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Dahlberg, Jan-Ake; ngen 119, Hä, gersten, SE); |
Cup anemometer
The present invention relates to a cup anemometer having at least two cups (1) each attached to an arm (2) of a hub (3) on a rotary shaft. By cup is meant a generally seen cup-shaped body with a concave inner surface (6) and a convex outer surface (7) which meet at the opening of the cup. The opening of the cup is directed essentially along the tangent to the rotational path of the cups. The invention is based on the fact that the cups are truncated at their opening by means of three cuts (14, 15, 16) which are esentially located in three planes that are parallel with the tangent of the rotational path of the cups at the opening and that, projected on a fourth plane (9) having the tangent as normal, essentially form a triangle. The cups are attached to their arms (2) at one of the three corners (10).
1. A cup anemometer with at least two cups (1) each attached to an arm (2) of a hub (3) on a rotary shaft, cup relating to a generally seen cup-shaped body having a concave inner surface (6) and a convex outer surface (7) which meet at the opening of the cup, the opening of the cups being directed essentially along the tangent to the rotational path of the cups, characterised in that the cups are truncated at their opening by means of three cuts (14, 15, 16) which are essentially located in three planes that are parallel with the tangent of the rotational path of the cups at the opening and that, projected on a fourth plane (9) having the tangent as normal, essentially form a triangle, and that each cup is attached to its arm (2) at one of the three corners (10).
2. A cup anemometer as claimed in claim 1, characterised in that the three corners (10, 11, 12) of the cups (1) are cut-off or rounded.
3. A cup anemometer as claimed in claim 1, characterised in that the rotary shaft extends in a narrow neck (4) which supports the hub (3) with arms (2) and cups (1), and that the hub has an extension (18) on its side facing away from the neck, and that the hub, as well as the extension in an area adjacent to the hub, has a cross-section which essentially conforms with the cross-section of the neck in an area adjacent to the hub, so that substantially current symmetry is obtained in the area of hub, arms and cups.
4. A cup anemometer as claimed in claim 1, characterised in that the cups (1), before being truncated, are rotationally symmetrical.
5. A cup anemometer as claimed in claim 4, characterised in that the highest point (8) of the arcuate recess in the cup wall, measured perpendicular from the plane (9) that touches the three corners of the cup, is essentially ⅓ of the maximum distance from said plane to the highest point (13) of the cup.
6. A cup anemometer as claimed in claim 4, characterised in that the cups (1), before being truncated, are cones.
7. A cup anemometer as claimed in claim 6, characterised in that the cones have an apex angle to their symmetry axis that is essentially 45°.
8. A cup anemometer as claimed in claim 1, characterised in that the triangle seen in said fourth plane (9) is essentially equilateral.
9. A cup anemometer as claimed in claim 7, characterised in that the circumferential surface of the cones is formed by seven curves A-G being allowed to define a plane surface, of which a sector S is excluded and the remaining surface is rolled into a cone, the curves being described in local coordinate systems (x,y) with the origin on the radius R and the angle φ plotted from the positive X-axis in a global coordinate system (X,Y), and the local coordinate systems having the y-axis directed, radially outwards and the x-axis directed in the negative φ direction and, in the local coordinate system, the curves for the corners having the formula ##EQU3##
and the curves for the sides having the formula ##EQU4##
and the constants a and b for each curve appearing from the TABLE Curve Angle φ° a b A -37.3 0.2581 19.0 B 5.1 0.3583 -0.3226 C 47.6 0.2581 19.0 D 90.0 0.3583 -0.3226 E 132.4 0.2581 19.0 F 174.9 0.3583 -0.3226 G -142.7 0.2581 19.0
and the location of the curves in the global coordinate system (X,Y) being obtained by the coordinate transformation
and the sector S being calculated as the difference between angle φ of curve A and angle φ of curve G, i.e. S=φA-φG=-37.3-(-142.7)=105.4°.
10. A cup anemometer as claimed in claim 7, characterised in that the circumferential surface of the cones is formed by seven curves A-G being allowed to define a plane surface, of which a sector S is excluded and the remaining surface is rolled into a cone, the curves being described in local coordinate systems (x,y) with the origin on the radius R and the angle φ plotted from the positive X-axis in a global coordinate system (X,Y), and the local coordinate systems having the y-xis directed radially outwards and the x-axis directed in the negative φ direction and, in the local coordinate systems, the curves for the corners having the formula ##EQU5##
and the curves for the sides having the formula ##EQU6##
and the constants a and b for each curve appearing from the TABLE Curve Angle φ a b A -37.3 0.2581 19.0 B 5.1 0.3583 -0.3226 C 47.6 0.2581 19.0 D′ 90.0 0.1928 -0.2731 E 132.4 0.2581 19.0 F′ 174.9 0.1735 -0.2667 G -142.7 0.2581 19.0
and the location of the curves in the global coordinate system (X,Y) being obtained by the coordinate transformation
and the sector S being calculated as the difference between angle φ of curve A and angle φ of curve G, i.e. S=φA-φG=37.3-(-142.7)=105.4°.
11. A cup anemometer as claimed in claim 8, characterised in that the radius, defined as the shortest distance between the rotary shaft and the symmetry axis of the cups (1), is about 95% of the diameter of the circle that encompasses the opening of the cup, ie touches the three outer-most corners (10, 11, 12).
12. A cup anemometer as claimed in claim 4, characterised in that the openings of the cups point slightly upwards to the extension (18) of the hub, the symmetry axes of the cups forming an angle of 1-2° to the plane of rotation of the anemometer.
13. A cup anemometer as claimed in claim 1, characterised in that a sheet (17) is placed in the concave interior of each cup and is positioned essentially in the plane of rotation or is parallel therewith.
14. A cup anemometer as claimed in claim 13, characterised in that the cups (1), before being truncated, are rotationally symmetrical and the sheet extends from the point (13) where the symmetry axis hits the bottom of a cup (1), along the symmetry axis to about 50% of the distance to the plane (9) that has the symmetry axis as normal and that just touches the corner (10, 11, 12) remotest from the point just mentioned.
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