Patent Publication Number: US-11641974-B2

Title: Pressure relief valve configuration for beverage machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a national stage filing under 35 U.S.C. § 371 of International Patent Application Serial No. PCT/US2018/035971, filed Jun. 5, 2018, which claims the benefit of U.S. Provisional Application Ser. No. 62/515,423, filed Jun. 5, 2017. 
    
    
     BACKGROUND 
     1. Field of Invention 
     This invention relates to beverage forming systems, such as coffee brewers that use a liquid to form a coffee beverage. 
     2. Related Art 
     Beverage forming systems that use a liquid, such as water, to form a beverage are well known. For example, U.S. Pat. No. 8,361,527 discloses a beverage forming system that uses a beverage cartridge containing a beverage material to make a beverage by introducing liquid into the cartridge. Liquid provided to the cartridge may be heated in a tank prior to delivery to the cartridge. 
     SUMMARY OF INVENTION 
     In some embodiments, aspects of the invention relate to a beverage forming apparatus including a brew chamber arranged to hold a beverage ingredient. For example, the brew chamber may include a cartridge holder arranged to hold a cartridge containing the beverage ingredient such that liquid is deliverable to the cartridge via a liquid inlet for combining with the beverage ingredient to form a beverage, and beverage may exit the brew chamber via a liquid outlet. A heater tank may have an inlet to receive liquid and an outlet fluidly coupled to the liquid inlet via a delivery line to deliver heated liquid from the heater tank to the brew chamber. A liquid pump may be fluidly coupled to the inlet of the heater tank via a supply line to deliver liquid to the heater tank, and a pressure relief valve may be fluidly coupled to the supply line between the liquid pump and the heater tank. The liquid pump may be arranged to deliver liquid to the heater tank at a pressure below that required to deliver heated liquid from the heater tank to the brew chamber. For example, a permanently open orifice may be fluidly coupled to the heater tank and arranged to permanently vent the heater tank to ambient pressure. The orifice may be arranged to vent the heater tank to allow the liquid pump to deliver liquid to the heater tank without causing the pressure relief valve to open, or liquid to be delivered to the brew chamber. In some embodiments, an air pump may be fluidly coupled to the heater tank and arranged to deliver air to the heater tank to move liquid from the heater tank to the brew chamber. That is, the air pump may be used to deliver liquid from the heater tank to the brew chamber rather than the liquid pump. In some cases, the air pump may have a maximum pressure that is less than the opening pressure of the pressure relief valve, and the orifice may be arranged to vent the heater tank even while the air pump pressurizes the heater tank deliver liquid to the brew chamber. 
     In some embodiments, a check valve may be provided in the supply line between the pressure relief valve and the liquid pump, and the check valve may permit flow from the liquid pump to the pressure relief valve, but resist flow from the pressure relief valve to the liquid pump. In some embodiments, a check valve may be provided in the delivery line that permits flow from the heater tank to the brew chamber, but resists flow from the brew chamber to the heater tank. A reservoir may store liquid for delivery to an inlet of the liquid pump, and the pressure relief valve may have an outlet fluidly coupled to the reservoir such that fluid released from the supply line by the pressure relief valve is directed to the reservoir. In some cases, a heater tank vent valve may be fluidly coupled to the heater tank and arranged to open with opening of the brew chamber. 
     In another embodiment, a beverage forming apparatus includes a brew chamber arranged to hold a beverage ingredient. For example, the brew chamber may include a cartridge holder arranged to hold a cartridge containing the beverage ingredient such that liquid is deliverable to the cartridge via a liquid inlet for combining with the beverage ingredient to form a beverage, and beverage may exit the brew chamber via a liquid outlet. A heater tank may have an inlet to receive liquid and an outlet fluidly coupled to the liquid inlet via a delivery line to deliver heated liquid to the brew chamber, and a permanently open orifice may be fluidly coupled to the heater tank and arranged to permanently vent the heater tank to ambient pressure. A liquid pump may be fluidly coupled to the inlet of the heater tank via a supply line to deliver liquid to the heater tank, and a pressure relief valve, which may have a fixed opening pressure, may be fluidly coupled to the supply line between the liquid pump and the heater tank. The liquid pump may be arranged to deliver liquid to the heater tank at a flow rate and at a pressure below that required to deliver liquid from the heater tank to the brew chamber. 
     In some embodiments, an air pump may be fluidly coupled to the heater tank and arranged to deliver air to the heater tank to move liquid from the heater tank to the brew chamber. For example, the permanently open orifice may be arranged to vent the heater tank during delivery of air to the heater tank by the air pump to move liquid from the heater tank to the brew chamber. The permanently open orifice may be arranged to vent the heater tank at a flow rate suitable to allow the liquid pump to fill the heater tank with liquid without causing the pressure relief valve to open. 
     In some cases, a check valve may be provided in the supply line between the pressure relief valve and the liquid pump, with the check valve permitting flow from the liquid pump to the pressure relief valve, but resisting flow from the pressure relief valve to the liquid pump. In some embodiments, a check valve may be provided in the delivery line that permits flow from the heater tank to the brew chamber, but resists flow from the brew chamber to the heater tank. A reservoir may store liquid for delivery to an inlet of the liquid pump, and the pressure relief valve may have an outlet fluidly coupled to the reservoir such that fluid released from the supply line by the pressure relief valve is directed to the reservoir. In some cases, a heater tank vent valve may be fluidly coupled to the heater tank and arranged to open with opening of the brew chamber. 
     These and other aspects of the invention will be apparent from the following description and claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Aspects of the invention are described below with reference to the following drawings in which like numerals reference like elements, and wherein: 
         FIG.  1    is a front perspective view of a beverage forming apparatus in an illustrative embodiment; 
         FIG.  2    is a front perspective view of the  FIG.  1    embodiment with the cartridge holder exposed to receive a cartridge; 
         FIG.  3    is a schematic diagram of components of a beverage forming apparatus in an illustrative embodiment; and 
         FIG.  4    is a cross sectional view of an integrated air filter and orifice assembly. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood that aspects of the invention are described herein with reference to certain illustrative embodiments and the figures. The illustrative embodiments described herein are not necessarily intended to show all aspects of the invention, but rather are used to describe a few illustrative embodiments. Thus, aspects of the invention are not intended to be construed narrowly in view of the illustrative embodiments. In addition, it should be understood that aspects of the invention may be used alone or in any suitable combination with other aspects of the invention. 
       FIGS.  1  and  2    show a perspective view of a beverage forming apparatus  100  in an illustrative embodiment that incorporates aspects of the invention. Although the beverage forming apparatus  100  may be used to form any suitable beverage, such as tea, coffee, other infusion-type beverages, beverages formed from a liquid or powdered concentrate, soups, juices or other beverages made from dried materials, in this illustrative embodiment the apparatus  100  is arranged to form coffee or tea beverages. As is known in the art, a beverage cartridge  1  may be provided to the apparatus  100  and used to form a beverage that is deposited into a container  2 , such as a user&#39;s cup. The cartridge  1  may be manually or automatically placed in a cartridge holder  3  of a beverage forming station  11  of the beverage forming machine  10 . For example, the cartridge holder  3  may be exposed to receive the cartridge  1  at an opening  31  of the holder  3  when the user operates a handle  5  or other actuator to open the beverage forming station or brew chamber  11 . In this embodiment, movement of the handle  5  or other actuator may cause a cover  8  to move relative to the cartridge holder  3  (or the cover  8  and holder  3  to otherwise move relative to each other, e.g., by having the holder  3  move) to expose the holder  3  for reception of a cartridge  1 . With the cartridge  1  placed in the cartridge holder  3 , the actuator  5  may be operated to close the brew chamber  11 , e.g., so that the cover  8  moves to cooperate with the holder  3  to at least partially enclose the cartridge  1  so water or other precursor liquid can be introduced into the cartridge  1  to form a beverage. For example, with the cartridge  1  held in the beverage forming station  11  by the cartridge holder  3 , the cartridge  1  may be pierced to form inlet and outlet openings through which water or other precursor liquid enters the cartridge  1  and beverage that exits the cartridge  1 , respectively. U.S. Pat. No. 8,361,527 describes a cartridge and a system for introducing liquid into the cartridge that may be used in embodiments of this invention, and is hereby incorporated by reference in its entirety. Of course, aspects of the invention may be employed with any suitably arranged apparatus  100 , including drip-type coffee brewers, carbonated beverage machines, and others arranged to form a beverage regardless of how the beverage is formed. For example, a cartridge  1  may include any suitable materials to form a beverage, such as a carbon dioxide source used to carbonate water, a beverage mix, etc. Alternately, beverage ingredients need not be contained in a cartridge  1 , but rather may be provided to the beverage forming station  11  or other brew chamber in a loose or uncontained form. In such embodiments, the brew chamber  11  may include a disposable or reusable filter to hold the beverage ingredient so that water or other liquid can be introduced to the brew chamber via an inlet and combined with the beverage ingredient to form a beverage that flows through the filter to an outlet of the brew chamber  11 . 
     If used with the apparatus  100 , cartridges may be arranged in different ways, and their configuration may depend at least in part on the nature of how a beverage ingredient in the cartridge is used to form a beverage. As will be understood, the cartridge  1  may contain any suitable beverage medium or ingredient, e.g., ground coffee, tea leaves, dry herbal tea, powdered beverage concentrate, dried fruit extract or powder, powdered or liquid concentrated bouillon or other soup, powdered or liquid medicinal materials (such as powdered vitamins, drugs or other pharmaceuticals, nutriceuticals, etc.), and/or other beverage-making material (such as powdered milk or other creamers, sweeteners, thickeners, flavorings, and so on). In some embodiments, a cartridge  1  may include a container that includes an interior space having a first chamber and a second chamber that are separated by a filter. The container may have a frustoconical cup shape with a sidewall and a top opening covered by a lid, although other arrangements are possible. Also, the container need not necessarily have a defined shape, as is the case with some beverage sachets and pods. 
     When using a cartridge  1  to form a beverage, the lid and/or the container may be pierced to introduce liquid into the cartridge and receive beverage from the cartridge. (As used herein, “beverage” refers to a liquid substance intended for drinking that is formed when a liquid interacts with a beverage medium or ingredient. Thus, beverage refers to a liquid that is ready for consumption, e.g., is dispensed into a cup and ready for drinking, as well as a liquid that will undergo other processes or treatments, such as filtering or the addition of flavorings, creamer, sweeteners, another beverage, etc., before being consumed.) The cartridge may be pierced in the brew chamber  11  by an inlet piercing element (e.g., a needle, multiple needles, a shower head, a solid or non-hollow needle, a cone, a pyramid, a knife, a blade, etc.) so that water or other liquid may be injected into the cartridge  1 . Similarly, the cartridge may be pierced by an outlet piercing element (e.g., including any one of the elements mentioned above regarding the inlet piercing element) to form one or more outlet openings to allow beverage to exit the cartridge. 
     In this embodiment, the beverage forming machine  10  includes a housing  17  that houses and/or supports components of the machine  10 , such as a user interface  14  used to receive information from and provide information to a control system, and defines a container receiving area  12  at which the container  2  is positionable to receive beverage dispensed by the machine  10  via a beverage outlet. Thus, at the container receiving area  12 , the container  2  is associated with the machine  10  to receive a dispensed beverage and may be supported by the housing  17 . The container  2  may be received at the container receiving area  12  so that the container  2  is at least partially surrounded by the housing  17 , or the container  2  may be more exposed when at the container receiving area  12 , as shown in  FIG.  2   . In some embodiments, the container receiving area  12  may include a drip tray arranged to receive and hold liquid that spills from the container  2  or is discharged from the beverage outlet of the brew chamber  11 . 
       FIG.  3    shows a schematic block diagram of various components that may be included in a beverage forming apparatus  100  in one illustrative embodiment. Those of skill in the art will appreciate that a beverage forming apparatus  100  may be configured in a variety of different ways, and thus aspects of the invention should not be narrowly interpreted as relating only to one type of beverage forming apparatus. In this embodiment, water or other precursor liquid may be provided by a liquid supply  15  to mix with a beverage ingredient at the brew chamber  11 . The liquid supply  15  in this embodiment controls the volume of liquid provided to the brew chamber  11  by filling a heater tank  152  to a liquid dispense level  159  and then pressurizing the tank  152  by way of an air pump  154  so that liquid in the heater tank  152  is forced out of the delivery line  156  to a liquid inlet of the brew chamber  11 . A check valve  157  may be provided in the delivery line  156  to allow flow from the heater tank  152  to the brew chamber  11 , but resist flow from the brew chamber  11  to the heater tank  152 . In this embodiment, the volume of liquid delivered to the brew chamber  11  is equal to the volume in the tank  152  between the liquid delivery level  159  and a post-delivery level  158  at a bottom of a conduit  156   a  in the tank  152  that extends downwardly from a top or upper portion of the tank to a location between the top and bottom of the tank  152 . Note that while only one liquid dispense level  159  is shown, two or more liquid dispense levels  159  may be used to allow the system to deliver different volumes of liquid to the brew chamber  11 . In other embodiments, the delivery line  156  may fluidly communicate with a bottom portion of the heater tank  152 , e.g., so that the heater tank  152  is completely or substantially emptied. 
     In accordance with an aspect of the invention, an air filter  4  is fluidly coupled to the air pump  154  so that pressurized air delivered from the air pump  154  passes through the air filter  4  before entering the heater tank  152 . Also, in accordance with an aspect of the invention, the air filter  4  is fluidly coupled to a permanently open orifice  6  such that fluid vented from the heater tank  152  (e.g., during filling of the tank  152  or heating of liquid) passes through the air filter  4  before passing to the orifice  6 . Thus, the air filter  4  has an inlet side arranged to receive air from the air pump  154  and an outlet side arranged to deliver filtered air to the liquid supply system  15  such that the air filter  4  is fluidly positioned in a gas line between the heater tank  152  and the orifice  6 . Such an arrangement may help resist passing unwanted materials from the air pump  154  to the heater tank  152 . For example, if the air pump  154  draws in dust from ambient air, the dust may be removed from the air flow to the tank  152  by the filter  4 . This may help keep such materials from being introduced into the water or other liquid in the heater tank  152 . In addition, or alternately, the filter  4  may help resist the passage of moisture or other unwanted materials to the air pump  154  and/or the orifice  6 . For example, the orifice  6  and the air filter  4  may be fluidly coupled to an upper portion of the heater tank  152  by a gas line  61  attached at or near a top of the heater tank  152 . The heater tank  152  may have a gas or vapor space such that water heated in the heater tank  152  may produce water vapor that flows from the heater tank  152  to the air filter  4  and then to the orifice  6 . Also, unwanted particles, such as portions of scale deposited formed in the heater tank  152  may pass from the heater tank  152  to the air filter  4 . Water vapor may cause problems such as contaminating portions of the air pump  154 , encouraging mold or other growth, etc., and particles in the fluid flow from the heater tank  152  may clog the orifice  6 . The air filter  4  may be arranged to resist the flow of water vapor and/or other materials (such as scale particles) through the air filter  4 , and thus help prevent the movement of water vapor to the air pump  154  and/or clogging of the orifice  6 . 
     It should be appreciated that use of an air filter fluidly positioned between a heater tank and a permanently open orifice may be employed in embodiments that do not use an air pump to deliver liquid from the heater tank  152  to the brew chamber  11 . Instead, an orifice  6  may be used to vent the heater tank  152  and the air filter  4  used to filter fluid that may pass from the tank  152  to the orifice  6  even though liquid may move from the heater tank  152  in other ways, such as by operating the liquid pump  151 , by gravity, etc. 
     In some embodiments, the air filter  4  and the orifice  6  may be incorporated into a single part. For example, as shown in  FIG.  4   , a housing  41  may define an internal space  42  in which an air filter element  43  is located. The air filter element  43  may be or include a porous filter paper, e.g., made of woven or non-woven cellulose or polymer fibers, or any other suitable component or components. The housing  41  may have an inlet port  46  fluidly coupled to the inlet side of the air filter element  43  and an inlet side of the orifice  6 , an outlet port  45  coupled to an outlet side of the orifice  6  (an upper side of the orifice  6  in  FIG.  4   ), and a common port  44  coupled to the outlet side of the air filter  43 . The common port  44  may be fluidly coupled to the heater tank  152  via a line, e.g., a conduit or gas line  61 , such that pressurized air entering the housing  41  via the inlet port  46  from the air pump  154  may pass through the air filter element  143  and flow out of the common port  44  to the heater tank  152 . The pressurized air may also flow through the orifice  6  to the outlet port  45 , and the outlet port  45  may be fluidly coupled to a line that directs fluid in the line to the ambient environment, a drip tray, a water reservoir or other suitable location. However, the orifice  6  may be suitably sized so that the air pump  154  is capable of delivering air at a suitable flow rate and pressure to cause liquid in the heater tank  152  to move to the brew chamber  11  via the delivery line  156 . In some embodiments, the orifice  6  has a size of 0.25 mm and the air pump  154  has a maximum output pressure of 4 psi (at zero flow rate), and a normal operating pressure of 2.5 psi at a flow rate of about 5-6 ml/sec, e.g., 5.4 ml/sec. Thus, the orifice  6  may continuously vent the heater tank  152  while the air pump  154  delivers air to pressurize the tank  152  and cause liquid to flow to the brew chamber  11 , but the orifice  6  and the air pump  154  may be arranged so that air is delivered to the tank  152  at a suitable pressure and flow rate to move liquid to the brew chamber  11 . In some embodiments, a volume of liquid of about 250 ml may be moved to the brew chamber in about 45-60 seconds. The check valve  157  may have a crack, or opening pressure of about 0.5 psi such that the check valve  157  opens with pressure in the heater tank  152  produced by the air pump  154 . 
     Forming the air filter  4  and orifice  6  as a single part, e.g., with an integral housing  41  that supports an air filter element  43  and an orifice  6 , may simplify assembly and/or operation of the beverage machine  10 , as well as potentially reduce costs. In some embodiments, the filter element  43  and the orifice  6  element may be co-molded or otherwise secured to, or formed at the same time as, the housing  41 . In other embodiments, one of the filter element  43  or orifice  6  element may be co-molded, formed unitarily with, or otherwise attached to the housing  41  or a portion of the housing  41 , and the housing  41 , filter element  43  and orifice  6  may be later assembled together. For example, the orifice  6  may be molded as part of an upper housing  41  section, and the filter element  43  may be attached to a lower housing  41  section that is made separately from the upper housing  41  section. The upper and lower sections may be assembled together, e.g., at a portion of the housing  41  between the filter element  43  and the orifice  6 , so that the air filter  4  and orifice  6  are integrated into a single part. 
     In the embodiment of  FIG.  3   , the liquid supply  15  provides liquid to the tank  152  via a liquid pump  151  that is coupled to a source W. The source W may have any suitable arrangement, e.g., may provide liquid from a storage tank or reservoir like that shown schematically in  FIG.  3   , a mains water supply or other source. Thus, in some cases, the liquid provided to the tank  152  may vary in temperature by a wide degree depending on various factors, such as time of year, a temperature of a room in which the machine  10  is located, etc. For example, if the source W is a reservoir that is filled by a user, the temperature of liquid in the reservoir may vary between room temperature (e.g., if liquid sits in the reservoir for an extended time) and a cooler temperature (e.g., if the reservoir has just been filled with water that is dispensed from a tap). 
     To provide liquid to the tank  152  in this embodiment, the liquid pump  151  is controlled by the control circuit  16  to provide a desired volume of liquid to the tank  152 . For example, if the tank  152  is empty or at the post-dispense level  158 , the liquid pump  151  may be operated until a conductive probe or other liquid level sensor in the tank  152  provides a signal to the control circuit  16  that indicates when liquid arrives at the dispense level  159 . In other embodiments, the liquid pump  151  may be arranged to provide a specified volume of liquid, e.g., the liquid pump  151  may be a piston pump, diaphragm pump, syringe pump or other type of pump that delivers a known volume of liquid for each pump stroke or other operation such the control circuit  16  can cause the liquid pump  151  to operate a specified number of cycles or a specified time to deliver a desired volume of liquid. Alternately, the system may include a flow meter or other device to detect liquid flow from the liquid pump  151  and thereby determine a volume of liquid delivered to the heater tank  152 . This information may be used to control the liquid pump  151  to stop when a desired amount of liquid has been delivered. 
     Although in this embodiment a liquid level sensor is used including a conductive probe capable of contacting liquid in the tank  152  and providing a signal (e.g., a resistance change) indicative of liquid being present at respective dispense level  159  in the tank  152 , a liquid level sensor may be arranged in other ways. For example, the sensor may include a microswitch with an attached float that rises with liquid level in the tank  152  to activate the switch. In another embodiment, the liquid level sensor may detect a capacitance change associated with one or more liquid levels in the tank, may use an optical emitter/sensor arrangement (such as an LED and photodiode) to detect a change in liquid level, may use a pressure sensor, may use a floating magnet and Hall effect sensor to detect a level change, and others. Thus, a liquid level sensor is not necessarily limited to a conductive probe configuration. Moreover, the liquid level sensor may include two or more different types sensors to detect different levels in the tank. For example, a pressure sensor may be used to detect liquid at one dispense level (e.g., complete filling of the tank  152  may coincide with a sharp rise in pressure in the tank  152  that is detected by the pressure sensor), while a conductive probe may be used to detect liquid at another dispense level, such as dispense level  159 . 
     In accordance with an aspect of the invention, a pressure relief valve may be provided between the liquid pump and the heater tank. This positioning, optionally in combination with other machine features, may provide various advantages. For example, positioning the pressure relief valve upstream of the heater tank  152  may allow the pressure relief valve to vent to a location at which a user has access, but with reduced concern for discharging hot water from the pressure relief valve. That is, pressure in the heater tank  152  (possibly caused by heating of liquid in the tank  152 ) may cause the pressure relief valve  7  to open to release pressure in the supply line  71  between the liquid pump  151  and the heater tank  152 . However, since the pressure relief valve  7  is located in the supply line  71 , which contains unheated liquid, and is in fluid communication with a lower portion of the heater tank  152 , which has water at a lower temperature than other portions of the heater tank  152 , fluid released by the pressure relief valve  7  may be at a relatively low temperature. In some embodiments, as in  FIG.  3   , the pressure relief valve  7  may vent to a drain line  72  that expels liquid into the water reservoir W. However, the pressure relief valve  7  may vent to other locations to which a user has access, such as at a drip tray, or to other locations not accessible by a user, such as at a location internal to the housing  17 . 
     In accordance with another aspect of the invention, the pressure relief valve may be arranged so that an opening pressure at which the pressure relief valve vents pressure from the supply line may be less than a maximum pressure that the liquid pump can produce in the supply line, but the liquid pump and other system components may be arranged to provide liquid to the heater tank to fill the tank at a pressure below a pressure required to deliver liquid to the brew chamber. In some embodiments, the orifice  6  may vent the heater tank  152  at a flow rate such that the liquid pump  151  can fill the tank  152  without causing the pressure relief valve  7  to open or causing flow to the brew chamber. For example, the liquid pump  151  may deliver liquid at a flow rate (e.g., about 5 ml/sec or less) and pressure (e.g., a normal operating pressure of about 2 psi) so that the heater tank  152  can be filled, but liquid is not delivered via the delivery line  156  to the brew chamber  11 . The orifice  6  may vent the heater tank  152  sufficiently so pressure in the tank  152  remains at or below a pressure required to deliver liquid to the brew chamber  11  for the pressure and flow rate of the liquid pump  151 . This may help the system ensure that the heater tank  152  is suitably filled with water or other liquid during a fill operation. That is, the liquid pump  151  may be capable of producing a relatively high pressure to force water into the heater tank  152 , yet the pressure relief valve  7  will not open to vent pressure from the supply line  71 . Pressure in the heater tank  152 , and consequently in the supply line  71 , may be vented by the orifice  6 , allowing the heater tank  152  to fill with liquid without forcing liquid to flow out via the delivery line  156  as well. Rather than opening because of pressure created by the liquid pump  151 , the pressure relief valve  7  may open for other reasons, such as unusually high pressures created by heating liquid in the heater tank  152 . 
     In some embodiments the air pump  154  may be arranged such that a maximum pressure of the air pump  154  is below the opening pressure of the pressure relief valve  7 . For example, even if the orifice  6  is clogged and prevents venting while the air pump  154  is delivering pressurized air into the heater tank  152 , the pressure relief valve  7  will not open. This may prevent heated liquid from being vented by the pressure relief valve  7 . In one example, the maximum pressure of the air pump  154  may be about 4 psi, while the opening pressure of the pressure relief valve  7  is about 15 psi. (The air pump  154  may generate pressure in the heater tank  152  of about 2.5 psi during normal operation when forcing water to flow from the tank  152  to the brew chamber  11 .) With this configuration, the pressure relief valve may open only during high pressure events related to liquid pump operation (the liquid pump  151  may have a maximum operating pressure of about 30 psi), and when the pressure relief valve opens, only relatively cool liquid may be vented by the pressure relief valve  7  because of the valve&#39;s  7  placement between the liquid pump  151  and the heater tank  152 . 
     In some embodiments, the pressure relief valve  7  may have an opening pressure that is higher than the opening pressure of the check valve  157 . For example, the opening pressure of the pressure relief valve  7  may be about 15 psi, while the crack or opening pressure of the check valve  157  may be about 0.5 psi (e.g., 0.3 to 0.7 psi). This may allow liquid to be directed from the heater tank  152  to the brew chamber  11  when the air pump  154  pressurizes the tank  152  without releasing liquid from the pressure relief valve  7 . As noted above, the air pump  154  may deliver pressurized air to the heater tank  152  at a pressure and flow rate (e.g., about 5 ml/sec or more) suitable to generate about 2.5 psi in the heater tank  152  while the heater tank  152  is vented by the orifice  6  and liquid is delivered to the brew chamber  11 . In this embodiment, the pressure relief valve  7  has a fixed opening pressure, although in other embodiments the pressure relief valve  7  may have a variable or controllable opening pressure, e.g., which may be controlled by the control circuit  16 . Also provided in this embodiment is a check valve  73  between the pressure relief valve  7  and the liquid pump  151 . This check valve  73  may permit flow from the pump  151  to the heater tank  152 , but resist flow from the heater tank  152  to the pump  151 . This may help ensure that pressure vented by the pressure relief valve  7  is vented by the pressure relief valve  7  and not through the pump  151 . 
     Liquid in the tank  152  may be heated by way of a heating element  153  whose operation is controlled by the control circuit  16  using input from a temperature sensor or other suitable input. Of course, heating of the liquid is not necessary, and instead (or additionally) the apparatus  100  may include a chiller to cool the liquid, a carbonator to carbonate the liquid, or otherwise condition the liquid in a way that alters the volume of liquid in the tank  152 . (Generally speaking, components of the liquid supply  15  that heat, cool, carbonate or otherwise condition liquid supplied to the brew chamber  11  are referred to as a “liquid conditioner.”) 
     In the embodiment of  FIG.  3   , the beverage machine  10  also includes a vent  155 , which can be opened or closed to vent the heater tank  152 . The vent  155  is linked to the actuator  5  and/or to the cover  8  such that when the actuator  5  and/or cover  8  are in the closed position (in which the brew chamber  11  is closed), the vent  155  is closed. However, if the actuator  5  and/or the cover  8  are moved from the closed position toward an open position, the vent  155  is opened to vent the heater tank  152 . Unlike the orifice  6 , the vent  155  may provide a relatively large cross-sectional area for flow or otherwise allow a relatively large volume of fluid at a relatively large flow rate to pass through the vent  155  when open. This may help reduce pressure in heater tank  152  to ambient pressure and/or to a pressure at which liquid is not caused to flow from the heater tank  152  to the brew chamber  11 . Thus, opening the vent  155  may help prevent flow to the brew chamber  11 , even if the air pump  154  continues to run, because the vent  155  releases and vents pressure in the tank  152  at a flow rate that exceeds the flow rate of the air pump  154 . 
     The brew chamber  11  may use any beverage making ingredient, such as ground coffee, tea, a flavored drink mix, or other beverage medium, e.g., contained in a cartridge  1  or not. Alternately, the brew chamber  11  may function simply as an outlet for heated, cooled or otherwise conditioned water or other liquid, e.g., where a beverage medium is contained in the container  2 . Once liquid delivery from the tank  152  to the station  11  is complete, the air pump  154  (or other air pump) may be operated to force air into the delivery line  156  to purge liquid from the brew chamber  11 , at least to some extent. 
     Operation of the liquid pump  151 , air pump  154  and other components of the apparatus  100  may be controlled by the control circuit  16 , e.g., which may include a programmed processor and/or other data processing device along with suitable software or other operating instructions, one or more memories (including non-transient storage media that may store software and/or other operating instructions), temperature and liquid level sensors, pressure sensors, input/output interfaces, communication buses or other links, a display, switches, relays, triacs, or other components necessary to perform desired input/output or other functions. 
     Prior to forming a beverage, the beverage machine  10  operates to suitably fill the heater tank  152  to the dispense level  159  (or to one of the dispense levels if more than one is used). To do so, the liquid pump  151  under the control of the control circuit  16  draws water from the reservoir W, which may be a cold water tank, a plumbed supply, etc. Optionally, the water may be filtered prior to entering the inlet of the liquid pump  151 . The liquid pump  151  pumps water into the supply line  71 , causing water to flow through the check valve  73  and the pressure relief valve  7  and to the heater tank  152 . As water is forced into the heater tank  152 , the liquid level in the tank  152  rises and air or other gas is forced out of the heater tank  152  and into the gas line  61 . This causes air or other gas (such as water vapor) to flow through the air filter  4  and out of the orifice  6 . If the vent valve  155  is open, e.g., because the actuator  5  and/or cover  8  are moved from the closed position, air or other gas may exit the heater tank  152  via the vent valve  155  as well. However, during filling of the heater tank  152 , the pressure relief valve  7  may not open to vent pressure in the supply line  71 , and the check valve  157  in the delivery line  156  may not open to permit flow to the brew chamber  11 . Instead, the orifice  6  and the liquid pump  151  may be arranged to deliver water or other liquid to the heater tank  152  at a pressure and flow rate (e.g., 2 psi and at a flow rate of 5 ml/sec or less), and to vent air or other gas from the heater tank  152 , such that pressure in the delivery line  156  and the supply line  71  do not cause the pressure relief valve  7  to open or flow to the brew chamber  11  to occur. In some embodiments, the liquid pump  151  may be operated so it is incapable of creating sufficient pressure in the heater tank  152  to cause the pressure relief valve  7  or the check valve  157  to open, e.g., because the orifice  6  vents the heater tank  152  at a sufficiently high flow rate. 
     Liquid is delivered to the heater tank  152  by the liquid pump  151  until a desired volume is present in the heater tank  152 , e.g., determined by the control circuit  16  when the liquid level in the tank  152  reaches the dispense level  159  as detected by a conductive probe, optical sensor, pressure sensor, timed operation of the liquid pump  151 , detected volume delivery by a flow meter in the supply line  71 , etc. The liquid pump  151  is stopped, and if desired, liquid in the heater tank  152  is heated by the heating element  153  under the control of the control circuit  16 . During heating, the liquid and/or gas in the heating tank  152  may expand in volume, and the expanding gas and/or liquid may flow into the gas line  61 , through the air filter  4  and out of the orifice  6  to maintain pressure in the heater tank  152  at approximately ambient pressure. However, if the orifice  6  is clogged or otherwise not operating to vent pressure, and the delivery line  156  is blocked, the pressure relief valve  7  may open if necessary to vent pressure from the supply line  71  and the heater tank  152 . This may allow relatively cooler water to be released from the liquid supply  15 , rather than relatively warmer water. 
     With the liquid in the heater tank  152  suitably heated, if desired and as detected by a thermocouple, thermistor, or other temperature sensor linked to the control circuit  16 , liquid may be delivered from the heater tank  152  to the brew chamber  11 . To do so, the control circuit  16  may turn the air pump  154  on, forcing air into the gas line  61  via the air filter  4 . This causes air flow into the heater tank  152 , as well as through the orifice  6 , and air may pass directly from the air pump  154  to the orifice  6  without passing through the air filter  4 . However, the orifice  6  size or other flow restriction characteristic and the flow rate and pressure of the air pump  154  may be arranged such that pressure in the heater tank  152  rises (e.g., to about 2.5 psi or more) to force liquid to flow into the conduit  156   a  and into the delivery line  156  even while the orifice  6  vents pressure in the gas line  61 . Reverse flow in the supply line  71  is prevented by the check valve  73 , and under normal operation where the opening pressure of the pressure relief valve  7  (e.g., about 15 psi) is higher than the opening pressure of the check valve  157  (e.g., about 0.5 psi), the pressure relief valve  7  may remain closed such that liquid flows through the check valve  157  and to the brew chamber  11 . If in other embodiments the opening pressure of the pressure relief valve  7  is lower than the opening pressure of the check valve  157 , the pressure relief valve  7  may open during liquid delivery to the brew chamber  11 , but the pressure relief valve  7  may provide a restriction to flow so that a relatively small volume of liquid exits via the pressure relief valve  7 . 
     Operation of the air pump  154  is continued by the control circuit  16  until the liquid level in the heater tank  152  drops to the post dispense level  158  or a suitable volume of liquid is otherwise delivered to the brew chamber  11 . In this illustrative embodiment, once the liquid level in the heater tank  152  drops to the post dispense level  158 , air is forced into the conduit  156   a  and the delivery line  156 , helping to purge the delivery line  156  of liquid as well as help purge beverage from the brew chamber  11 . In some embodiments, a pressure sensor in the tank  152  may detect the drop in pressure in the tank  152  once the liquid level drops to the post dispense level  158  and air is forced into the delivery line  156 , causing the control circuit  16  to stop air pump  154  operation, e.g., after a suitable delay to purge the delivery line  156 . Alternately, a drop in pressure in the heater tank  152  may be detected by a reduced load, and thus reduced current draw, at the air pump  154 . In cases where the pressure in the heater tank  152  rises to an overpressure level, e.g., while the air pump  154  is running, but the liquid inlet at the brew chamber  11  is clogged or otherwise restricts flow, and the orifice  6  does not vent suitable pressure from the heater tank  152 , the pressure relief valve  7  may open to relieve pressure from the heater tank  152  (or not). The control circuit  16  may detect this condition, e.g., using a pressure sensor in the liquid supply  15 , using a sensor that detects the pressure relief valve  7  opens, etc., and stop operation of the air pump  154 . The control circuit  16  may prompt a user to take corrective action, e.g., by displaying a message at the user interface  14 , and/or stop operation. Pressure in the heater tank  152  may also be vented if the vent valve  155  is opened by moving the actuator  5  and/or cover  8  from the closed position. 
     As noted above, since air from the air pump  154  is passed through the air filter  4  prior to passing to the heater tank  152 , possible contaminants in the air, such as dust, may be prevented from being introduced into the heater tank  152 . The air filter  4  may also help resist the passage of moisture or other materials from the gas line  61  to the air pump  154  and orifice  6 , e.g., when expanding gas or liquid is caused to flow into the gas line  61  during heating in the heater tank  152 , or during filling of the heater tank  152  by the liquid pump  151 . 
     Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.