WO1997026126A1

WO1997026126A1 - Method and apparatus for blow molding, filling and sealing a beverage container

Info

Publication number: WO1997026126A1
Application number: PCT/US1997/001615
Authority: WO
Inventors: Samuel J. Rupert
Original assignee: Ecco, Inc.
Priority date: 1996-01-22
Filing date: 1997-01-21
Publication date: 1997-07-24
Also published as: AU2253697A

Abstract

A method of blow molding, filling and sealing a plastic container (10) while the mold remains adjacent to an extrusion die head (38). The method includes the steps of intermittently extruding a parison of molten plastic resin from the die head (38), closing a mold about the parison with the parison forming a seal between the mold and the die head (38), blow molding the parison into the shape of the container (10) with a liquid product, removing the product fill tube (48) from the container (10), sealing the opening into the molded container (10) and, subsequently, opening the mold to break the seal between the mold and the extrusion die (40) and to remote the filled and sealed container (10) from the mold.

Description

METHOD AND APPARATUS FOR BLOW MOLDING, FILLING AND SEALING A BEVERAGE CONTAINER

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to blow molding, filling and sealing of a beverage container and in particular to the filling and sealing of a container while the container remains in a blow mold located at the outlet of an extrusion die head. Sealed containers with unitary closures are known. Such containers typically have a body, a neck and a closure structure to close and seal the opening in the neck. It is also known to provide such containers with means for permitting the containers to be opened by breaking off a sealed closure at the top of the container or neck. To facilitate such opening of the container, a frangible web is provided in the container neck. The frangible web is made of a reduced thickness region in the wall of the container at the container neck. Such a container is opened by twisting or bending the part of the container above the frangible web, relative to the part of the container below the frangible web. This ruptures or severs the frangible web to remove the closure and open the container.

Containers incorporating the above described frangible web structure are typically formed of a thermoplastic material. Such containers are conventionally fabricated by blow and/or vacuum forming. Typically the thermoplastic material is extruded as a length of parison in the form of a vertically oriented, elongated, hollow tube, between a pair of mold halves for forming the container. In many prior methods, such as that disclosed in U.S. Patent No. 4,540,542, after extrusion of the parison, the mold halves close upon the parison and move the parison from the extrusion die to a second stage, where the parison is blown, and the container filled and sealed prior to opening of the mold. Such a "two stage" process can result in a lengthy cycle time to allow for movement of the mold between the two stages. In addition, this two stage process exposes the open top of the parison to the ambient atmosphere as the parison is moved from the extrusion die to the blow and fill stage. It is one object of the present invention to provide a method and apparatus for extruding a parison, blow molding the parison in a mold, filling the container and sealing the container while leaving the mold in place at the outlet of the extrusion die head.

It is a further object of the present invention to perform the above in the production of narrow necked plastic containers in which the container opening, at the neck of the container, is significantly smaller than the body portion of the container. One example of a narrow necked container is a two liter carbonated beverage container. Examples of large necked containers are peanut butter and mayonnaise jars. One difficulty which must be overcome in molding, filling and sealing a narrow necked container is dealing with the relatively small size of the opening for both blow molding the container as well as filling the container with a liquid product. The overall cycle time will be dependent upon the rate at which gas can be introduced into the parison to blow mold the parison and the rate at which the liquid contents can be dispensed into the container. Thus, the size of the blow and fill tubes have a significant impact on the production cycle time.

It is a further object of the present invention to provide a method of forming a container and filling the container in the mold which can be used with temperature sensitive products, such as milk. To avoid carmalization of the milk sugars, and the resulting change in flavor, it is necessary to ensure that the beverage will not be excessively heated by the molding apparatus. At the same time, however, it is necessary to ensure that the resin at the upper end of the container remains molten to enable the container to be sealed after it has been filled with the beverage.

With the method of the present invention, the parison is intermittently extruded using a reciprocating screw extruder. Following extrusion of the parison, the mold is closed about the parison immediately below the die head. The parison resin produces a seal between the mold and the die head. A pressurized gas is blown into the parison, forcing the parison outward, into contact with the refrigerated surface of the mold cavity, to form the plastic container. A sterile gas is used to blow mold the parison to maintain the sterility of the parison and container. Furthermore, if the parison is extruded with an open end, a small amount of the sterile blow air or gas is introduced into the parison during extrusion. This creates a positive pressure within the parison to prevent airborne contaminants from entering the parison open end, thus maintaining the sterility of the parison

A fill tube is inserted into the molded container, and after venting of the pressurized gas from the molded container, the container is filled with a liquid product. Following removal of the fill tube, a pair of slides, one carried by each mold half, are pressed against the parison at the open end of the container to pinch the container closed. After the container has been sealed, the mold is opened and the container is removed.

The extrusion die head has an annular outlet for extruding a cylindrical parison. Within this annular outlet is an annular air passage for introducing pressurized gas into the interior of the parison for blow molding the parison. Within the air passage is a reciprocating fill tube which is raised and lowered by a linear actuator, such as a pneumatic or hydraulic cylinder, at the upper end of the extrusion die head.

The mold portion forming the container body is cooled so that the molten resin is cooled immediately upon contact with the mold surface. This avoids excessive heating of the liquid contents when the container is filled. The neck and upper flash portions of the mold are maintained at a higher temperature so the container can be sealed after filling.

While the invention is shown and described with a single extrusion die head and a single cavity mold, it is understood that the invention is preferably carried out with a multiple cavity mold and multiple extrusion die heads to increase productivity. Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of the blow molded container made according to the present invention;

FIG. 2 is a side elevational view of the container shown in FIG. 1 ; FIG. 3 is an elevational view showing one mold half and the cavity therein;

FIG. 4 is an elevational sectional view of the extrusion die head used in the present invention;

FIG. 5 is a sectional view of the extrusion die head as seen from substantially the line 5-5 of FIG. 4; and FIG. 6 is a side elevational view of a sealing pin used to seal the container after filling with the beverage product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the plastic container made according to the present invention is shown in FIGS. 1 and 2 and designated generally at 10. The container 10 includes a main body 12 designed to contain the liquid beverage. At the upper end 14, the container includes a neck 16 in which the diameter of the container is reduced, leading to a small diameter opening 18. A closure 20, integrally formed with the container, closes the opening 18 to seal the container thereof. The closure 20 includes a hollow disk 22 connected to and immediately above the neck 16. The closure 20 also includes a flange 24 connected to the disk. The flange 24 is formed as flash by pressing the parison between the two mold halves. The flange 24 is integral with and joined to the disk 22. The line of contact 26 between the flange 24 and the neck 16, however, is formed with knife edges, resulting in a pinch-off between the flange 24 and the neck 16, enabling the flange to be readily detached from the neck.

At the opening 18, the disk 22 is joined to the neck with a frangible web 28 having a thickness less than the container wall thickness. This enables the container to be open by gripping the flange 24 and twisting the closure 20 relative to the body 12 of the container. This causes the frangible web 28 to break, allowing the closure 20 to be removed and the container to be opened at the opening 18.

With reference to FIG. 3, a mold half 30 used to mold the container 10 is shown. The mold half 30 includes a cavity 32 shaped to correspond with the desired shape of the container 10. The mold has a body portion as indicated in FIG. 3 which forms the body 12 of the container. Above the body portion, the mold includes a neck portion in which the neck 16 and flange 24 are formed. Above that, the mold includes a flash portion in which an upper flash is formed. The upper flash of the container is attached to the flange 24 along a pinch-off line, formed by mold knife edge 80, for easy removal of the flash. The mold is made with a protuberance 34 that is substantially wedge-shaped in cross- section and extends into the mold cavity. The protuberance 34 forms a continuous circumferential ridge 36 at the opening 18 into the container. When the parison is blown during molding, it is stretched over this ridge. The stretching results in a frangible web 28 of plastic overlying the ridge 36, having a thickness that is less than the container wall thickness. This frangible web is torn when the flange 24 is subsequently twisted relative to the container body 12. Once the web 28 is torn, the container is opened at the opening 18.

With reference to FIG. 4, an extrusion die head 38 is shown which is used to form a cylindrical parison of molten resin. At its lower end, the extrusion die head 38 has a die 40. Resin enters the die head from a screw extruder 41 which is preferably a reciprocal screw extruder to produce intermittent extrusion of the parison. Alternatively, any means to produce intermittent extrusion of the parison can be used. At the lower end of the extrusion die head 38, an annular resin outlet 42 enables a cylindrical parison of the molten resin to be extruded. Within the resin outlet 42 is an annular air passage 44 through which pressurized gas is blown into the parison to expand the parison outward in the mold. This same air passage is used to vent the pressurized gas after molding. The air passage 44 extends upward through die head 38 to a coupling 46 where it is attached to a two directional valve 47 that intermittently connects to a source of pressurized gas and to the atmosphere to blow mold and vent the blown container, respectively.

A sterile gas is used to blow mold the parison to maintain the sterility of the parison and container. Furthermore, if the parison is extruded with an open end, the valve 47 is opened slightly to allow a small amount of the sterile blow air or gas into the parison during extrusion. This creates a positive pressure within the parison to prevent airborne contaminants from entering the parison open end, thus maintaining the sterility of the parison.

The inner surface of the air passage 44 is formed by a fill tube 48 which extends through the die 40 into the extrusion die head. The fill tube 48 is connected to an intermediate tube 50 which extends upwardly through the die head to a coupling 52 where it is connected to a source of supply for the liquid product. The coupling 52 is also connected to a linear actuator 54, such as an air or pneumatic cylinder, at the top of the die head for vertically moving the fill tube 48 as shown by the arrow 56 and described below. A bushing 58 is used to support and guide the fill tube 48 at the lower end of the die head.

Since this bushing is located within the air passage 44, the bushing is formed with a plurality of radially extending legs 60 for contact with the die head mandrel 62. The legs 60 provide a- passages 64 in between the bushing and the mandrel for air to flow through the passage 44. At th upper end of the die head, an O-ring seal 66 surrounds the intermediate tube 50, above th. compressed gas coupling 46, to provide a seal to prevent the compressed gas from leaking from the die head. The mandrel 62 extends downward slightly below the die 40 forming a lip 68. When the mold is closed about a parison, the mold is placed immediately below the die 40. The mold, together with the die and lip 68, forms a seal with a small portion of the resin between the die and the mold. Once the mold has closed, compressed gas is delivered through the passage 44 to the interior of the parison which blows the parison outward against the surface of the mold cavity. The entire container is molded by the gas blown into the parison. There is no blow pin or mandrel to press the parison into the container neck to form the neck. After molding, the fill tube 48 is lowered into the molded container. Simultaneously to or after venting of the compressed gas from the container, the container is filled with a liquid product. After filling, the fill tube 48 is removed. After removal of the fill tube, it is necessary to seal the open upper end of the container. A pair of sealing pins 70 (FIG. 6) are inserted in opposite directions through openings 72 in the mold halves. The sealing pins pinch the parison closed along the upper end of the flange 24. The contact surface of the pins has a lower portion 74 and an upper portion 76 which are separated by a knife edge 78. The knife edge 78 is aligned with the knife edge 80 in the mold, forming a pinch-off between the flange 24 and the upper mold flash. Following the sealing of the container, the mold is open and the container is removed.

The neck and flash portions of the mold are maintained at a high enough temperature so that the resin remains molten in these regions during the blowing and filling process. This enables a seal to be formed from the resin in the neck and flash after the fill tube has been removed. However, the body portion of the mold is chilled, using conventional devices and methods for chilling a mold. Chilling is accomplished by circulating a refrigerated liquid through a passage 82, in the mold. The passage 82 is in communication with a fitting 84. For certain beverages it is important that the beverage never be heated above a maximum temperature. For milk based beverages, the maximum short term temperature is approximately 160°F. Above this temperature, the milk sugar begins to carmalize and produce an undesirable taste. However, the molten resin, e.g., high density polyethylene, may be as hot as 350°F when it leaves the extrusion die head. To rapidly cool the resin, the body portion of the mold is chilled using refrigerated water or other chilled liquid circulating through passage 82 within the mold. For milk products, it is preferred to cool the mold to approximately 32°F to 34°F. Upon contact of the blown parison with the mold, the plastic resin will quickly cool. When the liquid product is introduced to the container, the product itself will not be excessively heated by the resin, thereby avoiding carmalization of the milk sugar. The need for this cooling of the mold will be dependent on the beverage product being packaged and the temperature of the refrigerant will be dependent upon the desired mold temperature and the extruded resin temperature. Another fitting 86 and passage 88 is provided in the neck portion of the mold. The passage

88 can be used to circulate either a cooling or heating fluid through the mold to maintain the neck and flash portion of the mold at a higher temperature than the body portion of the mold. The neck and flash portions of the mold are maintained at a sufficiently high temperature to keep the resin forming the flange 24 and upper flash molten so that a seal can be formed to close the container opening after the container has been filled. The temperature of the cooling liquid in the upper portion of the mold will depend upon the required resin temperature for sealing of the container. Due to the need to rapidly cool the body portion of the container while keeping the neck and upper flash portion molten requires maintaining different portions of the mold at different temperatures. This is accomplished by the different cooling/heating passages in the different portions of the mold.

The method of the present invention has been described in the context of intermittent extrusion. The invention can also be practiced with continuous extrusion using a reciprocating mold or reciprocating extrusion head.

The method and apparatus of the present invention provides an economical way of producing containers that are blow molded, filled and sealed within the mold while the mold remains adjacent to the extmsion die head outlet. The method and apparatus can be used with a variety of plastic resins that are suitable for extrusion blow molding, including, but not limited to high density polyethylene.

It is to be understood that the invention is not limited to the exact construction and method illustrated and described above, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims

I CLAIM

1. A method of blow molding, filling, and sealing a plastic container comprising the steps of: extruding a parison of molten plastic resin from an extrusion die head; closing a mold about the parison with the parison forming a seal between the mold and the die head, the mold having a cavity in the shape of the plastic container; introducing a pressurized gas into the parison to expand the parison outward toward the walls of the mold cavity to form the parison to the shape of the plastic container; venting the molded container to allow the pressurized gas to flow out of the container; lowering a product fill tube through the opening into the molded container; filling the container with a liquid product; removing the product fill tube from the molded container; sealing the opening in the molded container to close the molded container; and opening the mold to break the seal between the mold and the extrusion die and to remove the filled and sealed container from the mold.

2. The method of claim 1 wherein the mold has a lower zone containing a body portion of the cavity shaped to form the body of the molded container, a neck zone containing a neck portion of the cavity to form the neck of the molded container above the body and a flash portion forming a removable flash above the neck portion of the container, the method further comprising the steps of; cooling the body portion of the mold to a predetermined temperature whereby the parison is cooled by the mold upon contact of the parison with the mold surface to avoid undue heating of the liquid product upon filling of the molded container with the product; and maintaining the flash zone of the mold at a higher temperature than the body portion to keep the plastic resin in the flash zone molten for sealing of the opening in the container subsequent to filling the container.

3. The method of claim 1 wherein the entire parison, after blowing, is in contact with the mold surface.

4. The method of claim 1 wherein the sealing step is performed by pinching the parison from opposite sides with a pair of side members guided by said mold.

5. The method of claim 1 wherein the pressurized gas and the liquid product are both sterile.

6. The method of claim 1 wherein the parison is extruded with an open end and sterile gas is introduced into the parison during extrusion to create and maintain a positive pressure within the parison to prevent airborne contaminants from entering the parison open end.

7. An apparatus for blow molding, filling, and sealing a plastic container comprising: an extrusion die head having a die forming an annular resin outlet through which a cylindrical parison of molten resin is extruded; a mold having a pair of mold halves movable between an open position in which said mold halves are spaced from one another to a closed position in which said mold halves are adjacent one another and surrounding the parison and sealed against the die by resin from the parison, the mold forming a cavity having a surface shaped to the desired shape of the plastic container; the extrusion die further having an annular air passage concentric to and within the annular resin outlet for injecting pressurized gas into the parison within the mold for blow molding the parison to conform with the shape of the mold cavity; the extrusion die further having a product fill tube within the annular air passage through which a liquid product is dispensed into the molded container within the mold; and means for moving the fill tube into the mold for filling of the plastic container and for retracting the fill tube from the plastic container after filling the plastic container.

8. The apparatus of claim 7 wherein; the mold has a lower zone containing a body portion of the cavity shaped to form the body of the molded container, a neck zone containing a neck portion of the cavity to form the neck of the molded container above the body and being of a smaller size than the body and a flash portion forming a removable flash above the neck of the container; and the cavity in the neck portion having protuberance that is substantially wedge- shaped in cross-section extending into the mold cavity to form a continuous circumferential ridge over which the parison is stretched by the pressurized gas during blow molding to form a frangible web having a thickness less than the container wall thickness.

9. The apparatus of claim 8 further comprising means for maintaining the neck zone of the mold at a higher temperature than the lower zone of the mold.