Rotary tong incorporating interchangeable jaws for drill pipe and casing

DETAILED DESCRIPTION We claim: 1.
In a power tong, the combination of: a housing; a generally annular rotor carried by said housing and rotatable relative to said housing about an axis extending generally perpendicular to the opposite sides of said housing; cam surfaces formed on diametrically-opposite sides of the inner periphery of said annular rotor; drive means carried by said housing for rotating said rotor; a jaw assembly comprising plate members on opposite sides of said housing and said annular rotor; movable bolt members interconnecting said plate members; two sets of interchangeable jaw elements either of which can be used independently of the other as a cooperating pair of pipe-gripping elements on said jaw assembly, each jaw element in each set having at least one bore through which an associated one of said bolt members is adapted to pass to secure a respective set of the jaw elements to said plate members; each jaw element in each set of interchangeable jaw elements having a cam follower adapted to engage an associated one of the cam surfaces of said annular rotor, the jaw elements on one set being movable radially inwardly along a straight-line path of travel upon relative movement of the plate members and said annular rotor due to movement of said cam followers on associated ones of said cam surfaces, and the jaw elements in the other set comprising arms pivotally connected to their associated bolt members and pivotal radially inwardly about said bolt members upon relative movement of the plate members and said annular rotor due to movement of said last-mentioned cam followers on associated ones of said cam surfaces; and friction means for restraining rotation of said plate members.
2.
The power tong of claim 1 wherein the jaw elements in said one set each comprise a hollow casing, and a grip-carrying element reciprocable within said casing and having a cam follower on the end thereof opposite said grip.
3.
The power tong of claim 2 including spring means for urging said grip-carrying element radially outwardly to move said cam follower into engagement with an associated cam surface