Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact steam to disinfect or sterilize
Reexamination Certificate
2000-09-15
2003-07-08
Thornton, Krisanne (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using direct contact steam to disinfect or sterilize
C422S027000, C422S028000, C422S031000, C422S033000, C422S292000, C422S295000, C422S297000
Reexamination Certificate
active
06589478
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
2. Description of the Background Art
The invention relates to a process and a device for carrying out the disinfection of flat and enclosing surfaces using steam, which comes into contact with the surfaces to be disinfected.
Surfaces are disinfected in a number of different ways in order to avoid the transferral of undesirable pathogenic micro-organisms to humans and animals. The most common method is disinfection using chemicals, the use of which, together with the prescription of antibiotics in the past, has been associated with environmental problems, and is also increasingly leading to the development of higher levels of resistance to micro-organisms.
This means that, especially in hospitals, there is increasing concern about the development of multi-resistant disease pathogens, which no longer react in the desired way to various disinfectants or combinations thereof.
Another recognized method which is mostly used for smaller objects, such as medical instruments, is heat disinfection. However, this requires such long times and high temperatures to be effective that its application in many areas is either impractical or economically unviable, especially where enclosing surfaces are concerned.
Therefore, a disinfection device which works simply and without the use of harmful chemicals and which adequately removes all pathogenic and undesirable micro-organisms would be useful in a number of places where hygiene plays a crucial role, such s as hospitals, canteens, animal holding and storage centers for food manufacturers and sanitary areas.
There are indications that a technically simple, cost-effective steam cleaning method could be considered as a new method of disinfection. The example applications published to date work on the assumption that the temperature and the pressure of a steam cleaner have a disinfecting effect providing the time is measured properly.
Most of the advertising statements about alleged disinfection effects made in the past by various manufacturers have had to be withdrawn because the disinfection results tested at random did not stand up to closer scientific scrutiny and therefore did not fulfil the requirement of reliability which is crucial to any disinfection process.
A doctorate commenced in 1994 at the Institut for Tierhygiene, Verhaltenskunde und Tierschutz [institute for animal hygiene, behavioural science and animal welfare] at the Ludwig-Maximilian University in Munich investigated steam cleaning as a potential method of disinfection.
The results of these investigations were published at the 6th Hohenheim Seminar from Sep. 23-24, 1996 by A Haas, S Platz and J Unshelm, in a presentation on the subject of “Environment and animal hygiene”. The results showed that the effective time required for the use of steam, which had been calculated on the basis of results for thermal disinfection, could actually be drastically reduced to 5-10 seconds. However, these results relied on the apparatus tested (Uninova Hausgeräte GmbH) which had specific technical characteristics including a cloth stretched over the steam outlet and a minimum distance of 2.5 cm from the cloth to the specimen slide. The results were only achieved under laboratory conditions, and did not answer the question as to whether the system could be applied in practice on an economically viable basis, especially for relatively large surfaces.
Patent specification DE 41 08 538 A1 describes a process for heat disinfection of surfaces, especially sealed areas through which an agent could flow. During the process described, a heated medium which forms a mist and is capable of flowing is brought into contact with the surfaces to be disinfected. The is specifications suggest that a pipe connected with the pathogen Pseudomonas aeriginosa was free of bacteria after only a few minutes of contact with steam, as the mist-forming medium, at a temperature of between 70 and 90° C.
This process is primarily used for rinsing out pipes with steam, and not for the heat disinfection of relatively large surfaces using water alone (as detailed above), as the above patent specification suggests that the disinfectant could also be added to the water or that the disinfectant could be used alone.
An illustration of the way that steam cleaners work, published by B Bullemer on Nov. 15, 1993 to clarify the scientific background, comes to the conclusion that the reaction that supplies the energy for steam cleaning is the recombination of steam molecules into water. A hypothermic energy supply from condensing steam was proposed as an alternative disinfection method by the same source on Apr. 10, 1995.
However, the fact that it cannot be assumed that the user has adequate knowledge of the principles of thermodynamics proved to be a major problem. Even the aforementioned doctorate to explain the disinfecting effect of steam cleaners does not go into detail on the physical principles at work and the publication detailed presents the results of experiments under laboratory conditions, although external conditions which are constantly changing, such as those that can be caused by different temperatures or pressures on different surfaces, are not taken into consideration.
SUMMARY OF THE INVENTION
Therefore, the aim of the invention is to provide a process and a device to carry out the process, as described at the beginning, such as to enable cost-effective disinfection of flat and enclosing surfaces with as short as possible an effective time for the superheated steam used and to increase significantly the levels of reliability under application conditions which are constantly changing, thus increasing the range of applications to as many micro-organisms as possible.
In order to achieve this aim, the invention proposes guiding the steam through a specially designed disinfection head. The disinfection head should be movable, connected to the inlet hose for the steam via a holder with a handle, then connected via a preliminary chamber to a nozzle assembly which maintains a distance of 2.5 cm (considered to be the optimum distance) from the surface to be disinfected and forms a steam chamber with the front section of the housing of the disinfection head.
The disinfection head is surrounded by a suction bell and sucks away the condensed steam produced via suction nozzles on the disinfection head.
The suction nozzles flow into a joint outlet suction hose inside the plastic holder holding the disinfection head and take the condensed material to a collection container, from where it is again, taken back to the initial evaporator cell of the device and sterilized.
An important element of the disinfection head is the nozzle assembly through which the steam is guided such that when it reaches the surface to be disinfected, it does not contain a drop of liquid water.
The nozzle assembly controls the main flow of steam by initially retarding it and then distributing it on a surface which can be used economically.
At the same time, the nozzle assembly prevents the steam coming out onto the surface to be disinfected at too high a pressure, causing unnecessary disruption to the micro-organisms. The fact that the flow of steam is split up into a number of steam channels increases the number of condensation processes in the steam chamber. As a multiple of the average heat energy of the boiling point of water is discharged onto the disinfection surface, which is riddled with micro-organisms, for every condensation process, an increased number of openings through the nozzle assembly improves the utilization of energy, which is critical to the success of the disinfection process.
It transpired that the effective time could be reduced if the number of openings was increased. The results were checked on test cultures of Staphylococcus aureus and Pseudomonas aeruginosa under the following variable external environmental conditions and on different surfaces: wooden surfaces in cold stores at temperature of 6° C., metal surfaces in operating theaters at a temperature of 17° C. and und
Keim Bettina
Schaffer Martin
Genoveva Beurer
Thornton Krisanne
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