GB2125845A

GB2125845A - Reinforced elongate support member

Info

Publication number: GB2125845A
Application number: GB08318992A
Authority: GB
Inventors: James Charles Ollinger; Melvin Herbert Shaub
Original assignee: Armstrong World Industries Inc
Current assignee: Armstrong World Industries Inc
Priority date: 1982-07-19
Filing date: 1983-07-13
Publication date: 1984-03-14
Also published as: FR2530315A1; AU1245683A; DE3317705A1; GB2125845B; JPS5918845A; BE896777A; CA1202166A; GB8318992D0; NL8302124A; LU84810A1; DE8314392U1

Abstract

The strength and/or stiffness of a T-bar grid 2 having a double web 4 and cap 12 can be increased by coating the inside portion of the cap strip 12, or the bottom sides of the flanges 8 and 10 with a hot melt adhesive 16. Cooling sets the adhesive and results in the two parts of the grid member becoming a unitized structure. <IMAGE>

Description

SPECIFICATION Reinforced elongate support member and method of reinforcing an elongate support member The invention relates to a method of fabricating an elongate member, especially an elongate member suitable for use as a support member for a suspended ceiling, and reinforcing the ceiling support member by using an adhesive in conjunction with mechanical bonding.

United States Patent No. 4,206,578 is directed to a typical double web capped T bar grid. United States Patent No. 3,845,544 is directed to a method of forming sheet metal structures wherein the sheet metal components are glued together.

United States Patent No. 3,725,169 is directed to a sheet metal structure where two metallic sheets are bonded together. United States Patent No.

3,029,914 is directed to a sheet metal structure where two sheet metal structures have been adhesively joined together and the sheet metal structures have also been fabricated to a specific shape.

The invention is directed to a method of making a ceiling support member. The first step invoives the forming of an elongate T-shaped member with a vertical web and two horizontal flanges at the base of the web (with respect to the usual orientation of the finished member when used as a suspended ceiling support member) with one horizontal flange being disposed perpendicularly on each side of the vertical web.

A strip of material is applied to the underside of both horizontal flanges with the side edge portions of the strip of material extending beyond the side edges of the horizontal flanges. Each side edge portion of the strip of material is wrapped around and slightly over the edge of the horizontal flange, encasing the bottom and edges of the horizontal flanges in the strip of material. According to the invention, an adhesive material is applied to the interface of the horizontal flanges and the strip of material prior to their assembly. This adhesive is heat activated after the product is mechanically assembled to bond the strip of material and the inverted T-shaped member together.

The invention also provides a structure which results from the application of the method according to the invention to form a product.

It is an object of the invention to provide a method by which it is possible to add strength or stiffness to a T bar grid fabricated with a double web and cap system. More particularly, it is desirable to be able to add stiffness in terms of both load weight per unit deflection and torque stiffness against twisting. The addition of strength can be achieved-by coating the inside portion of the cap strip or the bottom sides of the flanged areas which attach to the cap strip with a "hot melt" adhesive. The precoated metal is assembled in the rolling mill by existing techniques. After assembly, the fabricator applies heat to the T bar which activates the adhesive and permits the adhesive to flow or wet the surfaces which contact one another. Cooling sets the adhesive and results in the grid gaining a "unitized" structure.Heat may be applied by contacting the grid with a hot surface, for example, hot rolls or by passing the grid through a heat tunnel using infrared lights. Either heating system has proved capable of use with conventional hot melt adhesives. Testing has also shown that reheating the grid to approximately 1 400F (600C) will soften the adhesive, but the original strength returns on cooling. A number of advantages result from the utilisation of the process herein. It is possible now to reduce the number of bends incorporated in the cross-sectional configuration.

Perhaps lighter gauge metals may now be used while attaining the same properties as current grid structures not containing the hot melt adhesive.

There is added value to the grid in that the customer can feel by a comparison the improved stiffness of the grid herein as compared to other grid structures not containing the hot melt adhesive, and the greater stiffness of the T bars makes them easier to handle during installation of the ceiling.

One form of elongate member constructed in accordance with the present invention, and a method of constructing it, will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is an end elevation view of the member; and Fig. 2 is perspective view of the member.

A grid member for the supporting grid of a suspended ceiling is conventionally formed by taking a piece of sheet metal of .010" to .013" to mm) thickness steel and through the use of conventional metal forming technique converting it into an elongate member of generally T-shaped cross-section, such as the member indicated generally by the reference numeral 2 in Fig. 1. The single piece of metal is basically bent in its centre to form a vertical rib form with a web 4. The member 2 is shown as provided with an enlarged top 6 but it could stead be simply formed by bending the piece of sheet metal at its midpoint with a 1 800 fold. The ends of the piece of sheet metal are bent out at a 90" angle from each side of the vertical web 4 to form two horizontal flanges 8 and 10.These flanges 8 and 10 are disposed perpendicularly to the vertical web 4 at the base of the web as shown in Fig. 1.

Conventionally, a cap strip of material 12 is applied to the horizontal flanges of the grid both for a decorative effect and also to cover up the gap that exists between the two layers of material forming the vertical web 4 of the member 2. The cap strip 12 is of .010" ( mm) thickness steel and is slightly wider than the combined width of the horizontal flanges 8 and 10 as measured from the free edge of one horizontal flange to the free edge of the other horizontal flange. Through a conventional metal forming technique the side edge portions 14 of the strip of material 1 2 are folded around the edges of the horizontal flanges 8 and 10 and are placed slightly above the top edges of the horizontal flanges to form the structure shown in Fig. 1.Consequently the bottom of the member 2 and the edges of the horizontal flanges 8 and 10 are encased in a strip of material.

The parts of the construction described above have previously been proposed and are disclosed in United States Patent No. 4,206,578. The structure shown in Fig. 1 differs from that previous proposal in that a hot melt adhesive is applied to either the undersides of the flanges 8 and 10 or the upper surface of the strip of material 1 2 before those elements are assembled together. One form of hot melt adhesive that is suitable is the adhesive of Roberts Consolidated Industries sold under the trade name Superstick. After the adhesive coating is applied, the flanges 8 and 10 and the piece of material 12 are assembled in a conventional manner as described above.Instead of a hot melt adhesive, any adhesive or even solder could be used which would tend to bond together the two elements forming the horizontal flange of the inverted T shaped member. If a hot melt adhesive is used, the adhesive would be heated to an appropriate temperature, which might, for example, be around 1 050C, which will soften the adhesive and upon its cooling the adhesive will be bonded to the metal surfaces and consequently bond together the metal surfaces.

As a result of the use of the adhesive, the torque stiffness is noticeably improved compared with a conventional support member of similar construction. If one were to take the conventional capped structure, and grasp it at both ends and twist it in the directions shown by the arrows in Fig. 2, there would be an application of torque to the structure and this would provide an indication of the torque stiffness of the structure. The presence or absence of the adhesive makes a very noticeable change in the torque stiffness and there is a substantial increase in the torque stiffness of the inverted T-shaped member using an adhesive at the interface between the bottoms of the horizontal flanges 8 and 10 and the top of the piece of material 12.The placement of the adhesive can also affect the load strength which is the load the runner will support on its horizontal flanges.

As shown in Fig. 1 , the adhesive 1 6 is placed over the whole surface of the bottom of the horizontal flanges 8 and 10 and even extends partly between the halves of the vertical web 4.

Instead, the adhesive may be applied only between the halves of the vertical web and not on the horizontal flanges, or only on the outer edge portions of the horizontal flanges and not on the rest of the horizontal flanges (the central region of the flanges) or between the halves of the vertical web. Placing the adhesive only between the halves of the vertical web has been found to give improved torque strength, but no appreciable improvement in vertical load strength while placing the adhesive only at the outer edge portions of the horizontal flanges increases both torsional and vertical load strengths and stiffnesses.

Claims

1. A method of making an elongate support member comprising the steps of: forming an elongate T-shaped member with a web and two horizontal flanges along one edge of the web with one horizontal flange disposed perpendicularly on each side of the web; applying a strip of material to the face of both horizontal flanges that is away from the web with side edge portions of the strip of material extending beyond the free edges of the horizontal flanges; and wrapping each side edge portion of the strip of material around and over the respective edge of the horizontal flanges in such a way that the said face and the side edges of the horizontal flanges are encased in the strip of material; wherein an adhesive material is applied to the interface between the flanges and the strip of material prior to their assembly together.

2. A method as claimed in claim 1, wherein the said adhesive material is a heat-activated adhesive material, comprising the step of heatactivating the adhesive material after the strip of material has been wrapped around the edges of the horizontal flanges.

3. A method of making an elongate support member, substantially as hereinbefore described with reference to the accompanying drawings.

4. An elongate member suitable for use as a support member of a suspended ceiling, comprising: an elongate element of T-shaped cross-section having a web with two flanges along one edge of the web with one flange disposed perpendicularly on each side of the web; a strip of material positioned against the faces of the horizontal flanges away from the web with the edges of the strip of material extending around and slightly over the outer edges of the flanges; and an adhesive coating at least in the region of the interface of the flanges and the strip of material.

5. A member as claimed in claim 4, wherein the T-shaped element is formed of one piece of material bent in half to form the web of two thicknesses of material and then bent near its edges to form the flanges disposed perpendicularly to the web.

6. A member as claimed in claim 5, wherein the adhesive coating is at the interface of the flanges and the strip of material and further partly between the two thicknesses of the material forming the web.

7. A member as claimed in claim 5, wherein the adhesive coating is only between the two thicknesses of material forming the web.

8. A member as claimed in claim 4 or claim 5, wherein the adhesive coating is only at the interface of the flanges and the strip of material at the ends of the horizontal flanges.

9. An elongate member substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.