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Title:
WALL SAW
Document Type and Number:
WIPO Patent Application WO/2014/168531
Kind Code:
A1
Abstract:
A wall saw comprising: - a carriage (2) comprising a chassis (31); - a saw arm (11) pivotally mounted to the chassis; - a rotatable spindle (10) rotatably mounted to the saw arm and configured for connection to a saw blade; and - an electric drive motor (13) for rotating the spindle. The chassis (31) comprises a wall (32) and a flange (33) protruding from this wall (32), wherein the saw arm (11) is mounted to the chassis on a first side of said wall (32) and a motor cavity (34) is provided in the chassis on an opposite second side of said wall (32), this motor cavity (34) being delimited in one axial direction by said wall (32) and in the radial direction by said flange (33). The stator (35) and rotor (36) of the drive motor (13) are accommodated in the motor cavity (34).

Inventors:
JOHNSEN, Anders (Alderbäcken 72, Borlänge, S-781 93, SE)
Application Number:
SE2013/050399
Publication Date:
October 16, 2014
Filing Date:
April 12, 2013
Export Citation:
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Assignee:
JOHNSEN, Anders (Alderbäcken 72, Borlänge, S-781 93, SE)
International Classes:
B28D1/04; B23D45/04; B23D47/02; B23Q1/48; B23Q5/38; B23Q9/00; B27B5/18
Foreign References:
US20030172917A1
US3722497A
Attorney, Agent or Firm:
LÖFGREN, Jonas et al. (Bjerkéns Patentbyrå KB, Box 1274, Gävle, S-801 37, SE)
Download PDF:
Claims:
CLAI MS

1 . A wall saw comprising :

- a carriage (2), which is to be mounted to a guide rail (3) so as to be moveable along the guide rail , the carriage (2) comprising a chassis (31 );

- a saw arm ( 1 1 ) pivotally mounted to the chassis (31 );

- a rotatable spindle (10) configured for connection to a saw blade (9), the spind le (10) being rotatably mounted to the saw arm ( 1 1 );

- an electric drive motor (13), which is mounted to the chassis (31 ) and which is provided with a stator (35), a rotor (36) and an output shaft ( 14); and

- a transmission mechanism ( 15) for transmitting torque from the output shaft ( 14) of the drive motor (13) to the spind le

(10), the spindle ( 10) being rotatable under the effect of the drive motor (13) via the output shaft (14) and the transmission mechanism (1 5),

characterized in :

- that the chassis (31 ) comprises a wall (32) and a flange (33) protruding from this wall (32), wherein the saw arm (1 1 ) is mounted to the chassis (31 ) on a first side of said wall (32) and a motor cavity (34) is provided in the chassis (31 ) on an opposite second side of said wall (32), this motor cavity (34) being delimited in one axial direction by said wall (32) and in the radial direction by said flange (33); and

- that the stator (35) and rotor (36) of the drive motor ( 13) are accommodated in the motor cavity (34). 2. A wall saw according to claim 1 , characterized in that a lid (55) is fixed to said flange (33) at the outer free end thereof, said wall (32) of the chassis forming a first end wall of the motor cavity (34) and the lid (55) forming an opposite second end wall of the motor cavity (34).

3. A wall saw according to claim 2, characterized in : - that the lid (55) and the drive motor (13) form part of a motor modu le (60) which is detachably mounted to the chassis (31 ); and

- that the motor module (60) comprises a cylindrical sleeve (61 ) which is rigid ly connected to the lid (55) and projects therefrom into the motor cavity (34), the stator (35) of the drive motor (1 3) being fixed to the sleeve (61 ) on the inner side thereof. 4. A wall saw according to claim 3, characterized in that the rotor (36) of the drive motor (1 3) is rotatably mounted to the lid (55).

5. A wall saw according to claim 3 or 4, characterized in that an outer peripheral surface of the sleeve (61 ) abuts against an inner peripheral surface of said flange (33), at least one channel (62) for cooling fluid being provided in the interface between the outer peripheral surface of the sleeve (61 ) and the inner peripheral surface of the flange (33).

6. A wall saw according to claim 5, characterized in that said cooling fluid channel (62) extends in the circumferential direction of the sleeve (61 ). 7. A wall saw according to any of claims 2-6, characterized in that the lid (55) is fixed to said flange (33) by means of fasten ing members (57) in the form of screws or bolts.

8. A wall saw according to any of claims 2-7, characterized in :

- that the wall saw (1 ) comprises an electronic unit (63) which comprises electron ic components for controlling the power supply to the stator (35) of the drive motor (1 3); and

- that the electronic unit (63) is fixed to the lid (55) on the side thereof facing away from the motor cavity (34).

9. A wall saw according to any of claims 1-8, characterized in that the output shaft (14) of the drive motor (13) extends through an opening (37) in said wall (32) of the chassis. 10. A wall saw according to any of claims 1-9, characterized in that the drive motor (13) is a switched reluctance motor.

11. A wall saw according to any of claims 1-9, characterized in that the drive motor (13) is a permanent magnet motor.

Description:
Wall saw

FI ELD OF THE I NVENTION AND PRIOR ART The present invention relates to a wall saw according to the preamble of claim 1 .

A wall saw is a sawing machine primarily used for cutting walls, ceilings or floors made of concrete or similar materials. A con- ventional wall saw comprises a carriage which is moveable along a guide rail by means of a feeding device. A saw blade is mounted to a spindle, which is rotatably mounted to a saw arm . The saw arm is in its turn pivotally mounted to the carriage. The spindle is rotated by means of a drive motor, which is mounted to the carriage and operatively connected to the spindle through a transmission mechanism accommodated in the saw arm. When the saw arm is pivoted , the saw blade is moved upwards or downwards for adjustment of the depth of the cut. The saw arm may be pivoted by means of a motor or a manually operated ac- tuating device mounted to the carriage.

Wall saws of the above-mentioned type are for instance disclosed in WO 2009/108094 A1 , US 3 722 497 A and US 2007/01 63412 A1 .

OBJECT OF THE I NVENTION

The object of the present invention is to provide a wall saw with a new and favourable design .

SUMMARY OF THE I NVENTION

According to the present invention , said object is ach ieved by a wall saw having the features defined in claim 1 .

The wall saw according to the invention comprises: - a carriage, which is to be mounted to a guide rail so as to be moveable along the guide rail, the carriage comprising a chassis;

- a saw arm pivotally mounted to the chassis;

- a rotatable spindle configured for connection to a saw blade, the spindle being rotatably mounted to the saw arm ;

- an electric drive motor, which is mounted to the chassis and which is provided with a stator, a rotor and an output shaft; and

- a transmission mechanism for transmitting torque from the output shaft of the drive motor to the spindle, the spindle being ro- tatable under the effect of the drive motor via the output shaft and the transmission mechanism.

The chassis comprises a wall and a flange protrud ing from th is wall, wherein the saw arm is mounted to the chassis on a first side of said wall . The stator and rotor of the drive motor are ac- commodated in a motor cavity provided in the chassis on an opposite second side of said wall, this motor cavity being delimited in one axial direction by said wall and in the radial direction by said flange. By this arrangement of the saw arm and the drive motor on opposite sides of a wall included in the chassis of the carriage, the wall saw can be given a very compact and rig id construction .

In the wall saw according to the invention , the stator and rotor of the drive motor for the saw blade spindle are mounted inside a cavity integrated in the chassis of the carriage and not, as in a conventional wall saw, in a separate motor housing which is attached to and protrudes from a housing of the carriage. The drive motor for the saw blade spindle is hereby integrated in the carriage in a simple and space-saving manner.

Accord ing to an embod iment of the invention , a lid is fixed to said flange at the outer free end thereof, said wall of the chassis forming a first end wall of the motor cavity and the lid forming an opposite second end wall of the motor cavity.

Another embodiment of the invention is characterized in : - that the lid and the drive motor form part of a motor module which is detachably mounted to the chassis; and

- that the motor module comprises a cylindrical sleeve which is rigidly connected to the lid and projects therefrom into the motor cavity, the stator of the drive motor being fixed to the sleeve on the inner side thereof.

Hereby, the drive motor is mountable to the chassis in a simple and rapid manner and is easily detachable from the chassis for repair or maintenance. In this case, the rotor of the drive motor is preferably rotatably mounted to the lid .

Accord ing to another embod iment of the invention , the outer side of said sleeve of the motor module abuts against the inner side of said flange of the chassis, at least one channel for cooling fluid being provided in the interface between the outer side of the sleeve and the inner side of the flange. Hereby, a channel for the cooling fluid required for the cooling of the drive motor is integrated in the carriage in a very simple and efficient manner. Accord ing to another embodiment of the invention , the drive motor is a switched reluctance motor. A switched reluctance motor can be designed to be comparatively short in the axial direction . Thus, by using such a drive motor for the saw blade spindle, the wall saw can be designed with a comparatively short extension in the direction perpendicular to the saw blade, which will facilitate the handling of the wall saw and the use thereof is narrow spaces.

Further advantages as well as advantageous features of the wall saw according to the invention will appear from the following description and the dependent claims.

BRI EF DESCRI PTION OF THE DRAWI NGS With reference to the appended drawings, a specific description of preferred embod iments of the invention cited as examples follows below. In the drawings: is a perspective view of a wall saw accord ing to an embod iment of the present invention , is a perspective view of the wall saw of Fig 1 , as seen from another direction and with a saw blade mounted to the wall saw, is a perspective view of a carriage and a saw arm in- eluded in the wall saw of Fig 1 , is a partially sectioned lateral view of the carriage and saw arm included in the wall saw of Fig 1 , shows a part from Fig 4 in a larger scale, shows another part from Fig 4 in a larger scale, is a sectioned front view of the saw arm included in the wall saw of Fig 1 , is a perspective view of an actuating device included in the wall saw of Fig 1 , is a perspective view of a chassis included in the carriage of the wall saw of Fig 1 , is a perspective view of the chassis of Fig 9, as seen from another direction , is an exploded view of a motor module and the carriage included in the wall saw of Fig 1 , is a longitudinal section through a safety clutch in- eluded in the wall saw of Fig 1 , and is an exploded view of the safety clutch of Fig 12. DETAI LED DESCRI PTION OF EMBODI MENTS OF THE I NVENTION A wall saw 1 accord ing to an embod iment of the present invention is illustrated in Figs 1 and 2. This wall saw 1 is primarily intended to be used for cutting walls, ceilings or floors made of concrete or similar materials. The wall saw 1 comprises a carriage 2, which is to be mounted to an elongated guide rail 3 so as to be moveable along the guide rail. The guide rail 3 is mounted to a floor or other supporting surface by means of support members 4, which are secured to the guide rail 3.

Guide rollers 5a-5d are rotatably mounted to the carriage 2. These guide rollers 5a-5d are in engagement with guide tracks 6a, 6b on the guide rail 3 and are arranged to keep the carriage 2 in place on the guide rail 3, while allowing the carriage 2 to move along the guide rail 3 in the longitudinal direction thereof. In the illustrated embodiment, the guide rail 3 is provided with an upper guide track 6a and a lower guide track 6b, wh ich extend in parallel with each other along the guide rail. In the illustrated embod iment, two guide rollers 5a, 5b are in engagement with the upper guide track 6a from above and two other guide rollers 5c, 5d are in engagement with the lower gu ide track 6b from below.

A cog track 7 is fixed to the guide rail 3 and extends in the longitudinal direction thereof in parallel with the guide tracks 6a, 6b. The carriage 2 is moveable along the cog track 7 by means of a feeding device, which comprises a feed gear wheel 8 (see Fig 3) rotatably mounted to the carriage 2. The feed gear wheel 8 is in engagement with the cog track 7. The feeding device also comprises a feed motor (not shown) mounted to the carriage 2, by means of which the feed gear wheel 8 is rotatable in order to move the carriage 2 along the guide rail 3. The feed motor is preferably an electric motor, but could alternatively be a hydraulic motor. A circu lar saw blade 9 (see Fig 2) is to be attached to a rotatable spindle 10. In Fig 1 , the wall saw is shown without any saw blade attached to the spind le 10. The saw blade 9 is detachably attachable to the spindle 10 by means of a suitable coupling . The spindle 10 is rotatably mounted to a saw arm 1 1 by means of suitable bearings 1 2 (see Fig 4) and is rotatable about a first axis of rotation A1 . The spind le 10 is driven in rotation by means of an electric drive motor 13, which is mounted to the carriage 2. Driving torque is transmitted from an output shaft 14 of the drive motor 13 to the spindle 1 0 through a transmission mechanism 15 (see Figs 4 and 7). Thus, the spindle 10 is rotatable under the effect of the drive motor 1 3 via the output shaft 14 and the transmission mechanism 15. The transmission mechanism 15 comprises a set of gear wheels acting between the output shaft 14 of the drive motor and the spind le 1 0. One gear wheel 16 of the transmission mechanism 1 5 is non-rotatably fixed to the output shaft 14 of the drive motor 13 and another gear wheel 1 7 of the transmission mechanism 1 5 is non-rotatably fixed to the spindle 10. These gear wheels 1 6, 1 7 are operatively connected to each other via a number of intermed iate gear wheels 18a, 18b, 18c rotatably mounted in an external housing 20 of the saw arm 1 1 . I n the illustrated example, two of said intermed iate gear wheels 18b, 18c are non-rotatably connected to each other. As an alternative to gear wheels, the transmission mechanism 15 could be provided with a driving chain or driving belt for transmitting driving torque from the output shaft 14 of the drive motor to the spindle 1 0.

The output shaft 14 of the drive motor 1 3 is rotatable about a second axis of rotation A2, which extends in parallel with and at a distance from said first axis of rotation A1 . The saw arm 1 1 is pivotally mounted to the carriage 2 by means of suitable bearings 21 , 22, 23 and is pivotable about a pivot axis A3, which is perpendicular to the longitudinal axis of the guide rail 3 and coin- cides with said second axis of rotation A2. The saw arm 1 1 is adjustable into different rotational positions in relation to the carriage 2 by being pivoted about the pivot axis A3. In the illustrated embod iment, a ring gear 24 (see Figs 4 and 6) is non-rotatably fixed to the saw arm housing 20 by means of fasten ing members 25 in the form of screws. A gear wheel 26 (see Fig 8) is rotatably mounted to the carriage 2 and in engagement with the ring gear 24. The wall saw 1 comprises an actuating device 27 (see Fig 8) , by means of which said gear wheel 26 is rotatable in order to rotate the ring gear 24 and thereby pivot the saw arm 1 1 in relation to the carriage 2 about the pivot axis A3. The actuating device 27 comprises a motor 28 mounted to the carriage 2, by means of which said gear wheel 26 is rotatable. Said motor 28 is preferably an electric motor, but could alternatively be a hydraulic motor. The actuating device 27 also comprises a transmission mechan ism 29 for transmitting torque from the output shaft of said motor 28 to said gear wheel 26. In the illustrated example, this transmission mechanism 29 comprises a worm screw 30a non-rotatably connected to the output shaft of the motor 28 and a number of intermediate gear wheels 30b, 30c, 30d acting between the worm screw 30a and said gear wheel 26. The gear wheel 26 is non-rotatably connected to the last one 30d of said intermediate gear wheels.

The drive motor 1 3 and the saw arm 1 1 are carried by a chassis 31 included in the carriage 2. The chassis 31 is vertically oriented and is preferably of metallic material, such as for instance steel. The chassis 31 comprises a vertical wall 32 (see Figs 4, 9 and 10) and a flange 33 protrud ing in a horizontal direction from this wall 32. This vertical wall 32 and the flange 33 are preferably formed in one piece, but are alternatively formed as separate pieces which are rigidly joined to each other by welding . The saw arm 1 1 is pivotally mounted to the chassis 31 on a first side of said wall 32 and a motor cavity 34 is provided in the chassis 31 on an opposite second side of said wall 32. In the following , said first side of the wall 32 is denominated the outer side of the wall, whereas said second side of the wall 32 is denominated the inner side of the wall. The motor cavity 34 is delimited in one axial direction by said wall 32 and in the radial direction by said flange 33, which forms a cylindrical inner wall of the motor cavity 34. The stator 35 and rotor 36 of the drive motor 13 are accommodated in the motor cavity 34. Thus, the stator 35 and rotor 36 of the drive motor 1 3 are protected by said wall 32 and flange 33 of the chassis 31 . The output shaft 14 of the drive motor extends through an open ing 37 in the wall 32.

In the illustrated embod iment, a first axial bearing 21 and a second axial bearing 22 are provided between the saw arm 1 1 and the carriage 2 , as illustrated in Figs 4 and 6. The first axial bearing 21 comprises a flat and ring-shaped first sliding element 38, preferably in the form of a disc of plastic material, clamped between a contact surface 39 of the saw arm 1 1 and a corresponding contact surface 40 on the outer side of the wall 32. The second axial bearing 22 comprises a flat and ring-shaped second sliding element 41 , preferably in the form of a ring of plastic material, clamped between a lateral surface 42 (se Fig 6) on the ring gear 24 and a clamping member 43 fixed to the chassis 31 . The clamping member 43 is of metallic material. The clamping member 43 is flat and ring-shaped and comprises an outer part 43a (see Figs 6 and 1 1 ), through which the clamping member is fixed to the chassis 31 , and an axially springy part 43b which extends rad ially inwards from the outer part 43a and bears against the second sliding element 41 in a pre-tensioned manner. The axially springy part 43b of the clamping member is pre-ten- sioned against the second sliding element 41 so as to keep the second sliding element 41 clamped between the clamping member 43 and said lateral surface 42 on the ring gear under the effect of a spring force exerted by the clamping member. The outer part 43a of the clamping member is fixed to the chassis 31 by means of fastening members 44 in the form of screws. The above-mentioned contact surface 39 of the saw arm 1 1 is pressed towards the corresponding contact surface 40 on the outer side of the wall 32 under the effect of the clamping member 43. The saw arm 1 1 is retained in engagement with the chassis 31 under the effect of the spring force exerted by the clamping member 43. Thus, the clamping member 43 keeps the saw arm 1 1 secured to the carriage 2 in a pre-tensioned manner. In the illustrated embodiment, a radial bearing 23 (see Figs 4 and 6) is provided between an outer circular cylindrical surface 45 of the chassis 31 and an inner circular cylindrical surface 46 of the saw arm 1 1 . The radial bearing 23 comprises a sliding element 47, preferably in the form of a band of plastic material, arranged between said surfaces 45, 46.

In the illustrated embod iment, the ring gear 24 is received in an annular recess 50 (see Figs 6 and 10) in the chassis 31 and the outer part 43a of the clamping member 43 is fixed to a part 51 of the chassis which surrounds said recess 50. Furthermore, the guide rollers 5a-5d and the feed gear wheel 8 are rotatably mounted to the chassis 31 , and the feed motor and the motor 28 of the actuating device 27 are received in a cavity 52 (see Fig 9) provided in the chassis 31 .

The carriage 2 may be lifted and carried by means of handles 54 mounted to the chassis 31 .

A lid 55 is fixed to the flange 33 of the chassis at the outer free end thereof by means of fastening members 57 (see Figs 3 and 1 1 ) in the form of screws or bolts. The above-mentioned wall 32 of the chassis forms a first end wall of the motor cavity 34 and the lid 55 forms an opposite second end wall of the motor cavity 34. In the illustrated embod iment, the lid 55 and the drive motor 13 form part of a motor module 60 (see Fig 1 1 ) which is detach- ably mounted to the chassis 31 . The motor module 60 comprises a cylindrical sleeve 61 which is rigidly connected to the lid 55 and projects therefrom into the motor cavity 34, the stator 35 of the drive motor 13 being fixed to the sleeve 61 on the inner side thereof. An outer peripheral surface of the sleeve 61 abuts against an inner peripheral surface of the above-mentioned flange 33 of the chassis 31 . A channel 62 for cooling fluid is pro- vided in the interface between the outer peripheral surface of the sleeve 61 and the inner peripheral surface of the flange 33, as illustrated in Fig 4. This cooling fluid channel 62 extends in the circumferential direction of the sleeve 61 . In the illustrated example, the cooling flu id channel 62 is formed by a groove in the inner peripheral surface of the flange 33 and a corresponding groove in the outer peripheral surface of the sleeve 61 .

As an alternative, the sleeve 61 may be omitted . In this case, the stator 35 of the drive motor 13 is fixed d irectly to the flange 33 of the chassis 31 on the inner side thereof. In the illustrated embodiment, the rotor 36 of the drive motor 13 comprises a rotor hub 66 (see Figs 4 and 5) , which is rotatably mounted in the carriage 2 through at least one first bearing 72, for instance in the form of a ball bearing or a roller bearing , provided on the outer side of the rotor hub 66 at a first end thereof and at least one second bearing 74, for instance in the form of a ball bearing or a roller bearing , provided on the outer side of the rotor hub 66 at an opposite second end thereof. In the illustrated example, said at least one first bearing 72 is provided between a flange 73 on the inner side of the lid 55 and an outer peripheral surface at the first end of the rotor hub 66, and said at least one second bearing 74 is provide between a flange 75 on the inner side of the wall 32 of the chassis 31 and an outer peripheral surface at the second end of the rotor hub 66. In the illustrated embod iment, the stator 35 of the drive motor 13 is located on the outside of the rotor 36. As an alternative, the stator 35 of the drive motor 13 may be located between an outer part of the rotor 36 and the rotor hub 66. In the latter case, the stator 35 is fixed to the lid 55 of the motor module 60.

In the illustrated embod iment, the rotor hub 66 is operatively connected to the output shaft 14 of the drive motor through a safety clutch 67 so as to allow torque to be transmitted from the rotor hub 66 to the output shaft 14 via the safety clutch 67. The safety clutch 67 is configured to allow mutual rotation between the rotor hub 66 and the output shaft 14 when said torque reaches a given threshold value. The safety clutch 67 is accom- modated in a space inside the rotor hub 66 and comprises one or more first clutch members 68 (see Figs 5, 12 and 13), each of which being non-rotatably fixed to the rotor hub 66, and one or more second clutch members 69 each of which being non-rotata- bly fixed to the output shaft 14. Said first and second clutch members 68, 69 are pressed towards each other under the effect of a spring member 70 so as to allow torque to be transmitted from the rotor hu b 66 to the output shaft 14 via these clutch members 68 , 69. The spring member 70 is also accommodated in the space inside the rotor hub 66. Said first and second clutch members 68, 69 and the spring member 70 are located between an inner peripheral surface of the rotor hub 66 and an outer peripheral surface of a part 14a of the output shaft 14 surrounded by the rotor hub 66. The above-mention threshold value is given by the spring force of the spring member 70.

In the illustrated embodiment, said first and second clutch members 68, 69 have the form of ring-shaped discs and are arranged side by side in frictional engagement with each other. The output shaft 14 extends through a central opening in each clutch member 68, 69. The clutch members 68, 69 are moveable in the axial direction of the output shaft 14 and the rotor hub 66. In the illustrated example, each first clutch member 68 is provided with teeth 76 on its outer periphery, which teeth 76 are in engagement with internal splines in the rotor hub 66 so as to force the clutch member 68 to rotate together with the rotor hub 66, while at the same time allowing the clutch member 68 to slide axially in relation to the rotor hub 66. Each second clutch member 69 is provided with teeth 77 on its inner periphery, which teeth 77 are in engagement with external splines 78 on the output shaft 14 so as to force the clutch member 69 to rotate together with the output shaft 14, while at the same time allowing the clutch member 69 to slide axially on the output shaft 14. The first and second clutch members 68, 69 are arranged alternately side by side and are pressed towards each other by the spring member 70 so as to allow torque to be transmitted from the rotor hub 66 to the output shaft 14 by the frictional engagement between the clutch members.

In the illustrated embod iment, the spring member 70 is clamped between an internal shoulder 79 (see Fig 5) on the rotor hub 66 and an axially outermost one of said clutch members 68, 69. The spring member 70 preferably comprises one or more Belleville washers 71 , the output shaft 14 extending trough a central opening in each Belleville washer. In the illustrated example, the spring member 70 comprises four Belleville washers 71 arranged side by side.

The spring force of the spring member 70 is adjustable by means of an adjustment member 86, which is provided with an external thread 87 that is in engagement with a corresponding internal thread 88 in the rotor hub 66 at the above-mentioned first end of the rotor hub, as illustrated in Fig 5. The adjustment member 86 abuts against an axially outermost one 68' of the first clutch members (see Fig 1 2) . The position of the adjustment member 86 in the axial direction of the rotor hub 66, and thereby the axial pre-tensioning and spring force of the spring member 70, is adjustable by screwing the adjustment member 86 in either direction in relation to the rotor hub 66. At least one locking screw 90 is received in an axial through hole 91 in the adjustment member 86. An inner end 90a of this locking screw 90 is engageable in a recess 93 in the last-mentioned clutch member 68' in order to lock the adjustment member 86 to this clutch member 68' and thereby prevent mutual rotation between the adjustment member 86 and the rotor hub 66. Thus, when the end 90a of the locking screw 90 is received in a recess 93 in the clutch member 68' , the adjustment member 86 will be locked in its prevailing position in relation to the rotor hub 66. The locking screw 90 is provided with an external thread 89a that is in engagement with a corresponding internal thread 89b in said through hole 91 , as illus- trated in Fig 12. In the illustrated example, two such locking screws 90 are used . To make possible an accurate adjustment of the position of the adjustment member 86, the clutch member 68' is provided with several recesses 93 distributed around the centre axis of the clutch member and/or the adjustment member 86 is provided with several threaded through holes 91 distributed around the centre axis of the adjustment member.

The above-mentioned space inside the rotor hub 66 is limited in a first axial direction by the above-mentioned shoulder 79 on the rotor hub 66 and in the opposite axial direction by the adjustment member 86.

At the above-mentioned first end of the rotor hub 66, the output shaft 14 of the drive motor 13 is rotatably mounted to the rotor hub 66 through the adjustment member 86. In the illustrated example, a stub shaft 94 fixed to the output shaft 14 is rotatably re- ceived in an axial recess 95 in the centre of the adjustment member 86. The stub shaft 94 is mounted in a recess 97 at the end of the output shaft 14, for instance by press fit. In the illustrated example, the adjustment member 86 is ring-shaped and the above-mentioned recess 95 is formed as an axial through hole in the adjustment member 86.

At the above-mentioned second end of the rotor hub 66, the output shaft 14 of the drive motor 1 3 is rotatably mounted to the rotor hub 66 through a sleeve-shaped sliding element 98 provided between the rotor hub 66 and the output shaft 14. This sliding element 98 is clamped between a shou lder 96 on the output shaft 14 and a Belleville washer 71 of the spring member 70, as illustrated in Fig 12. As an alternative, the output shaft 14 and the rotor 36 of the drive motor 13 may be non-rotationally connected to each other directly without any intermed iate safety clutch .

The wall saw 1 also comprises an electronic unit 63, which com- prises electron ic components for controlling the power supply to the stator 35 of the drive motor 13. In the illustrated embod iment, the electronic unit 63 is fixed to the lid 55 on the side thereof facing away from the motor cavity 34. The adjustment member 86 is accessible through an opening 99 (see Fig 5) in the lid 55 when the electronic unit 63 has been detached from the lid . The drive motor 13 is preferably a switched reluctance motor, but may alternatively be a permanent magnet motor or any other suitable electric motor.

The invention is of course not in any way restricted to the embodiments described above. On the contrary, many possibilities to modifications thereof will be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention such as defined in the appended claims.