US3761224A

US3761224A - Method and apparatus for continuous ehtylene oxide sterilization

Info

Publication number: US3761224A
Application number: US00291910A
Authority: US
Inventors: R Ernst
Original assignee: Sybron Corp
Current assignee: MDT Corp; Raytheon Co
Priority date: 1972-09-25
Filing date: 1972-09-25
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25

Abstract

A SYSTEM FOR THE CONTINUOUS, IN-LINE STERILIZATION OF

ARTICLES WITH ETHYLENE OXIDE GAS MAINTAINED IN A STERILIZING CHAMBER COMPLETELY CLOSED AND SEALED FROM ATMOSPHERE EXCEPT FOR INLET AND OUTLET TUBES THROUGH WHICH THE ARTICLES ARE CONVEYED. THE TUBES EXTEND ABOVE THE CHAMBER TO PREVENT THE HEAVIER-THAN-AIR GAS FROM ESCAPING.

Description

Sept. 25, 1973 ERNST I 3J$L2Z4 METHOD AND APPARATUS FOR CONTINUOUS ETHYLENE OXIDE STERILIZATION Original Filed March 26, 1969 United States Patent Int. Cl. A61l13/00 US. C]. 21-58 62 Claims ABSTRACT OF THE DISCLOSURE A system for the continuous, in-line sterilization of articles with ethylene oxide gas maintained in a sterilizing chamber completely closed and sealed from atmosphere except for inlet and outlet tubes through which the articles are conveyed. The tubes extend above the chamber to prevent the heavier-than-air gas from escapmg.

This is a continuation of application Ser. No. 810,540, filed Mar. 26, 1969, now abandoned.

BACKGROUND OF THE INVENTION Field of the inveniton This invention relates to a method and apparatus for sterilizing articles with ethylene oxide gas and more particularly to a continuous sterilizing system wherein openings are provided in the sterilizing chamber for conveying articles into and out of the chamber while at the same time the ethylene oxide gas is prevented from escaping from the chamber through such openings.

Description of the prior art Continuous, gaseous sterilizing apparatuses have been proposed that provide a sterilizing chamber and conveying means for carrying articles into, through and out of the sterilizing chamber. However, such apparatuses require complex equipment for preventing the sterilizing gas from escaping from the sterilizing chamber and for preventing air from entering into the chamber.

SUMMARY OF THE PRESENT INVENTION A method and apparatus for the continuous sterilization or articles with heavier-than-air ethylene oxide gas, including a sterilizing chamber, a conveyor for continuously carrying articles to be sterilized into, through and out of the sterilizing chamber, and means for preventing escape of the sterilizing gas from the sterilizing chamber. The sterilizing chamber is sealed from atmosphere except for an inlet tube and an outlet tube, each of which is open to atmosphere; the tubes extend above the top level of the ethylene oxide gas in the chamber so as to trap the gas within the sterilizing chamber, wherein the gas is maintained in a substantial quiescent condition. The conveyor extends into and out of the sterilizing chamber through the inlet and outlet tube, respectively. Condensing coils can be provided in the inlet and outlet tubes to aid in preventing the escape of ethylene oxide gas from the sterilizing chamber. Control means can be provided for controlling the concentration and the humidity of the sterilizing gas in the sterilizing chamber. Preliminary to passing into the sterilizing chamber, the conveyor can extend through an inverted U-shaped tube in which heat and moisture are trapped, for preconditioning the articles to be sterilized.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood 3,761,224 Patented Sept. 25, 1973 DETAILED DESCRIPTION OF THE PRESENT INVENTION With reference to the drawing, the apparatus of the present invention comprises an inverted, U-shaped, preconditioning tube 10, a sterlizing vessel 12 having an inlet tube 14 and an outlet tube 16, and a conveyor 18 for carrying the articles to be sterilized through the tube 10, and into, through and out of the sterilizing vessel 12.

Referring initially to the sterilizing vessel 12, it is constructed of front and

rear walls

20 and 22, respectively,

sidewalls

24 and 26, and top and

bottom walls

28 and 30, respectively. The sterilizing vessel 12 encloses a sterilizing chamber 32, which chamber is sealed from atmosphere except for

passageways

34 and 36 extending through the inlet and

outlet tubes

30 and 32 respectively. The

passageways

34 and 36 are in fluid communication with the chamber 32, through openings (not shown) in the top wall 28, around which openings the tubes 14 and 16 are connected.

The inlet tube 14 has an inlet opening 38 and the outlet tube 16 has an outlet opening 40. The inlet tube 14 is provided with a cold trap or a condenser 42 including cold condensing coils (not shown) adjacent and/or inside of the passageway 34 to help prevent the escape of ethylene oxide gas from the sterilizing chamber 32. A condenser is not absolutely necessary; a simple cooling coil can be sutficient because the cold high density gas tends to run back into the sterilizing vessel 12. Similarly, the outlet tube 16 is provided with a cold trap or a condenser 44 including cold condensing coils (not shown) adjacent and/or inside of the passageway 36. Condensers and cooling coils are well-known to those skilled in the art and any one of a number of different, well-known condensers and cooling coils can be used, therefore, the condensers 42 and 44 need not be described in detail here.

A controller 46 is connected to the sterilizing vessel 12 through

fluid communication lines

48 and 50. The controller 46 includes means for sensing and controlling (for example by introducing additional quantities of ethylene oxide gas) the concentration of the ethylene oxide sterilizing gas or mixtures of gases, such as the fluorocarbon-12- ETO mixture, within the sterilizing chamber 32, through line 48. The controller 46 also includes means for sensing and controlling the humidity within the sterilizing chamber 32 through fluid communication line 50. Control means for sensing and controlling gas and humidity conditions are well-known to those skilled in the art, and such need not be described in detail herein. A heater means 52 (diagrammatically shown) is operatively associated with the sterilizing vessel 12 for maintaining the temperature of the vessel 12 at a predetermined temperature or within a predetermined temperature range; the walls of the vessel 12 are preferably maintained in the range of 70 to F. Heating of the vessel 12 can provide increased speed of sterilization and can help keep the ethylene oxide gas from condensing out.

The preconditioning tube 10 comprises an inverted U-shaped tube 54 having a passageway 56 extending therethrough from a ninlet opening 58 at one end thereof to an outlet opening 60 at the other end thereof. The preconditioning tube 10 is supported in any suitable manner, such as by

supports

62 and 64, and is preferably positioned with its outlet opening 60 aligned with the opening 38 of the inlet tube 14 of the sterilizing vessel 12, but spaced therefrom by an air gap 66; the air gap 66 is desirable but not necessary. The inverted U-shaped tube 54 is designed so as to trap heat and moisture at its upper portion so as to condition the articles to be sterilized, prior to their introduction into the sterilizing chamber 32. A control means 68 is operatively associated with the passageway 56 of the tube 54 [for example, by means of a fluid conduit (not shown)] for controlling the temperature and humidity therein. The heat and moisture control means 68 preferably maintains a temperature within the passageway 56 of between about 130 and 160 F., and also maintains between about 40% and 70% relative humidity therein. The construction and operation of means for maintaining temperature and humidity conditions are well-known to those skilled in the art, therefore, a detailed description of control means 68 is not necessary.

The conveyor 18 continuously carries the articles to be sterilize dfrom a loading area adjacent the inlet opening 58 of the preconditioning tube to a discharge area adjacent the outlet opening 40 of the outlet tube 16 of the sterilizing vessel 12. The conveyor 18 can be supported within the inverted U-shaped tube 54 and within the sterilizing vessel 12 by means of brackets 70 or the like. The conveyor 18 is adapted to carry and to continuously move a plurality of baskets 72 adapted to carry the articles to be sterilized. A control means 74 is provided for controlling the speed at which the conveyor 18 moves the baskets 72 through the preconditioning tube v10 and the sterilizing vessel 12. The length of the preconditioning tube 10 and the length of the conveyor -18 in the sterilizing vessel 12 are designed to be sufficient to precondition and sterilize the articles to be sterilized, by properly adjusting the speed control means 74. The sterilizing vessel 12 is preferably a large box-shaped container with a serpentine-shaped conveyor path therein.

Ethylene oxide gas is considerably heavier than air and the apparatus of the present invention is designed to take advantage of this fact to entrap the ethylene oxide gas within the sterilizing chamber 32. This is accomplished by enclosing and sealing the chamber 32 from atmosphere except for the inlet and

outlet passageways

34 and 36 for the conveyor 18, and by positioning at least a portion of the length of the

passageways

34 and 36 above the top level of the gas in the sterilizing chamber 3-2. The sterilizing chamber 32 is preferably completely filled up with sterilizing gas beyond the top wall 28 and up into the

passageways

34 and 36, to

levels

76 and 78 therein, respectively. The control means 46 can include a sensor 80 mounted on each of the tubes 14 and 16 (or on just one of the tubes) and having a sensing means (not shown) inside of the

passageways

34 and 36, for controlling the introduction of additional ethylene oxide sterilizing gas into the chamber 32 when the

levels

76 and 78 fall below a predetermined preferred location. The

levels

76 and 78 are air-sterilizing gas interfaces or boundaries between a layer of sterilizing gas and a layer of air, which layers are stratified as a result of the difference in density between the two gases. The remainder of the tubes 14 and 16 above the interfaces or

levels

76 and 78 can take any desired shape, for example, they can bend back down so that the openings 38 and 40 are positioned at floor level. The important feature is not where the openings 38 and 40 are, but that at least a portion of the length of each of the

passageways

34 and 36 is above the top level of the gas in the chamber 32, so as to estab

lish interfaces

76 and 78 above said top level, to trap the sterilizing gas within the chamber 32.

In this manner, a heavier-than-air sterilizing gas can be maintained in a quiescent or substantially quiescent condition and used in a continuous, in-line, low cost sterilizing process which does not require complex apparatuses and procedures for preventing the escape of the sterilizing gas.

The operation of the present invention is as follows.

The articles to be sterilized are placed in the baskets 72 attached to the conveyor 18, and carried through the preconditioning tube 10, across air gap 66, and into, through and out of the sterilizing chamber 32. The time or period of sterilization is controlled by control means 74. Upon leaving the outlet opening 40 of the outlet tube 16, the articles can be moved to a storage area for any required incubation period.

FIG. 2 shows an embodiment of the present invention in which the tubes 14 and 16 are connected to the

sidewalls

20 and 22, respectively, of the vessel 12, adjacent the bottom wall 30, whereby the inlet and

outlet passageways

34 and 36, respectively, are in fluid communication with the chamber 32 at the bottom of the chamber.

While the present invention has been described with reference to the preferred embodiment thereof, it is to be understood that the present invention is not limited thereto. For example, other heavier-than-air sterilizing gases than ethylene oxide can be used. The preconditioning tube 10 is not an essential part of the present invention; it can be eliminated. Any of a great variety of different types of conveyors can be used; it is not necessary to use a conveyor of the type shown in the figure. While in the preferred embodiment the sterilization period is controlled by controlling the speed of the conveyor (by means of control means 74), it is also possible to control the sterilization period by controlling the length of the conveyor path within the sterilizing chamber 32. In the preferred embodiment of the present invention, the articles to be sterilized are moved down into the sterilizing chamber 32 and up and out of the sterilizing chamber 32 through openings 38 and 40 which are positioned higher than or above the top level of the sterilizing gas within the sterilizing chamber. The conveyor 18 can move intermittently rather than continuously, especially where the vessel 12 of the present invention is preferred to be used in a batch type process. It is possible to use other means for introducing and removing the articles being sterilized than a continuous conveyor. Furthermore, the sterilizing vessel 12 can be provided with a single tube in fluid communication with the sterilizing chamber 32, through which tube the conveyor 18 can pass twice, once for carrying incoming articles and once for carrying outgoing articles. Also, more than two tubes can be employed, as for example, when more than one conveyor per sterilizing chamber is used. The tubes 14 and 16 can be connected to the top wall 28 as shown or to any of the sidewalls 20-26 or even to the bottom wall 30.

I claim:

1. A sterilizer for sterilizing articles to be sterilized With a sterilizing gas comprising:

a sterilizing vessel,

a sterilizing chamber in said vessel and being permanently open to ambient,

a quantity of heavier-than-air sterilizing gas in said chamber,

means for maintaining said quantity of heavier-thanair sterilizing gas in said chamber in a quiescent condition, and

means for conveying articles to be sterilized into,

through and out of said sterilizing gas.

2. The apparatus according to claim 1 wherein said conveying means includes means for continuously conveying said articles into, through, and out of said chamber.

3. The apparatus according to claim 2 including means for sealing said chamber from atmosphere except for passageways into said chamber through which said articles are conveyed.

4. The apparatus according to claim 3 including an inlet tube and an outlet tube each connected to said chamher and having an inlet and an outlet passageway respectively in fluid communication with said chamber.

5. The apparatus according to claim 4 wherein said inlet and outlet tubes are connected to said chamber at the bottom of said chamber for conveying articles to be sterilized into said chamber at the bottom of said chamber and out of said chamber at the bottom of said chamber.

6. The apparatus according to claim 5 including COOIing coils connected to each of said tubes.

7. The apparatus according to claim 5 wherein each of said tubes and respective passageways includes a portion thereof positioned above the top level of said sterilizing chamber.

8. A sterilizer for use with a sterilizing gas comprising:

a sterilizing vessel having a sterilizing chamber adapted to retain a quantity of sterilizing gas,

at least one tube connected to said sterilizing vessel and having a passageway in fluid communication with said sterilizing chamber,

a conveyor, for carrying articles to be sterilized, extending into and out of said sterilizing chamber through said passageway, and

means for controlling the concentration of the sterilizing gas within said sterilizing chamber.

9. The apparatus according to claim 8 wherein said at least one tube is connected to said vessel at the bottom of said vessel and said passageway is in fluid communication with said chamber at the bottom of said chamber.

10. The apparatus according to claim 8 wherein said at least one tube consists of two tubes, each of which has a passageway in fluid communication with said chamber and wherein said conveyor extends into said chamber through one passageway and out of said chamber through the other passageway and including means for completely sealing said chamber from atmosphere except for said passageways.

11. A sterilizer for use with a sterilizing gas comprising:

a sterilizing vessel having an enclosed sterilizing chamber adapted to retain a quantity of sterilizing gas;

at least one tube connected to said vessel and having a passageway in fluid communication with said cham her, said chamber being permanently open to ambient through said passageway, and said passageway having a cross-sectional area sufiiciently large to allow articles to be conveyed into and out of said chamber;

means for sealing said chamber from atmosphere except for said passageway;

said sterilizing chamber being adapted to retain a quantity of heavier-than-air sterilizing gas and wherein each of said tubes includes a portion thereof positioned above the top level of said sterilizing chamber such that a length of each of said passageway is also positioned above said top level; and

12. The apparatus according to claim 11 wherein each of said inlet and outlet tubes is connected to said chamber at the bottom of said chamber.

13. The apparatus according to claim 11 wherein said at least one tube comprises an inlet tube and an outlet tube, and including a conveyor positioned in said inlet and outlet tubes for carrying articles to be sterilized into and out of said chamber.

14. The apparatus according to claim 13 wherein said conveyor includes means for continuously conveying articles into and out of said chamber.

15. The apparatus according to claim 14 wherein said tubes are connected to the bottom of said vessel and said passageways are in fluid communication with said chamber at the bottom of said chamber.

16. The apparatus according to claim 15 including condensing coils connected to said tubes for condensing out any sterilizing gas existing in said passageways above an interface between air and a quantity of sterilizing gas in said passageways.

17. The apparatus according to claim 16 including means for varying the speed of said conveyor.

18. The apparatus according to claim 17 including means for heating any sterilizing gas in said sterilizing vessel.

19. The apparatus according to claim 11 including a quantity of heavier-than-air sterilizing gas filling said chamber up to a predetermined level.

20. The apparatus according to claim 19 wherein said gas is ethylene oxide.

21. The apparatus according to claim 11 including means for maintaining an interface, between air and said quantity of sterilizing gas, in said length of each of said passageways.

22. The apparatus according to claim 21 including condensing coils connected to said tubes for condensing out any sterilizing gas existing in said passageways above said interface.

23. The apparatus according to claim 11 including means for varying the speed of said conveyor.

24. The apparatus according to claim 11 including means for heating said sterilizing vessel.

25. The apparatus according to claim 11 including an inverted, U-shaped, preconditioning tube positioned adjacent said inlet tube, in spaced-apart relationship thereto, and said conveyor extending through said U-shaped tube and then into said inlet tube.

26. The appartaus according to claim 11 wherein said at least one tube is connected to said vessel at the bottom of said vessel wherein said passageways are in fluid communication with said chamber at the bottom of said chamber.

27. A sterilizer for sterilizing articles to be sterilized with a sterilizing gas comprising:

a sterilizing vessel having a sterilizing chamber;

means for maintaining a quantity of a more dense sterilizing gas in said chamber with a gas-to-gas interface between said sterilizing gas and a less dense first gas located above said sterilizing gas;

means for conveying articles to be sterilized down into said sterilizing gas through said interface, through said sterilizing gas, and up out of said sterilizing gas through said interface; and

means for controlling the concentration of said steri lizing gas within said chamber.

28. A sterilizer for use with a sterilizing gas comprising:

an inlet and an outlet tube connected to said vessel, and having inlet and outlet passageways, respectively in fluid communication with said chamber;

means for sealing said chamber from atmosphere except for said passageways;

a conveyor positioned in said inlet and outlet tubes for carrying articles to be sterilized into and out of said chamber, respectively;

said sterilizing chamber being adapted to retain a quantity of heavier-than-air sterilizing gas and wherein each of said tubes includes a portion thereof positioned above the top level of said sterilizing chamber such that a length of each of said passageways is also positioned above said top level;

an inverted, U-shaped, preconditioning tube positioned adjacent said inlet tube, in spaced-apart relationship thereto, and said conveyor extending through said U-shaped tube and then into said inlet tube, and

means for controlling the heat and moisture conditions within said U-shaped tube.

29. The apparatus according to claim 28 wherein said inlet and outlet tubes are connected to the bottom of said vessel such that said inlet and outlet passageways are in fluid communication with said chamber at the bottom of said chamber.

30. The method of sterilizing articles comprising:

conveying articles to be sterilized into and out of an enclosed sterilizing chamber filled with heavier-than-air sterilizing gas through enclosed inlet and outlet passageways, respectively, extending from a position above the top level of said chamber down into said chamber, and

maintaining said chamber open to ambient through said passageways during said conveying step and during sterilization of said articles. 31. The method according to claim 30 wherein said conveying step comprises conveying articles into and out of said chamber at the bottom of said chamber.

32. The method according to claim 30 including maintaining an air-sterilizing gas interface in each of said passageways and above said top level.

33. The method according to claim 32 wherein said conveying step comprises conveying articles into and out of said chamber at the bottom of said chamber and including sealing said chamber from atmosphere except for said passageways.

34. The method according to claim 30 including sealing said chamber from atmosphere except for said passageways.

35. A method for use in sterilizing articles comprising: maintaining a quantity of a heavier-than-air sterilizing gas in a sterilizing chamber sealed from ambient except for the hereinafter recited passageways,

maintaining an inlet and an outlet passageway in fiuid communication with said chamber, maintaining at least a portion of said passageways above the top level of said chamber to substantially prevent said gas from escaping from said chamber, and

maintaining said chamber permanently open to ambient through said passageways.

36. The method according to claim 35 including maintaining said chamber full of said gas, maintaining an airsterilizing gas interface in said portion of said passageways, employing for said passageways, passageways of suificient cross-sectional area to allow articles to be sterilized to be conveyed into and out of said chamber through said passageways, and controlling the concentration of the sterilizing gas in said chamber.

37. The method according to claim 36 including maintaining said inlet and outlet passageways in fluid communication with the bottom of said chamber.

38. The method of sterilizing articles comprising:

maintaining heavier-than-air sterilizing gas in a quiescent condition in a sterilizing chamber,

continuously conveying articles to be sterilized into said chamber, through said sterilizing gas, and out of said chamber, and preventing said sterilizing gas from escaping from said sterilizing chamber.

39. The method of sterilizing articles to be sterilized in a continuous manner, and with heavier-than-air sterilizing gas, comprising:

conveying said articles through a first enclosed passageway, said first passageway extending into a sterilizing chamber from a position above the top level of said chamber down into said chamber, said chamber containing heavier-than-air sterilizing gas,

maintaining said araticles in said chamber and exposed to said gas for a predetermined time period,

conveying said articles up out of said chamber through a second enclosed passageway extending above said top level,

maintaining said chamber sealed from atmosphere except for said passageways, and

maintaining said chamber open to ambient through said passageways during said conveying and maintaining steps.

40. The method according to claim 39 including maintaining said chamber full of said gas and maintaining an air-sterilizing gas interface in each of said passageways.

41. The method according to claim 40 wherein said conveying steps comprise conveying articles into and out of the bottom of said chamber through said passageways connecting with the bottom of said chamber.

42. The method according to claim 41 including con- 8 trolling the concentration of the sterilizing gas in said chamber and controlling the humidity in said sterilizing chamber.

43. The method accordng to claim 39 including:

controlling the sterilization period by controlling the speed at which said articles are conveyed into and out of said chamber.

44. The method according to claim 39 including:

maintaining said sterilizing chamber at a temperature of between about 70 and F.

45. The method according to claim 39 including:

controlling the concentration of the sterilizing gas and the humidity in said sterilizing chamber.

46. A method for sterilizing articles in a sterilizing gas comprising:

confining a quantity of a sterilizing gas in a chamber open to a first gas, said sterilizing gas being more dense than said first gas, such that a gas-to-gas interface is formed between said sterilizing gas and said first gas, and

feeding articles to be sterilized down into said sterilizing gas through said interface, and then up out of said sterilizing gas through said interface, to expose said articles to said sterilizing gas. 47. The method according to claim 46 wherein said first gas is air and wherein said feeding step comprises continuously feeding said articles down into, through, and up out of said sterilizing gas.

48. The method according to claim 47 including preventing said sterilizing gas from escaping from said chamber.

49. The method according to claim 47 including maintaining said chamber full of said sterilizing gas, maintaining said interface in at least one passageway extending above a top level of said chamber, and maintaining said chamber enclosed except for said at least one passageway.

50. The method of sterilizing articles to be sterilized, in a continuous manner, and with heavier-than-air sterilizing gas, comprising:

conveying said articles through a first enclosed passageway, said first passageway extending into a sterilizing chamber from a position above the top level of said chamber down into said chamber, said chamber containing heavier-than-air sterilizing gas, maintaining said articles in said chamber and exposed to said gas for a predetermined time period,

maintaining said chamber sealed from atmosphere except for said passageways,

maintaining said chamber full of said gas,

maintaining an air-sterilizing gas interface in each of said passageways, and

condensing out sterilizing gas existing in said passageways above said interfaces. 51. The method according to claim 50 wherein said conveying steps comprise conveying said articles into the bottom of said sterilizing chamber and conveying articles out of said chamber at the bottom of said chamber.

52. The method of sterilizing articles to be sterilized, in a continuous manner, and with heavier-than-air sterilizing gas, comprising:

preconditioning said articles by conveying said articles through an inverted U-shaped tube prior to conveying them into said chamber, and controlling the heat and moisture conditions in said inverted U-shaped tube.

53. The new use of a sterilizer of the continuous type including a sterilizing chamber permanently open to atmosphere and a conveyor for continuously moving articles to be sterilized into, through and out of said chamber, said new use comprising:

maintaining a quantity of heavier-than-air sterilizing gas in said chamber in a quiescent condition, and sterlizing articles in said chamber.

54. The new use of a sterilizer of the continuous type including a sterilizing chamber permanently open to atmosphere and a conveyor for moving articles to be sterilized into, through and out of said chamber, said new use comprising:

maintaining a quantity of heavier-than-air sterilizing gas in said chamber in a quiescent condition, continuously conveying articles to be sterilized into,

through and out of said chamber, and

preventing said gas from escaping from said chamber.

55. The new use according to claim 54 wherein said preventing step comprises maintaining said chamber sealed from atmosphere except for at least one passageway and wherein said conveying step comprises conveying said articles through said at least one passageway, and wherein said preventing step also comprises maintaining at least a portion of said at least one passageway above the top level of said sterilizing gas.

56. The new use according to claim 55 including: maintaining an air-sterilizing gas interface in said portion of said passageways.

57. The new use according to claim 54 including maintaining said chamber sealed from atmosphere except for an inlet passageway and an outlet passageway, and conveying said articles into and out of said chamber through said inlet and outlet passageways, respectively.

58. The new use according to claim 57 wherein said continuously conveying step comprises conveying articles into and out of the bottom of said chamber.

59. The new use of a sterilizer of the continuous type including a sterilizer chamber and a conveyor for moving articles to be sterilized down into, through, and up out of said chamber, said new use comprising:

introducing a quantity of a more dense sterilizing gas into said chamber such that a gas-to-gas interface is formed between said sterilizer gas and a less dense first gas located above said sterilizing gas, and continuously conveying articles to be sterilized down into, through, and up out of said sterilizing gas.

60. The new use according to claim 59 wherein said first gas is air and including the step of controlling the concentration of said sterilizing gas in said chamber.

61. The new use of a sterilizer of the continuous type including a sterilizing chamber open to atmosphere and a conveyor for moving articles to be sterilized into, through and out of said chamber, said new use comprising:

through and out of said chamber,

preventing said gas from escaping from said chamber,

said preventing step comprising maintaining said chamber sealed from atmosphere except for at least one passageway,

said conveying step comprising conveying said articles through said at least one passageway,

said preventing step also comprising maintaining at least a portion of said at least one passageway above the top level of said sterilizing gas,

maintaining an air-sterilizing gas interface in said portion of said at least one passageway, and

condensing out sterilizing gas present in said at least one passageway above said interfaces.

62. The new use according to claim 61 wherein said continuously conveying step comprises conveying articles into and out of the bottom of said chamber.

References Cited UNITED STATES PATENTS Re. 20,359 5/1937 Robertson 134-11 1,227,101 5/1917 Wehmiller 99214 1,987,414 l/1935 Omsted 99362 2,273,939 2/1942 Dammers 13411 UX 2,660,512 ll/ 1953 Webster 21-56 2,704,869 3/1955 Meakin 21-56 X 2,896,640 7/1959 Randall et al 13411 X 3,105,335 10/1963 Hickey 21DlG. 4 3,252,405 5/1966 Mencacci 2192 X 3,481,691 12/1969 Trainham 21 94 3,501,318 3/1970 Wilson 99--214 X 3,088,179 5/1963 Leuthner 21--DIG. 4 3,372,980 3/1968 Satas 21--DIG. 4 3,547,577 12/1970 Lovercheck 2161 MORRIS O. WOLK, Primary Examiner D. G. MILLMAN, Assistant Examiner US. Cl. X.R. 21-91, DIG. 4