TECHNICAL FIELD

The present invention in particular relates to a tensioning ar- rangement for a power saw, which may be a gas power saw or an electric power saw.

BACKGROUND

In general, power saws comprise mechanisms for tensioning the saw chain supported by a saw guide bar .

Known tensioning mechanisms, such as for example disclosed in US 2011/0232110 Al and US 4,920,650 use screw based tensioning mechanisms, in which a pin, coupled to a tensioning screw, pass- es through a pin-hole in the guide bar such that rotating the screw leads to a linear movement of the pin and hence a linear displacement of the guide bar in lengthwise direction. By moving the guide bar in the lengthwise direction, the saw chain engaging a drive pinion and supported by the guide bar can be ten- sioned and also released again.

However, the known tensioning mechanisms under certain circumstances are comparatively cumbersome and not very easy to handle, in particular in cases where the saw chain has to be re- assembled to the guide bar or where saw chain replacement has to be carried out. In case the tensioning mechanism includes a pin and a pin-hole, and the pin projects from a clutch cover mount- able to a power saw body and the pin-hole being formed in the guide bar, the mounting of the clutch cover to the power saw body can be both complicated and time consuming. This, since the guide bar must be adjusted in its length direction into the position for which the pin can be inserted into the pin-hole before tensioning the saw chain and before tightening of the clutch cover to the power saw body.

SUMMARY Therefore it is an object of the invention to provide a tensioning arrangement for tensioning and releasing a power saw chain, which is comparatively easy to handle and which allows a comparatively rapid and simplified reassembly and replacement of saw chains . Further, a power saw chain guide bar, a power saw clutch cover and a corresponding power saw shall be provided. object is solved by the claims 1, 12, 16 and 18. Embod in particular result from respect dependent claims . to c

ning

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provided .

The saw chain in the ordinary operational configuration is wrapped around a drive pinion and the guide bar, and by increasing the distance between the guide bar and pinion, the tension of the saw chain can be adapted. Increasing the distance in gen- eral involves a displacement of the guide bar in its lengthwise direction .

According to the present invention, a thread of a rod type threaded linear actuator of the tensioning arrangement during displacement of the guide bar directly meshes a complementary linear threaded structure . Preferably, the complementary linear threaded structure extends on the guide bar in lengthwise direction thereof . The complementary linear threaded structure in particular shall mean and relate to a structure or array that linearly extends over a predefined length and is threaded with a thread complementary to that of the linear actuator .

Alternatively, a toothed wheel could be provided instead of the threaded linear actuator, in which case a linear steering rack or a guide bar integrated cogged engagement array could be used as complementary linear threaded structures; Accordingly, a pow- er saw chain tensioning arrangement for tensioning and releasing a power saw chain by lengthwise displacement of a chain guide bar supporting the saw chain may be provided, wherein teeth of the toothed wheel of the tensioning arrangement during displace- ment of the guide bar directly mesh the complementary structure of the guide bar such that rotation of the wheel on its own axis results in a displacement between the wheel and the structure and thus in the lengthwise displacement of the guide bar, wherein the complementary structure is implemented directly on the guide bar .

The threaded linear actuator and the complementary linear threaded structure are implemented and configured such that the meshing cooperation between them is such that rotation of the linear actuator on or around its own axis, i.e. rotational axis, results in a linear displacement, i.e. linear relative movement, between the threaded linear actuator and complementary linear threaded structure. The displacement of the linear threaded structure in turn results in the lengthwise displacement of the chain guide bar. This in particular is the case as the complementary threaded structure according to the invention is implemented directly on or at the guide bar, in particular in or on a surface area of the guide bar . The complementary linear threaded structure in particular may be implemented on the guide bar such that it can be coupled to the threaded linear actuator, which for example may be a threaded rod, simply by placing the linear threaded structure on the threaded linear actuator or bringing them into contact, i.e. simply by overlaying the threaded linear actuator and linear threaded structure.

As compared to the known state of the art, the present invention does not require to pass a pin of a tensioning drive through a corresponding pin-hole in the chain guide while mounting a new saw chain. This is due to the fact that the tensioning arrange- ment and tensioning mechanism according to the invention allow a pin-less tensioning and releasing of the saw chain. A pin-based tensioning and releasing system for the saw chain in most cases is very cumbersome and annoying, as the position of the tensioning pin almost never fits instantaneously with the position of the pin-hole provided in the chain guide bar .

The tensioning arrangement and mechanism as proposed herein allows a comparatively simple replacement and exchange of a saw chain, wherein the saw chain may be put onto or wrapped around the guide bar and wrapped around the drive pinion of the power saw. Then, a clutch cover comprising the threaded linear actuator may be placed on the mounting face of the saw chain and power saw and adequate fastening elements may be fastened to clamp the guide bar between power saw main body and clutch cover.

Upon putting the clutch cover in its ordinary position to cooperate the guide bar, the threaded linear actuator and complementary linear threaded structure automatically are aligned and mesh with each other . Then, before finally tightening the fastening elements, in particular fastening screws, the guide bar can be displaced in its lengthwise direction, away from the drive pinion by operating the tensioning arrangement in order to obtain an optimal or suitable tension of saw chain.

As can be seen, the proposed invention in contrast to the state of the art does not require actions like adequately positioning and passing a tensioning pin through a pin-hole of the guide bar. Hence, the proposed invention is suitable to provide simplified handling options in particular with respect to saw chain tensioning, saw chain mounting and saw chain replacement.

In embodiments, the threaded linear actuator is implemented as a male threaded rod and the linear threaded structure of the guide bar is implemented as a female threaded deepening in the guide bar . In particular the threaded deepening may be implemented as a threaded cup or threaded steering rack worked into the guide bar .

The male thread therefore preferably comprises an outer convex shape, in particular thread structure, while the female thread preferably represents a counterpart concave inner thread. The female thread may be in the form of a shell , for example a half or quarter threaded shell . The proposed embodiment allows a space saving construction of the tensioning arrangement. In particular, the female threaded structure can be implemented with comparatively little technical complexity on or at the guide bar. Further, respective threaded structures can be worked into the guide bar without inadequately weakening the mechanical stability of the guide bar.

The male thread, in particular the threaded rod, can be imple- mented and mounted on or at a lutch cover of the power saw, or on or at an attachment area of the main body of the power saw, where in both cases sufficient constructional space shall be available .

In embodiments, the threaded linear actuator and linear threaded structure both extend, more or less, in parallel to the length- wise direction of the saw chain guide. Such a configuration requires comparatively little technical and mechanical efforts for implementing a mechanism for lengthwise displacement of the guide bar in order to tension or releasing tension of the saw chain .

In further embodiments, the linear threaded structure may be implemented as a type of steering rack, in particular as a ladder type steering rack. The steering rack in its overall geometry may be flat, but may also be adapted in its cross sectional cur- vature to the curvature of the threaded linear actuator . It may also at least in part project out of the guide bar, such that the threaded structure includes shallow recesses or no recesses in relation to surrounding surfaces of the guide bar. Thread sections of the linear threaded structure may involve helical threads, worm threads, but also may involve linear or curved de- pressions or slits formed or worked into the guide bar.

In embodiments, the threaded linear actuator may be implemented as a threaded rod comprising or involving helical threads, worm- threads, a trapezoidal thread or a buttress thread. Preferably, the threads run circumferentially around the rod with a suitable pitch. Preferably, the threads are implemented as partial threads, extending in lengthwise direction of the rod only over a predefined, preferably central, section. The linear threaded structure of the guide bar may comprise at least sections of a respective complementary female thread. The threads as proposed beforehand are comparatively robust, in particular with respect to force transmission, and are particularly suitable for the comparatively harsh working environment of power saws . In embodiments, the chain tensioning arrangement may further comprise a set or adjustment element, such as for example a screw or wheel, which is coupled to the threaded linear actuator such that a rotational movement of the adjustment element can be translated into a rotational movement of the linear actuator.

Rotation of the linear actuator which engages the linear threaded structure will lead to a relative displacement between the linear actuator and the guide bar. This in turn can change the tension of the saw chain wrapped around the guide bar and a driving pinion of the power saw.

The proposed adjustment element can be positioned in locations that are easily accessible by the user of the power saw from the outside. In contrast thereto, the linear drive comprising the threaded linear actuator and the linear threaded structure probably will be more or less hidden and not be accessible for di- rect operation. The adjustment element may for example be posi- tioned at a front or lateral side face of the power saw, easily accessible during operation. In a preferred variant of the previous embodiment, the adjustment element is coupled with a rotary shaft or rod of the linear actuator via a gear drive such that a rotational movement of the adjustment element can be translated into a rotational movement of the linear actuator. The gear drive may be designed to obtain optimal and suitable power transmission as well as adequate op- erability of the tensioning arrangement, in particular such that a tensioning operation of the saw chain can be efficiently carried out. In embodiments, the tensioning arrangement further comprises a clutch cover . The clutch cover may be implemented, and in general is implemented, to cover and hide the clutch and related drive pinion for driving the saw chain. The threaded linear actuator according to the present embodiments is mounted to be ro- tatable on its own axis to the clutch cover. Further, thread sections of the linear actuator project from a guide bar contact or mounting face of the clutch cover such that the thread sections can mesh or engage complementary thread sections of the linear threaded structure when the guide bar is positioned on the contact or mounting face.

It has already been mentioned further above, that mounting the threaded linear actuator to a clutch cover may be advantageous with respect to construction and design space. However, other locations for the threaded linear actuator also come into consideration; in particular a mounting surface for the guide bar located at the power saw main body, opposite to the mounting face of the clutch cover when mounted to the power saw main body. Herein, the term 'clutch cover', in particular if no clutch is present or being differently arranged, may analogously include 'drive wheel cover' or 'sprocket cover'. According to claim 9 , a power saw chain guide bar is provided. The guide bar comprises an attachment area or surface for clamping attachment of the guide bar to a power saw, in more detail for clamping the attachment area between opposite mounting areas or faces of the power saw main body and clutch cover.

The chain guide bar in the proposed embodiment comprises in the attachment area a complementary linear threaded structure run- ning in lengthwise direction of the saw guide bar. In this configuration, thread sections of the complementary linear threaded structure are oriented or run transversal to the lengthwise direction . The complementary linear threaded structure further is adapted to cooperate with a threaded linear actuator in a power saw chain tensioning arrangement according to at least one of the solutions and embodiments as described above and further above. The complementary linear threaded structure may be implemented as described in any embodiment and solution further above. In particular the linear threaded structure may be implemented as a type of steering rack, in particular as a ladder type steering rack .

As to advantages, reference is made to the description above. In addition it shall be mentioned that the proposed chain guide bar can be mounted to a power saw in a comparatively easy and straightforward way. In particular, as the complementary linear threaded structure may be provided at or on one of the flat faces of the chain bar, it can automatically be coupled and engaged to the threaded linear actuator during assembly.

It is not required to additionally fit a tensioning pin through a corresponding pinhole as is required in conventional solutions . The pin and pinhole concept of the state of the art in the present invention is replaced by a treaded linear actuator meshing with a complementary linear threaded structure which is imple- mented directly on the guide bar .

The linear threaded structure in particular may comprise a bowl or cylinder-shaped deepening provided in the saw guide bar, wherein the turns of the complementary thread are provided in the deepening. Preferably, sections of the threads of the threaded structure are oriented transversally to the lengthwise direction of the guide bar. The bowl-shaped or cylinder-shaped deepening in particular may be in the form of a half or quarter bowl, cylinder or shell or similar.

The deepening may comprise a plurality of indentations, m par- ticular forming sections of a female thread, adapted to mesh corresponding sections of a male thread of the threaded linear actuator .

In embodiments, the chain guide bar may comprise in the attachment area a slotted hole extending in lengthwise direction of the guide bar. The slotted hole may be adapted for passing through fastening elements for clamp fastening the guide bar to a power saw main body.

Further, in the previous embodiment, the complementary linear threaded structure may be positioned below the slotted hole relative to the assembled state and ordinary operating condition. Preferably, the complementary linear threaded structure is centred relative to the slotted hole. The proposed positions of the threaded structure may be advantageous with respect to adequate utilization and availability of space for installing the threaded linear actuator . The length of the threaded structure may extend over a defined length, for example over half the length of the slotted hole, on the guide bar, in particular such that the total displacement path provided and allowed by the lengthwise dimension of the slotted hole can be utilized. Note that the total displacement length may depend on the dimension of the slotted hole and a mutual distance between mounting bolts or studs passing through the slotted hole in the assembled state. According to claim 12, a power saw clutch cover is provided. The clutch cover comprises an attachment area, in particular an attachment surface or face, for clamping attachment of a chain guide bar to a power saw. Further, a rod type threaded linear actuator is attached to the clutch cover to be rotatable on its own axis. The threaded linear actuator is adapted to cooperate with a complementary linear threaded structure in a power saw chain tensioning arrangement according to any of the solutions and embodiments as described above and further above. The threaded linear actuator in particular may be implemented as described in any embodiment, variant or example above. In particular the linear actuator may be implemented as or comprise a threaded rod, in particular a partial threaded rod in which threads are provided preferably in a mid-section of a rod of the threaded rod.

Providing and mounting the threaded linear actuator to or at the clutch cover may be advantageous with respect to utilization and availability of mounting space, which has already been addressed further above .

In embodiments, the power saw clutch cover comprises a guide bar mounting area, in particular a mounting face or surface . The mounting area is considered to be an area which is adapted and configured to get into contact with the guide bar during mounting and in the mounted state, and upon tightening the fastening elements, urges the guide bar by a pressing force towards the power saw main body so as to fixedly clamp the guide bar between the power saw main body and the clutch cover . Note that the fastening elements may be implemented according to the state of the art such that they exert a pressing force to the clutch cover which in turn clamps the guide bar between main body and clutch cover . With the previously mentioned clutch cover, it may be provided that thread sections of the threaded linear actuator, in particular a section of the threaded section of the linear actuator, project from the mounting face or surface such that the threaded sections at least partially mesh with the complementary threaded structure in case that a respective guide bar, in particular as described in any embodiment above, is positioned on the mounting face relative to the ordinary operational configuration . Designing the linear actuator such that thread sections overhang or project from the mounting face is a comparatively robust and mounting space optimized possibility to obtain automatic engagement between the linear actuator and linear threaded structure . In particular in case that the thread sections project from the mounting face, the complementary linear threaded structure may be implemented as a depression to obtain lateral assembly widths at least comparable to those available in the state of the art . In further embodiments, the clutch cover may comprise a fastening or fixing arrangement for fastening the clutch cover to a power saw main body, in particular for exerting a pressing force to the clutch cover towards the power saw main body. The fastening arrangement in particular may for example comprise through holes or screw fittings for passing through fastening bolts or fastening screws fixed to the main body of the power saw .

The linear actuator may be positioned in the region of the fas- tening arrangement. Here adequate coupling and sufficiently strong engagement between the threads of the linear actuator and the threaded structure may be obtained.

Preferably, the linear actuator is arranged and positioned such that it is oriented essentially parallel to the lengthwise di- rection of the chain guide bar in the ordinary mounting posi- tion .

In yet further embodiments of the clutch cover, the fixing ar- rangement may comprise two mutually spaced screw fittings. Preferably the screw fittings are spaced apart essentially relative to the lengthwise direction of the guide bar in the ordinary mounting position. The linear actuator may be arranged in a region between the screw fittings, and, relative to the ordinary mounting and operating position, below the connecting line of the screw fittings. This mounting position may be advantageous with respect to available mounting space, and may also improve accessibility of the linear actuator in particular with respect to connecting the linear actuator with adjustment elements operable from or at an outer site of the power saw.

According to cla

main body, a ten

ventive solution

erably a clutch

embodiment as de The main body of the power saw in particular may comprise the motor, handles, fuel and oil tanks, electronics, clutch, chain drive pinion, the mounting face for mounting the guide bar, and others .

With the proposed power saw, the linear actuator may be provided at or on the clutch cover. However, the linear actuator of the tensioning arrangement of the power saw may also be provided at or on the main body of the power saw, in particular in an attachment area or face for the guide bar of the main body. In embodiments, the power saw may further comprise a power saw chain guide bar according to any of the inventive solutions and embodiments as described above and further above. Here, the guide bar may be sandwiched and clamped between the main body and the clutch cover by a fastening arrangement generating a clamping or pressing force between the main body and the clutch cover to clamp the guide bar therebetween.

In particular in this configuration, the complementary linear threaded structure of the guide bar meshes with or engages the threaded linear actuator in accordance with the inventive tensioning arrangement as described above and further above.

As to advantages and advantageous effects of the power saw, reference is made to the description relating to the inventive ten- sioning arrangement, clutch cover and guide bar.

In all it shall become clear, that the proposed tensioning arrangement, clutch cover, guide bar and power saw are adequate for easing assembly and tensioning of a saw chain to a power saw. Further it has become obvious that the proposed tensioning arrangement allows a comparatively rapid and simplified reassem bly and replacement of saw chains .

With the proposed tensioning arrangement, mounting or exchanging a saw chain of a power saw can be conducted as follows : First, the saw chain may be wrapped around the chain guide bar, and may be positioned together with the guide bar on the mounting face of the power saw main body. In particular, the guide bar may be positioned with its attachment area to the mounting face. In doing so, fastening bolts may be passed through the slotted hole of the guide bar and the saw chain may be engaged with the drive pinion.

After adequately positioning the guide bar to the main body, the clutch cover may be coupled to the attachment area of the guide bar opposite to mounting face of the main body. In assembling the clutch cover to the main body and guide bar, the fastening bolts are passed through the screw fittings of the guide bar and the linear actuator of the clutch cover and the linear threaded structure of the guide bar are automatically brought into contact with each other such that threaded sections of the linear actuator and linear threaded section mesh with each other.

After slightly fastening the clutch cover to the main body, the tensioning assembly can be operated, by adequately rotating the adjustment screw. Rotating the adjustment screw leads to a rotatory movement of the linear actuator, which in turn causes the threaded structure to move along the linear actuator, which means that the guide bar is moved in lengthwise direction. Ade- quate operation of the adjustment screw will lead to a suitable tension of the saw chain.

As the proposed invention works completely without tensioning pins projecting from linear actuators and which have to be passed through corresponding pinholes of the guide bar, the assembly of the saw chain and guide bar with the inventive tensioning arrangement is less elaborate and can be conducted more quickly. This in particular is the case as it is not required to preset the positions of elements of the tensioning arrangement, as is the case for example with the known tensioning pins and corresponding pinholes which have to be adequately positioned in order to fit the guide bar and clutch cover to the main body of the power saw.

Tensioning elements of the tensioning arrangement according to the invention, in particular thread sections of the linear actuator and thread sections of the linear threaded section on the guide bar can, during mounting a saw chain, essentially always be meshed with each other without requiring further adjustment. This in particular is the case as mutual engagement of the thread sections of the linear actuator and linear threaded section is essentially invariant with respect to the rotatory position of the linear actuator . Mutual engagement of the threaded sections at most may requires a displacement of the guide bar by half the pitch of the thread.

It shall be noted, that the linear threaded section of the guide bar may be provided only on one side of the guide bar. Preferably, both sides of the guide bar comprise linear threaded sections such that the guide bar can be mounted in its two possible configurations, which originate from each other by a 180 degree rotation around the longitudinal center axis of the guide bar.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention will now be described in connection with the annexed figures, in which:

FIG. 1 shows a perspective exploded view of a section of a power saw; and FIG. 2 shows a perspective cross sectional view of a detail

Fig. 1.

DETAILED DESCRIPTION

FIG. 1 shows a perspective exploded view of a section of a power saw; while FIG. 2 shows a perspective cross sectional view of a detail of FIG. 1. In more details, FIG. 1 shows a clutch cover 1 and a saw chain guide bar 2. The clutch cover 1 is configured and adapted to be mounted to a main body 3 of a power saw 4, to thereby hide or cover a drive pinion 5 for driving a saw chain 6 wrapped around the guide bar 2 and drive pinion 5, and to fix the guide 2 bar to the main body 3.

For fixing or mounting the clutch cover 1 to the main body 3, there are provided two threaded bolts 7 projecting from a mounting area 8 of the main body 3, and two corresponding screw fittings 9 provided on the outer side of the clutch cover 3.

For fixing the guide bar 2 to the main body 3, the screw fittings 9 and corresponding threaded bolts 7 are screwed together. In doing so, the clutch cover 1 is urged and pressed towards the mounting area 8 of the main body 3 to thereby clamp the guide bar 2 between the main body 3 and clutch cover 1.

For the reason of securely fixing the guide bar 2 to the power saw 4, the guide bar 2 comprises a slotted hole 10 through which the threaded bolts 7 pass in the assembled state.

The longitudinal extension of the slotted hole 10 is larger than the distance between the threaded bolts 7 such that the guide bar 2 can be moved in its lengthwise direction. Moving the guide bar 2 in the assembled state in lengthwise direction will change the tension of the saw chain 6.

For adequately adjusting the tension of the saw chain 6, the power saw 4 comprises a tensioning arrangement, which will be described in more details below.

The tensioning arrangement comprises a threaded linear actuator 11 and a linear threaded structure 12 which is integrally formed on the guide bar 2. The linear threaded structure 12 in the present case is formed as a rectangular shaped deepening in the guide bar 2. Note that other general shapes such as rectangular may be used.

The threaded linear actuator 11 comprises a rod 13 which is aligned essentially parallel to the lengthwise direction of the guide bar 2, and which is pivotably supported in bearing shells of the clutch cover 1.

The linear actuator 11 further comprises approximately in the middle of the rod 13 a longitudinal partial thread 14 comprising helical or worm type windings running circumferentially on a thickened section of the rod 13. The partial thread 14 prefera- bly is implemented as a trapezoidal thread or a buttress thread.

The rod 13 of the linear actuator 11 on one end between the thickened section and a bearing shell is configured as a gear wheel 15 cooperating with a further gear wheel (not shown) which is connected to an adjustment screw 16. The adjustment screw 16 is accessible from a lateral side of the clutch cover 1. The gear wheels are designed and adapted in such a way that rotary movement of the adjustment screw 16 is translated into a rotary movement of the rod 13, and thereby into a rotary movement of the partial thread 14 of the linear actuator 11.

As can in particular be seen from FIG. 1, thread sections of the partial thread 14 project or hang over a mounting face 17 of the clutch cover 1 such that they automatically mesh with a counter- part thread section of the linear threaded section 12 in case that the guide bar 2 is or comes into contact with the mounting face 17, as illustrated in FIG. 2.

As can be seen from a combination of FIG.l and FIG. 2, once the clutch cover 1 and guide bar 2 are brought into contact in the course of the ordinary assembly, the threaded sections of the linear actuator 11 and linear threaded structure 12 automatically mesh with each other. In this configuration, a rotational movement of the adjustment screw 16 will be translated in a rotational movement of the linear actuator 11, which will urge the linear threaded structure 12 to move forth or back. This in the end leads to a corresponding displacement of the guide bar 2 in its lengthwise direction. Note, that rotational or linear movements as described before are indicated in FIG. 2 by double arrows .

In particular from FIG. 2 it becomes clear, that the angular rotational position of the threaded section or rod 13 of the linear actuator 11, except for at most half a thread pitch, is irrelevant for an automatic mutual engagement between the linear actuator 11 and the linear threaded structure 12. Therefore, the clutch cover 1 and guide bar 2 can be easily set together such that the linear actuator 11 and linear threaded structure 12 mutually engage. This is far more comfortable than state of the art solutions, where a tensioning pin has to be aligned such that it can pass through a pinhole of the guiding bar .

The linear threaded structure 12 in particular is implemented as a concave depression worked into the guide bar 2, wherein in the depression there are provided female thread sections complementary to the thread sections of the linear actuator 11, i.e. partial thread 14, and configured to mesh with male thread sections of the linear actuator 11.

It shall be noted that the linear threaded section 12 is considered linear as its overall structure linearly extends in parallel to the lengthwise direction of the guide bar 2. Further it shall be noted that in the examples shown in the figures, the depression representing the linear threaded section 12 has a concave shape or lateral cross section. However, it is also pos- sible that the depression as such has a general flat structure, or that the linear threaded section does not involve a depression as such but rather individual slits or cut-outs acting as complementary threads .

Flat structures in particular may be considered if the linear threaded structure, which can also be considered as an array, is implemented as a gear rack, steering rack, in particular ladder type rack. Steering or ladder type racks may be implemented by a series or an array of subsequent individual slits worked into the guide bar .

In general, any type of thread combinations can be used. However, trapezoidal or buttress threads may be advantageous as they have been shown to cope with the operating conditions usual or common for power saws .

In the embodiment shown in the figures, as can in particular be seen from FIG. 1, the liner threaded structure 12 which is in- tended to mesh with the linear actuator 11 is arranged below and centered relative to the slotted hole 10. Further, the linear actuator 11 is located in the region between the screw fittings 9, and, relative to a connection line of the screw fittings 9, below the screw fitting 9. Such an arrangement of the linear ac- tuator 11 and the linear threaded structure 12 may be advantageous with respect to mounting space.

In all it becomes clear form the preferred embodiments described in connection with the figures that the proposed tensioning mechanism and arrangement provides a comparatively rapid, straightforward and efficient method for mounting and tensioning saw chains of power saws . List of reference numerals

1 clutch cover

2 guide bar

3 main body

4 power saw

5 drive pinion

6 saw chain

7 threaded bolt

8 mounting area

9 screw fitting

10 slotted hole

11 linear actuator

12 linear threaded structure

13 rod

14 partial thread

15 gear wheel

16 adjustment screw

17 mounting face