JPH05133488A - Liner for pipe joint using shape memory alloy - Google Patents

Abstract

PURPOSE:To keep off any corrosion in a pipe or liner to be produced in contact with heterogenous metal materials by forming it with resin with an insulating capacity into a cylindrical form, and installing a positioning projection, protuber ant in the inner circumferential direction, in the axial central part of an inner circumferential surface. CONSTITUTION:A liner 1 is pressed in a heat contractive cylinder 5, and two pipes 2, 3 are inserted into this liner 1 so as to make their ends 2a, 3a butt at each other with each projection 4. When the heat contractive cylinder 5 is heated up to the form restoration ending temperature in this state, the cylinder 5 contracts in the circumferential direction, and the liner 1 being softened by heating is compressed from the circumferential direction. With this compression, an inner circumferential surface of the liner 1 is stuck close to each outer circumferential surface of the pipes 2, 3, sealing this part, thus these two pipes 2 and 3 are connected to each other. Since the liner 1 is molded by resin with an insulating capacity, electric corrosion is not produced in these pipes 2, 3, and further since these pipes 2, 3 are connected through the projections 4, even in the case of heterogenous metals themselves, this electric corrosion will in no case occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe joint liner used when two pipes are connected by using a heat-shrinkable cylinder made of a shape memory alloy as a fixing means.

[0002]

2. Description of the Related Art A conventional pipe joint liner that uses a heat-shrinkable cylinder made of a shape memory alloy as a fixing means is made of a metal such as an aluminum alloy and has an inner diameter of two pipes of the same diameter to be connected. It is molded to be slightly larger than the outer diameter. The heat-shrinkable cylinder made of shape memory alloy is shaped so that its inner diameter is slightly smaller than the outer diameter of the liner, and is given a stretching strain in the circumferential direction at room temperature, and the diameter shrinks when heated to the shape recovery end temperature. Manufactured to shrink in the direction of

When connecting two pipes, a liner is press-fitted into a heat-shrinkable cylinder, and the two pipes are inserted into the liner with their ends facing each other. Heat up to. Then, the heat-shrinkable cylinder recovers to the memorized shape and contracts in the circumferential direction, compresses the liner to bring the inner peripheral surface of the liner into close contact with the outer peripheral surfaces of the two pipes, and seals the two parts to seal the two inner surfaces. Connect the tubes.

[0004]

By the way, a heat-shrinkable cylinder made of a shape memory alloy is nickel-titanium (Ni-T).
i) or copper (Cu) based alloy is used, and the liner used at this time is generally made of copper (Cu) or aluminum (Al). Therefore, for example, the liner is made of Cu, one of the connecting pipes is made of Al, and the other pipe is made of Cu.
If it is made of aluminum, the Al tube comes into contact with the Cu liner to cause corrosion, and there is a disadvantage that a hole is formed in the tube and the fluid inside leaks or the tube comes out of the liner.

Also, the liner is made of Al and the one pipe is made of iron (F
If the tube made of e) and the other tube made of Cu are made, the liner made of Al comes into contact with the tube made of Fe or the cylinder made of shape memory alloy to cause corrosion, and the same inconvenience occurs. This is because many metals show a potential higher than the pitting potential of aluminum. Therefore, an object of the present invention is to prevent corrosion of a pipe or a liner caused by contact of different kinds of metal materials.

[0006]

A liner for a pipe joint using a shape memory alloy according to the present invention is formed of a resin having an insulating ability into a cylindrical shape, and is formed in a central portion in an axial direction of an inner peripheral surface in an inner peripheral direction. It is characterized in that it is provided with a protrusion for positioning which rises.

[0007]

In the present invention, when two pipes are connected, the liner according to the present invention is press-fitted into the heat-shrinkable cylinder made of shape memory alloy, and the two pipes are inserted into the liner from both ends thereof. To do. Since the positioning projection is formed on the inner peripheral surface of the central portion of the liner in the axial direction, the two pipes stop in a state where they are abutted with each other. When the heat-shrinkable cylinder is heated to the shape recovery end temperature in this state, the heat-shrinkable cylinder recovers to the memorized shape, and the liner softened by heating is compressed from the circumferential direction so that the inner circumferential surface of the liner becomes the outer circumference of the two tubes 2 by sticking to the surface and sealing this part
Connect the two tubes.

Since the liner according to the present invention is formed of a resin having an insulating ability, no electric corrosion occurs even when the pipe comes into contact with the liner, and the liner itself also comes into electrical corrosion even when it comes into contact with the heat shrinkable cylinder or the pipe. Does not happen. Further, since the two pipes are separated by the projection of the liner, even different metals do not come into contact with each other and electro-corrosion does not occur.

[0009]

1 is a sectional view showing a first embodiment of a pipe joint liner according to the present invention. FIG. A shows a state before connecting pipes to each other, and FIG. B shows a state after connecting pipes to each other. Indicates the state of.

In the figure, the liner 1 is made of a heat-resistant resin having an insulating ability, for example, a fluorine-based resin such as tetrafluoroethylene polymer, and is formed into a cylindrical shape. It is set slightly larger than the outer diameter of the two tubes 2 and 3 of diameter. A ring-shaped positioning projection 4 is formed on the inner circumferential surface of the liner 1 along the circumferential direction at the center of the liner 1. The projections 4 are two pipes inserted from both ends of the liner 1. It functions as a positioning stopper for connecting 2 and 3 at the center of the liner 1.

The heat-shrinkable cylinder 5 made of a shape memory alloy is formed so that its inner diameter is slightly smaller than the outer diameter of the liner 1, and is subjected to circumferential extension strain at room temperature and heated to the shape recovery end temperature. Then, it is manufactured so as to shrink in the direction in which the diameter decreases. The heating temperature required to end the shape recovery of the heat-shrinkable cylinder 5 and the temperature range in which the shape after the shape recovery is maintained are selected as the composition of the alloy when the heat-shrinkable cylinder 5 is manufactured. And it is set freely by selecting the processing conditions. For example, the heat-shrinkable cylinder 5 used in this embodiment is made of Cu-Zn-Al alloy, has a wall thickness of 3.5 mm, and has a thickness of 3-5 in the circumferential direction at room temperature.
% Elongation strain is given, the shape recovery end temperature is 150 ° C., and the shape is processed until the shape is recovered up to about −40 ° C.

When connecting the pipes 2 and 3, the liner 1 is press-fitted into the heat-shrinkable cylinder 5, and the pipes 2 and 3 are inserted into the liner 1 so that the ends 2a and 3a of the projections 4 abut each other. .. When the heat-shrinkable cylinder 5 is heated to the shape recovery end temperature in this state, the heat-shrinkable cylinder 5 shrinks in the circumferential direction, recovers the stored shape, and compresses the liner 1 softened by heating from the circumferential direction. .. As a result, the inner peripheral surface of the liner 1 comes into close contact with the outer peripheral surfaces of the pipes 2 and 3, and this portion is sealed to connect the two pipes 2 and 3.

Since the liner 1 is formed of a resin having an insulating ability, even if the pipes 2 and 3 come into contact with the liner 1, no electric corrosion occurs, and the liner 1 itself also has the heat-shrinkable cylinder 5 and the pipe 2. No electrical corrosion occurs even if it comes in contact with 3.
Also, since the tubes 2 and 3 are connected via the protrusion 4,
Electrolytic corrosion does not occur even if they are different metals.

FIG. 2 is a sectional view showing a second embodiment of the pipe joint liner according to the present invention. This embodiment is the same as the first embodiment described above except that the projection 4 is composed of three semicircular projections 4a, 4b and 4c which are continuous in the axial direction. It has the same configuration. In this case, the projections 4a and 4c are formed so that the diameter r of the circle connecting the ridges along the circumferential direction is slightly smaller than the outer diameter L of the tubes 2 and 3, and the projections at the center are formed. 4b is formed such that the diameter R of the circle connecting the ridges along the circumferential direction is sufficiently smaller than the outer diameter L of the tubes 2 and 3.

In this structure, when the pipes 2 and 3 are inserted into the liner 1, the ends 2a and 3a thereof are protruded 4a.
And 4c to be crimped or press-fitted, and the two pipes 2 and 3 are temporarily locked in a state in which they are in contact with each other by the protrusion 4b. Therefore, according to this configuration, the two pipes 2 and 3 to be connected can be temporarily locked in the liner 1, so that jigs and tools for temporary locking can be provided when the pipes 2 and 3 are connected. Can be done without using,
Work efficiency can be improved.

FIG. 3 is a sectional view showing a third embodiment of the pipe joint liner according to the present invention. This embodiment is the same as the first embodiment described above except that the protrusion 4 has a skirt portion 4d that is gently tapered in the axial direction.
It has the same configuration as the embodiment. In this case, the protrusion 4
The ridge portion 4e is formed such that the diameter R of the circle connecting along the circumferential direction is sufficiently smaller than the outer diameter L of the connecting pipes 2 and 3.

In this structure, when the pipes 2 and 3 are inserted into the liner 1, the ends 2a and 3a of the pipes gradually bite into the tapered skirt 4d, and the temporary engagement is made in the state of abutting each other in the vicinity of the ridge 4e. Be stopped. Therefore, according to this structure, as in the second embodiment described above, the connection 2
The two tubes 2 and 3 can be temporarily locked in the liner 1.

In the above embodiment, the liner 1
Although the whole is formed of a heat resistant resin having an insulating ability, the present invention is not limited to this, and the surface of a metal (for example, copper, aluminum, etc.) may be coated with these resins.

Further, in the above-described embodiment, the projection 4 is formed on the inner peripheral surface of the liner 1 in a ring shape along the circumferential direction, but the invention is not limited to this, and the circumferential direction on the inner peripheral surface is not limited to this. It may be formed at one place or a plurality of places intermittently along. In this case, for example, the projection 4 is provided at one place on the inner peripheral surface.
When forming, the height of the protrusion 4 needs to be set so that the circle C having a diameter r connecting the ridges of the protrusion 4 along the circumferential direction is eccentric as shown in FIG.

[0020]

According to the present invention, since the liner is made of the resin having the insulating ability, it is possible to prevent the corrosion of the pipe or the liner due to the contact of different kinds of metal materials, and the pipe has a hole. It is possible to eliminate the inconvenience that the fluid inside the pipe leaks and the pipe comes out of the liner.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a pipe joint liner according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the pipe joint liner according to the present invention.

FIG. 3 is a sectional view showing a third embodiment of the pipe joint liner according to the present invention.

FIG. 4 is a cross-sectional view showing another example of protrusions formed in the liner.

[Explanation of symbols]

 1 Liner 2,3 Tube 4 Protrusion 5 Heat shrink cylinder

Claims (1)

[Claims] 1. A pipe using a shape memory alloy, which is formed into a cylindrical shape from a resin having an insulating ability, and is provided with a positioning protrusion protruding in the inner peripheral direction at an axial center portion of the inner peripheral surface. Liner for fittings.