Power Tool

Patent metadata

Field	Value
Publication number	US-10744633-B2
Application number	US-201615749003-A
Country	US
Kind code	B2
Filing date	Jun 27, 2016
Priority date	Jul 31, 2015
Publication date	Aug 18, 2020
Grant date	Aug 18, 2020

Abstract

In order to provide a tool in which a motor is assuredly prevented from being restarted when power is turned on again after a power supply interruption due to a contingency, a disk grinder 1 includes a motor 2 and a switch 12 switchable between an ON position at which the motor is driven by an operator and an OFF position at which the motor is stopped. Furthermore, first and second restart prevention means 60, 90 are provided to disable driving of the motor until the switch is turned again to the ON position when power supplied to the motor 2 falls below or under a predetermined value.

First claim

The invention claimed is:

1. A power tool comprising:
a motor;
a switch switchable between an ON position and an OFF position by an operator, the ON position causing the motor to be driven, the OFF position causing the motor to be stopped; and
first and second restart prevention circuits for preventing the motor from being driven in a case where power supplied to the motor falls below or to a predetermined value, until the switch is switched again to the ON position,
wherein each of the first and second restart prevention circuits is configured to determine whether the motor can be restarted.

2. The power tool according to claim 1 , further comprising on-lock mechanism for maintaining the switch to the ON position.

3. The power tool according to claim 1 , wherein the first restart prevention circuit comprises a microcomputer for controlling driving of the motor.

4. The power tool according to claim 1 , wherein the second restart prevention circuit comprises a switch unit physically integrated with the switch, the switch unit comprising a switching element connected in series with a current path to the motor for turning on and off power supply to the motor,
wherein by turning off the switching element, the power supply to the motor is stopped until the switch is turned again to the ON position.

5. The power tool according to claim 4 , wherein the second restart prevention circuit comprises a microcomputer provided internally of the switch unit.

6. The power tool according to claim 3 , wherein the second restart prevention circuit is provided on an input side of a power generation circuit for generating power to be supplied to the microcomputer, and power supply to the power generation circuit is stopped until the switch is turned again to the ON position.

7. The power tool according to claim 6 , further comprising an inverter circuit for outputting power to the motor,
wherein the switch comprises a first switch and a second switch, the first switch being switchable between an ON position at which power supply to the inverter circuit is allowed and an OFF position at which the power supply to the inverter circuit is stopped, the second switch being switchable between an ON position at which operation of the microcomputer is allowed and an OFF position at which the operation of the microcomputer is not allowed,
wherein the microcomputer controls power supply from the inverter circuit to the motor to control drive of the motor, and
wherein the second restart prevention circuit stops power supply to the power generation circuit until the second switch is turned again to the ON position.

8. A power tool comprising:
a motor;
an inverter circuit for outputting power to the motor;
a microcomputer for controlling the inverter circuit;
a first switch switchable between an ON state and an OFF state by an operator, the ON state being for allowing power supply to the inverter circuit, the OFF state being for stopping the power supply to the motor;
a second switch switchable between an ON state and an OFF state by an operator, the ON state being for allowing operation of the microcomputer, the OFF state being for stopping the operation of the microcomputer;
an on-lock mechanism for maintaining the first switch on the ON state; and
a restart prevention circuit for stopping the power supply to the microcomputer in a case where power supplied to the motor falls below or to a predetermined value, until the first switch is turned again to the ON state.

9. The power tool according to claim 8 , further comprising a power generation circuit for supplying power to the microcomputer,
wherein the second switch is provided between the power generation circuit and the microcomputer, and
wherein the restart prevention circuit stops power supply from the power generation circuit to the microcomputer until the second switch is turned again to the ON state.

10. A power tool comprising:
a motor;
a switch switchable between an ON position and an OFF position by an operator, the ON position causing the motor to be driven, the OFF position causing the motor to be stopped; and
first and second restart prevention circuits configured to perform restart-preventing-control under a condition that the power supplied to the motor falls below or to the predetermined value, causing the motor driving to stop, the restart-prevention-control being such a control for preventing resumption of the motor driving even if the power supplied to the motor restores the power exceeding the predetermined value and even if the switch is held in the ON position,
wherein the first and second restart prevention circuits are configured to perform the restart-preventing-control independently of each other.

Assignees

• Hitachi Koki Kk
• Koki Holdings Co Ltd

Inventors

• Yoshinari Takuya
• Kawano Yoshikazu
• Funabashi Kazuhiko
• Koizumi Toshiaki

Classifications

• B25F5/00 Primary

  Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for · CPC title

• B25F5/02 Primary

  Construction of casings, bodies or handles {(B25F5/006, B25F5/008 take precedence)} · CPC title

• H02P3/18

  for stopping or slowing an AC motor · CPC title

• H02M7/5387

  in a bridge configuration · CPC title

• B24B47/12

  by mechanical gearing or electric power (B24B47/16 takes precedence) · CPC title