阅读说明：本技术 流体传感器和控制系统 (Fluid sensor and control system ) 是由 M.T.费克图 S.J.西尔 K.M.瑟尔 于 2018-12-06 设计创作，主要内容包括：一种电容式传感器和控制系统,其被配置成检测容器内流体的存在(或不存在)。配置在深油炸器的桶或油炸锅中的传感器确定油炸锅内的液位何时等于或高于传感器的液位。传感器与控制系统通信,并且传感器向控制系统发送信号,该信号表示油炸锅内是否存在液体以及是否处于传感器水平处。控制器接收来自传感器的信号,并且当从传感器接收的信号指示液体设置在油炸锅内的传感器的水平处或以上时,控制器允许用于加热油炸锅的一个或多个热源的操作,并且当从传感器接收的信号指示液体没有设置在油炸锅内的传感器的水平处或以上时,控制器阻止一个或多个热源的操作。(A capacitive sensor and control system configured to detect the presence (or absence) of a fluid within a container. A sensor disposed in the barrel of the deep fryer or the fryer determines when the liquid level in the fryer is equal to or above the liquid level of the sensor. The sensor is in communication with the control system and sends a signal to the control system indicating whether liquid is present in the fryer and is at the sensor level. The controller receives signals from the sensor and allows operation of the one or more heat sources for heating the fryer pot when the signals received from the sensor indicate that liquid is disposed at or above the level of the sensor in the fryer pot, and prevents operation of the one or more heat sources when the signals received from the sensor indicate that liquid is not disposed at or above the level of the sensor in the fryer pot.)

1. A fryer system comprising:

a barrel for receiving a volume of fluid;

a capacitive sensor disposed within the tub such that the sensor is disposed in communication with a volume of fluid within the tub;

one or more heat sources positioned to generate heat to heat a volume of fluid in the barrel;

a controller that receives a signal from the capacitive sensor indicative of a capacitance value and controls operation of the one or more heat sources based on the capacitance value, wherein the controller allows operation of the one or more heat sources to generate heat to heat a volume of fluid in the drum when the signal received from the capacitive sensor indicates that liquid is disposed within the drum at or above the level of the capacitive sensor, and wherein the controller prevents operation of the one or more heat sources to prevent generation of heat to heat the volume of fluid within the drum when the signal received from the capacitive sensor indicates that liquid is not disposed within the drum at or above the level of the capacitive sensor.

2. The fryer of claim 1, wherein the capacitive sensor comprises a radiator structure at a first end and a jacket at an end remote from the radiator structure, and a coaxial cable having an inner conductor electrically connected to the radiator structure and a portion of the jacket.

3. The fryer of claim 1, wherein said capacitive sensor is located near an interior metal corner of said vat.

4. The fryer of claim 1, wherein said capacitive sensor is calibrated to detect liquid in said vat.

5. The fryer of claim 2, wherein the radiator of the capacitive sensor comprises a cylindrical hollow housing within which is disposed a socket for connecting a coaxial cable within the radiator.

6. The fryer of claim 1, wherein the one or more heat sources comprises a burner tube disposed proximate to the capacitive sensor, and wherein a top surface of the capacitive sensor is aligned with a top of the burner tube.

7. The fryer of claim 1, wherein said radiator is secured to an insulator disposed in a standpipe extending within said vat.

8. The fryer of claim 1, wherein the volume of fluid is cooking oil and the controller is configured to determine whether the cooking oil is disposed within the vat at the level of the capacitive sensor.

9. The fryer of claim 1, wherein the controller prevents operation of the one or more heat sources based on the signal received from the capacitive sensor when the liquid level within the vat corresponds to a liquid level covering less than about 90% of the height of the sensor.

10. A sensor and control system for determining the presence of fluid in a barrel, comprising:

a capacitive sensor disposed within the tub such that the sensor is disposed in communication with a volume of fluid within the tub;

sensor electronics that process signals in electronic communication with the capacitive sensor;

a controller that receives a signal from the sensor electronics representative of a capacitance value from the capacitive sensor and transmits a control signal to the lock-out device to control operation of the one or more devices based on the capacitance value, wherein the controller allows operation of the one or more devices when the signal received from the capacitive sensor represents that fluid is disposed within the drum at or above the level of the capacitive sensor, and wherein the controller prevents operation of the one or more devices when the signal received from the capacitive sensor represents that fluid is not disposed within the drum at or above the level of the capacitive sensor.

11. The sensor and control system of claim 10, wherein the one or more devices are one or more heat sources, and wherein the controller allows operation of the one or more heat sources to generate heat to heat the volume of fluid in the tub when the signal received from the capacitive sensor indicates that fluid is disposed within the tub at or above the level of the capacitive sensor, and wherein the controller prevents operation of the one or more heat sources to prevent generation of heat to heat the volume of fluid in the tub when the signal received from the capacitive sensor indicates that fluid is not disposed within the tub at or above the level of the capacitive sensor.

12. The sensor and control system of claim 11, wherein the controller further comprises a look-up table associated with the controller.

13. The sensor and control system of claim 10, wherein the capacitive sensor comprises a radiator structure at a first end and an outer jacket at an end remote from the radiator structure, and a coaxial cable having an inner conductor electrically connected to the radiator structure and a portion of the outer jacket.

14. The sensor and control system of claim 10, wherein said fluid is cooking oil and said vat is a cooking fryer pot in a vertical fryer.

15. A method of operating to control one or more heat sources for heating fluid in a barrel, comprising the steps of:

disposing a capacitive sensor within a barrel such that the sensor is disposed in communication with a volume of fluid within the barrel;

determining a capacitance value read by a capacitive sensor;

controlling operation of one or more heat sources based on the capacitance value from the capacitive sensor, wherein the controller allows operation of the one or more heat sources to generate heat to heat the fluid in the tank when the capacitance value from the capacitive sensor represents that the fluid is placed in the tank at or above the level of the capacitive sensor, and prevents operation of the one or more heat sources to prevent generation of heat to heat the fluid in the container when the capacitance value from the capacitive sensor represents that the fluid is not placed in the tank at or above the level of the capacitive sensor.

16. The method of claim 15, further comprising the step of accessing a look-up table to determine an operating parameter based on the capacitance value.

17. The method of claim 15, further comprising the step of transmitting an operation signal from the controller to the lockout device to affect operation of the one or more heat sources.

18. The method of claim 15, wherein the step of determining the capacitance value read by the capacitive sensor comprises determining whether the capacitance value is within a safe operating window defined by a minimum and maximum capacitance range.

19. The method of claim 15, wherein the step of controlling operation of the one or more heat sources comprises controlling at least one of a fuel-fired burner or an electric heating element.

20. The method of claim 15, further comprising the step of outputting an electronic communication signal to a switching mechanism to enable or disable operation of the one or more heat sources.

Technical Field

This description relates to control systems for heat sources, and sensors implemented in conjunction with such control systems.

Background

Control systems are known for controlling the operation of energy or heat sources, for example in controlled cooking systems. In some known systems, such as deep fry cooking systems, a control system and associated sensors may be used to control the heat source or burner in operation under certain conditions. For example, in a fryer environment, a control system and associated sensors may be implemented to prevent fryer operation when the level of water or cooking oil, such as for cleaning, is below a desired level for heating fluid, such as heat effective for cleaning or removing burners effectively.

Known control systems may include a sensor, such as a level sensor, that directly senses the level of the fluid based on the position of the float on the shaft. In a cooking system environment, the environment in which the sensor is used may be detrimental to smooth, continuous operation. For example, in a fryer environment, debris may be present in the fluid in the system and impede the free travel of the float along the shaft. The float may be stuck in a position that does not indicate the actual liquid level. In such systems, float jamming can create problems, such as providing for operation of the burner/heater when there is insufficient fluid in the system.

Capillary sensors are also known for liquid level detection. The capillary sensor receives liquid entering the capillary and determines the liquid level based on the position of the liquid within the tube. In a cooking environment, such as a fryer environment for determining the level of liquid in a fryer vat, a capillary sensor may be problematic due to differences in fluid viscosity that need to be sensed. For example, certain cooking fluids at certain temperatures will be partially in the solid phase, rendering capillary action within the capillary ineffective and unable to detect liquid level (e.g., if the fluid is solid at low temperatures, such as in the case of lard).

Furthermore, capillary sensors may retain fluid in the capillary tube, creating unsanitary conditions when used in food-related environments, as the space in the capillary tube where the fluid is retained is not easily cleaned. In addition, air pockets or bubbles that may remain within the capillary tube can be affected (sometimes extreme) by temperature changes, which can lead to sensor failure.

Disclosure of Invention

The present disclosure provides a sensor and control system that operates over a wide range of fluid viscosities, from partial solids to low viscosities. A highly reliable and hygienic sensor is realized as a capacitive sensor, which determines the capacitance of the fluid surrounding the sensor. In one illustrative embodiment, a sensor according to the present disclosure is disposed proximate a grounded structure of a container containing a fluid, such as near a vat in a fryer or a wall(s) of a fryer, where the fluid in the vat may be a fluid used for cooking (e.g., cooking oil, lard, etc.) or a cleaning fluid (e.g., water, etc.). The sensor is configured and arranged to sense a capacitance of the fluid in which the sensor is located, for example a capacitance between the sensor and a wall of the vat or fryer, to determine the relative capacitance of the fluid in the vat (and whether that capacitance is present).

A system according to the present disclosure includes a capacitive sensor in communication with sensor electronics. The sensor electronics interface with a microcontroller or processor that communicates with a locking system for controlling the subsystem. In the context of an exemplary cooking vat, the microcontroller communicates with a heating system lockout device that controls (e.g., enables or disables) a heating system, such as one or more fuel burners used to heat fluid in the vat (e.g., for cooking or cleaning).

In operation, in the illustrative embodiment, the capacitance of cooking oil (e.g., heated or at about room temperature) is significantly different from the capacitance of air. The capacitance of air is also significantly different from that of water. A controller receiving a signal from the sensor electronics representative of the measured capacitance from the sensor may determine the presence (and/or type) of fluid in the vicinity of the sensor, thereby activating the lock-up device to allow operation of the heating system (e.g., burner) or prevent operation of the heating system.

In some embodiments, the sensor may be calibrated such that the sensed capacitance (and thus the presence and level of fluid in the vicinity of the sensor) is based specifically on the position of the sensor relative to the walls and/or structures of the vat or fryer.

In an exemplary embodiment of the fryer, the fryer has a vat forming the fryer for receiving a volume of oil. The sensor is disposed within the barrel such that when oil is disposed within the fryer pot, the sensor is in contact with a volume of oil within the fryer pot. The sensor is configured to detect the presence of oil in the fryer when the level of oil in the fryer is at or above the level of the sensor. The capacitive sensor communicates with the controller and sends a signal to the controller via the sensor electronics indicating whether oil is present in the fryer pot at the level of the sensor. The controller is connected to the heating system locking device and controls the state of the locking device. The heating system lock-out, in turn, controls operation of one or more heat sources (e.g., burners) extending through the tub. The condition or state of the lockout device enables or disables operation of the one or more heat sources. When the signal received from the sensor indicates that fluid (e.g., oil for cooking or water for cleaning) is placed at or above the sensor level within the fryer pot, the controller places the locking device in a state that allows operation of the heat source based on the signal from the capacitive sensor via the sensor electronics. The controller places the locking device in a state that prevents operation of the one or more heat sources when the signal received from the sensor indicates that fluid is not being placed at or above the sensor level within the fryer.

The advantages of this invention will become apparent to those skilled in the art from the following description of specific embodiments thereof, which are shown and described by way of illustration. As will be realized, the disclosed subject matter is capable of other and different embodiments, and its details are capable of modification in various respects. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

Drawings

Fig. 1 is an exploded view of a capacitive sensor according to the present invention.

FIGS. 2A-2E are detailed views of components and assemblies of the capacitive sensor of FIG. 1

FIG. 3 is a functional block diagram of a control system utilizing the capacitive sensor of FIG. 1.

FIG. 4 is a flow chart of the operation of the capacitive sensor of FIG. 1 controlled by the control system of FIG. 3.

FIG. 5 is a perspective view of an illustrative embodiment of a fryer having a capacitive sensor for determining the presence of oil in the fryer in accordance with the present disclosure.

Fig. 6 is a detailed view of fig. 5.

FIG. 7 is a front cross-sectional view of the fryer of FIG. 5.

FIG. 8 is another front cross-sectional view of the fryer of FIG. 5.

Fig. 8A is a detailed view of the view of fig. 8.

FIG. 9 is a top view of a portion of the fryer with the stand removed for clarity.

Detailed Description

In accordance with the present disclosure, a capacitive sensor probe configured for installation in a fluid environment is shown in FIG. 1. The sensor probe 100 is configured and constructed to operate over a wide range of fluid viscosities, from partial solids to low viscosities, at a wide range of temperatures, and is typically constructed of "food safe" materials, as these materials can be used in cooking environments in contact with food products. In operation, as described in more detail below, the capacitive sensor probe acts as a "plate" of a capacitor, in conjunction with a metallic portion of the environment (e.g., a portion of a metal fryer pot) that houses the probe 100, with the fluid disposed in the environment acting as the dielectric of the capacitor.

The sensor 100 is implemented as a capacitive sensor that senses the capacitance of the fluid surrounding the sensor. In an illustrative embodiment, a sensor according to the present disclosure is disposed between walls of a vat, for example, in a fryer, wherein the fluid in the vat may be a fluid used for cooking (e.g., cooking oil, lard, etc.) or a cleaning fluid (e.g., water, etc.). The sensor is configured and arranged to sense a capacitance between the sensor and the wall of the bucket to determine the relative capacitance of fluid in the bucket (or the absence of fluid), from which it can be determined that sufficient fluid is present to provide relevant information to the control system.

A capacitive sensor probe according to the present disclosure is best shown in fig. 1, 2A-2E and 8A. The sensor 100 may include a metal cylindrical housing or probe radiator 102 disposed at an end (e.g., top) of the sensor assembly. The housing/radiator 102 includes a recess 103 (best seen in fig. 2B) that receives a plug 104 press fit into the housing 102 for electrically conductive engagement with the housing 102. The plug 104 is configured to receive a stripped cable end 105 (detail a of fig. 2A) of a coaxial cable having a center conductor, a dielectric surrounding the center conductor, and an outer conductor, forming a coaxial electrode 106. The center conductor is electrically connected to the radiator 102. The radiator 102 abuts an insulator 107 configured to be mounted adjacent the radiator. In this illustrative embodiment, the insulator 107 has threads configured to screw into the recess 103 of the radiator 102. An O-ring 111 can be disposed between the radiator 102 and the insulator 107. The insulator 107 may be made of PTFE, PEEK, or other insulating material that prevents electrical and/or thermal transmission, and is also capable of withstanding temperatures up to, for example, about 500 degrees fahrenheit. The sensor mount 108 is disposed adjacent to and abuts the insulator 107 and may have an O-ring disposed therebetween. The insulator 107 and sensor mount 108 are hollow so that the coaxial electrode 106 can extend through these bodies. The coaxial electrode 106 may be encapsulated in a PTFE heat shrink tube 109. The stripped cable end 110 of the coaxial electrode 106 remote from the radiator 102 is connected to a connector housing 113 and the outer conductor of the coaxial cable is electrically connected to the housing portion of the connector housing 113. In some embodiments of the capacitive sensor 100, fittings (not shown in fig. 1, 2A-2E, and 8A) may be disposed under the radiator 102 or under the insulator 107 to configure the sensor 100 for attachment to or removal from a standpipe for inspection, cleaning, replacement, and the like.

As shown in fig. 3, in a system according to the present disclosure, the capacitive sensor probe 100 is in electrical/electronic communication with sensor electronics 140. The sensor electronics can include capacitive sensor electronics in electrical communication with the sensor probe 100. In the illustrative embodiment, the sensor electronics 140 include the texas instruments FDC 10044 channel capacitance-to-digital converter Integrated Circuit (IC), or a substantial equivalent. The capacitive channel of the IC is electrically connected to the inner conductor of the coaxial electrode 106, which in turn is connected to the radiator 102 of the sensor probe 100. The IC and metal portion(s) of the box are grounded to a common ground. The outer conductor of the coaxial electrode 106 acts as an active or sensing shield with the IC to reduce electromagnetic interference and parasitic capacitance from sources other than the sensor probe 100. The sensor electronics 140 convert the analog capacitance signal generated by the sensor electronics to a digital signal for passing I²The C serial bus communicates with a microcontroller or processor 142.

Still referring to FIG. 3, a microcontroller 142, such as the STM32 series microcontroller available from STMicroelectronics of Geneva, Switzerland, receives digital signals from the sensor electronics 140. The digital signal represents the capacitance level produced by the fluid surrounding the sensor probe 100 and is communicated to the microcontroller 142 as a capacitance value. The microcontroller 142 communicates with a lock-out system (e.g., a heating interlock system) 144, and the lock-out system 144 controls a heating system 146 (enabled/disabled) that communicates with the lock-out system 144.

Referring now to FIG. 4, an illustrative process for microcontroller 142 is shown. Microcontroller 142 reads digital capacitance value 410 from sensor electronics 140. An exemplary control process implemented by the microcontroller program code then determines whether the capacitance value is within the minimum and maximum acceptable ranges for the sensor probe 100 and the sensor electronics 140. An exemplary acceptable range for capacitance determination in a fryer container application may be, for example, 0 picofarads (pF) (minimum) to 16pF (maximum). If the capacitance value is within the minimum/maximum range, the controller may access the lookup table 414 and determine the appropriate operating or control signal to output 416 to the lock-up system (e.g., enable or disable) for controlling the heating system 146. In an illustrative embodiment, the locking system 144 may include a solid state relay to enable or disable the heating system 146.

Still referring to fig. 4, if the capacitance value read by the microcontroller 142 is not within the minimum/maximum range and exceeds the maximum acceptable capacitance value (indicating that there are conditions outside the set specifications for the capacitive sensor probe 100 and electronics 140), the microcontroller issues a control signal that may disable or reduce operation of the heating system, or it may notify the operator. In this case, the microcontroller 142 may prompt the operator to decide whether to maintain or disable operation. In one embodiment, if the capacitance value read by the microcontroller 142 is not within the min/max range and exceeds the maximum acceptable capacitance value (indicating that there is an out of design specification condition for the capacitive sensor probe 100 and electronics 140), the microcontroller disables 418 the latch 144, which in turn disables the heating system. A determination may be made to determine whether the capacitance value read by microcontroller 142 is at the minimum acceptable capacitance value 420. The microcontroller 142 can be programmed to determine if the capacitance value is at or near a minimum acceptable level and, if so, to activate the latch 144, but to control the heating system 422 with the heat limit. Alternatively, if the capacitance value is not at or near the minimum acceptable level (e.g., well below the minimum acceptable level), then lockout device 144 may be disabled and the controller may issue an operator notification 424.

In an exemplary cooking environment (e.g., where the capacitive sensor 100 is disposed in a cooking vat or fryer, as described in detail below), the microcontroller 142 communicates with a heating system lockout 144 that controls, e.g., enables or disables, a heating system, e.g., one or more fuel burners for heating fluid in the cooking environment, e.g., where fluid for cooking or cleaning may be present. Based on the capacitance value received by the microcontroller 142, the microcontroller sends a signal to the heating system lockout 144.

The sensed capacitance of cooking oil (e.g., heated or at about room temperature) is significantly different from the capacitance of air. The capacitance of air is also significantly different from that of water (or water containing a cleaning solution or the like). The controller 142 receives a capacitance value signal from the sensor electronics 140 that is representative of the measured capacitance from the sensor 100, and the controller 142 may determine the presence (and in some configurations the type) of fluid in the vicinity of the sensor to initiate a lock-up to allow the heating system (e.g., burner) to operate, or to prevent the heating system from operating.

Turning now to fig. 5-9, an embodiment of a fryer 10 implementing a capacitive sensor 100 and control system according to the present disclosure is shown in more detail. The fryer has a vat 42 that contains and holds a volume of cooking oil or other cooking medium/liquid for cooking food to be introduced into the fryer. The heat source 32 is configured to apply heat to cooking oil disposed within the vat 42. The tub 42 is configured to receive one or more baskets (not shown) that hold food products to be cooked in contact with or submerged in the heated cooking liquid for a desired period of time.

Fryer 10 may be heated with a heat source 32, such as a gas burner or an electric heating element, to generate heat that is transferred to the cooking oil. In embodiments using a gas burner, the burner may be positioned to ignite a flame outside the tub 42, with the products of combustion being conveyed through a burner tube 32 extending below the tub, with the surface of the burner tube 32 transferring heat to the cooking liquid. In embodiments using an electric heater, the heater may be disposed directly within the tub such that a surface of the heater contacts the cooking liquid to transfer heat to the cooking liquid.

Gas burners or electric heaters generate a large amount of heat during the operation of heating cooking liquids to cook food. In some embodiments where the cooking liquid is cooking oil, the heat source operates to heat the cooking oil in the vat to a temperature in the range of, for example, 350 to 400 degrees Fahrenheit. To bring the entire cooking oil temperature within the vat 42 to this temperature range, the heater source needs to operate at a higher temperature than this range in order to transfer heat from the heat source to the cooking oil. During operation of the burner system and the electric heater, it is important to remove the heat generated by these burners/heaters from these components during operation, preventing these components from being at too high a temperature, which can lead to unsafe conditions such as malfunction or damage to fryer components or fire. Operation of the burners or heaters in fryer 10 with little or no fluid in vat 42 (e.g., cooking oil or cleaning liquid) can cause undesirable heat build-up during operation. Accordingly, embodiments of the capacitive sensor 100 and control system as described herein can prevent the heating source from operating when the bucket 42 does not include enough fluid to remove heat. However, it should be understood that the capacitive sensor and control system described herein may be implemented in other environments where a latch portion (e.g., an enable/disable mechanism) may be used and the capacitance value of the fluid within the container may be used to control the latch portion (e.g., any of a variety of systems having a fluid reservoir and a delivery control component, etc.). It should be noted that the same operations described will also be applicable to other situations, for example for the operational purpose of cleaning a tub when cleaning liquid is present or not present in the tub.

As shown, for example, in FIG. 5, fryer 10 with burner lock includes vat 42. The tub includes a front wall 26, opposing right and left side walls 22, 24, and a rear wall 28. The burner tube 32 extends through the bottom of the barrel 42, typically through the front wall 26 and the rear wall 28. A grill 40 may be provided above the burner tube 32, the grill 40 providing a surface upon which a frying basket (not shown, but conventional) may rest when frying food in the basket in cooking oil, particularly in heated cooking oil provided above the burner tube 32.

As described above with respect to fig. 1, 2A-2E and 3, the capacitive sensor 100 is disposed within the tub 42 at a location where the radiator (102, best shown in fig. 1) is at a level indicative of a desired minimum cooking oil level within the tub of heat required to be removed from the burner tube 32 for safe operation reasons. For safety operation reasons, the sensor 100 is configured to detect the presence of cooking oil at a desired level and provide a signal to the microcontroller 142 (fig. 3). The sensor provides a capacitance value signal to the controller 142 via the sensor electronics 140 (as described above) that indicates whether edible oil is present near the sensor at the requisite height within the vat 42. The microcontroller 142 receives the capacitance value signal and provides a control signal to the heating system lock-out 144 based on the received signal to either allow burner operation (when the signal indicates that cooking oil is present at the requisite level) or prevent burner operation (when the signal indicates that cooking oil is not present at the requisite level).

Example locations of capacitive sensors according to the present disclosure are shown in fig. 6-9. As shown in fig. 7, in the case of a cooking oil drum, a portion of the sensor 100 may rest on a stand pipe 120 extending within the drum. The height of the standpipe 120 places the radiator 102 of the sensor 100 at a height optimized for the appropriate liquid level. Coaxial communication cable 106 extends through riser 120 and is connected to sensor electronics (140, fig. 3), which in turn is electrically connected to microcontroller 142. The capacitive sensor 100 produces a capacitance value that is a function of the fluid surrounding the sensor, i.e., between the sensor and the barrel wall (in the position shown in the figure, the front wall 26 and the adjacent wall 22 of the barrel 46), with the sensor probe as one plate of the capacitor and the barrel wall(s) as the second plate of the capacitor. The capacitance of the cooking oil (heated or about room temperature) is significantly different from the capacitance of air, such that the microcontroller 142 receives a capacitance value signal representative of the measured capacitance of the fluid present. Based on the capacitance value, the microcontroller 142 sends a control signal to the heating system lockout 144 to allow burner operation, or to prevent burner operation. It will be appreciated that, through appropriate programming, the microcontroller 142 can determine which type of fluid is in the vicinity of the sensor, or can determine whether debris or other material is present in the fluid.

In some embodiments, the sensor 100 may be calibrated such that the sensed capacitance (and thus the presence and level of fluid in the vicinity of the sensor) is based specifically on the positioning of the sensor 100 within the bucket. That is, the value of the capacitance sensed may be a function of the position of the sensor relative to, for example, the walls 22, 26 of the tub, or in another example, relative to the side wall of the burner tube 32. While the system may be calibrated relative to the structure of the bucket based on the particular location of the sensor within the bucket, one of ordinary skill in the art will appreciate that the calibration may be based on a non-bucket structure placed near the sensor and forming part of the circuitry/system, as described herein. Generally, for a certain amount of fluid to be positioned between a sensor and a structure, there should be sufficient space between the sensor and the structure (e.g. a wall) to achieve a reliable and repeatable level of capacitance of the fluid (e.g. edible oil).

As described above, the microcontroller receives a signal from the sensor 100 via the sensor electronics 140 that is proportional to the capacitance of the fluid present, which can be calibrated based on the type of fluid. A memory (e.g., a look-up table) associated with the microcontroller maintains capacitance information based on the type of fluid (e.g., an appropriate range or "window" of capacitance values) associated with the control signal sent to the system lock 144 to allow or prevent burner operation based on the determined type of fluid.

In a particular illustrative embodiment, the sensor may be positioned as shown in fig. 8, 8A and 9, with the sensor 100 disposed in a space 99 within the tub 42 adjacent the side wall 32b of the burner tube and the front and right walls 26, 22 of the tub 42. This positioning allows sensor 100 to interact with the cooking oil (or no cooking oil) in vat 42, but is protected by the vat walls and sides of the burner tube to minimize damage during use of fryer 10. As shown, the sensor may be positioned with its center 112 substantially evenly spaced between the right sidewall 22 and the adjacent burner tube 32, as indicated by the spacing X. In this example, the center 112 of the sensor 100 is disposed about 0.9 inches from the right sidewall 22 and about 0.9 inches (distance Z) from the burner tube 32. In the illustrative embodiment, the outer perimeter of the sensor 100 (and particularly the outer perimeter of the radiator 102) is about 0.75 inches, creating a space of about 0.52 inches between the outer and right walls 22 of the radiator 102 and the burner tube 32. In this embodiment, the center 112 of the sensor is positioned about 0.6 inches from the front wall 26(Y) of the tub 42 and about 0.6 inches from the wall 29, which wall 29 is substantially parallel to the front wall 26 and forms the side of the inward recess 22b of the right side wall 22(W), as described below. Since a certain amount of cooking oil is disposed in the space between the radiator 102 and the various walls of the tub 42 and the side walls of the burner tube 32, the capacitance value of a particular fluid (i.e., cooking oil) in the space is significantly different from the value of the induced capacitance of air in the space disposed between the radiator and the walls of the tub 42. Similarly, in situations where water may be placed in the space (e.g., for cleaning operations), the sensed capacitance value of the fluid (e.g., cooking oil) is significantly different than the sensed capacitance value of water.

As shown in FIGS. 8 and 8A, in the exemplary embodiment, sensor 100 is positioned vertically with respect to a top surface 32a of burner tube 32 proximate sensor 100. The top of the sensor may be aligned just below the top surface 32a of the burner tube, as indicated by distance T. The distance T may be about 0.25 inches. In other embodiments, the top of the sensor 100 may be at the same height (i.e., 0 inches from the distance T) as the top surface 32a of the burner tube 32. In such embodiments, the sensor 100 may be no higher than the top surface 32a of the burner tube 32 to avoid interaction of the sensor with a fryer disposed within the vat 42 (which is typically placed on a metal shelf 40, as shown in FIGS. 5 and 6).

The vertical position of the sensor 100 within the tub 42 may be generally aligned with the top surface 32a of the burner tube 32 such that the capacitance, the presence or absence of oil based on measurements by the sensor 100, represents the oil level required to coat the burner tube in order to adequately conduct heat away from the burner tube 32 and transfer heat to the cooking oil within the tub 42.

In some embodiments, the sensor 100 and system may be calibrated to provide a signal that is interpreted by the controller as: when the sensor 100 is completely covered by cooking oil (in some embodiments, particularly the emitter housing 102), the cooking oil surrounds the sensor 100, i.e., the cooking oil surrounds the entire axial side surface of the sensor 100. In some embodiments, the sensor 100 and system may be calibrated to provide a signal that is understood by the controller to encompass the sensor 100 when approximately 90% of the vertical height (or in other embodiments 90% of the total circumferential area) of the sensor 100 is encompassed by the cooking oil. Other calibrations are contemplated and are within the scope of the present disclosure.

While the embodiments depicted in fig. 8, 8A, and 9 and discussed herein include sensors disposed at specific locations within the tub, those skilled in the art will appreciate that the sensors may be located or otherwise disposed at other locations within the tub.

In some embodiments, the controller may be programmed to provide an error message to the user (by message board, digital reading, warning light, etc.) when the measured capacitance is not within the value (or range of values) of the calibrated capacitance of cooking oil (from room temperature to hot), water, or air. In this case, the sensor 100 may not be operating properly, or the surface of the sensor 100 or the surface of the wall near the sensor 100 (the side wall 22, the burner tube 32, etc.) is covered with foreign matter, so that the measured capacitance is different from the normally calibrated capacitance. The error message may prompt the user to investigate the cause and take action to address the problem, for example, mechanically cleaning the surface of the sensor 100 or the wall of the tub 42 in an attempt to clear the error message.

7-9, in some embodiments, the right and left side walls 22, 24 may be configured to maximize the amount of oil in the tub 42 disposed above the burner tube and to minimize the amount of oil in the tub at the sides of the burner tube 32. This configuration improves oil circulation within the oil drum so that local heating of the oil is minimized for extending the life of the oil. In some embodiments, the right and left side walls may include a narrowed region 22b (the left side wall 24 having the same design as the right side wall 22), with the portion of the right side wall 22b aligned with the side of the burner tube 32 extending inwardly to minimize the space between the right side wall and the side of the burner tube 32 while allowing the volume of the barrel above the burner tube to be wider above the burner tube.

Although in exemplary embodiments, the sensor as described herein is configured and arranged to sense the capacitance between the sensor and the vat wall to determine the relative capacitance of the fluid in the vat (or the absence of fluid) and thereby determine that sufficient fluid is present to provide relevant information to the control system, it will be understood by those skilled in the art that the sensor may be used as described to determine the capacitance between the sensor and another structure in addition to the metal/conductive wall of the vat, and that the capacitive sensor and control system according to the present disclosure may be used in environments other than a frying vat. For example, in a non-fryer environment (or a non-metallic or metallic container environment), a conductive structure (rather than a wall of surrounding structure) may be provided in the vicinity of the sensor and operated in accordance with the present disclosure to sense the capacitance of the container contents.

While the locking system and the heating system are described and illustrated herein as separate systems, it should be understood that the locking mechanism that controls the controlled system (e.g., the heating system) due to the capacitance value may be an integrated system, with the locking mechanism being an integrated part of the controlled system (e.g., the heating/combustion system).

While various embodiments are disclosed herein, it will be understood that the invention is not limited thereto and can be modified without departing from the disclosure. The scope of the disclosure is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.