Patent Publication Number: US-2018028044-A1

Title: Warewasher with ultrasonic-based ware detection

Description:
TECHNICAL FIELD 
     This application relates generally to warewashers such as those used in commercial applications such as cafeterias and restaurants and, more particularly, to systems and methods to utilize ultrasonic for detecting and locating wares in connection with such warewashers. 
     BACKGROUND 
     Commercial warewashers commonly include a housing which defines one or more internal washing and rinsing zones for dishes, pots pans and other wares. In conveyor-type machines, wares are moved through multiple different spray zones within the housing for cleaning (e.g., pre-wash, wash, post-wash (aka power rinse) and rinse zones), and potentially a drying zone as well. One or more of the spray zones includes a tank in which liquid to be sprayed on wares is heated in order to achieve desired cleaning. In batch-type machines, wares are typically manually moved into a generally stationary location within a chamber cleaning (e.g., wash sprays and rinse sprays are applied while the wares remain in the same, stationary location in the machine), and then the wares are manually removed from the machine upon completion of all operations/steps of the cleaning cycle. 
     Increased environmental regulation and other factors contributed to a need for greater efficiency of such machines (e.g., lower water use, lower chemical use and lower energy use). 
     It would be desirable to provide a warewasher system and method that takes advantage of ultrasonic ware detection and locating to achieve greater efficiency by enhanced control of one or more cleaning cycle parameters. 
     SUMMARY 
     In one aspect, a warewash machine for washing wares includes a housing defining a chamber for receiving wares, the chamber having at least one spray zone, a wash spray system for spraying wash liquid onto wares and a rinse spray system for spraying rinse liquid onto wares. At least one ultrasonic transducer is located for detecting wares feeding into the chamber and/or for detecting wares within the chamber. A controller is associated with the ultrasonic transducer and configured to identify one or more of ware location, ware movement, ware size, ware shape and/or ware material based upon outputs from the at least one ultrasonic transducer. The controller is further configured to control at least one operating parameter of the machine based at least in part upon identified ware location, identified ware movement, identified ware size, identified ware shape and/or identified ware material such that the at least one operating parameter is suitable for the identified ware location, identified ware movement, identified ware size, identified ware shape and/or identified ware material. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side elevation of one embodiment of a warewasher showing ware moving toward an ultrasonic transducer; 
         FIG. 2  is a schematic side elevation of one embodiment of a warewasher showing ware moving away from an ultrasonic transducer; and 
         FIG. 3  is a graph comparing emitted ultrasonic energy (Io) with reflected ultrasonic energy (Ir). 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a warewash machine  10  includes a housing  12  defining an internal chamber  14  for receiving wares. The housing defines an inlet end  16  and outlet end  18  of the chamber (e.g., openings covered by curtains that enable wares to move into and out of the chamber, respectively). The chamber includes multiple spray zones  20 ,  22  and  24 . Here, zone  22  represents a main wash spray zone, and zone  24  represents a rinse spray zone downstream of the wash spray zone  22 . Zone  20  may or may not be present, and could be a pre-wash zone and/or an automatic soil removal (ASR) zone. A drying zone  26  is located downstream of the rinse spray zone  24 . 
     The illustrated wash spray zone  22  includes a collection tank  30  with a heating element  32  for maintaining the wash liquid as a set temperature, which may be detected by a temperature sensor  34 . A recirculation line  36  runs from the collection tank to multiple wash spray nozzles  38  (e.g., associated with upper and lower wash spray arms) and a wash pump  40  is located along the recirculation line. 
     The rinse spray zone  24  includes a rinse valve or a rinse pump  42  for controlling flow of rinse liquid from a water heating unit  44  (e.g., a booster heater with associated heating element  46  and temperature sensor  47 ) along a rinse liquid line  48  to multiple rinse spray nozzles  50  (e.g., associated with upper and lower rinse spray arms). The water heating unit  44  receives water from a fresh water input of the machine. Here, two fresh water inputs are provided (e.g., one for hot water and one for cool water, or one for tap water and one for softened water or demineralized water) and selection of the water input feed is by respective valves  49  and  51 . 
     The drying zone  26  including an air flow delivery system  52 , which may include, for example one or more blowers  54  and one or more air heating elements  56 , along with an air temperature sensor  58 . 
     A conveyor  60  is provided for carrying wares through the chamber for cleaning. By way of example, the conveyor may be a continuous loop type conveyor or may be a reciprocating conveyor, in either case the movement of which is powered by a motor  62 . The conveyor  60  includes a portion external of the chamber at the inlet end or infeed end to enable operators to place wares thereon for feeding into the chamber  14  by the conveyor. 
     A controller  100  is provided for controlling operation of the machine  10 , and may be connected to each machine component and each machine sensor as needed for such purpose. As used herein, the term controller is intended to broadly encompass any circuit (e.g., solid state, application specific integrated circuit (ASIC), an electronic circuit, a combinational logic circuit, a field programmable gate array (FPGA)), processor(s) (e.g., shared, dedicated, or group—including hardware or software that executes code), software, firmware and/or other components, or a combination of some or all of the above, that carries out the control functions of the machine or the control functions of any component thereof. 
     A chemical dosing circuit  64  includes a chemical valve or a chemical pump  66  for delivering a chemical from a reservoir  68  along a chemical feed line  70 . Here, the dosing circuit feeds wash chemical (e.g., detergent) to the wash tank  30 . Alternatively, the wash chemical could be fed to the wash line  36 . Moreover, other chemical dosing circuits could also be provided (e.g., to feed wash chemicals to other wash zones and/or to feed a rinse chemical (e.g., rinse agent) to the rinse water unit  44  or the rinse water line  48 ). 
     As shown, an ultrasonic transducer  80  is provided for detecting wares feeding into the chamber. As used herein the term ultrasonic transducer is broadly used to encompass an ultrasonic device in which the ultrasonic emitter and ultrasonic detector share some common circuitry, as well as an ultrasonic device in which an ultrasonic emitter and an ultrasonic detector are paired, but may not share common circuitry. Alternatively, or in addition to ultrasonic transducer  80 , one or more ultrasonic transducers  82  could be located within the chamber  14  as shown. In both cases, the ultrasonic transducers  80  and  82  may be located outside of the ware path (e.g., to one side or above or below) and oriented to direct ultrasonic emissions toward the ware path for ware detection purposes. Generally, the ultrasonic transducer(s) may, for example, be used for the purpose of identifying any one or more of ware location, ware movement, ware size, ware shape and/or ware material based upon outputs from the at least one ultrasonic transducer (e.g., with the controller  100  receiving transducer outputs and carrying out the identification). The general principles regarding use of the ultrasonic transducer for such purposes is explained below. 
     Ultrasonic-Based Ware Location and Ware Movement 
     The location of the ware at any time (Lt) in or on the warewash machine  10  can be determined based upon the duration of time (t) between ultrasonic transducer emission of ultrasonic energy and subsequent reception the reflected ultrasonic energy per Equations (1a) and (1b) below. The constant “2” is used in the equations because the ultrasonic energy travels out and back along its travel path from the transducer, to the ware and back to the transducer after reflection. 
       2 L   t   =Ct   (1a)
 
         t= 2 L   t   /V   (1b)
 
     Here the “V” is the known speed of the ultrasonic wave in an existing media, which is constant for the media. However, the speed may vary depending on location of ultrasonic transducer in the machine because of the different moisture contents. For example, the machine loading area external of the chamber at the inlet end is mostly room air with light moisture and may have refractive index close to 1, whereas inside the chamber a high level of moisture may exist, and hence the reflective index may be different from 1. This means speed of the ultrasonic wave may be different for the different zones in the machine but will typically be constant for each zone. The proper value for “V” can be predetermined for the various locations in the machine based upon testing, with the controller using the appropriate V value for each ultrasonic transducer.  FIG. 3  shows the duration t between ultrasonic emission and reflected ultrasonic reception by an exemplary graph  200 . 
     In the case of two (2) successive emitted and received ultrasonic energies intercepting a moving ware, the change in the location of the ware ΔL (i.e., L 1 −L 2 ) is predicted by the change in duration of time Δt (i.e., t 1 −t 2 ) the ultrasonic transducer sends and receives ultrasonic as in Equation (2a) 
     
       
         
           
             
               
                 
                   
                     
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                     - 
                     
                       t 
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                       2 
                     
                   
                   = 
                   
                     
                       2 
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                       ( 
                       
                         
                           L 
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                           1 
                         
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                           L 
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     The initial time or location of a ware is denoted by subscript “1” while a new time or location is denoted by subscript “2.”. Where “2/V” is a constant for a given condition. Equations (2b) and (2c) are defined from Equation (2a) and show the proportionality of the time difference Δt between t 1  and t 2  as a measure of ware location change (ΔL) between L 1  and L 2  of a ware moving toward a transducer  80  as shown in  FIG. 1 . 
       | t   1   −t   2 |α|( L   1   −L   2 )|  (2b)
 
       Δ tαΔL   (2c)
 
     Where Δt=t 1 −t 2  and ΔL=L 1 −L 2 . 
     Given  FIG. 1 , for a ware  102  moving toward the transducer  80  and at a maximum set distance L 1  from the transducer, the difference in time Δt corresponding to two (2) successive times t 1  and t 2  the transducer  80  emits ultrasonic energy  104  and receives back reflected ultrasonic energy  106  could be set to a maximum predetermined value T, where the ware reaching a closer location L 2  after a predetermined time t p  for the machine causes the controller to initiate the required machine processes for incoming ware. Here, the ultrasonic emission  104  has a primary direction that is substantially opposite the conveying direction of the conveyor and travel direction of wares. 
       Δ t=t   1   −t   2   ≦T   (3a)
 
     Where t 1 &gt;t 2  and L 1 &gt;L 2 , and t 1  and t 2  correspond to L 1  and L 2 , respectively. 
     In the warewash machine  110  of  FIG. 2 , which is similar to the machine  10  of  FIG. 1  except that an ultrasonic transducer  112  is located at the far end of the machine infeed, with the ware moving away from the transducer  112 . For a minimum set distance L 1  from the transducer  112  the difference in duration of time Δt corresponding to two (2) successive times t 1  and t 2  the ultrasonic transducer  112  emits ultrasonic energy  114  and receives back reflected ultrasonic energy  116  could be set to a maximum predetermined value P where the ware at location L 2  after a predetermined time T p  for the machine causes the controller to initiate the required machine processes for incoming ware. 
       Δ t=t   1   −t   2   ≦P   (4a)
 
     Where t 1 &lt;t 2  and L 1 &lt;L 2 , t 1  and t 2  correspond to L 1  and L 2 , respectively. 
     Equations (3a) to (4a) will provide information on ware locations relative to an ultrasonic transducer in or around a machine (e.g., regardless of whether the ultrasonic transducer is in the chamber or outside of the chamber). The different location of the ware(s) may be used to control the machine effectively to achieve the desired wash quality while saving energy and maximizing the machine efficiency (e.g., turning certain operations ON/OFF as needed according to ware location). 
     Ultrasonic-Based Ware Material Differentiation 
     Ultrasonic reflection is a function of the nature of the surface and material type against which the ultrasonic energy impacts. In addition, different material thicknesses can result in different energy absorption, which also impacts the amount of reflected ultrasonic energy. A perfect reflection will result in the ultrasonic transducer receiving sufficient reflected ultrasonic energy back while a diffuse reflection may not. In real-life, the emitted energy (Io) incident on a ware or material is distributed into reflected energy (Ir), absorbed energy (Ia) and transmitted energy (It) as in Equations (5a) and (5b). 
         Io=Ir+Ia+It   (5a)
 
       1=( Ir/Io )+( Ia/Io )+( It/Io )  (5b)
 
     Where Ir/Io is reflectivity, Ia/Io is absorptivity and It/Io is transmissivity. However, from Equation (5b) the combined absorptivity and transmissivity can be defined as in Equation (5c) and can be used to differentiate ware materials, ware shape and/or ware location. 
       ( Ia+It )/ Io =( Io−Ir )/ Io   (5c)
 
     The reflected energy is what goes back to the ultrasonic transducer while the absorbed and transmitted energies are what the material absorbs and transmits, respectively. The graph  200  of  FIG. 3  shows that the reflected energy received back by the ultrasonic transducer is generally lower than that emitted. The different material types with different densities will result in different intensities of the reflected energy (Ir) as well as absorbed energy (Ia). The emitted energy (Io) compared with the reflected energy (Ir) ( FIG. 3 ) is what is used to identify the different materials to control the machine efficiently for the necessary savings while achieving the wash quality while maximizing the machine productivity. 
     From Equation (5a) or (5b) either absorptivity, transmissivity or reflectivity could be used but, reflectivity (Ir/Io) will be used for illustration. 
     To deal with the variation in the nature of the surfaces as well as the various thicknesses of the same ware material and ultrasonic energy attenuation, an operational range of reflectivity, absorptivity or transmissivity that distinguishes each predetermined ware material type may be defined and used. Hence, for reflectivity and combined absorptivity and transmissivity the following ranges could be defined for each material type with the following as examples. 
     
       
         
           
             
               Stainless 
                
               
                   
               
                
               steel 
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                
               wares 
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                
               a 
             
             ≤ 
             
               Ir 
               Io 
             
             ≤ 
             
               b 
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               or 
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                 a 
                 1 
               
             
             ≤ 
             
               
                 Io 
                 - 
                 Ir 
               
               Io 
             
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               b 
               1 
             
           
         
       
       
         
           
             
               Ceramics 
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               wares 
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               c 
             
             ≤ 
             
               Ir 
               Io 
             
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               d 
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               or 
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                 c 
                 1 
               
             
             ≤ 
             
               
                 Io 
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                 Ir 
               
               Io 
             
             ≤ 
             
               d 
               1 
             
           
         
       
       
         
           
             
               Plastics 
                
               
                   
               
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               wares 
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               e 
             
             ≤ 
             
               Ir 
               Io 
             
             ≤ 
             
               f 
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               or 
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                 e 
                 1 
               
             
             ≤ 
             
               
                 Io 
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                 Ir 
               
               Io 
             
             ≤ 
             
               f 
               1 
             
           
         
       
       
         
           
             
               Aluminum 
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               wares 
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               g 
             
             ≤ 
             
               Ir 
               Io 
             
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               h 
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               or 
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                 g 
                 1 
               
             
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                 Io 
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                 Ir 
               
               Io 
             
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               h 
               1 
             
           
         
       
     
     Ultrasonic-Based Ware Size and Shape Determination or Imaging 
     This functionality may typically employ sets of ultrasonic transducers positioned to use either the reflected, absorbed or transmitted ultrasonic energy to determine the size and shape of wares. The same arrangement could also be used to determine material type and location. Considering the reflectance concept, emitted ultrasonic energy with no ware interception will result in no reflected energy back to the ultrasonic transducer(s). The various reflected energy from a ware is what defines the size and shape of the ware. Knowledge of the shape or size of the ware will enhance controlling the machine appropriately for the required wash quality and use of resources. 
     The identified ware material type, size, conveyor ware load and/or ware speed can be used by the controller  100  as a measure of how much energy will be required to keep, for example, the wash tank  30 , at the minimum required operating temperature, facilitating proper control of heating element  32 . In addition, knowing the ware material type, shape, size and/or location will enable the controller  100  to control machine parameters to achieve expected wash quality while using resources accordingly. 
     Exemplary Sequence of Operation 
     In one example, the ultrasonic transducer(s) is/are ready for operation once the machine is ready to wash, and the transducers are activated when the conveyor starts to move. The ultrasonic transducer(s), once activated, emit and receive energy. Intersection of emitted energy with ware(s) produces reflected energy which is received by the transducer(s) to determine the location, size, shape and/or material type of the ware. Processed ultrasonic emitted and received energy is used to control or regulate one or more of the machine operating parameters simultaneously or in series to better operate the machine to meet the need of the specific wares and includes, for example, regulating the conveyor speed to a constant speed or vary in between zones; regulating the heating elements to a constant temperature or vary in between zones; regulating wash pressures in the various zone by regulating the pump in the zones; regulating the rinse rate or rinse volume per rack or cycle for the different ware types, size and/or shape; regulating the rinse temperature for the different ware types, size and shape; changing the water input source if machine is connected with multiple water sources (e.g., tap water, softened water, demineralized water) based on ware types; regulating chemical dosage for washing, rinsing, sanitizing and/or deliming; and/or regulating blower dryer heat or air flow rate. 
     In reality, the wares are mixed and sensing the same material over a predetermined time will switch the machine mode to better serve the material(s) to be washed or being washed until a new material(s) sensed switches the machine to suit the new material. Machine switches in-between modes to suit the ware material, shape, and size to optimize machine and use resources appropriately is thereby achieved. Scheduling of wares is possible across multiple manually or automatically fed machines based upon machine capacity, operational configuration (e.g. equipment package, chemicals, etc.), or other relevant status. Sorting of wares is also possible across multiple manually or automatically fed machines with the capacity or operational configuration (e.g. equipment package, chemicals, etc.), to wash a particular ware type. 
     It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. For example, while conveyor-type warewash machines are primarily shown and described, ultrasonic transducers could be incorporated into the chamber of a batch-type machine for detecting ware location, size, shape and/or materials and responsively controlling machine operating parameters. Accordingly, other embodiments are contemplated and modifications and changes could be made without departing from the scope of this application.