JPH0143595Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a bayonet joint for joining vacuum double pipes and the like used for transporting ultra-low temperature fluids such as liquid nitrogen.

[Conventional technology]

Transport of ultra-low-temperature fluids such as liquid nitrogen is achieved by using a double tube, using the inner tube as a flow path for the ultra-low-temperature fluid, and creating a nearly vacuum between the inner and outer tubes to create a highly adiabatic state. It is being done. This type of vacuum double tube uses the highly insulating effect of the vacuum part between the inner and outer tubes to insulate the inner tube, so the overall diameter can be set significantly smaller. This kind of double pipe joint is not based on a bayonet joint, but as shown in FIGS. 1 and 2, a joint plate 2 is attached to the end of one vacuum double pipe 1, and This was accomplished by attaching a joint plate 4 to the end of the other vacuum double tube 3, and then tightening bolts or the like by bringing the joint plates 2 and 4 into contact with each other. 5 and 7 are inner tubes, and 6 and 8 are outer tubes. However, in such a joining method, the joint plates 2 and 4 are cooled by the ultra-low temperature fluid in the inner tubes 5 and 7, causing frosting or icing. In other words, since external heat is transmitted into the inner tubes 5 and 7 through the joint plates 2 and 4, heat intrusion from the joint plates 2 and 4 has been a problem.

[Problem that the invention attempts to solve]

Therefore, it has been proposed and partially implemented to use a bayonet joint for the above-mentioned joint. The bayonet joint is made by Cryogenetic Systems.
It is described on page 510 of the McGraw-Hill Series In Mechanical Engineering (published in 1966), and as shown in Figures 3 and 4, the closed end of one vacuum double tube 9 is connected to the outer tube 10. By making the diameter smaller, the male-shaped part 11 is formed, and
The joint plate 12 is raised from the root of the small diameter outer tube 10, and the closed end of the other vacuum double tube 13 is made into a female shaped portion 1 by making the inner tube 14 have a large diameter.
5, and the joint part 16 is raised from the inlet part of the large diameter inner pipe 14. Then, a concave portion is provided along the circumference on the outer peripheral surface of the tip of the outer tube 10 of the male-shaped portion 11, and a concave portion is provided therein with a partially open O-ring 17 (see Fig. 5, a portion 17a is open for easy fitting). (Although it is sealed when installed), insert this partially open O-ring 17 into the other vacuum double tube 1.
3, the male shaped part 11 is inserted into the female shaped part 15 in a state where it is in contact with the inner peripheral surface of the inner tube 14 of No. 3, and the joint part 12,
The equal parts A and B of 16 are brought into contact with each other, and both double pipes 9 and 1
3 in the axial direction. 10a is an inner tube of one vacuum double tube 9, and 14a is an outer tube of the other vacuum double tube 13. The bayonet joint has the advantage of being able to join pipes while effectively blocking heat from entering from the outside. However, when the ultra-low temperature fluid is first flowed into the inner tubes of the double vacuum tubes 9 and 13 while the double vacuum tubes 9 and 13 are fixed in the axial direction by the contact parts A and B, , in the male part 11 of one double pipe 9, the inner pipe C
is cooled to a low temperature, but since the outer tube D remains at room temperature, only the inner tube C contracts, and the tip of the male shaped part 11
At C', the entire body curves inward and the opening becomes narrow. As a result, a gap is created between the O-ring 17 and its outer peripheral wall 14, from which the cryogenic fluid flows into the gap E between the male-shaped outer circumference and the female-shaped inner circumference.
The liquid enters the water and undergoes an alternating gas-liquid change (it vaporizes on the contact portions A and B, moves to the opposite side, cools, and liquefies).
Then, this process is repeated), and as a result, the cold heat of the internal fluid is dissipated, causing frost to form around the joints 12 and 16, or in some cases, a large amount of ultra-low temperature fluid that has entered the above-mentioned voids evaporates. As a result, large pressure is generated, causing serious problems such as deformation or cracking of the pipe body. Next, when the flow of the ultra-low temperature fluid reaches a steady state, both the inner and outer tubes C and D are cooled in the male section 11, so that the tip
The inward curvature at part C' returns to its original state, but due to the contraction of the entire inner and outer tubes C and D due to cooling, the inner and outer tubes C,
D moves entirely to the left (shrinking direction) in the drawing.
Due to this movement, the position of the O-ring 17 is also shifted to the left. In this case, if the finishing accuracy of the inner tube 14 of the female shaped part 15 is not good, fluid leakage will occur, but since there is a limit to improving the finishing accuracy of the inner tube 14,
The cryogenic fluid enters the gap E due to the movement. The alternating gas-liquid change causes frost to form around the joints 12 and 16, and cold heat is released to the outside. As described above, even with the above-mentioned conventional bayonet joint, the prevention of heat intrusion from the joint portions 12 and 16 has not been sufficiently satisfactory. In addition, in some cases, serious problems such as deformation and cracking of the tube body occur, so improvements in these problems have been desired.

[Means for solving problems]

This idea was created in view of the above circumstances, and the female part of one double pipe whose closed end is a male part is replaced with a female part whose closed end is a corresponding female part. The root portion of the male portion and the portion of the female portion corresponding to the root portion are brought into contact with each other via a sealing member, and the two portions are connected to each other. In a bayonet joint in which heavy pipes are fixed in the axial direction, the distal end edge of the male-shaped part of one of the double pipes is formed into a stepped part, and a threaded part is formed on the outer periphery of the distal end of the stepped part. At the same time, a ring-shaped elastic packing having a U-shaped cross section is placed on the outer periphery of the rear end side, with the U-shaped opening facing forward and the vertical side of the U-shaped portion being in contact with the wall surface of the step. With its end pressed against the tip of the U-shaped lower side of the ring-shaped elastic packing, a fixing screw is engaged with the threaded portion on the outer periphery of the tip of the step, and the male-shaped elastic packing is fitted with a fixing screw. The inner corner of the female shaped part facing the stepped part is formed into a tapered surface that tapers toward the back, and when the male shaped part and the female shaped part are fitted, the tapered surface has a The gist of this is a bayonet joint in which the tip of the U-shaped upper side of the ring-shaped elastic packing is brought into pressure contact.

[Effect]

In other words, this bayonet joint presses the tip of the upper side of the U-shaped ring-shaped elastic packing with a U-shaped cross section provided on the male-shaped tip step part with the tapered surface of the inner corner of the female-shaped part. Because of this, during the initial stage of transport when the ultra-low temperature fluid is first flowed into the inner tubes of both double tubes, only the inner tube of the male-shaped section is cooled by the cold heat of the ultra-low-temperature fluid and contracts. Even if the opening at the tip of the male-shaped tip is curved into a concave state and the distance between the outer periphery of the male-shaped tip and the female-shaped tapered surface becomes wide, the ring-shaped elastic gasket on the stepped part of the male-shaped tip remains U-shaped. The U-shaped opening is opened by the pressure of the ultra-low temperature fluid to be transported, and a sealed state is ensured by preventing the upper end of the U-shape from separating from the tapered surface.

Therefore, a phenomenon in which the ultra-low temperature fluid flows between the male and female sections and radiates cold heat does not occur. When the ultra-low temperature fluid enters a steady state of transport, the entire male-shaped part contracts, and the ring-shaped elastic packing also moves from its initial position in the direction of contraction. The tip of the upper side of the shape moves with it in contact with the tapered surface, and the degree of opening of the U-shaped opening is automatically adjusted by the tapered surface according to the amount of movement, ensuring a sealing condition. . As described above, the bayonet coupling of this invention makes it possible to stop and restart transport when transporting ultra-low temperature fluids such as liquid N ₂ and _He , which are not always flown in a constant amount but are flowed intermittently as necessary. This is preferable because a good sealing condition is ensured even during repeated use. Moreover, in the bayonet joint of this invention, the distal end edge of the male-shaped part is formed into a stepped part, a threaded part is formed on the outer periphery of the distal end of this stepped part, and a cross-sectional core is formed on the outer periphery of the rear end. A ring-shaped elastic packing is provided around the ring with the U-shaped opening facing forward and the vertical side of the U-shape in contact with the wall surface of the stepped part. Since the fixing screw is engaged with the threaded part on the outer periphery of the stepped part while the end of itself is pressed against the tip of the lower side of the step, the finished dimensional accuracy between the male tip and the inner inner part of the female shape is accurate. Even if the gap between the two parts to be sealed by the ring-shaped elastic packing is slightly inconsistent, the U-shaped upper side of the ring-shaped elastic packing can be protruded by adjusting the screwing degree of the fixing screw. You will be able to adjust the amount and absorb the variation. That is, when the above-mentioned gap is somewhat larger than the designed dimension, when inserting the male end into the inner part of the female shape, screw the fixing screw a little further than the proper position. As a result, the U-shaped lower side of the ring-shaped elastic packing having a U-shaped cross section is pushed in, and due to the pushing force, the entire ring-shaped elastic packing becomes slightly raised. In this state, when the male tip is inserted into the inner part of the female part, the U-shaped upper side of the raised ring-shaped elastic packing is pushed by the tapered surface of the inner corner of the female part.
The U-shaped lower side of the ring-shaped elastic packing is forced into the space between the wall surface of the male-shaped end step and the fixing screw from a floating state. At this time, the distance between the wall surface of the male end step and the fixing screw is narrowed by the amount of extra screwing of the fixing screw, and the U-shaped lower side of the ring-shaped elastic packing cannot fit into it. , the part that does not fit completely goes around the upper side of the U-shape via the vertical side of the U-shape. As a result, the U-shaped upper side of the ring-shaped elastic packing protrudes more forward and comes into contact with the tapered surface at the innermost part of the female shape in a good condition. Conversely, if the gap is somewhat smaller than the design dimension, the screwing amount of the fixing screw is reduced. This creates a gap between the U-shaped lower side of the ring-shaped elastic packing and the fixing screw.
In this state, when the tip of the male shape is inserted into the inner part of the female shape, the U-shaped upper side of the ring-shaped elastic packing is strongly pressed by the tapered surface of the inner corner of the female shape. Since the vertical side of the U-shape is pushed in between the wall surface of the male-shaped tip step and the fixing screw by the amount of space created between the lower side of the U-shape and the fixing screw, the ring The amount of protrusion of the upper end of the U-shaped elastic packing is slightly reduced, and the upper end of the U-shaped elastic packing comes into contact with the tapered surface at the innermost part of the female shape in a good condition. In this way, variations in the gap due to poor finished dimensional accuracy between the male tip end and the inner inner part of the female shape are absorbed, and a good sealing condition is ensured.

Next, this invention will be explained based on embodiment drawings.

〔Example〕

Fig. 6 is a sectional view taken along the axial direction of one embodiment of this invention, and Fig. 7 is a sectional view taken along B'-B''. The closed end of the outer tube 21 is made into a male-shaped portion 23 by making the diameter of the outer tube 22 smaller, and the joint portion 24 is raised from the root portion of the thin outer tube 22, and the outer tube 22 of the male-shaped portion 23 is A step part 25 is provided in the circumferential direction at the tip end, and a ring-shaped elastic packing 26 having a U-shaped cross section is provided around the step part 25 with the U-shaped open part facing forward. The closed end of the double pipe 27 is made into a female part 29 by increasing the diameter of the inner pipe 28, and the joint part 30 is raised from the inlet of the large diameter inner pipe 28, and the female part 29 is made to have a large diameter. The inner corner of the inner tube 28 has a tapered surface 31.The male section 23 of one vacuum double tube 21 is connected to the female section 29 of the other vacuum double tube 27. Insert it into the joint part 2.
4 and 30 are brought into contact with each other via the O-ring 32, and the tapered surface 31 of the female part 29 presses the U-shaped upper end of the ring-shaped elastic packing 26, and the outer tube 22 of the male part 23 is pressed. Stopper shaped part 29
The space 33 between the inner tube 28 and the inner tube 28 is made airtight,
In this state, tighten the joint parts 24 and 30 with a fastener (not shown), and
1 and 27 are fixed in the axial direction by the abutting portions A and B of the joint portions 24 and 30. 3
4 is a fixing screw of a ring-shaped elastic packing, 35 is an inner tube of one vacuum double tube 21, and 36 is an outer tube of the other vacuum double tube 21.

In this way, as shown in FIG. 8, this bayonet joint has a tapered surface 31 on the inner tube 28 of the female section 29, and the male section 23
In order to seal the gap 33 by pressing the U-shaped upper end of the ring-shaped elastic packing 26, an ultra-low temperature fluid is first flowed into the inner tubes of both the double tubes 21 and 27, and the cold heat causes the male-shaped part to seal. Even if only the inner tube C of 23 contracts and the tip C' of the male section 23 curves inward, and the distance between the outer periphery of the tip of the male section 23 and the tapered surface 31 of the female section 29 widens. ,
The ring-shaped elastic packing 26 on the male-shaped tip step opens the U-shaped opening under the pressure of the transported cryogenic fluid, and ensures a sealed state by preventing the upper tip of the U-shape from separating from the tapered surface 31. When the flow of the ultra-low temperature fluid reaches a steady state, the inner and outer tubes C and D of the male-shaped portion 23 contract, and the ring-shaped elastic packing 26 also moves from its initial position to the left in the figure. Also, the ring-shaped elastic packing 26 moves with its U-shaped upper end in contact with the tapered surface 31, and as it moves, the degree of opening of the U-shaped opening is automatically adjusted by the tapered surface 31. Since the adjustment is made, the original sealing condition can be maintained even if the dimensional accuracy of the gap is somewhat poor. In this way, this bayonet joint can sufficiently prevent heat from entering from the joint parts 24 and 30 without being affected by the dimensional accuracy of the air gap 33.
30 does not have frosting on the outer periphery as in the conventional case. Furthermore, since the ring-shaped elastic packing 26 with a U-shaped cross section is attached with the U-shaped opening facing forward, there is a risk that ultra-low temperature fluid may enter the gap 33 and evaporate, increasing the pressure inside. However, the upper side of the U-shape of the gasket 26 is pushed down by the pressure, and the objects that have entered the gap are automatically returned to the inner tube, so that the effect that the tube body does not break can also be obtained.

[Effect of idea]

The bayonet joint of this invention has a ring-shaped elastic packing with a U-shaped cross section, and is installed around the ring with the U-shaped opening facing forward and the vertical side of the U-shaped part contacting the wall surface of the step. , when the male part and the female part are fitted together, on the tapered surface of the inner corner of the female part,
Since the ends of the U-shaped upper sides of the packing are pressed together, the seal will not become incomplete even if the joint condition of the joint deteriorates. In other words, in the vacuum double pipes connected by the bayonet joint of the present application, the joint is difficult to operate when resuming the transport from an interrupted state in the transport of intermittent ultra-low temperature fluids such as He _{and N2} . Even if the fitting condition deteriorates and the distance between the outer periphery of the tip of the male part and the tapered surface of the inner corner of the female part becomes large (when transportation is resumed, only the male part will be cooled and contracted by the ultra-low temperature fluid). The U-shaped opening of the packing is automatically opened by the gas pressure of the transported ultra-low temperature fluid, and the upper end of the U-shape does not separate from the tapered surface, thus ensuring a sealed state. Therefore, the seal will not be incomplete. In addition, even if the sealing condition deteriorates and the ultra-low temperature fluid to be transported enters the gap between the male and female sections, and this vaporizes due to the intruding heat and builds up a large pressure within the gap, the pressure As a result, the U-shaped upper side of the gasket is pushed down and the vaporized material smoothly returns to the inner tube of the vacuum double tube, so that the tube body is not deformed or cracked due to large pressure. In the present application, the size of the gap between the male shaped part and the female shaped part is approximately proportional to the distance between the outer peripheral surface of the male shaped part and the inner tapered surface of the female shaped part, and As the distance between the surface and the inner tapered surface of the female section increases, the amount of the transported cryogenic fluid that enters the gap between the male section and the female section increases, and the vaporization pressure thereof also increases. In the present invention, the tip of the U-shaped lower side of the ring-shaped elastic packing is pressed by a fixing screw, and when the distance between the outer peripheral surface of the male-shaped part and the inner tapered surface of the female-shaped part is wider than the standard,
By manipulating the fixing screw and pushing in the U-shaped lower side of the packing, the protruding amount of the U-shaped upper side is increased to correspond to the amount of protrusion. This also means increasing the protruding area of the U-shaped upper side that blocks the entrance to the gap between the male-shaped part and the female-shaped part, and as a result, the transport that enters the gap is increased. Even if the amount of ultra-low temperature fluid increases, the area of the upper side of the U-shape per unit amount of cryogenic fluid is appropriately secured, and the vaporized ultra-low temperature fluid returns smoothly into the inner tube of the vacuum double tube. In this way, the bayonet joint of the present invention is sufficiently designed to deal with unexpected situations, and can prevent major accidents from occurring. In addition, by operating the fixing screw, it is possible to adjust the distance between the outer circumferential surface of the male part and the inner tapered surface of the female part to be wider or narrower than the standard, making it possible to absorb variations in finished dimensional accuracy. can.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the conventional example, and Figure 2 is its A-
A′ sectional view, FIG. 3 is a longitudinal sectional view of an improved example, FIG. 4 is an A''-A sectional view, FIG. 5 is a plan view of a partially open O-ring used in this, and FIG. A longitudinal sectional view of one embodiment of the invention, FIG.
B'' sectional view, and FIG. 8 is an enlarged sectional view of the main parts. 21, 27... Vacuum double pipe, 23... Male shaped part, 24, 30... Joint part, 25... Step part, A ，
B... Contact portion, 26... Ring-shaped elastic packing,
29...Female shaped part, 31...Tapered surface.

Claims (1)

[Scope of utility model registration request] Place the male part of one double pipe whose closed end is a male part into the female part of the other double pipe whose closed end is a corresponding female part. In a bayonet joint in which the double-pipe pipe is fixed in the axial direction by fitting the male-shaped part into contact with the female-shaped part corresponding to the root part through a sealing member, The distal end edge of the male-shaped part of one of the double pipes is formed into a stepped part, and a threaded part is formed on the outer periphery of the distal end of the stepped part, and a U-shaped cross section is formed on the outer periphery of the rear end. A ring-shaped elastic packing is provided around the circumference with the U-shaped opening facing forward and the U-shaped vertical side in contact with the wall surface of the stepped portion, and the U-shaped elastic packing is With the end of itself pressed against the tip of the lower side, fit the fixing screw to the threaded part on the outer periphery of the tip of the step,
The corner of the innermost part of the shaped part that faces the stepped part of the male shaped part is formed into a tapered surface that tapers toward the back, and when the male shaped part and the female shaped part are fitted together, A bayonet joint characterized in that the tip of the U-shaped upper side of the ring-shaped elastic packing comes into pressure contact with the tapered surface.