GB2339871A

GB2339871A - Punch and coupling

Info

Publication number: GB2339871A
Application number: GB9814335A
Authority: GB
Inventors: Brian Rex; Paul Joseph Morrow
Original assignee: Glynwed Pipe Systems Ltd
Current assignee: Glynwed Pipe Systems Ltd
Priority date: 1998-07-03
Filing date: 1998-07-03
Publication date: 2000-02-09
Also published as: GB9814335D0

Description

2339871 PUNCH AND COUPLING The present invention relates to a punch and

coupling for making a hole in a wall of for example a conduit and establishing a connection to such a hole.

A fitting known as a punch tee has been widely used in the pipeline industry for many years. The known punch tee is designed to connect a lateral service pipe to the top of a steel main conduit. The tee comprises a steel body which is welded to the outside wall of the steel main conduit. An elongate hardened steel punch with a threaded cylindrical outer surface is screwed into a fine thread formed on the inside surface of a bore defined in the body. One end of the punch can be engaged by a suitable tool to enable it to be rotated relative to the body, and the other end which is ad acent the conduit has a substantially tubular portion defining at its end an edge which is profiled and hardened so that as the punch is rotated relative to the body it progressively trepans a hole in the wall of the steel pipe to which the body is welded. Once a hole has been formed, the punch is withdrawn by reversing the direction of its rotation relative to the body, leaving a hole in the steel main conduit. That opening communicates with a passageway extending through the body to either a compression socket or a weld-prepared end to receive the connecting service lateral. The end of the body remote from the steel main conduit is closed with a completion cap to ensure that no leakage can occur through the bore.

With the known punch, as the cutting tip penetrates the wall of a conduit, a coupon made up of a section of the conduit wall is formed and is received into the hollow end of the tubular cutting tip. The coupon is not cut cleanly from the conduit wall however as just before the cutting tip completes the cutting operation the coupon breaks away from the conduit wall. A thin rim of conduit wall material remains attached to the coupon, that rim extending radially outwards from the coupon such that the rim can project to a diameter greater than the outside diameter of the cutting tip. As a result, as the punch is retracted there is a substantial risk that the coupon rim will catch on the edge of the hole cut in the conduit, causing the coupon to fall from the punch cutting tip.

2 It is highly desirable to avoid leaving coupons within conduits to which a connection has been made. Accordingly in the known punches, the body of the punch immediately adjacent the cutting tip has an outside diameter slightly greater than the outside diameter of the cutting tip. Thus as the punch is advanced during a cutting operation, the enlarged diameter portion of the punch acts on the edge of the hole being cut in the conduit, causing the hole to be widened slightly. Such widening is sufficient to ensure that a coupon can be safety withdrawn from a formed hole without catching on the hole edge.

Generally punch tees are operated manually. With the conventional punch tee, it has been found that the formation of a l3mm hole in a steel pipe requires torque of about 100 Nm. Such a torque can be delivered manually for the relatively short period of time taken to form a hole. Using a conventional punch tee to form a larger hole requires a substantially greater torque. For example a 20mm hole would require a torque of around 400 Nm which is far beyond the capability of a normal operator. This problem cannot be overcome simply by reducing the pitch of the thread which interengages the punch and the body. The reduction in torque given practical thread structures is insufficient and a very fine thread structure is vulnerable to contamination with dirt.

A power tool could be used to deliver the required torque. Unfortunately, there are cost constraints which would be difficult to satisfy using a complex powered machine and furthermore safety may be compromised unless a complicated torque resisting device was provided.

The above problem has been addressed in practice by providing a torque multiplier in the form of an epicyclic gearbox which fits over the body into which the punch is screwed to provide reaction to the applied torque and is operated with a standard ratchet wrench. This approach avoids the safety problems inherent in the use of power tools in such an application but nevertheless still relies upon the provision of non-standard equipment which is neither convenient nor economical.

It is often desirable to install a shut off valve in a service lateral close to a main conduit to which the service lateral is coupled. With the known punch tee, this 3 can only be achieved by providing a service valve as a separate unit which must be coupled to the punch tee. It is not generally possible to provide an arrangement in which the punch can be removed and replaced by a valve spindle as in most applications connections are made to "live" mains which are under pressure. The surface of the pipe around the hole has not been considered suitable to act as a valve seat.

It is an object of the present invention to obviate or mitigate one or more of the problems outlined above.

According to the present invention, there is provided a punch for forming a hole in a wall of less than a predetermined thickness, comprising a body, a cutting tip extending from the body, and a hole widening formation defined by the body adjacent the cutting tip, the body being adapted to be screwed into a support mounted on the wall such that the cutting tip is driven in an axial direction through the wall to form a hole and the hole widening fori-nation is driven through the hole so as to widen the hole, wherein the cutting tip and hole widening formation are separated by a distance sufficient to ensure that the cutting tip and hole widening formation do not engage the wall simultaneously.

Preferably the hole widening formation comprises a plurality of axially extending ribs projecting from the body. For example six ribs may be provided, each in effect defining a cutting edge.

As the cutting tip and widening formation are axially separated so that they do not both act on the conduit wall simultaneously, the torque required to use the punch of the invention is relatively small and can be delivered by an operator without the assistance of gearing or power equipment.

Ile present invention also provides a coupling for making a connection to a conduit, comprising a body through which a passage extends between an inlet opening and an outlet, and a punch mounted in the body and displaceable between a retracted position in which a cutting tip of the punch is within the body and an extended position in which the cutting tip projects out of the body through the inlet opening, the coupling being formed such that with the punch retracted the body may be secured to 4 a conduit with the inlet opening facing a wall of the conduit, and such that when the punch is in the retracted position the passage is not obstructed, wherein the punch defines a shoulder adapted when the punch is in the extended position to form a seal with the edge of a hole through a conduit wall on which the body is secured and in which the hole has been formed by extending the punch from the retracted to the extended position.

The shoulder which may be a simple 45 chamfer is in use pressed down hard against the edge of a hole formed in the conduit and forms a seal which may be less than perfect but is often sufficient in low pressure applications. Leakage around the punch may be further reduced if a portion of the punch body extending between the widening formation and the shoulder has an outside diameter which makes it a tight fit in a hole cut into the conduit by the punch.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which; Figure I is a side view of a punch in accordance with the present invention; Figure 2 is an end view of the punch of Figure I in the direction of lines 2-2 of Figure 1; Figure 3 is a partly cut-away enlarged view of the cutting tip and widening formation of the punch of Figure 1; Figure 4 is a section through the punch of Figure 1 on the lines 4-4 of Figure 2; Figure 5 is an enlarged view of the cutting tip end of the section of Figure 4; C and Figure 6 is a part-sectional illustration of a coupling in accordance with the present invention incorporating a modified form of the punch of Figures I to 5.

Referring to Figures I to 5, the illustrated punch comprises a body 1 from one end of which a tubular cutting tip 2 extends and from the other end of which a hexagonal projection 3 extends. The outer surface of the body I is threaded to enable the punch to be screwed into a support mounted on for example a pipe so as to drive the cutting tip through a wall of the pipe.

The cutting tip defines a saw tooth cutting edge 4 shaped to minimise the resistance to rotation of the body as the cutting tip is advanced through the wall of a pipe. The cutting tip has an axial length greater than the thickness of any pipe wall on which the punch is intended to be used and the body supports adjacent the cutting tip an array of six ribs 5 the outer diameter of which is greater than the outer diameter of the cutting tip.

In use, the punch of figures I to 5 is advanced so that the cutting edge 4 bears against the wall of for example a pipe in which a hole is required. The punch is then advanced further by rotating it in an appropriate support, causing the cutting tip to be driven through the pipe wall. A coupon cut from the pipe wall is retained within the hollow cutting tip, edges of the coupon projecting radially outwards beyond the outer edge of the cutting tip. Thus if the punch was withdrawn immediately after the coupon was cut from the pipe wall, there would be a risk that the coupon would be pushed off the cutting tip as it is withdrawn. To prevent this happening, after the coupon has been cut from the pipe wall, the punch is advanced further until the ribs 5 engage the edges of the hole in the cut pipe so as to widen the hole sufficiently for the coupon to be withdrawn through the hole.

Referring to Figure 6 a punch in accordance with the present invention is shown mounted in a body 6 secured to the wall of a pipe 7. The same reference numerals are used in Figure 6 as in Figures I to 5 and it will be seen that in the embodiment of Figure 6 the body I of the punch does not support a hexagonal nut structure on one end but rather receives one end of an allen key 8 which projects through an O-ring seal 9 carried by an end cap 10 of the support body 6. A further 0ring I I provides a seal between the end cap 10 and the support body 6. The support body also includes a side connection 12 which communicates with the space inside the support body occupied by the punch. The connection 12 defines an end 13 which in use will be connected to a branch service connection. The support body also defines a skirt 14 which in use is welded to the pipe 7.

In use, the support body alone is mounted on a pipe and welded in position. The punch is then inserted into the support body and the end cap 10 and associated 6 seals positioned as shown. The punch is then rotated by connecting an appropriate tool to the end of the allen key 8 projecting from the end cap 10 so that the cutting edge 4 of the tip 2 is forced against and through the wall of the pipe 7. A coupon is cut form the pipe and retained within the cutting tip. The punch is further advanced until the ribs 5 are forced through the hole previously cut in the pipe, thereby widening the pipe sufficiently to enable the punch to be withdrawn carrying with it the retained coupon.

The punch may be withdrawn such that the cutting edge 4 is located at the level indicated by broken line 15, enabling fluid within the pipe 7 to pass to the connection 12. The junction between the connection 12 and the support body proper may be shaped so as to minimise the spacing between the line 15 and the adjacent pipe wall without reducing the internal cross-section of the connection. This reduces the overall height of the tee structure.

In normal use fluid will flow from the pipe 7 to the connection 12. The seals 9 and I I ensure that there is no leakage from the assembly. In circumstances where it is desired to cut off the supply of fluid to the connection 12 however the tee can be screwed down to the position shown in Figure 6 such that a shoulder defined on the punch body above the ribs 5 is forced against the outside edge of the hole cut through the pipe. This will effectively block the hole as a result of contact between the punch and the hole edge. The sealing may not be perfect but will be sufficient for most circumstances.

As shown in Figure 6, the shoulder 16 is immediately adjacent the ribs 5, the shoulder 16 enabling the formation of a seal between the edges of a hole cut in the pipe 7 and the punch. Given the circumferential spacing of the axially extending ribs 5, the punch does not make a tight fit with the interior of the hole edges. A better fit which would reduce the rate of any leakage which might occur after the shoulder 16 is forced into contact with the edge of the hole could be achieved with a punch configuration such as that shown in Figure I where there is a shoulder but that shoulder is separated from the ribs 5 by a smooth-surface cylindrical portion dimensioned to be a tight fit in a hole cut in the conduit by the cutting tip.

7

Claims

A punch for forming a hole in a wall of 'less than a predetermined thickness, comprising a body, a cutting tip extending from the body, and a hole widening formation defined by the body adjacent the cutting tip, the body being adapted to be screwed into a support mounted on the wall such that the cutting tip is driven in an axial direction through the wall to form a hole and the hole widening formation is driven through the hole so as to widen the hole, wherein the cutting tip and hole widening formation are separated by a distance sufficient to ensure that the cutting tip and hole widening formation do not engage the wall simultaneously.
2. A punch according to claim 1, wherein the hole widening formation comprises a plurality of axially extending ribs projecting from the body.
3. A coupling for making a connection to a conduit, comprising a body through which a passage extends between an inlet opening and an outlet, and a punch mounted in the body and displaceable between a retracted position in which a cutting tip of the punch is within the body and an extended position in which the cutting tip projects out of the body through the inlet opening, the coupling being formed such that with the punch retracted the body may be secured to a conduit with the inlet opening facing a wall of the conduit, and such that when the punch is in the retracted position the passage is not obstructed, wherein the punch defines a shoulder adapted when the punch is in the extended position to form a seal with the edge of a hole through a conduit wall on which the body is secured and in which the hole has been formed by extending the punch from the retracted to the extended position.
4. A punch substantially as hereiribefore described with reference to Figures I to 5 or Figure 6 of the accompanying drawings.

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5. A coupling substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.