WO1997035672A1

WO1997035672A1 - Equipment for cleaning spray guns

Info

Publication number: WO1997035672A1
Application number: PCT/GB1997/000532
Authority: WO
Inventors: Gordon Boyd
Original assignee: Edwin Trisk Systems Limited
Priority date: 1996-03-28
Filing date: 1997-02-26
Publication date: 1997-10-02
Also published as: GB2311475A; GB9606528D0; GB9703975D0; AU1888797A

Abstract

Equipment for cleaning spray guns includes a cleaning chamber (10), means (33) to support at least one spray gun (11) therein, a number of liquid spay nozzles (12, 13, 14) to spray cleaning liquid onto the spray gun, and an electric pump (20) to convey cleaning liquid to and through the spray nozzles.

Description

"Equipment for Cleaning Spray Guns".

This invention relates to the cleaning of spray guns of the type used to apply a paint coating to a surface. More specifically the invention comprises equipment for cleaning spray guns.

Spray guns of the foregoing type are widely used, in particular in the automotive industry, for applying a decorative and/or functional coating to a surface such as a vehicle panel, usually in the process of repairing damaged vehicle bodywork. A single such gun may be used successively for spraying paints of a range of different colours and must therefore be cleaned between spraying operations. Of course the cleaning must be comprehensive, since any paint remaining within or upon the spray gun from one spraying operation would seriously contaminate a coating applied in a subsequent spraying. However it is equally important that the cleaning should be carried out efficiently and as quickly as possible, since it is desirable that the spray gun being cleaned should be available for further use without undue delay. Similarly, it is desirable that the time which the spraying operative must devote to cleaning the gun should be kept to a minimum.

The requirement to provide spray gun cleaning equipment to meet some at least of these criteria has hitherto been addressed in different ways. For example, in Patent Specification EP 0300248 B, apparatus for cleaning spray guns and parts is described which comprises a cleaning cabinet into which cleaning fluid is ejected through a plurality of outlets by means of a pneumatically actuated fluid pump, the operation of which is controlled by a pneumatic time valve. Patent Specification EP 0443421 B describes an alternative device comprising a cleaning space in which spray guns may be mounted, preferably one at a time, and into which solvent is sprayed by means of pressurised air and without the use of a liquid pump; at least one additional nozzle is provided to enable manual cleaning of the gun.

These prior forms of spray gun cleaning equipment both rely upon pressurised air for their operation. However our own research suggests that effective, efficient and quick cleaning of spray guns requires a combination of solvent pressure, volume and velocity which is difficult to achieve satisfactorily and economically using pressurised air. Uneconomically large pneumatic pumps or the use of levels of air consumption not readily available in most vehicle bodyshops would be entailed. Against this background, it is an object of the present invention to provide an improved form of equipment for cleaning spray guns, by means of which some at least of the disadvantages of prior such equipment may be reduced or avoided. The spray gun cleaning equipment according to the present invention is distinguished from prior such equipment in that the jets of cleaning fluid are electrically powered.

Thus the equipment according to the invention comprises a cleaning chamber, means to support at least one spray gun therein, a plurality of liquid spray nozzles whereby to spray cleaning liquid on to the spray gun, and an electric pump to convey cleaning liquid to and through the spray nozzles. By virtue of the adoption of an electric pump to drive the sprays of cleaning liquid, it becomes possible to obtain a more effective cleaning of the spray gun and to carry out the cleaning economically even with the often restricted resources normally available within or in the region of a spray booth. In addition, once the use of an electric pump has been accepted, then extensive opportunities for enhanced operation and control of spray gun cleaning equipment become available, as will be explained hereinafter.

The cleaning chamber preferably contains several spray nozzles, preferably arranged in groups, which nozzles are desirably so orientated as to ensure that liquid impinges upon the whole of the outer surface of the gun. The gun is preferably mounted upon a support having associated with it means to retain the liquid channel through the gun in an open condition. In order to ensure that the interior of the spray gun is thoroughly cleaned, cleaning liquid should also preferably be directed through the paint inlet of the gun. In one particularly preferred form of the equipment according to the invention, a compressed air line is connected to the air inlet of the spray gun, in order further to enhance the effectiveness of the cleaning of the gun interior.

The cleaning chamber is preferably provided with drainage means whereby to collect cleaning liquid after it has been sprayed on to the gun and to convey such used liquid away to be recovered and/or recycled. Preferably at least one additional spray nozzle is provided, within or adjacent to the cleaning chamber, to allow a spray gun to be further cleaned manually if such additional cleaning proves to be necessary.

It is important to ensure that electrical power is kept isolated from any contact with the cleaning liquid, because the liquid used for cleaning spray guns is usually a volatile, and therefore potentially explosive, solvent. To that end, the electric pump motor is preferably contained in an enclosure which is continuously or intermittently purged of air or otherwise isolated from solvent.

Thus the pump motor may be contained within a firebox designed specifically for the purpose, from which only the operating head of the pump projects.

Because the use of electric power to drive the liquid pumps opens up various control possibilities, for example enabling the cleaning of one or more spray guns to be carried out wholly automatically, then it is desirable to provide an electric control box to operate the cleaning equipment and/or to monitor its operation. Such an electric control box is preferably also located within a suitable isolation cabinet, which may also contain the pump motor. Where circulation of the liquid is directed and diverted by electrically operated valves, at least the electrical parts of the valves should also preferably be similarly isolated w th other electric components. Alternatively, the valves may be located wholly outside the control box and may then be operated as required by mechanical means driven in turn by one or more motors located within the control box. In a strongly preferred form of the present invention wherein tne cleaning operation is largely or wholly automatic, the progress of the cleaning operation and the condition of the solvent, of the cleaning equipment and/or of the spray gun being cleaned may very advantageously be monitored and/or indicated by means of display dials or preferably simple indicator lamps. For example, the condition of the solvent and/or the spray gun, that is how clean or dirty it is, may be shown by one or more indicator bulbs. Similar indicators showing the condition of the equipment or of components thereof may further be provided.

The speed of operation of the electric pump may be designed to be variable manually but in a preferred form of the invention the speed may be variable automatically, for example cyclically or in regular or irregular pulses , to enhance the cleaning effect. Thus, for example, the cleaning cycle may be open to selection by the simple pressing of a control button, such as to select fast, slow or pulsed washes.

The invention will now be further described, by way of example only, with reference to the accompanying drawing, which is a schematic illustration of one preferred embodiment of the spray gun cleaning equipment according to the present invention.

The illustrated spray gun cleaner comprises a lidded chamber 10 into which the spray gun is positioned for cleaning. The spray gun 11 is mounted upon a support 33 whereon it is held with its fluid inlet nozzle in an open position. The gun is surrounded by three arrays ( in the illustrated example) of spray nozzles 12, 13 and 14 by means of which cleaning fluid in the form of a solvent for the paint is sprayed upon the outer surface of the gun. By a line 15, a further supply of solvent s fed through the interior of the gun via its fluid inlet.

Compressed air, supplied to the gun cleaner via a line 16, is fed by a line 17 to the spray gun inlet and by a line 18 to a vapour extraction system 19.

The circulation of cleaning fluid through the system is effected by an electrically driven pump 20. The pump 20 is mounted within a flame-proof enclosure 21, with the pump head only extending through the wall of the enclosure. By means of the pump 20, the cleaning fluid is fed to the spray nozzles within the chamber 10 and, when required, to a further spray 22 sited outside the chamber, by means of which a spray gun may be cleaned manually if necessary, optionally with the assistance of compressed air supplied by the line 34.

Spent or "dirty" cleaning fluid is drained from the chamber 10, via a line 23, to a fluid collector 24, the level of fluid therein being monitored by a detector 25. From the collector 24, spent fluid is withdrawn as required, via a line 26, for recycling or recovery as necessary. Clean fluid is supplied from a vessel 27.

The selection between spent and clean fluid for supplying to the spray nozzles is controlled by a three-way valve 28. A valve 29 directs the cleaning fluid either to the nozzles 12 and 13 or to the nozzles 14 and the gun inlet. The nozzles 12 and the nozzles 14 are grouped upon rotary spray bars 35 and 36 respectively; the nozzles 13 form a fixed array. Control of the compressed air supply is by a valve 30. In the illustrated embodiment of the invention, the valves 28, 29 and 30 are located in the wall of the flame-proof enclosure 21, with their electrical parts within the enclosure.

The illustrated gun cleaner is designed to be operated automatically, under the control of a control box 31, in response to activation by an on/off switch 32 The operating programme may be varied as desired.

Claims

CLAI MS

1. Equipment for cleaning spray guns, comprising a cleaning chamber (10), means (33) to support at least one spray gun (11) therein, a plurality of liquid spray nozzles (12, 13, 14) whereby to spray cleaning liquid on to the spray gun, and an electric pump (20) to convey cleaning liquid to and through the spray nozzles.

2. Cleaning equipment according to Claim 1, characterised in that it comprises several spray nozzles, arranged in groups upon rotary spray bars (35, 36).

3. Cleaning equipment according to Claim 1 or Claim 2, characterised in that the spray gun support (33) has means to retain the liquid channel through the gun in an open condition.

4. Cleaning equipment according to Claim 3, further characterised by having means (17) to connect a compressed air line (16) to the air inlet of the spray gun (11 ).

5. Cleaning equipment according to any of the preceding claims, further characterised by having drainage means (23) to collect cleaning liquid after spraying and to convey the liquid away for recovery or recycling.

6. Cleaning equipment according to any of the preceding claims, further characterised by having at least one additional spray nozzle (22), within or adjacent to the cleaning chamber, to permit manual cleaning of a spray gun.

7. Cleaning equipment according to any of the preceding claims, characterised in that the electric motor of said pump (20) is contained in an enclosure (21) which is isolated from cleaning liquid.

8. Cleaning equipment according to Claim 7, characterised in that the operating head of the pump (20) projects from said enclosure (21).

9. Cleaning equipment according to any of the preceding claims, further characterised by an electric control box (31) to operate said equipment and/or to monitor its operation.

10. Cleaning equipment according to Claim 9, characterised in that circulation of cleaning liquid is directed by electrically operated valves (28, 29, 30), of which at least the electrical parts are isolated from cleaning liquid.

11. Cleaning equipment according to any of the preceding claims, characterised in that the progress of the cleaning operation and the condition of the solvent are monitored and/or indicated by display dials or indicator lamps.

12. Cleaning equipment according to any of the preceding claims, characterised in that the speed of operation of the electric pump (20) is variable automatically.