US 3490580 A
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United States Patent O 3,490,580 CONTAINERS AND PROCESS FOR ASEPSIS Robert C. Brumfield, Emerald Bay, Calif. (P.0. Box 1919,
Costa Mesa, Calif. 92626), and John T. Nafi, Costa Mesa, and Alonzo T. W. Robinson, Huntington Beach,
Calif.; said Naif and said Robinson assignors to said Filed July 29, 1968, Ser. No. 748,427 Int. Cl. B65d 1/34; B61b 19/07 U.S. Cl. 20663.2 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION There has been a continuing commercial requirement for aseptic medical products which are pre-packaged and sealed in disposable packages prior to sterilization. The package container means and the sterilizing process must be cooperatively adapted to both contain and not deteriorate the medical product, and also to provide aseptic product protection in storage after the sterilization process. The steam sterilization process is well known in the prior art; however, the standard minimum sterilization temperature of 121 C. associated with the process is destructive to many packaging or container materials which can be used for the medical products. The steam sterilization process is also notably time consuming and slow.
Cold sterilization of the medical products can also be accomplished using ethylene oxide gas as the sterilant gas. Again this is a comparatively slow process, requiring removal of air from the vessel containing the product packages and the introduction of the ethylene oxide gas at atmospheric pressure. Typically, the asepsis process requires 3 hours at 85 F. ambient temperature and 48 minutes at 140 F. ambient temperature in a relatively humid atmosphere.
Both of the above described common processes require extensive time periods to produce an effectively aseptic product. The invention taught in this application produces an aseptic product in a few seconds, representing a marked advance over the prior art. The combustible hazard of ethylene oxide and the high pressure hazard of a steam autoclave are also eliminated.
SUMMARY OF THE INVENTION This invention teaches container structure and process cooperatively adapted to provide aseptic medical dressings or the like when utilized in conjunction with the process and apparatus taught and claimed in the copending U.S. patent application titled Microwave Reactor and Process for Asepsis, filed this date by these co-inventors. The container structure has at least two confronting sheet faces, a first sheet face having at least a substantial area consisting of microporous paper and a second sheet face having local field strength concentrators preferably disposed on the inner container face of said second sheet. The hermetically edge sealed containers, enveloping medical dressings, are subjected to a low pressure gaseous glow discharge in an evacuated cavity. The glow discharge is generated by a microwave energy input impinging on the field strength "ice concentrators, the field strength concentrators are disposed in the cavity normal to and opposed to the direction of the incoming waves entering the cavity.
Included in the objects of this invention are:
First, to provide sealed containers for aspetic medical products, having at least a first microporous paper sheet wall, and electric field strength concentrators disposed in a second sheet wall adjacent the inner face of said second sheet wall of the container, said walls being sealed together.
Second, to provide sealed containers for aseptic medical products, having at least one microporous paper sheet wall, and a second thin flexible metal sheet wall, said walls being sealed together.
Third, to provide sealed containers for aseptic medical products, having at least one microporous paper sheet wall, and a second thin flexible, low dielectric constant material wall, said second wall having electric dipoles disposed on the inner container face thereof, and said walls being sealed together.
Fourth, to provide a process for rapidly producing aseptic medical dressings and the like, said dressing being prepackaged in containers having electric field strength concentrators disposed in said containers.
Other objects and advantages of this invention are taught in the following description and claims.
BRIEF DESCRIPTION OF THE DRAWING The description of the invention is to be read in conjunction with the following drawing, in which:
FIGURE 1 is an elevational perspective view of one container of this invention, having an electrical field strength concentrator.
FIGURE 2 is a cross sectional view through 22 of FIGURE 1.
FIGURE 3 is an elevational perspective view of another container of this invention, illustrating another type of electric field strength concentrator incorporated in said container.
FIGURE 4 is a cross sectional view through 44 of FIGURE 3.
FIGURE 5' is an elevational perspective view of still another container of this invention, illustrating a further type of RF electric field strength concentrator incorporated in the container.
FIGURE 6 is a partial sectional view through 66 of FIGURE 5 illustrating the details of the container construction.
FIGURE 7 is a cross sectional view illustrating the inventive advances in asepsis art now taught in sterilizing the packages of medical dressings disposed in the sealed containers of this invention, utilizing the apparatus and process disclosed, taught and claimed in the copending U.S. patent application of this date, titled Microwave Reactor and Process for Asepsis.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGURES 1 and 2 together, a pouch container 1 is first shown in elevational perspective view. A container perimeter sealed rim 2 is located inside the exterior edge 3 of the microporous paper sheet 4. The sealed rim 2 completely traverses inside the exterior edge 3 of paper sheet 4, providing a hermetic rim seal to the coextensive thin, flexible aluminum foil sheet 5.
FIGURE 2 illustrates further details of the container 1 construction. The thin, flexible aluminum foil sheet 5 is shown to be the sheet hermetically sealed to the sheet 4 at the perimeter rim 2. A medical dressing 6 is disposed inside the pouch container 1. A center line 8 bisects the sealed container 1. An ambient air atmosphere 6 is shown in the container 1. The thin, flexible aluminum foil sheet 5, typically 0.001 to 0.005 inch thick, functions as the electric field strength concentrator for this container 1 construction. The microporous paper sheet 4 typically has multiple 5 micron size, or the like, channel opening therein, which extend from a first face of the paper sheet 4 to the second face of the sheet. The microscopic channels provide openings in the paper sheet 4 for gas transpiration into and out of the container 1 for gas molecules such as oxygen or nitrogen of the atmosphere 6, and similar low molecular weight gases. The 5 micron size channel openings are too small to provide a passage for migration of the larger size bacteria, yeast, molds, spores or viruses in either direction. The microporous paper sheet 4, or the like, is typically a 35 pound weight bleached white kraft sheet, free from spots, dirt, holes. The sheet is sized to prevent liquid penetration. The paper sheet typically has a Gurley air porosity minimum of 80 seconds/ 100 cc. air leak. Thus by sealing a medical dressing 7 in a container 1 and then killing or permanently deactivating all living organisms inside the container 1, an aseptic dressing 7' can be prepared and stored in the container 1 prior to a required medical application.
The container 1 with the dressing 7 sealed therein, is cooperatively treated in the microwave reactor the copending application of this date by these coinventors, using the electric field strength concentrator foil sheet 5 to provide an aseptic dressing 7' in container 1, as taught below.
Referring to FIGURES 3 and 4 in detail, another pouch container 30 is shown in FIGURE 3 as a flattened rectangular container, having a hermetically sealed perimeter rim 31. The rim 31 is formed symmetrically about the center line 32, the rim 31 being formed by hermetically sealing together the microporous paper sheets 33 and 34. The microporous paper sheets 33 and 34 are of the same properties as paper sheet 4 and function in the same manner. Multiple, thin aluminum foil dipoles 35, 35', 35" of regulated length L and narrow width W are afiixed to the interior container face 36 of sheet 34, by adhesive or the like. At least one dipole 35 is required and more may be utilized for large containers. The dipoles length L is one-half the microwave length, and must be less than the inside breadth B of the container 30, providing termination of the dipoles inside the container volume. The gas atmosphere 37 inside the container 30 is typically air. The dipoles 35, 35' and 35" function as electric field strength concentrators in the process of producing a prepackaged aseptic medical dressing 38 in the container 30.
Still another modification of an electric field strength concentrator is illustrated in FIGURES 5 and 6 together. A multiplicity of point field strength concentrators 50 are shown in a partial sectional elevational view in FIG- URE 5. The point concentrators 50 are shown in exaggerated scale in the drawing, for they are actually metal particles to 50 microns in a length dimension, and they can he rodlets, spheres, cubes or irregular shaped. The metals are typically aluminum, iron, copper or the like. In FIGURE 6, the particles 50 are shown cooperatively affixed to the interior face 51 of the microporous papersheet 52. The container 53 has a hermetically sealed paper sheet 52. The container 53 has a hermetically sealed perimeter rim 54, which secures together two sheets of microporous paper 52 and 55. The point concentrators 50 can be adhesively affixed to the interior faces 51 and 56 of microporous paper sheets 52 and 51 respectively. The medical dressing 57 is located inside the container 53, in a gas atmosphere 58, typically air. The point concentrators 50 are typically disposed at an area concentration of 100 to 1000 particles per square inch of interior faces 51 and 56, being permanently secured to them by known means, such as adhesive films.
It is well known that the fieldstrength changes rapidly around a metal point, here represented by fine metal particles, located in the electric field. The electrical field E. around a point of radius R is E-V/R, where V is the impressed field voltage; hence, the smaller radius R produces the higher field strength E near the point. Thus, the greater rate of voltage drop near the points 50 produces field emission of electrons and subsequent avalanching of electrons to produce a low pressure gaseous glow discharge.
FIGURE 7 illustrates the utility of the containers 1, 30 and 53 in cooperatively adapting these containers and their respectively contained medical dressings 7, 38 and 57 to the apparatus and process taught and claimed in the copending application of this date by these co-inventors, titled Microwave Reactor and Process for Asepsis. In FIGURE 7 the container illustrated above in FIGURES l and 2 is shown cooperatively located in a cavity 70, operatively disposed for the sterilizing or asepsis process. The electric field strength concentrator sheet 5 of container 1 is disposed in a plane normal to and opposed to the transmission input direction 71 of the incoming microwave energy in the 2450'mHz. wave band. The microwave energy is transmitted through the glass window plate 72, which is transparent to the microwave energy. The metal reflector plate 73 reflects the incoming microwaves from the interior plate face 74. As taught and claimed in the above listed copending application, the center line 77 of the dressing 7 in the container 1 is disposed A wave length distance from the electric field strength concentrator sheet 5.
The container 1 is distended in the evacuation process in the cavity 70, due to the low rate of gas transmission through the paper sheets, as compared to the rate of gas removal from the cavity 70. The cavity atmosphere 6" and the container atmosphere 6' are reduced to the pressure range of 10 to 0.01 mm. Hg. At the higher air pres sure the glow discharge must be less than /2 second length to avoid ignition of the package and dressing. At 0.05 mm. Hg pressure, the glow discharge can proceed for up to 10 seconds without package destruction. Typically in a cavity of about 8 inches circular diameter, the cavity 70 can receive a power input of about 1000 watts at 2450 mHz. frequency.
The microwave frequency available for this process ranges from 890 to 22,250 mHz. Applying the wavelength formula )t=vc/f, where vc=microwave velocity, and f: microwave frequency; the wavelength is approximately 12.3 cm. and the wavelength is 3.1 cm. At the A wavelength distance of 3.1 cm. inside the container 1, the constructive interference of the microwaves reflected from the electric field strength concentrator sheet 5 is a maximum, and the microwave field strength voltage reinforcement is a maximum due to the standing waves. Hence at this distance, 3.1 cm. inside the container 1, there is maximum field voltage available to initiate low pressure gaseous glow discharge inside the container 1, due to electron avalanching in the ionized low pressure gas.
When using the A wavelength of 3.1 cm. at 2450 mHz., the containers 1 and 30 and the like, must be thick packages. When using the microwave frequency of 22,250 mHz., the wavelength 7\ is approximately 1.34 cm. and the wavelength is 0.34 cm.; hence, the containers 1 and 30 then can be relatively thin. When the point electric field strength concentrators 50 are used, the microwave frequency can be varied over the wide frequency range using the apparatus of FIGURE 7. The point concentrators 50 can operate effectively in activating glow discharge, due to the high potential drop about the points 50.
In the sterilization process taught in this invention the containers 1 and 30 and the like must be cooperatively disposed in the cavity 70 and the like in a position placing the electric field strength concentrator means 5 or 35, or the like, parallel to and opposed to the cavity wall transparent to the microwave range frequency. This geometrical arrangement disposes the A wavelength voltage reinforcement zone inside the containers 1 and 30, if
they are of the necessary thickness to accommodate the wavelength used. If the electric field strength concentrators 50 are used as in container 53 or the like, the containers 53 or the like can be randomly disposed in the cavity 70 or the like, parallel to the window 72 or the like, due to the righ potential drop about the points 50, making a precise geometrical positioning less critical.
In commercial production of medical dressing products product control containers of gauze medial sponges of construction typical of containers 1, 30 and 53 are placed in the sterilization apparatus and subjected to the sterilization process, along with the commercial production, to measure sterilization effectiveness. The control samples of gauze sponges are inoculated with the organism Bacillus pumilis, a bacteria having a very resistant spore. After sterilization of the commercial production lot, the control samples are removed and incubated for a period of up to three weeks on a broth of thio-glycollate. If the spores are not killed in the sterilization process, there is heavy growth of Bacillus pumilis in 24 hours.
Samples of gauze sponges inoculated with Bacillus pumilis, were sealed in containers 1, 31 and 53 and used as test samples for this invention. The containers were placed in the cavity 70 of a microwave reactor and evacuated to 100 micron air pressure, the containers lying on the window plate 72. Each dressing center line 77 was A distance from the inside face of the electric field strength concentrator, for the microwave frequency 2450 mHz. Approximately one kw. of generated microwave energy was transmitted down the wave guides and the expander horn of the reactor for a period of 1 sec. A second set of dressing samples were likewise irradiated for 2 sec. Both irradiated sets of samples had low pressure glow discharges generated inside each container. The treated gauze sponges when used to inoculate a thioglycollate broth, showed 100% bacterial kill after a period of three weeks incubation.
Many modifications and variations of our improvements in containers and process for asepsis may be made in the light of our teachings.
1. A flexible container useful for sterilizing medical products in a low pressure gaseous glow discharge asepsis reactor comprising: a completely enveloping container holding medical products disposed therein, having a hermetic perimeter sealed rim; a substantial first area section of said container being a thin, flexible, microporous paper sheet; and a second area section of said container having a microwave dipole electric field strength concentrator means; said first area section and said second area section being joined by said hermetic sealed rim, said container and medical products adapted to irradiation in a low pressure gaseous glow discharge.
2. In a flexible container of claim 1, the modification wherein said second area section of said container sheet has at least one thin, flexible, metal foil microwave dipole cooperatively adapted to adhere to said second area section inner face, the dipole length L being one-half the microwave length and the dipole having termini inside said second area section inner face.
3. In a flexible container of claim 1, the modification wherein said second area section of said container has at least one micro-sized metal particle dipole electric field strength concentrator cooperatively adapted to said second area section inner face.
4. In a process for sterilizing medical products prepackaged in a sealed, thin, flexible wall container, a substantial first area section of said container being thin microporous paper sheet, and a substantial second area section of said container having electric field strength concentrator means, the steps comprising: placing said sealed container in an evacuable cavity having at least one planar cavity wall transparent to microwave frequency, disposing said container in a position placing said second area section having electric field strength concentrator means parallel to and opposed to said cavity wall transparent to said microwave range frequency; evacuating said cavity and its contents to a gas pressure range of 10.0 to 0.01 mm. Hg; and irradiating said container for the time required to make the product aseptic, utilizing the low pressure gaseous glow discharge produced inside said cavity and said container by said microwave energy input transmitted into said cavity through said window.
References Cited UNITED STATES PATENTS 2,069,335 2/1937 Salfisberg 2293.5 2,937,279 5/1960 Artandi et al. 250-83 3,219,460 11/1965 Brown 21910.55 3,271,552 9/1966 Krajewski 21910.55 3,271,169 9/1966 Baker et al. 99-221 3,229,813 1/1966 Crowe, et al. 20663.2 3,302,632 2/1967 Fichtner 2l910.55 3,422,239 1/1969 Ojelid 21910.55
WILLIAM T. DIXSON, JR., Primary Examiner US. Cl. X.R.