Field of the Invention

The present invention relates to a structural decking sheet .

The present invention also relates to a method of forming a structural decking sheet.

The term "structural decking sheet" is understood herein to mean profiled sheets, typically made from steel, that are suitable for use as formwork for concrete slabs or as a reinforcement in composite slabs .

Examples of structural decking sheets manufactured by the applicant are marketed under the registered trade marks LYSAGHT BONDER and LYSAGHT POWERDEK .

Typically, structural decking sheets are roll- formed from steel strip that has a corrosion-resistant metal coating on both surfaces of the strip and comprise a pan and side edge formations that enable the sheets to be positioned side by side in overlapping relationship. The structural decking sheets may also comprise one or more than one rib that extend from the pan and are parallel with the side edge formations . The ribs divide the pan into a series of parallel pan sections on opposite sides of the rib or ribs. Hence, in the most straightforward form, the structural decking sheets comprise a pan and side edge formations on opposite sides of the pan, such as the LYSAGHT POWERDEK product of the applicant. In more complex arrangements, the structural decking sheets comprise one or more than one parallel rib, pan sections on opposite sides of the rib or ribs , and side edge formations on opposite sides of the sheet, such as the LYSAGHT BONDER product of the applicant. The present invention provides an alternative structural decking sheet to structural decking sheets known to the applicant.

The above description is not to be taken as an admission of the common general knowledge in Australia and elsewhere.

Summary of the Invention

The present invention provides a structural decking sheet that comprises a pan, side edge formations that enable a plurality of the sheets to be positioned side by side in overlapping relationship, and a plurality of transverse flutes that extend from the pan and are parallel to each other and are at a non-square angle to a lengthwise extending direction of the sheet.

The term "flute" is understood herein to mean an elongated formation (that could also be described as a rib) that is formed, for example, by being pressed or otherwise formed in a flat surface. The formation may be a formation that extends from one or both surfaces of the flat surface.

The term "lengthwise extending direction of the sheet" is understood herein to mean a direction that is parallel to the direction of the side edge formations .

The transverse flutes of the above-described cladding sheet, arranged at a non-square angle to the lengthwise extending direction of the sheet as described above, significantly improve the stiffness of the pans and the overall stiffness of the sheet. This is important in supporting loads on the sheets , particularly wet loads when the sheets are used in the constuction of concrete slabs. In addition, the transverse flutes, by being arranged as described above, are a more self-washing surface when compared to known cladding sheets and this is advantageous from the viewpoint of corrosion resistance. Furthermore, the construction of the cladding sheet with the transverse flutes has advantages in manufacture of the sheet, for example in reducing manufacturing "noise".

The structural decking sheet may comprise one or more than one parallel rib that extends from the pan and divides the pan into pan sections on opposite sides of the rib or ribs. With this arrangement, the transverse flutes extend from at least one pan section and are parallel to each other and are at a non-square angle to a lengthwise extending direction of the sheet.

The transverse flutes may extend from one surface of the pan or the pan section only.

Alternatively, the transverse flutes may extend from both surfaces of the pan or the pan section. An example of such an arrangement is the ridge and grove profile shown in the Figures of Australian patent 2002244501 in the name of the applicant. The disclosure in the patent is incorporated herein by cross-reference.

Typically, the transverse flutes are at an angle of at least 70° to the lengthwise extending direction of the sheet.

Typically, the transverse flutes are at an angle of 75-87° to the lengthwise extending direction of the sheet.

Preferably the transverse flutes are at an angle of 84-87° to the lengthwise extending direction of the sheet. Typically, the transverse flutes extend substantially across the whole width of the pan or the pan section.

Typically, the transverse flutes extend at least 80% across the whole width of the pan or the pan section.

Typically, the transverse flutes extend substantially along the length of the pan or the pan section.

Typically, the transverse flutes extend at least 80% along the whole length of the pan or the pan section.

Typically, the transverse flutes are spaced apart at least 20 mm.

Preferably the transverse flutes are spaced apart at least 30 mm.

Typically, the transverse flutes comprise opposed sides and a top that separates the sides . With this arrangement, typically the transverse flutes extend from one side only of the pan.

Typically, the top is flat.

Typically, the top is 4-6 mm wide.

Typically, the height of the transverse flutes is 1-3 mm above the pan.

Typically, each pan section includes transverse flutes . According to the present invention there is also provided a method of forming a structural decking sheet that includes the steps of:

(a) roll forming a sheet to have a pan and side edge formations that enable a plurality of the structural decking sheet to be positioned side by side in overlapping relationship and thereby partly forming a structural decking sheet; and

(b) forming a plurality of transverse flutes in the pan of the partly-formed structural decking sheet produced in step (a) to complete forming the structural decking sheet, with the transverse flutes extending parallel to each other and at a non-square angle to a lengthwise extending direction of the sheet.

Typically step (b) of forming the transverse flutes in the pan includes cold forming, for example by embossing, the pan.

Preferably step (b) of forming the transverse flutes in the pan includes cold forming, for example by embossing, substantially only the material in the pan that is required to form the transverse flutes .

Preferably step (b) of forming the transverse flutes in the pan includes cold forming, for example by embossing, the pan so that the flutes extend from one surface of the pan.

Preferably step (b) of forming the transverse flutes in the pan includes passing the partly-formed structural decking sheet produced in step (a) through the nip between a pair of embossing rolls having complementary male and female formations that are shaped to cold form the flutes in the pan. Preferably the step (b) of forming the transverse flutes in the pan includes passing the partly-formed structural decking sheet produced in step (a) through the nips between successive pairs of embossing rolls having complementary male and female formations that are shaped to progressively cold form the flutes in the pan.

Step (a) may comprise roll forming the sheet to have one or more than one parallel rib extending from the pan that divides the pan into a plurality of pan sections on opposite sides of the rib or ribs .

In such a situation, step (b) comprises forming the transverse flutes in at least one pan section of the partly-formed structural decking sheet produced in step (a) to complete forming the structural decking sheet, with the transverse flutes extending parallel to each other and at a non-square angle to a lengthwise extending direction of the sheet.

Brief Description of the Drawings

The present invention is described further by way of example only with reference to the accompanying drawings , of which :

Figure 1 is a perspective view of one embodiment of a structural decking sheet in accordance with the present invention;

Figure 2 is a top view of the structural decking sheet shown in Figure 1 ;

Figure 3 is a top view of a section of the structural decking sheet shown in Figure 1; Figure 4 is a section along the line A-A of Figure 3 ; and

Figure 5 is a front view of a pair of embossing rolls for cold forming the transverse flutes in the pan in the structural decking sheet shown in Figure 1 in accordance with one embodiment of a method of forming the structural decking sheet in accordance with the present invention .

Detailed Description of the Embodiments

The structural decking sheet, generally identified by the numeral 3 in the Figures, is a typical structural decking sheet of the type marketed by the applicant under the registered trade mark LYSAGHT POWERDEK in the sense that it is roll-formed from strip steel and includes a pan 11, a leading side edge formation 5, and a trailing side edge formation 7.

The structural decking sheet 3 may be of any suitable length and width.

The pan 11 includes a plurality of parallel, spaced-apart flutes 17 that extend transversely, i.e. at a non-square angle to the lengthwise extending direction 37 (see Figure 3) of the structural decking sheet 3.

In this particular embodiment, the flutes 17 are spaced apart by 50 mm and are at an angle of 85° to the lengthwise extending direction 37 of the sheet. The spacing and the angle may be any suitable spacing and angle .

The flutes 17 are relatively small. As shown in Figure 4, each flute 17 includes a flat top 21 and opposed inclined sides 23 that merge with the flat sections of the pan 11. In this particular embodiment, the top 21 of the flutes 17 are 5 mm wide and the flutes 17 are 1.6 mm high from the flat section of the pan 11. The width of the top 21 and the height of the flutes 17 may be any suitable dimensions .

The embodiment of the structural decking sheet 3 described above has been found to be an effective structural decking sheet in test work carried out by the applicant. Specifically, the flutes 17, arranged as described above, significantly improve the stiffness of the pan 11 and the overall stiffness of the sheet. This is advantageous in supporting loads , particularly wet loads when the sheets are used in the constuction of concrete slabs. In addition, the flutes 17, by being arranged transversely as described above, are a more self- washing surface when compared to known structural decking sheets and this is advantageous from the viewpoint of corrosion resistance.

The general steps of one embodiment of a method of forming the structural decking sheet 3 in accordance with the present invention are as follows :

(a) roll forming strip steel, such as metal coated steel, to have the pan 11 and the leading and trailing side edge formations 5, 7; and

(b) cold forming the flutes 17 in the pan 11 of the partly-formed structural decking sheet produced in step (a) to complete forming the sheet.

More particularly, in this embodiment, the flutes 17 are cold formed by passing the partly-formed structural decking sheet produced in step (a) through the nip between a pair of embossing rolls having complementary male and female formations . Figure 4 is a front view of the pair of embossing rolls for forming the flutes 17 in the pan 11 in Figure 1. The lower roll 25 has parallel male formations 29 extending from the outer surface of the roll around the circumference of the roll. The male formations 29 have the same sectional profile as the flutes 17, as shown in Figure 4. The upper roll 27 has a plurality of parallel female formations 31 in the outer surface of the roll spaced apart around the circumference of the roll . The male and female formations 29, 31 are transverse to the longitudinal axes X-X of the rolls 25, 27. The female formations 31 in the upper roll 27 are complementary to the male formations 29 in the lower roll 25 in terms of the profiles of the formations and in the sense that pairs of the male and female formations 29, 31 coincide in the nip 35 between the rolls when the rolls are rotated about the longitudinal axes X-X of the rolls .

It can be appreciated that pushing and/or pulling the pan 11 through the nip between the rolls 25, 27, with the rolls 25, 27 rotating around the axes of the rolls, cold forms the material in the pans 11 that contacts the pairs of complementary male and female formations 29, 31 in the nip 35 between the rolls 25, 27 and forms the flutes 17.

It can also be appreciated that forming the flutes 17 as transverse flutes means that the there is a substantially uniform applied force required along the length of the rolls 25, 27 and around the circumference of the rolls to cold form the flutes 17 in the pans 11 as compared to the applied force distribution required to form flutes that are parallel or perpendicular to the lengthwise direction of the structural decking sheet. This results in advantages in the areas of manufacturing "noise" and load requirements . In summary, the structural decking sheet 3 shown in the Figures has the following advantages :

(a) increased section capacity compared to known structural decking sheets;

(b) reduced "noise" in manufacture of the structural decking sheet (as described above) compared to manufacture of known structural decking sheets;

(c) a more self-washing surface compared to known structural decking sheets that improves long term corrosion performance of the structural decking sheet; and

(d) reduced load on embossing rolls used in the manufacture of the structural decking sheet (as described above) compared to known structural decking sheets.

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

For example, the flutes 17 may vary in cross- sectional profile to that shown in the Figures .

In addition, unlike the described embodiment, the flutes 17 may extend the full width of the pan 11.

In addition, the structural decking sheet 3 may have one or more than one rib that divides the pan 11 into a plurality of pan sections, with the flutes 17 in at least one pan.

All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.

In the above description of the present invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", that is the features specified may be associated with further features in various embodiments of the invention.