Method and apparatus for installation of cables by blowing and using an upstream lubricator

Abstract

A method of installing a cable through a duct by blowing the cable with a stream of compressed air. The method comprises dispersing a nebulized lubricant in the stream of compressed air, causing the stream of compressed air to deposit the nebulized lubricant onto the cable and to blow it into the duct. An apparatus for carrying out the method is also disclosed.

Claims

1. A method of installing a cable through a duct, the method comprising: dispersing, using a lubricator, a nebulized lubricant into a stream of compressed air; and blowing, using a cable blowing head, the cable into the duct with the stream of compressed air containing the nebulized lubricant, the blowing causing the stream of compressed air to deposit the nebulized lubricant onto the cable, wherein the cable blowing head includes a compressed air inlet that receives the stream of compressed air and a cable inlet that receives the cable, the cable inlet separate from the compressed air inlet; and wherein the lubricator is arranged upstream with respect to the compressed air inlet.

2. The method of claim 1, wherein the duct already contains at least one further cable.

3. The method of claim 1, further comprising providing an opening in the duct and blowing the cable into the duct through said opening.

4. The method of claim 1, wherein the lubricant is or includes an aqueous emulsion of silicone.

5. An apparatus for installing a cable into a duct by blowing the cable with a stream of compressed air, the apparatus comprising: a cable blowing head having a compressed air inlet for receiving the stream of compressed air, a cable inlet separate from the compressed air inlet and for receiving the cable to be installed and a cable outlet for delivering the cable blown by the stream of compressed air; and upstream with respect to the compressed air inlet, a lubricator configured to disperse into the stream of compressed air a nebulized lubricant substance.

6. The apparatus of claim 5, wherein the lubricator includes a fogger.

7. The apparatus of claim 5, wherein the lubricator is a micro-fog lubricator.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) These and other features and advantages of the method and apparatus according to the present disclosure will be made apparent by the following detailed description of embodiments thereof, provided merely by of non-limitative examples, which should be read by referring to the attached drawings for better intelligibility.

(2) In the drawings:

(3) FIG. 1 schematically depicts an application scenario of using embodiments of the methods and apparatuses of the present disclosure;

(4) FIG. 2 depicts in greater detail a “Y” coupler used in the scenario of FIG. 1;

(5) FIG. 3 depicts in cross-section a micro-fog lubricator which can be used in embodiments of the method and apparatus of the present disclosure, and

(6) FIG. 4 schematically depicts another application scenario of using embodiments of the methods and apparatuses of the present disclosure.

DETAILED DESCRIPTION EXAMPLE

(7) Referring to FIG. 1, there is schematically depicted a scenario of use of an embodiment of the method and apparatus of the present disclosure.

(8) A duct 105 for optical cables is assumed to be already deployed. In the considered example, the duct 105 is deployed underground, buried under the ground surface 110.

(9) The duct 105 may contain one or more optical cables (thus the installation of a further or an additional cable is by overblowing), or may be empty (thus the installation of a cable is by blowing). In the considered example (as shown in the detail A in FIG. 1, where a part of duct 105 is shown with an exploded view), the duct 105 already contains an optical legacy cable 107, thus it is an example of installation by overblowing. For example, the duct 105 can be a duct of 20 mm of internal diameter, and the optical cable 107 can have a diameter of 13 mm.

(10) An (additional) optical cable 127 is inserted into the duct 105 at a position P and run through the duct 105 along with the legacy cable 107 (as shown in the detail B in FIG. 1, where, similarly to detail A, a part of the duct 105 is shown with an exploded view). For example, the optical cable 127 to be inserted into the duct 105 can have a diameter smaller than that of the cable 107, e.g., a diameter of 5 mm.

(11) In a hand-hole or manhole 115, a “Y” coupler 120 is installed. The “Y” coupler 120, also known as “Y” connector, is a device employed for increasing the number of fiber cables in a duct like duct 105.

(12) An example “Y” coupler 120 for blow cable installation is shown in FIG. 2. The “Y” coupler 120 has a duct inlet 205, a duct outlet 210, a cable inlet 215 and a compressed air inlet 220.

(13) Referring back to FIG. 1, an end 206 of the section of the duct 105 downstream the manhole 115 where the “Y” coupler 120 is installed (i.e., on the left looking at FIG. 1) is inserted into the duct inlet 205. An end 211 of the section of the duct 105 upstream the manhole 115 is inserted into the duct outlet 210. An arrow 106 indicates the downstream direction. An end 126 of a duct (mini-duct) 125 containing the new cable 127 to be installed in the duct 105 enters the “Y” coupler 120 at the cable inlet 215. An end 131 (delivering outlet) of a hose 130 conveying compressed air is connected to the compressed air inlet 220 of the “Y” coupler 120.

(14) The hose 130 has an opposite end 133 connected to a source of compressed air, for example a compressor 135.

(15) The mini-duct 125 containing the new cable 127 to be installed has an end 129 opposite to the end 126 that is connected to cable inlet 215. The end 129 is connected to a cable blowing head (or launching unit or blowing apparatus) 140, e.g., set up close to the manhole 115. The blowing head 140 receives the new cable 127 to be blown into the duct 105 from a cable drum 150 where a supply of new optical cable is wound. A cable straightener can optionally be provided between the cable drum 150 and the blowing head 140 to straighten the cable 127 entering the blowing head 140. The blowing head 140 is fed with compressed air by the compressed air source, e.g., compressor 135 via a compressed air feed hose 155.

(16) The blowing head 140 can be a combination pushing and blowing cable insertion equipment, of the type described for example in U.S. Pat. No. 4,850,569.

(17) Along the compressed air feed hose 155, e.g., at or close to a compressed air inlet 160 of the blowing head 140, a lubricator (or lubricant feeding device) 165 is provided.

(18) The lubricator 165 is a device configured to spray, nebulize or atomize a suitable lubricant so as to create a fog or mist of small airborne lubricant droplets that are injected into the stream of compressed air delivered through the hose 155. In this way, the compressed air used by the blowing head 140 to blow the cable 127 is loaded with tiny droplets of lubricant, which form a nebulized or fog of lubricant. When compressed air containing the fog of lubricant meets the cable 127, the cable 127 is lubricated by droplets of lubricant depositing onto the sheath of the cable 127.

(19) In an embodiment, the lubricator 165 can be a lubricating assembly that may include a reservoir holding a supply of a lubricant, for example in the liquid state, and a fog generator, as it will be shown in detail in FIG. 3. The lubricator 165 atomizes a liquid lubricant to create a fog or mist of small airborne lubricant droplets that are then dispersed in the compressed air flow.

(20) Any lubricator suitable to atomize a liquid lubricant to fine particles can be used according to the present disclosure.

(21) For example, in some embodiments, the lubricator 165 is or includes a fogger or a micro-fog lubricator. An example of a micro-fog lubricator is shown in FIG. 3, where it is globally designated as 300. In some embodiments, a micro-fog lubricator produces a fine mist or fog of oil (of micrometric size) and introduces this mist or fog into the system, which in this context is the flow of compressed air supplied to the blowing head 140. This mist or fog can travel long distances (up to about 15 meters) in piping, even with numerous bends and fittings before it reclassifies (i.e., before the droplets grows in dimension).

(22) The micro-fog lubricator 300 injects a finely divided “fog” of lubricant into the flowing stream of compressed air supplied by the compressor 135 to the blowing head 140, so as to load the compressed air with nebulized lubricant. The density of the fog or mist is controlled by a drip rate adjusting knob 305: for example, counterclockwise rotation increases and clockwise rotation decreases the fog density.

(23) The lubricant is metered into the air line only when there is a flow of air through the lubricator 165, 300. A small portion of the air flowing through the lubricator 165, 300 is diverted through the fog generator 310 into a reservoir 315. The major portion of the air passes around a flow sensor 320 to the downstream system (i.e., to the blowing head 140).

(24) The high velocity air flowing through the fog generator 310 aspirates air from a sight-feed dome 325, creating a low-pressure area. Lubricant in the reservoir 315 is drawn upward through a siphon tube 330 into the sight-feed dome 325 where it drips into the fog generator 310. The adjusting knob 305 controls the drip rate. The lubricant drops are atomized by the high velocity air flow through the air jets in the fog generator 310, creating a high concentration of fine lubricant aerosols (fog) in the upper part of the reservoir 315.

(25) The larger drops settle out into the reservoir 315. The smaller drops remain airborne and are carried through a passage 335 into the downstream air line 155 and then to the compressed air inlet 160 of the blowing head 140. A check ball 340 prevents loss of prime during periods of no flow.

(26) The flow sensor 320 functions as a variable restriction in the lubricator's throat. It produces a pressure drop between inlet and outlet that is proportional to the air flow through the lubricator 165, 300. These variations in outlet pressure, sensed in the lubricator reservoir 315, cause a proportional change in the velocity of the air flowing through the venturi of the fog generator 310. The change in air velocity results in a proportional change in the amount of lubricant drawn across a metering orifice 345.

(27) In an embodiment, a micro-fog lubricator like the example micro-fog lubricator 300 can be inserted in line along the compressed air feed line (like the hose 155).

(28) Various lubricants are available from commercial sources and can be used for cable lubrication purposes. An aqueous emulsion of silicone is a suitable lubricant.

(29) Using a micro-fog lubricator like the micro-fog lubricator 300, a lubrication rate of approximately 25 drops/minute ensures that the stream of compressed air is loaded with a sufficiently dense lubricant fog.

(30) The method and apparatus of the present disclosure can be advantageously used for the overblown installation of a small (e.g., 5.0 mm) outer diameter cable into a sub-duct (e.g., of 20 mm internal diameter) that already contains a legacy cable (e.g., a cable of 13 mm of outer diameter). Installing a small outer diameter cable into a sub-duct that already contains a legacy cable has recently become of great interest to network providers. The main issue with this process is that the lack of lubrication on the legacy cable already installed in the sub-duct reduces the maximum installation distance. Up to now, in order to overcome this problem, a large quantity of lubricant is poured into the sub-duct in hopes that when the compressed air is introduced into the sub-duct the lubricant is distributed through the route, typically up to 700 m.

(31) It is not possible to blow a sponge through the sub-duct containing the legacy cable, because the sponge can become trapped between the cable and sub-duct in correspondence of bends.

(32) The method and apparatus of the present disclosure offer a cost-effective approach, by injecting lubricant into the compressed air stream prior to the blowing head. The lubricant, in the form of a mist or fog, lubricates the cable sheath within the blowing head and as it passes along the moving cable within the mini-duct.

(33) The method and apparatus of the present disclosure can also be used for conventional blown cable installation where a cable is installed into an empty duct (sub-duct or mini-duct), or, alternatively, an optical cable contained in a mini-duct is directly buried, as depicted in FIG. 4. In this installation, no Y coupler 120 is present and no hose 130 is provided, while the cable 127 is blown into the duct (e.g., mini-duct) 125 directly by the blowing head 140.

(34) The method and apparatus of the present disclosure is applicable for blowing cables in mini-ducts (having an outer diameter of about 8-16 mm vs the sub-duct outer diameter of about 20-50 mm) and/or for long distance (up to 3,000 m for blowing and up to 1,200 m for overblowing).

(35) The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

(36) These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.