WO2004067854A1

WO2004067854A1 - A gripping tool

Info

Publication number: WO2004067854A1
Application number: PCT/GB2004/000247
Authority: WO
Inventors: Roger Alfred Bacon
Original assignee: Bsw Limited
Priority date: 2003-01-28
Filing date: 2004-01-22
Publication date: 2004-08-12
Also published as: GB0301895D0

Abstract

A tool for gripping tubular objects such as pipes or hollow piles by contact with opposed internal or external surfaces thereof to enable the object to be recovered from its location such as in a subsea application. The tool comprises a mandrel (1) carrying several annular arrays of gripping members each comprising a body (2) a ramped wedge member (15) and a ball or roller cage (18). Hydraulic actuators (29) and control rods (31) are connected to tendons (12) which are themselves connected to the wedge members (15) and ball or roller cages (18) thus, upon engagement of the actuators (29) to draw the roller cages (18) and wedges (15) into a condition to grip the surface of the object, and selectively then to draw the wedges (15) and ball or roller cages (18) out of engagement with the surface of the object thus positively to release the tool from the object.

Description

A GRIPPING TOOL

THIS INVENTION concerns a tool for gripping tubular

objects such as pipes or hollow piles by contact with opposed internal or

external surfaces thereof thus to enable the object to be recovered from its

location.

Such a tool may be required for recovery of submerged piles

or pipes of large scale whilst allowing for any surface irregularities or

ovality of the tubular member to be gripped.

Gripping and lifting tools for this purpose often include

sliding wedges which are located on ramps such that they are deployed

into contact with a surface of the object to be gripped. However, upon

release of such a tool, the wedges tend to become jammed thus preventing

release.

Other such tools may include ball or roller cages to grip the

object surface, but these devices are rather too precise and involve only

slight movement to grip and release the object which is insufficient to

accommodate surface irregularities in large objects to be gripped. An object of the present invention is to provide a gripping

tool which substantially overcomes the problems experienced in the use of

the aforesaid known tools.

According to the present invention, there is provided a tool

for gripping a tubular object by contact with opposed surfaces thereof;

comprising a mandrel having means for attachment to lifting gear, at least

one pair of gripping assemblies attached to the mandrel, each gripping

assembly comprising a body member, a wedge member slidably movable

on an individual ramp with respect to the body member towards and away

from the mandrel, and a ball or roller cage slidably movable with respect to

the wedge member and having at least one ball or roller movable with the

ball or roller cage, on an inclined ramp with respect to the wedge member

thus to grip one of said opposed surfaces of the tubular object to be

gripped.

Preferably, there is attached to the mandrel an annular

array of such gripping assemblies, each with a wedge member and a ball

or roller cage, such that each ball or roller is caused to make annular

contact with the wall surface of the tubular object of circular section. Preferably, the mandrel carries a plurality of arrays of

gripping assemblies, spaced respectively along the longitudinal axis of the

mandrel.

Drive means may be connected to the or each gripping

assembly to advance the or each ball or roller cage into a position wherein

the or each ball or roller engages the surface to be gripped.

The drive means is so connected to the or each gripping

assembly as to retract the or each ball or roller cage into a position

wherein the or each ball or roller is disengaged from the surface.

Means may be provided normally to retain the or each ball

or roller of each ball or roller cage in a retracted condition.

One or more fluidic actuators may be attached to the

mandrel to advance and retard the wedge members and the ball or roller

cages with respect thereto.

An embodiment of the invention will now be described, by

way of example only, with reference to the accompanying drawings, in which:- Fig. 1 is an isometric view of a gripping tool made in

accordance with the invention;

Fig. 2 is a side elevation thereof;

Fig. 3 is an end view;

and Fig. 4 is a cross-sectional view about line A-A of Fig. 3.

Referring now to the drawings, in Fig 1 there is shown a

central mandrel 1 which is attachable to lifting gear by means of an

aperture 50.

Surrounding the mandrel 1 are three series or arrays of

gripping assemblies 51 together with an annular series of hydraulic

actuators 29.

Referring now to Fig. 4, each gripping assembly comprises a

body member 2 mounted on the mandrel 1 and fixed relative thereto. Slidably mounted on an inclined ramp 14 with respect to

the body member 2 is a wedge member 15. Slidably mounted on the

wedge member 15 is a ball cage 18 housing three balls 16 each movable

along inclined ramps 17 on an outer surface (with respect to the mandrel

1) of the wedge member 15.

Attached to each ball cage 18 is one end of a tendon 12

which passes around pulleys 54 and 55 and is anchored at its other end to

the wedge member 15 at an end thereof remote from the end of the ball

cage to which the tendon is attached. Springs, not shown, are provided

which are active to maintain each wedge member 15 and its associated

ball cage 18 in the position shown in Fig. 4 whereby the balls 15 are at the

bottom of their ramps 17.

Each gripping assembly comprising body member 2, wedge

member 15 and ball cage 18, is separately mounted upon the mandrel 1

and individually operable relative thereto as will be described. As can be

seen from Fig. 3, each array of gripping assemblies comprises some 20

such assemblies spaced evenly around the longitudinal axis of the

mandrel 1. Each hydraulic actuator 29 has attached to its piston 30 a

control rod 31.

Each control rod carries a bank of control flanges 8 each

attached to a tendon 12 of one of the gripping assemblies, and so the

control rods 31 are operatively connected to the gripping assemblies to

move the parts thereof as will be described.

The control rods 31 are housed within tubular tie rods 7

upon which the arrays of gripping assemblies are mounted. Thus, the

entire tool is maintained by the tie rods 7. Slots in the walls of the tie rods

permit longitudinal movement relative thereto of the control flanges 8

attached to the control rods 31.

In use, the tool may be lowered by lifting gear into the

interior of, for example, a tubular submerged pile of circular cross-section

in order to lift the pile from its location.

As the tool is lowered the gripping assemblies are

maintained in the condition illustrated in Fig. 4 with the wedge members

15 at the radially innermost end of their ramps 14 and with the balls 16 at

the innermost end of their ramps 17. The hydraulic actuators 29 are also in the position illustrated in Fig. 4 with the pistons 30 in a lowermost

position as the tool is lowered into the pile.

The actuators 29 may then be operated to withdraw the

pistons 30 and the control rods 31 in an upwards direction causing the

control flanges 8 to pull the tendons 12 also in an upwards direction

which in turn overcomes the aforementioned springs and advances the

wedge members 15 downwardly and outwardly on their ramps 14 to a

position in which the balls 16 make contact with the internal wall surface

of the pile to be gripped.

Dampers (not shown) are incorporated to allow

accommodation of any surface irregularities or ovality of the pile until all

of the gripping assemblies are advanced with the balls 16 in firm contact

with the internal surface of the pile.

Then, by lifting the mandrel 1 the balls 16 grip the internal

wall surface of the pile tightly, any fine surface irregularity of the pile being

accommodated by the balls 16 advancing outwardly along the ramps 17.

Thus, the balls 16 bite into the internal wall surface of the pile so that the

tool and the pile are firmly held together. In this way, the pile may be

elevated from its location to a required position. The tool is disengaged from the pile by initially removing the

force applied by the lifting gear and returning the hydraulic actuators 29

to the positions illustrated in Fig. 4. Thus, the wedge members 15 and the

ball cages 18 are retracted by their associated tendons 12 and the tool can

then be lifted out of the pile.

It will be appreciated that a gripping tool made in

accordance with the invention is capable of gripping and lifting large scale

structures, with the wedge members providing course adjustment and the

ball cages providing fine adjustment thus to ensure the integrity of the tool

in contact with the internal wall surface of the pile or other tubular object

to be gripped. The ball cages permit easy release of the tool when

required.

Conceivably, the use of wedges and ball cages on body

members can be reversed around a gripping tool adapted to grip an

external wall surface of a rod or pipe by reversing the construction such

that the gripping assemblies are mounted internally within a framework

having the control capabilities of the tool as described such that the

wedges and ball cages can be moved simultaneously into contact with the

surface to be gripped.

Claims

1. A tool for gripping a tubular object by contact with opposed

surfaces thereof; comprising a mandrel having means for

attachment to lifting gear, at least one pair of gripping assemblies

attached to the mandrel, each gripping assembly comprising a

body member, a wedge member slidably movable on an individual

ramp with respect to the body member towards and away from the

mandrel, and a ball or roller cage slidably movable with respect to

the wedge member and having at least one ball or roller movable

with the ball or roller cage on an inclined ramp with respect to the

wedge member thus to grip one of said opposed surfaces of the

tubular object to be gripped.

2. A tool according to Claim 1 , including an annular array of such

gripping assemblies attached to the mandrel, each with a wedge

member and a ball or roller cage, such that each ball or roller is

caused to make annular contact with the wall surface of the object

of circular section.

3. A tool according to any preceding claim, wherein the mandrel

carries a plurality of arrays of gripping assemblies, spaced

respectively along the longitudinal axis of the mandrel.

4. A tool according to any preceding claim, including drive means

connected to the or each gripping assembly to advance the or each

roller cage into a position wherein the or each ball or roller engages

the surface to be gripped.

5. A tool according to Claim 4, wherein the drive means is so

connected to the or each gripping assembly as to be adapted to

retract the or each ball or roller cage into a position wherein the or

each ball or roller is disengaged from the gripped surface.

6. A tool according to any preceding claim, including means normally

to retain the or each ball or roller of each ball or roller cage in a

retracted condition.

7. A tool according to any preceding claim, including an hydraulic

actuator having a piston and control rod the latter being connected

via a tendon to one or more of said gripping assemblies.

8. A tool according to Claim 7, wherein the or each tendon is

connected at one end thereof to a respective wedge member, and at

the other end thereof to an associated ball or roller cage movable

with respect to said wedge member, the tendon being so disposed

that movement thereof in one direction draws the ball or roller cage

and its associated wedge into a gripping condition whereas

movement of the tendon in an opposite direction draws the wedge

and its associated ball or roller cage into a non-gripping condition.

. A tool according to any preceding claim, including at least one

damper to allow accommodation of any surface irregularities or

ovality of the surface to be gripped until all of the gripping

assemblies are advanced with the balls or rollers thereof in firm

contact with the surface to be gripped.

10. A tool according to any preceding claim, in which the gripping

assemblies are mounted about the mandrel and disposed so as to

grip an internal surface of a tubular object.

1 1. A tool according to any one of Claims 1 to 9, wherein the gripping

assemblies are mounted about the mandrel and are disposed so as

to grip an external surface of an object.