WO1998021799A1

WO1998021799A1 - Clamp type cable closure end seal

Info

Publication number: WO1998021799A1
Application number: PCT/US1997/004047
Authority: WO
Inventors: James R. Miller
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1996-11-12
Filing date: 1997-03-12
Publication date: 1998-05-22
Also published as: AU2326197A

Abstract

A cable end seal (10) includes a one-piece body (12) having cylindrical cable ports (14). The body (12) has first and second relatively movable interconnected portions (16, 18). Each port has an inner circumferential surface formed in part by the first body portion (16) and in part by the second body portion (18). The body portions (16, 18) are movable between open and closed positions. In the open position, the inner circumferential surface parts are separated. In the closed position, the inner circumferential surface parts are joined and the first and second body portions abut. A cable (45) can extend through each port (14). A sealant strip (54) can be provided to extend along the abutment between the first and second body portions (16, 18) and along the inner circumferental surface of each cable (45) containing port (14). Electrical or electromagnetic stimulation can be provided to heat the strip (54) and bond each cable (45) and the body portions (16, 18) into a sealed unit.

Description

CLAMP TYPE CABLE CLOSURE END SEAL

Background of the Invention

This invention relates generally to a cable-closure end seal and more particularly to a clamp type end seal for use in sealing the area at the end of a closure, or terminal, through which cables are positioned, and sealing the area about the cables to restrict moisture or other contamination from entering the closure.

There are various methods for joining or splicing telecommunication cable ends together. In so doing, there are many important considerations such as the use of compatible materials, how many cables are being spliced, is the spliced cable to be buried in soil, immersed in water or suspended in the air, what heat source is required to make the joint, i.e. flammable gasses, will the splice need to be reopened and remade without interruption of working circuits, will the joint have sufficient mechanical strength and is the cost feasible? Communication cables are typically constructed of a conductor bundle, surrounded by a metal strength and interference sheathing and an outer protective coating, typically of polyethylene. When such cables are spliced and rejoined, the strength and integrity of the rejoined cable is critical. An enclosure or a closure body is used to sealingly surround the splice. One persistent problem in the use of splice closures involves the need for a complete seal about the splice or closure body. Many prior art splice closures accomplish sealing by providing a complex array of nuts and bolts, clamps, gaskets and heat shrink tubing, as well as potting gels and resins, in various combinations. Besides the fact that these closure methods require significant assembly time, the closures still often suffer leaks or ruptures, particularly along their seals. This problem is even more acute at the sealing of the closure to the cable jacket, where even the slightest defect can result in the migration of moisture along the jacket or the inner surface of the closure. A lack of a complete (hermetic) seal can also be particularly detrimental for pressurized closures. Although these seals may be strengthened by the use of adhesives, the adhesive bonds formed are normally relatively weak due to the low surface energy of the material of the closure and cables, typically polyethylene. An alternative technique for sealing thermoplastic polymers such as polyethylene is that of fusion bonding This technique generally involves the heating of the material until it becomes molten at its sealing surfaces, causing it to flow together at the interfaces, and can be used for butt welds, coupling joints and repair sleeves Two specific methods of fusion bonding (1) direct heating, and (n) induction heating, may also be used to activate thermoset and thermoplastic (hot-melt) adhesives, as well as thermoelastic (heat-shπnk) tubing Induction heating is sometimes referred to as electromagnetic bonding (EMB)

In direct heating (also known as resistance heating), heat is applied to the thermoplastic article to be bonded by directly attaching heating elements to the article Current flowing through the elements heats them The current is supplied by a power source directly connected to the elements, but the heating is not always efficient One advantage of such a system is that it does not involve emission of radiation, but there are disadvantages such as non-uniform heating of the material Induction heating has been widely used to seal and bond polymeric mateπals A composite bonding material (CMB) is formed by dispersing magnetically reactive susceptors in a thermoplastic earner which is compatible (irascible) with the thermoplastic bodies to be welded When this material is placed in an alternating electromagnetic field, the H field induces heating in the magnetic mateπal Heating may be caused by one of two effects hysteresis loss, or resistive loss from induced eddy currents The E field does not interact with the magnetic particles Direct and induction heating techniques may be combined

End seals can be used with hot melts as an alternative bonding material Hot melt is placed between the resistance wires and the resistance wires are heated to form a bond between the cables and the end seal surfaces Hot melt bonding can be used with different end seal mateπals such as foams, elastomers and thermoplastics, but the bond strength is weaker than the fusion bond seal

The pπor art related to end seals for splice closures or terminations is replete with systems for fitting a variety of closure ends One of these seals comprises a core portion of a flexible, resilient, self-adhesive mateπal The core portion has an outer peπphery and openings extending therethrough The openings communicate with the outer peπphery An elongated, flexible tail portion is integral with and extends from the core peπphery to be wrapped about the core portion and the cables placed in the openings However, this mateπal may not be suitable for some applications Another end seal configuration compπses a closure which consists of a closure body having two segmented end seals Each of these segmented end seals includes a central support structure surrounded by segmented seal members The end sections are sized and configured for mating with the support structure Each of the end sections has a portion of its peπphery which compπses a segment of the peπphery of the assembled segmented end seal so that when the end sections and the support structure are mated together the assembled segmented end seal has a uniform peπphery At least one of the pie-shaped end sections contains an aperture for receiving a cable wherein the aperture is located entirely within the peπphery of the section Still another end seal configuration comprises a segmented expansion seal for sealing pipe through which electrical cables are arranged to pass The seal compπses an elastic πng, a plurality of upper clamping plates and a plurality of lower clamping plates each preferably of plastic or rubber mateπal The elastic πng is supported between a plurality of the upper and lower clamping plates at the circumference of the elastic ring, and has a slit to allow insertion of a cable therein and to cover the cable easily The elastic ring and cable are locatable in a cable pipe and fixed at one end of the cable pipe by screw bolts When the bolts are tightened and a compressive force is applied on the upper clamping plates, the elastic πng extends inwardly to fill the space between the inner wall of the elastic ring and cable, and extends outwardly to fill the space between the elastic sealing πng and inner surface of the cable pipe, to prevent liquid, mud and moisture from enteπng into the cable pipe Conveniently, the expansion seal can be applied to pipes of different inner diameters and cables of different outer diameters

Unfortunately, a suitable solution to the problems associated with ease of installation, seal integπty and strength has not been satisfactory addressed bv the prior art Therefore, what is needed is an end seal for use in sealing the area at the end of a closure, or terminal, through which cables are positioned, and sealing the area about the cables to restrict moisture or other contamination from enteπng the closure It is also highly desirable to provide a device which is easy to install, is capable of maintaining seal integπty and strength, and can accommodate vaπous numbers of cables and cable sizes

Summary of the Invention

The present invention, accordingly, provides an apparatus for sealing the ends of cable closure bodies used to sealingly cover and protect cable splices to restπct moisture or other contamination from enteπng the closure To this end, a cable end seal compπses a body having a plurality of cable ports formed therethrough Each port has an inner circumferential surface A first arcuate portion of the port surface is formed by a first portion of the body and a second arcuate portion of the port surface is formed by a second portion of the body The first and second body portions are movable between open and closed positions In the open position, the first and second body portions and the arcuate port surface portions are apart In the closed position, the first and second body portions and the arcuate port surface portions are joined to form an enclosure including the ports for engaging peπpheral surfaces of the cables to be placed therein

A principal advantage of the present invention is that a one piece end seal can capture a plurality of cables extending through ports in the end seal An electπcal stimulus can be used to heat and bond abutting cable and seal member surfaces together into a sealed unit This can be enhanced by utilizing a continuous sealant stπp having conductors embedded therein to heat and seal the cables in the ports and to seal the engaged surfaces of the body portions when they are joined together

Brief Description of the Drawings Fig 1 is a frontal view illustrating an embodiment of the closed end seal according to the present invention

Fig 2 is an isometric view illustrating the open end seal according to the embodiment of Fig 1 of the present invention

Fig 3 is a partial isometric view illustrating the open end seal according to the embodiment of Fig 1 of the present invention

Fig 4 is a further isometric view illustrating the open end seal according to the embodiment of Fig 1 of the present invention

Fig 5 is a frontal view illustrating another embodiment of the closed end seal according to the present invention

Fig 6 is an isometric view illustrating the open end seal according to the embodiment of Fig. 5 of the present invention

Fig. 7 is an isometric view illustrating the open end seal according to the embodiment of Fig 5 of the present invention Description of the Preferred Embodiment

Referring to Figs 1 and 2, a cable end seal is generally designated 10 and comprises an enclosure body 12 formed of a polyolefin elastomer material having a plurality of cable ports 14 formed therethrough A first body portion 16, and a second body portion 18 are interconnected and move between an open position as illustrated in Fig 2 and a closed position as illustrated in Fig 1 Each port 14 is cylindrical and includes a segmented inner circumferential surface 20 having a first arcuate portion 20a formed by first body portion 16 and a second arcuate portion 20b formed by second body portion 18

In one embodiment, illustrated in Figs 1 and 2, body 12 has an outer peripheral surface 22 which is circular In this embodiment, first body portion 16 includes a hub 17 and three integral radially outwardly extending arms 16a, \6b,

16c Each arm tapers to an end point 24 From end point 24, a pair of opposed planar sides 26 and 28 of each arm diverge toward hub 17 and toward an adjacent arm At approximately the hub 17 area where each arm 16α, 16b, 16c is joined with an adjacent one of the arms, the first of the arcuate surface portions 20α are located Second body portion 18 includes three adjacent segments of a circle 30 ,

30Z>, 30c, serially connected and each having an arcuate outer surface portion 32 and a pair of planar walls 34, 36 The walls 34, 36 extend from adjacent the surface portion 32 and angularly converge toward each other but prior to intersecting, the planar walls 34, 36 are separated by the second of the arcuate surface portions 20b

A pivotal interconnection 38 between each segment 30a, 30b, 30c and a similar connection 40 between segment 30c and first body portion 16 are each formed by a flexible portion of the matenal forming body 12 A tab 42 on one side of body 12 extending from segment 30α, engages a portion of segment 30c when body 12 is in the closed position Simultaneously, a similar tab 44 on an opposite side of body 12, extending from segment 30c, engages a portion of segment 30 when body 12 is in the closed position

As it can be appreciated from Figs 1 and 2, when body 12 is in the open position, the first and second body portions 16, 18, respectively, and the first and second arcuate surface portions 20α, 20b, respectively, are apart When body 12 is in the closed position, the planar sides 26, 28 abut the planar walls 34, 36, respectively, and the first 20α and second 20b arcuate surface portions are joined to form the enclosure body 12 including the cyhndπcal ports 14 for engaging peπpheral surface 43 of a cable 45 to be placed in one of the ports 14

Each port 14 includes a plurality of concentπc segmented rings 46 interconnected in a bellows type of construction, Fig 3 The rings 46 are selectively removable for adjusting the size of port 14 to engage surface 43 of cable 45 Each πng 46 has a different diameter than each other ring 46 Thus, each port 14 is of an adjustable size Also, one or more of the ports 14 can include a plug 48 formed as the innermost concentπc ring so that for example, where body 12, Fig 2, is provided with three ports 14 and only two cables are being sealed by end seal 10, one of the ports 14 can remain blocked by plug 48 and thus sealed

In another embodiment, illustrated in Figs 5 and 6, an end seal 110 includes a body 112 has an outer peπpheral surface 122 which is oblong In this embodiment, a first body portion 116 is pivotally interconnected to a second body portion 1 18 by a flexible portion 138 of the mateπal forming body 112 First body portion 116 includes a continuous surface 126 which comprises a plurality of planar walls 134 alternately formed with a plurality of first arcuate surface portions 120α Second body portion 118 includes a continuous surface 128 which compπses a plurality of planar walls 136 alternatively formed with a plurality of second arcuate surface portions 1206 First and second arcuate portions 120α, 1206 form a plurality of cylindrical ports 114 and comprise a segmented inner circumferential surface 120

As it can be appreciated from Figs 5 and 6, when body 112 is in the open position, Fig 6, the first and second body portions 116, 1 18, respectively, and the first and second arcuate surface portions 120α, 1206, respectively, are apart When body 112 is in the closed position, Fig 5, the planar walls 134, 136 abut and the first body portion 116 and second body portion 118 are joined to form the enclosure body 112 including cyhndπcal ports 114 for engaging a peπpheral surface 143 of a cable 145 to be placed in one of the ports 114, Fig 7

Each port 114, Fig 6, includes a plurality of concentπc segmented rings 146 interconnected in a bellows type of construction The rings 146 are selectively removable for adjusting the size of port 114 Each ring 146 has a different diameter than each other πng 146 Thus, each port 114 is of an adjustable size Also, one or more of the ports 114 can include a plug 148 formed as the inner most concentπc πng so that, for example, where body 112 is provided with three ports 114 and only two cables are being sealed by end seal 110, one of the ports 1 14 can remain blocked by plug 148 and thus sealed Tabs 142, 144, Fig 5, only one of which is shown, engage portions 116, 118 respectively, when body 112 is in the closed position

Material selection for the end seal of present invention requires good bonding capabilities to provide proper sealing as well as providing resistance to contamination, moisture and pressure Bonding of joints to be sealed involves bonding of the selected mateπal to itself, to cable jackets and to sealants which may be used Since sealing is accomplished by heating, the selected material must also be suitably responsive to fusion bonding As such, polyolefin elastomers are suitable and of that group, the flexible ethylene alphaolefin copolymer sold under the name ENGAGE by the Dow Chemical Company of Midland, Michigan, is preferred

Mateπal selection for the sealant of the present invention requires an affinity to produce satisfactory fusion bonding Thus, where a sealant is used in the present invention there are several alternatives First, however, it should be understood that a suitable bond may be in some instances accomplished by resistance heating of abutting surfaces by the placement of nichrome wire at or -near the abutting surfaces. Electrical stimulation of the wire will heat surrounding material sufficiently to bond all heated abutting surfaces, and with pressure applied through the curing process, suitable welds can be produced. The nichrome wire can be in the typical round wire form or a flat strip and can be coated, imbedded or laminated in a strip of suitable sealant material such as polyethylene. Electrical stimulation of the wire will heat the surrounding sealant material and the abutting surfaces to be sealed. All abutting surfaces can be sealed in this manner enhanced by the additional or surplus sealant material which will assist in providing suitable seals with pressure applied through the curing process.

In addition to using a wire coated by, imbedded in or laminated in a strip of sealant material such as polyethylene, a susceptor containing material can be added to the sealant which absorbs RF energy and transfers it into heat energy. In this case, the wire is preferably copper and functions as an antenna. The heat produced causes the susceptor containing material including a polyethylene binder and the abutting surfaces to be sealed. Here again, sealing is enhanced by the additional or surplus material which will assist in providing suitable seals with pressure applied through the curing process.

While it is not necessary to discuss every possible iteration of combining sealant material, susceptor material and wire types, it is clear that sealing is enhanced in view of the foregoing.

According to the present invention, Fig. 4, a fusion bonded seal is provided between planar sides 26, 28 of each arm 16a, 16b, 16c, and abutting planar walls 34, 36, respectively, of each of the segments 30a, 30b and 30c. The fusion bonded seal is also provided along annular surface 20 of each port 14. The seal is accomplished by providing a resistance wire 52 imbedded in a sealant strip 54 applied to the above-mentioned surfaces. The resistance wire 52 forms a closed circuit in which alternating current (AC) or direct current (DC) is applied for power. In addition, although not shown, sealant strip 54 can also be provided to outer peripheral surface 22 of end seal body 12. In this manner, when seal body 12 is mounted in an end of a splice closure housing 56, illustrated in phantom outline in Fig 1, which is in abutment with outer surface 22 of the seal body 12, the body 12 can be bonded to housing 56 Also, cable surface 43 is bonded to surface 20 of port 14, Fig 4 The resistance wire 52 can be of rounded cross-section but is preferably in the form of a flat ribbon molded or laminated into sealant strip 54 of polyethylene material. Thus, the strip 54 may be placed along the appropriate surfaces as aforesaid

Also, according to the present invention, a fusion bonded seal as described above is provided between abutting planar walls 134, 136, Fig. 7, of body portions 116, 118, respectively The fusion bonded seal is also provided between annular surface 120 of each port 114 and cable surface 143 The seal is accomplished by wire 52 in sealant strip 54 as aforesaid In addition, although not shown, wire 52 and strip 54 can also be provided to outer peripheral surface 122 of end seal body 112 In this manner, when seal body 112 is mounted in an end of a splice closure housing 156, illustrated in phantom outline in Fig 5, which is in abutment with outer surface 122 of seal body 112, the body 112 can be bonded to housing 156

In operation, cables are placed in the appropriate ports of the open end seal and the seal is closed Resistance wires imbedded in the sealant strip along the abutting surfaces between body portions and between the arcuate walls of the ports and the surfaces of cables therein, provide sufficient heat, when power is applied, to cause the surrounding seal material to bond all contact surfaces Similarly, when the end seal is placed in the splice closure housing, the wires in the sealant stπp around the outer periphery of the end seal can provide the bonding required to seal the end seal within the closure body

As it can be seen, the principal advantage of the present invention is that it provides a one-piece device when joined around cables extending through the ports which forms seals between the cable peripheral surfaces and the ports and also forms seals between the movable body portions of the end seal when those portions are joined together

The fusion bonded end seal has advantages over previous approaches to end seal integrity According to the present invention, the end seal is flexible to accommodate a multiple range of cable diameters and includes adjustable size ports Fusion bond strength between cables and end seal is higher than with a conventional hot melt system The end seal is a one piece design comprising a plurality of interconnected segments and no trimming is required for multiple cable diameters The end seal material can be re-entered and removed from the cables by cutting the material The end seal of the present invention does not require the use of a torch for heating.

Utility of the invention allows the end seal to be a main sealing member for cable closure bodies in that it seals to the cable surfaces and also is sealed to the adjoining cable closure body This forms an air tight, pressure and moisture seal to external elements Basic features of the end seal provide built in strain relief, acceptance of different cable diameters, and total seal integrity between the relatively movable end seal body portions, the cables extending therethrough, and the closure body it is mounted in Furthermore, the use of a continuous sealant strip to seal the cables in the ports and to seal the engaged surfaces of the body portions when they are engaged together, provides for facilitated installation

Although illustrative embodiments of the invention have been shown and described, a wide range of modifications, change and substitution is contemplated in the foregoing disclosure and in some instances, some features of the present invention may be employed without a corresponding use of other features Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention

Claims

What is claimed is

1 A cable end seal comprising: a body having a plurality of cylindrical cable ports formed therethrough, each port having an inner circumferential surface, a first arcuate portion of the surface being formed by a first portion of the body, and a second arcuate portion of the surface being formed by a second portion of the body, the first and second body portions being interconnected and movable from an open position wherein the first and second body portions and arcuate surface portions are apart, to a closed position wherein the first and second body portions and arcuate surface portions are joined to form an enclosure including the cylindrical ports for engaging peripheral surfaces of cables to be placed therein

2. The end seal as defined in claim 1 wherein each port is of an adjustable size

3 The end seal as defined in claim 1 wherein each port includes a plurality of concentric rings selectively removable for adjusting the size of the port

4. The end seal as defined in claim 1 wherein the body has an outer peripheral surface which is substantially circular.

5. The end seal as defined in claim 1 wherein the body has an outer peripheral surface which is substantially oblong.

6. The end seal as defined in claim 4 wherein the first portion of the body forms a central body core and the second portion of the body forms a segmented outer shell encompassing the core.

7 The end seal as defined in claim 6 wherein the central core includes a plurality of radially outwardly extending arms.

8 The end seal as defined in claim 1 wherein at least one of the ports includes a sealing plug formed therewith

9 A cable end seal comprising. a body having a plurality of cylindrical, adjustable size cable ports formed therethrough, the body including first and second relatively movable interconnected portions, each port having an inner circumferential surface formed in part by the first body portion and in part by the second body portion, the first and second body portions being movable from an open position wherein the inner circumferential surface parts are separated, to a closed position wherein the first and second body portions abut and the inner circumferential surface parts of each port are joined to engage a peripheral surface of a cable to be placed therein

10 The end seal as defined in claim 9 wherein each port includes a concentric bellows adjustment member

11 The end seal as defined in claim 9 wherein each port includes a plurality of concentric rings selectively removable for adjusting the size of the port

12 The end seal as defined in claim 9 wherein the body has an outer peripheral surface which is substantially circular.

13 The end seal as defined in claim 9 wherein the body has an outer peripheral surface which is substantially oblong.

14 The end seal as defined in claim 12 wherein the first portion of the body forms a central body core and the second portion of the body includes a plurality of pivotally interconnected segments forming an outer shell encompassing the core

15 The end seal as defined in claim 14 wherein the central core includes a plurality of radially outwardly extending arms

16 The end seal as defined in claim 9 further compπsing tab means for secuπng the body in the closed position

17 A cable end seal compπsing a one-piece body having a plurality of cylindrical cable ports formed therethrough, the body including first and second relatively movable interconnected portions, each port having an inner circumferential surface formed in part by the first body portion and in part by the second body portion, the first and second body portions being movable from an open position wherein the inner circumferential surface parts are separated, to a closed position wherein the inner circumferential surface parts are joined to form the cyhndπcal ports and the first and second body portions abut, means extending along the abutting surfaces of the first and second body portions and along the inner circumferential surface of each port, said means being responsive to electrical stimulation for heating adjacent mateπal of the body and port surface for bonding the body and cables to be placed in the ports into a sealed unit

18 The end seal as defined in claim 17 wherein the body has an outer peπpheral surface which is substantially circular

19 The end seal as defined in claim 18 wherein the first portion of the body forms a central body core pivotally connected to the second portion of the body, the second portion of the body being a plurality of interconnected segments forming an outer shell encompassing the core

20 The end seal as defined in claim 17 wherein the body portion has an outer peπpheral surface which is substantially oblong

21. A cable end seal comprising: a one-piece body having a plurality of cylindrical cable ports formed therethrough, the body including first and second relatively movable interconnected portions, each port having an inner circumferential surface formed in part by the first body portion and in part by the second body portion, the first and second body portions being movable from an open position wherein the inner circumferential surface parts are separated, to a closed position wherein the inner circumferential surface parts are joined and the first and second body portions abut; a cable extending through at least one port, the cable having an outer periphery engaged with the inner circumferential surface of the respective port; a sealant strip extending along the abutment between the first and second body portions and along the inner circumferential surface of each port; and means in the strip responsive to electrical stimulation for heating the sealing strip for bonding each cable and the body portions into a sealed unit.