JPH0348394B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to connection with flexible pipe bodies such as tubes and hoses used for transferring various fluid substances such as air and liquids. In particular, the present invention relates to a pipe joint that exhibits little deterioration in pull-out strength and airtightness even when a plastic tube whose elasticity decreases when used in a high-temperature atmosphere is connected.

[Conventional technology]

In recent years, tubes made of thermoplastic resins such as polyamide, polyurethane, and polyvinyl chloride have been widely used because of their advantages such as flexibility, light weight, and non-staining properties. Typical pipe fittings used to connect these tubes are:
There are pipe fittings specified in Japanese Industrial Standard B8381-1985 "Pneumatic pipe fittings".

By the way, such a pipe joint has tapered surfaces on both sides in the axial direction, and when the sleeve that is fitted onto the end of the tube to be connected is tightened with a tightening nut (union nut), the tapered surface of the sleeve is tightened with the tightening nut (union nut). The diameter is reduced by engaging the tapered surface provided inside and the tapered surface provided inside one end of the fitting body, and the tube is held between the insert part of the fitting body that fits inside the tube. Therefore, when devices using these pipe joints and tubes are used to flow high-temperature liquids or used in high-temperature atmospheres, several problems arise. In other words, when the temperature rises, the plastic tube softens and its elasticity decreases, resulting in a significant reduction in the tightening effect of the sleeve, and the tightness between the tube and the insert of the pipe joint at the connection point decreases, causing fluid to leak from the connection point. There is a problem that not only does this cause the tube to fall out easily, but it also makes it easier for the tube to fall out. Therefore, the above Japanese Industrial Standards stipulate that the ambient temperature and the air temperature used should be 60°C or less, which places significant restrictions on usage conditions, so the development of pipe fittings that can be used at high temperatures is awaited. Ta.

[Problem that the invention seeks to solve]

Therefore, in view of the above-mentioned problems of the prior art, the present invention provides a pipe joint in which fluid does not leak from the connection point and the tube does not come off even when plastic tubes are connected and the tube is used in a high-temperature atmosphere. Its purpose is to provide.

[Means for solving problems]

In order to solve the above-mentioned problems of the prior art, according to the present invention, the diameter of the sleeve fitted over the end of the pipe to be connected is mechanically reduced by screwing the joint main body and the tightening nut. In a pipe joint in which a pipe body is joined by being clamped between an insert part that fits inside, the sleeve is made to recover its shape and further contract in diameter near the softening temperature of the pipe body to be connected. A pipe joint made of shape memory alloy is constructed.

In this configuration, if the sleeve is made of a bidirectional shape memory alloy, the tube will always be optimally tightened depending on the temperature on the cold side and the hot side when used in a place subject to thermal cycling. This is suitable because it can be tightened at a high rate.

[Effect]

According to this invention, as described above, the diameter of the sleeve fitted onto the end of the tube is mechanically reduced by tightening the tightening nut that is threadedly engaged with the joint body, and the insert section is fitted inside the tube. In a pipe joint that clamps and connects a pipe body between the sleeve and the pipe body, the sleeve is made of a shape memory alloy that recovers its shape and further reduces its diameter near the softening temperature of the pipe body to be connected. For example, if the sleeve is made of a shape-memory alloy that recovers its shape near the softening temperature of the plastic tube to which it is connected, and the diameter is expanded by a predetermined amount at room temperature, the sleeve will first be inserted into the insert at room temperature. The plastic tube can be clamped between the parts and the plastic tube to ensure a secure connection. Furthermore, if this is used in a high temperature atmosphere or when a high temperature fluid is passed through it, the connected plastic tube will soften and its elasticity will decrease.
The sleeve reduces in diameter and further presses the tube from the outer circumferential surface, and even when the elasticity of the tube decreases during high-temperature use, the closeness between the tube and the insert portion is maintained well and stably, so that fluid leakage does not occur. Also, the tube's pull-out strength is maintained, so it does not come off like in the conventional case.

Here, if the sleeve is made of a bidirectional shape memory alloy that can be repeatedly deformed, the sleeve will not remain contracted in diameter on the high temperature side when used in a place that is subjected to thermal cycles. Since the sleeve automatically expands in diameter when the ambient temperature etc. decreases, the tube will not be tightened more than necessary when the elasticity of the tube recovers as the temperature decreases. Therefore, no creep occurs in the tube, and a good tightening state can be maintained at both the low temperature side and the high temperature side.

〔Example〕

The figure is a partial longitudinal sectional view showing an embodiment of the pipe joint according to the present invention. The illustrated pipe joint 1 is composed of a joint body 10, a tightening nut 20, and a sleeve 30. In the embodiment, the joint body 10 includes an insert portion 11 that fits inside the tube T to be connected, and a tapered portion that is located closer to the tube end than the tip of the insert portion 11 and whose diameter decreases in the tube insertion direction. 12 on the inner peripheral surface thereof, and substantially concentrically surrounds the insert portion 11 to form a tube receiving groove 13 therebetween for receiving the tube T.
4 at one end. A male thread 15 is provided on the outer circumferential surface of the outer cylindrical portion 14, and a spanner hook portion 16 is provided at the intermediate portion, and a male thread portion 17 for connection to equipment is provided at the other end.

The tightening nut 20 has a female threaded portion 21 that is screwed into the male threaded portion 15 of the outer cylinder portion 14 of the joint body 10.
Further, following this female threaded portion 21, facing the tapered portion 12 of the outer cylinder portion 14, a sleeve 3 is provided.
The tapered portion 22 is provided with a tapered portion 22 that engages through the 0.

The sleeve 30 is made of a shape memory alloy and has a tubular body T.
a tapered portion 31 that is fitted onto the end of the joint body 10 and slides on the tapered portion 12 of the outer cylindrical portion 14 of the joint body 10 and the tapered portion 22 of the tightening nut 20, respectively, when the joint body 10 and the tightening nut 20 are screwed together; It is equipped with 32.

Next, the manner of use of the pipe joint 1 according to the present invention will be explained. As shown in the figure, the tightening nut 20 is first inserted, and then the sleeve 30 is inserted.
After inserting the tube body T into the tube body receiving groove 13 of the joint body 10, the tightening nut 20 is screwed into the male threaded portion 15 of the joint body 10 and tightened.
As this tightening nut 20 is tightened, the sleeve 30 is pushed toward the distal end of the tubular body T by the tapered portion 22 of the tightening nut 20, and the sleeve 30
The tapered portion 31 on the distal end side of the tube abuts against the tapered portion 12 of the outer cylinder portion 14 of the joint body 10. When further tightened, the sleeve 30 is deformed inward from its tip and its diameter is reduced, and as a result of pressing the tube T from the outer peripheral surface, the tube T is clamped and locked between the sleeve 30 and the insert part 11 of the joint body 10. This results in good pull-out strength and airtightness.

By the way, as the Japanese Industrial Standards "Pneumatic Pipe Fittings (for Flexible Pipe)" specifies that the ambient temperature and working air temperature be 60°C or less, when used at a temperature of 60°C or higher, In conventional pipe joints, the softening of the tube reduces the tightening effect of the sleeve and reduces the closeness between the inner circumferential surface of the tube and the outer circumferential surface of the insert, preventing a decrease in airtightness and pull-out strength. do not have. On the other hand, in the above embodiment, the sleeve 30 of the pipe joint 1
For example, if a shape memory alloy whose operating temperature is set around 60℃ is made smaller than its normal size (inner diameter) by a predetermined amount and expanded to its normal size, it can be used at temperatures above 60℃. In this case, the sleeve 30 is reduced in diameter to its original size before being enlarged, and the tube body T is strongly tightened. Therefore, when the tube T softens and its elasticity decreases, the tube T is further pressed from the outer circumferential surface, so that the degree of closeness between the outer circumferential surface of the insert portion 11 and the inner circumferential surface of the tube T is reduced. It holds well and can be used at higher temperatures than conventional pipe fittings.

Note that the shape memory alloy forming the sleeve 30 includes, for example, Ni-Ti alloy, Cu-Zn alloy, Cu-
It is possible to use Zn-Al alloy, etc., and the material
The shape, operating temperature, shrinkage rate, etc. may be appropriately selected depending on the operating temperature, the material of the connected pipe body, etc.

Moreover, in addition to shape memory alloys that exhibit irreversible operating characteristics called unidirectional, those that exhibit bidirectional operating characteristics that perform repeated operations may also be used. This bidirectional shape memory effect is obtained when the alloy is heavily worked or heat treated in a restrained state.This memorizes the shape on the high and low temperature sides, and depending on the transformation temperature, the shape on the high temperature side and the shape on the low temperature side are respectively memorized. It can be deformed to the shape on the low temperature side as many times as desired. Therefore, the sleeve 3 is made of bidirectional shape memory alloy.
If 0 is formed, when used in a place subject to thermal cycles, the elasticity of the tube T can be adjusted depending on temperature changes by setting in advance so that the tightening rate is optimal on the low temperature side and the high temperature side respectively. Even when dimensions change, the tube body can always be stably clamped and locked without over-tightening.

〔Effect of the invention〕

As explained above, according to the present invention, the diameter of the sleeve fitted externally on the tube is mechanically reduced by tightening the tightening nut, and the tube is inserted between the sleeve and the insert section fitted inside the tube. In the pipe fitting that is connected by clamping, the sleeve is made of a shape memory alloy that recovers its shape and stores the memory to further contract in diameter near the softening temperature of the pipes to be connected, so it is not a plastic material. When connecting tubes, by using a sleeve whose shape recovery operation temperature is set near the softening temperature of the plastic tube, first, the sleeve will clamp the plastic tube and the insert part at room temperature, ensuring a secure connection. Then, when used at temperatures above the softening temperature of the tube, the sleeve shrinks in diameter and further presses the plastic tube from the outer periphery, effectively compensating for the decrease in elasticity of the plastic tube at high temperatures and improving airtightness. and prevent a decrease in pull-out strength. Therefore, if the pipe joint according to the present invention is used, it can be used in a high temperature range, whereas conventionally it was impossible to use it at temperatures near or above the softening temperature of the tube due to the decrease in elasticity of the tube. The practical effect is extremely large.

In this case, if the sleeve is made of a bidirectional shape memory alloy and the inner diameter on the cold side and hot side is set to a predetermined size, the tube can be tightened at the optimum rate when used in a place subject to thermal cycles. Can be tightened. By making the inner diameter on the low-temperature side somewhat larger than on the high-temperature side, the sleeve will expand in diameter, especially when the temperature changes from the high temperature side to the low temperature side, and this will prevent creep from occurring at the plastic tube connection due to over-tightening. A stable connection is always maintained.

Note that the present invention is not limited to the above-mentioned embodiments. For example, the insert portion that fits inside the pipe body may be made separate from the joint body, or the shape of the joint body may be changed to an elbow shape. Of course, various modifications within the technical idea of this invention are possible.

[Brief explanation of drawings]

The figure is a partial longitudinal sectional view showing an embodiment of the pipe joint according to the present invention. 10: Joint body, 11: Insert part, 12,
22, 31, 32: Tapered part, 14: Outer cylinder part, 2
0: Tightening nut, 30: Sleeve.

Claims (1)

[Claims] 1. A sleeve fitted over the end of the pipe to be connected is mechanically reduced in diameter by screwing together the joint body and a tightening nut, and the sleeve is clamped between the insert part that fits inside the pipe to connect the pipe. 1. A pipe joint for connecting pipes, wherein the sleeve is made of a shape memory alloy that recovers its shape near the softening temperature of the pipes to be connected and is stored to further contract in diameter.