AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: BLUESCOPE STEEL LIMITED Invention Title: COATED CLIPS The following statement is a full description of this invention, including the best method of performing it known to us: -2 COATED CLIPS The present invention relates to clips for fixing 5 roof, wall or other types of cladding sheets to an underlying support structure. The present invention relates particularly, although by no means exclusively, to clips for fixing a 10 roof cladding sheet to an underlying roof support structure. Typically, roof cladding sheets are roll-formed from painted or unpainted metal (such as steel) strip and 15 include one or more parallel ribs with opposed sides, pan sections, and side edge formations that enable the sheets to be positioned side by side in overlapping relationship. Known clips for securing cladding sheets to an 20 underlying structure include retaining members or tabs that can engage re-entrant portions of the ribs and thereby retain the sheets to the clips. These clip assemblies enable concealed fixing of cladding sheets to an underlying structure. 25 In use, the concealed fixing retaining clips are secured to an underlying structure at spaced intervals related to the spacing between the ribs of the cladding sheets. Thereafter, cladding sheets are positioned on the 30 clips in overlapping relationship by successively pressing the sheets down onto the clips so that the sides of the ribs are initially forced outwardly to allow the re entrant portions of the ribs to pass over the retaining members and then snap inwardly into engagement with the 35 retaining members. There are a number of known concealed fixing H:\ange1a1\keep\RM Speci\Bluescope\Coated Clips.doc 5/06/06 - 3 retaining clips. The clips include a series of clips disclosed in International application PCT/GB91/00450 (WO 91/12392) in the name of Stramit Industries Limited, a clip disclosed in Australian patent 685102 and other 5 Australian patents and patent applications in the name of Stramit Corporations, and a series of clips disclosed in International applications PCT/AU01/00818 (WO 01/02666) and PCT/AU2003/000985 (WO 2004/013430) in the name of the applicant (marketed in Australia under the trade mark 10 KLIPLOK). An object of the present invention is to provide an improved concealing fixing retaining clip that has advantages over one or more of the above-described known 15 clips. The present invention provides a concealed fixing retaining clip that is adapted to engage and retain a cladding sheet to an underlying structure, which clip 20 includes a metal body and a coating of a polymeric material that electrically isolates the metal body from the cladding sheet at least on a section of the metal body that is an operative section of the clip. 25 The term "operative section" is understood herein to mean the section of the clip that, in use of the clip, comes into contact with a cladding sheet that is engaged and retained by the clip to an underlying structure. 30 The coating material makes it possible to use the clip with cladding sheets made from any material without concerns that contact between dissimilar metals of the clips and the cladding sheets will accelerate corrosion of the clips. 35 4446535_1 (GHMatters) P60889.AU 8/07/13 -4 Preferably the coating material is a polyamide. One polyamide that has been found to be suitable by the applicant is a polyamide that is sold in a powder 5 form under a product name of Rislan T powder by Atofina (Australia) Pty. Ltd. The coating may be any suitable thickness. 10 The clip may be any suitable shape that can function as a concealed fixing retaining clip. Suitable clip shapes include the known clips described above, particularly the KLIPLOK clips described in International applications PCT/AU01/00818 (WO 01/02666) and 15 PCT/AU2003/000985 (WO 2004/01343) in the name of the applicant. The disclosure in each International application is incorporated herein by cross-reference. The present invention also provides a method of 20 manufacturing the above-described coated concealed fixing retaining clip that includes the steps of: (a) heating the uncoated metal body of the clip to a temperature that is sufficiently high 25 to cause at least partial melting of powders of a polymeric material that has electrical insulation properties that has been selected to form the coating on the metal body, and 30 (b) positioning the heated metal body in a fluidised bed of the powders of the polymeric material and at least partially melting powders that contact the metal body 35 and forming the coating of the polymeric material on at least the operative section of the clip. Ht\angelal\keep\GRM Speci\Bluescope\Coated Clips.doc 5/06/06 - 5 The present invention is described by way of example hereinafter with reference to the accompanying drawings, of which: 5 Figure 1 is a perspective view of one embodiment of a clip in accordance with the present invention in an as-manufactured form; 1o Figure 2 is a side elevation of the clip shown in Figure 1 in the direction of the arrow "A" in Figure 1; Figure 3 is a side elevation of the clip shown in Figure 1 in the direction of the arrow "B" in Figure 1; 15 Figure 4 is a top view of the clip shown in Figure 1; Figure 5 is a bottom view of the clip shown in 20 Figure 1; The Figures illustrate one embodiment of a clip 3 formed in accordance with the present invention. 25 The clip 3 is formed by folding a flat metal, preferably steel (but not necessarily spring steel), blank into the configuration shown the Figures and forming a metal body of the clip and thereafter coating the clip with a suitable coating material in the form of a 30 polyamide sold as a powder under the product name Rislan T by Atofina (Australia) Pty. Ltd. The clip 3 includes: 35 (a) a base 5; a pair of side walls 7 that extend from the 4934812_1 (GHMatters) P60889.AU - 6 base and converge towards each other; and (c) a pair of flanges 9 that define retaining members for engaging re-entrant portions of 5 ribs of cladding sheets, with one flange 9 extending from an upper end of one side wall 7 and the other flange 9 extending from an upper end of the other side wall 7. 10 The base 5 includes an opening 63 to facilitate securing the clip 3 to an underlying roof structure, such as a roof purlin (not shown). The side walls 7 and the base 5 are straight 15 walls and define a substantially triangular structure in side view shown in Figure 2. In the as-manufactured form shown in Figures 1 to 5 the side walls 7, whilst converging towards each other, 20 do not actually contact each other and there is a gap G between the side walls 7 at the upper end of the side walls. However, in use, the side walls 7 are forced into contact with each other at the upper ends of the side walls when a cladding sheet is positioned on the sides 25 walls. The upper ends of the side walls 7 are shaped to define a generally circular opening 13 that facilitates insertion of a screw-driver (not shown) to install the 30 clip to an underlying structure. Each flange 9 terminates in a sharp lower outwardly facing (as opposed to inwardly turned) end that forms a contact surface 25 for engaging a re-entrant 35 portion of one of the ribs of a cladding sheet. Each flange 9 includes in-turned sections 17 at H:\angelal\keep\GRM Speci\Bluescope\Coated Clipa.doc 5/06/06 -7 the two corners at the lower ends of the flange 9. The corner sections 17 form contact surfaces 21 that extend transversely to the contact surface 25 of the outer end of the flange. 5 The coating is formed on exposed surfaces of the metal body of the clip 3 by a method that includes the following steps: 10 (a) heating the metal body in an oven to a temperature of between 320-400*C, well above the melting point of 175 0 C of powders of a Rislan T polyamide, and 15 (b) passing the heated metal body by way of an automated conveyor through a fluidised bed of Rislan T polyamide powders, whereby powders that contact the metal body are at least partially melted by the heat of the 20 metal body and form a coating of the polyamide material on the exposed surfaces of the metal body. The thickness of the coating may be controlled by 25 appropriate selection of the density of powders in the bed, the exposure time of the metal body of the clip 3 in the bed, and the temperature of the metal body. The coated, concealed fixing retaining clip 3 has 30 a major advantage that the coating electrically isolates the operative section of the clip from the cladding sheet and, therefore, the clip can be used with cladding sheets made from any material without concerns that contact between dissimilar metals of the clips and the cladding 35 sheets will accelerate corrosion of the clips. The coated, concealed fixing retaining clip has a H:\angelal\keep\GRM Speci\Bluescope\Coated Clips.doc 5/06/06 -8 number of additional advantages, including the following advantages. 1. Increased durability. 5 2. Reduction of fretting. 3. Abrasion resistance. 10 4. More controlled thermal expansion. 5. Ease of installation. Many modifications may be made to the embodiment 15 of the present invention shown in the drawings without departing from the spirit and scope of the present invention. By way of example, whilst the embodiment 20 described above includes a coating of the polyamide on all of the exposed surfaces of the clip, the present invention is not so limited and extends to coatings that are confined to the operative section of the clip. 25 Further, whilst the embodiment described above includes a coating of a particular polyamide, namely a Rilsan T polyamide, the present invention is not so limited and extends to any coating material that can electrically isolate a metal body of a clip from a 30 cladding sheet. It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part 35 of the common general knowledge in the art, in Australia or any other country. 3939056_1 (GHMatters) P60889AU 24/01/13 - 8a In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary s implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 10 3939056_1 (GHMatters) P60889.AU 24/01/13