WO2018166654A1

WO2018166654A1 - Brake having permanent magnets for launching life-saving equipment

Info

Publication number: WO2018166654A1
Application number: PCT/EP2018/000128
Authority: WO
Inventors: Ørjan TVEIT
Original assignee: Heron Davits As
Priority date: 2017-03-31
Filing date: 2018-03-28
Publication date: 2018-09-20
Also published as: ES2685287B1; ES2685287A1

Abstract

Brake (1) having permanent magnets for launching life-saving equipment, characterised in that it comprises: - two coaxial parts having relative rotational movement therebetween around the common shaft (4), - wherein a first part comprises permanent magnets (6), and - wherein the second part comprises at least a solid body (9) of paramagnetic material adjacent to said magnets (6). such that the relative displacement thereof within the extent of the lines of flux induces eddy currents generating forces in opposition to the relative movement between the two parts.

Description

BRAKE HAVING PERMANENT MAGNETS FOR LAUNCHING LIFE-SAVING

EQUIPMENT

OBJECT OF THE INVENTION

The present invention relates to a brake having permanent magnets for the control of the speed of descent of life-saving equipment in emergency situations from the launching davits thereof. BACKGROUND OF THE INVENTION

The launching of life-saving equipment (lifeboats, emergency boats, life rafts, etc) from ships or other types of platform (quays, oil rigs, etc) is realised by means of hoists or davits. Said davits comprise a frame having upper arms wherefrom the boat is suspended by one or more points of suspension by means of ropes or cables. This frame may be pivoting, in which case it pivots about a horizontal axis parallel to the side such as to retract the boat to its inboard parked position or extended to an outboard launching position, wherefrom it will be launched, reeling out the ropes or cables of suspension from the pertinent winding devices (known as winches in the technical sector of the art of navigation, comprising an assembly of motor, reducer, and winding drum of the cable or rope). There are also other configurations wherein the davit is rigid (not pivoting) and on other occasions the movement of the boat out to the launching position is occasioned by gravity. Given that on large ships, and on other types of platform (oil rigs for example), the launching of the boat may signify the descent or raising thereof from dozens of metres in height, equivalent to several floors of a conventional land structure, and furthermore the launching of the boat normally occurs with persons within the interior thereof, it is very important to maintain a safe speed of descent and to implement means against dropping to prevent the free fall thereof in the case of breakdown of the winch or in the absence of electrical supply ('dead ship' situation).

At the present time the control of speed of descent when launching boats from davits is normally realised by means of centrifugal brakes or hydraulic brakes. The centrifugal brakes comprise a bell stator and brake linings mounted upon a rotor by means of supports pivoting in a radial sense, the rotor rotating within the interior of the bell stator such that, as the speed of rotation increases, the brake linings tend to open and make contact with greater or lesser force upon the interior of the bell stator, realising the corresponding braking in a manner similar to a centrifugal clutch. They present the disadvantage of the wear of the brake linings and of the exposure thereof to the marine environment and consequently require periodic inspections and replacements. Furthermore, in the case of failure of the brake linings during operation the brake ceases to function and may occasion the free fall of the boat. The hydraulic brakes comprise a flow control valve limiting the quantity of oil entering the hydraulic motor driving the winch. Moreover, they may cease to function in the case of rupture of the valve or flexible hoses. Additionally, in the case of rupture the spillage of contaminant hydraulic fluid occurs with the consequent environmental problem.

In hoisting in general there are also known instantaneous or progressive brakes for lift apparatus comprising wedges of plates or rollers triggered by the tension of a cable running through a speed limiter, being a centrifugal device which is blocked when the speed of rotation (corresponding to the linear speed of the cable joined to the cabin of the lift) exceeds a given speed. This brings about the blockage of the movement of the cable and the actuation of the wedges. It presents the disadvantage of complexity (it requires an auxiliary cable and the speed limiter) together with the maintenance of the speed limiter itself. In other technical sectors, for example self-propulsion, induction brakes are known, basically comprising electromagnets generating a magnetic field in the heart whereof there moves an induced rotor, formed in turn by windings wound upon cores of ferromagnetic material such that, supplying the electromagnets to a greater or lesser degree, a greater or lesser induced current is generated in the rotor together with the corresponding magnetic effects and eddy currents tending to oppose the relative movement between rotor and stator. It presents several disadvantages for the utilisation thereof in marine environments: in the first place, the cable windings are very prone to attack by the marine environment (corrosion, in the case of copper) and, in general, are prone to failure, whilst the protection thereof by means of hermetic coatings renders difficult the required dissipation of heat during the braking which may generate overheating and damage the installation thereof and, as a consequence, produce short- circuits or failures. In the second place, the requirement of electrical supply is not always available, for example in cases of dead ship where all electrical supply is lost, the disposition of auxiliary electrical supply being required in the best of cases.

DESCRIPTION OF THE INVENTION The brake of the invention presents a configuration permitting the utilisation of braking through induction when launching life-saving equipment (for example lifeboats on ships or oil rigs) without the need for electrical supply to the brake. Furthermore, it is a matter of a totally passive and robust element, having minimum maintenance and reliable operation in practically any situation.

The principle of operation thereof is based upon converting the dynamic braking energy into heat through eddy currents magnetically induced in the body of paramagnetic material (aluminium, copper, etc) (Joule effect). Along any looped route or line which may be considered in the body there will exist a variation in the magnetic flux inducing a current (Foucault current) opposing said variation, in conformity with Lenz's law.

According to the invention, the brake comprises: two coaxial parts presenting relative rotational movement therebetween (basically a stator and a rotor) around the common shaft, wherein a first part comprises permanent magnets, and wherein the second part comprises at least a solid body of paramagnetic material adjacent to said magnets such that the relative displacement thereof within the extent of the lines of flux induces eddy currents, generating forces in opposition to the relative movement between said two parts. In the present document the term adjacent signifies that the body lies within the extent of influence of the lines of flux of the magnets. Similarly, solid body signifies that it is a monobloc body (without windings), although it may carry machinings or perforations having any geometric configuration.

In order to make it operate the operator (situated within the boat or life-saving equipment, the davit being in the outer or launching position) simply pulls upon a cord (or other similar system), mechanically (or electrically) releasing the brake of the electric motor of the winch. Once this has been realised the magnetic brake comes into operation, making the boat fall at a controlled speed. Logically, the types of magnet and the position thereof, together with the geometry or separation, position and strength thereof and the size and geometry of the solid body, are calculated for each case as a function of the weight and load of the boat and the desired speed of descent. The following principal advantages are obtained from the configuration proposed:

It does not require electric current to activate electromagnets, this also permitting that the system be much more compact, simple and economic, achieving the life-saving equipment always falling at constant speed (normally 60 m/min in conformity with regulations of the sector).

It minimises the possibility of accidents.

It is free of wear and maintenance by virtue of the fact that there is no friction consequently there is no wear of components, furthermore it may operate under adverse conditions (for example, humidity, the parts being soiled or damaged, etc).

It also works in situations of overload without breaking. - It eliminates the hydraulic system.

Additionally, the following have been found to be further advantages or effects over and above those anticipated: In addition to serving for emergency drops, it assists in reducing the power of the motor in lowering in normal mode if it is connected or clutched to the same, consequently reducing the power required by the electric motor to lower the life-saving equipment in normal functioning by virtue of the fact that it assists in braking the load.

Smaller size, permitting locating it on the flange of the electric motor of the winch.

Several brakes may be situated in series to increase the strength of braking.

It may be installed directly or with the interposition of a mechanism of selective coupling (manual or automatic clutch).

It may adopt designs valid for all the versions of motors and reducers.

It may be easily adapted to different sizes, speeds and loads.

DESCRIPTION OF THE DRAWINGS Figure 1 shows a perspective view of a variant of the brake of the invention wherein a rotor having two first rotary discs, wherein the magnets are housed, are located at both sides of a stator comprising a second disc of paramagnetic material.

Figure 2 shows a diametral cutaway view of the brake of the invention according to the variant of figure 1 .

Figure 3 shows a diagram of another variant of the brake of the invention having the magnets in the stator and the solid body in the rotor. Figure 4 shows a diagram of the centrifugally sliding positioning of the magnets in guides of a rotary disc of a rotor.

Figure 5 shows a diagram of the positioning of the magnets in a parked and in an operational position.

Figure 6 shows a view of the positioning of the brake of the invention upon a davit in launching position.

Figure 7 shows a view of the positioning of the brake of the invention upon a davit in launching position in a variant wherein the winch is located at the base of the davit.

Figure 8 shows a detail of the coupling of the brake between the motor and the drum of the davit.

PREFERENTIAL EMBODIMENT OF THE INVENTION

The brake (1 ) having permanent magnets for launching life-saving equipment of the invention comprises (see figs. 1 and 2): two coaxial parts having relative rotational movement therebetween about the common shaft (4), - wherein a first part comprises permanent magnets (6), and wherein the second part comprises at least a solid body (9) of paramagnetic material adjacent to said magnets (6) such that the relative displacement thereof within the extent of the lines of flux induces eddy currents generating forces in opposition to the relative movement between the two parts.

In a very preferential manner, the magnets (6) are disposed in pairs (5), wherein each pair (5) comprises poles (7, 8) of opposite sign located face-to-face parallelly to the common shaft (4) such as to generate lines of flux between said opposite poles (7, 8), by virtue of the fact that in this manner they will present a greater quantity of flux, the solid body (9) of paramagnetic material being interposed between the magnets (6) of the pairs (5). One of the parts may comprise a rotor (1 1 ) comprising at least a first rotary disc (12), wherein are housed the permanent magnets (6), and the other part comprises a stator

(14) wherein the solid body (9) comprises at least a second disc (15) of paramagnetic material parallel to the first disc (12) and wherein are induced the eddy currents. In an embodiment of this variant, seeking the disposition of the magnets (6) in pairs (5), the rotor (1 1 ) will comprise at least a pair of parallel first rotary discs (12) located face-to-face and wherein are housed the permanent magnets (6) having opposite poles (7, 8), the second disc (15) belonging to the stator (14) interposed between the two first discs (12) of the pair. Furthermore, several pairs of first discs (12) may be implemented in a cascaded manner, advantage being taken of both faces of the same, and disposing therebetween the corresponding second discs (15).

The most simple embodiment of this variant is shown in figs. 1 and 2, whereby one of the parts comprises a rotor (1 1 ) comprising a pair of parallel rotary first discs (12) wherein are housed the permanent magnets (6) having opposite poles (7, 8) located face-to-face, and the other part comprises a stator (14) wherein the solid body (9) comprises a second disc

(15) of paramagnetic material interposed between the first discs (12) and wherein are induced the eddy currents. Additionally, through the mounting of the magnets (6) upon first discs (12), whether one first disc (12), two first discs (12), or more, the magnets (6) may be mounted upon the first discs (12) in radial guides (16), in the interior whereof are disposed springs (17) thrusting the same towards the interior, having the objective of varying the distance thereof to the common shaft (4) as a function of the speed of rotation, through the effect of the centrifugal force (see fig. 4), such that they attain the most favourable position of actuation, being more distant radially the greater the requirement of braking.

Logically, the invention also contemplates the alternative embodiment wherein one of the parts comprises a stator (24) comprising at least a first disc (12a) wherein are housed the magnets (6), and the other part comprises a rotor (21 ) having the solid body (9) comprising at least a second rotary disc (15a) of paramagnetic material and wherein are induced the eddy currents. Figure 3 shows a diagram of a variant of this embodiment wherein the stator (24) comprises at least two parallel first fixed discs (12a) (specifically two in the figure) and the rotor (21 ) comprises at least a second fixed disc (15a) of paramagnetic material (specifically one in the figure), wherein are induced the eddy currents, disposed between each two first discs (12). By virtue of the small size thereof and absence of electric supply, brake (1 ) may (see figs. 6, 7, 8) be ideally coupled to the motor (30) of the launching drum (33) of the life-saving equipment (31 ) (for example, a lifeboat) (on motor controlled davits (35)), for which purpose it comprises couplings (36) in the stator and keys (37) in the rotor for coupling to the shaft of the motor (30) of the launching winch of the life-saving equipment (31 ) (see fig. 1 ). A reducer (38) will normally be located between the motor (30) and the drum (33).

Although in the figures the magnetic brake (1) is situated between the motor (30) and the reducer (38) it may be disposed at any other location whereat it fulfils the function thereof, these variants not being shown in the figures, for example at the opposite extremity of the shaft of the motor, if it disposes of dual output, or removing the brake (1 ) from the axial position of the shaft of the motor (30)/drum (33) by means of a deviated transmission. This latter option presents the advantage that, by means of a multiplying or reducing transmission the speed in the brake may be increased such that the motor (30) does not rotate at high speeds in the case of emergency descent.

With the objective of disabling the operation thereof in case it may hinder the normal functioning of the drum (33), it is provided that the magnets (6) may be contained (see fig. 5) in housings (60), wherein they do not generate eddy currents by virtue of being beyond the extent of the solid body (9), comprising means of thrusting the same towards operating positions (61 ) whereat they will be situated within said extent and will generate these currents. Said means of thrusting may for example comprise a cam (62) actuated by a lever or other system of mechanical type.

Furthermore, the possible disposition of means of deblocking between the rotor and the shaft of the coiler is provided such that it may solely rotate during the descent of the life- saving equipment (31 ) and not during the ascent, having the same purpose. Said means of deblocking comprise, for example, a unidirectional bearing (45) (utilised as anti-return device) which may be appreciated in fig. 2 located upon the rotor (1 1 ). Said unidirectional bearing (45) may be conceptually similar to a bearing of rolling type, presenting the difference that the rotary movement between the two rings composing it is possible in solely one direction. This type of operation is rendered possible by means of a particular construction of the rolling elements themselves or of the ball races wherein they are housed which, in the preestablished direction of 'free' rotation, do not oppose the movement between the exterior and interior rings, whilst at the moment whereat the direction of rotation is inverted said elements oppose the movement, blocking the system. With the system 'blocked' the freewheels operate as a clutch permitting the transmission of drive/braking torque between shaft and housing.

Other means of deblocking may be by clutch or by means of a manual system (for example a guillotine type lever) lowering the magnets to the position thereof in the case of need. In terms of the permanent magnets (6), these ideally comprise magnets of neodymium, although they may be of any type of permanent magnet.

And in terms of the paramagnetic material, this ideally comprises aluminium or copper, although it may be of any type.

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.

Claims

1. Brake (1 ) having permanent magnets for launching life-saving equipment, characterised in that it comprises: two coaxial parts having relative rotational movement therebetween around the common shaft (4), wherein a first part comprises permanent magnets (6), and wherein the second part comprises at least a solid body (9) of paramagnetic material adjacent to said magnets (6).

2. Brake (1 ) having permanent magnets for launching life-saving equipment according to claim 1 , characterised in that the magnets (6) are disposed in pairs (5), wherein each pair (5) comprises poles (7, 8) of opposite sign located face-to-face parallelly to the common axis (4) such as to generate lines of flux between said opposite poles (7, 8), the solid body (9) of paramagnetic material being interposed between the magnets (6) of the pairs (5).

3. Brake (1 ) having permanent magnets for launching life-saving equipment according to any of the foregoing claims, characterised in that one of the parts comprises a rotor (1 1 ) comprising at least a first rotary disc (12) wherein are housed the permanent magnets (6), and the other part comprises a stator (14) having the solid body (9) comprising at least a second disc (15) of paramagnetic material parallel to the first disc (12) and wherein are induced the eddy currents.

4. Brake (1 ) having permanent magnets for launching life-saving equipment according to claim 3, characterised in that the rotor (1 1 ) comprises at least a pair of parallel first rotary discs (12) located face-to-face wherein are housed the permanent magnets (6) having opposite poles (7, 8), the second disc (15) belonging to the stator (14) being interposed between the first two discs (12) of the pair.

5. < Brake (1) having permanent magnets for launching life-saving equipment according to either of claims 3 and 4, characterised in that the magnets (6) are mounted upon the first discs (12) in radial guides (16) in the interior whereof are disposed springs (17) thrusting the same towards the interior having the objective of varying the distance thereof to the common axis (4) as a function of the speed of rotation through the effect of the centrifugal force.

6. Brake (1 ) having permanent magnets for launching life-saving equipment according to claim 1 or 2, characterised in that one of the parts comprises a stator (24) comprising at least a first disc (12a) wherein are housed the magnets (6), and the other part comprises a rotor (21 ) having the solid body (9) comprising at least a second rotary disc (15a) of paramagnetic material and wherein are induced the eddy currents.

7. Brake (1 ) having permanent magnets for launching life-saving equipment according to claim 6, characterised in that the stator (24) comprises at least two first parallel fixed discs (12a) and the rotor (21 ) comprises at least a second fixed disc (15a) of paramagnetic material disposed between each two first discs (12).

8. Brake (1) having permanent magnets for launching life-saving equipment according to any of the foregoing claims, characterised in that it comprises couplings (36) in the stator and keys (37) in the rotor for coupling to the shaft of the motor (30) of the launching winch of the life-saving equipment (31 ).

9. Brake (1 ) having permanent magnets for launching life-saving equipment according to any of claims 3 to 8, characterised in that the rotor (1 1 , 21 ) is connected to the motor (30) launching the life-saving equipment (31 ) by means of a multiplying or reducing transmission.

10. Brake (1 ) having permanent magnets for launching life-saving equipment according to any of the foregoing claims, characterised in that the magnets (6) are contained in housings (60) comprising means of thrusting the same towards operating positions (61 ).

1 1. · Brake (1 ) having permanent magnets for launching life-saving equipment according to claim 10, characterised in that the means of thrusting comprise a cam (62) actuated by a lever.

12. Brake (1 ) having permanent magnets for launching life-saving equipment according to any of claims 3 to 1 1 , characterised in that it comprises a coiler and means of deblocking between the rotor (1 1 , 21 ) and the coiler such that it may solely rotate during the descent of the life-saving equipment (31 ).

13. Brake (1 ) having permanent magnets for launching life-saving equipment according to claim 12, characterised in that the means of deblocking comprise a unidirectional bearing (45).

14. Brake (1 ) having permanent magnets for launching life-saving equipment according to any of the foregoing claims, characterised in that the permanent magnets (6) comprise magnets of neodymium.

15. Brake (1 ) having permanent magnets for launching life-saving equipment according to any of the foregoing claims, characterised in that the paramagnetic material comprises aluminium or copper.