DETAILED DESCRIPTION

FIG. 1 shows a manufacturing arrangement 1 for producing preforms for a wind turbine blade. It shows a mold 2 comprising a mold base 3 and a removable mold carrier 4, which is already partially removed from the mold base 3. Although only one mold 2 is shown, the manufacturing arrangement 1 comprises several of these molds 2 arranged side by side, all of which are modular molds comprising a mold base 3 and a removable mold carrier 4.

Arranged on the mold carrier 4 is preform building material 5 which is covered by a vacuum sealing foil 6. The building material 5 comprises fiber material like mats made of glass or carbon fibers, optionally at least one or several core elements for example made of wood like balsa wood or of a polymer foam or the like, and a binding agent usually in powder or granular form. The binding agent is provided only locally so that the building material respectively the mats and if provided the core elements are only locally fixed, when the binding agent has been molten and cooled again, as will be explained below. The building material 5 is vacuum-fixated on the mold carrier 4, as the vacuum sealing foil 6 seals a space between the foil 6 and the mold carrier 4, which is evacuated by a respective evacuation pump. The vacuum is maintained so that the mold carrier 4 can be transported.

The mold carrier 4 is, as shown by the arrow P1, partially already removed from the mold base 3 and loaded onto a transport means 7, here in form of a rack, where already several other mold carriers 4 with the respective building material 5 and vacuum sealing foils 6 are arranged. The transport means 7 moves on rails 8 along the row of molds 2 and receives the respective covered mold carriers 4. This rail guided movement is shown by the arrow P2.

The transport means 7 moves to an unloading position in which it is arranged adjacent to an oven 9, which has an opening 10, into which all covered mold carriers 4 can be loaded from the transport means 7. This unloading is shown by the arrow P3.

In the oven, the preform building material 5 is heated so that the binding agent melts and wets respectively embeds the other building material like the fiber mats and core elements into a respective binder matrix. After this temperature treatment, the heated mold carriers 4 are unloaded from the oven 9 through a rear opening 11 as shown in FIG. 2 and are moved into a cooling means 12, where it is cooled down to room temperature. The cooling means 12, also box-like like the oven 9, comprises a respective front loading opening and a rear unload opening. The mold carrier transfer from the oven 9 into the cooling means 12 is shown by the arrow P4.

After the preform building material 5, which is fixed by the binding agent, is cooled, it is removed from the cooling means 12 as shown by the arrow P5. The mold carriers 4 with the respective finished preform elements may then either be stored until the respective preform is needed or they may be directly transported to a construction site where the blade is built. It is also possible to remove the finished preform element from the mold carrier 4 after the cooling stage and to store the fixed and form-stable preforms either in a storage or to transport only the preforms to the construction site.

FIG. 2 shows a perspective principle illustration of the in part cut-open oven 9. The oven 9 comprises a housing 15 having a bottom 16, a top wall 17 and two side walls 18, 19. The housing 15 is open at both ends having a front opening 10 and a rear opening 11. Both openings 10, 11 are closable via roller doors 13, 14, which are open in FIG. 2.

At the side walls 18, 19 respective receiving means 20 in form of guiding rails 21 are provided which extend almost over the entire length of the side walls 18, 19. The length of the housing 15 corresponds to the length of the mold carriers 4, which are received on the respective receiving means 20. The receiving means 20 respectively the guide rails 21 are arranged in different heights so that the separate mold carriers 4 are arrangeable one above the other, as shown in FIG. 2. The guiding rails 21 may be provided with roller elements 22, while also sliding elements may be provided. Both are easing the loading and unloading process, during which each mold carrier 4 is placed on a pair of guide rails 21 and pushed into the oven 2 respectively pulled out of the oven 2, as shown in FIG. 2. The upper mold carrier 4 is pushed into the oven 2, while the lowest mold carrier 4 is pulled out of the oven 2. This loading and unloading process may be performed manually or automatically.

As already mentioned, the guide rails 21 are arranged at the side walls 18, 19. When the mold carriers 4 are loaded into the oven 9, they separate the whole oven chamber into respective smaller spaces 23, as shown in the FIGS. 3-6. In these examples, four plate- or trough-like mold carriers 4 are arranged on the respective receiving means 20 respectively guide rails 21. They extend from one side wall 18 to the other side wall 19. As mentioned, the length of the oven chamber corresponds to the length of the mold carriers 4, so that each mold carrier 4 separates a respective space 23.

To each space 23 a heating means 24 is assigned, which heating means 24 is, according to the embodiment of FIG. 3, realized as a hot air heating means, which comprises several hot air inlets 25, here arranged at the side wall 19, and several hot air outlets 26 arranged at the side wall 18. To each separate space 23 a respective number of inlets 25 and outlets 26 is assigned. Several inlets 25 are arranged side by side along the length of the side wall 19, the same is true for the outlets 26 at the side wall 18. The inlets 25 arranged to each space 23 are arranged in a horizontal row, the same is true for the respective outlets 26. The inlets 25 are directly opposite to the outlets 26 in each level respectively space 23.

Via the inlets 25 hot air, which has a temperature exactly corresponding to the desired temperature in the oven 9, is blown into the respective space 23, as shown by the arrows P6. It exits the chamber respectively space 23 via the respective outlets 26. Both, the inlets 25 and outlets 26 are connected to respective pipes 27, 28 as shown in FIG. 3, which pipes 27, 28 are coupled to an air temperature device which heats the air before it is blown into the chamber. A respective control is provided which controls the temperature and airflow. To control this, airflow sensors 29 and/or temperature sensors 30 may be arranged in the oven chamber respectively in each space 23. Although FIG. 3 shows only one airflow sensor 29 and one temperature sensor 30, several of these sensors may be distributed in each separate space 23 in order to measure each space specific airflow and temperature in order to specifically control the airflow respectively the heating via the overall control device. This may be done for example by controlling respective valves which are connected for example to the respective inlets 25 in order to vary the airflow respectively amount of air, or by controlling the air temperature etc.

FIG. 4 shows another embodiment of an oven 9, in which again four mold carriers 4 are loaded. They again divide the oven chamber into five separate spaces 23. Each chamber 23 is assigned with a number of heating elements 31. Each heating element is for example a resistance heating element 32, which is connected via respective cables 33 to a not shown power source so that they can be heated by controlling a respective current. Each resistance heating element 32 is for example designed like a longitudinal rod or the like, which extends in a transverse direction, so that in each space a certain number of these resistance heating elements 32 are arranged in a row and parallel to each other.

As shown, the resistance heating elements emit the heat as well to the upper surface of each mold carrier 4, where the building material is arranged, as to the bottom side of the respective mold carrier 4, so that also this type of heating element 31 allows a very even tempering of the mold carriers 4 respectively the building material in order to melt the binding agent.

Again, several temperature sensors 30 are distributed within the spaces 23 allowing to monitor the temperature respectively temperature distribution within each chamber. These measured values are provided to the control device controlling the heating elements 31, which may be individually controlled so that it is possible to immediately react if any inconsistency regarding the temperature distribution respectively the temperature level is recognized.

Alternatively, this kind of heating elements 31 could also be realized as radiation elements, i.e. radiation lamps, which emit an ultraviolet or infrared radiation. These radiation elements respectively lamps may be of cylindrical shape so that they emit the radiation in all directions. Also, these radiation elements are connected to a power source and may be individually controlled by a control device, again based on temperature sensor information. These radiation elements respectively radiation lamps also allow to evenly temper the building material for melting the binding agent.

Another embodiment of an oven 9 is shown in FIG. 5. Again, four mold carriers 4 with respective building material 5 are arranged on the respective receiving means 20 respectively the guiding rails 21, just like in the other embodiments. The mold carriers 4 divide the chamber volume into five separate spaces 23.

In this embodiment, the heating means comprises hot air heating means and heating elements. As shown, to the spaces 23, which are above the upper side of each mold carrier 4 respectively the building material, hot air heating means comprising hot air inlets 25 and hot air outlets 26 are provided, wherein several inlets 24 and outlets 25 are arranged in a row and are assigned to each respective space 23. The inlets 24 and outlets 25 again may be arranged opposite to each other in the respective side walls 18, 19.

In addition to the hot air heating means, also separate heating elements 31 are provided, which are again resistance heating elements 32, here in the form of heating wires which are connected to a respective power source which is controlled by a control device, just like the hot air heating means. The resistance heating elements 32 are arranged directly below each mold carrier 4 so that they almost directly heat the mold carrier 4 from below and thus heat the building material from below. The several resistance heating elements 32 assigned to a space 23 are arranged in parallel along the length of the space 23, but extend in a transverse direction.

Airflow sensors 29 are provided to sense the airflow in the respective chambers, as well as temperature sensors 30 in order to sense the temperature in the respective space 23.

In this embodiment, the control device may control two different types of heating means so that several degrees of freedom in controlling the heating of the respective space are provided. So, the control device may, depending on the respective sensor information, individually control either one or all of the hot air heating means or one or all of the heating elements in order to control an even temperature distribution.

FIG. 6 shows an example of an oven 9, again comprising four loaded mold carriers 4 with respective building material which divide the oven chamber into five spaces 23. Also, in this embodiment, different types of heating means are provided. In the spaces 23, above the upper side of the mold carriers 4 and therefore above the building material, separate heating elements 31, here in form of radiation elements 34, simplified shown as light bulbs, are provided which are connected via respective cables 35 to a power source and a control device. As shown, several of these separate radiation elements 34 respectively infrared or ultraviolet light bulbs are arranged in a row extending in a transverse direction. In each chamber 23, several of these rows are arranged. As shown, they radiate towards the upper side of each carrier 4 and therefore directly towards the building material.

Just like at the embodiment of FIG. 5, in addition also further heating elements 31 in form of radiation heating elements 34 are provided, again directly underneath each mold carrier 4. They are used to heat the mold carrier 4 and the building material from below. They extend in a transverse direction, while several of these separate resistance heating elements 32 are arranged in parallel, seen in the longitudinal chamber direction, in each space 23.

Again, the control device is adapted to control different types of heating elements, i.e. radiation heating elements 34 and resistance heating elements 32, which are separately controllable in order to control a constant and even temperature distribution.

FIG. 7 shows another embodiment of an oven 9, in which only hot air heating means 24 are provided. These hot air heating means 24 comprise several first hot air inlets 25, and several first hot air heating outlets 26, which are arranged at the respective side walls 18, 19, and which are assigned to each respective space 23, as the oven chamber again is divided into the respective spaces by the loaded mold carriers 4, which are not shown.

The first inlets 25 and outlets 26 are arranged at both ends of the housing