Power tool with circuit protection capability

Abstract

A power tool includes a battery-operated power supplying unit adapted to be connected to a battery unit and to generate battery status information, a driving unit adapted to be coupled to a tool bit, a protection unit for making and breaking an electrical circuit between the power supplying unit and the driving unit, a user-actuated unit for enabling operation of the protection unit to make the electrical circuit, and a control unit for enabling operation of the protection unit to break the electrical circuit when the control unit detects an abnormal condition from the battery status information.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:

FIG. 1 is a perspective view of the preferred embodiment of a power tool according to the present invention;

FIG. 2 is a schematic side view of the preferred embodiment;

FIG. 3 is a schematic circuit block diagram of the preferred embodiment; and

FIG. 4 is a schematic electrical circuit diagram of the preferred embodiment.

Claims

1. A power tool comprising: a battery-operated power supplying unit adapted to be connected to a battery unit and to generate battery status information;a driving unit adapted to be coupled to a tool bit;a protection unit connected electrically to said power supplying unit and said driving unit, and operable in one of a circuit-making state for making an electrical circuit between said power supplying unit and said driving unit to enable drive operation of said driving unit, and a circuit-breaking state for breaking the electrical circuit between said power supplying unit and said driving unit to disable the drive operation of said driving unit;a user-actuated unit connected electrically to said protection unit and manually operable so as to switch operation of said protection unit from the circuit-breaking state to the circuit-making state; anda control unit connected electrically to said power supplying unit and said protection unit, and operable so as to switch operation of said protection unit from the circuit-making state to the circuit-breaking state when said control unit detects one of an insufficient battery voltage condition and an overload condition from the battery status information.

2. The power tool as claimed in claim 1, wherein said protection unit includes a transistor coupled to said control unit and selectively operable in one of the circuit-making and circuit-breaking states.

3. The power tool as claimed in claim 1, further comprising a bias voltage source connected electrically to said user-actuated unit, said user-actuated unit being manually operable so as to control electrical connection between said bias voltage source and said protection unit to thereby switch operation of the protection unit between the circuit-making and circuit-breaking states.

4. The power tool as claimed in claim 3, wherein said protection unit includes a field effect transistor having a gate connected electrically to said user-actuated unit and said control unit, a drain connected electrically to said driving unit, and a grounded source.

5. The power tool as claimed in claim 4, wherein said power supplying unit includes a battery charger adapted to be connected to the battery unit and operable so as to recharge the battery unit.

6. The power tool as claimed in claim 5, wherein said bias voltage source includes a capacitor connected to said battery charger and further connected to said control unit, said bias voltage source having a bias voltage with a first voltage component across said capacitor and a second voltage component from said control unit,the first voltage component being stored in said capacitor when recharging the battery unit,the bias voltage being larger than a battery voltage of the battery unit.

7. The power tool as claimed in claim 1, wherein said power supplying unit includes a battery charger adapted to be connected to the battery unit, and operable so as to recharge the battery unit.

8. The power tool as claimed in claim 7, wherein said power supplying unit further includes: an input power detector connected electrically to said control unit and adapted for detecting supply of an input power signal to said battery charger; anda battery monitor adapted to be connected to the battery unit, connected electrically to said control unit, and operable so as to generate the battery status information.

9. The power tool as claimed in claim 8, wherein said power supplying unit further includes a power saver connected electrically to said battery charger, said battery monitor and said control unit, said control unit being operable so as to deactivate said power saver to disable operation of said battery charger and said battery monitor.

10. The power tool as claimed in claim 9, wherein said battery monitor includes a reference voltage loop and a battery voltage loop connected in parallel and adapted to be connected to the battery unit, said reference voltage loop including a resistor and a Zener diode connected in series, said reference voltage loop being connected to said control unit at a junction of said resistor and said Zener diode for providing a reference voltage level to said control unit,said battery voltage loop including a pair of resistors connected in series, said battery voltage loop being connected to said control unit at a junction of said resistors of said battery voltage loop for providing a battery voltage fraction to said control unit,the reference voltage level and the battery voltage fraction serving as the battery status information.

11. The power tool as claimed in claim 1, further comprising a handheld housing having said power supplying unit, said driving unit, said protection unit, and said control unit mounted therein, said user-actuated unit including a button mounted operably to said housing.