bottle and against outward bowing in response to the increased pressure in the bottle, as previously described. Increased pressure in bottle 60 flexes hinge 72 to permit the entire dome to move downwardly relative to body 12 to increase the volume of the bottle without stressing the dome. The hinge permits lowering of the domes sufficiently below base 62 so that the bottle sits on dome edge 70.

The domes in bottles 10 and 56 each include two reinforcing pads located to either side of a diametrical pinched seal beam. The four pads in the dome are spaced at 90 degree intervals around the circumference of the dome. The pads are generally trapezoidal in shape with a greater width adjacent the dome edge and a reduced width at the end of the pad adjacent the pinched seal beam. The strong, vertical reinforcing side walls on each pair of pads on one side of the beam face each other and away from the pinch seal beam. Angled reinforcing side walls face the pinch seal beam. The length of the pinch seal beam depends upon the diameter of the parison from which the bottle is blow molded. For instance, the parison from which bottle 10 is molded has a diameter greater than the parison from which bottle 58 is molded so that pinch seal beam 22 extends fully across dome 20 and pinch seal beam 68 extends only partially across the dome 66. Bottles may be blown from parisons which are not captured between the mold halves before blowing. These bottles have domes with reinforcing pads as described but without pinch seal beams.

Claims

Graham Engineering Corporation 3-2628-PCT

1. A blow molded plastic bottle comprising a body and a base, the base including a heel and a concave dome inside the heel, a pinch seal beam extending across the dome, and four strengthening pads on the dome, each pad including a generally flat wall spaced from the dome, a first angled strengthening wall facing the pinch seal beam, and a vertical strengthening wall facing away from the pinch seal beam.

2. The bottle as in claim 1 wherein each pad extends approximately 45 degrees around the circumference of the dome and is spaced from adjacent pads.

3. The bottle as in claim 1 wherein the vertical wall of one pad faces the vertical wall of an adjacent pad.

4. The bottle as in claim 1 wherein each pad includes a second angled reinforcing wall adjacent said first angled reinforcing wall.

5. The bottle as in claim 1 wherein the pinch seal beam extends completely across the dome.

6. The bottle as in claim 1 wherein the pinch seal beam extends partially across the dome.

7. The bottle as in claim 1 including a circumferential hinge between the dome and the heel base .

8. The bottle as in claim 1 wherein two pads are located on each side of the pinch seal beam.

9. The bottle of claim 8 wherein the vertical strengthening walls of the pads on each side of the pinch seal beam face each other.

10. The bottle of claim 1 wherein the generally flat walls are below the dome. Graham Engineering Corporation 3-2628-PCT

11. The bottle as in claim 1 including feet on the heel .

12. A bottle blow molded from an extruded parison, the bottle comprising a heel, a concave dome located inside the heel, a plurality of reinforcing pads formed in the dome, each reinforcing pad including a pad wall on one side of the dome, the pad wall joining the dome adjacent an outer dome edge and extending toward the center of the dome, a generally U-shaped sidewall extending around each pad wall between the dome and the pad wall, said sidewalls each including an angled strengthening portion and a vertical strengthening portion, said angled and strengthening portions facing in appropriate directions .

13. The bottle as in claim 12 wherein for each pad the angled sidewall portion is located on two sides of the pad and the vertical sidewall portion is located on one side of the pad.

14. The bottle as in claim 12 wherein the dome includes a pinch seal beam, the angled sidewall portions facing the pinch seal beam and the vertical sidewall portions facing away from the pinch seal beam.

15. The bottle as in claim 12 including a circular hinge between the heel and the dome .

16. The bottle as in claim 12 wherein each pad extends below the concave surface of the dome and the dome is above the heel .

17. The method of blow molding a plastic bottle with a reinforcing dome, comprising the steps of: Graham Engineering Corporation 3-2628-PCT

A) capturing a parison between open mold halves and closing the mold halves in the parison;

B) expanding the parison against the mold halves to form a bottle having a base with a heel, a concave dome located inside the heel and a plurality of reinforcing pads in the dome extending to one side of the dome;

C) forming reinforcing walls partially surrounding each pad with a vertical reinforcing wall portion and an angled reinforcing wall portion; and

D) opening the mold, moving parts of the mold against the angled wall portions to eject the bottle from the mold.

18. The method of claim 17 including the step of:

E) forming a pinch seal beam extending across the dome, locating the vertical reinforcing wall portions in the pads to face away from the pinch seal beam and locating the angled reinforcing wall portions in the pads to face toward the pinch seal beam.