GB2589009A

GB2589009A - An apparatus for cutting a duct and a method of cutting a duct

Info

Publication number: GB2589009A
Application number: GB2016213.7A
Authority: GB
Inventors: Richardson Barry
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-11-13
Filing date: 2020-10-13
Publication date: 2021-05-19
Anticipated expiration: 2040-10-13
Also published as: GB202016213D0; GB2589009B

Abstract

An apparatus for cutting a duct 3 surrounding a core comprises a cutting head 22 that rotates about a longitudinal axis 11 and includes a cutting face 23 normal to the longitudinal axis; a rear face; an aperture extending therethrough along the longitudinal axis; and multiple cutting blades, where each blade has a cutting edge lying in the plane of the slicing face. The multiple knives comprise at least one first blade and one second blade. The cutting edge of the first knife lies along a radial line which extends from the longitudinal axis across the cutting face in the plane of the cutting face, where the cutting edge of the second knife is inclined to the radial line. A drive assembly 9 grips the duct and pulls it along the longitudinal axis onto the cutting head. The invention further includes a method of stripping a duct using the apparatus.

Description

An apparatus for cutting a duct and a method of cutting a duct The present invention relates to an apparatus for cutting a duct. More particularly, but not exclusively, the present invention relates to an apparatus for cutting a duct comprising a cutting head adapted to rotate about a longitudinal axis and a drive assembly adapted to grip the duct and pull it along the longitudinal axis onto the cutting head. The present invention also relates to a method of cutting a duct. More particularly, but not exclusively, the present invention relates to a method of cutting a duct comprising the steps of gripping the duct and pulling it along a longitudinal axis onto a cutting head rotating about the longitudinal axis.

Around the world there are many millions of miles of conduits buried under the ground. Each of these conduits carry one or more communications cables. Each cable is arranged in a duct which is in turn arranged in the conduit. The purpose of the duct is to protect the cable when an additional cable is installed. A problem arises when the conduit is filled with ducts as then no more cables can be installed in the conduit.

Apparatus for removing ducts around cables within a conduit are known. EP17176562.1 discloses an apparatus which pulls the duct longitudinally onto a fixed blade. The fixed blade splits the duct which can then be removed.

A problem with such an apparatus is that the duct, whilst split, is required to be manually guided since it is removed in a single length which could be many hundreds of meters long. This requires street management and public protection during the operation. Further, following removal of the split duct further processing and chopping is required to reduce the split duct into smaller more manageable pieces. This requires additional machinery and operators. Use of such known apparatus is therefore problematic and expensive.

CN109586214A discloses a waste electric wire peeling mechanism. The mechanism comprises a blade which is rotated around the outside of the wire to cut a spiral pattern into the plastic sheath surrounding the wire. The mechanism further comprises a fixed blade which splits the sheath into four. The combination of fixed blade and rotating blade splits the plastic sheath into sections. Such an apparatus requires multiple knives and is complex and unreliable.

The present invention seeks to overcome the problems of the prior art.

Accordingly, in a first aspect, the present invention provides an apparatus for cutting a duct which surrounds a core, the apparatus comprising a drive assembly and a cutting assembly, the cutting assembly comprising a cutting head adapted to rotate about a longitudinal axis, the cutting head comprising a cutting face substantially normal to the longitudinal axis a rear face an aperture extending from the cutting face to the rear face along the longitudinal axis a plurality of cutting blades, each cutting blade comprising a cutting edge which lies in the plane of the cutting face the plurality of cutting blades comprising at least one first cutting blade and at least one second cutting blade, the cutting edge of the at least one first cutting blade lying along a radial line which extends from the longitudinal axis across the cutting face in the plane of the cutting face and the cutting edge of the at least one second cutting blade is inclined to a radial line which extends from the longitudinal axis across the cutting face in the plane of the cutting face through the cutting edge the drive assembly being adapted to grip the duct and pull the duct along the longitudinal axis into contact with the cutting head.

The rotating cutting head cuts the duct into small lengths without damaging the core. The small lengths can then be bagged and removed by a single operative without any on site cutting being necessary. Further, as the lengths are relatively short very little street management is required. Further, only one cutting head is required.

Preferably the apparatus comprises a plurality of first cutting blades and a plurality of second cutting blades Preferably the first and second cutting blades are interdigitated.

Preferably the apparatus further comprises a rotation mechanism engaged with the cutting head and adapted to rotate the cutting head about the longitudinal axis.

Preferably the rotation mechanism comprises a motor and at least one drive wheel arranged between the motor and the cutting head.

Preferably the apparatus further comprises a mandrel arranged in the aperture between the cutting head and longitudinal axis to shield the core from the cutting head.

Preferably the mandrel is a tube defined by a mandrel wall, the mandrel extending along the longitudinal axis through the aperture in the cutting head with the mandrel wall spaced apart from the longitudinal axis, the mandrel being connected to a support plate proximate to the rear face.

Preferably the mandrel is adapted to be split into two separate halves.

Preferably the apparatus is adapted to be divided into a plurality of portions which can be arranged around the core and connected together.

Preferably the cutting head is adapted to be split into a plurality of portions, preferably two portions.

Preferably the drive assembly comprises at least one, preferably a plurality of tracks adapted to grip the duct.

In a further aspect of the invention there is provided a method of cutting a duct comprising the steps of (a) providing an apparatus as claimed in any one of claims 1 to 11; (b) arranging the core within the aperture of the cutting head; (c) gripping the duct within the drive assembly; (d) driving the drive assembly to pull the duct along the longitudinal axis into contact with the cutting head; and, (e) rotating the cutting head around the longitudinal axis to cut the duct Preferably the step of arranging the core within the aperture of the cutting head comprises the steps of (0 dividing the cutting head into a plurality of portions; (ii) arranging the portions around the core; and (iii) connecting the portions together to form the cutting head with the core arranged in the aperture of the cutting head.

Preferably the cutting head is divided into two equal portions.

The present invention will now be described by way of example only and not in any!imitative sense with reference to the accompanying drawings in which Figure 1 shows a conduit in end view having a plurality of ducts and cores therein; Figure 2 shows the conduit of figure 1 with the ducts removed and a further duct added.

Figure 3 shows a service pit in vertical cross section; Figure 4 shows the service pit of figure 3 with an apparatus for cutting a duct according to the invention arranged therein; Figure 5 shows an apparatus for cutting a duct according to the invention in vertical cross section along the longitudinal axis; Figure 6 shows the drive assembly of figure 5 in vertical cross section in a plane normal to the longitudinal axis; Figure 7 shows the cutting assembly of figure 5 in exploded view; and, Figure 8 shows the cutting face of the cutting head of the apparatus according to the invention in plan view; Figure 1 shows an end view of a conduit 1 defined by a conduit wall 2. The conduit 1 is typically arranged underground. Arranged within the conduit 1 is a plurality of ducts 3, each duct 3 surrounding a core 4. In this example the ducts 3 are plastics pipes and the cores 4 are telecommunications cables (typically copper or fibre optic cables) although as explained below the invention is not so limited. As can be seen, the ducts 3 substantially fill the conduit 1 and so adding new cores 4 can be problematic.

In order to add new cores 4 one must remove the existing ducts 3 without damaging the existing cores 4. One can then cover the existing cores 4 with a protective material 5, if required, and add a new duct 3 and optionally a new core 4 as shown in figure 2.

Such conduits 1 can often extend for several miles underground. In order to service the cores 4 within the conduit 1 service pits 6 are arranged at spaced apart points along the length of the conduit 1. Such a service pit 6 is shown in schematic cross section in figure 3. The conduit 1 does not extend into the service pith so that within the service pit the duct 3 and core 4 are exposed. Arranged within the pit 6 is a connector 7. The core 4 is divided at the connector 7 and connected to the two ends of the connector 7 as shown.

In order to remove the duct 3 from around the core 4 an apparatus 8 for cutting a duct 3 according to the invention is positioned within the service pit 6 as shown in figure 4. The apparatus 8 is held in place with struts or the like (not shown) which abut the walls of the pit 6. The core 4 is then passed through the apparatus 8 and the duct 3 engaged with the apparatus 8. The apparatus 8 pulls the duct 3 along a longitudinal axis 11 onto a cutting head 22 within the apparatus 8 so cutting the duct 3 into chips as is described in more detail below. One the required length of duct 3 has been removed the apparatus 8 is removed from the service pit 6 and the core 4 reconnected to the connector 7.

Figure 5 shows an apparatus 8 for cutting a duct 3 according to the invention in vertical cross section. The apparatus 8 comprises a drive assembly 9 and a cutting assembly 10. A longitudinal axis 11 passes through the apparatus 8.

The drive assembly 9 comprises a plurality of tracks 12. Each track 12 extends around spaced apart gearwheels 13. Attached to each track 12 is a plurality of shoes 14 each having a V cross section as shown in figure 6.

Returning to figure 5, in use the gearwheels 13 are displaced in a direction perpendicular to and towards the longitudinal axis 11 until the shoes 14 abut the duct 3. The V shaped profile of the shoes 14 ensures an even grip on the duct 3 around a portion of the circumference of the duct 3. Twin linked drive motors 15 drive the gearwheels 13 so rotating the tracks 12 and drawing the duct 3 along the longitudinal axis 11 towards the cutting assembly 10.

The drive motors 15 have both forward and reverse options for displacing the duct 3 both towards and away from the cutting assembly 10. By turning the motors 15 in reverse the duct 3 can be displaced away from the cutting assembly 10 if necessary.

A safety relief valve 16 is connected to the drive motors 15. The safety relief valve 16 prevents the shoes 14 from exerting a pulling force on the duct 3 in excess of a threshold limit which would cause the duct 3 to break.

Also attached to the drive motors 15 is a control system 17. The control system 17 is equipped with a rotary measurement device which measures the number of turns of the gearwheels 13 and hence the length of extracted duct 3. The control system 17 also measures the torque applied by the gearwheels 13 on the tracks 12 and hence the pull force on the duct 3. The control system 17 is adapted to send a control signal to the motors 15 to maintain the pull force within a predefined range. The control system 17 is also adapted to measure the squeeze force applied by the shoes 14 on the duct 3 and to send a message to the motors 15 to cease rotation of the gearwheels 13 if the squeeze force lies outside a predetermined range. In an alternative embodiment of the invention the control system 17 is adapted to adjust the positions of the gearwheels 13 slightly if the squeeze force lies outside a predetermined range to return the squeeze force to back within the range.

Figure 5 also shows the cutting assembly 10 in vertical cross section though the longitudinal axis 11. The cutting assembly 10 comprises a main plate 18 having a main plate aperture 19 extending therethrough. The longitudinal axis 11 passes through the center of the main plate aperture 19. Connected to the main plate 18 and covering the main plate aperture 19 is a main drive wheel 20. The main drive wheel 20 is free to rotate about the longitudinal axis 11. A main drive wheel aperture 21 extends through the main drive wheel 20 along the longitudinal axis 11 as shown.

Detachably connected to the main drive wheel 20 is a cutting head 22. The cutting head 22 comprises a cutting face 23 and a rear face 24 and has an aperture 25 extending therebetween extending along the longitudinal axis 11 as shown.

The cutting assembly 10 further comprises a support plate 26 arranged proximate to the main plate 18 on the opposite side of the main plate 18 to the cutting head 23. Attached to the support plate 26 is a mandrel 27. The mandrel 27 is shaped as a tube defined by a mandrel wall 28. The mandrel 27 extends along the longitudinal axis 11 through the main plate 18, through the main drive wheel 20 and through the cutting head 22 as shown with the mandrel wall 28 spaced apart from the longitudinal axis 11.

Figure 7 shows the cutting assembly 10 in perspective exploded view. The cutting assembly 10 further comprises a secondary drive wheel 29 connected to the main plate 18 and free to rotate about a drive axis 30. The teeth of the secondary drive wheel 29 are engaged with the teeth of the main drive wheel 20. The cutting assembly 10 further comprises a main motor 31 connected to the secondary drive wheel 29 through the main plate 18.

As can be seen from figure 7 the cutting head 22 comprises a plurality of cutting blades 32 each having a cutting edge 33. Each cutting edge 33 is arranged in the plane of the cutting face 23. The cutting face 23 is normal to the longitudinal axis 11.

In use the core 4 and duct 3 are passed along the longitudinal axis 11 through the drive assembly 9 until the core 4 is received in the mandrel 27. The mandrel 27 protects the core 4 from the cutting head 22. The gearwheels 13 are displaced towards the duct 3 until the shoes 14 grip the duct 3. The main motor 31 is then turned. This turns the secondary drive wheel 29 which in turn turns the main drive wheel 20 so turning the cutting head 22 about the longitudinal axis 11. The main drive wheel 20, secondary drive wheel 29 and main motor 31 are collectively referred to as the rotation mechanism. The rotation mechanism is engaged with the cutting head and is adapted to rotate the cutting head about the longitudinal axis. In alternative embodiments of the invention, other forms of rotation mechanism are possible as would be known to one skilled in the art.

At the same time as the cutting head 22 turns the drive motors 15 turn so drawing the duct 3 onto the cutting face 23 of the cutting head 22 so cutting the duct 3 into chips. The chips can then be collected and removed.

Shown in figure 8 is the cutting face 23 of the cutting head 22 in plan view, i.e looking along the longitudinal axis 11 normal to the cutting face 23. Only the cutting edges 33 of the cutting blades 32 are shown. The cutting blades 32 can be divided into two groups. The first group comprises the first cutting blades 32. The cutting edge 33 of each first cutting blade 32 lies along a radial line 34 which extends from the longitudinal axis 11 across the cutting face 23 in the plane of the cutting face as shown. The second group comprises the second cutting blades 32. The cutting edge 33 of each second cutting blade 32 is inclined to a radial line which extends from the longitudinal axis 11 across the cutting face 23 in the plane of the cutting face 23 through the cutting edge 33 as shown. The first cutting blades 32 and second cutting blades 32 are interdigitated or in other words as one passes around the cutting face 23 in the direction of the guide arrow one alternately passes a first cutting blade 32 then a second cutting blade 32. The scissor action of the first and second cutting blades 32 cuts the duct 3 into chips.

The present invention has been described with reference to cutting a plastics duct 3 surrounding a core 4 which is a telecommunications cable. The invention however is not so limited. In alternative embodiments the core 4 could be a hydraulic cable, a pneumatic pipe or a pipe filled with a liquid. The duct 3 is not necessarily a plastics material. It could for example be rubber or metal. The duct 3 can be a sleeve.

The apparatus may also be used in service pits 6 which do not contain a connector 7. In this case one cannot disconnect the core 4 from the connector 7 to produce a free end of the core 4 which is fed into the aperture extending through the cutting head.

Accordingly, in an alternative embodiment of the invention, the apparatus is adapted to be divided into several parts. These parts can then be connected together to surround the core 4 with the core 4 extending along the aperture in the cutting head 22.

In particular, the cutting head 22 is adapted to be divided into a plurality of parts. These parts are then arranged around the core and connected together to form the cutting head 22 with the core 4 extending along the aperture in the cutting head. The cutting head 22 could be adapted to be split into a plurality of equal parts, for example two equal parts, with each part containing an equal portion of the aperture.

Claims

CLAIMS1. An apparatus for cutting a duct which surrounds a core, the apparatus comprising a drive assembly and a cutting assembly, the cutting assembly comprising a cutting head adapted to rotate about a longitudinal axis, the cutting head comprising a cutting face substantially normal to the longitudinal axis; a rear face; an aperture extending from the cutting face to the rear face along the longitudinal axis; a plurality of cutting blades, each cutting blade comprising a cutting edge which lies in the plane of the cutting face; the plurality of cutting blades comprising at least one first cutting blade and at least one second cutting blade, the cutting edge of the at least one first cutting blade lying along a radial line which extends from the longitudinal axis across the cutting face in the plane of the cutting face and the cutting edge of the at least one second cutting blade is inclined to a radial line which extends from the longitudinal axis across the cutting face in the plane of the cutting face through the cutting edge the drive assembly being adapted to grip the duct and pull the duct along the longitudinal axis into contact with the cutting head.
2. An apparatus as claimed in claim 1 comprising a plurality of first cutting blades and a plurality of second cutting blades.
3. An apparatus as claimed in claim 2, where the first and second cutting blades are interdigitated.
4. An apparatus as claimed in any one of claims 1 to 3 further comprising a rotation mechanism engaged with the cutting head and adapted to rotate the cutting head about the longitudinal axis.
5. An apparatus as claimed in claim 4 where the rotation mechanism comprises a motor and at least one drive wheel arranged between the motor and the cutting head.
6. An apparatus as claimed in any one of claims 1 to 5, further comprising a mandrel arranged in the aperture between the cutting head and longitudinal axis to shield the core from the cutting head.
7. An apparatus as claimed in claim 6, wherein the mandrel is a tube defined by a mandrel wall, the mandrel extending along the longitudinal axis through the aperture in the cutting head with the mandrel wall spaced apart from the longitudinal axis, the mandrel being connected to a support plate proximate to the rear face.
8. An apparatus as claimed in claim 7, wherein the mandrel is adapted to be split into two separate halves.
9. An apparatus as claimed in any one of claims 1 to 8 wherein the apparatus is adapted to be divided into a plurality of portions which can be arranged around the core and connected together.
10. An apparatus as claimed in any one of claims 1 to 9 wherein the cutting head is adapted to be split into a plurality of portions, preferably two portions.
11. An apparatus as claimed in any one of claims 1 to 10, wherein the drive assembly comprises at least one, preferably a plurality of tracks adapted to grip the duct.
12. A method of cutting a duct comprising the steps of (a) providing an apparatus as claimed in any one of claims 1 to 11; (b) arranging the core within the aperture of the cutting head; (c) gripping the duct within the drive assembly; (d) driving the drive assembly to pull the duct along the longitudinal axis into contact with the cutting head; and, (e) rotating the cutting head around the longitudinal axis to cut the duct.
13. A method as claimed in claim 12, wherein the step of arranging the core within the aperture of the cutting head comprises the steps of (i) dividing the cutting head into a plurality of portions; (ii) arranging the portions around the core; and (iii) connecting the portions together to form the cutting head with the core arranged in the aperture of the cutting head.
14. A method as claimed in claim 13 wherein the cutting head is divided into two equal portions.