Electromagnetic powder coupling device

An electromagnetic powder coupling device which utilizes forced air cooling comprising, a pair of brackets each rotatably receiving said drive shaft at an input side and an output side, respectively, a field member including a yoke and a coil assembly and being tightly received by said brackets, a hollow cylinder of magnetic material coaxially disposed in an inner space of said field member and supported by a pair of side plates each being disposed, respectively at an input side and an output side so as to be integrally rotatable with said drive shaft, a rotor disposed coaxially around an axis of rotation and axially between said side plates, an annular magnetic flux shielding ring of non-magnetic material inserted through a central part of said cylinder for shielding magnetic flux from by-passing through said cylinder, magnetic powder being filled in a space between said cylinder and said rotor for effecting magnetic coupling between said cylinder and said rotor when said field member is excited and releasing said magnetic coupling when said field member is not excited, and a blower disposed at said output side axial end for blowing cooling air radially and slantedly outward to cool the periphery of said field member, a heat pipe axially laid adjacent to the outlet of said blower and radially at the inner side of said bracket at the output side and being provided with a plurality of fins attached on the outer surface of said heat pipe, a plurality of cooling fins disposed along the side wall of said side plate, a vent gate slantedly opening through the wall of said bracket at the output side, and a plurality of vent passages formed inside the radially outermost end of said output side bracket, wherein;

• said bracket at the output side is formed as a double-walled type having an outer wall and an inner wall and the bracket at the input side is formed to have a plurality of exit vents at positions radially corresponding to said cylinder at the outer part of said rotor,
• and wherein a forced draft of air blown by said blower is introduced in and discharged outside by passing through three paths, a first path passing radially and slantedly outwards through the space between the outer wall and the inner wall of said double-walled bracket at the output side, a second path passing radially and slantedly outwards along the inner face of said double-walled bracket, and a third path which extends from the downstream part of the second path and passes axially through a vent passage defined between an outer surface of the cylinder and an inner surface of the field member and then flows outside through said exit vents such that the third path provides a cooling effect to a region adjacent to the coupling powder as forced air passes axially through the vent passage between the inner surface of the field member and the outer surface of the cylinder, wherein the inner surface of said field member includes a plurality of axially extending vent grooves passing from the output side to the input side to form said third path for said forced draft of the cooling air.