Abstract:
A non-contact capacitance sensor having a base and an array disposed on the base is provided. The array has a first electrode and a second electrode disposed opposite one another so that the array senses a change in capacitance between the first and second electrodes.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention is related to non-contact liquid sensing. More particularly, the present invention is related to an apparatus and method for sensing liquid used in commercial dish and glass washing machines without contacting the liquid being sensed.  
           [0003]    2. Description of Related Art  
           [0004]    Commercial food preparation establishments, such as restaurants and cafeterias, often use industrial or commercial washing machines for cleaning their drinking glasses, dishes, flatware, food preparation equipment, and the like. These commercial washing machines usually use one or more chemicals in the cleaning process. For example, it is common for these washing machines to use chemicals, such as, but not limited to, a detergent, a sanitizing agent, and a rinse agent, during the cleaning process.  
           [0005]    In the use of such automated cleaning equipment, it is good sanitary practice to ensure that the chemicals needed by the washing machine during the cleaning process are, in fact, delivered to the machine. The National Sanitation Foundation (NSF) is a non-governmental organization that develops standards for public health and safety in the areas of food safety. The NSF has developed standards for commercial dish and glass washing machines (e.g., NSF Standard 3), and is currently considering modifying these standards to require chemical delivery confirmation. In order to continue to meet the increasing demands on commercial washing machines systems, new washing machines will need to be fitted with chemical delivery sensing systems. Further, and perhaps a more difficult task due to the large number of existing systems, will be retrofitting existing machines with a chemical delivery sensing system.  
           [0006]    Conventional sensing systems are capable of sensing the presence or absence of a liquid in a conduit. However, many conventional sensing systems are contact systems, namely, they require the sensor to be installed directly in the conduit so as to contact the liquid being sensed. These contact sensing systems have proven to be ineffective in the dishwashing industry. For example, the chemicals used by commercial washing machines can be damaging to such contact sensing systems. In addition, when retrofitting washing machines that are already in use, such contact sensing systems require high cost installation, such as, cutting or replacing of existing conduits, as well as substantial labor and wiring.  
           [0007]    Still others have developed non-contact sensing systems, which have also proven ineffective in the dishwashing industry. For example, many non-contact sensing systems are complex and can require sophisticated calibration and maintenance. Some non-contact sensing systems, such as ultrasonic sensing systems, are not effective at the low flow rates that are typically found in the chemical delivery conduits of commercial washing machines.  
           [0008]    Accordingly, there is a continuing need for a simple, low cost liquid sensing apparatus for new and existing washing machines in order to detect the delivery of chemicals during the washing process.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    A non-contact capacitance sensor having a base and an array disposed on the base is provided. The array has a first electrode and a second electrode disposed opposite one another so that the array senses a change in capacitance between the first and second electrodes.  
           [0010]    A non-contact capacitance sensor having a base and a capacitance-detecting array disposed on the base is also provided. The base has at least one securing member. The capacitance-detecting array has a first electrode opposite a second electrode. The securing member is configured to secure a conduit between the first and second electrodes so that the capacitance-detecting array detects a change in capacitance indicative of a presence or an absence of a liquid in the conduit.  
           [0011]    A system for detecting a presence or an absence of a liquid in a conduit is also provided. The system includes a first portion, a capacitance-detecting array, a securing member, and an indicator. The first portion is mountable in a desired location with respect to the conduit. The capacitance-detecting array and the securing member are disposed on the first portion. The capacitance-detecting array has a first electrode and a second electrode opposing one another. The securing member secures the conduit between the first and second electrodes so that the capacitance-detecting array detects a change in capacitance indicative of the presence or the absence of the liquid in the conduit. The indicator indicates the presence or the absence.  
           [0012]    A method of sensing a liquid in a conduit is also provided. The method includes securing the conduit to a base so that the conduit is in a selected position with respect to a sensing array; calibrating the sensing array to a predetermined calibration level; and signaling when the sensing array detects a change from the predetermined calibration level.  
           [0013]    A method of sensing a liquid in a conduit is also provided that includes securing the conduit in a selected position with respect to a capacitance-detecting array so that the capacitance-detecting array detects a capacitance in the conduit; calibrating the capacitance-detecting array to a predetermined calibration level; and notifying an operator when the capacitance deviates from the predetermined calibration level.  
           [0014]    The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a schematic illustration of a liquid sensing apparatus in use with a commercial dishwashing machine;  
         [0016]    [0016]FIG. 2 is a bottom exploded perspective view of an exemplary embodiment of a liquid sensing apparatus according to the present invention;  
         [0017]    [0017]FIG. 3 is a front view of the liquid sensing apparatus of FIG. 2;  
         [0018]    [0018]FIG. 4 is a top view of the liquid sensing apparatus of FIG. 2;  
         [0019]    [0019]FIGS. 5 and 6 are opposing exploded side views of the liquid sensing apparatus of FIG. 2;  
         [0020]    [0020]FIGS. 7 and 8 are top exploded perspective views of the liquid sensing apparatus of FIG. 2; and  
         [0021]    [0021]FIG. 9 is an enlarged top view of circle  9 - 9  of FIG. 8. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Referring now to the figures and in particular to FIG. 1, an exemplary embodiment of a liquid sensing apparatus  10  according to the present invention is schematically illustrated in use with a commercial washing machine  12 . Apparatus  10  is configured to detect the presence or absence of liquid in the chemical delivery conduit(s) of machine  12  in a non-contact manner. Further, apparatus  10  is configured to be easily installed about the conduit(s) in a simple quick-connect manner. Thus, apparatus  10  offers the ability to fit new and/or retrofit existing commercial machines  12  with a chemical delivery verification means.  
         [0023]    For purposes of clarity, machine  12  is described herein as a commercial washing machine, such as a ConserverXL Dish Washing Machine manufactured by Jackson, MSC, Inc. of Barbourville, Ky. However, it should be recognized that apparatus  10  can find use in other applications where the simple installation and use of a non-contact sensor for detecting the presence or absence of a liquid in a conduit is required.  
         [0024]    During the cleaning process, machine  12  is adapted to treat a plurality of dishes  14  with one or more chemicals, such as, but not limited to, detergent, sanitizing agent, rinse agent, and others. Machine  12  draws or pumps liquid chemicals through conduits  16  from one or more supply containers  18  into various portions of the machine. Machine  12  is illustrated using three different liquid chemicals and, thus, having three conduits  16  and three containers  18 . Of course, it is contemplated by the present invention for machine  12  to use more or less than three chemicals.  
         [0025]    Apparatus  10  is adapted to be easily installed or connected about the exterior of conduits  16 . In this installed position, apparatus  10  can be configured to sense the presence or absence of a liquid chemical in each of conduits  16  without coming into contact with the liquid passing through the conduit (i.e., non-contact). Once apparatus  10  senses an absence of liquid in any one of conduits  18 , the apparatus can alarm the operator, can turn off machine  12 , or both.  
         [0026]    It has been determined that the chemicals typically used by machine  12  (e.g., detergent, sanitizing agent, rinse agent, etc.) are conductive liquids. It has also be found that conduit  16  is typically made a dielectric or non-conductive material, such as polyethylene tubing, which can withstand the properties of the chemicals used by machine  12 . Accordingly, it has been determined that the capacitance of conduit  16  when the liquid is present as compared to the capacitance of the conduit when the liquid is absent can be used to detect the presence or absence of liquids in the conduit.  
         [0027]    Liquid sensing apparatus  10  is described in detail below with simultaneous reference to FIGS. 2 through 9. Apparatus  10  has a first or base portion  20  configured to be mounted in a desired location, such as on a wall adjacent to containers  18 . First portion  20  is preferably mounted proximate machine  12  to ensure that the liquid chemicals are delivered to machine  12 . For example, first portion  20  can include one or more mounting members  22 , such as, but not limited to, holes for securing first portion  20  to the desired location by way of fasteners (e.g., screws, bolts, rivots, etc.). Of course other means for mounting first portion  20  in a desired location on machine  12 , such as, but not limited to, adhesives, mounting brackets, welding, hook and pile type fasteners, and others are contemplated by the present invention.  
         [0028]    First portion  20  has one or more conduit-retaining clips or holders  24  (“clips”) and a capacitance plate array  26  for each conduit  16 . Preferably, first portion  20  has two retaining clips  24  for each array  26 , where clips  24  are position on opposite sides of array  26  as illustrated. In this manner, clips  24  secure conduit  16  in a desired position with respect to capacitance plate array  26 . By way of example, clips  24  can have a pair of resilient biasing arms  28  configured to releasably secure conduit  16  therebetween in a snap fit manner. Of course, other releasable and non-releasable members for securing conduit  16  to first portion  20  are contemplated by the present invention.  
         [0029]    Array  26  has a first or ground dielectric plate  30  and a second or measuring dielectric plate  32  defining a gap  34  therebetween as shown in FIG. 9. Gap  34  is, preferably, sized to be provide a minimum tolerance between conduit  16  and first and second plates  30 ,  32 , respectively. Clips  24  are configured to maintain conduit  16  in a desired location between first and second plates  30 ,  32 , respectively. For example, clip  24  can maintain conduit  16  in a centered relationship with respect to first and second plates  30 ,  32 .  
         [0030]    Apparatus  10  propagates an electric field from first plate  30  to second plate  32  through gap  34  such that any medium (i.e., conduit  16  and any liquid therein) between plates  30 ,  32  result in a change in the capacitance of the electric field at second plate  32 . Apparatus  10  uses power from a power source (not shown) to generate the electrical field. The power source can be internal to apparatus  10 , such as a battery, or can be external to the apparatus, such as a 110-volt power source. In this embodiment, first portion  20  can include a power port  35  for providing power into apparatus  10 .  
         [0031]    After conduit  16  is installed in clip  24 , apparatus  10  is calibrated to detect the presence or absence of liquid in the conduit. For example, apparatus  10  can have an automatic calibration function. In this embodiment, apparatus  10  is configured to take a first reading when it is first powered up. The first reading can be representative of only conduit  16  between first and second plates  30 ,  32  (i.e., absence of liquid). Once the liquid becomes present in conduit  16 , apparatus  10  will use its current capacitance reading as a calibration level. Apparatus  10  can then notify an operator any time apparatus  10  detects a capacitance other than the calibration level. Preferably, apparatus  10  notifies the operator any time apparatus  10  detects a change in capacitance more than a selected amount (i.e., a set point) from the calibration level. Apparatus  10  preferably has a constant set point. However, it is contemplated by the present invention for the set point to be adjustable.  
         [0032]    In an alternate embodiment, apparatus  10  can have a manual calibration function. In this embodiment, first portion  20  can include a calibration button  36 . When button  36  is depressed, apparatus  10  establishes the current detected capacitance as the calibration level. In the event that apparatus  10  is used to detect the presence of liquid in conduit  16 , the operator depresses button  36  after conduit  16  is installed in first portion  20 . Here, the calibration level would represent the capacitance detected by apparatus  10  of conduit  16  only. The flow of liquid through conduit  16  would cause the capacitance detected by apparatus  10  to change from the calibration level more than the set point, causing the apparatus to notify the operator. In the event that apparatus  10  is used to detect the absence of liquid in conduit  16 , the operator depresses button  36  after conduit  16  is installed in first portion  20  and conduit  16  has been filled with the desired liquid. Here, the calibration level would represent the capacitance detected by apparatus  10  of both conduit  16  and the liquid. Any interruption in the flow of liquid through conduit  16  would cause the capacitance detected by apparatus  10  to change from the calibration level by a selected amount, which would cause the apparatus to notify the operator.  
         [0033]    Apparatus  10  can notify the operator in any suitable or known manner. In one embodiment, apparatus  10  includes a visual indicator  38 , such as an indicator light, for each conduit  16 . Visual indicator  38  can have a first state when apparatus  10  is detecting the calibration level and a second state when the apparatus is detecting a capacitance other than the calibration level. For example, visual indicator  38  can be illuminated in green when apparatus  10  is detecting the calibration level and can be illuminated in red when the apparatus is detecting a capacitance the selected amount from the calibration level. Of course, visual indicators other illumination in green and red are contemplated by the present invention.  
         [0034]    In another embodiment, apparatus  10  includes an audible indicator  40 , such as a speaker. Audible indicator  40  can have a first state when apparatus  10  is detecting the calibration level and a second state when the apparatus is detecting a capacitance other than the calibration level. For example, audible indicator  38  can be off when apparatus  10  is detecting the calibration level and can be provide an audible noise when the apparatus is detecting a capacitance other than the calibration level. In addition, it is contemplated for apparatus  10  to include a volume control  42  for changing the sound level of audible indicator  40 .  
         [0035]    In still another embodiment, apparatus  10  includes one or more output relay connections  44 . Each output relay connection  44  can be placed in electrical communication with a device external to apparatus  10 . For example, an electric wire (not shown) can be used to place machine  12  in electrical communication with one of output relay connections  44 . First portion  20  can further include a mounting boss  46  for securing the electric wires to apparatus  10 . In this example, apparatus  10  can provide a first output to output relay connection  44  and, thus to machine  12 , when apparatus  10  is detecting the calibration level. Further, apparatus  10  can provide a second output and, thus, to machine  12 , when the apparatus is detecting a capacitance other than the calibration level. Here, machine  12  can be prevented from operating or stopping when apparatus  10  detects that the liquid is not present in conduit  16 . It should be recognized that machine  12  is only one example of the external device that output relay connection  44  can be in electrical communication with. It is contemplated by the present invention for apparatus  10  to be in electrical communication with any desired external device via output relay connections  44 .  
         [0036]    In addition, it is contemplated by the present invention for apparatus  10  to include any combination of the forgoing means to notify the operator.  
         [0037]    Apparatus  10  can also include a second or cover portion  48 , which can be mounted to first portion  20  to protect one or more portions of the apparatus. For example, second portion  48  can be used to cover clips  24 , arrays  26 , and output relay connections  44 . First and second portions  20 ,  48 , respectively, can include cooperating mounting holes  50  for securing first and second portions  20 ,  48  to one another by way of fasteners (e.g., screws, bolts, rivots, etc.). Of course other means for securing second portion  48  over first portion  20 , such as, but not limited to, adhesives, mounting brackets, welding, hook and pile type fasteners, and others are contemplated by the present invention.  
         [0038]    As described herein apparatus  10  can be easily installed and, thus, can make the retrofitting of existing machines  12  simple and cost effective. Further, as described herein apparatus  10  can be easily incorporated into the design and installation of new machines  12 . In fact, the use of apparatus  10  merely requires mounting first portion  20  in a desired location, snapping conduits  16  in clips  24 , and using button  36  to calibrate the capacitance reading for the presence or absence of the desired liquid in each conduit  16 . The method can further include installing second portion  48  onto first portion  20  and/or placing relay output connection(s)  44  in electrical communication with machine  12  or other external devices.  
         [0039]    It should also be noted that the terms “first”, “second”, “third”, “upper”, “lower” and the like may be used herein to modify various elements of the present invention. It is intended that these modifiers do not imply a spatial, sequential, or hierarchical order to the modified elements unless specifically stated.  
         [0040]    While the invention has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.