1. Field of the Invention

The present invention relates to a sealing tube for a cable entry port. Specifically, the exemplary sealing tube is able to provide stable air tightness over time. 2. Background of the Invention

Optical fiber is increasingly being used for broadband applications. An enclosure is the necessary component in an optical fiber network to protect the interconnection or termination point of the optical fiber cables that carry the broadband signals between two points. However, conventional sealing members for the fiber cable entry port do not have satisfactory sufficient air tightness, especially after they have been in service for an extended period of time (i.e. upon aging the air tightness of the enclosure can be diminished). In addition, the conventional enclosures typically have only a limited number of entrance ports, so that only few cables can enter the enclosure.

Similar to the problems of the optical fiber discussed above, the requirement of air tightness between cable and a port when the cable enters into an enclosure via the port of the enclosure also exists in other products.

Therefore, a need exists in the art for a means of sealing around a cable within the entry port of an enclosure that has stable aging air tightness and/or can enable an enclosure to be provided with a higher density of entry ports.

SUMMARY OF THE INVENTION

The present invention has been made to overcome or alleviate at least one of the problems or disadvantages in the prior art.

According to an aspect of the present invention, there is provided a sealing tube for a cable entry port comprising: a body having a first end; a second end opposite to the first end; and at least one passage extending axially through the body from the first end to the second end and adapted to receive a cable therein; a first tubular portion located between the first end and the second end, preferably at a distance from the first end; a groove formed circumferentially in the first tubular portion; and a substantially conical portion tapering from the first tubular portion towards the first end. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a sealing tube according to an embodiment of the present invention;

FIG. 2 is a schematic view of the sealing tube shown in FIG.1 fitted over a cable;

FIG. 3 is a schematic sectional view of the sealing tube shown in FIG.1 ;

FIG. 4 is a schematic view of the sealing tube mounted to an inline enclosure;

FIG. 5 is a schematic view of the sealing tube mounted to a dome enclosure;

FIG. 6 is a schematic view of another sealing tube according to an embodiment of the present invention;

FIG. 7 is a schematic sectional view of the sealing tube shown in FIG.6;

FIG. 8 is a schematic view of yet another sealing tube according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A further description of the invention will be made as below with reference to embodiments of the invention taken in conjunction with the accompanying drawings.

The description below will be given with reference to the optical cable, but it can be understood that the optical cable can be replaced by other cable or pipe and the sealing tube disclosed in the present invention can be used to seal other kinds of cables or pipes, e.g. electrical power cable, with an entry port.

As illustrated in FIGS. 1-3, an exemplary sealing tube 100 is shown that can be fitted into a fiber cable entry port of an enclosure. The sealing tube 100 includes a body 100B. The body 100B has a first end 101 , a second end 103 opposite to the first end 101 , and a passage 11 1 extending axially through the body from the first end 101 to the second end 103 and adapted to receive an optical fiber cable 10 therein. While the present disclosure is directed to a sealing tube for use with an optical fiber cable, use of the present invention with electrical conductor cables and hybrid or composite cables which carry both electrical and optical conductors is considered within the scope of the current invention.

In an exemplary aspect, the sealing tube may have a single passage 11 1 extending therethrough as shown in FIG. 3. The passage 1 11 may have approximately the same inner diameter (ID) extending along the length of the passage. Alternatively, the passage 1 11 may have varied inner diameter extending along the length of the passage, for example, the passage 1 11 may have a larger inner diameter at the middle portion while having a comparatively smaller inner diameter at and/or near the first end 101 and/or the second end 103. The inner diameter of the passage 1 11 of the sealing tube 100, at least at the portion near the first end 101 and/or the second end 103, is less than an outer diameter (CD) of the optical fiber cable 10 to be passed therethrough, thereby making an airtight interference fit between the sealing tube 100 (or the passage 1 11) and the fiber cable 10 when the cable is installed therein. In the instance that the passage 1 11 has a larger inner diameter at the middle portion, this structure will bring easier installation of the cable through the passage 1 11.

In an exemplary aspect, the passage 1 11 can have an elliptical or circular cross sectional profiles as shown in FIG.3 although other profiles like polygon can be used that corresponds to the outer cross-section of the cable to be inserted therein. It would be easier to form airtight interference fit and improve the airtight performance if the passage 11 1 and the cable have an elliptical or circular profile.

As illustrated in FIGS. 1-3, the sealing tube 100 further includes a first tubular portion 105 located between the first end 101 and the second end 103. In an exemplary aspect, the first tubular portion 105 is disposed at a distance from the first end 101. The first tubular portion 105 can be characterized by a first outer diameter, D1. A groove 107 is formed circumferentially in the first tubular portion 105 forming a reduced diameter portion relative to the first outer diameter D1. The groove 107 is configured to be interlocked with the entry port and to form interference fit with the entry port. In an exemplary aspect, the first tubular portion 105 may have a substantially cylindrical shape or a shape of a substantially circular cylinder although other external profiles may be used that is configured to anchor the sealing tube in the entry port so that the sealing tube can not pass through the entry port.

As illustrated in FIGS. 1-3, the sealing tube 100 may further include a substantially conical portion 109 tapering from the first tubular portion 105 towards the first end 101. The conical portion can act as a guide or lead-in to facilitate in insertion of the sealing tube into a complimentary shaped entry port in an enclosure. The first tubular portion 105 and the conical portion 109 may have substantially the same cross-section at a junction point therebetween. The first tubular portion 105 and the conical portion 109 may axially extend longitudinally along the body 100B. In an exemplary aspect, the conical portion 109 can have a shape of a substantially circular cone, and the first tubular portion 105 can have a shape of a substantially circular cylinder. In this instance, the first tubular portion 105 and the conical portion 109 may have substantially the same diameter (i.e., the first diameter D1) at the junction point therebetween so that a smooth transition between the first tubular portion 105 and the conical portion 109 is achieved, thereby facilitating insertion of the sealing tube into a fiber cable entry port of an enclosure.

As illustrated in FIGS. 1-3, the sealing tube 100 may further comprise a second tubular portion 110 extending between the first end 101 and the conical portion 109. The second tubular portion 1 10 may extend axially. The second tubular portion 1 10 may have a substantially cylindrical shape or a shape of a substantially circular cylinder. The second tubular portion 110 and the conical portion 109 have substantially the same cross-section at a junction point therebetween. When the second tubular portion 110 has a shape of a substantially circular cylinder and the conical portion has a shape of a substantially circular cone, the second tubular portion 1 10 and the conical portion 109 have substantially the same diameter (i.e. the second diameter D2) at the junction point therebetween.

Alternatively, the conical portion 109 may extend from the first tubular portion 107 to the first end 101 without the second tubular portion 110.

As illustrated in FIGS. 1-3, the sealing tube may further comprise a third tubular portion 102. The third tubular portion 102 extends between the second end 103 and the first tubular portion 105 and has a cross-section smaller than that of the first tubular portion 105. The third tubular portion 102 may axially extend. The third tubular portion 102 may have a shape such as a substantially cylindrical shape, substantially conical shape, a shape of a substantially circular cylinder or a shape of a substantially circular cone. The first tubular portion 105, the conical portion 109, the second tubular portion 1 10, and the third tubular portion 102 may coaxially extend. Alternatively, the sealing tube may not comprise the third tubular portion 102.

As illustrated in FIGS. 1-3, the groove 107 has opposite sidewalls 1071 and a bottom surface 1072. The bottom surface 1072 may have a shape such as a substantially cylindrical shape or a shape of a substantially circular cylinder or other shape which can match with the shape of the entry port of the enclosure.

In an exemplary aspect, as illustrated in FIGS. 1-3, the first tubular portion 105 has a first external diameter D1 , the second tubular portion 110 has a second external diameter D2, the third tubular portion 102 has a third external diameter D3, and the bottom surface 1072 of the groove 107 has a fourth external diameter D4 and a width W1 from the first sidewall 1071 to the second side wall 1072. The fourth external diameter D4 of the bottom surface 1072 of the groove 107 is smaller than the first external diameter D1 of the first tubular portion 105. Preferably, the fourth external diameter D4 of the bottom surface 1072 of the groove 107 may be substantially equal to or slightly larger than the inner diameter of the port 201 , thus an airtight interference fit between the groove 107 and the port 201 can be achieved from the circumferential direction when the sealing tube 100 is installed in the port 201. Preferably, the width W1 of the groove 107 is substantially equal to or slightly smaller than the thickness W2 of the wall 202 of the port 201 , thus an airtight interference fit or an airtight contact between the groove 107 and an edge portion 2013 of the port 201 can be achieved from the axial direction of the sealing tube. The second external diameter D2 of the second tubular portion 1 10 is sized such that the second tubular portion 1 10 can pass through the port 201 and the pipe 2011 as described hereinafter. The first external diameter D1 of the first tubular portion 105 is larger than the inner diameter of the port 201. Thus, in an exemplary aspect, D2<D4<D1.

As illustrated in FIGS. 1-3, the sealing tube may further comprise a closing piece 121 for closing the passage 11 1 at the first end 101 of the body 100B. Alternatively, the closing piece 121 may be located at any other appropriate position and may be formed as a film (not shown) disposed within the passage 1 11 such that the passage is completely blocked by the film.

In an exemplary aspect, the sealing tube 100 may be made of resilient material such as elastomer, rubber or other elastic material. In another aspect, the sealing tube may be integrally formed having a single monolithic body. The resilient material can bring the convenience to the installation and improve the airtight performance due to its resilient deformation.

As illustrated in FIGS. 4 to 5, the sealing tube 100 according to the embodiment may be applied to any appropriate enclosure such as an inline enclosure 200, for example, a 2178CM mechanical in-line enclosure that is commercially available from 3M China Ltd., (FIG. 4 shown without its cover), or a dome enclosure 300, for example, a 2178CD mechanical dome enclosure that is commercially available from 3M China Ltd., (FIG. 5, shown without its cover).

As shown in FIG 4, the enclosure 200 comprises a plurality of drop cable ports or fiber cable entry ports 201. The entry ports 201 are formed in a wall 202 of the enclosure 200. Preferably, a pipe 2011 may be disposed outside of the enclosure 200 and substantially coaxially with the entry ports 201 and connected to the wall 202. The pipe 201 1 can prevent the cable from bending by an outside force, which is helpful to keep the airtight performance. During installation, the sealing tube 100 is inserted into the entry ports 201 from an inside of the enclosure 200, and then the sealing tube 100 is pulled until the groove 107 of the sealing tube 100 is engaged with entry ports 201. The first tubular portion 105 of the sealing tube 100 has an outer diameter (i.e. the first external diameter D1) bigger than an inner diameter of the entry ports 201 , and the groove 107 has an external diameter (D4) substantially equal to or slightly larger than the inner diameter of the entry ports 201 , thereby making an airtight interference fit between the sealing tube 100 and the entry port 201 between the bottom surface 1072 of the groove 107 and the edge portion 2013 of entry ports 201. An airtight contact may be formed between the outer surface of a part of the conical portion 109 and the inner surface of the pipe 201 1 , between the bottom surface 1072 of the groove 107 and the edge portion 2013 of entry ports 201 , and/or between the sidewalls 1071 of the groove 107 and the wall 202 of the enclosure 200. In an exemplary aspect, the inner surface of the pipe 201 1 and the outer surface of the first tubular portion 105 and/or the outer surface of a part of the conical portion 109 each may have substantially a circular cross-section.

When the cable 10 is inserted in the sealing tube 100, the inner surface 104 of the sealing tube 100 will be in an airtight contact with the outer surface or jacket 11 of the cable 10. As the cable diameter is bigger than the sealing tube inner diameter, when the cable runs through the sealing tube, the sealing tube will wrap the cable tightly. In other words, the sealing tube 100 can be stretched (i.e. the inner diameter of the passage can be increased) to accommodate cable 10 when it is inserted into the sealing tube 100.

As the sealing tube can create an interference fit between the cable entry port and the groove, as well as between passage and the cable, high air pressure from inside or outside of the enclosure will not cause air leakage, and the sealing performance is stable. Especially, when the sealing tube has only one passage in the tube body and the second tubular portion and the third tubular portion have a certain length, if there is air pressure difference between the inside and outside of the enclosure, the higher air pressure in either of the inside and the outside may exert pressure uniformly around the outside surface of the tube body at the second tubular portion or the third tubular portion, and thereby the tube body tightly enclosing the cable and help keep stable airtight performance even the higher air pressure is larger than the interference pressure between the passage and the cable .

Advantageously, the inner surface of the pipe of the entry port and the outer surface of the first tubular portion are round and thus the sealing tube made of resilient material such as rubber is compressed uniformly. As a result, a more stable sealing performance is achieved.

FIGS. 6-7 illustrate another sealing tube 500 according to an embodiment of the present invention. The sealing tube 500 includes a tube body 500B. The body 500B has a first end 501 , a second end 503 opposite to the first end 501 , and four passages 51 1 extending axially through the tube body 500B from the first end 501. It can be understood that in other embodiments, there may be have a plurality of passages, such as four or six passages, in the tube body.

As illustrated in FIGS. 6-7, the passage 51 1 has a substantially rectangular cross section. It can be understood that in other embodiments, the passage 511 may have a cross section in any appropriate shape, for example polygonal shape, to accommodate other standard drop cables. For example, the passage may have a cross section in a shape to match the FRP cable.

As illustrated in FIG 7, the four passages 51 1 includes four small passages 511 a, from the first end 501 along the second tubular portion 510 to a position 519 between the first end 501 and the second end 503, and a big passage 51 1 b from the second end 503 to the position 519. The big passage 51 1 b is connected and commutated to each of the small passages 511 a. The passage within tube body 500B includes the big passage 511 b and the small passages 511 a, and the big passage 511 b branches within the tube body 500B such that it has a single entry portion at the second end 503 having a characteristic internal diameter and a plurality of exit passages at the first end 501 having a different characteristic size. In this instance, such structure can bring the advantage that the sealing tube 500 can accommodate more than one cable to enter into the enclosure through one single entry port, meanwhile bring an easier installation of the cables through the big passage, while the engagement of the cable with the small passage can provide air tightness. In other embodiments, it can be understood that the plurality of passages may be located within the tube body separately with each other from the first end 101 to the second end 103, without any branch.

Other parts of the sealing tube 500 can be same or similar to the sealing 100 as described above, so detailed description is not repeated.

FIG. 8 illustrates another sealing tube 600 according to an embodiment of the present invention. The sealing tube 600 differentiates from the sealing tube 100 mainly in that the first tubular portion 607 and the conical portion 609 of the sealing tube 600 have a cross section in a shape of a polygon such as a hexagon. However, it can be understood that the first tubular portion and the conical portion of the sealing tube may have a cross section in any appropriate shape so that the sealing tube may fit within the ports of the other enclosures.

The sealing tube according to the embodiments can be mounted conveniently and the cable can be re-enterable without any new sealing material. Furthermore the cost of the sealing tube is low and its sealing performance is stable.

With the sealing tube according to some embodiments of the present invention, the sealing tube may have multiple passages and each can accommodate one cable, consequently one entry port of the enclosure can receive multiple cable, thus a high density entry can be achieved. In addition, the sealing tube can be easily mounted and has a low cost.

Although some embodiments for the general concept of the present disclosure have been shown and explained, the skilled person in the art will appreciate that modifications to the above embodiments can be carried out without departing from the spirit and principle of the present general inventive concept. The scope of the present disclosure should be defined by the appended claims and equivalents thereof.