Protected back-up rings for metal face seals and earth boring tools incorporating the same

An earth-boring rotary drill tool, comprising:

• a bit body comprising at least one bearing pin;
• at least one roller cone rotatably mounted over the at least one bearing pin;
• and
• a seal assembly disposed between the at least one pin and the at least one roller cone, the at least one seal assembly comprising at least a first, second, and third ring;
• the first ring comprising:
• interior and exterior sidewall surfaces, wherein the distance between the interior and exterior sidewall surfaces defines the radial thickness of the first ring,
• a distal surface proximate a surface of the at least one roller cone to form a seal between the distal surface of the first ring and the surface of the at least one roller cone, and
• a proximal surface spanning the radial thickness of the first ring, wherein the proximal surface is generally U-shaped, and the interior and exterior sidewall surfaces tangentially intersect the proximal surface;
• the second ring comprising an incurvated surface, located and configured to interface with the proximal curved surface of the first ring;
• wherein the third ring is adjacent to, and concentric with, the second ring, the second ring being disposed radially inward the third ring;
• and
• wherein the first, second, and third rings remain stationary relative to the at least one bearing pin as the at least one roller cone rotates about the at least one pin.

A method of assembling a seal assembly for an earth-boring rotary drill tool, the method comprising:

• positioning a first ring adjacent a base of a bearing pin carried by a body of an earth-boring rotary drill bit, wherein a first surface of the first ring contacts an area of a surface of the bearing pin;
• positioning a second ring adjacent the base of the pin and adjacent the first ring;
• positioning a third ring adjacent to, and radially outward from, the first ring, wherein the third ring is concentric with the first ring;
• and
• translating a roller cone towards the base of the bearing pin along an axis of the pin to mount the roller cone on the bearing pin, wherein a first surface of the second ring contacts an area of a surface of the roller cone, and wherein translating the roller cone biases a generally U-shaped second surface of the second ring onto a concave second surface of the first ring, wherein a curvature of the concave second surface of the first ring is complementary to a curvature of the generally U-shaped second surface of the second ring.