U.S. patent number 3,789,099 [Application Number 05/196,949] was granted by the patent office on 1974-01-29 for methods of manufacturing waterproof cable.
This patent grant is currently assigned to Western Electric Company, Incorporated. Invention is credited to Carl Eugene Garrett, William Henry Kinsley, Jr., Larry Dean Moody.
United States Patent |
3,789,099 |
Garrett , et al. |
January 29, 1974 |
METHODS OF MANUFACTURING WATERPROOF CABLE
Abstract
Successive sections of a cable core having twisted pairs of
insulated conductors stranded together are moved axially
longitudinally through a series of in-line chambers having
interconnecting dies of an apparatus with facilities for the
pressure application of a heated waterproofing compound having a
jelly-like consistency into the interstices between the stranded
pairs of conductors. The apparatus is designed to direct the
compound inwardly radially of the core after which a flow path of
the compound is established into an upstream direction relatively
longitudinally of the advancing cable core to more completely fill
the interstices of the completed core. Provisions are made for
cooling the cable core both prior to the filling thereof to limit
the movement upstream of the compound and subsequent to the filling
of the core to solidify and render self-sealing the compound.
Subsequently, the successive sections of the compound filled core
are advanced through various stations whereat a core wrap and
sheath are applied thereto together with additional applications of
the waterproofing compound. A plastic jacket is extruded about the
sheath and cooled prior to taking up of the successive sections of
the jacketed cable onto a take-up reel.
Inventors: |
Garrett; Carl Eugene (Stone
Mountain, GA), Kinsley, Jr.; William Henry (Omaha, NB),
Moody; Larry Dean (Ralston, NB) |
Assignee: |
Western Electric Company,
Incorporated (New York, NY)
|
Family
ID: |
22727418 |
Appl.
No.: |
05/196,949 |
Filed: |
November 9, 1971 |
Current U.S.
Class: |
156/48;
264/261 |
Current CPC
Class: |
H01B
13/323 (20130101) |
Current International
Class: |
H01B
13/32 (20060101); B32b 031/06 () |
Field of
Search: |
;264/261,174 ;117/115
;156/48 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: White; Robert F.
Assistant Examiner: Balhoff; T. E.
Attorney, Agent or Firm: Somers; E. W.
Claims
What is claimed is:
1. A method of filling substantially the interstices of an already
stranded core of a communications cable with a waterproofing
compound, which includes the steps of:
advancing successive sections of the stranded core along a
predetermined path; through a laterally confined pressure relief
chamber and then through a filling chamber;
directing a plurality of streams of the compound in a semifluid
state generally radially inwardly of the longitudinal axes of the
successive sections of the stranded core in the filling chamber at
a velocity and pressure sufficient to cause the compound to
displace the air within the interstices of the core and to fill the
interstices thereof, while creating a pressure differential between
the filling chamber and the pressure relief chamber to establish a
flow path of the compound which has been moved in engagement with
the core longitudinally along the core and move portions of the
compound from the filling chamber within the stranded core to the
pressure relief chamber to cause the interstices of the core to
become filled substantially; and
providing a cooling chamber along the path downstream of the
filling chamber and through which the core is advanced to cool the
core and the compound associated with the successive sections of
the core in the interstices and on the surface thereof to a
consistency having a viscosity sufficient to facilitate the
retention of the compound with the core independently of any
supporting structure.
2. The method of claim 1, wherein the plurality of streams of
compounds are arranged in a single plane transverse of the axes of
the successive sections of the core.
3. The method of claim 1, wherein the plurality of streams of
compound are spaced along the longitudinal axes of the successive
sections of the core.
4. A method of applying a compound to a stranded core of a
communications cable, which comprises the steps of:
advancing successive sections of the stranded core along a path of
travel;
directing streams of the compound in a semifluid state generally
inwardly of the successive sections of the stranded core;
establishing a flow path of the compound longitudinally along the
advancing successive sections of the stranded core in a direction
opposite to the path of travel;
the velocity of the streams and the flow paths and the pressure of
the compound being sufficient to cause the compound to displace the
air within the interstices of the stranded core and to fill the
interstices of the stranded core;
cooling the successive sections of the stranded core prior to the
entry of the sections into the flow path of the compound to place
in a jelly-like state any portions of the compound which are drawn
from the flow path in a direction opposite that of the path of
travel to preclude further movement of the compound along the path
of travel; and
conditioning the compound associated with the stranded core to a
consistency having a viscosity sufficient to limit the flow path
and to facilitate the retention of the compound with the stranded
core independently of any supporting structure.
5. A method of applying a compound to an elongated stranded
article, which comprises the steps of:
moving successive sections of the stranded article along a path of
travel successively through a cooling chamber, a pressure-relief
chamber and compound-filling chamber;
directing a plurality of streams of compound in a semifluid state
into the compound-filling chamber and into engagement with the
successive sections of the stranded article at a pressure
sufficient to move the compound into the interstices of the
successive sections of the stranded article;
establishing a flow path of the compound from the filling chamber
in a direction opposite to the path of travel of the successive
sections of the stranded article to move the compound from the
filling chamber along and within the stranded article into the
pressure-relief chamber;
the cooling chamber being effective to preclude further movement of
the filling compound in the direction opposite to the path of
travel; and
conditioning the compound associated with the stranded article to a
consistency having a viscosity sufficient to facilitate the
retention of the compound with the stranded article independently
of any supporting structure.
6. A method of applying a compound to an elongated stranded
article, which comprises the steps of:
moving successive sections of the stranded article through a
compound-applying chamber;
moving amounts of the compound in a semifluid state into the
compound-applying chamber and into contact with the successive
sections of the stranded article at a pressure sufficiently high to
displace the air in interstices of the stranded article with
compound; then
moving the compound relatively generally longitudinally of the
movement of the successive sections of the stranded article, the
moving of the compound into contact with the article and then
relatively generally longitudinally thereof causing the compound to
be moved first into the interstices and then along the article to
facilitate the displacement of the air within the interstices
throughout the cross-sectional area of the stranded article to
insure that substantially all the interstices are filled with the
compound;
moving the compound-filled stranded article through an environment
whereat the semifluid compound is conditioned to place the compound
in a jelly-like state so that the compound is non-flowable and is
retained within the interstices and on the surface of the stranded
article independently of any other supporting structure; and
cooling the successive sections of the stranded article prior to
the entry of the portions into the flow path of the compound to
place in a jelly-like state any portions of the compound which are
drawn from the compound-applying chamber along the flow path to
preclude further movement of the compound.
7. A method of applying a compound to an elongated stranded
article, which comprises the steps of:
advancing successive sections of the stranded article in a first
direction along a path of travel;
cooling initially the successive sections of the stranded article;
and then
directing streams of the compound in a smeifluid state generally
radially inwardly of the successive sections of the stranded
article;
establishing a flow of the compound relatively longitudinally of
the stranded article in a second direction opposite to the first
direction;
the pressure of the compound and the flow paths of the compound
being sufficient to displace the air from the interstices of the
stranded article and to fill the interstices with the compound;
the cooling of the successive sections prior to the application of
the compound being sufficient to condition the compound to a
consistency having a viscosity sufficient to seal the stranded
article and preclude further longitudinal movement of the compound;
and
cooling the successive sections of the article subsequent to the
directing of the compound into engagement therewith to condition
the compound to a consistency having a viscosity sufficient to
facilitate retention of the compound with the stranded article
independently of any supporting structure.
8. The method of claim 7 wherein the directing of the streams and
the longitudinal flow of the compound is caused to occur in an
enclosed environment.
9. The method of claim 7, which further includes:
heating the compound to a predetermined temperature prior to the
directing of the streams thereof into engagement with the
successive portions of the stranded article.
10. A method of applying a compound to an elongated stranded
article, which comprises the steps of:
advancing successive sections of the stranded article in a first
direction along a path of travel;
cooling initially the successive sections of the stranded article;
and then
directing streams of the compound in a semifluid state generally
radially inwardly of the successive sections of the stranded
article;
establishing a flow of the compound relatively longitudinally of
the stranded article in a second direction opposite to the first
direction which includes the steps of;
reducing the pressure intermediate the directing of the streams and
the cooling initially of the successive sections of the stranded
article; and
moving compound in excess of that required to fill the interstices
and to cover the surface of the stranded article out of engagement
with the stranded article;
the pressure of the compound and the flow paths of the compound
being sufficient to displace the air from the interstices of the
stranded article and to fill the interstices with the compound;
the cooling of the successive sections prior to the application of
the compound being sufficient to condition the compound to a
consistency having a viscosity sufficient to seal the stranded
article and preclude further longitudinal movement of the compound;
and
cooling the successive sections of the article subsequent to the
directing of the compound into engagement therewith to condition
the compound to a consistency having a viscosity sufficient to
facilitate retention of the compound with the stranded article
independently of any supporting structure.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods of manufacturing waterproof
cable, and more particularly, to methods of pressure filling the
interstitial voids of a stranded cable core with a waterproofing
compound to facilitate the construction of an essentially
waterproof cable having a core wrap, sheathing and jacketing
together with additional applications of the waterproofing compound
over the core.
2. Technical Considerations and Description of the Prior Art
In the manufacture of various communications cables, such as those
contemplated for use as underground or buried cable in telephone
communications systems, individual bare conductors are extrusion
coated with an insulative coating with the insulated conductors
being twisted in pairs. A plurality of the twisted pairs of the
insulated conductors are subsequently stranded together to form a
cable core with a binding ribbon then being wound helically about
the successive sections of the cable core for coding purposes. A
thermal and dielectric barrier tape, commonly referred to in the
art as a core wrap, and a metallic shield are wrapped about the
advancing successive sections of the cable core. Then a jacketing
layer of a plastic insulating material is extruded over the
successive sections of the enclosed cable core.
Provisions must be made to protect the insulated conductors of the
cable core to minimize the entry of moisture into the cable core.
Since communications cables of the type described hereinbefore may
be contemplated for underground or buried environments, moisture
diffusion into the interior of the core is likely with accompanying
corrosive attack causal of damage to the conductors and change in
capacitance. Further, the presence of moisture in the cable core
would result in the inefficient, and in some cases, the failure of,
the operation of the telephone circuits formed by the conductors.
There is also the possibility that the jacket and the metallic
barrier could be broken open by external forces, such as shifting
rock formations in the buried configurations or inadvertent blows
to above-ground portions of the cable which could expose the cable
core to moisture.
A presently used technique for minimizing moisture penetration into
the cable core of a communications cable includes the use of metal
strip precoated with an adhesive material and which is wrapped
longitudinally about the core wrapped cable core. A jacket of hot
plastic material is extruded about the adhesive coating on say one
outwardly facing surface of the moisture barrier with the heat of
extrusion causing the metal barrier to be bonded to the inner wall
of the jacket to thereby form a bonded sheath about the cable core.
The bonded sheath provides a moisture barrier which reduces the
penetration of corrosive, damaging moisture into the core of the
cable. Additionally, the cable core may be pressurized
subsequently, which further tends to reduce the penetration of
moisture into the core.
Another technique used to minimize the entry of moisture into a
cable core includes the flooding of the interstitial voids in the
core structure of the cable with a compound which possesses
properties sufficient to minimize the entry of moisture into the
core. Ideally, the compound would fill all of the air spaces and
voids within the cable which comprise the interstitial structure of
the cable core. Because of the stranding together of twisted pairs
of insulated conductors to form the core, difficulties have been
experienced with prior art processes in insuring that all of the
voids of the interstitial structure are filled with the
waterproofing compound, particularly those which occupy the axially
central portions of the core.
One approach in attempting to insure that all of the voids are
filled with the waterproofing compound has been to advance the
individual twisted pairs of conductors through a flooding chamber
to coat each pair. Subsequently, the twisted pairs, having
waterproofing compound adhered thereto, are stranded together into
units which are then reflooded and cabled together to form a cable
core. The cable core is advanced longitudinally with a protective
tape or core wrap formed about the core and bound.
The wrapped cable core is advanced through a forming tube into
which waterproofing compound under pressure, which may be as high
as 50 psi, is introduced to coat the cable core assembly. The
coated cable core is enclosed with an aluminum tape which is later
covered with waterproofing compound prior to a jacketing operation.
The process of covering the wrapped core is described in an
application Ser. No. 69,837 filed 9-4-70 in the name of L. D.
Moody. (See also U.S. Pat. No. 3,607,487 issued 9-21-71.)
Another method of cable filling is that shown in U.S. Pat. No.
1,681,566, in which successive sections of a cable are advanced
through two vacuum chambers to evacuate the interstices of the
loaded conductor. A filling chamber is connected to the downstream
end of the vacuum chambers to fill the interstices within the
cable. The compound could be maintained under pressure to force the
compound most effectively into the interstices of the cable.
Subsequently, a second compound chamber could apply a thin layer of
compound to the surface of the cable after which the cable is fed
directly into the core tube of an extrusion apparatus where a
covering of, say, gutta percha, is applied over the cable. The
compound is in a relatively fluid state with the pressures of
application of the compound and gutta percha equalized to prevent
deformation of the compound.
One prior art patent, U.S. Pat. No. 1,892,663, also shows methods
and apparatus for impregnating solid insulating material of cables
with an insulating fluid with the solid insulating material being
surrounded by a sheath of say, lead, for example. A portion of the
lead sheath is removed and a perforated or pemerable metallic
sheath is inserted in contact with the solid insulation and a
casing is applied to the cable to replace the removed portion of
the sheath and is arranged to leave a space between the inner
surface thereof and the outer surface. A pressure device is
connected to the casing for completing and/or maintaining the
impregnation of the cable by maintaining a predetermined pressure
within the cable and preventing the formation of ionizable
voids.
Viscous lubricants have also been incorporated into rope material
by methods such as that shown in U.S. Pat. No. 2,028,158. A
lubricant nozzle is positioned over the area of convergence of a
plurality of individual fibers with the strands being stranded
downstream of the nozzle. The lubricant is ejected under pressure
to form an annulus about the rope with the lubricant being forced
into the interstices between the individual fibers by a wiper.
Another method of lubricating wire rope is disclosed in U.S. Pat.
No. 2,195,461, in which the lubricant may be applied "cold".
Unheated lubricant is applied to individual fibers as the fibers
are advanced into a forming die. Once the lubricant has been
brought into contact with the moving wire, further movement of the
wires pulls the lubricant outward of the container thereof. The
flow continues as long as the individual fibers are advanced into
and through a forming die to assemble a rope.
In the prior art, methods of saturating fibrous coverings on wires
and cables are typified by that disclosed in U.S. Pat. No.
2,252,755 in which the covered wires or cables are advanced through
a tank of coating material. The coated wire is then pulled through
a chamber having orifices designed to increase the pressure in the
saturating material as the wire is drawn through the chamber to
force the saturating material into the pores or interstices of
fibrous covering on the wire or cable. The wire or cable is pulled
through a plurality of chambers each of which is partially closed
by orifices of form and size to create a pressure. Each successive
orifice is smaller than the previous one thereof to successively
squeeze back some of the saturating material. This builds up a
pressure in an enlarged chamber just upstream of each orifice to
move the material into the interstices of the wire covering. Relief
valves are provided to prevent the build-up of unduly high
pressures.
Another patent, U.S. Pat. No. 3,533,870, discloses methods of
fabricating a flexible impregnated glass fiber tether which
converges a plurality of filaments into a fixture charged with a
thermosetting resin followed by passing the bundle of resin coated
fibers into a vessel having facilities for removing air from the
resin and then through a die sized to generate a high pressure to
force the resin into the filament bundle. Then the bundle is passed
into an oven to decrease the viscosity of the resin and then
through a double vacuum to remove all volatiles in the air and then
through sealing and sizing dies.
In one prior art patent, U.S. Pat. No. 3,538,235, issued on Nov. 3,
1970, moisture prevention is sought by disposing a powder mixture
in the space between the wires of the core and is loosely packed
over the full length of the cable. The mixture is capable, on
contact with moisture, of rapidly swelling into a viscous material,
inhibiting axial penetration of moisture along the cable and also
capable after a longer period of time of expanding to many times
its axial volume on having an even higher viscosity than
before.
In U.S. Pat. No. 3,601,967 issued on Aug. 31, 1971, it is disclosed
that in the manufacture of plastic insulated multi-conductor cables
that are filled throughout with water impermerable filling
material, it has been considered necessary to transfer such
material from a storage vessel to the cable and to apply it to the
cable under super-atmospheric pressure by some form of pump. To
pump such material in a solid condition is difficult because of
almost inevitable cavitation and degradation of the material and
the lowering of the viscosity thereof thereby rendering it less
capable of forming a barrier permanently resistant to water under
pressure.
The aforementioned patent alleges that the degradation may be
reduced if pumping takes place while the material is at a
temperature just above the temperature at which crystallization
begins, i.e., just above that at which the sealing material is in a
sufficiently liquid state to permit pumping of the material to be
effected with substantially no degradation of the material
occurring.
There is shown a cable wire provided with sealing material which is
pumped to a feeding station and to the core while at the
recrystallization temperature. The material is cooled to effect
crystallization by abstractions of heat by the insulated conductors
of the core and cause the material to become solidified to form a
moisture barrier. The patent discloses that it is not necessary to
cool the sealing material while it is transferred from the cable
feeding station to the cable core.
The sealing material is applied through a die having three entry
ports which are distributed uniformly about the axis of the die and
which are inclined to impart to the liquified material a component
of movement in the same axial direction as the direction of travel
of the cable core being advanced through the die. Heating coils are
provided for use when the sealing material has been allowed to go
solid, as for example, when commencing circulation of the sealing
material in preparation for applying sealing material to a cable
core.
The sealing material is applied through a sealing die which is
detachably secured to the entry end of the closing die of a
stranding head, with another feeding station used where two or more
conductors may be brought together to form a core under which other
groups are laid up. Surplus material is allowed to fall into an
associated collecting tank to be reheated and recirculated.
The above described apparatus is used to fill each layer of a
layered cable with the compound being "bled" off a feeder line and
directed into a plurality of spaced applicator dies which are
positioned individually at each stranding head. At each stranding
head die, a "pool" of material is maintained to cover the strand or
layer with a volume flow applied thereto. There is no creation of a
definite positive pressure within the applicator facility, but
rather application by volume flow.
Moreover, the material is applied by the applicator dies through
angled ports so that there is a component of flow in the direction
of travel of the layered strands. As the layer is advanced, the
layer tends to pull the material from the angled ports to force the
material downwardly against the layer. Of course, the material must
only be pulled down one layer.
It is an object of this invention to provide methods of and
apparatus for pressure filling the interstices of a completed cable
core.
Also the above recently issued patent depends on the conductors to
act as a heat sink to cool the compound. This may be effective when
dealing with a single layer but may not be as effective when
filling a completed core.
It is also an object of this invention to provide methods and
apparatus for pressure filling the interstices of a cable core with
provisions for cooling the compound.
Since the waterproofing compound desirably replaces the air in the
interstitial structure of the cable core, the compound must have
excellent electrical properties so that the compound-filled cable
maintains transmission characteristics at least as good as those of
cables having an air-filled core and which use other techniques of
moisture exclusion. In addition, the compound must have excellent
resistance to flow at atmospheric temperature since portions of the
cable must be brought above ground for terminating purposes.
Further, the compound must possess low-temperature properties, such
as adhesion and resistance to cracking due to handling of the
cables in cold environments. The compound must not possess any
toxic properties which would be objectionable from the standpoint
of handling by installation personnel who may come into intimate
contact with the compound.
It has been found that a mixture of petrolatum and low-density
polyethylene in a precise blend satisfied the above-outlined
requirements. Facilities have been developed and are disclosed in
co-pending, commonly assigned application, Ser. No. 155,055, filed
June 21, 1971 in the names of E. L. Franke, Jr., W. J. Hyde and R.
G. Schneider, for overcoming problems and high costs encountered
when the petrolatum-polyethylene waterproofing compound was blended
at a distant location and transported to a core filling
station.
The above-identified application, Ser. No. 155,055, filed June 21,
1971, also discloses still other methods and apparatus for
manufacturing waterproof cable. Air is evacuated from the
interstitial structure of the core of a cable, a waterproof
compound in a workable state is deposited into the air-evacuated
voids of the cable core, and the waterproofing compound is placed
into a nonflowable state so that the deposited compound remains in
the voids of and on the surface of the cable core independently of
any other supporting structure to substantially preclude the entry
of moisture into the core. This process overcomes some of the prior
art difficulties in that the filling operation is accomplished
during the final sheathing operation which prevents air entrapment
that may occur if the core is filled during an earlier
manufacturing operation.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide new and
improved methods of manufacturing waterproof cable.
Another object of this invention is to provide improved methods of
injecting and depositing a preblended waterproofing compound into
the voids of the interstitial structure of a cable core.
A still further object of this invention is to provide methods of
depositing a waterproofing compound into the voids of the
interstitial structure of an axially moving stranded cable
core.
A method embodying certain principles of the invention may include
the steps of advancing successive sections of a cable core,
directing streams of the compound in a semifluid state generally
inwardly and then relatively longitudinally of the stranded cable
core to cause the compound to displace the air within the
interstices of the stranded core and conditioning the compound
associated with the stranded core to a consistency having a
viscosity sufficient to facilitate the retention of the compound
with the stranded core independently of any supporting
structure.
Other objects and advantages of the present invention will be
apparent from the following detailed description when considered in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing a portion of a communications
cable;
FIG. 2 is a sectional view of the communications cable showing
waterproofing compound located within the interstices of the core
as well as other portions of the cable;
FIG. 3 is a view in elevation showing an apparatus for directing
waterproofing compound into the core of a cable and embodying
certain principles of this invention;
FIG. 4 is a sectional view in plan view showing a typical end
portion of the apparatus of FIG. 3 which includes provisions for
cooling the waterproofing compound;
FIG. 5 is an end sectional view of the cooling chamber shown in
FIG. 4;
FIG. 6 is a detail view in elevation of a portion of the apparatus
showing a pressure filling chamber in which waterproofing compound
is directed into the interstices of the cable core;
FIG. 7 is a detailed view in perspective showing a pressure filling
device; and
FIG. 8 is an alternative embodiment of the pressure filling device
shown in FIG. 7.
DETAILED DESCRIPTION
Referring to FIG. 1, there is shown a length of a a communications
cable, designated generally by the numeral 11. The cable 11
includes a cable core, designated generally by the numeral 12, and
which is composed of a plurality of insulated conductors 13--13
which have been twisted into pairs and then stranded into cable
units. Colored binder ribbons 16--16 are wrapped about the cabled
units to provide a visual color code indication as to certain
characteristics of cable core 12. A core wrap 17, made from a
plastic thermal barrier and dielectric tape, is wrapped
longitudinally about the cable core 12. Then one form of moisture
protection, a corrugated aluminum shielding tape 18, is wrapped
longitudinally about the core wrap 17, to prevent the ingress of
moisture into the core and to provide a lightning shield for the
cable core. Finally, a jacket 19 of insulating material is extruded
over the corrugated aluminum shielding tape 18 to complete the
construction of the cable 11.
As can best be seen in FIG. 2, the twisted conductors 13--13 and
the stranded cable units 14--14 are constructed in a manner which
creates air voids in the form of interstices 21--21 in the cable
core 12. In order to reduce the probability of moisture diffusion
into and collection in the interstices 21 of the cable core 12, the
air voids of interstices are filled with a waterproofing jelly-like
compound comprised of a mixture of petrolatum and polyethylene. An
example of a range of proportions in ingredients of a waterproofing
compound which may be used includes a mixture of approximately 85
percent petrolatum and 15 percent low density polyethylene to a
mixture of 95 percent petrolatum and 5 percent low density
polyethylene.
In order to more fully provide optimum waterproof protection for
the cable 11, additional amounts of the waterproofing compound are
added to the cable. For example, waterproofing compound is applied
in a space 22 between the core wrap 17 and corrugated aluminum
shielding tape 18. Also, waterproofing compound is applied in a
space 23 between the outwardly facing surface of the corrugated
aluminum shielding tape 18 the extruded jacket 19, The so-called
filled cable 11, as shown in FIG. 2 has been found to be
substantially impervous to moisture. Adequate protection is thereby
against moisture degradation of the conductors 13--13 of the cable
11, and eliminates the problems experienced when moisture diffuses
into the cores of cables used in the communications industry.
The stranded structure of the cable core 12 is arranged with air
voids existing throughout the cross-sectional configuration of the
core. It should be obvious that difficulties may be encountered in
insuring that the air voids of the centermost ones of the
interstices 21--21 will be filled or will be filled with as much
waterproofing compound as the air voids of the outermost
interstices. In order to overcome this problem, methods or
apparatus were developed which facilitated the application of the
waterproofing compound to the cable core 12 in such a manner that
substantially all the voids of the interstices 21--21 of the core
are filled with the compound.
Referring now to FIG. 3, there is shown a compound applying
apparatus, designated generally by the numeral 40, for carrying out
the principles of the method of this invention for applying
waterproofing compound into the interstices 21--21 of the cable
core 12. The apparatus 40 includes a support frame 41 mounted on a
stationary floor 42. Moreover, the apparatus includes an upstream
cooling chamber, designated generally by the numberal 43, a
pressure relief chamber, designated generally by the numeral 44, a
pressure filling chamber, designated generally by the numeral 46,
and a second or downstream cooling chamber, designated generally by
the numeral 47, with successive sections of the cable core 12 being
advanced through the aforementioned chambers in seriatum with the
waterproofing compound being supplies to the pressure filling
chamber 46 by a supply system, designated generally by the numeral
48.
The construction details of the cooling chambers 43 and 47 can best
be seen by referring to FIG. 4. Although the upstream one 47 of the
cooling chambers is shown there, the construction of both is
identical.
As can best be seen in FIG. 4, the upstream cooling chamber 43
includes an outer tubular member 51 having a flanged internally
threaded end 52 and an opposite end 53. It must be appreciated that
in the upstream cooling chamber 43, the end 53 is positioned
upstream of the flanged end 52. The cooling chamber 43 also has an
internal sleeve 54 concentric and contiguous with the outer tubular
member 51 extending from the external face of the flanged end 52 to
an internal face of an internally threaded recess 56 formed at the
end 53.
As can best be seen in FIGS. 4 and 5, the sleeve 54 has a pair of
opposed baffle plates 57--57 extending radially inwardly toward a
longitudinal axis 58 of the apparatus 40. The baffle plates 57--57
are longitudinally extending the length of a passageway 59 enclosed
by the sleeve 54 and are adjacent to, but spaced slightly from the
outer circumferential surface of a longitudinally extending tube
61. The successive sections of the cable core 12 are advanced
through the end 53 into the cooling chamber 43 and through the
longitudinally extending tube 61.
The longitudinally extending tube 61 is formed with a flared
entrance portion 62 (see FIG. 4) which extends past a closed end 63
of the tube 61 at the flanged end 52 of the cooling chamber. The
tube 61 has a tapered transition section 64 at the other end of the
cooling chamber 43 connected to an entrance portion 66 having
uniform cross section and which opens to the recess 56. The section
66 is in abutting fixed engagement with the inwardly facing surface
of the inner sleeve 54. It should be observed from FIG. 4 that the
baffle plates 57--57 are formed with sloped edges adjacent the
tapered section 64 and spaced slightly therefrom. On the other
hand, the ends of the baffle plates 57--57 are spaced considerably
from the closed end 63. The construction of the baffle plates
57--57 with respect to the end portions of the cooling chamber 43
and the tube 61 is to effect a particular mode of cooling and
sealing of the apparatus 40. Finally, a flared entrance portion 67
is connected to and extends axially longitudinally from the tube 61
through the section 64 and the portion 66.
It should be observed that the unitary construction of the sleeve
54 and tube 61 and the assembly thereof with the outer tubular
member 51 permits the interchangeability of tubes to accommodate
different size cores 12--12. The tube 61 may be conveniently slid
longitudinally and replaced with a tube of the required
diameter.
In order to complete the construction of the subassembly cooling
chamber 43, an insert 68 includes a knurled threaded end 69 and
having an externally threaded boss 71 extending therefrom. The
insert 68 has a bore 72 formed therethrough concentric with the
flared entrance portion 67 and with the axis of the bore 59 and
connected to the inwardly facing surface of the insert. The insert
68 is designed so that the longitudinal axis thereof is aligned
with the longitudinal axis 58 of the tube 61.
In order to cool the successive sections of the cable core 12 which
are advanced through the cooling chambers 43 and 47, water is
introduced through inlet tubes 73 and 74, respectively, (see FIG.
3) into the portion of the chamber between the inwardly facing
surface of the sleeve 54 and the outwardly facing surface of the
tube 61. The water is circulated through the cooling chambers 43
and 48 and then removed therefrom through outlet tubes 76 and 77
for return to a pump and chilling apparatus (not shown) for
subsequent cooling. The chilled water which is supplied to the
cooling chambers 43--43 is at a temperature of approximately
55.degree.F which is sufficient to remove heat from the successive
sections of the cable core 12 being advanced through the tube
61.
Successive sections of the cable core 12 which have been advanced
through the upstream one 43 of the cooling chambers 43 and 47 are
then moved into a pressure relief chamber 44 connected to the
downstream end of the upstream one of the cooling chambers. The
pressure relief section 44 includes a housing 81 having a bore 82
formed therethrough with an upstream end of the housing having a
reduced diameter externally threaded portion 80 (see FIG. 6) to be
attached threadably with the internally threaded flanged end 52 of
the upstream one 43 of the cooling sections 43 and 48. A die 83
having an opening 84 therethrough is positioned within the upstream
end of the bore 82. The downstream end of the housing 81 includes
an internally threaded portion 86 with a die 87 having an opening
88 and positioned just upstream of the internally threaded portion.
The die 83 and the die 87 are connected by longitudinal rods
89--89.
The dies 83 and 87 are formed with the central openings 84 and 88,
respectively, concentrically disposed within the housing 81 to
provide movement axially therethrough of the successive sections of
the cable core 12. It should be appreciated that different size
cable cores 12--12 must be accommodated by the apparatus 40.
Accordingly, the dies 83 and 87 are mounted in the housing 81 to
permit removal thereof and replacement at selected periods with
dies to accommodate different size cable cores 12--12. For example,
the cable core 12 could include 25, 50, 200 or 200 twisted pairs of
conductors 13--13. Of course, the external diameter of the dies 83
and 87 remain the same to permit insertion and mounting within the
upstream and downstream ends of the housing 81.
The pressure relief section 44 also includes a drain line 85 having
an adjustable relief valve 90 for regulating the pressure in the
pressure filling chamber 46. Another function of the drain line 85
and pressure relief valve 90 is to establish together with the
pressure filling facilities a continuous flow of waterproofing
compound in a direction opposite to that of the travel of the core
12. The axial longitudinal flow of the compound has been found to
be effective to insure a more complete penetration of the core 12
than had heretofore been achieved.
After the successive sections of the cable core 12 are advanced
through the pressure relief section 44, successive sections of the
cable core are moved into and through the pressure filling chamber
46. The pressure filling chamber 46 includes an outer tubular
member 91 having an externally threaded upstream end 92 onto which
is turned the internally threaded end 86 of the pressure relief
section 44 during the assembly of the apparatus 40. The pressure
filling chamber 46 is provided with at least one, and preferably
three, filling devices, designated generally by the numeral
93--93.
The filling devices 93--93 are mounted within the tubular member 91
and are spaced longitudinally along the axis thereof with spacers
94--94 being interposed therebetween. As can best be seen in FIG.
7, each of the filling devices 93--93 includes a pair of spaced
flanges 94 and 96 connected by a sleeve 97. The outside diameter of
the flanges 94 and 96 is designed to mate with the inwardly facing
surface of the tubular member 91. The internal diameter of the
sleeve 97 is designed to accommodate a particular size cable by
having an anticipated number of twisted pairs of conductors 13--13.
Provisions are made for removing the pressure filling devices
93--93 to provide interchangeability with others required to
accommodate different size cable cores. In the alternative, the
internal diameter of the sleeve 97 may be designed to accommodate
the largest anticipated core size thereby eliminating the necessity
of changing the filling devices 93--93 for each size core being
processed. The filling device 93 also includes a plurality of
openings 98--98 for directing the waterproofing compound into
engagement with the successive sections of the cable core 12 being
advanced through the sleeve 97.
As can best be seen in FIG. 6, the pressure filling devices 93--93
are positioned within the tubular member 91 so that the annular
space between the flanges 94 and 96 of each is aligned with a
feeder pipe 99 extending through an opening 101 in the tubular
member. The feeder pipes 99--99 include shut-off valves 102--102
and are designed to convey waterproofing compound from a supply
manifold 103 to the filling devices 93--93.
Referring now to FIGS. 3 and 6, it can be seen that the supply
system 48 for supplying waterproofing compound to the pressure
filling compound chamber 46 includes a central supply 104 which is
connected along a conduit 106 to a first pump 107 and then along a
conduit 108 to a central pumping system 109 and from there along a
conduit 111 to supply conduit 112. The supply conduit 112 extends
through an opening 113 in the end 114 of the supply manifold 103
and terminates at the other end thereof. A threaded thermocouple
116 is turned threadably through a threaded opening 117 formed in
the end of the supply manifold 103. The thermocouple 116 is
utilized to monitor and/or regulate the temperature of the supply
compound.
The supply conduit 112 includes a plurality of openings 118 formed
along a length therof which is positioned within a passage 119 of
the supply manifold. Moreover, the supply 103 is provided with a
plurality of portable strip heaters 121--121 which may be used to
maintain the temperature of a particular composition waterproofing
compound to a predetermined temperature which has been found to be
advantageous to the filling process. A plurality of strip heaters
122--122 are also spaced along and connected to the outside surface
of the tube 91 as shown in FIG. 6.
Referring now to FIG. 6, the downstream end of the tube 91 has an
externally threaded section 123 for receiving an internally
threaded end 124 of an extension section 126 of the cooling chamber
46. The section 126 is aligned concentrically with the tube 91 and
the longitudinal axis 58 of the apparatus 40. The extension 126
also includes a sleeve 127 concentrically disposed within a bore
128 formed within the extension section. Of course, the section 126
need not be a separate element but could just as well have been
constructed as an integral continuation of the tubular member 91. A
pressure gauge 129 is connected into an opening 131 through the
section 126 and the sleeve 127 to communicate with the sleeve
passage to indicate to an operator the pressure therewithin.
A die 132 having an opening 133 designed to accommodate a
particular core 12 having a predetermined number of twisted
conductors 13--13 is mounted within the downstream end of the
extension 126 and is designed to engage with the flared entrance 62
of the downstream one of the cooling chambers 43 and 47 (see FIG.
5). Also, the die insert 132 is adapted to be removed and
interchangeable with other dies having varying openings 133--133 to
accommodate different size cable cores 12--12. Of course, the dies
132--132 are constructed with the same outside diameter to permit
reception within the bore 128.
As can best be seen in FIG. 6, the extension 126 has an externally
threaded end 134 for reception within the internally threaded
opening of the flanged end 52 of the cooling chamber 47. When the
downstream one 47 of the cooling chambers 43 and 47 is connected to
the downstream end of the extension section 126, the flared end 62
of the tube 61 engages the die.
The construction of the cooling chambers 43 and 47 prevents the
cooling medium from escaping therefrom. As can be seen in FIG. 4,
the flared end portion 62 and the entrance portions 66 are
connected to the sleeve 54. As cooling medium flows into the inlet
tube 73 and say upstream in the cooling chamber 47, the portion of
the cooling medium which does not trickle downwardly by gravity
past the baffle plates 57--57 into the lower portion of the chamber
is contained by the end member or closure plate 63 from moving
further upstream and contaminating the waterproofing compound. The
opening between the closure plate 63 and the baffle plates 57--57
permits the bulk of the cooling medium to enter the lower portion
of the cooling chamber 47. Similarly, at the downstream end of the
chamber 47, the connection of the portion 66 to the sleeve presents
escape of the cooling medium.
ALTERNATIVE EMBODIMENT
It has been found that improvements may be made in the pressure
filling device 93. For example, as shown in FIG. 8, an improved
pressure filling device 140 may include a cylindrical portion 141
having an outside diameter approximately equivalent to the internal
diameter to the tube 91 with a plurality of the devices arranged in
tandem within the tube and maintained in a spaced relationship by
the spacers 94--94 interposed therebetween.
The improved pressure filling device 140 has a passageway 142
formed therethrough, through which successive sections of the cable
core 12 are advanced. Moreover, the cylindrical portion 141
includes a raceway 143 formed helically thereabout with a plurality
of openings 144--144 communicating the raceway with the passageway
142. In this way, the waterproofing compound is moved, for example,
through the openings 101--101 which are aligned with an upstream
portion of the raceway 143 of an associated one of pressure filling
devices 140--140. The compound under pressure of approximately 50
psi is urged along the raceway helically about the cylindrical
portion 14 in a downstream direction and through successive ones of
the openings 144--144 into engagement with the advancing cable core
12.
It is believed this arrangement of the openings in seriatum rather
than in an opposed radial relationship may more completely fill the
interstices of the advancing cable core 12.
Operation
Referring now to FIGS. 3 and 6, successive sections of the cable
core 12 are moved axially from a supply stand (not shown) or from
other apparatus of a tandem line and through the in-line elements
of the compound applying apparatus 40. The successive sections of
the cable core 12 are advanced through the bore 72 of the insert 68
and into the flared opening 67 of the first cooling chamber 43.
Because of the essentially close openings of the flared entrance 67
(see FIG. 4), the flared entrance forms an essentially air-tight
entry for the cable core 12 into the compound applying apparatus
40. Thereafter, the successive sections of the cable core 12 are
advanced into and through the tube 61 of the cooling chamber
43.
Chilled water is pumped from the pumping system (not shown) into
the water inlet tubes 73 and 74 and into a topmost portion of the
chamber 43 between the tube 61 and the sleeve 54. The water under
pressure moves in a downstream direction in the cooling chamber 43
simultaneously having portions thereof trickle through the space
between the baffle plates 57--57 and the tube 61 to fill the lower
portion of the chamber. The bulk of the water is moved within the
upper portion of the chamber toward the downstream end thereof and
flows between the closed end 63 and the end portions of the baffle
plates 57--57 upstream of the flared end 62 of the tube 61 and into
the lower chamber. The water in the lower portion of the chamber is
evacuated therefrom through the water outlet tubes 76 and 77 for
recirculation to chilling apparatus and subsequent
redistribution.
Simultaneously, the water in the downstream cooling chamber moves
upstream with portions thereof trickling between the baffle plates
57--57 and the tube 61 to drop into the lower portion of the
cooling chamber. The majority of the water descends into the lower
portion of the chamber at the upstream end of the cooling chamber
43 between the end of the sleeve 54 and the flared entrance portion
62.
Successive sections of the cable core 12 are then moved into and
through the pressure relief section 44 of the apparatus 40 with the
cable core 12 first engaging with the walls of the die 83 and then
with the walls of the die opening 88.
Subsequently, the successive sections of the cable core 12 are
moved into and then into the compound filling chamber 46 and
successively through each one of the pressure filling devices
93--93 or 140--140, in the alternative. The waterproofing compound
is pumped from the supply 104 along the lines 106 and 108 and the
line 111 into the supply conduit 112. From there, the waterproofing
compound is urged through the openings 118--118 into the passage
119 of the supply manifold 103. The heaters 121--121 are rendered
effective to maintain the waterproofing compound to a particular
temperature composition so that compound may more appropriately
fill the interstices 21--21 of the cable core 12. The waterproofing
compound is moved from the supply manifold 103 through the the
feeder pipes 99--99.
Waterproofing compound at a pressure of approximately 50 pounds per
square inch is then moved through the openings 101--101 in the wall
of the tube 91 and into the annular space formed between the
flanges 94 and 96 of the associated pressure filling device 93.
From there, the waterproofing compound is urged through the
openings 98--98 and radially inward into engagement with the core
12. As the heated waterproofing compound is continually moved into
engagement with the outer ones of the insulated conductors 13--13,
the waterproofing compound is moved inwardly of the cable core 12
to displace the air from and to fill the interstices 21--21.
The pressure within the filling chamber 46 causes the waterproofing
compound to be urged axially longitudinally of the chamber in an
upstream direction toward the pressure relief chamber 44. In the
upstream direction, the waterproofing compound is squeezed past the
die opening 88 and into the pressure relief chamber 44. Any of the
waterproofing compound which has passed or moved into the pressure
relief chamber 44 passes into the discharge pipe 85 to be returned
to the central pumping system 109 for recirculation to the supply
manifold 103.
It should be observed that even though the cable core 12 may be
very close fitting within the die opening 88, that some of the
waterproofing compound may be urged axially longitudinally within
the interstices of the core itself so that to find a path into the
pressure relief chamber for discharge into the recirculated system.
This is extremely important in being able to fill the interstices
of the cable core 12. A flow path of the compound is established to
more positively direct the compound to be moved internally through
the plural core units or layers to insure a complete filling. A
combination of the velocity of the compound and the pressure has
been found adequate to fill the very largest cores
manufactured.
In order to prevent the waterproofing compound from moving still
further in an upstream direction, the apparatus 40 incorporates the
upstream one 43 of the cooling chambers 43 and 47. The operation of
the cooling chamber 43 is closely allied to the character of the
compound which is that the compound becomes very viscous at lower
temperatures. The compound cools and tends to be self-sealing at
temperatures such as those of the chilled water which is supplied
to the cooling chambers 43 and 47. Consequently, any of the
waterproofing compound which is urged within the interstices 21--21
of the cable core 12 in an upstream direction from the pressure
relief section 44 tends to become very viscous and self-sealing to
prevent a mass exodus of waterproofing compound into the cooling
chamber 43. This, in effect, tends to stabilize the system and
maintain the flow of the waterproofing compound only so far as the
pressure relief chamber 44 from where the compound is pulled into
the conduit 85 by the pump 109.
Similarly, in the downstream direction, the construction of the
apparatus 40 tends to inhibit the disassociation of the compound
from the core 12 beyond the insert 68 of the cooling chamber 47.
The die 132 sizes the layer of waterproofing compound on the
surface of the core 12. Then the temperature of the waterproofing
compound both within and on the surface of the core 12 is rendered
viscous by the advance of the successive sections of the cable core
through the cooling chamber 47. The waterproofing compound is
rendered non-flowable and is retained within the interstices of the
core 12 independently of any other supporting structure.
The cable core 12 which now includes the waterproofing compound
essentially filling the interstices thereof is then advanced
through a series of operations in which the core wrap 17 is wrapped
longitudinally about the cable core. Then additional amounts of the
waterproofing compound may be applied to the cable core 12 after
which a band or ribbon is wrapped helically about the core wrap.
Subsequently, corrugated aluminum shielding tape 18 is wrapped
longitudinally about the core wrap.
As the corrugated aluminum shielding tape 18 is being formed for
subsequent longitudinal wrapping about the cable core 12 and the
core wrap 17, the cable core and the core wrap may be passed
through a mandrel into which is injected additional amounts of the
waterproofing compound immediately prior to the longitudinal
forming of the aluminum shielding tape 18 about the core wrap. This
feature of the operation is disclosed in a co-pending application,
Ser. No. 69,837, filed in the name of L. D. Moody on Sept. 4,
1970.
Thereafter, cable core 12 having the core wrap 17 and the
corrugated aluminum shielding tape 18 wrapped thereabout is passed
through a path (not shown) of the waterproofing compound so that
the compound fills essentially the valleys of the corrugations of
the shielding tape. The cable core 12 with the core wrap 17 and the
aluminum shielding tape 18 is then passed through an extruder head
(not shown) where the polyethylene jacket 19 is applied. The
jacketed product is then passed through a cooling trough (not
shown) and on to a take-up reel (not shown).
The waterproofing compound may be prepared in a compound
preparation area with facilities which are described in co-pending
application, Ser. No. 155,055, filed in the names of E. L. Franke,
Jr., W. J. Hyde and R. G. Schneider on June 21, 1971.
The waterproofing compound is generally heated by the strip heaters
121--121 and the strip heaters 122--122 to a temperature of
approximately 200.degree.F. This temperature has been found to be
adequate to render the waterproofing compound semifluid and of a
consistency sufficiently viscous to fill the interstices 21--21 of
the cable core 12.
Although the hereinbefore described apparatus 40 included
facilities for heating the waterproofing compound, it is within the
scope of this invention to fill the interstices 21--21 of the cable
core 12 with a compound at an ambient temperature of approximately
75.degree.F. In those instances a different composition compound
may be used with the apparatus 40 and with the strip heaters 121
and 122 not being used. Also, when using waterproofing compound at
an ambient temperature especially with the larger size cable cores,
it may be necessary to use an injection pressure in the range of
100 to 150 psi. For smaller size cables, pressure of approximately
50 psi is acceptable with the compound applied at an ambient
temperature.
Should it be decided to waterproof a particular cable core 12 with
waterproofing compound at ambient temperature, the cooling chambers
43 and 47 need not be rendered effective. Therefore, valves (not
shown) may be operated to discontinue the supply of chilled water
to the cooling chambers 43 and 47.
Moreover, the flow path of the waterproofing compound which is
established subsequent to the directing of the streams of compound
into the pressure filling chamber 46 may be varied depending upon
such variables as the composition of the compound used and pair
size of the cable cores. For example, it would be within the scope
of this invention to have the waterproofing compound moved
relatively longitudinally in a downstream direction with the
advancing cable core 12 as opposed to movement in an upstream
direction as described hereinbefore. In that event, provisions must
be made, say in the extension section 126 for pulling the compound
from the pressure filling devices 93-93 in a downstream direction,
i.e., the same direction as the path of travel of the cable core
12, to establish a flow path of the compound to more completely
fill the interstices 21--21.
It is to be understood that the above-described arrangements are
simply illustrative of the invention. Other arrangements may be
devised by those skilled in the art which will embody the
principles of the invention and fall within the spirit and scope
thereof.
* * * * *