关键词: 液气大钳, 结构设计, 钳头, 夹紧机构, 动力钳, 浮动体, 接头, 开口钳, 方案, 制动扭矩

Abstract: Various structures of open-head type drilling string power tongs are compared,with their advantages and disadvantages analyzed,laying particular stress on the Q10Y-M hydropneumatic power tong and its new and unique features as that the rotary tong and the back tong are built in one body; the tong body is stationary while the tong head is floating,and also the inclusion of a two-stage reducer for the pneumatic gear,the shifting of gear without stopping operation,the hydraulic-pneu-matic control system and the resetting mechanism ete.Its excellent performances in oit field drilling relative to personal safety,reliability of operation,relief of crew from fatigus,high operating efficiency,reduced bending of drill-pipes,controllable make-up torque,ability in coring and handling emergencies etc.are described.As a key to the designing of clamping mechanism,the concept of the ration of angential force to radial force is introdoced,together with its varistions during the tentire process of clamping,It serves as the theoretical basis for designing a portable and reliable clamping device.A simple methed for calculating the closed-gear chain,essential to the power tong is also proposed.In the last part of the paper,the technical and economic effectes of the Q10Y-M hydropneumatjc power tong aer examined.