EP0778929A1

EP0778929A1 - Reinforced, variable-sized coupling for conduit

Info

Publication number: EP0778929A1
Application number: EP95927256A
Authority: EP
Inventors: Roger Keith; Gordon L. Ackland; Janice M. Wentworth
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1994-08-29
Filing date: 1995-07-17
Publication date: 1997-06-18
Also published as: CA2196300A1; JPH10505149A; WO1996007049A1

Abstract

A connector assembly (10) for connecting the ends of two pieces (12, 14) of conduit or other substantially cylindrical objects including a spirally-wound sleeve (18) and an elastic tube (16). The sleeve (18) is positioned to cover both conduit ends and is spirally wound to adjust to the diameter of the conduit by winding the sleeve in a tighter or looser spiral and the tube (16) is allowed to contract over the sleeve and is preferably dimensioned to extend beyond in the ends of the sleeve to contact the conduit ends when contracted.

Description

REINFORCED. VARIABLE-SIZED COUPLING FOR CONDUIT

FIELD OF THE INVENTION

The present invention relates generally to the joining of two pieces of tubing, and more particularly, to the joining of the ends of polymeric conduit used to insulate and protect electrical cables.

BACKGROUND OF THE INVENTION One method of protecting underground electrical cables is by the use of polymeric conduit, usually polyethylene, which surrounds the cable and provides protection from environmental elements such as water and dirt. The conduit may also provide electrical insulation, although this function is not its primary purpose. Since the conduit comes in finite lengths, it is necessary to join the ends of serial lengths of conduit to accommodate long lengths of cable. The present invention provides a means for joining the ends of conduit which may be easily accomplished in the field. Additionally, the present invention allows the connection of the cable insulation itself in addition to or instead of merely connecting the conduit which contains the cable.

SUMMARY OF THE INVENTION The present invention includes a connector assembly for joining the ends of two lengths of conduit, which connector assembly comprises a spirally-wound, reinforcing sleeve positioned to span the distance between the ends of the conduits and overlie the conduit ends and at least one elastic tube which covers the sleeve and preferably extends beyond the ends of the sleeve to contact the two conduits. The elastic tube may be one tube having a length sufficient to extend from one conduit to the other or may be two elastic tubes, each of which covers one conduit, the joint between the reinforcing sleeve and the conduit and a portion of the sleeve. The connector assembly may also include an injector port as a part of the reinforcing, spirally- wound sleeve, to permit the injection of waterproofing or other fluid into the joint between the conduit ends or into the gap between the ends of the insulation of two cables.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more thoroughly described with respect to the accompanying drawings, wherein like numbers refer to like parts in the several views, and wherein: Figure 1 is a perspective view illustrating two conduit ends and a connector assembly of the present invention; Figure 2 is a perspective view of a reinforcing, spirally-wound sleeve forming a portion of the connector assembly of figure 1; Figure 3 is a perspective view illustrating two conduit ends and an elastic tube of the connector assembly of Figure 1; Figure 4 is a top view of an alternate embodiment of the spirally-wound sleeve of the present invention; Figure 5 is a plan view of the sleeve of Figure 4 prior to coiling; Figure 6 is an end view of the sleeve of Figure 4; and Figure 7 is a side elevational view of an alternate embodiment of the connector assembly of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 illustrates a connector assembly, generally indicated as 10, of the present invention as it is utilized to cover and connect the ends of two conduits 12 and 14. Although the invention will be described throughout as joining two sections of hollow conduit, it is equally applicable to joining two cable ends by bridging the insulation of the cable, or, most generally, joining any two substantially cylindrical or tubular objects. The connector assembly 10 includes an outer, elastic tube 16 and an inner, reinforcing, spirally- wound sleeve 18. The reinforcing sleeve 18 is also illustrated in Figure 2 where the spiral nature of the sleeve 18 is more readily apparent. It is desirable that the sleeve 18 be spirally wound, wherein a longitudinal edge 20 of the sleeve 18 overlaps and covers a portion of the sleeve 18, so that the sleeve 18 may accommodate a wide variety of conduit 12 and 14 diameters by uncoiling or more tightly coiling the spiral of the sleeve 18. The sleeve 18 is preferably manufactured of a polymeric material, such as high density polyethylene, but may also be fashioned from sheet metal, if desired. A preferred method of forming the sleeve 18 is longitudinally slitting an extruded tube, but other methods, such as coiling a flat sheet, are acceptable. Figure 3 illustrates the conduit ends 12 and 14 as the conduit ends 12 and 14 are disposed prior to assembly of the connector assembly 10. Figure 3 also illustrates the elastic tube 16 in one form in which it may be conveniently applied to the conduit 14. The elastic tube 16 is in a form described in U.S. Patent No. 3,515,798, assigned to the assignee of the present invention and herein incorporated by reference, wherein the elastic tube 16 is pre-stretched and supported on a removable core 24. The core 24 is scored along a helical path 26 and may be removed in a long, continuous strip by pulling on the end 28 which unwinds the core 24 along the helical scoring 26. Removal of the core 24 allows the tube 16 to contract to its original dimensions. Other methods for retaining the tube 16 in the expanded state have been proposed and could be used in the present invention. Examples may be found in U.S. patents nos. 4,070,746 and 4,656,070 wherein the tube is held in the expanded state by an external, rigid tube which is adhesively bonded to the tube. To allow the tube to contract, the external tube may be broken and peeled away from the tube or the adhesive bond between the tube and the external tube chemically broken. Figure 3 illustrates an intermediate step in the assembly of the connector assembly 10 to the conduit ends 12 and 14. As shown in Figure 3, the tube 16, in an expanded condition, has been assembled to the conduit 14 by displacing one conduit end 14 from its alignment with the other conduit end 12 and sliding the tube 16 along the conduit 14. The next assembly step is to position the sleeve 18 over the conduit ends 12 and 14 by likewise displacing one of the conduit ends 12 or 14 from alignment with the other conduit end 12 or 14 and sliding the sleeve 18 over the conduit 12 or 14. The sleeve 18 is then retracted along the conduit 12 or 14, the ends of the conduit 12 and 14 again aligned and the sleeve 18 slid towards the other conduit end 12 or 14 to span the gap therebetween and cover both conduit ends 12 and 14 to a substantially identical extent. Once the sleeve 18 is positioned over the conduit ends 12 and 14, the tube 16 is then slid to cover the sleeve 18 and preferably extend beyond the ends of the sleeve 18 to cover the conduit ends 12 and 14, substantially as illustrated in Figure 1. Once the tube 16 is positioned over the sleeve 18, the core 24 is removed from the tube 16 and the tube 16 thus permitted to contract to compress the reinforcing sleeve 18 and seal to the conduit ends 12 and 14. It is preferable that the ends of the tube 16 extend beyond the ends of the sleeve 18 so that the tube 16 can provide a seal to protect the connection from environmental contaminants. However, it has been found that a tube 16 which partially covers the sleeve 18 produces adequate alignment of the conduit ends 12 and 14 and strength at the junction. In the past, it has been attempted to join the conduit ends 12 and 14 by using only an elastic tube 16 such as that illustrated in Figure 3. This solution does not work well because the tube 16 shrinks into the gap between the conduit ends 12 and 14 where it may interfere with the ability to pull cable through the conduit 12 and 14 and because the edges of the conduit ends 12 and 14 may puncture the tube 16. The addition of the sleeve 18 solves these problems and has been found to also aid in the alignment of the conduit ends 12 and 14 and add a great deal of stiffness to the junction of the cable ends 12 and 14. Figures 4-6 illustrate an alternate embodiment of a spirally-wound sleeve 30 of the present invention. The spirally-wound sleeve 30 includes injection ports 32 which are accommodated by slots 34 in the sleeve 30. As best seen in Figure 5, the slots 34 extend from one longitudinal edge 36 and partially into the width of the sleeve 30, in the direction which will become the circumference of the sleeve 30 when it is spirally wound, and in alignment with injection ports 32. Figure 5 illustrates the sleeve 30 in a flat condition while Figures 4 and 6 illustrate from the top and side, respectively, the sleeve 30 as spirally wound for assembly to the conduit ends 12 and 14. The slots 34 are provided to allow the spiral of the sleeve 30 to be more or less tightly wound and, as discussed above, accommodate a range of conduit 12 and 14 diameters. The injection ports 32 are provided to permit a waterproofing or other useful fluid to be injected into the junction between the conduits 12 and 14 or between two cable ends after the sleeve has been assembled to the conduit 12 and 14. If the sleeve 30 of figures 4-6 is utilized, the tube 16 may be assembled over the sleeve 30 as shown in Figure 1, but the injection ports 32 may interfere with the assembly of a single tube 16 to cover such a sleeve 30. An alternative is to utilize two tubes 16 by assembling one expanded tube to each conduit end 12 and 14 and positioning the sleeve 30 between the two tubes 16. Each tube 16 would then cover a conduit end 12 or 14 and the portions of the sleeve 30 which extend from the injection ports 32 to the ends of the sleeve 30. The sleeve 30 is shown provided with two injection ports 32 to allow fluid to be injected into one port 32 while air escapes from the other. It is equally possible to provide the sleeve 30 with only one injection port 32 if air entrapment is not a problem. In this case, only one slot 34 in alignment with the single injection port 32 would be necessary. Also, the injection port 32 is illustrated as being a boss which extends from the sleeve 30. The port 32 could equally well be simply a hole in the sleeve 30. Figure 7 illustrates an embodiment of a connector assembly 40 which includes two features which may make assembly of the connector assembly 40 to the conduit ends 12 and 14 more convenient. The first is that the connector assembly 40 is provided with two support cores 42 and 44. In this fashion, the cores 42 and 44 may be stripped from both ends of the connector assembly 40 and neither need be pulled the entire length of the cable assembly 40. Secondly, the connector assembly 40 is provided with a spirally-wound sleeve 46 which is disposed between the elastic tube 48 and the cores 42 and 44 which support the tube 40. Thus the connector assembly 40 may simply be positioned over the conduit ends 12 and 14 as a unit rather than individually as was described above. When the cores 42 and 44 are removed, the tube contracts towards the conduit ends 12 and 14 and forces the sleeve 46 to wind into a tighter spiral and contact the conduit 12 and 14.

Claims

CLAIMS :

1. A connector assembly for joining the adjacent ends of two substantially cylindrical or tubular objects, comprising: a spirally-wound sleeve dimensioned to circumferentially cover both object ends and capable of compressing radially to engage said object ends; at least one elastic tube in contact with and covering at least a portion of said spirally-wound sleeve, said sleeve being dimensioned so as to be radially expanded when in contact with said sleeve so that a radially inward compression force is applied to said sleeve which forces and maintains said sleeve in contact with said object ends to join the two ends.

2. A connector assembly according to claim 1 including two elastic tubes, each covering an end and a portion of said sleeve and extending beyond said sleeve to contact the objects.

3. A connector assembly according to Claim 1 further including at least one injection port and a slot extending from the terminal longitudinal edge of said sleeve and partially into said sleeve, said slot being aligned with said port so that said sleeve may be adjusted in diameter by sliding said longitudinal edge around said sleeve relative to said port.