Fabricating a Metal Beam

DESCRIPTION Field of the Invention

The invention relates to methods of fabricating metal beams as structural building members in building construction. The beams, made by cutting and welding from flat metal sheet material, can have the final form of an I-section beam or a box section beam without incurring the expense and weight associated with hot rolled beam components.

Background Art

It is known to construct actual building members from sheet steel by a cold rolling process. It is also known that the strength of such building members can be increased by welding or brazing reinforcing steel sheets across known profiles to create reinforced profiles. For example, the strength of sheet steel cold-rolled into a C- section can be increased by welding face plates at intervals across the open edge of the C-section. A combination of cold-rolling and welding or brazing is therefore well known as a method of fabricating lightweight metal beams with good structural strength.

If the cold-rolling step is omitted, then the fabrication of a beam relies wholly on the welding or brazing process. It is necessary to hold the component panels in a very strict alignment one relative to the other while welding or brazing takes places, and the setting up time prior to welding or brazing is therefore very significant.

It is an object of the invention to provide a simpler method of fabrication that would create, from flat sheet metal components, a metal beam comprising two face plates of sheet steel held mutually spaced apart by a reinforcing web or webs extending perpendicularly to each of the face plates and secured thereto by welding or by brazing.

The Invention

The invention provides the method of fabricating a metal beam as specified in claim 1. Those edge portions which extend completely through the face plates as projecting lugs may be gripped by pliers, for example by one man working alone, and twisted so that they cannot retreat back through the slots through which they extend. In this way a temporary fixing can be obtained, with the reinforcing web extending perpendicularly to the face plates and holding them spaced apart and preferably mutually parallel one to the other. While thus temporarily retained, the face plates can be welded or brazed to the supporting web. That welding or brazing can be from the outside face of the face plates, being the side on which the projecting lugs extend through the slots; or it can be the inside edge junction, where the reinforcing web was initially presented up to the row of slots in each face plate.

The fabrication of the face plates and of the reinforcing web can easily be achieved using a laser cutter. The laser cutter can cut the rows of slots quickly and accurately. It can also cut the longitudinal edges of the reinforcing web into a crennelated shape, so as to create the array of edge projections sized and spaced to engage with the slots in the face plates.

The line of the junction between the reinforcing web and the face plates may be linear or non-linear. Preferably it is non-linear, because that adds strength and rigidity to the final beam. For example, even if the face plates are long plates of rectangular shape, the reinforcing web preferably extends other than longitudinally along the centre of the face plates. Preferably the reinforcing web extends in a zig-zag or sinuous path along the length of the face plates, passing alternatively from one side to the other of a longitudinal centre line of the beam.

The face plates do not have to be long and rectangular in shape. They could be cut into a flat annular or part-annular curve or arc, with the reinforcing web following generally the centreline of the curve or an outer and/or inner edge of the curve but

preferably spaced slightly inwardly from that edge. Along that intended line of engagement between the face plate and the reinforcing web, the laser cuts a row of slots into the face plate. The reinforcing web is then presented up to that arcuate row of slots, bending it as appropriate until the edge projections of the reinforcing web extend into or through the slots in the arcuate row. A sufficient number of the edge projections are sized to pass as lugs completely through the slots with which they engage to ensure that as long as those edge projections or lugs extending through the face plates are sufficiently regular and close together to hold the assembly together, then the twisting or bending of the lugs is sufficient to create a robust temporary retention.

Drawings

Figure 1 is a plan view from above of an arcuate metal beam of box section constructed by the method of the invention; Figure 2 is a section taken along the plane A-A of Figure I ₅ showing the box construction of the finished beam;

Figure 3 is a perspective view of a portion of the beam during construction;

Figure 4 is a plan view from above of another beam according to the invention, being a longitudinal beam with a reinforcing web extending the length of the beam in a sinuous manner;

Figure 5 is a perspective view of the beam of Figure 4;

Figure 6 is a detailed view of one edge of a reinforcing web of a beam according to the invention; and

Figure 7 is a perspective view of a portion of the edge of a box section metal beam during the fabrication method of the invention, with one of the edge projections of the reinforcing web extending through a slot formed in the top face plate and twisted to achieve temporary retention of the face plate on the reinforcing web.

Referring first to Figures 1 to 3, there is shown in Figure 1 a beam of box section that is a complete semi-circle. That is to say, a top face plate 2 and a bottom face plate 3 are each semi-circular and annular in shape. That shape can be achieved with minimal stock wastage by constructing the semi-circle from six sectors which fit

together with laser-cut dovetail joints. The joint lines 4 between the adjacent sectors are welded or brazed together as a final step at the end of the fabrication process, as described below.

Parallel to each edge of the semi-circular face plates, and slightly spaced from that edge, is a row of laser-cut slots 5 depicted schematically in Figures 1 and 3 by broken lines. Each row of slots 5 follows a line which is the intended line of engagement between the respective face plate 2 or 3 and a reinforcing web 6. Each reinforcing web 6 is cut from a flat sheet of metal and has opposite parallel edges cut into a crenellated shape as shown in Figure 6. That crenellation forms the edges of the reinforcing plates into a linear array of edge projections 7 which are accurately cut so as to fit closely into the laser-cut slots 5. Some of the edge projections 7 pass completely through the slots and extend as lugs 8 above or below the associated face plates as shown in Figure 3, and are twisted so as to provide a temporary anchorage between the enforcing web and the face plates. That twisting is shown in Figure 3, and can readily be achieved by one man working with a pair of pliers only. Because the reinforcing webs extend close to the outer and inner curved edges of the semicircular beam, the resultant box section has considerable structural rigidity.

From the temporarily retained condition of Figure 3, the face plates 2 and 3 are welded or brazed to the supporting web 6 along the line of engagement therebetween. For example that line of welds or brazes could be a series of spot welds or spot brazes shown at 9 in Figure 3, along the inside edge between the abutting face plates and the reinforcing web. Alternatively the spot welds or spot brazes could be along the top and bottom faces of the respective face plates 2 and 3. The non-linear shape of the reinforcing web 6 gives the resulting beams optimum strength. Preferably it is at this stage, after assembly, that all excessive metal projecting above the outer faces of the face plates, including the twisted edge projections which form the temporary retention of the face plates on the reinforcing web, are removed by grinding.

Figures 4 and 5 show a similar construction of a fabricated beam in which the face plates 2 and 3 are generally long and rectangular, and the reinforcing web 6 runs

longitudinally down between them, passing from near one side to near the other side for maximum strength.

Figures 6 and 7 show in more detail the edge projections of the reinforcing web, and the direction in which the lugs 8 are twisted. Of course that twisting would not take place until the series of adjacent edge projections 7 had been presented up to the line of slots 5 in the associated face plate, and would then be bent over only if that edge projection extended far enough beyond the opposite side of the slot to enable it to be twisted by pliers.