Electromotive chain saw

Abstract

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.

What is claimed is:  
     
       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  claim 1 , further including a hand brake device comprising a hand guard, a linkage and a steel brake band, said linkage connects a forward end of said brake band to said hand guard, said brake band is wound around a circumference of said brake drum, and said hand brake device is operated by pushing said hand guard away from an operator such that a spring is extended thereby pulling an end of said brake band to tighten said brake band and exert a braking force opposite in direction to the braking force exerted by said mechanical brake resulting in extended life for said brake band. 
     
     
       3. The electromotive chain saw according to  claim 1 , wherein said a bent rod couples said common trigger member to said mechanical brake. 
     
     
       4. The electromotive chain saw according to  claim 3 , wherein said mechanical brake is located in a clearance of a chain saw case using said bent rod without increasing the size of said chain saw. 
     
     
       5. The electromotive chain saw according to  claim 1 , wherein a rotary drive force is supplied to a drive sprocket from said electric motor via a centrifugal clutch mechanism when a rotational speed of said electric motor exceeds a predetermined number of rotations, and said rotary drive force disconnects said drive sprocket from said electric motor via said centrifugal clutch mechanism when the rotational speed of said electric motor is lower than said predetermined number of rotations. 
     
     
       6. The electromotive chain saw according to  claim 1 , wherein 
       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  claim 1 , wherein said mechanical brake comprises a movable member operatively connected to said common trigger member and secured to a second end of a brake band, which extends around a circumference of said brake drum, such that said brake band is pulled and tightened around said brake drum when said trigger member is in said OFF position, and said brake band is released and loosened from said brake drum when said trigger member is in said ON position. 
     
     
       8. The electromotive chain saw according to  claim 1 , wherein said mechanical brake is provided with a brake shoe for engaging with an outer periphery of said brake drum. 
     
     
       9. The electromotive chain saw according to  claim 2 , in which said mechanical brake is provided with a brake shoe for engaging with an inner periphery of said brake drum. 
     
     
       10. The electromotive chain saw according to  claim 9 , wherein when said common trigger member is in said OFF position, said brake shoe contacts said brake drum to apply said braking force to said brake drum and when said common trigger member is in said ON position, said brake shoe is removed from contact with said brake drum thereby removing said braking force from said brake drum. 
     
     
       11. The electromotive chain saw according to  claim 1 , further comprising a trigger link brake circuit having: 
       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  claim 11 , wherein said electric motor, provided with said trigger link brake circuit, comprises a single-phase series commutator motor, 
       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  claim 12 , wherein 
       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  claim 1 , wherein said brake mechanism is a steel brake band wound around a circumference of said brake drum, when said trigger member is in said OFF position said steel brake band is tightened resulting in application of said braking force to said brake drum, and when said trigger member is in said ON position said steel brake band is loosened from said brake drum thereby removing said braking force from said brake drum. 
     
     
       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.  
       
     
     
       16. A chain saw according to  claim 15 , wherein the common trigger is directly coupled to both the electric brake circuit and the mechanical brake, the first trigger position corresponds to an ON position and the second trigger position corresponds to an OFF position.  
     
     
       17. A chain saw according to  claim 15 , further comprising a clutch coupled to the cutting chain, the electric motor and the common trigger, wherein the clutch disengages the electric motor from the cutting chain when the common trigger is in the second trigger position.  
     
     
       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.  
       
     
     
       19. A chain saw according to  claim 18 , wherein in the ON position the common trigger concurrently causes the mechanical brake to move to a disengaged position and the electric brake to not apply the electrical braking force to the electric motor, and in the OFF position the common trigger concurrently causes the mechanical brake to apply the mechanical braking force to the brake drum and the electric brake to apply the electrical braking force to the electric motor.  
     
     
       20. A chain saw according to  claim 19 , further comprising a clutch coupled to the cutting chain, the electric motor and the common trigger, wherein the clutch disengages the electric motor from the cutting chain when the common trigger is in the OFF position.  
     
     
       21. A chain saw according to  claim 18 , further comprising a clutch coupled to the cutting chain, the electric motor and the common trigger, wherein the clutch disengages the electric motor from the cutting chain when the common trigger is in the OFF position.  
     
     
       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.  
       
     
     
       23. A chain saw according to  claim 22 , wherein the means for simultaneously actuating both the first means and the second means is a trigger switch.  
     
     
       24. A chain saw according to  claim 23 , wherein the trigger switch has an ON position and an OFF position, in the ON position the first means does not apply the mechanical braking force to stop the cutting chain and the second means does not apply the electrical braking force to the electric motor, and in the OFF position the first means applies the mechanical braking force to stop the cutting chain and the second means applies the electric braking force to the electric motor.  
     
     
       25. A chain saw according to  claim 24 , further comprising a clutch coupling the cutting chain to the electric motor, wherein the clutch disengages the electric motor from the cutting chain when the trigger switch is in the OFF position.  
     
     
       26. A chain saw according to  claim 22 , further comprising a clutch coupling the cutting chain to the electric motor, wherein the clutch disengages the electric motor from the cutting chain when the first means and the second brake means have been simultaneously actuated.  
     
     
       27. An apparatus as in  claim 22 , further comprising a power switch coupled to the third means, wherein movement of the power switch to an OFF position simultaneously and concurrently operates both the first means and the second means via the third means to quickly stop the rotation of the cutting chain.  
     
     
       28. The apparatus as in  claim 27 , further comprising a handguard coupled to the third means, wherein movement of the handguard to an OFF position simultaneously and concurrently operates both the first means and the second means via the third means to quickly stop the rotation of the cutting chain.  
     
     
       29. The apparatus as in  claim 28 , further comprising a clutch coupled to the cutting chain, the electric motor and the third means, wherein the clutch disengages the electric motor from the cutting chain when the third means is activating the first and second means.  
     
     
       30. The apparatus as in  claim 22 , further comprising a handguard coupled to the third means, wherein movement of the handguard to an OFF position simultaneously and concurrently operates both the first means and the second means via the third means to quickly stop the rotation of the cutting chain.  
     
     
       31. The apparatus as in  claim 30 , further comprising a clutch coupled to the cutting chain, the electric motor and the third means, wherein the clutch disengages the electric motor from the cutting chain when the third means is activating the first and second means.  
     
     
       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.  
       
     
     
       33. The apparatus as in  claim 32 , further comprising a power switch coupled to the trigger member, wherein movement of the power switch to an OFF position simultaneously and concurrently operates both the mechanical brake and the electrical brake via the trigger member to quickly stop the rotation of the cutting chain.  
     
     
       34. The apparatus as in  claim 33 , further comprising a handguard coupled to the trigger member, wherein movement of the handguard to an OFF position simultaneously and concurrently operates both the mechanical brake and the electrical brake via the trigger member to quickly stop the rotation of the cutting chain.  
     
     
       35. The apparatus as in  claim 34 , further comprising a clutch coupled to the cutting chain, the electric motor and the trigger member, wherein the clutch disengages the electric motor from the cutting chain when the trigger member is in the OFF position.  
     
     
       36. The apparatus as in  claim 32 , further comprising a handguard coupled to the trigger member, wherein movement of the handguard to an OFF position simultaneously and concurrently operates both the mechanical brake and the electrical brake via the trigger member to quickly stop the rotation of the cutting chain.  
     
     
       37. The apparatus as in  claim 36 , further comprising a clutch coupled to the cutting chain, the electric motor and the trigger member, wherein the clutch disengages the electric motor from the cutting chain when the trigger member is in the OFF position.