GB2212204A - Actuable mechanism and control therefor - Google Patents

Abstract

An actuable mechansim, such as a fastening arrangement 20 (Figs. 1(a)/(b)) for a subsea module 14 in container 15 comprises fastening bolts 21, movable radially by axial motion of the sleeve 38 on upstanding shaft 24. The shaft and sleeve have abutment flanges 46, 47 which have shoulders against which axial forces are acted and reacted to contain forces in the mechanism. A control body 53 which sits on shoulder 48 carries sliding holding dogs 56 to grip shoulder 49 co-axially slidable actuation cylinder 60 itself sitting on sleeve shoulder 50 and carrying holding dogs 68 to grip shoulder 51 of 47. Sliding of cylinders permits displacement of dogs for attachment to shaft and sleeve and application of forces in both axial directions. Sleeve motion motion of sleeve 38 is inhibited by a slidable ratchet detent dog 40 of the sleeve engaging with grooves 44 on the shaft. A control cylinder 76 is profiled at 82 to release detent dog 40 when the cylinder 76 is moved downwardly to engage dogs 68 in an action which couples the sleeve 58 to the actuating cylinder 60. All control motions are by simple controllable piston/cylinder action and all operation on the mechanism by wedge-like linear forcing against inclined surfaces with no pivoted parts. <IMAGE>

Description

ACTUABLE MECHANISM AND CONTROL THEREFOR This invention relates to actuable mechanisms movable and actuable by removably disposable control means and particularly to such mechanisms used in circumstances unsuited to human intervention and the disposition and operation of the control means remotely.

Circumstances unsuited to human intervention may be produced by the scale of the mechanism, where its movement and actuation requires more strength than can be applied manually or is too small to manipulate in a particular environment and/or when the environment itself makes human working therein difficult or impossible.

One particular set of operating circumstances which may be considered as an example for the purposes of this specification is found at great water depths and an exemplory mechanism used in such environment is a releasable fastening arrangement employed to install and attach a bulky control module to a sub-sea structure or hydrocarbon wells.

The nature of such a control module is not pertinent to the invention but briefly they comprise electronic and/or hydraulic control elements which receive electrical and hydraulic power from, and deliver them to, electrical and hydraulic terminals on the well structure. For convenience such coupling terminals are hereinafter called generically electro-hydraulic terminals irrespective of type.

Installation of such a module requires it to be brought into positional relationship with the structure, pressed into engagement therewith to mate the electrical and hydraulic terminals and to be held there.

As is well known electrical and hydraulic terminals of couplings used sub-sea are self-sealing when separated by means of spring loaded shutters and tend to exert on any module or the like joined by such terminals considerable resistance to initial mating of the module and structure to overcome the shutting of the terminals and thereafter a continuous separating force.

Further problems to be considered are that such modules may be operated in position sub-sea for a considerable period, possibly years, and are employed at such a depth as to make manual intervention impossible, work only being possible by a remotely operated submersible vehicle (ROV) or by a surface line, both controlled by a surface operator with the visual assistance provided by television camera. It is therefore important that any fastening arrangement used to locate such a module and also positioned sub-sea with long period of inactivity is able to operate when called upon and provide such separation forces as are exacerbated by the inactive immersion to ensure reliability of eventual removal.

Particular constructional embodiment of such a releasable fastening arrangement having parts arranged to be operatively disposed with respect to one body thereof an actuation unit for disposing the parts in operative and inoperative relationships and removably disposable actuation contact means are described fully in copending British Application No. 88.03174. The constructional embodiments described therein require the use of pivotally movable component which may be considered as susceptible to operating problems after long term submersion and be relatively expensive to construct in such a manner or to alternate such potential problems.

According to the present invention a mechanism includes a body carrying (i) parts arranged to be operatively disposed with respect to the body, (ii) an actuation unit for disposing the parts in operative and inoperative relationships, the actuation unit including (a) a shaft fixed at one said end thereof to the body to provide an upstanding other end, (b) a sleeve coaxially surrounding the shaft and slidable along the common axis to effect disposition of the parts, the shaft and sleeve each being provided with abutment means having abutment shoulders facing axially towards and away from said upstanding other end of the shaft whereby axial forces on the sleeve abutment shoulders can be reacted into oppositely facing abutment shoulders of the shaft, and (c) a detent arrangement between the sleeve and shaft comprising at least one detent dog member carried by, and radially slidable with respect to, the sleeve and biased towards the shaft, at least a portion of the shaft surface and the end of each dog engageable therewith having cooperating profiles to inhibit by such engagement axial motion between the sleeve and the shaft in at least one direction, and (iii) hydraulic actuation control means removably disposable with respect to the shaft and sleeve at said upstanding other end thereof and comprising (a) a control body adapted to be attached to the abutment means of the shaft, (b) a hydraulic actuation cylinder surrounding the control body which forms a piston therefor, the actuation cylinder having an axially extending skirt portion able to surround at least a portion of the sleeve having the abutment means and carrying in an apertured wall thereof radially displaceable sleeve holding dogs, and (c) a control cylinder surrounding the actuation cylinder which forms a piston therefor internal walls of which control cylinder are profiled to free or restrain radially outward displacement of the sleeve holding dogs by its disposition with respect to the actuation cylinder, the actuation control means being operable in response to hydraulic fluid pressure in the control cylinder and in the actuation cylinder in a non-actuation operation to dispose the control cylinder with respect to the actuation cylinder to radially free the sleeve holding dogs and move the skirt portion of the actuation cylinder axially with respect to the sleeve to place the sleeve holding dogs into or out of axial alignment with a shoulder of the sleeve abutment means and in an actuation operation to dispose the control cylinder with respect to the actuation cylinder to restrain outward radial displacement of the holding dogs and permit the actuation cylinder to apply axial force to an abutment shoulder of the sleeve by way of the holding dogs, said control cylinder being movable with respect to the actuation cylinder to bear against each detent dog of the sleeve with a further surface profile to slide the detent dog against the bias and disengage it from the shaft, thereby permitting axial motion of the sleeve with respect to the shaft by notion of the actuation cylinder.

The mechanism may be employed as a releasable fastening arrangement for two relatively movable coaxial components, the inner component being fixed to the mechanism body with the common axis of shaft and sleeve extending along the commen axis of the movable components, the outer component having a plurality of bolt recesses and the mechanism body having a plurality of bolt members, the inner end of each having an actuation surface, disposed about the shaft and extending substantially radially thereof to comprise the operatively displaceable parts of the mechanism, an actuation member carried by the sleeve having engagement faces inclined to the shaft to cooperate with the actuation surfaces of the bolt members when disposed adjacent thereto and transfer axial movement of the sleeve towards the bolt members into outward radial movement of each bolt member into a corresponding recess in the outer component and withdrawal means responsive to axial displacement of the sleeve away from the bolt members to transmit a corresponding substantially radially inward displacement to each bolt member to withdraw it from the corresponding recess in the outer component.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure l(a) is a sectional elevation through a releasable fastening arrangement embodying a mechanism according to the invention showing bolt members and actuation means thereof inoperatively disposed and actuation control means arranged with respect to actuation means immediately after bringing to, or immediately prior to removal from, the actuation means, Figure l(b) is a sectional elevation through the arrangement of Figure l(a) showing the actuation control means and actuation means disposed to operatively position the bolt members of the fastening arrangement, Figure 2(a) is a sectional elevation through the arrangement of Figure l(b) showing the actuation control means disposed with respect to the actuation means to move the actuation means to inoperatively position the bolt members, Figure 2(b) is a sectional elevation through the arrangement of Figure 2(a) showing the actuation means moved by the actuation control means to the inoperative position, Figures 3(a) and 3(b) are sections through a portion of shaft or sleeve with abutment means and cooperating holding dogs illustrating an operational configuration different from that of Figures 1 and 2, Figure 4(a) is a section through a portion of shaft or sleeve with abutment means and cooperating holding dogs showing a different configuration to that shown in Figures 1 and 2, Figure 4(b) is a section similar to Figure 4(a) but showing an alternative form of abutment means, Figure 5 is a perspective view of a spacer employed in emergency breakout of the fastening arrangement according to the present invention, Figure 6(a) is a sectional elevation through the arrangement with the bolt members and actuation neans operatively disposed as in Figure l(b) with the actuation control means and spacer disposed to release the actuation means by break-away of the shaft, and Figure 6(b) is a sectional elevation similar to Figure 6(a) but showing the disposition of actuation means and actuation control means after break-away of the shaft.

Referring to Figures l(a) and l(b) a sub-sea structure 10 has hydraulic and/or electrical lines 11 brought to coupling terminals at 12 and organised to mate with corresponding electro-hydraulic terminals 13 of a control module 14 located with respect to the structure by forming it as the inner component of a coaxial pair with outer component 15, the common axis being shown at 16. The contents and functions of the module 14 and structure of the majority of the outer component 15 are not important to understanding the present invention and are shown by broken lines only and without further description.

The electro-hydraulic terminals 12 and 13 are equally unimportant and of conventional design, the only point of interest being that their self-sealing nature requires a considerable degree of contact pressure to make and maintain the connections.

A releasable fastening arrangement, shown generally at 20 as an axial extension of the module 14, is employed to hold the module 14 positioned within the outer component 15, essentially by means of substantially radially extending bolt members 21 engaging in corresponding recesses 22 in the component 15.

The releasable fastening arrangement 20 represents a mechanism according to the invention and forms an inner component of a coaxial pair with the outer component 15, with the bolt members 21 comprising operatively disposable parts of the mechanism.

The mechanism further carries actuation means 23 for drawing and withdrawing the bolt members. A shaft 24 extends along the common axis 16 of the components and is fixed at one end thereof to the mechanism body 25 which supports a plurality of the aforementioned bolt members 21 disposed about the shaft and extending substantially radially thereof. The bolt members are slidable along their length across the mechanism body 25 and the inner end 21(a) of each bolt member has an actuation surface formed by a face 26 inclined to longitudinal axis of the bolt member and to the shaft 24.

The actuation means 23 also comprises an actuation member 28 reciprocable along the direction of the common axis 16 and having engagement faces 29 inclined to the shaft to cooperate with the actuation surfaces 26 of the bolt members when disposed adjacent thereto. The inclined engagement faces 29 of the actuation member 28 and actuation surfaces 26 of the bolt members are conveniently planar and form wedge-like contact with an extensive area of contact between them. There may conveniently be four bolt members disposed at 900 to each other so that the actuation member has four tapered faces in the manner of a truncated pyramid.

The actuation means 23 also comprises withdrawal means which responds to axial displacement of the actuation member 28 from the bolt members, to transmit a radially inward displacement to the bolt members.

As shown, the withdrawal means comprises at least one bar-like projection 30 carried by the actuation member 28 and extending laterally of the bolt members, that is, transversely to the longitudinal axis of the shaft 24 and the bolt member 21, from each side of the bolt member. The projections are of circular cross section and may be rotatable about their longitidinal axes.

Each bolt member 21 carries at the inner end 21(a) and adjacent the inclined engagement face 26 a slotted member 31 in the slot of which the bar like projection 30 is able to slide as the bolt member 21 is displaced radially from the inoperative withdrawn position shown in Figure l(a) to the operative drawn position shown in Figure l(b). Bounding wall 33 of the slot 32 which faces the inclined engagement face 29 is adapted to be engaged by the projection 30 as the abutment member is moved towards the upstanding end of the shaft and which projection, in moving along the slot, applies a radially inward withdrawing force to the bolt member.

The shaft 24 is fixed at one end only thereof 35 to the mechanism body by a frangible shear pin 36 referred to hereinafter and the other end 37 is upstanding with respect to the mechanism body sharing the common axis 16 of the components 14 and 15.

A sleeve 38 carrying the actuation member 28 coaxially surrounds the shaft and is slidable therealong to and from the upstanding end 37 within the constraints of a detent arrangement 39.

The detent arrangement comprises at least one detent dog member 40 carried by the sleeve and radially slidable with respect to the shaft axis 16 and biased towards the shaft by resilient means 41 such as a spring or block of elastomeric material tolerant of the operating environment. Each detent dog 40 also has a portion 42 providing an upstanding release surface 43 extending generally parallel to, and facing, the shaft 24. The shaft 24 is provided with a set of parallel circumferential teeth 44 over part of its length and the end of each detent dog adjacent the shaft is provided with teeth 45 of cooperating profiles.As shown, the cooperating profiles comprise ratchet teeth having sawtooth projections the ramp surfaces of which when engaged by the resilient bias means 41 permit axial motion of the sleeve along the shaft in a direction away from the upstanding end 37 but prohibit sleeve motion in the other axial direction without disengagement of the detent dogs radially against the resilient bias by a radial component of force acting on the release surface 43. It will also be seen that the circumferential teeth 44 may be limited to that part of the shaft length that the detent dogs reach when the sleeve 38 is disposed so that the actuation member 28 are holding the bolt members 21 radially extended, as shown in Figure lob).

The shaft 24 and sleeve 38 are provided with abutment means 46, 47 respectively, each abutment means having abutment shoulders facing axially towards and away from the upstanding end 37 of the shaft whereby axial forces on the sleeve abutment shoulders can be reacted into oppositely facing abutment shoulders of the shaft.

In particular the shaft abutment means 46 is conveniently, but not necessarily, disposed at the upstanding end 37 of the shaft and comprises a radially extending flange at opposite sides of which abutment shoulders 48 and 49 are formed. The sleeve abutment means 47 is disposed at the end of the sleeve closest to the shaft abutment means and likewise comprises a radially extending flange at opposite sides of which abutment shoulders 50 and 51 are formed.

The abutment shoulders 49 and 51 are inclined to the axis 16 to enable the transfer of forces both axially and radially.

The fastening arrangement as thus far described is intended to be operated submerged both to fasten and permit retrieval of the component 14 and remain submerged with the component between such operations. The operations furthermore are relatively simple requiring the sleeve to be moved axially of the shaft away from its upstanding end to deploy or draw the bolt members and requiring the sleeve to be moved axially of the shaft towards its upstanding end, having released the detent means, to withdraw the bolt members, being an adjunct to positioning and removing the arrangement.

Hydraulic acutation control means 52 is arranged to act as a means of lowering the mechanism (including attached component 14) into position and lifting it therefrom and for performing the actuation operations thereon, being removable from and disposable with respect to the submerged and fastened arrangement.

The actuation control means comprises a control body 53 adapted to be removably attached to the abutment means 46 of the shaft 24. The control body 53, which may be hollow is adapted to abut the shaft abutment shoulder 48 and has an axially extending skirt portion 54 arranged to surround that portion of the shaft having the abutment flange 46. The skirt portion 54 is apertured at 55 at a number of circumferential portions and carries in each aperture a radially displaceable shaft holding dog 56. The shaft holding dog is slidable in the aperture, radially inward displacement being limited by abutment of shoulders 57 and 58 of the dog and aperture respectively.At such limit of inward displacement (as shown in Figure l(b)) the dog projects beyond the shaft abutment shoulder 49 and has at least one bevelled shoulder 59 which overlies it and is able to abut it upon movement of the control body in an axial direction, such abutment transmitting not only axial force between the control body and the shaft but also radial outward force on the dog.

If the dog is free to move outwardly such axial motion of the control body causes the dog to displace radially and permits the control body to be moved axially from attachment with the abutment means.

Restraint of the shaft holding dogs is provided when required by a hydraulic actuation cylinder 60 surrounding the control body 53 which forms a piston therefor. The piston is formed by a radial projection 61 of the control body wall carrying a seal 62 and is contained within an annular cylinder formed by a recess 63 in the internal wall of the cylinder.

The actuation cylinder is axially movable relative to the control body by the introduction of pressured hydraulic fluid into the cylinder recess 63 by one of the connections 64, 65 at each end thereof. The actuation cylinder has an axially extending skirt portion 66 carrying in apertures 67 radially slidable sleeve holding dogs 68 and able, with the holding dogs radially free, to surround at least the portion of the sleeve 38 having the abutment flange 47 when axially displaced with respect to the control body to align the sleeve holding dogs axially with respect to the shoulder 51, or possibly 50, of the sleeve abutment flange.

The internal surface of the actuation cylinder skirt is profiled to provide a radially inwardly extending shoulder at 69 for abutment with the sleeve abutment flange shoulder 50 in movement of the actuation cylinder away from the upstanding end of the shaft, which abutment both provides for movement of the sleeve with the actuation cylinder and axially aligns the sleeve holding dogs 68 with respect to sleeve abutment shoulder 51.

The profile of the inner surface of the actuation cylinder skirt is also arranged to free or restrain the shaft holding dogs in radial motion by its axial displacement relative to the control body, having a greater diameter portion 70 to free the holding dog to pass the abutment flange as shown in Figure l(a) and a lesser diameter portion 71 which restrains the dog into alignment with the abutment flange shoulder 49 as shown in Figure l(b), the portions 70 and 71 being joined by a chamfered portion 72 and/or a chamfered corner 73 being provided on the shaft holding dog.

The sleeve holding dog 68 is provided with a similar chamfered corner 74 and is radially freed or restrained by correspondingly profiled inner surface 75 of a control cylinder 76 surrounding the actuation cylinder 60, the actuation cylinder forming a piston for the control cylinder by way of radial projection 77 carrying a seal 78 and contained in a recess 79 which forms an annular cylinder.

The annular cylinder has hydraulic fluid connections 80, 81 at opposite ends thereof which permit the control cylinder to be moved axially with respect to the actuation cylinder and in doing so to free or restrain the sleeve holding dogs 68 radially.

The control cylinder 76 is movable with respect to the actuation cylinder and has a further surface profile 82 formed by an outer surface of the control cylinder as a variation in cylinder wall thickness with distance from the end of the control cylinder, that is, as an axially tapered end of the control cylinder, which forms a cam to bear against the release surface 43 of each detent dog when moved axially towards it and translate such movement into outward radial motion of the detent dog against its inward bias.

The further surface profile 82 may be arranged to engage the detent dog only after the control cylinder has moved axially sufficiently to restrain the sleeve holding dog 68 or both may happen together.

The outer wall of the control cylinder is also provided with a breakout shoulder 83 facing towards the profiled end 82, the purpose of which will be described hereinafter.

An annular ring 84 of greater inside diameter than the control cylinder 76 is supported by spacing members 85 clear of the base 25 of the mechanism body by such a distance that the actuation member 28 abuts against the underside thereof to limit its axial travel and that of the sleeve 38.

The ring 84 is useful as a lifting ring but has other functions associated with breakout shoulder 83 which will be described hereinafter.

Considering operating of mechanism in the form of subsea fastening arrangement, and already attached to a component 14 at a surface vessel, the control actuation means 52 is attached to the shaft 24 of the actuation means by initially disposing the actuation cylinder 60 with respect to control body 53 and control cylinder 76 with respect to actuation cylinder 60 as shown in Figure l(a), such that the shaft and sleeve holding dogs are free to move radially outwards, and bringing it into axial engagement with the shaft by abutment of the control body with the shaft abutment shoulder 48. The shaft holding dogs pass around the abutment means 46, being displaced radially by the shoulder 48 if necessary, to align axially with abutment shoulder 49.

The actuation cylinder is the moved axially with respect to the control body so that the chamfered shoulder 72 thereof transfers the change in actuation cylinder profile into radially inward motion of each shaft holding dog 56, which is thereafter restrained in overlapping relationship with shaft abutment shoulder 49, and the shoulder 69 abuts shoulder 50 of the sleeve abutment means 47 and sleeve holding dog 68 passes the abutment means 47 into axial alignment with shoulder 51.

The control cylinder 76 may then be moved axially with respect to the actuation cylinder to likewise restrain the sleeve holding dog with respect to sleeve abutment shoulder 51.

The control means is then lifted by a crane (not shown) at eye 86 and suspended for lowering, the fastening arrangement 20 (and attached component 14) being lifted by abutment between the shaft holding dog 56 and the shaft abutment shoulder 49.

The actuation cylinder may be disposed with respect to the control body such that part, or indeed all, of the lifting force is transmitted between the sleeve holding dogs 68 and the ring 84 by way of sleeve abutment shoulder 51 and the actuation member 28, carried by the sleeve.

The suspended arrangement is lowered into the water and into the other component 15 with the bolt members 21 rotationally aligned with respect to recesses 22.

Further axial movement between the actuation cylinder and control body by the introduction of hydraulic pressure causes the actuation cylinder bearing on the sleeve at 69 to force the sleeve along the shaft with little resistance from the ratchet action detent means 39 and for each actuation member 28 to bear on the appropriate bolt member 21 and force it outwards into the recesses 22.

The reaction to the forces exerted on the bolt members in the control body is transmitted into the mechanism body by way of the shaft holding dog 56 and shaft 24, the disposition of the elements of the actuation means and actuation control means at this stage being as shown in Figure l(b). The detent means 30 operates with detent dog teeth 45 engaging shaft teeth 44 to prevent the sleeve from rising on the shaft under the action of any forces tending to withdraw the bolt members from the recesses.

Such forces may exist by chamfering the ends of the bolt members and/or recess walls as at 21(b) and 22(b) to provide by engagement between bolt member and recess an axial force of component 14 into component 15 sufficient to mate the self sealing electro-hydraulic terminals 12 and 13.

With the components installed and retained by the fastening arrangement the actuation control means is removed by axially sliding the actuation cylinder towards the upstanding end 37 of the shaft to free the shaft holding dog 56 for radial movement and permit the control body 53 to be lifted from the shaft and the actuation control means clear of the fastening means and actuation means which remains on the subsea component.

To raise the component 14 the actuation control means is lowered onto the shaft and the actuation control means extended to take up the previously assumed position of Figure l(b).

Then, as shown in Figure 2(a), the control cylinder 76 is extended relative to the actuation cylinder. Its inner surface profile at 75 inwardly displaces and retains the shaft holding dog 68 adjacent the sleeve abutment shoulder 51 and its further surface profile 82 bears thereafter on the upstanding release surface 43 of the detent dog and displacing it radially outwards to release the detent mechanism.

The actuation cylinder is then moved with respect to the control body the force being transferred between sleeve abutment shoulder 51 and shaft abutment shoulder 48, axially moving the projection 30 of the actuation member bearing on edge 32 to withdraw the bolt members radially from recesses 22.

The axial motion of the sleeve is limited by abutment of the actuation member 28 with the ring 8L or the travel limit of the actuation cylinder with respect to the control body, the disposition being as shown in Figure 2(b).

The actuation control means may then be lifted to raise the fastening arrangement and component 14, either by supporting the weight solely between the control body and shaft after releasing abutment between actuation member and sleeve and radially freeing sleeve holding dog 68 with axial movement of the control cylinder, or by supporting the arrangement both by abutment between the shaft holding dogs and shaft and between the sleeve holding dogs and sleeve, the latter holding the sleeve against the ring 84.

It will be seen that the arrangement provides for transportation and operation of the mechanism with only a few operations of the actuation control means confined to simple relative axial motions between few parts.

Also, it will be appreciated that the operations may be performed in substantially the same way with minor variations of construction, so that the one described and shown in detail should not be considered limited except by the appended claims.

The detent means is not limited to ratchet teeth which permit the sleeve to slide in one direction without use of the control cylinder, but may then require modification to cause the detent dogs to be released by the control cylinder preparatory to moving the sleeve in either direction.

It will be appreciated that the profiles of the shaft and sleeve abutment means, holding dogs and actuation and control cylinders may be varied in accordance with standard practice in the art to effect a corresponding operation.

For instance the holding dogs 56 and 68, which are shown with chamfered cam edges and rectilinearly slidable only in the cylinder skirts, may be replaced by cylindrical or spherical rollers which are capable of both radial displacement and restrained abutment with the abutment means 46 and 47.

Furthermore the abutment means may take other forms than shown in Figures 1 and 2.

Abutment between the shoulders 48 and 50 of the shaft and sleeve abutment means and the control body and actuation cylinder is by fixed shoulders formed within the body or cylinder, as at 69. As shown in Figures 3(a) and 3(b) the abutment flange the holding dogs 56 and 68 may be caused to bear on either of the opposite abutment shoulder of a flange by appropriately disposing the holding dog axially and restraining it radially.

Additionally or alternatively, and as shown in Figure 4(a), the abutment shoulders may be formed by a radial recess 87 in the shaft and/or sleeve, the walls of which provide abutment shoulders 88, 89 facing towards and away from the upstanding end of the shaft and engaged by the profiled holding dog 90 when radially restrained and forced to move in either axial direction. That is, forces in both axial direction are transmitted by way of the holding dog and not by a fixed shoulder, such as 69, in one direction. The recess 87 may be formed directly in the uniform peripherial wall of the shaft or sleeve or, as shown in Figure 5(b), may be formed on a radial flange 91 the edge of which flange might still be used for abutment by a fixed shoulder, such as 69 of the sleeve.

The abutment means 46 and 47 are shown at the ends of the shaft and sleeve respectively and it will be appreciated that whether in the form shown in Figures 1 and 2 or in Figures 4(a) or (b) the abutment means may be displaced from the end regions of the shaft and/or sleeve.

The action freeing and restraining the holding dogs is a result of linear motion between coaxial parts of changing internal profiles. It will be understood that such motion insofar as it effects the holding dogs may be in some other direction, such as rotating motion between the coaxial parts, with the axial motion to position the parts with respect to abutment means of shaft and sleeve be considered and effected separately.

Similarly the motion of the control cylinder with respect to the actuation cylinder to effect withdrawal of the detent dog could be rotational instead of axial.

However, the axial motion detent dog release may usefully be employed in implementing a further function.

It is a common requirement for sub-sea mechanisms, particularly those used beyond diving depth, to be removable by force should they fail to operate in the normal manner and this may be accommodated by the present invention.

It may be expected that failure of the arrangement to operate will result from failure of the sleeve 38 to move along shaft 24 either by seizure between them or by failure of the detent means to release.

Such removal by force is known as breakout or break-away and may be effected in its simplest form by pulling on the actuation control means by way of the suspension cable and eye 86 in order to tension the shaft 24 until the aforementioned shear pin 36 fractures to release the shaft, the sleeve seized to it and the actuation members 28 carried by the sleeve, the upward motion of the sleeve withdrawing the bolts which then permit raising of the whole arrangement and separation of components.

It will be appreciated that such actuation has unpredictable and therefore undesirable consequences. For instance, until the shaft 24 breaks from the mechanism body the tension applied by the lifting cable is transferred into the outer component by way of the bolt member and accommodating recess walls, possibly making their release more difficult.

Also, when the shaft does break and/or the bolts withdraw the detached parts move suddenly and impact restraining parts placing unpredictable shock loadings on the mechanism.

In effecting such emergency breakaway or breakout in accordance with the present invention use is made of a spacer 92 shown separately in Figure 5 and with the mechanism in Figures 6(a) and 6(b), having a semicircular shape adapted to seat on the ring 84 and fit about the part of the control cylinder between the breakout shoulder 83 and the profiled end 82 but not about the remainder, that is, when seated on the ring, to abut the breakout shoulder and prevent further axial motion of the control cylinder with respect to the mechanism body.

The spacer 92 is not part of the actuation means or actuation control means in respect of normal operation and is only employed should normal operation fail. The spacer is conveniently, but not necessarily, carried separately from the mechanism hereinbefore described by a machine capable of manipulating it into position underwater, such as a submersible vessel like a ROV 93.

Referring to Figure 4(a), with both actuation and control cylinder retracted and the holding dogs radially free so that the piston shoulder 77 of actuation cylinder abuts the end shoulder of annular cylinder recess 79 the actuation control means is brought onto the end of the shaft. The ROV 93 rests the spacer 92 on the ring 84 so that it surrounds the smaller diameter end portion of control cylinder 76. The actuation cylinder is then forced to move axially with respect to the control body 53, the first part of the motion disposing the shaft holding dog 55 against the shoulder 49 of the shaft to prevent the control body lifting free and further movement bringing the control cylinder into contact with the spacer 92 which prevents further axial motion of the actuation cylinder with respect to the mechanism body.

The axial force produced by the pressurised hydraulic fluid in the actuation cylinder acts on the control body and produces a tension in the shaft which is sufficient to break the shear pin 36 and lift the shaft axially with respect to the mechanism body, carrying the sleeve 38 and actuation member 25 with it.

The motion withdraws the bolt members 21 from the recesses 22 in component 15 and is stopped when the actuation member abuts the ring 84 preventing further motion of the sleeve and/or the actuation cylinder reaches its extreme of travel with respect to the control body.

Although the shaft is broken from the mechanism body 25 the parts are held by the relationship defined by between control body and actuation cylinder of the actuation control means, as shown in Figure 6(b), the mechanism being thereafter raised by way of eye 86 of the control body 53.

Thus the simple relatively axially displaceable cylindrical parts provide in addition to normal axial operating forces reacted within the arrangement for disposing operative parts of the mechanism an emergency breakout means and ready removal of these powered control parts from the remainder of the mechanism during periods when operation is not required.

The hydraulic actuation control means is able to be constructed readily to produce reliable and considerable actuation forces and displacements by way of rectilinear or rotational displacements and direction changes between the applied forces and the moved operative parts, the bolt members, detent dogs and holding dogs is effected by simple cam action on inclined faces, enabling a construction in which had few vulnerable moving parts such as pivots, and in which a wide variation in actuating forces can be derived.

It will be appreciated that the mechanism defined in accordance with the present invention is not limited to subsea operation or to a fastening arrangement as described but may involve any mechanism in which operative parts are disposed between operative and inoperative positions by axial sliding of a sleeve along a shaft.

Claims (18)

1. A mechanism including a body carrying

(i) parts arranged to be operatively disposed with respect to the body, (ii) an actuation unit for disposing the parts in operative and inoperative relationships, the actuation unit including (a) a shaft fixed at one said end thereof to the body to provide an upstanding other end, (b) a sleeve coaxially surrounding the shaft and slidable along the common axis to effect disposition of the parts, the shaft and sleeve each being provided with abutment means having abutment shoulders facing axially towards and away from said upstanding other end of the shaft whereby axial forces on the sleeve abutment shoulders can be reacted into oppositely facing abutment shoulders of the shaft, and (c) a detent arrangement between the sleeve and shaft comprising at least one detent dog member carried by, and radially slidable with respect to, the sleeve and biased towards the shaft, at least a portion of the shaft surface and the end of each dog engageable therewith having cooperating profiles to inhibit by such engagement axial motion between the sleeve and the shaft in at least one direction, and (iii) hydraulic actuation control means removably disposable with respect to the shaft and sleeve at said upstanding other end thereof and comprising (a) a control body adapted to be attached to the abutment means of the shaft (b) hydraulic actuation cylinder surrounding the control body which forms a piston therefor, the actuation cylinder having an axially extending skirt portion able to surround at least a portion of the sleeve having the abutment means and carrying in an apertured wall thereof radially displaceable sleeve holding dogs, and (c) a control cylinder surrounding the actuation cylinder which forms a piston therefor internal walls of which control cylinder are profiled to free or restrain radially outward displacement of the sleeve holding dogs by its disposition with respect to the actuation cylinder, the actuation control means being operable in response to hydraulic fluid pressure in the control cylinder and in the actuation cylinder in a non-actuation operation to dispose the control cylinder with respect to the actuation cylinder to radially free the sleeve holding dogs and move the skirt portion of the actuation cylinder axially with respect to the sleeve to place the sleeve holding dogs into or out of axial alignment with a shoulder of the sleeve abutment means and in an actuation operation to dispose the control cylinder with respect to the actuation cylinder to restrain outward radial displacement of the holding dogs and permit the actuation cylinder to apply axial force to an abutment shoulder of the sleeve by way of the holding dogs, said control cylinder being movable with respect to the actuation cylinder to bear against each detent dog of the sleeve with a further surface profile to slide the detent dog against the bias and disengage it from the shaft, thereby permitting axial motion of the sleeve with respect to the shaft by motion of the actuation cylinder.

2. A mechanism as claimed in claim 1 in which the control cylinder is arranged to be displaced axially with respect to the actuation cylinder to bear against each detent dog.

3. A mechanism as claimed in claim 1 or claim 2 in which the further surface profile is formed by an outer surface of the control cylinder.

4. A mechanism as claimed in claim 3 in which the further surface profile formed by an outer surface of the control cylinder is provided by a variation in cylinder wall thickness with displacement distance to form a cam and each detent dog has a cam following surface adapted to cooperate therewith and translate displacement of the control cylinder into radial movement of the detent dog.

5. A mechanism as claimed in claim 4 when dependent on claim 2 in which the further surface profile is an axially tapered end of the control cylinder.

6. A mechanism as claimed in any one of the preceding claims in which the further surface profile is arranged to engage the detent dog only upon disposition of the control cylinder with respect to the actuation cylinder in which the profiled internal wall of the control cylinder restrains the sleeve holding dogs radially with respect to the actuation cylinder skirt.

7. A mechanism as claimed in claim 6 in which the further surface profile is arranged to engage the detent dog only upon disposition of the actuation cylinder with respect to the sleeve at which the sleeve holding dogs are in axial alignment with an abutment shoulder.

8. A mechanism as claimed in any one of the preceding claims in which the cooperating profiles of the detent means comprise ratchet teeth having sawtooth projections the ramp surfaces of which permit axial motion of the sleeve along the shaft in a direction away from said one upstanding other end of the shaft and the control cylinder is disposable with respect to the actuation cylinder to permit said actuation cylinder to apply axial force to the sleeve abutment means in a direction to slide the sleeve from said one end of the shaft without the control cylinder engaging and releasing the detent dogs.

9. A mechanism as claimed in any one of the preceding claims in which the sleeve abutment means is a radially extending flange providing at opposite sides thereof abutment shoulders, the actuation cylinder skirt is dimensioned to pass over the flange with the sleeve holding dogs radially unrestrained and the inner surface of the skirt is provided with a radially inwardly extending shoulder adapted to bear against the flange shoulder facing said one end of the shaft and each sleeve holding dog is disposed axially with respect to the shoulder to overlie the flange shoulder facing away from said one end of the shaft when radially restrained by the control cylinder.

10. A mechanism as claimed in any one of the preceding claims in which the control cylinder is arranged to be displaced axially with respect to the actuation cylinder to free or restrain the sleeve holding dogs radially.

11. A mechanism as claimed in claim 2 or claim 10 in which the actuation cylinder has a radial projection defining a piston and the control cylinder has a recess in the inner wall thereof defining an annular cylinder space for the piston, the projection and recess end walls defining abutment surfaces at extremes of axial displacement of the control cylinder with respect to the actuation cylinder and by abutment of which at said displacement extremes the control cylinder comprises an extension of the actuation cylinder skirt and by way of which the actuation cylinder is able to exert axial force.

12. A mechanism as claimed in claim 11 in which the shaft is breakable from the mechanism body upon a predetermined axial tension in the shaft and arranged thereupon to move axially carrying the sleeve and disposing the mechanism parts into inoperative relationships, the mechanism including breakout means operable to exert an axial tension in the shaft with respect to the mechanism body comprising a breakout shoulder formed on the control cylinder and facing the mechanism body and a spacer insertable between the breakout shoulder and the mechanism body operable prevent motion of the actuation member away from said upstanding other end of the shaft and on to transmit axial force exerted between the actuation cylinder and control body to the shaft by way of the control body attachment to produce said predetermined axial tension therein with respect to the mechanism body.

13. A mechanism as claimed in claim 12 in which the mechanism body carries a ring member of greater diameter than the control cylinder and coaxial therewith and the breakout shoulder is formed on the outer peripheral surface of the control cylinder, said spacer having an annular shape extending at least part way about the ring and of radial width extending between the ring and breakout shoulder.

14. A mechanism as claimed in claim 13 in which the sleeve carries radial projections adapted to engage the side of the ring remote from said upstanding end of the shaft as the sleeve is moved towards said upstanding end away from the mechanism body and permit axial motion of the mechanism body and actuation means by axial force exerted on the sleeve by way of the actuation control means.

15. A mechanism as claimed in any one of claims 12 to 14 in including a manipulator machine operable to carry the spacer and position it between the breakout shoulder and mechansim body.

16. A mechanism as claimed in claim 15 adapted to operate underwater in which the manipulator machine is a submersible vessel.

17. A mechanism as claimed in any one of the preceding claims in which the control body is adapted to abut the shaft abutment shoulder facing said upstanding other end of the shaft and has an axially extending skirt portion arranged to surround at least a portion of the shaft having the abutment means and carry in an apertured wall of the skirt radially displaceable shaft holding dogs axially aligned with the abutment shoulder facing away from said upstanding other end of the shaft and the internal walls of the surrounding actuation cylinder are profiled to free or restrain radially outward displacement of the shaft holding dogs by disposition of the actuation cylinder with respect to the control body.

18. A mechanism substantially as herein described with reference to and as shown in the accompanying drawings.