Note: Descriptions are shown in the official language in which they were submitted.
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MINE ROOF SUPPORT SYSTEM HAVING TORQUE INDICATING WASHER
SCOPE OF THE INVENTION
The present invention relates to a wall or mine roof support system, and more
particularly
a support system which includes an anchor or reinforcing rod or bolt having a
threaded end, a nut
or other threaded fastener for mated engagement with the threaded end of the
bolt, and a torque
indicating member, such as a washer, which provides an installer with a visual
indication of the
application of a first predetermined minimum torque on the nut. The torque
indicating member
enables the installer to better gauge torque forces on the nut and prevent
over-tensioning of the
rod in a mine roof or wall bore hole.
BACKGROUND OF THE INVENTION
In wall and mine roof support systems, the use of anchor rods or bolts under
tension for
ground control is well known. Typically, conventional support systems include
a four or eight
foot steel anchoring or reinforcing rod or bolt which is threaded at one end
and a tensioning nut.
The anchor rod is embedded in a bore hole formed in the wall or mine roof to a
depth selected
such that when inserted, the threaded end of the rod projects outwardly a
distance beyond the
wall or rock face. To secure the anchor rod in the bore hole, the distal inner
end of the rod may
be provided with a wedge shaped mechanical anchoring member which is adapted
to be drawn
outwardly, wedging the distal end of the rod against the sides of the bore
hole. Alternately, one
or more adhesive resin cartridges are inserted into the bore hole ahead of the
distal end of the
rod. The subsequent insertion of the rod into the bore hole ruptures the
cartridge to release the
adhesive and secure the inner distal end of the anchor rod against removal
from the bore hole.
Following the placement of the anchor rod in the bore hole, the nut is
threaded along the
projecting threaded proximal end portion of the rod, and tightened axially
against the wall or
rock face, to consolidate forces within the rock and control ground movement.
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To achieve the desired placement of mechanical wedge anchors and/or initial
mixing of
the resin, the threaded nuts used to tension the rod may be provided with
either a deformable end
or a releasable end cap, as for example is disclosed in United States Patent
No. 5,873,689 to
Mensour et al which issued February 23, 1999. Mensour et al discloses the use
of a dome nut
having a covered end which is adapted to release upon the application of
relatively lower torque
forces, such as those below 100 ft.lbs. The domed or covered end of the nut
initially prevents its
movement axially along the threaded end of the rod. This results in the rod
spinning about its
axial length with the nut to either achieve mechanical placement of the wedge
anchor or mixing
of the adhesive resin, prior to the securement of the distal end relative to
the bore hole.
Following securement of the rod by wedge anchor placement or setting up of the
resin, the nut is
torqued with sufficient force to release or distort the end cap, allowing the
nut to be threaded
along the rod and tightened against the rock face.
Heretofore, the applicant has appreciated a disadvantage with prior art wall
and mine roof
support systems and their methods of installation. Following the release of
the nut end cap and
the running of the nut along the threaded proximal end against the rock face,
the inadvertent
over-torquing of the nut against the wall or rock face may result in the
anchor rod tearing Ollt of
the set resin or, in the case where mechanical wedge fasteners are used,
failing outright. If this
occurs, the installed bolt will be of no effective use in consolidating rock
forces. In particular,
prior art rock support systems suffer the disadvantage in that in the initial
tensioning of the nut to
compress the rock complex, as the nut is tightened, the installer is unaware
as to precisely when
the nut and/or any intervening washer plates and/or mesh screening seats
against the exposed
rock face as tensioning torque is applied. As a result, where a power drive is
used to install the
nut, it is liable to be overtorqued prior to the installer realizing that the
nut has been fully seated
against the rock face.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a torque indicating
member or
washer which includes a dome-shaped portion and one or more radial flanges.
The flanges are
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adapted to deflect from a first position to a second position upon the
compression of the dome-
shaped portion, as for example which occurs by tightening a nut against the
torque indicating
member with a predetermined first minimum torque.
Another object of the invention is to provide a torque indicating member or
washer which
has a bent generally dome-shaped portion which extends in an axial direction,
and which upon
the application of a second compressive force achieved by tightening a nut
against the washer
with a torque selected greater than a first predetermined minimum torque,
substantially collapses
in the direction of applied compressive force.
A further object of the invention is to provide a method of installing a wall
or mine roof
support system which includes a reinforcing rod, a threaded fastener and a
torque indicating
member or washer which is adapted to provide an installer with a visual
indication of the
application of a first predetermined minimum torque on the threaded fastener,
and wherein part
or all of the torque indicating member has applied thereto a high visibility
coating or colour
selected to provide enhanced visibility in low light conditions experienced in
underground mice
operations.
Another object of the invention is to provide a concrete wall or mine roof
support system,
(hereinafter also generally referred to as mine roof support systems), which
includes an anchor
rod sized for insertion in a bore hole formed into a wall, a threaded
tensioning nut and a torque
indicating washer which is provided as either a stand alone component or as
part of the anchor
nut, and which provides a visual indication of the application of a
compressive force achieved by
tightening the nut with a first predetermined minimum torque selected less
than a torque
necessary to achieve tear-out of the anchor rod from the bore hole.
To overcome at least some of the disadvantages associated with prior art
support systems
and methods, a mine roof support system is provided which includes a
conventional steel anchor
rod or bolt, a threaded fastener and a torque indicating member. The anchor
rod is elongated
along a longitudinal axis, extending from a distal end portion to an
externally threaded proximal
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end portion. The threaded fastener is preferably a steel or iron tensioning
nut of a conventional
design used in mine roof support applications, and is adapted to threadedly
engage the proximal
end of the anchor rod to tension the anchor rod once secured in a bore hole.
The torque
indicating member is adapted to be positioned between the rock face and the
tensioning nut so
that the tightening of the nut along the threaded end of the rod exerts a
compressive force
thereon.
The torque indicating member may be provided either as a separate element or
as part of
the tensioning nut and is adapted to provide a visual indication to an
installer of a selected
compressive force being applied thereto by the threaded fastener. Preferably,
the torque
indicating member includes one or more radially extending rods, pins, members
or generally
flanges which may be planar, bent or curved (the foregoing hereinafter
generally indicated as
flange portions) and which are selected to move, deflect or otherwise distort
under a compressive
force achieved by tightening the nut with a first predetermined minimum
torque. The first
predetermined minimum torque is preferably selected less than the torque
required to cause tear-
out or failure of the anchor rod from the bore hole. The movement of the
flanges thus provides a
visual indication to an installer that a first torque force is being applied
on the tightening nut.
In one other aspect, the present invention provides a torque indicating member
which is
adapted for positioning between a rock face and a tensioning nut used in mine
roof support
systems, to provide a rock bolt installer with a visual indication of the
application of certain
torque forces on the threaded fastener when tensioning a rock bolt. The torque
indicating
member includes a bent portion which is configured to extend, in use, in a
generally axial
elongated direction of an installed anchor bolt or rod. More preferably, the
torque indicating
member includes an opening therethrough which is sized to permit placement of
the member
over a projecting threaded end of an anchor rod which has been positioned in a
bore hole as a
washer. In a simplified construction, planar tabs or flanges extend radially
from the bent portion
of the washer and are adapted to deflect, deform or distort following the
application of a first
compressive force on the torque indicating member achieved by tightening the
tensioning nut
thereagainst with a first predetermined minimum torque.
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In a preferred construction, the torque indicating member is formed as a dome
washer
having a bent and more preferably generally dome-shaped portion which curves
in an axial
direction, and one or more flange portions which extend radially from a
peripheral edge of the
dome-shaped portion. An opening is provided through the axial center of the
dome-shaped
portion to enable the washer to be slid over the threaded proximal end portion
of an anchor rod.
ahead of the tensioning nut, with the dome-shaped portion curving from its
peripheral edge
outwardly away from the rock face. Once the rod has been secured in place with
its distal end in
a bore hole, tightening of the nut results in the application of an axially
compressive force
against the dome-shaped portion and initial radially outward deflection of the
peripheral edge.
The initial outward deflection of the peripheral edge results in radial
outward forces being
applied to the flanges where they join with the dome-shaped portion. The
outward forces in turn
result in the twist deformation andlor bending of the flange members,
providing the installer with
the visual indication that the nut is being tightened with the first
predetermined torque.
Although not essential, most preferably the dome-shaped portion curves with a
radial
diameter selected at between about 1 cm and 8 cm, and a radius of curvature
selected at between
about .3 and 1.5 cm. Preferably, the flange portions are joined along portions
of the peripheral
edge of the dome-shape portion, such that the application of the compressive
force on the dome-
shape portion achieved by tightening the nut with the first predetermined
minimum torque is
selected less than compressive force necessary to substantially collapse
and/or compress the
dome-shaped portion, while producing the radial outward deflection of the
peripheral edge. In
this manner, the radial outward deflection of the peripheral edge, in turn,
produces strain along
the flange portion/peripheral edge interface, to elastically deform at least
part of the flange
portions so as to move axially.
In a most simplified construction, the torque indicating washer is formed as a
dome
washer which is stamped from a single, generally planar sheet of 8 to 20 gauge
metal, such as
steel, however, other metal thicknesses and/or types may also be used.
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Accordingly, in another aspect the present invention resides in a method of
installing a
mine roof support system in a bore hole formed in a rock face, the support
system comprising,
an elongated anchor member extending axially from a distal end portion to a
threaded
proximal end portion,
a generally semi-spherical member for placement generally proximate to said
rock face,
the semi-spherical member having an opening therethrough sized to permit
sliding placement of
said member over said proximal end portion, and including a generally
hemispherical surface
portion and a generally planar surface portion,
a torque indicating washer having a radially extending peripheral portion and
a generally
dome-shaped portion which curves convexly forward relative to said peripheral
portion and
which further comprises a generally centrally positioned aperture sized for
enabling placement of
said torque indicating washer over said proximal end portion,
a threaded fastener sized for threaded coupling with the proximal end portion
of the
anchor member,
the mine support system installed by,
inserting the distal end of the anchor member into the rock wall bore hole so
that the
proximal end projects at least partially outwardly therefrom past said rock
face,
with the semi-spherical member positioned over the distal end portion such
that the
hemispherical surface portion faces inwardly and the torque indicating washer
positioned over
the proximal end portion spaced outwardly from the semi-spherical member and
oriented with
the dome-shaped portion curving convexly outwardly, rotating the threaded
fastener along the
proximal portion relative to said anchor rod to move the fastener axially
towards initial
engagement with the torque indicating washer,
applying a first predetermined minimum torque on said threaded fastener to
impart a
compressive force by said fastener against said torque indicating washer and
produce an initial
deflection of said peripheral portion to provide a visual indication of said
fiirst minimum torque,
and
applying a second minimum torque on said threaded fastener to compress and at
least
partially deform said dome-shaped portion towards contact with said planar
surface portion of
said semi-spherical member.
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In yet another aspect, the present invention resides in a method of installing
a support
system in a bore hole formed in a rock or wall face, the support system
comprising,
an anchor rod being elongated along an axis from a distal end portion to an
externally
threaded proximal end portion,
a seating member for placement generally proximate to said rock or wall face,
the seating
member having an opening therethrough sized to permit sliding placement of
said seating
member over said proximal end portion,
a torque indicating washer having a radially extending peripheral portion and
a dome-
shaped portion which curves convexly forward relative to said peripheral
portion and further
comprising an aperture therethrough sized for enabling sliding placement of
said torque
indicating washer over said proximal end portion,
a threaded fastener sized for threaded coupling with the proximal end portion
of the
anchor rod, whereby rotation of said fastener relative to said anchor rod
moves the fastener
axially along the proximal end portion,
the support system being installed by,
inserting the distal end of the anchor member into the bore hole so that the
proximal end
projects at least partially outwardly therefrom past said rock or wall face,
with the seating member and torque indicating member positioned over the
distal end
portion such that the torque indicating member is spaced outwardly ti-om the
seating member and
in an orientation with the dome-shaped portion curving convexly outwardly,
rotating the
threaded fastener along the proximal portion relative to said anchor rod to
move the fastener
axially into engaging contact with the torque indicating washer,
wherein the application of a first predetermined minimum torque on said
threaded
fastener against said torque indicating washer produces an initial outward
deflection of said
peripheral portion to provide a visual indication of said first minimum
torque, and
the application of a second minimum torque on said threaded fastener
compresses and at
least partially deforms said dome-shaped portion towards juxtaposed contact
with said seating
member.
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In a further aspect, the present invention resides in a torque indicating dome
washer for
use in a mine or wall support system the washer comprising
a generally dome-shaped portion extending generally axially forward from a
peripheral
edge, said dome-shaped member having a radius of curvature selected such that
the application
of a selected compressive force axially thereon produces partial radial
deflection of said
peripheral edge, and
at least one flange portion extending radially outwardly from said peripheral
edge of said
dome-shaped portion, wherein the partial radial deflection of said peripheral
edge produces a
compressive strain on said flange portion to distort or deform said flange
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference may now be had to the following detailed description taken together
with the
accompanying drawings in which:
Figure 1 illustrates schematically a conventional mine roof support system in
an installed
configuration in a rock complex;
Figure 2 illustrates a schematic perspective plan view of a torque indicating
dome washer
in accordance with a preferred embodiment of the invention;
Figure 3 illustrates a cross-sectional view of the dome washer shown in Figure
2 taken
along line 3-3';
Figure 4 illustrates an enlarged schematic plan view of the torque indicating
dome washer
of Figure 2;
Figure 5 illustrates an exploded view showing the installation of the dome
washer of
Figure 2 as part of a mine roof support system used in the support of a rock
complex;
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Figure 6 illustrates a cross-sectional side view of the torque indicating dome
washer of
Figure 2 in an initial installed position next to a spherical seat used in the
support system of
Figure 5;
Figure 7 illustrates a schematic cross-sectional view of the torque indicating
dome washer
of Figure 6 following the application of a compressive load by rotating the
threaded nut of the
mine roof support system of Figure 5 thereagainst with a first predetermined
minimum torque;
Figures 8 to 11 show a series of schematic and cross-sectional views of a rock
structure,
illustrating the installation of the mine roof support and reinforcement
system of Figure ~ in
accordance with the present invention;
Figure 12 illustrates a schematic perspective view of a threaded nut having a
torque
indicating washer integrally joined thereto, in accordance with an alternate
embodiment of the
invention; and
Figure 13 illustrates schematically a perspective plan view of a torque
indicating washer
in accordance with a further embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference is first made to Figure 1 which illustrates a prior art mine roof
support system
used to consolidate ground movement in a rock complex 8. The support system 10
includes a
threaded cast or capped steel dome nut 12 and a steel anchor rod 14. The
anchor rod 14 is
elongated along its longitudinal axial length, and extends from a threaded
outer proximal end
portion 16 to an inner distal end portion 18. In the embodiment shown, the
distal portion 18 is
secured in place in a bore hole 20 formed in the rock complex 8 by a set
adhesive resin 22.
In installation, the bore hole 20 is drilled into the rock complex 8 to a
desired diameter
and depth. A number of two-part resin cartridges (shown as reference numerals
24a,24b in
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Figure 8) are then inserted into the bore hole 20 ahead of the distal end
portion 18 of the steel rod
14. The distal end portion 18 of the rod is next inserted into the bore hole
20 to pierce the
cartridges 24a,24b and mix the resin. Optionally, secondary reinforcing
components, such as a
steel reinforcing plate 26 and/or mesh screen, may be positioned over the
projecting proximal
end 16 of the rod 14. The nut 12 is then threaded onto the proximal end 16 and
tightened against
the plate 26 and outer face 30 of the rock complex 8. The tensioning of the
nut 12 against the
plate 26 compresses the rock complex 8 to provide the desired degree of ground
control. If;
however, as a result of inadvertence, the installer over-torques the nut 12,
this may result in the
tearing out of the rod 14 from the anchoring resin 22, resulting in rod
failure, and necessitating
the installation of a second anchor rod in an adjacent location.
Figures 2 and 3 illustrate a torque indicating washer 36 for use with the nut
I 2, rod 14
and reinforcing plate 26 of the mine roof support system 10 of Figure l, and
which is adapted to
minimize the likelihood of anchor rod 14 tear out. As will be described, the
washer 36 is adapted
to be used in conjunction, not only with an anchor rod 14, threaded nut 12 and
anchor plate 26,
but optionally also a cast steel semi-spherical seat 70 (Figure 5) in the
tensioning and ground
control of the rock complex 8.
The washer 36 includes a central generally dome-shaped portion 38 which curves
forwardly from a peripheral radial edge 40 in a forward direction along axis
Ai-A, (Figure 3).
An opening 42 is formed through the axial apex of the dome-shaped portion 38.
The opening 42
is sized marginally greater than the diameter of the rod 14 to enable the
washer 36 to be slid over
the projecting threaded proximal end 16 of the anchor rod 14 following its
placement in a bore
hole 20. The dome-shaped portion 46 has a preferred radial diameter d~ of
between about 2 and
4 cm, and a radius of curvature of approximately .6 to 1.2.
In the embodiment shown, the dome-shaped portion 46 is stamped from a
generally
square sheet of 12 gauge steel. The overall size of the sheet is selected such
that following its
formation, the dome-shaped portion 38 extends substantially to the mid-lateral
edges 44 of the
washer 36, so as to substantially define four radially projecting generally
triangular flange
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portions 52a,52b,52c,52d integrally formed therewith. Each of the flange
portions 52 is formed
as a generally planar metal tab or flange which, prior to deformation of the
washer 36, are
substantially coplanar to each other. Each flange portion 52a,52b,52c,52d
further merges along a
respective radial quadrant A,B,C,D (Figure 4) with the peripheral edge 40 of
the dome-shaped
portion 38, and projects outwardly to a radial distance dt outwardly therefrom
of between about
.7 and 3 cm.
The dome-shaped portion 38 of the torque indicating washer 36 is formed so
that the
application of a compressive force in the axial direction on the dome-shaped
portion 38 results in
the initial partial radial outward deflection of the peripheral edge 40, as
for example in the
direction of arrows 60 (Figure 4). Most preferably, the deflection of the
peripheral edge 40
occurs radially about the axis A-A~, and where the compressive force required
for deflection is
selected as the force directly or indirectly on the washer 36 achieved by
tightening the nut 12
along the threaded portion 16 of the rod with a first treated predetermined
minimum torque. The
first predetermined torque is selected less than the torque necessary to
completely deform and
flatten the dome-shaped portion 38 and/or result in tear out of the anchor rod
14 from set
anchoring resin 22.
In the preferred mine roof assembly 10 shown in Figure S, the dome washer 10
is used in
conjunction with a semi-spherical seat 70 which is adapted to translate any
tensioning forces at
the rock face 30/bore hole 20 interface in a direction generally parallel to
the rod axis. The semi-
spherical seat 70 is formed as a cast steel member having a planar forward
side surface 72, and a
generally hemispherical rearward surface 74. A bore hole 76 having a diameter
greater than the
diameter of the threaded proximal end 16 of the anchor rod 14 extends
perpendicularly from the
planar surface 74 and through the apex of the hemispherical surface 74. As
will be described,
the bore hole 76 allows the seat 70 to be slid over the projecting threaded
proximal end 16 of the
rod 14.
Preferably, the diameter d~ of the dome-shape portion 38 is selected less than
the
maximum radial diameter ds (Figure 5) of the planar surface 72 of the semi-
spherical seat 70,
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allowing the peripheral surface 40 to be fully supported by the seat 70.
Although not essential,
the dome-shaped washer 36 preferably has a maximum width w (Figure 3) from the
tip of flange
52a to the tip of the radially opposite flange 52b of about 2 and 6 cm, and
which is selected
marginally greater than the minimum radial diameter of the threaded nut 12,
and more preferably
greater than the maximum diameter of the nut 12. As will be described, with
this configuration,
in installation of the mine roof support system 10 the flange portions
52a,52b,52c,52d project
radially outward beyond the nut 12 so as to remain visible during the
tightening of the nut 12
along the threaded end 16.
Figures 6 and 7 illustrate best the use of the torque indicating washer 38 as
providing the
installer with a visual indication when a predetermined minimum torque is
first applied on nut 12
in the tensioning of the anchor rod 14. As the nut 12 compresses the washer 36
and is turned
with a torque equal to the first predetermined torque, the peripheral edge 40
deforms outwardly.
As the peripheral edge 40 moves radially outward in the direction of arrows
60, the outward
deflection of the dome-shaped portion 38 at radially offset locations relative
to each of the
flanges 52,52b,52c,52d results in the planar flanges distorting and curling
forwardly in the
direction of arrows 62 (Figure 7). Because of their lateral extent beyond the
diameter of the nut
12, the deflection of the flanges 52a,52d is visible readily to the installer.
This deflection enables
the installer to determine that the washer plate 26 and spherical seat 70 have
been fully seated
against the rock face 30 and that the first torque force is being applied on
the tightened nut 12.
The visual indication of torque forces on the nut 12 provide the installer
with an
opportunity to more gradually tighten the nut 12 downwardly against the rock
complex 8,
minimizing the likelihood that the nut 12 may be over-torqued.
Following the application of the first predetermined minimum torque, the nut
12 is
preferably rotated at a second greater torque force to apply a higher
compressive axial force on
the torque indicating washer 36. The second torque force is preferably
sufficient to at least
partially and more preferably substantially collapse the dome-shaped portion
38 against the
planar surface 72 of the spherical seat 70, as for example is shown in
phantom, but which is
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13
selected less than the torque force necessary to achieve tear out of the
anchor rod 14 from the set
resin 22 (Figure 1).
Figures 6 to 11 illustrate best the installation of the mine roof/wall
anchoring system 10
utilizing the torque indicating washer 38 of Figure 2. As shown best in
Figures 6 and 7, a bore
hole 20 is conventionally drilled in the rock complex 8 generally
perpendicular to the rock force
30 and to a depth of about 8 feet. A number of resin cartridges 24a,24b are
next inserted into the
bore hole 20. A conventional steel reinforcing rod 14 having an overall axial
length selected
approximately two to six inches longer than the bore hole 20 and an externally
threaded proximal
end portion 14 which extends two to six inches from the proximal endmost tip
66 is next inserted
into the bore hole 20. The distal end portion 18 of the rod 14 is slid into
the bore hole 20 to
rupture the cartridges 24a,24b, releasing the resin therefrom.
The washer plate 26 and semi-spherical seat 70 are then positioned over the
portion of the
proximal end 16 which extends past the rock face 30. The semi-spherical seat
70 is positioned so
that the hemispherical surface 74 of the seat 70 is oriented towards the rock
complex 8 and in
juxtaposed contact with the plate washer 26. As will be described, with this
positioning, the
tightening of the nut 12 along the threaded proximal portion 16 results in
tensioning forces being
substantially maintained axially along the length of the anchor rod 14.
Following the positioning of the reinforcing plate 26 and semi-spherical seat
70, the
torque indicating washer 36 is next positioned over threaded proximal end 14.
The washer 36 is
slid against the semi-spherical seat 70 so that the dome-shaped portion 38
curves forwardly.
outwardly from the bore hole 20, and with the flanges 52 and peripheral edge
surface 40 moved
against the planar surface 72.
Next, a capped dome nut 12 which has a releasable cap member 110 secured
thereto is
threaded onto the end tip 66 of the rod 14, as for example is shown in Figure
10. While the resin
remains unset, the dome nut 12 is rotated about the rod axis by means of a
power winch, thereby
turning the rod 14 about its axial length to mix the released resin. Once the
resin has set securing
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the distal end 18 of the rod 14 in the bore hole 20, the nut 12 is rotated at
a high torque force of
about 50 to 75 ft.lbs. or less. The higher torque forces on the nut 12
relative to the secured rod
14 results in its deformation and the detachment of the cap member 110
enabling the nut 12 to be
run axially along the rod 14 towards the rock face 30.
The tightening of the nut 12 initially slides the plate 26, spherical seat 70
and torque
indicating washer 36 to a first position snugly pushed against the rock face
30. As the installer
continues to rotate the nut 12 relative to the anchor rod 14, the tightening
of the nut 12 provides
an axial compressive force on the dome-shaped portion 38 of the washer 36 in
the direction of
arrows 100 (Figure 7). Once the compressive force equals that applied by the
first predetermined
minimum torque force on the nut 12, and which most preferably is selected at
between about 80
and 125 ft.lbs., the compression of the dome-shaped portion 38 produces a
slight outward
deflection of the peripheral edge 40. The radial deflection of the edge 40
produces compressive
strain at the peripheral edge 40/flange 52 junction as the peripheral edge 40
moves marginally
radially outward. The radial outward movement of the peripheral edge 40 thus
results in the
flange portions 52a,52b,52c,52d deforming forwardly providing the visual
indication of the first
torque to the installer. Thereafter the installer adjusts the torque forces on
the nut 12, and
tightens the nut with the second torque force, such that the dome-shaped
portion 38 substantially
collapses to the flattened position in juxtaposed contact with the planar
surface 72 of the
spherical seat 70 as is shown in Figure 11.
Although not shown, optionally following the tightening of the nut 12 to the
fully seated
position of Figure 11, push plates or mesh screening may be affixed to the
remaining projecting
proximal end 16 of the rod 14 which extends outwardly therefrom in a
conventional manner.
Although Figures 2 to 5 illustrate the torque indicating dome washer as
comprising a
separate component adapted for placement interposed between the semi-spherical
seat 70 and nut
12, the invention is not so limited. Figure 12 illustrates an alternate
embodiment where like
reference numerals are used to identify like components. In Figure 12, a
washer nut 120 is
provided with a torque indicating washer 32 joined thereto as an integral
unit. In Figure 12, the
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torque indicating washer 38 has essentially the identical construction as that
shown in Figure 2.
The washer 32 is spot welded directly to the inner end face 122 of a capped
dome nut 12 as a
single unit. The torque indicating washer 38 is joined to the dome nut end
face 122 with the
opening 42 co-axially aligned with a releasable end cap 110 and the threaded
interior of the nut
12. Preferably, the dome-shaped portion 38 of the washer 36 is joined to the
nut 12 only about
the immediate periphery of the opening 42. This construction advantageously
ensures that the
coupling of the washer 36 to the nut 12 does not adversely affect the outward
deflection of the
peripheral edge 40, or the compression of the dome-shaped portion 38 upon the
application of
axial forces. It is to be appreciated that the washer nut 120 of Figure 12, in
addition to providing
a more compact design, avoids the requirement to separately position the
torque indicating
washer 36 on the rod 14 ahead of the nut 12.
Although the preferred embodiment of the invention describes the positioning
of the plate
anchor 26, semi-spherical seat 70, torque indicating washer 36 and tensioning
nut 12 following
the placement of the anchor rod 14 in the bore hole 20, the invention is not
so limited. Tt is to be
appreciated that in an alternate construction, the washer plate 26, semi-
spherical seat 70, torque
indicating dome washer 36 and nut 12 could be prepositioned over the threaded
proximal end 16
of the anchor rod 14, prior to the insertion of the distal end 18 in the bore
hole 20 and the rupture
of the resin cartridges 24a,24b thereby.
Although the preferred embodiment of the invention describes and illustrates
the torque
indicating washer 36 as having four planar flanges 52a,52b,52c,52d which are
integrated with the
peripheral edge 40, the invention is not so limited. It is to be appreciated
that other flange
configurations which are adapted to deform or deflect under a predetermined
compressive force
are also possible and will now become readily apparent. In addition, the
torque indicating
washer 36 could be provided with fewer or larger number of different shaped
flanges which are
adapted to distort under a predetermined axial load without departing from the
spirit and scope of
the invention. Reference may be had to Figure 13 which illustrates one
alternate possible
embodiment of the invention wherein like reference numerals are used to
identify like
components. In Figure 13, the torque indicating washer 36 is provided with
only two flanges
CA 02504058 2005-04-11
16
52a,52b at radially opposite locations. As with the embodiment described with
reference to
Figures 2 and 3, the application of an axial compressive force on the dome-
shaped portion 38 of
the washer 36 results in the deflection of the flanges 52a,52b, to provide the
installer with the
visual indication that a tensioning nut has been tightened with the first
predetermined minimum
torque.
Although not essential, more preferably at least the flanges 52a,52b, and in a
simplified
construction the entire forward surface of the dome washer 36 has a high
visibility coating 90
applied thereto. By way of non-limiting example, the high visibility coating
90 could comprise a
fluorescent paint selected to provide enhanced visibility of the washer 36 in
low light conditions
which, for example, would be typically experienced in underground mining
operations.
Although the preferred embodiment of the invention describes the securement of
the
anchor rod 14 in the rock complex bore hole 20 by the use of mixed resin 22,
the invention is not
so limited. It is to be appreciated that the present invention is equally
suited for use with anchor
rods which are held in place by means of mechanical anchors including, without
restriction, the
use of wedge bolts and the like.
Although the detailed description describes the support system 10 as including
an anchor
rod 14, tensioning nut 12, semi-spherical seat 70, plate anchor 26 and dome
washer 36, the
invention is not restricted to the specific components. It is to be
appreciated that the support
system 10 could be provided with fewer or additional components used in
concrete wall
reinforcement and/or mine roof reinforcement. These components could include
without
restriction mesh screening, push plates or other components used in
conventional support
systems provided in place of or in addition to the spherical seat 70 and/or
washer plate 26
illustrated in Figure 4.
Although the detailed description describes and illustrates various preferred
embodiments, the invention is not so limited. Many modifications and
variations will now occur
CA 02504058 2005-04-11
17
to persons skilled in the art. For a definition of the invention, reference
may be had to the
appended claims.
