Abstract:
A system for measuring the state of degradation of cooking oil or fat includes at least one fryer pot. A conduit is fluidly connected to the fryer pot for transporting cooking oil from the fryer pot and returning the cooking oil back to the fryer pot. A pump is provided for re-circulating cooking oil to and from the fryer pot. A sensor is disposed in fluid communication with the conduit and measures an electrical property of the cooking oil as the cooking oil flows past the sensor and is returned to the at least one fryer pot.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation Application of U.S. application Ser. No. 13/923,418, filed on Jun. 21, 2013, which is a Continuation application of U.S. application Ser. No. 12/456,389, filed on Jun. 16, 2009, which issued as U.S. Pat. No. 8,497,691 on Jul. 30, 2013, and which is a Continuation-in-Part application of U.S. application Ser. No. 12/215,307, filed on Jun. 26, 2008, which claims benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Ser. Nos. 60/937,513, filed on Jun. 28, 2007, and 60/995,527, filed on Sep. 27, 2007, the contents of each of which are incorporated by reference herein. 
     
    
     BACKGROUND OF THE DISCLOSURE 
       [0002]    1. Field of the Disclosure 
         [0003]    This disclosure relates to an oil quality sensor that is installed in a fryer for the purpose of indicating when the cooking oil should be changed for one or more fryer pots. 
         [0004]    This disclosure, more particularly, relates to oil quality sensor that measures an electrical property of the oil and is disposed in a filtration loop of a fryer that is external to the one or more fryer pots. 
         [0005]    2. Description of Related Art 
         [0006]    During use, the oil in a fryer is degraded and loses its proper cooking capacity. Specifically, the degradation is caused by oxidation, cyclic temperature increases and hydrolysis from released water. Impurities that are generated during the frying process are collectively called total polar materials (TPMs) or total polar compounds (TPCs). The TPMs are created during the deep-frying process as triglycerides break into free fatty acids and lipid molecule residues. These substances are characterized by an increased polarity and dielectric constant compared to the original triglycerides in the oil. Thus, an increased capacitance measurement of the cooking oil is indicative of an increased level of TPMs in the cooking oil. 
         [0007]    There are several methods for testing the quality of cooking oil. Simple methods such as testing the taste, smell and color of the oil are excessively subjective, inaccurate and too time consuming. Other methods test the smoke point or viscosity of the oil. Again, while these measurements are fairly simple, they are too dependent on factors such as oil type and oil debris to be universally reliable. 
         [0008]    Processes that include chemical or chromatographic methods are generally more comprehensive and accurate than the simpler methods. For example, currently the most widely used test tests the fatty acids that are released from glycerines during the frying process. This test depends strongly on the moisture of the frying goods. Testing for polymeric triglycerides that are formed from frying triglycerides is often time consuming and expensive. 
         [0009]    Accordingly, there is a need for an oil quality sensor that is able to detect the level of all deterioration products or TPMs for installation in an oil return line of a fryer that uses a capacitance sensor to determine the change of dielectric constant of the cooking oil to unacceptable levels. 
       SUMMARY 
       [0010]    The present disclosure provides for a sensor disposed externally to a deep fryer that is able to indirectly measure the level of TPMs in cooking oil by measuring the an electrical property of the cooking oil. 
         [0011]    The present disclosure also provides for a capacitance sensor for a deep fryer pot that measures the capacitance of frying oil that is located in a conduit in fluid communication with the fryer pot. 
         [0012]    The present disclosure also provides for a sensor for a deep fryer pot that is one of a capacitance sensor, a coaxial sensor or a resonant sensor that is disposed external to the fryer pot to measure an electrical property of the cooking oil when such oil flows past the sensor. 
         [0013]    The present disclosure further provides for a sensor that measures the capacitance of the cooking oil in the return line of a fryer pot after the oil has been filtered. 
         [0014]    The present disclosure also provides for a capacitance sensor that is disposed in the oil return line of a deep fryer that is optimally positioned to ensure that the flow of the oil cleans the sensor before measurement of the capacitance of the cooking oil. 
         [0015]    The present disclosure further provides for a sensor that measures the capacitance of the oil and is disposed in a filtration loop between the filter pan and the return valve to be returned to a plurality of fryer pots. 
         [0016]    The present disclosure also provides for a capacitance sensor that is in the return line of a plurality of fryer pots. The capacitance sensor repeatedly measures the capacitance of the filtered oil during the entire return flow duration and obtains an average value of the capacitance of the oil that is returned to each of the plurality of fryer pots. 
         [0017]    The present disclosure provides for an adapter that houses a capacitance sensor for the measure of a dielectric constant. The adapter is installed between two portions of a return pipe of a fryer pot to enable filtered oil to flow past sensor for measurement before returning to the fryer pot. An indication is provided when the dielectric constant of the cooking oil has exceeded an unacceptable level. 
         [0018]    A system for measuring the state of degradation of cooking oil or fat includes at least one fryer pot; a conduit fluidly connected to the fryer pot for transporting cooking oil from the fryer pot and returning the cooking oil back to the fryer pot. A means for re-circulating cooking oil to and from the fryer pot; and a sensor disposed in fluid communication with the conduit that measures an electrical property of the cooking oil as the cooking oil flows past the sensor and is returned to the at least one fryer pot is provided. 
         [0019]    A system for measuring the state of degradation of cooking oil in a deep fryer includes at least one fryer pot and a conduit fluidly connected to the at least one fryer pot for carrying cooking oil from the at least one fryer pot through a filtration unit back to the at least one fryer pot. A sensor disposed in fluid communication with the conduit for measuring a dielectric constant of the cooking oil as the cooking oil is pumped between the at least one fryer pot and through the filtration unit is provided. A controller and measurement electronics in electrical communication with the sensor that computes the dielectric constant of the cooking oil for communication to a display or an alarm are provided. 
         [0020]    A device for installation in a deep fryer for measuring the state of degradation of cooking oil includes a sensor disposed on a support surface and in fluid communication with a conduit containing cooking oil that measures an electrical property of the cooking oil. The device also includes a connector for connection to a controller and measurement electronics in electrical communication with the sensor that computes the dielectric constant of the cooking oil that flows past the sensor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0021]    Other and further benefits, advantages and features of the present disclosure will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure. 
           [0022]      FIG. 1  illustrates an exemplary fryer housing a sensor of the present disclosure; 
           [0023]      FIG. 2  illustrates an oil quality sensor according to the present disclosure incorporated into the return pipe of the filtration loop of the fryer of  FIG. 1 ; 
           [0024]      FIG. 3  illustrates an oil quality sensor according to the present disclosure incorporated into the drain pipe of the filtration loop of the fryer of  FIG. 1 ; 
           [0025]      FIG. 4  illustrates an oil quality sensor according to the present disclosure incorporated into the filter pan of the filtration loop of the fryer of  FIG. 1 ; 
           [0026]      FIG. 5  illustrates an oil quality sensor according to the present disclosure incorporated into the filter pan of the filtration loop having a single pipe associated with the fryer pot; 
           [0027]      FIG. 6  illustrates a partial cross-section view of the sensor of  FIG. 2  along line  6 - 6 ; and 
           [0028]      FIG. 7  illustrates a further partial cross-section view of the sensor of  FIG. 2  along line  7 - 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    Referring to  FIG. 1 , an illustration of an exemplary fryer is shown, and generally represented by reference numeral  10 . Deep fryer  10  has a housing  5 , a pair of fryer pots  15  and a pair of filter pans  40 . Each of the pair of filter pans  40  contains a pre-filtering medium, such as a sieve  35  that is used to remove large particles from the used cooking oil. Alternatively, both fryer pots  15  could share a common filter and return system. While fryer  10  is shown as only having two fryer pots  15 , there could be as many as twelve fryer pots depending upon the needs of the food service professional. Fryer  10  also has a controller  20  for monitoring and maintaining overall operation the fryer  10 . Deep fryer housing  5 , also has a display panel  31  that displays various measurements of deep fryer and accepts input for programming of controller  20 . The present application is not limited to cooking oil, thus fat or shortening could also be used in the present application. 
         [0030]    Referring to  FIG. 2 , filtration loop  50  of fryer  10  incorporates a sensor and is shown, and referenced using reference numeral  100 . Sensor  100  is shown in the return line  70  of filtration loop  50 ; however, sensor  100  preferably is disposed along filtration loop  50  external to fryer  10 , in accordance with the present disclosure. Thus, sensor  100  is disposed in filtration loop  50  external to fryer pot  15  independent of the configuration of filtration loop  50 , as shown in  FIGS. 3 through 5 . Further, sensor  100  is capable of measuring an electrical property of cooking oil  75  such, as the dielectric constant, of oil. Sensor  100  is preferably one of a capacitance sensor, an open ended coaxial sensor, a conductivity or a resonant type sensor. 
         [0031]    Referring again to  FIG. 2 , filtration loop  50  has a drain line  55 , and a pre-filtration sieve  35 , and a fine filtration pad  30 . Cooking oil  75  is returned through plumbing  70  by pump  65 . Prior to reaching pump  65 , sensor  100  in flow of returning filtered cooking oil  75  is able to sample the an electrical property as oil  75  is being returned to fryer pot  15 . A filtration loop that services multiple fryer pots would have a gate valve  42  and common drain plumbing  43  disposed upstream of pan  40  to collect used oil  75  from multiple fryer pots  15 . Similarly, a return line splitter  82  and a valve  83  would direct filtered oil to specific fryer pots  15 . 
         [0032]    Referring to  FIG. 3 , sensor  100  is disposed in drain pipe  55  of filtration loop  50 . In this embodiment, an electrical property of cooking oil  75  is repeatedly sampled as oil  75  is drained from fryer pot  15 . A filtration loop  50  that services multiple fryer pots  15  would have a gate valve  42  and common drain plumbing  43  disposed upstream of pan  40  to collect used oil  75  from multiple fryer pots. Similarly, a return line splitter  82  and a valve  83  would direct filtered oil to specific fryer pots  15 . 
         [0033]    Referring to  FIGS. 2, 3, 6 and 7 , sensor  100  is contained within T-shaped adapter  105  that extends within housing  5  generally beneath fryer pot  15 . T-shaped adapter  105  is connected in return-line of cooking oil of pipe  70 . T-shaped adapter  105  is preferably connected between two portions of return pipe  70 , upstream portion  71  and downstream portion  72 , in a mating relationship via mating threads disposed on interconnecting portions thereof. Oil sensor  100  extends within adapter  105  and is positioned to lie in the stream of flow of oil  75 , such that the flow of oil  75  from upstream portion  71 , through adapter  105  to downstream portion  72  is uninterrupted. Additionally, the flow of oil  75  is coincident with longitudinal axis of upstream portion  70 , downstream portion  72  and adapter  105  installed between portions  71  and  72 . Oil sensor  100  extends within and is protected by adapter  105 . 
         [0034]    Referring to  FIG. 4 , sensor  100  is disposed in filtration loop  50 , in filter pan  40 . In this configuration, the dielectric constant of filtered cooking oil is sampled in pan  40  prior to passing through filtration pad  30  and returning to fryer pot  15 . 
         [0035]    Referring to  FIG. 5 , filtration loop  50  configuration also has sensor  100  disposed to sample an electrical property of oil external to fryer pot  15 . In this configuration, sensor  100  is disposed in filtration loop  50 ; however, there is only a single conduit  80  that is in fluid communication with fryer pot  15 . In this configuration valve  81  is a three-way valve that is controlled by controller  20  to direct cooking oil through pipe  55  during a draining cycle and to open to permit filtered oil to be pumped back and return to fryer pot via pipe  80 . In this configuration, sensor  100  could have been disposed within pipe  55 , or  70  external to fryer pot  15 . In this configuration, pump  65  can service multiple fryer pots  15 . 
         [0036]    Oil sensor  100  is located in an adapter  105  in the filtration loop of fryer pot  15  as shown in  FIGS. 2 and 3 . Sensor  100  is located to measure and continuously sample an electrical property of cooking oil  75  before it re-enters fryer pot  15 , independent of its location external to fryer pot  15 . When the triglycerides of filtered cooking oil  75  break into fatty acids and lipid molecules during the heating and cooking cycles the polarity of oil  75  increases. The accumulation of polar materials lowers the insulating properties of cooking oil and elevates the dielectric constant of cooking oil  75  to higher values. This increased polarity correlates with an increased dielectric constant of oil  75 . Thus, sensor  100  is able to measure the change of the TPM values by measuring the dielectric constant of cooking oil  75  as pump  65  returns oil to fryer pot  15 . When sensor  100  detects an unacceptable level of TPMs an indication is provided to an operator to change the oil. Thus, sensor  100  ensures that oil  75  is not wasted by being prematurely changed or overused thereby tainting food and harming consumers. 
         [0037]    Oil sensor  100  is operatively connected to measurement electronics  44  and controller  20  of fryer  10  via plugs  110 . Electronics  44  and controller  20  enable periodic measurements made by sensor  100  for calculation of TPM values are averaged before oil  75  returns to fryer pot  15 . 
         [0038]    Referring to  FIGS. 6 and 7 , sensor  100  is disposed on a support surface  115  that extends within adapter  105 . Sensor  100 , in one embodiment as a capacitor  111 , is made from highly conductive wires  101  that are preferably printed onto support surface  115 . Sensor  100  is configured such that a constant space is between separate highly conductive wires  101  thereby forming a capacitor  111 . Highly conductive wires  101  are preferably made of gold, although other materials having highly conductive properties could also be used. Capacitor  111  is preferably printed on support surface  115  that is made from a ceramic material. Capacitor  111  has two ends  102  that are each connected to leads  103  that are also printed on support surface  115 . Leads  103  are connected at one end to capacitor  101  and at the other connector end to plugs  110  via cable  104  for connection to measurement electronics  44  and controller  20 . Thus, the non-conductive quality of ceramic support surface  115  provides electrical insulation between adjacent wires of capacitor  111  and leads  103 . When sensor  100  is not part of an adapter  105 , sensor  10  extends within filtration unit as shown in  FIGS. 4 and 5 . 
         [0039]    Prior to measurements, sensor  100  achieves operational temperatures by being in the flow of quickly moving cooking oil  75  caused by pump returning oil to fryer pot  15 . The quickly flowing cooking oil  75  also acts as a scrubber to clean sensor front  106  and sensor back  107  as it passes thereby to be returned to fryer pot  15 . Sensor  100  must be clean to provide accurate measurements of oil capacitance and an indication of when oil must be changed. Sensor  100  must be properly positioned such that sensor front  106  and sensor back  107  are cleaned. Thus, sensor  100  and support surface  115  on which sensor  100  is disposed are, optimally positioned/angled to take advantage of the approaching flow of oil  75  that is flowing through or in-line with both portions  71  and  72  of return pipe  70 . The placement angle  130  of approximately 20° to 50° relative to the direction of oil flow shown by centerline or longitudinal axis of pipe  70  having portions  71  and  72  and adapter  105  ensures that the oncoming filtered cooking oil will clean sensor front  106 . Sensor  100  is cleaned by the impulse of the flow on the high pressure side in front of sensor  100  and the vortex generation of the low pressure side down-stream of sensor  100 . Thus, flow of oil contacts sensor front  106  at an angle of from 20° to 50°. Were sensor  100  not properly angled, insufficient cleaning of the sensor front  106  and sensor back  107  would occur and the sensor measurements would be compromised and inaccurate. Additionally, sensor  100  must be clean to enhance the useful life of sensor  100 . 
         [0040]    Support surface  115  also includes a temperature sensor  120  proximate sensor  100 . Temperature sensor  120  is preferably formed as an electrical resistor. Temperature sensor  120  is connected by electrical leads  103 , as sensor  100 , for connection to controller  20  and measurement electronics  44 . Controller  20  continuously receives signals via amplifier and A/D converter from capacitance sensor  100  and temperature sensor  120 , for measurements of oil capacitance and oil temperature. Thus, the dielectric constant of the oil is constantly being measured at various temperatures as oil flows through adapter  105  by sensor  100  at it returns to fryer pot  15 . Measurements are provided to display to indicate the actual degree of decomposition of the oil  75 , so that operator may know when oil should be changed. 
         [0041]    Sensor  100  repeatedly samples TPM in cooking filtered cooking oil  75 , these data are sent to measurement electronics  44  and controller  20  via cable  104  and connector  110 . The measurements are averaged over the duration of the return of filtered cooking oil  75  to fryer pots  15 . Thus, the calculated averaged value of the TPMs can be calculated and compared to known accurate values to detect the dielectric constant of the cooking oil. Controller  20  is capable of storing acceptable dielectric values of clean cooking oil for comparison to the measured values. Should the dielectric constant of filtered cooking oil  75  exceed a predetermined threshold, an indicator, such as an audible or visible alarm, is engaged. Additionally, display on display panel  31  shows measurements. 
         [0042]    Optionally, visible alarms can be color-coded to indicate a level of measured dielectric acceptability. For example, a color such as green indicates good quality oil, amber would indicate that oil needs replacement shortly and red would indicate that the oil is of poor quality and needs to be immediately changed. 
         [0043]    The present disclosure 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 disclosure as defined in the appended claims.