Abstract:
A warewash machine includes at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine. An overflow path leads from the collection tank, and an automated valve controls flow along the overflow path. A controller is configured to control an open/closed state of the automated valve based at least in part upon status of pump operation

Description:
TECHNICAL FIELD 
       [0001]    This application relates generally to commercial warewash machines and, more specifically, to commercial warewash machines that utilize recirculating sprays of liquid in one or more wash zones. 
       BACKGROUND 
       [0002]    Commercial warewashers commonly include a housing area which defines spray zones in the nature of washing and rinsing zones for dishes, pots pans and other wares. In certain zones, wash liquid (e.g., water or water and detergent) is typically pumped from a tank through a pump intake, delivered to the wares via a spraying operation from multiple nozzles located in one or more spray arms and collected in the tank for recirculation through the spray system. One or more of the spray zones may also include an overflow to drain (e.g., which may be a standpipe type overflow or may be an overflow through the sidewall of the tank). As fresh water is added into the machine (e.g., through the rinse arms) dirtier water overflows to drain. 
         [0003]    The liquid in the spray recirculation line, pump and in the actual sprays of a spray zone can be referred to as liquids in suspension because at any given time they do not contribute to the volume of liquid in the collection tank of the zone. 
         [0004]    In the current operation of known warewash machines, especially the conveyance-type machines (e.g., rack conveyance or flight-type conveyance through the spray zones), substantial loss of water, chemicals and/or energy occurs anytime a tank recirculation pump shuts down. By way of example, such shut down may occur as a result of any of a dish limit activation after some time, running the machine in idle mode while maintaining tank temps, or an operator opening the machine door for some reason, which automatically interrupts washing and stop the recirculation pumps. These intermittent stops results in loss of energy, chemical and water as results of the suspended hot solution overflowing to drain. Specifically, the liquid in suspension, which may, for example be between six and ten gallons for a given spray zone, falls down into the collection tank, causing the tank level to rise above an overflow level, such that a large volume (e.g., six to ten gallons) of liquid moves to drain. In a machine with multiple spray zones, the liquid volume lost to drain is even more (e.g., in a machine with three recirculating spray zones 18 to 30 gallons may be lost by overflow to drain in such cases). 
         [0005]    Upon restarting wash operations after such a stop, fresh, generally cold water from the rinse and/or tank fill lines replenishes the lost fluid. In addition, chemicals (especially detergents) are added to achieve to the correct detergent concentration for washing. The addition of the fresh cold water to make up for the lost water drops the overall wash tank temperatures, which requires time and energy to heat the tank contents to acceptable tank liquid temperatures. 
         [0006]    Moreover, in the current machine in which the hot wash solution falling out of suspension goes to drain makes the machine prone to cavitation, foaming and possible pump problems, upon restarting the machine for the next wash cycle, because part of the tank fluids need to be suspended while the rinse and fill are on to replenish the suspended fluids. This often takes some time and depends on the type of machine. 
         [0007]    It would be desirable to provide a machine that is configured to avoid unnecessary losses such as those described above. 
       SUMMARY 
       [0008]    In one aspect, a warewash machine allows liquid in suspension to be collected/retained within a collection tank of the machine without overflowing to drain so that the liquid can be re-used. 
         [0009]    In another aspect, a method is provided for operating a warewash machine that includes at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine. The method involves: utilizing an automated valve to control overflow draining from the collection tank; while the pump is operating to recirculate wash liquid, maintaining the automated valve in an open condition to allow liquid to overflow from the tank as the water level in the tank rises due to addition of water by dilution or capture of final rinse liquid; and automatically closing the automated valve in conjunction with stopping operation of the pump so that at least some liquid in suspension falls into the collection tank and liquid level in the collection tank rises above a normal overflow level of the collection tank. 
         [0010]    In another aspect, a warewash machine includes at least one collection tank for collecting wash liquid that is recirculated by a pump and sprayed for cleaning wares within a spray zone of the machine. An overflow path leads from the collection tank, and an automated valve controls flow along the overflow path. A controller is configured to control an open/closed state of the automated valve based at least in part upon status of pump operation. 
         [0011]    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 
         [0012]      FIG. 1  is a schematic depiction of one embodiment of a warewash machine; 
           [0013]      FIG. 2  is a schematic depiction of another embodiment of a warewash machine; and 
           [0014]      FIG. 3  is a schematic depiction of another embodiment of a warewash machine. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    A warewash machine is configured to reduce losses upon machine or recirculation pump shutdown. In particular, the machine is configured to capture some or all of the hot wash solution that falls out of suspension during a stop, preventing it from going to drain, so that it can be reused in the next wash cycle. An automatic valve can be used for this purpose, and will significantly improve the warewash machine operational sequence to save energy and material(s) (e.g., chemicals and water). 
         [0016]    Referring to  FIG. 1 , a schematic end elevation of an exemplary conveyance-type machine  10  is shown. The machine includes a housing  12  defining a tunnel through which the wares are delivered by a conveyance mechanism  14  (ware movement would be in or out of the page in this end view). An exemplary spray zone  20  of the machine includes one or more upper spray arms  22  and/or one or more lower spray arms  24 , it being recognized that in some cases a spray zone may, in addition or as an alternative, include one or more side spray arms (not shown) as well. A wash liquid recirculation system includes a liquid collection tank  26 , recirculation line  28  back to the spray arms  22 ,  24  and pump  30  for moving the wash liquid along the path. An overflow path  32  to drain is also provided from the tank, and an automated valve  34  is located along the path  32 . Path  32  may be direct to drain, or may be a path that passes through one or more additional tanks of other spray zones before flowing to drain. 
         [0017]    A machine controller  100  is connected for controlling operation of both the pump  30  and valve  34 . As used herein, the term controller is also 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 (e.g., shared, dedicated, or group—including hardware or software that executes code) or other component, 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. 
         [0018]    During machine operation, the liquid in the tank  26  does not exceed the level indicated by dashed line  36  due to the overflow drain path  32 , because the automated valve  34  is maintained in an open condition while the pump  30  is operating to provide the recirculating spray flow. When the pump  30  is shut down for some reason, the controller  100  effects closure of the valve  34  so that the overflow path  32  is effectively closed, allowing the liquid in suspension to be captured in the tank, in which case the liquid level rises to the level indicated by dashed line  38 . The difference between the liquid levels  38  and  36  represents the amount of liquid savings achieved by automatic closure of the valve  34 , which in turn results in savings of both energy and detergent that would have been needed if the liquid had been permitted to overflow to drain. The overall savings on water, energy and chemicals can be significant, particularly for machine installations in which temporary shut downs occur more frequently. 
         [0019]    With respect to closure of the automated valve  34 , in some implementations it may be desirable to close the valve  34  substantially simultaneously with the shutdown of the pump  30  (e.g., just before, at the same time as, or just after), resulting in capture and retention of substantially all of the liquid in suspension so that it is not lost to drain. In other implementations, it may be desirable allow some of the liquid in suspension to overflow before shutting down the valve. For example, the valve  34  could be maintained open for a set time period after shut down of the pump  30  (e.g., valve  34  maintained open for between 1-5 seconds (such as 1-2 seconds) after pump shutdown), so that only a portion (e.g., at least 50%, such as between 50% and 90%, such as between 60% and 80%) of the volume of liquid in suspension is precluded from following the overflow path. It is recognized that the exact timing of valve closure, whether substantially simultaneous or after some time period, could be a settable feature of the machine. For example, the controller  100  could include a user interface  102  that that enables an end user, or on some cases only maintenance or service personnel, to adjust the timing of valve closure relative to the timing of pump shutdown, thereby enabling the portion of the volume of liquid in suspension that will be prevented from overflowing to drain to be set at virtually any percentage (e.g., between 5% and 100%). 
         [0020]    Upon restart of the machine for operation, specifically when operation of the pump  30  is restarted, the controller  100  again effects opening of the valve  34  to permit normal overflow operations as desired. Although closure of the valve  34  may in some cases be substantially simultaneous with the restart of the pump  30 , it is recognized that it will typically take some amount of time for the previously captured liquid (represented by the difference in liquid levels  38  and  36 ) to again be put into suspension. Accordingly, closure of the valve  34  may more commonly be effected by the controller at some time after restart of the pump  30  (e.g., after a set or settable time period, or after detecting, such as by way of a level sensor  40 , that a liquid level in the tank  26  has dropped to a certain level). 
         [0021]    As described above, a typical conveyance-type warewash machine include multiple spray zones. In this regard, reference is made to the schematic side elevation of the exemplary warewash machine  110  of  FIG. 2 , which includes recirculating spray zones  112 ,  114 ,  116 ,  118  and  120 , each zone having respective tanks  122 ,  124 ,  126 ,  128  and  130 , respective pumps  132 ,  134 ,  136 ,  138  and  140  and respective spray arm(s)  142 ,  144 ,  146 ,  148  and  150 . Ware travel through the machine is from left to right as indicated by arrows  152 . Zone  112  represents an automated soil removal zone, where the largest soils are removed from incoming wares. Zone  114  represents a prewash zone, zone  116  represents a main wash zone, zone  118  represents a power rinse zone (aka post wash zone) and zone  120  represents a dual rinse zone (aka secondary rinse zone). A final rinse zone  154  is also provided, and sprays fresh hot rinse liquid as may be delivered by pump  156  from booster heater  158 . One or more drying zones (not shown) could also be provided. 
         [0022]    Generally, all pumps are turned ON/OFF simultaneously, except the fresh hot rinse liquid pump  156  which turns ON when wares are in the final rinse zone  154  and off when no ware is present in the final rinse zone  154 . During cleaning operations with the pumps on, fresh rinse liquid is delivered into the machine in zone  154  and the used rinse liquid is diverted to the tank  130  of the dual rinse zone  120 . Overflow paths  160 ,  162 ,  164  and  166  are provided between the tanks, resulting in a reverse cascade overflow path from tank  130  to tank  122 . Tank  122  includes an overflow path  168  to drain through a master manual valve MV and an automated valve AV connected in parallel. Each tank also includes a respective manual drain valve M 1 -M 5  that can be used to fully drain the tank for machine cleaning. An exemplary operational sequence for machine  110  is described below. 
         [0023]    When the machine is in operation the master manual drain valve MV and the individual manual drain valves M 1 , M 2 , M 3 , M 4  and M 5  are closed, while the automatic valve AV is opened. The automatic master drain valve AV is maintained in an open condition so long as the final rinse pump  156  is operating to allow for draining of the used final rinse water, which cascades sequentially through the various tanks  130 ,  128 ,  126 ,  124  and  122  to sweeten or dilute the wash solutions in each tank as the liquid level in each tank rises due to the incoming fresh final rinse water. The cascade finally goes to drain via overflow line  168  from tank  122 . While the spray zone pumps  132 - 140  are operating, but when the final rinse pump  156  is not operating (i.e., no wares in the final rinse zone  154 ), the automated drain valve AV can be closed if desired because new water is not being added to the machine. However, it may more typically be maintained open. The automatic master drain valve AV closes when the wash pump  136  shuts down. Note that the wash pump  136  and the other tank pumps  132 ,  134 ,  138  and  140  typically all shutdown simultaneously. 
         [0024]    When the wash pump  136  stops, the automatic drain valve AV closes to capture suspended hot wash solution from going to drain. As used herein, closing the valve “when operation of the pump is stopped” could be achieved by closing the valve just before, simultaneous with or just after the wash pump is turned off. Moreover, a set delay in closure of the automated valve AV could also be used as described above. The water levels in all of the tanks rise above the normal overflow levels because both the automated drain valve AV and the master manual valve MV are closed, thereby capturing and retaining a large volume of the liquid in suspension (e.g., in this case potentially between 30 gallons and 50 gallons, assuming between 6 and 10 gallons in suspension in each zone  122 ,  124 ,  126 ,  128  and  130 ). Upon initiating the next wash cycle (e.g., restarting the machine pumps), the captured wash solution is reused. Operation of the pump(s) again moves some of the liquid into suspension and the water levels in the tanks fall back below the overflow levels. Thus, at restart the required fresh water add is significantly reduced, which likewise reduces the amount of chemical add required as well as the amount of energy needed to maintain the tank liquid at required temperature. 
         [0025]    The automated drain valve AV is automatically opened as part of the machine restart. In one example, the valve may be opened at the same time the pumps start. In another example, as previously noted, the valve may be opened a specified time period after the pumps start to provide some time for liquid to go into suspension, or after liquid level in the tank has dropped a specified amount due to resuspension of liquid. 
         [0026]    During a machine start-up from empty, the valve AV would be maintained closed to allow all tanks to fill. 
         [0027]    Draining the tank(s) for refill after dumping or at shutdown will typically involve opening all the manual valves including main valve MV, as well the automatic valve AV for quicker draining. 
         [0028]    Referring now to  FIG. 3 , a schematic side elevation of another exemplary machine  210  is shown, which is similar in configuration to the machine  110  is shown. However, in the case of machine  210  the automated valve AV is located in series with the master manual valve MV, rather than in parallel. Thus, in this configuration, during normal operation of the machine the master valve MV would be maintained in the open condition to allow for overflow draining from the machine. Otherwise, operation of the machine  210  is the same as that described above for machine  110 . 
         [0029]    The above machines and processes can save energy, chemicals and water. Initial onset of pump cavitation, foaming can be reduced as well as protection of machine parts. Reuse of captured solution in suspension for subsequent operation reduces colder water refills required to replenish any lost wash solution, chemical make-up required and time for the machine to get to temperature suitable for wash operations. 
         [0030]    It is to be clearly understood that the above description is intended by way of illustration and example only, is not intended to be taken by way of limitation, and that other changes and modifications are possible.