NZ225552A - Cable laying apparatus: cable drawn through duct by suction - Google Patents

Description

225552 Patents form No 5 Number 2 255 5 2 PATENTS ACT 1953 Dated -July 2D,—1 988' i m'c COMPLETE SPECIFICATION A CABLE LAYING APPARATUS T^s. 11/SfltE COLIN FRANK BRADLEY, a Dritioh citizen, of 428 Church Street, Palmerston North, New Zealand do hereby declare the invention for which l/we pray that a Patent may be granted to me/M9£ and the method by which it is to be performed, to be particularly 225552 The invention comprises an apparatus for laying a cable in a cable pipe or duct.

Cabling for communications, electricity supply, and the like is often laid through underground cable pipes or ducts. Once an underground cable duct has been laid it is necessary to lay the cables in the duct. Increasing usage of communications technology increases the information carrying capacity and thus cabling required. In addition, conventional copper or co-ax cabling is being increasingly replaced with fibre optics cabling.

Presently cables are laid within a cable duct by either pushing the cable through the duct from one end to another with a long flexible steel rod or tape, or by blowing a canvas sock having a light line attached through the duct with a large air compressor. The light line is then in turn used to draw the cable through the duct, into position. Pushing a cable through using a flexible steel tape or rod may only be used for laying cables over very short distances. Blowing a light line through with compressed air may be used to lay a cable over longer distances but this system still suffers from the disadvantage that the rough interior surfaces of older cable ducts, resulting from rust or corrosion and dirt accumulation, considerably reduce the flow rate and pressure of air over longer distances. 225552 The present invention provides an improved or at least alternative form of apparatus for laying a cable in a cable duct.

In broad terms the invention may be said to comprise apparatus for laying a cable in a pipe or duct, comprising a carrier member adapted to seal against the interior of and move forwardly under suction within a duct, and to tow through the duct a light line, and a machine comprising or forming part of a self contained mobile vehicle and comprising a vacuum pump capable of providing sufficient suction to draw the carrier member through the cable duct of at least 100 mm diameter over a distance of at least three kilometres and to draw together with said carrier member accumulated water or other debris in the duct, a prime mover for driving the vacuum pump, water and debris separation and collection means comprising a collection tank of a size to collect said water and debris drawn from at least three kilometres of the cable duct, and a flexible connection pipe for connecting the vacuum pump through the water and debris collection tank to an end of the cable duct.

Preferably the machine is self propelled and comprises an operators position and controls for driving the machine from the operators position into position for use.

Preferably the machine comprises a body enclosing the machine components and the machine is of a size that it may easily be transported to location on a truck or lorry, or by towing behind a truck or lorry or other vehicle. 225552 Preferably the level of vacuum applied to the cable duct for drawing through the carrier member is variable.

A preferred form of cable laying apparatus of the invention is illustrated in the accompanying drawings, wherein: Fig. 1 is a view of the preferred form cable laying machine, Fig. 2 is a block diagram of the internal components of the machine, Fig. 3 shows the end of the flexible connection piping which connects to the cable duct and a preferred form of fitting and two versions of one form of carrier member, and Fig. 4 shows another form of carrier member.

Reference numeral 1 in the drawings indicates the body of the preferred form machine. The preferred form machine is self propelled and comprises driving wheels 2 on either side and a dolly wheel 3 at the front of the machine. The machine moves at approximately 4 km/h. In use the preferred form machine is carried on the back of a truck or lorry to location and is then driven under its own power 225552 into position adjacent a cable manhole or the like. In other non self propelled forms of the machine the machine could be towed directly into position by a truck, four wheel drive vehicle, or the like. It is also possible within the invention that the apparatus may be permanently mounted to the tray of a dedicated truck or the like.

The preferred form machine comprises an operators position in which an operator is shown standing in Fig. 1, on the platform 4 extending from the rear of the machine carrying a rail 5. Controls 6 are provided for driving the apparatus. The left control controls drive to the left driving wheel 2 whilst the right control controls drive to the right driving wheel 2, so that the machine may be steered by way of the controls in a similar manner to steering of a bulldozer.

In an alternative form of the machine the rear drive wheels may be conventionally driven by a motor through a differential and the front wheel or wheels may be used for steering.

A flexible connection pipe 7 connects at one end to a fitting 7 at the front of the machine as shown. The pipe 7 is of a suitable length for any application and the other end of the pipe 7 carries a fitting 8 for connecting to the end of a cable duct within a manhole or the like, which is more particularly shown in Fig. 3. 225552 The vacuum pump, motor and other components of the preferred form machine are mounted within the body 1. Referring to Fig. 2, a petrol motor or other suitable form of prime mover drives the vacuum pump of the machine. The suction inlet of the vacuum pump is in turn connected to a collection tank and via the fitting 7 to the flexible pipe 7 for connecting the machine to a cable duct.

The collection tank receives water and debris from air drawn from the cable duct into the machine. Water and debris are collected at the bottom of the collection tank whilst air drawn from the cable duct passes from the collection tank to the pump inlet. The connection of the pump inlet to the separator tank is towards the top of the tank and the connection of the pipe 8 through the fitting 7 is towards the base of the tank.

The collection tank is of approximately 396 litres in volume. A large amount of water is often present in cable ducts together with debris such as small pebbles and stones and other dirt and foreign matter and this is collected in the collection tank. Referring to Fig. 1, an access door through the exterior of the machine into the collection tank 1 provided with a suitable cover 9 enables removal of collected debris from time to time when the machine is in use. A tap 10 on the front of the machine may be opened to drain collected water from the separator tank during operation. 225552 In the preferred form machine the vacuum pump is a water ring pump capable of delivering a vacuum of zero to twenty five inches of mercury and having a flow rate of 2,600 liters of air per minute. The capacity of the vacuum pump is variable and a gauge 14 on the front of the machine provides an indication of the level of vacuum applied to a cable duct at any time. So that the machine need not always be operated near a tap or other water supply, in the preferred form machine the water used by the water ring pump is recycled. Within the body of the machine a second water/air separation tank is provided. The exhaust outlet of the vacuum pump is connected to tank, the water/air separation towards the top of the tank and the water supply to the pump is taken from towards the base of the tank. Air exhausted from the vacuum pump exits from towards the top of the water air separation tank.

The prime mover is connected to the vacuum pump and also to an hydraulic pump. The hydraulic pump provides hydraulic fluid under pressure through appropriate hydraulic circuits to the left and right drive wheels through control valves operated by the levers 6 and 7, and hydraulic fluid under pressure is also supplied to a capstan 11 (see Fig. l) controlled by a lever 12 on the front of the machine. A gauge 13 provides an indication of the strain applied by the capstan 11 to a line being drawn in by the capstan.

Although not shown in the drawings, in some cases it may be desirable to be able to adjust the maximum line pull applied 225552 by the capstan to avoid possible damage to the cable being drawn through a duct. A suitable manually controllable hydraulic relief valve enabling adjustment of the maximum lie pull achievable by the capstan could be provided.

Fig. 3 shows two versions of one preferred form of carrier member. The carrier member 15 comprises a generally cylindrical piece of sponge foam 16 which is compressed onto a central rod 17 and which is retained thereon by more rigid foam discs 17 at either end. The ends of the rod 17 are formed as loops so that the light line to be towed through the duct by the carrier member may be attached to what in use will be the rear end of the carrier member. A number of carrier members of differing diameters may be provided for use with different diameters of cable pipes or ducts. The smaller carrier member 19 shown is of a similar construction and is intended to tow a bristled cleaning brush 2 0 through the duct for cleaning the duct before a new cable is laid.

The form of carrier member of Fig. 4 comprises a number of resiliently flexible loops 30, of Bowden cable for example, in a general 'egg whisk1 form as shown. The ends of the loops are retained in a hollow tube 31. The end of the tube 31 is formed as a loop for connecting to the light line. In use the carrier member is covered with a plastic shroud i.e. sheet material, which is wrapped over the loops 30 and taped around the tube 31. The plastic material may thus be easily replaced after each use. 225552 A preferred form of fitting 8 for the end of the connection pipe 6 for connecting the end of the connection pipe to the end of a cable duct within a manhole is also shown in Fig. 3. The fitting 8 is generally cylindrical as shown and is suitably formed of a plastics material. It has a sight glass 21 into the interior of the fitting, and two spaced bars 22 extend through the interior of the fitting on one side of the sight glass 21 as shown. In use when the carrier member 15 has been drawn through a cable duct it will stop against the bars 2 2 adjacent the sight glass 21. Similarly, larger items of debris such as large stones within the duct will be prevented by the bars 22 from entering the machine.

In use of the apparatus of the invention the machine is transported to location and the machine is off loaded' from the truck or lorry and is driven under its own propulsion to adjacent the manhole into the ground. The end of the connection pipe is taken down the manhole and is connected to the exposed end of the cable duct by way of the fitting 8. At the other end of the duct, which may be some kilometers distant, the carrier member 15 is inserted into the duct and the end of a light line, suitably on a reel, is attached to the rear end of the carrier member. The pump is started so that suction is applied to the duct. The carrier member 15 will be drawn through the duct bringing with it the light line. When the carrier member arrives at the other end of the duct it will be visible through the sight <> 2 5 5 o glass 21 of the fitting 8. The vacuum pump of the machine is then turned off and the fitting 8 removed from the duct. <7 The light line connected to the capstan 11 and at the other end of the duct is attached to the cable to be laid. The capstan is then operated so that the cable is drawn through the duct.

It has been found that the machine of the invention can successfully draw the carrier member with light line attached through a 100mm diameter duct to distances of many kilometers.

The foregoing describes a preferred form of the machine and other forms employing the principles of the invention will be apparent to those skilled in the art. The scope of the invention is defined in the following claims.

Claims (8)

- 11 225552 WHATI/^CLAIMIS

1. Apparatus for laying a cable in a cable duct, comprising a carrier member adapted to seal against the interior of and move forwardly under suction within a duct, and to tow through the duct a light line, and contained mobile vehicle and comprising a vacuum pump capable of providing sufficient suction to draw the carrier member through the cable duct of at least 100 mm diameter over a distance of at least three kilometres and to draw together with said carrier member accumulated water or other debris in the duct, a prime mover for driving the vacuum pump, water and debris separation and collection means comprising a collection tank of a size to collect said water and debris drawn from at least three kilometres of the cable duct, and a flexible connection pipe for connecting the vacuum pump through the water and debris collection tank to an end of the cable duct.

2. Apparatus as claimed in claim 1, including a fitting for connecting the flexible connection pipe to the end of the cable duct, comprising means for preventing larger items of debris from entering the machine and a sight glass in a side of the fitting enabling sighting of the arrival of the carrier member after drawing through the cable duct and/or of such larger items of debris. l a machine comprising or forming part of a self - 12 -

3. Apparatus as claimed in either one of claims 1 and 2, wherein the machine is self propelled and comprises controls at an operators position on the machine for driving the apparatus into location for use.

4. Apparatus as claimed in any one of the preceding claims, wherein the machine comprises a capstan for winding in the light line and cable attached through the duct.

5. Apparatus as claimed in claim 4, wherein the prime mover also drives wheels of the machine on either side for propelling the machine and driving the winding capstan.

6. Apparatus as claimed in any one of the preceding claims, wherein the machine comprises a body enclosing the machine components and wherein the machine is of a size that it may be conveyed to location on a truck or lorry.

7. Apparatus as claimed in any one of the preceding claims, wherein the level of vacuum applied to the cable duct by the machine is variable.

8. Apparatus for laying a cable in a pipe or duct, substantially as described herein with reference to the accompanying drawings.