The invention also relates to an automatic washing apparats for washing units and comprising a wash zone, a rinse zone, a wash conveyor for conveying the units to be washed through the washing apparats, feeding means for feeding washing solution to the wash zone and nozzles for spraying rinsing water to the rinse zone, and a control unit for controlling the washing apparats, the control unit being arrange to control the wash conveyor to move in cycles.

In restaurants, hotels, hospitals and other large establishments, a great number of dishes are washed daily. Nowadays this is carried out on automatic wash lines. For washing, the dishes are usually placed in racks which are placed onto a conveyor which conveys the racks and dishes through the wash line. On the wash line, prewash is usually carried out for rinsing off most of the food remains, followed by the main wash and then rins- ing. The use of such a wash line consumes energy, water and detergents, which constitute the operating costs of the main wash line. Usually, when a wash line is operated, dish racks cannot be fed into it continuously to make them immediately follow each other continuously through the wash line. Simi- larly, during use, the wash line may operate without any rack to be washed being located on the wash line. Such idle run points and times cause unnec- essary costs up to over FIM 100,000 annually in a kitchen washing 500 stan- dard-sied racks daily. Finnish publication print 96661 discloses a method and a washing apparats in which the operation of the wash line is interrupted im- mediately if no new rack follows a rack arriving at the wash line, and washing is not restarted until a new rack arrives from the inlet of the wash line and comes into contact with the previous rack. This has been implemented by pro- viding the inlet of the wash line with a sensor which senses if a rack follows the current rack, and in lack thereof, stops the conveyor which extends over the length of the wash line, and the feed of water and detergent. In some cases the wash line does not have to be completely stoppe, but savings in

costs are, however, desirable.

Washing apparatuses are also known in which the speed of move- ment of the conveyor can be controlled. This means that the speed of the con- veyor is slowed down, which results in a better washing result, but simultane- ously the consumption of detergents and water per item to be washed in- creases significantly. Furthermore, a complex and expensive driving engine which is susceptible to soiling has to be used to enable changing the speed of the conveyor. A washing apparats is also known, in which a conveyor is op- erated in cycles for example such that the conveyor moves for a cycle of about 1.5 seconds and the conveyor is then stopped for about 0.5 seconds. This way the washing result is also improved compare with a situation in which the conveyor would operate continuously, but also in this case the consump- tion of detergents and water per unit to be washed rises considerably.

The object of the present invention is to provide a method and a dish washing apparats which save costs significantly without the washing apparats having to be completely stoppe. The method of the invention is characterized in that the washing apparats is operated in cycles so that dur- ing an operating cycle, washing solution and rinsing water are fed to the washing apparats and the units to be washed are conveyed in the direction of movement of the washing apparats and that during a break cycle the movement of the units is stopped and the feed of rinsing water to the rinse zone is interrupted.

The washing apparats of the invention is characterized by com- prising a timer for controlling the operation of the washing apparats so that the washing apparats is operated in cycles in such a way that it comprises an operating cycle, during which the units to be washed are conveyed forward on the wash conveyor, and simultaneously washing solution is fed to the wash zone and, similarly, rinsing water to the rinse zone, and a break cycle, during which the wash conveyor is switched off and the feed of rinsing water to the rinse zone is interrupted.

It is an essential idea of the invention that the washing apparats is controlled in cycles, whereby it comprises an operating cycle during which the conveyor of the washing apparats moves at its normal speed, and washing solutions and rinsing water are fed to the washing apparats, and, corre- spondingly, a break cycle, during which the conveyor is stopped and the feed of rinsing water to the rinse zone is interrupted. Another essential idea of the

invention is that the operating cycle is so dimensioned that during the operat- ing cycle, the transfer distance of a unit to be washed, such as a rack, is the length of a rack or a multiple thereof. According to a preferred embodiment of the invention, when no new rack immediately follows a rack which has entered the wash line, the conveyor of the washing apparats is stopped and the en- tire wash is interrupted until a new rack arrives at the inlet of the wash line. In this case the cost of almost 60%, caused by the fresh rinsing water, decreases significantly, as do the entire operating costs of the washing apparats. It is an avantage of the invention that merely by stopping the conveyor and the feed of fresh water considerable savings are achieved and simultaneously for ex- ample the disturbing variation in noise level some times caused by starting and stopping the entire apparats can be avoided. In addition, in the prewash and wash, the used solution in the tank is only circulated without being puri- fied, whereby the actual operating costs of the pumps are minor compare with other costs.

The invention will be described in greater detail in the attache drawing, wherein Figure 1 schematically shows a washing apparats of the invention, Figure 2 schematically shows the avantage achieved by the in- vention in the operating costs of a washing apparats.

Figure 1 is a schematic side view of the automatic washing appa- ratus of the invention. The washing apparats comprises a wash conveyor 1 for conveying racks through the washing apparats. Furthermore, the washing apparats may comprise a prewash zone 2, followed by a main wash zone 3 and rinse zone 4. The washing apparats is preceded by a feed conveyor 5 for conveying dish racks, and, similarly, a discharge conveyor 6 at the outlet end. The washing apparats further comprises schematically shown tanks 7 and 8 for storing washing solution for prewash and main wash, respectively, and from which it is circulated by means of pumps 9 and 10 to both zones separately by means of nozzles 11 and 12 therein, to be sprayed on the dishes to be washed. It also comprises a tank 13 for collecting the water used for rinsing in the rinse zone 4 and transferring the used water to the wash zone. The rinse zone comprises nozzles 14 for feeding fresh water by means of a pump 15 to effect rinsing. The washing apparats further comprises tanks 16 and 17 for feeding necessary washing chemicals to be mixed with the washing solutions of the prewash and wash zones. The washing apparats

further comprises a sensor 18 at the inlet of the prewash zone for identifying a rack arriving at the prewash zone 2 and also for detecting if a new rack does not immediately follow the rack that bypassed. The sensor 18 is coupled to a control unit 19 which also comprises a timer 20 for controlling the washing apparats. The wash conveyor 1 only has one speed for conveying the units to be washed, such as racks 21, containing dishes, through the washing appa- ratus, whereby the wash conveyor 1 can be operated by a structurally simple, and hence inexpensive, motor, and, correspondingly, the section required for controlling the engine in the control unit 19 can be simpler, more inexpensive and operationally more reliable.

The timer 20 is used to control the wash conveyor 1 and the feed of rinsing water in the washing apparats. In this case, when a rack enters the washing apparats, the wash conveyor 1 moves at quite a high speed, for ex- ample 200 racks per hour. However, the racks 21 or other units in the washing apparats are conveyed forward in cycles, so that during one operating cycle the transfer equals the length of one rack or unit, or a multiple thereof. Simul- taneously, the rack 21 is stopped for example for a time corresponding to the length of the operating cycle, whereby the conveyor 1 and feed of rinsing wa- ter in the washing apparats are stopped for the time of the break cycle. The feed of rinsing water during the break cycle can be stopped simply by stopping the pump 15 which feeds the rinsing water. However, most advantageously the pump 15 is allowed to run the whole time and the apparats is provided with valves 22 and 23 for stopping the flow of the water to be fed. In this case the pump 15 is not subjected to stress caused by stops and starts. However, the cost caused by extensive consumption of water can be avoided. The pump 15 for feeding rinsing water is not always needed in the apparats, but the rinsing water may be fed under the pressure of the pipeline network. In this case the flow of rinsing water can be stopped simply, for example by a mag- netic valve arrange in the water pipe. If a queue of racks is dispose on the feed conveyor, the racks are then again conveyed in turns for the duration of an operating cycle and again stopped for the duration of the break cycle, whereby the feed of rinsing water is also interrupted. The duration of an oper- ating cycle may be for example 18 seconds and that of a break cycle 18 sec- onds, too. If the speed of the conveyor 1 is such that while it moves the whole time, 200 racks would pass through the washing apparats in an hour, then the capacity of the washing apparatus employing the above operating and

break cycles is 100 racks per hour. The rinse zone 4 is so dimensioned that rinsing is sufficiently effective as the racks 21 are conveyed through the rinse zone at said quite high speed. However, the breaks serve to lower the con- sumption of rinsing water and, consequently, the operating costs of the wash- ing apparats per unit washed can be kept quite low. Since the racks 21 are washed in the wash zone 3 also during the break cycle, the washing result is extremely good. Another avantage is that the speed of the conveyor 1 does not have to be adjusted, allowing the use of a simple, and, consequently, in- expensive and reliable conveyor engine, and, at the same time, the structure of the control unit 19 becomes simpler and less expensive. The same principle can be used in applying the invention for example to cycling the timing of the washing apparats for lower capacity such that after an operating cycle corre- sponding to a transition of the length of a rack 21, a longer break cycle follows such that the racks 21 are always located at the same points during the oper- ating cycle. The break cycle may also be shorter than the operating cycle. At its shortest, the break cycle may be for example about 5 seconds long, this, however, being so long that the feed of rinsing water can be interrupted so that it will still be beneficial.

On the basis of information obtained from the sensor 18, the control unit 19 is arrange to stop the conveyor 1 of the washing apparats and the washing of the entire washing apparats in case no new rack follows immedi- ately after a rack 21 which has entered the wash line. The stop will last until a new rack 21 arrives at the inlet of the wash line. This being the case, the racks 21 in the washing apparats are dispose in succession substantially without any gaps. This also ensures that a rack is displaced at every point of the wash zone 3 during a break cycle, whereby detergent and water are not wasted. In this case the wash zone 3 can be quite short with no fear of some part of a rack 21 not being subjected to the washing process.

The invention is also applicable in an apparats which normally washes for example 200 racks per hour such that the conveyor is continually moving. The washing result can be improved by lowering the capacity of the machine to for example 100 racks per hour by stopping the conveyor and the feed of rinsing water to the rinse zone 4 during the break cycle as defined in the invention. This results in an improved washing result, without any essen- tial rise in the total costs per unit to be washed.

Figure 2 schematically shows the savings in costs to be achieved

by means of the invention when a machine is operated at low capacity as compare with its maximum capacity. The figure shows proportioned total costs and unit costs at full capacity, half capacity and 1/3 of the capacity, con- trolled in the manner described in the invention. In Figure 2, the first bars A and B represent the total costs of a washing apparats per unit of time, and the costs per unit to be washed when the washing apparats is operated at full capacity. Bars C and D, in turn, represent the total costs per unit of time and the unit costs when the washing apparats is operated at half capacity, and bars E and F represent the costs per unit of time and the unit costs when the washing apparats is operated at 1/3 of the capacity. As the figure shows, the total costs at a lower capacity are only slightly higher than the exact rela- tive portion with respect to the capacity as compare with full capacity. Simi- larly it may be noted that as the capacity falls, unit costs show only a marginal increase, and hence the method and washing apparats of the invention bring about significant savings as compare with using half or 1/3 of the capacity during the wash by slowing the speed of the conveyor of the washing appara- tus in a known manner. In prior art, costs per unit of time accrued in known manners are the same as in a wash effected at full capacity, whereby at half capacity, unit costs rise in the manner shown in Figure 2 by bars G and H, respectively, which is manifold compare to the unit cost achieved in the man- ner described in the invention.

The invention has been described above and in the figures by way of example, and is in no way restricted thereto. The washing apparats may comprise a prewash step or the prewash step may be completely separate. It is essential that in addition to a wash zone, the washing apparats comprises a rinse zone, whereby the feed of rinsing water in the manner of the invention can be interrupted in such a manner that there are successive operating cy- cles during which rinsing water is fed to the rinse zone and break cycles dur- ing which the conveyor is stopped and no rinsing water is fed to the rinse zone.