Abstract:
A programmable control system for controlling the ratio of heating time “on” compared to time “off”. The digital control can be set to an “on”/“off” time duty cycle, and power level that determines the temperature of the cooking surface. The cooking surface can be divided into separately controllable zones. The need to actually sense the temperature at the roller tube is eliminated. The time based control can be set to cook at higher temperatures by increasing the “on time” relative to the “off time” or inversely, reducing the “on time” to the “off time”. A “pre-heat” cycle is provided to raise the grill to a predetermined set point for holding the elements full “on” for a selectable time period. Then, after the selectable time period has been reached, the control automatically sets the programmed “cook” time and temperature.

Description:
[0001]    This application claims benefit of U.S. Provisional Application Ser. No. 61/650,919 filed on May 23, 2012 pursuant to 35 USC §119(e). 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to commercial cooking assemblies, in particular, a temperature control system for a roller grill. 
       BACKGROUND OF THE INVENTION 
       [0003]    The use of a roller grill to cook hot dogs dates back at least as early as 1939. At that time, Dumas, in U.S. Pat. No. 2,185,979, recognized the advantage of using a plurality of rollers to quickly and uniformly cook hot dogs, bratwursts, sausages and other food products having an elongated shape. Since that time, the roller grill has been associated with America&#39;s food icon, the hot dog. 
         [0004]    Heat controls in the prior art traditionally have used what is called an “infinite control”. The “infinite control” contains an internal heat switch that opens and closes the circuit with respect to temperature. As this switch opens and closes, the heating elements turn “on” and “off” for a certain period of time, thus creating a duty cycle. 
         [0005]    Another system that has been used is having two or more settings, which can vary the number of elements that are “on” verses the number that are “off”. U.S. Pat. No. 6,707,015, issued to Huegerich et al. on Mar. 16, 2004 discloses the use of a control system that automatically adjusts the temperature of a roller grill without the involvement of an operator by use of a temperature sensor in communication with the control system. 
         [0006]    There is not found in the prior art a control system for controlling the ratio of heat “on” compared to time “off” (duty cycle) using a digitally controlled timer. The digital control can be set by the user to a specific element “on”/“off” time duty cycle, this, in turn, determines the temperature of the cooking surfaces. This eliminates the need to actually sense the temperature at the roller tube, which is difficult due to the rotation of the tube. A time base control eliminates the need for temperature reading programming to feedback temperature information, which approximates the roller temperature, thus making costly probes and controls unnecessary. Further, there is no prior art having a time based control that can be set to cook at higher temperatures by increasing the “on time” relative to the “off time” or inversely, reducing the “on time” to the “off time”, such that the food can be held at lower temperatures for a longer period of time. 
         [0007]    Additionally, no prior art device has a “pre-heat” cycle, which is provided to raise the grill to a predetermined set point for holding the elements full “on” for a selectable time period and, then, after the selectable time period has been reached, the control sets the pre-set “cook” time and temperature. 
         [0008]    Finally, no prior art roller grill provides a feature that once a cycle has been completed, the control will reduce the “pre-heat” time or duty cycle for a predetermined amount of time for the next cycle. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an aspect of the invention to provide a digital roller grill control apparatus that controls the ratio of heat “on” to “off” time. 
         [0010]    It is another aspect of the invention to provide a digital roller grill control apparatus that measures the time the heating elements are “on” and compares that to the time the heating elements are “off”. 
         [0011]    It is still another aspect of the invention to provide a digital roller grill control apparatus that provides the user with an approximated temperature of the product on the roller grill. This is accomplished by use of a temperature sensing device position in a manner to reflect the product temperature on the roller grill. This temperature sensor has no influence on controlling the duty cycle; it is only acting as a thermometer for the user. 
         [0012]    Another aspect of the invention is to provide a digital roller grill control apparatus that eliminates the need to directly sense the temperature at the roller tubes while the roller tubes are turning. 
         [0013]    Still another aspect of the invention is to provide a digital roller grill control apparatus that eliminates the need for a temperature reading and programming to provide feedback temperature information which approximates the roller grill temperature, thus, eliminating the need for costly probes and controls. 
         [0014]    Another aspect of the invention is to provide a digital roller grill control apparatus that can be set to a higher temperature by increasing the “on” time relative to the “off” time. 
         [0015]    Still another aspect of the invention is to provide a digital roller grill control apparatus that can hold the food product at a “hold” temperature by reducing the element “on” time to the element “off” time. 
         [0016]    Another aspect of the invention is to provide a digital roller grill control apparatus that has a “pre-heat” cycle to raise the grill temperature to a predetermined set point by controlling the heating elements to a full “on” setting for a selectable time ranging from 0 to 999 minutes. 
         [0017]    It is an aspect of the invention to provide a digital roller grill control apparatus that automatically goes into a “cook” mode once the “pre-heat” cycle time has been achieved. 
         [0018]    Another aspect of the invention is to provide a digital roller grill control apparatus that can feature alarms for indicating the end of any cycle by use of lights or audible indicators well known in the art. 
         [0019]    It is also an aspect of the invention to provide a digital roller grill control apparatus that is easy to program and operate. 
         [0020]    Another aspect of the invention is to provide a digital roller grill control apparatus that has a display that can be easily interpreted when viewed at a distance. 
         [0021]    It is still another aspect of the invention to provide a digital roller grill control apparatus that once one program cycle has been completed with program cycle defined as the completion of a “pre-heat”, “cook” and “hold” time has completed as the invention will automatically reduce the “pre-heat” time or cycle time by a predetermined amount on the next program cycle. 
         [0022]    Finally, it is an aspect of the invention to provide a digital roller grill control apparatus that during the “hold” mode after a predetermined amount of time in that “hold” mode, the duty cycle will be reduced to extend the product “hold” time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is an isometric view of the digital roller grill control apparatus installed on a typical roller grill in accordance with the invention. 
           [0024]      FIG. 2  is an exploded view of the digital roller grill control circuit board and relays. 
           [0025]      FIG. 3  is a detailed view of the control panel. 
           [0026]      FIG. 4  is an isometric view of the typical roller grill apparatus shown in  FIG. 1  identifying the location of the temperature sensor on the apparatus. 
           [0027]      FIG. 5  is a detailed view of the sensor identified in  FIG. 4 . 
           [0028]      FIG. 6  is a side view of the typical roller grill apparatus shown in  FIG. 1 . 
           [0029]      FIG. 7  is a detailed cross-sectional view of section C-C shown in  FIG. 6 . 
           [0030]      FIG. 8  is an alternative isometric view of a roller grill apparatus with an optional warming drawer in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    As shown in  FIG. 1 , the control panel of invention  10  is shown mounted on a typical roller grill apparatus  12 . The typical roller grill apparatus  12  shown is Slant Model-50 HRDi made by APW Wyott of Dallas, Tex. However, the invention is not limited to this particular roller grill but could be used with any roller grill. 
         [0032]    Referring now to  FIG. 2 , invention  10  is shown in an exploded view being mounted to the front panel of apparatus  12 . The main components are circuit board  18  that is mounted to the front panel using spacers  20  and solid-state relays  14 ,  16  which are mounted to apparatus  12  using bolts. Circuit board  18  is preferably the type made by Quantum Corporation of Ewing, N.J. 
         [0033]    As shown in  FIG. 3 , the control panel of invention  10  includes an “on/off” switch  50 ; setting button  44 ; control buttons  46 ,  48 ; indicator lights  52 ,  54 ,  56 ,  58 ,  60 ,  62 ,  64  and  66 ; and display  42 . 
         [0034]      FIG. 4  shows the placement of temperature sensor assembly  21  on roller grill  12 . Note that one sensor  21  is placed near the front of the roller grill, while another is placed near the rear so that the front part of the grill can be set at a different temperature than the rear rollers. 
         [0035]    Referring to  FIG. 5 , sensor assembly  21  is described in detail. Sensor  28  is preferably a K-type thermocouple such as those made by Durex Industries of Cary, Ill. Assembly  21  is mounted to apparatus  12  using mounting plate  24  and screw  26  as shown in the exploded view. 
         [0036]    The preferential placement of sensor assemblies  21  is shown in  FIGS. 6 and 7 . Note that sensor  28  is immediately adjacent to one of the rollers of roller grill  12  with one assembly  21  in one of the front rollers and a second assembly  21  in one of the rear rollers, assuming that it is desired to be able to control the temperature of the front rollers at a different temperature than that of the rear rollers. The placement of sensor  28  is positioned so that it is centered between two roller tubes, isolated from the heating element. This was determined to be the best positioning to accurately reflect product temperature on the roller grill. 
         [0037]    As shown in  FIG. 8 , invention  10  could also be used in an alternative embodiment with the control panel set in a vertical position rather than horizontal as shown in  FIG. 1 . In this embodiment, roller grill apparatus  12  features a bun warmer drawer  32  with a temperature control knob  34 . 
         [0038]    Referring back to  FIG. 3 , the operation of invention  10  is described in detail. Again, note that the preferred embodiment of invention  10  utilizes controls for both front and rear temperature control of the roller grill surface, however, that is not essential. Invention  10  could just as easily be used as a single temperature zone or even three or more zones depending on the user&#39;s needs and requirements. 
         [0039]    The user will first turn on the apparatus by flipping rocker switch  50  to the “on” position. This will initiate power to invention  10  as well as turn on power to the rollers. LED display  42  will indicate “---” which tells the user that no mode of operation has been selected as yet. Button  46 , rear indicator light  52 , “pre-heat” light  56 , “cook” light  60  and “hold” light  64  all relate to the operation and programming status of the rear zone of the roller grill surface of roller grill  12  while button  48 , front indicator light  54 , “pre-heat’ light  58 , “cook” light  62  and “hold” light  66  all relate to the operation and programming status of the front zone of the roller grill surface of roller grill  12 . 
         [0040]    The operation and programming of the front roller grill surface only will be described in detail since the rear roller grill surface operation and programming is identical to the front zone except the user will use the rear button and lights instead of the front button and lights. Note that if both the front zone and rear zone are activated, display  42  will cycle between the front and rear zones. 
         [0041]    To activate the front zone, button  48  is pushed once to initiate the “pre-heat” mode. Indicator light  54  becomes lighted throughout the entire cycle. Further, “pre-heat’ light  58  becomes lit indicating that the front zone of apparatus  12  is in the “pre-heat” mode. Display  42  shows the countdown time set by the user for the initial “pre-heat” time. During this time, the power to the heating elements is set to the initial “pre-heat” power level. Note that any time during the “pre-heat” mode, the user can hold down button  48  for approximately 3 seconds to change the mode to “cook”, if desired. 
         [0042]    After the “pre-heat” time (shown on display) reaches zero, apparatus  12  automatically shifts to “cook” mode. Thus, “cook” indicator light  62  becomes lit and “pre-heat” indicator light  58  goes out. Display  42  now shows the countdown from the user set “cook” time. Again, during the “cook” mode, the user can hold down button  48  for approximately 3 seconds to change the mode to “hold”, if desired. 
         [0043]    After the “cook” time ends, apparatus  12  automatically goes into “hold” mode. The “hold” indicator  66  becomes lit and “cook” light  62  goes out. The “hold” mode causes apparatus  12  to have the power drop to the “hold” temperature. Display  42  shows the product temperature based on the temperature measured at sensor  28  minus a factory provided offset. If the temperature is greater than a predetermined “hold” temperature, then display  42  reads “HI”; if too low, then display  42  reads “LOW”. Generally, any temperature less than 140 degrees Fahrenheit would cause display  42  to read “LOW” and any temperature greater than 180 degrees would cause display  42  to read “HI”. 
         [0044]    It is important to note that there is no temperature adjustment or power adjustment by invention  10  using sensor  28 . After “hold” time has counted down to zero, indicator lights  54 ,  58 ,  62  and  66  flash and apparatus  12  remains in “hold” mode until the user presses button  48  and then the elements in the front zone of the grill surface turn off. 
         [0045]    As noted above, the rear zone is operated in the same manner as the front zone by using the rear zone button  46  and indicator lights  52 ,  56 ,  60  and  64 . When both front and rear zones are operated at the same time, indicator lights and display  42  will cycle 10 seconds between front and rear zones. If apparatus  12  is in the “hold” mode for at least 30 minutes and the normal program cycle is started over, the “pre-heat” mode will use secondary “pre-heat” settings. To reset the unit to the initial “pre-heat” settings, merely turn switch  50  “off” and then back “on” again. 
         [0046]    Invention  10  can be easily programmed by the user using buttons  46 ,  48  and display  42  in combination with setting button  44 . Each mode, that is, “pre-heat”, “cook” and “hold” have power and time settings associated with it that are easily settable by the user. 
         [0047]    To change the “pre-heat” setting, turn power switch  50  on. Note that there is only one “pre-heat” setting to control the front and rear zones. Immediately, press and hold setting button  44 . Both zone indicator lights and “pre-heat” indicator lights will flash and display  42  will show the initial “pre-heat” power setting. 
         [0048]    The “pre-heat” power settings can be changed from 1 through 10. The default setting is 10 which corresponds to 100% “on”. The power duty cycle of invention  10  is based on 10-second increments. If the user sets power to 4.5, for example, the elements in the roller tubes will cycle “on” for 4.5 seconds and “off” for 5.5 seconds. To decrease the setting from 10 to something lower, press button  48  (marked with indicia “−” which also indicates a minus sign thus reducing the power setting.) To increase the power setting from 4, for example, to 5, merely press button  46  (marked with indicia “+” which indicates a plus sign thus increasing the power setting.) 
         [0049]    Again, pressing the setting button  44  will save the new “pre-heat” power level and cause display  42  to show the “pre-heat” time. Default “pre-heat” time is 15 minutes shown on display  42  as 00:15. The “pre-heat” time can be set from one minute to 10 hours in one-minute increments using the plus or minus buttons  46 ,  48 . 
         [0050]    Pressing setting button  44  again will save the new “pre-heat” time setting and cause display  42  to show the secondary “pre-heat” setting. Both front and rear zone lights  52 ,  54  will flash. Again, adjust the control panel using the plus or minus buttons  46 ,  48  respectively, as before. 
         [0051]    Pressing setting button  44  will cause the new secondary power setting to be saved and display  42  will now show the secondary “pre-heat” time. Again, to change this time, use the plus or minus buttons  46 ,  48 . 
         [0052]    Press the setting button  44  to save the new secondary “pre-heat” time and both front and rear zone “hold” indicator lights  64 ,  66  will flash. Display  42  will show the whole setback power setting. Again, to change this time setting, press plus or minus button  46 ,  48 . Press setting button  44  to save this new setting. 
         [0053]    To program the “cook” and “hold” settings for either the front or rear zones, after turning the unit “on” using switch  50  or if just programming the prior setting options, display  42  must show “---”. 
         [0054]    Begin by pressing and holding setting button  44  while also pressing and holding either the front or rear buttons  46 ,  48 . This causes display  42  to indicate “cook” power for either the front or rear zone depending on which of button  46 ,  48  is used. Then, release both buttons. Change the level of “cook” power by pressing just the plus or minus button to increase or decrease the power level. Then, again, press just the setting button, which saves the new “cook” power level setting and also causes display  42  to show the “cook” time. Again, “cook” time is adjusted by using the plus or minus buttons. Pressing setting button  44  again, causes the new “cook” time to be saved and the display  42  now shows the “hold” power that by default is 45%. 
         [0055]    Again, the “hold” power is adjusted using the plus or minus buttons  46 ,  48 . Pressing setting button  44  again saves the new “hold” power level setting and causes the display to show the “hold” time setting. Again, the “hold” time setting is adjusted using the plus and minus buttons  46 ,  48 . Pressing the setting button  44  again will save the new setting and display  42  will now indicate “---”. The other zone is programmed in the same manner except using its corresponding button  46  or  48 . As before, zone button  46 ,  48  is now used and held with the setting button  44  and the process is repeated. 
         [0056]    Although the present invention has been described with reference to certain preferred embodiments thereof, other versions are readily apparent to those of ordinary skill in the preferred embodiments contained here.