Abstract:
Water dispenser, which comprises, in addition to a water container, a filter element contained within a filter housing having an inlet and a dispensing outlet, a source of pressure and first valve and first conduit means for feeding water from the container to the filter housing inlet; means for feeding gas to the filter inlet to create gas pressure at the inlet, consisting of a reservoir, and the control means comprise the third conduit and valve means for permitting or preventing the admission of water into the reservoir, second valve and conduit means for controlling the level of the water in the reservoir, a pressure gauge for monitoring the pressure at the filter inlet; and control means for controlling the gas feeding means to cause or stop the feeding. The source of pressure may be a compressed gas cylinder provided with valve and conduit means for controlling the admission of compressed gas from the cylinder into the water container, and the means for feeding gas to the filter inlet comprise conduit and valve means for feeding gas to the inlet directly from the gas cylinder.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a water dispensing apparatus, which provides filtered water free of specific microorganisms, and comprises means for assuring the filter integrity. The dispensing apparatus of this invention is particularly intended for drinking water in domestic use. 
     BACKGROUND OF THE INVENTION 
     Various types of domestic drinking water purification systems, which claim to provide microorganism-free filtered water, are known in the art The most commonly used systems remove protozoan cysts, such as  cryptorsproridium Parvum  and  giaria Lablia , which may be found in insufficiently chlorinated water supplies. As the cysts are from 5-10 microns in size, they are typically removed by a one micron rated microporous filter element, usually fabricated from carbon block, so that it simultaneously removes chlorine and other impurities to improve taste. Submicron microporous filters fabricated from ceramic or synthetic polymeric materials, with a maximum pore size of 0.2 micron, are also known. Such filters are capable of removing pathogenic bacteria such as  pseudomonas Aurigena , which may also be found in domestic, treated water supplies. The danger is that the users of such filters may be given a false sense of security at times when such organisms are discovered in the local water supply and a “boil water” alert is issued by the authorities. Although several such filters may be performance-tested when certified for the validity of their claims, few, if any, claim to 100% quality assure every filter unit sold Thus, some finite fraction of units sold do not in fact meet the claimed retention In addition, the filter element might either have been damaged prior to being installed, or might be improperly installed by the user in the housing, such that leakage of unfiltered water into the final product is possible. Finally, glue seals to the filter in the fabricated filter element can sometimes fail over time in an aqueous environment, depending on factors such as pH and temperature and the number of mechanical shocks given to the system during opening and closing the water supply to the system. In all of the above instances, since such purification systems do not comprise means for testing the integrity of the filter, the user has no way to verify if the system will in fact perform according to claimed performance specifications. 
     Means for testing filter integrity are also known in the art. Thus, U.S. Pat. No. 4,872,974 discloses a membrane filter testing method, which comprises increasing the pressure at the primary side of a membrane filter fixedly accommodating the housing and wetted with a liquid, by a gas at a predetermined rate, and checking whether the pressure at the primary side of the membrane filter is within a specified judging range after the lapse of a predetermined period of time. 
     U.S. Pat. No. 5,417,101 discloses a method and apparatus for isolating defective filter elements by measuring a gas flow rate under known pressure conditions through said elements. 
     U.S. Pat. No. 5,594,161 discloses a method of testing the integrity of a filter element in a filter assembly which includes wetting the filter, subjecting the inlet side of the filter to a gas pressure, measuring the pressure in the outlet conduit as a function of time, and determining whether a pressure measurement at a preselected time exceeds a reference pressure by a predetermined amount. 
     An article entitled “Predicting . . . Removal Performance of membrane Systems using In Situ Integrity Testing”, published in Filtration and Separation, January, February 1998, pp. 26-29, describes two main methods for testing membrane systems integrity, the first of which consists in applying air at a pressure bubble point to one side of the membrane, isolating and then measuring the declining pressure over time. The bubble point hereinbefore referred to, or more exactly, the bubble point pressure, is defined as the pressure required for forcing the air to flow through the pores of a membrane whose pores have been initially completely filled by a liquid. The other method consists in filling the shell of the module with a liquid and allowing the air leakage to displace liquid from the shell. The flow rate of displaced liquid is then a direct measure of the membrane integrity. 
     The testing methods of the prior art, as summarized hereinbefore, and in general, all the methods of the art, require the measurement of a physical quantity, be it a volume or a pressure, and therefore, a certain degree of expertise on the operator&#39;s part and the presence of the required measurement components. They are, therefore, unsuited to a domestic drinking water apparatus. On the other hand, domestic apparatus should be provided with methods for testing the integrity of the filter, to avoid the danger of a supply of unsafe water. 
     It is therefore a purpose of this invention to provide a domestic water-dispensing apparatus that is provided with the means for testing the integrity of the filter. 
     It is another purpose of the invention to provide a domestic water-dispensing method and apparatus that do not require the measurement of physical quantities, and judge the integrity of the filter by visual inspection or by sensing of a physical property for the presence of air bubbles. 
     It is a further purpose of this invention to provide such a method and apparatus that are simple and of simple and secure operation and require no expertise on the user&#39;s part. 
     It is a still further purpose of this invention to provide a domestic water-dispensing apparatus, comprising means for determining the filter integrity, which are simple in structure and operation and economical. 
     It is a still further purpose of this invention to provide a domestic water-dispensing apparatus, comprising automatically controlled means for determining the filter integrity. 
     Other purposes and advantages of the invention will appear as the description proceeds. 
     SUMMARY OF THE INVENTION 
     The water dispenser with filter tester according to this invention comprises: 
     1—a water container, 
     2—a filter contained within a pressurizable housing having an inlet and a dispensing outlet connected to the filtered fluid side of the filter; 
     3—a source of pressure; 
     4—first valve and conduit means for leading water from said container to the filter housing inlet; and further comprises: 
     5—means for feeding gas to said filter housing inlet to generate gas pressure at said inlet; 
     6—a pressure gauge or transducer for monitoring the pressure at the filter housing inlet; and 
     7—control means for controlling said gas feeding means to cause or stop said feeding. 
     In a form of the invention, the means for feeding gas to said filter housing inlet comprise: 
     a—a reservoir, 
     b—second valve and conduit means for controlling the level of the water in said reservoir; and 
     c—third conduit and valve means for connecting said reservoir to said filter housing at a second inlet; 
     and the control means for controlling the gas feeding to the filter housing inlet comprise third valve and conduit means to permit or prevent the admission of water into said reservoir. 
     In said first form of the invention, the source of pressure is preferably a pump or a cylinder containing compressed gas and provided with valve and conduit means for controlling the admission of compressed gas from said cylinder into said water container. If the source of pressure is a pump, said second valve and conduit means connect said reservoir to said pump and/or to said filter housing inlet or disconnect said reservoir from said pump and/or said filter housing inlet If the source of pressure is a compressed gas cylinder, said second valve and conduit means connect said reservoir to said water container when compressed gas has been admitted into it and/or to said filter housing inlet or disconnect said reservoir from said container and/or to said filter housing inlet. 
     In a second form of the invention, the source of pressure is a compressed gas cylinder provided with valve and conduit means for controlling the admission of compressed gas from said cylinder into said water container, and the means for feeding gas to said filter housing inlet comprise conduit and valve means for feeding gas to said filter directly from said gas cylinder. 
     In said first form of the invention, said second valve and conduit means, when open, selectively allow said source of pressure to feed water into said reservoir, whereby to displace air therefrom or to draw water therefrom, selectively to cause water partially to fill said reservoir to a predetermined, normal level or to a higher testing level. 
     Said third conduit and valve means, when open, permit to introduce into said second filter housing inlet air displaced by water fed into said reservoir and to displace air and/or water from the inlet side of said filter housing. Preferably, said filter housing is provided, in addition to said dispensing outlet, with a second outlet on the inlet side of the filter, which is more preferably a feedback outlet connected to conduit means for returning, to said water container, water displaced from said filter. 
     The control means are programmed, in the first form of the invention, so as to actuate the source of pressure when said second valve and conduit means connect it to said reservoir, and stop it when said pressure measurement means indicates that the air pressure at the filter housing inlet has reached a predetermined test pressure, which is lower than the bubble point pressure of the filter. The predetermined air pressure is chosen in relation to the pore size and function of the filter and the meaning of the test of integrity. If one defines gross mechanical failure as a defect of 10 microns or more, then the predetermined integrity test pressure is set at a value whose minimum is 0.2 bar , and whose maximum is a pressure equal to 80% of the bubble point pressure of the filter. 
     In said second form of the invention, the conduit and valve means for feeding gas to the filter directly from said gas cylinder are activated to stop said gas feeding when the pressure at the filter housing inlet has reached said predetermined test pressure, lower than the bubble point pressure. 
     If at the test pressure bubbles appear at the filter housing outlet, this means that filter integrity is lost. Then an alarm, with which the dispenser is provided, gives an acoustic or optical alarm signal, such as e.g. a warning light or a writing, to indicate that the integrity of the filter has been compromised and water from the outlet may not be of the specified purity which the filter is meant to deliver. The machine is then disactivated until the filter has been replaced. If no bubbles appear at the filter outlet, then the filter is normally fictional and the water is restored in the reservoir to a normal level, and the apparatus can be used, immediately or whenever required, as a filtered water dispenser. 
     It will be understood, therefore, that the water dispenser of the invention has three modes: the inactive mode, the dispensing mode, in which it operates as a conventional dispenser, and the testing mode, in which it permits a test of the integrity of the filter. In the inactive mode, all valves are closed. In the dispensing mode, the first valve and conduit means are open. In the test mode, gas is fed to the second filter housing inlet The control means are programmed to place the water dispenser in the dispensing or the testing mode, or to inactivate it, depending on a command which the dispenser user can give in any convenient, even conventional, way, e.g. by means of a key or keys connecting it to or disconnecting it from a power source, whether a power line or an independent source, such as battery, or selectively controlling circuits of a microprocessor, or the like. The dispenser is inactivated when it is efficient, but no water is to be dispensed, or when the filter is being replaced. After the test has been terminated and the filter has been replaced or it has been found that it should not be replaced, the apparatus is inactivated and is ready to be returned to the dispensing mode, or is directly returned to it It also follows logically from the above that the control means to the apparatus may be programmed to automatically carry out some combination of the three modes upon a single command by the user. Thus, after each dispense activation, or some preset number of dispense activations, the test may be automatically initiated. 
     While the invention is of particular interest for domestic water dispensers, this is not a limitation of the invention, since it is applicable to water dispensers in general, including industrial or public dispensers, regardless of their size or their specific use. 
     Correspondingly, the invention comprises a method for testing a filter contained within a pressurizable housing in a household water dispensing apparatus, which, in the first form of the invention, comprises the following steps: 
     1—providing a reservoir, 
     2—feeding water into it to a predetermined level; when it is desired to test the filter: 
     3—filling the filter housing with water and forcing water into all pores of the filter, 
     4—feeding water into said reservoir to raise the water level therein, while allowing air contained therein to flow out of said reservoir into the second filter housing inlet; thereby displacing the water contained in the inlet side of the filter housing through the second outlet, 
     5—monitoring the air pressure at the second filter housing inlet; 
     6—discontinuing the feeding of water into said reservoir when said pressure has become the test pressure; and 
     7—verifying whether air bubbles appear in the water issuing from a filter housing outlet, and if they do appear, substituting the filter, while if they do not appear, using the dispensing apparatus in the normal way. 
     It is obvious that the water is fed into the reservoir by means which depend on the source of pressure, and thus by pumping it if the source of pressure is a pump or by connecting the reservoir to the water container when this latter is under gas pressure, if the source of pressure is a compressed gas cylinder. 
     In the second form of the invention, after the housing and filter have been filled with water, the method comprises testing the filter by: 
     I—feeding gas to the housing inlet from the compressed gas cylinder; 
     II—monitoring the air pressure at the filter housing inlet; 
     III—discontinuing the feeding of gas when said pressure has become the test pressure; and 
     IV—verifying whether air bubbles appear in the water issuing from a filter outlet, and if they do appear, substituting the filter, while if they do not appear, using the dispensing apparatus in the normal way. 
     Since raising the water to the higher level serves to create the predetermined test pressure by compressing the air above the water, different level ratios of the test level to that of the normal level may be adopted in individual cases, depending on the dimensions of the various parts of the apparatus, to achieve the correct pressure. 
     The filter be of any used in a water dispensing apparatus, particularly domestic ones, but may be, for example only, a microporous, 0.2 micron filter prepared from a synthetic polymer, such as polysulphone or nylon, or an inorganic polymer such as a ceramic material. Such filters have a bubble point pressure, when wetted with water, from 3.5 to 4.5 bar. Typically, such filters have intrinsic pure water flows of 20-40 cc/sq.cc. filter area/bar. 
     The volumes of the various parts of the apparatus depend on its use. By way of example, in a domestic dispenser, the water container may have a capacity from 0.5 to 5 liters, and the reservoir a volume from 50 cc to 1.5 liter. 
     The invention further comprises a method of operating a water dispenser, particularly a domestic one, having an inactive, a dispensing and a test mode, which comprises placing the dispenser in the test mode, carrying out the testing method hereinbefore described, substituting the filter if it is found to be faulty, and placing the dispenser back into the dispensing mode. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a schematic representation of an apparatus according to an embodiment of the invention; 
     FIG. 2 schematically illustrates an embodiment of automatic bubble signaling device; and 
     FIG. 3 is a schematic representation of an apparatus according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, numeral  10  designates the water container, which is filled by means not illustrated, and may be either manual or automatic in nature. Numeral  12  is a pump, and numeral  13  is the filter housing containing a filter  14 . These are the normal components of a water-dispensing apparatus, and can be of any type known in the art other than what is specifically described herein. The filter is preferably chosen from among the group consisting of microporous synthetic membranes or microporous filters prepared from ceramic materials, metal, or carbon, with a nominal pore size of a value sufficient or smaller than that required to retain 99% or more of  cryptosporidium Parvum, giardia Lablia  and  pseudomonas Aurigena.    
     Numeral  15  indicates a reservoir. In the normal dispensing operation, the water in reservoir  15  is at the level indicated by arrow  16 , which will be called hereinafter the “normal level”. Above that level, reservoir  15  is filled with air which can enter it through a valve  17 , when this is open. 
     Water container  10  is connected to the inlet of pump  12  by conduit  20 , which includes a valve  21 . The inlet of pump  12  is also connected to reservoir  15  through pipe  22  and valve  23 . The outlet of pump  12  is connected to a pipe  25 , which has two branches, the first connected to valve  26  and through it to reservoir  15 , and the second connected to valve  27  and through it to an opening into the inlet side of filter housing  13 . Another such opening leads through a valve  29  into a conduit  28 , which leads back to water container  10 . Another opening on the inlet side of the filter housing is connected to a pipe  30 , on which is mounted a pressure switch or transducer means  37 , for confirming that the desired test pressure has been reached, and which branches out into branch  31 , having a valve  32  and leading back to water container  10 , and a branch  38 , connected through valve  34  to reservoir  15 . The filtered water outlet side of the filter housing is connected to a dispensing pipe  35  on which is mounted a one way dispensing check valve  36 , which opens to dispense liquid upon the application of a small pressure (e.g. 0.05 bar) sufficient to overcome the force of the check valve. This valve seals the system against microbiological intrusion from the pure water side and also prevents dripping from the filter outlet when the dispense mode is not in operation. A bubble detector  39  is connected to pipe  35 . 
     The operation of the machine, in its three modes, takes place according to the following stages. 
     Inactive mode: 
     1. When the machine is inactive, all valves are closed. 
     Dispensing mode: 
     2. To start the dispensing mode, a start signal is given in any appropriate way, e.g. by depressing a key which closes a circuit and connects the operative portions of the machine to a source of power. 
     3. Valve  21  opens, valve  27  opens, pump  12  starts, and water is pumped at a pressure sufficient t assure that it is transported from container  10  to the filter housing  13 , through the filter  14  to dispensing valve  36 , and, water is dispensed. 
     Test mode: 
     4. To stop the dispensing mode and prepare for the filter integrity check, a stop signal is given in any appropriate way, which resets all valves to the inactive, closed mode and closes pump  12 . 
     5. Then valve  29  opens—to prevent further water being dispensed and reduces the pressure to atmospheric pressure in the filter. 
     6. Valves  26  and  21 , and  34  open, and the pump is activated. This pumps water into reservoir  15  to allow the air in the reservoir to be pushed into the filter housing  13  and displace the water back to container  10  through exit pipe  28 . 
     7. As soon as air is detected through the exit pipe  28 , valve  29  closes, and air pressure builds in the filter housing  13  as more water enters reservoir  15 . 
     8. The integrity check of the filter  14  starts now. The pressure at the filter inlet rises, until the test pressure, (e.g. 0.5 bar, which is preferably well below the filter&#39;s bubble point pressure) has been reached. At this point, the water in reservoir  15  will have reached the level indicated at  11 , which is the highest level it is assumed to reach. Pressure switch or transducer means  34  will then confirm by appropriate signal that the test pressure has been reached and pump  12  will cease operation. If the filter  14  is integral, no air will pass  35 , which is filled with water from the previous dispense cycle. If bubbles appear in it, bubble detector  39  will be activated and will generate an appropriate signal to indicate tat the filter is defective and must be replaced. At this point, the integrity check is finished, and valves  26  and  34  return to their closed state. 
     Return to inactive mode: 
     9. If the filter is found to be in satisfactory condition, or otherwise has been replaced, the machine must be readied for normal operation. For this purpose, an appropriate signal is given, valves  21  and  23  open to reduce pressure to atmospheric pressure and return water back to container  10  via valve  21 . Air is now back in the top of the reservoir  15  and the level of water therein returns to the normal level. 
     10. Valve  21  closes, and valves  27 ,  17  and  32  open, pump  12  starts , and water is pumped from reservoir  15  into the filter housing  13  (timed such that it pumps all of the water and some additional air). 
     11. Valve  21  opens, valves  23  and  17  close, and water is pumped from container  10  to expel any additional air that may be in the filter housing  13  via valve  32  and pipe  31 . 
     12. Pump  12  stops, and valves  21 ,  27  and  32  close. All valves are now closed and the machine is now inactive, but ready to be reactivated. 
     The water in tube  35  during the integrity test must be checked, as has been said, to determine whether bubbles are exiting from filter  14 . The check could be a visual one, and such a check is included in the scope of the invention. However it is possible and preferred to effect the check by a device  39  that senses a physical parameter that is affected by the presence of bubbles, and generates a signal if bubbles are present. Said signal can produce a visual or acoustic alarm, or automatically set forth the procedure programmed for this case, which involves disactivating the machine and readying it for reactivation after the filter has been changed, as hereinbefore set forth in describing the operating cycle of the machine. 
     An example of optical-electronic, automatic bubble checking device is the following, illustrated in FIG.  2 . It comprises an infrared transmitter/receiver pair (briefly, an “IR TD”), comprising an IR transmitter  50 , an IR receiver  51 , optical means, generally indicated at  42 , for collecting the IR radiation from transmitter  50  and reflecting it back to receiver  51 , an electronic alarm not shown, monitoring the intensity of the reflected radiation and so adjusted that it generates a signal if the intensity of the reflected IR radiation exceeds a predetermined threshold value. The water to be tested flows through a pipe  43 , which is either transparent or has a transparent window  44 , in front of said IR TD. If no bubbles are present, the reflected radiation sensed by IR sensor  41  has a certain value, which is taken as the threshold value. If bubbles pass in front of the IR TD, the increased reflection due to the bubbles causes the reflected radiation to exceed the threshold value, and the alarm means to react as programmed. 
     As stated hereinbefore, the invention is not limited to the use of a pump, but any source of pressure can be used, in particular compressed gas, as e.g. in apparatus for carbonating beverages. Such an embodiment is illustrated, by way of example only, in FIG.  3 . All the components of the embodiment of FIG. 3 that are or may be equal or equivalent to components of the embodiment of FIG. 1, are indicated by the same numerals. In this embodiment, a gas cylinder  40  is mounted on a cylinder holder generally indicated at  41 . The cylinder holder may be of any kind adapted for liquid aerating machines and may be, in particular, such as described in EP 0 472 995 B1 or in PCT patent application IL 98/00470, and is therefore not described in detail. It will generally comprise means, such as screw means, for attaching the gas cylinder  40  to it, and a gas cylinder valve, unless this is part of the gas cylinder itself. As described in the aforesaid applications, the gas cylinder valve can be opened by any suitable means, such as a lever  45  to allow gas to escape from the gas cylinder. However, while the cylinder valve control means illustrated is a lever, that is normally hand-operated, this is merely a schematic illustration It is preferred that the apparatus be provided with control means, that will place it in the inactive, dispensing or test mode in response to a simple command given by the user, e.g. by depressing a key or the like; and therefore, when a compressed gas cylinder is used as a source of pressure, it is desirable to provide a cylinder valve that may be opened or closed by said control means, without direct manual intervention, and such valves are within the state of the art and need not be described or illustrated. 
     When the valve opening means is actuated and the cylinder valve is opened, the gas escapes through conduit  46 . As described in the aforesaid PCT application, the inlet of said conduit may pass through a pre-filter, such as a small block of porous material fixed to the outlet of the cylinder holder and which retains unwanted particles that may block the subsequent gas passageways. Such a pre-filter will also perform as a safety feature, as it will reduce the risk of liquid carbon dioxide entering the main filter unit. 
     A water container  48 , which has the same purpose as container  10  of FIG. 1, has an inlet in which opens gas conduit  46 . It is further provided with a dip tube  47 . Dip tube  47  is continued by conduit  49 , leading to valve  21  and through it to conduit  25 . Conduit  25  leads through valve  27  to filter housing  13  and branches out into two branches  22 , both if which lead, through valves  23  and  26  respectively, to reservoir  15 , as in the embodiment of FIG.  1 . As in said embodiment, conduits  28  and  31  are feed-back conduits to water bottle  48 . 
     The operation of this embodiment of the invention is the same as that of the first embodiment hereinbefore described, except that, instead of staring/stopping the pump to create or discontinue pressure, this is achieved by opening/closing the gas cylinder valve. 
     As has been said, in a second form of the invention the test of the filter can be carried out by feeding gas directly from a gas cylinder, such as cylinder  40 , to the filter inlet. In that case, the reservoir  15 , and conduits leading to and from it, can be omitted and conduit means can be provided leading directly from the gas cylinder to the filter inlet. Valve means will be provided selectively to connect the gas cylinder to the water container, when the apparatus is in the dispensing mode, or to the filter, when the apparatus is in the testing mode. Said valve means will be controlled, preferably by a program, to close and discontinue the gas feeding when the test pressure has been reached. In all other respects, the operation of the apparatus may be the same as described with reference to the first form of the invention. 
     It would also be possible, though less desirable, to provide the apparatus both with a pump and with a compressed gas cylinder, using the first to dispense water and the second to provide gas at test pressure to the filter, or to replace the water container by a direct connection to the water mains and provide gas for testing by a compressed gas cylinder. 
     Although embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, without departing from its spirit, or exceeding the scope of the claims.