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Title:
FLOORING GRID
Document Type and Number:
WIPO Patent Application WO/1997/043500
Kind Code:
A1
Abstract:
A flooring grid comprising a first set of rectilinear, spaced apart, mutually parellel, load-bearing bars (10) and a second set of rectilinear, spaced apart, mutually parallel, transverse bars (12), each of said transverse bars (12) crossing a plurality of load-bearing bars (10) and the transverse bars (12) being forge welded directly to the load carrying bars (10) where the bars mutually cross and wherein the upper edges of the load-bearing bars (10) lie in an upper surface of the flooring grid, wherein at least each load-bearing bar (10) comprises a configuration comprising two opposite end parts (33, 34) the end parts having end surfaces of breadth (B) which are spaced apart by a depth (D), and the end parts being interconnected by a reduced breadth part having two opposite concave curved side surfaces (37) each of which joins the opposite end parts.

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Inventors:
HOUSEMAN JOHN HOWARD (GB)
Application Number:
PCT/GB1997/001290
Publication Date:
November 20, 1997
Filing Date:
May 12, 1997
Export Citation:
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Assignee:
REDMAN FISHER ENG LTD (GB)
HOUSEMAN JOHN HOWARD (GB)
International Classes:
E04C2/42; (IPC1-7): E04C2/42
Foreign References:
GB296579A1928-09-06
US2404570A1946-07-23
US2187529A1940-01-16
Download PDF:
Claims:
CLAIMS
1. A flooring grid comprising a first set of rectilinear, spaced apart, mutually parallel, loadbearing bars and a second set of rectilinear, spaced apart, mutually parallel, transverse bars, each of said transverse bars crossing a plurality of loadbearing bars and the transverse bars being forge welded directly to the load carrying bars where the bars mutually cross and wherein the upper edges of the loadbearing bars lie in an upper surface of the flooring grid, wherein at least each loadbearing bar comprises a configuration comprising two opposite end parts, the end parts having end surfaces of breadth B which are spaced apart by a depth D, and the end parts being interconnected by a reduced breadth part having two opposite concave curved side surfaces each of which joins the opposite end parts.
2. A flooring grid according to Claim 1 wherein each loadbearing bar has configuration function f and the depth D of the loadbearing bar multiplied by the configuration function f may be at least equal to a depth DR of a rectangular shape, having said depth DR, and a breadth B and having the same moment of inertia as said loadbearing bar about the midtransverse axis XX (Ix x).
3. A flooring grid according to Claim 2 wherein the configuration function f lies in the range 0.5 to 0.99.
4. A flooring grid according to any one of the preceding Claims wherein each load bearing bar has two parallel side surfaces spaced apart by the breadth B.
5. A flooring grid according to Claim 4 wherein the parallel sides have a depth DL of up to 40% of D.
6. A flooring grid according to Claim 5 wherein the parallel sides have a depth DE of 20% of D.
7. A flooring grid according to any one of the preceding claims wherein the reduced breadth part is of symmetrical shape so as to have at least one waisted part.
8. A flooring grid according to any one of Claims 1 to 6 wherein the reduced breadth part is asymmetrical to have a reduced breadth part on opposite sides of said part at different positions longitudinally between said end parts.
9. A flooring grid according to Claim 7 wherein the waisted part has a minimum breadth B min which is 10% to 97% of the breadth B and preferably 25% to 75% of B.
10. A flooring grid according to Claim 9 wherein B min is 33% to 50% of B.
11. A flooring grid according to any one of the preceding claims wherein the flooring grid comprises a plurality of elongate rectilinear intermediate elements bars disposed to lie between and parallel to each pair of adjacent load bearing bars and be attached to a plurality of bars of the second set where they mutually cross by forge welding.
12. A flooring grid according to any one of the preceding claims wherein a nosing bar of the grid comprises said configuration.
13. A method of making a flooring grid wherein the flooring grid comprises a first set of rectilinear, spaced apart, mutually parallel, loadbearing bars and a second set of rectilinear, spaced apart, mutually parallel, transverse P 13 bars, each of said transverse bars crossing a plurality of loadbearing bars and the transverse bars being forge welded directly to the load carrying bars where the bars mutually cross and wherein the upper edges of the load bearing bars lie in an upper surface of the flooring grid wherein the crosssection of each load bearing bar is determined by ascertaining the depth DR and the breadth B of the rectangular bar that would be required to provide a loadbearing bar of a desired strength, providing a bar of a configuration which comprises two opposite end parts, the end parts having end surfaces which have breadth B and are spaced apart by a depth D, and the end parts being interconnected by a reduced breadth part having two opposite concave curved side surfaces each of which joins the opposite end parts and of a configuration function f and wherein the depth D of the loadbearing bar is determined by dividing the configuration function f into the depth DR of the rectangular shape, to provide a loadbearing bar of depth D, breadth B and having the same moment of inertia as said rectangular load bearing bar about the midtransverse axis XX (Ixx).
14. A method of making a flooring grid according to Claim 13 wherein the configuration function f lies in the range 0.5 to 0.99.
15. A method according to Claim 13 or Claim 14 wherein the bar has two parallel side surfaces spaced apart by the breadth B.
16. A method of making a flooring grid according to any one of Claims 13 to 15 wherein the reduced breadth part is of symmetrical shape so as to have at least one waisted part.
17. A method of making a flooring grid according to any one of Claims 13 to 15 wherein the reduced breadth part is asymmetrical to have a reduced breadth part on opposite sides of said part at different positions longitudinally between said end parts.
18. A method of making a flooring grid according to any one of Claims 13 to 17 wherein the waisted part has a minimum breadth B min which is selected to be in the range 10% to 97% of the breadth B and preferably 25% to 75% of B.
19. A method of making a flooring grid according to Claim 18 wherein B min is 33% to 50% of B.
20. A flooring grid constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.
21. A method of making a flooring grid substantially as hereinbefore described.
Description:
Title: Flooring Grid

Description of Invention

This invention relates to a flooring grid and to a method of making a flooring grid.

A known flooring grid comprises a first set of rectilinear, spaced apart, mutually parallel, load-bearing bars and a second set of rectilinear, spaced apart, mutually parallel, transverse bars, each of said transverse bars crossing a plurality of load-bearing bars and the transverse bars being forge welded directly to the load carrying bars where the bars mutually cross and wherein the upper edges of the load-bearing bars lie in an upper surface of the flooring grid.

Hitherto the load-bearing bars have been of rectangular cross-section.

A problem with known flooring grids is that they are relatively heavy, particularly when used in relatively large amounts in, for example, offshore installations. It is accordingly an object of the present invention to provide a flooring grid wherein the above-mentioned problem of relatively high weight is overcome or is reduced and, at the same time, to retain the desired strength of the flooring grid.

According to one aspect of the present invention we provide a flooring grid comprising a first set of rectilinear, spaced apart, mutually parallel, load- bearing bars and a second set of rectilinear, spaced apart, mutually parallel, transverse bars, each of said transverse bars crossing a plurality of load-bearing bars and the transverse bars being forge welded directly to the load carrying bars where the bars mutually cross and wherein the upper edges of the load-bearing bars lie in an upper surface of the flooring grid, wherein at least each load- bearing bar comprises a configuration comprising two opposite end parts, the end parts having end surfaces of breadth B which are spaced apart by a depth D, and the end parts being interconnected by a reduced breadth part having two opposite concave curved side surfaces each of which joins the opposite end parts.

Each load-bearing bar may have a configuration function f and the depth D of the load-bearing bar multiplied by the configuration function f may be at least equal to a depth D R of a rectangular shape, having said depth D R , and a breadth B and having the same moment of inertia as said load-bearing bar about the mid-transverse axis X-X (Ix-x) and wherein the configuration function f lies in the range 0.5 to 0.99.

Accordingly, a bar in accordance with the present invention has a Moment of Inertia Ix-x which is at least equal to that of a rectangular shape of a depth D R and breadth B by virtue of making the depth of the section embodying the invention equal to D R multiplied by the configuration function f. Moreover, because the cross-section of the bar in accordance with the invention is of said reduced breadth shape having said configuration function f, it has less cross-sectional area than the rectangular shape and so has less material therein and is correspondingly lighter. As a result a grid comprising a plurality of load- bearing bars embodying the invention has a weight which is considerably reduced compared with the weight of a grid known hitherto having rectangular base, whilst at the same time providing a grid of the same strength. This is because the Moment of Inertia is proportional to D 3 , hence a small increase in D compensates for a relatively large reduction in area due to waisting.

The bar may have two parallel side surfaces spaced apart by the breadth B.

The parallel sides may have a depth D E of up to 40% of D and typically about 20% D.

The reduced breadth part may be of symmetrical shape so as to have at least one waisted part, or may be asymmetrical to have a reduced breadth part on opposite sides of said part at different positions longitudinally between said end parts.

When the reduced breadth part is single waisted the waisted part may have a minimum breadth B min which may be 10% to 97% of the breadth B, preferably 25% to 75% of B and may be about 33% to 50% of B.

The flooring grid may comprise a plurality of elongate rectilinear intermediate elements bars disposed to lie between and parallel to each pair of adjacent load-bearing bars and be attached to a plurality of bars of the second set where they mutually cross by forge welding.

A nosing bar of the grid may comprise said configuration.

According to a second aspect of the invention we provide a method of making a flooring grid wherein the flooring grid comprises a first set of rectilinear, spaced apart, mutually parallel, load-bearing bars and a second set of rectilinear, spaced apart, mutually parallel, transverse bars, each of said transverse bars crossing a plurality of load-bearing bars and the transverse bars being forge welded directly to the load carrying bars where the bars mutually cross and wherein the upper edges of the load-bearing bars lie in an upper surface of the flooring grid wherein the cross-section of each load-bearing bar is determined by ascertaining the depth D R and the breadth B of the rectangular bar that would be required to provide a load-bearing bar of a desired strength, providing a bar of a configuration which comprises two opposite end parts, the end parts having end surfaces which have breadth B and are spaced apart by a depth D, and the end parts being interconnected by a reduced breadth part having two opposite concave curved side surfaces each of which joins the opposite end parts and of a configuration function f and wherein the depth D of the load-bearing bar is determined by dividing the configuration function f into the depth D R of the rectangular shape, to provide a load-bearing bar of depth D, breadth B and having the same moment of inertia as said rectangular load-bearing bar about the mid-transverse axis X-X (Ix-x) and wherein the configuration function f lies in the range 0.5 to 0.99.

The bar may have two parallel side surfaces spaced apart by the breadth B.

The reduced breadth part may be of symmetrical shape so as to have at least one waisted part, or may be asymmetrical to have a reduced breadth part

on opposite sides of said part at different positions longitudinally between said end parts.

When the reduced breadth part is single waisted the waisted part may have a minimum breadth B min which may be selected in the range 10% to 97% of the breadth B, preferably 25% to 75% of B and may be about 33% to 50% of B.

In this specification by "strength" we mean "force per unit deflection".

An example of a flooring grid embodying the invention will now be described with reference to the accompanying drawings wherein:

FIGURE 1 is a diagrammatic representation of a perspective view of part of flooring grid embodying the invention,

FIGURE 2 is a diagrammatic representation showing a cross-section on line 2-2 of Figure 1 and drawn to an enlarged scale,

FIGURE 3 is a view similar to that of Figure 2 but showing a notional load-bearing bar of rectangular configuration, and

FIGURE 4 is a diagrammatic perspective view showing part of an apparatus for use in carrying out a method according to the invention.

Referring to Figure 1, a flooring grid, shown in Figure 1, comprises a plurality of rectilinear, spaced apart, load-bearing bars 10 which are mutually parallel to one another and which extend longitudinally of the grid. As viewed in transverse cross-section each bar 10 has a depth which is a plurality of times greater than its width. Typically, the depth of these bars is in the range four to ten times the width. The bars 10 have a planar upper surface 11, each of which lies in a plane which, in use, is generally horizontal, and thus the surfaces 11 define an upper surface of the grid.

The grid further comprises a plurality of transverse bars 12 which are also rectilinear, spaced apart and mutually parallel, and are perpendicular to the load-bearing bears 10. Where the flooring grid is a rectangle, as is usually the case, each transverse bar 12 extends across all of the load-bearing bars.

As viewed in a cross-section in a plane transverse to its length, each of the transverse bars 12 has a square cross-section which approximates to the width of the load-bearing bars. The transverse bars are preferably, and as shown, twisted about their respective longitudinal axes. Preferably the bars are twisted through 90° between adjacent load-bearing bars 10 but they may be twisted through other angles if desired such as 180° In the illustrated example the load- bearing bars have a breadth of 5mm and a depth of 30mm whilst the transverse bars are 6mm square. Whilst in this example the depth of the load-bearing bars and the transverse bars is in the ratio 5:1 if desired the ratio may lie in the range 1:1 to 20:1.

The pitch of the load-bearing bars in the example is 30mm and to close this gap a plurality of intermediate element bars 13 are provided, one of which lies between each pair of adjacent load-bearing bars 10 and are arranged so as to be rectilinear and extend parallel to the load-bearing bars 10. In the present example the intermediate element bars are rectangular in cross-section having a width of 5mm and a depth of 10mm. Whilst the load-bearing bars and the intermediate elements have a depth which lies in the ratio 3:1 if desired the ratio may lie in the range 1:1 to 20: 1.

When the grid is in use, portions of the undersides of the load-bearing bars rest on supports, for example, beams supported by pillars or by walls of a building or by another structure in which the flooring grid is provided. Any downward load which is applied to a transverse bar in use is transmitted to a support through the intermediary of the load-bearing bars. Any downward load which is applied through an intermediate element, in use, is transmitted to a support through the intermediary of transverse bars and load-bearing bars.

Intermediate elements 13 may be arranged so that the upper surfaces 14 thereof are co-planar with the upper surfaces 11 of the transverse bars or may be spaced therebelow a small distance for example 2mm - 3mm. The upper edge of the transverse bars 12 likewise are co-planar with the surfaces 11.

It will be noted that the cross-sectional area of each intermediate element 13 is a plurality of times less than the cross-sectional area of each load- bearing bar 10.

A method described with reference to Figure 4 will now be described. In this method the required number of load- bearing bars 10 and intermediate elements 13 are supported in the required relative positions by a support or jig 15. The support is in the form of a platform having in its upwardly presented face recesses 16 for the load-bearing bars 10 and recesses 17 for the intermediate elements 13. The depth of each recess 16 is less than the depth of the load- bearing bars by an amount of approximately equal to the depth of the transverse bars 12 so that the load-bearing bars 10 project upwardly from the support. The depth of each of the recesses 17 is arranged so that the intermediate elements project from the support by a desired amount arranged so as to ensure that the top surface of the intermediate elements is at a desired level relative to the upper surfaces 11 of the load-bearing bars 10. The support 15 extends along only a part of the length of the load-bearing bars 10 and intermediate elements 13, typically for a distance between one and two times the pitch of the transverse bars 12.

The apparatus for producing the flooring grid further comprises a pair of electrodes 18, 19 which are disposed downstream of the support 15 and each has a length approximately equal to the length of the support so that the electrodes extend across the entire width of the flooring to be produced.

The electrodes are spaced apart in a direction along the length of the load-bearing bars 10 so that respective longitudinal centre lines of the electrodes are spaced apart by a distance equal to the pitch of the transverse bars 12. The electrodes are mounted, by means not shown, for reciprocation towards and away from the support 15 and so as to be capable of applying a desired pressure to the transverse bars 12.

An anvil 20 is disposed between the electrode and below the load- bearing bars 10 and transverse elements 13.

With the electrodes 18, 19 raised clear of the load-bearing bars 10 and intermediate elements 13 which are supported by the platform 15, the desired plurality of transverse bars 12 are laid across the exposed edges of the load- bearing bars 10 at positions directly below the respective ones of the electrodes. The electrodes are then lowered into contact with respective ones of the transverse bars 10 and an electric current is passed from the electrode 18 through the corresponding transverse bar 12, through the load-bearing bars 10 and the other transverse bar to the electrode 19. This causes resistance heating of the longitudinal bars at the positions where they are crossed by the transverse bars and the transverse bars are forced downwardly by the electrodes so as to be forge welded to the load-bearing bars. Depending upon the level of the intermediate elements 13 the transverse bars initially or subsequently come into contact with the intermediate elements 13. An electric current is then conducted by the intermediate elements also so that heating occurs at the positions where the transverse bars cross the intermediate elements and again forge welding of the transverse bars to the intermediate elements takes place. By pressing the load- bearing bars against the anvil 20 a slight set or permanent deformation is imparted to the grid to counteract the tendency which otherwise occurs for the grid to bow downwardly between the transverse bars.

In this manner, the transverse bars are forge welded to both the load- bearing bars and to the intermediate elements with each transverse bar being continuous along its length at the upper surface of the flooring, whereas the longitudinal bars are effectively notched, as are the intermediate elements where each transverse bar crosses them.

When one pair of transverse bars has been thus forge welded with the load-bearing bars and intermediate elements the electrodes 18 and 19 are withdrawn upwardly, the longitudinal bars and intermediate elements are advanced by a distance equal to twice the pitch of the transverse bars and a further pair of transverse bars is then forge welded into place.

The flooring panel may be completed by the provision of a nosing bar connecting together the free ends of the load-bearing bar.

The load-bearing bars 10 are each of a configuration best illustrated in Figure 2. More particularly, each load-bearing bar has opposite end parts 31, 32 each having opposed end surfaces 33, 34. The end surfaces 33, 34 are spaced apart by a depth D. In the present example D = 25.4mm but it may lie in the range 10mm - 100mm. The end surfaces 33, 34 have a breadth which in the present example is 5mm. If desired, B may lie in the range 3mm - 10mm. Extending perpendicularly to the end surfaces 33, 34 are parallel side surface parts 35 of the end parts 31, 32. Each parallel surface part 35 has a depth D E which in the present example is 5.5mm but which may lie in the range 20-40% B. If desired, the parallel surface parts may be of lesser extent or omitted altogether if other means are provided to hold the bars upright in the forging apparatus.

The end parts 31, 32 are interconnected by a waisted part 36 having curved concave side surfaces 37 which in this example are of cylindrical configuration and which join the parallel side surfaces 35 of the end parts 31, 32. The waisted part 36 has a minimum breadth B min at its mid-section of, in this example, 2.5mm. If desired, B min may lie in the range 10% to 97% B, preferably 25% to 75% B and may be about 33% to 50% B.

If desired, the waisted part may be of other than cylindrical shape. For example, each concave side surface 37 may be a surface of revolution but not of a flat shape taken in a cross-sectional plane parallel to the end surfaces of the bar. The cross-sectional shape may be curved and may be convex or concave, or may be of any other desired shape. Alternatively, or in addition, each side surface may be generally concave taken in a further plane perpendicular to the first-mentioned plane and containing said end surfaces, ie a plane parallel to the side view illustrated in Figure 2. As a result of the generally concave surfaces, the side surfaces provide a generally waisted part. These may be of any other desired configuration including, for example, an elliptical shape or an oval shape where curved end parts are interconnected by a planar part or any other desired waisted

shape, including a configuration where there is more than one waist at different positions longitudinally of the bar.

The configuration of the cross-section shown in Figure 2 and described hereinbefore is chosen so as to have a cross-sectional shape having a configuration function f which lies in the range 0.5 to 0.99 but which in the present example is 0.984. The above-described shape and configuration function are determined so that if a notional rectangular shape is considered as illustrated in Figure 3, having a breadth B equal to the breadth B of the load-bearing bars described hereinbefore and having a depth D R where D multiplied by the configuration function f provides the depth D R of the rectangular section, and the rectangular section has a moment of inertia, ie second moment of area about the mid-axis X-X which is equal to or less than the moment of inertia I about the mid-axis X-X of the load-bearing bar shown in Figure 2. At the same time, the cross-sectional area of the load-bearing bar shown in Figure 2 is less than a cross- sectional area of the rectangle shown in Figure 3 by 18.4%. If desired, the % reduction in area may lie in the range 40% to 2%.

Accordingly, the profile of the load-bearing bars as illustrated in Figure 2 provides a moment of inertia which is at least the same as the moment of inertia of the rectangular shape shown in Figure 3 for an increase in D of 0.4mm whilst at the same time it provides a reduction in area compared with the area of the rectangle shown in Figure 3 which is 18.4% and which may lie in the range 40% to 2% less.

In the present example the grid comprises transverse bars and intermediate element bars of the configuration described above and shown in the Figures, but they may be of other shape. If desired, the grid may have a nosing bar of the same kind of configuration as the load-bearing bar.

Accordingly, a grid made in accordance with the invention, whilst having a depth which is slightly greater than the depth which would need to be provided with load-bearing bars of the rectangular configuration shown in Figure 3, it has a cross-sectional area which is considerably reduced and thus there is a

considerable reduction in weight for a bar the same strength, ie a bar able to resist the same force per unit deflection.

In the present example an 18.4% reduction in weight of the load- bearing bar is achieved.

The significance of the moment of inertia, ie the second moment of area lies in the flexural rigidity of the bars which is determined by Young's modules times the second moment of area. In addition, the second moment of area is one of the significant factors in determining the stress in the bars.

Whilst in the above-described embodiment the end parts are interconnected by a reduced breadth part having a single waisted configuration, if desired the end parts may be interconnected by a waisted part having a plurality of waists at spaced positions longitudinally of the section between said end parts or, alternatively, the end parts may be interconnected by a reduced breadth part which is of asymmetric configuration having at least one recess on one side of the section and at least one further recess on the other side of the section, the recesses being longitudinally offset so as to be asymmetrical. As a result, the end surfaces are connected by a part which is of reduced breadth on opposite sides of said part at different positions longitudinally of the section between said end parts.

A bar embodying the present invention is particularly easy to make by rolling as the waisted or other shape described hereinbefore is relatively easy to make by a rolling operation.

The features disclosed in the foregoing description, 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, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.