Support system for power tong assembly
A tong assembly having a powered tong mounted over a backup tong is supported at its rear by a post with torque measuring means. The powered tong is supported at its front, near its throat, by one or more struts that extend downwardly to the backup tong. Such strut (s) provide support for the powered tong when the assembly is placed on a support surface for storage. The struts each have a joint with a retracted condition in which the joint is rigid when the tong is placed on a support surface, and an extended condition in which the joint allows a degree of lateral displacement when the tong assembly is applying torque to a pipe string. This maximizes the amount of torque passing through the rearward post, and therefore ensures a more accurate sensing of applied torque by the torque-measuring device.
1. A power tong assembly of the type having a suspension including struts extending downwardly from an upper, powered tong to a lower, backup tong, wherein the struts comprise joints either located within the strut or that operatively connect the strut to one of the tongs, said struts being configured to be selectively rigid or flexible so as to:
1) allow the struts to be effectively rigid when supporting at least part of the vertical load of the powered tong when the tong assembly is placed on a support surface; and
2) allow lower portions of the struts to have a degree of lateral and angular freedom of motion when the power tong assembly is suspended for engaging pipe.
2. A power tong assembly according to claim 1 , wherein the struts each incorporate, or end in, a joint which has interacting surfaces which come together to make the joint rigid when the struts are under compression and are retracted, as when the upper tong is being supported by said struts, said surfaces becoming separated to allow deflection of the struts to occur when the struts are under tension and are extended, as when the backup tong is suspended from the upper tong.
3. A power tong assembly comprising:
an upper powered tong having a forward throat portion for receiving, holding and rotating an upper pipe section and having a rearward portion,
a lower backup tong having a forward throat portion for receiving and holding a lower pipe section and a rearward portion,
a torque measuring device connecting portions of said tongs, and
extendible suspension members connecting the forward portions of the upper and lower tongs, each said suspension members having a retracted condition and an extended condition,
wherein said suspension members each include a strut incorporating a joint having an upper joint portion and a lower joint portion, said strut having a lower portion connected to support the lower backup tong,
and wherein said upper and lower joint portions have interacting surfaces which hold said upper and lower joint portions rigid with each other when the strut is supporting the upper tong and when the suspension members are in the retracted condition,
and wherein said interacting surfaces are separated when the upper tong is supporting, by suspension, the lower tong and when the suspension members are in the extended condition, in which extended condition the strut allow limited free movement of the lower backup tong relative to the upper tong.
4. A power tong assembly according to claim 3 , wherein said upper joint portion is rigidly attached to the upper tong, and wherein the lower joint portion is flexibly connected through said strut to said lower tong by resilient springs.
5. A power tong assembly according to claim 3 , wherein said suspension members include spring means urging the upper and lower joint portions into the retracted condition.
6. A power tong assembly according to claim 3 , wherein said interacting surfaces are wedging surfaces.
7. A power tong assembly according to claim 6 , wherein said wedging surfaces comprise a conical recess in one of said upper and lower joint portions, and a spigot carried by the other of said joint portions and which engages within the recess in the retracted condition of the suspension members.
8. A power tong assembly according to claim 6 , wherein said wedging surfaces comprise a conical recess in said upper joint portion and a spigot forming the said lower joint portion and which spigot engages with the recess in the retracted condition of the suspension means,
and further comprising spring means acting between said upper and lower joint portions tending to advance the spigot into the recess.
9. A power tong assembly according to claim 8 , wherein said spigot is hollow, and wherein a shaft extends within said recess and within said hollow spigot and carries a stop member, and wherein said spring means is a compression spring surrounding said shaft and mounted between said stop member and a part of said spigot above said stop member.
10. A power tong assembly as in claim 1 wherein said upper and lower tongs are mounted on a common support post and further comprising torque measurement means coupled to said post for measuring torque developed in said post between said upper and lower tongs.