How to join TPE tubes

Abstract

A method of joining thermoplastic elastomer (TPE) tubes is provided that includes abutting an end face of a first TPE tube (2) against an end face of a second TPE tube (4), providing a TPE sleeve (6) around the first and second tubes to cover the end faces, providing a compression member (8) around the sleeve configured to apply a radial force around the sleeve, and fusing the first and second tubes and the sleeve together by applying heat to the sleeve while applying a radial force to the sleeve using the compression member.

Description

[Technical field]

[0001] The present invention relates to a method for joining TPE tubes. [Background technology]

[0002] Thermoplastic elastomer (TPE) tubing or other components are commonly used in pharmaceutical and bioprocessing applications due to their desirable properties. In particular, TPE tubing can be used in conjunction with peristaltic pumps.

[0003] TPE tubes can be connected together using mechanical connectors and clamps, however this creates the possibility of contamination and leakage. TPE tubes can be welded, but many welding processes are not suitable due to processing constraints (e.g., material compatibility, cycle time, etc.) and quality attributes (e.g., poor surface quality, weld joint opening issues, particle generation, etc.).

[0004] Therefore, there is a need to provide a TPE tubing joining method that addresses the problems associated with existing technology. Summary of the Invention [Means for solving the problem]

[0005] According to one aspect of the invention, there is provided a method of joining thermoplastic elastomer (TPE) tubes, the method including abutting an end face of a first TPE tube against an end face of a second TPE tube, providing a TPE sleeve around the first and second tubes to cover the end faces, providing a compression member around the sleeve configured to apply a radial force around the sleeve, and fusing the first and second tubes and the sleeve together by applying heat to the sleeve while applying the radial force to the sleeve using the compression member.

[0006] The compression member may be heat shrink tubing.

[0007] The heat shrink tubing may have a length greater than the length of the sleeve and may be positioned to overhang both ends of the sleeve.

[0008] The sleeve may have an inner diameter corresponding to the outer diameter of the first and second tubes.

[0009] A longitudinal pressure may be applied to the first and second tubes during welding.

[0010] Longitudinal pressure may be applied for only a portion of the time that heat is applied.

[0011] The sleeve may have a wall thickness less than a wall thickness of the first and second tubes.

[0012] The sleeve may have a wall thickness that is between 25% and 75% of the wall thickness of the first and second tubes.

[0013] The wall thickness of the sleeve may be 50% of the wall thickness of the first and second tubes.

[0014] The compression member may be removed after fusing.

[0015] Embodiments will now be described, by way of example only, with reference to the drawings in which: [Brief description of the drawings]

[0016] [Figure 1] 1 is a flow chart of a method according to an embodiment of the invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a first step in the method. [Diagram 3] FIG. 2 is a cross-sectional view showing a second stage of the method. [Figure 4] FIG. 4 is a cross-sectional view showing a third stage of the method. [Diagram 5] FIG. 4 is a cross-sectional view showing a fourth stage of the method. [Figure 6] 4 shows a cross section of the sample after bonding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 illustrates the method of joining two thermoplastic elastomer (TPE) tubes as described with reference to FIGS.

[0018] In a first step S1, the end face of the first tube 2 is brought into contact with the end face of the second tube 4, as shown in FIG.

[0019] In this example, the first and second tubes 2, 4 have the same inner diameter (i.e. bore size), outer diameter and wall thickness. The first and second tubes 2, 4 are positioned such that the bores are aligned at the interface between the first and second tubes 2, 4. The first and second tubes 2, 4 may be prepared to ensure that they are clean and have vertical end faces.

[0020] The first and second tubes 2, 4 may have an inner diameter of 0.5 mm to 25.4 mm and a wall thickness of 1.6 mm to 4.8 mm. For example, the tubes may range from a tube having an inner diameter of 0.5 mm and a wall thickness of 1.6 mm (hence an outer diameter of 3.7 mm) to a tube having an inner diameter of 25.4 mm and a wall thickness of 4.8 mm (hence an outer diameter of 35 mm). In this example, the tubes 2, 4 have an inner diameter of 12.7 mm and a wall thickness of 3.2 mm, hence an outer diameter of 19.1 mm.

[0021] In a second step S2, a TPE sleeve 6 (which may be of the same grade as the first and second tubes 2, 4) is provided around the first and second tubes 2, 4 so as to cover the end faces at the interface between the first and second tubes 2, 4. In this example, the interface between the first and second tubes 2, 4 is located in the centre of the sleeve 6 so that the sleeve 6 extends an equal distance over the first and second tubes 2, 4.

[0022] The sleeve 6 is a short tube having an inner diameter corresponding to the outer diameter of the first and second tubes 2, 4. Thus, in this example, the inner diameter of the sleeve 6 is 19.1 mm. In other examples, the sleeve 6 may have an inner diameter smaller than the outer diameter of the first and second tubes 2, 4 such that an interference fit is provided between the first and second tubes 2, 4 and the sleeve 6. The sleeve 6 and / or the first and second tubes 2, 4 may be sufficiently soft (i.e., have a sufficiently low durometer value) to allow sufficient deformation so that the first and second tubes 2, 4 can be easily inserted into the sleeve 6. It will be appreciated that when an interference fit is provided, the inner diameter of the sleeve 6 corresponds to the outer diameter of the first and second tubes 2, 4 when the first and second tubes 2, 4 are inserted into the sleeve 6. The sleeve 6 may have a wall thickness smaller than the wall thickness of the first and second tubes 2, 4. For example, the wall thickness of the sleeve 6 may be 25% to 75% of the wall thickness of the first and second tubes 2, 4. In this example the sleeve 6 has a wall thickness of 1.6 mm, and is therefore 50% of the wall thickness of the first and second tubes 2, 4. In this example the sleeve 6 has a length of 20 mm, although in other examples the sleeve 6 may have a different length.

[0023] The sleeve 6 may be slid fully onto the first tube 2 and then partially slid back onto the second tube 4 once the end faces abut one another. Alternatively, the sleeve 6 may be slid partially onto the first tube and then the second tube 4 may be inserted into the sleeve 6 until it abuts the first tube 2.

[0024] As shown in FIG. 3, in a third step S3, a compression member is placed around the sleeve 6. In this example, the compression member is a heat shrink tube 8, which may be made of polyolefin or other heat shrink material. As shown, the heat shrink tube 8 has a length greater than the length of the sleeve 6, such that it extends beyond both ends of the sleeve 6. The heat shrink tube 8 is positioned to provide equal overhang beyond both ends of the sleeve 6. In this example, the heat shrink tube 8 has a length of 35 mm, such that it extends beyond both ends of the sleeve 6 by approximately 7.5 mm. The length (L) of the sleeve 6 at both ends is also equal to the length (L) of the sleeve 6. S ) to Sleeve 6 wall thickness (WT S ) plus the length (L HST ) of the heat shrink tube 8 (i.e., L HST ≧L S +2WT S ) is preferred. The length of the heat shrink tubing 8 may also decrease during heating (by about 5-10%) and this should be taken into consideration (i.e., added) when considering the desired length.

[0025] The heat shrink tubing 8 has an inner diameter (as delivered) that is larger than the outer diameter of the sleeve 6. In this example, the inner diameter of the heat shrink tubing 8 is 25.4 mm (compared to the outer diameter of the sleeve of 22.3 mm). The heat shrink tubing 8 has a 2:1 shrink ratio, although other shrink ratios may be suitable.

[0026] 4 and 5, in a fourth step S4, heat is applied to the assembly, and in particular to the heat shrink tube 8. This causes the heat shrink tube 8 to shrink into engagement with the outer surface of the sleeve 6. Thus, as the assembly continues to be heated, the heat shrink tube 8 compresses the sleeve 6 and exerts a radial force around the sleeve 6. The heat shrink tube 8 has a sufficient length to completely cover both ends of the sleeve 6 and to contact the outer surfaces of the first and second tubes 2, 4 over a small portion on either side of the sleeve 6.

[0027] While heat is being applied to the assembly, in addition to the radial force exerted by the heat shrink tube 8, longitudinal pressure (indicated by the arrows) is exerted in the tubes 2, 4 such that the end faces are forced together.

[0028] In this example, heat is applied by hot air from a heat gun. The heat gun is set at a temperature of 300° C. and is applied throughout the area for a total of 70 seconds. During part of the time that heat is applied, longitudinal pressure is applied to the tubes 2, 4. Notably, in this example, longitudinal pressure is only applied during the first 30 seconds.

[0029] The heat, compression and longitudinal pressure creates a bond between the end faces of the first and second tubes 2, 4, and also between the inner surface of the sleeve 6 and the outer surfaces of the first and second tubes 2, 4. Thus, as shown in the sample of Figure 6, the first and second tubes 2, 4 and the sleeve 6 are sufficiently fused together to form a single integrally formed component.

[0030] 6, the heat shrink tubing 8 is removed from the assembly after heating. In other examples, the heat shrink tubing 8 may be left in the assembly.

[0031] Although the method has been described as using heat shrink tubing 8, it will be appreciated that other forms of compression members may be used that exert a radial force around the sleeve to aid in fusion. For example, the compression member may be a mechanical device such as an expanding ring having a variable diameter that can exert a radial force on the sleeve 6 when it shrinks.

[0032] To avoid abrupt steps and reduce the risk of restricting the inner bore, both ends (or portions thereof) of the sleeve 6 may be inclined so as not to be perpendicular to the outer surfaces of the first and second tubes 2, 4, and thus tapered to the outer surfaces of the first and second tubes 2, 4. Alternatively, the tapered shape of the sleeve 6 may be formed upon melting. This may be achieved by applying additional force to the sleeve 6 to extrude material sideways from both ends of the sleeve 6.

[0033] It will be appreciated that one of the tubes may form part of a connector component, such as a cross, Y, or T fitting, or a flange component for use with a clamp. The sleeve 6 and heat shrink tube 8 (or other compression member) may comprise the connector component. Where the connector has multiple legs (such as a cross, Y, or T fitting), the legs may be connected to separate tubes simultaneously. For example, a single heat gun may include an adapter manifold that provides hot air to each of the legs simultaneously.

[0034] Although not shown, either or both of the tube and / or connector components may include a shoulder, such as a flange or boss, against which the sleeve 6 abuts to longitudinally position the sleeve 6 .

[0035] The invention is not limited to the embodiments described herein, which may be modified or altered without departing from the scope of the invention. [Explanation of symbols]

[0036] 2 1st tube 4 2nd Tube 6 Sleeve 8 Heat shrink tubing

Claims

1. 1. A method for joining thermoplastic elastomer (TPE) tubing, comprising the steps of: abutting an end surface of the first TPE tube against an end surface of the second TPE tube; providing a TPE sleeve around the first and second tubes to cover the end surfaces; providing a compression member about the sleeve configured to apply a radial force about the sleeve; applying heat to the sleeve while applying a radial force to the sleeve using the compression member to fuse the first and second tubes and the sleeve together; The method includes:

2. The method of claim 1 , wherein the compression member is heat shrink tubing.

3. The method of claim 2 , wherein the heat shrink tubing has a length greater than a length of the sleeve and is positioned to overhang both ends of the sleeve.

4. The method of any one of claims 1 to 3, wherein the sleeve has an inner diameter corresponding to an outer diameter of the first and second tubes.

5. The method of any one of claims 1 to 4, wherein longitudinal pressure is applied to the first and second tubes during welding.

6. The method of claim 5 , wherein the longitudinal pressure is applied for only a portion of the time that heat is applied.

7. A method according to any preceding claim, wherein the sleeve has a wall thickness which is less than a wall thickness of the first and second tubes.

8. The method of claim 7, wherein the sleeve has a wall thickness that is between 25% and 75% of the wall thickness of the first and second tubes.

9. The method of claim 8 , wherein the wall thickness of the sleeve is 50% of the wall thickness of the first and second tubes.

10. The method of any one of claims 1 to 9, wherein the compression member is removed after fusing.

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