Power tool with signal generator

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 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;
• wherein the signal generator comprises a switch mounted on the housing;
• 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 in response to the electrical signal to cause the gear transmission mechanism to vary the gear reduction ratio;
• wherein the driving mechanism is electromagnetically actuatable and operatively engages the movable member, wherein the control unit is operative to apply electric current to the driving mechanism to drive the movable member.

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 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;
• wherein the signal generator comprises a switch mounted on the housing;
• 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 in response to the electrical signal to cause the gear transmission mechanism to vary the gear reduction ratio;
• wherein the control unit is capable of determining whether there is a load applied to the power tool before actuating the driving mechanism.

A power tool for varying 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 comprising:
• 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 ratio;
• and
• a 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;
• wherein the mechanism comprises a bi-directional keep solenoid capable of retaining the movable member at the first or the second position without electricity.

A power tool for varying 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 comprising:
• 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 ratio;
• and
• a 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;
• 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;
• wherein the movable member comprises a ring gear which when located at the first position engages the planet gears and the planet carrier and when located at the second position engages the planet gears and the rotationally fixed structure.

A power tool for varying 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 comprising:
• 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 ratio;
• and
• a 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;
• wherein the control system further comprises a control unit operative to apply electric current to the mechanism to drive the movable member;
• wherein the control system comprises an H-bridge circuit for changing the direction of the electric current applied to the mechanism.