US3556146A

US3556146A - Liquid dispensing device automatically operated by proximity of a hand thereto

Info

Publication number: US3556146A
Authority: US
Inventors: Johannes Groen
Original assignee: METAALWARENFABRIEK VENLO NV
Current assignee: METAALWARENFABRIEK VENLO NV
Priority date: 1969-03-11
Filing date: 1969-03-13
Publication date: 1971-01-19
Anticipated expiration: 1988-01-19
Also published as: DE1912901A1; CH496281A; GB1202663A

Abstract

A liquid dispensing device, in particular for hospitals and clinics, whereby the supply of hot or cold water to a wash bowl or the like may be controlled without touching any valves by hand. The water supply is regulated by an electromagnetic valve controlled by a proximity detector operating as a variable voltage divider. The proximity detector is fed with a high frequency signal and delivers an output voltage which may be influenced by putting the hand near the proximity detector. Separate proximity detectors for controlling the supply of hot and cold water, respectively, are mounted on the outlet pipe of the wash bowl in such manner that they may be actuated either separately or simultaneously, os that hot, cold or tepid water may be supplied as desired.

Description

United States Patent [72] Inventor Johannes Groen Loenen Vecht, Netherlands [2]] Appl. No. 806,946 [22] Filed Mar. 13, 1969 [45] Patented Jan. 19, 1971 [73] Assignee N. V. Metaalwarenfabriek Venlo" Venlo, Netherlands [54] LIQUID DISPENSING DEVICE AUTOMATICALLY OPERATED BY PROXIMITY OF A HAND THERETO 16 Claims, 5 Drawing Figs.

2 [52] US. Cl 137/606,

137/801, 251/129, 340/258 [51] Int. Cl. E03c 1/04, F 16k 19/00 [50] Field ofSeareh 4/166, elec.

flush; 137/606, 607 801; 251/129; 340/258, 258C [56] References Cited UNITED STATES PATENTS 3,151,340 10/1964 Teshima 4/l66 3,415,278 12/1968 Y-amamotoetal. 137/607 FOREIGN PATENTS 60,971 3/1968 Germany 4 166 1,124,436 2/1962 Germany 4/(ElCC.)

Primary Examiner-Robert G. Nilson Attorney-Waters, Roditi, Schwartz, and Nissen ABSTRACT: A liquid dispensing device, in particular for hospitals and clinics, whereby the supply of hot or cold water to a wash bowl or the like may be controlled without touching any valves by hand. The water supply is regulated by an electromagnetic valve controlled by a proximity detector operating as a variable voltage divider. The proximity detector is fed with a high frequency signal and delivers an output voltage which may be influenced by putting the hand near the proximity detector. Separate proximity detectors for controlling the supply of hot and cold water, respectively, are mounted on the outlet pipe of the wash bowl in such manner that they may be actuatedeither separately or simultaneously, so that hot, cold or tepid water may be supplied as desired.

PATENTEU JAN 1 9 l97| SHEET 1 []F 4 LIQUID DISPENSING DEVICE AUTOMATICALLY OPERATED BY PROXIMITY OF A HAND TI-IERETO BACKGROUND OF THE INVENTION It is known to regulate the supply of water to a wash bowl by means of a proximity detector inserted in the frequency determining circuit of a high frequency oscillator. When a hand is brought into the vicinity of the detector, the operation of the oscillator is modified or even interrupted, whereby a signal is generated that may be used to control an electromagnetic valve. This arrangement has the limitation that a separate oscillator is required for each valve to be controlled.

It is also known to regulate the supply of water to a wash bowl by the interception of light impinging on a photo cell. With such an arrangement, it may occur that the water supply is actuated at an undesired time by an accidental interception of the light rays. Furthermore, photoelectric devices of this kind are rather susceptible to the flickerings generated by luminescent lamps upon their ignition.

SUMMARY OF THE INVENTION It is the main object of the invention to provide an improved liquid dispensing device of the above mentioned kind wherein the limitations of the known devices have been overcome.

A further object of the invention is to provide a liquid dispensing device of the above-mentioned kind wherein separate proximity detectors for controlling the supply of hot and cold water to a wash bowl. may be actuated either separately or simultaneously, so that hot,cold or tepid water may be supplied as desired.

Another object of the invention is to provide a liquid dispensing device of the above-mentioned kind wherein several electromagnetic valves may be controlled with the aid of a common high frequency oscillator.

According to the invention, the outlet pipe carries at least one proximity detector operating as a variable voltage divider, to which a high frequency signal is supplied and of which the output voltage may be influenced by putting the hand near the proximity detector, the said output voltage being used to control an associated electromagnetic valve.

Two different constructions for the proximity detector will be disclosed hereinafter. In the first construction, the proximity detector comprises two series connected condensers having one electrode in common and each having one separate electrode. The highfrequency signal is supplied to one of the separate electrodes and the output voltage is taken from the other separate electrode. The output voltage may be influenced by putting the hand near the common electrode.

In the second construction, the proximity detector comprises a dielectric plate carrying on one of its sides three juxtaposed electrodes of which the middle one is grounded. The high frequency signal is supplied to one of the outer electrodes and the output voltage is taken from the other outer electrode. The other side of the'plate carries a continuous grounded electrode facing the three juxtaposed electrodes. The output voltage may be influenced by putting the hand near the three juxtaposed electrodes.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the circuit diagram of a device according to the invention provided with two proximity detectors.

FIG. 2 shows a first embodiment of the receiver connected with each of the two proximity detectors in FIG. 1.

FIG. 3 shows a sensing head mounted on the outlet pipe of a wash bowl and comprising two proximity detectors, which may be used in the device according to FIG. 1.

FIG. 4 shows a cross section of the sensing head according to the line lV-IV in FIG. 3.

FIG. 5 shows a second embodiment of the receiver, in combination with an alternative embodiment of the proximity detector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, K1 and K2 denote two feed terminals to which a DC voltage of v. is supplied, the DC voltage being obtained by rectification of AC voltage at the mains. By means of a voltage divider comprising the series connection of a resistor R1 and a Zener diode ZI,a DC ,voltage of 3.6 v.-is obtained which is used to feed an impulse generator lG.

The impulse generator IG produces a series of rectangular impulses having a frequency of 50--2OO kc, which is supplied through a resistor R2 to thebase of a transistor T1, of which the emitter is grounded and the collector is connected through a resistor R3 to the potential of 80 v. Furthermore, the collector of transistor T1 is grounded through a Zener diode Z2, having a Zener voltage of about 40 v., so that rectangular impulses with a constant amplitude of 40 v. may be taken from said collector. These impulses are supplied to the sensing head OK through a coaxial cable LI. 7

The sensing head OK contains two proximity detectors turned away from each other in such manner that they may be separately influenced by hand. The first proximity detector comprises two series connected condensers C l and C2, each having a capacity of 0.5 pF, for instance, and having a common electrode E1. The second proximity detector is carried out in exactly the same manner, and comprises two series connected condensers C3 and C4 with a common electrode E2. The common electrodes E1 and E2 lie on the outside of the sensing head. If the hand is put near one of these electrodes, a capacitive ground connection is formed, whereby the output voltage is considerably reduced.

The output voltages of the two proximity detectors are each supplied through an associated coaxial cable L2, or L3, respectively, to an associated

receiver

01, or 02, respectively.

The arrangement may be such that the receiver 01 controls an electromagnetic valve for the supply of hot water, and that the receiver 02 controls an electromagnetic valve for the supply of cold water. Thus, the supply of hot water may be initiated or terminated by putting the hand near the first proximity detector, and the supply of cold. water may be initiated or terminated by putting the hand near the second proximity detector. If desired, the two valves may be opened simultaneously to obtain a supply of tepid water.

The construction of the

receivers

01 and 02 is shown in FIG. 2. The output voltage of the associated proximity detector as taken from cable L2 or L3 is supplied to the terminals K3 and K4. The terminal K3 is connected with the base of a transistor T2 to which a suitable bias voltage is supplied through a resistor R4. The emitter of transistor T2 is grounded, and the collector is connected with the feed line through a resistor R5. The collector voltage of transistor T2 is supplied to the base of a transistor T3 operating as an emitter follower. The emitter of transistor T3 is grounded through a resistor R6 and a condenser C6 in parallel with each other, and connected with the base of a transistor T4 through the series connection of a condenser C6 and an a adjustable resistor R7. The network R6, C5 integrates the current impulses produced by transistor T3, so that a DC voltage occurs across said network. Variations of this DC voltage are transmitted to transistor T4 through elements C6 and R7 The base of transistor T4 is connected with the feed line through a resistor R8 in order to produce a suitable bias voltage. The emitter of transistor T4 is grounded, and the collector is connected with the feed line through a resistor R9. The collector voltage of transistor T4 is supplied to the base of a transistor T5 of which the emitter is grounded through a diode D1, and the collector circuit contains the series connection of a resistor R10 and the energizing winding of a relay RA; a condenser C7 is connected in parallel with this winding in order to render the relay slow to deenergize. The relay RA has a switch-over contact ra.

It is pointed out that the feed voltage for transistors T4 and T5, amounting to about 20 v., is derived from the 80 v. voltage by means of a voltage divider consisting of a resistor RI 1 and a Zener diode BRIEF DESCRIPTION OF THE DRAWINGS Under normal circumstances the DC voltage at the base of transistor T4 has such a value that this transistor is conductive. Transistor T is cutoff in this case. However, if a hand is put near the proximity detector, the AC voltage supplied to the receiver is reduced to such an extent, that the DC voltage across network R6, C5 vanishes, whereby a negative voltage impulse is transmitted to transistor T4, so that the latter is cut off. Transistor T5 is now rendered conductive, so that relay A is energized. Thus, relay RA is energized at each proximity, i.e. every time when the hand is put near the proximity detector.

When relay RA is energized for the first time and contact ra is changed over, relay RB is energized through contacts m and re. A diode D2 is connected in parallel with the energizing winding of relay RB. Relay RB changes over its contacts rbl and rb2, and the magnet M of the electromagnetic valve is energized through contact rb2, so that the valve is opened.

After a delay determined by a condenser C7, relay RA is deenergized. Relay RB remains energized through contacts ra and rbl. At the same time, relay RC is energized,; a diode D3 is connected in parallel with the energizing winding of this relay. Contact rc interrupts the energizing circuit of relay RB comprising contact ra.

If the hand is again put near the proximity detector, so that relay RA is energized anew, the holding circuit of relay RB is interrupted, so that this relay is deenergized. Contact rb2 interrupts the circuit of magnet M, so that the liquid supply is terminated. Relay RC remains energized through contacts ra and re, so that the direct energizing circuit of relay RB remains interrupted. As soon as relay RA is deenergized, relay RC is also deenergized, and the circuit returns to the initial condition.

The circuits of relays RB and RC comprise decoupling diodes D4, D5 and D6. Relays RB and RC are fed through a Zener diode Z5 having a Zener voltage of 56 v., so that only a voltage of 24 v. is available for these relays. The effect of this arrangement is that relays RB and RC are deenergized and the valve is closed when the feed voltage drops below a predetermined value; in this case, the actuation by means of the proximity detectors is rendered impossible, so that the valve cannot be closed by these detectors any more.

Diode D7 serves to discharge condenser C6 when the feed voltage disappears; otherwise an impulse operating the valve might occur when the feed voltage returns.

The transistors are operated as switches, so that they are either cut off or saturated; the sensitivity to outside interference is reduced to a minimum in this manner.

In FIG. 3, the outlet pipe of a wash bowl is indicated at 1. The water leaves the outlet pipe through an outlet opening 2. A rectangular recess has been provided in the body of the outlet pipe at the upper left of FIG. 3, so as to obtain a platform carrying the sensing head. The sensing head is provided with a housing 3 made of a synthetic material and closed at the side turned towards the outlet pipe by means of a metal lid 4 attached to the housing by means of an adhesive. The lid 4 is provided with two conical projections 5 fitting into corresponding recesses of the outlet pipe and adapted to receive screws (not shown) with a countersunk head, by means of which the sensing head is secured to the outlet pipe. These screws are accessible through bores in two block-shaped bodies 6 and 7 placed on the bottom of the housing. After the screws have been fastened, these bores are filled up with casting resin or a similar hardening mass.

As appears from FIG. 4, which shows a cross section of the sensing head according to line IV-IV in FIG. 3, the proximity detectors 8 and 9 are arranged between the bodies 6 and 7 and the side walls of the housing. The detectors are screened with respect to each other by means of a plate 10.

The lid 4 is provided with an opening llI (FIG. 3) for passing the connecting lines for the detectors 8 and 9. These lines are led, as indicated at 12, through the inside of the utlet pipe in an insulated fashion.

Each of the detectors 8 and 9 comprises two condenser electrodes 13 and 14, separated by a dielectric plate 15 from a common electrode, which is situated near the side wall of the housing, so that it may readily be influenced from the outside.

When the hand is put in front of the sensing head, the two detectors are influenced simultaneously, so that the electromagnetic valves are actuated at the same time; in this manner, a supply of tepid water may be obtained.

Preferably, the housing 3 is filled up,'after the electric components have been mounted, with a casting resin or a similar hardening mass. The lid 4 may be left out, as desired; in this case, the sensing head is secured to the outlet pipe by means of longer screws e:.tending through the bores of bodies 6 and 7.

Lines Lll, L2 and L3 (FIG. I) may be combined into a coaxial cable with three inner conductors.

Referring to FIG. 5, each of the proximity detectors comprises a plate 16 made of a dielectric materials, and carrying three juxtaposed electrodes 17, I8 and 19 on one side, and a continuous electrode 20 on the other side. The electrodes 18 and 20 are grounded. A common impulse generator IG, which may be followed by an amplifier in the manner as shown in FIG. 1, supplies a high frequency signal to each of the electrodes 17. The output voltage of each proximity detector is taken from the electrode 19, and supplied to an associated control circuit; only one of these control circuits is shown in the drawing. Since the capacity between the electrodes 17 and 19 is small, and a relatively low frequency is used, the proximity detectors have a very high output impedance. For this reason, the output voltage taken from the electrode 19 is first supplied to an impedance transformer 21, which may comprise the combination of a field-effect transistor and an ordinary transistor; in practice, such a combination may have, for instance, an input impedance of megohms, and an output impedance of 199 ohms.

The output voltage of impedance transformer 21 is supplied through an amplifier 22 to a rectifier 23 converting the high frequency impulses into a direct voltage. It is advisable to use a voltage doubling rectifier, for instance of the Greinacher type, and to select the polarity in such manner that a negative direct voltage is obtained. This direct voltage is supplied through an emitter follower 24 to a Schmitt-trigger 25. Thus, whenever the hand is brought into the vicinity of the proximity detector, so that the output voltage of the same is considerably reduced, a positive impulse is supplied to the Schmitt trigger, whereby the latter is changed over and delivers an output impulse to a flip-flop 26.

Thus, the flip-flop 26 is changed over from the zero-condition to the one-condition by a first proximity, returned to the zero-condition by a second proximity, and so on. The output voltage delivers by the flip-flop in its onecondition is used to energize the associated electromagnetic valve.

For this purpose, the said output voltage is supplied to the gate electrode of a thyristor 27, connected with an AC source in series with the electromagnetic valve 28. As long as the flip flop 26 is in its one-condition, the thyristor is fired during each cycle of the AC voltage, so that the valve is energized. When the flip-flop returns to its zero-condition, the valve is put out of action. If desired, the thyristor may be fed with a pulsating voltage taken from a rectifier bridge, so that the thyristor is fired during each half cycle.

When the device is switched on, care must be taken that the flip-flop 26 is brought into its zero-condition, since otherwise the liquid supply would start immediately. For this purpose, a

resetting circuit 29 has been provided, which supplies a long voltage impulse to the flip-flop 26, whereby the latter is brought into and/or kept in its zero-condition. The said voltage impulse is taken from the charging circuit of a condenser, so that it vanishes as soon as the condenser has been fully charged.

Iclaim:

l. A liquid dispensing device, comprising an outlet pipe, at least one electromagnetic valve regulating the flow of a liquid through said outlet pipe, a proximity detector operating as a variable voltagedivider, associated with said electromagnetic valve and attached to said outlet pipe,'a high frequency oscillator, means connecting said high frequency oscillator with said proximity detector, a control circuit adapted to receive an input voltage and to actuate said electromagnetic valve in dependence on said input voltage, and means for supplying the output voltage of said proximity detector to said control circuit, the arrangement being such that the output voltage of the proximity detector may be influenced by putting the hand near the same.

2. A liquid dispensing device as claimed in claim 1, wherein said proximity detector comprises two series connected condensers having one electrode in common and each having one separate electrode, one of the said separateelectrodes being connected withsaid high frequency oscillator and the other one with said control circuit, the arrangement being such that the output voltage of said proximity detector may be influenced byputting the hand near said common electrode.

3. A liquid dispensing device as claimed in claim 1, wherein said proximity detector comprises a dielectric plate, three juxtaposed separate electrodes on one side of said plate, a continuous electrode facing the said separate electrodes on the other side of said plate, ground connections for said continuous electrode and for the middle one of the said separate electrodes, and means connecting one of the outer separate electrodes with said highfrequency oscillator and the other outer separate electrode with said control circuit, the arrangement being such that the output voltage of said proximity detector may be influenced by putting the hand near the said separate electrodes. v

4. A liquid dispensing device as claimed in claim 3, further comprising an impedance transformer between said proximity detector and said control circuit. f

5. A liquid dispensing device, comprising an outlet pipe two electromagnetic valves regulating the flow of different liquids, through said outlet pipe, two proximity detectors operating as variable voltage dividers, each associated with one of the said electromagnetic valves attached to said outlet pipe, a common high frequency oscillator, means connecting said high frequency oscillator with each of the said proximity detectors, two control circuits each associated with one of the said electromagnetic valves and each adapted to receive an input voltage andto actuate the associated electromagnetic valve in dependence on said input voltage, and means for supplying the output voltage of each of the said proximity detectors to the associated control circuit, the arrangement being such that the output voltage of each of the said proximity detectors may be influenced by putting the hand near the same.

6. A liquid dispensing device as claimed in claim 5, wherein the two electromagnetic valves regulate the flow of hot and cold water through said outlet pipe, respectively.

7. A liquid dispensing device asclaimed in claim 5, wherein the two proximity detectors are arranged on opposite sides of said outlet pipe.

. 8. A liquid dispensing device as claimed in claim 5, wherein the two proximity detectors are arranged on said outlet pipe in such positions that they may be simultaneously influenced by one hand. i i

9. A liquid dispensing device as claimed in claim 5, further comprising an insulating housing attached to said outlet pipe and enclosing the two proximity detectors, and means within said housing to screen the two proximity detectors with respect to each other.

10. A liquid dispensing device as claimed in claim 5, further comprising a group of connecting lines for each proximity detector, means for insulating each of the said groups, and means forleading the said insulated groupsthrough said outlet pipe.

11. A liquid dispensing device, comprising an outlet pipe, at least one. electromagnetic valve regulating theflow of a liquid through said outlet pipe, a proximity detector operating as a variable voltage divider, associated with said electromagnetic valve and attached tosaid outlet ipe, a high frequency oscillator, means connectmg said hig frequency oscillator with said proximity detector, means for amplifying the output voltage of said proximity detector, rectifying means converting said amplified output voltage into a direct voltage, and control means actuating said electromagnetic valve in dependence on said direct voltage in such manner that said valve is opened by a first proximity, and closed again by a second proximity.

12. A liquid dispensing device as claimed in claim 11, wherein the said control means comprises a first, a second and a third relay each having at least one contact, said first relay being energized at each proximity, an energizing circuit for said second relay extending through a :make contact of said first relay and a break contact of said third relay, a circuit for holding said second relay and for energizing said third relay extending through a break contact of said first relay and a first make contact of said second relay, a holding circuit for said third relay extending through a make contact of said first relay and a make contact of said third relay, and an energizing circuit for said electromagnetic valve extending through a second make contact of said second relay.

13. A liquid dispensing device as claimed in claim ll, wherein the said control means comprise a Schmitt trigger fired at each proximity, a flip-flop changed over at each firing of said Schmitt trigger and having a zero-output and a oneoutput and means for energizing said electromagnetic valve connected with the one-output of said flip-flop.

14. A liquid dispensing device as claimed in claim 12, further comprising a DC source for feeding the said control means, and a Zener diode inserted between said DC source and the said control means.

15. A liquid dispensing device as claimed in claim 13, further comprising an AC source, a thyristor having a gating electrodes, means for connecting said electromagnetic valve with said AC source through said thyristor, and means connecting the gating electrode of said thyristor with the one-output of said flip-flop.

16. A liquid dispensing device as claimed in claim 13, further comprising a resetting circuit for said flip-flop, a condenser in said resetting circuit, charging means for said condenser, means for deriving a voltage impulse from the said charging means, and means for supplying said voltage impulse to said flip-flop in such manner, that said flip-flop is kept in its zero-condition during a predetermined interval following the time at which the liquid dispensingdevice is switched on.

Claims

1. A liquid dispensing device, comprising an outlet pipe, at least one electromagnetic valve regulating the flow of a liquid through said outlet pipe, a proximity detector operating as a variable voltage divider, associated with said electromagnetic valve and attached to said outlet pipe, a high frequency oscillator, means connecting said high frequency oscillator with said proximity detector, a control circuit adapted to receive an input voltage and to actuate said electromagnetic valve in dependence on said input voltage, and means for supplying the output voltage of said proximity detector to said control circuit, the arrangement being such that the output voltage of the proximity detector may be influenced by putting the hand near the same.

2. A liquid dispensing device as claimed in claim 1, wherein said proximity detector comprises two series connected condensers having one electrode in common and each having one separate electrode, one of the said separate electrodes being connected with said high frequency oscillator and the other one with said control circuit, the arrangement being such that the output voltage of said proximity detector may be influenced by putting the hand near said common electrode.

3. A liquid dispensing device as claimed in claim 1, wherein said proximity detector comprises a dielectric plate, three juxtaposed separate electrodes on one side of said plate, a continuous electrode facing the said separate electrodes on the other side of said plate, ground connections for said continuous electrode and for the middle one of the said separate electrodes, and means connecting one of the outer separate electrodes with said high frequency oscillator and the other outer separate electrode with said control circuit, the arrangement being such that the output voltage of said proximity detector may be influenced by putting the hand near the said separate electrodes.

4. A liquid dispensing device as claimed in claim 3, further comprising an impedance transformer betweEn said proximity detector and said control circuit.

5. A liquid dispensing device, comprising an outlet pipe , two electromagnetic valves regulating the flow of different liquids through said outlet pipe, two proximity detectors operating as variable voltage dividers, each associated with one of the said electromagnetic valves attached to said outlet pipe, a common high frequency oscillator, means connecting said high frequency oscillator with each of the said proximity detectors, two control circuits each associated with one of the said electromagnetic valves and each adapted to receive an input voltage and to actuate the associated electromagnetic valve in dependence on said input voltage, and means for supplying the output voltage of each of the said proximity detectors to the associated control circuit, the arrangement being such that the output voltage of each of the said proximity detectors may be influenced by putting the hand near the same.

7. A liquid dispensing device as claimed in claim 5, wherein the two proximity detectors are arranged on opposite sides of said outlet pipe.

8. A liquid dispensing device as claimed in claim 5, wherein the two proximity detectors are arranged on said outlet pipe in such positions that they may be simultaneously influenced by one hand.

10. A liquid dispensing device as claimed in claim 5, further comprising a group of connecting lines for each proximity detector, means for insulating each of the said groups, and means for leading the said insulated groups through said outlet pipe.

11. A liquid dispensing device, comprising an outlet pipe, at least one electromagnetic valve regulating the flow of a liquid through said outlet pipe, a proximity detector operating as a variable voltage divider, associated with said electromagnetic valve and attached to said outlet pipe, a high frequency oscillator, means connecting said high frequency oscillator with said proximity detector, means for amplifying the output voltage of said proximity detector, rectifying means converting said amplified output voltage into a direct voltage, and control means actuating said electromagnetic valve in dependence on said direct voltage in such manner that said valve is opened by a first proximity, and closed again by a second proximity.

12. A liquid dispensing device as claimed in claim 11, wherein the said control means comprises a first, a second and a third relay each having at least one contact, said first relay being energized at each proximity, an energizing circuit for said second relay extending through a make contact of said first relay and a break contact of said third relay, a circuit for holding said second relay and for energizing said third relay extending through a break contact of said first relay and a first make contact of said second relay, a holding circuit for said third relay extending through a make contact of said first relay and a make contact of said third relay, and an energizing circuit for said electromagnetic valve extending through a second make contact of said second relay.

13. A liquid dispensing device as claimed in claim 11, wherein the said control means comprise a Schmitt trigger fired at each proximity, a flip-flop changed over at each firing of said Schmitt trigger and having a zero-output and a one-output and means for energizing said electromagnetic valve connected with the one-output of said flip-flop.

16. A liquid dispensing device as claimed in claim 13, further comprising a resetting circuit for said flip-flop, a condenser in said resetting circuit, charging means for said condenser, means for deriving a voltage impulse from the said charging means, and means for supplying said voltage impulse to said flip-flop in such manner, that said flip-flop is kept in its zero-condition during a predetermined interval following the time at which the liquid dispensing device is switched on.