The present invention relates to securing devices. In particular, it relates to a device for securing an aircraft (for example a helicopter) to the deck of a ship. It is anticipated, however, that the invention in its broadest form may also be susceptible of other applications.

Devices suitable for securing or locking a helicopter to the deck of a ship are often known as "deck locks". Such locks generally comprise a stowable arm which can be extended beneath the fuselage of the helicopter, as it is landing on the deck. At the end of the arm there are a pair of jaws which clamp securely around a suitable grid set into the deck itself. Once the jaws are securely clamped onto the grid, a telescopic actuator within the arm operates to pull the helicopter down and to hold it against the deck.

It is an object of the present invention to provide a Decklock with improved reliability and/or maintainability.

It is a further object to provide a Decklock in which wear on at least some of the operating parts is reduced.

It is a further object to achieve at least some of these aims in securing devices of other types.

According to a first aspect of the present invention there is provided a lock comprising a pair of engaging members defining jaws adapted to engage a member to which the lock is to be secured and a striker plate positioned for contact with the said member when located between the jaws, the plate having a detent

position in which the jaws are prevented from engaging the member, and a second position in which, on the operation of actuating means, the jaws may engage the member.

Preferably, the lock is a Decklock, and the jaws define respective hooks which are adapted to engage around the member to which the lock is to be secured. This member may, for example, be a mesh or grid forming part of or let into the deck of a ship or forming part of a fixed or movable member mounted on the deck.

Preferably, the striker plate is biased toward the detent position, so that the jaws cannot accidentally close to engage the member unless the member is properly positioned between them.

The actuating means may comprise a pneumatically or hydraulically actuated locking plunger which is adapted to be inserted between rollers secured to the engaging members, so forcing them apart at one end and causing them to rotate about pivotal axes. In this way, the separation of the engaging members at one end thereof, will cause the closure of the jaws at the other end thereof.

Where each engaging member is pivotally mounted on its own axis, so that separation of the engaging members at one end will cause closure of the jaws at the other, the engaging members may be prevented from separating when the striker plate is in the detent position by virtue of lateral restraint means which abut the edges of the engaging members. These may, for example, be pins which abut sloping edges of the engaging members.

The striker plate may be slidable between the detent position and the second position so that, in the

detent position, the plate prevents the engaging members from rotating about their own respective parallel axes, and in the second position the plate moving clear of the engaging members so allowing them to rotate.

The striker plate may be generally flat and may be mounted for sliding movement within slots contained within the engaging members.

In a particularly convenient embodiment, each of the engaging members is mounted for rotation about its own axis. The actuating means comprises a locking plunger which forces apart the engaging members at one end, so causing the jaws to close at the other end. The striker plate is then generally of W shape, and has side abutments adjacent the ends of the W which prevent the engaging members from being separated by the locking plunger when the striker plate is in the detent position. When the member to which the lock is to be secured presses against the angle formed by the central portions of the W, the abutments move away from the engaging members so allowing them to be separated and the jaws to close.

In all of the above arrangements, coupling means may be provided between the engaging members and the striker plate to cause the jaws to open as the striker plate moves from the second to the detent position. Likewise, the coupling means may cause the jaws to tend to close as the striker plate is moved in the opposite direction.

Where the striker plate is in the form of a W, as discussed above, these means may comprise pins attached to outer portions of the W. The pins may be arranged to slide on outer portions of the engaging members, so

assisting or causing the jaws to open or close.

In some cases the member to which the hook is to be secured will have a sharp ridge on it, hard repeated contacts between this ridge and the lock tending to result in significant wear or damage. To alleviate this, the striker plate may be shaped so that the member is received between angled surfaces thereof. Where these angled surfaces meet, part of the striker plate may be radiused or cut away to ensure that the ridge on the member can never impinge directly at the point at which the two angled surfaces meet each other.

In a particularly advantageous form of the Decklock, the actuating members may be mounted on respective parallel pivotal axes to a support and/or housing. This may itself be removably connected to an end mounting which is rigidly secured to a piston rod or ram by means of which the entire lock may be extended or retracted which respect to the member to which it is to be secured. The end mounting may include a pair of trunnion plates to which the housing is secured by first and second bolts which also act as the pivots for the engaging members. This enables the housing and consequently the engaging members and the striker plate easily to be removed for maintenance or replacement. The rigid connection between the housing and the ram eliminates the cost and weight of thrust bearings; the ram is desirably permitted to rotate with the housing so that the lock does not need to be disengaged if it is desired for example to rotate the helicopter with respect to the deck grid to which it is attached.

A locking plunger for actuating the engaging members may be operated by means of an inner piston,

extending within the piston rod or ram. This has the significant advantage that the two securing bolts, and thus the housing, may be removed without disturbing any hydraulic or pneumatic seal.

Restraining means, for example one or more restraining spars, may be provided to limit movement of the actuator in a direction perpendicular to that of the piston rod. The restraining means may be secured to an outer muff or sleeve within which the piston rod may rotate. Between the outer muff and the piston rod may be located an inner sleeve or muff which is longitudinally movable. A manual release lever, for releasing the locking plunger, may be provided, this release lever being coupled to the locking plunger by the intermediary of the inner muff. The coupling may be so arranged that in normal operation of the locking plunger, the release lever is not affected; this de¬ coupling of the release lever and the locking plunger reduces both operating loads and operating wear.

This aspect of the invention may also be embodied in a mechanism using electrical or mechanically stored energy, such as a spring, as the motive power for the main ram or arm and the locking plunger.

According to a second aspect of the invention there is provided a securing and release mechanism for selectively coupling first and second members, the mechanism comprising a pneumatic or hydraulic actuator having a ram extendible between a retracted position and an extended position, mounting means for mounting the actuator to the first member, and securing means for automatically securing the ram to the second member, and control circuit means arranged to cause the ram to tend to retract when the ram is so secured,

pulling together the first and second members, the control circuit means including a check valve positioned between pressure lines extending one to each side of the ram. Such a pressure regulator may be used to lower the entire system pressure, and therefore the impact load on the second member, as the ram is being extended. This lowered pressure results, effectively, from the pressure being applied to extend the ram passing through a pressure regulating valve, and the output pressure from this pressure regulating valve being applied at the same time on the opposite side of the ram via the check valve.

On the other hand, when the ram is being retracted, the retraction pressure is applied simply to the retraction side of the ram, the other side being maintained at a regulated pressure.

The control means may be arranged to actuate a selector valve, in a first position of which the supply pressure is provided to the pressure regulating valve and following that partly directly to the "extension" side of the ram and partly via the check valve to the "retraction" side of the ram, and in a second position of which the supply pressure is provided directly to the "retraction" side of the ram. Alternatively, in the second position the supply pressure may be applied to the "retraction" side via a flow limiter.

Such an arrangement of valves means that once the securing means are secured to the second member, and the ram is put into tension, the pressure regulating valve is then isolated from the main supply pressure. Since it is the pressure regulating valve which is likely to be the greatest cause of leakage, such a configuration provides the longest possible period of

high securing tension should the controlling hydraulic or pneumatic power supply be disrupted. Both the selector valve and the check valve may have soft seats, so ensuring that the leakage at those valves is particularly small.

According to a third aspect of the prevention there is provided a securing and release mechanism for selectively coupling first and second members comprising a pneumatic or hydraulic actuator having a ram extendible between a retracted position and a extended position, mounting means for mounting the actuator to the first member, and securing means for automatically securing the ram to the second member and control circuit means arranged to cause the ram to tend to retract when the ram is so secured, pulling together the first and second members, the control means including reversal means arranged to put the ram into compression prior to uncoupling of the securing means.

In this way, the tensile securing loads between the first and second members are cancelled prior to uncoupling of the securing means. This reduces wear both on the securing means themselves, and also on the second member to which they are attached. The reversal means may include delay means arranged to retract the ram following a time delay to allow for uncoupling of the securing means.

The delay means may comprise a delay circuit on a potted printed circuit board.

In either of the two preceding aspects, the control circuit means may include automatic retry means arranged automatically to re-attempt securement of the ram to the second member should the first attempt fail. The retry means conveniently incorporates a pressure

switch, sensitive to the thrusting pressure of the ram, and delay means arranged to cause the re-attempted securement should the pressure remain above a limit value for a given period.

The present invention extends to any one or compatible combination of features shown or described in this patent application, whether in the preamble or in the specific embodiment.

The invention may be carried into practice in a number of ways and one specific embodiment will now be described, by way of example, with reference to the drawings, in which:

Figure 1 is a schematic perspective view of a Decklock embodying the present invention;

Figure 2 is a longitudinal section through the probe of figure l;

Figure 3 is a longitudinal section through the hook assembly at the end of the probe; Figure 4 is a schematic hydraulics diagram; Figure 5 is a schematic electrical diagram, showing the system stowed and unarmed; Figure 6 illustrates the engage sequence; Figure 7 illustrates the first part of the release sequence;

Figure 8 illustrates the second part of the release sequence.

Turning first to Figure 1 there is shown schematically an exemplary embodiment of a Decklock according to the present invention. The Decklock shown comprises a main arm or probe 10 which is pivotally secured at its upper end 12 to the underside of a helicopter (not shown) . At the distal end of the probe there is a hook assembly 14 which is capable of being

extended downwardly by means of an actuator 16 within the probe. The purpose of the hook assembly 14 is automatically to grasp and to secure onto a grid 18 set into the deck (not shown) of a ship on which the helicopter is about to land. The grid 18 comprises a strong rigid metal mesh having generally circular apertures therein.

As the helicopter comes into land, the hook assembly 14 is dragged over the grid 18, the probe 10 pivoting about the aircraft attachment point 12 at its upper end. Typically, this attachment may be a simple spherical bearing or alternatively a set of gimbals, giving the probe sufficient freedom to move in a conical fashion about its nominal vertical axis on the helicopter. A pair of telescopic struts 22, 24, extending between respective aircraft attachment points 26, 28 and trunnion mountings 30, 32 at the lower end of the probe, control the angular motion of the probe. Instead of the struts 22, 24 it would in some applications be convenient to allow the Decklock to swing freely within a larger conical space and to provide a mechanism to stow the probe 10 against the underside of the helicopter when it is not in use, or alternatively to lock it on its nominal axis.

Mounted on the probe 10 there is an electronic components module 34, containing most of the electronics necessary for the control of the Decklock. Similarly, there is a valve module 36 which contains most of the hydraulic control components.

Near the distal end of the probe 10, just above the hook assembly 14, there is a manual release lever 38 by which the hook assembly 14 may be released from the grid 18 in the event of a failure of the electrical

and hydraulic systems. A rigid steel bar ( not shown) placed under the manual release lever 38 and with one end on the deck of the ship, may be used to lever off the hook assembly by means of an upward motion applied to the other end of the bar.

The probe 10 is shown in more detail in the sectional view of figure 2. In this embodiment it comprises a single stage ram within a rigid outer body 40. The hook assembly 14 is secured to the end of a main piston rod 42, by means of which it may be extended or retracted from the body 40 according to varying hydraulic pressures applied via the valve module 36. An inner piston 44 controls engagement of the hook assembly 14 onto the grid 18, and its release. This will now be described in more detail with reference to Figure 3, which is a cross sectional view of the hook assembly 14.

Rigidly screwed to the end of the piston rod 42 is a hollow extension rod 46, at the end of which there is a trunnion mounting 48 for a beak assembly 50. In Figure 3, only the upper portion of the mounting 48 can be seen, where it is cut by the sectional plane, and the general shape may be seen more easily in figure 1. The beak assembly 50 is retained within the two parallel sides of the trunnion mounting by means of beak attachment bolts 52.

The beak assembly 50 itself comprises a first downwardly-extending rigid beak portion 54, and a similar rather shorter beak portion 56. The longer beak portion surrounds and encloses, except for a vertical slot, a first hook 58 which is pivotally attached to the mounting 48 at one of the beak attachment bolts 52. Similarly, the other beak 56

generally encloses another hook 60, pivoted to the other beak attachment bolt 52; on this side, however, the hook 60, being somewhat longer than the beak portion 56, extends further downwardly with the result that the beak portion 56 effectively amounts to a pair of protective side plates on either side of the hook 60.

The upper ends of the hooks 58, 60 are provided with respective operating rollers 62. In the position shown in Figure 3, the rollers are touching or almost touching each other, with the result that the hooks 58, 60 remain in the open or retracted position within their respective beak portions 56. When the inner piston 44 is extended, however, this acts upon a locking plunger 64, contained within the hollow extension rod 46, to push the rollers 62 apart and so close the jaws of the hooks.

To prevent the inner piston 44 being extended before the jaws of the hooks are actually in position around the grid 18, a locking mechanism is provided in the form of a W-shaped striker plate 66. The striker plate 66 is mounted for vertical sliding movement within slots 68, 70 in the hooks 58, 60 and is biased downwardly into the position shown in figure 3 by means of a leaf spring 72 which extends perpendicularly to the plane of the section. As the striker plate is forced downwardly under the biasing force provided by the spring 72, laterally extending pins 54, 56 press against the curved outer edges of the hooks 58, 60 so pivoting them about the beak attachment bolts 52 and causing them to take up the open position shown in the diagram. In this position, the pins 54, 56 prevent the rollers 62 from moving apart from each other, and

accordingly the hooks are locked in their open position. In this locked position they cannot accidentally be closed by the pilot of the helicopter inadvertently actuating the inner piston 44.

As the helicopter touches down, the beak portions 54, 56 of the beak assembly pass one either side of one of the bars 78 making up the deck grid 18. The pressure of the bar 78 on the inclined lower surfaces 80 of the striker plate 66 forces the plate upwardly, against the leaf spring 72, so moving the pins 54, 56 away from the sides of the hooks. Once this has occurred, actuation of the inner piston 44 pushes the locking plunger 64 between the rollers 62, and so locks the hooks firmly around the bar 78.

As the striker plate 66 rises, the centre portion 88 of the W moves upwardly between pivot tubes 90 mounted to the hooks around the beak attachment bolts 52. The rotation of these tubes tends to move the hooks into their closed position.

To reduce damage to the beak assembly and to the grid as the helicopter touches down, the lower ends of the beak portion 54 and the hook 60 are provided with respective hardened tips 82, 84. The angle between the inclined lower edges 80 of the striker plate 66 is cut away or radiused as indicated at 86 to avoid direct impacts of the striker plate on the crest of the grid bars.

Surrounding the extension rod 46 is an inner sleeve or muff 92, and surrounding this there is an outer sleeve or muff 94 carrying the securement points 30, 32 of the restraining struts (see figure 1) . The trapping of the outer muff between the piston rod 42 and the beak assembly 50 provides a secure anchorage.

The manual release lever 38 is transmitted to the locking plunger 64 via the inner muff 92 (the exact details of the connection not being shown in Figure 3) . This arrangement means that the release lever is not affected by normal operation of the locking plunger, so eliminating the large dynamic forces on the lever which otherwise would have arisen if the lever were to be fixedly connected to the locking plunger.

The beak assembly and the piston rod are free to rotate with respect to the outer muff 94. This has the significant advantage that, without having to remove the hooks from the grid, the entire helicopter can be rotated on the deck of the ship should this prove necessary for example in order to position the aircraft to take off into the wind.

The beak and muff assemblies can be removed easily from the piston rod for repair without disturbing any hydraulic seals. Ease of maintenance is also provided by the fact that the entire beak assembly 50 can be removed merely by undoing the two beak attachment bolts 52. If necessary, the beak assembly can be replaced with the Decklock still fitted to the aircraft, given adequate access from below.

The hydraulics control system is shown in detail in Figure 4. As shown, the Decklock is in its inactive (retracted) state.

Hydraulic pressure supplied by an accumulator 100 on the helicopter is supplied by an interface manifold 102 to a main supply line 104 which extends to the valve module 36. Inside the valve module, the supply pressure is applied to an engage selector valve 110 which, in the position shown, applies it along the line 112 to the underside of the main actuator. This holds

the hook assembly 14 in the withdrawn position. In this position, the rest of the probe is at return line pressure.

An engage solenoid valve 108 is provided for operating the engage selector valve 110, and in a second position of the latter the supply pressure is sent along a line 113 to the upper end of the main actuator. This causes the actuator to be extended. The pressure at the upper end of the actuator is detected by means of a pressure switch PSW.

Also contained within the valve module is a release solenoid valve 112, supplied with hydraulic pressure by means of a line 106 extending from the interface manifold 102. The release solenoid valve 112 is effectively an on/off valve by means of which pressure can be selectively applied beneath the locking plunger 64, so retracting the hooks 58, 60 back into their respective beak portions 54, 56.

All of the hydraulic components contained within the valve module 36 are located within a separate manifold body. This provides a separate testable sub assembly, and is a fully interchangeable spare item.

The engage selector valve 110 has a soft seat poppet which provides virtually complete sealing to the pressure line when the valve is not selected.

A pressure regulator 137 in the line 114 after the engage selector valve 110 is designed to operate in two modes. As the pressure builds up during extension of the actuator, it acts as a reducing valve producing a controlled pressure at its output independent of he supply pressure. Prior to actuation of this valve, orifices provide smooth controlled extension of the actuator. When the system is retracting or at rest,

the valve 137 acts as an unloading valve, venting excess pressures should the actuator be forced back into the actuator body by some sudden movement of the helicopter.

Connecting the lines 114 and 113, respectively at the upper and lower ends of the actuator, there is a pilot operated check valve 139. During extend operations, both sides of the main actuator accordingly operate at a reduced pressure, so minimising impact forces with the grid and ensuring a good operating margin for a pressure switch PSW whatever the pressure supply. A further advantage is that the upward force on the helicopter and the consequent disturbance to the crew on landing or take off is minimised, especially when a two-stage actuator is used. This valve 139 has a soft poppet design.

Sharp edge orifice type restrictors control the extension and retraction stoke rates. These orifices are set during development, and are not expected to be adjustable during normal operation.

The circuit configuration of the pressure control valve 137, and the two soft valves, the engage selector valve 110 and the check valve 139, is designed to minimise internal seepage once the Decklock has secured the helicopter. The main potential loss of fluid is via the pressure regulator, and losses are reduced by isolating this valve from the system accumulator fluid by switching off the engage solenoid valve 108 and thus the engage selector valve 110 once the lock is secured. This significantly improves the period for which the accumulator may maintain tension when the hydraulic supply has been isolated.

The electric circuit corresponding to the

hydraulic circuit of Figure 4 is shown in Figure 5. This circuit, the purpose of which is to actuate at the appropriate times the solenoid valves 108 and 112, may be split up into a number of separate portions, as follows.

An instrument panel 118 includes the main power on/off switches 117 and white, green and red indicator lights, the purpose of which will be described below. The panel 118 is connected via a shock absorber switches circuit 119 to the pilot 120 and co-pilot 122 control panels. These are then connected via an interface connector 123 and a number of further switches and relays 124 to the electronics module 34 which has already been mentioned. The outputs of the electronics module 34 are applied to the solenoid engage valve 108 and the solenoid release valve 112.

The hydraulic and electrical circuits shown in Figures 4 and 5 are drawn assuming that the Decklock is in is inactive (withdrawn) state. In this position, all of the aircraft electrical switches are off, and the main actuator is held in the withdrawn position by the system pressure applied to the underside of the actuator.

In preparation for landing, the air crew of the helicopter first select "power on" (not shown) in the instrument panel 118. If the probe is properly installed, the white light lights up to indicate that the Decklock is ready.

Once the helicopter has landed, either the pilot or co-pilot may place the engage/release switch into the "engage" position as is shown in Figure 6, causing power to be supplied to the solenoid engage valve 108, so extending the main actuator. The green light on the

panel 118 simultaneously indicates that the Decklock is armed. In Figure 6, and indeed in Figures 7 and 8 to be described later, the initiating act is indicated by means of an open triangular symbol, the reaction caused (that is, the path along which the operating current flows) is indicated by double lines, and the subsequent operation of switches and relays is indicated by means of arrows.

In an alternative to the connections shown in Figure 6, the circuit may require both pilot and co¬ pilot to move their respective switches to the "engage" position before the solenoid engage valve 108 operates. Alternatively, either or both pilots may choose to pre¬ select the "engage" position, allowing the shock absorber switches 119 to initiate the sequence by detecting when the weight of the helicopter falls onto its wheels.

As soon as the actuator leaves its retracted position a microswitch MS3 operates, as is shown in

Figure 6. When the striker plate 66 meets one of the grid bars 78 the locking mechanism will start to move, and this will operate the "hook unlocked" switch MS2, again as is shown in Figure 6. Finally, as the actuator ceases its motion, the pressure switch PSW will operate, indicating that the thrust load is high.

When the hooks are secured to the deck grid and the locking mechanism is fully engaged, the "hook locked" switch MSI will operate, de-energising the engage solenoid 108. The operation of this switch MSI causes the red light on the instrument panel 118 to go on, and the main actuator to go into tension so securing the helicopter to the deck. That ends the engage sequence.

If, for any reason, the normal engagement sequence

fails, the main actuator will withdraw, re-set its controls, and repeat the attempt. This repeat cycling feature is provided by means of a delay circuit which blocks the output of the pressure switch PSW for a short period of time. If, for example, the tip of the beak assembly strikes a damaged area of grid and fails to engage, the switch PSW will remain on for long enough for the time delay 130 to operate, so energising a relay RCR in the electronics module 34. One contact of the relay RCR breaks the supply to the solenoid engage valve 108, causing the actuator to withdraw. While all of the aircraft switches are set to "engage" the probe system will continue to repeat this cycle until a successful engagement is achieved.

Turning now to Figures 7 and 8, the release sequence will be described. To reduce load on the hook lock mechanism, and to reduce wear and maintenance requirements both of the the probe and of the deck grid, a system has been devised which momentarily puts the actuator into compression at the beginning of the release cycle.

The cycle is initiated, as is shown in Figure 7, by the pilot or co-pilot placing his engage/release switch into the "release" position, so supplying power to the solenoid engage valve 108 via the "hook unlocked" switch MS2 which will, of course, at this time be in the "on" position. Since the actuator is already more or less fully extended, it will very quickly stall, operating the pressure switch PSW. Following a short time delay caused by the delay circuit 130, the RCR relay is energised, so that power is now switched via MS3 to the release solenoid 112. This latter position is illustrated in Figure 8.

As the locking plunger is unloaded, it withdraws rapidly, first re-setting the "hook locked" switch MSI and then the "hook unlocked" switch MS2. The solenoid release valve 112 is de-energised and the main actuator is withdrawn. Both the relay RCR and the solenoid 112 are latched on by the "ram retracted" switch MS3 until it re-sets after the actuator has re-housed within the probe body.

As will be appreciated from the foregoing description, the purpose of the delay circuit 130 is to ensure that short spikes from the pressure switch PSW do not operate the repeat cycle relay RCR.

All of the electronic components within the electronics module 34 are mounted on a double sided printed circuit board, which also provides all the circuit interconnections. The printed circuit board is enclosed in a purpose designed casing, and is potted.

The present embodiment has been described particularly in relation to the securement of a helicopter to the deck of a ship. It will, however, of course be appreciate that very similar embodiments might be useful in other applications where rapid, remotely operated securing and releasing mechanisms are required.