Abstract:
A food heating device usable as a toaster, fryer or warmer uses a metal plate having separately heated regions separated by a thermal break. The separately heated regions use separately energized and controlled heating elements embedded to the material from which the metal plate is made. One region can be kept hot while the other region is shut off or kept at a lower temperature until demand requires both sides to be heated. Separating the regions by a thermal break reduces heat transfer from the hot side to the cool side.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to an energy-efficient platen for warming and toasting food products that include bread slices, sandwich buns, rolls, croissants, bagels, muffins and flat bread. It is particularly useful in continuous-feed toasters used in fast food restaurants. It can also be used to fry foods. 
       BACKGROUND OF THE INVENTION 
       [0002]    Platen toasters, i.e., toasters that toast or brown foods using a hot, flat plate, are preferred by many food services and fast food restaurants because they are fast, provide an almost completely-uniform color change (Maillard reaction) across the surface of a food item and they tend to dry a food item less than radiant energy toasters. Platen toasters are fast because they supply the Maillard reaction-generating heat energy through a direct, physical contact, instead of infrared transmitted from a hot wire. They produce a uniform color change across the surface of a food item because the platen surface is smooth and the platen&#39;s temperature is uniform or nearly uniform. They tend to retain moisture in foods because the surface of the food product being browned or toasted is carmellized before significant water loss can occur, sealing water into the food product. 
         [0003]    A problem with platen-equipped toasters is their energy inefficiency. A platen won&#39;t effectuate a Maillard reaction, i.e., it won&#39;t toast or brown food, unless its temperature is between about 250 degrees and 600 degrees ° F. A cold platen, i.e., a platen at room temperature, will require a significant amount of time for it to pre-heat before it can be used. When a platen toaster used in a fast food restaurant, the platen must be kept at or near operating temperature all the time, which requires energy to be continuously supplied to the platen in order for it to be able to toast and brown foods relatively quickly or on demand. Reducing the energy consumed by a platen toaster, such as those used in high-volume food services and fast food restaurants would be an improvement over the prior art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a side view of a metal plate or platen having two, separately heated sections that are separated from each other by an air-filled opening defined by thin, narrow connecting blocks; 
           [0005]      FIG. 2  is a cross section of the metal plate shown in  FIG. 1  taken along section lines  2 - 2 ; 
           [0006]      FIG. 3  is a top view of the metal plate shown in  FIG. 1 ; 
           [0007]      FIG. 4  is a side view of a metal plate used as a platen, a separately heated region of which how two sections with different thicknesses; 
           [0008]      FIG. 5  is a top view of the metal plate shown in  FIG. 4 ; 
           [0009]      FIG. 6  is a side view of a metal plate having two, separately heated sections that are separated from each other by a block of thermally-insulating material; 
           [0010]      FIG. 7  is a top view of the metal plate shown in  FIG. 6  and showing that the two separately heated sections have different thicknesses; 
           [0011]      FIG. 8  is a perspective view of a frusto-pyramidal metal “plate” divided into two, separately heated sections separated from each other by a thermally-insulative layer; 
           [0012]      FIG. 9  is a side or end view of the metal plate depicted in  FIG. 8 ; 
           [0013]      FIG. 10  is a perspective view of a metal plate having a first section in the shape of a frusto-pyramid and a second section in the shape of a rectangular parallel piped; 
           [0014]      FIG. 11  is an end view of the metal plate depicted in  FIG. 10 ; 
           [0015]      FIG. 12  is a perspective view of a metal plate having two, separately heated regions defined by a thermal break embodied as a void embedded within the plate; and 
           [0016]      FIG. 13  is a perspective view of a metal plate having a thermal break embodied as a slot or channel formed into the plate between two, separately heated regions; 
           [0017]      FIG. 14  is a side view of a metal plate having two, separate sections heated by embedded, electrically resistive heating elements that are crenellated; 
           [0018]      FIG. 15  is a top view of the metal plate shown in  FIG. 14 ; 
           [0019]      FIG. 16  is a metal plate having two separate sections that are separately heated but which are separated by a non-linear thermal break, which resembles an inverted truncated pyramid-shaped region filled with thermally insulating material; 
           [0020]      FIG. 17  is a cross sectional view of a continuous feed toaster equipped with a conveyor and a platen having separately heated sections, such as the platens depicted in  FIGS. 1-16 . 
           [0021]      FIG. 18  is a side view of an alternate embodiment of a platen, having an opening in one section to allow a food product to pass through the platen; 
           [0022]      FIG. 19  is a side view of two separately heated platens; 
           [0023]      FIG. 20  is a side view of a toaster using the two platens depicted in  FIG. 19 ; and 
           [0024]      FIG. 21  is a top view of a toaster using the platens depicted in  FIG. 19 . 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  is a side view of a metal plate, which is also referred to herein as platen  10 , having bifurcated heating surfaces. Stated another way,  FIG. 1  is a side view of a metal plate having two, separately heated sections  12 ,  14 , which are also referred to herein as regions, separated from each other by thermal break,  16 . The thermal break  16  in the platen of  FIG. 1  is embodied as an elongated, rectangular air-filled gap or channel  18 . The long sides of air-filled gap  18  are defined by the side edges of the two separately heated sections  12 ,  14  that face each other. The short sides of the air-filled gap are defined by two thin, narrow connecting blocks  20  and  22  that hold the two sections  12  and  14  fixedly attached to each other and which can provide an electrical conduit as set forth below. The connecting blocks  20  and  22  are spaced apart from each other as shown, to enhance the flow of cooling air between the two heated sections  12  and  14 . 
         [0026]    The two separately-heated sections  12 ,  14  can be made from separate platens connected to each using screws, bolts or other fasteners that extend through the connecting blocks and at least part way through the sections  12  and  14 . For purposes of clarity, however, the fasteners holding the sections  12  and  14  together are not shown in the figures. The two separately-heated sections can also be molded using a single casting with resistive conductors embedded within them. 
         [0027]    The electrically-resistive heater conductor wires  24  and  26  embedded within the material forming the platen can follow virtually any path. In order to evenly heat the platen, however, the conductors preferably follow a uniform pattern, such as a boustrophedonic path as shown or a crenellate path not shown. The number of loops and their spacing from adjacent loops in each region  12  and  14  is a design choice but increasing the number of boustrophedonic or crenellate loops tends to reduce temperature variations across the surface of the respective regions  12  and  14 , i.e., more loops provide a more even temperature throughout the heated regions&#39; surface area. 
         [0028]      FIG. 2  is a cut-away view of the platen  10  taken along section lines  2 - 2 .  FIG. 3  is a top view of the platen  10  shown in  FIG. 1  and depicting the top view of a conveyor  15  used in a continuous toaster and which drags a food product along the platen. It can be seen in  FIGS. 2 and 3  that the platen  10  is relatively thin and flat. The opposing sides of the platen  10  are planar or substantially planar and parallel to each other. 
         [0029]    Since the regions  12  are  14  are provided with separate conductors, the operating temperatures of the regions  12  and  14  are therefore individually and separately controllable if the heater conductors  24  and  26  are connected to separate and individually-controllable electrical power sources. Such power sources are not shown in the figures, but well known to those of ordinary skill in the art. The thermal break  16  between the regions  12  and  14  keeps one region from sinking heat energy from the other region. The ability to control the temperature of the regions separately and independently in combination with the thermal break between them enables a restaurant or food service operator to keep at least part of a platen at or near operating temperature at all times with the added ability to have a larger hot area brought on line when demand increases. Keeping a relatively small-area platen hot with the ability to provide a much larger hot surface area can provide an energy savings as compared to what would be required to keep hot all the time, a platen that is large enough to handle peak demand requirements. 
         [0030]    It can be seen in the figures that the first conductor  24  extends through the second region  14  of the platen  10  before it reaches the first region  12 . In such an embodiment, the connector blocks  20  and  22  provide a conduit for the embedded conductor  24  and mechanically hold the two sections  12  and  14  together. In an alternate embodiment, however, the electrical connections to the two heater conductors do not need to pass through the connector blocks  20  and  22  but can instead extend from one or two different edges of the two different regions  12  and  14 . 
         [0031]      FIGS. 4 and 5  depict an alternate embodiment of the platen  10  depicted in  FIGS. 1-3 . In  FIG. 4  the platen  40  has two separately heated sections  42  and  44  that are separated from each other by the thermal break  16 . As can be seen in  FIG. 5  however, which is a top view of the platen  40 , the platen  40  has two, separately heated sections  42  and  44 , one of which has two different portions or sub-sections  46  and  48 , which are of different thicknesses. More particularly, the left-side or first section  42  of the platen  40  has two sub-sections  46  and  48 , which are of different thicknesses. The different thickness sub-sections  46  and  48  of the platen  40  can accommodate cooking, frying or toasting different thickness foods evenly, using a single conveyor. 
         [0032]    When the platen  40  of  FIGS. 4 and 5  is used in a continuous feed toaster with a conveyor  15  that extends across the entire platen  40  as shown, the conveyor  15  will exert a substantially equal compressive forces on food products having different thickness that correspond to the different separation spacings between the conveyor  15  and the different thickness sub-sections  46  and  48 . Changing the thickness of sections of the platen can therefore accommodate the ability to cook, e,g., toast, fry or brown different thickness food or bread products at the same time. 
         [0033]      FIGS. 6 and 7  are side and top views respectively of yet another embodiment of a platen  60  having separately heated regions  62  and  64  separated by a thermal break  66 . As can be seen in  FIG. 7 , the left-side or first regions  62  has a thickness greater than that of the right-side or second region  64 . As with the embodiment depicted in  FIGS. 4 and 5 , the different thickness regions can accommodate food products of different thicknesses. When the platen  60  is used with a conveyor  15  parallel to the platen  60 , the left-side  62  will thus accommodate a thicker bun or other food product than will the right side  64 . The platen depicted in  FIGS. 6 and 7  can accommodate the heating (toasting, frying) of different food products, including different food products of different thicknesses by adjusting the left side  62  and right side  64  temperatures, the different thicknesses and the spacing of the conveyor  15  away from the platen  40 . 
         [0034]      FIG. 8  is a perspective view of yet another embodiment of a platen  80  having two, separately heated sections  82  and  84  separated from each other by a thermal break  86 , which is embodied as a slab of thermally insulative material.  FIG. 9  is an end or side view. Electrically separate and separately controlled heating elements are embedded in the two sections  82  and  84 , just as they are shown in  FIGS. 1 and 4  but in  FIGS. 8 and 9 , the heating elements embedded in the two sections  82  and  84  are omitted from the figures for clarity and simplicity. 
         [0035]    In  FIG. 8 , the shape of the “platen” is reminiscent of an inverted truncated pyramid, which is also referred to herein as a frustrum of a rectangular pyramid. A top portion  88  of both sections  82  and  84  has a thickness “T” greater than the thickness “t” near the bottom portion  90 . The differing thickness between the top portion and bottom portion, which is exaggerated in the figures, imbues the “platen” with a taper. When used with a planar and level conveyor  15 , the conveyor will urge a food product against the top portion  88  with a greater force than it will urge a food product against the lower or bottom portion  90  due to the fact that a planar conveyor and the thicker top portion  88  will tend to squeeze or urge a food product against the “platen”  80  with more force than at the thinner bottom portion  90 . The platen depicted in  FIGS. 8 and 9  can thus be used to effectuate the initiation of the Maillard process faster at the thicker top portion  88  than at the bottom portion  90 . 
         [0036]    The platen embodiment depicted in  FIGS. 10 and 11  is similar to the embodiment depicted in  FIGS. 8 and 9 . In  FIGS. 10 and 11 , the two separately heated sections  102  and  104  are separated by a thermal break  105 , preferably embodied as a solid block of thermally insulative material. Unlike the embodiment depicted in  FIGS. 8 and 9 , in  FIGS. 10 and 11 , only one of the two separately heated sections  102  and  104  is tapered. Stated another way, the top portion  108  of the first heated section  102  is wider than the bottom portion  110  of the first section whereas the second heated section  104  is a regular rectangular prism having a substantially uniform thickness from its top  112  to its bottom  114 . Such an embodiment enables a rapid initial toasting on the first side  102  with a conventional toasting on the second side  104 . 
         [0037]      FIG. 12  depicts yet another embodiment of a platen  120  having first and second separately heated sections or regions  122  and  124  separated by a thermal break  126 .  FIG. 12  differs from the other embodiments depicted in  FIGS. 1-11  in that the thermal break  126  is embodied as a void region formed into the material from which the platen  120  is cast. The void region  126  thus inhibits heat transfer between the two sides  122  and  126  to that which can be conducted through the material surrounding the void  126  while enabling the platen  120  surface to be seamless, owing to the fact that no other material is sandwiched between the two separately heated regions  122  and  124 . 
         [0038]      FIG. 13  depicts a platen  130  wherein the separately heated sections  132  and  134  are separated by a thermal break embodied as an air filled channel  136  that extends only part way through the thickness of the platen  130 . As with the other embodiments depicted in  FIGS. 1-12 , separately controlled heating elements are embedded in each section  132  and  134  but they are not shown in the figure for clarity and simplicity. 
         [0039]    Those of ordinary skill in the art will recognize that heat will conduct from one section  132  or  134  to the other  134  or  132  through the material that remains at the bottom of the channel  136 . For that reason, in order to minimize heat transfer between the two sections  132  and  134 , the channel  136  is preferably made to be as deep and as wide as possible. 
         [0040]      FIGS. 14 and 15  depict respectively a side view and a top view of yet another embodiment of a platen  150  having separately heated sections separated by a thermal break. In  FIG. 15 , the separately heated sections  152  and  154  are separated from each other by thermal break embodied as the air gaps  156  and  158  defined by a single connection block  160 . As can be seen in  FIG. 15 , the single connection block  160  is thinner than either of the two heated sections  152  and  154  in order to reduce the cross sectional area of platen material that can conduct heat energy between the two sections  152  and  154 . 
         [0041]    In addition to having a single connection block  160 , the platen  150  employs electrically resistive heater wires  151  and  153 , the end sections of which form crenellations. The crenellate-shaped wire heaters  151  and  153  can provide more uniform heating of the platen  10  near the edges. 
         [0042]      FIG. 16  shows a side view of yet another embodiment of a platen  160  having first and second separately heated regions  162  and  164  separated by a non-linear thermal break  166 , which is embodied in  FIG. 16  as a trapezoidal-shaped block of thermally insulating material. 
         [0043]    Finally,  FIG. 17  shows a side view of a continuous feed toaster  170  implemented with a platen having two, separately heated regions separated by a thermal break, such as the platen  10  depicted in  FIGS. 1-3 . A top portion  174  of a bun is driven downward in the toaster  170  by the conveyor  15 . As the bun moves along the platen, it is toasted by the platen and drops into a heated storage compartment  180 , the temperature of which is kept above ambient by a heater element  172  at the bottom of the compartment  180 . The inclination angle of the platen relative to the conveyor is such that the conveyor and platen tend to squeeze or compress the food product as it moves along the cooking path, having been at least partially cooked in the process. Squeezing the food product can effectuate the release of grease and other liquids from meat products. 
         [0044]      FIG. 18  depicts an alternate embodiment of a platen  190  having separately heated sections  192  and  194  separated from each other by a thermal break  18 . The separately heated sections are coupled together by the aforementioned connecting blocks  20  and  22 . The thermal break is comprised of an air-filled gap. Each section  192  and  194  includes an electrically resistive heating element embedded in the sections as described above. The heating sections can be of virtually any geometry, preferred ones being either boustrophedonic (shown) or crenellated (not shown in  FIG. 18 ). 
         [0045]    In  FIG. 18 , one of the separately heated sections  192  includes a window or opening  196  through which a food product can pass from one side of a heated platen  190  to the other side (not shown). In such an embodiment, a food product is conveyed part way down the one side  192  of the platen  190  being heated on one side. When the food product meets the window  196 , it is translated through the window  196 , by a lip on the window&#39;s lower edge or a ramp, not shown, to the opposite side of the platen  190 . A conveyor on the opposite of the platen (not shown), continues to move the food product along the platen  190  such that the food product is heated on its other side. 
         [0046]      FIG. 19  shows a side view of another alternate embodiment of a platen  200 , which is comprised of two, separate and individually heated platens  202  and  204 , which are completely separated from each other by a thermal break  206  embodied as an air-filled gap between the platens  202  and  204 .  FIG. 20  shows a side or end view of the platens shown in  FIG. 19 , which also shows the conveyor  15  used to move food products along the platens  202  and  204 .  FIG. 21  shows a top view of the toaster. 
         [0047]    It is important to note that the platens  202  and  204  in  FIG. 19  are not coupled to each other but are instead fixed in place relative to each other by brackets (not shown). As with the platens described above and depicted in the other figures, the each section  202  and  204  includes heating sections embedded in the sections, which can be of virtually any geometry, the preferred ones being either boustrophedonic (shown) or crenellated (not shown in  FIG. 19 ). 
         [0048]    It is also important to note that the platen depicted in  FIGS. 19-21  is an example of how each of the platens depicted in  FIGS. 1-18  can be modified such that the separately-heated sections are completely separated from each other as shown in  FIGS. 19-21 . Stated another way, each of the platens depicted in  FIGS. 1-17  can be alternately embodied by keeping the separately heated sections, separated from each other by an air gap. Such alternate embodiments of the platens should also be considered to be within the scope of the appurtenant claims. 
         [0049]    The platens described above and shown in the figures are preferably formed using a thermally conductive material, such as cast aluminum, which has a relatively high heat transfer coefficient k. Thermal insulation between the separately heated sections can be provided by any appropriate material having a thermal transfer coefficient less than the material from which the heated sections are formed such as glass, ceramics and high-temperature plastics. Air can also be used as a thermal break. 
         [0050]    In each of the embodiments described herein, the surfaces of the platens are optionally provided with one or more layers of non-stick or friction-reducing material applied to the surfaces or, one or more sheets of non-stick or friction-reducing material. One such material is polytetrafluoroethylene (PTFE), which is also known as TEFLON™. The application of PTFE to a metal surface is well known in the art. Other embodiments use one or more discrete, replaceable sheets of PTFE draped over and held adjacent to surfaces of the platens used to cook (toast or brown, heat or fry) foods. PTFE sheets are known in the art but often use fiberglass fibers to strengthen them such that they resist tearing. Since the platens described herein are used to prepare foods, it is preferable that PTFE sheets used with the platens herein be either completely free fiberglass or essentially free of fiberglass to reduce the likelihood of fiberglass fibers being transferred into a food product. The PTFE sheets used with the platens described herein preferably employ PTFE filaments that interlock each other at angles between 15 and 175 degrees, to improve their tensile strength, necessitated by the fact that they are free of fiberglass or essentially free. 
         [0051]    In the embodiments shown in the figures and described above, the separately heated sections are depicted as rectangular. Each section therefore has a corresponding height and a width and a corresponding surface area. While the descriptions of each embodiment refer to sections or regions, which are shown in the figures as being rectangular and which are shown in the figures as being of unequal areas, it should be understood that separately heated regions do not need to be rectangular or of any other particular geometric shape. Other equivalent alternate embodiments include separately heated sections that are trapezoidal, triangular or semi-circular. Moreover, areas of the separately heated regions are not necessarily equal or unequal. Equivalent alternate embodiments include platens having separately heated regions or sections, the areas of which are both equal and unequal, all of which are considered to be within the scope of the appurtenant claims. 
         [0052]    The platens described above and depicted in the figures provide bifurcated heating sections, by which is meant, two or more separately heated regions thermally separated from each other by a thermal break. Such a platen enables a food service or restaurant that serves food products like toasted bread slices, sandwich buns, rolls, croissants, bagels, muffins and flat bread to be able to cook them on demand. It also enables food services and restaurants to be able to fry foods on a hot, flat surface, keeping at least one region at or near the relatively high operating temperature, at all times, or nearly all times. When demand increases over the course of a day, as usually happens in most restaurants, the second region of the platen can be brought on line, i.e., heated to an appropriate operating temperature range, typically between 250 and 600 F°, simply by turning on the power, thereby significantly increase food processing capacity. As demand wanes, the second region can be shut off or its input power reduced in order to reduce energy consumption. 
         [0053]    While each embodiment described above is considered to be within the scope of the appurtenant claims, the scope of invention is not defined by embodiments described above but is instead defined by the appurtenant claims.