DE102008051807B4 - parabolic trough collector - Google Patents

Abstract

A parabolic trough collector having a reflective surface which concentrates the sunlight onto an absorber extending in the focal line, the reflective surface being disposed on at least one panel having a parabolic cross section and a straight extension in the longitudinal direction of the parabolic trough collector and a support structure disposed on the convex underside of each panel is, which is hingedly connected to a parabolic trough collector supporting substructure, characterized in that - the support structure (4) on the convex underside of the parabolic trough collector (1) arranged transversely to its longitudinal direction (8) extending supporting ribs (9a-c) In that on each supporting bulkhead (9a-c) a rotary bearing (3) for rotatably arranging the parabolic trough collector (1) about a rotation axis (27a-c) parallel to its longitudinal axis (8) is arranged, and that for the rotation of the parabolic trough collector (1 ) about its axis of rotation ( 27a-c) engage a plurality of synchronized drives (44) at least on the longitudinally outer support ribs (9a, c).

Description

The invention relates to a parabolic trough collector having a reflective surface which concentrates the sunlight onto an absorber running in the focal line, the reflective surface being arranged on at least one panel with a parabolic cross section and a straight extension in the longitudinal direction of the parabolic trough collector and on the convex underside of each Paneels a support structure is arranged, which is hingedly connected to a parabolic trough collector supporting substructure.

Parabolic trough collectors essentially consist of parabolic curved reflective surfaces, which concentrate the sunlight onto an absorber running in the focal line. The focal line and the apex of the parabola span the plane of symmetry of the parabolic-shaped reflecting surface. Depending on the type of construction, the length of such collectors is usually between a few meters and 150 meters. Shorter parabolic trough collectors can be combined as individual modules to form a collector field. In the absorbers, the concentrated solar radiation is converted into heat and released to a circulating fluid, in particular water or another liquid or gaseous medium.

For reasons of cost, the parabolic troughs are usually designed to be pivotable only about one axis, and to this extent the solar irradiation direction is tracked.

The European patent EP 1 397 621 B1 discloses such a parabolic trough collector having a plurality of self-supporting panels having a parabolic cross-section and a longitudinally straight extension. The panels serve to support the thin reflective surface associated with them. With its convex side, the panel is disposed on a longitudinally extending tubular support member provided with automated means for rotation about the axis of the support member so that the reflective surfaces can follow the panels of the solar movement. The panels may either be attached directly to the annular support member or may be supported on the transverse support ribs disposed on the tubular support member.

In either case, the prior art parabolic trough collectors require a solid and solid support structure to provide the panels with sufficient rigidity. The requirements on the dimensional accuracy and static stiffness of the supporting structures supporting the reflecting surfaces of parabolic trough collectors are extremely high, since in particular bending and torsional forces due to dead weight and wind loads must be taken without exceeding a definable, maximum deformation of the parabola leads to a loss of power ,

Due to the high demands on the accuracy of the parabolic shape, it is necessary to produce parabolic trough collectors in specially equipped fabrication plants. This circumstance results in high costs from transport logistics to assembly on the construction site, because the components are very fragile on the one hand and very bulky on the other hand.

In order to enable a low-cost production and a simple use even by inexperienced forces, the document discloses US 2 906 257 A a parabolic trough collector with a reflective layer which focuses the sunlight onto an absorber running in the focal line. The absorber is located at the parabolic trough collector in extension of lateral pivot pins which are arranged on end pieces of the parabolic trough collector. On the convex underside of the reflective layer, a support structure is arranged, which is formed from downwardly extending, at a central point below the collector converging bracing struts and metal tubes and laterally bounded by the end pieces. The end pieces constitute a support for an upwardly extending support. The support is formed from side cheeks fastened to the end pieces, which are connected to one another via a tube arranged above the focal line. At a central point of this tube are four wires which run diagonally to the corners of the parabolic trough collector. Each wire rope has a turnbuckle to bias the wires.

The structure of the parabolic trough collector formed from complex substructure on the underside and Drahtseilabspannung at the top of the US 2 906 257 A is statically sufficiently stable. Due to the high forces exerted by the Drahtseilabspannung on the tube of the support, this must be quite large dimensions. In that regard, the necessary pipe diameter causes undesirable shading of the reflective surface. Another disadvantage is that with increasing length in the Parabolic trough collector greater bending stresses occur, so that its maximum length is limited in the interest of still reasonable maximum deformation of the parabola.

The GB 2 235 786 A discloses a parabolic trough collector with a concave mirror that focuses incident sunlight onto an absorber. At the end faces of each mirror are braces formed from arms, which converge in bearing sleeves along the focus line of the absorber. The sleeves each sit on a bearing on a support on both sides of the parabolic trough collector. Centered at the bottom of the concave mirror is an auxiliary frame which is substantially perpendicular to the mirror's focus line. The outer, curved edge of the subframe is provided with a toothing, which meshes with a gear on a drive shaft. The drive shaft, which runs parallel to the axis of rotation of the absorber, is the same for all parabolic trough collectors arranged next to one another, so that they can all be simultaneously rotated by means of the drive shaft.

The post-published DE 10 2007 026 473 B4 discloses a parabolic trough collector having a reflective surface which concentrates sunlight onto an absorber extending in the focal line, the reflective surface being disposed on at least one panel having a parabolic cross section and a straight line in the longitudinal direction of the parabolic trough collector and a convex underside of each panel Supporting structure is arranged, which is hingedly connected to a parabolic trough collector supporting substructure. Starting from the end-side support frames, an upwardly extending support is arranged on each second support bulkhead, wherein at least four elongated power transmission means are arranged on the support. The power transmission means extend between the support and the support structure, the power transmission means forming the side edges of a straight pyramid whose tip lying in the plane of symmetry of the parabolic shaped reflecting surface is formed by the force transfer means converging on the support. To rotate the parabolic trough collector engages on the two end support ribs of the support structure to a rotary drive.

The WO 2005/120172 A2 discloses a thermal collector that produces a virtual parabolic geometry for a reflector assembly that is mounted on a planar modular grid tube frame. The collector has means for varying the angle of reflector elements with respect to the flat top of the lattice frame. The lattice frame is rotatably mounted in floor supports and can be rotated by means of a drive about an axis of rotation, so that the collector can follow the course of the sun. Further, the collector has brake means to set the Gitterrohrahmen in stormy conditions. The braking means comprise a balance weight coupled via a cable.

The DE 101 49 620 A1 discloses a solar collector with an absorber tube and a reflector assembly that concentrates solar energy on the absorber. During operation, the reflector is tracked so that the focal line lies in the absorber tube. The tracking of several matching collectors by means of a common drive.

The DE 10 2004 044 841 B4 discloses a heliostat device comprising a plurality of mirror devices with movable mirror surfaces, a drive for moving mirror surfaces and a coupling device for coupling mirror surfaces such that they are movable together. For coupling the drive to the mirror devices, the coupling device ensures that the torque of the drive is transmitted to the coupled mirror devices. The drive drives a plurality of drive wheels on which a transmission element, such as a chain, a belt or rope is mounted. The transmission element is moved linearly via the rotation of the drive wheel, whereby this movement can be transmitted to the mirror devices and converted there into a rotational movement. Based on the state of the art according to the EP 1 397 621 B1 The invention is based on the object to provide a parabolic trough collector, which is structurally simple, easy to assemble and therefore can be transported in parts and still ensures high parabola accuracy with high rigidity and great maximum length.

The solution is based on the idea to make a complex support structure on the underside of the reflective surface of the parabolic trough collector dispensable and at the same time optimally dissipate the static and dynamic forces occurring at the parabolic trough collector.

• – dass die Tragkonstruktion an der konvexen Unterseite des Parabolrinnenkollektors angeordnete, sich quer zu dessen Längsrichtung erstreckende Stützspanten aufweist,
• – dass an jedem Stützspant eine Drehlagerung zur drehbeweglichen Anordnung des Parabolrinnenkollektors um eine zu dessen Längsachse parallele Drehachse angeordnet ist und
• – dass zur Drehung des Parabolrinnenkollektors um dessen Drehachse mehrere miteinander synchronisierte Antriebe zumindest an den in Längsrichtung äußeren Stützspanten angreifen.

In detail, the problem is solved in a parabolic trough collector of the type mentioned, characterized

• - That the support structure arranged on the convex underside of the parabolic trough collector, extending transversely to its longitudinal direction supporting frames,
• - That at each Stützspant a rotary bearing for rotatably mounting the parabolic trough collector is arranged about a rotation axis parallel to the longitudinal axis and
• - That engage for rotation of the parabolic trough collector about the axis of rotation a plurality of synchronized drives at least on the outer longitudinal support ribs.

In order to immediately dissipate the resulting wind forces that cause torsion on the substructure, engage with the rotation of the parabolic trough collector about the axis of rotation a plurality of synchronized with each other drives at least to the longitudinal outer support ribs. Synchronization, refers to the temporal coordination of processes. The synchronization thus ensures that all drives simultaneously rotate by matching rotation angle and stop in matching rotational positions and further rotation of the driven frames is prevented.

In particular, if a drive acts on each supporting bulkhead, it is possible to dispense with further measures for stiffening to absorb and dissipate wind-induced torsional forces. Only the small piece of the panel between two adjacent pivot bearings is possibly twisted by torsional forces, while the torsional forces are absorbed on the support frames by the actuators acting there and derived to the substructure. The drives form with their power transmission links the abutment for the derivation of the torsional forces to the stable substructure. Since it is possible constructively reduce the distance between the supporting ribs, there are virtually no problems with torsional forces.

Preferably, all drives have a common rotary drive, in particular a motor which centrally generates a relatively small torque, which is transmitted by means of a gear reduction as a larger torque to the drives of the supporting ribs and thus at several points synchronously to the parabolic trough collector.

The drives for rotating the parabolic trough collector can optionally have individually or in combination at least one drive cable, at least one spindle or at least one worm gear. If the drives have a drive cable, this may in particular be designed as a steel cable. The rigid in the pulling direction steel cable ensures a sufficiently rigid torque coupling of the driven support ribs to the substructure. Nevertheless, the steel cable can stretch under tensile load. All the more, the longer the steel cable is. Torsional forces generated by wind can thus introduce potential energy into the tensioned steel cable. In conjunction with the polar moment of resistance, the stored energy can then alternate between potential and dynamic energy. In principle, this created a vibratory system. By a rope drive is structurally the possibility of the resulting natural frequency constructively set so high that it can come to no dangerous vibrations.

As a point of application for the power transmission elements of the drive, each support frame connected to a drive preferably has a subframe extending vertically downwardly from the convex underside of the parabolic trough collector subframe with an arcuate, in particular arcuate contour, wherein the ends of the arc transverse to the axis of rotation of the parabolic trough collector on the Stützspant begin.

If the drives have at least one drive cable, this is guided along the circular arc-shaped contour of the subframe and fastened, for example, at the end of the arcuate contour or on Stützspant itself. In order to enable the rotation of the parabolic trough collector in both directions of rotation, either two opposing drive cables are guided over the arcuate contour of the subframe or a drive cable wraps around the subframe, wherein the attachment of the drive cable, for example at the level of the axis of rotation on the subframe.

A particularly inexpensive embodiment of the synchronous drives of the supporting ribs with high storage capacity for potential energy is characterized in that the drive cables of adjacent drives are connected to each other to a circulating cable having a single common movement drive for the circulating rope thus formed. The leadership of the circulating rope via arranged on the base stationary pulleys or cable guides.

If the parabolic trough collector with rope drive to wind stimulation to react more rigidly, each drive cable is attached to a coupling element with a spindle nut, the rotational movement of a Spindle converts into a translational movement of the coupling element. The translational movement of the coupling element is converted by means of the attached ends of the drive cable in a rotational movement of the parabolic trough collector. Conversely, wind forces acting on the panels of the parabolic trough collector are taken up by the relatively short drive cable attached to the coupling element and discharged to the substructure via the spindle. For this purpose, a worm wheel is preferably non-rotatably arranged on the spindle, which meshes with a worm, wherein the worms of all drives are preferably arranged on a common shaft. The common shaft allows the use of a common motion drive to rotate all the drives engaging the support frames. Furthermore, the common shaft ensures a simple mechanical synchronization of all drives. Power surges, which are generated by wind, act on the drive cable on the spindle, which prevents a reverse rotation of the parabolic trough collector due to the power surge due to the self-locking.

If along the arcuate contour of the subframe, a toothing is arranged and the toothing meshes with a worm, which is arranged on a round rod, an extremely rigid drive is provided which removes the basis of a wind excitation of the panels of the parabolic trough collector. The oscillations still occurring in a cable drive in a cable drive are avoided. By executing the drive as a worm drive, there is a desired self-locking, which prevents a reaction of the torsional forces caused by wind on the movement drive.

If the individual drives are not self-locking, it must be ensured by other suitable measures that after rotation of the parabolic trough collector locking the drive in the desired rotational position is possible. This can be ensured for example by braking and / or locking devices, such as pawls, or by maintaining a torque counteracting a rotation in the rotary drive.

Even with the directly splined drive synchronization can be realized in a simple manner by the fact that on the worm carrying round rods of all drives each rotatably a worm wheel is arranged, which meshes with a worm, the worm arranged all the drives on a common shaft are. The common shaft is preferably provided with a common rotary drive.

In a further preferred embodiment of the invention, the drive acting on the support ribs drive is designed as a lever construction, which in particular comprises a toggle lever. In order to enable the rotational movement of the parabolic trough collector with the articulated lever and at the same time to ensure the desired self-locking after setting the desired rotational position, the articulated lever preferably has a guided in a guide link push rod which is pivotally connected to a threaded rod of a spindle. The guide slot is fixed to the Stützspant, while the threaded rod associated spindle nut is stationary but rotatably mounted, so that a rotation of the spindle nut causes a translation of the threaded rod of the hinge lever and thus rotation of the parabolic trough collector about its axis of rotation. In order to synchronize all lever drives in a simple manner, the invention is provided in an advantageous embodiment that rotatably on the spindle nuts of all drives a worm wheel is arranged that meshes with a worm, the worms of all drives are arranged on a common shaft. The common shaft is preferably connected only to a common rotary drive, which allows a synchronous rotation of all support ribs.

The required torsional stiffness of the parabolic trough collector can be improved or supported, that the support structure has at least three supporting ribs, starting from the end support ribs on each second Stützspant an upwardly extending support is arranged, that at least four elongated force transmission means are arranged on the support and in that the force transmission means extend between the support and the support structure, the force transmission means forming the side edges of a straight pyramid whose apex lying in the plane of symmetry of the parabolic shaped reflecting surface is formed by the force transfer means converging on the support.

By the interaction of the support structure with the above the parabolic trough pyramidally arranged power transmission means, a derivative of the torsional forces is achieved on the substructure.

Preferably two panels each, in particular in the form of structural plates with the associated dimensionally stable frames form the basis for a straight pyramid, formed from the support, which is supported on the central bulkhead and one of the power transmission means, preferably wire ropes, formed between a stop for the wire ropes on the support to the corners of the pyramid - preferably the outer end portions of the outer frames. As a result, optimal leverage ratios are ensured in the introduction of force. However, the attachment points can also be located at other positions of the support structure, provided that the connection of the force transmission means is ensured with the support structure on both sides of the plane of symmetry of the parabolic-shaped reflective surface at the same distance. However, a greater distance from the plane of symmetry brings about an improved dissipation of the forces acting on the parabolic trough collector.

The support structure must be capable of transferring shear stresses occurring in the panels. This can be done either by sufficiently rigid panels in conjunction with extending transversely to the longitudinal direction of the parabolic trough collector supporting frames. If less rigid panels are used, for. As structural plates, the support structure in the longitudinal direction Längsaussteifungen, especially at the edges of the frames. In addition, V-shaped profiles may optionally be arranged in the longitudinal direction on the underside of the panels. The Längsaussteifungen at the edges of the structural plates are preferably fixedly connected to the underside, in order to firmly clamp the structural plate both sides in the edge regions and thus to avoid local deformation of the structural sheet, for example by attacking wind loads. In addition, the structural sheet can be angled for stabilization near the edge around the longitudinal reinforcement.

The frames are a supporting component of the supporting structure and at the same time bear the panels. This design saves a lot of weight compared to a solid support structure.

The inventive arrangement with pyramidally arranged power transmission means is torsionally rigid with low design effort and weight. The thin rods or wire ropes of the bracing result in extremely low shading of the reflective surface. In addition, the particular rod-shaped support can be equipped at the same time with a holder for the absorber and thus fulfill a dual function.

By juxtaposing similar pyramids, a high torsional stiffness of a parabolic trough collector can be generated in conjunction with the drives acting on the supporting ribs over almost any length. The absorbed by the tension forces are derived via the pivot bearing arranged on each Stützspant to the dimensionally stable substructure and shift the operating effort to be operated by the dimensionally accurate parabolic trough on the less complex substructure.

At regular intervals determined by the required torsional rigidity, the distance of which is limited by the available production widths of the mirror films (currently not more than 1.25 m), the dimensionally stable frames are arranged and connected to one another by the panels, preferably in the form of structural sheets. The attachment of the structural plates to the frames is done in such a way that arranged on the structural plate connecting elements, for. B. welded angle pieces are bolted to the frames. The screw openings are arranged on the frames in such a way that the desired parabolic shape of the pattern sheets is produced via the screw connection.

• – Die Formgenauigkeit der reflektierenden Oberfläche ist alleine durch die Tragkonstruktion, insbesondere in Form der Spanten und ggf. Längsaussteifungen sowie der Paneele, insbesondere in Form der Strukturbleche gegeben. Statische Biegekräfte brauchen nicht berücksichtigt zu werden.
• – Der formstabile Unterbau übernimmt über die an jedem Stützspant angeordneten Lager die statischen Kräfte.

The parabolic trough collector according to the invention results in a separation of the functions:

• - The dimensional accuracy of the reflective surface is given solely by the support structure, in particular in the form of ribs and possibly Längsaussteifungen and the panels, in particular in the form of the structural plates. Static bending forces need not be taken into account.
• - The dimensionally stable substructure assumes the static forces via the bearings arranged on each support frame.

The punctual deviations of the parabolic trough from the local ideal parabolic cross section are minimal, so that the intercept factor becomes maximum. The focal width (due to the expansion of the reflected sunray cone) is smaller than in all previously realized parabolic troughs and the absorber tube diameter can exceed the focal width, whereby the intercept factor is 100%.

In an advantageous embodiment of the invention tolerances of the substructure can be compensated by adjustable to the substructure rotary bearings for the supporting structure. This allows the substructure be produced by any company based on site with little expertise and does not need to be produced in a specialized manufacturing plant and then transported.

The invention will be explained in more detail with reference to an embodiment. Show it

1 a perspective view of a parabolic trough collector seen from the bottom,

2 a perspective view of the parabolic trough collector after 1 seen from the top,

3a -C the static force relationships on a parabolic trough collector 1 and 2 .

4 the reaction forces on the rotary bearings on a parabolic trough collector with seven supporting ribs,

5 the static force conditions on a parabolic trough collector taking into account an asymmetrically acting additional force caused by wind loads,

6 a perspective view of a pivot bearing of the parabolic trough collector after 1 and 2 .

7 a perspective view of an embodiment of a support of the parabolic trough collector after 1 and 2 .

8th a schematic side view of a dynamic wind forces exposed parabolic trough collector,

9 a perspective rear view of a parabolic trough collector after 8th to illustrate the pivot bearing on each Stützspant,

10a -C schematic diagrams illustrating different concepts for the synchronized drive of the supporting ribs of a parabolic trough collector according to the invention and

11a -D total representations of three cooperating synchronous drives according to the concepts of the 10a -C for a parabolic trough collector with three support frames.

The parabolic trough collector ( 1 ) consists essentially of a substructure ( 2 ), which has rotary bearings ( 3 ) with a supporting structure ( 4 ) for two panels ( 5 ) connected is. On the off 2 recognizable surface of the panels ( 5 ) is a reflective mirror foil ( 6 ), which irradiates the sunlight incident on its surface onto an absorber running in the focal line (FIG. 7 ) bundles. The panels ( 5 ) of parabolic cross section extend longitudinally ( 8th ) of the parabolic trough collector ( 1 straightforward.

The total with ( 4 ) designated support structure of the parabolic trough collector ( 1 ) is arranged by three on the convex underside of the parabolic trough collector, transverse to its longitudinal direction ( 8th ) extending supporting ribs ( 9a . 9b . 9c ) as well as longitudinal reinforcements ( 19a - 19d ), wherein the between the two end support ribs ( 9a . 9c ) arranged support frame ( 9b ) an unspecified in the figures holder for a rod-shaped support ( 10 ) wearing. The holder may for example be designed so that on the upwardly facing narrow side of the middle Stützspantes ( 9b ) a pin is arranged in a corresponding, at the lower end of the support ( 10 ) arranged recess engages positively. The support ( 10 ) itself is in the plane of symmetry of the through the panels ( 5 ) Parabolically spanned surface, wherein the axis of the parabola over the entire length of the parabolic trough collector in the plane of symmetry. The axis of the parabola denotes the degrees of connection from the focal point of the parabola to its apex. The frames ( 9a C) are transverse to the longitudinal axis ( 8th ) of the parabolic trough collector formed parabolic and in profile preferably profiled in such a way that they in the direction of the longitudinal axis ( 8th ) opposing forces oppose a high moment of resistance. As profile cross sections are for example rectangular profiles, T-profiles or I-profiles into consideration.

At a distance ( 11 ) to the attachment of the support ( 10 ) on the support frame ( 9b ) are in matching height four wire ropes ( 12a , b, c, d) are struck with their opposite ends with the outer end portions ( 13a . 13b . 13c . 13d ) to the middle support frame ( 9b ) adjacent supporting ribs ( 9a . 9c ) are connected. The four wire ropes ( 12a , b, c, d) form the side edges of a straight pyramid whose apex from the at the support ( 10 ) converging wire ropes is formed. The wire ropes all have a matching length. The edges of the base of the through the wire ropes ( 12a -D) are parallel to the long edges ( 14a , b) or front edges ( 15a . 15b ) of the parabolic trough.

Below the stop ( 16 ) for the wire ropes ( 12a -D) shows the support ( 10 ) one in the axial direction of the support ( 10 ) effective suspension ( 17 ) on which the wire ropes ( 12a -D) pretensions. The suspension ( 17 ) is constructed in the manner of a Teleskopfederung and additionally equipped with a spring damper, not shown, which prevents the build-up of vibrations in the parabolic trough collector.

At the top of the prop ( 10 ) is a hollow cylindrical holder ( 18 ) for receiving the tubular absorber ( 7 ) arranged in the focal line of the through the panels ( 5 ) parabolic trough is located.

As already stated, the supporting structure ( 4 ) longitudinal ( 8th ) over at the edges of the panels ( 5 ) between the supporting ribs ( 9a , b, c) bolted longitudinal reinforcements ( 19a -D) stabilized. In addition, V-profiles ( 20 ) can be arranged.

The substructure ( 2 ) has a total of three legs ( 21a -C), where the legs ( 21a , b) by a cross member ( 22 ) are interconnected. The use of three legs allows safe installation even on uneven terrain. The leg ( 21c ), but also the legs ( 21a , b) are in clamps ( 23 ) and can therefore be for a horizontal orientation of the parabolic trough collector ( 1 ) adjust in height without problems. Between the leg ( 21c ) and through the legs ( 21a , b) supported cross tube ( 22 ) extends a cylindrical support member ( 24 ) on the top of each Stützspant ( 9a -C) associated pivot bearing ( 3 ) is arranged. Each pivot bearing ( 3 ) consists of two cheeks arranged parallel to each other ( 25 ) between each of which a rotation axis ( 27a C) about which the parabolic trough collector is pivotable. All rotary axes ( 27a C) are aligned with each other and extend through mutually aligned passages in semicircular approaches ( 26a -C) on the supporting ribs ( 9a c).

The tracking of the parabolic trough collector is done by pivoting the parabolic trough collector ( 1 ) around the through the pivot bearing ( 3 ) defined axis of rotation ( 27a C), wherein the pivoting movement by means of acting on the supporting ribs, for the sake of clarity in the 1 and 2 unillustrated drives ( 44 ), which is used to derive and absorb torsional forces in the parabolic trough collector at the end support ribs (FIG. 9a . 9c ), in particular on the semicircular downwardly extending subframe in the form of the profiles ( 28 ), attack.

All at the parabolic trough collector perpendicular to the longitudinal axis ( 8th ) attacking forces are directly via the pivot bearing ( 3 ) on the substructure ( 2 ) and the foundations are derived. Due to these forces, no bending stresses occur in the rotatable parabolic trough collector ( 1 ).

How out 3a) can be seen by means of a prestressed suspension in the form of a compression spring in the direction of the vertical rod-shaped support ( 10 ) a compressive force D, which by vectorial decomposition in turn in the wire cables ( 12a -D) generates a constant rope tension S in the direction of the wire ropes.

Out 3b) combined with 3c) It can be seen that this tensile force generated by the cable tension S also acts as a vector on the end regions (FIG. 13a -D) the supporting ribs ( 9a -C) works. If this vector is decomposed into components, it can be seen that a transverse force Q as compressive force causes the longitudinal stiffeners (FIG. 19a -D) charged. The horizontal component H and the vertical component V of the force both act on the end regions (FIG. 13a -D) the supporting ribs ( 9a -C) and generate via the leverage in the supporting bulkhead ( 9a . 9c ) a bending moment that must be taken up by its structure.

In 4 is shown in a longitudinal section through a seven supporting ribs having parabolic trough collector, as the reaction forces F on the respective bearings ( 3a -D). It can be seen that the direction of action of the reaction forces F alternates and the sum of all reaction forces is zero. The reaction force generated by each support in the associated bearings ( 3b ) is four times as large as the vertical component V of the individual cable tensions S. The reaction forces F / 2 at the repositories ( 3a . 3c ) are only half the size of the other camps ( 3b . 3d ) between the repositories ( 3a . 3c ).

The in the 3a) -C) and 4 shown static force relationships do not take into account external forces that produce torsions in the parabolic trough collector and thus the mirror; to absorb these forces, the parabolic trough collector ( 1 ) also be stiffened against torsion. The torsional stiffness is determined by the front side subframe ( 28 ) attacking drives ( 44 ) and additionally achieved by the pyramidal bracing on top of the parabolic trough collector.

When external forces act, the static system reacts in such a way that, although all the reaction forces F equalize to 0, shifts between the height of the bearings ( 3a -D) occurring reaction forces F whose size must be limited in order to limit the deformation of the parabolic surface of the mirror at all permitted external forces so that no energy losses are to be expected by defocusing.

The most important external forces are the wind loads which act on the parabolic trough collector acting as an aerodynamic profile, which reacts to the air inflow with static and dynamic forces, whereby the dynamic forces due to resonance vibrations can damage the parabolic trough collector.

In 5 is shown schematically how a z. B. caused by wind asymmetric additional force Z, simulated by a vertical force in an end region ( 13c ), affects the internal distribution of forces of the parabolic trough collector. As a result of the additional force Z, the original cable tension S increases by an amount ZS 1 in the wire ropes ( 12a . 12c ), which results from the vectorial decomposition of the acting force in the running direction of the rope, while the cable force S in the wire ropes ( 12b . 12d ) is reduced along the intersecting side edge of the pyramid by an amount ZS 2.

The suspension ( 17 ) is compressed due to the changed compressive force D. The attack ( 16 ) of the wire ropes ( 12a -D) thus shifts slightly downwards. In the parabolic trough collector occurs a rotation about the longitudinal axis. The resistance to this twist is called torsional resistance. It is the deciding factor for the absorption of wind loads. The torsional resistance is determined by the transverse rigidity of the supporting ribs ( 9a -C) to the longitudinal axis of the parabolic trough collector, the longitudinal extent of the wire ropes ( 12a -D) and the spring stiffness of the suspension ( 17 ) and the types of drive described below ( 44 ) certainly. The rigidity of the supporting ribs ( 9a C) and the length extension of the wire ropes is preferably determined so that by the displacement of the stop ( 16 ) against the force of the suspension ( 17 ) almost the entire additional force Z is recorded, wherein the displacement is to be limited so that all still on the mirror film ( 6 ) impinging sun rays on the absorber ( 7 ).

On the substructure ( 2 ), which can be created with relatively large manufacturing tolerances of low-skilled enterprises, are supplied rotary bearings ( 3a - d) mounted so that by adjustment of the pivot bearings ( 3a D) only the axes of rotation ( 27a C) must be aligned with each other. A precise adjustment of the distance between the bearings, however, is not necessary because preferably only one pivot bearing ( 3a ) longitudinal ( 8th ) non-displaceable as a fixed bearing and all other bearings ( 3b , c, d) are arranged displaceably in the longitudinal direction as a movable bearing, in particular also to compensate for temperature-induced expansion changes.

To explain the adjustment of the pivot bearings ( 3a - d) shows 6 as a detail only one opposite the support element ( 24 ) of the substructure ( 2 ) adjustable pivot bearing ( 3b ). Deviating from the embodiment of the 1 and 2 is the only partially illustrated support element ( 24 ) here as a U-profile and not designed as a hollow cylindrical tube. Decisive for the choice of the support element is merely that this is rigid due to the profiling. With the top of the U-shaped support element ( 24 ) are four vertically upstanding studs ( 29 ) for adjustable recording of the pivot bearing ( 3b ) attached. The pivot bearing ( 3b ) comprises parallel, vertically upwardly extending cheeks ( 25 ), which at its lower edge over a plate ( 30 ) are kept at a distance from each other. The plate ( 30 ) has in its corners four slots whose passage cross-section larger than the diameter of the studs ( 29 ).

About the at the bottom of the plate ( 30 ) adjacent support nuts ( 31 ), the height of the pivot bearing ( 3b ) adjust precisely. The elongated holes allow a limited displacement of the plate ( 30 ) in the plate plane and thus together with the height adjustment by the support nuts ( 31 ) an alignment of the axis of rotation ( 27b ) to the other axes of rotation ( 27a , c) the adjacent pivot bearings ( 3a . 3b ). In the 6 illustrated pivot bearing ( 3b ) is designed as a floating bearing. For this purpose, the one in the Passage of the approach ( 26b ) of the support frame ( 9b ) fixed bearing ring ( 32 ) on the axis ( 27b ) performed with axial play. The bearing ring ( 32 ) is in the illustrated embodiment in the passage of the approach ( 26 ) by two on both sides of the approach ( 26b ) adjoining and screwed together clamping rings ( 33 ) fixed. After correct alignment of the pivot bearings ( 3a -C) to each other by the screwed from above on the studs lock nuts ( 34 ).

The following is based on 7 a preferred support ( 10 ) for the pyramidal bracing of the supporting structure ( 4 ):
The rod-shaped support ( 10 ) is at its lower end of one on every other Stützspant ( 9b ), in 7 not shown holder added. At a distance to this at the lower end of the support ( 10 ) engaging bracket is a longitudinal direction of the rod-shaped support ( 10 ) immovable support flange ( 35 ), the support ( 10 ) surrounding. On the support flange ( 35 ) a disc spring column ( 36 ), whereby the passages ( 37 ) to the disc spring column ( 36 ) stacked single-plate springs at least the cylindrical cross-section of the rod-shaped support ( 10 ), so that the disc spring column ( 36 ) from above the support flange ( 35 ) section ( 38 ) of the support ( 10 ) can be recorded.

About the diaphragm spring column ( 36 ) is a hollow cylindrical sleeve ( 39 ), which at the upper end face a passage ( 40 ) for the section ( 38 ) of the support ( 10 ), while the lower end face is fully opened. The inner diameter of the hollow cylindrical sleeve ( 39 ) is greater than the outer diameter of the disc spring column and the support flange ( 35 ), so that the sleeve ( 39 ) with its inner lateral surface along the outer edge of the support flange ( 35 ) can slide.

The sleeve ( 39 ) forms at the same time the stop ( 16 ) for the four wire cables or thin rods ( 12a -D) the pyramidal bracing of the supporting structure ( 4 ) of the parabolic trough collector ( 1 ).

Constructive is the attack ( 16 ) on the sleeve ( 39 ) by four evenly over the circumference of the sleeve ( 39 ) mounted on the upper edge of holders ( 41 ), each holder ( 41 ) at its radially outwardly facing end face an upwardly open and extending in the vertical direction groove ( 42 ) having. Thickened ends ( 43 ) of the wire ropes ( 12a -D) engage behind the grooves ( 42 ) and can therefore easily with the sleeve ( 39 ) get connected.

• a) Reibung zwischen der die Kraft einleitenden Hülse (39) und den Einzeltellerfedern der Tellerfedersäule (36),
• b) Reibung zwischen den sich berührenden Oberflächen der gleichsinnig ineinander liegenden Einzeltellerfedern der Tellerfedersäule (36) sowie
• c) Reibung zwischen dem Abschnitt (38), der Stütze (10) und den Durchgängen (37) der Tellerfedersäule (36).

Preferably, the single-plate springs of the disc spring column ( 36 ) layered in the same direction. As a result, the spring force multiplies, without changing the spring travel. This takes account of the requirement that the wire ropes ( 12a -D) in the column ( 10 ) introduced forces completely from the disc spring column ( 36 ) can be recorded without a maximum permissible displacement of the stop ( 16 ), which would result in a defocusing of the parabolic trough collector. Another decisive advantage of disc spring columns consists in the friction occurring in disc springs, which counteracts the force applied from the outside. The frictional forces occur as hysteresis in the force-travel characteristic of the disc spring column in appearance. The frictional forces are generated by

• a) friction between the force-introducing sleeve ( 39 ) and the single-plate springs of the disc spring column ( 36 )
• b) friction between the contacting surfaces of the mutually intimate single-plate springs of the disc spring column ( 36 ) such as
• c) friction between the section ( 38 ), the support ( 10 ) and the passages ( 37 ) of the diaphragm spring column ( 36 ).

The friction also causes the suspension through the disc spring column ( 36 ) is damped against vibrations. This vibration damping, which must be achieved with other spring shapes by a separate vibration damper, can therefore be in a structurally advantageous and inexpensive manner by using an at least partially co-layered disc spring column in the support ( 10 ) integrate.

The basis of 7 closer explained support ( 10 ) can also be used directly with the support frame ( 9b ). Furthermore, the support does not have to be rod-shaped. All that is decisive for the design of the support is that the force-transmitting means form the side edges of a straight pyramid, while the peak lying in the plane of symmetry of the parabolic-shaped reflecting surface is formed by the force-transmitting means converging on the support. Furthermore, the support is symmetrical about the plane of symmetry of the parabolic-shaped reflecting surface and longitudinally too form the support supporting bulkhead, so that a uniform force is ensured in the Stützspant.

8th illustrates that dynamic wind forces generate torques that have to be derived statically. From the in 9 illustrated special way of storage ( 3 ) of the parabolic trough collector ( 1 ) on each support frame ( 9a . 9b . 9c ), the possibility arises over the length of the parabolic trough collector ( 1 ) at any number of places a drive ( 44 ) to track, which in detail in the 10 and 11 is shown. At these points, the wind forces are dissipated. The torsion moments are proportional to the length of the sections of the parabolic trough collector ( 1 ) between two with drives ( 44 ) provided supporting ribs ( 9a . 9b . 9c ). From the theory of periodic wind excitation and from practical wind tunnel tests is known that the lower natural frequency of the mirror must always be appreciably larger than the frequency of wind excitation. The mirror according to the invention is preferably designed so that its lower natural frequency is at least twice as high as the excitation frequency of about two to three Hertz.

The presentation of different drive concepts in the 10a to c and the 11a for the sake of clarity omit the complete illustration of the parabolic trough collector ( 1 ), in particular with reference to the 1 and 2 was explained in detail. Deviating from the representation in the 1 and 2 is the subframe ( 28 ) not as a profile, but schematically as a circular segment with a circular arc-shaped contour ( 45 ).

Based on 10a combined with 11a First, the concept of a drive ( 44 ) with a drive cable ( 46 ) explained. The drive cable ( 46 ) is along the arcuate contour ( 45 ) of the subframe ( 28 ), in particular from 10a recognizable, guided in such a way that the drive cable ( 46 ) the subframe ( 28 ) completely wraps around. The ends of the arcuate contour ( 45 ) are about a grade extending, a secant ( 47 ) forming contour interconnected. In the middle of this secant ( 47 ) at the level of the rotary axes ( 27a to c), the drive cable ( 46 ), for example by means of a clamping screw ( 48 ).

The two ends of the drive cable ( 56 ) are approximately flush with each other in the opposite direction and are connected to the substructure ( 2 ) rotatable, but fixedly mounted pulleys ( 49 ) with the drive cable ( 46 ) of the respective adjacent drive ( 44 ) to a circulating rope ( 49 ) connected. The circulating rope ( 49 ) is used for tracking the parabolic trough collector with a common movement drive ( 50 ) in one or the other in 10a illustrated arrow direction ( 51a . 51b ) emotional. After reaching a desired rotational position of the parabolic trough collector locks the motion drive ( 50 ), so that the locked drive cables ( 46 ) of the drives ( 44 ) can absorb occurring in the supporting ribs, caused by wind forces torques.

The drive ( 44 ) to 11b corresponds with regard to the guidance of the drive cable ( 46 ) the drive ( 44 ) to 11a , so that for explanation on the local statements and the presentation in 10a Reference is made. Differences arise to the extent that the drive cables ( 46 ) of adjacent drives ( 44 ) are not interconnected. Rather, the two ends of the drive cable ( 46 ) on a coupling element ( 52 ) with a spindle nut, which controls the rotational movement of a spindle ( 53 ) in a translational movement of the coupling element ( 52 ) converts. As a result of the translational movement, the ends of the drive cable ( 46 ) in the direction of the arrow ( 51a , b) moved back and forth, so that by turning the spindle ( 53 ) Different rotational positions of the parabolic trough collector can be adjusted. The locking of the drive ( 44 ) in the respective rotational position takes place by the self-locking of the spindle ( 53 ). At the front end of the spindle ( 53 ) is a worm wheel ( 54 ) rotatably arranged that with a screw ( 55 ) on a wave ( 56 ) combs. The neighboring drives ( 44 ) are all constructed consistently. The snails ( 55 ) of the neighboring drives ( 44 ) are on the same wave ( 56 ), so that only one movement drive ( 50 ) is required to synchronously rotate the parabolic trough collector with the three on the support ribs ( 9a to c) attacking drives ( 44 ) to effect. The movement drive shown only schematically ( 50 ) includes a motor and a shaft ( 56 ) acting reduction gear.

11c shows in conjunction with 10b a drive ( 44 ), in which along the circular arc-shaped contour ( 45 ) of the subframe ( 28 ) a gearing ( 57 ) is arranged. The gearing ( 57 ) combs with a snail ( 58 ) on a round rod ( 59 ) is arranged (see. 10b ). At the round bars ( 59 ) of all identically constructed drives ( 44 ) is in each case a worm wheel ( 60 ) arranged in turn with a screw ( 61 ), the snails ( 61 ) all drives ( 44 ) on a common wave ( 56 ) with a movement drive ( 50 ) are arranged.

11d shows in conjunction with 10c a drive ( 44 ) with a toggle lever ( 62 ). The articulated lever ( 62 ) has one in a guide ( 63 ) guided push rod ( 64 ), which by means of a joint ( 65 ) hinged with a threaded rod ( 66 ) is connected to a spindle. The threaded rod ( 66 ) associated spindle nut ( 67 ) is stationary, but rotatable on the substructure ( 2 ), so that a rotation of the spindle nut ( 67 ) a translation of the threaded rod ( 66 ) of the articulated lever ( 62 ) causes. On the spindle nut ( 67 ) of the drive ( 44 ) is non-rotatably a worm wheel ( 68 ), which with a snail ( 69 ) combs. The adjacent drives are all constructed in the same way. The snails ( 69 ) of all adjacent drives ( 44 ) are on a common wave ( 56 ) with a common motion drive ( 50 ) for the synchronous rotations of the parabolic trough collector on all support ribs ( 9a . 9b . 9c ).

It is advantageous if only one movement drive ( 50 ) on the drives ( 44 ) the tracking acts to achieve a synchronous rotation of the driven frames.

The drives ( 44 ) after the 11a -D have different effects on the vibration behavior of the parabolic trough collector ( 1 ) under dynamic wind load. In the execution after 11a forms the drive cable ( 46 ) a spring, the the driven support ribs ( 9a -C) depending on the length of rope elastic to the substructure ( 2 ). Through targeted structural design, it is possible, despite the still possible vibration of the parabolic trough collector, to achieve a cost-effective compromise between necessary stiffening and system costs.

In the execution after 11b Vibrations are greatly reduced because a relatively short drive cable is used.

In the versions after the 11c and 11d prevents the self-locking of the drive ( 44 ) a vibration, because the wind can not overcome the self-locking. LIST OF REFERENCE NUMBERS No. description No. description 1 parabolic trough collector 40 passage 2 substructure 41 bracket 3a-d pivot bearings 42 groove 4 supporting structure 43 thickened end 5 panels 44 drive 6 mirror film 45 contour 7 absorber 46 drive cable 8th longitudinal direction 47 secant 9a-c supporting ribs 48 clamping screw 10 support 49 circulating rope 11 distance 50 motion drive 12a-d wire ropes 51a-b arrow 13a-d end regions 52 coupling element 14a, b longitudinal edges 53 spindle 15a, b frontal edges 54 worm 16 attack 55 slug 17 suspension 56 wave 18 bracket 57 gearing 19a-d longitudinal reinforcements 58 slug 20 V-Profile 59 round bar 21a-c legs 60 worm 22 transverse spar 61 slug 23 clamp 62 articulated lever 24 supporting member 63 guide link 25 cheek 64 pushrod 26a-c approaches 65 joint 27a-c rotational axes 66 threaded rod 28 Profile (drive) 67 spindle nut 29 studs 68 worm 30 plate 69 slug 31 support nut 32 bearing ring 33 Retainers 34 locknut 35 support flange 36 Spring support 37 passage 38 section 39 shell

Claims (33)

A parabolic trough collector having a reflective surface which concentrates the sunlight onto an absorber extending in the focal line, the reflective surface being disposed on at least one panel having a parabolic cross section and a straight extension in the longitudinal direction of the parabolic trough collector and a support structure disposed on the convex underside of each panel which is hingedly connected to a parabolic trough collector supporting substructure, characterized in that - the supporting structure ( 4 ) on the convex underside of the parabolic trough collector ( 1 ), transversely to its longitudinal direction ( 8th ) extending supporting ribs ( 9a -C), - that at each supporting bulkhead ( 9a -C) a pivot bearing ( 3 ) for the rotatable arrangement of the parabolic trough collector ( 1 ) about its longitudinal axis ( 8th ) parallel axis of rotation ( 27a C) is arranged and - that for rotation of the parabolic trough collector ( 1 ) about its axis of rotation ( 27a C) several synchronized drives ( 44 ) at least on the longitudinal outer support ribs ( 9a , c) attack. Parabolic trough collector according to claim 1, characterized in that at each Stützspant ( 9a , b, c) a drive ( 44 ) attacks. Parabolic trough collector according to claim 1 or 2, characterized in that all drives ( 44 ) a common movement drive ( 50 ) exhibit. Parabolic trough collector according to one of claims 1 to 3, characterized in that the drives ( 44 ) at least one drive cable ( 46 ) exhibit. Parabolic trough collector according to one of claims 1 to 4, characterized in that the drives ( 44 ) at least one spindle ( 53 ) exhibit. Parabolic trough collector according to one of claims 1 to 5, characterized in that the drives at least one worm gear ( 54 . 55 ) exhibit. Parabolic trough collector according to one of claims 1 to 6, characterized in that each with a drive ( 44 ) associated support frame ( 9a , b, c) extending from the convex underside of the parabolic trough collector ( 1 ) downwardly extending subframe ( 28 ) with an arcuate contour ( 45 ) having. Parabolic trough collector according to claim 7, characterized in that the contour ( 45 ) is circular arc-shaped and the ends of the circular arc transverse to the axis of rotation ( 27c ) of the parabolic trough collector ( 1 ) on the support frame ( 9a , b, c). Parabolic trough collector according to claim 8, characterized in that at least one drive cable ( 46 ) along the arcuate contour ( 45 ) of the subframe ( 28 ) is guided. Parabolic trough collector according to claim 9, characterized in that the drive cables ( 46 ) of adjacent drives ( 44 ) with each other to a circulating rope ( 49 ) with a common motion drive ( 50 ) for the circulating rope thus formed ( 49 ) are connected. Parabolic trough collector according to claim 9, characterized in that each drive cable ( 46 ) on a coupling element ( 52 ) is attached to a spindle nut which controls the rotational movement of a spindle ( 53 ) in a translational movement of the coupling element ( 52 ) converts. Parabolic trough collector according to claim 11, characterized in that on the spindle ( 53 ) rotatably a worm wheel ( 54 ) arranged with a screw ( 55 ) combs. Parabolic trough collector according to claim 12, characterized in that the screws ( 55 ) of all drives ( 44 ) on a common wave ( 56 ) are arranged. Parabolic trough collector according to claim 7 or 8, characterized in that along the arcuate contour ( 45 ) of the subframe ( 28 ) a gearing ( 57 ) is arranged. Parabolic trough collector according to claim 14, characterized in that the toothing ( 57 ) with a snail ( 58 ) combing on a round rod ( 59 ) is arranged. Parabolic trough collector according to claim 15, characterized in that on the round rods ( 59 ) of all drives ( 44 ) each rotatably a worm wheel ( 60 ) arranged with a screw ( 61 ), the snails ( 61 ) of all drives ( 44 ) on a common wave ( 56 ) are arranged. Parabolic trough collector according to one of claims 1 to 16, characterized in that the drive is a toggle lever ( 62 ). Parabolic trough collector according to claim 17, characterized in that the toggle lever ( 62 ) one in a leadership setting ( 63 ) guided push rod ( 64 ) which articulates with a threaded rod ( 66 ) is connected to a spindle, the guide slot ( 63 ) rotatably with the support frame ( 9a , b, c) connected to the threaded rod ( 66 ) associated spindle nut ( 67 ) stationary, but is rotatably mounted, so that a rotation of the spindle nut ( 67 ) a translation of the threaded rod ( 66 ) of the articulated lever ( 62 ) causes. Parabolic trough collector according to claim 18, characterized in that on the spindle nuts ( 67 ) of all drives ( 44 ) each rotatably a worm wheel ( 68 ) arranged with a screw ( 69 ), the snails ( 69 ) of all drives ( 44 ) on a common wave ( 56 ) are arranged. Parabolic trough collector according to one of claims 1 to 19, characterized in that - the supporting structure ( 4 ) at least three supporting ribs ( 9a C), starting from the end support ribs ( 9a . 9c ) on every second support frame ( 9b ) an upwardly extending support ( 10 ), that - at least four elongated power transmission means ( 12a -D) are arranged on the support and - that the power transmission means ( 12a -D) between the column ( 10 ) and the supporting structure ( 4 ), wherein the power transmission means ( 12a -D) form the side edges of a straight pyramid whose plane of symmetry in the parabolic-shaped reflecting surface (FIG. 6 ) lying tip is formed by the converging on the support force transmission means. Parabolic trough collector according to claim 20, characterized in that the edges of the base each by the power transmission means ( 12a -D) spanned pyramid parallel to the longitudinal or frontal edges ( 14a . 14b . 15a . 15b ) of the parabolic trough collector ( 1 ). Parabolic trough collector according to claim 20 or 21, characterized in that the force transmission means ( 12a -D) traction means or rods. Parabolic trough collector according to claim 20 to 22, characterized in that starting from the end-side supporting ribs ( 9a . 9c ) on every second support frame ( 9b ) arranged on the convex underside of the parabolic trough collector holder ( 9b ) for the upwardly extending support ( 10 ) and at a distance ( 11 ) to the attachment of the support ( 10 ) on the bracket ( 9b ) the power transmission means ( 12a -D) are arranged on the support. Parabolic trough collector according to one of claims 20 to 23, characterized in that the power transmission means ( 12a -D) between each column ( 10 ) and the outer end regions ( 13a -D) of the adjacent supporting ribs ( 9a . 9c ). Parabolic trough collector according to one of claims 20 to 24, characterized in that the particular rod-shaped support ( 10 ) below a stop ( 16 ) for the power transmission means ( 12a -D) one in the direction of the attack ( 16 ) effective suspension ( 17 ) having. Parabolic trough collector according to claim 25, characterized in that the suspension ( 17 ) is associated with a vibration damper. Parabolic trough collector according to claim 25 or 26, characterized in that the suspension comprises at least one disc spring. Parabolic trough collector according to one of claims 20 to 27, characterized in that the particular rod-shaped support ( 10 ) at the same time as a holder ( 18 ) is designed for the absorber. Parabolic trough collector according to one of claims 1 to 28, characterized in that at each Stützspant ( 9a -C) several, the desired parabolic shape for each panel ( 5 ) and the reflective surface ( 6 ) predetermining connecting elements are arranged. Parabolic trough collector according to one of claims 1 to 29, characterized in that the reflective surface ( 6 ) detachable with each panel ( 5 ) of the parabolic trough collector ( 1 ) connected is. Parabolic trough collector according to one of claims 1 to 30, characterized in that the reflective surface ( 6 ) Part of one on each panel ( 5 ) is applied film. Parabolic trough collector according to one of claims 1 to 31, characterized in that in the longitudinal direction ( 8th ) of the parabolic trough collector ( 1 ) between the supporting ribs ( 9a - c) longitudinal reinforcements ( 19a -d, 20 ) are arranged. Parabolic trough collector according to one of claims 1 to 32, characterized in that the at each Stützspant ( 9a -C) arranged rotary bearing ( 3a -D) on the substructure ( 2 ) is adjustable.

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