Worm-drive power tong

Abstract

A tong for applying torque to a tubular and a method of using a tong, of which the tong includes a rotary ring defining an inner profile through which the tubular is received, the inner profile defining a plurality of pockets extending radially outward and a plurality of cam surfaces circumferentially between the plurality of pockets, and a plurality of engaging members disposed within the rotary ring. The plurality of engaging members are movable from a retracted position at least partially in the plurality of pockets to an engaging position in which the plurality of engaging members are positioned along the plurality of cam surfaces. The tong also includes a plurality of cam followers extending through the rotary ring, and a worm drive including a helical ridge. The plurality of cam followers engage the helical ridge so as to transmit a substantially tangential force to the rotary ring.

What is claimed is: 
     
         1 . A tong for applying torque to a tubular, comprising:
 a rotary ring defining an inner profile through which the tubular is received, the inner profile defining a plurality of pockets extending radially outward and a plurality of cam surfaces circumferentially between the plurality of pockets;   a plurality of engaging members disposed within the rotary ring, wherein the plurality of engaging members are movable from a retracted position at least partially in the plurality of pockets to an engaging position in which the plurality of engaging members are positioned along the plurality of cam surfaces;   a plurality of cam followers extending through the rotary ring; and   a worm drive comprising a helical ridge, wherein the plurality of cam followers engage the helical ridge so as to transmit a substantially tangential force to the rotary ring, to rotate the rotary ring.   
     
     
         2 . The tong of  claim 1 , wherein the plurality of cam surfaces each comprise an arcuate shape. 
     
     
         3 . The tong of  claim 1 , wherein the plurality of engaging members each comprise a roller that rolls along one of the plurality of cam surfaces when the rotary ring is rotated relative to the engaging members. 
     
     
         4 . The tong of  claim 1 , wherein the plurality of cam surfaces each define a stepped profile comprising a first arcuate surface, a second arcuate surface, and a transition ramp positioned therebetween. 
     
     
         5 . The tong of  claim 1 , wherein the plurality of engaging members are configured to rotate with the rotary ring after moving along at least a portion of the plurality of camming surfaces. 
     
     
         6 . The tong of  claim 1 , further comprising a cage plate coupled to the rotary ring, wherein the plurality of engaging members are coupled to the cage plate such that the plurality of engaging members are slidable with respect to the cage plate in a radial direction, but are prevented from moving circumferentially relative to the cage plate. 
     
     
         7 . The tong of  claim 6 , wherein the cage plate comprises a plurality of radial slots, the radial slots slidably receiving the engaging members. 
     
     
         8 . The tong of  claim 6 , further comprising:
 a stationary body, the rotary ring being rotatable relative to the stationary body; and   a brake band coupled to the stationary body and received at least partially around the cage plate, to apply a friction force on the cage plate that resists rotation of the cage plate relative to the stationary body.   
     
     
         9 . The tong of  claim 8 , wherein a portion of the rotary ring and a portion of the stationary body are movable to allow lateral removal of the tubular from within the rotary ring. 
     
     
         10 . The tong of  claim 8 , wherein the rotary ring defines one or more arcuate backing slots, the tong further comprising:
 a top guard comprising openings, wherein the cage plate comprises a make pinhole and a break pinhole, the make pinhole being aligned with one of the openings and the break pinhole being aligned with another one of the openings; and   a backing pin received through one of the openings and through the make pinhole or the break pinhole, and into the backing slot, wherein the backing pin in the backing slot limits a range of relative rotation between the cage plate and the rotary ring.   
     
     
         11 . The tong of  claim 1 , wherein the plurality of cam followers each comprise a first roller configured to engage the helical ridge, a second roller seated on the rotary ring, and a shaft extending therebetween. 
     
     
         12 . The tong of  claim 1 , wherein the plurality of cam followers extend axially into the rotary ring and the helical ridge and the rotary ring are radially overlapping. 
     
     
         13 . A method for rotating a tubular using a tong, comprising:
 receiving a tubular into a receiving hole in a tong; and   activating a motor, wherein activating the motor causes a helical ridge to rotate in a first direction, the helical ridge applying a linear force on one or more cam followers connected to a rotary ring, causing the rotary ring to rotate relative to a plurality of engaging members, wherein rotating the rotary ring relative to the plurality of engaging members causes the plurality of engaging members to move radially inwards into engagement with the tubular and to rotate the tubular after engaging the tubular.   
     
     
         14 . The method of  claim 13 , further comprising reversing a direction of the motor, wherein reversing the direction of the motor causes the helical ridge to rotate in a second direction, opposite to the first direction, which causes the rotary ring to rotate in a reverse direction, wherein the rotary ring rotating in the reverse direction allows the plurality of engaging members to retract radially outwards. 
     
     
         15 . The method of  claim 14 , further comprising laterally removing the tubular from within the rotary ring, after reversing the direction of the motor. 
     
     
         16 . The method of  claim 14 , further comprising axially removing the tubular from within the rotary ring, after reversing direction of the motor. 
     
     
         17 . The method of  claim 14 , further comprising, after activating the motor and before reversing the direction of the motor:
 de-activating the motor;   removing a backing pin from a slot formed in the rotary ring and from a make opening defined in a cage plate that is aligned with the slot, wherein the cage plate is connected to the plurality of engaging members such that the engaging members are slidable radially with respect thereto, but prevented from moving circumferentially with respect thereto; and   inserting the backing pin through a break opening aligned with the slot and into the slot, wherein the backing pin limits a relative rotation between the rotary ring and the cage plate by engaging the slot.   
     
     
         18 . The method of  claim 17 , wherein the cage plate is initially prevented from rotating with the rotary ring by a brake band connected to a stationary body of the tong, and wherein the cage plate is rotatable relative to the stationary body when a friction force applied by the brake band on the cage plate is overcome. 
     
     
         19 . The method of  claim 14 , wherein the plurality of engaging members retract radially outward into respective pockets formed in the rotary ring. 
     
     
         20 . A tong, comprising:
 a motor;   a helical ridge coupled to the motor such that the motor drives the helical ridge to rotate;   a rotary ring defining a plurality of pockets and a plurality of cam surfaces in an inner profile thereof;   a plurality of cam followers connected to the rotary ring and extending axially therefrom, the plurality of cam followers being positioned to be engaged by the helical ridge, wherein the helical ridge applies a linear force on the plurality of cam followers when the cam followers are engaged by the helical ridge, and wherein the linear force causes the rotary ring to rotate; and   a plurality of jaws movable along the inner profile of the rotary ring, wherein the plurality of jaws are positioned at least partially within respective pockets of the plurality of pockets when the tong is in a retracted position, and wherein the plurality of jaws engage the plurality of cam surfaces when the tong is in an engaging position.   
     
     
         21 . The tong of  claim 20 , wherein the rotary ring comprises a removable section to allow lateral removal of a tubular from within the inner profile of the rotary ring.