Power tool

Abstract

A power tool 1 is connected to a battery pack 5 including an overcurrent detector 533 which detects overcurrent of a battery module 51 and outputs a detection signal, and an overdischarge detector 532 which detects overdischarge of the battery module 51 and outputs a detection signal. The power tool 1 includes a motor 2 which is driven by electric power supplied from the battery pack 5 , a trigger switch 31 for setting the power supply from the battery pack 5 to the motor 2 in ON/OFF state, and an FET 410 which sets the power supply to the motor 2 in ON/OFF state on the basis of the detection signal from the overcurrent detector 533 or the overdischarge detector 532.

1 - 6 . (canceled) 
     
     
         7 . A power tool comprising:
 a detachable battery pack;   a drive part that is driven by electrical power supplied from the detachable battery pack;   a first switching unit to turn a supply of electrical power to the drive part from the detachable battery pack ON and OFF by way of user interaction with the first switching unit;   a second switching unit, connected in series with the first switching unit, that turns a supply of electrical power to the drive part ON and OFF; and   a signal generating unit that generates a signal to turn OFF the second switching unit if the detachable battery pack is reconnected to the power tool while the first switching unit is turned ON and maintains the signal when the first switching unit is turned ON.   
     
     
         8 . The power tool according to  claim 7 , wherein the signal generating unit is operable to retain the power supply to the drive part OFF when the first switch unit is in an ON state and the power supply to the drive part is interrupted by the second switch unit. 
     
     
         9 . The power tool according to  claim 7 , further comprising:
 an overcurrent monitoring unit that detects when current flowing to the drive part exceeds a predetermined value,   wherein the signal generating unit generates the signal to turn the second switching unit OFF if the overcurrent monitoring unit detects an overcurrent.   
     
     
         10 . The power tool according to  claim 7 , wherein
 the second switch unit is disposed on the power tool and comprises an FET.   
     
     
         11 . The power tool according to  claim 7 , wherein
 the signal generating unit is operable to prevent the flow of current to the drive part when the power tool is connected to the detachable battery pack when the first switch unit is in its ON state.   
     
     
         12 . The power tool according to  claim 7 , wherein the detachable battery pack comprises a plurality of serially connected lithium-ion battery cells.