GB2485360A

GB2485360A - Thread-type pipe connector

Info

Publication number: GB2485360A
Application number: GB1018979.3A
Authority: GB
Inventors: John Stobbart
Original assignee: Vector International Ltd
Current assignee: Freudenberg Oil and Gas Technologies Ltd
Priority date: 2010-11-10
Filing date: 2010-11-10
Publication date: 2012-05-16
Anticipated expiration: 2030-11-10
Also published as: GB201018979D0; GB2485360B

Abstract

An all metal pipe connector for joining hubs or pipes of nominally equal bore comprises a coupling sleeve 1 including a first end section 5 which screws along the outside of a first hub 2 via mating threads 6 having a first diameter and pitch and couples onto a second hub 3 via mating threads 7 having a larger diameter and pitch. While being screwed onto the second hub, the hubs are forced together with a force inversely proportional to the pitch difference. This pre-energize a seal ring 4 located between the hubs. The diameter difference allows the higher pitch thread in the sleeve to pass over the lower pitch thread on the first hub during movement. Pins 11 and 13 keep the hubs aligned.

Description

Thread-type pipe connector The present invention relates to a thread-type pipe connector arrangement and a sleeve-like coupling element therefor.

It is well known to employ as a pipe connector a union nut which draws together a flanged pipe end and a threaded pipe end. It is also well known to employ as a connector a sleeve-like coupling element having a right-hand internal thread at one end and a left-hand internal thread at the other. When rotated the coupling element draws together or moves apart correspondingly threaded rod or pipe ends which have been screwed into it.

European Patent Application EP0060549 Al (FMC CORPORATION) and German Patent Application DE3825779 Al (BAYERISCHE MOTOREN WERKE AG) disclose pipe connectors in which a sleeve-like coupling element comprising two internally threaded end sections having threads on the same hand and different pitches is employed. As a result of its differential action such a connector depending on the direction it is rotated draws together or moves apart correspondingly threaded pipe ends. The main advantage of these differential arrangements is that the pipe ends are drawn together with an increased force which can compress a seal ring or seal element. The mechanical advantage gained varies inversely with the difference between the two pitches.

In these known differential arrangements the two internally threaded end sections have the same diameter. Neither end section can be screwed onto a pipe end so that at least part of the other threaded end section surrounds that pipe end. In consequence the coupling element cannot give full access to a pipe end while it is screwed on that pipe end. It also necessitates separation of the two internally threaded end sections by a relieved area of sufficient length to prevent interference between threads of different pitches. This has the further disadvantage of increasing the minimum length of the coupling element and its cost and weight.

According to a first aspect the present invention provides an all metal pipe connector arrangement comprising; a sleeve-like coupling element including a first end section internally threaded with a first internal thread having a first pitch and a second end section internally threaded with a second internal thread having a second pitch larger than said first pitch, said first and second threads being on the same hand; a first hub having a first external thread along which said first internal thread can be screwed; and a second hub having a second external thread onto which said second internal thread can be screwed; the minor diameter of said second internal thread being larger than the major diameter of said first external thread.

This ensures that the sleeve-like coupling element can be unscrewed sufficiently far onto the first hub to fully expose any seal between said hubs.

When used in this specification the word "hub" refers to a pipe end element which can be attached to a pipe end (e.g. by welding or screwing).

Preferably the whole of said first hub can pass through said second internal thread without interference therebetween.

Preferably the connector includes a metal seal ring for forming a seal between said hubs.

According to a second aspect the present invention provides a metal sleeve-like coupling element including a first end section internally threaded with a first internal thread having a first pitch and a second end section internally threaded with a second internal thread on the same hand as the first internal thread and having a second pitch larger than said first pitch, said first end section opening out into said second end section so that the first end section can be screwed along an externally threaded pipe end which mates with said first internal thread from a position in which at least part of the second internal thread surrounds that pipe end to a position in which said part is located beyond that pipe end.

In either aspect the second internal thread may be a multi-start thread. The first internal thread may also be a multi-start thread.

The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a pipe connector when fully tightened, Figure 2 shows the connector in a standoff condition.

The connector is an all metal construction preferably using metals from the ASME 800 series of alloys to allow a working temperature of 800°C. These are nickel-iron-chromium super-alloys having excellent properties of high temperature strength and resistance to oxidation, carburization and other types of high temperature corrosion.

A sleeve-like coupling element 1 holds, when fully tightened as shown in Figure 1, two pipe ends in the form of hubs 2 and 3 in engagement with a sea Iring 4. The pipes to which the pipe ends are to be connected or form part are normally of nominally equal bore. Preferably the sealring is of pressure energised type and is pre-energised when the coupling element is fully screwed down to its lowest position as shown. it can be further energised by pressure in the pipe.

The coupling element 1 has a first end section 5 internally threaded with a first internal thread 6 having a first pitch and a second end section 7 internally threaded with a second internal thread 8 having a second pitch greater than the first pitch, both threads being on the same hand. The first hub has a first external thread matching in pitch, diameter and hand the first internal thread and the second hub has a second external thread matching in pitch, diameter and hand the second internal thread. The hubs would normally have equal internal diameters.

Alignment means, such as a first pin 11 which protrudes downwardly from the first hub into a bore 12 in the second hub 3 and a second pin 13 which protrudes upwardly from the second hub into a bore 14 in the first hub 2, ensure (with or without the aid of the sealring) that the hubs are correctly aligned is preferably provided. The bores if provided should be of sufficient depth to ensure that the pins do not bottom therein. The alignment means may be in the form of mating castellations on the two hubs. The alignment means may also serve to transmit any torque applied to one hub to the other. Slots 15, holes or projections in or on a flanged portion of the coupling element 1 to be turned by a spanner and/or hammer impact.

Figure 1 shows the coupling element in its lowest position in which the sealring 4 is firmly clamped between the hubs and thus pre-energised by deflection of sealing lips thereon against sealing surfaces on internal walls of the hubs so as to form a metal to metal seal between the hubs. As the coupling element 1 is screwed upwardly from this position to a position in which the coupling element becomes completely unscrewed from the second hub 3, the two hubs are progressively forced apart because the external thread on the second hub and the second internal thread are greater in pitch than the external thread on the first hub 2 and the first internal thread. The coupling element can then be screwed upwardly on the first hub to the position shown in Figure 2 in which the sealring can be removed and replaced, and if desired to a position in which the coupling element is no longer screwed onto either hub. So that the coupling element can be screwed upwardly to a position such as that shown in Figure 2, at least a portion of said second internal thread must be able to pass without interference over at least a portion of said first external thread. This implies that the second internal thread has a minor diameter larger than a major diameter of the first external thread.

If when screwing the coupling element downwardly it engages the second hub 3 with the second internal and external threads out of phase, further rotation of the coupling element forces the hubs to separate slightly so that the second internal and external threads are in phase. This allows the coupling element to be screwed down onto the second hub. According to the direction in which the coupling element is rotated, the hubs are drawn together or moved apart with a force inversely proportional to the difference in the two pitches.

Various thread profiles may be employed including ISO metric, ACME and trapezoidal thread. The number of turns for each thread, the first and second pitches and thus the pitch difference between them can be chosen to suit the application taking into account the desired extent of forced travel between hubs, the size of the connector and the required mechanical advantage. The first internal and external threads may for example have a 10 mm pitch while the second internal and external threads may have an 11 mm pitch. The two pitches would normally be of the same order of magnitude giving at least an order of magnitude in the mechanical advantage obtained.

The second internal thread may be a multi-start thread. The first internal thread may also be a multi-start thread.

Claims

Claims 1. An all metal pipe connector arrangement comprising; a sleeve-like coupling element including a first end section internally threaded with a first internal thread having a first pitch and a second end section internally threaded with a second internal thread having a second pitch larger than said first pitch, said first and second threads being on the same hand; a first hub having a first external thread along which said first internal thread can be screwed; and a second hub having a second external thread onto which said second internal thread can be screwed; the minor diameter of said second internal thread being larger than the major diameter of said first external thread.
2. An all metal pipe connector arrangement as claimed in claim 1, in which the whole of said first hub can pass through said second internal thread without interference therebetween.
3. An all metal pipe connector arrangement as claimed in claim 1 including a metal seal ring for forming a seal between said hubs.
4. An all metal pipe connector arrangement as claimed in any of claims 1 to 3, the second internal thread being a multi-start thread.
5. An all metal pipe connector arrangement as claimed in claim 4, the first internal thread also being a multi-start thread.
6. An all metal pipe connector arrangement as claimed in any of claims 1 to 5, including alignment means to ensure that the hubs are correctly aligned.
7. An all metal pipe connector arrangement as claimed in claim 6, in which said alignment means comprises a first pin which protrudes from the first hub into a bore in the second hub and a second pin which protrudes from the second hub into a bore in the first hub.
8. An all metal pipe connector arrangement as claimed in claim 6, in which said alignment means is in the form of mating castellations on the two hubs.
9. A metal sleeve-like coupling element including a first end section internally threaded with a first internal thread having a first pitch and a second end section internally threaded with a second internal thread on the same hand as the first internal thread and having a second pitch larger than said first pitch, said first end section opening out into said second end section so that the first end section can be screwed along an externally threaded pipe end which mates with said first internal thread from a position in which at least part of the second internal thread surrounds that pipe end to a position in which said part is located beyond that pipe end.
10. A sleeve-like coupling element as claimed in claim 9, the second internal thread being a multi-start thread.
11. A sleeve-like coupling element as claimed in claim 10, the first internal thread also being a multi-start thread.