| C L A I S 1. A method for moving fish in a fish sparing way from a first point, situated relatively higher, to a second point situated relatively lower, wherein water containing the fish is introduced near the higher situated point via an opening into a tray of a wheel, which wheel in the circumferential direction of the wheel possesses fixed trays having retention thresholds that are distributed over the wheel and meet mutually, the wheel is turned and because of the turning of the wheel the fish in the tray is carried towards the point that is situated lower in such a way that the retention threshold of the tray passes the water surface of a body of water and by further turning of the wheel the content of the tray is released via the opening below the water surface of the body of water into the body of water for releasing the fish from the tray. 2. A method according to claim 1, wherein water containing fish is collected at a collecting point, fish is carried from the collected water towards the point that is situated relatively higher, leaving water cleared of fish for a utility purpose, and the fish with water is introduced into the tray of the wheel and is subsequently carried towards the point that is situated lower. 3. A method according to claim 2, wherein the water cleared of fish for the utility purpose is cooling water. 4. A method according to claim 2 or 3, wherein for carrying the fish towards the higher point, a band screen is used which is provided with troughs that are tiltable for removing the fish from the trough. 5. The method according to any of the preceding claims, wherein the body of water into which the fish is released is the same body of water from which the water is collected and the distance between the collecting point and the location where the fish is released to the body of water is at least 25 m, preferably at least 50 m, more preferably at least 100 m, and even more preferably at least 150 m. 6. The method according to any of the preceding claims, wherein before the fish with water is added to the tray, water not containing fish is added to the tray. 7. The method according to any of the preceding claims, wherein a rotating speed of the wheel can be regulated. 8. Wheel for use in the method according to any of the claims 1 to 7, which wheel possesses fixed trays having retention thresholds that are distributed in the circumferential direction of the wheel and follow each other. 9. Wheel according to claim 8, wherein a median of the tray is at an angle β relative to a tangent at the circumference of the wheel of minimally 25°, preferably minimally 30°, more preferably minimally 35°, and maximally 75°, preferably maximally 50°, more preferably maximally 45 ° . 10. Wheel according to one of claims 8-9, wherein a length of the tray in the direction of the median is larger is than a maximum thickness of the tray, measured as a largest distance of opposite walls of the tray in a direction perpendicular to the median and in a direction of rotation of the wheel. |
The present invention relates to a method for moving fish in a fish sparing way from a first point that is situated relatively higher to a second point that is situated relatively lower.
It is known to give fish the opportunity to move from a point that is situated relatively high towards a point that is situated relatively low, for instance in order to let them pass an obstacle such as in a watercourse such as a canal. Herewith for instance use is made of an aid such as a fall tube.
A disadvantage of the known aids is that these may injure or even kill the fish. Especially juvenile fish are extra vulnerable in that respect. This may lead to a variety of undesired effects, varying from disturbance of the equilibrium in an ecosystem to the loss of fish for the purpose of sports or consumption.
The object of the present invention is to provide a method for moving fish wherein the likelihood of injuries to the fish is reduced .
To this end the invention provides a method for moving fish in a fish sparing way from a first point that is situated relatively higher to a second point that is situated relatively lower, wherein water containing the fish is introduced near the higher situated point via an opening into a tray of a wheel, which wheel in the circumferential direction of the wheel possesses fixed trays having retention thresholds that are distributed over the wheel and meet mutually, the wheel is turned and because of the turning of the wheel the fish in the tray is carried towards the point that is situated lower until the retention threshold of the tray passes the water surface of a body of water and by further turning of the wheel the content of the tray is released below the water surface of the body of water via the opening into the body of water for releasing the fish from the tray.
Thus fish may be moved in a fish sparing way from the point situated relatively high towards the point situated relatively low. In . comparison to for instance a fall tube turbulence is strongly limited, whereby any objects present in the water that otherwise could forcibly come into contact with the fish will now not injure the fish or at least less .
An important embodiment of the method is characterized in that water containing fish is collected at a collecting point, fish is carried from the collected water towards the point that is situated relatively higher, leaving water cleared of fish for a utility purpose, and the fish with water is introduced into the tray of the wheel and is subsequently carried towards the point that is situated lower.
Thus water cleared of fish may be obtained in a fish sparing way which water may for instance be used for the preparation of drinking water.
According to a preferred embodiment the water cleared of fish obtained in this way, is water that for the utility purpose is cool- ing water.
Hereby fish kill, as currently occurs at cooling using surface waters, for instance at power stations, may be strongly reduced.
According to a practical embodiment for carrying the fish towards the higher point a band screen is used which is provided with troughs that are tiltable for removing the fish from the trough.
These band screens are known in the art, for instance the so called "Travelling band screen" of the firm Passavant Geiger. Thus the fish can be carried in water towards the point that is situated relatively high.
For instance with the above applications (preparation of drinking water and cooling) , the fish will be carried back to the same body of water as from which it was taken. In such a case it is preferable that a sufficiently large distance is maintained between the location where the fish is returned and the inlet point, since other- wise fish, (notably small ones) will immediately be taken up again at the collecting point. Therefore it is preferable that the distance between the collecting point and the location where the fish is released to the body of water is at least 25 m, preferably at least 50 m, more preferably at least 100 m, . and even more preferably at least 150 m.
According to an advantageous embodiment, for very vulnerable fish, water not containing fish may be added to the tray before the fish with water is added to the tray. This avoids the fish from falling into an empty tray and thus sustaining injuries. This reduces the chance that the fish comes into contact with the wall of the tray in such a way that the fish sustains injuries.
According to an advantageous embodiment the rotating speed can be regulated.
Thus, the level of filling of the trays can be adjusted. This is of importance in order to prevent that, in case of a low water level of the body of water into which the fish is released, the fish is precociously released over the retention threshold and falls from an undesirably large height into the body of water. Variances in the height of the water level of the body of water may occur as a result of various causes such as seasonal variations, pumping, low tide and high tide, etc.
In addition, the invention relates to a wheel for use with the method according to the invention, which wheel possesses fixed trays having retention thresholds, which trays are distributed in the circumferential direction of the wheel and follow each other. Such a wheel may on a relatively higher point be suitably filled with water containing fish which by turning of the wheel is moved towards a relatively lower point where the water containing fish is released to a receiving body of water. The term "follow each other" means that trays are provided over the entire circumference of the wheel.. Between the trays, however, an interspace may be provided. Between the trays following each other along the circumference of the wheel, however, a connecting partition will be provided so that along the circumference of the wheel no gap is present between the trays following each other.
The invention also relates to a wheel wherein a median of the tray is at an angle β relative to a tangent at the circumference of the wheel of minimally 25°, preferably minimally 30°, more preferably minimally 35°, and maximally 75°, preferably maximally 50°, more preferably maximally 45° .
It has been shown that with such an orientation of the tray in the wheel a suitable filling of the tray with water containing fish may be obtained wherein the fish is introduced into the tray in a fish sparing way and at the same time a gradual release of the fish into the receiving body of water is achieved. The median runs through a point at the circumference halfway between two retention thresholds of two adjacent trays.
A preferred embodiment of the invention envisions that a length of the tray in the direction of the median is larger than a maximum thickness of the tray, measured as a largest distance of opposite walls of the tray in a direction perpendicular to the median and in a direction of rotation of the wheel.
Such a shape can provide a proper filling of the tray with a small degree of filling as well as a satisfactory capacity at a larger degree of filling. The term "in a direction perpendicular to the median and in a direction of rotation of the wheel" means, phrased differently, perpendicular to the median and in a plane perpendicular to the rotational axis of the wheel. The present invention will now be illustrated with reference to the drawing.
fig. 1 shows a schematic view of a use of the wheel according to the invention,
fig. 2 shows a schematic representation of the wheel at a flood water level of the receiving body of water,
fig. 3 shows a schematic representation of the wheel at a low water level of the receiving body of water,
fig. 4A, 4B, 4C and 4D show subsequent stages during the filling of a tray,
fig. 5A-5D shows four shapes of the tray near the filling point, and
fig. 6A-6D shows the four shapes of the tray near the receiving body of water. The embodiments shown in the figures are merely shown as an indication of a possible implementation of the invention. Identical and equivalent parts are indicated by identical reference numerals. Further, not all parts that are necessary in practice have been shown in the figures. Only the parts necessary for understanding the invention have been shown in the figures.
Fig. 1 schematically shows an implementation of the present invention. A wheel 1, at its circumference provided with trays 2, as shown in more detail in fig. 2 and fig. 3, is part of a system to re- turn fish that have been taken in from a body of water 3 and are moved towards an installation using water, back to that body of water 3. The system comprises an inlet channel 4 which at an inlet side opens in the body of water 3 and comprises a grate 5 in order to pre- vent that large fish and debris enter the channel 4. Small fish can pass the grate 5 unimpeded. The fish and debris taken in via the channel are removed from the water via a band screen 6 known in the art which is provided with troughs 7 and passed to a chute 8. From the chute 8 the fish and the water carried along with the fish by the band screen 6 are carried towards the wheel 1 via a chute pipe 9 where it is collected in the trays 2. The wheel 1 is rotating continuously with such a speed that the trays 2 are at least partially filled with water, as will be explained further hereinafter.
When the content of the trays 2 is in contact with the receiv- ing body of water 10, fish and debris present in the trays 2 will be released and be returned via the channel 11 to the body of water 3. Because of a continuous supply of water to the body 10 a flow in the channel 11 will be generated through which displacement of debris and fish from the channel 11 takes place in a simple way.
In fig. 1 a low water level 12 and a flood water level 13 are shown. The moment at which the content of a tray 2 comes into contact with the receiving body of water 10 is affected by the water level. Fig. 2 shows an application of the wheel 1 during use at a flood water level 13. In fig. 2 it is shown that the trays 2 contain a rela- tively large quantity of water whereby on rotating the wheel 1 the water level in the trays 2 for a position of the flood water level 13 is equal to the retention threshold 14. By choosing the degree of filling of the trays 2 such that the water level in the trays 2 reaches the retention threshold 14 at the moment that the retention threshold 14 reaches the water level of the receiving body of water 10 (the trays have a desired degree of filling) , the advantage is obtained that no marked inflow of water from the body of water 10 takes place, nor outflow out of the tray 2 causing fish to fall from a height in the receiving body of water 10.
Fig. 3 shows the situation for a low water level 12, wherein the trays 2 are filled with less water than is the case at a flood water level 13. Consequently, the water level in the trays 2 reaches the retention threshold 14 at a lower position of the tray 2 than was the case with the flood water level. However, in both cases of fig. 2 and fig. 3 the water level in the trays 2 reaches the retention threshold 14 when the retention threshold 14 reaches the level of the water in the receiving body 10: the trays have a desired degree of filling (i.e. adapted to the water level). This may be obtained in a simple way by varying the rotational speed of the wheel 1 (given an unchanged supply flow rate of water to the trays 2 from the tube 9) , and such that the degree of filling of the trays is such that the hereinbefore described desired degree of filling is obtained. Each water level has its own degree of filling of the tray 2. When the degree of filling of a tray 2 deviates from the desired degree of filling, the rotational speed of the wheel will be increased or decreased .
The figures 4A-4D show in various stages the position of the chute tube 9 near a tray 2 in order to fill this. The wheel 1 rotates in the direction of the arrow 15. The exit end 16 of the tube 9 is at first on the retention threshold 14 and lowers on rotation of the wheel 1 onto an inlet wall 17 of the tray 2. If so desired, this will be done while damping the fall of the end of the chute tube 9, for instance by using an air spring or by suitably chosen material properties of the chute tube 9. Water from the tube 9 flows into the tray 2. On further rotation of the wheel 1, as shown in fig. 4D, the tube 9 slides over the inlet wall 17 in the direction of the retention threshold 14' of the next tray (not shown in fig. 4A-4C) .
Filling of a tray 2 takes place before the tray 2 has reached the highest point, as can clearly be seen in the figures. Thus, the supply tube 9 can be situated substantially horizontal on the inlet wall 17 while filling tray 2, thus obtaining a steady inflow and filling of the tray 2.
Fig. 5 shows four different shapes of trays 2 at the location of the filling point. Shape 5A has proven to be very suitable for relatively large volumes of flow rates of water. Shape 5B is notably suitable for moving smaller flow rates because therewith a suitable water level is formed in the tray 2 at a low degree of filling, irre- spective of the spatial positioning of the tray 2 (that is to say the position taken by the tray 2 in the wheel 1 between the filling point and the point of release to the body of water 10) . Fig. 5C shows a shape of the tray 2 that can be manufactured economically. Because of the absence of rounded shapes this shape can be manufactured from straight, flat pieces of sheet metal or the like .
Fig. 5D shows a so-called hybrid shape of a tray 2. Herein the walls 18, 19 of a tray 2 shown in fig. 5D are divider walls of an adjacent tray. The walls 18, 19 are similar in shape. The wall 18 of a first tray hence at the same time forms a wall 19 of an adjacent tray. A wheel 1 having such trays 2 can be manufactured in a rela- tively simple and inexpensive way.
Fig. 6A-6D show the trays according to fig. 5A-5C in the position the trays take at the point of release, where the content of the trays 2 comes into contact with the receiving body of water 10.
After the retention threshold 14 has passed the level of the body of water 10, the shapes 6A, 6C and 6D will entirely fill up with water, whereas in the tray having the shape according to fig. 6B some air will remain. During the further displacement through the body of water 10 this may cause a turbulence which will let the fish actively leave the tray 2.
The same shapes as shown in fig. 5A-5D will be displaceable towards the position as shown in the fig. 6A-6D.
Any fish that are still present in the trays when the trays are moved out of the body of water, on moving of the wheel further, will be released from the trays 2 in a simple way because of the movements occurring then.
As shown in particular in fig. 1, the wheel 1 has the shape of a hoop. The wheel is especially preferably a spokeless hoop, that is to say a round going ring without interior elements. Thereby the wheel 1 can be powered at the interior of the hoop shape. Fig. 1 shows a drive 21. The drive 21 is preferably of such a type that no lubricated parts come into contact with the wheel, whereby pollution of the water current is prevented. Preferably, the drive is a hydraulic drive 21 (hydro engine) , wherein a hydraulic generator for driv- ing the hydro engines is placed in a housing outside the space of the wheel. The drive 21 has such a dimension that the wheel 1 is carried by the drive 21. For a stable guidance of the wheel 1 guiding wheels 22, 23 are provided. The number of guiding wheels may be larger than shown in the figures in order to obtain a greater stability. However, the drive 21 is dimensioned such that it can carry the weight of the entire wheel. The guiding wheels merely serve for stabilising the wheel 1.
Fig. 2 and 3 show nozzles 24 which clean the empty trays 2 and clear them of any residual dirt. These may suitably be high-pressure nozzles .
The dimensions of the wheel 1 and the trays 2 depend among others on the flow rate to be moved in the trays 2. Assuming that the rotating speed of the wheel is in the order of 0.1 to 2 revolutions per minute and the diameter is in an order of magnitude of 4 to 12 meter, the width of the trays 2 may amount to for instance 1 meter. The width is measured in the direction perpendicular to the plane of the drawing. According to a preferred embodiment the retention threshold 14 of a tray 2 (in the direction of width of the tray, relative to the axis of rotation of the wheel 1) is at an angle other than 0°, for instance an angle of 0.5° to 5°. In other words, de edge of the retention threshold is not parallel to the rotational axis of the wheel 1. Thereby, when moving the tray 2 out of the body of water 10 the retention threshold 14 will sooner pass the water level at one lateral side of the tray 2 than at the other lateral side of the tray. Thereby a steady (calm) discharge of water from the tray 2 is obtained. According to a variant the retention threshold may have a V-shape or the shape of a rounded arch.
The invention is not limited to the embodiments shown in the figures and hereinbefore described. For instance the trays 2 may have a shape other than shown in the figures. Any combination of shapes of walls shown in the figures is possible, but also shapes differing there from are applicable within the present invention. A person skilled in the art can easily conceive and develop other shapes.
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