Battery-powered chainsaw comprising a brake assembly with a brake state indicator

Abstract

A battery-powered chainsaw comprises a hand guard (32) mechanically coupled to a brake assembly via a brake operation mechanism. The hand guard (32) is movable between a brake engagement position, in which the hand guard (32) brings the brake assembly (53) to an engaged state, a brake release position, in which the hand guard (32) brings the brake assembly (53) to a disengaged state, and a neutral position, between the brake engagement and brake release positions, in which the hand guard (32) does not change the state of the brake assembly (53). A brake state detector arrangement (64) detects when the hand guard (32) brings the brake assembly (53) to the engaged state and when the hand guard (32) brings the brake assembly (53) to the disengaged state. A brake state indicator (66) maintains the latest brake state when the hand guard (32) is in the neutral position, and indicates the maintained latest brake state to the control circuitry (30).

Description

[0001] BATTERY-POWERED CHAINSAW COMPRISING A BRAKE ASSEMBLY WITH A BRAKE STATE INDICATOR

[0002] Field of the invention

[0003] The present invention relates to a battery-powered chainsaw.

[0004] Background

[0005] Battery-powered chainsaws are comfortable and easy to use. They generally generate very little noise and vibration, and can be put in operation through the simple press of a button. However, there is an incessant strive to make such battery- powered chainsaws both safer and more ergonomic and easy to use.

[0006] Summary

[0007] It is an object of the present invention to solve, or at least mitigate, parts or all of the above mentioned problems. To this end, there is provided a battery-powered chainsaw comprising an electric motor carried by a chassis; control circuitry configured to operate the electric motor based on user input received via a trigger; a transmission arrangement coupled to the electric motor, wherein the electric motor is configured to drive a saw chain via the transmission arrangement; a brake assembly configured to selectably brake the transmission arrangement for stopping the saw chain; and a hand guard mechanically coupled to the brake assembly via a brake operation mechanism, wherein the hand guard is movable between (a) a brake engagement position, in which the hand guard brings the brake assembly to an engaged state in which a friction element of the brake assembly engages with and brakes the transmission arrangement, (b) a brake release position, in which the hand guard brings the brake assembly to a disengaged state in which the friction element’s engagement with the transmission arrangement is released, and (c) a neutral position, between the brake engagement and brake release positions, in which neutral position the hand guard does not change the state of the brake assembly, wherein the chainsaw further comprises a brake state detector arrangement configured to detect when the hand guard brings the brake assembly to the engaged state and / or when the hand guard brings the brake assembly to the disengaged state; and a brake state indicator configured to, when the hand guard is in the neutral position, maintain a latest brake state detected by the brake state detector arrangement, and indicate the maintained latest brake state to the control circuitry. The brake state indicator enables the control circuitry to e.g. control the operation of the electric motor based on the maintained brake state also when the hand guard is in a neutral position. This adds another level of safety to the chainsaw. The neutral position may comprise more one or more neutral positions of the hand guard between the brake engagement and release positions. For example, the hand guard may be configured to assume a first neutral position when the brake assembly is in the engaged state, and a second neutral position when the brake assembly is in the disengaged state. According to embodiments, the brake state indicator may be configured as a mechanical toggle mechanism configured to toggle between two positions in response to movement of the hand guard between the brake engagement position and the brake release position. Alternatively, the brake state indicator may be implemented in software or hardware in the control circuitry, for example as a brake state flag stored in computer memory, for example within the control circuitry. The brake state detector arrangement may comprise one or more brake state detectors. For example, the brake state detector arrangement may comprise a switch, operated by the brake state indicator, the switch being configured to break the supply of electric power to the electric motor.

[0008] According to embodiments, the chainsaw may comprise a battery compartment configured to receive a battery for powering the chainsaw. Alternatively or additionally, the chainsaw may be configured to be connected to e.g. a backpack battery. A typical suitable DC battery voltage range for providing power to the electric motor may be between 18V and 100V, and more preferably, from 36V to 72V. The electric motor may be configured to provide an output power in an exemplary power range of e.g. 1 ,8 kW - 3,5 kW. Preferably, the brake assembly is configured to operate independent of the position of the trigger. Thereby, safe operation in all situations can be obtained.

[0009] According to embodiments, the hand guard may be biased from the brake engagement position towards a neutral rest position, and / or from the brake release position towards a neutral rest position. The bias from the brake engagement position towards a neutral rest position enables the hand guard to automatically return to a neutral position once the brake assembly has been brought to the engaged state. This facilitates reaching the hand guard, using the fingers of a hand holding a front handle of the chainsaw, for resetting the brake by moving the hand guard to the brake release position. The bias from the brake release position towards a neutral rest position automatically generates a convenient space between the front handle and the hand guard, such that a hand wearing a glove may easily enter said space. Preferably, in the neutral position obtained by the bias from the brake release position, the hand guard is positioned at least 35 mm from a front handle of the chain saw. The bias further enables a long stroke length of the hand guard between the brake engagement and release positions, while at the same time ascertaining that the hand guard will always return to a rest position where it may be conveniently reached. A long stroke length facilitates e.g. pre-tensioning a brake bias element configured to press the friction element against the transmission arrangement when the brake assembly assumes the engaged state.

[0010] According to embodiments, the battery-powered chainsaw may further comprise a transmission cover removably coupled to the chassis. According to further embodiments, the friction element may be arranged in the transmission cover. The transmission arrangement may typically comprise a wear element, such as a brake drum or a brake disc, with which the friction element engages in the engaged state of the brake assembly, and a saw chain drive sprocket which drives the saw chain. The position of the friction element in the transmission cover enables the wear element, e.g. brake drum or brake disc, to be positioned at an axial position between the saw chain drive sprocket and the transmission cover, which in turn enables positioning the saw chain drive sprocket closer to the lateral centre of the chainsaw. This results in a well-balanced chainsaw which is comfortable to operate, and also enables obtaining a small lateral width of the chainsaw. Moreover, the guide bar can be removed or replaced without having to disassemble the brake assembly. According to embodiments, the brake drum may double as a centrifugal clutch drum, wherein a radially outer face of the brake drum may be engaged by the friction element, and the radially inner face of the brake drum may be engaged by clutch shoes rotationally locked to a drive shaft of the electric motor. Preferably, the hand guard is pivotally suspended in the chassis, and not in the transmission cover. The large width of a chassis enables a strong and reliable pivotal suspension of the hand guard, for example using two axially separated hand guard pivots. An axial separation of two hand guard pivots also enables making the hand guard itself thin and light without undue flexing of the hand guard.

[0011] According to embodiments, the brake state detector arrangement may be carried by the chassis separately from the transmission cover, and may be configured to detect a movement of the hand guard. This reduces any need for electronics in the transmission cover, as the case may be, which reduces cost and facilitates assembly of the chainsaw. According to embodiments, the chassis may comprise a chassis wall having a first side facing the transmission cover and a second side facing the electric motor, wherein the brake state detector arrangement is positioned on the second side of the chassis wall. Thereby, it will be protected from dirt.

[0012] According to embodiments, the brake state indicator may be carried by the chassis separately from the transmission cover. According to embodiments, the chassis may comprise a chassis wall having a first side facing the transmission cover and a second side facing the electric motor, wherein the brake state indicator is positioned on the second side of the chassis wall. Thereby, it will be protected from dirt.

[0013] According to embodiments, the brake state indicator may comprise a mechanical indicator element configured to be moved by the brake operation mechanism, and the brake state detector arrangement is configured to detect a position of the mechanical indicator element, wherein the mechanical indicator element is coupled to the brake operation mechanism with a play, such that when the hand guard is moved from the brake engagement position to a neutral position, the mechanical indicator element remains in a first indicator position associated with the brake engagement position of the hand guard, and when the hand guard is moved from the brake release position to a neutral position, the mechanical indicator element remains in a second indicator position associated with the brake release position of the hand guard. This results in a simple and inexpensive detection arrangement, because the mechanical indicator element operates as a brake state memory without the need for any electronics.

[0014] According to embodiments, the brake state detector arrangement may comprise a single electronic switch configured to be operated by the mechanical indicator element between an open position and a closed position when the mechanical indicator element moves between the first indicator position and the second indicator position. This results in a particularly simple and inexpensive detection arrangement, because only one single switch is needed. Electronic components are particularly expensive due to classification requirements for outdoor use.

[0015] According to embodiments, the mechanical indicator element may be biased towards each of said first and second indicator positions in a bistable manner to define a toggle mechanism configured to toggle between the first and second positions. Such a configuration is particularly simple and reliable. The bias may be provided by a resilient element such as a spring or a rubber band. A particularly simple mechanism is provided by a flat spring interacting with a cam face of the mechanical indicator element.

[0016] According to embodiments, the hand guard may be pivotally connected to the chassis to pivot between the brake engagement position and the brake release position about a hand guard pivot axis, and the mechanical indicator element may be configured to pivot about the hand guard pivot axis. This is a particularly compact arrangement. According to embodiments, the mechanical indicator element may be pivotally suspended on a hand guard pivot pin.

[0017] According to embodiments, the hand guard may be connected to the mechanical indicator element via an indicator drive dog offset from the hand guard pivot axis, which drive dog is trapped with a play between a pair of tangentially separated drive dog engagement surfaces. Thereby, a large play can be obtained within a small mounting space. The drive dog may be rigidly connected to the hand guard, and the drive dog engagement surfaces may be surfaces of the mechanical indicator element.

[0018] According to embodiments, the friction element may comprise a brake band configured to apply a clamping force on a radially outer face of a brake drum. According to further embodiments, the brake drum may double as a clutch drum of a centrifugal clutch. Alternatively, the brake assembly may comprise e.g. a disc brake, i.e. the friction element may comprise one or more brake shoes configured to engage with a brake disc rotating with the transmission arrangement.

[0019] According to embodiments, the control circuitry may be configured to, based on the latest brake state maintained by the brake state indicator: disable operation of the electric motor when the brake assembly is in the engaged position, and / or electronically brake the electric motor when the brake assembly is in the engaged position, and / or indicate the latest brake state maintained by the brake state indicator to a user of the chainsaw via a user interface.

[0020] It is noted that embodiments of the invention may be embodied by all possible combinations of features recited in the claims.

[0021] Brief description of the drawings

[0022] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and nonlimiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:

[0023] Fig. 1 is a perspective view of a battery-powered chainsaw;

[0024] Fig. 2 is a perspective view of a chainsaw body of the chainsaw of Fig. 1 with a partially exploded view of a transmission cover and a transmission arrangement inside the transmission cover;

[0025] Fig. 3A is a plan view of an inside face of the transmission cover of Fig. 2 with a brake assembly in a disengaged state;

[0026] Fig. 3B is a plan view of the inside face of the transmission cover of Fig. 2 with the brake assembly in an engaged state;

[0027] Fig. 4A is a longitudinal section of the chainsaw body of Fig 2 with a hand guard in a neutral position, and a magnified plan view of a brake state indicator and a brake state detector arrangement according to a first embodiment;

[0028] Fig. 4B is a longitudinal section of the chainsaw body of Fig 2 with the hand guard in a brake engagement position, and a magnified plan view of the brake state indicator in a first indicator position corresponding to the engaged brake state of Fig. 3B;

[0029] Fig. 4C is a longitudinal section of the chainsaw body of Fig 2 with the hand guard in a brake release position, and a magnified plan view of the brake state indicator in a second indicator position corresponding to the disengaged brake state of Fig. 3A; and

[0030] Fig. 5 is a schematic plan view of a brake state indicator and a brake state detector arrangement according to a second embodiment.

[0031] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted.

[0032] Detailed description of the exemplary embodiments

[0033] Fig. 1 illustrates a handheld battery-powered chainsaw 10. The chainsaw 10 has a chainsaw body 12 comprising a chassis 13 provided with a pair of handles 14a, 14b, by means of which an operator (not illustrated) may hold and operate the chainsaw 10. The pair of handles comprises a front handle 14a, typically for holding with the left hand, and a rear handle 14b, typically for holding with the right hand. A cutting assembly comprising a saw chain 16, and an elongate guide bar 18 guiding the saw chain 16 in an elongate loop, extends from a front end of the chainsaw body 12 along a longitudinal direction X of the chainsaw 10. A rear end of the guide bar 18 is positioned behind a transmission cover 19. The chainsaw 10 further comprises a removable battery 20 configured to be connected to a battery compartment 22, and an electric motor 24. The electric motor 24 is positioned inside the chainsaw housing 26; in the view of Fig. 1 , only the approximate position of the motor 24 within the housing 26 is pointed out. A finger-operated trigger 28 permits the operator to selectively mobilize the saw chain 16 using the electric motor 24. The chainsaw 10 further comprises control circuitry 30, which is also inside the chainsaw housing 26; only the approximate position of the control circuitry 30 within the housing 26 is pointed out in the view Fig. 1 . The control circuitry 30 is configured to control the electric motor 24 based on input from the trigger 28. The trigger 28 extends downwards from a bottom face of the rear handle 14b, and is movable between a depressed position (not illustrated), responsive to which the electric motor 24 is operated to move the saw chain 16, and a released position (illustrated), responsive to which the saw chain 16 is stopped. A hand guard 32 in front of the front handle 14a is operatively connected to a brake assembly for stopping the saw chain 16 in case of a kick-back. The brake assembly is a safety feature which operates independent of the position of the trigger 28.

[0034] Fig. 2 illustrates the chainsaw 10 without the saw chain 16 and the guide bar 18 (Fig. 1 ), and with the transmission cover 19 removed to expose a transmission arrangement 34 configured to transmit rotary power from the electric motor 24 (Fig. 1 ) to the saw chain 16 (Fig. 1 ). The transmission arrangement 34 comprises an output shaft 36 of the electric motor 24 (Fig. 1) which is configured to rotate about a motor rotation axis M, a worm screw 38 of a worm drive for driving a saw chain oil pump (not illustrated), a brake drum 40 configured to cooperate with a brake band (not illustrated) operated by the hand guard 32, and a saw chain sprocket 42. The exemplary saw chain sprocket 42 is of rim type, but it may of course be any type suited for meshing with a saw chain 16 (Fig. 1 ). The worm screw 38 and the brake drum 40 are rotationally locked to the output shaft 36 in a non-illustrated manner, and the saw chain sprocket 42 is rotationally locked to the brake drum via mating splines 44a, 44b on the saw chain sprocket 42 and the brake drum 40, respectively. Two pins 46a, 46b serve to support the guide bar 18 (Fig. 1 ) in a manner known per se. The transmission cover 19 is configured to be removably coupled to the chassis 13 by means of a set of nuts 48a, 48b mating with threaded free ends of the pins 46a, 46b, such that the guide bar 18 (Fig. 1 ) is clamped between the transmission cover 19 and the chassis 13. A chassis wall 15 has a first, outer side 15a which faces the transmission cover, and a second side (not visible in Fig. 2) which faces an interior space of the chassis 13 which houses the motor 24 (Fig. 1 ). The hand guard 32 is pivotally suspended in the chassis 13 so as to pivot about a hand guard pivot axis H. Two hand guard pivots P1 , P2 are axially separated along the hand guard pivot axis H; the magnified view at the bottom of Fig. 2 illustrates a first hand guard pivot P1 , at which the hand guard 32 is pivotally coupled to a hand guard pivot pin 50. The first hand guard pivot P1 forms part of a brake operation mechanism 52, via which the hand guard 32 operates the brake. For the purpose, the brake operation mechanism

[0035] 52 comprises a brake knee joint drive dog 54 extending in the direction of the hand guard pivot axis H from the first hand guard pivot P1 towards the transmission cover 19.

[0036] Fig. 3A illustrates the inside face, facing towards the transmission arrangement 34 (Fig. 2), of the transmission cover 19. The transmission cover 19 houses a brake assembly 53 comprising parts of the brake operation mechanism 52 and a brake band 60. The brake operation mechanism 52 further comprises a knee joint assembly 56 via which the hand guard 32 (Fig. 2) selectably tensions and releases a brake spring 58. The knee joint assembly 56 comprises a first knee joint link 56a and a second knee joint link 56b, which are pivotally connected to each other at a knee joint 57. The brake band 60 is a flat metal band which follows a circular loop, and encloses the brake drum 40 (Fig. 2) when the transmission cover 19 is attached to the chassis 13 (Fig. 2). As such, the brake band 60 operates as a friction element which may be selectably tightened about the brake drum 40 (Fig. 2) so as to selectably brake the rotation of the brake drum 40, as well as the rotation of all other rotating components which rotate with the brake drum 40, thereby stopping the saw chain 16 (Fig. 1 ). An end of the brake band 60 is attached to a brake band tensioner 62, which interconnects a movable end of the brake spring 58 and the knee joint assembly 56.

[0037] Fig. 3A illustrates the brake assembly 53 with the brake spring 58 locked in a compressed state by the knee joint assembly 56. When the brake spring 58 is locked in the compressed state, the brake band 60 is slacked, such that the brake assembly

[0038] 53 is in a disengaged state in which the brake drum 40 (Fig. 2) is not impeded from rotating by the brake band 60. When the hand guard 32 (Fig. 2) is pushed forward, the brake knee joint drive dog 54 drives the first knee joint link 56a to rotate about the hand guard pivot axis H in the direction of the arrow of Fig. 3A, such that the knee joint assembly 56 leaves the locked state of Fig. 3A and allows the brake spring 58 to expand. Thereby, the brake assembly 53 assumes the engaged state illustrated in Fig. 3B, in which the brake spring 58 pushes the brake band tensioner 62 in the direction of the arrow, and the brake band tensioner 62 pulls the brake band 60 to be tightened about, and brake, the brake drum 40 (Fig. 2).

[0039] The brake assembly 53 can be reset to its disengaged state by pulling the hand guard 32 (Fig. 2) backwards, such that the brake knee joint drive dog 54 drives the first knee joint link 56a to rotate about the hand guard pivot axis H in a direction opposite to that illustrated by the arrow in Fig. 3A, and thereby, via the second knee joint 56b and the brake band tensioner 62, compresses the brake spring 58 and slacks the brake band 60 about the brake drum 40.

[0040] Now with reference to Figs. 4A-4C, the hand guard 32 is movable about the hand guard pivot axis H between a plurality of positions. Fig. 4A illustrates a neutral position of the hand guard 32, which is assumed during normal running of the chainsaw, i.e. when the saw chain 16 (Fig. 1 ) is mobilized by the motor 24. Fig. 4B illustrates a brake engagement position of the hand guard 32, in which the hand guard 32 brings the brake assembly 53 (Fig. 3A) to the engaged state (Fig. 3B) in which the brake band 60 engages with and brakes the transmission arrangement 34 (Fig. 2) via the brake drum 40 (Fig. 2). Lastly, Fig. 4C illustrates a brake release position of the hand guard 32, in which the hand guard 32 brings the brake assembly 53 to the disengaged state (Fig. 3A) in which the brake band’s 60 braking engagement with the brake drum 40 (Fig. 2) is slacked. As apparent from the drawings, the neutral position of Fig. 4A is between the brake engagement position of Fig. 4B and the brake release position of Fig. 4C. The hand guard 32 is resiliently biased towards the neutral position in a non-illustrated manner, such that if the handguard 32 is released in any of the brake engagement position of Fig. 4B and the brake release position of Fig. 4C, it automatically returns to the neutral position of Fig. 4A. As such, the neutral position of Fig. 4A is a neutral rest position. When in the neutral position, the hand guard 32 does not change the state of the brake assembly 53 (Fig. 3A), i.e. when returning from the brake engagement position of Fig. 4B, the brake assembly 53 remains in the engaged state (Fig. 3B), and when returning from the brake release position of Fig. 4C, the brake assembly 53 remains in disengaged state (Fig. 3A).

[0041] Fig. 4A also schematically illustrates the electric motor 24 along with the control circuitry 30, which is embodied as a controller board 65. The first hand guard pivot P1 penetrates the chassis wall 15 from the first side 15a illustrated in Fig. 2 to the second side 14b illustrated in Fig. 4A.

[0042] Magnified portions of Figs 4A, 4B and 4C illustrate a brake state detector arrangement 64 and a brake state indicator 66, the function of which will be elucidated in the following. The brake state detector arrangement 64 is configured to detect whenever the hand guard 32 changes the state of the brake assembly 53 (Fig. 3A), i.e. whenever the hand guard 32 brings the brake assembly 53 from the disengaged state (Fig. 3A) to the engaged state (Fig. 3B) or vice versa. The brake state indicator 66 is configured to maintain the latest brake state which was detected by the brake state detector arrangement 64 when the hand guard 32 has moved back to its neutral position (Fig. 4A) from either of the brake engagement position (Fig. 4B) and the brake release position (Fig. 4C), and to indicate this maintained latest brake state to the control circuitry 30 via the brake state detector arrangement 64. Thereby, the brake state indicator 66 operates as a brake state memory which enables the control circuitry 30 to e.g. control the operation of the electric motor 24 based on the maintained brake state also when the hand guard 32 is in a neutral position (Fig. 4A).

[0043] Starting with Fig. 4A, the brake state indicator 66 comprises a mechanical indicator element 70 configured to be moved by the brake operation mechanism 52 (Fig. 2) via an indicator drive dog 72 coupled to the first hand guard pivot P1 . The mechanical indicator element 70 is pivotally suspended to pivot about the hand guard pivot axis H via the hand guard pivot pin 50. The indicator drive dog 72 is axially offset from the hand guard pivot axis H, and is thereby configured to move along a circlular arc about the hand guard pivot axis H. The indicator drive dog 72 is trapped with a play between first and second drive dog engagement surfaces 70a, 70b of the mechanical indicator element 70. Moving the hand guard 32 forward to the brake engagement position of Fig. 4B moves, via engagement between the indicator drive dog 72 and the first drive dog engagement surface 70a, the mechanical indicator element 70 to a first indicator position illustrated in Fig. 4B. As described hereinabove, moving the hand guard 32 forward to the brake engagement position of Fig. 4B also brings the brake assembly 53 (Fig. 3B) to the engaged state of Fig. 3B. Thereby, the first indicator position is associated with the engaged state (Fig. 3B) of the brake assembly 53 (Fig. 3B). When releasing the hand guard 32 after having engaged the brake, the hand guard 32 returns to its neutral position illustrated in Fig. 4A, whereas the brake assembly 53 (Fig. 3B) remains in the engaged state of Fig. 3B. The indicator drive dog 72 disengages from the first drive dog engagement surface 70a and moves, within the play between the first and second drive dog engagement surfaces 70a, 70b, to the position illustrated in broken lines in Fig. 4B. Thereby, when the hand guard 32 returns from the brake engagement position (Fig. 4B) to the neutral position (Fig. 4A), the mechanical indicator element 70 remains in the first indicator position (Fig. 4B) associated with the brake engagement position (Fig. 4B) of the hand guard 32 and the engaged state (Fig. 3B) of the brake assembly.

[0044] Similarly, and now referring to Fig. 4C, when the hand guard 32 is moved backwards, towards the front handle 14a (Fig. 1 ), the indicator drive dog 72 engages with the second drive dog engagement surface 70b, and moves the mechanical indicator element 70 to a second indicator position. The second indicator position illustrated in Fig. 4C is associated with the disengaged state (Fig. 3A) of the brake assembly 53 (Fig. 3A). When releasing the hand guard 32 after having disengaged the brake, the hand guard 32 returns to its neutral position illustrated in Fig. 4A, whereas the brake assembly 53 (Fig. 3A) remains in the disengaged state of Fig. 3A. The indicator drive dog 72 disengages from the second drive dog engagement surface 70b and moves, within the play between the first and second drive dog engagement surfaces 70a, 70b, to the position illustrated in Fig. 4A. Thereby, when the hand guard 32 returns from brake release position (Fig. 4C) to the neutral position (Fig. 4A), the mechanical indicator element 70 remains in the second indicator position (Figs 4A and 4C) associated with the brake release position (Fig. 4C) of the hand guard 32.

[0045] A flat spring 74 is held on the second chassis wall 15b and interacts with a cam face 70c of the mechanical indicator element 70 such that mechanical indicator element 70 is biased towards each of the first indicator position (Fig. 4B) and the second indicator position (Figs 4A and 4C) in a bistable manner. Thereby, the mechanical indicator element 70 defines, together with the flat spring 74, a mechanical toggle mechanism configured to toggle between the first indicator position, illustrated in Fig. 4B, and the second indicator position illustrated in Figs 4A and 4C, in response to movement of the hand guard 32 between the brake engagement position (Fig. 4B) and the brake release position (Fig. 4C).

[0046] The brake state detector arrangement 64 comprises an electronic switch 76, which is operated by the mechanical indicator element 70 via a switch pressing element 70d of the mechanical indicator element 70. The electronic switch 76 is closed by the mechanical indicator element 70 in the second indicator position of Figs 4A and 4C, and resi liently opens when the mechanical indicator element moves to the first indicator position of Fig. 4B. The electronic switch is connected to the control circuitry 30 via leads 78a, 78b and the control circuitry 30 is configured in such a manner that, when the electronic switch 76 is open and the electric motor 24 is not operating, the supply of power to the electric motor 24 is broken. Moreover, when the hand guard 32 is moved to the brake engagement position of Fig. 4B while the electric motor 24 is rotating, the electric motor may be electrically braked in any manner known per se, for example by short-circuiting or reversing the polarity to electric motor windings. Thereby, the saw chain 16 (Fig. 1 ) may be brought to a full stop faster than by using the brake assembly 53 alone.

[0047] The latest brake state, maintained by the brake state indicator 66, is also communicated to the user of the chainsaw via a user interface 80 (Fig. 2) positioned on the chainsaw body 12.

[0048] Referring back to Fig. 4A, when in its neutral rest position, the hand guard 32 is positioned at a shortest distance d from the front handle 14a of about 40 mm. Preferably, the distance d is within the range 35 mm - 60 mm.

[0049] Fig. 5 illustrates a brake state detector arrangement 164 and a brake state indicator 166 according to a second embodiment. The brake state detector arrangement 164 may be mounted e.g. on the first side 15a of the chassis wall 15 (Fig. 2), and directly detect the position of the hand guard 32. The brake state detector arrangement 164 comprises a first proximity sensor 176a and a second proximity sensor 176b, each of which is configured to detect a respective end position of the hand guard 32. Accordingly, the first proximity sensor 176a detects a brake engagement position of the hand guard 32, indicated in broken lines to the left of the handguard 32, which position is assumed when the hand guard 32 brings the brake assembly 53 (Fig. 3B) to the engaged state, whereas the second proximity sensor 176b detects a brake release position of the hand guard 32, indicated in broken lines to the right of the handguard 32, which position is assumed when the hand guard 32 brings the brake assembly 53 to the disengaged state (Fig. 3A).

[0050] The brake state indicator 166 is configured as a digital memory register readable by the control circuitry 30, and digitally stores and maintains the latest brake state detected by the brake state detector arrangement 164. Thereby, the control circuitry may read the latest brake state from the brake state indicator 166 whenever the hand guard 32 is in the neutral position, i.e. the position of the hand guard 32 indicated in solid lines.

[0051] According to a still further variant (not illustrated), the brake state detector arrangement may be configured to directly detect the state of the brake assembly 53 (Fig. 3A) in the transmission cover 19, for example by detecting, using e.g. a proximity detector, the position of any of the elements of the knee joint assembly 56 (Fig. 3A).

[0052] The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. For example, the invention has been described with reference to a chainsaw of rear-handle type. However, it will be appreciated that the teachings herein are equally applicable to a chainsaw of tophandle type. The mechanical brake state indicator 66 has been illustrated so as to be mechanically operated by the first hand guard pivot P1 . Alternatively, it may be operated by the second hand guard pivot P2. Still alternatively, the hand guard may be connected to the chassis via a single pivot only, or even still alternatively, in a manner so as to translate without pivoting. The brake drum 40 may double as a centrifugal clutch drum, wherein the radially outer face of the brake drum 40 is configured to be engaged by the brake band 60 as described in detail, and the radially inner face of the brake drum 40 is engaged by clutch shoes connected to the output shaft of the electric motor 24, such that the saw chain drive sprocket is only rotated if the output shaft of the electric motor 24 exceeds a certain rotation speed.

[0053] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

Claims

Claims1 . A battery-powered chainsaw (10) comprising an electric motor (24) carried by a chassis (13); control circuitry (30) configured to operate the electric motor (24) based on user input received via a trigger (28); a transmission arrangement (34) coupled to the electric motor (24), wherein the electric motor (24) is configured to drive a saw chain (16) via the transmission arrangement (34); a brake assembly (53) configured to selectably brake the transmission arrangement (34) for stopping the saw chain (16); and a hand guard (32) mechanically coupled to the brake assembly (53) via a brake operation mechanism (52), wherein the hand guard (32) is movable between a brake engagement position, in which the hand guard (32) brings the brake assembly (53) to an engaged state in which a friction element (60) of the brake assembly (53) engages with and brakes the transmission arrangement (34), a brake release position, in which the hand guard (32) brings the brake assembly (53) to a disengaged state in which the friction element’s (60) engagement with the transmission arrangement (34) is released, and a neutral position, between the brake engagement and brake release positions, in which neutral position the hand guard (32) does not change the state of the brake assembly (53), wherein the chainsaw (10) further comprises a brake state detector arrangement (64; 164) configured to detect when the hand guard (32) brings the brake assembly (53) to the engaged state and / or when the hand guard (32) brings the brake assembly (53) to the disengaged state; and a brake state indicator (66; 166) configured to maintain a latest brake state detected by the brake state detector arrangement (64; 164), and indicate the maintained latest brake state to the control circuitry (30), when the hand guard (32) is in the neutral position.

2. The battery-powered chainsaw according to claim 1 , wherein the hand guard (32) is biased from the brake engagement position towards a neutral rest position, and / or from the brake release position towards a neutral rest position.

3. The battery-powered chainsaw according to any of the preceding claims, wherein the battery-powered chainsaw (10) further comprises a transmission cover (19) removably coupled to the chassis (13).

4. The battery-powered chainsaw according to claim 3, wherein the friction element (60) is arranged in the transmission cover (19).

5. The battery-powered chainsaw according to any of the claims 3-4, wherein the brake state detector arrangement (64; 164) is carried by the chassis (13) separately from the transmission cover (19), and is configured to detect a movement of the hand guard (32).

6. The battery-powered chainsaw according to any of the claims 3-5, wherein the brake state indicator (66; 166) is carried by the chassis (13) separately from the transmission cover (19).

7. The battery-powered chainsaw according to any of the preceding claims, wherein the brake state indicator (66) comprises a mechanical indicator element (70) configured to be moved by the brake operation mechanism (52), and the brake state detector arrangement (64) is configured to detect a position of the mechanical indicator element (70), wherein the mechanical indicator element (70) is coupled to the brake operation mechanism (52) with a play, such that when the hand guard (32) is moved from the brake engagement position to a neutral position, the mechanical indicator element (70) remains in a first indicator position associated with the brake engagement position of the hand guard (32), and when the hand guard (32) is moved from the brake release position to a neutral position, the mechanical indicator element (70) remains in a second indicator position associated with the brake release position of the hand guard (32).

8. The battery-powered chainsaw according to claim 7, wherein the brake state detector arrangement (64) comprises a single electronic switch (76) configured to be operated by the mechanical indicator element (70) between an openposition and a closed position when the mechanical indicator element (70) moves between the first indicator position and the second indicator position.

9. The battery-powered chainsaw according to any of the claims 7-8, wherein the mechanical indicator element (70) is biased towards each of said first and second indicator positions in a bistable manner to define a toggle mechanism configured to toggle between the first and second positions.

10. The battery-powered chainsaw according to any of the claims 7-9, wherein the hand guard (32) is pivotally connected to the chassis (13) to pivot between the brake engagement position and the brake release position about a hand guard pivot axis (H), and the mechanical indicator element (70) is configured to pivot about the hand guard pivot axis (H).11 .The battery-powered chainsaw according to claim 10, wherein the hand guard (32) is connected to the mechanical indicator element (70) via an indicator drive dog (72) which is offset from the hand guard pivot axis (H), which indicator drive dog is trapped with a play between a pair of tangentially separated drive dog engagement surfaces (70a, 70b).

12. The battery-powered chainsaw according to any of the preceding claims, wherein the friction element (60) comprises a brake band configured to apply a clamping force on a radially outer face of a brake drum (40).

13. The battery-powered chainsaw according to any of the preceding claims, wherein the control circuitry (30) is configured to, based on the latest brake state maintained by the brake state indicator (66; 166): disable operation of the electric motor (24) when the brake assembly(53) is in the engaged position, and / or electronically brake the electric motor (24) when the brake assembly (53) is in the engaged position, and / or indicate the latest brake state maintained by the brake state indicator (66; 166) to a user of the chainsaw (10) via a user interface (80).

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