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INCUBATION STATION FOR TEST SAMPLE CARDS bioMerieux Vitek, Inc.C:30317

INCUBATION STATION FOR TEST SAMPLE CARDS

BACKGROUND OF THE INVENTION 10 A. Field of the Invention

This invention relates generally to the field of analytical instruments forconducting biological sample testing, and more particularly to an incubation station for ananalytical instrument that incubates test sample cards or the like. The test sample cardshave one or more wells for containing a fluid or test sample containing a microbiologicalagent (such as a microorganism) and a reagent. The incubation station maintains the testsample card at a predetermined desired temperature (such as 35.5 0 C) so as to promote areaction between the microbiological agent and the reagent. 15 B. Description of Related Art A variety of test sample cards are described in the patent literature which have awell or reaction site for receiving a fluid sample containing a microbiological agent, suchas a microorganism, and a reagent. Several representative patents include Meyer et al., 20 U.S. No. 4,318,994, Charles et al., U.S. No. 4,116,775; Fadler et al., U.S. No. 4,038,151, O’Bear et al., U.S. No. 5,609,828 and Charles et al., U.S. No. 4,118,280. These patentsdescribe a test sample card having a plurality of wells arranged in the test sample cardbody. The reagent is typically loaded in the wells of the card during the completion ofmanufacture of the card. The reagent typically comprises a growth medium for the 25 microbiological agent. It is known to load a different reagent in each of the wells of thecard in order to perform identification testing of a fluid sample containing an unknownmicrobiological agent or organism. It is also known to use the cards to test themicrobiological agent for susceptibility to antibiotics by loading various antibioticreagents into the wells.

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In the sample testing system described in the Charles et al ‘280 patent, after thewell of the test sample card has been loaded with the fluid sample, the card is incubatedfor a period of time (typically between 2 and 18 hours at a temperature of approximately35° C) so as to promote a reaction between the microorganism and the reagent, i.e., 5 growth of the microorganism. During the incubation period, the well is periodicallysubject to optical analysis by a transmittance light source and a detector which arepositioned on opposite sides of the well, or by alternate detection methods. If the growthmedium or reagent is specifically suited for or “matches up” with the particularmicroorganism in the fluid sample, the population of the microorganism increases 10 substantially, or some other predetermined reaction, i.e., chemical reaction, takes place,which results in the well turning cloudy and thus having a change in light transmissioncharacteristics. The detector determines the amount of light that is transmitted from thesource through the well. By comparing the transmittance measurement over a period oftime, typically several hours at least, with an initial transmittance measurement, it is 15 possible to determine whether in fact the reagent and microbiological agent are matchedby virtue of the change in transmittance measurement reaching a threshold value, such as25 or 30 percent. The change in light transmission characteristics therefore can be usedto indicate the presence of a specific microorganism in the well for purposes ofidentification or determine its sensitivity to antibiotics. Identification and susceptibility 20 may also be detected by other optical measurements such as fluorescence where afluorescent agent is provided in the growth medium. These methods could also be usefulfor other temperature dependent kinetic assays such as analytical chemistry or nucleicacid probe based testing.

Due to the fact that the test sample cards described above are often used in clinical 25 and industrial laboratories to identify unknown microorganisms in human test samples, 2 10 15 20 or food test samples generally for the purpose of diagnosing or detecting disease causingmicroorganisms, the art has recognized that the time required for incubation of the testsample card should be kept to a minimum, so that results can be obtained as quickly aspossible. Further, since multiple cards are typically incubated simultaneously in ananalytical instrument, it is important that the incubation station be designed such that allof the cards be maintained at the same incubation conditions for relatively long periods oftime. Additionally, the card should be incubated in a manner in which all parts of thecard are maintained at the same temperature and air flow, so as to provide an eventemperature and oxygen distribution to all the wells in the test sample card.

The incubation and reading station described in the above-reference Charles et al.‘280 patent meets these requirements fairly well, and has been commercialized withsuccess by the assignee of the present invention. However, the station is essentially amanual station, in that it requires the test sample cards to be externally prepared andmanually loaded into station. As such, this design is not optimal for use in a fullyautomated analytical instrument in which the cards are prepared (i.e., loaded with the testsample) and introduced into and removed from the incubation station automatically.Achieving the above-described performance criteria for an incubation station in a fullyautomated analytical instrument is a particularly difficult task.

The present inventors have developed an incubation station for an analyticalinstrument that is a part of a fully automated system. The station is described in detailherein. In the process of developing the station, they have made several discoveries.First, the physical structures or framework that hold the cards in place in the incubationstation can adversely effect the even flow and distribution of warm air introduced into theincubation station. Second, this disruption in the distribution of warm air, caused by thecarousel structures can lead to localized pools of warmer and cooler air or variances in air 3

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10 15 20 25 flow across the card, which can adversely affect the even or uniform incubation of thecard and prolong the amount of time required to incubate the card sufficient to achieve atest result. Third, the inventors have also discovered that the temperature and/or airflowat various locations in the incubation station are different relative to card position by anamount that is also sufficient to adversely affect the time needed to obtain test results.The inventors have also discovered that the solution to these problems has been toincorporate novel features in the construction of the incubation station that optimizes theflow of warm air over the test sample cards, and that accounts for or is accord with thegeometry and spatial distribution of wells in the card and structures that hold the cards inplace in the incubation station.

As a result of these findings, the inventors have created a design of a incubationstation for a test sample card that is not only particularly well suited for use in anautomated analytical instrument, in that it is a fully automatic system, but have alsodesigned the incubation station to achieve a substantially constant temperaturedistribution and air flow around the test sample cards for as long a period of time asrequired to incubate the test sample card.

Accordingly, a principle object of the invention is to provide a fully automatedincubation station for an analytical instrument for test sample cards that does not requiremanual loading of the cards into the incubation station.

Another object of the invention is to provide an incubation station for an analyticalinstrument that provides for even temperature distribution and air flow throughout theincubation station, so as maintain all of the test sample cards at the proper temperature and air flow throughout the incubation period. (

Yet another object of the invention is to provide an incubation station for ananalytical instrument that maintains the entire test sample card at the proper temperature 4

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10 and air flow and avoids localized differences in air flow or warm or cool sites on the test sample card.

Yet still another object of the invention is to provide an incubation station that isof a relatively compact size and construction, so as to reduce the volume of space required for the incubation station.

Still another object of the invention is to provide a novel air distribution tablestructure in an incubation station that has an arrangement of openings that promotes theeven distribution of air flow over the test sample cards installed in a carousel in the incubation station.

Another object of the invention is to provide a novel carousel structure in whichthe carousel is divided into discrete segments, and provide a means to remove thecarousel segments to promote easy insertion and removal of the segments for cleaning and maintenance. 5

SUMMARY OF THE INVENTION

An incubation station for a plurality of test sample cards is provided. Theincubation station includes a circular carousel having a plurality of slots for receiving thetest sample cards. The carousel has a front side portion and an opposite rear side portion.An enclosure is provided for enclosing the carousel and which has at least one openingtherein for admitting warm air into the enclosure.

An air distribution plate or airflow table is provided adjacent to the rear sideportion of the carousel and in communication with the opening, for directing said warmair over a plurality of card receiving slots in the carousel from the rear side portion of thecarousel. In order to improve air flow over the slots of the carousel, the rear side portionof the carousel adjacent to the air distribution plate is substantially open and free ofobstructions so as to permit uninterrupted air flow over the test sample cards sufficient tomaintain a substantially evenly distributed and substantially constant temperature and airflow over the test sample cards in the carousel. The front side of the carousel is alsosubstantially open so as to allow recirculation of the air.

In a preferred embodiment of the invention, the air distribution plate comprises afirst or front surface having a plurality of elongate openings through which the warm airflows towards the carousel. It has been discovered that air flow and even temperaturedistribution is promoted by arranging the elongate openings in the surface of the airdistribution plate in a manner such that each of the elongate openings are oriented at anangle relative to the slots of the carousel, such that the elongate openings overlap at leasttwo of the slots of the carousel. In this manner, each of the test sample cards in the slotsreceives warm air from at least two elongate openings in the air distribution plate. Apreferred embodiment of this arrangement comprises the arrangement of the elongateopenings in a symmetrical, ring-shaped pattern in substantial registry with the rear side 6

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portion of the carousel. Other alternative openings designs are also envisioned, such as aplurality of concentric rings, or alternatively, arcuate sections, formed in the airdistribution plate.

Another feature of the invention is that the carousel may be constructed in a 5 plurality of discrete, separable carousel segments, for example, four pie-shaped segmentseach forming approximately 90 degrees of an arc. Each of the segments are mountedtogether in the enclosure to a mounting plate to form a circular carousel, but areseparately removable from the enclosure. This feature promotes an easier manufacturingand insertion and removal of the carousel from the enclosure for cleaning and 10 maintenance. Recessing the front surface of the carousel also promotes even flow of the return air.

In this embodiment of the invention, it has been discovered that air flow over the cards within discrete, separable carousel segments is achieved by forming the rear sidesurface of the segment with a substantial void so as to improve air flow from the air 15 distribution plate over the test sample cards. Scallop or other void features provided onthe end walls of the segments also assist is providing sufficient air flow over the testsample cards and promotes efficient recirculation of the air.

These and still other objects, advantages, and features of the invention aredescribed below in the following detailed description of presently preferred embodiments 20 of the invention. 1 7

BRIEF DESCRIPTION OF THE DRAWINGS 10 15 20 25 A presently preferred embodiment of the invention is described below inconjunction with the appended drawing figures, wherein like reference numerals refer to like elements in the various views, and in which:

Figure 1 is a perspective view of a preferred automatic biological sample testinginstrument that incorporates the incubation station in accordance with the invention. Thecard disposal station and cover panels for the instrument are removed in order to moreclearly show the other features of the machine.

Figure 1A is a block diagram of the all of the principal stations in the instrument of

Figure 1;

Figure 2 is a perspective view of the instrument of Figure 1, with the diluting andpipetting stations removed to better illustrate the vacuum station, and with the stackingdisposal station included to show its relationship to the sample card transport and optical systems;

Figure 3 is an end view of the instrument, partially in section, as seen from the right-hand side of the instrument in Figure 1 looking toward the center mount, showing, amongother things, a mechanism for loading the test sample cards into the carousel and amechanism for separating the cards within the cassette to better enable a bar code positionedat the top of the card to be read by an optical reader;

Figure 4 is a detailed perspective view of the vacuum chamber of the vacuum stationof Figure 2 engaging the top surface of the boat, as it would be when the fluid samples are loaded into the cards;

Figure 5 is a detailed perspective view of the cut and seal station, showing the hotcutting wire cutting through the transfer tubes for the cards when the boat is advanced pastthe hot cutting wire, thereby sealing the interior of the cards; 8

Figure 6 is a front perspective view of the carousel of Figure 1 installed in theincubation station, with several of the cover panels of the incubation station removed inorder to illustrate the carousel;

Figure 7 is a perspective view of the incubation station of Figure 6 with the5 carousel, drive shaft and mounting plate removed, in order to better illustrate the air distribution table and cover plate features of the incubation station;

Figure 8 is a perspective view of the incubation station of Figure 7, with the airdistribution cover plate of the air table removed in order to illustrate the internal structures of the air table; 10 Figure 9 is a perspective view of the rear portion of the incubation station with the cover panels removed, illustrating the drive system for rotating the carousel and the fan andheater assemblies that direct warm air through an aperture in the bulkhead into the air tableof Figures 7 and 8 for distribution over the carousel;

Figure 10 is an isolated perspective view of one segment or section of the carousel 15 in accordance with a preferred embodiment of the invention;

Figure 11 is an isolated perspective view of one section of the carousel showing the mounting of the section to the mounting plate by a spring loaded pin assembly;

Figure 11A is an isolated perspective of two carousel segments as seen from the rear, showing the positioning tabs used by an optical switch to correctly position the 20 carousel slots to receive and eject test sample cards from the carousel;

Figure 1 IB is a perspective of the entire carousel as seen from the rear;

Figure 12 is a perspective view of two sections of the carousel positioned over the air table, showing the relationship of the elongate openings in the air distribution cover plateof the air table with respect to the card-receiving slots in the carousel; 9

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10 15 20

Figures 12A -12H depict other possible arrangement of openings in the airdistribution cover plate that should promote good air flow over the carousel and test samplecards contained therein;

Figure 13 is a perspective view of the carousel in an installed condition showing theeasy manual removal and insertion of a section of the carousel from the instrument;

Figure 14 is a perspective view of the section of the carousel installed;

Figure 15 is a detailed perspective view of the spring loaded pin, mounting table andflange of the carousel section just prior to insertion of the section;

Figure 16 is detailed perspective view of the spring loaded pin and carousel sectionas the carousel section is being inserted into the instrument;

Figure 17 is a perspective view of a push mechanism located at the top of thebulkhead of Figure 6 that pushes the cards out of the slots in the carousel of FIG. 2 into thesample card transport system of Figure 1;

Figure 18 is a perspective view of the push mechanism as seen from the rear of the bulkhead;

Figure 19 is a graph of the growth curves of microorganisms in the wells of the testsample cards as a function of time for the incubation station and instrument of the preferredembodiment, as compared to the growth curves for the instrument without the improved air flow features;

Figure 20 is a graph of temperature as a function of time inside the incubationstation for a four hour period, showing the very small temperature variation that occurs inside the incubation station in accordance with the invention;

Figure 21 is a graph of the growth time profile for dispersed wells in a test samplecard incubated in an incubation station that does not have the improved air flow features 10 10 described herein, showing the undesirable wide variation in growth time across the cardswhich is directly attributable to poor air flow characteristics;

Figure 22 is a graph of the growth time profile for dispersed wells in a test samplecard incubated in an incubation station that has the improved air flow features describedherein, showing the minimal variation in growth time across the cards, a desirable result of the invention;

Figure 23 is a perspective view of a card separation and detection device that is apreferred alternative to the card separation mechanism illustrated in Figure 3;

Figure 24 is a side elevational view of the alternative card separation and detectiondevice of Figure 23;

Figure 25 is a front elevation view of the alternative card separation and detection device;

Figure 26 is an exploded perspective view of the alternative card separation and detection device; 15 Figure 27 is a side view of the alternative card separation and detection device, partially in section, showing the position of the threaded shoulder screw within the body ofthe housing, and the flag on the actuator relative to the optical sensor; and

Figure 28 is a bottom plan view of the alternative card separation and detectiondevice, partially in section, showing the position of the shoulder screw within the body of 20 the housing. 11

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10 15 .....................................' ........ ·................ 124363/2.....-......— DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTOverview of Preferred Automatic Sample Testing Machine

The preferred embodiment of the inventive incubation station will be described inconjunction· with a presently preferred fully automated biological sample testing instrumentfor test sample cards. It will be appreciated, however, the invention is not limited to theparticular automated biological sample testing instrument illustrated, as the incubationstation could be used with other machine designs, test methodologies such as analyticalchemistry or nucleic acid probe based assays, and can even be used in a less fully automatedmachine or even a manual system.

Figure 1 is a perspective view of a biological sample testing machine or instrument20 that conducts analysis of test sample filled cards 28 according to a preferred embodimentof the invention. The instrument 20 has a set of removable cover panels covering themachine and presenting an aesthetically pleasing appearance and allowing user access tosystem components, that are not shown, in order to better illustrate the functional aspects ofthe machine. In Figure 1, a stacking card disposal station for the cards 28 has been removedin order to illustrate the other components of the instrument. The card disposal station 900is shown in Figure 2. Figure 3 is an end view of the machine, partially in section, showingthe position of the test sample cards 28 as they are processed in several of the stations in themachine 20. Figure 1A is a block diagram of the machine 20 as a whole, showing thelayout of the stations and the path of a boat and cassette assembly and test sample cardsthrough the machine in a preferred embodiment of the invention.

Referring now primarily to Figures 1, 1A, 2 and 3, the biological sample testingmachine 20 includes a biological test sample positioning system 100, consisting of fourindependent motor-driven paddles, which pulls a sample tray 22 (referred to herein as a 25 "boat") incorporating a cassette 26 across a base pan 24 around the machine 20 to several 12

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124363/2 _ ; discrete stations, where various operations are performed on the cards and receptacles in thecassette 26. The cassette 26 consists of a holder that fits snugly into the boat 22 having aplurality of slots for receiving the test sample cards 28, with each of the slots having enoughfore and aft separation distance so as to permit the cards 28 to be rocked slightly, in themanner described below, as the cassette 26 and boat 22 are moved past the bar code rpiriingstation 90 in the machine.

Prior to the start of the procedure, a technician loads a cassette 26 with a plurality oftest cards 28 and receptacles such as test tubes 30 containing biological or control samplesto be tested. Each test card 28 has an L-shaped transfer tube 32 protruding therefrom forpermitting the fluids containing biological samples to be drawn from the test tubes 30 intothe reagent-filled wells of the test cards 28. The technician places the loaded cassette 26into the boat 22 at a loading station for the machine, such as the front, right hand comer ofthe base pan 24 shown in Figure 1. The combined boat 22 and loaded cassette 26 are thenautomatically moved as a unit over the surface of the base pan 24 about the machine 20 by 15 the test sample positioning system 100.

In a typical microbiological testing scenario, described below for purposes ofillustration but not limitation, the test cards 28 come in two varieties: (1) identificationcards, in which particular different growth media are placed in each of the wells of the card2S when the cards are manufactured, and (2) susceptibility cards, in which different 20 concentrations of different antibiotics are also placed in each of the wells of the card 28. t

The identification cards are used to identify the particular unknown biological agent, i.e.,microorganism, present in the sample. The susceptibility cards are used to determine thesusceptibility of the biological agent to various concentrations of antibiotics or other drugs.

In the test procedure described below, identification and susceptibility tests can be 25 performed on a single sample in one cycle of operation of the machine 20 (i.e., one test 13

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run). To accomplish this, the cassette 26 is loaded such that a test tube 30A containing abiological sample, connected via a transfer tube 32 to an identification card 28A, is placedadjacent to an empty test tube 30B connected via a transfer tube 32 to a susceptibility card 28B. 5 The cards 28 preferably contain bar codes as well as other identifying indicia on the upper portion of the card for reading by a bar code reader 90 (Figure 3) built into themachine 20. The bar codes are unique to each card, and identify card information such ascard type, expiration date, and serial number, and are used to correlate test data and/orresults from the cards with the patient and the biological sample. In addition, the entire boat 10 or cassette may have sample information for all of the cards loaded in the cassette stored onone or more memory devices affixed to the cassette 26, such as a memory button or "touchbutton” available from Dallas Semiconductor Corp., 4401 S. Beltwood Parkway, DallasTexas. A card identification reading station, including a card separation device forpromoting reading of the cards, is described in detail below. 15 In the representative example shown in Figure 1, seven or eight ofthe test tubes 30 in the boat 22 contain biological samples, and are in fluid communication with identificationcards 28A by the straw-like transfer tube 32. The biological sample test tube 30A and itsassociated identification card 28A can be thought of as a set. The biological sample testtubes and identification cards are typically arranged in an alternating pattern in the cassette 20 26. Each biological sample test tube 30A and identification card 28A set is adjacent to an empty test tube 30B placed in communication with a susceptibility card 28B via a transfertube 32. It will be appreciated that the cards and associated test tubes could be ordered inany order in the cassette 26 depending on the particular testing requirements for thesamples. For example, the cards could be arranged as follows: identification (ID), 14

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10 15 20 25 - T24363/2 -..... susceptibility (SU), ID, ID, ID, SU, SU, ED, SU . . . . Further examples would be allidentification cards and all susceptibility cards.

The test sample positioning system 100 operates to move the boat 22 and cassette 26over the base pan 24 to the bar code reading and card detection station 90, described below,and then to a diluting station 200. The diluting station contains a rotating shot tube 202, bywhich a predetermined volume of diluent (such as saline solution) is added to the emptysusceptibility test tubes in the cassette 26, e.g. test tube 30B. Other types of fluids may beadded to the test tubes by a rotating shot tube, such as reagents or growth media, thusdiluting station 200 is not limited to just adding a diluent to the test tubes. As the leadingedge of the boat 22 is moved to the left during this process, it passes under a pipettingstation 300. The pipetting station 300 includes a mechanism that automatically removes apipette 302 from a source of pipettes 304, lowers the pipette 302 into the biological sampletest tube 30A, and removes with vacuum a predetermined volume of biological fluid fromthe biological sample test tube 30A using the pipette 302.

The test sample positioning system 100 then moves the boat 22 to the left by an amount equal to the separation distance between adjacent test tubes 30A and 30B, e.g. 15 mm. The pipetting station 300 then lowers the pipette 302 containing the biological fluid

from the biological sample test tube 30A into the adjacent susceptibility test tube 30B (having already received a quantity of diluent from the diluting station 200), expels the fluid into the test tube 30B, mixes the fluid in the test tube 30B and drops the pipette 302 into the/ susceptibility test tube 30B. The process of movement of the boat 22 by the test samplepositioning system 100, adding diluent to the susceptibility test tubes 30B at the dilutingstation 200, and transferring of biological samples from the biological sample test tubes 30Ato the adjacent susceptibility test tubes 30B at the pipetting station 300, continues until all ofthe identification and/or susceptibility test tubes sets (if any) in the boat 22 have been so 15 i

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124363/2 processed. By virtue of the close spacing of the pipetting station 300 and the diluting station200, simultaneous diluting and pipetting operations can be performed on multiple test tubesin a single boat 22. After the last pipetting operation has been performed, the test samplepositioning system 100 then moves the boat 22 all the way to the left-hand edge of the basepan 24.

It will be understood by persons skilled in the art that the cassette 26 may be loadedentirely with biological samples in the test tubes 30 and identification cards 28, such as thecase where a batch of biological samples are to be tested to identify the contents of thesamples. In this example, the diluting and pipetting operations are not necessary. However, 10 in other types of sample testing, growth media, other diluents or reagents or fluids may beadded to or withdrawn from the test tubes. In the example of where no diluting or pipettingoperations are performed (e.g, where the pipetting and diluting operations were performedoff-line), the cassette 26 is loaded with test tubes and cards, and the positioning system 100would simply move the boat 22 and loaded cassette 26 directly past the diluting station 200 15 and the pipetting station 300 without stopping, all the way to the left hand edge of the basepan 24.

Once at the left hand edge of the base pan 24, the test sample positioning system 100operates to move the boat 22 along the left hand edge to a vacuum station 400. The vacuumstation 400 is seen better in Figure 2, which is a perspective view of the machine 20 with the 20 diluting station 200 and the pipetting station 300 removed, and in Figures 4 and 5. At thevacuum station 400, a vacuum chamber 402 is lowered onto the boat 22 such that thebottom surface of the vacuum chamber 402 sealingly engages the top peripheral surface 23of the boat 22. The vacuum chamber has tubing 406, 408 (Figure 4) that are incommunication with a conventional vacuum source for the machine (not shown in Figure 25 4). Vacuum is applied to the chamber 402 under microprocessor control, causing air in the 16

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10 15 20 25 124363/2 interior or tne rest sample cards 28 to evacuate out of their associated test tubes and to bewithdrawn from the chamber 402. The vacuum cycle is precisely managed to optimizefilling by using a closed loop servo system to regulate the rate of change of vacuum and thetiming of the complete vacuum cycle. After a predetermined period, the chamber 402 isvented to atmosphere under microprocessor control. The venting of the cards causes thefluid in the test tubes 30 to be drawn into the cards 28, filling the wells in the cards 28.After the chamber 402 is vented, the chamber is raised up by a vacuum chamber drive ' mechanism 410 so as to permit the boat to be moved to the other stations of the machine 20.

The test sample positioning system 100 then operates to advance the boat 22 to theright across the rear of the base pan 24 to a cut and seal station 500, located behind thecenter mount 34 in Figures 1 and 2. Referring to Figures 4 and 5, the cut and seal station 500 consists of a hot cutting wire 506 and attached support plate 504, and a drivemechanism 502 (e.g., stepper motor, drive belt and lead screw) that lowers the cutting wireand support plate 504 to the same elevation as the top portion of the transfer tubes 32adjacent to where the transfer tubes 32 enter the test cards 28. As the boat 22 is advancedpast the cut and seal station 500, the transfer tubes 32 are forced past the hot cutting wire506. By virtue of the assistance of fore and aft constraints placed on the movement of thecards 28 by the walls of the cassette 26, and the lateral constraints on the movement of thecard 28 by the cassette and wail structures of the machine 20, the hot cutting wire cuts thetransfer tubes 32 by melting of the transfer tube material as the boat 22 is slowly advancedpast the hot cutting wire 506. A small stub of transfer tube material is left on the exterior ofthe card 28. The stub seals the interior of the card 28 from the atmosphere (except, incertain types of cards, for possible diffusion of gasses such as oxygen through oxygenpermeable tape covering the sample wells). When the boat is advanced past the station 500,the wire 506 is raised up to its upper position. 17

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10 15 20 25 ....... 124363/2 —— |

Referring to Figures 1 and 3, the test sample positioning system 100 then advances - the boat 22 across the rear of the base pan 24 behind the center mount 34 to the inventivecarousel incubation station 600. A reciprocating rack and pinion driver 610 is mounted tothe center mount 34 opposite a slot 602 in the machine that pushes the cards off the cassette26 one at a time through the slot 602 into a vertically oriented carousel 604. The carousel604 is housed in an enclosure that is maintained at an appropriate incubation temperature.

The enclosure is partially removed in Figures 1 and 2 in order to show the carousel 604.

The carousel 604 is rotated by a drive system 612 in synchronism with the movement of theboat 22 over the rear of the base pan 24 by the test sample positioning system 100, so as toplace the next slot in the carousel 604 in line with the slot 602 opposite the next card in thecassette 26. If the carousel is only going to be partially loaded with cards, the operatingsystem of the machine may control the carousel 604 rotation to load the cards into non-adjacent slots to equally distribute the cards in the carousel in order to balance out theweight distribution in the carousel 604. For example, where the carousel has 60 slots andonly 30 cards are to be processed, the cards could be loaded into every other carousel slot.

Additional incubation capacity required for processing a larger number of cards atone time can be provided by using a larger carousel, adding an additional incubationstation(s) to the base pan, and adjusting the dimension of the base pan and drive systemcomponents as necessary. Additional optics stations may be provided for additionalcarousels. For example, if the carousel 604 has sixty slots and each cassette holds 15 cards,four full cassettes 26 (Figure 1) can be processed at once. If a second carousel is added, upto 120 cards could be processed at once. Of course, different capacities could be providedfor the cassette 26 and the carousel 604.

After all of the cards 28 have been loaded into the slots of the carousel 604, the boat22 is advanced along the right hand edge of the base pan 24 back to its starting position 18 124363/3 (snown in figures i ana 2) or to an exit position for removal o’f the cassette 26 (containing 10 15 20 25 the test tubes, pipettes 302, if any, and transfer tubes remnants) and receipt of a newcassette. Alternatively, the boat 22 could be moved to an exit station located, for example,in the rear or right hand side of the base pan 24.

As the cards 28 are being incubated in the incubation station 600, the cards areperiodically, sequentially pushed out of the slots of the carousel 604 at the top of thecarousel 604, one at a time, by a reciprocating rack and pinion driver 620 and an associatedstepper motor. The cards 28 are moved by an optical scanner card transport station 700 pasta fluorescence and/or transmittance optics station 800 having a transmittance substation802 and/or a fluorescence substation 804. The wells of the card 28 are selectively subject tosets of transmittance and/or fluorescence optical testing according to the analysis needed tobe performed by the transmittance and fluorescence optics station 800. The transmittanceand fluorescence optics station 800 includes detectors and processing circuitry to generatetransmittance and fluorescence data for the wells in the cards 28, and to report the data to acentral processing unit for the machine 20. If the test is not complete, the transport station 700 moves the card 28 back into its slot in the carousel 604 for more incubation and additional reading.

Typically, each test sample card will be ejected into the transport station 700 forreading every 15 minutes as the carousel makes one revolution. The rate of rotation couldbe faster or slower, of course. Typical incubation times for the cards 28 are on the order ofone to eighteen hours, consisting of roughly four'transmittance and/or fluorescence data setsper hour, each data set consisting of multiple readings, for each of the wells in the card 28subject to the optical analysis requirements.

After the testing is complete, the cards are moved by the optical scanner transportsystem 700 into a card output station 900 shown in Figure 2 and Figure 3. The card output 19

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124363/2 station 900 consists of a detachable tray or magazine 902 and associated support structurethat is positioned to the side of the optical station 800 at approximately the same elevationas the optical station 800. The station 900 has a pressure slide 914 that is moveable withinthe magazine 902 and a constant force spring biasing the pressure slide towards the front ofthe magazine. The cards are stacked in the magazine between the pressure slide 914 andoppositely opposed resilient snap elements integrally formed in the sides of the magazine902. The technician removes the magazine 902 from the machine 20 as needed or when themagazine is full of cards, empties the cards into a suitable biohazard disposal unit, andreplaces the magazine 902 back into the machine 20. 10

Incubation Station Operational Features

Figure 6 is a front perspective view of the carousel 604 and incubation station 600 ofFigure 1, with several of the cover panels 619 of the incubation station removed in order tobetter illustrate the carousel 604. The cover panels 619 form an enclosure for the carousel 15 604 and isolate the carousel 604 from ambient conditions.

The carousel 604 is vertically mounted and rotates about a horizontal axis. An airduct 622 is provided on the upper portion of the station 600 to allow air to circulate from thefront portion of the incubation station (containing the carousel 604) to the rear of the stationbehind the bulkhead 652. A small hole is placed in the rear cover panel parallel to and 20 positioned behind the bulkhead 652 to allow a controlled amount of ambient air into thestation. The duct 622 includes an aperture in the bulkhead 652 to allow air to flow down ±erear side of the bulkhead between the bulkhead and the rear cover panel, where it is blownover a heater which heats the air, and blown by a second fan 639 (Figure 9) into an airdistribution table 624 positioned behind the carousel 604, in the manner described in detail 25 below. 20 10

I 15 20 25

The carousel 604 has a plurality of slots 614 for receiving the test sample cards.The carousel has a substantially open front side portion 623 through which the cards areintroduced into the slots 614 at the lowermost portion of the carousel (see Figure 3), andan opposite rear side portion facing the air table 624 and the bulkhead 652.

Figure 7 is a perspective view of the incubation station of Figure 6 with the carousel604 removed, in order to better illustrate the air table 624 and air distribution cover plate 625 features of the incubation station. The air table 624 receives warm air from a heater and fan assembly behind the bulkhead 652. The air table 624 has an air distribution coverplate 625 that encloses the air table 624 which is positioned in registry with the slots 614 ofthe carousel 604. The cover plate 625 has a plurality of elongate openings 626 formedtherein that direct the warmed air over the rear side portion of the carousel and over thecards in the carousel slots. In order to promote adequate air flow over the cards, the rearside portion of the carousel adjacent to and opposite the air distribution cover plate 625 issubstantially open and free of obstructions so as to permit substantially uninterrupted airflow over the test sample cards. Thin reinforcing ribs connecting the inner and outercircular carousel walls may be provided for strength and molding purposes, but such ribsshould be sized so as to occupy a small as possible a surface area in the rear side portionof the carousel. The front portion of the carousel 604 is also spaced from the front coverpanel (not shown) of the incubation station and made substantially open and free ofobstructions, as shown, so as to promote the efficient recirculation of the air.

Referring to Figures 6, 7 and 12, it has been found that the size and arrangementof openings 626 in the air distribution cover plate 625 is important to promoting theoptimal air flow over the test sample cards and maintaining an even or uniform airtemperature distribution over the test sample cards. Preferably, the openings 626 arearranged in a manner such each of the openings 626 are oriented at an angle relative to 21

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10 15 20 the slots 614 of the carousel 604 such that the elongate openings 626 overlap at least twoof the slots 614 of the carousel. This results in each card receiving air from at least twoopenings 626. Referring to Figures 6 and 7, the elongate openings 626 are preferablydistributed in a symmetrical, ring-shaped pattern in substantial registry with the slots 614in the carousel. Preferably, at least 10 such openings 626 are provided, and in the embodiment 24 such openings are shown. The elongated openings are preferred over adesign such as small holes so as to minimize the risk of dust and dirt clogging the slotsand interfering with the air flow. The particular design of the openings is determined bythe particular air flow characteristics for establishing uniform air flow distribution andproviding a substantially constant and even temperature distribution in the incubationstation. The design of the carousel may of course affect the design of the openings 626.

Thus, other options are possible for the pattern and arrangement of the openings626. One is an arrangement of the openings 626 in concentric circles in registry with thecarousel, as shown in Figure 12A. Another possibility is forming the openings 626 as aplurality of overlapping arcuate segments as shown in Figure 12B. Other possibilitiesinclude rings of cross-shaped openings 626 (Figure 12C), elongate arcuate openings in aspiral pattern (Figure 12D), semicircular openings 626 arranged in a ring pattern (Figures12E and 12F), a plurality of circular openings 626 arranged in concentric rings (Figure12G), and a plurality of “L”-shaped openings 626 arranged in a ring (Figure 12H). Whatshould be avoided is an arrangement in which a card in the carousel, with the carousel atrest, that substantially obstructs the air flowing out of any one opening in the airdistribution cover plate 625, hence the angled design in Figure 12 and the offset arcuatesegments in Figure 12B. Note that in Figures 12 - 12 H, a card in a carousel card slotwill only obstruct a relatively small portion of any particular opening 626. A primarygoal of the design of the opening is that air flow out of the air distribution cover plate 25 22 should be substantially independent of the presence or absence of a card in the carouselslot. Within these teachings, persons of skill in the art may arrive at other suitableconfigurations within the scope of the invention.

Figure 8 is a perspective view of the incubation station of Figure 7, with the cover5 plate 625 of the air table 624 removed in order to illustrate the internal structures of the airtable 624. The air table 624 consists of a pair of circular walls 627 and 628 that define andenclose a ring-shaped region 630 in registry with the carousel. An opening 631 at the lowerportion of the bulkhead 652 allows warmed air from the rear of the bulkhead 652 to beintroduced into the ring-shaped region 630. The gap 617 at the top of the air table is to 10 allow the reciprocating driver 620 (Figure 3) to move through an aperture in the bulkhead652 and push the test sample cards out of the top of the carousel into the test sample cardtransport station 700 of Figure 3.

Figure 12 is an isolated, elevational view of one section 670 of the carouselpositioned over the mounting plate 678, showing the angled relationship of the elongate 15 openings 626 in the air distribution cover plate 625 of the air table 624 with respect to the slots 614 in the carousel.

Figure 9 is a perspective view of the rear portion of the incubation station 600 withthe cover panels covering the rear of the station 600 removed, illustrating the drive system612 that rotates the carousel 614. The drive system 612 comprises a stepper motor 632, a 20 first belt 633, a second belt 634 and a pulley 635 that is rotated by belt 634. The pulley 635is connected to a shaft 611 (see Figure 3) that passes through an aperture 609 in the bulkhead which is attached to and rotates the carousel 604. A first fan 637 is positioned behind and below the air duct 622 (Figure 6) which blows ambient air down over a heater assembly 638 which warms the air. The air inlet hole25 in the rear cover panel (not shown) is above the elevation of the fan 637. A second fan 639 23

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is positioned immediately behind the aperture 631 (Figure 8) and directs air warmed by theheater 638 through the aperture 631 in the bulkhead and into the air table 624 of Figures 7and 8 for distribution over the carousel 604. Thermistors are provided, one in the rear of thebulkhead below the heater 638 and one behind the air distribution cover plate of air table624 for controlling the operation of the heater and the temperature of the air exiting the air table 624.

In a preferred embodiment, the carousel 604 is constructed as a plurality of discrete,separable arcuate carousel segments or sections, such as four pie-shaped segments, eachreferred to as a “quad” or a “quadrocell”, each of the segments separately removable from 10 the incubation station enclosure in order to facilitate easy removal of the carousel forclearing or maintenance. Figure 10 is an isolated perspective view of one such segment670 of the carousel 604. The segment comprises a first end wall 671, a second end wall672, an inner arcuate wall 673, and a concentric outer arcuate wall 674. The rear side 675portion is substantially open, allowing air to circulate from the slots 626 in the air 15 distribution cover plate of the air table of Figure 7 to freely pass over test sample cardsplaced in the slots 614. The slots 614 have opposed ramp faces 614A (Figures 10 and 11)to promote the easy insertion of the test sample cards into the slots 614. A least onereinforcing rib 676 is provided that extends between the inner wall 673 to the outer wall674 to give adequate strength to the carousel segment 670 and improve moldability of the 20 segment 670. Further, the end walls 672 are formed with substantial scalloped voidregions 669, which has been found to improve the air flow over the test sample cards. Thefront surface of the carousel segment is spaced from the front cover panel of the incubationenclosure to allow efficient air return via duct 622 (Figure 6). A mounting flange 677 is provided integral with the inner wall 673 which is used 25 to mount the segment 670 to a mounting plate 678 (Figure 11) connected to the end of the 24 10 15 20 drive shaft 611 (Figure 3). The mounting flange 677 has a guide ramp 681 to assist inplacement of a pair of downwardly depending cylindrical legs or projections 679 formedon the bottom surface of the flange 677 into a pair of corresponding holes 680 formed inthe mounting plate 678. The segment 670 is held in place by the action of a spring loadedpin 682 positioned within a retaining hub 683 clamping the flange 677 against themounting plate 678.

Figure 11A is a perspective view of the rear of two carousel segments 670A and670B in which a plurality of upstanding tabs 691 are provided on the rear surface 675 ofthe outer peripheral arcuate wall 674. Figure 11 B is a perspective view of the rear of anentire carousel. 604. The tabs 691 are positioned in registry with the carousel slots 614.The tabs 691 are used in conjunction with an optical position sensor 693 comprising aslotted optical switch that is positioned adjacent to the bulkhead 652 (Figure 8) within theincubation station immediately behind the rear surface 675 of the carousel such that thetabs 691 pass in the slot 694 between the emitter 695 and detector 696 of the opticalposition sensor 693 (Figure 11A) as the carousel rotates. The optical position sensor 693is mounted in any convenient position adjacent to the bulkhead such that the placement ofa tab 691 between the emitter and detector results in the slots 614 of the carousel beingcorrectly placed to receive a test sample card from the card loading mechanism 610 ofFigure 3, and correctly placed for the card ejection mechanism 648 of Figure 17 and 18 topush a test sample card out of the slot 614 in the carousel. It is important that the opticalinterrupts are positioned such that there is a gap between the carousel segments 670A and 670B in the location 697.

Figure 13 is a perspective view of the carousel 604 in an installed condition showingthe easy manual removal and insertion of a section 670 of the carousel 604 from the 25

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instrument 20. Figure 14 is a perspective view of the section 670 of the carousel 604 installed.

Figure 15 is a detailed perspective view of the spring loaded pin 682, mounting plate678 and flange 677 of the carousel section 670. As the section is moved inwardly in the 5 direction of the arrow towards the center of the mounting plate 678, the spring loaded pin682 rides up the ramp 681 against the force of a biasing spring (not shown) inside the hub683. The front surface 685 of the flange 677 abuts the flat planar portion 686 of the hub683, positioning the cylindrical legs 679 (Figure 10) into the holes 680. The spring loadedpin 682 then presses against the flat planar portion 687 of the flange 677 to lock it in place. 10 Figure 16 is detailed perspective view of a section 670 of the carousel being inserted,showing the ramp 681 in alignment with the spring loaded pin 682 immediately before thesection 670 is locked into place.

Figure 17 is a perspective view of a push mechanism 648 located at the top of thebulkhead of Figure 6 that pushes the cards out of the slots in the carousel of FIG. 2 into the 15 sample card transport system 706, 704, 710 and 718 of Figure 17. The air table has beenremoved in order to better illustrate the push mechanism. Figure 18 is a perspective view ofthe push mechanism as seen from the rear of the bulkhead. Referring to Figures 17 and 18,in order to place the card 28 into the sample card transport system 700, a rack and pinionpush mechanism 648 is provided to push the card 28 out of the carousel 604. The push 20 mechanism includes an alignment block 654 mounted to the bulkhead'652 and a driver 656that reciprocates back and forth relative to the block 654. A motor 660 having a gear 662 ismounted behind the bulkhead 652. The teeth of the gear 662 cooperate with a set of teeth658 on the driver 656, such that rotation of the gear 662 backwards and forwards causes thedriver 656 to move in the direction shown by the arrow 664 (Figure 18) in the space 25 between a lower slot 666 and an upper slot 668 in the block 654. The end of the driver 656 26 10 15 20 25 is positioned in alignment with the top slot 614 in the carousel 604. When the driver 656 isoperated by the motor 660 such that the driver 656 is pushed into the slot 614, the card 28within the slot 614 is pushed out of the slot into the space between an internal slot in a ledge718 and a drive belt 710. The optical detector 693 for the carousel tabs 691 (Figure 11A)may be mounted above the block 654.

The card transport station 700 includes a cover plate 704, a card slot 706 definedbetween a drive belt 710 and the ledge 718 to move the cards 28 back and forth betweenthe carousel 604 and the optical stations 802 and 804 of Figures 1 and 3. Further detailson this drive system are set forth in greater detail in the above-referenced patentapplication of Mark J. Fanning et al. serial no. 08/604,672 which is incorporated by reference herein.

The advantages of the improved air flow features described above compared to anincubation station without these features are illustrated in Figures 19-22. Figure 19 is agraph of the growth curves of microorganisms in the wells of the cards as a function of timefor the incubation station and instrument of the preferred embodiment described in Figures 6-18 (line 690), as compared to the growth curves for the instrument without the improvedair flow features (line 692). Line 690 indicates that after a few hours of incubation, at timetl the growth of the microorganism begins to increase at a steady rate until time t2, when thegrowth levels off. During the time between time tl and time t2, the cards are moved in andout of the incubation station and shuttled back and forth to the optical stations for reading.At a population level of Gl, the light transmittance characteristics have .changed from aninitial measurement at time tl such that that a positive reading of the well would occur in the optical system at time t3.

It is also believed that the improved air flow techniques of the present inventionimprove oxygen transfer through the oxygen-transmissible tape that covers the wells of the 27

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10 15 20 25 card. Since the reactions occurring within the cards are typically aerobic reactions,increasing the supply of oxygen helps promote the reaction within the wells of the card and shorten the time needed to obtain a test result.

In a system without the improved air flow features resulting in zones of coolertemperatures in the vicinity of the card, the organism growth does not begin until about timet3, and reaches a maximum at time t4. The time at which a positive reading occurs at time t5. Time t5 is later than time t3 by an amount At, which could be as much as several hours.

This shortening in the incubation time by the amount At was found to be the direct result ofimproving the air flow over the cards by adding a second fan 639 (Figure 9) in the rear inthe bulkhead opposite the opening 631 in the bulkhead (Figure 8), adding the voids 669 inthe end walls of the carousel segments (Figures 10 and 11), reducing the width of thecarousel, opening the rear side portion of the carousel 604 to the air table 624, and providingthe elongate slots 626 in the manner described above (see Figure 7) in the air distributioncover plate of the air table.

Figure 20 is a graph of temperature as a function of time inside the incubationstation for a four hour period, showing the very small temperature variation that occurs inside incubation station in accordance with the invention. Without the above-referenced air flow improvements, air temperature variation away from the desired temperature of 35.5degrees C in the incubation station was on the order of several degrees C, whereas with theimprovements it was reduced to less than 1 degree C over a four hour period. This eventemperature characteristic would be expected to be maintained for longer incubationperiods, such as 12 or 18 hours.

Figure 21 is a graph of the growth versus time difference profile for sample wells ina test sample card incubated shown in Figure 3, in an incubation station that does not havethe improved air flow features described herein, for example, without the second fan, 28

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10 15 20 without a reduced width quadrocell, without the open rear of the carousel, and using a singleopening for air distribution instead of slots in the cover plate of the air table (Figure 7). Thegrowth profiles of some of the bacteria or antibiotic combinations are directly related to thetemperature (and air flow)in the slots of the carousel, with greater temperatures and air flowmay result in faster growth and lower temperatures and less air flow may result in slowergrowth. Even temperature and air flow and hence growth across all the wells is the desiredresult. Figure 21 illustrates the undesirable wide variation in growth time across the cards,with the wells at in the eighth or left hand column S8 having markedly longer growth timesas compared to the wells in the first column S1.

Figure 22 is a graph of the growth time profile for sample wells in a test samplecard incubated in an incubation station that has all of the improved air flow featuresdescribed herein, showing the substantially reduced variation in growth time across thecards. While columns S3-S8 exhibit slightly longer growth times as compared to columnS1, the difference is much less pronounced than that shown in Figure 21. The difference ingrowth time profiles shown in Figure 22 would not be expected to adversely impact thesample testing procedure. Further, by virtue of the rotation of the carousel at a rate of onerevolution per 15 minutes, and all incubation times being on the order of more than onehour, each card in the carousel 604 would be expected to exhibit the temperature pattern andhence growth profile shown in Figure 22.

It is contemplated that various degrees of air flow improvement and eventemperature distribution would be observed with various combinations of each of thespecific air flow improvement features described above, and not all of them neednecessarily be adopted. Thus, the invention should not be considered limited toincorporation of all of the features in any given system. The particular requirements ofthe incubation system at issue, the geometry of the carousel and its relation to surrounding 25 29 structures, the available space, the specifications of the fan and designed temperature, andstill other considerations may impact the selection of features.

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10 15 20

Card Detection Device Detailed Description

In Figure 3, a card separation device comprising a wheel 94 attached to an arm thatpivots about a pin 98 is shown. As the boat 22 and cassette 26 pass by the wheel 94, thewheel 94 rocks the cards 28 back within the slots of the cassette 26 to expose the uppersurface of the card 28 and bar code affixed at this location to an optical reader 90 located forward of and above the card in the machine.

Figure 23 is an isolated perspective view of an alternative and more preferred cardseparation device 102 that is also capable of card detection. Figure 24 is a side elevationalview of the card separation and detection device 102. Figure 25 is a front elevation view ofthe device 102. Figure 26 is an exploded perspective view of the device 102 .

Referring to these figures, in conjunction with Figures 1, 2 and 3, the device 102 ismounted to a flange off of the center mount 34 in essentially the same manner and locationas shown for the device 94 in Figure 3, in a position “upstream” of the reading device 90and in optical alignment with the reading device 90. The card separation and detectiondevice 102 includes a housing 104 having flanges 106 that are attached to structures in theinstrument (such as cross-member 92 or mounting flange 91 depending from cross-member 92 in Figure 3) in proximity to the pathway that the cards 28 move along withinthe instrument. In Figure 3, the motion of the boat 22 on the lower left hand side of theillustration is into the page, thus the card separation device separates the cards 28 as thecards are moved past the device so that the optical reader 90 can read bar codes positionedat the top of the card facing the optical reader 90. 30

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10 15 20

The device 102 includes an actuator 108 reciprocating relative to the housing 104between a first or extended position and a second or retracted position. The actuator 108has a head portion 110 with a first card contact surface 112. When the card 28 contactsthe card contact surface 112 as the card 28 is moved past the device 102, the actuator 108is moved by the card from its extended position, against the force of a biasing spring 114surrounding a threaded shoulder screw 120, to a retracted position relative to the housing104 in the manner suggested by the arrow in Figure 23.

The actuator 108 carries an optical interrupt flag 118 on the lower surface 120 ofthe head portion 110. When the actuator 108 is moved to the retracted position, the flag118 is moved into the optical path of an optical detector 122. The optical detector 122 ismounted to the housing 104 immediately below the actuator 108. The movement of theflag 118 into the optical path of the detector 122 triggers the optical detector 122, andsends a signal to the central computer system for the instrument indicating that a card wasdetected by the device 102.

The action of the card 28 contacting the surface 112 actuator 108 also results in amovement of the card relative to the cassette and the automated reading station 90 suchthat the indicia or bar codes positioned on the top edge of the cards 28 are better positionedfor reading by the reader 90. Specifically, the card is rocked back in the slot in thecassette 26 to an angle, and moved away from the card in front of it in the cassette 26,such that the bar code or other indicia is clearly exposed to the reader 90. As the card ismoved further past the actuator 108, the actuator 108 is moved by the biasing spring 114back to its first or extended position, at which time a second card contact surface 124contacts the card 28 and pushes the card forward in the slot in the cassette 26. This helpsseparate one card from the next in the cassette. 31 10 15 20

In Figures 23-26, the flag 118 is shown attached to the actuator 108 with theoptical detector 122 mounted to the housing 104. These positions could be reversed, but with the same result achieved of detection of a card when the actuator is moved to the retracted position.

As shown in Figure 26, the actuator 108 reciprocates in an oval aperture 124 in thehousing 104. The shoulder 126 of the actuator 108 is given an oval cross-sectional shapeand dimension so as to fit inside to the aperture 124 and not result in any rotational or side to side translational motion.

Figure 27 is a side view of the device 102 in an assembled condition, partially insection, showing the position of the threaded shoulder screw 120 within the body of thehousing 104, and the flag 118 on the actuator relative to the optical sensor 122 when theactuator 108 is in the extended position. Note that when the actuator 108 is moved to theretracted position, the flag 118 is moved into the optical path 130 of the optical sensor 122.Note also in Figure 27 that the spring 114 has one end thereof that seats against the rearsurface of the head portion 110, and a second end that seats against an inner vertical wall132 in the housing 104. The threaded shoulder screw 120 has a tip 134 that is connectedto the head 110. A clearance exists between the head 110 and the walls of the aperture 124(see Figure 26) allowing the head 110 of the actuator 108 to freely move back and forthwithin the aperture 124.

Figure 28 is a bottom plan view of the device, partially in section, showing theposition of the shoulder screw 120 within the housing 104. A screw 138 mounts the opticalsensor 122 to the housing 104 in proximity with the flag 118 such that the flag 118reciprocates with the actuator 108 into the space between the source and detector of theoptical sensor 122. 32

Persons of skill in the art that variation may be made to the preferred andalternative embodiments described above without departure from the true spirit and scopeof the invention. This true spirit and scope is determined by the appended claims, to beinterpreted in light of the foregoing. 33