Patent Document

TECHNICAL FIELD 
     The invention is directed to a lowerable platform with an integrated float for watercrafts, according to the preamble of the first claim. 
     STATE-OF-THE-ART 
     Lowerable platforms, in particular for swimmers, divers and tenders, are known in the art and described, for example, in the patents DE 196 02 331, US 2001/0027740 A1, or partially lowerable swimming pools with walkable surfaces, as described in the patent EP 0253745. 
     Also known are spacer-type fastening means with height adjustment for outboard motors on the stern of watercrafts, in order to attain by the height adjustment speed advantages, and to not take up space in the cockpit of the watercraft when the outboard motor is tilted upward, as described in the U.S. Pat. No. 3,075,490 or U.S. Pat. No. 4,657,513. 
     DESCRIPTION OF THE INVENTION 
     It is an object of the invention to attach on the stern of a watercraft a lowerable platform, also for applications with outboard motors, which also has buoyancy means for keeping the lowerable platform unaided above the water line, whereby the buoyancy means provide, at a corresponding speed of the watercraft, also hydrodynamic support, or can form a container for various technical means. 
     Lowerable platforms have a considerable tare weight and essentially include the deformation-resistant lowerable platform itself, pivoting arms, articulated joints, hydraulic cylinders and fastening components on the stern of the watercraft. A lowerable platform can be used to enhance the comfort for swimmers, divers, to get in and out of the water, or to relax on the platform and to just sit at the same level as the water line and be splashed by the water and/or for putting a tender or jet ski in the water, which can be parked and secured in dry condition on the lowerable platform when not in use. 
     Persons and the tender vehicle can weigh many times the tare weight of the lowerable platform, thus representing a large load for the stern structure of a watercraft. Such weight can also substantially change the trim of a watercraft, even at low speed, and many even cause the propeller of the bow thruster to partially rise above the surface, so that port maneuvers can no longer be effectively performed. The dynamic stresses in the stern region of a watercraft are also considerably greater when the watercraft is moving through waves and when at the same time a tender or jet ski is attached on the lowerable platform. The hydraulics must also be able to permanently absorb the full weight and the impact from the waves of the lowerable platform, possibly supported only by hooks and bolts which help to prevent the lowerable platform from becoming detached from the secured position. 
     The invention solves these problems by providing the lowerable platform with buoyancy means which help to absorb the tare weight or the weight of the useful load by way of the floats, thereby additionally improving the safety of the moving watercraft, supporting the trim of the watercraft and ensuring that the lowerable platform cannot be uncontrollably lowered, and that the fluid cylinders need not move large loads. The pivot arms can then have a much thinner and lighter shape. 
     Because the platform is lowered by about 0.6 to about 1.5 m below the water line, it is technically not difficult to provide the buoyancy means with technical means, such as trim flaps, steering rudder, underwater lights, exhaust gas piping, extendable stilts, transverse jet rudder and the like, and to route the hydraulic and electric lines accordingly. The buoyancy means can have openings, so that pivot levers can freely move therein and are protected from environmental harm, within the protection is provided also to the swimmers, because they cannot get caught in the mechanism of the pivot arms. 
     The buoyancy means can be constructed as one unit or made of modules and are suitably attached to the lowerable platform. To provide optimal buoyancy with respect to the tare weight and the weight of the useful load, variable hollow bodies can be provided in the buoyancy means, so that depending on the size of a hollow body, this can produce more or less buoyancy, so that positive weight balancing can be performed easily and accurately. 
     The height of the contact position of the platform on the stern can be limited, on one hand, by the mechanical properties of the pivot arm or the fluid cylinders or, on the other hand, with a mechanical limit stop placed between the platform and the rear wall of the watercraft. This limiting feature can be implemented by aligning the buoyancy means with the bottom of the watercraft hull so that they are subjected to the same flow, or by forming a corresponding step. Alternatively, limit stop on the platform or on the buoyancy means can be varied, while the watercraft is moving, depending on the speed of the watercraft, so that the buoyancy means are more or less wetted by the water flow. 
     In a particular application, the lowerable platform can be attached to a watercraft having an outboard motor. Such watercraft leave very little space behind the motors, because the motor must be pivoted upward when the propeller hits bottom or in the rest position, so that according to the invention a means, on which the lowerable platform is located, is interposed between the watercraft and the outboard motor, so that the lowerable platform can be lowered laterally. Such an embodiment would not be realistic without a float, because the watercraft could tilt strongly to the side when someone walks on the lowerable platform, in particular with the solution having an additional horizontal extension, which would compromise the safety and would be detrimental for a substantially tilt-free lowering of the platform. 
     This is attained with the invention with the features of the first claim. 
     The core idea of the invention is to reduce loading of a lowerable platform with respect to the stern of a watercraft, to safely maintain the position of the lowerable platform, to guarantee the trim and roll stability of the watercraft, in particular when applying a lowerable platform in conjunction with outboard motors, and to use the lowerable platform as means for simultaneously attaching various technical means in the stern region, as well as to improve the hydrodynamic properties of the watercraft, without requiring additional installation work on the stern of the watercraft. 
     Additional advantageous embodiments of the invention are recited in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will be described hereinafter with reference to the drawings. Identical elements in the various figures have the same reference symbols. 
         FIG. 1  shows schematically a side view of the lowerable platform with the float and integrated technical means, the lifting mechanism and a self-lock; 
         FIG. 2  shows schematically a side view of the lowerable platform with the float in a horizontally extended position and the lifting/sliding mechanism; 
         FIG. 3  shows schematically a side view of the lowerable platform with the float and the lifting/sliding mechanism in the horizontally extended and additionally raised position, as well as a barrier; 
         FIG. 4  shows schematically a top view of a watercraft with an outboard motor with laterally extendable and lowerable platform with a float attached thereto, in the laterally extended position; 
         FIG. 5  shows schematically a side view of the lowerable platform with the float and the lifting/sliding mechanism in the horizontally extended position, with a tender boat mount; 
         FIG. 6  shows schematically a stern view onto a watercraft with a lowerable platform with modular floats and integrated lifting mechanisms; 
         FIG. 7  shows schematically a side view of the lowerable platform with the float, with a movable mechanical height limit and lock, as well as a controller for the working cylinder by way of the rotation speed or speed of the watercraft; 
         FIG. 8  shows schematically a side view on a float with integrated stackable hollow bodies; 
         FIG. 9  shows schematically a side view on a float with adjustable volume of the hollow body, manually or automatically via sensors; and 
         FIG. 10  is a schematic diagram of the working cylinder control based on the sensors, lift position, rotation speed, gear position and Z-drive position. 
     
    
    
     Only the elements required for a fundamental understanding of the invention are schematically illustrated. 
     APPROACH FOR IMPLEMENTING THE INVENTION 
       FIG. 1  shows schematically a side view of the lowerable platform  1  with the float  2  attached thereto, which is a watertight hollow body  43  illustrated with an air volume L and partially submerged, as illustrated by the waterline WL. However, the watertight hollow body  43  may also contain a water-repellent light foam with an equivalent air volume L. The lifting mechanism  3 , consisting of a working cylinder  4  as well as a lower pivot arm  5  and an upper pivot arm  6 —representing a parallelogram, whereby at least two parallelograms are mounted for each lowerable platform  1 —and are attached accordingly on the lowerable platform  1  or on the float  2  and are connected on the opposite side to the stern  8  of the watercraft  10  by way of an articulated joint mount  7  with the screw connection  9 . 
     The float  2  can also include various technical means  13 , for example trim flaps  13   a , underwater lighting, rudder elements and the like, wherein the technical means  13  are separated from the float  2  to prevent water from entering the hollow body  43  of the float  2 . This is effectively accomplished by filling the hollow body  43  with foam. 
     The lift limiting means  11  have a large a surface as possible to avoid localized pressure exerted on to the stern  8 , while simultaneously allowing adjustment of the upper contact position of the lowerable platform  1 . The lowerable platform  1  is lowered, optionally below the water line WL, as indicated by the lifting/pivoting line HS, by activating the working cylinder  4  on the lifting mechanism  3 . 
     Due to the buoyancy force A generated in the float  2 , which is produced by the air volume L and corresponds to the static buoyancy D 2 , the lowerable platform  1  is not lowered by gravity, but is instead pushed into the lowering direction by the thrust force K 1  of the working cylinder  4 . This has the advantage that in the event of a failure of the hydraulic, the lowerable platform  1  is automatically raised by the buoyancy force A, so that the working cylinder  4  therefore never has to push the entire tare weight of the lowerable platform  1  and of the lifting mechanism  3 . A self-lock  12  is attached on the stern  8 , so that when the lowerable platform  1  is raised by the buoyancy force A to the lift limiting means  11 , the platform  1  is automatically secured with the self-lock  12  in the contact position and the float  2  also smoothly fits the hull  10   a  for optimal flow S during travel. The self-lock  12  is released by activating the locking cylinder  41 . The self-lock  12  is constructed to hold the position of the lowerable platform  1  even when the watercraft is moved to a dry dock. 
     If a tender boat  27  or people are on the platform  1  and if the useful load N is greater than the buoyancy force A, then the working cylinder  4  brakes the lowering of the platform and supports lifting the platform  1  with the useful load N by applying the pulling force K 2 . 
     The float  2  can also have a hydrodynamic shape, from which the watercraft  10  can benefit with respect to the stability, fuel consumption and the like. The float  2  can also have a float lock  12   a , so that the lifting mechanism  3  is not subjected to uncontrolled forces from large hydrodynamic forces caused by the flow S; instead, the forces are already absorbed on the float  2 , preferably in the lower region thereof. The float lock  12   a  can be passive, in that when the platform  1  contacts the stern  8 , a formfitting coupling  12   b ,  12   c  of the float  2  with the stern  8  is produced, or active where a second self-lock  12  is used in conjunction with a locking cylinder  41  that can be unlocked. 
     Of course, the hydraulics which may be double-acting, can also be implemented pneumatically or with an electric spindle drive, and a linear rail system can be substituted for a parallelogram of the lifting/pivoting region HS. 
       FIG. 2  shows schematically a side view of the lowerable platform  1 , with the float  2  attached thereto, in the horizontally extended position P, indicated by the arrow X, which is achieved with a sliding mechanism  14  located under a second fixed upper platform  1   a . The sliding mechanism  14  can be a slide rail or a rail/roller combination, so that the lowerable platform  1  can be moved back and forth horizontally on the lifting support  15 . The horizontal displacement is performed either manually or with a horizontal working cylinder  31 . The lifting support  15  can simultaneously also form a mount for the pivot arms  5 ,  6 . When the lowerable platform  1  slides horizontally, the attached float  2  is moved by the buoyancy force A and therefore only slightly changes the trim of the watercraft  10 , even when a tender boat is attached, as compared to a variant without floats  2 . 
     The lifting support  15  can also be raised so that the lowerable platform  1  attains a position above a shortened upper platform  1   a , and the lowerable platform  1  is moved, by way of un-illustrated openings in the floats  2 , horizontally according to the arrow X to an upper lift limiting means  11   a , where it can be placed on the upper platform  1   a.    
       FIG. 3  shows schematically a side view of the lowerable platform  1  with the float  2  attached thereto in the horizontally extended and additionally raised lifting position P 1 , as indicated by the vertical arrow Z. By completely extending the lowerable platform  1  beyond the region of the upper platform  1   a , the lift on the working cylinder  4  can be additionally raised, so that the lowerable platform  1  forms a plane with the upper platform  1   a . In this way, a very large flat platform surface is attained, which can be used as an additional standing surface for persons and goods and which can provide sufficient buoyancy due to the float  2 , so that the watercraft can does not become submerged in the stern region. To protect the persons and goods, insertion element  16 , for example holes, are provided in the lowerable platforms  1 ,  1   a  for insertion of barrier elements  17 , such as posts  17   a  with rope barriers  17   b.    
       FIG. 4  shows schematically a top view onto a watercraft  10  with an outboard motor  19  with laterally extendable and lowerable swim platform  1  having a float  2  attached thereto. One or more supports  20  which support a cross brace  21  and a freestanding transverse platform  1   b  are located on the stern  8 , with the articulated joint mount  7  and the lifting mechanism  3  attached to one support  20 , wherein the lifting mechanism  3  allows the lowerable platform  1  to be pivoted out transversal to the travel direction of the watercraft  10 . The lowerable platform  1  can be positioned above or below the transverse platform  1   b , or the transverse platform  1   b  covers only one half of the area between the cross brace  21  and the stern  8 , indicated by the measure M, so that the lowerable platform  1  can operate without horizontal lift X and rotated directly into or out of the water. The cross brace  21  supports the outboard motor  19 , or several, as well as the cover  22 , so that a safe separation exists between the swimmer on the lowerable platform  1 , the lifting mechanism  3  and the outboard motor  19 , in particular the propeller of the outboard motor, also during high waves. 
     Damping means  18  for damping the vibrations from the outboard motor  19  can be interposed in the screw connection  9  between the support  20  and the stern  8 , to prevent to the greatest extent possible a transmission of vibrations from the motor to the watercraft  10 . 
       FIG. 5  shows schematically a side view of the lowerable platform  1 , with the float  2  attached thereto, in the horizontally extended position P, wherein the lowerable platform  1  have a tender mount  23 , which is at one end fixedly connected with the lowerable platform  1  by way of an articulated joint  24  and which has at the other end a movable roller pair  25 . The tender mount  23  can have a sensor  26  which informs the operator of the watercraft or the controller  38  if a tender boat  29  is located on the tender mount  23 , or if it is properly positioned. The tender mount  23  can also have corresponding un-illustrated mounting devices for securely holding the tender boat  27  on the watercraft  10 , as indicated by the mounting device sensor  58 . If the tender boat  27  rests on the tender mount  23  and the lowerable platform is in the position P, then the buoyancy force A produced by the float  2  preferably fully compensates the useful load N on the lowerable platform. If the lowerable platform  1  is oriented horizontally with respect to the stern  8 , then the tender mount  23  secured to the articulated joint  24  moves up the ramp  28  of the upper platform  1   a  on its roller pair  25 , continues until shortly before the end of the horizontal movement, descends the second ramp  29  into the opening  30  having a corresponding hole dimension, so that the tender mount  23 , or the roller pair  25 , now again rests directly on the lowerable platform  1 , thereby unloading the upper platform  1   a.    
       FIG. 6  shows schematically a stern view onto a stern  8  with a lowerable platform  1  with attached modular floats  2   a  and integrated lifting mechanisms  3 . If an obstacle  34  is located on the stern  10 , such as a Z-drive or an exit opening of a jet drive or the like, then it makes little sense to use a continuous float  2 , but rather corresponding modules which can be quickly and easily installed individually on the lowerable platform  1 . These modules can also perform hydrodynamic tasks and can also include technical means  13 . Advantageously, watercrafts  10  can also have different widths, while the slope of the ship&#39;s bottom is mostly the same. For example, a certain modular float  2   a  with a slope of 19° can advantageously be attached to a watercraft  10  having a width of 3 m or 4 m, together with a suitable dimensioned lowerable platform  1 . 
     Besides lowering the platform  1  below the water line (WL) and then raising it, it may be desirable to leave the platform  1 , e.g., in a submerged position and have the swimmers instead use a swim ladder. For this purpose, a telescopable swim ladder  33  is provided which, on one hand, is rotatably attached to the stern  8  or the platform  1   a  and, on the other hand, is attached to the float  2 , with the swim ladder  33  being shortened or extended according to the lift/pivot line. 
       FIG. 7  shows schematically a side view of the lowerable platform  1  with an attached float  2 , wherein the lifting height of the float  2  is limited by a variable limiting means  11   b , so that the bottom edge U of the float  2  is located in the water flow S, or alternatively is only partially wetted or can be completely moved out of the flow. The lift may also be limited by the working cylinder  4 . The length of the watercraft can then be changed and, if desired, the submerged length of the hull  10   a  of the watercraft  10  can be shortened or lengthened the watercraft  10  by submerging the float  2  arranged on the lowerable platform  1 . Tests on hydro-gliding watercrafts  10  have shown that it is advantageous up to a certain speed to have an additional hull length exposed to the water flow, because the additional hull length produces additional hydrodynamic buoyancy D 1 , whereas after further increase in speed, the friction on the additional hull length adversely affects efficiency. A measurement transducer  37  which records the rotation speed and the travel speed  37 , respectively, can transmit a command to the hydraulic units  39  via a controller  38 , to retract or extend the working cylinder  4 , wherein the effective position is acknowledged by the position measuring sensor  40 . When the working cylinder  4  is operated, the locking cylinder  41  is first unlocked to release the lock  42 , which can be a toothed gear, allowing the float  2  to move freely. The lock  42  allows various fixed positions, so that the float  2  can be locked at each full lift position H, so that a watercraft can with the lowerable platform  1  can safely jump over waves. 
     A simpler way to affect the hull length of a sliding watercraft  10  as a function of speed is to install one or more step edges U 1 , U 2  on the lower edge U of the float  2 , because the faster a hydro-gliding watercraft  10  with V-shaped hull travels, the higher it lifts out of the water, so that it is desirable to further shorten or decrease the friction surface at the hull end. 
     Also contemplated is a solution wherein the lowerable platform  1  is not moved when adjusting the float ( 2 ), and wherein instead the variable lifting limit  11   b  is located between the platform  1  and the float  2 , with un-illustrated variable spacers allowing a correct adjustment of the float  2 . The height can also be varied manually or with hydraulic or electrical means. 
     Accordingly, there is always a buoyancy A on the float  2 . When the watercraft  8  is at rest, the float  2  produces a static buoyancy D 2 . When the speed of the watercraft  8  increases, then the static buoyancy D 2  is reduced and dynamic buoyancy D 1  is created. The two types of buoyancy, either the first or the second type or the combination, are combined here to form the buoyancy A. 
       FIG. 8  shows schematically a side view on a lowerable platform  1  with an attached float  2  having a basic fill level  35  integrated in a hollow space  43 , as well as stackable hollow bodies  44  each having an air volume L 1 , which are secured on the bottom section  47  of the float  2  by using, for example, a threaded rod  45  and a nut  46 . Instead of using air in the hollow bodies  44 , these can also be filled with foam. The opening  48  allows the hollow body  43  to be filled with water or to be drained, as illustrated by the arrow E. The boatyard or the ship&#39;s owner can thereby balance the buoyancy A on the float  2  and accurately set a positive, neutral or negative total buoyancy with respect to the tare weight or with respect to the additional useful load, and accurately adjust the desired value. 
       FIG. 9  shows schematically a side view on a float  2  with an adjustable hollow body  49  integrated in the hollow space  43 , for example in form of a bellow, wherein the air volume L 2  in the bellow can be varied manually or automatically with a pressure sensor  50  or a tender sensor  51 . The volume is increased or decreased through the line  52  using an air pump  53 . Automatic filling or venting is triggered by a pressure sensor  50  which measures the forces at the pivot arm  4  or  5 , wherein the measured pressure value is transmitted to the controller  38 , which in turn transmits the command to the air pump  53  and changes the volume in the adjustable hollow body  49  until the pressure sensor  50  indicates the desired value. The same applies to the tender sensor  51 , which measures a predetermined weight of a tender boat  27  via the sensor  26  and thereby controls the effective useful load N by blowing into or venting from the adjustable hollow body  49  a corresponding air volume L. By increasing or decreasing the volume of the adjustable hollow body  49 , the hollow space  43  is filled through the opening  48  with more or less water, thereby varying the buoyancy, while always maintaining a basic fill level  35 , and hence a basic buoyancy A. 
     Instead of air, any medium lighter than water can be selected. 
       FIG. 10  is a schematic diagram of the control of the working cylinder  4  with the controller  38  based on the various sensors  32 ,  40 ,  54 ,  55 ,  56 ,  57 ,  58 , such as the horizontal lift measurement sensors  32  of the horizontal working cylinder  31 , travel position  40  of the working cylinder  4 , rotation speed level  54 , gear position  55 , Z-drive position  56 ,  57 , with the latter subdivided in turn position  56  and excursion position  57 , as well as mounting device sensor  58  and travel position sensor  32  of the horizontal working cylinder  31 . For safety reasons, the watercraft  10  should not be operated with the platform  1  lowered, so that the transmission is locked when the engine is operating, so as to prevent travel, or only slow travel is permitted by limiting the rotation speed of the engine. If the tender boat  27  is still mounted on the tender mount  23 , or on the lowerable platform  1 , as indicated by the mounting device sensor  58 , then the lowerable platform  1  cannot be lowered past a predetermined lift value. The lowerable platform  1  should also not be extended beyond a predetermined value, as long as to the obstacle  34 , for example the trim position  56  and the excursion position  57  of the Z-drive, are not with in a predetermined position field, because the housing of the Z-drive could otherwise damage the lowerable platform  1 . 
     It will be understood that the invention is not limited to the illustrated and described exemplary embodiments. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  lowerable platform 
           1   a  upper platform 
           1   b  transverse platform 
           2  float 
           2   a  modular float 
           3  lifting mechanism 
           4  working cylinder 
           5  lower pivot arm 
           6  upper pivot arm 
           7  articulated joint mount 
           8  stern 
           9  screw connection 
           10  watercraft 
           10   a  watercraft hull 
           11  lift limiting means 
           11   a  upper limiting means 
           11   b  variable limiting means 
           12  self-lock 
           12   a  float lock 
           12   b  coupling element  1   
           12   c  coupling element  2   
           13  technical means 
           13   a  trim flaps 
           14  slider mechanism 
           15  lifting support 
           16  insertion elements 
           17   a  post 
           17   b  rope barrier 
           18  damping means 
           19  outboard motor 
           20  support 
           21  cross brace 
           22  cover 
           23  tender mount 
           24  articulated joint 
           25  roller pair 
           26  sensor 
           27  tender boat 
           28  ramp 
           29  second ramp 
           30  opening 
           31  horizontal working cylinder 
           32  horizontal lift measurement sensor 
           33  swim ladder 
           34  obstacle 
           35  basic fill level 
           36  propeller 
           37  measurement sensor 
           38  controller 
           39  hydraulic unit 
           40  distance sensor 
           41  locking cylinder 
           42  lock 
           43  hollow space 
           44  hollow body 
           45  threaded rod 
           46  nut 
           47  bottom part 
           48  opening 
           49  adjustable hollow body 
           50  pressure sensor 
           51  tender sensor 
           52  supply line 
           53  air pump unit 
           54  rotation speed level 
           55  gear position 
           56  Z-drive trim position 
           57  Z-drive excursion position 
           58  mounting device sensor 
           40 ,  54 ,  55 ,  56 ,  57 ,  58  sensors 
         WL waterline 
         HS lift/pivot line 
         A buoyancy 
         D 1  hydrodynamic buoyancy 
         D 2  static buoyancy 
         L air volume 
         L 1  air volume stackable 
         L 2  air volume variable 
         X horizontal lift 
         Z raised lift 
         P extended position 
         E water exchange 
         H lift position 
         S (water) flow 
         U bottom edge 
         U 1 , U 2  stepped edge 
         N useful load 
         M dimension transversal platform small

Technology Category: 7