GB2292612A

GB2292612A - Pipe joint adjustable template

Info

Publication number: GB2292612A
Application number: GB9515756A
Authority: GB
Inventors: Gordon James Kingston; Robert William Field
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-08-02
Filing date: 1995-08-01
Publication date: 1996-02-28
Also published as: GB9515756D0; GB9415600D0

Abstract

The template or saddle joint jig for reproducing the line of contact of a first tube in relation to a second tube so that the first tube, when cut along that line, may be joined in end-to-edge abutment to the second tube in that same relation, which jig comprises: (i) a band that, in use, is capable of circumferentially encircling the first tube and which has a plurality of substantially parallel pockets or sleeves across the breadth thereof; and (ii) a plurality of pins each of which is slidingly held in use within a respective one of said plurality of pockets or sleeves to allow each pin to slide longitudinally and extend from the respective pocket or sleeve when a force is applied thereto; (iii) first engagement means provided at or near a first end of the band and adapted to cooperatively engage with second engagement means located at or towards a second end of the band such that the band, when wrapped around a tube and overlapped on itself can be fastened to itself to hold it in place on the tube; wherein the band comprises a single strip of inelastic material adapted to be substantially non-stretchable along its longitudinal axis.

Description

LIGHTVVEIGHT SADDLE-JOINT JIG Field of the Invention The present invention relates to saddle-joint jigs.

Background to the Invention In many fields there is a need to join tubes together at various angles to their longitudinal axes - such joints are known as saddle joints and, by way of example, one is shown schematically in Figure 1. In order to join a first tube end on to the side of a second tube in this way it is necessary to cut the end of the first tube so that it matches the exterior shape of the second tube allowing it to be joined to the second tube in end-to-edge abutment. In even the simplest cylindrical case, involving circular-cylindrical tubes9 where a first tube joins a second tube at any angle it is a relatively complex operation to determine exactly the shape that the end of the first tube needs to be cut to in order to fit the second tube.

The conventional method for reproducing the necessary shape of the end of the first pipe in order for it to fit to the second pipe involves the use of relatively complex Euclidean geometry calculations to arrive at a curve which can be drawn on a piece of paper. The paper is then wrapped around the tube and used as a guide-line along which a cut is made.

A skilled and experienced technician is generally required to carry out these calculations and the process is a protracted one. Alternatively a skilled technician may rely on his own ad hoc techniques or even guess-work.

Furthermore, in such a lengthy and complex process there is always a significant risk that an error may be made, which can result in an expensive mistake.

Adjustable markers, known as saddle joint jigs have been developed over the years in an effort to provide a practical device for making the necessary determinations and markings with the minimum effort and in the minimum time. Some examples of these devices are to be found in the patent literature namely, US 2,671,273 (Barnes), US 4,807,369 and US 4,956,924 (Hu Ming Chin), none of which have yet proved to be a practical success. Generally these devices appear cumbersome, prone to failure, difficult or impossible to adapt to irregular-shaped tubes or pipes and as a result have failed to gain wide acceptance in the trade.

A significant advance was documented in WO 92/09841 (Doerr & Field) which described a saddle joint jig made from a flexible band made up of two superimposed webbing strips. The webbing strips are stitched together to form parallel pockets to accommodate pins. An example of this type of arrangement is shown in Figures 2 and 3. One advantage of this type of jig is that it is so flexible, being made of webbing, that it can be overlapped on itself when wrapped around a pipe and can thus be used on a wide variety of pipe sizes. Strips of hook and loop fastener, shown as 12 and 14 in Figure 3, are conveniently used to keep the jig in place around the pipe.

Although this type of device has proved to be an improvement over the previous arrangements it is not without its disadvantages, most of which arise from the weight of the jig itself. In order to appreciate these disadvantages a number of practical aspects of using these jigs must be appreciated.

Firstly, for some applications it is an absolute requirement that the saddle joint jig has no longitudinal elasticity. This is because in use the jig is wrapped tightly around a pipe and the pins pushed into contact with a second pipe. The jig can then be unwrapped from the first pipe, laid out on a flat surface and used to mark and manufacture a template with which to mark the end of the first pipe and any subsequent pipes for similar joints. It will thus be appreciated that if the webbing strap is in any way elastic then the template will be inaccurate.

As a consequence the webbing must be both strong and highly resistant to deformation by tensional forces. In the past this has been achieved by superimposition of two tough webbing strips and stitching them tightly together across their width to form a series of pockets. However the use of two strips adds to the weight of the device.

Secondly these jigs are often used on large diameter pipes in which case long pins are required to make contact with the second pipe. In order to keep the pins in alignment, two webbing straps are used side by side as shown in Figure 4. The consequence of both the extra strap and the long pins is that the jig becomes too heavy for one person to operate safely or effectively.

The object of the present invention is to overcome or mitigate these disadvantages.

Summary of the Invention According to a first aspect of the present invention, in its broadest sense, there is provided a saddle joint jig for reproducing the line of contact of a first tube in relation to a second tube so that the first tube, when cut along that line, may be joined in end-to-edge abutment to the second tube in that same relation, which jig comprises: (i) a band that in use is capable of circumferentially encircling the first tube and which has a plurality of substantially parallel pockets or sleeves extending across the breadth thereof; and (ii) a plurality of pins each of which is slidingly held, in use, within a respective one of said plurality of pockets or sleeves to allow each pin to slide longitudinally and extend from the respective pocket or sleeve when a force is applied thereto; characterised in that the band comprises a single strip of material which incorporates said plurality of substantially parallel pockets or sleeves.

Preferably the strip comprises webbing material.

Preferably the thickness of the webbing along one or both lateral edges exceeds that of the webbing there between.

Preferably the pockets are formed from material with a degree of elasticity such that the pockets or sleeves can accommodate pins of varying diameters.

Preferably the pins are hollow.

In a particularly preferred embodiment pins are constructed from a rigid lightweight composite material.

Brief Description of the Drawings Preferred embodiments of the present invention will now be more particularly described by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a schematic representation of a saddle joint involving two hollow circular-cylindrical tubes; Figure 2 is a diagrammatic plan view of a jig in accordance with the prior art; Figure 3 is a diagrammatic front view of the jig shown in Figure 2 with the stitching removed for clarity; Figure 4 is a representation of a series of pins held in substantially parallel alignment by two webbing strips.

Description of the Preferred Embodiment Two methods have been identified to reduce the weight of these saddle joint jigs. Firstly, improved means of constructing the webbing strap have been developed. Rather than using two strips of webbing superimposed one on another, it has unexpectedly been discovered that a single webbing strip can be used. Preferably this has pockets woven into it, the pockets extending substantially across the breadth of the strip, in much the same fashion as curtain heading tape. In effect this is like a webbing strip of constant thickness with pockets formed intermittently along its length wherein the pockets form an additional thickness. Between the pockets the strip returns to its original dimensions.

This method of construction brings with it a number of advantages: (a) The thread or fabric used to construct the pockets can have a degree of elasticity so the pockets can expand to take even the largest pins.

(b) Since the pockets no longer contribute to the inelastic construction of the jig this means that the thickness of material used to create the pockets can be thinner than would otherwise be possible. The thinner the pocket, the closer the pins lies to the pipe in use and the more accurate is the jig tool.

(c) The pockets can be subdivided by stitching along their length and across the breadth of the strip. This means that the number of pins per unit length of strip can be doubled at least. Taking this modification to its logical conclusion it is possible to create a hybrid between the earlier jig described in WO 92/09841 and this current version. That is to say, elongate pockets can be woven into a single strip of material and these pockets subdivided by stitching into a plurality of narrower pockets.

(d) The thickness of the strip need not be uniform across its width. In particular the thickness along one or both lateral edges can exceed that of the main body of the webbing. This is a most important feature, and is one not easily achieved in the known version, because the increased peripheral thickness tends to retain the pin within the pockets and prevent unwanted lateral movement. In effect it exerts a positive gripping action on the pins and acts as a restraining means on the pins as the strip is flexed in use, such flexing tending to open and close the pockets and thus temporarily release the pins and allow them to move in an unwanted fashion.

In a further embodiment the pockets need not extend substantially across the breadth of the strip. Instead the pocket can take the form of a series of substantially parallel sleeves in end-to-end alignment, i.e. an intermittent series of retaining sleeves designed to keep a pin substantially at right angles to the strip. For practical purposes there must be at least two of these short sleeves, one at each lateral edge of the strip. In one example these sleeves could take the form of a strong string or cord or the like threaded through the length of the webbing strip proximate to each edge of the strip, the cord emerging from the body of the webbing in a series of loops adapted to accommodate pins. As in the previous example the cord could posses a degree of elasticity to accommodate different sized pins.It will be appreciated that in this example the pocket or sleeve-forming material extends throughout the length of the webbing strip.

In a further variation the cord could be pulled tight after the pins have been inserted, thus tending to restrain the pins in place. The cord will need to be secured after tightening by some securing means, such as tying it in a knot or clamping it by any suitable means.

It will therefore be appreciated that one definition of sleeve in this context is a narrow pin-retaining means, a series of sleeves performing the same or similar function of that of a pocket. A combination of various types of sleeve can be used across the strip as specified by the designer.

All these variations have one thing in common; they are lighter in weight than a complete webbing strip.

In an alternative embodiment the single strip is constructed in such a way that holes can be drilled, punched, or otherwise created through the body of and across the width of the strap to accommodate the pins. If the pins are rigid and pointed, the pins themselves can be used to create these holes.

In a still further embodiment a pocket comprises two holes punched or otherwise formed through the thickness of webbing strip rather than through the body of the strip, the holes being near to the opposing edges of the strip and on a line at right angles to the longitudinal axis of the strip. A pin can then be threaded through the two holes in an under-over-under arrangement such that the pin extends on either side of the strip and yet at the same time the pin may be slid backwards and forwards through the hole.

As well as the stated advantages, all these embodiments share the feature that the single strip can be lighter in weight than the original double strip version.

However, a further major weight saving can be achieved by using hollow rather than solid pins. The pins must be very strong and rigid to prevent bending or flexing in use and this is generally been achieved using hightensile steel rods. It has now proved possible to use hollow metal rods, such as would be used in the construction of modern arrows for example. But an even greater weight saving can be achieved by turning to composite material eg. a fibre-reinforced plastic or resin. These are not only extremely light in weight but virtually unbreakable. This combination of features is particularly attractive to this sort of application because working conditions on for example an oil rig installation, where these tools find application can be particularly hostile and demanding.

The physical-chemical properties of this composite are important to the tool's effective operation. Non-fraying fibre filaments set in resin are preferred and to achieve this it is preferably that the filaments should not be monodirectional.

The hollow pins can have any suitable diameter and can be tapered at the ends to form a point. Alternatively, the operative ends of the pins can contain a pointed insert to facilitate in marking the opposing pipe.

One method of securing the saddle joint jig around a pipe is to use hook and loop fastener fixing. The use of this modified strip with pockets that do not necessarily extend across the whole width of the strip provides an opportunity to use different fixings to keep the jig in place around a pipe. It is possible, for example, to use hooks which themselves hook into these pockets, preferably with one hook at each end of the pocket such that the strain is taken symmetrically along the strip. Alternatively a series of hooked claws can be provided which dig into the webbing and effectively engage with the weave of the webbing itself at one or more points.

In either of these embodiments, but particularly with the former, it is advantageous to interpose an elastomeric portion or component between the engagement means and the body of the jig. This is because for any particular pipe the hook means may not coincide exactly with the pockets. The elastomeric portion means that the end of the jig can be stretched to allow engagement with the next or adjacent pocket and thus retain a tight fit around any size of pipe.

The introduction of an elastomeric component at or towards one end of the jig allows practically any form of fixing to be used. Examples are press studs or similar popper fixings, a belt buckle arrangement or even an over-centre action buckle. This gives a degree of design flexibility not seen with any previous type of jig.

The reader is directed to the disclosure in patents specification WO 92/09841 for any further details he may need to put the invention into practise.

This novel form of construction is equally applicable to the manufacture of profile gauges and this specification should therefore be read in conjunction with GB 94 10177.1

Claims

CLAIMS 1. A saddle joint jig for reproducing the line of contact of a first tube in relation to a second tube so that the first tube, when cut along that line, may be joined in end-to-edge abutment to the second tube in that same relation, which jig comprises: (i) a band that, in use, is capable of circumferentially encircling the first tube and which has a plurality of substantially parallel pockets or sleeves across the breadth thereof; and (ii) a plurality of pins each of which is slidingly held in use within a respective one of said plurality of pockets or sleeves to allow each pin to slide longitudinally and extend from the respective pocket or sleeve when a force is applied thereto; (iii) first engagement means provided at or near a first end of the band and adapted to cooperatively engage with second engagement means located at or towards a second end of the band such that the band, when wrapped around a tube and overlapped on itself can be fastened to itself to hold it in place on the tube; wherein the band comprises a single strip of inelastic material adapted to be substantially non-stretchable along its longitudinal axis.
2. A saddle joint jig as claimed in Claim 1 wherein the band comprises a webbing strip incorporating a series of pockets woven into the body of the strip.
3. A saddle joint jig as claimed in Claim 1 or Claim 2 wherein the pockets are subdivided transversely to the longitudinal axis of the strip and thus adapted to incorporate additional pins.
4. A saddle joint jig according to any proceeding claim wherein one or both lateral edges of the strip incorporate a restraining means adapted to restrict movement of the pins in use.
5. A saddle joint jig according to Claim 4 wherein the restraining means comprise an increased peripheral thickness in the construction of the strip.
6. A saddle joint jig according to any preceding claim wherein each pocket takes the form of a plurality of pin retaining means in end to end alignment across the breadth of the strip.
7. A saddle joint jig according to Claim 6 wherein the pin retaining means comprise a series of loops formed from cord, wire or the like incorporated into the body of the strip.
8. A saddle joint jig according to any preceding claim wherein the pockets incorporate an adjustment means and are thus adapted to accommodate pins of varying diameters.
9. A saddle joint jig according to Claim 8 wherein the pockets are constructed from elastic material, thus providing an expandable pocket.
10. A saddle joint jig according to any of claims 1, 4 or 5 wherein the pockets comprise a series of holes formed through the body of the strip.
11. A saddle joint jig according to any preceding claim wherein the pins are hollow.
12. A saddle joint jig according to any preceding claim wherein the pins comprise composite material, for example fibre-reinforced plastics.
13. A saddle joint jig according to Claim 12 in which the composite material comprises non-fraying fibre filaments which are preferably not mono-directional.
14. A saddle joint jig according to any preceding claim wherein the first and second engagement means comprises hook and loop fastening.
15. A saddle joint jig according to any of Claims 1 to 12 wherein the first engagement means comprises one or more hooks adapted to engage directly into the strip or into the pockets as a second engagement means.
16. A saddle joint jig according to Claim 15 wherein the band further incorporates an elastomeric region adapted to provide sufficient adjustment to enable the hooks to engage with the pockets when the diameter of the tube being joined does not allow for direct engagement of the hooks in the pockets.
17. A saddle joint jig substantially as herein described.