Cam follower for power tongs and other uses
A power tong or back-up tong has a jaw assembly that is advanced into engagement with a pipe through a cam follower that contacts the camming surface on the inside circumference of a ring gear, the cam follower being in the form of a series of roller elements arranged as a circulating bearing. In a preferred form, the roller elements are cylindrical roller bearings and the jaw assembly is mounted for sliding advancement towards the pipe to be engaged. In an alternate variant the cam follower includes an indexing guide that maintains the cylindrical roller bearings in proper alignment.
1. A power tong comprising:
(a) a ring gear having a central pipe-receiving region, the ring gear having an inner surface facing such central region;
(b) a camming surface formed on the inner surface of the ring gear;
(c) twin cage plates rotationally mounted with respect to the ring gear on opposite sides of the ring gear, said cage plates being free to rotate with respect to the ring gear, but being constrained to maintain a center of rotation corresponding to the center of the ring gear;
(d) pipe receiving jaw means mounted between said cage plates and positioned to receive pipe to be positioned centrally within the ring gear;
(e) at least one jaw assembly supported between the upper and lower cage plates and carrying a jaw positioned to bear, upon advancement towards a pipe-engaging position in the central region of the tong, against pipe to be placed therein, said jaw assembly comprising a circular roller bearing passageway;
(f) a cam follower means carried by the jaw assembly and, positioned to contact and advance along the camming surface to effect advancement of the jaw into said pipe-engaging position when the ring gear is rotated with respect to the jaw assembly;
wherein the cam follower means comprises a plurality of roller elements that are constrained to circulate in a circulating path along said roller bearing passageway, said circulating path comprising a portion which exposes the roller elements so that they are directed towards the camming surface, and said jaw assembly carrying an alignment guide provided with indexing elements positioned to extend into the roller bearing passageway and maintain the cylindrical roller elements in an orientation that ensures that their longitudinal axes lie perpendicularly to their path of travel.
2. A power tong as in claim 1 wherein said alignment guide comprises an indexing shaft mounted with it's axis parallel to the axes of the cylindrical roller elements when they are properly aligned.
3. A power tong as in claim 2 wherein said indexing elements comprise flutes extending along the length of the indexing shaft.
4. A power tong as in claim 3 wherein said roller elements comprise a full complement of cylindrical rollers.
5. A power tong as in claim 2 wherein said indexing elements comprise sprocket teeth mounted at the two outer ends of said indexing shaft.
6. A power tong as in claim 5 wherein said roller elements comprise a full complement of cylindrical rollers.
7. A power tong as in claim 2 wherein said roller elements comprise a full complement of cylindrical rollers.
8. A power tong as in claim 1 wherein said roller elements comprise a full complement of cylindrical rollers.
9. A roller bearing comprising a full complement of cylindrical rollers positioned within a roller bearing passageway along which the cylindrical rollers may follow a path of travel, said roller bearing carrying an alignment guide provided with indexing elements positioned to extend into the roller bearing passageway and maintain the cylindrical rollers in an orientation that ensures that their longitudinal axes lie perpendicularly to their path of travel and wherein said alignment guide comprises an indexing shaft mounted with its axis parallel to the axes of the cylindrical rollers when they are properly aligned.
10. A roller bearing as in claim 9 wherein said indexing elements comprise flutes extending along the length of the indexing shaft.
11. A roller bearing as in claim 9 wherein said indexing elements comprise sprocket teeth mounted at the two outer ends of said indexing shaft.