Herein a hand-held power tool comprising an internal combustion engine (4) is disclosed. The hand-held power tool comprises, a working tool (6), a centrifugal clutch (8), and a control system (10). The internal combustion engine (4) has a clutch-in speed (C) above which the internal combustion engine (4) drives the working tool (6). A speed limitation controller (14), is configured to limit an engine speed at a limitation speed below the clutch-in speed (C). The control system (10) is configured to calculate an integral of the rotational speed of the internal combustion engine (4), and to deactivate the speed limitation controller (14) after the integral reaches an integration limit value, such that the internal combustion engine (4) is rotatable above the limitation speed (L) to drive the working tool (6) via the centrifugal clutch (8).

Herein a hand-held power tool comprising an internal combustion engine (4) is disclosed. The hand-held power tool comprises, a working tool (6), a centrifugal clutch (8), and a control system (10). The internal combustion engine (4) has a clutch-in speed (C) above which the internal combustion engine (4) drives the working tool (6). A speed limitation controller (14), is configured to limit an engine speed at a limitation speed below the clutch-in speed (C). The control system (10) is configured to calculate an integral of the rotational speed of the internal combustion engine (4), and to deactivate the speed limitation controller (14) after the integral reaches an integration limit value, such that the internal combustion engine (4) is rotatable above the limitation speed (L) to drive the working tool (6) via the centrifugal clutch (8).

A hand-held power tool comprising an internal combustion engine (4), a working tool (6), a centrifugal clutch (8), and a control system (10) is disclosed. The engine (4) has a clutch-in speed, above which the engine (4) drives the working tool (6). The control system (10) comprises a rotation speed sensor (12), and a speed limitation controller (14), which is configured to limit an engine speed at a limitation speed below the clutch-in speed. It is active or activated during a starting procedure of the internal combustion engine (4). The control system (10) is configured to deactivate the speed limitation controller (14) upon sensing at least one acceleration at a level above the limitation speed and sensing at least one deceleration at a level above the limitation speed, such that the engine (4) is rotatable above the limitation speed to drive the working tool (6).

Herein a hand-held power tool comprising an internal combustion engine (4) is disclosed. The hand-held power tool comprises, a working tool (6), a centrifugal clutch (8), and a control system (10). The internal combustion engine (4) has a clutch-in speed (C) above which the internal combustion engine (4) drives the working tool (6). A speed limitation controller (14), is configured to limit an engine speed at a limitation speed below the clutch-in speed (C). The control system (10) is configured to calculate an integral of the rotational speed of the internal combustion engine (4), and to deactivate the speed limitation controller (14) after the integral reaches an integration limit value, such that the internal combustion engine (4) is rotatable above the limitation speed (L) to drive the working tool (6) via the centrifugal clutch (8).

An engine-driven working machine according to the present invention has a controller and a muffler. The controller is operated from starting of the engine in a rotational speed limitation mode in which the engine is prevented from rotating at a rotational speed that is higher than the predetermined limitation rotational speed. The controller forces to stop the engine, after a predetermined period has passed, during which the engine operates in the rotational speed limitation mode.

A chainsaw which has a low profile chain cover and a chain bar tightening clutch system. The chain bar tightening clutch system can have a bar tightening knob which drives a clutch which governs the amount of pressure applied to the chain bar by operating the bar tightening knob. The chainsaw can have a chain bar tensioning system which can have a tensioning drive member in an offset position from the tensioning post which positions the tensioning post to achieve a chain tension and compact chainsaw design. The chainsaw can also have an oil cap with a lock channel having a detent with produces a sound when moved from a disengaged to an engage position with an oil reservoir.

A chainsaw which has a low profile chain cover and a chain bar tightening clutch system. The chain bar tightening clutch system can have a bar tightening knob which drives a clutch which governs the amount of pressure applied to the chain bar by operating the bar tightening knob. The chainsaw can have a chain bar tensioning system which can have a tensioning drive member in an offset position from the tensioning post which positions the tensioning post to achieve a chain tension and compact chainsaw design. The chainsaw can also have an oil cap with a lock channel having a detent with produces a sound when moved from a disengaged to an engage position with an oil reservoir.

An operator operates a throttle lever and by maximizing the extent of said operation, the drive state is initiated, and the crank shaft rotation rate R increases and reaches the maximal value (RC) thereof. Subsequently, the operator operates the dressing operation lever so as to be in a second state at elapsed time (t0) while keeping the extent of the throttle lever operation maximized. Because a microswitch is turned off, the crank shaft rotation rate (R) is controlled in a range of R1<R<R2. By placing the saw chain in contact with a grindstone fixed to the dressing operation lever simultaneously with said action, dressing work is performed. After the microswitch is turned off at elapsed time (t0), the output of an ignition coil is controlled cyclically by a control unit at a cycle (T1+T2) so as to be on (ignition) during period (T1) and off (flame off) during period (T2).

An operator operates a throttle lever and by maximizing the extent of said operation, the drive state is initiated, and the crank shaft rotation rate R increases and reaches the maximal value (RC) thereof. Subsequently, the operator operates the dressing operation lever so as to be in a second state at elapsed time (t0) while keeping the extent of the throttle lever operation maximized. Because a microswitch is turned off, the crank shaft rotation rate (R) is controlled in a range of R1<R<R2. By placing the saw chain in contact with a grindstone fixed to the dressing operation lever simultaneously with said action, dressing work is performed. After the microswitch is turned off at elapsed time (t0), the output of an ignition coil is controlled cyclically by a control unit at a cycle (T1+T2) so as to be on (ignition) during period (T1) and off (flame off) during period (T2).

A chain saw includes a chain, a guide plate, and a locking device for tensioning the chain. The locking device includes an operating member rotatable about a first axis, a driving member for driving the guide plate to move to tension the chain, a first clutch coupling with the operating member, and a second clutch including meshing teeth cooperating with the first clutch. The driving member is connected with the second clutch, each of the meshing teeth includes a first sloped surface having a first slop and a second sloped surface having a second slop, the absolute value of the first slope is greater than that of the second slope.