Medical tube connection

Abstract: An improved assembly composed of a hard member (2) and a soft tube (1) fitted onto the hard member (2) for a medical use is formed with a plurality of projections (5) on the side wall of a flange (4) of the hard member (2). The projections (5) project toward the soft tube (1) side to firmly hold the foremost end part of the soft tube (1) between the projections (5) and a fitting portion (3) of the hard member (2) in a clamped state when the soft tube (1) is fitted onto a fitting portion (3) of the hard member (2). The foremost end surface of the soft tube (1) may slantwise be cut to define a certain angle relative to the center axis of the assembly such that the foremost end part of the soft tube (1) comes in tight contact with the side wall of the flange (4) when the soft tube (1) is fitted onto the fitting portion of the hard member (2). The soft tube (1) may be formed with a plurality of cutouts which are arranged along the periphery of the foremost end surface of the soft tube (1) in a spaced relationship. Each cutout preferably exhibits a V-shaped contour which defines a certain opening angle symmetrically relative to the center axis of the assembly.

Description: The present invention relates generally to an assembly composed of a hard member and a soft tube fitted onto the hard member for medical applications. More particularly, the present invention relates to an improvement in the assembly of soft tubes and hard members often used as essential components for blood transfusion sets, infusion sets or the like medical devices. Many soft tubes each molded of soft synthetic resin, e.g., polyvinyl chloride or the like material have been heretofore used for blood transfusion sets, infusion sets or the like medical devices. Each soft tube is practically used by connecting it to another component in the form of a hard member to provide an assembly composed of the hard member and the soft tube for use in a medical device. When such a soft tube, molded of soft polyvinyl chloride or the like material, is connected to the hard member, molded of hard synthetic resin, e.g., polyethylene, polypropylene or the like material, firm connection is usually carried out by a manual simple fitting operation, because a suitable adhesive employable for a combination of soft and hard synthetic resin is not available at present. In practice, a tight fitting operation is physically performed by dimensioning the inner diameter of the soft tube to be appreciably smaller than the outer diameter of the hard member and forcibly fitting the soft tube onto a fitting portion of the hard member in opposition of a contractive force and a frictional force generated by contraction of the soft tube. Over time, a slight loosening appears between the soft tube and the hard member. This often leads to trouble in that the soft tube is undesirably disconnected from the fitting portion of the hard member due to reduction of the tightening force which has been induced therebetween. To solve the foregoing problem, the inventors closely observed disconnection malfunctions as described above. As a result of their observations, they found that disconnections occurred very easily when the close contact region between the soft tube and the hard member disappeared. Fig. 4 is a side view of a typical conventional assembly composed of a hard member 2 and a soft tube 1 fitted onto a fitting portion 3 of the hard member 2 for medical use. Fig. 5 is a fragmentarily exploded side view of the assembly in Fig. 4. When an intense thrusting force is imparted to the soft tube 1 which has been fitted onto the fitting portion 3 of the hard member 2 under the influence of a reduced magnitude of tightening force, as shown in Fig. 4, the foremost end of the soft tube 1 comes in close contact with the side wall of a flange 4. As a result, the diameter of the foremost end of the soft tube 1 is enlarged with an axial compressive force (see Fig. 5). Consequently, the close contact region between the soft tube 1 and the hard member 2 disappears. If the soft tube 1 is pulled rearwardly to a slight extent while the foregoing state is maintained, disconnection occurs easily with the soft tube 1 because no tightening force exists. In particular, when the conventional assembly is heated during sterilization, the tendency of disconnecton of the soft tube 1 becomes remarkably increased. In view of such malfunctions, it has been proposed that the diameter of the fitting portion 3 of the hard member 2 be dimensioned to become larger towards the flange 4 so as to allow a tightening force to increase correspondingly. Although the tightening force has been increased to some extent with this arrangement, a sufficient improvement has not been obtained with this proposal with respect to prevention undesirable disconnection from occurring with the soft tube 1. In addition, other proposal has been disclosed in an official gazette of Japanese Laid-Open Patent NO. 283651/1988. According to this prior invention, a lower cap for the drip chamber of an infusuion set is connected to a soft tube with an improved structure for the purpose of avoiding the problem of undesirable disconnection of the soft tube. However, the improved structure is complicated and therefore the resultant assembly composed of the lower cap and the soft tube is fabricated with many difficulties. Additionally, it was disclosed that a member made of polyvinyl chloride could be adhered to a member made of polyolefin by using a chlorinated polyolefin-based adhesive. However, once the hard member is coated with this adhesive, it becomes very difficult to insert the hard member into the soft tube because of an increased frictional force. Therefore, this proposal can not be put to practical use. FR-A-2 493 150 teaches a coupling member for a tube which comprises projections around a fitting portion. These projections are provided with teeth on the inside to clamp the tube. It is, however, difficult to insert a soft tube between those projections and the fitting portion. Further, the teeth on the projections may damage the tube. Also, the coupling member is of a complicated configuration and is thus expensive to produce. To substantially improve the conventional assembly composed of a hard member and a soft tube fitted onto the hard member for a medical use in that way, the inventors conducted a number of development works and determined that a plurality of projections formed on a flange of the hard member were very effective for preventing the soft tube from being disconnected from the hard member. Further, the inventors found out that particular configurations employed for the soft tube were likewise very effective for the same purpose. The present invention has been made with the foregoing background in mind. An object of the present invention is to provide an assembly composed of a hard member and a soft tube fitted onto the hard member for medical uses, where a malfunction of disconnection of the soft tube from the hard member does not occur. Another object of the present invention is to provide an assembly composed of a hard member and a soft tube fitted onto the hard member for medical uses, wherein the assembly is easily fabricated at inexpensive cost. To accomplish the above objects, there is provided according to the present invention an assembly composed of a hard member and a soft tube fitted onto the hard member for medical uses as disclosed in claim 1. The soft tube may be formed with a plurality of cutouts along the foremost end surface thereof in a spaced relationship. It is desirable that each cutout exhibits a V-shaped contour which defines a certain opening angle symmetrically relative to the center axis of the assembly. Other objects, features and advantages of the present invention will become apparent from the following description which has been made with reference to the accompanying drawings. The present invention is illustrated in the following drawings in which: Fig. 1 is a side view of an assembly composed of a hard member and a soft tube fitted onto the hard member for medical uses in accordance with a first embodiment of the present invention in a disassembled state; Fig. 2 is an end view of the assembly in Fig. 1 as seen in the axial direction. Fig. 3 is a fragmentarily exploded side view of the assembly in Fig. 1; Fig. 4 is a side view of a conventional assembly composed of a hard member and a soft tube fitted onto the hard member for medical uses; and Fig. 5 is a fragmentarily exploded side view of the conventional assembly in Fig. 4. Now, the present invention will be described in detail hereinafter with reference to the accompanying drawings which illustrate preferred embodiments thereof. Fig. 1 is a side view which illustrates the disassembled components of the assembly of a hard member and a soft tube fitted onto the hard member for medical uses (hereinafter referred to simply as an assembly) in accordance with a first embodiment of the present invention. Fig. 2 is an end view of the assembly as seen in the axial direction. The assembly of the present invention comprises a soft tube 1 molded of soft synthetic resin, e.g. soft polyvinyl chloride, ethylene-vinyl acetate copolymer or the like material, and a hard member 2 molded of hard synthetic material, e.g. polyethylene, polypropylene or the like material. The hard member 2 includes a fitting portion 3 and a flange 4 so that the foremost end of the soft tube 1 comes in close contact with the side wall of the flange 4 in the same manner as the conventional assembly which has been described above with reference to Figs. 4 and 5. According to the present invention, the flange 4 is formed with a plurality of projections 5 (two projections in the shown embodiment). As will be readily apparent from Fig. 3, when the soft tube 1 is fitted onto the fitting portion 3 of the hard member 2, the foremost end of the soft tube 1 is brought in tight contact with the side wall of the flange 4 in cooperation with the projections 5 much more than the conventional assembly. Specifically, as a certain intensity of squeezing force is imparted to the soft tube 1, the foremost end of the soft tube 1 is tightly clamped between the fitting portion 3 of the hard member 2 and the projections 5 thereby creating a frictional contact state therebetween which reliably prevents the soft tube 1 from being undesirably disconnected from the fitting portion 3 of the hard member 2. In the shown embodiment, the flange 4 is formed with two projections 5. However, the present invention is not limited to only two projections. The number of projections 5 and a size of each projection 5 may be determined, as desired. It should be noted, however, that if a single projection is formed on the flange 4, a clamping force is reduced excessively. Therefore, it is preferable that the flange 4 is formed with at least two projections 5 which are arranged along a common circle in a spaced relationship. As will be readily apparent from the above description, the assembly of the present invention has advantageous effects in that a firm and reliable fitting function is assured with a simple structure and therefore the assembly can easily be fabricated at inexpensive cost. While the present invention has been described above with respect to a preferred embodiment thereof, it should of course be understood that the present invention should not be limited only to that embodiment but various changes or modifications may be made without departure from the scope of the invention as defined by the appended claims.

Claims: An assembly composed of a hard member (2) and a soft tube (1) fitted onto said hard member (2) for medical uses, said hard member (2) being molded of hard synthetic resin and including a flange (4) and a fitting portion (3) onto which said soft tube (1) is fitted and said soft tube (1) being molded of soft synthetic resin, wherein: said flange (4) is formed with a plurality of projections (5) which are arranged along a common circle in a spaced relationship, said projections (5) projecting toward the foremost end of said soft tube (1) and arranged to engage and compress the foremost end of said soft tube (1) to firmly hold said soft tube (1) between the projections (5) and the fitting portion (3) of the hard member (2) in a clamped state when said soft tube (1) is fitted onto the fitting portion (3) of the hard member (2) and the foremost end of the soft tube (1) comes in close contact with a side wall of the flange (4) of the hard member (2), said foremost end being held in said clamped state due to a force pressing said soft tube (1) onto said flange (4) resulting from the placement of said projections (5) and said fitting portion only when a pressing force is present; wherein said hard member, said flange and said projections are integrally formed as a single unit, characterized in that the projections (5) are wedge-shaped and are substantially shorter than said fitting portion (3). The assembly as claimed in claim 1, wherein the mumber of said projections (5) is two. The assembly as claimed in claim 1, wherein said hard member (2) is made of polyethylene or polypropylene and said soft tube (1) is made of polyvinylchloride.

Inventors: IWATA MINORU, YAMASHITA HIDEYUKI, IWATA, MINORU, YAMASHITA, HIDEYUKI
Applicants: JMS CO LTD, JMS CO., LTD.
Application year: 1990
Main classification: A61M39
IPC codes: F16L33, A61M39