JP6604176B2 - Double pipe - Google Patents

Description

  The present invention relates to a double tube for storing collected specimens.

  There is a blood collection tube as a container for storing the collected specimen, specifically, blood. Some blood collection tubes contain a liquid additive in advance in order to enable a predetermined analysis and are subjected to a decompression process so that the inside of the blood collection tube is in a vacuum state. Therefore, the double blood tube structure is employed for the blood collection tube in order not to evaporate the liquid additive and maintain a vacuum state even when the blood collection tube is not used for a long period of time. As such a blood collection tube, for example, a container assembly as disclosed in Patent Document 1 is known.

  The container assembly has an outer tube body, an inner tube body, and a lid, and the inner tube body is inserted into the outer tube body to form a double tube together with the outer tube body. In the container assembly, the opening end portion of the outer tube body is closed by a lid, and the inside of the double tube is in a vacuum state by performing a decompression process.

Japanese Patent No. 4534506

  The collected blood has various uses, and is used for testing blood components or for testing genes. There is frozen storage as a method for storing the collected blood, but red blood cells contained in blood are destroyed when stored frozen. When a component test or the like is performed, the test value may change if the red blood cells are destroyed, so that the whole blood cannot be stored frozen. On the other hand, since the gene is not destroyed by freezing, in the genetic test, the whole blood is frozen at a low temperature of around −80 ° C. and stored for a long time in order to store the blood for a long time.

  When freezing whole blood, the water in the blood begins to freeze at 0 ° C. or less, and the water in the blood begins to expand due to freezing. As the moisture in the blood expands, an expansion stress directed radially outward acts on the inner tube, causing a portion of the inner tube to expand radially outward. The part that expands eventually hits the outer tube, and the water in the blood causes the outer tube to expand radially outward with the inner tube. As a result, the outer tube may be damaged, or the inner tube may be damaged by the outer tube suppressing the expansion of the inner tube.

  The inventor examined the case where the container assembly of Patent Document 1, which is assumed to be used when storing blood at room temperature, was used in frozen storage after grasping that such a phenomenon could occur. . In a straight tube such as the inner tube of Patent Document 1, the inner diameter of the inner tube in the axial direction is substantially uniform. In this case, the stress acting on the inner tube is substantially constant regardless of the position of the inner peripheral surface. Therefore, the site | part by the side of the opening top part of an inner side pipe body may expand | swell. In this case, when the expanded portion hits the outer tube and pushes the outer tube outward, the outer tube is separated from the top of the opening of the inner tube, and the gap between the inner tube and the outer tube is outside and Communicate. When the lid is opened after the blood is thawed in this state, the outer tube passes through the communication portion between the inner tube and the top of the inner tube, and the outside air (i.e., air) flows between the inner tube and the outer tube. It passes through the gap between them, and further flows through the damaged part of the inner tube into the inner tube. As a result, bubbles are generated in the blood in the inner tube, and further, the bubbles climb to the liquid surface and burst there, so that the blood in the inner tube may scatter and jump out of the container assembly.

  Therefore, the present invention suppresses the communication between the inner tube body and the outer tube body outward even when the inner tube body is greatly expanded, and prevents the blood from leaking outside. The purpose is to provide.

  The double tube of the present invention is a double tube for storing a collected sample, and the inner tube body is formed so that a gap is formed between the inner tube body having a bottom and into which the collected sample is placed. A bottomed outer tube attached to the inner tube so that the tube is inserted and the opening side of the gap is sealed, and a plug member for sealing the inner tube, the lower surface of the inner tube Is slidably in contact with the bottom surface of the outer tubular body, and the inner tubular body has a reduced diameter on the bottom side compared to the opening side of the inner tubular body.

  According to the present invention, the lower surface of the inner tube can be slidable on the bottom surface of the outer tube, so that when the inner tube expands and hits the outer tube, the outer tube opposes the inner tube. Can be pushed back to the side. That is, the inner tube body can be allowed to expand as much as it can be pushed back, and the allowable amount for the sample expansion can be increased. Thereby, even if the inner tube expands greatly, it is possible to prevent the gap between the inner tube and the outer tube from communicating outward, and to prevent blood from leaking outside.

  ADVANTAGE OF THE INVENTION According to this invention, even if an inner side pipe body expand | swells, it can suppress that the clearance gap between an inner side pipe body and an outer side pipe body communicates outward, and can prevent that blood leaks outside.

It is the front view which looked at the double pipe which is embodiment of this invention from the front. It is sectional drawing which cut | disconnected the double tube | pipe of FIG. 1 by cut surface II-II. It is sectional drawing which shows the inner side pipe body with which the double pipe of FIG. 2 is equipped. It is an expanded sectional view which expands and shows the area | region X1 of the double tube | pipe of FIG. It is an expanded sectional view which expands and shows the area | region X2 of the double tube | pipe of FIG.

  Hereinafter, a double pipe 1 according to an embodiment of the present invention will be described with reference to the drawings described above. In addition, the concept of the direction used in the following description is used for convenience in description, and does not limit the direction of the configuration of the invention in that direction. Moreover, the double pipe 1 demonstrated below is only one Embodiment of this invention. Therefore, the present invention is not limited to the embodiments, and additions, deletions, and changes can be made without departing from the spirit of the invention.

  A double tube 1 (hereinafter referred to as “double tube 1”) shown in FIG. 1 is used when a collected specimen, for example, blood is stored frozen at a temperature of −15 ° C. or lower. Specifically, the double tube 1 is stored at −30 ° C. or lower in order to stop the reaction of the enzyme contained in the sample (medical freeze), or the sample used for genetic testing is stored for a long period (deep freeze). Therefore, it is used when storing at −70 ° C. or less. The double pipe 1 used in this way includes a pipe body 2 and a plug member 3.

  The tube body 2 is a so-called double tube, and has an inner tube body 11 and an outer tube body 12 as shown in FIG. The inner tube 11 is a long bottomed tube extending along the axis L1, and blood collected from the blood vessel can be placed therein. The inner tube 11 is made of a light-transmitting thermoplastic resin such as polyethylene (PE), polyethylene terephthalate (PET), PP (polypropylene), glycol-modified polyester, PS (polystyrene), and the like, for example, by injection molding. It is manufactured. Further, as shown in FIG. 3, the inner tubular body 11 is formed in a tapered shape in which a cylindrical portion 11a constituting a side surface portion is reduced in diameter toward the bottom side.

  The cylindrical portion 11a will be described in more detail. The cylindrical portion 11a has an intermediate tapered portion 11b at an intermediate portion thereof, an opening-side tapered portion 11c on the opening end side of the intermediate tapered portion 11b, and further an intermediate tapered portion. A bottom taper portion 11d is provided on the bottom side of the portion 11b. These three taper portions 11b to 11d have a tapered shape whose diameter is reduced toward the bottom side, and the intermediate taper portion 11b is smoothly connected to the opening side taper portion 11c and the bottom side taper portion 11d. Further, the gradient of the intermediate taper portion 11b is larger than the gradients of the opening-side taper portion 11c and the bottom-side taper portion 11d. Thus, by increasing the gradient of the intermediate taper portion 11b, the opening-side taper portion 11c is increased. The inner diameter of the bottom side taper portion 11d is made smaller.

  Further, a flange 11e protruding outward in the radial direction is formed at the opening end portion 11h of the inner tube body 11, and the outer peripheral surface of the flange 11e extends substantially straight along the axis L1. That is, the opening end portion 11h is a straight tube. Further, as shown in FIG. 4, the bottom portion 11 f of the inner tube body 11 has a partial spherical shape, and the lower surface 11 g of the bottom portion 11 f of the inner tube body 11 and the portion around the axis L <b> 1 is the inner side of the inner tube body 11. It is recessed. Thereby, the lower surface 11g of the inner tube 11 is formed in an annular shape. The inner tube body 11 having such a shape is inserted into the outer tube body 12.

  As shown in FIG. 2, the outer tubular body 12 is a long bottomed cylindrical straight tube extending along the axis L2, for example, polyethylene (PE), polyethylene terephthalate (PET), PP (polypropylene), It consists of a thermoplastic resin having translucency such as glycol-modified polyester and PS (polystyrene). In the present embodiment, the outer tubular body 12 is made of PET having a glass transition point higher than that of PE. However, the combination of materials of the inner tube body and the outer tube body is not limited to those illustrated, and the glass transition point of the material of the outer tube body 12 may be lower than the glass transition point of the inner tube body 11. The outer tube body 12 is manufactured by, for example, injection molding. For this reason, the cylindrical portion 12a of the outer tubular body 12 has a draft, but its inner peripheral surface is formed substantially straight along the axis L2. As shown in FIG. 4, the bottom portion 12 b of the outer tube body 12 also has a partial spherical shape, and a portion around the axis L <b> 2 on the lower surface 12 c of the bottom portion 12 b of the outer tube body 12 is inside the outer tube body 12. It is recessed. Further, the bottom surface 12d of the outer tubular body 12 (that is, the inner surface of the bottom portion 12b) is flat so as to be substantially orthogonal to the axis L2, and the lower surface 11g of the inserted inner tubular body 11 becomes the bottom surface 12d. It is in contact.

  The outer tube body 12 formed in this way is formed longer than the inner tube body 11 so that the entire inner tube body 11 can be accommodated in the outer tube body 12. That is, the entire inner tube 11 is covered with the outer tube 12. Further, as shown in FIG. 5, the outer diameter of the inner tube body 11 is the largest in the flange 11e portion, and the inner peripheral surface of the outer tube body 12 is fitted in a state where the flange 11e achieves a seal. The insertion part 12h is fitted. That is, the outer diameter of the flange 11 e portion of the inner tube body 11 is formed to be substantially the same (or larger diameter) as the inner diameter of the outer tube body 12. On the other hand, the inner tubular body 11 has a tapered shape in which the cylindrical portion 11a excluding the opening end portion 11h is reduced in diameter toward the bottom, and the inner peripheral surface of the outer tubular body 12 is substantially straight along the axis L2. Is formed. Therefore, a gap 15 is provided between the inner peripheral surface of the outer tubular body 12 and the outer peripheral surface of the inner tubular body 11. In the present embodiment, the inner peripheral surface of the outer tubular body 12 and the outer peripheral surface of the opening-side tapered portion 11c are not in contact with each other in the gap 15, and the inner peripheral surface of the outer tubular body 12 and the outer peripheral surface of the opening-side tapered portion 11c The space between is the narrowest. Further, the gap 15 is widest between the inner peripheral surface of the outer tubular body 12 and the outer peripheral surface of the bottom taper portion 11d (particularly near the bottom portion 11f). Further, the interval H of the gap 15 is a predetermined range between the inner peripheral surface of the outer tube body 12 and the outer peripheral surface of the bottom taper portion 11d, for example, 0.1 mm ≦ H ≦ 2.5 mm, preferably 0.5 mm. ≦ H ≦ 1.0 mm. In this embodiment, the interval H1 at the boundary between the bottom taper portion 11d and the intermediate taper portion 11b is 0.8 mm (see FIG. 4), and the interval H2 at the boundary portion between the bottom taper portion 11d and the bottom portion 11f. Is 0.9 mm (see FIG. 1).

  In the tube body 2 configured in this way, the inner tube 11 is inserted into the outer tube 12 so that the axes L1 and L2 of the tube body 2 are substantially coincident with each other, and the lower surface 11g of the inner tube 11 is the outer tube 12. Is in contact with the bottom surface 12d. Further, the opening end portion 11h of the inner tube body 11 is positioned lower than the opening end of the outer tube body 12 in the axial direction (the direction along the axis lines L1 and L2), and as shown in FIG. The flange 11 e is accommodated in the outer tube body 12.

  The flange 11e is fitted to the inner peripheral surface of the outer tubular body 12 in a state where a seal is achieved, whereby the gap 15 between the inner tubular body 11 and the outer tubular body 12 is sealed. In the tube main body 2, the outer peripheral surface of the flange 11e (that is, the outer peripheral surface of the opening end portion 11h) is formed in a straight shape in accordance with the shape of the insertion portion 12h of the outer tubular body 12, so that the flange 11e and the outer tube The contact area with the fitting insertion part 12h of the body 12 can be widened, and higher sealing performance can be ensured. In the present embodiment, the flange 11e is fitted to the inner peripheral surface of the outer tubular body 12 to ensure the sealing performance between the inner tubular body 11 and the outer tubular body 12, but the flange 11e is disposed outside. You may make it ensure sealing performance by adhering to the pipe body 12 (for example, ultrasonic welding).

  As described above, the tube body 2 is configured as a double-structure tube having the gap 15 between the outer tube body 12 and the inner tube body 11. The tube body 2 configured as described above has an opening 2a (an opening 12e of the outer tube body 12) on one side in the axial direction, and the plug member 3 is fitted to the opening end 2b of the tube body 2. As a result, the opening 2a is closed.

  The plug member 3 is a so-called rubber plug, and is made of, for example, synthetic rubber. The plug member 3 is formed in a substantially columnar shape, and a distal end side portion 3 a extends to the inner tube body 11. Further, the base end side portion 3b of the rubber plug protrudes outward from the opening end portion 12f of the outer tubular body 12, and the base end side portion 3b of the rubber plug has a flange 3c formed over the entire circumference in the circumferential direction. Have. The outer diameter of the flange 3c is formed to be larger than the outer diameter of the outer tube body 12, and abuts against the opening end 12f of the outer tube body 12 when the plug member 3 closes the opening 2a of the tube body 2. It is like that. Thereby, by contact | abutting with the opening end part 12f of the outer side tubular body 12, compared with the case where it is not contact | abutting, the expansion | swelling in a bottom part is easy to be prevented. The plug member 3 having such a shape seals the inside of the outer tube body 12 in which the inner tube body 11 is housed, so that the gas and liquid in the inner tube body 11 are not released to the outside by being sealed. It has become.

  The double tube 1 configured as described above is evacuated by reducing the pressure inside the inner tube 11, and blood can be collected by using a holder with a blood collection needle (not shown). Yes. That is, the blood collection needle of the holder with a blood collection needle is punctured into the blood vessel, and then the double tube 1 is attached to the holder with the blood collection needle, whereby blood in the blood vessel flows into the inner tube 11 that has been decompressed. Yes. Then, when an appropriate amount of blood is collected, the double tube 1 is removed from the holder with a blood collection needle. Thereby, the blood collected in the inner tube 11 can be stored in a sealed state.

  The double tube 1 is frozen together with blood in order to store the collected blood in a frozen state. For example, when the collected blood is used for genetic testing, it may be stored for a long time, and the double tube 1 is stored frozen at −70 ° C. or less together with the blood. When the blood is frozen, the water contained in the blood begins to freeze at 0 ° C. or less, and the blood begins to expand accordingly. The expanding water proceeds toward the plug member 3 in the inner tube 11, that is, the upper side, and eventually freezes from the water on the upper side in the inner tube 11. If it does so, expansion | swelling to the upper side of a water | moisture content will be suppressed gradually, As a result, the expansion | swelling of the water | moisture content in the blood will change not to an axial direction but to the radial direction outer side. Therefore, the inner tube body 11 receives expansion stress radially outward from moisture in the blood to be expanded. The closer the freezing point of water in the blood is to the bottom side of the inner tube body, the more difficult the expansion in the axial direction becomes, and the inner tube body 11 is pushed outward in the radial direction, and the inner tube body 11 is easily damaged. .

  Furthermore, the expansion stress of the moisture in the blood does not act uniformly on the inner peripheral surface of the inner tube 11, and the magnitude changes according to the inner diameter of the inner tube 11. That is, the larger the inner diameter of the inner tube body 11, the smaller the expansion stress that acts, and the smaller the inner diameter, the larger the expansion stress that acts.

  Even in the bottom taper portion 11d, the vicinity of the bottom portion 11f, which has a high rigidity due to the curved surface, is difficult to deform, and the portion near the intermediate taper portion 11b is less deformed than the bottom portion 11f. It tends to occur (see, for example, the deformed portion 16 of the two-dot chain line in FIG. 4). Deformation associated with blood expansion occurs locally at the bottom taper portion 11d of the inner tube body 11, and the deformed portion 16 continues to expand in response to blood expansion. As the blood continues to expand, the deformed portion 16 eventually hits the inner peripheral surface of the outer tubular body 12. Thereafter, when the blood continues to expand, the outer tube body 12 is pushed radially outward by the deformed portion 16. As a result, the inner peripheral surface of the outer tubular body 12 may be deformed, but the deformed portion 16 can be separated from the flange 11e by generating the deformed portion 16 at the bottom taper portion 11d. Thereby, the deformation | transformation location 16 of the inner side tubular body 11 can expand | swell, and it can prevent that the space | gap 15 communicates with the exterior away from the flange 11e and the fitting insertion site | part 12h of the outer side tubular body 12. FIG.

  Further, in the double tube 1, the inner tube 11 is supported only by the opening end portion 11 h (specifically, the flange 11 e) and the bottom surface 12 d of the outer tube 12, and the inner tube 11 opens in the outer tube 12. It can be swung in all radial directions with the end 11h as a base point. Further, in the double tube 1, the bottom surface 12 d of the outer tube body 12 is formed flat, and the gap 15 between the bottom taper portion 11 d and the inner peripheral surface of the outer tube body 12 is wide. The bottom portion 11f of the inner tube body 11 can be slid on the bottom surface 12d, and the movement of the inner tube body 11 is not restricted in any radial direction. Therefore, by generating the deformed portion 16 at the bottom taper portion 11d, the inner tube 11 is moved to the outer tube 12 in the opposite direction even when blood further expands in contact with the inner peripheral surface of the outer tube 12. Can be pushed back. Thereby, it can suppress that the outer side tubular body 12 is deformed and damaged.

  Moreover, since the inner tube body 11 can be pushed back to the opposite side of the direction in which the deformed portion 16 expands, the blood can be allowed to expand by the amount that can be pushed back. In other words, the blood can be allowed to expand by about twice the interval H of the gap 15. Therefore, as compared with the case where the inner tube 11 is fixed in the outer tube 12, the interval H of the gap 15 that is open to allow blood expansion can be reduced. Thereby, the external dimension of the double tube 1 can be suppressed.

  In the double tube 1, the blood swells greatly in the radial direction depending on the method of freezing the blood, etc., and the deformed inner tube 11 may not be able to endure and may be locally damaged. However, as described above, the outer tube body 12 is not damaged, so that it is possible to prevent blood from leaking out of the double tube 1 even when blood is thawed when used for genetic testing or the like.

  Further, in the double pipe 1, the flange 11 e is fitted to the inner peripheral surface (fitting insertion portion 12 h) of the outer tubular body 12 in a state where the sealing is achieved, and the gap between the outer tubular body 12 and the inner tubular body 11 is achieved. The gap 15 is sealed. Since the gap 15 is sealed in this way, even if the inner tube 11 is broken, the blood in the inner tube 11 is less likely to enter the gap 15 even if the inner tube 11 is connected to the gap 15. Therefore, it is possible to suppress blood in the inner tubular body 11 from being drawn into the gap 15 by capillary action. As a result, the amount of blood that flows out into the gap 15 and cannot be removed can be reduced, and a decrease in the amount of blood that can be used in a test or the like can be prevented. Even if it flows, the gap H of the gap 15 is small, so that the amount of blood that flows out into the gap 15 and cannot be taken out can be suppressed.

  In the double pipe 1, since the gap 15 is sealed, even if the inner pipe 11 is broken and the inside of the inner pipe 11 is connected to the gap 15, the gap 15 becomes a negative pressure at the time of opening the gap. It is possible to suppress the outside air (air) from flowing into 15. Thereby, the air that has flowed into the gap 15 does not enter the inner tube body 11 through the damaged portion. Thereby, bubbles are generated in the inner tubular body 11 at the time of opening, and the bubbles can be prevented from rupturing and blood scattering.

  Further, in the double pipe 1, an intermediate taper portion 11b having a larger gradient than the gradient is formed between the opening-side taper portion 11c and the bottom-side taper portion 11d. The difference in outer diameter with the side taper portion 11d can be increased. Thereby, the space | interval H of the clearance gap 15 around the bottom side taper part 11d can be enlarged, enlarging the outer diameter of the opening side taper part 11c and reducing the expansion stress which acts there.

  The inner tube body 11 and the outer tube body 12 are formed so that the distance H between the inner circumferential surface of the outer tube body 12 and the outer circumferential surface of the bottom taper portion 11d is 0.5 mm ≦ H ≦ 1.0 mm. ing. When the distance H is less than 0.5 mm, the outer tube 12 may be damaged without being able to absorb the expansion of the deformed portion 16 due to the gap 15, and when it is 1.0 mm or more, the deformed portion 16 is locally expanded. The deformation part 16 may be damaged due to too much. In view of the above, the distance H between the inner peripheral surface of the outer tubular body 12 and the outer peripheral surface of the bottom taper portion 11d is 0.1 mm ≦ H ≦ 2.5 mm, preferably 0.5 mm ≦ H ≦ 1. It is preferable to be within the range of 0.0 mm.

  In a tube for storing a specimen such as the double tube 1, the outer diameter of the outer tube body 12 is determined in advance so as to be attached to a testing apparatus or the like. Even when the gap 15 is provided, there is no exception, and it is difficult to increase the outer diameter of the outer tubular body 12 of the double pipe 1. Therefore, in order to secure the gap 15, it is necessary to reduce the outer diameter of the inner tube 11. When the inner tube body 11 and the outer tube body 12 are straight tubes, the inner tube body is brought into contact with the open end portion 12e of the outer tube body 12 and the open end portion 11h of the inner tube body 11 in order to seal the gap 15. The outer diameter of 11 and the inner diameter of the outer tube 12 need to be approximately the same. If it does so, it will become difficult to ensure the clearance gap 15 which accept | permits expansion | swelling. On the other hand, when the outer diameter of the inner tube 11 is small, the gap 15 is widened, so that the heat insulation is enhanced and the freezing of water in the blood is delayed. In view of these, by setting the interval H between the inner peripheral surface of the outer tubular body 12 and the outer peripheral surface of the bottom taper portion 11d within the above range, the inner tubular body 11 is expanded along with the expansion of moisture in the blood. At the same time as securing the gap 15 to allow expansion, it is possible to suppress the slowing of the freezing rate of water in the blood in the inner tubular body 11.

  In the double tube 1 configured as described above, for example, the inner tube 11 is made of PE, and the outer tube 12 is made of PET. That is, the material of the inner tube 11 has a lower glass transition point than the material of the outer tube 12, and the viscosity of the inner tube 11 is smaller than the viscosity of the outer tube 12. Therefore, the inner tube body 12 is more easily stretched and less likely to be damaged than the outer tube body 11, and the outer tube body 12 can be further prevented from being damaged when blood expands.

<Other embodiments>
The double tube 1 of the present embodiment is used as a blood collection tube for collecting blood, but the collected sample is not limited to blood. The collected sample may be, for example, digestive fluid such as saliva and gastric juice, or secretory fluid such as sweat.

  Further, in the inner tubular body 11, the opening-side tapered portion 11c and the bottom-side tapered portion 11d are formed on both sides in the axial direction of the intermediate tapered portion 11b, but both sides in the axial direction of the intermediate tapered portion 11b are necessarily tapered. There is no. The outer diameters on both sides in the axial direction of the intermediate taper portion 11b may be different from each other, and both sides in the axial direction of the intermediate taper portion 11b may be formed substantially straight. Further, by forming the intermediate tapered portion 11b in the intermediate portion of the inner tube body 11, the outer diameter of the inner tube body 11 can be changed smoothly, so that stress concentration can be prevented from occurring. The intermediate taper portion 11b is not necessary, and a step may be formed in the intermediate portion of the cylindrical portion 11a so that the outer diameters of the opening side and the bottom side of the cylindrical portion 11a are different. When forming a step, it is preferable that the step be R-shaped in order to increase durability against stress.

  Furthermore, the inner tube body 11 does not necessarily need to be lower than the outer tube body 12 and may be the same height as the outer tube body 12. In the case of such an embodiment, the flange 11e of the inner tubular body 11 is fitted into the open end 12f of the outer tubular body 12. The double pipe of this embodiment also has the same effect as the double pipe 1 of this embodiment. Furthermore, the lower surface 11g of the inner tube 11 does not necessarily have to be recessed around the axis L1, and may be flat or spherical.

DESCRIPTION OF SYMBOLS 1 Double pipe 3 Plug member 11 Inner tube 11b Middle taper part 11c Opening side taper part 11d Bottom side taper part 11g Lower surface 11h Opening end part 12 Outer pipe body 12d Bottom surface 12h Insertion part 15 Gap

Claims (7)

A double tube for storing the collected sample, and a bottomed inner tube to hold the collected sample,
A bottomed outer tube attached to the inner tube so that the inner tube is inserted so that a gap is formed between the inner tube and the opening side of the gap is sealed;
A plug member for sealing the inner tube body,
The lower surface of the inner tube is slidably in contact with the bottom surface of the outer tube,
The inner tube is a double tube having a reduced diameter on the bottom side compared to the opening side of the inner tube. The inner tube body has an intermediate taper portion in an axial middle portion thereof,
The double tube according to claim 1, wherein the intermediate taper portion is reduced in diameter toward the bottom side of the inner tube body. The inner tubular body has a bottom taper portion formed on the bottom side from the intermediate taper portion, and an opening side taper portion formed on the opening side from the intermediate taper portion,
The bottom taper portion and the opening taper portion are expanded in diameter from the bottom side of the inner tubular body toward the opening side,
The double pipe according to claim 2, wherein a gradient of the bottom taper portion and the opening taper portion is smaller than a gradient of the intermediate taper portion.   The double pipe according to claim 3, wherein an interval of the gap between the bottom taper portion of the inner tube body and the outer tube body is formed to be 0.1 mm or more and 2.5 mm or less. The gap spacing between the bottom tapered portion of the inner tube and the outer tube is 0 . The double tube according to claim 4, wherein the double tube is formed in a range of 5 mm to 1.0 mm. The outer peripheral surface of the opening end portion of the inner tubular body is formed substantially straight along the axis thereof, and is fitted in a state of being in close contact with the insertion portion of the inner peripheral surface of the outer tubular body.
The double tube according to any one of claims 1 to 4, wherein the insertion portion is formed substantially straight along the axis of the outer tube body. The outer tube body and the inner tube body are made of a resin material,
6. The double tube according to claim 1, wherein the resin material of the inner tube body is a resin material having a glass transition point lower than that of the resin material of the outer tube body.

Images