In the accompanying drawings, which are incorporated in and constitute a part of this specification, embodiments of a brewing method and device are illustrated. These drawings, together with the general description of the brewing method and device given above and the detailed description given below, serve to example the principles of this invention.
Referring now to the drawings in which like numerals designate like parts throughout the various views, preferred embodiments of a brewing method and device are shown.
In operation, the brewing device 10 uses a supply of brewing liquid from the storage reservoir 12 in a brewing operation within the brewing unit 14 to produce a brewed beverage such as coffee. The brewing device 10 then dispenses the brewed beverage out of the spout 20 and into a cup or other receptacle disposed on or over the drip tray 16. To accomplish this, various fluid conduits are present in the brewing device 10 to form a brewing liquid supply line, as will be understood by one of ordinary skill in the art. The drip tray 16 catches and holds brewed beverage which may be accidentally dispensed through the spout 20 without a cup or receptacle disposed underneath it, or which may spill from the cup or receptacle.
Typically the brewing material is disposed in a brewing chamber (not shown) within the brewing unit 14. Usually the brewing material is placed in the brewing chamber on top of one or more pieces of filter material, or entirely disposed within a surrounding filter material pod which is inserted as a unit into the brewing chamber. Whatever its form, the filter material operates to contain the brewing material within the filter chamber throughout the brewing process, while permitting brewed liquid to pass through the filter material and out the spout 20. Thus the brewing material is prevented from entering the user's cup or clogging up the system downstream of the brewing chamber. When pods are used, they may advantageously contain more than one brewing material. For example, a first chamber of the pod can contain ground up coffee and a second chamber can contain milk, thus creating a latte as a brewed beverage. The term “milk” as used herein includes all forms of milk and milk substitutes, in whatever form, such as for example whole milk, skim milk, raw milk, pasteurized milk, condensed milk, dry milk, evaporated milk, powdered milk, cream, half-and-half, buttermilk, and the like. Sugar or other brewing materials may also advantageously be placed in a pod. The brewing chamber may be formed by a brew basket which is removable from the brewing unit 14 to allow cleaning and maintenance operations to be performed.
A brewing system 100 may incorporate several different elements, and
The brewing liquid may be stored in a storage reservoir 101, such as the storage reservoir 12 of the brewing device 10 shown in
The pump 104 pumps the brewing liquid under pressure to and through a heater 106 to reach a brewing chamber 108, such as the brewing chamber of the brewing device 10. A representative pump for this application is a vibration pump which may be obtained from ULKA Srl in Pavia, Italy as Model ER Type EP8R.
Once the brewing liquid is heated by the heater 106 to a desired temperature, it travels to the brewing chamber 108 where it is mixed, steeped, soaked, boiled or otherwise brewed with a brewing material in order to make a brewed beverage. The brewed beverage is then dispensed from the brewing device, typically under the force of gravity or pressure supplied by the pump 104. The brewed beverage may advantageously be dispensed from a spout 109, such as the spout 20 of the brewing device 10, to fall into a cup, pot or other receptacle for consumption.
The representative embodiment of
The representative embodiment of
The vacuum vent valve 114 connects the surrounding atmosphere 116 to the brewing system 100. The vacuum vent valve 114 is a check valve which opens to let air into the brewing system 100 if the pressure within the system drops far enough below atmospheric pressure by some minimum pressure differential, for example 0.2 psi. This typically occurs near or at the end of a brewing cycle, when the pump 104 stops applying pressure and steam left over in the system 100 begins to condense. This decreases the pressure within the system 100. Opening of the vacuum vent valve 114 prevents any liquid remaining in the brewing chamber from being drawn back into the line 111 by vacuum pressure.
Rigid tube connectors 120a, 120b and 120c respectively connect the temperature sensor 110, pressure relief valve 112, and vacuum vent valve 114 to the central tube 120. Electrical connectors (not shown) may extend away from the temperature sensor 110 to an electronic controller. A flexible tube or other conduit may be connected to an outlet end 136 of the vacuum vent valve 114 to lead to the atmosphere 116 or other air supply.
In the embodiment of
The manifold 118 may, of course, be configured in several ways which are different from the representative embodiment shown in
The heating reservoir 142 houses a coiled cal rod heating element 148. Contacts 150, 152 extend outside of the reservoir 142 to be electrically connected to a voltage source, perhaps controlled by an electronic controller. Although the heating element 148 is shown disposed inside the heater body 140, it may alternatively be disposed on or near the exterior of the heater body 140. Varying the applied voltage to the heating element 148 changes the power output of the heating element 148, and therefore changes the temperature of the heating element 148. Heat generated by the heating element 148 is transferred to the brewing liquid to heat it up. Heating element power is discussed further below.
The heating reservoir 142 has a length dimension L along a first axis, and a width dimension W along a second axis which is perpendicular to the first axis, such as shown for example in
The heater body 140 may include one or more receptacles 156 to receive a resettable thermal cut off or a permanent thermal cut out. Such devices are conventional. They could be mounted to the outside of the heater body 140, such as in a receptacle 156, to sense the temperature of the brewing liquid indirectly through the temperature of the body 140. Or, they may be disposed inside the body 140 itself, to sense the temperature of the brewing liquid directly.
A conventional resettable thermal cut off has a temperature sensor and a circuit breaker. In the event the temperature sensor exceeds a predetermined value, for example 120° Celcius, the circuit breaker breaks the circuit providing power to the heater 106, thus shutting it down. The thermal cutoff may, of course, be connected to an electronic controller to shut down the entire brewing process at the same time. Once the temperature of the heater 106 drops below the predetermined value, the circuit breaker closes and thus permits the heater 106 to turn back on and/or permits a brewing operation to continue. Such a resettable thermal cut off is useful to ensure the brewing liquid is not too hot to produce satisfactory beverages, or for safety purposes to ensure the brewing liquid does not get hot enough to cause damage to the system.
A conventional permanent thermal cut out (often called a thermal fuse), like a resettable thermal cut off, has a temperature sensor and a circuit breaker. However, the permanent thermal cut out is not resettable. Thus, at some predetermined temperature the circuit breaker permanently prevents power from being supplied to the heater 106. Such a temperature might be, for example, 216° Celsius. A permanent thermal cut out is typically used for safety purposes to ensure the heating system does not get hot enough to cause damage. It may be used as a back-up mechanism for a resettable thermal cut off, where the permanent thermal cut out is set to operate at a higher temperature than the resettable thermal cut off.
The same results can of course be alternatively obtained with a temperature sensor, such as a thermister 500, disposed on or in the heater body 140 in combination with an electronic controller. In this scenario, the electronic controller operates as the circuit breaker. But the electronic controller can additionally use the temperature information received from the thermister 500 in other parts of a brewing operation. For example, the temperature information may be used to determine when the brewing liquid in the heater 106 is hot enough to begin a brewing process, or has reached a boiling point to generate steam.
As discussed above, a relatively large volume capacity heating reservoir can lead to long start-up times for the brewing process. On the other hand, a relatively small volume capacity heating reservoir can lead to difficulties in controlling the temperature of the brewing liquid during a brewing operation. It is believed a heating reservoir volume capacity of between about 50 ml and about 150 ml, or more preferably between about 75 ml and about 125 ml, and most preferably of about 100 ml, is advantageous.
In addition, when trying to optimize a heater for use in a brewing device, the power of the heating element can be considered along with heating reservoir volume capacity. Heating elements are often rated by their maximum wattage output. Typical ratings of heating elements used in brewing devices range from 900 watts to 1400 watts. These power ratings are usually nominal ratings, so that the actual maximum wattage output of a heating element at a given point in time will be within some predetermined range of the stated value. The actual power output of a heating element may be varied in a controlled manner, from 0 watts to the maximum wattage output of the heating element, by varying the voltage applied to the heating element. Using a higher rated heating element operated at full wattage may permit a larger heating reservoir to be used, while still obtaining satisfactory results in start-up time and temperature control.
Thus, it has been found convenient to consider a “watt density” characteristic of a heater. The watt density of a heater is defined as the ratio between the total average power output of the heating element or elements during a brewing operation (expressed in or converted to watts) and the volume capacity of the heating reservoir (expressed in or converted to milliliters). As used herein, “volume capacity” means the volume available within a heating reservoir to store a liquid, excluding space in the reservoir taken up by components such as heating elements, temperature sensors, and the like. Table 1 below illustrates watt density values for a range of average heating element power values and heater reservoir capacities typically seen in coffee brewers:
It is preferred to have a heater with a watt density of no less than about 6 watts/ml, more preferred to have a heater with a watt density of no less than about 9 watts/ml, and most preferred to have a heater with a watt density of no less than about 12 watts/ml. It is preferred to have a heater with a watt density of no more than about 30 watts/ml, more preferred to have a heater with a watt density of no more than about 22 watts/ml, and most preferred to have a heater with a watt density of no more than about 16 watts/ml. In addition, a specific watt density of about 14 watts/ml has proven to be a good design. Various combinations of these preferred values may be made to generate different ranges of advantageous values for the watt density.
Alternatively or additionally in consideration of a watt density, it has also been found convenient to consider a residence-to-lag time ratio. The residence time numerator of this ratio is the average residence time of the brewing liquid within the heating reservoir. Assuming a hydrostatically full system, where there are no significant air pockets in the brewing liquid, the residence time numerator may be approximated by dividing the average flow rate of the brewing liquid into the volume capacity of the heating reservoir. The lag time denominator of this ratio is the amount of time it takes for the temperature sensor, upon the brewing liquid changing from an old temperature to a new temperature, to reflect 97% of the expected change in temperature.
The lag time denominator may be empirically determined for a given temperature sensor. For example, a first pool of liquid may be kept at a first known temperature such as 25° Celsius, and a second pool of liquid may be kept at a second known temperature such as 100° Celsius. A temperature sensor to be tested is placed in the first pool until it reflects the first temperature. The temperature sensor is then placed in the second pool The expected change in temperature is calculated from the difference between the first and second temperatures, which in this example is 75° Celsius. Ninety-seven percent of that expected change is about 73° Celsius. Thus the lag time denominator is the time it takes the temperature sensor to reach 98° Celsius after it is placed in the second pool (the starting temperature of 25° plus a 73° increase). Use of two pools of liquid in this manner is only one method of measuring the lag time denominator of the residence-to-lag ratio; others will be readily apparent to one of ordinary skill in the art.
As an example, if the average flow rate of the brewing liquid is 5 ml per second, and the volume capacity of the heating reservoir is 100 ml, then the average residence time of brewing liquid in the reservoir is 20 seconds. If the lag time of the temperature sensor is then 5 seconds, the residence-to-lag time ratio is 4. Physically, this means the brewing liquid spends about four times as long in the heating reservoir getting warmed up than it takes for the temperature sensor to measure the temperature of the brewing liquid.
If the residence-to-lag time ratio is very small, the brewing liquid is flowing too fast for the temperature sensor to keep up with brewing liquid temperature changes. This typically occurs in small volume capacity heating reservoirs. If the residence-to-lag time ratio is very large, the brewing liquid temperature changes slowly enough for the temperature sensor to keep up. However, this can concomitantly result in long start-up times before brewing can begin. This latter situation typically occurs in large volume capacity heating reservoirs.
Therefore, it is preferred to have a residence-to-lag time ratio of no less than about 2, more preferred to have a residence-to-lag time ratio of no less than about 3, and most preferred to have a residence-to-lag time ratio of no less than about 4. It is preferred to have a residence-to-lag time ratio of no more than about 10, more preferred to have a residence-to-lag time ratio of no more than about 8, and most preferred to have a residence-to-lag time ratio of no more than about 6. A residence-to-lag time ratio of no more than about 4 has been found to be advantageous. Various combinations of these preferred values may be made to generate ranges of advantageous values for the residence-to-lag time ratio.
“Logic,” as used herein, includes but is not limited to hardware, firmware, software and/or combinations of each to perform a function(s) or an action(s), and/or to cause a function or action from another component. For example, based on a desired application or need, logic may include a software controlled microprocessor, discrete logic such as an application specific integrated circuit (ASIC), or other programmed logic device. Logic may also be fully embodied as software.
“Software,” as used herein, includes but is not limited to one or more computer readable and/or executable instructions that cause a computer or other electronic device to perform functions, actions, and/or behave in a desired manner. The instructions may be embodied in various forms such as routines, algorithms, modules or programs including separate applications or code from dynamically linked libraries. Software may also be implemented in various forms such as a stand-alone program, a function call, a servlet, an applet, instructions stored in a memory, part of an operating system or other type of executable instructions. It will be appreciated by one of ordinary skill in the art that the form of software is dependent on, for example, requirements of a desired application, the environment it runs on, and/or the desires of a designer/programmer or the like.
Turning now to the diagram of
A representative temperature control logic 300 for a brewing operation is shown in
The controller 202 then verifies 306 whether the closure mechanism 18 is shut and locked. The controller 202 may do this by, for example, determining whether a limit switch disposed proximate to the closure mechanism 18 has been tripped. If it appears the closure mechanism 18 is not closed, the controller 202 prevents a brew from starting 308 and indicates to the user a problem has occurred 310. Such a problem signal could include a stop light, a buzzer, or a similar signal. The user then corrects the problem 312 and presses the desired brew buttons 304 to start the process 300 over again.
Once the closure mechanism 18 is closed, the controller 202 begins the brew process and indicates to the user the process has begun 314. A voltage is applied to the heating element 148 in the heater 106 to start heating up the brewing liquid left over in the heater 106 from the last brew. The power of the heater is initially set to its maximum rated value. From the heater temperature data 210 the controller 202 determines 316 whether the brewing liquid in the heater 106 has a sufficient minimum temperature Tmin to start a brewing process. Tmin is set at the minimum temperature for effective brewing of a good beverage. If the temperature of the brewing liquid in the heater 106 is less than Tmin, the controller waits 318 until Tmin is reached as a result of the liquid being heated by the heating element 148.
Once the brewing liquid in the heater 106 reaches Tmin, the controller 202 starts 320 the pump 104 to begin pumping brewing liquid to the brewing chamber 108. The controller 202 checks 322 the flow meter data 206 to make sure the flow is greater than zero. If the controller 202 determines there is no flow, the controller 202 deactivates 324 the pump 104 and heater 106, and notifies 326 the user a problem has occurred. The user corrects the problem 312, such as by adding brewing liquid to the brewing reservoir 101, and presses the desired brew buttons 304 to start the process 300 over again.
If the controller 202 determines the flow is greater than zero at step 322, it next checks 328 the temperature of the brewing liquid in the heater 210 to determine whether it exceeds some maximum temperature Tmax. Tmax might be set, for example, as a maximum temperature of brewing liquid which leads to a satisfactory brewed beverage. If the maximum temperature is exceeded, the controller 202 deactivates 324 the pump 104 and heater 106, and notifies 326 the user a problem has occurred. The user corrects the problem 312, such as by adding brewing liquid to the storage reservoir 101, and presses the desired brew buttons 304 to start the process 300 over again.
If the check 328 indicates the temperature of the brewing liquid in the heater 310 does not exceed the maximum temperature Tmax, the controller checks 330 the data 212 for temperature of the brewing liquid in the fluid flow path 111. If that temperature 212 differs from the target temperature for the type of brew selected by the user 304, the controller 202 follows a primary/secondary control process to vary the temperature.
As a primary control, the controller 202 adjusts the flow rate of the brewing liquid by adjusting the brewing liquid flow rate, thereby controlling the temperature of the brewing liquid in line 111. It may do this by applying, for example, a proportional control, a proportional derivative control, a proportional integral control, a proportional integral derivative control, or similar control loop. If the brewing liquid temperature 212 is too low, the speed of pump 104 is decreased, so that brewing liquid spends more time in heater 106 and thus reaches a higher temperature in the line 111. If the brewing liquid temperature 212 is too high, the speed of pump 104 is increased, so that brewing liquid spends less time in heater 106 and thus does not reach as high a temperature in the line 111. Pump adjustments may be made in a step-wise fashion as the process 300 continually loops back through the checking step 330 until the volume target is met 332. If the error between target temperature and measured temperature is relatively large, then the pump speed may be changed by a relatively large amount. If the error between target temperature and measured temperature is relatively small, then the pump speed may be changed by a relatively small amount. Mechanisms other than pump speed can be used to vary the brewing liquid flow rate, such as for example a variable size orifice disposed downstream of the pump.
A secondary control is provided, relying on the heating element 148 in the event the primary flow rate control is not sufficient. More particularly, if the flow rate has reached the maximum pumping capability of the particular pump being utilized, and the brewing liquid temperature still needs to be decreased, the controller 202 reduces the power of the heating element 148 in the heater 106. Similarly, if the flow rate has reached the minimum pumping capability of the particular pump being utilized, and the brewing liquid temperature still needs to be increased, the controller 202 increases the power of the heating element 148 in the heater 106. Varying the flow rate is used as the primary control because the flow rate can be controlled in a much more precise and responsive manner than the power of the heating element 148. Thus, in the usual operation of the temperature control process 300, the power of the heating element 148 is usually not changed much, if at all. Rather, it usually stays at a relatively high level, with changes in the brewing liquid flow rate controlling the brewing liquid temperature. But of course, heating element power may alternatively be used as the sole temperature control, or the primary temperature control in conjunction with other controls.
After adjusting the temperature of brewing liquid 330, the controller 202 checks 332 the volume of brewing liquid which has been pumped during the brewing process. The controller 202 can determine the amount of brewing liquid which has been pumped by tracking the flow meter data 206 throughout the process 300, and integrating the flow over time. For example, if a pulse meter is used, the controller can count the number of pulses and determine volume from the known volume of brewing liquid pumped per pulse. If the target volume for the brew selected by the user has not been met, the pumping continues 334 and the process 300 loops back to the check flow meter step 322. If the target volume has been met, the controller 202 either shuts down the system or, if desired, begins a purging process.
One example of a purging process is shown in
The heater shown in
At the beginning of the purging process, the brewing liquid surface level 164 may be disposed at or near the level of the outlet 146. In that event, for some amount of time, relatively large amounts of excess unvaporized brewing liquid may remain trapped in the flow of steam as it exits the heating reservoir 142. However, as that trapped liquid is carried away and other liquid is converted to steam, the surface level 164 falls. At some point after steam begins generating, the surface level 164 reaches a low enough level in the heating reservoir 142 that most of the liquid carried in the steam falls back into the pool 158 before the steam reaches the outlet 146. This makes for improved reproducibility from brew to brew of liquid volume output during the purging process.
Once the brewing liquid boiling point temperature is reached, a purging timer 401 is started 408. The purging timer 401 may, for example, be incorporated as part of the controller 202 as shown in
For generating one or two cups of black coffee, it is advantageous to have a steam time of no less than about 5 seconds, or no less than about 7 seconds, or no less than about 9 seconds. For generating one or two cups of a combination of coffee and cream brewed together in the brewing chamber, it is advantageous to have a steam time of no less than about 10 seconds, or no less than about 12 seconds, or no less than about 14 seconds.
For generating one or two cups of black coffee, it is advantageous to have a steam time of no more than about 15 seconds, or no more than about 13 seconds, or no more than about 11 seconds. For generating one or two cups of a combination of coffee and cream brewed together in the brewing chamber, it is advantageous to have a steam time of no more than about 20 seconds, or no more than about 18 seconds, or no more than about 16 seconds.
Instead of starting the purging timer 401 (
Once the brewing liquid boiling point temperature is reached, it may be advantageous to reduce the power of the heating element 410 for the remainder of the steam generation process. For example, the heating element power may be reduced by as much as 50 percent of the power needed to heat the brewing liquid during the brewing operation. This helps prevent generating too much steam, which can result in splashing of the hot brewed beverage as it is dispensed into a cup for consumption, as well as over-pressurizing the system.
Once the set time period has elapsed, or the purging process otherwise ended, the heater 106 is turned off 412. As discussed above, a vacuum vent valve 112 may be disposed within the fluid flow path 111 to relieve a vacuum occurring in the fluid flow path 111 as a result of steam condensation forming in the path 111 after the heater 106 is turned off. It may also be advantageous to turn the pump 104 on 414 to refill the heater 206 at this point in the process 400. This would replace brewing liquid lost during the steam generation process, and ensure a sufficient amount of brewing liquid is in the heater 106 when the brewing process begins again. The user is notified that the brew process is complete 416. It may be advantageous to provide a delay between the time the heater 106 is turned off 412 and the time of user notification 416. Such a delay would permit the steam remaining in the system to further dry the brewing material and filter paper in the brewing chamber, and to allow the system to depressurize.
While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended for this to restrict or in any way limit the scope of the claimed invention to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, although the steps of the temperature control process 300 and the purging process 200 have been described in some detail and in a particular order, of course different or additional steps may be used, or the described steps performed in a different order. Therefore, the invention in its broader aspects is not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the general inventive concept.