US 12,134,169 B2
Rotary impact tool
Jacob P. Schneider, Cedarburg, WI (US)
Assigned to MILWAUKEE ELECTRIC TOOL CORPORATION, Brookfield, WI (US)
Filed by MILWAUKEE ELECTRIC TOOL CORPORATION, Brookfield, WI (US)
Filed on Jan. 17, 2023, as Appl. No. 18/155,396.
Application 18/155,396 is a continuation of application No. 16/738,113, filed on Jan. 9, 2020, granted, now 11,554,468.
Claims priority of provisional application 62/816,263, filed on Mar. 11, 2019.
Claims priority of provisional application 62/790,350, filed on Jan. 9, 2019.
Prior Publication US 2023/0150098 A1, May 18, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. B25B 21/02 (2006.01); B25B 23/00 (2006.01)
CPC B25B 21/023 (2013.01) [B25B 23/0007 (2013.01)] 22 Claims
OG exemplary drawing
 
1. A rotary impact tool comprising:
a housing;
an electric motor supported in the housing;
a drive assembly for converting a continuous torque input from the motor to consecutive rotational impacts upon a workpiece, the drive assembly including
an anvil having a bore in a distal end thereof for receipt of the workpiece or a tool bit for performing work on the workpiece, the bore defining a hexagonal cross-sectional shape in a plane oriented transverse to a rotational axis of the anvil, the bore having a nominal width of 7/16 inches,
a hammer that is both rotationally and axially movable relative to the anvil for imparting the consecutive rotational impacts upon the anvil, and
a spring for biasing the hammer in an axial direction toward the anvil;
a battery pack supported by the housing for providing power to the motor, the battery pack having a nominal voltage of at least 18 Volts and a nominal capacity of at least 5 Ah;
wherein the rotary impact tool has an overall weight including the battery pack that is less than or equal to 7.5 lbs,
wherein a mechanism efficiency of the rotary impact tool is defined as:

OG Complex Work Unit Math
wherein BPM is the number of impacts per minute, KEHammer,Drilling is a kinetic energy of the hammer during a loaded condition and prior to impact with the anvil, Voltagemotor is a voltage across the motor, and Currentmotor is a current drawn by the motor,
wherein a second performance ratio (PR2) of the rotary impact tool is defined as:

OG Complex Work Unit Math
wherein RPMno-load is a rotational frequency of the impact mechanism under a no-load condition and Inertiahammer is a moment of inertia of the hammer, and
wherein the second performance ratio of the rotary impact tool is greater than 2.