GB1566058A

GB1566058A - Powder filling of cables

Info

Publication number: GB1566058A
Application number: GB7877/77A
Authority: GB
Original assignee: Northern Telecom Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1976-03-31
Filing date: 1977-02-24
Publication date: 1980-04-30
Also published as: SE7703061L; DE2712820A1; BR7701996A; ES457347A1; JPS52118580A; IT1076636B; BE853133A; DK125877A; FI770975A; NL7703081A; FR2360966A1; NO771112L

Description

(54) POWDER FILLING OF CABLES (71) We, NORTHERN TELECOM LIMITED, a Canadian company of 1600 Dorchester Boulevard, West, Montreal, Quebec, Canada H3H lRl do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the production of powder filled electric cables.

To protect multi-stranded, sheathed electric cables against the entry and migration of water it has normally been the practice to fill the voids within the sheath by coating the conductors with petroleum jelly. Because this method is slow and expensive and the product is greasy, it has recently been the practice to use powder for filling the interstices between the conductors, as described in British Patent No. 1,535,840. One method of applying the powder to the cable core is to pass the wire conductors through an electrostatic powder coating bed before stranding but that method is slow and cannot meet the normal stranding speed of the cable.

The invention consists of a method of continuously producing an electric cable containing powder, comprising passing one or more elongate components of the cable within a closed chamber, continuously contacting the cable components with powder by recirculating into the path of said components powder which has settled in the chamber, measuring a variable which depends on the quantity of powder in the chamber, and introducing additional powder into the chamber in a controlled manner in response to the value of the measured variable so as to maintain a desired quantity of powder in the chamber.Preferably, the cable has a plurality of conductors forming a stranded core enclosed in a sheath or jacket, the voids within the sheath or jacket being at least partially filled with powder, and the conductors are passed in spaced lateral relationship through the closed chamber and then brought together.

Preferably the strands are oil coated prior to their entry into the chamber and the powder is blown into the chamber to impinge directly on the strands. The method may alternatively comprise powder filling the space between the inner and outer sheaths of a multi-sheathed cable.

In another aspect the invention consists of apparatus for continuously producing an electric cable containing powder, comprising a closed chamber, means for passing one or more elongate components of the cable within said chamber, means for continuously contacting the cable components with powder by recirculating into the path of said components powder which has settled in the chamber, means for measuring a variable which depends on the quantity of powder in the chamber, and means for introducing additional powder into the chamber in a controlled manner in response to the value of the measured variable so as to maintain a desired quantity of powder in the chamber. The apparatus may be used to provide a powder filling between the inner and outer sheaths of an electric cable or for at least partially filling the voids in a cable having a plurality of conductors forming a stranded core.

An example embodiment of the invention is shown in the accompanying drawings in which: Figure 1 is a plan view in cross-section showing an apparatus for powder filling a multi-stranded, sheathed electric cable, Figure 2 is a sectional view in elevation taken along line 2-2 of Figure 1.

The example apparatus illustrated in the drawings consists of a housing 10 providing a closed rectangular chamber 12 and having a top 14, opposed side walls 16, opposed end walls 1 8a and 1 8b, and a bot tom trough 20 of semi-cylindrical shape. A first screw conveyer 22 is located coaxially in trough 20 and is journally mounted in end walls 18 of housing 10. A layplate 24 is located in one end wall 18a of housing 10 adjacent top 14 and a closing die 26 is located in the opposite end wall 1 8b in axial alignment with layplate 24. Below layplate 24 the outlet 27 of an upstanding blower chute 28 projects through end wall 1 8a into chamber 12.

The central shaft 29 of first conveyor 22 carries at its ends a pair of pulleys 30 which are connected by belts 32 to a common shaft 34 journalled in mounts 36 outside housing 10. One pulley 30a is coupled with a drive motor 38 axially aligned with shaft 29 of first conveyor 22. Shaft 29 of first conveyor 22 also carries an impeller 40 located in main chamber 41 of blower chute 28 outside housing 10. Trough 20 is connected to chamber 41 of chute 28 through an opening 42 in end wall 18a of housing 10.

A hopper 43 abuts one side wall 16a of housing 10 with a semi-cylindrical bottom trough 44 in which a second journally mounted screw conveyor 46 is coaxially located. One end of second conveyor 46 terminates at an opening 48 in side wall 16 of housing 10 and the other end of the second conveyor is axially coupled with a drive motor 50.

In the operation of the example embodiment conductors 60 pass through layplate 24 into chamber 12 of housing 10 in spaced laterial relationship, horizontally traversing upper zone 62 of the chamber and at the same time converging to pass through closing die 26, whence they emerge from chamber 12 as a cable core 64 in known manner.

Hopper 43 is charged with powder which is moved by second conveyor 46 through opening 48 to drop into trough 20 at the bottom of chamber 12. First conveyor 22 then moves the powder through opening 41 in end wall 18 of housing 10 into chamber 42 of chute 28 where it is forced upwardly by impeller 40 and through outlet 27 into zone 62 of chamber 12.

The outlet opening of chute 28 is designed and oriented to direct the powder into the upper portion of chamber 12 at a velocity sufficient to produce a cloud of the material in zone 62 of the chamber in the path of strands 60. Preferably the powder is directed by chute 28 to form a cloud in the path of the conductors 60. To improve the adhesion of the powder to conductors 60, the conductors are usually lightly coated with oil by suitable means not shown. Another method of causing the powder to adhere to conductors 60 is to locate a high voltage electrode at the exit to chute 28 which imparts an electrical charge to the powder as in electrostatic powder coating.

Excess powder drops back into trough 20 of chamber 12 where it is recirculated by conveyor 22 through chute 28 into upper zone 62 of the chamber. As the powder recirculating through chamber 12 is depleted the chamber is recharged from hopper 42 by further conveyor 46. Any suitable means can be employed to recharge chamber 12 automatically. For example by governing the speed of motor 50 inversely proportional to the torque on motor 38 a decrease in torque on conveyor 22 caused by depletion of powder in trough 20 will cause further conveyor 46 to speed up which will discharge powder more rapidly into chamber 12. The electrical connections for establishing such a relationship between motors 38 and 50 are well known. Hopper 42 can be charged periodically by any suitable means either manual or automatic.Other devices such as probe sensors could also be used to measure powder flow rate through the system to govern the speed of motor 50. Of course other suitable means could be employed to feed additional powder to trough 20 in chamber 12. For example first conveyor 22 could be extended from chamber 12 outwardly through end wall 1 8b into a bin similar to hopper 43.

It will be appreciated that the electrical cable may be only partially filled with powder for effective water blockage, as described in above-mentioned U.K. Patent No.

1,535,840, and the present invention may be employed for that purpose. Also, the invention may be used to interpose powder between the inner and outer sheaths of a cable as described in U.K. Patent No.

1,535,840. The method and apparatus of the present invention may also be employed to fill a cable with other particulate matter such as mineral powder to provide insulation or flame retardant powder.

WHAT WE CLAIM IS: 1. A method of continuously producing an electric cable containing powder, comprising passing one or more elongate components of the cable within a closed chamber, continuously contacting the cable components with powder by recirculating into the path of said components powder which has settled in the chamber, measuring a variable which depends on the quantity of powder in the chamber, and introducing additional powder into the chamber in a controlled manner in response to the value of the measured variable so as to maintain a desired quantity of powder in the chamber.

2. A method according to claim 1, in which the cable has a plurality of conductors forming a stranded core enclosed in a sheath or jacket, the voids within the sheath or jacket being at least partially filled with

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. tom trough 20 of semi-cylindrical shape. A first screw conveyer 22 is located coaxially in trough 20 and is journally mounted in end walls 18 of housing 10. A layplate 24 is located in one end wall 18a of housing 10 adjacent top 14 and a closing die 26 is located in the opposite end wall 1 8b in axial alignment with layplate 24. Below layplate 24 the outlet 27 of an upstanding blower chute 28 projects through end wall 1 8a into chamber 12. The central shaft 29 of first conveyor 22 carries at its ends a pair of pulleys 30 which are connected by belts 32 to a common shaft 34 journalled in mounts 36 outside housing 10. One pulley 30a is coupled with a drive motor 38 axially aligned with shaft 29 of first conveyor 22. Shaft 29 of first conveyor 22 also carries an impeller 40 located in main chamber 41 of blower chute 28 outside housing 10. Trough 20 is connected to chamber 41 of chute 28 through an opening 42 in end wall 18a of housing 10. A hopper 43 abuts one side wall 16a of housing 10 with a semi-cylindrical bottom trough 44 in which a second journally mounted screw conveyor 46 is coaxially located. One end of second conveyor 46 terminates at an opening 48 in side wall 16 of housing 10 and the other end of the second conveyor is axially coupled with a drive motor 50. In the operation of the example embodiment conductors 60 pass through layplate 24 into chamber 12 of housing 10 in spaced laterial relationship, horizontally traversing upper zone 62 of the chamber and at the same time converging to pass through closing die 26, whence they emerge from chamber 12 as a cable core 64 in known manner. Hopper 43 is charged with powder which is moved by second conveyor 46 through opening 48 to drop into trough 20 at the bottom of chamber 12. First conveyor 22 then moves the powder through opening 41 in end wall 18 of housing 10 into chamber 42 of chute 28 where it is forced upwardly by impeller 40 and through outlet 27 into zone 62 of chamber 12. The outlet opening of chute 28 is designed and oriented to direct the powder into the upper portion of chamber 12 at a velocity sufficient to produce a cloud of the material in zone 62 of the chamber in the path of strands 60. Preferably the powder is directed by chute 28 to form a cloud in the path of the conductors 60. To improve the adhesion of the powder to conductors 60, the conductors are usually lightly coated with oil by suitable means not shown. Another method of causing the powder to adhere to conductors 60 is to locate a high voltage electrode at the exit to chute 28 which imparts an electrical charge to the powder as in electrostatic powder coating. Excess powder drops back into trough 20 of chamber 12 where it is recirculated by conveyor 22 through chute 28 into upper zone 62 of the chamber. As the powder recirculating through chamber 12 is depleted the chamber is recharged from hopper 42 by further conveyor 46. Any suitable means can be employed to recharge chamber 12 automatically. For example by governing the speed of motor 50 inversely proportional to the torque on motor 38 a decrease in torque on conveyor 22 caused by depletion of powder in trough 20 will cause further conveyor 46 to speed up which will discharge powder more rapidly into chamber 12. The electrical connections for establishing such a relationship between motors 38 and 50 are well known. Hopper 42 can be charged periodically by any suitable means either manual or automatic.Other devices such as probe sensors could also be used to measure powder flow rate through the system to govern the speed of motor 50. Of course other suitable means could be employed to feed additional powder to trough 20 in chamber 12. For example first conveyor 22 could be extended from chamber 12 outwardly through end wall 1 8b into a bin similar to hopper 43. It will be appreciated that the electrical cable may be only partially filled with powder for effective water blockage, as described in above-mentioned U.K. Patent No. 1,535,840, and the present invention may be employed for that purpose. Also, the invention may be used to interpose powder between the inner and outer sheaths of a cable as described in U.K. Patent No. 1,535,840. The method and apparatus of the present invention may also be employed to fill a cable with other particulate matter such as mineral powder to provide insulation or flame retardant powder. WHAT WE CLAIM IS:

1. A method of continuously producing an electric cable containing powder, comprising passing one or more elongate components of the cable within a closed chamber, continuously contacting the cable components with powder by recirculating into the path of said components powder which has settled in the chamber, measuring a variable which depends on the quantity of powder in the chamber, and introducing additional powder into the chamber in a controlled manner in response to the value of the measured variable so as to maintain a desired quantity of powder in the chamber.

powder, and the conductors are passed in spaced lateral relationship through the closed chamber and thereafter brought together to form said core.

3. A method according to claim 1 of continuously producing an electric cable having an inner sheath and an outer sheath with powder interposed between the two sheaths, in which the inner sheathed cable is passed through the closed chamber; and powder is introduced into the chamber continuously in the path of the inner sheathed cable.

4. A method as claimed in claim 2 or claim 3, in which the powder is blown into the chamber in a direction to impinge on the conductors passing therethrough.

5. A method as claimed in any preceding claim, including the step of applying a coating of oil to the components prior to the entry of the components into the chamber.

6. A method as claimed in any preceding claim, in which the powder introduced into the chamber is electrically charged.

7. Apparatus for continuously producing an electric cable containing powder, comprising a closed chamber, means for passing one or more elongate components of the cable within said chamber, means for continuously contacting the cable components with powder by recirculating into the path of said components powder which has settled in the chamber, means for measuring a variable which depends on the quantity of powder in the chamber, and means for introducing additional powder into the chamber in a controlled manner in response to the value of the measured variable so as to maintain a desired quantity of powder in the chamber.

8. An apparatus according to claim 7, further comprising means to introduce powder into the chamber to form a cloud in the path of the conductors.

9. An apparatus as claimed in claim 8, in which the means to introduce the powder into the chamber comprises a chute opening into the upper portion thereof, impeller means to direct the powder through the chute, and means to drive the impeller.

10. An apparatus as claimed in claim 9, in which the means to recirculate the powder comprises a first screw conveyor constructed and arranged to feed powder to the impeller, and means to drive the first conveyor.

11. An apparatus as claimed in claim 10, in which the impeller and the first screw conveyor are coaxial and have a single drive means.

12. An apparatus as claimed in any of claims 9 to 11 in which the chute is directed to impinge powder on the components passing through the chamber.

13. An apparatus as claimed in any of claims 7 to 12, in which the means to charge additional powder into the chamber comprises a hopper having a second screw conveyor therein, and means to drive the second screw conveyor.

14. An apparatus as claimed in claim 13, including means to sense the variation in the quantity of powder settling in the chamber, and means to govern the speed of the second conveyor drive means inversely proportional to said variation.

15. An apparatus as claimed in claim 14, in which the means to sense the variation in the quantity of powder settling in the chamber comprises means to sense the variation in the torque on the first screw conveyor.

16. An apparatus as claimed in any of claims 7 to 15, in which the means to pass the components through the chamber comprises a layplate and a closing die in opposing walls thereof.

17. An apparatus according to claim 16, in which the layplate in one wall of the housing is arranged such that a plurality of conductors may be passed through the layplate into the chamber in spaced lateral relationship and the closing die is arranged such that the conductors may be passed out from the chamber through the closing die as a cable.

18. A method substantially as hereinbefore described with reference to the accompanying drawings.

19. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.