Abstract:
A water heater for an aircraft beverage brewing apparatus includes a three way electrical conduit for conducting electrical power in three separate phases. The heater has a housing with a fluid inlet port at a first removable end piece and a fluid outlet port at a second removable end piece. The hollow cylindrical core incorporates a heating element wound around the core, and the housing includes three resettable temperature sensors at the outlet, each of the three resettable temperature sensors connected to a separate phase of power from the three way electrical conduit.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Application No. 62/020803, filed Jul. 3, 2014, the contents of which is fully incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    Coffee makers are prevalent in many environments because of society&#39;s affection for the beverage, and thus many industries endeavor to offer their customers or patrons coffee as a way to make the experience more enjoyable. From automobile service stations to bookstores, there are few places where a customer cannot get a cup of coffee these days. One such place that patrons can expect a cup of hot coffee is during commercial airplane flights of medium to large distances. Passengers have come to expect this service on commercial flights, and airline manufacturers have developed special coffee brewing machines that meet the specific requirements and limitations of electrical appliances on aircraft. 
         [0003]    All coffee brewing apparatus include some form of water heating element to raise the temperature of the water to a level where the oils and extracts of the coffee beans can be released. Water is pumped through a tubing with a resistive heating element that heats the water as it flows through the tubing. The resistive heating element is typically a coiled wire, similar to the element in an electric toaster, that heats up when electricity is run through it. In a resistive element like this, the coil is embedded in a plaster to make it more rugged. The heating element serves multiple purposes, namely to initially raise the temperature of the supply water to brewing temperature, and then when the coffee is made, the heating element keeps the coffee warm. 
         [0004]    The resistive heating element may be sandwiched between a warming plate and an aluminum water tube. The resistive heating element presses directly against the underside of the warming plate, and white, heat-conductive materials such as grease make sure the heat transfers efficiently. The coffee maker&#39;s power switch turns power to the heating element on and off, and to keep the heating element from overheating there are sensors and fuses. In coffee makers, sensors detect if the coil is getting too hot and, if so, cut off the electrical current. When the coil cools down, the sensor turns the current back on. By cycling on and off like this, coffee brewers keep the coil at an even temperature. Similarly, fuses simply cut the power if the temperature reaches a certain level. Fuses are a safety measure in the event that the main sensor fails. Coffee makers also typically employ a one-way valve. The one-way valve lets cold water into the aluminum tube, but forces the bubbles of boiling water to flow up the brew tube. 
         [0005]    The present invention is directed to a flow-through type water heater for a beverage maker, and more particularly to a flow-through water heater for an aircraft galley appliance for making beverage, the appliance having three-phase power capability and a removable baffle core. Most flow-through heating assemblies use a single phase power source to energize the heating element. Examples of such heating assemblies include plasma-sprayed circuit flow-through heaters from Watlow Electric Manufacturing Company of St. Louis, Mo. These heaters receive a flow of water from a water supply and heat the water to a temperature that is appropriate for brewing coffees, teas, espressos, and the like. However, there are several characteristics of such heating units that make them unsuitable for use in aircraft. First, aircraft power systems utilize a three-phase power that cannot be used with the aforementioned single phase heaters. Second, the core of the prior art heating units are fixed, which makes it challenging to determine if deposits are affecting the performance of the heating core. That is, traditional heater assemblies are welded together into a single piece, so the core and end fittings can not be removed. Thus, the inner passage way of the heater that the water flows through cannot be well monitored for hard water scale buildup. In addition, the current baffles are made from stainless steel, which is much heavier than the PEEK plastic used to fabricate the removable baffle core of the present invention. Third, such cores are typically made of a solid metal, adding weight to the beverage maker that is undesirable to aircraft components. Fourth, these cores lack the capability to effectively monitor the temperature of the water inside the core, which can lead to safety concerns as well as inefficiencies in the heating operation. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is designed to overcome these shortcomings and provide a three-phase heating unit for an aircraft beverage maker that includes a removable light-weight baffle core that can be easily removed and inspected to determine if maintenance is required. In a preferred embodiment, the heating unit includes integrated resistance temperature detectors (RTDs) that allow the actual heater temperature to be monitored directly, thereby avoiding an over-temperature condition, and incorporates fast-response temperature control. The heating unit of the present invention uses a custom circuit for three-phase power to manage the unique power requirements of an aircraft while providing efficient power management. 
         [0007]    Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings, which illustrate, by way of example, the operation of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an illustration of an assembled heater unit; 
           [0009]      FIG. 2  is an illustration of the components of the heater unit of  FIG. 1 ; and 
           [0010]      FIG. 3  is a circuit diagram for a three-phase power supply used on an aircraft. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0011]    The present invention comprises enhancements to prior art plasma-sprayed circuit flow-through heaters to make such heaters suitable for aircraft beverage maker applications. The enhancements include: 1) a high-performance, light weight plastic baffle core; 2) removable end fittings and baffle core, which allows for inspection of the core to check for hard water scale buildup inside the heater and enables maintenance and cleaning; 3) integrated RTDs, which allows the actual heater temperature to be monitored directly, thus avoiding an over-temperature situation and enabling fast-response temperature control in operation; and 4) a custom-designed circuit that incorporates three-phase power (essential for operation on aircraft) and dry steam production capability (particularly for espresso beverages) aboard aircraft. 
         [0012]    The present invention is designed to be used in aircraft beverage makers with rapid in-line water heating and/or controlled steam production. The traditional heater design for non-aircraft use incorporates a single-phase electrical circuit. However, modern aircraft use a 400 Hz three-phase power supply to comply with FAA regulations. Thus, a multi-phase circuit must be incorporated into the heater. The heater of the present invention includes a plasma-sprayed circuit applied to a stainless steel substrate tube. Integrated resistance temperature detectors, or “RTD”s, are incorporated into the heater circuit that enables direct monitoring of the heater temperature. This not only provides for better temperature control of the heater circuit, but allows for improved safety as well. 
         [0013]      FIG. 1  illustrates a fully assembled heating unit  10  of the present invention, with a three-way electrical conduit  12  that couple the heating unit  10  to a power supply (not shown). A steel tube body  14  houses a plastic baffle core  16 , and end fittings  18 , 20  are threaded or otherwise removably attached to allow access to the core  16 . A pair of O-rings  22  or washers are disposed between the end fittings  18 , 20  and the housing body  14 . At the end of the housing are three resettable temperature sensors  24   a,    24   b,    24   c,  one for each phase of the input power. By monitoring and regulating each phase of the power, the present invention provides a far more accurate evaluation of the temperature of the core  16 , which in turn provides a measure of the water temperature and system performance. The three way electrical conduit  12  includes one jack  26  for each phase of the electrical power from the power supply, establishing a three-phase power system to convey the voltage to the heating unit  10  in three phases. 
         [0014]    The removable end fittings  18 , 20  of the housing  14  preferably incorporate machined screw threads  28  that screw into tapped holes  30  on each end of the baffle core  16 . The end fittings  18 , 20  also have grooves on a mating surface that allow for seating and sealing of the end fittings when the unit  10  is assembled. The ability to quickly and easily disassemble the heater  10  also allows for flexibility with various end fittings for functional efficiency and enables easier cleaning and maintenance. 
         [0015]      FIG. 2  illustrates an exploded view of the present invention of  FIG. 1 , where the housing  14  is separated from the removable end pieces  18 , 20  and the plastic baffle core  16  is exposed. Each fitting  18 , 20  inserts into the core  16 , and water is heated by the resistive heater  32  inside the housing  14  as it is circulated around the core  16  from one end to the other. Each end piece  18 , 20  includes a stem  38  that fits into fitted holes  30  at the opposite ends of the baffle core  16 . The inlet end piece  18  includes a port  40  for receiving a water stream, and the outlet end piece  20  includes a port  42  for the water to exit the heating unit  10 . A washer  22  is preferably incorporated into each end piece  18 , 20  to resist leakage at the junctures with the housing  14 . The core  16  may be made of plastic, such as PEEK, to reduce the weight of the core and thereby reduce the weight of the heating unit  10 . The pitch of the threads  28  on the baffle core  16  may be selected so as to allow the residence of the water in the heating unit  10  to coincide with the heating characteristics of the resistive heating element  32  to efficiently heat the water therein. 
         [0016]      FIG. 3  illustrates the plasma sprayed circuit  50  for the flow-through heater  10  of the present invention as incorporated into a brew heater. The power supply (not shown) is a 115 volt, three-phase power each having 805 watt maximum, for an 2415 watt total single zone at an operating temperature of 195° F. The wye configuration is shown in  FIG. 3 , including phase C (blue)  52 , phase B (yellow)  54 , and phase A (red)  56 . The ground or heater return  58  is shown as well (white). The housing  14  is preferably 155 mm, although other sizes are possible, and the wires can be selected to be approximately 12 inches in length. The RTDs  24  (1kΩ, Class 1B) are attached at the outlet end of the housing as shown in  FIG. 1 . In an alternate embodiment, the phases are each 533 watts for a total wattage of 1600 watts at an operating temperature of 300° F., which is used when the heater operates as both a water heater and a steam generator. 
         [0017]    The three-phase heating unit for an aircraft beverage maker of the present invention incorporates a removable light-weight, easily removed baffle core allowing inspection of possible scale buildup in the heater. In a preferred embodiment, the heating unit includes integrated resistance temperature detectors (RTDs) that allow the actual heater temperature to be monitored directly, thereby avoiding an over-temperature condition and fast response temperature control. The heating unit of the present invention uses a custom circuit for three-phase power to manage the unique power requirements of an aircraft while providing efficient power management. 
         [0018]    It will be apparent to those of ordinary skill in the art from the foregoing that while certain presently known preferred embodiments of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.