GB2469344A

GB2469344A - Movable mount for supporting a solar radiation collector

Info

Publication number: GB2469344A
Application number: GB0912853A
Authority: GB
Inventors: Iain Chapman
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-07-23
Filing date: 2009-07-23
Publication date: 2010-10-13
Anticipated expiration: 2029-07-23
Also published as: GB0912853D0; GB2469344B; WO2011010081A1

Abstract

A movable mount 1 for supporting a radiation reflecting, receiving or transmitting device, comprises a base 4 and a mounting surface 2 on which the radiation reflecting, receiving or transmitting device is mountable. The mounting surface is selectively rotatable about first and second axes 9, 20 relative to the base. The mount further comprises a first input device 7, a second input device 15, and a bearing assembly connecting the mounting surface to the first and second input devices. The first input device is rotatable about the first axis which is fixed relative to the base, the first input device being operable to rotate the mounting surface about the first axis. The second input device is rotatable about the second axis which is fixed relative to the base, the second input device being operable to rotate the mounting surface about the second axis. The bearing assembly comprises first and second members 12, 13, arranged to be concentric and rotatable relative to each other about a third axis 14, where all three axes intersect a common point 'A' which is fixed relative to the base. Preferably, the mount is used with a solar radiation collector or reflector for tracking the sun.

Description

Moveable Mounting The present invention relates to a moveable mount. In general terms, the present invention relates to a mount which enables a mounted object to be moved about a number of different axes. In particular, the present invention is described herein as a mount for a solar radiation collector or reflector for tracking the sun, commonly known as a "solar tracker". However, it is applicable to other uses, such as receiving or transmitting radiation from a wide portion of the electromagnetic spectrum.

Solar tracker devices are commonly employed for orientating a reflector, photovoltaic panel, parabolic dish, lens, or other such article, either toward the sun or such that solar radiation incident on the article is reflected toward one or more target collectors. By tracking the sun, the amount of radiation incident on the article can be increased, thus increasing the effectiveness of the device.

To enable the orientation of the article to be varied, typical solar tracker devices are rotated about either one or two axes. The former type are commonly referred to as "single axis trackers" and the latter "dual axis trackers".

A single axis tracker can be rotated about a single axis, usually parallel to the axis of rotation of the earth and or parallel to a ground plane, in order to track the apparent motion of the sun through the day. Since the orientation of a single axis tracker remains stationary in relation to other axes, multiple single axis trackers may be arranged to share a common drive arrangement. Thus, complexity and cost can be reduced. Although a single axis tracker can provide more effective solar radiation collection or reflection than a stationary device, such a tracker does not compensate for the apparent northward-southward shift in the path of the sun over the course of a year (the "solar elevation") . Therefore, the effectiveness of a single axis tracker is reduced when used at higher latitudes where the seasonal change in solar elevation is pronounced.

A dual axis tracker can be rotated about two axes such that, in addition to tracking the apparent motion of the sun through the day, the angle of declination of the article can be adjusted in order to compensate for the seasonal change in solar elevation. Dual axis solar trackers can be of particular benefit when used at higher latitudes, where the change in solar elevation is pronounced.

One common type of dual axis tracker employs an altitude-azimuth structure. This form of dual axis tracker can be rotated about an axis parallel to the ground plane ("altitude" adjustment) and an axis perpendicular to the ground plane ("azimuth" adjustment) such that it can be orientated to any location in the upward hemisphere. Since the orientation of the axis parallel to the ground plane is not fixed with respect to a fixed datum point, when positioned in an array, each altitude-azimuth tracker positioned on a ground plane will require separate drive means for rotation about each axis.

An alternative dual axis tracker design is one whereby an article can be rotated about a fixed first axis parallel to the ground plane and can be rotated about a second axis which is not parallel to the first axis. One such example can be found in O 02/070966 in which a dual axis "heliostat" is provided. This "heliostat" can be rotated about the fixed first axis by a drive shaft lying parallel to the first axis and can be rotated about the second axis by a drive member connected to the rear of a reflector element of the "heliostat" by a lockable ball joint. The drive member is then caused to pivot by a linearly moveable motion translating shaft. Since the effective length of the drive member will change as it is caused to pivot, either the drive member must be telescopic or the motion translating shaft must be displaced toward, or away from the reflector element. Further, since the second axis is not fixed in relation to a fixed datum point, the motion translating shaft must also rotate with the "heliostat" as it rotates about the first axis. This results in a complicated and inherently unreliable structure.

Thus, although dual axis tracker systems can be orientated to provide more effective solar radiation collection or reflection, current systems are complicated, and thus costly and unreliable.

It is an object of the present invention to provide a movable mount which addresses the above problems.

The present invention provides a movable mount for supporting a radiation reflecting, receiving or transmitting device, comprising a base and a mounting surface on which the radiation reflecting, receiving or transmitting device is mountable, wherein the mounting surface is selectively rotatable about first and second axes relative to the base, the mount further comprising a first input device which is rotatable about the first axis which is fixed relative to the base, the first input device operable to rotate the mounting surface about the first axis, a second input device which is rotatable about the second axis which is fixed relative to the base, the second input device operable to rotate the mounting surface about the second axis, and a bearing assembly connecting the mounting surface to the first and second input devices, the bearing assembly comprising first and second members, arranged to be concentric and rotatable relative to each other about a third axis, wherein all three axes intersect a common point which is fixed relative to the base.

Preferably, the first input device comprises a first arm pivotally secured to the base for rotation about the first axis and pivotally secured to the bearing assembly.

The first arm may comprise a semi-circular arc pivotally secured to the base at the centre of the arc, and pivotally secured to the bearing assembly towards each end of the arc.

Preferably, the second input device comprises a second arm pivotally secured to the bearing assembly and constrained to rotate about the second axis only. The second arm may comprise a semi-circular arc, pivotally secured to the bearing assembly towards each end of the arc.

Preferably, the movable mount further comprises guide means on the base operable to constrain the second arm to rotate about the second axis only.

Preferably, the first and second arms lie in planes perpendicular to one another.

Preferably, the first member is pivotally secured to the first arm, the second member is pivotally secured to the second arm and the mounting surface is secured to either the first member or the second member.

Preferably, the moveable mount further comprises co-operating structures on the first and second members operable to constrain the members to be concentric but allowing relative rotation about the third axis.

Preferably, the first member comprises a first ring and the second member comprises a second ring. The co-operating structures may comprise a flange associated with one ring against which at least part of the other ring is slidably received.

Preferably, the ratio of the amount of movement of the first input device about the first axis to the amount of rotation of the mounting surface about the first axis is constant.

Preferably, the ratio of the amount of movement of the second input device about the second axis to the amount of rotation of the mounting surface about the second axis is constant.

Preferably, the first input device engages directly with a first input drive means and the second input device engages directly with a second input drive means.

Alternatively, the first input device may engage with a first input drive means through a first linkage assembly and the second input device may engage with a second input drive means through a second linkage assembly.

The present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front perspective view of a moveable mount in accordance with one embodiment of the present invention, showing a mounting surface in a first, "neutral" position; Figure 2 is a front perspective view of the moveable mount of Figure 1, showing a mounting surface in a first, "neutral" position with a solar radiation reflector mounted thereon; Figure 3 is a front perspective view of part of the moveable mount of Figure 1, with the ring assembly removed for ciLarity; Figure 4 is an exploded, perspective view of part of the ring assembly of the moveable mount of Figure 1; Figure 5 is a front perspective of the moveable mount of Figure 1, with the first ring removed for clarity; Figure 6 is a front perspective view of the moveable mount of Figure 1, showing the mounting surface rotated about a first axis in the positive direction; Figure 7 is a front perspective view of the moveable mount of Figure 1, showing the mounting surface rotated about the first axis in the negative direction; Figure 8 is a front perspective view of the rnoveable mount of Figure 1, showing the mounting surface rotated about a second axis in the positive direction; Figure 9 is a front perspective view of the moveable mount of Figure 1, showing the mounting surface rotated about the second axis in the negative direction; Figure 10 is a front perspective view of the moveable mount of Figure 1, showing the mounting surface rotated in the positive direction about both the first and second axes; Figure 11 is a front perspective view of the moveable mount of Figure 1, showing the mounting surface rotated in the negative direction about the first axis and in the positive direction about the second axis; Figure 12 is a front perspective view of the moveable mount of Figure 1, showing the mounting surface rotated in the negative direction about both the first and second axes; Figure 13 is a front perspective view of the rnoveable mount of Figure 1, showing the mounting surface rotated in the positive direction about the first axis and in the negative direction about the second axis; * Figure 14 is a front perspective view of a moveable mount in accordance with a second embodiment of the present invention, showing a mounting surface in a first, "neutral" position.

Figure 15 is a front perspective view of part of the moveable mount of Figure 14, with the ring assembly removed for clarity.

As indicated above, this invention relates to a moveable mount, and more particularly, though not exclusively, to a moveable mount for supporting a solar radiation collecting or reflecting article such as a planar or parabolic mirror, photovoltaic module, lens or parabolic dish, in such a manner that the article may be selectively rotated about two fixed axes simultaneously.

The moveable mount has the further function of permitting an article mounted thereon to be rotated about either one of the two fixed axes without changing the orientation about the other fixed axis. In addition, the ratio of the amount of movement of the input actuator to the angular rotation of the article is constant irrespective of the starting angular position.

With reference to Figures 1 to 5, a moveable mount 1 in accordance with one embodiment of the present invention is shown with a mounting surface 2 in a first, "neutral" position. An item, for example, a solar radiation collector or reflector 3 is mountable on the mounting surface 2, as shown in Figure 2. The mounting surface 2 is moveable about a number of axes, thus enabling universal movement, as will be described in greater detail below. In this example, the solar radiation collector or reflector 3 is hexagonal, with a maximal diameter of approximately 250mm, and area of approximately 0.04 square metres.

The moveable mount 1 comprises a base 4, comprising base legs 5. In use, the legs 5 are secured to a fixed datum surface. In this example, the base 4 comprises two substantially parallel base legs 5, the two base legs 5 being connected by cross members 6.

The moveable mount 1 has a first arm 7, rotatably mounted on the base 4 by means of a base pivot 8 such that the first arm 7 is substantially perpendicular to and rotatable about a first arm axis 9 of the base pivot 8. In this example, the first arm 7 is a substantially semi-circular arc mounted to base pivot 8 by two substantially radial arms 7A, the base pivot 8 being at the centre of the arc of first arm 7. Typically, when moveable mount 1 is in use, first arm axis 9 is substantially parallel to the ground plane.

The first arm 7 comprises two first arm pivots bA, lOB, each of the first arm pivots bOA, lOB disposed toward each end of the first arm 7 and orientated such that they are coaxial along a first arm pivot axis 11, the first arm pivot axis 11 being substantially perpendicular to the first arm axis 9 and intersecting the first arm axis 9 and the arc centre of first arm 7 at a central datum point A. The moveable mount 1 further comprises a first ring 12 rotatably mounted on the first arm 7 by means of the first arm pivots bOA, lOB and rotatable about the first arm pivot axis 11. The moveable mount 1 further comprises a second ring 13 concentric with the first ring 12 about a ring axis 14. The ring axis 14 is substantially perpendicular to the first arm pivot axis 11 and intersects the first arm axis 9 and the first arm pivot axis 11 at the central datum point A. In this example, the first ring 12 has an outer diameter which is slightly less than the inner diameter of the second ring 13 such that the first ring 12 fits inside the second ring 13 and is located in the same plane as the second ring 13.

The second ring is integral with or secured to an annular flange 13A upon which the first ring 12 is slidably supported such that the first ring 12 can rotate about the ring axis 14 relative to the second ring 13 while remaining concentric with the second ring 13.

The moveable mount 1 has a second arm 15. In this example, second arm 15 is a semi-circular arc, the centre of which also lies at point A, which lies in a plane substantially perpendicular to the plane of first arm 7.

Second arm 15 is rotatably mounted on the second ring 13 by means of two second arm pivots 16A, 16B, each of the second -10 -arm pivots 16A, 16B disposed toward each end of the second arm 15 and orientated such that they are coaxial along a second arm pivot axis 17. The second arm pivot axis 17 is substantially perpendicular to the ring axis 14 and it intersects the first arm axis 9, the first arm pivot axis 11 and the ring axis 14 at the central datum point A. The mounting surface 2, on which the solar radiation collecting or reflecting article 3 may be mounted, may be defined by the upper surface of either first or second rings 12, 13 or may be formed of an addition surface mounted on, or offset from, first or second rings 12, 13. In this example, the mounting surface 2 is defined by the upper surface of the second ring 13, which is planar and substantially perpendicular to ring axis 14.

The base 4 further comprises a first opening 18 between base legs 5, and a second opening 19 between the base legs 5 and cross members 6, both openings 18, 19 disposed below the base pivot 8. The first arm 7 passes through the first opening 18 and the second arm 15 passes through the second opening 19, as best seen in Figure 3.

The first opening 18 allows rotation of the first arm 7 about the first arm axis 9 but precludes rotation of the first arm 7 about the first arm pivot axis 11, and any translation parallel to first arm axis 9. In this manner, the first arm 7 is constrained to be rotatable about the first arm axis 9 only and the first arm axis 9 is thus substantially fixed in relation to the base 4.

The second opening 19 constrains the second arm 15 to move in a plane perpendicular to second arm axis 20, preventing rotation of the second arm 15 about the second arm pivot axis 17, and any translation parallel to second arm axis 20. In this manner, the second arm 15 is -11 -constrained to be rotatable about a second arm axis 20 only.

This second arm axis 20 is substantially perpendicular to the plane in which the second arm 15 lies and intersects the first arm axis 9, the first arm pivot axis 11, the ring axis 14 and the second arm pivot axis 17 at the central datum point A. Thus, the second arm axis 20, about which the second arm 15 is rotatable, is also fixed in relation to the base 4. Typically, when moveable mount 1 is in use, second arm axis 20 is substantially parallel to the ground plane.

With reference to Figures 6 and 7, the moveable mount 1 is shown with the mounting surface 2 rotated about the first arm axis 9. The first arm 7 is rotated about the first arm axis 9 by a first input drive means (indicated schematically by arrows Ii) whilst passing through the first opening 18.

As first arm is a substantially semi-circular arc, the first input drive means may engage directly with the first arm 7. The input drive means may, for instance, comprise a wheel, whose axis of rotation is substantially parallel to first arm axis 9 in frictional contact with the outer arc surface of first arm 7. The rotation of the first arm 7 causes the first arm pivots iDA, lOB disposed thereon to rotate with the first arm 7, causing the first arm pivot axis 11 and first ring 12 also to rotate about the first arm axis 9. Since the first ring 12 is supported by the annular flange 13A, the first ring 12 and the second ring 13 remain concentric. Thus, as the first ring 12 rotates about the first arm axis 9, the second ring 13 is caused to rotate on the second arm pivots 16A, 16B about the second arm pivot axis 17. When rotated about the first arm axis 9 by the rotation of the first arm 7, the ring axis 14 remains perpendicular to the first and second arm pivot axes 11, 17 -12 -and all five axes previously described still intersect at the central datum point A. Thus, input Ii to first arm 7 causes mounting surface 2 and any item mounted thereon to rotate about the first arm axis 9, whereby the first arm axis 9 defines a first output axis of the mounting surface 2.

With reference to Figures 8 and 9, the moveable mount 1 is shown with the mounting surface 2 rotated about the second arm axis 20. The second arm 15 is rotated about the second arm axis 20 by a second input drive means (indicated schematically by arrows 12) whilst passing through the second opening 19. As second arm 15 is a substantially semi-circular arc, the second input drive means may engage directly with the second arm 15. The input drive means may, for instance, comprise a wheel, whose axis of rotation is substantially parallel to second arm axis 20 in frictional contact with the outer arc surface of second arm 15. The rotation of the second arm 15 causes the second arm pivots 16A, 165 disposed thereon to rotate with the second arm 15, causing the second arm pivot axis 17, second ring 13 and mounting surface 2 to rotate about the second arm axis 20.

As with the rotation described above in relation with Figures 6 and 7, since the first ring 12 is supported by the annular flange 13A of the second ring 13, it remains concentric with second ring 13 along the ring axis 14.

Thus, when the second ring 13 rotates about the second arm axis 20, the first ring 12 is caused to rotate on first arm pivots lOA, lOB about the first arm pivot axis 11. When rotated about the second arm axis 20 by the rotation of the second arm 15, the ring axis 14 remains perpendicular to the first and second arm pivot axes 11, 17 and all five axes -13 -previously described still intersect at the central datum point A. Thus, input 12 to second arm 15 causes mounting surface 2 and any item mounted on it to rotate about the second arm axis 20, whereby the second arm axis 20 defines a second output axis of the mounting surface 2.

With reference to Figure 10, if inputs Ii and 12 operate simultaneously, to rotate both the first arm 7 and second arm 15 from the "neutral" position of Figure 1 to the positive position of Figure 10, in the manner described above in reference to Figures 6 -9, the geometry of the arrangement causes the first and second rings 12, 13 to rotate about the ring axis 14 relative to each other.

Consequently, first arm pivot bA is rotated about the ring axis 14 towards second arm pivot 16A and first arm pivot lOB is rotated about the ring axis 14 toward second arm pivot 16B. Since the mounting surface 2 is defined in this example by the upper surface of the second ring 13, the ring axis 14 thus defines a third output axis of the mounting surface 2.

As described above, the rotation of the first arm 7 results in the rotation of the mounting surface 2 about the first arm axis 9. As also described above, the rotation of the second arm 15 results in the rotation of the mounting surface 2 about the second arm axis 20. During the simultaneous rotation of first arm 7 and second arm 15, ring axis 14 rotates about first and second pivot arm axes 11 and 17 in such a way that it remains perpendicular to first and second pivot arm axes 11 and 17 and therefore perpendicular to mounting surface 2 at all times.

Consequently, when first and second arms 7, 15 rotate simultaneously about first and second arm axes 9, 20, a -14 -solar radiation collecting or reflecting article, or other item (not shown), mounted on the mounting surface 2 is rotated about the first arm axis 9 and the second arm axis simultaneously. Indeed, it is the construction of the arrangement, with the concentric rings 12, 13 which are rotatable about the ring axis 14 relative to each other, which allows rotation of the mounting surface 2.

Simultaneous rotation of the mounting surface 2 about its first and second axes 9, 20 is only possible because this rotation about the third axis 14 is possible.

Despite the rotation of the first arm 7 and the second arm 15 about the first and second arm axes 9, 20, all five axes previously described remain intersecting at the central datum point A. With reference to Figure 11, as the first arm 7 is rotated by the input Ii about the first arm axis 9 from the position of Figure 10 to that of Figure 11, the first arm pivots bA, lOB, first arm pivot axis 11 and first ring 12 are also caused to rotate about the first arm axis 9, as described above in reference to Figures 6 and 7. Since the second arm 15 is stationary, the geometry of the arrangement is such that the first ring 12 rotates about the ring axis 14 in an anti-clockwise direction (as viewed from the front face of the mounting surface 2) relative to the second ring 13. Consequently, first arm pivot 1OA is rotated about the ring axis 14 towards second arm pivot 16B and first arm pivot lOB is rotated about the ring axis 14 towards second arm pivot 16A.

A projection of ring axis 14 onto a plane perpendicular to second arm axis 20 maintains a constant angle in that plane with respect to any fixed datum line (in that plane) at all times during the transition from the position of -15 -Figure 10 to the position of Figure 11. Since ring axis 14 is perpendicular to the mounting surface 2 at all times, the orientation of mounting surface 2 in any plane perpendicular to second arm axis 20 does not change during this transition. In other words, the mounting surface 2, and the solar collecting or reflecting article 3 attached thereon (as shown in Figure 2), can be rotated about the first arm axis 9 without affecting its orientation about the second arm axis 20.

With reference to Figure 12, as the second arm 15 is rotated by the input 12 about the second arm axis 20 from the position of Figure 11 to that of Figure 12, in the manner described above in reference to Figures 8 and 9, the geometry of the arrangement causes the second ring 13 and the mounting surface 2 to rotate about the ring axis 14 in an anti-clockwise direction (as viewed from the front face of the mounting surface 2) relative to the first ring 12.

Consequently, second arm pivot 16A is rotated towards first arm pivot iDA and second arm pivot 16B is rotated towards first arm pivot lOB. As described above, the rotation of the second arm 15 about the second arm axis 20 results in a corresponding rotation of the mounting surface 2 about the second arm axis 20.

A projection of ring axis 14 onto a plane perpendicular to first arm axis 9 maintains a constant angle in that plane with respect to any fixed datum line (in that plane) at all times during the transition from the position of Figure 11 to the position of Figure 12. Since ring axis 14 is perpendicular to the mounting surface 2 at all times, the orientation of mounting surface 2 in any plane perpendicular to first arm axis 9 does not change during this transition.

-16 -In other words, the mounting surface 2, and the solar collecting or reflecting article 3 attached thereon (as shown in Figure 2), can be rotated about the second arm axis without affecting its orientation about the first arm axis 9.

Referring now to Figure 13, as the first arm 7 is rotated by the input Ii about the first arm axis 9, from the position of Figure 12 to that of Figure 13, in the manner described above in reference to Figures 6, 7 and 11, the first ring 12 is caused to rotate about the ring axis 14 in an anticlockwise direction (as viewed from the front face of the mounting surface 2) relative to the second ring 13.

Consequently, first arm pivot lOA is rotated about third axis 14 toward second arm pivot l6B and first arm pivot lOB is rotated towards second arm pivot 16A (not visible in Figure 13) . As described above, the rotation of the first arm 7 about the first arm axis 9 results in a corresponding rotation of the mounting surface 2 about the first arm axis 9 without affecting its orientation about the second arm axis 20.

It will be appreciated that, since the first arm axis 9 and second arm axis 20 remain stationary with respect to the base 4, the point at which inputs Ii and 12 act upon first and second arms 7, 15 can remain unchanged irrespective of the orientation of the mounting surface 2 of the moveable mount 1. Therefore, a plurality of moveable mounts 1 arranged in a line such that the first arm axis 9 of each is in alignment can be controlled about their first arm axis 9 by a single drive means. This drive means may comprise, for instance, a drive shaft, whose axis of rotation is -17 -substantially parallel to first arm axis 9, in frictional contact with the outer arc surface of the first arm 7 of each moveable mount 1. Similarly, a plurality of moveable mounts 1 arranged in a line such that the second arm axis 20 of each is in alignment can be controlled about their second arm axis 20 by a single drive means.

By arranging a plurality of moveable mounts 1 in a grid formation, with rows aligned along the first arm axis 9 of each, and columns aligned along the second arm axis 20 of each, the entire array of moveable mounts 1 can be controlled about their first and second axes 9,20 by a number of drive means equal to the sum of the number of rows and the number of columns.

By mechanically joining the drive means for all the rows (with timing belts for instance) and mechanically joining the drive means for all the columns, the entire array of moveable mounts 1 can be controlled about their first and second axes 9,20 by just two drive means. Thus, regardless of the starting alignment of each individual mounting surface 2 (about either its first arm axis 9 or its second arm axis 20), a single drive means can rotate all the mounting surfaces 2 of the whole array of moveable mounts 1 by the same angular deflection about their first arm axis 9, and another single drive means can rotate all the mounting surfaces 2 of the whole array by the same angular deflection about their second arm axis 20.

The moveable mount 1 is generally formed from a rigid plastics material, steel or other suitable material which is durable and resistant to degradation. Additionally, a -18 -lubricant or low friction insert (such as a bush, or ball bearing) may be employed between moving parts. For example, between the first and second rings 12, 13, between first arm 7 and upright members 5, between first arm 7 and first arm pivots 1OA, lOB, and between second arm 15 and second arm pivots 16A, 16B.

It will be appreciated that many modifications may be made to the above described embodiment without departing from the scope of the invention. For instance, although the mounting surface 2 is described as being defined by the upper surface of the second ring 13, equally, the mounting surface 2 could be defined by the first ring 12.

Although the embodiment described above is of a scale such that the solar collecting or reflecting article 3 has an area of approximately 0.04 square metres, many different sizes of moveable mount 1 may be built in accordance with the present invention, including those with a solar collecting or reflecting article 3 of many square metres.

The base legs 5 may be non-parallel. Alternatively, the base 4 may comprise a single base leg 5, or indeed more than two base legs 5, or base members.

The first arm pivots bA, lOB can be disposed on the first arm 7 such that the first arm pivot axis 11 is not substantially perpendicular to the first arm axis 9, provided the two axes still intersect at datum point A. In this embodiment, however, the ratio of the amount of movement of input Ii to the angular rotation of the mounting surface 2 about first arm axis 9 varies depending on the -19 -starting angular position. Similarly, the second arm pivots 16A, 16B can be disposed on the second arm 15 such that the second arm pivot axis 17 is not substantially perpendicular to the second arm axis 20, provided the two axes still intersect at datum point A. In this embodiment, however, the ratio of the amount of movement of input 12 to the angular rotation of the mounting surface 2 about second arm axis 20 varies depending on the starting angular position.

Annular flange 13A need not be defined by second ring 13. It can be defined by first ring 12. Alternatively, it can be formed of a further component, or components, mounted on the first or second rings 12, 13, provided it is arranged to ensure first and second rings 12, 13 remain concentric along ring axis 14.

The first and second arm axes 9, 20 have been described as being substantially perpendicular. However, these axes may be disposed at any angle, provided they still intersect at datum point A and are non-parallel. In such an embodiment, however, the rotation of first arm 7 about first arm axis 9 will affect the orientation of the mounting surface 2 about second arm axis 20. Also, rotation of second arm 15 about second arm axis 20 will affect the orientation of the mounting surface 2 about first arm axis 9.

The base 4 can comprise one opening only. Provided base pivot 8 constrains first arm 7 sufficiently to preclude any movement except rotation about first arm axis 9, first opening 18 can be excluded.

-20 -Either of the first and second openings 18, 19 can be arranged such that the respective arms passing through them are precluded from being displaced toward the datum point A. Thus a reaction force may be provided against a driving means at the point where inputs Ii and 12 are acted upon first and/or second arms 7, 15 to improve accuracy of rotational output.

It will be appreciated that, within the scope of this invention, manufacturing tolerances, provision for thermal expansion etc. may cause the various axes not to intersect precisely at a single point A at all times, but rather all pass through a very small sphere centred at point A. Other forms of first and second arms 7, 15 can be used in place of the arc members described above. With reference to Figures 14 and 15, first arm 7 is substantially straight, with first arm pivots 1OA, lOB towards both ends, and a first arm lever pivot 32 towards one end. The first arm lever pivot axis 23 is substantially parallel to first arm axis 9. A cutout 33 allows first arm 7 to be pivotally attached to the upper end of a first upright lever 27 by first arm lever pivot 32. At its lower end, first upright lever 27 is pivotally attached to first base levers 28 by first base lever pivot 31, the first upright lever 27 and first base levers 28 being rotatable relative to each other about first base lever axis 22. First base lever axis 22 is substantially parallel to first arm axis 9. First base levers 28 are fixedly attached at their other end to first rod 35. First rod 35 is constrained by base legs 5 to rotate about first rod axis 21, this axis being fixed and substantially parallel to first arm axis 9. A first input -21 -drive means (indicated schematically by arrows Ii) acts upon first rod 35, such that the rotation of first rod 35 rotates the mounting surface 2 about first arm axis 9 without affecting the orientation of mounting surface 2 about second arm axis 20. Provided that, in a plane perpendicular to first arm axis 9, the distance between first arm axis 9 and first arm lever pivot axis 23 is equal to the distance between first rod axis 21 and first base lever axis 22, and that a line joining first arm axis 9 to first arm lever pivot axis 23 is parallel to a line joining first rod axis 21 to first horizontal lever axis 22, then the ratio of the amount of movement of the first input Il to the angular rotation of the mounting surface 2 is constant irrespective of the starting angular position.

In this second embodiment, second arm 15 comprises a central arc section, centred on second arm axis 20, and radial arms l5A, with second arm pivots l6A, 16B at both ends, and a second arm lever pivot 30 towards one end. The second arm lever pivot axis 26 is substantially parallel to second arm axis 20. A cutout 34 allows second arm 15 to be pivotally attached to the upper end of a second upright lever 37 by second arm lever pivot 30. At its lower end second upright lever 37 is pivotally attached to second base levers 38 by second base lever pivot 29, the second upright lever 37 and second base levers 38 being rotatable relative to each other about second base lever axis 25. Second base lever axis 25 is substantially parallel to second arm axis 20. Second base levers 38 are fixedly attached at their other end to second rod 36. Second rod 36 is constrained by base leg protrusion 39 to rotate about second rod axis 24, this axis being fixed and substantially parallel to second arm axis 20. A second input drive means (indicated -22 -schematically by arrows 12) acts upon second rod 36, such that rotation of second rod 36 rotates the mounting surface 2 about second axis 20 without affecting the orientation of mounting surface 2 about first axis 9. Provided that, in a plane perpendicular to second arm axis 20, the distance between second arm axis 20 and second arm lever pivot axis 26 is equal to the distance between second rod axis 24 and second base lever axis 25, and that a line joining second arm axis 20 to second arm lever pivot axis 26 is parallel to a line joining second rod axis 24 to second base lever axis 25, then the ratio of the amount of movement of the second input 12 to the angular rotation of the mounting surface 2 is constant irrespective of the starting angular position.

Thus, the first and second arms 7, 15 engage with first and second input drive means Ii, 12 indirectly.

Further embodiments may have an upright lever 27, 37 disposed toward each end of the first arm 7 and second arm 15. In such a configuration, the upright levers 27, 37 may be replaced with wires (for instance steel cables) Thus, an improved moveable mount with a simplified structure is provided for rotating a mounted object about two fixed axes in such a manner that the mounted object may be rotated about either one of the axes without affecting its orientation relative to the other axis and whereby the ratio of the amount of movement of the input to the angular rotation of the mounted object is constant irrespective of the angular starting position.

Claims

-23 -CLAIMS1. A movable mount for supporting a radiation reflecting, receiving or transmitting device, comprising: a base and a mounting surface on which the radiation reflecting, receiving or transmitting device is mountable, wherein the mounting surface is selectively rotatable about first and second axes relative to the base; the mount further comprising a first input device which is rotatable about the first axis which is fixed relative to the base, the first input device operable to rotate the mounting surface about the first axis; a second input device which is rotatable about the second axis which is fixed relative to the base, the second input device operable to rotate the mounting surface about the second axis; and a bearing assembly connecting the mounting surface to the first and second input devices, the bearing assembly comprising first and second members, arranged to be concentric and rotatable relative to each other about a third axis, wherein all three axes intersect a common point which is fixed relative to the base.
2. A movable mount as claimed in claim 1, wherein the first input device comprises a first arm pivotally secured to the base for rotation about the first axis and pivotally secured to the bearing assembly.
3. A movable mount as claimed in claim 2, wherein the first arm comprises a semi-circular arc pivotally secured to the base at the centre of the arc, and pivotally secured to the linkage assembly towards each end of the arc.

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4. A movable mount as claimed in any preceding claim wherein the second input device comprises a second arm pivotally secured to the bearing assembly and constrained to rotate about the second axis only.
5. A movable mount as claimed in claim 4, wherein the second arm comprises a semi-circular arc, pivotally secured to the bearing assembly towards each end of the arc.
6. A movable mount as claimed in claim 4 or claim 5, further comprising guide means on the base operable to constrain the second arm to rotate about the second axis only.
7. A movable mount as claimed in any of claims 2 to 6, wherein the first and second arms lie in planes perpendicular to one another.
8. A movable mount as claimed in any preceding claim, wherein the first member is pivotally secured to the first arm, the second member is pivotally secured to the second arm and the mounting surface is secured to either the first member or the second member. * 25
9. A movable mount as claimed in claim 8, further comprising co-operating structures on the first and second members operable to constrain the members to be concentric but allowing relative rotation about the third axis.

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10. A moveable mount as claimed in any preceding claim, wherein the first member comprises a first ring and the second member comprises a second ring.
11. A movable mount as claimed in claim 10, wherein the co-operating structures comprise a flange associated with one ring against which at least part of the other ring is slidably received.
12. A movable mount as claimed in any preceding claim, wherein the ratio of the amount of movement of the first input device about the first axis to the amount of rotation of the mounting surface about the first axis is constant.
13. A movable mount as claimed in any preceding claim, wherein the ratio of the amount of movement of the second input device about the second axis to the amount of rotation of the mounting surface about the second axis is constant.
14. A movable mount as claimed in any preceding claim, wherein the first input device engages directly with a first input drive means and the second input device engages directly with a second input drive means.
15. A movable mount as claimed in any of claims 1 to 13, wherein the first input device engages with a first input drive means through a first linkage assembly and the second input device engages with a second input drive means through a second linkage assembly.
16. A movable mount substantially as hereinbefore described and with reference to the accompanying drawings.Amendments to the claims have been filed as follows 26 -CLAIMS1. A movable mount for supporting a radiation reflecting, receiving or transmitting device, comprising: a base and a mounting surface on which the radiation reflecting, receiving or transmitting device is mountable, wherein the mounting surface is selectively rotatable about first and second axes relative to the base; the mount further comprising a first input device which is rotatable about the first axis which is fixed relative to the base, the first input device operable to rotate the mounting surface about the first axis; a second input device which is rotatable about the second axis which is fixed relative to the base, the second input device operable to rotate the mounting surface about the second axis; and a bearing assembly connecting the mounting surface to the first and second input devices, the bearing assembly comprising first and second members, arranged to be concentric and rotatable relative to each other about a third axis, wherein all three axes intersect a common point which is fixed relative to the base.2. A movable mount as claimed in claim 1, wherein the *** first input device comprises a first arm pivotally secured * to the base for rotation about the first axis and pivotally secured to the bearing assembly.I S..3. A movable mount as claimed in claim 2, wherein the first arm comprises a semi-circular arc pivotally secured to *. the base at the centre of the arc, and pivotally secured to the bearing assembly towards each end of the arc.4. A movable mount as claimed in any preceding claim wherein the second input device comprises a second arm pivotally secured to the bearing assembly and constrained to rotate about the second axis only.5. A movable mount as claimed in claim 4, wherein the second arm comprises a semi-circular arc, pivotally secured to the bearing assembly towards each end of the arc.6. A movable mount as claimed in claim 4 or claim 5, further comprising guide means on the base operable to constrain the second arm to rotate about the second axis only.7. A movable mount as claimed in any of claims 2 to 6, wherein the first and second arms lie in planes perpendicular to one another.8. A movable mount as claimed in any preceding claim, wherein the first member is pivotally secured to the first arm, the second member is pivotally secured to the second arm and the mounting surface is secured to either the first member or the second member. * * 25 ** * 9. A movable mount as claimed in claim 8, further comprising co-operating structures on the first and second * members operable to constrain the members to be concentric I..but allowing relative rotation about the third axis. *I* *10. A movable mount as claimed in any preceding claim, wherein the first member comprises a first ring and the second member comprises a second ring.11. A movable mount as claimed in claim 10, wherein the co-operating structures comprise a flange associated with one ring against which at least part of the other ring is slidably received.12. A movable mount as claimed in any preceding claim, wherein the ratio of the amount of movement of the first input device about the first axis to the amount of rotation of the mounting surface about the first axis is constant.13. A movable mount as claimed in any preceding claim, wherein the ratio of the amount of movement of the second input device about the second axis to the amount of rotation of the mounting surface about the second axis is constant.14. A movable mount as claimed in any preceding claim, wherein the first input device engages directly with a first input drive means and the second input device engages directly with a second input drive means. 25 15. A movable mount as claimed in any of claims 1 to 13, IIII* * wherein the first input device engages with a first input drive means through a first linkage assembly and the second input device engages with a second input drive means through a second linkage assembly. ** * * ._** 16. A movable mount substantially as hereinbefore described and with reference to the accompanying drawings.