U.S. patent application number 14/649278 was filed with the patent office on 2015-11-12 for expandable bolt with thrust element.
The applicant listed for this patent is FCI HOLDINGS DELAWARE, INC.. Invention is credited to Jeremy Ross Arnot, David A. Martin.
Application Number | 20150322786 14/649278 |
Document ID | / |
Family ID | 47560416 |
Filed Date | 2015-11-12 |
United States Patent
Application |
20150322786 |
Kind Code |
A1 |
Martin; David A. ; et
al. |
November 12, 2015 |
Expandable Bolt With Thrust Element
Abstract
The present invention includes a rock bolt having a
longitudinally expandable tube. The tube includes a longitudinally
extending depression that defines a temporary enclosed longitudinal
passageway. The rock bolt further includes a shielded distal end to
prevent debris from entering the temporary enclosed longitudinal
passageway. The distal end includes a thrust element that
facilitates movement of loose material across the rock bolt as it
is advanced in a borehole. The present invention also includes a
method of making such a rock bolt and a method of using such a rock
bolt.
Inventors: |
Martin; David A.; (New
Lambton, AU) ; Arnot; Jeremy Ross; (Mt. Hunter,
AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FCI HOLDINGS DELAWARE, INC. |
Wilmington |
DE |
US |
|
|
Family ID: |
47560416 |
Appl. No.: |
14/649278 |
Filed: |
December 4, 2012 |
PCT Filed: |
December 4, 2012 |
PCT NO: |
PCT/US12/67719 |
371 Date: |
June 3, 2015 |
Current U.S.
Class: |
405/259.3 |
Current CPC
Class: |
E02D 5/805 20130101;
E21D 21/008 20130101; E21D 21/0073 20160101; E21D 21/0033 20130101;
E21D 20/00 20130101; E21D 21/0093 20130101 |
International
Class: |
E21D 21/00 20060101
E21D021/00; E02D 5/80 20060101 E02D005/80; E21D 20/00 20060101
E21D020/00 |
Claims
1. A rock bolt comprising: an expandable tube having a
longitudinally extending depression disposed between a pair of
outer portions of the tube, wherein the exterior of the tube
defines a temporary, enclosed longitudinal passageway; and a thrust
element positioned at a distal end of the rock bolt to facilitate
movement of material past the rock bolt when installed in a
borehole.
2. The rock bolt according to claim 1, wherein the thrust element
includes a plurality of projections and at least one channel
between the projections that facilitates material flow across the
rock bolt as it is advanced in a borehole.
3. The rock bolt according to claim 1, wherein the thrust element
is tapered from a thrust end to an engagement end.
4. The rock bolt according to claim 1 wherein the thrust element
includes a plurality of facets extending between the thrust end and
the engagement end.
5. The rock bolt according to claim 1, further comprising a cover
covering the temporary longitudinal passageway, wherein the thrust
element is adapted to engage with, or form part of the cover.
6. The rock bolt according to claim 1, further comprising a
stiffener tube surrounding the distal end of the expandable tube,
wherein the thrust element is adapted to engage the stiffener
tube.
7. The rock bolt according to claim 6, wherein the thrust element
comprises an engagement portion received within the stiffener
tube.
8. A method of using a rock bolt comprising: providing a rock bolt
comprising an expandable tube having a temporary enclosed
longitudinal passageway with an open distal end and an end fitting,
and a thrust element at a distal end of the expandable tube
covering the temporary longitudinal passageway; inserting the rock
bolt in a borehole, whereby material in the borehole is deflected
by the thrust element as it is advanced in the borehole; expanding
the tube by providing pressurized fluid to the interior of the
tube, thereby providing frictional engagement between an exterior
of the tube and an interior of the borehole; and draining the fluid
from the interior of the tube.
9. The method according to claim 8, wherein the thrust element
includes a plurality of projections and at least one channel
between the projections.
10. The method according to claim 8, wherein the thrust element is
tapered from a thrust end to an engagement end.
11. The method according to claim 8, wherein the thrust element
includes a plurality of facets extending between the thrust end and
the engagement end.
12. The method according to claim 8, further comprising a cover
covering the temporary longitudinal passageway, wherein the thrust
element is adapted to engage with, or form part of, the cover.
13. The method according to claim 8, further comprising a stiffener
tube surrounding the distal end of the expandable tube, wherein the
thrust element is adapted to engage the stiffener tube.
14. The method according to claim 13, wherein the thrust element
comprises an engagement portion received within the stiffener
tube.
15. The method according to claim 8, wherein the rock bolt is
inserted into a borehole with a percussive force.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a rock bolt having an expandable
tube and a shielded distal end bearing a thrust element, a method
of making such a rock bolt, and a method of using such a rock
bolt.
[0003] 2. Description of Related Art
[0004] Rock bolts are used in underground mines, such as coal
mines, to support the roof and ribs. Installation of conventional
rock bolts involves drilling a borehole into the rock to a desired
depth using an elongated drilling tool (termed the "drill steel"),
removing the drill steel from the borehole, optionally inserting
adhesive resin cartridges, and retaining the cartridges in the
blind end of the borehole while a bolt, optionally bearing an
expansion anchor, is installed into the borehole. The free end of
the bolt extending out of the borehole is received by a chuck of a
bolting machine. The bolting machine rotates the bolt within the
borehole to mix the adhesive resin and/or expand the expansion
anchor.
[0005] Other rock bolts comprise a longitudinally expandable tube
that includes a longitudinally extending depression between two
curved outer portions where the tube is partially collapsed on
itself. The ends of the tube are folded over to create two enclosed
cavities in the curved outer portions of the tube while a temporary
passageway defined by the depression remains open on the ends.
After placing the rock bolt in the pre-drilled borehole,
pressurized fluid is delivered into the two cavities to force the
depression outward, expand the tube, and compress it against the
surrounding rock. Until the expansion has been completed, the ends
of the passageway defined by the depression are open so that debris
from the borehole can fall into the passageway defined by the
depression.
SUMMARY OF THE INVENTION
[0006] The present invention includes a rock bolt having a
longitudinally expandable tube. The tube includes a longitudinally
extending depression that defines a temporary, enclosed
longitudinal passageway. A thrust element is positioned at a distal
end of the rock bolt and may be arranged in use to deflect loose
material disposed in the bore as the rock bolt is inserted, thus
facilitating movement of the material past the rock bolt when
installed in a borehole.
[0007] The thrust element may assist insertion of the rock bolt in
the bore and/or may inhibit compaction of that material in the
blind end of the bore. Compaction of loose material in the bore is
problematic as it reduces the effective length of the bore and may
prevent the rock bolt from being fully inserted into bore unless
that borehole is of extended length.
[0008] The thrust element may form part of a cover of the rock bolt
to prevent debris from entering the temporary, enclosed
longitudinal passageway, ease insertion of the rock bolt into the
borehole, and assist in alignment of the rock bolt in the borehole.
Alternatively the thrust element may form an extension of that
cover and be fixed to the cover. The cover may be a plug or a cap
and may provide a rounded tip for the rock bolt. The plug may be
spherical. The cap may be attached such that its proximal end abuts
the distal end of the rock bolt, is inserted into the distal end of
the rock bolt, or extends beyond the distal end and along the
sidewall of the rock bolt. In another form, the thrust element may
be fixed directly to the rock bolt.
[0009] In one form, the thrust element is fixed in place by
welding, but may be fixed by other means such as crimping, or
through a coupling (such as a threaded coupling arrangement) or by
adhesive bonding. In a particular form, the connection is only
loaded in compression as the rock bolt is driven into the bore
without requiring rotation. In one form, this drive action is by a
percussive force.
[0010] The thrust element may take various forms but in general
includes a profiling that promotes radial deflection of the
material as the rock bolt is inserted axially into the bore. In one
form, the thrust element may be conical or frustoconical having a
wall surface that extends from an apex of the element to an
engagement end where the element is mounted to the rock bolt. The
surface of the thrust element extending between the apex and the
engagement end may be faceted.
[0011] In another form, the thrust element may be more akin to a
drill bit and may include channels or flutes that allow for radial
flow of material as the rock bolt is inserted into the bore.
[0012] The present invention also includes a method of
manufacturing a rock bolt, including providing an expandable member
including an expandable tube and an end fitting where the
expandable tube has a longitudinally extending depression disposed
between a pair of outer portions of the tube, the exterior of the
tube defines a temporary, enclosed longitudinal passageway having
an open distal end, and the outer portions of the tube have closed
distal ends, and enclosing the expandable member with a cover such
that a distal open end of the temporary, enclosed longitudinal
passageway of the expandable tube is covered. The cover may be a
plug or a cap and may provide a rounded tip for the rock bolt. The
cover may also include a thrust element arranged in use to deflect
loose material disposed in the bore as the rock bolt is inserted,
thus facilitating movement of material past the bolt when installed
in a borehole. The method may also include placing a stiffening
tube on a proximal end of the expandable tube such that the
stiffening tube surrounds the proximal end of the expandable tube
and has an opening that aligns with a corresponding opening in the
expandable tube, thereby providing fluid communication to an
interior of the expandable tube.
[0013] The present invention further includes a method of using a
rock bolt, including providing a rock bolt having an expandable
member including an expandable tube having a temporary, enclosed
longitudinal passageway with an open distal end, and a cover at a
distal end of the rock bolt covering the temporary longitudinal
passageway; drilling a borehole in rock; placing the rock bolt in
the borehole; expanding the tube by providing pressurized fluid to
the interior of the tube, thereby providing frictional engagement
between an exterior of the tube and an interior of the borehole;
and draining the fluid from the interior of the tube. The cover may
be a plug or a cap and may provide a rounded tip for the rock
bolt.
[0014] The present invention further includes a method of using a
rock bolt including providing a rock bolt having an expandable
member including an expandable tube having a temporary enclosed
longitudinal passageway with an open distal end, and a thrust
element at the distal end; drilling a borehole in rock; inserting
the rock bolt in the borehole whereby loose material in the bore is
deflected by the thrust element; expanding the tube by providing
pressurized fluid to the interior of the tube, thereby providing
frictional engagement between an exterior of the tube and an
interior of the tube thereby providing frictional engagement
between an exterior of the tube and an interior of the borehole;
and draining fluid from the interior of the tube. The thrust
element may generally include a profiling that promotes radial
deflection of the material as the rock bolt is inserted axially
into the bore. The thrust element may comprise a cover for the
distal end or may form an extension of that cover.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a side view of a rock bolt produced according to
the present invention;
[0016] FIG. 2 is a cross-section taken along lines 1-1 of FIG.
1;
[0017] FIG. 3 is a cross-section taken along lines 2-2 of FIG. 1,
as installed in rock strata;
[0018] FIG. 4 is a longitudinal cross-section of the distal end of
a rock bolt according to one embodiment of the present
invention;
[0019] FIG. 5 is a longitudinal cross-section of the distal end of
a rock bolt according to a second embodiment of the present
invention;
[0020] FIG. 6 is a longitudinal cross-section of the distal end of
a rock bolt according to a third embodiment of the present
invention;
[0021] FIG. 7 is a longitudinal cross-section of the distal end of
a rock bolt according to a fourth embodiment of the present
invention;
[0022] FIG. 8 is a side view of a distal end of rock bolt according
to a fifth embodiment of the present invention;
[0023] FIG. 9 is a longitudinal cross-section of the distal end of
a rock bolt according to FIG. 8;
[0024] FIG. 10 is a side view of a thrust element for use in the
rock bolt of FIG. 8;
[0025] FIG. 11 is a perspective view of a thrust element for use in
the rock bolt of FIG. 8;
[0026] FIG. 12 is a longitudinal cross-section of the distal end of
a rock bolt according to a sixth embodiment of the present
invention;
[0027] FIG. 13 is a perspective view of a thrust element for use in
the rock bolt of FIG. 12;
[0028] FIG. 14 is a side view of a thrust element for use in the
rock bolt of FIG. 12;
[0029] FIG. 15 is a longitudinal cross-section of the distal end of
a rock bolt according to a seventh embodiment of the present
invention;
[0030] FIG. 16 is a perspective view of a thrust element for use in
the rock bolt of FIG. 15;
[0031] FIG. 17 is a side view of a thrust element for use in the
rock bolt of FIG. 15;
[0032] FIG. 18 is a longitudinal cross-section of the distal end of
a rock bolt according to an eighth embodiment of the present
invention;
[0033] FIG. 19 is a perspective view of a thrust element for use in
the rock bolt of FIG. 18; and
[0034] FIG. 20 is a side view of a thrust element for use in the
rock bolt of FIG. 18.
DETAILED DESCRIPTION OF THE INVENTION
[0035] Referring now to the drawing figures in which like reference
numbers refer to like elements, FIG. 1 shows a rock bolt 2 which
includes an expandable tube 4 having an initial cross-sectional
profile as shown in FIG. 2. The tube 4 is partially collapsed upon
itself (such as by rolling or drawing) so as to provide a depressed
region 6 between two curved outer portions 8, 10 extending
longitudinally along the tube 4. The tube 4 is produced from a
steel alloy or the like having sufficient strength to function in
rock support, even after deformation from internal hydraulic
pressure as described below. A first stiffening tube 14, having a
sidewall and two open ends, is attached to and surrounds a proximal
end 15 of the tube 4. A lip 18 may extend from stiffening tube 14
for engaging with a rock surface when the rock bolt 2 is inserted
in the borehole.
[0036] A second stiffening tube 20, having a sidewall and two open
ends, is attached to and surrounds a distal end 21 of tube 4
leaving the end of the tube 4 uncovered. A cover 22 covers the
opening in a distal end 23 of second stiffening tube 20, the tube
4, or both and may be fixed thereto by welding or the like. The
outer curved portions 8, 10 of tube 4 abut one another to define a
temporary main passageway 26 as well as interior passageways 28,
30. Main passageway 26 is open at the distal end 21 of tube 4 while
interior passageways 28, 30 are closed as shown in FIGS. 4-7. As
shown in FIG. 1, the first stiffening tube 14 defines an opening 34
which is aligned with an opening (not shown) in tube 4, such that
the openings are in fluid communication with interior passageways
28, 30.
[0037] In operation, a borehole is drilled into the rock to the
desired depth and the bolt 2 is inserted through a bearing plate
and into the borehole. A source of pressurized fluid, such as
water, is delivered through the opening 34 of the first stiffening
tube 14 and an opening in tube 4 into interior passageways 28, 30.
When passageways 28, 30 are filled, the further addition of fluid
creates sufficient hydraulic pressure to force open the tube 4,
such that passageways 28, 30 are conjoined as an interior 35 of the
tube 4 expanding the tube 4, and ultimately compressing the tube 4
against the surrounding rock of the borehole. See FIG. 3. As a
result, main passageway 26 no longer exists. When the tube 4 is
fully expanded and no further fluid is received therein, the fluid
supply is removed and the fluid is drained. In this manner, the
expanded tube 4 frictionally anchors into and/or against the
surrounding rock R.
[0038] The cover 22 may take the form of a plug or a cap. In one
embodiment, the cover 22 is a plug 122 or a plug 222, as shown in
FIGS. 4 and 5, respectively. The plug 122, 222 is placed in the
opening in the distal end 23 of tube 20 such that a first portion
124, 224 thereof is exposed and a second portion 125, 225 is in the
interior of the tube 20. The plug 122, 222 may take any suitable
shape (such as rounded) as long as the main passageway 26 is
covered. The plug 122, 222 may be made of steel or any other
suitable material. The plug 122, 222 may be fixed to the rock bolt
102, 202 by welding or the like. For example, tack welds 32, spaced
apart around the circumference of the plug 122, 222 may be used to
attach the plug 122, 222 to tube 20.
[0039] In one embodiment, such as for rock bolt 102, shown in FIG.
4, plug 122 is spherical. Plug 122 may be placed such that the
first exposed portion 124 is one hemisphere of spherical plug 122
and the second portion 125 inside the opening in the distal end 23
of second stiffening tube 20 is the other hemisphere as shown.
Alternatively, the plug 122 may be placed such that less of plug
122 is exposed or more of plug 122 is exposed as long as the main
passageway 26 is covered. Plug 122 may take the form of a polished
or unpolished ball bearing.
[0040] In another embodiment, such as for rock bolt 202, shown in
FIG. 5, the first exposed portion 224 of the plug 222 may be dome
shaped and the second portion 225 extending into tube 20 may be
cylindrical. The second cylindrical portion 225 may further have a
beveled edge 227 as shown.
[0041] Alternatively, the cover 22 may be a cap 322 or a cap 422,
as shown in FIGS. 6 and 7, respectively. Cap 322, 422 may take any
suitable shape (such as rounded) as long as the main passageway 26
is covered. The cap 322, 422 may be made of steel or any other
suitable material. Cap 322, 422 may be fixed to the rock bolt 302,
402 by welding or the like. For example, tack welds 32 spaced apart
around the circumference of the proximal end 329, 429 of cap 322,
422 may be used to attach cap 322, 422 to respective tube 20.
[0042] In one embodiment, such as for rock bolt 302, shown in FIG.
6, cap 322 is hemispherical, and the open proximal end 329 of cap
322 abuts distal end 23 of tube 20. Cap 322 is shown to be hollow
but it could also be solid (not shown), for example, a sphere, such
as plug 122 in FIG. 4, cut in half.
[0043] In another embodiment, such as for rock bolt 402, shown in
FIG. 7, cap 422 has a closed distal end 434, an open proximal end
429, and a sidewall 436 extending from the closed distal end 434 to
the open proximal end 429 creating an inner cavity 438. Cap 422 is
placed over tube 20 such that tube 20 and the distal end 21 of tube
4 are received in the inner cavity 438. The sidewall 436 of cap 422
extends along the sidewall of tube 20. Cap 422 can be fabricated
using any suitable means including, but not limited to, stamping,
molding, or attaching a cover portion to a cylindrical tube. The
distal end 434 of cap 422 may be hollow (as shown) or may be solid
(not shown) as described above for cap 322 of rock bolt 302.
[0044] In another embodiment (not shown), cap 422 could be sized
such that its sidewall 436 fits inside the distal end 23 of tube 20
such that distal end 434 of cap 422 extends beyond distal end 23 of
tube 20. A portion of sidewall 436 may extend beyond the distal end
23 of tube 20 or the length of the sidewall 436 may be adjusted so
that only distal end 434 extends beyond distal end 23 of tube
20.
[0045] In further embodiments such as for inserting the rock bolt
into risible ground or ground into which it is difficult to insert
an expandable bolt, a thrust element (522, 622, 722, or 822) may be
provided at the distal end 23 of the rock bolt as shown in FIGS.
8-20. The thrust element may comprise a cover for the distal end
23, or may be otherwise associated with the distal end 23, such as
being directly connected to the distal end, or form an extension of
the cover 22.
[0046] The thrust element may be arranged in use to deflect loose
material disposed in the bore as the rock bolt is inserted. This
may assist insertion of the rock bolt in the bore and/or may
inhibit compaction of that material in the blind end of the bore.
Compaction of loose material in the bore end is problematic as it
reduces the effective length of the bore and may prevent the rock
bolt from being fully inserted into a bore unless that borehole is
of extended length. It is undesirable to extend the length of the
borehole as this adds both time and expense to the strata support
operation.
[0047] In the form illustrated in FIGS. 8-11, thrust element 522 is
in the form of a cone and extends from an apex 540 to an engagement
end 542. The tapered surface of the element 522 extending between
the apex 540 and the engagement end 542 comprises a plurality of
angled facets 544. These angled facets allow loose material within
the bore to be deflected in a radial direction (relative to the
axis of the bore). Such movement of the loose material may aid
insertion of the rock bolt in the bore and may inhibit compaction
of the loose material in the end of the bore.
[0048] In some forms the engagement end 542 comprises an engagement
portion 525 adapted to be inserted into the distal end 23 of the
stiffening tube 20. In the form illustrated in FIGS. 8-11, the
engagement portion 525 is in the form of a hemisphere adapted to be
inserted into the distal end 23. The engagement portion further
includes a collar section 526 that bears against the interior of
the distal end 23 and a downwardly facing engagement shoulder 527
that locates over the distal end 23, thereby providing a cover for
the distal end 23. Further, as illustrated the thrust element 522
which is typically made from metal, is fixed to the distal end 23
by tack welds 32. It will be appreciated that the thrust element
522 may be fixed by other means such as by crimping, a coupling
(such as a threaded coupling) or by adhesive bonding.
[0049] In the form illustrated in FIGS. 12-15, thrust element 622
is frustoconical and extends from a truncated apex 640 to an
engagement end 642. The surface of the element 622 extending
between the apex 640 and the engagement end 642 comprises a
plurality of angled facets 644. Similar to the previous embodiment,
these angled facets 644 allow loose material within the bore to be
deflected in a radial direction (relative to the axis of the bore).
Again, the thrust element 622 forms the cover for the distal end 23
and may be welded by tack welds 32 to the end 23 with the
engagement end 642 comprising an engagement portion 625 and being
adapted to be inserted into the distal end 23 of the stiffening
tube 20. In the form illustrated in FIGS. 12 through 14, the
engagement portion 625 includes a hemisphere adapted to be inserted
into the distal end 23, a collar section 626 which bears against
the interior of the of the distal end 23 and a downwardly-facing
engagement shoulder that locates over the distal end 23.
[0050] In the form illustrated in FIGS. 15-17, thrust element 722
extends from a thrust end 740 to an engagement end 742. The element
722 is made akin to a drill bit and the thrust end 740 is in the
form of a profiled head having opposing angled blade surfaces 746
spaced apart about an upper surface of the thrust end 740. A
central depression 747 is positioned intermediate the angled blade
surfaces 746. The engagement end comprises an engagement portion
725 which comprises an engagement shoulder 748 that bears against
the distal end 23 and an engagement flange 749 that locates in
facing relation with the interior of the distal end 23. In this
way, the thrust element 722 also forms a cover for the distal end
23. Channels 750 extend longitudinally along the element 722
between the blades 746. These channels are arranged to allow loose
material to flow past the thrust element 722 as the rock bolt is
advanced along the bore during insertion thereby inhibiting
compaction of material at the end of the bore. Again, in the
illustrated form, the thrust element 722 is welded to the distal
end 23 by tack welds 32.
[0051] In a further form illustrated in FIGS. 18-20, thrust element
822 extends from a thrust end 840 to an engagement end 842. The
thrust end 840 is in the form of a profiled head having two
protrusions 846 spaced apart about an upper surface of the thrust
end 840. A domed surface 847 is positioned intermediate the
protrusions 846. The engagement end 842 comprises an engagement
shoulder 848 which locates over the distal end 23 and a threaded
shaft 849. The shaft 849 locates within the distal end and is
arranged to engage with a complementary interior thread 36 formed
on the interior of the tube 20 to secure the element 822 to the end
23. The spacing between the protrusions 846 allows material flow
across the element 822 on insertion of the rock bolt into a bore
containing loose material.
[0052] The rock bolt can be made by providing an expandable member
which includes an expandable tube 4 and an end fitting (stiffening
tube 20) on the distal end 21 of the expandable tube 4. The
expandable tube 4 has a longitudinally extending depression 6
disposed between a pair of curved outer portions of the tube 8, 10.
The exterior of the tube defines a temporary, enclosed longitudinal
passageway 26 having an open distal end 23 and the outer portions
of the tube 4 define internal passageways 28, 30 which have closed
distal ends 23. The distal end of the tube 4 is then enclosed with
a cover 22 so as to cover the distal open end 23 of the temporary,
enclosed longitudinal passageway 26. The cover 22 may be in the
form of a plug 122, 222 or a cap 322, 422 and may be rounded. The
cover 22 may be secured to the expandable tube 4 by welding or any
other suitable method. The method may also include placing a
stiffening tube 20 on a proximal end 15 of the expandable tube 4
such that the stiffening tube 20 surrounds the proximal end 15 of
the expandable tube 4 and has an opening 34 that aligns with a
corresponding opening in the expandable tube 4, thereby providing
fluid communication to an interior of the expandable tube 4. The
stiffening tube 20 may be attached to the expandable tube 4 by
welding, crimping or any other suitable method.
[0053] The cover keeps debris from entering the main passageway of
the rock bolt when the rock bolt is in the unexpanded condition. It
also allows the rock bolt to be more easily inserted and centered
in the borehole. The domed end of the rock bolt created by the
cover eliminates the sharp angles at the distal end of the rock
bolt which can tend to get caught on the sides of the borehole. The
domed end also allows the rock bolt to be centered more easily in
the borehole.
[0054] The cover also has the advantage of reduced manufacturing
costs compared to other methods of rounding the end, for example,
building up weld metal on top of a blank to round the end. The
cover may be held in place with a minimal number of tack welds as
described above simplifying fabrication and reducing costs. In
addition, manufacturing becomes even easier when producing a rock
bolt according to embodiment 102, shown in FIG. 4. The spherical
plug 122 may be placed in tube 20 in any orientation simplifying
assembly and, thus reducing assembly time.
[0055] In general use, the expandable rock bolt with thrust element
is inserted into a pre-drilled borehole, without rotation thereof
necessary, although in certain instances the expandable rock bolt
with thrust element may be at least slightly rotated about its
longitudinal axis. Such pre-drilled boreholes may at least
partially refill with loose rock or the like. The thrust element
deflects such loose material to ease the insertion of the bolt into
the borehole, with the remainder of installation of the expandable
rock bolt with thrust element being the same or similar to the
expandable bolt with shielded tip as described above.
[0056] The thrust element positioned on the distal end of the
expandable rock bolt reduces the difficulty of inserting the
expandable rock bolt into a bore made in risible or gravelly earth.
In these circumstances the material tends to move past or be
deflected by the element into the wall of the bore. The thrust
element allows the bolts to be more easily inserted by compacting
the loose material against the wall of the bore or moving loose
earth material away from the advancing front of the rock bolt as it
is being inserted in the bore. This allows the expandable bolt to
be inserted into the bore without the risk that there will be a
build up of material in the end of the bore that would prevent the
rock bolt from being fully inserted. The use of a thrust element on
the rock bolt is particularly useful when a percussive force is
applied to drive the rock bolt in place and typically does not
require any rotation to be applied to the bolt.
[0057] The foregoing description sets forth the preferred
embodiments of the invention at the present time. Various
modifications, additions, and alternative designs will, of course,
become apparent to those skilled in the art in light of the
foregoing teachings without departing from the scope of the
invention. The scope of the invention is indicated by the following
claims rather than by the foregoing description. All changes and
variations that fall within the meaning and range of equivalency of
the claims are to be embraced within their scope. Specifically,
while embodiments herein have been described as having a rounded
cover, covers having any shape that covers the main passageway of
the rock bolt are considered within the scope of the invention.
* * * * *