INTRODUCTION

This invention relates to a device for use in the sterilization of liquids, in particular turbid liquids, the device comprising a UV source and an elongate tube with an arrangement of protruding members on the inner wall thereof, which in use, disrupts the flow of the liquid flowing through the tube, thereby increasing the exposure to the UV source.

BACKGROUND

The use of ultraviolet (UV) light for the purpose of sterilizing a liquid is well known. A problem that arises with a turbid liquid is that the light does not penetrate sufficiently far into the liquid, hence liquid furthest from the UV lamp may not be sterilized at all, or may not be sterilized to a desired level. South African patent no. 96/8029 discloses an elongate sterilizer in which a fluorescent tube is within, and co-axial with, an elongate housing. The sterilization chamber is between the fluorescent tube and the housing. The liquid inlet and liquid outlet are arranged tangentially with respect to the housing in an effort to cause the liquid to swirl and overcome the difficulty referred to above. It has been found, however, that the swirling motion imparted to the liquid as it enters the housing does not continue throughout the length of the housing, thus limiting the beneficial effect.

Other structures are known, such as that shown in U.S. Pat. No. 5,675,153, in which there is a helical vane in the space between the fluorescent tube and the housing, the vane extending from one end of the housing to the other. The vane is slotted and there is a gap between the vane and the inner surface of the housing. Such a structure would be completely unsuitable for the sterilization of milk, because of the many sharp corners where flow would stagnate and bacteria would be able to multiply.

There is a tendency for solids in milk to deposit on the surfaces defining the flow passage, in regions where there is insufficient flow velocity, so that the structure of U.S. Pat. No. 5,675,153 if it were to be used for the sterilization of milk, would suffer from deposits and as a consequence would require frequent cleaning. The structure would, in any event, be difficult to clean to the degree that is required in apparatus that is used for the handling of milk.

WO2001/37675 discloses a sterilizer that attempts to address the shortcomings experienced by devices and arrangements disclosed in South African patent no. 96/8029 and U.S. Pat. No. 5,675,153. This sterilizer also comprises a liquid inlet and liquid outlet that are arranged tangentially to the outer housing and the internal tube such as disclosed in 96/8029, but introduces circular or helical protuberances on the inner wall of the tube to attempt to maintain the swirling motion imparted to the liquid at the inlet throughout the length of the tube. However, this arrangement relies on the internal configuration of the tube exclusively to maintain turbulence created at the inlet. As a result of the particular arrangement, it will also be appreciated that this device is rather sensitive to variations in flow rate.

There is therefore a need for an arrangement that at least partially addresses the shortcomings of the prior art and provides for a sterilization device with improved performance.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a liquid sterilization device, suitable for the use in reducing the bacterial count in a liquid, the device comprising: an elongate housing having an inlet and outlet at opposing ends thereof, the housing being adapted to receive a UV source in use, and an elongate tube extending along the length of the elongate housing, wherein the elongate tube comprises complementary sets of opposing protruding members, there being a space between the UV source and the inner wall of the tube and the protruding members extending therefrom for the liquid to pass through, such that in use a disruptive mixing motion is imparted to the liquid by the protruding members as the liquid passes through the tube from the inlet to the outlet.

In one embodiment of the invention the housing further comprises a UV light transparent sleeve which is adapted to receive the UV source in use.

In a preferred embodiment of the invention the inlet and outlet to the housing are located substantially along a vertical central plane passing through the housing. In one embodiment of the invention the complementary sets of opposing protruding members are arranged in longitudinal rows along the length of the elongate tube.

Preferably, the tube comprises four or more longitudinal rows of opposing protruding members.

More preferably, the tube comprises four or six longitudinal rows of opposing protruding members.

In a particularly preferred embodiment, consecutive sets of opposing protruding members are circumferentially staggered in respect of another.

The protruding members may be provided in the form of dimples, indentations, or knobs extending from the inner wall of the tube.

According to a second aspect of the present invention there is provided a method for sterilizing a turbid liquid, the method comprising the steps of: providing a liquid sterilization device according to the invention, passing a liquid to be sterilized through the device to expose the liquid to UV light from the UV source, and collecting the sterilized liquid.

In a preferred embodiment, the turbid liquid is selected from the group consisting of alcohol containing liquids including wine and beer, biological fluids including blood, liquids for human consumption including milk, petrochemicals including all oils, and contaminated aqueous solutions including waste water.

In a particularly preferred embodiment, the turbid liquid is milk, blood, or waste water. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the following non-limiting embodiments and figures in which:

Figure 1 shows a side view of the device according to the present invention;

Figure 2 shows a longitudinal section of one end of the device according to the present invention;

Figure 3 shows a cross section on line Ill-Ill of Figure 1 ;

Figure 4 shows a plain view of part of an elongate tube according to one embodiment of the present invention;

Figure 5 shows a cross section on the line V-V of Figure 4;

Figure 6 shows a plain view of part of an elongate tube according to another embodiment of the present invention; and

Figure 7 shows a cross section on the line VI-VI of Figure 6.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention will now be described more fully hereinafter with reference to the accompanying figures, in which some of the non-limiting embodiments of the invention are shown.

The invention as described hereinafter should not be construed to be limited to the specific embodiments disclosed, with slight modifications and other embodiments intended to be included within the scope of the invention. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

As used herein, throughout this specification and in the claims which follow, the singular forms "a", "an" and "the" include the plural form, unless the context clearly indicates otherwise.

The terminology and phraseology used herein is for the purpose of description and should not be regarded as limiting. The use of the terms "comprising", "containing", "having", "including", and variations thereof used herein, are meant to encompass the items listed thereafter, and equivalents thereof as well as additional items.

The present invention provides for a device for use in the sterilization of liquids, in particular turbid liquids, the device comprising a UV emitting source and an elongate tube with an arrangement of protruding members on the inner wall thereof, which in use, disrupts the flow of the liquid flowing through the tube, thereby increasing the exposure to the ultra-violet (UV) source. The UV emitting source may be a UV light fluorescent tube.

With reference to Figures 1 - 3, the device 10 illustrated is designed specifically for the purpose of sterilizing turbid liquids. The turbid liquids may be selected from the group consisting of alcohol containing liquids such as wine and beer, biological fluids such as blood, and liquids for human consumption such as milk and petrochemicals including all oils. The device 10 comprises an elongate stainless steel outer housing 12 which is circular in cross section. A mounting plate 14 is tack welded to the housing 12 midway between its ends.

A problem that arises with the sterilization of a turbid liquid is that the UV light, emitted from a central source, does not penetrate sufficiently far into the liquid as a result of the turbidity thereof. As a result some of the turbid liquid passing through a sterilizer, furthest from the UV source, may not be sterilized at all, or may not be sterilized to a desired level. Therefore, it is desirable to provide means that disrupt or agitate the otherwise smooth flow of the liquid passing through the sterilizer.

At one end of the housing 12 there is an inlet 16.1 and at the other end of the housing 12 there is an outlet 16.2. In use the inlet 16.1 receives a flow of unsterilized liquid from a feed source, the liquid flowing through the device 10 and out through outlet 16.2 at the other end of the housing 12 to a holding tank or to further processing steps.

The inlet and outlet are each configured at the ends 20 thereof to secure inlet and outlet lines according to the particular process in which the device is used.

In one example, in the dairy industry, the ends may be configured to secure a female dairy fitting, thereby enabling a typical dairy process hose to be secured thereto. As can be seen from Figure 3 in combination with Figures 1 and 2, the inlet 16.1 and outlet 16.2 may be arranged substantially along a vertical central plane passing through the housing 12, and not towards one side or the other thereof.

The inlet and outlet does not have to be arranged tangentially to the outer housing, although it is envisaged that the robust nature of the internal arrangement of the tube 26 is such that any inlet and outlet arrangement would provide comparable sterilization results, including a tangential arrangement. As a result of the robust nature of the internal arrangement of the tube 26 an inlet and outlet configuration may be selected based on other factors, such as manufacturing cost, the particular application envisaged, and ease of operation.

The inlet 16.1 and outlet 16.2 have openings which are aligned with corresponding openings 26a and 26b in the tube 26 (see also Figures 4 to 7) The tube 26 (see also Figures 4 and 5) extends along the full length of the housing 12 between the inlet 16.1 and outlet 16.2 thereby creating a path for the liquid to flow from the inlet 16.1 , through the opening 26a, along the length of the tube 26, through the opening 26b, and out through the outlet 16.2.

As is shown in Figure 3, the housing 12 has internally threaded sockets 28 at the ends thereof. An externally threaded bush 30 is screwed into each socket 28 and there is a sealing o-ring 32 between each bush 30 and the wall of the housing 12.

A UV light transparent sleeve 27, for receiving the UV source 34 in use, passes through the sockets 28, bushes 30, and sealing rings 32. When the bushes are tightened the sealing rings 32 are compressed against the outer wall of the housing 12 thereby expanding and gripping the sleeve 27 to form liquid-tight seals at the ends of the housing 12. It will be appreciated by those skilled in the art that a certain element of risk is associated with direct contact and exposure of the UV source 34 with the liquid passing through the tube 26. A breakage of the UV source 34 could lead to a physical or chemical contamination of the liquid which may not be suitably addressed by downstream filtration.

Referring now to Figure 4, in one embodiment of the invention the tube 26 may be formed with four longitudinal rows of protruding members 36. The protruding members may be dimples or indentations in the tube, or may be protruding knobs extending from the inner wall of the tube 26. The rows of protruding members 36 are equally spaced from one another around the circumference of the tube 26. The tube 26 may be made from stainless steel or any other desirable material according to the particular liquid to be passed through the tube in terms of the selected application.

The protruding members 36 in diametrically opposed rows are diametrically opposed to one another and therefore act in a complementary manner to disrupt the flow of liquid through the tube 26. Thus pairs of complementary protruding members are at opposite ends of common diameters. One such diameter is shown at D in Figure 4. The pitch length between protruding members in a row is designated P in Figure 4. The protruding members 36 in adjacent rows are displaced axially with respect to one another by half a pitch length as indicated by the double headed arrow A in Figure 4. Thus the protruding members in each row are staggered axially with respect to the protruding members in adjacent rows by half a pitch length.

Internally this provides a pattern of protruding members as shown in Figure 5. The protruding members designated 36.1 are in one plane and the protruding members 36.2 are half a pitch length from the protuberances 36.1 in the axial direction. They are also at ninety degrees with respect to them in the circumferential direction.

Referring now to Figures 6 and 7, in another embodiment of the invention the tube 26 may be formed with six longitudinal rows of protruding members 37. Again, the rows of protruding members 37 are equally spaced from one another around the circumference of the tube 26, with consecutive sets of opposing complementary protruding members 37.1 , 37.2 and 37.3 being circumferentially staggered with respect to another.

Referring to Figure 4 and 5, liquid flowing through the sterilizer 10 passes through the gaps between the sleeve 27, containing the UV source 34, and the inner wall of the tube 26 with the dimples, indentations, or knobs 36 extending inwardly from the inner wall towards the sleeve 27. The liquid also flows axially between a first set of dimples, indentations, or knobs which lie in one radial plane and then impinges on the staggered protruding members which are one and a half pitch length displaced along the tube from the first set.

As the liquid flows into the sterilizer device 10 a disruptive mixing motion is imparted to it by the first set of protruding members encountered along the length of the tube 26. The sets of complementary protruding members 36 staggered along the length of the tube 26 maintain and increase the turbulence which is created in the liquid as is flows through the tube 26. The effect of the particular arrangements of protruding members exemplified above is that turbulence created at the inlet to the tube is not merely maintained throughout the tube, but rather maintained and increased as the liquid hits each consecutive set of complementary protruding members 36. This arrangement is therefore a lot less sensitive to variations in flow rate and fluid viscosity than prior arrangements which rely on the internal configuration of the tube to merely maintain turbulence in the liquid. The disruptive mixing motion created by the complementary protruding members ensures total exposure of the liquid to the UV light prior to the liquid exiting the device.

This above description of some of the illustrative embodiments of the invention is to indicate how the invention can be made and carried out. Those of ordinary skill in the art will know that various details may be modified thereby arriving at further embodiments, but that many of these embodiments will remain within the scope of the invention. For example, it will be appreciated that several configurations of the sets of opposing protruding members, including the number of longitudinal rows and the shape and size of the protrusions, would be possible whilst achieving the same disruptive motion effect on the liquid passing through the tube.