|Publication number||US3600126 A|
|Publication date||Aug 17, 1971|
|Filing date||Feb 5, 1968|
|Priority date||Feb 5, 1968|
|Publication number||US 3600126 A, US 3600126A, US-A-3600126, US3600126 A, US3600126A|
|Inventors||Hellund Emil J|
|Original Assignee||Hellund Emil J|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (19), Classifications (8)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Aug- 17, l977l E. J. HELLUND 3,600,126
AsEPsIs PnocEss AND APPARATUS Filed Feb. s, 1968 2 sheets-sheet A POWER SOLJQCE'.
INI/NTOR. E14/L `I2 HELLUAJD Aug. 17, 1911 Filed Feb. 5, 196B E J. HELLUND ASEPSIS PROCESS AND APPARATUS 2 Sheets-Sheet 2 Elaja povvclz SOUQFE Sou POWE? RCF,
E10/L -JL .HEL/.UND
?United States Patent O' ce 3,600,126 ASEPSIS PROCESS AND APPARATUS Emil J. Hellund, 31281 Holly Drive, South Laguna, Calif. 92677 Continnation-in-part of abandoned application Ser. No.
533,767, Feb. 21, 1966. This application Feb. 5, 1968,
Ser. No. 702,929
Int. Cl. A611 1/00, 3/00 U.S. Cl. 21-54 25 Claims ABSTRACT OF THE DISCLOSURE A process and apparatus for rendering aseptic a contaminated surface or surfaces of an object being treated, by establishing an electric eld through the object and through Ia gas which contacts the object, in a relation producing a glow discharge in the gas, with the contamination on the object (for example bacteria, viruses or other microorganisms) serving as a secondary anode and/ or a secondary cathode to the glow. By virtue of this functioning of the contamination itself as a secondary electrode to the glow, the contaminants are bombarded by electrons and/ or ions which impact against and thereby kill or otherwise disable the contaminants. The impedance to 'by-passing of current past the object being treated is maintained high enough to force the contamination to serve its intended function as an anode or cathode to the glow.
CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of my copending application Ser. No. 533,767, filed Feb. 21, 1966, entitled Asepsis Process and now abandoned.
BACKGROUND OF THE INVENTION This invention relates to an improved process and apparatus for sterilizing the exposed surfaces of an object, such as for example a lfood product, items used for rst aid, hygienic or medical purposes, containers, tools, clothing, and the like. The process and apparatus function to very effectively kill, reactivate or chemically alter microorganisms such as bacteria, virus, fungus and molds, and act to decompose contaminant organic chemical compounds, all in a manner rendering the surfaces of the object being treated completely sterile.
Though various expedients have been proposed and utilized in the past for sterilizing objects being treated, all of these prior processes of which I am aware have had certain disadvantages preventing their use in many of the instances in which sterilization is desired. For instance, it is of course well known that ultraviolet light of certain wave lengths is germicidal, and lamps producing such ultraviolet light have been used commercially to kill microorganisms. However, this ultraviolet light does not penetrate well into a shadow zone around an object, and therefore is not highly effective in killing microorganisms in such a shadow zone. Further, ultraviolet light can be dangerous to persons in the vicinity, if not controlled and shielded properly.
Similarly, high energy particle bombardment, employing beta, gamma, and X-rays, can also be utilized Ifor the purpose of killing microorganisms, but requires extremely expensive energy generation sources, and is even more hazardous to health than are ultraviolet rays, requiring extensive safety precautions and highly skilled operating personnel.
Another previously utilized and well known -method of sterilizing items has been by simply heating them, and thereby raising their temperature high enough to destroy the microorganisms. This type of process has been satis- 3,600,126 Patented Aug. 17, 1971 factory for many purposes, but in other situations has had various disadvantages, including especially the tendency to alter the condition of the item being treated as a result of the heat developed. In the case of certain food items, for example, such an elevation of temperature can so drastically change the taste or condition of the food as to render it completely inedible.
SUMMARY OF THE INVENTION The process and apparatus of the present invention are capable of sterilizing initially contaminated surfaces of a food product or other item or object being treated in a very effective manner achieving complete surface sterilization almost instantaneously, and yet overcoming the various disadvantages of the above discussed and other prior processes for this purpose. As will appear, the microorganisms and other contaminants are killed and deactivated by a process which does not substantially alter the condition of the food product or other object being treated, either internally or externally, so that the product remains in substantially its original condition except for the sterilization of its outer surfaces. Also, the process does not involve diflicult radiation shielding problems, and can be performed without any radiation hazard to operating personnel or others. Additionally, I avoid the above discussed shadow problem which is inherent in the use of ultraviolet type radiation.
To achieve these results, I employ a system in which an electric eld is established, in a relation such that the field extends through the object being sterilized, and through a body of gas which contacts a surface or surfaces of the object. The intensity of the electric eld is predetermined at a value to produce a glow discharge in the gas, with the conditions being so controlled that the contaminants themselves on the surface of the object being treated serve as an electrode or electrodes, that is, an anode and/ or cathode, to the glow. Stated differently, the glow is made to attach to the contamination and to the surface of the object which carries the contamination in a secondary electrode relationship. Because the contamination and the sur-face on which it is carried are serving as an anode and/or cathode to the glow, the contamination is very effectively bombarded by electrons or ions moving rapidly toward the contamination by virtue of its electrode status, with resultant collisions of the electrons or ions with the contaminants in a manner destroying the integrity of the contaminants and killing or deactivating them. When the contamination functions as an anode, the bombardment of the contaminants is by electrons and often by some negative ions. When the contamination functions as a cathode, on the other hand, the bombardment is by positive ions.
In order to assure functioning of the contaminated surface as a secondary electrode to the glow, I maintain sufficiently high impedance along all possible by-passing paths to prevent electrical conduction of the energy along such paths, and thereby lforce devlopment of the desired anode or cathode relationship between the contaminated surface and the glow. For this purpose, I may employ a high impedance `baille or barrier, or may alternatively utilize an electromagnetic field for directing the charged particles along the desired path.
In some instances, the electric field may be set up by a direct current power source, preferably producing a pulse of very short duration. In other situations, I may employ an alternating current power source, acting to repeatedly change the electrode status of a particular contaminated surface from anode to cathode, back to anode, etc. In this instance, the contaminants may be caused to themselves produce the very electrons by which they are destroyed, since in their cathode condition they produce electrons which tend to move into the glow plasma, and since the same electrons may subseqeuntly reverse their direction of movement and return rapidly toward and bombard the contamination when the latter is in its anode condition.
Certain additional advantages can be attained by utilizing alternating current of a type having an asymmetric wave form, so that the duration, wave shape or amplitude of the electric eld in one direction is different than the corresponding characteristics of the eld in the opposite direction, in a predetermined relationship serving to cause the electrons and negative ions on one half cycle to bombard the contaminants in a different manner than do the positive ions on the other half cycle. It will be apparent that many variations of asymmetric waves maybe employed as may be found desirable for most effectively killing or disabling microoragnisrns of different types encountered in different sterilizing situations.
BRIEF DESCRIPTION OF THE DRAWING The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiments illustrated in the accompanying drawings, in which:
FIG. 1 is a diagrammatic representation of a first form of apparatus to be utilized for performing a sterilizing process in accordance with the invention;
FIG. 2 is a transverse section taken on line 2 2 of FIG. 1;
FIG. 3 is a diagrammatic representation of another process embodying the invention, in this case for sterilizing a bottle;
FIG. 4 shows diagrammatically a system in which the electric eld is generated by a changing current in a coaxial coil;
FIG. 5 is an enlarged transverse section taken on line 5--5 of FIG. 4;
FI-G. 5a is an enlarged detail of a portion of FIG. 5;
FIG. 6 is a diagrammatic perspective view of another arrangement for sterilizing an object by a process embodying the invention;
FIG. 7 is a section taken on line 7-7 of FIG. 6;
FIGS. 8 and 9 are views similar to FIG. l, but showing two additional forms of the invention; and
FIG. shows a typical asymmetric alternating current Wave form which may be used as the exciting power in my process.
DESCRIPTION lOF THE PREFERRED EMBODIMENTS Referring to FIG. 1 in detail, I show a gaseous glow discharge generating electrical circuit l, having an electrically insulated, gas tight container 2. Two plate electrodes 3 and 5 are connected by electrical leads 4 and 6 respectviely to a power source 7. A gas atmosphere 8, suitable for the generation of a desirable glow discharge, lls the container 2.
The gas employed within container 2 may be any gas capable of producing a glow discharge when subjected to the electric field resultant from the energization of plates 3 and S. For best results, it is in most instances preferred that the gas be selected from the group consisting of oxygen, nitrogen, carbon dioxide, helium, neon, argon, and mixtures of these gases. The pressure of the gas or gases may be any pressure at which the glow discharge can be effectively produced, in most instances at or below atmospheric pressure, and for best results substantially sub-atmosphreic (preferably between about 30 mm. and 50 microns of mercury).
The object to be treated is illustrated at 9 in FIG. l, and is preferably located between the two plates 3 and 5. This object may typically be a food product, hygienic or medical article or tool, or any other item to be sterilized, and may of course assume any of numerous different structural shapes instead of the typically and rather diagrammatically illustrated circular shape of FIG. 1. When the object 9 is tirst placed in container 2, the upper and lower surfaces 10 and 11 of the object are assumed to carry layers of contamination designated 12 and 13, containing bacteria, molds, viruses and the like which are to be destroyed by the treating process. About the object 9, there is provided a batle or barrier 14, which may be formed of glass, an appropriate resinous plastic material, or any other electrically insulative material capable of preventing by-passing of electric current vertically past object 9. If the object 9 is of the illustrated circular cross section, the baflle or barrier 14 may be annular, to externally and annularly contact the inner surface of the typically spherical container 2, and to internally and annularly Contact the peripheral surface 15 of object 9. The container itself may also be formed of, or at least be lined with, an appropriate electrically non-conductive material, such as glass or a resinous plastic material.
The two plates 3 and 5 may be circular about the vertical axis 16 of FIG. l, and may be formed of an appropriate highly electrically conductive metal, such as copper. These plates 3 and 5, and the surfaces 10 and 11 of object 9, may all be disposed transversely of axis 16, as shown.
Power source 7 may be either a direct current source or an alternating current source, with the latter being prefered in many instances. For purposes of description, assume first of all an installation in which the power source is of the direct current type, and functions when actuated to supply an instantaneous uni-directional pulse or predetermined potential to plates 3 and 5. This direct current source may be connected to plates 3 and 5 in either direction, that is, so that electrode 3 is the cathode and electrode 5 the anode, or vice versa. When, as an example, electrode 3 is operated as a cathode, electrons from power source 7 tend to ilow from this cathode 3 downwardly toward anode 5 (usually along with some negative ions), while positively charged ions of the gas 8 tend to flow from the anode 5 upwardly toward cathode 3. The voltage employed is so selected, in conjunction with the electrical characteristics of object 9 and the other parameters of the system, as to energize gas 8 to an extent producing a gaseous glow discharge in the space between electrode 3 and upper surface 10 of object 9, and in the space between electrode S and lower surface 11 of object 9, with the plasma of this glow discharge including electrons, positive ions and a relatively fewer negative ions. The voltage is not allowed to reach a value high enough to cause arcing between the electrodes and surfaces 10 and 11.
The conditions are so controlled that the contamination 12 and surface 10 at the top of object 9 function as a secondary anode to the glow which is above object 9, while contamination 13 is undersurface 11 at the bottom of the object function as a secondary cathode to the glow which is beneath the object. To achieve this result, it is of course necessary to provide a high enough voltage between plates 3 and 5 to allow for the potential drops which must necessarily occur at and near surfaces 10 and 11 when they serve the desired anode and cathode functions. As is well known, in order for the contamination on undersurface 11 to serve as a cathode, there must be a cathode potential drop of at least about 300 volts directly adjacent that surface. Similarly, there must be an anode potential drop adjacent upper surface 10, though this anode drop is of course small as compared with the cathode drop.
If the dielectric barrier 14 were not provided in FIG. l, the glow and the electric current conducted thereby could in many instances easily flow vertically past or by-pass the outer edge of object 9, from the upper side of the object to its underside and vice versa. The barrier 14, however, is of such high impedance as to prevent such by-passing of the current and glow past object 9, and to thereby force or require the contamination on the upper and lower surfaces of object 9 to function as anode and cathode respectively to the glow, so that the glow in effect attaches itself directly to the contaminants, with the latter functioning as secondary electrodes in the system.
Under these glow discharge conditions, with the contaminants 12 and 13 serving as electrodes to the glow, electrons and negative ions from upper plate 3 move downwardly toward and bombard the contaminants 12 on the upper surface of object 9, while the positive ions from lower plate 5 move upwardly toward and bombard the contaminants 13 on the undersurface of the object. The resultant collisions of electrons and ions with the contaminants are of suicient energy to break at least some of the molecular bonds within the organic contaminants, and to thereby very effectively kill or deactivate those contaminants. I preferably maintain the glow, and subject the object 9 to this process of bombardment, for only a very limited period of time, desirably not more than about one second, and in most instances only a small fraction of a second. In one installation utilizing direct current in an arrangement such as that shown in FIG. 1, the direct current power source 7 generated 2000 volts and produced a current flow of l milliamperes per square decimeter over the cathode 3, with the gas 8 being argon.
In -many situations, the object 9 to be sterilized is essentially non-conductive electrically, or very poorly conductive, as for instance in the case of most food products such as meat. In such cases, the glow discharge will of course be maintained only during build up of the electrical charges on the upper and lower surfaces of the object 9. However, this very limited almost instantaneous subjection of the contaminant pathogens to bombardment is sufiicient to destroy them. When object 9 is of an electrically conductive nature, as for instance if the object is a surgical knife or instrument formed of metal, current may flow directly through that metal, but the contaminants on the surfaces of the metal will still, under proper voltage and proper guidance, which may take the form of magnetic scanning or sweeping, and with an adequate dielectric barrier thereabout, function as an anode and as a cathode, and be bombarded by electrons and ions in the manner discussed.
The advantage of performing the bombardment under glow discharge conditions resides in the fact that the characteristic energy made available in a glow for a given bond transformation by collision happens to be just the right energy for breaking the types of bonds which occur in biological compounds, that is, the compounds of which the contaminant pathogens are formed, and yet is not great enough to harm the object being sterilized. Specifically, the energy spectrum available for bond transformation in a glow is .03 ev. to 300 ev. (approximately, for most gases), which range completely encompasses the spectrum of bond energies of all biological compounds. This particular energy spectrum is not supplied in any other type of electrically energized sterilization or treatment process with which I am familar. For example, in a dielectric heating system, the characteristic energy made available for a given bond transformation is 0.025 ev. to 0.035 ev., a value far too low to achieve the present purposes effectively. In an ultraviolet system, the characteristic energy is approximately 3 ev., and does not cover adequately the range required for proper sterilization. In a Van der Graaff generator arrangement, the characteristic energy made available is far too great, specifically in the range of 1 mev. to mev., and can be very detrimental to the object being treated. Thus none of these systems can destroy biological bonds with the effectiveness and safety attainable in a secondary electrode glow discharge bombardment of the type provided by the present process.
If the connections between power source 7 of FIG. 1 and the two primary electrodes 3 and 5 are reversed, the polarities of these plates and of the upper and lower contaminant layers are also of course reversed from the condition typically illustrated in FIG. 1; but the destructive action on the contaminants is essentially the same as discussed hereinabove.
Up to this point in the description of the FIG. 1 arrangement, it has been assumed that power source 7 is a direct current source. In many instances, however, it is preferred that source 7 supply alternating rather than direct current. One advantage of the use of such alternating current resides in the fact that, when alternating current is used, the polarities of the electrodes 3 and 5, and therefore the polarities of contaminant layers 12 and 13, are reversed repeatedly and regularly through many cycles, with the result that the contaminants themselves are made to produce the very projectiles (electrons) by which they are destroyed. That is, when one of the contaminant layers 12 or 13 is functioning as a cathode, the collisions of positive ions with the contaminants of that layer cause electron bonds to be broken in the contaminant pathogens, freeing electrons from those contaminants, while on the next reversal of potential, when these contaminants commence to function as an anode, the same electrons previously freed from them are driven back against the contaminants to kill them. Further, the treatment can obviously be continued for a longer period of time in an alternating current system than in most direct current systems, since in the latter a glow can usually be maintained only during the charging period. When alternating current is employed, it may be at virtually any frequency at which a glow may be maintained, preferably between about 60 cycles per second and 200 megacycles per second, and including audio frequency, intermediate frequency, and radio frequency ranges, or possibly microwave frequencies in special situations.
In a gaseous glow discharge as utilized in the present invention, with the gas desirably being at low sub-atmospheric pressure, the ionization potential of the gas may range up to about 24.4 volts (the value for helium); and in addition a cathode potential fall of about 300 volts at each cathode (both the primary cathode and the secondary cathode on the object being treated) is required to maintain the plasma, as well as a smaller anode drop at both the primary and secondary anodes. To supply these requirements and attain an effective sterlizing action, the power source, whether A.C. or D.C., should desirably have a value between about 1,000 and 40,000 volts, and preferably between about 1,000 to 15,000 volts.
The electron density in the glow is very close to the positive ion density. At an electron density of 103 lectrons/cc. to 1014 electrons/cc. and an electron velocity of 10S-l0g cm./sec. near the cathode, an 8 micron long bacillus, with a 2 micron diameter, is bombarded with 1013 electron impacts per second under average conditions. In about one second, the impacts deliver about ergs to a bacterium. Since the bacterium volume is about 10-11 cc., the one second dosage is about 1013 ergs per gram of tissue or about 1011 reps, where one rep denotes an energy absorption of 83 ergs per gram of tissue.
Prior art has established that approximately 105 to 106 rep energy absorption is lethal to single microorganisms, as well as destroying or grossly altering many simple organic chemical compounds. (Bellamy, W. D., Goldblith, S. A., Colovos, G. C., and Niven, C. P., Bact. Rev. 266 (1955); and also Kertesy, Z. I., Prog. Report, U.S. Army Quartermaster Corps. Con. No. DA 129-Qm 329 (January l-February 29 (1956).) Hence my process kills microorganisms or grossly alters organic chemical structure in about 10*5 seconds. Therefore, a one millisecond pulse of my low pressure glow discharge produces an overkill of undesirable microorganisms, Viruses or organic chemicals.
A decided advantage of the present process and apparatus resides in the relatively low power requirements of the system. I typically utilize current densities of only about 2 to 30 ma. per square decimeter of electrode. to
generate the gaseous glow discharge at the preferred operating pressure range of 30 mm. to 50 microns of mercury.
Referring next to FIG. 3, I show a gaseous glow discharge electrical circuit 20, having a gas tight, electrically insulated container 21 lwith a vertically extending wire electrode 22 having a lead wire 23 connecting it to a power source 26. A horizontally extending second electrode or plate 24 is connected by a second lead wire 25 to the opposite side of the power source 26. A gas atmosphere 27 Capable of supporting a glow discharge lls the container 21. A glass bottle 28 may rest on the horizontal electrode plate 24, with vertical wire 22 extending downwardly into the bottle to approximately its lower end, along the vertical central axis of the bottle (which may typically be of conventional circular cross section). The bottle is filled with the same gas as is container 21, and has its upper end closed by an element 29 which is formed of an electricaly non-conductive material such as glass, and serves the function of the dielectric bafiie or barrier 14 of the FIG. l arrangement. Element 29 at its lower end may typically take. the form of a cap adapted to fit over and thus close the upper end of the bottle. The cap or element 29 encircles and insulates the electrode 22 as it extends upwardly above thebottle to the top of the container, so that the electrode 22 is exposed to the gas atmosphere only at a location within the bottle. The two electrodes 22 and 24 may of course be formed of any appropriate electrically conductive material, such as copper.
To describe the functioning of the apparatus of FIG. 3, assume first of all that power source 26 is of the direct current variety, operating for example at 1000 volts, and is so connected as to cause wire 22 to function as a cathode while plate 24 serves as an anode. Also, assume that source 26 supplies a timed pulse of say 0.5 second duration, with a current density of, for example, 20 milliamperes per square decimeter of anode plate area. Such a pulse will ionize helium gas both within and about the bottle to a glow discharge condition, with any contamination on the internal surface of bottle 28 serving as an anode to the glow within the bottle, while any contamination on the outer surface of the bottle becomes a cathode to the external glow. That is, as in FIG. l, the glow attaches directly to the contamination in secondary electrode relation and kills or deactivates all living microorganisms by the previously discussed bombardment with electrons and ions. To assure functioning in this manner, the insulative element 29 is given a high enough impedance to by-passing of current between the primary cathode 22 and anode 24 to require the discussed establishment of the contaminant surfaces as secondary electrodes. Element 29 may of course be suitably sealed with respect to the wall of container 20, as at 30, to maintain the gas tight integrity of the container. The arrangement of FIG. 3 may of course also be operated in reverse manner or be energized by alternating rather than direct current.
In the variational arrangement of FIGS. 4, 5 and 5a, there is shown another type of gaseous glow discharge circuit illustrated generally at 50, operating in a hermetically sealed typically spherical container 51 formed of electrcally insulative material. A helical coil 52 within the container is connected by leads 53 and 54 to an alternating current power source typically illustrated as a transformer 55. An atmosphere of ionizable gas or gases, typically air in this instance, is maintained within container 51, preferably at a sub-atmospheric pressure, such as for example 5 millimeters of mercury. The alternating current supplied to coil 52 produces an electric field within the coil following a circular path about axis 57 of the coil, with that path being illustrated at 58 in FIG. 5. The coil is operated at a potential which will give the circular' field along path 58 a value sufficient to set up a glow discharge through the gas, with the glow discharge of course also following the defined circular path (and other similar circular paths). The object or objects to be sterilized are positioned in the path of the electric field and the glow discharge, two such objects being illustrated at S9 and 66 in the figures. These objects may be located at opposite sides of axis 57, and each may typically in this particular example take the form of a hollow rectangular container 61 formed of a suitable resinous plastic material and containing a hot food product 62. As in the other forms of the invention, a dielectric barrier is provided for preventing by-passing of the glow discharge current about the peripheries of the two objects or packages 59 and 60. This barrier is illustrated as taking the form of a circular disc or plate 63 of glass or other non-conductive material extending diametrically across the sperical container 51 and dividing the interior of the container into two compartments 64 and 65 (FIG. 5. Barrier 63 may contain rectangular openings 66 and 67 dimensioned to exactly receive objects 59 and 60 and continuously contact those objects about their peripheries. The barrier also of course contains openings through which the various turns of the coil pass. Within the food containers 61, there is provided an atmosphere of gas (typically air) capable of supporting a glow discharge, and maintained at a pressure at which the discharge can be produced under the excitation conditions encountered.
When coil 52 is energized, the circular field following path 58, and other similar circular paths about axis 57, acts to produce a glow discharge within each of the containers 61, as well as at the outside of the containers. Whatever contamination is present on the vertical walls of containers 61, as well as on the vertical surfaces of the food 62 itself, serves as an anode or cathode to the glow, in the same manner that the contamination on the upper and lower surfaces of the object 9 in FIG. 1 functions as an anode or cathode. More specifically, referring to the upper treated object 59 of FIG. 5, as enlarged in FIG. 5a, when the alternating current power supply is in a first half of its cycle, the circular electric field within the coil acts to cause the contamination on the left surface of the left hand wall 166 of the food container 61 to assume a positive charge, and thereby function as an anode to the glow at the outside of the package, while the right hand surface of this wall 166 assumes a negative charge, and functions as a cathode to a glow extending from that surface rightwardly to the left hand (anode) surface of the food product 62. The right hand surface of the food product and the left hand surface of a final container wall 167 serve as cathode and anode respectively to a second glow extending therebetween, while the right hand surface of wall 167 becomes a cathode to an external glow extending semi-circularly to the lower package 60. Thus, the impacting of electrons and ions against the contamination on these various surfaces of the containers 61 and their contents effectively kills the contaminants on those surfaces. The glass partition 63 provides a sufiiciently high impedance to by-passing of the current past the periphery of the packages 59 and 60 to require the establishment of the discussed anode and cathode conditions on the container walls. Also, the food product 62 of each package may typically contact the walls of its container 61 continuously about the periphery of the food product, so that the impedance to by-passing of current past the product within the container is high enough to require functioning of the surfaces of the food product itself as electrodes. As will be apparent, when the direction of the alternating current reverses, all of the secondary electrode polarities discussed in connection with FIG. 5a also reverse, to attain the previously discussed advantages of such alternating polarization (the term secondary electrode being defined in this application as applying to the arrangement of FIGS. 4, 5 and 5a even though the system of these figures does not in fact include any primary electrodes).
ln a typical arrangement of the type illustrated in FIGS. 4, and 5a, coil 52 may be operated at an audio frequency, say for example 15,000 cycles per second, and at a suitable potential for producing and maintaining the desired glow and secondary electrode conditions, typically for example at a potential gradient of 200 volts per centimeter of glow length. The alternating current power may be applied for a suitable relatively short interval, for example 100 milliseconds, predetermined to be short enough, and at a low enough oxygen gas pressure, to assure that the taste of the food will not be altered substantially by oxidation processes.
As a further example, I may employ a coil type circuit generally similarto that of FIGS. 4, 5' and 5a, but in which a radio frequency rather than audio frequency power source and coil are utilized, typically at a frequency in the 1 to 2100 megacycle range. The radio frequency coil may as an example have a power input of l0 to 2() watts at a potential gradient of 200 volts/cm. Sterilization of the food in such an arrangement can be attained in much less than a second, with the pressure of the air in container 51 and within the food package desirably being relatively low, as for example about 20 mm. of mercury. The container 61 of the food should be non-metallic, to prevent electromagnetic shielding of the food contained therein. It is also of course possible to use intermediate frequencies as well as the mentioned audio and radio frequencies.
I-n order to assure sterilization of all of the various external surfaces of a particular object being treated, the glow producing eld may be established within that object in a plurality of different directions, either by rotating or otherwise turning the object to different positions for successive energization in different directions, or by use of a plurality of different electrodes or coils. FIGS. 6 and 7 show diagrammatically such a multiple electrode arrangement in which a typically cubical object 70 is to be sterilized by three different pairs of electrodes, including a rst pair 71 at two opposite sides of the object and disposed perpendicular to a rst axis 72, a second pair of electrodes 73 at two other sides of the object and disposed perpendicular to an axis 74, and a third pair of electrodes 75 at the iinal sides of the object and disposed perpendicular to a third axis 76. As will be apparent, the three axes 72, 74 and 76 of the different pairs of electrodes are mutually perpendicular. All of the electrodes may be carried by an essentially cubical body 77 of electrically non-conductive high impedance barrier material serving the function of the dielectric barrier 14 of FIG. 1 (body 77 being shown in broken rather than full lines in FIG. 6 for clarity). As seen in the FIG. 7 sectional view (which may be considered as representing the cross section of the unit in each of three mutually perpendicular planes), the dielectric material of body 77 iills in all possible current by-pass locations, leaving unoccupied thereby only the various gas spaces 78 between the electrodes and the outer surfaces 170 of object 70, so that glow discharges may be developed in these spaces between the electrodes and the contaminants on surfaces 170, with the contaminants serving as secondary electrodes between each pair olf primary electrodes 71, 73l or 75. The glow thus bombards the contaminants on surfaces-170 with electrons and ions and thereby attains the desired sterilization of the object.
'It is contemplated that the three sets of electrodes 71, 73, and 74 may be energized either successively, to successively sterilize different sides of the object, or simultaneously to attain the complete sterilization result at one time. To simplify and clarify the drawings, the power source or sources are not illustrated in FIGS. 6 and 7, but of course may be either of the direct current or alternating current type, and may be of voltages and frequencies and other characteristics corresponding to those discussed above in conjunction with the other forms of the invention. Also, the system of FIGS. `6 and 7 should desirably be mounted in a suitable air tight container, with the gas 1U within the glow discharge areas 78 being at an appropriate pressure for ionization.
lFIG. 8 shows another form of the invention which may be identical to that illustrated in FIG. l except for the substitution of a different method of preventing by-passing of the current about the periphery of the object. In FIG. 8, instead of utilizing a dielectric baffle as shown at 14 in F'IG. 1, I provide an electromagnetic coil 80 extending about the treated object 9a, and within the air tight container 2a, and centered about the axis 16a of the electric field. This coil 80 is energized by a direct current power source 81 acting to produce a magnetic eld extending axially within the coil, parallel tol axis 16a, which magnetic eld serves to guide the electrons and ions in the same axial direction, and prevent them from deflecting laterally from their axial course. Thus, the impedance to the electric field along any by-passing path is increased, so that the electric current is required to be maintained within the object, in a vertical direction as seen in FIG. 8, to require the functioning of contaminants on the upper and lower surfaces of object 9a as secondary electrodes to the glow, with the bombardment result and destruction described in connection with FIG. l and the other forms of the invention. It may be noted that magnetic field guidance or bafing of this type is especially useful in sterilizing closed and sealed packages of food or the like, as shown at 59 in FIG. 5a, since such guidance may be the only convenient way of requiring certain surfaces of the product `within the package to function as secondary electrodes.
FIG. 9 shows another formi of the invention in which the impedance to by-passing of the current is increased in another way, specically by cooling the space around the periphery of the object, and at the location occupied by dielectric baille 14 of FIG. l. In FIG. 9, an annular body of heat conductive material 83 may be provided instead of the baille 14, with cooling coils 84 embedded within this element 83, and conducting a cooling iluid therethrough acting to reduce the temperature of element 83 to a value well below the temperature of the glow discharge, so that the glow discharge has a very high impedance path through element 83 and peripherally about the object 9b, and is thereby forced through the object, to cause the development of the desired secondary electrodes on its upper and lower surfaces.
In any of the different forms of the invention, I may encourage the discharge of electrons from the secondary electrode surfaces by directing ultraviolet light against those surfaces, as by ultraviolet sources 85 represented in FIG. 9 directed against the secondary electrodes surfaces 10b and 11b and/or the primary electrode surfaces of electrodes 3b and 5b. I may also employ dielectric heating in conjunction with the discussed glow discharge sterilization procedure, if in certain instances a rise in temperature of the treated object is desired, or if the contaminant can be discriminantly heated by the glow and by dielectric heating. The synergism encountered in the use of both glow and dielectric heating should be particularly noted. The glow will elevate the surface temperature (contaminant). This elevation of temperature makes the contaminant the more vulnerable to dielectric heating corresponding to the elevation of molecular relaxation frequencies.
When such dielectric heating is to be utilized, the power source whcih energizes the primary electrode plates, as for instance source 7 of FIG. l, may be designed to provide two types of power, one of the character described hereinabove and capable of producing the desired glow discharge and secondary electrode conditions, while the other is of a proper alternating current frequency, matching the relaxation frequency of molecular dipole orientation, to attain substantial dielectric heating in the object. For example, the glow discharge power may be alternating current of one frequency, say for example 0.1 megacycle per second, while the dielectric heating power is of ll another frequency, say for example l() megacycles per second.
As mentioned previously, when the exciting potential in my process is alternating current, this potential may have an asymmetric wave form, in order to attain an optimum unbalanced relation between the ion and electron bombardment of the contaminants on a particular stuface. For example, the alternating potential may have the asymmetric wave form shown at 90 in FIG. l0, in which the positive potential portion 91 of the curve is of very short duration and the negative potential portion 92 is of much longer duration, or `vice versa (or may be of a different amplitude or wave shape), so that the bombardment by electrons may be of a different duration or character than the bombardment by ions, in whatever relation is found optimum for a particular sterilizing situation.
Although I have `shown and described certain specific embodiments of the invention, it will be understood that numerous modications of the invention can be made, and are to be considered as part of the invention so long as they fall within the scope of the appended claims.
1. The process of rendering aseptic a surface of an object having contamination thereon that comprises establishing an electric field through a gas to said surface and then from said surface through the object to a second surface thereof, predetermining the intensity of said field at a value to produce a glow discharge in said gas which leads to said first mentioned surface and which attaches to said contamination with the latter serving as an anode or cathode to the glow, maintaining the impedance to by-passing of current past said object high enough to preclude by-passing of sair surfaces by said current and thereby to require said contamination to serve as said anode or cathode to the glow, and thereby disabling said contamination by bombardment with electrons or ions which impact against it in its function as an anode or cathode.
2. The process as recited in claim 1, in which said gas is maintained at a sub-atmospheric pressure.
3. The process as recited in claim 1, in which said gas is maintained at a pressure between about 30 millimeters and 50 microns of mercury.
4. The process as recited in claim 1, in which said gas is selected from the group consisting of oxygen, nitrogen, carbon dioxide, helium, neon, and argon.
5. The process as recited in claim 1, wherein said electric field and said glow are produced by a short duration direct current pulse.
6. The process as recited in claim 1, wherein said field is energized by an alternating current acting to alternate the direction of the eld repeatedly.
7. The process as recited in claim 1, wherein said field is energized by an alternating current of asymmetric wave form acting to alternate the direction of the field repeatedly and asymmetrically and to provide a predetermined relationship between ion and electron excitation of the biological bonds of the pathogens.
8. The process as recited in claim 1, in which said impedance is maintained by providing a high impedance batiie along a possible current by-pass path.
9. The process as recited in claim 1, in which said impedance is maintained by providing a magnetic field through said object in essentially the direction of said electric field to prevent said by-passing of current past the object.
10. The process as recited in claim 1, wherein said electric field is passed through said object in a plurality of different directions to disable contamination on a plurality of different sides thereof.
11. The process of rendering aseptic two surfaces of an object having organic contamination thereon that comprises establishing an electric field through a gas to a rst of said surfaces. then from said first surface through the object to the second surface, and then from said second surface into a gas, predetermining the intensity of said field at a value to produce a glow discharge in the gas adjacent both of said surfaces which attaches to said contamination on the two surfaces with said contamination serving as a cathode and an anode to the glow, maintaining the impedance to by-passing of current past said object high enough to preclude by-passing of said surfaces by said current and thereby to require said contamination on the two surfaces to serve as said cathode and anode respectively to the glow, and thereby disabling said contamination by bombardment with electrons and ions which impact against it in its function as an anode and cathode.
12. The process as recited in claim 11, in which said gas is selected from the group consisting of oxygen, nitrogen, carbon dioxide, helium, neon and argon and is maintained at a sub-atmospheric pressure.
13. The process as recited in claim 12, wherein said field is energized by an alternating current acting to alternate the direction of the field repeatedly.
14. The process as recited in claim 13, wherein an electric field of the character defined is directed through said object in essentially three mutually perpendicular directions to disable contamination on all sides thereof.
15. Apparatus for rendering aseptic a surface of an object having contamination thereon, comprising means for establishing an electric field through a gas to said surface and then from said surface through the object to a second surface thereof, said field being of an intensity producing a glow discharge in the gas which leads to said first mentioned surface and which attaches to said contamination with the latter serving as an anode or a cathode to the glow, said apparatus including means to maintain the impedance to by-passing of current past said object high enough to preclude by-passing of said surfaces by said current and thereby to require said contamination to serve as said anode or cathode to the glow, whereby said contamination is disabled by bombardment with electrons or ions which impact against it in its function as an anode or cathode.
16. Apparatus as recited in claim 15, wherein said impedance-maintaining-means comprises a high impedance battle positioned to prevent said by-passing flow of current past said object.
17. Apparatus as recited in claim 15, wherein said impedance-maintaining-means comprises means for establishing a magnetic field through said object in essentially the direction of said electric field to resist said bypassing fiow of current `past the object.
18. Apparatus as recited in claim 15, further including means forming a chamber containing said gas at a subatmospheric pressure and in contact with both of said surfaces of the object in glow discharge condition, with said two surfaces serving as anode and cathode respectively to the glow to disable contamination on both surfaces.
19. Apparatus as recited in claim 15, in which said means for establishing the electric field includes two oppositely charged plates.
20. Apparatus as recited in claim 15, in which said means for establishing the electric field includes an electromagnetic coil producing said field.
21. Apparatus as recited in lclaim 15, in which said means for establishing the electric `field includes an alternating current power source acting to alternate the direciton of the electric field repeatedly.
22. Apparatus as recited in claim 15, in which said means for establishing the electric field includes an alternating current power source of asymmetric wave form acting to alternate the direction of the electric field repeatedly and asymmetrically.
23. Apparatus as recited in claim 15 further including means for producing an electric field of the character dened through the object at an angle to the first mentioned field to disable contamination on another surface or surfaces of the object.
24. Apparatus as recited in claim 15, including means for producing electric fields of the character defined through said object in essentially three different mutually perpendicular directions, and with a glow discharge produced by each field attached to opposite sides of the object as an anode and cathode respectively, to disable contamination on all sides of the object.
25. Apparatus as recited in claim 15, in which gas is in contact with both of said surfaces of the object in glow discharge condition, with said two surfaces serving as anode and cathode respectively to the glow to disable contamination on both surfaces.
References Cited UNITED STATES PATENTS 2,122,741 7/19'38 Haddad 21-54 2,132,708 10/1938 Smith 2l-54 14 Alexander et al. 21-54UX Robinson Z50-49.5 Zoubek Z50-49.5
Parks Z50-49.5 Trump 250-49.5 Frhlich 2S0-49.5X Skala Z50-49.5
Menashi 21-54 Frhlich 250-49.5(62)UX Shepard Z50-49.5(62) MORRIS 0. WOLK, yPrimary Examiner B. S. RICHMAN, Assistant Examiner U.S. C1. X.R.
2l--l02; 204-165, 312; Z50-49.5
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|U.S. Classification||422/23, 422/186.5, 250/324, 204/165|
|International Classification||A61L2/02, A61L2/14|