Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BACKGROUND OF ~HE INVENTION
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The present invention relates to rock reinforcing
apparatus and metllods and, more spec~flcally, to a combined
mechanical-resin rock bolt anchorlng system such as typically
used in the support o~ mine roofs, and the like.
In mlne work, such as coal mining, or in underground
~ormations such as tunnels or excavations, it is often nece~sary
to reinforce or support the roof and/or walls of the excavating
to prevent rock ~alls or cave-ins, The most common means presently
in use for e~fecting such support include elongated bolts or bars
which are inserted in blind drill holes to hold a metal support
plate in close engagement with the roof or wall surface. The bolt
or bar is securely fixed in the hole by anchoring means such as a
mechanical expansion anchor, a hardenable resin which surrounds
the end of the bolt within the hole, or both.
Many variations of the basic mine roof expansion anchor
have been proposed and numerous styles and models are currently
- in wide-spread use. Common attributes of such anchors are the
expansion shell, or other such radially expansible members, and
a tapered nut having a threaded opening into which one end of the
rock bolt may be threadedly advanced. As the bolt is rotated with
the shell and nut constrained against rotation, the nut is
gradually drawn into the shell to cause radial expansion thereof
into tightly engaged contact with the wall of the drill hole.
Resin anchoring is also commonly used to fixedly
secure the rock bolt or bar in the drill hole. The use of
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polyester resins in underground formation was disclosed at
least as early as the June 4, 1963, U.S. Patent No. 3,091,935
of ~rown and Pritchard entitled "Rock Treatment". It has
been found expedient to provide the resin grouting materials
in two components each of which remains in a semi-liquid or
thixotropic phase until mixed with the other, whereupon curing
progresses to the stage that the steel bolt or bar will fail
before the resin bond fails. The two components, a polyester
resin~and a catalyst, curing or hardening agent, are commonly
provided in a single cartridge where~n they are a single cart-
ridge wherein they are physically separated in individual com-
partments, such as disclosed, for example, in U.S. Patent No.
3,324,663. Upon insertion of the resin cartridge and-bolt in-
to the drill hole the rock bolt or reinforcing bar itself, or
other suitable means, is used to rupture the resin cartridge
and mix the two components so that the curing and hardening
necessary to retain the bolt in the hole may take place.
In addition to the many varieties of mechanical
anchors and resin grouting systems used individually, it has
also been proposed to combine the two so that a rock bolt or
reinforcing bar may be secured by both anchoring systems.
Such a dual anchoring system is disclosed, for example, in
Montgomery Patent No.3,618,326 wherein a conventional expansion
anchor is used in combination with a novel two-compartment
resin cartridge. Patent No. 3,702,060 likewise discloses a
conventional expansion anchor threaded on the end of rock bolt
and modified to carry a special resin container. Other U.S.
patents, such as Nos. 2,829,50~ of Demsey, 3,188,815 of Schuer-
mann, et al, and aforementionèd 3j324,663 of McLean, disclose
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the combination of expansible shell mechanical-type anchors
with resin grouting systems.
OBJECTS OF THE INVENTION
The roof bolting systems of the prior art whieh com-
bine meehanieal and resin anehoring depend, for the most part,
upon speeial paekaging of the resin materials which are re-
leased and mixed by threaded advancement of the bolt into the
expansion anehor or by means external to the drill hole. Where
the bolt is threaded into the expansion anehor nut as mixing
takes plaee, the mixture may be incomplete when the bolt reaehes
the limit of its travel. Considerable savings in fabrieation
and installation eosts eould be achieved by using conventional
resin paekages in combination wIth expansion anchors and bolts
whieh are structurally modified, but not significantly more
expensive than, presently existing anchors and whieh përmit
immediate loading after a simple and rapid i~nstallation.
Accordingly, it is a principal objeet of the plesent
invention to provide a combined mechanieal-resin roek bolting
system wherein a eonventional resin package is used and in-
stallation allowing full loading immediately after setting the
mechanieal anchor is rapidly effeeted.
A further object is to provide a rock bolt and ex-
pansion anchor assembly having eoopera~ive structure on the
bolt and anehor whieh enhanees use of the assembly in eom-
bination with a frangible resin eartridge.
Another object is to provide a novel mine roof ex-
pansion anchor having structural attributes which promote its
use in improved anchorage systems~
A still further objeet is to provide a novel method
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of installing in a drill hole a combined mechanical-resin type
bolt anchoring system.
Still anothex object is to provide novel structure
for use with a mine roof bolt and expansion anchor assembly in
order to control in a desired manner the relative rotatability
of the bolt and anchor.
Other objects will in part be obvious and will in
part appear hereinafter.
SUMMARY OF THE INVENTION
In accordance with the foregoing objects, the inven-
tion contemplates the use of a conventional resin cartridge
with a rock bolt and expansion anchor which, although other-
wise conventional, include cooperative structure affecting
their relative rotatability. That is, the anchor may be held
stationary in the usual manner as the bolt is rotated in the
direction of threaded advancement ~nto the tapered nut of the
anchor, thereby radially expanding the anchor shell as the nut
is moved axially thereinto. However, once the anchor nut has
been threaded onto the bolt to a predetermined extent, the
cooperative structure formed integrally with and/or carried
upon the bolt and/or anchor prevents relative rotation of the
two in a direction tending to unthread or withdraw the bolt
from the nut. Thus~, as the bolt is counter-rotated the anchor
rotates therewith as a single unit and the bolt and nut are
not disengaged, but upon rotation in a direction advancing it
into the threads of the nut the anchor may be held rotationally
stationary to permit axial movement of the nut into the shell,
with consequent expansion of the latter into firm engagement
with the surrounding walls of a drill hole.
A conventional, two-compartment resin capsule
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is inserted in a blind drill hole formed for such purpose in
the structure to be supported. The rock bolt and anchor as-
sem~ly are ;nserted into the hole behind the capsule to ~upport
the latter on the end of the bolt carrying the anchor. The
head of the bolt carries a support plate in the usual manner.
The bolt head is engaged by a socket tool forming a
portion of a conventionaI bolting machine and forced into the
hole against the resin cartridge as it is counter-rotated,
i.e., turned in a direction tending to unthread the bolt from
the nut, but instead rotating the bolt and anchor as a single
unit. This serves to rupture the resin cartridge and mix the
contents of the two compartments thereof.
After counter-rotation of the bolt and anchor as-
sembly to the extent required to effect complete mixing of the
resin grouting components, the direction of rotation of the
socket tool is immediately reversed. The anchor wi`ll then be
held rotationally stationary by the wall of the drill hole as
the bolt is rotated. The tapered nut will thus ~e moved axially
into the anchor shell, causiny radi;al expansion thereof into
tight engagement with the wall of the drill hole. The socket
tool may then be immediately removed from the head of the bolt
without regard to the setting time of the resin-since it is no
longer required for support.
BRIEF DESCRIPTION OF THE DRAWIN~S
Figure 1 is a-cross sectional view through a rock
structure having a drill hole formedt~ereln showing, in front
elevation, a first embodiment of the rock bolt and anchor
construction of the invention inserted in the hole together
with a resin cartridge, thereby also illustrating an initial
step in the method of the invention;
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Figure 2 is a like view showing the elements at a
subsequent stage of the anchoring operat.ion;
Figure 3 is a like view showing the elements in their
final positions anchoring the rock bolt in the drill hole;
Figure 4 is a perspective view of the tapered nut
of.the anchor bolt constructior.~ of Figures 1-3;
Figure 5 is a fragmentary, perspective view of the
end of the bolt of the Figures 1-3 construction;
Figures 6-8 are a series of views corresponding to
lQ Fi~ures 1-3 and showing a second embodiment o~ bolt and anchor
construction;
Figure 9 IS a fragmentary, perspective vi;ew of the
lower portion of the anchor shell construction of Figures 6-8;
Figure 10 is a fragmentary, perspective view of a
portion of the rock bolt of Figures 6-8;
Figure 11 is a front elevational view of a metal
stamping to be formed i~nto an element used in another em-
bodiment of the invention;
Figure 12 is a perspective view of the element
after forming and mounting upon the bolt-anchor assembly in
another embodiment of the invention;
Figure 13 is a fragmentary, side elevational view
of a bolt-anchor assembly with the element of Figure 11
mounted thereon, the element and a portion of the anchor being
shown in half section; and
Figure 14 is a sectional view on the line 14-14 of
Figure 13.
DETAILED DESCRIPTION
Referring now to the drawings, in Figures 1-3 is
shown a cross section of a rock structure 10, such as the
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roof of a coal mine, in which a blind drill hole 12 has been
formed with conventional drilling tools for the purpose of
installing elements which will serve to suppoxt surface 1~
and the surrounding rock structure. Elongated rock bolt 16
has a square head 18 at one end and is threaded for a portion
of l~t~s length from the other end 20. Support plate 21 is
carried upon headed end 18 of bolt 16.
An expansion anchor comprising tapered nut 22 and
expansion shell 24 is carried upon threaded end 20 of bolt 16.
The smaller end of nut 22 extends into the upper end of shell
24, the lower end of w~ich is supported by ears 26 extending -
integrally from bolt 16 although other conventional support
means such as wire bails, so-called Palnuts, and the like
may alternatively be used. A second set of ears 27 at a
position further from end 20 than ears 26 serve to support a
washer-like member 29, the purpose of which will be explained
later.
Conventi`onal res~n cartridge 28 includes two com-
partments physically separating components 3Q and 32 of a
resin grouting mix. Such cartridges are commercially avail- -
able from a variety of sources and include a polyester resin
as one of the components and a reaction agent such as a
catalyst or curing or hardening agent as the other. The two
components remain in a semi-liquid or thixotropic phase until
mixed, whereupon the resi`n begins to solidify. Curing and
solidification continue until an extremely strong bond is
formed by the resin grout.
As seen in Figure 1, cartridge 28 has been placed
in bore hole 12 and is supported therein upon end 20 of bolt
16. Cartridge 28 is forced against the end o~ hole 12 as
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bolt 16 is moved upward as indicated in Figure 1 by arrow 34.
Head 18 is engaged by a socket tool (not shown) such as em-
ployed in bolting machines commonly used in coal mines and
elsewhere, which is power-driven to move the bolt upwardly
into the drill hole and to rotate it in either direction.
End 20 of bolt 16 and nut 22 are threaded in the conventional
manner so that clockwise rotation of the bolt advances it in-
to the threads of the nut. In conventional rock bolt and
anchor assemblies, counterclockwise rotation of the bolt
would simply disengage i`t from the nut since the anchor is
restrained to some extent from rotation by contact with the
interior of the drill hole.
The bolt and anchor assembly of the present invention
include cooperable structure for preventing relative rotation
in a counterclockwise di~rection from the relative position
of the bolt and anchor shown in Figure 1. Such structure
comprises, in the embodiment of Figures 1-5, fixed pin 36
extending radially from bolt 16 at end 20 thereof and boss
38 extending integrally from upper surface 40 (Fig. 4) at
the larger end of tapered nut 22. Pin 36 is, inserted into
' hol,e 42 (Fig. 5~ in end 20 of the bolt after the latter has
been threaded through nut 22, preferably to an extent that
hole 42 is beyond the end of boss 38.
As bolt 16 is~continued to be moved upwardly from
the position of Figure 1 to that of Figure 2, it is rotated
in a counterclockwise direction, as indicated by arrow 44 in
Figure 2. Either on the first or a subsequent revolution, as
bolt 16 tends to be unthreaded from nut 22, pin 36 will contact
surface 46 (Fig. 4) of boss 38, preventing further relative
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counterclockwise rotation oE the bolt and anchor. The anchor
will then rotate with the bolt, as indicated by arrow 48, as
the bolt is advanced, thereby serving to rupture cartridge
28 and effect thoroug~ mixing of the two components 30 and
32 thereof. Immediately after bolt 16 has been fully in- ;
serted to bring support plate 21 into contact with surface 14
and sufficient counterclockwise rotation of bolt and anchor
has occurred to achieve thorough mixing, the direction of
rotation is reversed. Since bolt 16 was counter-rotated to
bring pin 36 into contact with surface 46, the pitch of the
threads will advance the bolt sufficiently that upon one
complete clockwise rèvolution there will no longer be an
interference between the pin and boss. Therefore, the anchor
may remain rotationally stationary as the bolt is rotated in
a clockwise direction, as indicated by arrows 50 in Figure 3,
thereby moving nut 22 downwardly into the end of shell 24, as
indicated by arrow 52. As the larger end of nut 22 begins to
move into the shell, radial expansion occurs in the usual
manner to cause teeth 54 on the outside of shell 24 to bite
into the rock surface within dri11 hole 12, thus firmly
anchoring bolt 16.
The mixed resin components will ~ill the space
within the drill hole around end 20 of the bolt and the
anchor, washer member 29 serving to limit the extent by which
the semi-liquid mixture can flow downwardly. After hardening,
which requires varying amounts of time depending on the type
of resin mix used, an extremely strong bond is formed to
anchor bolt 16 essentially permanently in drill hole 12,
With most currently available resin cartridges, counterclock-
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wise spin for 10 to 20 seconds at the usual bolting machine
speeds of 600 to 1,000 rpm is sufficient to achieve thorough
mixing, and 10 to 20 seconds of clockwise rotation is suf-
ficient to set the anchor. Thus, the entire operation may be
completed in about a half minute or less, and the bolting
machine may be immediately disengaged from the bolt head
without regard to the setting time of the resin grouting mix.
In the embodiment of Figures 6-10, reference numerals
common to those used in description of the embodiment of
F~gures 1-5 are ~sed to denote corresponding elements in the
two constructions. In this construction nut 22 has no boss,
being entirely conventional, and bolt 16 is not fitted with
a pin at end 20. Ears 26 which serve to support shell 24
upon bolt 16 in both constructions also ser~e here-as the
fixed members which extend radially from the bolt for-contact
with.cooperating structure on the anchor, in this case pro-
vided on the shell rather than th.e nut. Shell 24 includes
at its base a collar-like portion 56, as is conventional
with expansion anchor shells. In the illustrated form,
collar 56 is an unitary, continuous structure, haying
~inner and outer cylindrical surfaces 57 and 59, respecti~ely,
jo$ned at the base of the shell by planar, and annular sur-
face 58.
A pair of spiral or tapered surfaces are formed in
the base of collar 56 beginning.at points 6Q at the juncture
of surfaces 57 and 58 and extendi~ng gradually deeper into the
collar to terminate at steps 62. One of the tapered surfaces
may be seen in Figure 9 and is denoted by reference numeral
64. Surfaces 64 are widest at steps 62, which lie at 180
opposite one another and in planes substantially radial with
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respect to the shell, which are narrower than the dist~nce
between inner and outer surfaces 57 and 59. It may be seen
that, with surface 58 of shell 24 resting upon ears 26,
when bolt 16 is rotated in a counterclockwise direction, as
in Figure 7, ears 26 will contact stepped surfaces 62 and
rotate the anchor together with the bolt. When the bolt is
rotated clockwise, as in Figure 8, the anchor may be held
rotationally stationary as ears 26 travel about surface 58,
over steps 62 and across tapered surfaces 64 to again ride on
surface 58. Thus, nut 22 may be drawn into shell 24 to
- effect radial expansion thereof in the same manner as the
previously described embodiment.
Turning now to Figures 11-14, the invention-is
disclosed in an embodiment which requires modification of
neither the nut nor the shell of the expansion anchor.
Insteadr a separate element is carried upon the bolt stem
for cooperative engagement with portions of the conventional
expansion anchor. The element is preferahly formed as a
stamping from flat sheet metal of suitable gage and then bent
to the desired shape. In any case, the material must have
some degree of resilience or flexibility in order that por-
tions thereor may return to an original or unflexed position
after being temporarily bent away from such a position, and
is therefore preferably of spring steel or similar material.
The stamping is shown in Figure 11 and includes a
generally rectangular base portion 66 with two relatively
narrow legs 68 and 70 extending integrally from one edge
thereof. A pair of slots 72 extend into the opposite edge.
Edges 74 and 76 forming the free ends of legs 68 and 70 are
cut at an angle (of other than 90) with respect to the
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parallel side edges of the legs, which lie at 90 to the
edge of base portion 66 ~rom which they extend.
AEter the stamping is cu-t from the sheet metal blank
in the usual manner, legs 68 and 70 and base portion 66 are
permanently bent to place the element in the configuration
shown in Figure 12, wherein it is generally denoted by reference
numeral 77. The base now forms a cylindrical collar 78 with
legs 68 and 70 spaced at 180, as are slots 72. Each leg is
bent twice, at 80 and 82, near its connection with collar 78
and the free ends are bent to form inwardly facing tabs 84 and
86.
Element 77 is formed with the inside diameter of
collar 78 thereof slightly larger than the diameter of the
roof bolt with which it is to be used. It is mounted upon
bolt 16 simply by inserting the threaded end of the bolt
through collar 78 and moving element 77 down the bolt until
ears 26 on the bolt stem enter slots 72, thus supporting
elemènt 77 upon the bolt and preventing relative rotation of
the two in either direction. A conventional expansion anchor,
denoted generally by reference numeral 88 in Figure 13 and
including tapered nut 90 and shell 92, is then assembled with
bolt 16 in the usual manner. That is, the threaded end of
the bolt is placed through the open end of shell 92 and
threaded into nut 90.
As anchor 88 is moved downwardly on bblt 16 during
threaded advancement thereof through nut 90, legs 68 and 70
are flexed apart to the extent necessary to allow the lower
or open end of shell 92, which constitutes a continuous,
circular base, to pass between the inner ends of tabs 84 and
86. Conventional expansion anchor shells include a plurality
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of fingers extending integrally from the circular base, shell
92 having a total of four such fingers, each denoted by reference
numeral 94, with spaces between the adjacent fingers.
After advancement of the threaded end of bolt 16 in-
to nut 90 by a sufficient distance, the assembly will appear
as in Figure 13 with collar 78 of element 77 encircling bolt
16, ears ~6 of which extend into slots 72 of the collar, and
tabs 84 and 86 extending into spaces between fingers 94 on
opposite sides of shell 92. This is also apparent in the
sectional plan view of Figure 14. Since ears 26 are positioned
in slots 72, rotation of bolt 16 in either direction will
result in like rotation of element 77. Rotation in one direc-
tion will bring angled edges 74 and 76 of tabs 84 and 86 into
contact with the vertical edges of two of fingers 94 between
which the tabs are positioned, while rotation in the opposite
direct~on will bring the straight side edges of the tabs in-
to contact with the vertical edges of the other two fingers
94. When frictional resistance to rotation of anchor 88 is
provided, as when the anchor contacts the inside of a drill
hole, ~olt 16 and element 77 may rotate in a counterclockwise
direction, viewed from above as in Figure 14, while anchor
88 is held stationary by the frictional resistance. That is,
the bolt and element may rotate relative to the anchor since
legs 68 and 70 will flex outwardly as element 77 is rotated
with angled edges 74 and 75 in contact with fingers 94.
Although legs 68 and 60 flex inwardly again when tabs 84 and
86 are aligned with the next succeeding spaces between fingers
94, they are again flexed outwardly by continued rotation of
the bolt and element with the anchor held stationary.
On the other hand, when bolt l6 is rotated in a
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clockwise direction as viewed from above, the vertical edges
of finges 94 are contacted by the straight edge portions of
ta~s 84 and 86 which are essentially perpendicular to the
edges of the fin~ers. Thus, there is not outward flexure of
legs 68 and 70, as in the opposite direction of rotation of
the bolt and element; the frictional resistance to rotation
of anchor 88 is overcome and there is no relative rotation,
i.e., anchor 88 rotates together with bolt 16 and elemen~ 77.
Since counterclockwise rotation viewed from above is clockwise
when viewed from below, and vice versa, and clockwise rota-
tion will advance a right-hand threaded bolt into a stationary
nut, rotation of bolt 16 in a direction advancing it into nut
90 will allow anchor 88 to be held stationary during such rota-
tion with consequent axial movement of nut 90 into shell 92
and expansion of the latter.
Thus, it can be seen that the -Figs. 11-14 embodi-
ment of the invention proviae operation in the same manner as
the other two, except that a separate element is utilized
instead of a modification of the shell or bolt structure.
Since ears 26 on bolt 16 serve to support element 77 and the
base of shell 90 is supported on collar 78 of the element, no
bail, Palnut, or other such means is required to support the
anchor upon the bolt as ;s the case with other conventional
expansiGn anchor assemblies. The bolt and anchor assembly
may be inserted into a drill hole behind a frangible plastic
container holding the resin in its separated, 2-component
form. Rotation of the bolt in a counterclockwise direction
as seen from below (clockwise as seen from above, as in Fig.
11) will serve to rotate element 77 and anchor 88, thereby
fracturing the resin container and mixing the chemical com-
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ponents. Reversal of the direction of rotation will allow
anchor 88 to be held stationary as bolt 16 and element 77 are
rotated, with shell 92 being expanded into tightly engaged
contact with the drill hole. The present embodiment thus
provides the same control of relative rotation of bolt and
anchor as the previously described embodiments, allowing
relative rotation in the direction of threaded advancement
of the roof bolt into the expansion anchor nut and preventing
relative rotation in the opposite direction. Although in
the form shown and described the separate element is positively
driven in both directions by rotation of the bolt and trans-
mits such rotation to the anchor in only one direction, the
reverse of this operation could be provided if desired. That
is, the separate element could be carried upon the anchor and
arranged relative to cooperable portions of the bolt for
rotation thereby in only one direction. It should also be
noted that element 77 could be affixed directly to bolt 16 for
transmission of rotation from the bolt to the element, there-
by requiring no ears or other lateral projections or modi-
fications of the standard bolt construction.
From the foregoing it is apparent that the present
invention provides a method of combined mechanical-resin rock
bolt anchoring which is advantageous, among other reasons, in
that it greatly reduces the time required for the bolting
machine to complete an anchorage installation while utilizing
entirely conventional resin packages. The invention is
practised with, and also encompasses, novel expansion anchor
structure wherein cooperable portions of the bolt and anchor
allow the bolt to be counter-rotated without unthreading from
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the tapexed nut, and novel elemerlts çarric~d upc~r~ t~ separatc
from the bol-t to provide the same action witho~lt l~odi~ic:ation
of the anchor st.ructure.
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