CA1072716A

CA1072716A - Disposable liquid sterilizer unit

Info

Publication number: CA1072716A
Application number: CA316,301A
Authority: CA
Inventors: James H. Lewis
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-11-15
Filing date: 1978-11-15
Publication date: 1980-03-04

Abstract

DISPOSABLE LIQUID STERILIZER UNIT
Abstract of the Disclosure A disposable liquid sterilizer unit incorporating an ultra-violet tube designed to generate radiation at approximately 2537 Angstroms is disclosed. The unit comprises an elongated cylindrical plastic jacket opaque to ultra-violet radiation concentrically mounted about the tube to provide a chamber between the jacket and the tube for the flow of liquid to be exposed to radiation generated by the tube. The tube extends beyond the ends of the jacket and includes electrical connectors at each end for removably mounting the unit to make electrical connection with electrical connections in a casing. A seal is provided adjacent each end of the jacket against liquid flow from the chamber between the tube and the walls of the jacket to the exterior of the jacket. Inlet and outlet connections for the flow of water to and from the chamber are provided as well as a viewport through the plastic jacket. The invention is characterised by the fact that the tube is double-walled, providing a sealed and preferably evacuated space between the walls to provide thermal insulation between the radiation generating parts (gas and electrodes) inside the inner wall and the outer surface of the outer wall which is exposed to cold water in the flow chamber.

Description

~)7~ 6 This invention relates to a disposable :Liquid . sterilizer unit and more particularly to a water sterilizer employing ultra-violetor other radiationj e.g. gamma ray radiation, to kill bacteria~
Although sterilization of water by use of ultra-violet radiation has an excellent reputation for ~illing bacteria, such sterilizers have tended to be expensive and to require specialized skills for installation and r~a:intenance.
There is a need for a water sterilizer that a home or cottage owner can afford and can install and maintain without special-ized skills.
Such a sterilizer has been provided by my prior invention disclosed in Canadian patent application Serial No.
248,630 filed March 24, 1976 (U.S. patent No. 4,1~1,686 issued February 27, 1979).
Such prior construction provides a disposable unit that consists essentially of an elongated tube for generating the sterilizing radiation and a similarly shaped outer jacket opaque to the radiation. The tube extends coaxially along the jacket while forming a flow chamber between them, i.e. between an outer cylindrical surface of the tube and an inner cylind-rical surface of the jacket. Water is caused to travel along .~ this flow chamber from an inlet at one end of the jacket to an outlet at the other end. The quartz sheath -that had trad-itionally been located around the tube in the majority of . prior art constructions (see for example Canadian patent ... 610,989 issued December 20, 1960 to R.F. Myers) has been .

.~. omitted from my prior construction, the water coming into ~ ~, direct contact with the tube surface. This omission of the ; 30 intermediate quartz sheath represented a significant cost : saving and was largely responsible for the ability to make

- 2 -~072'7116 the unit a disposable one. By reference to "disposable" it is intended to state that the tube is or can be non-removably mounted in the jacket by means of liquid tight seals at each end, so that when the tube is burnt out the whole unit is discarded.
In the specific form of unit disclosed in my earlier application (patent), the ends of the tube project beyond the ends of the jacket in which they are mounted. These projecting tube ends providing terminals that serve both for establishing the necessary electrical connections and for mechanically supporting the unit in an outer protective casing.
In using a "disposable" unit, no attempt is made to remove a used tube from its jacket. Once a year or as found necessary, the whole unit is removed from the casing and discarded, and a new unit is fitted. This operation can be carried out by an unskilled person as easily as changing an electric light bulb. Such an operation contrasts with the practice prior to my earlier invention, which involved the - services of a skilled technicial to remove the old tube from the jacket and replace it with a new one, while handling the quartz sheath very carefully. Even so it was often found impossible to avoid breakage of the quartz sheaths.
My prior development was thus a significant step forward in the art, in that it reduced the cost of each unit (jacket and tube) and simplified the mounting thereof in a casing.
This simplification was sufficient to render it economically ~; preferable to treat each unit as a disposable one and thus avoid the need for the services of a skilled technician. As a result, my prior development has already enjoyed significant success in the market place.
However, the direct contact between the water and the tube that resulted from elimination of the quartz sheath has one disadvantage along with its many advantages. Apart from the cost advantage of a disposable unit that has already been _3_ ~7Z7~L6 discussed, another advantage was climlnation of the condensation and dust build up that had previously been experienced in the air space between the tube alld the sheath.
The disadvantage, on the other hand, arose from the fact that the direct contact between the often cold incoming water and the tube could sometimes lower the temperature of the tube below its operational optLmum, thus reducing the amount of ultra-violet emission. In practice, this problem could lead to the use of a tube larger than that normally required, in order to have sufficient spare capacity to be able to compensate for the lowered efficiency of the tube under adverse temperature conditions.
The present invention is an improvement over my prior development described above, in that it avoids this disadvantage without going back to the problems of the earlier sheath-type of construction. In other words, the present invention retains .
the essential merits of my prior development, i.e. cheapness ~; and ease of installation and hence disposability, while at the same time recapturing and improving upon an advantage afforded by the sheath type design, namely thermal insulation of the , :"~
tube from cold incoming water. "
This aim has been achieved in the present invention by - making the tube a double-walled tube, i.e. a tube having inner `` and outer cylindrical walls sealed together and spaced apart "' from each other so as to define a sealed space between them.
The outer surface of the outer wall is in contact with the liquid in the flow chamber defined between the tube and the ` jacket, while the conventional means for generating the radiation is located within the inner wall. As a result, the intermediate space, which may be evacuated,provides thermal insulation between such generating means and any cold liquid in the flow chamber.

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~{~7Z~7~6 An emhodiment of this invention will now be described, by way of example, with reference to the accompanying drawings in which:
Figure 1 is a perspective view of a disposable water sterilizer unit;
Figure 2 is a plan view of the same unit;
Figure 3 is a horizontal sectional view of the unit taken along lines III-III of Figure 1, showing the tube and the end sealing arrangements;
Figure 4 is a sectional view on an enlarged scale taken along line IV-IV of Figure 3 showing details of the tube and o a water inlet connection; and Figure 4a is a fragmentary, longitudinal section of a tube end illustrating details of the construction thereof.
~ Description of Embodiment :, ', Figures 1 to 4a show a disposable water sterilizer unit 20, which essentially comprises an elongated cylindrical plastic jacket 21, typically made of plastic tubing, and a double-walled, : ~
ultra-violet lamp or tube 22 designed to radiate light at a wavelength of approximately 2537 Angstroms to sterilize water or other liquid exposed to this ultra-violet radiation.
The jacket 21 is composed of a central portion 21' and end portions 23 and 24. These end portions are injection moulded parts and are fixed to the central portion 22 at 25 and 26 by means of a suitable adhesive. Of course, the jacket 21 can be formed of a single moulded part.
As can be seen from Figure 3, the jacket 21 is concentrically mounted about the cylindrical tube 22 to provide a chamber 27 between the internal surface of the jacket and the external surface of the tube for the flow of water to be sterilized.
The tube 22 passes through and beyond the end portions 23 and 24 of the jacket. The tube 22 is non-removably supported by the end portions 23 and 24 by means of a close fit between the , :

~C~727~6 tube and neoprene sealing rings 28 and 29 Located in grooves 30 and 31 in reduced diameter extreme ends 23' and 24'. These rings 28, 29 also provide a seal against wa~er flow from the chamber 27 to the exterior of the jacket 21.
Water inlet and outlet connections 32 and 33 are also moulded as part of the end portions~ 23 and 24 respectively, to provide connections to and from a water supply with access to the chamber 27. It can be seen that the connections 32 and 33 are threaded at their ends for easy connection to the plumbing system.
Prongs or terminals 34 and 35 at the ends of the tube 22 serve as electrical and mechanical connection means externally of the jacket to mount the unit 20 in a casing (not shown~. The casing and mounting method can be as shown in my prior application (patent) referred to above. - ' ~ . .
`` As can best be seen in Figure 4, the end portion 24 has moulded therewith a fin 37 which deflects or imparts - turbulence to the water flowing into the jacket via the connection 33.
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The internal structure of the double-walled tube 22 is shown in Figs. 4 and 4a. This tube comprises an inner wall 91 and an outer wall 92 with a sealed cylindrical space 93 there-between, which space preferably is evacuated. The electrode 94 is conventional and is conventionally mounted in a glass bead 95 projecting axially inward from the end of the inner tube wall 91. The electrode 94 is connected by leads 96 to the external terminals 35 which are supported in an insulating ~:37Z7~6 disc 99 mounted between a body 97 of epoxy resin and an inturned end rim on a metal tubular cap 9U secured to the end of the tube walls 91 and 92 where they meet and are fused together. The opposite end of the tube 22 is similar.
It will be apparent that the unit 20 as a whole has retained the feature of disposability whiLe achieving the advantage of providing thermal insulation to the inner wall 91 of the tube 22 and hence to the radiation generating means, i.e.
gas and electrodes within such inner wall. The temperature and hence efficiency of the tube 22 is thus retained. Moreover, in contrast to the old method described above of protecting - the tube with a separate sheath, the use of a unitary double-wall construction enables the use of a vacuum in the space 93 between the walls. No dust or condensate can appear in this . space and the thermal insulation is still further improved.
The entire unit can continue to be supported by a single mounting at each end (terminals 34, 35) as shown in my prior application (patent). The outer wall 92 is fused to the inner wall 91 at each end of the tube and thus there is no need for any further mounting means. This is in contrast to the separate sheath style of construction in which it was necessary to provide in the jacket separate mounting arrangements for the ends of the sheath and separate means for providing liquid tight seals between the ends of the sheath and the ends of the tube.
If preferred, an inert gas can be used instead of a vacuum in the space 93, or even dry air which of course, minimises the manufacturing costs. Whatever the medium in this space, it is positively sealed from the exterior of the tube by the permanently fused double-wall structure, and therefore the problems of dust and condensate are avoided. Clearly, from the viewpoint of thermal insulatlon, a vacuum is best.

.. . ,., ~ ::, ~3'7~7~ 6 It has been found e~pcr:Lmentally tllat the add:itional reliability of performance of the present invention over my prior development under adverse conditions ~water at or around O C) has enabled a shorter tube to be used (as short as half the length oE that formerly needed) while maintaining effective sterilization of the same throughput of water, i.e. the eame r~tint.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A disposable unit for sterilizing a liquid comprising (a) an elongated jacket having an inner surface and opposing ends, (b) an elongated tube including means for generating radiation to sterilize liquid in the jacket, said tube extending along the interior of the jacket and having an outer surface, said inner and outer surfaces together defining a flow chamber for the liquid and said jacket being substantially opaque to said radiation, (c) means adjacent said opposing ends of the jacket for providing an inlet and an outlet for flow of liquid into the chamber and into direct contact with said outer surface of the tube for sterilization by the radiation therefrom and finally out of said outlet, and (d) liquid tight seals at the ends of the jacket engaging respective ends of the tube to prevent outflow of liquid from the flow chamber except through said outlet, characterised in that (e) said tube is a double-walled tube having inner and outer cylindrical walls sealed together and spaced apart from each other, said outer surface of the tube being the outer surface of said outer wall and said means for generating radiation being located within said inner wall whereby the sealed space between said walls serves to provide thermal insulation between said generating means and the liquid in the flow chamber.

2. A unit according to claim 1, wherein said sealed space between the tube walls contains a dry gas.

3. A unit according to claim 1 or 2, wherein said sealed space between the tube walls is substantially evacuated.