Tensionable threaded rebar bolt

Abstract

Embodiments of the present invention comprise hot-rolled threaded rebar bolts that are less costly to manufacture but maintain the same or similar structural benefits of more costly manufactured bolts presently in use. One embodiment of the invention is directed generally to bolts for use in mine roof support applications, or other structural support applications, that are manufactured by hot-rolling a steel bar into a threaded bolt. Hot-rolling threads onto a bar results in eliminating costly processes to prepare the rebar for threading and mechanically threading the rebar via standard thread-cutting schemes, and creates bolts efficiently in large quantities that have semi-continuous threads and minor or no longitudinal ribs. The threaded rebar bolts are rotatable in cured resin nuts, making them tensionable, and can be adapted for use with a columnar resin nut disposed in bore holes in geological structures.

What is claimed is: 
     
         1 . An apparatus, comprising:
 a threaded rebar shaft formed from a hot-rolling process, comprising a substantially cylindrical core, semi-continuous threads comprising a first thread section and a second thread section, and longitudinal areas between the first thread section and the second thread section that have longitudinal area heights that are substantially the same height as a core surface of the substantially cylindrical core; and wherein the threaded rebar shaft is capable of having a head operatively coupled to an end of the threaded rebar shaft to form a fastener.   
     
     
         2 . The apparatus of  claim 1 , wherein the threaded rebar shaft is rotatable in a resin nut formed around the substantially cylindrical core and semi-continuous threads. 
     
     
         3 . The apparatus of  claim 1 , wherein the longitudinal area height is even with or below the core surface of the cylindrical core. 
     
     
         4 . The apparatus of  claim 1 , wherein the first thread section and the second thread section each span at least 130 degrees of the circumference of the threaded rebar shaft. 
     
     
         5 . The apparatus of  claim 1 , wherein the height of the semi-continuous threads tapers to the core surface of the cylindrical core of the threaded rebar shaft at the longitudinal areas between the first thread section and the second thread section. 
     
     
         6 . The apparatus of  claim 1 , wherein the threaded rebar shaft is formed with the longitudinal area extending substantially the entire length of the threaded rebar shaft. 
     
     
         7 . The apparatus of  claim 1 , further comprising semi-continuous threads that extend along substantially the entire length of the threaded rebar shaft. 
     
     
         8 . The apparatus of  claim 1 , wherein the threaded rebar shaft has a threads per inch to outer thread diameter ratio in the range of approximately 2.5 to 4. 
     
     
         9 . The apparatus of  claim 1 , wherein the semi-continuous threads and longitudinal areas allow for enhanced mixing through rotational turbulence of resin and catalyst to form a resin nut. 
     
     
         10 . The apparatus of  claim 1 , further comprising a shaft core diameter for a three-fourths inch bolt of approximately 0.680 inches. 
     
     
         11 . The apparatus of  claim 1 , further comprising an external thread diameter for a three-fourths inch bolt of approximately 0.750 inches. 
     
     
         12 . The apparatus of  claim 1 , further comprising a thread width of approximately 0.062 to 0. 125 inches. 
     
     
         13 . A apparatus, comprising:
 a threaded rebar shaft formed from a hot-rolling process, comprising a substantially cylindrical core, a first thread section and a second thread section, and longitudinal areas between the first thread section and the second thread section that have longitudinal area heights that are substantially the same height as a core surface of the substantially cylindrical core.   
     
     
         14 . The apparatus of  claim 13 , wherein the first threaded section and second threaded section are formed to comprise a semi-continuous thread. 
     
     
         15 . The apparatus of  claim 13 , wherein the threaded rebar shaft is rotatable in a resin nut formed around the substantially cylindrical core, first thread section, and second thread section. 
     
     
         16 . The apparatus of  claim 13 , wherein the first thread section, the second thread section, and the longitudinal areas allow for enhanced mixing through rotational turbulence of resin and catalyst to form a resin nut. 
     
     
         17 . A apparatus, comprising:
 a threaded rebar shaft formed from a hot-rolling process, comprising a substantially cylindrical core, a first thread section and a second thread section, and longitudinal areas between the first thread section and the second thread section that have longitudinal area heights that are below the core surface of the cylindrical core.   
     
     
         18 . The apparatus of  claim 19 , wherein the first threaded section and second threaded section are formed to comprise a semi-continuous thread. 
     
     
         19 . The apparatus of  claim 17 , wherein the threaded rebar shaft is rotatable in a resin nut formed around the substantially cylindrical core, first thread section, and second thread section. 
     
     
         20 . The apparatus of  claim 17 , wherein the first thread section, the second thread section, and the longitudinal areas allow for enhanced mixing through rotational turbulence of resin and catalyst to form a resin nut.