Abstract:
A surface drive that includes a shaft housing; a propeller; a propeller shaft that passes through the shaft housing with the propeller mounted at an end of the propeller shaft; and mounted to the shaft housing is at least one of a container, wherein a self-locking or automatic locking pitch change mechanism that is configured to adjust a propeller blade of the propeller is partially located in the container, or a propeller ventilation unit that is configured to direct exhaust gas to or away from the propeller based on a travel condition of the surface drive.

Description:
BACKGROUND 
     The invention relates to a surface drive that is attached to the stern of a watercraft. 
     Drives attached to the sterns of watercraft are relatively well-known; they include sterndrives and surface drives. The main difference between the two systems, for example, is that the engine exhaust outlet has to be behind the propeller in sterndrives. When the surface propeller rotates and the propeller is fully submerged, the engine exhaust gas is supposed to be in front of the propeller blades for propeller ventilation (see, for example, U.S. Pat. No. 5,046,975). Moreover, for sterndrives, the propeller thrust is transferred to an underwater unit via axial bearings and to the watercraft in part via trim cylinders and in part via an above-water unit (see, for example, U.S. Pat. No. 3,589,204). For surface drives, the propeller thrust affects the rear of the watercraft, directly in the case of rigid drives and directly in the case of pivoting drives (see, for example, U.S. Pat. No. 4,645,463). 
     Furthermore, an appropriate distance is needed between the propeller of the surface drive and the stern of the watercraft. An appropriate distance is needed because the efficiency of the propeller when the watercraft travels in reverse declines the closer the propeller is located to the stern of the watercraft because a part of the propeller circumference directs the propeller thrust directly against the stern of the watercrart, thus resulting in a flow loss. A technical solution to this problem can be found in U.S. Pat. No. 4,371,350. 
     The introduction of a controllable-pitch propeller is problematic in that there is not as much space available in a surface drive as there is in sterndrives as described in U.S. Pat. No. 6,250,979. In addition, a hollow shaft design is required for large seagoing vessels (see, for example, WO 8602901), which incurs a high cost. Moreover, the successive changes in load impacting the adjustment mechanism at each blade immersion and emergence for each revolution of the propeller is considerable due to the changes in spindle force applied to the propeller blades when they rotate about a hub. This necessitates a rigid structure and a safe and secure blade location should the hydraulic system fail. 
     SUMMARY 
     The invention is based on the above concerns, and relates to a surface drive for a watercraft. In particular, the invention is directed to attaching a self-locking or automatic locking pitch change mechanism for a controllable-pitch propeller with a sensor in order to prevent any uncontrolled change in propeller pitch or trim in the case of a sudden failure of the hydraulic cylinder. In addition, the design of the shaft housing and the flaps fitted to the side of the shaft housing are improved in order to achieve improved hydrodynamic buoyancy and water spray channeling characteristics and to enhance the maneuverability of the watercraft. Furthermore, the flow of exhaust gases changes based on whether the surface drive is used to drive the watercraft forward or reverse, or whether the watercraft is maintained at a neutral position (i.e., a travel condition of the surface drive), wherein the watercraft does not travel forward or in reverse (i.e., travel conditions of the surface drive). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various exemplary aspects of the invention will be described with reference to the drawings, wherein: 
         FIG. 1  is a schematic, side cross-section of a ship drive; 
         FIG. 2  is a schematic, top view of a ship drive; 
         FIG. 3  is a schematic cross-section of the pitch change mechanism; 
         FIGS. 4   a - 4   c  are schematic, rear-view cross-sections through the ship drive; 
         FIG. 5  is a schematic, side cross-section of a ship drive; 
         FIG. 6  is a schematic, side cross-section of a ship drive; and 
         FIG. 7  is a schematic visualization of the flap system in a lowered and raised state. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a schematic, side cross-section of a ship drive, specifically the surface drive  1 . The surface drive  1  includes a shaft housing  2  and a container  3  in which part of a pitch change mechanism  4  for activation of a mechanism  5  used to adjust the propeller is located. The container  3  is an easily accessible element that is watertight when closed and connected to the shaft housing  2 . The container  3  is designed such that engine exhaust and coolant extraction A (which are examples of a flow that are drawn out of the surface drive  1 ) can occur in an unimpeded manner via duct  6  of the duct housing  6   a . Engine exhaust and coolant extraction A occurs from an engine  8  into the duct  6  via an exhaust manifold  7 . Pivot cylinders  9   a ,  9   b  for articulating the surface drive  1  are attached to an upper mounting  10  and a side mounting  11  on one side, and to mountings  13   a ,  13   b  on the watercraft stern  12  on the other side. The pivot cylinder  9   a  is used to trim the surface drive  1  and vary the amount by which the propeller blades  17   a  are immersed in the water. 
     The engine drive output is transferred either directly to propeller shaft  15  via gear  14  or to the propeller  17  via a second drive shaft  16 . The propeller shaft  15  is mounted in the shaft housing  2  and the thrust forces generated by the propeller  17  are transferred to the axial bearing package  18  and transferred to the shaft housing  2 . The thrust forces of the propeller  17  are transferred into a housing  22  via bearing pins  29  and a pivot pin  30 , as shown in  FIG. 2 , and passed on to the watercraft stern  12  via elastic damping elements  46 . 
     The drive shaft  16  is equipped with a length compensation element  19  (e.g., piston) and a second cardan or homo-kinetic joint  21  (e.g., constant velocity joint). The drive shaft  16  further dampens the vibration of the drive, and allows the engine  8  to be positioned at more locations. 
     Moreover, the shaft housing  2  is equipped with a guard  23  as well as a hydrodynamic buoyancy area  24 , which is an enclosed area that helps to maintain the shaft housing  2  afloat. The buoyancy area  24  functions like a trim tab when the watercraft accelerates and helps the bow of the watercraft to lower as quickly as possible in order to ultimately position the watercraft at a shallow and a favorable angle of travel. The surface propellers  17  spray water when the propellers  17  rotate. A propeller cover  25  is fitted to the duct housing  6   a  in order to effectively reduce the extent by which the water is sprayed. The propeller cover  25  can be shaped to be an arch-shaped tunnel, a simple T shape or a similar shape. In the event that the duct housing  6   a  is made of a synthetic material, the propeller cover  25  can also be fitted directly to the container  3  via a flange element  25   a  or can be an integral component of a cover of a side flap. 
     In order to improve the harbor maneuverability of a watercraft with the surface drive  1 , the engine exhaust and coolant extraction A is redirected when the watercraft moves in reverse (which is one of the driving conditions that also include a forward direction and a neutral position). The engine exhaust and coolant extraction A is redirected through a side duct  26  via a reversing flap  27 , which are moved together via an adjustment unit  31  (e.g., piston) when the control lever for the reverse gear or blade pitch for reverse thrust is operated. 
       FIG. 2  shows a schematic, top view of the surface drive  1 , the duct housing  6   a , the propeller  17 , and the propeller cover  25 , as well as the pivot cylinder  9   a  for trimming and the pivot cylinder  9   b  for steering the watercraft via the horizontal movement of the surface drive  1 . A pivot and hoist frame  28  is located in the housing  22 . The bearing pins  29  trim the surface drive  1  and absorb the thrust that the surface drive  1  generates, and the pivot pin  30  is used for side pivoting and to absorb the thrust from the surface drive  1 . The first cardan or homo-kinetic joint  20  (e.g., constant velocity joint) is located centrally to pivot and hoist the frame  28  and the bearing pins  29  and the pivot pins  30  that are accommodated in the housing  22  and are used for the low-friction pivoting of the surface drive  1 . 
       FIG. 3  shows a schematic cross-section of the pitch change mechanism  4  integrated in the shaft housing  2 . An adjustment unit  31 , for example a hydraulic or electric motor or a linear drive with a rack or similar activated drive via an angle gear, drives a shaft  34  that is connected to a gear wheel  33  and an eccentric cam  35 . With a turn of the shaft  34  and the eccentric cam  35 , the distance between the eccentric cam  35  and a sensor  36  adjacent to the eccentric cam  35  changes. The sensor  36  measures the distance between the eccentric cam  35  and the sensor  36  such that the distance between the eccentric cam  35  and the sensor  36  can be logged electrically. 
     The gear wheel  33  drives a gear wheel  37 , which is larger than the gear wheel  33  and is connected to a self-locking spindle  38 . The spindle  38  is self-locking (thus creating a self-locking pitch change mechanism  4 ) because of the thread pitch of the spindle  38 . An adjustment axial bearing  39  is located at the end of the spindle  38 . A mechanical link via the connection element  41  attached to the axial housing  40  to the adjustment mechanism  5  of the propeller  17  is thus assured in order to change the pitch of the propeller  17 . The parts  37 ,  38  and  39  are hollow inside such that the propeller shaft  15  is mounted and can rotate without contact. The gear wheel  33  is axially supported without any play if possible, while the gear wheel  37 , the spindle  38 , the adjustment axial bearing  39 , the axial housing  40  and the connection element  41  move axially when the gear wheel  33  rotates by being driven by the adjustment unit  31  via the shaft  34  as indicated by the arrows. 
     The spindle  38  is fitted with a cone  42 . As should be appreciated, when the cone  42  moves axially as indicated by the arrows, the distance between the cone  42  and the sensor  36  changes. The cone  42  can thus be used instead of the eccentric cam  35 . The sensor  36  can also be used in the shaft housing  2  to the side of the gear wheel  37  in order to measure changes in distance between the gear wheel  37  and the sensor  36  when the gear wheel  37  moves axially as indicated by the arrows. The gear wheel  38  can thus be used instead of the eccentric cam  35 . All of the sensors  36  are positioned to the side of the propeller shaft  15 . 
     The container  3 , in which parts of the pitch change mechanism  4  are located, is also used as a flange element  25   a  for the mounting propeller cover  25 . The container  3  also houses a line  32  connected to the adjustment unit  31  and a line  43  connected to the sensor  36 . 
     The pitch change mechanism  4  is used to set the pitch of the propeller blades  17   a  and the pitch change mechanism  4  is self-locked or automatically locked. As discussed above, the pitch change mechanism  4  is self-locked because of the thread pitch of the spindle  38 . The pitch change mechanism  4  can also be automatically locked using a worm gear or via a locking unit that locks the propeller blades  17   a  until a different pitch of the propeller blades  17   a  is used. For example, a side lock  49  (which is an example of a locking device) includes a pin that is inserted into the gear wheel  33 . 
       FIGS. 4   a - 4   c  show a schematic, rear-view cross-section through the shaft housing  2  with various flange-mounted, hydrodynamic buoyancy areas  24  that, with one and the same shaft housing design, can be completed a) for port, b) for starboard and c) for a single drive via the hydrodynamic buoyancy areas. The areas can thus be configured quickly and inexpensively for the various watercraft types and uses, i.e., with slimmer or broader areas, shorter or longer versions. The buoyancy areas  24  enable the watercraft to remain at a stable position in rough water as well as reduce bow rise when the watercraft accelerates from a standing position. 
       FIG. 5  shows a schematic, side cross-section through the surface drive  1  in a stern unit  44 , which is connected to the watercraft stern  12  via elastic vibration and damping elements  45 , whereby the pivot cylinders  9   a ,  9   b  are fitted to the stern unit  44 . Via the installation of the entire surface drive  1  in the stern unit  44 , the absorption of vibrations impacting on the watercraft between the watercraft stern  12  and the stern unit  44  is achieved by way of the vibration and damping elements  45 , particularly if use is made of the second joint  21  and the corresponding drive shaft  16 , such that the engine  8  can be supported in an appropriately comfortable manner. Any movement of the drive shaft  16  that may occur can be cushioned via an appropriate seal element  47  such as a shock absorber and a standard shaft seal. 
       FIG. 6  shows a schematic, side cross-section through the surface drive  1  that is located in the stern unit  44 , whereby, during reverse maneuvers, engine exhaust and coolant extraction A occurs through the side duct  26  in the duct housing  6   a  via the reversing flap  27  that is adjustable because of the adjustment unit  31 . The engine exhaust and coolant extraction A occurs between the watercraft stern  12  and the stern unit  44  by way of an outlet duct  48 . 
     As a result, the propeller  17  is not blown on during reverse travel. The reversing flap  27  is connected via a propeller reversing unit coupling (not shown) or reversing gear. The outlet duct  48  can also be used for normal travel as it ventilates the underwater part of the stern unit  44 , thereby reducing its frictional resistance in the water. Moreover, the Venturi effect can also be achieved in this way, thus helping to make the extraction of engine exhaust more effective. 
       FIG. 7  shows a schematic visualization of the side flap  50  with the cover  55  in a flat and hence travel and resting position as well as in the raised position R used for reversing. As an individual element to the left or right of the surface drive  1  or as a one-part element with an appropriate opening or covering of the shaft housing  2 , the valve can be mounted directly on the shaft housing  2  or on the watercraft stern  12  or on the stern unit  44  via pivoting elements  51 . The side flap  50  acts as an additional hydrodynamic buoyancy element, as a water spray guard due to the water swirled up by the propeller blades  17   a  when they emerge from the water and as a propeller thrust flow deflector located underneath the watercraft when the watercraft reverses. Operation of the side flap  50  occurs via a hoist mechanism  52  that is fitted to the shaft housing  2 , the housing  22 , the watercraft stern  12  or the stern unit  44  via a link unit  53   a  and to a flap bracket  53 . 
     Hoist activation of the side flap  50  occurs via the coupling to the propeller reverse control (not shown) or to the reverse gear by way of the reverse lever located on the helm controls. If the side flap  50  is mounted directly on the shaft housing  2 , the side flap  50  moves when the surface drive  1  is trimmed or steered. 
     The invention is, of course, not restricted to the application shown and described above.