Excavator thumb assembly

A method for changing working positions of an excavator stiff link thumb assembly having a link member coupled to a thumb member and a base member, the method comprising:

• providing the base member with a first link mounting aperture, a second link mounting aperture, a first catch spaced a first predetermined distance from the first link mounting aperture, and a second catch spaced a second predetermined distance from the second link mounting aperture, the second predetermined distance being substantially equal to the first predetermined distance;
• providing the link member with a base mounting aperture, the link member having a first working position, in which the base mounting aperture is adjacent to the first link mounting aperture, and a second working position, in which the base mounting aperture is adjacent to the second link mounting aperture;
• providing the link member with a projection shaped complementary to the first and second catches, and spaced a third predetermined distance from the base mounting aperture, the third predetermined distance being substantially equal to the first and second predetermined distances so that the projection provides a first visual indication that the link is substantially in the first working position when the projection mates with the first catch, and a second visual indication that the link is substantially in the second working position when the projection mates with the second catch;
• disconnecting the link member from the base member;
• rotating the link member and thumb member until the projection engages one of the first and second catches;
• and
• reconnecting the link member to the base member.

An excavator comprising:

• a lifting arm pivotally coupled to a bucket;
• a thumb assembly pivotally coupled to the lifting arm, the thumb assembly comprising:
• a base member coupled to the lifting arm, the base member including a link member mounting plate defining a first link mounting aperture and a second link mounting aperture, and a thumb mounting lug;
• a thumb member defining a first pivot joint and a second pivot joint, the thumb member being pivotally connected to the thumb mounting lug at the second pivot joint;
• a link member having a first end defining a base mounting aperture and a second end defining a thumb mounting aperture, the link member being pivotably coupled to the thumb member first pivot joint at the thumb mounting aperture, the link member having a first working position, in which the base mounting aperture is adjacent to the first link mounting aperture, and a second working position, in which the base mounting aperture is adjacent to the second link mounting aperture;
• a removable pin sized for insertion through the first and second link mounting apertures and the base mounting aperture to connect the link member to the base member;
• and
• a connection-assist system including:
• a first catch formed on the link member mounting plate positioned a first predetermined distance from the first link mounting aperture;
• a second catch formed on the link member mounting plate positioned a second predetermined distance from the second link mounting aperture, the second predetermined distance being substantially equal to the first predetermined distance;
• and
• a projection coupled to the link member first end, shaped complementary to the first and second catches, and spaced a third predetermined distance from the base mounting aperture, the third predetermined distance being substantially equal to the first and second predetermined distances so that the projection provides a first visual indication that the link is substantially in the first working position when the projection mates with the first catch, and a second visual indication that the link is substantially in the second working position when the projection mates with the second catch.