APPARATUS AND METHOD FOR APPLYING A FLUID TO A COMPONENT
Apparatus for applying a fluid to a target area of a component is provided, the apparatus comprising a fluid applicator 10 and means 12, 300, 400 for guiding the fluid applicator 10 along a predetermined path with respect to the component 26; the fluid applicator 10 comprising a body 14 and an application head 50, 100, 200 mounted on the body 14 and operable in use to be brought into physical contact with the component 26.
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The present invention relates to an apparatus and method for applying a fluid to a component. The invention is particularly but not exclusively related to an apparatus and method for applying a chemical etchant to a target area of a component.
Chemical etching is a commonly used technique for removing one or more surface layers from a metallic component. An acid, base, or other chemical etchant fluid is applied to an area of a component for a period of time and dissolves a surface layer of the component. Various methods may be used to bring the etchant fluid into contact with the component.
One known method involves filling a large tank with etchant fluid and immersing a component in the fluid. Masking material may be used to prevent the etchant fluid removing a surface layer from the entirety of the component. Etch tanks may have a negative environmental impact, as well as being inefficient and costly to run. They may also produce large quantities of gas and fluid emissions. Specialist disposal of used and waste product is required, increasing maintenance and running costs. Additional finishing operations are also often required to counteract the effects of the etchant fluid where etching was not required, even when a suitable masking material is used.
Another known method of applying etchant fluid to a component is “swab etching”, where a liquid etchant is painted on to a surface of a component for a given time. This often results in unsightly and inconvenient “runs” of etchant fluid straying into areas where surface etching was not required. Swab etching is also a comparatively labour intensive method of surface etching, involving close operator contact with hazardous chemicals
Etchant fluids may be heated or subjected to ultraviolet stimulation to increase etch rate. However, in combination with the above methods, these practices involve high capital cost as well as increased labour and etchant response is subject to line of sight and illumation issues
A particularly difficult problem in surface etching is the removal of material from fine surface features such as are found in laser cut, machined or welded surfaces and the interfaces between such surfaces. Weld contours, particularly in root and toe regions, present difficulties for the manipulation of line of sight based material removal processes. Welds constitute points of material micro structural variation and it is therefore undesirable to unduly thin a weld region or to introduce additional stresses through machining.
SUMMARY OF INVENTIONAccording to the present invention, there is provided apparatus for applying a fluid to a target area of a component, comprising a fluid applicator and means for guiding the fluid applicator along a predetermined path with respect to the component; the fluid applicator comprising a body, an application head mounted on the body and operable in use to be brought into physical contact with the component, and means for controlling the temperature of the fluid to be applied to the component.
The fluid may be any one of a chemical etchant, scale conditioner, washing fluid and/or neutralising solution. The fluid may be of increased viscosity and may be a paste or gel. The paste may be thixotropic.
The body may be formed from a deformable material. The body may thus accommodate variations in surface geometry of the component such as convex and concave regions, edge regions and re-entrant features.
The application head may comprise a brush having a brush head and a plurality of agitators which may be bristles or fins. Advantageously, the agitators of the brush act to scrub a component surface, forcing etchant fluid into fine surface features and also removing unwanted fluid from such features.
The brush head may comprise an opening, suitable to deposit or collect fluid. The apparatus may further comprise means to apply positive and/or negative pressure at the opening. The brush head may comprise at least two such openings and the apparatus may further comprise means to apply positive pressure at one opening and negative pressure at another opening. The openings may comprise two or more independent sections of a single orifice, thus allowing simultaneous deposition and collection of fluid.
The apparatus may comprise means for controlling the temperature of the fluid to be applied to the component. It may be desirable for the fluid to be delivered at a raised temperature or at a controlled ambient temperature, according to the particular fluid to be applied.
The brush may be mounted for rotation about an axis that is substantially parallel to a surface of the body on which it is mounted, a surface of the brush head from which the agitators project being substantially cylindrical. In this manner, the brush may pass over the component surface in a manner similar to that of a vacuum cleaner, the agitators scouring the component surface.
The plurality of agitators may project from the surface of the brush head in a helical pattern that winds about the brush head. The plurality of agitators may project from the surface of the brush head in at least one chevron pattern, which may be formed about the at least one opening of the brush head.
The brush may be mounted for rotation about an axis that is substantially normal to a surface of the body on which it is mounted, a surface of the brush head from which the agitators project being substantially planar.
The brush may comprise at least two regions, the regions being operable to rotate in different directions. The regions may be concentric.
The plurality of agitators may project from the planar surface in a spiral configuration.
The length and stiffness of the agitators may vary across the brush. The brush may comprise regions of different length and/or stiffness agitators.
The brush may be mounted for rotation in both clockwise and anticlockwise directions.
The agitators of the brush head may comprise bristles or they may comprise fins.
A plurality of brushes may be mounted for rotation on the body of the fluid applicator about parallel axes.
At least two of the plurality of bushes may comprise different agitator configurations.
The means for guiding may comprise a mechanical manipulation arm on which the fluid applicator may be operable to be mounted.
The means for guiding may comprise a track, along which the fluid applicator may be operable to be driven. The track may be formed from a deformable material and may be assembled into a frame. The track may comprise a racked surface/rack and pinion arrangement.
The means for guiding may further comprise means for manipulating the component.
According to another aspect of the present invention, there is provided a method of applying a fluid to a target region of a component using an apparatus of the first aspect of the present invention, comprising connecting a fluid supply to the fluid applicator, mounting the fluid applicator on the means for guiding the applicator along a predetermined path, bringing the applicator head into physical contact with the target region of the component, causing the applicator to be guided along the predetermined path while depositing fluid through the applicator from the fluid supply, and controlling the temperature of the fluid to be applied to the component.
The fluid may be any one of a chemical etchant scale conditioner, washing fluid and/or neutralising solution. The fluid may be of increased viscosity and may be a paste or gel. The paste may be thixotropic.
The means for guiding may comprise a flexible track and the method may further comprise locating the flexible track about the component, such that the applicator traces the predetermined path along the component when travelling along the track. Locating the flexible track may comprise constructing a frame of the flexible track about the component.
The means for guiding may comprise a mechanical manipulation arm and the method may further comprise programming the mechanical manipulation arm to move the applicator such that the applicator traces the predetermined path along the component.
The method may further comprise mounting the component for rotation.
The means for guiding may further comprise means for manipulating the component, the method may further comprise mounting the component on the means for manipulating the component, and the various means for guiding may cooperate to cause the applicator to be guided along the predetermined path.
Depositing fluid through the applicator may comprise applying pressure to the fluid at a fluid opening in the application head. Depositing fluid through the applicator may also comprise causing the application head to rotate.
The method may further comprise collecting fluid under a negative pressure applied at the opening in the application head.
The method may further comprise controlling the temperature of the component. The method may further comprise heating and/or cooling the component.
According to another aspect of the present invention, there is provided a chemical etchant comprising titanium dioxide as a thickening agent. The viscosity of the etchant may be above that of the constituent etchants and more specifically between 400-7500 cP. Viscosity enhancing media may also include inert oxide powders or gels.
According to another aspect of the present invention, there is provided an applicator for depositing a fluid on a component surface, comprising a body, a brush mounted for rotation on the body, the brush comprising a brush head and a plurality of bristles and a fluid passage extending through the brush head and comprising at least one opening that communicates with a bristled surface of the brush head.
The fluid may comprise etchant, detergent containing wash fluid, scale conditioner or neutralising agents.
The fluid passage may comprise two sub passages, operable to be brought into communication with each other.
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings in which:
The present invention relates to an apparatus and method for applying a fluid such as a chemical etchant to a target area of a component. The following description uses the example of a weld line as a target feature of a component, an area of which may be appropriate for chemical etching.
One aspect of the present invention involves the development of a particularly advantageous chemical etchant for use with the apparatus and method of the invention. Known etchant combinations, such as those employing Hydroflourosilic acid with Nitric acid or Hydrofluoric acid with Nitric acid are enriched with Titanium Dioxide. TiO2 acts as a thickening agent, increasing the viscosity of the etchant to that of a paste. Water based gel and other inert oxide powders may also be employed as a thickening agent to achieve the required viscosity, at which the paste will substantially adhere to a component surface, and will not run along the surface. It is a requirement of the etchant paste that it must remove a controlled and uniform layer of between 0.5 and 15.0 μm. Certain applications may require removal of a layer of up to 75.0 μm.
With reference in particular to
It will be appreciated that the outer extent of the target area 8 over which the etchant fluid is deposited is defined by the extent of the safety zone 6. It may be desirable to vary the width of the safety zone 6 during application of etchant fluid. Such variation may be achieved through appropriate brush selection and manipulation of the separation between the fluid applicator 10 and the component 26.
Each of the example brushes 50 illustrated in
Etchant fluid is deposited via the application head brushes as mentioned above. A central opening in the brush head allows fluid etchant to be deposited, while the rotating action of the brush encourages spread of the fluid over the entire contact area. Positive pressure may be applied to fluid at the opening to encourage deposition. Once the surface of the component has been etched to the required depth, it is necessary to remove the fluid and to clean the component surface. The same central opening may be used to collect spent etchant fluid, assisted by negative pressure or a vacuum applied at the opening. Positive or negative pressure may be applied at the opening of a fluid conduit that is in communication with the opening and also with a fluid reserve and other external mechanisms. A water feed may be incorporated to assist with the collection/cleaning of the component surface. Deposition/spreading and collection of fluid etchant may be assisted by the bristle configuration of the brushes.
It has been discussed above that agitation of the etchant fluid while on the component surface assists with mixing and ensuring efficient material removal. Agitation ensures that a layer of depleted etchant fluid and evolved gaseous product from the etching reaction does not build up immediately adjacent to the component surface. One desirable way of agitating and ensuring efficient surface removal is to cycle etchant fluid during the etch process. Continually depositing and collecting fluid ensures that the fluid remains well mixed and spent fluid is not allowed to accumulate. In addition, deposited fluid may be collected and reheated or cooled before being redeposited, thus ensuring the fluid retains optimal efficiency within predefined specification limits within the range 10-90° C. This also ensures that a previously discussed wash stage may act to pre-heat the component to aid in temperature control of the fluid once deposited. Recycling fluid in this way ensures that the minimum amount of fluid is used to achieve the required depth of material removal, providing both economic and environmental advantages.
Further detail of the attachment arms and means for guiding 12 is illustrated in
A first embodiment of the means for guiding the fluid applicator 10 is illustrated in
The use of CAD software to determine a predetermined path for the fluid applicator to follow, and then to instruct a manipulation arm or direct the construction of a frame allows a high degree of accuracy to be achieved while minimising operator contact with etchant media. In each case, the predetermined path may involve several discrete sections, over which the fluid applicator may need to pass but which should not have etchant media applied. The flow of etchant fluid to the fluid applicator may be stopped as the fluid applicator passes over such regions. In addition, or in the alternative, the fluid applicator may be offset from the component surface as it passes over such sections.
It will be appreciated that it may be desirable to vary the offset of the fluid applicator from the component surface during treatment so as to vary the thickness of the deposited layer of etchant fluid. For example, the fluid applicator may be in close physical contact with the component surface during deposition, slightly further away during manipulation/agitation of the etchant fluid so as to merely mix the etchant rather than remove if from the surface, and then in close contact again for etchant removal. The actual process cycle may be more complicated than has so far been described. For example, a full process cycle may include the following steps:
-
- i) Wash—a first pass of the target area is conducted to thoroughly scrub the target area
- ii) Scale condition—a viscous scale conditioner is applied using the fluid applicator 10 to prepare the surface
- iii) Wash—a third pass is conducted to remove the scale conditioner and clear the surface
- iv) Etch—a layer of etchant fluid is applied as described above
- v) Agitate—several passes may be made cycling and agitating the etchant paste to ensure even and thorough removal of the required thickness of surface layer
- vi) Wash—a penultimate pass is made to remove the etchant and clear the surface
- vii) Dry and Clean—a final pass is made to scrub the surface and remove any last loose material an air-knife approach may be used.
It will be appreciated that the bristle requirements for the different process stages may be different. For example firmer bristles are required for depositing layers of fluid while longer, softer bristles may be preferred for agitation and cleaning. The various requirements may be accommodated in a single applicator by employing several different brushes on a single applicator and by employing variable bristle types on individual brush heads, as described above. It may also be desirable to employ specific brushes within the applicator for specific tasks. For example it may be desirable to use different brushes for the application and removal of the scale conditioner to those employed for application, agitation and removal of the etchant fluid. Different brushes, tailored to the specific process stage requirements, can be mounted on a carousel and moved between operating and holding positions as required. A water feed may be incorporated to assist with the wash process stages as required.
It will be understood that variations can be made to the specific embodiments of apparatus described above without departing from the scope of appended claims. For example, additional agitation or temperature control may be provided by steam or gas jets delivered either from the applicator body or through the application heads of the fluid applicator. Additional agitators may also be provided in the form of flutes, ribs or supplementary bristles. Such agitators may be mounted on the application heads or may be mounted on separately on the body. Heating or cooling may be provided via the circulatory control unit, body or application heads to increase or decrease the temperature of the scale conditioning, wash or etchant fluid. It will be understood that heating etchant fluid may increase the rate at which surface material is removed, although this may result in an increased health and safety concern. Depth probes and/or a surface scanner/analyser may also be incorporated into the fluid applicator, with the potential for incorporation of electrolytic fluid monitoring and control.
The temperature of the component may be controlled. The temperature of the component may be controlled by cooling and/or heating the component directly or by cooling and/or heating the atmosphere in which the component is held throughout the process.
The component may be maintained at a temperature of about 293K by the temperature control means for scale conditioning part of the process. The component may be maintained at about 363K by the temperature control means for the cleaning and etching parts of the process.
It will be further understood that while various aspects of the present invention have been described in combination, such combinations are not intended to be limiting in scope. Any aspect of the present invention may be employed in combination with any other aspect of the present invention above described.
The present invention has been described with particular reference to the surface processing of a weld line. However, the present invention is applicable to any circumstance in which surface treatment of a target area of a component is required. The maneuverability and versatility of the apparatus of the present invention renders it particularly suited to the treatment of curved components such as aerofoils for gas turbine engines. The adaptability and fine control provided by the apparatus of the present invention enables accurate treatment of convex and concave surface areas including edge and tip surfaces and re-entrant features such as weld crowns and underbeads. It will be appreciated, however, that the apparatus of the present invention can be employed for the treatment of any kind of component. Such treatment is not limited to the particular application of etchant fluid described, but may also include non destructive testing applications and cleaning as well as surface preparation, diffusion bonding and chemical milling. The apparatus is suitable for use with metallic as well as glass and other material components.
It will be appreciated that the present invention provides an efficient and environmentally sound apparatus and method for applying an etchant or other fluid to a component surface. Fine control is provided to enable exact distribution of fluid and hence accurate surface material removal by etchant media. The apparatus is extremely versatile and adaptable to a wide range of component shapes and sizes. Accurate treatment of target surface areas by the apparatus retains component thickness and reduces chemical usage. The apparatus is self contained, not requiring the use of sealant or masking material. The invention also contains scope for miniaturisation, use on bimetallic components or assemblies and use on assemblies containing non-metallics such as seals, foams, rubbers and hard polymers.
To avoid unnecessary duplication of effort and repetition in the text, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention.
Claims
1. Apparatus for applying a fluid to a target area of a component, comprising
- a fluid applicator; and means for guiding the fluid applicator along a predetermined path with respect to the component; the fluid applicator comprising:
- a body;
- an application head mounted on the body and operable in use to be brought into physical contact with the component; and
- means for controlling the temperature of the fluid to be applied to the component.
2. Apparatus as claimed in claim 1, wherein the application head comprises a brush having a brush head and a plurality of agitators.
3. Apparatus as claimed in claim 2, wherein the brush is mounted for rotation about an axis that is substantially parallel to a surface of the body on which it is mounted, a surface of the brush head from which the agitators project being substantially cylindrical.
4. Apparatus as claimed in claim 3, wherein the plurality of agitators projects from the surface of the brush head in a helical pattern that winds about the brush head.
5. Apparatus as claimed in claim 3, wherein the plurality of agitators projects from the surface of the brush head in at least one chevron pattern.
6. Apparatus as claimed in claim 2, wherein the brush is mounted for rotation about an axis that is substantially normal to a surface of the body on which it is mounted, a surface of the brush head from which the agitators project being substantially planar and the plurality of agitators projects from the surface of the brush head in a spiral configuration.
7. An applicator as claimed in claim 2, wherein the agitators comprise fins.
8. Apparatus as claimed in claim 1, wherein the application head comprises an opening and the apparatus further comprises means to apply positive and/or negative pressure at the opening.
9. Apparatus as claimed in claim 8, wherein the application head comprises at least two such openings and the apparatus further comprises means to apply positive pressure at one opening and negative pressure at another opening.
10. Apparatus as claimed in claim 2, comprising a plurality of brushes mounted for rotation on the body of the fluid applicator about parallel axes.
11. An applicator as claimed in claim 10, wherein at least two of the plurality of brushes comprise different agitator configurations.
12. A method of applying a fluid to a target region of a component using an apparatus as claimed in claim 1, comprising:
- connecting a fluid supply to the fluid applicator;
- mounting the fluid applicator on the means for guiding the applicator along a predetermined path;
- bringing the applicator head into physical contact with the target region of the component,
- causing the applicator to be guided along the predetermined path while depositing fluid through the applicator from the fluid supply, and
- controlling the temperature of the fluid to be applied to the component.
13. A method as claimed in claim 12, wherein depositing fluid through the applicator comprises applying pressure to the fluid at a fluid opening in the application head.
14. A method as claimed in claim 13, wherein depositing fluid through the applicator further comprises causing the application head of the applicator to rotate.
15. A method as claimed in claim 13, the method further comprising collecting fluid under a negative pressure applied at the opening in the application head.
Type: Application
Filed: Apr 5, 2011
Publication Date: Oct 20, 2011
Applicant: ROLLS-ROYCE PLC (London)
Inventors: Daniel CLARK (Belper), David W. MILLS (Bewdley)
Application Number: 13/080,124
International Classification: A46B 11/00 (20060101);