Heliostat

Abstract

The invention relates to a heliostat (1) having a mirror (3) which is fastened to a holding device (5) so as to be pivotable about an elevation axis (14) and having a stand device (7) on which the holding device (5) is supported by means of a rotary bearing apparatus (9) so as to be rotatable about an azimuth rotational axis, wherein the holding device (5) has an elevation drive (15) by means of which the mirror (3) can be driven in a pivotable manner about the elevation axis (14), characterised in that the elevation drive (15) has a rotationally drivable threaded spindle (17) with a spindle axis (17a), wherein the threaded spindle (17) is fastened in a pivotable manner, with a predefined distance from the elevation axis (14), to a rear side (3a) of the mirror (3) by means of at least one first joint (18), and a ball body (21) guided in a ball holder (19), wherein the ball holder (19) is arranged with the ball body (21) on the holding device (5) at a distance adapted to the predefined distance from the elevation axis (14), and the ball body (21) has an inner thread which penetrates the ball body (21) through a centre of curvature of the ball body (21), wherein the threaded spindle (17) engages into the inner thread and wherein the ball holder (19) prevents a rotation of the ball body (21) about the spindle axis (17a).

Description

[0001] Heliostat

[0002] The present invention relates to a heliostat having a mirror which is mounted on a holding device so as to be pivotable about an elevation axis and having a stand device on which the holding device is mounted so as to be pivotable about an azimuth rotation axis by means of a pivot bearing device, wherein the holding device has an elevation drive by means of which the mirror can be driven so as to be pivotable about the elevation axis.

[0003] Heliostats are sun-tracking mirror systems used to concentrate solar radiation for solar tower systems. Heliostats are typically designed for a service life of approximately 30 years, which places very high demands on accuracy. Since heliostats are exposed to wind loads throughout their service life, maintaining the required accuracy while keeping costs as low as possible is a major challenge.

[0004] The mirror of heliostats is usually tracked to the sun, with a drive around the vertical azimuth rotation axis and the horizontal elevation axis.

[0005] However, designing a drive around the elevation axis is quite complex, as sometimes complicated gimbals must be used. These are necessary to compensate for manufacturing tolerances so that the spindle axis and the spindle nut thread axis are always aligned and so that no moment arises transverse to the spindle axis, which could significantly reduce the service life of the drive. The heliostats described above are part of the applicant's general knowledge but do not refer to any specific, published prior art.

[0006] It is therefore the object of the present invention to provide a heliostat of the type mentioned above which has a simple and cost-effective construction.

[0007] In the heliostat according to the invention, comprising a mirror which is pivotably mounted on a holding device about an elevation axis and comprising a stand device on which the holding device is mounted by means of a pivot bearing device about an azimuth rotation axis, wherein the holding device has an elevation drive by means of which the mirror can be driven pivotably about the elevation axis, it is provided that the elevation drive has a rotationally drivable threaded spindle with a spindle axis which is pivotably mounted at a predetermined distance from the elevation axis on a rear side of the mirror by means of at least one first joint, and a spherical body guided in a ball holder, wherein the ball holder with the spherical body is arranged on the holding device at a distance from the elevation axis adapted to the predetermined distance, and the spherical body has an internal thread,that penetrates the spherical body through a center of curvature of the spherical body, wherein the threaded spindle engages in the internal thread and wherein the ball holder prevents rotation of the spherical body about the spindle axis.

[0008] In the heliostat according to the invention, an elevation drive can be created in a simple manner by means of the spherical body guided in the ball mount and the rotatably driven spindle, wherein the threaded spindle can be driven in rotation in a structurally simple manner. Because the spherical body guided in the ball mount is prevented from rotating about the spindle axis, the threaded spindle can rotate relative to the internal thread, thereby causing a lifting and lowering movement by the threaded spindle. At the same time, the spherical body in the ball mount, together with the threaded spindle, can perform a pivoting movement in a vertical plane that runs, for example, orthogonally to the mirror, as may be necessary when pivoting the mirror about the elevation axis.Furthermore, the ball body in the ball mount, together with the threaded spindle, can also perform a pivoting movement in a plane containing the elevation axis and the spindle axis to compensate for manufacturing tolerances. This allows the ball body and its bearing to be implemented in a simple manner, avoiding the need for complex cardan suspensions.

[0009] Preferably, the spherical body has a spherical center segment shape with upper and lower cutting surfaces, with the internal thread penetrating the upper and lower cutting surfaces. In principle, the internal thread can also penetrate the spherical body at a curved surface, but the provision of upper and lower cutting surfaces offers advantages from a manufacturing perspective.

[0010] The ball retainer can have a ball socket in which the ball body is mounted. The ball body has at least one projection on its outer surface that engages a groove in the ball socket. The projection is arranged in a common vertical plane with the spindle axis, and the groove extends in this vertical plane. The projection, which engages in the groove, advantageously guides the ball body together with the threaded spindle during the pivoting movement of the ball. At the same time, the projection in the groove prevents rotation of the ball body about the spindle axis.

[0011] In a preferred embodiment, the spherical body has two projections on its outer surface which are arranged coaxially and run orthogonal to the spindle axis and engage in two opposite grooves in the spherical shell. With this embodiment, a particularly advantageous guidance of the spherical body is possible, since it is guided by two projections in two grooves. The projections can, for example, be formed integrally with the spherical body. In principle, it is also possible for the projections to be formed by bolts which are introduced into the spherical body. The projection(s) can be arranged on a curved region of the outer surface or on a flattened region of the outer surface. The projections are preferably cylindrical in shape to enable rotation of the spherical body about the axis formed by the projections, whereby manufacturing tolerances can be compensated.

[0012] In an alternative embodiment, the spherical body has a spherical center segment shape with lateral cut surfaces that run parallel to a vertical plane of the spindle axis, wherein the internal thread penetrates the spherical body at its outer surface and wherein the ball holder has a spherical shell with guide surfaces that interact with the cut surfaces. In this embodiment, the spherical body is guided laterally by the spherical shell by means of the lateral cut surfaces and the guide surfaces of the ball holder, wherein these surfaces prevent rotation of the body about the spindle axis by abutting against one another. The internal thread can penetrate the spherical body in a curved area of ​​the outer surface or in a flattened area of ​​the outer surface.

[0013] The ball socket preferably has an opening above the ball body with a smaller diameter than the ball body, through which the threaded spindle is guided. This allows the ball socket to absorb tensile forces transmitted from the threaded spindle to the ball body.

[0014] Preferably, a second plane running orthogonal to the back of the mirror, in which the elevation axis lies, is spaced from the center of gravity of the mirror in the direction of an upper edge of the mirror. In other words, the mirror is mounted with its mass off-center with respect to the elevation axis. The center of gravity can be arranged on the side of the second plane facing away from the first joint. As a result, the mirror is always pulled into a vertical position by its own weight. The movement is maintained by the threaded spindle, so that it is always subject to tensile stress. This has the advantage that the threaded spindle is not subjected to buckling stress, allowing a very small diameter for the threaded spindle to be realized, which is advantageous in terms of costs. Furthermore, tensile stress on the threaded spindle has virtually no effect on any play between the threaded spindle and the internal thread.This allows the accuracy requirements of the threaded spindle and the internal thread to be kept low, so that the entire elevation drive is almost backlash-free during operation.

[0015] The threaded spindle can be connected to the first joint via a rotary drive motor of the elevation drive, wherein the first joint is preferably designed as a cardan joint. Such an arrangement has proven particularly advantageous because the rotary drive motor can drive the threaded spindle rotationally independently of its pivoting.

[0016] It is preferably provided that the stand device is designed as a pylon.

[0017] The pylon can have a pylon tube with a wall thickness between 0.5 mm and 2 mm, preferably between 0.5 mm and 1 mm. The heliostat according to the invention also allows for pylons with a pylon tube with a larger outer diameter, thus ensuring high stability even with a small wall thickness. For example, the pylon tube can have an outer diameter between 100 mm and 200 mm, preferably 140 mm.

[0018] The pylon tube can be designed as a ramming tube, allowing for easy installation of the pylon on the ground without the need for complex foundations. In a preferred embodiment of the invention, the holding device comprises horizontal beam supports, on the underside of which the pivot bearing device is arranged. This design enables a particularly stable design of the holding device.

[0019] The beam supports can be arranged in a T-shape, with a cross member running parallel to the back of the mirror, the cross member being connected to the back of the mirror via at least two second joints that form the elevation axis. A longitudinal member can be arranged orthogonally to the cross member, the longitudinal member and the cross member meeting above the stand device, and the ball mount being arranged on the longitudinal member. The ball mount can be arranged, for example, at an end region of the longitudinal member facing away from the cross member. Such a design of the holding device offers the advantage that a pivotable bearing, which forms the elevation axis, can be implemented in a stable manner by means of the two second joints, while at the same time a simple and cost-effective construction is possible.Furthermore, the T-shape of the beam supports advantageously creates a receptacle for the ball holder with the spherical body, which interacts with the threaded spindle, so that the elevation drive of the heliostat according to the invention can be realized in a simple manner.

[0020] The invention is explained in more detail below with reference to the following figures.

[0021] They show:

[0022] Fig. 1 is a schematic view of an inventive

[0023] Heliostats, Fig. 2 a schematic detailed view of the holding device and the elevation drive arranged thereon and

[0024] Figs. 3a and 3b are schematic representations of the ball holder with the spherical body in which the threaded spindle of the elevation drive is accommodated.

[0025] Fig. 1 schematically illustrates the heliostat 1 according to the invention. The heliostat 1 comprises a mirror 3 pivotably mounted on a support device 5. The support device 5 is rotatably mounted on a stand device 7.

[0026] The stand device 7 is designed as a pylon and installed on a floor.

[0027] As can be seen from Fig. 2, the holding device 5 is rotatably mounted on the upper side of the pylon via a pivot bearing device 9.

[0028] The holding device 5 has beam supports 11 arranged in a T-shape. A cross member 11a is arranged parallel to the mirror 3, and a longitudinal member 11b is arranged orthogonally to the cross member 11a. The longitudinal member 11b and the cross member 11a meet above the pylon.

[0029] An elevation drive 15 is arranged above the holding device 5 and engages one end of the longitudinal beam 11b by means of a rotationally driven threaded spindle 17. The elevation drive 15 can move the mirror 3 about the elevation axis 14 and thus erect it. The elevation drive 15 has a rotary drive motor 16, which is connected to a rear side 3a of the mirror 3 via a first joint 18, which is designed as a cardan joint. The threaded spindle 17 is thus fastened to a rear side 3a of the mirror 3 at a predetermined distance from the elevation axis 14. Second joints 13 are arranged at the ends of the cross member 11a, which form the elevation axis 14 and are connected to the rear side 3a of the mirror 3.

[0030] Mirror 3 is mounted off-center with respect to elevation axis 14. Thus, a center of gravity 3b of mirror 3 is offset from elevation axis 14. As a result, mirror 3 is always pulled into a vertical position by its own weight. This movement is maintained by threaded spindle 17, so that it is subjected to tensile stress. The tensile force is transferred to longitudinal support 11b.

[0031] As best seen in Figs. 3a and 3b, the threaded spindle 17 is connected to the longitudinal beam 11b of the holding device 5 by means of a ball retainer 19 and a ball body 21 guided therein. The ball retainer 19 is arranged at a distance from the elevation axis 14 that is adapted to the predetermined distance between the threaded spindle 17 and the elevation axis 14. An internal thread is arranged in the ball body 21, which penetrates the ball body 21 through a center of curvature, with the threaded spindle 17 engaging the internal thread.

[0032] The ball mount 19 has a spherical socket 23 in which the spherical body 21 is mounted. On its outer surface 21a, the spherical body 21 has projections 25 that engage in grooves 27 in the spherical socket 23. A pivoting movement of the spherical body 21 is guided via the cylindrical projections 25 and the grooves 27. The projections 25 run coaxially and in a direction orthogonal to a spindle axis 17a of the threaded spindle 17 at the height of the center of the spherical body 21. The projections 25, the grooves 27, and the spindle axis 17a are arranged in a common vertical plane, so that when the inclination of the mirror 3 changes, the threaded spindle 17 can pivot in this plane. In addition, the threaded spindle 17 can be pivoted in the plane passing through the elevation axis 14 and the spindle axis 17a in order to compensate for manufacturing tolerances.At the same time, the projections 25 and the grooves 27 prevent the ball body 21 from rotating together with the threaded spindle 17 about the spindle axis 17a, so that the threaded spindle 17 can be twisted within the thread. This can cause a lifting and lowering movement of the threaded spindle 17.

[0033] The ball socket 23 has an upper opening 23a through which the threaded spindle 17 is guided. The diameter of the opening 23a is smaller than the diameter of the ball body 21, so that a tensile force exerted by the threaded spindle 17 can be transmitted to the ball socket 23 and thus to the ball holder 19.

[0034] The spherical body 21 can, for example, have a spherical center segment shape with upper and lower cutting surfaces. This simplifies the introduction of the internal thread into the spherical body 21.

[0035] The pivot bearing device 9 has a guide ring 22, which is attached to the pylon and has a toothing 22a on its outer side. A drive device 24 engages this toothing. The drive device 24 is arranged on the longitudinal beam 11b and has a drive pinion 24a. A chain drive (not shown) can be driven by the drive pinion 24a, which engages the toothing 22a of the guide ring 22. In this way, the holding device 5 can be advantageously rotated about the pivot bearing device 9 and thus about the azimuth axis of rotation.

[0036] The pylon of the stand device 7 comprises a pylon tube 26 with a comparatively thin wall thickness of, for example, 0.5 mm. The guide ring 22 is arranged on the upper side of the pylon tube 26 and protects the upper edge of the pylon tube 26 while simultaneously increasing stability.

[0037] The pylon tube 26 can, for example, have an outer diameter of 140 mm. The heliostat according to the invention thus has a simple and cost-effective design.

[0038] Reference symbol list

[0039] 1 Heliostat 3 Mirror 3a Back

[0040] 5 Focus

[0041] 7 Stand device

[0042] 9 Pivot bearing device

[0043] 11 Beam support 11a Cross beam lib Longitudinal beam 13 Joints 14 Elevation axis 15 Elevation drive 16 Rotary drive motor

[0044] 17 Threaded spindle 17a Spindle axis 18 Joint

[0045] 19 Ball holder 21 Ball body

[0046] 21a Shell surface 22 Guide ring 22a Toothing 23 Ball socket 23a Opening 24 Drive device 24a Drive pinion

[0047] 25 projection 26 pylon tube 27 groove

Claims

Patent claims 1. A heliostat (1) comprising a mirror (3) pivotably mounted on a holding device (5) about an elevation axis (14), and comprising a stand device (7) on which the holding device (5) is mounted by means of a pivot bearing device (9) for rotation about an azimuth axis of rotation, wherein the holding device (5) comprises an elevation drive (15) by means of which the mirror (3) can be driven pivotably about the elevation axis (14), characterized in that the elevation drive (15) comprises a rotationally drivable threaded spindle (17) having a spindle axis (17a), wherein the threaded spindle (17) is pivotably mounted at a predetermined distance from the elevation axis (14) on a rear side (3a) of the mirror (3) by means of at least one first joint (18), and comprises a spherical body (21) guided in a ball holder (19),wherein the ball holder (19) with the ball body (21) is arranged on the holding device (5) at a distance from the elevation axis (14) adapted to the predetermined distance, and the ball body (21) has an internal thread that penetrates the ball body (21) through a center of curvature of the ball body (21), wherein the threaded spindle (17) engages in the internal thread and wherein the ball holder (19) prevents rotation of the ball body (21) about the spindle axis (17a).

2. Heliostat according to claim 1, characterized in that the spherical body (21) has a spherical center segment shape with upper and lower cutting surfaces, wherein the internal thread penetrates the upper and lower cutting surfaces.

3. Heliostat according to claim 1 or 2, characterized in that the ball holder (19) has a spherical shell (23) in which the spherical body (21) is mounted, wherein the spherical body (21) has at least one projection (25) on its outer surface (21a) which engages in a groove (27) in the spherical shell (23), wherein the projection (25) is arranged in a common vertical plane with the spindle axis (17a), and the groove (27) runs in this vertical plane 4. Heliostat according to claim 3, characterized in that the spherical body (21) has on its outer surface (21a) two projections (25) which are arranged coaxially and extend orthogonally to the spindle axis (17a) and engage in two opposite grooves (27) in the spherical shell (23).

5. Heliostat according to claim 1, characterized in that the spherical body (21) has a spherical center segment shape with lateral cut surfaces which run parallel to a vertical plane of the spindle axis (17a), wherein the internal thread penetrates the spherical body (21) at its outer surface (21a) and wherein the ball holder (19) has guide surfaces which interact with the cut surfaces.

6. Heliostat according to one of the preceding claims, characterized in that a second plane extending orthogonally to the rear side (3a) of the mirror (3), in which the elevation axis (14) lies, is spaced from the center of gravity in the direction of an upper edge of the mirror (3).

7. Heliostat according to claim 6, characterized in that the center of gravity is arranged on the side of the second plane facing away from the first joint (18).

8. Heliostat according to one of the preceding claims, characterized in that the threaded spindle (17) is connected to the first joint (18) via a rotary drive motor (16) of the elevation drive (15), wherein the first joint (18) is preferably designed as a cardan joint.

9. Heliostat according to one of the preceding claims, characterized in that the stand device (7) is designed as a pylon.

10. Heliostat according to claim 9, characterized in that the pylon comprises a pylon tube (26) having a wall thickness between 0.5 mm and 2 mm, preferably between 0.5 mm and 1 mm.

11. Heliostat according to claim 10, characterized in that the pylon tube (26) has an outer diameter between 100 mm and 200 mm.

12. Heliostat according to one of the preceding claims, characterized in that the holding device (5) has horizontal beam supports (11), on the underside of which the pivot bearing device (9) is arranged.

13. Heliostat according to claim 12, characterized in that the beam supports (11) are arranged in a T-shape, with a cross member (11a) running parallel to the back side (3a) of the mirror (3), the cross member (11a) being connected to the back side (3a) of the mirror (3) via at least two second joints (13) which form the elevation axis (14).

14. Heliostat according to claim 13, characterized in that a longitudinal beam (11b) is arranged orthogonally to the cross beam (11a), wherein the longitudinal beam (11b) and the cross beam (11a) meet above the stand device (7), and wherein the ball holder (19) is arranged on the longitudinal beam (11b).

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