Composite concrete slabs include profiled steel decking sheets, concrete that has been poured onto and set on the sheets, and reinforcement (such as mesh or bars) embedded in the concrete.

The present invention relates particularly, but by no means exclusively, to profiled steel decking sheets that are used as formwork in the construction of composite concrete slabs that form the floors of buildings.

Conventional profiled steel decking sheets include a plurality of upstanding parallel ribs that extend along the length of the sheets and are separated by flat pans. The sheets are usually roll-formed from zinc coated, high tensile steel strip in base metal thicknesses of 0.6-1. 0 mm. The strip may have a spangled surface.

The ribs are provided to resist downward deflection of the profiled steel decking sheets in response to the weight of wet concrete poured onto the sheets during on-site construction of composite concrete slabs.

When the concrete hardens and reaches a sufficient compressive strength, the profiled steel decking sheets provide reinforcement for the composite concrete slabs. In addition, the ribs mechanically interlock the concrete and the profiled steel decking sheets.

A significant problem associated with the above-

described profiled steel decking sheets is that the zinc coating is a very reflective surface that produces a substantial amount of glare. This is a significant safety issue for workers using the profiled steel decking sheets, particularly in the construction of high rise buildings.

Another problem associated with the above- described profiled steel decking sheets is that the upstanding ribs of the sheets are a safety hazard for workers and it is important for workers to be able to see the ribs to ensure that they have a sure footing on the sheets and do not trip up on the ribs. Even in low glare situations, it can be difficult to differentiate the ribs from the other sections of the sheets. Medium-high glare situations greatly increase the difficulties in differentiating the ribs from the other sections of the sheets.

An object of the present invention is to provide profiled steel decking sheets that alleviate the surface glare problem described above.

Another object of the present invention is to provide profiled steel decking sheets that highlight the location of the ribs of the sheets.

According to one aspect of the present invention there is provided a method of manufacturing profiled steel decking sheets that are suitable for use as formwork in the construction of composite concrete slabs on a roll forming line, the method including the steps of: uncoiling a steel strip and passing the strip through a series of roll-former stands and progressively roll forming the steel strip to form one rib or a plurality of parallel ribs extending from the plane of the strip and thereafter cutting/shearing the profiled strip into pre-determined lengths and thereby forming a plurality of profiled steel

decking sheets, the method being characterised by the steps of: (a) forming a coating on at least one surface of the strip upstream of a first roll-former stand, the coating being selected to reduce the glare of the profiled steel decking sheets produced by the method ; and (b) at least partially drying the coating before the strip reaches the first roll-former stand.

In the context of this patent specification the term"coating"can mean ink or paint. The term"ink"can be interchanged with the term"paint".

The present invention makes it possible to provide a compact coating facility with a short drying section that can readily be retro-fitted into an existing roll-forming line or can be economically fitted into a new roll-forming line.

Roll-forming lines tend to be compact, and it is not usual to combine roll-forming and pre-painting in the one production line. This is more specifically true for compact painting facilities that could readily be retro- fitted into a roll-forming line. Compact painting facilities for liquid paints are not well known in the art, particularly when the paint drying ovens are included as a part of the painting facility. Without resorting to specialised paint curing systems, including UV-cure or electron beam cure systems, typical paint drying on coil painting lines requires paint drying times in the order of greater than 8 seconds and more usually in the order of 20 to 30 seconds, and these drying times are too great to fit the constraints of typical roll forming lines. Another constraint is that roll-forming lubricants may adversely

affect the integrity of a partially dried paint or a partially cured paint. In the circumstances, the method of the present invention of forming a coating on at least one surface of the strip upstream of a first roll-former stand and thereafter at least partially drying the coating before the strip reaches the first roll-former stand is contrary to the general expectation of the industry.

Preferably the strip is made from zinc coated, steel strip.

Preferably the coating is fast drying.

Preferably the coating has non-slip characteristics when dry.

Preferably the dried coating is chemically inert with respect to concrete.

A preferred coating is water based and contains an organic resin and is free of heavy metals.

The organic resin of the coating may be substantially thermoplastic in nature. However the final properties of the coating may be enhanced by providing sites for cross-linking of the polymer chains.

The coating may be an acrylic, and more particularly may be a styrinated acrylic.

The coating may contain a small volume of organic solvent to assist rapid drying. However, the total organic solvent content must be such that the coating remains non-flammable and non-explosive.

The coating may contain between 15% and 65% volume solids.

Preferably the dried coating has gloss of less than 40 gloss units as measured by a BYK Gardner Micro- Tri-Gloss Glossmeter in accordance with ASTM D523: 1999- Standard Test Method for Specular Gloss.

More preferably the dried coating has gloss of less than 30 gloss units.

Preferably step (a) includes forming the coating with a thickness of less than 7 micron.

More preferably step (a) includes forming the coating with a thickness of less than 5 micron.

More preferably step (a) includes forming the coating with a thickness of less than 3 micron.

Preferably step (a) includes forming the coating by roller coating the coating onto the surface of the strip.

Preferably step (a) includes forming the coating by roller coating the coating onto the surface of the strip using a roller coater assembly that is driven by contact of an applicator roll of the assembly with the strip.

Preferably step (a) includes forming lengthwise extending bands of the coating on sections of the strip that form the pans of the profiled steel decking sheets produced by the method.

In addition to reducing glare of the profiled steel decking sheets, the coated pans highlight the location of the uncoated rib or ribs of the sheets.

Preferably the colour of the coating is selected to highlight the location of the uncoated rib or ribs of the sheets.

Preferably step (b) includes at least partially drying the coating by blowing heated air onto the coated surface of the strip.

In an alternative embodiment, preferably step (b) includes at least partially drying the coating by passing the coated strip through a heated chamber before roll forming the strip.

Preferably the heated chamber is heated by heated air supplied to the chamber.

Preferably step (b) includes at least partially drying the coating within 2 seconds of applying the coating to the strip.

Preferably the heated air does not heat the strip above a temperature of 140°C.

Preferably the method includes controlling, for example by limiting, the application of roll-forming lubricant or the volume of applied roll-forming lubricant so as not to adversely affect the efficacy or integrity of the least partially dried or partially cured coating.

Preferably the method includes passing the strip along the roll forming line at a line speed of at least 30m/min.

Typically the line speed is up to 50m/min.

Preferably the method includes passing the strip from an uncoiler to the first roll-former stand in a time

period of less than 10 seconds.

Preferably the time period is less than 8 seconds.

More preferably the time period is less than 6 seconds.

According to the present invention there is also provided a low glare profiled steel decking sheet produced by the above-described method.

According to the present invention there is also provided a profiled steel decking sheet suitable for use as formwork in the construction of a composite concrete slab that includes: one upstanding rib or a plurality of parallel upstanding ribs that extend along the length of the sheet, pans that separate the rib or ribs, and a coating (i) on the pans or (ii) on the rib or ribs or (iii) on the pans and on the rib or ribs, that reduces the overall glare of the sheet and highlights the presence of the ribs.

The coating may be restricted to the pans, it may partially cover the sides of the main ribs, or it may wholly cover the sides of the main ribs.

Preferably the coating is on the pans and the ribs are uncoated.

According to the present invention there is also provided a roll forming line for manufacturing profiled steel decking sheets that are suitable for use as formwork in the construction of composite concrete slabs, the line including : (a) an uncoiler for a coil of steel strip ;

(b) a means for forming a coating on at least one surface of strip uncoiled from the coil ; (c) a means for drying the coating on the strip ; (d) a series of roll former stands for progressively roll forming the coated strip to form parallel ribs extending from the plane of the strip ; and (e) a means for cutting/shearing the coated profiled strip into pre-determined lengths of profiled steel decking sheets that include the ribs separated by pans.

Preferably the coating assembly includes a roller coater assembly.

Preferably the roller coater assembly includes a roll for picking up coating from a reservoir, an applicator roll for transferring coating from the pick-up roll to a surface of the strip and thereby forming the coating on the strip.

Preferably the applicator roll has a series of raised lands that extend around the circumference of the roll at spaced intervals along the length of the roll whereby the lands define surfaces for transferring coating from the pick-up roll to the strip to form a series of spaced apart lengthwise extending coating bands on sections of the strip that form the pans of the profiled steel decking sheets. With this arrangement the applicator roll does not coat the sections of the strip that form the rib or ribs of the sheets. In some instances the sides of the rib or ribs may be partially or wholly coated.

Preferably the applicator roll is arranged to be driven by contact with the strip and the pick-up roll is arranged to be driven by contact with the applicator roll.

Preferably the roller coater assembly further includes a pressure roll for contacting the opposite surface of the strip to that contacted by the applicator roll to force the strip against the applicator roll.

Preferably the roller coater assembly further includes a scraper member for scraping coating from the pick-up roll upstream of the applicator roll and thereby controlling the coating thickness on the pick-up roll.

Preferably the scraper member is adjustable.

Preferably the drying means includes a first heated air blower between the coating assembly and a first roll forming stand.

Preferably the drying means includes a second heated air blower between roll forming stands that are downstream of the first roll forming stand in the direction of movement of the strip along the line.

In an alternative embodiment, preferably the drying means includes a heated chamber between the coating assembly and a first roll forming stand through which the coated strip passes prior to reaching the first roll forming stand.

In an alternative embodiment, preferably the drying means includes infra-red heating means between the coating assembly and a first roll forming stand through which the coated strip passes prior to reaching the first roll forming stand.

Preferably the drying means includes a means for supplying heated air to the chamber.

Preferably the roll forming line includes a means for controlling the amount of lubricant applied to the strip during roll-forming to prevent excessive contact between the coating and the roll-forming lubricant.

The term"excessive contact"is understood herein to mean that the lubricant does not cause visual damage to the overall appearance of the coated decking.

Drips of lubricant onto the coating in the pan during bundling of the decking sheets is considered to be excessive.

The roll forming line may include means, such as felt pads, to remove excess lubricant off the roll forming rolls or off the strip during the roll-forming operation.

According to the present invention there is also provided a roller coater assembly for forming a coating on at least one surface of a steel strip which includes a roll for picking up coating from a reservoir, an applicator roll for transferring coating from the pick-up roll to a surface of the strip and thereby forming the coating.

Preferably the applicator roll has a series of raised lands that extend around the circumference of the roll at spaced intervals along the length of the roll whereby the lands define surfaces for transferring coating from the pick-up roll to the strip to form a series of spaced apart lengthwise extending coating bands on sections of the strip that form the pans of the profiled steel decking sheets.

Preferably the applicator roll is adapted to be

driven by contact with the strip and the pick-up roll is adapted to be driven by contact with the applicator roll.

Preferably the roller coater assembly further includes a pressure roll for contacting the opposite surface of the strip to that contacted by the applicator roll to force the strip against the applicator roll.

Preferably the roller coater assembly further includes a scraper member for scraping coating from the pick-up roll upstream of the applicator roll and thereby controlling the coating thickness on the pick-up roll.

Preferably the scraper member is adjustable.

The present invention is described further by reference to the accompanying drawings, of which: Figure 1 is a side elevation of one embodiment of a roll forming line in accordance with the present invention ; Figure 2 is a side elevation of a preferred embodiment of a roller coater assembly that forms part of the line shown in Figure 1 ; Figure 3 is a front elevation of the roller coater assembly ; Figure 4 is a front elevation of an applicator roll that forms part of the roller coater assembly ; Figure 5 is a front elevation of a pick-up roll that forms part of the roller coater assembly ; Figure 6 is a perspective view of part of one embodiment of a preferred embodiment of a profiled steel

decking sheet in accordance with the present invention that can be formed in the roll forming line shown in Figure 1 ; Figure 7 is a side elevation of another embodiment of a roll forming line in accordance with the present invention ; and Figure 8 is a section along the line 8-8 of Figure 7.

The preferred embodiment of the profiled steel decking sheet shown in Figure 6 is representative of a general type of decking sheet that includes a series of parallel upstanding ribs 3 separated by flat pans 5.

An alternative profile may include just one major upstanding rib in the profile.

The present invention is not limited to the particular profile shown in Figure 6 and extends to the general type of decking sheet.

The particular profile of the sheet shown in Figure 6 is a standard profile marketed by the applicant under the Registered trade mark BONDEK.

The sheet is formed from zinc coated, high tensile steel strip.

The sheet is characterised in that the pans 5 are coated with a low glare coating and the ribs 3 are not coated ie the surface of the ribs 3 is the surface of the zinc coated steel.

The coated pans 5 substantially reduce the overall glare resulting from the sheet.

In addition, selectively coating the pans 5 and leaving the ribs 3 uncoated has the effect of highlighting the location of the ribs 3. At one level, the location of the ribs 3 is highlighted by the difference between the glare of the ribs 3 and the glare of the pans 5. At another level, the location of the ribs 5 is further highlighted by appropriate selection of the colour of the coating.

The applicant retained an external consultant to carry out test work on the profiled steel decking sheets shown in Figure 6 and a standard uncoated sheet.

The external consultant made gloss measurements of three sample sheets.

Two of the sheets were in accordance with Figure 6, with one of the sheets having a series of scratches- as would be expected in the field. The sheets were coated with a blue coloured"ink". The"ink"was water based and was selected on the basis of being able to dry quickly to form a non-slip low glare surface.

The third sheet was an uncoated sheet, ie a standard sheet formed from zinc coated, steel strip-as supplied to the building industry.

Gloss is a measurement of reflection of illuminated light and therefore provides an indication of the extent of glare resulting from a surface.

Gloss measurements were made with a BYK Gardner Micro-Tri-Gloss Glossmeter in accordance with ASTM D523: 1999-Standard Test Method for Specular Gloss. A 60 degree gloss reading geometry was used according to the above standard.

For each sheet, 25 measurements were taken evenly to provide a good representation of the gloss and a variation in gloss over each sheet. Results are expressed below in terms of gloss units.

The results are summarised in Tables 1 and 2.

Table 1. Gloss (Gloss Units) Uncoated Coated sheet Coated sheet sheet (bare (unscratched) (scratched) steel) Mean (Gloss 121.8 8.4 22. 7 Units) Std Dev 21. 5 6. 7 15. 3 Table 2. Reduction in gloss (%) Coated sheet Coated sheet (unscratched) (scratched) Percentage 93. 1 81. 4 reduction (%) The unscratched and scratched coatings of the Figure 6 sheets reduced gloss by 93 and 81 percent respectively when compared to the bare steel sheet.

Hence, the blue coating would reduce glare significantly at building sites.

The coated profiled steel decking sheet shown in Figure 6 can be manufactured on the roll forming line shown in Figure 1.

The roll forming line shown in Figure 1 includes an uncoiler 23 that holds a coil 25 of zinc coated steel strip so that the strip 71 can be unwound from the coil as

a flat sheet and passed successively to and thereafter through a roller coater assembly 11 and a series of conventional roll-former stands 9.

The roller coater assembly 11 forms a coating on the lower surface of the flat strip as the strip moves along the line prior to the strip reaching the roll former stands 9. The roll coater assembly 11 is described in more detail hereinafter with reference to Figures 2 to 5.

The roll-former stands 9 progressively roll form a series of ribs in the coated flat strip 71 and thereby form the profile of the coated profiled decking sheet shown in Figure 6. Each roll-former stand 9 includes a pair of lubricated shaped rolls 21.

The roll forming line also includes a shear station 27 that shears the coated profiled steel strip into pre-determined lengths, thereby to form the Figure 6 decking sheets.

With reference to Figures 2 to 5, the roll coater assembly 11 includes a tray 29 that contains a reservoir of a coating (such as the"ink"used in the testwork reported above), a roll 31 that picks up coating from the tray 29, and a roll 33 that contacts the pick-up roll 31 and transfers coating from the pick-up roll 31 to the downwardly facing surface of the strip and thereby applies the coating on the strip.

The roller coater assembly 11 further includes a roll 35 that contacts the upwardly facing surface of the strip and applies downward pressure to the strip and thereby forces the strip against the applicator roll 33.

The arrangement of the pick-up roll 31, the applicator roll 33, and the pressure roll 35 is such that

the rolls are driven by contact with the strip.

Consequently, the amount of coating transferred to the strip is independent of the strip speed and variations in strip speed are taken into-account directly by the rolls 31,33.

With particular reference to Figure 4, the applicator roll 33 has a series of lands 37 that extend around the circumference of the roll at spaced intervals along the length of the roll. The lands 37 define surfaces that transfer coating from the pick-up roll 31 to the strip and form a series of spaced apart lengthwise extending coating bands on the sections of the strip that ultimately form the pans 5 of the profiled steel decking sheet shown in Figure 6. The arrangement is such that the applicator roll 13 does not transfer coating to the sections of the strip that ultimately form the top of the ribs 3 of the Figure 6 decking sheet.

The roller coater assembly 11 further includes an adjustable scraper bar 39 that is positioned in relation to the pick-up roll 31 so that it removes excess coating from that roll 31 before the roll 31 rotates to the applicator roll 33. The scraper bar 39 is adjustable whereby the initial coating thickness on the pick-up roll 31 can be varied, as may be required.

The scraper bar 39 provides an initial coating thickness control for the roll coater assembly. Further coating thickness controls are provided by the contact between the pick-up roll 31 and the applicator roll 33 and by the contact pressure of the applicator roll 33 and the strip.

The described roll coater assembly 11 applies wet coatings of less than 7 micron, preferably less than 3 micron, on the strip.

The roll forming line also includes two hot air blowers 13,15 and a cool air blower 17 downstream of the roll coater assembly 11 that blow hot and cool air against the coated strip.

The first air blower 13 is positioned between the roller coater assembly 11 and the first roll-former stand 9 and is operated to substantially dry the coating before the strip reaches the first roll-former stand 9.

This is an important issue for a coating that is soluble in standard roll former lubricants and would be removed as the strip passes through the roll-former stands 9 unless the coating is at least substantially dry before the strip reaches the stands 9.

The apparatus may include a means to enable controlled application or wiping of lubricant to prevent damage of the coating by the lubricant.

At a typical line speed of 50 m/min and a typical spacing of approximately 2m between the roller coater assembly 11 and the first roll-former stand 9, there is a time period of the order of 1.5 to 2 seconds only in which to substantially dry the coating. This time constraint places considerable practical constraints on line design and coating selection, particularly when retrofitting the roll coater assembly 11 to existing roll forming lines where space is limited. A further constraint is that the drying process should not heat the strip to temperatures in excess of 140°C in order to avoid adversely effecting the solids coalescence of the coating.

The second air blower 15 is positioned between the third and fourth first-roll forming stands and is operated to complete the process of drying the coating.

The third air blower 17 is positioned towards the end of the series of roll-formers 9 and is operated to remove any residual water/lubricant that may have accumulated on the strip as it passed through the line.

The roll forming line shown in Figure 1 may be constructed as a green field site or the above-described roller coater assembly 11 and dryers 13,15 of the roll forming line may be retrofitted to existing roll forming lines.

The coated profiled steel decking sheet shown in Figure 6 can also be manufactured on other roll forming lines, such as the roll forming line shown in Figures 7 and 8.

The roll forming line shown in Figures 7 and 8 includes the same basic components as the roll forming line shown in Figures 1 to 5, and the same reference numerals are used to describe the same components in both groups of drawings.

Specifically, the roll forming line shown in Figures 7 and 8 includes an uncoiler 23 that holds a coil of zinc coated steel strip, a roller coater assembly 11 for forming lengthwise extending coating bands on the sections of the strip 71 that ultimately form the pans 5 of the coated profiled steel decking sheet shown in Figure 6, and a series of roll-former stands 9 for roll forming the ribs 3 of the decking sheet.

The main difference between the two embodiments of the roll forming lines is the arrangement for drying the wet coating applied to steel strip by the roller coater assembly 11.

Specifically, in the embodiment shown in Figures 7 and 8 the coated strip 71 is passed through a heated chamber 45 before being roll formed. This is a different arrangement to the hot air blowers 13,15 used in the embodiment shown in Figures 1 to 5.

With reference to Figure 8, the chamber 45 includes an upstream inlet end 61 for wet coated strip 71 and a downstream outlet end 63 for dried coated strip 71.

The strip 71 passes through the chamber 45 with the wet coating bands (identified by the numeral 75 in Figure 8) facing downwardly. The moving coated strip is supported in the chamber 45 by a series of guide rollers 47 on opposite sides of the strip, above and below the strip, within the chamber 45. The rollers are positioned so that there is no direct contact between the rollers and the wet coated strip moving through the chamber 45. The chamber 45 is heated by hot air that is supplied to downstream end of the chamber 45 via ductwork 77 and flows through manifolds 49 that extend along the length of the chamber and is discharged from the upstream end of the chamber 45 via ductwork 79. The manifolds 49 include openings 51 in the upper and side walls thereof that allow heated air to escape into the chamber 45 and contact the moving strip.

The above-described heated chamber 45 is an effective arrangement for drying the wet coating applied to steel strip by the roller coater assembly 11.

Many modifications may be made to the preferred embodiments of the present invention described above without departing from the spirit and scope of the invention.

By way of example, whilst the preferred embodiment shown in Figures 1 to 5 includes drying the coating with two hot air blowers 13,15, the present

invention is not so limited and extends to any number of hot air blowers and to the use of any other suitable drying means. One example of another suitable drying means is by infra-red radiation. Another suitable drying means is the heated chamber shown in Figures 7 and 8.

Another suitable drying means is provided by induction heating.

In addition, whilst the preferred embodiments include driving the rolls 31,33, 35 of the roll coater assembly 11 by contact with the moving strip, the present invention is not so limited and extends to arrangements in which the rolls are driven independently of the moving strip.

In addition, whilst the coating on the profiled steel decking sheet shown in Figure 6 can be manufactured on the roll forming lines shown in Figures 1 to 5 and 7 and 8 and with the coating being applied upstream of the roll formers, the present invention is not so limited and the coating can be applied at any suitable stage in the process for manufacturing steel decking sheets, ie in pre- , post-, and during the roll forming stages of the process.