GB2243216A

GB2243216A - Gauge for marking profiles on pipes

Info

Publication number: GB2243216A
Application number: GB9108373A
Authority: GB
Inventors: Derek Cahill
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-04-19
Filing date: 1991-04-19
Publication date: 1991-10-23
Also published as: GB9008775D0; GB9108373D0

Abstract

A gauge 7 for marking profiles 5, 6 on pipes 1, (2) which are to be welded together comprises a parallel substantially equal length rods 9 mounted in a tubular arrangement by, for example, an annular housing 8 so that they are slidable relative to one another. The external diameter of the narrow end 13 of the rod arrangement is equal to the internal diameter of the wide end 12, both being equal to the outer diameter of the pipe (2). The gauge 7 is placed on pipe 1 at the angle at which the pipes 1, (2) are to be joined, and the rods 9 are extended from their aligned position 14 to contact pipe 1. Cut line 5 is then drawn on pipe 1 around rod end 13 and cut line 6 is drawn on pipe (2) around the opposite rod end 12. The two cut lines 5, 6 will correspond to the correct profiles for joining the pipes 1, (2) since the rods 9 are of equal length. Instead of an annular housing 8 to frictionally support the rods, the rods may support each other in dovetail fashion. The cut lines 5, 6 may be drawn with soapstone or chalk. <IMAGE>

Description

Gauge for Marking Profiles on Pipes The present invention relates to a gauge for marking profiles on pipes, and, in particular, to a gauge for marking cut lines on pipes which are to be joined together.

It is often the case that pipe fitters have to join a branch pipe to a main header pipe. In order to do this, one end of the branch must be cut so that it fits closely with the surface of the header, and a corresponding opening must be cut in the header for communication between the two pipes, the branch being welded to the header around the periphery of the opening.

The shapes of the branch end and the header opening depend on the angle at which the pipes are to be joined and also on the pipe sizes.

As shown in Figs l(a) and l(b), it is common practice to lay out the cut lines by placing the uncut branch 2 in position on the header 1 at the angle required for the joint. A soapstone or chalk 3 is then placed flat against the branch 2 so that it is aligned in the direction of the branch 2 and extends past the end of the branch 2 to contact the header 1. The soapstone or chalk 3 is then rotated about the circumference of the branch 2 whilst being kept aligned in the direction of the branch 2 and in contact with the header 1. The cut line 5, thus marked on the header 1, defines the opening for communication between the two pipes.

To mark the branch cut line 6, the exercise is repeated but this time a straight edge 4 is rotated about the branch 2 and the soapstone or chalk 3 is held in place a fixed distance along the length of the straight edge 4.

This method has a number of disadvantages, one being that it requires two people to carry it out (one to hold the pipe and the other to mark the cut lines).

It is also rather difficult to implement in practice, usually taking a long time to complete, and often being inaccurate, thereby causing a large number of pipes to be discarded due to inadequate fitting. This can be very costly particularly when the badly fitting joint is at the end of a series of joints, in which case the whole of the series may have to be refabricated.

Another known method of joining a branch to a header is to cut a length from the header and replace it by a prefabricated joint. Such joints are however rather expensive and only available for specific joint angles. Moreover, their use means that three welds must be made instead of only one, thereby producing a potentially less reliable joint.

The present invention seeks to overcome the abovementioned problems, and provides a gauge for marking a profile on a pipe, comprising a plurality of elongate rods of substantially equal length, mounted generally parallel to one another in a tubular arrangement so as to be slidable relative to one another in their lengthwise direction parallel to the axis of the tubular arrangement, the rods being so mounted and shaped that the internal diameter of the arrangement of rods at one, first, end of the rods is substantially equal to the external diameter of the arrangement at the other, second, end of the rods.

In practice a gauge will be provided for use with a particular size of pipe and the said internal and external diameters will be substantially equal to the external diameter of the pipe.

Such a gauge provides a quick and simple method for marking out the necessary cut lines on a pair of branch and header pipes which are to be joined together. The narrower (second) end of the gauge is simply placed against the header at the angle required for the joint, and the rods are then extended until they meet the header. This produces a profile at the narrower end of the gauge which is reproduced at the wider (first) end due to the fact that the rods are of the same length.

The cut line for the opening in the header is marked by drawing around the rod profile at the narrower end of the gauge, and the cut line for the branch pipe is marked out by inserting the branch into the wider end of the gauge and then drawing around the profile of the rods at that end.

The above method may be carried out by only one person and provides for accurate marking out of the cut lines, the accuracy being improved with the use of a larger number of thinner rods.

In order for the inner diameter of the rod arrangement at the wider end to be substantially equal to the outer diameter of the rod arrangement at the narrower end, many different shapes of rod can be envisaged. For example, the rods could have cut out stepped portions on their inner and outer facing surfaces at their first and second ends respectively.

The rods could however be of substantially the same thickness throughout their length and be provided with offsets or kinks therealong.

The rods may be frictionally mounted in a housing, which may be annular in shape and have holes therethrough in which the rods are frictionally held.

However, other mounting means can also be envisaged, for example, the rods could be held between an inner tubular member and an elastic or resilient outer member or vice versa, or could be clampingly held in position when not being slid relative to one another.

In one preferred embodiment, there is no separate housing per se. Rather, the rods are slideably interconnected to one another, preferably by means of interengaging grooves and projections provided on their adjacent sides. These could take the form of, for example, dove-tail joints. Such gauges can, if the grooves and projections extend to near the end of the rods at the second end, provide an added advantage in that they prevent the rods from splaying out when contacting, for example, a header pipe.

It is possible that a pipe could be misaligned with the rod arrangement when inserted into the wider end of the gauge thereby deforming the rod arrangement and thus producing inaccuracies in the pipe cut line. Preferably, therefore, a core is provided, which extends coaxially into the wider end of the rod arrangement and has an outer diameter equal to the inner diameter of the pipe, whereby, in use, the pipe to be marked is inserted over the core, the core thus supporting the pipe and preventing it from becoming misaligned.

A raised portion may be provided on the core which contacts with the inner surface of the rods at their first end and has an outer diameter equal to the outer diameter of the pipe. This helps to stop the rods from being deformed inwardly, out of their tubular arrangement.

When the rods are located in a housing, the core may be integral with the housing, and when the rods are interconnected to one another without the use of a housing, for example, by using the interengaging grooves and projections mentioned above, then the core may be integral with one of the rods. In the latter case, part of the core could abut against the surface with which the rods are to contact, and thus prevent the rod integral with it from extending far enough to meet the surface. Therefore, the rod integral with the core would need to remain stationary whilst the other rods were extended to form the required profile, i.e. by being the rod which first contacts the surface when the gauge is initially placed on the surface.

In order that the profile of the rods at the wider end of the gauge may be accurately marked out onto the pipe, a collar may be provided on the outside of the rod arrangement such that, in use, the collar may be slid along the outside of the rods, after the pipe has been inserted into the gauge, so as to positively hold the rods against the pipe. This stops the rods from moving whilst their profile is being drawn and so provides for a more accurate cut line.

The gauge may be made of any suitable material, and the housing, core and raised portion may be formed as an integral, one-piece, plastics unit.

The gauge may also be provided with means for positioning it at a set angle to a pipe (i.e. at the angle to a header pipe at which a branch pipe is to be attached). The means could comprise a sleeve within the rod arrangement, formed at one end to sit snugly on the pipe when the gauge is perpendicular thereto (e.g. by having a pair of diametrically opposed arcs cut out of its end) and having graduated marks at its other end.

In use, the gauge (with the sleeve inside) is placed on and at right angles to the pipe, so that the formed sleeve end fits snugly on the pipe and sets the gauge in position. Next, the sleeve is pulled upwardly until a graduated mark showing the desired joint angle is in line with the top edge of the rod arrangement. By this movement, the formed sleeve end is moved upwardly out of engagement with the pipe. The gauge may then be tilted to the side until the formed sleeve end again touches the pipe, at which point the gauge will be unable to tilt any further. Clearly, the amount by which the sleeve is initially lifted corresponds to the amount by which it may be tilted, and the graduations on the sleeve are marked accordingly to show the angle of tilt obtainable when the sleeve has been lifted to the graduation.Thus, the sleeve allows the gauge to be positioned at the correct joint angle to the pipe. The sleeve may be in two parts, so that its formed end may be changed for different pipe sizes.

Of course, a gauge according to the present invention is not limited to use in joining branch and header pipes, but may be used in a variety of different situations where a pipe must be fitted to another pipe or other object. For example, where two pipes are to be joined end to end and at an angle, the gauge may be placed at half the required joint angle against a flat surface. The rods may then be extended to contact the surface, to thereby produce the required cut line profile at the wider end of the gauge for both of the pipes.

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, wherein: Figures l(a) and l(b) show side views of a prior art method of marking cut lines on a pair of pipes to be joined, Figure 2 shows a perspective view of a gauge according to a first embodiment of the present invention with only four rods in place, Figure 3 is a side view showing a gauge according to the present invention being used to mark out cut lines on a pair of pipes to be joined; Figure 4 is a cross-sectional view of a gauge according to a second embodiment of the invention; Figure 5 is a cross-sectional view of a gauge according to a third embodiment of the invention; Figure 6 is a plan, first, end view of a gauge according to a third embodiment of the invention;; Figure 7 is a plan first end view of a rod used in a gauge according to the third embodiment; Figure 8 is a side view of a variation of a rod for use in the third embodiment of the invention; Figure 9 is a sectioned view along line IX-IX of Figure 8; Figure 10 is a side view of a rod of figure 8 having an integral core; and Figure 11 is a cross-sectional view along line XI XI of Figure 10.

Referring to Figure 2, a gauge 7 comprises an annular housing 8 and a plurality of elongate rods 9, only four of which are shown. The rods 9 are each of the same length and are frictionally mounted in holes 10 in the housing 8 to form a tubular arrangement as shown in Figure 3. The rods 9 are held loosely enough so that they may be moved in their lengthwise directions, but firmly enough so that they will not slip out of position.

Each rod 9 has a kink 11 along its length so that the tubular arrangement has one end 12 wider than the other end 13. The inner diameter of the wider end 12 and the outer diameter of the narrower end 13 are equal to the outer diameter of the pipe with which the gauge 7 is to be used. Of course, the exact measurements of the gauge will depend upon the size of the pipe, and a number of different sizes of gauge can be made for different sizes of pipe. For instance, for a 7.6 cm (3") internal diameter pipe, its outer diameter will typically be 8.3 cm (3.25"), and so the inner diameter of the wider end 12 of the gauge and the outer diameter of the narrower end 13 will be 8.3 cm (3.25").

Figure 3 shows the gauge 7 being used to mark cut lines 5 and 6 on header pipe 1 and branch pipe 2 respectively. The size of the gauge 7 corresponds to the size of the branch pipe 2 as detailed above.

The gauge 7 is placed on the header 1 at an angle 0, which is the angle at which the joint between the two pipes will eventually be made. The rods 9, which are originally level with one another along the dotted line 14, are then extended until they meet with the surface of header 1.

In order to ensure that the gauge 7 is properly positioned on the header 1, a pair of diametrically opposed rods 15a and 15b are marked on the gauge 7 and are aligned with a line 16 drawn down the centre of the header 1.

A cut line 5 for an opening in the header 1 is marked out by drawing around the profile of rods 9 contacting the surface of the header 1, and, since the outer diameter of the narrower end 13 of the gauge 7 is equal to the outer diameter of the branch 2, the opening defined by cut line 5 will match with the outer profile of the branch 2 when it is welded to the header 1.

Due to the fact that the rods 9 are of equal length, the profile of the wider end 12 of the gauge 7 will correspond to that produced at the narrower end 13.

Thus, the branch 2 can be inserted into the wider end of the gauge 7, and a cut line 6 can be marked out by drawing around the profile formed at that end by the rods 9. The gauge 7 can, of course, be removed from the header 1 before inserting the branch 2, since the frictionally held rods 9 will retain their profile.

After the cut lines 5 and 6 have been marked out, the two pipes can be cut therealong and then welded together to form the required joint.

The accuracy of the gauge 7 can be improved by using a larger number of thinner rods. Also, the rods can be made wider at the wider end 12 of the gauge 7 so that they remain circumferentially contiguous with one another.

In the above embodiments it is possible that the branch 2 could be inserted into the gauge 7 in a misaligned fashion, or could become misaligned during the marking out of the cut line 6. This may cause the rods 9 to bend and produce an inaccurate profile for the cut line 6.

A second embodiment of the invention which aims to solve this problem is shown in cross-section in Figure 4.

In this embodiment, the rods 9 are constructed as before, but the housing 8 now includes a core 17. The core 17 extends coaxially with the rod arrangement into the wider end 12 of the gauge 7, and comprises a rod supporting portion 18 and a pipe supporting portion 19.

The rod supporting portion 18 has the same outer diameter as the pipe 2, and contacts with the inside of the rods 9 at the wider end 12 of the gauge 7 in order to prevent the rods 9 from being bent inwardly when the gauge 7 is being used. This portion 18 can also act as a stop to prevent the pipe from being pushed too far into the gauge 7 and deforming the rods outwardly.

The pipe supporting portion 19 is of the same diameter as the inside of the pipe 2 and extends out from within the wider end 12 of the gauge 7. Thus, when the pipe 2 is inserted into the wider end 12 of the gauge 7, it is guided and supported by the pipe supporting portion 19 so that it is not misaligned and does not deform the rods 9, thus allowing for a more accurate cut line 6 to be drawn on the pipe 2.

A collar 20 is also provided in the second embodiment. This collar 20 is slidable along the gauge 7 to hold the rods 9 tight against the pipe 2 so that the profile can be more accurately drawn onto the pipe 2, without the rods 9 becoming displaced.

Of course, many other embodiments of the invention can also be envisaged. For example, instead of frictionally holding the rods 9 in holes 10, the rods could be clamped in place, with the grip being loosened to allow the rods to slide relative to one another and then tightened to retain the resulting profile.

In a third embodiment of the invention, shown in Figures 5, 6 and 7, no means are provided for housing the rods 9. Instead, each rod 9 is slidably interconnected with its neighbouring rods by means of grooves 21 and projections 22 formed on its sides.

As can be seen from Figures 6 and 7, the grooves 21 and projections 22, in this embodiment, form a dove-tail joint, although many other types of joint can also be envisaged.

Referring to Figure 5, the rods of this third embodiment are in the form of straight lengths which taper towards a point 23 at one end, so that, as before the inner diameter of the wider end 12 is equal to the outer diameter of the tapered narrower end 13.

In order to strengthen the narrower end 13, an extra portion 24 is formed on the rod 9. This portion 24 extends out from the point 23 to provide more room for a chalk or soapstone to draw around the profile of the narrower end 13.

A stop 25 is also provided on each rod 9 at the wider end of the gauge 7, so that when a pipe is inserted into gauge 7, it will abut against one of the stops and thereby prevent any over-insertion of the pipe into the gauge. Of course, the specific stop 25 against which the pipe 2 abuts is dependent on which rod remains stationary when the gauge is used to profile an object, i.e. the rod which initially contacts the surface of the object when the gauge 7 is first placed against it.

In the first two embodiments, it is possible that the rods at the narrower end 13 could splay out from one another when they contact, for example, the header pipe 1. This tendency becomes greater the further the rods must be extended to contact the surface of the header. In the third embodiment, however, the rods are connected to one another, and so any tendency to splay out is substantially prevented, thereby providing for more accurate cut lines.

In Figures 8 and 9, a variant of the rod used in the third embodiment is shown. Again, this rod 9 has grooves 21 and projections 22 for slidably interconnecting it with its neighbours. In this variant, however, the rod is formed from two portions 26 offset from one another, each section having separate grooves 21 and projections 22.

As in the first embodiment, it is possible that a pipe could be inserted into a gauge of the third embodiment in a misaligned fashion and so could deform the rod arrangement. In order to prevent this, a core may be provided. As, however, the rods are not held in a housing, the core must be made integral with one of the rods themselves. Such an integral rod and core is shown in Figures 10 and 11. In these Figures the rod variant shown in Figure 8 is used.

The gauge 7 may also be used in many other ways.

For example, where two pipes are to be joined end to end and at an angle to one another, an appropriately sized gauge could be positioned against a flat surface at half the required joint angle. The rods 9 could then be extended to meet the surface and provide a profile at the wider end 12 which could be used to mark out the necessary cut line on both pipes.

The gauge 7 is useful in all situations in which a pipe has to be joined to another pipe or other object.

Claims

1. A gauge for marking a profile on a pipe, comprising a plurality of elongate rods of substantially equal length, mounted generally parallel to one another in a tubular arrangement so as to be slidable relative to one another in their lengthwise direction parallel to the axis of the tubular arrangement, the rods being so mounted and shaped that the internal diameter of the arrangement of rods at one, first, end of the rods is substantially equal to the external diameter of the arrangement at the other, second, end of the rods.

2. A gauge according to claim 1, wherein said internal and external diameters are substantially equal to the external diameter of the pipe.

3. A gauge according to claim 1 or 2, wherein the rods have cut out stepped portions on their inner and outer facing surfaces at their first and second ends respectively.

4. A gauge according to claim 1 or 2, wherein said rods are substantially the same thickness throughout their length and are provided with offsets or kinks therealong.

5. A gauge according to any preceding claim, wherein said rods are frictionally mounted in a housing.

6. A gauge according to any of claims 1 to 4, wherein said rods are held between a tubular member and an elastic or resilient member.

7. A gauge according to any of claims 1 to 4, wherein said rods are clampingly held in position when not being slid relative to one another.

8. A gauge according to any of claims 1 to 4, wherein the rods are slideably interconnected to one another,

9. A gauge according to claim 8, wherein the rods are slideably interconnected by interengaging grooves and projections provided on their adjacent sides.

10. A gauge according to claim 9, wherein said grooves and projections extend to near the end of the rods at the second end.

11. A gauge according to any preceding claim, wherein a core is provided, which extends coaxially into the wider end of the rod arrangement and has an outer diameter substantially equal to the inner diameter of the pipe, whereby, in use, the pipe to be marked is inserted over the core.

12. A gauge according to claim 11, wherein a raised portion may be provided on the core which contacts with the inner surface of the rods at their first end and has an outer diameter equal to the outer diameter of the pipe.

13. A gauge according to claim 11 or 12, when dependent on claim 5, wherein said core is integral with said housing.

14. A gauge according to claim 11 or 12, when dependent on claim 8, wherein said core is integral with one of said rods.

15. A gauge according to any preceding claim, wherein a collar is provided on the outside of the rod arrangement at said first end such that, in use, the collar may be slid along the outside of the rods, after the pipe has been inserted into the gauge, so as to positively hold the rods against the pipe.

16. Gauges substantially as hereinbefore described with reference to Figures 2 to 11.