EP2186600B1 - Surface grinder, especially concrete grinder - Google Patents

Description

The invention relates to a surface grinder, in particular a concrete grinder according to the preamble of claim 1.

In a known generic concrete grinder ( CH 694 756 A5 ) is mounted in a Getriebehals a drive shaft to which a concrete grinding wheel is detachably connected. In addition, the concrete grinder has a funnel-shaped suction hood, which covers the grinding wheel from above and engages over the edge with a protective ring. The suction hood is fastened in the region of a central opening for the gear neck by means of a holding device.

Specifically, the known concrete grinder is designed as a hand-held angle grinder with a motor housing for an electric motor and an attached angle gear, which has the gear neck and the central drive shaft with an end-side threaded pin for mounting and holding the concrete grinding wheel by means of a clamping nut. A suction device can be connected to the suction hood via a suction pipe and the grinding dust is extracted by suction. In addition, the suction hood also has a protective function for a user by retaining abraded grit. The funnel-shaped suction hood consists here in one piece of a funnel neck and a hood bell part formed thereon, wherein the suction hood with the funnel part is fixedly screwed to the gear neck. Commercially available concrete grinding wheels which can be used with the known concrete grinder consist of a plate-shaped, curved base disk with a central connection opening and with through openings for the sanding dust extraction. On the base disk projecting, web-shaped, segment-like grinding elements are attached to the grinding surface as diamond grinding stones. These abrasive elements wear out and wear out over time as the concrete grinder operates, reducing the useful grinding element height.

• Der beim Schleifen auf der Schleiffläche aufliegende Dichtbürstenring bremst die Schleifbewegung, wodurch ungünstig die Kraft für die Handhabung erhöht wird. Zudem wechselt diese Kraft ihre je nach Auflage und Stellung der Bürstenringelemente, so dass für eine Bedienperson der wünschenswerte unmittelbare Kontakt zur Schleiffläche verloren geht. Ebenso wie die Höhe der Schleifelemente im Laufe des Betriebs abnimmt wird auch die Borstenlänge des Dichtbürstenrings durch Verschleiß geringer. Wenn nun eine durch Verschleiß verbrauchte Schleifscheibe durch eine neue ersetzt wird, kann die Borstenlänge des Dichtbürstenrings gegebenenfalls nur noch so lang sein, dass dieser bei noch nicht abgenutzten Schleifelementen nicht mehr auf der Schleiffläche aufliegt, sondern ein relativ großer Spalt zwischen dem Dichtbürstenring und der Schleiffläche besteht, durch den große Mengen von Schleifstaub und abgetragenem Schleifgut in unzulässiger Weise nach außerhalb der Absaughaube gelangen können. Dieser Mangel kann allenfalls nur durch den Ersatz der gesamten Absaughaube mit einem neuen Bürstenring behoben werden.

In the known concrete grinder a sealing brush ring is attached to the open edge of the hopper, which engages over the edge of the grinding wheel and rests on the grinding surface during operation. The sealing brush ring largely prevents sanding dust from the extraction hood during grinding. In addition, the space required for the suction of air from the environment for the extraction of the grinding dust is created between the bristles of the sealing brush ring. However, such a suction hood with a sealing brush ring has the following disadvantages:

• The sealing brush ring resting on the grinding surface during grinding slows down the grinding movement, which unfavorably increases the handling force. In addition, this force changes their depending on the support and position of the brush ring elements, so that is lost to an operator of the desirable direct contact with the grinding surface. Just as the height of the grinding elements decreases during operation, the bristle length of the sealing brush ring is reduced by wear. If a grinding wheel consumed by wear is replaced by a new one, the bristle length of the sealing brush ring may possibly only be so long that it no longer rests on the grinding surface with not yet worn grinding elements, but a relatively large gap between the sealing brush ring and the grinding surface is due to the large amounts of sanding dust and eroded abrasive in an inadmissible manner outside the extraction hood. This deficiency can only be remedied by replacing the entire suction hood with a new brush ring.

Next is a concrete grinder known ( DE 10 2006 041 671 A1 ) with a suction hood, the edge partially, in particular by a hinged lid can be opened so that in the open hood segment a grinding wheel is exposed to its outer edge and thus grinding operations by leading to a corner in this edge region are possible.

The DE 89 14 346 U1 describes a motor driven to a rotational movement tool with a sleeve-shaped, longitudinally adjustable suction hood. The suction hood has at the same time in the longitudinal and circumferential direction extending slots, which are guided on projections formed by screws on a drive unit.

In the DE 103 39 335 A1 a grinding hand tool machine is described with a hollow cylindrical guard. The protective hood is designed in two parts with a substantially flat lid and a jacket. The jacket is axially displaceable and fixed on the lid. However, the protective cover is not used here as a suction hood.

The WO 2008/033377 A2 discloses a grinding tool in which a brush ring assembly is height adjustable attached to a support portion of the tool head.

The object of the invention is to develop a generic concrete grinder so that an effective extraction of sanding dust and sanding material can be ensured regardless of the degree of wear of the grinding elements of the grinding wheel.

This object is achieved with the features of claim 1.

According to claim 1, the holding device for attaching the suction hood on a height adjusting device with which the suction hood is guided in the axial direction of the drive shaft directly or indirectly with respect to the transmission neck, height adjustable and fixable, wherein a funnel neck of the suction hood as the central passage opening comprises the gear neck and there by each assigned interlocking guide elements is guided adjustable in height. According to the invention, a clampable clamping ring surrounds the funnel neck for fixing the respective height adjustment.

Thus, a distance compensation according to the wear of the grinding elements can be performed by a height adjustment of the suction hood. It is thus possible, a minimum distance of about 1 to 3 mm, preferably of about 2 mm, between the free edge of a protective ring of the suction hood, which engages over the concrete grinding wheel edge and adjust a grinding surface, which with increasing wear of the grinding elements or optionally at Replacement by a new grinding wheel is adjustable. The distance of the guard ring edge to the grinding surface is thus on the one hand chosen so large that the required air intake is ensured by the environment for the suction and on the other hand by the relatively small gap gap no grinding dust from the hood penetrates to the outside. If there is too little clearance, especially if the protective ring edge of the suction hood rests on the grinding surface, it will be sucked in impermissibly. On the other hand, grinding dust can penetrate to the outside due to an excessive gap distance. Both states, which require an altitude adjustment of the extraction hood, are readily communicated to the user during operation. Since the abrasive elements wear only gradually or an exchange of grinding wheels is required only at longer intervals, is also a corresponding readjustment The height adjustment of the suction hood can only be carried out at longer intervals.

As can be seen in the inventive arrangement "flexible" and wear compensating elements on the free funnel edge of the suction hood, such as the known brush ring or also known for the same purpose rubber slats completely omitted, so that the associated and explained above disadvantages are no longer present. Optionally, however, such flexible edge formations in connection with the inventive arrangement can be used for special applications, in which case the wear of such flexible edge formations by an inventive height adjustment of the suction hood is avoidable or at least considerably reduced.

In a particularly preferred embodiment according to claim 2, the funnel neck for realizing the height adjustment of the exhaust hood from an inner sleeve which is rotatably supported on Getriebehals and with an engaging nose as a first guide element directly or indirectly in a helically mounted spiral groove on Getriebehals as associated second guide element intervenes. This can be done easily and accurately with a screwing by rotation of the inner sleeve relative to the Getriebehals a continuous height adjustment for distance compensation at a wear of grinding elements. A certain height adjustment can then be fixed with the inner sleeve comprehensive clamping ring. If the engagement nose is formed directly on the inner sleeve, this and / or the inner surface of the inner sleeve for fixing by the clamping ring on the gear neck must be pressed, for which it may be necessary to perform the inner sleeve partially slotted.

In a modified embodiment according to claim 3, the engagement nose is designed as a radially inwardly facing clamping lug on the clamping ring. In this case, this clamping lug engages through an associated slot-shaped recess of the inner sleeve into the spiral groove on the gear neck. The engagement nose can thus act in a further function when contracting the clamping ring as a clamping nose, which exerts a clamping fit at the bottom of the spiral groove.

If the inner sleeve is formed as part of the height adjustment with the screw mechanism of engaging nose and spiral groove integral with the downwardly adjacent hood bell part, this twists with a Schraubverdrehung the inner sleeve and thus possibly also connected to this hood part suction tube, which then in the different rotational positions the inner sleeve or the associated height settings projecting in different angular positions on the concrete grinder. This can interfere with handling. In order now to give the hood bell part and an attached suction pipe a non-rotatable position on the concrete grinder, it is proposed with claim 4 to form the suction hood in several parts, such that the inner sleeve is rotatably received as funnel neck in the central passage opening of a subsequent hood bell part of the suction hood. The passage opening edge of the hood bell part is held between a lower radially projecting support flange of the inner sleeve and an upwardly spaced spring ring, preferably a snap ring on the inner sleeve, whereby a simple running pivot bearing between the inner sleeve and the hood bell part is formed. Preferably, between the spring ring and the passage opening edge of the hood bell part, a protective disk is used to improve the ease of pivoting and as protection against scratching. In addition, the hood bell part and / or an adjoining suction tube has an upwardly projecting extension as Torque pick-up, which engages in a height-displaceable in a respect to the transmission neck fixed torque support. As a result, with a screw rotation of the inner sleeve and thus carried out height adjustment of the suction hood the hood bell part and optionally connected thereto a suction tube is held non-rotatably on the concrete grinder. Likewise, forces are supported on the suction tube by a connected suction hose. In this construction, the clamping ring is arranged above the snap ring.

A height adjustment is easy to carry out when the inner sleeve is rotatable together with the clamping ring, in particular when the engagement nose is formed as a clamping lug on the clamping ring and engages through the slot-shaped recess of the inner sleeve into the spiral groove. For this purpose, it is proposed with claim 5 that at least one radially inwardly directed driving lug is attached to the clamping ring, which engages in an associated driving opening on the inner sleeve. In a suitable concrete embodiment, a respective driver nose can be attached to the dividing edge of the clamping ring as a vertical web and the driver opening is designed as an associated vertical slot in the inner sleeve.

To set the clamping ring appropriate in its axial position on the inner sleeve, a horizontally encircling engagement groove is formed according to claim 6 on the outer side of the inner sleeve into which engages the clamping ring with a correspondingly associated inner web.

According to claim 7, the clamping ring may be designed in the manner of a clamp, wherein in each case at the dividing edge region, a radially projecting clamping block is attached. By means of these clamping blocks, a tangential clamping screw which can be manually operated via a knurling wheel is guided. Instead of a clamping screw could also be a known tension lock be provided. Advantageously, so that the entire height adjustment and wear tracking, both the Schraubverdrehung the inner sleeve with the clamping ring and the fixation of the clamping ring, without tools and quickly carried out by hand.

In principle, the above height adjustment of the suction hood for wear compensation of the grinding elements can be used in different constructed concrete grinders. This technique is particularly well suited according to claim 8 for a concrete grinder in the form of a hand-held angle grinder, in particular a concrete floor grinder with a tubular, usable as a handle motor housing for an electric motor and an angle gear connected to the Getriebehals. In Getriebehals the central drive shaft is housed in pivot bearings with an end-side threaded pin for attaching the concrete grinding wheel and for mounting by means of a clamping screw.

With claim 9, a suction pipe with the suction hood, in particular with a hood bell part connected so that it extends with a hand engagement distance below and parallel to the motor housing and expedient for ergonomic handling about the length of the motor housing. A torque support for the non-rotatable hood bell part or the suction tube is executed in a structurally suitable design as a housing-fixed, from the motor housing downwardly facing and transversely extending U-support bracket with an insertion for integrally formed on the hood bell part or the suction torque transducer.

In a simple to manufacture and easy to clean design, the suction tube is formed in two parts, wherein a lower shell is integrally formed on the suction hood, in particular on the hood bell part. The upper shell is as a separately manufactured component on the lower shell put on and attached, in particular clipped. For a Ansaugschlauchanschluss while end of the suction tube a connection-clamping ring is provided.

In a further development according to claim 11 is provided as a further handle in addition to the motor housing a transversely extending bow handle, which is arranged above the angle gear about a transverse axis pivotable and fixable so that the handle portion is in a forward pivoted position on a front angular segment of the hood and is pivoted in a zurückgeschwenkten position from this area to the rear and lies approximately above the angle gear. With this bow handle part a good leadership of the concrete grinder is possible and it can be applied ergonomically a large pressure force on the grinding wheel when needed, with the other hand on the motor housing also a guide of the concrete grinder takes place.

Suitably, the bow handle is U-shaped and open on one side with a longer U-leg as a handle part, wherein the shorter U-leg is selectively connected to the left or right of the engine or transmission housing pivotable and lockable. This provides an ergonomically favorable grip shape for both left-handed and right-handed users.

In order to be able to carry out sanding work, in particular in floor corners to adjacent side walls, it is necessary to grind with the grinding wheel edge into such corners. For this purpose, it is provided according to claim 13 that a forwardly facing hood segment part of the suction hood, in particular a hood bell part for releasing an underlying grinding wheel segment is designed to be pivotable in a horizontal plane.

For this purpose, it is proposed for a specific construction with claim 14 that the hood segment part with a hood segment ring part, the inner sleeve pivotally surrounds. In the closed position, the hood segment part covers a segment free space of the suction hood from above and in the open position, the hood segment part is pivoted out of the region of the Segementfreiraums, so that this, and thus a rotating in Segementfreirarum grinding wheel edge area are released. The hood segment part is thus held captive on the suction hood or the inner sleeve and can be pivoted without tools in its respective functional position. Advantageously, the hood segment part is then held in both the closed position and in the open position by überdrückbare latching connections.

A training example of the invention will be explained in more detail with reference to a drawing.

Fig. 1

eine perspektivische Ansicht eines Betonschleifers mit einem geschlossenen Haubensegmentteil;

Fig. 2

den Betonschleifer nach Fig. 1 mit offenem Haubensegmentteil;

Fig. 3

eine Seitenansicht des Betonschleifers mit offenem Haubenseg- mentteil und nach oben geschwenktem Griffteil;

Fig. 4

eine Ansicht von unten auf eine Schleifscheibe und eine Absaughaube bei geschlossenem Haubensegmentteil;

Fig. 5

eine Ansicht entsprechend Fig. 4 mit geöffnetem Haubenseg- mentteil;

Fig. 6

einen Vertikalschnitt durch die Längsmitte des Betonschleifers;

Fig. 7

einen vergrößerten Ausschnitt aus Fig. 6 im Bereich der Absaughaube;

Fig.8

eine Ansicht von vorne auf den Betonschleifer und die abgenommene Absaughaube;

Fig. 9

eine perspektivische Ansicht einer Innenhülse mit Schutzring und eines Klemmrings;

Fig. 10

eine perspektivische vergrößerte Ansicht der Absaughaube im Bereich des montierten Klemmrings;

Fig. 11

eine perspektivische Ansicht im Bereich eines Drehmoment- aufnehmers in dessen unterer Stellung; und

Fig. 12

eine Ansicht entsprechend Fig. 11 mit dem Drehmoment- aufnehmer in der oberen Stellung.

Show it:

Fig. 1

a perspective view of a concrete grinder with a closed hood segment part;

Fig. 2

after the concrete grinder Fig. 1 with open hood segment part;

Fig. 3

a side view of the concrete grinder with open hood segment part and upwardly pivoted handle part;

Fig. 4

a view from below of a grinding wheel and a suction hood with hood part closed;

Fig. 5

a view accordingly Fig. 4 with open hood segment part;

Fig. 6

a vertical section through the longitudinal center of the concrete grinder;

Fig. 7

an enlarged section Fig. 6 in the area of the extraction hood;

Figure 8

a view from the front of the concrete grinder and the removed suction hood;

Fig. 9

a perspective view of an inner sleeve with guard ring and a clamping ring;

Fig. 10

a perspective enlarged view of the suction hood in the region of the mounted clamping ring;

Fig. 11

a perspective view in the region of a torque sensor in its lower position; and

Fig. 12

a view accordingly Fig. 11 with the torque transducer in the upper position.

In the Fig. 1 to 3 views of the complete concrete grinder 1 are shown, which is designed as a hand-held angle grinder, in particular for concrete floor grinding work with a tubular, usable as a handle motor housing 2, in which an electric motor is received, which can be switched on and off with a switch 3.

To the front of the motor housing (2) is followed by an angle gear 4 with a gear neck 5, in which a drive shaft 6 projects with an end-side gear pin 7 down to which a grinding wheel 8 is attachable and is held with a (not shown) clamping nut ( see Fig. 6 and 7 ).

At the gear neck 5 a funnel-shaped suction hood 9 is fixed in the region of a central passage opening for the transmission neck 5, wherein the holding device has a height adjustment device 10, which will be described in detail below.

The suction hood 9 is designed in several parts and consists in particular of an inner sleeve 11, which comprises a clamping ring 12 and a hood bell part 13. The inner sleeve 11 is rotatably mounted in the hood bell part 13, wherein the hood bell part 13, the grinding wheel 8 engages over the edge with a guard ring 14.

The cowl bell part 13 has a forwardly directed portion as a segment clearance 15, which can be covered by a forwardly facing hood segment part 16. For this purpose, the hood segment part 16 is pivotably held by a hood segment ring part 17 on the inner sleeve 11. In the closed position of the hood segment part 16 (FIG. Fig. 1 ), the segmental space 15 is covered and the suction hood 9 is closed as a whole. In the position of the hood segment part 16 pivoted into the open position, the area of the segment free space 15 is released ( Fig. 2 ), so that there protrudes a portion 18 of the rotating grinding wheel 8, for example, for grinding work on the ground in a corner region to a side wall. By überdrückbare latching connection elements 19, the hood segment part 16 is set and held in two functional positions. The functional positions of the hood segment part 16 on the suction hood 9 are also clear from the Fig. 4 and 5 can be seen, which show a view from below of the suction hood 9 with mounted grinding wheel 8. The grinding wheel 8 is fitted with a central opening on the threaded pin 7 of the drive shaft 6 and held with a clamping nut 20. The grinding wheel 8 consists of a convex towards the center (see Fig. 6 ) Projecting base disk part 29 of the edge side and at a center offset circle segment-like grinding elements 22 in the manner of diamond grinding stones to the concrete grinding plane out with a certain grinding element height. In addition, 8 offset flow openings 23 are arranged for the extraction of sanding dust in the grinding wheel.

In Fig. 4 the hood segment part 16 is closed and in Fig. 5 to open the segment free space 15 shown open.

At the suction hood 9 and the hood bell part 13, a suction pipe 24 is connected, which extends below and parallel to the motor housing 2. The suction tube 24 is formed in two parts, wherein a lower shell 25 is integrally formed on the hood bell part 13 and a separate upper shell 26 is clipped onto the lower shell 25. For the connection of a suction hose (not shown), a connection clamping ring 27 is provided at the end of the suction pipe 24, which also holds the upper shell 26 and lower shell 25 of the suction pipe 24 together.

Transverse to the motor housing 2 extends a U-shaped bow handle 28 having a longer U-leg as a handle portion 29, wherein the shorter U-leg 30 is either left or right on the motor housing 2 or slightly offset to the front of the transmission housing pivotally connected and lockable.

In the Fig. 1 and 2 the handle member 29 is pivoted forward in a working position, which is particularly suitable for grinding work with a closed hood segment part 16. When working with open hood segment part 16, however, the handle member 29 can be pivoted upward, as in Fig. 3 shown, so that a hand on the handle 29 in a corner area does not abut against a side wall.

• Auf dem Getriebehals 5 ist die Innenhülse 11 verdrehbar aufgesteckt. Die Innenhülse 11 weist an der unteren Endseite einen radial abstehenden Stützflansch 31 auf, wobei das Haubenglockenteil 13 dort von oben her mit einem Durchtrittsöffnungsrand 32 einer Durchtrittsöffnung abgestützt und gehalten ist. Weiter nach oben schließt sich daran das Haubensegmentringteil 17 an, mit dem das Haubensegmentteil 16 schwenkbar gelagert ist. Anschließend ist eine Schutzscheibe 33 eingelegt und diese übereinanderliegenden Wandlagen werden durch einen darüber angebrachten Seegerring 34 axial gehalten.

Based on 6 to 12 In the following, the height adjusting device 10 for the suction hood 9 and the hood bell part 13 with respect to the gear sleeve 5 for a distance adjustment at a height reduction by wear and tear of the grinding elements 22 is explained in:

• On the Getriebehals 5, the inner sleeve 11 is slidably mounted. The inner sleeve 11 has at the lower end side a radially projecting support flange 31, wherein the hood bell part 13 is supported and held there from above with a passage opening edge 32 of a passage opening. Farther upward, the hood segment ring part 17 connects to it, with which the hood segment part 16 is pivotally mounted. Subsequently, a protective plate 33 is inserted and these superimposed wall layers are held axially by an overlying Seeger ring 34.

About the snap ring 34 of the clamping ring 12 is mounted, each having a driving lug 35, 36 at the dividing edge, which engage in a vertical slot 37 of the inner sleeve 11, so that the inner sleeve 11 and the clamping ring 2 are rotatable together. In the area of the driving lugs 35, 36, radially protruding clamping blocks 38, 39 are formed on the clamping ring 12, through which a clamping screw 41 which can be manually operated via a knurled wheel 40 is guided. In addition, for an axial relative fixing between the clamping ring 12 and the inner sleeve 11, on the outside of a horizontally encircling engagement groove 42 is mounted, in which engages an integrally formed on the clamping ring 12 inner web 43.

On the clamping ring 12, a radially inwardly projecting clamping nose 44 is formed, which engages through an associated slot-shaped recess 45 of the inner sleeve into a spiral groove 46 on the gear neck 5. The clamping nose 44 and the slot-shaped recess 45 are also inclined according to the inclination of the spiral groove 46.

At the hood bell part 13, an upwardly projecting extension is formed as Drehmomentaufnehmer 47 in the region of the connection point of the suction tube 24, which is height-displaceably held in an insertion 48 of a housing-fixed, from the motor housing 2 facing downwards and transversely extending U-support bracket 49.

• Bei einer Verdrehung der Innenhülse 11 zusammen mit dem Klemmring 12 am Getriebehals 5 erfolgt durch den Eingriff der Klemmnase 44 in die Spiralnut 46 eine Höhenverstellung der Absaughaube 9 bzw. des Haubenglockenteils 13 mit dem Schutzring 14 bezüglich des Getriebehalses 5 und damit auch bezüglich der Schleifelemente 22 der Betonschleifscheibe 8. Damit kann der untere Schutzringrand des Haubenglockenteils 13 so positioniert werden, dass gegenüber dem Schutzringrand die Schleifelemente um etwa 2 mm nach unten vorstehen und damit ein entsprechend großer Spalt zwischen der Schleiffläche und dem Schutzring 14 des Haubenglockenteils 13 geschaffen ist, der einerseits eine ausreichende Luftansaugung erlaubt und andererseits keinen Schleifstaub austreten lässt. Durch die einfache werkzeuglose Höhenverstellung ist eine einfache und schnelle Anpassung an eine Abnutzung der Schleifelemente möglich. Die jeweilige Höheneinstellung kann mit dem Klemmring 12 einfach und schnell fixiert werden.
• Durch die schwenkbare Lagerung der Innenhülse 11 an der zentralen Durchtrittsöffnung des Haubenglockenteils 13 in Verbindung mit dem Drehmomentaufnehmer 47 und dem U-Stützbügel 49 ist sichergestellt, dass zwar die relative Höhenlage des Ansaugrohrs 24 und des Haubensegmentteils 16 gegenüber dem Getriebehals 5 verstellt wird, jedoch die Lage des Absaugrohrs 24 parallel unter dem Motorgehäuse 2 und die nach vorne gerichtete Lage des Segmentfreiraums 15 zusammen mit dem Haubensegmentteil 16 erhalten bleibt.

The height adjustment device 10 has the following function:

• In a rotation of the inner sleeve 11 together with the clamping ring 12 on the gear neck 5 is carried out by the engagement of the clamping lug 44 in the spiral groove 46, a height adjustment of the suction hood 9 and the hood bell part 13 with the guard ring 14 with respect to the Getriebehalses 5 and thus also with respect to the grinding elements 22nd Thus, the lower guard ring edge of the hood bell part 13 can be positioned so that opposite the guard ring edge, the grinding elements project downwards by about 2 mm and thus a correspondingly large gap is created between the grinding surface and the guard ring 14 of the hood bell part 13, on the one hand allows sufficient air intake and on the other hand, no sanding dust leak. Due to the simple tool-free height adjustment, a simple and quick adaptation to wear of the grinding elements is possible. The respective height adjustment can be easily and quickly fixed with the clamping ring 12.
• Due to the pivotal mounting of the inner sleeve 11 at the central passage opening of the hood member 13 in conjunction with the torque transducer 47 and the U-support bracket 49 ensures that although the relative height of the intake pipe 24 and the hood segment part 16 is adjusted relative to the transmission neck 5, however Position of the suction tube 24 is maintained parallel under the motor housing 2 and the forward position of the segmental clearance 15 together with the hood segment part 16.

In Fig. 11 the suction hood 9 and thus also the torque transducer 47 is shown in the insertion opening 48 of the U-support bracket 49 in the lowermost position in which the guard ring 14, the grinding elements 22 of the grinding wheel 8 are covered. In Fig. 12 on the other hand, the suction hood 9 and thus the torque sensor 47 is shown in the uppermost setting position, in which, in the case of a grinding wheel with new or slightly worn grinding elements 22, they protrude below the guard ring 14. Due to the easy-to-use height adjustment device 10, the above-explained gap setting of about 2 mm can be set and fixed for optimum grinding dust extraction between these two extreme positions.

Claims (14)

1. Surface grinder, especially concrete grinder,
   with a drive shaft (6) positioned in a gearbox extension (5), on which drive shaft a concrete grinding wheel (8) is detachably attached, and
   with a funnel-shaped suction hood (9), which covers the concrete grinding wheel (8) and overlaps on the edge side with a protective ring (14), whereby the suction hood (9) is attached in the region of a central through-passage aperture for the gearbox extension (5) by means of a holding device,
   whereby the holding device comprises a height adjustment device (10), with which the suction hood (9) is height adjustable and can be fixed in the axial direction of the drive shaft (6) directly or indirectly, with regard to the gearbox extension (5),
   whereby a funnel neck of the suction hood (9) includes the gearbox extension (5) as a through-passage aperture, and is guided there in a height-adjustable manner by respective assigned guiding elements (44, 46) engaging in one another,
   characterised in that,
   a clamping ring (12), which can be clamped together, surrounds the funnel neck in order to fix the height adjustment.
2. Surface grinder according to claim 1, characterised in that for execution of the height adjustment (10), the funnel neck of the suction hood (9) consists of an inner sleeve (11), which is rotatably supported on the gearbox extension (5), and which, with an engaging protrusion (44) as a guiding element, engages directly or indirectly in a helically installed helical groove (46) as an associated second guiding element on the gearbox extension (5), in such a way that a rotation of the inner sleeve (11) causes a height adjustment with regard to the gearbox extension (5), which can be fixed by the clamping ring (12) including the inner sleeve (11).
3. Surface grinder according to claim 2, characterised in that the engaging protrusion is designed as a clamping nose directed radially inwards on the clamping ring, which engages in the helical groove on the funnel neck by means of an associated slit-shaped recess of the inner sleeve, whereby the clamping ring is installed above a snap ring.
4. Surface grinder according to claim 2 or 3, characterised in that the inner sleeve (11) is rotatably accommodated as a funnel neck in the central through-passage aperture of a connected hood bell part (13) of the suction hood (9), whereby the through-passage aperture edge of the hood bell part (13) is maintained between a lower radially protruding support flange (31) of the inner sleeve (11) and a spring ring (34) in the form of a snap ring, spaced apart upwards, on the inner sleeve (11), preferably with a protective screen (33) lying between, and that the hood bell part (13) and/or a suction pipe (24) comprises an upwardly projecting protrusion as a torque transducer (47), which engages in a height-adjustable manner in a torque support (48, 49), which is fixed in position with regard to the gearbox extension (5), so that in a screw rotation of the inner sleeve (11) and height adjustment of the suction hood (9), the hood bell part (13), and the suction pipe (24) if necessary, is non-rotatably held.
5. Surface grinder according to claim 3 or 4, characterised in that on the clamping ring (12), at least one driving lug (35, 36), which is directed radially inwards, is arranged, which engages in an associated lug opening (37) on the inner sleeve (11), whereby each driving lug (35, 36) is arranged on the separation edge of the clamping ring (12) as a vertical web, and the lug opening (37) is an associated vertical slit in the inner sleeve (11).
6. Surface grinder according to claim 5, characterised in that a horizontally running engaging groove (42) is arranged on the outer side of the inner sleeve (11), and that a correspondingly assigned internal web (43) is formed on the clamping ring (12).
7. Surface grinder according to any one of claims 1 to 6, characterised in that a radially projecting clamping block (38, 39) is arranged on the separation edge region of the clamping ring (12) in each case, and that a tangential clamping screw (41), which is manually operated by a thumb wheel (40), is guided through the clamping blocks (38, 39).
8. Surface grinder according to any one of claims 1 to 7, characterised in that the concrete grinder is designed as a hand-held angle grinder, particularly as a concrete grinding wheel, with a tubular motor casing (2), used as a grip for an electric motor, and with an angular gear (4) attached thereto, which comprises the gearbox extension (5) and the central drive shaft (6) with an end-sided threaded pin (7) for attaching the concrete grinding wheel (8) and for mounting by means of a clamping nut (20).
9. Surface grinder according to claim 8, characterised in that a suction pipe (24) is connected to the suction hood (9), particularly to a hood bell part (13), which runs at a distance for manual intervention below and parallel to the motor casing (2), whereby, if necessary, a torque support is applied as a U-support brace (49), which is fixed on the casing, directed downwards from the motor housing (2) and running transversely, with an axial plug-in opening (48) for the torque transducer (47).
10. Surface grinder according to claim 9, characterised in that the suction pipe (24) is formed in two parts, whereby a lower shell (25) is formed in one piece on the suction hood (9), particularly on a hood bell part (13), and an upper shell (26) is attached, particularly clipped, as a separately manufactured component, whereby a connection clamping ring (27) is preferably provided for a suction hose connection on the end on the suction pipe.
11. Surface grinder according to any one of claims 8 to 10, characterised in that as a further handle in addition to the motor casing (2), a transversely running bow-type handle (28) is provided, which is arranged above the angular gear, pivotable about a transverse axis, and which can be fixed in such a way that the handle (29), when it is in a position pivoted forwards, lies above a front angular segment of the suction hood (9), and when it is in the position which has been pivoted back, is pivoted backwards from this region, and lies approximately over the angular gear (4).
12. Surface grinder according to claim 11, characterised in that the bow-type handle (28) is designed in a U-shape with a longer U-shoulder as a handle (29), whereby the shorter U-shoulder (30) is connected to the motor casing or gear casing (2) optionally on the left or right side in such a way that it is pivotable and lockable.
13. Surface grinder according to any one of claims 1 to 12, characterised in that the hood segmental part (16) of the suction hood (9), particularly of a hood bell part (13), is implemented for releasing an underlying grinding wheel segment in a loss-secure, pivotable manner.
14. Surface grinder according to claim 13, characterised in that the hood segmental part (16) pivotably surrounds the inner sleeve (11) with a hood segmental ring part (17), and in the closed position, covers a segment free space of the suction hood (9) from above, and that in the open position, the hood segmental part (17) is pivoted from the region of the segment free space (15), whereby the hood segmental part is held in the closed position and is held in the open position by locking connections (19), which can be pressed over.

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