Joint mechanism and connection method for steel pipe

Abstract

Contemplated are simplification and cost reduction in arrangement of connecting a pair of steel pipes to each other. A joint mechanism for a pair of steel pipes 1 A, 1 B include inner joints 10 A, 10 B and an outer joint 20 disposed circumferentially across and between the inner joints 10 A, 10 B. The outer joint 20 incudes inward key portions 23 engageable with outward circumferential grooves 13 of the inner joints 10 A, 10 B. The outer joint 20 is formed of a plurality of unit members 12 disposed side by side around the inner joints 10 A, 10 B. A standard unit member 21 A includes an engaging projecting portion 24 whereas the inner joints 10 A, 10 B respective include an engaging sunk portion 14 engageable with the engaging projecting portion for preventing detachment of the standard unit member 21 A to the outside. A wall face constituting the engaging sunk portion 14 includes a cutout portion 15 A, 15 B which allows insertion of the standard unit member 21 A to a position where the engaging projecting portion 24 is engageable with the engaging sunk portion 14.

1 . A joint mechanism for a steel pipe comprising:
 a first inner joint provided at one end of one steel pipe;   a second inner joint provided at the other end of the other steel pipe;   an outer joint disposed circumferentially between and across the first inner joint and the second inner joint for connecting a pair of the steel pipes to each other when the first inner joint of one steel pipe is placed adjacent the second inner joint of the other steel pipe;   an engaging portion provided in one of an outer circumference of the first inner joint and the second inner joint respectively and an inner circumference of the outer joint; and   an engaged portion provided in the other of the outer circumference and the inner circumference to be engaged with the engaging portion for preventing relative movement between the pair of steel pipes along a longitudinal direction of these steel pipes;   wherein the outer joint comprises a plurality of unit members disposed side by side around the first inner joint and the second inner joint;   the plurality of unit members include a standard unit member having engaging projecting portions at an end portion thereof on the first inner joint side and an end portion thereof on the second inner joint side, respectively;   the first inner joint and the second inner joint respectively has an engaging sunk portion engageable with the engaging projecting portion for preventing detachment of the standard unit member to the outside; and   at least a portion of a wall face constituting the engaging sunk portion includes a cutout portion capable of inserting the engaging projecting portion of the standard unit member to a position corresponding to the engaging sunk portion.   
     
     
         2 . The joint mechanism according to  claim 1 , wherein the plurality of unit members further include a closing unit member having a shape to be in flush with an outer circumferential face around the cutout portion when this closing unit member is disposed within the cutout portion, and there is provided a fixing mechanism for fixing the closing unit member to at least the first inner joint or the second inner joint. 
     
     
         3 . The joint mechanism according to  claim 1 , wherein:
 the cutout portion includes a first cutout portion provided in the first inner joint and a second cutout portion provided in the second inner joint; and   the first inner joint and the second inner joint respectively includes a positioning mechanism for positioning the first cutout portion and the second cutout portion in fixed opposition to each other along the longitudinal direction of the steel pipes when the first inner joint of one steel pipe is placed adjacent the second inner joint of the other steel pipe for connection of the pair of steel pipes to each other.   
     
     
         4 . The joint mechanism according to  claim 3 , wherein the positioning mechanism comprises a hole portion provided in a mutually opposing face of the first inner joint and the second inner joint respectively and a positioning pin to be inserted into the hole portion. 
     
     
         5 . The joint mechanism according to  claim 1 , wherein:
 the engaged portion comprises an outward circumferential groove provided in an outer circumference of the first inner joint and the second inner joint respectively; and   the engaging portion comprises an inward key portion provided in an inner circumference of the outer joint and engageable with the outward circumferential groove for preventing the relative movement between the pair of steel pipes in the longitudinal direction thereof.   
     
     
         6 . The joint mechanism according to  claim 1 , wherein:
 the engaging portion comprises an outward key portion provided in an outer circumference of the first inner joint and the second inner joint respectively; and   the engaged portion comprises an inward key portion provided in an inner circumference of the outer joint and engageable with the outward circumferential groove for preventing the relative movement between the pair of steel pipes in the longitudinal direction thereof.   
     
     
         7 . The joint mechanism according to  claim 1 , wherein:
 the first inner joint and the second inner joint respectively comprises a straight seam steel pipe; and   a bonding portion included in the straight seam steel pipe is disposed at a position not overlapped with the cutout portion formed in the first inner joint or the second inner joint.   
     
     
         8 . The joint mechanism according to  claim 1 ; wherein:
 the outer joint comprises a straight seam steel pipe; and   a bonding portion included in the straight seam steel pipe is disposed in the standard unit member.   
     
     
         9 . A connection method for connecting a pair of steel pipes to each other with using the joint mechanism according to  claim 1 , the method comprising the steps of:
 placing a first inner joint provided at one end of one steel pipe and a second inner joint provided at the other end of the other steel pipe adjacent each other;   positioning a first cutout portion provided in the first inner joint and a second cutout portion provided in the second inner joint in fixed opposition to each other along a longitudinal direction of the steel pipes;   disposing an outer joint circumferentially between and across the first inner joint and the second inner joint by inserting, via the first cutout portion and the second cutout portion, a standard unit member having engaging projecting portions at an end portion thereof on the first inner joint side and an end portion thereof on the second inner joint side, respectively, the standard unit member being included in a plurality of unit members constituting the outer joint;   engaging an engaging portion provided in one of an outer circumference of the first inner joint and the second inner joint respectively and an inner circumference of the outer joint with an engaged portion provided in the other of the outer circumference and the inner circumference for preventing relative movement between the pair of steel pipes along the longitudinal direction of these steel pipes;   sliding the engaging projecting portion in the circumferential direction of the steel pipes along an engaging sunk portion provided in the first inner joint and the second inner joint respectively, with maintaining engagement between the engaging portion and the engaged portion;   inserting a closing unit member included in the plurality of unit members constituting the outer joint and having a shape to be in flush with an outer circumferential face around the cutout portion when this closing unit member is disposed within the cutout portion through the first cutout portion and the second cutout portion, thereby to establish engagement between an outward circumferential groove and an inward key portion or between an outward key groove and an inward circumferential groove; and   fixing the closing unit member to at least the first inner joint or the second inner joint.   
     
     
         10 . The method according to  claim 9 , wherein at the step of positioning the first cutout portion provided in the first inner joint and the second cutout portion provided in the second inner joint in fixed opposition to each other along the longitudinal direction of the steel pipes, before the step of placing the first inner joint and the second inner joint adjacent each other, the closing unit member is disposed in advance within the first cutout portion or the second cutout portion, and then, the first cutout portion and the second cutout portion are placed in opposition to each other along the longitudinal direction of the steel pipes with utilizing the closing unit member and then the closing unit member is temporarily removed after the positioning.