Abstract:
A propulsion system for a ship having one front and one rear propelling engine (M 1 , M 2 ), the propulsion powers of which can be coupled to an output shaft ( 7 ) via a gear system ( 6 ). The shafts of the gear mechanism are disposed on top of each other in an essentially vertical manner. The ship output shaft ( 7 ) extends below the rear propelling engine (M 2 ). It is proposed that an input gear ( 14 ), disposed upon a rear input shaft ( 10 ), is permanently meshed with an intermediate gear (Z 2 ) disposed upon a first axis of rotation ( 1 ), and that an output gear ( 13 ) disposed upon a gear output shaft ( 11 ) likewise meshes with an intermediate gear (Z 1 ) disposed upon the first axis of rotation ( 1 ) whereby a large vertical axial distance results between the rear input shaft ( 10 ) and the gear output shaft ( 11 ) despite the small gear diameter.

Description:
FIELD OF THE INVENTION 
     The invention relates to a system of propulsion for a ship comprising a front and a rear propelling engine the propulsion powers of which can be coupled to an output shaft via a gear system, said output shaft being passed through below the rear propelling engine. 
     BACKGROUND OF THE INVENTION 
     Already known are propulsion systems for ships in which two propellers can be driven by two—equal or different—propelling engines. Depending on the power requirement propulsion systems for ships, having several prime movers, permit driving only one or more prime movers. A lower fuel consumption is hereby achieved in the area of a part load. Besides, the reliability of operation increases, since even in case of failure of individual propelling engines, the ship remains capable of maneuvering. 
     Particularly in heavy-duty ships, such as catamaran ferries which can attain very high speeds, special requirements are placed on the propulsion system. They must have light weight and claim only narrow installation space because of the narrow hulls. Between conventionally used, high-speed diesel engines and their ship output shaft, which drives a propeller or other output element of the ship, only relatively small ratios are needed in the gear between the input shafts and the output shaft due to the high speeds of the ship under certain propelling variants. 
     Large ships are usually optimized especially to a provided use profile. Different propulsion plans with stationery or adjustable propellers with so-called waterjet propulsions are used here. Accordingly different demands are placed on the ship propulsion systems and the ship gear mechanism thereof which demands as a rule require, expensive special solutions. 
     By prior use has become known, a ship gear system in which two propelling engines are disposed consecutively in longitudinal direction and their propulsion powers can be coupled to a ship output shaft, via a gear mechanism, situated between the propelling engines, the ship output shaft being passed through below the rear propelling engine. Determined by the kind of construction, the input shaft of the rear propelling engine has only a small axial distance from the output shaft. In order that the ship output shaft can be passed through below, the rear propelling engine, in this gear system the rear propelling engine is coupled to the gear mechanism with large axial distance by means of a suitable cardan shaft. The required large axial installation space made necessary by a large engine space is disadvantageous here. But large continuous spaces, uninterrupted by a partition, are unfavorable for safety reasons. In addition, the rear propelling engine is installed, tilted in relation to the other components of the propulsion system. By the cardan shaft that extends inclined, undesirable vibrations can be excited in the drive chain. Both propelling engines also have, relative to each other, a horizontal offset so that the propulsion system is altogether built wider than were actually needed, based on the measurements of the individual propelling engines. 
     EP 0 509 712 A1 has finally disclosed a ship propulsion system, having a front and a gear propelling engine, the propulsion powers of which can be coupled to a ship output shaft, via a gear system, consisting of two interconnected gears. Both the input shafts and the output shaft of said gear system are only vertically offset in relation to each other so that both propelling engines can be situated in the ship hull without horizontal offset thus saving space. The vertical axial distance between the rear input shaft and the output shaft is large enough for a cardan shaft to be omitted between the rear propelling engine and the gear system. This ship propulsion system, of course, has some disadvantages. The use of two interconnected gears results in a higher total weight and the need of a larger axial installation space. In the fitting in the ship, great expenditure in assembly and alignment is required in order to prevent mutual restraints. The gear system also has a very large number of parts. In the arrangement shown with opposite output sides of the propelling engines, it is also required to use propelling engines having opposite directions of rotation. 
     Therefore, the problem on which this invention is based is to provide a ship propulsion system which is of simpler construction, needs less installation space, has a light weight despite a relatively small ratio and allows the utilization of propelling engines that rotate in the same direction. The ship propulsion system must also be adaptable at low expense to the requirements established by different propulsion plans. 
     SUMMARY OF THE INVENTION 
     The inventive propulsion system for ships has one gear mechanism in which the front input shaft is situated upon a first axis of rotation, the rear input shaft upon a second axis of rotation and the output shaft upon a third axis of rotation. The second axis of rotation extends vertically here above the first axis of rotation and the first axis of rotation vertically above the third axis of rotation. One input gear placed upon the rear input shaft is permanently meshed with an intermediate gear placed upon the first axis of rotation of the front input shaft and an output gear placed upon the gear output shaft is simultaneously engaged with an intermediate gear placed upon the first axis of rotation. Hereby results a large vertical axial distance between the rear input shaft and the gear output shaft. 
     With a relatively small ratio of 2:1, for example, between the input and the output shaft, there can also be used gear wheels of smaller diameter, since the axial distance between the axes of rotation is added. The point of gravity of the front propelling engine is lower in the ship hull than in the rear propelling engine, which is favorable with regard to a stablest possible position of the ship. 
     Sparing place both propelling engines can be disposed without horizontal axial distance when the second axis of rotation extends without horizontal offset exactly in vertical manner over the first axis of rotation. The maximum axial distance between the rear input shaft and the gear output shaft is obtained when the third axis of rotation extends without horizontal offset in exactly vertical manner below the first and the second axes of rotation. 
     In a preferred embodiment, the first, the second and the third axes of rotation extend parallel to each other. Only cylindrical spur gears are necessary here in the gear mechanism and both propelling engines can be installed parallel to each other. Alternatively a so-called down-angle arrangement is also possible in which the gear output shaft extends downwardly inclined. The gear output step is, in this case, a bevel gear step. The advantage of such an arrangement consists in that both propelling engines can be installed horizontally in the ship while the ship output shaft can be passed through the bottom of the hull with an angle of inclination. 
     Together with the inventive ship gear system and the developments thereof, protection is claimed also for a ship gear mechanism of such a ship gear system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
     FIG. 1 diagrammatically shows a side view of an inventive ship propulsion system; 
     FIG. 2 is a top view upon the gear diagram of a ship gear mechanism according to FIG. 1; 
     FIG. 3 is a gear diagram of an embodiment in side view; 
     FIG. 4 is a top view upon the gear diagram of the embodiment according to FIG. 3; 
     FIG. 5 is a gear mechanism diagram of an embodiment in side view; 
     FIG. 6 is a top view upon the gear diagram of the embodiment according to FIG. 5; 
     FIG. 7 is a gear diagram of an embodiment in side view; 
     FIG. 8 is a top view of the gear diagram of the embodiment according to FIG. 7; 
     FIG. 9 is a gear diagram of an embodiment in side view; 
     FIG. 10 is a top view upon the gear diagram of the embodiment according to FIG. 9; and 
     FIG. 11 is a table of the shift states of the separating clutches. 
    
    
     In the Figures, positions corresponding to each other are provided with the same reference numerals. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, a rear propelling engine M 2  and a front propelling engine M 1  of a ship propulsion system is designated. Both propelling engines M 2 , M 1 , designed as diesel engines, for example, can be coupled via one gear system  6 , the driving power being fed via a ship output shaft  7  to an output element (what is shown is a variable pitch propeller  8 ). The gear mechanism  6  has one front input shaft  9  allocated to the front propelling engine M 1 ; one rear input shaft  10  allocated to the rear propelling engine M 2  and one gear output shaft  11  allocated to the ship output shaft  7 . The front input shaft  9  has a first axis of rotation  1 , the rear input shaft  10  a second axis of rotation  2  and the gear output shaft  11  a third axis of rotation  3 . 
     As can be seen from FIG. 2, the first axis of rotation lies vertically above the third axis of rotation and the second axis of rotation is vertically above the first axis of rotation. The axial distance between the rear input shaft  10  and the gear output shaft  11  is large enough to allow the ship output shaft  7  to extend through below the rear propelling engine in direction to the ship stern. Upon the first axis of rotation  1  a first intermediate gear Z 1  is rotatably supported by an intermediate shaft  12 . The intermediate gear Z 1  can optionally be coupled by a first separating clutch K 1  to the front input shaft  9  and/or by mean of a second separating clutch K 2  to a second intermediate gear Z 2  which is also rotatably supported upon the first axis of rotation. The intermediate gear Z 1  is permanently meshed with the output gear  13  situated upon the gear output shaft  11 . The intermediate gear Z 2  is permanently meshed with a rear input gear  14  non-rotatably placed upon the gear input shaft  10 . Outside the gear housing  15 , made of light metal, a rear and a front input flangel  16 ,  17  are located, the same as the gear output flange  18 . A great vertical axial distance exists between the rear input shaft  10  and the gear output shaft  18  so that the ship output shaft  7  can be passed through without a problem below the rear propelling engine M 2 . 
     The embodiment shown in FIG. 1, makes the ship output shaft  7  optionally possible to actuate by the front propelling engine M 1  and/or the rear propelling engine M 2 . With closed separating clutch K 1 , the front propelling engine M 1  is coupled to the ship output shaft  7  with closed separating clutch K 2 , the rear propelling engine M 2  is coupled to the ship output shaft  7 . The separating clutches K 1 , K 2  are hydraulically actuatable, power shiftable, wet disc clutches. This type of clutch makes smooth shifting operation possible. The separating clutches of the ship gear mechanism  6  can be controlled preferably by an electrohydraulic control device. The embodiment of FIG. 1 is especially suitable for ships where the output element is a variable propeller  8  in which a negative angle of incidence of the propeller blades can be controlled for reverse travel and the power consumption for the operation with only one propelling engine can be adapted by a small angle of incidence of the propeller blades. The rear input gear  14  forms with the intermediate gear Z 2 , a ratio step with the reduction ratio  1  so that both propelling engines M 1 , M 2  are coupled to the ship output shaft  7  with the same reduction ratio. Since the propelling elements upon the first axis of rotation have a direction of rotation opposite to the propelling elements upon the second axis of rotation and the propelling sides of both propelling engines M 1 , M 2  face each other, the two propelling engines have the same direction of rotation. Therefore, two identical propelling engines can be used. The plan of the represented ship propulsion system can be expanded so as to also meet requirements resulting from the use of other ship output elements. 
     In FIGS. 3 and 4 is shown an embodiment in which the ship output shaft  7  can optionally be actuated by the front and/or the rear propelling engine and, optionally, with a first ratio step—a first gear—or a second ratio step—a second gear. Such a ship propulsion system is adequate for propelling a so-called waterjet propulsion  308  where backward thrust is produced by a flap  19  tiltable in front of the water discharge opening. The embodiment according to FIG. 3 or FIG. 4 has the following additional elements: coaxially to the rear input shaft  10  is rotatably supported upon the second axis of rotation by an intermediate shaft  20  an intermediate gear Z 3  which is permanently meshed with an intermediate gear Z 4  which is connected upon the first axis of rotation, via the intermediate shaft  12 , with the intermediate gear Z 1 . The intermediate gear Z 3  can be optionally coupled via a separating clutch K 3  to the rear input shaft  10  or via a separating clutch K 4  to an intermediate gear Z 5 . The intermediate gear Z 5  is likewise rotatably supported around the second axis of rotation and is permanently meshed with a front input gear  21  situated upon the front input  9 . The reduction ratio formed between the intermediate gear Z 3  and the intermediate gear Z 4  is operative in first gear and is smaller than the reduction ratio formed between the rear input gear  14  and the intermediate gear Z 2 . To operate both propelling engines in the second gear, the clutches K 1  and K 2  are closed while the clutches K 3  and K 4  are open. The propelling power of the rear propelling engine is here transmitted via the gears  14 , Z 2 , Z 1  and  13  to the gear output  11 . The propelling power of the front propelling engine is transmitted via the gears Z 1  and  13  to the gear output shaft  11 . The reduction corresponds to a top speed driving gear. If only the rear propelling engine is operated, only the separating clutch K 3  is closed while the separating clutches K 1 , K 2  and K 4  are open. The power is transmitted via Z 3 , Z 4 , Z 1  and  13  to the gear output  11 . 
     The intermediate gear Z 5  and the front input gear  21  are gear wheels having the same number of teeth so that they form a ratio step with the reduction ratio  1 . 
     In this shifting state, therefore, the intermediate shaft  12  and the gear output shaft  11  rotate slower than the rear gear input shaft  10 . The low rotational speed of the ship output shaft  11  or of the waterjet propulsion  308  produces a lower power consumption adapted to the propulsion power of a propelling engine. For exclusive operation of the front propelling engine, the separating clutch K 4  is closed while the separating clutches K 1 , K 2  and K 3  are open. The propelling power is transmitted, via the front input gear  21 , to the intermediate gear Z 5  and from there, via the intermediate gear Z 3 , to the intermediate gear Z 4  again to the intermediate shaft  12 . From there, in turn, via the output steps Z 1  and  13 , to the gear output shaft  11 . It is further possible to also couple both propelling engines simultaneously to the first gear corresponding to a slow moving gear upon the ship output shaft  7 . This is advantageous, for example, in a motion with increased resistance. Here the separating clutches K 3  and K 4  are closed while the separating clutches K 1  and K 2  are open. 
     The gear diagram shown in FIG.  5  and FIG. 6, concerns an embodiment of the invention where the ship output  7  can optionally be actuated by the front and/or the rear propelling engine and this clockwise or counterclockwise. The gear mechanism has a fourth axis of rotation  4  which is horizontally offset relative to the first and the third axes of rotation  1 ,  3  and is situated in vertical direction between the first and the third axes of rotation so that the centers of the first, third and fourth axes of rotation form a triangle. Upon the fourth axis of rotation  4  is rotatably supported a reversing gear  22  by an intermediate shaft  23  which can be optionally coupled by a separating clutch K 5  to a coaxial intermediate gear Z 7 . The reversing gear  22  is permanently meshed with the output gear  13 . The intermediate gear Z 6  is permanently meshed with the intermediate gear situated upon the first axis of rotation and the intermediate gear Z 7  is permanently meshed with the front input gear  21  non-rotatably placed upon the front input shaft  9 . 
     To actuate the ship output shaft  7  clockwise by both propelling engines, the separating clutches K 1  and K 2  are closed while the separating clutches K 5  and K 6  are open. To actuate the ship output shaft  7  counterclockwise by both propelling engines, both separating clutches K 5  and K 6  are closed while the separating clutches K 1  and K 2  are open. To actuate the ship output shaft  7  clockwise by the front propelling engine, only the separating clutch K 1  is closed while all the other separating clutches are open. With the same front engine, they can be actuated in opposite direction of rotation when the separating clutch K 6  is closed and all the others are open. To actuate the ship output shaft  7  clockwise by the rear engine, only the separating clutch K 2  is to be closed, to actuate with the rear propelling engine in opposite direction of rotation, exclusively the clutch K 5  has to be closed. This embodiment is especially suitable when the gear output element is a fixed pitch propeller  508 . 
     In FIGS. 7 and 9 is shown an embodiment where the ship output shaft  7  can optionally be actuated by the front and/or rear propelling engine and optionally clockwise or counterclockwise and with a first ratio step or a second ratio step. The gear mechanism has all the elements already described in FIG.  3  and FIG.  5 . There is also a fifth axis of rotation  5  which is radially offset relative to the fourth axis of rotation  4 . Upon the fifth axis of rotation  5  is rotatably supported by the intermediate shaft  24  an intermediate gear Z 8  which can optionally be coupled by means of a separating clutch K 7  to a coaxial intermediate gear Z 9  and/or by a separating clutch K 8  to a coaxial intermediate gear Z 10 . The intermediate gear Z 8  is permanently meshed with an intermediate gear Z 11  which is non-rotatably connected upon the fourth axis of rotation  4  by the intermediate shaft  23  with the reversing gear  22 . The intermediate gear Z 9  located upon the fifth axis of rotation is permanently meshed with the intermediate gear Z 6  situated upon the fourth axis of rotation. The intermediate gear Z 10  is permanently meshed with the intermediate gear  27 . The reduction ratio formed between the intermediate gear Z 11  and the intermediate gear Z 8  is larger than the reduction ratio formed between the intermediate gear Z 6  and the intermediate gear Z 9 . The gears  14 , Z 5 , Z 2 ,  21 , Z 6 , Z 7 , Z 9  and Z 10  advantageously have the same toothing geometry or are equal parts. For the respective two gears Z 3  and Z 8 , Z 1  and  22 , the same as Z 4  and Z 11 , equal parts are likewise used. This embodiment is particularly adequate in combination with a fixed pitch propeller  708 . On the basis of this embodiment can be derived an embodiment having only one reverse gear by omitting the elements disposed on the fifth axis of rotation. Should there be provided a gear mechanism with two forward gears and one reverse gear which, on the output, has opposite direction of rotation, there are needed, based on the embodiment shown in FIG. 7, only the front input gear  21  and the intermediate gear Z 2  upon the first axis of rotation and only the rear input gear upon the second axis of rotation. 
     In the synoptic table shown in FIG. 11 with a black dot are identified the separating clutches K 1  to K 8  which are closed for the individual shifting states. 
     FIG.  9  and FIG. 10 finally show a gear diagram of an embodiment where the ship output shaft  7  can be optionally actuated by the front or rear propelling engine. The direction of rotation runs opposite to the embodiment shown in FIG.  1 . Upon the first axis of rotation  1 , the front input gear  21  is situated upon the front input shaft  9 . Coaxially but independently thereof, an intermediate gear Z 2  is rotatably supported, which is permanently meshed with the rear input gear  14  placed upon the rear input shaft  10 . Upon the fourth axis of rotation  4 , a reversing gear  22  is rotatably supported, which can be optionally coupled by means of a rear separating clutch K 5  to another rear intermediate gear Z 6  and/or by means of a front separating clutch K 6  to another front intermediate gear Z 7 . The reversing gear  22  is permanently meshed with the output gear  13 . The other rear intermediate gear Z 6  is permanently meshed with the intermediate gear Z 2  and the other front intermediate gear Z 7  is permanently meshed with the front input gear  21 . This embodiment of a ship propulsion system, which is adequate for combination with a feathered propeller  908 , can be disposed, for example, in a hull of a catamaran ferry while in another hull an embodiment is provided such as shown in FIG.  1  and FIG.  2 . In this manner, it is possible, therefore, to use four equal propelling engines altogether wherein the two propellers have opposite directions of rotation. 
     The inventive ship propulsion system is adaptable to various utilizations because of the variable construction of the gear mechanism. The individual configurations shown have very different jointly existing components like gear wheels and separating clutches which have identical construction. Hereby the maintenance and preservation of substitute parts is simplified. 
     All axes of rotation of the embodiments shown extend parallel to each other so that cylindrical gear wheel scan be used. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Reference numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 axis of rotation 
               
               
                   
                  2 
                 axis of rotation 
               
               
                   
                  3 
                 axis of rotation 
               
               
                   
                  4 
                 axis of rotation 
               
               
                   
                  5 
                 axis of rotation 
               
               
                   
                  6 
                 ship gear mechanism 
               
               
                   
                  7 
                 ship output shaft 
               
               
                   
                  8 
                 feathered propeller 
               
               
                   
                  9 
                 front input shaft 
               
               
                   
                 10 
                 rear input shaft 
               
               
                   
                 11 
                 gear output shaft 
               
               
                   
                 12 
                 intermediate shaft 
               
               
                   
                 13 
                 output gear 
               
               
                   
                 14 
                 rear input gear 
               
               
                   
                 15 
                 gear housing 
               
               
                   
                 16 
                 flange 
               
               
                   
                 17 
                 flange 
               
               
                   
                 18 
                 flange 
               
               
                   
                 19 
                 hinged flap 
               
               
                   
                 20 
                 intermediate shaft 
               
               
                   
                 21 
                 front input gear 
               
               
                   
                 22 
                 reversing gear 
               
               
                   
                 23 
                 intermediate shaft 
               
               
                   
                 24 
                 intermediate shaft 
               
               
                   
                 308 
                 waterjet propulsion 
               
               
                   
                 508 
                 fixed pitch propeller 
               
               
                   
                 708 
                 fixed pitch propeller 
               
               
                   
                 908 
                 feathered propeller 
               
               
                   
                 K1-K8 
                 separating clutches 
               
               
                   
                 AZ1-Z11 
                 intermediate gears 
               
               
                   
                 M1 
                 front propelling engine 
               
               
                   
                 M2 
                 rear propelling engine