A hand-held electrically powered cut-off tool with a kickback mitigation function

Patent metadata

Field	Value
Publication number	US-2023390963-A1
Application number	US-202118032250-A
Country	US
Kind code	A1
Filing date	Sep 20, 2021
Priority date	Oct 19, 2020
Publication date	Dec 7, 2023
Grant date	—

Abstract

A hand-held electrically powered cut-off tool ( 100 ) for cutting concrete and stone by a rotatable cutting disc ( 105 ), the cut-off tool ( 100 ) comprising an electric motor ( 130 ) arranged to be controlled by a control unit ( 110 ) via a motor control interface ( 120 ), wherein the control unit ( 110 ) is arranged to obtain data indicative of an angular velocity of the cutting disc ( 105 ), and to detect a kickback condition based on a decrease in angular velocity, wherein the control unit ( 110 ) is arranged to determine an angular acceleration associated with the electric motor ( 130 ), and to detect the kickback condition based on a comparison between the determined angular acceleration and a detection threshold, wherein the detection threshold is configured at an angular acceleration between 5000 rad/s 2 and 35000 rad/s 2 , and preferably between 10000 rad/s 2 and 30000 rad/s 2 , and more preferably between 20000 rad/s 2 and 30000 rad/s 2 .

First claim

1 . A hand-held electrically powered cut-off tool for cutting concrete and stone by a rotatable cutting disc, the cut-off tool comprising an electric motor arranged to be controlled by a control unit via a motor control interface,
wherein the control unit is arranged to obtain data indicative of an angular velocity of the cutting disc, and to detect a kickback condition based on a decrease in angular velocity, wherein the control unit is arranged to determine an angular acceleration associated with the electric motor, and to detect the kickback condition based on a comparison between the determined angular acceleration and a detection threshold, wherein the detection threshold is configured at an angular acceleration between 5000 rad/s 2 and 35000 rad/s 2 .

2 . The hand-held electrically powered cut-off tool according to claim 1 , wherein the control unit is arranged to detect the kickback condition also based on an angular velocity associated with the electric motor by conditioning kickback detection based on a minimum angular velocity.

3 . The hand-held electrically powered cut-off tool according to claim 2 , wherein the minimum angular velocity is between 400 rad/s and 800 rad/s.

4 . The hand-held electrically powered cut-off tool according claim 1 , wherein the tool diameter of the rotatable cutting disc is between 9-11 inches, wherein the detection threshold is configured at an angular acceleration between 5000 rad/s 2 and 35000 rad/s 2 .

5 . The hand-held electrically powered cut-off tool according to claim 1 , wherein the tool diameter of the rotatable cutting disc is between 11-13 inches, wherein the detection threshold is configured at an angular acceleration between 25000 rad/s 2 and 35000 rad/s 2 .

6 . The hand-held electrically powered cut-off tool according to claim 1 , wherein the tool diameter of the rotatable cutting disc is between 13-15 inches, wherein the detection threshold is configured at an angular acceleration between 25000 rad/s 2 and 35000 rad/s 2 .

7 . The hand-held electrically powered cut-off tool according to claim 1 , wherein the tool diameter of the rotatable cutting disc is between 15-17 inches, wherein the detection threshold is configured at an angular acceleration between 15000 rad/s 2 and 25000 rad/s 2 .

8 . A hand-held electrically powered cut-off tool for cutting concrete and stone by a rotatable cutting disc, the cut-off tool comprising an electric motor arranged to be controlled by a control unit via a motor control interface,
wherein the control unit is arranged to obtain data indicative of an angular velocity of the cutting disc, and to detect a kickback condition based on a decrease in angular velocity, wherein the control unit is arranged to determine an angular acceleration associated with the electric motor, and to detect the kickback condition based on a comparison between the determined angular acceleration and a detection threshold if the angular velocity of the cutting disc is above a velocity threshold.

9 . The hand-held electrically powered cut-off tool according to claim 8 , where the detection threshold is a variable detection threshold.

Assignees

• Husqvarna Ab

Inventors

• Rosén Magnus
• Johansson Victor
• Dufke David
• Berg Johan

Classifications

• H02P6/08

  Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) · CPC title

• H02P23/20

  Controlling the acceleration or deceleration · CPC title

• H02P21/18

  Estimation of position or speed · CPC title

• H02P21/141

  Flux estimation · CPC title

• H02P21/06

  Rotor flux based control involving the use of rotor position or rotor speed sensors · CPC title