Patent Publication Number: US-7901518-B2

Title: Commercial dishwasher with air deflector arrangement

Description:
The present application is based on, and claims priority from, German Application Number 10 2005 023 428.3, filed May 20, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     The invention relates to a commercial dishwasher which has a spray chamber for holding items to be washed, and which is designed for loading and unloading batches of items to be washed, according to the patent claims. 
     Commercial dishwashers, which are designed for loading and unloading a spray chamber with batches of items to be washed, are in particular front-loader dishwashers or hood-type dishwashers. In front-loader dishwashers, the items to be washed are placed in a rack and the rack which is loaded with items to be washed is placed in the spray chamber through a front door and, after cleaning, is removed again through the front door. In hood-type dishwashers, the dish racks which are loaded with items to be washed are pushed manually into the spray chamber from an entry side and manually removed from the spray chamber from an exit side when a washing programme is complete. Front-loader dishwashers and hood-type dishwashers contain only a single spray chamber for treating the items to be washed. The front-loader dishwashers may be under-counter dishwashers (under-counter warewashers) or top-counter dishwashers (top-counter warewashers). Items to be washed are usually cleaned by at least one cleaning process, during which the items to be washed are sprayed with a cleaning liquid, and at least one subsequent final-rinse process, during which the items to be washed are sprayed with final-rinse liquid. The final-rinse liquid may be fresh water or a mixture of fresh water and rinsing agent. Commercial dishwashers which are designed to be charged with batches are also called batch dishwashers (batch warewashers). 
     Items to be washed may be, in particular, dishes, glasses, cutlery, bowls, pots and pans, trays, boxes etc. 
     In contrast to domestic dishwashers, in which a washing programme which involves at least one cleaning process and at least one subsequent final-rinse process lasts for between 30 mins and 2.5 hours, the cycle time for a washing programme including at least one cleaning process and at least one subsequent final-rinse process in a commercial dishwasher is between one minute and six minutes. 
     A drying process in a domestic dishwasher lasts between 10 minutes and 30 minutes and usually takes place inside the said domestic dishwasher. 
     In commercial dishwashers, it is customary to remove the items, which have been washed and are still hot, from the machine after the final-rinse process, and to leave them to dry in the ambient air for 4 to 10 minutes. In order to dry the items which have been washed, they are usually left in the racks in which they were arranged to be cleaned in the dishwasher. 
     U.S. Pat. No. 3,807,420 describes a domestic dishwasher having an air outlet in an upper region of the spray chamber and an air inlet in a lower door region, with a fan for sucking air through the air outlet being arranged below the spray chamber. 
     EP 0 978 250 A2 discloses arranging an electric fan at an outlet of a duct in a domestic dishwasher in order to pass an air/steam mixture out of a spray chamber in the dishwasher over a heat-exchange surface in the duct. The heat-exchange surface here is at a temperature which is below the dew point of the air/steam mixture, with the outlet of the duct again issuing into the washing tank. 
     U.S. Pat. No. 4,179,821 and U.S. Pat. No. 3,398,756 disclose dishwashers which, by heating up air at the bottom of a washing chamber, produce a convection flow of moisture-laden air through an outlet arranged in an upper region of the washing chamber, and out of the dishwasher. The air flowing out of the dishwasher is in this case replaced by ambient air which enters through a gap between a front door and a lower housing part of the dishwasher. 
     EP 0 711 528 A1 describes a dishwasher having a fan which is arranged below the spray chamber and extracts air through an air outlet in the top of the spray chamber. Ambient air enters the spray chamber through an inlet in a side wall of the spray chamber and flows through the items which have been washed from the side. 
     On account of the short cycle times of washing programmes in a commercial dishwasher, known drying methods for domestic dishwashers cannot be used in a commercial dishwasher. The aim of the invention is to achieve the object of drying the items which have been washed in a commercial dishwasher in a short time with a satisfactory drying result. 
     According to the invention, this object is achieved by the attached patent claims. Further features of the invention can be found in the subclaims. 
    
    
     
       The invention is described below with reference to the drawings using preferred embodiments as examples. In the drawings: 
         FIG. 1  shows a sectional side view of a commercial dishwasher according to the invention; 
         FIG. 2  shows a perspective view of the commercial dishwasher from  FIG. 1 ; 
         FIG. 3  shows a sectional side view of a further embodiment of a commercial dishwasher according to the invention; 
         FIG. 4  shows a schematic sectional view of yet another embodiment of a commercial dishwasher according to the invention; 
         FIG. 5  shows a partial sectional view of yet another embodiment of a commercial dishwasher according to the invention; 
         FIG. 6  shows a partial sectional view of yet another embodiment of a commercial dishwasher according to the invention; 
         FIG. 7  shows a partial sectional view of yet another embodiment of a commercial dishwasher according to the invention; 
         FIG. 8  shows a perspective partial view of a commercial dishwasher according to the invention; and 
         FIG. 9  shows a partial sectional view of an embodiment of an outlet duct according to the invention from above. 
     
    
    
       FIG. 1 ,  FIG. 3  and  FIG. 4  show a longitudinal section through a commercial dishwasher  2  which has a spray chamber  4  for holding items  6  to be washed and has a door  8  for closing a loading and unloading opening  10 . The dishwasher  2  is designed for loading and unloading batches of items  6  to be washed into and from a region  12  for items to be washed in the spray chamber  4 . An air inlet  14  into the spray chamber  4  is arranged below the door  8  at a point which is lower than the region  12  for items to be washed. An air outlet  16  out of the spray chamber  4  at a point which is higher than the region  12  for items to be washed is arranged at a point higher than the air inlet  14 . The dishwasher  2  has a fan  18  for producing an air stream  20  along an air path  21 , the air path  21  extending from the air inlet  14 , through the spray chamber  4 , to the air outlet  16 . The air stream  20  in the spray chamber  4  is passed through the region  12  for items to be washed in order to dry the items  6  which have been washed. A deflector arrangement  22  having at least one deflector  23  (see  FIG. 8 ) is arranged and designed to act on the air stream  20  entering the spray chamber  4  through the air inlet  14  and thus to cause the air stream to enter the region  12  for items to be washed in a uniformly distributed manner from below. 
     The spray chamber  4  has a volume of between 60 l and 280 l, for example. 
     The term “items  6  to be washed” includes, in particular, dishes, glasses, cutlery, pots and pans, containers, boxes, trays etc. The term “washing” includes, in particular, at least one of the processes “pre-cleaning”, “cleaning”, “post-cleaning”, “final-rinsing” etc. 
     The region  12  for items to be washed is a region in the spray chamber  4  in which the items  6  to be washed are positioned in order to be cleaned. The items  6  to be washed are preferably arranged in a rack  24  in this case. The spray chamber  4  can contain one or more rack holders, for example as illustrated a single rack holder  26 , on each of which a rack  24  is or can be positioned. As an alternative, two rack holders which are arranged one above the other may be provided for example. 
     A multiplicity of spray nozzles  28  are arranged in the spray chamber  4  for spraying washing liquid  38 , for example cleaning liquid or final-rinse liquid, onto the items  6  to be washed. Separate spray nozzles  28  may be provided in each case for spraying cleaning liquid and final-rinse liquid. The spray nozzles  28  can, as illustrated, particularly be formed on rotatable spray pipes, on stationary spray pipes or in a spray-chamber wall. In the illustrated embodiments, the loading and unloading opening  10  is formed in a front-end spray-chamber wall  30 . The spray-chamber floor  32  has a passage opening  34  into a tank  36  or into a reservoir which is provided for holding washing liquid  38 . The passage opening  34  in the spray-chamber floor  32  is preferably covered by a tank screen  40 . The dishwasher  2  is preferably intended to reuse at least some of the washing liquid  38  in the tank  36  for a further washing programme, that is to say for a new batch of items  6  to be washed. In particular, the dishwasher  2  may be designed to regenerate washing liquid  38 . 
     The operating temperature of the washing liquid  38  in the tank  36  is preferably between 55° C. and 65° C. and is maintained by a suitable temperature-control apparatus. A temperature-control apparatus may be provided for final-rinse liquid (not illustrated), for example outside the spray chamber  4 , which temperature-control apparatus preferably sets the temperature of the final-rinse liquid to between 63° C. and 85° C. 
     According to an embodiment illustrated in  FIG. 1 ,  FIG. 4  and  FIG. 5 , the air inlet  14  is formed between guide elements  42 ,  44  which are connected to a machine housing  46  or are formed by it. In this case, an upper guide element  42  and a lower guide element  44  form at least one gap or slot. The lower guide element  44  is preferably inclined downwards towards the spray chamber  4  here. The upper guide element  42  is preferably inclined away from the spray chamber  4 . 
     A nozzle may be provided in place of a slot or a gap (not illustrated). One of the guide elements  42 ,  44 , in particular the upper guide element  42 , may be formed by the door  8  or be connected to the door  8 , as illustrated in  FIG. 6  and  FIG. 7 . 
     The air inlet  14  is preferably designed to produce an air stream  20  which covers the entire width of the region  12  for the items to be washed. 
     An air-inlet path  48  extends from a front face  50  of the dishwasher  2 , through the lower gap  52  in the door, as far as the air inlet  14 . As an alternative, the air-inlet path  48  can extend from an opening in a housing part or from an opening in the door  8  to the air inlet  14 . The air-inlet path  48  is preferably labyrinthine ( FIG. 1 ,  FIG. 3 ,  FIG. 7 ) in order to prevent washing liquid  38  escaping from the dishwasher  2  through the air-inlet path  48  during operation of the spray nozzles  28 . A particle filter  54 , for example a dust filter, may be arranged in the air-inlet path  48  (illustrated by way of example in  FIG. 5 ). 
     The deflector arrangement  22 , which is arranged in the air path  21  of the air stream  20 , may be designed in one piece. As an alternative, the deflector arrangement  22  may be of multipartite design and have at least two deflectors  23 , as is schematically illustrated in  FIG. 8 . The at least two deflectors  23  may be arranged at a distance from one another. In  FIG. 8 , the deflectors  23  are arranged at a distance from one another in a direction transverse to the air stream  20 . In this way, a partial air stream  20 - 1  of the air stream  20 , which does not strike a deflector  23 , enters the region  12  for items to be washed in a rear part  55  of the region  12  for items to be washed, whereas a partial air stream  20 - 2  of the air stream  20 , which strikes a deflector  23 , enters the region  12  for items to be washed in a front part of the region  12  for items to be washed (see  FIG. 4 ). 
     In the embodiments of a dishwasher  2  according to the invention illustrated in  FIG. 1  and  FIG. 3 , the deflector arrangement  22  is arranged at a distance from the air inlet  14 . In particular, the deflector arrangement  22  can be arranged on the spray-chamber floor  32 , as illustrated in  FIG. 1  and  FIG. 3 . As an alternative, the deflector arrangement  22  or at least one of its deflectors  23  can be arranged on the tank screen  40 , as illustrated in  FIG. 8 . The deflector arrangement  22  can alternatively be arranged adjacent to the air inlet  14 , for example on a spray-chamber wall. The air outlet  16  is arranged in an upper rear region  56  of the spray chamber  4 . The air path  21  or the air stream  20  thus extends diagonally through the spray chamber  4 , as a result of which a satisfactory drying result is achieved. As an alternative, the air outlet  16  may be arranged at another point above the region  12  for items to be washed. 
     An outlet duct  58  extends in the direction of flow downstream of the air outlet  16  from this air outlet  16  as far as a machine outlet  60  which is preferably arranged on the front face  50  of the machine, as illustrated in  FIG. 1  to  FIG. 4 . The outlet duct  58  preferably extends above the spray chamber  4 , as illustrated in  FIG. 1 ,  FIG. 3  and  FIG. 4 . An outlet cover  62  may be provided in order to conceal the machine outlet  60  in accordance with the desired appearance of the dishwasher. 
     An oblique run-off surface  61  can be formed below the machine outlet  60  in order to carry drops formed at the outlet back inward and behind the door  8 . In the illustrated embodiment, the oblique run-off surface  61  is formed in one piece with the outlet cover  62 . As an alternative, the oblique run-off surface  61  may be formed by a separate part, for example a housing part. In the illustrated embodiment, the drops which run off collect in a region  63  above the door seal  65  and when the door  8  is opened run down the door  8  into the spray chamber. 
     In the illustrated embodiments, the fan  18  is arranged in a region between the air outlet  16  and the machine outlet  60 , and for sucking air out of the spray chamber  4 . The fan  18  is preferably arranged at the air outlet  16 . As an alternative to the illustrated embodiments, the fan may be arranged for blowing air into the spray chamber. 
     A condensate run-off  64  extends from the outlet duct  58  into the spray chamber  4 , so that condensate or washing liquid which splashes into the outlet duct  58  can run off into the spray chamber  4 . A bottom region  66  of the outlet duct  58  is preferably inclined towards the condensate run-off  64 , so that condensate which collects at the bottom region  66  runs off towards the condensate run-off  64 . As illustrated in  FIG. 1  and  FIG. 3 , provision may particularly be made for a rotary shaft of a fan rotor  68  of the fan  18  to be inclined towards the condensate run-off  64 , so that liquid in the fan  18  runs off towards the condensate run-off  64 . 
     A condenser  70  (illustrated in dashed lines in  FIG. 1  and  FIG. 3 ) is arranged in the outlet duct  58  and serves for condensing moisture from air which is flowing out and thus dehumidifying the air which is flowing out. The condenser  70  is arranged downstream of the air outlet  16 . In particular, the condenser  70  can be arranged downstream of the fan  18 , as illustrated in  FIG. 1  and  FIG. 3 . The condenser  70  can, for example, be formed by a heat exchanger which makes the heat of condensation, which is released during the condensation, available to the dishwasher  2  again. As an alternative, the condenser  70  can be cooled by cooling liquid, such as cooling water, or by cooling air, in order to dissipate the heat of condensation. 
     A closure element  72  is preferably arranged in the outlet duct  58 , as illustrated in  FIG. 1  and  FIG. 3 , for closing the outlet duct  58  when the fan  18  is switched off. The closure element  72  particularly prevents a spray mist moving out of the dishwasher  2  through the outlet duct  58  and the machine outlet  60  during operation of the spray nozzles  28 . The closure element  72  may be a controllable closure element which is controlled by a control device (not illustrated). However, as illustrated, the closure element  72  is preferably formed by a flap which is automatically opened by the air stream  20  produced by the fan  18  and is automatically closed when the fan  18  is switched off. For this purpose, the flap is preferably mounted at its upper end  74 , so that the flap is automatically closed by gravitational force when the fan  18  is switched off, as illustrated in  FIG. 1  and  FIG. 3 . 
       FIG. 9  shows a further embodiment of an outlet duct  58  from above. The air outlet  16  out of the spray chamber and the fan inlet  75  (illustrated in dashed lines) of the fan  18  can be found on the lower face of the fan  18  here, in accordance with the configuration in  FIG. 1  and  FIG. 3 . Furthermore, an auxiliary fan  76  is provided for supplying ambient air  78  to the air stream  20  in the direction of flow of the air stream  20  downstream of the fan  18  and downstream of the air outlet  16 . The auxiliary fan  76  is arranged so as to convey ambient air  78  into the outlet duct  58  through an auxiliary air duct  80 . In the illustrated embodiment, a fan inlet  79  (illustrated in dashed lines) of the auxiliary fan  76  is arranged on the lower face of the auxiliary fan  76 , but may be arranged at any other desired point in accordance with the type of fan used. An issue region  82 , in which the auxiliary air duct  80  issues into the outlet duct  58 , acts as a mixing chamber for mixing the ambient air  78 , which is conveyed through the auxiliary air duct  80 , and the air stream  20  from the spray chamber  4 . As illustrated in  FIG. 9 , flow-guide elements  84  may be provided in order to improve thorough mixing of the two air streams. Flow-guide elements  86  may be provided in the direction of flow downstream of the issue region  82  for reducing turbulence in the resulting air stream  88 . Conveying ambient air into the air stream  20  flowing out of the spray chamber  4  reduces a condensation effect, which is caused by the moisture-laden air flowing out of the spray chamber  4 , outside the dishwasher  2 . A closure element  90  may be arranged in the auxiliary air duct  80  for closing the auxiliary air duct  80  when the auxiliary fan  76  is switched off. The closure element  90  of the auxiliary air duct  80  may be formed, in particular, by a closure element, as has been described above with reference to the outlet duct  58 . 
     In the illustrated embodiment, the fan  18  is designed to produce an air stream  20  at a rate which corresponds to 6 times to 12 times the volume of the spray chamber per minute. 
     A recirculation duct  92  which issues into the spray chamber  4  may be connected to the outlet duct  58  in the direction of flow downstream of the condenser  70 , in order to at least partially recirculate dehumidified air from the outlet duct  58  into the spray chamber  4 , as illustrated in  FIG. 3 . As illustrated, a flow-adjustment element  94  may be provided which can adjust the proportion of air which is recirculated into the spray chamber  4  from the outlet duct  58 . By way of example, the flow-adjustment element  94  may be formed by a flap which can be moved into a first position in which the entire air stream  20  flowing through the outlet duct  58  is recirculated into the spray chamber  4  again. The flow-adjustment element  94  can preferably be moved into a second position in which the entire air stream  20  flowing through the outlet duct  58  is conducted out of the dishwasher  2  through the machine outlet  60 . Furthermore, the flow-adjustment element  94  may be designed to set at least one intermediate position  96  in which an out-flowing part  98  of the air stream  20  flowing through the outlet duct  58  is conducted out of the dishwasher  2  through the machine outlet  60 , and a recirculated part  100  of the air stream  20  is recirculated into the spray chamber  4 . The flow-adjustment element  94  can be operated manually. The flow-adjustment element  94  may also be designed such that it can be controlled by the control apparatus  110  (see  FIG. 4 ). 
     As illustrated in the drawings, the fan  18  is preferably arranged to suck air out of the spray chamber  4 . 
     In the embodiments illustrated in  FIG. 1  and  FIG. 3 , a splash guard  102  is arranged in front of the air outlet  16  in order to prevent or reduce liquid passing from the spray chamber  4  through the air outlet  16 . The splash guard  102  may be equipped with a grease filter. In the illustrated embodiment, the splash guard  102  is arranged in relation to the condensate run-off  64  in such a way that condensate running off through the condensate run-off  64  drips onto the splash guard  102  and is conducted from the said splash guard to an edge region  104  of the spray chamber  4  and thus past the region  12  for items to be washed. 
     According to one embodiment of the dishwasher  2  illustrated in  FIG. 4 , a further fan in the form of a distributor fan  106  is provided for circulating air in the spray chamber  4  and thus achieving a more uniform drying result. In the illustrated embodiment, a rotor  108  of the distributor fan  106  is arranged in the spray chamber  4 . However, the rotor of the distributor fan may also be arranged outside the spray chamber  4  (not illustrated). 
     A control apparatus  110  is provided for controlling the fan  18  and is illustrated by way of example in  FIG. 4 . The control apparatus  110  can also be provided for controlling further parts of the dishwasher  2 , in particular for controlling one or more parts from amongst the auxiliary fan  76 , distributor fan  106 , closing element  74 ,  90 , and flow-adjustment apparatus  94 . The control apparatus  110  is preferably designed to operate the dishwasher  2  to provide one or more of the following features:
         1. Varying the output of the fan  18  during the drying cycle for items which have been washed. For example, the output can be reduced at the beginning of the drying cycle for items which have been washed, in order to control the release of steam;   2. Operating the fan  18  at intervals;   3. Operating the fan  18  after a final-rinse cycle;   4. Switching on the fan  18  during a final-rinse cycle. This makes it possible to reduce the outlet of steam from the dishwasher  2 .   5. Operating the auxiliary fan  76  with a constant output and operating the fan  18  with a reduced output at the beginning of the drying cycle for items which have been washed. This allows the ratio of the two air streams (air stream  20  through the outlet duct  58 , ambient-air stream  78  through the auxiliary air duct  80 ) to be varied and thus allows the liquid content for each volume of air flowing out of the dishwasher  2  to be varied. These measures reduce the condensation effect outside the dishwasher  2 , without the drying performance being significantly reduced with a comparable cycle time.       

     Parameters which primarily influence the drying result are:
         1. The through-flow rate of the air stream  20  through the spray chamber  4 ;   2. The speed of the air stream  20  along the items  6  to be washed;   3. The achieved final temperatures of the items  6  to be washed, of the rack and of the washing chamber;   4. The optimized final-rinse distribution;   5. The design of the rack in which the items  6  to be washed are or will be arranged, in particular the water-repellent properties of the rack; the thermal capacity of the rack; a minimum number of areas of contact with the items  6  to be washed; choice of rack design such that water cannot flow off the rack  24  and over the items  6  to be washed;   6. The tank  36  which is covered by the tank screen  40 ;   7. The liquid level  112  in the tank  36 , which level is regulated to stay below the tank screen  40  by the control apparatus  110 ; at least one level sensor  114  or at least one level switch may be provided for detecting an actual level value.       

     The invention provides the following advantages in particular:
         1. Drying of the items  6  which have been washed in the dishwasher  2  in an acceptable time which is between 1 min. and 5 mins, and is preferably less than 3 mins;   2. Items  6  which have been washed can be used immediately (“ready to use”) and without an additional waiting time, this being advantageous for the “work flow”;   3. An improved uniform drying result is achieved, in particular for hollow items  6  which have been washed, such as glasses;   4. No steam escapes when the door  8  is opened; the items  6  which have been washed are cooled after the washing programme is complete; the items  6  which have been washed can be stored immediately after the washing programme is complete.       

     The illustrated embodiments implement the combination of a high air through-flow rate with air-guide apparatuses and/or deflectors  23 , so that the drying result is based not only on the dehumidification of the spray-chamber atmosphere, but on air being blown from below through the rack  24  or racks and along the items  6  which have been washed. 
     A person skilled in the art understands that features which are illustrated and explained only in one or some of the described embodiments, such as the distributor fan  106 , the level sensor  114  or the auxiliary fan  76 , can also be combined with any of the other embodiments of the invention.