EP0361690A1

EP0361690A1 - Mine roof anchor assembly supporting nut

Info

Publication number: EP0361690A1
Application number: EP89308771A
Authority: EP
Inventors: Paul Yacisin
Original assignee: Jennmar Corp
Current assignee: Jennmar Corp
Priority date: 1988-08-30
Filing date: 1989-08-30
Publication date: 1990-04-04
Also published as: AU4089289A; ZA896596B

Abstract

A mine roof anchor assembly (10) with a support nut (32) is provided. The mine roof anchor assembly may include a destructible capsule (16) containing resin bonding material components in separate compartments that are combined with each other when the capsule is ruptured and the components are mixed. The mine roof anchor assembly (10) has an expansion shell (26) that cooperates with a tapered plug (22). The expansion shell (26) has an annular collar (28) with a plurality of axially extending expansion fingers (30) formed integrally with the annular collar. When the tapered plug (22) is threaded onto the mine roof bolt (18) and the plug (22) and the collar (28) moved toward each other, the expansion fingers (30) are forced radially outwardly into contact with the bore hole in which the anchor assembly is positioned. A cylindrical support nut (32) having at least four complete threads on the internal surface of the nut is provided to support the expansion shell prior to and during expansion. The outer cylindrical surface (34) of the support nut (32) is smaller than the outer cylindrical surface of the annular collar (28) on the expansion shell so that the flow of resin downwardly around the expansion shell is not impeded by the support nut.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to mine roof anchors and particularly to a mine roof anchor assembly for small diameter bore holes which utilizes a supporting nut having desirable characteristics for the purpose.

2. Description of the Prior Art

It is well-known in the art of mine roof support to provide roof anchor assemblies which have mechanical expansion shells that grip the interior of a blind bore hole formed upwardly into the mine roof. Such mechanical expansion shells may also be utilized with resin bonding material to securely anchor the mine roof bolt into the rock strata above the mine roof.
U.S. Patent No. 4,413,930, U.S. Patent No. 4,419,805, U.S. Patent No. 4,516,885 and U.S. Patent No. 4,518,292 disclose examples of mine roof anchors which utilize both a mechanical expansion shell and resin bonding material to anchor the roof bolt within the rock strata.
Mechanical expansion shells are often supported on mine roof bolts with support nuts stamped from sheet metal. These stamped, sheet metal nuts are known commercially as "PAL" nuts. They are usually placed below a mine roof bolt expansion shell that has an annular collar with a plurality of expansion fingers integrally formed with the annular collar and extending axially upwardly from the annular collar. A tapered plug cooperates with the expansion fingers to force them outwardly against the wall of the bore hole when the tapered plug is threaded onto the roof bolt and moves toward the annular collar on the roof bolt.
Other types of support nuts have also been utilized for supporting this type of expansion shell. U.S. Patent No. 3,941,028 shows a sheet metal support nut which clamps to the annular collar of an expansion shell. Other mechanical anchor assemblies which do not utilize support nuts at all are disclosed in U.S. Patent No. 3,385,155 and U.S. Patent No. 4,278,006.

SUMMARY OF THE INVENTION

I have found that it is often desirable to utilize a smaller bore hole than is conventionally utilized in anchoring a mine roof bolt into a mine roof. Ordinarily, a 1 3/8" diameter hole is bored upwardly into the mine roof. A mine roof bolt having a diameter of 5/8" or 3/4" is utilized with an appropriate mechanical shell. I have found that utilizing 5/8" diameter roof bolts or 3/4" diameter roof bolts in a 1 1/16" bore hole can be useful in reducing the power required to drill the hole and reducing the amount of resin required to help anchor the bolt when resin is utilized in combination with the mechanical roof bolt.
When the smaller diameter bore hole is utilized, certain modifications must be made to permit effective anchoring of the roof bolt within the hole. I have found that one critical feature is to provide an appropriate support nut for the mechanical expansion shell.
In accordance with the present invention, there is provided a mine roof anchor assembly that includes a bolt having a threaded end portion. A tapered plug that has a threaded opening extending axially through it is threadingly received on the bolt threaded end portion. A hollow expansion shell is provided to surround the bolt. The hollow expansion shell has an annular collar at one end and a plurality of expansion fingers extending integrally from the collar in an axially direction. The expansion shell cooperates with the tapered plug whereby axial movement of the plug toward the annular collar flexes the expansion fingers radially outwardly from the bolt and into contact with the wall of the bore hole into which the anchor assembly is placed. A support nut is threaded onto the bolt threaded end portion and abuts the expansion shell annular collar. The support nut has at least four complete internal threads and also has a maximum outside dimension that is less than the outside diameter of the shell annular collar.
Further in accordance with the present invention, there is provided a mine roof anchor assembly for anchoring a mine roof bolt in a blind bore hole formed in the mine roof. The mine roof anchor assembly includes a destructible capsule containing resin bonding material components in an unmixed condition in separate destructible compartments within the capsule. The capsule is positioned within the bore hole against the blind end of the bore hole. A bolt having a threaded end portion is provided. A tapered plug that has a large end and a small end and a threaded opening extending axially through it threadingly receives the bolt threaded end portion. The tapered plug has a shear pin that extends diametrically across the threaded opening closer to the large end of the plug than to the small end. The bolt threaded end portion abuts the shear pin when the bolt is threaded into the plug small end.
A hollow expansion shell surrounding the bolt and having an annular collar at one end and a plurality of expansion fingers extending integrally from the collar in an axial direction cooperates with the tapered plug, whereby axial movement of the plug toward the annular collar flexes the expansion fingers radially outwardly into contact with the wall of the bore hole when the bolt is positioned within the bore hole. A support nut is threaded onto the bolt threaded end portion and abuts the expansion shell annular collar. The support nut has at least four complete internal threads and has a maximum outside dimension that is less that the outside diameter of the shell annular collar.
The bolt, the tapered plug, the expansion shell and the support nut are moved axially as a unit to rupture the destructible capsule and thereafter they are rotated as a unit to mix the resin bonding material components. When the resistance of the mixed resin bonding material to rotation of the expansion shell causes the shear pin to break, the bolt rotates relative to the tapered plug and causes the expansion shell to expand. The mixed resin is able to flow downwardly in the blind bore hole beyond the expansion anchor without being impeded by the support nut.
Accordingly, the principal object of the present invention is to provide a mine roof anchor assembly having a support nut that can be utilized in a relatively small diameter bore hole which is strong enough to support the expansion shell assembly and which does not extend radially outwardly beyond the annular collar of the expansion shell assembly.
Another object of the present invention is to provide a support nut for a mechanical expansion shell which permits resin to flow down beyond the support nut without being impeded when the mechanical shell is utilized with resin bonding material to anchor it in the bore hole.
These and other objects of the present invention will be more completely disclosed and described in the following specification, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side elevation of the anchor assembly of the present invention positioned within a blind bore hole before the destructible resin capsule is ruptured.
Figure 2 is a view similar to Figure 1 showing the anchor assembly with the mechanical expansion shell expanded and resin bonding material from the capsule surrounding the expansion shell within the bore hole.
Figure 3 is a perspective view of the support nut of the present invention.
Figure 4 is a perspective view of a conventional nut.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, there is shown a mine roof anchor assembly 10 positioned within a blind bore 12 formed within the rock strata 14 above a mine roof. A destructible resin capsule 16 is positioned against the end of the blind bore as shown in Figure 1.
A mine roof bolt 18 having a threaded end portion 20 is threaded into a tapered plug 22. The tapered plug 22 has a shear pin 24 which extends diametrically across the threaded bore within tapered plug 22. The roof bolt 18 is threaded into tapered plug 22 from the small end of tapered plug 22 until it abuts the shear pin 24. The shear pin 24 is closer to the large end of tapered plug 22 than it is to the small end of tapered plug 22.
An expansion shell 26 having an annular collar 28 surrounds the bolt 18. The expansion shell 26 has expansion fingers 30 which are formed integrally with the annular collar 28 and which extend in an axially direction upwardly from collar 28 as viewed in Figures 1 and 2.
In conventional fashion, the expansion fingers 30 cooperate with the external surface of tapered plug 22 so that when tapered plug 22 is threaded onto bolt 18 toward the annular collar 28, the surface of tapered plug 22 forces the expansion fingers 30 radially outwardly and into contact with the wall of the blind bore 12 as shown in Figure 2. As depicted in Figures 1 and 2, there are four expansion fingers 30 extending axially upwardly from annular collar 28. There may be more or fewer than four expansion fingers utilized.
A support nut 32 is threaded onto bolt 18 to support the expansion shell 26. As best seen in Figure 3, the support nut 32 has a cylindrical outer surface 34 and internal threads 36.
I have found that in order to provide adequate strength for the support nut 32, there should be at least four complete internal threads 36 on the interior of support nut 32. As seen in Figures 1 and 2, the outer diameter of the cylindrical outer surface 34 of support nut 32 is substantially smaller than the outer diameter of annular collar 28 on expansion shell 26.
A conventional nut 38 is shown in Figure 4 for comparison purposes. The conventional nut 38 is of hexagonal configuration and it may readily be seen that if such a nut were threaded onto bolt 18 to support expansion shell 26, at least the portions of the exterior surface where the flat surfaces join each other would extend radially outwardly beyond the annular collar 28.
In installing the mine roof anchor assembly of the present invention in a blind bore within the mine roof, the support nut 32 is first threaded onto the bolt threaded end portion 20. The expansion shell 26 is then placed over the bolt and contacts the support nut 32. The tapered plug 22 is then threaded onto threaded end portion 20 of bolt 18 until the shear pin 24 engages the end of bolt 18.
The destructible resin capsule 16 is placed within the bore hole 12 and then the bolt 18 with the expansion shell assembly on the end of it is placed into the bore hole. The bolt 18 and the expansion shell assembly comprising tapered plug 22, expansion shell 26 and support nut 32 are moved as a unit upwardly into the bore hole 12 until they contact and then rupture the destructible resin capsule 16.
After the resin capsule has been ruptured, the bolt 18, tapered plug 22, expansion shell 26, and support nut 32 are rotated as a unit to mix the resin bonding components that had been contained within the destructible resin capsule. The mixed resin bonding components flow downwardly around and over the expansion shell 26 and support nut 32. After the resistance of the resin causes the expansion shell 26 to turn relative to the plug 22 within the bore hole 12, continued rotation of the bolt 18 will cause the shear pin 24 to break. The continued rotation of bolt 18 will cause tapered plug 22 to move downwardly as viewed in Figures 1 and 2 to cause the expansion fingers 30 of expansion shell 26 to be forced radially outwardly into forceful contact with the wall of bore 12.
Because the diameter of the outer surface 34 of support nut 32 is substantially smaller than the outer diameter of annular collar 28, the support nut 32 does not impede the flow of resin material downwardly around the shell and beyond the support nut 32.
According to the provisions of the Patent Statutes, I have explained the principle, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. However, it should be understood that, within the scope of the appended claims, the invention may be practiced otherwise than and as specifically illustrated and described.

Claims

1. A mine roof anchor assembly comprising:
a bolt having a threaded end portion;
a tapered plug having a threaded opening extending axially therethrough threadingly receiving said bolt threaded end portion,
a hollow expansion shell surrounding said bolt and having an annular collar at one end and a plurality of expansion fingers extending integrally from said collar in an axial direction and cooperating with said tapered plug whereby axial movement of said plug toward said annular collar flexes said expansion fingers radially outwardly from said bolt into contact with the wall of a bore hole into which said anchor assembly is placed; and
a support nut threaded onto said bolt threaded end portion and abutting said shell annular collar, said support nut having at least four complete internal threads and having a maximum outside dimension that is less than the outside diameter of said shell annular collar.

2. The mine roof anchor assembly of Claim 1 wherein said support nut has a cylindrical outer surface.

3. The mine roof anchor assembly of Claim 2 wherein said support nut cylindrical outer surface has a diameter smaller than the outside diameter of said shell annular collar.

4. A mine roof anchor assembly for anchoring a mine roof bolt in a blind bore hole formed in the mine roof comprising:
a destructible capsule containing resin bonding material components in an unmixed condition in separate destructible compartments within said capsule, said capsule being positioned within said bore hole against the blind end thereof;
a bolt having a threaded end portion;
a tapered plug having a large end and a small end and a threaded opening extending axially therethrough threadingly receiving said bolt threaded end portion, said plug having a shear pin that extends diametrically across said threaded opening closer to said plug large end than to said plug small end whereby said bolt threaded end portion abuts said shear pin when said bolt is threaded into said plug small end;
a hollow expansion shell surrounding said bolt and having an annular collar at one end and a plurality of expansion fingers extending integrally from said collar in an axial direction and cooperating with said tapered plug whereby axial movement of said plug toward said annular collar flexes said expansion fingers radially outwardly from said bolt into contact with the wall of said bore hole when said bolt is positioned within said bore hole;
a support nut threaded onto said bolt threaded end portion and abutting said shell annular collar, said support nut having at least four complete internal threads and having a maximum outside dimension that is less than the outside diameter of said shell annular collar;
said bolt, said tapered plug, said expansion shell and said support nut being moved axially as a unit to rupture said destructible capsule and thereafter being rotated as a unit to mix said resin bonding material components until the resistance of said mixed resin bonding material to rotation of said expansion shell causes said shear pink to break whereby said bolt rotates relative to said tapered plug to expand said expansion shell;
said mixed resin being able to flow downwardly in said blind bore beyond said expansion anchor without being impeded by said support nut.

5. The mine roof anchor assembly of Claim 4 wherein said support nut has a cylindrical outer surface.

6. The mine roof anchor assembly of Claim 4 wherein said support nut cylindrical outer surface has a diameter smaller than the outside diameter of said shell annular collar.

7. The mine roof anchor assembly of Claim 5 wherein said support nut cylindrical outer surface has a diameter smaller than the diameter of said blind bore hole.