Impact tool

A powered rotary impact tool, comprising:

• a housing;
• a handle coupled to a first end portion of the housing;
• an output spindle at least partially received in the housing and extending along a longitudinal axis;
• a tool holder coupled to and configured to rotate with the output spindle;
• a motor drive unit disposed in the housing and including an output shaft extending along a motor axis;
• a transmission coupled to the output shaft;
• and
• a rotary impact mechanism including:
• a cam shaft rotatably driven by an output member of the transmission, the cam shaft extending along a transmission axis and including a first cam groove;
• a hammer received over the cam shaft and having a second cam groove;
• a ball movably disposed in the first cam groove and the second cam groove;
• an anvil coupled to the output spindle;
• and
• a spring biasing the hammer toward the anvil,
• wherein, in response to a torque on the output spindle is less than or equal to a threshold torque value, the hammer continuously engages the anvil so that the hammer and the anvil rotate together, and in response to a torque on the output spindle is greater than the threshold torque value, the hammer applies intermittent rotational impacts to the anvil, and
• wherein a length of the motor drive unit along the motor axis is less than approximately 70 mm, a cross-sectional area of the motor drive unit in a plane transverse to the motor axis is less than approximately 130 cm{circumflex over ( )}2 and a length of the transmission along the transmission axis is less than approximately 10 mm, the transmission providing a speed reduction within a range of approximately 1:1 to approximately 8:1, and
• wherein the motor drive unit, the transmission, and the impact mechanism are configured to generate an output torque enabling the tool holder to tighten a threaded fastener to a fastening torque of greater than or equal to approximately 3600 ft-lbs. within approximately 10 seconds of initiation of rotational impacts imparted on the anvil by the hammer.

A powered rotary impact tool, comprising:

• a housing;
• a handle coupled to the housing;
• an output spindle at least partially received in the housing and extending along an output axis;
• a tool holder coupled to the output spindle and configured to rotate in response to rotation of the output spindle;
• a motor drive unit disposed in the housing, the motor drive unit having a first axial length along a motor axis and a first width transverse to the motor axis;
• a transmission coupled to the motor drive unit and configured to provide a speed reduction, the transmission having a second axial length along a transmission axis and a second width transverse to the transmission axis;
• and
• a rotary impact mechanism, including:
• a cam shaft rotatably driven by an output member of the transmission, the cam shaft extending along a cam shaft axis and including a first cam groove;
• a hammer received over the cam shaft, the hammer having a second cam groove;
• a ball movably disposed in the first cam groove and the second cam groove;
• an anvil coupled to the output spindle;
• and
• a spring biasing the hammer toward the anvil,
• wherein, in response to a torque on the output spindle is less than or equal to a threshold torque value, the hammer continuously engages the anvil so that the hammer and the anvil rotate together, and in response to a torque on the output spindle that is greater than the threshold torque value, the hammer applies intermittent rotational impacts to the anvil, the hammer having a moment of inertia;
• wherein the motor drive unit, the transmission, and the impact mechanism are configured to generate an output torque enabling the tool holder to tighten a threaded fastener to a fastening torque within approximately 10 seconds of initiation of rotational impacts imparted on the anvil by the hammer, and
• wherein a ratio of the fastening torque to a product of the first axial length of the motor drive unit and a cross-sectional area of the motor drive unit transverse to the motor axis is between approximately 4 ft-lbs/cm{circumflex over ( )}3 and approximately 11 ft-lbs/cm{circumflex over ( )}3.