TECHNICAL FIELD

Embodiments herein relate to the field of chain saws, and, more specifically, to a chain saw comprising a chain sharpening member configured to sharpen links of a saw chain as they traverse a drive sprocket of the chain saw.

BACKGROUND

Chain saws are typically used to fell trees, trim branches, and cut various materials. In order to maintain a proper cutting efficiency, frequent sharpening of a saw chain of a chain saw is necessary. The sharpening process may be performed manually or automatically.

WO2012122061 A2 discloses a chain saw comprising a chain sharpening member arranged for sharpening various links of a top-sharpenable saw chain while the saw chain is mounted on a drive sprocket and guide bar of the chain saw. The chain sharpening member is positioned within the housing of the chain saw so as to contact the various saw chain links as they traverse a drive sprocket.

SUMMARY OF THE INVENTION

An object of the embodiments herein is to provide an improved chain saw providing a simplified automatic chain sharpening procedure. The chain saw shall be easy to manufacture at a low cost, and comprise a minimum of components.

According to a first aspect the object is at least partially achieved by means of a chain saw comprising a chain sharpening member connected to a body portion of the chain saw and arranged for sharpening links of a saw chain mounted on a guide bar and a drive sprocket of the chain saw. The chain sharpening member is selectively displaceable from a resting position in which the chain sharpening member is separated from the saw chain, to a sharpening position in which the chain sharpening member engages one or more links of the saw chain as the links traverse the drive sprocket. The chain saw furthermore comprises a chain brake mechanism and a front hand guard pivotably connected to the body portion and operatively connected to the chain brake mechanism. The front hand guard is selectively pivotable relative to the body portion from an idle position associated with an inactivated state of the chain brake mechanism to a first activated position associated with an activated state of the chain brake mechanism. The chain saw is characterized in that the front hand guard is operatively connected to the chain sharpening member and in that the front hand guard is selectively pivotable relative to the body portion from the idle position associated with the resting position of the chain sharpening member to second activated position associated with the sharpening position of the chain sharpening member.

Since the front hand guard is operatively connected to the chain sharpening member, there is no need for a separate actuator for activating the chain sharpening member. The front hand guard is already present in all chain saws. Accordingly, a simple chain saw comprising a minimum of components is provided.

The reduced number of components facilitates cost-efficient manufacture of the chain saw.

The operator can easily reach and pivot the front hand guard when he or she wants to initiate a chain sharpening operation. Thereby, an enhanced usability of the chain saw is provided as compared to a chain saw in which the chain sharpening arrangement requires a separate lever.

Furthermore, the reduced number of components facilitates manufacturing a chain saw having a reduced weight. A reduced weight results in a chain saw which is more convenient to use for the operator. According to some embodiments the chain sharpening member comprises a front hand guard engaging portion and a chain sharpening portion.

According to some embodiments the chain sharpening portion is pivotable relative to the body portion about a first pivot axis, and the front hand guard is pivotable relative to the body portion about a second pivot axis. The front hand guard comprises an engagement portion, configured to selectively engage the front hand guard engaging portion and to activate rotation of the chain sharpening portion about the first pivot axis upon rotation of the front hand guard about the second pivot axis.

Thereby, an efficient mechanical construction which is easy to manufacture is achieved. According to some embodiments the chain sharpening member comprises a biasing member. The biasing member is configured to delimit a force exerted by the chain sharpening member on the links when the chain sharpening member is in the sharpening position.

Thereby, the risk of premature wear of the saw chain and/or the sharpening member is reduced. Even if the operator presses the front hand guard unnecessarily hard towards the second activated position, the pressure that the chain sharpening member exerts on the saw chain is delimited. According to some embodiments a first end of the front hand guard engaging portion is pivotably connected to the chain sharpening portion in a first pivot point and the biasing member interconnects a second end of the front hand guard engaging portion and a biasing member receiving portion of the chain sharpening portion. According to some embodiments the front hand guard engaging portion and a sharpening element holding portion of the chain sharpening portion are integrally formed.

Thereby a simple chain sharpening member which can be manufactured at a low cost is achieved. According to some embodiments a first end of the front hand guard engaging portion is pivotably connected to the chain sharpening portion in a first pivot point, and a second end of the front hand guard engaging portion is slidably connected to the engagement portion of the front hand guard. According to some embodiments the engagement portion of the front hand guard comprises an elongate opening, arranged to slidably receive a pin member connected to the second end of the front hand guard engaging portion.

Thereby, manufacturing of a compact engagement portion is facilitated, so as to enable provision of additional space between the front hand guard and a front handle of the chain saw.

According to some embodiments the first pivot axis and the second pivot axis coincide.

According to some embodiments the first pivot axis is separated from the second pivot axis. Still other objects and features of embodiments herein will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits hereof, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. DEFINITIONS

As used herein, the following terms have the following meanings:

The forward, rearward, upward and downward directions refer to directions as seen by an operator holding the chain saw in an operating position.

The longitudinal direction of the chain saw is the direction in which the guide bar extends. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments herein will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings, in which:

Fig. 1 is a partial perspective view of chain saw according to a first embodiment, with a chain sharpening member in a resting position and the hand guard in an idle position. Figs. 2 and 3 show the chain sharpening member in a sharpening position and the hand guard in a second activated position.

Fig. 4 shows the chain sharpening member in a resting position, and the hand guard in a first activated position.

Fig. 5a is a partial perspective view of a chain saw according to a second embodiment, with a chain sharpening member in a resting position and the hand guard in an idle position.

Fig. 5b shows the chain sharpening member of Fig. 5a in a sharpening position and the hand guard in a second activated position.

Fig. 5c shows the chain sharpening member of Figs. 5a and 5b in a resting position, and the hand guard in a first activated position.

Fig. 6a is a partial perspective view of a chain saw according to a third embodiment, with a chain sharpening member in a resting position and the hand guard in an idle position. Fig. 6b shows the chain sharpening member of Fig. 6a in a sharpening position and the hand guard in a second activated position. Fig. 6c shows the chain sharpening member of Figs. 6a and 6b in a resting position, and the hand guard in a first activated position.

DESCRIPTION OF PREFERRED EMBODIMENTS

In Fig. 1 a chain saw 100 in accordance with a first embodiment is illustrated.

As shown in Fig. 1 , the chain saw may be a battery driven chain saw, but it is to be understood the chain saw could also comprise a combustion engine or a motor driven by mains electricity.

The chainsaw 100 comprises a body portion 110, a guide bar 400, and a drive sprocket 500. A saw chain 300 is mounted on the guide bar 400 and the drive sprocket 500. The guide bar 400 is only partly shown in Fig.1 (and in the other Figs, as well). Furthermore, in order to make the components of embodiments herein visible, a clutch cover, which is mounted to the body portion so as to cover the drive sprocket and the proximal part of the guide bar during operation of the chain saw, is omitted in Fig.1 (and in the other Figs, as well).

The saw chain 300 may include various links 310, for example, cutting links having a cutting edge that is suited for top surface sharpening.

The saw chain is driven around the guide bar 400 by the drive sprocket 500 during operation. In Figs 2-6, the saw chain 300 is only schematically illustrated.

The chain saw 100 may have a rear handle and a front handle. A front hand guard 600 is arranged in front of the front handle. In a conventional manner, the front hand guard is selectively pivotable relative to the body portion 110 about a pivot axis 900 and is configured to protect a hand of the operator during use of the chain saw and to function as an actuator of a chain brake mechanism (not shown in the figures).

The chain brake mechanism is used to prevent movement of the saw chain e.g. by applying a steel brake band around a driven clutch drum of the chain saw. Clamping force for the brake band may be provided by a spring. The chain brake mechanism has two purposes. First, it can be used to secure the chain when changing position, moving between cuts or starting a cold saw, which requires a partly open throttle. This would otherwise lead to uncontrolled chain movement, a major hazard in older saws. Secondly, the chain brake can activate under kickback conditions to prevent the operator from being 5 struck by a running chain.

The chain brake mechanism may be activated by the front hand guard 600 being pushed forward from an idle position 650 towards a first activated position 660 to engage the brake, and pulled back to disengage. The spring-loaded action allows powerful braking 10 under emergency conditions and can halt a chain under full power in a fraction of a

second.

The chain brake mechanism may be activated deliberately by the operator, or

automatically by the force of a kickback event. In the former, the operator usually rotates

15 his left wrist and knocks the front hand guard 600 forward with the back of his hand, resetting it by reaching forward with his fingers to pull the top hand guard backwards. In the case of a kickback event the operator's left hand may be violently dislodged from the handle and the top hand guard will be thrown onto his hand, forcing activation of the chain brake mechanism. The chain brake mechanism may also be configured so as to be

20 activated in other ways, such as an "inertia" chain brake mechanism which will allow

activation of the chain brake mechanism even if the operator's left hand is not removed from the handle.

The front hand guard 600 may also be referred to as a kickback lever 600 or a top hand 25 guard 600. It may also be referred to as a hand guard 600.

According to various embodiments herein, a chain sharpening member 200 may be rotatably connected to the body portion of the chain saw, and pivotable about a pivot axis 800. The chain sharpening member may be positioned proximate to the drive sprocket 30 500.

According to various embodiments herein, the front hand guard 600 comprises an engagement portion 610, configured to selectively engage a front hand guard engaging portion 210 and to activate rotation of the chain sharpening portion 220 about the first pivot axis 800 upon rotation of the front hand guard 600 about the second pivot axis 900 from an idle position 650 to a second activated position 670.

Hereinafter, the pivot axis of the chain sharpening member is referred to as a first pivot 5 axis 800, and the pivot axis of the front hand guard 600 is referred to as a second pivot axis 900.

In the embodiments shown in the figures herein, the first pivot axis 800 is separate from the second pivot axis 900. According to an alternative embodiment the first 800 and the 10 second pivot axes 900 coincide.

The first 800 and the second 900 pivot axes may be essentially parallel. According to some embodiments, the first and the second pivot axes are essentially perpendicular to a longitudinal direction of the chain saw.

15

The chain sharpening member may comprise a chain sharpening portion 220 and a front hand guard engaging portion 210.

According to various embodiments herein, the front hand guard 600 comprises an 20 engagement portion 610, which is configured to selectively engage the front hand guard engaging portion 210 and to activate rotation of the chain sharpening portion 220 about the first pivot axis 800 upon rotation of the front hand guard 600 about the second pivot axis 900.

25 According to some embodiments the engagement portion 610 is a plate member 610 attached to a lower end of the front hand guard. The engagement portion may have a shape which is adapted to cooperate with the chain sharpening member

The chain sharpening portion 220 may comprise a sharpening element holding portion 30 222. A sharpening element, such as a grinding stone (not shown) may be detachably or permanently attached to the sharpening element holding portion 222. The sharpening element may have a curved surface, so as to fit to the curvature of the chain as it traverses the drive sprocket. The chain sharpening portion is selectively pivotable about the first pivot axis 800, from a resting position 250 to a chain sharpening position 260. The chain sharpening portion 220 may be biased, e.g. spring loaded, towards the resting position 250 of the chain sharpening member.

The body portion 110 may comprise recesses or protrusions configured so as to define surfaces on which the chain sharpening member may abut when it is in the resting position. Fig. 1 is a partial perspective view of a chain saw 100 according to a first embodiment, with a chain sharpening member in a resting position 250 and the hand guard in an idle position 650. The chain brake mechanism, which is not shown, is inactivated when the front hand guard is in the idle position. Accordingly, Fig .1 illustrates a chain saw in a state to perform a normal cutting operation.

Fig. 2 illustrates a state in which the operator has pressed the front hand guard rearwardly from the idle position 650 towards a second activated position 670, so as to bring the chain sharpening member 200 to its chain sharpening position 260. The chain brake mechanism is not activated in this state, and the chain is free to move around the guide bar and drive sprocket.

According to the embodiment shown in Figs. 1 -4, the chain sharpening member comprises a biasing member 230. The biasing member is configured to delimit a force exerted by the chain sharpening member on the links when the chain sharpening member is in the sharpening position. The functionality of the biasing member 230 is illustrated by Fig. 3.

Fig. 3 shows a state in which the front hand guard is pressed more than necessarily towards the second activated position. Then, the biasing member 230 activates and delimits the movement of the chain sharpening portion 220 towards the links of the chain 300.

Thereby, the risk of premature wear of the saw chain and/or the sharpening member is reduced. Even if the operator presses the front hand guard unnecessarily hard towards the second activated position, the pressure that the chain sharpening member exerts on the saw chain is delimited.

The biasing member 230 may be a coil spring

As shown in Figs. 1 -4, the front hand guard engaging portion 210 of the chain sharpening member 200 may comprise a lever 210.

A first end 211 of the lever 210 may be pivotably connected to the chain sharpening portion 220 in a first pivot point 213. The biasing member 230 may interconnect a second end 212 of the front hand guard engaging portion 210 and a biasing member receiving portion 221 of the chain sharpening portion 220.

When the operator releases the rearwardly directed pressure on the front hand guard 600, the chain sharpening member 200 will return to its resting position 250, and the front hand guard will return to its idle position 650.

The state of the chain brake mechanism is not influenced by pivoting of the front hand guard between the idle position and the second activated position. The only way for the front hand guard to activate the chain brake mechanism is by pivoting from the idle position towards the first activated position.

Figs. 5a- 5c illustrate a chain saw according to a second embodiment. In Fig. 5a the chain sharpening member is in a resting position and the front hand guard is in an idle position.

Fig. 5b shows the chain sharpening member of Fig. 5a in a sharpening position and the front hand guard in a second activated position.

Fig. 5c shows the chain sharpening member of Figs. 5a and 5b in a resting position, and the hand guard in a first activated position.

The chain sharpening member of Figs. 5a-5c differs from the chain sharpening member of Figs. 1 -4 in that the front hand guard engaging portion 210 and a sharpening element holding portion 222 of the chain sharpening portion 220 are integrally formed in the embodiment shown in Figs 5a-5c. Thereby a simple chain sharpening member which can be manufactured at a low cost is achieved. The front hand guard engaging portion 210 may comprise a protrusion 214, arranged to engage the engagement portion 610 of the front hand guard, when the front hand guard is pivoted towards the second activated position. The front hand guard engaging portion may also comprise a slight recess 215 arranged to receive a portion of the engagement portion when the front hand guard is pivoted from the idle position to the first activated position. The provision and

configuration of the protrusion 214 and recess 215 ensures that the chain sharpening member is influenced by pivoting of the front hand guard from the idle position to the second activated position, whereas the chain sharpening member is not influenced by pivoting of the front hand guard from the idle position to the first activated position.

Figs. 6a- 6c illustrate a chain saw according to a third embodiment.

In Fig. 6a the chain sharpening member is in a resting position and the front hand guard is in an idle position.

Fig. 6b shows the chain sharpening member of Fig. 6a in a sharpening position and the front hand guard in a second activated position.

Fig. 6c shows the chain sharpening member of Figs. 6a and 6b in a resting position, and the hand guard in a first activated position. According to the embodiment shown in Figs. 6a-6c, the front hand guard engaging portion 210 may comprise a lever 210. A first end 211 of the lever 210 may be pivotably connected to the chain sharpening portion 220 in a first pivot point 213 , and a second end 212 of the front hand guard engaging portion may be slidably connected to the engagement portion 610 of the front hand guard.

The engagement portion 610 of the front hand guard may comprise an elongate opening 611 , arranged to slidably receive a pin member connected to the second end 212 of the front hand guard engaging portion 210. Although certain embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope. Those with skill in the art will readily appreciate that embodiments may be implemented in a very wide variety of ways. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that embodiments be limited only by the claims and the equivalents thereof.