US20040232096A1

US20040232096A1 - Coating processes

Info

Publication number: US20040232096A1
Application number: US10/816,704
Authority: US
Inventors: Peter Smith
Original assignee: PROTECTIVE FINISHING GROUP Ltd
Current assignee: PROTECTIVE FINISHING GROUP Ltd
Priority date: 2001-10-03
Filing date: 2004-04-02
Publication date: 2004-11-25
Also published as: WO2003028897A1; EP1432523A1

Abstract

A carrier for use in a coating process, the carrier being generally elongate and having a plurality of support members which, in use, support articles during the coating process, the support members each having an opening leading to a recess, the recess extending from the opening in a direction generally parallel to a longitudinal axis of the carrier.

Description

DESCRIPTION OF INVENTION AND SUMMARY OF THE PRIOR ART

This invention relates, in general terms, to industrial processes for coating electrically conductive articles, wherein the articles are engaged with an electrically conductive support member, and are given, via the support member, an electric charge prior to being brought into contact with coating (e.g. paint) particles having an opposite electric charge.

Such processes, as will be appreciated by those well-versed in the relevant art, include electro-plating, powder-coating and electro-coating, and will henceforth be referred to generically, for the sake of convenience, as coating processes “of the kind specified”.

A key requirement of such support members is that they are able to make good electrical contact with the articles supported thereby, with the applicants' prior International patent application (WO00/54889) and prior British patent application (GB 0108916.8) disclosing a number of ways in which the support members can be cleaned in order to effect this.

An equally important factor to consider is the “packing density” of articles that the support members allow, as it is clearly desirable to coat as many articles during a given process run as possible. Furthermore, it is important to minimize the number of articles that become dislodged from the support members during the coating process, with it being an object of the present invention to provide a carrier that satisfies these and other requirements. Other objects of the present invention are the provision of an improved method of making a carrier and support members, the provision of an improved method of removing surface coating material from a support member, an improved support member and an improved method of unloading a carrier.

According to a first aspect of the present invention, there is provided a carrier for use in a coating process of the kind specified, the carrier being generally elongate and having a plurality of support members which, in use, support articles during the coating process, the support members each having an opening leading to a recess, the recess extending from the opening in a direction generally parallel to a longitudinal axis of the carrier.

The carrier preferably lies within a plane, with the support members conveniently lying in, or close to, the plane.

The carrier may be generally planar, and may be formed from sheet or sheet-like material. Preferably, the carrier is formed from sheet metal.

The support members may also be formed from sheet or sheet-like material, with the support members conveniently being integral with the carrier.

The carrier and support members may be formed using a laser cutting operation, conveniently from a single sheet.

Thus, the carrier and support members may lie within or close to a single plane.

The carrier may comprise a strengthening element to resist bending, the strengthening element conveniently comprising a lip or flange.

The strengthening element may comprise a deformed edge part of the carrier, and may be generally parallel to the longitudinal axis of the carrier.

The carrier may further comprise barriers disposed in relation to each of said plurality of support members to hinder removal or disengagement of articles therefrom.

The barriers may be provided by connecting limbs of the support members. The connecting limbs may extend away from the carrier at an acute angle to the longitudinal axis.

The connecting limbs may be generally in-line with the openings of the support members.

The connecting limb of a support member may be located adjacent or close to the opening of a neighboring support member. Said connecting limb may be generally elongate and may lie generally parallel to the opening.

The connecting limbs may extend partly into the openings of neighboring support members.

Distal ends of the support members may be disposed, when the axis of the carrier is generally horizontal, beneath part of a neighboring connecting limb.

The connecting limbs may provide a guide surface for use during engagement or disengagement of articles with or from the support members.

The carrier and support members may be formed from stainless steel sheet.

In accordance with a second aspect of the present invention, there is provided a method of making a carrier and support members for use in a coating process of the kind specified, comprising procuring metal sheet material and laser cutting the sheet to obtain a desired profile.

The method may further comprise deforming an edge part of the carrier to provide a strengthening element.

The method may comprise the initial steps of designing a profile and conveying the profile, in machine-readable format, to a laser cutter.

The profile may be designed using a CAD package, conveyed electronically using DXF (Digital Exchange Format) and read by the laser cutter using the or a further CAD package.

The invention also provides a rack for use in a coating process of the kind specified, comprising a plurality of carriers and support members substantially in accordance with one or more of the preceding paragraphs.

In accordance with a third aspect of the present invention, there is provided a method of removing surface coating material from a support member on a coating rack, comprising engaging an article to be coated with a support part of the support member and vibrating the support member to induce movement of the article relative to the support member which is effective to abrade the surface coating, characterized in that the support member is attached to or integral with a carrier, the support member having a connecting limb, part of the connecting limb serving as a barrier to hinder disengagement of an article engaged with a neighboring support member.

To this end, a distal end of a support member may be disposed beneath part of a neighboring connecting limb during the vibration stage.

In accordance with a fourth aspect of the present invention, there is provided a support member for use in supporting an article during a coating process of the kind specified, the support member having a stop formation to hinder swinging movement of the article supported thereby.

The stop formation may be attached to or integral with a free end of the support member.

Preferably, the stop formation comprises a protrusion extending from the free end. Conveniently, the free end is generally “V” or “U”-shaped, with the stop formation conveniently extending from the apex of the “V” or “U”.

Preferably, the extension depends from the support member.

The stop formation may be operative, in use, to hinder suspension of the article from the support member.

The support member may have a support part which, in use, is in electrical contact with the article, the stop formation being operative to contact the article at a position remote from a vertical plane in which the electrical contact point is contained.

The stop formation may be operative, in use, to cause at least part of the article to be inclined to the vertical.

The invention also provides a carrier having a plurality of support members associated therewith, the support members being in accordance with the fourth aspect of the present invention.

Furthermore, the invention provides a rack for use in a coating process of the kind specified, comprising a plurality of carriers in accordance with the preceding paragraph.

In accordance with a fifth aspect of the present invention, there is provided a method of unloading a carrier in accordance with one or more of the preceding paragraphs, the method comprising tilting the carrier towards a generally vertical axis such that the articles may fall therefrom.

Specific and non-limiting embodiments of the invention, in its various aspects, will now be described in greater detail, strictly by way of example only, with reference to the accompanying drawings, of which: [0038]
FIG. 1 is a plan view of a carrier and support members; [0039]
FIG. 2 is a plan view of part of a slightly modified carrier and support members; [0040]
FIG. 3 is a section along the line III-III of FIG. 2; [0041]
FIG. 4 is a perspective view of an electro-coating rack suspended from a conveyor; [0042]
FIG. 5 shows a carrier suspension unit; [0043]
FIG. 6 is a plan view of a preferred form of carrier and support members with a schematic illustration of articles supported thereby; [0044]
FIG. 7A shows a preliminary unloading step; [0045]
FIG. 7B shows a later stage in the unloading process, with the articles being shown falling from the support members; and [0046]
FIG. 8 shows, in side view, apparatus to impart vibrations to the carriers.[0047]
FIG. 1 shows part of a generally [0048] elongate carrier 10 having a body 11 and a plurality of integral support members 12. Each support member 12 has a somewhat hook-like configuration, in that a connecting limb 13, extending from the body 11 of the carrier 10 terminates in an upturned distal end 14. Openings 15 lead to a plurality of recesses 16, with the bottom of the “V” configuration 17 serving as a support part for suspending articles, in generally conventional manner.
Both the [0049] carrier 10 and the support members 13 are cut, using laser cutting apparatus, from stainless steel sheet material, with the accuracy of the laser cutting process allowing a very precise configuration to be arrived at.
It will be appreciated from FIG. 1 especially that the acute angle at which the connecting limbs lie, in relation to the principal longitudinal axis of the carrier, provides a [0050] guide surface 18 over which part of an article to be coated can travel, as the article is engaged or disengaged from the support members. Moreover, the angle and relative positioning of the connecting limbs in relation to the distal ends 14 means that those parts of the limbs 19 that face towards the recesses 16 can act as barriers which hinder removal or disengagement of articles from the support members. This is illustrated schematically by the washer 20 (shown in dotted outline) which, it will be appreciated, can only be removed by tilting it somewhat in a clockwise direction, prior to it being withdrawn from the support member through a gap 21 between the distal end 14 of a given support member and a lower part of a connecting limb of a neighboring support member.
The generally planar nature of the carrier and support members allows articles or components to be loaded onto the carrier so that they lie generally transverse to its principal axis. [0051]
As will be understood, this enables far more components to be loaded onto a carrier of given length than prior art carrier/support member constructions which have the support members extending generally transversely of the axis, such as is shown in WO00/54889, for example. [0052]
FIG. 2 shows a somewhat similar part of a carrier and support members, although the shape of the support members is slightly different, in that the spacing of the support members is increased so as to accommodate larger articles or components. As shown in FIG. 3, the carrier of FIG. 2 is provided with a strengthening element in the form of a folded/[0053] bent flange 30 which reduces the carrier's susceptibility to bending in the direction shown generally by arrow A. It will be understood that the downward forces exerted on the carrier when it is fully laden with metal components can be high, and it is thus important to ensure that no unwanted deformation of the carrier occurs, bearing in mind the close packing of carriers that can occur in an electro-coating rack—see FIG. 4.
FIG. 4 shows a generally conventional electro-[0054] coating rack assembly 40 having a plurality of carriers 10, carried at each end by a current carrying rod 41. Welded to the rods 41 are a plurality of diamond-shaped locator elements 42 which guide and receive indented notches 43 of the carriers, shown in FIGS. 1 and 2. The electro-coating rack assembly is suspended from a conveyor 44 which transports the electro-coating rack assembly between the various conventional stages of the electro-coating process. The electro-coating rack is suspended from a pair of parallel load-bearing bars 45, with the assembly 40 being held, via T-bars 46, by a hanger 47 which is moveable along the conveyor 44 in generally conventional manner. As shown, the T-bars 46 are releasably engageable with the hanger 47, thus enabling the electro-coat rack assembly 40 to be deposited and picked up at a number of different locations.
FIG. 5 shows an improved construction of a carrier suspension unit, or hanger, which, as with the carriers and support members of FIGS. [0055] 1 to 3, is laser cut from a sheet metal material such as stainless steel.
The [0056] hanger 50 has a rear side 51 and an open front side 52 through which carriers may be introduced for location within one of the many notches 53 provided on the plurality of support bars 54. In use, the hanger 50 is introduced to the coating rack assembly as a replacement for a number of superposed bars (41) and locator elements (42) such as are shown in FIG. 4. Thus, the open side 52 of the hanger 50 would lie to the right of the construction shown in FIG. 4, with two opposing hangers being used to provide a complete rack assembly.
The serrated nature of the carrier bars [0057] 54, in conjunction with the notch formation of the carriers 10, enables the carriers to be positioned readily and securely, in a more closely packed arrangement than is permitted, for example, by the conventional diamond-shaped locator elements shown in FIG. 4.
The use of laser cutting in this invention provides a number of advantages, not least in that the design and manufacture of carriers, support members and rack hangers is vastly simplified and hence reduced in cost. Laser-cut metal sheet is also especially well-suited to uses in coating processes of the kind specified, as it allows profiles to be produced from relatively hard wearing materials (e.g. carbon steel) and corrosion resistant materials such as stainless steel. [0058]
Laser cutting also gives rise to relatively sharp kerfs which, as disclosed in the applicants' earlier applications (WO00/54889 and GB 0108916.8) allows a greater degree of paint removal to be effected when the support members are vibrated with the components in situ. As discussed in WO00/54889, effecting vibration of the support members with the components in situ causes the components to move, relative to the support members, with an inner surface of the components (defined by the apertures therein) being brought into vibratory (and hence abrading) contact with the [0059] support parts 17, with this being effective to remove any surface coating or paint material which may have built up in that region. The vibration is continued up to the point at which metal-to-metal contact is made possible which, in practice, has been found by the applicants to take two to six minutes or thereabouts, upon application of a suitable vibration. Vibration of the support members and components may be effected by a vibrating device of the type shown in FIG. 8. With such a device, the amplitude and frequency of the vibration may be varied, with an appropriate amplitude and frequency being determined, at least in part, by the mass of the suspended components and the materials from which they are made. The relatively sharp kerfs produced during a laser-cutting process can assist in the vibratory abrading process by penetrating through any build-up of coating material or paint, with the small surface area defined by the sharp kerfs serving to maximise the amount of vibrational energy which is transferred between the support members and components, per unit area. The increased strength provided by laser-cut materials such as carbon steel means that more forceful vibrations can be applied during such a cleaning process, as the support members are less susceptible to bending and damage, meaning, in turn, that the components are less likely to become dislodged during the vibration step.
The generally planar and unitary nature of the carriers and support members also reduces the likelihood of so-called “teddy bearing”—a phenomenon known in the relevant art relating the build up of paint and other undesired deposits at weld joints, seams and the like. [0060]
In hand with that, the applicants have noticed a considerable reduction in the amount of “carry-over” of treatment solutions from tank-to-tank, which it is thought is due to the use of the generally flat carrier and support member profile. As mentioned above, laser cutting gives rise to relatively sharp kerfs, which reduces the likelihood of any paint traps being formed, which, in the case of prior art welded constructions, are produced quite commonly near welds, joints and seams. This reduced “carry-over” also reduces coating material consumption, leading to substantial operational cost savings. [0061]
The generally flat upper surface of the limbs of the “V”—in particular, the bottom of the “V” [0062] configuration 17—also reduces the tendency of relatively lightweight components to become dislodged by turbulent liquid flow in the electro-coating tanks. This, as will be appreciated, compromises the electrical contact between the components and the associated support members and can thus lead to unsatisfactory finishes which necessitates removal of the part-finished coating (such as by shot blasting or burning off) and a repeat of the coating operation. It will be appreciated that components having a generally circular aperture will be supported by such a generally flat profile at at least two (usually four) distinct areas, which hinders movement of the components in a direction transverse to the axis of the carrier.
Referring next to FIG. 6, this shows, in plan view, a somewhat modified [0063] carrier 60 having a body 61 and a plurality of modified integral support members 62. Each support member 62, like the support members 12 shown in FIG. 1, has a somewhat hook-like configuration comprising a connecting limb 63 and an upturned distal end 64. However, the support members 62 are also provided, in this example, with a generally downwardly-depending stop formation 65 which extends away from the free end of each support member 62. As shown, an abutment surface 66 is operative, when an article 70 is supported thereby, to come into contact with a surface of the article, and thus to cause the article to be inclined to the vertical.
In hand with that, it will be understood that the presence of the extended stop formation prevents—or at least hinders—any swinging movement that the [0064] article 70 could otherwise undergo (see FIG. 1, for example) which in turn is effective to constrain the component 70 during a vibratory cleaning process of the type hereinbefore described. What this means is that the vibrational energy transmitted to the support member is concentrated in a reduced area, which, in turn, allows a greater degree of paint removal—at an appropriate location—to be effected when the support members are vibrated with the components in-situ.
A further advantage of the configuration shown in FIG. 6 is that the components, when engaged with the distal ends [0065] 64 of the support members 62, undergo a “self-locking” action, in that each adopts a substantially similar orientation, which allows the number of components that can be supported per unit length of carrier, to be maximised. This is because the components, being “held” in position, are far less susceptible to movement during the electro-coating process and during handling of the carriers. It will of course also be understood that the inclusion of the stop formation, on the support member 62, can readily and inexpensively be effected during manufacture of the carrier 60, by modifying the CAD profile that the laser cutter employs.
FIGS. 7A and 7B illustrate two positions adopted by the carriers described above, as the supported components are unloaded therefrom. The planar nature of the carrier and support members allows unloading to be effected by a simple tilting operation, which causes the carrier to undergo angular movement from a generally horizontal orientation towards a generally vertical orientation. Referring to FIGS. 1 and 6, it will be understood that this is effected by rotating the [0066] carriers 10/60 in a generally vertical plane, in an anti-clockwise direction. Movement of this type causes the distal parts 14/64 to approach a generally horizontal orientation, subsequent to which the components 20/70 are free to slide along the upper surface of the distal limb, and then to fall from the support member, under gravity. The importance of this unloading step should not be underestimated, in that it allows a fully laden carrier to be discharged as a result of a simple movement, without an operation being required to manually release any of the components from the support members. Whilst, theoretically, it has previously been possible to discharge carriers by rotation thereof about their principal axes (see WO00/54889, for example), unloading carriers by effecting movement thereof in a vertical plane greatly reduces the area of container that is required to receive the discharged components. This is shown in FIG. 7B, where the horizontal component of the tilted carrier (a function of the cosine of the angle it adopts with the horizontal), is clearly less than the length of the carrier itself. By varying the configuration of the “V” of the support members, the carrier angle at which the components are discharged may be altered, with an increase in the angle leading to a reduced horizontal component, which in turn allows a smaller receiving container to be employed.
The embodiments shown in FIGS. 6, 7A and [0067] 7B also provide advantages where it is desirable to reduce the occurrence of air-locks in the supported components, as the coating process takes place. The “off-vertical” orientation of the components allows open parts of the components to face generally upwardly, thus allowing air or other unwanted gases to float freely to the surface of the tank concerned.
Should the support members require cleaning, for example to remove any unwanted paint build-up or the like, conventional burning techniques may be employed, although the applicants also consider that a stripping operation could be effected, conveniently by the use of wire brushes that could be caused to rotate, and to abrade appropriate portions of the support members. Such brushes could be disposed side-by-side, defining an aperture through which the carrier is passed. [0068]
Referring lastly to FIG. 8, this shows, in somewhat schematic form, an embodiment of apparatus used to impart vibrations to the carriers [0069] 10 (see FIG. 4) and hence to the support members 12. The apparatus comprises a pair of generally U-shaped vibration transmission elements 160 which, as shown, are configured to locate beneath, but in contact with, the load bearing bars 45 of the electro-coating rack assembly 40. A vibration element 161, powered electrically via a power lead 162, is disposed beneath a cover plate 163, the cover plate 163 being in vibration transmissible contact with the transmission elements 160. Vibration insulating blocks 164 are provided beneath the cover plate 163 to ensure that the vibrational energy is transmitted primarily to the electro-coating rack, rather than to a support frame above which the vibration element is positioned. As will be understood, energizing of the vibration element 160 causes the electro-coating rack assembly 40 to vibrate, thus causing relative movement to occur between the components and the support members, which in turn induces abrasion of the support members at the areas at which they are borne upon by the suspended components. It will be understood that where flammable gases are in existence, for example, pneumatic or hydraulic operation of the vibration element may be used. As mentioned above, control means (not shown) may be effective to alter the frequency and/or amplitude of the vibration, so that the vibration may be tuned in accordance with the loading of the rack. Similarly, timing means may be provided to enable the duration of the vibration to be selected, as appropriate.
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof. [0070]

Claims

I claim:

1. A carrier for use in a coating process, the carrier being generally elongate and having a plurality of support members which, in use, support articles during the coating process, the support members each having an opening leading to a recess, the recess extending from the opening in a direction generally parallel to a longitudinal axis of the carrier.

2. A carrier according to claim 1 wherein the carrier lies within a plane, and wherein the support members lie in, or close to, the plane.

3. A carrier according to claim 2 which is generally planar.

4. A carrier according to claim 3 formed from sheet or sheet-like material.

5. A carrier according to claim 4 formed from sheet metal.

6. A carrier according to claim 5 wherein the support members are formed from sheet or sheet-like material.

7. A carrier according to claim 1 wherein the support members are integral with the carrier.

8. A carrier according to claim 1 wherein the carrier and support members are formed using a laser cutting operation.

9. A carrier according to claim 1 wherein the carrier and support members are formed from a single sheet.

10. A carrier according to claim 9 wherein the carrier and support members lie within or close to a single plane.

11. A carrier according to claim 1 further comprising a strengthening element to resist bending.

12. A carrier according to claim 11 wherein the strengthening element comprises a lip or flange.

13. A carrier according to claim 12 wherein the strengthening element comprises a deformed edge part of the carrier.

14. A carrier according to claim 11 wherein the strengthening element is generally parallel to the longitudinal axis of the carrier.

15. A carrier according to claim 1 further comprising barriers disposed in relation to each of said plurality of support members to hinder removal or disengagement of articles therefrom.

16. A carrier according to claim 15 wherein the barriers are provided by connecting limbs of the support members.

17. A carrier according to claim 16 wherein the connecting limbs extend away from the carrier at an acute angle to the longitudinal axis.

18. A carrier according to claim 17 wherein the connecting limbs are generally in-line with the openings of the support members.

19. A carrier according to claim 18 wherein the connecting limb of a support member is located adjacent or close to the opening of a neighboring support member.

20. A carrier according to claim 19 wherein the connecting limb is generally elongate and wherein the limb lies generally parallel to the opening.

21. A carrier according to claim 20 wherein the connecting limbs extend partly into the openings of neighboring support members.

22. A carrier according to claim 21 wherein distal ends of the support members are disposed, when the axis of the carrier is generally horizontal, beneath part of a neighboring connecting limb.

23. A carrier according to claim 22 wherein the connecting limbs provide a guide surface for use during engagement or disengagement of articles from the support members.

24. A carrier according to claim 23 wherein the carrier and support member are formed from stainless steel sheet.

25. A method of making a carrier and support members for use in a coating process, comprising laser cutting a metal sheet material to obtain a desired profile.

26. A method according to claim 25 further comprising deforming an edge part of the carrier to provide a strengthening element.

27. A method according to claim 25 comprising the initial steps of designing a profile, and conveying the profile, in machine-readable format, to a laser cutter.

28. A method according to claim 27 wherein the profile is designed using a CAD package, conveyed electronically using digital exchange format and read by the cutter using the or a further CAD package.

29. A rack for use in a coating process, comprising a plurality of carriers and support members substantially in accordance with claim 1.

30. A method of removing surface coating material from a support member on a coating rack, comprising engaging an article to be coated with a support part of the support member and vibrating the support member to induce movement of the article relative to the support member which is effective to abrade the surface coating, wherein the support member is attached to or integral with a carrier, the support member having a connecting limb, part of the connecting limb serving as a barrier to hinder disengagement of an article engaged with a neighboring support member.

31. A method according to claim 30 wherein a distal end of the support member is disposed beneath part of a neighboring connecting limb during the vibration stage.

32. A support member for use in supporting an article during a coating process, the support member having a stop formation to hinder swinging movement of the article supported thereby.

33. A support member according to claim 32 wherein the stop formation is attached to or integral with a free end of the support member.

34. A support member according to claim 33 wherein the stop formation comprises a protrusion extending from the free end.

35. A support member according to claim 34 wherein the free end is generally “V” or “U”-shaped and wherein the stop formation extends from the apex of the “V” or “U”.

36. A support member according to claim 35 wherein the extension depends from the support member.

37. A support member according to claim 36 wherein the stop formation is operative, in use, to hinder suspension of the article from the support member.

38. A support member according to claim 37 having a support part which, in use, is in electrical contact with the article, the stop formation being operative to contact the article at a position remote from the vertical plane in which the electrical contact point is contained.

39. A support member according to claim 38 wherein the stop formation is operative, in use, to cause at least part of the article to be inclined to the vertical.

40. A carrier having a plurality of support members associated therewith, the support members being in accordance with claim 39.

41. A rack for use in a coating process, comprising a plurality of carriers in accordance with claim 43.

42. A method of unloading the carrier of claim 40, comprising tilting the carrier towards a generally vertical axis such that the articles may fall therefrom.