Arrangement for fastening a cutting head; portable work appliance having an arrangement for fastening a cutting head

An arrangement includes an output shaft, a cutting head, at least one cutting tool arranged on the cutting head, and a hood. The cutting head is mounted on the output shaft by a screw element held in a rotationally fixed manner on the cutting head. The hood is held on the output shaft in a rotationally fixed manner, and has ribs in the inner region, and a first grip region in the outer region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of EP 18 169 970.3, filed Apr. 27, 2018, the priority of this application is hereby claimed and these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to an arrangement for fastening a cutting head on an output shaft. Further, the invention relates to a portable work appliance having an arrangement for fastening a cutting head.

Brushcutters are known, arranged on the output shaft of which is a cutting head having a cutting tool. The cutting head is mounted on the output shaft by means of a press-fit connection. A disadvantage of such brushcutters is that it is difficult for end users themselves to change the cutting head of the brushcutter. To demount and mount the cutting head, the end user needs a special tool in order to undo the press-fit connection, and then to mount the new cutting head on the output shaft again by means of a press-fit connection. Alternatively, the end user can bring the brushcutter into a corresponding specialist workshop that undertakes changing of the cutting head.

SUMMARY OF THE INVENTION

The invention is based on the object of creating an arrangement for fastening a cutting head to an output shaft of a motor-driven work appliance, that enables the cutting head to be mounted on, and demounted from, the work appliance in a simple and rapid manner without the use of tools.

This invention is furthermore based on the object of creating a portable work appliance having an arrangement for fastening a cutting head to an output shaft of a motor-driven work appliance, that enables the cutting head to be mounted on, and demounted from, the work appliance in a simple and rapid manner without the use of tools.

It is provided that the arrangement for fastening a cutting head to an output shaft of the motor-driven work appliance comprises an output shaft, a cutting head and at least one cutting tool arranged on the cutting head. The cutting head is mounted on the output shaft by means of a screw element held in a rotationally fixed manner on the cutting head, and in particular held on the output shaft by frictional force. For the purpose of mounting, the cutting head, together with the screw element inserted in a rotationally fixed manner therein, is rotated, in a mounting direction of rotation, onto the output shaft. The arrangement additionally comprises a hood. The hood is divided in the radial direction starting from the rotation axis, into an inner region and an outer region that adjoins the inner region. Accordingly, the distance of the outer region from the rotation axis is greater than the distance of the inner region from the rotation axis. A width of the inner region, measured radially in relation to the rotation axis, corresponds to at least 3 times a width of the outer region, measured radially in relation to the rotation axis. The hood is held against rotation preferably by positive engagement, preferably by frictional force, in particularly adhesive-bonded, preferably pressed, on the output shaft. The hood may also be held directly on the output shaft in a rotationally fixed manner by means of other types of fastening. The hood has ribs in the inner region, and a first grip surface in the outer region.

To demount the cutting head, the cutting head must be unscrewed from the output shaft. In order that the output shaft does not rotate concomitantly, and thus prevent the cutting head from being released, the output shaft must be held fast. Access to the output shaft, however, is blocked by the cutting head, the hood or also by the front housing of the work appliance, such that the output shaft cannot be held fast directly. The hood is carried on the output shaft. The hood is held by positive engagement against rotation on the output shaft. In addition, a relative rotation between the hood and the cutting head is possible. Thus, the output shaft can be indirectly held fast against rotation via the hood while the cutting head is being released from the output shaft.

In addition, there is a first grip surface provided on the housing. The first grip surface is arranged in the outer region of the housing, and is thus easily accessible. The housing preferably has an inner side that faces toward the cutting head, and an outer side that faces away from the cutting head. The first grip surface is preferably realized in the outer region, on the outer side of the hood. To demount or mount the cutting head, the operator must hold the hood fast with one hand at the first grip surface, and with the other hand twist the cutting head from the output shaft. The operator can thereby release the cutting head by hand, or fasten it to the output shaft, without requiring a tool for this purpose. Mounting and demounting of the output shaft are effected without the use of tools.

The ribs on the hood increase the stiffness of the hood, such that the holding force exerted by the operator, starting from the first grip surface, can also be transmitted, via the ribs, to the output shaft. In addition, deformation of the hood while it is being held fast can substantially be avoided.

The hood is preferably realized as a pot shape. The hood preferably has an inner side, the inner side delimiting an interior space. Advantageously, the cutting head is accommodated, at least partly, in the interior space. Owing to the pot-shaped design of the hood, it is delimited along its circumference and in its axial direction. The contour delimiting the hood may have a rectilinear and/or curved course. There may also be discontinuities in the course of the contour. The inner region and the outer region of the hood advantageously meet at the radial delimitation of the interior space.

The hood comprises a hood base that extends in the radial direction from the rotation axis, and a hood wall that adjoins the hood base. The outer region advantageously corresponds to the hood wall. The hood wall extends substantially in the direction of the rotation axis. However, the outer diameter of the hood wall may vary along the rotation axis. Accordingly, the hood wall is not fixed to a cylindrical contour, but may also have, in particular, a curved course. The hood wall is of a thickness that corresponds to the distance, measured in the radial direction in relation to the rotation axis, between the outer side and the inner side of the hood. The thickness of the hood wall is, in particular, less than 5% of the maximum diameter of the hood. Accordingly, the hood has a small wall thickness in relation to its extent. The hood may have a greater thickness directly adjacent to the output shaft. Owing to the pot-shaped design of the hood, the cutting head can be arranged, at least partly, in the hood. As a result, the cutting head is partly enveloped by the hood. Advantageously, the inner side of the hood forms a counter-contour to the outer side of the cutting head, such that the hood closely surrounds the cutting head.

The ribs are preferably realized only on the outer side of the hood. As a result, the cutting head can be positioned doser to the hood base, and a more compact arrangement of the hood and cutting head is made possible.

Preferably, on its inner side the hood has a bearing contact surface, via which the hood is tensioned on the output shaft. The cutting head is preferably tensioned with full surface contact against the bearing contact surface of the hood. The hood is thereby tensioned and fastened on the output shaft, in the axial direction of the rotation axis, by the cutting head. Advantageously, the bearing contact surface is realized on the inner side of the hood base, in the inner region of the hood. The hood has a length, measured in the direction of the rotation axis, the bearing contact surface preferably being arranged approximately at half of the length of the hood. In particular, owing to the bearing contact surface being realized close to the output shaft, a short, direct flow of force is ensured between the output shaft, cutting head and hood. The closed flow of force runs, starting from the output shaft, via the screw element, into the cutting head, via the contact bearing surface to the hood, via a support bearing and via a shaft shoulder back again into the output shaft.

When the cutting head is in the mounted state, the hood and the cutting head are tensioned to each other, in the direction of the rotation axis, via the bearing contact surface. Accordingly, the hood and the cutting head are connected to each other only by frictional force in the circumferential direction. Upon release of the cutting head, the hood and the cutting head can rotate relative to each other in the circumferential direction, in relation to the rotation axis. Thus, when the hood is held fast, the cutting head can be released from the output shaft and tensioned on it.

The inner side of the hood and the cutting head, in particular the outer side of the cutting head, contact each other in a sealing manner, preferably in a sealing surface. The sealing surface is preferably at a distance from the rotation axis that corresponds to at least one quarter of the outer diameter of the hood. Owing to the sealing surface between the hood and the cutting head, the ingress of dirt, between the cutting head and the hood, during operation of the work appliance is avoided. As a result, in particular the bearing contact surface for tensioning the hood and the cutting head remains free of dirt, such that a reliable transmission of tensioning forces can be ensured.

The hood is preferably realized as a fan wheel. The fan wheel may be used to cool the motor of the work appliance. The hood may advantageously also be used as a blower fan for generating an airflow against accretion of dirt on the front housing. Thus, air is blown out by the blower wheel between the front housing and the cutting head, and ingress of dirt into the transmission interior is avoided. The grasses that are swirled upward, for example, in the case of a brushcutter are blown radially outward by the airflow of the blower wheel even before they reach the front housing. Preferably, two defined locations are provided at which the air blows from the blower wheel in the direction of a guard. The guard is a constituent part of the front housing. As a result, the front housing remains free of dirt accretion.

It Is advantageously provided that the hood comprises a hub that is arranged in a rotationally fixed manner on the hood, the hub producing a positive-engagement connection between the hood and the output shaft. As a result of the hub being realized separately, it can be made of a material different from that of the hood, in particular of a material having a greater strength and lesser wear, in particular a metal alloy. As a result, comparatively high driving torques can be transmitted from the output shaft to the hood, without damaging the hood. The hood itself, in turn, may be composed of a less strong, but therefore lighter, material, to save weight. The hood is arranged in a rotationally fixed manner on the hub, and the hub is connected by positive engagement to the output shaft. Via the hub, therefore, the output shaft can be held fast in the circumferential direction of the rotation axis by means of the hood.

The first grip surface of the hood preferably overlaps the cutting head in the direction of the rotation axis. Preferably, the first grip surface overlaps the cutting head in the direction of the rotation axis in its entire length, measured in the direction of the rotation axis. The first grip surface of the hood is therefore rendered more accessible to the operator. The operator can achieve a better grip on the hood, and can more easily manually apply the counter-torque, necessary for releasing or chucking the cutting head, to the hood. Since the available structural height of the cutting head is used to provide the grip surface, the structural height is not increased, or is increased only slightly, because of the grip surface. Since the grip surface covers the cutting head axially, the grip surface is then also freely accessible when the cutting head and the front housing directly adjoin each other in the axial direction.

The hood preferably, along the first grip surface, has clearance in relation to the cutting head, in the radial direction starting from the rotation axis. When the hood is being held at the first grip surface, and possibly even when the first grip surface is being slightly pressed-in in the direction of the cutting head, the clearance avoids the cutting head being contacted by the hood. Contact between the hood, at the first grip surface, and the cutting head would result in the cutting head also being held fast by the hood. The mutual rotation of the hood and cutting head would thus be rendered more difficult. Owing to the clearance between the hood and the cutting head, it can be ensured that the hood, at the first grip surface, and the cutting head do not mutually obstruct each other during mounting or demounting.

The first grip surface of the hood and a second grip surface, which is realized on the cutting head, are preferably freely accessible. Accordingly, the operator, when mounting or demounting the cutting head, can easily hold the cutting head fast with one hand at the second grip surface, and with the other hand hold the hood fast at the first grip surface, and rotate them against each other. Owing to the ease of accessibility, with the hood being held fast the cutting head can be unscrewed and demounted from the output shaft by hand, without the use of further tools.

The portable work appliance comprises the arrangement according to the invention and a front housing. It is provided that the hood projects, with its outer region, advantageously completely, out of the front housing. It is thereby ensured that the grip surface located in the outer region is freely accessible, and is not covered by the front housing. Consequently, the operator can manually grip the hood. Advantageously, the ribs arranged in the inner region overlap axially with the front housing. Advantageously, the front housing projects over the ribs of the hood in the direction of the rotation axis, in particular completely. The gap between the front housing and the hood is thereby reduced. The transmission interior space is protected against accretion of dirt. In addition, due to the overlapping of the ribs, the fan power, and consequently the cooling power, is increased.

Advantageously, both the grip surface and the ribs are arranged on the outer side of the hood, such that the cutting head can bear against the inner side of the hood.

DETAILED DESCRIPTION OF THE INVENTION

Shown schematically inFIG. 1is a portable work appliance, which in the exemplary embodiment is embodied as a brushcutter. Other embodiments of the portable work appliance27may also be expedient. The portable work appliance27is held by an operator. The work appliance27has a rear end, having a rear housing28, and a front end, having a front housing2, from which an output shaft5projects. A stem29connects the rear end and front end. Arranged on the stem29are handles33for guiding the work appliance26. Adjoining the front end of the work appliance26is a cutting head3. The cutting head3is fastened to the output shaft5, and is driven in rotation about a rotation axis6by a drive motor, not shown. The drive motor is, in particular, an electric motor, which is arranged in the front housing2. Advantageously, there is also a transmission in the front housing2. However, an arrangement in which the drive motor is arranged in the rear housing28, and a drive shaft5extends in the stem29, may also be expedient. It may also be provided that the drive shaft transitions into the output shaft5, and accordingly there is no intermediately connected transmission. On the side that, during operation, faces toward the operator, the cutting head3is covered by a protective hood30. The cutting head3has at least one cutting tool4, which serves to cut clippings such as grass, undergrowth or the like. Realized on the cutting head3is an underside32, which during operation faces toward the ground31and which is arranged on the side of the cutting head3that faces away from the stem29. The protective clothing that must necessarily be worn by the operator for operating a work appliance27is not shown in the simplified representation ofFIG. 1.

Shown inFIG. 2is an exploded representation of a first exemplary embodiment of the arrangement according to the invention. The arrangement1for fastening a cutting head to an output shaft of a work appliance comprises an output shaft5, a hood7, having a hub12, and a cutting head3.

As shown inFIG. 2, the output shaft5has a dihedron35. When the arrangement1is in the mounted state, the hub12of the hood7is pushed onto the output shaft5and, by means of the dihedron35, is held with positive engagement, against rotation about the rotation axis6, on the output shaft5. Other connections, between the hub12and the output shaft5, that result in a rotationally fixed connection between the hub7and the output shaft5may also be expedient. The connection may also expediently be realized as a frictional or materially bonded connection. Examples for a corresponding connection are adhesive bonding, press-fit, parallel-key connection, connection by means of set screw. However, the rotationally fixed connection between the output shaft5and the hood7must always be configured so as to be independent of the connection of the cutting head3to the output shaft5. In particular, no application of force such as, for example, a squeezing or pressing action, on the cutting head3is required for connecting the output shaft5and the hood7in a rotationally fixed manner. In the exemplary embodiment, it is sufficient that the hood is positioned, in the direction of the rotation axis6, in a region of the output shaft5in which there is positive engagement between the output shaft5and the hood7. A rotationally fixed connection of the output shaft5and the hood7—independently of the cutting head3—is then already possible. The hub12has a toothing34, on which the hood7is arranged. The hood7is connected to its hub12, by means of the toothing34, by positive engagement in the circumferential direction of the rotation axis6, and is held, secured against rotation, on the output shaft5. The hood7is held in a rotationally fixed manner in the direction about the rotation axis6. Other connections between the hub12and the hood7, such as, for example, frictional or materially bonded connections, may also be expedient. At its end that faces toward the ground31(FIG. 1), the output shaft5has a thread36. The cutting head3is screwed onto the thread36of the output shaft5via a screw element8(FIG. 3) that is fastened, secured against rotation, in the cutting head3. In the exemplary embodiment, inserted in the cutting head3there is a screw element8that, together with the cutting head3, is screwed onto the thread36of the output shaft5. In the exemplary embodiment, the screw element8is realized as a threaded nut. The screw element8is held on the cutting head3in a rotationally fixed manner, in such a manner that a rotation of the cutting head3causes a rotation of the screw element8. Also, a rotation of the screw element8causes a rotation of the cutting head3. The screw element8and the hood7can be rotated against each other about the rotation axis6. The screw element8, together with the cutting head3, can be rotated with respect to the output shaft5, in the direction about the rotation axis6. The cutting head3, the hood7with its hub12, and the output shaft5are arranged coaxially with the rotation axis6. In addition, on its outer side22the hood7has first grip surfaces13,13aand ribs17. The cutting head3, on its outer side26, has second grip surfaces14,14a. The first, fluted grip surfaces13of the hood7have a fluting. The first, smooth grip surfaces13aare smooth. In the exemplary embodiment, both first, fluted grip surfaces13and first, smooth grip surfaces13aare provided. It may also be provided that exclusively first, smooth grip surfaces of the hood are provided. A single first, smooth grip surface, extending around the outer circumference of the hood, may also be provided. The second, fluted grip surfaces14of the cutting head3have a fluting. The second, smooth grip surfaces14aof the cutting head3are smooth. In the exemplary embodiment, both first, fluted grip surfaces14and second, smooth grip surfaces14aare provided. It may also be provided that exclusively second, smooth grip surfaces of the cutting head are provided. A single second, smooth grip surface, extending around the outer circumference of the cutting head, may also be provided.

As can be seen inFIG. 3, radial access to the output shaft5is blocked, both in the case of mounting and in the case of demounting of the cutting head. It is not possible for the operator directly to hold the output shaft fast by hand in order to prevent it from rotating concomitantly as a result of the screwing motion. The following steps therefore ensure for mounting and demounting the cutting head3:

To mount the cutting head3onto the output shaft5, the cutting head3has to be screwed onto the thread36of the output shaft5by means of the screw element8. In order that the output shaft5does not rotate concomitantly as the cutting head3is being mounted, the output shaft5has to be held fast, via the hood7, at the grip surfaces13,13a. In this case, the holding force of the operator is transmitted from the grip surface13,13a, via the hood7, onto the hub12, to the output shaft5. The output shaft5can thus be held fast via the grip surfaces13,13aon the hood7while the cutting head3is being held at the second grip surfaces14,14aand is being screwed onto the thread36of the output shaft5. The cutting head3in this case comes to bear, with its outer side26, against the hood7, in the direction of the rotation axis6. Via its hub12, the hood7is supported, in the direction of the rotation axis6, on a support bearing47(FIG. 3) that is fastened on the output shaft5. As a result of the output shaft5being held fast via the hood7, the cutting head3can be screwed onto the output shaft5by hand with a sufficiently high tightening moment.

To demount the cutting head3, the operator can hold fast the hood7with one hand, at the first grip surfaces13,13a, and thus block the output shaft5in the direction of rotation. At the same time, with the other hand, the operator can grip the cutting head3at its second grip surfaces14,14a, and unscrew the cutting head3from the thread36of the output shaft5, without concomitantly rotating the output shaft5. The tool head3can thus be mounted or demounted by hand, without the use of tools, without the output shaft5being directly accessible to the operator.

Shown inFIG. 3is the second exemplary embodiment of the arrangement according to the invention, of the cutting head3, the hood7and the output shaft5, mounted in the front housing2of a work appliance according to the invention.

The output shaft5is rotatably mounted in the front housing2. A transmission and/or a drive motor may be arranged in the front housing2, such that the front housing2is expediently realized as a transmission housing or as a motor housing.

As shown inFIG. 3, the cutting head3comprises the screw element8, which is fastened in a rotationally fixed manner to the cutting head3. In the exemplary embodiment, the screw element8is secured, by means of a toothed lock washer48, against axial separation from the cutting head3. The screw element8may also be an insert that is inseparably accommodated in the cutting head3. The cutting head3is screwed onto the thread36of the output shaft5via the screw element8. The cutting head3is supported axially via a bearing contact surface15of the hood7. The tensioning force between the cutting head3and the hood7is transmitted substantially via the bearing contact surface15. The hood7is arranged on the hub12and is supported against it, in the direction of the rotation axis6, in a first contact surface49. The hub12, in turn, is tensioned against a support bearing47, which is arranged on the output shaft5and which strikes against a shaft shoulder51in the direction of the rotation axis6. The hub12contacts the support bearing47, in the inner bearing shell thereof, in a second contact surface50. Accordingly, a closed flow of force is ensured, starting from the screw element8of the cutting head3, in the direction of the rotation axis6, via the hood7and the hub12, as far as the output shaft5.

As shown byFIG. 3, the moments acting upon the output shaft5at the hood7are transmitted via the hub12. The toothing34of the hub12connects the hub12to the hood7by positive engagement, in the circumferential direction of the rotation axis6. The hub12is held on the output shaft5, by positive engagement in the circumferential direction of the rotation axis6, by the dihedron realized on the output shaft5.

As shown inFIG. 3, the front housing2projects with its circumferential wall over the hood7, in particular the ribs17of the hood7, in the direction of the rotation axis6. In addition, however, the hood7projects with its first grip surfaces13,13a, at least partly, out of the front housing2, in the direction of the rotation axis6. The grip surfaces13,13aare thus accessible to the operator. Further, the front housing2and the hood7delimit an annular gap41. Owing to the ribs17of the hood7, when the work appliance27is in operation an airflow42is generated, which blows outward into the environment, via the annular gap41, from a transmission interior space43that is enclosed by the front housing2. Accordingly, the annular gap41forms a gap seal that prevents the ingress of dirt into the transmission interior space43.

InFIG. 4, the hood7, with its hub12, is shown in a sectional representation. In the exemplary embodiment, the hood7is realized as a pot shape. The shape of the hood7advantageously follows the outer contour of the region of the cutting head3that is covered by the hood. In the exemplary embodiment, the cutting head3has a substantially cylindrical form. The hood7comprises a hood base46, extending in the radial direction from the rotation axis6, and a hood wall25that adjoins the hood base46. The hood wall25extends in the direction of the rotation axis6. The hood7has an inner side21that faces toward the cutting head3, and an outer side22that faces away from the cutting head3(FIG. 5). The inner side21delimits an interior space23of the hood7. In the exemplary embodiment, the inner side21is divided into an underside10at the hood base46, and a circumferential inner side18at the hood wall25. The outer side22of the hood7is divided into an upper side9at the hood base46, and a circumferential outer side11at the hood wall25. The hood7has an outer diameter d with regard to the circumferential outer side11. In the exemplary embodiment, the outer diameter d Increases slightly, starting from the hood base46, in the direction of the rotation axis6. Nevertheless, in the exemplary embodiment the hood wall46has a substantially cylindrical contour course. The cutting head3may have, for example, a spherical form. The pot-shaped hood7advantageously also follows there the outer contour of the region of the cutting head3that is covered by the hood, such that the hood base46and the hood wall25have a curved course. At the hood wall46the hood7has a thickness h, which corresponds to the distance between the circumferential outer side11and the circumferential inner side18. The thickness h of the hood wall46preferably corresponds to less than 5% of the maximum outer diameter d of the hood7.

As shown inFIG. 4, the hood7, starting from the rotation axis6, is divided in the radial direction into an inner region19and an outer region20that adjoins the inner region19. The inner region19has a width a, which corresponds to the distance, measured radially in relation to the rotation axis6, between the outer region20and the rotation axis6. The outer region20has a width b, which corresponds to the distance, measured radially in relation to the rotation axis6, between the circumferential outer side11and the inner region19. In the exemplary embodiment, the width a of the inner region corresponds to at least 3 times, in particular at least 5 times, preferably approximately 6 times, the width b of the outer region20. The inner region19preferably extends from the rotation axis6as far as the circumferential inner side18of the hood wall25. The outer region20preferably extends from the circumferential inner side18to the circumferential outer side11of the hood wall25.

As shown inFIG. 4, the bearing contact surface15is realized on the inner side21of the hood7. In the exemplary embodiment, the bearing contact surface15is realized on the underside10of the hood base46, adjacently to the hub12, and is at a distance e from the rotation axis6. The bearing contact surface15is, in particular, an annular surface. The bearing contact surface15is perpendicular to the rotation axis6, but in an alternative exemplary embodiment may also be oriented obliquely in relation to the rotation axis6. The bearing contact surface15is arranged at approximately half the length c of the hood7. The length c of the hood7is measured in the direction of the rotation axis6. Further, there is a sealing surface24realized on the inner side21of the hood7. The sealing surface24is realized on the underside10of the hood base46, adjacently to the hood wall25. The sealing surface24is, in particular, an annular surface. In the exemplary embodiment, the sealing surface24is arranged perpendicularly in relation to the rotation axis6. In an alternative exemplary embodiment, the sealing surface24may also be oriented obliquely or parallel to the rotation axis6. The sealing surface24is at a distance f from the rotation axis6, which corresponds to at least 4 times, in particular approximately 5 times, the distance e between the bearing contact surface15and the rotation axis6. In addition, the distance f of the sealing surface24corresponds to at least one quarter, in particular at least one third, of the outer diameter d of the hood7.

As shown inFIG. 5, the bearing contact surface15of the hood7serves as a contact surface for the cutting head3, for tensioning the cutting head3to the hood7. The cutting head3is tensioned with full surface contact against the bearing contact surface15of the hood7. Realized on the bearing contact surface15of the hood7, to enable the tensioning forces to be taken up, there is an elongation44that extends in the direction of the rotation axis6. In the region of the elongation the hood7is preferably realized by ribbings. It is thereby ensured that the hood7has a sufficiently high strength in the region of the main flow of force between the cutting head3and the hood7. In addition, the outer side26of the cutting head3and the inner side21of the hood7contact each other at the sealing surface24of the hood7, and thus form a seal against dirt. Since the sealing surface24is arranged adjacently to the hood wall25, and thus radially outside the bearing contact surface15, accretion of dirt on the bearing contact surface15, between the hood7and the cutting head3, is avoided. Both the sealing surface24and the bearing contact surface15are arranged in the inner region19.

As shown inFIG. 5, the hood7, on its inner side21, does not contact the cutting head3in the outer region20of the hood7. In the outer region20of the hood7, the hood7and the cutting head3have a clearance45extending in the radial direction of the rotation axis6. The clearance45is formed by a distance between the circumferential inner side18of the hood wall25and the outer side26of the cutting head3. In the exemplary embodiment, the clearance extends in the direction of the rotation axis6, and runs along the entire hood wall25, in particular along the first grip surface13,13a, as far as the underside10of the hood base46. This avoids the hood7being pressed onto the cutting head3in the region of the first grip surface13,13aduring mounting or demounting of the cutting head3, and thus interfering with the releasing or fastening of the cutting head3.

InFIG. 6the hood7is represented in a perspective top view. There are ribs17realized on the outer side22of the hood7. The ribs17run in the radial direction of the rotation axis6, and extend in the direction of the rotation axis6. In the exemplary embodiment, the ribs17are realized only on the upper side9of the hood base46. On the upper side9, the ribs17run through the inner region19, and project into the outer region20. The ribs17may expediently be realized only in the inner region19of the hood7. In a preferred exemplary embodiment, the ribs17may expediently run from the upper side9as far as the circumferential outer side11of the hood wall25. In an alternative exemplary embodiment, the ribs17may also expediently be realized on the inner side21of the hood7. The ribs17are arranged, in particular in a star formation, around the rotation axis6. The ribs17may also be arranged in the form of an arc in relation to the rotation axis6. The sealing surface24lies in the form of a ring around the rotation axis6.

In the exemplary embodiment, the ribs17and the sealing surface24are arranged on opposite sides of the hood7. The ribs17serve to stiffen the hood7, such that deformation of the hood7is avoided when the hood7is gripped. Upon rotation of the hood7, the ribs17of the hood7generate an airflow, such that the hood7can be used, for example, as a fan wheel or as a blower wheel. In the exemplary embodiment, the hood7is realized as a fan wheel.

As shown inFIG. 6, there are first grip surfaces13,13arealized on the hood7. The first grip surfaces13,13aare realized in the outer region20, on the outer side22of the hood7. In the exemplary embodiment, the first grip surfaces13,13aare realized on the circumferential outer side11of the hood wall25. In the exemplary embodiment, the first, fluted grip surfaces13of the hood7are uniformly spaced apart from each other, in the circumferential direction of the rotation axis6, on the circumferential outer side11of the hood7. A non-uniform arrangement of the first, fluted grip surfaces13or a single first, fluted grip surface13along the entire circumferential outer side11may also be expedient. The first, fluted grip surface13has a fluting structure that is composed of individual fluting elements39. The fluting elements39run approximately in the direction of the rotation axis6. As a result, when the hood7is held fast at the first, fluted grip surfaces13, a particularly good transmission of force is obtained in the circumferential direction of the rotation axis6.

As shown inFIG. 7, there are two grip surfaces14,14arealized on the outer side26of the cutting head3. The second, fluted grip surfaces14are uniformly spaced apart from each other, on the outer side26of the cutting head3, in the circumferential direction of the rotation axis6. It may also be expedient to provide a non-uniform arrangement of the second, fluted grip surfaces14, or only a single second, fluted grip surface14, on the outer side26of the cutting head3. The second, fluted grip surface14of the cutting head3has fluting elements40, running approximately in the direction of the rotation axis6, which assist a transmission of force when the cutting head3is held at the second, fluted grip surfaces14. Both the first grip surface13,13aof the hood7and the second grip surface14,14aof the cutting head3may expediently have other grip structures. Both the first grip surface13,13aof the hood7and the second grip surface14,14aof the cutting head are freely accessible to the operator.

As shown inFIG. 7, the grip surface13,13ais at a distance i from the rotation axis6, which distance corresponds to at least 30%, in particular at least 35%, of the maximum outer diameter j of the cutting head3. The maximum outer diameter d of the hood7corresponds to not more than 120%, in particular not more than 110%, of the maximum outer diameter j of the cutting head3.

As shown inFIG. 8, the first grip surface13,13ahas a length g, measured in the direction of the rotation axis6. The cutting head3is arranged in the interior23of the hood7, such that the hood7at least partly envelops the cutting head3. The hood7in this case projects over the cutting head3, in the direction of the rotation axis6, to such an extent that the hood7overlaps the cutting head3with the entire length g of the first grip surface13,13a.

As shown inFIGS. 7 and 8, cutting tools4are mounted on the cutting head3. It may be expedient for only one cutting tool4, or also a plurality of cutting tools4, to be fastened to the cutting head3.

In the exemplary embodiment, the cutting tools4are realized as cutting blades. Additionally provided on the cutting head are fastening devices52for fastening a cutting cord. Thus, when the cutting head3is in operation, cutting blades and/or cutting cords may be used as a cutting tool.

Common to the cutting heads3in the exemplary embodiments inFIGS. 2 and 3is that they are each unscrewed as a unit from the output shaft5. Although the cutting head3may be composed of a plurality of parts, they are not moved relative to each other in order to demount the cutting head3from the output shaft5.

Shown inFIG. 9is a detail representation of an exemplary embodiment of a work appliance27, in which the arrangement1according to the invention is arranged directly on the stem29. Accordingly, the cutting head3is coupled to the stem29, not via a front housing2, but directly. The output shaft5is mounted in the stem29via the support bearing47. The drive shaft, not represented, transitions directly into the output shaft5. Arranged on the output shaft5, according to the invention, are the hood7and the cutting head3.