WO2007091021A1

WO2007091021A1 - Chuck and method

Info

Publication number: WO2007091021A1
Application number: PCT/GB2007/000322
Authority: WO
Original assignee: In-Situ Oilfield Services Limited; Robb, Stewart
Priority date: 2006-02-08
Filing date: 2007-01-31
Publication date: 2007-08-16
Also published as: GB0602449D0

Abstract

The invention provides a chuck (10) and a method of centring an object in a chuck. The chuck (10) comprises two pairs of jaws, wherein each pair of jaws has one jaw arranged in substantially opposing relation relative to the other jaw. The jaws of at least one of the pairs of jaws are coupled together for simultaneous movement. Preferably, each pair of jaws has one jaw coupled to the other jaw in that pair for simultaneous movement. The jaws can be arranged such that movement of one jaw in a pair causes corresponding radial movement of the other jaw in that pair. The jaws in each pair can be located in substantially diametrically opposing relation to one another. One pair of jaws can be arranged substantially perpendicular relative to the other pair. Each pair of jaws is preferably movable independently of the other pair of jaws.

Description

"Chuck and Method"

The present invention relates to a chuck and a method of centring an object in a chuck. In particular, the chuck and method of the invention is useful for centring a tubular member.

The machining of tubulars typically involves gripping the tubular in two or more jaws to resist the cutting forces and to centre the tubular to establish relative concentricity between the machined and unmachined sections of the tubular. Conventional chucks typically have three jaws disposed radially around the tubular for simultaneous movement and centring of the tubular. Typically, the exterior of the tubular is never perfectly round, but has a quasi-oval shape. As a result, the mean centre of the tubular when gripped using these chucks can be erroneous, resulting in uneven machining.

In an attempt to avoid this problem it is commonplace to independently manipulate each of the jaws to compensate for the centring error resulting from the quasi-oval shape of tubular. However, this is time consuming and often inaccurate.

According to a first aspect of the invention, there is provided a chuck comprising two pairs of jaws, wherein each pair of jaws has one jaw arranged in substantially opposing relation relative to the other jaw, and wherein the jaws of at least one of the pairs of jaws are coupled together for simultaneous movement.

Both pairs of jaws can have one jaw coupled to the other jaw in that pair for simultaneous movement. The jaws can be arranged such that movement of one jaw in a pair causes or controls corresponding radial movement of the other jaw in that pair. The jaws in each pair can be located in substantially diametrically opposing relation to one another. Thus movement of one jaw automatically causes or controls a corresponding movement of the other jaw of that pair.

One pair of jaws can be arranged substantially perpendicular relative to the other pair. Each pair of jaws can be movable independently of the other pair of jaws.

The chuck can comprise a gearing assembly coupled to each jaw to effect or control simultaneous movement of the other jaw in that pair. Thus, the opposing jaws of each pair can be mechanically linked such that movement of one jaw causes or controls corresponding movement of the other jaw.

Each jaw in a pair can be movable by an actuating means coupled to the gear assembly. The actuating means can provide a linear force to radially advance and retract the jaws coupled thereto.

One actuating means can be coupled to each pair of jaws. According to this embodiment, the gear assembly can transmit the force for radial movement of each of the jaws. Alternatively, one actuating means can be provided for each jaw such that the gear assembly can act to synchronise the movement of the jaws. According to this arrangement, the gear assembly transmits minimal (or no) force.

The actuating means can comprise a ram. The ram can be provided with teeth for meshing with a pinion. The pinions meshing with the teeth of opposing jaws in a pair can be coupled for movement together via a large diameter gear wheel. A separate large diameter gear wheel can be provided for each pair of jaws.

The large diameter gear wheels can be spaced from one another, e.g. axially with respect to the bore of the chuck. The pinions of one pair of jaws can be provided with forwardly protruding shafts, each shaft having a separate gear wheel fixed thereto for meshing with the respective large diameter gear wheel. The pinions of the other pair of jaws can be provided with rearwardly protruding shafts, each shaft having a separate gear wheel fixed thereto for meshing with the respective large diameter gear wheel.

A primary hydraulic actuating cylinder can be coupled to a first jaw of each pair to drive the ram coupled thereto. A secondary hydraulic cylinder can be coupled to a second jaw of each pair and can be operable at the same pressure (and optionally from the same pressure source) as the primary hydraulic cylinder. Thus the gearing assembly can cause or guide corresponding movement of the jaws but the primary thrust required to move the jaws radially inwardly can be provided by each actuating means in the form of the hydraulic cylinders attached to respective jaws, thereby reducing the force that is required to be transferred by the gear assembly.

The jaws can be provided with extension members to extend the radial inward reach of each jaw. The extension members can have at least two feet, each foot having a contact surface for contacting an object in the chuck. The at least two feet can be arranged longitudinally with respect to an object in the chuck.

Each contact surface for contacting an object in the chuck can be at least partially arcuate. One pair of jaws can be longitudinally offset along the axis of the tubular from the other pair of jaws. This arrangement improves lateral alignment of the object in the chuck.

According to a second aspect of the invention, there is provided a method of centring an object in a chuck with two pairs of jaws, wherein each pair of jaws has one jaw disposed substantially opposite the other, and wherein the jaws of at least one pair are coupled together for simultaneous movement, the method comprising the steps of: moving each pair of jaws towards the object to be centred; contacting the object with each jaw; and centring the object.

The method can include coupling the jaws of each pair of jaws for simultaneous movement. The method can include arranging the pairs of jaws substantially perpendicular to one another. The method preferably includes moving each pair of jaws independently of the other pair of jaws.

The method can include coupling each pair of jaws to a separate gear assembly. The method can include actuating the jaws by coupling an actuating means thereto.

The method can include coupling a ram to each jaw; providing each ram with teeth; meshing the teeth of each ram with a respective pinion; and coupling each pinion to a large diameter gear wheel. The method can include providing a large diameter gear wheel for each pair of jaws.

One embodiment of the invention will now be described with reference to and as shown in the accompanying drawings, in which:- Fig. 1 is a part sectional view of a chuck according to the present invention;

Fig. 2 is a sectional view of a hydraulically operated ram along the line Z-Z in Fig. 1 ; Fig. 3 is a sectional view of a hydraulic ram along the line X-X in

Fig. 1 ; and

Fig. 4 is a part sectional view of a modified chuck with a tubular positioned therein.

A chuck is provided generally at 10 in Fig. 1. The chuck 10 has a first pair of hydraulic rams 50 and a second pair of hydraulic rams 60. The rams in each pair are arranged substantially diametrically opposite one another across the axis of the bore of the chuck 10. The first rams 50a and 50b are disposed above and below the bore of the chuck 10, on a substantially vertical axis. The second pair of rams 60a, 60b are disposed to the left and right of the bore of the chuck 10, on a substantially horizontal axis. Thus the pairs of rams 50, 60 are disposed substantially perpendicular to one another. Each ram 50a,b 60a,b is radially movable and projects via bushings (not shown) into a bore 12 of the chuck 10.

The upper and lower first rams 50a, 50b have rack teeth 51 a, 51 b along a periphery thereof. Each set of teeth 51a, 51b mesh with a respective first pinion 52a, 52b. The diametrically opposing pinions 52a, 52b are fixed to forwardly protruding first pinion shafts 54a, 54b. The first pinion shafts 54a, 54b are attached to a first small diameter gear wheel 55a, 55b, as shown in Fig. 3.

Similarly, two pinions 62a, 62b meshing with rack teeth 61a, 61b of the second pair of horizontally disposed rams 60a, 60b are attached to rearwardly protruding second pinion shafts 64a, 64b. Each of the second pinion shafts 64a, 64b is attached to a second small diameter gear wheel 65a, 65b as shown in Fig. 4. According to one embodiment, the size of teeth of the pinions 52, 62 attached to the respective pinion shafts 54, 64 is not identical. However, this is not a fundamental requirement of the invention.

Towards the front of the chuck 10, a first large diameter gear wheel 58 is provided. The teeth of the first large diameter gear wheel 58 mesh with both the upper and lower first small diameter gear wheels 55a, 55b attached to the first pinion shafts 54a, 54b.

Towards the rear of the chuck 10, a second large diameter gear wheel 68 is provided. Similarly, the teeth of the second small diameter gear wheels 65a, 65b attached to the second pinion shafts 64a, 64b mesh with the second large diameter gear wheel 68. The small diameter gear wheels 55, 65 run in respective bearings 59. 69.

A primary actuating hydraulic cylinder 56 is coupled to the first ram 50b meshed with the first pinion 52b on the corresponding first pinion shaft 54b. Another primary actuating hydraulic cylinder 66 is arranged to move the second ram 60b and cause rotation of the second pinion 62b connected to one of the second pinion shafts 64. Each of the primary actuating hydraulic cylinders 56, 66 can be actuated separately at variable pressures to move the rams 50b, 60b radially.

A secondary cylinder 57 is coupled to the first ram 50a. A similar secondary cylinder 67 is coupled to the second ram 60a. The secondary cylinders 57, 67 are arranged substantially diametrically opposite the respective primary hydraulic actuating cylinders 56, 66. The secondary cylinders 57, 67 are operable at the same pressure as the primary hydraulic actuating cylinders 56, 66 and hence the radial thrust on the tube and the gripping force is enhanced in use.

The leading ends of each ram 50, 60 can be provided with jaws of different sizes in order to accommodate varying sizes of tubular in the bore 12 of the chuck 10 and also to increase the stability of the tubular within the chuck 10. An example of one such modification is shown in Fig. 4 where the hydraulic rams 50a, 50b are each coupled to a jaw 20a, 20b. Each jaw 20a, 20b is provided with two feet 22a, 22b. The feet 22a, 22b increase the surface area in contact with a tubular 16 in the chuck 10, and follow the arcuate outer surface of the tubular 16. Additionally, the feet 22a, 22b are arranged longitudinally along the length of a tubular 16 to thereby stabilise and support the tubular 16 within the jaws 20a, 20b of the chuck 10, and substantially restrict the tubular 16 from deviation under its own weight. The feet 22a, 22b have arcuate contact surfaces to allow the tubular 16 and typically permit sliding of the tubular within the chuck 10 during the centring operation.

The jaws 20a, 20b are particularly suited for use with tubulars having a small diameter and a low stiffness. Additional supports (not shown) are provided elsewhere along the length of the tubular 16 to maintain the throughbore of the tubular 16 substantially perpendicular to that of the contact surface of the feet 22a, 22b. Similarly, the rams 60a, 60b are provided with jaws (not shown) having similar feet with arcuate contact surfaces. The jaws 20a, 20b substantially support the tubular 16 against sagging between the supports and reduce the risk of angular offset of the throughbore of the tubular 16 at the point the tubular 16 is gripped. This alleviates the possibility that the tubular 16 in the region of the chuck 10 is eccentric even when the jaws 20a, 20b and the chuck 10 accurately locate the central point. Before use of the chuck 10, the tubular 16 is positioned between the jaws 20a, 20b coupled to the rams 50a, 50b, in order to ensure that the tubular 16 is substantially horizontal with its throughbore perpendicular to the contact surfaces of the chuck 10.

The first primary actuating hydraulic cylinder 56 and opposing secondary cylinder 57 can be actuated to advance the first upper and lower rams 50a, 50b towards the tubular 16. This radial movement is synchronised by means of the teeth 51 a, 51 b of the first rams 50a, 50b, engaged with the pinions 52a, 52b, attached to the pinion shafts 54a, 54b and the first small diameter gear wheels 55a, 55b, meshed with the first large diameter gear wheel 58. The mutual contact of substantially diametrically opposing rams 50a, 50b with the large diameter gear wheel 58, results in a corresponding movement of the rams 50a, 50b.

Due to small discrepancies in the degree of ovality of the tubular 16, the feet 22a, 22b attached to the rams 50a, 50b are unlikely to contact the tubular 16 simultaneously. However, the first of the feet 22a, 22b arriving at the tubular 16 will continue to advance, pushing the tubular 16 until the later arriving feet 22a, 22b engage at a point diametrically opposite therefrom, and this has the effect of centring the tubular in the vertical plane.

Similarly, the second primary hydraulic actuating cylinder 66 and secondary cylinder 67 causes corresponding movement of the second pinions 62a, 62b attached to the pinion shafts 64a, 64b by means of the teeth 61a, 61 b provided on the second rams 60a, 60b. As a result of the small diameter gear wheels 65a, 65b meshing with the second large diameter gear wheel 68 there is corresponding movement of the diametrically opposing jaws. The first arriving jaws in the horizontal plane will contact the tubular 16 and push it towards the opposing jaws. When the second pair of jaws contact the tubular 16, the tubular 16 slides within the vertical jaws until the tubular 16 is then centred in the horizontal plane.

In this way, there is corresponding radial movement of each jaw 20a, 20b within each pair. Additionally, by virtue of the two large diameter gear wheels 58, 68, each pair is moveable independently of the other pair. This achieves a higher degree of accuracy than manual alteration of the jaws 20a, 20b. Two vertically disposed jaws and two horizontally disposed jaws enable the tubular 110 to be centred in two planes and at four points around the tubular 16 circumference. Thus, utilising two pairs of independently actuated jaws, with each pair moveable simultaneously ensures that the tubular 16 is accurately aligned and centred at the four points of contact to compensate for the ovality of the tubular 16.

The secondary cylinder 57 differentially reduces the torque transmitted by the gearing, so that for a given radial gripping force, the required torque transmitted by the gearing is less, thereby improving durability of the chuck 10.

The chuck 10 can be further modified by providing the feet 22a, 22b with an arcuate contact surface to improve distribution of the clamping load and avoid crushing of thinner tubes.

Additional pairs of opposing jaws can be provided and each jaw is preferably coupled for simultaneous movement with the other jaw in that pair. For example three pairs of jaws can be provided, although four pairs is preferred for centring operations. Modifications and improvements can be made without departing from the scope of the invention.

Claims

1. A chuck comprising two pairs of jaws, wherein each pair of jaws has one jaw arranged in substantially opposing relation relative to the other jaw, and wherein the jaws of at least one of the pairs of jaws are coupled together for simultaneous movement.

2. A chuck according to claim 1 , wherein each pair of jaws has one jaw coupled to the other jaw in that pair for simultaneous movement.

3. A chuck according to claim 1 or claim 2, wherein the jaws are arranged such that movement of one jaw in a pair causes corresponding radial movement of the other jaw in that pair.

4. A chuck according to any preceding claim, wherein the jaws in each pair are located in substantially diametrically opposing relation to one another.

5. A chuck according to any preceding claim, wherein one pair of jaws is arranged substantially perpendicular relative to the other pair.

6. A chuck according to any preceding claim, wherein each pair of jaws is movable independently of the other pair of jaws.

7. A chuck according to any preceding claim, wherein the chuck comprises a gearing assembly coupled to each jaw to effect simultaneous movement of the other jaw in that pair.

8. A chuck according to any preceding claim, wherein the opposing jaws of each pair are mechanically linked such that movement of one jaw in a pair causes corresponding movement of the other jaw in that pair.

9. A chuck according to any preceding claim, wherein each jaw in a pair is movable by an actuating means coupled to the gear assembly.

10. A chuck according to claim 9, wherein the actuating means provide a linear force to radially advance and retract the jaws coupled thereto.

11. A chuck according to claim 9 or claim 10, wherein one actuating means is coupled to each pair of jaws.

12. A chuck according to claim 11 , wherein the gear assembly transmits the force for radial movement of each of the jaws.

13. A chuck according to claim 9 or claim 10, wherein one actuating means is provided for each jaw and wherein the gear assembly acts to synchronise the movement of the jaws.

14. A chuck according to any of claims 9 to 13, wherein the actuating means comprises at least one ram.

15. A chuck according to claim 14, wherein each ram is provided with teeth for meshing with a pinion.

16. A chuck according to claim 15, wherein each pinion meshes with the teeth of opposing jaws in a pair and the pinion is coupled via a gear wheel for simultaneous movement.

17. A chuck according to claim 16, wherein a separate gear wheel is provided for each pair of jaws.

18. A chuck according to claim 17, wherein the gear wheels are axially spaced from one another with respect to a bore of the chuck.

19. A chuck according to any of claims 14 to 18, wherein a primary hydraulic actuating cylinder is coupled to a first jaw of each pair to drive the ram coupled thereto.

20. A chuck according to claim 19, wherein a secondary hydraulic cylinder is coupled to a second jaw of each pair and is operable at the same pressure as the primary hydraulic cylinder.

21. A chuck according to any preceding claim, wherein each jaw is provided with extension members to extend the radial inward reach of the jaw.

22. A chuck according to claim 21 , wherein the extension members have at least two feet, each foot having a contact surface for contacting an object in the chuck.

23. A chuck according to claim 22, wherein the at least two feet is spaced axially with respect to the bore of the chuck.

24. A chuck according to any preceding claim, wherein each contact surface for contacting an object in the chuck is at least partially arcuate.

25. A chuck according to any preceding claim, wherein one pair of jaws is axially offset with respect to the bore of the chuck from the other pair of jaws.

26. A method of centering an object in a chuck with two pairs of jaws, wherein each pair of jaws has one jaw disposed substantially opposite the other, and wherein the jaws of at least one pair are coupled together for simultaneous movement, the method comprising the steps of: moving each pair of jaws towards the object to be centred; contacting the object with each jaw; and centering the object.

27. A method according to claim 26, including coupling the jaws of each pair for simultaneous movement.

28. A method according to claim 26 or claim 27 including arranging each pair of jaws substantially perpendicular to one another.

29. A method according to any of claims 26 to 28, including moving each pair of jaws independently of the other pair of jaws.

30. A method according to any of claims 26 to 29, including coupling each pair of jaws to a separate gear assembly.

31. A method according to any of claims 26 to 30, including actuating the jaws by coupling an actuating means thereto.