Electric heating – Metal heating – Work holders
Reexamination Certificate
1999-08-18
2001-02-06
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
Work holders
C219S659000, C219S607000, C228S044500, C228S212000
Reexamination Certificate
active
06184493
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vertical diffusion bonding apparatus, and particularly to a vertical diffusion bonding apparatus serving as a preferred apparatus for diffusion-bonding metal pipes, such as oil well tubes for drilling, tubing or casings disposed vertically.
2. Description of the Related Art
In a diffusion bonding method, bonding members to be bonded to each other are held in close contact with each other, and pressed to a degree which does not cause plastic deformation, so that the bonding members are bonded by using diffusion of atoms which takes place in the interface between the bonded surfaces.
The diffusion bonding method, the solid-phase diffusion bonding method and a liquid-phase diffusion bonding method are known. In a solid-phase diffusion bonding method, members to be bonded are brought into direct and close contact with each other to cause atom elements to be diffused while the solid state is maintained. In the liquid-phase diffusion bonding method, an insertion material having a low melting point is inserted into a space between the members, and then, the insertion member is temporarily melted to cause dissipation of specific elements in the liquid phase in the member and isothermal solidification to occur to bond the members to each other.
The diffusion bonding method is different from the mechanical bonding method, such as a bolt fixing method and a rivet bonding method, in that saving of materials and reduction in the number of man-hours are obtained. Moreover, bonding exhibiting satisfactory bonding strength, airtightness, pressure resistance and the like can be obtained. In addition, the time required to produce each bonding is shorter than time required for the welding method. Since the above-mentioned advantages can be obtained, the diffusion bonding method has been widely used as a method of bonding oil well tubes for drilling oil, anti-corrosion pipes for use in the chemical industry, line pipes for transporting crude oil and elongated stainless steel pipes for use in seawater heat exchangers.
Usually oil wells exist at positions thousands of meters underground. Therefore, when oil well tubes are embedded underground, metal pipes each having a length of 10 meters to 15 meters must sequentially be bonded to one another, and then moved downwards in a vertical hole formed underground. A vertical diffusion bonding apparatus has been employed to diffusion-bond the oil well tubes to one another, the apparatus being arranged to dispose metal pipes in the vertical direction and perform diffusion bonding while supplying the metal pipes from an upper position to the lower position.
Many types of vertical diffusion bonding apparatuses have been suggested. For example, one diffusion bonding apparatus has been suggested in EP 0 882 539 A2. The apparatus incorporates a lower block for holding a lower pipe member and an upper block for holding an upper pipe member and pressing the held upper pipe member against the lower pipe member. In the apparatus, an elevating member for holding the upper pipe member is moved downwards by using three or more hydraulic cylinders so as to press the upper pipe member against the lower pipe member.
FIG. 9
is a schematic view showing a vertical diffusion bonding apparatus having a structure similar to prior art diffusion bonding apparatus. Referring to
FIG. 9
, the vertical diffusion bonding apparatus
10
is provided with a lower block
14
, an upper block
16
, a pressurizing mechanism
18
and a heating mechanism
20
.
The lower block
14
is secured to the lower portions of four frames
18
a.
Two lower clamping mechanisms
14
a
and
14
b
disposed apart from each other for a predetermined distance are provided on the lower block
14
. A metal pipe (a lower pipe member)
22
a
disposed at a lower position is held at two positions.
The upper block
16
can move vertically in the perpendicular direction because the upper block
16
is slidably disposed above the frames
18
a
through sliders
16
c.
Two upper clamping mechanism
16
a
and
16
b
disposed apart from each other for a predetermined distance are provided for the upper block
16
so that a metal pipe (an upper pipe member)
22
b
supplied from an upper position is held at two positions.
The pressurizing mechanism
18
has four frames
18
a,
a main beam
18
b,
a holding beam (not shown) secured to the main beam
18
b
and three pressurizing cylinders
18
c.
The three pressurizing cylinders
18
c
are disposed at angular intervals of about 120° to surround the metal pipe
22
b.
The ends of the pressurizing cylinders
18
c
are secured to the holding frame (not shown), while the other ends are secured to the upper block
16
.
The heating mechanism
20
has a two-piece heating coil
20
a
for induction-heating an area in the vicinity of the interface between the metal pipes
22
a
and
22
b
to be bonded; and two-piece shield chamber
20
b
for maintaining a predetermined atmosphere in the vicinity of the foregoing interface. Wheels
18
d
are disposed at the lower ends of the frames
18
a.
Thus, the overall body of the vertical diffusion bonding apparatus
10
is able to move forwards/rearwards along rails
24
a
provided for a base frame
24
.
The metal pipe
22
a
and
22
b
are diffusion-bonded to each other by using the vertical diffusion bonding apparatus
10
shown in
FIG. 9
in accordance with the following procedure. As shown in
FIG. 10A
, which is a side view, the vertical diffusion bonding apparatus
10
is retracted rearwards (in the right-hand direction in
FIG. 10A
) along the rails
24
a
provided on the base frame
24
. The metal pipe
22
a
held by a tube clamp
26
is moved downwards by using a crane
28
and held by a tube clamp
30
secured to the base frame
24
.
Then, as shown in
FIG. 10B
, the tube clamp
26
which was holding the metal pipe
22
a
is released, and then the tube clamp
26
is secured to the other metal pipe
22
b
that is to be bonded to the metal pipe
22
a.
Then, the crane
28
(not shown in
FIG. 10B
) is operated to move the metal pipe
22
b
to a position above the metal pipe
22
a.
At this time, the metal pipe
22
a
and the metal pipe
22
b
are not brought into contact with each other, that is, they are separated from each other by a predetermined distance. As shown in
FIG. 10C
, the metal pipes
22
a
and
22
b
are moved to the central portion of the vertical diffusion bonding apparatus
10
by moving the vertical diffusion bonding apparatus
10
forwardly along the rails
24
a
(in the left-hand direction in FIG.
10
C).
Then, as shown in
FIG. 11A
which is a front view, the lower clamping mechanism
14
a
and
14
b
provided for the lower block
14
is secured to the metal pipe
22
a.
Also, the upper clamping mechanism
16
a
and
16
b
provided by the upper block
16
holds the metal pipe
22
b
at an upper position. Then the tube clamp
26
is released. If an end surface of the metal pipe
22
a
or the metal pipe
22
b
has a flaw, such as a nick, an end-surface finishing machine
32
associated with the vertical diffusion bonding apparatus
10
may be operated to flatten the end surface of the metal pipe
22
a
or the metal pipe
22
b.
Then, as shown in
FIG. 11B
, the pressurizing cylinders
18
c
are operated to press the metal pipe
22
b
against the metal pipe
22
a.
Then, the two-piece heating coil
20
a
is moved to a position adjacent to the interface between the surfaces to be bonded, and then the portion in the vicinity of the interface between the bonded surfaces is covered with the shield chamber
20
b.
Then, a purging operation using inert gas is performed. Moreover, high frequency waves are applied to the heating coil
20
a
so as to heat the interface between the surfaces to be bonded to a predetermined temperature. Thus, the metal pipes
22
a
and
22
b
are diffusion-bonded.
After a predetermined time has elapsed and thus the temperature of the interface between the bonded surfaces has been sufficiently lowered, the sh
Bacon & Thomas PLLC
Daido Tokushuko Kabushiki Kaisha
Heinrich Samuel M.
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