# US 11,897,111 B2 · Power tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,897,111 B2 - Document ID: US11897111B2 - Status: Granted - Kind: B2 - Application number: 17/740,503 - Filed: 2022-05-10 - Published: 2022-12-01 - Granted: 2024-02-13 - Earliest claimed: 2021-05-28 - Assignees: Makita Corporation - Applicants: Makita Corporation - Inventors: Yasumasa Nakane; Luyen Van Tong - Web page: https://patentgrep.com/patent/US11897111B2 ## CPC - B25F 5/001: {Gearings, speed selectors, clutches or the like specially adapted for rotary tools} - B24B 23/04: with oscillating grinding tools; Accessories therefor - B25F 1/02: with interchangeable or adjustable tool elements - B25F 3/00: Associations of tools for different working operations with one portable power-drive means; Adapters therefor - B25F 5/006: {Vibration damping means} - B25F 5/02: Construction of casings, bodies or handles {(B25F5/006, B25F5/008 take precedence)} - B26B 7/00: Hand knives with reciprocating motor-driven blades - 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)} - 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 - B26B: HAND-HELD CUTTING TOOLS NOT OTHERWISE PROVIDED FOR (for harvesting A01D; for horticulture, for forestry A01G; for butchering or meat treatment A22; for manufactering or repairing footwear A43D; nail clippers or cutters A45D29/02; kitchen equipment A47J; {vegetable slicers, julienne cutters and similar devices and holders therefor, B26D3/28}; for surgical purposes A61B; for metal B23D; cutting by abrasive fluid jets B24C5/02; plier-like tools with cutting edges B25B7/22; pincers B25C11/02; handles for hand implements, in general B25G; guillotine-type cutters B26D; {perforating by non-mechanical means, e.g. by fluid jet, B26F1/26}; for erasing B43L19/00; for textile materials D06H) ## Abstract A power tool has a motor having a rotary shaft, an eccentric shaft configured to be rotated around a rotation center axis of the rotary shaft, and a balancer configured to rotate with the rotary shaft. When viewed along the rotation center axis, (1) a first imaginary line passes the rotation center axis and an eccentric axis, (2) an imaginary perpendicular line crosses perpendicularly to the first imaginary line and passes the rotation center axis, (3) a center of gravity of the balancer is located in a region on a side opposite to the eccentric axis across the imaginary perpendicular line; and (4) a second imaginary line passes the rotation center axis and the center of gravity of the balancer and (5) the second imaginary is inclined at an inclination angle larger than 0° and smaller than 90° in a direction opposite to a rotating direction of the rotary shaft. ## Claims ### Claim 1 A power tool configured to process a workpiece by driving a tool accessory in an oscillating manner, the power tool comprising: a motor having a rotary shaft that is rotationally driven in one direction; an eccentric shaft that extends from one end of the rotary shaft and is configured to be rotated around a rotation center axis of the rotary shaft, at a position that is eccentric from the rotation center axis of the rotary shaft in a radial direction orthogonal to the rotation center axis, by rotation of the rotary shaft; a motion converting mechanism that is configured to connect the tool accessory and the eccentric shaft and convert one revolution of the eccentric shaft to one reciprocating oscillation of the tool accessory; and a balancer that is mounted onto an outer periphery of the rotary shaft and configured to rotate together with the rotary shaft, wherein: when viewed along the rotation center axis, (1) a first imaginary line passes the rotation center axis and an eccentric axis, which is a center axis of the eccentric shaft, (2) an imaginary perpendicular line crosses perpendicularly to the first imaginary line and passes through the rotation center axis, (3) a center of gravity of the balancer is located in a region on a side opposite to the eccentric axis across the imaginary perpendicular line, (4) a second imaginary line passes the rotation center axis and the center of gravity of the balancer, and (5) the second imaginary line is inclined at an inclination angle larger than 0° and smaller than 90° in a direction opposite to a rotating direction of the rotary shaft relative to the first imaginary line. ### Claim 2 (depends on 1) The power tool as defined in claim 1, wherein the balancer has an asymmetrical shape to the first imaginary line when viewed along the rotation center axis. ### Claim 3 (depends on 1) The power tool as defined in claim 1, wherein the balancer has a base through which the rotary shaft is inserted in a thickness direction of the base, and a projection protruding from a side face of the base in a direction parallel to the rotation center axis. ### Claim 4 (depends on 3) The power tool as defined in claim 3, wherein the projection is provided on an outer edge part that is farthest from the rotation center axis in the radial direction in the base, or in a position closer to the outer edge part than to the rotation center axis in the radial direction. ### Claim 5 (depends on 1) The power tool as defined in claim 1, wherein the inclination angle is larger than 10° and smaller than 60°. ### Claim 6 (depends on 1) The power tool as defined in claim 1, further comprising: a housing that houses the motor, the eccentric shaft, the motion converting mechanism and the balancer, wherein: the motion converting mechanism includes: a spindle that has a tool mounting part for mounting the tool accessory at an end and is configured to oscillate the tool accessory by reciprocatingly rotating in a circumferential direction; and a connection arm that has a first end fixed to the spindle and a second end connected to the eccentric shaft and is configured to be reciprocatingly rotated around the spindle by rotation of the eccentric shaft, the spindle is supported to be reciprocatingly rotatable in the circumferential direction by a first bearing part provided within the housing and a second bearing part provided between the first bearing part and the tool mounting part within the housing, and the first bearing part is held by the housing via an elastic member. ### Claim 7 (depends on 6) The power tool as defined in claim 6, wherein the second bearing part comprises a ball bearing. ### Claim 8 (depends on 1) The power tool as defined in claim 1, wherein the motor is arranged such that the rotation center axis crosses an oscillation axis of the tool accessory. ### Claim 9 (depends on 2) The power tool as defined in claim 2, wherein the balancer has a base through which the rotary shaft is inserted in a thickness direction of the base, and a projection protruding from a side face of the base in a direction parallel to the rotation center axis. ### Claim 10 (depends on 9) The power tool as defined in claim 9, wherein the projection is provided on an outer edge part that is farthest from the rotation center axis in the radial direction in the base, or in a position closer to the outer edge part than to the rotation center axis in the radial direction. ### Claim 11 (depends on 9) The power tool as defined in claim 9, wherein the inclination angle is larger than 10° and smaller than 60°. ### Claim 12 (depends on 10) The power tool as defined in claim 10, wherein the inclination angle is larger than 10° and smaller than 60°. ### Claim 13 (depends on 2) The power tool as defined in claim 2, wherein the inclination angle is larger than 10° and smaller than 60°. ### Claim 14 (depends on 3) The power tool as defined in claim 3, wherein the inclination angle is larger than 10° and smaller than 60°. ### Claim 15 (depends on 4) The power tool as defined in claim 4, wherein the inclination angle is larger than 10° and smaller than 60°. ### Claim 16 (depends on 4) The power tool as defined in claim 4, further comprising: a housing that houses the motor, the eccentric shaft, the motion converting mechanism and the balancer, wherein: the motion converting mechanism includes: a spindle that has a tool mounting part for mounting the tool accessory at an end and is configured to oscillate the tool accessory by reciprocatingly rotating in a circumferential direction, and a connection arm that has a first end fixed to the spindle and a second end connected to the eccentric shaft and is configured to be reciprocatingly rotated around the spindle by rotation of the eccentric shaft, the spindle is supported to be reciprocatingly rotatable in the circumferential direction by a first bearing part provided within the housing and a second bearing part provided between the first bearing part and the tool mounting part within the housing, and the first bearing part is held by the housing via an elastic member. ### Claim 17 (depends on 16) The power tool as defined in claim 16, wherein the second bearing part comprises a ball bearing. ### Claim 18 (depends on 15) The power tool as defined in claim 15, further comprising: a housing that houses the motor, the eccentric shaft, the motion converting mechanism and the balancer, wherein: the motion converting mechanism includes: a spindle that has a tool mounting part for mounting the tool accessory at an end and is configured to oscillate the tool accessory by reciprocatingly rotating in a circumferential direction; and a connection arm that has a first end fixed to the spindle and a second end connected to the eccentric shaft and is configured to be reciprocatingly rotated around the spindle by rotation of the eccentric shaft, the spindle is supported to be reciprocatingly rotatable in the circumferential direction by a first bearing part provided within the housing and a second bearing part provided between the first bearing part and the tool mounting part within the housing, and the first bearing part is held by the housing via an elastic member. ### Claim 19 (depends on 18) The power tool as defined in claim 18, wherein the second bearing part comprises a ball bearing.