Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 60/954,191, filed Aug. 6, 2007, which is hereby incorporated by reference as if fully set forth herein. 
     
    
     TECHNICAL FIELD 
       [0002]    This application relates generally to ovens for cooking food and, more particularly, to such an oven with a wireless temperature sensor. 
       BACKGROUND 
       [0003]    Various types of ovens are used for cooking food product. Rotisserie ovens are commonly used in commercial food service and food retail environment to cook chickens and other food products in a manner that permits viewing the food product during cooking. The ovens use convection and radiant heating for cooking and can hold up to 30 or more chickens or other types of meat. 
       SUMMARY 
       [0004]    In an aspect, an oven includes a housing including a heating chamber. A door has an open position for allowing operator access to the heating chamber and a closed position for preventing user access to the heating chamber. A heating system heats a food product located within the heating chamber. A wireless temperature sensor is configured to be inserted into the food product by an operator for measuring food product temperature and to provide a wireless signal indicative of food product temperature. An oven control system includes a sensor communicator for receiving the temperature indicative signal from the wireless temperature sensor. The oven control system operates in response to the wireless signal. 
         [0005]    In another aspect, a wireless temperature sensor for use in ovens includes a probe end and an opposite end. A wireless transmitter transmits a temperature indicative signal. A thermobattery (or thermopile) provides power to the wireless transmitter and includes a cold sink at or proximate to the probe end and a hot sink positioned at or proximate to the opposite end. 
         [0006]    In another aspect, a passive wireless temperature sensor includes a probe end and an opposite end. A resonant circuit includes a temperature sensitive component located toward a probe end of the wireless temperature sensor such that a resonant frequency of the circuit varies with temperature of the food product. 
         [0007]    The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of an embodiment of a rotisserie oven; 
           [0009]      FIG. 2  is a perspective view of another embodiment of a rotisserie oven; 
           [0010]      FIG. 3  is a diagrammatic, section view of an embodiment of a rotisserie oven; 
           [0011]      FIG. 4  is a diagrammatic view of the rotisserie oven of  FIG. 1  during a cooking operation; 
           [0012]      FIG. 5  is a diagrammatic illustration of an embodiment of a tag including a temperature sensitive component for use in measuring temperature of a food product during a cooking operation; 
           [0013]      FIG. 6  is a diagrammatic representation of communication between a tag and a reader; 
           [0014]      FIGS. 7 and 8  are a diagrammatic illustrations of an embodiment of a tag and temperature sensor for use in measuring temperature of a food product during a cooking operation; 
           [0015]      FIG. 9  is a diagrammatic illustration of a system for measuring temperature of a number of food products during a cooking operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring to  FIG. 1 , a rotisserie oven  10  includes an upper rotisserie oven  12 A stacked on top of a lower rotisserie oven  12 B. Each rotisserie oven  12 A and  12 B includes a respective control interface  14 A and  14 B, which may include a variety of components, such as an informational display area  16 A and  16 B, a numeric keypad input  18 A and  18 B, On/Off buttons, function specific keys and/or various indicator lights. Each oven includes a vertically hinged access door  20 A and  20 B with a handle  22 A and  22 B and glass front viewing panel  24 A and  24 B for viewing the rotisserie operation. The rear side of the ovens  12 A and  12 B may also include a viewing window, which in some embodiments, is part of a rear door. 
         [0017]    A rotisserie rotor  26 A and  26 B is located within the heating chamber of each rotisserie oven  12 A and  12 B. The rotisserie rotors  26 A and  26 B are each driven by a motor, which rotates the rotisserie rotors  26 A and  26 B at desired rate. Each rotisserie rotor  26 A and  26 B includes a wheel  28  that includes a number of support members  30  extending outwardly from an inwardly facing surface of the wheel. Referring briefly to  FIG. 2  illustrating another embodiment of a rotisserie oven  12  located on a cabinet  13 , each of the support members  30  can be used to support a spit  32 , which are used to support a food product thereon (e.g., chickens  34 ) as the rotisserie rotors  26  rotate during cooking. In some embodiments, each rotisserie rotor  26  can support up to 30 chickens or more for a cooking operation. An exemplary suitable rotisserie oven is an HR or KA Series Rotary Oven, commercial available from Hobart Corporation, Troy, Ohio. 
         [0018]      FIG. 3  is a side, diagrammatic view of an exemplary heating chamber  36  of the rotisserie oven  12  including rotisserie rotor  26 . During a cooking operation, the rotisserie rotor  26  rotates (see arrow  37 ) and heat is generated by heating system  38 . In the illustrated embodiment, the heating system  38  is formed by heating elements  40  located above an upper plate or shield  42 . The shield  42  includes one or more intake openings  44  with associated convection fans  46  arranged to draw air into the openings  44  from the heating chamber  36  and to push air forward and rearward across the heating elements  40  to pick up heat before the heated air is directed back into the heating chamber at forward and rearward slots  48  and  50 . The space above shield  42  may include various directional plates or baffles to produce a desired air flow. 
         [0019]    Referring to  FIG. 4 , the rotisserie oven  12  includes an automatic temperature measurement acquisition system (generally referred to as element  52 ) that is used to monitor the internal temperature of the food products. The automatic temperature measurement acquisition system  52  includes a wireless transmitter  54  (transmitter/receiver or transponder equipped to send and receive energy at selected electromagnetic frequencies) and temperature sensor  56  that is integrated with or located near the wireless transmitter. The wireless transmitter  54  transmits temperature indicative signals generated using the temperature sensor to a sensor communicator (e.g., reader  58 ). The reader includes an antenna  60  capable of receiving the wireless signal from the wireless transmitter  54 . In some embodiments, the reader  58  and antenna  60  may be incorporated within the rotisserie oven  12 , as shown. For example, the reader  58  may located in the oven housing  62  (but outside the heating chamber  36 ) and the antenna  60  may be connected to the door  20  ( FIG. 1 ) or elsewhere within or on the rotisserie oven  12 . In some embodiments, the reader  58  and/or antenna  60  may be separate from the rotisserie oven  12 . 
         [0020]    In one embodiment, the wireless transmitter and temperature sensor may be incorporated into a radio-frequency (RF) tag  64  that resonates at a frequency based on an LCR circuit built into the tag. Referring to  FIG. 5 , the tag  64  including the LCR circuit includes a capacitor  66 , an inductor  68  and a thermistor  70  that varies the resonant frequency based on temperature in a fashion that correlates with food product temperature by locating the thermistor  70  (e.g., such as a thermistor probe) within the food product. 
         [0021]    Referring also to  FIG. 6 , energy to transmit and sense temperature is obtained by the tag  64  from an electromagnetic field  65  (e.g., a near-field RF signal) generated by the reader  58  using antenna  60  at predetermined intervals, for example, or upon request from an operator. Referring back to  FIG. 4 , the antenna  60  can be a square planar looped design (e.g., formed of copper wire) that is tuned with a variable capacitor to a desired resonant frequency. 
         [0022]    Referring to  FIGS. 7 and 8 , in another embodiment, a wireless transmitter  72  is incorporated into an tag  74  (including an active RF transmitter) that is powered by a thermobattery  76 . The thermobattery  76  can be formed by a number of thermocouples  77  (e.g., formed of Type E thermocouples) connected together to develop a drive potential from the sum of the individual potentials. A temperature sensor  78  provides a signal to the tag  74  indicative of temperature within the food product. Food product temperature may be sampled by the temperature sensor at any suitable rate, such as every minute, every second, 10 times a second, etc. The tag  74  can send all or only some of the temperature indicative signals generated based on input from the temperature sensor  78  to the reader  58  using power from the thermobattery  76 . In some embodiments, the tag  74  may include memory for storing a number of temperature indicative signals. 
         [0023]    The thermobattery  76  includes a cold sink  82  that is inserted into the food product  84  and a hot sink  86  that is exposed to the oven&#39;s ambient temperature within the heating chamber  36  thereby creating a temperature gradient for operation of the thermobattery with an insulated portion  83  extending therebetween. The hot and cold sinks may be constructed of any suitable insulating material such as epoxy or silicone and permit the hot and cold ends of the thermopile to be coupled to the external environment. In some instances, a maximum temperature within the food product may be 185° F., while a maximum temperature within the heating chamber may be 400° F., thereby providing a temperature gradient for battery operation throughout the cooking cycle. Additionally, placement of the tag  74  within the food product provides some insulation from the higher temperatures outside the food product within the heating chamber  36 . An outwardly extending stop  89  is provided for inhibiting the hot sink from entering the food product  84 . 
         [0024]    Referring back to  FIG. 4 , the reader  58  includes an oven control system  87  including a processor  88  and a storage component  90  (e.g., including random access memory). In some embodiments, the reader  58  may be part of a computer with the antenna  60  connected thereto. The processor  88  includes logic that converts the signals received from the wireless transmitter  54  (e.g., the tags  64  or  74 ) into a temperature value. In some embodiments, the processor  88  may also associate a timestamp with the temperature value and save the temperature value and timestamp in the storage component  90 , for example, to create a log of temperature values. 
         [0025]    The food product temperature values determined using the temperature sensor may be displayed to an operator on display  16  ( FIG. 1 ). As another example, the food product temperature values may be conveyed to the operator using different methods and systems, such as via a text message, e-mail, phone message, remote display such as over the Internet on a remotely connected computer, etc. The operator can then know when the food product has or has not reached a desired temperature and may adjust oven temperature manually, if desired, using the control interface  14  ( FIG. 1 ), over the phone, return text message, remote computer control, etc. 
         [0026]    In some embodiments, the rotisserie oven  12  including oven control system  87  may utilize the temperature values to follow a recipe for cooking the food product saved in memory. For example, the rotisserie oven  12  including oven control system  87  may automatically adjust its cooking temperature upward or downward based on a measured food product temperature and target temperature based on recipe instructions. Such a recipe may be provided to the rotisserie oven  12  by the manufacturer or the operator. As another example, a recipe may be downloaded to memory over the Internet or provided to the oven by any other suitable process such as using a diskette, EPROM (such as a FLASH memory drive), etc. 
         [0027]    Referring to  FIG. 9 , the operator may place a wireless transmitter  54  and temperature sensor  56  in a number of food products  84  to provide an even sample distribution. The reader  58  can then obtain temperature indicative signals from each of the wireless transmitters  54  based on measurements taken by the temperature sensors  56 . In some embodiments, the wireless transmitters  54  may also transmit a unique identifier (e.g., using a RFID tag whether passive or active), which can be used by the operator to identify a specific food product or transmitter/sensor. For example, the control interface  14  may allow the operator to cycle through temperature values provided by each transmitter  54  to view temperatures for each food product in which a temperature sensor  56  has been placed. An irregular temperature reading might indicate an overcooked or undercooked food product or that the particular temperature sensor/transmitter is not operating properly. In some embodiments, the oven  12  automatically monitors each temperature value and displays an average temperature value (or some other predetermined value such as median temperature) to the operator. If one or more of the measured values fall outside a predetermined temperature range, the oven  12  may display a message to the operator indicating this. 
         [0028]    The above-described automatic temperature measurement acquisition system  52  can provide a number of advantages. The transmitters  54  communicate wirelessly with the reader  58  which allows the rotisserie rotor  26  to rotate freely without interference with any wired connections between the temperature sensors and reader. The components forming the wireless transmitters  54  and sensors  56  can be formed of and/or encased or otherwise housed within food grade materials that can be washed and reused repeatedly and that can withstand temperatures within the heating chamber  26  during cooking operations. The automatic temperature measurement acquisition system  52  can allow real time monitoring of food product cooking temperatures which can be used to manually or automatically adjust cooking temperatures, for example, based on a programmed recipe or based on operator experience. 
         [0029]    It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. For example, the automatic temperature measurement acquisition system  52  may be used with other oven types. Accordingly, other embodiments are contemplated and modifications and changes could be made without departing from the scope of this application.

Technology Category: 3