AU2004203037A1 - An apparatus and method for the deposition of material - Google Patents

Description

12377AU

ORIGINAL

Complete Specification Applicant: AHT Pty Ltd Title: An apparatus and method for the deposition of material LESICAR PERRIN, 49 Wright Street, Adelaide, South Australia 5000, Australia Address for Service: The following statement is a full description of this invention, including the best method of performing it known to melus: 2 An apparatus and method for the deposition of material The present invention refers to an apparatus for depositing a uniform coating of material to a surface of a structure, the apparatus including two or more spray guns, as well as to a method for applying such a coating.

BACKGROUND OF THE INVENTION A particular application of the present invention may be in relation to wind generator towers that need to be sprayed with a non-corrosive coating such as zinc particles. These towers are generally of a cylindrical configuration. Although the following discussion will be in relation to wind towers, it is to be understood that the present invention is not to be limited to any specific structure, nor to any type of material to be deposited thereon.

The type of material deposition exemplified herein is that of thermal spraying which involves the melting or at least softening of heat fusible material such as a metal or ceramic, and propelling the softened material in particulate form against a surface to be coated. The heated particles strike the surface where they are quenched and bonded thereto to produce a coating. Thus the wind tower heavy metal structure is protected against corrosion on its outer surfaces due to exposure to wind and rain by a uniform layer of such coatings.

Current methods of coating structures such as wind towers include the manual spraying of a structure by skilled workers using high-pressure applicators, typically by hand held apparatus that include hoses and a spray nozzle. The use of high pressure tends to lead to overspray that leaves a residue that needs to be manually scraped down after the spraying process. As such not only is it a difficult manual task but it is also highly time-consuming. Alternatives to manual spraying such as traversing spraying systems are known. These systems attempt to coat a structure with a uniform coating by means of back and forth traversal of an applicator or depositor.

However, for the reasons discussed below, both manual and traversing systems often fall short in providing the typical requirement of a 60-70 micron thick coat uniformly across the surface.

Firstly the tower needs to be rotated once the accessible area has been sprayed. Since such structures are quite large and heavy, it is impractical due to their inertia, to rotate them through a pre-set angle only. Accordingly these towers are typically continually rotated as a worker or system applies the material through the high-pressure system.

It is easy to appreciate that there needs to be a very fine balance between the rotation of the tower and the manual application of the material to ensure that not only is there sufficient material deposited but that there is not too much. This thus requires one to utilise quite skilled employees. In the case of traversing systems it would be impractical to have a variable rate of rotation so that to ensure that the minimum thickness of any one area is say 70 microns, there will always be overlapping sections that will be more than that (typically double). This is not only a waste of material but the excess can bubble and for that reason typically needs to be scraped off.

Although one solution may be to control the rotation of the structure so that it remains stationery during a single back and forth traversal to then rotate so that an adjacent layer may then be coated, this is not feasible when rotating heavy inertial structures such as the abovementioned wind generator tower sections. One may further suggest that the single layer sections may be 'touched up', however, this is also more time consuming and therefore expensive.

Although one can appreciate the savings in cost and time in using a system that does not require the employ of skilled workers in both completing the spraying task and subsequently scraping down the coated surface, current traversing systems do not obviate the problem.

Yet a further problem that may result from using existing systems of depositing a material onto a surface, and in particular in thermal spraying, includes 'hot spots' which appear in the areas of high thickness during thermal spraying. The hot spots are highly undesirable due to their detrimental effect on the physical and chemical properties of the metal.

Whilst further existing remedies to some of the abovementioned problems include moving the applicator off the edge of the structure for each reversal, multiple traversing cycles for smoothing out thickness variations, and alternate motions of the spray gun such as circular, oval or figure-eight motions, none of these systems adequately solve the problem of non-uniformity and as a result, the deposition process often takes longer, the quality of the coating is not adequate resulting in residue, and often requires the use of complex and expensive componentry.

It is therefore an object of the present invention to provide an apparatus and method, which overcomes at least some of the aforementioned problems, or to provide the public with a useful alternative.

The present invention therefore relates to an apparatus and method for the deposition of material, and more particularly, to an apparatus and method involving two or more depositors or applicators spaced apart a pre-set distance whereby horizontal traversal of the applicators together with constant rotation of the structure results in the surface of the structure being deposited with a hitherto unachievable uniform thickness of material. It is however to be understood that the variation in the material deposited may even be of the order of some 10-20%. Although this variation is large, and typically the result is much better, compared to existing systems it is a huge improvement.

SUMMARY OF THE INVENTION Therefore in one form of the invention there is proposed an apparatus for depositing material on a surface of a constantly rotating structure rotating around a longitudinal axis, said apparatus including: at least two spaced apart traversing material applicators each applicator adapted to deposit material onto said surface, said material applicators defining a deposition footprint on said structure, the distance separating the applicators in a direction generally perpendicular to the longitudinal axis of said structure being generally the same as the height of the deposition footprint on said structure in a direction also generally perpendicular to the longitudinal axis; said applicators adapted to traverse back and forth parallel to said longitudinal axis between a first and a second position, the length of the traverse and the speed of rotation of said structure selected so that during one traverse the angular movement of said surface is generally equal to the deposition footprint height.

In a further form of the invention there is proposed an apparatus for applying a uniform coat to a surface of a structure, said apparatus including: a rotation means for rotating said structure; and a support means for slidably supporting a spraying assembly, said spraying assembly including two spray means each adapted to apply a spray pattern having a footprint of generally the same height onto said surface, said spray means being offset by a vertical distance that corresponds with said height, said spraying assembly configured to traverse back and forth along said rotating structure such that said uniform coat is formed by the combination of said spray patterns.

In preference the combination of the rotation of said structure and traversal of said spray assembly results in two zig-zag style footprints positioned adjacently one below the other wherein individual overlapping sections of said footprints combine to form said uniform coat.

In preference said uniform coat is achieved in one revolution of said rotation unit.

Preferably said support frame is moveable and anchorable along the length of the structure.

Preferably said spraying assembly is belt driven.

In preference the spraying assembly traverses between two spaced apart sensing means moveably mounted to said support structure.

In preference the rate of rotation of the structure and speed of traversal of the spraying assembly is also controllable via a control means.

In a further form of the invention there is proposed a method of providing a uniform double, or any multiple of two, coats to a surface of a vertically moving, longitudinal structure, said method incorporating the following steps: moving said structure at a pre-determined, constant rate of vertical movement; traversing a first and a second application device back and forth along the length of at least a portion of said structure; depositing a first footprint of material onto said surface using said first application device, said first footprint being in the form of opposed diagonal strokes that overlap at their ends, said overlap defining a first overlapping area; depositing a second footprint of material at the same time as said first footprint using said second application device, said second footprint being identically shaped to said first footprint such that it too overlaps at its ends wherein said overlap defines a second overlapping area, said second footprint disposed a step below said first footprint such that the area in which said first and second footprints overlap defines a third overlapping area such that said first, second and third areas are independent of one another and together form said double coat.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings: Figure 1 illustrates a perspective view of an apparatus for the metallic treatment of a structure in accordance with the present invention; Figure 2 illustrates a perspective view of the apparatus of Figure 1 from an alternate angle, including an indication of the relative motions of the structure and the traversing spraying assembly; Figure 3 illustrates a rear view of the apparatus of Figure 1; Figure 4 illustrates an end view of the apparatus of Figure 1; Figure 5 illustrates an enlarged end view of the spray gun apparatus of the present invention; Figure 6 illustrates an enlarged rear view of the spray gun apparatus of Figure Figure 7 illustrates a front perspective view of the spray gun apparatus of Figure Figure 8 illustrates a schematic view of the spray pattern of the upper spray gun of Figure Figure 9 illustrates a schematic view of the spray pattern of the lower spray gun of Figure and Figure 10 illustrates a schematic view of the combined spray pattern of the spray gun apparatus of Figure DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description of the invention refers to the accompanying drawings.

Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

The present invention relates to an apparatus 10 and a method for the deposition of material onto a structure 12. It is to be understood that the present invention may be applied to other systems involving a structure to be coated, however, the system exemplified herein involves a spray gun assembly 14 adapted to thermally treat a structure 12. The coating assembly 14 overcomes the drawbacks of prior methods of depositing material onto structures in that a double layer of material may be uniformly deposited on the structure while it rotates or moves at a constant rate. This is achieved using a novel depositor or applicator arrangement that is controllably traversed back and forth along the rotating structure 12. A benefit in using such a system is that there is no longer a need for multiple workers or for the application assembly to involve complex robotic machinery.

It is to be understood that any reference to a spraying assembly or spray guns is by way of example only, and the method of application of the present invention is not to be limited to spraying. For example, there may be instances where the material to be deposited may be in the form of radiation whereby spraying per se is not involved.

Figures 1-4 illustrate various perspectives of the apparatus 10 of the present invention, used for the metallic treatment of structures. In this case, the structure is in the form of a section 12 of a wind generator mast or tower. As previously mentioned, the present invention is not to be limited to use on any particular type of structure, as long as the structure can be rotated or moved and material able to be deposited thereon in a traversing manner.

The assembly 10 includes a structure rotator unit 16, a spray assembly support frame 18, and a traversing spray assembly 14 slidably mounted above the support frame 18. The working of these assemblies and their corresponding components will now be explained in greater detail.

Tower section 12 is of a substantially conical shape having two generally equal diameter flanges 20 at opposed ends thereof. Each flange 20 of each section 12 is supported above structure rotator units 16 which are essentially transverse beams 22 fixedly mounted to the ground including two transversely spaced apart rotatable wheels 24 and 26 upon which each flange rests. Those skilled in the art would realise that the wheels 22 of the structure rotator units 16 are motorised and capable of rotating the structure 12 at a predetermined rate in direction 27, or alternatively in the opposite direction. This system is also preferably controllable such that one may input a desired rate of rotation. Considering the large sizes and weights of such wind generator sections 12 and the obvious danger posed by a rotating structure of this size, it is further preferable that a controlling means (not shown) be located remotely from the rotating structure 12.

In a preferred form of the invention, the rate of rotation of the section 12 is controllable by simply entering an input rate of rotation into a nearby workstation (not shown) or the like. It is to be further understood that the rotator unit 16 be of a robustness and strength to sufficiently support the weight of such large structures.

Spray assembly support frame 18 is both moveable and anchorable along the length of the structure 12. The skilled addressee would realise that during spraying operations, the support frame 18 is fixedly mounted to the ground. When the spraying of a portion of section 12 is complete, that is, after section 12 has completed a full revolution, the spray assembly support frame 18 is capable of being moved along the length of the section 12 to then start spraying operations on the adjacent portion of the section 12. The capability of the support frame to be fixed as well as being moveable to thereby spray portions of the structure 12 is the subject of a copending application by the same applicant.

The support frame 18 is made up of two longitudinally spaced apart, transversely extending base members 28 and 30, an upper panel 32 and a lower panel 34 connected to the upper panel 32 by a series of truss members 36. The lower panel 34 includes end panels 38 and which extend substantially perpendicularly there from. The end panels 38 and 40 are spaced a short distance above the base members 28 and 30 respectively, each member being separated by support blocks 31. The base members 28 and 30 each include castor wheels 42 suspended from opposed transverse ends thereof. Furthermore, adjacent each wheel 42 is one or more jacking feet 44.

As mentioned, the support frame 18 is adapted to be either fixed to the ground or moveable along the length of section 12. When required to be moved, support frame 18 is configured to be supported by the castor wheels 42 so that it may be simply rolled to a new position. When required to be fixed, the jacking feet 44 are to be operated which effectively lift the castor wheels 42 off the ground such that the jacking feet 44 now support the frame. It is to be understood that the present invention is not to be limited to any particular style of wheels or jacking feet, as long as they are of a suitable strength to support the combined weight of the frame 18 and the traversing spray assembly 14. In preference, the jacking feet 44 are of the hydraulic toe-jack type having a lever (not shown) that when pressed, causes the height of the jacking feet 44 to increase and thereby lift the support frame 18.

Since the outer end of the support frame 18 supports the larger proportion of weight, the Figures illustrate two such jacking feet 44 on the outer side as opposed to one jacking foot 44 on the inner side. In fact, in order to further balance the considerable weight resulting from the traversing spray assembly 14 and support frame 18, two counter-balance weights 46 and 48 are located on inner ends of base members 28 and 30 respectively, to prevent the support frame 18 and the spray assembly 14 from tipping over. It is to be understood that alternate methods of balancing the weight of the apparatus may be used and that the support frame 18 includes other supporting and reinforcing members that are not explicitly referred to herein.

The traversing spray assembly 14 includes two spray guns or applicators 50 and 52, which are housed within a dust extraction hood 54, this shown clearly in Figures 5-7. Assembly 14 further includes a vertical gun height adjustment frame 56 between which is mounted the dust extraction hood 54 and spray guns 50 and 52. The height of the extraction hood 54 and guns and 52 are adjustable and lockable within and along the height adjustment frame 56. The fact that the height of the spray guns is adjustable allows for different shaped structures to be sprayed appropriately. For example, sections of wind generator towers that are to be base sections or sections that are closer to the ground are obviously substantially larger in diameter than are those sections located at the top of the towers. This means that the height of the spray assembly 14 needs to be altered according to the section of tower being sprayed.

Assembly 14 further includes spray gun cable clamps 58 located on an outwardly extending stand 60 at the rear of the extraction hood 54. The clamps 58 are for preventing tangling of cables (not shown) which are connected to the guns 50 and 52.

As mentioned, the spraying assembly 14 is slidably mounted above the support frame 18.

More specifically, the upper panel 32 of the support frame 18 includes a longitudinal track 62 to which is mounted the spraying assembly 14 in a configuration which allows the assembly to slidably traverse back and forth along the track 62 when driven. Those skilled in the art would realise that there are various ways in which the assembly 14 may be mounted and driven along the upper panel 32 and for this reason the present invention is not to be limited to any one of these methods. Preferably, the spray assembly 14 is belt driven, and may further include a second driving or stabilising mechanism associated with the lower panel 34.

Located on one end of the support frame 18 is an electronic control cabinet 64 which houses a control means (not shown), and a horizontal drive motor with associated gearbox 66 which is configured to drive the spray assembly 14 in a direction 63 either forwards or backwards along the upper, longitudinal panel 32. This can perhaps best be appreciated in Figure 2 which illustrates the spray assembly 14 in a second position 67 along the panel 32.

Located at a spaced apart interval along the upper panel 32 are two adjustable travel limit switches 68 and 70, which are well known electro-mechanical devices that consist of an actuator (not shown) mechanically linked to a set of contacts (not shown) such that when an object comes into contact with the actuator, the device operates the contacts to make or break an electrical connection therewith. The object in this case is in the form of a trigger bracket 74 mounted to the rear left-hand side of the dust extraction hood 54 of the spray assembly 14. In this context, making or breaking the electrical connection of either limit switch 68 or 70 causes the drive motor 66 to reverse direction. One may appreciate that track 62 extends a distance past limit switch 70 to accommodate for the width of the spraying assembly 14. However, it is to be understood that the position of bracket 74, that is whether it is on the left or right hand side of the assembly 14, is not critical. For example, if it were mounted on the right-hand side of the assembly 14, track 62 would simple need to extend a greater distance in the opposite direction. For obvious reasons, it is preferable for the bracket 74 to be located on the side of the drive motor and gearbox 66.

The control cabinet 64, rotator unit 16, drive motor and gearbox 66, and limit switches 68 and 70 are electrically coupled in a configuration which causes the spray assembly 14 to traverse the path between the two limit switches 68 and 70 in a back and forth motion. The control system 64 provides that the speed of the traversal is proportional to the rate of rotation of the structure 12 in order to achieve a required spray pattern. These variables, including rate of rotation and speed of traversal, may be altered to suit the specific requirements of a particular spraying situation, for example, when using spray heads of different size and structures of different lengths and/or heights.

As can be seen in Figures 5-7, the dust extraction hood 54 includes a curved internal edge 72 so that it may be placed closer to the curved structure 12 than would be possible if the edge were flat. The spray guns 50 and 52 are positioned adjacent and diagonal to one another, that is, they are horizontally adjacent and vertically offset. As mentioned, thermal spraying involves the melting of metal and spraying of metal particles that are then quenched and bonded to the structure surface. In this case, the metal that is fed through the spray guns 50 and 52 is a zincbased metal and the resulting spray is a combination of zinc and zinc oxide particles 75. Those skilled in the art would realise the anti-corrosive properties of this material. As shown in Figure 7, there is a dust extraction duct 77 mounted at the base of the dust extraction hood 54 that draws excess dust particles therethrough, thereby providing for a clean working environment.

Conventional dust extraction systems generally involve the use of fans and ductwork which serve to draw dust out of a room in which such spraying is taking place. The configuration of the dust extraction hood 54 and associated components serve to localise the particulate matter so that it may be drawn away from the working area immediately, this being disclosed in a further copending application by the applicant.

It is important to realise that the guns 50 and 52 themselves do not move but are fixed.

Therefore, traversal of the guns back and forth between the limit switches 68 and 70 is done along a horizontal plane. This is advantageous over existing systems in that complex and expensive electronic or robotic componentry is not required. In preference, the spraying assembly is made to traverse between limit switches 68 and 70 and the structure 12 made to rotate before spraying commences. This gives the user the ability to first visualise the spray pattern that will appear on the structure 12, and further be given the opportunity to tweak the apparatus 10 to achieve an optimal spray pattern.

Illustrated in Figures 8 and 9 are a method of spraying the tower section 12. More specifically, Figure 8 shows a spray pattern or footprint 76 on the surface of tower section 12 after being sprayed by spray gun 50, and Figure 9 is the spray pattern or footprint 78 resulting from spray gun 52. Figure 8 may also be used to indicate the resultant spray pattern using a single spray gun as used in existing systems. As can be seen, there are areas that are not covered and areas that do not overlap and hence results in a non-uniform coating of material.

The spray patterns in Figure 8 and 9 result from the controlled rotation 27 of the structure 12 together with the controlled velocity traversal of the spraying assembly 14. As can be seen in each of the spray patterns 76 and 78, there are self-overlapping sections 80 and 82 respectively.

These overlapping sections 80 and 82 effectively constitute a double layer of material.

The spray patterns from each gun are usually the same. However, spray gun 52 is positioned approximately one footprint height lower than spray gun 50. Figure 10 illustrates a spray pattern 84 resulting from the combination or superimposition of spray patterns 76 and 78.

As can be seen, spray patterns 76 and 78 overlap at sections 86. Therefore, it is evident that each of the overlapping sprayed sections 80, 82 and 86 constitute a uniform double coat of material that is independent of the other. Each layer of coating applied by a single pass of a spray gun is approximately 30 micron. Therefore, the double layers formed at each of the overlapping sections are approximately 60 micron thick which is sufficient to provide adequate protection to the tower section surface. Therefore, during a single constant revolution of the structure 12, a uniform double layer of material may be deposited on the structure 12 in a minimum amount of time by simply using a novel applicator arrangement.

It is to be understood that in order for uniform layers to be deposited on the structure, there must be two or more spray guns or applicators, which traverse back and forth along the structure. It is a requirement that there be two or more spray guns because otherwise, as those skilled in the art would realise, the further applicator(s) completes the coating process. In using only one applicator, a non-uniform coating will result. It is to be further understood that there is no requirement for the applicators to be spaced horizontally apart. So long as they are spaced vertically apart a distance that substantially corresponds with the height of the spray pattern, then the resultant pattern will be uniform.

The apparatus of the present invention also allows one to experiment with alternative spray patterns that may be suited to other structures. Some of the parameters of the apparatus that may be varied include the spaced apart distance of the limit switches 68 and 70, the vertical and horizontal distance between the spray heads and the structure surface, the size of the spray gun heads, the velocity of the traversing spraying assembly 14, the height of the spraying assembly 14, the rate of rotation of the structure 12 and the longitudinal position of the support frame 18.

The benefits provided by the present invention should thus now be realised. The present invention provides for an apparatus 10 for the deposition of material onto a structure wherein the apparatus includes two or more spray guns or applicators that are vertically spaced apart according to the height of the application footprint and which traverse along the length of the structure providing a uniform coat thereon. The present invention also proposes a method of spraying the structure whereby the structure is set at a constant pre-determined rotation, and in traversing the two applicators along the revolving structure, the overlap resulting from the two spray patterns is uniform throughout. The present invention proposes cost and time savings in that multiple skilled workers are no longer required to spray the structures which often results in over-sprayed patches and residue on the surface of the structures. Further, it overcomes the drawbacks of other traversing systems in that a highly uniform coating is achieved without the use of any highly technological equipment, another cost saving advantage.

Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

In any claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.

Dated this 7 July 2004 AHT Pty Ltd By his Patent Attorneys LESICAR PERR1N

Claims (9)

1. An apparatus for depositing material on a surface of a constantly rotating structure rotating around a longitudinal axis, said apparatus including: two spaced apart traversing material applicators each applicator adapted to deposit material onto said surface, said material applicators defining a deposition footprint on said structure, the distance separating the applicators in a direction generally perpendicular to the longitudinal axis of said structure being generally the same as the height of the deposition footprint on said structure in a direction also generally perpendicular to the longitudinal axis; said applicators adapted to traverse back and forth parallel to said longitudinal axis between a first and a second position, the length of the traverse and the speed of rotation of said structure selected so that during one traverse the angular movement of said surface is generally equal to the deposition footprint height.

2. An apparatus for applying a uniform coat to a surface of a structure, said apparatus including: a rotation means for rotating said structure; and a support means for slidably supporting a spraying assembly, said spraying assembly including two spray means each adapted to apply a spray pattern having a footprint of generally the same height onto said surface, said spray means being offset by a vertical distance that corresponds with said height, said spraying assembly configured to traverse back and forth along said rotating structure such that said uniform coat is formed by the combination of said spray patterns.

3. An apparatus as in claim 2 wherein the combination of the rotation of said structure and traversal of said spray assembly results in two zig-zag style footprints positioned adjacently one below the other wherein individual overlapping sections of said footprints combine to form said uniform coat.

4. An apparatus as in claim 2 or 3 wherein said uniform coat is achieved in one revolution of said rotation unit.

An apparatus as in any one of claims 2-4 wherein said support frame is moveable and anchorable along the length of the structure.

6. An apparatus as in claim 5 wherein said spraying assembly is belt driven.

7. An apparatus as in any one of claims 2-6 wherein the spraying assembly traverses between two spaced apart sensing means moveably mounted to said support structure.

8. An apparatus as in any one of claims 2-7 wherein the rate of rotation of the structure and speed of traversal of the spraying assembly is also controllable via a control means.

9. A method of providing a uniform double, or any multiple of two, coats to a surface of a vertically moving, longitudinal structure, said method incorporating the following steps: moving said structure at a pre-determined, constant rate of vertical movement; traversing a first and a second application device back and forth along the length of at least a portion of said structure; depositing a first footprint of material onto said surface using said first application device, said first footprint being in the form of opposed diagonal strokes that overlap at their ends, said overlap defining a first overlapping area; and depositing a second footprint of material at the same time as said first footprint using said second application device, said second footprint being identically shaped to said first footprint such that it too overlaps at its ends wherein said overlap defines a second overlapping area, said second footprint disposed a step below said first footprint such that the area in which said first and second footprints overlap defines a third overlapping area such that said first, second and third areas are independent of one another and together form said double coat.