GB2308396A

GB2308396A - Grating and method for it's manufacture

Info

Publication number: GB2308396A
Application number: GB9526008A
Authority: GB
Inventors: Malcolm Stewart
Original assignee: KENNEDY LIONWELD Ltd
Current assignee: KENNEDY LIONWELD Ltd
Priority date: 1995-12-20
Filing date: 1995-12-20
Publication date: 1997-06-25
Also published as: GB9526008D0

Abstract

An open bar grating comprises a set of mutually parallel load bearing bars 2 and a set of mutually parallel transverse bars 3, each transverse bar of which crosses at least a plurality of the load bearing bars. The load bearing bars have slots 5 in their upper surface and the transverse bars are located in these slots and forge welded directly to the load-bearing bars where the bars cross each other. The lower part of each transverse bar comprises two surfaces arranged at an angle to each other to form a downwardly facing apex, in at least those parts of the transverse bar which engage in the slots of the load-bearing bars. The slots in the upper surfaces of the load-bearing bars may be made rectangular, comprising at least one inwardly facing edge 10. The apex may be V-shaped or U-shaped.

Description

Gratina. and method and aDDaratus for its manufacture The present invention relates to a grating or grid such as is used in the form of a floor grating for use in the construction of industrial facilities as walkways and platforms etc. There are several requirements to be fulfilled when designing and manufacturing a flooring grating. These are to use the minimum amount of material to form a grating capable of bearing the required load (this is important both to keep the cost of the material itself and also to keep the weight of the material to a minimum), the provision of adequate support for the foot wear of persons who walk on the flooring and the provision of adequate resistance to slipping of the footwear on the flooring. A further important consideration is that the grating should be durable and able to withstand both short immediate impacts which it may be subject to and also to endure continued heavy use over a long period of time. The grating should also be cheap to manufacture.

The grating of the invention is of the type which has a rectilinear pattern formed by a number of mutually parallel rectilinear load bearing bars usually arranged longitudinally along the side of greater length and transverse bar which are also rectilinear and each of which crosses the longitudinal load bearing bars. Such a grating is shown in US-A-3057272.

It is known from this prior art that the transverse bars are secured to the longitudinal bars by means of forge-welding. In this process, a rectilinear transverse bar 2 is laid across the load bearing bars. A further top bar 3 is placed on top of the load bearing bars and parallel therewith. The top bars 3 are engaged by rolling electrodes and electrical current is transmitted between the electrodes via the top bars, the transverse bars and the longitudinal bars. Resistance heating of the bars occurs, particularly at the positions where the transverse bar crosses the longitudinal bars and the top bars. Pressure is exerted on the bars by means of the electrodes to force the transverse bar into rectangular slots 4 of the longitudinal bars until the transverse bar is at the desired height to form a flush surface, with the top bar 3 which is placed on top of the longitudinal bars, at what will be the upper surface of the flooring grid when in use.

It is known from US-A-3057272 to incorporate in forge-welded flooring grids longitudinal and transverse bars which have recesses in there uppermost edges top facilitate gripping of the flooring by the foot wear of the persons who walk on the flooring. The recesses are provided on the upper edge of the top bar 3. In US-A-3057272 the welding of the top bar 3 onto the longitudinal bars 1 is facilitated by the notches 8, 9 to provide the necessary rigidity and strength to the weld.

However there are a number of disadvantages with the grating disclosed in US-A-3057272. Firstly, the requirement of an additional top bar makes the manufacturing process expensive in that additional process steps are required to manufacture the top bar itself and assemble it in position on top of the corresponding longitudinal bar. Secondly the use of the top bar 3 adds significantly to the amount of material used which adds to the weight and also to the cost of the grating itself. Thirdly complete welding tends only to occur between the top bar 3 and the upper surface of the load bearing bars 1 and does not occur between the inward surfaces of the slots 4 and the lower surface and sides of the transverse bars 2. This absence of complete welding leaves gaps which allow water to penetrate during use which leads to corrosion and premature failure of the grating.

The invention eliminates these disadvantages without compromising the other essential requirements of a floor grating.

According to the invention there is provided an open bar grating comprising a set of mutually parallel load bearing bars and a set of mutually parallel transverse bars each of which transverse bars crosses at least a plurality of the load bearing bars, said load bearing bars having slots in the upper surface thereof, and wherein the transverse bars are located in said slots and forge welded directly to the load bearing bars where the bars cross each other, characterised in that the transverse bars comprise in the lower part thereof in at least those parts of the transverse bar which engage in the slots of the load bearing bars comprise two surfaces arranged at an angle to each other forming a downwardly facing apex.

According to a second aspect of the invention there is provided an open bar grating comprising a set of mutually parallel load bearing bars and a set of mutually parallel transverse bars each of which transverse bars crosses at least a plurality of the load bearing bars, said load bearing bars having slots in the upper surface thereof, and wherein the transverse bars are located in said slots and forge welded directly to the load bearing bars where the bars cross each other, characterised in that before the forge welding has occurred the slots are rectangular and comprise at least one inwardly facing ledge.

Preferably there are two inwardly facing ledges one on each side of the slot.

The ledges preferably comprise a sharp corner at approximately 90 degrees.

The corner may be less than 90 degrees.

In a further preferred embodiment a second pair of inwardly facing ledges are provided on either of the slot.

The transverse members are preferably triangular in their lower part with a downwardly facing apex, but may also be U shaped with a generally convex shaped downwardly facing surface. Preferably the lower part of the transverse bar comprises a triangular cross section along the whole of its length.

Preferably the transverse bars and the load bearing bars comprise recesses on their upper surface, and the load bearing bars comprise a flat upper landing surface in the regions where the transverse bars cross over on either side of the slots such that a continuous flat surface is formed by the top surface of the transverse bar and the landing surface after the forge welding operation is complete.

According to a further aspect of the invention there is provided a method of making an open bar grating wherein each of a plurality of longitudinal bars is formed along one of its edges with a series of slots and each of a plurality of transverse bars is formed with a downwardly facing 'V' or 'U' - shaped profile, wherein the longitudinal bars are supported in mutually parallel relation and each transverse bar is positioned across longitudinal bars, said downwardly facing 'V' or 'U' shaped profile of the transverse bars engaging in the slots of the longitudinal bars, and wherein the transverse bars and longitudinal bars are contacted by respective electrodes and forge welded together.

Preferably the slots are provided with inwardly facing ledges which provide point contact between the transverse and longitudinal bars causing heat concentration at the point of desired fusion between the two bars.

The invention will now be described in greater detail by means of exemplary embodiments and with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a first embodiment of a floor grating of the invention, Fig. 2 is a diagrammatic exploded end view of the grating of fig. 1 in the region of the end of a transverse bar, Fig. 3 is a diagrammatic end view in the region of a transverse bar of an alternative embodiment of the invention, Fig. 4 is a diagrammatic end view in the region of a transverse bar of an alternative embodiment of the invention, Fig. 5 is a diagrammatic end view in the region of a transverse bar of an alternative embodiment of the invention, Referring to figure 1 there is shown an open bar grating 1 comprising a set of mutually parallel load bearing bars 2 and a set of mutually parallel transverse bars 3 each of which transverse bars 3 crosses at least a plurality of the load bearing bars 2. The load bearing bars 2 having slots 5 in the upper surface 4 thereof, and the transverse bars 3 are located in said slots 5 and forge welded directly to the load bearing bars 2 where the bars cross each other. The transverse bars 3 comprise in the lower part thereof comprise two surfaces 7 arranged at an angle to each other forming a downwardly facing apex 8.

Before the forge welding has occurred the slots 5 are rectangular and comprise at least one inwardly facing ledge 9 as shown diagrammatically in figure 2.

Before welding the transverse bars are placed in position across the load bearing bars 2. The downwardly facing apex 8 of the lower pat of the transverse bars 3 locating in the slots 5 of the load bearing bars 3. The inwardly facing corners of the ledges 9 of the slot 5 contact with the angled surfaces 7 of the lower part of the transverse bars 3. Thus providing a sharp point of contact between the slot and the lower part of the transverse bars 3.

The apex 8 of the lower triangular part of the transverse bars 3 may also be a further point contact with the lower surface of the slot 5.

In this embodiment the gratings 1 are manufactured by supporting the longitudinal bars 2 in mutually parallel relation and each transverse bar 3 is formed with a downwardly facing 'V' or 'U' - shaped profile and is positioned across longitudinal bars, said downwardly facing 'V' or 'U' shaped profile of the transverse bars engaging in the slots of the longitudinal bars. The transverse bars 3 are then contacted by respective electrodes which are lowered down and make contact at the cross over points of the bars an they are forge welded together.

The slots 5 are provided with inwardly facing ledges 9 to provide point contact between the transverse and longitudinal bars causing heat concentration at the point of desired fusion between the two bars.

During conventional manufacture rectilinear shaped transverse bars are used which are placed on top of the spaced longitudinal bars in line with the slots 5 before the electrodes are lowered down. The problem with this method is that during the application of the electrodes movement of the transverse bars may occur so that they become out of line with the slots 5 and may become located in one of the neighbouring recesses 12. In the method of the invention the transverse bars are located precisely in the slots by means of the shape of the under side of the transverse bars 3.

The point contacts between the bars also provide sources of heat concentration which causes complete fusion of the contacting surfaces of the transverse and load bearing bars. By this means complete welding at every junction of the grating is ensured. This is advantageous both from the point of view of the immediate maximum physical strength and durability of the grating but also from the point of view of the elimination of any gaps between the contacting parts of the transverse and load bearing bars which may become filled with water or other corrosive fluids and lead to early failure of the grating.

Referring to figure 2 there are two inwardly facing ledges 9 one on each side of the slot 5. The ledges 9 preferably comprise a sharp corner at approximately 90 degrees. The corner may be less than 90 degrees.

Referring to figure 3 the slot 5 comprises a second pair of inwardly facing ledges 10. In this embodiment additional point contacts are provided. This may be particularly advantageous for large or heavy duty gratings with transverse bars having long angled surfaces 7 to ensure that fusion occurs along the whole length of the angled surfaces.

The transverse bars 3 are preferably triangular in their lower part with a downwardly facing apex 8, and for convenience the triangular profile will extend along the whole length of the transverse bar. However it will be apparent that the triangular section is only required on those parts of he transverse bars which engage into the slots 5.

Referring to figure 4 a further embodiment is shown where the lower part of the transverse bar 3 is generally U shaped with a generally convex shaped downwardly facing surface 11. The convex surface 11 enables the transverse bar to be lowered into the slot and for the convex surface 11 to make point contact with the inwardly facing corners of the ledges 9 of the slots 5.

Referring to figure 5 the transverse bars 3 and the load bearing bars 2 comprise recesses 12 on their upper surfaces 4, and the load bearing bars 2 comprise a flat upper landing surface 14 in the regions where the transverse bars 3 cross over on either side of the slots 5 such that a continuous flat surface 15 is formed by the top surface of the transverse bars 3 and the landing surfaces 14 after the forge welding operation is complete. This serves to control the welding operation and also ensures that the transverse bars are arranged in the required exact dimensional position with respect to the load bearing bars so that the upper surfaces of each together provide at level supporting surface.

Claims

1. An open bar grating 1 comprising a set of mutually parallel load bearing bars 2 and a set of mutually parallel transverse bars 3 each of which transverse bars 3 crosses at least a plurality of the load bearing bars 2, said load bearing bars 2 having slots 5 in the upper surface 4 thereof, and wherein the transverse bars 3 are located in said slots 5 and forge welded directly to the load bearing bars 2 where the bars cross each other, characterised in that the transverse bars 3 comprise in the lower part thereof in at least those parts of the transverse bar 3 which engage in the slots 5 of the load bearing bars 2 comprise two surfaces 7 arranged at an angle to each other forming a downwardly facing apex 8.

2. An open bar grating 1 comprising a set of mutually parallel load bearing bars 2 and a set of mutually parallel transverse bars 3 each of which transverse bars 3 crosses at least a plurality of the load bearing bars 2, said load bearing bars 2 having slots 5 in the upper surface 4 thereof, and wherein the transverse bars 3 are located in said slots 5 and forge welded directly to the load bearing bars 2 where the bars cross each other, characterised in that before the forge welding has occurred the slots 5 are rectangular and comprise at least one inwardly facing ledge 9.

3. An open bar grating according to claim 2, characterised in that there are two inwardly facing ledges 9 one on each side of the slot 5.

4. An open bar grating 1 according to claim 2, characterised in that the ledges 9 preferably comprise a sharp corner at approximately 90 degrees.

5. An open bar grating 1 according to claim 2, characterised in that the ledges 9 comprise a sharp corner at less than 90 degrees.

6. An open bar grating 1 according to claim 3, characterised in that a second pair of inwardly facing ledges 10 are provided on either of the slot 5.

7. An open bar grating according to any one of the preceding claims, characterised in that the transverse bars 3 are triangular in their lower part with a downwardly facing apex 8.

8. An open bar grating 1 according to claim 7, characterised in that the lower part of the transverse bars 3 comprise a triangular cross section along the whole of their lengths.

9 An open bar grating according to any one of the preceding claims 2 to 6 characterised in that the transverse bars 3 are U shaped in their lower part with a generally convex shaped downwardly facing surface 11.

10. An open bar grating according to any one of the preceding claims, characterised in that the transverse bars 3 or the load bearing bars 2 comprise recesses 12 on their upper surfaces 4.

11. An open bar grating according to any one of the preceding claims, characterised in that the load bearing bars 2 comprise a flat upper landing surface 14 in the regions where the transverse bars 3 cross over on either side of the slots 5 such that a continuous flat surface 15 is formed by the top surface of the transverse bars 3 and the landing surfaces 14 after the forge welding operation is complete.

12. A method of making an open bar grating wherein each of a plurality of longitudinal bars is formed along one of its edges with a series of slots and each of a plurality of transverse bars is formed with a downwardly facing 'V' or 'U' - shaped profile, wherein the longitudinal bars are supported in mutually parallel relation and each transverse bar is positioned across longitudinal bars, said downwardly facing 'V' or 'U' shaped profile of the transverse bars engaging in the slots of the longitudinal bars, and wherein the transverse bars and longitudinal bars are contacted by respective electrodes and forge welded together.

13. A method of making an open bar grating wherein each of a plurality of longitudinal bars is formed along one of its edges with a series of slots and each of a plurality of transverse bars is formed with a downwardly facing shaped profile which is smaller than the width of the slots, wherein the longitudinal bars are supported in mutually parallel relation and each transverse bar is positioned across longitudinal bars, said downwardly facing profile of the transverse bars engaging in the slots of the longitudinal bars to locate them in position, and wherein the transverse bars and longitudinal bars are contacted by respective electrodes and forge welded together.

14. A method according to claim 12 or 13, characterised in that the slots are provided with inwardly facing ledges which provide point contact between the transverse and longitudinal bars causing heat concentration at the point of desired fusion between the two bars.