Patent Publication Number: US-11377188-B2

Title: Saildrive arrangement

Description:
This application is a national stage completion of PCT/EP2018/051493 filed Jan. 23, 2018 which claims priority from German Application Serial No. 10 2017 203 979.5 filed Mar. 10, 2017. 
     FIELD OF THE INVENTION 
     The present invention concerns a saildrive arrangement with an upper unit to be positioned inside a hull of a sailboat and a lower unit which is arranged to protrude from the bottom of the hull, wherein the upper unit comprises an input shaft to be connected to an engine and the lower unit comprises a propeller shaft. The invention further relates to a sailboat with a hull and with a corresponding saildrive. 
     BACKGROUND OF THE INVENTION 
     In recent years saildrives have become more and more common on modern sailboats. A saildrive is a motorized drive system for a sailboat. The horizontally aligned input shaft of a typical saildrive is driven by an inboard engine. 
     Said input shaft drives via an upper bevel gear mechanism a vertical intermediate shaft extending downward through the bottom of the sailboats hull. The input shaft and the upper bevel gear mechanism are parts of an upper unit which is fastened inside the hull. The intermediate shaft drives at its lower end via a lower bevel gear mechanism a horizontal propeller shaft which is supported in a lower unit of the saildrive beneath the hull. There are steerable saildrives which have a pivotable lower unit, which can be turned around a vertical axis to influence the steering of the sailboat and there are saildrives with a fixed lower unit. Sailboats with a fixed lower unit do the steering mainly by the rudder of the sailboat. 
     Traditional sailboat propulsion systems instead have a horizontal output shaft extended rearward from the engine. The output shaft being coupled to a propeller shaft which extends through the stern via a stuffing box and the propeller is mounted at a downward angle. Compared to these traditional sailboat propulsion systems a saildrive takes less space in the stern of the sailboat, its propeller shaft is oriented horizontal with the effect of high thrust efficiency, and it causes less vibration and noise during operation. 
     It is known for a long time that a sailing vessel which can also be driven by a propeller faces undesired drag by the propeller when the vessel is under sail. A solution for this problem has already been proposed in U.S. Pat. No. 278,182 in the year 1882. This solution proposed a locking device on the propeller shaft for locking the propeller in such position that its two blades will be maintained in a position behind a stern-post when desired. 
     Another possibility to minimize drag losses of a propeller is the use of folding propellers. A folding propeller is a type of propeller whose blades automatically fold out when the propeller shaft rotates at least with a certain speed, and then fold back when rotation stops. Generally it is intended to have the blades of the folding propeller fold in when the engine is stopped in order to reduce drag in this situations. But even with folded blades of such a folding propeller the water flow around the blades during sailing can force the propeller into rotation, thus leading to partially, if not completely, open blades which would again result in undesired drag for the vessel. 
     In the U.S. Pat. No. 7,506,737 B2 it is proposed to use a locking device on an output shaft of a marine reversing gear assembly which can be used with a traditional sailboat propulsion system. The locking device in this marine reversing gear assembly locks the output shaft by the energizing force of a locking spring when the combustion engine is not operating. Essential parts of the locking device are fixed on the external surface of a housing that supports the output shaft. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a saildrive arrangement which allows a saildrive and a sailboat with improved performance and efficiency. These objects are attained by the present invention. 
     The present invention provides a saildrive arrangement comprising an upper unit to be positioned inside a hull of a sailboat and a lower unit which is arranged to protrude from the bottom of the hull. The upper unit comprises an input shaft to be connected to an engine and the lower unit comprises a propeller shaft. A brake to lock the rotational movement of the propeller shaft is located in the upper unit. This means that all parts of the brake are located inside the hull. The brake can be located inside a housing of the upper unit. The rotation of the propeller shaft can be stopped and locked by the brake so that a propeller which is fixed to the propeller shaft cannot rotate. 
     An important aspect of the invention is the fact, that any element of the saildrive arrangement which is located outside the hull will cause more disturbances in the water flow and undesired drag. Any additional element outside the hull increases the space outside the hull which is necessary to accommodate the element, for example in a casing of the lower unit. One aim of the invention is therefore to minimize the amount of elements outside the hull and to integrate as much of the elements as possible inside the hull in a preferably compact construction. 
     The location of the brake in the upper unit, hence inside the hull instead of outside, helps to reduce the protrusion of saildrive elements into the water flow paths around the hull, thereby reducing unwanted disturbances in the water flow around the hull and around the lower unit of the saildrive. This improves the planing characteristics of the sailboat and the thrust efficiency of the saildrive. 
     Generally the invention can be applied to saildrives with fixed blade propellers and to saildrives with folding propellers. In case of a folding propeller, the propeller blades will stay in the folded in condition due to the locked propeller shaft. The undesired drag in the water flow around the lower unit of the saildrive with the propeller can be significantly reduced. This allows higher speed of the sailboat. Reduced fuel consumption can be achieved when the sailboat is driven by a first saildrive while the engine of a second saildrive is not running and the second propeller is folded in due to the locked second propeller shaft. 
     According to a preferred embodiment the upper unit of the saildrive arrangement comprises an upper bevel gear mechanism connecting the input shaft to an intermediate shaft and the lower unit comprises a lower bevel gear mechanism connecting the intermediate shaft to the propeller shaft. This means that the intermediate shaft extends from the upper unit to the lower unit connecting the upper bevel gear mechanism with the lower bevel gear mechanism. The lower bevel gear mechanism and the propeller shaft are arranged in the lower unit. Such an arrangement of the shafts and bevel gear mechanisms allows the typical saildrive layout with the horizontal input shaft aligned to a horizontal crank shaft of the engine, with the intermediate shaft arranged vertically and the propeller shaft arranged horizontally, so that the propeller can rotate around a horizontal axis. The horizontal rotation axis of the propeller increases the thrust efficiency of the saildrive compared to a traditional sailboat propulsion system with a propeller rotating at a downward angle. The invention can be applied with steerable saildrives and with fixed saildrives. Steerable saildrives have a lower unit which can be turned around a vertical axis to influence the steering of the sailboat by the pivotable thrust vector of the propeller, while the lower unit of a fixed saildrive is fixed to an upper unit or to the hull. 
     The term horizontal, as used in this description and in the accompanying claims, means that the related element is generally horizontal when the vessel is in an upright position and floating in water such that a vertical element is substantially normal, i.e. perpendicular to a top surface of the water. 
     A rotatable element of the brake can be rotationally fixed to a hub of a first bevel gear of the upper bevel gear mechanism and a stationary element of the brake can be rotationally fixed to a housing of the saildrive arrangement. Hence, the rotatable element of the brake and the hub of the first bevel gear are arranged to rotate together around a common rotation axis while the stationary element is fixed to the housing, at least in rotational direction. Said housing preferably is the housing of the upper unit which encases the upper bevel gear mechanism and the brake. In other embodiments said housing could also be a common housing of the upper unit and the lower unit. The rotation axis of the first bevel gear can be the rotation axis of the input shaft. This means that the brake in this embodiment is located in the immediate vicinity of the input shaft, what enables a very compact design also of the upper unit. This is advantageous to have more free space available inside the hull. 
     Preferably the first and the second element comprise at least one friction disk, so that the brake can be formed for example as a multi-disk brake. The friction type brake is better than a form-locking devices, because in case any overload occurs the friction brake will slip and not break any mechanical part. The friction disks of the rotatable and the stationary element of the brake provide friction surfaces which cause the brake effect when pressed against each other by a friction force. The friction force can be provided by an elastic element like a spring for locking the propeller shaft. 
     According to another preferred embodiment of the invention the brake is engageable by a locking spring and disengageable by hydraulic pressure provided by a hydraulic pump which is driven by the input shaft. With other words the brake is spring-actuated and hydraulically released. Such a brake is also called a negative brake. 
     With this embodiment it can be ensured that a rotation of the propeller shaft is prevented when the engine is not running. The locking spring shall have such a spring tension and force, that an engagement of the brake and the standstill of the propeller shaft are ensured, as long as the engine of the saildrive is not running and the hydraulic pump is not driven. 
     According to a further preferred embodiment the upper bevel gear mechanism comprises the first bevel gear and a second bevel gear which are both arranged rotatable around a rotation axis of the input shaft and both are constantly meshing with a third bevel gear which is rotationally fixed to the intermediate shaft, wherein the first and the second bevel gear are selectively fixable to the input shaft by a first and a second clutch in order to engage a forward or reverse propulsion direction. 
     In such an arrangement the first clutch and the second clutch can both be hydraulic multi-disk clutches which are selectively engageable by a pressure provided by the hydraulic pump which is driven by the input shaft. With regard to the target of a compact size of the saildrive arrangement it is preferred to have the hydraulic pump, the brake and the first and second clutch located in the immediate vicinity of the inlet shaft. 
     The same hydraulic pump which provides the hydraulic oil and pressure for the disengagement of the brake can also be used to provide the hydraulic oil and pressure for the first and second clutch. This way a simple and cost-efficient layout of the hydraulic system of the saildrive can be achieved. Preferably all components of the hydraulic system for the brake and the first and second clutch are part of the upper unit or located inside the housing of the upper unit. 
     A further improvement related to compact size and simple construction can be reached, if there are hydraulic pressure channels provided inside the input shaft to connect the hydraulic pump with the first clutch and the second clutch. More precisely the pressure channels connect the outlet of the hydraulic pump with pressure chambers of the first and second clutch. A hydraulic valve can be provided in these hydraulic lines to select the desired clutch. 
     In order to achieve a very compact design of the saildrive arrangement, the hydraulic pump can be positioned inside a cover of a housing of the upper unit of the saildrive arrangement. The cover can for example be a sealing cover or a bearing cover at the feedthrough of the input shaft. The pressure side of the hydraulic pump can be advantageously connected to the pressure chambers of the brake by pressure channels inside the walls of said housing. 
     Especially for applications with a fixed propeller one embodiment of the invention provides a brake which can be mechanically disabled by a disabling element. Such a saildrive arrangement can be equally applied on sailboats with folding and fixed propellers without constructive modification. In applications with folding propellers the brake can be enabled to block propeller rotation during sailing, whereas in applications with fixed propellers the brake can be mechanically disabled to allow propeller rotation during sailing. 
     In a disabling position the disabling element can positively lock the pressure piston of the brake in a disengaged position of the brake, so that the brake is mechanically disabled. In an idle position of the disabling element the pressure piston of the brake is not blocked by the disabling element. Preferably the disabling element is a threaded pin which can be screwed into a housing of the saildrive arrangement until a front part of the disabling element positively locks the pressure piston of the brake in the disengaged position. 
     The invention covers a sailboat with a hull and a saildrive that comprises an engine which is positioned inside said hull and a saildrive arrangement as described above. The high degree of integration of functions and elements inside the upper unit of the saildrive enables a very compact and slim design of the whole saildrive arrangement. Especially the integration, of the brake inside the upper unit instead of the lower unit enables a slim and streamlined design of the lower unit and its fairing. This way the planing characteristics of the sailboat and the thrust efficiency of the saildrive are enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of a preferred embodiment of the invention in connection with the accompanying drawings will help to understand the objects, features and advantages of the invention, wherein: 
         FIG. 1  shows a schematic layout of a saildrive and an arrangement according to the invention; 
         FIG. 2  shows a partial section of the upper unit of a saildrive arrangement according to the invention; 
         FIG. 3  shows another partial section with the disabling element in an idle position and 
         FIG. 4  shows the partial section of  FIG. 3  with the disabling element in a disabling position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A saildrive arrangement  1  can be seen in  FIG. 1 . It is driven by an engine  2 , for example an internal combustion engine, which is located inside the hull  5  of a sailboat  7 . The output shaft  3  of the engine  2  is coupled to an input shaft  4  of the saildrive arrangement  1 . Input shaft  4  enters into a housing  21  of an upper unit  13 . The upper unit  13  is also located inside the hull  5 . The engine  2  and the upper unit  13  are fastened to the hull  5  or to structural parts inside of the hull  5 . 
     The upper unit  13  includes an upper bevel gear mechanism  11  and a brake  15  in the form of a multi-disk brake. The upper bevel gear mechanism  11  and the brake  15  are located inside the housing  21  of the upper unit  13 . The upper bevel gear mechanism  11  connects the input shaft  4  to a vertically arranged intermediate shaft  8  and a lower bevel gear mechanism  12  connects the intermediate shaft  8  to a horizontally arranged propeller shaft  9 . A propeller  10  is rigidly fixed to the propeller shaft  9 . The lower bevel gear mechanism  12  and the propeller shaft  8  are arranged in a lower unit  14  which protrudes from the bottom  6  of the hull  5 . 
     The brake  15  comprises stationary elements  16  and rotatable elements  17  in the form of friction disks. The rotatable friction disks  17  of the brake  15  are rotationally fixed to a hub  24  of a first bevel gear  18  of the upper bevel gear mechanism  11 . The rotatable friction disks  17  and the first bevel gear  18  are arranged to rotate together around rotation axis  22  which is also the rotation axis of the input shaft  4 . Hence, the rotatable frictions discs  17  of the brake  15  with the first bevel gear  18  are coaxially aligned with the input shaft  4 . The stationary disks  16  are rotationally fixed to the housing  21 . 
       FIG. 2  shows the upper unit  13  of the saildrive arrangement  1  more detailed. The brake  15  is engageable by a locking spring  27  and disengageable by hydraulic pressure provided by a hydraulic pump  29  which is driven by the input shaft  4 . When the engine  2  is running the input shaft  4  is driven by the output shaft  3  and the hydraulic pump  29  on the input shaft  4  provides hydraulic pressure to a pressure chamber  26 . The hydraulic pressure in pressure chamber  26  acts on a pressure piston  28  and moves it in axial direction away from the friction disks  16 ,  17  of the brake  15  as soon a certain pressure level is reached. In  FIG. 2  the assembly it shown when the engine  2  is running and the brake  15  is disengaged by the hydraulic pressure. 
     As soon as the hydraulic pressure decreases below said pressure level, the locking spring  27  will press the pressure piston  28  in axial direction towards the friction disks  16 ,  17  of the brake  15 , thereby locking the brake  15 . Hence, the propeller shaft  9  is locked. This will happen as soon as or shortly after the engine  2  is stopped. The locking spring  27  is formed by several cup springs which press the pressure piston  28  against the friction disks  16 ,  17 . The cup springs are biased against the housing  21  to enable the cup springs to generate the friction force for the spring-actuated brake  15 . This way it is ensured, that a rotation of the propeller is prevented when the engine is not running. 
     The upper bevel gear mechanism  11  comprises a first bevel gear  18 , a second bevel gear  19  and a third bevel gear  20 . The first bevel gear  18  and the second bevel gear  19  are both arranged rotationally around a rotation axis  22  of the input shaft  4 . The first and second bevel gears  18  and  19  are constantly meshing with the third bevel gear  20  which is rotationally fixed to the intermediate shaft  8 . The third bevel gear  20  is fixed to the intermediate shaft  8  and rotates together with the intermediate shaft  8  around a vertical axis  23  during operation of the saildrive. 
     The first bevel gear  18  and the second bevel gear  19  are selectively fixable to the input shaft  4  by closing the corresponding first clutch  26  or second clutch  27  in order to engage a forward or reverse propulsion direction. This means that either first bevel gear  18  or the second bevel gear  19  can be fixed to the input shaft  4 . When both clutches  26  and  27  are open, none of the bevel gears  18 ,  19  is fixed to the input shaft  4 . In this case the saildrive runs in an idle gear with no driving connection between the engine  2  and the propeller shaft  9  is realized. 
     The first clutch  30  and the second clutch  32  are both hydraulic multi-disk clutches which are engageable by a pressure provided by hydraulic pump  29  which is driven by the input shaft  4 . There is only one hydraulic pump  29  to provide hydraulic pressure to the brake  15  and to the first clutch  30  and the second clutch  32 . 
     Inner clutch disks of the first clutch  30  are rotationally fixed to a first inner clutch disk carrier  31 . Said first inner clutch disk carrier  31  is fixed to the first bevel gear  18 . The first inner clutch disk carrier  31  is supported on the input shaft  4  by a first needle bearing  42 . Inner clutch disks of the second clutch  32  are rotationally fixed to a second inner clutch disk carrier  33 . Said second inner clutch disk carrier  33  is fixed to the second bevel gear  19 . The second inner clutch disk carrier  33  is supported on the input shaft  4  by a second needle bearing  43 . 
     Outer clutch disks of the first and second clutch  30  and  32  are rotationally fixed to outer clutch disk carrier  36 . The outer clutch disk carrier  36  is fixed to the input shaft  4 . Additionally the outer clutch disk carrier  36  carries a first and a second clutch piston  34  and  35  which limit the pressure chambers of the first and the second clutch  30 ,  32  and provide the necessary force for clutch engagement as soon as hydraulic pressure is provided to the corresponding pressure chamber. 
     The hydraulic pump  29  in this embodiment is a positive displacement pump which is positioned right beside the feedthrough for the input shaft  4  in housing  21 . Rotatable parts of the hydraulic pump  4  are fastened directly on the input shaft  4 . Stationary parts of the hydraulic pump  4  are fastened inside a sealing cover  38  of housing  21  of the upper unit  13 . All parts of the hydraulic pump  29  are positioned inside the sealing cover  38 . The sealing cover  38  is equipped with a sealing ring  39  around the input shaft  4  at said feedthrough to protect the upper unit  13  from oil leakage and contamination from the outside. 
     Pressure bores  40  and a hydraulic valve  41  are provided inside a wall of the housing  21  of the upper unit  13  to selectively connect the pressure chambers  26  of the brake  15  or the first or second clutch  30 ,  32  with hydraulic pressure. There are further hydraulic pressure channels  37  provided inside the input shaft  4  and inside the outer clutch disk carrier  36  to connect the hydraulic pump  29  with pressure chambers of the first clutch  30  and the second clutch  32 . This means that all components of the hydraulic system for the brake  15  and the first and second clutch  30  and  32  are part of the upper unit  13  and located inside the housing  21  of the upper unit  13 . 
       FIG. 3  and  FIG. 4  both show a section of a part of the upper unit  13  with the disabling element  44 . By means of the disabling element  44  the brake  15  can be disabled mechanically, for example in sailboats with fixed propellers which shall rotate during sailing.  FIG. 3  shows the disabling element in an idle position, so that the brake is enabled.  FIG. 4  shows the disabling element  44  in the disabling position, so that the brake  15  cannot be used and the disengaged position of the brake  15  is secured by the disabling element  44 . 
     The disabling element  44  is formed as a threaded pin which can be screwed into the housing  21  of the saildrives upper unit  13 . In the disabling position in  FIG. 4  a front part  45  of the threaded pin  44  positively locks the pressure piston  28  of the brake  15  in a disengaged position of the brake  15 . The brake  15  is mechanically disabled. 
     Whereas in the idle or retracted position of the threaded pin  44  as shown in  FIG. 3  the pressure piston  28  of the brake  15  is not blocked by the front part  45  of the threaded pin  44 . The pressure piston  28  will be pressed against the stationary and rotatable elements  16 ,  17 , that are the pressure plates of the brake  15  by the force of spring  27 , as long as the force generated on the pressure piston  28  by the hydraulic pressure in pressure chamber  26  is lower than the force of spring  27 . A spacer  47  is arranged between the head  46  of the threaded pin  44  and the housing  21  in order to fasten the threaded pin  44  in its predefined idle position. Hence, the brake can easily be enabled and disabled from outside of the housing  21 , by screwing in or out the threaded pin  44  and placing the spacer  47  as indicated. 
     REFERENCE NUMERAL 
     
         
           1  saildrive arrangement 
           2  engine 
           3  output shaft 
           4  input shaft 
           5  hull 
           6  bottom 
           7  sailboat 
           8  intermediate shaft 
           9  propeller shaft 
           10  propeller 
           11  upper bevel gear mechanism 
           12  lower bevel gear mechanism 
           13  upper unit 
           14  lower unit 
           15  brake 
           16  stationary element 
           17  rotatable element 
           18  first bevel gear 
           19  second bevel gear 
           20  third bevel gear 
           21  housing 
           22  rotation axis 
           23  vertical axis 
           24  hub 
           25  brake disk carrier 
           26  pressure chamber 
           27  spring 
           28  pressure piston 
           29  hydraulic pump 
           30  first clutch 
           31  first inner clutch disk carrier 
           32  second clutch 
           33  second inner clutch disk carrier 
           34  first clutch piston 
           35  second clutch piston 
           36  outer clutch disk carrier 
           37  pressure channels 
           38  sealing cover 
           39  sealing ring 
           40  pressure bores 
           41  hydraulic valve 
           42  first needle bearing 
           43  second needle bearing 
           44  disabling element 
           45  front part 
           46  head 
           47  spacer