US3316797A - Rock bolt with conduit - Google Patents

Description

C. I. WILLIAMS May 2, 1967 ROCK BOLT WITH CONDUIT 2 Sheets-Sheet 1 Filed Jan. 29, 1964 F l G.

FIG. 2

F l G. 3

l. WILLIAM S 25 C HE STE I?v IN VEN TOR.

F I G. 4

C. I. WILLIAMS May 2, 1967 ROCK BOLT WITH CONDUIT 2 Sheets-Sheet 2 Filed Jan. 29, 1964 FIG. 5,

FIG. 8

F I G. I l

l. WILLIAMS CH ESTER INVENTOR.

F I 6. IO

grouting (where the hole United States Patent 3,316,797 ROCK BOLT WITH CONDUIT Chester I. Williams, 347 Green Briar SE.,

Grand Rapids, Mich. 49506 Filed Jan. 29, 1964, Ser. No. 341,076 1 Claim. (Cl. 85-74) rock. An anchoring device is usually applied at the mner end of the rod, and the installation is completed by pumping the space in the hole around the rod with a cementitious composition known as grout. When the grout sets, the resulting encasement of the rod provides a protective sheath inhibiting corrosion, and also elfects a bond between the rod and the adjacent rock.

It is not uncommon for these rods to extend twenty feet or so into the holes in the rock, and grouting presents a problem in providing for the displacement of air as the grout flows into the hole. It is common practice to install tubing along the side of the rod for its full lenth, and also a short tube at the entrance to the hole. In overhead grouting, as encountered in the construction of tunnels, the grout is pumped in at the short tube as air is exhausted from the interior of the hole via the longer tube terminating near the end of the rod. In down extends in a downward slope from the entrance), the reverse procedure is followed.

This conventional tubing arrangement provides adequately for the application of grout, provided that the tubes are functioning. As a practical matter, the long tube is preferably secured to the rod and inserted with it, as it isdifficult to shove the tube into the hole separately. The actuationof the anchor device, however, normally requires a rotation of the rod; and this rotation has a tendency to distort and break the tube lying along beside the rod. .One answer of this problem has been the use of a rod drawn with a small central hole, which eliminates the long exterior tubing. The manufacture of this type of rod, however, is a rather tricky procedure. The cost of the hollow rod is therefore considerably higher than that of solid rod.

This'invention provides the advantage of a drawn tubular. rod at a substantially reduced cost. The purpose of the invention, stated briefly, is the provision of a conduit approximately co-terminal with the rod, and disposed within the circumscribed circle of the cross section of the rod so that rotation of the rod will not tend to knock the conduit out of place. It is very desirable to contact the grout beyond the anchoring device, and it is therefore necessary to continue the tube or conduit through or past the anchor.

One modification of the invention receives a length of tubing in a protected recess rolled or machined in the side of an otherwise solid rod. The tubing is either secured in the groove by the staking or other subsequent deformity of the rod, or .it may be snapped or pressed into the groove upon suitably close control of tolerances. Another modification of the invention provides a protected conduit by rolling or drawing a groove in the side of a rod which is initially formed in such a manner that the groove may be subsequently closed to form a complete conduit in a rod having a circular peripheral cross section.

Another modification of the invention provides for a formation of a tubular rod of substantially the same finished proportions as the drawn hollow rod, but constructed from helically-wound strip material which is welded to produce a substantially continuous piece. This general type of tube formation is well-known, and was used in producing the early Kentucky rifle barrels. To accommodate the conditions encountered in use of rock bolts, however, the procedure is altered and specialized as discussed herein. In an other modification of the invention, a strip of material of substantially trapezoidal cross section is formed initially into by bending along an axis parallel to the length of the rod, and subsequently closing this trough-shaped piece to form a complete tube.

The several features of the invention will be analyzed in further detail through a discussion of the particular embodiments illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is an axial section showing the inner extremity of a rock bolt with its anchoring device, and illustrating a tube installed in an axial groove along the side of the rod.

FIGURE 2 is a section of plane 22 of FIGURE 1.

FIGURE 3 shows a modified form of the invention involving a closed groove providing for a snap-in retention of the tube. 1

FIGURE 4 is a section at the surface of the rock bolt shown at FIGURE 1 where it emerges from the hole in the rock formation.

FIGURE 5 shows a modified form of the invention, and illustrates an intermediate condition of the rod as a integral conduit is formed.

FIGURE 6 shows the final form of the rod illustrated in FIGURE 5.

FIGURE 7 shows a cross section of a rod formed into a tubular configuration from an initially flat strip.

' FIGURE 8 shows the preferred trapezoidal cross sec tion of the strip used to form the rod cross section shown in FIGURE 7.

FIGURE 9 shows an intermediate condition of the rod as it is altered from 'the formation shown in FIGURE 8 to that of FIGURE 7.

FIGURE 10 shows a rod formed from helically-wound strip.

FIGURE 11 is a URE 10.

Referring to FIGURE 1, the bolt rod 10 is initially formed with the groove 11 rolled or otherwise machined as shown, and extending substantially throughout the length of the rod. A portion of reduced diameter is provided at 12 to present a shoulder against which the thrust ring 13 may act as the threading of the portion 12 pulls the internally-threaded cone 14 into the expansible sleeve 15. Preferably, lugs as shown at 16 and 17 are provided to inhibit rotation of the cone 14 as the rod 10 is rotated to actuate the anchoring device. This portion of the structure forms no part of the present invention. It is significant, however, that the groove 11 should be of sufiicient depth to permit the tube 18 to be disposed sufiiciently near to the center of the rod that it will not interfere with the threaded engagement between the portion 12 and the cone 14. The tube 18 may be retained in place after assembly by a group of local deformities caused by staking as shown at 19 and 20 in FIGURE 2-. The staking operation should be applied at particular intervals along the length of the rod which will be sufficient to assure that the tubing is adequately retained in place.

Referring to FIGURE 4, the emergence of the rod 10 from the hole 21 in the rock formation 22 presents a problem similar to that encountered at the anchoring device shown in FIGURE 1. The tube 18 must traverse the assembly at the surface, which includes the bearing plate 23, the bevelled washer 24, and the nut 25. The disposition of the tube near the center of the rod will permit the tube to emerge to the exterior where it is accessible for either the application of grout or to exsectionon the plane 1111 of FIG- a U-shaped section haust the air from the interior of the bore as grout is applied. The short tube 26 emerges through a special hole in the plate 23 (not shown), and does not rotate with the rod as the anchor device is set.

The modification shown in FIGURE 3 differs from that of FIGURE 2 primarily in the manner of retention of the tube 18. The groove 27 of the rod 28 is formed with a partially closed relationship of the sides of the groove so that the width of the groove is less at the periphery of the rod than it is near the center. This will provide for a snap-in retention of the tube 18.

Referring to FIGURES and 6, this modification of the invention does not require the application of a separate piece of tubing to form the protected conduit. The rod itself is initially formed in the cross section shown in FIGURE 5, in which the rod 29 has portions 30 and 31 which extend radially outward beyond a circle which defines the remainder of the cross-section of the rod. A groove 32 is defined by these projections, and a subsequent rolling or drawing operation can bring the projections 30 and 31 together to enclose an axially-extending space to form a conduit 33. The junction between the portions 30 and 31 may be welded to seal the opening and increase the torsional rigidity of the rod.

FIGURES 7, 8, and 9 show steps in the formation of a tubular rod from initially fiat stock by bending along an axis parallel to the length of the rod. The initial form of the strip is shown in FIGURE 8, and is essentially trapezoidal. The strip 34 has the parallel sides 35 and 36, and the inclined sides 37 and 38. This strip is initially formed by bending into a configuration approximating that of FIGURE 9, and is subsequently closed to form the cross section shown in FIGURE 7. Depending upon the hardness and other characteristics of the material, the dimensions of the initial strip as shown in FIGURE 8 must be selected so that the position of the neutral axis in bending will result in a shortening of the side 35 and a lengthening of the side 36 so that a substantially closed seam results as the sides 37 and 38 are brought together. It is also readily conceivable that the friction of the bending operation against the dies will sufiiciently alter the flow characteristics of the material that the sides 37 and 38 may have to be somewhat curved to ultimately produce a flat surface. If welding of the seam between the sides 37 and 38 is desired, it will ordinarily be preferable to provide that these sides come together to form V-shaped opening rather than the full closure.

Referring to FIGURES and 11, a tubular rod 39 is formed by helically winding a strip 40 about a mandrel, and subsequently welding the helical junction thus formed. Since the actuation of the anchor device shown in FIG- URE 1 will normally involve a right-hand rotation under the driving of an impact wrench, it is desirable to minimize the shock loading on the resulting helical weld. For this reason, the strip 40 is wound in a left-hand configuration to form a c r p nd g ft-ha d ic weld 41. The right-hand torsion applied during the setting of the anchor will therefore have a minimum tendency to crack or strain the weld 41. Because of the extreme tension applied to the rod 39, it is desirable that the weld 41 extend all the way in to the interior of the joint, as it is obvious that the application of tension to the rod will be limited by the transfer of tensile and shear stresses across the weld seam.

The particular embodiments of the present invention which have been illustrated and discussed herein are for illustrative purposes only and are not to be considered as a limitation upon the scope of the appended claims. In these claims, it is my intent to claim the entire invention disclosed herein, except as I am limited by the prior art.

I claim:

A rock bolt assembly adapted to be grouted in a hole, comprising:

a bolt rod having an axial recess extending along the entire length thereof and being open throughout its length at the outer surface of said rod, said rod having an externally threaded inner end portion;-

said recess being narrower adjacent the periphery.

of said rod than at a position nearer to the center thereof; an anchor device received on said threaded inner end portion, said anchor device including a threaded cone and an expansible sleeve surrounding said cone, said sleeve being adapted to expand upon rotation of said cone relative to said bolt rod; and a tube received in said axial recess, said tube extending to the outer extremity of said bolt rod, and

said tube being received in said recess in a forced fit, said recess having means extending inwardly from the opposite sides thereof adjacent the radially outermost extremities of said recess for retaining the said tube therein.

References Cited by the Examiner UNITED STATES PATENTS CARL W. TOMLIN, Primary Examiner. R. S. BRITTS, Assistant Examiner,

' Converse 72-367

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