UV LED sterilizing tank

A water tank configured to store water from a water supply includes an inlet configured to receive water from the water supply, and an outlet configured to dispense water. The water tank includes a reflective coating positioned on an inner surface of the tank, and an end wall including a light emitting diode oriented toward the outlet. The light emitting diode and the reflective coating are operable to disinfect water from the water supply.

FIELD OF THE INVENTION

The present invention relates to a water tank configured to hold and disinfect water at point-of-use.

BACKGROUND

Water tanks are widely used to store treated water. Typically, the water tanks are oversized to ensure customers constantly have access to treated water. Therefore, it is easy for bacteria to grow in the tank during long periods of storage time. Microorganisms from the air additionally contaminate tank water via a tank outlet, or other tank openings.

Often times, water tanks are lined with a reflective liner in order to use total internal reflection (TIR) to conserve UV light and irradiate bacteria. However, TIR methods require the liner to include a lower refraction index than that of the water within the tank, which is expensive to manufacture. Additionally, more cost-effective polymer options, such as liners composed of PFA or acrylic, do not meet the refraction index requirements for TIR. Finally, these methods typically include an air gap positioned between an outer wall of the tank and the liner, which complicates the manufacturing process.

SUMMARY

In one aspect, the invention provides a water tank configured to store water from a water supply, including an inlet configured to receive water from the water supply, an outlet configured to dispense water, a reflective coating positioned on an inner surface of the tank, and an end wall including a light emitting diode oriented toward the outlet, wherein the light emitting diode and the reflective coating are operable to disinfect water from the water supply

In another aspect, the invention provides a water tank configured to store water from a water supply, including an inlet configured to receive water from the water supply, an outlet configured to dispense water, a light emitting diode positioned on the inner surface, and a control system operable to modify an operating current of the light emitting diode based on a state of the tank.

In another aspect, the invention provides water tank configured to store water from a water supply, including an inlet configured to receive water from the water supply, an outlet configured to dispense water, a reflective coating positioned along an inner surface of the tank, a first light emitting diode positioned on a first wall of the tank, a second light emitting diode positioned a second wall of the tank, wherein the second wall is positioned perpendicular relative to the first wall, and a control system operable to control the intensity output of the first and second light emitting diodes.

DETAILED DESCRIPTION

The invention includes a water tank10embodying the invention. The water tank10includes a water inlet14and a water outlet18, such that the inlet14receives water from a water supply and dispenses water at the outlet18.

The tank10may be molded into a main water treatment system or be used separately from the system. Specifically, the tank10is operable to hold a filtered water supply (e.g., water from a filtration unit such as a reverse osmosis system, a carbon filter, etc.) prior to consumption. The water supply may therefore be characterized as downstream from the filtration unit and upstream of the inlet14. A flow of water from the water supply into the inlet14is defined as being a downstream water flow. An upstream direction is defined as opposite the downstream water flow. In alternative embodiments, the water supply may be characterized as water received from a municipal water supply, optionally purified or treated or filtered.

With references toFIGS.1-6, the tank10is substantially rectangular. More specifically, the tank10includes four side walls22, a first end wall26, and a second end wall30. The side walls22are positioned between the first and second end walls26,30, such that the side walls22are oriented approximately 90 degrees relative to the end walls26,30. In the shown embodiments, the side walls22and end walls26,30are substantially flat and rectangular. In alternative embodiments, the tank10may include different shapes (e.g., circular, conical, and/or alternative flexible shapes), thereby providing rounded side walls22and/or rounded end walls26,30. The inlet14is positioned on one of the side walls22, and the outlet18is positioned on another of the side walls22, such that the inlet and outlet are positioned on opposite ends of the tank10. In alternative embodiments, the inlet14and outlet18may be positioned at alternative locations on the tank10.

The side walls22and the end walls26,30are constructed of substantially reflective materials. More specifically, the tank10may be constructed from metals (e.g., stainless steel, etc.), plastics (e.g., polypropylene, polyethylene, POM, ABS, PTFE, etc.), or alternative materials. The tank10additionally includes a reflective coating32. More specifically, the reflective coating32may be applied to an inner surface22aof the side walls22, an inner surface26aof the first end wall26, and/or an inner surface30aof the second end wall30. With reference toFIG.7, the reflective coating32is comprised of the following: (1) a first layer, or primer36, applied to the inner surface22a,36a,30aof the side walls22and/or the end walls26,30; and (2) a second layer, or UV clear top coat40, applied on top of primer36. In the embodiments described herein, the primer36is a high aluminum content primer. However, in alternative embodiments, the primer36may be composed of alternative materials that reflect UV light sufficiently to achieve the anti-bacterial effect of the present invention. Additionally, in the shown embodiments, the top coat40is composed of a thin film of PFA (perfluoroalkoxy), acrylic, or silicon. However, in alternative embodiments, the UV clear top coat40may be composed of alternative embodiments. Application of the primer36prior to the UV clear top coat40ensures that UV clear top coat40, rather than the primer36(e.g., aluminum), is in direct contact with the tank water.

In some embodiments, the reflective coating32may include a film composed of porous PTFE (polytetrafluoroethylene), such as a PTFE membrane and/or expanded PTFE. In such instances, the reflective coating32does not include the UV clear top coat40, and the PTFE is secured (e.g., glued) onto the inner surface22a,26a,30aof one of the walls22,26,30(preferably on the end walls26,30). In such instances, a backside of the film may be covered with a polymer including a surface energy higher than that of the PTFE (e.g., polypropylene), thereby facilitating attachment of the film to the tank10. The thickness of the PTFE film is approximately 0.05-1.50 mm.

With reference toFIGS.1-6, the water tank10additionally includes at least one UV LED34. More specifically, the UV LED34is positioned on the inner surface22a,26a,30aof one of the side walls22, the first end wall26, or the second end wall30. In some embodiments, the UV LED34may be sealed within a waterproof housing within the tank10. Specifically, the UV LED34forms a high intensity zone capable of irradiating microbes and other bacteria found within the water in the tank10. The UV LED34is specifically positioned on one of the side walls22or end walls26,30such that it reflects light directly toward the outlet18. More specifically, the UV LED34and the reflective coating32radiate such that water exiting the tank10is irradiated of microbes. The UV LED34includes a wide viewing angle of at least 100 degrees, preferably 120-140 degrees. When the UV LED34is positioned on the first end wall26or the second end wall30, the UV LED34is positioned at an angle less than ½ of the viewing angle of the UV LED34relative to the outlet18. Therefore, the UV radiation is able to reach the outlet tip directly.

In some embodiments, the UV LED34may be positioned such that it may disinfect the entire opposite side wall22of the tank10from which it is mounted. In still further embodiments (FIG.4), reflective tubing (e.g., PTFE tubing)38may be inserted into the outlet18in order to provide additional reflection within the outlet18. In some embodiments (FIG.9), the tank10includes several UV LEDs34. The position of reflective coating32within the tank10depends on the position of the UV LED34. In some embodiments, the tank10may only be partially coated with the reflective coating32. More specifically, the reflective coating32may only be applied to the inner surface of the wall positioned opposite the wall including the UV LED34(e.g., the wall to be irradiated via the UV LED). For example, if the UV LED34is positioned on the first end wall26, then the reflective coating32may only be applied to the inner surface30aof the second end wall30. In alternative embodiments, the reflective coating32may only be applied to the inner surfaces26a,30aof first end wall26and the second end wall30.

The shape of the tank10depends on the position of the UV LED34. For example, the tank10may be molded to a conical shape, or other alternative shape, to ensure the surface area of the wall including the UV LED34is greater than the surface area of the wall opposite to the UV LED34, thereby improving tank reflection.

The position of the UV LED34and the reflective coating32impact the presence of bacteria (e.g.,E coli) within the tank water. With reference toFIG.8, altering the location of the UV LED34and the application of the reflective coating32, impacts the levels ofE-coliin stagnant tank water. Specifically, the results shown inFIG.8were obtained from an 8.5 L tank including one UV LED34and the reflective coating32. More specifically, the test duration time was 20 minutes, during which the UV LED34was illuminated. The test was conducted on three different tanks: a first tank including the UV LED34positioned on the first end cover26without the reflective coating32, a second tank including the UV LED34positioned on the first end cover26including the reflective coating32, and a third tank including the UV LED34positioned on the second end cover30including the reflective coating32. With continued reference toFIG.8, the second tank displayed the greatest rate of change in the reduction ofE-coliover time. Therefore, the optimal parameters for the tank10are positioning the UV LED34on the first end wall26and including the reflective coating32.

The UV LED34is in connection with a control system44(FIG.9) of the main treatment system. The control system44is operable to control the operation of the UV LED34. Specifically, the control system44periodically operates the UV LED34at different currents to inhibit bacteria growth within the tank10. In the shown embodiments, the control system44operates the UV LED34continuously with varying current settings. Additionally or alternatively, the control system44turns on the UV LED34and operates the UV LED34at a maximum operating current when the main treatment system is introducing water into the tank10via the inlet14, and/or when the water is exiting the tank10via the outlet18.

Operation of the tank10is initiated when a user operates the main treatment system, thereby initiating the flow of water from the water supply into the main treatment system. When the main treatment system is operating, the inlet14is opened to the system and the UV LED(s)34is turned on. The UV LED34remains on while water is flowing into the tank10via the inlet14, and may remain turned on for a predetermined period of time immediately after the water supply stops flowing into the inlet14. The tank10may store the water for extended periods of time, until the user opens the outlet18to remove the water from the tank10. During periods of extended time where the main treatment system is off (e.g., not delivering additional water into the tank10via the inlet14or exiting water from the tank10via the outlet18), the at least one UV LED34may be turned on in order to disinfect stagnant water held within the tank10at lower currents. Current may be varied based on operating status and stagnation hours. When the tank outlet18is opened, the UV LED34is turned on and the water may flow out of the tank10, such that the water is disinfected as it is exiting the tank10. After the outlet18is closed, the UV LED34remains on and is operated at a lower current.

In some embodiments, the cycle time and current output of the UV LED(s)34is variable during operating of the tank10. Specifically, the control system44changes the duration time and intensity of the UV LED34depending on the operation status. When water is flowing into the tank10via the inlet14, the control system44operates the UV LED34at a first, maximum intensity (e.g., a maximum current) and continues to operate at the maximum current for a predetermined period of time (e.g., within a range of 10-60 minutes after the water supply stops flowing). When the water supply stops flowing and the water within the tank10is stagnant, the control system operates the UV LED34at a second, lower intensity.

For example, the tank illustrated inFIG.9includes four UV LEDs: a first UV LED34a, a second UV LED34b, a third UV LED34c, and a fourth UV LED34d. The first and second UV LEDs34a,34bare positioned on the inner surface22aof the sidewalls22, and the third and fourth UV LEDs34c,34dare positioned on the inner surface26aof the first end wall26. When the user operates the main treatment system, the inlet14is opened. The control system44operates the UV LEDs34a-34dat the first, or maximum, operating current to reach a maximum intensity level (e.g., a 100% intensity level). The UV LEDs34a-34dremain operating at the maximum operating current as the tank10continues to fill with water.

When the user stops the main treatment system, thereby stopping the flow of water from the water supply into the main treatment system, the water in the tank10becomes stagnant and the tank10enters a transition state. The control system44then operates the four UV LEDs34a-34dat the second operating current to achieve a lower intensity level. The second operating current is less than the first operating current, such that the UV LEDs34a-34doperate at a second intensity level, which is 50%-100% of the maximum intensity level. The control system44operates the UV LEDs34a-34dat the second operating current for a predetermined period of time. In the illustrated embodiments, the predetermined period of time is within a range of 10-30 minutes. However, in other embodiments, predetermined the period of time may be longer or shorter.

After the predetermined period of time, the tank10enters a stagnation state. The control system44turns off the first and second UV LEDs34a,34b, and operates the third and fourth UV LEDs34c,34dat a third operating current to achieve a lower intensity level. The third operating current is less than the second operating current, such that the UV LEDs34c,34doperate at a third intensity level, which is 20%-80% of the maximum intensity level. The control system44alternates the operation of the third UV LED26cand the fourth UV LED26d. More specifically, the control system44will operate the third UV LED26cat the third operating current while the fourth UV LED26dremains off for a duration of time, and then operates the fourth UV LED26dat the third operating current while the third UV LED26cremains off for the same duration of time. In the illustrated embodiments, the duration of time is 60 minutes. However, in other embodiments, the time period may be longer or shorter. Operating one of the UV LEDs34a-34dduring stagnation time maintains the tank10at a biostatic state and prevents regrowth of bacteria within the tank10. Furthermore, alternating the operation between different UV LEDs conserves the LED life.

In some embodiments, the operating current of the UV LEDs34a-34dis ramped up during the stagnation state, thereby gradually increasing the intensity level of the UV LEDs34a-34d. For example, as illustrated in Table 1, at the initiation of the stagnation state (e.g., 1 hour), the control system44operates one of the UV LEDs (e.g., the first UV LED34a) at a first current (e.g., 20 mA). After a period of time (e.g., 1 hour of stagnation and 2 hours of total operation), the control system44operates the UV LED34aat a second current, which is greater than the first current (e.g., 30 mA). The control system44gradually increases the operating current until the UV LED34areaches the third operating current (e.g., 80 mA). In the illustrated embodiments, the UV LED34areaches the third operating current after 5 hours of stagnation of 6 hours of total operation. If the tank10remains in the stagnation state after the UV LED34aachieves the third operating current (e.g., after 6 hours of stagnation and 7 hours of total operation), the control system44then operates the UV LED34sat the first current value (e.g., 20 mA), restarting the operation. Alternating the current output of the UV LEDs34a-34d, and operating the UV LEDs34a-34dat an operating current less than the maximum operating current conserves the LED life. In some embodiments, the tank10includes a battery back-up, thereby allowing the UV LED(s)34a-34dto continuously operate in the event of a power outage. An example operation schedule is shown in Table 1. In the example operation, the maximum current operation of the LEDs34a-34dis 100 mA.

TABLE 1Operating Current Output of UV LED during Stagnation TimeTimeOperating CurrentOperating Status(hours)Output (mA)Filling tank0100Post-filling tank0.5100Stagnation120Stagnation230Stagnation340Stagnation450Stagnation560Stagnation670Stagnation780Stagnation820
As shown in Table 1, the current of the LEDs34a-34dis modified based on operating status and stagnation time. During the tank filling cycle, the LEDs34a-34dare operated at the maximum output to disinfect the incoming water. After filling the tank10, the LEDs34a-34dare continually operated at the maximum current output to completely disinfect the water and minimize the bacteria level (e.g., <10 cfu/ml). The tank10switches to a lower current output during stagnation. As the stagnation period gets longer, there is a higher possibility for bacteria regrowth. Therefore, the operating current gradually increases after a predetermined period of time (e.g., increasing 80% intensity every hour). As the LED current increases, disinfection rate includes and the bacterial level is minimized. If the stagnation period exceeds a predetermined period of time (e.g., 6 hours of stagnation, 7 hours of total operation), the system decreases to 20% current output and the cycle restarts. In some alternative embodiments, a single, low output current can be used through the entire stagnation period.

In some embodiments, the tank10may include only one UV LED positioned on the first end wall. In such instances, the UV LED remains on throughout the duration of the stagnation state. In some embodiments, the control system44may alternate operation of all of the UV LEDs34a-34d. For example, the control system44may operate the first UV LED34afor a duration of time, then turn off the first UV LED34aand operate the second UV LED34bfor a duration of time, then turn off the second UV LED34band operate the third UV LED34cfor a duration of time, etc.

In some embodiments, the tank10may additionally include a pump48operable to recirculate water within the tank10. In such instances, the pump48is operable to recirculate the water during the stagnation state in order to facilitate mixing of the water within the tank10. The pump48may be initiated in predetermined time increments. For example, the pump48may operate every 2 minutes. Alternatively, the pump48may continuously operate during the stagnation state. In some instances, the pump operation initiates when one of the UV LEDs34a-34dturns on.