Fairlead mechanism with synchronized sheaves

A fairlead mechanism for guiding reciprocating travel of a rope connected to a working tool of an excavating machine such as a dragline, said fairlead mechanism comprising

• a support having a main frame and a subframe mounted on said main frame for oscillatory movement about a generally vertical pivot axis,
• a pair of first guide sheaves each having a first annular groove, said first sheaves being rotatably mounted on said support to present said first grooves in facing relation to define between said sheaves a first guide path portion through which the rope passes in frictional contact with at least one of said first guide sheaves to cause said one first guide sheave to stop-start cycle between rotating and nonrotating modes as the rope reciprocates,
• a first synchronizing mechanism for causing said first pair of guide sheaves to counterrotate in unison in response to frictional contact of the rope with either one of said pair of first sheaves to minimize scrubbing between the rope and the first guide sheaves,
• a pair of second guide sheaves each having a second annular groove, said second guide sheaves being rotatably mounted on said support to present said second grooves in spaced facing relation to define between said second sheaves a second guide path portion spaced from said first guide path portion and through which said rope also passes in frictional contact with at least one of said second guide sheaves to cause said one second guide sheave to stop-start cycle between nonrotating and rotating modes, and
• a second synchronizing mechanism for causing said pair of second guide sheaves to counterrotate in unison in response to frictional contact of the rope with either one of said second guide sheaves to minimize scrubbing between the rope and said second guide sheaves.

An excavating machine such as a dragline, said machine comprising:

• a chassis;
• a boom mounted on said chassis for raising, lowering, and side-to-side movements;
• a working tool mounted on said boom for movement relative to said chassis;
• a rope actuating mechanism mounted on said chassis and including a rotatable drum, a prime mover operatively connected to rotate said drum, and a rope connected between said drum and said working tool for reciprocating travel toward and away from said chassis during movement of said working tool;
• and
• a fairlead mechanism for guiding said rope during said reciprocating travel, said fairlead mechanism including a support on said chassis, said support including a main frame and a subframe mounted on said main frame for oscillatory movement about a generally vertical pivot axis, a guide mechanism including a pair of first guide sheaves rotatably mounted on said main frame and lying in a first generally horizontal plane, and a pair of second guide sheaves rotatably mounted on said subframe and lying in a second generally vertical plane, said guide sheaves each having an annular groove, said guide sheaves of each of said pairs being mounted on said support to present said grooves in facing relation to define between said sheaves of each of said pairs a guide path portion through which said rope passes in frictional contact with at least one of said guide sheaves of each of said pairs to cause said one guide sheave of each of said pairs to stop-start cycle between rotating and nonrotating modes as said rope reciprocates, a first synchronizing mechanism for causing said pair of first guide sheaves to simultaneously stop or counterrotate in unison in response to rope contact with either one of said first guide sheaves to minimize wear induced by scrubbing between the rope and said first guide sheaves, and a second synchronizing mechanism for causing said pair of second guide sheaves to simultaneously stop or counterrotate in unison in response to rope contact with either one of said second guide sheaves to minimize wear induced by scrubbing between said rope and said second guide sheaves.