Note: Descriptions are shown in the official language in which they were submitted.
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Method for embedding rock anchors
The invention relates to a method for embedding rock anchors.
Such method is known from DE 102 34 255 Al. 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.
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withdrawn; the lance is then immediately withdrawn from the hole and a rock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.
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.
A method for embedding rock anchors, whereby an anchor rod having an
internal passage is inserted in a drilled hole, through which internal passage
a
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free-flowing, self-curing composition is forced, comprising filling the
finished
drilled hole with the composition such that the composition cures in the
drilled
hole with the anchor rod remaining in the drilled hole, wherein the method
comprises the steps of:
= drilling the drilled hole with a drill rod and a drill chuck retaining
the drill rod
wherein the drill rod does not contain a hardenable plastics material;
= making the curable composition from a mixture of a hardenable plastics
material and a hardening plastics material;
= feeding plastic materials comprising the hardenable plastics material and
the hardening plastics material in a mixed state to the internai passage of
the drill rod for
= a predetermined feed time F;
= selecting the plastics materials and bringing the plastic materials
together,
at a mixing point located in the internai passage, and mixing the plastic
materials to form the mixture in such a mixing ratio as to yield a defined
curing time H, wherein the feed time F and the curing time H are
coordinated to one another such that the feed time substantially
corresponds to the curing time and leads to substantially complete filling
with the curable composition of the flow path between the mixing point and
the outlet of the drilled hole.
= 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.
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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.
Suitable curable and hardening plastics are described, for example, in
DE 103 15 610 B4, DE 101 24 466 Cl 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.
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.
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,
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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.
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.
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.
It is ensured according to the step of flushing the internal passage and the
drilled hole with air during and/or after the drilling, and in any case prior
to the
introduction of the curable mixture 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.
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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.
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 x 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. These advantages are obtained by the
preferred features of the invention that the viscosity of the curable mixture
in
the curing time is at least 100 000 Pa x sec and that the curable mixture
hardens sufficiently 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.
In an advantageous development comprising including in the step of making
the curable composition the step of admixing a substance or synthetic
material which causes pre-crosslinking of the components, with an increase in
viscosity to more than 500 Pa X sec, within the curing time, to the curable
mixture or to one of its components; and wherein the plastics materials
comprises the substance or synthetic material which causes pre-crosslinking
of the components, 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 preferred
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step of blocking the inlet of the internal passage of the drill rod by a non-
return
valve which is open in the filling direction 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 x sec, preferably greater than
1000 Pa x 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.
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.
The preferred step of blocking the inlet of the internal passage of the drill
rod
by a non-return valve which is open in the filling direction 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.
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.
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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.
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.
In the preferred feature that the feed time for the filling volume V to be
filled
downstream of the mixing point conforms to the equation (taking account of
the characteristic curve of the feed rate of the hardenable and hardening
plastics materials):
V=Kx f (qA + qH)dt (I), where
0
V = filling volume of internal passage downstream of mixing point plus
filling volume of drilled hole
qA = feed quantity per time unit of hardenable plastics material
qH = feed quantity per time unit of hardening plastics material
dt = time increment
H = curing time
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K = constant taking account of location-independent factors, in
particular temperature and constitution of rock,
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 pump 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.
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.
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.
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 defined by equation (I) above.
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 the preferred feature that the feeding step comprises feeding the
plastics through an injection head:
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= which is permanently connected via conduits to feed pumps of the plastics
material carried on a transport vehicle;
= which is guided movably between a rest position and an operating position
on the transport vehicle, 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
has special importance. The preferred feature that the feeding step comprises
feeding the plastics through the said injection head 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.
The preferred feature that the injection head has a stop valve for closing and
opening each conduit located in each of the conduits of the plastics materials
within the injection head wherein both stop valves can be opened and/or
closed only synchronously in normal operation 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.
The preferred feature that the 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
surface serves a similar purpose and at the same time ensures effective
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cleaning of parts of the feed system where plastics deposits cause
malfunction.
An embodiment of the invention is described below with reference to the
drawings, in which:
Fig. 1 shows schematically a drill rod with drill chuck and
feed
adapters (injection head);
Figs. 1A and 3A show schematically a static mixer, mixer housing
and
non-return valve;
Fig. 2 is a feed rate graph;
Figs. 3 and 4 show schematically a drill rod with drill chuck
and feed
adapters (injection head); and
Fiq. 4A shows schematically opposed half shells having
recesses.
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.
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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.
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.
The bore-crown 2 is fitted with teeth 7. These teeth 7 define a drilled
hole cross-section having a diameter D1. The diameter D1 is greater than the
external diameter DA of the drill rod 1 and therefore also greater than the
internal diameter of the thread D1. The volume of the drill rod can be
calculated with sufficient accuracy from the mean diameter
D2 = (DA + Di) /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.
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
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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.
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:
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 D1 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.
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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.
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 onwards and,
secondly,
the drilled hole, i.e.:
Vges = Vi + VBohrloch - VBohrstange = pi/4 (LB x (D12 - D22) + L1 x
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.
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 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
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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 x 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 x sec), even before the curing reaction itself begins or takes
effect.
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.
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.
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,
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would be ideal. In any case, the aim is that the pumps start running with a
progressive action, in order to avoid pressure shocks.
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:
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.
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
connecting chamber) exceeds a preset limit value G to be determined by
experimentation.
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Fig. 3 differs from the above in that:
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.
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.
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.
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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 halt-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.
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.
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
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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.
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 bath pump drives/motors 24, 26.
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 clearing, of the outlet face.
List of reference signs
1 Drill rod, anchor rod 1
2 Bore crown 2
3 Drill chuck 3, connecting piece
4 Feed direction 4
5 Direction of rotation 5
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6 Nut 6, union nut 6
7 Teeth 7, drilling teeth 7
8 Internal passage, central passage 8
9 Collecting chamber 9
10. Outlet passages 10
11 Adapter 11, injection head
12 Internal passage 12
13 Internal passage 13
14 Feed pump 14
Reservoir for a hardenable plastics composition
15 16 Feed pump 16
17 Reservoir 17 for the hardening plastics composition
18 Collecting passage 18, intermediate space
19 Rock 19
Static mixer 20, mixing elements
20 21 Insert component 21 mixer housing
22 Non-return valve/ball valve 22
23 Pressure sensor 23
24 Motor 24, pump drive
Hose 25, conduit
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26 Motor 26, pump drive
27 Hose 27, conduit
28 Control device 28, control unit
29 ON/OFF switch, switch 29
30 Sealing ring, seal
31 Half-shell 31
32 Half-shell 32
33 Recess 33
34 Recess 34
35 Widened portion 35
36 Widened portion 36
37 End face, outlet face 37
38 Stop valve 38, solenoid
39 Stop valve 39, solenoid
40 Line 40
41 Line 41
Drilled hole cross-section with diameter D1
External diameter DA of drill rod 1
Internal diameter D1 of thread
Mean diameter D2 = (DA + D1) /2.
