GB1564465A

GB1564465A - Tube coupling

Info

Publication number: GB1564465A
Application number: GB38758/77A
Authority: GB
Original assignee: Gambro Dialysatoren GmbH and Co KG
Current assignee: Gambro Dialysatoren GmbH and Co KG
Priority date: 1976-11-17
Filing date: 1977-09-16
Publication date: 1980-04-10
Also published as: DE2750418A1; IT1109467B; SE7612815L; BE859058A; FR2371630A1; BR7707065A; JPS5363793A; NL7710874A

Description

(54) IMPROVEMENTS IN AND RELATING TO TUBE COUPLING (71) We, GAMBRO DIALYSATOREN GmbH & Co. K.G., a German Company of Ermelesstrasse 76, D-745 Hechingen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a coupling for the joining together of two flexible tubes or the like with a third tube e.g. an injection needle, having a smaller bore than either of said two tubes to which it is to be connected and provides said coupling and a method of its use.

The coupling is primarily intended for the joining together of two blood tubes with a needle intended for the alternating with drawal and return of blood from a blood vessel in conjunction with a so-called "single-needle" method in blood dialysis.

Such a method is described in greater detail in an article entitled "Single Needle Dialysis" by Tore Lindholm in Opuscula Medico Technica Lundensia published at Lund, Sweden in 1973 and therefore needs no further explanation in connection with the present invention. To those versed in the art it will be clear however that the coupling and method according to the invention can also be used in many other cases where it is required to join together two somewhat larger-sized tubes with a single small-calibre duct.

According to a first aspect of the present invention, there is provided a coupling for joining first and second tubes to a third tube wherein the coupling is formed in one piece and has a channel connecting a first seat for the third tube with a second seat for both the first and second tubes, wherein said second seat is of larger cross-section than the said first seat and said second seat is substantially cylindrical with approximately elliptical cross-section and is terminated internally in a planar shoulder connecting said second seat with the channel.

According to a second aspect of the present invention, there is provided a coupled assembly comprising first, second and- third tubes, and a coupling connecting both the first and second tubes to the third tube wherein the coupling is formed in one piece and has a channel connecting a first seat, in which the third tube, which has a smaller bore than either of the first and second tubes, is located in fluid-tight manner, with a second seat, which is of larger cross-section than the first seat and in which respective free ends of both the first and second tubes are located in fluid-tight manner.

According to a third aspect of the present invention, there is provided a method of joining first and second tubes to a third tube having a smaller bore than either of the first and second tubes which comprises providing a coupling cast in one piece and having a channel connecting a first seat for the third tube with a second seat of a size sufficient to accommodate the respective free ends of both the first and second tubes and locating an end of the third tube in fluidtight manner in the first seat and said free ends of both the first and second tubes in fluid-tight manner in the second seat.

The fact that the coupling in accordance with the invention is cast in a single piece, beside having economic advantages, also has the advantage that good conditions of flow can be achieved with considerable safety.

After the assembly of the two tubes in the common seat, the coupling is preferably calibrated in a mould of such dimensions that these tubes are made to fill up completely the common seat. Preferably, the coupling is made of thermoplastic material so that the second or ]arger seat can be heat sealed around the ends of the tubes. Further, it is especially preferred that the tubes are also made of thermoplastic material so that the calibration can be carried out with simultaneous heating, e.g. by means of high-frequency heating, in such a manner that the coupling and the tubes are fused together.

Preferably, the first and second tubes are flexible and the said calibration is done appropriately by making use of a supporting core in the flexible tubes, so that these have substantially the same inner cross-section after the calibration as before the same.

In a suitable embodiment of the coupling assembly and the method in accordance with the invention, the common seat for the two tubes is substantially cylindrical with an approximately elliptical cross-section and is terminated internally by a plane base or shoulder which within a continuous frame encloses an end opening for the channel connecting the seats. This plane base serves also as a stop for the introduction of the two tubes during the assembly of the same.

The said end opening of the channel connecting the seats is appropriately given a cross-section which substantially corresponds to the sum of the inner cross-sections of the first and second tubes. Thereafter this channel is adapted so that it converges to a cross-section which substantially corresponds to that of the third tube. Such a design provides good conditions of flow.

The invention is described in greater de- tail in the following with reference to the enclosed drawings which as an example describe a preferred embodiment of the coupling in accordance with the same. In the drawings: Fig. 1 shows the coupling with a needle assembled in it; Figs. 2-5 show the coupling without the needle and without the flexible tubes, seen from four different sides; Fig. 6 shows the same end view as Fig. 5 but with the flexible tubes introduced which are shown in section and also shows schematically the calibration mould used; and Fig. 7 shows a section corresponding to that in Fig. 6 but after calibration and melting together of the flexible tubes with the coupling itself.

The coupling shown in Fig. I consists of a coupling piece 1 with two hinged wings 2a and 2b. The coupling piece 1 is provided at its one end la with a "first" seat 3 for a needle or cannula 6 and at its other end with a larger-size "second" seat 4 intended for two flexible tubes 7 and 8. The latter are shown in Fig. 6.

The two seats 3 and 4 are connected by a converging channel 5, whose end, opening out into the seat 4, is designated 9. See also Fig. 5.

The seat 3 is enlarged at its outer end 3a to receive glue or other adhesive to reinforce the press fit otherwise used for fixing of the needle 6.

The base 2c of the wings 2a and 2b is intended to be attached to the patient's skin when the needle 6 is introduced into a vein.

To facilitate the introduction, the wings 2a and 2b always assume the same position in relation to the front opening 6a of the needle 6 produced by bevelling, when the wings are folded up so as to enclose the narrower font part la af the coupling piece 1. The introduction is also facilitated in that the 2~ç > forms a small angle a in relation to the axis lb of the coupling piece 1. See Fig. 3.

For assembly, the flexible tubes 7 and 8 are introduced into the seat 4 up to the base of the same, which is designated 10. This base or shoulder forms a continuous frame around the end opening 9 of the channel 5.

The area of the end opening 9 is appropriately substantially identical with the combined inner cross-section of the flexible tubes 7 and 8. From this larger area the channel 5 then converges continually to a smaller cross-section which substantially corresponds to the inner cross-section of the channel 6b of the needle 6.

After the introduction of the flexible tubes 7 and 8 into the seat 4, the coupling piece is introduced wholly or partly between two calibration tools 11 and 12, the inner moulding spaces 13 and 14 of which have the shape which is ultimately desired for the coupling piece, that is to say a shape that is somewhat smaller than the original. The tool halves 11 and 12 are appropriately combined with a high-frequency heating device (not shown) or some other suitable means of heating.

The calibration is appropriately carried out with the use of supporting cores 15 and 16 for the flexible tubes 7 and 8. These cores are shown schematically in Fig. 6 by a simple sectioning. Thanks to the cores, the inner cross-section of the flexible tubes can be maintained substantially unchanged during the calibration.

The final result is shown in Fig. 7 which indicates that the flexible tubes 7 and 8 are fused together with- the coupling piece 1.

Naturally the invention is not limited simply to the embodiment described above but can be carried within the scope of the following patent claims. The various details included may, for example, be varied within wide limits both with regard to their shape and their function, without thereby exceeding the scope of the invention as defined in

Claims

the claims. WHAT WE CLAIM IS:

1. A coupling for joining first and second tubes to a third tube wherein the coupling is formed in one piece and has a channel connecting a first seat for the third tube with a second seat for both the first and second tubes, wherein said second seat is of larger cross-section than said first seat and said second seat is substantially cylindrical with approximately elliptical cross-section and is terminated internally in a planar shoulder connecting said second seat with the channel.

2. A coupling as claimed in Claim 1 which is made of thermoplastic material.

3. A coupling as claimed in either of the preceding Claims including a pair of wings hinged to the first seat to facilitate gripping of the coupling.

4. A coupling substantially as hereinbefore described with reference to and as shown in Figs. 1 to 5.

5. A coupled assembly comprising first, second and third tubes and a coupling connecting both first and second tubes to the third tube, wherein the coupling is formed in one piece and has a channel connecting a first seat, in which the third tube, which has a smaller bore than either of said first and second tubes, is located in fluid-tight manner with a second seat, which is of larger cross-section than the first seat and in which respective free ends of both the first and second tubes are located in fluidtight manner.

6. An assembly as claimed in Claim 5 wherein the first and second tubes are flexible tubes.

7. An assembly as claimed in Claim 6 wherein the first and second tubes are blood tubes for conveying blood respectively to and from the third tube.

8. An assembly as claimed in any one of Claims S to 7 wherein the third tube is a needle or cannula.

9. An assembly as claimed in any one of Claims 5 to 8 wherein the coupling is made of thermoplastic material and the second seat is heat-sealed around the accommodated ends of the first and second tubes.

10. An assembly as claimed in Claim 9 wherein the tubes are made of thermoplastic material and the second seat is heat fused to the accommodated ends of the first and second tubes.

11. An assembly as claimed in any one of Claims 5 to 10 wherein the second seat is substantially cylindrical with approximately elliptical cross-section and is terminated internally in a planar shoulder connecting the second seat with the channel.

12. An assembly as claimed in any one of Claims 5 to 11 wherein the opening between the channel and the second seat substantially corresponds to the combined inner perimeter of the said accommodated ends of the first and second tubes.

13. An assembly as claimed in any one of Claims 5 to 12 wherein the channel converges from the second seat to a cross-section which substantially corresponds to the inner perimeter of the third tube.

14. An assembly as claimed in any one of Claims 5 to 13 including a pair of wings hinged to the first seat to facilitate gripping of the coupling.

15. An assembly as claimed in Claim 5 and substantially as hereinbefore described with reference to and as shown in Figs. 1 to 7.

16. A single-needle blood dialysis apparatus including a coupling as claimed in any one of Claims 5 to 15.

17. A method of joining first and second tubes to a third tube having a smaller bore than either of said first and second tubes which comprises providing a coupling cast in one piece and having a channel connecting a first seat for the third tube with a second seat of a size sufficient to accommodate the respective free ends of both the first and second tubes and locating an end of the third tube in fluid-tight manner in the first seat and said free ends of both the first and second tubes in fluid-tight manner in the second seat.

18. A method as claimed in Claim 17 wherein the tubes are flexible tubes.

19. A method as claimed in Claim 18 wherein the tubes are blood tubes for conveying blood respectively to and from said third tube.

20. A method as claimed in either of Claims 17 to 19 wherein the third tube is a cannula or needle.

21. A method as claimed in any one of Claims 17 to 20 wherein the coupling is made of thermoplastic material and is heated to seal the second seat around said free ends of the first and second tubes.

22. A method as claimed in Claim 21 wherein the tubes are made of thermoplastic material and the heating fuses the second seat and free ends of the first and second tubes together.

23. A method as claimed in Claim 23 or Claim 24 wherein respective supporting cores are inserted in the first and second tubes to maintain their internal diameter substantially constant during the heating stage.

24. A method as claimed in any one of Claims 17 to 23 wherein the second seat is substantially cylindrical with approximately elliptical cross-section and is terminated internally by a planar shoulder connecting the second seat with the channel.

25. A method as claimed in any one of Claims 17 to 24 wherein the opening between the channel and the second seat substantially corresponds to the combined inner perimeter of the said free ends of the first and second tubes.

26. A method as claimed in any one of Claims 17 to 25 wherein the channel con verges from the second seat to a cross-section which substantially corresponds to the inner perimeter of the third tube.

27. A method as claimed in any one of Claims 17 to 26 wherein a pair of wings are hinged to the first seat to facilitate gripping of the coupling.

28. A method as claimed in Claim 17 and substantially as hereinbefore described with reference to and as shown in Figs. 1 to 7.