Rotation unit for torque tong comprising a rotational part with teeth
A rotation unit for a torque tong for making and/or breaking threaded connections between pipes and/or spinning pipes during screwing and/or unscrewing of pipes, primarily pipes used in petroleum production. The unit includes a fixed part and a rotary part arranged to grip a pipe to be rotated. The rotary part includes at least one movable gripping jaw arranged to be moved into engagement with the pipe. The rotary part includes toothing arranged to engage at least one chain, which is operatively connected to an actuator in order to move the chain and so impart rotary movement to the rotary part.
1. A rotational unit for a torque tong, comprising:
a fixed part; and
a rotary part designed to grip a pipe to be rotated, said rotary part comprising:
at least one movable gripping jaw arranged to be moved into engagement with the pipe;
toothing arranged to engage at least one chain, the toothing including teeth, said at least one chain being operatively connected to an actuator in order to move the at least one chain and so impart rotary movement to the rotary part; and
an opening at a periphery thereof for introduction of a pipe,
wherein the at least one chain extends across a sector of a circle larger than the opening, thus ensuring that the at least one chain and the toothing on the rotary part are engaged at all times, the opening is arranged to be kept open during the rotation of the rotary part, and a rectilinear distance over which the at least one chain extends between the teeth of the toothing located closest to and on either side of the opening is equivalent to a whole number of teeth,
wherein the distribution of the teeth on the rotary part is defined by:
t
2
·
1
sin
(
2
·
π
-
α
2
·
N
2
)
=
0
(
1
)
2
·
a
sin
(
N
1
·
t
2
·
r
)
-
α
=
0
(
2
)
in which:
t is the chain pitch, in mm,
N 1 is the number of teeth that will fit between the two teeth nearest the opening,
N 2 is the number of teeth along the curved section of the rotary part 40,
α is the angle (in radians) between the teeth nearest the opening, and
r is the radius of the rotary part at the at least one chain, the radius being the distance from a center of the rotary part to a center of the chain.
2. A unit according to claim 1 , characterized in that N 1 is equal to 8.
3. The unit according to claim 2 , wherein the rotary part engages at least two chains that act synchronously.
4. The unit according to claim 2 , wherein the rotary part has replaceable teeth.
5. The unit according to claim 2 , wherein the at least one chain extends over a first cogwheel operatively connected with a motor, and a second cogwheel that acts as a turning wheel, which cogwheels are spaced apart at the periphery of the rotary part.
6. The unit according to claim 1 , wherein the rotary part engages at least two chains that act synchronously.
7. The unit according to claim 6 , wherein the at least two chains are arranged on diametrically opposite sides of the rotary part.
8. The unit according to claim 1 , wherein the rotary part has replaceable teeth.
9. The unit according to claim 1 , wherein the at least one chain extends over a first cogwheel operatively connected with a motor, and a second cogwheel that acts as a turning wheel, which cogwheels are spaced apart at the periphery of the rotary part.
10. The unit according to claim 1 , wherein the rotary part is slidingly supported on a plate on the fixed part.