Microwave/steam sterilizer

• US 4,861,956 A
• Filed: 10/17/1986
• Issued: 08/29/1989
• Est. Priority Date: 10/17/1986
• Status: Expired due to Fees

• Current Assignee: Magnetronics Incorporated
• Original Assignee: Magnetronics Incorporated
• Inventors: Courneya, Calice G.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Fuller, Leon K.
• Application Number:
  US06/920,572
• Time in Patent Office: 1,047 Days
• Field of Search: 219/10.55 A, 219/10.55 F, 219/10.55 R, 219/10.55 B, 219/10.55 M
• US Class Current: 219/696
• CPC Class Codes: A61L 2/06 Hot gas
• CPC Class Codes: A61L 2/12 Microwaves

Abstract

In the most preferred form, a microwave/steam sterilizer and its method of operation are disclosed including a waveguide having a waveguide conduit including a terminal aperture located one quarter wavelength from the bottom of a water reservoir and including a series of subapertures spaced in the range of one quarter wavelength from each other. The waveguide further includes a mitered corner moveable to shift the microwave standing waves to communicate with the terminal aperture and/or the series of subapertures in response to conditions sensed in the working cavity. The waveguide and the walls of the working cavity are angled with respect to each other to avoid reflection of microwave energy back to the microwave energy generator. The sterilizer hydrates potential pathogens and subjects them to relatively uniform electromagnetic energy without arcing and without self-destruction of the microwave source by reflected microwave energy.

Claims

1. Microwave waveguide structure for use in conducting microwave energy in a path intermediate a microwave energy generator and a working cavity comprising, in combination:

a first waveguide conduit having a first end and a second end;

a second waveguide conduit having a first end, with the first and second waveguide conduits being connected together by their first ends at an intersection generally perpendicularly to each other;

with the first waveguide conduit extending from the microwave energy generator into the working cavity and with the second waveguide conduit located in the working cavity, with the microwave energy generator applying the microwave energy adjacent to the second end of the first waveguide conduit resulting in standing waves;

means in the second waveguide conduit for introducing microwave energy generated by the microwave energy generator into the working cavity; and

means located at the intersection of the first and second waveguide conduits for communicating the microwave energy from the first waveguide conduit continuously into the second waveguide conduit and for selectively shifting the standing waves of the microwave energy in the second waveguide conduit.

2. The microwave waveguide structure of claim 1 wherein the second waveguide conduit has a second end;

wherein the introducing means comprise, in combination;

a terminal aperture formed in the second end of the second waveguide conduit, and a series of subapertures located along the second waveguide conduit and spaced one quarter wavelength of the microwave energy generated by the microwave energy generator; and

wherein the communicating and shifting means shifts the standing waves of the microwave energy in the second waveguide conduit between a first position to not communicate substantially with the series of subapertures and a second position to substantially communicate with the series of subapertures.

3. The microwave waveguide structure of claim 2 wherein the communicating and shifting means comprises means for shifting the standing waves of the microwave energy between the first and second positions in response to the temperature in the working cavity.

5. The microwave waveguide structure of claim 2 further comprising, in combination:

a shallow reservoir for water, with the reservoir having a bottom, with the terminal aperture located substantially one quarter wavelength of the applied microwave energy from the bottom of the reservoir.

6. The microwave waveguide structure of claim 5 wherein the terminal aperture extends below the water in the reservoir forcing steam generated by the applied microwave energy to enter the working cavity through the series of subapertures in the second waveguide conduit.

7. The microwave waveguide structure of claim 1 wherein the working cavity has at least a first wall and wherein;

the introducing means guides the microwave energy into the working cavity at the wall of the working cavity at a nonperpendicular angle to prevent first order reflection of the microwave energy from re-entering the introducing means.

8. The microwave waveguide structure of claim 2 wherein the working cavity includes a wall opposite to the series of subapertures, with the series of subapertures being misaligned in a nonparallel relation with respect to the wall opposite to the series of subapertures to avoid the coincidence of first order reflection with the series of subapertures.

4. Microwave waveguide structure for use in conducting microwave energy in a path intermediate a microwave energy generator and a working cavity comprising, in combination:

a first waveguide conduit having a first end and a second end;

a second waveguide conduit having a first end, with the first and second waveguide conduits being connected together by their first ends at an intersection generally perpendicularly to each other;

with the first waveguide conduit extending from the microwave energy generator into the working cavity and with the second waveguide conduit located in the working cavity, with the microwave energy generator applying the microwave energy adjacent to the second end of the first waveguide conduit resulting in standing waves;

means in the second waveguide conduit for introducing microwave energy generated by the microwave energy generator into the working cavity; and

a mitered corner at the intersection of the first and second waveguide conduits movable between a first position and a second position for communicating the microwave energy from the first waveguide conduit into the second waveguide conduit and for shifting the standing waves of the microwave energy in the second waveguide conduit.

9. Apparatus comprising, in combination:

means for generating electromagnetic waves;

a working cavity;

means for sensing a condition within the working cavity; and

means for conducting the electromagnetic waves from the generating means into the working cavity resulting in standing waves and for shifting the standing waves in response to the condition within the working cavity sensed by the sensing means.

10. The apparatus of claim 9 wherein the conducting and shifting means includes a terminal aperture and at least one subaperture;

and wherein the conducting and shifting means shifts the standing waves between a first position to substantially communicate with the terminal aperture and a second position to substantially communicate with the subaperture.

11. The apparatus of claim 10 further comprising, in combination:

means separate from the load subjected to the electromagnetic waves in the cavity for trapping reflected electromagnetic waves not absorbed by the load for preventing self-destruction of the electromagnetic wave generating means comprising means for absorbing the electromagnetic waves located adjacent to the terminal aperture.

12. The apparatus of claim 11 wherein the absorbing means comprises a reservoir for water.

13. The apparatus of claim 12 wherein the absorbing means is supported on a lower wall of the working cavity, with the terminal aperture located in the range of one quarter wavelength of the generated electromagnetic waves from the lower wall of the working cavity.

14. The apparatus of claim 13 wherein the terminal aperture extends below the water of the reservoir forcing water vapor to enter the working cavity through the subaperture.

15. The apparatus of claim 13 wherein the working cavity further includes a wall opposite to the subaperture, with the subaperture being misaligned in a nonparallel relation with respect to the wall opposite to the subaperture to avoid the coincidence of first order reflection with the subaperture.

16. The apparatus of claim 15 further comprising, in combination:

a series of subapertures spaced in the range of one quarter wavelength of the electromagnetic waves generated by the generating means.

17. The apparatus of claim 10 wherein the working cavity includes a lower wall, with the terminal aperture located in the range of one quarter wavelength of the generated electromagnetic waves from the lower wall of the working cavity.

18. The apparatus of claim 9 wherein the condition sensing means comprises, in combination:

means for sensing temperature in the working cavity.

19. The apparatus of claim 18 wherein the temperature sensing means comprises a bimetallic strip located in the working cavity.

20. The apparatus of claim 9 wherein the conducting and shifting means comprises, in combination:

a first waveguide conduit having a first end and a second end;

a second waveguide conduit having a first end and a second end;

with the first and second waveguide conduits being connected together by their first ends at an intersection generally perpendicularly to each other;

with the first waveguide conduit extending from the electromagnetic wave generating means into the working cavity and with the second waveguide conduit located in the working cavity, with the electromagnetic wave generating means introducing the electromagnetic waves adjacent to the second end of the first waveguide conduit;

means in the second waveguide conduit for introducing the electromagnetic waves into the working cavity; and

means located at the intersection of the first and second waveguide conduits for continuously communicating the electromagnetic waves from the first waveguide conduit into the second waveguide conduit and for selectively shifting the standing waves in response to the condition within the working cavity sensed by the sensing means.

21. The apparatus of claim 20 wherein the communicating and shifting means comprises a mitered corner at the intersection of the first and second waveguide conduits movable between a first position and a second position by the sensing means.

22. The apparatus of claim 21 wherein the condition sensing means comprises, in combination:

means for sensing temperature in the working cavity.

23. The apparatus of claim 22 wherein the temperature sensing means comprises, in combination:

a bimetallic strip located in the working cavity; and

a linkage between the bimetallic strip and the movable mitered corner.

24. The apparatus of claim 20 wherein the introducing means comprise, in combination:

a terminal aperture formed in the second end of the second waveguide conduit; and

a series of subapertures located along the second waveguide conduit and spaced in the range of one quarter wavelength of the electromagnetic waves generated by the generating means.

25. Microwave apparatus comprising, in combination:

a microwave energy generator;

a working cavity for receiving the microwave energy, with the working cavity having at least a first wall;

means for guiding of the microwave energy from the microwave energy generator into the working cavity at the wall of the working cavity at a nonperpendicular angle to the wall to prevent first order reflection of the microwave energy from re-entering the guiding means.

26. The microwave apparatus of claim 25 wherein the guiding means includes an aperture for introducing the microwave energy into the working cavity, with the aperture misaligned in a nonparallel relation with respect to the wall of the cavity.

27. Microwave apparatus comprising, in combination:

a microwave energy generator;

a working cavity for receiving a load for subjection to the microwave energy;

means for guiding the microwave energy into the working cavity having a terminal aperture;

means for trapping reflected microwave energy not absorbed by the load for preventing re-entry of the reflected microwave energy from the working cavity through the terminal aperture for preventing self-destruction of the microwave energy generator comprising means located adjacent the terminal aperture for absorbing the microwave energy.

28. The microwave apparatus of claim 27 wherein the guiding means further comprises, in combination:

at least one subaperture for conducting microwave energy into the working cavity generally perpendicularly from the microwave energy conducted into the working cavity by the terminal aperture.

29. The microwave apparatus of claim 28 wherein the subaperture is misaligned in a nonparallel relation with respect to the working cavity to avoid first order reflection of microwave energy back through the subaperture.

30. The microwave apparatus of claim 28 wherein the guiding means comprises, in combination:

a first waveguide conduit having a first end and a second end;

a second waveguide conduit having a first end and a second end;

with the first and second waveguide conduits being connected together by their first ends at an intersection generally perpendicularly to each other;

with the first waveguide conduit extending from the microwave energy generator into the working cavity and with the second waveguide conduit located in the working cavity, with the microwave energy generator applying the microwave energy adjacent to the second end of the first waveguide conduit, with the terminal opening formed in the second end of the second waveguide conduit, with the subaperture being formed intermediate the first and second ends of the second waveguide conduit; and

means located at the intersection of the first and second waveguide conduits for continuously communicating the microwave energy from the first waveguide conduit into the second waveguide conduit.

31. The microwave apparatus of claim 30 further comprising, in combination:

a series of subapertures located along the second waveguide conduit intermediate the first and second ends and spaced from each other in the range of one quarter wavelength of the microwave energy generated by the microwave energy generator.

32. The microwave apparatus of claim 31 wherein the guiding means results in standing waves;

and wherein the communicating means includes means for selectively shifting the standing waves of the microwave energy in the second waveguide conduit between a first position to substantially communicate with the terminal aperture of the second waveguide conduit and to not communicate substantially with the series of subapertures and a second position to substantially communicate with the series of subapertures.

33. The microwave apparatus of claim 27 wherein the absorbing means comprises a reservoir of water located in the working cavity.

34. The microwave apparatus of claim 33 wherein the water of the reservoir has a surface and wherein the terminal aperture is located below the surface of the water.

35. The microwave apparatus of claim 27 wherein the working cavity includes a wall, with the absorbing means being supported on the wall, with the terminal aperture located in the range of one quarter wavelength of the microwave energy generated by the microwave energy generator from the wall.

36. Method of guiding microwave energy in a path from a microwave energy generator and into a working cavity comprising the steps of:

a) guiding the microwave energy in a first waveguide conduit from the microwave energy generator towards the working cavity to a first point;

b) continuously reflecting the microwave energy guided in the first waveguide conduit from the first point into a second waveguide conduit for introduction into the working cavity, with the microwave energy being reflected at an angle; and

c) selectively shifting the angle of reflection of the microwave energy into the second waveguide conduit for shifting the standing waves in the second waveguide conduit.

37. The method of claim 36 further comprising the step of:

sensing a condition; and

wherein the step of shifting the angle of reflection is in response to the condition sensed.

38. The method of claim 37 wherein the step of sensing a condition comprises the step of sensing temperature in the working cavity.

39. The method of claim 36 further comprising the step of providing a terminal aperture and at least one subaperture;

and wherein the step of shifting the angle of reflection comprises shifting the angle of reflection of the microwave energy for shifting the standing waves between a first position to substantially communicate with the terminal aperture and a second position to substantially communicate with the subaperture.

40. The method of claim 39 further comprising the step of trapping reflected microwave energy not absorbed by the load subjected to the microwave energy in the working cavity for preventing re-entry of the reflected microwave energy from the working cavity through the terminal aperture by providing a substance for absorbing the microwave energy adjacent to the terminal aperture.

41. The method of claim 40 wherein the step of providing a substance comprises the step of providing water adjacent to the terminal aperture for trapping reflected energy.

42. The method of claim 40 wherein the working cavity has a wall;

and wherein the method further comprises;

locating the terminal aperture in the range of one quarter wavelength of the microwave energy from the wall.

43. The method of claim 39 wherein the working cavity has a wall;

and wherein the method further comprises the step of;

angling the subaperture in a nonparallel relation with respect to the wall for communicating the standing waves at a nonperpendicular angle to the wall for preventing first order reflection of the microwave energy from re-entering the subaperture.

44. Process comprising the steps of:

a) providing a working cavity;

b) sensing a condition;

c) generating microwave energy;

d) guiding the generated microwave energy into the working cavity resulting in standing waves; and

e) shifting the standing waves in response to the condition sensed.

45. The process of claim 44 wherein the step of sensing a condition comprises the step of sensing temperature within the working cavity.

46. The process of claim 44 further comprising the step of:

providing means in the working cavity for hydrating potential pathogens;

wherein the step of shifting the standing waves comprises the step of shifting the standing waves between a first position for direct communication with the hydrating means in the working cavity and a second position for direct communication with the working cavity.

47. Process comprising the steps of:

a) providing a working cavity having a wall;

b) generating microwave energy; and

c) guiding the generated microwave energy into the working cavity at the wall of the working cavity at a nonperpendicular angle to the wall to prevent first order reflection of the microwave energy off the wall from being reflected straight back towards the microwave energy generation.

48. The process of claim 47 wherein the guiding step comprises the steps of:

providing a microwave waveguide for guiding the generated microwave energy into the working cavity through an introduction aperture; and

misaligning the introduction aperture of the microwave waveguide in a nonparallel relation with respect to the wall of the working cavity to prevent first order reflection of the microwave energy off the wall from re-entering the microwave waveguide.