Patent Application
20050166601
The present invention generally relates to insulated containers, and more specifically relates to insulated containers having refrigeration units.
Insulated containers are prevalent in contemporary life. The insulated containers are often used for picnics or for outdoor activities such as camping or sporting events. In addition, insulated containers are commonly used in the medical industry, for example to move transplant organs and other articles that need to remain cold during transport. Insulated containers are also used to transport commercial goods such as perishable food, drink, and medicine, and other items that need to stay cool or cold, such as environmental samples.
One downside to current insulated containers is the limited length of time that an insulated container can keep something cold. For example, if ice is used in an insulated container, the ice will often melt after a relatively short period of time, because an insulated container typically cannot maintain the colder interior temperatures needed to prevent melting of the ice. Frozen ice packs do not last much longer.
Another downside to most contemporary insulated containers is that the inside cannot be maintained at freezing temperatures for very long. To solve this problem, many companies often use dry ice to keep the contents of an insulated container below freezing (i.e., 32 degrees Fahrenheit). However, even dry ice has time limitations, and use and handling of dry ice can be difficult.
One solution that has recently been used for providing insulated containers that can maintain cold temperatures for long periods of time is to provide refrigeration units in the insulated containers. However, this solution has not always been convenient. For example, traditional vapor cycle systems, while efficient, are quite large and heavy. In addition, such refrigeration units typically must be plugged into an AC outlet or a car cigarette lighter to provide cooling. While such a cooling unit works well for cooling items in the insulated container, an AC outlet or similar power supply is not always readily available. A few 12 volt or 24 volt systems are available today; however, these systems are also large and heavy. The vapor cycle 12 and 24-volt systems also may have problems with vibrations during transportation.
In addition, there exists absorption and adsorption refrigerators, but these fail if enough vibrations exist and improper orientation may also cause the units to fail. Like the vapor cycle refrigerators, these cooler systems are heavy and hard to handle.
The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later.
In accordance with an embodiment of the present invention, an insulated container is provided that utilizes Stirling cooler technology. The insulated container may include a self-contained, portable power source associated with them. Controls are provided for operating the Stirling cooler.
The controls may include a temperature sensor for a compartment of the insulated container, and a speed control for the Stirling cooler. The speed control reduces or increases the speed of operation of the Stirling cooler responsive to temperature readings by the temperature sensor. For example, if the temperature inside the compartment is sensed to be higher than the desired range, then the speed control can increase the speed of the Stirling cooler so that increased cooling is provided. Likewise, if the temperature is below a desired range then the speed of the Stirling cooler can be decreased.
In accordance with an embodiment of the invention, the controls may include an overheat sensor for the Stirling cooler. In accordance with an embodiment, the controls may have several temperature ranges associated therewith, and in response to sensing overheating of the Stirling cooler, the temperature range may be automatically set to a higher temperature range. Once overheating issues are resolved, the temperature range may be returned to the original temperature range.
In accordance with an embodiment of the invention, as part of the controls for the Stirling cooler, a control panel may be provided as a user interface for a user to control operation of the Stirling cooler. In an embodiment, the control panel includes a plurality of temperature setting buttons corresponding to different temperature ranges at which the compartment within the insulated container may be set. In response to pressing one of these buttons, the Stirling cooler is operated so as to cool the compartment to the desired/selected temperature range. If desired, an indicator may be provided, such as a flashing light emitting diode (LED), that indicates that the Stirling cooler is working to cool the compartment to the desired temperature range. A second indicator, such as a solid LED, may be provided to indicate that the compartment has reached the desired temperature range.
If desired, other features may be provided in the controls. For example, a low voltage indicator may be provided. In addition, a voltage sensor and a voltage reducer may be provided for determining whether voltage provided to the Stirling cooler is too high and for reducing the voltage to the Stirling cooler, respectively.
Other features of the invention will become apparent from the following detailed description when taken in conjunction with the drawings, in which:
In the following description, various embodiments of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.
Referring now to the drawings, in which like reference numerals represent like parts throughout the several views,
In general, a Stirling cooler (e.g., the Stirling cooler 20) includes a hermetically sealed capsule that contains a small amount of a working fluid, such as helium. The capsule contains two moving components: a piston 22 and a displacer 24. The piston 22 is driven back and forth by an AC linear motor 26.
The Stirling cooler cycle starts with voltage input to the linear motor 26. This input drives a magnet ring 32 which is rigidly attached to the piston 22. The piston 22 is driven by the linear motor 26 because the piston 22 is rigidly attached to the moving magnet ring 32. The oscillating motion of the piston 22 compresses and expands the working fluid.
The displacer 24 is free floating in the upper portion of the Stirling cooler 20. This upper portion is called the regenerator 36. The working fluid is free to flow back and forth around the displacer 24. The displacer 24 shuttles the working fluid back and forth from a cold side of the Stirling cooler 20, called a heat acceptor 28, to a warm side, called a heat rejecter 30. During expansion heat is absorbed at the heat acceptor 28, and during compression heat is rejected at the heat rejecter 30. The Stirling cooler 20 shown in
Briefly described, embodiments of the present invention utilize the heat acceptor 28 (cold portion) of a Stirling motor (e.g., the Stirling cooler 20) to provide refrigeration or freezing in an insulated container. A variety of different configurations for the insulated container and for structures that utilize the heat acceptor 28 for refrigeration or freezing may be used. Some examples are disclosed in application Ser. No. 10/254,437, filed Sep. 24, 2002, and entitled “Portable Insulated Container with Refrigeration” (the “'437 application”) although the invention herein is not limited to those examples.
In accordance with one embodiment, a structure, such as a heat sink, is provided on the heat rejecter 30 (hot portion) of the Stirling cooler 20 for dissipating heat that is generated during operation of the Stirling cooler. The structure is preferably arranged outside a compartment or compartments of the insulated container that are to be cooled, as is further described in the '437 application. As an example, the heat dissipating structure may be a wrap-around heat sink 40 such as is shown in
As is known in the art, a heat sink such as the wrap-around heat sink 40 increases the surface area that is available for dissipating heat in a structure. The heat rejecter 30 is a very narrow band. The wrap-around heat sink 40 works particularly well because it focuses on the narrow heat rejecter 30 and increases the surface area of material that is thermally connected to the heat rejecter so that heat dissipation is more effective.
As an example of how cooling may be supplied by the Stirling cooler, a thermal transfer device may be attached or otherwise associated with the heat acceptor 28 to remove heat through the heat acceptor from one or more compartments of an insulated cooler (i.e., the heat acceptor provides cooling of those compartments). For example, the thermal transfer device may include a heat sink that is connected with the heat acceptor 28 and that dissipates or spreads the cooler temperatures that are generated at the heat acceptor 28 (i.e., removes heat at the heat acceptor). This heat sink may be used to dissipate the cooler temperatures that are generated at the heat acceptor 28, for example, into a compartment in an insulated container. In this manner, the heat sink removes heat from the compartment of the insulated container, and provides refrigeration or freezing for the compartment.
Alternatively, other thermal transfer devices may be used. Examples are described in the '437 application, and will not be described in detail here. However, one example of a heat transfer device, in the form of a heat sink 50, is shown in
A fan 52 may be mounted on a top portion of the heat sink 50 shown in
The insulated container 60 includes a front wall 62, a rear wall 64, a left side wall 66, and a right side wall 68. The insulated container may include insulation. The insulation may be formed, for example, of polyurethane, polystyrene, polypropylene, ABS, polyethylene, vacuum panels, or another suitable insulating material. The insulation preferably has sufficient thermal insulating qualities so that an insignificant amount of heat is lost though the sides and top of the insulated container 60. Preferably a lid for the insulated container 60 is well-fitted, and is sealed with a lid seal and a latch such as is known in the art or with a suitable magnetic lid gasket. Such a structure minimizes heat loss that otherwise might occur through the closure for the lid.
The Stirling cooler 20 may be mounted through one of the walls 62, 64, 66, 68, or through a top or bottom of the cooler. In the example shown, the Stirling cooler 20 is mounted through the right side wall 68. A hole (not shown) in the right side wall 68 is provided for this purpose, and is sized so that the hole fits tightly around the regenerator 36 and is aligned with the gap 56. In accordance with one aspect of the present invention, the heat sink 50 and the heat acceptor 28 are mounted inside the compartment that is to be cooled in the insulated container 60, and the wrap-around heat sink 40 and the heat rejecter 30 are mounted outside the cooled compartment.
A fan 70 is positioned to blow air across the wrap-around heat sink 40. The fan 70 may be mounted in an enclosure 71 that is attached to the side of the insulated container 60. The enclosure 71 may also house the Stirling cooler 20. Although the fan 70 is shown as blowing air across the heat sink 40, the fan 70 may be alternatively arranged so that it faces outward (i.e., out of a hole 76 on the side of the enclosure 71), so that the fan may draw heat out of the enclosure 71.
The arrangement shown in
By structurally separating the heat producing components of the Stirling cooler 20 from the cooler air producing components, the cool air from the heat sink 50 and the heat acceptor 28 is provided to the refrigerated interior portion of the insulated container 60, and heat is directed away from the refrigerated portion, e.g., by the fan 70 and out the hole 76 (or in the enclosure 71). Moreover, the fan 70, the battery 72, the control box 74, and the charge port 58 may all be easily accessed without having to open cooled portion of the insulated container 60.
In accordance with embodiments of the present invention, controls are provided for operation of the Stirling cooler 20.in the insulated container 60. The various embodiments described for the controls are not limiting; other combinations of the features in the description or additional features may be incorporated with the controls.
The power source 110 may be one of many different sources for power, including solar or battery. Preferably, the power source 110 is portable so that the insulated container utilizing the Stirling cooler 20 does not have to be near an AC outlet. Moreover, the power source 110 is preferably self-contained (i.e., mounted on or in the insulated container). This feature permits the insulated container to be fully portable. Because the power source 110 is self-contained, the refrigeration components of the insulated container are operational during movement and away from power outlets.
A block diagram representing components of the controls 112 is shown in
In an embodiment, the controls 112 may provide a speed control 122 that provides regulation of the speed of reciprocation of the piston 22 for the Stirling cooler 20. As such, the speed control 122 provides an adjustment to the temperature of the heat acceptor 28. In this manner, the temperature provided by the Stirling cooler 20 may be adjusted.
The speed control 122 may be, for example, a device that is capable of varying the current supplied to the linear motor 26 of the Stirling cooler 20. Other mechanisms may be used for altering the speed of the Stirling cooler 20. The variations of speed may be infinite, or may be a finite number of settings. As an example, the speed control 122 may include a switch that allows the operation of the Stirling cooler 20 to be changed between, for example, two different speeds that represent freezer and refrigerator modes. In the freezer mode, the piston 22 would oscillate faster than in the refrigerator mode. The speeds needed for freezer verses refrigerator operation may be determined empirically, and may be set in a manner in accordance with the trade.
The controls 112 may also include at least one temperature sensor 124 connected with one or more of the compartments of the insulated container 60. Such a temperature sensor 124 provides temperature information regarding an internal compartment temperature to the controls 112. The controls 112 may use this information, for example, to adjust the power input to the Stirling cooler 20 to raise or lower the internal temperature of the compartment to a desired temperature, for example a range or temperature set by a user. That is, if the temperature is too low, the Stirling cooler 20 is slowed down, and if the temperature is too high the Stirling cooler 20 is sped up. The speed of the Stirling cooler 20 may be changed by the speed control 122.
Other components may be included in the controls 112. For example, as shown in
The controls 112 additionally include a user interface in the form of a control panel 140. An example of a control panel 140 that may be used to operate the Stirling cooler 20 is shown in
In the embodiment shown, the fourth and fifth temperature setting buttons 152 and 154 are configured for frozen modes of the insulated container 60. The freeze settings represent temperatures below freezing (i.e., 32 degrees Fahrenheit). One of these, for example, the freeze temperature setting button 154, may represent a deep freeze, wherein the other may represent a temperature range which is only slightly below 32 degrees Fahrenheit.
The temperature setting button settings described above are examples and other temperature ranges or numbers of buttons could be used. However, in accordance with an embodiment of the invention, the temperature ranges corresponding to the temperature setting buttons 146-154 decreases from one end to the other, in
The control panel 140 additionally includes a safety warning indicator 170, such as an LED. In addition, the control panel 140 includes a low battery indicator 172, which may also be an LED.
Generally described, the five temperature setting buttons 146-154 may be used by a user to set an operating temperature range for the insulated container 60. The controls 112 are utilized to operate the Stirling cooler 20 so that the insulated container 60 may reach the selected temperature range and stay within it, if possible. However, because the insulated container 60 may be used in a variety of different conditions, including high or low ambient temperatures, windy conditions, or rain, the controls 112 include a number of features that adjust operation of the Stirling cooler 20, and prevent overheating of the Stirling cooler 20.
Beginning at step 800, a determination is made whether or not the on/off button 142 has been turned on. Typically, a user beginning operation of the Stirling cooler 20 will depress the on/off button 142. A “press and hold” feature may be added to prevent the Stirling cooler 20 from being accidentally turned on. In addition, if desired, an indicator, such as a beeper, a light, or another suitable signal, may be provided to indicate the beginning of operation.
The controls 112 may be configured such that pressing any of the temperature setting buttons 146-154 may also begin operation of the Stirling cooler 20. In either event, the beginning of operation of the Stirling cooler 20 causes the LED 144 to be lit, and operation to begin.
If the on/off button 142 has not been selected, then the process loops back until the on/off button 142 has been depressed or the Stirling cooler 20 has otherwise been turned on. If the on/off button 142 is on, then step 800 branches to step 802, where a determination is made whether or not a temperature setting has been stored within the controls 112. The temperature setting may be, for example, stored in the memory 130. In accordance with an embodiment, the temperature setting that is stored is the most recently used temperature setting button 146-154. For example, if the temperature setting button 152 corresponds with the last temperature setting at which the Stirling cooler 20 and the insulated container 60 were set, then the temperature setting that is stored corresponds with that temperature setting button 152. Alternatively, the stored setting may be a most frequently used setting, a default setting set by the user or by the controls 112, or a setting stored in accordance with other logic.
If a temperature setting is stored, then step 802 branches to step 804, where the corresponding LED 156-164 for the associated temperature setting button 146-154 flashes. If a temperature setting is not stored, then step 802 branches to step 806, where the temperature setting button 146 for the highest temperature is flashed, i.e., the LED 156 for the temperature setting button 146.
In accordance with an embodiment, when one of the temperature setting buttons 146-154 is selected (by pressing, pressing and holding, or otherwise selecting), a beep is provided, and the corresponding LED 156-164 for the temperature setting button flashes until the interior of the insulated container 60 reaches the temperature range (measured, for example, by the compartment temperature sensor 124) corresponding to the selected temperature setting button. At that point, the corresponding LED 156-164 remains solid. The temperature of the compartment of the insulated container 60 may be measured, for example, by the compartment sensor 124.
In any event, at step 807, a determination is made whether or not input voltage for the Stirling cooler 20 is greater than a determined maximum. If so, step 807 branches to step 808 where the input voltage is reduced to an acceptable value. This process may be done, for example, by the rheostat 134. Alternatively, in accordance with an embodiment, the Stirling cooler 20 may be shut off if the input voltage is too high.
If the input voltage is not above the maximum, then step 807 branches to step 810. At step 810, the fan 70 is turned on and power is supplied to the Stirling cooler 20. At step 812, a determination is made if input voltage into the Stirling cooler 20 is below a minimum limit. If so, step 812 branches to step 814, where the battery low LED 172 is flashed. If the input voltage is not low, then step 812 branches directly to step 816.
As an example, the controls 112 may be configured so that the Stirling cooler 20 operates only when the voltage for the system is between 9 and 18 volts. If above that range, power to the Stirling cooler 20 may be cut, for example at step 808. If below the range, then power may be cut and the battery low LED may be flashed, for example at step 814. If desired, if a cigarette lighter adapter is provided, a delay may be provided to provide for a drop in voltage when the automobile is started. For example, a 10 second delay may be permitted in which the voltage is permitted to go under the minimum. During this period, the voltage may be permitted to drop to a lower threshold, for example 4.5 volts.
At step 816, a determination is made whether or not the user has depressed one of the temperature setting buttons 146-154. If so, then after a 1 second delay, step 816 branches to step 818, where the corresponding LED 156-164 is flashed, and the temperature setting corresponding to the selected temperature setting button 146-154 is stored in memory 130. If a user has not depressed one of the buttons, then step 816 branches directly to step 820.
At step 820, a determination is made if the inside of the insulated container 60 is within the set temperature range, i.e., is within the temperature range of the selected or flashing temperature setting button 146-154. If so, then step 820 branches to step 822, where the corresponding LED 156-164 is solidified. The process then proceeds to step 824, where the fan 70 is turned off if the Stirling cooler 20 is idling. If the temperature is not within the set temperature range, then step 820 branches directly to step 826.
At step 826, a determination is made whether or not the Stirling cooler 20 is overheating, for example, because of operating at too high of a cycle for too long of a period of time. This determination may be made, for example, by the Stirling cooler temperature sensor 136.
If the Stirling cooler 20 is overheating, then step 826 branches to step 848, where the fan 70 is turned on if it has previously been turned off (e.g., at step 824). At step 850, an indicator (with or without time delay, such as 20 seconds) provides information that the Stirling cooler 20 is overheating. For example, a beeper may be provided by the controls 112 (beeper not shown, but known in the art), and/or the safety warning LED 170 may be flashed.
At step 852, a determination is made whether the on/off button 142 has been actuated. For example, a user, when seeing the safety warning light 170 flash may press the on/off button 142, to turn off the Stirling cooler 20. If the on/off button 142 has been actuated, then step 852 branches to step 844, where the Stirling cooler 20 is shut down and all of the LEDs and the fan 70 are shut off. The process then stores the most recently used temperature setting at step 846, and the process loops back to step 800.
If a user did not actuate the on/off button 142, then step 852 branches to step 854, where a determination is made whether or not the current temperature setting is equal to the first temperature setting button 146 (i.e., in the example above, “COOL 1”). If not, then step 854 branches to step 856, where the new setting is set to the current setting minus one, and the LED of the new setting is flashed. For example, if the Stirling cooler 20 is overheating when at the temperature setting corresponding to the temperature setting button 152, then through the process of steps 854 and 856, the setting is indexed down one temperature setting button to temperature setting button 150, so that the Stirling cooler may try to operate to maintain the compartment at the temperature range that corresponds to that temperature setting button 150. The Stirling cooler 20 may be able to operate at the new, higher temperature setting without overheating.
This feature of adjusting the temperature setting in response to overheating permits the Stirling cooler 20 to continue operation, perhaps at a higher temperature setting, until it restore itself to the temperature setting that was selected by a user. Such a system permits the Stirling cooler 20 to operate in conditions where it cannot produce the desired temperature range. Such conditions may exist, for example, when the insulated container 60 is left in the trunk of a car and the trunk temperature makes it impossible for the Stirling cooler to maintain a low temperature range, or the insulated container 60 is exposed to direct sunlight for a prolonged period of time, as examples.
After the new setting has been set, then a thirty-second delay occurs at step 858, and the process then branches back to step 810. If the current temperature setting does correspond to the temperature range for the first temperature setting button 146, then step 854 branches to step 860, where the Stirling cooler 20 is shut down, all LEDs are shut off except for the safety warning LED 170 and the on/off LED 144. The process then proceeds to step 862, where a determination is made if the on/off button 142 has been actuated by a user, for example, in response to the safety warning LED 170 being lit. If not, the process continues to loop until the user turns off the controls 112, for example by actuating the on/off button 142. If the user does actuate the on/off button 142, then step 862 branches to step 864, where the safety warning LED 170 and the fan 70 are turned off. The process then branches to step 846, which has already been explained.
If desired, although not shown in
Returning now to step 826, if the Stirling cooler 20 is not overheating or is no longer overheating, then step 826 branches to step 828, where the safety warning LED 170 is turned off, if previously turned on, for example at step 850. At step 830, a determination is made if the current setting is equal to the original setting. That is, whether the current temperature range being utilized by the controls 112, for example as set by step 856, is equal to the original setting that was selected by the user or which was set as stored by step 804. If the current setting is not equal to the original setting, then step 830 branches to step 832, where the new setting is set to the original setting and the LED 156-164 of the current setting is flashed. If desired, a beeper or other indicator may be used to indicate that the controls 112 have returned to the original setting.
Alternatively, although not shown in the drawings, the new setting may index only one from the previous setting, which may or may not cause the setting to return to the original setting. Indexing may give the Stirling cooler 20 a chance to gradually return to the original setting. The process then branches back to step 810.
If the current setting is equal to the original setting, then step 830 branches to step 834. At step 834, a determination is made whether or not the battery or other power source has been disconnected. If so, step 834 branches to step 836, where the microprocessor, i.e., the microcontroller 120 and/or the controls 112 starts a sleep mode. A determination is then made at step 838 whether or not the battery has been reconnected. If not, the process loops back until the battery has been reconnected. Once the battery is reconnected, the sleep or hold operation of the microprocessor ends at step 840.
At step 842, a determination is made whether or not the on/off button 142 has been actuated by a user. If not, the process branches back to step 810. If so, then the process branches from step 842 to step 844, which has already been described.
As can be seen, the logic shown in
Other features may be provided in the controls 112. For example, a safety feature may be provided to prevent operation of the Stirling cooler 20 if the polarity of the power source 110 is reversed. Such a function may be provided, for example, by a relay and a diode (both not shown).
Other safety features may be provided. As an example, in one embodiment a thermosyphon may be used in connection with the Stirling cooler 20 to transfer heat from a compartment being cooled to the Stirling cooler. The function and operation of a thermosyphon is well known, but a brief description is given here for the benefit of the reader. In general, a thermosyphon includes a working fluid constantly flowing along its length. For a thermosyphon, cooled liquid leaves a cooling source (e.g., the heat acceptor 28), and flows through the pipe, downward and then back up to the cooling source. The liquid evaporates on its travel through the downward portion of the loop, as it absorbs heat from inside the compartment. The fluid often turns completely into a vapor before it has returned to the cooling source. The vapor is then condensed at the cooling source, and starts downward again, repeating the cycle. The flow of liquid downward keeps the fluid moving in the system, without moving parts. The thermosyphon is maintained at close to the same temperature as the cooling source, and may be used to cool or freeze the interior of a compartment.
Because a thermosyphon works on gravity, it is important that the cooling source remain higher than the rest of the pipe. Otherwise, the working fluid may freeze. In such an embodiment, if desired, a safety mechanism may be provided for the thermosyphon to prevent freezing. Such a device may be a tilt sensor, for example, or a temperature sensor that senses dramatic changes in cooling within the compartment.
Other variations are within the spirit of the present invention. Thus, while the invention is susceptible to various modifications and alternative constructions, a certain illustrated embodiment thereof is shown in the drawings and has been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
