OBJECT OF THE INVENTION The present invention relates to a drive mechanism for pivoting davits installed upon ships, oil rigs and similar launching sites.

BACKGROUND OF THE INVENTION The stowage and launching of lifeboats from ships, oil rigs and similar launching sites is realised by means of complex hoists, known as davits in the corresponding technical sector, which have evolved with the passage of time.

The document US6357380 describes a rescue hoist for storing, launching and retrieving a rescue boat having an A-shaped lifting arm supporting- the rescue boat in a stowed position and rotating approximately 20° about the base of the A-shaped frame to assist in hoisting and lowering the rescue boat. A sheave assembly and a hoist stop assembly are mounted upon the apex of the A-shaped frame lifting arm and accommodate a winch line at the apex of the A-shaped frame. An electrical winch raises and lowers the rescue boat, by means of a cable, and a stop ring on said cable operates in conjunction with the hoist stop fitting to cause the cable to rotate the A-shaped frame lifting arm forwards. A post assembly mounted outboard of the ship provides a support for the electrical winch and supports the A-shaped structure lifting arm. It presents the disadvantage that the rescue boat is at all times suspended outboard by virtue of the fact that the post assembly does not retract inboard with the limited movement of 20 degrees of the lifting arm around the base thereof. Nor does it present a suitable form for housing the rescue boat in an inboard position.

US6626126 describes a hoisting device suspended over an associated boat comprising suspended and telescopically displaceable horizontal hoist arms to move the boat from a position of inboard stowage to a position of outboard launching, and vice versa, whilst a raising device may move the boat vertically, wherein the raising device is fixed to the hoist arms and the vertical and horizontal movements may be realised independently, in a controlled manner. It is complex by virtue of the fact that it requires suspending the hoist arms and, consequently, an upper strong structure, such as a deck or beams having large projections. US6955519 describes a hoisting system including an elongate base having a rectilinear part and a leading part downwardly inclinable in relation to the rectilinear part. Through the interior slides a cradle transporting the boat from an interior withdrawn position to an interior position and, in order that it may be that of introduction into the water, said inclinable leading part must attain the water. It presents the disadvantage that it would not be utilisable when the height whereat the boat is stowed is very great, being the normal situation in large ships wherein the deck may be at dozens of metres above the level of the water.

US2009050046 divulges an assembly of hoists for launching a boat from a ship comprising two separate hoists, each whereof includes a substantially horizontal arm, a hoisting cable extending downwards from a suspension frame upon the boom and includes at least one fixing device at the end thereof, such that the hoists move between an inward position wherein the suspension frames extend inward and an outward position, wherein the suspension frames extend outboard rotating in a horizontal plane around the (vertical) axes of each of the hoists, and wherein the suspension frames are movable along the arms such that a distance between said suspension frames remains constant during the rotation of the arms between the two positions when the boat is moved from a parked position to the launching position. It presents the disadvantage that it requires a coordination of movements between both hoists.

To solve the foregoing problems, pivoting hoists or davits are known comprising a frame provided with one or more upper arms (for suspension, raising or launching the boat) supported by the corresponding columns which, in turn, comprise a supporting base or soleplate upon a fixed part of the ship, usually the deck thereof, the base being joined to said fixed part of the ship by means of an anterior horizontal articulation substantially parallel to the side the ship such that, on the frame pivoting about said articulation between two extreme positions, the boat is parked inboard or alternatively hung outboard to then lower it by means of cables of those hanging from the upper arms. For example, the patent document US2647269 shows a possible embodiment of this variant, wherein the articulation is complex and wherein the pivoting of the hoist is realised by means of ropes or cables joined to the hoist and which are also utilised for launching the boat. It presents the disadvantage that the davit is operated by gravity and controlled by cables (the same cable for raising and lowering the boat and for moving it out to the lowering position). In this version the ropes or cables are exposed to the action of corrosion and require constant inspection and maintenance and may fail at the moment of launching. In order to circumvent this disadvantage, nowadays the utilisation of hydraulic cylinders is selected. This is the most usual situation at the present time, there being two possible options: a first option wherein the cylinders are located within the interior of the davit upon the soleplate or base thereof, being whereat there is the necessary space, but having the disadvantage that in this position the extremities thereof cannot be applied at the most favourable points and presenting very unfavourable angles of thrust, this requiring cylinders of greater weight and cost, in addition to a larger and more powerful and expensive hydraulic unit. Furthermore, the overdimensioning of the thrust points of the davit and/or of the deck is required to support the greater stresses, the second option being disposition of the cylinders in the most favourable position, that is to say between the deck and the columns of the frame, however this option presents the problem of the cylinders being external to the davit, leaving them exposed to corrosion and, in the case of rupture of flexible hoses or seals, involving the spillage of the hydraulic fluid to the exterior and the consequent environmental problem. In addition, in respect of the invention, the following documents are known relating to the utilisation of rack and pinion assemblies in lifting:

US3924710 relates to a rack and pinion hoist focused upon worksite hoists to raise and lower a cage and disposing of a rack and pinion safety braking mechanism in the case of overspeed. It describes the corresponding reduction gearbox and the motor being supported upon the driveshaft, they being permitted to float in relation to the cage such that the gearbox is not obliged to support any lateral load upon the pinion, and the bearings within the gearbox solely require to support the weight of the gearbox itself, this permitting a limited movement of the motor with respect to the cage to absorb and reduce the shocks when the motor starts and stops. It only permits linear movements of the cage, with a fixed rack. The document US6023989 describes a transmission device for converting a torque from a rotary movement to a linear movement including a rack having a plurality of teeth and a pinion having rollers meshing with the teeth of the rack, with pressure provided therebetween. The rack has an arcuate tooth flank diametrically greater than each of the rollers of the pinion. The rack also has a tooth face having an approach profile progressively moving away from the path of contact of each of the rollers along which each of the rollers would otherwise engage with the tooth face. A plurality of each of the rollers of the pinion simultaneously mesh with the corresponding teeth of the rack. Another embodiment converts a torque between rotary and linear movement and comprises a pinion having a plurality of teeth and a rack having a plurality of rollers to mesh with the teeth of the pinion. The device achieves reduced transmission resistance, a silent intermeshing movement with no substantial noise and vibration, together with a reduced wear on the teeth and rollers. Similarly it only provides for a linear movement. The document EP2390220 describes a lift having a mobile car within a void, a rack extending along the void, the rack having a toothed profile with wave troughs and wave crests and a drive to the rack such that the drive interacts with the rack to move the cabin. The drive includes a roller pinion unit fixedly mounted upon a shaft and having a predetermined number of roller pinions disposed in a circle around the shaft and extending parallel to the shaft. The roller pinion unit interacts with the toothed profile of the rack. The drive furthermore includes a motor unit configured to rotate the shaft. Optionally, the drive includes a brake unit configured to act upon the shaft.

In all the foregoing cases the rack is disposed in fixed positions, by virtue whereof it may only realise linear movements without rotation. Consequently, they are not appropriate for realising movements of raising and lowering.

DESCRIPTION OF THE INVENTION

The drive mechanism for pivoting davits of the invention is applied to davits of the pivoting type, comprising a frame provided with one or more upper arms of suspension of a boat (whether lifeboats or auxiliary boats) or of a fender type protection supported by the corresponding columns, they in turn comprising a supporting base or soleplate upon a fixed part of installation the davit, the base being joined to said fixed part by means of an anterior horizontal articulation substantially parallel to the edge of said fixed part with the water (the side of the ship for example) to pivot the frame from a parked position of the boat inboard of the edge to another launching position outboard of the edge and, in accordance with the invention, it comprises: - at least a gear-rack assembly interposed between at least one of the columns of the frame and the fixed part of installation of the davit, wherein the rack comprises a single point of fixation to said fixed part disposed at one of the extremities thereof, and means of driving the gear (normally at least a motor or crank).

In this manner the force is applied at the most appropriate point such as to considerably reduce the power of the drive, permitting fixing the movement of the rack at a single extreme point to adapt to the curving movement of pivoting of the frame, thus permitting the implementation of a purely electromechanical drive in a davit, without the disadvantages of the utilisation of hydraulic cylinders, on considerably reducing the power requirements. Within the possible points of fixation upon the corresponding column, preferentially the zone will be selected disposed at a sufficient distance from the horizontal articulation and from the point of fixation of the rack to the fixed part of installation of the davit such as to achieve the minimum operating power necessary, normally being that wherein the travel of the rack along the gear is greatest, depending on the particular design of the frame in each case.

In a position of the frame corresponding to a parked position of the boat, the gear-rack assembly can be disposed substantially completely within the interior of the frame. In a position of the frame corresponding to a launching of the boat, the gear-rack assembly can be disposed at least partially within the interior of the frame. In particular, in a position of the frame corresponding to a launching of the boat, the gear and the means of driving the gear can be disposed substantially completely within the interior of the frame and the rack can be disposed at least partially within the interior of the frame.

In the present document, by fixed part of installation of the davit is to be understood the deck of a vessel or ship, or part of the structure of an oil rig or location or fixed structure adjacent to the water whereat the davit is installed.

Furthermore, the following additional advantages are achieved through the invention:

Substantial reduction of noise. - Reduction in forces.

Less consumption of power, both in normal and in emergency operation.

Reduction in the number of components (elimination of hydraulic system) and increase in efficiency.

Less deck loading (by virtue of the fact that the weight changes and the centre of gravity is different with respect to the utilisation of cylinders), this entailing less manufacturing costs.

100% electrical solution through total elimination of the hydraulic system. There is no risk of contamination through spillage of hydraulic oil.

Environmentally friendly.

Less maintenance. Optimisation of the electric accumulators, should the same be provided, achieving reduction in the size thereof.

However, as an additional unexpected effect, improved control is obtained of the speeds of operation and of the positioning, permitting greater safety in launching the boat together with greater manual drive facility in the case of supply failure simply by cranking.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows lateral views of the davit in parked or inner position of the boat and in launching or outer position, in a first variant of the invention.

Figure 2 shows a detail of the gear-rack assembly in said first variant, wherein the gear comprises a first pinion and the rack a rigid toothed track.

Figure 3 shows a magnified detail of the connection between the first pinion and the rigid toothed track. Figure 4 shows a side view of a davit in launching position in a second variant of the invention, wherein the gear-rack assembly comprises a pinion and the rack comprises an open chain or belt mounted upon a rigid rectilinear bar.

Figure 5 shows a detail of an assembly formed by a first pinion and rigid toothed track whereupon are disposed two tracks in parallel.

Figure 6 shows a detail of a gear-rack assembly having a pinion and a rectilinear drive chain mounted upon a rigid rectilinear bar. Figure 7 shows a detail of a gear-rack assembly having a pinion and a toothed belt mounted upon a rigid rectilinear bar.

Figure 8 shows a rear elevation view of a davit in a variant wherein the frame comprises two upper arms.

PREFERENTIAL EMBODIMENT OF THE INVENTION The drive mechanism (1 ) for pivoting davits (100) of the invention (see fig. 1 ) is applied to davits (100) of the type comprising a frame (2) provided with one or more upper arms (3) of suspension of a boat (4) supported by the corresponding columns (14), they in turn comprising a supporting base or soleplate (18) upon a fixed part (6) of installation of the davit (100) (the deck of a ship, for example), the base (18) being joined to said fixed part (6) by means of an anterior horizontal articulation (5) substantially parallel to the edge (7) of said fixed part with the water (the side of the ship in this example) to pivot the frame (2) from a parked position of the boat (4) inboard of the edge (7) to another position of launching outboard of the edge (7) and, according to the invention, it comprises: at least one gear (11)-rack (12) assembly (10) interposed between at least one of the columns (14) of the frame (2) and the fixed part (6) of installation of the davit (100), wherein the rack (12) comprises a single point of fixation (15) to said fixed part (6) of installation of the davit (100) disposed at one of the extremities thereof, and means of driving the gear (1 1).

The means of driving the gear (11 ) comprise very preferentially at least a motor (16), although they may be others, for example cranks.

Furthermore, it is provided that the gear (11 )-rack (12) assembly (10) is ideally located within the interior of the frame (2) this, for this purpose, being suitably hollow. This protects the assembly (10) from the elements and from spray, and especially the motor (16) of the gear (11 ). Furthermore, it additionally cooperates in producing a clear deck or fixed part (6) in the zone or fixed part of installation of the davit (100).

In order to achieve an adequate strength it is provided that the gear (1 1 )-rack (12) assemblies (10) may comprise one or more tracks (14) (double or triple) in parallel to distribute stresses. In fig. 5 there may be observed a double helicoidal gear (1 1) (having two tracks (14) having the teeth in V-form) and the double rack (12) thereof. Very preferentially the gear (11) is fixed to the frame (2) and the rack (12) is fixed to the fixed part (6) of installation of the davit (100) (as may be observed in the variants in figures 1 and 4), by virtue of the fact that in this manner the most complex part of the mechanism may be held upon the frame (2), the deck being clear in all situations. Furthermore, should these elements be within the interior of the frame (2) they are more protected.

A very preferential first variant of the invention shown in figures 1 to 3 provides that the gear (1 1 ) comprises at least a first pinion (11 a), and the rack (12) comprises at least a rigid toothed track (12a). This configuration prevents possible entanglements or elongations which may occur in other chain or belt variants and has very reduced maintenance, in addition to being the most economical. In this case the single point of fixation (15) of the rigid toothed track (12a) to the deck or fixed part (6) of installation of the davit (100) comprises an end hinge permitting the rotation of the track (12a) to adapt to the movement of lowering. The first pinion (1 1 a) may be of teeth or of rollers, the track (12a) being prepared for each case (it may correspondingly be of teeth of rollers).

In a second variant of the invention shown in fig. 4 the gear (1 1) comprises at least a pinion (11 b) and the rack (12) comprises an open chain or belt (12b) mounted upon a rigid rectilinear bar (120), the sole point of fixation (15) being an end hinge disposed upon the bar (120). In fig. 6 there may be observed a detail of the open chain or belt (12b) upon the bar (120) and of the pinion (11 b) connected to the same.

The open chain or belt (12b) may comprise either a rectilinear drive chain comprising the pinion (11 b), a pinion of radial teeth, or a toothed belt, the pinion (1 1 b) comprising a toothed pulley.

Moreover, provision is made for the possible disposal of elements to force the contact between gear (1 1 ) and rack (12), in the case of the rigid track these may be counterpressure pinions or counterpressure rollers (43) (see fig. 3) acting upon the face opposite to the first pinion (11 a) of the rigid toothed track (12a), or deflectors (19) or tensioners in the case of the chains or belts (see fig. 7). There has also been provided the disposition of a mechanical stop (20) upon the rack (12) to prevent it coming apart at the free extremity (see figs. 1 and 2).

As may be observed in detail in fig. 2, there has additionally been provided the possible disposition of a reducing transmission (21 ) between the motor (16) and the gear (1 1 ) to adapt the speed of commercial motors and the power thereof to the requirements of the movement of the davit (100), the gear (11 ) ideally being supported by bearings (23) on both sides to prevent the shaft thereof bending (see fig. 3).

For boats of large dimensions, such as those on large ships having large capacities of transport of persons, the invention has provided for the disposal of several gear (11 )- rack (12) assemblies (10) (see fig. 8) disposed upon the column (14) or columns of a large frame (2) necessary to carry a large boat (4), comprising at least an element of synchronisation between said assemblies (10) to prevent the launching or raising taking place in an uneven manner. Said elements of synchronisation may be, for example, synchronising drives (30) (for example, a shaft synchronising the pinions of the assemblies (10)) and/or an electromagnetic synchronisation (encoders (31) upon each gear (1 1 ) or travel sensors) and logic unit, not shown, coordinated with the supply of the corresponding motors (16). All the elements described may be rendered by means of any type of material and the most appropriate material will be selected in each case.

The nature of the invention having been sufficiently described it is declared that the description of the same and the preferential manner of embodiment thereof shall be interpreted in a non-limitative manner, and that it embraces the totality of the possible variants of embodiment which may be deduced from the content of the present memorandum and of the claims.