Patent Publication Number: US-2015086261-A1

Title: Miter coupling and method

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to techniques and devices for welding or otherwise joining metal support structures together. More specifically, the present invention includes a miter coupling and a method of using such a miter coupling to join together a pair of metal tubes at a desired angle. 
     Typically, when charged with the task of joining together a pair of metal tubes having a square cross section (square metal tubes), a metal worker must cut an end of each tube to the desired angle, weld the four sides of the tubes together, and then grind the weld down so that the joint has a smooth outer surface. This procedure, which is used during the production of many types of products, such as supports, frames, scaffolding, and the like, is very labor intensive and results in a joint that has inherently limited strength. Alternatively, when it is necessary to join the square metal tubes to form a 90 degree angle, instead of cutting each tube to form a 45 degree angle and welding the cut edges together, a metal worker may simply weld the open end of one tube to the side of the second tube adjacent the open end thereof. However, this method leaves an open end of the second tube exposed (thus requiring an end cap in many applications), further requires a grinding of the weld, and again results in an inherently weak joint. 
     Therefore, it would be desirable to provide a device and method for welding together two square metal tubes at a desired angle in a way that would provide for a high strength joint, and would be less labor intensive and less expensive than other methods. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a miter coupling is provided, together with a method for using the miter coupling to join a pair of square metal tubes at a desired angle using a welding process. The miter coupling, in a preferred embodiment, comprises a single piece of metal formed into a shape that is adapted to receive the ends of two square metal tubes at a desired angle. The miter coupling is shaped to form a pair of parallel elbow members, where the elbow members are formed into a desired angle, and the elbow members are interconnected by a cross support. 
     The square metal tubes used in conjunction with the miter coupling have ends that are cut in a transverse, 90 degree direction with respect to the longitudinal direction of the tube. The elbow members of the miter coupling have a first section pointing in a first direction, and a second portion pointing in a second direction. Each elbow section is adapted to receive the end of a square metal tube oriented in the direction specified by that section. In use, the end of a first square metal tube is positioned within the first section of the elbows, and the end of a second square metal tube is positioned within the second section of the elbows. Welds are placed at the distal ends of the elbow sections, in a transverse direction with respect to the longitudinal direction of the square metal tubes. Thus, four welds are generated at the distal ends of the elbows. Additionally, fifth weld may be added to the seam where the square metal tubes contact each other. If necessary for additional strength, other welds may be added. 
     This device and process allows a pair of square metal tubes to be attached, end to end, at any desired angle in a manner that is less expensive, less time consuming and labor intensive, and which provides a stronger joint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG. 1  is a perspective view of a prior art mitered joint between two square metal tubes; 
         FIG. 2  is a perspective view of a prior art Tee joint between two square metal tubes; 
         FIG. 3  is a top view of one embodiment of a miter coupling in a flat plane, prior to being formed into a three dimensional shape; 
         FIG. 4  is a perspective view of one embodiment of a miter coupling; 
         FIG. 5  is an exploded view of one embodiment of a miter coupling with two square metal tubes at a 90 degree angle; 
         FIG. 6  is a perspective view of one embodiment of a miter coupling joining two square metal tubes at a 90 degree angle; 
         FIG. 7  is an exploded view of one embodiment of a miter coupling with two square metal tubes at an obtuse angle; 
         FIG. 8  is a perspective view of one embodiment of a miter coupling joining two square metal tubes at an obtuse angle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention includes a miter coupling device and method for joining together two square metal tubes at a desired angle.  FIGS. 1 and 2  illustrate common methods for joining square metal tubes at a 90 degree angle.  FIG. 1  shows two square metal tubes, each having one end cut at a 45 degree angle, wherein the square metal tubes are joined to form a 90 degree angle. In order to join the square metal tubes in accordance with  FIG. 1 , the tubes are cut at the proper angle, welded around the four seams, and then the welds are ground down to form a smooth seam. This method is time consuming, labor intensive and expensive. Cutting the tubes to the proper angles consumes valuable time and labor, as does the grinding operation to smooth the welds for a proper finish. Additionally, the strength of the joint produced by this method is limited.  FIG. 2  shows an alternate joint and method, wherein the square metal tubes are cut in a transverse direction with respect to the longitudinal direction of the tube, and the end of a first tube is welded to the side of a second tube adjacent an open end of the second tube (a standard T joint). This method also produces a joint having limited strength, and requires that an end cap be inserted into the open end of the second tube. 
     The miter coupling  2  of the present invention, in a preferred embodiment, comprises a single piece of metal formed into a shape that is adapted to receive the ends of two square metal tubes  4  at a desired angle, as shown in  FIGS. 4-8 . The miter coupling  2  is shaped to form a pair of parallel flat elbow members  6 , where the elbow members are formed into a desired angle, and the elbow members are interconnected by a cross support  8 . The miter coupling  2  may be manufactured by cutting or stamping a shape from a flat piece of metal, as shown in  FIG. 3 . Then, the miter coupling  2  may be shaped into the 3-dimensional article shown in  FIG. 4 , by bending the elbow members  6  at a 90 degree angle with respect to the cross support  8 , as shown. 
     The square metal tubes  4  used in conjunction with the miter coupling  2  have ends that are cut in a transverse, 90 degree direction with respect to the longitudinal direction of the tube. The elbow members  6  of the miter coupling  2  each have a first section  10  pointing in a first direction, and a second portion  12  pointing in a second direction. Corresponding elbow sections are adapted to receive the end of a square metal tube  4  oriented in the direction specified by that section  10 ,  12 , as shown in  FIGS. 5-8 . In use, the end of a first square metal tube  4  is positioned within the first section  10  of the elbow members  6 , and the end of a second square metal tube  4  is positioned within the second section  12  of the elbow members  6 . Welds  14  are placed at the distal ends  16  of the elbow sections  10 ,  12 , in a transverse direction with respect to the longitudinal direction of the square metal tubes  4 . Thus, four welds  14  are generated at the distal ends  16  of the elbow sections  10 , 12 . Additionally, fifth weld  14  may be added to the seam where the square metal tubes  14  contact each other. If necessary for additional strength, other welds may be added at any other seam or contact points between the miter coupling  2  and a square metal tube  4 . 
     The miter coupling  2  and the square metal tubes  4  may be made from any suitable metal, although carbon steel, stainless steel and aluminum are particularly suitable for this application. Additionally, various types of welds and welding techniques may be utilized, including but not limited to MIG (metal inert gas) or TIG (tungsten inert gas) welding. 
     This arrangement provides a fast, strong, and efficient method for attaching a pair of square metal tubes at any desired angle, which avoids the steps of cutting the tubes at various angles and grinding the welds to form a smooth finish. 
     Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein. All features disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.