Variable speed drive for engine cooling fans

A variable speed fan drive assembly comprising:

• a cantilevered support member having a fixed longitudinal axis;
• an input drive member mounted on said support member and which is subject to rotation thereabout, said input drive member defining an expandable chamber;
• a hub assembly mounted on and subject to rotation about said support member and including a splined member which rotates with said hub assembly, wherein said input drive member and said hub assembly are provided with complimentary means for preventing cord debris from entangling thereabout;
• axially spaced bearing means rotatably mounting said input drive member and said hub assembly on said support member, said bearing means including a first bearing set disposed between said input drive member and said support member, a second bearing set disposed between said input drive member and said hub assembly, and a third bearing set disposed between said hub assembly and said support member;
• a wet clutch assembly operably connected between said input drive member and said splined member in a manner providing a slippable coupling between said input drive member and said hub assembly;
• a fluid operated ram cooperatively arranged with said expandable chamber for engaging and disengaging said clutch as a function of pressure applied by said ram against said clutch and in a manner whereby substantially no axial thrust load is exerted on said bearing means during engagement of said clutch;
• and
• means for admitting fluid pressure to said expandable chamber in a manner controlling the pressure applied by said ram and thereby the effectiveness of said clutch.

A variable speed fan drive assembly comprising:

• a mounting bracket having a cantilevered arm with a fixed longitudinal axis;
• an input drive member and a fan hub both of which are supported by bearing means on said mounting bracket for rotation about the longitudinal axis of said arm, said input drive member being provided with a chamber;
• a wet clutch assembly for releasably engaging said fan hub with said input drive member, said clutch assembly including at least two clutch members operably attached respectively to said input drive member and to said fan hub for establishing a slippable connection between same and whose operable effectiveness is determined by the axial compression force exerted thereagainst;
• a pressure responsive ram cooperatively arranged within said chamber rotation with said input drive member to exert an axial compression force on said clutch assembly when fluid is introduced into said chamber and in a manner whereby said ram exerts substantially no axial thrust load on said bearings during operation;
• and
• means for admitting fluid pressure to said chamber;
• said input drive member and said fan hub including complementary means for preventing debris from becoming entrained thereabout.