Abstract:
A method and system for brewing coffee that allows for control of the temperature of the water as it hits ground coffee and that is adapted for changes in the environment. A coffee machine may include: a water reservoir, a pump, a heating element, a filter holder, a temperature sensor, and a control element. Instead of using boiling water to drive the flow of water from the water container to the filter holder, which method relates the outlet temperature to the water&#39;s boiling point, which, in turn, is dependent on altitude and other factors, the coffee machine described herein uses a pump to deliver water from the water container to the heating element and on to the filter holder. The coffee machine also includes a heating element that is not susceptible to frost damage, which may include a silicone layer sandwiched between two metal components, such as aluminum blocks.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    n/a 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    n/a 
       FIELD OF THE INVENTION 
       [0003]    The present invention relates to a coffee machine, more precisely a pump and heating system and a method for preparing coffee. 
       BACKGROUND OF THE INVENTION 
       [0004]    In the following, the function of a traditional coffee machine will be described. Note that the term “coffee machine” also includes “coffee brewer” and “coffee maker” in the following discussion. 
         [0005]    A traditional coffee maker normally works by admitting water from a cold water reservoir into a flexible hose in the base of the reservoir leading directly to a thin metal tube or heating chamber (usually, of aluminum), where a heating element surrounding the metal tube heats the water. The heated water moves through the machine using the thermo siphon principle. Thermally-induced pressure and the siphoning effect move the heated water through an insulated rubber or vinyl riser hose, into a spray head, and onto the ground coffee, which is contained in a brew basket mounted below the spray head. The coffee passes through a filter and drips down into the carafe. A one-way valve in the tubing prevents water from siphoning back into the reservoir. A thermostat attached to the heating element turns off the heating element as needed to prevent overheating the water in the metal tube (overheating would produce only steam in the supply hose), then turns back on when the water cools below a certain threshold. 
         [0006]    It is crucial for the quality of the coffee that the water temperature as it hits the ground coffee is properly adjusted. Too low or too high a temperature will degrade the taste of coffee. Ninety-two degrees Celsius is often referred to as the ideal outlet temperature. The problem with prior art coffee makers is that even if they control of the temperature as it leaves the heater, there is no actual control of the temperature as the water hits the ground coffee. This is partly because traditional coffee makers use steam as a driving force for water movement between the water tank and filter holder. Further, coffee makers are not adapted to changes in the environment related to pressure, humidity and temperature, in addition to being poorly protected against frost damage that may occur in the piping in and around the heating element. Frost damage typically occurs if a machine is used in a house that is not insulated winter, and when the coffee is maker not emptied of water. 
         [0007]    It is therefore desired to provide a coffee machine that allows for control of the temperature of the water as it hits the ground coffee and that is adapted for changes in the environment. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention advantageously provides a method and system for brewing coffee that allows for control of the temperature of the water as it hits the ground coffee and that is adapted for changes in the environment. A method for brewing coffee in a coffee machine including a water reservoir, a heating element a water pump, and a coffee flask with a filter holder positioned above the coffee flask, may include: measuring an ambient temperature in the coffee machine with a temperature sensor; estimating a temperature reduction of water from the heating element to the filter holder using a predefined model; providing power to the heating element, the heating element heating water from the water tank, the water then passing from the heating element through a conduit to the filter holder; when a temperature of said heating element reaches a first predefined temperature, activating the water pump for a first time interval until the heating element is filled with water; disabling the water pump for a second time interval until the temperature of the water in the heating element has reached a second predefined temperature; estimating a throughput level in the heating element that provides a predefined output temperature of the water when the water contacts ground coffee beans contained in the filter holder, the throughput level being based on the estimated temperature reduction and measured ambient temperature; and activating the water pump with a voltage level that provides the estimated throughput level. The method may further include: monitoring an actual temperature reduction, and if the actual temperature reduction differs significantly from the estimated temperature reduction, then: estimating a modified throughput level in the heating element that provides the predefined output temperature of the water when the water contacts the ground coffee beans contained in the filter holder using an adjusted estimated temperature reduction based on an adjusted predefined model and the measured ambient temperature; and altering the pump voltage level to a different voltage level that provides the estimated modified throughput level. The second predefined temperature may be equal to the first predefined temperature. Further, the predefined output temperature may be in the range of between approximately 90° C. and approximately 96° C. The second time interval may be equal to the first time interval, and the first time interval may be, for example, approximately two seconds. The heating element may include one or more metal elements and one or more silicone layers in thermal contact with the one or more metal elements, the one or more silicone layers defining one or more channels through the thermal element from which the water flows into the conduit. For example, the heating element may include two metal elements (composed of a metal such as aluminum), with the one or more silicon layers being positioned between the two metal elements. The filter holder may include a rotatable ring for aroma control, and the coffee machine may also include a water outlet for dispensing water onto the ground coffee contained in the filter holder. 
         [0009]    A machine for brewing coffee may generally include a water reservoir, a pump and a heating element in fluid communication with the water reservoir, a temperature sensor, and a control element in communication with the pump, the temperature sensor, and the heating element. The temperature sensor may be configured to measure an ambient temperature in the machine and measure a temperature of the heating element. The machine may further include a filter holder in fluid communication with the heating element. The control element may be programmed to: estimate a reduction in a temperature of water within the heating element and a temperature of the water as it is delivered to the filter holder from the heating element; activate the pump for a first period of time to deliver water from the water reservoir to the heating element when the temperature sensor measures a temperature of the heating element that is equal to or greater than a first predefined temperature; and disable the pump for a second period of time until the temperature sensor measures a temperature of water within the heating element that is equal to or greater than a second predefined temperature. The control element may further be programmed to: estimate a throughput level in the heating element that provides a predefined output temperature of the water when the water is delivered to the filter holder from the heating element, the throughput level being based at least in part on the estimated reduction in temperature and measured ambient temperature; and activate the pump with a voltage level that provides the estimated throughput level. The control element may further be programmed to: monitor an actual reduction in the temperature of water within the heating element and the temperature of the water as it is delivered to the filter holder from the heating element, the actual reduction based at least in part on temperature measurements received from the temperature sensor; estimate a modified throughout put level in the heating element that provides the predefined output temperature of the water when the water is delivered to the filter holder using an adjusted estimated temperature reduction based on an adjusted predefined model and the measured ambient temperature; and adjust the pump voltage level to a different voltage level that provides the estimated throughput level. As a non-limiting example, the predefined output temperature may be between approximately 90° C. and approximately 96° C. The heating element may include a first aluminum element and a second aluminum element and one or more silicone layers between and in thermal contact with the first aluminum element and the second aluminum element, the one or more silicone layers defining one or more channels through the thermal element that are in fluid communication with the water reservoir. 
         [0010]    A machine for brewing coffee may include: a water reservoir; a pump and a heating element in fluid communication with the water reservoir; a filter holder in fluid communication with the heating element; a temperature sensor; and a control element in communication with the pump, the temperature sensor, and the heating element, the control element being programmed to: estimate a reduction in a temperature of water within the heating element and a temperature of the water as it is delivered to the filter holder from the heating element; activate the pump for a first period of time to deliver water from the water reservoir to the heating element when the temperature sensor measures a temperature of the heating element that is equal to or greater than a first predefined temperature; disable the pump for a second period of time until the temperature sensor measures a temperature of the heating element that is equal to or greater than a second predefined temperature; estimate a throughput level in the heating element that provides a predefined output temperature of the water when the water is delivered to the filter holder from the heating element, the throughput level being based at least in part on the estimated reduction in temperature and measured ambient temperature; and activate the pump with a voltage level that provides the estimated throughput level. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
           [0012]      FIG. 1  shows a schematic diagram of a coffee machine; 
           [0013]      FIG. 2  shows a pump and heating element of the coffee machine; 
           [0014]      FIG. 3  shows a cutaway view of an exemplary heating element having water channels; 
           [0015]      FIG. 4  shows a water container for the coffee machine; 
           [0016]      FIG. 5  shows a close-up view of the water container seated in a coffee-holder base; 
           [0017]      FIG. 6  shows a water outlet mounted above a filter holder of the coffee machine; 
           [0018]      FIG. 7  shows the filter holder; 
           [0019]      FIG. 8  shows a close-up view of a base of the filter holder; 
           [0020]      FIG. 9  shows a close-up view of a filter holder aroma control mechanism; 
           [0021]      FIG. 10  shows a close-up view of the filter holder and a coffee flask for use with the coffee machine; 
           [0022]      FIG. 11  shows an exemplary coffee flask for use with the coffee machine; 
           [0023]      FIG. 12  shows a filter support bracket; and 
           [0024]      FIG. 13  shows a filter support bracket base. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    In the following, example embodiments are described by referring to the accompanying drawings. 
         [0026]      FIG. 1  shows elements of one embodiment of the coffee machine  10 . The coffee machine  10  may generally include a water tank or container  12 , a pump  14 , a heater (heating element)  16  and a temperature sensor  18 . 
         [0027]    In the following, the different parts of a coffee machine according to the presented embodiment are discussed in greater detail with reference to the  FIGS. 2-13 . 
         [0028]      FIG. 2  shows an example of the pump  14  and the heating element  16  with control functions. The pump  14  should be able to empty the water container  12  and a heating element  16 . It should have a low noise level and a life cycle of at least 10 years. It may be, for example, a peristaltic pump, vane pump or centrifugal pump. The heating element  16  should be able to heat at least 1.2 liters of water in approximately four minutes, but at the same time require a relatively small space. Exemplary heating elements may include standard flat elements, flow-through elements or a block of aluminum element  20  which, in turn, may have channels  22  formed in a silicon layer  24  through which the water flows. For example, a cutaway view of an exemplary heating element  16  including channels  22  with a silicone layer  24  is shown in  FIG. 3 . In addition, there must be a system control element  19 , such as a process control block (PCB) that can control the heating element  16  according to a flow rate of about 300 cc/min, which is able to adjust the water temperature in the range of approximately 91° C. to approximately 97° C. The PCB  19  may be in communication with the temperature sensor  18  and the heating element  16 , such that the PCB  19  may receive measurements from the temperature sensor  18  of, for example, an ambient temperature in the coffee machine  10  and/or a temperature of the heating element  16  and use that data to, for example, estimate a temperature reduction of water from the heating element  16  to ground coffee waiting to be brewed, activate the pump  14  for a period of time when the temperature of the heating element  16  reaches a predetermined level, disable the pump for a period of time, instructing the provision of power from a power source to the heating element  16  and/or pump  14 , estimating a throughput level in the heating element  16  that provides a predetermined output temperature of the water, and the like. 
         [0029]    The coffee machine  10  should preferably also have some kind of frost protection. Frost protection can be achieved by the heating element  16  consisting of two aluminum elements  20  with a silicone layer  24  between, where said channel  22  is formed. Such an arrangement will provide efficient heating of the water through heat transfer from the aluminum blocks  20  to the water through the silicon layer  24 . Also, the silicone should have features that allow it to expand and contract so that the heating element  16  is less susceptible to frost damages when there is water remaining in the channels. Silicon also has the advantage of being thermally stable, water resistance, and having a good electrical insulation and being chemically reactive. 
         [0030]      FIG. 4  shows an example of a water container  12 . The container  12  may include an outer container  26 , an internal container  28 , a valve  30 , a spring valve  32 , a shelf  34 , a lid  36 , and a decorative cover. The water container  12  should be easily disassembled for filling water and easily replaced in the socket. It should be able to accommodate approximately 1.2 liters of water, and should be placed on a table without the risk of opening the valves  30 ,  32  to allow water to leak out. It should also be dishwasher safe. 
         [0031]      FIG. 5  is an illustration of how the water container  12  is placed in the coffee-holder base  38 . The base  38  should have a foundation  40  in the form of a recess  42  which fits the container  12  so that it remains firmly with any locking mechanism when it is inserted into the foundation  40 . Furthermore, it should be a valve hole  44  in the foundation  40  which is designed to open the valve  32  and allow water to flow freely into the pump  14  which is preferably positioned directly below the foundation  40 . Pump  14  and PCB  19  may also be located directly below the foundation  40 . 
         [0032]      FIG. 6  shows a shower head-shaped water outlet  48  that is mounted above the filter holder  50 . The water outlet  48  is designed as a shower head to achieve a good distribution of water over the ground coffee in the filter holder  50 . The water outlet  48  should be easy to disassemble and clean. The water outlet  48  is connected to a water conduit  52  from the heating element  16  and may include a plurality of ports  54  for delivering the water onto the ground coffee. 
         [0033]      FIG. 7  shows of a filter holder  50  which may be used in connection with the coffee machine  10 . The filter holder  50  is designed to direct water toward the filter bottom  56 . It should be easy to assemble and disassemble, and easy to clean. 
         [0034]      FIG. 8  shows a base  58  of a filter holder  50 , which can be used in connection with the coffee machine  10 . The filter holder base  58  consists of a valve  60 , a rotatable ring  62  for aroma control, a slider  64 , a telescopic ring  66 , and a spring element  68 . The base  58  should be adjusted so that when the filter holder  50  is removed from the coffee machine&#39;s bracket, the valve  60  will close and prevent the coffee from running out from the bottom of the filter holder  50 . It should also be possible to place the filter holder  50  on a surface without the coffee running out from the bottom of the filter holder  50 . 
         [0035]      FIG. 9  shows the filter holder aroma control mechanism in more detail. The aroma control mechanism consists of a rotatable adjusting ring  62  with threads  70  of the slider  64 . By rotating the ring  62 , the slider  64  is twisted, and the speed of the water flow will change. The valve  60  should not be closed completely, but always have a minimum opening while it is placed on the bracket to prevent coffee or water overflows. 
         [0036]      FIG. 10  shows the connection between the filter holder  50  and a coffee flask or carafe  72  in more detail. The valve  60  opens when the coffee flask  72  is placed under the filter holder  50 , so that the coffee can flow into the coffee flask  72 . Likewise, the valve  60  closes when the coffee flask  72  is removed so that the coffee is no longer flowing out of the filter holder  50 . The flow rate of water from the filter holder  50  should always be higher than the water flow rate from the pump  14  into the filter holder  50 . 
         [0037]      FIG. 11  shows an exemplary coffee flask  72  that can be used in connection in the coffee machine  10 . In approximately the middle of the lid  74  of the coffee flask  72  there is a lifting mechanism  76  to activate the valve  60  in the bottom of the filter holder  50 . The coffee flask lid  74  is also equipped with a drip stop  78  along the edge with drainage holes  80  down to the flask. 
         [0038]      FIGS. 12 and 13  show examples of a filter holder support bracket  82  and the bracket base  84  respectively. 
         [0039]    In the following, the functions and assemblies according to various embodiments of the present invention are discussed in more detail. 
         [0040]    The purpose of the pump  14  is to control the outlet water temperature more precisely and partially independent of the use of different altitudes and barometric pressures. The goal is to have a controlled outlet temperature of, for example, 92° C. The outlet temperature of the water may preferably also be changed by the user, for example within a range of approximately 90° C. to approximately 99° C. 
         [0041]    At a low pressure, the water boils earlier than at a higher pressure. At a low barometric pressure, the boiling point will be at approximately 2° C. to approximately 3° C. lower compared with an average barometric pressure. Further, an altitude of 1000 feet above mean seal level (MSL) will lower the boiling point by about 3° C. 
         [0042]    The traditional structure of a coffee machine uses boiling water to drive the flow of water from the container to the filter holder  50 . Thus, the outlet temperature will be related to the boiling point, and might be approximately 6° C. below the boiling point. The temperature drop is partly due to heat loss to the surroundings through the various components of the machine  10 . Furthermore, the heating element is often designed so that the heat supply is uneven. This creates steam in the water, although the average temperature is a few degrees below the boiling point. 
         [0043]    By being able to control the flow through the heating element by means of the pump, so the temperature may partly be controlled independently. The outlet temperature from the heating element may thus be, for example, 94° C., then controllably allowing a temperature drop of approximately 2° C. from the heater to the funnel. 
         [0044]    However, this may imply that in certain cases is not possible to get the desired temperature, when the boiling point has dropped significantly due barometric pressure and/or elevation. Then it becomes necessary to lower the discharge temperature to a level where the heating may occur at an acceptable level of vapors. 
         [0045]    Several pump types are possible to achieve the desired function, including centrifugal pumps, peristaltic pumps, vane pumps, and gear pumps. Only the peristaltic pump and to some extent the gear pump are also able to pump air. When the system is not empty, there may be residual water in the system, which can cause bacterial growth and possible frost rings. 
         [0046]    Frost-induced leaks can be avoided by providing spaces or tubes containing water that are able to expand by approximately 10%. With regard to bacterial growth, it is considered that the solution should be comparable with other coffee machines, which also accommodate for residual water left in the pipes and the heating element. 
         [0047]    When this is the basis for selection of the pump, the preferred choice seems to be the centrifugal pump. It does not have the best characteristics of the desired function, as it is difficult to use for dosing and requires a check valve. The features are, however, sufficient for the purpose herein, and it is relatively inexpensive to produce because it does not have many moving parts. 
         [0048]    In a preferred embodiment, a 12-volt automotive sprinkler pump is utilized. It is produced in large quantities and has a lower price than most other pumps. 
         [0049]    In the embodiment herein, when a centrifugal pump is used, a check valve is also required if the heating element  16  is to be emptied after brewing. The check valve might also contain an aperture, so the flow through the aperture/pump can be varied more precisely. Alternatively, the pump/directional valve might be some kind of a needle valve, so that an automatic purification of deposits in the valve could be achieved. Spring-loading is considered as an advantage, so that water is not penetrating through the valve and heating element when the pump is inactive. 
         [0050]    Taking the above considerations into account, the inventors have realized the following embodiment and its equivalents as the optimal process of coffee brewing: 
         [0051]    Measure the ambient temperature by using a temperature sensor  18  in the heating element  16 , so that cooling from the heating element  16  to the funnel can be estimated. For the purpose of calibration, consider if the measured temperature is realistic. The estimation preferably requires a predefined model dependent on, for example, the length and diameter of the pipe connecting the heat element  16  and the outlet  48 . 
         [0052]    Then, connect a power supply to the heating element  16 . 
         [0053]    Wait until the heating element  16  temperature is equal to or greater than a first predetermined or target temperature. For example, the predetermined temperature may be approximately 90° C. 
         [0054]    Once the first predetermined temperature is achieved, activate the pump  14  for a first period of time (for example, approximately two seconds) until the heating element  16  is filled with water. Measure a possible a decrease of the value of the temperature sensor  18 . 
         [0055]    Deactivate the pump  14  for a second period of time (for example, approximately two seconds) to heat the water in the heating element until the heating element  16  temperature is equal to or greater than a second predefined temperature. The first period of time during which the pump is activated and the second period of time during which the pump is deactivated may be the same or different. 
         [0056]    Restart (reactivate) the pump  14  at an estimated throughput level. That is, restart the pump with a corresponding voltage level that provides the estimated throughput level, thereby providing the desired output temperature. The throughput level may be estimated by the PCB  19  using a predefined model, the estimation based at least in part on the estimated temperature reduction and the measured ambient temperature. 
         [0057]    Check the outlet temperature and possibly adjust the predefined model for calculating the output temperature, so that the flow is adjusted accordingly. 
         [0058]    Also control the predefined model for account for whether the estimated air pressure is too low. If so, the outlet temperature of the water is decreased. 
         [0059]    Introduce a break if interval brewing or extended brewing has been requested. 
         [0060]    Repeat the two last mentioned steps until the power consumption of the pump  14  indicates dry running Switch off the pump  14 . 
         [0061]    Switch off the heating element  16  and maintain the temperature of the coffee flask  72  by a heating element. This may be the same heating element  16  that heated up the water in the pump, or an independent heating element. If an independent heating element is used, it should also include an additional temperature sensor with over-temperature protection. If using the same heating  16  element for both functions, the heating element  16  might be moved and/or insulated somewhat from the surface of the coffee machine  10 . 
         [0062]    One of the advantages of the present invention is that it provides better control of the temperature of the water when it first hits the ground coffee. Furthermore, it enables the coffee machine  10  to be more robust against changes in the environment related to pressure, humidity and temperature without degrading the quality of the coffee significantly. 
         [0063]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.