JPS6247072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for operating a spray pistol with an oscillating armature drive, as well as a device for implementing this method.

Spray pistols with an oscillating armature drive have a piston (plunger) that is slidable within a pump cylinder. The piston is pretensioned into the suction position by a pretensioning spring and is moved by an electromagnet against the force of the pretensioning spring in order to convey the aspirated liquid in the direction towards the injection head of the spray pistol. It is made to be wet.

The piston, electromagnetic armature, and pretension spring cooperate with each other to continuously supply the energy needed to atomize the liquid from the AC power source.

In such known spray pistols, the spray capacity, ie the amount of liquid sprayed per unit time, is adjusted as follows. That is, the suction stroke of the pump piston is limited by an adjustable mechanical stop.

However, such a mode of regulation can only reduce the spray capacity to about 300 grams per minute. This is because if the piston suction stroke is made any smaller, the liquid is no longer atomized satisfactorily.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for operating a spray pistol with an oscillating armature drive, as well as an operating circuit thereof, which makes it possible to atomize liquid satisfactorily even at low injection powers. That's true.

According to the invention, an excitation signal having a steeply rising waveform and pulse width modulated is supplied to the oscillating armature drive in order to reduce the amount of liquid sprayed per unit time by the spray pistol. a control circuit for generating a control signal having a steeply rising waveform; and a controllable switch connected between a voltage supply source and an oscillating armature, the method comprising: A device characterized in that the control terminal of the control circuit is connected to the outlet of the control circuit, or a signal generator for generating a control signal having a steeply rising waveform, and a power supply connected after the signal generator. The above problem is solved by a device comprising a power amplifier, the outlet of the power amplifier being connected to an oscillating armature drive.

In the conventionally known method, the adjustment of the atomizing power in a spray pistol driven by an oscillating armature is carried out by adjusting the end of the suction stroke, and the end of the conveying stroke is selected independently of the atomizing power. If the forced operation of the non-return valves on the conveying side, that is on the discharge side, was carried out at the same time by the pump piston, adjustments were made, if necessary, according to the viscosity of the liquid to be sprayed (Swiss patent no.
360625).

In contrast, in the method of the invention, in which the end point of the suction stroke is fixed in advance, the end point before the piston transport stroke is varied by varying the effective power supplied to the oscillating armature drive. In this case, therefore, only a small amount of liquid can be delivered to the injection head per stroke of the piston by stopping the piston immediately after it has passed through the suction hole located in the side wall of the pump cylinder. It becomes possible to do so.

In this way, despite the small throughput of liquid, it is ensured that at the injection head the high pressure required to transform the liquid into a fine mist is obtained. This is because, in the method according to the invention, the oscillating armature drive is excited with successive pulses with a steeply rising waveform, and thus the piston can be accelerated accordingly in an abrupt manner. It is.

Moreover, when comparing the present invention with the known technology, it is found that according to the present invention, the noise generated during operation is significantly reduced, and once the injection capacity is adjusted, this
This is even more advantageous since it can be kept fairly constant.

Thus, in the case of the known spray pistol, at the end of the suction stroke, the armature connected to the piston comes into sharp contact with a stop fixed to the housing, so that a very unpleasant impact noise is generated. Such a strong abutment can lead to fluctuations in the previously set position of the stopper and to an increase in the spray force, which is extremely disadvantageous for delicate painting operations.

According to an advantageous embodiment of the invention, it is provided that an excitation signal, which also has a steeply falling waveform and is modulated in pulse width, is supplied to the oscillating armature drive, so that: The pump piston is stopped particularly abruptly.

It is therefore possible to adjust the injection power particularly small, and in that case, during rapid movements of the pump piston between a sudden acceleration and a sudden stop, a desired value of pressure can be applied to the injection of the spray pistol. It can be generated within the head.

As in another embodiment of the present invention, methods are readily available in which steeper waveforms are produced by switching the power supply signal more slowly compared to the rise time of the waveform. It is particularly easy to implement using a standard power supply. In this case, the power source to be used is
Usual AC power sources as well as DC power sources can be considered.

Next, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

The spray pistol 10 shown schematically in FIG. 1 has an oscillating armature drive (not shown), which actuates a horizontally displaceable piston in a pump cylinder. A suction hole is provided in the wall of the pump cylinder;
It is connected via a suction pipe to a storage container 12 of the liquid to be sprayed.

The suction side of the piston pump, which is formed by the piston and the pump cylinder, is not provided with any special suction valve; on this suction side, the pump is operated by slit control by the piston itself. On the other hand, on the discharge side, a check valve is provided in the pump cylinder, via which the liquid is delivered to the injection head 14.

Note that the details of the pump structure and the oscillation armature drive device are well known to those skilled in the art, and therefore are not shown in the drawings.

The operating circuit for the spray pistol 10 shown in FIG.
and a signal generator 20.

Advantageously, the voltage supply source 16 is, for example, a battery or a direct current source obtained by rectifying an alternating current with a rectifier. Advantageously, the signal generator 20 operates with pulses of adjustable width and, in addition, with adjustable frequency. The controllable switch 18 can be constructed as a semiconductor switch, in particular a power transistor, or as a thyristor.

These electronic components are known per se and are commercially available in different versions, so they will not be described in detail here.

Next, the operation of the apparatus shown in FIG. 1 will be described.

The signal generator 20 generates a square wave signal having a steeply rising and steeply falling waveform. This control signal, activated by a small output, is used to modulate the supply voltage waiting at the input of the switch 18. Thus, at the outlet of the switch 18, a spray pistol excitation signal is obtained which has the same frequency keying ratio (period to pulse width) as in the control signal, but with a higher output.

As a result, a magnetic field is periodically and very rapidly generated and extinguished in the field coil of the oscillating armature drive in the spray pistol, and the pump piston is correspondingly suddenly accelerated and braked. be done.

The amplitude of the pump stroke is reduced by increasing the keying ratio of the control signal. The reason for this is that in this case the energy simultaneously supplied on average per unit time to the oscillating armature drive is correspondingly reduced, and, as mentioned above, the magnetic field is generated and dissipated very quickly. This is because they are made to do so.

Due to the small amplitude of the oscillating armature drive and the effective matching to the pump dynamics, it is possible to vary the frequency of the control signal somewhat simultaneously with the keying ratio. In practice, this frequency follow-up is forced in conjunction with variations in the keying ratio, e.g. in a square wave signal generator, by a mechanical coupling of two potentiometers that predetermine the pulse width and period. I am made to do so.

The operating circuit shown in FIG. 2 is almost the same as the circuit of FIG. 1, except that a power amplifier 22 is provided instead of a voltage supply and a controllable switch.

This amplifier 22 amplifies the control signal originating from the signal generator 20 as an excitation signal to be supplied to the spray pistol 10.

The operating type of this operating circuit is ultimately the same as that of the operating circuit shown in FIG.

FIG. 3 shows details of an operating circuit similar to that of FIG. The difference in this case from the one in FIG. 1 is that the voltage supply source is replaced by AC power supply terminals 24 and 26.

As a controllable switch, thyristor 28
is provided. This thyristor 28 is connected in series with a coil 30 of the oscillating armature drive and a manually operable main switch 32.

The gate terminal of the thyristor 28 is connected to a phase-rotating voltage divider circuit via a double diode (bi-diode) 34. The voltage divider circuit includes a series circuit consisting of an adjustable resistor 36 and a capacitor 38 connected in series to the AC terminals 24,26. Capacitor 38 is further bridged by another series circuit consisting of resistor 40 and capacitor 42.

The circuit connection point between resistor 40 and capacitor 42 forms the exit of a phase-rotating voltage divider circuit, with 2
It is connected to a heavy diode 34.

By adjusting the resistor 36, the phase angle at which the conduction of the thyristor 28 is controlled is adjusted. At this point of conduction control, the rapidly rising waveform causes
A voltage is applied to the coil 30, causing a rapid acceleration of the pump piston.

By increasing the phase angle at which conduction of the thyristor 28 is controlled, the keying ratio can be increased and the amplitude of the pump piston movement can be reduced. In practice, the phase angle is set between 15° and 170°, so that the stroke of the pump piston can be varied within very large tolerance limits.

The operating circuit shown in FIG. 3 together with the oscillating armature drive can be easily accommodated in the casing of the spray pistol.

If a triax is used instead of the thyristor 28, the oscillating armature drive can be operated at twice the frequency of the alternating current network.

[Brief explanation of the drawing]

1 shows a schematic diagram of a spray pistol with an oscillating armature drive and an associated operating circuit; FIG. 2 a schematic diagram of a spray pistol with a different operating circuit from the embodiment of FIG. 1; FIG. 3 shows an operating circuit for a spray pistol with an oscillating armature drive. 10...Spray pistol, 12...Storage container, 1
4... Injection head, 16... Voltage supply source, 18...
...Switch, 20... Signal generator, 22... Power amplifier, 24, 26... AC power supply terminal, 28...
Thyristor, 30... Coil, 32... Main switch, 34... Double diode, 36, 40...
...Resistor, 38,42...Capacitor.

Claims (1)

[Scope of Claims] 1. A method for operating a spray pistol having an oscillating armature drive, in which the oscillating armature drive is excited by an electrical alternating signal, in which A method characterized in that, in order to reduce the amount of liquid sprayed, an excitation signal having a steeply rising waveform and pulse width modulated is supplied to the oscillating armature drive. 2. A method according to claim 1, characterized in that a pulse width modulated excitation signal having a steeply falling waveform is supplied to the oscillating armature drive. 3. Claim 1, characterized in that a waveform with a steep slope is produced by switching the power supply signal that can be changed slowly compared to the waveform rise time.
or the method described in paragraph 2. 4. The keying ratio of the pulse-width modulated signal is increased while maintaining its amplitude in order to reduce the atomizing capacity. the method of. 5. Device for implementing a method for operating a spray pistol with an oscillating armature drive excited by an electrical alternating signal, the control circuit 20 generating a control signal with a steeply rising waveform.
a controllable switch 1 connected between the voltage supply source 16 and the oscillating armature drive;
8, and a control terminal of the switch 18 is connected to an outlet of the control circuit 20. 6. In the device according to claim 5, in which the voltage supply source is an AC power supply, the control circuit includes phase shift circuits 36 to 4 connected to the AC power supply terminals 24 and 26.
2, and the controllable switch is formed by a thyristor 28 or a triax. 7 Outlets of phase shift circuits 36 to 42 and thyristor 2
8. The device according to claim 6, further comprising a double diode (34) connected between the control terminal of the triac and the control terminal of the triac. 8. Device according to claim 5, characterized in that the control circuit 20 is formed by a square wave signal generator or a sawtooth signal generator. 9. The device according to any one of claims 5 to 8, characterized in that a manually operable switch 32 is connected in series to the controllable switches 18, 28. 10. Device for implementing a method for operating a spray pistol with an oscillating armature drive excited by an electrical alternating signal, a signal generator 20 producing a control signal with a steeply rising waveform; A device characterized in that it comprises a power amplifier 22 downstream of the signal generator 20, the outlet of the power amplifier 22 being connected to an oscillating armature drive.