REINFORCING BAR SPLICE WITH CUTTING EDGE BOLTS

BACKGROUND OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to reinforcing bar splices and to bolts usable in such splices.

DESCRIPTION OF THE RELATED ART

[0002] In steel reinforced concrete construction, there are generally three types of splices or connections; namely lap splices; mechanical splices; and welding. Probably the most common is the lap splice where two bar ends are lapped side-by- side and wire tied together. The bar ends are of course axially offset which creates design problems, and eccentric loading whether compressive or tensile from bar-to- bar. Welding is suitable for some bar steels but not for others and the heat may actually weaken some bars. Done correctly, it requires great skill and is expensive. Mechanical splices normally require a bar end preparation or treatment such as threading, upsetting or both. They also may require careful torquing. [0003] Improvements are continually being sought in mechanical splices and splicing methods, for instance to improve performance, cost, and/or ease of installation.

SUMMARY OF THE INVENTION

[0004] According to an aspect of the invention, a bolt has a convex end with cutting edges. The cutting edges may be knurls (grooves) and/or ridges. [0005] According to another aspect of the invention, a bolt has an end with cutting edges, and a shear head. The cutting edges may be knurls (grooves) and/or ridges. [0006] According to still another aspect of the invention, a bolt has a conical end with cutting edges. The cutting edges may be knurls (grooves) and/or ridges. [0007] According to yet another aspect of the invention, a bolt has knurled spiral grooves.

[0008] According to a further aspect of the invention, a bolt has a rounded end with cutting edges. The cutting edges may be knurls (grooves) and/or ridges.

[0009] According to a still further aspect of the invention, a reinforcing bar splice includes a sleeve for receiving reinforcing bar ends, and plural bolts that pass through threaded holes in the sleeve, wherein at least one of the bolts have ends with cutting edges. The cutting edges may be knurls (grooves) and/or ridges. The cutting edges may be spiral cutting edges.

[0010] According to another aspect of the invention, a reinforcing bar splice includes a sleeve for receiving reinforcing bar ends, and plural bolts that pass through threaded holes in the sleeve, wherein at least one of the bolts has a rounded end, and wherein at least one of the bolts has a pointed end. At least one of the bolts may have cutting edges, although it is possible that none of the bolts have cutting edges.

[0011] According to yet another aspect of the invention, a bolt has cutting edges and substantially circular cross-section on the end with the cutting edges.

[0012] According to still another aspect of the invention, a reinforcing bar splice includes a sleeve for receiving reinforcing bar ends, and bolts that engage threaded holes in the sleeve, wherein the bolts have cutting means for cutting into the reinforcing bar ends.

[0013] According to a further aspect of the invention, a method of splicing reinforcing bar ends includes placing bar ends of the reinforcing bars into a sleeve, and securing the reinforcing bar ends by screwing bolts having ends with cutting edges into threaded holes in the sleeve, thereby cutting the bolts into the reinforcing bar ends. The cutting into the reinforcing bar ends may include using the cutting edges to push material of the reinforcing bar ends out of the holes created by the bolts.

[0014] According to another aspect of the invention, a reinforcing bar splice includes: a sleeve having openings for receiving bar ends of reinforcing bars; and threaded bolts that engage threaded holes in the sleeve to press against the reinforcing bar ends. At least some of the threaded bolts include respective tips with respective cutting edges.

[0015] According to yet another aspect of the invention, a method of joining reinforcing bar ends includes the steps of: placing the reinforcing bar ends in openings on opposite sides of a sleeve; and screwing bolts through threaded holes in the sleeve, wherein the screwing the bolts includes using cutting edges on tips of

the bolts to cut into the reinforcing bar ends, thereby securing the reinforcing bar ends within the sleeve.

[0016] According to still another aspect of the invention, a bolt includes: a threaded shaft; a head attached to a first end of the threaded shaft; and a convex tip at a second end of the threaded, opposite the first end. At least part of the convex tip includes cutting edges. The convex tip has a substantially circular cross-section. [0017] According a further aspect of the invention, a method of making a bolt includes the steps of: forming a convex tip on the bolt; and stamping the convex tip against a die to form knurls in the convex tip.

[0018] To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0019] In the annexed drawings, which are not necessarily to scale: [0020] Fig. 1 is an oblique view of a bolt with cutting edges, in accordance with an embodiment of the invention; [0021] Fig. 2 is a side view of the bolt of Fig. 1 ; [0022] Fig. 3 is an end tip view of the bolt of Fig. 1 ; [0023] Fig. 4 is a side view the cone tip of the bolt of Fig. 1 ; [0024] Fig. 5 is a sectional view along the section 5--5 of Fig. 4, showing the cross-section shape of the knurls;

[0025] Fig. 6 shows an alternative cross-section shape for the knurls of the bolt of Fig. 1 ;

[0026] Fig. 7 is an oblique view of a portion of a die that may be used to make the bolt of Fig. 1 ;

[0027] Fig. 8 is an end tip view of a first alternative cutting edge configuration; [0028] Fig. 9 is an end tip view of a second alternative cutting edge configuration;

[0029] Fig. 10 is an end tip view of a third alternative cutting edge configuration;

[0030] Fig. 11 is an end tip view of a fourth alternative cutting edge configuration;

[0031] Fig. 12 is an end tip view of a fifth alternative cutting edge configuration;

[0032] Fig. 13 is alternative bolt configuration according to an embodiment of the present invention, a bolt with a rounded end;

[0033] Fig. 14 is an exploded view of a reinforcing bar splice in accordance with the present invention, utilizing bolts with cutting edges; and

[0034] Fig. 15 is an oblique view of the reinforcing bar splice of Fig. 14, installed to couple together reinforcing bars.

DETAILED DESCRIPTION

[0035] A bolt has a pointed end with cutting edges. The cutting edges may have knurls (grooves) or ridges, and may have a spiral arrangement, which may be substantially evenly arrayed about the circumference of the bolt. The bolt may have a convex end, such as a cone end or a curved end. The bolt may also have a shear head, such as a shear hex head, that shears off at a predetermined torque. [0036] A plurality of bolts may be used as part of a reinforcing bar splice that also includes a sleeve. The bolts engage threaded holes of the sleeves, with ends of the bolts entering bar-receiving areas within the sleeve. As the bolts are tightened, they bore into the receiving bar ends, securing the bar ends within the sleeve. Cutting edges on the bolts aid in boring the ends of the bolts into the reinforcing bar ends. The bolts may include cone end bolts and round end bolts, with the round end bolts being used in the holes farthest from the center of the sleeve. Using cutting edges on the bolt ends allows deeper penetration of the bolts into the reinforcing bar ends, without increasing the amount of torque used. In addition, forces from the bolts to the sleeve are reduced, which may result in less deformation of the sleeve and improved structural integrity of the sleeves.

[0037] Referring initially to Figs. 1-4, a bolt 10 has a threaded shaft 12, with a head 14 at one end of the shaft 12 and a convex tip 16 at the opposite end of the shaft 12. The convex tip 16 in the illustrated embodiment is a cone tip, although a wide variety of other convex tips are possible, some of are described below. The cone tip 16 of the illustrated embodiment has an included angle of 90 degrees,

although it will be appreciated that the cone tip 16 may have a different included angle.

[0038] The tip 16 has a smooth region 20, farthest from the shaft 12, culminating in a sharp point 22. The tip 16 also has a cutting region 24, between the smooth region 20 and the shaft 12, on which cutting edges 26 are arrayed. The cutting region 24 may stop within a distance, such as 0.5 mm, of the minor diameter of threads of the threaded shaft 12. The cutting edges 26 of the embodiment shown in Figs. 1-4 are knurls 28, grooves in the material of the cutting region 24. However the cutting edges may be ridges or other sorts of protrusions or depressions used for cutting into, scraping, abrading or moving material as the bolt 10 is screwed into an object, such as a reinforcing bar. This is in contrast to bolts without cutting edges, which use compression to move material they are driven into. [0039] The knurls 28 have a spiral or helical shape in the illustrated embodiment. The knurls 28 have a curved shape that changes its circumferential location along length of each of the cutting edges (in the longitudinal direction along the surface of the cutting region 24, from the smooth region 20 to the beginning of the threaded shaft 12). The curved knurls 28 are curved such that the inside of their curves are at the leading edges of the knurls 28 as the bolt is screwed in. This is a left hand spiral, projected on the sharp point 22 at the center of the smooth region 20. In other words, looking at the pointed end of the bolt 10, as one goes from the sharp point 22 radially outward, the knurls 28 deviate in a counterclockwise circumferential direction from a straight radial direction. At a boundary 30 between the smooth region 20 and the cutting region 24, the knurls 28 may be substantially perpendicular to the boundary 30, as shown in the illustrated embodiment. It will be appreciated that the knurls 28 alternatively may have straight shapes or other types of curved shapes. The cutting edges may have a different orientation from that shown in the illustrated embodiment.

[0040] The knurls 28 are evenly circumferentially spaced about the cutting region 24. There are 16 of the knuris 28 in the illustrated embodiment, although it will be appreciated that a greater or lesser number of knurls 28 may be used as an alternative. !n addition, alternatively the knurls 28 may be unevenly spaced about the cutting region 24.

[0041] The knurls 28 do not extend into the smooth region 20 about the point 22, in order to avoid weakening the material in the vicinity of the point 22. The smooth region 20 may have a length along its surface (from the sharp point 22 to the boundary 30) of 2 mm, for example.

[0042] The bolt 10 has a substantially circular cross section shape at any longitudinal location along the convex tip 16. Of course the knurls 28 do cause the cross section to deviate from a circular cross section, but a substantially circular cross section is defined herein to encompass deviations from circularity due to the knurls 28 or other cutting edges.

[0043] Referring now in addition to Figs. 5 and 6, the knurls 28 may be grooves with a rounded cross section shape, as shown in Fig. 5. The rounded cross-section shape may be a semicircle shape or may have a U shape. An alternative configuration, shown in Fig. 6, is for the knurls 28 to have a V shape. The cross section of the knurls 28 may be symmetric, as shown in the illustrated examples, or may be non-symmetric. It will be appreciated that other shapes may be used for the knurls 28.

[0044] The knurls 28 may have a depth of about 0.25 mm (0.01 inch). More broadly the knurls 28 may have a depth of 0.13 mm (0.005 inch) to 0.38 mm (0.015 inch), or a depth of 0.13 mm (0.005 inch) to 0.76 mm (0.03 inch). It will be appreciated that other knurl depths are possible.

[0045] The knurls 28 may have a uniform depth and width along their lengths. Alternatively the knurls 28 may vary in width and/or depth along their lengths. For example, the knurls 28 may get wider as they move away from the boundary 30. [0046] The head 14 of the bolt 10 may be a hex head, as in the illustrated embodiment. It will be appreciated that the head 14 may have other types of configurations, such as a square head. As another alternative, the head 14 may have a socket shaped to receive an Allen wrench or other keyed device. The head 14 may have any shape suitable for receiving a tool to tighten the bolt 10. [0047] The bolt 10 has a shear band 34, a reduced diameter portion between the threaded shaft 12 and the head 14. The shear band 34 is configured to allow the head 14 to be sheared off when a predetermined torque on the head 14 has been exceeded. The shear band 34 prevents overtightening of the bolts 10 while ensuring uniform tightening. In addition the shearing of the head 14 makes the bolt 10 more

compact when installed, and advantageously prevents loosening of the bolt 10 with a tool. However it will be appreciated that alternatively the shear band 34 may be omitted.

[0048] The bolt 10 may be made of any of a variety of suitable materials, such as a suitable steel. Examples of suitable materials are 4118 steel, 8620 steel, and stainless steel. The material may be heat treated for hardness.

[0049] The knurls 28 may be formed by any of a variety of suitable methods.

Examples of such methods include stamping, cutting, embossing, coining, forging, or using a rotational knurling tool, for example on a lathe.

[0050] The bolt 10 may be formed from wire stock, with the head formed by heading into a hex-shaped die to form the head 14. The cone tip 16 and the knurls

28 may then be formed in a stamping process. Alternatively the bolt 10 may be made from hex stock, with the threaded shaft 12 and the cone tip 16 machined. The knurls 28 may then be formed by use of a rotational knurling tube.

[0051] Fig. 7 shows a portion of a die 50 that is used in a stamping process for forming the cone tip 16 with the knurls 28. The portion shown is in Fig. 7 is roughly half of the actual die, with only a portion shown for illustration purposes. The die portion 50 has a round opening 52 to a cylindrical hollow 54 for receiving the shaft of a bolt 10. At the bottom the cylindrical hollow 54 is a conical surface 56 with protrusions 60 in the shape of the knurls 28 (Fig. 1 ). The conical surface 56 has an opening 62 at its center.

[0052] In use of the die, a length of wire material is inserted into the hollow 54.

The material is then driven against the conical surface 56 to form the cone tip 16 with the knurls 28. The smooth region 20 of the cone tip 16 is formed in the central opening 62 in the conical surface 56. After formation of the knurls 28 in the cone tip

16, threads are rolled on the shaft 12, and the bolt 10 is heat treated or otherwise treated to harden its surface.

[0053] Figs. 8-12 show alternative configurations of the cutting edges 26. Fig. 8 shows spiral knurls 68 that have a left hand spiral for the cutting edges 26.

[0054] Fig. 9 shows straight knurls 70 that proceed straight back from the front boundary 30 of the cutting region 24 to the where the cutting region 24 meets the threaded shaft 12. The knurls 70 are thus radial in orientation in the view shown, straight at the bolt tip. The knurls 70 are shown tapered, as having variable width.

The width of the knurls 70 varies linearly along their length, being narrowest at the boundary 30. It will be appreciated that the knurls 70 may alternatively be constant- width knurls. Also, it will be appreciated that the knurls may also alternatively be tilted, with some variation of their circumferential location.

[0055] Fig. 10 shows a drill bit configuration that has fewer but wider and deeper knurls or grooves 74. For instance, there may be three and four knurls or grooves 74 perhaps evenly circumferentially spaced, having a depth greater than the depths described above for the knurls 28 (Fig. 1 ). The knurls or grooves 74 provide some of the same benefits as the smaller but more numerous knurls 28 (Fig. 1 ). However, experiments have found that smaller knurls or grooves provide better results, reducing the amount of torque required to obtain the same amount of biting into an object.

[0056] Fig. 11 shows a crosshatched pattern of knurls 76. The illustrated embodiment shows the knurls 76 as curved knurls that are a combination of left- hand and right-hand spirals. It will be appreciated that other types of crosshatched patterns may be employed, such as combinations of tilted knurls that appear straight in an end view of the bolt tip. It will be appreciated that such knurls are curved to some extent in that they change circumferential location along the conical cutting region 78.

[0057] Fig. 12 shows a bolt tip with ridges 80 instead of recesses like grooves or knurls. The ridges may have any of the variety of sizes and layouts as the knurls or grooves described herein.

[0058] Fig. 13 shows another embodiment, a bolt 90 with a round tip 92 having cutting edges 94 such as knurls or grooves 96. The round tip 92 is convex and has a substantially circular cross section at all longitudinal locations, characteristics also shared by the bolt 10 (Fig. 1 ). Unlike the bolt 10, the knurls 96 may extend all the way to the apex 98 of the round tip 96, since weakening is less of a concern in a round tip 92 than in a conical tip. The round tip 92 may have a radius greater than a nominal (major) radius of threads 99 of the bolt 90. It will be appreciated that the cutting edges 94 may have the characteristics of the cutting edges described above with regard to cone tip bolts. Thus the cutting edges 94 may have a wide variety of configurations.

[0059] Figs. 14 and 15 show one employment of the bolts described above, as part of a reinforcing bar splice 100 for joining together two reinforcing bar ends 102 and 104. The splice 100 includes a sleeve 110 that has openings 112 and 114 for receiving respective of the bar ends 102 and 104. The openings 112 and 114 may be openings of a bore 116 that passes all the way through the sleeve 110. [0060] The sleeve 110 has a series of threaded holes 120 for receiving bolts 10 and 90 for securing the reinforcing bar ends 102 and 104 within the sleeve 110. The threaded holes 120 may be in a single line, or may be in a zigzag or other pattern. [0061] The sleeve 110 may have a toothed or threaded surface 122 that aids in retaining the bar ends 102 and 104 within the sleeve 110. The bolts 10 and 90 press into and against the bar ends 102 and 104, driving the bar ends 102 and 104 into engagement with the toothed or threaded surface 122. The sleeve 110 may include features disclosed in U.S. Patent Nos. 7,093,402 and 7,107,735, and in U.S. Patent Publication No. 2005/0169701 , the specifications and drawings of all of which are hereby incorporated by reference.

[0062] In use, the bar ends 102 and 104 are inserted into the openings 112 and 114 of the sleeve 110. The bolts 10 and 90 are then screwed into the threaded holes 120 and into the reinforcing bar ends 102 and 104. It has been found that the splice 100 has improved performance if some of the bolts are not cone end bolts. Placement of round end bolts 90 at the outermost of the threaded holes 120, furthest from the center of the sleeve 110, has been found to reduce stresses on the sleeve 110. This improves performance of the splice 100. As shown in Fig. 15, the bolts 10 and 90 are tightened so that the heads 14 are sheared off.

[0063] Although there are some advantages to using bolts with different types of ends, it will be appreciated that alternatively all of the bolts may be of the same type. Bolts of all the different types and configurations shown and described herein may be used as part of a reinforcing bar splice.

[0064] The splice shown in Figs. 14 and 15 is only an example of a possible configuration for a reinforcing bar splice. It will be appreciated that the number of bolts, and the relative locations of the bolts in the sleeve, may vary of a wide range of suitable possibilities. In addition, it will be appreciated that the splice 100, or variations thereof, may be used to splice together a wide variety of objects other than reinforcing bars.

[0065] Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a "means") used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.