WO1998016263A1

WO1998016263A1 - Sterilization system for compressed air

Info

Publication number: WO1998016263A1
Application number: PCT/CA1997/000725
Authority: WO
Inventors: Pierre Charbonneau
Original assignee: Purilair Inc.
Priority date: 1996-10-11
Filing date: 1997-10-03
Publication date: 1998-04-23
Also published as: AU4448297A; CA2187700A1

Abstract

This invention comprises a method and apparatus for sterilizing air to be used for such things as pneumatic medical instruments, respirators, cabins for aircraft, clean-rooms, and other such environments where bacteria and germ free air is required. The apparatus is comprised of three chambers with an air inlet and an air outlet. In the second chamber air is heated to approximately 200 °C and passed through a replaceable filter. The outcoming resultant air is 100 % sterilized.

Description

STERILIZAΗON SYSTEM FOR COMPRESSED AIR

Field of the Invention This invention relates to a system for sterilizing air and more particularly to an apparatus to accomplish the same task.

Background

Ambient air may contain a great deal of humidity, debris, and pathogenic bacteria. When humid air is used by an air compressor for such things a medical or dental pneumatic tools, i.e. dentist drills, water condenses out of the air and provides an excellent incubator for the micro-organisms which are present. Although filters are often used, these tend to also provide conditions ideal for the growth of such micro-organisms as bacteria. In addition to the need to sterilize compressed air for pneumatic tools, there also exists a need to sterilize air used in such places as pressurized cabins in aircraft or submarines. The continuous recycling of the exhaust air back into pressurized compartments and cabins tends to encourage the proliferation of bacteria and other micro-organisms. Thus, a need exists to sterilize the air prior to its being used in such quarters.

The inventor of the present invention solved this problem with two apparatuses disclosed in his issued Canadian Patent 2,042,997 and laid-open Canadian patent application 2,128,140. Patent 2,042,997 and application 2,128,140 disclose sterilizing apparatuses comprising: a copper tubing (through which air is fed) with an electπc heating element coiled inside the copper tubing to heat it to approximately 200°C, thus sterilizing the air.

In pending application 2,128,140 the air is fed through a heat exchanger that recovers approximately 50% of the input energy.

It is an object of the present invention to provide an improved apparatus. Therefore, this invention seeks to provide an air sterilization apparatus for sterilizing inlet air comprising: an air inlet, an air outlet, a plurality of air chambers, a source of heat, and a filter.

This invention also seeks to provide an air sterilizing apparatus comprising a first air chamber in direct communication with an air inlet, a second air chamber in direct communication with said first air chamber, said second air chamber including said filter and a source of heat therein, a third air chamber in direct communication with said second air chamber and said air outlet, wherein, in operation, inlet air enters into said air inlet, thereafter flows into said first air chamber, and thereafter into said second air chamber, where it is heated and filtered, and thereafter said air flows into said third air chamber and exits said air outlet.

The invention also seeks to provide a method for sterilizing compressed air for use with pneumatic tools comprising the steps of: 1 ) directing said compressed air into a first air chamber; 2) directing said air over a heater coil in a second air chamber and heating said air to a predetermined temperature; 3) directing said air through a filter in said second air chamber; and 4) directing said air to a third air chamber and out an air outlet to a pneumatic tool.

The invention further seeks to provide a method of sterilizing recycled air from a chamber such as an aircraft passenger compartment, a submarine crew compartment, a plant or livestock containment facility or a clean room, comprising the steps of: 1 ) directing said air into a first chamber; 2) directing said air through a source of heat in a second air chamber and heating said air to a predetermined temperature; 3) directing said air through a filter in said secondary chamber; and 4) directing said air to a third chamber and out an air outlet to a pressurized chamber. In one embodiment of the present invention, contaminated compressed air circulates at an average pressure of 100-150 psi and a flow rate of approximately 100 cfm through a first chamber, passing through a first channel. Thereafter, it enters a second chamber comprising a ceramic cartridge filter through which air is forced and heated to 200°C by an electπc element coiled around the cartridge filter. Sterile air then enters a third chamber located between the first and second chambers and travels its way out through the air outlet to pneumatic instruments. In so doing, hot air in the third chamber gives off its heat to air in said first chamber. At the bottom of the unit a screwing lid is provided for filter replacement. In the preferred apparatus of the present invention three chambers fit within each other. The first chamber is bounded by the outside wall of the apparatus. The first chamber is the air entry chamber. The second chamber is the sterilization chamber comprising the ceramic cartridge filter and the electric band which fits around the ceramic filter. The third chamber, called the exhaust chamber, fits between the first and second chambers and gives off its heat to the incoming air in the first chamber to thereby improve the efficiency of the device. The device is also provided with channels which allow air to flow between the first and second chambers, and then between the second and third chambers. Although the invention is primarily constructed for use with compressed air, the apparatus and method of sterilization can be used in any situation where there is a pressure differential which will move the air from the inlet through the sterilization device to the outlet. For example, air from an aircraft passenger compartment can be circulated through the device and back into the passenger compartment. The apparatus can also be used to sterilize exhaust air from biohazard test chambers or biohazard containment facilities.

The heat source to effect the sterilization can be in many forms. For instance, a tubular heating element coiled around a filter can be used alternatively. A heat cartridge located within the filter, or an electrical heat band located outside of and around the filter could be used. The heat source could also be in the form of hot air produced from the turbine engines of a jet aircraft, or the nuclear reactor of a submarine.

Numerous types of filters can be used as long as they are capable of being heated to high temperatures and have a filtering capacity of between .5 and 1 micron. In a preferred embodiment, a ceramic filter is used, however a carbon filter or one constructed of wire mesh or spherodized brass would also be acceptable. In a preferred embodiment the apparatus is round and elongate. The first chamber is annular in shape and is bounded by the outer wail of the apparatus. This connects through a channel to the second chamber which is cylindrical in shape and located in the middle of the apparatus. The third chamber is annular in shape and is interposed between the first and second chambers and connects by channels to the air outlet and the second chamber.

In a preferred embodiment the air is heated to a temperature of equal to or greater than 200°C. By so doing, tests have shown that 100% of the bacteria such as bacillus stearothermophilus, penicillium notatum, aspergillus niger, staphylococcus, streptococcus, pasteurella spp, alcaligenes spp, moraxella, pseudomonas paucimobilis, actinomyces viscosus, and bacteroides gingivalis are killed. Furthermore, molds such as mortierella, will also be killed.

Brief Description of the Drawings Figure 1 is a sectional view of the apparatus of the present invention; and

Figure 2 is a top plan view of the apparatus as shown in Figure 1. In Figures 1 and 2, air from a compressor, or some other source, enters the apparatus through air inlet 7. Thereafter the air travels into the first chamber marked 4. The first chamber is bounded by the outer wall of the apparatus and the outer wall of chamber 3. The air travels through channel-way 9 to pass into the second chamber. This is the middle chamber and is of cylindrical form. It contains electric element 1 and ceramic cartridge filter 3. The air is heated by the element 1 and thereafter passes through cartridge filter element 3, and then upwardly to the top of the apparatus. The air is heated to 200°C for sterilization by the electrical element 1. The sterile air then enters a third chamber 2. The hot air circulating in air chamber 2 gives off heat to the incoming air in chamber 4, thus making the device more efficient. The sterile air exiting through air outlet 6 will reach a desired user's temperature. The apparatus is also equipped with a screw lid 8 which can be removed in order to facilitate cleaning or replacement of the ceramic filter 3.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An air sterilization apparatus for sterilizing inlet air comprising: an air inlet, an air outlet, a plurality of air chambers, a source of heat, and a filter.

2. An air sterilization apparatus as claimed in claim 1 , wherein said inlet air is produced by an air compressor for use with pneumatic tools and respirators.

3. An air sterilization apparatus as claimed in claim 1 , wherein said inlet air is recycled air from chambers such as passenger compartments in aircraft and crew compartments in submarines.

4. An air sterilization apparatus as claimed in claim 1 , wherein said inlet air is recycled air from containment facilities such as those used for plant production and livestock housing.

5. An air sterilization apparatus as claimed in claim 1 , wherein said air is directed to clean rooms for medical use, food production, product development, testing, manufacturing, quarantine, or general use.

6. An air sterilization apparatus as claimed in claim 1 , wherein said inlet air is exhaust air from biohazard test chambers or biohazard containment facilities.

7. An air sterilization apparatus as claimed in claim 1 , comprising: a first air chamber, said first air chamber being in direct communication with said air inlet and a source of air having a pressure differential with that of the air at said air outlet; a second air chamber in direct communication with said first air chamber, said second air chamber including said filter and said source of heat therein; a third air chamber in direct communication with said second air chamber and said air outlet, wherein, in operation, said inlet air enters said air inlet, and thereafter flows into said first air chamber, and thereafter into said second air chamber where it is heated and filtered, and thereafter said air flows into said third air chamber and exits said air outlet.

8. An air sterilization apparatus as claimed in claim 1 or 7, wherein said source of heat is an electrical resistance heater.

9. An air sterilization apparatus as claimed in claim 1 , wherein said source of heat is a tubular heating element coiled around said filter.

10. An air sterilization apparatus as claimed in claim 1 , wherein said source of heat is a cartridge heating element located inside said filter.

11. An air sterilization apparatus as claimed in claim 1 , wherein said source of heat is a heat band located outside of, and around, said filter.

12. An air sterilization apparatus as claimed in claim 1 , wherein said source of heat is hot air produced by a turbine engine such as that located in a jet aircraft.

13. An air sterilization apparatus as claimed in claim 1 , wherein said source of heat is hot air produced by a nuclear reactor, such as that located in a submarine.

14. An air sterilization apparatus as claimed in claim 1 , wherein said filter is capable of withstanding being heated to high temperatures and has a filtering capacity of between .5 and 1 micron.

15. An air sterilization apparatus as claimed in claim 1 or 14, wherein said filter is a ceramic filter.

16. An air sterilization apparatus as claimed in claim 1 or 14, wherein said filter is a carbon filter.

17. An air sterilization apparatus as claimed in claim 1 or 14, wherein said filter is constructed from wire mesh.

18. An air sterilization apparatus as claimed in claim 1 or 14, wherein said filter is constructed from "spherodized" brass.

19. An air sterilization apparatus as claimed in claim 7, wherein said apparatus is round and elongate; said first chamber being annular in shape and being bounded by an outer wall of said apparatus; said second chamber being cylindrical in shape and being located in the middle of said apparatus; and said third chamber being annular in shape and being interposed between said first and said second chambers.

20. An air sterilization apparatus as claimed in claim 8, wherein said electrical resistance heater is in the form of an electrical wire coiled between said filter and a wall of said second chamber.

21. An air sterilization apparatus as claimed in claim 7 or 14, wherein said apparatus is detachably connected to allow said filter to be removed and cleaned or replaced.

22. An air sterilization apparatus as claimed in claim 7, wherein said first air chamber is in communication with said second air chamber, and said second air chamber is in communication with said third air chamber by means of air channels.

23. A method for sterilizing compressed air for use with pneumatic tools comprising the steps of: 1 ) directing said compressed air into a first air chamber;

2) directing said air over a heater coil in a second air chamber and heating said air to a predetermined temperature;

3) directing said air through a filter in said second air chamber; and

4) directing said air to a third air chamber and out an air outlet to a pneumatic tool.

24. A method according to claim 23, wherein said air is heated to a temperature of at least 110°C.

25. A method according to claim 24, wherein said air is heated to a temperature of equal to or greater than 200°C.

26. A method according to claim 23, wherein said air is directed through said air chambers at a pressure differential up to 2000 pounds per square inch.

27. A method of sterilizing recycled exhaust air from a chamber such as an aircraft passenger compartment, a submarine crew compartment, a plant production containment facility or a clean room, comprising the steps of:

1 ) directing said air into a first chamber;

2) directing said air through a source of heat in a second air chamber and heating said air to a predetermined temperature;

3) directing said air through a filter in said secondary chamber; and

4) directing said air to a third chamber and out an air outlet to said pressurized chamber.

28. A method according to claim 27, wherein said air is heated to a temperature of at least 150°C.

29. A method according to claim 28, wherein said air is heated to a temperature equal to or greater than 200°C.