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Title:
THREAD-ENGAGING MEMBERS FOR TENSIONERS
Document Type and Number:
WIPO Patent Application WO/2007/000573
Kind Code:
A2
Abstract:
A thread-engaging member (7) for a tensioner (1), comprising a body portion (9) of the form of a sleeve and having a threaded interior and a flange portion (8), in which there is further provided a containment component (12) which is arranged to restrict relative movement of the flange portion (8) and the body portion (9) should the flange portion (8) and the body portion (9) separate. Typically, the containment component (12) engages the body portion (9) by engaging the thread of the interior of the body portion (9). The thread-engaging member (7) may also be provided with a weakening (13) arranged so that, if the thread-engaging member (7) is to fail by separating, the failure occurs at all about the weakening (13).

Inventors:
SCRIVENS ANTHONY (GB)
Application Number:
PCT/GB2006/002265
Publication Date:
January 04, 2007
Filing Date:
June 21, 2006
Export Citation:
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Assignee:
TENTEC LTD (GB)
SCRIVENS ANTHONY (GB)
International Classes:
B65B29/02; B23P19/06; B25B29/02
Foreign References:
DE9316464U11994-01-20
DE4341707A11995-06-01
DE1300474B1969-07-31
DE3047674A11982-07-15
DE7600965U11976-06-03
DE1297557B1969-06-12
Attorney, Agent or Firm:
BARKER, Brettell (Edgbaston, Birmingham B16 9PW, GB)
Download PDF:
Claims:

CLAIMS

1. A thread-engaging member for a tensioner, comprising: a body portion of the form of a sleeve and having a threaded interior; and a flange portion, in which there is further provided a containment component which is arranged to restrict relative movement of the flange portion and the body portion should the flange portion and body portion separate.

2. The thread-engaging member of claim 1 in which the containment component engages the body portion.

3. The thread-engaging member of claim 2 in which the containment component engages a thread of the interior of the body portion.

4. The thread-engaging member of any preceding claim in which the containment member is arranged to substantially prevent, on separation of the flange portion from the body portion, the flange portion from moving more than a predetermined distance from the body portion.

5. The thread-engaging member of any preceding claim in which the containment component is arranged to engage both the flange portion and the body portion should the flange portion separate from the body portion.

6. The thread-engaging member of claim 5 in which the flange portion is of annular form, and a surface of the containment component that engages the flange portion on separation of the flange and body portions has a maximum diameter that is larger than the minimum internal diameter of the flange portion.

7. The thread-engaging member of any preceding claim, in which the containment component and the body or flange portions have corresponding profiles such that, on separation of the body and flange portions, the corresponding profiles run over one another to absorb impact energy.

8. The thread-engaging member of claim 7, in which the profiles are shaped such that impact energy is absorbed, in use, in deformation of the flange or containment portion.

9. The thread-engaging member of claim 8 in which the impact energy is absorbed in plastic deformation of the flange or containment portion.

10. The thread-engaging member of any of claims 7 to 9 in which the profiles are on the containment component and the flange portion and comprise two sloped portions, which slope away from an axis of the thread-engaging member away from the body portion

11. The thread-engaging member of claim 10 in which the slope of the profile of the containment component away from the axis of the thread- engaging member is greater than that of the profile of the flange portion.

12. The thread-engaging member of any of claims 7 to 11 in which the profiles comprise two cooperating lips, one on each of the containment component and the flange portion.

13. The thread-engaging member of claim 12 in which the lips are at the end of the travel of the profiles over one another.

14. The thread-engaging member of any of claims 7 to 13 in which the profiles comprise the threads by which the body portion and containment component engage one another.

15. The thread-engaging member of any preceding claim in which the thread-engaging member is provided with a weakening arranged so that, if the thread-engaging member is to fail by separating, the failure occurs at or about the weakening.

16. A thread-engaging member for a tensioner, comprising: a body portion of the form of a sleeve and having a threaded interior; and a flange portion, in which the thread-engaging member is provided with a weakening arranged so that, if the thread-engaging member is to fail under load by the body portion and flange portion separating, the failure preferentially occurs at or about the weakening.

17. The thread-engaging member of claim 15 or claim 16, in which the weakening is between the flange portion and the body portion.

18. The thread-engaging member of any of claims 15 to 17 in which the weakening comprises a groove in the body portion.

19. The thread-engaging member of claim 18 in which the groove is on the interior of the body portion.

20. The thread-engaging member of claim 18 or claim 19 in which the thread of the threaded interior has a major diameter at a trough of the thread and the groove has a minor diameter at its crest that is substantially the same as the major diameter of the thread.

21. The thread-engaging member of any of claims 18 to 20 in which the groove has substantially the same depth as the depth of the thread of the threaded interior.

22. A tensioner for threaded members, the tensioner comprising first and second parts defining a pressure space therebetween, the first and second parts being arranged to be urged apart upon introduction of a fluid into the pressure space, and further comprising a thread-engaging member according to any preceding claim arranged to engage a threaded member, in which the first part is arranged to abut or to be fixed to a surface and the second part is arranged to transmit the force caused, in use, by the first and second parts being urged apart by the introduction of fluid into the pressure space to the thread-engaging member and thence to the threaded member.

23. The tensioner of claim 22 in which the fluid is hydraulic fluid such as mineral oil.

Description:

THREAD-ENGAGING MEMBERS FOR TENSIONERS

This invention relates to tensioners, particularly bolt tensioners and those of the type having an interchangeable thread-engaging member and especially, but not exclusively to hydraulic bolt tensioners. It also relates to a thread-engaging member for such a tensioner.

It is known in the prior art to provide bolt tensioners for a threaded member such as a stud, bolt or the like, which comprise inner and outer coaxial generally cylindrical annular bodies which are placed around the threaded member. The inner body threadedly engages the threaded member. A space between the inner and outer bodies defines a pressure space, into which fluid, typically hydraulic fluid, can be introduced to drive the bodies apart along their common axis.

The outer body is arranged to abut a surface fixed relative to the threaded member such that the inner body, on introduction of the fluid, is urged away from the outer body along the threaded member to place the threaded member in tension. If a nut is run along the threaded member to abut the fixed surface, the tension generated in the threaded member can be stored and applied to the fixed surface. The bolt tensioner can then be released and removed, leaving a fastened nut and threaded member.

In this way, the threaded member and nut can be used to fasten a plurality of objects together; this can be most easily be seen in the case where the threaded member is a bolt where a number of objects of sheet form can be held between the nut and the head of the bolt.

It is also known to use an interchangeable thread-engaging member with such a tensioner. In order to be able to use the tensioner with a range of different threaded members, instead of the inner body engaging the

threaded member directly, the inner body can engage a separate thread- engaging member, which engages the threaded member. This allows a variety of thread-engaging members to be provided which engage a variety of differently sized threaded members.

Typically, the thread-engaging member comprises a cylindrical sleeve with a threaded interior for engaging the threaded member (and hence which can be varied between different thread-engaging members for engaging differently-sized threaded members) with an exterior diameter slightly smaller than that of the interior diameter of the inner body. A flange at one end of the thread-engaging member engages the end of the inner body distal from the fixed surface so that, when the inner body is urged away from the outer body and hence the fixed surface, the inner body pushes against the flange and hence the force is transmitted by means of the thread-engaging member to the threaded member.

However, there are problems with the provision of such a thread-engaging member. It is well known that threading a body provides weak spots where a body under tension may fail. As the thread-engaging member will be placed under tension, there is a possibility that this member could fail in use. The possible outcome of this is that the end of the thread- engaging member comprising the flange could become separated from the portion of the sleeve engaging the threaded member; the part comprising the flange would therefore not be restrained in any way. Given that a large force is likely to be being applied to the flange, that part of the thread-engaging member could be ejected at high speed from the tensioner, possibly causing damage and injury.

According to a first aspect of the invention, there is provided a thread- engaging member for a tensioner, comprising:

a body portion of the form of a sleeve and having a threaded interior; and a flange portion, in which there is further provided a containment component which is arranged to restrict relative movement of the flange portion and the body portion should the flange portion and body portion separate.

Accordingly, the containment component may, at least partially, reduce the possibility of the flange portion of the thread-engaging member becoming detached and being ejected from a tensioner. In normal use, the body portion and flange portion remain connected, and indeed form a single body. If a fracture or other separation occur in use, the body portion is likely to remain with the tensioner due to its threaded engagement with a threaded member.

Advantageously, the containment component engages the body portion, typically by engaging the thread of the interior of the body portion. This gives the containment component a purchase on the body portion so that it can stay fixed relative to the body portion should the flange portion and body portion separate. The containment portion preferably engages three, or at least three, turns of the thread.

On separation of the flange portion from the body portion, the containment member may substantially prevent the flange portion from moving more than a predetermined distance from the body portion. It may be arranged to engage both the flange portion and the body portion should the flange portion separate from the body portion. Where the flange portion is of annular form, a surface of the containment component that engages the flange portion may have a maximum diameter that is larger than the minimum internal diameter of the flange portion.

Preferably, the thread-engaging member is provided with a weakening arranged so that, if the thread-engaging member is to fail by separating, the failure occurs at or about the weakening. This provides a predictable point where the thread-engaging portion may fracture or otherwise break under extreme loads. The weakening is preferably between the flange portion and the body portion. Where the containment member engages the body portion, the weakening may be between the position at which the containment member engages the body portion and the flange portion. This increases the likelihood that the containment member is attached to one part of the thread-engaging member should the thread-engaging member fail.

The weakening may typically comprise a groove between body portions and flange, preferably about the interior of the body portion. Where the thread has a major diameter at the trough of the thread, the groove may have minor diameter at its crest that is the same as the major diameter of the thread. The groove may also have the same depth as the depth of the thread, and may have the same profile. Such an arrangement has been found to repeatably cause the thread-engaging member to fracture, under extreme loads, at the groove. The groove provides a weakening that is predictably weaker than the thread, which would otherwise provide a plurality of points - the troughs of the thread - where fracture may occur.

The containment component and the body or flange portions may have corresponding profiles such that, on separation of the body and flange portions, the corresponding profiles run over one another to absorb impact energy. This is advantageous, as the flange portion is likely to have been imbued with a large amount of kinetic energy if the flange and body portions have separated; absorbing the energy on impact is a useful method of dissipating such energy. The profiles may be shaped such that impact energy is absorbed in deformation of the flange or containment

portion, and preferably the containment portion. Preferably the energy is absorbed in plastic deformation.

In the preferred embodiment, the profiles are on the containment component and the flange portion. These may comprise two sloped portions, which slope away from an axis of the thread-engaging member away from the body portion, preferably with differing slopes. In the case where the body portion of cylindrical sleeve form, the axis may the axis of the sleeve. Preferably, the containment component is positioned in the interior of the body portion; in such a case the slope of the profile of the containment component away from the axis of the thread-engaging member is greater than that of the profile of the flange portion.

The profiles may also comprise two cooperating lips, one on each of the containment component and the flange portion. The lips are preferably at the end of the travel of the profiles over one another. Accordingly, this acts as a final check against the containment component allowing the release of a separated flange portion.

Additionally or alternatively, the profiles may comprise the threads by which the body portion and containment component engage one another. Should a separated flange portion impact the containment component, then these threads may ride over one another, deforming and absorbing energy.

According to a second aspect of the invention, there is provided a thread- engaging member for a tensioner, comprising: a body portion of the form of a sleeve and having a threaded interior; and a flange portion,

in which the thread-engaging member is provided with a weakening arranged so that, if the thread-engaging member is to fail under load by the body portion and flange portion separating, the failure preferentially occurs at or about the weakening.

This provides a predictable point where the thread-engaging portion may fracture or otherwise break under extreme loads. The weakening is preferably between the flange portion and the body portion.

The weakening may comprise a groove typically between the body and flange portions, preferably on the interior of the body portion. Where the thread has a major diameter at the trough of the thread, the groove may have minor diameter at its crest that is the same as the major diameter of the thread. The groove may also have the same depth as the depth of the thread, and may have the same profile. Such an arrangement has been found to repeatably cause the thread-engaging member to fracture, under extreme loads, at the groove. The groove provides a weakening that is predictably weaker than the thread, which would otherwise provide a plurality of points where fracture may occur.

According to a third aspect of the invention, there is provided a tensioner for threaded members, the tensioner comprising first and second parts defining a pressure space therebetween, the first and second parts being arranged to be urged apart upon introduction of a fluid into the pressure space, and further comprising a thread-engaging member according to the first or second aspects of the invention arranged to engage a threaded member, in which the first part is arranged to abut or to be a surface and the second part is arranged to transmit the force caused, in use, by the first and second parts being urged apart by the introduction of fluid into the pressure space to the thread-engaging member and thence to the threaded member.

Preferably, the fluid is hydraulic fluid such as mineral oil.

There now follows, by way of example only, an embodiment of the invention, described with reference to the accompanying drawings, in which:

Figure 1 shows a cross section through the thread-engaging member of the embodiment of the invention without a containment component fitted;

Figure 2 shows a cross section through the thread-engaging member of Figure 1 with a containment component fitted;

Figure 3 shows an enlargement in cross section of the engagement of the containment component of Figure 2 in the thread-engaging member; and

Figure 4 shows a cross section an assembled tensioner using the thread-engaging member of Figures 1 to 3.

The accompanying Figures show the tensioner 1 according to an embodiment of the invention. The tensioner 1, as best seen in Figure 4 of the accompanying drawings, is of the form of a generally cylindrical body. It comprises a first, outer part, portion 2 and a second, inner part or piston 3. A pressure space 4 is defined between first part 2 and piston 3, although this is shown in the most retracted position of piston 3 and is hence of negligible volume. Introduction of hydraulic fluid into this space by means of port 5 will cause piston 3 and first part 2 to separate. The first part 2 and piston 3 share a common inner diameter to define a bore 10 there within.

It will also be observed that the first part 2 rests on an extension collar 6; this allows the tensioner to be positioned away from a fixed surface, which the extension collar rests on instead. The extension collar 6 merely provides a body for the first part to push against.

Accordingly, when the introduction of hydraulic fluid urges the piston 3 away from first part 2, it presses against the flange 8a of an annular flange portion 8 of a thread-engaging member 7. This thread-engaging member comprises a body portion 9 of the form of a cylindrical sleeve that fits within the bore 10. The interior of the sleeve defines a threaded bore 11 , which engages the threaded member 30 to be tensioned.

The flange portion 8 mentioned above is positioned at the end of the body portion 9 and abuts the piston 3 such that the force generated by the piston 3 being urged away from the first part 2 is transmitted to the flange 8a, through the flange portion 8 and body portion 9 then through the threaded bore 11 to the threaded member 30. Nut 31 can then be run down threaded member 30 to keep the member in tension and cause the nut 31 to press against the fixed surface once the tension due to the fluid in the pressure space 4 has been released

Thread-engaging member 7 is generally made of low alloy steels.

When the thread-engaging member 7 is put under load, there is a possibility that it could fail. This could lead to the flange portion 8 detaching from the body portion 9. If a large force is being applied to the flange 8a at the time the flange portion 8 detaches, then the flange portion 8 could be expelled from the tensioner 1 at high speed, giving the flange portion 8 a large amount of kinetic energy. This could be dangerous for people and equipment in the vicinity.

In order to control where a fracture may occur under load, a weakening of the form of a groove 13 is provided in the interior of the thread- engaging member. The groove has the same depth D as the depth of the thread 11 as both start from the same diameter - the groove into the interior of the thread-engaging member and the thread protruding out of it. Therefore, fracture preferentially occurs at the apex 14 of the groove 13, as schematically shown at F in Figure 3 of the accompanying drawings, rather than at any of the apexes 15 of the thread 11 as would occur previously.

Whilst controlling where a fracture may occur is useful, it is still desirable to control a separated flange portion 8. Accordingly, a containment component 12 is provided, which has an annular, but varying diameter, cross-section. The containment component has a lower portion 12a that is a threaded fit within the interior of the body portion 9. It extends into the central void of flange portion 8.

The containment component also has a profiled upper portion 12b, having a profile such that, should the flange portion detach or separate from the body portion 9, then the flange portion will impact the upper portion 12b of the containment component 12 - the outer diameter of part of the upper portion 12b is large than the minimum diameter of the void of the flange portion 8. This makes it unlikely that the flange portion 8 will pass over the containment component 12, as some deformation would need to occur.

The profile of the upper portion 12b is shaped so as to cooperate with a profiled section 16 of the interior of the flange portion 8. These both comprise surfaces that slope outwards as they extend away from the body portion 9. The slope of the profiled section 16 of the flange portion 8 is greater than that of the corresponding profile of the upper portion 12b of

the containment component. This has the effect that, should the flange portion 8 detach from the body portion 9 typically at position F the leading edge 17 of profiled section 16 of flange portion 8 will impact the profiled upper portion 12b of the containment component. The two profiled portions will ride over one another, causing deformation of especially the containment component 12. Especially where this is plastic deformation, the deformation absorbs the impact energy of the flange portion 8 on the containment component.

At the end of each of the profiled portions of the containment component 12 and the flange portion 8 are lips 18, 19, which cooperate once the profiled sections have reached the end of their travel. This serves as a final check against movement of the flange portion 8 relative to the containment component 12.

Furthermore, the threads comprising the threaded engagement of the lower portion 12a of the containment component can ride over the corresponding threads 11 in the body portion 9. This causes deformation of the threads and can dissipate further energy; whilst this will render the threads unusable the separation of the flange portion 8 from the body portion 9 will have rendered the thread-engaging member useless in any case.