GB2146091A - Improvements in or relating to clamps - Google Patents

Abstract

A clamp 10 comprises a tubular support 20 having a number of axially spaced sets of angularly spaced apertures 22 for receiving spheres 24 engageable with the exterior of pipe 27 and tapered surfaces 14, 14a, 14b, 14e. Springs 29 urge the support 20 down in relation to body 11 to cause the spheres to grip the pipe. Rams 31 can raise the support to release the clamp, whereupon the spheres can enter recesses 15. The apertures may be axially elongated to accommodate a degree of pipe ovality. A form of the clamp for gripping a pipe interior is also described. (See Fig. 4). <IMAGE>

Description

SPECIFICATION Improvements in or relating to clamps This invention relates to clamps.

According to the invention, a clamp device comprises a body providing a surface inclined to an axis, and a movable element engageable with the surface and extending through a support for said element for operative engagement with a member to be clamped.

The device may comprise means urging the movable element into engagement with the surface; for example spring means.

The body may define a recess for receiving the element when not engaging the surface.

The element may be a sphere.

The surface may be on a tore through the body, the support being tubular and apertured to receive the element.

The surface may be on the exterior of the body, the support being tubular and apertured to recieve the element.

There may be a damping device pivotally connected to the body and the support and permitting a degree of movement of the body within the support.

The aperture for the element may have a greater axial dimension than circumferential dimension.

The surface may be annular and engageable by a plurality of said elements.

There may be a plurality of said surfaces and elements spaced axially.

The invention may be performed in various ways and two specific embodiments with possible modifications will now be described by way of example with reference to the accompanying drawings, in which: figure I is a half vertical section through a clamp or collet associated with a length of pipe; Figure 1A is an enlarged view of part of Fig. 1; Figure IB shows a modification; Figure 2 is a side elevation showing clamps of Fig. 1 in association with a pipe; Figure 3 is a diagrammatic view of an oil drilling arrangement; Figure 4 is a half vertical section of an internal clamp; and Figures 4A and 48 are similar to Figs. 1A and 1 B.

Referring to Fig. 1, a clamp or collet 10 comprises a body 11, for example of forged steel, in the form of a ring having a central longitudinal circular cross-section aperture 12 therethrough. Aperture 12 has at the upper end a first recess 8 providing tapered surface portion 13, which extends inwardly uniformly as it extends downwardly, leading to a second tapered surface portion 14 inclined inwardly, at a smaller angle to the longitudinal axis 9 than the tapered portion 13. The tapered portion 14 leads to a radially enlarged recess 15 which has a lower tapered surface 13a similar to surface 13 which leads to tapered portion 14a similar to portion 14. Tapered portion 14a leads to a recess 15a similar to recess 15, and so on. In the arrangement shown there are four recesses 8, 15 etc. and four tapered portions 14, 14a etc.There could be one, two, three, or more than four, such sequential recesses and tapered surface portion, depending on particular uses. The upper surface 18 of recess 15 is at right angles to axis 9 abd is connected to surface portion 13a by curved portion 19. The taper surface 14 etc, are case hardened.

A ball cage or support 20 comprises a tubular portion 21 extending in the aperture 12 and a flat horizontal top portion 21a. The portion 21 is parallel to axis 9. Portion 21 has a number of axially spaced rows of apertures 22, the apertures in each row being equiangularly spaced about the axis 9. Each aperture 22 is of circular section with the surface 23 defining the aperture 22 diverging uniformly as it extends radially outwardly. Each aperture 22 in the position shown receives a spherical ball 24, for example of hardened steel, the balls 24 engaging the outer surface 26 of a pipe 27 and the surfaces 14, 14a, 14b, 1 4c.

The radially inner end of aperture 22 has a diameter less than the diameter of the associated ball 24.

A plurality of equi-angularly spaced bolts 28 are removably threaded into threaded bores in the upper part of the body 11 and extend through the flat cage portion 21a.

Helical compression springs 29 extend between cage portion 21 a and the heads 30 of the bolts 28 to urge the cage downwards, with balls 24 on surfaces 14, 1 4a, 14b, 14c.

There may for example be twenty four balls in each set but there could be a different number, for example one.

Because of the balls 24 engage tapered surfaces 14, 14a 1 4b, 14c they are urged radially inwardly with a wedging action by downward movement of the cage 20 to grip firmly the surface 26 and prevent downward movement of the pipe 27. In this condition the upper edges of the apertures would engage the balls.

If the cage 20 is moved upwards, the balls 24 move up the taper surfaces thus moving radially outwardly and may respectively move into recesses 8, 15, 15a, 15b, so that the pipe 26 is no longer clamped. In this condition the lower edges of the apertures would engage the balls. For clarity a radial clearance is shown at 23a between the illustrated balls and the inner ends of the apertures; this could occur if only some balls are gripping due to non-uniformity of pipe.

The cage 20 can be moved up or down to engage or disengage the wedge by a plurality of angularly spaced hydraulic cylinder/piston rams 31, in addition to the effect of gravity.

The pistons 31 a of the rams 31 are connected to the portion 11 conveniently through pivotal connection 31b, and the cylinder body of the ram 31 is connected to plate 21a by a flange connection.

In a modification the recesses 8, 15, 15a, 15b, are omitted.

In a preferred arrangement the balls 24 effect a gripping action under gravity i.e. the springs 29 could be omitted.

Because of the diverging shape of surface 23 the surface 23 may tend to roll the associated ball which may be helpful in some circumstances.

The balls 24 will be wedged between the pipe 27 and the tapered surfaces under the action of gravity. Because of the effect of gravity, the pipe 27 will move downwards.

Friction between the balls and the pipe will cause the balls to roll down the tapers and thus apply a radial load to grip the pipe 27 and prevent any further downward movement of the pipe. The clamp is thus self-engaging which is to be contrasted with a hydraulically engaged wedge which requires an external power source.

The springs 29 could be replaced by hydraulic rams, for example the rams 31 could be modified so as to be capable of being energized to assist the gripping of the clamp.

In a modification, the balls 24 are arranged to engage the interior surface of a pipe. Thus the portion 21a is radially inwards of cage 21 and the tapered surfaces are formed on the exterior of body 11 which is arranged to extend into the pipe.

One use of the clamp 10 is in the oil industry, specifically drilling.

In a known method of drilling, a platform 40 Fig. 3 includes legs 41 resting on the sea bed 42. A barge 43 carries lengths 44 of pipe or drill casing and a large crane 45 for transferring the casing lengths 44 to the platform 40. A large crane 46 is mounted on the platform and holds the assembled lengths of drill casing 47. A drill extends down the inside of the casing 47. The crane 46 must be sufficiently large to support or hold the entire length of casing 47.

With the present arrangement as decribed below, the crane 46 can be reduced in size.

A device 50 (Fig. 2) as shown in Fig. 1 has its body 11 fixed to the top of platform 40.

Mounted on plate 21 are a plurality of equiangularly spaced hydraulic rams/cylinders 51 (only two shown in Fig. 2) The cylinders 51 are pivoted to plate 21 at 52. The pistons 53 are pivoted at 54 to brackets 55 at the bottom of the body of a device 60 the same as the device 50 and the device 10. Fixed to the top of the device 60 is a clamp device 70 the same as devices, 60, 50, 10 but inverted.

Device 70 thus resists upward movement of the casing. Cylinders 51 (and cylinders 31 of each clamp device) are connected to suitable sources of pressure fluid e.g. pumps.

In Fig. 2 a new length 56 of casing is being added to the existing casing, using known casing connector 57 on casing length 27.

When connecting length 56 to connector 57, the cylinders 31 of clamp device 50 are energized so that the balls 24 of device 50 clamp the length 27 and support the assembled casing lengths. Devices 60, 70 may also be clamped. When the connector 57 is to pass through devices 50, 60, 70 their cylinders 31 are energized as required to move their respective balls 24 into the recesses 8, 15, 15a, 15b, to unclamp the pipe and allow the connector 57 through. At all material times the assembled casing is held in one or more of the clamps. In the present case the clamp devices may assist in movement of the casing.

To feed the casing or pipe upwards, devices 50, 60 are used, device 70 being unclamped.

Device 60 is clamped against the pipe and rams 51 are energized to move the clamped pipe and device 60 upwards, the device 50 being unclamped. Device 50 is then clamped to hold the pipe, device 60 is unclamped, and rams 51 lowered to lower devices 60, 70.

Device 60 is then clamped, device 50 is then unclamped, rams 51 are extended to raise the pipe, and so on.

To feed the pipe down under its own weight, device 70 is unclamped and devices 50, 60 are used. In Fig. 2 the rams 51 are in extended position. Device 50 is in unclamped condition and device 60 is in clamped condition to carry the weight of the lengths of assembled casing. The rams 51 are then retracted to lower the pipe with devices 60, 70.

Device 50 is then brought to clamped condition to hold the pipe, device 60 is then unclamped, the rams 51 are then extended to raise devices 60, 70, device 60 is then brought to clamped condition, and so on.

To push the pipe downwards in addition to its own weight, devices 50, 60 are unclamped and device 70 is clamped. Rams 51 are in lowered (reteracted) condition. Clamp 50 is then engaged, clamp 70 is then disengaged, rams 51 are then extended to raise devices 60, 70 whilst clamp 50 holds the casing, clamp 70 is then re-engaged, clamp 50 is then disengaged, the rams 51 are then retracted to lower devices 60, 70 and the casing, and so on.

To clamp a pipe connector 57 onto a length of pipe or casing, clamp 60 is disengaged.

The pipe 27 is held in clamp 50 and is in a position such that connector 57 is on pipe 27 and between devices 60, 50. The new pipe length 58 is held in clamp 70 and rams 51 are then retracted to lower the end of pipe length 56 into the connector 57.

It will be understood that connector 57 (shown in chain-dotted in Fig. 1) can move freely upwardly in devices 50, 60 because it displaces the balls 24 outwardly but it cannot move downwardly through the ball cage 21 unless the rams 31 are energized to raise the cage. For inverted device 70, the connector 57 can move freely downward but not upwardly.

Instead of cylinders 31, a screw device can be used for example manually operated.

When used in drilling, the clamp device or devices may be used to grip the drill string, or the casing through which the drill string may extend. In some cases the drill bit is carried on the casing.

It will be understood that the pipe or casing could be rotated whilst being supported by the clamp or clamps against axial movement.

Fig. 4 shows an internal form of the clamp, which is self-engaging and self-dis-engaging.

On being lowered, the ball cage 20 enters the pipe 27 and allows the body 11 to move down and the balls 24 to retract radially inwards. The load is then slowly applied by raising body 11 and the pipe gripped by the balls 24 which are moved outwards. On disengagement, the load is removed and the body 11 moves down as before. The clamp is then quickly removed and dis-engaged. A hydraulic damper 58 pivoted to cage 20 and body 11 is attached to the body and cage by pins one of which is engaged in an axial slot 59 and allows a certain amount of free movement of the body 11 within the ball cage 12.

The damper acts as a time delay 58. Thus, when it is desired to release the pipe, the body 11 is lowered, compressing the damper 58, and the balls 24 move inwardly releasing the grip. Before the damper 58 can return to its extended datum position the whole clamp is lifted out of the end of the pipe or casing.

The clamp has a lifting eye 1 la.

Typical use of the clamp Fig. 4 is for the automatic stacking of drill pipes or for the handling of drill casings, making the use of pad eyes and hydraulic clamps unnecessary.

In another internal form of clamp the arrangement of Fig. 4 is provided with springs 29 and rams 31 as in Fig. 1. Dependent on the radial clearance between the pipe and sleeve 21 a degree of ovality can be accommodated whilst retaining all the balls as gripping elements.

In order to better accommodate a degree of ovality in the pipe particularly large diameter pipes e.g. 90 cm, where a given tolerance in diameter means a greater ovality, the apertures 22 may be axially elongated so as to form a parallel sided slot, as seen in Figs. 1 B and 4B in which case all the balls may grip simultaneously. The axial dimension would depend on the angle of inclination to the axis of the taper surfaces 13, 13a, 13b, 1 3c and the amount of ovality it is desired to accommodate. The angle of inclination can be differ- ent in different embodiments. For example the angle of inclination could be between 4 and 20 . The smaller the angle the greater the radial loading for a given downward load.

The ovality may be-caused in manufacture of the pipe or subsequently.

Claims (12)

1. A clamp device comprising a body providing a surface inclined to an axis, and a movable element engageable with the surface and extending through a support for said element for operative engagement with a member to be clamped.

2. A clamp as claimed in Claim 1, comprising means for urging the movable element into engagement with the surface.

3. A clamp device as claimed in Claim 2, in which the urging means comprises spring means.

4. A clamp device as claimed in any preceding claim, in which the body defines a recess for receiving the movable element when not engaging the surface.

5. A clamp device as claimed in any preceding claim, in which the element is a sphere.

6. A clamp device as claimed in any preceding claim, in which the surface is on a bore through the body, the support being tubular and apertured to receive the element.

7. A clamp device as claimed in any of Claims 1 to 5, in which the surface is on the exterior of the body, the support being tubular and apertured to receive the element.

8. A clamp device as claimed in claim 7, including a damping device pivotally connected to the body and the support and permitting a degree of movement of the body within the support.

9. A clamp device as claimed in claim 6 or claim 7 or claim 8, in which the aperture for the element has a greater axial dimension than circumferential dimension.

10. A cramp device as claimed in any preceding claim, in which the surface is annular and engageable by a plurality of said elements.

11. A clamp device as claimed in any preceding claim, comprising a plurality of said surfaces and elements spaced axially.

12. A clamp device substantially as hereinbefore described with reference to and as shown in Figs. 1 and 1A, or Fig. 1 B, or Fig.

1, or Figs. 4 and 4A, or Fig. 4B, of the accompanying drawings.