U.S. patent number 3,775,548 [Application Number 05/228,876] was granted by the patent office on 1973-11-27 for filled telephone cable.
This patent grant is currently assigned to Essex International, Inc.. Invention is credited to Joseph Connelly, Frederick M. Zinser, Jr..
United States Patent |
3,775,548 |
Zinser, Jr. , et
al. |
November 27, 1973 |
FILLED TELEPHONE CABLE
Abstract
In a filled telephone cable, the core is filled with a
composition comprising petroleum jelly in the amount of about 80
percent by weight, polyethylene and/or polybutene-1 in the amount
of about 10 percent by weight, and polyisobutylene in the amount
also of about 10 percent weight.
Inventors: |
Zinser, Jr.; Frederick M.
(Decatur, IL), Connelly; Joseph (Decatur, IL) |
Assignee: |
Essex International, Inc. (Fort
Wayne, IN)
|
Family
ID: |
22858894 |
Appl.
No.: |
05/228,876 |
Filed: |
February 24, 1972 |
Current U.S.
Class: |
174/23C; 174/107;
174/116; 174/25C; 174/110PM |
Current CPC
Class: |
H01B
13/328 (20130101); H01B 11/00 (20130101); H01B
13/322 (20130101) |
Current International
Class: |
H01B
11/00 (20060101); H01B 13/32 (20060101); H01b
007/18 (); H01b 003/30 () |
Field of
Search: |
;174/23R,23C,25C,27,24,11PM,113R,116,107,12R,36 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,095,639 |
|
Dec 1967 |
|
GB |
|
757,395 |
|
Sep 1956 |
|
GB |
|
767,836 |
|
Feb 1957 |
|
GB |
|
776,174 |
|
Jun 1957 |
|
GB |
|
Primary Examiner: Gilheany; Bernard A.
Assistant Examiner: Grimley; A. T.
Claims
What is claimed is
1. A composition for filling communication cables, said composition
comprising a mixture of:
petroleum jelly in the amount of about 80 weight percent of said
composition,
a polymer selected from the group consisting of polyethylene,
polybutene-1 and mixtures thereof in the amount of about 10 weight
percent of said composition, and
polyisobutylene in the amount of about 10 weight percent of said
composition.
2. The composition of claim 1 wherein said polyethylene is low
density polyethylene.
3. A filled communication cable comprising,
a core including a plurality of insulated conductors and a filler
composition filling the spaces between and surrounding said
conductors, said composition comprising a mixture of:
petroleum jelly in the amount of about 80 weight percent of said
composition,
a polymer selected from the group consisting of polyethylene,
polybutene-1 and mixtures thereof in the amount of about 10 weight
percent of said composition, and
polyisobutylene in the amount of about 10 weight percent of said
composition, and
an exterior sheath covering said core.
4. The cable of claim 3 wherein said polyethylene is low density
polyethylene.
5. The cable of claim 3 wherein said exterior sheath includes a
tape wrapped about said core, said tape being impregnated with said
filler composition.
6. The cable of claim 5 wherein said exterior sheath also includes
an insulative coating surrounding said tape.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to filled telephone cables and a filler
composition therefor.
In various underground cable installations, such as multiple
conductor telephone cables, water and water vapor must be prevented
from entering the cable through punctures in the cable's outer
jacket which may result either from lightning, defects in the
cable's outer jacket or excavation damage. Entry of water will
result in a substantial reduction in the performance of the cable,
if not complete destruction for its intended purpose.
In order to reduce the likelihood of damage to such underground
cables, for example underground telephone cables, various fillers
have been employed in the past to prevent exposure of the cable
conductors to water. Such filled cables generally take the form of
a core in which the multiple conductors of the telephone cable are
embedded in a soft resilient filler material during manufacture the
purpose of which is to fill all the voids within the cable. This
core is then wrapped with a suitable dielectric tape, is covered
with a metallic sheath and is coated with the external insulative
sheath of the cable. One such filler composition which has been
employed in the past comprises a mixture of 85-95 percent petroleum
jelly and 5-15 percent polyethylene. During the manufacture of the
cable, the filler material is heated to a temperature at which it
is a flowable heavy viscous liquid which is coated upon the
multiple conductors so as to fill the voids between the conductors.
Upon cooling to ambient temperature, the filler composition assumes
a non-flowable, pliable, tacky form and is closely contained in the
cable core by the external sheathing of the cable.
It has been found that prior petroleum jelly -- polyethylene
mixtures tend to dry and crack after injection into the cable. As
such, when the cable is bent during installation, voids may occur
in the cable core which might allow moisture to penetrate the
conductor insulation. It is believed that such drying and cracking
is due to the absorption of the light ends of the petroleum jelly
into the polyvinyl chloride, polyethylene or polypropylene cable
insulation and which causes this insulation to swell somewhat. This
swelling itself is not critical, but results in a loss of material
from the filling mixture causing the mixture to subsequently crack
and separate from the conductor insulation and cable sheath.
The present invention is directed to a filling composition for
filled cables which substantially reduces the tendency of such
cables to dry out and crack and thereby substantially increases the
life and operating performance of these cables. Moreover, the
composition of the present invention is not appreciably more
expensive than the prior filling compositions and may be readily
applied during manufacture of the cable by well known processes
which were previously employed in the application of the prior
filling compositions.
In a principal aspect of the present invention, a composition for
filling filled conductive cables comprises a mixture of about 80
weight percent petroleum jelly, about 10 weight percent of either
polyethylene and/or polybutene-1 and about 10 weight percent of
polyisobutylene.
In another principal aspect of the present invention, a filled
communication cable comprises a core having a plurality of
insulated conductors therein and a filler composition filling the
spaces between and surrounding the conductors. The filler
composition comprises a mixture of about 80 weight percent of
petroleum jelly, about 10 weight percent polyethylene and/or
polybutene-1 and about 10 weight percent polyisobutylene and an
exterior sheath covers the core.
These and other objects, features and advantages of the present
invention will become evident upon consideration of the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWING
In the course of this detailed description, the drawings will be
referred to in which:
FIG. 1 is a cross-sectioned view of a filled telephone cable
construction incorporating the principles of the present invention;
and
FIG. 2 is a schematic presentation in which a preferred sequence of
construction steps are shown for making a filled telephone cable
incorporating the principles of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a filled telephone cable constructed in
accordance with the principles of the present invention is shown
which comprises a core, generally 10, which is surrounded by an
external sheath, generally 12. The core 10 includes a plurality of
spaced conductor pairs 14 which are twisted together. Each of the
conductors 16 in the given pair 14 comprises a suitable conductor
wire 18, such as an aluminum or copper wire, which is surrounded
with an insulative coating 20, such as polyethylene, polypropylene
or polyvinyl chloride. Each of the conductor pairs are spaced from
each other and the spaces between the pairs are filled with the
filler composition 22 of the present invention as shown in FIG.
1.
The filler composition of the present invention comprises a mixture
of petroleum jelly, polyethylene, and polyisobutylene, the latter
of which is a tackifying agent. The petroleum jelly is present in
the filler in the amount of 80 percent by weight, the polyethylene
in the amount of 10 percent by weight, and the polyisobutylene in
the amount of 10 percent by weight. It has been found that a
mixture of these materials in the above mentioned amounts provides
a filler composition which exhibits suitable melting temperatures
which are important in the application of the filler composition to
the conductors, as will be explained in further detail later. Such
composition has also been found to be sufficiently tacky, but not
overly tacky, and is capable of relatively easy mixing. Finally
and, most importantly, this composition substantially reduces the
tendency of the filled cable to dry and crack.
The percentages of the filler mixture components are important in
achieving a filler composition which is both readily workable and
which reduces drying and cracking of the filler in the cable. Where
the percentage of petroleum jelly is reduced to 78 percent and the
percentage of polyisobutylene is increased to 17 percent, the
resulting mixture becomes too tacky and the melt temperature of the
filler material is increased by an unacceptable amount. Conversely,
a mixture of 86 percent petroleum jelly -- 10 percent polyethylene
-- 4 percent polyisobutylene was found to be not sufficiently
tacky. When the amount of polyethylene is reduced to 2 percent, the
melting temperature of the mixture is not sufficiently high to
prevent loss of the filler from the end of the cable at
temperatures which might be experienced in installations in hot
geographic regions, e.g. 160.degree.F.
Although, polyethylene is preferred, it is contemplated that
polybutene-1 may also be substituted in whole or in part for the
polyethylene. Where polyethylene is employed, the low density form
is preferred and polyethylenes having average molecular weights in
the range of from 3,000 to 400,000 have been found to be suitable.
A suitable polyisobutylene is Vistanex, available from Enjay
Chemical Co.
Referring again to FIG. 1, the sheath 12 surrounds the core 10 and
comprises a wrapped layer of a suitable dielectric tape 24, such as
a polyester type. This tape layer is also preferably impregnated
with the filler mixture. Surrounding the tape layer 24 of the
cable, is a suitable metallic sheath 26, such as aluminum and,
finally, the cable is covered with an exterior flexible insulative
layer 28, such as polypropylene or polyvinyl chloride.
Although it is believed that the foregoing description of the
filled cable is ample for a full understanding of the principles of
the invention, a brief description of a suitable method for making
such cable follows.
Referring to FIG. 2, the already insulated individual conductors 16
are drawn from individual reels 30 and a pair of these conductors
are twisted together at 31 to form pairs 14. These pairs 14 are
then passed through filler flooding tanks 32 in which each of the
respective pairs is saturated and coated with the filler mixture
earlier described. The heated filler is introduced to the flooding
tanks 32 at a temperature of approximately 210.degree. F at which
temperature, the filler mixture takes the form of a heavy, viscous
liquid and readily flows between and coats the conductor pairs.
Since the conductor pairs 16 enter tanks 32 at substantially
ambient temperature, the temperature of the filler mixture which is
coated upon the pairs will be reduced such that the filler on the
pairs will become tacky and grease-like and will therefore adhere
to the pairs as they leave tanks 32.
A plurality of these coated pairs 14 are then brought into
proximity to each other at 34 and enter a second flooding tank 36
to which additional filler mixture has also been introduced in the
liquid state. In this flooding tank 36, the filler will now flow
between the conductor pairs 14 to fill the spaces between the pairs
and will surround the entire conductor bundle as shown in FIG. 1.
Again contact with the proximate conductor pairs will result in a
reduction in the temperature of the filler mixture, causing it to
become greasy and tacky in consistency as previously described.
The core 10 which has now been formed will then pass to a core wrap
station 38 where the core is wrapped with the polyester tape 24.
The wrapped core 10' then proceeds to a metallic sheath application
station 40 in which the metallic sheath 26 is applied. Finally,
this sheathed bundle 10" passes to an insulator sheath forming
station 42 where the external insulative sheath is applied and
cured. From this station, the filled final cable product may be
stored on reels 44.
It will be understood that the embodiment of the present invention
which has been described is merely illustrative of one of the
applications of the principles of the invention. Numerous
modifications may be made by those skilled in the art without
departing from the true spirit and scope of the invention.
* * * * *