Tee-nuts are widely used in the manufacture and assembly of wood products such as wooden furniture and the like. The Tee-nuts are embedded in many positions in the wood. They provide a means for securing two pieces of a wooden product together or for securing items to a wooden product, by means of threaded fasteners fitting in the threaded sleeves of the Tee-nuts.
As is well known, such Tee-nuts are embedded in the work piece by means of a high speed setting machine, used on a production line. In many cases the setting machine will incorporate a feed mechanism consisting of a gravity feed slide, and a hopper. The hopper vibrates and introduces the Tee-nuts into the slide, and the Tee-nuts then slide down the slide under the influence of gravity until they reach the setting position of the apparatus. Typical Tee-nut setting machines are shown in U.S. Pat. Nos. 3,460,217, and 4,821,940. It is, however, well known that from time to time the Tee-nuts in the slide may jam. In addition, the movement of the Tee-nuts down and/or along the slide tends to cause relatively rapid wear, which increases the likelihood of feed problems. One of the principle causes of feed problems is the fact that the Tee-nuts are formed by stamping out of sheet metal. In the normal stamping operation, portions of the sheet metal are displaced out of the plane of the sheet metal, leaving minute imperfections or burrs. These burrs cause friction within the slide, which in itself can cause the Tee-nuts to jam. In addition, however, as these burrs pass along the slide they cause rapid wear and in fact form grooves in the metal of the slide. The burrs, and grooves may interfere with the free movement of the Tee-nuts in the slide so that miss-feeds become more frequent.
In another form of Tee-nut feed mechanism, the Tee-nuts are formed into a strip by means of, for example adhesive tape or the like. The location of the burrs on the Tee-nuts is such that they can interfere with the tape, and make it difficult to adhere to, or may cause it to tear.
Tee-nut setting machines may be designed to punch the Tee-nut downwardly into a work piece. Other designs of machines are known which punch the Tee-nut upwardly into a work piece. The problems created by the burrs on the Tee-nuts arise in both types of machines.
The location of the burrs is such that they occur on the edges of the flanges, which are formed around the threaded sleeve. In the past the only way to limit the formation of the burrs was to resharpen the tooling with which the Tee-nuts were made, at frequent intervals. This in turn shortens the life of the tooling dramatically, since repeated sharpening operations would cause it to wear down, more frequently than normal operation would require. Clearly, it would be desirable to provide a Tee-nut with a smooth facefree of burrs.
This, therefore, is one general objective of the invention.
Another alternative solution, however, is to provide a Tee-nut in which the burrs are still present, but in which the location of the sheet metal edges where the burrs are formed has been displaced, out of the plane of the metal surface of the flange so that the burrs no longer cause friction and abrasion in the feed slide. This, therefore, is another general objective of the invention.
Either the smoothing down of the burrs altogether, or the displacement of the burrs so that they are located in a position where they cannot cause friction and abrasion, will generally be satisfactory and provide a solution to the problem.