Self-adjusting electromagnetic clutch

An electromagnetic clutch apparatus for torque transmission comprising:

• an input shaft;
• output means coaxially disposed with said input shaft and free to rotate thereon, said output means having a frustro-conical friction face tapering radially inwardly and a flat annular pole face disposed normal to the axis of said input shaft;
• clutch actuating means mounted adjacent to said output means, said actuating means including an electromagnetic winding;
• an armature coaxially disposed with said input shaft opposite to said pole face of said output means, said armature being movable axially toward and away from said pole face of said output means in response to said clutch actuating means, said armature having an outer cylindrical threaded surface and an inner cylindrical surface having a first and second portion, said first portion of said inner surface having serrations and said second portion of said inner cylindrical surface having a shoulder portion;
• means for biasing said armature in a direction away from said pole face of said output means, said means being adapted to flex axially upon energizing the de-energizing of said clutch actuating means;
• a driving friction ring member having an inner cylindrical threaded surface adapted to engage the outer surface of said armature, said inner surface further having a plurality of angularly spaced axial grooves to permit axial movement of said ring member;
• an annular torque transmitting member having an outer surface with a plurality of angularly spaced axially aligned protrusions adapted to engage said plurality of axial grooves in said ring member and means for mounting said annular torque transmitting member to the inut shaft;
• and
• an annular retarder member disposed coaxially with said armature, said retarder member having means for biasing said armature whereby said biasing means allows rotational movement of said armature in one direction and prevents rotational movement of said armature in another opposite direction;
• whereby said clutch actuating means produces a circuitous flux path when energized, said flux path passing through said pole face and said armature moving said armature into engagement with said pole face thereby imparting rotational momentum to said output means, said armature being threadably engaged with said friction ring member such that upon engagement of said armature with said pole face of said output means said armature moves rotatably on said helical thread towards said friction ring member thereby causing said friction ring member to engage said output means until nearly all the torque transmitted between said input shaft and said output means is carried by the mating frictional surfaces of said ring member and said output means.

In combination with an electromagnetic clutch of the type wherein torque is transmitted from an input means to an output means upon energizing an electromagnetic coil means and wherein an armature is disposed coaxial with said clutch axis for engagement with a magnetic pole face on the output means, said armature having an outer cylindrical helical threaded surface, the improvement comprising:

• an annular driving friction ring member having an inner cylindrical helical threaded surface adapted to engage the outer surface of said armature, said annular member having a plurality of angularly spaced axial grooves to permit axial movement of said annular member with respect to said armature;
• means for biasing said armature in a direction away from said pole face of said output means, said means adapted to flex axially upon energizing and de-energizing of said electromagnetic coil means;
• a torque transmitting means interposed between said angularly spaced axial grooves of the annular friction ring member and said input means for imparting rotational motion to said annular friction member;
• and
• an annular retarder member disposed coaxialy with said armature, said retarder member having unidirectional retarder means whereby said unidirectional retarder means allows the rotational movement of said armature in one direction and prevent rotational movement of said armature in another opposite direction;
• whereby upon energizing said electromagnetic coil means said helical threaded cylindrical connection between said armature and said annular friction member causes said armature to move axially and rotatably with respect to said friction member and thereby engage said output means.