CN114683356A

CN114683356A - Chain tensioning device for chain saw

Info

Publication number: CN114683356A
Application number: CN202111633151.7A
Authority: CN
Inventors: C·斯穆特克
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2020-12-29
Filing date: 2021-12-29
Publication date: 2022-07-01
Also published as: DE102020216581A1

Abstract

The invention is based on a chain tensioner for a chain saw, having two hand wheels, in particular two hand wheels which are held against one another, are advantageously surrounded by a mutual bowl, and are preferably designed as outer and inner hand wheels, which are rotatable relative to one another about a common axis of rotation, wherein a first of the two hand wheels, in particular the outer hand wheel, is provided for rotation of an eccentric which is designed to longitudinally displaceably displace a stop element which can be fastened to a saw blade of the chain saw relative to a chain wheel of the chain saw which is flush with the saw blade in order to adjust the chain tension of a saw chain of the chain saw, and wherein at least one second of the two hand wheels, in particular the inner hand wheel, is provided for fastening the chain tensioner to the chain saw, in particular by screwing onto a positioning bolt of the chain saw, wherein the chain tensioner further has a chain wheel cover on which the first hand wheel can be locked in a form-locking manner against rotation, in particular, the first hand wheel is held captive on the chain wheel cover.

Description

Chain tensioning device for chain saw

Technical Field

The invention relates to a chain tensioner for a chain saw.

Background

Such a chain tensioner is known, for example, from EP 1159112B 1.

Disclosure of Invention

The present invention relates to a chain tensioner and a chain saw having such a chain tensioner.

The invention is based on a chain tensioner for a chain saw, having two hand wheels, in particular two hand wheels which are held against one another, advantageously in a mutually bowl-shaped manner, and which are preferably designed as an outer hand wheel and an inner hand wheel, which are rotatable relative to one another about a common axis of rotation, wherein a first of the two hand wheels, in particular the outer hand wheel, is provided for the rotation of an eccentric wheel which is designed for the longitudinally displaceable displacement of a stop element which can be fastened to a saw blade of the chain saw relative to a chain wheel of the chain saw which is flush with the saw blade, in order to set a chain tension of a saw chain of the chain saw, and wherein at least one second of the two hand wheels, in particular the inner hand wheel, is provided for fastening the chain tensioner to the chain saw, in particular by screwing onto a positioning bolt (gewendestehbolz), wherein the chain tensioner further has a chain wheel cover, the first hand wheel can be locked in a form-locking manner in a rotationally fixed manner on the chain wheel cover, in particular wherein the first hand wheel is held in a loss-proof manner on the chain wheel cover. "provided" is to be understood in particular to mean specially designed and/or equipped. The object is provided for a specific function, in particular to be understood as meaning that the object fulfills and/or executes the specific function in at least one application and/or operating state.

It is proposed that the first hand wheel can be coupled in a rotationally fixed manner to the chain wheel cover by means of an axial form-locking connection in the direction of the axis of rotation, in particular by means of at least one axial form-locking element, preferably an axial tooth segment, which engages in a corresponding axial form-locking element, preferably an axial tooth ring, of the chain wheel cover. Advantageously, a chain tensioner comprising stable and/or less complex and/or fewer components may thereby be provided. Advantageously, a resistance-free adjustment of the desired chain tension can be achieved. The fixing of the chain tensioner in the desired position can be achieved without an overgauge clamping, in particular without an overgauge clamping connector (ulerastkupplungsfrei). This increases the operating comfort, prevents wear and increases the service life of the chain tensioner.

It is proposed here that at least one axial tooth section of the first hand wheel, in particular of the first hand wheel, can be axially positively fixed relative to the sprocket cover by means of the second hand wheel, in particular by means of an axial stop surface of the second hand wheel, advantageously by means of an axial stop ring, and the above-mentioned advantages apply here as well.

It is proposed that at least one axial form-locking element of the first hand wheel, preferably at least one axial tooth segment, is axially displaceable elastically relative to an axial stop surface of the first hand wheel, in particular axially displaceable elastically in accordance with a tooth height dimension of the teeth of the at least one axial tooth segment and/or of the toothed ring. Advantageously, a resistance-free adjustment of the desired chain tension can thereby preferably be achieved. The fixing of the chain tensioner in the desired position can be achieved without an offside snap-in connector. This makes it possible to open or release the chain tensioner with little wear and effort and to increase its service life.

It is proposed that the tooth tips of at least one axial form-locking element of the first hand wheel, preferably of the teeth of at least one axial tooth segment, lie flush (or are set back) against the axial running surface in the axially unloaded state, and project beyond the axial running surface in the axially loaded state, in particular with a tooth height which corresponds approximately to the teeth of the tooth segment. The advantages mentioned above are also achieved thereby.

It is proposed that at least one axial form-locking element of the first hand wheel is held by an axially elastically displaceable spring tongue on the first hand wheel, in particular wherein the spring tongue has a stop face for the second hand wheel, in particular for an axial stop face, advantageously an axial stop ring of the second hand wheel, on the side facing away from the form-locking element. This prevents overloading of the axial form-locking element, in particular of the axially elastically displaceable spring tongue.

It is proposed that the eccentric cam has a support means, in particular an axial stop surface, in particular an axial ring surface, which is provided for supporting a corresponding axial form-locking element of the form-locking connection, in particular of the sprocket cover, preferably an axial toothed ring of the sprocket cover, in particular of the sprocket cover, for supporting the corresponding axial ring surface of the corresponding axial form-locking element, in particular against excessive deformation, in particular against being able to do soOffside clamping connection with existing shape locking connection

Is supported by the deformation. In this case, undesired loosening of the chain tensioner during operation can be prevented, in particular also in the case of very high operating and/or handling forces during use of the chain saw and/or the chain tensioner.

It is proposed that the axial play (in the fixed state) between the support means and the corresponding axial ring surface of the sprocket cover, which supports the corresponding axial form-locking element of the sprocket cover, is smaller than the tooth height of the tooth segments or of the tooth rings by a small amount, in particular by at most half the tooth height, preferably by less than one fifth of the tooth height. The eccentric can thereby be rotated with low resistance. The adjustment of the chain tension can thus be effected simply/with little effort.

It is proposed that the first and second hand wheels and the sprocket cover are held in a loss-proof manner, in particular as an assembly, to each other and can be removed from the chainsaw, and/or that at least the stop element and the eccentric element are held in a loss-proof manner, in particular as an assembly, to each other, in particular by means of a sleeve with a shoulder and can be removed from the chainsaw. This increases the operating comfort and makes it difficult to lose the components.

This can improve the safety of the chain tensioner and/or the chain saw.

Furthermore, a chain saw is proposed, which has the chain tensioning device described above. The chain saw advantageously has the chain tensioning device described above either assembled or not yet assembled. Advantageously, a resistance-free adjustment of the desired chain tension can be achieved with such a chainsaw. The chain tensioning device can be fixed on the chain saw in a desired position without the need for an over-center engagement of the hand wheel, in particular without an over-center engagement connector. This increases the operating comfort and increases the safety, while at the same time avoiding wear and increasing the service life of the chain saw.

Drawings

Further advantages result from the following description of the figures. An embodiment is shown in the drawings. The figures, description and claims contain a combination of features. The person skilled in the art expediently considers the individual features individually and summarizes them as meaningful further combinations.

The figures show:

FIG. 1: a perspective view of a chainsaw according to the present invention;

FIG. 2 is a schematic diagram: a perspective exploded view of at least the components associated with the chain tensioner according to the present invention;

FIG. 3: an exploded side view of the components associated with the chain tensioner according to the present invention according to FIG. 2;

FIG. 4 is a schematic view of: a) a perspective cross-sectional view of the assembled and undamped chain tensioner and b) a side cross-sectional view;

FIG. 5: a) a perspective cross-sectional view of the assembled and clamped chain tensioner and b) a side cross-sectional view;

FIG. 6: the chain tensioner is not clamped as in fig. 4b, but in a sectional view that is offset by 90 ° with respect to fig. 4 b;

FIG. 7 is a schematic view of: a) a detail of the chainsaw in the region of the chain tensioner with the sprocket cover removed and b) the partial sectional view of fig. 7 a;

FIG. 8: the front and rear side of the outer hand wheel.

Detailed Description

Fig. 1 shows a perspective view of a chainsaw 10 having a housing 12 with a saw blade 14 protruding from the housing 12. The saw blade 14 is surrounded by a saw chain 16, which is guided around the saw blade and is shown in a simplified manner as a dashed and dotted line. The housing 12 has a handle 18 with a switch 20 for switching on a motor, not shown. Furthermore, the chainsaw 10 has an additional handle 17 for guiding the chainsaw 10 and a brake actuation lever 19 for braking and/or for quickly switching off the saw chain drive. The chainsaw 10 has a chain tensioner 28.

On the side of the housing 12, the chainsaw 10 carries a sprocket cover 26. The chain wheel cover 26 is part of the chain tensioner 28 (see fig. 2 to 7), wherein a first (outer) hand wheel 36 (see also fig. 8) and a second (inner) hand wheel 38 are also visible here. The second (inner) hand wheel 38 has a gripping tab (Griffsteg)39 for tool-free tightening and loosening of the chain tensioner 28. The saw blade 14 has a deflection pulley 24 on its blade tip, via which the saw chain 16 is deflected. The chain saw 10 is, for example, mains operated (the cable of which is partially visible) and has an electric motor (no reference numeral here). However, the chainsaw 10 may also be battery powered or run on fuel as an internal combustion engine chainsaw. I.e. the chain saw 10 may be combustion engine or motor driven or have other drive means. These and, if necessary, further components and/or elements of chain saws are generally known to the person skilled in the art.

Below the chain wheel cover 26, on the housing side, a chain wheel 22 is mounted (see fig. 2, 3 and in particular fig. 7a, 7b), by means of which chain wheel 22 the saw chain 16 (see fig. 1) can be placed in such a way that a form-locking connection is produced between the two and the saw chain 16 can be driven in rotation when the chain wheel 22 rotates. The saw blade 14 has a recess 1400 (see, for example, fig. 2) on its edge, by means of which the saw chain 16 is held and guided on the saw blade 14 in a form-fitting manner. The chain wheel 22 is advantageously connected to a drive, not shown, by a transmission, not shown, and/or advantageously by a coupling, not shown.

Fig. 2 shows an exploded perspective view of at least the components and/or parts of the chainsaw 10 associated with the chain tensioner 28 along with the chain tensioner 28. In fig. 3, they are shown in exploded side view. Fig. 4a, 4b, 5a, 5b show a sectional view of at least assembled components at least substantially associated with the chain tensioner 28, wherein a) is a perspective view and b) is a side view, wherein the chain tensioner 28 is released in fig. 4a, 4b and clamped in fig. 5a, 5 b. Fig. 6 shows the chain tensioner 28 loosened as in fig. 4b, however, the section is shown offset by 90 ° about the longitudinal axis of the positioning bolt 34 or about the rotational axis 134 of the chain tensioner 28 compared to the section of fig. 4 b. Fig. 8 shows a perspective view of the front and rear side of the first or outer hand wheel 36. While the various figures combine to provide a better understanding of the invention. Not all components are numbered consecutively in all figures, but repetition of the same components is generally for better understanding.

Fig. 7a shows a perspective view of a part of the chainsaw 10 in the region of the chain tensioner 28 with the chain wheel cover 26 removed. The housing 12 and at least a part of the saw blade 14, the sprocket 22, the stop plate 32, the positioning bolt 34 or positioning bolt, and the claw stop 68 (krallensschlag) can be seen. Furthermore, the shifting unit 130 or the eccentric 30 (which is integrally formed here) is visible in the perspective view of fig. 7a and in the perspective sectional view of fig. 7 b. The shifting unit 130 or the eccentric 30 has a claw clutch 31 on the side facing the observer in fig. 7a, in order to be connected in a force-transmitting, in particular torque-transmitting, but releasable manner to a corresponding claw clutch 37 of the first or outer hand wheel 36. The direction of rotation for increasing (+) or decreasing (-) chain tension is illustrated by the arrow in direction (+) or (-).

Fig. 7b shows a partial cross-sectional view of fig. 7 a. The cross section passes through the eccentric 30 transversely to the rotational axis 134 or to the longitudinal extension of the locking bolt. Portions of at least one drive shaft (not numbered) of the sprocket 22, the set bolt 34, and the stop plate 32 are likewise cut away. The saw blade 14 is held on the side of the housing 12 in the region of its elongated hole 15. In order to ensure the saw blade position, a projection 1681 (formed by a metal part which is formed integrally with the catch stop 68) as shown in fig. 2, 3 and 6 enters the elongated hole 15. Furthermore, the positioning bolt 34 (which is anchored in the housing 12 of the chainsaw 10 both rotationally and axially fixedly about/relative to the axis of rotation 134) passes approximately centrally through the elongated hole 15 and projects beyond the planar side of the saw blade 14 (with respect to fig. 7b) facing the viewer and through an opening of the displacement unit 130 or the eccentric 30. The sleeve 54, which holds the displacement unit 130 or the eccentric 30 and the stop plate 32 together as an assembly 540, in particular together in a loss-proof manner, preferably by means of a radial, shouldered end, in particular in a loss-proof manner, radially surrounds the positioning bolt 34 and is arranged concentrically thereto. The set bolt 34 extends along the rotational axis 134 of the chain tensioner 28.

The eccentric 30 has a spiral winding 290 according to fig. 7 b. The longitudinal position of the saw blade 14 can be adjusted in the direction of the arrow 100 relative to the housing 12 by means of the radial stop face 29 of the eccentric 30 or of the spiral winding 290. Here, a stop plate 32 arranged between the saw blade 14 and the eccentric 30 serves as a coupling means. The stop plate 32 is supported on the one hand on the saw blade 14 by engaging the laterally projecting holding projection 133, while the laterally projecting supporting projection 33 on the other hand rests against the radial stop surface 29 or the eccentric 30. The support projection 33 is supported, as it were, on the periphery of the spiral profile of the eccentric 30 or of the spiral winding 290. The position of the stop plate 32 and thus of the saw blade 14 can be adjusted by rotation of the eccentric 30 about the setting screw 34 or the axis of rotation 134. The rotation of the eccentric 30 about the axis of rotation 134 or about the positioning bolt 34 in this case results in, for example, a longitudinal displacement of 5mm of the stop surface 32 or of the saw blade 14 relative to the sprocket 22 or the housing 12 or relative to the positioning bolt 34. Since the eccentric 30 has approximately 2 and 1/4 turns (21/4) of the spiral winding 290, the saw blade 14 can be adjusted by more than 10mm in the longitudinal direction of the saw blade 14 by means of the chain tensioning device 28. As is also explained in terms of function further below, the sprocket cover 26 has a toothed ring 27. The toothed ring here has, for example, ninety teeth on a 360 ° toothed ring 27, whereby one tooth is provided on the toothed ring 27 every 4 °. The chain tensioner 28 or the first hand wheel 36 can thus be fixed relative to the sprocket cover 26 in 4 deg. increments, which corresponds to a longitudinal movement of the radial stop face 29 of 5mm divided by 90 teeth, i.e. about 56 μm/increment. The longitudinal position of the saw blade 14 can thus be adjusted or fixed in 56 μm steps. This is relatively fine. By means of the longitudinal displaceability of the saw blade 14 relative to the housing 12, the distance between the saw blade 14 and the sprocket 22 is variable, in order to be able to tension the saw chain 16 more or less tightly.

Fig. 2 to 6 show a chain tensioning device 28 for the chain saw 10 or a chain saw, respectively or at least in combination. The chain tensioner 28 has two

hand wheels

36, 38, in particular two

hand wheels

36, 38 which are held together in a loss-proof manner, are advantageously surrounded by a mutual bowl, and are preferably designed as outer and

inner hand wheels

36, 38, which are rotatable relative to one another about a common rotational axis 134. A first of the two hand wheels 36, in particular the outer hand wheel 36, is provided for the rotation of an eccentric 30 which is designed for longitudinally displaceably displacing a stop plate 32 which can be fastened to the saw blade 14 of the chainsaw 10 relative to the sprocket 22 of the chainsaw 10 which is flush with the saw blade 14 in order to adjust the chain tension of a saw chain (not shown here) of the chainsaw 10. At least one second hand wheel 38 of the two hand wheels, in particular the inner hand wheel 38, is provided for fixing the chain tensioning device 28 on the chain saw 10, in particular by screwing the second hand wheel 38 onto the positioning bolt 34 of the chain saw 10. The chain tensioner 28 furthermore has a sprocket cover 26 on which the first hand wheel 36 can be locked in a form-locking manner against rotation, in particular wherein the first hand wheel is held in a loss-proof manner on the sprocket cover 26, in particular by corresponding form-locking

elements

1361, 1270 on the first hand wheel 36 and the sprocket cover 26. The first hand wheel 36 can be coupled in a rotationally fixed manner in the direction of the axis of rotation 134 to the sprocket cover 26 by means of an axial form-locking connection 1470, in particular can be coupled in a rotationally fixed manner axially by means of at least one axial form-locking element 147, preferably by means of an axial toothed segment 47, which engages in a corresponding axial form-locking element 127, preferably an axial toothed ring 27, of the sprocket cover 26. In particular, according to fig. 8, three tooth segments 47 are arranged offset by 120 ° around the rotational axis 134 on the first hand wheel 36. These three tooth segments each have, for example, two offset teeth 1472, in particular teeth 1472 which are arranged offset by 4 ° from one another in the circumferential direction. The toothed ring 27 (best seen clearly in fig. 2) has 90 regularly distributed teeth. One tooth is arranged every 4 ° in the circumferential direction.

At least one axial form-locking element 147 or axial tooth segment 47 of the first hand wheel 36, in particular of the first hand wheel 36, can be fixed in an axially form-locking manner relative to the sprocket cover 26 by means of the second hand wheel 36, in particular by means of the axial stop face 138 of the second hand wheel 38, advantageously by means of the axial stop ring 1380.

At least one axial form-locking element 147 or at least one axial tooth segment 47 (here three axial tooth segments 47) of the first hand wheel 36 is axially elastically displaceable relative to the axial stop face 136 of the first hand wheel 36, in particular axially elastically displaceable by a dimension corresponding to (depending on the dimension) the tooth height of the at least one axial tooth segment 47 and/or the teeth 1472 of the toothed ring 27 (corresponding to the dimension from the tooth root to the tooth tip) or corresponding to the dimension of the axial form-locking elements 147, 127 of the alternating axial projection or retraction (zurtkstehend). At least one axial form-locking element 147 of the first hand wheel 36, preferably the tooth tips 1471 of the teeth 1472 of at least one axial tooth segment 47, lies flush against the axial sliding surface 1362 or with respect to a sliding plane or is displaced back from the axial sliding surface 1362 in the axially unloaded state (while the axial form-locking element 147 is not in engagement). In the axially loaded state (in this case by screwing the second or inner hand wheel 38 onto the positioning bolt 34 and the at least one tooth segment 47 being loaded by means of an axial displacement of the axial stop surface 138), at least one axial form-locking element 147 of the first hand wheel 36, preferably the tooth point 1471 of the teeth 1472 of the at least one axial tooth segment 47, projects beyond the axial sliding surface 1362, in particular a tooth height substantially corresponding to the tooth height of the teeth 1472 of the tooth segment 47 and/or a tooth height substantially corresponding to the tooth height of the toothed ring 27.

At least one axial form-locking element 147 of the first hand wheel 36 is held by a spring tongue or by an axially elastically displaceable spring tongue 46 on the first hand wheel 36, in particular wherein the spring tongue 46 has a stop face 146 for the second hand wheel 38, in particular the axial stop face 138, advantageously the axial stop ring 1380 of the second hand wheel 38, on the side facing away from the form-locking element 147. The spring tongue 46 extends in a circumferential direction around the rotation axis 134. One end of the spring tongue 46 is fixedly connected to the first hand wheel 36, and the other end is free and carries a tooth segment 47.

The eccentric 30 has a support means 1300, in particular an axial stop face 1301, in particular an axial ring face 1302, which is provided for supporting the form-locking connection 1470, in particular the corresponding axial form-locking element 127 of the chain wheel cover 26, preferably at least indirectly the axial toothed ring 27 of the chain wheel cover 26, in particular the corresponding axial ring face 1260 of the chain wheel cover 26 (for supporting the corresponding axial form-locking element 127), in particular against excessive deformation, in particular against deformation which enables an offside snap-in of the form-locking connection 1470.

In the fixed state of the chain tensioner 28 (see fig. 5a, b), the axial gap a between the support means 1300 and the corresponding axial ring surface 1260 of the chain wheel cover 26 (which supports the corresponding axial form-locking element 127 of the chain wheel cover 26, in particular the toothed ring 27) is smaller by a fraction than the axial height h of the corresponding form-locking element or of the tooth segments 47 or the teeth 1472 of the toothed ring 27. In particular, the clearance a is at most the teeth of the tooth segment 47 or the toothed ring 271472 tooth height h is half, preferably less than one fifth. The distance h between the axial stop surface 138 or the axial stop ring 1380 of the inner hand wheel 38 and the corresponding axial stop surface 136 of the outer hand wheel 36₂(see fig. 5b) is zero in the clamped state (see fig. 5 b). In the unclamped state, spacing h₁(see fig. 4b) corresponds at least to the tooth height h, the clearance a being the same here.

The first and

second wheels

36, 38 and the chain wheel cover 26 are held together in a loss-proof manner, in particular as an assembly 260 (see fig. 2), and can be removed from the chainsaw 10. At least the stop element 32 and the eccentric 30 are held together in a loss-proof manner, in particular as an assembly 540, in particular by means of a preferably shoulder-bearing bush 54 and can be removed from the chainsaw 10.

Accordingly, a chain tensioner 28 is disclosed for tensioning the saw chain 16 and for securing the saw blade 14 to the housing 12 of the chainsaw 10 in a position that ensures a desired chain tension. The chain tensioner 28 can be fastened to the positioning bolt 34 or the housing 12 by means of a second or outer handwheel 38. The rotary connection between the outer hand wheel 36 and the eccentric 30 is configured as a

claw clutch

31, 37. The inner and

outer handwheels

36, 38, which are designed as loss prevention assemblies 260, can thus preferably be easily separated and connected together with the chain wheel cover 26 from an assembly 540, which is likewise designed as loss prevention, the assembly 540 being formed in particular from the eccentric 30 and the stop plate 32 and being held together by the sleeve 54, and at the same time also comprising the saw blade 14 secured to the stop plate 32 by means of the screw 64.

By rotating the outer hand wheel 36 together with the eccentric 30 in the clockwise direction or in the (+) direction according to fig. 1 or fig. 7a, the saw blade 14 can be moved in the direction of increasing distance from the sprocket 22 or towards the saw blade tip, thereby gradually tensioning the saw chain 16 (and vice versa for slackening). The rotational resistance at the outer hand wheel 36 is increased if the saw chain 16 substantially rests against the longitudinal edge of the saw blade 14 (in this state the saw chain can also be raised by typically a few millimeters, preferably 3-4mm, from the longitudinal edge of the saw blade 14 under a tensile force normal to the longitudinal edge of the saw blade 14 in order to ensure that the saw chain 16 has little friction on the saw blade 14, but is reliably swivelled). Thereafter, the inner hand wheel 38 can be tightened further on the set screw 34 axially toward the housing 12. In this case, the inner handwheel loads and clamps the saw blade 14 in the desired position on the housing 12 axially in the direction of the positioning screw 34. During the tightening, the axial clamping surface 135 of the inner handwheel 38 is pressed against the corresponding clamping surface 131 of the eccentric 30. The axial clamping surface 132 of the eccentric 30 in turn transmits this pressure force to a corresponding clamping surface 1320 of the stop plate 32. The axial clamping surface 1321 of the stop plate 32 presses in turn against the corresponding clamping surface 140 of the saw blade 14. The saw blade 14 is finally pressed with its axial clamping surface 141 against the housing-side clamping plate 168 and is thus fixed to the clamping surface 1680 of the clamping plate 168. As a result, the saw blade 14 is fixed at least indirectly via the inner handwheel 38 to the housing 12 of the chainsaw 10 when the second or inner handwheel 38 is tightened.

Furthermore, when the second or inner handwheel 38 is screwed, the axial stop surface 138 of the inner handwheel 38 is also pressed in the direction of the corresponding axial stop surface 136 of the first or outer handwheel 36. During the tightening, the axial stop face 138 of the inner hand wheel 38 first contacts the axial stop face 146 of the spring tongue 46 of the outer hand wheel 36 or three axial stop faces 146 of the spring tongue 46 of the outer hand wheel 36. The spring tongues 46 each carry an axial tooth segment 47 on the side opposite the stop face 146. The axially elastically displaceable spring tongue 46 projects in the direction of an axial stop face 138 of the inner handwheel 38 in the initial state or in a state not yet axially clamped by the inner handwheel 38. As a result, the axial tooth segments 47 are not yet engaged in the corresponding axial toothed ring 27 of the sprocket cover 26, and an axial form-locking connection is not yet produced. The outer handwheel 36 can thus be rotated without resistance and the desired position of the eccentric 30 or the longitudinal position of the saw blade 14 or the chain tension can be adjusted in this way in a simple manner. The stop face 146 of the spring tongue 46 projects beyond the stop face 136 by about 1-2mm, in particular by about 1.4mm, in the unloaded state. This corresponds approximately to the tooth height of the teeth 1472 of the tooth segment 47.

By tightening the inner hand wheel 38, the axially elastically displaceable spring tongues 46 are axially displaced and the tooth segments 47 engage in the corresponding axial toothed ring 27 of the sprocket cover 26. Rotation of the outer hand wheel 38 relative to the sprocket cover 26 is now prevented by the intermeshing of the tooth segments 47 and the toothed ring 27 (see fig. 5a, b). Axially elasticThe spring tongue 46, which is displaced in a sliding manner, is also prestressed in the direction of the inner handwheel 38 or the axial stop face 138 or the axial stop ring 1380 thereof, since it is displaced/clamped in an elastic manner in the axial direction by an amount of 1-2mm, in particular 1.4 mm. This can act against rotation (drehhemesend) on the inner handwheel 38, almost as an axially prestressed securing ring on the axial stop face 138 of the inner handwheel 38. Over-extension of the axially elastically displaceable spring tongue 46 of the outer hand wheel 36

Or overloading is precluded, since the inner hand wheel 38 bears not only against the spring tongue 46 but also over a large area against the flat axial stop face 136 of the outer hand wheel 36. This almost achieves overload protection and eliminates an over-displacement, which can sometimes lead to a fracture of the spring tongue 46. Thus, the tightening of the inner and/or

outer handwheels

36, 38 can be carried out completely without an offside detent clutch (as is known from the prior art) which is sometimes susceptible to wear or the chain tensioner 28 is insufficiently tightened, because, for example, the user's hand force required for an offside detent is selected to be insufficient or too small.

Fig. 4a to 5b show a schematic cross section of the chainsaw 10 in the region of the chain tensioning device 28 in a perspective view and in a side view (transversely to the longitudinal direction of the saw blade 14), while fig. 6 shows a longitudinal section (in the longitudinal direction of the saw blade) which is offset by 90 ° in relation thereto. Fig. 4a, b and 6 show the chain tensioner 28 in an undamped state, while fig. 5a, b show the chain tensioner in a clamped state. A set bolt 34 is anchored in the housing 12. The positioning screw has an external thread, by means of which the remaining chain tensioning device 28 is fixed or clamped to the chain saw 10. An internally threaded part 35, in particular of metal, is mounted on the inner hand wheel 38. The internal thread element is anchored in a rotationally fixed and non-captive manner in an inner hand wheel 38, which is in particular also made of plastic. The internal thread 35, with which the internal hand wheel 38 projects through the recess 1360 (see fig. 8) of the outer hand wheel 36 in order to apply an axial pressing force to the corresponding counter-clamping surface 131 of the eccentric 30, projects circumferentially and axially opposite the catch lug 39, and the internal hand wheel 38 has an axial clamping surface 135 (see fig. 3), in particular an axial stop ring 1380.

An eccentric 30 with a helical radial stop face 29 is supported on a lateral support projection 33 of a stop plate 32. The stop plate 32 is fixed to the flat side of the saw blade 14 by screws 64. Furthermore, the stop plate 32 engages with a fastening projection 133, which projects laterally toward the saw blade 14, into the elongated hole 15 of the saw blade 14 and is supported in the elongated hole on the front edge of the elongated hole. Thus, when the stop face 29 of the eccentric 30 rolls relative to the support projection 33, the stop plate 32 together with the saw blade 14 is moved more or less forward in the longitudinal direction depending on the eccentricity of the eccentric 30 and thus the saw chain 16 guided by the saw blade 14 is tensioned more or less tightly, depending on: how the spacing between the saw blade 14 and the sprocket 22 changes.

The outer hand wheel 36 is held axially but rotatably on the sprocket cover 26. For this purpose, the radial latching projections 1361 (here three latching projections arranged offset by 120 ° from one another, see in particular fig. 8b) bridge corresponding form-locking means of the inner handwheel 38 in the form of radial rings 1270 (see fig. 2, 3). The radial ring 1270 carries the toothed ring 27, in particular, slightly radially outwardly offset. The toothed ring is arranged on the side of the sprocket cover 26 facing the inner and

outer handwheels

36, 38. The corresponding axially elastically displaceable tooth segments 47 of the outer hand wheel 36 can engage in a form-locking manner in the toothed ring. This takes place with three axial tooth segments 47 which are machined on the ends of the spring tongues 46 oriented in the circumferential direction into the flat bottom of the outer hand wheel 36, which is advantageously bowl-shaped, in particular made of plastic. Each tooth segment 47 carries an axial toothing, which engages in the axial teeth of the toothed ring 27 and is fixed thereto. Undesirable over-riding jamming, especially in the event of very high forces during operation of the chain saw, is prevented, in particular, by: on the counter side of the axial toothing of the sprocket cover 26 or the toothed ring 27, an axial support ring is arranged, which has an axial ring surface 1260. The axial support ring/axial ring face is constructed in particular integrally with the sprocket cover 26. The annulus 1260 is provided for support on a corresponding axial annulus 1302 of the eccentric 30. At least in the unloaded state, a small axial gap a is provided between the respective ring surfaces 1260, 1302, in this case less than the tooth height, in particular a small fraction of the tooth height, in particular less than 1mm, preferably about 0.1 to 0.3 mm. As soon as large forces occur during operation of the chain saw 10, which sometimes lead to deformation of the sprocket cover 26 and/or the toothed ring 27, axial displacement of the toothed ring 27 axially away from the toothed segments 47 or axial displacement of the toothed segments 47 axially away from the toothed ring 27 is substantially prevented, in particular because the respective ring surfaces 1260, 1302, which are separated by the axial gap a by a small gap, are limited to a small dimension, which is preferably significantly smaller than the tooth height of the teeth 1472 of the toothed ring 27 or of the respective toothed segments 47.

To replace the saw chain 16, the inner hand wheel 38 is rotated in the loosening direction (counterclockwise or (-) with reference to fig. 7 a) for such a long time that the internal thread piece 35 is completely released from the set bolt 34. As soon as the axial form-locking connection 1470 is removed, in particular between the axial form-locking element 147 or the axial tooth segment 47 and the corresponding axial form-locking element 127 or the axial toothed ring 27, the outer hand wheel 36 can be rotated in the counterclockwise direction in order to loosen the saw chain 16. Subsequently, the sprocket cover 26 together with the outer and

inner handwheels

36, 38 can be removed axially from the positioning screw 34, in particular as an assembly 260. The second assembly 540 may then be separated and the saw chain 16 may be replaced, maintenance performed, etc. therein.

Claims

1. A chain tensioner (28) for a chain saw (10) having two hand wheels (36, 38), in particular two hand wheels (36, 38) which are held against loss and which are advantageously surrounded in a bowl-shaped manner and which are preferably designed as outer and inner hand wheels (36, 38), which can be rotated relative to one another about a common axis of rotation (134), wherein a first of the two hand wheels (36), in particular the outer hand wheel (36), is provided for the rotation of an eccentric (30) which is designed for the longitudinally displaceable displacement of a stop (32) which can be fastened to a saw blade (14) of the chain saw (10) relative to a sprocket (22) of the chain saw (10) which is flush with the saw blade (14), in order to adjust the chain tension of a saw chain (16) of the chain saw (10), and wherein at least one second of the two hand wheels (38), In particular an inner hand wheel (38), is provided for fastening the chain tensioner (28) to the chain saw (10), in particular by screwing onto a positioning bolt (34) of the chain saw (10), wherein the chain tensioner (28) further has a chain wheel cover (26) on which the first hand wheel (36) can be locked in a form-locking manner against rotation, in particular wherein the first hand wheel is held in a loss-proof manner on the chain wheel cover (26), characterized in that the first hand wheel (36) can be coupled in a form-locking manner with the chain wheel cover (26) in the direction of the axis of rotation (134) by means of an axial form-locking connection (1470), in particular can be coupled in a form-locking manner with at least one axial form-locking element (147), preferably an axial tooth segment (47), which engages into a corresponding axial form-locking element (127) of the chain wheel cover (26), Preferably an axial toothed ring (27).

2. Chain tensioner (28) according to claim 1, characterized in that at least one axial tooth segment (47) of the first hand wheel (36), in particular of the first hand wheel (36), can be fixed axially with a form-fit relative to the sprocket cover (26) by means of the second hand wheel (36), in particular by means of an axial stop face (138) of the second hand wheel (38), advantageously by means of an axial stop ring (1380).

3. Chain tensioner (28) according to claim 1 or 2, characterized in that at least one axial form-locking element (147) of the first hand wheel (36), preferably the at least one axial tooth section (47), is axially elastically displaceable relative to an axial stop face (136) of the first hand wheel (36), in particular in a dimension corresponding to the tooth height (H) of the teeth (1472) of the at least one axial tooth section (47).

4. Chain tensioner (28) according to at least one of the preceding claims, characterized in that at least one axial form-locking element (147) of the first hand wheel (36), preferably the tooth tip (1471) of the teeth (1472) of the at least one axial tooth segment (47), is placed flush against or set back from the axial sliding surface (1362) of the first hand wheel (36) in the axially unloaded state, and projects beyond the axial sliding surface (1362) of the first hand wheel (36) in the axially loaded state, in particular projects substantially corresponding to the tooth height (H) of the teeth (1472) of the tooth segment (47).

5. Chain tensioner (28) according to at least one of the preceding claims, characterized in that at least one axial form-locking element (147) of the first hand wheel (36) is held by an axially elastically displaceable spring tongue (46) on the first hand wheel (36), in particular wherein the spring tongue (46) has a stop face (146) for the second hand wheel (38), in particular the axial stop face (138), advantageously an axial stop ring (1380) of the second hand wheel (38), on the side facing away from this form-locking element (147).

6. Chain tensioner (28) according to at least one of the preceding claims, characterized in that the eccentric (30) has a support means (1300), in particular an axial stop face (1301), in particular an axial ring face (1302), which is provided for supporting the form-locking connection (1470), in particular a corresponding axial form-locking element (127) of the chain wheel cover (26), preferably an axial toothed ring (27) of the chain wheel cover (26), in particular a corresponding axial ring face (1260) of the chain wheel cover (26), in particular against excessive deformation, in particular against deformation enabling an offside snap-in of the form-locking connection (1470), wherein the corresponding axial ring face of the chain wheel cover serves to support the corresponding axial form-locking element (127).

7. Chain tensioner (28) according to claim 6, characterized in that the axial gap (a) between the support means (1300) and the corresponding axial ring surface (1260) of the sprocket cover (26) for supporting the corresponding axial form-locking element (127), in particular the sprocket ring (27), of the sprocket cover (26) is smaller than a small part, in particular at most half, preferably less than one fifth, of the tooth height (H) of the tooth segment (47) or of the tooth (1472) of the sprocket ring (27).

8. Chain tensioner (28) according to at least one of the preceding claims, characterized in that the first and second hand wheels (36, 38) and the chain wheel cover (26) are held captive to each other, in particular as an assembly (260) and removable from the chain saw (10), and/or at least the stop (32) and the eccentric (30) are held captive to each other, in particular as an assembly (540), in particular by means of a sleeve (54) preferably with a shoulder and removable from the chain saw (10).

9. A chainsaw (10) having a chain tensioning device (28) according to any of the preceding claims.