Channel or U-shape strut is widely used in the construction industry. It is used to form vertical, horizontal or even angular framing. It may be hung from ceilings or attached to or embedded in walls or ceilings. Conventional struts are U-shape or channel shape, and the legs terminate in a rolled or inturned short radius circular fold so that the inturned legs terminate in an inwardly facing edge. The opening of the channel is thus restricted, and the legs are in the form of two continuous hooks. A wide variety of fasteners, hangers or brackets are used to support utilities, such as pipes, conduit, lighting, cable trays, and air conditioning or ventilation duct work, for example.
One of the most common adjustable hanging or supporting devices used is the common threaded rod. To connect the rod to the strut, a strut nut is normally employed. The strut nut has two parallel grooves in one surface which are designed to seat on the parallel inturned edges of the channel legs. The strut nut is usually a machined block rectangular in shape, so that it has a narrow dimension enabling it to be inserted into the channel between the inturned edge legs and rotated 90.degree. to span the edges of the legs. This normally has to be done by hand with the installer's fingers being inserted in the channel and twisting the nut. The nuts are often provided with unwieldy compression springs to push the nut from the bottom of the channel once seated to maintain the grooves on the inturned leg edges. Trying to thread a rod into the nut may compress the spring excessively causing the nut to slip and making the proper insertion of the rod difficult.
In some arrangements, particularly with square nuts, the nuts have to be inserted or threaded into the end of the channel. Square nuts are sometimes used with strut or channel that has a series of holes in the back, with the rod threaded in the nut extending downwardly through the hole. Sometimes the nuts are simply loose in the channel or strut, relying solely only on the weight of the load to keep them in place. Some systems use one kind of nut for the open side of the channel or strut, and another for the other or back of the channel.
A rod can also be secured to a strut using what is known as a hammerhead which seats on the outer turned portion of the strut legs. The rod extends through the hammerhead and through the bottom of the strut. Conventional nuts and optionally washers are threaded to bear against the hammerhead and bottom of the strut, respectively. Proper alignment or adjustment either axially of the rod or along the strut is difficult and time consuming. Final installation is also difficult and time consuming, requiring the positioning and tightening of at least two nuts. If adjustment is required, then loosening, repositioning and retightening are required.
Hammerheads and nuts can be utilized together with a common fastener such as a bolt. Such assemblies are used sometimes to splice strut sections or to act as stops for other type fasteners securing pipe, for example, to the strut. Examples of such assemblies are seen in prior U.S. Pat. No. 4,783,040 to Lindberg, et al.
There is a need for a fastening system which can firmly clamp a length of threaded rod to the strut and support the rod and any load on the strut for full compressive or tensile loading on the rod. There is also a need for a rod-strut connecting system which can easily be preassembled and inserted in the channel for adjustment, both along the strut, or axially of the rod, before being tightly clamped and affixed to the strut.