MXPA96002263A - Liquid supply apparatus and deoperac method - Google Patents

Abstract

The present invention relates to a liquid supply system for supplying a pump with liquid, through a pump supply path, the system comprising: a liquid containment system having a ventilated replaceable bulk container and a reservoir seal fed by the bulk container, through a conduit, a sensor for limits between air and liquid in the conduit, a vent conductor of the reservoir in fluid communication with the reservoir, a controlled valve for the vent of the reservoir a pump to remove the liquid from the tank, for use on request, and a controller to close the controlled valve during the detection of a liquid-to-air limit that passes the sensor, to operate the pump, and to open the controlled valve during the detection of an air-to-liquid limit that passes the sens

Description

"LIQUID SUPPLY APPARATUS AND OPERATING METHOD" FIELD OF THE INVENTION The invention relates to analyzer instruments and, more particularly, to liquid supply systems used in analyzer instruments.

BACKGROUND OF THE INVENTION As is known in the art, there is a tendency in hospitals, clinics, laboratories and other sites to carry out tests (tests, on samples of patient specimens, such as blood, spinal fluid, urine, serum, plasma and the like using automated immunoassay analyzer systems The relatively sophisticated automated analyzer systems typically accept a plurality of samples from different patient specimens and carry out different tests on each of the different samples. Another way using liquids that are provided by the system depends on the type of analyzer system used, the type of assay being carried out and other factors, including but not limited to the desired concentration of the material analyzed. Arousal in automated analyzer systems is that the analyzer that provided the fluids of processing may be exhausted before a trial is completed. Some trials require multiple washing steps. In some test protocols, different reagents are added during different time periods in the cycle. Consequently, different liquids within the automated analyzer system are used at different rates and, therefore, must be replenished for different periods of time. If a liquid runs out before a cycle is completed, the entire test would have to be repeated and it may be necessary to readjust the system and replenish different reagents or other liquids, such as washing liquids, for example. Therefore, it would be desirable to provide an automated liquid system that replenishes liquids and that allows liquids to be replaced relatively easily without stopping the operation of the analyzer system.

SUMMARY OF THE INVENTION In accordance with the present invention, a liquid module includes a bulk liquid container in fluid communication with a reservoir via a liquid supply line. A device such as a pump or a diluent is capable of periodically removing a volume of known liquid from the liquid module. An air vent solenoid valve placed next to the bulk liquid container provides selective air discharges from the reservoir to the ambient atmosphere through an air vent tube. In order to detect when a bulk liquid container is not delivering the liquid to the reservoir, either because the liquid inside the bulk liquid container has been consumed or alternatively a user has removed the bulk liquid container of the system, a sensor is placed next to the liquid supply line. This sensor, which in a first mode is a capacitive sensor, detects a liquid / air transition within the liquid supply line. A cap sensor is placed next to the lid covering a container with a respective bulk liquid. The lid sensor detects when the lid is not in position above the container. The air vent valve closes when both the capacitive sensor has detected a liquid / air transition and when the lid sensor has been decoupled to allow the pump to siphon off the liquid from the bulk liquid container. The capacitive sensor continues to monitor the liquid supply line for an air / liquid transition indicative that the liquid is being discharged by siphoning from the bulk liquid container to the reservoir. The air vent valve then opens. While an indication is expected that the bulk liquid container has been replaced and the liquid is being discharged by siphoning into the reservoir. An associated control system keeps track of the number of iterations of the pump that have occurred, each one removing a known volume from the deposit. Knowing the total volume available for withdrawal at the point where the liquid / air transition is detected, the control system calculates the number of pump iterations that can be carried out before the deposit is dry and maintains the count of the remaining number Once the air / liquid transition is detected, the air vent solenoid is disconnected providing the reservoir with an air vent and the system again works allowing the gravity feed from the bulk container to the reservoir. In one embodiment, a bulk liquid container lid sensor provides an indication to the associated processor of whether a bulk liquid container is installed in the system, thereby preventing a misperception that the bulk liquid reservoir is has resupplied. In addition, the liquid module is installed in a sliding extractor in another useful mode. Bulk liquid containers have mechanical handling means placed between the containers and a rear wall of the extractor in yet another embodiment. Therefore, the present invention allows a pump or similar device to continue withdrawing the liquid from the present system, even when the supply of the withdrawn liquid is being increased. The replacement of liquid bulk containers in the present system is a relatively simple task.

BRIEF DESCRIPTION OF THE DRAWINGS This invention is pointed out with particularity in the appended claims. The foregoing and other advantages of this invention can be better understood by reference to the following description taken in conjunction with the accompanying drawings, in which: Figure 1 is an isometric view of an automated analyzer instrument employing the delivery apparatus of the invention. liquid of the present invention, Figure 2 is a partial view of an automated analyzer instrument showing the liquid supply apparatus in accordance with the present invention; Figure 3 is a simplified perspective view of the liquid delivery apparatus of the invention; Figure 2; and Figure 4 is a side view of the liquid supply apparatus of Figure 2.

DETAILED DESCRIPTION OF THE INVENTION Referring now to Figure 1, an automated processing system 10 in a first embodiment includes a control system 12 based on a microprocessor. Specifically, in one embodiment of the present invention, the processing system 10 is an automated test system for carrying out tests with a minimum of manual intervention. The processing system 10 further includes a liquid module 40 that includes a plurality of containers 42a-42e of bulk liquid to which reference is generally made as 42, and a corresponding plurality of liquid parts 44a-44e, to which reference is generally made to 44. The liquid module 40 also includes a plurality of dilution apparatuses and pumps in a pump module 46. In this specific view, the pumps are not visible. The liquid module 40 allows the processing system 10 to operate continuously while the required liquids that are provided from the bulk liquid containers 42 and the tanks 44 are being replenished. Therefore, as will be described in further detail below, the liquid module 40 allows an operator to place the bulk liquid containers 42 without having to interrupt the operation of the processor system. Referring now to Figure 2, the liquid module 40 includes the bulk liquid containers 42 and the liquid reservoirs 44. The liquid module 40 is placed in an extractor 47 coupled with the rollers 48. The extractor 47, therefore, is allowed to open providing easy access to the bulk liquid containers 42 and the liquid reservoirs 44.

Each of the bulk liquid containers 42 engages a corresponding reservoir of the plurality of liquid reservoirs 44. Thus, for example, in the illustrated embodiment, the container 42a of the bulk liquid remains in fluid communication with the reservoir 44a. The reservoir 42a may be in communication with any combination of pumps through a series of valves. One embodiment including these pumps 46 is illustrated in Figure 2. In the illustrated embodiment, each bulk tank 42 and the respective tank 44 form a liquid supply subsystem 49, and this liquid module 40 includes four of these subsystems 49 for liquid supply, even though other numbers may be used in the alternative modes. By taking the bulk container 42a as representative of the containers 42b-42e a cover 50a is movably coupled with a frame above the upper surface of the bulk liquid container 42a, to cover an opening in the upper surface of the container 42a. As will be described in detail below in relation to Figures 3 and 4, the liquid is sucked from the bulk liquid container 42a through a liquid path having a termination in an inner portion of the bulk liquid container 42a, the path being partially placed in the cover 50a. In one embodiment, the bulk containers retain approximately 2 liters of liquid and the reservoirs retain approximately 270 milliliters of liquid. The specific amounts are selected depending on the needs of the processing system 10. Thus, when a capacitive sensor (to be described subsequently) detects a liquid-to-air transition in the liquid path from the bulk liquid container to the reservoir, the system 10 can continue to pump a predetermined liquid volume after which it stops the process. This predetermined volume typically allows enough time to replace the bulk liquid container. In a further embodiment of the present system, a user is informed of the empty state of the bulk liquid container and the pending and actual system is stopped by some form of annunciator, such as a warning screen in a display unit or display, which is associated with the processing system 10 and the control system 12. As can be seen, bulk liquid containers slide out as a unit in an extractor 47, thus providing easy access to bulk liquid containers. When little or no liquid remains in the bulk liquid container, an operator removes the bulk liquid container 42 from the extractor 47 by lifting the lid 50 of the respective bulk liquid container, which activates a lid sensor 59 shown in FIG. Figure 4. This lid sensor 59 is in communication with the control system 12 which in this way calculates the condition of the lid 50. If the bulk container 42 is removed from the extractor 47 but a container of replacement in the extractor when the lid 50 falls beyond a predetermined level (horizontal in a first mode), this lid sensor 59 indicates to the control system 12, that a replenishment container 42 has not been installed. Therefore, the only time where the lid sensor 59 does not provide a signal to the control system 12, is when a bulk liquid container 42 has been properly placed in the extractor 47. In a first embodiment of the present invention , the lid sensor 59 is a slotted optical detector wherein a portion of the lid 50 is placed between an optical emitter and the detector when the lid 50 is closed above a bulk liquid container 42. Otherwise, the lid 50 does not block the optical signal between the emitter and the detector, and a signal is conveyed to the control system 12. In one embodiment of the present invention, the control system 12 incapacitates removal of liquid from the liquid subsystem 49 when the lid sensor 59 indicates that a bulk liquid container 42 has not been properly positioned in the extractor 47. In an alternative mode, continuous pumping as will be described below and the control system 12 records the signal from the lid sensor 59 in a system sales record. It should be noted that in certain embodiments the liquid can simply be added to the bulk liquid container 42 to replenish the liquids stored therein. In a preferred operating or operating method, however, the empty bulk liquid container 42 is replaced by a filled bulk liquid container 42 having the appropriate liquid. In one embodiment, a second sensor circuit (not shown) is placed to directly detect whether a bulk liquid container 42 is or not placed in the extractor 47. This sensor may be optical, magnetic, aural or mechanical. In still another embodiment, the bulk liquid containers 42 each have a mechanical key positioned on a back surface to prevent inadvertent installation of the incorrect bulk liquid container 42 at a position in the extractor 47. This mechanical key is intended for coinciding with a cooperation key on the rear wall surface of the drawer 47. Referring now to Figures 3 and 4, the liquid supply subsystem 49 includes the container 42a of the bulk liquid and the liquid container 44a. In Figure 3, for reasons of simplifying the various details such as that of the lid 50, the tubes 77 have been removed. The pump line 77 couples the liquid tank 44a and a pump 51 to the pump module 46. An output of the pump 51 is coupled with a portion of the system 10, wherein the liquids stored in the tank 44a and the bulk container 42a are, of course, necessary, which is referred to as the liquid application point 53 in Figure 3. When an operator lifts the lid 50a, a tube 66 placed in the bulk liquid container forming part of the fluid path 58 between the container 42a and the bulk liquid of the reservoir 44a, is withdrawn from the container 42a thereby separating the container 42a from the bulk liquid from the reservoir 44a. The container 42a of the bulk liquid can then be removed. The container 42a of the bulk liquid is provided either as a disposable container or as a refillable container. The reservoir 44a can also be removed for rinsing and cleaning purposes depending on the specific type of liquid stored therein. In a first embodiment, the tanks are provided having a length typically of approximately 17.78 centimeters, a width typically of approximately 6.35 centimeters and a height typically of approximately 6.35 centimeters. Referring to the simplified view of Figure 3, the general operation of the present invention is described. A principal aim of the illustrated elements is to allow the continuous pumping of a liquid even when the content of the bulk liquid container 42a is low or has been exhausted. This is usually achieved by allowing the pump to remove the liquid from the reservoir 44a until the bulk container 42a has been replaced or replenished. Specifically, the pump 51 is connected to the reservoir 44a through the line 75 of the pump, which passes through a reservoir connector 76 and extends to the reservoir 44a. The reservoir 44a receives a supply of liquid from the container 42a of the bulk liquid through the fluid path 58. Each respective extremity of this path 58 extends towards the bottom of the reservoir 44a, and the container 42a of the liquid in bulk. The reservoir 44a is further provided with an air vent tube 83 having a first end that matches the reservoir connector 76 (not shown in Figure 3), and a second end that matches a "normally open" connection 93. or N / 0 of an air vent valve 94 positioned next to an upper surface of the container 42a of the bulk liquid. The other connection 95 in valve 94 is left open to the environment. Therefore, the air ventilation tube 83 normally provides a path by which the air found in the reservoir 44a is removed. The reservoir connector 76 can be configured to incite trapped air within the reservoir 44a which is discharged through the ventilation tube 83, for example, having a concave bottom surface centered around the interface of the area ventilation tube 83 toward the connector 76. Placed below the container 42a of the bulk liquid and close to the fluid path 58, there is a capacitive sensor 84. This sensor operates by detecting a change in capacitance between the detector 84 and the fluid path 58, resulting from passing a liquid / air transition within the path 58. It depends on an indication of this transition for the control system 12 in a first modality. The control system 12 closes the air valve 94 closing the air path between the reservoir and the environment when both the capacitive sensor 84 detects a liquid / air transition as when the lid sensor 59 detects the movement of the cap 54 of bulk fluid. When the air / liquid transition is detected by the sensor 84 and the lid sensor 59 indicates that the lid 50 is in its position, the control system 12 is informed of this and the air valve 94 is sent from a control knob. which is delayed towards the normally open state by again connecting the tank 44 to the environment. The aforementioned elements of the liquid supply subsystem 49 operate in the following manner. Assume that the reservoir 44a is full, and that the bulk container 42a contains a relatively large amount of a similar liquid therein. At this initial point, the air vent valve 94 would be disconnected with the normally open position thereby forming an air path between the reservoir 44a and the environment. Any air found in the evacuation tank 44a out of the air ventilation tube 83. Since the bulk liquid container 42a is open to the environment, the liquid levels within the air vent tube 83 and the bulk container 42a tend to equalize. Suppose further that the fluid path 58 has been fully charged or in other words, it is filled with liquid. A pump 51 or diluent (not shown) connected to the subsystem 49 removes a known volume of liquid from the reservoir 44a, each time the pump is activated. This volume taken from the reservoir 44a is replaced by an equal volume from the bulk liquid container 42a through the fluid path 58. As the level of the liquid within the bulk container 42a decreases after each successive removal, the level of liquid within the air vent tube 83 is similarly reduced. Eventually, bulk container 42a will be free of liquid. Then, each withdrawal by means of the pump 51 attracts the air in addition to the tube 66 placed inside the container 42a of the liquid in bulk. Another way of manifesting this is that a liquid / air transition proceeds through the path 58 of fluid from the container 42a of the bulk liquid to the reservoir 44a. As this transition proceeds, the level of liquid within the air vent tube 83 is equalized with respect to the liquid remaining within the fluid path 58. Eventually, the liquid / air transition proceeds beyond the capacitive sensor 84 which is positioned close to the fluid path 58. As will be seen, this sensor 84 detects the liquid / air transition and sends signals to the control system 12 of what has occurred. Any subsequent transition of the lid sensor 59 sends signals to the system 12 to close the air vent valve 94 by closing the air vent tube 83 from the environment. Therefore, the liquid remaining in the air ventilation tube 83 is retained therein. At the point of detection of the liquid / air transition by the sensor 84, a known volume of liquid available for pumping in the subsystem 49 remains. This known volume is a volume that can be accurately pumped before a risk of that the air penetrates in the volume pumped. Using this known volume, the control system 12 is able to calculate how many times the pump can be activated without replacing the bulk liquid container. If a new bulk container 42a has not been installed in time, the system is stopped and the user is notified of this condition. In an alternative embodiment, a user may be notified of the empty state of the container 42a of the bulk liquid and of the pending pumping cessation due to a low volume of liquid available in the reservoir 44a. This notification may be effected through a display terminal (not illustrated) associated with the control system 12 or some other similar device. When a user has installed a new or refilled bulk container 42a as indicated to the control system 12 through the lid sensor 59, the liquid is again removed through the fluid flow path 58 during each iteration of the pump, forming in it an air / liquid transition. Eventually, this transition will advance beyond the capacitive sensor 84 that transmits what has happened to the control system 12. In response, the control system 12 deactivates the air vent valve 94 allowing the air vent tube 83 to expel air that has accumulated within the reservoir 44a and the fluid flow path 58. Even when the lid sensor 59 provides an indication to the control system 12 that a bulk liquid container 42 has been installed, the control system 12 keeps track of the number of pump iterations that have occurred since the liquid / air transition was detected. These are necessary because an empty container 42 may have been installed. Therefore, the control system does not stop the count of the iterations of the pump until the air / liquid transition is detected by the capacitive sensor 84 and the control system 12 detects the proper installation of a container 42a of the liquid a bulk through the lid sensor 59. Once these are detected the air vent valve 94 is disconnected allowing the liquid supply subsystem 47 to be primed again. The bulk container 42a can also be replaced before it dries. For example, liquids placed in it may have exceeded shelf life. In this case, the air is attracted to the fluid path 58 when the lid 50 is opened and the tube 66 is removed from the container 42a of the bulk liquid just when the container 42a has dried. The liquid supply subsystem 49 will now be described in further detail with reference to Figure 3, and in particular to Figure 4. The container 42a of the bulk liquid has a threaded neck portion 54 through which is placed a first end 56a of a bulk fluid connector 56. The bulk liquid connector 56 includes a portion of the fluid path 58. A pair of fittings 60, 62 are coupled with the first and second ends of the connector 56. The first of the fittings 60 is placed through the neck region 54 and inside the interior region 64 of the container 42a of the bulk liquid.

The connector 56 couples with a cover 50a. A first end of the lid engages a hinge 61 thereby allowing the lid to pivot about the hinge 61 from a closed position as shown, to an open position, where the container 42a can be removed or removed of liquid in bulk. A tube 66, which is provided with a curved plastic tube (polyethylene) in a first embodiment, has a first end positioned above a toothed portion of the accessory 60 and a second end positioned toward a lower surface of the inner portion 64 of the 42a container The tube 66 is curved in such a way that when the lid 50a is lifted from the upper surface of the container 42 around the hinge 61, the connector 56, the accessory 60 and the tube 66 are lifted out of the container 42a. The container 42a can then be easily removed from a drip tray 70 that is contoured to receive the bulk liquid container 42a. Any material not adversely affected by the liquid in the bulk liquid container and having similar structural characteristics can alternatively be used for the tube. A second pipe 72 has a first end coupled with a serrated portion of the fitting 62 and a second end coupled with an inlet 74 of the reservoir, of the reservoir 44a of the liquid. A second end of the inlet 74 engages a connector 76 of the reservoir having a channel 78 positioned therein. The channel opens into a second fitting 80 which is placed in the inner region 45 of the reservoir 44a of the liquid. A tube 82 has a first end positioned above the toothed portion of the fitting 80, and a second end placed near the lower surface of the reservoir 44a of the liquid. Coupled with an intermediate region of the fluid pipe 72 is a "U" shaped bracket 82 that separates a capacitive sensor 84 at a predetermined distance from the pipe 72. As will be seen, the capacitive sensor provides a non-invasive technique, so of monitoring the fluid path 58, thereby reducing the possibility of contamination that is due, for example, to liquids being collected in the orifices of a sensor and crystallizing after the bulk liquid container and the liquid are empty. sensor does not have a liquid flowing through it. This crystallization would affect the functioning of the sensor. However, in a modality of the liquid supply subsystem 49 where crystallization is not a threat to operation, a pressure sensor or an optical through-flow sensor may alternatively be employed.

Having shown the preferred embodiment, those skilled in the art will understand that many variations are possible that are still within the scope and spirit of the claimed invention. Therefore, the intention is to limit the invention only as indicated by the scope of the claims.

Claims (27)

CLAIMS:

1. A liquid supply system for supplying a liquid to a pump through a pump delivery path, the system comprises: a liquid containment system having a replaceable loose bulk container discharged and a sealed reservoir that is fed through the Bulk container through a conduit; a sensor for the limits between the air and the liquid in the duct; a tank ventilation duct; a controlled pump for the ventilation duct of the tank; a pump to remove the liquid from the tank for use on request; and a controller that closes the controlled valve during the detection of the limit of the air liquid passing through the sensor, to operate the pump and to open the controlled valve during the detection of an air to liquid limit that passes to that sensor.

The liquid delivery system according to claim 1, further comprising: an air vent path having first and second ends, the first end is positioned within the reservoir, and the second end is connected to the valve controlled 3.

The liquid delivery system according to claim 1, wherein the sensor is a non-invasive capacitive sensor.

The liquid delivery system according to claim 1, wherein the bulk package further comprises: a hinge on a top surface thereof; and a lid attached to the bulk container in the hinge, where the duct is placed adjacent to the lid and removed or removed from the bulk container when the lid is lifted away from the second container.

The liquid delivery system according to claim 4, wherein the hinge further comprises a lid position sensor for detecting the position of the lid relative to the bulk container.

6. The liquid supply system according to claim 1, further comprising an extractor where the bulk container is placed.

7. A liquid supply system according to claim 6, wherein the extractor further comprises a drip tray in which the bulk container is placed.

The liquid delivery system according to claim 7, wherein the drip tray is contoured to securely receive the bulk container.

The liquid delivery system according to claim 6, wherein the extractor further comprises a rear wall adjacent to the second liquid container.

10. The liquid supply system according to claim 9, further comprising a device identifying the bulk container placed on the rear wall of the extractor.

11. A liquid supply system according to claim 10, wherein the device identifying the bulk container further comprises a single mechanical key placed on the rear wall of the extractor, the mechanical key of the rear wall is facing the Mechanical cooperation key placed in the bulk container.

12. A liquid supply system for continuously supplying a pump with the liquid through a pump supply path, the system comprising: a liquid container; a container supply path having first and second ends, the second end being positioned within the liquid container; a reservoir placed under the container and capable of communicating with the pump through a pump delivery path, the reservoir has an interior volume in which the quantity of the liquid is stored and removed by the pump regardless of the state of the liquid container; a sensor positioned close to the package delivery path to detect liquid / air and air / liquid transitions within the package delivery path; an air ventilation path having first and second ends, the first end is placed inside the tank; an air vent valve positioned proximate to the liquid container, the second end of the air vent path being connected to a normally open orifice; and a control system based on the microprocessor in electrical communication with the sensor and the air vent valve to close the air vent valve and count a number of pumping iterations of known volume that is removed by the pump from the reservoir after the sensor detects a liquid / air transient within the supply path from the container, and to open the air vent valve when the sensor detects an air / liquid transient within the supply path from the container , whereby the pump receives the liquid from the reservoir when liquid is not provided by the liquid container through a delivery path, and otherwise from the liquid container.

13. The liquid delivery system according to claim 12, the liquid container further comprising: a hinge on the upper surface thereof; a lid fixed to the liquid container in the hinge; wherein the flow path of the container is placed adjacent to the lid and removed from the liquid container when the lid rises away from the liquid container.

The liquid delivery system according to claim 13, wherein the lid further comprises a lid position sensor for detecting the position of the lid relative to the liquid container.

15. The liquid supply system according to claim 12, further comprising an extractor in which the liquid container is placed.

16. The liquid supply system according to claim 15, wherein the extractor further comprises a drip tray in which the liquid container is placed.

17. The liquid delivery system according to claim 16, wherein the drip tray is contoured to securely receive the liquid container.

18. The liquid supply system according to claim 15, wherein the extractor further comprises a rear wall adjacent to the liquid container.

19. The liquid supply system according to claim 18 further comprising a single mechanical key placed in the liquid container, the mechanical keys allow proper seating of the liquid container only if the mechanical key of the container is configured approximately with with respect to the mechanical key on the back wall.

20. A continuous liquid supply module having a support structure comprising: a bulk liquid container having a hole positioned in an upper surface thereof; an articulated lid fixed to pivot in the support structure and extending above the upper surface of the bulk liquid container; an arcuate tube having a first end capable of being placed inside the container of the liquid in bulk and which is understood behind and below the container of the liquid in bulk to end at a second end of the arcuate tube; a capacitive sensor placed near the arcuate tube below the bulk liquid container to detect the limits of liquid and air within the arcuate tube; a sealed unloaded tank placed underneath the bulk liquid container, the second end of the arched tube being placed inside the tank.

The module according to claim 20, further comprising: an air vent tube having a first end positioned within the reservoir extends upward to a second end; and an air vent valve positioned above the highest liquid level within the bulk liquid container and the second end of the air vent tube is positioned in the air vent valve.

22. The module according to claim 21, further comprising a lid sensor positioned in the support structure to detect a position of the hinged lid.

The module according to claim 22, further comprising a microprocessor-based control system in electrical communication with the capacitive sensor, the air vent valve and the lid sensor.

24. The module according to claim 21, further comprising an extractor c horizontally capable of moving where the support structure is placed, the extractor further comprises a drip bath configured to receive the liquid bulk container.

The module according to claim 24, wherein the drip tray further comprises parallel linear recesses, and wherein the bulk liquid container comprises parallel linear cooperating protuberances capable of being placed within the parallel linear recesses.

26. A liquid supply system that provides an uninterrupted liquid supply as an empty bulk liquid source is replaced by a full bulk source, the system comprising: a bulk liquid container to be delivered; a liquid withdrawal conduit selectively placed in and out of contact with the liquid in the bulk container, in order to respectively permit the withdrawal of the liquid therefrom and the removal of a bulk container for replacement with another bulk container; a liquid reservoir supplied with the liquid through the withdrawal line; a pump for moving the liquid from the withdrawal conduit to a point of use; and a valve system for automatically withdrawing the liquid including the air from the withdrawal duct during the replacement of the bulk container and for purging the air in the container attracted from the bulk container through the withdrawal duct later.

27. A method for supplying a liquid of the first and second containers interconnected to a pump through a pump flow path comprising: pumping a volume of liquid from the first container to the pump through the pump flow path; withdrawing an equal volume of liquid from the second container to the first container through a flow path of the container, monitoring the flow path of the container for a liquid / air transition indicative of an interruption in the liquid flow from the second container; decreasing a known liquid volume available to the pump from the first container when the first container is not being supplied by the second container as indicated by the monitored liquid / air transition; monitoring the flow path of the container for an air / liquid transition indicative of a resumption of supply of liquid from the second container to the first container; restarting the known volume available to the pump from the container when the first container is again being supplied by the second container as indicated by the supervised air / liquid transition; and stopping the withdrawal from the first container if the known liquid volume has been decreased to zero. SUMMARY OF THE INVENTION A liquid supply module includes one or more sets of bulk liquid containers each supplying a respective reservoir through a liquid supply line. Bulk liquid containers and tanks are discharged above the highest liquid level in the system. A pump periodically removes a known volume of liquid from a reservoir that is replenished from a bulk liquid container. A sensor detects a liquid / air transition in the liquid supply line to the reservoir, indicative of the depletion of the liquid re-supply from the bulk liquid container. An air vent solenoid valve in communication with the reservoir closes when an empty bulk liquid container is replaced. The normal operation of the pump discharges the liquid out of the bulk container by means of siphonic action after the replacement of the container. A control system follows the iterations of the pump and calculates a number of executable iterations that remain before the tank becomes dry. With a new bulk container in place, the air vent solenoid opens the reservoir air reservoir during the detection of an air / liquid transition, allowing liquid to flow by gravity from the bulk container into the reservoir. A bulk container lid sensor indicates whether a bulk liquid container has been properly installed in the system. The liquid module is disposable in a sliding extractor and can include unique mechanical handling means to ensure that each bulk liquid container fits in only one position in the liquid supply module.