METHOD AND CONNECTING PIECE FOR JOINING TUBES

Abstract: Conduits (3a, 3b, 3c) are joined with a one-piece tubular connecting piece (1) by inserting support members (5a, 5b, 5c) through a sealable opening (6) in the connecting piece to support the conduit ends whilst said ends are secured to the connecting piece to communicate with openings (4a, 4b, 4c) in the connecting piece. After securing the conduit ends to the connecting piece, the support members are withdrawn through the sealable opening and that opening is then sealed. The support members can also act as electrodes for welding the conduit ends to the connecting piece, especially when the conduit ends and connecting piece are formed of thermoplastics. The method has particular, but not exclusive, application to smoothly connecting tubes for conveying blood.

Description: TITLE METHOD OF JOINING CONDUITS WITH A CONNECTING PIECE AND CONNECTING PIECE FOR USE IN THE METHOD TECHNICAL FIELD The invention relates to and provides a method of joining two or more conduits with a tubular connecting piece wherein ends of the conduits are located at respective openings in the connecting piece and are secured to said connecting piece to communicate with the respective openings. The invention also provides a tubular connecting piece for use in the method. The invention has particular, but not exclusive, application to welding thermoplastics tubes to a thermoplastics connecting piece. BACKGROUND ART It is well known to join two or more conduits with a tubular connecting piece by locating the conduit ends to be connected at respective openings in the connecting piece and securing said ends to the connecting piece to communicate with the respective openings. In particular, this method is used to connect thermoplastics tubes by welding the tubes to a thermoplastics connecting piece. The conduit ends require supporting whilst being secured to the connecting piece and it is known to provide this support by inserting support means into the connecting piece through one of the openings for a conduit end. Obviously, however, it-has not been possible to support all of the conduits from inside the connecting piece because the support means must be withdrawn from said opening to allow the respective conduit end to be connected to the connecting piece to communicate with said opening. It is an object of the present invention to provide a method whereby all of the conduit ends can I Ϊ ΛTREAIΓ OMPI _ be supported from inside the connecting piece whilst they are secured to the connecting piece. DISCLOSURE OF INVENTION According to one aspect of the present invention, there is provided a method of joining two or more conduits with a one-piece tubular connecting piece wherein the ends of the conduits are located at respective openings in the connecting piece and are secured to said connecting piece to communicate with the respective openings, characterised in that support means is inserted through a sealable opening in the connecting piece to support at least one conduit end at the respective opening, said at least one conduit end is secured to the connecting piece whilst being supported by said support means, the support means is withdrawn through said sealable opening, aΛd the sealable opening is then sealed. The conduit ends can be secured to the connecting piece by any of the means conventionally used for connecting conduits to a connecting piece but it is preferred that they are welded to the connecting piece. Advantageously, the conduit ends and/or the connecting piece are formed of thermoplastics. As mentioned previously, the invention has particular application to the joining of thermoplastics tubes with a thermoplastics connecting piece. Suitable thermoplastics include polyvinylchloride and polyurethane. The support means usually, but not necessarily, will be used to support all of the conduit ends during the time that they are being secured to the connecting piece. It will be appreciated however that the conventional method of inserting support means through an opening intended for communication with a conduit end can be employed for all except the last conduit end and the method of the invention used for securing that last conduit end to the connecting piece. " According to a second aspect of the present invention, there is provided a one-piece tubular connecting piece for use in the method of the invention having two or more openings adapted to be secured to respective conduit ends, characterised in that the connecting piece has a sealable opening adapted to receive support means for supporting at least one conduit end at the respective opening whilst said at least one conduit end is secured to the connecting piece to communicate with the respective opening and to permit withdrawal of said support means after the said at least one conduit end has been so secured to the connecting piece. Advantageously, the sealable opening is a slot and preferably the connecting piece is elongate and the slot extends longitudinally of the elongate connecting piece. Flaps preferably are provided integrally with the connecting piece for use in sealing the sealable opening. When the said opening is a slot, two flaps suitably are provided to extend longitudinally at the respective sides of the slot. These two flaps preferably have plane-convex opposed (i.e. facing) surfaces whereb3>- the said surfaces smoothly mutually diverge outwardly from the slot. It is also preferred that any flaps integral with the connecting piece are formed of thermoplastics so that the opening can be sealed by heating and pressing the flaps together over the opening. Usually, the openings in the connecting piece for communication with the conduits will be tubular end portions of the connecting piece and the conduit ends will be inserted into or placed over the respective tubular end portions of the connecting piece. The sealable opening can be located at any convenient position in the connecting piece but suitably is located opposite an opening for a conduit end to facilitate insertion of the support means into that openin c OMPI_ The connecting piece can be of any suitable shape provided that it serves to connect the conduits together in the required manner. Advantageously however, the central axis of tubular end portions are substantially coplanar and the connecting piece has a "Y" or "T"-shaped axial section in said plane. Conveniently, the support means constitutes at least one electrode for use in welding the respective conduit end to the connecting piece. BRIEF DESCRIPTION OF DRAWINGS The following is a description, by way of example only and with reference to the accompanying, drawings of the presently most preferred embodiment of the method and apparatus aspects of the invention. In the drawings:- Fig. 1 is a side view of a connecting piece according to the most preferred embodiment of the invention having three tubes welded to tubular ends of the connecting piece; Fig. 2 is an enlarged axial section of the connecting piece of Fig. 1, but without the tubes welded thereto; Fig. 3 is a further enlarged cross-section of the connecting piece along the line III-III in Fig. 2; and Fig. 4 is a corresponding axial section to Fig. 2 of the connecting piece of Fig. 1, but with the respective tubes being arranged in the tubular ends of the connecting piece while being supported by supporting means. BESTMODE OF CARRYING OUT THE INVENTION Referring to Figs. 1 to ,a connecting piece, " designated 1, comprises a tubular portion 2 having three open tubular ends 4a, 4b, 4c_. The tubular portion 2 is provided with a hole 6, through which three support members 5a, 5b, 5 are intended to be inserted into the connecting piece 1 so as to support tubes 3a, 3b, 3£ when B U O these are being welded to the connecting piece. The hole 6, which is sealable, is a longitudinal slot and is provided opposite to the open tubular end 4b. The hole 6 has two parallel, longitudinal flaps 7a, 7b extending along its respective edges as shown in Fig. 3» These flaps are each integrally formed with the tubular portion 2 and have plane-convex surfaces 8a and 8b, respectively, facing each other, whereby said surfaces smoothly mutually diverge radially outwardly from the slot 6. The outer surfaces of the respective flaps 7a, 7b are planar. The axes of the open tubular ends 4a, 4b, 4£ are provided in the same plane and so that the tubular portion 2 has a T-shaped axial section in said plane. The connecting piece 1 as well as the respective tubes are made of a weldable thermoplastic material, for example polyurethane and preferably polyvinylchloride (PVC). As shown in Fig. 3 the tubular portion 2 is some- what thicker just opposite to the hole 6 in order to increase the strength of the portion 2. In welding together the respective end portions of the tubes 3a, 3b, 3£ to the corresponding open tubular ends 4a, 4b, 4£ of the connecting piece 1 in accordance with the present invention, separate supporting members 5a, 5b, 5£ are inserted into the tubular portion 2 through the sealable hole 6 to be received in the respective tubes. It is to be noticed that these supporting members (which together constitute support means) can be inserted into the tubular portion 2 at the same time, whereby all the tubes can be supported simultaneously. The supporting members 5a, 5b, 5£ are so dimensioned that, in place within the tubular portion, as is shown in Fig. 4, they are closely surrounded by the tubes 3a, 3b, 3£. In that way there is provided sufficient support to the tubes 0 In high frequency welding, which is the most -BUREAZΓ OMPl preferred welding method according to the present invention, these supporting means may be the welding electrodes. The other electrodes (not shown), are constituted by conventional 'brass jaws , which externally surround the respective open tubular ends 4a, 4b, 4£ of the connecting piece 1. When the tubes as well as the welding electrodes, inclusive of the separate supporting members 5a, 5b, 5£, are in place, all the tubes can be welded simultaneously to the respective open tubular ends 4a, 4b, 4£ of the connecting piece 1. When the tubes have been welded to the tubular ends 4a, 4b, 4£ of the connecting piece, the supporting members 5a, 5b, 5£ are withdrawn, and the hole 6 is then sealed. The sealing is preferably performed by welding, wherein jaws (not shown) or the like, acting as electrodes, press the longitudinal flaps 7a, 7b against each other, as is shown by arrows F in Fig. 3. The flaps 7a, 7b are melted together due to the heat generated during the welding. Molten material flows radially outwardly (downwardly in Fig. 3) along the plane-convex surfaces 8a, 8b of the flaps and not into (upwardly in Fig. 3) the tubular portion 2 through the hole 6. This is due to the fact that the surfaces 8a, 8b have the plane-convex' shape shown in Fig. 3. As a result there is obtained a connecting piece which, since the hole has been sealed, has smooth inner surfaces without any sharp edges. INDUSTRIAL APPLICABILITY A preferred application of the invention will be the connecting of a heparine tube to a blood tube via a connecting piece in medical devices for, for example, extracorporeal treating of blood. In this case it is very important that the connecting piece with the tubes in place does not display any irregularities in the flow path of the blood_ Sharp edges or substantially altered flowing conditions, which may lead to substantial turbulence, can be deleterious to the blood. According to the present invention there can be obtained a connecting piece without "any irregularities or the like which may lead to deleterious turbulence in the blood stream. It will be appreciated that the invention is not restricted to the details described above but that numerous modifications and variations can be made without departing from the scope of the invention as claimed in the following Claims. For example, instead of the tubes 3a, 3b, 3£ being inserted into the tubular ends 4a, 4b, 4£ of the connecting piece 1 they can be welded to the connecting piece outside the end portions 4a, 4b, 4£ thereof. In such a case the tubes 3a, 3b, 3£ are slipped over the connecting piece 1 at the tubular end 4a, 4b, 4£ portions"thereof and are welded to said portions outside the connecting piece. Further, the connecting piece can be of a different shape, for example the tubular portion 2 can have a "Y"-shape in the plane of the axes of the tubular ends 4a, 4b, 4£ instead of the "T"-shape shown.

Claims: CLAIMS 1. A method of joining two or more conduits(3a, 3b, 3£) with a one-piece tubular .connecting piece (1) wherein the ends of the conduits are located at respective openings (4a, 4b, 4£) in the connecting piece and are secured to said connecting piece to communicate with the respective openings, characterised in that support means (5a, 5b, 5£) is inserted through a sealable opening (6) in the connecting piece to support at least one conduit end at the respective opening, said at least one conduit end is secured to the connecting piece to communicate with the respective opening whilst being supported by said support means, the support means is withdrawn through said sealable opening, and the sealable opening is then sealed. 2. A method as claimed in Claim 1, wherein the ends of the conduit (3a, 3b, 3£) are secured to the connecting piece (1) by welding. 3.- A method as claimed in Claim 2 wherein the ends of the conduit (3a, 3b, 3£) and/or the connecting piece (1) are formed of thermoplastics. 4. A method as claimed in Claim 1, wherein the conduits (3a, 3b, 3£) are tubes. 5. A method as claimed in Claim 1, characterised in that the supporting means (5a, 5b,. 5£) supports each of the said conduits (3a, 3b, 3£) whilst they are secured to the connecting piece (1). 6. A method as claimed in Claim 1, characterised in that the sealable opening (6) is a slot. 7. A method as claimed in Claim 6 wherein the connecting piece (1) is elongate, •• characterised in that the slot (6) extends longitudinally of the connecting piece. 8. A method as claimed in any one of the preceding Claims, characterised in that the sealable opening (β) is sealed using flaps (7a, 7b) extending integrally from the connecting piece. -ftU 0 9. A method as claimed in Claim 8, characterised in that the flaps (7a, 7b) are formed of thermoplastics and the opening (6) is sealed by heating and pressing the flaps together over the o-pening (6). 10. A method as claimed in Claim 2, characterised in that the support means (5a, 5b, 5£) constitutes at least one electrode which is used in welding said at least one conduit end (3a, 3b, 3£) to the connecting piece. 11. A method as claimed in Claim 1 wherein the connecting piece openings for communication with the conduits are defined by open tubular end portions (4a, 4b, 4c) of said connecting piece (1) and the conduit ends are tubular and are inserted intoor surround the respective tubular end portions of the connecting piece. 12. A one-piece tubular connecting piece for use in a method as claimed in Claim 1 having two or more openings adapted to be secured to ends of respective conduits, characterised in that the connecting piece (1) has a sealable opening (6) adapted to receive support means (5a, 5b, 5£) for supporting at least one conduit end (3a, 3b, 3£) at the respective opening (4a, 4b, 4£) whilst said at least one conduit end is secured to the connecting piece to communicate with the respective opening and to permit withdrawal of said support means after the said at least one conduit end has been so secured to the connecting piece. 13. A connecting piece as claimed in Claim 12 characterised in that the sealable opening (6) is a slot. 14. A connecting piece as claimed in Claim 13 wherein the connecting piece (1) is elongate characterised in that the slot (6) extends longitudinally of the connecting piece. 15. A connecting piece as claimed in Claim 12 characterised in that flaps (7a, 7b) are formed integrally with the connecting piece for use in sealing the opening (6). 16. A connecting piece as claimed in Claim 13 or Claim 14 characterised in that two flaps (7a, 7b) extend longitudinally at respective sides of the slot (6) for use in sealing the slot. * ' 17. A connecting piece as claimed in Claim 16 characterised in that the opposed surfaces (8a, 8b) of the flaps (7a, 7b) are plane-convex surfaces whereby the said surfaces smoothly mutually diverge outwardly from the slot (6). 18. A connecting piece as claimed in Claim 12 characterised in that the sealable opening (6) is located opposite an opening (4b) in the connecting piece for a conduit end. 19. A connecting piece as claimed in Claim 12 wherein the openings (4a, 4b, 4£) in the connecting pieces for the conduit ends are tubular end portions of the connecting piece (1) adapted to surround or be surrounded by the respective conduit ends (3a, 3b, 3 ~ . 20. A connecting piece as claimed in Claim 19 wherein* the central axes of said tubular end portions (4a, 4b, 4£) are substantially coplanar and the connecting piece (1) has a "Y" or "T" shaped axial section in said plane. 21. A connecting piece as claimed in Claim 12 formed of thermoplastics. 'BU

Inventors: STENBERG K
Applicants: GAMBRO AB, STENBERG K
Application year: 1978
Main classification: B29C27
IPC codes: A61M39, B29C65, F16L47