Patent Application
20140310965
The present invention relates to a chainsaw having an engine housing including an engine, a guide bar extending forwardly from the engine housing for guiding a saw chain driven by the engine, a front handle, a trigger handle including a throttle trigger for throttling the engine, and a front hand guard including a protective structure, projecting in front of the front handle, pivotably attached to the engine housing by at least one lever for releasing a brake to brake the movement of the saw chain when the front hand guard is pivoted.
The word “toggle” usually is a reference to a kind of mechanism or joint consisting of two arms, which are almost in line with each other, connected with an elbow-like pivot. In a phrase like “toggle switch”, it specifically refers to one kind of mechanism that can be used to implement a positive “snap-action”. In the present context, the term “toggle-link mechanism” is used to designate a snap-action mechanism consisting of three links or arms, which are almost in line with one another and biased against one another along said line.
The words “front” and “rear” are used to designate relative locations along a longitudinal axis of a handheld power tool such as a chain saw, for example. In a chain saw, the saw chain guide bar is located at front end of the saw, while the opposite end is the rear end of the saw.
The words “left” and right” are used to designate relative locations in relation to the longitudinal axis as if a user holds the chain saw.
Due to safety regulations chainsaws are equipped with a brake arrangement for stopping the movement of the chain if a kick back occurs. A front hand guard releases the kick back brake when pivoted. This may occur when the user's forehand hits the hand guard or due to the inertia of the hand guard from a rapid kickback. U.S. Pat. No. 5,984,054 shows an example of a chainsaw having a hand guard activated kick back brake.
Another example is shown in U.S. Pat. No. 5,233,750. Chainsaws such as the one disclosed in U.S. Pat. No. 5,233,750 are referred to as top handle saws. A top handle chainsaw is mainly used in trees in combination with a climbing harness or in a skylift. The saw is then used in different positions for example pruning branches. To prevent unnecessary damage to the tree it is desirable to have a good sight on the cutting equipment in all positions. A hand guard may disturb the view presented to the user of the area in which the chainsaw is to be used.
Sometimes the chainsaw is tied to a rope to hoist the saw to the desired location. In such situations a problem that may occur is that objects such as twigs or branches may get stuck in the hand guard and thereby cause damage to the tree or hindering the hoisting process. Twigs may also get stuck in other situations when operating the chainsaw. This is undesirable.
There is therefore a need for arranging a motor driven chainsaw with a hand guard that does not unduly hinder the user from viewing the work area while also reducing the risk of the saw getting stuck or unnecessary damage the tree when in use or during hoisting.
An object of the invention is to provide a chainsaw with a hand guard which at least minimizes one of the problems stated above, while considering present and expected safety regulations.
In a chain saw of the kind referred to in the introductory portion above, this object is achieved by providing a protective structure that includes:
A front hand guard with such a protective structure is particularly suitable for top handle saws, i.e. where the trigger handle (6) is located on top of the housing.
Preferably the see through means is provided by having at least one opening in the protective structure enabling at least partial visibility through the protective structure.
Preferably the at least one opening is at least five openings, preferably more than 10 openings, more preferably more than 20 openings. Thereby visibility through the protective structure is improved.
Preferably the openings forms at least 30%, preferably at least 50% of the protective structure's forward facing area.
The shapes of the openings can be of any shapes, for instance circular or polygonal, preferably hexagonal shapes.
Preferably the twig preventing means is provided is provided by having the protective structure void of any openings larger than 4 cm2, preferably void of any openings larger than 2 cm2, more preferably void of any openings larger than 1 cm2, even more preferably void of any openings larger than 0.5 cm2. The smaller the openings are the less the risk is for a twig or similar object to get stuck in the protective structure.
Alternatively at least one of the at least one opening has a opening area larger than 4 cm2, and where the twig preventing means is provided by covering at least the largest opening in the protective structure, and where the see through means are provided by having a transparent material as the covering material, preferably at least openings larger than 4 cm2 are covered by a transparent material. Preferably the numbers of the at least one opening are less than five.
Alternatively the see through means is provided by having the protective structure made in a transparent material, where preferably the protective structure is void of any openings.
Preferably the protective structure is pivotably attached to the engine housing by two spaced apart levers, preferably to the crankcase of the engine. Thereby any side covers of the engine housing, e.g. the clutch cover, can be easily removed without dismantling the hand guard.
Preferably the guide bar extends from the right hand side of the engine housing and the protective structure is located to the left of the guide bar enabling an operator free vision of the guide bar, preferably to the left of the trigger handle. Thereby the vision of the guide bar is improved for the user.
Preferably at least one of the levers includes a stop member adapted to cooperate with a corresponding stop surface at the engine housing to set a limit for the pivotal movement of hand guard. Thereby the brake mechanism is subjected to less wear when the kick back brake is engaged by pivoting the hand guard.
In the following, the invention will be described in more detail with reference to preferred embodiments and the appended drawings.
a-6d shows examples of the inner surface of a hand guard.
The trigger handle 6 includes a throttle trigger 7 and a throttle trigger lock 8 and is attached to the upper part of the engine housing. The throttle trigger lock 8 has to be pressed down to permit the throttle trigger 7 to move, thereby preventing an inadvertent throttling of the engine 3. The top handle 6 extends in the forward direction and is approximately located in the middle above the chainsaw 1 as best seen in
Behind the clutch cover 9 there is a brake drum (not shown) rotatably mounted on the engine housing. The outside of the drum is used for braking, while the inside is affected by the engine's centrifugal clutch (not shown) and the drum is operatively connected to a sprocket (not shown) for driving the saw chain.
The protective structure 21 includes see through means 24 in the form of a pattern of openings 35 (see e.g.
In
The first 25 of the two levers 25, 26 has circular hole 30 at its lower end to interact with a corresponding sprint (not shown) at the engine crank case 4 for pivotally joining the first lever 25 to it, and is at its upper end secured to the right lower end of the front protective structure 21. The first lever further includes a clutch coupling 28 for interacting with a hand guard coupling 15 such as e.g. shown in
As seen in
a-6d shows a number of examples of the pattern of openings 35 providing the see through means 24. In
According to a further embodiment the entire protective structure 21 is made in a transparent material, preferably a transparent polymer. Thus the inner surface 23 and the frame 22 are of the same material, where preferably the inner surface 23 is without any openings. Such an embodiment efficiently prevents objects such as twigs to get stuck in the hand guard while enabling vision through the hand guard. A disadvantage with such a solution is that transparent polymers that are strong enough are comparably expensive.
According to a further embodiment the protective structure 21 is a frame structure with comparably large openings, i.e. openings that would allow twigs to get stuck in the protective structure 21. However, these large openings are covered by a transparent material, preferably a polymer, i.e. as a window with a reinforcing frame. The advantage with such a solution is that the frame could be made in a strong less expensive non transparent material, while the transparent material does not need to be as strong since its purpose is only to prevent twigs to get stuck in the frame while enabling clear vision through the protective structure. Also one big opening is feasible covered by a transparent material on one side or on two sides. The latter creating a both flat and strong box structure 1.
Whereas the invention has been shown and described in connection with the preferred embodiments thereof it will be understood that many modifications, substitutions, and additions may be made which are within the intended broad scope of the following claims. From the foregoing, it can be seen that the present invention accomplishes at least one of the stated objectives.
Preferably, the protective structure's height is shorter than its width to securely protect the front handle 5 while minimizing the visual disturbance of it by keeping it low, i.e. it has as an oblong shape.
Preferably the front hand guard 20 is made in a reinforced polymeric material. Preferably casted as a single unit for instance by injection moulding.
Further, the protective structure 21 could be without the outer frame 22 or to have it only partly circumcise the inner surface 23, for instance only at the top and side portions of it. Also the protective structure 21 may include inner frames to strengthen the inner surface 23.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13054463 | Mar 2011 | US |
| Child | 14320383 | US |
