Abstract:
An anti-rolling gyroscopic stabilizer for boats provides a stationary frame fixed to the hull, an oscillating frame and a flywheel. The angular velocity of oscillation of the oscillating frame is limited by hydraulic dampers. Elastic return elements are coupled to the dampers and urge the oscillating frame so as to orient the axis of rotation of the flywheel towards a given angular position in which the gyroscopic device acts with maximum efficiency.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an anti-rolling gyroscopic stabilizer for boats, comprising a stationary frame having, connected thereto, a frame rotatable about a first axis and supporting a flywheel rotatable about a second axis perpendicular to the first axis. 
     An anti-rolling gyroscopic stabilizer of the aforementioned type makes use of the gyroscopic effect in order to dampen the rolling oscillation of the boat on which the stabilizer is mounted. 
     The gyroscopic effect occurs when a mass, caused to rotate about a generic first axis, owing to the action of an external force is subject to a rotation about a second axis perpendicular to the first axis, thereby generating a precession movement of the first axis in a direction perpendicular to the plane defined by the first and second axes. 
     The gyroscopic stabilizer performs the aforementioned damping action, opposing rolling movement with a reaction which is in counter-phase with respect thereto. For example, if it is assumed that the rolling movement has a sinusoidal characteristic (usually in phase with the acting force, or with the wave, in the case of a boat), the ideal reaction of the stabilizer would have a characteristic, which is also sinusoidal, offset or out of phase by 180° with respect to the acting force. 
     Furthermore there exists the problem of preventing the action, exerted by the gyroscopic effect on the flywheel support elements, from being concentrated within time transients which are too short, so as not to stress these support elements excessively. The prior art envisages, as a solution to the aforementioned problem, the use of devices for damping the precession velocity, which act on at least one of the pivots connecting together the fixed frame, integral with the boat, and the frame supporting the flywheel. Generally, the flywheel frame is suspended in an oscillating manner with respect to the fixed frame. 
     Oscillation of the flywheel frame must be limited, not only in terms of velocity, but also in terms of angular amplitude, such that it does not adversely affect the gyroscopic effect which helps stabilize the rolling movement. In fact, with an increase in the oscillation amplitude, the rolling opposition function of the gyroscopic effect will tend to diminish all the more, while increasing yawing of the boat. Therefore, it can be deduced that maximum stabilization of rolling by the gyroscopic effect is obtained with amplitudes of the precession movement which are close to zero, with respect to the direction which the axis of rotation of the flywheel would assume, relative to a fixed reference point integral with the external frame, assuming a condition of the stationary frame/oscillating frame/flywheel being undisturbed by external forces. 
     On the other hand, damping elements intended to limit the amplitude and velocity of oscillation of the frame do not help restore the optimum configuration. This is because the damping elements prevent (or at least do not facilitate) the return of the axis of rotation of the flywheel into the position which it would have assumed, relative to a fixed reference point integral with the external frame, in the case of an undisturbed condition of the stationary frame/oscillating frame/flywheel assembly. 
     This functional deficiency results in two main problems which concern: the efficiency of the device, since the capacity of influencing stabilization of the rolling movement is limited, owing to the fact that there is no active solution for restoring the optimum configuration of the relative positions of stationary frame, oscillating frame and flywheel; the reactivity of the device, since it tends to remain in the disturbed configuration as a result of inertia. This prevents, for example, any counter-turning manoeuvre where a first turning movement to one side of the hull is followed rapidly by a second turning movement to the opposite side. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes all the aforementioned drawbacks by associating the aforementioned damping means with elastic means which, following a disturbance induced externally on the stationary frame/oscillating frame/flywheel assembly, reposition the stabilizer in its optimum operative configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structural and functional characteristics of a plurality of preferred, but non-limiting embodiments of an anti-rolling gyroscopic stabilizer according to the invention will now be described, with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view which shows an anti-rolling gyroscopic stabilizer for boats, according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional side view of the stabilizer according to  FIG. 1 ; 
         FIG. 3  is a perspective view of the stabilizer according to another embodiment; 
         FIG. 4  is a top plan view of the stabilizer according to  FIG. 3 ; 
         FIG. 5  is a cross-sectional view along the line V-V of the stabilizer according to  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before a plurality of embodiments of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. 
     With reference now to  FIGS. 1 and 2 , a gyroscopic stabilizer  10  comprises a stationary frame  12  which is integral with the hull of a boat. The stationary frame  12 , by means of uprights  14 , supports an oscillating frame  16  via hubs  24 . The frame  16  can be oscillated, with respect to the stationary frame  12 , about an axis A. 
     A flywheel  18 , rotatable about an axis V by means of a motor  20 , is connected to the oscillating frame  16 . A top plate  22  may be arranged so as to close the oscillating frame  16 . 
     The hub  24  comprises a pivot  28 , which extends along the axis A, and a flange  26 , which extends transversely with respect to the axis A. The flange  26  has crown wheel  27  on its outer contour. Elastically damping devices  30  are connected to the flange  26  by means of the crown wheel  27 . The devices  30  comprise, in the illustrated embodiment, a hydraulic damping element  34 , of the type known per se, which performs essentially the function of limiting the maximum velocity of oscillation of the oscillating frame  16 . Optionally, the hydraulic elements  34  are provided with suitable internal valves by means of which the hydraulic elements  34  are able not only to limit in the upper region the velocity of oscillation of the oscillating frame  16 , but also adjust it in a preset manner. 
     In other embodiment, the damping element  34  is of the pneumatic, and not hydraulic type. 
     The hydraulic elements  34  include, in the illustrated embodiment, a pair of single-acting telescopic dampers which have a same internal volume capacity and are connected hydraulically to each other by means of pipes, not shown, such that the emptying of one causes the filling of the other. The hydraulic element  34  comprises an outer cylindrical casing  35  which is fixed to the stationary frame  12  by means of fastening elements, not shown. 
     According to an advantageous embodiment, an elastic element  32  is coupled, by means of a stem  36 , to each hydraulic element  34 . The elastic element  32  exerts a recall force on the oscillating frame  16  so that the axis of rotation V of the flywheel  18  is arranged in the position which it would have assumed, relative to the stationary frame  12 , in the case of an undisturbed configuration of the stationary frame/oscillating frame/flywheel system. In this case, the undisturbed configuration, i.e. the relative position of the flywheel  18 , the oscillating frame  16  and the stationary frame  12  which ensures the maximum stabilization of the rolling movement, is obtained when the axis V of the flywheel  18  has a direction perpendicular to the supporting plane of the stationary frame  12  which is integral with the hull of the vessel. 
     The recall action, exerted by the elastic element  32 , is achieved by means of meshing of the crown wheel  27 , which is integral with the flange  26 , with a rack  40 , which is integrally joined to the stem  36  by means of a support rod  38 . 
     The elastic element  32  comprises a tubular seat  44  Which is fixed to the stationary frame  12  by means of fixing elements, not shown. The tubular seat  44  houses a helical spring  46  which has a distal end  46   a  to which an adjusting screw  50  is connected. A contact block  48 , which is integral with a proximal end  36   a  of the stem  36 , is connected to a proximal end  46   b  of the spring  46 . The expressions “distal” and “proximal” must be understood as referring to a reference point centred on the hub  24 . 
     A hollow cylindrical guide  49 , projecting from the contact block  48 , guides the spring  46  during its deformation, to a maximum travel position where an inner base  49   a  of the guide  49  abuts on a proximal end  50   a  of the screw  50 . By adjusting the screw  50 , it is possible to modify the end-of-travel position in which the inner base  49   a  of the guide  49  abuts against the proximal end  50   a  of the screw  50  in a fully compressed condition of the spring  46  where there is maximum inclination of the oscillating frame  16 . Moreover, in an advantageous embodiment, the screw  50  is used for adjustment not only of the end-of-travel, but also of the pre-tensioned condition of the spring  46 . In this way it is possible to vary the elastic response of the spring  46 . 
     Therefore, the oscillation of the frame  16  about the axis A is dampened in terms of velocity by means of the hydraulic elements  34 , opposed by the action of the elastic means  32 . Oscillation of the frame  16  is limited in terms amplitude by the maximum stroke of the elastic elements  32 . That maximum stroke is determined by the maximum distance between the inner base  49   a  of the guide  49  and the proximal end  50   a  of the screw  50 . 
     In order to prevent the stems  36  from betiding owing to the dual stress produced by the hydraulic elements  34  and the elastic elements  32 , the stems  36  are preferably guided by support structures  42  comprising a support housing  52 , integral with the stationary frame  12 , and a roller  54  rotatable on the stem  36 . 
     According to the embodiment shown in  FIGS. 1 and 2 , there are two single-acting dampers and two helical springs coupled thereto by means of stems provided with racks. According to another embodiment, not shown, a single double-acting damping element  34  is provided (capable therefore of working both under traction and under compression) connected to the crown wheel  27  by means of the rack  40  of a stem  36  having its proximal end  36   a  which is free, i.e. not connected to the elastic element  32 . On the other hand, the elastic element  32  may be mounted, instead, with respect to the hub  24 , in a mirror-image position diametrically opposite to the hydraulic element  34 . In turn, the elastic element  32  may be connected to the crown wheel  27  by means of the rack  40  of a stem  36  having its proximal end  36   a  free, i.e. not connected to the hydraulic element  34 . 
     According to another embodiment, not shown, the elastic elements  32 , instead of comprising the helical spring  46 , comprise air springs. In this case, the maximum compression stroke, instead of being between the proximal end  50   a  of the screw  50  and the end  49   a  of the guide  49 , will be optionally defined by the distance of two contact blocks situated inside the springs and integral with the outer flanges to which the flexible membranes of the air springs are fixed. 
     With reference now to  FIGS. 3, 4 and 5 , a further embodiment of a gyroscopic stabilizer according to the invention will be described. A gyroscopic stabilizer  59  comprises a flywheel  60 , an oscillating frame  62  and an external stationary frame  64 . The frame  64  can be integrally fixed to the hull of the boat. The oscillating frame  62  comprises in this example a base ring  62   a , two vertical uprights  62   b , which support the flywheel  60  by means of pivots  61 , and an inner ring  62   c . The base ring  62   a  is rotatable and concentrically seated inside the stationary frame  64 . 
     The flywheel  60  is rotatable about an axis B. Axis B is parallel to the plane in which the stationary frame  64  is fixed to the hull of the boat and perpendicular to the longitudinal axis of the boat. The oscillating frame  62  is instead rotatable about an axis C, which has a direction perpendicular to the fixing plane of the stationary frame  64 . 
     Therefore, a rolling oscillation about an axis perpendicular to the axis B of rotation of the flywheel  60  generates, owing to the gyroscopic effect, a rotation of the oscillating frame  62  about the axis C, with respect to the stationary frame  64 . 
     The stationary frame  64  comprises an outer ring  64   a  arranged on top of a ring-shaped base plate  64   b . The base ring  62   a  of the frame  62  oscillates concentrically with respect to the base plate  64   b . Preferably, the base ring  62   a  has, on its outer rim, a seat  87   b  which, when coupled with a matching seat  87   a  formed in the base plate  64   b , forms a seat  87  housing rolling members  86 , in the illustrated example, the seats  87   a  and  87   b  have a semi-toroidal shape and therefore, when coupled together, form a toroidal seat  87  able to house rolling balls. According to another embodiment, not shown, the seat  87 , which is suitably shaped, houses rolling rollers, instead of balls. 
     The rolling members  86  facilitate relative rotation of the base plate  64   b  and the base ring  62   a , allowing the oscillating frame  62  to be rotatable about the axis C. 
     Curved tracks  66 , each of which seats a spring  70 , are formed between the outer ring  64   a  and inner ring  62   c . Each spring  70  extends between a surface  68   b  of a fixed shoulder  68 , which is integral with the fixed frame  64 , and a rotatable bracket  74 , which is integral with the oscillating frame  62 . The springs  70 , optionally, are guided internally by a curved rod  72 , which is also secured at its ends to the surfaces  68   b  of the two shoulders  68 . The curved segment  77 , situated between the surfaces  68   a  of the two shoulders  68 , contains a curved or circular rack  82  on which a hydraulic operating machine  78  meshes, by means of a pinion  82 , which pinion  82  is rotatable about an axis K. The hydraulic operating machine  78  is a pump of the known type, contained inside a casing  79 , integral with the oscillating frame  62  by means of brackets  80 . 
     The rotation of the oscillating frame  62  about the axis C, due to the gyroscopic effect produced by the rolling movement of the flywheel  60 , is counterbalanced by the damping effect ensured by the hydraulic operating machine  78  and by the recall action due to the springs  70 , which urge the oscillating frame  62  back into a position of maximum efficiency (in the case in question, the position which ensures the transverse arrangement of the axis B of rotation of the flywheel  60  with respect to the longitudinal axis of the boat). 
     The recall action of the oscillating frame  62  into its position of maximum efficiency is ensured by the springs  70  which are actuated by the rotatable bracket  74  also integral with the oscillating frame  62 , such that the oscillating frame  62 , rotating about the axis C, by means of the rotating bracket  74 , receives the recall thrust of the springs  70  and returns into its operating position of maximum efficiency. 
     The main advantage of a stabilizer provided in accordance with the present invention, in the embodiment illustrated in  FIGS. 3, 4 and 5 , consists in the possibility of using a recall force which is provided by the springs  70  and allows restoration of the optimum operating condition of the stabilizer.