The present invention relates to a transmission assembly for coupling a forerunning gearbox stage to a generator of a wind turbine. The present invention further relates to a gearbox for a wind turbine comprising the transmission assembly. The present invention further relates to a drive train of a wind turbine comprising the gearbox. The present invention further relates to a wind turbine comprising the drive train.

Wind turbines are increasingly used for the generation of electrical energy. A wind turbine comprises a tower and a nacelle mounted on the tower, to which a hub is attached. A rotor is mounted at the hub and coupled to a generator. A plurality of blades extends from the rotor. The blades are oriented in such a way that wind passing over the blades turns the rotor, thereby driving the generator. Hence, the rotational energy of the blades is transferred to the generator, which then converts the mechanical energy into electricity and transfers the electricity to the electrical grid.

A main drive shaft in the nacelle connects the rotor of the wind turbine to a gearbox, which in turn drives a shaft that turns the rotor in an electrical generator. The role of the gearbox is to couple the low-speed but high-torque drive shaft of the wind turbine rotor with the high-speed and low- torque generator rotor.

The majority of geared drive trains in existing wind turbines of ratings >1 MW utilize multiple gear stages to achieve gear ratios ranging from about 1:70 up to about 1:110. Usually, the gearbox comprises the three following stages: a simple planetary or epicylic first stage, followed by two parallel offset stages, comprising a bull gear and pinion gears, or a second simple planetary stage followed by a parallel offset stage. The high gear ratio enables a generator that is substantially smaller and lower cost than the gearbox. Hence, the output shaft of the gearbox is a high-speed shaft. It is des irable to keep the parallel stages of a wind turbine gearbox in a good alignment for a correct engagement of the gears in the gear mesh so as to withstand gear forces and moments in all directions and to be able to dismantle the components easily in the field . In particular , a good alignment is desirable between the intermediate and high-speeds shafts , which endure higher temperatures and thermal expansion .

Gearboxe s are expensive , heavy and often dif ficult to maintain and repair over a 20 year lifetime .

A more optimal configuration of a geared drive train i s therefore desirable by the wind industry to provide increased reliability and availability, reduced cost , reduced ma s s and size , eas ier maintenance and increased efficiency .

A known solution to the above challenge is to use two or three bearings located at each side of the gears . The most wide spread solution in this category, is based on using two tapered roller bearings with "X" configuration al so known as face-to-face configuration , on one side and one cylindrical bearing on the opposite side . However , this known solution has the drawback that it needs a lot of axial space in the gearbox housing , uses 3 relative expensive bearings and additionally enough axial space has to be provided to dismantle the high-speed shaft and the inner bearings .

Other known solution is the use of one tapered roller bearing on one end of the shaft , and another tapered roller bearing at the opposite end of the shaft , both arranged in "0" configuration , al so known a s back to back configuration . However , in this solution it is neces sary to provide a split housing for the bearings where a heavy cover has to be dismantled in order to get acces s to the bearings .

The current development of the technology of wind turbines tends to an increa sed si ze of wind turbines for harvesting more wind energy, with longer blades and higher towers . As more energy is produced, the size and weight of the drive train components, i.e. the gearbox, the generator or the power electronics, and the components connected to the drive train components have increased in size as well.

Thus, the space for the drive train components is very limited and it is an object of the invention to provide a simple transmission assembly which efficiently transfers the torque and requires less components than the transmission assemblies or gearboxes in general known in the art, which results in a reduced weight and a reduced manufacturing cost.

This is achieved by a transmission assembly according to claim 1, a gearbox according to claim 12, a drive train according to claim 13 and a wind turbine according to claim 15.

According to the invention, a transmission assembly for coupling a forerunning gearbox stage to a generator of a wind turbine is divided into an input side and an output side and comprises an intermediate speed shaft, a high-speed shaft, and a gear mesh.

The intermediate speed shaft is supported by an intermediate speed shaft bearing arrangement and comprises an intermediate speed shaft gear.

The intermediate speed shaft is configured to rotate about an intermediate speed rotational axis.

The high-speed speed shaft is supported by a high-speed shaft bearing arrangement and comprises a high-speed shaft gear.

The high-speed shaft is configured to rotate about a highspeed rotational axis.

The high-speed shaft is configured to rotate faster than the intermediate speed shaft, as the role of the transmission as- sembly is to couple the low-speed but high-torque intermediate speed shaft with the high-speed and low-torque generator rotor .

The gear mesh is formed by an engagement of the intermediate speed shaft gear and the high-speed shaft gear, wherein the gear mesh is configured to transfer a torque between the intermediate speed shaft and the high-speed shaft.

A separation plane arranged at the gear mesh perpendicular to the intermediate speed rotational axis and the high-speed rotational axis separates the two sides of the transmission assembly into an input side and an output side. The input side is the side of the transmission assembly where torque enters the transmission assembly, and therefore the side where the shaft of the transmission assembly receives the torque from an external component. The output side is the side of the transmission assembly where torque exits the transmission assembly, and therefore the side where the shaft of the transmission assembly transmits the torque to an external component .

Hence, the expression "divided into an input side and an output side" means that a separation plane arranged at the gear mesh perpendicular to the intermediate speed rotational axis and the high-speed rotational axis separates the input side from the output side of the transmission assembly.

According to the invention, both the intermediate speed shaft and the high-speed shaft comprise each a coupling end. The coupling end of the intermediate speed shaft is arranged at the input side and is configured to be coupled to an output of the forerunning gearbox stage. The coupling end of the high-speed shaft is arranged at the output side and is configured to be coupled to an input of the generator. In particular, the coupling can be a direct or an indirect coupling . According to the invention, the high-speed shaft gear and/or the intermediate speed shaft gear are supported by the respective bearings in a cantilever manner.

Supported in a cantilever manner means that the bearing arrangement is arranged only on one side of the gear and the gear is in radial direction unsupported on the other side. In particular, the bearing arrangement is arranged either on the input side of the transmission assembly or on the output side of the transmission assembly for the respective shaft, but the shaft is not supported on both the input side and the output side by the bearing arrangement.

In other words, cantilever manner means that the shaft is only supported by a bearing arrangement which is situated either on the input side or on the output side of the respective shaft.

By arranging the bearing arrangement only on one side of the shaft gear, enough support is provided for each the highspeed shaft and the intermediate speed shaft while reducing the number of bearings used in the transmission assembly, thereby reducing space requirements and having an economical solution which efficiently transfers torques. In addition, the shafts are at least partially loaded by the couplings at each coupling end between the input of the transmission assembly and a torque transferring component, such as a forerunning gearbox stage like a planetary gearbox stage, which transfers the torque to the transmission assembly or between the output of the transmission assembly and a torque receiving component, such as the generator, which receives the torque from the transmission assembly. In special arrangements, a coupling might be designed in a way that the shaft is partially supported by the coupling.

The shafts are also loaded by the gear mesh. However, the shafts are only supported on one side between the shaft gear and the end of the shaft . Even if this cantilever support requires a slightly stiffer des ign of the shaft and bearing support , this conf iguration results in total in a reduced weight and reduced manufacturing cost , in particular by shortening the shafts of the parallel stages and by avoiding the need for heavy detachable housing for the bearings .

The coupling between the coupling end of the high-speed shaft and the input shaft of the generator can be a direct or an indirect coupling . Similarly, the coupling between the coupling end of the intermediate speed shaft and the forerunning gearbox stage can be a direct or an indirect coupling .

In particular , both the intermediate speed shaft and the high-speed shaft compri se each a radially supported shaft portion at which the respective bearing arrangement is arranged and a gear portion at which the respective shaft gear is arranged in such a way that the shaft s are radially supported in a cantilever manner .

If the bearing arrangement i s arranged at the opposite side from where the coupling end of the shaft is located, then the shaft comprises a free end, which is a part of the shaft axially extending from the gear towards the opposite side of the coupling end and which i s not conf igured to be coupled to any other component or to transmit the torque to any other component . The free ends of both the intermediate speed shaft and the high-speed shaft are ends of the shafts which do not transfer the torque and are not in the pathway of the torque being transmitted from the coupling end of the intermediate speed shaft to the coupling end of the high-speed shaft . The shaft is then supported at the free end by the bearing arrangement and the portion of the shaft between the gear portion and the coupling end of the shaft is radially unsupported . In a preferred embodiment , the coupling is a direct coupling , what means that the generator input shaft runs with the same speed than the high-speed shaft . The invention is most beneficial if used for a shaft directly coupled to the generator input shaft , as often the axial space between gearbox and generator is very limited and the compact de sign of the invention allows for reduced size and weight of drive train by still allowing easy maintenance in the limited available space .

According to another preferred embodiment of the invention , the high-speed shaft bearing arrangement is arranged at the opposite side of the intermediate speed shaft bearing arrangement relative to the separation plane . In other words , one of the high-speed shaft bearing or the intermediate shaft bearing is arranged on the input s ide and the other one is arranged on the output s ide . This arrangement is advantageous as it provide s an optimal bearing support for the transmission as sembly .

According to another preferred embodiment of the invention , the high-speed shaft bearing arrangement is arranged at the output side and the intermediate speed shaft bearing arrangement is arranged at the input side . This configuration is particularly advantageous to counteract deflections of the shaft originating from the rotation of the shaft , as the cantilever support acts against the deflections , thereby minimiz ing the radial distance between the gears of the gear mesh and allowing the shafts to stay substantially parallel during rotation .

According to another preferred embodiment of the invention , the high-speed shaft bearing arrangement is arranged at the input side and the intermediate speed shaft bearing arrangement is arranged at the output side . This is another alternative to counteract deflections of the shafts . According to another preferred embodiment of the invention , the high-speed shaft bearing arrangement is arranged at the same side as the intermediate speed shaft bearing arrangement relative to the separation plane . In other words , both the high-speed shaft bearing and the intermediate shaft bearing are arranged either on the input s ide or on the output side . Thi s configuration allows for a shorter transmis s ion a s sembly, as the bearing arrangements can be arranged compactly with a radial distance from one another .

According to another preferred embodiment of the invention , both the high-speed shaft bearing arrangement and the intermediate speed shaft bearing arrangement are arranged at the output side . Both bearing arrangements can then be supported on the gearbox housing or on the generator housing .

According to another preferred embodiment of the invention , both the high-speed shaft bearing arrangement and the intermediate speed shaft bearing arrangement are arranged at the input side . Both bearing arrangements can then be supported on the gearbox housing .

According to a preferred embodiment of the invention , the radially supported shaft portion of the high- speed shaft is arranged only between the high-speed shaft gear and the coupling end of the high-speed shaft . Thi s arrangement i s advantageous as it provides best load transfer from the gear and the coupling end into the bearing support .

According to another preferred embodiment of the invention , the radially supported shaft portion of the high-speed shaft is arranged only between the high-speed shaft gear and the free end of the high-speed shaft . This arrangement has the advantage that the high-speed shaft can be easily dismounted by pulling it out in direction of the coupling end .

According to another preferred embodiment of the invention , the radially supported shaft portion of the intermediate speed shaft is arranged only between the intermediate speed shaft gear and the coupling end of the intermediate speed shaft . Thi s arrangement again allows for best load transfer to the bearing support .

According to another preferred embodiment of the invention , the radially supported shaft portion of the intermediate speed shaft is arranged only between the intermediate speed shaft gear and the free end of the intermediate speed shaft . Thi s arrangement is advantageous for exchange of the intermediate shaft bearing in case of bearing damage .

According to another preferred embodiment of the invention , the high-speed shaft bearing arrangement and/or the intermediate speed shaft bearing arrangement compri se a pair of tapered roller bearings coaxially arranged to the respective shaft .

An advantage of the incorporation of at least one pair of tapered roller bearings i s that the shaft can be shorter compared with conventional shaft s , which implies weight and cost reduction of the transmi s sion as sembly .

Hence , the pair of tapered roller bearings are coaxially mounted either on the high-speed shaft , on the intermediate speed shaft or on both shafts .

According to another preferred embodiment of the invention , the pair of tapered roller bearings is arranged in an "X" or face-to-face configuration .

According to another preferred embodiment of the invention , the pair of tapered roller bearings is arranged in an "0" or back-to- back configuration . The ”0" arrangement allows for best support of the shaft against misalignments .

The pair of tapered roller bearings can withstand loads and bending moment s in any direction and they can be set to the neces sary endplay or preload to cope with temperatures . In particular , the two tapered roller bearings in back-to-back configuration , withstand axial forces equally in both axial directions , and are les s sens itive to temperatures than the "X" conf iguration .

An additional advantage of the above-des cribed bearing arrangement is that the position of the tapered roller bearings may be designed so that the shaft deflection of the highspeed shaft and the intermediate speed shaft , goes in the same direction , such that an optimum gear mesh alignment i s realized .

By choos ing a conf iguration of the arrangement of the bearings in a way that the rotational axis of the shaft gears stays substantially parallel even in deflected state , the radial distance between the gears will slightly increase but such a deformation i s much better for the load distribution in the gear me sh than other bearing arrangements , where due to the small deflections in the shaft the gears will not stay substantially parallel . In these other configurations , there is les s contact at the gear mesh and a les s efficient load transfer between the axe s .

According to another preferred embodiment of the invention , the tapered roller bearings are axially retained between a radial abutment of the shaft and a retention ring .

According to another preferred embodiment of the invention , the intermediate speed shaft bearing arrangement and/or the high-speed shaft bearing arrangement is supported on a housing .

The hous ing at which the intermediate speed shaft bearing arrangement is supported can be different from the housing at which the high-speed shaft bearing arrangement is supported . For example , the intermediate speed shaft bearing arrangement can be supported at the gearbox housing and the high- speed shaft bearing arrangement can be supported at the generator housing .

Alternatively, the housing at which the intermediate speed shaft bearing arrangement is supported can be the same as the housing at which the high-speed shaft bearing arrangement is supported. For example, both the intermediate speed shaft bearing arrangement and the high-speed shaft bearing arrangement can be supported at the gearbox housing.

Yet another aspect of the invention relates to a gearbox for a wind turbine comprising a forerunning gearbox stage and a transmission assembly coupled to the output of the forerunning gearbox stage.

Such a gearbox has the advantages of an efficient gear mesh between the shafts of parallel stages, and that is less sensitive to temperatures.

According to another preferred embodiment of the invention, the housing is a gearbox housing.

Yet another aspect of the invention relates to a drive train of a wind turbine comprising a main bearing unit, a main shaft coupled to an output of the main bearing unit, a transmission assembly coupled to the main shaft and a generator coupled to an output of the transmission assembly.

Yet another aspect of the invention relates to a drive train of a wind turbine comprising a main bearing unit, a main shaft coupled to an output of the main bearing unit, a gearbox coupled to the main shaft and a generator coupled to an output of the gearbox, wherein the transmission assembly is arranged between the forerunning gearbox stage and the generator .

Yet another aspect of the invention relates to a wind turbine comprising a drive train. In the present disclosure, the terms axial, axially or coaxially refer to the direction of the rotation axis of a shaft, such as the high-speed shaft or the intermediate speed shaft, or a direction parallel to that rotation axis .

In order to facilitate the understanding of the characteristics of the invention and being an integral part of this specification, some drawing sheets are attached on which figures, with an illustrative but not limiting character, the following is represented:

Figures 1 and 2 show a pair of tapered roller bearing in "X" and in "0" configuration, respectively.

Figures 3 to 6 show a gearbox of a wind turbine in different configurations.

Figures 7 to 10 show schematic drawings of transmission assemblies in the configuration shown in Figures 3 to 6 respectively .

Figures 11 and 12 show a wind turbine with different configurations of the drive train.

Figure 1 shows a cross-sectional view of the topology of a double tapered roller bearing (1) in a "X" or face-to-face configuration. As shown in the figure, each tapered roller bearing (1) has a plurality of tapered rollers arranged relative to the rollers of the other tapered roller bearing (1) , such that load reaction lines (2) of the rollers converge towards the axis (y) of the bearing, in a way that these load reaction lines (2) configure an "X" shape, or it could be said that the rollers of one tapered roller bearing (1) face the rollers of the other tapered roller bearing (1) . Each roller has a rotation axis, and the respective load reaction line (2) of each roller, is generally orthogonal to its rotation axis. Figure 2 shows a cross-sectional view of the topology of a double tapered roller bearing (1) in an "0" or back-to-back configuration. As shown in the figure, each tapered roller bearing (1) has a plurality of tapered rollers arranged relative to the rollers of the other tapered roller bearing (1) , such that load reaction lines (2) of the rollers diverge towards the axis (y) of the bearing, in a way that these load reaction lines (2) configure an "0" shape, or it could be said that the rollers of one tapered roller bearing (1) back the rollers of the other tapered roller bearing (1) .

Figures 3 to 6 show a gearbox (18) of a wind turbine (14) in different configurations. The gearbox (18) comprises a forerunning gearbox stage (19) followed by a transmission assembly (3) comprising a parallel offset stage. Both the forerunning gearbox stage (19) and the transmission assembly (3) are supported by bearings arranged between the housing (11) of the gearbox (18) and the respective shaft.

The transmission assembly (3) is configured to couple the forerunning gearbox stage (19) to a generator (16) of the wind turbine (14) .

The transmission assembly (3) comprises an intermediate speed shaft (5) comprising an intermediate speed shaft gear (25) coupled to an output of the forerunning gearbox stage (19) , a high-speed shaft (4) comprising a high-speed shaft gear (24) and being configured to be coupled to an input of the generator (16) , wherein the high-speed shaft (4) is configured to rotate faster than the intermediate speed shaft (5) , and a gear mesh (6) formed by an engagement of the intermediate speed shaft gear (25) and the high-speed shaft gear (24) , wherein the gear mesh (6) is configured to transfer a torque between the intermediate speed shaft (5) and the high-speed shaft ( 4 ) . The transmission assembly (3) is divided into two sides by the separation plane (30) , which are the input side (20) coupled to an output of the forerunning gearbox stage (19) and the output side (21) configured to be coupled to an input of the generator (16) .

The expression "divided in two sides by the separation plane" means that a separation plane (30) arranged at the gear mesh (6) perpendicular to the intermediate speed rotational axis (29) and the high-speed rotational axis (28) separates the input side from the output side (20, 21) of the transmission assembly.

The intermediate speed shaft (5) is supported on the housing (11) only by an intermediate speed shaft bearing arrangement (23) arranged between the housing (11) and the intermediate speed shaft (5) and the high-speed shaft (4) is supported on the housing (11) only by a high-speed shaft bearing arrangement (22) arranged between the housing (11) and the highspeed shaft ( 4 ) .

Each of the intermediate speed shaft (5) and the high-speed shaft (4) comprise a coupling end (26) and a free end (27) , wherein the coupling end (26) and the free end (27) are separated by the shaft gear (24, 25) .

The coupling end (26) of the intermediate speed shaft (5) is coupled to the output of the forerunning gearbox stage (19) . The coupling end (26) of the high-speed shaft (4) is configured to be coupled to the input of the generator (16) of the wind turbine (14) .

Both the intermediate speed shaft (5) and the high-speed shaft (4) comprise each a radially supported shaft portion at which the respective bearing arrangement (22, 23) is arranged and a gear portion at which the respective shaft gear (24, 25) is arranged in such a way that the shafts (4, 5) are radially supported in a cantilever manner. In Figure 3, the high-speed shaft bearing arrangement (22) at the radially supported shaft portion is arranged only between the high-speed shaft gear (24) and the coupling end (26) of the high-speed shaft (4) and the intermediate speed shaft bearing arrangement (23) at the radially supported shaft portion is arranged only between the intermediate speed shaft gear (25) and the coupling end (26) of the intermediate speed shaft ( 5 ) .

In Figure 4, the high-speed shaft bearing arrangement (22) at the radially supported shaft portion is arranged only between the high-speed shaft gear (24) and the free end (27) of the high-speed shaft (4) and the intermediate speed shaft bearing arrangement (23) at the radially supported shaft portion is arranged only between the intermediate speed shaft gear (25) and the coupling end (26) of the intermediate speed shaft (5) . Thus, the high-speed shaft bearing arrangement (22) and the intermediate speed shaft bearing arrangement (23) are arranged at the same side of the separation plane (30) radially separated and at least partially axially overlapping, that means both bearings (22, 23) are arranged on the input side (20) of the transmission assembly (3) .

In Figure 5, the high-speed shaft bearing arrangement (22) at the radially supported shaft portion is arranged only between the high-speed shaft gear (24) and the coupling end (26) of the high-speed shaft (4) and the intermediate speed shaft bearing arrangement (23) at the radially supported shaft portion is arranged only between the intermediate speed shaft gear (25) and the free end (27) of the intermediate speed shaft (5) . Thus, the high-speed shaft bearing arrangement

(22) and the intermediate speed shaft bearing arrangement

(23) are arranged at the same side of the separation plane (30) radially separated and at least partially axially overlapping, that means both bearings (22, 23) are arranged on the output side (21) of the transmission assembly (3) . In Figure 6, the high-speed shaft bearing arrangement (22) at the radially supported shaft portion is arranged only between the high-speed shaft gear (24) and the free end (27) of the high-speed shaft (4) and the intermediate speed shaft bearing arrangement (23) at the radially supported shaft portion is arranged only between the intermediate speed shaft gear (25) and the free end (27) of the intermediate speed shaft (5) .

Figures 7 to 10 show schematic drawings of transmission assemblies (3) in the configuration shown in Figures 3 to 6 respectively. The high-speed shaft bearing arrangement (22) and the intermediate speed shaft bearing arrangement (23) of each transmission assembly (3) comprises a pair of tapered roller bearings (1) in "0" or back-to-back configuration. The pair of tapered roller bearings (1) of the high-speed shaft bearing arrangement (22) is axially retained at the high-speed shaft (4) between a radial abutment (8) of the shaft (4) and a retention ring (9) for each figure. Figures 7, 8 and 9 show the pair of tapered roller bearings (1) of the high-speed shaft bearing arrangement (22) axially retained at the highspeed shaft (4) between a radial abutment (8) of the shaft (4) and a retention ring (9) . In addition, Figure 9 and 10 also show the pair of tapered roller bearings (1) of the intermediate speed shaft bearing arrangement (23) axially retained at the intermediate speed shaft (5) between a radial abutment (8) of the shaft (5) and a retention ring (9) .

The transmission assembly (3) of Figures 7 to 10 is divided into two sides by the separation plane (30) , which are the input side (20) configured to be coupled to an output of the forerunning gearbox stage (19) and the output side (21) configured to be coupled to an input of the generator (16) . As seen in the Figures, the before-mentioned separation plane (30) is arranged at the gear mesh (6) perpendicular to the intermediate speed rotational axis (29) and the high-speed rotational axis (28) and separates the two sides (20, 21) of the transmission assembly (3) . Both the intermediate speed shaft (5) and the high-speed shaft (4) comprise each a radially supported shaft portion at which the respective bearing arrangement (22, 23) is arranged and a gear portion at which the respective shaft gear (24, 25) is arranged in such a way that the shafts (4, 5) are radially supported in a cantilever manner.

The configuration shown in Figure 7 is particularly advantageous. By having this configuration, the shaft deflection is considerably reduced, and the load line is transmitted through the complete length of the shaft gears (24, 25) . Due to the torque transmission, the intermediate speed shaft (5) is deflected at its free end (27) away from the high-speed shaft (4) and this deflection is blocked by the intermediate speed shaft bearing arrangement (23) being arranged at the opposite side of the free end (27) of the intermediate speed shaft (5) . Similarly, the high-speed shaft (4) is deflected at its free end (27) away from the intermediate speed shaft (5) and this deflection is blocked by the high-speed shaft bearing arrangement (22) being arranged at the opposite side of the free end (27) of the high-speed shaft (4) . The result of these small deflections is that the high-speed rotational axis (28) and the intermediate speed rotational axis (29) stay substantially parallel even in deflected state, but the radial distance between the gears (24, 25) will slightly increase. Nevertheless, such a deformation is much better for the load distribution in the gear mesh than in the configurations of Fig 8 and 9, where due to the (small) deflections in the shaft, the gears (24, 25) will not stay substantially parallel .

In the configuration of Fig. 10, the shaft deflections will behave in the same manner as described for Fig. 7, but as the bearings are arranged on both shafts near the free end of the shafts, the overall deformations might be slightly larger than in the configuration of Fig. 7. Figures 11 and 12 show a wind turbine (14) with different configurations of the drive train. The drive train comprises a main bearing unit (17) supporting the main shaft (15) coupled to the rotor of the wind turbine (14) and a generator (16) for generating electric power.

In Figure 11, the main shaft (15) is directly coupled to the intermediate speed shaft (5) of the transmission assembly (3) and the high-speed shaft (4) is directly coupled to the generator (16) .

In Figure 12, the main shaft (15) is coupled to a forerunning gearbox stage (19) . The output of the forerunning gearbox stage (19) is coupled to the intermediate speed shaft (5) of the transmission assembly (3) and the high-speed shaft (4) is directly coupled to the generator (16) . Both the forerunning gearbox stage (19) and the transmission assembly (3) form the gearbox (18) of the drive train.

Reference numbers

1 tapered roller bearing

2 load reaction line

3 transmission assembly

4 high-speed shaft

5 intermediate speed shaft

6 gear mesh

8 radial abutment

9 retention ring

11 housing

12 gearbox housing

13 generator housing

14 wind turbine

15 main shaft

16 generator

17 main bearing unit

18 gearbox

19 forerunning gearbox stage

20 input side 21 output s ide

22 high-speed shaft bearing arrangement

23 intermediate speed shaft bearing arrangement

24 high-speed shaft gear 25 intermediate speed shaft gear

26 coupling end

27 free end

28 high-speed rotational axis

29 intermediate speed rotational axis 30 separation plane