Forming of cable splice closures

Forming an encapsulated splice region between cables in which conductors of one cable are electrically connected to conductors of the other cable to form splices. After electrically isolating splices from one another, a barrier layer is provided which extends axially across and beyond the splices onto the cables and then a plastic encapsulation is molded so as to enclose the barrier layer. The materials of the molding and barrier layer are such that they do not unite at any interfacial region between them. This construction makes it easier to open the splice region subsequently.

This invention relates to the forming of cable splice closures. 
A telecommunications cable extending from a central office and for 
underground or aerial use comprises a core having a plurality of pairs of 
individually insulated conductors. There may up to 3600 pairs of 
conductors in the core. When laying cable, it is sometimes necessary to 
join cables together, end-to-end, to achieve a required length of laid 
cable. Conventionally, in such situations, conductors are spliced together 
from cable-to-cable by removing the end portions of core surrounding 
material, i.e. cable sheaths and jackets so that the cores project beyond 
them, bringing the cable cores close together and then joining the 
conductor ends to form splices while retaining them between the cable 
sheaths and jackets. Splices are then sealed and a closure is placed over 
the region of the splices, i.e. to bridge the gap between and extend over 
the sheaths. The type of closure which has been used successfully in 
commercial practice is one in which it is formed as an encapsulation by 
molding techniques. Such a construction is described in U.S. Pat. Nos. 
4,152,539 granted May 1, 1979 and 4,322,573 granted Mar. 13, 1982, both 
patents being in the name of L. J. Charlebois. 
While the construction using a molded encapsulation is commercially 
successful and is cheaper than more established closure practices 
including the use of heat shrinkable materials, nevertheless problems have 
been found when it is required to open an encapsulated splice region. The 
methods discussed in the abovementioned U.S. patents, involve the location 
of heat softenable material around the splices for the purpose of forming 
seals. The heat softenable material is raised above its heat softening 
temperature by the heat produced during the molding operation and fuses 
into a single mass to form a seal around each splice. Also the material of 
the encapsulation successfully bonds to the softened sealing material to 
produce a further seal. The problem, however, it that when it is required 
to open the encapsulated splice region to reach individual splices, then 
the removal of the encapsulation and the heat softenable sealing material 
is a lengthy and difficult process. 
The present invention concerns a process of forming an encapsulated splice 
region between two cable ends and an assembly of two cables including such 
a region in which the above problem is reduced. The present invention also 
extends to a process and an assembly of two cables having an encapsulated 
splice region in which the cables are gas pressurizable. 
Accordingly, the present invention provides a method of forming an 
encapsulated splice region joining two cables comprising locating two 
cable end portions close together and substantially in axial alignment; 
electrically connecting conductors of one cable with those of the other to 
form splices and enshrouding each individual splice with dielectric 
material to electrically isolate it from other splices in the region; 
covering the splices by surrounding the cable end portion at each side of 
the splices with a barrier layer which extends also over the splices and 
between the cable end portions to enclose a region between the cable end 
portions; and forming a plastic molded encapsulation extending around the 
cables and over the splices so as to enclose the barrier layer, the 
materials of the encapsulation and of the barrier layer being separate and 
distinct from one another by any interfacial regions of the materials. 
In the above method, the splices in one preferred arrangement are sealed 
from one another by enclosing each individual splice within a sealing 
material which extends around at least one of the cables and surrounding 
the sealing material with the barrier layer before forming the 
encapsulation. In an alternative arrangement in which the cables are gas 
pressurizable, a barrier layer which is preformed and is of substantially 
cylindrical configuration is located in a position surrounding one of the 
cables before forming the splices and is then moved axially of the cables 
into a final position surrounding at least one of the cables axially at 
each side of the splices and bridging the splices so as to form a chamber 
containing the splices. A seal is then provided between the encapsulation 
and the jackets of the cables to enable the chamber to be pressurizable. 
The invention also includes an assembly of two telecommunications cables 
disposed with conductors of each cable electrically connected together to 
form splices with the splices electrically insulated from one another, a 
barrier layer extending over the splices, surrounding adjacent end 
portions of both cables axially at each side of the splices and extending 
between the adjacent end portions to enclose a region between the end 
portions, and a molded plastic encapsulation extending over the cable so 
as to enclose the barrier layer, the encapsulation and barrier layer being 
separate and distinct from one another at any interfacial region of the 
materials.

In a first embodiment as shown in FIG. 1, an encapsulated splice region 10 
formed between two cables 12 and 14 disposed end-to-end, comprises a 
plurality of splices 16 arranged in groups of circumferentially extending 
splices disposed at different axial positions surrounding the cable 14 as 
shown in FIG. 1. The number of splices depends upon the numbers of 
conductor pairs in each of the cables and in this particular embodiment, 
each cable includes 900 pairs of conductors. 
The splice region is formed in the manner described in U.S. patent 
application Ser. No. 752,745 entitled "Forming Of Cable Splice Closures" 
filed July 8, 1986 in the names of L. J. Charlebois, J. R. Scott and R. R. 
D'Aoust. As described in the aforementioned copending application, a 
ground bar 18 and a rigid metal support 20 are disposed at 
circumferentially opposite positions one on each side of the two cables 12 
and 14 as shown in FIG. 1. The ground bar and the metal support are each 
sealed by wrappings 22 of heat softenable tape material such as 
ethylene-propylene rubber, which are wound around the cables both beneath 
and over the ground bar and the support. Over the upper layer of wrappings 
22 is formed a stiffening material in the form of overlapped windings 24 
of vinyl tape which extend completely axially across the windings 22 so as 
to bridge the windings 22 and the grounding bar and the support. The 
wrappings 24 assist in the stiffening of the connection between the two 
cable ends so that substantially all of the movement between the cable 
ends is eliminated. 
With the conductor ends projecting through the vinyl layer wrappings 24, as 
described in the aforementioned application, individual conductors of one 
cable are electrically connected to individual conductors of the other to 
form the splices 16. A first group of the splices is then positioned with 
the splices of the group circumferentially spaced-apart around the cable 
14. To seal the first group of splices in position, a layer 26 of 
deformable sealing material is first positioned over the vinyl layer 24 
before the splices are located in position. A second layer 28 of the 
deformable material is then disposed over the first layer so as to cover 
the first group of splices. The deformable sealing material of layers 26 
and 28 is ethylene-propylene rubber sealing tape. 
A layer 30 of resilient sealing tape is then wrapped around the layer 28 in 
a localized axial position, i.e. so as to lie around the conductors of the 
first group of splices. This layer of resilient tape material is of any 
suitable material for the purpose of permanently compressing the 
ethylene-propylene tape material. A requirement for the resilient tape 
material is that it may be stretched sufficiently so as to apply a degree 
of radial compression to the layers 26 and 28 to cause their permanent 
deformation under the compressive force. A suitable material for the layer 
30 includes a tape referred to throughout the telecommunications cable 
industry as "DR Tape" or a neoprene rubber tape. Subsequent groups of 
splices are then located around the cable in the manner discussed above 
with each of the splices in each group being circumferentially spaced from 
others in the group. Each group of splices is laid between its own two 
layers of deformable material such as layers 32 and 34 are shown in FIG. 
1. Thus the method of laying the further groups of splices is similar to 
that previously discussed. Over each group of splices is applied a further 
layer of resilient sealing tape such as layer 36 which is disposed over 
the conductors of its respective group in a manner similar to the 
positioning of the layer 30 discussed above. 
After the splices have been located in the positions shown and have been 
provided with their layer of resilient tape material, then, according to 
an essential feature of the present invention, a barrier layer 38 is 
positioned over the splices so as to extend around the cables axially at 
each end of the splices. As shown in FIG. 1, this barrier layer 38 is 
formed from wrappings of vinyl tape which extend axially between the 
adjacent end portions to enclose a region between the end portions, and 
which may extend completely axially over the ends of the previous 
wrappings so as to completely enclose them. Preferably, however, and as 
shown in the present embodiment, the vinyl wrappings terminate axially 
short of the top layer, i.e. layer 34 of the ethylene-propylene tape 
forming the compressible material. 
The formed splice region 40 is then disposed in a mold as shown by FIG. 2. 
The mold comprises two mold halves 42 only one of which is shown as the 
view is taken on the parting line of the mold. Moldable material is 
extruded through inlet gate 44 into the mold cavity 46 to mold the 
encapsulation 48 (see FIG. 1) with polyethylene material. The polyethylene 
flows through the mold and fills the cavity and completely encloses the 
vinyl layer 38. Upon the mold becoming full of material, it switches off 
automatically by the use of a switch means 50 which is operated 
automatically. This switch is described in detail in U.S. Pat. No. 
4,490,315 granted Dec. 25, 1984 in the name of L. J. Charlebois et al and 
entitled "Methods of Moulding of Plastics Articles". 
It is a requirement of the present invention that the ethylene-propylene 
rubber tape layers should be softened sufficiently to cause them to merge 
together while also ensuring that the production of toxic gases is 
minimized. The temperatures for molding are therefore carefully controlled 
so that no fusion will take place between the molding material and the 
jackets for the cables. In this embodiment, the jacket material is 
basically polyetheylene and it is intended to use a different grade of 
polyethylene for the molding operation. A required temperature for the 
molding material is below 204.degree. C. and preferably between 
160.degree. C. and 190.degree. C. as the molding material enters the mold. 
It has been found that with a molten temperature set at about 190.degree. 
C. immediately before the molding material enters the mold, this provides 
a molten temperature of about 145.degree. C. (maximum) when contacting the 
cable jackets in a suitably designed aluminum mold which is water or air 
cooled to a temperature of around 20.degree. C. Under such controlled 
conditions, no fusion takes place between the two different polyethylene 
materials used for the plastics moldings and the cable jacket. The degree 
of heat retention, which is related of course to the rate of heat 
dissipation, is also an important factor and this is dependent upon the 
type of material used for the mold and the temperature to which it is 
cooled. 
In addition to the fact that the molding temperature is such that a fusion 
bond does not take place between the plastic molding forming the 
encapsulation 48 and the cable jackets, the resilient material in each of 
the layers 30 and 36 is not heated sufficiently to soften it, as it is 
required to these layers to remain in their stretched condition. In 
contrast to this, the heat retention and the temperatue of molding is 
sufficiently high for a fusion bond to take place between the 
ethylene-propylene rubber layers and between these layers and the 
encapsulation at any interfacial region between them such as occurs along 
the region 52 which projects axially at each end from the barrier 38. 
Hence it follows that the ethylene-propylene rubber layers which contact 
each other are merged into a single mass completely surrounding each 
individual splice and also surrounding the conductors where these pass 
between the layers. Thus, although the encapsulation 48 is not bonded to 
the jackets, moisture cannot reach the splices 16. 
Because of the use of the two completely different types of materials in 
the barrier layer and in the encapsulation, then no bonding takes place 
between these two materials at the molding temperature. However, if 
moisture should penetrate between the jackets and the ends of the 
encapsulation at their interfacial regions which is possible because no 
bond exists between them, then the bonding action which takes place at the 
projecting regions 52 of the ethylene-propylene rubber to the 
encapsulation forms a seal which prevents moisture from penetrating into 
the interfacial region between the barrier 38 and the encapsulation. 
As can be seen from the above description, the embodiment provides an 
encapsulated splice region in which the splices are adequately sealed from 
contact by moisture by the various heat softenable layers which are merged 
into a integral whole surrounding each of the splices. This is the case 
even though the jacket material is not bonded directly to the 
encapsulation at the two ends of the encapsulation and even though a bond 
is not provided between the layer 38 and the encapsulation. 
As can be seen from the above description, should it be necessary to open 
the encapsulated splice region for any purpose, then the only area in 
which the encapsulation is bonded to the splice region is around the 
axially narrow regions 52. It has been shown in practice that these 
regions need only be approximately 0.5 inches in axial width to provide 
all the seal which is necessary to prevent moisture from travelling over 
and under the barrier layer. The encapsulation is removed simply by 
forming a crack along its axial length, for instance with the use of a 
chisel. Apart from at the bonded positions 52, the encapsulation is then 
easily removable by splitting it into two halves which, conveniently, 
simply move away from the surface of the barrier layer 38. The narrow bond 
area provided by the regions 52 at each end is easily cut away. 
While it is preferred to have seals at the two ends of the barrier layer 
38, e.g. as shown at the regions 52, such fused seals are, in fact, not 
essential. It is essential in this embodiment that the ethylene-propylene 
layers completely merge together around each splice so as to seal it. It 
is also necessary according to the invention that the sealing material is 
sealed to each conductor insulation extending to a splice to prevent 
moisture tracking along the insulation. For this reason in this 
embodiment, the resilient layers, such as layers 30 and 36 are essential. 
In a modification (not shown) of the first embodiment in which the barrier 
layer 38 extended completely over the ethylene-propylene layers so that no 
regions 52 were provided, it was found that moisture reached none of the 
splices even though no seal was used to prevent moisture seepage over and 
under the barrier layer. In the modification, as in the first embodiment, 
no fused seal was used to prevent moisture from passing between the jacket 
of each cable and the contacting layer of ethylene-propylene layer. The 
only seal was formed as a mechanical seal formed under molding compression 
and subsequent shrinkage of the encapsulation. This caused the 
encapsulation to readily compress itself against the barrier layer 38 and 
to compress the innermost ethylene-propylene layer against the cable 
jackets. 
Tests were performed both upon an encapsulated splice according to the 
embodiment and according to the modification. In all tests, the regions of 
the cable extending from and closest to the encapsulations were immersed 
with the encapsulations in a bath of water or ice. The cable regions 
remote from the encapsulations were raised out of the bath to enable the 
conductors at each side of the splice region to be suitably connected up 
to equipment for making an insulation resistance test on all conductor 
pairs. The regions of the cables beneath water were cut into to enable 
water to reach the outside of the conductor insulations in the cores and 
water was pumped along the cables to ensure that it penetrated into the 
region 54 (FIG. 1) between the opposed cable ends and laying within the 
splice region. In the test, the temperature of the bath was cycled for at 
least 50 cycles between -40.degree. C. and +60.degree. C. The insulation 
resistance test on all pairs showed that the resistance remained above 
10.sup.9 ohms which was a clear indication that the water in the bath did 
not penetrate to any of the splices. Not only is this a clear indication 
that the fused together ethylene-propylene rubber layers form an effective 
seal, but also that water was prevented by the layers 30 and 36 from 
penetrating from the region 54 under pressure and to any of the splices. 
In a second embodiment, as shown in FIG. 3, two cables 60 and 62 are gas 
pressurizable and are joined end-to-end by forming splices 64 between 
their conductors. These splices are individually sealed with a sealing 
material so as to electrically isolate them from one another. These 
splices are left as can be seen by FIG. 3, within the region between the 
two cables 60 and 62 and without securing them to either one cable or the 
other. 
The two cable ends are surrounded with a deformable means 66 which is 
composed of overlaid wrappings 67 of ethylene-propylene rubber tape 
material with the wrappings in each layer being overlapped. It is 
convenient for the layers to be narrower in the radially outer regions so 
that a tapered effect to the deformable means is provided as shown by FIG. 
3. A barrier layer 68 is then located so as to extend axially between the 
cable ends and across the formed splices. This barrier layer is preformed 
in substantially cylindrical configuration and is disposed axially along 
one of the cables before the conductors are aligned together. After the 
splices are made and the deforming means 66 is constructed, the barrier 
layer is then moved axially into its position shown in FIG. 3 in which it 
surrounds the two cable ends and bridges the splices so as to surround 
them and provide a chamber 70 which contains the splices. In this 
position, the barrier layer is supported at its ends by the deformable 
means 66. The barrier layer should be of any material which will not bond 
to the encapsulation material at the molding temperatures. This may be 
because the softening temperature of the barrier layer lies above the 
molding temperature of the encapsulation or because the barrier layer is 
of a material which does not soften. In this particular case, the barrier 
layer is formed from a grade of cardboard of sufficient strength to 
prevent it from collapsing under the low molding pressures used in molding 
the encapsulation. These molding pressures are extremely low in this 
process and would not exceed 100 lbs psi. In fact in the process as 
followed commercially, the pressures do not exceed 15 lbs to psi. 
Prior to the forming of the splices, a ground bar 72 is positioned between 
the two cable ends in conventional fashion and this ground bar is capable 
of taking some of the axial tensions across the splice region. In addition 
to this, however, the structure in FIG. 3 is provided with a strain relief 
device 74 at each end of the splice region. This strain relief device 
comprises a strap member which is bent around each of the cables 60 and 62 
and has flanges 76 upstanding from a base 78 which contacts the cable. 
Each of the bases is formed with a piercing means in the form of prongs 80 
which project into the cable jacket to hold the base in position. As the 
encapsulation is molded in position, then the flanges become embedded in 
the material of the encapsulation. Thus, after manufacture if any tensile 
load is placed across the encapsulated splice region, then this load is 
taken from each cable jacket through the prongs 80 into the base and then 
from the flanges 76 into the encapsulation which itself is then placed in 
tension from end-to-end. The strength of the encapsulation is thus 
improved above that merely provided by the grounding bar 72. A 
construction using a strain relief device of this type is described in a 
copending Canadian Patent Application No. 462,241, filed Aug. 31, 1984 
(U.S. Ser. No. 648,461 filed Sept. 7, 1984), entitled "Cable Encapsulation 
and Strain Relief" in the name of L. J. Charlebois. In addition to this, a 
seal 82 is disposed around each cable end. Each seal 82 is disposed 
axially outwardly from the wrappings 67 and is of a construction described 
in a U.S. Pat. No. 4,570,032 entitled "Cable Splice Encapsulation Seal", 
in the names of L. J. Charlebois and K. H. Dick, issued Feb. 11, 1986. As 
described in the latter specification, the seal 82 comprises an inner 
wrapping layer 84 of a material which is deformable so that under 
compression it will intimately engage the surface of the jacket so as to 
form a first seal to prevent moisture ingress along the jacket surface 
towards the splices and the chambers 70. Such a material for the inner 
layer is an ethylene-propylene rubber. An outer layer 86 which is wrapped 
around it, needs to be a resilient tape material which is stretched very 
tightly so as to provide the required compressive force upon the layer 84. 
This layer may be a neoprene rubber tape or that known as "DR Tape" in the 
telecommunications cable industry. With this construction, because the 
layer 84 in the final structure is compressed, it forms a permanent 
compressive seal against the outer surface of its respective jacket, and 
the outer regions of the layer 84 which form an interface with the 
encapsulation are bonded thereto during the encapsulation process by heat 
softening of the ethylene-propylene rubber. It follows that when the 
encapsulation 88 is formed by the molding process in a manner similar to 
that described in the first embodiment, then a seal is provided at each 
end of the encapsulation by the seal 82 thereby preventing the escape of 
gas under pressure from the chamber 70 notwithstanding that the 
encapsulation itself is not bonded to the jacket of either of the cables 
60 and 62. 
During the forming of the encapsulation 88, no bond takes place between the 
encapsulation material and the cardboard forming the barrier. In this 
embodiment, a bond will take place between the deformable means 66 and the 
encapsulation. This bond and the small bond existing between each of the 
seals 82 and the encapsulation is the only resistance offered to removal 
of the encapsulation when it is split axially along its length for removal 
purposes. As can be seen, the bonds at these positions are over a very 
small area and this is easily cut away. 
In a modification of the embodiment shown in FIG. 3 (not shown), a layer of 
material such as vinyl tape may be wrapped over the deformable means 66 in 
each case to act as a barrier between and prevent any bond taking place 
between the deformable means 66 and the encapsulation. In this case, the 
encapsulation 88 is more easily removed as it does not bond at any 
position between the seals 82 at the ends and there may be a slight 
mechanical grip between the flanges 76 and the encapsulation as it is 
removed. 
It should be added that the deformable means 66 is provided for the purpose 
of ensuring that no cracking takes place in the encapsulation such as is 
caused by thermal cycling. Should there be temperature variations causing 
differences in expansion of the encapsulation as compared to the barrier 
layer and to the cables, then the deformable means will act as a damping 
means which distorts under the stresses involved to prevent any cracking 
of the encapsulation because of excessive stress.