Actuating mechanism

Abstract

An actuating mechanism (111) comprising an inner member (113) and an outer member (115) axially slidable relative to each other, the inner and outer members (113, 115) cooperating to define an internal passage (117) for the flow of a fluid therethrough. The inner member (113) being configured such that upon a predetermined change in pressure between a first region (119) and a second region (120) the actuating mechanism (111) is caused to move between a first condition and a second condition.

Description

FIELD OF THE INVENTION

The present invention generally relates to an actuating mechanism for use in an apparatus to effect movement of the apparatus between two or more modes of operation. For instance, the actuating mechanism can be used in a flushing device incorporated in a drilling stem used in mining to open and shut the device.

BACKGROUND ART

The current invention can be applied in many different types of tools and devices. For instance it may be incorporated in under reamers, casing cutters, ball valves and other type of valves, packers and tools for deep mineral air drilling.

The invention would also be useful in flushing devices used in drilling strings in oil and gas explorations and extraction. As well paths in exploration and extraction activities in mining industries become increasingly longer and the network more complicated, new challenges are constantly being faced in the area of well boring. One of these challenges is in respect of maintaining suitable conditions for the operation of the drill head or bit to cut through the medium.

When drilling well bores, slurry, used to operate the drill head, is pumped from the surface through a drill stem assembly to the drill head. This slurry, upon reaching the end of the bore is caused to return to the surface, passing through the annular space between the sidewalls of the bore and the drill stem assembly before reaching the surface, whereby the returning slurry suspends the cuttings, made during the drilling process, transporting them back to the surface. The removal of the cuttings ensures the bore remains relatively clean, providing optimal conditions for drilling. Failure to remove the cuttings, or a suitable percent of the cuttings can create blockages and jamming, resulting in costly down time and may even result in the equipment being irretrievable.

A build up of cuttings may result in a reduction in the flow of slurry to and from the drill head, it may place unnecessary loads on the drill head and stem assembly and may also cause the drill head to be wedged or jammed in the bore. Furthermore, with the increase in use of horizontal bores in well networks, a build up of cuttings on the lowermost or bottom surface of the bore may cause side displacement of the drill head which will result in the bore taking on a new and incorrect direction.

Several areas of the drilling process have been investigated and improvements have been made which enhance the process of returning the cuttings to the surface. These solutions have included improvements to the slurry composition used to drive the drill head, as well as improvements to the actual drill head and the speed in which it may operate. However, improvements are still required in order to increase and improve the removal of cuttings from the bore.

Increasing the flow rate of the slurry and hence the return rate of the slurry to the surface does not sufficiently solve the problem. Owing to the narrow gap of the annular space, cuttings still tend to collect in this area. This not only inhibits the drilling process but is also problematic when introducing pipe linings. Also during subsequent cementing, additional problems are experienced if the hole is not clean.

Several mechanical flushing devices have been developed to assist in the clearing of the cuttings. These devices are incorporated with the drill stem assembly and, when in a closed condition allow the passage of the slurry to pass therethrough before proceeding to the drill head. When required the flushing device is caused to move to an open condition. In this condition a percentage of the slurry is diverted from the main flow passage, through ports located on the outside of the flushing device and into the annular space between the flushing device and the bore wall. The flushing device is remotely operated from the surface and typically requires the pumps to be switched off before the state of the flushing device may be changed.

As the annular space between the drill stem assembly and the bore wall is particularly narrow, it is often the cause of packing or wedging of cuttings in this region. It is therefore highly desirable to keep this region clear. Hence, diverting a portion of the fluid as it passes through the flushing member to the annular space assists in flushing this area and maintaining a clear passage for the flow of return fluid and cuttings to the surface.

Several of these flushing devices are referred to in U.S. Pat. No. 6,161,632. The invention disclosed in U.S. Pat. No. 6,161,632 provides a flushing device which remains in a closed state by the weight of the drill stem which acts downwardly. Relieving this weight by applying a relative pull upon the drill stem results in the flushing device moving to an open state, causing a predetermined percentage of the slurry to be diverted from the main passage into the annular space for as long as the weight of the drill stem assembly has been relieved.

Subsequent, to the return of the weight loading, the ports close and the full flow of the slurry is again delivered to the drill head allowing the drilling process to continue.

Hence, in order to maintain the flushing device in a closed state a compressive force must be maintained upon the flushing device. Similarly, in order to maintain the flushing device in an open state a tractive force must be maintained upon the flushing device. If the compressive or tractive force is not constantly applied to the flushing device during the required condition, the flushing device may automatically and uncontrollably move to the alternate condition.

The outer valve part and inner valve part of the flushing device disclosed in U.S. Pat. No. 6,161,632 are connected in permanent rotation via key and keyway slots between the valve parts. The manner in which these parts are coupled together result in high concentrations in forces at this junction, leading to failures at this interface, requiring costly repairs to be made.

A further deficiency in this device is in relation to the bleed holes located on the outer wall of the tool. These bleed holes allow cuttings to get into the flushing device, contaminating the various parts within the flushing device and resulting in tool failure.

Another type of flushing device currently available overcomes some of the deficiencies of the device disclosed in U.S. Pat. No. 6,161,632 in that a tractive force does not need to be maintained upon the device in order for it to remain open. However, a compressive force must be maintained in order to keep the device in a closed state. Loss of compression will automatically result in the tool moving to an open state, regardless of whether the surface pump(s) are in operation or not. This is undesirable during a drilling operation. Furthermore, this particular device is constructed such that the major moving components operate in the slurry, leading to reliability problems with the parts. Similarly to U.S. Pat. No. 6,161,632, breather ports also allow cuttings to enter the device, causing additional problems in relation to the reliability of the device.

This device relies on hydraulic pressure to achieve the required tensile loading. Owing to the configuration of the device, hydraulic lock can occur resulting in a build up of pressure. When the pressure builds beyond a predetermined value, a relieve disc bursts causing the device to default to an open state, requiring the drill stem assembly to be brought back to the surface so that the flushing device can be repaired or replaced.

Further variations of these type of tools have also been developed. However, they often comprise many moving parts, which reduce the reliability of the tool, particularly in the operational conditions experienced, and/or require components to mechanically lock with other components, which under sufficient pressure result in the failing or deformation of these components, rendering the tool useless.

The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.

It is against this background, and the problems and disadvantages associated therewith, that the present invention has been developed.

SUMMARY OF INVENTION

The present invention provides an actuating mechanism comprising:

• • an inner member and an outer member axially slidable relative to each other, the inner and outer members cooperating to define an internal passage for the flow of a fluid therethrough;
  • the inner member being configured such that upon a predetermined change in pressure between a first region and a second region the actuating mechanism is caused to move between a first condition and a second condition.

Preferably the first region is in the internal passage of the actuating mechanism.

Preferably the second region is external of the actuating mechanism. The pressure in the second region may be transmitted to a third region located within the actuating mechanism. Preferably the third region is located substantially between the inner and outer members. In this arrangement a change in pressure in the second region affects the pressure in the third region.

Preferably at least a section of the inner member is exposed to both the first and third regions. Preferably an inner surface of the inner member is exposed to the first region and an outer surface of the inner member is exposed to the third region. When there is a pressure difference between these regions unequal forces are exerted across the inner member. Preferably when this inequality reaches the predetermined value the actuating mechanism is caused to move between its first and second conditions.

Preferably the inner member and outer members are in the form of pipes.

The inner member may comprise a wash pipe which is configured to have a first end with an outer diameter larger than the outer diameter at the second end. Preferably the wash pipe has a portion having a tapered outer diameter. The portion may have a constant inner diameter.

Preferably the wash pipe has a first seal assembly located along the outer diameter adjacent the first end and a second seal assembly located along the outer diameter adjacent the second end. Preferably the first seal assembly and the second seal assembly each have at least one seal. Preferably the at least one seal of the second seal assembly has a smaller cross section than the at least one seal of the first seal assembly.

The degree of change in pressure required between the first region and the second region to operate the actuating mechanism may be varied by changing the cross sectional diameter of the at least one seal of the second seal assembly. Preferably an internal portion of the outer member against which the second seal assembly slidingly engages can be varied according to changes in cross sectional diameter of the at least one seal in the second seal assembly.

Preferably a cavity is defined between the inner member and outer member. Preferably the cavity is filled with a lubricant such as oil. The cavity may have an opening which opens into a chamber of an equalising device. The equalising device may be in the form of a floating sleeve which is slidingly retained on an outer portion of the outer member and which surrounds the chamber. Preferably, volumetric changes in the cavity result in the floating sleeve moving with respect to the opening. Preferably the floating sleeve is in communication with the second region such that pressure in the second region is transmitted to the cavity. Preferably the cavity provides the third region.

Preferably the cavity is sealed from the internal passage such that the cavity may not be contaminated. Preferably the cavity is also sealed from the area external the actuating mechanism to again ensure the cavity remains free from contamination. This ensures that the moving parts of the actuating mechanism are retained in an environment where contaminants cannot affect the operation of the actuating mechanism, increasing its reliability.

The equalising device may also balance and cushion the movement between the inner and outer sleeve.

Preferably the actuating mechanism comprises an indexing mechanism which indexes between a first position, wherein the actuating mechanism is in the first condition and a second position wherein the actuating mechanism is in the second condition.

Preferably the indexing mechanism is located between the first and second members. Preferably the indexing mechanism operates within the cavity. Preferably the indexing mechanism engages the inner member. The indexing mechanism may comprise an indexing sleeve, a travel stop and a positioning sleeve.

The indexing sleeve may be fixed rotationally to the inner member, this may be by way of a key way arrangement. Preferably the indexing sleeve is axially movable relative to the inner member.

The travel stop may be mounted on the inner member such that it may rotate about the longitudinal axis thereof. Preferably the travel stop is substantially constrained against axial movement relative to the inner member.

The positioning sleeve may be fixed rotationally to the inner member, this may be by way of a key way arrangement. Preferably the positioning sleeve is axially movable relative to the inner member.

The indexing sleeve and travel stop may be biased away from each other. The biasing force may be provided by a first spring. The travel stop and positioning sleeve may also be biased away from each other. The biasing force may be provided by a second spring.

Preferably the travel stop is adapted to co-operate with the indexing sleeve during the indexing sequence.

The indexing sleeve may have a first end which provides a bottom face and a second end having a projection, defining a pawl, extending in an axial direction from the periphery of said second end.

The travel stop may have a first end adapted to engage and mesh with the projection on the indexing sleeve and a second end adapted to engage and mesh with the positioning sleeve. Preferably a first end of the positioning sleeve is shaped to engage and mesh with the second end of the travel stop.

Preferably the second end of the travel stop is configured to provide a plurality of fingers and corresponding slots, which co-act with corresponding fingers and slots integral with the positioning sleeve. Each finger and slot of the travel stop may terminate in at least one depression or trough. Each finger and slot of the positioning sleeve may terminate in at least one peak. Each peak may be complimentary in shape to each trough so that upon engagement each finger on the travel stop aligns with a finger and/or slot on the positioning sleeve depending on whether the indexing mechanism is in its first position or second position.

Preferably when the indexing mechanism is in its first position the fingers on the travel stop align and mate with the fingers on the positioning sleeve. In this condition the fingers are opposed.

Preferably when the indexing mechanism is in its second position the slots on the travel stop align and mate with the fingers on the positioning sleeve, whilst the fingers on the travel stop align and mate with the slots on the positioning sleeve. In this condition the fingers are interlaced.

In one configuration of the indexing mechanism each finger and each slot on the travel stop each have one trough, and each finger and each slot on the positioning sleeve each have one peak.

In this configuration the actuating mechanism actuates, or cycles, between the first and second conditions in alternating fashion.

In another configuration of the indexing mechanism each finger and each slot on the travel stop each have one trough, and each finger on the positioning sleeve has one peak, whilst each slot on the positioning sleeve has two peaks.

In this configuration the actuating mechanism actuates, or cycles, from first condition to second condition to second condition before returning to the first condition.

Other configurations of the indexing mechanism will obviously allow for a variety of different cycles depending on the number of troughs each finger and/or slot on the travel stop has, and/or the number of peaks each finger and/or slot on the positioning sleeve has.

Obviously, the peaks may be on the fingers and slots of the travel stop whilst the troughs may be on the fingers and slots on the positioning sleeve.

The actuating mechanism may comprise at least one retention mechanism to releasably retain the actuating mechanism in one condition until the predetermined pressure differential between the first and third regions is reached whereupon the actuating mechanism is able to move from one condition to the other.

The retention mechanism may be a detent.

The retention mechanism may comprise a ball fixed relative to the inner member but biased radially outward from the inner member. The outer member may have a first groove and a second groove on its inner surface spaced a distance from each other. Preferably this distance is substantially equal in length to the axial distance the inner member moves relative to the outer member as the actuating mechanism moves between its first and second conditions. Each groove may be annular with a cross section complimentary to the ball so that the ball can be received therein and hold the inner member relative to the outer member.

Alternatively, the ball may be fixed relative to the outer member and biased radially inward from the outer member, the inner member may have the first groove and the second groove on its outer surface spaced a distance from each other substantially equal in length to the axial distance the inner member moves relative to the outer member as the actuating mechanism moves between its first and second conditions.

Preferably the actuating mechanism is capable of flexing whilst still capable of effective operation. The actuating mechanism may incorporate a joint capable of allowing pivotal movement relative to the longitudinal axis. Preferably the joint is in the form of a knuckle joint and allows the inner member to pivot. The joint allows the actuating mechanism to operate effectively even when loads applied to the outer member cause it to deflect between its ends.

Preferably the actuating mechanism is incorporated in an apparatus, such as a tool, for actuating the apparatus between first and second operational condition.

In one aspect of the invention the apparatus is a flushing device, whereby the actuating mechanism causes the flushing device to move between the first operable condition, wherein the flushing device is closed and the second operable condition wherein the flushing device is open.

Preferably an inner sleeve of the flushing device comprises the inner member of the actuating mechanism, whilst an outer sleeve of the flushing device comprises the outer member of the actuating mechanism. The flushing device also has an internal passage which incorporates the internal passage of the actuating mechanism.

The outer sleeve may incorporate openings. These openings may be blocked from the internal passage when the flushing device is in the closed operable condition, and register with the internal passage when the flushing device is in the open operable condition.

Preferably the flushing device is configured such that the flushing device remains in the selected open or closed operable condition regardless of any expansive or compressive force.

When in use the inner sleeve and outer sleeve are in mutual support.

Preferably the openings provide a flushing outlet, whereby when the flushing device is in an open operable condition a predetermined percentage of the fluid is diverted from the passage.

The flushing outlet preferably comprises a plurality of apertures in the inner sleeve, an annular chamber in the outer sleeve and a plurality of nozzles. The flushing outlet may form a passage between the annular chamber and the outside of the flushing device when the flushing device is in its open operable condition. Each nozzle may be shaped so as to direct diverted fluid backwards, away from the drill head.

Preferably a fluid tight seal is provided between the inner and outer sleeve as the flushing device moves from a closed operable condition to an open operable condition. The flushing device may comprise an intermediate sleeve located between the inner and outer sleeve and located between the flushing outlet and the inlet of the flushing device to provide the fluid tight seal.

In another aspect of the invention the apparatus is an under reamer or casing cutter whereby the actuating mechanism causes the under reamer or casing cutter to move between a first operable condition, wherein a cutting device is contained within the under reamer or casing cutter, and a second operable condition wherein the cutting device protrudes from the under reamer or casing cutter to cut as required. Alternatively the actuating mechanism may cause the cutting device to move between a first operable condition, wherein the cutting device is off, and a second operable condition wherein the cutting device is on. An under reamer is a tool used to smooth the wall of a well, enlarge the hole, help stabilize the bit, straighten the well bore and/or to drill directionally.

In another aspect of the invention the apparatus is a valve, such as a ball valve, whereby the actuating mechanism causes the valve to move between a first operable condition, wherein the valve is closed and a second operable condition wherein the valve is open.

Other applications of the actuating mechanism also include the operation or activity of a packer, use in deep mineral ore drilling, use with single shot operation for permanent installations.

The present invention also provides a flushing device comprising:

• • an inner sleeve and an outer sleeve, moveable relative to each other between an open operable condition, wherein a percentage of the fluid passing through a central passage of the flushing device can be diverted through a plurality of flushing outlets, and a closed operable condition, wherein the fluid outlets are blocked from the passage,
  • an actuating mechanism operable between the inner and outer sleeves, and having first and second conditions which correspond to the open and closed operable conditions, the actuating mechanism being responsive to a fluid pressure differential between a cavity defined between the inner and outer sleeves, and the pressure in the internal passage, for movement between its first and second conditions, whereby the actuating mechanism, when in the first or second condition couples the inner sleeve to the outer sleeve to prevent movement of the inner sleeve relative to the outer sleeve until predetermined value of pressure differential is reached.

The invention also provides a flushing device for flushing diverted fluid upwards into an annular space between a drill stem and a hole, where a slurry passes through a central passage of the flushing device to a drill head, whereupon it reverses direction, passing through the annular space before returning to the surface with cuttings from the drilling process suspended in the return slurry, the flushing device is adapted to change between an open operable condition, whereby a predetermined percentage of fluid is diverted from the passage to the annular space to assist in maintaining a clean bore, and a closed operable condition, whereby the full flow of the slurry is delivered to the drill head, and is configured such that the increase or reduction of pressure in the internal passage relative to the pressure external the flushing device causes an actuating mechanism located in the device to cycle between a first and second condition whereby the flushing device correspondingly cycles through open and closed operable conditions.

The present invention also provides a flushing device comprising:

• • an inner sleeve, slidingly received in an outer sleeve, the inner and outer sleeves cooperating to define an internal passage for the flow of a fluid, and are permanently coupled such that there is no rotational movement between the two sleeves;
  • the outer sleeve having a plurality of flushing outlets
  • an actuating mechanism comprising an inner and outer member, incorporated within the inner and outer sleeves, an internal passage which is common with the internal passage of the flushing device, the actuating mechanism being caused to cycle between open and closed conditions with change in the pressure differential acting upon the inner member;
  • an indexing mechanism which indexes as a result of the operation of the actuating mechanism, the indexing mechanism indexes between first and second positions such that the flushing device moves between an open operable condition, whereby the plurality of flushing outlets are open for discharging a quantity of the fluid from the internal passage, and a closed operable condition, whereby the plurality of flushing outlets are closed, the operable condition depending on the position of the indexing mechanism.

DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the following description of a specific embodiment thereof as shown in the accompanying drawings in which:

FIG. 1 is a sectional view of the invention used in a flushing device;

FIG. 2 is a sectional view of the invention in a closed condition during operation;

FIG. 3 is a view similar to FIG. 2 but in an open condition;

FIG. 4 is a sectional view of the inlet end of the flushing device depicted in FIG. 1;

FIG. 5 is a sectional view of the inlet end of the flushing device depicted in FIG. 2

FIG. 6 is a sectional view of the inlet end of the flushing device depicted in FIG. 3

FIG. 7 is a sectional view of the outlet end of the flushing device depicted in FIG. 1;

FIG. 8 is a sectional view of the outlet end of the flushing device depicted in FIG. 2

FIG. 9 is a sectional view of the outlet end of the flushing device depicted in FIG. 3

FIG. 10 is a view of an indexing mechanism in an opposed relation;

FIG. 11 is a view similar to FIG. 4 but in an interlaced relation;

FIG. 12 is a view of the indexing mechanism according to the sequence of positions as it moves between an opposed to interlaced relation.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

The invention according to an embodiment is in the form of an actuating mechanism 111 comprising an indexing mechanism 80, an inner member 113 and an outer member 115, which cooperates with the inner member 113 to provide an internal passage 117 through which fluid passes. The internal passage 117 also provides a first region 119, whilst a second region 120 is defined by an area external to the outer member 115.

Referring to FIGS. 1 to 9 the actuating mechanism 111 is incorporated in a flushing device 20.

Flushing Device

The flushing device 20, comprises an inner sleeve 21 and an outer sleeve 23, which cooperate to provide a fluid passage 32 having an inlet 22b and an outlet 22a. The fluid passage 32 incorporates the internal passage 117 of the actuating mechanism 111.

The inner sleeve 21 comprises the inner member 113 of the actuating mechanism 111 and provides a plurality of apertures 38 spaced annually therearound, as shown in FIGS. 1 to 6.

The outer sleeve 23 of the flushing device 20, comprises the outer member 115 of the actuating mechanism 111 and defines the inlet 22b and the outlet 22a of the flushing device 20.

The outer sleeve 23 is adapted to be releasably incorporated in the drill stem assembly and provides a plurality of flushing outlets 33. The flushing outlets 33 allow fluid to pass from passage 32 to the annular space between the flushing device 20 and the bore wall (not shown) when the flushing device 20 is in an open condition, as represented in FIG. 6.

Each flushing outlet 33 comprises an annular chamber 35 located on the inner face of the outer sleeve 23, and a plurality of nozzle assemblies 36 in communication with the annular chamber 35 and spaced around the perimeter of the flushing device 20. Each flushing outlet 33 extends obliquely outwards and backwards.

Wash Pipe

As best shown in FIG. 1, the inner member 113 of the actuating mechanism 111 incorporates a portion called a wash pipe 121. The wash pipe 121 has a constant internal diameter whilst a portion of the outer diameter tapers inwardly from a first end to a second end, the first end being closer to the inlet 22b of the flushing device 20.

The inner member 113 has a second seal assembly 93 comprising a pair of seals 96 located along an outer diameter and adjacent its second end. The inner member 113 also incorporates a further set of seals 35b comprising a pair of seals 95 adjacent the annular chamber 35. The seals 96 of the second seal assembly 93 have a smaller cross section than the seals 95 of the set of seals 35b.

The actuating mechanism 111 also comprises a cavity 153 located between the inner member 113 and the outer member 115. The cavity 153 defines a third region 122.

An internal portion 165 of the outer member 115 provides a surface 167 against which the second seal assembly 93 of the inner member slidingly engages.

The pressure differential required between the first region 119 and the third region 122 in order for the actuating mechanism 111 to alternate between first and second conditions can be varied by changing the cross sectional diameter of the seals 96 in the second seal assembly 93. Changes in cross sectional diameter of the seals 96 are accommodated by changes in the diameter of the internal portion 167 of the outer member 115, against which the second seal assembly 93 slidably engages varies according to

Indexing Mechanism

The indexing mechanism 80 is best shown in FIGS. 10, 11 and 12. The indexing mechanism 80 comprises an indexing sleeve 29, rotating travel stop 62, and a positioning sleeve 129.

The inner sleeve 29 provides a pawl 68 projecting from an end thereof. Referring to FIG. 1, the indexing sleeve 29 is rotationally fixed relative to the inner member 113 by a key way arrangement 131. The indexing sleeve 29 also comprises a projection 29a extending inwardly from a first end of the indexing sleeve 29, as best shown in FIG. 10. The portion 29a of the indexing sleeve 29 provides a face upon which first spring 67 acts to bias the indexing sleeve 29 towards a shoulder 171 on the internal surface of the outer member 115.

As shown in FIG. 10 to 12, the positioning sleeve 129 comprises a plurality of fingers 28a and slots 28b which are configured to provide a peak at their periphery. The positioning sleeve 129 is rotationally fixed relative to the inner member 113 by a key way arrangement 133, as shown in FIG. 1. The outer member 115 provides a shoulder 163 against which the positioning sleeve 129 abuts.

As shown in FIG. 10 to 12, the rotating travel stop 62 provides a ratchet 69 comprising a plurality of indents 69a which are adapted to receive pawl 68. In particular, each indent 69a comprise a ramp 69b which slidingly engages pawl 68. Travel stop 62 also provides a plurality of fingers 27a and slots 27b which are configured to provide a trough at their periphery. These troughs mate with corresponding peaks of the positioning sleeve 129 when the travel stop 62 engages therewith.

Operation of the Indexing Mechanism

The operation of the indexing mechanism 80 is best described with reference to FIG. 12. Movement of the inner member 113 towards an inlet of the internal passage 117 with respect to the outer member 115 will result in a bottom face 70 of the indexing sleeve 29 abutting shoulder 171 of the outer member 115, preventing further downward movement of the indexing sleeve 29.

Continued downward movement of the inner member 113 will result in travel stop 62 moving towards indexing sleeve 29 causing the fingers 27a to disengage from the fingers 28a, as shown in FIG. 12b. The travel stop 62 is biased towards the indexing sleeve 29 by second spring 127 acting between the travel stop 62 and the positioning sleeve 129, as shown in FIG. 1.

Continued downward movement will result in the ratchet 69 engaging the pawl 68 which is offset sufficiently from the plurality of indents 69a so that the front region of the ramp 69b of an indent 69a sufficiently engages the top portion of the pawl 68 as best shown in FIG. 12b.

Continued downward movement will result in travel stop 62 rotating as the ramp 69b slides down the face of the pawl 68. This will continue until the indent 69a completely receives the pawl 68, as shown in FIG. 12d.

Referring to FIG. 1, when the inner member 113 is caused to move upwardly as a result of the change in pressure differential acting across the wash pipe 121, a bottom surface 137 of the travel stop 62 is caused to abut a shoulder 139 located on the outer surface of the wash pipe 121. Continued movement of the inner member 113, in addition to the biasing force exerted by first spring 27 between the indexing sleeve 29 and the travel stop 62, results in disengagement therebetween as the travel stop 62 moves towards the positioning sleeve 129.

As indicated in FIG. 12e, the fingers 27a do not entirely align with slots 28a. However, due to the configuration of the peaks 82, continued upward movement of the inner member 113 results in the fingers 27a sliding over the fingers 28a causing further rotation of the travel stop 62 until the fingers 27a align with slots 28a of the positioning sleeve 129, such that the fingers are interlaced. Continued upward movement of the inner member 113 will result in the engagement of the fingers 27a with the slots 28b. When the fingers 27a and 28a are interlaced the actuating mechanism 111 is in its second condition, and the flushing device 20 is in its open operable condition, as shown in FIG. 1.

A similar process will in turn cause the rotating travel stop 62 to be indexed to a second position whereby the fingers 27a align with fingers 28a such that they are in an opposed relation. When the fingers 27a and 28a are opposed the actuating mechanism 11 is in its first position, and the axial movement of the inner member 113 is sufficient only for the pawl 68 to disengage the ratchet 69.

The axial movement of the rotating travel stop 62 is restricted to the movements of the inner member 113. Downward movement of the travel stop 62 relative to inner member 113 is prevented by shoulder 139. The biasing force exerted by second spring 127 prevents upward movement of the travel stop 62 relative to the inner member 113. The rotational movement of the travel stop 62 is governed by the flushing device 20 and the travel stops 62 position with respect to indexing sleeve 29, and fingers 28a and slots 28b.

The operation of the indexing mechanism 80 with respect to the operation of the flushing device 20 is further discussed below.

Retention Mechanism

As best shown in FIGS. 4 to 6, the actuating mechanism 111 also comprises a retention mechanism 141 to releasably retain the actuating mechanism 111 in one condition until the predetermined pressure differential between the first region 119 and third region 122 is reached, whereupon the actuating mechanism 111 is permitted to move from one condition to the other.

The retention mechanism 141 is provided by a plurality of detents comprising a ball 143 fixed axially relative to the inner member 113 but biased radially outwardly from the inner member by detent spring 145. The outer member 115 has a first groove 147 and a second groove 149 on the inner surface, each being spaced a distance from each other substantially equal in length to the axial distance the inner member 113 moves relative to the outer member 115 when the actuating mechanism 111 moves between its first and second conditions.

Each groove 147, 149 is annular and has a cross section complimentary to that of the ball 143 such that the ball 143 is snugly received therein so as to hold the inner member 113 relative to the outer member 115.

Operation of the Retention Mechanism

In operation, when the actuating mechanism 111 is in its first condition the ball 143 is received in the first groove 147, as shown in FIG. 1. As the pressure difference between the first region 119 and third region increases to a predetermined value, the ball 143 is forced inwardly by the action of the axial force on the inner member 113 caused by the pressure of the fluid flowing through the passage. When the ball 143 is caused to disengage from the first groove 147, the inner member 113 moves rapidly to either an intermediate position between the first groove 147 and second groove 149, as shown in FIG. 2, or until the actuating mechanism 111 is in its second condition, as shown in FIG. 3, wherein the ball 143 aligns and engages with the second groove 149, whereby the actuating mechanism 111 is held in its second condition.

When the actuating mechanism 111 is in its second condition, a drop in the pressure differential between the first region 119 and third region 122 to a predetermined value, will result in the ball 143 moving inwardly due to the axial force acting on the inner member 113, and disengaging the second groove 149, allowing the inner member 113 to move rapidly with respect to the outer member 115, and the actuating mechanism 111 moves back to its first condition.

Upon disengagement of the ball 143 from the first groove 147, the extent to which the inner member 113 moves with respect to the outer member 115 is dependant on the position of the indexing mechanism 80. If the indexing mechanism 80 is in its first position the fingers of the travel stop 62 are in opposed relation to the fingers on the positioning sleeve 129. This restricts the axial movement of the inner member 113 with respect to the outer member 115 so that the inner member 113 is only able to move to an intermediate position between the first and second grooves as best shown in FIG. 2.

If the indexing mechanism 80 is in its second position the fingers of the travel stop 62 are interlaced with the fingers on the positioning sleeve 129. This allows for greater axial movement of the inner member 113 with respect to the outer member 115 so that the actuating mechanism 111 is able to move to its second condition, as shown in FIG. 3.

Knuckle

The actuating mechanism 111 incorporates a knuckle joint 151 capable of allowing pivotal movement of the inner member 113 relative to its longitudinal axis. The knuckle joint 151 allows the actuating mechanism 111 to operate effectively even when loads applied to the outer member 115 cause it to deflect between its ends.

Cavity

Referring now to FIGS. 1 to 3, the cavity 153, defined between the inner member 113 and the outer member 115, filled with a lubricant such as oil. The cavity 153, which is sealed to prevent the ingress of any contaminants, houses the indexing mechanism 80 and the retention mechanism 141, and ensures reliable conditions for the functioning of these components.

In use, the volume of the cavity 153 changes as the inner member 113 moves relative to the outer member 115. To ensure the volume of the cavity is free to fluctuate according to movement of the inner member 113, the actuating mechanism 111 incorporates an equalising device 155. The equalising device comprises a floating sleeve 157 which is slidingly retained on an outer portion 159 of the outer member 115, and provides a chamber 161 which is in fluid communication with the cavity 153 through an opening 154. As the inner member 113 moves, the volume of the cavity 153 changes accordingly. When the volume is reduced, the lubricant exits the cavity 153 through opening 154 and into the chamber 161, causing the floating sleeve 157 to move accordingly to allow for the increase in volume in the chamber 161. Similarly, when the volume of the cavity 153 increases, lubricant is caused to move from the chamber 161 into the cavity 153, and the floating sleeve 157 is caused to move accordingly. Hence, the floating sleeve 157 moves relative to the opening 154 to accommodate volumetric changes within the cavity 153.

The floating sleeve 157 is in communication with the second region 120. As a result the pressure in the second region 120 is transmitted to the chamber 161 and the cavity 153. Hence, the pressure, and volume, of the third region 122 provided by the cavity 153, is representative of the pressure in the second region 120. As outer surfaces of the wash pipe 121 are exposed to the cavity 153, the pressure in the second region 120 affects the operation of the actuating mechanism 111.

The equalising device 155 balances and cushions the movement between the inner and outer members.

The outer member 115 also provides a port 37 which is in communication with the cavity 153 allowing it to be filled with lubricant if so required.

The equalising device 155 is provided with seals to seal the interface between the floating sleeve 157 and the outer member 115.

Intermediate Sleeve

The flushing device 20 also comprises an intermediate sleeve 42 located between the inner sleeve 21 and the outer sleeve 23.

Referring to FIGS. 4 to 6 the intermediate sleeve 42 comprises a outwardly extending shoulder 46 at its first end, and terminates at its other end with a sloping face 42a. The sloping face 42a mates with upwardly sloping face 42b located on the inner sleeve 21 to provide a seat.

The intermediate sleeve 42 also contains a plurality of holes 43 which receives a plurality of balls 44. Each ball 44 has a diameter greater than the radial thickness of the intermediate sleeve 42 such that when the intermediate sleeve 42 is at its lower most position each ball 44 protrudes beyond the interface between the intermediate sleeve and the inner sleeve 21 and rests against the downwardly sloping face 45 of the inner sleeve 21. The mating of seat portion 42a of the intermediate sleeve 42 with the upwardly sloping face 42b of the inner sleeve 21 is at a predetermined distance from the plurality of holes 43 such that the balls 44 are not permitted to enter aperture 38.

The intermediate sleeve 42 is rotationally fixed to the outer sleeve 23 by key way arrangement 142. This arrangement assists in ensuring the interface between the intermediate sleeve 42 and outer sleeve 23 does not become clogged with fluid (slurry) passing through the flushing device 20.

Operation of Flushing Outlet

In operation, movement of the inner sleeve 21 in an upward direction causes the downwardly sloping face 45 to abut against the ball 44, as shown in FIG. 7, causing the intermediate sleeve 42 to move upwardly with the inner sleeve 21. Continued upward movement will be restricted by the intermediate sleeve 42 abutting against projection 47. This abutment occurs as the ball 44 aligns with annular groove 48 allowing ball 44 to be received therein, as shown in FIG. 6.

This enables the inner sleeve 21 to continue to move upwardly whilst intermediate sleeve 42 remains locked in position. Continued upward movement of inner sleeve 21 will result in the plurality of apertures 38 being open to the flushing outlet 33, as shown in FIG. 6.

The operation of the intermediate sleeve 42 ensures the apertures 38 remain closed until the aperture 38 begins to align with annular chamber 35 of the flushing outlet 33. When a gap is introduced between the sloping face 42b and conical face 42a, the passage which allows the fluid to pass from the passage 32, through the slots 38 and through the flushing outlet 33 opens.

The annular chamber 35 has a set of seals 35a, 35b adjacent each side thereof. These seals render the interface between the inner sleeve 21 and outer sleeve 23 fluid tight, preventing slurry passing from the passage 32 and into the interface and the cavity 153 when the flushing device 20 is in an open operable condition. When the flushing device is in a closed operable condition a first section 49a of the inner sleeve 21 co-acts with seals 35a to provide a seal. As the inner member 113 moves upwardly relative to the outer member 115, the intermediate sleeve 42 moves upwardly to co-act with the seals 35a and provide a seal below the annular chamber 35, preventing fluid passing through the apertures 38 and ingressing between the inner sleeve 21 and outer sleeve 23.

When the flushing device 20 moves to a closed operable position as shown in FIGS. 4 and 5, the inner member 113 moves downwardly relative to the outer member 115, providing a barrier between the inner passage 32 and the annular chamber 35 of the flushing outlet 33. Continued movement of the inner member 113 will result in the sloping face 42b abutting mating conical face 42a of the intermediate sleeve 42 whilst simultaneously the downwardly facing slope 45 passes groove 48. The plurality of balls 44 will then be forced to move in an inward direction resulting in the intermediate sleeve engaging the inner sleeve 21 to move downwardly with further downward movement of the inner sleeve 21.

Sloping face 42b and conical face 42a remain in intimate contact until they have passed seals 35a.

Operation of the Flushing Device

The operation of the flushing device 20 between an open operable condition and a closed operable condition, and vice versa, is extremely simple and reliable, and allows the flushing device 20 to remain in the required condition by maintaining a predetermined pressure differential between the first region 119 and third region 122.

Referring to FIGS. 1 to 6, the passage 32 through which fluid passes is partly defined by the inner wall of the inner sleeve 21. This inner Wall substantially provides a barrier, preventing the ingress of slurry in to the cavities between the inner sleeve 21 and outer sleeve 23. Where apertures 38 are provided, seals are provided to prevent leakage of the slurry.

In the closed operable condition the indexing mechanism 80 is arranged such that the fingers 27a are in opposed relation with fingers 28a, as shown in FIGS. 2, 5, 8 and 12a. In this mode the flushing outlet 33 is closed.

In order for the flushing device 20 to move from the closed operable condition, shown in FIG. 2, to the open condition, shown in FIG. 3, the surface pumps are momentarily switched off such that no slurry is passing through the flushing device 20. This results in a change in pressure differential between the first region 119 and third region 122, causing the inner member 113, and hence the inner sleeve 21, to move relative to the outer sleeve 23 in a direction towards the inlet 22b.

As a result of this movement the travel stop 62 is free to move in the same axial direction, being biased to do so as the second spring 127 forces the travel stop 62 to disengage from the positioning sleeve 129.

Continued movement of the inner member 113 results in compression of first spring 67 as the travel stop 62 moves towards the indexing sleeve 29, which is prevented from downward movement by shoulder 171 against which it abuts. As previously discussed the travel stop 62 engages the pawl 68 on the indexing sleeve 29. Further movement of inner sleeve 21 towards inlet 22b results in the ramp 69b of the indent 69a to slidingly abut the pawl 68, causing the travel stop 62 to rotate until the indent 69a fits over pawl 68 (FIG. 12d). At this point the travel stop 62 has rotated so that the fingers 27a are nearly aligned with corresponding slots 28b of the end portion 85.

At this point the ball 143 aligns with first groove 147, and due to detent spring 145, engages the first groove 147 to hold the inner member 113 axially fixed relative to the outer member 115, as shown in FIG. 4.

The pumps are then started and the pressure in the first region 119 increases. When the pressure differential between the first region 119 and third region 122 is large enough to overcome the force of the ball 145 acting in the first groove 147, the ball 147 disengages the first groove 147 and the inner member 113 is caused to move rapidly with respect to the outer member 115.

This causes shoulder 139 to move the travel stop 62 away from the indexing sleeve 29 (FIG. 12e). As the force acting on the inner member 113 due to the pressure differential is greater than the force of the second spring 127, the inner member 113 moves towards the positioning sleeve 129. As the travel stop 62 approaches positioning sleeve 129, the end of fingers 27 contact the end of fingers 28a. Owing to the peak configuration 82 of fingers 28a the travel stop 62 is caused to further rotate such that the fingers 27a now align with slots 28b (FIG. 12f).

Continued movement of the inner member 113 towards the outlet 22a will result in the end of fingers 27a abutting the bottom surface of the slots 28a such that the fingers 27a and 28a are in an interlaced configuration.

At this point the ball 143 of the retention mechanism 141 is aligned with the second groove 149, whereupon the ball 143 engages the second groove 149 holding the inner member 113 relative to the outer member 115, as shown in FIG. 2.

As the fingers 27a and 28b become interlaced the upward movement of the inner member 113 has caused the inner sleeve 21 to disengage intermediate sleeve 42 and allow the apertures 38 to align with flushing outlets 33. This condition is depicted in FIGS. 3 and 6.

The retention mechanism 141 prevents the closure of the flushing outlet 33 until the force exerted by spring 127 is able to overcome both the force of the retention mechanism 141 holding the inner member 113 relative to the outer member 115, and the pressure differential between the first region 119 and the third region 122.

When the flushing device 20 is in an open condition, a percentage of fluid is diverted from passage 32 through flushing outlet 33, exiting from the flushing device 20 into the annular space between flushing device 20 and the wall of the bore. The percentage of fluid diverted is largely dependant on the size of the orifice of nozzle assembly 36, and may be adjusted accordingly. The diverted fluid is used to assist in cleaning the bore of cuttings.

To close the flushing outlet 33 and cause the flushing device 20 to move to a closed condition, the pressure differential between the first region 119 and third region 122 is reduced so that the force of spring 127 is greater than the force exerted by the retention mechanism 141, at which point the ball 143 disengages the second groove 149, allowing the inner member 113 to rapidly move with respect to the outer member 115 towards the inlet 22b. Simultaneously the travel stop 62 disengages from the positioning sleeve 129 and moves towards the indexing sleeve 29, ready to cycle to a new position.

Continued downward movement will result in the indexing sleeve 29 abutting the shoulder 171 and the ball 143 of the retention mechanism 141 will once again aligning with and engaging first groove 147. Simultaneously, the ratchet 69 on the travel stop 62 engages pawl 68 causing the travel stop 62 to rotate. Upon an increase in pressure differential sufficient to overcome the force exerted by the retention mechanism 141, the inner member 113 is again caused to move relative to the outer member 115 towards the outlet 22a. As the travel stop has indexed to a new position, the troughs 81 of fingers 27a engage the peaks 82 of fingers 28a of the positioning sleeve 129 so that the fingers are in opposed configuration, as best shown in FIG. 12a. In this position the inner member 113 is prevented from full axial movement relative to the outer member 115 due to fingers 28a and 27a being in opposed relation. The flushing device 20 is in a closed operable condition, as shown in FIG. 2.

During the indexing process, the downward movement of inner member 113 has resulted in the inner sleeve 21 re-engaging intermediate sleeve 42, and blocking the path between the inner passage 32, closing the flushing outlets 33.

The switching between the two conditions of the flushing device 20 may be controlled remotely by the operator on the surface. The operator will know to activate and deactivate the flushing device 20 according to the behaviour of the drilling stem assembly, the drilling head, and the slurry which is being returned to the surface.

The operational condition of the flushing device 20 can only be changed by deliberate actions on the part of the operator.

The flushing device 20 may be placed anywhere along the drilling stem assembly, its position depending on the application. Indeed the drilling of a well may require the inclusion of one or more flushing devices 20 to be used to maintain the required conditions in the bore.

Where required the surface of the components are coated with a hard, wear resistant coating and ground to a fine finish in order to prevent scouring of the surface by the action of the drilling fluid. This also assists in prolonging the life of the seals.

The required pressure differential between the first region 119 and third region 122 can be varied by varying the force exerted by detent spring 145 on ball 143.

The retaining mechanism 141 provides a retaining force equal to or slightly greater than the load differential of the spring 127 as it is compressed from its original length (flushing device 20 in its closed operable condition) to its compressed length (flushing device 20 in its open operable condition). Hence the wash pipe 121 (and therefore inner member 113 and inner sleeve 23) will not move until the pressure differential is sufficient to fully compress spring 127. At this point the ball 143 is forced to retract and the wash pipe 121 will snap to the fully open condition (when fingers of indexing mechanism 80 are interlaced), where the ball 143 will engage the second groove 149, such that the flushing device 20 is in its open operable condition.

Upon falling pressure, the retention mechanism 141 holds the flushing device 20 open until the pressure differential falls below the force generated by the spring 127, at which point the ball 143 will retract from the second groove 149 and the wash pipe 121 will snap back, moving the flushing device 20 to its closed operable condition.

The retention mechanism 141 also prevents partial opening and closing of the actuating mechanism 111. At the point were the pressure differential is sufficient to move the actuating mechanism 111 to its next condition, the ball 143 retracts from the appropriate groove (depending upon position) and the actuating mechanism snaps into its next condition—there being no gradual movement between the first and second conditions of the actuating mechanism 111.

Furthermore the pressure differential required to operate the actuating mechanism may be varied by varying the diameter of the seals 96 of the second seal assembly 93, as previously discussed. This does not however affect the ratio between opening and closing pressures.

In another embodiment of the invention, the flushing device 20 does not include the intermediate sleeve 42. In such an embodiment the inner sleeve 21 is configured to ensure a fluid tight seal exists between the inner sleeve and the outer sleeve.

Whilst only one application of the invention has been described it is to be appreciated that the invention can be used in relation to many other applications. For instance, it may be used in operating or actuating a ball valve or any type of valve, an under reamer or casing cutter, it can be easily converted to a single shot operation for a permanent installation, and it may be used for deep mineral air drilling.

Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.

Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

1-84. (canceled)

85. An actuating mechanism comprising: an inner member and an outer member axially slidable relative to each other, the inner and outer members cooperating to define an internal passage for the flow of a fluid therethrough;the inner member being configured such that upon a predetermined change in pressure between a first region and a second region the actuating mechanism is caused to move between a first condition and a second condition.

86. The actuating mechanism according to claim 85 wherein the first region is in the internal passage of the actuating mechanism.

87. The actuating mechanism according to claim 85 wherein the second region is external of the actuating mechanism.

88. The actuating mechanism according to claim 85 wherein the pressure in the second region is transmitted to a third region located within the actuating mechanism, such that a change in pressure in the second region affects the pressure in the third region.

89. The actuating mechanism according to claim 88 wherein the third region is located substantially between the inner and outer members.

90. The actuating mechanism according to claim 88 wherein at least a section of the inner member is exposed to both the first and third regions.

91. The actuating mechanism according to claim 88 wherein an inner surface of the inner member is exposed to the first region and an outer surface of the inner member is exposed to the third region.

92. The actuating mechanism according to claim 88 wherein the actuating mechanism is caused to move between its first and second conditions when the pressure difference between the first region and third region reaches a predetermined value, due to the unequal forces being exerted across the inner member.

93. The actuating mechanism according to claim 85 wherein the inner member and outer members are in the form of pipes.

94. The actuating mechanism according to claim 85 wherein the inner member comprises a wash pipe having a first end with an outer diameter larger than an outer diameter at a second end, the wash pipe has a portion having a tapered outer diameter.

95. The actuating mechanism according to claim 94 wherein the wash pipe has a first seal assembly located along the outer diameter adjacent the first end and a second seal assembly located along the outer diameter adjacent the second end.

96. The actuating mechanism according to claim 95 whereby varying the cross sectional diameter of an at leak one seal of the second seal assembly varies pressure differential required between the first region and the second region to operate the actuating mechanism.

97. The actuating mechanism according to claim 95 whereby an internal portion of the outer member against which the second seal assembly slidingly engages can be varied according to changes in cross sectional diameter of the at least one seal in the second seal assembly.

98. The actuating mechanism according to claim 85 wherein a cavity is defined between the inner member and outer member, the cavity being filled with a lubricant such as oil.

99. The actuating mechanism according to claim 98 wherein the cavity has an opening which opens into a chamber of an equalising device.

100. The actuating mechanism according to claim 99 wherein the equalising device is in the form of a floating sleeve which is slidingly retained on an outer portion of the outer member and which surrounds the chamber, whereby volumetric changes in the cavity result in the floating sleeve moving with respect to the opening.

101. The actuating mechanism according to claim 100 wherein the floating sleeve is in communication with the second region such that pressure in the second region is transmitted to the cavity.

102. The actuating mechanism according to claim 96 wherein the cavity provides the third region.

103. The actuating mechanism according to claim 96 wherein the cavity is sealed from the internal passage such that the cavity may not be contaminated.

104. The actuating mechanism according to claim 85 wherein the actuating mechanism comprises an indexing mechanism which indexes between a first position, wherein the actuating mechanism is in the first condition and a second position wherein the actuating mechanism is in the second condition.

105. The actuating mechanism according to claim 104 wherein the indexing mechanism is located between the first and second members.

106. The actuating mechanism according to claim 104 wherein the indexing mechanism operates within the cavity.

107. The actuating mechanism according to claim 104 wherein the indexing mechanism comprises an indexing sleeve, a travel stop and a positioning sleeve.

108. The actuating mechanism according to claim 107 wherein the indexing sleeve is fixed rotationally to the inner member.

109. The actuating mechanism according to claim 107 wherein the indexing sleeve is axially movable relative to the inner member.

110. The actuating mechanism according to claim 107 wherein the travel stop is mounted on the inner member such that it may rotate about the longitudinal axis thereof, and wherein the travel stop is substantially constrained against axial movement relative to the inner member.

111. The actuating mechanism according to claim 107 wherein the positioning sleeve is fixed rotationally to the inner member.

112. The actuating mechanism according to claim 107 wherein the positioning sleeve is axially movable relative to the inner member.

113. The actuating mechanism according to claim 107 wherein the indexing sleeve and travel stop are biased away from each other.

114. The actuating mechanism according to claim 107 wherein the travel stop and positioning sleeve are biased away from each other.

115. The actuating mechanism according to claim 107 wherein the travel stop is adapted to co-operate with the indexing sleeve during the indexing sequence.

116. The actuating mechanism according to claim 107 wherein the indexing sleeve has a first end which provides a bottom face and a second end having a projection, defining a pawl, extending in an axial direction from the periphery of the second end.

117. The actuating mechanism according to claim 116 wherein the travel stop has a first end adapted to engage and mesh with the projection on the indexing sleeve and a second end adapted to engage and mesh with the positioning sleeve.

118. The actuating mechanism according to claim 117 wherein a first end of the positioning sleeve is shaped to engage and mesh with the second end of the travel stop.

119. The actuating mechanism according to claim 117 wherein the second end of the travel stop is configured to provide a plurality of fingers and corresponding slots, which co-act with corresponding fingers and slots integral with the positioning sleeve, wherein each finger and slot of the travel stop terminates in at least one depression or trough, whilst each finger and slot of the positioning sleeve terminates in at least one peak complimentary in shape to the depression/trough so that upon engagement each finger on the travel top aligns with a finger and/or slot on the positioning sleeve depending on whether the indexing mechanism is in its first position or second position.

120. The actuating mechanism according to claim 119 whereby when the indexing mechanism is in its first position the fingers on the travel stop align and mate with the fingers on the positioning sleeve, such that the fingers are opposed and when the indexing mechanism is in its second position the slots on the travel stop align and mate with the fingers on the positioning sleeve, whilst the fingers on the travel stop align and mate with the slots on the positioning sleeve, such that the fingers are interlaced.

121. The actuating mechanism according to claim 119 wherein the number of peaks/troughs on each finger/slot determines whether the actuating mechanisms cycles between the first condition and second condition.

122. The actuating mechanism according to claim 85 wherein the actuating mechanism comprises at least one retention mechanism to releasably retain the actuating mechanism in one condition until the predetermined pressure differential between the first and third regions is reached whereupon the actuating mechanism is able to move from one condition to the other.

123. The actuating mechanism according to claim 122 wherein the retention mechanism is a detent, comprising a ball fixed relative to the inner member but biased radially outward from the inner member.

124. The actuating mechanism according to claim 85 wherein the outer member may have a first groove and a second groove on its inner surface spaced a distance from each other, whereby the distance there between is substantially equal in length to the axial distance the inner member moves relative to the outer member as the actuating mechanism moves between its first and second conditions.

125. The actuating mechanism according to claim 124 wherein each groove is annular with a cross section complimentary to the ball so that the ball can be received therein and hold the inner member relative to the outer member.

126. The actuating mechanism according to claim 122 wherein the retention mechanism comprises a ball fixed relative to the outer member and biased radially inward from the outer member, the inner member having a first groove and a second groove on its outer surface spaced a distance from each other substantially equal in length to the axial distance the inner member moves relative to the outer member as the actuating mechanism moves between its first and second conditions.

127. The actuating mechanism according to claim 85 wherein the actuating mechanism is incorporated in an apparatus, such as a tool, for actuating the apparatus between first and second operational condition.

128. The actuating mechanism according to claim 127 wherein the apparatus is a flushing device, whereby the actuating mechanism causes the flushing device to move between the first operable condition, wherein the flushing device is closed and the second operable condition wherein the flushing device is open.

129. The actuating mechanism according to claim 128 wherein an inner sleeve of the flushing device comprises the inner member of the actuating mechanism, an outer sleeve of the flushing device comprises the outer member of the actuating mechanism, and an internal passage of the flushing device incorporates the internal passage of the actuating mechanism.

130. The actuating mechanism according to claim 129 wherein the outer sleeve incorporate openings, the openings being blocked from the internal passage when the flushing device is in the closed operable condition, and register with the internal passage when the flushing device is in the open operable condition.

131. The actuating mechanism according to claim 128 wherein the flushing device is configured such that the flushing device remains in the selected open or dosed operable condition regardless of any expansive or compressive force.

132. The actuating mechanism according to claim 130 wherein the openings provide a flushing outlet, whereby when the flushing device is in an open operable condition a predetermined percentage of the fluid is diverted from the passage to the outside of the flushing device.

133. The actuating mechanism according to claim 132 wherein the flushing outlet comprises a plurality of apertures in the inner sleeve, an annular chamber in the outer sleeve and a plurality of nozzles.

134. The actuating mechanism according to claim 129 wherein a fluid tight seal is provided between the inner and outer sleeve when the flushing device moves from a closed operable condition to an open operable condition.

135. The actuating mechanism according to claim 134 wherein the flushing device comprises an intermediate sleeve located between the inner and outer sleeve between the flushing outlet and the inlet of the flushing device, the intermediate sleeve being adapted to provide the fluid tight seal.

136. The actuating mechanism according to claim 127 wherein the apparatus is an under reamer or casing cutter whereby the actuating mechanism causes the under reamer or casing cutter to move between a first operable condition, wherein a cutting device is contained within the under reamer or casing cutter, and a second operable condition wherein the cutting device protrudes from the under reamer or casing cutter to cut as required.

137. The actuating mechanism according to claim 127 wherein the apparatus is an under reamer or casing cutter whereby the actuating mechanism causes the cutting device to move between a first operable condition, wherein the cutting device is off, and a second operable condition wherein the cutting device is on.

138. The actuating mechanism according to claim 127 wherein the apparatus is an under reamer or casing cutter whereby the apparatus is a valve, such as a ball valve, whereby the actuating mechanism causes the valve to move between a first operable condition, wherein the valve is closed and a second operable condition wherein the valve is open.

139. A flushing device comprising an inner sleeve and an outer sleeve, moveable relative to each other between an open operable condition, wherein a percentage of the fluid passing through a central passage of the flushing device can be diverted through a plurality of flushing outlets, and a closed operable condition, wherein the fluid outlets are blocked from the passage,an actuating mechanism operable between the inner and outer sleeves, and having first and second conditions which correspond to the open and closed operable conditions, the actuating mechanism being responsive to a fluid pressure differential between a cavity defined between the inner and outer sleeves, and the pressure in the internal passage, for movement between its first and second conditions, whereby the actuating mechanism, when in the first or second condition couples the inner sleeve to the outer sleeve to prevent movement of the inner sleeve relative to the outer sleeve until predetermined value of pressure differential is reached.

140. A flushing device for flushing diverted fluid upwards into an annular space between a drill stem and a hole, where a slurry passes through a central passage of the flushing device to a drill head, whereupon it reverses direction, passing through the annular space before returning to the surface with cuttings from the drilling process suspended in the return slurry, the flushing device is adapted to change between an open operable condition, whereby a predetermined percentage of fluid is diverted from the passage to the annular space to assist in maintaining a clean bore, and a closed operable condition, whereby the full flow of the slurry is delivered to the drill head, and is configured such that the increase or reduction of pressure in the internal passage relative to the pressure external the flushing device causes an actuating mechanism located in the device to cycle between a first and second condition whereby the flushing device correspondingly cycles through open and closed operable conditions.

141. A flushing device comprising: an inner sleeve, slidingly received in an outer sleeve, the inner and outer sleeves cooperating to define an internal passage for the flow of a fluid, and are permanently coupled such that there is no rotational movement between the two sleeves;the outer sleeve having a plurality of flushing outletsan actuating mechanism comprising an inner and outer member, incorporated within the inner and outer sleeves, an internal passage which is common with the internal passage of the flushing device, the actuating mechanism being caused to cycle between open and closed conditions with change in the pressure differential acting upon the inner member;an indexing mechanism which indexes as a result of the operation of the actuating mechanism, the indexing mechanism indexes between first and second positions such that the flushing device moves between an open operable condition, whereby the plurality of flushing outlets are open for discharging a quantity of the fluid from the internal passage, and a closed operable condition, whereby the plurality of flushing outlets are closed, the operable condition depending on the position of the indexing mechanism.