GB2385396A

GB2385396A - A method for connecting two structures together using a strap, a tensioning device for use in such method and a device for forming an eye at an end of a strap

Info

Publication number: GB2385396A
Application number: GB0203148A
Authority: GB
Inventors: Stefan Lindby; Benny Drastrup Christensen
Original assignee: ROBLON IND FIBER
Current assignee: ROBLON IND FIBER
Priority date: 2002-02-11
Filing date: 2002-02-11
Publication date: 2003-08-20
Anticipated expiration: 2022-02-11
Also published as: GB2385396B; GB0203148D0

Abstract

A method and an apparatus for connecting two structures together, for example for connecting a first pipe to a second pipe or for connecting a hydrodynamic element to a pipe, in particular for connecting two structures of or for a subsea installation, comprises a strap and a tensioning device for the strap. The tensioning device comprises a U-shaped yoke having first and second limbs connected by a base portion of said yoke, a pin passing through said first and second limbs generally parallel to a plane of said base portion, said pin being secured against movement in its axial direction out of said limbs, a tensioning bolt having an axially extending slot passing through it, said tensioning bolt extending through said first and second limbs generally parallel to said pin and having a head at one end permitting rotation of said tensioning bolt by a wrench applied to said head, said tensioning bolt further having a ratchet disc rotationally secured to it, there being a pawl pivotally mounted on said tensioning device and engageable with ratchet teeth of said ratchet disc to prevent rotation of said tensioning bolt in one direction but permitting rotation of said tensioning bolt in an opposite direction.

Description

A method for connecting two structures together using a strap, 5 a

tensioning device for use in such method and a device for forming an eye at an end of a strap The present invention relates to a method for connecting two structures 10 together using a strap, to a tensioning device for use in such method and to a device for forming an eye at an end of a strap.

Various kinds of strap are known in prior art. For example US Patent

6 098 932 assigned to the present applicant describes straps sold by the 15 Roblon Company under the none "Orbit Strap". An Orbit Strap consists of several strings or cables of ararnide fibres with a plurality of adjacently . disposed strings being jointly covered with a thermoplastic polyurethane.

These bands are used in the offshore oil production as strapping for buoy ancy modules and have become increasingly used in deep waters. US 20 Patent 6 098 932 describes a method of manufacturing a pipe mounting apparatus, for example in the form of a generally U-shaped clamp, by placing a plurality of lengths of strap adjacent to one another in a heated shaped mould and pressing the lengths of strap against one another while softening the thermoplastic resin using the heated mould so that the 25 bands fuse together to form a unitary item useful in mounting pipes to a substrate.

The present invention relates to an alternative use for straps of the same general type of construction as the Orbit Straps.

There is a particular need in the offshore exploration industry to provide 5 fastening systems using straps which meet a demand for reduced weight and installation cost. For example, there is a need to use straps in the securing of subsea pipe systems and/or of subsea pipeline attachments.

For example a first pipe can be used to carry a second pipe which is con-

nected by straps to the first pipe. This type of system is referred to as a 10 "piggy-back" system. Equally there is a need to attach other items such as VIV strakes to such pipe systems. VIV strakes are hydrodynamic aids which improve the flow of water over the pipes when the pipes are located in areas where flowing water is encountered (for example in tidal regions).

15 Accordingly there is a need to provide a method of connecting two struc-

tures such as pipes together using a strap and a tensioning device, with the method and the tensioning device providing a system which is of low weight, which is easy to install, which achieves reduced installation time on site, which is easy to handle and which can be provided at a relatively 20 low cost. Moreover it is the specific aim of the invention to provide a method of installing a strap which permits the strap to be tensioned by the correct amount in a simple manner using simple tools.

In order to satisfy this object method-wise there is provided a method of 25 connecting two structures together, for example for connecting a first pipe to a second pipe or for connecting a hydrodynamic element to a pipe, in particular for connecting two structures of or for a subsea installation, the method comprising the following steps:

- taking a strap comprising a plurality of strength giving yarns ori ented in parallel along the length of the strap and embedded in a thermoplastic material, said strap having a first end with an eye and 5 a second free end; - passing a pin through a first limb of a generally U- shaped yoke, through said eye and through a second limb of said generally U shaped yoke and securing said pin in said yoke, - passing said strap around said first and second structures, 10 - passing said free end through a slot in a tensioning bolt, said ten sioning bolt passing through said first and second limbs of said U shaped yoke generally parallel to said pin, said tensioning bolt hav ing a head for the engagement of a wrench to permit rotation of said tensioning bolt and tensioning of said strap and a ratchet disc rota 15 tionally fixedly connected to said tensioning bolt and having ratchet teeth, there being a pawl pivotally mounted on said U-shaped yoke .. À - and engageable with said ratchet teeth to prevent unwinding rota . tion of said tensioning bolt, and - subsequently rotating said tensioning bolt by said wrench to tension 20 said strap and engaging said pawl with said ratchet teeth to prevent À loosening of said strap.

Furthermore the invention relates to a tensioning device for a strap corn-

prising a U-shaped yoke having first and second limbs connected by a 25 base portion of said yoke, a pin passing through said first and second limbs generally parallel to a plane of said base portion, said pin being secured against movement in its axial direction out of said limbs, a ten-

sioning bolt having an axially extending slot passing through it, said tensioning bolt extending through said first and second limbs generally

parallel to said pin and having a head at one end permitting rotation of said tensioning bolt by a wrench applied to said head, said tensioning bolt further having a ratchet disc rotationally secured to it, there being a pawl pivotally mounted on said tensioning device and engageable with ratchet 5 teeth of said ratchet disc to prevent rotation of said tensioning bolt in one direction but permitting rotation of said tensioning bolt in an opposite direction. Finally the invention also relates to a device for forming an eye at an end 10 of a strap comprising strength giving yarns disposed parallel to one an-

other in a thermoplastic matrix, said device comprising first and second heated plates engageable with opposite sides of two limbs of a loop of strap defining said eye and being adapted to be pressed together to weld the two limbs of strap forming the loop to each other or to opposite sides of a 15 further strap inserted between said two limbs.

As is evident from the foregoing, the present invention recognizes that it is a simple matter to form a strap of the initially named kind, i.e. a strap comprising a plurality of high strength yarns extending parallel to one 20 another in a thermoplastic matrix, into an eye by folding one end of the strap back on itself and heating the folded back length of the strap and the length of strap adjacent to it in a heated pressing device so as to weld the thermoplastic material together. Because the weld can take place over a relatively long length of strap a tensile load applied to the strap via the 25 eye can easily be carried without the danger that the strap will fail prema-

turely at the eye.

In an alternative way of forming an eye a first length of strap can be formed into a U-shape and the end of a second length of strap can be

inserted into the U. The sandwich comprising the two limbs of the U-

shaped strap and the free end of the second strap can be heated in the heated pressing device to fuse all three strap lengths of the sandwich together, which again results in a high strength joint between the strap 5 forming the eye and the free end of the second strap. Since these two ways of forming an eye are very simple and can be done with a relatively simple tool, i.e. the heated pressing device, it is possible for the user of the sys-

tem to form straps in any length he may require using such a tool.

10 Having formed the strap with an eye at one end it is an easy matter to pass the pin of the yoke through the eye and then to place the strap around the two or more structures which are to be connected together.

The end of the strap remote from the eye is then passed through the slot in the tensioning bolt and the tensioning bolt is rotated to wind the strap 15 around it and tension the strap. The ratchet disc and the cooperating pawl form a simple but effective way of preventing the tensioning bolt rotating in a direction so as to loosen the strap when tensioned. Since the tension j:: ing bolt can be operated via a torque wrench, the level of tension applied to the strap can be set by the torque applied via the torque wrench.

- Since the pawl can be engaged with the ratchet disc simply by the user pressing on it, it is possible for the user to ensure that the ratchet disc comes into operation once the strap is being tensioned.

25 Since the tensioning device simply comprises a U-shaped yoke with a pin and a tensioning bolt passing through it, with the tensioning bolt carrying a ratchet disc and a pawl conveniently rotationally mounted on the pin, the entire tensioning device is a relatively simple construction of low

weight which can be made in a cost-effective manner. Nevertheless the system comprising the strap and the tensioning device is very effective in use. 5 By using high strength yarns in a thermoplastic matrix of high tempera-

ture resistance it is also possible to preassemble subsea installations on the shoreline in hot climates without the danger that the strap loses its tension by softening of the matrix before the preassembled installation is placed on the sea bed. Indeed it is possible for pre- finished modules to be 10 present on the shoreline for several months in hot climates without the danger arising that the straps lose the pre- tension due to softening of the thermoplastic matrix material.

Preferred embodiments of the invention are set forth in the subordinate 1 5 claims.

The invention will now be described in more detail with reference to the accompanying drawings in which are shown: 20 Fig. 1 a cross-section through a high temperature resistant strap .. or tape used for the strapping system, c::. Fig. 2 an illustration of a length of strap wound onto a reel, 25 Fig. 3 a diagram to illustrate the formation of an eye at one end of the strap using a device comprising a pair of heated press plates,

Fig. 4 a diagram illustrating an alternative way of forming an eye using two lengths of the strap, but with the eye formation being carried out using the same device as in Fig. 1, 5 Fig. 5 a plan view of a tensioning device for use with the strap of Figs 1 and 1A, Fig. 6 a view of the tensioning device of Fig. 5 seen from the right hand side of Fig. 5 in the direction of the arrow VI, Fig. 7 a drawing illustrating the use of a torque wrench with the strap and tensioning device of the previous Figures to con nect two pipes together in piggy-back fashion, 15 Fig. 8 a drawing identical to that of Fig. 6 apart from the pawl which has a modified shape, and c. ( .. Fig. 9 a drawing showing an alternative design of the pawl of Fig. 6. Fig. 1 shows a cross-section through a strap 10 for use in the present it, at. invention. The strap 10 comprises a plurality of three ply aramide yarns 12 and a plurality of three ply polyester yarns 14. In the drawing of Fig. 1 the three ply aramide yarns 12 are shown in cross-section as circles and 25 the three ply polyester yarns 14 are similarly shown in cross-section as circles but with cross hatching to distinguish them from the three ply aramide yarns. It can be seen that in the specific construction of Fig. 1 there are seven aramide yarns 12 at each side of the strap and seven

polyester yarns at the centre of the strap. The yarns all extend parallel to one another in one plane in the longitudinal direction of the strap 10, which is shown coiled on a reel 16 in Fig. 2, and are embedded in a ther-

moplastic matrix 18.

The specific construction of the strap 10 shown in Fig. 1 and 2 is as fol-

lows. Each of the total of the fourteen aramide yarns 12 are of 9990 dtex with the construction -1-3-85s-47z. The aramide yarns comprise three identical strings or plies each with 85 turns per meter in the Sdirection 10 and the three strings are twisted together with 47 turns per meter in the Z-direction to form the yarn. Each string consists of 2000 individual (end-

less) substantially identical filaments totalling 3330 dtex. The seven poly-

ester yarns 14 are each of 10020 dtex and have a construction 1-3-9Os-

47z. Thus each yarn is formed of three identical strings each with 90 15 turns per meter in the S-direction and the three strings are twisted to-

gether with 47 turns per meter in the Z-direction. For the polyester yarns each string consists of 2 x 210 = 420 identical (endless) filaments totalling 3340 dtex. It should be noted that these yarn types and yarn construc-

tions are given purely by way of example and can be varied as desired by 20 the user/ manufacturer.

The yarns are embedded in a high temperature resistant thermoplastic matrix consisting in this case of an ethylene acrylic acid based (EAA) polymer from Dow Chemical. In this strap it is the aramide yarns which 25 provide the tensile strength, the polyester yarns are simply provided be-

cause the same strap can also be used with a bolt tensioning system as shown at the centre of Fig. 7, for which purpose it is necessary to cut out a portion from the centre of the strap and it would be wasteful to provide

aramide yarns here. If they are provided the function of the polyester yarns is simply to act as a carrier for the matrix material 18 in which the yarns are embedded. It will be apparent from the foregoing that the poly-

ester yarns can be omitted from the construction if desired when the strap 5 is simply intended for use with a tensioning device as proposed herein, i.e. does not have to be simultaneously used with a bolt tensioning device as shown at the centre of Fig. 7.

It will be appreciated that any thermoplastic matrix material can be used 10 which has a sufficiently high temperature resistance that there is no danger of it softening during storage or use. This can be a problem with subsea installations which are assembled on shore in hot climates or transported on board ships through hot climate zones, which is why it is preferred to use a high temperature resistant thermoplastic matrix which 15 can for example be fused to itself under pressure at 125 C or higher.

., In addition the high strength yarns do not have to be aramide yarns. They could for example also be Zylon AS or HM (PRO timbre) yarns or Eglass yarns or Vectran yarns, which are made of melt spun LCP fibres.

Moreover the construction of the tape is not restricted to the specific numbers of yarns quoted above. In the example given the yarns are typi cally 1 mm thick and the strap has an overall thickness of 2.5 mm. Fur thermore it is not essential for all the yarns to lie in one plane. They could 25 lie in two or more planes arranged parallel to one another and could in such a case be made finer to minimise the thickness of the strap.

In practice it is intended to sell straps of this kind in five different strength ratings of 1500 kg, 2500 kg, 3750 kg, 5000 kg and 10,000 kg breaking strength. The straps with 1500 and 2500 kg breaking strength are 60 mm wide whereas the straps with 3750, 5000 and 10,000 kg breaking strength 5 are 90 mm wide. The different strengths are achieved for the widths given by varying the numbers of strength giving aramide yarns or similar in the straps. If it is necessary to have more yarns present in the strap in order to ensure that the matrix material is properly supported throughout the strap then this can be achieved by adding polyester yarns or the like 10 which act as a carrier for the matrix material.

Turning now to Fig. 3 there is shown a device 21 in accordance with the present teaching for the formation of an eye 20 at one end of a length of strap such as is shown in Figs. 1 and 2. As can be seen from Fig. 3 a 15 length of the straps indicated generally by "L" of the strap is folded back onto a portion of the strap P adjacent the length L so as to form the eye lo. 20. The folded back length L and the portion P are inserted between upper and lower heated plates 22, 23 in a pressing device so that the eye 20 projects beyond one end 24 of the heated plates whereas the free end 25 of 20 the length L is positioned at the other end 26 of the heated plates. The heated plates, which in this example are used with the matrix material described above (ethylene acrylic acid based polymer), are heated to 125 C and the upper plate can be pressed against the lower plate, as indicated by the double-arrow 28. At this temperature the thermoplastic material of 25 the length L within the device becomes soft as does the thermoplastic material of the length P within the device and the two thermoplastic coat-

ings fuse together over the length shown. Over this considerable length the thermoplastic coating provides a strength such that when an excessive

load is applied to the eye 20 the strap breaks not at the overlapping por-

tion but elsewhere within the length of the strap.

Fig. 4 shows an alternative way of forming an eye. In the embodiment of 5 Fig. 4 a first length S of strap lo is taken and is folded into a generally U-

shaped configuration with the base of the U forming the eye 20. The free end 30 of a second length of strap 10 ( which can be identical to or differ-

ent from the first length of strap 10 formed into a U-shape) is then in-

serted between the two limbs 32 and 34 of the U-shaped strap length to 10 form a three layer sandwich which extends through the length of the device 21, which is the same as the device 21 of Fig. 3. By movement of the heated plates 22, 23 towards one another in the direction of the dou-

ble-arrow 28 and application of pressure the thermoplastic material of the U-shaped strap and of the sandwiched end of the second strap 10 are 15 softened and fused together. Again a strength can be ensured by a suit-

able length of the overlapped joint which is greater than the breaking strength of the first or second straps 10.

Having formed an eye at one end of the length of the strap, which is cut 20 from the reel 16 as shown in Fig. 2, the eye is connected to the tensioning device 40 of Fig. 5. As can be seen from Figs. 5 and 6 the tensioning de vice 40 comprises a U-shaped yoke 42 having first and second limbs 44, 46 connected by a base portion 48 of the yoke. A pin 50 in the form of a nut and bolt passes through first and second circular apertures 52, 54 25 formed in the limbs 44 and 46 respectively, and on tightening the nut the bolt is secured within the yoke 42 generally parallel to the base 48.

Above the pin 50 in Fig. 5 there is shown a tensioning bolt 58 which is generally similar to the pin 50 but is provided with an axially extending through-going slot 60. The tensioning bolt 58 also passes through the first and second litnbs 44 and 46 through respective circular apertures 62 and 5 64 which are provided there. The tensioning bolt 58 has a head 66 adja cent the second limb 46 of the yoke 42 and its other end protrudes through the first limb 44 and carries a ratchet disc 70 having a plurality of ratchet teeth 72 as can be seen from Fig. 6. The pawl 78 has a circular aperture through which the pin 50 passes with slight clearance so that the 10 pawl can rotate about the axis of the axis 84 of the pin 50.

When used for the tensioning of the strap the user can apply pressure to the actuating side 84 of the pawl in the direction of the arrow 86 to push it into engagement with the ratchet disc while rotating the tensioning bolt 58 15 using a wrench applied to the head 66 of the tension bolt. The tension applied to the strap tries to rotate the tensioning bolt in the opposite direction to the wrench, but this is prevented by the pawl because the angle a between a line joining the tip 88 of the pawl to the axis 84 of the pin 50 relative to a line joining the axis 84 of the pin 50 to the axis 86 of 20 the tension bolt 58 is a positive angle such that clock-wise rotation of the pawl trying to reduce the acute angle will lead to a compressive stress in the pawl which prevents reduction of this angle, thus locking the ratchet disc to prevent unwinding of the strap.

25 In practice the tensioning device of Fig. 5 and 6 is used with the strap of Figs. 1 and 2 after an eye has been formed on it in accordance with Fig. 3 or Fig. 4 as follows. First of all the pin 50 is removed from the yoke 42 and then reinserted so that the pin 50 passes through the eye 20 of the length

of strap which is located between the two limbs 44 and 46 of the yoke 42.

The pin is then secured in place by tightening the nut onto the pin so that the pin cannot move in its axial direction out of the yoke. It should be noted that the nut cannot be tightened to such an extent that the pawl is 5 trapped by the head of the bolt against the limb 44 of the yoke because otherwise the pawl would not be able to rotate. One way of enabling tight-

ening of the pin without nipping the pawl so that it cannot rotate is to use a self-locking nut on the pin 50 so that no axial clamping load is applied to the pawl. The pin 50 cannot, however, be lost from the yoke 42 by an 10 intentional loosening of the nut, since this is prevented by the self-locking action of the nut. Alternatively, the bolt can have a collar underneath the head which is of greater diameter than the portion of the bolt located in the limb 44 and between the limbs 44 and 46 so that a shoulder is formed adjacent to the collar which bears on the limb with the collar having an 15 axial length such that the pawl is free rotatably mounted thereon.

. c, Moreover it is not essential to use a nut and bolt for the pin 50. Instead the pin could be a headed rivet which is simply riveted over at one end after insertion through the yoke or it could be a clevis pin which is se-

20 cured by a hair spring clip or the like.

i Moreover, as an alternative to first forming the loop and then removing the pin 50 from the yoke to allow the eye 20 to be passed over the pin when the pin is reassembled to the yoke, the pin can be permanently assembled 25 to the yoke and the eye 20 can be formed around the pin 50. That is to say when using the apparatus of Fig. 3 the length L of the strap 10 is first passed under pin 50 which is already assembled into the yoke and then folded back on itself around the pin prior to use of the heated pressing

device 21. In the arrangement of Fig. 4 the U-shaped length S of strap material 10 is passed around the pin 50, which is already inserted into the yoke, the free end of the second strap 10 is then inserted between the two limbs of the U-shaped strap S and the assembly is bonded together in the 5 heated pressing device of Fig. 4.

Fig. 7 shows a typical section of a "piggy-back" mounting system where a pipe 90 provided, in this case, with a sleeve 92 is mounted parallel to a second pipe 94 which, in this embodiment, is also provided with a sleeve 10 96. The sleeves 92 and 96 can be omitted if desired. Between the sleeves is a spacer member 98 of generally trapezoidal shape in plan view with contoured opposing sides which match the rounded shapes of the sleeves 92 and 96 respectively. The free end of the strap is then passed around the sleeves 92 and 96 at the position of the spacer 98 and is passed 15 through the axial slot 60 in the tensioning device 40. The strap is pulled tight by hand and then a torque wrench 100 with a socket 101 is applied to the head of the tensioning bolt 60 in order to rotate the tensioning bolt in the clock-wise direction as seen in Fig. 6, so that the free end of the strap 10 is wound around the tensioning bolt and tensioned. During this 20 the user presses against the actuating side 84 of the pawl so that it con-

tacts the ratchet disc 70, which prevents the tensioning bolt 58 rotating under the tension applied to the strap and becoming loose again. The torque setting of the torque wrench can be used to control the degree of tensioning which is applied to the strap.

Beneath the top illustration of the strap system of the invention in Fig. 6 there is also an illustration of a different arrangement using a tensioning bolt 110 which passes through two pins 112, 114. This type of connection

is well known in the aircraft industry and is used there with stainless steel straps. The bottom strap is simply shown as part of the illustration, it can be 5 designed in precisely the same way as the top strap in Fig. 7 or omitted, it is simply part of the model from which the drawing was made. Clearly straps such as the top strap in Fig. 7 are provided at suitable intervals along the length of the pipes. It is preferably for the yoke 42 of the ten-

sioning device 40 in Fig. 7 to be positioned just before the strap runs onto 10 the jacket, so that the jacket is not unduly deformed by the flat base of the yoke 40. However, this is not critical, and the tensioning device could for example be disposed adjacent to the straight side of the spacer (as effec-

tively shown in Fig. 7 or indeed be present at some position around either of the jackets 92 and 96).

Fig. 8 shows a slight modification of the arrangement of Fig. 6 where the l, actuating side 84 of the pawl is extended beyond the top side of the limb .. 44 to facilitate access by the user. Finally Fig. 9 shows that the pawl 78 can have a berit over tab 122 which makes it more comfortable for the 20 user to apply pressure to the pawl. Although not shown in drawings it is theoretically possible for the pawl to be biased into engagement with the ratchet teeth via a spring member, for example a hair spring having one limb engaging the yoke 42 and the other limb applying pressure to the pawl 78 in the clockwise direction in Fig. 6 or Fig. 8.

It should be noted that the yoke 42 and the pins are preferably made in a stainless steel, for example in a quality at least equal to AlS1-316 to avoid corrosion in a subsea installation.

The system of the invention is easy to install even when used under water by divers. Its light weight and easy installation making it much easier to assemble and tension under water. The formation of the eye from one or 5 more lengths of strap material makes it easy to make straps of any length on site with a minimum of equipment and material.

.. ...DTD:

Claims

1. A method of connecting two structures together, for example for connecting a first pipe to a second pipe or for connecting a hydrody 5 namic element to a pipe, in particular for connecting two structures of or for a subsea installation, the method comprising the following steps: taking a strap comprising a plurality of strength giving yarns oriented in parallel along the length of the strap and embedded 10 in a thermoplastic material, said strap having a first end with an eye and a second free end; - passing a pin through a first limb of a generally U- shaped yoke, through said eye and through a second limb of said generally U shaped yoke and securing said pin in said yoke, 15 - passing said strap around said first and second structures, À, - passing said free end through a slot in a tensioning bolt, said tensioning bolt passing through said first and second limbs of said U-shaped yoke generally parallel to said pin, said tensioning bolt having a head for the engagement of a wrench to permit ro 20 tation of said tensioning bolt and tensioning of said strap and a I. ratchet disc rotationally fixedly connected to said tensioning bolt and having ratchet teeth, there being a pawl pivotally mounted on said U-shaped yoke and engageable with said ratchet teeth to prevent unwinding rotation of said tensioning bolt, and 25 - subsequently rotating said tensioning bolt by said wrench to ten sion said strap and engaging said pawl with said ratchet teeth to prevent loosening of said strap.

2. A method in accordance with claim 1, wherein said ratchet pawl is journalled on said pin for rotation about the axis of said pin and has an actuating side, the method further comprising a step of applying pressure to said actuating side to press said pawl into engagement 5 with said ratchet disc,

3. A method in accordance with claim 2, wherein said actuating side projects beyond a limb of said U-shaped yoke and is pressed by a user when tightening said tensioning bolt.

4. A method in accordance with any one of said preceding claims? com prising the further step of inserting at least one spacer between said first and second structures to hold them in a desired spaced position, said strap being passed around said first and second structures at or 15 adjacent the position of a said spacer.

5. A method in accordance with any one of said preceding claims and comprising the step of using a torque wrench engaging said head of said tensioning,bolt to tighten said tensioning bolt to a predetermined 20 torque corresponding to a predetermined tension in said strap.

6. A method in accordance with claim 1 and comprising the step of forming said eye at said first end of said strap by folding a length of said strap back onto a portion of said strap adjacent said length and 25 welding the thermoplastic material of said folded back length of strap to said portion of said strap.

7. A method in accordance with claim 1 and comprising the step of forming said eye at said first end of said strap by folding a first length of strap material into a U-shape, receiving a first end of a further length of strap within said U and welding both limbs of said U 5 shaped strap onto said first end.

8. A method in accordance with any one of said preceding claims, wherein said eye is formed before said pin is inserted.

10

9. A method in accordance with any one of said preceding claims 1 to 7, wherein said eye is formed around said pin.

10. Tensioning device for a strap comprising a U-shaped yoke having first and second limbs connected by a base portion of said yoke, a pin 15 passing through said first and second limbs generally parallel to a plane of said base portion, said pin being secured against movement in its axial direction out of said limbs, a tensioning bolt having an - axially extending slot passing through it, said tensioning bolt extend ing through said first and second limbs generally parallel to said pin 20 and having a head at one end permitting rotation of said tensioning bolt by a wrench applied to said head, said tensioning bolt further having a ratchet disc rotationally secured to it, there being a pawl pivotally mounted on said tensioning device and engageable with ratchet teeth of said ratchet disc to prevent rotation of said tensioning 25 bolt in one direction but permitting rotation of said tensioning bolt in an opposite direction.

11. A tensioning device in accordance with claim 10, wherein said pawl is pivotally mounted on said pin.

12. A tensioning device in accordance with claim 10 or claim 11, wherein 5 said pawl has a side projecting beyond a said limb of said yoke for ac tuation by a user to press said pawl into engagement with said ratchet disc.

13. A tensioning device in accordance with any one of claims 10 to 12, n 10; said pawl being a sheet metal stamping.

- I..,...

14. A tensioning device in accordance with any one of said preceding claims 10 to 14, said pawl having a tab turned generally right angles to the plane of the pawl for engagement of a user.

IS. A tensioning device in accordance with any one of the claims 10 to it. - - 14, wherein, when said pawl engages one of said ratchet teeth of said ratchet disc, a line drawn from a tip of said pawl to an the axis of ro tation of said pawl forms a positive acute angle to a line connecting 20 said axis of rotation of the pawl to the axis of rotation of the ratchet .; - disc, i.e. of the tensioning bolt, so that attempted rotation of said - ratchet disc opposite to the tensioning direction of said tensioning bolt tries to reduce said acute angle which is resisted by compression in said pawl.

16. A tensioning device in accordance with any one of said preceding claims, wherein said pin comprises a nut and bolt.

17. A tensioning device in accordance with any one of said preceding claims 10 to 15 wherein said pin comprises a rivet having either a head at one end and a rivet flange at the other end or having a rivet flange at both ends.

18. A tensioning device in accordance with any one of claims 10 to 15, wherein said pin comprises a clevis pin (19).

19. A tensioning device in accordance to any one of the preceding claims 10 10 to 18, wherein said U-shaped yoke comprises a metal stamping.

20. A tensioning device in accordance with any one of said preceding claims 10 to 18, wherein said ratchet disc is welded to said tension-

ing bolt.

-

21. A tensioning device in accordance with any one of said preceding O O I claims 1 to 18, wherein said ratchet disc has two D-shaped slots separated by a web said ratchet disc engaging around said tensioning bolt with said web engaging into said slot.

In 20 .

22. A device for forming an eye at an end of a strap comprising strength (. > giving yarns disposed parallel to one another in a thermoplastic ma trix, said device comprising first and second heated plates engageable with opposite sides of two limbs of a loop of strap defining said eye 25 and being adapted to be pressed together to weld the two limbs of strap forming the loop to each other or to opposite sides of a further strap inserted between said two limbs.