Note: Descriptions are shown in the official language in which they were submitted.
TITLE
METHO~ AND APPAR~l'US FOR COMBINIMG RESIN
BO~ING AND MEC~NICAL ANCHORIN~ OF A
BOLT IN A ROCK FORMATIOM
~ J C~ I~r~INVENTION
1. Field of the Invention
mis invention relates to a meth~d and apparatus for cGmbining
resin bonding and mechanical anchoring of a bolt in a rock formation
and more particularly to an expansion shell assembly adapted for use with
bond;ng material where mixing of the bonding material components and
expansion of the shell take place upon continuous rotation of the bolt in
one rotational direction.
2. Description of the Prior Art
It is well known in the art of mine roof support to tension
bolts anchored in bore holes drilled in the mine roof to relnforce the
unsupported rock formation above the roof. Conventionally a hole is
drilled through the roof into the rock formation. The end of the bolt
in the rock formation is anchored by either engagement of an expansion
shell on the end of the bolt with the roc]c formatlon or adhesively bonding
the bolt by a thermosetting resin to the rock formation surrounding the
bore hole. The resin also penetrates onto the surrounding rock formation
to adhesively unite the rock strata and to firmly hold the bolt in position
in the bore hole. me resin mixture fills the annulus between the bore
hole wall and the rod along a substantial length of the rod. With a
conventional expansion shell it is also known to chamfer the end of the
bolt so that the threads on the end of the bolt that receive the expansion
shell terminate at a point spread from the extreme end of the bolt.
mis arrangement prevents damage to the threads to permit recovery and
reuse of the bolt.
United States Patents 3,324,662 and 3,394,527 disclose adhe-
sively bonding a rod positioned in hole drilled in a rock formation by
a thermosetting polyester resin composition having thixo-tropic properties.
l. _
It is well known that a bolt which is adhesively bonded in a bore hole
can not be tensioned; on the other hand, a bolt mechanically anchored
in a mine roof is capable of being tensioned but the contact of the
roof bo]t with the rock formation is confined to engagement of the ex-
panded shell with the bore hole wall. Also, it is well known that dete-
rioration of the rock formation surrounding the expanded shell reduces
the contact area between the shell and the rock formation. Consequently
the expanded shell slips and the tension on the bolt decreases, thereby
reducing the roof support. Slippage of a tensioned mechanical roof
bolt occurs most commonly in rock formations, such as shale, sandstone,
mudstone, and the like.
In an attempt to resolve the disadvantages of anchoring by
resin bonding or anchoring by expansion shells various types of mine
roof support systems have been developed that combine mechanical anchoring
and resin anchoring. m e two systems have been combined by threading
a bolt into a seperate member such as a nut or coupling which is attached
to a "rebar" anchored in the bore hole by a resin. A bolt with a plate
held against the surface of the mine roof surrounding the bore hole
is threaded into the seperate member. Tightening the bolt places the
bolt under tension.
United States Patent 3,702,060 discloses an expansion shell
assembly that includes a resin container which is fixed to the end of
an expander positioned within an expansion shell. The container is
ruptured after the shell begins to expand. Rotation of the bolt mixes
the resin components, and the resin mixture surrounds the shell to embed
the shell in the cured resin to bond the shell to the rock strata. When
the resin is fully cured, a nut on the end of the bolt opposite a roof
plate on the bolt is rotated to bring the roof plate to its fully seated
position against the mine roof to fully tension the bolt.
1~0~
Combining bolt tensioning and resin bonding of a mine roof
bolt in the bore hole is disclosed in United States Patents 3,877,235
and 4,051,683. The devices disclosed in these patents utilize an intern-
ally threaded member such as a nut or coupling which is connected at one
to a "rebar" anchored within the bore hole by the mixed and cured resin.
A bolt is then connected to the other end of the nut or coupling and
includes a bearing or roof plate advanced into abutting relation with the
mine roof. A stop means provided in the coupling limits axial advancement
of the bolt into the coupling to prevent relative rotation of the coupling
and the bolt as the assembly is rotated to break the resin cartridge and
mix the resin components. When the resin cures the "rebar" above the
coupling is adhesively bonded to the rock formation. Thereafter rotation
of the bolt in the coupling fractures the stop means to permit the bolt to
move upwardly in the bore hole so that sufficient torque is applied to the
bolt to tension the bolt.
Similar devices which utilize a rod anchored within the drill
hole by resin bonding and connected to a bolt by a coupling with a stop
device to restrain relative rotation between the members of the assembly
until the resin hardens so that the bolt can be tensioned are disclosed
in United States Patents 4,122,681 and 4,192,631. These devices rely
upon the bonding of the elongated rod to the rock formation by the resin
mixture. They do not utilize a mechanical anchor.
United States Patents 4,160,614 and 4,162,133 disclose a mech-
anical anchor in combination with resin bonding of the bolt and the
rock formation. Rotation of the bolt with the mechanical anchor attached
to the end thereof in a first direction effects mixing of the resin
components of a ruptured cartridge. An anti-rotation device prevents
relative rotation between the camming plug and the bol~ so that the plug
is not threaded off the end of the bolt during mixing of the resin compo-
nents. With this arrangement the resin components are thoroughly mixed
~4(~
before the shell is expanded. After a period of time sufficient for
mixing the resin and before the resin hardens direction of rotation of the
bolt is reversed to disengage the anti-rotation device. The camming plug
is then free to advance downwardly on the bolt and expand the shell into
gripping engagement with the wall of the bore hole.
The point anchor resin roof bolt support system utilizes the
concept of anchoring a reinforcing rod in a mine roof by resin bonding
and tensioning the bolt. The rod is anchored at its upper end in the
bore hole by resin. A nut is positioned on the threaded end of the
rod that emerges from the bolt hole and abuts a roof plate positioned
in contact with the mine roof. The end of the rod at the nut is rotated
to effect mixing of the resin. Rotation is terminated for a period
of 30 to 60 seconds while the resin mixture cures. After the resin is
set, then the bolt is rotated at a preselected torque to tension the
bolt.
While it has been suggested by the prior art systems to anchor
a roof bolt in a bore hole by combination resin bonding and bolt tension-
ing where mechanical anchors have been used it has not been possible
to mix the resin and set the anchor by continuous rotation of the bolt
in one directon. With the known systems the bolt must be rotated in
a first direction to mix the resin while preventing expansion of the
shell. When the mixed resin has begun to cure, then the directon of
rotation of the bolt is reversed to expand the shell and set the anchor.
Consequent y careful attention must be given to rotating the bolt in the
proper direction to mix the resin before the shell is set and not expand
the shell before the resin is mixed. Furthermore when the bolt is rotated
in the direction to effect mixing of the resin, necessary means must
be provided to prevent threading the expander plug off the end of the
bolt.
1~4~162
Therefore there is need in the system of combining resin bonding
and mechani_al anchoring of a bolt in a rock formation to provide a roof
bolt anchor assembly that permits continuous rotation of a roof bolt in a
single rotational direction to carry out both the operations of mixing the
resin and expanding the shell.
S~MMARY OF THE INVEN?ION
In accordance with the present invention there is provided
a roof bolt assembly for securing a bolt in a bore hole having a bond-
ing material therein that includes a bonding material adapted to the
positioned in an unmixed condition in a bore hole. A roof bolt with
a threaded end portion has a camming plug with an internally threaded
bore and an outer surface threadedly engaged to the bolt threaded end
portion~ m e camming plug is positioned to move axially on the bolt upon
rotation of the bolt in a preselected direction. An expandable shell with
a plurality of longitudinally extending fingers that have an inner surface
and an outer surface is positioned with a portion of the inner surface of
the fingers abutting a portion of the camming plug outer surface and a
portion of the inner finger outer surface adapted to engage the wall of
the bore hole. The expandable shell fingers are arranged to expand
outwardly to engage the outer surface of the fingers to the wall of the
bore hole by longitudinally movement of the camming plug relative to the
bolt threaded end portion and the expandable shell. Means are provided
for mixing at least a portion of the bonding material in the bore hole
upon rotation of ,the bolt in a preselected direction in the bore hole
while maintaining the expansion fingers in an unexpanded condition. Means
are also provided for moving the camming plug axially on the bolt threaded
end portion and relative to the expandable shell fingers upon rotation of
the bolt ~n the same preselected direction to expand the fingers and
anchor the bolt in the bore hole.
_5_
iX4~16;~:
Further in accordance with the present invention there is
provided a method of anchoring a bolt in a bore hole including the
steps of positioning a camming plug having an internally threaded bore and
an outer surface into the upper portion of an expansion shell with a
portion of the camming plug outer surface in abutting relation with a
portion of the inner surface of a plurality of finqers extending upwardly
from a lower ring portlon of the expansion shell. The expansion shell is
positioned on the threaded end portion of the bolt and threadedly engages
the camming plug to the end of the threaded portion of the bolt so that
the camming plug is movable longitudinally on the bolt threaded portion.
A bonding material is inserted into a bore hole. The bolt with the
camming plug threadedly engaged thereto is thereafter inserted into the
bore hole. The bolt is rotated in a preselected direction while the
camming plug is maintained in fixed relation with the expansion shell to
thereby mix at least a portion of the bonding material. mereafter the
bolt is rotated in the same preselected direction to move the camming plug
on the bolt to expand the fingers of the expansion shell and apply a
tension to the bolt in the bore hole.
Prior to insertion of the expansion shell assembly and the
bolt in the bore hole a suitable bonding material, such as an adhesive
resin material, packaged in a breakable cartridge, is inserted in the
bore hole. The cartridge is advanced to the blind end of the bore hole
by upward extension of the bolt with the expandable shell assembly attach-
ed to the bolt. Further upward advancement of the bolt fractures the
cartridge, and thereafter the bolt together with the expansion shell
assembly are rotated in a preselected direction to begin mixing the
components of the adhesive material that were seperated within the cart-
ridge. Rotation of the bolt agitates the components to interact and form
a curable adhesive mixture.
-6-
6~
The stop means in one embodiment includes a shearable pin
extending through a bore of the camming plug. End portions of the pin
are retained in aligned bores of the camming plug. The pin passes trans-
versely through the bore of the plug that receives the threaded upper end
of the bolt. Preferably, the upper end of the bolt terminates in a
reduced diameter end portion formed by tapering the end of the bolt.
The bolt tapers to a preselected diameter determined by the diameter
of the bolt and the type of shearable pin used. For example, a bolt
having a diameter of 5/8 inch is tapered at an angle of about 45 degrees
at the end of the bolt, and the longitudinal length of the taper is
about 1/4 inch. The tapered end of the bolt abuts the pin to prevent
initial downward axial movement of the plug on the bolt during rotation of
the bolt to effect mixing of the adhesive components.
With the camming plug being restrained from downward movement
on the bolt there is no relative rotation between the camming plug
and the bolt. Thus the bolt, camming plug, and shell rotate as a single
unit to effect mixing of the adhesive components in the bore hole.
m e curable mixture flows downwardly into contact with the shell and
camming plug and fills the voids between the shell and the wall of the
bore hole. The presence of the shear pin prevents downward movement of
the ca~ming plug on the bolt for the period of time required to complete
mixing of the resin components. For a quick setting-type of adhesive
material expansion of the shell is delayed for about 20 to 30 seconds to
permit complete mixing of the adhesive components before the shell is
expanded.
As the adhesive mixture begins to harden around the shell
and the camming plug, the mixture exerts a force upon the shell and
camming plu~ resisting rotation of the shell and plug. When the torque
a~plied to the bolt excee s a predetenmine~ torque the anti-rotation
--7--
~0~.6~
forces exerted by the curing adhesive material exceed the material stren-
gth of the pin and the pin fractures or is dislodged from the camming plug
at the point of contact of the camming plug with the tapered end of the
bolt. The tapered configuration at the end of the bolt and abutting the
pin assures dislodgement of the pin from the camming plug when the torque
applied to the bolt exceeds a predetermined torque. The plug is then
free to advance downwardly on the bolt upon continued rotation of the
bolt in the same direction for mixing to expand the fingers of the shell
outwardly to grip the bore hole wall.
Expansion of the shell occurs after a preselected time period
of continued rotation of the bolt in one rotational direction. Thus
the bolt is rotated in a single direction to effect both mixing of the
adhesive material and expansion of the bolt. This arrange~ent eliminates
the need for reversing the direction of rotation of the bolt to expand
the shell after the adhesive material is mixed.
For an adhesive material of the quick setting resin-type,
the mixed resin begins to harden within 20 seconds after rupture of
the cartridge. The stop means in the embodiment of a shearable pin is
constructed of a preselected material and has a preselected cross sec-
tional area to control the material strength of the pin. Thus the pin is
operable to fracture when the mixing stage is complete and before the
resin mixture hardens. This assures that the shell will expand before
the resin cures and after the resin is completely mixed. For a selected
resin system the pin is designed to fracture or shear in the bore of the
camming plug when the torque applied to the bolt exceeds a predetermined
torque. Preferably, the predetermined torque required to shear the pin
is not reached until after, for example, the bolt is rotated for 20 to 30
seconds, i.e., the period of time required for mixing the resin compon-
ents.
--8--
~ X~Ql~
The stop means in one embodiment includes a pin fabricated
of aluminum and having a preselected diameter. In another embcdiment
the stop means includes a steel pin having a length and diameter diff-
ering from that of the aluminum pin because of the difference in material
strength of aluminum and steel. Further the location of the pin rela-
tive to the plug is selective, i.e. it can be retained in a selected axial
position in the plug and abutting the tapered end of the bolt or it can be
retained in the bolt only and abutting the bottom of the plug. In each
case by selecting the material composition and size of the pin, as well
as, the position of the pin, the fracturing or shearing of the pin is
controllable to meet the specifications of the resin system utilized.
muS a stop means is provided to permit mixing of the resin system for the
period of time required for the selected resin system used before the
shell is expanded upon continuous rotation of the bolt in one direction.
Further in accordance with the present invention there is
provided a method of anchoring a bolt in a bore hole that includes
the steps of threadedly engaging a camming plug to the end of the bolt
for axial movement thereon. An expandable shell having a plurality
of longitudinally extending fingers is positioned in surrounding relation
with the camming plug on the bolt. Axial movement of the camming plug on
the bolt is prevented by a stop means associated with the bolt upon
rotation of the bolt in a preselected rotational direction. The stop
means is displaced by the bolt as the bolt continues to rotate in said
preselected rotational direction when a torque in excess of a predeter-
mined torque is applied to the bolt. Thereafter the camming plug is moved
on the bolt upon displacement of the stop means to expand the fingers to
anchor the bolt in the bore hole.
Accordingly, the principal object of the present invention
is to provide a method and apparatus for combining resin bonding and
mechanical anchoring of a mine roof bolt in a rock formation by an
expansion shell assembly provided with stop means that restrains expansion
of the shell as the bolt is rotated in a preselected direction until a
torque in excess of a predetermined torque is applied to the bolt to
displace the stops means and permit expansion of the shell.
Another object of the present invention is to provide a mech-
anical anchor for a mine roof bolt that is also adhesively bonded within
a bore hole where the bolt is continuously rotated in a preselected
direction to permit the sequential operations of mixing the resin material
and thereafter expanding the shell after the resin is mixed but before
it is cured to engage the wall of the bore hole.
A further object of the present invention is to provide a stop
device associated with an expandable shell assembly that is operable to
restrain the expansion of the shell for a period of time required to
permit mixing of resin components in a bore hole where expansion of the
shell is delayed until a preselected torque is applied to the bolt and
after the resin is mixed but before the resin is cured.
An additional object of the present invention is to provide
a roof bolt with a selectively dimensioned tapered end portion operable
to facilitate shearing of a stop device associated with an expandable
j shell assembly after an initial period of rotation of the shell to
mix a resin system surrounding the shell where expansion of the shell is
~ delayed until after the resin components are mixed.
¦ These and other objects of the present invention will be
more completely disclosed and described in the following specification,
the accompanying drawings, and the appended claims.
BRIEF DE9CRIPTION OF THE DRAWINGS
Figure 1 is a fragmentary enlarged view in side elevation
of an expansion shell assembly positioned on the threaded end of an
elongated bolt, illustrating a stop device carried by a ~camming plug
and engaging an upper end of the bolt for restraining movement of the plug
` on the bolt.
-10-
%
Figure 2 is a top plan view of the expansion shell assembly
shown in Figure 1, illustrating the stop device in the form of a
shearable pin extending through the bolt and having end portions retained
in the camming plug.
Figure 3 is an enlarged fragmentary view in side elevation
of the configuration of the threaded upper end of the bolt, illustrat-
ing a tapered end of the bolt to facilitate shearing of the pin stop
device.
Figure 4 is a fragmentary exploded view of the expansion
shell assembly of the present invention, illustrating the shearable
pin which is retained in a bore of the camming plug and arranged to
abut the tapered end of the bolt.
Figure 5 is a fragmentary sectional view in side elevation
of the camming plug positioned on the bolt with the shell removed,
illustrating the shearable pin extending through the camming plug and
abutting the tapered end of the bolt.
Figure 6 is a view similar to Figure 5, illustrating the
pin in a lower position in the camming plug and provided with parallel
grooves on the opposite ends of the pin to control shearing of the
pin.
Figure 7 is a view similar to Figure 1, illustrating the
stop device used with a bail-type expansion shell assembly.
Figure 8 is a view similar to Figures 5 and 6 illustrating
the shearable pin extending through the bolt only and positioned in
abutting relation with the lower end of the camming plug.
Figure 9 is a side elevation partially in section of the
first step in the method of installing the roof bolt in the bore hole,
illustrating a resin cartridge in position at the end of the bore hole for
rupture by the expansion shell assembly of the present invention.
~ .?~
Figure 10 is a view similar to Figure 9, illustrating mixing
of the components of the ruptured cartridge by rotation of the bolt
with the stop device restraining downward movement of the plug during
mixing.
Figure 11 is a view similar to Figures 9 and 10, illustrat-
ing a further step of continuing rotation of the bolt in the same direct-
ion to fracture the stop device after the mixing step to permit the plug
to advance downwardly on the bolt and expand the shell.
Figure 12 is a view further illustrating the method of the
present invention where the plug is advanced downward on the bolt to
fully expand the shell fingers into engagement with the wall bore hole
with the cured and hardened resin surrounding and embedding the expanded
shell.
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
Referring to the drawings and particularly to Figures 1 and
4 there is illustrated an expansion shell assembly generally designated
by the numera-l 10 for securing a bolt 12 in a bore hole 14 drilled
in a rock formation 16 (illustrated in Figures 9-12) to support the
rock formation 16 that overlies an underground excavation, a mine passage-
way, or the like. The bolt 12 has a threaded upper end portion 18 which
is positioned in the upper blind end of the bore hole 14. The bore hole
14 is drilled to a preselected depth into the rock formation 16 as deter-
mined by the load bearing properties to be provided by the expansion shell
assembly 10 and the bolt 12.
The bolt 12 has an enlarged opposite end portion 20 as seen
in Figures 9-12 which extends from the open end of the bore hole 14.
A roof or bearing plate 22 is retained by the bolt enlarged end portion
20 on the end of the bolt 12. Further in accordance with the present
invention a breakable cartridge 24 containing a conventional t~o component
bonding material, such as disclosed in United States Patents 3,324,662 and
-12-
3,394,527 is initially inserted in the bore hole 14 and advanced to the
blind end cf the bore hole 14, as shown in Figure 9, by upward advancement
of the bolt 12 in the bore hole 14. Cnce the cartridge 24 is ruptured and
the components thereof are mixed by rotation of the bolt 12 in a presel-
ected direction, a stop device generally designated by the numeral 26
restrains expansion of the shell assembly 10 until the roof plate 22 is in
abutting relation with the surface of the rock formation 16 and the
adhesive components are mixed.
The bolt is continuously rotated in the same preselected
direction for a period of time sufficient to complete mixing of the
components of the bonding material. The stop device 26 prevents expan-
sion of the shell assembly 10 during the mixing stage. The bolt contin-
ues to rotate in the same initial directon. When the torque applied
to the bolt exceeds a predetermined torque, as determined by the time
for mixing the bonding material, the stop device 26 fractures. The
expansion shell assembly 10 is then free to expand into gripping engage-
ment with the wall of the bore hole 14. The continuous rotation of the
bolt in the same initial direction completes the setting of the assembly
10. Thus the bolt is both mechanically anchored and adhesively bonded in
the bore hole to prevent slippage of the expanded assembly 10 so that the
bolt 12 remains tensioned to support the rock formation.
Now referring in greater detail to the structure of the expan-
sion shell assembly 10 there is provided a shell member 28 conventional
in design and including a solid ring end portion 30. The shell member
28 is expandable and has a plurality of longitudinally extending fingers
32 that extend axially from the ring end portion 30. Each of the fingers
32 has a lower end portion 34 connected to the ring end portion 30 and
an upper end portion 36. Longitudinally slots 38 (only one of which
is shown in Figure 1) divide the fingers 32 from one another. Each of
the slots 38 has a closed end portion 40 adjacent the ring end portion
30 and an open end portion 42 adjacent the upper end portion 36 of the
respective finger 32.
-13-
Each finger 32 includes an outer gripping surface 44 and
an inner smooth surface 46. The outer surface 44 includes a gripp-
ing portion 48 that extends from the finger upper end portion 36 to
a position spaced from the finger lower end portion 34. The gripp-
ing portion 48 of each finger 32 includes a series of spaced parallel,
tapered horizontal grooves 50. The grooves 50 from a series of downwardly
extending serrations that are operable upon expansion of the shell member
28 to engage the wall of the bore hole 14 as the fingers 32 bend cut-
wardly.
The gripping portion 38 of each finger 32 is urged into contact
with the wall of the bore hole 14, as seen in Figures 10 and 11, by a
camming plug or wedge generally designated by the numeral 52. The camming
plug 52 includes a threaded axial bore 54 threadedly engaged to the bolt
threaded end portion 18. The camming plug 52 has a tapered configuration
with an enlarged upper end portion 56 and a reduced lower end portion 58.
A portion of the inner surface 46 of each finger 32 abuts a tapered planar
surface 68 of the camming plug 52.
As illustrated in Figure 1, the camming plug 52 and the shell
member 28 are maintained in assembled relation on the bolt threaded end
portion 18 prior to anchoring the assembly in the bore hole 14 drilled in
the mine roof. Also as well known in the art and illustrated in Figure 7,
the camming plug 52 and the shell member 28 are connected by a yieldable
strap or bail 60. The bail 60 is conventional and extends across the top
of the camming plug 52. The bail 60 includes leg portions 62 that extend
downwardly on opposite sides of the shell member 28. The leg portion 62
are positioned in a pair of opposed slots 64. The leg portions 62 termin-
ate in in-turned end portions 66 that extend into the slots 64 and into
engagement with the inner surface 46 of the shell member 28. With this
arrangement the bail 60 is engaged to the shell member 28 to maintain the
ctr~ing plug 52 asssr~lsd within the shsll r~ lbsr 22.
-14-
As illustrated in Figure 4, the camming plug 52 includes
a plurality of tapered planar surfaces 68 divided from one another
by longitudinally extending grooves 70. As described above, the inner
surface 46 of each finger 32 abuts a respective tapered planar surface
68. In one embodiment of the present invention as seen in Figure 5 the
stop device 26 is positioned in a bore 72 that extends through the camming
plug 52 transversely to the threaded bore 54 of the camming plug 52. As
seen in Figure 5, the transverse bore 72 includes opposite end portions 74
that extend through the plug 52 and emerge through a pair of oppositely
aligned grooves 70 of the plug 52.
Further as illustrated in Figures 1 - 5, the stop device
26 includes a shearable pin 76 fabricated of a preselected yieldable
material and having a preselected size and in the case of a circular
pin, a preselected diameter. The pin 76 is retained in the transverse
bore 72 and includes respective end portions 78 and 80. The pin end
portions 78 and 80 are retained in the bore end portions 74 of the plug 52
as illustrated in the embodiment of the stop device 26 in Figures 1 - 7.
The intermediate body portion of the pin 76 extends transversely through
the plug longitudinal bore 54.
The shearable pin 76 is selectively positioned to extend
through the plug threaded bore 54 at a location to obstruct or prevent
axial movement of the bolt threaded end portion 18 beyond a preselected
depth into the camming plug bore 54. Thus upon initial assembly of the
expansion shell assembly 10, the bolt threaded end portion 18 is advanced
into the camming plug 52 until the bolt end portion 18 abuts the shearable
pin 76 and can advance no further into the camming plug threaded bore
54.
-lS-
12401~;~
The location of the transverse bore 72 through the camming plug 52
for positioning the shearable pin 76 is selective along the longitudinal
length of the camming plug 52. To this end, as illustrated in Figure 5,
the shearable pin 76 is positioned in the camming plug transverse bore 72
at a location adjacent the plug upper end portion 56. In the embodiment
of the present invention illustrated in Figure 6, the shearable pin 76 is
positioned in a plug transverse bore 82 located adjacent the plug lower
end portion 58.
With the embodiment illustrated in Figure 5 the length of
the bolt threaded end portion 18 that extends into the camming plug bore
54 is less than that length when the shearable pin 76 is retained in the
camming plug 52 adjacent the plug upper end portion 56. In the position
of the shearable pin 76 in the camming plug s2, as illustrated in Figure
6, the camming plug 52 is threaded on the bolt 12 to engage only several
of the threads on the bolt end portion 18. The intermediate body portion
of the shearable pin 76 prevents the bolt 12 fram passing any further into
the camming plug threaded bore 54.
The material from which the shearable pin 76 is fabricated is
selective, as for example in one embodiment the pin 76 can be fabricated
of 1/4 inch diameter steel; while, in another embodiment it can be fabric-
ated of 5/16 diameter aluminum. The type of material comprising the
pin 76, as well as, the dimensions and cross sectional area of the pin
76 are selective to control the shearing or fracturing of the pin depend-
ing upon the type of bonding material utilized and the period of time
required for mixing of the material camponents. Further to ensure shear-
ing or fracturing of the stop device 26 before the curable mixture hardens
a stop device, such as a steel pin 77 illustrated in Figure 6, is pro-
vided with deformations, such as longitudinally extending, parallel
spaced grooves or recesses 84 positioned on the opposite end portions
78 and 80 of the pin 77.
-16-
~2~
The material composition and structural design of the stop
device 26, such as the pins 76 and 77 illustrated in Figures 5 and 6,
are selected in accordance with the curing time of the particular type
of bonding material utilized. For ex~mple with a commercially available
quick setting type of resin system which begins to harden within 20
to 30 seconds or less following the rupture of the cartridge 24 and
mixing of the components, the size and material composition of the stop
device 26 are selected to permit fracture after 20 seconds or less of
rotation of the bolt 12. l'hus when the resin mixture begins to harden
a force is applied to the assembly 10 tending to resist rotation of the
shell member 28 and plug 52. The anti-rotational forces increase to a
magnitude where the stop device 26 fractures.
Fracture of the stop device 26 occurs when the torque applied
to the bolt 12 exceeds a predetermined torque. When the stop de~ice
26 is no longer capable of resisting the anti-rotational forces of the
adhesive material applied to the rotating shell assembly 10, the stop
device 26 fractures or shears. Relative rotation between the camming
plug 52 and the bolt 12 is no longer prevented. The camming plug 52 is
then free to move downwardly on the bolt 12 as the bolt 12 continues to
rotate in the same preselected rotational direction.
The ability to control the shearing of the pin 76 provides
a versatile expansion shell assembly 10 operable for use in combination
with adhesive materials of varying curing characteristics, such as a
quick setting-type resin curable within 20 seconds or less of mixing
or the type of adhesive material requiring 2 to 3 minutes of mixing
before hardening begins. By selecting the material composition and
cross sectional area of the stop device 26 in the form of a shear pin, as
well as, the location of the shear pin relative to the camming plug 52,
expansion of the shell member 28 is prevented ~ntil after lapse of the
time required to effect the necessary mixing of the adhesive components.
-17-
L6;~:
Once the curable mixture is formed and begins to harden, the
mixture exerts anti-rotational forces upon the camming plug 52 rotating
with the bolt 18. When the shear pin is no longer capable of resisting
these forces, the pin fractures or is dislodged from the camming plug
52 freeing the bolt 18 to rotate relative to the camming plug 52. This
action commences downward movement of the plug 52 and expansion of the
shell 28. Significantly, the entire operation is carried out by contin-
uous rotation of the bolt 18 in the same or a single rotational direction~
Preferably the shear pin fractures before the adhesive mixture completely
solidifies or hardens so that the expandable fingers 32 are movable
outwardly into gripping engagement with the wall of the bore hole 14.
Now referring to Figure 3 there is illustrated in greater
detail the configuration of the threaded upper end 18 of the bolt 12.
The bolt threaded upper end 18 terminates in a tapered end portion
generally designated by the numeral 71. The tapered end portion 71
is tapered for the maximum diameter of the bolt 12 to a reduced diameter
at the extreme end 73 of the bolt 12. The bolt tapered end portion
71 has a preselected dimension, that is, an angle A and a longitudinal
length B. The magnitude of angle A and length s is selected as deter-
mined, for example, by the diameter of the bolt 12, the size and material
of the shear or stop device 26, the type of bonding material used, and
the nature of the rock formation in which the bolt 12 is anchored.
Thus with the above arrangement, a cone frustum is formed at the threaded
upper end 18 of the bolt 12.
6~
For example in one embodiment of the present invention, a
bolt 12 having a diameter of 5/8 inch is used in combination with a
1/4 inch diameter steel pin stop device 76. The tapered end portion 71
has an angle A of 45` and a length B of 1/4 inch. Thus the bolt 12
tapers from a 5/8 inch diameter to 1/8 inch diameter at the extreme end
73 of the bolt 12. The extreme end 73 of the bolt 12 is flat and bears
against the pin 76.
The tapered end 71 of the bolt 12 applies a concentrated
force upon a portion of the pin 76 as opposed to applying a force upon the
full length of the portion of the pin 76 that is positioned in the plug
bore 54. By tapering the bolt end portion 71 in accordance with the above
example, a 1/8 inch section of the bolt extreme end 73 abuts the pin 76
rather than the full 5/8 inch diameter of the bolt 12. This ensures
breaking the pin 76 or dislodging the pin 76 from a position in the plug
bore 54 obstructing downward movement of the plug 52 when a preselected
torque is applied to the bolt 12 after mixing of the bonding components
is complete.
As stated the dimensions A and B of the bolt tapered end portion
71 are æ lected to meet the specific circumstances and conditions for
the type of expansion shell assembly 10 and bolt 12 used with a part-
icular bonding material. For example, the tapered end portion 71 can
be provided with an angle A that varies in the range between about 15`
to 65` and a length B that varies in a range corresponding to the angle
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~O~i?~
A. However, regardless of the selected dimensions of the taper angle
A and length B, the presence of the tapered end portion 71 on the bolt
12 facilitates removal of the pin 76 frcm a position in the plug bore 54
obstructing downward movement of the plug 52 on the bolt 12 by concent-
rating the upward thrust exerted by the bolt 12 on a portion of the pin
76.
A further embodiment of the shear device 26 is illustrated
in Figure 8. In this embcdiment a shear pin 79 is retained solely in
a bore 86 extending transversely through the threaded end portion 18 of
the bolt 12 adjacent the tapered end portion 71 thereof. The shear pin 79
includes an intermediate portion 81 retained in the transverse bore 86 and
a pair of opposite end portion 83 and 85. The pin end portions 83 and 85
extend outwardly from the bore 86 and in the assembly 10 are positioned
oppositely of a pair of slots 38 between adjacent shell fingers 32. The
camming plug 52 is advanced downwardly on the bolt until the lower end
portion 58 of the plug 52 abuts the pin end portions 83 and 85. The pin
end portions 83 and 85 abutting the camming plug 52 prevent further
downward vement of the camming plug 52 on the bolt 12.
As with the above described embodiments of the stop device
26 the shearable pin 79 resists relative rotation between the bolt 12
and the camming plug 52 until a torque in excess of a predetermined torque
is applied to the end of the bolt. At this torque the resistance orfered
by the curable bonding mix~ure to rotation of the plug 52 results in
fracturing of the pin 79. The pin 79 is designed so that it does not
fracture until the mixing of the bonding materials is ccmplete and the
mixture begins to harden. The pin end portions 83 and 85 break off
frcm the intermediate portion 81 and are free to move through the shell
slots 38.
When the torque for breaking the pin 79 is reached, the mixing
is complete. The pin 79 breaks permitting downward movement of the
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~24~ 6~
camming plug 52 to expand the shell member 28. Expansion of the shell
member 28 is delayed until the bonding material is mixed but not after
the mixture rigidifies in the bore hole 14.
It should also be understood that the stop device 26 includes
any suitable device that restrains axial movement oE the plug 52 on
the bolt 12 beyond a preselected point on the threaded end portions 18
of the bolt 12, as for example, an obstruction member suitably retained
in the plug threaded bore 54. The obstruction member is operable to
restrain relative rotation between the bolt 18 and the plug 52 until
a preselected torque is applied to the bolt 18. Before the preselected
torque is applied, the bonding material is mixed. When a torque in excess
of the preselected torque is applied, the obstruction member is either
broken or displaced in the plug bore 54 to the extent permutting relative
rotation between the bolt 18 and the plug 52 permitting downward movement
of the plug 52 on the bolt. This results in expansion of the shell member
28 and anchoring of the assembly 10 in the bore hole 14.
The stop device 26 in another embodiment can include an ob-
struction which is not required to break or shear before expansion of
the shell member 28 begins. This type of stop device 26 can include
a flexible member, such as wire or the like, having end portions secured
to the camming plug 52 and extending through the plug bore 54 obstructing
the path of the rotating bolt 18. The wire abutting the extreme end
73 o~ the bolt tapered end portion 71 prevents downward movement of the
plug 52 on the bolt 18. Movement of the plug 52 is restrained until
the anti-rotational forces of the bonding mixture applied to the plug
52 results in yielding or bending of the wire permitting downward movement
of the plug 52 on the bolt 12 upon continued rotation of the bolt 12.
The application of the torque which results in bending of the wire
corresponds to the formation of a curable bonding mixture and the in-
itiation of expansion of the shell member 28.
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16~
Now referring to Figures 9 - 12, there is illustrated the
method of anchoring the apparatus 10 and the bolt 12 in the bore hole
14 of the rock formation 16. Initially, as illustrated in Figure 9, the
resin cartridge 24 is inserted in the hole 14 drilled in the mine roof or
rock formation 16 by upward advancement by the bolt 12 with the apparatus
10 attached to the threaded end portion 18 of the bolt 12. The cartridge
24 is pushed to substantially the blind end of the bore hole 14. With the
cartridge 24 inserted in the upper part of the bore hole 14, as illu-
strated in Figure 9, the bolt 12 is thrust upwardly to rupture the
cartridge 24.
Thereafter, the entire assembly 10 is rotated in a preselected
direction as indicated by the arrow in Figure 9 by applying a torque
to the bolt enlarged end ~ortion 20. The stop device 26 in the form of
the shear pin 76 illustrated in Figures 9 - 12, fabricated of a preselect-
ed material and of a preselected size prevents relative rotation between
the camming plug 52 and the bolt 12 during the initial rotation of the
bolt 12 to rupture the cartridge and mix the resin components. In this
manner the camming plug 52 is restrained from moving downwardly on the
bolt 12 by the bolt tapered end portion 71 abutting the shear pin 76
during the initial rotation of the bolt 12.
Rotation of the bolt 12 effects mixing of the resin components
which are released from the cartridge 24 when the cartridge 24 is rup-
tured. Preferably the resin components include a thermoplastic resin
and a catalyst. As the bolt 12 is rotated the resin and the catalyst are
mixed to form a curable resin mixture 88. Ihe resin mixture 88 by virtue
of its thixotropic characteristics is retained within the bore hole 14.
To effectively retain the volume of the mixture 88 in surrounding relation
with the assembly 10 a suitable device, such as a washer 90, is retained
on the bolt 12 adjacent the bolt threaded end portion 18. The washer
90 has a diameter sufficient to permit the washer to move freely in the
-22-
o~
bore hole 14 with the bolt 12 into position. In one embodiment, the
washer 90 is fabricated of metal and may be either welded or press fit on
the bolt 12 spaced a preselected distance below the bolt threaded portion
18. In another embodiment the washer 90 is fabricated of an elastomeric
material. The elastomeric washer 90 is retained in gripping engagement on
the bolt 12 below the threaded end portion 18.
The resin mixture 88 polymerizes at room temperature, i.e.
a temperature in the range between about 40` to 90` F. The bolt 12
is rotated continuously in the direction indicated by the arrow in Figure
10 to effect mixing of the resin. The shear pin 76 abutting the extreme
end 73 of the bolt tapered rotation between the camming plug 52 and
the bolt 12. This prevents the camming plug 52 from moving downwardly
on the bolt 12 until the mixing of the resin components is complete.
The period of time for mixing quick setting-type resin is generally
between about 20 to 30 seconds. During the mixing stage as seen in
Figure 10 the bolt 12 is held in position within the bolt hole 14 with
the roof plate 22 abutting the rock formation 16 around the open end
of the bolt hole 14.
The shear pin 76 by restraining downward move~ent of the camming
plug 52 on the bolt 12 ensures complete mixing of the resin components
before the shell 28 is expanded. However, due to the shear character-
istics of the pin 76 designed for the resin system utilized, the shell 28
expands before the resin mixture 88 completely hardens around the shell
member 28. From the time the cartridge 24 is ruptured, the bolt 12 is
continuously rotated in one direction only, i.e. either clockwise or
counterclockwise, to mix the resin components, as well as, expand the
shell member 28. As the bolt 12 rotates the curable resin mixture 88
flows into the fissures and faults of the rock formation 16 surrounding
the bore hole 14. In this well known manner, the rock strata are adhes-
ively united to further reinforce the rock formation.
-23-
0~62
After the mixing stage, resin mixture 88 begins to cure or
harden in the bore hole 14. As the resin mixture 88 begins to harden
it exerts forces on the rotating shell member 28 and the camming plug
52 resisting their rotation. At a predetermined torque applied to the
bolt 12, which is reached after an elapse of time to complete the mixing,
the material strength of the shear pin 76 is exceeded by the anti-rotat-
ional forces exerted by the resin mixture 88 and the pin 76 fractures or
shears. Consequently, the intermediate portion of the pin 76 in the plug
bore 54 abutting the bolt tapered end portion 71 is bent and broken off
from the pin end portions 78 and 80 which are retained in the plug, as
seen in Figure 11. This permits the pin 76 to be displaced in the camming
plug bore 54 so that the plug 52 is free to move downwardly on the bolt
threaded end portion 18.
Referring to Figure 11, downward movement of the camming plug
52 on the bolt 12, upon rotation of the bolt 12 in the same direction
for forming the resin mixture 88, expands the shell member 28. The
fingers 32 are bent outwardly about the shell ring end portion 30 to move
the outer gripping surfaces 34 into gripping engagement with the wall
of the bore hole 14. m e rotation of the bolt 12 is continuous in the
direction indicated by the arrows in Figures 10 and 11 through the resin
mixing and shell expanding stages. Rotation of the bolt 12 continues
until a preselected torque is applied to the bolt 12. ~en the preselect-
ed torque is applied, the shell member 28 is fully expanded and the
gripping portions 48 of the fingers 32 are embedded in the rock formation
to securely anchor the bolt 12 in the bore hole 14.
When the shell member 28 is expanded the resin mixture 88
is cured. By anchoring the bolt 12 in the bore hole 14 by the expansion
shell member 28, the bolt 12 is tensioned. m e addition of the cured
resin in surrounding relation with the bolt 12 and the expanded shell
member 28 prevents slippage of the shell member 28 in the bore hole
-24-
6~
14. Tension on the bolt is thus maintainæ and is not reduced by slippage
of the expanded shell member 28 in the bore hole.
By the provision of the stop clevice 26, the expansion shell
assembly 10 is operable as a mixing tool to admix the components of
the resin cartridge 24 to form the curable mixture 88 before the shell
member 28 is expanded. The stop device 26 prevents downward movement of
the camming plug 52 on the bolt 12 during the period in which the resin
components are mixed. Also by the provision of the stop device 26,
the bolt 12 is continuously rotated in the same preselected direction
to effect both mixing of the resin canponents and expansion of the shell
member 28. Thus it is not necessary with the present invention to
rotate the bolt 12 in a first direction to effect mixing of the resin
components and then followed by reversal of the direction of rotation
of the bolt 12 to effect expansion of the shell member 28.
The provision of the stop device 26 associated with the camming
plug 52 substantially improves the efficiency and ease of installation
of a roof bolt that is both mechanically anchored and resin bonded within
a bolt bore hole. It should also be understood even though the direction
of rotation for both mixing the resin components and expanding the shell
member 28 is illustrated in a counterclockwise direction in Figures
11 and 12, the direction of rotation can be clockwise as well depending
upon whether the bolt end portion 18 is left-hand threaded or right-hand
threaded.
According to the provisions of the patent statutes, I have
explained the principle, preferred construction and mode of operation
of my invention and have illustrated and described what I now consider
to represent its best embodiments. However, it should be understood
that, within the scope of the appended claims, the invention may be
practiced otherwise than as specifically illustrated and described.
This application is a division of Canadian application
Serial No. 390,107, filed November 16, 1981.
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