Disposable Cartridge for an Electrolytic Cell

Abstract

Illustrative embodiments of the present invention are directed to a cartridge for use with an electrolytic cell having an interface. The cartridge includes a reservoir for containing a catholyte solution. The reservoir is removably coupleable with the cell. The cartridge also includes at least one cartridge port that is removably coupleable to an interface on the electrolytic cell. The port of the cartridge is also configured to cycle a catholyte solution between the reservoir and the electrolytic cell when the cartridge port is coupled to the interface of the electrolytic cell.

Description

PRIORITY

The present application claims the benefit of U.S. Application Ser. No. 61/173,411, filed Apr. 28, 2009, which application is incorporated herein, in its entirety, by reference.

TECHNICAL FIELD

The present invention relates to electrolytic cells, and more particularly, to electrolytic cells having catholyte reservoirs.

BACKGROUND ART

Electrolytic cells may be used for the production of various chemistries (e.g., compounds and elements). One application of electrolytic cells is the production of ozone. Ozone is an effective killer of pathogens and bacteria and is known to be an effective disinfectant. The Food and Drug Administration (FDA) approved the use of ozone as a sanitizer for food contact surfaces and for direct application to food products. Accordingly, electrolytic cells have been used to generate ozone and dissolve ozone directly into source water, thereby removing pathogens and bacteria from the water. As a result, electrolytic cells have found application in purifying bottled water products and industrial water supplies.

SUMMARY OF THE INVENTION

Illustrative embodiments of the present invention are directed to a cartridge for use with an electrolytic cell having an interface. The cartridge includes a reservoir for containing a catholyte solution. The reservoir is removably coupleable with the cell. The cartridge also includes at least one cartridge port that is removably coupleable to an interface on the electrolytic cell. The port of the cartridge is also configured to cycle a catholyte solution between the reservoir and the electrolytic cell when the cartridge port is coupled to the interface of the electrolytic cell.

In another illustrative embodiment of the cartridge, the cartridge is for use with an electrolytic cell that has an anode and a housing. The cartridge includes a cathode and a reservoir for containing a catholyte solution. The reservoir is configured to provide the catholyte solution to the cathode when the cell is in use and when the reservoir contains the catholyte solution. The cartridge also has a port that is removably coupleable to an interface of the housing of the electrolytic cell. Furthermore, the cathode is spaced from the anode of the electrolytic cell when coupled to the interface of the housing.

Various embodiments of the cartridge may also include a cartridge outlet port for allowing passage of the catholyte solution from the reservoir and a cartridge inlet port for allowing passage of the catholyte solution to the reservoir. Some embodiments may also include at least one valve to prevent the escape of catholyte solution when the cartridge port is decoupled from the interface of the electrolytic cell.

Illustrative embodiments of the present invention are also directed to an apparatus for generating ozone and dissolving ozone into a water source. The apparatus includes a housing forming an interior and an electrolytic cell within the interior. The cell has a cathode, a diamond anode, and a membrane between the cathode and the diamond anode. The apparatus also includes a cartridge that has a reservoir for receiving a catholyte solution. The reservoir is removably coupleable to the electrolytic cell. The cartridge also includes at least one cartridge port in fluid communication with the reservoir. The housing has an interface for removably coupling with the at least one cartridge port. The cartridge port and interface are further configured to cycle a catholyte solution between the reservoir and the cathode.

In exemplary embodiments of the apparatus, the cartridge port includes a cartridge outlet port for allowing the passage of the catholyte solution from the reservoir and a cartridge inlet port for allowing the passage of the catholyte solution to the reservoir. The apparatus may also include corresponding structures on the interface. For example, the interface may include a cathode inlet port for fluid communication with the cartridge outlet port and to allow passage of the catholyte solution from the reservoir to the cathode. Also, the interface may include a cathode outlet port for fluid communication with the cartridge inlet port and to allow passage of the catholyte solution from the cathode to the reservoir. In some embodiments, the interface further includes at least one valve to prevent the escape of catholyte solution when the interface is decoupled from the cartridge port. Additionally or alternatively, the cartridge port includes at least one valve to prevent the escape of catholyte solution when the cartridge port is decoupled from the interface.

In another illustrative embodiment of the apparatus, the apparatus includes a housing having an anode and a cartridge. The cartridge includes a cathode, a reservoir for containing a catholyte solution and for providing the catholyte solution to the cathode. The cartridge has a port that is removably coupleable to an interface of the housing. When coupled to the interface of the housing, the cathode is spaced from the anode of the electrolytic cell.

In other exemplary embodiments, the housing of the apparatus includes an anode inlet port and an anode outlet port such that source water flows through the anode inlet port to contact the anode and then flows through the anode outlet port. In various embodiments of the invention, the anode generates ozone from the source water in contact with the anode and dissolves the ozone in the source water. Additionally or optionally, the apparatus includes at least one valve to prevent the escape of source water when the cartridge is decoupled from the interface of the housing.

In exemplary embodiments of the cartridges and apparatuses described above, the cartridge or apparatus includes a membrane that is spaced between the cathode and the anode. In some embodiments, the electrolytic cell includes the membrane. In other embodiments, the cartridge includes the membrane. Furthermore, in exemplary embodiments, the membrane is a solid proton exchange membrane that provides for the exchange of protons between the cathode and the anode.

In other exemplary embodiments of the cartridges and apparatuses, a catholyte solution is contained within the reservoir. In some embodiments, the catholyte solution is in a solid form. For example, the catholyte solution may be in a pre-mixed powdered form.

In various embodiments of the above described cartridges and apparatuses, the reservoir includes a hydrophobic membrane that contains the catholyte solution while also allowing the passage of hydrogen gas from the reservoir.

In other exemplary embodiments of the cartridges and apparatuses described above, the cartridge or apparatus may include a sensor configured to monitor the performance of the electrolytic cell. The sensor senses, for example, the pH of the catholyte solution, conductivity of the catholyte solution, volume of the catholyte solution, and voltage draw in a power supply of the electrolytic cell. Additionally or alternatively, embodiments of the invention may also include an indicator for indicating when the cartridge needs to be replaced.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of an electrolytic cell and cartridge in accordance with one embodiment of the present invention;

FIG. 2 is a schematic, exploded view of an electrolytic cell in accordance with one embodiment of the present invention;

FIG. 3 is a schematic, assembled view of a cartridge in accordance with one embodiment of the present invention;

FIG. 4. is a schematic, exploded view of a cartridge in accordance with one embodiment of the present invention;

FIG. 5 includes two schematic views of an electrolytic cell and cartridge in accordance with one embodiment of the present invention;

FIG. 6 is a schematic, assembled view of a cartridge and electrolytic cell in accordance with one embodiment of the present invention;

FIG. 7 is another schematic, assembled view of a cartridge and electrolytic cell in accordance with one embodiment of the present invention;

FIG. 8A-8E schematically show several embodiments of a removably coupleable connection in accordance with illustrative embodiments of the present invention;

FIG. 9 schematically shows a cartridge and an electrolytic cell in accordance with one embodiment of the present invention;

FIG. 10 schematically shows another view of the cartridge of FIG. 9;

FIG. 11 schematically shows another view of the electrolytic cell of FIG. 9;

FIG. 12 schematically shows a cartridge and an electrolytic cell in accordance with one embodiment of the present invention;

FIG. 13 schematically shows another view of the cartridge of FIG. 12;

FIG. 14 schematically shows another view of the electrolytic cell of FIG. 12;

FIG. 15 schematically shows a cartridge and a base portion in accordance with one embodiment of the present invention;

FIG. 16 schematically shows another view of the cartridge of FIG. 15; and

FIG. 17 schematically shows another view of the base portion of FIG. 15.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In illustrative embodiments, an electrolytic cell receives its catholyte solution from a removably coupled cartridge. This cartridge may have a reservoir for containing the catholyte solution, portions of the cell, such as the cathode, or both the reservoir and portions of the cell. Details of various embodiments are discussed below.

FIG. 1 is a schematic representation of an electrolytic cell 100 in accordance with one embodiment of the present invention. The electrolytic cell 100 has two electrodes: an anode 120 and a cathode 122 that is spaced from the anode. To form ozone, a water source is applied to the anode 120 and a positive electric potential is applied to the anode while a negative electric potential is applied to the cathode 122. On the anode side of the cell 100, the difference in electric potential breaks up water molecules into 1) oxygen and 2) hydrogen cations. The oxygen forms into ozone, which dissolves into the water source. The hydrogen cations are pulled from the anode side of the cell 100 to the cathode side by the negative electric potential applied to cathode 122. Once on the cathode side of the cell 100, the cations form hydrogen bubbles 123.

During this reaction, it is possible for scale (e.g., calcium carbonate) from the source water to build up or deposit on the anode 120, the cathode 122, or other components of the cell 100. Eventually, if it does build up as noted, the scale impedes the electrochemical reaction within the cell 100. Moreover, such deposits within the electrolytic cell 100 can shorten useful cell life, or require disassembly and cleaning of internal components to restore cell performance and efficient production of target chemistries, such as ozone.

Accordingly, illustrative embodiments of the present invention flow a catholyte solution 110 along a surface of the cathode 122 to prevent the build up of scale on the cathode, thus improving cell efficiency. Without the catholyte solution 110, it is anticipated that the efficiency of the electrolytic cell 100 would decrease.

Any of a variety of catholyte solutions can be used. In illustrative embodiments of the present invention, a catholyte solution 110 with sodium chloride and citric acid facilitates the movement of cations from the anode 120 to the cathode 122. The sodium chloride and citric acid act to “pull” cations through the anode 120, the cathode 122 and ion exchange materials (e.g., a proton exchange membrane) without “clogging” components of the electrolytic cell 100, thereby effectively reducing scale deposits within the cell. Furthermore, citric acid helps regenerate the ion exchange materials used in water softeners by reacting with metal ions to form citrate complexes. In this way, the citric acid strips off the metal ions that accumulate on the ion exchange materials of the cell 100.

Illustrative embodiments of the present invention include a reservoir 104 (e.g., a tank or a container) that supplies the catholyte solution 110 to the cathode 122. To provide a large supply of catholyte solution 110 to the electrolytic cell 100, prior art electrolytic cells known by the inventors imbed the electrolytic cells as portions of larger systems or treatment facilities. When the catholyte solution 110 is depleted, the old catholyte solution is replaced with a new solution. The operation of changing catholyte solution 110 is typically messy and inconvenient. Trained personnel are often required to service such systems to ensure proper replacement and mitigate the mess. Often, redundant elements (e.g., electrolyte tanks and/or piping) are deployed in parallel so that the supply of catholyte solution 110 can be switched to another supply while the first supply is serviced. In other cases, the cathode 122 may be fed by plumbing some of the source water to the cathode. Undesirably, this prior art strategy can decrease the efficiency of the cell 100 because the source water may contain impurities that deposit and/or build up on the surface of the cathode. The inventors discovered that many of these problems could be avoided by using an easily replaceable cartridge 102 containing the catholyte solution 110. The inventors realized the use of illustrative embodiments of such a cartridge 102 1) reduced the complexity of the electrolytic cell 100, 2) typically maintained the useful life of the electrolytic cell, and 3) made the replacement of catholyte solution 110 more user-friendly.

Illustrative embodiments of the present invention thus avoid or significantly lengthen the useful life of electrolytic cells 100 and avoid service calls, cell exchanges, and/or other events that would require intervention from trained personnel. Illustrative embodiments of the present invention use simple and easy to change cartridges 102 that help prevent the deposit of scale and other impurities by collecting and removing the bulk of these impurities from the cathode 122.

As explained above, illustrative embodiments of the electrolytic cell 100 include an anode 120 and a cathode 122 to facilitate the formation of ozone. This electrolytic cell 100 is contained in the interior of a housing 118 (see FIG. 2) having an interface 119 (see FIG. 5) for removably coupling with the cartridge 102. The cartridge 102 includes the reservoir 104, which has walls 106 that define an interior 108 (e.g., recess) for containing the catholyte solution 100. To exchange fluids with the cell 100, the cartridge 102 includes an inlet port 112 and an outlet port 114 that are in fluid communication with the interior 108 of the reservoir 104. The interface 119 on the housing 118 thus removably couples with the cartridge ports 112, 114 such that the ports and interface fluidly communicate the cathode 122 with the reservoir 104 (see FIG. 5).

The anode 120 is spaced from the cathode 122 in the electrolytic cell 100. To facilitate the movement of protons (e.g., hydrogen cations) from the anode 120 to the cathode 122, in some embodiments, a solid membrane is used as an electrolyte and placed between the anode 120 and cathode 122 (e.g., a proton exchange membrane (PEM), such as Nafion®). Additionally, in some cases, the membrane 136 is used as a barrier to separate the catholyte solution 110 in the cathode 122 from source water flowing in the anode 120. To provide structural integrity to the membrane 136, the membrane may also include a supporting matrix (not shown).

In some embodiments, the anode 120 includes a diamond or a diamond layer that has been deposited by, for example, a chemical vapour deposition process. The diamond layer enables the formation of ozone in the source water supply. In some cases, the diamond is doped with boron, which further enhances the ozone forming properties of the diamond. The cathode 122 correspondingly includes a conductive material such as titanium. The negative electric potential applied to the conductive titanium cathode 122 pulls the hydrogen cations from the anode side of the electrolytic cell 102 towards the cathode side. In some embodiments, the conductive material may be platinum plated to increase its resistance to corrosion. The cathode 122 may also be formed from an expanded metal mesh that creates small passageways and/or pores through which the catholyte solution 110 and reaction by-products may pass. The expanded metal mesh allows for intimate contact between the cathode 122, the catholyte solution 110, and the membrane 136.

The housing 118 or the anode 120 itself includes an anode inlet port 124 and an anode outlet port 126. Piping 128 provides source water to the anode 120 such that the water flows through the anode inlet port 124 to contact the anode 120 (e.g., the diamond layer), and then flows through the anode outlet port 126. As the source water flows past the anode 120, water molecules are broken apart and hydrogen cations are pulled towards the anode 120 while ozone is created from the remaining oxygen. The ozone dissolves directly into the water and starts to kill off bacteria and pathogens, thereby purifying the water. The treated water then flows from the anode 120 through anode outlet port 126 and into piping 128 for use as, for example, drinking water.

The housing 118 and/or the cathode 122 itself includes a cathode inlet port 130 and a cathode outlet port 132. The cartridge inlet port 112 is in fluid communication with the cathode outlet port 132 through piping 134. In a similar manner, the cartridge outlet port 114 is in fluid communication with the cathode inlet port 130 through piping 134. In such an arrangement, catholyte solution 110 flows from the reservoir 104, through the cartridge outlet port 114, and into the piping 134. Then, the catholyte solution 110 flows through the cathode inlet port 130 to contact the cathode 122. In this manner, fresh catholyte solution 110 is supplied to the cathode 122.

As the catholyte solution 110 flows past the cathode 122, it collects the hydrogen bubbles 123 produced by the electrolytic reaction. As explained above, the inventors believe that the catholyte solution 110 also helps “pull” cations through the membrane 136 and may prevent build up of scale on the cathode 122. The depleted (or partially depleted) catholyte solution 110 then exits the cathode 122 through the cathode outlet port 132, flows through the piping 132 and the cartridge inlet port 112, and into the catholyte reservoir 104. In this way, the ports 112, 130, 122, 132 are configured to cycle fresh catholyte solution 110 from the reservoir 104 to the cathode 122, and depleted catholyte 110 back from the cathode to the reservoir.

In some embodiments, as shown in FIG. 3, the cartridge outlet port 114 is located below the cartridge inlet port 112 so that the force of gravity can help cycle catholyte solution 110 from the reservoir 104 into the cathode 122, and then back to the container. Furthermore, the cathode outlet port 132 may be placed vertically above the cathode inlet port 130, and the cartridge inlet port 112 may be located above the cathode outlet port so that the buoyant hydrogen bubbles 123 that are produced from the electrolytic reaction naturally rise through the cathode outlet port 132 and into the reservoir 104. In this manner, the generation of buoyant hydrogen bubbles 123 drives the flow of depleted catholyte 110 solution into the reservoir 104 and, in turn, fresh catholyte solution flows under the force of gravity from the reservoir 104 into the cathode. Whereas, if the cathode 122 were deployed horizontally, rather than vertically, bubbles 123 would exit from both ports 130, 132 and fresh catholyte solution would not reach the cathode 122 as efficiently, thereby hindering the generation of ozone. Additionally or alternatively, a pump may be used to flow depleted catholyte solution from the cathode 122 to the reservoir 104, and to help fresh catholyte solution flow from the reservoir towards the cathode.

As the catholyte solution 110 and the gas bubbles 123 flow into the reservoir 104, the bubbles collects at the top of the reservoir. To vent those bubbles 123 from the reservoir 104, some embodiments include a vent 116 in the cartridge. The vent 116 may employ a hydrophobic material as the vent media, but other materials may also be used. The inventors have discovered several factors to be considered in selecting a vent media:

• Pore size of the vent media
• Surface area of the vent media
• Wettability of the vent media
• Gas flow rate of the hydrogen gas through the vent media
• Maximum fluid pressure (e.g., force of the catholyte solution 110 on the vent media)
  For example, to prevent the vent 116 from leaking catholyte solution 110, it may be advantageous to decrease the pore size of the vent media. This approach, however, may decrease the gas flow rate through the vent 116. If the gas does not vent properly from the reservoir 104, the reservoir and/or the cathode 122 may fill with gas, thereby hindering the production of ozone. Nonetheless, the inventors have discovered that by using a vent 116 with a greater surface area, one may still be able to provide an acceptable gas flow rate and thus, avoid hindering the production of ozone.

Furthermore, exemplary embodiments of the present invention prevent the deposition of impurities (e.g., calcium carbonate) on the cathode 122 by collecting them in the reservoir 104. To that end, in some embodiments, the reservoir 104 includes a sump construction wherein a ridge or protrusion rises above the cartridge outlet port 114 so that the impurities in the depleted catholyte solution 110 settle under the force of gravity around the port, and are not swept back towards the cathode 122. Alternatively or additionally, the cartridge outlet port 114 may include a screen or filter so that the impurities do not flow through it and back towards the cathode 122.

The cyclical flow of catholyte solution 110 continues until the catholyte solution 110 is consumed (i.e., some or all of its solutes are depleted). Once depleted, the catholyte solution 110 is replaced with a new supply of catholyte solution. Illustrative embodiments of the present invention facilitate the exchange of catholyte solution 110 by simply interchanging the cartridge 102 with a new cartridge 102. To that end, in illustrative embodiments of the invention, the interface 119 delivers a removably coupleable connection for quick and easy exchange of the cartridge 102. The inventors have discovered several factors to be considered in selecting an interface 119:

• The fluid resistance through the interface 119.
• Bubble 123 migration through the interface 119.
• Ease of ex-changing the cartridge 102.
• Preventing spillage during an ex-change of the cartridge 102.
• Cost of the interface 119 and cartridge 102 (e.g., use of disposable materials).
• Reliability of the interface 119 (e.g., the cartridge should remain properly installed over its useful lifetime).
• Material compatibility between parts in the interface 119, cartridge 102, and/or cell 100.
  If the fluid resistance through the interface 119 is too great, there may be insufficient flow of catholyte solution 110 to the cathode 122. Undesirably, this insufficient flow may decrease the production of ozone in the electrolytic cell 100. Also, if the interface 119 constricts the flow of hydrogen gas out of the cathode 122 and into the cartridge 102 (e.g., it has obstructions or dimensions that are too small), hydrogen gas may build up in the cathode and exit through both cathode ports 130, 132 of the cell 100. This would prevent the cyclical flow of fresh catholyte solution 110 into the cathode 122, consequently hindering ozone production. Illustrative embodiments of the present invention avoid such issues. In the embodiment shown in FIGS. 5, 6, and 7, which is one of many ways to solve this problem, the interface 119 includes two right angle elbows 121 through which fluid flows between the cartridge 102 and the cell 100. The cathode inlet 130 and outlet ports 132 are positioned at the end of the elbows and are in fluid communication with the cartridge outlet 114 and inlet ports 112, respectively. The interface 119 permits the flow of catholyte solution 110 from the cathode 122 to the cartridge 102. The exemplary embodiments shown in FIGS. 5, 6, and 7 also allow hydrogen gas bubbles 123 to rise with gravity and flow out of the cathode 122.

Furthermore, as noted, the exemplary embodiment of the cartridge 102 shown in FIG. 5 is easy to install onto the electrolytic cell 100. Toward this end, the cartridge 102 may be installed by aligning cathode ports 130, 132 with cartridge ports 112, 114 and then applying a small downward force on the cartridge 102. Also, exemplary embodiments of the cartridge 102 are removably coupleable with electrolytic cell 100 and, therefore, are easily removable and exchangeable with another cartridge.

The term “removably coupleable” should be considered in the context of the ozone generation art. For example, one skilled in the art would not consider a cartridge to be “removably coupled” to the housing if it normally must be cut, forcibly broken from the housing, or if it required specialized training-beyond the minimal, “lay-person” training required for the cartridges described herein. Thus, a cartridge that requires significantly less time and complexity to replace, when compared to prior art ozone cartridges known by the inventors, should be considered “removably coupleable.” Below is a summary of some possible removable connections that should provide the desired results.

FIG. 8A shows an illustrative embodiment of one type of removably coupleable connection. In such an embodiment, the interface 119 includes a male connector 802 with an o-ring groove 804 on the outer diameter of the connector. An o-ring 806 disposed within the groove 804 forms a raised surface onto which a female connector 808 from one of the cartridge ports 112 and 114 is forced (e.g., interference fit). The female connector 808 may include a matching inner diameter o-ring groove 810. Thus, as the female connector 808 is forced over the o-ring 806, it “snaps” into place once the o-ring groove 810 slides over the male o-ring 806. Such “push to lock” connector elements may provide a tactile indication that the cartridge is properly installed. In other words, the user applies a force and “feels” and/or “hears” as the cartridge 102 properly snaps into place.

FIG. 8B shows another illustrative embodiment of a removably coupleable connection. In this embodiment, the o-ring 806 is not used. Instead, the o-ring is replaced with an integral contoured protrusion 812 extending from the outer diameter of the male connector 802 (e.g., an outer rib). The groove 810 in the female connector locks into place on the integral contoured protrusion 812. The integral protrusion 812 may be located on the outer diameter of the male connector 802 or on the inner diameter of the female connector 808 (e.g., an inner rib).

In the exemplary embodiment shown in FIG. 8C, the female connector 808 does not include a groove. Instead, the female connector 808 is a ductile tube that is placed over an outer rib 812 of the male connector 802. In an alternative embodiment, the male connector 802 constitutes the ductile tube and is forced into an inner rib of the female connector 808. The interference fit between the rib 812 and the ductile tube holds the cartridge 102 in place and seals the fluid connection between the cartridge 102 and the cell 100. A sufficient separating force between the cell 100 and the cartridge 102 would decouple the cathode ports 130, 132 from the cartridge ports 112, 114.

FIG. 8D shows yet another embodiment of a removably coupleable connection. In the embodiment shown, the interface 119 of the cell 100 may include at least one barb 814 onto which a ductile tube 816 (e.g., hose) from one of the cartridge ports 112 and 114 is forced. Or vice-versa, the cartridge ports 112 and 114 may include barbs onto which flexible tubes from the interface 119 are forced.

In another exemplary embodiment shown in FIG. 8E, the interface 119 of the cell 100 may include a male threaded connection 818 and the connection from the cartridge ports 112 and 114 may include corresponding female thread 820, or vice versa. Also, in the embodiment shown in FIG. 8E, the female connector 808 includes a swivel 822 so that a user can more easily secure the female thread 820 onto the male thread 818.

It should be emphasized that the examples shown in FIGS. 8A-8E are not intended to be an exhaustive list of all removable connections. Those skilled in the art thus could use any number of other removably coupleable connections.

Illustrative embodiments of the present invention also aim to provide for quick and easy exchange of catholyte solution 110 without spilling catholyte solution from the cartridge 102 and/or cathode 122. To contain the catholyte solution 110 in the reservoir 104 during the exchange, the cartridge 102 includes valves 138 (e.g., check valves and/or normally closed valves) to seal off the cartridge inlet port 112 and outlet port 114 (see FIGS. 3 and 4). Additionally or alternatively, the interface 119 on the housing 118 may include one or more valves 139 to seal off the cathode inlet 130 and/or outlet ports 132 of the electrolytic cell 100 (see FIGS. 6 and 7). The valves in the cathode inlet 130 and outlet ports 132 prevent escape of residual fluid in the cathode 122 and subsequent spillage from the cell 100 when the cartridge 102 is changed or refilled. The valves 138 may be normally closed valves. In other words, when connected or engaged, a mechanism, such as a spring, opens the valve and allows fluid to pass. When not connected or engaged, however, the spring pushes the valve closed to prevent fluid flow. Additionally or alternatively, the valves 138 may be check valves that allow fluid to flow in only one direction. When the fluid starts to flow in the wrong direction, the valves close and prevent the flow of fluid. Such check valves may be arranged to allow cyclical flow of catholyte solution 110 between the cartridge 102 and the electrolytic cell 100, but prevent a counter flow of catholyte solution.

In FIG. 5, valves 138 are located at cartridge ports 112 and 114 of the cartridge 102. The valves 138 are normally closed valves and thus, include springs that forcibly seal the ports 112, 114 when they are disconnected from the cell 100. When connected to the cell 100, the springs are forced back to allow fluid flow between the cartridge 102 and the cell 100. The valves 138 help prevent fluid and effluence spills from the cartridge 102 when it is exchanged. With respect to the cathode 122 side, when the cartridge 102 is exchanged, some catholyte solution 110 remains in the cathode 122. In some embodiments, no valves are provided on the cathode ports 130, 132 so that the catholyte solution 110 drains out of the inlet cathode port 130 under the force of gravity. Yet, in other embodiments, valves 139 (see FIGS. 6 and 7) are provided on the cathode ports 130, 132 to prevent or reduce spillage of catholyte solution 110 from the cathode 122. Furthermore, the interface 119, cartridge 102, and cell 100 can be designed to allow for different amounts of effluence. For example, in industrial settings, effluence of a few ounces of fluid from the electrolytic cell 100 may be acceptable, whereas, for consumer applications, effluence of only a few drops may be unacceptable.

In more specific exemplary embodiments, the valves 138 are integral to the removably coupleable connection of the interface 119 and the cartridge ports 112, 114. In that regard, illustrative embodiments of the present invention may use, for example, HFC series quick couplings supplied by the Colder Products Company™, which facilitate easy replacement of the cartridge while also preventing spillage.

The above described cell and cartridge arrangement 100, 102 is only an illustrative embodiment of the present invention. Other cell and cartridge arrangements 100, 102 are also within the scope of the present invention. For example, piping 134 may be eliminated by directly interfacing the cartridge inlet port 112 with the cathode outlet port 132 and directly interfacing the cartridge outlet port 114 with the cathode inlet port 130. Thus, catholyte solution 110 would flow directly from the reservoir 104 into the cathode 122, and vice versa. In other embodiments, there may be only one port between the cathode 122 and the reservoir 104. In such an embodiment, a first portion of the port may be dedicated to the flow of catholyte solution 110 from the reservoir 104 while a second portion of the port may be dedicated to flow of catholyte solution to the reservoir. In additional or alternative embodiments, the cathode 122 may be disposed within or partially within the reservoir 104.

In this regard, FIG. 9 shows an alternative illustrative embodiment of the present invention. In this embodiment, no piping 134 is present to cycle the catholyte solution 110 between the cartridge 102 and the electrolytic cell 100. Instead, the cartridge outlet port 114 is directly connected to the cathode inlet port 130 and the cartridge inlet port 112 is directly connected to the cathode outlet port 132. Furthermore, the cartridge 102 is located horizontally from the electrolytic cell 100, not vertically as shown in FIGS. 3, 4, 5, 6, and 7. In this horizontal embodiment, the buoyant force of the hydrogen bubbles 123 cycles catholyte solution 110 between the cathode 122 and the reservoir 104.

FIG. 9 also shows in more detail the configuration of the anode 120, the cathode 122, and the membrane 136 of the electrolytic cell 100. The electrolytic cell 100 includes an anode inlet port 124 and an anode outlet port 126 so that source water can flow through and contact the anode 120. Although the membrane 136 often can sufficiently prevent both catholyte flow to the anode side of the cell 100 and water flow to the cathode side of the cell 100, some embodiments also use a sealing gasket 900 (FIG. 9) to prevent fluid flow around the perimeter of the membrane 136. FIG. 10 shows a cross-sectional view of the electrolytic cell 100 with the sealing gasket 900 providing a barrier to fluids around the perimeter of the membrane 136.

The electrolytic cell 100 of FIG. 9 also includes a current spreader 902 that is attached to an electrical lead 904. The current spreader 902 is a sheet or mesh of conductive material (e.g., titanium, copper, or aluminum) that is in electrical contact with the anode 120. Some anodes 122, such as boron doped diamonds, have high electrical resistance. Thus, there is a power loss (and efficiency loss) as current from a singular electrical connection travels across the entire area of the diamond. The current spreader 902 limits such a power loss because it allows current from the electrical lead 904 to travel through a low resistance conductive material before it enters the diamond. FIG. 11 shows a cross-sectional view of the anode 120 and the current spreader 902. The anode 120 includes two boron doped diamonds having faces that are in electrical contact with the current spreader 902. In this manner, current is distributed to the entire face of each diamond.

In the embodiments shown in FIGS. 3, 4, and 9, the cartridge 102 includes the reservoir 104, and is removably coupled to the electrolytic cell 100. Some embodiments of the cartridge 102, however, have more than a removably coupleable reservoir. For example, FIG. 12 shows an embodiment of a cartridge 102 that includes both a reservoir 104 and a cathode 122. The inventors discovered that a cartridge 102 with both the cathode 122 and the catholyte reservoir 104 has several advantages. First, the configuration is advantageous because most of the scale, if any, forms on the cathode 122—whereas the anode 120 is less susceptible to scale—and thus, replacement of the cathode 120 may increase the efficiency of the cell 100. Accordingly, when removed, the spent reservoir 104 and corroded cathode 122 are replaced with a scale-free cathode 122 and fresh catholyte reservoir 104. Second, the anode 120 typically has a longer useful life than the cathode 122. Therefore, replacing the cathode 122 while preserving the anode 122 better utilizes the useful life of the anode. Third, some anodes 120 are formed from expensive materials such as diamond. As a result, preserving the anode 120 within the electrolytic cell 100 may provide further cost reduction.

In the embodiment shown in FIG. 12, the cathode 122 defines a portion of the reservoir 104 and thereby receives a constant source of fresh catholyte solution 110 from the reservoir. The cartridge 102 also includes a membrane 136 that is adjacent to the cathode 122. FIG. 13 provides a cross-sectional view of the cathode 122 and the membrane 136. It is advantageous to include the membrane 136 (e.g., a solid proton exchange membrane) because, during the cartridge exchange, the membrane 136 can prevent the outflow of catholyte solution 110 from the cathode 122. In some cases, this arrangement eliminates the need for additional valves to prevent out-flow of catholyte solution 110. In other embodiments, however, the cartridge 102 does not include the membrane 136. In such embodiments, the membrane 136 may remain affixed to the electrolytic cell 100 and/or the catholyte solution 110 is contained within the reservoir 104 and cathode 122 using valves and/or temporary barriers, such as adhesive sheets.

The cartridge 102 also includes a port 1200 that is removably coupleable to an interface 1202 on a housing 118 of the electrolytic cell 100. In the embodiment of FIG. 12, to secure the cartridge 102 to the cell 100, the port 1200 includes two flanges 1204, 1206 that each have a groove 1205, 1207 and the interface 1202 includes two latches 1208, 1210. The two latches 1208, 1210 engage, respectively, the two grooves 1205, 1207 of the port 1200. In this manner, the port 1200 and the interface 1202 are removably coupleable. To prevent water and catholyte solution 110 from leaking between the interface 1202 and port 1200, the electrolytic cell 100 may also include a sealing gasket 1212 that presses against the port 1200 of the cartridge 102 when the cartridge is coupled to the electrolytic cell 100.

Various other removably coupleable connections are also within the scope of the present invention. For example, in one specific exemplary embodiment, the port 1200 of the cartridge 102 and the interface 1202 of the electrolytic cell 100 are round. The port 1200 includes a flange around the perimeter of the port. The inner diameter of the flange includes female threads, while the outer diameter of the interface 1202 includes male threads. Using such an arrangement, a user can “screw” the cartridge 102 onto the interface 1202 of the electrolytic cell 100.

In various other exemplary embodiments, the removably coupleable connection uses guides or guide fingers to properly align and/or support the cartridge 102 when installed to the electrolytic cell 100. Once properly aligned, a locking mechanism firmly secures and removably couples the cartridge 102 to the electrolytic cell 100. For example, in some cases, the locking mechanism has an interference fit (e.g., press fit) between the port 1200 and the interface 1202 of the electrolytic cell 100. In other examples, the locking mechanism includes latches, adhesives, screws, snap fittings, and/or bolted assemblies, each of which can be used to firmly secure and removably couple the cartridge 102 to the cell 100.

In the embodiment of FIG. 12, to create the necessary electric potential at the cathode 122, one of the latches 1210 provides an electrical current to the cartridge 102. The cartridge 102 includes an electrical lead 1214 that is coupled to the cathode 122 and an electrical contact 1216 on the groove 1207. When the cartridge 102 is coupled to the electrolytic cell 102 and the cell is operating, current is applied to the latch 1210 and the latch makes contact with the electrical contact 1216 in the groove 1207. Current can then flow through the electrical lead 1214 to the cathode 122. In this manner, current can be provided to the cartridge 102 for the cathode 122 and other electrically dependent functionalities (e.g., indicators, pumps, displays, or sensors). On the anode side, a current spreader 902 and electrical lead 904 provide current to the anode 120. This configuration creates the electrical potential between the anode 120 and the cathode 122 that is necessary for the cell 100 to create ozone.

Illustrative embodiments of the present invention include valves 1216, 1218 to prevent spillage of source water when the cartridge 102 is decoupled from the electrolytic cell 100. The electrolytic cell 100 includes an anode inlet port 124 and an anode outlet port 126 so that source water can flow through and contact the anode 120. In the embodiment of FIG. 12, the electrolytic cell 100 includes valves 1216, 1218 that prevent the flow of source water to and from the anode 120 when the cartridge 102 is decoupled. In some embodiments, the valves 1216, 1218 are normally closed valves that use stems 1220, 1222 to engage the cartridge 102. When the cartridge 102 is decoupled, springs 1224, 1226 force the valves 1216, 1218 closed and prevent the flow of source water. When the cartridge 102 is coupled to the electrolytic cell 100, however, the cartridge pushes against the valve stems 1220, 1222 and thereby opens the valves 1216, 1218 so that source water can flow to the anode 120. This configuration prevents spillage of source water when the cartridge 102 is decoupled, but allows the flow of source water when the cartridge is coupled to the cell 100. FIG. 14 provides another view of the valves 1216, 1218 and their arrangement within the electrolytic cell 100.

FIG. 15 shows yet another embodiment of the present invention wherein the cartridge 102 includes the reservoir 104 and even more principal components of the electrolytic cell 100 (e.g., the anode 120, cathode 122, and the membrane 136). In such an embodiment, the cartridge 102 is configured to be removably coupleable to a base portion 1500. The base portion 1500 includes a source water supply. Additionally, the base portion 1500 may include other components (e.g., power source, displays, sensors, and indicators). In some embodiments, the base portion 1500 may be part of a point-of-use application, such as water lines in appliances and/or cleaning equipment (e.g., washing machines or power washing equipment).

The embodiment shown in FIG. 15 is similar to the embodiment shown in FIG. 12. Thus, much of the description of the embodiment shown in FIG. 12 applies equally to embodiment shown in FIG. 15 and, therefore, that description will not be repeated here.

One of the differences between the embodiment of FIG. 12 and the embodiment of FIG. 15 is that the anode 120 is included within the cartridge 102 in the embodiment of FIG. 15. The cartridge 102 also includes a current spreader 1502 for distributing current to the anode 120. To provide an electric potential to the anode, a second latch 1208 on the base portion 1500 provides current to an electrical contact 1504 on the groove 1207 when the latch is engaged with the cartridge 102. A second electrical lead 1506 provides current from the second electrical contact 1504 to the current spreader 1502. In this manner, current is provided from the base portion 1500 to the anode 120. As explained above with respect to FIG. 12, the other latch 1210 provides electrical current to the cathode 122. This configuration creates the necessary electrical potential between the anode 120 and the cathode 122. FIG. 16 provides another view of the anode 120, the cathode 122, the current spreader 1502, and the membrane 136 and their arrangement within the cartridge 102.

Additionally, in some embodiments of the present invention, the base portion 1500 includes a protrusion 1508 or a series of protrusions (e.g., ribs) that support the anode 120 when the cartridge 102 is coupled to the base portion 1500. The protrusions 1508 allow for source water to flow through them and contact the anode 120. FIG. 17 provides another view of the protrusions 1508 and their arrangement within the base portion 1500.

Illustrative embodiments of the cartridge 102 use materials that are compatible with the catholyte solution 110, ozone, and by-products of the electrolytic reaction. For example, a small fraction of ozone or other aggressive chemical may cross the membrane 136 and flow into the reservoir 104 of the cartridge 102. Therefore, in some embodiments, the cartridge 102 should be constructed from materials that will withstand the corrosive effects of the chemicals (e.g., metals and ceramics). On the other hand, the lifetime and disposability of the cartridge 102 may also be a factor. The use of cartridge materials that corrode when exposed to aggressive chemicals (e.g., plastics and polymers) may be mitigated by the cost of less expensive materials and/or if the cartridge is replaced before corrosion becomes a problem. In other words, the intended life-span of the cartridge 102 should be considered when selecting materials.

In some embodiments, the reservoir 104 contains a catholyte solution 110 that is in liquid form. In other words, the catholyte solution 110 includes chemical solutes, such as sodium chloride, potassium chloride, citric acid, acetic acid and/or other mild acids, dissolved in water (e.g., solutes include 8.3% of solution by weight). However, transportation and installation of cartridges 102 containing catholyte solutions 110 in liquid form may be expensive and difficult because of the excess weight of the water. Accordingly, in other embodiments of the invention, the solutes are present in the reservoir 104 in dry form. A predetermined amount of solute is present in the reservoir 104 to produce a solution with a predetermined concentration when mixed with water. Once the cartridge 102 is installed, a user can simply add water to dissolve the solutes and produce an appropriate catholyte solution 110. The water can be added manually by a user or, in other embodiments, the water can be added automatically through a replenishment valve 144 (e.g., solenoid valve, see FIG. 1). The replenishment valve 144 may also be used to relieve pressure in the electrolytic cell 100 and/or level off the amount of catholyte solution 110 in the reservoir 104. In some embodiments, the cartridge 102 can be provided without a solute. In such a case, a user adds the catholyte solution 110 to the reservoir 104, or adds a premixed powdered solute to the reservoir and then a predetermined amount of water. The water may be added manually or automatically injected into the reservoir 104 (e.g., via the solenoid valve). In other embodiments, the solutes may be added in the form of a solid mass (e.g., brick or tablet). The solid mass might be prefabricated with a predetermined dosage of solutes as a single solid body. A user can add the solid mass into the reservoir 104, avoiding the need to handle the powder form of the solute or liquid form of the catholyte solution 110.

In further illustrative embodiments of the present invention, there may be a plurality of the above-described cartridges 102 supporting (and removably coupleable) to a single electrolytic cell 100. An arrangement with multiple cartridges 102 may provide redundancy that allows one or more cartridges to be changed without cell 100 down time. In other embodiments, there may be a single cartridge 102 supporting (and removably coupleable) to a plurality of electrolytic cells 100. The single cartridge 102 might support cells 100 generating various ozone output levels and/or plumbed into different water circulation networks. In yet another embodiment, a single electrolytic cell 100 includes a plurality of different removably coupleable cartridges 102. For example, a first cartridge having a reservoir 104 may be removably coupleable to a second cartridge having a cathode 122. The second cartridge, in turn, is removably coupleable to the electrolytic cell 100. This configuration allows for the reservoir 104 and the cathode 122 to be replaced at different time intervals.

Illustrative embodiments of the present invention may also include an indicator to indicate when the catholyte solution 110 is depleted and/or when depletion is imminent. The indicator may be a light or a display device such as an LCD. In some cases, the indicator may automatically shut off power to the cell 100 when the catholyte solution 110 is depleted. The indicator may be triggered by a sensor 140 (or a plurality of sensors) (see FIG. 1) that monitors the performance of the electrolytic cell 100 by measuring certain variables such as the pH of the catholyte solution 110, the conductivity of the catholyte solution 110, and the volume of the catholyte solution in the reservoir 104 (e.g., height of the catholyte solution level in the reservoir). The pH, volume, and conductivity sensors 140 may be placed in the reservoir 104 of the cartridge 102, or, in other embodiments, the pH and conductivity sensors may be located at the cathode 122. Additionally or alternatively, in some embodiments, the sensor 140 may be a voltmeter that measures the voltage draw of the electrolytic cell 100. At constant current, as scale builds up on the cathode 122, the voltage draw of the electrolytic cell 100 increases. When the voltage reaches a certain value, an indicator may indicate that it is time to change the catholyte solution 110, the cathode 122, and/or the anode 120. In yet other embodiments, a sensor 140 measures the amount of ozone produced by the cell 100 and, after a certain amount has been produced, indicates that a cartridge 102 change is required or imminent. Some or all of these variables may be used in conjunction to determine when replacement of the catholyte solution 110 is necessary.

Illustrative embodiments of the present invention may include a microprocessor 142 to control various cell actions and variables (see FIG. 1). For example, the microprocessor 142 may be used to monitor measurements coming from sensors 140 and monitor other parameters of cell performance, such as source water flow rate, source water temperature, source water pressure, as well as catholyte solution 110 flow rate, catholyte solution pressure, and catholyte solution temperature. The microprocessor 142 may perform certain actions based on those measurements. For example, the microprocessor 142 may open or close solenoid valve 144 in order to relieve pressure or to add water to further dilute the catholyte solution 110. The microprocessor 142 may also keep track of total power-on hours and, in the event of variable output systems, the history and duty cycle of total power-on hours (e.g., on for 1 hour/week at full power, 2 hours/week at ½ power, etc . . . ). In some embodiments, the microprocessor 142 may be programmed with an algorithm to predict when cartridge change is required based on prior cell 100 characterization, operating conditions, and/or summing total power-on hours.

Although various exemplary embodiments of the invention have been disclosed, it should be apparent to those skilled in the art that various changes and modifications may be made which will achieve some of the advantages of the invention without departing from the true scope of the invention.

Claims

1. A cartridge for an electrolytic cell having an interface, the cartridge comprising:

a reservoir configured to contain a catholyte solution and being removably coupleable with the cell; and

at least one cartridge port for removably coupling with the interface of the electrolytic cell, the port being configured to cycle a catholyte solution between the reservoir and the electrolytic cell when the cartridge port is coupled to the interface of the electrolytic cell.

2. An cartridge according to claim 1, further comprising:

a catholyte solution contained within the reservoir.

3. An cartridge according to claim 1, wherein the at least one cartridge port comprises:

a cartridge outlet port configured to allow passage of the catholyte solution from the reservoir; and

a cartridge inlet port configured to allow passage of the catholyte solution to the reservoir.

4. A cartridge according to claim 1, wherein the cartridge port further comprises:

at least one valve to prevent the escape of catholyte solution when the cartridge port is decoupled from the interface.

5. A cartridge according to claim 1, wherein the reservoir includes a hydrophobic membrane that contains the catholyte solution while providing for the passage of hydrogen gas from the reservoir.

6. A cartridge according to claim 2, wherein the catholyte solution is in a solid form.

7. A cartridge according to claim 6, wherein the catholyte solution is in a pre-mixed powdered form.

8. A cartridge according to claim 1, further comprising:

an indicator for indicating when the cartridge needs to be replaced.

9. An apparatus for generating ozone and dissolving ozone into a water source, the apparatus comprising:

a housing forming an interior;

an electrolytic cell within the interior, the cell having a cathode, a diamond anode, and a membrane between the cathode and the diamond anode; and

a cartridge including: a reservoir for receiving a catholyte solution and being removably coupleable with the cell; and at least one cartridge port in fluid communication with the reservoir;

the housing having an interface for removably coupling with the at least one cartridge port, the at least one cartridge port and interface configured to cycle a catholyte solution between the reservoir and the cathode.

10. An apparatus according to claim 9, wherein the at least one cartridge port comprises:

a cartridge outlet port configured to allow passage of the catholyte solution from the reservoir; and

a cartridge inlet port configured to allow passage of the catholyte solution to the reservoir.

11. An apparatus according to claim 10, wherein the interface comprises:

a cathode inlet port configured to be in fluid communication with the cartridge outlet port and to allow passage of the catholyte solution from the reservoir to the cathode; and

a cathode outlet port configured to be in fluid communication with the cartridge inlet port and to allow passage of the catholyte solution from the cathode to the reservoir.

12. An apparatus according to claim 9, wherein the interface further comprises:

at least one valve to prevent the escape of catholyte solution when the interface is decoupled from the cartridge port.

13. An apparatus according to claim 9, wherein the cartridge port further comprises:

at least one valve to prevent the escape of catholyte solution when the cartridge port is decoupled from the interface.

14. An apparatus according to claim 9, wherein the reservoir includes a hydrophobic membrane that contains the catholyte solution in the reservoir while providing for the passage of hydrogen gas from the reservoir.

15. An apparatus according to claim 9, wherein the catholyte solution is contained within the reservoir and is in a solid form.

16. An apparatus according to claim 15, wherein the catholyte solution is in a pre-mixed powdered form.

17. An apparatus according to claim 9, wherein the housing includes an anode inlet port and an anode outlet port such that source water flows through the anode inlet port to contact the diamond anode and then flows through the anode outlet port.

18. An apparatus according to claim 17, wherein the diamond anode generates ozone from the source water in contact with the diamond anode and dissolves the ozone in the source water.

19. An apparatus according to claim 9, wherein the membrane is a solid proton exchange membrane that provides for the exchange of protons between the cathode and the anode.

20. An apparatus according to claim 9, further comprising:

a sensor configured to monitor the performance of the electrolytic cell.

21. An apparatus according to claim 20, wherein the sensor senses at lease one of pH of the catholyte solution, conductivity of the catholyte solution, volume of the catholyte solution, and voltage draw in a power supply of the electrolytic cell.

22. An apparatus according to claim 9, further comprising:

an indicator for indicating when the cartridge needs to be replaced.

23. A cartridge for an electrolytic cell having an anode, the cartridge being used with a housing, the cartridge comprising:

a cathode; and

a reservoir for containing a catholyte solution and configured to provide the catholyte solution to the cathode during use when the reservoir contains the catholyte solution;

the cartridge having a port that is removably coupleable to an interface of the housing, the cathode being spaced from the anode of the electrolytic cell when coupled to the interface of the housing.

24. A cartridge according to claim 23, wherein the reservoir includes a hydrophobic membrane that contains the catholyte solution while providing for the passage of hydrogen gas from the reservoir.

25. A cartridge according to claim 23, wherein the catholyte solution is contained within the reservoir and is in a solid form.

26. A cartridge according to claim 25, wherein the catholyte solution is in a pre-mixed powdered form.

27. A cartridge according to claim 23, further comprising:

an indicator for indicating when the cartridge needs to be replaced.

28. A cartridge according to claim 23, further comprising:

a membrane spaced between the cathode of the cartridge and the anode of the electrolytic cell when the cartridge is coupled to the interface of the housing.

29. A cartridge according to claim 28, wherein the membrane is a solid proton exchange membrane that provides for the exchange of protons between the cathode and the anode.

30. An apparatus for generating ozone and dissolving ozone into a water source, the apparatus comprising:

a housing having an anode; and

a cartridge including: a cathode; a reservoir for containing a catholyte solution and configured to provide the catholyte solution to the cathode;

the cartridge having a port that is removably coupleable to an interface of the housing, the cathode being spaced from the anode of the electrolytic cell when coupled to the interface of the housing.

31. An apparatus according to claim 30, wherein the cartridge includes:

a membrane is spaced between the cathode of the cartridge and the anode of the electrolytic cell when the cartridge is coupled to the interface of the housing.

32. An apparatus according to claim 31, wherein the membrane is a solid proton exchange membrane that provides for the exchange of protons between the cathode and the anode.

33. An apparatus according to claim 30, wherein the reservoir includes a hydrophobic membrane that contains the catholyte solution in the reservoir while providing for the passage of hydrogen gas from the reservoir.

34. An apparatus according to claim 30, wherein the catholyte solution is contained within the reservoir and is in a solid form.

35. An apparatus according to claim 34, wherein the catholyte solution is in a pre-mixed powdered form.

36. An apparatus according to claim 30, wherein the housing includes an anode inlet port and an anode outlet port such that source water flows through the anode inlet port to contact the anode and then flows through the anode outlet port.

37. An apparatus according to claim 36, wherein the anode generates ozone from the source water in contact with the anode and dissolves the ozone in the source water.

38. An apparatus according to claim 36, wherein the housing includes:

at least one valve to prevent the escape of source water when the cartridge is decoupled from the interface on the housing.

39. An apparatus according to claim 30, further comprising:

an indicator for indicating when the cartridge needs to be replaced.