Electric sander and motor control therefor

• US 20050245183A1
• Filed: 04/12/2005
• Published: 11/03/2005
• Est. Priority Date: 04/13/2004
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Gorti., Bhanuprasad V., Deshpande, Uday S., Waikar, Shailesh P., Hilsher, William F.
• Granted Patent: US 7,270,591 B2
• Time in Patent Office: Days
• US Class Current: 451/357
• CPC Class Codes: B24B 23/03 the tool being driven in a combined movement

Abstract

A hand held orbital sander has a housing having an electronically commutated motor disposed therein and an orbit mechanism disposed beneath the housing. A motor controller is coupled to the motor. The motor controller changes the speed of at which it runs the motor from an idle speed to a sanding speed upon the motor speed dropping from idle speed to an idle speed threshold value and changes the speed at which it runs the motor from sanding speed to idle speed upon the motor speed increasing from sanding speed to a sanding speed threshold value. The sander may have a mechanical brake that brakes the orbit mechanism and the motor controller also dynamically brakes the motor.

Claims

1. A hand held orbital sander, comprising:

a. a housing having an electronically commutated motor disposed therein and an orbit mechanism disposed beneath the housing; and

b. a motor controller coupled to the motor, the motor controller changing the speed at which it runs the motor from an idle speed to a sanding speed upon the motor speed dropping from idle speed to an idle speed threshold value and changing the speed at which it runs the motor from sanding speed to idle speed upon the motor speed increasing from sanding speed to a sanding speed threshold value.

2. The apparatus of claim 1 wherein the motor controller slows the motor by reverse commutation when it changes the speed of the motor from sanding speed to idle speed.

3. The apparatus of claim 2 including a mechanical brake that, upon actuation, brakes the orbit mechanism.

4. The apparatus of claim 3 wherein the mechanical brake and the motor controller slowing the motor by reverse commutation brake the orbit mechanism to idle speed in no greater than about two seconds.

5. The apparatus of claim 3 wherein the sander is a random orbital sander.

6. The apparatus of claim 1 wherein the sander has an on/off switch and the motor controller senses whether the on/off switch is on when the sander is first coupled to a source of power and if it is, does not start the motor until the on/off switch is first switched off and then back on.

7. The apparatus of claim 1 wherein the sander is a random orbital sander.

8. The apparatus of claim 1 wherein the sander is a pad sander.

9. The apparatus of claim 1 wherein the motor is an AC synchronous motor.

10. The apparatus of claim 1 wherein the motor is a brushless DC motor.

11. The apparatus of claim 1 wherein the sander has an on/off switch and the motor controller senses a collapse in an input voltage when the on-off switch is turned off and reverse commutates the motor to brake it.

12. A hand held orbital sander, comprising:

a. a housing having an electronically commutated motor disposed therein and an orbit mechanism disposed beneath the housing;

b. a motor controller coupled to the motor;

c. a current sensor coupled to the motor controller that provides a signal indicative of motor current; and

d. the motor controller changing the speed at which it runs the motor from an idle speed to a sanding speed based upon at least one of change in motor current and change in motor speed as the sander is removed from a work piece and changing the speed at which it runs the motor from sanding speed to idle speed based upon at least one of change in motor current and change in motor speed as the sander is applied to the work piece.

13. The apparatus of claim 12 including a platen coupled to the orbit mechanism and a sensor coupled to the platen that senses whether the platen is applied to a workpiece, the motor controller changing the speed at which it runs the motor from idle speed to a sanding speed based upon at least one of change in motor current, change in motor speed and a change in a signal from the sensor as the sander is removed from a work piece and changing the speed of at which it runs the motor from sanding speed to idle speed based upon at least one of change in motor current, change in motor speed and change in the signal from the sensor as the sander is applied to the work piece.

14. The apparatus of claim 13 wherein the sensor includes at least one of a pressure sensor and a force sensor.

15. The apparatus of claim 12 wherein the motor controller slows the motor by reverse commutation when it changes the speed of the motor from sanding speed to idle speed.

16. The apparatus of claim 15 including a mechanical brake that brakes the orbit mechanism.

17. The apparatus of claim 16 wherein the mechanical brake and the motor controller slowing the motor by reverse commutation brake the orbit mechanism to idle speed in no greater than about two seconds.

18. The apparatus of claim 12 wherein the sander has an on/off switch and the motor controller senses whether the on/off switch is on when the sander is first coupled to a source of power and if it is, does not start the motor until the on/off switch is first switched off and then back on.

19. The apparatus of claim 12 wherein the sander has an on/off switch and the motor controller senses a collapse in an input voltage when the on-off switch is turned off and reverse commutates the motor to brake it.

20. In a hand held sander, a method of controlling the speed of a motor, comprising:

a. changing the speed at which the motor is run from an idle speed to a sanding speed upon the motor speed dropping from idle speed to an idle speed threshold value; and

b. changing the speed at which the motor is run from sanding speed to idle speed upon the motor speed increasing from sanding speed to a sanding speed threshold value.

21. In a hand held orbital sander, a method of controlling the speed of a motor, comprising:

a. determining motor current from a current sensor coupled to the motor; and

b. changing the speed at which the motor is run from an idle speed to a sanding speed based upon at least one of change in motor current and change in motor speed as the sander is removed from a work piece and changing the speed at which the motor is run from sanding speed to idle speed based upon at least one of change in motor current and change in motor speed as the sander is applied to the work piece.

22. The method of claim 21 including sensing pressure on a platen of the sander and changing the speed at which the motor is run from idle speed to sanding speed based upon at least one of change in motor current, change in motor speed and change in pressure on the platen as the sander is removed from a work piece and changing the speed at which the motor is run from sanding speed to idle speed based upon at least one of change in motor current, change in motor speed and change in pressure on the platen as the sander is applied to the work piece.

23. The method of claim 21 including sensing force on a platen of the sander and changing the speed at which the motor is run from idle speed to sanding speed based upon at least one of change in motor current, change in motor speed and change in pressure on the platen as the sander is removed from a work piece and changing the speed at which the motor is run from sanding speed to idle speed based upon at least one of change in motor current, change in motor speed and change in pressure on the platen as the sander is applied to the work piece.

24. The method of claim 21 including slowing the motor by reverse commutation when changing its speed from sanding speed to idle speed.

25. The method of claim 24 including a mechanically braking the orbit mechanism with a mechanical brake.

26. The method of claim 25 wherein mechanically braking the orbit mechanism and slowing the motor by reverse commutation includes slowing the orbit mechanism to idle speed in no greater than about two seconds.

27. The method of claim 21 including sensing whether an on/off switch of the sander is on when the sander is first coupled to a source of power and if it is, not starting the motor until the on/off switch is first switched off and then back on.

28. The method of claim 21 including sensing a collapse in an input voltage when an on-off switch is turned off and reverse commutating the motor to brake it.