GB2303653A - Grating - Google Patents

Abstract

A walkway grating is made by fitting cross-beams 18 into parallel members 10 which lie at right angles thereto. After beams 18 are fitted they are turned to lock them in position, this being achieved in that notches 28 in the beams 18 engage webs 12 of members 10. Either the notches or the webs or both are of varying thickness so that as the beams are turned, there is increasing interference between the webs and beams and the beams become locked to the webs. Additional secure connection may be provided by the use of adhesive at the points of engagement of beams 18 and webs 12.

Description

STRUCTURAL SUPPORT SYSTEM AND METHOD FOR ITS MAN U FACTU RE PULTRUDED GRP GRATING TECHNICAL FIELD This invention relates to structural plastic gratings for use in e.g.

floors, such as catwalks, which are particularly suitable for easy or automated manufacture.

BACKGROUND ART Floor gratings have found many industrial applications, particularly in off-shore and certain corrosive environments. Gratings of this kind are particularly suitable in locations where the floor must be resistant to wear and provide traction, yet provide apertures for drainage for corrosive liquids, unobstructed air circulation or simply visibilitv. They are often employed at elevated floor levels.

Conventionally, such gratings are manufactured from steel, aluminium alloys or reinforced fibre glass. This type of grating generally comprises a series of elongate parallel beams interconnected by a plurality of cross rods disposed and bonded at regular intervals. The beams are normally evenly spaced and may have various cross sections such as that of an I, T or other suitable shape. The gratings are generally supported at the beam ends or, if in long lengths, at regularly spaced intervals, providing a free, usually horizontal, span between these supports.

Various methods are known for producing such gratings. In most cases, however, the gratings are hampered by some particular drawback. Some do not provide sufficient support for the beam sections, while the assembly of others is unreasonably timeconsuming. There are numerous examples of gratings where after extended use, the stress levels at connection points have been high enough to cause the individual bonds to rupture and, consequently, the grating to disassemble.

In the US Patent 4,244,768 to Wiechowski et al a resin bonded fibre glass grating is disclosed, wherein cross rods are adhesively attached to elongate beams. The components are fitted together whereupon glue is applied on each of the cross rods at the intersection of said cross rods with the beams. The primary problem with this arrangement is that it requires the post-assembly application of glue or adhesive at the rod/beam intersections and the subsequent heating of said adhesive. This is not conducive to easy or automated systems.

US Patent 469,519 to Hale discloses a metallic grating utilising a key bar/locking bar combination to retain the vertical rail bars in a predetermined spaced relationship. The key bar and the locking bar are not bonded together, in fact which has given rise to problems. A further problem occurs if the side of the grating for some reason has to be cut away, as this causes the grating to disassemble.

US Patent 4,522,009 (Fingerson) has the substantial disadvantage of employing three-piece tie bars, whose parts have to be pre-glued and assembled in their respective position. This is a time-consuming and expensive procedure.

DISCLOSURE OF THE INVENTION The present invention seeks to provide a floor grating system which avoids the inconvenience associated with previously known devices, in that the locking arrangement is integral with the cross bars. Each of these consists of one single component, as does each support beam. This arrangement is particularly suitable for easy or automated assembly of gratings, ensuring maximum life and performance from the grating, reducing the assembly time and, hence, the costs.

The invention therefore provides a grating comprising a plurality of spaced parallel elongate beam members and a plurality of one-piece cross bars, each cross bar extending transversely through aligned apertures in webs in the parallel beams, thereby interconnecting said beams, and said sne-piece cross bars are provided with a notch or a series of circumferentially aligned notches in register with said apertures, said notches allowing said tie bars to be rotated in said apertures, characterised in that the thickness of said webs and/or the width of said notches is/are selected to produce an increased interference fit as the cross bars are rotated thereby serving to secure the beams rigidly in a predetermined spaced relationship.

Preferablv, the bars are non-circular and the apertures are of a complementary shape.

The notches are provided in several longitudinal positions on the cross bars. The spacing of the retaining notches corresponds to the required spacing of the beams.

The one-piece cross bars, or spacers, are introduced through complementarily profiled apertures in the webs of the beam members, which preferably are I-beams. Once the individual bars have been introduced through the webs of the beams they can be temporarily held in a position just short of their final location, allowing glue to be applied in the notches, prior or after being manually or, preferably, automatically pushed home, so that the notches are aligned with the apertures. The tie bars are turned with increasing friction so as to be securely locked simultaneously into the webs of all the beams. This assembly process is easily and possibly fully automated.

The holes which are cut in the central webs of the I-beam members are preferably shaped in such a way that they introduce the minimum stress raising effect on the beams. This is only made possible by novel or advanced cutting methods.

The said webs are preferably of varying cross section to provide the interference effect.

The cross section variation may comprise a central narrow section in which the apertures are formed, flanked by increasing tapering sections leading to thick sections where the web meets the respective beam flanges.

The ends of the cross bars can be prepared in such a way as to facilitate their passing through the beams and the shape of the locking mechanism will also encourage location and retention of the beams and the required glue.

Although a wide variety of rod shapes are envisaged, the preferred embodiment employs a shape which in cross section comprises a large circle with arcuate lugs. By this shape, the apertures in the beam webs can be easily formed.

The beams may have T or any other section, the upper flange of which may be considerably wider than the base of the section. In high capacity gratings, where the beams have a sufficiently large section for the webs to accommodate mutually offset rods, the rods may be staggered or otherwise distributed.

The beams and cross rods may be made of plastic, suitably of pultruded fibre-reinforced plastic, and the adhesive may e.g. be an epoxy-based glue.

The system has the added advantage that when portions of the grating have to be removed the grating does not disassemble or deteriorate as a consequence. The product is fully locked in a secure way which will provide a long life and good performance.

The said notches may be of constant width.

The grating according to the invention is not encumbered with the problems associated with some other systems which require even flow of the adhesives over long lengths between the components of the cross members.

The adhesive need only be applied where it is required, i.e. to the notch regions. This not only saves on adhesive but results in a much more attractive finished grate which looks far more professional than some of the present systems. It also provides for far better manufacturing control and greater consistency in the grating performance than before. Needless to say, glue may be applied to parts of or the entire bar, if this for some reason should be required.

Although variation of the viscosity of the glue can be utilised to obtain optimum results, a variety of viscosities may be used in the production of these gratings. Furthermore, although suitable adhesives are available today, it is envisaged that the gluing systems may well be further developed in the future.

A further advantage of this invention is that adhesives, due to the mode of application, need not rely on thixotropic properties to obtain the required wetting of the areas of contact. This system provides far better control of the application of the adhesive into the required area. Although this adhesive will cure naturally at room temperature, there are occasions where the application of some heat may be introduced to speed the curing process, to production advantage.

Yet another advantage of this system is that gratings can be customized with respect to size and the jig for manufacture adjusted accordingly. This allows the waste, and hence the production costs, to be minimised. In this way, the production of standard size gratings which are subsequently cut to size, with considerable waste, to non-standard finished size requirements, can be avoided.

A further advantage of this invention is that it optimises the cutting and assembly procedures to generate the maximum performance by giving the minimum disturbance to the products in cutting and assembly. This gives an optimised solution for the use of these materials in combined form to produce a grating.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will hereinafter be described with reference to the accompanying drawings, wherein: Fig. 1 shows a perspective view of grating beams and a cross bar suitable for use in connection therewith; Figs. 2, 3 and 4 show plan, end and side elevations of the grating beams of Fig. 1; Figs. 5 to 8 respectively show similar to Figs. 1 to 4 an alternative embodiment of the invention; Figs. 9 and 10 show the two forms of apertures respectively shown in Figs. 5 to 8 and 1 to 4; Figs. 11 and 12 show a modified form of aperture and different positioning of same in the grating beam; Figs. 13 and 14 respectively show sectional elevations of the beams shown in Fig. 9 and 10 and Figs. 11 and 12;; Figs. 15 and 16 a show first modified form of cross section for the grating beams for the particular advantage of this embodiment of the invention, the figures being on different scales; Figs. 17 and 18 show similar to Figs. 15 and 16 an alternative form of cross section of beam; Figs. 19 and 20 show on large and small scales, cross sectional shape of the preferred cross rod of the grating; Fig. 21 shows in sectional elevation the beam of Fig. 18 in cross section with the cross rod of Fig. 20 fitted thereto; and Fig. 22 shows the arrangement of Fig. 1, but with the cross rod in the locking posititon.

Referring to the drawings, and firstly to Figs. 1 to 4, grating is made up of a plurality of parallel grating bars 10 of the cross section shown. The grating bars 10 suitably are of plastics material which has been extruded or pultruded. In this case, the cross section of the beams 10 is in the form of a T and comprises a central web 12, a top rail 14 and a narrow foot rail 16. The cross sectional shape of the beams 10 can vary within wide limits, and for example as shown in Fig. 5, the beams 10 are more of an I shape in cross section wherein the top rail 14 is approximately the same width as the foot rail 16.

Reverting to Figs. 1 to 4, in the completed grating, the beams 10 are held together by cross rods 18, only one of which is shown in Fig. 1.

The cross rod 18 fits along the axis 20 and passes through the central partitions 12 of the beams 10 through apertures 22 of appropriate configuration and which will be described in more detail hereinafter.

Basically, the cross rod 18 is shaped so as to have a major central circular region 24 and a pair of diametrically opposite lobes 26 of semicircular cross section and much lesser diameter. The lobes are provided with notches 28 arranged in pairs and the notches of each pair are diametrically opposite. The pitching between the notch pairs 28 along the length of the rod 18 is equal to the spacing between the beams 10 and therefore it can be seen that with the beams 10 appropriately mounted, the rods 18 can be passed through the apertures 22 which have a corresponding cross section to the cross section of the rod 18, until the respective pairs of notches 28 are in the same planes as the webs 12 whereupon the rod 18 can be turned for example through 90 , in order to lock the rod 18 in position.The regions of the apertures 22 may be provided with suitable adhesive in order to bond the rods 18 to the grating beam partitions 12 to lock the structure together, or alternatively the adhesive can be applied after the rod has been positioned as described above.

It will be appreciated that for a complete grating there will be a plurality of said rods 18, and the beam webs 20 will be provided with apertures 22 spaced equally along the lengths of the partitions 12, in order to give the complete assembly.

Figs. 2 and 3 show a cross rod 18 in the locking position at position A, whilst position B in Fig. 2 shows a rod 18 in the inserted but unlocked position.

In the embodiment of Figs. 5 to 8, the only difference is that the rod 18 is of a different cross sectional shape, and the apertures 22 are of corresponding shape. This shape as shown in Fig. 5 comprises an ovaloid form with parallel sides and generally semicircular ends.

This form can be created by taking a large circular sectioned rod, followed by the formation of flats on opposite sides thereof. The notches 28 are formed by milling or other cutting.

The apertures 22 can be formed by drilling pairs of apertures which overlap using a circular drill.

In the case of the apertures 22 shown in Fig. 1, these can be formed by drilling or machining initially a circular hole of large diameter followed by the drilling or machining of two smaller circular holes of smaller diameter.

It is an important preferred feature of the present invention that the apertures 22 should be capable of being formed in the partitions 12 in a simple manner using conventional tools such as circular drills. If the profile is too complicated, then special cutting techniques which delay production have to be used.

Figs. 9 and 10 are illustrative of the two different forms of apertures 22 in the Figs. 4 to 8 and 1 to 4 embodiment respectively, whilst in Figs. 11 and 12, a slightly modified form of aperture 22 is shown which comprises a major circular portion 24 provided at diametrically opposite locations with notches 26 made up of a curved section and a flat section. Fig. 11 shows that the aperture 22 can be provided closer to the top rail 14, rather than being centrally located as indicated in Fig. 12, and also in Figs. 9 and 10.

It is of particular advantage if the partition 12 and/or the notching 28 can be such that as the cross rod 18 is turned, there will be increasing frictional interference between the cross rod and partition 12, assisting in the locking of the cross rods to the partitions.

One way of achieving this is to provide that the notches 28 are of varying width, but to do this would require special machining techniques, which would delay production, and a more convenient method of achieving this is to provide as shown in Figs. 15 to 18 that the partition 12 is of varying cross section. Figs. 15 to 18 show the two embodiments of the beams 10 which are preferred, and these figures also show respective dimensions to assist in providing the reader with an idea of a preferred size of beam 10.

In the arrangement of Figs. 15 and 16, the partition 12 is made up of a central constant cross section region 12A to the top and bottom of which are tapering regions 12B leading to the top rail 14 and bottom rail 16 respectively. The regions 12A and 12B have 5 slopes, and the narrow ranges 30 and 32 provide locking faces for the side walls of the notches 28 in the cross bars 18 when they are inserted in the partitions 12 and are rotated as described above. In the embodiments of Figs. 15 to 18, the apertures 22 for receipt of the rods 18 are centrally located in the partitions 12.

As shown more clearly in Figs. 17 and 18, the regions 30 and 32 of the partition portions 12A and 12B have a 15 sloping face on each side for engagement by the side walls of the notches 28, and the portions 12A and.12B are 0.5 mm thicker than the central portion 12A.

Figs. 19 and 20 show in greater detail the dimensions of the cross rod (of the form shown in Fig. 1) for,fitting into the beams shown in Figs. 15 to 18.

Finally, Figs. 21 and 22 show how the beams 10 and cross rods 18 are interconnected, and how they interfit having regard to the configurations shown in Figs. 15 to 20.

In Fig. 21, a beam 10 is as shown in Figs. 17 and 18, and a cross rod 18 as shown in Figs. 19 and 20 has been inserted into the aperture 22, but has not yet been rotated. Notch 28 is in the same plane as the partition 12, and is of a width slightly less than the thickest portion of the partition 12, but greater than the central portion 12A. Thus, as the rod 18 is turned to the position shown in Fig. 22, the notches 28 engage regions 30 and 32 and become wedged there against as shown in Fig. 22 providing extra locking between the rod 18 and the beam 10.

This provides for extra gripping between the rods and beams and enhances the rigidity and structure of the final grating.

Gratings constructed in this way can be used in many areas for example in stairs, platforms and the like which are required to be erected quickly, and have particular application in out of doors and in corrosive locations.

The grating arrangement described has a number of advantages including that: 1. By shaping the central partition of the beam assembly and locking interference is enhanced.

2. By shaping the cross rod appropriatly, the corresponding aperture in the beam partition can be created easily.

3. By adopting a particular shape of cross rod production can be facilitated.

4. The particular combination of cross rod and hole shape provide a sound foundation for gluing. Gluing can be on both sides of the partition, in which case the glue portions from respective sides run easily together. The shaping of the cross rod and aperture promote easy glue penetration and promote solid quick and tidy gluing.

5. The cross rods described are easy to notch.

6. Fabrication of the components is simple and the shape is practical and provides for best compromise in a large number of different site conditions.

Further advantages of particular features are that by positioning of the apertures 22 for example as shown in Fig. 11, the cross rods can be arranged to cam lock under the top rails 14, or if required by appropriate positioning of the apertures on top of the lower rails 16, when the cross rods are rotated.

The apertures 22 need not be arranged in alignment, but could be staggered to provide better structural rigidity or for any other reason.

The shape of the load bearing bars could be I T or any other suitable shape.

Claims (14)

CLAIMS.

1. A grating comprising a plurality of spaced parallel elongate beam members and a plurality of one-piece cross bars, each cross bar extending transversely through aligned apertures in webs in the parallel beams, thereby interconnecting said beams, and said onepiece cross bars are provided with a notch or series of circumferentially aligned notches in register with said apertures, said notch or notches allowing said tie bars to be rotated in said apertures, characterised in that the thickness of said webs and/or the width of said notch or notches is/are selected to produce an increased interference fit as the cross bars are rotated thereby serving to secure the beams rigidly in a predetermined spaced relationship.

2. A grating according to claim 1, wherein the bars are non-circular and the apertures are of a complementary shape.

3. A grating according to claim 1 or 2, wherein the or each of the notches is/are provided in several longitudinal positions on the cross bars the spacing of the retaining notches corresponding to the required spacing of the beams.

4. A grating according to claim 1,2 or 3, wherein the one-piece cross bars, or spacers, are introduced through complementarily profiled apertures in the webs of the beam members, which preferably are Ibeams.

5. A grating according to claim 1, 2, 3 or 4, wherein the holes which are cut in the central webs of the I-beam members are, shaped in such a way that they introduce the minimum stress raising effect on the beams.

6. A grating according to any preceding claim, wherein the said webs are of varying cross section to provide the interference effect.

7. A grating according to claim 6, wherein the cross section variation comprises a central narrow section in which the apertures are formed, flanked by increasing tapering sections leading to thick sections where the web meets the respective beam flanges.

8. A grating according to any preceding claim, wherein the ends of the cross bars are prepared in such a way as to facilitate their passing through the beams and the shape of the locking mechanism encourages location and retention of the beams.

9. A grating according to any preceding claim, wherein adhesive is provided at the intersections of the beams and cross members.

10. A grating according to any preceding claim, wherein the cross beams have a cross section comprising a large circle with arcuate lugs

11. A grating according to any preceding claim, wherein the beams have a T section, the upper flange of which is considerably wider than the base of the section.

12. A grating according to any preceding claim, wherein the rods are staggered or otherwise distributed.

13. A grating according to any preceding claim, wherein the beams and cross rods are made of plastic, suitably of pultruded fibre reinforced plastic, and the adhesive when used is an epoxy-based glue.

14. A grating according to any preceding claim. Wherein the said notches are of constant width.