Robot arm device capable of conveying an article in circumferential and radial directions

A robot arm device comprising:

• an expandable arm portion including an arm member, a forearm arm member, and a hand member;
• an arm drive wheel fixedly connected at a base end of the arm member;
• a transmission mechanism including a transmission wheel disposed coaxially with the arm drive wheel and rotatable independently from the arm drive wheel;
• a forearm drive wheel disposed at a leading end of the arm member and rotatable independently from the arm member and fixedly connected at a base end of the forearm member;
• a stationary wheel disposed coaxially with the forearm drive wheel and fixedly connected with the arm member;
• a hand drive wheel disposed at a leading end of the forearm member, and rotatable independently from the forearm member, and fixedly connected at a base end of the hand member, and having a diameter twice greater than the stationary wheel, and an axis of the hand drive wheel being spaced from an axis of the stationary wheel the same distance as an axis of the forearm drive wheel is spaced from an axis of the arm drive wheel;
• an arm drive motor operable to rotate the arm drive wheel;
• a forearm drive motor operable to rotate the forearm drive wheel via the transmission mechanism;
• a first endless member wound on the transmission wheel and the forearm drive wheel;
• a second endless member wound on the stationary wheel and the hand drive wheel;
• and
• a controller operable to control the driving of the arm and forearm drive motors to:
• rotate the arm and forearm drive motors in the same direction to thereby rotate the arm portion in a specified circumferential direction;
• and
• rotate the arm drive motor in a specified direction and rotate the forearm drive motor in the opposite direction at such an angular speed as to rotate the forearm drive wheel twice faster than the arm drive wheel via the transmission mechanism and the first endless member in combination with a relative rotation of the forearm drive wheel due to the rotation of the arm member to thereby move the hand member in a straight radial direction.