EP0495181B1 - Grinding power tool with quick coupling means - Google Patents

Description

The invention relates to a portable grinding machine with a motor-driven drive shaft and a quick-action clamping device for a grinding tool, in which the quick-action clamping device comprises a spindle which is coaxial with the drive shaft and which braces against the drive shaft in the axial direction via a spring and by means of a clamping lever in the axial direction is displaceable relative to the drive shaft, an outer free end of the spindle holding the grinding tool, which can be removed from the free end in a release position when the free end of the spindle is extended and the spring is tensioned, and partially and in a clamping position when the free end of the spindle is retracted relaxed spring is in a rotationally fixed connection with the drive shaft.

A grinding machine of the type mentioned above is known from EP-OS 152 564.

The known grinding machine is an angle grinding machine and the grinding tool is a rigid grinding wheel. In the release position, the free end of the spindle protrudes from the grinding machine housing and the grinding wheel can be screwed onto the free end of the spindle. In one embodiment of the known grinding machine, this is done in that the projecting free end of the spindle is provided with a threaded section which extends through the grinding wheel and on which a fastening nut can be screwed on from the outside and which covers the grinding wheel in its central region. In another embodiment of the known grinding machine, the protruding end of the spindle is provided with a central bore, at the bottom of which there is a collet-like element with an internal threaded bore. A screw bolt, the thickened end of which covers the central area of the grinding wheel, can be inserted from the outside through a central opening in the grinding wheel and inserted into the central bore of the spindle. The screw bolt carries at its inner free end a threaded section which engages in the collet-like element. In a third embodiment of the known grinding machine is one with the last-mentioned embodiment Similar arrangement is used, in which a screw bolt is screwed into a central bore of the drive spindle. However, there is still a fastening sleeve between the thickened outer end of the screw bolt and the grinding wheel.

The above-mentioned embodiments of the known grinding machine therefore have in common that in the release position with the free end of the drive spindle extended, an element (nut or screw bolt) must be screwed on from the outside in order to fix the grinding tool in the form of a rigid grinding wheel on the drive spindle. If the clamping position is then taken up by actuating the clamping lever, the drive spindle with the grinding tool fixed thereon is drawn in and the grinding tool is in frictional contact with the drive shaft under the force of the partially relaxed spring.

It has now been found in practice that the known grinding machine is somewhat cumbersome to handle in certain applications. This applies in particular when a flexible grinding plate is used as the grinding tool, which has an inner-conical contact surface for an abrasive paper, which is peripherally connected to a flat contact surface in the rest position.

With grinding tools of this type, the sanding paper is pressed into the inner-conical contact surface when it is fastened in the central area. In this situation, screwing in a nut or a bolt can be cumbersome, especially if a relatively thick sandpaper is used, as is usually used for roughing, for example. In such an application, it can also happen that when screwing in a nut or a bolt there is an undefined screw-in depth, so that when the quick-action clamping device is tensioned, there is no secure frictional engagement between the grinding tool and the drive shaft, at least for the first time. This frictional engagement occurs automatically in the known grinding machine because the grinding tool tightens itself, but this is not desirable in all applications because defined and safe clamping conditions are desired from the start.

A portable grinding machine of another type is known from EP 0 147 545, in which a bayonet connection is provided for the detachable fastening of a grinding wheel.

Another grinding machine, in which a bayonet connection is provided for fastening the grinding tool, is known from US-A-2 781 618.

The invention has for its object to develop a grinding machine of the type mentioned in such a way that the fixing process of the grinding tool is simplified.

This object is achieved in a grinding machine of the type mentioned in that the free end is designed as a bayonet end, which extends through the grinding tool, that a fastening sleeve with a bayonet opening can be placed on the bayonet end from the outside , wherein the fastening sleeve partially covers the grinding tool from the outside, that the bayonet end has a first, outer Bayonet section of larger cross-sectional area and a second, inner bayonet section of smaller cross-sectional area that the cross-sectional shape of the first bayonet section has that of a regular triangle with three straight and three circular sections, that the cross-sectional shape of the second bayonet section has three circular sections with the radius of the inner circle of the triangle and 60 ° circumferential angle, three first straight sections that are aligned with the straight sections of the triangle and take up half of their width, and three second straight sections that connect at 120 ° to the first straight sections and have their width, and that the bayonet Opening of the fastening sleeve has a cross-sectional shape which substantially corresponds to that of the first bayonet section.

It is thus possible with a single movement to fix the fastening sleeve on the free end of the spindle by means of the bayonet arrangement. All that is required is for the fastening sleeve with the bayonet opening to be pushed onto the bayonet end and rotated in order to fix the grinding tool. The fact that bayonet arrangements can only be tightened regularly in an axial position also results in a defined clamping path for the grinding tool, so that with appropriate dimensioning of the quick-action clamping device or the displacement path of the drive spindle, the grinding tool is securely clamped from the start, i.e. is held under full friction.

Another advantage is that a bayonet mount is created that is simple in shape and therefore reliable in long-term use, especially taking into account the harsh operating conditions of grinding machines, for example angle grinders. Furthermore, the configuration mentioned has the advantage that the fastening sleeve on the bayonet end is simple Attachment and twisting can be fixed without the fastening sleeve having to be moved outward again by an axial amount, as is the case with some bayonet sockets.

In a further embodiment of the invention, the grinding tool can be designed as a brush tool on which the fastening sleeve with its bayonet opening is provided.

In this way it is possible to fix a brush-shaped grinding tool on the free end of the spindle in the manner described above with a single handle. This is possible without using an adapter. Another advantage can be seen in the fact that, in contrast to conventional brush tools, attachment takes place without a central screw attachment. Because of the often narrow cup-shaped brush tools, it is difficult to reach a screw in the cavity of conventional brush tools. There is also a risk of injury to the sharp bristles of the grinding tool when slipping. In the solution according to the invention, the risk of injury is considerably reduced, since the grinding tool can be gripped from the outside and manipulation in the middle of the brush-shaped tool is not necessary.

In a preferred embodiment of the grinding machine according to the invention, the disc-shaped grinding tool comprises a flexible grinding plate which has an inner region with an inner-conical contact surface for an abrasive paper, the fastening sleeve comprising an outer-conical section for pressing the sanding paper against the inner-conical contact surface.

This measure has the advantage that with flexible grinding tools of this type, simple and reliable fixing of the sanding paper to the flexible grinding plate is possible without the disadvantages of the prior art described above occurring.

It is preferred in this exemplary embodiment if the axial length of the spring is a multiple, preferably 3 to 10 times the axial height of the inner conical contact surface.

This measure has the advantage that a reliable clamping of the sanding paper on the flexible sanding plate is possible with such a long stroke clamping device.

This applies in particular if the displacement path of the spindle which can be adjusted by means of the clamping lever between the release position and the clamping position is at least as large as the axial height of the inner-conical contact surface.

This measure has the advantage that, even if the sanding paper is loosely placed on the flexible sanding plate, it is reliably tensioned under frictional engagement.

In a particularly preferred development of the invention, the bayonet end rests on the bayonet opening without a slope over radial end faces.

This measure has the advantage that the construction and thus the manufacture of the bayonet is simplified because the fastening sleeve with its bayonet opening is only rotated in the circumferential direction relative to the bayonet end of the free end of the spindle, but does not have to be screwed onto it. This is achieved in particular in the previously described exemplary embodiment, in which a wedge effect occurs in the circumferential direction of the bayonet connection, with which the fastening sleeve is fastened to the bayonet end of the spindle without having to be screwed.

In a further preferred exemplary embodiment of the invention, the bayonet end is provided at the free end of the spindle with an extension which, when the bayonet connection is closed, positively engages in an outer opening of the bayonet sleeve.

This measure has the advantage that the positively active elements of the bayonet connection are secured against contamination, because the extension in the outer opening represents a closure of the inner elements of the bayonet connection with respect to the outside.

In a further preferred embodiment of the invention, the grinding tool has bristles which are held between an outer, cup-shaped bristle holder and an inner, cup-shaped bristle holder.

In this way, a simple and secure attachment of the bristles is possible.

In a further preferred embodiment of the invention, the outer bristle holder is welded to the fastening sleeve.

This has the advantage that the same fastening sleeve as in the previously described embodiment can be used for a disk-shaped grinding tool.

In a further embodiment of the invention, a plate disk is arranged between the inner bristle holder and the outer bristle holder for fixing the bristles, in which edge-side bores are provided, through which the individual bristles are looped.

This design ensures a particularly secure and durable fixation of the bristles.

In a further advantageous embodiment of the invention, the bristle receptacles and the plate washer are held on a cylindrical carrier body and are fixed between a collar and a peripheral edge flange of the carrier body.

This ensures a particularly simple assembly. First, the bristle receptacles are pushed together with the bristles fixed on the plate washer onto the cylindrical carrier body, which is then pressed from the outside, so that the circumferential edge flanging is created, through which a secure hold of the arrangement on the carrier body is ensured.

Further advantages result from the description and the attached drawing.

Fig. 1

eine Seitenansicht, im Schnitt und teilweise äußerst schematisiert, durch ein vorderes Ende eines Ausführungsbeispiels einer erfindungsgemäßen Schleifmaschine in Gestalt eines Winkelschleifers;

Fig. 2

in stark vergrößertem Maßstab einen Axialschnitt durch eine Befestigungshülse, wie sie bei der Schleifmaschine gemäß Fig. 1 verwendet wird;

Fig. 3

eine Draufsicht auf die in Fig. 2 dargestellte Befestigungshülse;

Fig. 4

ebenfalls in stark vergrößertem Maßstab eine Seitenansicht durch eine Antriebsspindel, wie sie bei der Schleifmaschine gemäß Fig. 1 verwendet wird;

Fig. 5

eine Ansicht, von unten, auf die Antriebsspindel der Fig. 4, in Richtung der Pfeile V-V von Fig. 4;

Fig. 6

einen Radialschnitt durch die in Fig. 4 dargestellte Antriebsspindel, in Richtung der Pfeile VI-VI von Fig. 4;

Fig. 7

eine Darstellung, ähnlich Fig. 6, jedoch in weiter stark vergrößertem Maßstab zur Erläuterung der Geometrie einer Bajonettverbindung;

Fig. 8

einen Axialschnitt durch das äußere Ende der Spindel in vergrößerter Darstellung, auf die in alternativer Ausführung ein bürstenförmiges Schleifwerkzeug aufgesetzt ist.

An embodiment of the invention is shown in the drawing and is explained in more detail in the following description. Show it:

Fig. 1

a side view, in section and partially extremely schematic, through a front end of an embodiment of a grinding machine according to the invention in the form of an angle grinder;

Fig. 2

on a greatly enlarged scale an axial section through a fastening sleeve, as is used in the grinding machine according to FIG. 1;

Fig. 3

a plan view of the mounting sleeve shown in Figure 2;

Fig. 4

likewise in a greatly enlarged scale, a side view through a drive spindle, as is used in the grinding machine according to FIG. 1;

Fig. 5

a view, from below, of the drive spindle of Figure 4, in the direction of arrows VV of Fig. 4.

Fig. 6

a radial section through the drive spindle shown in Figure 4, in the direction of arrows VI-VI of Fig. 4.

Fig. 7

a representation, similar to Figure 6, but on a further greatly enlarged scale to explain the geometry of a bayonet connection.

Fig. 8

an axial section through the outer end of the spindle in an enlarged view, on which in an alternative embodiment, a brush-shaped grinding tool is placed.

In Fig. 1, 10 designates a total of an angle grinder of a conventional type. The angle grinder 10 has a housing 11 in which a motor shaft 12 is mounted. The motor shaft 12 is driven by a motor, not shown, for example an electric motor, a pneumatic motor or the like, as indicated by an arrow. At the left free end of the motor shaft 12 in FIG. 1, a conical first pinion 13 is arranged in a rotationally fixed manner. The first pinion 13 meshes with a second pinion 14, which is also conical, so that an angular gear is formed.

The second pinion 14 is non-rotatably connected to a hollow drive shaft 15. The drive shaft 15 has a non-circular inner profile 16 at its lower free end.

A drive spindle 20 is arranged concentrically with and in the drive shaft 15. A non-circular section 21 of the spindle 20 is adapted to the non-circular inner profile 16 of the drive shaft 15, so that the spindle 20 is arranged in the drive shaft 15 in a rotationally fixed but axially displaceable manner.

The spindle 20 is formed at its upper end in FIG. 1 as an elongated bolt 22. The bolt 22 carries a stop 23 at its upper free end. A disk spring assembly 24 occupies a space between the bolt 22 and the drive shaft 15. The plate spring assembly 24 is supported at the top by the stop 23 and at the bottom by a shoulder 25 of the drive shaft 15.

The spindle 20 with the stop 23 is connected in the axial direction to an eccentric disk 30 via an axially movable pressure piece 26. The eccentric disc 30 is rotatable about an axis 31 running perpendicular to the plane of the drawing in FIG. 1. For this it is provided with an elongated lever 32 which can be pivoted in the plane of the drawing in FIG. 1, as indicated by an arrow 33.

The drive shaft 15 is axially rigid in the housing 11 in a manner not shown. The shoulder 25 is therefore fixed in space relative to the housing 11.

In Fig. 1, a clamping position is shown in which the plate spring assembly 24 braces the stop 23 upwards, with the result that the spindle 20 is drawn into the housing 11. This is possible because the eccentric disc 30 is in a position in which the pressure piece 26 is at a minimal distance from the axis 31.

If, on the other hand, the lever 32 is pivoted upward in the direction of the arrow 33, the pressure piece 26 is pressed downward due to the widening eccentric disk 30. Because of this, the stop 23 is also moved axially downward, with the result that the disk spring assembly 24 is compressed. At the end of the pivoting path of the lever 32, the spindle 20 is in its lower end position, which serves as a release position, as will be explained further below.

In the release position, a lower end of the spindle 20, which is designed as a bayonet end 40, projects as far as possible from the drive shaft 15.

The arrangement is such that a fastening sleeve 41 can be plugged and fixed onto the bayonet end 40. The fastening sleeve 41, the details of which are shown in FIGS. 2 and 3, covers the central region of an abrasive paper 42 from the outside and presses it against a flexible one Sanding plate 43. The sanding plate 43 is provided on its side facing the housing 11 with a rigid disk 44 which, from the outside, bears against a radial end face of the drive shaft 15.

The flexible grinding plate 43 has an outer region 45 with an outer, flat contact surface 46 and an inner region 47 with an outer, inner-conical contact surface 48.

Correspondingly, the fastening sleeve 41, as is clearly shown in FIGS. 2 and 3, has a hollow-conical section 50, the inclination of which is adapted to that of the inner-conical contact surface 48. In the center, a cylindrical section 51 adjoins the hollow-tapered section 50 of the fastening sleeve 41.

2 that the cylindrical section 51 is divided in the axial direction into a lower area 52 and an upper area 53. While the lower region 52 has a cylindrical inner surface, the upper region 53 is provided with an original opening 54, namely a triangular profile. The triangular profile consists of three straight sections 55 and three circular sections 56.

The upper region 53, which is consequently narrowed over part of the circumference with respect to the lower region 52, thus has end faces 57 on the underside in the illustration in FIG. 2. The end faces 57 lie strictly in a radial plane.

Furthermore, a peripheral collar 58 adjoins the lower region 52, which is provided with an opening 59 in its center. The opening 59 has, as FIG. 3 clearly shows a diameter which is smaller than the smallest radius at the three straight sections 55. The opening 59 is preferably designed as a cylindrical opening, but can also be conical by opening upwards in FIG. 2.

4 to 6 show that the bayonet end 40 of the spindle 20 is divided into a first, lower bayonet section 60 and a second, upper bayonet section 61. The first bayonet section 60, as can clearly be seen in FIG. 6, has a larger cross-sectional area than the second bayonet section 61, so that a protrusion 62 is formed in some areas.

At the lower end of the spindle 20, an axial extension 64 can also be seen below the first bayonet section 60, which is preferably designed as a cylindrical extension. The shape of the extension 64 is selected so that it fits in a form-fitting manner in the opening 59 in the collar 58 of the fastening sleeve 41.

In this way it is achieved that when the bayonet connection is closed, the extension 64 forms a closure in the opening 59, which prevents dirt from penetrating into the axially behind regions of the elements forming the bayonet connection.

The cross-sectional shape of the first bayonet section 60 is the same as the cross-sectional shape of the opening 54, apart from a slight play. The axial thickness of the upper region 53 also essentially corresponds to the axial thickness of the second bayonet section 61.

As a result, the fastening sleeve 41 with the opening 54 can be pushed over the first bayonet section 60 and then rotated. The fastening sleeve 41 is now axially secured in the region of the straight sections 55 of the opening 54 by abutment on the projections 62.

This bayonet connection is functional because the second bayonet section 61 has the shape shown in detail in FIG. 7 in relation to the first bayonet section 60 or the opening 54 corresponding in cross-sectional shape.

The cross-sectional shape of the first bayonet section 60 is then divided into three arcuate sections 70, which lie on a common circumference 71 and three straight sections 72.

The cross-sectional shape of the second bayonet section 61, on the other hand, is subdivided into three first straight sections 74 and three second straight sections 75 as well as three arcuate sections 76 which lie on an incircle 77 of the straight sections 72. The radius of the circumference 71 is R₁ and the radius of the inscribed circle 77 is R₂.

The first straight sections 74 are aligned with the straight sections 72 and each take up half of their width. The first straight sections 74 are each adjoined at 120 ° by the second straight sections 75, the width of which corresponds to that of the first straight sections 74. In between are each the arcuate sections 76, each of which has a circumferential angle of 60 °.

Because of this geometry, it is possible to slide the fastening sleeve 41 with the opening 54 over the first bayonet section 60. The straight sections 55 of the opening 54 slide axially past the straight sections 72 of the first bayonet section 60 and therefore also past the first straight sections 74 of the second bayonet section 61. Since the arcuate sections 76 have only the radius R₂ of the incircle 77, the mounting sleeve 41 can now be rotated. The straight sections 55 of the opening 54 roll on the arcuate sections 76 and finally come into contact with the second straight sections 75. The twisting path is ended there because the second straight sections 75 also form a stop in the circumferential direction.

Since the fastening sleeve 41 is wedged in the circumferential direction by relative rotation on the lower bayonet end 40 of the spindle 20, a further fastening in the axial direction is not necessary. The end faces 57 and 62 lying against one another when the bayonet connection is closed can therefore be of strictly radial design, which simplifies production.

In this way, with only a 60 ° rotation, the fastening sleeve 41 can be axially fixed on the bayonet end 40 of the spindle 20. If you now move the lever 32 against the direction of the arrow 33 from the release position to the clamping position, the fastening sleeve 41 is pulled upwards in FIG.

For this purpose, the arrangement is such that the maximum eccentricity E of the eccentric disk 30 is at least as large as the axial height H₂ of the inner conical contact surface 48. Because of this, in extreme cases it is even possible to do so first press the flat sandpaper 42 only slightly or not at all into the center when the fastening sleeve 41 is placed on the bayonet end 40. The eccentricity E is then sufficient to measure the entire axial path corresponding to the height H₂.

In order to accomplish this, it is preferred if the axial length H 1 of the plate spring assembly 24 is dimensioned substantially greater than the height H 2 of the inner conical contact surface 48. Preferably H₁ is 3 to 30 times, especially 5 times as large as H₂.

If the entire twist travel of 60 ° has not been set when the fastening sleeve 41 is placed on the bayonet end 40, this is unproblematic because the arrangement is such that the fastening sleeve 41 tightens itself when the motor starts.

Another embodiment is shown in FIG. 8.

The angle grinder, designated overall by the number 80, corresponds completely in structure and function to the angle grinder 10 described above. Instead of a disk-shaped grinding tool, a brush-shaped grinding tool is provided in this exemplary embodiment, which is generally designated by the number 82. The grinding tool 82 is fastened in the manner described above to the free end of the spindle 20, which is designed as a bayonet end 40. Here, too, a bayonet opening 91, which is provided in a fastening sleeve 81, can be plugged and fixed onto the bayonet end 40.

Since the structure and mode of operation of the fastening sleeve 81 with the bayonet opening 91 is completely the same as that previously described Agree, there is no need for a further description of the bayonet lock at this point. The fastening sleeve 81 has a conical extension 93 on its outer end facing away from the bolt 22. This extension 93 is welded on the edge to the cup-shaped brush tool 82 via a weld 83.

In order to ensure the necessary distance of the brush tool 82 from the drive shaft 15 and to prevent contamination of the rotating parts from the outside, a cylindrical spacer sleeve 80 is pressed onto the fastening sleeve 41, which protrudes relative to the fastening sleeve 41 in the direction of the spindle 20 and on the end face of the Drive shaft 15 is present.

The grinding tool 82 has bristles 84 which are held between an outer, cup-shaped bristle holder 85 and an inner, cup-shaped bristle holder 86 by means of a disk 87. In the plate disk 87, bores 90 are provided on the edge in the axial direction, through which the individual bristles 84 are passed in the manner of a loop. The bristle receptacles 85 and 86 and the intermediate disk 87, on which the bristles 84 are held, are fastened on a cylindrical carrier body 89. The cylindrical carrier body 89 is closed on its side facing the fastening sleeve 81 by a collar 92 which projects slightly outwards and against which the outer bristle receptacle 85 bears.

During assembly, the outer bristle receptacle 85 is first pushed onto the cylindrical carrier body 89 until the latter strikes the collar 92. Then the plate 87 with the bristles 84 and the inner bristle holder 86 on the Carrier body 89 pushed. The carrier body 89 is now pressed on the edge against the inner bristle holder 86, so that a circumferential flange 88 is formed, by means of which the inner bristle holder 86 is held under tension on the carrier body, so that the bristles 84 are pressed in between the two bristle holders 85, 86 and protrude outwards.

As already mentioned, the outer bristle receptacle 85 is welded to the conical extension 93 on the edge side.

The bristles can be arranged so that a pot-braid brush is created. In addition, of course, any other common embodiments, e.g. possible as a pot brush.

The grinding tool 82 is changed in the manner previously described with reference to FIGS. 1 to 7.

Claims (12)

1. Portable grinder having a motor-driven drive shaft (15) and a rapid-action clamping device for a grinding tool (18, 82), in which the rapid-action clamping device comprises a spindle (20) which is coaxial to the drive shaft (15) and which is braced, by means of a spring (24), in the axial direction against the drive shaft (15) and can be displaced, by means of a clamping lever (32), in the axial direction relative to the drive shaft (15), an outer free end of the spindle (20) holding in place the grinding tool (18, 82), which, in a release position in which the free end of the spindle (20) is extended and the spring (24) is tensioned, can be removed from the free end, and, in a clamping position in which the free end of the spindle (20) is retracted and the spring (24) is partially relaxed, is in rotationally secure connection with the drive shaft (15), characterized in that the free end is configured as a bayonet end (40) extending through the grinding tool (18, 82), in that a fastening sleeve (41, 81) having a bayonet opening (54, 91) can be placed from outside onto the bayonet end (40), the fastening sleeve (41, 81) partially covering, from outside, the grinding tool (18, 82), in that the bayonet end (40) exhibits a first, outer bayonet segment (60) of larger cross-sectional area and a second, inner bayonet segment (61) of smaller cross-sectional area, in that the cross-sectional form of the first bayonet segment (60) has that of a regular trihedron having respectively three straight (72) and three circular-arc-shaped (70) segments, in that the cross-sectional form of the second bayonet segment (61) comprises three circular-arc-shaped segments (76) having the radius (R₂) of the inner circle of the trihedron and a 60° peripheral angle, three first straight segments (74), which are aligned with the straight segments (72) of the trihedron and take up one-half of their width, and three second straight segments (75), which adjoin the first straight segments (74) at an angle of 120° and have their width, and in that the bayonet opening (54) of the fastening sleeve (41, 81) has a cross-sectional form which conforms essentially to that of the first bayonet segment (60).
2. Grinder according to Claim 1, characterized in that the grinding tool (82) is configured as a brush tool, on which there is provided the fastening sleeve (81) having its bayonet opening (91).
3. Grinder according to Claim 1, characterized in that the grinding tool is of wheel-shaped configuration and comprises a flexible grinding disc (43), which exhibits an inner region (57) having an inner-conical bearing surface (48) for an abrasive paper (42) and in that the fastening sleeve (41) comprises an outer-conical segment (50) for forcing the abrasive paper (42) against the inner-conical bearing surface (48).
4. Grinder according to Claim 1 or 3, characterized in that the axial length (H₁) of the spring (24) amounts to many times, preferably between 3 and 10 times, that of the axial height (H₂) of the inner-conical bearing surface (48).
5. Grinder according to Claim 3 or 4, characterized in that the path of displacement (E) of the spindle (20) between the release position and the clamping position, which path of displacement can be adjusted by means of the clamping lever (32), is at least as great as the axial height (H₂) of the inner-conical bearing surface (48).
6. Grinder according to one of the preceding claims, characterized in that the bayonet end (40) bears against the bayonet opening (54) without any gradient over radial end faces (57, 62).
7. Grinder according to one of the preceding claims, characterized in that the bayonet end (40) at the free end of the spindle (20) is provided with a continuation (64) which, when the bayonet connection is closed, engages positively in an outer opening (59) of the bayonet sleeve (41).
8. Grinder according to one of Claims 2, 6 or 7, characterized in that the grinding tool (82) exhibits bristles (84), which are held between an outer, pot-shaped bristle holder (85) and an inner, pot-shaped bristle holder (86).
9. Grinder according to Claim 8, characterized in that the outer bristle holder (85) is welded to the fastening sleeve (81).
10. Grinder according to Claim 8 or 9, characterized in that there is disposed between the inner bristle holder (86) and the outer bristle holder (85), for the fixing of the bristles (84), a disc wheel (87) in which there are provided at the margin, running in the axial direction, bores (90) through which the individual bristles (84) are guided like loops.
11. Grinder according to one of Claims 8 to 10, characterized in that the bristle holder (85, 86) and the disc wheel (87) are held in place coaxially on a cylindrical carrier element (89).
12. Grinder according to Claim 11, characterized in that the bristle holder (85, 86) and the disc wheel (87) are fixed between a collar (92) and a circumferential marginal beading (88) of the carrier element (89).

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