Note: Descriptions are shown in the official language in which they were submitted.
2~c~l~a
PATENT APPLICATIO~
27855/30713
M~NE ~OO~ ~PPORT SY~TE~
CROSS REFER~NCE $O RELATED APPLICATION
This application is related in part to
Canadian Patent File No. 2,059,514, filed on January 16,
1992.
TECHNICA~ F~ELD O~ THE 1N~.IO~
The present invention relates to a mine roof
support system for supporting the roof of a mine.
B~C~GROU~D OF THE l~ TION
There are numerous methods other than vertical
or angled roof ~olting for supporti~g the roof of an
underground mine whic~ is dug for the extraction of coal
or other minerals or ores. One such method is the cross-
bar method wherein wood, steel, rail, fiberglass, or
15 aluminum beams are placed against a mine roof. Each end
of the beam can be supported by posts made ~rom any of
the materials used in ma3cing the beams or, in addition,
from concrete. The crossbar method has the disadvantage
that t~e posts can be accidentally knocked out by moving
~achinery, thus endangering the miners. To protect min-
ers in such situations, cable or steel straps are bolted
into the roof in order to support the beam should a post
be knocked out. The beams can also be drilled an~ bolted
directly to the roof. Installing crossbars is a slow and
2~921SO
PATENT APPLICATION
27855/30713
2 --
labor-intensive process, the materials are expensive, and
installation can be ha2ardous. Moreover, wood is not a
permanent material even if it is treated.
In another method, continuous bolt trusses are
fabricated from angled roof bolts anchored into the roof
by mechanical shells or adhesive resins. The bolts are
connected by means of a tie-rod and tension is produced
by a turnbuckle. Tie-rods or other length compensating
devices are connec~ed in sections of from two to fi~e
lo connecting rods. The tension in the bolts and tie-rods
is essentially equal as they are continuously connected
together. Tightening of the tie-rod turnbuckle can pro-
duce compressive forces in ~he roof rock which increases
the strength of the rock. ~owever, as the turnbuckle
length or take-up is limited, the roof bolt holes must be
precisely located or, otherwise, various lengths of tie-
rods m~st be availa~le to be connected to the roof bolts
and turnbuckles in order to allow the truss system to be
tensio~ed. The threads, ~hich are cut or rolled into the
ends of the roof bolts and tie-rods, act as stress con-
centration points and also reduce the effecti~e area of
the bolt/tie-rod, ~hus reducing the effective ultimate
streng~h of the system. F~ne machine threads are subject
to damage, rust, and corrosion. Assembly of the continu-
ous bolt multi-segment tie-rod truss system is time-con-
suming.
2~32~0
P~TENT APPLICATIoN
2785~307~3
- 3 -
In a third method, multiple angled bolt trusses
are fabricated by securing one end of each of two bo}ts
at angles in the roof of the mine and by passing the
other ends of the two bolts through plates or brackets
such that each bolt is tensioned separately. Tie-rods,
in two to five sections, are connected to the plates or
brackets using turnbuckles or tensioning bolts and cou-
plers such that the turnbuckles or tensioning bolts can
tension the tie-rods. Since the tie-rods and bolts are
tensioned separa~ely, the compressive forces on the roof
rock may be unequal. This may result in one bolt being
overloaded close to failure while the tie-rod and oppo-
si~e b-olt have little or no stress. T~e roo~ bolt holes
must be located at precise distances to allow tensionin5
within the limited range of a turnbuckle or tensioning
bolt or else several sections of various lengths of tie-
rods must be available to achieve ~he proper tie-rod
leng~h. The threads which are cut or rolled into the
threaded ends of the roof bolts and tie-rods ac~ a~
stress concentration points, and also reduce the effec-
tive area of the boltJtie-rod thus reducing the effective
ultimate stren~th of the truss system. Fine machine
~hreads are subject to damage, rust, and corrosion.
Assembly of the roof truss system is time-consuming.
In a fourth method, cable bolts or slings of
lengths of wire rope are inserted into bore holes in the
roof of a mine on either side of the mine passageway.
2~9$1SO
PATENT APPLICATION
27855/30713
-- 4 --
Grout or grout car~ridges are inserted into the holes in
order to secure the cables to the mine roof. As each
cable is one continuous piece, the tension in each c~ble
can be equal in all segments. The cable or sling can be
tensioned by attaching it to a split tube and by driving
the split tube up into the cement-filled bore hole by a
split tube driver which can be an air or hydraulic impact
~ool. However, variations in bore hole diameter due to
drilling and/or rock movement hinder the passage of the
split tube such that there is little control of the ten-
sion on the cable or sling. After installation, some
cables have no tension and must be blocked with wood to
the roof and tightened with wedges. Also, the tubes
require special air or hydraulic jack legs whic~ are not
normal coal mining equipment, thus ~equiring an air com-
pressor and air hoses laid to the work area. Moreover,
the impact driving of the split tubes is slow and ~ery
noisy, and requires three operators to install a cable
sling. Furthermore, impact dri~ing of the split tubes
can disturb the roof and ribs and may dislodge material
thus endangering miners.
SUMMARY OF THE I~v~lIQN
These disadvantages can be elim~nated and/or
minimized by the present invention. In one aspect of t~e
invention, a roof suppor~ system for supporting a roof of
a mine includes a first rod which extends generally along
209`2 1 ~0
-- 5
the roof of the mine and which is secured to a first
bore in the roof. A second rod extends generally along
the roof of the mine and is secured to a second bore in
the roof. A connector connects the first and second
rods together so as to support the roof of the mine.
The connector has a connector body with first and
second faces. The connector body has first and second
holes extending from the first face to the second face.
The first and second rods are secured to the connector.
The first hole is partially bevelled to form a first
elliptical opening in the first face and the second
hole is partially bevelled to form a second elliptical
opening in the second face. The first and second
elliptical openings allow the first and second rods to
bend in order to relieve strain on the roof support
system. The connector body is generally canted, and
each of the holes has a center line which intersects
the first and second faces at non-right angles, the
first and second holes being substantially parallel to
one another such that the first and second holes are
offset from one another in a direction along their
center lines.
In another aspect of the invention, a
connector, which connects together two rods of a mine
roof support system, has first and second sides, first
and second faces, and first and second holes extending
between the first and second faces. The first and
second sides and the first and second faces form a
generally canted connector body wherein the first side
and the second face generally form an obtuse angle and
wherein the first face and the second side generally
form an obtuse angle. Each of the first and second
holes has a center line intersecting the first and
292150
-- 6
second faces at non-right angles. With this
arrangement, the first and second holes are offset from
one another in a direction along their center lines.
The first hole forms a first opening in the first face
and a second opening in the second face, and the second
hole forms a third opening in the first face and a
fourth opening in the second face. The first and
fourth openings are elliptical.
In yet another aspect of the invention, this
canted connector can be used in a roof support system
wherein first and second rods, which are secured to
bores in the roof of a mine, are also secured to the
canted connector in roof supporting fashion. The first
and fourth elliptical openings allow the first and
second rods to bend so as to increase the load carrying
capacity of the first and second rods.
In still another aspect of the invention, the
first and second rods may be of unitary construction.
In a still further aspect of the invention, a
roof support system for supporting a roof of a mine
includes a first rod which extends generally along the
roof of the mine and is secured to a first bore in the
roof. A second rod extends generally along the roof of
the mine and is secured to a second bore in the roof.
A connector connects the first and second rods together
so as to support the roof of the mine. The connector
has a connector body with first and second faces. The
connector body has a first hole extending from the
first face to the second face and a second hole
extending from the first face to the second face. A
first rod is threadably secured within the first hole
through the first face, and a second rod extends into
the second hole through the second face and has an end
2o92l50
exiting the second hole through the first face. The
connector body is canted, and each of the holes has a
center line which intersects the first and second faces
at non-right angles, the first and second holes being
substantially parallel to one another such that the
first and second holes are offset from one another in a
direction along their center lines. A nut is threaded
over the end of the second rod. The connector and the
nut hold the first and second rods together in roof
supporting fashion.
The invention also discloses methods of
supporting a mine roof by use of the several systems
described above.
In the present invention, there is no need
for multiple tie-rods. A single nut can be used for
tensioning the whole system and the tension anywhere in
the roof support system is equalized. The rods are
made sufficiently long such that precise location of
roof bolt holes is not required because the system can
easily accommodate any excess rod extending through the
connector. The roof truss system according to the
present invention has few parts and is easier and
faster to assemble, which is important because
installation of a mine roof support system must follow
as soon as possible after the extraction of rock, coal
or other mineral, or ore in order to maintain roof rock
strength and avoid roof falls.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages will
become more apparent from a detailed consideration of
the invention when taken in conjunction with the
drawings in which:
2~2~
PATENT APP~ICATION
27855/30713
Figure l shows one arrangement of the roof
truss system according to the present invention;
Figure 2 shows another embodiment of a roof
truss system according to the present invention;
Figures 3 and 4 illustrate one embodiment of a
connector such as that used in Figures l and 2;
Figure 5 shows the connector of Figures 3 and 4
attached to roof supporting rods;
Figures 6, 1 and 8 illustrate a second embodi-
ment of a connector such as that used in Figures l and 2;
Figure 9 shows the result of kinking of a rod
fastened to the connector shown in Figures 3-8;
Figure 10 is a cross-sectiona} view of another
connector embodiment which can be used in ~he roof sup-
port systems shown in Figures l and 2;
Figure ll is an end view of the connector shown
in Figure 10;
Figure 12 is a cross-sectional view ta~en along
the lines 12-12 of Figure 10;
Figure 13 shows the longer bending arc for a
rod fastened to the connector shown in Figures 9-11,
appearing with Fig. 9; and
Figures 14, 15 and 16, together with a table
disclosed herein, show an exemplary set of dimensions for
the connector shown in Figures 9-11.
2Q~2lso
PATENT APPLICATION
27~55/30713
DE~AI~ED DEæcRIpTIoN
~ In Figure 1, a roof truss system 10 supports a
roof 11 of a passage 12 of a mine. A typical mine would
incorporate a plurality of such roof truss systems 10
each separated by a predetermined distance from the sys-
tem on either side of it. The roof truss system 10 in-
cludes a first rod 13 which is inserted into a bore
formed at an angle thro~gh the roof 11 and into the roof
roc~ 14. Any s~itable means such as an anchor, epoxy
resin, or cement can be used to retain the first rod 13
in its bore. A second rod 15 is inserted into a ~ore,
spaced oppositely to the bore which receives the rod 13,
formed at an angle through the roof 11 and into the roof
rock 14. The second rod 15 may be of unitary construc-
1~ tion; that is, the rod 15 may ~e a single rod. The sec-
ond rod 15 can be secured within its bore by any suitable
means such as an anchor, epoxy, or cement. The rod 13 is
secured to a tie-rod 16 by a connector 17 s~ch that the
rod 1~ and the tie-rod 16 ~re screwed into opposite ends
of the connector 17. The other end of the tie-rod 16 is
inserted into a first hole of a connector 20 through a
first connector face 23. The tie-rod 16 can be secured
to the connector 20 by any suitable mechanism such as
threads within the first hole of the connector 20 or a
nut 21. The second rod 15 is inserted into a second hole
in the connector 20 through a second connector face 24
and has a threaded end which exits the connec~or 20
2~9~150
PATENT APPLICATlON
27855130713
-- 10 --
through the first face 23. A nut 22 is threaded over
this threaded end and can be adjusted against the connec-
tor 20 in order to create the desired amount of tension
in the rod 13, the rod 15 and the tie-rod 16. If a pre-
S cise amount of tension is required, a torque wrench canbe used for tightening the nut 22. The connector 1~ can
be replaced by a connector such as the connector 20.
In an alternative embodiment shown in Figure 2,
the tie-rod 16 and the connector 17 are eliminated and a
io rod 13' of extended length is used in thei~ place. The
rod 13' is secured to the connector 20 by inserting the
rod 13' into the first hole o~ the connector 20 ~hrough
the first face 23 such that a threaded end of t~e rod 13'
exits the second face 24. The nut 21 is then threaded
onto the threaded end of the rod 13'. The rod 13' can be
of unitary construction. Otherwise, the construction o~
the roof truss system lO' is the same as that shown in
Figure 1.
~he connector 20 i5 shown in more detail in
Figures 3-5. The connector 20 has a first hole 31 ex-
tending through the connector 20 so that it creates open-
ings in both the first face 23 and the second face 24.
The connector 20 also has a second hole 32 extending
through the connector 20 so that it creates openings in
both the first face 23 and the second face 24. The hole
31 has a bevelled rim 34 in the second face 24 but an
elliptical hole in the first face 23 forming a partia~ly
~092150
PATENT APP~ICATION
27855/30713
bevelled rim 39. Similarly, the hole 32 has a bevelled
rim 35 in the first face 23 but an elliptical hole in the
second face 24 forming a partially bevelled rim 38. The
partially bevelled rims 38 and 39 allow bending of the
rods fastened thereto and twisting of the roof truss
system in order to relieve strain there-n. The fully
bevelled rims 34 and 35 accommodate spherical faces of
the nuts 21 and 22.
As shown in Figure 5, the rod 13' (or 16) is
inserted through the first face 23, the hole 3~, and
exi~s the second face 24. The nut 21 is threaded onto
the rod 13' (or 16). The rod 15 is inserted through the
second f~cê 24, the hole 32, and exits the firs~ face 23.
The nut 22 is threaded over the rod 15. Either nut can
then be tigh~ened to place the prescrï~ed tension on the
rods 15 and 13' (or 15 and 16).
As an alternative embodiment, a connector 20'
is shown in more detail in Figures 6-8. The connector
20' has a first hole 31' extending through the connector
20' so ~hat it creates openings in both a first face 23'
and a second face 24'. The connector 20' also has a
second hole 32' extending through the connector 20' so
that ~t creates openings in both the first face 23' and
the second face 24'. The hote 31' has a bevelled rim 33
in ~he first face 23' and a bevelled rim 34' in the sec-
ond face 24~. Similarly, the hole 32~ has a bevelled rim
35' in the first face 23' and a bevelled rim 36 in the
2~32150
PATENT APPLICAT~ON
27855/30713
second face 24'. These bevelled rims are provided for
each hole in each face in order to allow the connector
20' to be a bidirectional device, to recei~e a spherical
nut, and to facilitate twisting of the truss system in
order to relieve strain.
The system according to this in~ention is sim-
ple having only five parts in the system shown in Fig-
ure 2 and se~en parts wi~h respect ~o the system shown in
~igure 1. A single nut is adjusted for adjusting the
0 tension in the entire system so that the tension will be
e~ual everywhere in the roof support system. Precise
location of the bore holes in the mine roof is not re-
quired since a deviation in the distance between the bore
holes sec~ring the rods ~3 and 1~ is accommodated by the
amount of extra rod extending through the connec~or 20.
Accordingly, rods of different length do not ha~e to ~e
inventoried, thus reducing cost.
Although Figures 1 and 2 do not show any sup-
porting plates between the roof support system and the
roof, it may be desirable to use such plates in order to
provide contact between the roof support system 10 and
the roof 11.
As shown in Figure 9, the weight of the roof
supported by the rods t5 and 16 creates ~ension therein.
The tension in the rods 15 and 16 causes the connector 20
to rotate and the rods 15 and 16 to bend with respect to
the connector 20. The rod 15 bends along a surface of
20~iS0
PATENT APPLICATION
27855t30713
- 13 -
the wall defining the hole 31 between poin~s 42 and 44.
This surface between the points 42 and 44 may be curved,
if desired, with a radius to define a bending radius for
the rod 15 as it bends between the points 42 ~nd 44.
S This surface of the wall defining the hole 31 ~etween the
points 4Z and 44 is defined ~s the bending arc provided
by the connector 20 for the rod 15. The connector 20
provides a similar ~ending arc for the rod 16 between
points 46 and 18.
As long as the rods 15 and 16 are straight, any
tension in these rods is, for the most part, dis~ributed
evenly across the cross-~ections thereof. However, if
the tension in ~he rods 15 and 16 increases sufficiently,
~he connector 20 rotates ~nd the rods 15 and 16 bend
around the points 42 and 46 of the connector 20. As the
rods 15 and 16 bend around the points 42 and 46, the
tension in the rods 15 and 16 is no longer distributed
evenly across the cross-sections of the rods; instead,
stress is concentrated in the rods 15 and 16 near the
points 42 and 46. If this stress in the rods lS and 16
is great enough, kinks form ~herein at the points 42 and
46. The kinks at the points 42 and 46 can result in the
premature fracturing and failure of ~he rods 15 and 16.
The degree to which stress is concentrated in
2S the rods 15 and 16 near the points 42 and 46 and, thus,
the likelihood that kinks will form in ~he rods 1~ and 16
depends upon the length of the bending arcs and the
'~921~0
PATENT APPLICATION
27855130713
aforementioned bending radii provided fo~ the rods 15 and
16 by the connector 20 between the points 42 and 44 and
~etween the points 46 and 48. Longer bending arcs and
larger bending radii result in less concentration of
stress than do shorter bending arcs and sma~ler bending
radii. Therefore, the li~elihood that kinks will form in
the rods 15 and 16 can be reduced by increasin~ the
length of the bending arcs and of the bending radii be-
tween the points 42 and 44 and between the points 46 and
48. The length of these bending arcs associated with the
rectangular connector 20 can be increased ~y increasin~
the size of the connector 20. However, increasing the
size of the connector 20 results in an undesirable in-
crease in the weight of the connector 20.
The connecto~ 50 shown in Figures ~0-12, on the
other hand, increases the length of the bending arcs for
the rods attached thereto without a substantia~ increase
in weight. Accordingly, the connector 50 has a first
face or end 52 and a second face or end 5~. The connec-
tor 50 also has a first side 56 and a second side 58. As
viewed in Figure 10, ~he angles between the face 52 and
the side ~6 and between the face 54 and the side 58 are
acute. Similarly, the angles between the face 52 and the
side 58 and between the face 54 and the side 56 a~e ob-
~use. Thus, the connector 50 is c~nted or skeved as
compared to the rectangul~r connector 20 and, in the pre-
ferred embodiment shown in ~igures 10-12, the connector
.. ..
2~32150
PATE~T APPLICATION
27855/30713
50 is generally in the shape of a rhom~oid in cross-sec-
tion. This canted shape of the connector 50 contri~utes
to a longer bending arc for the rods fastened thereto
withou~ a subs~antial increase in weight as compared to
the primarily rec~angular connector 20.
A pair of holes 60 and 62 of the connector 50
extend through the connector 50 between the first face 52
and the second face 54. The holes 60 and 62 have corre-
sponding center }ines 61 and 63 which intersect the faces
52 and 54 at non-right angles. The center lines 61 and
63 are generally parallel to an axis 64 o the connector
50. As is`seen in Figure 10, because of the canted shape
of the connector 50 and the orientation of ~he holes 60
and 62 within the connector 50, the ho~es 60 and 62 are
offset with respect to one another a~ong the direc~ion of
the axis 64 (i.e. along the direction of the center lines
61 and 63 of the holes 60 and 62).
The hole 60 has a partially bevelled rim or
surface 66 adjacent the face 52 and a substantially fully
bevelled rim 68 adjacent the face 54. Similarly, the
hole 62 has a substantially fully bevelled rim ~0 ad~a-
cent the face 52 and a partially bevelled rim or surface
72 adjacent the face 54. As can be seen in Figure 11,
the partially bevelled surface 66 of the hole 60 results
in the opening formed by the hole 60 in the face 52 of
the connector 50 having a generally elliptical appear-
ance. Simil~rly, the partially bevelled surface 72 of
2~3215~
PATE~T APPLICATIO~
27855/30713
- 16 -
the hole 62 results in the opening formed by ~he hole 62
in the face 54 of the connector 50 having a generally
elliptical appearance. Also, as can be seen in Figure
11, the substantially fully bevelled rim 70 of the hole
62 results in the opening formed by the hole 62 in the
face S2 of the connector 50 ha~ing a generally circu~ar
appearance. Similarly, the substantially fully bevelled
rim 68 of the hole 60 results in the opening formed by
the hole 60 in the face 54 of the connector 50 having a
generally c~rcular appearance.
The connector 50 can be used in a manner simi-
lar to the previously described connectors. That is, as
shown~in Figure 13, a first roof s~pporting rod 74 i5
inserted through the first face 5Z and through the hole
60 so that a threaded end of this first rod 74 exits the
hole 60 through the second face 54. ~ first nut 76 may
be threaded over the thread~d end of the first rod 74
which exits the hole 60 through the second face 54. The
bevelled rim 68 accommodates~a spher~cal head on the
first nut 76. A second roof supporting rod ?8 is insert-
ed through the second face 54 and through the hole 62 so
th~t a threaded end of this second rod 78 exits the hole
62 through the first face 52. A second nut 80 may be
threaded over a threaded end of the second rod 78 which
exits the hole 62 through the first face 52. The bev-
elled rim 70 accommodates a spherical head on the second
nut 80. One or both of the nuts 76 and 80 may be tight-
20921~0
PA~ENT APPLICATION
27855/30713
- 17 -
ened with respect to the other in order to put a prede-
termined ~mount of tension on the roof supporting rods 74
and 78.
As shown in Figure 13, the bending arc for the
rod 74 fastened to the connector 50 extends along the
bevelled surface 66 between poin~s 82 and 84. The bev-
elled surface 66 of the hole 60 between the points 82 and
84 may be curved with a radius 86. The bending arc for
the rod 78 may ~e substantially the same length as the
length of the bending arc for the rod 74 and ~he bevelled
surface 72 of the hole 62 may be curved with a radius
similar to the radius 86. These bending arcs provided by
the connector 50 allow the rods 74 and 78 to bend smooth-
ly along the partially bevelled rims or surfaces 66 and
72 of the holes 60 and 62 as ~he connector 50 rotates
with respect to t~e rods ~4 and 78 due to tension in the
rods 74 and 78.
The lengths of these bending arcs are deter-
mined by the amount of canting of the connector 50 (i.e.
the amount of the aforementioned offset ~etween the holes
60 and 62 of the connector 50). This c~nting of the con-
nector 50 allows longer bending arcs than the bending
arcs of the connector 20 without 2 substan~ial inc~ease
in connector weight. The longer bending arcs of the
connector 50 allow ~he connector ~0 to distribute the
tension on the rods 74 and 7 8 across a grea~er portion of
the cross-section of t~ese rods than is the case with the
..... .
~as2ls~
PATENT APPLICATION
27855/30713
- 18 -
connector 20. The longer ~ending arcs, therefore, reduce
the likelihood of kinking in the rods 74 and 78 and, as a
result, a greater portion of the load carrying capacity
of the rods fastened to the connector 50 is used.
The table below shows exemplary values for the
dimensions o~ th~ connector 50 identified in Figures 14-
16. These dimensions are exemplary only and should not
~e considered as limiting the scope of the invention. ln
the table, t~e first colu~n identifies the dimensions
indicated by the reference letters in Figures 16-18, the
second column specifies the exemplary va}ues of the di-
mensions in inches (unless otherwise noted), and the
third ~column specifies the exemplary values of the dimen-
sions in millime~ers. The dimensions A and B are~ the
radii of curvature of the par~ially surfaces 66 and 72
while ~he dimension S is the radius of the indicated
surface of the connector 50.
2~92150
PATENT APPL~CATION
27855/30713
-- 19 --
TABLE
Reference
~etter Di~ension
A 3.5 (88.9)
B 3.5 (88.9)
C 1.312 (33.3)
D 45
E 3.607 (91.6
F 2.0 (50.8)
G 4.085 ~ 103.8)
H 90
I 4.512 ~114.6)
J 2.256 (57.3)
K 0.925 (23.5)
L 4.919 (124.9
M 1.839 (46.7)
N 2.082 (52.9)
O 0.758 (~.3)
P 38.9O
Q 2.5 (63.5)
R 2.837 (72.1)
S 0.2 (5.1)
~any embodiments, modif ications ~nd ~ariations
haYe been shown herein and many more are poss ible in
25 light of the above ~eachings. For example, the connector
.,,
20~21~0
PA~ENT APPL~CATION
27855130713
- 20 -
50 may have a shape other than a rhomboid (s~ch as a
rhombus or any other parallelogram) as long as the con-
nector 50 is canted to allow th~ holes 60 and 62 to be
offset sufficiently to increase the bending radius of the
rods connected thereto. The~efore, it is to be under-
stood that the invention ~ay be practiced otherwise than
as specifically described.
. .
