EP0624118A1

EP0624118A1 - Divice for grinding a cylindrical surface, especially a roller of a paper machine.

Info

Publication number: EP0624118A1
Application number: EP93922488A
Authority: EP
Inventors: Urs Maier
Original assignee: Farros Blatter AG
Current assignee: Farros Blatter AG
Priority date: 1992-11-25
Filing date: 1993-10-20
Publication date: 1994-11-17
Anticipated expiration: 2013-10-20
Also published as: KR100276091B1; FI98500B; FI98500C; ATE139723T1; JPH07503189A; KR950700148A; FI943406A; ES2089851T3; WO1994012315A1; JP3299279B2; EP0624118B1; FI943406A0; US5538458A; CA2128610A1; DE59303079D1

Abstract

PCT No. PCT/CH93/00248 Sec. 371 Date Jul. 21, 1994 Sec. 102(e) Date Jul. 21, 1994 PCT Filed Oct. 20, 1993 PCT Pub. No. WO94/12315 PCT Pub. Date Jun. 9, 1994A device for grinding a cylinder surface is provided, the cylinder being one of at least three substantially parallel, axially offset cylinders. The device includes a central body member and at least three supporting elements, each of the supporting elements being associated with a corresponding one of the cylinders, the supporting elements supporting the central body member relative to the cylinders. One or more belt grinder assemblies are provided, each belt grinder assembly including a belt grinder and a device for mounting the belt grinder on the central body member. Each belt grinder includes a contact wheel, an abrasive belt, extending around the contact wheel, and a device for supporting the contact wheel relative to a one of the cylinders to be ground. The supporting device includes a device for adjusting a position of the contact wheel relative to the one of the cylinders to be ground.

Description

Device for grinding a cylinder surface, in particular a roller of a paper machine

The invention relates to a device for grinding a cylinder surface, in particular a roller of a paper machine, according to the preamble of claim 1.

Devices of the type mentioned at the outset are known several times, for example from EP-OS 0 359 304. The disadvantage here is that this grinding device requires a special carrier, which must be arranged along the cylinder surface in each case before a grinding process in order to move the belt grinding device along the To guide the cylinder surface. It is therefore not possible to use such a grinding device between several closely spaced cylinder surfaces; the corresponding cylinders must be removed for a grinding process.

The object of the invention is to design a grinding device of the type mentioned at the outset in such a way that it can be used between cylinders which are close together.

The object is achieved according to the invention by the characterizing features of claim 1.

Because the frame has three pairs of star-shaped support members that contain foot parts that can be moved on a base, the frame can be narrow are inserted at adjacent cylinders and are supported on the cylinder surfaces of the cylinders, so that no additional support is required. The belt grinder has a support arm, which is preferably pivotably arranged on the frame and carries a bearing block for the contact disk, which can be attached to a cylinder surface to be ground. The necessary contact pressure as well as the spacing is ensured by a support device which is arranged between the bearing block and a base, ie a cylinder. With the help of the grinding device, a cylinder surface can be ground from closely spaced cylinders without having to be removed.

Advantageous embodiments of the grinding device are described in claims 2 to 19.

An embodiment according to claim 2 is particularly advantageous, as a result of which the frame can be adjusted to the respective distances between the cylinders.

A wide variety of drive types are possible for moving the frame and thus the grinding device along the cylinder surface. For example, a drive device can be provided at the ends of the cylinders, which moves the frame along the cylinder surface by means of a pulling element or a drive spindle. However, an embodiment according to claim 3 is particularly advantageous.

The feet of the support members can have rollers or balls, by means of which they are supported on a base, ie a cylinder surface. However, a configuration according to claim 4 is particularly advantageous, which not only ensures a particularly smooth, vibration-free run, but also the lowest frictional resistance offers and in particular allows that movement in different directions is possible. The frame can thus be moved along a stationary as well as a rotating cylinder surface.

A particularly simple attachment of the bearing block to the support arm describes claim 5. It is particularly advantageous if the bearing block is pivotally connected to the support arm according to claim 6, whereby the alignment of the contact disk on the cylinder surface to be ground is facilitated. The cardanic suspension of the contact disk according to claim 7 is particularly advantageous. However, a floating mounting of the axis of the contact disk is also possible.

There are various possibilities for the formation of the delivery device. For example, this can be integrated in the support device between the bearing block and a base. In the simplest case, the support device can be supported directly on the base by means of a roller or, according to claim 12, on a guide ruler connected to the base to improve the guidance. An advantageous delivery device is described in claim 9. A configuration according to claim 10 and in particular in a further development according to claim 11 is more advantageous.

A further development of the grinding device according to claim 12 is also particularly advantageous in order to ensure exact alignment and guidance of the contact disk on the cylinder surface to be ground, regardless of the quality of the base. Claim 13 describes a particularly simple and effective possibility of fastening the base device to the base, in particular to the cylinder surface of an adjacent cylinder. A training according to claim 14 of Advantage. This can compensate for unevenness on the base used as a support. The embodiment according to claim 15 provides a reference variable for aligning the guide ruler. Claim 16 describes a particularly expedient type of arrangement and possibility of tensioning the steel wire. The development according to claim 17 makes it possible to determine the radial orientation of the guide device with respect to the base and the surface to be ground, which is given when both sensors indicate the same value. The setting itself is made by rotating the pad.

To control the position of the contact disk on the surface to be ground, a further development of the grinding device according to claim 18 is advantageous. With the help of the sensors, an exact radial alignment of the contact disk on the cylinder can be determined.

The arrangement of the drive motor according to claim 19 is particularly space-saving and enables a very compact design of the device.

Exemplary embodiments of the grinding device according to the invention are described in more detail below with reference to the drawings, in which:

Figure 1 shows a first arrangement of the grinding device between three cylinders, in view transverse to the direction of travel;

Figure 2 shows a second arrangement of the grinding device between three cylinders, in view transverse to the direction of travel; Figure 3 shows the grinding device in section

III-III of Figure 1;

Figure 4 shows the contact plate with the support device in view IV-IV of the figure

1;

FIG. 5 shows the arrangement according to FIG. 4 with the contact roller at a minimal distance from the base;

Figure 6 shows the support device in the view

VI-VI of Figure 1;

Figure 7 shows the support device of Figure 6 in

Section VII-VII of Figure 6;

Figure 8 shows the base of the support device in

View transverse to the direction of displacement; and

Figure 9 shows the support device of Figure 6 in

Section IX-IX;

Figure 10 shows a device for arranging and

Tensioning of steel cables, in plan;

Figure 11 shows the device of Figure 10 in

Section XI-XI of Figure 10;

FIG. 12 shows the arrangement of a further simplified grinding device between three cylinders, viewed transversely to the direction of travel; Figure 13 shows the grinding device of Figure 12 in section XIII-XIII of Figure 12; and

FIG. 14 shows the arrangement according to FIG. 13 in

View XIV-XIV of Figure 12.

FIGS. 1 and 2 show the overall view of a grinding device in different positions on three cylinders Z ₁ , Z ₂ , Z ₃ , the axes of which form the corners A, B, C of a triangle, the cylinder surfaces having a mutual radial distance X ₁ , X ₂ , X _{3 have} different sizes. The cylinders can in particular be rollers of a paper machine.

The grinding device contains a frame 2 with a central body 4, on which two three support members 6 ₁ , 6 ₂ , 6 ₃ are arranged in pairs and in a star shape, which are located on base parts 8 ₁ , 8 ₂ on base parts, ie the cylinders Z ₁ , Z ₂ , Z ₃ support. The foot parts 8 ₁ are designed as cushions 10 which have air outlet openings 12 for the discharge of compressed air against the cylinder surface in order to form an air cushion there. On the support member 6 ₁ 2 foot parts 8 _{1 are} pivotally arranged on a crossbar 16 and 16 adjustable in position by means of screws 18. The support member 6 ₂ has a foot part 8 _{1 which is} adjustable via a screw spindle 20. The support member 6 ₃ is designed as a drive device and has a foot part 8 ₂ , which is designed as an impeller that can be driven by a drive motor 22. The impeller 8 ₂ interacts with the surface of the cylinder Z ₁ and serves to move the grinding device along the cylinders, parallel to their axis. Each support member 62,62,63 contains interchangeable spacers 23 to the support members on the respective distance X ₁ , X ₂ , X _{3 of} the cylinder surfaces.

At least one belt grinder 24 is preferably arranged on the frame 2, two belt grinders 24 ₁ , 24 ₂ are arranged, each of which contains a support arm 26 articulated on the central body 4, which supports a bearing block 28 for a contact disk 30 and a deflection roller 32 with a tensioning device 34. The drive motor 35 of the belt grinder 24 is accommodated in the central body 4 and drives the grinding belt 36 guided over the contact disk 30 and the deflection roller 32.

A support device 38 is arranged between the bearing block 28 and the cylinder Z ₁ serving as a base. This contains base devices 40 which can be connected to the cylinder Z ₁ and which carry a guide ruler 42 which contains a guide rail 44 on which a guide chute 46 can be moved. The guide carriage 46 is connected to the bearing block 28 of the contact disk 30 via a spacer 48. The spacer 48 can be exchanged for such other dimensions, so that the length of the support device can be adjusted to the distance X ₁ , X ₂ , X _{3 of} the cylinder surfaces, as a comparison of the arrangements according to FIGS. 1 and 2 and 4 and 5 shows. The axis 50 of the support device is aligned coaxially with the radial jet 52, which connects the axes of the cylinders Z ₁ , Z ₂ .

Figures 3 to 5 show further details of the design of the belt sander. It can be seen from FIG. 3 that the grinding device has two belt grinding devices 24 ₁ , 24 ₂ , which are of identical design and are arranged in mirror image. In the central body 4 of the frame 2, the drive motor 35 is arranged, which drives the grinding belt 36 by means of a drive disk 54, which over the contact disk 30 and the deflection roller 32 is guided. The deflection roller 32 is connected to the support arm 26 via an indicated tensioning device 34 and via a corresponding clamping device 56. The deflection roller 32 is mounted in a fork guide 58 and can be preloaded by means of a piston / cylinder unit 60.

The bearing block 28 carrying the contact disk 30 contains an infeed device 62 for feeding and / or adjusting the contact disk to the cylinder surface to be ground. For this purpose, the axis 64 of the contact disk 30 is fastened to a slide 66 which can be moved on a slide guide 68 of the bearing block 28. An adjusting spindle 74, which is driven by a drive motor 70 via a belt drive 72, interacts with the slide 66 and serves for the controlled adjustment thereof. The bearing block 28 is connected on the one hand via a joint 76 to a clamping device 78 which holds the bearing block 28 on the support arm 26. With the help of the joint 76, the bearing block can be pivoted about an axis 80 which runs parallel to the axis of the contact disk 30. The bearing block 28 is further fastened to the spacer 48 of the support device 38 and is thus further supported on the guide carriage 46 of the guide rail 44 of the guide ruler 42, as already mentioned above. Measuring sensors 82 are arranged on both sides of the slide 66, which probe the surface of the base, ie the cylinder Z ₂ , and by means of which the radial alignment of the guide device with the radial jet 52 can be determined. This radial alignment is given when both sensors 82 display the same value.

FIG. 5 shows the design of the support device for the smallest possible distance X of the cylinder surfaces, in which case the bearing block 28 is connected directly to the guide slide 46, ie no spacer 48 is used. Further details of the support device are shown in FIGS. 6 to 9. The base device 40 contains a base plate 84 to which four magnetic feet 86 are fastened. These contain permanent magnets, not shown in any more detail, which can be switched from an inactive position to an active position by means of a switch 88, in which the magnetic feet 86 adhere to the base, ie the cylinder surface. Via a height adjustment device 90, a support plate 92 is adjustably connected to the base plate 84, to which the guide ruler 42 is attached. The height adjustment device 90 contains a wedge 94 which is connected to a servomotor 98 via a threaded spindle 96. The wedge 94 cooperates with an inclined surface 100 on the base plate 84. By actuating the servomotor 98, the wedge 94 can be displaced along the inclined surface 100 and thereby adjust the support plate 92 in the height direction. The position of the wedge 94 can be determined by means of a dial gauge 102, so that the height or a change thereof can be read taking into account the incline. As already mentioned above, the guide ruler 42, which carries the guide rail 44, is fastened to the carrier plate 92. The latter has a rail head 104 with a preferably circular cross section. The mentioned guide chute 46 can be moved on the guide rail 44. On the guide chute 46, measuring sensors 106 are arranged on both sides of the guide rail 44, which interact with the guide ruler 42 and determine whether the guide slide 46 is correctly aligned, ie perpendicular to the guide ruler 42, about the axis of the rail head 104. As a result, by rotating the cylinder Z _{1, it is} possible to align the bearing block 28 and thus the contact disk 30 around the guide rail 44, preferably in such a way that the support device 38 with its axis 50 perpendicular to the guide ruler 42 and coaxial to the radial jet 52 between the cylinders Z ₁ and Z _{2 is} aligned. If necessary, the rail head 104 can also have a polygonal cross-section, ie be prismatic, then an articulated connection must be present in the support device 38, which enables pivoting about an axis which is parallel to the guide rail 44.

In order to align the guide ruler 42 on a possibly inaccurate base, ie inaccurate cylinder surface, two parallel steel wires 108 ₂ and 108 ₂ running on both sides of the guide rail 44 are tensioned at both ends of the guide ruler, by means of which the guide ruler 42 can be aligned. For this purpose, measuring sensors 110 are arranged on both sides of the guide rail 46 on the guide chute 46, which cooperate with the steel wires 108 ₂ , 108 ₂ and measure the distance of the guide carriage 46 from the steel wires 108 ₂ , 108 ₂ . The guide ruler is correctly aligned when the guide carriage 46 is radially aligned in the manner described above and the sensors 110 along the entire displacement path of the guide carriage 46 on the guide rail 44 indicate the same distance from the steel wires 108. If the distance varies, the guide ruler 42 must be adjusted using the height adjustment device 90 until the constant distance is reached over the entire length of the guide guide 42.

FIGS. 10 and 11 show a device for arranging the steel wires 108 ₁ , 108 ₂ , which form sections of a continuous steel wire 108, the ends 112 ₁ , 112 _{2 of} which are fastened to a first holder 114, which in turn is fixed to one end of the guide rule 42 is arranged. The steel wire runs along the guide guide to the other end of the guide guide 42, to which a second holder 116 with guide rollers 118 ₁ , 118 ₂ , 118 ₃ , 118 _{4 is} fastened. The steel wire 108 is guided around the deflection rollers 118 ₂ , 118 ₂ , 118 ₃ , 118 ₄ and then runs along the guide rail 42 to the first holder 116 back, where it is guided around a further deflection roller 120 to a measuring device 122 to which the end 1122 of the steel wire 108 is fastened. The measuring device 122 is in turn connected to the first holder 114 via a clamping device 124. The first end 1122 of ^the steel wire 108 is firmly clamped on the first holder 114. The tension of the steel wire 108 can now be changed by means of the tensioning device 124, the tension of the steel wire being readable on the dial gauge 122. This allows optimal and always constant clamping conditions to be set on the steel wire 108 and thus its sections 108 ₁ , 108 ₂ . In the area of the two ends of the guide ruler 42 there are also fixed points 126, on which the steel wire sections 1082, 108 rest and between which the guide ruler 42 is aligned in the manner described above.

Figures 12 to 14 show a further grinding device, which is identical in terms of the arrangement between the cylinders Z ₁ , Z ₂ , Z ₃ with the grinding device described above, so that the same parts are provided with the same reference numerals. In turn, the grinding apparatus includes a frame 2 having a central body 4 of the two sets of three support members 6 _1, 6 _2, ₃ are arranged in pairs and star-shaped, which extends over foot portions 8 _1, 8 ₂ on a base, ie the cylinders Z _1, Z ₂ , Support Z ₃ . With regard to further details and the drive for moving the frame 2 along the cylinders, reference is made to the above statements.

At least one belt grinder 128 is in turn arranged on the frame, which contains a support arm 130 articulated on the central body 4, which is no longer free-swinging, but is supported on the central body 4 via a further support arm 132 and thus forms a joint triangle with the first support arm 130. The first support arm 130 carries one Bearing block 134, which is arranged on the support arm 130 by means of an adjustable clamping device, not shown. The axle 138 of the contact disk 140 is mounted in a gimbal suspension 136 on the bearing block 134. The outer frame 142 of the gimbal 136 is connected at one end to the bearing block 134 via a joint 144. At the other end of the frame 142, a feed device 146 of the support device 148 is articulated via a joint 145. The latter contains a rocker arm 150, which on the one hand is pivotally attached to the bearing block 134 via a joint 152 and is connected at the other end to the delivery device 146 via a further joint 154, which can be, for example, a piston / cylinder unit or a motor-driven adjusting spindle. On the rocker arm 150, a bracket 156 is fastened between the joints 152, 154, which carries a roller 158, which cooperates directly with the cylinder Z ₁ . The connection between the bearing block and the rocker arm 150 is preferably adjustable in length in order to be able to adapt the belt grinding device to cylinders of different distances. Spacers mentioned earlier can serve this purpose or a corresponding adjusting spindle. If necessary, the effective length of the support arm 132 can also be variably connected to the support arm 130 in order to be able to adapt the latter and thus also the bearing block 134 and the associated support device between the cylinders and in particular to be able to align it along the radial jet 52.

As described in the example above, the contact disk 140 is driven by means of a drive motor 35 arranged in the central body 4, the grinding belt 36 being guided over the drive disk 54, the contact disk 140 and the deflection roller 32, the latter in turn being arranged on the support arm 130 by means of a tensioning device 34 is. With the help of the present grinding devices, it is possible to grind adjacent cylinders in the simplest way without removing the cylinder and with minimal assembly work for the grinding device.

REFERENCE SIGN LIST

A corner of a triangle

B corner of a triangle

C corner of a triangle

X ₁ distance of the cylinder surface

X ₂ distance of the cylinder surface

X ₃ distance of the cylinder surface

Z ₁ cylinder

Z ₂ cylinders

Z ₃ cylinders

2 frames

4 central body

6 ₁ support link

62 support member

6 ₃ support link

8 ₁ foot section

8 ₂ foot section

10 pillows

12 air outlet opening

14 crossbars

16 outriggers

18 set screw

20 screw spindle

22 drive motor

23 spacer

24 belt grinder

24 ₁ belt sander

24 ₂ Belt grinder

26 support arm

28 bearing block

30 contact disk

32 pulley

34 tensioning device

35 drive motor 36 sanding belt

38 support device

40 base device

42 guide ruler

44 guide rail

46 guide slides

48 spacer

50 axis

52 radial

54 drive pulley

56 clamping device

58 fork guide

60 piston / cylinder unit 62 feed device 64 axis

66 sledges

68 slide guide

70 drive motor

72 belt drive

74 adjusting spindle

76 joint

78 clamping device

80 axis

82 sensors

84 base plate

86 foot of magenta

88 switches

90 Height adjustment device 92 Carrier plate

94 wedge

96 threaded spindle

98 servomotor

100 sloping surface

102 dial gauge

104 rail head 106 sensors

108 steel wire

108 ₁ section of steel wire

108 ₂ steel wire section

110 sensors

112 ₁ end of 1082

112 ₂ end of 1082

114 first holder

116 second holder

118 ₁ pulley

118 ₂ pulley

118 ₃ pulley

118 ₄ pulley

120 pulley

122 measuring device

124 clamping device

126 fixed location

128 belt grinder

130 support arm

132 support arm

134 bearing block

136 gimbals

138 axis

140 contact disk

142 frames

144 joint

145 joint

146 delivery device

148 support device

150 rocker arms

152 joint

154 joint

156 bearing block

158 roller

Claims

PATENT CLAIMS

1. Device for grinding a cylinder surface, in particular a roll of a paper machine, with at least one belt grinder (24, 24 ₁ , 24 ₂ , 128) arranged on a frame (2) and movable along a surface line of the cylinder surface, the contact disk (30, 140) of which an infeed device (62, 146) is connected, characterized in that

the frame (2) has two three support members (6 ₁ , 6 ₂ , 6 ₃ ) arranged in pairs and in a star shape with foot parts (8 ₁ , 8 ₂ ) which can be moved on a base (Z ₁ , Z ₂ , Z ₃ ),

- The belt grinder (24, 24 ₁ , 24 ₂ , 128) has a support arm (26, 130) arranged on the frame (2), which carries a bearing block (28, 134) for the contact disk (30, 140),

- A support device (38,148) between the bearing block (28,134) and a base (Z ₁ , Z ₂ , Z ₃ ) is available.

2. Device according to claim 1, characterized in that the frame (2) has a central body (4) on which the support members (6 ₁ , 6 ₂ , 6 ₃ ), preferably by means of spacers (23), adjustable in length are.

3. Device according to claim 1 or 2, characterized in that the support foot (8 ₂ ) of a support member (63) is designed as a drivable roller.

4. The device according to claim 1 or 2, characterized in that the support feet (82) of at least two pairs Support members (6 ₁ , 6 ₂ ) are designed as cushions (10) with air outlet openings (12) directed towards the base to form air cushions.

5. Device according to one of claims 1 to 4, characterized in that the bearing block (28,134) along the support arm (26,130), preferably by means of a clamping device (78), is adjustably attached to the support arm (26,130).

6. Device according to one of claims 1 to 5, characterized in that the bearing block (28, 134) is attached to the support arm (26, 130) so as to be pivotable about an axis (80, 152) aligned parallel to the axis of the contact disk (30, 140).

7. Device according to one of claims 1 to 6, characterized in that the bearing block (134) has a gimbal suspension device (136) for the axis (138) of the contact disk (140).

8. Device according to one of claims 1 to 7, characterized in that the support device (148) is supported directly on the support (Z ₁ ) via a roller (158).

9. Device according to claims 7 and 8, characterized in that the gimbal suspension device (136) is articulated on one side (152) with a bracket (130) attached to the bracket (134) and at the opposite end a feed device (146) which interacts with the free end of a rocker arm (150) which is also articulated on the bearing block (134), the latter between the articulation points len (152, 154) carries the roller (158) of the support device (148), which is supported on the support (Z ₁ ).

10. The device according to one of claims 1 to 9, characterized in that the bearing block (28, 134) has the feed device (62, 146) for closing and / or adjusting the contact disk (30, 140) to the cylinder surface to be ground (Z ₂ ).

11. The device according to claim 10, characterized in that the axis of the contact disc (30) is attached to a carriage (66) of the feed device (62), the carriage (66) in a carriage guide (68) on the bearing block (28) by means of a drivable adjusting spindle is guided.

12. Device according to one of claims 1 to 8, characterized in that the support device (38) with the base (Z ₁ , Z ₂ , Z ₃ ) has connectable base devices (40) which carry the common guide ruler (42) which contains a guide rail (44) with a rail head (104) which is preferably circular in cross section, on which a guide chute (46) can be moved, which is connected to the bearing block (28) of the contact disk (30) in an adjustable-length manner, preferably via a spacer (48) is.

13. Device according to claim 12, characterized in that the base device (40) has a base plate (84) which can be connected to the base (Z ₁ , Z ₂ , Z ₃ ) via switchable magnetic feet (86) and on which a height adjustment device (90 ) a support plate (92) for receiving the guide rail (42) is arranged.

14. The device according to claim 13, characterized in that the height adjustment device (90) has a wedge (94) connected to a drive device (96, 98), which has an inclined surface (100) on the base plate (84) and / or carrier plate ( 92) cooperates, a measuring device (102) connected to the wedge (94), preferably a dial gauge, being used to determine the change in position of the wedge (94) and thus the change in position of the carrier plate (92).

15. Device according to one of claims 12 to 14, characterized in that it contains means (108, 108 ₁ , 108 ₂ , 110) for straightening the guide rail (42), which preferably two arranged parallel to and on both sides of the guide rail (44) Have steel wires (108 ₁ , 108 ₂ ), which are clamped at the ends of the guide rail (42) at fixed points (114, 116) and can be scanned by sensors (110) arranged on the guide chute (46).

16. The apparatus according to claim 15, characterized in that the steel wires (108 ₁ , 108 ₂ ) are formed by sections of a single steel wire (108), the ends (112 ₂ , 112 ₂ ) on a first holder (114) on a first End of the guide rail (42) are fastened and are guided on a second holder (116) at the second end of the guide rail (42) via deflection rollers (108 ₁ , 108 ₂ , 108 ₃ , 108 ₄ ), with a tensioning device (124) for Tensioning the steel wire (108) and preferably a measuring device (122) for measuring the tension of the steel wire (108) are present.

17. Device according to one of claims 12 to 16, characterized in that on the guide carriage (46) on both sides of the guide rail (44) measuring sensors (106) are arranged which cooperate with the guide ruler (42).

18. Device according to one of claims 1 to 16, characterized in that sensors (82) which cooperate with the cylinder surface to be ground are arranged transversely to and on both sides of the axis of the contact disk (30).

19. The apparatus according to claim 2, characterized in that the belt grinder (24, 128) has a drive motor (35) which is arranged in the central body (4) of the frame (2).