Note: Descriptions are shown in the official language in which they were submitted.
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MINE ROOF TRUSS WITH BENT ANGLE BOLTS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an underground mine roof supporting
system and, more particularly, to a truss having bent angle bolts and a
horizontal tying
cable.
2. Brief Description of the Prior Art
Roof trusses or roof support systems for mines are well-known
methods for providing support to the immediate roof strata. U.S. Patent Nos.
4,946,315 and 5,018,907 disclose typical roof truss systems utilizing
interconnected
tie rods extending between rigid roof bolts. The bolts are connected by means
of a tie
rod and tension is produced in the truss by a turnbuckle or the like.
Tightening of the
tie rod or turnbuckle can produce compressive forces in the rock of the roof
which
increases the strength of the rock. A variation of a mine roof truss formed
from solid
bolts is disclosed in U.S. Patent Nos. 5,193,940 and 5,238,329 which disclose
mine
roof trusses having angle bolts which are inserted into a bore hole and then
formed at
an angle below the mine roof to extend horizontally. Connecting members are
positioned on the ends of the bent angle bolts and a tie rod extends between
the
connecting members. The horizontal ends of the angle bolts and the ends of the
tie rod
are threaded. Nuts are threaded onto the ends of the angle bolts and the tie
rod and
nuts are tightened against the connecting members to induce tension in the
truss. The
connecting members typically are solid bodies having holes drilled
therethrough with
beveled edges to allow the nuts to be partially received in the holes. These
specialized
connectors add significantly to the cost of the truss. In addition, the amount
of tension
applied to the truss is not known with much accuracy.
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Another drawback to these rigid mine roof trusses is that the
horizontal tie rod is difficult to handle underground, particularly, in mine
passages
with low seam height.
Accordingly, a need remains for a mine roof truss utilizing rigid
S angle bolts, but which is easier to install underground.
SUMMARY OF THE INVENTION
A mine roof truss of the present invention includes a first angle bolt
and a second angle bolt. The first angle bolt has a first end extending into a
first
bore hole formed in a mine roof strata and a second end bent to an angle
substantially horizontal to the mine roof strata. The second angle bolt has a
third
end extending into a second bore hole formed in the mine roof strata and a
fourth
end bent to an angle substantially horizontal to the mine roof strata.
A first splice tube is positioned adjacent the second end of the first
angle bolt. A second splice tube is positioned adjacent the fourth end of the
second angle bolt. The second end of the first angle bolt and the fourth end
of the
second angle bolt may each include a drivehead, wherein the first splice tube
and
the second splice tube each have a larger diameter than the driveheads.
Alternatively, the second end of the first angle bolt and the fourth end of
the
second angle bolt can also be threaded, with a nut received by the second end
of
the first cable bolt and the fourth end of the second angle bolt. 'The first
and
second splice tubes preferably have a larger diameter than the nuts.
A cable, having a first end and a second end, extends between the
first and second splice tubes. A first barrel and wedge assembly is positioned
adjacent the first end of the cable and a second barrel and wedge assembly is
positioned adjacent the second end of the cable. A first bearing plate may
also be
positioned between the first splice tube and the mine roof.
Tension is applied to the mine roof truss by urging the first barrel
and wedge assembly against the first splice tube and pulling the first end of
the
cable in an opposite direction. Further tension can be applied to the mine
roof
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truss by urging the second barrel and wedge assembly against the second splice
tube arid pulling the second end of the cable in an opposite direction.
One method of installing a truss for supporting a mine roof includes
the steps of-.
(a) drilling a first bore hole and a second bore hole in a mine
roof;
(b) inserting a first resin package into the first bore hole and a
second resin package into the second bore hole;
(c) positioning a first splice tube adjacent the second end of the
first angle bolt;
(d) positioning a second splice tube adjacent the fourth end of the
second angle bolt;
(e) inserting a first end of a first angle bolt into the first bore hole
bore;
(f) inserting a third ead of a second angle bolt into the second
bore hole;
(g) rotating the first angle bolt;
(h) rotating the second angle bolt;
(i) bending a second end of the first angle bolt in a position
substantially parallel to the mine roof;
(j) bending a fourth end of the second angle bolt in a position
substantially parallel to the mine roof;
(k) slidably attaching a first end of a cable to the first splice tube;
(1) slidably attaching a second end of the cable to the second
splice tube;
(m) positioning a first barrel and wedge assembly adjacent the
first end of the cable and a second barrel and wedge assembly adjacent the
second
end of the cable;
(n) pulling on the first end of the cable;
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(o) moving the first barrel and wedge assembly in a direction
toward the first splice tube;
(p) pulling on the second end of the cable;
(q) moving the second barrel and wedge assembly in a direction
toward the first splice tube; and
(r) positioning a first bearing plate between the first splice tube
and the mine roof.
The present invention is tensionable from both ends, is easier to install
in cramped spaces than rigid bar type trusses, and can be tensioned with a
greater
degree of accuracy than rigid bar type trusses.
Further aspects of the invention are as follows:
A mine roof truss for supporting a mine roof strata comprising:
a first angle bolt having a first end extending into a first bore hole
formed in the mine roof strata and a second end bent to an angle substantially
horizontal to the mine roof strata;
a second angle bolt having a third end extending into a second bore
hole formed in the mine roof strata and a fourth end extending into a first
bore hole
formed in the mine roof strata;
a first splice tube positioned adjacent said second end of said first
angle bolt;
a second splice tube positioned adjacent said fourth end of said second
angle bolt;
a cable, having a first end and a second end, extending horizontally
between said splice tubes;
a first barrel and wedge assembly positioned adjacent said first end of
said horizontal cable; and
a second barrel and wedge assembly positioned adjacent said second
end of said horizontal cable.
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A method of installing a truss for supporting a mine roof comprising
the steps of:
(a) drilling a first bore hole and a second bore hole in a mine roof;
(b) inserting a first resin package into said first bore hole and a
S second resin package into said second bore hole;
(c) positioning a first splice tube adjacent a second end of a first
angle bolt;
(d) positioning a second splice tube adjacent a fourth end of a
second angle bolt;
(e) inserting a first end of said first angle bolt into said first bore
(f) inserting a third end of said second angle bolt into said second
bore hole;
(g) rotating said first angle bolt;
(h) rotating said second angle bolt;
(i) bending said second end of said first angle bolt in a position
substantially parallel to the mine roof;
(j) bending said fourth end of said second angle bolt in a position
substantially parallel to the mine roof;
(k) slidably attaching a first end of a cable to said first splice tube;
(1) slidably attaching a second end of said cable to said second
splice tube;
(m) positioning a first barrel and wedge assembly adjacent said first
end of said cable and a second barrel and wedge assembly adjacent said second
end of
said cable;
(n) pulling on said first end of said cable; and
(o) moving said first barrel and wedge assembly in a direction
toward said first splice tube.
A complete understanding of the invention will be obtained from the
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following description when taken in connection with the accompanying drawing
figures wherein like reference characters identify like parts throughout.
These and other advantages of the present invention will be clarified in
the Detailed Description of the Preferred Embodiment taken together with the
attached drawings in which like reference numerals represent like elements
throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side view of the mine roof truss installed in a mining
chamber according to the present invention; and
Fig. 2 is a plan view of the splice tube used in the truss illustrated in
Fig. 1 with ends of a bolt, a cable, and a bearing plate installed therewith.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For purposes of the description hereinafter, the terms "upper", "lower",
"right", "left", "vertical", "horizontal", "top", "bottom" and derivatives
thereof shall
relate to the invention as it is oriented in the drawing figures. However, it
is to be
understood that the invention may assume various alternative variations and
step
sequences, except where expressly specified to the contrary. It is also to be
understood that the specific devices and processes illustrated in the attached
drawings,
and described in the following specification, are simply exemplary embodiments
of
the invention. Hence, specific dimensions and other physical characteristics
related to
the embodiments disclosed herein are not to be considered as limiting.
Fig. 1 schematically illustrates a mine roof truss 10 for supporting the
roof strata 12 of a mine. The truss 10 includes a pair of spaced apart bore
holes 14
drilled into the roof strata 12. The bore holes 14 may extend substantially
vertically
into the roof strata at an angle thereto, as shown in Fig. 1, as is well-known
in the art.
A rigid bolt 16, preferably formed from rebar and having a drivehead 18 is
secured
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within each bore hole 14 by a cured resin mixture 20. Alternatively, the bolt
16 may
have a threaded end onto which a nut or other drivehead is threaded instead of
the
drivehead 18.
During installation, the resin 20 is normally forced in the bore hole 14
before the bolt 16. The bolt 16 is advanced and rotated, rupturing the resin
packages
and mixing the resin during the installation procedure. The advancing and
rotation of
the bolt 16 is accomplished by engaging the drivehead 18 with appropriate
bolting
equipment. Following the mixing of the resin 20, the resin 20 is allowed to
cure
securing the leading end of the bolt 16 within the bore hole 14.
An exposed end 22 of the bolt 16 extends from the bore hole 14. After
the resin 20 has set, the mine roof bolting equipment is used to apply
pressure to the
exposed end 22 to bend the exposed end 22 as shown in Fig. 1 such that a
substantial
portion of the exposed end 22 extends substantially parallel to the mine roof
strata.
A splice tube, such as disclosed in U.S. Patent No. 5,836,720, is
positioned on each of the exposed end portions 22. When the bolt 16 includes a
drivehead 18, the splice tube 24 is slipped over the opposite end of the bolt
16 before
the bolt is inserted into the bore hole. Alternatively, as described above,
the exposed
end 22 of the bolt 16 may be threaded and the splice tube 24 may be slipped
over the
exposed end after
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installation of the bolt and a nut (not shown) may be threaded onto the
exposed
end 22. The integral drivehead 18 or a nut threaded onto the exposed end 22
prevents the splice tube 24 from slipping off the exposed end 22 of the bolt
16.
Preferably, the splice tube 24 is formed of an elongated conduit
between a pair of spaced ends. The conduit receives the exposed end 22 of the
bolt 16 therethrough. The drivehead 18 has a diameter larger than the inner
dimensions of the conduit of the splice tube such that the drivehead 18 abuts
one
end of the splice tube 24.
A horizontal cable 26 extends between the splice tubes 24. The
horizontal cable 26 is attached to the splice tube 24 via a barrel and wedge
assembly 28 mounted on each end thereof, as shown in Fig. 2. The ends of the
horizontal cable 26 extend beyond the barrel and wedge assemblies 28. At least
one end and preferably both ends of the horizontal cable 26 extends beyond the
barrel and wedge assembly 28 adjacent thereto by about one to two feet. The
longer ends of the horizontal cable 26 are used for gripping the cable 26 to
induce
tension in the truss. A hydraulic tensioner or other hydraulic jacking device
is used
to exert tension in the truss by pulling on the horizontal cable 26 in a
direction
away from the corresponding splice tube 24 and urging the corresponding barrel
and wedge assembly 28 towards the corresponding splice tube 24.
The truss 10 may be installed with a pair of bearing plates 30 each
positioned between a splice tube 24 and the mine roof as shown in Fig. 1.
The mine roof truss of the present invention is easier to handle
underground in mine passageways than the conventional trusses utilizing rigid
tie
rods. In addition, the truss of the present invention uses relatively simple
components. The splice tube, horizontal cable, and barrel and wedge assemblies
are presently commonly used in mine roof support. Because the truss is
tensioned
with a hydraulic tensioning unit, the amount of tension applied to the truss
can be
specifically determined.
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The invention has been described with reference to the preferred
embodiment. Obvious modifications and alterations will occur to others upon
reading and understanding the preceding detailed description. It is intended
that
the invention be construed as including all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents
thereof.
