Abstract:
Controlled atmosphere cabinet has enclosure ( 110;210 ) with means providing visibility ( 110 F;  210 F) of its interior from outside, gas supply ( 113-116, 212-216 ) for desired or target composition of internal atmosphere, controlled lock-type access ( 112 ) for manual introduction and removal of items, and hand/arm access port provision ( 111 A, B;  211 A, B) for manipulation of said samples in the cabinet. Gas supply associated control means ( 230-240 ) serves during use of the cabinet (other than normal atmosphere augmenting in use of the lock-type access) for additional gas supply further to correct or compensate for effects actually or potentially adverse to maintaining the desired or target internal atmosphere composition, via operator-actuated input means ( 121 t,  123; 222 ) and/or means ( 122, 124, 139; 225 ) for sensing prescribed conditions to which the control means is responsive for said additional gas supply.

Description:
DESCRIPTION 
     This invention relates to controlled atmosphere equipment, such as, but not limited to cabinets useful in microbiology laboratories for maintaining a prescribed or prescribable atmosphere, not necessarily anaerobic. 
     Typical so-called variable atmosphere microbiological nurture cabinets are known, including as we have previously supplied commercially, with provision for an operator to set a desired internal atmosphere composition, typically relative to content levels of hydrogen and/or carbon dioxide and/or oxygen and/or nitrogen. Such desired composition can be set by flow rates of constituent gases, typically from cylinders as compressed supplies thereof. 
     Aspects of this invention arise by way of seeking to improve actual internal cabinet atmosphere in terms of better maintaining or departing less from a desired or specified target for the atmosphere actually within the cabinet, effectively to compensate or correct for actually or potentially adverse relevant effects, say from greater/other than normal use including as to loading and unloading the cabinet, or due to the microbiological activity taking place within the cabinet having differential effects on component gases of target atmosphere. 
     In a first incentive aspect, a specified gas mixture for supply purposes in setting up some target internal atmosphere is subsequently further supplied after such setting up not only so as to maintain any desired internal normally slightly positive atmospheric pressure, say as demanded by reference to a pressure switch or transducer, but also on a regular basis- which may be adjustable, whether by operator selection or in response to sensed conditions, say effectively as a prescribable circulation involving both gas-supply and removal or venting. 
     Such circulation can, with advantages be done by injection of more gas before removal or venting, i.e. increasing normal overpressure, say until sensed by a suitable device then automatically causing opening of gas removal or venting valve provision, whether simply relative to achieving such overpressure or for a further prescribed time of gas supply and/or relative to reducing to a lower, say normal, overpressure at least after such prescribed further times of further gas supply. 
     It is found to be particularly convenient for at least such prescribable regular further gas supply to be accompanied by positive removal of any accumulated condensate, say preferably using a peristaltic pump which can also contribute to or assist in cabinet atmosphere removal, at least after condensate removal is complete. 
     Beneficial effect can be simply to increase tendency towards maintaining a prescribed or target atmosphere, say as represented by flow rates of constituent gas. Further beneficial effect can be gained by taking account of such effects of particular microbiological action(s) of current interest as may be known or determined by further investigation in terms of differential effects on component gases, say than by further prescribed modification of supplied gas mixture, as further supplied, say increasing flow rate(s) of one more and/or reducing other(s), i.e. compared to normal target mix flows, god according to type of such action(s) or further as to number(s) of samples involved. 
     Yet closer internal atmosphere control can be obtained by sensing particular content(s) of one or more or all of constituent gases and computing individual gas flow rates to compensate, whether wholly or partly. 
    
    
     Specific implementations in practical embodiments of this invention will now be indicated and described, by way of example, with reference to the accompanying diagrammatic drawings, in which 
     FIG. 1 is an outline atmospheric gas flow control provision for a first embodiment; 
     FIGS.  2 . and  3  are modifications or alternatives; 
     FIG. 4 is an outline atmosphere control provision for another embodiment; and 
     FIGS. 5A, B, C show flow diagram(s) for the show embodiment of FIG.  4 . 
    
    
     The embodiment and modifications/alternatives of FIGS. 1-3 were first developed as add-on provisions for anaerobic cabinets found to experience unexpected loss of adequate anaerobic internal atmosphere conditions; and afforded an immediate solution irrespective of reasons for such loss, as well as having wider application to other controlled atmosphere cabinets and immediately appreciated scope for further development and refinement eventually resulting in the embodiment of FIGS. 4 and 5. 
     In FIG. 1, a controlled atmospheres cabinet  110 , specifically an anaerobic cabinet with user access porting  111 A,  111 B through its transparent front  110 F and entry lock provision  112  (which could be internal and/or associated with the porting  111 A, B), is shown supplied with a pressurised gas mixture from a regulated cylinder  113  over conduits or pipes  114 A,  114 B through conventional relay-and/or solenoid-operated valve  115 . A separate entry lock provision  112  as shown may well have atmosphere flushing etc, whether from the main chamber of the cabinet  110  for branched from supply  113 ,  114  and separately controlled. In use, the valve  115  is opened whenever and whilst internal cabinet atmosphere pressure falls and remains below some predetermined level, usually a small over-pressure compared with external ambient pressure, causing a pressure switch  116  to open the valve  115 , see electrical connection from its terminal  117 A connected to line  119 . 
     The valve opening line  119  is also shown fed from output of a timer  121 , which may be variable, see dashed for setting provision  121 S. The timer  121  is preferably settable both as to interval between energisations of its output and as to durations of such output energisations, whether by service, etc engineers&#39; settings or by operator setting, see line  121 T, including through such as analogue potentiometer etc type knob(s) or slider(a) etc or such as numeric keyboard operation. 
     Usually, in order to ensure that an anaerobic cabinet not to go aerobic,, perhaps due to greater that expected rates or times of loading/unloading when act up for maximum economy and/or using gas mixtures of below 10% hydrogen content, it is has been established as normally sufficient to have only a few seconds of timer-controlled duration of atmosphere enhancement each hour or so, though that is a matter for variation as required or preferred, including greater or lesser durations at longer or shorter intervals. The timer  121  is shown interlocked with complementary output  112 B from tie pressure switch  116 , whether at each or selected operations of the pressure switch  116 , simply to assure independence of respective valve opening control, perhaps temporarily to disable or to interrupt incrementing of a timer counter or to reset its interval timing; or to ensure enhancement immediately or otherwise predeterminedly after each loading/unloading usage of the cabinet, say by forcing a counter state; and/or temporarily to select alternative duration for opening the valve  115 ; or whatever condition may be found to be helpful in terms of timer control. 
     FIG. 1 further bas dashed indication of other provision(s)  122  for operating the timer  121  according to some other parameter, including as an on-demand operation of its output for its set or some selected duration, see line  123 . Alternatively, another and independent timer, or different duration setting provision  124 , may be made feeding directly to the valve operating line  119 . Such other parameter may be of atmosphere or other conditions inside the cabinet  110 , or of usage rate/durations of entry lock provisions, or of environmental conditions such as ambient humidity outside the cabinet  110 , all as can be detected automatically by suitable sensors or control system monitoring; or of samples being cultured, as may be pre-set but requiring entry via selection to provisions of the cabinet control system. There can, of course, be as many other parameter provisions  122  as required or desired, and some may be of efficiently combined and/or multiplexed regarding timing etc, say using programmed microprocessor control. 
     FIG. 2 shows a modification or alternative where an additional supply  125 , say of hydrogen (or some other additive appropriate to some other parameter), is activated by branch  126  from feed connection to line  119  and applied to the normal atmosphere maintaining gas(es) through an appropriate mixing provision  127 , whether of passive, nature, or active and requiring actuation (see further dashed branch from line  119 ). 
     Such additional component supply could, of course, be directly to the cabinet  110 , as at  131  in FIG. 3, which shows at  132  plural other parameter-dependent operating provisions OP 1 -OFN each with its own duration setting stage  132 S (though some could share same if appropriate), for operation of its own additional component supply means  133  through a delivery manifold  134 . It will be appreciated that programmed microprocessor control will be of useful simplifying effect as interface input, between sensors and output signals each readily timed as to their occurrence and durations. Further provision is shown for other or standard atmosphere gas(es) to scour the delivery manifold and/or appropriately dilute the added component, by way of opening valve  135  in a branch line  136  from the basic atmosphere gas supply  114 A, as may be useful for at least some of the added components for which outputs are shown taken through OR-gate  137  to valve control line  139 . 
     It will be appreciated that such provisions  131 - 139  may be extra provisions compared with basic and/or more sophisticated operation by way of extra pulses of pressurised atmospheric gas alone. 
     Turning to FIG. 4, prescribable atmosphere cabinet shown with gloved/sleeved manipulation access ports  211 A, B through transparent front  210 F; related individual gas supplies  212 A-D and associated flow valves  213 A-D; overall gas manifold  215  and supply isolation valve  216 ; control/instrument ate panel  220  in relation to a data display  221  and data entry keypad  222  (both further shown separately for convenience); and programmable logic controller  230  typically affording PROM program storage, digital data processing, configurable logic, and input and output provisions  231  and  232  additional to display output and data input bus provisions  233  and  234  associated with display  221  and keypad  222 . 
     The cabinet  210  may provide access through lock provisions built into the ports  211 A, B as we have lately been providing. However, other access lock provisions could be made, say, normally as at  112  in FIG. 1, or otherwise, say as we have also lately been providing. 
     Prescribing atmosphere for interior of the cabinet  210  is under operator control through keypad  222 , but preferably code-word protected. One particular arrangement of keypad  222  and associated display  221  has keys or touch-pads for various generally conventional purposes, including data message display M, which may be considered/used as a normal display mode, say showing current prescribed atmosphere, which, in the illustrated case, will be as percentages of hydrogen ( 225 B), oxygen ( 225 C), carbon dioxide ( 225 D) and nitrogen ( 225 A), perhaps further indicating any departure (s) therefrom where the cabinet  210  has individual component gas sensor,(s), say for up to each of hydrogen, oxygen and carbon dioxide with nitrogen being treated as a computable balance. Use of the key/pad (A) for adjustment preferably will call for code/pass-word entry say as a decimal number using up to four or more digit positions using the plus (+) and minus (−) keys/pads for each digit position and the arrow keys for moving between digits, making such use as may be required of the clear (C) key/pad before using the entry (E) key/pad. Correct entry of the code/pass-word will give access for similar data entry relative to the desired change of prescribed atmosphere. A highly useful and advantageous feature is preferably built into the logic-controller  30 , namely capability for disallowing certain atmosphere specifications, whether in view of established effectiveness criteria or for other reasons such as safety, e.g. for the gases shown in the drawing, not allowing more than predetermined maxima for hydrogen (say up to 9%) and/ or oxygen (say up to 20%) and/or carbon dioxide (say up to 20%), nor permitting an explosive, even flammable or flame supporting, mixture—say limited against known objectionable percentages of 5% or more hydrogen in 6% or more oxygen. 
     Two other keys/pads are shown, one (O) being an overall options menu, including to give access to such as making changes to the code/pass-word, and the other serving the well-known purpose of giving engineers&#39; access to data concerning actual functioning and/or diagnostics for the cabinet  210 . 
     Relative to any particular prescribed atmosphere, the programmable logic controller  230  will compute individual gas supply requirements, which, at simplest, may be as times for individual gas flows at nominal flow rates from compressed cylinders  212 A-D therefor through preset types of valves  213 A-D. However, it is further feasible and practicable for actual individual gas flow rates to be sensed and times computed accordingly. Alternatively, settings might be computed for application to output valve gear of the cylinders  212 A-D and/or for application to variable flow-rate types of valves  213 A-D, and for such settings to be applied automatically over suitable further connection provisions than are presently illustrated. 
     Other controller inputs  235  are shown including outputs from normal over-pressure and higher over-pressure sensors  236  and  237 : actually being shown further additional to lines from the individual gas content sensors  225 A-C. Specific venting valve  238  is also shown for the cabinet  210  along with preferably peristaltic type condensate removal pump  239 , see as controlled by respective outputs  240  of the programmable logic controller  230  having other outputs to control individual gas supply valves  213 A-D and overall isolating valve  216 . 
     Operation matching what is already known can involve response to lower than normal slight over-pressure, sensed at  236 , causing simple or computed operation of the valves  213 A-D (if appropriate  216 ) for supply of gases according to prescribed proportions until or so that normal slight over-pressure is reached, perhaps usefully ensuring small excess to require operation of venting at  238 . Additional operation to add periodic, i.e. regular, or on-demand, i.e. including according to some specific criteria, further amounts of gases is readily afforded by programming and/or operators&#39; command and/or according to entered data at and by the controller  230 . Such further gas supply operation can be simply in accordance with atmosphere as originally or nominally specified; or different as might be entered by an operator for corrective or other reasons; or according to information and/or computation relative to differential gas effects for actual or intended samples in or for the cabinet  210 ; or, indeed, as a direct response to individual gas content sensed at  225 A-C requiring individual or other adjustment. 
     Operational options further include either not venting for additional gas supply resulting in between normal overpressure ( 236 ) and higher (but still safe) over-pressure ( 237 ), or perhaps venting less quickly than such supply will increase overpressure. Combination of positive additional gas supply and cabinet atmosphere removal or venting is seen a beneficial circulation at least better approaching nominal atmosphere specification. Convenience suggests simultaneous removal of accumulated condensate by at least partially synchronous operation of the peristaltic pump  239 , which can, of course, itself contribute to circulation and atmosphere removal and replacement. 
     Operator usage, particularly loading and unloading, and amount of microbial growth of particular loads, will obviously affect need for additional supply of gas(es), and relevant data entered by the operator can facilitate useful calculation by the controller to set parameters including durations and intervals between such actions. 
     One practical flow diagram for program-controlled microprocessor-based, control logic and processing block  230  is given in FIG. 5 relative to decision-making (diamond), function-performing (parallelogram) and various flag-setting (rectangle) steps well-known for computer programs, and all of which are believed to be self-explanatory in the light of preceding description.