# US 11,027,389 B2 · Handheld power tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,027,389 B2 - Document ID: US11027389B2 - Status: Granted - Kind: B2 - Application number: 16/314,438 - Filed: 2017-06-22 - Published: 2020-04-23 - Granted: 2021-06-08 - Earliest claimed: 2016-07-06 - Assignees: Hilti Aktiengesellschaft - Applicants: Hilti Aktiengesellschaft - Inventors: Michael Wierer; Roland Schaer; Philipp Lorenz - Web page: https://patentgrep.com/patent/US11027389B2 ## CPC - B23Q 11/0092: {actuating braking or stopping means} - B25D 16/006: {Mode changers; Mechanisms connected thereto} - B25F 5/00: Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for - F16D 59/02: spring-loaded and adapted to be released by mechanical, fluid, or electromagnetic means - B25D 2211/003: Crossed drill and motor spindles - B25D 2211/068: Crank-actuated impulse-driving mechanisms - B25D 2250/145: Electro-magnetic parts - B25D 2250/201: for speed, e.g. drilling or percussion speed - B25D 2250/221: Sensors - B25D 2250/371: Use of springs - F16D 2121/22: for releasing a normally applied brake - 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 - B25D: PERCUSSIVE TOOLS {(percussive machines for forging B21J; hand-held drilling machines, in general B23B45/00, for wood B27C3/08; drilling machines, used for mining or quarrying, with reciprocating tool which is turned intermittently when out of contact with the working face E21B1/00)} - B25F: COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR {(machines or arrangements of machines for performing specified combinations of different metal-working operations not covered by a single other subclass B23P23/00 and subgroups)} - F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES ## Abstract A handheld power tool includes a tool holder for holding a tool, an electric motor, a shaft connecting the tool holder and the electric motor, and a protective device for stopping the tool holder in an uncontrolled situation. The protective device includes a sensor for detecting the uncontrolled situation, a switchable current source and a normally closing magnetic brake. The switchable current source outputs a first current not equal to zero in response to signals of the sensor if an uncontrolled situation is not detected; the current source does not output a current or outputs a second current different from the first current if an uncontrolled situation is detected. The normally closing magnetic brake engages on the shaft and does not apply a torque to the shaft when energized by the first current. The normally closing magnetic brake applies a torque counteracting the rotational movement of the shaft when not energized or when energized by the second current. ## Claims ### Claim 1 A handheld power tool comprising: a tool holder for holding a tool; an electric motor; a shaft connecting the tool holder and the electric motor; and a protective device for stopping the tool holder in an uncontrolled situation, the protective device including: a sensor for detecting the uncontrolled situation; a switchable current source outputting a first current not equal to zero in response to signals of the sensor if an uncontrolled situation is not detected and not outputting a current or outputting a second current different from the first current if an uncontrolled situation is detected; and a normally closing magnetic brake for engaging on the shaft and not applying a torque to the shaft when energized by the first current and applying a torque counteracting the rotational movement of the shaft when not energized or when energized by the second current; wherein the magnetic brake includes a stationary brake shoe and a brake disk movable relative to the brake shoe around the axis of the shaft and along the shaft and wherein the magnetic brake further includes a permanent magnet and a solenoid coil, a permanent magnetic field generated by the permanent magnet and a magnetic field generated by the solenoid coil, through which the first current flows, being antiparallel, and wherein the brake shoe and the permanent magnet are situated in a closing direction of the brake disk. ### Claim 2 (depends on 1) The handheld power tool as recited in claim 1 wherein a pole shoe surrounds the permanent magnet and the solenoid coil for the purpose of guiding the permanent magnetic field and the magnetic field generated by the solenoid coil. ### Claim 3 (depends on 2) The handheld power tool as recited in claim 2 wherein the pole shoe includes two annular projections, situated one inside the other and facing the brake disk. ### Claim 4 (depends on 1) The handheld power tool as recited in claim 1 wherein a flux density of the permanent magnetic field on an annular surface of the magnetic brake differs in terms of absolute value from the flux density of the magnetic field on the annual surface by less than 10%. ### Claim 5 (depends on 1) The handheld power tool as recited in claim 1 wherein the brake disk is formed from a soft magnetic material. ### Claim 6 (depends on 1) The handheld power tool as recited in claim 1 further comprising a spring placed against the brake disk exerting a force oriented away from the brake shoe on the brake disk. ### Claim 7 (depends on 1) The handheld power tool as recited in claim 1 wherein the second current is less than 20% of the first current, or the second current has a polarity opposite that of the first current. ### Claim 8 (depends on 1) The handheld power tool as recited in claim 1 wherein the sensor contains a rotational movement sensor detecting a rotational movement of a handle. ### Claim 9 (depends on 1) The handheld power tool as recited in claim 1 further comprising a striking mechanism driven by the electric motor. ### Claim 10 A control method for a handheld power tool including an operating switch, an electric motor, a tool holder, a shaft connecting the electric motor to the tool holder, a normally closing magnetic brake situated on the shaft, and a sensor for detecting an uncontrolled situation, wherein the magnetic brake includes a stationary brake shoe and a brake disk movable relative to the brake shoe around the axis of the shaft and along the shaft and wherein the magnetic brake further includes a permanent magnet and a solenoid coil, a permanent magnetic field generated by the permanent magnet and a magnetic field generated by the solenoid coil, through which the first current flows, being antiparallel wherein the brake shoe and the permanent magnet are situated in a closing direction of the brake disk, the control method comprising the steps of: energizing the magnetic brake by a first current; activating the electric motor for driving the shaft in response to an actuation of the operating switch and after the magnetic brake is energized; interrupting the energizing of the magnetic brake by the first current; and decoupling the electric motor from the power supply in response to a detection of a signal of the sensor indicating the uncontrolled situation. ### Claim 11 (depends on 10) The control method as recited in claim 10 wherein a power consumption of the electric motor is adjusted in response to a predefined rotational speed. ### Claim 12 (depends on 10) The control method as recited in claim 10 wherein the first current is a constant direct current.