JPS6317537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a connecting head at the end of a double-wound steel pipe that is used as a pipe for supplying oil or air to vehicles, machines, or various equipment. be.

Conventionally, the method of forming the connection head at the end of this type of double-wound steel pipe was to simply press the end from the outside in the axial direction, forming a tapered shape on the front side and on the tip side. A bulging head having an inclined surface that is in the same state as the surface of the pipe skin (during piping, it becomes a pressing sheet surface that abuts and engages with the conical opening inclined concave seat surface of the mating connection base; hereinafter referred to as the inclined surface). It merely consisted of the following. Therefore, a slight depression (approximately 0.07 m/m in depth to
0.1m/m), there was a problem in that leakage often occurred from these slight depressions located on the sloped surface when the connection was in pressure contact with the open surface of the mating base. .

The present invention effectively solves these conventional problems using an extremely simple molding method, and one embodiment of the method of the present invention will be described in detail below with reference to the drawings.

First, as shown in Figure 1, 1 is a double-wound steel pipe,
Due to its structure, as shown in FIG. 5, a part of the outer circumferential surface has a depression 8 along the length of the pipe at the end edge of the winding. As shown in FIG. 2, on the outer circumferential surface of the straight pipe end 1' of the double-wound steel pipe 1, a cross-section is cut in advance over a relatively small width using, for example, a knurled rotary cutter member 5. A large number of parallel grooves 2 in the circumferential direction having a serrated shape are constructed.

Next, as shown in FIG. 3, the parallel groove 2 is formed by a truncated conical recess provided in the axial center of the punch member 7, which is set coaxially with the pipe end on the constructed side. Then, the tube end side is pressed in the axial direction to form a bridge-like cross section with a tapered inclined surface 3 (see FIG. 4) on the tip side to form a bulging head. Note that 6 is a split chuck for fixing the double-wound steel pipe 1 during molding and pressing by the punch member 7.

In this way, a large number of parallel grooves 2 in the circumferential direction having a sawtooth cross section are constructed on the outer circumferential surface near the end of the pipe, which is already in a straight state, over a relatively small width along the outer circumferential surface. Then, in order to form a bridge-like bulging head 4 with the parallel grooves 2 as the slope 3, the slope is formed by a large number of circumferential parallel grooves having sawtooth cross sections. As a result, a certain depression 8 is cut in the circumferential direction,
In addition, there is a depression 8 on the sawtooth surface caused by the pressing process during molding and the screwing and tightening by a tightening nut installed on the back side of the inclined surface 3 and applied to the back surface at the time of connection.
This is an extremely effective molding method that completely and reliably prevents leakage from the 8 portions of the depressions of the inclined surface 3 due to the crushing effect.

Next, examples of the method of the present invention will be described below.

Double-wound steel pipe...Material SPCC-1, outer diameter 4.76
m/m, wall thickness 0.7 m/m, length 500 m/m Parallel groove machining...speed of rotation on the steel pipe side 350 rpm/min,
Width 3.5m/m, pitch 0.4m/m, depth 0.15
m/m Bulging head molding...Protrusion of tube end 7.0m/m, by crank press method.

As a result, the inclined surface has many parallel grooves,
A bulging head having an outer diameter of 7.2 m/m and a head height of 3.5 m/m was obtained by cutting out the depressions on the sloped surface formed by these grooves.

[Brief explanation of the drawing]

Figures 1 to 4 are explanatory diagrams showing the order of processing steps showing an embodiment of the method for forming a pipe end connection head in a double-wound steel pipe of the present invention, and Figure 5 is an illustration showing the end of winding of a double-wound steel pipe. FIG. 3 is a partially enlarged cross-sectional view of the vicinity of the edge. 1...double-wound steel pipe, 1'...outer peripheral surface, 2...parallel groove,
3... Inclined surface, 4... Swollen head, 7... Punch member.

Claims (1)

[Claims] 1. On the outer circumferential surface of the pipe end 1' of the double-wound steel pipe 1 in a straight pipe state, a large number of parallel grooves 2 in the circumferential direction are formed so as to have a serrated cross section over a relatively small width, and then, A punch member that is set coaxially with the pipe end 1' of the double-wound steel pipe 1 which protrudes from the distal end surface of the split chuck 6 and is gripped by the chuck. A truncated conical recess 7' provided in the axial center of 7 is pressed from the tube end side in the axial direction, and the parallel groove 2 section is made into a surface 3 tapering toward the tip side. A method for forming a pipe end connection head in a double-wound steel pipe, which comprises forming a bridge-like bulging head 4.