Centering abutment for viscous fluid drive

Claim 1

In a viscous fluid drive having a housing with an annular generally radially extending side member adapted to be rotated about an axis, a centrally located input shaft opening defined in said side member, a working chamber in said housing defined in part by an annular peripheral surface on said housing and an annular generally radially extending surface on said side member, a clutch member located within said working chamber and defined in part by an annular peripheral surface spaced radially from said peripheral surface on said housing by a distance of X units and an annular generally radially extending surface axially spaced from said radially extending surface on said side member, and a plurality of spaced interdigitated generally axially extending lands and grooves defined on said generally radially extending surfaces of said members intermediate said input shaft opening and said peripheral surface on said clutch member, the improvement comprising: a generally axially extending annular trough in one of said members on the radially extending surface of said one member defined in part by a generally cylindrically shaped surface, the axial depth of said trough being greater than the axial depth of said grooves on said one member; and a centering abutment located on said generally radially extending surface of said other member and being defined in part by a generally cylindrically shaped surface having an axial length of B units which is greater than the axial length of A units of said lands on said other member and radially spaced from said generally cylindrically shaped surface on said one member by a distance of Y units which is substantially less than said distance of X units to readily locate said clutch member relative to said side member for interdigitation of said lands and grooves.