GB1604972A - Branch duct attachments - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO BRANCH DUCT ATTACHMENTS (71) I, VICTORY PERCY FORTH, a British Subject, of Clydesdale, Dunswell Lane, Dunswell, Hull, Humperside, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a branch duct attachment for a main duct and to a method and apparatus for installing the branch duct attachment operable with the main duct.

It is well known in the art to provide a branch duct attachment for a main duct, the branch duct attachment allowing main duct contents to be tapped off at a predetermined location along the main duct and, for most applications when the main duct is a pipe or conduit, the branch duct attachment conveniently comprises a T juncton. To fit a T junction in an existing main pipe or duct it is only necessary to split the main duct, install the T junction between the split ends of the main duct so that the through flow path of the T junction is contiguous with the bore through the main duct, and the limb of the T junction then constitutes the branch duct attachment. The fitting of a Tjunction in, for example, a hot water system such as a domestic central heating system, can be carried out by a skilled pipe fitter or plumber in a very short time.

Whilst the actual fitting of a junction into a main duct is a relatively simple matter the method requires the main duct to be inoperative and drained of fluid contents whilst the main duct is being split and a T junction fitted, A serious problem thus exists when the main duct forms part of an operating liquid or gas circulation system, such as a hot or cold water system or a gas distribution system, when, to render the main duct inoperative and drained. it becomes necessary to stop fluid circulation and exhaust the system of its fluid contents. In many large systems the time spent in rendering the main duct inoperable and drained. and restarting fluid flow through the system after installation of the branch duct attachment, can take many hours, it is usual for skilled craftsmen to be in attendance during the whole of the draining and restarting cycle and thus not only is the "down time" of the system inconvenient but this prior art method of fitting a branch duct attachment is wasteful of man hours and thereby expensive.

The present invention seeks to provide a method and apparatus by which branch duct attachment which can be fitted with a main duct without exhausting the main duct of its fluid contents.

According to the present invention there is provided a method for forming an opening in the wall of a duct comprising the steps of clamping a branch duct attachment, including a valve in the branch duct, to the said duct, opening said valve, advancing a pilot drill along the axis of the flow passage through the said duct, advancing a tap into the pilot hole to form an internal thread in said hole, retaining the tap entered in said hole whilst advancing an annular cutter against the duct and rotating said cutter in the direction opposite to the direction of tapping to cut an annular section from the wall of the duct concentric with the pilot hole, and withdrawing said annular cutter, said tap with the annular member cut from the wall of the duct threaded thereon, and said pilot drill, away from the duct back through the open valve.

The method preferably includes the steps of sealing said branch duct to prevent loss of pressure fluid from the duct during the drilling, tapping and cutting operations, and during withdrawal of the drilling, tapping and cutting members through the open valve.

The invention also envisages apparatus, for performing the method according to the invention, and comprising, in combination, a branch duct attachment including a valve in the branch duct, an annular cutter member with an annular cutting head on one end and an external configuraton which allows said member to enter the branch duct, cutterhead leading, to pass through the valve when said valve is open, and to rotate within the branch duct attachement, a pilot drill member rotatable within the bore of the annular cutter and axially displaceable along said bore, a drill tip at that end of the pilot drill member adjacent the annular cutter of the cutter member, and tapping means presented by said pilot drill member and immediately adjacent said drill tip.

Preferably the annular cutter member is of generally cylindrical configuration.

Preferably that end of the branch duct remote from the main duct is closed by an end cap, the cutter member extends through said end cap to project externally thereof, and the pilot drill member has an axial length greater than the cutter member by at least the axial length of the drill tip and tapping section.

Preferably the cutter member externally of the end cap is adapted for engagement by a tool, for rotating the said cutter member, and that end of the pilot drill member externally of the cutter member is adapted for engagement by a tool for rotating said pilot drill member.

Preferably the apparatus includes sealing means between said end cap and the branch duct, and sealing means between said cutter member and said pilot drill member.

In a preferred embodiment the valve is a ball type valve with an opening through the ball closure member aligning with the flow passage through the branch duct when the valve is in an open condition, said opening having the same cross-sectional shape and a cross-sectional area equal to, or greater than, the shape and cross-sectional area of the flow passage through the branch duct.

Preferably the branch duct attachment comprises a duct member, intended to surround the duct, and the branch duct extends from said duct member in such manner that the axis of said branch duct intersects the axis of said duct.

In a preferred embodiment the duct member is split along a plane parallel to the axis of said member and the apparatus includes clamping means for clamping said duct member around a duct to frictionally retain said duct member with the duct passing therethrough.

Preferably the apparatus includes sealing means between said duct member and said duct.

The invention will now be described further by way of example with reference to the accompanying drawings in which: Fig. 1 shows one apparatus for connecting a branch duct to a main duct, viewed at right angles to the axes of said ducts and, Fig. 2 shows a centre-line cross-section through the arrangement at right angles to the direction in Fig. 1.

In the illustrated example a branch duct connection generally comprises a duct member 11 defining an annular bore 12, a semicircular clip 13 at one end of member 11 and integral therewith, and an externally threaded boss 14 on the end of member 11 remote from clip 13. The semi-circular clip 13 attaches, by screws 15, to a semi-circular member 16. An enlarged region of member 11 between clip 13 and threaded boss 14 houses a ball type valve 17 with an annular valve opening I 8 therethrough and the opening 18 has a diameter slightly greater than the diameter of bore 12. An actuating member 19 for valve 17 extends through the member 11 to project outwardly therefrom to permit valve 17 to be externally controlled.

The branch duct member 11 is attached to a main duct "M" by placing semi-circular clip 13 against the duct M, placing the semicircular member 16 on the opposite side of duct M. so that the parts 13 and 16 surround the duct M. and fitting and tensioning screws 15. In the event that the engagement of parts 13 and 16 with the duct M is inadequate to effect a fluid tight seal therebetween an annular sealing member 20 is provided to surround the duct M within the co-operating parts 13, 16. Thus, by the above described arrangement. the branch duct attachment may be fitted to the main duct M without affecting fluid flow through duct M. To connect the branch duct attachment in communication with the bore of duct M it becomes necessary to breach the wall of duct M exposed to the bore 12 and this breaching of duct M is effected by a drilling arrangement as follows.

The drilling arrangement comprises an annular cutter member 21 with a pilot drilling member 22 slidably supported within the bore 23 of member 21. Member 21 presents an annular cutter 24 at one end and, within cutter 24, the member 21 has an enlarged bore region 25 within which an enlarged diameter collar 26 on drilling member 22 is slidably disposed. The external diameter of cutter member 21 is smaller than the diameter of bore 12 and at its end regions spaced from the cutter 24 the member 21 has a first reduced diameter section 27 and a second reduced diameter region 28 which terminates in an external threaded section 29.

The pilot drilling member 22 presents, on that end adjacent the cutter 24, a drill tip 30 with a tapping section 31 between drill tip 30 and the collar 26.

To assemble the drilling arrangement 21-31 with the branch duct arrangement the member 21 is slidably inserted into the bore 12, cutter 24 leading, and, with the valve 17 in the open position, the member 21 slides freely through the opening 18 in valve 17. A first cap 32, having a bore 33 slidably receiving the cutter member 21 therein, is assembled a member 21 and an internally threaded part 34 of cap 32 engages on the coupling part (externally threaded boss 14) of the branch duct connection. An annular sealing member 35 between radial faces of boss 14 and cap 32 render the joint therebetween fluid tight, and remote from the internally threaded part 34 the cap 32 presents an external thread 36. A second cap 37 presents a bore 38 for slidably supporting the first reduced diameter section 27 of member 21, and an enlarged internally threaded section 39 engaged with the external thread 36 on cap 32. An annular sealing member 40 locates between radial faces of cap 32 and cap 37 to render the joint therebetween fluid tight.

A third cap 41 presents a bore 42 slidably receiving the pilot drill member 22 remote from drill tip 30 and cap 41 presents an internal threaded part 43 engaged on threaded section 29 of cutter member 21. An annular sealing member 44 locates between radial faces of cap 41 and the section 28 of cutter member 21 to render the joint therebetween fluid tight.

The end 45 of pilot drill member 22 remote from the drill tip terminates with a rectangular cross-section and the first reduced diameter section 26 of cutter member 21 has a hexagonal end 46.

The duct M breaching arrangement is intended to operate as follows.

With the cutter member 21 and pilot drill member 22 assembled with the branch duct arrangement and with the caps 32, 37 and 41 secured as described above, the pilot drill member 22 is rotated by engaging a tool (not shown) such as a tap wrench, on the end 45 to advance the drill tip 30 against the wall of duct M and drill a pilot hole therethrough, by continuing the rotation of member 22 in the direction of the lands of the tapping section 31, whilst maintaining axial loading on the member 22, the tapping section 31 forms an internal thread in the pilot hole and allows the tapped section 31 to enter the pilot hole until the leading radial face of the collar 26 engages the wall of duct M. It will be appreciated that as the collar 26 must be advanced into contact with duct M before the cutter member 21 is operative on duct M the pilot drill member 22 has an axial length greater than that of member 21 by at least the axial length of the drilling and tapping sections.

With the collar 26 in engagement with duct M rotation of pilot drill member 22 is terminated, the tool (a tap wrench) is removed, a tool, such as a spanner, is engaged on section 46 of member 21 and member 21 is axially loaded and rotated to drive the annular cutter 24 against the duct M and thereby to cut an annular section of the wall of duct M therefrom.

It should be noted that the rotation of cutter member 21 is in the opposite direction to the direction of tapping for tapping section 31 so that any rotational forces imparted to the cut-out annular section of duct M simply urge tightening of the cut-out section on tapping section 31 and, when the annular cutter 24 has fully penetrated the wall of duct M to separate the cut-out section there from, the cut-out section is firmly screwed onto tapping section 31.

It should also be noted that as the drill tip 30 breaches the wall of duct M fluid contents may flow from duct M into the bore 12 of the branch duct attachment but as, via the sealing members 35, 40 and 44 the bore 12 is sealed from atmosphere, the fluid within bore 12 is contained.

When the cut-out section of the wall of duct M is separated from said wall the breaching apparatus is withdrawn by simply drawing cutter member 21 outwardly and away from duct M, the pilot drill member 22 with the cut-out section threaded thereon is withdrawn with member 21, and, once members 21 and 22 have been withdrawn sufficient to clear valve member 17, the valve member 17 can be displaced to a closure condition. With valve member 17 in its closure condition the cap 32 can be unscrewed from threaded flange 14, the breaching arrangement can be fully withdrawn and removed from the branch duct arrangement, and an attachment, such as a tap or extension duct, may be secured onto threaded flange 14 as required to continue the branch.

Thus, by this means a branch duct attachment can be fitted to a main duct and the main duct breached to permit main duct contents to flow into the branch duct without any disruption of the fluid flow system including main duct M.

It will be observed that, when the breaching arrangement is fitted to the branch duct attachment as described above the enlarged collar 26 limits the displacement of pilot drill member 22 towards the right (as viewed in Fig. 1) relative to the cutter member 21 and the displacement of cutter member 21 towards the right is limited by the cup 37.

Thus, in the event that the main duct M is charged with high pressure fluid and is breached by the pilot drill to flood the branch duct with high pressure fluid the pilot drill member 22 and cutter member 21 cannot be blown away from the assembly and, once the pressure in the branch duct equalizes with the main duct M, the drilling and breaching can continue.

WHAT I CLAIM IS:- 1. A method for forming an opening in the wall of a duct comprising the steps of clamping a branch duct attachment, including a valve in the branch duct, to the said duct, opening said valve, advancing a pilot drill along the axis of the flow passage through the branch duct and through the open valve, rotating said pilot drill to drill a pilot hole through the wall of said duct,

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

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. boss 14 and cap 32 render the joint therebetween fluid tight, and remote from the internally threaded part 34 the cap 32 presents an external thread 36. A second cap 37 presents a bore 38 for slidably supporting the first reduced diameter section 27 of member 21, and an enlarged internally threaded section 39 engaged with the external thread 36 on cap 32. An annular sealing member 40 locates between radial faces of cap 32 and cap 37 to render the joint therebetween fluid tight. A third cap 41 presents a bore 42 slidably receiving the pilot drill member 22 remote from drill tip 30 and cap 41 presents an internal threaded part 43 engaged on threaded section 29 of cutter member 21. An annular sealing member 44 locates between radial faces of cap 41 and the section 28 of cutter member 21 to render the joint therebetween fluid tight. The end 45 of pilot drill member 22 remote from the drill tip terminates with a rectangular cross-section and the first reduced diameter section 26 of cutter member 21 has a hexagonal end 46. The duct M breaching arrangement is intended to operate as follows. With the cutter member 21 and pilot drill member 22 assembled with the branch duct arrangement and with the caps 32, 37 and 41 secured as described above, the pilot drill member 22 is rotated by engaging a tool (not shown) such as a tap wrench, on the end 45 to advance the drill tip 30 against the wall of duct M and drill a pilot hole therethrough, by continuing the rotation of member 22 in the direction of the lands of the tapping section 31, whilst maintaining axial loading on the member 22, the tapping section 31 forms an internal thread in the pilot hole and allows the tapped section 31 to enter the pilot hole until the leading radial face of the collar 26 engages the wall of duct M. It will be appreciated that as the collar 26 must be advanced into contact with duct M before the cutter member 21 is operative on duct M the pilot drill member 22 has an axial length greater than that of member 21 by at least the axial length of the drilling and tapping sections. With the collar 26 in engagement with duct M rotation of pilot drill member 22 is terminated, the tool (a tap wrench) is removed, a tool, such as a spanner, is engaged on section 46 of member 21 and member 21 is axially loaded and rotated to drive the annular cutter 24 against the duct M and thereby to cut an annular section of the wall of duct M therefrom. It should be noted that the rotation of cutter member 21 is in the opposite direction to the direction of tapping for tapping section 31 so that any rotational forces imparted to the cut-out annular section of duct M simply urge tightening of the cut-out section on tapping section 31 and, when the annular cutter 24 has fully penetrated the wall of duct M to separate the cut-out section there from, the cut-out section is firmly screwed onto tapping section 31. It should also be noted that as the drill tip 30 breaches the wall of duct M fluid contents may flow from duct M into the bore 12 of the branch duct attachment but as, via the sealing members 35, 40 and 44 the bore 12 is sealed from atmosphere, the fluid within bore 12 is contained. When the cut-out section of the wall of duct M is separated from said wall the breaching apparatus is withdrawn by simply drawing cutter member 21 outwardly and away from duct M, the pilot drill member 22 with the cut-out section threaded thereon is withdrawn with member 21, and, once members 21 and 22 have been withdrawn sufficient to clear valve member 17, the valve member 17 can be displaced to a closure condition. With valve member 17 in its closure condition the cap 32 can be unscrewed from threaded flange 14, the breaching arrangement can be fully withdrawn and removed from the branch duct arrangement, and an attachment, such as a tap or extension duct, may be secured onto threaded flange 14 as required to continue the branch. Thus, by this means a branch duct attachment can be fitted to a main duct and the main duct breached to permit main duct contents to flow into the branch duct without any disruption of the fluid flow system including main duct M. It will be observed that, when the breaching arrangement is fitted to the branch duct attachment as described above the enlarged collar 26 limits the displacement of pilot drill member 22 towards the right (as viewed in Fig. 1) relative to the cutter member 21 and the displacement of cutter member 21 towards the right is limited by the cup 37. Thus, in the event that the main duct M is charged with high pressure fluid and is breached by the pilot drill to flood the branch duct with high pressure fluid the pilot drill member 22 and cutter member 21 cannot be blown away from the assembly and, once the pressure in the branch duct equalizes with the main duct M, the drilling and breaching can continue. WHAT I CLAIM IS:-

1. A method for forming an opening in the wall of a duct comprising the steps of clamping a branch duct attachment, including a valve in the branch duct, to the said duct, opening said valve, advancing a pilot drill along the axis of the flow passage through the branch duct and through the open valve, rotating said pilot drill to drill a pilot hole through the wall of said duct,

advancing a tap into the pilot hole to form an internal thread in said hole, retaining the tap entered in said hole whilst advancing an annular cutter against the duct and rotating said cutter in the direction opposite to the direction of trapping to cut an annular section from the wall of the duct concentric with the pilot hole, and withdrawing said annular cutter, said tap with the annular member cut from the wall of the duct threaded thereon, and said pilot drill, away from the duct back through the open valve.

2. A method as claimed in Claim I including the steps of sealing said branch duct to prevent loss of pressure fluid from the duct during the drilling, tapping and cutting operations and during withdrawal of the drilling tapping and cutting members through the open valve.

3. Apparatus for performing the method set forth in Claims 1 or 2 and comprising, in combination, a branch duct attachment including a valve in the branch duct, an annular cutter member with an annular cutting head on one end and an external configuration which allows said member to enter the branch duct, cutter-head leading, to pass through the valve when said valve is open, and to rotate within the branch duct attachment, a pilot drill member rotatable within the bore of the annular cutter and axially displaceable along said bore, a drill tip at that end of the pilot drill member adjacent the annular cutter of the cutter member, and tapping means presented by said pilot drill member and immediately adjacent said drill tip.

4. Apparatus as claimed in Claim 3 in which the annular cutter member is of generally cylindrical configuration.

5. Apparatus as claimed in Claim 3 or 4 in which that end of the brach duct remote from the main duct is closed by an end cap, and the cutter member extends through said end cap to project externally thereof and the pilot drill member has an axial length greater than the cutter member by at least the axial length of the drill tip and tapping section.

6. Apparatus as claimed in claim 5 in which the cutter member externally of the end cap is adapted for engagement by a tool, for rotating the said cutter member, and that end of the pilot drill member externally of the cutter member is adapted for engagement by a tool for rotating said pilot drill member.

7. Apparatus as claimed in claim 5 or 6 including sealing means between said end cap and the branch duct, and sealing means between said cutter member and said pilot drill member.

8. Apparatus as claimed in claim 3, 4, 5, 6 or 7 in which the valve is a ball type valve with an opening through the ball closure member aligning with the flow passage through the branch duct when the valve is in an open condition, said opening having the same cross-sectional shape and a crosssectional area equal to, or greater than, the shape and cross-sectional area of the flow passage through the branch duct.

9. Apparatus as claimed in claim 3, 4, 5, 6, 7 or 8 in which the branch duct attachment comprises a duct member, intended to surround the duct, and the branch duct extends from said duct part in such manner that the axis of said branch duct intersects the axis of said duct.

10. Apparatus as claimed in claim 9 in which the duct member is split along a plane parallel to the axis of said member and including clamping means for clamping said duct member around a duct to frictionally retain said duct member with a duct passing therethrough.

11. Apparatus as claimed in claim 9 or 10 including sealing means between said duct member and said duct.

12. A method as claimed in claim 1 and substantially as described hereinbefore with reference to the accompanying drawings.

13. Apparatus, substantially as hereinbefore described with reference to and as illustrated in Figs. I and 2 of the accompanying drawings.