Note: Descriptions are shown in the official language in which they were submitted.
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PC-1182
The present invention is directed to an
expandable device for anchoring cables within drill holes
in an ore body.
B~CK~ROUND
Numerous mechanical devices have been developed
for supporting the walls of mine shafts and the ceilings
of mine tunnels. Generally, such devices are placed in
holes drilled in an ore body and an expansion device
actuated to afix the device at the end of the drill hol~.
This is readily accomplished in a bolt device by tightening
a nut against a plate thereby shortening the length of
the bolt and expanding a gripping device against the drill
; hole. Such rock bolts suppoxt the ceiling and walls in a
mine by absorbing stress that may be generated when cracks
develop in the rock layers. Rock bolts are limited in
their effectiveness by the length of bolt that can be
extended into the drill hole. That is, due to the relatiYe
inflexibility of a metal rod, maximum bolt lengths are
determined by the height and/or width of the tunnel.
In many instances, it is highly desirable to
provide support for mine ceilings by pro~iding an anchorage
many meters removed from the tunnel. To illus~rate, where
an unstable geologic formation is known to exist in the
vicinity of the tunnel, an anchorage in solid ground
may require the use of cabl~s as long as about thirty
meters. Needless to say, rock bolts are of little use in
such situations.
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In some instances, a flexible cable can be
used to secure such unstable ground; however, it is
necessary in methods such as those disclosed in U.S.
Patent No. 3,971,226 to extend the cable through drill
holes connecting different levels o the mine with con-
ventional cable ~astenin~ dev:Lces. This solution is
not entirely satisfac-tory, since the distance between
mine levels may be well in excess of 100 meters and
drilling holes this distance within a mine is not gen-
erally economically feasible.
Another method for fastening a cable within
a drill hole makes use o an explosive charge to spread
the end of a cable at the end of a bore hole (U.S. Patent
No. 3,389,561), followed by ~illing the hole with grout.
Also, along this same line, cables are commonly introduced
to the drill hole without any expandable end fitting and
the void between cable and drill hole ~illed with grout.
Both of these methods are not entirely satisfactory since
they rely on filling of a void space. Since cracks may
exist in the geologic structure, the grout may follow
a crack in the ore body rather than the void be~ween
cable and drill hole. In the event that this occurs,
an ineffective anchorage is obtained.
Still another cable anchoring device, described
in U.S. Patent No. 2,470,444, cannot be readily assembled
with simple hand tools and in fact is shown to use welding
during assembly. Furthermore, the device is explosively
actuated within the drill hole and therefore requires
special handling and personnel.
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SU~ARY OF THE INVENTION
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Generally speaking, -the present invention is
directed to a cable anchoring assembly adapted ~o anchor
a cable in a drill hole in a solid body and can be used,
for example, to support an ore body above a mine tunnel.
The assembly comprises a cable gripping means advantayeously
comprising a plurality of segmented frustoconical wedges
having toothed cable-engaging faces and having outer faces
tapered in the direction of cable loading and providing an
essentially 360 bearing face; hollow locking means
advantageously comprising a cylinder having an internal
bore sufficiently large to clear the cable, and internal
frustoconical surface adapted to engage the cable gripping
means and having outer wedge shaped planar surfaces tapered
in the direction of cable loading; expandable hole gripping
means advantageously having outer toothed faces adapted
to engage the hole surface into which the assembly is to
be engaged and internal planar wedge faces adapted to
engage the wedge surfaces on the locking cylinder so as
to expand the hole gripping means in response to tension
applied to the cable; and means for initially engaging the
cable gripping means to the cable surface advantageously
comprising a hollow wedge nut adapted to engage the top
surfaces of the cable gripping wedges and threadably
engaged to the top inner face of the locking cylinder so
that the wedge nut drives the cable gripping wedges
against the cable face when the nut is screwed into the
locking cylinder while the cable gripping wedges are in
place therein. The cooperating elements of the assembly
hold the assembly in place near the end of the cable during
insertion of the cable in the drill hole and serve to grip
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the cable as the expandable hole surface gripping means
engage the hole in response to tension applied to the cable
with the grip becoming ever tightQr to the cable and to the
hole surface as tQnsion on the cable is increased. Screw~ng
the wedge nut into a locking cylinder having an internal
conical surface, serves to force segrnented conical wedges
against a cable, thereby grlpping the cable so that th,e
assembly can be pushed lnto a drill hole. The expandabl,e
gripping means, piaced in contact wit~ the locking c~linder
prior to insertion, is expanded by a wedge shap~d plan"a,r
sur~ace on the locking c~linder so that the e~pa,n,dabl,e
gripping means gripS the wall o~ the dri11 hole ~hen a
tensile force is appl~ed to the caPle. T~e c~ble anch~n,g
device of the present invention c~n be readiiy ajssembled.
with simple hand tcol~ in close quarters, ,i~ not depend!e~-k
on grout to retain the cable, and dces not requ~re ex-.
plosives to Set the devxce in a drill hQie.
BRIEF DESCRIPTION OF THE'DR~WINGS
Figure 1 IS a } spectiv,e yIe~:of an, ~sse~m,b~e.d
cable anchormg deyice d,~ing use in a dr~ll holet
Fi~gur.e 2 is ~n e~plo~ed ~er~pectiye xe~ o~ ,a,
portion of the cable anchoring device Pr~o,x to ~ss~b~y
: Pigure 3 Xs a~ ex~loded FerSpest~ye ~Iew~f a
:~ : partiall~assembled çable an,chorln,g devXce.
Figure 4, Which appealx~s w~th.~gu,r,e~s,~7 and 8 ~n t~e
thiXd ~,heet of dra~in~, ~s a lon~tudinal cro~s se~c~o~ c~
partially assembled cable a~dhor~ng de~Xce taken Qn,
line 4-4 of Figure 3.
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Figure 5 is a longitudinal cross section of
a completely assembled cable anchoring device prior
to insertion in a drlll hole.
Figure 6 is a longitudinal cxoss section of
the cable anchoring device set i.n a drill hole taken
on line 6-6 of Figure 1.
Figure 7 is a transverse cross sectional
view taken on line 7-7 of ~'igure 1.
Figure 8 is a transverse cross sectional view
: 10 taken on line 8-8 of Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, .in which like
characters of reference indicate corresponding parts in
each figure, Figure 1 shows a perspective view of a cable
anchoring device installed in a drill hole 80 after
application of a tensile load on the cable 20. The wall
84 of the drill hole is gripped by an expandable gxipping
means 60 tha~ has been expanded by forward movement of
; the locking cylinder 30 and the resultan~ expanding action
of the wedge shaped planar outer surface 38. This action
~ is mora clearly evident if reference is made to the exploded
: perspective view of Figure 2.
In addition, Fiqure 2 shows the positioning of
: segmented conical wedges 40 which reside within and connect
the lockinq cylinder 30 to the cable 20. The segmented
~: conical wedges 40 are forced against the locking cylinder
: ~nd the cable 20 by screwing the wedge nut 50 into the
locking cylinder 30.
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Figure 3 shows an exploded perspective view of
the partially assembled cable anchoring device prior to
positioning of the expandable gripping means 60. Full assembly
is accomplished by sliding the expandable gripping means over
the locking cylinder 30 so that the straps 65 rest against, and
the cylindrical ring 66 rests at:op, the locking cylinder 30.
The expandable gripping means is temporarily held in place
around the locking cylinder 30 and cable 20 by a bridling
means 70 to afford ease of insertion into a drill hole.
A better understanding o~ the attachment of the
locking cylinder 30 to the cable 20 can be obtained by
referring to Figure 4 which shows a longitudin~l cross
; section along line 4-4 of Figure 3. The raised threaded
region 58 of the wedge nut S0 is shown threadably engaged
with the locking cylinder 30. The extended bearing surface
54 of the wedge nut 50 bears against the truncated bearing
surface 42 of the segmented conical wedges 40 so that these
are forced against the locking cylinder 30 and inwardly
against the cable 20.
The cross sectional view shown in Figure 5 repre-
sents a cable anchoring assembly xeady for insertion within
a drill hole. The end of a cable ~0, to be inserted within
the drill hole~ is kept from fraying by attachment of a
strand retainer means ~2 prior to cutting. A swaged band
of metal can be used as a strand retainer means.
The locking cylinder 30, which can be prepared
`~ from a plain carbon steel, has a first central bore 32
which is sufficiently large in diameter to fit over the
cable and strand retainer means~ At the opposite end
~ of the locking cylinder is a threaded second central bore 34
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which is connectecl to the first central bore by a conical
surface 36. The angle formed between the conical surface 36
and khe axis of the locking cylinder 30 should be from
about 4 to about 16, preferclbly from about 6 to about
10 and most preferably from about 7 to about 8. A portion
of the locking cylinder has a wedge-shaped planar outer
surface 38 which intersects the first central bore 32 at an
angle of from about 5 to about 15, pre~erably from about
8 to about 12 and most pref~rably at about 10.
A plurality of segmented conical wedges 40 are
shown adjacent the locking cylinder. Preferably, the
wedges 40 are prepared from a hardened steel. The larger
end of each wedge has a truncated bearing surface 42.
The opposite end of each wedge 44 can be pointed or
truncated. Adjacent to the truncated bearing surface
42, on the inner diameter of the wedge, is an inner
gripping surface 46 which serves to grip the cable.
-Preferably, the inner gripping surface 46 can have a
grooved pattern ressembling screw threads. About 6
pointed surfaces per centimeter having a gripping
surface angle of about 90 and a trailing surface angle
of about 45 have been found useful for this purpose.
Many other patterns (i.e., serrated, diamond, etc.)
are considered useful for this purpose and accordingly
within the scope of the present invention. Opposite
the inner gripping surface 46 and adjacent to the
truncated bearing surface 42 is an outer smooth surface
48 which is shown to slideably engage the conical
surface 36 of the locking cylinder 30. The angle
between the axis of the wedges and the outer smooth
surface 48 should be from about 6 to about 18,
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preferably from about 8 to about 12 and still more preferably
about 10. In order to obtain a locking action between
cable 20 and inner gripping surfaces 46, the angle between
the axis of the wedges and the outer smooth surface 48
should be ~reater than (prefe:rably at least about 2 greater
than) the angle formed between the conical surface 36 and
the axis of the locking cylinder 30.
A wedge nut 50 having a central passageway 52
to clear the cable 20 and strand retainer means 22 has an
extended bearing surface 54 which contacts the truncated
bearing surfaces 42 of the plurality o segmented conical
wedges 40. The extended bearing surace 54 has an outer
diameter selected to clear the threaded second central
bore 34 o~ the locking cylinder 30. The diameter of the
extended bearing surface 56 is selected to be sufficiently
small to avoid contact with the conical surface 36 of the
locking cylinder 30. Also, the diameter of the extended
bearing surface 56 is somewhat smaller than the diameter
of the truncated bearing sur~ace 42 of the conical wedges
: 20 40. The wedge nut 50 has a raised threaded region 58
adjacent to the extended bearing surface which threadably
engages the threaded second central bore 34 of the locking
cylinder 30. Just beyond the raised threaded region 58
is a wrenching surface 59O The wrenching surface 59 is
: used to screw the wedge nut 50 into the locking cylinder
s : 30 to engag~e the extended bearing surface 54 of the wedge
nut against the truncated bearing surfaces 42 of the
wedges 40. The wedges 40 slide against the conical surface
36 of the locking cylinder 30 and are orced inwardly
: against the cable 20 thereby locking the assembly con-
sisting of wedge nut 53, wedges 40 and locking cylinder 30
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to the cable 20. The wedge nut 50, which can be prepared
from a plain carbon steel, can be cylindrical so that it
can be tightened wi-th a pipe wrench or it may have flats
machined thereon so that it can be tiyhtened with an open-
ended or closed-box wrench.
It has been found expedient to tap the end of the
cable 20 with a hammer while screwing the wedge nut 50
into -the locking cylinder 30. This action helps to align
as well to set the segmented conical wedges 40 against the
cable 20.
An expandable gripping means 60, which can be
prepared from a low alloy steel or cast iron, is fitted
over and engages the wedge-shaped outer surface 38 of
the locking cylinder 30 along a V-shaped slot 62. The
expandable gripping means 60 has an outer ~ripping
surface 63 for engaging the surface of a drill hole~
The gripping surface 63 can consist of a series of circum-
ferential, wedge-shaped surfaces. Expandable gripping means
similar to that of the present invention are well known, and
a suitable device is described as an expansible anchoring
shell in the Dempsey U.S. Patent No. 2,753,750, granted
July lO, 1956. The expandable gripping means is attached
with fastening means 6~, e.g., rivets, welds, ettc~, to
st:raps 65 which, in turn, are connected to a cylindxical
ring 66 with joining means 67, e.g., rivets, welds, etc.~ and
is placed over the wedge nut 50. The cylindrical ring 66
and strap 65 ser~e to maintain the positioning of the
expandable gripping means 60 in close relation to the
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~ locking cylinder 30 during insertion of the assembly in
a drill hole~. A bridling means 70 i5 used to ~aintain
the expandable gripping means 60 in contact~with the wedge
shaped outer surface 38 of the locking cylinder 30.
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A polymeric material such as a piece of polyethylene
tubing of appropriate diameter has been ound to be useful
for this purpose.
Flgure 6 shows a cross sectional view along
line 6-6 of Figure 1 a~ter the anchoring device has been
pushed into a drill hole 80 to the end of ~he hole 82
and subsequently pulled forward. During insertion of
the anchoring device into the drill hole 80, the bridling
means 70 is generally self-removed due to abraslon with the
wall o the drill hole 84. Once the cable 20 has contacted
the end of the drill hole 82, the cable 20 is pulled forward
which causes the outer grippin~ surface 63 of the expandable
gripping means 60 to engage the walls of the drill hole 84.
During insertion of the assembled device into
the drill hole 30, the locking cylinder wedge nut 50 and
expandable gripping means 60 are held in place against
the cable 20 by the compressive action of the wedge n~t
50 against the wedges 40 and locking cylinder 30. Once
in place at the end of the drill hole 82, tensile orces
2Q applied to the cable 20 are also transmitted through
the wedges 40 to the locking cylinder 30, and from there
to the expandable gripping means 60 to ~he wall of ~he
drill hole. Thus, the assembled anchoring device restrains
the cable 20 in tension as well as in compression.
Figure 7 show~ a trans~erse cross sectional
view oP the a~sembled anchoring device taken along line
7-7 of Figure 1. The diameter of the assembly including
straps 65 is shown to be smaller than the diameter of the
drill hole wall 84. Three segmented conical wedges 40
are shown bearing against the locking cylinder 30 and the
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cable 20. A further transverse cross section through the
expandable gripping means 60 along line 8-8 oP Figure 1
is shown in Figure 8. The out:er gripping sur~ace 63
o the expandable gripping means is shown spread apart
by the action of the locking cylinder 30 against the
wall 84 of the drill hole.
For the purpose of giving those skilled in the
art a better understanding of the invention, the ~ollowing
illustrative example is given:
EXAMPLE
A 6 centimeter diameter by 18.4 cm long locking
cylinder was slipped over the end o~ a 2.54 cm diameter
cable and strand retainer with the wedge shaped outer surface
of the locking cylinder positioned away from the cable
end. The opposite end of the locking cylinder, having the
larger threaded central bore, was positioned at a location
removed about 8 cm from the end of the cable.
With the axis of the cable in the vertical
position, three conical wedges, having a 10 angle between
their outer smooth surface and their central axis, wexe
positioned through the threaded central bore of the locking
cylinder along the cable to rest in contact with the conical
surface of the locking cylinder and the surface of the cable~
A 5.1 cm outside diameter wedge nut having
a 4.3 cm outqide diameter extended bearing surface was
manually turned into the lockin~ cylinder until it con-
tacted the conical wedges. The end of the cable was
tapped with a hammer while an ordinary pipe wrench
having a 30 cm long handle was used to fully tighten the
wedge nut against the conical wedges.
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The partially assembled cable anchoring device
represented in Figure 4 was subjected to tensile testing
in a Baldwin tensile testing unit~ The cable was gripped
with conventional tensile testing grips at one end and
the partially assembled device restrained by a testing
fixture having a plate member with a 3 cm diameter hole.
The cable was loaded without failure to a load of 267,000
Newtons (60,000 pounds), representing the proo load for a
2.54 cm (1 inch) diameter cable.
Although the present invention has been described
in conjunction with preferred embodiments, it is to be
understood that modifications and variations may be resorted
to without departing from the spirit and scope of the
invention as those skilled in the art will readily understand.
Such modifications and variations are considered to be within
the purview and scope of the invention and appended claims.
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