WO2005089968A1

WO2005089968A1 - Conductive brush for cleaning metals

Info

Publication number: WO2005089968A1
Application number: PCT/AU2005/000383
Authority: WO
Inventors: Franco Fornasari; William Bunting
Original assignee: Franco Fornasari; William Bunting
Priority date: 2004-03-17
Filing date: 2005-03-17
Publication date: 2005-09-29

Abstract

A conductive brush (10) for cleaning a metal work piece (23) comprises a bundle of conductive filaments (16) secured in conductive relationship to a conductive receptacle (11). The brush (10) may be part of a cleaning system including a power pack (31), container (40) and pump (38). Hand piece (42) includes a control lever (44) for controlling the supply of power and cleaning solution to the brush (10).

Description

CONDUCTIVE BRUSH FOR CLEANING METALS TECHNICAL FIELD This invention relates to the cleaning of stainless steel and other metals subsequent to welding operations. BACKGROUND ART In the course of welding stainless steel surfaces, chromium is depleted and thereby exposing iron causing localised discolouration which must be removed to restore the polished appearance to the stainless steel. Metallic oxides in the form of scale can also form on the surface during the welding process and these need to be cleaned away or otherwise removed. Hitherto, surface staining and weld scale on stainless steel parts have been removed using a pickling gel of toxic acids including hydrofluoric and nitric acids. This prior art method requires a significant amount of time and occupational health and safety risks result. Existing electrically activated stainless steel weld cleaning devices utilise a non-conductive fabric sock that covers a solid or wire electrode. The sock acts as a separator between the electrode and the work piece as well as a reservoir for the acidic electrolyte cleaning solution. The sock is saturated with the cleaning solution which provides a short electrically conductive path between the electrode and the work piece. The cleaning solution is heated by the passage of electrical current through it and becomes more chemically active thereby cleaning the metal surface. One disadvantage with these prior art devices is that the fabric socks tend to dry out and then burn through with the heat of the process. Another disadvantage is that the electrode is essentially a rigid shape which cannot conform to the many odd shapes encountered in stainless steel fabricated constructions. DISCLOSURE OF INVENTION It is, therefore, an object of the present invention to provide an improved brush and process for cleaning metal subsequent to welding operations. According to one aspect of the invention there is provided a conductive brush for cleaning metals comprising a conductive receptacle, electrically conductive flexible filaments secured in conductive relationship to the receptacle. The electrically conductive filament bundle may also contain non- conductive filaments mixed in various ratios as required. In a preferred form of the invention, the conductive receptacle has a base and a cylindrical side wall which defines a chamber. One end of the flexible filament bundle is secured in the chamber by swaging, potting or sintering. In a preferred form of the invention an insulating sheath is provided at around at least a portion of the receptacle. Appropriate electrical connection means connect the exterior of the receptacle to an external power supply. According to another aspect of the invention there is provided a method of cleaning a metal work surface comprising:- (i) providing a conductive brush having a plurality of conductive flexible filaments secured to a conductive receptacle, (ii) providing a supply of acidic cleaning solution to the brush, (iii) providing a supply of electrical power to the conductive brush, and (iv) contacting the work surface with the conductive brush to close the electrical circuit and thereby heat the cleaning solution so as to effect cleaning of the work surface. Preferably, the cleaning solution is a phosphoric acid based electrolyte solution and the electrical supply is a low voltage electric current. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross sectional view of a conductive brush according to one embodiment of the invention, Fig. 2 is a perspective view of the conductive brush of Fig. 1 being applied to a welded assembly, Fig. 3 is a perspective view of a stainless steel cleaning apparatus or system according to one embodiment of the invention, and Fig. 4 is a partly broken away enlarged perspective view of the conductive brush shown in Fig. 3. The conductive brush shown in Figure 1 shows a conductive receptacle 11 having a base 12 and cylindrical side wall 13 which defines a chamber 14. One end 15 of a flexible conductive filament bundle 16 is secured in the chamber 14 by swaging, potting or sintering. The other end 17 of the filament bundle 16 extends away from the receptacle 11. The numbers of fibres in the filament bundle depends upon the current requirement. For example, a cross- section of 9mm loosely bundled fibres is appropriate for 35amp current. An insulating sheath 18 surrounds the conductive receptacle 11. The length of the sheath 18 depends on the application and the preference of the operator. An electrical power supply which passes through a hold 20 is connected to the outside face 19 of the base 12 of the receptacle 11. The method of cleaning a metal work surface according to the invention is shown in Fig. 2 where the conductive brush 10 is placed in contact with the weld-affected area on either side of the welded joint 21 of two stainless steel sheets 22 and 23. The conductive brush 10 is prior coated with the electrolyte solution and the current applied to the brush as it is moved along the surface to be cleaned. The cleaning solution can be a phosphoric acid based electrolyte solution. Several principles act to remove the surface discolouration at the weld site. Electrical current passing directly through the conductive brush to the work surface produces arcing at the surface thereby heating the work area and associated weld scale, causing the scale to break down which facilitates its removal. Also, electric current passes through the solution, heating it thereby increasing its reactivity and accelerating the cleaning process. Electrical activity also removes iron from the surface of the work surface by electrolytic action. The conductive brush may be hand operated or incorporated into a machine for fully automatic operation. The cleaning solution may be added to the brush by dipping the brush in a reservoir, by manually pouring the solution from a dispenser directly onto the brush and the work surface, or by pumping to the brush and work surface using an electro mechanical pump activated by the user. The cleaning system can be fully automated to include mechanical delivery of the acid based solution to the brush followed by mechanical delivery of neutralising and rinsing agents to the work piece to ensure all electrolyte solution is removed. The conductive brush may take a wide variety of shapes including, but not limited to, a solid circle, a circular ring, a rectangle, or a circular ring with bristle outwards. All of these brush configurations can have a large variety of dimensions. The length of the bristles can be varied to achieve different effects or to provide the best performance for a given work surface geometry. The controlled power supply provides low voltage, high current regulated electrical power to the brush. Electro-polishing, where the surface brilliance of the stainless surface is enhanced through the removal of both iron and chromium can be achieved by a variation of the current and voltage characteristics as provided by the controlled power supply. A preferred form of cleaning apparatus or system for cleaning a metal work piece is shown in Fig. 3. The cleaning system 30 includes a power pack 31 which has a power supply 32 controlled by an ON/OFF switch 33, a first output cord 34 leading to clamp 35, a second output cord 36 leading to the conductive brush 10 and a third output cord 37 leading to a pump 38. The pump 38 has an inlet 39 connected to a container 40 and an outlet 41 which delivers cleaning solution to the brush 10 via the hand piece 42. The outlet 41 is located within tubular casing 43 along with the second cord 36. The hand piece 42 has a control lever 44 controlling the supply of electrical power and cleaning solution to the brush 10. The hand piece 42 is connected to the brush 11 by a tubular rod 45. The power supplied to the clamp 35 and the brush 10 is controlled by knobs 46 and 47. Various modifications may be made in details and construction of the conductive brush and the method of cleaning a metal work surface without departing from the scope and ambit of the invention.

Claims

CLAIMS:

1. A conductive brush for cleaning metals comprising a conductive receptacle and a bundle of electrical conductive flexible filaments secured in conductive relationship to the receptacle.

2. A conductive brush according to claim 1 and further including non- conductive filaments mixed with the conductive filaments.

3. A conductive brush according to claim 1 or claim 2 wherein the filaments are secured in the receptacle by swaging, potting or sintering.

4. A conductive brush according to any one of the preceding claims and further including an insulating sheath around at least a portion of the conductive receptacle.

5. A conductive brush according to any one of the preceding claims and further including electrical connection means on the exterior of the receptacle adapted to be connected to an external power supply.

6. A conductive brush according to any one of the preceding claims wherein the conductive filaments are carbon fibre filaments.

7. A conductive brush according to any one of the preceding claims and further including a fluid passageway within the brush leading from an external supply of cleaning fluid to the conductive filaments.

8. A conductive brush according to claim 7 further including a flow control valve for controlling the flow of cleaning fluid through the fluid passageway.

9. A method of cleaning a metal work surface comprising:- (i) providing a conductive brush having a plurality of conductive flexible filaments secured to a conductive receptacle, (ii) providing a supply of acidic cleaning solution to the brush, (iii) providing a supply of electrical power to the conductive brush, and (iv) contacting the work surface with the conductive brush to close the electrical circuit and thereby heat the cleaning solution so as to effect cleaning of the work surface.

10. A method of cleaning a metal work surface according to claim 9 wherein the cleaning solution is a phosphoric acid based electrolyte solution.

11. A method of cleaning a metal work surface according to claim 9 or claim 10 wherein the electrical power supply is a controlled low voltage, high current regulated power supply.

12. A cleaning system for cleaning a metal work piece comprising:- (i) a power pack adapted to be connected to an electric supply and having first, second and third electrical output cords, (ii) a clamp adapted to be connected to the work piece and connected to the power pack by the first electrical output cord.

(iii) a container for containing a quantity of cleaning solution and having an outlet leading to an electric pump that is connected to the power pack by the second electrical output cord, and

(iv) a hand piece carrying a conductive brush, an outlet from the electric pump passing through control means in the hand piece to the conductive brush and wherein the third electrical cord is connected between the power pack and the electric brush through control means in the hand piece.