Power tool with signal generator

Abstract

A power tool comprising a housing, a motor, an output shaft, a gear transmission mechanism and a control system. The gear transmission mechanism is connected between the motor and the output shaft to transmit the rotary power of the motor to the output shaft. The power tool comprises a signal generator and a control system electrically coupled to the signal generator and operatively engaged with the gear transmission mechanism such that when the signal generator is manually activated, an electric signal is generated and transmitted to the control system to cause the gear transmission mechanism to vary the gear reduction ratio.

1 . A power tool capable of variable output speed comprising:
 a housing,   a motor contained in the housing for outputting rotary power;   an output shaft;   a gear transmission mechanism disposed between the motor and the output shaft for transmission of the rotary power of the motor to the output shaft at each of a plurality of gear reduction ratios;   a main switch for starting or stopping the motor;   a signal generator separate from the main switch; and   a control system electrically coupled to the signal generator and operatively engaged with the gear transmission such that when the signal generator is manually activated, an electric signal is generated and transmitted to the control system to cause the gear transmission mechanism to vary the gear reduction ratio.   
     
     
         2 . The power tool according to  claim 1 , wherein the signal generator comprises a switch mounted on the housing. 
     
     
         3 . The power tool according to  claim 2 , further comprising a handle coupled to the housing, wherein the handle is arranged at a predetermined distance from the switch such that the switch is operable by the hand of the user without removing the hand from the handle. 
     
     
         4 . The power tool according to  claim 2 , wherein the control system comprises:
 a control unit electrically connected to the switch to receive the electrical signal when the switch is activated; and   a driving mechanism actuated by the control unit is response to the electrical signal to cause the gear transmission mechanism to vary the gear reduction ration.   
     
     
         5 . The power tool according to  claim 4 , wherein the gear transmission mechanism comprises:
 at least one gear train; and   a movable member movable between a first position corresponding to a low gear reduction ration and a second position corresponding to a high reduction ration whereby to vary the gear reduction ration.   
     
     
         6 . The power tool according to  claim 5 , wherein the gear train is a planetary gear train which includes a plurality of planet gears, an adjacent planet carrier, and a rotationally fixed structure immovably associated with the housing. 
     
     
         7 . A power tool capable of variable output speed comprising:
 a housing,   a motor contained in the housing for outputting rotary power;   an output shaft;   a gear transmission mechanism disposed between the motor and the output shaft for transmission of the rotary power of the motor to the output shaft at each of a plurality of gear reduction ratios including a first gear reduction ratio and a second gear reduction ratio, the gear transmission mechanism comprises:   at least one gear train; and   a movable member variably engaged with the gear train, wherein the movable member is movable between a first position corresponding to the first gear reduction ratio and a second position corresponding to the second gear reduction; and   an electrical control system comprising a mechanism for driving the movable member to move from the first position to the second position and from the second position to the first position, the electrical control system further comprising an input/output circuit.   
     
     
         8 . The power tool according to  claim 7 , wherein the gear train is a planetary gear train which includes a plurality of planet gears, an adjacent planet carrier, and a rotationally fixed structure immovably associated with the housing. 
     
     
         9 . The power tool according to  claim 7 , wherein the control system further comprises a control unit operative to apply electric current to the mechanism to drive the movable member. 
     
     
         10 . A power tool capable of variable output speed comprising:
 a housing,   a motor contained in the housing for outputting rotary power;   an output shaft;   a gear transmission mechanism disposed between the motor and the output shaft for transmission of the rotary power of the motor to the output shaft at each of a plurality of gear reduction ratios including a first gear reduction ratio and a second gear reduction ratio, the gear transmission mechanism comprises:   at least one gear train; and   a movable member variably engaged with the gear train, wherein the movable member is movable between a first position corresponding to the first gear reduction ratio and a second position corresponding to the second gear reduction; and   a control system comprises a mechanism operative to drive the movable member to move from the first position to the second position and from the second position to the first position;   wherein the mechanism comprises a small motor and a transmission mechanism for transmission of the rotary power of the small motor to the movable member.   
     
     
         11 . The power tool according to  claim 10 , wherein the transmission mechanism comprises a circular sleeve and a small gear transmission mechanism disposed between the small motor and the circular sleeve. 
     
     
         12 . The power tool according to  claim 11 , wherein the circular sleeve is driven by the small gear transmission mechanism to rotate. 
     
     
         13 . The power tool according to  claim 11  or  claim 12 , wherein the small gear transmission mechanism comprises a steel wire, the circular sleeve has a pair of diametrically opposed grooves defined in the circumferential wall for receiving and guiding opposite distal ends of the steel wire. 
     
     
         14 . The power tool according to  claim 13 , wherein the movable member is driven by the circular sleeve to move linearly. 
     
     
         15 . A power tool capable of variable output speed comprising:
 a housing,   a motor contained in the housing for outputting rotary power;   an output shaft;   a gear transmission mechanism disposed between the motor and the output shaft for transmission of the rotary power of the motor to the output shaft at each of a plurality of gear reduction ratios including a low gear reduction ratio and a high gear reduction ratio; and   an automatic speed variation system for detecting an operating characteristic of a load applied to the output shaft and operatively associated with the gear transmission to vary the gear reduction ratios when the operating characteristic reach or exceeds a predetermined value;   a speed mode selector operative to select one of the three speed modes includes a a high speed mode and a low speed mode and an automatic speed mode, wherein the gear transmission mechanism transmit the rotational speed of the motor at the low gear reduction ratio and the automatic speed variation system deactivate when the speed mode selector is located at the high speed mode, the gear transmission mechanism transmit the rotational speed of the motor at the high gear reduction ratio and the automatic speed variation system deactivate when the speed mode selector is located at the low speed mode, the gear transmission mechanism transmit the rotational speed of the motor under the controlling of automatic speed variation system when the speed mode selector is located at the automatic speed mode.   
     
     
         16 . The power tool according to  claim 15 , wherein the automatic speed variation system comprises a driving mechanism associated with the gear transmission mechanism and an electrical control unit for detecting the operating characteristic and operative to control the driving mechanism to change the gear reduction ratio of the gear transmission mechanism when the operating characteristic reach or exceeds a predetermined value. 
     
     
         17 . The power tool according to  claim 16 , wherein the speed mode selector comprises three signal contacts corresponding to the three speed modes, the electrical control unit connect with the three signal contacts. 
     
     
         18 . The power tool according to  claim 17 , wherein the electrical control unit can receive a signal comes from the corresponding signal contact when the speed mode selector is selectively located at one of the three speed modes. 
     
     
         19 . The power tool according to  claim 18 , wherein the signal comprises a low state signal and a high state signal. 
     
     
         20 . The power tool according to  claim 19 , wherein the electrical control unit comprises a microcontroller provided with three input ports/output ports connected with the signal contacts. 
     
     
         21 . The power tool according to  claim 15 , wherein the speed mode selector comprises a selector button operatively slide on the housing corresponding to the three speed modes. 
     
     
         22 . A power tool capable of variable output speed comprising:
 a housing,   a motor contained in the housing for outputting rotary power;   an output shaft;   a gear transmission mechanism disposed between the motor and the output shaft for transmission of the rotary power of the motor to the output shaft at each of a plurality of gear reduction ratios including a low gear reduction ratio and a high gear reduction ratio, wherein the gear transmission mechanism comprises:   a gear case;   at least one gear train and a movable member disposed in the gear case, the movable member variably engaged with the gear train, wherein the movable member is movable between a first position corresponding to the low gear reduction ration and a second position corresponding to a high gear reduction ration; and   a control system comprises a solenoid operatively driving the movable member to move between the first position and second position, wherein the solenoid disposed in the housing adjacent to the gear case.   
     
     
         23 . The power tool according to  claim 22 , wherein the solenoid further comprises a coil, an iron core linearly movable through the coil and a push bar attached to the iron core and connected to the movable member. 
     
     
         24 . The power tool according to  claim 23 , wherein the control system further comprises a transmission member connected between the movable member and the push bar, the transmission member connect with the push bar fixedly. 
     
     
         25 . The power tool according to  claim 24 , further comprises a steel wire connected between the movable member and the transmission member. 
     
     
         26 . The power tool according to  claim 23 , further comprises an electronic control unit operative to apply an electric current to the solenoid to actuate the push bar to move linearly and then drive the movable member to move between the first position and the second position.