A mechanism for driving a robot hand mounted on a robot arm includes a pair of planetary gear assemblies coupled to motors for swinging the robot hand about a first shaft and for rotating the robot hand about a second shaft through transmission systems. During swinging motion of the robot hand about the first shaft, rotative power from the motor which causes such rotation is transmitted by the planetary gear assemblies to the second shaft also, so that rotation of the robot hand resulting from the swinging motion of the robot hand can be cancelled out.

A wrist mechanism for an industrial robot having a robot casing, robot arms capable of extending from and contracting to the robot casing, a robot hand for gripping a workpiece, and a wrist arranged between the robot arms and the robot hand, comprises: two reduction gears with a high reduction ratio connected respectively to each of two high speed rotational driving motors, the two reduction gears cooperating with one another for generating two individual reduced rotational outputs, and; two transmitting mechanisms, connectable to the hand, for transmitting respectively the two reduced rotational outputs to the hand, thereby causing respectively rotational motion and swinging motion of the hand.

Head for a robot or manipulator comprising a control casing and at least two shafts perpendicular to each other, with corresponding external members rotatably driven from separate control servo motors, one shaft being rigid with one of said members which supports the other shaft, said servo motors are fixedly mounted in said casing so as to drive at least two coaxial shafts, while the driving of at least one of said perpendicular shafts from one of said coaxial shafts takes place through a bevel gear of which the input pinion is rigid with this one coaxial shaft and the output pinion is rigid with the shaft concerned. This head construction permits assembling the servo motors into a readily accessible unit by providing said coaxial shafts with concentric toothed members in meshing engagement with driving pinion driven in turn from said servo motors, and is applicable notably to robot heads having two or three degrees of freedom.

A welding torch is disclosed in combination with an industrial robot, the industrial robot having an arm and a wrist at one end thereof, the wrist including a rotary casing having a rotary shaft extending in a direction along the axis of the arm and a pair of sprocket members disposed on the sides of the rotary shaft. The torch and robot further have a first central core wire guide within the rotary shaft and extending along the axis thereof, and a second central core wire guide within the welding torch and fixed to the rotary shaft, the second central core wire guide being aligned with and in communication with the first central core wire guide.