Patent ID: 8544537

Claim:
A drilling rig with a top drive assembly, wherein the drilling rig comprising: a. a derrick with a crown block positioned over a wellbore having a substructure supporting a drill floor; b. wire ropes connecting between the top drive assembly and a drawworks over the crown block; c. a mud pump and a mud pump tank for flowing drilling mud to the top drive assembly; and d. wherein the top drive assembly comprises: (i) a traveling block housing; (ii) an airbag mounted to a lower substantially horizontal airbag plate of the traveling block housing; (iii) an upper substantially horizontal airbag plate mounted to the airbag opposite the lower substantially horizontal airbag plate of the traveling block housing; (iv) a first substantially vertical link mounted on a first link second end to the upper substantially horizontal airbag plate, wherein the first substantially vertical link has a first slot; (v) a second substantially vertical link mounted on a second link second end to the upper substantially horizontal airbag plate, wherein the second substantially vertical link has a second slot; (vi) a first sheave between a first substantially vertical outside plate and a first substantially vertical inside plate of the traveling block housing; (vii) a second sheave between a second substantially vertical outside plate and a second substantially vertical inside plate of the traveling block housing; (viii) a first pin serving as an axle and as a load transfer pin extending through the first sheave to a first load carrying plate of the traveling block housing; (ix) a second pin serving as an axle and as a load transfer pin extending through the second sheave to a second load carrying plate of the traveling block housing; (x) a top drive for engaging a tubular supported by the traveling block housing through a first link first end of the first substantially vertical link and through a second link first end of the second substantially vertical link; and (xi) an air valve secured to the airbag for injecting low pressure air less than 300 psi from a reservoir into the airbag to expand the airbag, lifting the links while engaging the pins to a first position, and then allowing the low pressure air to exit from the airbag, allowing the links to lower while engaging the pins to a second position to provide thread compensation as the top drive installs or remove tubulars from the wellbore, or as the top drive makes up or breaks out a drill string of tubulars.