CH670964A5 - - Google Patents

Description

DESCRIPTION

The invention relates to a method according to the preamble of claim 1 and to a device according to the preamble of claim 2.

Methods and devices of this type are known in commercially available disinfection dishwashers which operate on the principle of tank washing machines.

From DE-OS 3 305 316 a dishwasher for laboratory use and for medical devices is also known, in which the amount of washing additive conveyed from a feed pump from a storage container into the washing compartment is recorded via a flow meter and depending on the measurement result in interaction the operation of the feed pump is influenced by an evaluation circuit. The aim is to enable detergent additives to be dosed as accurately as possible using simple feed pumps.

However, flow meters according to the construction principle described there are still relatively complex.

In disinfection dishwashers of the type mentioned at the outset, the problem arises of conveying detergent additives, in particular defoaming agents, into the washroom at the right time in the smallest possible but sufficient amount. If too much defoaming agent is dosed, the cleaning effect of the other detergent additives, in particular the detergents, is reduced; the

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Washing result is unsatisfactory. If, on the other hand, too little defoamer is added, the foam formation is not completely prevented and the washing result is also deteriorated.

The object of the invention is therefore to provide a method and a device of the type mentioned at the outset, in which the time and quantity of the defoamer to be supplied can be precisely regulated. A more exact dosage of the other detergent additives should also be guaranteed.

This object is achieved by the features specified in the characterizing part of claims 1 and 2. Advantageous refinements and developments of the invention can be found in the dependent claims.

The invention is based on the following finding: disinfection dishwashers operate with relatively high washing temperatures in the range from 90 to 93 C. Depending on the pressure conditions, vapor bubbles form at these temperatures, so that cavitation occurs at the circulation pump. The circulation pump then mostly only sucks in steam; the water circulation no longer takes place. Furthermore, the formation of foam is promoted by this vapor formation.

Furthermore, practically all detergent additives used today also develop a limited amount of foam, especially if they are mixed with proteins such as Blood come together, creating strength. This foam formation, which is relatively independent of the temperature, also means that hardly any water is circulated, so that the rinsing result is strongly influenced or no rinsing takes place at all.

In conventional disinfection dishwashers, only defoaming agents are conveyed into the washroom when foam occurs. However, the actual cause of the foam formation is not ascertained, so that the defoamer is almost always overdosed there, which leads to a severe impairment of the washing action of the detergents previously added.

According to the invention, foam formation is recognized in that the delivery pressure of the circulating pump drops. This is recognized by a pressure sensor or by measuring the electrical output of the feed pump. If such a drop in pressure and thus foam formation is now recognized, it is checked whether the cause of this is the high temperature of the wash water or not. If the cause is steam formation, i.e. If the temperature is too high, no defoamer is added, only the heating output is reduced. If, on the other hand, the temperature is below a predetermined value and thus vapor bubbles are excluded, defoamer is added in a precisely metered amount. A small amount of defoaming agent, which is sufficient to remove the foam, is added briefly more precisely. Since experience has shown that new foam is created when dirt is removed, this process is repeated at corresponding intervals, fully automatically.

When cleaning near the evaporation limit, the heating output is regulated so that work is always carried out at the upper limit of the temperature with full pump output. This ensures that the best combination of temperature and pressure is given, i.e. an optimization of the cleaning and disinfection effect.

It is particularly advantageous here if the circulation pump is arranged as far as possible at the lowest point of the machine, so that a limited static pressure is present at the outlet of the circulation pump.

Another favorable side effect of the invention is that the measured pressure also for controlling the

Water levels in the washroom can be used. So far, most machines have been used to control the water level, level sensors, which is designed as a pressure cell, which is arranged at a certain height in the washroom. The characteristic of such pressure cans is, however, largely temperature-dependent. The measurement result of this pressure can, which monitors the water level, can be considerably refined by using the pressure on the outlet side of the circulation pump for correction. Here, of course, a distinction is made as to whether the pressure drop is due to foam, steam bubbles or falling below the water level, due to the highly productive nature. Another important advantage of the invention is that the principle of pressure measurement used for the circulation pump can also be used for the metering of detergent additives of all kinds, including defoamers.

The invention is explained in more detail below on the basis of exemplary embodiments in conjunction with the drawing. It shows:

Figure 1 is a schematic diagram of the device according to the invention.

2 shows an electrical circuit diagram of part of the control logic;

Fig. 3 is a schematic sectional view of a first variant of a pressure sensor which is used in the invention;

4 shows a schematic sectional view of a second variant of a pressure sensor; and

Fig. 5 is a schematic sectional view of a third variant of a pressure sensor.

The same reference symbols in the individual figures denote the same or corresponding parts.

1 schematically shows a washroom 10 which is funnel-shaped at the bottom and has an outlet to the suction side of a circulating pump 11 driven by an electric motor. A circulation line 12 is connected to the pressure side of the circulation pump 11 and leads back into the wash room 10. This circulation line 12 can be connected there, for example, to rotating washing arms, to spray nozzles, etc., as is generally known in the prior art.

Furthermore, an electric heating device 13 for heating the washing water is arranged in the washing room 10. Finally, a temperature sensor 14 is provided, the sensing element of which also protrudes into the washroom, the temperature sensor 14 measuring the temperature of the circulated wash water.

Outside the washing room 10, a storage container 15 for defoaming agents and a storage container 16 for washing additives are provided. Suction lines project into both storage containers 15 and 16 and can be opened or shut off via solenoid valves 17 and 18, respectively. In the exemplary embodiment shown, both solenoid valves 17 and 18 are connected on the output side to a manifold 19, which is also the suction line of a feed pump 20. The pressure side of this feed pump 20 is connected to the washroom 10 via a pressure line 21, so that defoaming agents and wash additives can be conveyed into the washroom.

A pressure sensor 22 is installed in the circulation line 12 on the pressure side of the circulation pump 11 and measures the water pressure PI prevailing there. As an alternative to this, a device 22 'can also be provided which the circulating pump 11 measures the electrical power consumed. In the event of a pressure drop due to foam or steam formation, the load on the circulating pump 11 will drop, so that the electrical power consumed by it will also decrease

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falls off. The drop in electrical power is therefore also an indicator of a drop in pressure and thus of foam or steam formation.

In the pressure line 21 of the feed pump 20 there is also a pressure sensor 23 which measures the pressure prevailing in this line. The measured values detected by the individual sensors 14, 22, 22 'and 23 and converted into electrical signals are fed to a control logic 24, the essential components of which are explained in connection with FIG. 2. The control logic 24 in turn determines the control signals for the circulating pump 11, the feed pump 20, the heating device 13 and the solenoid valves 17 and 18 as well as further signals for an alarm generator (not shown) and / or a control signal for the program control unit of the dishwasher (also not shown) from the incoming measured values.

In particular, the control logic 24 controls the operation of the circulation pump 11 via a line 25, the operation of the heating device 13 via a line 26, the operation of the feed pump 20 via a line 30 and the switching position of the solenoid valves 17 and 18 via lines 31 and 32 .

Electrical signals corresponding to the measured values are fed from the temperature sensor 14 to the control logic 24 via a line 27. Correspondingly, the output of the pressure sensor 22 is connected to the control logic 24 via a line 28, the output of the power measuring device 22 'via a line 28' and the output of the second pressure sensor 23 (with the pressure value P2) via a line 29.

2 shows essential parts of the control logic 24. The output of the temperature sensor (measured temperature 9) is connected to an input of a comparator 33 (line 27). A preset value for a reference temperature 9r is fed to the other input of the comparator 33. The comparator then emits a digital output signal when the measured temperature 9 is higher than the reference temperature 9r. This signal is fed to an inverting input of an AND gate 34 and a non-inverting input of a second AND gate 34. Line 28 is connected to the other inputs of AND gates 34 and 35, which then carries a digital signal when the pressure value PI measured by the pressure sensor 22 is smaller than a predetermined pressure value Pir. If pressure sensors operating in an analog manner are used, a comparator similar to the comparator 33 can also be connected upstream.

The output of the second AND gate 35 is connected to a driver device 36, which is shown here as a relay and which operates the heating device 13.

The output of the first AND gate 34 is connected to a first timer 37, which is, for example, a non-retriggerable, monostable flip-flop. The output of this timer (line 30) is also connected to a driver device 38, which is also shown here as a relay which controls the feed pump 20 (FIG. 1). The output of the first timing element 37 is also connected to an input of a second timing element 39, the output of which is in turn connected to an input of an AND gate 40. The output of the second pressure sensor 23 is fed to the second, inverting input of the AND gate 40 (line 29). This line then carries a digital signal when the pressure P2 measured by the pressure sensor 23 is less than a predetermined reference pressure Pjr. If a pressure switch is used as the pressure sensor 23, its output can be used directly with the inverting input of the AND gate. Otherwise, a comparator, similar to comparator 33, must also be connected upstream.

The mode of operation of the device is explained below in connection with FIGS. 1 and 2. First, consider the undisturbed case in which the circulation pump is working and there is no foam or steam formation. The water pressure PI measured in line 12 by the pressure sensor 22 is then greater than the preset reference pressure Pir. No signal is present on line 28 and correspondingly at the inputs of AND gates 34 and 35, so that there is also no signal at the outputs of two AND gates 34 and 35. The dishwasher works in a conventional manner under the control and / or regulation of the program control unit, not shown. Temperature control is also carried out using the temperature sensor 14 in a conventional manner.

As soon as foam or steam occurs, the pressure in line 12 drops suddenly. Likewise, the electrical power consumed by the circulation pump 11 drops suddenly. This is detected by the pressure sensor 22 or the power measuring device 22 'and is reported via the lines 28 and 28' in such a way that a digital signal is present on the corresponding line. The preset pressure value Pir is of course set so that in this case of foam or steam formation the measured pressure value PI is less than the value Pir. The two AND gates 34 and 35 are activated by the signal on line 28. The AND gates 34 and 35 then check the signal at their other input. If the temperature 9 measured by the temperature sensor 14 is greater than the temperature 9r, the second AND gate 35 switches through and actuates the relay 36, which is connected to the heating device 13 such that in this case the heating power of the heating device 13 is reduced or possibly brought to zero. In this case, it was recognized that the pressure drop at the outlet side of the circulation pump was caused by steam formation or cavitation of the circulation pump 11. To counteract this, it was sufficient to reduce the heating output. This state is maintained until the measured temperature 9 has dropped below the reference temperature 9r. The reference temperature 9r is chosen so that there is definitely no steam formation or cavitation of the circulation pump 11. If the measured temperature has dropped below the reference temperature, the output signal of the comparator 33 disappears, the AND gate 35 switches off and the heating device 13 is controlled again in a conventional manner.

If the measured pressure PI is lower than the reference pressure Pir and at the same time the measured temperature 9 is lower than the reference temperature 9r, foam is present, so that defoaming agent must be added. In this case, the first AND gate 34 is turned on and drives the first timer 37. This emits a pulse to the driver device 38 for a preset time ti, which switches the feed pump 20 on for the short time tj. If, after this time period ti, a signal is still present at the input of the first timer 37, the timer 37 is switched through again and emits another pulse.

While the feed pump 20 is running, there must be a pressure on the pressure line 21 if defoamer or washing additives are being conveyed properly. This is monitored by the second pressure sensor 23 and reported to the third AND gate 40. The course of the feed pump 20 is reported to the other input of the AND gate 40. Since a certain time elapses between the start-up of the feed pump 20 and the pressure build-up, the second timer 39 is provided, which is triggered by the output signal of the first timer 37. Has after the delay time t: of the second delay element 39 since

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Start of the feed pump 20 (output signal of the first timer 37) no predetermined pressure (P2r) has built up in the line 21, the AND gate 40 switches through and emits a warning or error signal. This signal can trigger an optical or acoustic alarm and / or shut down the program control unit of the dishwasher, so that the washing or rinsing process is interrupted.

The delivery rate of the delivery pump is determined by the switch-on period of the first timer 37, taking into account the line cross sections and the delivery rate of the delivery pump 20.

This ensures a sufficiently precise dosage of the defoamer and / or the detergent additives.

In the version shown in FIG. 1 with a common feed pump 20 for detergent additives and defoaming agents, the choice between these two substances is made by means of the solenoid valves 17 and 18. The solenoid valve 17, which releases the suction line for the defoaming agent, can be activated via the driver device 38 also the feed pump 20 activated, operated. The circuit is such that when the activation signal appears on line 30, solenoid valve 17 is opened and feed pump 20 is switched on.

If, on the other hand, detergent additives are to be metered, the solenoid valve 18 and the feed pump 20 are actuated by the program control unit (not shown) of the dishwasher.

FIGS. 3 to 5 show different variants of pressure sensors which can be used both as pressure sensors 22 in the circulation line 12 and as pressure sensors 23 in the pressure line 21.

Other types of so-called pressure-voltage converters can also be used.

Since, in particular, the pressure line 21 has a relatively large opening cross section in relation to the relatively small amount of detergent additives or defoaming agents to be conveyed, a flow obstacle is used in all three variants to build up a precisely measurable pressure, so that a higher pressure forms upstream of this flow obstacle when the feed pump 20 is running. In the variant in FIG. 3, the flow obstacle is an orifice 41. In the variant in FIG. 4, it is a line constriction in the form of a tube insert 48, the through opening 49 of which has a smaller opening cross section than the line 21. In the variant 5, the flow obstacle is also a pipe section 51, which is at the same time the mounting flange of the line 21 opposite the wall 50 of the washroom 10. This pipe section 51 also has a through opening 53, the opening cross section of which is smaller than that of the line 21.

In Figures 3 to 5, the direction of flow is indicated by an arrow.

In Fig. 3, the pressure sensor 23 is now designed as a differential pressure meter. Measuring lines 42 and 43 branch off on both sides of the orifice 41, each of which opens into a chamber 45 or 46 of the pressure sensor 23. The two chambers 45 and 46 are separated from one another by a flexible membrane 47. Depending on the differential pressure in the two chambers 45 and 46, the membrane 47 is bent to one side or the other, whereupon switching contacts (not shown) are actuated, i.e. be closed or opened.

Instead of a membrane, the two chambers 45 and 46 can also be separated by a sealing piston or the like, in which case, for example, the piston rod can actuate the switching contacts. As soon as in the two chambers 45 and 46, i.e. builds up a differential pressure upstream and downstream of the orifice 41, this is a sign that a medium flows through the line 21. The switching threshold is set in such a way that, when air is conveyed by the feed pump 20, the differential pressure is not sufficiently high to let the pressure sensor 23 switch through.

It should also be emphasized that the pressure line 21 and the two measuring lines 42 and 43 are arranged such that liquids flow out under the influence of gravity, so that after the feed pump 20 is switched off, the lines 21, 42 and 43 and also the chambers 45 and 46 are empty flow.

3, only the absolute pressure is measured. Here, the pressure is sensed via a measuring line 55 arranged upstream of the flow obstacle 48 and passed to the pressure sensor 23. This is designed here as a pressure switch of conventional design and then emits a signal on line 29,

when there is a preset pressure at its inlet (measuring line 55). For example, a spring-loaded volumetric piston is used for this purpose, the piston rod of which actuates electrical switch contacts, the spring preload being adjustable and thus the preset pressure pir or P2r.

Here too, the pressure line 21 and the measuring line 5.5 are arranged such that the respective liquid can flow out under the influence of gravity when the feed pump is switched off.

The same also applies to the exemplary embodiment in FIG. 6, where the flow obstacle is combined with a connecting flange for the pressure line 21. As mentioned, the flow obstacle is formed here by a pipe section 51 which is fastened to a wall 50 of the washroom 10. The pipe section 51 has a circumferential collar 52 on its side facing the washroom 10 and is fastened there by a nut 54 attached to the other side of the wall 50. The end of the pressure line 21 is then plugged onto the pipe section 51. The measurement line 55 with the pressure sensor 23 is in turn mounted upstream of this flow obstacle. This is shown here as a membrane pressure switch, a flexible membrane 58 forming two chambers 56 and 58. An electrical switch contact is here on the membrane 58

59 attached, while the mating contact 60 is attached to a wall of the chamber 57. Lines 61 and 62 are connected to both contacts 59 and 60. As soon as the pressure in chamber 56 is greater than that in chamber 57, the membrane bends in the direction of chamber 57. If the pressure in chamber 56 reaches a predetermined value, which is determined by the spring constant of membrane 58, so the contacts 59 and

60 and a corresponding signal can be tapped on lines 61 and 62.

Finally, it should also be mentioned that the flow obstacle can take the form of a tube which can be inserted into the pressure line 21. The pressure line 21 is expediently made of plastic.

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3 sheets of drawings

Claims (10)

670 964 PATENT CLAIMS 1. A method for regulating the foam formation in disinfection dishwashers with water circulation and water heating, in which a defoamer is added in metered amounts in the case of excessive foam formation, characterized in that that the water pressure of the circulated water is determined that the temperature of the water is measured that if the pressure drops below a specified pressure value and at the same time a water temperature exceeds a specified temperature value, the heating output is reduced, and that if the pressure drops below the specified pressure value and a water temperature falls below the specified temperature value, the defoamer is added. 2. Device for performing the method according to claim 1, with a washroom, a circulation pump for circulating the wash water of the washroom, a metering device for detergent additives with defoamer with a heating device for heating the wash water and with a temperature sensor for measuring the wash water temperature, characterized by a pressure sensor (22, 22 ') for detecting the outlet-side water pressure of the circulating pump (11) and a feed pump (20) in a pressure line (21) as well as by a control logic (24) which then switches the heating device (13) to a lower • heating output when the detected water pressure (pi) is less than a predetermined pressure value (pir) and at the same time the temperature (&) measured by the temperature sensor (14) is greater than a predetermined temperature value (9r) and which then activates the feed pump (20) for the defoamer , if the detected water pressure (pi) is less than the specified pressure value (pir) and equ The measured temperature (9) is currently lower than the specified temperature value (3r). 3. Device according to claim 2, characterized in that the control logic (24) contains the following: a comparator (33) whose one input is connected to the temperature sensor (14) and whose other input the predetermined temperature value (9r) is supplied in the form of an electrical voltage; a first AND gate (34) the inverting input of which is supplied with the output signal of the comparator (33) and the other input of which is supplied with a digital signal which indicates that the measured water pressure is less than the predetermined pressure value; a second AND gate (35) with two non-inverting inputs, one of which is connected to the output of the comparator (33) and the other of which is connected to the non-inverting input of the first AND gate (34), and a first Timing element (37), which is connected downstream of the first AND gate (34), the output of the first timing element (37) activating the feed pump (20) for the defoamer, while the output of the second AND gate (35) heats the heating power Heating device (13) reduced. 4. The device according to claim 2 or 3, characterized in that the second pressure sensor is a pressure-dependent, electrical switch (22) which switches over when the inlet-side pressure reaches a preset pressure value, that in the pressure line (21) a flow obstacle (41 , 48, 51) and that this pressure sensor (23) is connected upstream of this flow obstacle to this line (21). 5. The device according to claim 4, characterized in that the flow obstacle is a tube insert (48) with a through opening (49) whose opening cross-section is smaller than that of the pressure line (21) (Fig. 4). 6. Apparatus according to claim 4 or 5, characterized in that the pressure sensor (23) is a membrane switch, the housing of which is divided into two chambers (45, 46; 56, 57) by a flexible membrane (47, 58), one of the chambers is acted upon by the pressure to be measured and electrical contacts (61, 62) are switched through the membrane (47, 58) (FIG. 3). 7. Device according to one of claims 4 to 6, characterized in that at least one pipe (42, 43; 55) from the pressure line (21) to the pressure sensor (23) is installed so rising that liquid under the influence of gravity from this line and flows out of the pressure sensor, and that the pressure line (21) is also installed increasing. 8. Device according to one of claims 4 to 7, characterized in that the flow obstacle is a tube insert (51) in the pressure line (21) (Fig. 5). 9. The device according to claim 3, characterized in that at the output of the first timer (37), which activates a collecting or suction line (19) for the detergent additive, a second timer (39) is connected, the output of which is connected to an input of an AND -Gatters (40), whose other inverting input is supplied with a signal which indicates whether the detergent additive (P2) has a delivery pressure which is less than a predetermined pressure value (par), the output of the AND gate ( 40) supplies a warning signal and / or a signal for switching off a program control unit of the dishwasher. 10. Device according to one of the preceding claims 2 to 9, characterized in that two separate storage containers (15, 16) are provided for detergent additives and defoaming agents, which are connected to the feed pump (20) via the suction line (19), in which Corresponding supply lines to the storage containers (15, 16) of the control logic (24) actuatable solenoid valves (17, 18) are switched on.