Patent Document

REFERENCE TO RELATED APPLICATION 
   This application claims priority to U.S. Provisional Patent Application Ser. No. 60/458,676 filed Mar. 27, 2003. 

   FIELD OF THE INVENTION 
   The present invention relates to a device and method for warming food. More particularly, the present invention relates to a kitchen appliance to warm thin, circular foods such as tortillas. 
   BACKGROUND OF THE INVENTION 
   Tortillas are often made in relatively large quantities and then refrigerated for consumption later. Although tortillas may be eaten cold, normally before a meal the tortillas are warmed which significantly enhances their flavor and texture. To heat tortillas there is presently one primary method, namely to heat them on a hot metal surface such as a griddle or frying pan. In Mexico, the use of a heavy iron skillet called “el comal” is the traditional and proven way of warming tortillas because this method achieves the best flavor and quality for warming corn and flour tortillas. Cooks using el comal and other conventional methods are aware that corn tortillas normally should be heated longer than flour tortillas. 
   Some drawbacks of using el comal and other conventional methods are that they are very time consuming, demand constant human supervision to assure quality and safety, and require the use of a “comal” or pan plus an external source of heat such as a stove or fire. Other methods exist such as by warming tortillas in a microwave, convection oven, or directly on top of a stove burner or a grill. However, these methods also require constant supervision; some are unsafe due to the danger of causing fire, and all are found unreliable in producing consistent results in flavor and quality for the warming of corn and flour tortillas. 
   In a home all members of the family normally eat at the same time and therefore it is preferable to heat a number of tortillas at once. Similarly, in a restaurant it is often desirable to heat many tortillas at the same time. 
   However, in a home environment the surface area for heating tortillas is limited and often may not be sufficient to heat enough tortillas for all members of the family at the same time. In a restaurant, depending on the circumstances there may at times be insufficient space to heat enough tortillas to meet the customer&#39;s requirements at a particular time. 
   A possible solution to the problem of heating a large number of tortillas simultaneously is a certain type of large capacity toaster. For example, U.S. Pat. No. 6,116,150 describes a “multi-level toaster”. The multi-level toaster described in the patent consists of a vertically extending, cylindrical structure having a plurality of modules which may be integrally joined together in a single housing or may be stacked separately one upon the other. Each module comprises at least one heating unit having a horizontally oriented aperture opening into the unit. Accordingly, it would be possible to heat tortillas in the multi-level toaster. However, the multi-level toaster has serious shortcomings if used as a tortilla warmer. For example, in the multi-level toaster each heating unit is separated from its vertical neighbors by a heat insulating layer and includes a food receiving grill, an upper heating element located above the grill, and a lower heating element located below the grill. Thus if a tortilla were heated on a grill, for each tortilla two heating elements would be required. 
   As yet another example of a shortcoming of the multi-level toaster if it were used as a tortilla warmer, it should be understood that air pockets trapped in tortillas can inflate the tortilla during heating. This could result in parts of the tortilla contacting the heating element which might burn the tortilla and create an unsafe condition by causing a risk of fire. Yet another example of a shortcoming of the multi-level toaster if it were used as a tortilla warmer, it should be understood that if a batch of tortillas are warmed at the same time then it is desirable to remove all of the tortillas from the heating device at the same time. However, although the multi-level toaster includes a mechanism to permit the removal of a plurality of slices of toast at the same time, the mechanism is complex, appears significantly expensive from a manufacturing standpoint, and is apparently less than completely practical or desirable from a functional perspective. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a device and method to heat a plurality of tortillas at the same time. 
   Another object is to provide a device for heating tortillas which minimizes the number of heating elements in the device. 
   Another object is to provide a device for heating tortillas which includes means to reduce or eliminate the likelihood that a tortilla will be burned when it is being warmed. 
   Another object is to provide a device for heating tortillas which includes a system to permit a cook to easily place a plurality of tortillas in the device at the same time and to easily remove the plurality of tortillas at the same time. 
   The present device operates with a standard electric alternating current ranging from 110 to 120 volts in the US and 220v–240v in other countries. This appliance is to be used in homes or in businesses for the purpose of warming either corn or flour tortillas in quantities ranging from one up to six at a time. However, it should be understood that the device can be used to warm other thin, relatively flat foods such as pita bread. 
   The electric current provides energy to heater elements located within the unit and thus provide the heat necessary to warm the tortillas placed on a plurality of circular loading trays. The loading trays are designed to work with a vertical pivot tube which allows the loading trays a pivot-swivel action for efficiency in the loading and unloading of tortillas. The device includes a control unit with selector buttons and switches programmed with default settings based on taste tests and specifically designed for the warming of corn or flour tortillas. Additional options in the control unit allow for default settings designed for the warming of one to six tortillas at a time. An additional selector for the individual user to adjust the heating period is also designed within the control unit. Once the tortillas are loaded and the selections are made in the control unit, a button or switch for “start” and “off” will turn the unit on for the warming cycle or will shut the unit off. 
   After the warming cycle is complete, a beep tone or other sound will inform the user that the tortillas are warm and ready. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate embodiments of the present invention and, together with the detailed description, serve to explain the principles and implementations of the invention. 
     In the drawings: 
       FIG. 1  is a front view of the tortilla warmer according to one embodiment of the present invention, with the trays in the closed position. 
       FIG. 2  is a rear view of the tortilla warmer of  FIG. 1   
       FIG. 3  is a front view of the tortilla warmer according to  FIG. 1  in the open position. 
       FIG. 4  is a side view of the tortilla warmer of  FIG. 3 . 
       FIG. 5  is a top view of one tray of the device of  FIG. 1 . 
       FIG. 6  is a top view of the trays of the device of  FIG. 1 . 
       FIG. 6   a  is a side view of the trays of the device of  FIG. 1 . 
       FIG. 6   b  is a sectional view of a part of the handle of the device of  FIG. 6   a  taken along line  6   b — 6   b.    
       FIG. 7  is a view of the device of  FIG. 1  with the back removed. 
       FIG. 8  is a top view of one heating element of the device of  FIG. 1 . 
       FIG. 9  is a view of the internal structure of the device of  FIG. 1 . 
       FIG. 10  is a view of one component of the compression grill system of the device of  FIG. 1 . 
       FIG. 11  is a view of another component of the compression grill system of the device of  FIG. 1 . 
       FIG. 12  is a view of the compression grill system of the device of  FIG. 1 . 
       FIG. 13  is a top view of the device of  FIG. 1   
       FIG. 14  is a cut-away side view of the device of  FIG. 13 , taken along the line  14 — 14 . 
       FIG. 15  is another cut-away side view of the device of  FIG. 13 , taken along the line  14 — 14 . 
       FIG. 16  is a flow chart illustrating the operation of the device of  FIG. 1 . 
       FIG. 17  illustrates the control panel of the device of  FIG. 1 . 
       FIG. 18  illustrates an alternative embodiment of the control panel of the device of  FIG. 1 . 
       FIG. 19  is a front view of an alternative embodiment of the tortilla warmer for conductive heating, in the open position. 
       FIG. 20  is a front view of the embodiment of the tortilla warmer shown in  FIG. 19 , in the closed position. 
       FIG. 21  is an internal view of the device of  FIG. 19 . 
       FIG. 22  is an internal view of the device of  FIG. 20 . 
       FIG. 23  is an internal view of a part of the device of  FIG. 19 . 
       FIG. 24  is an exploded view of part of the device of  FIG. 19   
       FIG. 25  is top view of a novel tortilla spatula. 
       FIG. 26  is side view of the novel tortilla spatula of  FIG. 25 . 
   

   DETAILED DESCRIPTION 
   Embodiments of the present invention are described herein in the context of an electric food warmer. Those of ordinary skill in the art will realize that the following detailed description of the present invention is illustrative only and is not intended to be in any way limiting. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations of the present invention as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts. 
   In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer&#39;s specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure. 
     FIGS. 1 and 2  are the front and back views, respectively, of one embodiment of the tortilla warmer  10  of the present invention. The tortilla warmer  10  comprises a generally cylindrical housing  12  which has a substantially flat top  14  and a plurality of trays  16 , which are in the closed position. A control panel  18  is located on the top  14 , and a power cord  20  is used to supply electric power to the device. 
     FIGS. 3 and 4  show the tortilla warmer  10  with the trays  16  in the open position for loading tortillas. A handle  24  is substantially rod shaped and connects to each of the trays  16  so that a user can hold the handle  24  and move all of the trays together simultaneously. When the trays are in the open position as shown in  FIGS. 3 and 4  a cook can place one tortilla on each of the trays  16 . 
     FIG. 5  shows one tray  16 , which comprises a circular support member  26  and a grill  28 . The support member  26  has a connector member  29  coupled to one edge of the support member, and the connector member  29  has a circular outer part  30  and a curricular inner part  32 , and the inner part includes a cylindrical hole  34 . The support member  26  includes a flange  36  around its inner periphery to support the grill  28  so that the grills can be lifted off the support members  26  and removed from the device for cleaning. Each grill  28  comprises a circular outer member  38  and a plurality of parallel, straight members  40  which are spaced apart from each other and have their ends connected to the circular outer member  38 . As shown in  FIG. 6  a plurality of trays  16  are located one above the other and spaced apart from one another. 
     FIGS. 6   a  and  6   b  illustrate the operation of the handle  24 . The handle  24  is substantially rod shaped and includes a slot  41  formed along most of its length, with the exception of the uppermost part of the handle. The slot cooperates with flanges  42  which are formed on each of the trays  16  so that the handle can be removed ( FIG. 6   a ) to enable to a user to rotate each tray separately, or the handle can be engaged with the flanges  42  by sliding it downward over the flanges. When the handle  24  is engaged with the flanges  42 , a user can rotate all the trays  16  together by gripping a member  43 . Also connected to the handle  24  is a sensor plate  44  which can be sensed by a proximity sensor  44  located in the housing  12  to determine whether the trays are open or closed. 
   In  FIG. 7  the device is shown with the back removed. Heating elements  46  are shown, and each heating element  46  is mounted to a vertical support column  48 . Electronic power and control components  50  are mounted to a flat plate  52  located beneath the top  14  and above the uppermost heating element  46 . 
     FIG. 8  shows one heating element  46 . There are seven heating elements  46  in the device. Each heating element  46  is comprised of two components: a resistive element  54  and a phenolic plate  56 . The resistive element  54  is a readily available, widely used, flat ribbon, Ni-chrome element. The phenolic plate  56  is a thermally resistant, electrically nonconductive material that is rigid and durable. The plate  56  is substantially circular and has notches cut into the perimeter to allow for the resistive element  54  to be wrapped around the plate  56 . These wraps will be referred to as turns. 
   The topmost and bottom-most heating elements  46  are referred to as single sided. This configuration has the resistive element  54  located on only one side of the plate so that the thermal output in the single sided configuration occurs primarily in one direction. The middle five heating elements  46  are double-sided and have the resistive element  54  on both sides of the plate  56 . This configuration results in heating in two opposite directions. Thus it can be seen that the food on a tray  16  is simultaneously heated from both above and below by thermal radiation from two heating elements  46 . 
   It should be understood that thermal uniformity in the heating chamber is desirable to ensure a consistent heating from the topmost food item to the bottom-most food item. In some cases the tendency for heat to accumulate at the top of the chamber may require variations in thermal output of individual heating elements  46 . Varying thermal output from one heating element to another can be accomplished by methods known in the art. For example, varying thermal output can be produced by varying the number of turns or length of the resistive element at each heating element  46 , or by controlling the amount of current into each heating element  46 . 
   Turning to  FIG. 9 , a cut away view of the device is shown. The heating elements  46  are mounted to a vertical support column  48 . An upper heating element  60  is located at the top of the device, and the upper heating element  60  is single sided in that the resistive element  54  is on the bottom of the phenolic plate  56  to direct heat primarily downward. Similarly, the lowest heating element  62  is located at the bottom of the device and is single sided in that the resistive element  54  is only on the top of the phenolic plate  56  to direct heat primarily upward. The other five heating elements  46  are double-sided and have resistive elements on both their top and bottom sides. A vertical pivot tube  58  is mounted to the housing  12 , and connector members  29  of the trays  16  are connected to the pivot tube. 
   A compression grill assembly  66  is shown in  FIGS. 10–12 . The compression grill assembly  66  comprises a mounting bracket  68  which is connected to the housing  12 . The mounting bracket  68  includes six flanged slots  70  formed to accommodate mounting members  72 . The compression grill assembly  66  also includes six compression grills  74 , each of which has two rings  76  and  78 , and the rings  76  and  78  are connected to members  80  and  82  which connect the rings to each other and to the mounting member  72 . The cooperation of flanged slots  70  and members  72  permits a user to remove the grills  74  from the device for cleaning. 
   It can be seen from  FIG. 9  that one compression grill  74  is located immediately above each tray  16  when the trays are in the closed position. It should be understood that air pockets trapped in tortillas can inflate the tortilla during heating. The proximity of the heating elements to the tortilla does not allow significant room for inflation. The compression grills  74  force the tortilla to remain relatively flat. The compression grills  74  ensure that the tortilla can be easily removed and that it does not touch the heating elements. 
     FIG. 13  shows a top view of the device.  FIGS. 14 and 15  show sectional views of the device taken along line  14 — 14  in  FIG. 13 .  FIG. 14  shows the device without the trays  16 , and  FIG. 15  shows the device with the trays  16 . 
   The operation of the device can now be understood. The trays  16  are all simultaneously swung to the open position (shown in  FIGS. 3–4 ) and thin foods are loaded onto the trays  16 . The trays  16  are swung by pivoting around the pivot tube  58 . Although all trays  16  are capable of swinging independently, they share a common handle  24 . The handle  24  allows the user one single point of control that eliminates having to open and close all six units individually. 
   The handle  24  also contains features that allow the control circuitry to sense when the trays are in the open or closed position. The feedback is done through a contact or proximity sensor  44 , and is intended as a safety feature as well as means to ensure a better heating environment. 
   The handle  24  can be removed which allows all trays  16  to move in a radial fashion independently. The removal of the handle is necessary in the event that a tray may need to be cleaned or replaced. 
   The pivot tube  58  is designed to also be removable and has features to lock the tube in place. The pivot tube  58  would be removed only to replace or clean a tray  16 . 
   The trays  16  contain removable grills  28 . This grill  28  snaps into place and is removable for cleaning and may be Teflon coated to eliminate sticking. 
   Once the foods have been loaded onto the trays  16 , the user closes the trays by swinging them to the closed position ( FIGS. 1–2 ). The user then operates the controls of the device as illustrated in  FIGS. 16 and 17  to control the electronic power and control components  50  which comprise a control system.  FIG. 16  schematically illustrates the operation of the device, and  FIG. 17  illustrates the control panel  18 .  FIG. 19  illustrates an alternate embodiment of the control panel  18 . 
   The on-off switch  99  allows the user to control the power to the device. The food type selection control  100  allows the user to select a predetermined setting dependent on the type of food to be heated/warmed. As it applies to tortillas, the selection allows for either corn or flour. (Step  102 ). We have found by our taste tests that corn tortillas take longer to heat for optimum taste and texture than do flour tortillas. More specifically, we have found that corn tortillas should be heated about 50% to about 80% (and normally about 65%) longer than flour tortillas. For example, the preferred embodiment of the tortilla warmer uses about 1200 watts of power, and at this level of power flour tortillas should be heated for about 35 seconds, and corn tortillas should be heated for about 58 seconds. Accordingly, when the user sets the type selection control  100  for “corn” the device automatically heats the tortillas 65% longer than if the user sets the control  100  for “flour.” In an alternative embodiment, instead of varying the time, the time could be the same for both corn and flour while the power could be varied so that more power is used for corn tortillas than for flour tortillas, preferably, about 50% to about 80% more power. In either case, the important factor is that for corn tortillas more heat should be applied than for flour tortillas. As another alternative, the selection may include settings for the Pita or other food which is denoted as “other” on  FIG. 16 . After the predetermined heating time has been completed the control system shuts off power to the heating elements  46  and causes a sound to alert the user. (Step  116 ). 
   The timing adjustment control  104  allows the user to vary the amount of time the food will be heated. The timing adjustment control  104  allows the user to select from a predetermined minimum or maximum amount of time (or any amount of time in between) programmed in the control circuitry. (Step  106 ) For example, if the user selects “corn” with the selection control  100 , the user can then vary the exact heating time with the timing adjustment control  104  so that the time is the preset value for “corn” or somewhat greater or lesser than the preset time depending on the user&#39;s preference. The quantity selection control  108  is an energy saving feature. The user may elect to heat only the three upper most chambers or all six depending on estimated consumption. (Step  110 ) For example, a person preparing a meal for him or herself may only consume 2 to 3 tortillas versus a family of four that may consume 6 to 12. The start button  112  allows for the user to begin the heating process once all selections have been made. (Step  114 ). 
     FIG. 18  illustrates an alternative embodiment of the control panel  18 . This alternative embodiment differs from the  FIG. 17  embodiment primarily in that the  FIG. 18  embodiment includes a timer countdown LCD display  120  and a timing/heat intensity LCD display  122 . Also, the  FIG. 18  embodiment provides visual feedback of the user&#39;s selections with indicators  124 . 
     FIGS. 19–24  show an alternative embodiment in which the tortillas are heated by conduction. This embodiment is similar in some respects to the embodiment described above, and similar features will not be repeated in the following discussion of this embodiment. The conductive-type tortilla warmer shown in  FIGS. 19–24  includes a housing  130  with a hinged door  132 , and a control panel  18  is mounted on the top of the housing  130 . Seven heating plates  134  are located inside the housing  130 , and in  FIG. 19  the heating plates  134  are shown in the open position, while in  FIG. 20  the heating plates are shown in the closed position. 
     FIGS. 21–23  show the heating plates  134  and the system to open and close them. Adjacent the plates  134  a first and second jack screw  140  and  142  are located. The jack screws  140  and  142  are connected to the plates  134  by linkages  144 . The linkages  144  are formed of a plurality of inner links  150  and outer links  152 , and each linkage  144  is connected to the plates  134  by pins  154 . Two pins  154  are mounted on each plate  134 , and the pins slide in slots  156  formed in the inner and outer links  150  and  152 . The uppermost outer links  152  adjacent each jack screw  140  and  142  are connected to a threaded connector  155  which in turn is in threaded engagement with the adjacent jack screw  140  or  142 . A motor and gear system  157  is located above the plates  134  to drive the jack screw  140 , and the motor and gear system  157  is connected by a toothed belt  158  to a gear  159  to drive jack screw  142 . In operation, the motor and gear system  157  can drive the jack screws  140  and  142  to raise and separate all the heating plates  134  from each other ( FIG. 21 ) so that a user can insert tortillas between the plates. Then the motor can be operated in the reverse direction to lower the plates  134  until the bottom plate contacts the floor of the device, and then each of the other plates  134  is lowered to contact the food on the plate  134  below ( FIG. 22 ). Then the plates  134  are heated to warm the tortillas by conduction. 
   As shown in  FIG. 24  each heating plate  134  includes an upper cylindrical plate  162  and a lower cylindrical plate  164  which has a lip  166  around its periphery. A resistive heating element  168  is located between the plates  162  and  164  to heat the plates. 
   Turning now to  FIGS. 25 and 26  a novel tortilla spatula  170  is shown. The tortilla spatula includes a flat portion  172  and a handle  174 , and a raised portion  176  is formed partially around the periphery of the spatula to provide mechanical strength. The tortilla spatula  170  can be used to insert tortillas into the tortilla warmer  10  and remove them from the device. 
   While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.

Technology Category: 1