Power tool having control system for changing rotational speed of output shaft

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:
• 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 low gear reduction ratio and a second position corresponding to the high gear reduction ratio, wherein the movable member has a rotational speed at the first position;
• and
• a control system operatively associated with the movable member which is capable of determining an operating characteristic indicative of a load applied to the output shaft, wherein the control system is operative to actuate the movable member to move from the first position to the second position and to reduce the rotational speed of the movable member when the operating characteristic reaches or exceeds a predetermined value;
• wherein the control system is configured to first reduce the rotational speed of the movable member and to then actuate the movable member to move from the first position to the second position.

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:
• 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 low gear reduction ratio and a second position corresponding to the high gear reduction ratio, wherein the movable member has a rotational speed at the first position;
• and
• a control system operatively associated with the movable member which is capable of determining an operating characteristic indicative of a load applied to the output shaft, wherein the control system is operative to actuate the movable member to move from the first position to the second position and to reduce the rotational speed of the movable member when the operating characteristic reaches or exceeds a predetermined value;
• wherein the gear train is a planetary gear train including a plurality of planet gears, an adjacent planet carrier, and a rotationally fixed structure immovably associated with the housing.

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:
• 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 low gear reduction ratio and a second position corresponding to the high gear reduction ratio, wherein the movable member has a rotational speed at the first position;
• and
• a control system operatively associated with the movable member which is capable of determining an operating characteristic indicative of a load applied to the output shaft, wherein the control system is operative to actuate the movable member to move from the first position to the second position and to reduce the rotational speed of the movable member when the operating characteristic reaches or exceeds a predetermined value;
• wherein the control system comprises:
• a control unit capable of determining the operating characteristic indicative of a load applied to the output shaft and reducing the rotational speed of the movable member;
• and
• a driving mechanism actuatable by the control unit to drive the movable member between the first position and the second position.

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:
• 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 low gear reduction ratio and a second position corresponding to the high gear reduction ratio, wherein the movable member has a rotational speed at the first position;
• and
• a control system operatively associated with the movable member which is capable of determining an operating characteristic indicative of a load applied to the output shaft, wherein the control system is operative to actuate the movable member to move from the first position to the second position and to reduce the rotational speed of the movable member when the operating characteristic reaches or exceeds a predetermined value;
• wherein the operating characteristic is the motor current.

A control system for a power tool which has a housing, a motor contained in the housing and having a rotational speed, an output shaft and a gear transmission mechanism for transmitting the rotational speed of the motor to the output shaft at each of a plurality of gear reduction ratios, the control system comprising:

• a driving mechanism operatively engaged with the gear transmission mechanism and actuatable to select each gear reduction ratio;
• an electronic detector for detecting an operating characteristic of the power tool;
• a speed modulator for modulating the rotational speed of the motor;
• and
• a controller operatively coupled to the detector, to the driving mechanism to actuate the driving mechanism to select each gear reduction ratio when the operating characteristic reaches or exceeds a predetermined value and to the speed modulator to assist the speed modulator to modulate the rotational speed of the motor when the operating characteristic reaches or exceeds a predetermined value.

A control system for a power tool which has a housing, a motor contained in the housing and having a rotational speed, an output shaft and a gear transmission mechanism for transmitting the rotational speed of the motor to the output shaft at each of a plurality of gear reduction ratios, the control system comprising:

• a driving mechanism operatively engaged with the gear transmission mechanism and actuatable to select each gear reduction ratio;
• a detector for detecting an operating characteristic of the power tool;
• a speed modulator for modulating the rotational speed of the motor;
• and
• a controller operatively coupled to the detector, to the driving mechanism to actuate the driving mechanism to select each gear reduction ratio when the operating characteristic reaches or exceeds a predetermined value and to the speed modulator to assist the speed modulator to modulate the rotational speed of the motor when the operating characteristic reaches or exceeds a predetermined value;
• wherein the controller assists the speed modulator to reduce the rotational speed of the motor when the operating characteristic reaches or exceeds a predetermined value;
• and
• wherein the controller assists the speed modulator to reduce the rotational speed of the motor and then actuates the driving mechanism to select each gear reduction ratio when the operating characteristic reaches or exceeds a predetermined value.

A control system for a power tool which has a housing, a motor contained in the housing and having a rotational speed, an output shaft and a gear transmission mechanism for transmitting the rotational speed of the motor to the output shaft at each of a plurality of gear reduction ratios, the control system comprising:

• a driving mechanism operatively engaged with the gear transmission mechanism and actuatable to select each gear reduction ratio;
• a detector for detecting an operating characteristic of the power tool;
• a speed modulator for modulating the rotational speed of the motor;
• and
• a controller operatively coupled to the detector, to the driving mechanism to actuate the driving mechanism to select each gear reduction ratio when the operating characteristic reaches or exceeds a predetermined value and to the speed modulator to assist the speed modulator to modulate the rotational speed of the motor when the operating characteristic reaches or exceeds a predetermined value;
• wherein the controller assists the speed modulator to reduce the rotational speed of the motor when the operating characteristic reaches or exceeds a predetermined value;
• and
• wherein the controller actuates the driving mechanism to select a gear reduction ratio higher then the present gear reduction ratio when the operating characteristic reaches or exceeds a predetermined value.

A control system for a power tool which has a housing, a motor contained in the housing and having a rotational speed, an output shaft and a gear transmission mechanism for transmitting the rotational speed of the motor to the output shaft at each of a plurality of gear reduction ratios, the control system comprising:

• a driving mechanism operatively engaged with the gear transmission mechanism and actuatable to select each gear reduction ratio;
• a detector for detecting an operating characteristic of the power tool;
• a speed modulator for modulating the rotational speed of the motor;
• and
• a controller operatively coupled to the detector, to the driving mechanism to actuate the driving mechanism to select each gear reduction ratio when the operating characteristic reaches or exceeds a predetermined value and to the speed modulator to assist the speed modulator to modulate the rotational speed of the motor when the operating characteristic reaches or exceeds a predetermined value;
• wherein the driving mechanism is electromagnetically actuatable.

A control system for a power tool which has a housing, a motor contained in the housing and having a rotational speed, an output shaft and a gear transmission mechanism for transmitting the rotational speed of the motor to the output shaft at each of a plurality of gear reduction ratios, the control system comprising:

• a driving mechanism operatively engaged with the gear transmission mechanism and actuatable to select each gear reduction ratio;
• a detector for detecting an operating characteristic of the power tool;
• a speed modulator for modulating the rotational speed of the motor;
• and
• a controller operatively coupled to the detector, to the driving mechanism to actuate the driving mechanism to select each gear reduction ratio when the operating characteristic reaches or exceeds a predetermined value and to the speed modulator to assist the speed modulator to modulate the rotational speed of the motor when the operating characteristic reaches or exceeds a predetermined value;
• wherein the operating characteristic is the motor current.