Image Number 4 for United States Patent #4505170.
An electric rotary power tool apparatus is adapted for loosening jammed or seized automobile wheel nuts or bolts and holdable by hand during operation. It comprises(1) an electric motor laid out to be driven by an electric direct current having an operational voltage of at least 8 to 30 volts and at least 20 up to 60 amperes, and comprising a stator, a rotor, first and second poles, and a driving shaft bearing said rotor and having a rotary axis, the speed of said motor, at a nominal voltage of 12 to 24 volts ranging from 8000 to 30000 r.p.m. under load;(2) a casing in which the motor is housed;(3) an on-off and reversing switch;(4) a tool socket being adapted for receiving a socket tool therein and comprising a driven shaft, the speed under load of which driven shaft is in the range of from 1200 to 4000 r.p.m.;(5) a speed-reducing unit comprising a gear transmission positively and drivingly connecting the driving shaft with the driven shaft and adapted for directly and uninterruptedly transmitting torque from the driving motor shaft to the driven shaft and reducing the speed of the former to the latter shaft in a ratio of from about 7:1 to about 12:1;(6) impact-producing structure comprising an impact mass separate from said motor and being associated with the tool socket for imparting impacts to the socket.The apparatus can also be used as a hobby tool by eliminating the impact-generating unit.