U.S. patent application number 13/543301 was filed with the patent office on 2013-01-10 for strand anchor.
This patent application is currently assigned to Hilti Aktiengesellschaft. Invention is credited to Frank Schmidt.
Application Number | 20130011205 13/543301 |
Document ID | / |
Family ID | 46318911 |
Filed Date | 2013-01-10 |
United States Patent
Application |
20130011205 |
Kind Code |
A1 |
Schmidt; Frank |
January 10, 2013 |
STRAND ANCHOR
Abstract
A strand anchor, especially for use in mining, comprising a
strand having several wires, an anchor head, an anchor plate
supported by the anchor head for placement onto the rock, should
make it possible to discharge the displaced air when the curable
material is being injected into a drilled hole, without the need
for a separate hose. At least one longitudinal channel, preferably
a plurality of longitudinal channels, is/are formed between the
wires of the strand, so that air can be discharged to the outside
through the strand through the at least one longitudinal channel
when the curable material is being injected into a drilled
hole.
Inventors: |
Schmidt; Frank; (Muenchen,
DE) |
Assignee: |
Hilti Aktiengesellschaft
Schaan
LI
|
Family ID: |
46318911 |
Appl. No.: |
13/543301 |
Filed: |
July 6, 2012 |
Current U.S.
Class: |
405/259.5 |
Current CPC
Class: |
E21D 20/028 20130101;
E21D 21/006 20160101; E21D 21/0026 20130101 |
Class at
Publication: |
405/259.5 |
International
Class: |
E21D 20/00 20060101
E21D020/00; E21D 21/00 20060101 E21D021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 7, 2011 |
DE |
DE 102011078767.4 |
Claims
1. A strand anchor comprising: a strand including a plurality of
wires; an anchor head; an anchor plate supported by the anchor head
for placement onto rock; the plurality of wires defining at least
one longitudinal channel between the wires of the strand, the at
least one longitudinal channel permitting air to be discharged to
an outside through the strand through the at least one longitudinal
channel when a curable material is injected into a drilled
hole.
2. The strand anchor as recited in claim 1 wherein the wires have
different diameters.
3. The strand anchor as recited in claim 2 wherein a first diameter
of a first wire of the plurality of wires is at least 10% larger
than a second diameter of a second wire of the plurality of
wires.
4. The strand anchor as recited in claim 3 wherein a first diameter
of a first wire of the plurality of wires is at least 20% larger
than a second diameter of a second wire of the plurality of
wires.
5. The strand anchor as recited in claim 4 wherein a first diameter
of a first wire of the plurality of wires is at least 30% larger
than a second diameter of a second wire.
6. The strand anchor as recited in claim 2 wherein at least one of
the following is present: the wires are configured with an
essentially circular cross section and lie on each other, so that
each longitudinal channel is delimited by the wires; and a
cross-sectional surface area of a flow, or a sum of the
cross-sectional surface areas of the flow, of the at least one
longitudinal channel is at least 0.1 mm.sup.2.
7. The strand anchor as recited in claim 6 wherein a
cross-sectional surface area of a flow, or a sum of the
cross-sectional surface areas of the flow, of the at least one
longitudinal channel is at least 0.5 mm.sup.2.
8. The strand anchor as recited in claim 7 wherein a
cross-sectional surface area of a flow, or a sum of the
cross-sectional surface areas of the flow, of the at least one
longitudinal channel is at least 1 mm.sup.2.
9. The strand anchor as recited in claim 8 wherein a
cross-sectional surface area of a flow, or a sum of the
cross-sectional surface areas of the flow, of the at least one
longitudinal channel is at least 2 mm.sup.2.
10. The strand anchor as recited in claim 9 wherein a
cross-sectional surface area of a flow, or a sum of the
cross-sectional surface areas of the flow, of the at least one
longitudinal channel is at least 5 mm.sup.2.
11. The strand anchor as recited in claim 10 wherein a
cross-sectional surface area of a flow, or a sum of the
cross-sectional surface areas of the flow, of the at least one
longitudinal channel is at least 10 mm.sup.2.
12. The strand anchor as recited in claim 6 wherein each
longitudinal channel is delimited by three wires.
13. The strand anchor as recited in claim 2 wherein the at least
one longitudinal channel includes a plurality of longitudinal
channels.
14. The strand anchor as recited in claim 13 wherein the plurality
of longitudinal channels includes at least 5 longitudinal
channels.
15. The strand anchor as recited in claim 14 wherein the plurality
of longitudinal channels includes at least 10 longitudinal
channels.
16. The strand anchor as recited in claim 15 wherein the plurality
of longitudinal channels includes at least 20 longitudinal
channels.
17. The strand anchor as recited in claim 16 wherein the plurality
of longitudinal channels includes at least 30 longitudinal
channels.
18. The strand anchor as recited in claim 1 further comprising a
plurality of individual wires and at least one spacer, the
individual wires being held concentrically with respect to the
strand by the at least one spacer.
19. The strand anchor as recited in claim 18 wherein the individual
wires are arranged at a distance from the strand.
20. The strand anchor as recited in claim 1 wherein the strand
anchor is a mining strand anchor.
21. The strand anchor as recited in claim 1 wherein the at least
one longitudinal channel includes a plurality of longitudinal
channels.
22. A method for setting a strand anchor comprising the following
steps: drilling a hole into rock; inserting a strand of the strand
anchor into the drilled hole; injecting curable material into the
drilled hole in the area of an entrance of the drilled hole; and
discharging from the drilled hole air displaced by the curable
material at least partially through at least one longitudinal
channel present in the strand.
23. The method as recited in claim 22 wherein the air flows through
a back end of the at least one longitudinal channel at a back end
of the strand into the at least one longitudinal channel and
through a front end of the at least one longitudinal channel at a
front end of the strand.
24. The method as recited in claim 23 wherein the front end is
outside of the drilled hole.
25. The method as recited in claim 22 wherein after the curable
material has been injected into the drilled hole, the curable
material is brought into contact with an outside of the strand so
that a mechanical connection is established with the strand after
the curable material has cured.
26. The method as recited in claim 25 wherein the strand anchor
includes a plurality of individual wires around the strand, and the
curable material forms a mechanical connection with an outside of
the individual wires and between the strand and the individual
wires.
27. The method as recited in claim 22 wherein, after the curable
material has cured, a tensile force is applied to the strand via an
anchor head.
28. The method as recited in claim 27 wherein the curable material
is mortar or synthetic resin.
29. The method as recited in claim 27 wherein the tensile force
also is applied to individual wires of the strand anchor
surrounding the stand.
30. The method as recited in claim 22 further comprising, after the
hole has been drilled and before the strand has been inserted,
inserting a cartridge containing another curable material into the
drilled hole.
31. The method as recited in claim 22 wherein the strand anchor
comprises: the strand including a plurality of wires; an anchor
head; an anchor plate supported by the anchor head for placement
onto rock; the plurality of wires defining the at least one
longitudinal channel between the wires of the strand, the at least
one longitudinal channel permitting air to be discharged to an
outside through the strand through the at least one longitudinal
channel when the curable material is injected into the drilled
hole.
32. The method as recited in claim 22 wherein the air is discharged
completely.
33. The method as recited in claim 22 wherein the at least one
longitudinal channel includes a plurality of longitudinal channels.
Description
[0001] This claims the benefit of German Patent Application DE 10
2011 078 767.4, filed Jul. 7, 2011 and hereby incorporated by
reference herein.
[0002] The present invention relates to a strand anchor, and to a
method for setting a strand anchor.
BACKGROUND
[0003] Strand anchors are employed in mining and tunnel digging in
order to prevent and to slow rock movement of the bedrock, or to
secure large-scale spalling of the bedrock, so as to allow safe
operation. The strand anchor is adhesively bonded to a curable
material, for instance, mortar or synthetic resin, and then set in
a hole that has been drilled into the bedrock.
[0004] After a hole has been drilled into the rock, a strand of the
strand anchor is inserted into the drilled hole, after which
curable material is injected into the drilled hole through the
entrance of the hole. In this process, the curable material
displaces the air that is in the drilled hole, and the air is then
discharged through an injection or venting line. For this purpose,
not only the strand, but also the injection and venting line has to
be inserted into the drilled hole, so that the air can be
discharged from the drilled hole while the curable material is
being injected into the drilled hole through its entrance. This is
a drawback since a separate injection and venting line has to be
provided and inserted into the drilled hole along with the strand.
It is disadvantageous that the venting line ends at places where
the venting does not really have to take place, so that an air
pocket can remain in the drilled hole after the curable material
has been injected. Moreover, it is necessary to drill a larger hole
and this involves more drilling work since the strand anchor
requires not only the strand but also the injection and venting
hose.
[0005] U.S. Pat. No. 5,738,466 discloses a strand anchor consisting
of several wires.
[0006] International patent application WO 2008/128301 A1 discloses
a strand anchor having a strand that consists of several wires.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide a strand
anchor with which the air that is displaced when the curable
material is injected into the drilled hole can be discharged from
the hole without the need for a separate hose.
[0008] The present invention provides a strand anchor, especially
for use in mining, comprising a strand having several wires, an
anchor head, especially with an anchor nut, an anchor plate
supported by the anchor head for placement onto the rock, whereby
at least one longitudinal channel, preferably a plurality of
longitudinal channels, is/are formed between the wires of the
strand, so that air can be discharged to the outside through the
strand through the at least one longitudinal channel when curable
material is being injected into a drilled hole.
[0009] A plurality of longitudinal channels are present on the
strand of the strand anchor between the wires, whereby the strand
is configured as a central strand. When the curable material is
injected into the drilled hole, the displaced air can be discharged
from the drilled hole through these longitudinal channels. This
advantageously means that the strand anchor does not have to have
an injection or venting line. As a result, it is advantageous that
the diameter of the drilled hole can be dimensioned considerably
smaller since essentially only the strand needs to be accommodated
in the drilled hole, thus translating into less drilling work.
Moreover, there is likewise no need for a complex procedure to
provide an injection or venting line when the strand anchor is
being inserted.
[0010] In particular, the strand comprises wires having different
diameters, especially with a diameter difference of at least 10%,
20% or 30%. The longitudinal channels are delimited by the wires of
the strand so that, if the diameters of the wires are different,
the wires delimit the longitudinal channels with a different
curvature radius.
[0011] In another embodiment, the wires are configured with an
essentially circular cross section and lie on each other, so that
each longitudinal channel is delimited by wires, preferably by
three wires, and/or the cross-sectional surface area of the flow or
the sum of the cross-sectional surface areas of the flow of the at
least one longitudinal channel is/are at least 0.1 mm.sup.2, 0.5
mm.sup.2, 1 mm.sup.2, 2 mm.sup.2, 5 mm.sup.2 or 10 mm.sup.2.
[0012] In a supplementary embodiment, the strand has a plurality of
longitudinal channels, especially at least 5, 10, 20 or 30
longitudinal channels.
[0013] Preferably, several individual wires are held concentrically
with respect to the strand by means of at least one spacer.
Preferably, the strand anchor comprises several spacers, and the
individual wires are held by the spacer at a distance from the
strand which is thus configured as a central strand. In this
context, the individual wires between the spacers can preferably
always be at an essentially constant distance to the strand which
is configured as a central strand, or else they can lie between the
spacers on the strand which is configured as a central strand.
[0014] In a variant, the individual wires are arranged at a
distance from the strand.
[0015] In a supplementary variant, the spacer is made of metal or
plastic.
[0016] In an additional embodiment, the wires of the strand and/or
the individual wires are made, at least partially, especially
completely, of metal, particularly steel.
[0017] In an additional configuration, the strand and/or the
individual wires are embossed or profiled on the outside. This
enhances the mechanical connection or the adhesive bond between the
curable material and the outside of the strand and preferably the
individual wires.
[0018] A method according to the invention for setting a strand
anchor, especially a strand anchor as described in this patent
application, comprises the following steps: drilling a hole into
the rock, inserting a strand of the strand anchor into the drilled
hole, injecting curable material into the drilled hole in the area
of its entrance, discharging from the drilled hole air that has
been displaced by the curable material, whereby the displaced air
is discharged from the drilled hole at least partially, preferably
completely, through at least one longitudinal channel, preferably
through several longitudinal channels, that are present in the
strand.
[0019] In one variant, the air flows through a back end of the at
least one longitudinal channel at a back end of the strand into the
at least one longitudinal channel and through a front end of the at
least one longitudinal channel at a front end of the strand,
preferably outside of the drilled hole.
[0020] Advantageously, the air also flows radially outside of the
back end into the longitudinal channels in the strand.
[0021] In another embodiment, after the curable material has been
injected into the drilled hole, the curable material is brought
into contact with the outside of the strand and preferably with the
outside of the individual wires, so that a mechanical connection is
established between the strand and preferably the individual wires
after the curable material has cured.
[0022] In particular, after the curable material, for instance,
mortar or synthetic resin, has cured, a tensile force is applied to
the strand and preferably to the individual wires by means the
pre-tensionable anchor head, preferably via its anchor nut. The
anchor head applies a compressive force onto the rock in the area
of the entrance of the drilled hole, thus stabilizing the outer
strata of rock, and this compressive force is introduced as a
tensile force into the strand and, from the strand, it is
transmitted adhesively with the curable material to the rock in the
area of the drilled hole.
[0023] Another preferred embodiment of the invention lies in the
fact that, after the hole has been drilled and before the strand
has been inserted, a cartridge containing another curable material
is inserted into the drilled hole. According to this embodiment,
the strand is anchored in the drilled hole with a short cartridge
before the pressing procedure, after which the rest of the drilled
hole is filled with curable material. Consequently, especially the
following sequence is conceivable: 1) drilling, 2) inserting the
cartridge into the drilled hole, 3) inserting the strand anchor
into the drilled hole, 4) mixing the curable material contained in
the cartridge by means of the strand anchor, 5) curing the curable
material contained in the cartridge, whereby the strand anchor is
pre-anchored in the drilled hole, 6) tensioning the strand anchor
and 7) injecting the curable material into the drilled hole in the
area its entrance and concurrently conveying out of the drilled
hole the air displaced by the curable material, whereby the
displaced air is discharged from the drilled hole at least
partially through at least one longitudinal channel in the strand.
The curable material contained in the cartridge can especially have
different characteristics from those of the curable material that
is injected in the area of the entrance of the drilled hole. For
instance, the material contained in the cartridge can be a
two-component material and/or the material that is injected in the
area of the entrance of the drilled hole can be cement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] An embodiment of the invention will be described in greater
detail below making reference to the accompanying drawings. The
following is shown:
[0025] FIG. 1: a longitudinal section of a strand anchor that has
been inserted into a hole that has been drilled into the rock,
after the curable material has been injected into the space between
the rock and the anchor tube;
[0026] FIG. 2: a cross section A-A of the strand anchor according
to FIG. 1.
DETAILED DESCRIPTION
[0027] A strand anchor 1 is employed in mining in order to
temporarily stabilize rock in tunnels. The strand anchor 1 is a
chemical anchor, that is to say, a strand 2 of the strand anchor 1
is adhesively bonded to the rock 18 by means of a curable material
11, e.g. synthetic resin 12 or mortar 13. For this purpose, a hole
19 has to be drilled into the rock 18 and subsequently, the strand
2 of the strand anchor 1 is inserted into the drilled hole 19.
[0028] The strand anchor 1 comprises not only the strand 2
comprising a plurality of wires 3 made of steel and having
different diameters but also seven individual wires 7 made of
steel. Several annular spacers 8 made of plastic hold the
individual wires 7 at a distance from the strand 2 that is
configured as a central strand 2. According to the depiction shown
in FIG. 1, the individual wires 7 are consistently held at an
essentially constant distance between the spacers 8 with respect to
the strand 2, so that the individual wires 7 do not touch the
strand 2. The strand 2 has a back end 5 in the area of a back end
of the drilled hole 19, and a front end 6 in the area of a work
space 21 outside of the drilled hole 19. The strand 2 as well as
the individual wires 7 are fastened to an anchor head 14 that is
only schematically indicated here, whereby the anchor head 14 in
the embodiment shown has an anchor nut 16 that is arranged on an
anchor-head thread 15. The anchor nut 16 rests on an anchor plate
17.
[0029] After the hole 19 has been drilled into the rock 18, the
strand 2 with the individual wires 7 as well as the spacers 8 are
inserted into the drilled hole 19. After the strand 2, the
individual wires 7 and the spacers 8 have been inserted, curable
but not yet cured material 11 is injected into the drilled hole 19
in the area of its entrance 20. As a result of this injection of
the curable material into the drilled hole 19, the curable material
displaces the air that is in the drilled hole 19 and conveys it
through the strand 2 through longitudinal channels 4 between the
wires 3 of the strand 2 at a back end 5 of the strand 2 that is
configured as a central strand 2, so that the air at the front end
6 of the strand 2 flows into the work space 21 and out of the
drilled hole 19. When the curable material is injected into the
drilled hole 19, it comes into contact with the outside 9 of the
strand 2 and the outside 10 of the individual wires 7. As a result,
after the curable material 11 has cured and after the curable
material 11 has been completely injected into the drilled hole 19,
an adhesive bond can be created between the cured material 11 and
the outside 9 of the strand 2 and the outsides 2 of the individual
wires 7 (FIG. 1). As a result, a compressive force can be applied
by the anchor nut 16 via the anchor plate 17 onto the rock 18 in
the area of the entrance 20 of the drilled hole. This compressive
force is introduced as a tensile force into the strand 2 and into
the individual wires 7, and subsequently introduced into the rock
18 at the drilled hole 19 due to the adhesive bond between the
curable material 11 and the outside 9 of the strand 2 as well as
the outsides 10 of the individual wires 7. An adhesive bond
likewise exists between the curable material 11 and the rock 18 at
the drilled hole 19.
[0030] All in all, considerable advantages are associated with the
strand anchor 1 according to the invention. The strand anchor 1
does not require an injection or venting line since the displaced
air that is in the drilled hole 19 can be discharged to the outside
through longitudinal channels 4 in the strand 2. As a result, the
diameter of the drilled hole 19 can be dimensioned considerably
smaller, that is to say, it can essentially match the diameter of
the strand 2 with the individual wires 7, thus translating into
less drilling work. Moreover, there is no longer a need for a
complex procedure to provide an injection or venting line.
[0031] In addition, due to the spaces which are created by the
spacers 8 and through which the cement flows, the complete steel
bundle comprising the strand 2 and the individual wires 7 has a
larger surface area for the bonding than a conventional steel
bundle of the same cross section.
[0032] An optional cartridge 100 with further curable material can
be placed in the drilled hole 19 and is shown schematically.
Cartridge 100 can be punctured by the strand anchor and temporarily
hold the strand anchor before the curable material is injected. The
amount or type of material in the cartridge can be such that the
end 5 remains free of the further curable material so that air can
still flow through end 5.
* * * * *