Abstract:
Frying apparatus for frying food, such as French fries, vegetables, bakery goods, meat fish, poultry and the like, in a heated fluid contained in a fry pot. The fluid is heated by a combustion burner that has a heat exchanger removably disposed in the heating fluid. When removed from the fluid, the heat exchanger and the fry pot can be easily cleaned. The air and/or gas is injected into the combustion chamber so as to provide an air gas ratio that supports clean combustion. A control monitors various temperatures and other parameters at various locations of the frying apparatus to control the efficiency of the frying apparatus to approximate a predetermined efficiency by altering the air/gas ratio.

Description:
[0001]    This Application claims the benefit of U.S. Provisional Application No. 60/323,895, filed Sep. 21, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to a frying apparatus with a removable heat exchanger. The present invention also relates to a frying apparatus and method for controlling the temperature of a cooking fluid thereof.  
         BACKGROUND OF THE INVENTION  
         [0003]    Commercial gas fryers generally have a fry pot for containing a cooking fluid and a means for heating the cooking fluid. One type of fry pot, known as the open pot design, requires heat to be applied to the exterior sides of the fry pot. The open pot design has an advantage of being easily cleaned. Open pot designs use either an atmospheric burner or a forced combustion burner. Open pot designs with an atmospheric burner achieve an efficiency of about 45%, while open pot designs with forced combustion burners achieve an efficiency of about 65 to 70%. The disposition of the burner adjacent the exterior sides of the fry pot has the disadvantage of heating the entire fry pot including the temperature sensitive wiring and controls.  
           [0004]    Another type of fry pot, known as the tube design, has heat applied by means of one or more tubes (typically, four for a standard pot) that are disposed in the fry pot below the cooking fluid level. The tube fryer has an efficiency that is about 3 to 5% greater than that of the open pot design with an atmospheric burner. The tube fryer is also difficult to clean due to the tubes that are permanently installed in the fry pot.  
           [0005]    There is need for a frying apparatus and method that achieves a high efficiency without an external burner.  
           [0006]    There is also a need for a frying apparatus that has a heat exchanger that is removably disposed to facilitate cleaning the fry pot.  
         SUMMARY OF THE INVENTION  
         [0007]    The method of the present invention controls the temperature of a cooking fluid in a frying apparatus in a manner that achieves a high efficiency. An air/gas mixture is supplied to a combustion burner that is disposed to heat the cooking fluid. One or more operating parameters of the frying apparatus are monitored to determine a deviation from a predetermined efficiency. The air and gas are adjusted to compensate for the deviation so as to maintain the operating parameters in a range that approximates the predetermined efficiency.  
           [0008]    According to one aspect of the method of the present invention, the gas flow is orificed or modulated and the compensating adjustment is made to the flow of the air to achieve the correct air/gas mixture. According to another aspect of the method, the airflow is acoustically modulated in response to the deviation to optimize the performance of the fryer.  
           [0009]    According to a further aspect of the method of the present invention, the operating parameters may include internal temperature of the combustion chamber of the combustion burner, temperature of a flue connected to the combustion chamber, flame current in the combustion chamber, temperature of the cooking fluid, cooking fluid rate of rise, temperature difference between a set point temperature and the instantaneous temperature of the cooking fluid, elapsed cooking time, remaining cooking time, absolute airflow for an optimum burn, or a comparison of current airflow with average flow rate over a predetermined number of previous combustion control cycles.  
           [0010]    According to another embodiment of the method of the present invention, a burner that is attached to a fry pot, or optionally a housing, of a frying apparatus is handled by moving the burner between a cooking position within the fry pot and a removed position at least partially outside of the fry pot without detachment from the fry pot or the optional housing. Preferably, the movement is pivotal.  
           [0011]    The frying apparatus of the present invention has a fry pot and a combustion burner (combustion chamber/heat exchanger combined) that is disposed to heat cooking fluid contained in the fry pot. By means of a modulated air supply and an orificed or modulated gas supply, an optimum mixture occurs in the combustion burner. One or more sensors sense an operating parameter of the frying apparatus to develop a feedback signal. A control responds to the feed back signal to adjust the air/gas supply for maximum efficiency and clean combustion.  
           [0012]    According to one aspect of the frying apparatus of the present invention, the control means acoustically modulates the airflow to the mixer in response to the feed back signal.  
           [0013]    According to another embodiment of the present invention, a frying apparatus includes a fry pot and a combustion burner. The combustion burner includes a combustion chamber and a heat exchanger with the combustion occurring below the oil line. The combustion burner is removably disposed in the fry pot below the cooking fluid level. A flue extends from the heat exchanger out of the cooking fluid. The combustion burner is disposed for motion between a cooking position where it is disposed in the cooking fluid and a removed position outside the cooking fluid for ease of cleaning.  
           [0014]    According to one aspect of this embodiment, the combustion burner is preferably coupled to the fry pot (or optionally to housing of) the frying apparatus for pivotal motion between the cooking position and the removed position. Additionally, the air and gas are supplied to separate swivel assemblies to facilitate pivoting the combustion burner from the fry pot. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the Figures of the drawing in which like reference characters denote like elements of structure, and:  
         [0016]    [0016]FIG. 1 depicts a frying apparatus of the present invention with the combustion burner in the cooking position; and  
         [0017]    [0017]FIG. 2 depicts the frying apparatus of FIG. 1 with the combustion burner in the cleaning position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Referring to the FIG. 1, a frying apparatus  20  includes a fry pot  24 , a gas orifice assembly  26 , a blower  28 , a gas valve  30 , a control  36  and a combustion burner  40 . Combustion burner  40  includes a combustion chamber  42 , a heat exchanger  44 , a flue  46  and an igniter  48 . Gas orifice assembly  26  is connected to combustion chamber  42  to provide optimum gas flow that is injected therein.  
         [0019]    Combustion chamber  42  includes an internal substantially cylindrical titanium liner within which the air/gas mixture is injected. Igniter  48  ignites or initiates combustion in combustion chamber  42 . Heat exchanger  44  is connected to combustion chamber  42  so as to convey the combustion gas along its length and flue  46  to atmosphere. Heat exchanger  44  and flue  46  may be formed of one integral piece or of two or more parts that are connected together as a one-piece assembly. Contained within the heat exchanger is a baffle  29  comprised of fins progressively sized/formed to provide uniform heating of heat exchanger  44 .  
         [0020]    Combustion burner  40  is preferably mounted to fry pot  24  at a pivot  50  via an air/gas swivel assembly  51  for pivotal or rotational motion between a cooking position and a removal position. In an alternate embodiment, fry pot  24 , combustion burner  40 , pivot  50  and air/gas swivel assembly  51  are mounted to an optional housing (not shown). When in the cooking position (as shown in FIG. 1), heat exchanger  44  is disposed in fry pot  24  below a level  54  of a cooking fluid  52 . When in the removed position (as shown in FIG. 2), heat exchanger  44  is disposed out of and above fry pot  24  so as to permit ease of cleaning of fry pot  24  and heat exchanger  44 . Preferably, air/gas swivel assembly  51  includes separate air and gas swivel assemblies for the conduits, channels or the like that carry the air and the gas. The pivotal motion may be manual or driven by a motor (not shown).  
         [0021]    According to another aspect of the present invention, control  36  is operable to adjust the ratio of air/gas that supports clean combustion in combustion burner  40  in response to a deviation from a predetermined efficiency so as to maintain the efficiency at approximately the predetermined efficiency. This adjustment is achieved by altering characteristics of the air or the gas, such as airflow, air pressure, gas energy, gas volume, gas pressure, gas flow, or any combination thereof. The air/gas supply is adjusted by controlling blower  28  and gas valve  30 . Blower  28  and gas valve  30  are connected to an air supply/filter assembly  32  and a gas supply  34 , respectively. According to one aspect of the invention, blower  28  is controllable by control  36  to modulate the airflow from air supply/filter assembly  32 , and thereby control the flow and pressure of air supplied to combustion burner  42 . Any suitable controllable blower may be used.  
         [0022]    The gas pressure and flow may also be regulated by controlling gas valve  30 . Gas valve  30 , for example, may be a multi-stage or modulated gas valve. For example, a suitable controllable gas valve may be obtained from Honeywell, Inc.  
         [0023]    Control  36  may be any suitable microprocessor that can accept a number of inputs, process the inputs and provide output signals for the control of blower  28  and/or gas valve  30 . For example, control  36  may be procured from National Instruments, Inc.  
         [0024]    The inputs to control  36  are the outputs of a plurality of sensors that are positioned in various locations of frying apparatus  20  to sense various operating parameters thereof. The plurality of sensors includes a sensor  60  that detects internal temperature of combustion chamber  42 , a sensor  62  that senses rectified flame current, a sensor  64  that senses flue temperature, a sensor  66  that senses temperature of cooking fluid  52 , a sensor  68  that senses level  54  of cooking fluid  52 , an atmospheric pressure sensor  70 , and an air density sensor  72 . The outputs of the aforementioned sensors are sampled to provide sample values that are used by control  36  to adjust the air/gas ratio to control the combustion efficiency to approximately the predetermined efficiency. A basket rack sensor  56  detects the presence and removal of a cooking basket  58  to provide automatic cook timer start and duration of the basket in the cooking oil. This feature permits automatic logging of the number of baskets cooked, under/over cook times vs. the programmed cook time and filtration of the cooking oil as a function of usage.  
         [0025]    Control  36  also derives from the sample values other parameters that include cooking fluid temperature rate of rise, temperature difference between a cooking fluid set point and the instantaneous temperature of the cooking fluid, difference between the current air flow rate and the average flow rate of the last n combustion cycles. For example, n can be any number, but is preferably about 100. Control  36  also uses other parameters to control the combustion efficiency that include elapsed cook time, remaining cook time, relative BTU variations in the gas, fryer construction/component differences (e.g., differences in material, dimensions, tolerance and the like) and absolute airflow rate required for optimum combustion.  
         [0026]    The combustion process controlled by control  36  in combustion burner  40  achieves very high efficiency in converting the hydrocarbon energy in the gas to extremely high temperature (on the order of 2,500° F.) combustion gases rich in infrared energy. In addition, the present invention achieves a difference between the cooking fluid temperature set point and the flue gas temperature of about 250° F. or less.  
         [0027]    Control  36  monitors the aforementioned sample values, as well as the voltage supply (not shown), gas supply  34  and air supply/filter assembly  32 , at a sample rate of many times (e.g., about 10) per second and compares these values with a domain of values required for normal and safe operation of frying apparatus  20 . If any parameter is missing or outside its domain and is correctable by a user, control  36  displays an error message on a display  74  for corrective action by the user. User correctable errors include, e.g., cooking fluid low or not present, gas supply line disconnected, low line voltage, and the like. Display  74  will conspicuously display the error message in a location that visually alerts the user. In addition, an audible signal can also be used.  
         [0028]    Display  74  may include a plurality of red, amber and green light emitting diodes (LEDs). A green status LED indicates frying apparatus  20  is ready for use. A green flashing LED indicates frying apparatus  20  is warming up. A red status LED indicates a fryer component failure and that a need for service has been sent to and acknowledged by a service company. An amber status LED indicates frying apparatus  20  is not usable, but the user can take corrective action. The type of corrective action may be displayed by an on site computer  80 . If any of the parameters are out of a defined range, control  36  will shut down frying apparatus  20  and indicate the nature of the shut down via display  74  and on site computer  80 .  
         [0029]    Control  36  also monitors the cooking cycle to assure the food product is neither undercooked nor overcooked. This is accomplished by basket sensor  56  that signals the times the basket  58  of product enters and leaves cooking fluid  52 . The difference between the entry and leaving times represents an actual cook time that can be compared with the required cook time. The cook time data can be stored in onsite computer  80  for review by restaurant personnel.  
         [0030]    Onsite computer  80  can be linked via a network  82  to a remote computer  84  so that the operating data of frying apparatus  20  can be processed by remote computer  84 . For example, remote computer  84  could process the data for maintenance purposes or could process the data for restaurant management purposes. Network  82  can be any suitable wired, wireless or optical network, such as the public telephone network, the Internet, the World Wide Web, or any combination thereof. Onsite computer  80  and remote computer  84  can be equipped with suitable network communication capability, such as a modem, a browser and/or a server capability.  
         [0031]    Fluid level sensor  68  is a non-intrusive cooking fluid sensor. Control  36  can monitor the sample values provided by fluid level sensor  68  to determine if the fluid level is low or zero or overfilled, adjust the cook time as needed to provide uniform cooking results, and ascertain when filtering of cooking fluid  52  is done relative to the food products being cooked. The exact level of the cooking oil affects the rate of change in cooking oil temperature down as the food product enters the oil and up when the burner turns on) and, thus the quality of the cook. Control  36  monitors the number of cook cycles per pot and displays the need for filtering an as needed basis.  
         [0032]    The present invention having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.