The present invention relates to a monitoring arrangement for the washing and rinsing cycles of a dishwashing machine, particularly of the industrial or commercial type, which is adapted to detect and indicate possible irregular operating conditions of the machine so as to enable the defective or irregularly operating component parts of the machine to be repaired, replaced or undergo maintenance, as the case may be, and the regular operating condition of the machine to be restored.

It is a well-known fact that dishwashing machines in general, and industrial or commercial dishwashing machines in particular, are usually equipped with two pairs of rotating spray arms for spraying the washing liquor and the rinsing water, respectively, onto the dishes forming the washload, said spray arms being arranged in correspondence of the upper and the lower portions of the machine and connected to the respective water supply circuit of the same machine, wherein the spray arms for the wash liquor are connected with at least a closed-loop recirculating pump, adapted to cause the washing liquor to be continuously recirculated, and the spray arms for the rinsing water are possibly connected with a further circulating pump for the rinsing water being heated in a boiler connected in the related portion of the water supply circuit of the machine, so as to enable respective washing and rinsing cycles to be performed by the machine to correctly handle the dishes forming the washload.

In view of ensuring a uniform, even distribution of the related jets of wash liquor and/or rinsing water, said spray arms are arranged so as to be caused to rotate by reaction around a central axis owing to the provision of respective rotating joints that connect them with the remaining portion of the respective water supply circuit of the machine. It may occur, for instance in the case of an irregular or defective operation of the recirculating pump associated therewith, or even in the case of an inadequate arrangement of the dishes in the related carrying baskets, that said spray arms are hindered in their rotation (under a sharp reduction in their angular velocity) or even prevented from rotating at all. It may easily be realized that, in all such cases, the washing effectiveness of the dishwashing machine would practically be almost totally disrupted, while the spray arm assemblies may quite easily become scaled in correspondence of the rotating joints following the build-up of limestone and dirt which proves quite difficult to remove and further contributes to the spray arms being blocked and hindered from rotating.

In order to timely draw the attention of the user on any such irregular operating condition of the machine that may possibly occur due to the above cited causes, and therefore to enable any such defective component part of the machine to be repaired, cleaned and/or replaced so as to restore the regular operating condition of the same machine, an arrangement is known (EU 0053231) for monitoring the rotation of each spray arms of the dishwashing machine. This arrangement, which is adapted to detect the rotation speed of the corresponding spray arm, comprises a detecting coil which is mounted in a fixed manner on the machine, is capable of being magnetically coupled with said spray arm when the latter is displaced into a pre-determined angular sector of rotation, and is connected in the electrical circuit of a generator so as to vary the output signal thereof each time that said coil becomes magnetically coupled with said spray arm, the output signal of the generator being adapted to drive, through a magnetic shunt, a discrete integrator whose binary output signal is capable of changing its state each time that the spray arm moves into and out of said angular sector of rotation at a speed which is at least equal to a pre-determined value.

In this way, said monitoring arrangement is able to indicate that the dishwashing machine is operating regularly as long as the spray arms are rotating at a minimum pre-determined speed, and to then indicate that the dishwashing machine is on the contrary operating irregularly each time that it detects that said spray arms are either rotating at a speed which is slower than said minimum pre-determined speed or are totally blocked.

It is the purpose of the present invention to provide a monitoring arrangement for dishwashing machines of the above specified kind, which is able, with a simple and reliable construction essentially based on the same operating principle of the afore described monitoring arrangement, to indicate the regular or irregular operating condition not only of the spray arms, but also of further component parts of the water supply and carrying circuits of the dishwashing machine, thereby ensuring a monitoring action covering practically all aspects being of significance in connection with the more or less regular way in which the various washing and rinsing cycles are actually being performed by the dishwashing machine.

Such a monitoring arrangement according to the present invention is provided with the features as substantially recited in the appended claims. Anyway, for a better understanding it will be hereinafter the subject of a further description, by way of non-limiting example, with particular reference to the attached drawings in which:

• Figures 1 and 2 show the circuit schematics of the monitoring arrangement according to the present invention, as provided to assure the correct performance of dish washing and rinsing cycles, respectively.

Referring in particular to Figure 1, it can be noticed that it is a schematical view of a dishwashing machine, in particular of the industrial/commercial type, comprising essentially a parallelepipedal outer enclosure 3 delimiting an inner washing tank 4 in which a respective upper rotating spray arm 5 and lower rotating spray arm 6 are housed, said spray arms being connected so as to be included in the washing portion of the water supply circuit of the dishwashing machine, which will be further described below in its various component parts, and are provided with respective spray nozzles 7 adapted to cause the washing liquor to be sprayed onto the dishes, which will have been arranged in appropriate dish-carrying baskets of a traditional type (not shown) loaded into said tank 4, during any of the washing cycles that can be selected for the machine to perform.

In particular, said portion of the water supply circuit of the dishwashing machine consists in a much usual way of a circulating pump 8, whose suction portion 9 and delivery portion 10 are connected through respective conduits 11 and 12 with a suction port 13, which is provided in the lower portion of said tank 4, and with two separate electromagnetic valves 14 and 15 that are located widely apart from each other and can be switched to open and to close so as to allow the washing liquor to flow through said conduits or to prevent it from flowing therethrough.

The spray arms 5 and 6 are in turn connected, through conduits 16 and 17, with said electromagnetic valves 14 and 15, respectively, and are in this way able to be selectively or simultaneously supplied with the washing liquor being recirculated by the pump 8 through said conduits 11, 12, 16 and 17.

Furthermore, in order to heat up the washing liquor to the temperature values required to carry out the different steps of each washing cycle being performed, the dishwashing machine is provided with one or more electric heating elements of a usual type (not shown), which are connected so as to be included in the electrical circuit of the machine along with the pump 8, the electromagnetic valves 14 and 15 and the remaining electro-mechanical component parts usually included in connection therewith (not shown, either), and whose operation is governed through a microprocessor-based control unit 18 that is provided so as to determine each selected washing cycle to go through its various operating steps.

According to the present invention, the monitoring arrangement provided to check the machine for correct operation comprises substantially a measurement transducer 19 associated with each rotating spray arm and provided so as to detect the rotating speed thereof, said measurement transducer comprising in this particular embodiment, as in the case of the afore cited monitoring arrangement of the per sè known type, at least a magnetic element 20, such as a permanent magnet attached to one of the outer ends of each rotating spray arm, as well as a respectively provided pick-up electric coil 21 applied against the wall of the outer enclosure 3 in a position corresponding to the one of each said magnetic element 20, and magnetically linked therewith, in such a way that for each rotation of each spray arm an electric voltage is generated by induction in said pick-up coil 21 when said magnetic element 20 passes by in correspondence of said coil.

Said measurement transducer arrangement 19 can of course be embodied also in some other way which is different from the afore described one, as long as it is able to always generate an electrical quantity which is in a proportion to the rotating speed of the spray arm associated therewith, said quantity being then sent to the control unit for processing, as in the afore described case, in order to find out whether the rotation of the related arm can be assumed to be correct or not, or even to detect a possible blocked condition of the same arm.

Each pick-up coil 21 is electrically connected with said control unit 18 so as to be able supply it with the electrical quantities that are generated in the same coil during the rotation of the associated spray arm, whereas said control unit 18 is in turn adapted to recognize said quantities and to signal the actual operating condition of the related rotating spray arm through an appropriate visual or acoustic indicator arrangement 22, or even any other appropriate indicator means of a per sè known type, connected with said control unit 18 accordingly.

In the herein described embodiment, in particular, said control unit 18 is adapted to switch off, or to keep switched off, said indicator arrangement 22 in the presence of an electrical quantity situated anywhere between a certain rated value and a certain pre-determined minimum value below the rated one, whenever the related rotating spray arm is rotatably driven at a normal rotating speed, and down to a pre-determined minimum rotating speed, so as to signify a correct operation of the dishwashing machine, whereas said control unit will on the contrary switch on said indicator arrangement whenever the level of said electrical quantity falls down below said pre-determined minimum value, or even drops to zero or near zero, to signify a stoppage condition or an irregular operation of the dishwashing machine.

Furthermore, the monitoring arrangement according to this invention comprises a plurality of further measurement transducers 23, each one of them comprising a structure formed by a rotor wheel 24 housed in a freely rotatable manner within a short portion of conduit 25 connectable at its ends with the corresponding conduits of the water supply and circulating circuit of the dishwashing machine, as well as by a small electric generator 26 of a per sè known type, which is housed in the structure separately from said rotor wheel 24 and is mechanically or magnetically linked therewith, in such a way that during the rotation of said rotor wheel, as brought about in the way described below, each electric generator 26 generates a corresponding electrical quantity and transmits it to the control unit 18 that is electrically connected therewith.

Said control unit 18 is in turn adapted to recognize also such electrical quantities and to signal the operating condition of each said rotor wheel through at least an appropriate visual or acoustic indicator arrangement, or any other appropriate indicator arrangement of a per sè known type, which may also be formed by the same afore cited indicator arrangement 22 or possibly even by an additional indicator arrangement 27 (represented with dashed lines in the drawing) to be connected with the control unit 18 correspondingly.

In particular, in this embodiment of the invention described by way of non-limiting example, the respective portions of conduit 25 of the measurement transducers 23 are connected with the corresponding conduits 12, 16 and 17 of the water supply and circulating circuit of the dishwashing machine, so that the washing liquor is caused to flow through said portions of conduit whenever corresponding dishwashing cycles are being carried on in the machine, so that the rotor wheels 24 being respectively housed in said portions of conduit are therefore driven to rotate.

It will therefore be clearly appreciated that each measurement transducer formed and arranged in the afore described or similar way is actually capable of signalling the circulation of an adequate, ie. rated, or inadequate flow rate of washing liquor, or even a failure of said washing liquor to circulate at all, through the conduits of the dishwashing machine under conditions reflecting a correct or an irregular operation of the same machine, respectively, so that, in the latter case, the user is enabled to timely provide for a maintenance, repair or replacement, as the case may be, of the defective component part of the water supply and circulating circuit of the dishwashing machine, thereby restoring the correct operation thereof.

To this purpose, the control unit 18 is adapted to switch off the indicator arrangement 22 (or the indicator arrangement 27, as the case may be), or to keep it in its switched off condition, in the presence of an electric quantity that, as measured by the related measurement transducer 23, is situated anywhere between a normal or rated value and a pre-determined minimum value below the rated one, in the condition of an adequate flow of washing liquor being circulated through the related conduits of the water supply and circulating circuit of the dishwashing machine, to signify that the machine is performing in a correct way, whereas said control unit is on the contrary adapted to switch on said indicator arrangement in the case that the value of said electric quantity should drop below said pre-determined minimum level, or should even drop to zero or near zero, in a condition of irregular operation of the dishwashing machine.

The measurement transducers 23 may of course be embodied also in a way differing from the one that has been described above by way of non-limiting example (for instance by means of electronic sensors of various kind, Hall-effect transducers and the like, correspondingly installed in the conduits of the water supply and circulating circuit of the dishwashing machine), as long as they are in all cases capable of enabling the flow rate of the liquor circulating through said conduits to be detected for the same reasons as cited above, without departing from the scopes of the present invention.

Referring now to Figure 2, which schematically shows solely that portion of the water supply and circulating circuit of the dishwashing machine which is provided to circulate the water needed to rinse the dishes, it can be noticed that it is essentially similar to the portion of water supply and circulating circuit described with reference to Figure 1, so that all of its component parts that are common therewith are given the same numerals as used in the circuit represented in Figure 1.

Furthermore, the circuit shown in Figure 2 is additionally provided in the usual way with a boiler 28 to heat up and store the hot water needed for rinsing, said boiler 28 being supplied with fresh water from the mains through an electromagnetic valve 29 or similar control means electrically connected with and controlled by said control unit 18, said boiler 28 being further arranged to deliver hot water by pressure or, in the case of an inadequate pressure, through a further circulating pump provided in the dishwashing machine (not shown in this Figure), as operationally connected with both the boiler and the conduit 12 of the water supply and circulating circuit of the machine.

Even in this case, therefore, the dishwashing machine is provided with an arrangement of the same measurement transducers 19 and 23 as afore described with reference to Figure 1, said measurement transducers being therefore adapted to monitor the operating condition of the rotating spray arms 5 and 6, as well as the flow rate of the liquor circulating through the conduits of the water supply and circulating circuit of the machine, in the same way and to the same purposes as specified in the previously described case.

The monitoring arrangement made in the afore described way according to the present invention is very simple and reliable both in its construction and operation, and it further ensures a practically complete monitoring over the most significant component parts of each dishwashing machine for correct operation, so as to enable the user to timely perform any maintenance, repair or replacement action that, in the case of an irregular operating condition or a malfunction, may prove necessary in order to remove any faulty condition that has occurred or might possibly occur, thereby restoring correct conditions for the machine to continue its washing and rinsing operation in a satisfactory way.