Electromagnetic clutch having a contractible friction shoe
First Claim
1. A normally disengaged clutch comprising a rotatable driving member having a hub, a driven member rotatable about the same axis as the driving member, a radially contractible shoe surrounding said hub, resiliently yieldable coupling means connecting said shoe and said driven member for rotation in unison, said coupling means enabling radial contraction of said shoe around said hub and normally holding said shoe out of radial engagement with said hub, a helically coiled spring telescoped over said shoe and having one end secured to said driven member to rotate with the latter, means associated with said driving member and selectively operable to cause the opposite end of said spring to rotate with said driving member thereby to cause said spring to wrap down on said shoe and contract said shoe radially into frictional gripping engagement with said hub to transmit torque (1) from said hub to said shoe (2) from said shoe to said coupling means and (3) from said coupling means to said driven member.
1 Assignment
0 Petitions
Accused Products
Abstract
Torque is transmitted between the driving and driven members of the clutch by a helical spring and a friction shoe. When an electromagnet is excited, pilot torque is applied to the spring to cause the spring to clamp downwardly around the shoe and cause the shoe to contract radially around the driving member and transmit torque to the driven member. The driving member, the driven member, the spring and the friction shoe are arranged in such a manner that the spring effects soft engagement of the clutch while amplifying the pilot torque sufficiently to enable a relatively small and light weight clutch to produce ample output torque.
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Citations
11 Claims
- 1. A normally disengaged clutch comprising a rotatable driving member having a hub, a driven member rotatable about the same axis as the driving member, a radially contractible shoe surrounding said hub, resiliently yieldable coupling means connecting said shoe and said driven member for rotation in unison, said coupling means enabling radial contraction of said shoe around said hub and normally holding said shoe out of radial engagement with said hub, a helically coiled spring telescoped over said shoe and having one end secured to said driven member to rotate with the latter, means associated with said driving member and selectively operable to cause the opposite end of said spring to rotate with said driving member thereby to cause said spring to wrap down on said shoe and contract said shoe radially into frictional gripping engagement with said hub to transmit torque (1) from said hub to said shoe (2) from said shoe to said coupling means and (3) from said coupling means to said driven member.
- 9. A normally disengaged electromagnetic friction clutch comprising a rotatable driving member having a hub, a driven member rotatable about the same axis as the driving member, a shoe telescoped over said hub, said shoe being radially contractible and normally being disposed in loose surrounding relationship with said hub, radially compliant and circumferentially stiff coupling means connecting said shoe to said driven member, said coupling means connecting said shoe and said driven member for rotation in unison while enabling radial contraction of said shoe, a flexible coiled element telescoped over said shoe and having one end secured to said driven member to rotate with the latter, an electromagnet associated with said driving member and operable when excited to attract the opposite end of said flexible element axially into engagement with said driving member thereby to cause said flexible element to wrap down on said shoe and contract said shoe radially into frictional gripping engagement with said hub to transmit torque (1) from said hub to said shoe (2) from said shoe to said coupling means and (3) from said coupling means to said driven member, said shoe being located relative to said driven member so as to be free of radial frictional engagement with said driven member at all times when said shoe is contracted whereby all of the torque transmitted from said hub to said shoe is transmitted from said shoe to said driven member through said coupling means.
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11. A normally disengaged electromagnetic friction clutch comprising a rotatable driving member having a hub of circular crosssection, a driven member rotatable about the same axis as said driving member, a substantially annular shoe telescoped over said hub, said shoe being radially contractible and normally being disposed in loose surrounding relationship with said hub, radially flexible means extending between said shoe and said driven member and positively coupling said shoe and said driven member for rotation in unison while enabling radial contraction of said shoe, a helically coiled spring telescoped over said shoe and having one end secured positively to said driven member to rotate with the latter, said shoe serving as a radial spacer between said spring and said hub and holding the full length of the inner side of said spring out of engagement with said hub at all times thereby to prevent said spring from being wrapped down by said hub when the latter is rotated, and an electromagnetic associated with said driving member and operable when excited to attract the opposite end of said spring axially into engagement with said driving member thereby to cause said spring to wrap down on said shoe and contract said shoe radially into frictional engagement with said hub to transmit torque between said hub and said driven member.
Specification