Note: Descriptions are shown in the official language in which they were submitted.
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Rotation unit, rock drilling unit and method for rock drilling
Background of the invention
[0001] The invention relates to a rotation unit for rock drilling, which
rotation unit has no percussion device. The purpose of the rotation unit is to
generate the required-rotation for drilling equipment to be connected thereto,
at
the outermost end of which equipment there is a drill bit for breaking rock.
[0002] Further, the invention relates to a drilling unit and a method
for rock drilling. The field of the invention is described in more detail in
the pre-
ambles of the independent claims of the application.
[0003] Holes can be drilled in rock by means of various rock drilling
machines. Drilling may be performed with a method combining percussions
and rotation (percussive drilling), or drilling may be based on mere rotation
without a percussive function (rotary drilling). Further, percussive drilling
may
be classified according to whether the percussion device is outside the drill
hole or in the drill hole during the drilling. When the percussion device is
out-
side the drill hole, the drilling is usually called top hammer drilling, and
when
the percussion device is in the drill hole, the drilling is typically called
down-the-
hole drilling (DTH). In a top hammer drilling machine, the percussion device
and the rotation device are combined into one entity, whereas in a rotary
drill-
ing machine and DTH drilling machine, there is a rotation unit which is com-
pletely without a percussion device. This application is specifically directed
to
such a rotation unit without a percussion device and to the use thereof.
[0004] The rotation unit comprises a main shaft that is rotated
around its longitudinal axis. Rotation force is generated by a rotating motor
connected to the main shaft through a gear system. As the drilling progresses,
more drilling tubes are connected to the drilling equipment and, corresponding-
_
ly, disconnected after the drill hole has been finished and it is time to
start drill-
ing a new drill hole. The drilling tubes are provided with connection threads,
due to which they require what is called a floating spindle that allows the
threads to be screwed and unscrewed without simultaneous accurate control
of the feeding movement. The floating spindle enables the required axial
movement that results from the pitch of the connection threads. Floating spin-
dles used nowadays are separate units which are connected to a rotation unit
before the first drilling tube. Such separate floating spindle units have,
howev-
er, turned out to cause problems to the durability of the equipment.
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Brief description of the invention
[0005] It is an object of this invention to provide a :novel and im-
proved rotation unit, rock drilling unit and method for rock drilling:7,
[0006] The rotation unit according to the invention is characterized
- -
in that the main shaft is supported to the body slid ingly in the
axiirdirectiofi.
[0007] The rock drilling unit according to the invention-is character-
ized in that the main shaft of the rotation device is supported to the body
slid-
ingly in the axial direction.
[0008] The method according to the invention is characterized by al-
lowing the main shaft of the rotation unit to move axially in relation to the
body
of the rotation unit when the drilling equipment and components of the
drilling
equipment are connected and disconnected.
[0009] The idea is that the main shaft of the rotation unit is bearing-
mounted on the body in such a way that it can slide an allowed, predetermined
axial length of movement in relation to the body.
[0010] Thus, an advantage is that the axial movement of the main
shaft allows the connection threads of the drilling equipment to be unscrewed
and screwed without there being a need to arrange any separate floating spin-
dle unit in the drilling equipment. Arranging a slide property in the rotation
unit
allows the structure to be more firm and durable than before.
[0011] The idea of an embodiment is that the main shaft is support-
ed to the body in the radial direction in the portion of the front end by
means of
a front bearing, and in the portion of the rear end by means of an end
bearing.
Both bearings are slide bearings and may be of a suitable slide bearing metal,
for example. The structure allows the axial distance between the bearings to
be arranged relatively long. Owing to this, the crosswise forces transmitted
from the drilling equipment to the main shaft during drilling car be received
well to the firm body of the rotation unit. Further, the durability of the
structure
is improved by the opportunity to arrange the front and end bearings in oil-
- -
lubricated spaces.
[0012] The idea of an embodiment is that the main shift is bearing
mounted on the body by means of a front bearing and an end bearing, the'axi-
al distance between these being great in relation to the diameter of the main
shaft. The bearings have an axial bearing distance, and the main shaft has
bearing diameters at the point of the bearings. According to observations, the
bearing of the main shaft is particularly firm when the ratio of the bearing
dis-
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tance to the greatest one of the bearing diameters is at least 3:1. The
bearing
diameters may be equal or unequal at the front and end bearings. The bearing
distance ialth-a,dimenSion between the functional middle points of the front
and
end bearings:',
[0013] The idea of an embodiment is that the transmission mem-
bers between the gear system and the main shaft comprise sliding members
which allow axial movement of the main shaft without any axial forces being
transmitted to the gear system. When there are no axial loads directed from
the main shaft to the gear system or the rotating motor, the durability of the
rotation unit is good.
[0014] The idea of an embodiment is that rotation force is transmit-
ted to the main shaft from the portion of its rear end. There is more space
for
the transmission members at the rear end of the main shaft, whereby they can
be dimensioned and positioned more freely than in solutions where rotation
force is transmitted from the portion of the front end of the main shaft.
[0015] The idea of an embodiment is that the rotating motor and the
gear system are positioned as an extension of the rear end of the main shaft.
The rotating motor, gear system and main shaft are then positioned succes-
sively on the same axial line. Thus, the rotation unit, seen in the lateral
direc-
tion, may be rather narrow. Although the length increases on the side of the
rear end of the rotation unit, this has not turned out to do any harm to the
struc-
ture or operation. Further, the rotating motor and gear system may be modules
which can be easily and quickly detached and replaced with a new one without
having to disassemble the rest of the rotation unit structure. There is plenty
of
space for handling--the modules at the rear end of the rotation unit. It is
also
feasible to provide the rear ,end of the rotation unit with modules having
differ-
ent powers and other properties-if it is desirable to affect the properties of
the
rotation unit.
[0016] ThOclea of an-embodiment is that the outer periphery of the
main shaft has at least one-feed-flange arranged to transmit axial feed force
between the. body atid:theoainLshaft. The feed flange has axial support sur-
faces which participate. in transmitting axial forces. Further, the body has a
slid-
ing space at the location of the feed flange. The sliding space is an
elongated
annular space around the Main shaft, having ends that define the sliding space
in the axial direction. The front end and the rear end comprise support
surfaces
which may participate in transmitting axial forces.
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[0017] The idea of an embodiment is that the feed flange and the
sliding space at the location thereof are positioned in' the portion of the
front
end of the main shaft. Then, axial forces are transmitted betWeen the main
-
shaft and the body as close to the front end of the rotation unitand the
drilling
equipment as possible. The axial forces do thus not stress the rear part:of
the
main shaft or the components of the rotation unit that are positiOned in the
rear
part. These aspects are also preferable with regard to the durability of the
rota-
tion unit.
[0018] The idea of an embodiment is that the feed flange is posi-
tioned in the sliding space on the front side of the front bearing supporting
the
main shaft. Thus, the front bearing transmits axial forces between the feed
flange and the rear end of the sliding space when the feed is towards the
drill-
ing direction. The front bearing serves as a radial bearing of the main shaft
and
as an axial bearing. The front bearing is a slide bearing that is extremely
capa-
ble of receiving great axial forces during drilling. The front bearing may be
ar-
ranged in the sliding space slidingly in the axial direction, whereby it may
be
arranged to move together with the main shaft. Further, the sliding space may
be oil-lubricated, which improves the durability of the front bearing even
more.
[0019] The idea of an embodiment is that the structure of the rota-
tion unit comprises an axial damper. The axial damper is thus integrated to
form a part of the rotation unit. The axial damper may be used for damping
vibration, impacts, shock waves and other axial stresses which affect the main
shaft and are transmitted to the main shaft from the drilling equipment. Such
an axial damper significantly reduces vibration and stress waves directed to
the body and body parts from the drilling equipment through, the main shaft,
whereby less stress is directed to the components behind the axial damper.
Further, the axial damper may also reduce stresses directed:tolhe compo-
nents on the front side of the damper, i.e. on the side of the drilling
equipment,
at least to some extent.
[0020] The idea of an embodiment is that the axiartiamper' corn-
_ prises at least one end damper arranged at the end of the slidirig Space.-
The
axial damper may comprise a rear end damper doing the damping in the drill-
ing direction, and a front end damper doing the damping in the return
direction.
In some cases, the damper may comprise only a rear end damper. The ad-
vantage of an end damper is that its structure is simple and that it is
inexpen-
sive and requires little maintenance.
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[0021] The idea of an embodiment is that the end damper is an an-
nular piebeilnadeofa .compressive elastic material. The end damper may be
of a polymer materiah SuCh as suitable polyurethane. Such dampers have
turned out resitwear surprisingly well.
(00221 The idea', of an embodiment is that the axial damper com-
prises at least one-pressure-medium-operated damper element. Such an axial
damper may have working pressure spaces into which pressure medium, such
as hydraulic fluid, may be conducted which affects the working pressure sur-
faces in the working pressure spaces. It is further feasible for the axial
damper
to comprise one or more damping pistons arranged to affect the main shaft in
the axial direction either directly or by means of appropriate intermediate
piec-
es. The pressure of the pressure medium may be directed to the damping pis-
tons to generate desired damping in the extreme positions of the sliding
movement of the main shaft.
[0023] The idea of an embodiment is that there are connecting
members at the front end of the main shaft of the rotation unit for rigid
mount-
ing in the axial direction. Thus, the drilling equipment is mounted on the
main
shaft without any axially directed sliding connection. The connecting members
may comprise connection threads to which the drilling tube, an adapter piece
or the like component can be attached. This embodiment reduces the loads
directed to the connection between the main shaft and the drilling equipment.
[0024] The idea of an embodiment is that the outer periphery of the
rear end of the main shaft comprises an axial set of grooves for transmitting
rotation force. Further, around the rear end of the main shaft, there is a
rotating
sleeve the inner periphery of which comprises a corresponding axial set of
- grooves. Thus, between the outer surface of the rear end of the main shaft
and the inner surface of the rotating sleeve, there is transmission connection
allowing axial moVernent of the main shaft. The rotating sleeve is bearing-
mounted on the body with axial bearings, whereby no axial forces are transmit-
ted from the maim shaft to the gear system through the transmission members.
These features are:pi-eferable:with regard to the durability of the structure.
[002513he icleaJ)f-: an embodiment is that the gear system is a plan-
etary gear. The planetary -gear may be physically rather small and also short
in
the axial direction, whereby it is easy to arrange at the rear end of the main
shaft.
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[0026] The idea of an embodiment is that the main shaft comprises
a first main shaft part and a second main shaft partarrangedon, the same axial
line and connected to each other. The connectioni-batwaan4ha main shaft
parts is axially rigid. On the outer periphery of the rear end of the first
main
shaft part, there is a set of grooves by means of whi-en rotation force can be
transmitted to the main shaft. The front end of the second 'Main shaft part,
in
turn, comprises a connection thread for attaching the drilling equipment. The
main shaft is bearing-mounted on the body by means of the front bearing and
end bearing of the first main shaft part only. The bearings are arranged at as
great an axial distance from each other as possible, whereby they receive the
crosswise loads well. Further, the feed flange may be arranged as a fixed part
of the second main shaft part. Alternatively, the feed flange may be a
separate
piece, for example an annular flange, which is arranged between the main
shaft parts.
[0027] The idea of an embodiment is that the portion between the
front bearing and the end bearing comprises a pressure medium space sur-
rounding the main shaft and in connection with a feed channel for pressurized
air or the like pressure medium. The main shaft has one or more channels for
conducting pressure medium from the pressure space into a centre channel in
the main shaft and further along it to the drilling equipment to be connected
to
the main shaft. The pressure space around the main shaft may be isolated
from the bearing spaces with shaft seals. Then, the pressure medium remains
separate from the lubrication oil of the bearing spaces.
[0028] The idea of an embodiment is that the rock drilling unit com-
prises a carriage which is moved on a feed beam by means.,of a feed device.
The body of the rotation unit is immovably attached to the carriage. Thus, the
rotation unit and its body always move along with the carriage,there being no
slidingly arranged body parts in the rotation unit.
[0029] The idea of an embodiment is that the rotation unit is intend-
ed for rotary drilling, in which drilling takes place by the
effectoUmerelotation
and feed force without any percussion device.
[0030] The idea of an embodiment is that the rotation unit is-intend-
ed for DTH drilling, in which the rotation unit and the percussion device are
in
opposite end portions of the drilling equipment. Hence, there is no percussion
= device in the rotation unit but it is in connection with the drilling
equipment. The
drill bit is typically attached directly to the percussion device.
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[0031] The idea of an embodiment is that the axial position of the
main::Shaft.- is monitored,- and this information may be transmitted to a
control
. ,
unit IhOf4Ontrols the handling device for drilling tubes in the rock drilling
unit.
Further,:the information on the position of the main shaft may be utilized in
controllitfg -thel:Strewing:and unscrewing of the threads. The position of the
main 'shaft may be monitored by means of one or more sensors or measuring
devices.
[0032] The idea of an embodiment is that the axial position of the
main shaft is monitored, and this position information is used as an aid in
con-
trolling the feed force during the drilling.
[0033] The idea of an embodiment is that the rotation unit compris-
es at least one axial damper as well as means for monitoring the axial
position
of the main shaft. The position information on the main shaft may be used for
monitoring the condition of the axial damper. The control unit may comprise a
control strategy for condition monitoring. The axial damper may comprise one
or more damper elements made of a compressible material and having a
planned functional compression area, for instance 10%. By means of the posi-
tion information, it can be observed if this planned compression is exceeded,
for example in cases where the damper element has permanently lost its elas-
ticity and resilience or has been damaged in another way. Owing to this em-
bodiment, damage of the axial damper can be observed in time.
[0034] The idea of an embodiment is that the main shaft is one inte-
gral shaft piece. The feed flange may be an integral undetachable part of the
main shaft. Alternatively, the feed flange may be a piece formed separately,
for
example =a ring flange, which may be immovably attached to the shaft piece.
[0035] The idea of an embodiment is that the rotating motor is a hy-
draulic motor. -
[0036] The idea of an embodiment is that the rotating motor is an
electric:
[0037yTher idea of-an embodiment is that the rotation unit does not
comprise:a geat system at all,but rotation force is transmitted to the main
shaft
by means of other transmission members. The rotation speed and torque of
the rotating motorcan be controlled in a versatile and accurate manner. The
rotating motor is of the type- called a direct drive motor. Motors of this
type are
available as hydraulically operated and electrically operated motors. As the
gear system can be left out of the rotation unit, there are fewer components
to
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be maintained and subject to damage. Further, the rotation unit can be made
smaller.
[0038] The idea of an embodiment is that thalransmission mem-
bers are provided with members for promoting the.towing'=of lubrication oil in
the lubrication space. Thus, a rotating hub or a-I-Otating .sleeve, , for
example,
may be provided with screw-like members which generate a flow of lubrication
oil by the effect of the rotating movement. In this way, durability of
transmission
surfaces, transmission components and bearings can be improved.
Brief description of the figures
[0039] Some embodiments of the invention will be explained in
greater detail in the attached drawings, in which
Figure 1 shows schematically a rock drilling rig provided with a rota-
tion unit for rotating drilling equipment around its longitudinal axis;
Figure 2 shows schematically the principle of DTH drilling and the
operation of a rotation unit in it;
Figure 3 shows schematically and greatly simplified the principle of
a rotation unit in accordance with the invention;
Figures 4 and 5 show schematically a partially cross-sectional top
view of a second rotation unit in accordance with the invention in two
different
axial extreme positions of the main shaft.
Figure 6 shows schematically a top view of yet another rotation unit
in which the main shaft is an integral piece and rotated by a direct drive
motor.
[0040] In the figures, some embodiments of the invention are shown
simplified for the sake of clarity. Like reference numerals refer to like
parts in
the figures.
Detailed description of some embodiments of the invention
-
[0041] Figure 1 shows a rock drilling rig 1 that comprises a movable
carrier 2 provided with a drilling boom 3. The boom 3 is provided, with a rock
drilling unit 4 comprising a feed beam 5, a feed device 6 and a ,rotation unit
7.
The rotation unit 7 may be supported to a carriage 8, or alternatively the
rota-
tion unit may comprise sliding parts or the like support members with, which
it is
movably supported to the feed beam 5. The rotation unit 7 may be provided
with drilling equipment 9 which may comprise one or more drilling tubes 10
connected to each other, and a drill bit 11 at the outermost end of the
drilling
equipment. The drilling unit 4 of Figure 1 is intended for rotary drilling in
which
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the rotation unit 7 is used for rotating the drilling equipment 9 around its
longi-
tudinalfaxis indirection R and, at the same, the rotation unit 7 and the
drilling
equipment 9ktonnetted to it are fed with feed force F by means of the feed
device6 in chilling direction A. Thus, the drill bit breaks rock due to the
effect of
rotaticiii:R antitfeed force F, and a drill hole 12 is formed. When the drill
hole 12
has been drilled to a-desired depth, the drilling equipment 9 can be pulled by
,means of the feed device 6 out of the drill hole 12 in return direction B,
and the
drilling equipment can be disassembled by unscrewing connection threads be-
tween the drilling tubes 10 by means of the rotation unit 7. The main shaft of
the rotation unit 7 is provided with a sliding function for screwing and
unscrew-
ing connection threads of the drilling equipment.
[0042] Figure 2 shows a second drilling unit 4, which differs from the
one in Figure 1 in such a way that the drilling equipment 9 is provided with a
percussion device 13. The percussion device 13 is thus at the opposite end of
the drilling equipment 9 in relation to the rotation unit 7. During drilling,
the
percussion device 13 is in the drill hole, and the drill bit 11 may be
connected
directly to the percussion device 13. The rotation unit 7 may consist of mod-
ules, whereby it may have a basic module 14 with a main shaft and its sliding
support, as well as a gear system module 15 and a rotating motor module 16.
The modules may be arranged successively on the same axial line.
[0043] Figure 3 shows one possible embodiment of the rotation unit
7 in a highly simplified manner. The rotation unit 7 comprises a main shaft
17,
the front end of which comprises connection threads 18 for attaching the drill-
ing equipment 9. In the portion of the opposite end of the main shaft 17,
there
may be an-axial set of grooves 19, to which rotation force is transmitted
through a rotating sleeve 20. The rotating sleeve 20 has a corresponding axial
set of grooves, _whereby the main shaft 17 can slide in the axial direction in
relation to the rotating sleeve 20. The rotating sleeve 20 may be bearing-
mounted to b-elMniovabld in the axial direction. Rotation force can be
transmit-
ted to the rotatihg'slee'Ve '20 from one or more gear systems 15 which are con-
nected to the rotating motor 16 As shown in the figure, it is possible to
transmit
rotation force*Orn aplurality of gear systems 15 to the main shaft. Then, the
gear systems :15 may be arranged on opposite sides of the main shaft 17 to
eliminate crosswise loading.
[0044] It is seen in Figure 3 that the main shaft 17 can be bearing-
mounted with an end bearing 21 and a front bearing 22. The bearings 21, 22
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are slide bearings, whereby they allow axial movement S of the main shaft 17.
The bearings 21, 22 are arranged at a great axiebearingAistance L from each
other, whereby the bearings 21, 22 are well: capable.'of -receiving crosswise
loads directed to the main shaft. The bearings 2fti:22 pbSitioned far from
each
other make good support for the main shaft...Atlhe bearing points, the main
shaft has diameters D1 and D2 which may, depending On the embodiment, be
either equal or somewhat unequal. The ratio of the bearing distance L between
the bearing points to the greater one of these diameters D1, D2 is at least
3:1.
The bearing point refers to the functional middle point of the bearing.
[0045] Figure 3 further shows support surfaces on which feed force
F is transmitted from a body 23 of the rotation device 7 to the main shaft 17.
The main shaft 17 may comprise one or more shoulders, flanges or the like
form surfaces with a support surface 24a for transmitting feed force in
drilling
direction A, and a support surface 24b for transmitting feed force in return
di-
rection B. The body 23 has corresponding support surfaces 25a and 25b.
Around the main shaft 17, there may be a sliding space 26 at the point of said
support surfaces. The axial end surfaces of the sliding space 26 may serve as
support surfaces 25a and 25b.
[0046] The pressure medium, such as pressurized air, may be fed
along a pressure channel 27 to the main shaft 17 and further to the drilling
equipment.
[0047] Figure 4 shows a second rotation device 17 in which some of
the features correspond to those shown in Figure 3. In the solution shown in
Figure 4, the main shaft 17 comprises a first main shaft part 17a on the side
of
the rear end, and a second main shaft part 17b on_ the ,side of the front end,
which are connected to each other with axially rigid connection 28, for
example
with a connection thread. The second main shaft partl 713 may comprise a
feed flange 29 the axial surfaces of which form support- Surfaces 24a, 24b.
Around the feed flange 29, there is a sliding surface 26,-,ivVhich.is an:
annular
space defined in the axial direction by ends 25a and 251:ia1so serving as sup-
port surfaces 25a, 25b in the body 23. The front bearing'22:is,a,slidel
bearing, _
and it is arranged in the sliding surface 26 on the side of therear.Surface of
the
feed flange 29. The front bearing 22 may slide in the :sliding Space 26 along
with the main shaft 17. When the feed takes place in drilling direction A,
feed
force is transmitted from the body 23 through the end 25a and front bearing 22
to the feed flange 29 and further to the main shaft 17. When the feed takes
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place in return direction B, feed force is transmitted from the body 23
through
the-end 25:band feed flange 29 to the main shaft 17. The sliding space 26 may
comprise.arr end 'damper 30, 31 either at one end or at both ends. The end
darriper 30--,31 may be an annular piece comprising elastic compressive mate-
.-riar..tThe end- damper enables damping of impacts and stresses transmitted
from the drilling equipment 9 to the main shaft 17 and further to the rest of
the
structure. In some cases, there are no end dampers 30 and 31, or alternative-
ly, only a rear end damper 30 is used. The sliding space 26 may be provided
with lubrication oil from a channel 32, whereby the front bearing 22, end
dampers and support surfaces are oil-lubricated.
[0048] Around the main shaft 17, there may be a pressure medium
space 33, into which pressurized air or the like can be fed from the channel
27.
The main shaft 17 comprises channels for conducting pressure medium to its
front end and further to the drilling equipment 9. The pressure medium space
33 may be separated with axial seals 35 and 36 from the sliding space 26 and
from a lubrication space 37 at the end bearing 21. The space 37 may be pro-
vided with lubricant from a channel 38, whereby also the end bearing 21 is oil-
lubricated.
[0049] On the outer periphery of the rear end of the first main shaft
part 17a, there is a set of grooves 19 to which a rotating sleeve 20 is
connect-
ed, having a corresponding set of grooves. The set of grooves allows move-
ment of the main shaft 17 in the axial direction. The rotating sleeve 20 is
sup-
ported to the body 23 by bearings 39 and 40 in such a way that it is immovable
in the axial direction. Rotation force can be transmitted to the rotating
sleeve
20 by means-of a rotating hub 41 connected to a shaft 42 or the like of the
gear system-15. Of course, it may be feasible to combine the structure of the
rotating sleeve 20 and rotating hub 41 into one entity. The gear system 15 and
rotating mator,16 may be module-structured, and they may be arranged on an
axial extertSiariolthe. main shaft 17.
140050y3Figure 5 shows a situation where the main shaft 17 has
moved intdaextrerne, front position in the axial direction. This sliding move-
ment mayltake'place.for.instance while the connection threads are connected.
[06511-The embodiment shown in Figure 6 deviates from the one
shown in Figures 4 and 5 in such a way that the main shaft 17 has not been
formed of two pieces but it is one integral shaft-like piece. The feed flange
29
may be an integral part of the main shaft 17, or it may be a piece
manufactured
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separately and attached to the shaft part of the main shaft. In Figure 6, a
bro-
ken line indicates the connection between .theJeed -flange and the shaft part,
which may be a welded joint, for example. Furter, the:rotationiunit 7 of
Figure
6 deviates in such a way that it has no gear system bUt the rotating motor 16
is
connected to a rotating hub 41 by means of ,a -shaft 42'or another
transmission
component. The rotating motor may be a 'direct drive motor dimensioned in
such a way that no separate gear system is needed.
[0052] It is seen in Figure 6 that the axial position of the main shaft
17 may be monitored by means of one or more sensors 50. The sensor 50
may be arranged at a suitable location in the structure of the rotation unit
7.
Instead of the sensor 50, a suitable measuring device can be used. Identifica-
tion information may be transmitted by means of a wireless or wire data trans-
mission connection 51 to a control unit 52 which may take the identification
information into account in controlling the actuators comprised by the rock
drill-
ing unit. Further, the position information may be used for controlling the
feed
force of the drilling and monitoring the condition of the axial damper.
[0053] Figure 6 further shows flow members 49 the purpose of
which is to generate flow of lubrication oil in the lubrication space and thus
to
improve lubrication of the components in the lubrication space. For instance a
thread, a spiral or projections on the outer periphery of the rotating hub 41
may
serve as the flow member 49.
[0054] Figure 6 shows yet another alternative embodiment where
the main shaft 17 is supported to the body 23 or a body part in quite the
front
part thereof with a radial bearing 53 shown by a broken line and greatly
simpli-
fied. Thus, the bearing distance L between the bearings 21 and 53 can be
made great. Further, in this embodiment, the bearing-22:may be an axial bear-
ing which does not have to participate in radial supporting of the main shaft
17
at all. There may be clearances between the bearing 22 and the main shaft 17
and between the bearing 22 and the sliding space 26:imaigh:a way that the
bearing 22 easily moves axially. This property may .tie-:preferable-with
regard
to damping axial stress waves. This embodiment MayYte'=also..utilized more
generally in the rotation unit 7 provided with an integrated axial damper. The
solution is thus not confined to the exact embodiment of Figure=6. -
[0055] It should be noted that in the above embodiments the rotat-
ing motor may a hydraulic motor or an electric motor. Further, a direct drive
motor may also be used in the rotation units 7 shown in Figures 3 to 5, in
CA 02829144 2013-09-05
WO 2012/140326 PCT/F12012/050364
13
which case, deviating from the solutions of the figures, they have no gear sys-
tem.
;[OQ56jdn.some cases, features disclosed in this application may be
used asT-4such, regardless of other features. On the other hand, when neces-
0ity, featuresi.rdiSelosed in this application may be combined in order to
provide
'varioustOmbinations.
. [0057] The drawings and the related description are only intended
to illustrate the idea of the invention. Details of the invention may vary
within
the scope of the claims.
