WO2011145033A1

WO2011145033A1 - A method and a system for anodising a profiled section made of aluminium or alloys thereof

Info

Publication number: WO2011145033A1
Application number: PCT/IB2011/052109
Authority: WO
Inventors: Massimiliano Gazzani
Original assignee: Massimiliano Gazzani
Priority date: 2010-05-21
Filing date: 2011-05-13
Publication date: 2011-11-24
Also published as: ITPR20100047A1

Abstract

A method for anodising a profiled section (8) of aluminium or alloys thereof comprising the following steps : - electrically connecting a negative pole of a direct current generator (7) to a cathode (5) and a positive pole of the direct current generator (7) to said profiled section (8); - polarising an electrically-conductive liquid by means of the cathode (5); said method being characterised by the step of directing the liquid polarised by the cathode (5) against said profiled section (8).

Description

A METHOD AND A SYSTEM FOR ANODISING A PROFILED SECTION MADE OF ALUMINIUM OR ALLOYS THEREOF .

TECHNICAL FIELD AND BACKGROUND ART.

The present Invention relates to a method and a system for anodising a profiled section made of aluminium or alloys thereof.

Anodising substantially consists in a transformation of an electrochemical nature of the surface of an object made of aluminium or alloys thereof. Anodising (also referred to as an anodic oxidation) determines formation of a layer of aluminium oxide on the object to be treated and protects it from corrosion. This improves the resistance properties of an object from the aggression of atmospheric agents. In the case of aluminium profiles for architectural use anodising enables, for example, to obtain a material which preserves an excellent qualitative and decorative appearance as long as possible, even if exposed to a highly-corrosive atmosphere, such as for example a marine environment.

A type of systems is known for anodising an aluminium profiled section in which the profiled section to be treated is immersed in an electrolytic bath located in an anodising tank. The negative pole of a direct current generator is electrically connected to a cathode which is immersed in the electrolytic bath. Such cathode is fixed to the internal edge of the tank. The positive pole of said generator is connected to suspended conveyors to which the sections to be treated are constrained by hooks. Normally said suspended conveyors are also made of aluminium while the electrolytic bath comprises a concentrated solution of sulphuric acid.

In order to enable anodising, the section to be treated is immersed in the electrolytic bath and is subjected to a strong direct current determined by said current generator (typically a current rectifier) ; the intensity of said current is in the order of 10000-20000 A.

Such a type of system is not free of drawbacks.

The anodising tank contains a high quantity of sulphuric acid (up to more than 100 m³) . It is therefore necessary to have sufficient space for containing such tanks; further, sulphuric acid is highly toxic and such tanks are therefore very expensive as they have to exhibit structural characteristics which take account of the dangerous nature of the liquid contained therein. During the anodising process, the large mass of chemical solution present in the anodising tank must also be continuously recycled and cooled by means of heat exchangers and large recycling pumps.

Large bridge cranes are required, which move the sections between the various pre-treatment tanks and the anodising tank. This further requires very high-roofed workshops as not only are the dimensions of the tank to be considered, but the dimensions of the profiled section too when in the position of complete extraction from the tank. Further, the suspended conveyors the sections to be treated are to be hung on must be able to support the passage of high-intensity currents. Also, the electrical contacts of the cathode, immersed in the tank, must be able to withstand the passage of high electric currents.

DISCLOSURE OF INVENTION.

In this context, the technical objective underlying the present invention is to provide a system and/or a method for anodising profiled sections which obviates the above-cited drawbacks of the prior art.

A particular aim of the present invention is to disclose a system and a method able to reduce the dimensions required for an anodising treatment.

A further aim of the present invention is to provide a system and a method which can increase productivity.

A further aim of the present invention is to avoid assembling large masses of toxic products, with the inevitable risks of an environmental character associated thereto.

A further aim of the present invention is to reduce production costs.

The described technical objective and the set aims are substantially attained by a system and/or an anodising method comprising the technical characteristics set out in one or more of the appended claims.

BRIEF DESCRIPTION OF DRAWINGS.

Further characteristics and advantages of the present invention will be more evident from the following description, given by way of non-limiting example, of a preferred but not exclusive embodiment of a system and/or an anodising method, as illustrated in the accompanying drawings, in which:

- figure 1 shows a schematic view of a system according to the present invention;

figures from 2 to 5 show portions of the system illustrated in figure 1.

BEST MODE FOR CARRYNG OUT THE INVENTION.

In the accompanying figures, reference number 1 denotes a system for anodising a profiled section made of aluminium or alloys thereof, comprising:

- a cathode 5 that polarises an electrically-conductive operative liquid (typically sulphuric acid) ;

- a direct current generator 7 having a negative pole in electrical communication with said cathode 5 and a positive pole electrically connectable to the profiled section 8.

Such direct current generator 7 is advantageously a current rectifier.

The system 1 comprises means 6 for moving the profiled section along a feed line 60.

By way of non-limiting example in figure 4, the means 6 for moving comprise:

- a conveyor 600;

- a guide 603 of the conveyor 600. Support means 9 of the profiled section are hookable to the conveyor 600. The conveyor 600 moves along the guide 603 (the conveyor 600 is preferably a chain conveyor) . For example, such support means 9 comprise at least a suspended conveyor

90 suitable for constraining the profiled section. In particular, the support means 9 comprise at least a hook

91 that can be constrained to the movement means 6 such as to hang said profiled section.

Said hook 91 develops between a first and a second end 93, 94 thereof. The first end 93 is constrained to the movement means 6, the second end 94 is constrainable to the profiled section. Between the first and the second end 93, 94, the hook 91 comprises a spring 92. The hook 91 is advantageously removably connected to the conveyor 600 and is destined to be engaged in an hole or an appropriate fashioned seating in the profiled section 8 (see for example figure 2) . For this purpose the hook 91, at the second end 94, might be curved in a crook shape. The guide 603 is fixed in the space and along it move sliding means 604 (for example facilitated by wheels) constrained to the conveyor 600. This makes the conveyor 600 sturdier and enables heavy loads to be moved.

The feed velocity of said conveyor 600 (and therefore of the profiled section hooked thereto) is preferably comprised between 0.5 and 2 metres per minute. The feed velocity of the conveyor 600 (and therefore of the profiled section hooked thereto) is advantageously constant. As will be better indicated in the following, the feed velocity of said conveyor 600 (and therefore of the profiled section) is one of the parameters which can regulate the thickness of the layer of oxide which forms on the anodised profiled sections (according to the desired characteristics of the final product the velocity of said conveyor 600 will be increased or reduced) .

The system 1 further comprises spraying means 3 of the operative liquid in a first area 61 of said feed line 60, said first area 61 being designed to be crossed by the profiled section. The profiled section is subjected to an electric potential difference following the combined action of an anodic contact (thanks to the positive pole of the generator 7) and of the liquid which places the profiled section in electrical communication with the cathode 5. The electric potential difference, in combination with the intervention of the liquid provided by the spraying means 3 determines a chemical reaction of surface oxidation of the profiled section.

The system 1 comprises an anodisation tunnel 2.

In the preferred solution illustrated in figure 1, the tunnel 2 in turn comprises an entry section 21 for the profiled section, an exit section 22 for the profiled section, an intermediate path 23 between the entry section 21 and the exit section 22. As exemplified in figure 1, the feed line 60 crosses said tunnel 2 between the entry section 21 and the exit section 22. The entry section 21 and the exit section 22 are advantageously distinct from one another; this enables the anodising process to be accelerated, enabling it to be realised in continuous operation (thus it is not necessary to wait for a profiled section to exit the anodisation tunnel 2 in order to be able to introduce the next profiled section to be treated into the tunnel 2} .

The anodisation tunnel 2 can be made of stainless steel panels or of PVC (or another anti-acid material) .

The movement means 6 entirely cross said tunnel 2 and project externally thereof both at the entry section 21 and at the exit section 22. The workpieces will therefore have no need, as in the prior art, to be displaced from a chain conveyor to suspended conveyors designed to be crossed by high-intensity currents.

The spraying means 3 are located along said intermediate path 23 of the tunnel 2 such as to spray the profiled section which is transiting in the tunnel 2 with said operative liquid polarised by the cathode 5. The spraying means 3 can advantageously also spray more than one profiled section contemporaneously {this also depends on the sizes of the profiled sections to be treated) .

The spraying means 3 are distributed at various heights with respect to an imaginary horizontal reference plane located below the system 1.

The spraying means 3 comprise first and second spraying means 35, 36 which face one another. The feed line 60 is interposed between said first and said second spraying means 35, 36. The profiled section is therefore designed to transit in a space interposed between the first spraying means 35 and the second spraying means 36, This enables a better spraying action over the whole surface of the profiled section. According to the intensity of the current crossing the profiled section, as well as the duration of the anodising treatment, variable thicknesses of oxide can be obtained (in accordance with requested characteristics) .

Obviously the duration of the treatment is a function of the feed velocity of the conveyor 600 {and therefore of the profiled section) as well as the extension of the spraying means 3 along the feed line 60.

The cathode 5 comprises at least a tubular conduit 50 made of an electrically-conductive material in which said electrically-conductive liquid transits. In particular, the spraying means 3 are integral with said cathode 5. The cathode 5 advantageously comprises a plurality of tubular conduits 50 in an electrically- conductive material in which said electrically- conductive liquid transits. The spraying means 3 coincide with exit openings for the liquid from said cathode 5. A plurality of conduits 50 are preferably adjacent to one another, and still more preferably form a single body.

At least a part of the spraying means 3 and the tubular conduits 50 are advantageously integrated in a first panel 37 internally of the tunnel 2. The spraying means 3 and the tubular conduits 50 of the cathode 5 are preferably integrated in a first and a second panel 37, 38 which are reciprocally facing. The tubular conduit 50 preferably coincides with a space internal of the first and/or second panel 37, 38. Such space could be shaped as a parallelepiped delimited by the thickness of the external portion of the first and the second panel 37, 38 (such thickness can also be of few millimetres) . The spraying means 3 are preferably distributed over the whole height of said first and/or second panel 37, 38. Said feed line 60 develops between the first and the second panel 37, 38. Said profiled section is therefore destined to pass between the first and the second panel 37, 38. The first spraying means 35 are integrated in the first panel 37, while the second spraying means 36 are integrated in the second panel 38.

The tubular conduits 50 of the cathode 5 are preferably realised in aluminium or lead and are advantageously obtained by extrusion.

The spraying means 3 comprise outlets 31 which spray said operative liquid under pressure (said outlets 31 are for example holes which preferably have a diameter comprised between 1 and 3 millimetres) . In a particular solution, not illustrated, the spraying means 3 can also comprise a slit from which said operative liquid exits in a cascade. Such a slit 34 exhibits a preponderant development direction along the feed line 60 of the profiled section (such slit 34 is thus a transversal slot) . Said slit 34 is advantageously located above said outlets 31.

The system 1 comprises recycling means 70 of the liquid exiting from the spraying means 3.

The recycling means 70 comprise a collection tank 701 for the liquid exiting from the spraying means 3 located below said feed line 60.

The recycling means 70 further comprise:

- a recycling conduit 702 which connects said tank 701 with said cathode 5;

- pumping means 703 which move said liquid from the tank 701 to said cathode 5 through said recycling conduit 702.

Along said recycling conduit 702 the system 1 advantageously comprises heat exchanger means 704 for cooling said liquid.

The system 1 comprises electrical connecting means 401 between said profiled section and said positive pole of the current generator 7. The electrical connecting means 401 comprise:

- a closed-loop rotating belt (41) which extends at least along said intermediate path 23 of the tunnel 2 and is intended to come into electrical contact with the profiled section;

- a sliding contact 410 which places said belt 41 and the positive pole of the direct current generator 7 in electrical communication.

Said belt 41 is advantageously located higher than the spraying means 3. This enables correct closing of the electric circuit between said positive pole and said negative pole of the electrical current generator 7.

The belt 41 is located at a lower height than the guide 603. The belt 41 advantageously extends along the whole at a same height .

The belt 41 comprises:

- a closed-loop supporting strip 412 which is coupled to at least a first and a second transmission element 413, 414;

- a plurality of contacts 411 projecting outward from said strip 412.

At said first and second transmission elements 413, 414 said projecting contacts 411 are disposed in a spoke- fashion. This is due to the fact that the first and second transmission elements 413, 414 are cogwheels, about a part of which the belt 41 winds. The belt 41 bends to follow the profile of the cogwheels and therefore the contacts that are orthogonal to the supporting strip 412 are disposed in a spoke-fashion. At least in a tract of the area interposed between the first and the second transmission element 413, 414 said contacts 411 are parallel to one another such as to retain the hooks 91.

Said at least a tract of the area interposed between the first and second transmission elements 413, 414 comprises one or more straight tracts interposed between the first and the second transmission elements 413, 414. The contacts 411 surmount the area destined for passage of the profiled sections.

The system 1 comprises means 42 for raising the hooks 91 of the profiled section such as to push the profiled section against said contacts 411. The hook-raising means 42 are integrated in said movement means 6. As previously mentioned, the movement means 6 comprise:

- said conveyor 600;

- said guide 603 of the conveyor 600 which extends along a predetermined trajectory. The hook-raising means 42 are integrated in said movement means 6, in particular they comprise a tract of the guide 603 that is shaped as an upwards-directed ramp 605.

At said ramp 605 the hooks 91 are raised upwards and consequently also the profiled sections are raised upwards to cause them to adhere to the overlying contacts 411. The feed line 60 of the profiled section comprises a first tract in which the raising means 42 don't intervene and a second tract in which the raising means 42 intervene. In the first tract the vertical distance between said belt 41 and said guide 603 is less than in the second tract. As it passes from the first tract to the second tract the distance between the first and the second end 93, 94 of the hook 91 increases, said second end 94 being encountered by the belt 41, determining a lengthening of the spring 92. The spring 92 in the second tract thus exerts an elastic force which returns the second end 94 towards the first end 93, maintaining the profiled section pressed against the belt 41. The raising means 42 lift the first end 93 of the hook 91 by a greater height than the vertical distance existing along the first tract between the second end 94 and said belt 41. This causes tensioning of the spring 92. The movement of the conveyor 600 and the belt 41 is synchronised such as to enable advancing of the contacts 411 and the conveyor 600 at the same velocity. The conveyor 600 surmounts a straight line developing between two branches of the belt 41 and connecting the first and the second transmission elements 413, 414. In this way the hooks 91 of the movement means 6, when they arrive at a transmission element, insert by themselves between two contacts 411 disposed in a spoke-fashion.

The object of the present invention is a method for anodising a profiled section 8 made of aluminium or alloys thereof. Such a method provides use of a system 1 exhibiting one or more of the characteristics previously described. Such a method comprises the step of electrically connecting the negative pole of the direct current generator 7 to the cathode and the positive pole of the direct current generator 7 to said profiled section 8.

In this way the profiled section 8, during the anodising process, becomes an anode.

A further step is polarising, by the cathode 5, an electrically-conductive liquid. Such an electrically- conductive liquid is for example a chemical solution comprising high concentrations of sulphuric acid.

The method further comprises the step of directing the electrically-conductive liquid, polarised by the cathode 5, against said profiled section 8, said liquid setting said cathode 5 in electrical communication with the profiled section 8.

The step of directing the electrically-conductive liquid against said profiled section 8 provides directing at least a continuous liquid jet, or even a plurality of continuous liquid jets, against said profiled section 8. The step of directing the electrically-conductive liquid against said profiled section 8 comprises the steps of spraying the liquid under pressure against said profiled section 8 and possibly spraying said profiled section 8 by means of a cascading liquid jet.

The step of directing the liquid polarised by the cathode 5 against said profiled section 8 occurs internally of said anodisation tunnel 2. The step of directing the liquid polarised by the cathode 5 against said profiled section 8 is performed by spraying means 3.

The step of directing the liquid polarised by the cathode 5 against said profiled section 8 is done from at least two distinct locations facing one another (with reference to the appended drawings the two distinct locations can coincide with said first and second spraying means 35, 36) .

The profiled section 8 to be anodised and the continuous flow of electrically-conductive liquid enable the circuit between the positive pole of the direct current generator 7 and the cathode 5 to be closed, thus enabling passage of the continuous current required for the anodising process.

The method provides causing said profiled section 8 to transit in the anodisation tunnel 2. The step of causing said profiled section 8 to transit through the anodisation tunnel 2 provides causing the profiled section 8 to enter the tunnel 2 through the entry section 21 and to exit from the tunnel 2 through the exit section 22, which is distinct from the entry section 21.

The step of causing said profiled section 8 to transit in the anodisation tunnel 2 provides causing said profiled section 8 to transit between said two distinct locations from which said liquid emanates.

The step of causing said profiled section 8 to transit in the anodisation tunnel 2 is preceded by the step of hanging said profiled section 8 from the movement means 6 of the profiled section 8 along a feed line 60.

With the aim of enabling closure of the electrical circuit, required for anodising, the step of electrically connecting said positive pole to said profiled section 8 occurs before or during the step of directing the liquid polarised by the cathode 5 against said profiled section 8.

The method advantageously provides that the step of causing said profiled section 8 to transit in the anodisation tunnel 2 occurs without any stop and restart. In particular, in the preferred solution the step of causing said profiled section 8 to transit in the anodisation tunnel 2 is done at a constant velocity. The step of causing said profiled section 8 to transit in the anodisation tunnel 2 is preferably done at a velocity comprised between 0.5 and 2 metres per minute. The step of causing said profiled section 8 to transit in the anodisation tunnel 2 provides moving said profiled section 8 by causing it to advance along the feed line 60. Such feed line 60 is straight at least internally of the anodisation tunnel 2.

The step of electrically connecting said positive pole to said profiled section 8 provides the sub-step of placing said profiled section 8 in contact with the closed-loop rotating belt 41, electrically-conductive and in electrical communication via first sliding contacts 410 with said positive pole of the generator 7. Preferably, the step of electrically connecting said positive pole to said profiled section 8 comprises the sub-steps of:

- inserting the support hook 91 of the profiled section 8 between two contacts 411 which project from the supporting strip 412 which is a part of the rotating belt 41;

lifting said hook 91 and the profiled section 8 suspended therefrom in order to compress the profiled section 8 against said contacts 411 (in this way the electrical connection of the profiled section 8 with the positive pole of the direct current generator 7 is optimised) .

The step of lifting said hook 91 provides more greatly lifting the first end 93 of the hook 91 (the end constrained to the movement means 6} with respect to the second end 94 (the end constrained to the profiled section 8) . This is possible thanks to the deformation of the spring 92 which will exert an elastic return force which will therefore compress the profiled section 8 against said belt 41.

The sub-step of inserting the supporting hook 91 of the profiled section 8 between the two contacts 411 which project from the supporting strip 412 occurs at one of the two transmission elements of said belt 41. The step of inserting the hook 91 supporting the profiled section 8 between two contacts 411 which project from the supporting strip 412 provides enveloping the belt 41 about a portion of one of the transmission elements, thus determining a spoke-fashion opening of said contacts 411.

The step of electrically connecting said positive pole to said profiled section 8 provides placing the belt 41 in contact with an area of the profiled section 8 that is close to an upper end of the profiled section 8. The electric current advantageously transits from the belt 41 to the profiled section 8 without crossing the hook 91 (which must therefore not be of such a size as to withstand currents of 10000-20000 A) .

The method further provides collecting, by force of gravity, the liquid directed towards said profiled section 8 in a tank 701 which is located below the spraying means 3. The liquid collected in such a tank 701 is then recycled and newly directed against a new profiled section 8 transiting in the tunnel 2. Before being newly directed against a profiled section 8 transiting in the tunnel 2, the liquid is advantageously cooled.

The invention provides important advantages.

Firstly, it enables an increase in productivity. Secondly, it enables profiled sections to be anodised using structures having much more contained sizes. Thirdly it reduces the quantity of toxic chemical solutions used.

The invention as it is conceived is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept characterising it. Further, all the details can be replaced with other technically-equivalent elements. Further, all the sizes can be of any type, according to requirements.

Claims

1. A method for anodising a profiled section (8) of aluminium or alloys thereof comprising the following steps :

- electrically connecting a negative pole of a direct current generator (7) to a cathode (5) and a positive pole of the direct current generator (7) to said profiled section (8) ;

- polarising an electrically-conductive liquid by means of the cathode (5);

said method being characterised by the step of directing the liquid polarised by the cathode (5) against said profiled section (8) .

2. The method according to claim 1, characterised in that said profiled section (8) is made to pass through an anodisation tunnel (2) , the step of directing the liquid polarised by the cathode (5) against said profiled section (8) taking place inside said anodisation tunnel (2) ; said step of electrically connecting said positive pole to said profiled section (8) taking place before or during the step of directing the liquid polarised by the cathode (5) against said profiled section (8) .

3. The method according to claim 2, characterised in that the step of passing said profiled section (8) through the anodisation tunnel (2) takes places without stops and restarts.

4. The method according to any of the preceding claims, characterised in that the step of electrically connecting said positive pole to said profiled section (8) involves placing said profiled section (8) in electrical contact with a closed-loop rotating belt (41) , which is electrically-conductive and in electrical communication with said positive pole via sliding contacts .

5. The method according to claim 4, characterised in that the step of placing said profiled section (8) in electrical contact with said rotating belt (41) involves compressing said profiled section against the rotating belt (41) .

6. A system for anodising a profiled section of aluminium or alloys thereof, comprising:

a cathode (5) that polarises an electrically- conductive operative liquid;

- a direct current generator (7) having a negative pole in electrical communication with said cathode (5) and a positive pole electrically connectable to the profiled section (8) ;

characterised in that it comprises: - means (6) for moving the profiled section along a feed line (60) ;

- means (3) for spraying the operative liquid in a first area (61) of said feed line (60), said first area (61) being designed to be crossed by the profiled section (8) .

7. The system according to claim 6, characterised in that it comprises an anodisation tunnel (2) comprising an entry section (21) for the profiled section, an exit section (22) for the profiled section, an intermediate path (23) between the entry section (21) and the exit section (22), said entry section (21) and said exit section (22) being distinct from each other; said feed line (60) passing through said tunnel (2), said spraying means (3) being located along said intermediate path (23) of the tunnel (2) so as to spray the profiled section (8) passing through the tunnel (2) with said operative liquid polarised by the cathode (5) .

8. The system according to claim 6 or 7, characterised in that said cathode (5) comprises at least one tubular conduit (50) made of electrically-conductive material through which said electrically-conductive liquid flows before being sprayed by spraying means (3) .

9. The system according to any of the claims 6 to 8, characterised in that said spraying means (3) are integral with said cathode (5) .

10. The system according to any of the claims 6 to 9, characterised in that it comprises first means for making an electrical connection between said profiled section and said positive pole of the current generator (7), said first electrical connection means comprising:

- a closed-loop rotating belt (41) which extends at least along said intermediate path (23) of the tunnel (2) and is intended to come into electrical contact with the profiled section;

- a sliding contact (410) which places said belt (41) and the positive pole of the direct current generator (7) in electrical communication.

11. The system according to claim 10, characterised in that it comprises a hook (91) constrained to the moving means (6) in order that said profiled section (8) may be suspended therefrom; said belt (41) comprising:

- a closed-loop supporting strip (412) which is coupled to at least a first and a second transmission element (413, 414);

- a plurality of contacts (411) projecting outward from said strip (412) , said outward projecting contacts (411) being disposed in a spoke-like fashion at said first and second transmission elements (413, 414), said outward projecting contacts (411) being parallel to one another in at least one section of the area between the first and second transmission elements (413, 414) in order to retain the hooks (91) .

12. The system according to claim 11, characterised in that said contacts (411) are situated above the area through which the profiled sections are intended to pass and characterised in that it comprises means (42) for raising the hooks (91) of the profiled section (8) so as to push the profiled section against said contacts (411).

13. The system according to any of the claims 6 to 12, characterised in that said spraying means (3) comprise outlets (33) through which said operating liquid is sprayed under pressure.

14, The system according to any of the claims 6 to 13, characterised in that said operative liquid is sulphuric acid.