Structural steel members lose their load bearing capacity quickly when exposed to high heat. As a result, insurance companies, building codes, and owners require fire protection on structural steel. Passive type fireproofing is employed to prevent premature collapse and eliminate extensive property damage.
Typical passive fireproofing entails the application of a material to the surface of the steel that will insulate the steel from the effects of fire. Historically, endothermic materials have been used to a large extent and are still in use today, such as gypsum, concrete and other cementitious products. Fireproofing material retards both temperature acceleration and flame spread, thus providing the necessary time for fire fighters to either gain control of a fire or to achieve safe shutdown of key areas in a structure or plant.
Fireproofing material is applied to various thicknesses. However, to achieve maximum protection in industrial and commercial settings, appropriate material thickness can only be achieved by way of mechanical reinforcement such as lath and corner beads. When applying a fireproofing material, it is generally desirable to provide a lath on the surface of the steel. The lath provides reinforcement for the fireproofing material and also attaches the fireproofing material to the steel surface.
There are a number of different metal laths being used for fireproofing. One common type is expanded metal lath. Another group of metal laths is wire fabric laths. Within this group, there are woven wire laths and welded wire laths which may be referred to as wire mesh.
At the corners, a corner bead is normally provided since it is either required by building codes, or by the builder or the owner to obtain a desired architectural result. The most commonly used corner beads are bent into a V-shape of approximately 70 degrees to 80 degrees. The general type of corner bead used in fireproofing is made from a grid of wires welded together, bent into a V-shape with a continuous longitudinal wire at the nose to act as the guide to form the corner.
The prior art welded wire corner beads generally consist of a series of sinusoidal wires and a series of longitudinal wires resistance welded together at their intersections and may also have a plastic cover around the nose wire.
When the corner bead is installed correctly, it becomes the depth gage or screed that will regulate the depth of the fireproofing material at the corners. In the art of installing corner bead for fireproofing structural steel, prior approaches conventionally comprise a v-shaped plastic nose corner bead having adjustable legs (flanges). The longitudinal base wires of the v-shaped corner bead are attached with a tie wire either onto a metal lath or onto a wire mesh, and further attached to the steel member to be fireproofed. It is also common to employ steel pins that have been embedded into the steel member, to anchor the corner bead and the lath.
The vertex of a V-shaped corner bead is represented by the nose wire, which may be covered in plastic. To establish the correct fireproofing thickness, one must shrink or expand the distance between the legs (flanges) of the corner bead defined by the vertex to establish the correct height of the vertex. Using this technique, the alignment of the corner bead with the adjacent surface is difficult and great skill and substantial time is required to install the corner bead for fireproofing structural steel.
Accordingly, the need exists for an improved corner bead installation method to avoid inaccuracy in gauging the thickness of the fireproofing material and to allow easy and efficient installation, and apparatus to achieve the said method. The clip of the present invention provides positional accuracy and greatly reduces labor for installing the corner bead to the steel member.
USPTO Backgrounds
USPTO Backgrounds