This invention relates to a locking device for gravity davits of the type comprising a main arm and a rocking arm which is pivotable about a horizontal axis on the main arm and at its outer end is provided with one or more pulleys- for a hoisting rope serving to launch a lifeboat, raft or the like.

It is previously known to provide a fixed locking piece at the outer end of the davit, possibly on a rocking arm, for securing the lifeboat or the like in the stowed position of the davit, the object being also to relieve the hoisting rope arrangement of the weight of the lifeboat during the long time- periods when the lifeboat is simply kept in its inboard position i.e. with the davit in its stowed position.

In International Patent Applications PCT/NO87/00057 and PCT/NO87/00058 in connection with the gravity davits of the abov type described therein, locking functions are mentioned for automatically fixing the main arm and the rocking arm in relatio to each other in outboard position, and securing of the rope end when the davit has not been swung out, respectively. In short, the present invention is directed to a locking device having a particular linkage which in a simple and practical, but at the same time reliable manner provides for the desired locking functions. The device is based on a pivotable locking piece, in contrast to previously known fixed locking pieces, which necessi tate a significant angular movement of the outer davit part in relation to the horizontal plane, when being swung out from stowed position to launching position.

The problem solved by this invention thus primarily is the one being present with gravity davits in which the hoisting rope arrangement must be secured and relieved in the stowed (inboard) position of the davit, as this securing should be released automatically before launching of the lifeboat, life raft or the like when the davit has reached the outboard position.

What is novel and specific in the device according to the invention consists therein that a locking piece is pivotable through a certain angle about a horizontal axis in relation to the rocking arm, that between pivot points on the main arm and the locking piece respectively, there is provided a linkage comprising a locking rod, a second ^" rod and an intermediate

rocking piece which is two-armed and journalled about an axis being fixed in relation to the rocking arm, that the locking rod has a longitudinal guide for a slide member provided on one arm of the rocking piece, that the locking rod further has a longitu¬ dinal engagement surface adapted to co-operate with a stop member in a first locking position, and that the end of the locking rod at the rocking piece is adapted to co-operate with a stop member serving to put the locking rod under compressive stress in a second locking position, in which the angle between the main arm and the rocking arm is changed in relation to the angle in the first locking position.

In addition to what is mentioned above, the invention also involves the substantial advantage that when the davit has been fully swung out, the rocking arm is locked in a fixed angular position in relation to the main arm, without any risk of angle changes which might lead to problems during launching, possibly the hoisting up of a lifeboat. Besides, this angular fixing is automatically released when the hoisting rope arrangement, possibly with a lifeboat or the like, is fully hoisted up to its upper position underneath a davit in its outboard position.

In the following description the invention shall be explai*- ned more closely with reference to the drawings, in which:

Fig.l shows the upper parts of a gravity davit with the main arm and the rocking arm in stowed (inboard) position,

Fig.2 shows the arrangement of fig.l in fully outboard position (launching position),

Fig.3 shows a second embodiment of a similar gravity davit as in fig.l and 2, in stowed position, and

Fig.4 shows the arrangement of fig.3 in outboard position.

In fig.l and 2 there is shown a rocking arm 2 which is pivotably supported at 9 on top of a main arm 1 being shown only in part. Moreover there is indicated a tension rod 3 which is incorporated into the supporting main structure of the davit. In the usual manner there is further provided a hoisting rope arrangement (not shown) with pulleys and so on belonging thereto. At the outer end of the rocking arm 2 (fig.2) there is indicated

a pulley 17 which in the case of a rope arrangement having a number of rope parts (multiple tackle) can be several pulleys side by side. There is also shown (in part) a movable block 19 which may be incorporated in a hoisting rope arrangement in a usual manner.

A locking piece 10 is mounted pivotably about an axle 10A which can possibly also be the axle for the pulley 17. As seen in particular from fig.l the locking piece has a projection IOC which can enter into an opening in the block 19 when being in it fully elevated position, so that the whole hoisting rope arange- ent is secured and the rope is relieved of the weight of the suspended lifeboat or the like.

At an angle in relation to the projection IOC the locking piece 10 has an arm 10E which at a pivot 10B is connected to a rod 7. At its opposite end this rod is articulatively connected to the outer end of an arm 12D on a rocking piece which is pivotable about an axle 13 and has a second arm 12A forming an angle to the arm 12B. The angle between the two arms of the rocking piece is chosen with due consideration to the geometry and otherwise the dimensions of the linkage connecting the pivot 10B on the locking piece 10 to a pivot 5 on the main arm 1. Thu the linkage further comprises a locking rod 6 having one end connected to said pivot 5 on the main arm, whereas the opposite end of this locking rod 6 has a particular design for co-opera¬ tion with the rocking piece 12A, 12B and elements associated therewith, for bringing about the two specific locking functions mentioned above, in a first locking position and a second lockin position, respectively.

For obtaining the desired function of the linkage it will b seen that the axle 13 for the rocking piece must be fixed in relation to the rocking arm 2, which is provided for by a bracke 4.

In the first locking position which corresponds to the stowed position as shown in fig.l, the rocking piece assumes an angular position being rotated to a maximum in the clockwise direction, whereby the arm 12B lies more or less in the prolonga¬ tion of the rod 7. A pin 14 on the arm 12A is located adjacent the inner end of a slot 16 in the locking rod 6, whereas an

engagement surface 6A on the underside of the locking rod 6 engages a stop member in the form of a rotatable sleeve 15 on the axle 13.

As seen from fig.l the load is thereby secured or locked, i.e. because the movable block 19 is prevented from being lowered since the projection IOC on the locking piece 10 enters an opening in the block 19. The load however, will tend to press the locking piece in the clockwise direction and thereby give a compressive force in the rod 7. As the rocking piece arm 12B has such a .direction that the point of connection between this arm and the rod 7 lies somewhat above the dead point in relation to the compressive force mentioned, the rocking piece will be urged in the anti-clockwise direction as indicated with the arrow in fig.l. However, the rocking piece and therefore the complete linkage is blocked against movement in this locking position because of the pin 14 in the slot 16 and the engagement between the surface 6A and the sleeve shaped stop member 15.

When the lifeboat shall be launched from a starting point i the stowed position of the davit as shown in fig.l, the davit must first be swung out. During this outboard movement the angl between the main arm 1 and the rocking arm 2 will be changed so that the locking rod 6 is retracted in a direction away from the rocking piece 12A, 12B, the pin 14 sliding in the slot 16 toward the opposite end thereof at the same time as the engagement surface 6A on the underside of the locking rod 6 is displaced in the lefthand direction in fig.l in relation to the stop sleeve 15. The pin 14 can be regarded as a slide member which can be moved in the longitudinal direction of the locking rod 7 in a guide formed by the slot 16. Since the sleeve 15 can rotate on the axle 13, the friction during this relative displacement movement will be somewhat reduced. This outboard movement with change of angle between the main arm 1 and the rocking arm 2 proceeds while the locking effect is maintained in the first locking position mentioned above, in which the locking piece 10 blocks the hoisting rope arrangement as represented by the movable block 19, until the davit reaches the fully outboard position (launching position) as illustrated in fig.2.

In the position of fig.2 which can be referred to as the

second locking position of the davit, the engagement surface 6A on the locking rod 6 has moved completely out of its previous engagements against the upper side of the sleeve 15, which results in pivoting of the rocking piece in anti-clockwise direction under the influence of the above mentioned compressive force from the rod 7 because of the weight of the lifeboat which acts on the locking member 10. Therefore the securing of the movable block 19 is eliminated and the same can be lowered by means of the hoisting rope arrangement in the usual manner.

In this second locking position the angle between the main arm 1 and the rocking arm 2 is fixed because the end face of the locking rod 6 is directly abutting against the sleeve 15. Thus, this sleeve also in this locking position constitutes a stop member in co-operation with the locking rod 6. If under some form of influence the rocking arm 2 should have a tendency to move downwards with its outer end in the direction of an angular position in relation to the main arm as in fig.l, the locking rod 6 will be put under compressive stress and thereby block the whole linkage so that the angular position shown in fig.2 is fixed. This locked position means a safe launching, or possibly elevating of a lifeboat, and this position is maintained until it may be terminated by operation of the davit for this purpose, in particular by hoisting up the movable block 19 so that this again enters into co-operation with the locking piece 10 and swings this back upwards to the position shown in fig.l. For this purpose the locking piece 10 is provided with a projecting nose 10D which catches the upper side of the block 19 at the termina¬ tion of the hoisting movement and gives the above swinging-up of the locking piece 10. Through the intermediary of the rod 7 this pivoting movement will pull the rocking piece arm 12B so that the rocking piece is rotated in the clockwise direction (as indicated with arrows in fig.2) which brings the end of the locking rod 6 out of its locking engagement against the sleeve 15. The engagement suface 6A on the underside of the locking rod again will be applied against the upper side of the sleeve 15 at the same time as the pin 14 slides in the slot 16 from the outer to the inner end thereof, as the mutual angular position of the main arm 1 and the rocking arm 2 is changed from the situation of

fig.2 to the one in fig.l.

From the above explanation it will appear that the result is an automatic and reliable locking function in the first and the second angular positions respectively, as represented by the respective fig.l (stowed davit) and fig.2 (fully outboard swung davit) .

In the embodiment of fig.l and 2 the sleeve 15 on the axle 13 has a dual stop function namely against the engagement surface 6A on the underside of the locking rod 6, and against the end of this rod respectively. As such it might be possible to split these two functions on two separate stop members, which moreover must not necessarily be provided in close association with the axle 13, as is the case with the rotatable sleeve 15. In order to obtain a smooth transition between the two fundamen¬ tally different mutual positions of the locking rod and the rocking piece, it is a great advantage however, that there is provided an integrated stop member in the form of the rotatable sleeve 15.

In the modified embodiment as shown in fig.3 and 4, there is provided a linkage which can be regarded as inverted in compari¬ son to the arrangement of fig.l and 2, concerning the angular movement of the davit's main arm 21 and the rocking arm 22 when moving from the stowed position (fig.3) to the launching position (fig.4). Between a pivot 20B on the locking piece 20 and a pivot 25 on the main arm 21 in this embodiment there is provided a linkage consisting of a locking rod 26, a rocking piece 32A, 32B and a rod 27 which is much shorter than the rod 7 in fig.l and 2. Another difference can be seen in the angular relationship between the two arms 32A and 32B of the rocking piece. Moreover, the locking rod 26 has a shorter slot 36 and a shorter engagement surface 36A than the corresponding elements of the locking rod 6 in fig.l and 2. However, an axle 33 for the rocking piece and a rotatable sleeve 35 on the axle, are designed in full analogy with the corresponding parts in the first embodiment described above.

Finally, it appears from fig.3 and 4 that the arm ratio of the locking piece, i.e. the distance between the supporting point 20A and the pivot 20B for connection to the rod 26, is relativel

shorter than in the first embodiment, in which a more characteri¬ stic and mainly downward extending arm gives a longer distance between the bearing 10A and the pivot 10B. Thus the embodiment of fig.l and 2 can be regarded as more suitable for large loads than the embodiment of fig.3 and 4.

From what is explained rather detailed above, regarding the function of the linkage in fig.l and 2, it should be apparent also how the function and the movement are performed in the modified embodiment of fig.3 and 4. The first locking position described above, thus corresponds to the fully outboard position of the davit in the second embodiment as shown ^* in fig.4. In this position the engagement surface 36A is applied against the upper side of the sleeve 35. The second locking position described is represented by fig.3, i.e. the stowed position of the davit, in which the end of the locking rod 36 is abutting against the righthand side of the sleeve 35.

There is shown a spring 38 which seeks to pull the linkage towards the position shown i fig.4, which means that the spring 38 contributes to keeping the locking piece 20 in the open or released position when the davit is fully swung out. In certain situations this spring can be an advantage in order to prevent random movements, shocks or impacts in the davit from moving the linkage so that the locking piece 20 could swing up to its secured position (fig.3) when the davit is in its outboard position. Also in fig.2 there is indicataed a spring 18 which can have a similar function, but this is regarded as less necessary in the first embodiment of the device.

In the embodiment of fig.3 and 4, where the maximum load can be lower than in the embodiment of fig.l and 2, there may be used a hoisting rope arrangement having only one rope part, and in such case it can be practical to design the nose portion 20D of the locking piece 20 as a loop surrounding the rope.

It will be realised that linkages having the fundamental function comprising rods and a rocking piece as discussed above with reference to the figures of drawings, in practice can be designed in various ways, for example by having the various parts which are included, arranged more or less in the same plane, or they may be duplicated in parallel ("twin rods") and with

different forms of guide, slide and stop members which in the principle have similar functions as the structural features being specifically described.