Technical Field The present invention concerns a liquid bubble eliminator in a liquid sterilant sterilization system.

Prior Art

Food products, such as milk, juice, dried and/or particulate foods such as soups and the like, are often packaged in sterilized containers to prolong the shelf life of the contents. Often the packaging process requires sterilization of the packaging material prior to filling of the containers formed of the packaging material. Various devices and arrangements are used to sterilize containers in form, fill and seal packaging machines. One common arrangement includes a vaporized hydrogen peroxide (VHP) sterilization system. Such systems are normally closed loop systems that include both a vaporizer and a dryer.

The hydrogen peroxide sterilant of VHP sterilization systems consists of hydrogen peroxide and water (normally 35% to 50% by mass hydrogen peroxide). The hydrogen peroxide is somewhat unstable and can break down into water and oxygen. Upon breaking down, the oxygen forms small bubbles. These bubbles may accumulate and form larger bubbles. VHP units have a vaporizer that converts the liquid sterilant into vapor. Bubbles flowing through the vaporizer cause a momentary reduction in the hydrogen peroxide concentration at the vaporizer outlet. Since most VHP units are used in enclosed spaces with sufficient volume having a relatively long decontamination time, the short duration of lower hydrogen peroxide concentration does not affect the overall bio-burden reduction. However, in package decontamination processes, the exposure time may be a matter of one or two seconds. Bubbles being formed in the injection lines on aseptic packaging units reduce momentarily the hydrogen peroxide concentration, creating a situation where the packages may not be sufficiently decontami- nated.

Summary of the Invention

In view of the above one object of the present invention is to design a bubble eliminator to be used in the liquid sterilant lines of VHP decontamination equipment. According to the invention a bubble eliminator in the form of an enclosure is formed. The enclosure has an inlet and an outlet for the liquid sterilant. Furthermore, a number of small hollow tubes are placed in the enclosure. The function of the tubes is to attract entrained air in the sterilant.

The bubble eliminator is designed for use with hydrogen peroxide at flow rates much lower than are normally used in water units. Since hydrogen peroxide is some- what unstable and can be broken down when exposed to catalytic surfaces, the bubble eliminator contains materials that are not catalytic to peroxide. It also has means to expel the accumulated air bubbles to prevent them from re-entering the liquid sterilant.

Further objects and advantages of the invention will be obvious to a person skilled in the art from reading the detailed description below.

Brief Description of the Drawings

The invention will be described further below by way of example and with reference to the enclosed drawing.

Fig. l is a sketch of a liquid peroxide bubble eliminator according to the pre- sent invention.

Detailed description of Preferred Embodiments

A liquid peroxide bubble eliminator according to the present invention is to be placed in a liquid sterilant line of VHP (vaporized hydrogen peroxide) equipment. The eliminator comprises an enclosure 1, with an inlet 2 and an outlet 3. The inlet 2 receives a flow of liquid sterilant 10, in the form of hydrogen peroxide. The flow of liquid sterilant leaves the enclosure 1 by means of the outlet 3.

A perforated plate 4 is placed inside the enclosure 1 , giving an upper space above the perforated plate 4 and a lower space below the perforated plate 4. The inlet 2 and the outlet 3 open into the lower space of the enclosure 1. In the upper space of the enclosure 1, i.e. above the perforated plate 4, a float switch 5 is arranged. The liquid sterilant 10 partially fills the enclosure 1 up to a level above the perforated plate 4. Above the liquid sterilant 10 a gas 11 in the form of air is enclosed. The float switch 5 controls a valve 6, expelling air (gas 11) in its open condition. In the lower space of the enclosure 1 a number of small hollow tubes 7 are placed. The tubes 7 are held enclosed by the walls and bottom of the enclosure 1 and the perforated plate 4.

The enclosure 1 is made of a material that is non-catalytic to peroxide, such as polycarbonate. Also the tubes 7 and the perforated plate 4 are made of a material that is non-catalytic to peroxide, such as polycarbonate. In the hydrogen peroxide entering the enclosure 1 by means of the inlet 2 air bubbles 8 are entrained. The air bubbles 8 are formed when the somewhat unstable hydrogen peroxide breaks down. It is beneficial if such air bubbles 8 are removed before the sterilant reaches a vaporizer, normally arranged in VHP equipments. The air bubbles 8 that is entrained in the liquid sterilant attaches to the tubes 7 of the lower space. As the air accumulates on each tube 7, larger air bubbles are formed when the smaller bubbles come in close proximity to one another. The larger bubbles work there way through the tubes 7 and are eliminated once a sufficient volume has accumulated. Thus, the larger formed air bubbles 8 will lift towards the top of the enclo- sure 1 and through the perforated plate 4.

The float switch 5 at the upper space of the enclosure 1 is used to open the valve 6 to expel accumulated air. The perforated plate 4 prevents the tubes 7 of the lower space from interfering with the operation of the float switch 5. When the volume of gas 11, above the liquid/gas interface, is sufficient to reduce the buoyancy on the float switch 5, the float drops, thereby closing an electrical switch 9 that energizes the valve 6. The valve 6 opens and expels the gas 11 until the buoyancy of the float is sufficient to lift the float switch 5, thereby opening the electrical switch 9, deenergizing (closing) the valve 6.

To achieve the desired effect, that all the incoming air bubbles 8 are collected and will not pass out through the outlet 3, the tubes 7 should be dimensioned in a suitable way. Thus, by amending the number of tubes 7, the tube lengths, and/or the inner and outer diameter of the tubes 7, it is possible to control the capacity to collect the bubbles 8. The tube length and the inner and outer diameters of the tubes 7 should be sized to promote accumulation of the bubbles. In one embodiment the dimensions of each tube 7 was as follows: length 18 mm, outer diameter 9.5 mm and inner diameter 6.2 mm. Furthermore, the enclosure 1 must be sized to ensure that fluid velocity is sufficiently slow for the bubbles 8 to work their way toward the top of the enclosure 1.