Controlled container headspace adjustment and apparatus therefor

Abstract

A sealing and pressure dosing apparatus, and container filling method, including a capping machine (102) which receives containers (1). Closures (80) are applied to the containers (1) immediately following the raising of pressure within the containers (1) by a pressure dosing system in a pressure sealing changer (84). Preferably a cooling system is integrated with the capping machine.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates generally to a sealing and pressure dosing apparatus and more particularly to a capping and / or sealing apparatus for applying closures to containers at high speed, and even more particularly to a capping apparatus including a pressure dosing system for providing a pressure medium into a head space of each of the containers prior to closure application by the apparatus. The pressure sealing may be undertaken either during the initial sealing of the container, or as a secondary operation after the initial sealing the container. The headspace pressurization increases the internal pressure within the container, providing for increased top-load capability of the container. This invention may further relate to hot-filled and pasteurized products packaged in heat-set polyester containers and for controlling the cooling of any containers filled with a heated liquid.BACKGROUND[0002]The present invention in one particular emb...

AI Technical Summary

Benefits of technology

The present invention is a capping and pressure dosing apparatus for containers, such as bottles. It includes a rotary capping machine and a pressure dosing system that seals the top of each container with a sealing chamber as it moves through the capping machine. The apparatus coordinates its pressure control with the capping machine to ensure consistent operation. The apparatus also includes a device for initiating the differential cooling process to prevent container sidewall temperatures from exceeding about 70 °C. The technical effects of the invention include optimized pressure control, enhanced operating efficiency, and consistent operation.

Problems solved by technology

However, as the nitrogen disperses immediately upon injection, the process for controlling accurate dosing is limited.

Some of the nitrogen will escape prior to capping, thus rendering the process inexact in terms of absolute pressurisation control.

Additionally, handling nitrogen systems can be costly and dangerous.

Nitrogen consumption can be reduced by as much as 80% using a liquid nitrogen dosing system instead of gaseous nitrogen tunnels, but as the capping or sealing of the container occurs at ambient pressure at the precise time of sealing, in both systems, the resulting pressure value is compromised.

However, as the nitrogen is dosed prior to sealing there is a loss of some of the nitrogen dose prior to sealing, the amount of which varies according to many factors.

This leaves the process inexact in terms of identifying the dose actually in the container after sealing.

Additionally, the dosing process becomes even more difficult to control in the hot fill environment, particularly at fast line speeds.

It will disperse much more quickly prior to capping or sealing leaving the consistency of dose much more uncertain.

Plastic bottles need to be pressurized at all line speeds, and if control over the exact pressure achieved inside a container is compromised then the speed of the system will also be compromised in order to correctly pressurise each container.

Using this method, any variation in head-space volume due to variations in fill level would cause under and over pressurized containers.

Therefore, in prior art it is not considered feasible to provide cooling simultaneously with the capping of filled containers, or the temperature of the contents is compromised before it may be utilized for internal sterilization purposes.

Not only would there be substantial risk in introducing foreign matter into the container prior to sealing, but the temperature of the product would be compromised and the efficacy of the pasteurization model would be corrupted.

Once the liquid cools down in a capped container, however, the volume of the liquid in the container reduces, creating a vacuum within the container.

This liquid shrinkage results in vacuum pressures that pull inwardly on the side and end walls of the container.

This in turn leads to deformation in the walls of plastic bottles if they are not constructed rigidly enough to resist such force.

In hot filling of beverages in PET containers, the thermal stability of the material of the container also constitutes a challenge.

PET has a low glass transition point of approximately 75 degrees C. When the headspace of a container is pressurized while the liquid contents are above about 70 degrees C., the container walls are subjected to particularly damaging forces.

In such nitro-dose applications there is significant container distortion when the PET material is above about 70° C. to 75° C. due to the high level of nitrogen pressure within the container.

Such distortion is non-recoverable.

The container effectively grows in volume and the base is disfigured and unstable.

Also for example, structures in the sidewall, such as ribbing, may be similarly affected causing uncontrolled container growth and distortion.

This distortion causes a weakness in any strengthening structures and is very undesirable.

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