Note: Descriptions are shown in the official language in which they were submitted.
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Arrangement for Cooling the Cutter Teeth of -the
Cutt:ing Tool of a Rock-cutting Machine and for Cooling
the Breast
Durin~ the operation of a rock-cutting machine, the
cutter teeth are heated to hiqh temperatures so that it is
desirable to cool the cutter teeth. But when coal is cut,
e.g., from a bed which includes hard rock or when beds of
hard barren rock must be cut too, this may result in a
formation of sparks, which give rise to a risk of an
explosion of the mine ~as which escapes from the bed.
For this reason it has already been proposed to
supply the cutter teeth with a coolant, which consisted
of water or a sprayed water-air mixture. To ensure a good
utiliæation of such coolant, the nozzles for dischar~ing
that coolant should be disposed as close as possible to
the cutter teeth, i.e., on the cutting tool or cutter
head. In that case, the cutting operation may result in a
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soiling or clogging of the nozzles. That risk can be
reduced only if the coolant is supplied to the nozzles
unter high pressure. The hi~h supply pressure involves
a high water consumption and the large quantities of water
which are discharged result in great difficulties because
they flood the area adjacent to the breast. The floor is
softened too so that the cutting machine may be deprived
of its support. The cutter teeth of a cutter head are in
engagement with the rock to be cut only during part of a
revolution of the cutter head. If the cutter head rotates,
the engagement takes place only during about one-fourth of
a complete revolution. Water wlll be consumed a-t an ex-
cessively high rate if the cutter teeth are continuously
supplied with the coolant.
For this reason it has already been proposed so to
control the supply of the coolant to the nozzles that the
supply to the cutter teeth is interrupted when the Iatter
do not engage the rock being cut. In the known arrangement
in which the cutter teeth are cooled with water atomized
with compressed air, the supply of water to the nozzles is
controlled by slip rings, which are mounted on the axle
of the cutter head. Such slip rings cannot seal against high
pressure. As air is used as a fluid under ~ressure in that known
arrangement, the water may be supplied to the air under a
relatively low pressure, which can be controlled by slin
rings. In that known arrangement the air flow is not inter-
rupted during the time in which the cutter tooth need not
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be cooled but the slip ring interrupt only the supply
of water to -the air stream during -that time. In order to
safely preclude the risk of an ignition by sparks, it is not
sufficient to cool only the cutter teeth but the breast it-
self must be sprayed and this cannot be properly accomplished
with an air-water mixture. If the su~ply of water to a
rotary cutter head is controlled in known manner, the control
can only be effected in that the water is supplied to those
nozzles which are associated with cutter teeth disposed in a
certain angular range. In view of existing conditions, however,
it may be desirable or even necessary to make an upward cut
at one time and a downward cut at another time. The cutter
teeth enga~e the rock substantially in the upper quadrant
facing the breast during an upward cut and approximately
in the lower quadrant facing the breast during a downward
cut. It is very complicated or even impossible to take
variations into account in a control effected by slip rings.
Besides, the cutter teeth do not always engage the rock
exactly during a rotation of the cutter head through an
angle of 90 but a smaller or larger range may be selected,
depending on the nature of the rock. For this reason, even
by slip rings the supply of water cannot be exactly controllRd
in the manner which would be required under the existing
conditions in order to prevent a loss of water as w~l as
an engagement of the rock by cutter teeth in an uncooled
region so that a formation of sparks cannot be reliably
prevented in this way.
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This invention relates to an arrangement for cooling
the cutter teeth of a cutting tool, preferably a rotary
cutter head, o~ a rock-cutting machine, which cutter teeth
are only temporarily in engagement with the rock to be cut,
and for cooling the breast, by means of a coolant which is
discharged from nozzles mounted on the cutting tool and
associated with respective cutter teeth, wherein control
means are provided which permit a supply of coolant to a
given nozzle only when the cutter tooth with which said
nozzle is associated engages the rock. It is an object of
the invention to reliably preclude an ignition of com-
bustible gases which are released as the rock is cut and
to avoid excessive losses of water. The invention resides
essentially in that the coolant consists in known manner
of water without an admixture of air and the supply of
coolant to a given nozzle is controlled in dependence on
the load on the cutter tooth with which said nozzle is
associated. Because the supply of coolant -to a cutter tooth
is controlled in dependence on the load on said cutter tooth,
it is ensured that the coolant will be supplied to each cutter
tooth throughout the time in which it engages the rock and
that no coolant will be supplied to said cutter tooth as
long as it is clear of the rock. This will be accomplished
regardless of the dire~tion of the cut and regardless of
the angular range in which the cutter teeth engage the
rock. In this way, the supply of coolant to the cutter teeth
can be controlled exactly and in accordance with the
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requirements. A formation of sparks during the engagemen-t
of a cutter tooth with the rock even within an extremely
small angular range will be reliably prevented and a loss
of water durinc the time in which a cutter tooth is clear
of the rock will be avoided too. As a result, the water
can be supplied to the nozzles under such a high pressure
that a clogging of the nozzles is virtually precluded. In
accordance with the invention the coolant may enter the
nozzle under a pressure of at least 20 bars and preferably
above 25 bars. That high ~ressure will ensure that the
nozzle passage will remain open. Because the supply of water is
exactly controlled and is restricted to the time in which the
cutter tooth engages the rock, the application of such a
high pressure will not result in an excessively high
consumption of water.
The nozzle is preferably directed to the groove
which has been cut by the cutter tooth. As a result, the
cutting tool is only indirectly cooled and there is no
risk of an embrittlement of the cutting edge of the cutter
tooth as a result of an excessively fast cooling. An im~ortant
result of the provision of a nozzle which is directed to the
grocve which has been cut by the cutter tooth resides in
that as the cutter tooth enters the rock so that there is
the highest risk of a formation of sparks, any sparks which
may then form will be rendered innocuous by a curtain of
water. There is onIy a lower risk of a formation of sparks
when the cutter tooth leaves the rock because hard inclusions
will simply be broken out. In any case the ~roo~e will be
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flooded with so much water even when the cutter tooth leaves
the rock that there will be no risk of a formation of sparks
at that time too.
In a preferred embodiment of the invention the shank
of the cutter tooth is axially slidably mounted in the tooth
holder and is resiliently biased generally in the direction
of the cutting pressure and the supply of coolant is
controlled in dependence on the displacement of the cutter
tooth. In accordance with the invention the valve for
controlling the supply of coolant to the nozzle is preferably
accommodated in the tooth holder. This arran~ement affords
the advantage that the flow path from the valve to the nozzle
is very short so that the cooling begins as soon as load is
applied to the cutter tooth and the flow of water is inter-
rupted as soon as said load has ceased. Other advanta~es
reside in that it is sufficient to machine the tooth holder
in order to permit the valve to be accommodated, that the
valve will be replaced together with the tooth holder,
and that the machining required ~or the valve can be carried
out in large series as each cutter head comprises a large
number of tooth holders. The arrangement is preferably such
that the valve for controlling the supply of coolant to the
nozzle is disposed on that side of the tooth shank which faces
the axis of the cutter head and the nozzle is disposed on that
side of the tooth shank which is remote from the axis of the
cutter head. As a result, the ~alve is disnosed in that
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portion of the tooth holderin which there is adequate space
for this purpose, and the nozzles are disposed very close to
the cutter teeth.
In accordance with the invention the arrangement
may be such that the valve member, which consists preferably
of a ball, is held in closing position only by the pressure
under which the coolant is supplied. This is possible because
the water is supplied under a high pressure and affords the
advantage that there is no need for elements which may break,
such as springs, although a spring may be provided, if
desired.
In a practical embodiment of the invention the tooth
shank has a radially protruding flange, which cooperates
with a pusher that actuates the valve member in a unseating
sense. This arrangement permits a simple transmission of
force from the cutter tooth to the valve. Besides, the means
for actuating the valve member c.onsist suitably of a piston,
which is guided and sealed in a bore and carries a rod, which
acts on the valye member. This piston provides a seal so that
water leaking through the valve can be conducted through the
.working chamber at that end of the piston which faces the
valve.
In another preferred embodiment of the invention the
valve cone of the valve has an outwardly.protruding portion,
such as an annular flange, which engages the tooth shank at
that end thereof which is remote ~rom the cuttin~ tip. The
arran~ement of the val~e-actuatin~ means at that end o the
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tooth shank which is remote from the cutting tip affords the
advantage that the parts servin~ to actuate the valve are
outside the region which is stressed during the cutting
operation and are thus protectedO In such an arrangement, the
valve and the nozzle may be disposed, in accordance with the
invention, on that side of the cutter tooth which is remote
from the axis of the cutter head because the means for
actuating the valve are anyway protected by the protruding
portions of the tooth holder. As the valve and nozzle are
now disposed on the same side of the cutter tooth, a
preferred arrangement according to the invention may be
adopted, in which the chamber which is upstream of the
nozzle directly adjoins the chamber which is downstream of
the valve seat. This arran~ement affords the advantage that
a pressure drop between the valve and nozzle is avoided and
the important advantage that water may enter the nozzle under
a very high pressure, which in accordance with the invention
may be about 200 bars or higher. Such a high supply pressure
will afford the further advanta~es that a clogging of the
nozzle will be reliably avoided and that the water jet
emer~ing under such a high pressure tends to decrease the
strength of the material to be cut so that the cutting work
of the cutter teeth is assisted by the water jet. The nozzle
is suitably directed to the groove which has been cut by the
cutting tooth.
In an arran~ement in which a part connected to the
valve cone en~a~es the rear end face of the tooth shank,
it is a feature of the invention that the valve cone is
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urged -toward the valve seat by a spring which is stressed
generally opposite to the working load acting on the cut-tinq
tooth. That spring will also restore the cutter tooth or
its shank when the cut-ter tooth has been relieved from the
working pressure.
Illustrative embodiments of the invention are
diagrammatically shown on the drawing.
Fig.1 is a sectional view showing a tooth holder.
Figs.2 and 3 show another embodiment, Fig.2 being a
sectional view showing the tooth holder and taken on line
II-II in Fig.3, shich extends in the axis of the cutter
tooth, and Fig.3 being a sectional view taken on line
III-III of Fig.4. Fig.2 shows the overall arrangement of the
rock-cutting machine with the cutter arm and the rotation
cutter heads at the breast.
Fig.1 shows a cutter head having a body 1, to which
tooth holders 2 have been welded. A bushing 3 is a force
fit in the tooth holder 2. A tooth shank 4 is mounted in the
bushing 3 and slidable therein in the direction of the axis 5
of the tooth shank. A sprin~ 6 urges the cutter tooth generally
opposite to the cutting pressure. The tooth shank 4 is shown
in the position assumed when it is subjected to the cutting
pressure so tha-t it has been forced back toward the spring 6
to the extent of the clearance 7. In this position, a flange 10
of the tooth shank 4 engages a flange 54 of the bushing 3.
A bushing 8 is inserted in the tooth shank 2.
A piston 9 is guided and sealed in the bushing 8. l~1hen the
tooth shank 4 has been forced back to the extent of the
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clearance 7, the piston 9, which engages the flange 10 of
the cutting tooth, is forced in the direction of the
arrow 11 so that a rod 12 carried by the piston 9 unseats the
ball 13 from the valve seat 14 to open the valve. The coolant
consisting of water flows through a bore 15 to a chamber 16
and from the latter through the valve seat 14 to a chamber 17
on the other side of the ball, further throu~h a bore 18
in the bushing 8 and a bore 19 in the body of the tooth
holder 2 into an annular space 20, defined by the bushing 3
and then through a bore 21 to the nozzle 22. In that arrangement,
water is dischar~ed from the nozzle as soon as the tooth
shank 4 is subjected to the cutting pressure. The water is then
discharged into the groove 23, which has been cut in the
breast 24 by the cutter tooth, and is subse~uently deflected
toward the cutter tooth.
- The ball ~3 is held in sealing contact with the valve
seat only by the pressure under which the water is supplied.
For this reason a rib 25 is required to hold the unseated
ball near the valve seat 14. Alternatively, a spring may be
provided which urges the ball ~3 towards the valve seat.
A cover plate 26 covers the piston 9 and limits its stroke.
- The water jet 27 discharged from the nozzle virtually
forms a water curtain, by which any sparks will be
extingulshed which may be formed as the cutter tooth enters
the rock. The cutter tooth is only indirectly-cooled by the
water which has been deflected~
The water enters the nozzle 22 under a very high
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pressure in excess of 25 bars so that a clogging of the
nozzle will be reliably prevented. The water is discharged
from the nozzle at a velocity of about 90m/sec.
In the embodiment shown in Figs. 2 and 3, both the
valve 31 and the nozzle 32 are disposed on that side of
the tooth shank 33 which is remote from the axis of the
cutter head. The tooth shank is again slidably mounted in
the tooth holder 34 and is displaceable to the extent of
a distance a of about 2 mm. A bushing 35 is inserted in
the tooth holder 34 and surrounds the valve cone 36 and
is formed with the valve seat 37. A spring 38 urges the
valve cone 36 toward the valve seat 37 to close the valve.
The valve cone 36 is provided with a stem 39, which is
guided and sealed in a ring 40, which is provided with a
seal. The end portion 41 protrudes from the bushinq 35
and is provided with an annular flange 42, which engages
the rear end ~ace 43 of the tooth shank 33. In this
arrangement, the spring 38 displaces the cutter tooth
to its unloaded position when it has been relieved from
the cutting pressure.
From the cutter head 44, the water flows through a
bore 45 to a passage 46 in the tooth holder and from said
passage through openings 47 in the bushing 35 into the
chamber which is upstream of the valve cone 36. The
chamber 48 which is downstream of the valve cone 36 is
directly succeeded by the chamber 49 which is upstream
of the nozzle 32 so that there will be no pressure drop
between the valve 31 and the nozzle 32. For this reason
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a very high water pressure, e.g., of more than 200 bars,
can be built up in the chamber 49 which is upstream of the
nozzle 32 and a solid, narrow jet is discharged, as is
indicated at S0. A strainer 51 may be inserted in the
chamber 49 which is upstream of the nozzle 32.
A screwed-in stud 52 extends into an annular
groove 53 of the tooth shank to prevent a loss of the
cutting tooth.
Fig. 4 shows the cutter head provided with tooth
holders and nozzles as shown in Fig. 1 in position at the
breast 24. The cutter head 28 rotates in the direction of
arrow 29. There will be a chip of decreasing thickness
during an upward cut and a chip of increasing thickness
during a downward cut. In both cases the water jet 27
dischar~ed from the nozzle will impinge at 30 the groove-
that has been dug by the cutter tooth.
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