The chain of an electromotive chain saw is quickly stopped by the combined use of an electric brake and a mechanical brake when a trigger member is turned off. The rear end of a brake band disposed to tighten a brake drum by operating a hand guard is secured to a bent rod. When the trigger member is released, the brake band is normally tightened around the outer periphery of a brake drum by the urging force of a coil spring. When the trigger member is released, a circuit provided with a brake winding is closed, thereby applying a dynamic braking force. When the dynamic brake force is applied, a centrifugal clutch is released quickly and the speed of stopping the brake drum is accelerated.
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0. 22. A chain saw comprising:
an electric motor, a cutting chain driven by the electric motor, first means for applying a mechanical braking force to stop the cutting chain, second means for applying an electrical braking force to stop the electric motor, and third means for simultaneously actuating both the first means and the second means in order to concurrently apply the electrical braking force to stop the electric motor and the mechanical braking force to stop the cutting chain.
0. 32. An apparatus comprising:
a cutting chain; an electric motor coupled to the cutting chain; a brake drum; a mechanical brake coupled to the brake drum, wherein activation of the mechanical brake results in a braking force on the brake drum that stops rotation of the cutting chain; an electrical brake circuit coupled to the electric motor, wherein activation of the electronic brake results in a dynamic braking force on the electric motor; and a trigger member coupled to the mechanical brake and the electronic brake circuit, wherein movement of the trigger member to an OFF position simultaneously and concurrently operates both the mechanical brake and the electronic brake circuit to quickly stop the rotation of the cutting chain.
0. 18. A chain saw comprising:
an electric motor, a cutting chain driven by the electric motor, a brake drum coupled to the cutting chain, a mechanical brake adapted to apply a mechanical braking force to the brake drum, an electric brake adapted to apply an electrical braking force to the electric motor, and a common trigger coupled to both the electric brake and the mechanical brake and adapted to simultaneously actuate both the electric brake and the mechanical brake, the common trigger having an ON position and an OFF position, wherein the mechanical braking force and the electrical braking force act concurrently with one another to stop the cutting chain and the electric motor, respectively, from rotating when the common trigger is in the OFF position.
0. 15. A chain saw comprising:
an electric motor having an armature, a cutting chain driven by the electric motor, a brake drum coupled to the cutting chain, a mechanical brake adapted to engage the brake drum, the mechanical brake having a first position, in which the mechanical brake is disengaged from the brake drum to permit the brake drum to freely rotate, and a second position, in which the mechanical brake engages the brake drum to exert a mechanical braking force on the brake drum, an electric brake circuit electrically coupled to the electric motor, the electric brake circuit having a first mode, in which the electrical braking force is not applied to the electric motor, and a second mode, in which the electric brake circuit applies an electrical braking force to the electric motor, and a common trigger coupled to both the electric brake circuit and the mechanical brake, the common trigger having a first trigger position and a second trigger position, the first trigger position causing the mechanical brake to disengage from the brake drum and the electric brake circuit to operate in the first mode, and the second trigger position causing the mechanical brake to engage the brake drum and the electric brake circuit to operate in the second mode, wherein the electric brake force is applied the electric motor concurrently with the mechanical braking force applied to the brake drum when the common trigger is in the second trigger position.
1. An electromotive chain saw comprising;
a guide bar having a track extending around a periphery thereof; a cutting chain being supported by said track of said guide bar and being rotatable therearound; an electric motor, having an armature, being drivingly-connected to said cutting chain, via a drive mechanism, to rotate said cutting chain about the periphery of said bar along said track, and said drive mechanism including a brake drum drivingly connected to said cutting chain for rotation with said cutting chain; a mechanical brake being arranged to engage with said brake drum, said mechanical brake having a disengaged position in which said mechanical brake is disengaged from said brake drum and permits rotation thereof, and said mechanical brake having an engaged position in which said mechanical brake engages with said brake drum and exerts a braking force on a surface of said brake drum to stop the rotation of thereof and, in turn, stop rotation of said cutting chain rotated thereby; a dynamic brake circuit being electrically coupled to said armature of said electric motor to supply power thereto and rotate said cutting chain, in an operation position of said dynamic brake circuit, and said dynamic brake circuit having a braking position in which said dynamic brake circuit applies a braking force to said armature of said electric motor to stop rotation thereof; and a common trigger member being directly linked to both said dynamic brake circuit and said mechanical brake such that actuation of said common trigger member to an ON position concurrently actuates both said mechanical brake to said disengaged position and said dynamic brake circuit to said operation position while actuation of said common trigger member to an OFF position concurrently actuates both said mechanical brake to said engaged position and said dynamic brake circuit to said braking position whereby both said dynamic brake force on said armature of said electric motor and said braking force on said brake drum are concurrently applied.
2. The electromotive chain saw according to
3. The electromotive chain saw according to
4. The electromotive chain saw according to
5. The electromotive chain saw according to
6. The electromotive chain saw according to
rotary drive force is transmitted from said electric motor to a drive sprocket via a clutch mechanism; said clutch mechanism comprises an engagement member formed on said brake drum, an engaging member rotated by said electric motor rotating with a rotation shaft, said engaging member is slidable in an axial direction on said rotation shaft and engages with said engagement member on said brake drum; an urging member for pushing and urging said engaging member against said brake drum; and a clutch release member which releases the engagement of said engaging member on said brake drum by sliding said engaging member back against said urging member when said trigger member is moved from said ON position to said OFF position.
7. The electromotive chain saw according to
8. The electromotive chain saw according to
9. The electromotive chain saw according to
10. The electromotive chain saw according to
11. The electromotive chain saw according to
a main winding and a brake winding provided in a field slot; a single-pole double-throw switch for driving and braking said electric motor, used to change between supplying a drive current to said armature and said main winding and supplying a counter electromotive force arising on said brake winding; and a single pole switch for disconnecting said brake winding from said main winding when said single-pole double-throw switch is changed over to supplying the drive current to said armature and said main winding.
12. The electromotive chain saw according to
when driving said electromotive chain saw, said single pole switch is changed over to open the connection of said brake winding with said armature and said main winding, a clutch mechanism is engaged, and said single-pole double-throw switch is changed over to connect a power source with said armature and said main winding, and when braking said electromotive chain saw, said single-pole double-throw switch is changed over to open the connection of the power source with said armature and said main winding and to connect said brake winding with said armature, said clutch mechanism is disengaged, and said single pole switch is changed over to connect said brake winding with said armature.
13. The electromotive chain saw according to
when driving said electromotive chain saw, after said single pole switch is changed over to open the connection of said brake winding with said armature and said main winding, said clutch mechanism is engaged and subsequently said single-pole double-throw switch is changed over to connect a power source with said armature and said main winding, and when braking said electromotive chain saw, after said single-pole double-throw switch is changed over to open the connection of the power source with said armature and said main winding and concurrently to connect said brake winding with said armature, said clutch mechanism is disengaged, and subsequently said single pole switch is changed over to connect said brake winding with said armature.
14. The electromotive chain saw according to
0. 16. A chain saw according to
0. 17. A chain saw according to
0. 19. A chain saw according to
0. 20. A chain saw according to
0. 21. A chain saw according to
0. 23. A chain saw according to
0. 24. A chain saw according to
0. 25. A chain saw according to
0. 26. A chain saw according to
0. 27. An apparatus as in
0. 28. The apparatus as in
0. 29. The apparatus as in
0. 30. The apparatus as in
0. 31. The apparatus as in
0. 33. The apparatus as in
0. 34. The apparatus as in
0. 35. The apparatus as in
0. 36. The apparatus as in
0. 37. The apparatus as in
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This invention relates to an electromotive chain saw.
In a conventional electromotive chain saw, a hand guard for protecting an operator's hands is provided in front of a handle. Additionally, a brake band is wound around a brake drum for stopping the operation of a cutting chain. By operating the hand guard and pulling one end of the brake band, the brake drum is tightened with the brake band, thereby stopping the cutting chain.
However, in such electromotive chain saws, even after a trigger member is released and a motor drive switch is turned off, the inertial rotation of the motor often results in the rotation of the cutting chain for several seconds. If the rotating chain contacts or hits the ground, it is often damaged, thereby requiring the replacement of the chain itself. The material in process is also inadvertently damaged. Furthermore, the operator cannot go to the subsequent steps of work until the chain is completely stopped. Thus, the work efficiency is deteriorated.
To solve the aforementioned problem, it is proposed in Japanese examined and published patent application No. 657401 that a circuit having a brake winding is provided in an electromotive motor and the circuit is closed when a trigger member is released, for the purpose of dynamic braking without any impact.
Such gradual stopping of the chain achieved in the proposal fails to satisfy a recent demand for stopping the chain quickly, for example, within one second after the trigger member is released.
Wherefore, an object of the present invention is to provide a brake device for a chain saw that can quickly stop the rotation of a cutting chain when a trigger member is released.
To achieve this or other object, the present invention provides an electromotive chain saw, having an electric motor for providing a rotary drive force to a drive sprocket on which a cutting chain is wound, a trigger member for energizing the electric motor when turned on and for stopping the electric motor when turned off, a trigger link mechanical brake for being engaged with a brake drum secured to the drive sprocket when the trigger member is turned off and for being disengaged from the brake drum when the trigger member is turned on, and a trigger link brake circuit for cooperating with the trigger member and applying a dynamic braking force to the electric motor when the trigger member is turned off.
In operation of the electromotive chain saw, when the trigger member is turned off, both the trigger link mechanical brake and the trigger link brake circuit are operated. The mechanical braking of the brake drum and the electric braking of the electric motor are concurrently carried out. As a result, the cutting chain is stopped directly stopped by the trigger link mechanical brake and indirectly by the trigger link brake circuit, more quickly as compared with the provision of only the trigger link brake circuit or only the trigger link mechanical brake.
The number of rotations of the electric motor can be quickly decreased, in the electromotive chain saw in which the rotary drive force is transmitted from the electric motor via a centrifugal clutch mechanism to the drive sprocket. This occurs, when a predetermined number of rotations of the electric motor is reached or exceeded and no rotary drive force is transmitted to the drive sprocket when the number of rotations is lower than the predetermined number of rotations. Since the centrifugal clutch is quickly released, the load on the trigger link mechanical brake can be reduced. Therefore, the cutting chain can be instantly stopped and the trigger link mechanical brake results in increased durability.
Instead of the centrifugal clutch mechanism, the clutch mechanism can be composed of a plurality of engagement teeth formed on the brake drum, an engagement member rotated together with a rotation shaft rotated by the electric motor and slidable in an axial direction relative to the rotation shaft for engaging with the engagement teeth on the brake drum, and an urging member for pushing and urging the engagement member toward the brake drum. The electromotive chain saw is further provided with a clutch release member for releasing the engagement of the clutch mechanism by pushing back the engagement member against the urging member when the trigger member is moved from its ON position to its OFF position.
In the conventional electromotive chain saw having the clutch release member, the cutting chain can be instantly stopped with a mechanical brake force when the trigger member is turned off. This occurs while gradually stopping the inertial rotation of the electric motor. In the present invention, the cutting chain and the electric motor are concurrently stopped, thereby eliminating discomfort given to an operator when the electric motor is inertially rotated even after the cutting chain is stopped.
In addition, a further advantage of the present invention is provided by the provision of the aforementioned dynamic braking. In actual operation of the conventional electromotive chain saw, when the released trigger member is turned on immediately after turning off, if the motor is still inertial rotated, the rotating clutch components are going to be engaged with one another and the rotary drive force of the electric motor is applied to an engagement detent and other components, thereby impairing the durability of the clutch mechanism. However, in the present invention, the electric motor is also stopped by the dynamic braking. Therefore, the durability of the engagement detent and other clutch components is enhanced.
In the electromotive chain saw, a conventional brake band can be wound around the brake drum, and a trigger link mechanical brake can be provided. By operating a hand guard and pulling the connected end of the brake band, the brake drum is tightened with the brake band, thereby stopping the cutting chain against the rotary drive force of the electric motor. Also, by releasing the trigger member, the cutting chain is stopped directly by the trigger link mechanical brake and indirectly by the trigger link brake circuit.
The trigger link mechanical brake of the electromotive chain saw is provided with an operable member secured to an end of the brake band, for cooperating with the trigger member, such that the brake band is pulled and tightened when the trigger member is released and the brake band is released or loosened when the trigger member is turned on.
An operable member is provided which is secured to one end of the brake band having the other end operatively connected to the hand guard, for cooperating with the trigger member. This adds only a slight structural change to the conventional structure and requires no complicated mechanical arrangement. When the trigger member is released, the end of the brake band, opposite the end operatively connected with the hand guard, is pulled, thereby tightening the brake band for stopping the cutting chain. Therefore, when braking by the trigger link mechanical brake is employed a frictional force is applied to the opposed part of the brake band resulting in a frictional force at the time of braking by the operation of the hand guard.
The trigger link mechanical brake can be provided with a brake shoe for engaging with the outer periphery of the brake drum, an urging member for normally urging or pressing the brake shoe to the brake drum, and a pulling member for disconnecting the brake shoe from the brake drum against the urging member when the trigger member is depressed or turned on.
The brake shoe is provided separately from the brake band and is operatively connected to the hand guard. When the trigger member is released, the brake shoe applies a braking force without giving any frictional force to the brake band.
Alternatively, the trigger link mechanical brake can be provided with a brake shoe operatively connected to the trigger member for engaging with the inner periphery of the brake drum. When the trigger member is released, the brake shoe is pushed onto the brake drum, and when the trigger member is turned on, the brake shoe is disconnected from the brake drum.
The trigger link brake circuit of the electromotive chain saw is provided with a main winding and a brake winding both in a field slot. The supply of a drive current to an armature and the main winding and the supply of a counter electromotive force arising with the brake winding to the armature are changed over with a single-pole double-throw switch, thereby driving and braking the electric motor. When the single-pole double-throw switch is changed over such that the drive current is supplied to the armature and the main winding, one end of the brake winding is disconnected from the armature via the single-pole double-throw switch, and the other end of the brake winding is disconnected from the main winding via a single pole switch.
During the operation of the electromotive chain saw, in the trigger link brake circuit, the brake winding is disconnected from the main winding by the single pole switch, and the brake winding is disconnected from the armature by the single-pole double-throw switch. Therefore, even when the main winding and the brake winding are wound in the same field slot, the brake winding and the main winding are completely insulated via the single pole switch and thus will not deteriorate and no field layer shortage thus occurs. Therefore, to provide the sufficient capabilities of the brake winding, the number of windings can be increased. The trigger link brake circuit is highly durable while it also fulfills its braking performance. For this purpose, the inexpensive single pole switch is provided, eliminating the need for a two-pole double-throw switch, which is cost effective.
To operate the electromotive chain saw, in the trigger link brake circuit, the single pole switch is switched over such that the brake winding is disconnected from the armature and the main winding. The clutch mechanism is engaged. Subsequently, the single-pole double-throw switch is changed over such that the power source is connected with the armature and the main winding.
To apply a braking force to the electromotive chain saw, the single-pole double-throw switch is changed over such that the power source is disconnected from the armature an the main winding and the brake winding is connected with the armature. The clutch mechanism is disconnected. Subsequently, the single pole switch is changed over such that the brake winding is connected with the armature.
When the electric motor is in operation and the single-pole double-throw switch is turned on, in the switching approach, no connection is made between the brake winding and the main winding, therefore, no field layer shortage arises.
Furthermore, when the chain saw is in operation, after the clutch mechanism is engaged, the single-pole double-throw switch is changed over to connect the power source with the main winding and the armature, and the electric motor is driven. When the chain saw is braked, after the single-pole double-throw switch is changed over to disconnect the power source from the main winding and the armature, the clutch mechanism is disengaged. The engagement and disengagement of the clutch mechanism can thus be easily carried out and the durability of the engagement detent can be enhanced.
The invention will now be described, by way of example, with reference to the drawings, in which:
As shown in
As shown in
When the hand guard 17 is in an initial position as shown by a solid line in
As shown in
The rear end of the bent rod 41 is engaged with an upwardly extending lever 51a of a movable member 51 rotatable about a rotational center 52. The movable member 51 is engaged with the forward end of the trigger lever 15 by its rearward lever 51b extending perpendicularly from the upwardly extending lever 51a. The trigger lever 15 is rotatably supported on a support 15a, and a forward end 15b, remote from the support 15a and is largely moved by turning on or off the power switch 19.
In operation, when the power switch 19 is turned off, as shown by the solid line in
When the trigger lever 15 is depressed and the power switch 19 is turned on, as shown by a two-dotted line in
The chain saw 10 is provided with an electric drive and brake device 60 as shown in FIG. 4. The electric drive and brake device 60 is composed of a drive circuit 61 for supplying a drive current to a main winding MW and an armature by a single-pole double-throw switch SW when the trigger lever 15 is turned on and of a brake circuit 62 for supplying a counter electromotive force arising on a brake winding BW to the armature by the single-pole double-throw switch SW when the trigger lever 15 is released.
In the first embodiment, when the trigger lever 15 is released, the aforementioned mechanical brake device 40 and the electric drive and brake device 60 for dynamic braking shown in
The hand guard brake device 20 cooperates with the hand guard 17 and the rear end 23b of the brake band 23 is operatively connected via the bent rod 41 with the mechanical brake device 40. Such brake mechanism is achieved with a minimum number of components and such a simple mechanical structure.
The mechanical brake device 40 cooperates with the power switch 19 and exerts a braking or tightening force to the brake band 23 in the direction opposite to the force exerted to the brake band 23 by the operation of hand guard 17. When the hand guard brake device 20 is operated, the frictional faces of brake band 23 and brake drum 21 are deviated from those when the mechanical brake device 40 is operated. The frictional face of brake band 23 is prevented from being worn quickly by the operation of the hand guard 17 for braking.
Furthermore, as shown in
A second embodiment is now explained. The second embodiment is the same as the first embodiment in that the brake circuit 62 for dynamic braking as shown in
In a chain saw 110 according to the second embodiment, as shown in
The wire 145 is inserted through a protective tube 147 having both ends securely positioned in a body case 110a. The trigger lever 115 is swingable on a support 115d between a connected end of wire 145 and a trigger contact 115a.
The trigger lever 115 is connected with the wire 145 by engaging a cylindrical block 145a at the end of wire 145 into a hole 115b shown in
In operation of mechanical brake device 140, as shown by a solid line in
When the power switch 19 is turned on, as shown by a two-dotted line in
In the chain saw 110 of the second embodiment, by depressing the trigger lever 115 and turning on the power switch 19, the brake drum 21 is permitted to rotate, thereby rotating the chain CH. By letting off the trigger lever 115 and turning off the power switch 19, the brake shoe 141 applies a braking force to the brake drum 21, thereby instantly halting the inertial rotation of chain CH.
As aforementioned, in the second embodiment, by turning off the power switch 19, the brake drum 21 is stopped by a frictional force applied by the brake shoe 141, thereby quickly stopping the chain CH.
The brake shoe 141, operatively connected to the hand guard 17, is provided separately from the brake band 23 of hand guard brake device 20. Therefore, the mechanical brake device 140 operatively connected with the power switch 19 can be added without affecting the conventional structure. The conventional structure can be easily modified in design to incorporate the mechanical brake device 140.
The mechanical brake device 140 operatively connected with the power switch 19 is provided with the components different from those of the mechanical brake device 20 operatively connected with the hand guard 17. The face of the brake band 23 for receiving the frictional force applied when the hand guard 17 is operated is prevented from being worn too quickly.
Furthermore, as shown in
The brake shoe 141 requires no restoring properties different from the brake band 23. The material of the mechanical brake device 140 is selected just by selecting a friction coefficient and consideration of durability. When the brake shoe 141 is pushed against the periphery of brake drum 21 for braking, the power switch 19 is turned off and no strong drive force is applied to the brake drum 21. Accordingly, the material of the brake shoe 141 is chosen to have a sufficiently large friction coefficient. The braking capabilities of mechanical brake device 140 can be optionally designed.
In the same manner as in the first embodiment, when the trigger lever 115 is released, the mechanical brake device 140 and the brake circuit 62 are operated concurrently. While a braking force is mechanically applied to the brake drum 21, the inertial rotary force of the electric motor is diminished by dynamic braking, quickly decreasing the number of rotations of the electric motor and releasing the centrifugal clutch. When the trigger lever 15 is released, no rotary drive force is transmitted to the brake drum 21. Therefore, without exerting excessive force to the brake shoe 141, the chain CH can be quickly stopped. The durability of brake drum 21, brake shoe 141 and chain CH can be enhanced.
A third embodiment is now explained referring to
In an electromotive chain saw 560 according to the third embodiment shown in
As shown in
As shown in
As shown in
A brake shoe 571 is fixedly supported on an arm 573e raised on the root surface of arm 573a of metal support fitting 573, and urged or pushed against an inner periphery of brake drum 521 by a coil spring 579 housed in a case 576c formed adjacent the raised arm 573e.
A free end 575b of swingable lever 575 is connected with a pin 578c to one end 580a of a link rod 580. The other end 580b of link rod 580 is connected with a pin 578d to the tip of an arm 585a of trigger member 585.
As shown in
When the trigger member 585 is depressed, a compression load is applied to the link rod 580. Therefore, the link rod 580, formed by pressing a metal plate, is bulged in its middle so as to have an improved buckling strength.
As shown in
The operation of trigger-linked mechanical brake 570 is now explained referring to
When the trigger member 585 is released, the link rod 580 and the swingable lever 575 are in the position shown by a solid line in FIG. 11A. The M-shaped part 573c is lowered to depress the swingable detent 577 as shown in the upper figure of FIG. 10C. In the clutch 590, as shown in
When the trigger member 585 is depressed, the link rod 580 and the swingable lever 575 are moved to the position shown by a two-dotted line in FIG. 11A. The M-shaped part 573c applies no depressing force to the swingable detent 577 as shown in the lower figure of FIG. 10C. The swingable detent 577 is rotated clockwise as seen in
An electric drive and brake device 600 according to the third embodiment includes, as shown in
As shown in
As shown in
The trigger member 585 is provided in the rearward handle 13 such that the trigger member 585 can contact the push buttons 613, 623, respectively. When the trigger member 585 is depressed in the rearward handle 13, both the push buttons 613, 623 are depressed in the housings 611, 621, respectively. When the trigger member 585 is released, the push buttons 613 and 623 are projected from the housing 511 and 521, respectively.
In the third embodiment, when the trigger member 585 is depressed, the contact P is first disconnected from the contact Q in the single pole switch SW2. Subsequently, in the single-pole double-throw switch SW1, the contact A is disconnected from the contact C and the contact B is connected to the contact C. When the trigger member 585 is released, first in the single-pole double-throw switch SW1, the contact B is disconnected from the contact C, and the contact A is connected to the contact C. Subsequently, in the single pole switch SW2, the contact P is connected to the contact Q.
In the third embodiment, when the trigger member 585 is depressed, after the male and female clutch members 593 and 595 are engaged with each other, the single-pole double-throw switch SW1 is changed over to the closed circuit connecting the electric power and the electric motor, thereby driving the electric motor. When the depressed trigger member 585 is released, the single-pole double-throw switch SW1 is changed over to the open circuit for disconnecting the electric power from the electric motor, thereby placing the electric motor in the inoperative condition. Subsequently, the male and female clutch members 593 and 595 are disengaged from each other. Therefore, while the electric motor is driven, no engagement or disengagement of the clutch members are performed, thereby enhancing the durability of the clutch detent members.
In the third embodiment, when the trigger member 585 is released, the clutch 590 is disconnected, and a mechanical braking force is applied by the brake shoe to the brake drum. Therefore, without loading much frictional force on the brake shoe, the chain can be stopped quickly. Also, the electric drive and brake device for dynamic braking is operated, thereby instantly stopping the inertial rotation of the electric motor. In the third embodiment, since the clutch 590 is forceably disconnected, the brake drum is not braked by the electric brake circuit and the electric motor itself is dynamically braked. However, the operator can recognize the chain as well as the motor instantly stopping, and can operate the chain saw comfortably. The clutch is mechanically disconnected before the electric motor is stopped. Therefore, only the inertial rotation of the electric motor is stopped through dynamic braking, and the period of time required for stopping the electric motor can be advantageously reduced. It can be appreciated that the third embodiment provides a function of stopping the electric motor quickly.
If, after disconnecting the clutch, no electric drive and brake device is operated, the electric motor will be inertially rotated for several seconds, without any load of the chain put thereon. If the trigger member is again depressed during such inertial rotation, the inertially rotating male clutch member 593 will be engaged with the mechanically stopped female clutch member 595. The drive force of the electric motor acting on the engagement of the clutch members will deteriorate the durability of the clutch members 593, 595.
In the third embodiment, however, the chain is instantly stopped by the trigger-linked mechanical brake and concurrently the electric motor is instantly stopped by the electric brake circuit 600. If the chain saw is again driven immediately after stopped, the male and female clutch members 593 and 595 are engaged with each other while the electric motor is stopped. No drive force of the electric motor acts on the clutch engagement and the durability of the clutch members 593, 595 is prevented from impairment. Since, in the actual operation of the chain saw, the trigger member 585 may be repeatedly turned on and off, the aforementioned advantage of the enhanced durability is remarkably effective in the electromotive chain saw provided with the trigger-linked mechanical brake having the aforementioned clutch disconnecting mechanism.
In the third embodiment the inner and outer peripheries of the brake drum are in contact with the brake device 570 operable when the trigger member is released and the hand guard brake device 20 operatively connected with the hand guard 17, respectively. These brake devices can be provided without increasing the size of the brake drum 521 or the entire size of the chain saw. These brake mechanisms can coexist in a compact structure.
In the third embodiment, by providing the M-shaped part 573c, as the clutch first begins to be released, and after the clutch is released, the braking force is applied. The time the clutch is released deviates from the time the braking force is applied. Therefore, a braking force can be easily applied. In the embodiment, the clutch is released and the brake device 570 is operated, using the action of a lever. The trigger member 585 can be depressed without requiring a strong depression force, thereby giving an operator comfort.
In a modified electric drive and brake device or circuit 600, during the operation of the chain saw, the brake winding BW can be disconnected from the main winding MW and the armature M via the single pole switch SW2. In this case, since the main winding MW and the brake winding BW, provided in the same field slot, are disconnected from each other via the single pole switch SW2, the windings fail to be deteriorated and no field layer shortage occurs. Therefore, to provide sufficient braking capabilities of brake winding BW, the number of windings of brake winding BW can be increased. The modified brake circuit can form a highly durable, highly capable brake device. Furthermore, the modified brake circuit can be inexpensively formed by adding an inexpensive single-pole switch to the brake circuit of the first embodiment, obviating the necessity of a two-pole double-throw switch.
A further modified brake circuit, as shown in
The electric drive and brake device 600 of the third embodiment can be used in the first and second embodiments.
In the third embodiment, the single pole switch SW2 is turned on or off by the arm 585a of trigger member 585. The single pole switch SW2 can be positioned such that the switch SW2 can be turned on or off by moving the link rod 580 provided with a projection.
This invention has been described above with reference to the preferred embodiments as shown in the figures. Modifications and alterations may become apparent to one skilled in the art upon reading and understanding the specification. Despite the use of the embodiment for illustration purposes, the invention is intended to include all such modifications and alterations within the spirit and scope of the appended claims.
Kondo, Masaki, Nakamura, Kazuya, Mizutani, Makoto
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