Patent Application
20120180543
This invention relates generally to the field of threaded rebar, and more particularly embodiments of the invention relate to methods and systems of manufacturing threaded rebar using standard rebar tooling and equipment.
Reinforcing metal bars (hereinafter “rebar”) are bars, often made of steel, having protruding ribs, which are typically used to reinforce concrete structures. The protruding ribs can take a number of shapes or geometries, including diamond shaped, X-shaped, V-shaped, etc. During the construction of bridges, buildings, and similar structures the rebar is often placed in a concrete form and concrete is poured around the rebar. The ribs in the rebar help to anchor the rebar within the concrete. The rebar adds strength to the structures in which it is used.
In typical rebar manufacturing heated bar stock is fed through rolls to form the cylindrical shaped rebar and protruding ribs. In some applications the ribs on the rebar can be manufactured to form threads that extend around the periphery of the core of the rebar. In such threaded rebar, the external threads are able to receive a nut, collar, coupling, or other apparatus, which has internal threads that engage the external threads on the threaded rebar. Threaded rebar can be used to attach the ends of successive rebar pieces together using a coupling that mates with the threads on the ends of successive pieces of rebar and transfers loads within casted concrete structures, precast concrete structural members, etc. Threaded rebar can also be used to secure metal structures to concrete and rebar foundations (i.e., lampposts, bridges, etc.). Furthermore, threaded rebar can be used as bolts, for example in such applications as rock bolts in mining operations.
Standard rebar and threaded rebar can be manufactured by cold rolling or hot rolling metal billets. In both processes a billet is fed between two cylindrical rolls that form the billet into the rebar. The cylindrical rolls have grooves with notches (i.e. knurls) formed therein to receive a bar and form the core rebar shape and protruding ribs as the bar passes through the rolls. In some rebar manufacturing processes flat dies can replace the cylindrical rolls. The flat dies also have grooves with notches formed therein, and are spaced apart to receive a bar that is rotated between them in order to create threads or ribs along the length of the rebar or a portion thereof.
When threaded rebar is manufactured using cold rolling, the bar is passed through the rolls below the recrystallization temperature of the metal, which increases the strength of the metal, improves the surface finish, and results in tighter tolerances on the rebar core and threaded ribs. However, cold rolling also causes work hardening of the metal, which results in the metal becoming brittle, and thus, more susceptible to cracking at the base of the formed threaded ribs. These problems are particularly acute where threaded rebar is used with a nut or a collar, and in these applications the cold rolled threaded rebar is susceptible to premature thread failure.
In a hot rolling process the bar is passed through the rolls above the recrystallization temperature of the metal, which prevents work hardening that can lead to thread failures. Threaded rebar made from hot rolling results in threaded rebar having uniform tensile strength and elongation characteristics, as well as ribs that are less likely to crack because they are an integral part of the bar and not work hardened. Furthermore, hot rolling allows for the use of steels with higher tensile strength, and hot rolling processes do not require additional bar peeling or swaging of the threaded rebar. The problems with threaded rebar manufactured through hot rolling include the formation of ribs that are coarse and unable to be used in applications requiring tight thread tolerances.
Threaded rebar can also be manufactured by forming standard rebar (utilizing either cold rolling or hot rolling), and thereafter, machining a portion of the rebar to add the desired threads. Machined threads result in tight tolerances; however, machined threads are weaker than cold rolled threads. Moreover, manufacturing threaded rebar by machining the threads significantly increases the manufacturing costs associated with the threaded rebar, as it requires multiple processing steps, as well as time consuming and expensive handling.
There are a number of problems associated with manufacturing threaded rebar using cylindrical rolls in a hot rolling process. Cylindrical rolls are used to form square, cylindrical, or other shaped bars into circular rebar with transverse threads formed into opposite sides of the circular rebar. The transverse threads formed are discontinuous and in some cases not aligned if the cylindrical rolls are not properly synchronized. Moreover, in these processes, two longitudinal ribs are formed along the length of the threaded rebar, which is a result of the excess metal from inconsistencies in the shape of the bar as well as the gap between the cylindrical rolls used to form the threaded rebar. The gap between the rolls is necessary so that the rolls do not rub against each other during the rolling process, since such rubbing may result in frictional heat that could damage the rolling system. The longitudinal ribs that result from processing prevent the threaded rebar from being freely rotatable within a nut or other mating internally threaded coupling. In order to manufacture threaded rebar without longitudinal ribs, additional steps are necessary that machine or shear off the longitudinal ribs. In some processes only the longitudinal ribs are machined off, however, in other processes the entire face of the bar with the longitudinal rib is machined into a flat surface. In still other processes the longitudinal ribs are sheared off using saw-tooth rotary dies, which are spaced apart to shear off sections of the longitudinal ribs located between the transverse ribs on the threaded rebar. In other processes the longitudinal ribs are ground off using a smooth groove rotary die that grinds down the longitudinal ribs. All of these methods present significant drawbacks, including additional processing steps, additional processing time, and additional processing equipment, all of which increase the cost of manufacturing the threaded rebar.
Continuous threaded rebar is more desirable than discontinuous threaded rebar since it increases the tensile strength of the rebar due to the increased surface area contact with the mating nut, threaded bore hole, etc. In some embodiments of the invention, a continuous or significantly continuous transverse rib can be produced through hot or cold rolling processes. However, in order to produce a continuous or significantly continuous spiral transverse rib more than two opposing dies are used (i.e. three or four opposing dies that form the threaded rebar at the same time), whereas in standard rebar manufacturing only two dies are used. The need for more than two dies results in increased equipment costs and increased die set-up costs when changing the tooling between standard rebar manufacturing equipment and continuous or significantly continuous threaded rebar manufacturing equipment. A continuous transverse rib can also be produced on bar stock using processes other than rolling, but these processes are also more time consuming and costly because of the additional equipment costs and tooling set-up times.
Therefore, there is a need to develop methods and systems that can be used to produce threaded rebar at reduced costs and in shorter manufacturing times.
Embodiments of the present invention address the above needs and/or achieve other advantages by providing systems and methods that are used to create threaded rebar with substantially continuous threads using a rolling process, wherein a majority of the circumference of the threaded rebar is covered by the discontinuous threads; and wherein no additional steps are required to remove longitudinal ribs in the threaded rebar.
Embodiments of the invention comprise forming a billet from molten steel and hot rolling the billet to reduce the cross-sectional area of the billet. Thereafter, the billet is hot rolled into a lead pass bar having a cross-sectional area comprising a reduced width dimension located adjacent to the center longitudinal axis of the bar. In one embodiment of the invention, the billet can be formed into a bar having a cross-sectional area in the shape of an hourglass or peanut (i.e., the hourglass lead pass bar) by feeding the billet through a first set of rolls (i.e., lead pass roll set). After the hourglass lead pass bar is formed, it is passed through a second set of rolls (i.e., threaded pass roll set) in order to form the substantially continuous threaded rebar without longitudinal ribs. As explained in further detail below the cross-sectional area of the lead pass bar helps to produce a substantially continuous threaded rebar product without longitudinal ribs using standard rebar manufacturing tooling and equipment.
Embodiments of the invention comprise methods of manufacturing threaded rebar and products made from the methods of manufacturing threaded rebar. One embodiment of the invention is a method of manufacturing threaded rebar comprising providing a lead pass bar comprising a body extending along a longitudinal axis, wherein at least one portion of the body has a cross-section defining a plane that intersects the longitudinal axis, wherein a first part of the plane has a first width and a second part of the plane has a second width and wherein the first width is not equal to the second width; and forming a threaded rebar from the lead pass bar.
In further accord with another embodiment of the invention, the plane has a height dimension substantially centered along the longitudinal axis, wherein the first part of the plane is located vertically adjacent to the longitudinal axis and the first width is smaller than the second width of the second part of the plane located vertically distal from the longitudinal axis.
In another embodiment of the invention, the first part of the plane is vertically adjacent to the longitudinal axis and the first width is smaller than the second width of the second part of the plane and a third width of a third part of the plane, wherein the second part of the plane and third part of the plane are located vertically distal from the longitudinal axis.
In yet another embodiment of the invention, the first part of the plane is rectangular in shape and the second part of the plane and third part of the plane are at least approximately circular, wherein the second part of the plane is located vertically above the first part of the plane and the third part of the plane is located vertically below the first part of the plane.
In still another embodiment of the invention, the plane is peanut shaped or the plane is hourglass shaped.
In further accord with another embodiment of the invention, the first width of the first part of the plane is less than or equal to ninety percent of the second width of the second part of the plane.
In another embodiment of the invention, providing the lead pass bar comprises forming the lead pass bar from a billet. In yet another embodiment of the invention, the lead pass bar is formed by rolling the billet though a lead pass roll set having opposed lead pass grooves that create the cross-section defining the plane that intersects the longitudinal axis comprising the first part of the plane having the first width and the second part of the plane having the second width.
In still another embodiment of the invention, the opposed lead pass grooves have a depth in the range of 0.178 and 0.2705 inches, a radius of curvature in the range of 0.1470 and 0.7442 inches, and a corner radius of curvature in the range of 0.3378 and 0.757 inches, all inclusive.
In further accord with an embodiment of the invention, the lead pass roll set has a first lead pass roll spaced apart from a second lead pass roll to create a gap between the first lead pass roll and the second lead pass roll in a range of 0.005 and 0.250 inches inclusive.
In another embodiment of the invention, the lead pass bar is formed through hot rolling at a temperature in the range of 1650 degrees to 2250 degrees Fahrenheit inclusive. In yet another embodiment of the invention, the lead pass bar is formed through rolling at a rate in the range of 300 to 2600 feet per minute inclusive.
In still another embodiment of the invention, forming the threaded rebar comprises rolling the lead pass bar though a threaded pass roll set having opposed threaded pass grooves with opposed threaded pass knurls in the opposed threaded pass grooves.
In further accord with an embodiment of the invention, the opposed threaded pass grooves have a depth in the range of 0.2015 and 0.386 inches, a groove radius of curvature in the range of 0.2358 and 0.4270 inches, and a corner radius of curvature in the range of 0.0355 and 0.0447 inches, all inclusive. In another embodiment of the invention, the opposed threaded pass knurls have a depth in the range of 0.040 and 0.0727 inches, and a knurl radius of curvature in the range of 0.2989 and 0.5002 inches, all inclusive.
In yet another embodiment of the invention, the threaded pass roll set has a first threaded pass roll spaced apart from a second threaded pass roll to create a gap between the first lead pass roll an the second lead pass roll in a range of 0.005 and 0.250 inches inclusive.
In still another embodiment of the invention, the threaded rebar is formed through hot rolling at a temperature in the range of 1650 degrees to 2250 degrees Fahrenheit inclusive. In further accord with an embodiment of the invention, the threaded rebar is formed through rolling at a rate in the range of 300 to 2600 feet per minute inclusive.
In another embodiment of the invention, forming the billet comprises melting scrap steel into molten metal in an electric arc furnace; transferring the molten metal from the electric arc furnace to a ladle for refining; transferring the molten metal from the ladle to a tundish; depositing the molten metal from the tundish into a water cooled mold to form a strand of steel; passing the strand of steel through rollers and water sprayers to solidify the strand of steel into the billet; cutting the billet into the desired lengths; heating the billet in a reheating furnace for rolling; and passing the billet through one or more rolling mill stands to reduce the cross-sectional area of the billet.
In yet another embodiment of the invention, the lead pass bar comprises the height dimension in the range of 0.8210 to 1.378 inches, a first part width dimension in the range of 0.4080 and 0.6490 inches, and a second part width dimension in the range of 0.3110 and 0.579 inches, all inclusive.
In still another embodiment of the invention, the method further comprises cutting grooves into a lead pass roll set for forming the lead pass bar. In further accord with an embodiment of the invention, the method further comprises installing a lead pass roll set. In another embodiment of the invention, the method further comprises cutting opposed threaded pass grooves into a threaded pass roll set for forming the threaded rebar, and cutting a plurality of opposed threaded pass knurls into the opposed threaded pass grooves of the threaded pass roll set for forming the threads of the threaded rebar.
In yet another embodiment of the invention, the method further comprises installing a threaded pass roll set for forming the threaded rebar. In still another embodiment of the invention, the method further comprises synchronizing a first threaded pass roll and a second threaded pass roll in a threaded pass roll set in order to substantially align top threads and bottom threads on the threaded rebar.
In further accord with an embodiment of the invention, forming the threaded rebar comprises forming the threaded rebar with substantially continuous threads. In another embodiment of the invention, a single thread of the substantially continuous threads covers ninety percent or more of the circumference of the threaded rebar.
Another embodiment of the invention comprises an apparatus for manufacturing threaded rebar. The apparatus comprises a lead pass roll set comprising a first lead pass roll and a second lead pass roll, wherein the first lead pass roll and the second lead pass roll have opposed lead pass grooves that form a lead pass bar having a body extending along a longitudinal axis, wherein at least one portion of the body has a cross-section defining a plane that intersects the longitudinal axis, wherein a first part of the plane has a first width and a second part of the plane has a second width and wherein the first width is not equal to the second width.
In further accord with an embodiment of the invention, the plane has a height dimension substantially centered along the longitudinal axis, wherein the first part of the plane is located vertically adjacent to the longitudinal axis and the first width is smaller than the second width of the second part of the plane located vertically distal from the longitudinal axis.
In another embodiment of the invention, the first part of the plane is vertically adjacent to the longitudinal axis and the first width is smaller than the second width of the second part of the plane and a third width of a third part of the plane, wherein the second part of the plane and third part of the plane are located vertically distal from the longitudinal axis.
In yet another embodiment of the invention, the first part of the plane is rectangular in shape and the second part of the plane and third part of the plane are at least approximately circular, wherein the second part of the plane is located vertically above the first part of the plane and the third part of the plane is located vertically below the first part of the plane.
In still another embodiment of the invention, the plane is peanut shaped or the plane is hourglass shaped. In further accord with an embodiment of the invention, the first width of the first part of the plane is less than or equal to ninety percent of the second width of the second part of the plane.
In another embodiment of the invention, the apparatus further comprises one or more mill stands, wherein the one or more mill stands receive a billet with a cross-sectional area and reduce the cross-sectional area of the billet, and wherein the lead pass roll set uses the billet to form the lead pass bar.
In yet another embodiment of the invention, the apparatus further comprises a threaded pass roll set, wherein the threaded pass roll set forms a threaded rebar from the lead pass bar.
In still another embodiment of the invention, the opposed lead pass grooves have a depth in the range of 0.178 and 0.2705 inches, a radius of curvature in the range of 0.1470 and 0.7442 inches, and a corner radius of curvature in the range of 0.3378 and 0.757 inches, all inclusive.
In further accord with an embodiment of the invention, the first lead pass roll is spaced apart from the second lead pass roll to create a gap between the first lead pass roll and the second lead pass roll in a range of 0.005 to 0.250 inches inclusive.
In another embodiment of the invention, the threaded pass roll set comprises a first threaded pass roll and a second threaded pass roll, wherein the first threaded pass roll and the second threaded pass roll have opposed threaded pass grooves with opposed threaded pass knurls in the opposed threaded pass grooves.
In yet another embodiment of the invention, the opposed threaded pass grooves have a depth in the range of 0.2015 and 0.386 inches, a groove radius of curvature in the range of 0.2358 and 0.4270 inches, and a corner radius of curvature in the range of 0.0355 and 0.0447 inches, all inclusive.
In still another embodiment of the invention, the opposed threaded pass knurls have a depth in the range of 0.040 and 0.0727 inches, and a knurl radius of curvature in the range of 0.2989 and 0.5002 inches, all inclusive.
In further accord with an embodiment of the invention, the first threaded pass roll is spaced apart from the second threaded pass roll to create a gap between the first threaded pass roll and the second threaded pass roll in a range of 0.005 to 0.250 inches inclusive.
In another embodiment of the invention, the apparatus further comprises an electric arc furnace, wherein the electric arc furnace melts scrap steel into molten metal; a ladle, wherein the ladle is used for refining the molten metal; a tundish, wherein the tundish holds the molten metal; a water cooled mold, wherein the water cooled mold forms a strand of steel from the molten metal received from the tundish; rollers and water sprayers, wherein the rollers and water sprayers solidify the strand of steel into a billet; a cutter, wherein the cutter cuts the billet into the desired lengths; and a reheating furnace, wherein the reheating furnace heats the billet for rolling.
In yet another embodiment of the invention, the apparatus further comprises a coupling box, wherein the coupling box synchronizes the first threaded pass roll and the second threaded pass roll in order to substantially align opposed threaded pass knurls for forming substantially aligned top threads and bottom threads on the threaded rebar.
The features, functions, and advantages that have been discussed may be achieved independently in various embodiments of the present invention or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.
Having thus described embodiments of the invention in general terms, reference will now be made to the accompanying drawings, wherein:
Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
In the present invention, threaded rebar 700 can be produced using conventional rebar processing equipment and without the additional steps and tooling that are used for removal of the longitudinal ribs 1100. Therefore, it is generally not necessary to use more than two rolls or more than two dies at a time to create the substantially continuous threaded rebar 700, or to use little to no additional machining, grinding, or shearing operations to remove a portion of the longitudinal ribs. The present invention results in threaded rebar 700 products that can be made utilizing standard rebar manufacturing tooling and equipment in less time and for less cost than conventional threaded rebar products made utilizing more complex manufacturing processes and equipment.
As illustrated by block 104 in
After the billets are cut to the required lengths, they are passed through a reheating furnace 216, (see block 116 in
As illustrated in
As illustrated in block 120, after the cross-sectional area of the billet is reduced to the proper size, the hot roll lead pass 218 shapes the billet 300 into a bar with the proper cross-sectional area for producing a threaded rebar product. The type of cross-sectional area of the bar will impact the surface quality and circular cross-section of the final threaded rebar product. If a bar with the proper cross-sectional area is not used excess material can build up between the gaps 760 in the rolls and create longitudinal ribs 1100 in the threaded rebar, as illustrated in
In order to create threaded rebar with little to no longitudinal ribs, a bar with a reduced width along or approximate to the y-axis is helpful in reducing or eliminating the material that spreads into the gaps 760 between the rolls. The greater the width of the cross-sectional area along the y-axis of the lead pass bar the larger the longitudinal ribs along the length of the threaded rebar might be. A longitudinal rib prevents the threaded rebar from being used in conjunction with a nut or other type of mating threaded part because the longitudinal ribs prevent the threaded rebar from turning within the nut, or alternatively, could damage the threads in the nut so as to prevent the desired tightening of the nut on the threaded rebar. Where the threaded rebar includes longitudinal ribs, additional stages of manufacturing are necessary to machine, file, shear, chip, or otherwise remove the longitudinal ribs in order to allow the threaded rebar to be used as a bolt. These additional processes add increased tooling, man-hours, manufacturing time, and floor space costs that ultimately increase the overall cost of manufacturing threaded rebar.
Alternatively, not having enough cross-sectional material along the y-axis of the lead pass bar prevents the formation of a circular threaded rebar with threads that span the majority of the circumference of the threaded rebar because the material will not properly flow into the grooves and knurls in the opposing rolls. This can lead to a threaded rebar product with less tensile holding strength, weakened threaded rebar that is more apt to fail, deformed threaded rebar that cannot be secured to a nut, etc. Therefore, it is important to create a lead pass bar with a cross-sectional area that results in a threaded rebar 700 product having the proper shape for tensile strength, but with little to no longitudinal ribs 1100.
The dimensions and shape of the cross-sectional area of the lead pass bar play a role in producing threaded rebar with little to no longitudinal ribs.
Table I illustrates ranges of dimensions for the hourglass lead pass bar 400 and the associated threaded rebar produced from the hourglass lead pass bar 400. Different combinations of dimensions in Table I may result in the same dimensions for the associated threaded rebar sizes. In one embodiment of the invention as illustrated in
In one embodiment of the invention, the first width dimension B is less than or equal to ninety (90) percent of the second width dimension A. For example, as illustrated in the previous example, the B dimension (0.4439) divided by the A dimension (0.5589) multiplied by one-hundred (100) equals approximately seventy-nine (79) percent, which is less than ninety (90) percent. In other embodiments of the invention other B dimensions and A dimensions may be used that result in other percentages that are less than, equal to, or greater than ninety (90) percent.
As previously discussed the shape of the lead pass bar illustrated in both
In the embodiment illustrated in
In order to create the hourglass lead pass bar 400, the rectangular billet 300 is fed through a lead pass roll system 500 that has opposing rolls, as illustrated in
Table II and
The rectangular billet 300 as illustrated in
The hot rolled threaded pass 220 uses a threaded pass roll system 600, which has two opposing rolls, in order to manufacture the threaded rebar 700, as illustrated in
As illustrated by block 122 in
As illustrated in
Another feature of the threaded rebar 700 produced using this lead pass bar 400 is that there are little to no longitudinal ribs that run along the surface of the threaded rebar 700 in the longitudinal direction, or at least along a partial length of the threaded rebar 700. As illustrated in
Even though there are little or no longitudinal ribs 1100 that run length of the threaded rebar in the present invention, because of the gap 760 between the first threaded roll 602 and the second threaded roll 604 the surface of the threaded rebar where the longitudinal ribs 1100 would have been located in typical rolling processes may have a surface finish that is more course then the surface finish of other parts of the threaded rebar.
Along with the dimensions of the hourglass lead pass bar 700, the gap distance G, as illustrated in
As illustrated by
There are three different sizes of threaded rebar 700 that are typically used in various applications; however, additional sizes may be produced in accordance with one of ordinary skill in the art in light of this specification. The three different sizes of threaded rebar 700 discussed as examples herein are set forth in Table I below and illustrated by
The dimensions used to create the hourglass lead pass bars 400 may be adjusted based on the composition of the metal, the rate that the bar is passed through the lead pass 218 and the threaded pass 220, and the temperature to which the rectangular billet 300 and lead pass bar 400 are heated before undergoing hot rolling. For example, compositions of metal that are harder and less ductile, which are more difficult to shape, may have A and B dimensions that are in the higher end of the range, while the C dimension may be in the lower end of the range of the hourglass lead pass bar dimensions illustrated in Table I. Furthermore, hourglass lead pass bars 400 that are passed through the rolls at a rate in the higher end of the range, may have A and B dimensions that are in the higher end of the range, while the C dimension may be lower in the range in Table I. This may be due to the fact that the lead pass bars 400 spend less time being shaped by the rolls, and, thus, the material may not have as much time to be formed into the proper shape. Also, hourglass lead pass bars 400 that are heated to the lower end of the temperature range, may have A and B dimensions that are in the higher end of the range, while the C dimension may be lower in the range. This may be due to the fact that at the lower temperatures the lead pass bars 400 may be more difficult to deform than lead pass bars 400 heated to higher temperatures.
Table II illustrates three different sizes of threaded rebar 700 along with the ranges of dimensions used to create the grooves 510 in the lead pass system 500, which results in forming of the hourglass lead pass bar 400 used to manufacture the three different sizes of threaded rebar 700.
Table III illustrates three different sizes of threaded rebar 700 along with the ranges of dimensions used to create the grooves 610 and knurls 620 in the rolls for the threaded pass system 600 that results in the desired threaded rebar 700 product.
An important part of the invention is that different types of threaded rebar can be produced by simply changing the dimensions of the grooves 510, 610 and knurls 620 in the lead pass rolls 502, 504 and threaded pass rolls 602, 604, as well as the gap 760 between the rolls. These changes can be made to create customized hourglass lead pass bars 400 that result in customized threaded rebar 700 with little to no longitudinal ribs 1100 based on the individual requirements of each customer, through an interchangeable and cost effective process utilizing standard rebar forming tooling and equipment.
In one embodiment of the invention the threaded rebar comprises various amounts of carbon, manganese, phosphorus, copper, vanadium, with the remaining composition being made up of iron and other amounts of various impurities. Table IV illustrates a range of compositions for one embodiment of the threaded rebar. However, it is to be understood that other compositions can be used to manufacture threaded rebar that comprises other amounts of the elements shown in Table IV, other compositions that do not include one or more of the elements illustrated, and/or include additional amounts of one or more elements not illustrated.
It is to be understood that the dimension ranges and compositions described in Tables I, II, III, and IV, as well as the temperature and rate ranges described herein, are provided as examples only, and that many different types and sizes of threaded rebar can be manufactured using various metal compositions, temperatures ranges, rolling rates, and dimensions. The dimensions for the grooves 510 in the lead pass system 500, grooves 610 and knurls 620 in the threaded pass system 600, and gap distance in both systems can be varied, in order to manufacture a lead pass bar 400 that results in the desired threaded rebar 700. In light of this specification one of ordinary skill in the art can determine the necessary metal compositions, temperatures ranges, rolling rates, and/or dimensions, which may or may not be specifically described herein, that produce the desired threaded rebar product with little to no longitudinal ribs using standard rebar manufacturing tooling and equipment. Therefore, in some embodiments of the present invention the threaded rebar that may be manufactured using this process can range from size three (3) rebar up to size eighteen (18) rebar in English units, or ten (10) mm rebar to fifty-seven (57) mm rebar in metric units. In other embodiments of the invention, threaded rebar can be manufactured in sizes outside of these ranges.
As illustrated in block 1004 of
After the first roll set (i.e., lead pass rolls) for the lead pass system 500 and the second roll set (i.e., threaded pass rolls) for the threaded rebar system 700 are created the first roll set and the second roll set are installed into the rebar processing system 200 illustrated in
The lead pass roll set and threaded pass roll set can be used to create multiple hourglass lead pass bars 400 and threaded rebar 700. Eventually, because of the continued use of the rolls, the grooves 510, 610 and the knurls 620 will become worn to the point where the threaded rebar 700 formed using the grooves 510, 610 and knurls 620 may no longer satisfy quality requirements. The lead pass roll set and threaded pass roll set have multiple grooves 510, 610 so that when one groove 510, 610 becomes worn the lead pass system 500, or threaded pass system 600 can be repositioned in a timely manner to use alternate sets of grooves 510, 610 on the same roll set, in order to continue to produce hourglass lead pass bars 400 and threaded rebar 700 with little to no lapses in the production schedule. In the case where all of the grooves 510, 610 in a roll set are worn the entire roll set may be replaced.
The threaded rebar manufactured in the present invention can be used for many applications. For example a bolt head can be attached to the threaded rebar 700 and a nut can be incorporated with the threaded rebar for use as a securing device. In some embodiments, the nut may be a machined or cast nut that works in conjunction with the threaded rebar 700 in concrete reinforcing applications, anchor tensioning applications, mine bolts, etc. In one embodiment the threaded rebar is especially useful in conjunction with a resin nut as a rock bolt in mining applications. In these applications, a pocket of resin is inserted in a core drilled in the mine ceiling or wall. Next, the threaded rebar 700 is inserted into the core and punctures the resin pocket. As the resin pocket is hardening, the resin pocket can be turned into a torquing resin nut by rotating the threaded rebar 700 in the resin pocket as it is hardening. The substantially continuous threads on the threaded rebar 700 carve grooves into the resin pocket, allowing the threaded rebar 700 to be turned at any point in the future for re-torquing or securing with the resin nut. Threaded rebar with longitudinal ribs cannot be rotated after the resin hardens because the longitudinal ribs prevent a thread from being carved into the resin nut.
The threaded rebar 700 can be used in many other applications to reduce the costs associated with using more expensive threaded rebar products. For instance, threaded rebar may be used as an alternative system for anchoring signs, cell towers, wind towers, as well as other foundation applications to concrete or other types of foundations, to name a few.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of, and not restrictive on, the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other changes, combinations, omissions, modifications and substitutions, in addition to those set forth in the above paragraphs, are possible. Those skilled in the art will appreciate that various adaptations, modifications, and combinations of the just described embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
