Apparatus in particular to supply liquid or slurried products are well-known from prior art (EP 0 369 722 A1). This prior art in particular relates to a dispensing apparatus for detergents, wetting agents, drying agents, rinse aids or the like for industrial cleaning processes, preferably, but not exclusively in dishwashing ma- chines, bottle washing machines, laundry washing machines or the like.

In apparatus as described before there is normally a large number of electromag- netic subassemblies like drive motors, pump drives and solenoid operated valves.

The operating state of those electromagnetic subassemblies must be controlled and this is normally done by a separate control unit of the apparatus. Sensor means for the operating state of the respective electromagnetic subassembly are assigned to the respective subassembly and are connected to the control unit to provide the necessary signal input.

The invention is related to a particular sensor means for such electromagnetic subassembly in an apparatus as described.

In order to sense the operating state of an electromagnetic subassembly normally the supply voltage or the supply current is monitored. This needs a sensor means attached to the electric supply system of the subassembly. This again needs con- siderable wiring and other efforts. Further, in high voltage applications in par- ticular a number of legal rules must be observed.

The object of the present invention is to provide an apparatus and a sensor means that reduces installation requirements.

In accordance with a first aspect of the invention the apparatus described above is characterized in that the sensor means is a self-contained Hall-effect sensor means separate from, but attached to the electromagnetic subassembly and monitoring the magnetic stray field of the electromagnetic subassembly.

Equally, according to claim 7, a sensor means in accordance with a main aspect of the invention is characterized in that the sensor means is a self-contained Hall- effect sensor means separate from, but attachable to the electromagnetically op- erated unit and designed to monitor the magnetic stray field of the electromag- netically operated unit.

Preferred details are subject of the sub-claims.

Following the invention instead of the supply voltage or the supply current of the electromagnetic subassembly just the magnetic stray field of the electromagnetic subassembly is monitored by a sensor means that is specifically adapted to achieve this effect. This sensor means is a self-contained Hall-effect sensor means that is basically separate from, but attached or attachable to the electro- magnetic subassembly. Installation of such self-contained sensor means is easy, because it needs no connection to the electric supply lines of the electromagnetic subassembly. A galvanic decoupling of the sensor means from the electromag- netic subassembly itself is provided without any additional efforts like an opto- coupler or the like.

The invention is particularly suitable for solenoid valves in an apparatus as de- scribed. However, other systems that generate magnetic stray fields can be monitored likewise.

A particularly advantageous version of the sensor means uses an adhesive at- tachment foil as carrier for the Hall-effect sensor means. Such adhesive attach- ment foil can be simply adhered to the outside of the electromagnetic subassem- bly or a housing thereof at a suitable position. Installation of such sensor means is extremely easy.

Other and further advantages and features of the invention will be apparent to those skilled in the art from the following detailed description thereof taken in conjunction with the accompanying drawings. In the drawings Fig. 1 is a schematic display of an apparatus according to the invention, Fig. 2 is a schematic, sectional view of a preferred embodiment of an electromagnetic subassembly, i. e. a solenoid of a solenoid valve, showing a sensor means according to the invention attached to its housing, Fig. 3 is a schematic view of a preferred embodiment of a self-contained Hall-effect sensor means according to the invention.

Fig. 1 shows a schematic and highly simplified view of an apparatus for the sup- ply or handling of products, here of a liquid product like a detergent in an indus- trial cleaning process. For example such apparatus may be part of an industrial dishwashing machine or the like.

This apparatus comprises a liquid pump 1, e. g. a pump for the liquid detergent from a reservoir 2. The liquid pump 1 is started only after an electromagnetic subassembly 3, here a solenoid operated valve, was first moved to its"open"po- sition. Fig. 1 shows such"open"position of the solenoid valve (electromagnetic subassembly 3). In line with the electromagnetic subassembly 3 is positioned a flow meter 4 and, thereafter, a nozzle means 5 intended to generate a spray of liquid detergent e. g. in a washing chamber of a dishwashing machine.

A control unit 6 is connected to the different parts and, in particular, to a sensor means 7 assigned to the electromagnetic subassembly 3. This sensor means 7 is adapted to sense the operating state of the electromagnetic subassembly 3, here the solenoid 8 of the solenoid valve that is the electromagnetic subassembly 3.

Fig. 2 shows in more detail a solenoid 8 of an electromagnetic subassembly 3 with a coil 9, an armature 10 (connected to the valve body of the solenoid valve) an armature stop 11, electric supply lines 12 and a housing 13. This is a sample

for an electromagnetic part of an electromagnetic subassembly 3. The movable armature 10 is pulled to a central position limited by the armature stop 11 when the coil 9 is energized by electric current sent through the coil 9 via the electric supply lines 12. This is a usual and well-known system.

The coil 9 generates a magnetic stray field. Fig. 2 shows as a sensor means 7 as self-contained Hall-effect sensor means that is separate from, but attached to the electromagnetic subassembly 3, here the housing 13 of the solenoid 8. This sen- sor means 7 is monitoring the magnetic stray field of the coil 9 of solenoid 8, i. e. of the electromagnetic subassembly 3. A Hall-effect sensor uses the Hall-effect to give an output voltage portional to the magnetic field strength of the magnetic stray field. The Hall-effect is the effect of development of a transverse electric field in a current-carrying conductor placed in a magnetic field. This effect is used here to monitor the magnetic stray field of the electromagnetic subassembly 3 and thus the status of the electromagnetic subassembly 3 without any need to use the electric supply lines 12 or the like. So there is a galvanic decoupling of the sensor system from the supply system and installation is extremely easy.

Fig. 2 shows a solution where the sensor means 7 is attached to the housing 13 by means of an attachment strap 14. However, Fig. 3 shows an even better solu- tion that is even easier to install. Here it can be seen that the sensor means 7 is provided with an adhesive attachment foil 15. The Hall-effect sensor means as such is positioned in the middle of a circular piece of adhesive attachment foil 15 which then can be easily adhered to the housing 13 at a convenient location. The diameter of such circular piece of adhesive foil 15 may be a couple of centime- tres, e. g. 2 to 3 cm.

Fig. 2 and 3 further show that here the sensor means 7 is provided with a con- necting cable 16 for connection with the control unit 6 of the apparatus.

Of course, the sensor means 7 as a self-contained Hall-effect sensor means can be manufactured and sold as such independent of an apparatus, but intended to be applied in connection with an electromagnetically operated unit, in particular a solenoid valve.