United States Patent: 3552688

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( 16721 of 16721 )

United States Patent	3,552,688
Baekken	January 5, 1971

HELICOPTER LANDING MEANS

Abstract

Trap means, for grasping a probe carried by a helicopter and used on board ship to secure a helicopter to the ship at the instant of touchdown, comprise a hydraulic system arranged to move together two arresting beams which trap the probe and hold it in trapped position.

Inventors:	Baekken; Asbjorn (Dartmouth, Nova Scotia, CA)
Assignee:	Fairey Canada Ltd. (Darmouth, Nova Scotia, CA)
Appl. No.:	04/805,608
Filed:	March 10, 1969

Foreign Application Priority Data


Sep 04, 1968 [CA]			029.185

Current U.S. Class: 244/115

Current International Class: B64F 1/04 (20060101); B64F 1/00 (20060101); B64F 1/12 (20060101); B64f 001/12 ()

Field of Search: 244/115,116,114,17.17 114/43.5

References Cited [Referenced By]

U.S. Patent Documents


3303807	February 1967	Stewart et al.
3392940	July 1968	Van Valkenburg

Primary Examiner: Buchler; Milton;
Assistant Examiner: Sauberer; Paul E.

Claims

I claim:

1. Trap means suitable for grasping a probe carried by an aircraft and comprising:

a. a housing;

b. an opening formed in the housing;

c. a first arresting beam arranged to extend across the opening;

d. a second arresting beam arranged to extend across the opening and extending parallel to the first arresting beam;

e. a first drive member;

f. first cable means connecting the first arresting beam to the first drive member and so arranged that as the drive member is moved the first arresting beam moves across the opening in a direction normal to its length and remains parallel to the second arresting beam;

g. a first hydraulic cylinder carried by the housing and arranged to effect movement of the first drive member;

h. a second drive member;

i. second cable means connecting the second arresting beam to the second drive member and so arranged that as the drive member is moved the second arresting beam moves across the opening in a direction normal to its length and remains parallel to the first beam;

j. a second hydraulic cylinder carried by the housing and arranged to effect movement of the second drive member;

k. catch means carried by one of the two arresting beams;

l. means, complementary to the catch means, carried by the other of the two arresting beams, the catch means being adapted and arranged automatically to engage the complementary means when the two beams are brought together; and

m. hydraulic valve means arranged to supply hydraulic fluid to and to vent hydraulic fluid from the first and second hydraulic cylinders to permit:

i. the two arresting beams to be moved apart to cocked positions adjacent opposite sides of the opening; and

ii. the two arresting beams to be driven together to engage a probe extending into the opening.

2. Trap means according to claim 1, and including: a. a first sprocket; b. a second sprocket; c. a chain extending round and joining together the first and second sprockets; d. a movable ram forming the operative part of the first hydraulic cylinder and connected to the chain to cause movement of the chain with movement of the ram; e. a keyed shaft on which one of the two sprockets is mounted and to which the sprocket is keyed against rotation; f. a third sprocket mounted on the keyed shaft and having a larger diameter than that of the said sprocket also mounted on this shaft; this third sprocket also being keyed to the said shaft against rotation; and g. a second chain extending about the third sprocket and connected to the first drive member whereby linear movement of the movable ram is accompanied by a proportional but greater linear movement of the first drive member.

3. Trap means according to claim 1, and in which the housing carries a hydraulic actuator, and the actuator is arranged when energized to effect release of the catch means from the complementary means.

4. Trap means according to claim 3, and in which an elongated member extends transversely of the two beams near one end thereof, the hydraulic actuator is arranged to move the elongated member between a first position and a second position, and this member in the first position is arranged to engage a mechanism carried by the second beam and is adapted when so engaged to move abutments which act on and displace the catch means from engagement with the said complementary means.

5. Trap means according to claim 3, in which an elongated member is arranged to extend transversely of the two arresting beams near one end thereof, and this member is arranged to assume a first position when the catch means are disengaged and a second different position when the catches are engaged, and the elongated member is arranged to provide an indication, a control, or the combination of an indication and control, in accordance with the state of the catch means.

6. Trap means according to claim 1, and in which stop means are provided adapted to hold the two arresting beams relative to the housing when they are in engagement with one another and with the probe, the stop means including:

a. a stop disposed between the two beams and normally movable by the beams as they travel to engage the probe; and

b. readily releasable holding means which when effective hold the stop and thus the two engaged arresting beams against further movement relative to the housing, the holding means including hydraulic actuating means by which the holding means can be changed between effective and released conditions.

7. Trap means as claimed in claim 6, wherein the stop means include a chain extending round two sprockets spaced apart and positioned adjacent the cocked positions of the two beams, the stop is carried by the chain, and the holding means include and/or act on one of the sprockets.

8. Trap means as claimed in claim 7, wherein the holding means include a body member in which the sprocket is journaled, the sprocket is arranged to rotate in unison with a first circular set of teeth, the body member is provided with a movable clutch member formed with a second circular set of teeth complementary to the first set of teeth, means are provided restraining the clutch member from rotating relative to the body member, and the hydraulic actuating means act on the movable clutch member to move it between an engaged position in which the first and second sets of teeth are in engagement to prevent rotation of the sprocket and a released position in which the two sets of teeth are capable of relative rotation without engagement.

9. Trap means as claimed in claim 1, wherein the housing carries electromagnetic actuators arranged to control valves by which hydraulic fluid can be fed to and vented from the hydraulic actuators, and the trap is controlled by an electrical cable extending to a remote control console.

10. Trap means as claimed in claim 1, wherein the housing carries a pressurized reservoir tank for hydraulic fluid and pipes and valves by which the tank can supply hydraulic fluid to the hydraulic actuators.

11. Trap means as claimed in claim 1, wherein the housing carries a low pressure sump tank in which hydraulic fluid vented from the hydraulic actuators is stored.

12. Trap means as claimed in claim 1, wherein the housing carries a pressurized reservoir tank for hydraulic fluid and pipes and valves by which the tank can supply hydraulic fluid to the hydraulic actuators, and a low pressure sump tank into which hydraulic fluid vented from the hydraulic actuators is stored, and pump means by which hydraulic fluid can be transferred from the sump tank to the reservoir tank.

13. Trap means as claimed in claim 1, wherein the housing is connected by hydraulic fluid flow lines to a remote control unit which is adapted to control the supply to, and the venting from, the various hydraulic actuators of hydraulic fluid.

Description

This invention relates to trap means suitable for grasping a probe carried by an aircraft, and finds particular utility in facilitating the landing of a helicopter, provided with the probe, on the deck of a ship at sea.

It has been proposed in copending Canadian Pat. application Nos. 887,011 and 914,140 (Pat. application Ser. No. 404,374, filed Oct. 16, 1964, now U.S. Pat. No. 3,303,807) that a helicopter shall be hauled down onto the deck of a ship at sea by a cable acting against the lift produced by the helicopter rotor. This enables the helicopter to land safely despite pitching of the ship and despite the action of wind on the aircraft. In that proposal, a probe carried by the helicopter is seized by a trap carried by the ship so that once the helicopter has landed it is held firmly against movement relative to the ship, and eventually the trap is used to transport the helicopter bodily into a hangar in which the helicopter is stored.

Those patent applications disclose trap means comprising a housing formed with an opening, first and second arresting beams arranged to extend across the opening and to extend parallel to one another, first cable means connected to the first beam and to a first drive member and so arranged that as the drive member is moved the first beam moves across the opening in a direction normal to its length and remains parallel to the second beam, second cable means connected to the second beam and to a second drive member and so arranged that as the drive member is moved the second beam moves across the opening in a direction normal to its length and remains parallel to the first beam, and driving means by which the first and second drive members can be moved to bring the two beams together to grasp a probe extending into the opening between the two beams.

In that earlier proposal, compressed air was used in actuator cylinders to provide the driving means, and in practice this lead to several difficulties.

According to the present invention, trap means suitable for grasping a probe carried by an aircraft comprises a housing formed with an opening, first and second arresting beams arranged to extend across the opening and to extend parallel to one another, first cable means connected to the first beam and to a first drive member and so arranged that as the drive member is moved the first beam moves across the opening in a direction normal to its length and remains parallel to the second beam, a first hydraulic cylinder carried by the housing and arranged to effect movement of the first drive member, second cable means connected to the second beam and to a second drive member and so arranged that as the drive member is moved the second beam moves across the opening in a direction normal to its length and remains parallel to the first beam, a second hydraulic cylinder carried by the housing and arranged to effect movement of the second drive member, catch means carried by one of the two beams and adapted automatically to engage complementary means on the other of the two beams when the two beams are brought together to grasp a probe extending into the opening between the two beams, and hydraulic valve means arranged to supply hydraulic fluid to and to vent hydraulic fluid from the first and second hydraulic cylinders to permit the two arresting beams to be moved apart to cocked positions adjacent opposite sides of the opening and to permit the two arresting beams to be driven together to engage a probe extending into the opening.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a side elevation of a helicopter in the final stages of being winched down onto the deck of a ship;

FIGS. 2A, 2B and 2C are diagrammatic representations in plan view of a trap shown in FIG. 1, these FIGS. showing the general operation of the trap in seizing a probe carried by the helicopter;

FIG. 3 is a perspective drawing of the trap shown in FIGS. 1 to 2C;

FIG. 3A is a sectional side elevation of a small part of a trap frame shown in FIG. 2A, and is taken on the line III-III of that FIG. and as viewed in the direction indicated by the arrows;

FIG. 4 is a diagrammatic representation of operating parts of the trap, in positions corresponding to the situation of FIG. 2A, an intermediate drive chain being omitted to clarify the FIG.;

FIG. 5 is a diagrammatic representation of the operating parts shown in FIG. 4 but in positions corresponding to the situation of FIG. 2C;

FIG. 6 is an exploded perspective drawing of driving means for two arresting beams shown in FIGS. 2 and 3;

FIG. 7 is a perspective drawing of release means for arresting beam locking catches shown in FIG. 3, and is shown as viewed from the right of FIG. 3;

FIG. 8 is a perspective drawing of position indicating means for the arresting beam locking catches, and is shown as viewed from the right in FIG. 3;

FIG. 9 is a perspective drawing of a holding device shown in FIG. 3, but drawn to a larger scale than in that FIG. and partly broken away to show detail normally hidden;

FIG. 10 is a schematic representation of a hydraulic system provided on the trap frame; and

FIG. 11 is a perspective drawing of an arresting beam shown in FIG. 2A.

Referring to the drawings of the present application, Canadian Pat. application No. 914,140 filed Oct. 16, 1964, in the names of William G. Steward and Asbjoern Baekken discloses a system (see FIG. 1) for hauling a helicopter 1 down onto the deck 3 of a ship at sea, the helicopter first picking up by messenger line a cable 5 from the ship flight deck 3, and then, after that cable has been secured to the helicopter, a controller on the ship by means of a constant tension winch hauling the helicopter down by the cable 5 against the lift of the helicopter rotor until a probe 7 on the underside of the helicopter is clamped within a trap 9 in the present drawing. The trap can then be moved forwardly of the ship (i.e. in the direction of the arrow 12), taking the helicopter with it, into a hangar.

As described in that earlier patent application, an electric motor (not shown) is coupled to the driving shaft of a variable displacement hydraulic pump, connected in closed circuit to a fixed displacement hydraulic motor. Such an arrangement is well known in the art, and commonly makes use of a pump with a tiltable swash plate or, as in the embodiment described, a pump with a fixed swash plate but an adjustable tilt head. The output shaft of this hydraulic motor is connected through a gearbox alternatively either to a drum 15 of a haul down winch or to a drum 21 of a trap traversing winch. The cable 5 has one end wound on the drum 15 and extends from the winch drum first over pulleys of a rope accumulator 23 and then round a guide sheave 25 and finally over a sheave 27 before passing upwardly through the deck 3 to the helicopter 1. The rope accumulator includes a first set of pulleys and a second set of pulleys, the two sets being biased apart by a pneumatic cylinder device 29 which has a force/displacement characteristic such that the force biasing the two sets of pulleys apart increases progressively as the two sets are forced closer together by the tension in the cable 5.

FIGS. 2A to 2C illustrate how the trap 9 operates: it includes a substantially rectangular frame 31 in which are mounted two parallel arresting beams 33. These beams can be forcibly moved in the directions of the arrows 35 towards one another from an initial "cocked" position shown in FIG. 2A. Each beam has on its inward side nine spring-loaded plungers 39 as shown. Between the two beams at about the centerline of the frame 31, are disposed two shuttles 41 which initially are free to move in the direction of the arrow 43. When the helicopter is in the position shown in FIG. 1, its probe 7 will lie between the two arresting beams 33. This is partly due to the skill of the pilot but mainly due to the pull in cable 5, which extends out of the bottom of the probe and into a port 45 in the deck 3 at the center of the frame 31. However, since there are lateral forces acting on the helicopter as well as the vertical component of the force in the cable 5, the probe 7 will usually strike the deck 3 at a point displaced from the port 45, e.g. as indicated in FIGS. 2A to 2C.

During the landing of the helicopter, the trap 9 is cocked to the state shown in FIG. 2A, and once the probe is suitably disposed between the two arresting beams 33 an operator "fires" these beams so that they are forced towards one another. After a travel which will depend upon the positioning of the probe 7, one of the arresting beams 33 will be stopped by engagement with the probe, and in FIG. 2B the lower arresting beam 33A is shown stopped in this manner. The other arresting beam 33B will continue to travel and in due course will engage the two shuttles 41. During continued travel, this arresting beam will carry the two shuttles with it, and eventually this arresting beam will come up against probe 7. This is the situation shown in FIG. 2C. In this situation, the probe 7 is held tightly between the two beams 33. The beams extend fore-and-aft of the ship, and thus prevent lateral movement of the helicopter probe 7 and thus the helicopter, while the butting spring-loaded plungers 39 prevent fore-and-aft movement of the probe 7 and thus of the helicopter.

The trap as described above and as shown diagrammatically in FIGS. 2A to 2C is substantially the trap in the prior patent application referred to above, whereas the trap to be described hereafter is an improved trap utilizing the same general principles. The embodiment of the improved trap described below is not adapted for traversing into a hangar, as is the trap of FIG. 1, but can readily be modified to provide that facility if and when required.

Referring now to FIGS. 2A to 3A, the frame 31 is built up from massive channel end sections 31A and 31B and from massive forged and welded composite side sections 31C and 31D, the cross section of section 31D being shown in FIG. 3A. These four sections are bolted together to form a massive and rigid frame which in the embodiment described is bolted down to the ship's deck, but which can if desired be fitted with wheels or rollers by which it can be moved by the winch 21 along the deck 3. Sections 31C and 31D are formed along their inner sides each with an upper groove 51, and grooves 51 accommodate the two ends of each of the two arresting beams 33. Each shuttle 41 is generally T-shaped as viewed in side elevation, as will be seen in FIG. 3, and is provided with four wheels 53 which run on the floor of grooves 55 and 57 in the side sections 31C and 31D, the shuttle being guided laterally by facing surfaces 59 and 61 on the side section.

Each arresting beam 33 is movable between its limiting positions by an arrangement of two double-acting hydraulic cylinders 71 and 73 shown in FIGS. 3, 4, 5 and 6. As will be seen most easily from FIGS. 3 and 6 the hydraulic cylinder 71 is provided with a ram 75 extending from one end and connected by an offset coupling 77 to an endless roller chain 79 having a lower run 79A to which the coupling is fitted and an upper run 79B. This chain extends over a first sprocket 81 and a second sprocket 83. Sprocket 81 is keyed to one end of a shaft 85 journaled in a bracket 87 mounted near one end of the frame side section 31C. Similarly, idler sprocket 83 is journaled on one end of a shaft 89 keyed in a bracket 91 mounted near the other end of the frame side section 31C. A second chain 93 is carried by two sprockets 95 and 97 respectively mounted on the two shafts 85 and 89, sprocket 95 being keyed to the shaft 85 and idler sprocket 97 journaled on shaft 89, and since sprocket 95 has twice as many teeth at the same pitch as the sprocket 81 movement of the chain 79 by the ram 75 is accompanied by travel of the chain 93 through twice the distance. The two ends of the chain 93 are connected respectively to opposite sides of a crosshead member 99. This member 99 is apertured to accept nipples at the ends of four wires 101, 103, 105 and 107. The arrangement of these wires may be seen most clearly from FIGS. 3 and 4. It will be seen that wire 101 extends from the crosshead member 99 round an idler pulley 109, across the width of the frame 31, round an idler pulley 111, through a passage 113 in arresting beam 33A to arresting beam 33B, where it is anchored at anchor point A. Wire 103 extends from the crosshead member 99 round an idler pulley 115 and an idler pulley 117 and an aperture 119 in the arresting beam 33A to an anchor point B on arresting beam 33B. It will be seen that anchor points A and B are disposed at opposite ends of arresting beam 33B, and that movement of the crosshead member 99 will tend to cause equal movements of both ends of that rail. Wire 105 extends from the crosshead member 99 round an idler pulley 121 and an idler pulley 123 (disposed near the end of side section 31C which is remote from pulleys 109 and 117) and is connected to anchor point C on arresting beam 33B. The fourth wire 107 extends from the crosshead member 99 round an idler pulley 125 disposed adjacent the pulley 121, along the side of the frame 31, round an idler pulley 127, and is anchored to arresting beam 33B at anchor point D.

The hydraulic cylinder 73 is similarly connected to an endless chain which drives a second chain 133 having a crosshead member 135. Four wires 137, 139, 141 and 143 extend from that member 135. Wire 137 extends from crosshead member 135 round an idler pulley 145 and an idler pulley 147 and through an aperture 149 through the arresting beam 33B, and at its end is connected to arresting beam 33A at anchor point E. Wire 139 extends from crosshead member 135 round an idler pulley 151, along the side of the frame 31, round an idler pulley 153 adjacent the pulley 123, through an aperture 155 in the arresting beam 33B, and is connected to the beam 33A at the anchor point F. The wire 141 extends from the crosshead member 135 round an idler pulley 157 and round an idler pulley 159 disposed adjacent the pulley 111, and is connected to the beam 33A at anchor point G. Wire 143 extends from crosshead member 135 round an idler pulley 161 disposed adjacent the pulley 157, along the side of the frame 31, round an idler pulley 163 disposed adjacent the pulley 117, and is connected to the beam 33A at anchor point H.

FIGS. 4 and 5 have been simplified by the omission of chain 79 and its equivalent and by showing the rams of the hydraulic cylinders 71 and 73 connected directly to the chains 93 and 133 respectively.

Movement of the ram of cylinder 71 pays out two of the associated wires and takes in the other two wires, and thus provides restraint of the two ends of arresting beam 33B which ensures that at all times that beam shall remain parallel to the fore-and-aft axis of the frame 31. Similarly, movement of the ram of cylinder 73 pays out two of the associated wires and takes in the other two wires, and thus provides restraint of the two ends of arresting beam 33A which ensures that at all times that beam shall remain parallel to the fore-and-aft axis of the frame 31. By the use of two uncoupled mechanisms to move the two arresting beams, one can be stopped by the probe, as described above in connection with FIG. 2B, and the other still be free to continue to move until it also engages the probe.

It is necessary to lock the two arresting beams 33A and 33B together, and to this end the beam 33A (see FIG. 3) carries two pivoted catches 165 and beam 33B carries two complementary lugs 167. The catches 165 are spring biased to the "secured" position, and as the two beams come together these catches are first forced to the open position against the action of their springs, and then snap into place to hold the two beams together. In order to enable an operator to disenable the two catches 165, a hydraulic actuator 169 is mounted on the side section 31D of frame 31 and has its ram 171 connected by a cranked lever 173 to an actuating bar 175 which extends along inside the side section 31D in a groove below that containing the ends of the arresting beams. This bar 175, being carried by two swinging levers, namely lever 173 and a second lever 177, remains parallel to the side section 31D but moves inwardly or outwardly relative to the ends of the arresting beams. A tension spring 179 biases bar 175 axially in such a direction that it tends to move outwardly of these beam ends. When the actuator 169 is operated to move the bar towards the rail ends, it engages a roller 181 provided on a cranked lever 183 pivotally mounted on the arresting beam 33B. The arrangement is such that this lever is rotated in a clockwise direction (viewed from above) (see FIGS. 7, 8 and 11) on the pivot pin 185 of this lever 183, engaging the catch 165 to rotate it away from its position of engagement with lug 167. A connecting rod 187 connects the lever 183 to a further lever 188 mounted on a pivot pin 190 at the other end of beam 33B, so that this lever 188 is also rotated in such a manner as to move the adjacent catch 165 from its "engaged" position. Lever 189 is connected with cable 192 to lever 184. This cable runs over a pulley on a lever 196 attached to lever 191 which extends towards this end of the beam and carries a roller 193 (see FIG. 8). The frame side section 31C carries an indicating channel 195 (see FIG. 8) disposed in a groove underneath that containing the beam ends and carried by two parallel pivoted links 197 and biased by a spring 199 so that the bar is always biased inwardly of the ends of the end of the beams 33. When the two catches 165 are in their "engaged" positions, the roller 193 presses the channel 195 outwardly away from the beam ends, and the beam then through a pivoted rocker 201 engages the operating plunger 203 of a switch 204 to provide a remote electrical indication that the catches are closed.

Each shuttle 41 has an endless chain 205 connected to one end of its elongated base, this chain extending along the groove 55 to a clutch sprocket 207 carried by frame member 31B, and returning from that sprocket along the groove 55 past the shuttle to a similar clutch sprocket 207 carried by the frame member 31A, and returning from that second sprocket to the shuttle 41, being connected to the second end of its elongated base.

The four clutch sprockets 207 respectively from parts of four holding devices 215 which are made effective, once the two arresting beams have gripped the probe to prevent the helicopter probe and thus the helicopter from moving laterally in a direction parallel to the lengths of the wires referred to above.

Referring now to FIG. 9, the holding device 215 includes a housing 251 provided with a cover plate 253 held in place by clamping bolts 255. The housing 251 is formed with a central bore 257 which accommodates a rotatable member 259 carried at its lower end by a needle roller bearing 261 carried by the housing and at its upper end by needle roller bearing 263 carried by the cover plate 253. An intermediate part of the member 259, disposed above the part engaging the bearing 261, is formed with splines 265 which engage a splined bore in chain sprocket 207. This sprocket lies within a tunnellike cavity 269 in a lower part of the housing 251, and the reason for the splined construction is to permit assembly of the sprocket 207 laterally into the tunnel and then engagement of the member 259 with the sprocket by lowering of the member in the bore 257. An integral radially extending flange 271 of the rotatable member 259 carries on its upper surface a first set of teeth 273 having a "saw-tooth" or ratchet profile. The part of the rotatable member 259 immediately below the flange 271 is provided with a hydraulic seal in the form of an O-ring 275 effectively engaging an encircling part of the bore 257 and similarly a part of the member 259 immediately above the flange 271 is provided with a hydraulic seal in the form of an O-ring 277 effectively engaging an encircling part of the bore 257. Axial movement of the rotatable member 259 is prevented in an upward direction by engagement of a frustoconical surface 279 on the member with a complementary surface 281 on the cover plate 253, and in a downward direction by engagement of an annular shoulder 283 below the O-ring 275 with an upper surface of the chain sprocket 207 and by engagement of an annular bearing surface 285 of the housing with a complementary surface on the underside of that sprocket 207.

An annular cylinder 287 concentric with the member 259 is defined on its radially outer side by the housing and on its radially inner side by a downwardly extending boss on the cover plate. Inside that annular cylinder is disposed an annular piston 289 formed on its underside with a second set of teeth 291 complementary to the teeth of set 273. This annular piston is provided on its radially outer side with a hydraulic seal in the form of an O-ring 293 and on its radially inner side acts against an O-ring 295 carried by the cover plate 253 to form a second hydraulic seal. The annular piston is held against rotation in its cylinder by four cylindrical steel plungers 297 extending downwardly from the cover plate 253 into complementary holes in the piston, these plungers 297 being formed with blind bores which contain compression springs 299 and being provided with external flanges which prevent upwardly movement of the plungers. Thus springs 299 can act to force the second set of teeth 291 down into effective contact with the first set of teeth 273.

A hydraulic supply pipe 301 is connected to a passageway 303 in the housing 251, this passageway terminating at the periphery of the cavity in the housing which accommodates the flange 271. A hydraulic vent pipe 305 is connected to the upper end of the cylinder 287, i.e. the part of the cylinder which lies above the annular piston 289, this vent pipe being connected to a suitable point to atmospheric pressure so that no appreciable pressure can build up in the space above the piston.

When the pressure of the hydraulic fluid supplied through pipe 301 is very low, the springs 299 are effective to lock the teeth of set 291 with the teeth of set 273, and this positively holds the sprocket 207 and thus the chain 205 with the shuttle 41 against displacement. By the use of teeth of "saw-tooth" profile, the danger that one set of teeth will lodge on the crests of the other set of teeth is removed. In order that no wedging apart of the teeth shall cause slipping of the holding device, the teeth of the two holding devices associated with the same shuttle have opposite "hands," so that one holding device will prevent movement of the chain 205 in a "clockwise" direction (viewed as in FIG. 3) and the other holding device will prevent movement of the same chain 205 in an anticlockwise direction.

When the pressure of the hydraulic fluid supplied through the pipe 301 is raised, for example to 1000 pounds per square inch, the upward force acting on the annular piston 289 forces that piston upwardly against the action of the four compression springs 299, and takes the second set of teeth 291 upwardly out of engagement with the first set of teeth 273. The rotatable member 259 is then free to rotate, and the shuttle 41 is no longer held against movement.

When it is desired to use the apparatus to land a helicopter, the shuttles 41 are disenabled by the application of fluid pressure to the pipe 301. The two shuttles 41 can then move freely, and the arresting beams 33A and 33B can trap the helicopter probe as described above. The pressure in the pipe 301 is then vented to atmosphere, activating the locking devices and locking the two shuttles in place and thus also locking the two arresting beams and the helicopter probe against lateral movement.

The holding device now proposed locks the two shuttles in place without the need for any continued rotation of the holding means to make a wraparound bank brake effective. The maximum slip which can occur at a holding device is equal to that produced by rotation through one tooth pitch, and in practice this is equal to a movement of about one-fourth inch of the shuttle 132. This is comparable with the running slack in the chain 135, and is within permissible limits.

When the two arresting beams are in the "cocked" position shown in FIG. 2A, the two levers 311 are depressed when contacting lugs 313, provided respectively on the beams 33A and 33B. This action closes two switches coupled in series and giving the controller a light indication that both beams are cocked. Rubber buffers 315 are engaged by the beams in this position.

Referring now to FIG. 10, this illustrates the use of a hydraulic system mounted on the trap frame 31 to activate the various parts of the trap. In this FIG. can be identified the double-acting hydraulic cylinders 71 and 73 which operate the arresting beams 33A and 33B; the hydraulic actuator 169 for the release of the catches 165 which lock the two arresting beams together and the four holding devices 215. Also mounted on the trap frame 31 is a hydraulic accumulator 321 partially filled with hydraulic fluid above which is trapped gas under a relatively high pressure, this gas serving to boost the flow of the working fluid. A hydraulic reservoir 323, working at atmospheric pressure, is also mounted on the trap frame, and is connected to the reservoir 321 by a pump 325 by which, when the trap is not in active use, hydraulic fluid can be pumped from the sump tank to the high pressure accumulator. Two electromagnetic actuators 327 and 328 provided on the trap frame controls the setting of a three-position four way hydraulic valve 329, and these actuators are connected by electric cables 331 and 332 to a controller's console by which a controller monitors the landing and the securement of the helicopter. These cables also include cores connecting the switches 204 and 312 (see FIG. 3) (providing an indication of the state of the locking catches 165) and beams cocked to suitable indicating lamps on the controller's console.

The liquid space of the reservoir 321 is connected by a pipe 333 to an inlet port of valve 329. In a first "cocked" position of the valve, the valve spool connects pipe 333 to pipes 335 connected to open ends of the cylinders 71 and 73, and the other ends of the cylinders are connected through pipes 337, the valve spool and pipe 339 to the reservoir 323. In a second "fired" position of the valve, the valve spool connects pipes 335 to pipe 339 and thus the reservoir, and connects pipes 337 to pipe 333 and thus to the pump and accumulator. In the third or "neutral" position, pipes 335 are connected to pipe 337, i.e., the two ends of each cylinder are connected together. It will be appreciated that with the valve in the "cocked" position both arresting beams will be forced outwardly and that with the valve in the "fired" position the arresting beams are forced rapidly towards one another. With the valve in the "neutral" position, the two beams can be manually displaced, and in some circumstances this can be a useful facility since it allows the probe to be gripped and yet moved relative to the frame of the trap.

Actuator 169 which controls the freeing of the catches 165 on the beams 33A and 33B is used only during a cocking cycle and therefore fed directly from the cocking pipe 335. Clutches are released simultaneously, being fed from pipe 335 through shuttle valve 316.

The general procedure for landing a helicopter on the deck of the ship using the constant tension hauldown cable 5 has been disclosed in the earlier patent applications discussed above and has been further described above in connection with FIGS. 1 and 2A to 2C. In use of the improved trap described above, prior to the commencement of the procedure for landing the helicopter, the two arresting beams 33A and 33B are brought to the "cocked" position by operation of the valve 329. Whey they reach this position, they are automatically locked in place by the counterbalance valve 314. The helicopter landing procedure is then commenced, and when the probe 7 of the helicopter is in the trap the ship-based controller through the valve 329 pressurizes the two cylinders 71 and 73 driving the two arresting beams 33A and 33B together. At this state of readiness, all four holding devices 215 are in their "free" state, fluid under pressure being fed through the shuttle valve 316 so that the shuttles 41 are free to move with their chains 205, and the catch actuator 169 is not actuated so that the catches 165 are free to engage. As described previously, the two arresting beams move together and first one and then the other engage the probe 7, so that it is gripped between the two beams. Immediately this happens, the catches 165 engage the lugs 167 to clamp the two beams together. This moves the indicating channel 195 outwardly to close the switch 204, providing an indication to the controller that the probe is secured. He then by means of returning the valve 329 to neutral position vents fluid under pressure from the cylinders 287 of the holding devices 215, which immediately assume their locked positions. This prevents movements of the chains 205, and thus of the shuttles 41, and since the two shuttles are between the two arresting beams and the two beams are locked together, this locks the beams in place relative to the trap frame 31.

As mentioned above, the subsequent handling of the landed helicopter can take different courses, and the mounting of the trap 9 will be dictated by the desired manner of use.

It will be seen that the improved trap described above represents a considerable improvement as regards simplicity above the earlier proposals, and the improved simplicity brings improved reliability and thus improved safety.

In the embodiment of the invention described above, the connection between the trap and the controller's console is by electric cable having several cores, and this by enabling the use of short hydraulic conduits between the valve devices and the various hydraulic devices improves the speed of response of the mechanisms to the controller's actions. However, if desired the hydraulic actuators can be connected by suitable rigid or flexible hoses to a separate hydraulic system positioned below the deck 3, although even in this case it will usually prove desirable to use an electrical control from the controller's console.

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Current U.S. Class:	244/115
Current International Class:	B64F 1/04 (20060101); B64F 1/00 (20060101); B64F 1/12 (20060101); B64f 001/12 ()
Field of Search:	244/115,116,114,17.17 114/43.5