GB2374304A

GB2374304A - Support member for electrostaic coating

Info

Publication number: GB2374304A
Application number: GB0108916A
Authority: GB
Inventors: Peter John Smith
Original assignee: PROTECTIVE FINISHING GROUP Ltd
Current assignee: PROTECTIVE FINISHING GROUP Ltd
Priority date: 2001-04-10
Filing date: 2001-04-10
Publication date: 2002-10-16
Anticipated expiration: 2021-04-10
Also published as: WO2002083319A1; GB2374304B; GB0108916D0

Abstract

A support member 11 for use in supporting an article during a coating process of the kind requiring electrical contact between a support part 16 thereof and an article to be coated, characterised in that said support part is non-circular in cross-section. This allows good electrical contact between article and support member. The support member may be vibrated, so as to abrade a surface coating on the article and ensure better electrical contact.

Description

Title: A support member, a rack for use in a coating process, a method of removing surface coating material from a support member, a method of making a plurality of support members and a coating process.

Description of Invention This invention relates to a support member, a rack for use in a coating process, a method of removing surface coating material from a-support member, a method of making a plurality of support members and a coating process.

In broad terms, the invention relates 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 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".

One consequence of coating articles in this way is that the support members which engage the articles during the coating process are themselves given an electric charge, meaning that, in addition to the articles, the support members too become coated with a layer of the coating material concerned. As many of the coatings used, such as paints and other such protective finishing, are electrically non-conductive, it becomes necessary, often after each coating operation, to clean the support members so as to ensure that, during subsequent use, good electrical contact can again be obtained between the support members and the articles supported thereby.

The applicants'prior International patent application, WOOO/54889, discloses a way in which cleaning of this type may be effected, by vibrating the support members with the articles in situ, prior to bringing the articles into contact with the coating material.

The apparatus and methods disclosed in WO'889 have been found by the applicants to operate very satisfactorily with a wide variety of articles, although it has also been found that relatively lightweight articles such as small clips and other automotive components do not always abrade the support members during vibration thereof to an extent which is sufficient to ensure that good electrical contact can be made between them.

It is thus an object of the present invention to provide a support member which alleviates this problem and to provide an associated rack for use in a coating process of the kind specified. It is also an object of the present invention to provide an improved method of removing surface coating material from a support member of a coating rack, to provide an improved method of making a plurality of support members for a coating rack and to provide an improved coating process of the kind specified.

According to a first aspect of the present invention, there is provided a support member for use in supporting an article during a coating process of the kind requiring electrical contact between a support part thereof and an article to be coated, characterised in that said support part is non-circular in cross- section.

Preferably, the support part has at least one surface which is flat or substantially flat in cross-section.

The flat or substantially flat surface, in use, is preferably generally horizontal.

The support part may be rectangular or substantially rectangular in cross-section and conveniently is square or substantially square in crosssection.

It will be appreciated by those skilled in the art that electrically conductive (e. g. metal) components of the type which are most suited to coating processes of the kind specified are invariably provided with a circular attachment aperture, such as may be formed by a punching or pressing operation. With this in mind, the present invention, which features a non-

circular support part, enables the area of contact between the article and the , support part to be reduced, when compared to the contact area which is obtained where a generally circular support part is used. This, in turn, increases the amount of energy per unit area which the article is able to impart to the support part when relative movement between them is caused by vibrating the support member, as shown in WO 00/54889.

Although the support member may be formed using a number of different manufacturing techniques, it is envisaged by the applicants that the support member will preferably be pressed, bent or otherwise formed from sheet or sheet-like material, conveniently sheet metal.

The support member may have an attachment part whereby the support member may be attached to a carrier at a number of different positions thereon.

The attachment part is preferably resiliently deformable, the support member thus being attachable to the carrier in a snap-fitting manner.

In this way, the amount of support members attached to the carrier may be varied, in accordance with loading requirements and the size of the articles to be loaded, for example. Similarly, any support members which, through use, become damaged or unusable, may easily be removed and replaced, as appropriate.

In order to be able to accommodate a variety of different articles, the cross-sectional area of the support member may decrease towards a distal part thereof.

Preferably, the support member is tapered towards said distal part.

Conveniently, in use, the support member is inclined upwardly from the

horizontal, whereby an article engaged therewith is able to move from the distal part towards the support part, under gravity.

Desirably, the support member, in use, is orientated vertically or substantially vertically.

In this way, articles having engagement apertures of differing diameters may be engaged by the support member, the tapered configuration allowing the articles to move along the support member from the distal part thereof to a point at which they are located securely on the support member.

The support member may be made from a carbon steel.

Alternatively, the support member may be made from a mild steel.

According to a second 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 cross-sectional area of the support member decreasing towards a distal part thereof.

Preferably, the support member is tapered towards the distal part thereof.

Conveniently, the support member, in use, is inclined upwardly from the horizontal, whereby an article engaged therewith is able to move from the distal part towards a support part thereof under gravity.

The invention, in its second aspect, may comprise one or more of the features set out in the preceding paragraphs.

According to a third aspect of the present invention, there is provided a rack for use in a coating process of the kind specified, comprising a plurality of support members to support articles during a said coating process, the support members having a support part which is non-circular in cross-section.

The support members may be as described in one or more of the preceding paragraphs.

According to a fourth aspect of the present invention, there is provided a method of removing surface coating material from a support member of a

coating rack, comprising engaging the article 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, characterised in that the article is engaged with the support member by passing a distal part of the support member through an opening in the article, and in that the opening and support part, when viewed in cross-section, are shaped differently.

Preferably, one of the opening and support part is non-circular in crosssection, the other of the opening and support part being generally circular in cross-section.

Conveniently, the support part is non-circular in cross-section.

The opening may be an aperture.

The invention, in its fourth aspect, may further comprise orientating the opening and the support part relative to each other so as to reduce the area of contact therebetween, thus increasing the amount of abrading energy transferred from the article to unit area of the support part.

In relation to the fourth aspect of the present invention, the support member may be as described in one or more of the preceding paragraphs.

In accordance with a fifth aspect of the present invention, there is provided a method of making a plurality of support members for a coating rack, comprising : a) procuring a sheet of conductive material, b) forming a plurality of fingers from the sheet, and c) shaping the fingers, such as by pressing or bending, to provide each finger with a support part, which, in use, makes electrical contact with an article supported thereby.

The conductive material preferably is carbon steel.

The method may also comprise forming an attachment part from the sheet, the attachment part serving to attach the plurality of support members to a carrier of the coating rack.

The attachment part may be resiliently deformable, and conveniently is provided as an elongate clip.

In accordance with a sixth aspect of the present invention, there is provided a coating process of the kind specified, the process comprising, prior to bringing the article into contact with the coating material, removing-surface coating material from a support member which, in use, supports the article to be coated, removal of the surface coating being in accordance with the fourth aspect of the present invention.

The invention, in its various aspects, will now be described in greater detail, but strictly by way of example only, by reference to the accompanying drawings, of which : Figure 1 is a perspective view of pat1 of a carrier bar and of articles supported thereby; Figure 2 is an end-on view of the carrier bar, a support member and a supported article ; Figure 3 is a front view, in schematic form, of part of the support member and supported article ; Figure 4 is a plan view of a blank from which support members may be formed ; Figure 5 is a side view of a support member so formed ; Figure 6 is a perspective view of a carrier bar and a plurality of differently configured, upstanding, support members ; Figure 7 shows an electro-coating rack suspended from a conveyer; Figures 8a, 8b and 8c illustrate, in schematic form, three different combinations of support member/component aperture shapes;

Figure 9 shows, in side view, apparatus to impart vibrations to the carrier bars; and Figure 10 shows, in schematic form, the various components of an electro-coating process plant.

Referring first to Figure 1, this shows a carrier 10 in the form of a metal bar, to which are releasably attached a plurality of support members 11. The carrier bar 10 in this example is provided with an external thread formation, as such bars are readily and relatively cheaply available, although it will be appreciated that the provision of such a thread is not necessary. As shown, the support members 11, whilst being generally flat in cross-section, are formed so as to provide a hook configuration, a somewhat V-shaped hook being defined by constrained and free arms 12 and 13 of the support member 11. The free arm has a distal pal1 14 which, as shown, extends upwardly from the horizontal, thus allowing an article 15 engaged therewith to fall towards a support part 16 of the support member 11 (the bottom of the"V"), under gravity.

As is well known in the industry, a very large number of different components are suitable for electrically assisted coating processes such as electro-coating, electro-plating and powder-coating, and the article 15 may thus be a metal automotive component (such as a pressing) which requires a paint coating to provide a protective outer layer and, possibly, to improve its appearance. As will also be understood by those well-versed in the relevant art, such components are invariably provided with a generally circular attachment aperture 17 (see Figure 3), to enable them readily to be attached to electrocoating racks of the type to which this invention relates.

Although, as indicated previously, the invention relates broadly to coating processes where electrical contact between the article to be coated and the associated support member is required, the invention can best be

exemplified by describing its application in relation to a wet electro-coating process.

During such a process, current is supplied to the articles 15 via the carrier bar 10 and the support members 11, and the carrier bar 10 and support members 11 thus also are prone to becoming coated with the coating material concerned. In the case of the carrier bar 10, this is usually of little consequence, but it will be appreciated that where the support member becomes coated with a layer of (electrically insulating) paint, this can prevent electrical contact being made between the support member 11 and a subsequently loaded article 15.

In order to clean the support member 11, at least in the area of contact between the article 15 and the support member 11 (i. e. the support part 16) the carrier bar 10, and conveniently the entire electro-coating rack, is caused to vibrate by a vibrating device (shown in more detail later), the amplitude and frequency of the vibration being determined, at least in part, by the mass of the article 15 and the material from which it is made. Vibration of this type causes the article 15 to move relative to the support part 16 of the support member 11, and the inner surface of the article 15 (defined by the aperture 17) is thus brought into vibratory (and hence abrading) contact with the support part 16, with this being effective to remove any surface coating material which may have built up in that region. The vibration is thus continued up to the point at which metal-to-metal contact is made possible which, in practice, has been found to take two to six minutes or thereabouts, upon application of a suitable vibration.

The generally flat cross-sectional configuration of the support member 11 is important in assisting this abrading process. As will be appreciated, where the articles 15 are light, the amount of kinetic energy which they are able to impart to the support part 16, and thus the amount of energy which is available to effect abrasion, is limited, and it is therefore important to ensure

that the available energy is transferred to a relatively small area of the support part 16. This, as shown in Figures 1 and 3, is achieved by ensuring that the support part 16 (at least) of the support member 11 is non-circular in crosssection. This reduces the area of contact between the invariably circular aperture 17 provided in the article 15 with the support part 16, thus greatly facilitating abrasion and hence removal of the surface coating at those reduced areas of contact.

Figure 2 shows this from a different perspective, illustrating, in addition, a further support structure 18 in which the carrier bar 10 rests, in use. The support structure 18, which is somewhat V-shaped, receives a bent end portion 19 of the carrier bar 10.

As shown in Figures 1 and 2, each support member 11 has an attachment part 20 defined by a part circular formation 21 and a freely extending limb 22, the formation 21 and limb 22 providing the support member with a degree of resilience, which enables the support member to be releasably attached to the carrier bar 10. Not only does this facilitate cleaning/replacement of the support members 11, but it enables the spacing of the support members 11 along the carrier bar 10 to be varied, in accordance with the required load, and the size of the articles to be treated.

Figure 3 shows, in somewhat schematic form, how the interaction between the non-circular support part 16 and the circular aperture 17 enables a very small contact area to be obtained. This, as will be appreciated, contrasts starkly with the situation where a circular (in cross-section) support part is used, as this gives rise to a much larger contact area, thus reducing the efficacy of the vibrational energy transferred from the moving component 15 to the support part 16. In addition, the relatively "sharp" comers 23 and 24 can bite into any coating (such as corrosion) which may be present on the surface of the

article 15, thus improving still further the electrical contact which may be t : p

effected therebetween. Alternative cross-sections of support part 16 are shown

in Figures 8a, 8b and 8c.

Referring next to Figure 4, this shows a generally flat carbon steel blank 30 which has been shaped, such as by stamping, in generally conventional manner, so as to provide a number of fingers 31 to 35. The blank, approximately 0.7mm thick, is then pressed, bent, or otherwise formed to provide five integral support members 11, shown in side view in Figure 5. Forming a number of inter-linked support members in this way is not only convenient, in that it is easier from a tooling point of view than it would be to manufacture individual support members 11, but also provides advantages from a practical, use, point of view. Specifically, where it is desired to attach a large number of support members 11 to a carrier bar 10, the provision of integral groups of support members 11 enables several (in this case five) support members to be attached in a single operation. Moreover, producing the blank from carbon steel reduces greatly the amount of wear which the support members might otherwise experience, with this being accentuated by post-work hardening and tempering to which carbon steel is especially well-suited. It will of course be appreciated that more or less fingers could be formed from the original flat blank, in accordance with a user's specific requirements.

Referring next to Figure 6, this shows a metal carrier bar 40 which is somewhat similar to the carrier bar 10 shown in Figure 1, but to which are attached a number of generally vertically upstanding support members 4 ! which taper towards their distal ends 42. The support members 41 are generally rectangular in cross-section, with it having been found by the applicants that so-called"vine eyes"are particularly well suited for the purpose of the present invention. As shown, the support members 41 are welded to the carrier bar 40, although it is envisaged that clip-type attachments may be provided towards their base, so as to enable releasable engagement of the support members 41 with the carrier bar 40.

The generally vertical orientation of the support members 41, in conjunction with their tapered configuration, allows for the engagement of a wide variety of differently sized components. Specifically, as differently sized components tend to be provided with differently sized circular attachment apertures, the components may simply slide down the support members 41 up to a point at which the increased width of the support member prevents further

sliding movement. At that point, the edges of the non-circular cross-section of p the support member 40 come into contact with the surface of the article 43, defined by its circular aperture 44, with the point at which the two parts engage being determined by the diameter of the aperture 44. Where heavy components are loaded onto the support members 41, it has been found by the applicants that the mere loading of the components, can, in some cases, be sufficient to remove an adequate amount of surface coating from the support member 41, thus obviating the requirement of any subsequent vibration. However, it will be appreciated that to ensure good electrical contact between the two parts, a subsequent vibration step will, in most cases, be desirable. Although the tapered support members 41 may conveniently be formed from a mild steel, other conductive materials could also of course be used.

Turning next to Figure 7, this shows a complete electro-coating rack assembly having a plurality of carrier bars 10, support structures 18 and support members 11, suspended from a conveyer 50 which conveys the electro-coating rack assembly between the various stages of the electro-coating process. Although Figure 7 shows a plurality of support members 11 along the lines of those described in Figure 1, it will be appreciated that the support members 11 could in theory be substituted for the more upstanding support members 41 described in relation to Figure 6, depending upon specific loading requirements. The electro-coating rack is suspended from a pair of parallel load bearing bars 51 from which depends the electro-coating rack assembly

indicated generally at 52. The assembly 52 is held, via T-bars 53 by a hanger ZD

54 which is moveable along the conveyer 50 in generally conventional manner.

As shown, the T-bars 53 are releasably engageable with the hanger 54, thus enabling the electro-coat rack assembly 52 to be deposited and picked up at a number of different locations.

Referring next to Figures 8a, 8b and 8c, these show, in schematic form, a number of differently configured support members 11 (in cross-section), with which are engaged a number of components 15, via differently shaped apertures 17 provided therein. Although, as will be appreciated, an almost limitless number of combinations of shapes are possible, the important point is that, in each case, the cross-sectional shape of the support part of the support members is different to the shape of the apertures provided in the suspended components. As shown, this ensures that the area of contact between the two is kept to a minimum-it will be understood that should the shapes be the same, a much greater contact area would be obtained, which, in turn, would spread the kinetic energy imparted to the support member by the moving component over a greater area. Figure 8c. in particular, is noteworthy, as it illustrates that careful orientation of the support member can assist in reducing the contact area. Similarly, Figure 8b illustrates that a standard, circular, support member 11 may be modified by grinding or otherwise flattening part of the circular configuration, which greatly reduces the contact area between the support member and the article suspended therefrom.

Referring next to Figure 9, this shows, in somewhat schematic form, the apparatus used to impart vibrations to the canier bars 10 (see Figure 1) and hence to the support members 11 connected thereto. The apparatus comprises a pair of generally U-shaped vibration transmission elements 60 which, as shown, are configured to locate beneath, but in contact with, the load bearing bars 51 of the electro-coating rack assembly 52. A vibration means 61, powered electrically via a power lead 62, is disposed beneath a cover plate 63, the cover plate 63 being in vibration transmissible contact with the transmission

elements 60. Vibration insulating blocks 64 are provided beneath the cover plate 63 to ensure that the vibration energy is transmitted primarily to the electro-coating rack, rather than to a support frame above which the vibration means is positioned. As will be appreciated, energisation of the vibration means 61 causes the entire electro-coating rack assembly 52 to vibrate, thus causing relative movement to occur between the articles 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 articles. The vibration means may conveniently be powered electrically, although where flammable gases are in existence, pneumatic or hydraulic operation may be preferable. Control means (not shown) may be provided 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.

Referring finally to Figure 10, this shows, in schematic form, an electocoating treatment system comprising a first treatment bath 70 in which the support elements are immersed, and which is normally provided with a cleaning fluid to enable the articles to be degreased prior to initiation of the electrocoating process. Further treatment baths are shown at 71 and 72. which may comprise the electro-coating treatment stage and a subsequent finishing stage, with a drying station being shown at 73. Positioned downstream of the drying station 73 is a loading/unloading station 74 at which the rack assemblies may be removed from or loaded onto the conveyer arrangement 75. The vibrational step is applied at a vibration station 76, located upstream (and hence before) the first treatment bath 70, which enables the supports members 11 to be cleaned/abraded in the manner previously described.

It will be appreciated from the foregoing that the invention, in its various aspects, provides a considerable improvement over known cleaning processes which are used in coating processes of the kind specified, by optimising the

amount of abrasion which can occur to the support members. In addition, the invention provides a particularly convenient way in which suitably configured support members may be produced, and enables the benefits to be obtained with a wide variety of differently configured components.

In the present specification"comprise"means"includes or consists of and"comprising"means"including or consisting of.

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 utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS: 1. A support member for use in supporting an article during a coating process of the kind requiring electrical contact between a support part thereof and an article to be coated, characterised in that said support part is noncircular in cross-section.

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2. A support member according to Claim 1 wherein the support part has at least one surface which is flat or substantially flat.
3. A support member according to Claim 2 wherein the flat or substantially flat surface, in use, is generally horizontal.
4. A support member according to Claim 1, Claim 2 or Claim 3 wherein said support part is rectangular or substantially rectangular.
5. A support member according to any one of the preceding claims wherein said support part is square or substantially square.
6. A support member according to any one of the preceding claims wherein the support member is pressed, bent or otherwise formed from sheet or sheetlike material.
7. A support member according to Claim 6 wherein the material is sheet metal.
8. A support member according to any one of the preceding claims wherein the support member has an attachment part whereby the support member may be attached to a carrier at a number of different positions thereon.

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9. A support member according to Claim 8 wherein the attachment part is resiliently deformable, the support member thus being attachable to the carrier in a snap-fitting manner.
10. A support member according to any one of the preceding claims wherein the cross-sectional area thereof decreases towards a distal part thereof.
11. A support member according to Claim 10 wherein the support member is tapered towards said distal part.
12. A support member according to Claim 10 or Claim 11 wherein, in use, the support member is inclined upwardly from the horizontal, whereby an article engaged therewith is able to move from the distal part towards the support part, under gravity.
13. A support member according to Claim 12 wherein the support member, in use, is orientated vertically or substantially vertically.
14. A support member according to any one of the preceding claims wherein the support member is made from a carbon steel.
15. A support member according to any one of Claims 1 to 13 wherein the support member is made from a mild steel.
16. A support member for use in a coating process of the kind specified wherein the cross-sectional area of the support member decreases towards a distal part thereof.

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17. A support member according to Claim 16 wherein the support member is tapered towards said distal part.
18. A support member according to Claim 16 or Claim 17 wherein, in use, the support member is inclined upwardly from the horizontal, whereby an article engaged therewith is able to move from the distal part towards a support part, under gravity.
19. A rack for use in a coating process of the kind specified, comprising a plurality of support members to support articles during a said coating process, the support members having a support part which is non-circular in crosssection.
20. A rack according to Claim 19 wherein the support members are in accordance with any one of claims 2 to 18.
21. A method of removing surface coating material from a support member of 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, characterised in that the article is engaged with the support member by passing a distal part of the support member through an opening in the article, and in that the opening and support pal1, when viewed in cross-section, are shaped differently.
22. A method according to Clam 21 wherein one of the opening and support part is non-circular in cross-section, the other of the opening and support part being generally circular in cross-section.

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23. A method according to Claim 21 or Claim 22 wherein the support part is non-circular in cross-section.
24. A method according to Claim 20, Claim 21 or Claim 23 wherein the opening is an aperture.
25. A method according'to any one of Claims 21 to 24 further comprising orientating the opening and the support part relative to each other so as to reduce the area of contact therebetween, thus increasing the amount of abrading energy transferred from the article to unit area of the support part.
26. A method according to any one of Claims 21 to 25 wherein the support member is in accordance with any one of claims 1 to 18.
27. A method of making a plurality of support members for a coating rack, comprising : a) procuring a sheet of conductive material, b) forming a plurality of fingers from the sheet, and c) shaping the fingers, such as by pressing or bending, to provide each finger with a support part, which, in use, makes electrical contact with an article supported thereby.
28. A method according to Claim 27 wherein the conductive material is carbon steel.
29. A method according to Claim 27 or Claim 28 further comprising forming an attachment part from the sheet, the attachment part serving to attach the plurality of support members to a carrier of the coating rack.

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30. A method according to Claim 29 wherein the attachment part is resiliently deformable.
31. A method according to Claim 29 or Claim 30 wherein the attachment part is an elongate clip.
32. A coating process of the kind specified, the process comprising, prior to bringing the article into contact with the coating material, removing surface coating material from a support member which, in use, supports the article to be coated, removal of the surface coating being in accordance with any one of claims 21 to 26.
33. A support member substantially as hereinbefore described and/or as

shown in the accompanying drawings.

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34. A rack substantially as hereinbefore described and/or as shown in the accompanying drawings.
35. A method of removing surface coating material from a support member of a coating rack substantially as hereinbefore described and/or as shown in the accompanying drawings.
36. A method of making a plurality of support members for a coating rack substantially as hereinbefore described and/or as shown in the accompanying drawings.

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37. A coating process of the kind specified substantially as hereinbefore described and/or as shown in the accompanying drawings.

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38. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.