Chemistry: molecular biology and microbiology – Apparatus – Bioreactor
Reexamination Certificate
1999-04-02
2001-01-30
Beisner, William H. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Bioreactor
C435S286600, C435S809000, C422S105000
Reexamination Certificate
active
06180397
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This application relates to the field of incubators and more particularly to the field of incubators having an external gas feed.
2. Description of Related Art
Incubators are used to cultivate cell cultures. It is desirable to maintain inside the incubator which receives the cell cultures, conditions which are most advantageous for providing optimum cell growth. Particularly important is a constant temperature and a high relative humidity.
Typically, incubators with an external gas feed also maintain in the interior space of the incubator an interior atmosphere with a constant mixing ratio between air and the added gas, which is typically CO
2
.O
2
or N
2
may also be added if desired. In order to compensate for disturbances that occur when the incubator with the external gas feed is opened, the gas concentration in the interior space is measured and the gas supply is regulated to maintain a constant gas-to-air mixing ratio.
Conventional incubators with an external gas feed typically include a fan to thoroughly and uniformly mix the added gas with the interior atmosphere. The fan can be implemented in form of a miniature fan, with the drive motor of the fan also arranged in the interior space. Alternatively, only the fan wheel can be placed within the interior space, while the drive motor is located outside the incubator housing. The fan with the drive represents a relatively complex and expensive component. The moving parts of the fan located in the interior space are typically heavy and are also difficult to clean and sterilize, so that the fan itself can pose a contamination risk. If the drive motor is located outside the interior space, then the drive shaft for the fan wheel has to penetrate the wall of the inner vessel of the incubator, which requires an opening and therefore also increases the contamination risk. Moreover, a fan tends to whirl the airborne germs that exist in the interior space, around and spread these germs over the cell cultures.
It is desirable to provide an incubator with an external gas feed that is less complicated and less expensive to build and that also reduces the contamination risk.
SUMMARY OF THE INVENTION
In general, according to one aspect of the invention, the gas is introduced into the interior space in form of a gas jet, wherein the injector effect of the gas jet is advantageously employed to mix the gas with the interior atmosphere. The gas injected through the gas nozzle entrains the air/gas mixture of the surrounding interior atmosphere, so that the injected gas is rapidly and thorough mixed with the interior atmosphere.
The injector effect may be improved by incorporating in the gas nozzle a jet tube, wherein the gas jet of the jet tube flows coaxially into a mixing tube. The injector effect of the gas jet creates in the annular space between the jet pipe and the mixing tube a reduced pressure which enhances the suction with which the surrounding interior atmosphere is drawn in and produces an improved mixing effect.
The gas nozzle is a simple component and may be made of stainless steel. The gas nozzle can be manufactured cost-effectively and does not require an external drive or a supply of energy. Due to the simple design and the choice of material for the gas nozzle, and more particularly due to the fact that the gas nozzle does not include moveable mechanical parts, the gas nozzle can be easily and thoroughly cleaned and sterilized.
During operation of the incubator with an external gas feed, only small quantities of gas have to be added to compensate for gas losses. The flow cross-section of the gas nozzle can therefore be kept small, which is advantageous for producing the required flow momentum of the gas jet. The small flow cross-section has the additional advantage of restricting the overall gas flow exiting the nozzle. In the event of, for example, a malfunction of the regulator which could allow gas to flow out of the gas nozzle unintentionally over a longer period of time, the total amount of gas that leaves the gas nozzle is still relatively small as a result of the small flow cross-section of the nozzle. This feature largely eliminates interruptions in a laboratory operation or injuries to the persons working in the laboratory.
The gas nozzle is preferably arranged on the top surface of the interior space of the incubator. With this arrangement, the gas jet is not obstructed in its downward motion inside the interior space and can therefore unimpededly draw in the interior atmosphere from all sides to optimally mix the gases. Typically, the supplied gas is CO
2
which is heavier than air. Consequently, the CO
2
gas entering the interior space moves downwardly also due to its higher specific gravity, thereby extending the path of the gas to attain a complete mixing with the interior atmosphere.
The concentration of the supplied gas is typically determined with a gas sensor located in the interior space. The measured concentration is used to regulate and control the mixing ratio of the interior atmosphere. The gas jet is preferably injected in close proximity to the gas sensor, allowing the gas sensor to respond quickly and thereby reducing the inertia of the control system.
Further features and advantages of the present invention will be apparent from the following description of preferred embodiments and from the claims.
REFERENCES:
patent: 4689303 (1987-08-01), Kraft et al.
patent: 5418131 (1995-05-01), Butts
patent: 5800335 (1998-09-01), Koch et al.
patent: 117 329 (1976-01-01), None
patent: 0 131 541 (1984-05-01), None
patent: 60-110284 (1985-06-01), None
patent: 6-245753 (1994-09-01), None
Beisner William H.
Foley Hoag & Eliot LLP
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