# US 10,478,933 B2 · Angle grinder, power tool and braking method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,478,933 B2 - Document ID: US10478933B2 - Status: Granted - Kind: B2 - Application number: 15/820,646 - Filed: 2017-11-22 - Published: 2018-05-31 - Granted: 2019-11-19 - Earliest claimed: 2016-11-25 - Assignees: Nanjing Chervon Industry Co., Ltd. - Applicants: Nanjing Chervon Industry Co., Ltd. - Inventors: Junya Duan - Web page: https://patentgrep.com/patent/US10478933B2 ## CPC - B23Q 11/0092: {actuating braking or stopping means} - B24B 27/08: being portable - B24B 47/12: by mechanical gearing or electric power (B24B47/16 takes precedence) - H02P 3/02: Details {of stopping control} - H02P 3/16: by combined electrical and mechanical braking - B23Q: DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING (tools of the kind used in lathes or boring machines B23B27/00); MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT - B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract An angle grinder includes a motor including a rotor and windings, a power supply for supplying power to the motor, a main switch for turning on/off an electrical connection between the windings of the motor and the power supply, an output shaft driven by the rotor to rotate, a rotor brake circuit for slowing down the rotor of the motor when the windings are short circuited or reverse connected, an output shaft brake circuit for producing a magnetic field to slow down the output shaft and a controller for detecting whether the rotor brake circuit short circuits or reverse connects with the windings. When the windings are short circuited or reverse connected for a time which reaches a preset value, the output shaft brake circuit produces the magnetic field to slow down the output shaft. ## Claims ### Claim 1 An angle grinder, comprising: a motor comprising a rotor and windings; a power supply for supplying power to the motor; a main switch for turning on/off an electrical connection between the windings of the motor and the power supply; an output shaft driven by the rotor to rotate; a rotor brake circuit for slowing down the rotor of the motor when the windings are short circuited or reverse connected; an output shaft brake circuit for producing a magnetic field to slow down the output shaft; and a controller for detecting whether the rotor brake circuit short circuits or reverse connects the windings; wherein when the windings are short circuited or reverse connected for a time which reaches a preset value, the output shaft brake circuit produces the magnetic field to slow down the output shaft. ### Claim 2 (depends on 1) The angle grinder of claim 1, wherein the preset value is less than or equal to 3 s. ### Claim 3 (depends on 1) The angle grinder of claim 1, further comprising an output shaft brake switch for turning on an electrical connection between the output shaft brake circuit and the power supply wherein the output shaft brake switch is connected electrically with the controller. ### Claim 4 (depends on 3) The angle grinder of claim 3, wherein the output shaft brake switch is a field effect transistor. ### Claim 5 (depends on 1) The angle grinder of claim 1, further comprises a mechanical braking device, the mechanical braking device comprising a magnetic element for responding to the output shaft brake circuit and producing a magnetic field to slow down the output shaft. ### Claim 6 (depends on 1) The angle grinder of claim 1, wherein the rotor brake circuit comprises a semiconductor switch and the semiconductor switch is connected electrically with the controller for turning on/off the rotor brake circuit. ### Claim 7 (depends on 1) The angle grinder of claim 1, further comprising a tank circuit wherein, when the main switch is powered on, electric energy is stored in the tank circuit and, when the rotor braking circuit is working, the electric energy is released from the tank circuit. ### Claim 8 (depends on 1) The angle grinder of claim 1, wherein the main switch is a single-pole double-throw switch or two linked single-pole double-throw switches. ### Claim 9 A power tool, comprising: a motor comprising a rotor and windings; an output shaft driven by the rotor to rotate; a rotor brake circuit for short circuiting or reverse connecting the winds so as to slow down the rotor; an output shaft brake circuit for producing a magnetic field to slow down the output shaft; and a controller for detecting whether the rotor brake circuit short circuits or reverse connects the windings; wherein, when the windings are in a short circuit state or a reverse connection state for a time which reaches a preset value, the output shaft brake circuit produces the magnetic field to slow down the output shaft. ### Claim 10 A method for braking a motor of a power tool, wherein the motor comprises a rotor and windings and the power tool comprises a rotor brake circuit and an output shaft brake circuit, the method comprising: detecting whether the rotor brake circuit short circuits or reverse connects with the windings and; when the windings are in a short circuit state or a reverse connection state for a time which reaches a preset value, producing via use of the output shaft brake circuit a magnetic field to slow down an output shaft associated with the motor.