Power tool and motor controller

• US 20050127862A1
• Filed: 11/23/2004
• Published: 06/16/2005
• Est. Priority Date: 12/06/2000
• Status: Active Grant

• Current Assignee: Milwaukee Electric Tool Corporation (Techtronic Industries Company Limited)
• Original Assignee: Milwaukee Electric Tool Corporation (Techtronic Industries Company Limited)
• Inventors: Glasgow, Kevin L., Crisp, Robert M.
• Granted Patent: US 7,116,071 B2
• Time in Patent Office: Days
• US Class Current: 318/280
• CPC Class Codes: B05C 17/00503 Details of the outlet element B05C17/00523 takes precedence; nozzles for deformable tubular containers B65D35/38
• CPC Class Codes: B05C 17/0103 with electrically actuated piston or the like
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: G01F 11/026 of the gun type hand operated grease guns F16N3/12
• CPC Class Codes: H02H 7/0858 by reversing, cycling or reducing the power supply to the motor
• CPC Class Codes: H02H 9/025 Current limitation using field effect transistors
• CPC Class Codes: H02P 7/04 by means of a H-bridge circuit
• CPC Class Codes: H02P 7/29 using pulse modulation

Abstract

A method and apparatus to automatically reverse the motor of a power tool, such as a dispensing gun or similar tool. In some constructions, a controller automatically reverses the direction of plunger movement and removes the plunger from contact with the back wall of a cartridge. The controller has a trigger switch that is coupled to a power source, such as a battery, and includes a main power on/off switch and a potentiometer. A protection or secondary switch is coupled in parallel to the main power on/off switch. A power supply circuit and a commutator are each coupled to the main and secondary switches. An overload sensor is coupled to the commutator. The controller includes a programmable device that is coupled to the power supply circuit, the potentiometer, the commutator, and the overload sensor. The programmable device is operable to sense actuation and deactuation of the main power on/off switch, read an electromotive force from the potentiometer, and, upon sensing deactuation of the main switch, send a control signal to the commutator to reverse current flow therethrough for a predetermined amount of time, and deactuate the secondary switch when the predetermined time has lapsed.

Claims

1. A power tool comprising:

a housing;

a motor supported by the housing;

a trigger switch movable in a first direction for actuating the motor in a first direction and in a second direction for actuating the motor in a second direction; and

a secondary switch coupled in a parallel path to the trigger switch, the secondary switch being actuated a predetermined amount of time after the trigger switch is moved in the first direction, the secondary switch being deactuated a predetermined amount of time after the motor is actuated in the second direction.

2. A power tool as claimed in claim 1 wherein the trigger switch includes a main switch and a potentiometer.

3. A power tool as claimed in claim 2 wherein the secondary switch is actuated after the potentiometer reaches a threshold voltage for two seconds.

4. A power tool as claimed in claim 3 wherein the threshold voltage is one volt.

5. A power tool as claimed in claim 1 wherein the power tool is a material dispensing gun.

6. A power tool as claimed in claim 5 wherein the movement of the trigger switch controls the speed at which material is dispensed.

7. A power tool as claimed in claim 1 wherein the secondary switch is deactuated after the trigger switch is released and 0.5 seconds after the motor is actuated in the second direction.

8. A method of controlling the direction of a motor in a power tool, the method comprising the acts of:

moving a trigger switch in a first direction;

actuating the motor in a first direction after the trigger switch has been moved in the first direction for a predetermined amount of time;

actuating a secondary switch;

moving the trigger switch in a second direction;

actuating the motor in a second direction for a predetermined amount of time after the trigger switch has been moved in the second direction; and

deactuating the secondary switch after the motor is actuated in the second direction for a predetermined amount of time.

9. A method as claimed in claim 8 further including the act of reading a voltage from the trigger switch.

10. A method as claimed in claim 9 wherein the act of actuating the secondary switch occurs after the trigger switch reaches a threshold voltage for two seconds.

11. A method as claimed in claim 10 wherein the threshold voltage is one volt.

12. A method as claimed in claim 8 wherein the act of moving the trigger switch further includes the act of controlling the speed of the motor.

13. A method as claimed in claim 8 wherein the act of deactuating the secondary switch occurs after the trigger switch is released and 0.5 seconds after the motor is actuated in the second direction.

14. A power tool comprising:

a housing;

a motor supported by the housing;

a trigger switch selectively coupling the motor to a power source; and

a secondary switch coupled in a parallel path to the trigger switch, the secondary switch being actuable upon actuation of the trigger switch for a predetermined amount of time;

wherein the motor is actuable in a first direction upon actuation of the trigger switch for a predetermined amount of time, and wherein the motor is actuable in a second direction upon actuation of the secondary switch and deactuation of the trigger switch for a predetermined amount of time.

15. A power tool as claimed in claim 14 wherein the trigger switch includes a main switch and a potentiometer.

16. A power tool as claimed in claim 14 further comprising a commutator coupled to the motor and operable to drive the motor in the first and second directions.

17. A power tool as claimed in claim 16 further comprising a programmable device coupled to the trigger switch and the commutator, the programmable device operable to sense actuation and deactuation of the trigger switch.

18. A power tool as claimed in claim 17 wherein the programmable device transmits a control signal to the commutator to drive the motor in the first direction upon sensing actuation of the trigger switch.

19. A power tool as claimed in claim 17 wherein the programmable device transmits a control signal to the commutator to drive the motor in the second direction upon sensing deactuation of the trigger switch.

20. A power tool as claimed in claim 16 wherein the programmable device transmits a control signal to the motor.