Description of the Related Art In general, when a tube or a pipe for transferring gas or air or for transferring fluid such as water or oil is used, the tube or the pipe needs to be connected to a specific device such as a valve or a distribution pipe.

Fig. 1 shows one of conventional tube joints. The conventional tube joint 412 includes a first coupling member 414, a second coupling member 416 and an insert member 418. The first coupling member 414 has a body 419, a hole 420 and an engaging hole 422. A screw thread 424 is formed on an inner surface of the engaging hole 422. The second coupling member 416 has a body 425 and a passage 426. The passage 426 is formed inside the body 425. An inlet portion of the passage 426 inclines so that an inlet of the passage 426 becomes gradually wide.

A screw thread 428 is formed on an outer surface of an end of the body 425. The screw thread 428 is engaged with the screw thread 424 of the first coupling member 414.

The insert member 418 has a body 429, a passage 430 and a flange 432.

The passage 430 is formed inside the body 429. A tube 410 is inserted into the passage 430. When the first coupling member 414 is engaged with the second coupling member 416, the inner diameter of one end of the passage 430 of the insert member 418 becomes small by the action of the slanted surface of the second coupling member 416. As a result, the tube 410 is pressed and transformed partly, whereby fixed not to missed.

However, because transforming merely a part of a tube, the conventional tube joint is weak in the binding force and cannot keep a sufficient sealing function.

Especially, when the difference in pressure between the inside and outside of the tube is big, fluid can leak from the inside to the outside of the tube, and vice versa.

Furthermore, once the tube is connected, the insert member is transformed plastically. Therefore, after the tube is separated, the insert member is not reusable.

Summary of the Invention It is, therefore, an object of the present invention to provide a tube joint that has a great binding force between a tube and the tube joint to improve its sealing function.

It is another object of the present invention to provide a tube joint that can be used whatever the type or material of the tube is.

According to the present invention, the tube joint for connecting a tube to a fluid passing member or a fluid containing apparatus includes a first coupling member, an insert member and a second coupling member. The first coupling member has a tube insert hole and a first engaging portion. The tube insert hole

has a first inner surface portion and a second inner surface portion. The insert member has a passage and a slanted outer surface. The inclined angle of the slant surface is smaller than that of the second inner surface portion. The second coupling member has a passage and a second engaging portion. The second engaging portion is engaged with the first engaging portion.

Brief Description of the Drawings Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 is a sectional view showing the connection of a tube to a conventional tube joint; Fig. 2 is a sectional view showing the connection of a tube to a tube joint according to a first preferred embodiment of the present invention; Fig. 3A is an exploded perspective view of the tube joint according to the first embodiment of the present invention and the tube; Fig. 3B is a perspective view of an example of a second coupling member; Fig. 4 is a sectional view showing the connection of a tube to a tube joint according to a second preferred embodiment of the present invention; Fig. 5 is a sectional view showing the connection of a tube to a tube joint according to a third preferred embodiment of the present invention; Fig. 6A is a sectional view of an integrally formed insert member and second coupling member according to another preferred embodiment of the present

invention; Fig. 6B is a sectional view of an integrally formed insert member and second coupling member according to another preferred embodiment of the present invention; Fig. 7A is a sectional view showing a construction for connecting a metal tube to a tube joint in accordance with another preferred embodiment of the present invention; Fig. 7B is a sectional view showing a construction for connecting a metal tube to a tube joint in accordance with another preferred embodiment of the present invention; Fig. 8A is a sectional view of an insert member, tube, and first coupling member of another tube joint according to another preferred embodiment of the present invention; and Fig. 8B is a sectional view of an insert member, tube, and first coupling member of another tube joint according to another preferred embodiment of the present invention.

Detailed Description of the Preferred Embodiment Referring to Figs. 2 and 3, a passage 11 is provided in a tube 10, which is a path through which fluid flows. It is preferable that the tube 10 is made of synthetic resin or plastic resin material having elasticity. However, it will be appreciated that other equivalent materials can be used for the tube without limitation to the above. The tube 10 is connected to a tube joint 12.

The tube joint 12 includes a first coupling member 14, a second coupling member 16 and an insert member 18. The first coupling member 14 has a body 22 at an end and a first engaging portion 26 at the other end. A tube insert hole 28 is provided in the middle of the first coupling member 14. A hexagonal bolt head is formed on the body 22 of the first coupling member 14, so that the first coupling member 14 is tightened with a tool such as a spanner. A screw thread 27 is formed on an outer surface of the first engaging portion 26. The tube insert hole 28 of the first coupling member 14 has a first inlet 30, a first inner surface portion 32, a second inner surface portion 34 and a second inlet 36 in order. The first inner surface portion 32 extends from the first inlet 30 to roughly the center of the tube insert hole 28. It is preferable that the first inner surface portion 32 has a uniform inner diameter. The second inner surface portion 34 becomes gradually wide in its inner diameter toward the second inlet. The first and second inner surface portions 32 and 34 come into contact with the outer wall of the tube 10. The inner diameter of the second inlet 36 is larger than that of the first inlet 30. It is preferable that the inner diameter of the second inlet 36, when the insert member 18 is inserted into the tube, is substantially equal to the size that comes from the sum of the twice thickness of the tube and the maximum outer diameter of the insert member 18.

The second coupling member 16 has a passage 42. A round engaging portion 48 is provided in an outlet portion of the passage 42. A screw thread 44 is formed on the inner surface of the engaging portion 48. The screw thread 44 is engaged with the screw thread 27 of the first coupling member 14. A step 40 is provided at the bottom of the engaging portion 48. As shown in Fig. 3B, the second coupling member 16 may be a heat sink of aluminum or aluminum alloy

material for heat exchange. A cavity 16a is provided in the heat sink 16. The engaging portion 48 communicates with the cavity 16a through the passage 42.

Both the inlet and outlet portions of the heat sink 16 have respective engaging portions 48. Refrigerant could be supplied to the heat sink via the tube.

Referring to Figs. 2 and 3, The insert member 18 has a body 45, a passage 46 and a cylindrical flange 50. The passage 46 is a path through which fluid flows.

A slanted outer surface 49 is formed on the outer surface of the body 45. The slanted outer surface 49 comes into contact with the inner surface of the tube 10 when assembled. The slanted outer surface 49 becomes gradually wide in its outer diameter toward the flange 50. The inclined angle of the slanted surface 49 of the insert member 18 is smaller than that of the second inner surface portion 34 of the first coupling member 14. Therefore, the interval between the slanted surface 49 of the insert member 18 and the first inner surface portion 32 of the first coupling member 14 becomes gradually small from the first inlet 30 to the inside. The interval is minimum at the center portion, and then, the interval between the slanted surface 49 of the insert member 18 and the second inner surface portion 34 of the first coupling member 14 becomes gradually wide toward the second inlet 36.

Meanwhile, the difference of the inclined angle between the slanted surface of the insert member and the second inner surface portion of the first coupling member 14 can be adjusted depending on the thickness and the material of the tube 10. For example, the inclined angle of the slanted outer surface of the insert member 18 may be 1.5 to 2.5 degrees and the inclined angle of the second inner surface portion 34 may be 3 to 5 degrees. Preferably, the inclined angle of the second inner surface portion 34 is twice the inclined angle of the slanted outer surface of the insert

member 18.

The cylindrical flange 50 of the insert member 18 is provided on a front end of the member where the outer diameter of the slanted surface 49 is larger. The outer diameter of the flange 50 is larger than that of the second inlet 36 of the first coupling member 14 and smaller than the inner diameter of the second engaging portion 48 of the second coupling member 16. An annular engaging groove 52 is formed at a portion of the flange 50, where the flange comes into contact with the slanted outer surface 49. The groove 52 can secure a transformed portion of the end of the tube 10. The groove 52 may be omitted in other embodiments. In this case, additional space needs to be provided to secure a transformed wall of the tube.

In another embodiment, the flange itself can be omitted. 0-rings 19 for sealing are inserted between the first coupling member 14 and the second coupling member 16 and between the second coupling member 16 and the insert member 18.

Referring to Figs. 2 and 3, the process for connecting the tube 10 and the tube joint 12 will be described hereinafter. First, the tube 10 passes the tube insert hole 28 of the first coupling member 14 through the first inlet 30, the first inner surface portion 32, the second inner surface portion 34 and through the second inlet 36 in order. The body 45 of the insert member 18 is inserted into an end opening 11 of the tube 10, whereby the end opening of the tube 10 is set onto the body 45 while spreading. In the state that the slanted outer surface 49 of the insert member 18 is inserted into the opening 11 of the tube 10, the flange 50 of the insert member 18 is located to touch the step 40 of the second engaging portion 48 of the second coupling member 16. After that, the first coupling member 14 is pushed inwardly, and screwed. The first coupling member 14 is continuously inserted until a front

end of the first engaging portion 26 of the first coupling member 14 touches the flange 50 of the insert member 18. Then the tube 10, as shown in Fig. 2, is interposed between the inner surface of the tube insert hole 28 and the slant outer surface 49 of the insert member 18. At this time, the wall of the tube is transformed in general, and since the gap in the center portion becomes smaller, the wall of the tube is transformed at the center portion in maximum. Therefore, the end portion of the tube 10, which is set on the insert member 18, can be fixed perfectly.

Fig. 4 shows the connection of a tube 110 to a tube joint 112 according to a second preferred embodiment of the present invention. The tube joint 112 includes a first coupling member 114, a second coupling member 116 and an insert member 118. The first coupling member 114 has a body 122, a tube insert hole 128 and an engaging portion 154. The body 122 has a structure for easily rotating a screw, for example, a hexagonal bolt head or a knurl. The tube insert hole 128 is substantially identical with the tube insert hole 28 of the first embodiment. A screw thread 156 is formed on an inner surface of the engaging portion 154. A step 155 is provided at the bottom of the engaging portion 154. The insert member 118 is identical with the insert member 18 of the first embodiment. The second coupling member 116 has a screw thread 158 on an outer surface thereof and a passage 142 formed on an inner surface. The screw thread 158 is engaged with the screw thread 156 of the first coupling member 114.

The process for connecting a tube with the tube joint 112 according to the second embodiment is similar to the process with regard to the first embodiment.

It will be appreciated that the second embodiment is identical with the first

embodiment in the construction except for the coupling structure.

Referring to Fig. 5, according to a third preferred embodiment of the present invention, a tube joint 212 includes a first coupling member 214, a second coupling member 216 and an insert member 218. The insert member 216 is identical with that of the second embodiment shown in Fig. 4. The first coupling member 212 is different from that of the second embodiment in that a coupling ring 220 is separated from a body 218. The body 218 of the first coupling member 212 has a step 222 on an outer surface thereof. The coupling ring 220 includes an end having a flange 224, which is engaged with the step 222 and directed inwardly, and the other end having a screw thread 226 formed on an inner surface thereof. The second coupling member 216 has a screw thread 228 formed on an outer surface of an end thereof. The screw thread 228 of the outer surface of the second coupling member 216 is engaged with the screw thread 226 of the coupling ring 220. The process or method for interposing a wall of a tube 210 between the insert member 218 and the coupling members 214 and 216 is equal to the above embodiments.

Because the first coupling member 214 of the third embodiment is divided into the body 218 and the coupling ring 220, only the coupling ring 220 rotates without the rotation of the body 218 during the assembly of the tube.

As shown in Fig. 5, the second coupling member 216 has a step 230 on an end portion thereof. A removable fixing ring 232 connects the second coupling member 216 and a third coupling member 234. The third coupling member 234, for example, may be an oil supplying end attached on a hydraulic apparatus. The removable fixing ring 232 includes an end portion having a flange 236, which is directed inwardly, and the other end having a screw thread 238 formed on an inner

surface thereof. The third coupling member 234 has a screw thread 240 on an outer surface thereof. The screw thread 240 of the third coupling member 234 is engaged with the screw thread 238.

First, the tube 210, the first coupling member 214, the second coupling member 216 and the insert member 218 are assembled. Before the assembly, the removable fixing ring 232 is set on the second coupling member 216. In this state, if necessary, the removable fixing ring 232 may be connected with the third coupling member 234. With the above construction, the tube that is connected with the first coupling member, second coupling member and insert member can be connected with or separated from the third coupling member 234 at need. A ring 242 for seal is inserted between the second coupling member 216 and the third coupling member 234.

Fig. 6 shows a construction of a coupling member 250 according to another preferred embodiment of the present invention. The coupling member 250 is in the form of that the previously described insert member and second coupling member are formed integrally. In Fig. 6A, a screw thread is formed on an inner surface of the coupling member 250 for connection. In Fig. 6B, a screw thread is formed on an outer surface of the coupling member 250.

Fig. 7 illustrates another preferred embodiment of the present invention for connecting a metal tube to a tube joint of the invention. Referring to Fig. 7A, a tube 300 is a metal tube. The metal tube 300 has an engaging portion 302 on an end thereof. The engaging portion 302 has a first inner surface portion 304 and a second inner surface portion 306 therein. The engaging portion 302 has a step 308 for engaging. An insert member 310, a second coupling member 312 and a

coupling ring 314 have the same constructions as corresponding those of the embodiment shown in Fig. 5. A pressure member 318 is inserted between a slanted surface 316 of the insert member 210 and an inner surface of the connection part 308 of the pipe 300. The pressing member 318 is made of transformable materials, e. g., rubber, plastic material or transformable metal material such as aluminum or copper.

Fig. 7B shows another preferred embodiment of the present invention for connecting a tube 360 to a tube joint 350. The construction of the tube joint 350 is substantially identical with that of the embodiment of Fig. 5. The tube 360 is a metal tube lacking of elasticity. The inner and outer diameters of an end opening 362 of the metal tube 360 become gradually larger so that the inclined angle of the slanted wall of the end opening 362 is substantially equal to that of a slanted surface 356 of an insert member 354.

A pressing member 358 is inserted between an outer surface of the pipe 360 and an inner surface of a tube insert hole 353 of a first coupling member 352.

When the first coupling member 352 is coupled with a second coupling member 354, the pressing member 358, while transformed, presses the slanted surface of the insert member 358 and an inner surface of the tube so that they closely contact with each other.

Fig. 8A shows a tube joint according to another preferred embodiment of the present invention. The tube joint 400 includes an insert member 402 and a first coupling member 404. The insert member 402 has a slanted outer surface 406.

The insert member 402 has a flange 408 formed on an end thereof and a hole 410 adjacent to the flange 408. The slanted outer surface 406 of the insert member 402

is inclined so that the outer diameter of the insert member 402 becomes gradually larger from the other end of the insert member 402 to the flange 408. However, the diameter of the slanted outer surface becomes smaller near the flange 408 to provide a hole 410.

In Fig. 8A, the first coupling member 404 includes a first inner surface portion 412 and a second inner surface portion 414 in the hole in a similar way to the above embodiments and further includes a third inner surface portion 416 extending from the second inner surface portion. The second inner surface portion 414 is inclined and the inclined angle is larger than that of the slanted outer surface 406 of the insert member 402. The third inner surface portion 416 is parallel with the first inner surface portion 412. A front end of the first coupling member 404 touches the flange 408 of the insert member 402 when assembled.

As you can see from Fig. 8A, it is preferable that the width Wl of the first coupling member 404, extending in the longitudinal direction of the tube 402, is larger than the length (W ;,ert), extending in the longitudinal direction of the tube 402, of a portion where the slanted surface and hole of the insert member are formed (i. e., a portion where the flange is excluded). In the embodiment shown in Fig. 8A, when the insert member 402 is inserted into the tube 420 and the first coupling member 404 is coupled, the hole is stuffed with an end portion of the tube 420 as it is transformed, thereby the tube 420 can be coupled firmly.

In Fig. 8B, a tube joint 400a is provided with an insert member 402a, and a groove 410a is formed on a position being adjacent to a flange 408a of the insert member. The groove 410a is hollowed inwardly in the radial direction from an outer surface of the insert member 402a to form a step 4101a. The construction of

Fig. 8B is identical with that of Fig. 8A except for the shape of the groove 410a.

Having now described the above embodiments, it should be apparent to those skilled in the art that the foregoing is merely illustrative and not limiting, having been presented by way of examples only. Various modifications and other embodiments are within the scope of one of ordinary skill in the art and are contemplated as falling within the scope of the invention.

For example, in the above embodiments, the inner diameter of the first inner surface portion of the first coupling member is uniform, but it is not limited to those.

The first inner surface portion may be inclined. In that case, it is preferable that the inclined angle is smaller than that of the slanted surface of the insert member.

Furthermore, in the above embodiments, the first coupling member has the coupling ring, which is separated from the body. However, not the first coupling member but the second coupling member may have the coupling ring, which is separated from the body.

Meanwhile, not shown in Figs. 2,4 and 5, a thin plate, which is made of metal material, may be inserted between the inner surface of the first coupling member and the tube, thereby preventing the damage of the tube when the first coupling member is coupled.

As described herein, the tube joint according to the present invention increases the binding force between the tube and the tube joint not to easily separated, thereby keeping the seal between the inside and outside of the tube.

Moreover, the tube joint can be used without regard to the kind or the material of the tube.