Abstract:
A light weight trailer for carrying elongated goods, especially for carrying at least two rotor blades of a wind energy system, having a front support frame; a rear support frame, with said front support frame and said rear support frame being adapted for supporting an elongated good; and a beam connecting said front support frame with said rear support frame, wherein said beam consists substantially of a light weight material. Further, a telescopic beam for a light weight trailer for carrying elongated goods and a method of constructing a light weight trailer are provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a light weight trailer, a telescopic beam and a method of constructing a light weight trailer. 
         [0002]    It is known that rotor blades for wind energy systems are transferred to construction sites of the wind energy systems on a regular basis using trailers. During manufacturing of the rotor blades certain ambient conditions are necessary. Therefore, the rotor blades are usually manufactured remotely of the construction sites, where the wind energy systems are to be set up. Hence a transfer of complete rotor blades is made necessary. 
         [0003]    During transportation of the rotor blades trucks and trailers are used. The trailers have to be arranged to accommodate a complete rotor blade, such that the trailers have to be long enough for supporting a complete blade. This makes the trailers heavy. In view of traffic regulations, which have to be observed, the payload of such trailers is only good enough for picking up a single rotor blade of a modern wind energy system. Therefore the payload of a trailer for an elongated good such as a rotor blade has to be enhanced. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In view of the above, a light weight trailer is provided for carrying elongated goods, especially for carrying at least one or two rotor blades of a wind energy system, including a front support frame and a rear support frame. The front support frame and the rear support frame are adapted for supporting elongated goods. Furthermore, a beam is provided which connects the front support frame with the rear support frame, wherein the beam consists substantially of a light weight material. 
         [0005]    According to another aspect, a telescopic beam is provided for a light weight trailer for carrying elongated goods including at least two beam members that can be telescoped into each other. At least one of the two beam members consists substantially of a light weight material. 
         [0006]    As used herein, telescopable beam members are understood in that the beam is extendable in order to form a beam of operational length e.g. by extracting a beam member out of the other. Further, the beam can be retracted to a shorter overall length e.g. when the beam is not used by inserting a part of the beam members into the others or by folding the beam. 
         [0007]    According to another aspect, a method of constructing a light weight trailer for carrying elongated goods is provided, wherein the method comprises providing a front support frame; providing a rear support frame; manufacturing a beam consisting substantially of light weight material for connecting the front support frame with the rear support frame; and mounting the beam between the front support frame and the rear support frame. 
         [0008]    According to a further aspect of the invention, a method of using a light weight trailer for carrying elongated goods, especially for carrying at least two rotor blades of a wind energy system, is provided. The light weight trailer typically includes a front support frame and a rear support frame. The front support frame and the rear support frame are adapted for supporting the elongated good. Furthermore, a beam is provided which connects the front support frame with the rear support frame, wherein the beam consists substantially of a light weight material. 
         [0009]    Further aspects, advantages and features of the present invention are apparent from the dependent claims, the description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures wherein: 
           [0011]      FIG. 1  is a schematic longitudinal-sectional view of an embodiment of of a tractor with a light weight trailer according to embodiments described herein. 
           [0012]      FIG. 2  is a schematic longitudinal-sectional view of an embodiment of a light weight trailer according to embodiments described herein. 
           [0013]      FIG. 3  is a schematic longitudinal-sectional view of an embodiment of a beam of a light weight trailer according to embodiments described herein. 
           [0014]      FIG. 4  shows a schematic cross-sectional view of an embodiment of a beam for a light weight trailer. 
           [0015]      FIG. 5  is a schematic longitudinal-sectional view of a telescoping device and a fixing device of an embodiment of a beam for a light weight trailer 
           [0016]      FIG. 6  is a schematic cross-sectional view of a wind energy system with rotor blades, wherein two of the rotor blades can be transported using the embodiment shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Reference will now be made in detail to the various embodiments of the invention, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the invention, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations. 
         [0018]      FIG. 1  is a schematic drawing of a tractor  100  with a light weight trailer  1   10 . The light weight trailer  110  comprises typically a front support frame  120  and a rear support frame  130 . On the front support frame  120  and the rear support frame  130  mounts  140  can be fixed, respectively. The mounts  140  are arranged for receiving two rotor blades of a wind energy system (rf.  FIG. 6 ), such that two rotor blades can be transferred using the truck and trailer combination of  FIG. 1 . During transport, the two rotor blades are fixed in alignment with the longitudinal axis of the trailer  110 . 
         [0019]    As described herein, the term “rotor blade” in the context of transporting the rotor blades is used as an example for elongated goods. Typical lengths of the elongated goods are at least 10 m, more typically at least 20 m, even more typically at least 25 m. In typical embodiments, the elongated goods are a complete rotor blade or part of a rotor blade of a wind energy system. Those rotor blades of modern wind energy systems that cannot be transported as a whole may therefore be transported split up in two or three parts. 
         [0020]    In typical embodiments, mounts for two rotor blades are fixed on the support frames. Other typical embodiments have mounts arranged for receiving more than two rotor blades. The maximum number of rotor blades which can be transported using embodiments described herein depends primarily on the weight and the dimension of the rotor blades since traffic regulations, especially regulations regarding the maximum gross vehicle weight have to be kept. The light weight trailer described herein may be suitable for transporting two, three or even four rotor blades. 
         [0021]    The light weight trailer of  FIG. 1  comprises a beam  150  connecting the front support frame  120  with the rear support frame  130 . In the embodiment of  FIG. 1 , the trailer  110  is a semitrailer-type trailer, wherein the rear support frame  130  serves as a chassis receiving three axles  160 . The front support frame  120  includes a coupling member  170  for coupling the trailer  110  with the tractor  100 . 
         [0022]    In typical embodiments semitrailer-type trailers are provided due to the ability of semitrailers to receive elongated goods. In other typical embodiments, two-pole-type trailers are used. Two-pole-trailers are trailers with two chassis connected by the beam. The front chassis is coupled to the tractor. In typical embodiments at least one of the axles of the trailer is a steering axle providing better maneuvering abilities for the tractor-trailer-combination. 
         [0023]    The beam  150  consists substantially of light weight material. In the embodiment shown in  FIG. 1 , the beam  150  consists substantially of aluminum. The beam  150  comprises extruded aluminum profiles manufactured using known techniques. 
         [0024]    Typically, the use of light weight material for the beam allows for transporting of at least two rotor blades of a wind energy system reducing transportation costs. In typical embodiments alloyed aluminum is used as light weight material, such that the beam consists substantially of alloyed aluminum. Alloys may be used to improve mechanical, corrosion or welding properties. Several aluminum alloys like 6061-alloys or 7075-alloys can be used in typical embodiments described herein. Alloys for alloying aluminum for typical embodiments include copper, zinc, manganese, silicon, or magnesium. Aluminium alloys are easy to manufacture. Aluminium alloys show good corrosion and durability properties. With a beam of aluminium, a trailer weighing less than trailers in the art can be provided. 
         [0025]    In typical embodiments having aluminium beams, the aluminium beam or the aluminium beam members are extruded. In other typical embodiments, aluminium plates are welded to form a beam or a beam member. Aluminium alloys used in typical embodiments are widely used and inexpensive. 
         [0026]    In further typical embodiments, composite material is used as light weight material for the beam, such that the beam consists substantially of composite material. Several composite materials can be used, like single cure composites or dual cure composites. Examples of dual cure composites used in typical embodiments are described in the European patent application EP 1 764 382 A1, assigned to the same assignee, which is incorporated herein by reference. In typical embodiments, composite materials comprise glass fibers and carbon fibers embedded in a matrix. Typically, the matrix is fiber reinforced. In typical embodiments, the carbon fibers are orientated substantially parallel to the longitudinal axis of the beam. This provides a maximum stiffness with respect to bending load. Composites used in typical embodiments are also described in the European patent application EP 1 798 412 A2, assigned to the same assignee, which is incorporated herein by reference. In further embodiments multilayer composite materials are used. Such multilayer materials are described in the U.S. Pat. No. 7,153,576 B2, assigned to the same assignee, which is incorporated by reference. Reference is made to the chemicals and the methods of manufacture described in the above-named European patent applications and the United States Patent. Typically, the beam comprising composite material is manufactured by laminating layers of fiber material. Typically glass fibers and carbon fibers are used, wherein the matrix comprises typically resin, such as epoxy resin. Composites are very light, such that the beam of composite material is very light and the trailer comprising such a beam has a maximum payload. Furthermore, composite materials provide high stiffness. Hence, deflection of the beam comprising composite material as the primary or the supporting material is kept low. 
         [0027]    The term “consists substantially of light weight material” as used herein embraces all constructions consisting substantially of aluminum, composite material or another light weight material, respectively. Typically, the beam comprises fixations for fixing the beam at the support frames. Theses fixations are part of the beam but can be of a different material as compared to the main part of the beam, such that most of the beam is made of light weight material except some special parts. Typically, the term “consists substantially of light weight material” as used herein means that the mass percentage of light weight material of the beam compared to the overall weight of the beam amounts to at least 75%, more typically 80%, even more typically 90% or even 95%. This applies similarly for the terms “consists substantially of aluminum” and “consists substantially of composite material”. Typical light weight materials used in embodiments described herein are aluminum and composite materials like glass-carbon-composites, glass-steel-composites and glass composites. In further typical embodiments combinations of composite materials with aluminum materials are used. 
         [0028]    In the embodiment shown in  FIG. 1 , the beam  150  is extendable. The beam  150  is a telescopic beam, which comprises three telescopic beam members  181 ,  182 ,  183 . The telescopic beam members  181 ,  182 ,  183  are hollow, wherein a smaller beam member can be moved at least partially into a bigger beam member. The beam member  183 , which is the biggest one of the beam members  181 ,  182 ,  183 , may be moveable into the rear support frame  130  thereby entering the rear support frame partly or completely. Hence, the rear support frame  130  can act as a fourth hollow beam member of the telescopic beam. Due to the telescopic beam  150 , the trailer  110  can be converted in a retracted position (not shown), such that the gross length of the trailer can be reduced remarkably. 
         [0029]    Typically, the beam is extendable. In typical embodiments described herein, the beam is a telescopic beam comprising at least two telescopable beam members. Also three, four or even more telescopable beam members are comprised in typical embodiments described herein. Typically, the beam comprises a fixing device for fixing the beam in a retracted position or an extended position. In further embodiments, the extendable beam is foldable, such that it can be transformed into a folded position. In use, the foldable beam is extended and used to connect the rear support frame and the front support frame. 
         [0030]      FIG. 2  is a schematic drawing of a light weight trailer according to embodiments described herein. With respect to  FIG. 2 , same reference numbers are used for same or equal parts compared to  FIG. 1  and the description of  FIG. 1 . However, the beam  150  of the embodiment shown in  FIG. 2  consists substantially of composite material. The composite material is a glass fiber and carbon fiber material, wherein the fibers are embedded in a matrix material. 
         [0031]      FIG. 3  is a schematic drawing of a beam of a light weight trailer according to embodiments described herein. With respect to  FIG. 3 , same reference numbers are used for same or equal parts compared to  FIG. 1  and the description of  FIG. 1 . The beam as described herein may be used for equipping a trailer with. Accordingly, trailers known in the art having beams of a high weight may be re-equipped with the beam as described herein. 
         [0032]      FIG. 4  shows a schematic cross-sectional view of the beam of  FIG. 3  along the indicated dotted line in  FIG. 3 . Again, same reference numbers are used for same or equal parts as in conjunction with  FIGS. 1 and 3 . The beam members  181  and  182 , of which a section is shown in  FIG. 4 , are extruded aluminum profiles arranged to be telescopable. Therefore, the section of the beam member  181  is slightly smaller than the section of the beam member  182 . The beam member  181  can be pushed or pulled or otherwise moved into the beam member  182 . For a low-friction movement of the beam member  181  in the beam member  182 , bearings  190  may be provided between the beam member  181  and the beam member  182 . 
         [0033]    Typically, bearings are provided between two telescopable beam members. The bearings are usually PTFE bearings. In other typical embodiments, roller bearings are used to ease the movement of one of the beam members in another one of the beam members. 
         [0034]    With reference to  FIGS. 1 to 4 , as explicit example, the beam member  181  may have a height of 416 mm and a width of 300 mm. The beam member  182  may have a height of 456 mm and a width of 350 mm. Finally, the beam member  183  may have a height of 506 mm and a width of 400 mm. The beam members may have a length of about 12 m, respectively. The minimum overlap of two beam members may be 1500 mm to ensure a reliable transmission of forces between the beam members. The thickness of the flanges of the hollow beam members may be reduced with the increasing width of the beam members  181 ,  182  and  183 : 20 mm (beam member  181 ), 15 mm (beam member  182 ) and 12 mm (beam member  183 ). The web thickness may be kept constant at 8 mm to prevent buckling of the web. The beam members may have a mass per unit length of roughly between 80 kg/m and 100 kg/m, depending which one of the beam members  181 ,  182  or  183  is regarded. The mass per unit length of the whole beam may be about 90 kg/m for aluminium as the light weight material. 
         [0035]    Typical embodiments use beam members having a minimum height of at least 300 mm. Hence, the beam has a minimum height of 300 mm. In further typical embodiments beams having heights of more than 400 mm, 500 mm, 600 mm or even more than 700 mm are used. Bigger heights provide better stiffness of the beam, such that the deflection in the middle of the beam can be restricted. Also the thicknesses of the flanges and the webs of the beam members can be reduced using beam members with bigger heights. However, possible buckling puts a boundary to even smaller webs and flanges, such that no further weight reduction can be achieved. Therefore, typical embodiments use beam members having a height of less than 800 mm, 700 mm or even less than 600 mm. The named measures of the beam members of typical embodiments apply for all light weight materials used in embodiments of the invention, especially for aluminium and composite material beams. Typical embodiments provide an overlap or the telescopable beam members of at least 1200 mm, 1300 mm or even 1400 mm. The overlap of the beam of typical embodiments in the extended situation is less than 1800 mm or less than 2000 mm. The whole beam of typical embodiments has a mass per unit length of less than 150 kg/m or even less than 120 kg/m. Other embodiments have a mass per unit length of less than 100 kg/m for the whole beam. A “mass per unit length of the whole beam” means an average value for the whole beam, wherein some of the beam members can be lighter or heavier. Of course, in overlapping sections of the telescopable beam members, the mass per unit length is increased compared to sections with a single beam member. 
         [0036]      FIG. 5  shows a detail of the embodiment of  FIG. 3  schematically. The beam members  181  and  182  are telescopable by using a telescopic device. The telescopic device is a rope-type device which is usable to push the beam member  181  such that the beam members  181  and  182  are pulled apart. For this reason, a rope  200  is drawn over a rope winch  210  arranged inside of the beam member  182  and fixed to the beam member  182 . The rope winch  210  can be used to move in the rope  200 . The rope  200  is further drawn over a rope pulley  220 , which is also fixed to the beam member  182 . Furthermore, a rope pulley  230  fixed to the beam member  182  and an end fixation  240  for the rope at the beam member  181  provide a tackle-type device, such that a moving in of the rope using the rope winch  210  causes a movement of the beam member  181  in the direction of an arrow  250 . The movement in the direction of the arrow  250  leads to an extraction of the telescopable beam members  181  and  182 . 
         [0037]    In typical embodiments, the telescopic beam comprises a telescopic device to retract or expand the beam. Typical telescopic devices are hydraulic devices or rope-type devices. Other known devices are used in further typical embodiments. Also manual telescoping devices are used in typical embodiments. The pulling force of the tractor is used in typical embodiments to expand the telescopic beam. Therefore, the rear chassis is fixed, such that the beam can be expanded or retracted by pulling or pushing the front support frame with the tractor. 
         [0038]      FIG. 6  is a schematic view of a wind energy system  300 , also referred to as a wind turbine. The wind energy system  300  includes a tower  310  to which a machine nacelle  320  is mounted at its top end. A hub  330  having three rotor blades  340  is mounted thereto. Typical embodiments of the invention allow for a transport of two of the rotor blades  340  with one truck not exceeding a maximum gross weight of 40 metric tons. Hence, traffic regulations regulating the gross weight and applying in many countries all over the world are not violated by such a truck transporting two rotor blades. 
         [0039]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.