Abstract:
A cell culture incubator ( 10, 72 ) is provided which includes one or more UV lamps ( 40, 116 ) allowing continuous or semi-continuous on-demand incubator sterilization. The incubator ( 10, 72 ) includes a thermally insulated cabinet ( 12, 74 ) having an internal working chamber ( 14, 76 ) and a hingedly mounted door ( 16, 78 ). The sterilizing UV lamp ( 40 ) may be mounted in a circulating airflow passageway ( 62 ) to continuously sterilize air circulating through the working chamber ( 14 ). Alternately or in addition thereto, the lamp ( 116 ) may be mounted in the door ( 78 ) with a reflector ( 114 ) for focusing the UV radiation into the working chamber ( 76 ). Preferably, short-wave UV lamps are employed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with incubators conventionally used for the incubation of cell-culture samples and which are improved by provision of an internal, continuous sterilization feature. More particularly, the invention pertains to such incubators equipped with internal ultraviolet (UV) lamps which can be user-controlled controlled to effect continuous or periodic sterilization of the internal working chambers of the incubators. 
     2. Description of the Prior Art 
     Cell culture incubators are ubiquitous in biological research laboratories. These units are designed to incubate cell culture samples, typically over a period of hours with closely controlled temperature and atmospheric conditions (e.g., 37° C. and 5% CO 2 ). Typically, incubators are in the form of an upright cabinet having an openable door and an internal working or incubating chamber equipped with a series of sample-holding shelves. Modern-day incubators normally have temperature and CO 2  sensors for maintaining desired internal conditions without operator intervention. 
     During the course of incubations, the internal working chambers of incubators can become contaminated with air borne or liquid contaminants. As a consequence, it is necessary to sterilize and decontaminate the internal working chamber and components of the incubators. Presently, such sterilization/decontamination is performed by one of two methods. In one technique, all removable components are autoclaved and non-removable components are manually wiped down with a germicidal solution. In another method, the incubator undergoes a sterilization cycle which heats the internal working chamber and its components to approximately 90° C. to kill any contaminants. Both of these prior methods are cumbersome and time-consuming. Manual decontamination requires significant labor, whereas a incubator sterilization cycle disrupts the incubator&#39;s operating temperature for several hours both during heating and the subsequent cool down period. 
     There is accordingly a need in the art for an improved cell culture incubator which avoids the sterilization/decontamination problems described above, and which allows continuous or intermittent sterilization/decontamination without upsetting the desired incubation conditions maintained within the working chamber of the incubator. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems outlined above and provides an improved incubator having an incubator cabinet presenting an internal working chamber wherein one or more ultraviolet lamps are operatively coupled with the cabinet for generating ultraviolet radiation capable of sterilizing the working chamber. 
     In preferred forms, the ultraviolet lamps are of the short-wave variety, generating UV radiation at about 200-280 nm. The lamps may be mounted at any convenient position within the incubator cabinet, e.g., proximal to the internal working chamber on a stationary wall thereof or on the cabinet door. The UV lamps may also be of any desired configuration such as tubular or serpentine in shape. 
     In one embodiment, a UV lamp is situated within an internal airflow path passing through the incubator working chamber. Thus, as incubation proceeds, the circulating air is continuously sterilized and decontaminated by the UV radiation. In another embodiment, the incubator cabinet door houses a UV lamp, and a reflector is used to direct sterilizing radiation into the incubator working chamber. 
     A particular advantage of the invention is that sterilization may be carried out with little or no disruption of the desired temperature and atmospheric conditions within the incubator working chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.1 is a perspective view of an incubator in accordance with the invention, shown with the shelves thereof removed; 
     FIG. 2 is a schematic vertical sectional view of an incubator in accordance with the invention, wherein the ultraviolet sterilizing lamp of the incubator is situated within a circulating airflow path; 
     FIG. 3 is a schematic vertical sectional view of another incubator in accordance with the invention, wherein the ultraviolet lamp is mounted within the incubator cabinet door; and 
     FIG. 4 is a vertical sectional view taken along line  4 — 4  of FIG.  3  and further depicting the configuration of the door-mounted ultraviolet lamp. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now the drawings and particularly FIGS. 1-2, an incubator  10  in accordance with the invention is illustrated. The incubator  10  is in the form of an upright cabinet  12  equipped with an internal working chamber  14  and a door  16 . The incubator  10  is adapted to receive and incubate a wide variety of biological samples. 
     In more detail, the cabinet  10  has a base  18 , upright sidewalls  20 ,  22 , rear wall  24  and top wall  26 . The base  18  and walls  20 - 26  are provided with thermal insulation as illustrated. The base  18  is equipped with an electrical resistance heater  28  whereas top wall  26  includes walls  30  defining a utility space  32 . The space  32  houses a blower assembly  34 , temperature sensor  36 , CO 2  sensor  38  and UV lamp  40 . 
     The working chamber  14  is made up of interior walls, namely bottom wall  42 , sidewalls  44 ,  46 , rear wall  48  and top wall  50 . The walls defining chamber  14  are located inboard of the outer cabinet walls, thus defining a surrounding plenum  52  which is adapted to receive an indirect heating medium such as air or water. Internally, the chamber  14  includes a top panel  54  apertured as at  55 , depending side panels  56 ,  58  and bottom panel  60 . It will be observed in this respect that the panels  54 - 58  are located inboard of the adjacent chamber walls  44 - 50 , thereby defining an airflow passageway  62  in surrounding relationship to the panels. This passageway terminates adjacent the lower end of chamber  14  with side marginal air outlets  64 . Finally, the outlet of blower assembly  34 , temperature sensor  36 , CO 2    38  and lamp  40  are all attached to top wall  50  and extend into the air flow passageway  62 . 
     The chamber  14  is typically provided with a series of vertically spaced shelves  66  which are perforated as at  68  to allow airflow therethrough. In addition, a water pan  70  is conventionally located atop bottom wall  42  to maintain appropriate humidity conditions within chamber  14 . 
     In the embodiment of FIGS. 1-2, the door  16  forming a part of cabinet  12  is entirely conventional and is hingedly mounted to cabinet sidewall  22  so as to completely enclose the chamber  14  when the door is closed. To this end, conventional seals (not shown) are employed to maintain an essentially airtight condition within the working chamber  14 . In the use of the embodiment of FIGS. 1-2, after appropriate temperature and CO 2  conditions are established (through the heating assembly and sensors  36 ,  38 ), samples to be incubated are placed on the shelves  66 . As incubation proceeds, air is circulated through the working chamber  14  by the action of blower assembly  34 . As shown by the air directional arrows in FIG. 2, air is directed from the blower assembly downwardly through the perforated shelves and passageway  62  where it then exits via outlets  64  and then passes upwardly through aperture  55 . In this connection, the provision of temperature controller  36  and CO 2  sensor  38  within the passageway  62  insures that appropriate temperature and CO 2  conditions can be maintained within chamber  14 . As those skilled in the art will appreciate, the sensor  36  is operatively coupled to the heating assembly for the incubator, and similarly the sensor  38  is used to insure constant C 0   2  concentrations. 
     The provision of UV lamp  40  also insures that the incubator may be continuously or semi-continuously sterilized. Typically, a short-wave (254 nm) UV lamp is employed in this context, which provides the necessary degree of sterilization without significantly raising the internal operating temperature. The duration of the UV lamp illumination may be controlled through circuitry program with the on-time duration for a particular incubation sequence. This permits user control of the duration of illumination of the UV lamp. In order to protect the user from potentially harmful UV radiation, a safety interlock system (not shown) in the form of a door switch is provided; the switch is operable to interrupt UV radiation from lamp  40  any time the door  16  is opened. 
     FIGS. 3-4 illustrate another incubator  72  having a controllable UV sterilization feature. In this case, the incubator  72  includes an upright cabinet  74  presenting an internal working chamber  76  and a hingedly mounted door  78 . The cabinet  74  and working chamber  76  are essentially conventional, i.e., the cabinet includes a base  80 , upright sidewalls, rear wall  82  and top wall  84 , all of which are provided with thermal insulation. The internal working chamber  76  includes top wall  86 , sidewalls  88 , bottom wall  90  and rear wall  92 , with vertically spaced sample-supporting shelves  93 . The latter chamber-defining walls are spaced from the primary cabinet walls so as to define a plenum  94  allowing introduction of indirect heat exchange media. The cabinet  74  is also equipped with an internal transparent glass door  96  which covers the front face of working chamber  76 ; appropriate peripheral seals  98  are provided for maintaining a substantially airtight condition within the chamber  76 . 
     The door  78  of cabinet  74  includes a bottom wall  100  equipped with an airflow passageway  102 , upright sidewalls  104 , front wall  106  supporting a resistance heater  107 , and top wall  108  having airflow passageway  110  therethrough. The walls  100 - 106  are provided with thermal insulation. As shown, the door  78  is generally U-shaped in vertical section, thus defining an internal concave area  112 . The area  112  houses a polished aluminum reflector  114  as well as a serpentine-shaped UV lamp  116  positioned adjacent and in front of the reflector  114 . Marginal seals  118  extend about the inner periphery of door  78  and engage corresponding surfaces on the cabinet  74 . 
     Although not shown in FIGS. 3-4, it will be understood that the incubator  72  has the usual internal condition control features, e.g., temperature and CO 2  controllers. Moreover, it also has the interlock feature of the first embodiment, namely a switch  120  associated with the door  78  so that upon opening thereof the UV lamp  116  is de-energized. 
     In the use of incubator  72 , desired temperature and CO 2  conditions are established within chamber  76  and doors  78  and  96  are opened to permit placement of samples on the shelves  93 . The doors are then closed and incubation proceeds in the normal fashion. As a part of the incubator procedure or thereafter, the lamp  116  (which again preferably is a short-wave 254 nm lamp) is activated. Radiation from this lamp is reflected by reflector  114  through the glass door  96 , thereby sterilizing the internal working chamber  76 . In order to provide the best sterilization control, the lamp  116  may be programmed for particular on-time duration(s). During such operations, air passes by convection upwardly through the passageways  102 ,  110  provided in the door bottom and top walls  100 ,  108 . 
     Although the embodiments of FIGS. 1-2 and  3 - 4  have been described separately, it will be understood that a given incubator could be provided with UV sterilization lamps both as a part of the stationary cabinet structure (as in FIGS. 1-2) and as a part of the cabinet door (as in FIGS.  3 - 4 ). In addition, UV lamp(s) may be situated at different positions so long as the UV radiation is effective for sterilizing the working chamber of the incubator.