WO2012144942A1

WO2012144942A1 - A clamping assembly for a chainsaw

Info

Publication number: WO2012144942A1
Application number: PCT/SE2011/050490
Authority: WO
Inventors: Pär MARTINSSON; Joakim Persson
Original assignee: Husqvarna Ab
Priority date: 2011-04-21
Filing date: 2011-04-21
Publication date: 2012-10-26

Abstract

A chain saw has a hand grip (5) engaging a stud bolt from a main saw body (1) for tightening a clutch cover (9) and a guide bar (4) against the main body (1). In one preferred embodiment the hand grip (5) is captively held in the cover (9) by retaining member (40) and cannot get lost. In another or the same preferred embodiment, the hand grip (5) includes two pivotal levers (10, 11) that are interconnected to be rotated in opposite directions from an inner collapsed position to an outer exposed position and back. The levers (10, 11) are biased toward both positions by means of at least one torsion spring (15, 16), which also provides the interconnection of the levers (10, 11). With no increase in hand grip size, the use of two levers (10, 11) increases the applied torque with about 50 %.

Description

A CLAMPING ASSEMBLY FOR A CHAINSAW

DESCRIPTION TECHNICAL FIELD

The present invention relates to a chainsaw comprising:

- a main body;

- a guide bar for guiding a saw chain wound around the guide bar, said guide bar having an elongated opening and defining a longitudinal axis;

- a stud bolt fixedly attached to the main body and extending transversely to the guide bar and through the elongated opening;

- a hand grip defining a rotational axis and including a nut member threadedly engaging said stud bolt, which hand grip can be tightened by rotation on said stud bolt to clamp the guide bar onto the main body and which can be released to permit displacement of the guide bar along said longitudinal axis so as to enable tensioning/slackening of the saw chain; and

- a cover member, wherein the hand grip is intended to clamp the cover member together with the guide bar onto the main body. It also relates to a chainsaw comprising:

- a main body;

- a stud bolt fixedly attached to the main body and extending transversely to the guide bar and through the elongated opening; and

- a hand grip threadedly engaging said stud bolt, which hand grip can be tightened by rotation on said stud bolt to clamp the guide bar onto the main body and which can be released to permit displacement of the guide bar along said longitudinal axis so as to enable tensioning/slackening of the saw chain.

It further relates to a guide bar clamping assembly comprising: - a guide bar for guiding a saw chain wound around the guide bar, said guide bar defining a longitudinal axis and having an elongated opening for receiving a stud bolt, the stud bolt being fixedly attached to a main body of a chainsaw;

- a hand grip defining a rotational axis and being adapted to threadedly engage the stud bolt, which hand grip can be tightened by rotation on said stud bolt to clamp the guide bar onto the main body and which can be released to permit displacement of the guide bar along said longitudinal axis so as to enable tensioning/slackening of the saw chain; and

- a cover member, wherein the hand grip is intended to clamp the cover member together with the guide bar onto the main body.

BACKGROUND ART

A conventional chain saw includes a body and a guide bar that supports the saw chain. A cover clamps the guide bar to the body by means of a tightening arrangement, comprising a bar bolt and a nut. For some reasons, e.g. for changing bars or if the chain has come off, the cover may have to be detached from the body. Before the cover can be detached, the tightening arrangement has to be loosened such that the nut is detached from the bar bolt.

A problem with conventional tightening arrangements, for which the nut is loose when detached from the bar bolt, is that an operator of the tool might lose the nut when detaching the cover from the body, especially if situated in a forest. The operator often puts the nut on the ground after detaching it from the bar bolt, and since the ground is usually covered by brushwood and scrub, finding the nut again may be difficult. Two arrangements for which the nut is carried by the cover, and consequently cannot be lost when detaching the cover, are disclosed in US 2010/023934. In the first version, the nuts are provided with hooks engaging protruding portions in a bore for the bar bolt through the cover, and the hooks permit a complete loosening of the nut from the bolt without simultaneously getting loose from the cover. In the second version, a spring connects the nut to the cover. The length of the spring between where it is fixed to the cover and where it is fixed to the nut is sufficient to permit a removal of the nut from the bolt. A disadvantage with this arrangement is that the chain saw operator has to use a wrench to loosen and tighten the nut. Another solution is disclosed in EP 2 036 688 A2, where a combined clamping/tensioning device is operative ly associated with a guide bar/saw chain assembly in such a manner that operation of the clamping/tensioning device acts to apply a predetermined tension to the saw chain, and then clamp the guide bar against the main body of the saw. The clamping/tensioning device includes a circular clamping knob, the circumference of which has alternating ridges and grooves to provide a grip between the thumb and the index finger of a hand of the user of the saw. In order to re-tension the chain the user turns the tensioning/clamping knob about half a turn in the anti-clockwise direction, so as to unclamp the guide bar, and then turns the knob in the clockwise direction, thereby applying correct tension to the saw chain, and thereafter by continued clockwise turning of the knob (thanks to a slip ring) the guide bar is clamped against a clamping surface of the main body. A problem with this solution is the difficulty of applying sufficient torque by hand to manage clamping the guide bar properly.

Other solutions for unclamping/clamping the guide bar and simultaneously tensioning the saw chain with a single rotary knob are disclosed in US 6,564,459 Bl and GB 2 403 686 A, for example. To facilitate the loosening and tightening of the knob, it has been suggested to use a wing knob as shown in US 5,522,143, US 7,434,502, US 7,107,689,US 6,560,879, for example. As an alternative to a wing knob, it has been suggested to use a lever extending

diametrically over the knob. As shown in US 7,600,323, the lever may be pivoted at one end and biased against an end surface of the knob by a spring, and a detent mechanism may be provided for maintaining the lever in a position where extends outward from the periphery of the knob. After use of the lever, the spring returns it to the original lever position across the knob. Especially when the operator is wearing gloves, it may be difficult to sense when the outer exposed position is entered completely and the snap lock is engaged. If the outer exposed position never was completely entered, a biasing spring will return the lever to its inner collapsed position when the operator releases his grip of the knob. This means that the operator will have to pull out the lever again when changing his grip.

Alternatively, as shown in US 7,676,934 and CN 200991925 Y, for example, the lever may be displaceable longitudinally to project outward from the knob periphery in order to increase the loosening and tightening force of the operator's hand.

Knobs having no lever make it difficult for an operator to apply sufficient torque to securely fix the clutch cover, which may result in a loose guide bar. With knobs having a pivotal lever biased against its position of rest by a spring, inexperienced operators may fold out the lever several times during loosening/tightening, and if left in its folded out position, the lever may easily fall back to its inward position, so that the operator has to take a new grip to open the lever again. SUMMARY OF THE INVENTION

One main object of the present invention is to provide a chainsaw having a cover member clamping the guide bar to the main body, wherein the cover member is a part of a cover assembly which assembly also includes a rotary hand grip for tightening of the guide bar onto the main body, and wherein the cover assembly is arranged in a manner such that no parts of the assembly will come loose and risk getting lost when disassembling the cover member from the main body of the chain saw without using any tools. In a chainsaw of the kind referred to in the first paragraph above this object is achieved in that in accordance with the present invention the hand grip is captively attached to the cover member by means of a retaining member, which permits at least the nut member of the hand grip to be displaced axially, i.e. along the rotational axis, a first maximum distance in relation to the cover member. By attaching the hand grip captively to the cover member, an assembly is formed, from which no parts of the assembly will come loose and risk getting lost when demounting the cover assembly from the chain saw without using any tools.

This object is also reached by a guide bar assembly referred to in the third paragraph above, wherein the hand grip is captively attached to the cover member by means of a retaining member, which permits the hand grip to be displaced axially, i.e. along the rotational axis, a first maximum distance in relation to the cover member. By attaching the hand grip captively to the cover member, an assembly is formed, from which no parts of the assembly will come loose and risk getting lost when demounting the cover assembly from the chain saw without using any tools.

Upon rotation of the hand grip, the nut member is movable a second maximum distance on the threaded portion of the stud bolt, and a ratio between the first maximum distance and the second maximum distance is larger than 0.3, suitably larger than 0.5, preferably larger than 0.7, and most preferably larger than 0.9. In an even more preferred embodiment, the first maximum distance is larger than the second maximum distance. Said relations between the first and the second maximum distances have proved to simplify mounting of the cover member to the main body as well as demounting. This, if having a captive hand grip, i.e. a hand grip that is retained to the cover member. Specifically, by arranging the retaining member such that the first maximum distance is larger than the second maximum distance, the nut member, upon demounting of the cover member, can be unscrewed completely before removing the cover member from the main body. This implies that the cover member can be kept in the same position as when clamped to the main body when turning the hand grip, which is favorable. Also, upon mounting of the cover member, the cover member can be put in place against the main body before having the nut member engage a threaded portion of the stud bolt and thus providing for simplified mounting.

To retain the hand grip to the cover member, the retaining member suitably includes at least one hook member.

Preferably, the retaining member is either a resilient member, such as a spring having at least two parallel axially extending hook members, or a washer having at least two parallel axially extending hook members. Thereby, as an example, it will be possible to attach the hand grip to the cover member simply by providing the hand grip with a special design retaining member and then insert the hand grip with the hook members in openings of suitable shape in the cover member.

A second main object of the present invention is to provide a chainsaw, wherein the hand grip, which is used for making a cover member clamp the guide bar against the main body of the chain saw, is designed so as to require less torque by the operator.

In a chainsaw of the kind referred to in the second paragraph above, this object is achieved in that in accordance with the present invention the hand grip comprises a first and a second movable grip member, each of which is movable along a path between an inner collapsed and an outer exposed position, the first movable grip member and the second movable grip member in their inner collapsed positions extending a first distance (Al and Bl, respectively) from a rotation axis of the hand grip, in their outer exposed positions they extend a second distance (A2 and B2, respectively) from the rotation axis, and the second distances are longer than the first distances. The distances being measured perpendicular to the rotation axis.

Thereby, the hand grip can be comparatively small and still enable applying the desired torque. In their outer exposed position, the two movable grip members provide good ergonomics and simplify for the operator to tighten the hand grip with sufficient torque. In comparison to hand grips having a single moveable grip member, two moveable grip members give a higher torque and more reliable clamping of the guide bar. In their inner collapsed position, the two movable grip members provide a knob-shaped hand grip having a substantially flat end surface, which is favorable, since neither the knob-shaped hand grip nor the two movable grip members will be in the way when operating the chainsaw.

Suitably, a ratio between one of the second distances and the associated first distance is larger than 1.2, preferably larger than 1.4, and most preferred larger than 1.6. Although at least one of the first and the second movable grip members may be pivotally mounted to a body member of the hand grip, it is preferred that both the first and the second movable grip members are pivotal about a first and a second pivot axis respectively, and that the axes are separated from each other and distanced from the rotational axis of the hand grip, and that said pivot axes preferably are substantially parallel.

For ergonomic reasons it is also suitable that movements of the first and the second movable grip members between their respective inner collapsed and their respective outer exposed positions correspond to rotations of at least 90° and preferably at least 110° and even more preferably at least 130° of respective movable grip member.

It is preferred that the movable grip members, when they are between respective first intermediate positions of the movable grip members and the respective inner collapsed positions, are biased towards their respective inner collapsed positions. Similarly it is preferred that the movable grip members, when they are between respective second intermediate positions of the movable grip members and the respective outer exposed positions, are biased towards their respective outer exposed positions. In this way, the grip members will not unintentionally be pulled out during operation. Also, the operator will easily put the grip members in their outer exposed positions. This, without needing to sense when the grip members snap into position (as for snap lock solutions), which may be difficult if e.g. wearing gloves. The risk that the grip members will be unintentionally be folded back to the collapsed position because of failing to enter the stable outer exposed position is therefore reduced, which means the operator will not need pull the grip members out again when changing his/her grip of the hand grip.

To reduce the number of components in the hand grip, it is preferred that one and the same biasing member acts to urge at least one of the first and the second movable grip members towards both the respective inner collapsed and outer exposed positions. Alternatively, two biasing members are both involved in urging the first and the second movable members towards both the respective inner collapsed positions and the outer exposed positions.

The first and the second movable grip members are preferably coupled to each other in a manner such that a movement of one grip member will move the other at least throughout substantial parts of the respective motion paths of the first and the second movable grip members. This is especially advantageous when starting from a collapsed position of the movable grip members and intending to pull out the members towards the outer exposed position, as the operator only needs to grip of one of respective end portions of the movable members.

Also for the same reason, the first and the second movable grip members are suitably coupled in a manner such that one member rigidly moves with the other at least when moving from the inner collapsed positions towards the outer exposed positions and at least for positions of the movable grip members close to the respective inner collapsed positions. A rigid connection is more rugged than a resilient one and preferable when starting the movement from the inner collapsed positions, at least at low environmental temperatures.

The first and the second movable members are preferably coupled in a manner such that when moving one member, the other moves in an opposite direction at least throughout a portion of the respective motion paths of the first and the second grip members. In addition, the movable grip members preferably are coupled by means of at least one resilient member, which acts both to have one of the first and the second movable grip members move with the other and to bias the first and the second movable grip members towards their respective inner collapsed and outer exposed positions. This is favorable as very few components are needed.

In a preferred embodiment, the hand grip is captively attached to a cover member, such as a clutch cover or sprocket cover, the hand grip being arranged to clamp the cover member together with the guide bar onto the main body. By attaching the hand grip captively to the cover member, an assembly is formed, from which no parts of the assembly will come loose and risk getting lost when demounting the cover assembly from the saw without using any tools.

The hand grip is suitably captively attached to the cover member by means of a retaining member, either a resilient member such as a spring having at least two axially extending parallel hooks or a washer having at least two axially extending parallel hooks. Thereby, as an example, it will be possible to attach the hand grip to the cover member simply by providing the hand grip with a special design retainer and then insert the hand grip with the spring in openings of suitable shape in the cover plate. Specifically, when the cover member is put in place against the main body of the chainsaw, and the nut member has not yet been screwed onto the bar bolt, the resilient member preferably is arranged to press the nut member against the bar bolt so as to simplify engagement of the nut member and bar bolt. Preferably, the resilient member, when the nut member is unscrewed completely and the cover member is put in place against the main body, is also arranged to hold the nut member and hand grip in a suitable orientation for simplifying engagement of the nut member with the bar bolt upon rotation of the hand grip.

If desired, the cover member is provided with a separate tensioner means for displacing the guide bar. Then, the tensioner means suitably is a tensioning wheel accessible from the outside of the chainsaw and operatively coupled to a tensioning mechanism, which preferably is housed in or attached to the cover member. A separate tensioner is less prone to malfunction than an automatic tensioner. Alternatively, a tensioning mechanism may be coupled to the hand grip in a manner such that rotation of the hand grip also is associated with a displacement of the guide bar and thereby tensioning of the chain. Such tensioning arrangement may be preferred by an inexperienced operator, who may find it difficult to adjust to a desired tension of the chain. Preferably, an opening for the hand grip through the cover assembly has a collar portion disposed essentially on a front side of the hand grip towards the guide bar. The collar portion suitably extends over at least 120° with respect to the rotational axis of the hand grip and more preferably approximately 180°. In this way, the interior portion of the hand grip will be protected from being hit by branches or getting stuck in twigs or the like. Most favourable is 150°- 180 °, which implies good protection of the interior portion of the hand grip as well as providing for easy gripping of one of the movable grip members.

Another object of the present invention is to provide a hand grip for a chainsaw of the kind described above.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail with reference to preferred embodiments and the appended drawings. Figs, la and lb are perspective views of a preferred embodiment of a chainsaw according to the present invention and including a cover assembly having a captively attached hand grip with two grip members that are movable between an inner collapsed and an outer exposed position (Fig. la and lb, respectively) in the hand grip. Fig. 2 is a side view of the chainsaw of Fig. 1 having a cover with the hand grip removed to illustrate the attachment of the guide bar to the main body of the chainsaw. Fig. 3 is a perspective view of the main body of the chainsaw having a stud bolt for attachment of the guide bar.

Figs. 4a and 4b are perspective views the cover assembly of Figs, la and lb, respectively.

Figs. 5a and 5b are exploded views from different angles of the cover assembly of Figs. 4a and 4b.

Fig. 6 is a top view of the hand grip of Figs. 1, 4 and 5 having the two grip members in their outer exposed position.

Fig. 7 is a cross sectional view taken along line VII- VII in Fig. 6.

Fig. 8 is a cross sectional view taken along line VIII- VIII in Fig. 6.

Fig. 9 is a cross sectional view taken along line IX-IX in Fig. 6.

Fig. 10 is a side view of the hand grip of Fig. 6. Fig. 11 is a cross sectional view taken along line XI-XI in Fig. 6.

Fig. 12 is a top view of the hand grip of Fig. 6 having the two grip members in an

intermediate position between the outer exposed position and the inner collapsed position.

Fig. 13 is a cross sectional view taken along line XIII-XIII in Fig. 12.

Fig. 14 is a top view of the hand grip of Figs. 6 and 12 having the two grip members moved to the inner collapsed position.

Fig. 15 is a cross sectional view taken along line XV-XV in Fig. 14.

Figs. 16 and 17 are perspective views of a hand grip including another preferred

embodiment of a retainer member having hook members for captively attaching the hand grip to a cover member.

Fig. 18 is an exploded view of details in an arrangement for providing the retaining

function in the hand grip of Figs. 16 and 17. Fig. 19 is a horizontal cross sectional view through the cover member with the captive ly attached hand grip in a position, where the hand grip is tightened by screwing onto a stud bolt of the chainsaw main body to clamp the saw chain guide bar against the main body.

Fig. 20 is a view of an enlarged section of Fig. 19 and shows the hand grip in its tightened position with the hook members inactive.

Fig. 21 is a horizontal cross sectional view similar to Fig. 19, but with the hand grip in a position where the hand grip is loosened to release the saw chain guide bar to permit tensioning of the chain.

Fig. 22 is a view of an enlarged section of Fig. 21 and shows the hand grip in its loosened position with the hook members active, i.e. stopped from further movement away from the cover member, to prevent the hand grip to come loose from the cover member.

Fig. 23 is a section of a perspective view showing the stud bolt and the support pins

protruding from the main body.

MODE(S) FOR CARRYING OUT THE INVENTION

The chainsaw shown in Figs, la and lb comprises a main body 1 housing an engine or electric motor, not shown, a guide bar 4 having an elongated opening 3 shown in Fig. 2 and defining a longitudinal axis, and a saw chain, not shown, wound around the guide bar 4 and driven by a sprocket 6, likewise shown in Fig. 2. A stud bolt 2, best shown in Figs. 3 and 23, has a treaded portion 2a and is fixedly attached to the main body 1 and extends transversely to the guide bar 4 and through the elongated opening 3. Also, two support pins 7 and 8 protrude from the chainsaw body 1 and are arranged to be received through similar elongated openings, or the same elongated opening 3, in the guide bar 4. A hand grip 5 includes a body member 12 having an embedded, or at least in any way attached, nut member 12' (best shown in Figs. 5b and 9), which threadedly engages said stud bolt 2, whereby the hand grip 5 can be tightened by rotation on the stud bolt 2 to clamp the guide bar 4 onto the main body 1 and be released to permit displacement of the guide bar 4 along the longitudinal axis so as to enable tensioning/slackening of the saw chain. Instead of being embedded or attached, the nut member 12' may be made integral with the body member 12, i.e. the body member has an internal thread matching the one of the stud bolt 2, provided that the body member is made of a sufficiently strong material. For some applications, aluminum can be used. Further, the chainsaw comprises a cover member 9, which together with the guide bar 4 is clamped by the hand grip 5 against the main body 1.

A preferred embodiment of the cover member 9 is best shown in Figs. 4a and 4b, where it together with the hand grip 5 forms an assembly to be described later. The hand grip 5 comprises a first and a second movable grip member 10 and 11, respectively, each of which is movable between an inner collapsed and an outer exposed position. In comparison to hand grips having a single moveable grip member, two moveable grip members enable a higher torque and more reliable clamping of the guide bar 4. As shown in Fig. 14, the first movable grip member 10 and the second movable grip member 11 in their inner collapsed positions extend a first distance Al and Bl, respectively, from a rotation axis of the hand grip 5. Similarly, in their outer exposed positions as shown in Fig. 10, the first movable grip member 10 and the second movable grip member 11 extend a second distance A2 and B2, respectively, from the rotation axis, and the second distance is longer than the first one, i.e. A2 > Al and B2 > Bl. The ratio A2/A1 and B2/B1 between one of the second distances A2, B2 and the associated first distance Al, Bl is suitably larger than 1.2, preferably larger than 1.4, and most preferably larger than 1.6, although advantageous are also larger than 1.3, 1.5 or 1.7. The first and the second movable grip members 10 and 11 have grip portions 10' and 11', respectively, which when the movable grip members 10 and 11 are in their outer exposed positions, are separated by at least 130° with respect to the rotation axis, and preferably separated by at least 150° and more preferably by substantially 180° as shown in Fig. 6. The grip portions 10' and 11' preferably have suitable structures, such as ribs, for improving the grip of the hand of the operator.

Although both of the movable grip members 10 and 11 could be movable in their longitudinal directions between the inner collapsed positions and the outer exposed positions, suitably at least one of the movable grip members is pivotally mounted to the body member 12 of the hand grip 5. However, as is obvious from the drawings, it is preferred that both of them are pivotally mounted to the body member 12.

The first and the second movable grip members 10 and 11 are pivotal on shafts 13 and 14, respectively, mounted in the hand grip body member. The shafts 13 and 14 are separate from each other and have pivotal axes 13' and 14', respectively, which are spaced from the rotational axis of the hand grip 5. The pivot axes preferably are substantially parallel and equidistantly spaced from the rotational axis of the hand grip 5 and located adjacent the periphery of the hand grip 5. The exploded views of Figs. 5a and 5b show the components of a cover assembly including the cover member 9 and the hand grip 5 except for the shafts 13 and 14. However, the shafts are shown in most of the subsequent cross sectional views. To the left in Figs. 5a and 5b, a thermal shield 9' is shown, which is to surround the hand grip 5 radially and can be attached to the cover member 9 by means of screws.

The movements of the first and the second movable grip members 10, 11 between their respective inner collapsed and their respective outer exposed positions suitably correspond to rotations of at least 90° and preferably at least 110° and even more preferably at least 130° of respective movable grip member. In the embodiment shown in Fig. 10, a most preferred value of 140° is used. Then, the two movable grip members 10, 11 are spread an angle preferably between 90° and 110° and more preferred approximately 100° from each other, i.e. longitudinal axes of the grip members together form said angle, which angle is seen from a side view as in Fig. 10. Suitably, the movable grip members 10, 11, when they are between respective first intermediate positions of the movable grip members 10, 11 and the respective inner collapsed positions, are biased towards their respective inner collapsed positions. Further the movable grip members 10, 11, when they are between respective second intermediate positions of the movable grip members 10, 11 and the respective outer exposed positions, are biased towards their respective outer exposed positions. To provide the biasing force, one and the same biasing member 15 or 16 conveniently acts to urge at least one of the first and the second movable grip members 10, 11 towards both the respective inner collapsed and the outer exposed positions. Preferably, one and the same biasing member acts to urge one and the same movable grip member towards both the inner collapsed position and the outer exposed position.

Additionally, the movable grip members 10, 11 may be coupled by means of at least one resilient member, which acts both to have one of the first and the second movable grip members 10, 11 move with the other and to bias the first and the second movable grip members 10, 11 towards their respective inner collapsed and outer exposed positions.

Consequently, anyone of the two biasing members 15 and 16, or both of them, can be said to be said at least one resilient member. This is achieved in that torsion springs 15, 16 in the general shape of those used in clothespins are used as biasing members. As best shown in Fig. 5a, such torsion springs 15, 16 have a central helical spring portion 17 terminated at each end by a spring leg 18 extending away from each other substantially at right angles to the helical spring portion 17 and ended by a transverse hook 19. The two hooks 19 are parallel to the helical spring portion 17 and to each other and extend away from each other. As best shown in Fig. 14, the hand grip 5 is knob-shaped and rotational symmetric, and the two movable grip members 10 and 11 are identical and mounted side by side flush fitted in the knob 5. As best shown in Fig. 5b and subsequent cross sectional views, the grip members 10 and 11 have a generally channel- shaped cross section, and at one end they have a transverse through tube 20 and 21, respectively, projecting outwards at one side for receiving the pivotal shaft 13 and 14, respectively. On the exterior bottom side of each of the tubes when the grip members are in their inner collapsed position, there is a longitudinal ridge 20' and 21', respectively, in which one of the hooks 19 of the biasing member 15 or 16 is fixed. The other hook 19 is fixed at a corresponding position inside the other generally channel-shaped grip member. Consequently, the two movable grip members 10, 11 are coupled in a manner such that when moving one member, the other moves in an opposite direction at least throughout a portion of the respective motion paths of the first and the second grip members 10, 11, and preferably the whole of the said motion paths. The cross sectional view in Fig. 14 shows the location of the biasing torsion spring 16 at the bottom of the knob 5 when the movable grip members 10, 11 are in their inner collapsed position. Fig. 13 shows that when the movable grip members 10, 11 is located at a position between the inner collapsed one and the outer exposed one, the biasing torsion spring 16 is lifted from its former bottom position. When finally the grip members 10, 11 are moved to their outer exposed end position shown in Fig. 10, the biasing torsion spring 16 is lifted to a top position as shown in Fig. 11. When the biasing torsion springs 15, 16 move upward and downward, the central helical portion 17 of the springs is laterally supported by guide surfaces extending upward from the bottom of the body member 12 of the hand grip 5. By careful selection of the locations where the hook 19 ends of the biasing torsion springs 15, 16 are attached to the movable grip members 10, 11, it is possible to make the resulting spring force change direction from biasing the grip members 10, 11 against the inner collapsed position to biasing them against the outer exposed position, and the other way around, when moving the grip members 10, 11 from one position to the other. Thus, the first and the second movable grip members 10, 11 are coupled to each other in a manner such that a movement of one of the grip members will resiliently move the other at least throughout parts of the respective motion paths of the first and the second movable grip members 10, 11. The first and the second movable grip members 10, 11 are also coupled in a manner such that one member rigidly moves with the other at least when moving from the inner collapsed positions towards the outer exposed positions and at least for positions of the movable grip members 10, 11 close to the respective inner collapsed positions. As is best shown in Fig. 4b, a rigid connection can be provided by a cam surface 36, 36' on each one of the grip members 10, 11, respectively, and a cooperating cam follower 37, 37', respectively, on the other. The cam surface or the cam follower may be a transversally projecting peg 36, 36', for example. Although the two movable grip members 10, 11 are identical, the pegs 36, 36' do not prevent their movement, because in an angular sector between the inner collapsed position and a position near where the pegs 36, 36' would knock against each other (and where the torsion springs 15, 16 take over the coupling), the rotation of one of the grip members 10, 11 has proceeded longer than that of the other. A rigid connection is more rugged than a resilient one and preferable when starting the movement from the inner collapsed positions, at least at low environmental temperatures.

In a preferred embodiment, the hand grip 5 is captively attached to the cover member 9, such as a clutch cover or sprocket cover, in such a manner that the hand grip 5 upon tightening will clamp the cover member 9 together with the guide bar 4 onto the main body 1. By attaching the hand grip 5 captively to the cover member 9, an assembly is formed, from which no parts of the assembly will come loose and risk getting lost when demounting the cover assembly from the saw without using any tools. Preferably, the hand grip 5 is captively attached to the cover member 9 by means of a resilient member such as a spring 22. The preferred spring is basically flat and is best shown in Figs. 5a and 5b. It has an annular central portion 23 with three equiangularly spaced spring arms 24, which first curve along the periphery of the annular center 23 to the vicinity of the next arm and then curve back radially outside thereof almost to their starting points. From there, they extend generally at right angles upward, if the annular center 23 is in a horizontal plane, and the free arm ends are curved outwards-downwards to form hooks 25 for attachment of the spring to the edge of a hole for the knob 5 through the cover member 9. These hooks are held in place by the thermal shield 9'. From two of the three starting points of the spring arms 24, two additional arms 26 extend first radially outward and then downward, and the free ends of these two additional arms 26 are curved outwards-upwards to form hooks 27 adapted to extend through the cover member 9 to the cover member side facing the main body 1 of the saw for attachment of the spring to the cover member 9.

Thus, when the nut member 12' is loosened so much that it does not engage the thread of the stud bolt 2, hooks 27 abut on the inner side of the cover member 9, i.e. the side facing the guide bar 4, while hooks 25 are lifted from their engagement with the outer side of the cover member 9 and project into a space formed between the cover member 9 and the thermal shield 9'. On the other hand, when the nut member 12' is tightened to a maximum on the thread of the stud bolt 2, hooks 27 are lifted from their engagement with the inner side of the cover member 9 and project into a space formed between the cover member 9 and the guide bar 4, while hooks 25 abut on the outer side of the cover member 9, thereby tensioning the spring 22.

As described above, the nut member 12' of the hand grip 5 is embedded in the bottom portion 12. As is best shown in Figs. 8 and 9, the nut member 12' has a lower cylindrical portion, on which the annular center 23 of spring 22 is fitted, and axially outside thereof a Belleville washer 28. The spring 22 and the Belleville washer 28 can rotate on the cylindrical portion of the nut but are kept in place in that the outermost end of the nut 12' is thin and is deformed radially outward. Thereby, the hand grip or knob 5 is captively attached to the cover member 9. Of course, it is immediately realized without any inventive activity that the captive attachment of the hand grip 5 to the cover member 9 to form a cover assembly is very useful also in cases where the hand grip 5 has other movable gripping members than 10 and 11 or even no movable gripping members at all. In the chainsaw shown in the drawings, the cover member 9 is provided with a separate tensioner means for displacing the guide bar 4 to tension the saw chain. As best shown in the exploded views of Figs. 5a and 5b, on that side of the cover member 9, which faces the main body 1 of the saw, the tensioner means includes a tensioning mechanism having a guide bar displacement screw 29 extending in the longitudinal direction of the guide bar 4. A mating nut 30 locked against rotation is mounted on the screw 29 to travel there along upon rotation of the screw. The nut member 30 has a peg 31 fitting in one of two matching bores 32 provided in the guide bar 4 and shown in Fig. 2. For rotating the screw 29, a tensioning wheel 33 for rotation by the fingers of an operator is attached on the outer side of the cover member 9 and extends therethrough, so as to operatingly engage the screw 29. More precisely, a gear is coaxially fixed to the wheel 33 and meshes with another gear fixed on the screw 29. The thermal shield 9' has an opening permitting access to the tensioning wheel 33.

Alternatively, a tensioning mechanism is coupled to the hand grip 5 in a manner such that rotation of the hand grip 5 also is associated with a displacement of the guide bar and thereby a tensioning of the chain. In view of the several examples of such couplings in the discussion of the prior art above, it is immediately realized without any inventive activity that such a coupling is possible and that it can be performed in several various ways.

Consequently, a figure illustrating such a coupling seems superfluous.

Further, as illustrated in Figs. 4a and 4b, the knob opening in the cover assembly (9 and 9') has a collar portion 34 disposed essentially on a front side of the knob 5. The front side is defined as the side directed towards a nose portion of the guide bar 4. The collar portion 34 is configured to surround approximately half of the circumference of the knob 5. In this way, the interior portion of the knob 5 will be protected from being hit by branches or getting stuck in twigs or the like. On the other hand, the back side of the knob opening has a collar portion 35 that is recessed as compared to the front side collar portion 34 and recessed as compared to the movable grip members 10 and 11. Such configuration enables an operator to easily grip an end portion 10' or 11' of at least one of the grip members 10 and 11, respectively. Both of the two collar portions 34 and 35 consist of an inner collar portion 34' and 35', respectively, included in the cover member 9 and an outer collar portion 34" and 35", respectively, included in the thermal shield 9'.

To assemble the cover assembly, the following steps are performed. First the movable grip members 10 and 11 and the torsion springs 15 and 16 are assembled to form a unit. Then, the unit is mounted in the body member 12 of hand grip 5 and locked pivotally therein by means of the pivotal shafts 13 and 14. In the next step, the flat spring 22 and the Belleville washer 28 are rotary mounted on the cylindrical portion of the embedded nut member 12', and the thin end of the nut member 12' is upset to retain the spring 22 and the washer 28 on the nut member. Thereafter the obtained hand grip unit and the tensioning wheel 33 are mounted in the cover member 9 and prevented from falling out by placing the thermal shield 9' on the cover member 9 and securing it by screws. Then the chain tensioner mechanism 29-31 is mounted in the cover member 9 from the reverse side and lock with a sheet metal plate (not shown). Finally, the obtained cover assembly is mounted on the main body 1 of the chainsaw.

In the embodiment shown in Figs. 1-15, the hand grip 5 is captively attached to the cover member 9 by means of a retaining member in the form of a resilient member such as a spring 22, which is basically flat and has an annular central portion 23 with three equiangularly spaced spring arms 24 ending in hooks 25 for engaging the outer side of the cover member 9. Two additional arms 26 ending in hooks 27 extend from the annular center 23 through openings provided in the cover member 9 to engage the inner side of the cover member 9, so that the hand grip 5 is captively attached to the cover member 9.

Figs. 16-23 show another preferred embodiment of a hand grip 39 including a retaining member 40 in the shape of a washer 41 having two axially extending parallel arms 42 ending in hooks 43 for captively attaching the hand grip to a cover member 9. More precisely, as shown in the drawings, each arm has a forked end with two springy tins, each of which has a hook. As shown in Figs. 16-18, the retaining member 40 in addition has two parallel guide arms 44, which extend axially from the washer 41 and are parallel with the hook arms 42. The guide arms 44 extend through openings, not shown, provided in the cover member 9 for guiding the hand grip 39 and preventing it from becoming upset when it upon rotation moves axially in the cover member 9.

Like in the embodiment shown in Figs. 8 and 9, the nut member 39' of the hand grip 39 has a lower cylindrical portion, on which the washer 41 of the retaining member 40 is fitted, and axially outside thereof a Belleville washer 28. The retaining member 40 and the Belleville washer 28 can rotate on the cylindrical portion of the nut, but are kept in place in that the outermost end of the nut 39' is thin and is deformed radially outward. Instead of being embedded in the hand grip 39, it may be made integral therewith, provided that the handgrip is made of a sufficiently strong material. For some applications, aluminum can be used.

As shown in Figs. 19-22, the hook arms 42 extend through openings (not shown) in the cover member 9. In Figs. 19 and 20, the hand grip 39 is tightened by screwing onto a stud bolt 2 (Fig. 23) of the chainsaw main body 1 to clamp the saw chain guide bar 4 against the main body 1. The axial outer end of the hand grip 39 is almost flush with the thermal shield 9' of the cover member 9. As is best shown in Fig. 20, in the tightened position of the hand grip 39, the hooks 43 are inactive. In Figs. 21 and 22, the hand grip 39 is loosened to release the guide bar 4 to permit tensioning of the chain. In fact, the hand grip 39 is shown in its maximum outer position, where, the nut 39' is not in engagement with the thread of the stud bolt 2. It is also shown that in this position, the axial outer end of the hand grip 39 protrudes axially from the thermal shield 9', and the hooks 43 engage the inner surface of the cover member 9 to hold the hand grip 39 captively attached to the cover member 9.

Thus, both in the embodiment of Figs. 1-15 and that that of Figs. 1-22, the retaining member 40 permits a at least the nut member 12' or 39' of the hand grip 5 or 39,

respectively, to move axially a first maximum distance CI (Fig. 20) in relation to the cover member 9 to engage a threaded portion 2a of the stud bolt 2. Further, upon rotation of the hand grip 5 and starting from a tightened state, the nut member 20 is movable a second maximum distance C2 on the threaded portion 2a of the stud bolt 2 as shown in Fig. 23, wherein the tightened state corresponds to when the hand grip 5 and nut member 12' or 39' have been fully tightened to clamp the guidebar and cover member onto the main body. However, it should be appreciated that C2 is not necessarily the length of the threaded portion of the bolt 2, but the length that the nut member 12' or 39' travels along the central axis of the bolt 2 from the position corresponding to a tightened state and to the position for which the threads of the nut member 12' or 39' are no longer engaged with the threads of the bolt 2, or vice versa. The ratio C1/C2 between the first maximum distance CI and the second maximum distance C2 is larger than 0.3, suitably larger than 0.5, preferably larger than 0.7, and most preferably larger than 0.9. In the best mode, the first maximum distance CI is larger than the second maximum distance C2.

As described above, the nut member 12' or 39' has a lower cylindrical portion, on which the retaining member 40, such as spring 22 or washer 41 is fitted. The outermost end of the nut member 12' is a thin tubular extension, and is deformed radially outward to keep the retaining member 40 in place. If desired, it would of course be possible to provide a third embodiment of the retaining member 40 by increasing the length of the thin tubular extension to get the length CI, and to deform the outermost end of the tubular extension radially outwards to such an extent that it forms a flange, which holds a Belleville spring of a size such that it cannot pass outward through the wall of the cover member 9, or which is of a size that in itself is sufficient to prevent it from passing outward therethrough. Of course, the cover member opening, through which the tubular extension extends, is of a size adapted to the outer diameter of the tubular extension.

Alternatively, the retaining member comprises a cylindrically shaped portion (not shown in any of the figures) adapted to rotate with the hand grip 5, the cylindrically shaped portion having a flange at its distal end with respect to the hand grip 5, the flange together with the cover member 9 defining an end position for the hand grip 5. Said end position corresponds to the displacement CI of the nut member relative to the cover member.

In the embodiment shown in Figs. 16-22, the hand grip 39 is provided with a single movable grip member 45, best shown in Fig. 17, as an alternative to the movable two grip members 10 and 11 in the embodiment of Figs. 1-15. The choice of retaining member 40 is independent of whether an embodiment with one or two movable grip members is chosen. No matter the choice of retaining member 40, the hand grip 5 may be provided with at least one grip member which extends radially a distance beyond a general radius of the hand grip 5, wherein said distance is at least 20% of the general radius. More preferred are at least

30%, 50% or at least 70%. Moreover, no matter the choice of retaining member 40 the hand grip 5 may be provided with at least one movable grip member, which is movable between an inner collapsed position and an outer exposed position, wherein in the outer exposed position, the movable grip member extends a distance from the rotation axis of the hand grip 5 which is greater than a general radius of the hand grip 5. Preferably, said distance is greater than 1.2 times the radius, or even more preferred at least 1.4 or at least 1.7 times the radius. INDUSTRIAL APPLICABILITY

A problem with conventional tightening arrangements for clamping a guide bar for a saw chain against a body portion of a chainsaw is that the nut is loose when detached from the bar bolt and may get lost when detaching the cover from the body, especially if occurring in a forest. The operator often puts the nut on the ground after detaching it from the bar bolt, and since the ground is usually covered by brushwood and scrub, finding the nut again might be difficult. In such a case, the chainsaw of the present invention is especially applicable, since the nut is secured in a hand grip such as a knob, which is captively held in the cover and cannot get lost.

Claims

A chainsaw comprising:

- a main body (1);

- a guide bar (4) for guiding a saw chain wound around the guide bar (4), said guide bar (4) having an elongated opening (3) and defining a longitudinal axis;

- a stud bolt

(2) fixedly attached to the main body (1) and extending transversely to the guide bar (4) and through the elongated opening

(3);

- a hand grip (5) defining a rotational axis and including a nut member (30)

threadedly engaging said stud bolt (2), which hand grip (5) can be tightened by rotation on said stud bolt (2) to clamp the guide bar (4) onto the main body (1) and which can be released to permit displacement of the guide bar (4) along said longitudinal axis so as to enable tensioning/slackening of the saw chain; and

- a cover member (9), wherein the hand grip (5) is intended to clamp the cover

member (9) together with the guide bar

(4) onto the main body (1),

characterized in that the hand grip (5) is captively attached to the cover member (9) by means of a retaining member (40), which permits at least the nut member (12') of the hand grip (5) to be displaced a first maximum distance (CI) in relation to the cover member (9) along the rotational axis.

A chainsaw according to claim 1, wherein the nut member (20) upon rotation of the hand grip (5) and starting from a tightened state is movable a second maximum distance (C2) in threaded engagement with the stud bolt (2), and a ratio (C1/C2) between the first maximum distance (CI) and the second maximum distance (C2) is larger than 0.3, suitably larger than 0.

5, preferably larger than 0.7, and most preferably larger than 0.9.

A chainsaw according to claim 2, wherein the first maximum distance (CI) is larger than the second maximum distance (C2).

A chainsaw according to any one of claims 1-3, wherein the retaining member (40) includes at least one hook member (25, 27; 43).

A chainsaw according to claim 4, wherein the retaining member (40) is a resilient member, such as a spring (22), having at least two parallel axially extending arms (24, 26) ending in hooks (25, 27).

6. A chainsaw according to claim 4, wherein the retaining member (40) is a washer (41), having at least axially extending parallel arms (42) ending in hooks (43).

A chainsaw according to any one of claims 1-3, wherein the retaining member comprises a cylindrically shaped portion adapted to rotate with the hand grip (5), the cylindrically shaped portion having a flange at its distal end with respect to the hand grip (5), the flange together with the cover member (9) defining an end position for the hand grip (5).

A chainsaw according to any of claims 1-7, wherein the hand grip (5) is provided with at least one grip member which extends radially a distance beyond a general radius of the hand grip (5), wherein said distance is at least 20% of said general radius.

9. A chainsaw according to any of claims 1-7, wherein the hand grip (5) is provided with at least one movable grip member, which is movable between an inner collapsed position and an outer exposed position, wherein in the outer exposed position, the movable grip member extends a distance from the rotation axis of the hand grip (5) which is greater than a general radius of the hand grip (5).

10. A chainsaw comprising:

- a main body (1);

- a guide bar (4) for guiding a saw chain wound around the guide bar (4), said guide bar having an elongated opening (3) and defining a longitudinal axis;

- a stud bolt (2) fixedly attached to the main body (1) and extending transversely to the guide bar (4) and through the elongated opening (3); and

- a hand grip (5) threadedly engaging said stud bolt (2), which hand grip (5) can be tightened by rotation on said stud bolt (2) to clamp the guide bar (4) onto the main body (1) and which can be released to permit displacement of the guide bar (4) along said longitudinal axis so as to enable tensioning/slackening of the saw chain, characterized in that the hand grip (5) comprises a first (10) and a second (11)

movable grip member, each of which is movable between an inner collapsed and an outer exposed position, the first movable grip member (10) and the second movable grip member (11) in their inner collapsed positions extending a first distance (Al and Bl, respectively) from a rotation axis of the hand grip (5), in their outer exposed positions they extend a second distance (A2 and B2, respectively) from the rotation axis, and the second distances are longer than the first ones (A2 > Al and B2 > Bl).

11. A chainsaw according to claim 10, wherein a ratio (A2/A1; B2/B1) between one of the second distances (A2; B2) and the associated first distance (Al; Bl) is larger than 1.2, suitably larger than 1.4, and preferably larger than 1.6.

12. A chainsaw according to any one of claims 10-11, wherein at least one of the first and the second movable grip members (10 and 11) is pivotally mounted to a body member (12) of the hand grip (5).

13. A chainsaw according to claim 12, wherein the first and the second movable grip

members (10 and 11) are pivotable about a first and a second pivot axis (13', 14') respectively, wherein said axes (13', 14') are separated from each other and spaced from the rotational axis of the hand grip (5), and said pivot axes (13', 14') preferably being substantially parallel.

14. A chainsaw according to claim 13, wherein movements of the first and the second

movable grip members (10, 11) between their respective inner collapsed and their respective outer exposed positions correspond to rotations of at least 90° and preferably at least 110° and even more preferably at least 130° of respective movable grip member (10, 11).

15. A chainsaw according to any one of claims 10-14, wherein the movable grip members, (10, 11) when they are between respective first intermediate positions of the movable grip members (10, 11) and the respective inner collapsed positions, are biased towards their respective inner collapsed positions, and wherein the movable grip members, (10, 11) when they are between respective second intermediate positions of the movable grip members (10, 11) and the respective outer exposed positions, are biased towards their respective outer exposed positions.

16. A chainsaw according to any one of claims 10-15, wherein at least one biasing member (15, 16) acts to urge at least one of the first and the second movable grip members (10, 11) towards both the respective inner collapsed and outer exposed positions.

17. A chainsaw according to any one of claims 10-16, wherein the first and the second movable grip members (10, 11) are coupled to each other in a manner such that a movement of one of the grip members (10, 11) will resiliently move the other at least throughout parts of the respective motion paths of the first and the second movable grip members (10, 11).

18. A chainsaw according to claim 17, wherein the first and the second movable grip

members (10, 11) are coupled in a manner such that one member rigidly moves with the other at least when moving from the inner collapsed positions towards the outer exposed positions and at least for positions of the movable grip members (10, 11) close to the respective inner collapsed positions.

19. A chainsaw according to any one of claims 17 or 18, wherein the first and the second movable members (10, 11) are coupled in a manner such that when moving one member, the other moves in an opposite direction at least throughout a portion of the respective motion paths of the first and the second grip members (10, 11).

20. A chainsaw according to any one of claims 17-19, wherein the movable grip members (10, 11) are coupled by means of at least one resilient member (15, 16), which acts both to have one of the first and the second movable grip members (10, 11) move with the other and to bias the first and the second movable grip members (10, 11) towards their respective inner collapsed and outer exposed positions.

21. A chainsaw according to any one of claims 10-20, wherein the hand grip (5) is

captively attached to a cover member (9), such as a clutch cover or sprocket cover, by means of a retaining member (40), the hand grip (5) clamping the cover member (9) together with the guide bar (4) onto the main body (1).

22. A chainsaw according to claim 21, wherein the retaining member (40) is a resilient member (22), such as a spring having at least two axially extending parallel hooks (25, 27), or the retaining member (40) is a washer (41) having at least two axially extending parallel arms (42) ending in hooks (43).

23. A chainsaw according to any one of claims 1-9, and 21-22, wherein the cover member (9) is provided with a separate tensioner means (29-33) for displacing the guide bar (4), wherein the tensioner means (29-33) is a tensioning wheel (33) accessible from the outside of the chainsaw and operatively coupled to a tensioning mechanism (29-31), which preferably is attached to the cover member (9).

24. A chainsaw according to any one of claims 1-23, wherein a tensioning mechanism is coupled to the hand grip (5) in a manner such that rotation of the hand grip (5) also is associated with a displacement of the guide bar (4) and thereby tensioning of the chain.

25. A chainsaw according to any one of claims 1-24, wherein a collar portion (34)

surrounds part of the circumference of the hand grip (5), said collar portion (34) preferably extending over at least 120° with respect to the rotational axis of the hand grip (5) and more preferably approximately 180°.

26. A hand grip (5) for a chainsaw according to any one of claims 10-25.

27. A guide bar clamping assembly comprising:

- a guide bar (4) for guiding a saw chain wound around the guide bar (4), said guide bar (4) defining a longitudinal axis and having an elongated opening (3) for receiving a stud bolt (2), the stud bolt (2) being fixedly attached to a main body (1) of a chainsaw;

- a hand grip (5) defining a rotational axis and being adapted to threadedly engage the stud bolt (2), which hand grip (5) can be tightened by rotation on said stud bolt (2) to clamp the guide bar (4) onto the main body (1) and which can be released to permit displacement of the guide bar (4) along said longitudinal axis so as to enable tensioning/slackening of the saw chain; and

- a cover member (9), wherein the hand grip (5) is intended to clamp the cover

member (9) together with the guide bar (4) onto the main body (1),

characterized in that the hand grip (5) is captively attached to the cover member (9) by means of a retaining member (40), which permits the hand grip (5) to be displaced a first maximum distance (CI) in relation to the cover member (9) along the rotational axis.

28. A guide bar clamping assembly according to claim 27, wherein upon rotation and

starting from a tightened state, the hand grip (5) is movable a second maximum distance (C2) in threaded engagement with the stud bolt (2) along the rotational axis, and a ratio (C1/C2) between the first maximum distance (CI) and the second maximum distance (C2) is larger than 0.4, suitably larger than 0.6, preferably larger than 0.8, and most preferably the first distance (CI) is larger than the second distance (C2).

29. A chainsaw having the guide bar clamping assembly according to any one of claims 27- 28.