WO2004044501A1

WO2004044501A1 - A stand

Info

Publication number: WO2004044501A1
Application number: PCT/SE2003/001677
Authority: WO
Inventors: Carl-Evert Gustafsson
Original assignee: Carl-Evert Gustafsson
Priority date: 2002-11-11
Filing date: 2003-10-30
Publication date: 2004-05-27
Also published as: SE0203308D0; SE523822C2; SE0203308L; AU2003275754A1

Abstract

A stand (2) for solar collectors, the stand comprising a long shaft element (10), and a framework (12) arranged to hold at least one solar collector (1), the framework being rotatably connected to the shaft element in at least two axially separated positions along the shaft element. The stand further comprises a bearing unit (16, 17) arranged such that the framework is rotatably mounted in relation to the shaft element, wherein the bearing unit is fixed from two sides in relation to the framework.

Description

A STAND

TECHNICAL FIELD

The present invention relates to a stand for solar collectors, the stand comprising a long shaft element, and a framework arranged to hold at least one solar collector, the framework being rotatably connected to the shaft element in at least two axially separated positions along the shaft element.

With the term solar collector is intended all types of devices collecting and exploiting the energy of the sun. Some solar collectors are used to produce heat and others to produce electricity. The solar collectors producing heat utilises the energy of the sun by letting the sun heat some liquid medium, usually water. The solar collectors producing electricity are denoted photo- volatics and usually utilises some chemical process to transform the solar energy into electricity. A stand according to the invention is especially useful for solar collectors that are large in size. The types of solar collectors used to produce heat, for example in order to heat houses, are considerably larger than the photo- volatics used to produce electricity. Thus the stand according to the invention is particularly suitable for this type of solar collectors.

PRIOR ART

A solar collector consists of a body of one or more planar solar collector elements, which are comprised in the framework. The solar collector elements are arranged adjacent to each other such that they together constitute a large continuous surface turned towards the sun. The solar collector elements comprise pipes carrying some kind of liquid being heated by the sun. The solar collectors are normally mounted on the ground or on the roof of a house. Usually the solar collectors are carried by a stand being fixedly mounted in the ground or on the roof. Since the solar collectors are very large in size they constitute a large surface exposed to the wind and thus the forces on the stand become very large when it is windy. A stand for a solar collector must thus be able to take care of large torques, especially in the points of suspension.

From the American patent no. 5,01 ,105 it is known with a stand for a solar collector comprising a vertical shaft element and a framework being arranged to hold a solar collector and being rotatably connected to the shaft element in two axially separated positions along the shaft element. In the upper position the framework is connected to an end sleeve surrounding the upper end of the shaft element. The framework is connected to one side of the sleeve in a point. In the lower position the framework is connected to a half circular element, which in turn is clamped against the shaft element with a clamp being held fast with the help of a screw. The framework is only connected to one side of the shaft element in the lower position also. The upper and the lower connections are also positioned on the same side of the shaft element. Such a stand is able to carry a smaller solar col- lector but it is not suitable to carry large solar collectors.

During the day the sun and the earth move in relation to each other. In order to absorb maximum solar energy, the solar collector should be able to follow the movement of the sun. The so- lar collector shown in the US patent described above is certainly adjustable by the clamp and the screw, but it has not the function and that it can follow the movement of the sun during the day. For smaller solar collectors, such as photovoltaics, it is known to use stands that follow the movement of the sun during the day. Such a stand is shown in the patent US 4,625,709. The stand shown follows the movement of the sun without consum- ing any electrical energy. The stand shown has the solar collector mounted directly on the vertical shaft element without any form of supporting framework. This stand is only intended for use for smaller solar collectors and cannot be used for the lar- ger types of solar collectors.

PURPOSE AND SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a rotatable stand being able to carry a large and heavy solar collector unit and being able to withstand the forces arisen in connection with though weather. Further the purpose is to provide a stand, which is simple, robust, have few components and is inexpensive to manufacture.

This purpose is achieved with the stand as mentioned in the introduction, which is characterised in that it comprises a bearing unit arranged such that the framework is rotatably mounted in relation to the shaft element, wherein the bearing unit is fixed from two sides in relation to the framework. With fixed from two sides is intended that the bearing unit is fixed against the framework from two substantially opposite sides. With such a construction there is at least one supporting point arranged on each of the two opposite sides of the shaft element in each of the two axial positions giving a distinct force allowance with symmetrically distributed forces from two oppositely supporting parts and a good transmittance of forces to the shaft element. Such a construction becomes both stiff and light and can be designed with few parts making the stand inexpensive to manufac- ture.

According to a preferred embodiment of the invention the framework is connected with the bearing unit in at least two substantially opposite sides of the shaft element. With advan- tage the framework comprises a first and a second part arranged on opposite sides of the shaft element and the first part of the framework is connected with one side of the bearing unit and the second part is connected with the other side of the bearing unit. In such a way a very stable construction with great ability to withstand torques is obtained.

According to a further preferred embodiment of the invention the bearing unit comprises two bearing members arranged at a distance from each other along the shaft element, wherein the shaft element is arranged to run through the bearing members and that the framework is fixedly connected with each of the bearing members on at least two substantially opposite sides of the shaft element. By arranging the bearing members at a distance from each other along the shaft element, a lever is created absorbing radial forces. In order for the load to be distributed there should be at least two bearing members arranged in separate positions along the shaft element.

According to a further preferred embodiment of the invention the bearing unit comprises two opposite, substantially planar sides and the framework is fixedly connected with said planar sides. These planar sides make it simple to attach the framework to the bearing unit and to achieve the correct angle between the different parts in the framework, facilitating the mounting of the stand. The planar surfaces constitute reference surfaces and facilitate manufacturing and mounting.

According to a further preferred embodiment of the invention the stand comprises a driving mechanism arranged to rotate the framework around the shaft element, the driving mechanism comprises a cam having a cam contour and a driving member arranged to cooperate with the cam contour, such that the cam and the driving member move in relation to each other. Such a driving mechanism occupies little space and may be integrated with the stand in a simple way. With advantage one of the cam and the driving member is arranged in connection with the framework and the other is arranged in connection with the shaft element. In such a way the entire driving mechanism can be arranged on the stand and be surrounded by the same casing as the stand giving a compact stand.

According to a preferred embodiment of the invention the cam contour is shaped such that it limits the movement of the framework between two positions: one starting position and one stop position. Since the sun moves within a limited circle sector, it is sufficient for the rotational movement of the framework to also be limited within this sector. If the rotational movement is unlimited there may be problems with the cables to the rotation mechanism, which may become entangled or be pulled to pieces. A cam contour can in a simple way be shaped such that the rotational movement is limited between two positions without demanding any additional parts.

According to a further preferred embodiment of the invention the cam is arranged in connection with the shaft element and is adjustable in a relation to the shaft element, wherein said starting positions is adjustable in relation to the shaft element. In such a way it is easy to calibrate the movement of the stand in relation to the sun.

According to a further preferred embodiment of the invention the driving mechanism is formed such that the framework is rotated step wise around the shaft element. In such a way the control of the rotational movement is simplified and the gear change of the gear can be made smaller in comparison with if the driving mechanism were formed such that it performed a continuous movement. Another advantage is that the engine does not need to be continuously operational but can be run only at intervals.

According to a further preferred embodiment of the invention the driving mechanism comprises a driving unit arranged to gener- ate a rotating movement driving the driving member, wherein the driving unit is arranged on the framework and a cam is arranged in connection with the shaft element. On the framework there is a lot of space for arrangement of the driving unit, which thus in a simple way may be integrated with the framework. This gives a compact and robust stand. With advantage the cam is arranged radially in relation to the shaft element. A cam arranged in this way can withstand a high load. With advantage the cam contour is a Malteser contour. The Malteser contour is a well-tried cam contour shown to be advantageous in this application thanks to the driving member being moved between a number of distinct positions along the contour giving rise to the stepwise movement which is suitable in this application. The larger radial contour of the driving member also makes it possible for the mechanism to be locked in a resting position. A further advantage with a Malteser contour is that it is simple to produce.

SHORT DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained with different, such as examples, described embodiments and with reference to the attached drawings.

Fig. 1 shows a solar collector unit being carried by a stand according to a first embodiment of the invention.

Figs. 2a and 2b show perspective views of the stand in fig. 1 , as seen from two different directions.

Fig. 3 shows an exploded view of the stand according to the first embodiment.

Fig. 4 shows a cam driver in a perspective view.

Fig. 5 shows a stand according to a second embodiment of the invention. Fig. 6 shows a stand according to a third embodiment of the invention.

Fig. 1 shows a solar collector unit 1 being carried by a stand 2 according to a first embodiment of the invention. The solar collector unit 1 comprises a number of planar solar collector elements 4 arranged such that they collect the rays from the sun and transform the solar energy into heat. The solar collector elements are fixed inside a framework comprising a number of par- allel transverse beams 7 and a longitudinal supporting element 8 arranged perpendicular to the transverse beams 7. The framework is individually designed depending on the manufacture of the solar collectors being used. The figures 2a, 2b and 3 show the stand 2 in closer detail. The stand 2 comprises an essen- tially vertically arranged long, tubular shaft element 10 and a framework 12, being arranged rotatable around the shaft element 10.

The framework comprises a first part 13 and a second part 14, which are arranged on opposite sides of the shaft element 10. Each of the first and the second part 13, 14 of the framework is connected with both the solar collector unit and with the bearing unit. Each of the parts 13, 14 of the framework comprises a longitudinal frame beam 15a, 15b, arranged substantially in parallel with the shaft element and designed to be rotatably connected with the shaft element 10 via the bearing members 16, 17, see fig 2. The frame beams 15a, 15b are arranged on opposite sides of the shaft element 10. From the upper ends of the frame beams 15a, 15b connecting elements 15c, 15d extend outwardly and being shaped to be connected with the framework of the solar collector unit. In this example the connecting elements 15c, 15d are connected with the longitudinal supporting element 8 of the body. From the lower ends of the frame beams 15a, 15b a supporting beams 15e, 15f extend towards the connecting ele- ment 15c, 15d, in order to stabilise the body. The body of the solar collector unit is made of for example aluminium and the beams of the framework are for example made of stainless steel or galvanized steel.

The stand 2 further comprises a bearing unit arranged such that the framework 12 is rotatably mounted in relation to the shaft element 10. The bearing unit comprises two axially separated bearing members 16, 17, cf. fig. 2b. Each of the bearing members 16, 17 comprises a friction-decreasing member 18, 19 and a bearing house 21 , 22 surrounding the friction decreasing members. The bearing houses 21 , 22 have the shape of a rectangular plate having at ieast two planar surfaces intended to be attached against the framework 12. The friction decreasing members 18, 19 are, in this example, bushings. The bushings 18, 19 are preferably made in some construction plastic, which is approved for outdoor applications, have good lubricating performance and high durability, for example Oilon ™, Nylatron GSM ™ or Robalon ™. The bearing houses 21 , 22 are provided with through openings and the friction decreasing members 18, 19 are arranged inside the openings. The shaft element 10 ex- tends through both the friction decreasing members 18, 19 and the bearing members 16, 17.

Each of the bearing members 16, 17 comprises two opposite, substantially planar sides 24, 26 connected with the frame beams 15a, 15b. The bearing members are thus fixed from two sides in relation to the framework 12. In this embodiment example the frame beams 15a, 15b are connected with the bearing members 16, 17 with screws. Each of the two opposite sides is connected with the framework with two screws. That means that there are four supporting points between the framework and each of the bearing members. Two supporting points are located at each side of the shaft element. Since the bearing members are arranged in two separate positions along the shaft element this means that the stand has eight supporting points, that is, four in each position. The advantage of fixing from two sides is that the solar collector unit is braced from two directions. Alter- natively the framework and the bearing members may be connected by welding.

The stand 2 is fixedly mounted on a base 28 which in turn is fixed for example in the ground or on a roof. The shaft unit 10 is in its lower part provided with an attachment plate 30, which is screwed fast with anchoring beams in the base 28. The distance ring 32 is welded to the shaft unit 10. The distance ring 32 carries the axial load and is in contact with a collar 34 of the lower bushing. The upper bushing 18 is in its upper end provided with a collar 36, the function of which is to hold the bushing in place in the bearing house 21 . The collar 36 is designed to carry radial loads. The collar 34 in the lower bushing 19 is somewhat larger than the collar 36 since it is to be able to carry both axial and radial loads. The collar 34 bear against the distance ring 32.

The stand 2 comprises a driving mechanism arranged to rotate the framework 12 around the shaft element 10. The driving mechanism, which is best shown in fig. 2, comprises a cam 40 provide with a cam contour and a driving member in the form of a cam drive 42 arranged to cooperate with the cam contour such that the cam 40 and the cam drive 42 moves in relation to each other. Further the driving mechanism comprises a driving unit, which in this embodiment example consists of an electrical en- gine 44 and a gear 45 bringing the cam drive 42 into rotation via its outgoing shaft 47. In this embodiment example the driving unit with the engine 44 and gear 46, are arranged on the framework, or, more exactly, on the supporting beam 15e. The outgoing shaft 47 of the gear is arranged substantially vertical. The framework 12 and the cam drive 42 are thus connected with each other through the driving unit. The cam 40 is fixedly connected with the shaft element through the distance ring 32. When the cam drive rotates, it moves along the cam contour, which causes the framework to rotate around the shaft unit. The cam 40 has the shape of a half circle shaped plate extending in a radial direction from the shaft element. The periphery of the cam is shaped such that it constitutes the cam contour. In this example the cam contour is a Malteser contour meaning that the cam is provided with a number of successive notches 48, 50 in which every other notch has a larger depth and a smaller width than the following notch. The cam 40 is fixedly connected to the distance ring 32 and is centred around it. The cam 40 is arranged such that it is adjustable in a relation to the shaft element 10 by being rotatable around the flange and then is fixed in a selectable position. Thanks to this possibility to rotate the cam in relation to the shaft element it is simple to calibrate and reset the motion. The orientation of the cam in relation to the shaft element 10 and the base 28 determines the starting angle for the movement, that is, the angle in which the movement is to begin in the morning. The extension of the cam contour along the periphery of the cam 40 determines the size of the movement, that is, how many degrees the stand will move during the day. In this embodiment example the cam contour corresponds to an angle of 150 degrees. The shaping of the cam contour with successive notches gives a stepwise displacement of the framework and the solar collector unit.

The cam contour comprises two different types of notches: a half circle shaped notch 48 and a longitudinal notch in the form of a slit 50. Fig. 4 shows in closer detail the design of a cam drive for a Malteser contour. The cam drive 42 comprises a driving pin 52 intended to cooperate with the slit 50 and a locking member 54 intended to cooperate with the notch 48. The locking member 54 has a bent surface, the form of which corresponding to the form of the notch 48. The first notch on the cam contour defines the starting position of the stand and the last notch on the profile defines the stop position of the stand. The driving mechanism also comprises a sensor 56 sensing the position of the driving pin 52. The driving mechanism is controlled by a control computer, not shown, generating control signals to the en- gine. The signals from the sensor 56 are transmitted to the control computer.

The movement of the stand is started in the morning by the con- trol computer giving a starting signal to the engine 44, which in turn drives the cam drive 42 in a rotating movement via the gear

45 and the outgoing shaft 47. The cam drive is moved along the cam contour and engages the next notch on the contour. In this example the first notch is a shallow notch 48 and the next notch a slit 50. In the starting position the cam drive is positioned such that the locking member 54 engages the notch 48. When the cam drive is rotated the driving pin is moved such that it enters into the slit 50 at the same time as the locking member 54 is moved such that it comes into contact with the next shallow notch 48 along the cam contour.

Two notches 48 together define a step. The slit 50 constitutes a gripping member for the driving pin 52. When the cam drive has been rotated such that the locking member 54 is completely in- side the shallow notch, the driving pin 52 points outwardly towards the sensor 56 detecting the driving pin. When the sensor 56 has detected the driving pin it transmits a signal to a control computer, which signal indicates that a step of the movement is completed. When the control computer receives information that a step is completed it transmits a stop signal to engine which stops. In such a way the framework will rotate stepwise around the shaft element. With even intervals during the day new control signals are transmitted to the engine, which starts the movement, wherein the cam drive moves a step further along the cam contour. When the day is to an end and the cam drive has reached its stop position the control computer generates a signal to the engine driving the cam drive backwards along the cam contour to the starting position such that the next day it is ready to once again begin at the starting position. In an alternative embodiment the cam 40 is positioned above the bearing unit directly on the shaft element. In an alternative embodiment it is also possible to put the cam on the framework and arrange the engine and the gear on the shaft element or on the stand. The cam in the example is arranged radially in relation to the shaft unit. The cam drive is arranged axially, i.e. it is arranged with its length axis substantially parallel with the shaft unit.

Fig. 5 shows a stand 60 according to a second embodiment of the invention. The components of the embodiment shown in fig. 5, which are identical with corresponding components of the embodiment shown in fig. 1 , have been assigned the same reference number and will not be described further. The difference between the second embodiment and the first is the design of the framework. The framework 62 comprises in this embodiment two angle shaped, parallel supporting beams, which each comprises two angled arms, which in their upper ends are attached against longitudinal beams 8 of the body of the solar collector unit. A number of substantially horizontal, transversal beams 66a, 66b are arranged between the angle shaped supporting beams 64a, 64b. The transversal beams 66c and 66d are arranged on each side of the shaft element 10 and are fixed against the bearing member 17. The transversal beam 66c is fixedly connected with the planar side 24 of the bearing member 17 and the transversal beam 66d is fixedly connected to the opposite planar side 26 of the bearing member 17. The fixed connection is carried out by means of a screw joint.

The framework further comprises two substantially horizontal transversal beams 66e and 66f, which are arranged between two longitudinal beams 8 of the body of the solar-collector unit. The transversal beam 66e is fixedly connected with the bearing member 16 through an attachment plate 68, and the transversal beam 66f is fixedly connected with an opposite side of the bearing member 16. The transversal beams 66e and 66f are ar- ranged oppositely on either side of the shaft element 10. The attachment against the bearing member 16 is carried out by means of screws.

Fig. 6 shows a third embodiment of a stand according to the invention. The difference between the third embodiment and from the two previous embodiments is the design of the cam contour and the driving member. The driving member in this embodiment is a tangentially mounted screw 70 designed such that it en- gages vertical cog elements arranged on the cam 72. The screw 70 is arranged such that it rotates around an axis, which is perpendicular to the length axis of the shaft element.

The invention is not limited to the embodiments shown but can be varied and modified within the framework of the following claims. For example the rectangular part of the bearing unit may be made in plastic having high durability. In such a way the bushings may be left out, wherein the number of parts in the bearing unit is reduced, meaning a lower cost of manufacture.

The bearing unit can also be fixed in relation to the framework by two diagonal corners of the bearing unit. In such an embodiment the framework can for example surround a part of the corner and the connection can be two screws, each on either side of the corner.

Claims

1. A stand (2, 60) for solar collectors, the stand comprising a long shaft element (10), and a framework (12, 62) arranged to hold at least one solar collector (1 ), the framework being rotatably connected to the shaft element in at least two axiaiiy separated positions along the shaft element, characterised in that the stand comprises a bearing unit (16, 17) arranged such that the framework (12, 62) is rotatably mounted in relation to the shaft element (10), wherein the bearing unit is fixed from two sides in relation to the framework.

2. A stand according to claim 1 , characterised in that the framework (12, 62) is connected with the bearing unit (16, 17) in at least two substantially opposite sides of the shaft element (10).

3. A stand according to claim 1 or 2, characterised in that the framework (12, 62) comprises a first (13) and a second (14) part arranged on opposite sides of the shaft element (10) and that both parts are connected with the bearing unit (16, 17).

4. A stand according to any of the previous claims, characterised in that the bearing unit comprises two bearing members (16, 17) arranged at a distance from each other along the shaft element (10), wherein the shaft element is arranged to run through the bearing members and that the framework is fixedly connected with each of the bearing members on at least two substantially opposite sides of the shaft element.

5. A stand according to any of the previous claims, characterised in that the bearing unit comprises two opposite, substantially planar sides (24, 26) and that the framework is fixedly connected with said planar sides.

6. A stand according to any of the previous claims, characterised in that it comprises a driving mechanism arranged to rotate the framework around the shaft element, the driving mechanism comprising a cam (40) having a cam contour, and a driving member (42) arranged to co-operate with the cam contour such that the cam and the driving member move in relation to each other.

7. A stand according to claim 6, characterised in that one of the cam (40) and the driving member (42) is arranged in connection with the framework (12) and the other is arranged in connection with the shaft element (10).

8. A stand according to claim 6 or 7, characterised in that the cam contour is shaped such that it limits the rotational movement of the framework between two positions, one starting position and one stop position.

9. A stand according to claim 8, characterised in that the cam (40) is arranged in connection with and adjustable in relation to the shaft element (10), wherein said starting position is adjustable in relation to the shaft element.

10. A stand according to any of the claims 6-9, characterised in that the driving mechanism is formed such that the framework rotates stepwise around the shaft element.

1 1 . A stand according to any of the claims 6-10, characterised In that the driving mechanism comprises a driving unit (44, 46) arranged to generate a rotating movement driving the driving member (42), wherein the driving unit is arranged on the framework (12) and the cam (40) is arranged in connection with the shaft element (10).

12. A stand according to any of the claims 6-1 1 , characterised in that the cam (40) is radially arranged in relation to the shaft element (10).

13. A stand according to any of the claims 6-12, characterised in that the cam contour is shaped such that the driving member (42) is displaceable between a number of distinct positions along the contour, such that a stepwise movement of the driving member is obtained.

14. A stand according to any of the claims 6-13, characterised in that the cam contour is a Malteser contour.