GB2153260A

GB2153260A - Electrostatic spray gun for spray coating

Info

Publication number: GB2153260A
Application number: GB08501037A
Authority: GB
Inventors: Karl Buschor; Gunther Fleig
Original assignee: Gema Switzerland GmbH
Current assignee: Gema Switzerland GmbH
Priority date: 1984-01-28
Filing date: 1985-01-16
Publication date: 1985-08-21
Also published as: IT1183311B; JPS60161764A; GB8501037D0; JPH0477623B2; IT8519241A0; CH663360A5; DE3402945A1; FR2558742B1; DE3402945C2; FR2558742A1; GB2153260B

Abstract

The spray gun has at least one electrode (10, 12) for the electrostatic charge of the coating material. At the rear end (18) of the gun is a display panel (20) facing rearwardly of a voltmeter (7) to provide an optical signal as a function of the power supply of the electrode. The operator can thus have the object, spray cloud and voltage reading in his field of vision and take appropriate action quickly in response to any deviations. <IMAGE>

Description

SPECIFICATION Electrostatic spray gun for spray coating The invention concerns an electrostatic spray gun for spray coating, with at least one electrodue for the electrostatic charge of the coating material, a handle and a gun burrel for atomising the coating material.

A special area of application of the invention is to electrostatic spray guns for spraying objects with a coating of liquid varnish. However the invention also concerns electrostatic spray guns for spraying objections with a coating of powdery coating material.

Spray guns of this type are known from German patent specification 20 30 388 and Swiss patent specifications 496 481, 583 476 and 623 489. The spray guns are supplied with the electric voltage required for the electrodes by switch cabinets. Switch cabinets are known which have luminous diodes to indicate the voltage of the electrodes. The objects are only covered with a very thin coating. Small modifications to the coating material atomised with the spray gun (quantity of material, material composition, spray-direction) result in visible defects in the coating.

Therefore the operator has to observe the coating operation continually and with concentration.

The invention is to solve the problem of avoiding defects in the coating caused by voltage failure or incorrect voltage of the electrodes in a simple and cheap way.

This problem is solved by the invention in that on the spray gun is provided with voltage indicating means, a voltmeter, e.g. having a display panel or the like arranged to face rearwardly of the spray gun and display an optical signal which is a function of the respective voltage of the electrode(s).

Thus, in accordance with the invention, it is possible for the operator to have both the object to be coated, the cloud of coating material atomised with the spray gun and also an indication of the voltage reading in his field of vision at the same time, so that he can identify deviations immediately and take appropriate action.

Preferably at least one luminous diode serves as the indicator. It has an almost unlimited life and small current consumption.

However, incandescent lamps, voltmeters and similar voltage-dependent optical indicators can be used.

An embodiment of electrostatic spray gun in accordance with the invention is described below with reference to the accompanying drawings, in which Figure 1 shows the spray gun in side elevation, connected to a switch box, Figure 2 is a rear view of the spray gun and Figure 3 is a diagram of an electrical circuit for the spray gun.

The electrostatic spray gun 1 essentially consists of a handle 2, a gun barrel 3 in the form of a plastic accessory with a fused high voltage cascade circuit 4 and detachably fixed to the handle 2, and a transformer housing 5 detachably fixed on to the handle 2 having a high voltage transformer 6 and voltage indicating means in the form of a voltmeter 7 with an indicating lamp positioned inside. It preferably contains one or more luminous diodes. A high voltage cascade circuit 4 is known, for example from German Patent Specification 20 30 388, and is therefore not described in detail here. The transformer 6 transforms a low alternating voltage of less than 100 volts, preferably approximately 10 volts on its primary side into a high alternating voltage of more than 50,000 volts, preferably approximately 70,000 volts, on its secondary side.The secondary side of the transformer 6 stores the high voltage cascade circuit 4 which transforms the high alternating voltage into a high direct voltage and consequently charges at least one electrode 10 and/or 1 2 which is sited in the powder flow channel 9 of the gun barrel 3 and/or in the flow path of the coating material sprayed at the end 1 4 of the gun barrel. The coating material is preferably liquid or powdery varnish. The indicating lamp 7 is situated at the rear end 1 6 of the spray gun in the transformer housing 5 and contains at least one luminous diode 1 7 in the rear wall 18 of the transformer housing 5. The display panel 20 of the indicating lamp 7 is formed by a red pane of glass and faces rearwardly of the gun.

The high voltage cascade connection 4 contains in accordance with Fig. 3 a per se known, so-called "Greinacher" circuit as specified in German Patent 20 30 388 with rectifiers 24 and condensors 26 to rectify the high alternating voltage. Between its output 25 and the electrodes 10 and 1 2 is situated a protective resistor 28. The input of the high voltage cascade circuit 4 is connected via a plug connection 30 to the secondary winding 34 of the transformer 6.

The luminous diode 1 7 is switched parallel to the primary winding 36 of the transformer and is situated in series connection between a resistor 38 and a rectifier 40 which both act as protective elements for the luminous diode 1 7. Consequently the luminous diode 1 7 burns more strongly or more weakly depending on the voltage at the input 42 of the primary winding 36. Thereby the brightness of the luminous diode 1 7 is a measure of the voltage at the electrodes 10 and 12. The voltage at the input 42 of the primary winding 36 may alter unintentionally and thereby result in defects in the coating of an object to be coated if the error is not noticed in good time. The input 42 of the primary winding 36 is connected via a power supply lead 46 to a voltage source 48 in a switch cabinet 50. In the power supply lead 46 is a voltage regulator 52 with which the voltage at the input 42 of the primary winding can be selectively adjusted.

According to Fig. 1 a supply appliance 56 for coating material is connected via a hose line 58 to the spray gun 1 which has an operating lever 60.

The voltmeter 7 therefore serves as a function indicator for the spray gun 1 and is situated at its rear end 1 8 in a position clearly visible to an operator so that the operator has both the spray gun 1 and the sprayed coating material 62 and also the indicator panel 20 of the voltmeter 7 in his field of vision at the same time. The operator therefore need not look away from the coating material sprayed to check the voltage.

Claims

1. An electrostatic spray gun for spray coating, having at least one electrode (10, 12) for the electrostatic charge of the coating material (62), a handle (2) and a gun barrel (3) for atomising the coating material (62), characterised in that on the spray gun is provided a voltage indicating (7) having a display panel or the like (20) facing rearwardly of the spray gun to display an optical signal which is a function of the respective voltage of the electrode(s) (10,1 2).

2. A spray gun according to Claim 1, characterised in that the voltage indicating means (7) is arranged at the rear end of the gun.

3. A spray gun according to Claim 1 or 2, characterised in that a high voltage generator circuit (4,5) is provided which converts a low alternating voltage at its input (25), in that the electrode (10,1 2) is stored by the direct voltage output (25), and in that the voltage indicating means (7) comprises a voltmeter with at least one indicator lamp, preferably a luminous diode (17), which is connected to the alternating voltage input (42) and illuminates the rearward facing indicator panel (20).

4. A spray gun according to Claim 3, characterised in that the high voltage generator circuit (4,6) has at its alternating voltage input (42) a transformer (6) which converts a low alternating voltage at its primary side (36) into a high alternating coltage at its secondary side (34), and in that the high voltage generator circuit has a high voltage cascade connection (4) with rectifiers (24) and condensors (26) which is connected to the secondary winding (34) of the transformer (6) and converts the high alternating voltage into high direct voltage.

5. A spray gun according to Claim 3 or 4, characterised in that the luminous diode (17) is connected in series between an electric resistor (38) and a rectifier (40) as overload protection elements.

6. A spray gun according to Claim 4 or 5, characterised in that the transformer (6) and the indicator lamp (7) are sited in a common housing (5) which is detachably ficed on the top to the handle (2).

7. A spray gun according to any one of Claims 4 to 6, characterised in that the high voltage cascade circuit (4) is sited in the gun barrel (3).

8. A spray gun according to Claim 7, characterised in that the gun barrel (3) is detachably fixed to the handle (2).

9. A spray gun according to any one of Claims 3 to 8, characterised in that the low alternating voltage is less than 100 volts, preferably approximately 10 volts, and in that the high direct voltage is greater than 50,000 volts, preferably approximately 70,000 volts.

10. An electrostatic spray gun constructed, arranged, and adapted for use substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.