Patent Application
20080035175
The present application relates to a dishwasher operating method and to a conveyor-type dishwasher with at least one wash zone and a final-rinse zone.
Among the machines used as commercial dishwashers are front-loading machines, rack push-through machines and conveyor-type dishwashers, while under-counter dishwashers are generally used in the domestic sector. The loading of front-loading machines with dish racks in which the dishes are held and the removal of the dish racks from front-loading machines takes place from the front. In the case of rack push-through machine, the dish racks, laden with dirty dishes, are manually pushed into the machine from a feeding side and, after completion of the cleaning program, are manually removed from the machine from a delivery side. Conveyor-type dishwashers, which are distinguished in comparison with the previously mentioned types of dishwasher by a high throughput of items to be washed per unit of time, have at least one spray zone, but usually more than one spray zone, through which the items to be cleaned are automatically conveyed.
In each spray zone of a conveyor-type dishwasher, at least one spray operation can be executed. In the case of conveyor-type dishwashers, it is generally customary for the dishes to be cleaned of major soil in a first spray zone (pre-wash zone) by spraying with a dishwashing detergent solution, while thorough cleaning of the dishes takes place in a subsequent spray zone (wash zone) by renewed spraying with a dishwashing detergent solution. Thereafter follows at least one, mostly two spray zones (rinse zones) in which dishes are sprayed with a rinse aid solution, in order to finally rinse the dishes completely clear of dirt particles and clear of dishwashing detergent solution. The final-rinse operation is generally carried out at temperatures of 80° C. to 85° C., before the dishes are then conveyed into a drying zone for drying.
A conveyor-type dishwasher with four spray zones is described in U.S. Pat. No. 3,598,131. The spray zones are designed as a pre-wash zone, as a wash zone, as a rinse zone and as a final-rinse zone, the items to be cleaned being conveyed continuously through these spray zones one after another in suitable dish racks. The individual zones are separated from one another by suspended flexible “curtains”. In the pre-wash zone, a solution at about 49° C. is sprayed onto the items to be cleaned by means of spray nozzles, in order to remove particles of food from the items to be cleaned. Subsequently, in the wash zone, a mixture of water and dishwashing detergent at about 66° C. and in turn, subsequently in the rinse zone, hot water at temperatures of about 77° C. is sprayed onto the items to be cleaned by means of spray nozzles. To achieve disinfection of the items to be cleaned, in the final-rinse operation, hot water at about 82° C. is sprayed onto the items to be cleaned by means of spray nozzles in the final-rinse zone.
A similar conveyor-type dishwasher, likewise with four spray zones, is known from U.S. Pat. No. 3,789,860. U.S. Pat. No. 3,789,860 describes a pre-wash zone, in which larger particles of food are removed, a subsequent main wash zone for accomplishing effective cleaning of the items to be cleaned, a main-rinse zone and, finally, a final-rinse zone. The temperature in the dishwasher is approximately 46° C. in the first zone and increases zone by zone up to a temperature of approximately 82° C. in the final-rinse zone.
The device of U.S. Pat. No. 4,231,806 is suitable for dishwashers with a number of spray zones and describes means for creating a barrier in the form of a fluid curtain, a fluid curtain preferably being created respectively at the entry and exit of a wash zone and at the entry and exit of a final-rinse zone. The fluid curtain at the entry and exit of the wash zone greatly reduces the escape of vapour from the wash zone.
In the medical sector, U.S. Pat. No. 6,632,291 discloses methods for the washing, rinsing and/or antimicrobial treatment of medical instruments, equipment, transporting carts and animal cages. Washing takes place at temperatures between 30° C. and 80° C., preferably between 35° C. and 40° C., while usually-rinse is carried out at temperatures between 40° C. and 80° C. and a final-rinse is carried out at increased temperatures at approximately 80° C. to 95° C. The antimicrobial treatment is performed with an antimicrobial agent. The method described can be carried out automatically in a wash apparatus which has a number of stations.
U.S. Pat. No. 4,788,992 describes an ultrasonic cleaning method and an apparatus for carrying out ultrasonic cleaning of elongated strip material. After the ultrasonic cleaning, the strip material is sent past dewatering blowers and subsequently past spray nozzles of a number of rinse chambers, before it is heated and dried in a final step.
U.S. Pat. No. 6,354,481 relates to the processing of electronic components and in particular to a compact apparatus for remelting and subsequently cleaning electronic components, in particular BGA components. The cleaning zone has a wash zone and a rinse zone, and a hot-air blower may also be arranged downstream of them, whereby temperatures in the wash zone are at 49° C. to 71° C. and in the rinse zone at 49° C. to 99° C.
U.S. Pat. No. 2,235,885 describes an apparatus for washing (cleaning) and disinfecting glassware, the apparatus having a chamber which can be tightly closed for the spray operation. Within the chamber, positioning carriers are provided for holding the glassware to be cleaned. Also arranged in the chamber, underneath the positioning carriers, are tubes with upwardly directed spraying means and, in the upper part of the chamber, there are tubes with downwardly directed openings, which are fed with hot water, cold water or steam through corresponding supply lines. The feeding in of hot water and steam into the pipework is manually set by means of a hot-water valve, and the feeding in of cold water into the pipework is manually set by means of a cold-water valve.
In the case of washing operation described in U.S. Pat. No. 2,235,885, glassware to be cleaned is first rinsed and disinfected with hot water and steam in the chamber. Subsequently, a cold-water valve is progressively opened and, after the cold-water valve has been opened, the hot-water valve is closed, so that then only cold water is introduced into the chamber and the glassware to be cleaned is chilled with cold water in the final-rinse operation.
In U.S. Pat. No. 4,070,204 a washing method is described which can be carried out in a dishwasher which includes a cleaning chamber into which cold water, hot water or a combination of both can be introduced optionally. The washing method begins with at least one cold pre-wash, which is followed by a hot wash. Subsequently, a cold-water rinse and at least one hot-water final-rinse are carried out.
The development of dishwashers and dishwashing methods, in particular in the commercial sector, is dominated today by the objective of energy and water conservation, which is becoming increasingly important for environmental reasons. Nevertheless, in particular in the case of commercial dishwashers, the throughput, which is the amount of items cleaned per unit of time, and the washing quality should not be deteriorated. The working conditions of the operator of a dishwasher are also considerably impaired in the region of the dishwasher by vapours which escape, with the result that an improvement in this area is also desirable.
Furthermore, apart from thorough cleaning, disinfection of the items to be cleaned should also be carried out. In the field of dishwasher technology, disinfection means killing micro-organisms at a level that is neither harmful to health nor impairs the quality of food. In the case of some wash methods, disinfection is achieved by the use of chemical disinfection components, but this has disadvantages from aspects concerning the environment and safety at work. Disinfection by adequately intense heating of the items to be cleaned is also known.
It would be desirable to provide an improved operating method and an improved conveyor-type dishwasher of the type as indicated which—while maintaining high cleaning quality—have in particular low energy and water consumption, are sufficiently productive and can be used without reservations from aspects concerning the environment and safety at work.
A conveyor-type dishwasher and related methods may be provided with one or more features to assist in low energy and/or water consumption, including one or more of (i) executing final-rinse of items with a consumption of final-rinse liquid that is 3.5 l/min or less; (ii) executing final-rinse of items with a consumption of final-rinse liquid of 3 l/m2 movement of the horizontal take-up plane of a dish carrier or less; (iii) executing final-rinse of items with one or more side-originating final-rinse liquid spray jets in combination with top-originating final-rinse liquid spray jets and bottom-originating final-rinse liquid spray jets; (iv) prior to a final rinsing step executing a cleaning operation or a subsequent hot post wash and/or a rinsing step using filtered and/or regenerated washing or rinsing solution that is produced from a used washing or rinsing solution in dependence on a contamination dependent or time dependent control signal; (v) subsequent to a final-rinse operation, passing items through a cold-water curtain; (vi) between a wash operation and a final-rinse operation, subjecting items to the action of steam; and (vii) after a wash operation, providing a hot post-wash operation using hot post-wash liquid that has a higher temperature than a final-rinse liquid.
One proposed method comprises at least one wash operation, that is to say spraying with a dishwashing detergent solution for thoroughly cleaning remains of food from the items to be cleaned, a so-called hot post-wash, and at least one final-rinse (German: Klarspülen), preferably with a rinse aid solution for rinsing off all dirt particles and dishwashing detergent solution from the items to be cleaned. Dishes, cutlery, forks, spoons, knifes and trays are regarded as items to be cleaned. Dishwashing detergent solution is water enriched with a dishwashing detergent, whereby the addition of the dishwashing detergent promotes thorough removal of remains of food from the items to be cleaned and counteracts renewed soiling of the items by the dishwashing detergent solution. The final-rinse aid solution is generally clean water mixed with a rinse aid, whereby the interfacial tension of the rinse aid solution is reduced by the rinse aid, to that optimum wetting of the cleaned items is achieved.
An important idea in this respect is that, in the case of conveyor-type dishwashers, high-temperature dishwashing operations, that is to say wash or rinse operations, are to be carried out in a central region of the machine, whereas low-temperature wash or rinse operations are to be carried out in the region of the entry or exit of the machine. This produces a temperature profile which drops from a maximum value in a central region towards the outer regions. By contrast, in the case of the previously known conveyor-type dishwashers, the temperature profile increases to the maximum value in the region of the exit, since disinfection of the items to be washed only takes place in the final-rinse operation (German: Klarspülen) at temperatures of 80° C. to 85° C. In the prior art, the preceding wash operations are carried out at temperatures around or below 70° C.
The novel temperatures profile has the effect of keeping energy losses low, since an escape of heat and vapour from the central region is suppressed by the two adjacent regions, and condensing of the vapour in the cooler outer regions is promoted. The heat of condensation can therefore still be used within the conveyor-type dishwasher.
Accordingly, hot post-wash may be performed with a high water temperature and, after that, final rinsing (German: Klarspülen) may be performed with a lower water temperature. The high water temperature during the hot post-wash operation is preferably higher than 70° C., so that a disinfection of the items to be cleaned is achieved, and the lower water temperature during the final-rinse operation is preferably lower than 65° C. and more preferably lower than 60° C., so that condensing is promoted by the temperature reduction. The hot post-wash operation may be carried out according to choice as a wash operation, that is with a dishwashing detergent solution, or as a final-rinse operation, that is with a rinse aid solution.
Furthermore, the items to be cleaned may be subjected to a significantly greater amount of wash solution during the hot post-wash operation than during the subsequent final-rinse operation, with the result that in the hot post-wash step a high level of heat application to the dishes is also realized by means of a high overall thermal capacity of the solution to which they are subjected. In particular, a hot post-wash solution throughput in the range between 5 and 30 l/min, preferably between 10 and 20 l/min, is provided during the hot post-wash operation, while the consumption of final-rinse aid solution is intended to be significantly less than half of that (preferably 2 to 3 l/min).
Also in the case of dishwashers with only one cleaning chamber, the heat of condensation, which is released in particular during the final-rinse operation with a lower water temperature, can be used. Furthermore, the escape of steam when the dishwasher is opened is reduced by the preceding condensation, so that the method is also advantageous for such dishwashers.
The final-rinse operation may advantageously be carried out at a temperature of the rinse aid solution in the range between 25° C. and 65° C., preferably between 25° C. and 60° C. In this temperature range, the temperature reduction in comparison with the preceding hot post-wash operation may be great enough to promote condensation, but excessive cooling of the items to be washed may also be prevented. Excessive cooling of the dishes and wasting of clean water may also be avoided if the final-rinse operation is executed at least partly in a spray mist. Furthermore, the finely distributed droplets of the spray mist can promote condensation of the vapour. The escape of vapour from the conveyor-type dishwasher may be reduced by the items to be cleaned passing through a cold-water curtain, in particular in the form of a cold-water spray mist, following the final-rinse operation.
If the hot post-wash operation is performed directly before the final-rinse operation at a water temperature in the range between 80° C. and 90° C., in particular at 85° C., only short contact times are necessary to achieve adequate disinfection of the items to be cleaned, on account of the high temperature level. Preferably, a wash operation at a water temperature of 65° C. is carried out before the hot post-wash operation, in order to get an effective cleaning of the dishes with relatively short contact times.
At least one rinse operation can also be performed under steam. If the items to be cleaned are subjected to the action of steam between the hot post-wash operation and the final-rinse operation, the level of heat transfer into the items to be cleaned is increased, and accordingly disinfection of the items is assisted. The introduction of steam also has the advantageous effect that is keeps down the evaporation losses, in particular during the wash operation and the hot post-wash operation.
Filtered and/or regenerated final-rinse aid solution may be used for executing the hot post-wash and/or a wash operation. Using already used final-rinse aid solution also for the hot post-wash and/or for a wash operation successfully reduces the amount of clean water required. Filtering the final-rinse aid solution which was already used and/or regenerating it with clean water has the effect of keeping down the consumption of clean water while maintaining the cleanness of the dishwashing detergent solution or final-rinse aid solution, in particular whenever the filtering and/or regeneration is carried out in dependence on the turbidity of the solution. This can reduce or prevent re-soiling of the items to be cleaned.
A further feature is to reduce the water consumption for the final-rinse operation, in comparison with the prior art, by a differentiated nozzle arrangement. Whereas in the case of the nozzle arrangements previously used in the final-rinse operation, with only upper and lower nozzles, a relatively strong spray jet of the individual nozzles was required, since concealed surface areas of the items to be cleaned were only reached by deflected spray jets, an advantageous nozzle arrangement with greater differentiation of the spray directions allows a large part of the surface areas of the items to be cleaned to be reached directly. Therefore, the final-rinse operation can be carried out with reduced water throughput. In particular in combination with the hot post-wash operation described above, a low water throughput during the final-rinse operation at lower temperatures has the advantageous effect that cooling of the items to be cleaned during the final-rinse operation is minimized as much as possible. This may even allows drying with blower air of a lower temperature (<50° C.) to be carried out after the final-rinse operation, since the still elevated temperature of the items assists drying of them.
Specifically, the final-rinse operation may be executed with the items to be cleaned being subjected to the action of final-rinse aid solution from at least three sides of a final-rinse zone, to be precise from the floor and from the ceiling surface and from at least one side wall. A large part of the surface areas of the items to be cleaned is then reached directly. Advantageously, the nozzles may be arranged on the side wall/side walls in such a way that the feeding of the final-rinse aid solution from the side walls takes place in each case at four positions in the central height region of the final-rinse zone, two of which in particular are positioned respectively close to each other. The nozzles on the floor and on the ceiling surface may be arranged in such a way that the feeding of the final-rinse aid solution from the floor and from the ceiling surface proceeds from five points of the floor and four positions of the ceiling surface of the final-rinse zone, which are respectively arranged essentially equidistant from one another and from the side walls. In order to achieve reduced use of water during rinsing, the final-rinse operation may be executed in spray mist with a consumption of final-rinse aid solution of 3.5 l/min or less, in particular of 2 l/min-3 l/min for a rinse capacity of typically 2500-5000 plates per hour or a comparable throughput of other items to be cleaned.
With regard to the apparatus, a conveyor-type dishwasher, in particular a multi-tank conveyor-type dishwasher, comprising several spray zones; a conveying device for conveying items to be cleaned through the spray zones; water feeds assigned to the spray zones for feeding dishwashing detergent solution and final-rinse aid solution respectively and for subjecting the items to be cleaned to them; and also means assigned to at least some of the water feeds for setting the temperature of the respective wash or rinse solution.
The conveying device for conveying items to be cleaned may take different forms; it may be designed as a dish conveyor belt, chains, or latching bars. The means for temperature setting may be designed either as controllable heaters in a reservoir of the spray solution, or else they may be formed simply by the systems of tubes which lead to a reservoir of the rinse solution. The term spray solution refers both to dishwashing detergent solution and to a final-rinse aid solution.
A conveyor-type dishwasher according to one aspect is characterised in that means are provided for setting the water temperature in a hot rinse operation (hot post-wash operation) to a first temperature value, in particular more than 70° C., and for setting the water temperature of a subsequent final-rinse operation to a lower value, in particular less than 65° C. or preferably less than 60° C.
According to a further apparatus-related aspect, a conveyor-type dishwasher is characterised in that a final-rinse zone is provided which has final-rinse water nozzles on the floor and on the ceiling surface and additional final-rinse water nozzles on at least one side wall.
Referring now to
In the conveying direction 12 of the items to be cleaned, the four spray zones 4, 6, 8, 10 are designed as a pre-wash zone 4 (pre-cleaning spray zone), a main wash zone 6 (main cleaning spray zone), a hot post-wash zone 8 (or hot cleaning spray zone, which may also be referred to in the art as an initial rinse zone) and a final-rinse zone 10 (German: Klarspülzone). In the drying zone 14, blower air 16 is sent by a blower 18 into the drying zone 14, whereby drying of items to be cleaned is achieved.
In the pre-wash zone 4, large remains of food are removed from the items to be cleaned by washing with dishwashing detergent solution. Dishwashing detergent solution is fed from a pre-wash reservoir 20 by means of a pump not shown and via corresponding lines to upper pre-wash nozzles 22 and lower pre-wash nozzles 24 (which may also be formed as simple openings in the lines). The upper pre-wash nozzles 22 are arranged in a downwardly directed manner in an upper part of the pre-wash zone 4 and the lower pre-wash nozzles 24 are arranged upwardly directed manner in the lower part of the pre-wash zone 4, so that dishwashing detergent solution is sprayed onto the items to be cleaned that are located in the pre-wash zone 4 from above and from below by the pre-wash nozzles 22, 24.
The pre-wash nozzles 22, 24 and further nozzles 30, 32, 38, 40, 46, 48 of the downstream spray zones 6, 8, 10 may be distributed or can be moved over the entire width, measured transversely to the conveying direction 12, of the respective spray zone 4, 6, 8, 10, so that over the entire width, over which items to be cleaned are conveyed through the conveyor-type dishwasher, the items to be cleaned can be sprayed with the corresponding liquid from the nozzles 22, 24, 30, 32, 38, 40, 46, 48. The nozzles may be fixed in place in the respective spray zone 4, 6, 8, 10, or else some or all of them may be attached to rotating or otherwise movable wash tubes. Furthermore, an overflow 26 may be provided at the pre-wash reservoir 20, allowing excess dishwashing detergent solution to be transferred from the pre-wash reservoir 20 into a waste-water line.
In the main wash zone 6, dishwashing detergent solution is fed by means of a pump not shown from a main wash reservoir 28 with an (optional) heating device 29 via corresponding lines to upper main wash nozzles 30 and to lower main wash nozzles 32. The upper main wash nozzles 30 are arranged in a downwardly directed manner in an upper part of the main wash zone 6 and the lower main wash nozzles 32 are arranged in an upwardly directed manner in a lower part of the main wash zone 6, so that dishwashing detergent solution is sprayed onto the items to be washed in the main wash zone 6 from above and from below by the main wash nozzles 30, 32.
For rinsing the items to be cleaned in the hot post-wash zone 8, in the embodiment shown, a final-rinse liquid or solution is fed from a heatable hot wash reservoir 34 by means of a pump 36 to upper hot post-wash nozzles 38 and to lower hot post-wash nozzles 40, by means of which spraying of the items to be cleaned takes place from above and from below in the hot post-wash zone 8. In the hot post-wash reservoir 34, which can be heated by means of a heating device 41, a high temperature of the hot solution may be set such that adequate disinfection of the items to be cleaned is achieved by heating the items to be cleaned in the hot spray operation by spraying the items to be cleaned with the hot solution.
The final rinsing in the final spray zone 10 is carried out with a final-rinse liquid that may include a rinse agent/aid that can be fed directly from the water supply line from a container 42 (heated or unheated) by means of a pump 44 (or by mains water line pressure) to upper and lower final-rinse nozzles, in particular to upper final-rinse nozzles 46 and lower final-rinse nozzles 48, which may be formed as simple openings. Also arranged on the side walls of the final-rinse zone are lateral final-rinse nozzles 50, with which lateral spraying of the items to be cleaned with final-rinse solution can be carried out. As shown, the lateral final-rinse nozzles 50 may be located upstream of the lower and upper final-rinse nozzles. Where spray jets from the lateral nozzles are angled with or against the conveying direction 12, such offsetting may aid in limiting or preventing the spray jets of final-rinse liquid from spraying out of the final-rinse zone (e.g., into the dryer zone) and/or out of the machine entirely. An arrangement of the final-rinse nozzles provided by way of example is shown in
Furthermore, spray curtains 51 may be provided in the entry and exit regions of the series of the spray zones and between the individual spray zones 4, 6, 8, 10 achieving a subdivision of the different spray zones 4, 6, 8, 10 and a reduction in the transfer of vapours between the individual spray zones. The spray curtains 51 may be designed for example in form of suspended, 10-15 cm wide sheets, which screen off the passages between the individual spray zones.
A blower 54 in the upper part of the conveyor-type dishwasher 2 sucks vapours upwards in the direction of an outlet 52, said vapours being passed through a heat exchanger 56 before they reach the extractor 52. Cold tap water is introduced via a corresponding supply line 57 into the heat exchanger 56, in which it is passed in a known way through cooling coils 58, in order to bring about a condensation of the moisture from the vapours which are flowing around the cooling coils. The transferred heat and the heat of condensation of the vapours is used for pre-heating the tap water. Such a heat exchanger for conveyor-type dishwashers is described for example in U.S. Pat. No. 3,598,131.
The tap water preheated in the heat exchanger 56 is passed via a system of lines 60, 62 and a buffer storage container 64 into the final-rinse container 42. Furthermore, a rinse aid/agent is added to the clean water to form the final rinsing aid solution. Accordingly, a clean final-rinse liquid or solution, formed from clean water and rinse aid, is used in the final-rinse zone 10. Once it has been used in the final-rinse zone 10, the final-rinse solution is guided into the heatable hot post-wash zone 8. Some or all of the hot solution used in the hot post-wash zone 8 is guided via baffles 66 into the heatable main wash reservoir 28. A dishwashing detergent is added to the solution in the main wash reservoir 28 to form a dishwashing detergent solution. A first part of the dishwashing detergent solution used in the main wash zone 6 is returned to the main wash reservoir 28, which may be assisted by baffles 68, and a second part is passed via the overflow line 70 into the pre-wash reservoir 20.
The pre-wash reservoir 20, the main wash reservoir 28, the hot post-wash reservoir 34 and the final-rinse container 42 are designed either as upwardly open reservoirs or else as tanks with an opening or a supply line, through which a solution already used in one of the spray zones 4, 6, 8, 10 or else clean water can be fed into the reservoir, the container or the tank. Respective lquids in reservoirs 20, 28 and 34 will typically be recirculated. Furthermore, the four reservoirs, containers or tanks 20, 28, 34, 42 respectively have a discharge line, through which solution can be fed, for example to the associated nozzles.
Furthermore, a bypass supply line 72 is provided from the hot post-wash reservoir 34 into the pre-wash reservoir 20, allowing hot solution to be fed from the hot post-wash reservoir 34 directly into the pre-wash reservoir 20 by means of the pump 36 when a valve 74, which may be designed for example as a solenoid valve, is opened. This may be required in particular when the conveyor-type dishwasher 2 is started for the first time, or if great contamination of the dishwashing detergent solution in the pre-wash reservoir 20 is detected, and consequently regeneration of the dishwashing detergent solution is required.
The main wash reservoir 28 can also be filled with clean water, preferably with warm clean water, directly via a main cleaning supply line 76 by opening a valve 78, which is preferably designed as a solenoid valve. Such filling via the main cleaning supply line 76 may likewise be required when the conveyor-type dishwasher 2 is started for the first time, or else if great contamination of the dishwashing detergent solution in the main cleaning reservoir 28 is detected, and consequently regeneration of the dishwashing detergent solution in the main wash reservoir 28 is required.
The temperature of the final-rinse liquid in the final-rinse zone 10 may be reduced considerably in comparison with the temperature of the hot solution in the hot post-wash zone 8. Accordingly, no heating is generally necessary in the final-rinse container 42, but a heating apparatus may be provided, as is shown by a way of example in
The items to be cleaned leave the final-rinse zone 10 in a still hot state, so that drying with unheated circulating air is sufficient in the drying zone 14. Accordingly, heating is not required for the final-rinse zone 10 or for the drying zone 14; in alternative configuration, however, the drying zone and the final-rinse zone may also be heated.
The temperature in the hot post-wash reservoir 34 may be set by a heating apparatus between 70° C. and 90° C., preferably at 85° C. The temperature of the final-rinse aid solution in the final-rinse container 42 lies within a relatively large range, since it depends on whether the clean incoming water used is warm or cold, whether the clean water is passed through the heat exchanger 56 before it is introduced into the final-rinse container 42 and furthermore, whether a heating apparatus is provided in the final-rinse container 42. The lower limit of the temperature range for the final-rinse aid solution in the final-rinse container 42 is that of unheated tap water and the upper limit may be 65° C. or preferably 60° C.
The temperature of the dishwashing detergent solution in the heatable main wash reservoir 28 may be about 65° C. or higher. The relatively high temperature allows the flow rate and the pressure with which the dishwashing detergent solution is sprayed onto the items to be cleaned to be kept comparatively low, without causing any deterioration of the dishwashing result.
Since comparatively little clean water is fed into the washing circuit in the case of the conveyor-type dishwasher 2 shown, there is consequently also a reduction in the amount of dishwashing detergent solution that is fed from the main wash zone 6 into the pre-wash reservoir 20 via the overflow line 70. The pre-wash reservoir 20 is not heatable, and, on account of the reduced feeding of dishwashing detergent solution of a higher temperature from the main wash zone 6, a temperature which is considerably lower than the temperature in the main wash reservoir 28 occurs in the pre-wash reservoir 20. It lies between 35° C. and 55° C., preferably between 40° C. and 50° C.
A similar effect as in the final-rinse zone 10 is achieved in the pre-wash zone 4, that is to say that the reduced temperature in comparison with the main wash zone 6 has the effect that vapours which enter the pre-wash zone 4 from the main wash zone 6 are condensed, and consequently the heat of condensation remains within the conveyor-type dishwasher 2 and the escape of vapours into the outside area is suppressed.
In
According to the embodiment shown in
The filter 84 allows the hot post-wash operation to be carried out with a relatively clean hot solution, also with the result that relatively clean water is passed on to the preceding wash zones 6, 4 and counteracts a contamination of the dishwashing detergent solution there. A particularly suitable filter is designed for the purpose of filtering out particles of more than 300 μm, preferably more than 150 μm; a configuration with a still smaller pore width may be advisable.
In alternatives to the configuration shown here, a filter may either be provided only in or at the pre-wash reservoir or only in or at the main wash reservoir or only in or at the hot post-wash zone. The filter solutions mentioned serve to get a reduction of the extremely small particles (so-called specks) before the items to be cleaned run through the clean-water final-rinse zone. Such extremely small particles may be entrained by a dishwashing detergent solution or by a rinse solution, which is contaminated (even if only slightly), onto the surfaces of the items to be cleaned. The use of filtered rinse solution in the hot post-wash operation described above allows a significant increase in its efficiency, which depends on the contamination of the wash tank(s) and the transfer of dirt from the wash tank/wash tanks into the pre-wash tank.
In preferred configurations, the filter or filters are designed as cyclone, membrane or piggyback filters, of a structural type of design that is essentially known.
Furthermore, a turbidity sensor 98 is provided in the main wash reservoir 28, a turbidity sensor 99 is provide in the hot post-wash reservoir 34 and a turbidity sensor 100 is provided in the pre-wash reservoir 20, allowing the cleanness of the dishwashing detergent solution to be checked. The amount of dishwashing detergent solution that is fed through the bypass lines 90, 94 is controlled in dependence on the signal of the turbidity sensors 98, 100. (Configurations with only one turbidity sensor are also possible).
Also in
According to the embodiment which is shown in
The upper final-rinse nozzles 146 are arranged in a row on an upper supply pipe 158 and the lower final-rinse nozzles 148 are arranged in a row on a lower supply pipe 160, via which they are supplied with final-rinse solution, the upper supply pipe and lower supply pipe running essentially horizontally and transversely to the conveying direction 12. The lateral final-rinse nozzles 150, 152 are also correspondingly arranged in a row on a left hand supply pipe 162 or a right-hand supply pipe 164, respectively, via which they are supplied with final-rinse solution, the left-hand supply pipe 162 and the right-hand supply pipe 164 extending essentially vertically and transversely to the conveying direction 12.
While in
A correspondingly modified configuration of the final-rinse nozzle arrangement is represented in
In addition or as an alternative, it may be provided that the lateral final-rinse nozzles 150, 152 are alternately turned upwards and downwards out of the horizontal alignment and that the upper and lower final-rinse nozzles 146, 148 are alternately turned to the left and to the right out of the vertical alignment. For example, upper lateral nozzle 150b′ could be oriented to direct its spray jet upward from horizontal as reflected by line 300 and lower lateral nozzle 150a′ could be oriented to direct its spray jet downward from horizontal as reflected by line 302.
The direction of a spray jet emanating from a nozzle is generally determined by a central axis of the spray jet that is output by the nozzle, regardless of whether the spray jet is in the form of a fane, cone, stream or other configuration.
Nozzles with relatively low throughput, for example with a respective throughput of 0.16 l/min at 0.5 bar, may be used as final-rinse nozzles 146, 148, 150, 152. Tests showed that, in the case of the arrangements shown in
The final-rinse nozzles of the final-rinse zone are advantageously designed in such a way that they produce an atomization of the solution into finely distributed droplets, whereby full-coverage rinsing of the items to be cleaned can be achieved with a low delivery rate of solution. In particular in the final-rinse zone, a fine atomization of the rinsing aid solution is also advantageous because the finely distributed droplets promote condensing of the vapours. By providing the lateral nozzles in addition to the typical upper and lower nozzles, a more effective distribution of final-rinse liquid onto items to be cleaned can be obtained, facilitating a reduction in total consumption of final-rinse liquid.
The invention is not restricted to the embodiments shown by way of example in
The conveyor-type dishwasher shown in
A carrier for accommodating items to be cleaned, in particular dishes, may be designed for example as a dish conveying belt in the form of an endless belt, which has a suitable structure, so that is can be loaded with individual items to be cleaned and the individual items can then be held in the most optimum possible rinsing position, in which the largest possible surface of the individual items is reached by the dishwashing detergent solution and the final-rinse aid solution. The conveyor-type dishwasher may accordingly be designed as a conveyor-belt dishwasher, in which items to be cleaned are automatically conveyed on the dish conveying belt through the various rinse zone and through a downstream drying zone.
Furthermore, the conveyor-type dishwasher may also be designed as a rack-conveying dishwasher. In the case of such an embodiment, dish racks are provided which can be loaded with individual items to be cleaned and in which the individual items to be cleaned can be held in the most optimum possible rinse position. Furthermore, a rack-conveying dishwasher has conveying means for conveying the dish racks through the various spray zones 4, 6, 8, 10 and the drying zone 14. Chains, latching bars or conveyor belts are known types of conveying means.
The conveyor-type dishwasher shown may also be designed as a multi-track dishwasher with a number of parallel-running conveying tracks. In the case of dishwashers of a small overall size and low dishwashing capacity, the pushing through of dishes, which are for example sorted into appropriate dish racks, may also take place manually.
Furthermore, the number and design of the spray zones is not restricted to the four spray zones 4, 6, 8, 10 that are shown, but may be adapted to the corresponding conditions. A drying zone 14 after the final-rinse zone 10 is not absolutely necessary.
As described in detail in the foregoing part, the escape of vapours from the machine is reduced and condensation within the machine is promoted by the lower temperature of the solution in the final rinse zone 10 and in the pre-wash zone 4 in comparison with the temperature in the main wash zone 6 and the hot post-wash zone 8. This effect may be further increased at the outer regions of the series of spray zones 4, 6, 8, 10 by a cold water curtain being created at the entry region 80 of the pre-wash zone 4 and/or at the exit region 82 of the final-rinse zone 10.
The cold water curtain may be formed for example by suitable nozzles or openings which can be supplied with cold water and which are arranged over the width of the entry region 80 and/or the exit region 82 of the conveyor-type dishwasher 2, or by an edge extending over this width and over which cold water can flow.
Shown in
To create a cold water curtain 166 in the entry region 80, the nozzles 164 can be supplied with cold water via a corresponding supply line 172 by opening a valve 168 of a cold water connection 170. A cold water connection 174 and a supply line 176 are also provided for nozzles 165 for the cold water curtain 167 in the exit region 82, so that cold water can be fed to the nozzles 165 by opening a valve 178.
A filter, as is shown in
A filter arrangement such as that shown in
For the hot post-wash reservoir 34, a regenerating arrangement may be designed in a way similar to the arrangement shown in
In
The arrangement of the final-rinse nozzles, by means of which the items to be cleaned are subjected to a solution from at least three sides, is not restricted to the embodiment shown in
Slight offsetting of the individual final-rinse nozzles 146, 148, 150, 152 in relation to one another in or transversely to the conveying direction 12 may also be provided. This may be realized by correspondingly shaped supply pipes 158, 160, 162, 164 and/or by additional supply lines to the individual final-rinse nozzles 146, 148, 150, 152.
In
The steam-subjecting zone 180 is arranged downstream of a hot post-wash zone and upstream of a final-rinse zone in the conveying direction of the items to be cleaned that is denoted by an arrow. A nozzle surround 182 is provided in the steam-subjecting zone 180. The nozzle surround 182 has a frame 184 with a through-opening 186, through which the items to be cleaned can be sent. On the inside of the frame 184, a multiplicity of inwardly directed steam nozzles 188 are arranged on all the peripheral sides. Arranged in the frame is a system of lines (not shown), which is in connection with a supply line via which steam is fed to the steam nozzles 188. Accordingly, steam is directed onto the items to be cleaned from all peripheral sides, so that largely the entire surface of the items to be cleaned is effectively subjected to steam.
In order to suppress the escape of steam into the neighbouring rinse zones, curtains 190, which are designed as an arrangement of suspended sheets, are respectively fitted between these zones and the steam-subjecting zone 180. The housing wall 192 of the steam-subjecting zone 180 may have an additional thermal insulation, so that the lowest possible heat losses to the outside occur. The zone 180 may be arranged such that the entire zone is filled with steam at a pressure higher than atmospheric. The curtains 190 reduce heat transfer into the neighbouring spray zones.
This concerns the turbidity sensors 98 and 100 in the main wash reservoir 28 and the pre wash reservoir 20, respectively, which may be based on an optical measuring principle, known per se, and produce a signal representing the degree of contamination of the respective wash solution in the reservoirs mentioned. The turbidity sensors 98, 100 are respectively connected to an input of a two-channel turbidity evaluation unit 192. The turbidity evaluation unit 192 is essentially constructed identically in the two channels 192 A and 192 B and each comprises a threshold-value memory 194 A and 194 B, respectively, for preprogrammed turbidity threshold values for the wash reservoirs 28 and 20, respectively, and a threshold-value discriminator 196 A and 196 B, respectively, both inputs of which are connected to the respectively associated turbidity sensor 98 or 100 and the respective threshold-value memory 194 A and 194 B.
In the present example, it is assumed that the threshold-value discriminators 196 A, 196 B are of a multistage configuration and also that a number of threshold values are respectively stored in the associated threshold-value memories 194 A, 194 B. In a corresponding way, here each threshold-value discriminator emits not only a digital signal (yes/no), but a quasi-analog signal, representing the exceeding of one or more threshold values.
On the output side, the evaluation device 192 is connected to a control device 198 which has four control sections 198 A1 to 198 B2. The control section 198 Al is designed as a valve controller for controlling the valve 78 for supplying clean water into the main wash reservoir 28. The control section 198 A2 is designed as a pump controller for controlling the pump 92 in the bypass 90 for passing wash solution from the main wash reservoir 28 through the filter arrangement 88. The control section 198 B1 is designed as a pump controller for controlling the pump 96 in the bypass 94 for passing wash solution from the pre-wash reservoir 20 through via the filter arrangement 88, and the control section 198 B2 is designed as a valve controller for controlling the valve 98 in the bypass 72 for directly passing wash solution from the hot post-wash reservoir 34 into the pre-wash reservoir 20. On account of the signal characteristics mentioned of the output signals of the threshold-value discriminators 196 A, 196 B, in each case an alternative or joint operation of the control sections 198 A1, 198 A2 and 198 B1, 198 B2, respectively, is possible, in order to control filtering and/or regeneration in dependence on the degree of contamination of the respective wash solution in an expedient way. For details in this respect, reference is made to the description provided further above.
As an alternative to use of turbidity sensors or other contamination measurement devices, the control system of
It goes without saying that the evaluation and control devices 192, 198 described can be constructed from commercially available hardware and software components in a way that can easily be appreciated by a person skilled in the art and according to the requirements of commercial use, and that the graphic representation and the description given here is intended only to show the essential functionality, but not to show details of the computational and logical signal processing.
In any embodiments of the invention, the final-rinse liquid used in the final-rinse zone 10 can be clean water or a mixture of water and rinse aid. The diagram of
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 030 015.1 | Jun 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US05/18895 | 5/31/2005 | WO | 12/15/2006 |
