U.S. patent application number 11/665959 was filed with the patent office on 2007-11-15 for method for embedding rock anchors.
Invention is credited to Archibald Richter.
Application Number | 20070264088 11/665959 |
Document ID | / |
Family ID | 35809725 |
Filed Date | 2007-11-15 |
United States Patent
Application |
20070264088 |
Kind Code |
A1 |
Richter; Archibald |
November 15, 2007 |
Method for Embedding Rock Anchors
Abstract
According to the invention, a drill rod comprising an inner
channel is drilled into the rock. A free-flowing, self-hardening
mass is pressed through the inner channel of the drill rod, filling
the drilled hole, so that it hardens with the drill rod remaining
in the drilled hole. The hardening mass is a mixture of a
hardenable plastic and a hardening plastic. Said plastics are
supplied to the inner channel of the drill rod over a
pre-determined transport time F which corresponds to the hardening
time. The hardening time is defined by the selection of the
plastics and the mixing ratio thereof such that the transport time
essentially corresponds to the hardening time and leads essentially
to the flow path of the hardened mixture being completely filled
between the mixing point and the output of the drilled hole.
Inventors: |
Richter; Archibald; (Essen,
DE) |
Correspondence
Address: |
HOFFMANN & BARON, LLP
6900 JERICHO TURNPIKE
SYOSSET
NY
11791
US
|
Family ID: |
35809725 |
Appl. No.: |
11/665959 |
Filed: |
October 21, 2005 |
PCT Filed: |
October 21, 2005 |
PCT NO: |
PCT/DE05/01880 |
371 Date: |
April 20, 2007 |
Current U.S.
Class: |
405/259.5 |
Current CPC
Class: |
E21D 20/025 20130101;
E21D 21/0053 20160101; E21D 20/028 20130101; E02D 5/808
20130101 |
Class at
Publication: |
405/259.5 |
International
Class: |
E21D 20/00 20060101
E21D020/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 2004 |
DE |
102004051498.4 |
Claims
1-19. (canceled)
20. Method for embedding rock anchors, whereby an anchor rod having
an internal passage is inserted in a drilled hole, through which
internal passage a free-flowing, self-curing composition is forced,
the finished drilled hole is filled with the composition and the
composition cures in the drilled hole with the anchor rod remaining
in the drilled hole, characterised in that the curable composition
is made from a mixture of a hardenable plastics material and a
hardening plastics material; the hardenable plastics material and
the hardening plastics material are fed in a mixed state to the
internal passage of the drill rod for a predetermined feed time F;
the plastics materials are so selected and brought together, at a
mixing point located shortly before or in the internal passage, and
are mixed to form the mixture in such a mixing ratio as to yield a
defined curing time H, the feed time F and the curing time H being
so coordinated to one another that the feed time substantially
corresponds to the curing time and leads to substantially complete
filling with the curable mixture of the flow path between the
mixing point and the outlet of the drilled hole.
21. Method according to claim 20, characterised in that the
internal passage and the drilled hole are flushed with air during
and/or after the drilling, and in any case prior to the
introduction of the curable mixture.
22. Method according to claim 20, characterised in that the mixer
is arranged in the internal passage.
23. Method according to claim 20, characterised in that the mixer
is a static mixer arranged upstream of the internal passage.
24. Method according to claim 20, characterised in that the
viscosity of the curable mixture in the curing time is at least 100
000 Pa sec.
25. Method according to claim 20, characterised in that the curable
mixture hardens to such a degree during the curing time that the
torque of the drill rod in the drilled hole is greater than the
torque required to detach the drill rod from the drill chuck
retaining same.
26. Method according to claim 20, characterised in that a substance
or synthetic material which causes pre-crosslinking of the
components, with an increase in viscosity to more than 500 Pa sec,
preferably more than 1000 Pa sec, within and preferably at the
start of the curing time, is admixed to the curable mixture or to
one of its components.
27. Method according to claim 20, characterised in that the inlet
of the internal passage of the drill rod is blocked by a non-return
valve which is open in the filling direction.
28. Method according to claim 20, characterised in that the
hardenable and the hardening plastics materials are conveyed at a
pressure-independent feed quantity per time unit during the feed
time F.
29. Method according to claim 20, characterised in that the supply
of plastics materials, and optionally of admixtures, is switched
off or otherwise terminated if a predefined limit pressure is
exceeded.
30. Method according to claim 20, characterised in that, taking
account of the characteristic curve of the feed rate of the
hardenable and hardening plastics materials, the filling time for
the filling volume V to be filled downstream of the mixing point
conforms to the equation: V=kx.sub.0f.sup.H(q.sub.A+q.sub.H)dt,
where V=filling volume of internal passage downstream of mixing
point plus filling volume of drilled hole q.sub.A=feed quantity per
time unit of hardenable plastics material q.sub.H=feed quantity per
time unit of hardening plastics material dt=time increment H=curing
time K=constant taking account of location-independent factors, in
particular temperature and constitution of rock.
31. Method according to claim 20, characterised in that the
plastics components are fed through an injection head (adapter 11)
which is permanently connected via conduits to the feed pumps of
the plastics components carried on a transport vehicle (drilling
carriage); which is guided movably between a rest position and an
operating position on the drilling carriage, and which in the
operating position is connectable in a pressure-sealed manner via a
connecting piece to the end of the anchor rod projecting from the
drilled hole.
32. Method according to claim 31, characterised in that a stop
valve for closing and opening the feed conduit is located in each
of the feed conduits of the plastics components within the
injection head; both stop valves can be opened and/or closed only
synchronously in normal operation, and preferably the drive motors
of the pumps can each be switched off by means of a pressure sensor
located in its respective feed conduit upon attainment of a
predefined maximum pressure.
33. Method according to claim 31, characterised in that the
plastics conduits formed in the injection head and connected to
hoses on the feed side open, on the side facing towards the
connecting piece (connection side of the connecting piece), into a
smooth, preferably flat surface which preferably can be flushed by
a high-pressure jet, preferably a water jet, upon uncoupling of the
connecting piece.
34. Method according to claim 31, characterised in that the
connecting piece consists of two half-shells which are movable
relative to one another perpendicularly to the flow direction of
the plastics materials conducted in the interior thereof and which
in the assembled state enclose in a pressure-sealed manner, or
otherwise connect, the injection head on one side and the end of
the anchor rod projecting from the drilled hole on the other.
35. Method according to claim 31, characterised in that the feed
conduits of the plastics materials are conducted separately from
one another in the injection head and in that the plastics
materials are brought together in the connecting piece.
36. Method according to claim 35, characterised in that the static
mixer is arranged in the internal passage of the anchor rod.
37. Method according to claim 35, characterised in that the static
mixer is arranged in the connecting piece.
38. Method according to claim 37, characterised in that the static
mixer has a tubular configuration with mixing elements arranged in
its mixing tube and preferably is surrounded by a plastics tube, in
that the half-shells of the connecting piece form in the assembled
state a guide passage fitting snugly around the mixing tube, in
which guide passage the mixing tube is fixed at both ends in a
preferably form-fitting but easily detachable manner for support
against the inlet pressure of the plastics materials entering the
mixer.
Description
[0001] The invention relates to a method for embedding rock anchors
according to the preamble of claim 1.
[0002] This method is known from DE 102 34 255 A1. In this method a
drilling/injection anchor, in the form of a drill rod having a
central internal passage, is driven into the rock to be
consolidated. Flushing with liquid is simultaneously carried out,
whereby the drilled hole is widened. Upon attainment of a
predetermined drilling depth injection of a viscous cement mixture
takes place through the internal passage of the drill rod, which
cement mixture fills the drilled hole and hardens to form a
concrete core in which the drill rod remains.
[0003] This method is intended in particular for soft and sandy
rock. In harder rock, as is encountered in particular during
headway timbering in underground mining or when tunnelling, curable
plastics materials are primarily used instead of concrete. These
curable plastics materials are introduced into the drilled hole
through a lance after the hole has been drilled and the drill rod
withdrawn; the lance is then immediately withdrawn from the hole
and a rock anchor driven into the drilled hole, which rock anchor
is then bonded by the curable plastics material to the surrounding
rock in a secure and load-carrying manner.
[0004] It is the object of the invention to provide a method
whereby, in a continuous work process, an anchor rod, which may
also be the drill rod, is embedded as a rock anchor by filling the
drilled hole with a curable plastics material, it being ensured,
firstly, that the drilled hole is filled with the plastics material
over its entire length and, secondly, that despite the usual
overhead working no significant quantities of plastics material
escape from the drilled hole.
[0005] This object is achieved by claim 1. In this solution,
account is taken of the fact that curable plastics materials yield
in a short curing time significantly greater hardness or viscosity
than a cement injection. On the other hand, it is avoided that the
curable plastics material causes contamination of the drilling
machine or the environment, or that relatively large quantities of
the plastics material are expended in an uneconomic manner.
[0006] To produce such hardening, a radical polymerisation of
curable components such as unsaturated polyester resins, vinyl
esters, epoxy acrylates and silicate resins is used--for example,
by admixing peroxides in a volume ratio of 1:1 to 10:1.
[0007] Suitable curable and hardening plastics are described, for
example, in DE 103 15 610 B4, DE 101 24 466 C1 and DE 102 18 718
C1. A major advantage of the invention is that it permits
substantially automatic filling of the drilled hole, the latter
being filled substantially completely from the tip of the drill rod
or rock anchor to the mouth of the drilled hole, and the drill rod
or rock anchor being completely encased with the hardened plastics
material. An essential safety requirement of mining and tunnelling
is thereby fulfilled.
[0008] One of the essential criteria of the invention is that the
feed time F and the curing time H are coordinated with one another.
The curing time H of the plastics material is determined by the
selection of the hardenable plastics material and of the hardening
plastics material and optionally of further components, and by the
mixing ratio of the components, but also by the temperature of the
environment, of the quantitatively major components and of the
rock.
[0009] The feed time F is defined as the time required for complete
filling of the flow path of the curable mixture. That is to say
that the hardening of the curable plastics material takes place
only after mixing of the hardenable and hardening plastics. The
flow path is therefore the distance between the mixing point and
the mouth (outlet) of the drilled hole. If the mixing of the two
components is effected by a static mixer, the mixing point is
located at this static mixer. In that case the flow path includes
the further internal passage as far as its outlet to the external
circumference of the drill, and therefore, generally, as far as the
drill tip. The flow path further includes the drilled hole
surrounding the anchor rod. The feed time is therefore so
calculated that, while taking account of the characteristic curve
of the feed rate of the pumps, in particular the
pressure-dependence of said characteristic curve, it is sufficient
for the volume of the internal passage and the volume of the
drilled hole surrounding the anchor rod to be filled.
[0010] The invention may be implemented by first drilling a hole
with a conventional drill rod and then immediately withdrawing the
drill rod from the hole and inserting instead a tubular anchor rod
(=rock anchor) having an internal passage. In addition to the other
advantages, this method has the advantage that the drill tip to be
used for hard rock, which is expensive, can be used multiple times.
However, it is also possible to drill the hole with a drill rod
equipped with an internal passage, which is configured at the same
time as a suitable anchor rod. This drill rod remains in the
drilled hole and is used after drilling as a rock anchor according
to the invention. The disadvantage of single use is compensated by
the operational advantage that time-consuming work steps are
dispensed with.
[0011] In the context of this application the use of the drill rod
as a rock anchor is described in particular; however, the invention
also applies to a method whereby, as described, a subsequently
inserted anchor rod having an internal passage is used instead of
the drill rod, the method being usable identically in both
cases.
[0012] It is ensured according to claim 2 that the curable mixture
does not form any cavities in the drilled hole and comes into
intimate contact with the wall of the drill rod and the wall of the
drilled hole. This measure can be used additionally to the flushing
of the drilled hole with water usual in the drilling operation, and
has the advantage that water residues are blown out of the drilled
hole and dried.
[0013] It should be pointed out that the drill rod may be provided
at its tip with a bore-crown, the cutting teeth of which describe a
drilled hole diameter which is greater than the external diameter
of the drill rod.
[0014] The curing of the hardenable plastics component involves an
increase in viscosity above the viscous and pasty range. A
viscosity of the hardenable component of at least 100 000
Pa.times.sec is aimed at, so that the bond between the plastics
composition and the drilled hole and the drill rod is so secure
that the drill rod cannot be pulled from the drilled hole or
rotated therein under the usual operating loads associated with the
drilling operation and the injection of the plastics composition.
This makes it possible to detach the drill chuck, in which the
drill rod is clamped for the purpose of drilling, and/or the
injection head (adapter for connecting the plastics feed pipes to
the internal passage of the anchor rod/drill rod), from the drill
rod without the aid of a holding device or gripping wrench for
retaining the drill rod--for example, by rotating the drill chuck
in the reverse direction (claims 5 and 6).
[0015] In an advantageous development according to claim 7 it is
provided that the plastics materials, after being brought together
and mixed, become crosslinked in a very rapid chemical reaction to
form what is here called a pasty mass. This is brought about by
admixing suitable substances, such as amines. With the method
according to claim 8 handling is simplified and operating safety
increased in that, after the components have been brought together
and mixed and before the start of the chemical reaction leading to
hardening, an increased viscosity (greater than 500 Pa sec,
preferably greater than 1000 Pa sec) is attained. This pre-reaction
is brought about by admixing to one of the components small
quantities of substances having suitable thixotropic properties,
for example, from the group of amines.
[0016] Through this initially slight but very rapid increase in
viscosity before the start of the curing finally intended
(thixotropic effect), it is achieved that the curable mixture of
plastics materials does not flow out of the drilled hole, thus
failing to permit the pressure increase which is required to fill
the entire drilled hole and all the cavities completely and without
gaps.
[0017] The development according to claim 8 serves to shorten the
duration of the drilling and injection process. This prevents
plastics composition not yet completely cured from running,
dripping or flowing from the internal passage of the drill rod
after its detachment from the drill chuck or after detachment of
the plastics feed conduit. In calculating the feed time and
coordinating same with the curing time, the characteristic curve of
the feed rate of the pumps by which the hardenable component and
the hardening component are fed to the internal passage of the
drill rod must be taken into consideration.
[0018] Ideally, pumps having a delivery rate per time unit, which
is not dependent on counterpressure, are sought. For this reason
piston pumps, in particular radial piston pumps, are especially
suitable. These are especially advantageous because a temperature
increase of the plastics materials, which could cause a change in
the characteristic curve of curing and in particular a shortening
of the curing time, is avoided.
[0019] To prevent liquid shocks and the consequent bursting of
conduits, it is/should be provided in the development of the method
that the pumps can start with a delay. A reduction in pump speed to
avoid pressure spikes is also advantageous shortly before the end
of the feed time.
[0020] Alternatively, pumps having a pressure-dependent
characteristic curve of feed rate may be used to convey the
hardenable plastics material and/or the hardening plastics
material. Such pumps--for example, gear pumps--have the advantage
of simple construction. Moreover, the pressure-dependent
characteristic curve of pump feed rate has the advantage that
pressure spikes are avoided. On the other hand, in the event of
internal run-back of surplus feed quantities, pressure-dependence
causes heating; the characteristic curve of curing, and in
particular the curing time, must therefore be suitably adapted.
[0021] In the development of the invention according to claim 11
the feed of hardenable and/or hardening plastics material is
switched off if the feed pressure exceeds a predefined limit value.
In this case, however, a run-down programme of the drive motors of
the pumps may be switched on, whereby the speed of the pumps is
reduced to zero continuously or in steps. Damage to the feed system
and possible contamination by one of the plastics components are
thereby avoided.
[0022] However, if in this case the pressure rise can be traced to
curing of the plastics material before complete filling of the
drilled hole, a new drilling must be carried out and in some cases
the drill rod may be lost. However, in this case incorrect
coordination of filling time and curing time has occurred. If
filling time and curing time are precisely coordinated, the
pressure-dependent switch-off occurs as precisely as possible at or
shortly before the time when the plastics material emerges from the
mouth of the drilled hole.
[0023] It is also possible, however, to predefine the feed time F
manually or by an adjustable clock. The aim is to achieve a curing
time, and therefore a filling time, of less than one minute.
[0024] The coordination of filling time and curing time may be
carried out by tests, although the characteristic curve of the pump
feed rate and the filling volume V of the internal passage and of
the drilled holes surrounding the drill rod should be taken at
least roughly into account. The algorithm to be applied in
coordinating filling time and curing time is given in claim 11.
[0025] In fully exploiting the advantage of the invention, namely
the rapid and secure embedding of a rock anchor in a drilled hole,
the development of the method according to claims 12 ff has special
importance. Claim 12 ensures the safe connection of the plastics
feed conduits to the internal passage of the anchor rod/drill rod
and avoids unnecessary assembly and adjustment operations serving
this purpose. To achieve this, use is made of an injection
head--also called an adapter in this application--which serves
firstly as the plastics conduit and secondly as a tool for
connecting the internal passage of the anchor rod to the plastics
pumps.
[0026] Claim 13 serves the purpose of avoiding untimely mixing of
the components, especially before they have reached the intended
mixing point and the static mixer, and therefore of preventing
premature curing of the plastics materials and contamination of the
conduit systems by hardening plastics materials.
[0027] Claim 14 serves a similar purpose and at the same time
ensures effective cleaning of parts of the feed system where
plastics deposits cause malfunction.
[0028] An embodiment of the invention is described below with
reference to the drawings, in which:
[0029] FIG. 1 shows schematically a drill rod with drill chuck and
feed adapters (injection head);
[0030] FIG. 2 is a feed rate graph;
[0031] FIGS. 3 and 4 show schematically a drill rod with drill
chuck and feed adapters (injection head).
[0032] It is illustrated in the Figures that a drill rod remains in
the hole that has been drilled therewith and is immediately
retained and embedded in the drilled hole as an anchor rod/rock
anchor. The drilling process is therefore also described in
relation to the Figures. However, if the drill rod is withdrawn
from the drilled hole after the production thereof, and is replaced
by an anchor rod as the rock anchor, the production of the drilled
hole no longer falls within the scope of this invention; otherwise,
however, the whole of the exposition describing the inventive
method for filling the internal passage of the anchor rod and the
drilled hole with a hardening plastics mixture (curable mixture),
is applicable. The following description applies to all the Figures
unless deviations are expressly pointed out in relation to
individual Figures.
[0033] The drill rod 1 having a bore-crown 2 is driven into a rock
19 of solid stone by the drill chuck 3. For this purpose the drill
chuck 3 is driven in the feed direction 4 and in the rotational
direction 5.
[0034] The drill rod consists of a plurality of parts, in this case
two, which can be joined together to yield a predefined length by
being screwed into a nut 6. For this purpose the drill rods are
provided on their external circumference with a screw thread which
fits into a corresponding thread of the union nut 6. This thread
also serves the purpose of enabling a good connection between the
drill rod 1 and the plastics material to be injected into the
drilled hole.
[0035] The bore-crown 2 is fitted with teeth 7. These teeth 7
define a drilled hole cross-section having a diameter D.sub.1. The
diameter D.sub.1 is greater than the external diameter D.sub.A Of
the drill rod 1 and therefore also greater than the internal
diameter of the thread D.sub.I. The volume of the drill rod can be
calculated with sufficient accuracy from the mean diameter
D.sub.2=(D.sub.A+D.sub.I)/2. Passing through the centre of the
drill rods 1, or of the partial sections of the drill rod, is an
internal passage 8 which opens in the bore-crown 2 into a
collecting chamber 9 and outlet passages 10. The internal passage
can be supplied, through the drill chuck 3 via suitable adapters,
first with water or air as flushing means and then, preferably also
via the drill chuck but also via another suitable connecting piece
which is illustrated, for example, in FIG. 4, with a hardenable
plastics composition and a hardening plastics material.
[0036] Only the parts of the device intended to be supplied with
plastics material are shown schematically here. These are the
injection head/adapter 11, which can be placed on the end face of
the connecting piece, here the drill chuck, and which includes
internal passages 12 and 13. The internal passage 12 is connected
via the hose 27 and the feed pump 14 to a reservoir 15 for a
hardenable plastics composition. The internal passage 13 is
significantly smaller in diameter than the internal passage 12; its
cross-sectional area is approximately 1/10 the cross-sectional area
of the internal passage 12. The internal passage 13 is connected
via the hose 25 and a feed pump 16 to a reservoir 17 for the
hardening plastics composition. Because the hardenable plastics
composition and the hardening plastics composition are mixed in a
ratio of 10:1 or less (as low as 1:1; see above), the feed pump 16
is designed correspondingly smaller. The internal passages are
brought together within the connecting piece/drill chuck 3 in a
collecting chamber 18 which communicates directly with the internal
passage 8 of the drill rod.
[0037] In FIG. 1 it is shown that the first segment of the drill
rod includes a static mixer 20 at the inlet of its internal passage
8. Such a mixer may also be located at the beginning of each
segment. If the static mixer is in the form of an insertable
component, it is sufficient if such a static mixer 20 is inserted
in the internal passage 8 of the last drill rod 1 to be installed.
The detail illustration shows an insert component 21 in which a
non-return valve/ball valve 22 is integrated, in addition to the
static mixer 20. The insert component 21 may, for example, be
screwed via a thread into the internal passage 8 of the last drill
rod to be installed before drilling.
The method is operated as follows:
[0038] To drive the drill rod 1 into the rock, only one drill rod
element is first placed in the drill chuck. The drill chuck is set
in rotation in the direction 5. At the same time a feed force 4
(not represented) is exerted on the drill rod. A drilled hole
having the diameter D.sub.1 of the bore-crown or of the cutting
teeth 7 on the bore-crown is thereby produced. When the drilled
hole has attained the length of the first segment of the drill rod,
the union nut 6 is screwed on to the free end and a further segment
of the drill rod 1 is screwed into the union nut 6, being fed (in a
manner not shown) through the drill chuck from behind. As this
happens the drilled hole may be flushed (in a manner not shown)
with water which is supplied through the internal passage of the
drill rod.
[0039] When the intended depth of the drilled hole has been
attained (e.g. approximately 2 m to 2.50 m) the drilling process is
ended. The collecting chamber 18 of the drilled hole is now charged
with air (in a manner not shown) through the internal passage 8 of
the drill rod, the drillings being thereby flushed from the drilled
hole and the drilled hole being cleaned and dried.
[0040] The drilled hole is then charged with a hardenable plastics
material which has been previously mixed with a hardening plastics
material. The volume to be filled is, firstly, the internal passage
8 from the mixer 20 onwards and, secondly, the drilled hole, i.e.:
V.sub.ges=V.sub.I+V.sub.Bohrloch-V.sub.Bohrstange=pi/4(L.sub.B.times.(D.s-
ub.1.sup.2-D.sub.2.sup.2)+L.sub.I.times.D.sub.I).sup.2.
[0041] Charging is effected by the pumps 14 and 16. These are, for
example, radial piston pumps which can provide a
pressure-independent feed quantity per time unit. However, they may
also be gear pumps, since, given the high viscosities of the
plastics materials to be conveyed, inadmissible losses are not to
be expected, so that the delivery law can be determined with
sufficient accuracy.
[0042] The feed rate is now so defined by suitable pre-setting and
speeds of the drive motors 24 and 26 of the pumps that, taking
account of the characteristic curve of pump feed rate and the
delivery law, the quantity of hardenable plastics material and
hardening plastics material to be charged is conveyed in precisely
the feed time which corresponds to the curing time. The curing time
of the plastics material can be determined, on the one hand, by the
selection of the plastics components and, on the other, by the
mixing ratio and the temperature. The temperature may be assumed to
be, for example, 30.degree. C. The hardness to be adopted by the
plastics material in the curing time is determined by practical
considerations. In particular, the plastics material should not
emerge freely from the mouth of the drilled hole, but should appear
at the mouth of the drilled hole at most as a pasty mass. Moreover,
it is advantageous for the speed of the whole drilling and charging
operation if the plastics material at the mouth of the drilled hole
has cured sufficiently for the drill chuck to be detached from the
drill rod without the need to hold the drill rod with special
auxiliary means, or to prevent it from falling out of the drilled
hole. A viscosity of 100 000 Pa sec may be sufficient, but
preferably is exceeded. Through suitable admixtures,
pre-crosslinking of the plastics mixture introduced may occur, with
an increase in viscosity (see above: more than 500 Pa sec), even
before the curing reaction itself begins or takes effect.
[0043] It is desirable to detach the drill chuck as quickly as
possible from the drill rod, at a time when the plastics mixture
last introduced has not reached the end of its curing time. For
this reason the non-return valve 22 is provided upstream of the
static mixer, opening in the charging direction and preventing the
plastics mixture introduced from flowing out of the internal
passage in the opposite direction.
[0044] After detachment of the drill chuck from the drill rod, the
connecting piece/drill chuck may be flushed with one of the
plastics components or with water. The corresponding apparatus is
not illustrated.
[0045] FIG. 2 shows schematically a feed rate graph of the plastics
components conveyed, that is, in particular the hardenable plastics
component and hardening plastics component and, optionally, the
further admixed substances. The curve of the feed quantity per time
unit over time is shown, and above it the corresponding pressure
curve in the collecting chamber 18 or at another point. The feed
rate depends, on the one hand, on the speed curve of the drive
motors of the pumps. In addition, with some types of pump, account
must be taken of the pressure-dependence of the feed rate. A
constant characteristic curve of feed rate, such as that of radial
piston pumps, would be ideal. In any case, the aim is that the
pumps start running with a progressive action, in order to avoid
pressure shocks.
[0046] The method according to the invention can therefore also be
carried out if the hardenable and hardening plastics materials are
conveyed during the feed time F at a variable feed rate according
to a predetermined curve of feed quantity per time unit, in
particular with a delayed and increasing feed rate at the start of
the feed time, or if the hardenable and hardening plastics
materials are conveyed during the feed time F at a feed quantity
per time unit which is pressure-dependent according to a
predetermined law. In any case, the following applies:
[0047] If, after attainment of the maximum set speed, the feed
quantity per time unit decreases as pressure increases--which
happens, firstly, because the flow path of the plastics mixture is
lengthening and, secondly, because viscosity is increasing--the
total feed time is so calculated that the charging quantity within
this feed time (represented in the graph by the hatched area below
the feed rate curve) corresponds, as described above, to the volume
of the internal passage and the drilled hole, and that this feed
time corresponds to the curing time. It is thereby achieved that
the plastics mixture arriving at the mouth of the drilled hole has
become sufficiently viscous to block said mouth and to encase the
drill anchor so securely that it withstands the torque applied
during detachment of the drill chuck, and that it does not fall out
of the drilled hole through its own dead weight.
[0048] Given this precondition, it is possible to operate the
control device 28 manually or by pre-setting an operating time for
the pump motors. However, control may also be provided via the
pressure sensor 23, by means of which the pumps are switched off or
(as illustrated) a run-down switching occurs when the pressure
upstream of the mixing device (for example, in the collecting
chamber) exceeds a preset limit value G to be determined by
experimentation.
[0049] FIG. 3 differs from the above in that:
[0050] Upon completion of the drilled hole, the drill chuck is
removed. The connection of the anchor rod/drill rod 1 to the
injection head/adapter 11 is effected by a connecting piece 3. The
latter consists (as shown in the detail illustration of FIG. 4) of
two half-shells 31, 32, each of which has a semicircular recess 33,
34 along its length. These recesses complement one another in the
closed state of the half-shells in the direction of the arrows to
form a circular-cylindrical internal passage having varying
diameters. The diameters are so designed that in the closed state
(as shown in FIG. 4) the internal passage fixes the connecting
piece in a form-fitting manner to the injection head 11 on one side
and to the anchor rod/drill rod 1 on the other. The injection head
therefore has a widened portion 35 which fits into a
correspondingly widened diameter of the internal passage 33, 34. To
retain the anchor rod/drill rod 1, the internal passage has a
coarse internal thread which corresponds to the external thread of
the anchor rod/drill rod 1.
[0051] It is shown in FIG. 3 that the space 18 between the end of
the injection head 11 and the end of the anchor rod/drill rod 1 is
bridged and radially sealed by means of an annular seal 30. Here,
too, the static mixer is located at the beginning of the anchor
rod/drill rod 1.
[0052] In the embodiment according to FIG. 4, by contrast, the
static mixer is located in the connecting piece 3 formed by the
half-shells 31, 32. To achieve this, the mixing elements 20 are
located here, too, in an insert component/mixer housing 21
configured as a circular-cylindrical tube. This tube has at its
beginning an outwardly widened portion 36 which, in the closed
state of the half-shells 31, 32 in the direction of the arrows, is
enclosed form-fittingly by a corresponding recess in the internal
passage of the half-shells 31, 32 and is fixed both axially and
radially. In addition, the internal passage of the half-shells 31,
32 fits snugly around the tube of the mixer housing.
[0053] This is especially important because the mixer housing 21 is
preferably made of plastics material and is only made sufficiently
pressure-resistant by its close abutment to the walls of the
half-shells firmly pressed together. Furthermore, it is especially
important that the mixer housing is also supported form-fittingly
in the axial direction at its outlet end, in order to prevent a
mixer housing made of plastics material from splitting or rupturing
axially. This axial fixing is effected in the example illustrated
by abutment of the mixer housing against the end face of the anchor
rod/drill rod 1 facing towards it, which anchor rod/drill rod 1 is
in turn fixed in the half-shells of the connecting piece. The
non-return valve illustrated and described with reference to FIGS.
1 and 3 is not shown in this case, but would also be used here with
corresponding advantage.
[0054] Upon expiry of the filling time and completion of the
charging of the drilled hole, the half-shells are moved apart
(against the arrow direction), so that the anchor rod/drill rod and
the injection head are released. As this happens the static mixer
which, as described, is in the form of a modular unit, may also be
ejected, because it is still filled with the hardening plastics
mixture. If necessary the injection head and/or the connecting
piece 3 are cleaned and a new modular unit is then inserted as the
mixer before said components are clamped to another anchor
rod/drill rod and charging thereof commences.
[0055] In the method according to FIG. 4 an extended form of
control is also used. The apparatus for charging a drilled hole is
switched on and off by the switch 29, which synchronously activates
the two stop valves 38 and 39 in the internal passages 12, 13 of
the injection head 11, to allow through-flow or to effect
pressure-proof blockage. At the start of charging the two pumps 24,
26 are set in operation by means of the control unit 28. When
pressure has built up in the supply conduits 25, 26, the stop
valves 38, 39 are synchronously opened by means of the switch 29,
so that the mixing and charging process begins immediately with
both components present. Upon expiry of the operating time/curing
time, as described previously, the switch 29 again activates the
stop valves 38, 39, causing synchronous and abrupt closing of the
stop valves 38, 39. It is thereby ensured that after blocking at
the outlet face 37, i.e. the end face oriented towards the mixer
20, none of the components can now emerge and cause contamination
thereof. It is additionally provided, however, that after opening
of the half-shells 31, 32, the outlet face is cleaned with a
pressurised water jet. At any rate, the outlet face 37 is
configured flat and without projections or recesses, so that it can
be easily and effectively cleaned.
[0056] When the stop valves have been switched to block the flow,
the two pumps build up a higher pressure in the conduits 25, 27.
This pressure is detected by pressure sensors 23 in each of the
conduits and is supplied to the control unit 28 via the lines 40,
41. The maximum limit pressure to which are each of the respective
conduits may be subjected is stored in the control device. If
either of these limit pressures is reached, the control device
switches off the pump drive concerned, preferably both pump
drives/motors 24, 26.
[0057] The embodiment according to FIG. 4 additionally includes the
special feature of the method, that the two plastics components, or
their feed lines 12, 13, are brought together at a Y- or T-junction
in the injection head, at a point located shortly before, or
optimally in, the outlet face 37. Precisely the last-mentioned case
facilitates keeping clean, or cleaning, of the outlet face.
LIST OF REFERENCE SIGNS
[0058] 1 Drill rod, anchor rod 1 [0059] 2 Bore crown 2 [0060] 3
Drill chuck 3, connecting piece [0061] 4 Feed direction 4 [0062] 5
Direction of rotation 5 [0063] 6 Nut 6, union nut 6 [0064] 7 Teeth
7, drilling teeth 7 [0065] 8 Internal passage, central passage 8
[0066] 9 Collecting chamber 9 [0067] 10 Outlet passages 10 [0068]
11 Adapter 11, injection head [0069] 12 Internal passage 12 [0070]
13 Internal passage 13 [0071] 14 Feed pump 14 [0072] 15 Reservoir
15 for a hardenable plastics composition [0073] 16 Feed pump 16
[0074] 17 Reservoir 17 for the hardening plastics composition
[0075] 18 Collecting passage 18, intermediate space [0076] 19 Rock
19 [0077] 20 Static mixer 20, mixing elements [0078] 21 Insert
component 21 mixer housing [0079] 22 Non-return valve/ball valve 22
[0080] 23 Pressure sensor 23 [0081] 24 Motor 24, pump drive [0082]
Hose 25, conduit [0083] 26 Motor 26, pump drive [0084] 27 Hose 27,
conduit [0085] 28 Control device 28, control unit [0086] 29 ON/OFF
switch, switch 29 [0087] 30 Sealing ring, seal [0088] 31 Half-shell
31 [0089] 32 Half-shell 32 [0090] 33 Recess 33 [0091] 34 Recess 34
[0092] 35 Widened portion 35 [0093] 36 Widened portion 36 [0094] 37
End face, outlet face 37 [0095] 38 Stop valve 38, solenoid [0096]
39 Stop valve 39, solenoid [0097] 40 Line 40 [0098] 41 Line 41
[0099] Drilled hole cross-section with diameter D.sub.1 [0100]
External diameter D.sub.A of drill rod 1 [0101] Internal diameter
D.sub.i of thread [0102] Mean diameter D2=(D.sub.A+D.sub.i)/2
* * * * *