Device for reversing a blade of a runner unit

Abstract

Embodiments of the present invention generally relate to a runner unit of a tidal power plant, and more particularly to a device for reversing a blade of the runner unit. The device according to the embodiments is lighter and more efficient with respect to known solutions which involve articulated mechanisms as it is based on a reversing servomotor including an annular piston which acts on the blade to be reversed.

Claims

1. A device for reversing a blade of a runner unit, the device comprising: an annular lever fixed to a trunnion portion of the blade and rotatably mounted on the runner unit; a main servomotor comprising a first piston cylinder adapted to reciprocate along a shaft of the runner unit and coupled to said annular lever so as to cause a first rotation of the blade until said first piston cylinder reaches a dead zone position, said annular lever comprising a pin eccentric with respect to an axis of rotation of said annular lever, said pin being hosted in a groove formed in said first piston cylinder; a reversing servomotor including a second piston cylinder arranged to cause a further rotation of the blade from said dead zone position; and a connecting rod having a first end connected to said second piston cylinder and a second end eccentrically fixed on said annular lever, wherein said second piston cylinder is annular-shaped and is arranged concentric with and surrounding said first piston cylinder, said first piston cylinder being received within second piston cylinder.

2. The device according to claim 1, wherein said reversing servomotor is adapted to reciprocate along the shaft of the runner unit.

3. The device according to claim 1, wherein said first end of said connecting rod has an eyelet arranged to cooperate with a pivot fixed on said second piston cylinder, wherein said eyelet is configured to establish a movement relative to said pivot during motion of said main servomotor.

4. The device according to claim 3, wherein said pivot is located on an internal wall of said second piston cylinder.

5. The device according to claim 1, wherein said reversing servomotor is oil-operated.

6. The device according to claim 1, further comprising a nut arranged around said pin and within said groove.

7. The device according to claim 1, wherein said main servomotor is oil-operated.

8. A system comprising: a runner unit having a shaft and at least one blade rotatably mounted on the shaft; and a device for reversing the blade, the device comprising: an annular lever fixed to a trunnion portion of the blade and rotatably mounted on the runner unit; a main servomotor comprising a first piston cylinder adapted to reciprocate along the shaft of the runner unit and coupled to said annular level to cause a first rotation of the blade until said first piston cylinder reaches a dead zone position, said annular lever comprising a pin eccentric with respect to an axis of rotation of said annular lever, said pin being hosted in a groove formed in said first piston cylinder; a reversing servomotor including a second piston cylinder arranged to cause a further rotation of the blade from said dead zone position; and a connecting rod having a first end connected to said second piston cylinder and a second end eccentrically fixed on said annular lever, wherein said second piston cylinder is annular-shaped and is arranged concentric with and surrounding said first piston cylinder, said first piston cylinder being received within second piston cylinder.

9. The system according to claim 8, wherein said reversing servomotor is adapted to reciprocate along the shaft of the runner unit.

10. The system according to claim 8, wherein said first end of said connecting rod has an eyelet arranged to cooperate with a pivot fixed on said second piston cylinder, wherein said eyelet is configured to establish a movement relative to said pivot during motion of said main servomotor.

11. The system according to claim 10, wherein said pivot is located on an internal wall of said second piston cylinder.

12. The system according to claim 8, wherein said reversing servomotor is oil-operated.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The objects, advantages and other features of the present invention will become more apparent upon reading of the following non-restrictive description of embodiments thereof, given for the purpose of exemplification only, with reference to the accompany drawing, through which similar reference numerals may be used to refer to similar elements, and in which:

(2) FIG. 1 shows a control mechanism for reversing a blade according to the prior art;

(3) FIGS. 2A, 2B, 2C, 2D, 2E, and 2F show a sequence of the various configurations of the control mechanism of FIG. 1 during operation;

(4) FIG. 3 shows a perspective view of a runner unit including a plurality of blades according to an embodiment of the present invention;

(5) FIG. 4 shows a side section view of a runner unit according to an embodiment of the present invention;

(6) FIGS. 5, 6, 7, 8, and 9 show a front section view of the runner in a sequence of steps to reverse the blade by means of a device according to an embodiment of the present invention.

(7) An exemplary embodiment will be now described with reference to the aforementioned drawings.

DETAILED DESCRIPTION

(8) With reference to FIG. 3, shown therein is a runner unit, generally indicated with numeral reference 30. The runner unit 30 is located within a tidal power plant which may be positioned between the sea and a lagoon basin (arrangement not shown). Runner unit 30 includes a hub body 33 to which a plurality of blades 2 are fitted. Each blade 2 comprises an airfoil mounted on the hub body 33 and it is moved by a flow of water which may occur in a direct mode, that is from the lagoon to the sea along verse indicated by arrow A, and in a reverse mode, that is from the sea to the lagoon along the direction indicated by arrow B. The flow of water generates a rotation of hub body 33 about an axis R that is transferred to a shaft (not visible) which is in turn connected to an electric generator (not shown) for the generating of electricity.

(9) The same working principle can also be applied with the runner operating in the so-called pump mode, where the runner is driven by its motor-generator to move a fluid for example from a lower reservoir to a higher reservoir.

(10) The following description is directed to a device for reversing a blade 2 around a rotational axis S arranged substantially perpendicular to the hub body 33. It will be appreciated that a device according to an embodiment of the invention will be provided for each blade 2 of the runner unit 30.

(11) Making now reference to following FIG. 4, it is shown a section view of runner unit 30 along a plane which contains both axis rotational axis R and S. The blade 2 is rotatably connected to hub body 33 by means of a trunnion portion 21 of the blade which is secured to an annular level 4, rotatable about the axis S on the runner unit 30. Annular lever 4 is coupled to a main servomotor 5 which comprises a piston 51 adapted to reciprocate along a shaft 31 of the runner unit 30. The coupling is arranged such that the position of the piston 51 along the shaft 31 determines the angular position of the blade with respect to rotational axis S, as it will be clear in the following detailed description of an embodiment.

(12) In an embodiment, the main servomotor is of an oil type, and the displacement of the piston 51 occurs by controlling, by a dedicated pressured fluid feeding system (not shown), the difference of pressure established within chambers 513 and 514. More specifically, when the thrust created by the pressure in chamber 513 exceeds the thrust created by pressure of chamber 514 the piston moves upwards, and vice versa.

(13) In this non-limiting exemplary embodiment, the annular lever 4 and the piston 51 are coupled by means of a pin 42, integral to the annular lever 4 and eccentric versus axis S, that is the axis of rotation of the lever. Pin 42 is hosted into a groove formed into the piston 51.

(14) The runner unit 30 internally includes a device, generally indicated with numeral reference 1, for the carrying out a partial rotation of the blade 2 beyond a dead zone. To this aim, device 1 according to an embodiment of the invention comprises a reversing servomotor 60, adapted to reciprocate along the shaft 31, which in turn includes a second piston 61 arranged to cause a further rotation of the blade 2 after main servomotor has positioned the latter in proximity of the dead zone, as it will be clearly explained with reference to the following figures.

(15) In an embodiment, the second piston 61, which is depicted in a section view, is annular shaped and is arranged concentric to the first piston 51 of main servomotor 5.

(16) Moreover, device 1 comprises a connecting rod 7 which has a first end 71 connected to the second piston 61 and a second end 72 which is in turn eccentrically fixed on the annular lever 4.

(17) With reference to the following sequence of FIGS. 5-9 the mode of operation of the device for reversing the blade will be described in details.

(18) FIG. 5 shows a front section of the runner unit 30 where the blade 2 is frontally visible. In this view, axis R is still visible whilst rotational axis S is perpendicular to the section plane shown.

(19) Connecting rod 7 is linked between the second piston 61 of the reversing servomotor and the annular lever 4. In the configuration shown in FIG. 5, after the runner 3 has been stopped for performing the blade inversion, the first piston 51 of the main servomotor is positioned downwards along its stroke relative to the shaft 31, whilst the servomotor 60 is in its upward position.

(20) Subsequently, as shown in FIG. 6, the first piston 51 is moved upwards such to rotate the blade 2 until the proximity of the dead zone is reached.

(21) The counter clockwise rotation of the blade 2 determines the correspondent rotation of the annular lever 4, which is in turn fixed to the second end 72 of the connecting rod 7, which is dragged into the rotational movement as well. Differently, as clearly visible in FIG. 6, the first end 71 of the connecting rod 7 has an eyelet 73 which is arranged to cooperate with a pivot 62 fixed on the second piston 61, more specifically located on an internal wall of the latter. The connection between rod 7 and the second piston 61 through the eyelet 73 establishes a movement of the rod 7 relative to the pivot 62 during the motion of the first piston 51.

(22) Consequently, during the upwards movement of the first piston 51 and the counter clockwise rotation of the blade 2 (and the annular lever 4) until the dead zone is reached, the second end 72 of the connecting rod 7 follows the rotation of the lever 4 and also determines a motion relative to the pivot 62 integral to the second piston 61, which then is not affected by said rotation.

(23) A suitable sizing of the eyelet, taking into account of the overall geometry of the runner (including for example the dimensions of the annular lever 4 and eccentricity of the connecting rod 7 on the latter) is necessary to ensure a correct synchronization of the main and reversing servomotors 5 and 6.

(24) With reference to FIG. 7, with the blade 2 being positioned into the dead zone, the second piston 61 starts a downward motion until pivot 62 abuts against a low end of the eyelet 73. In this fashion, piston 61 may be considered the master, whilst piston 51 the slave.

(25) The reversing servomotor, and particularly second piston 61, is also oil-operated and is associated to an oil feeding circuit (not shown in the figure) for enabling its reciprocating motion along shaft 31 of the runner unit 30. More particularly, two separated circuits are provided within the runner unit, that is one for the upward movement and a second for the downward movement.

(26) With reference to FIG. 8, the motion of piston 61 drives the connecting rod 7 downwards, and therefore the annular lever 4 is further rotated counter clockwise. The further rotation of the annular lever 4 thus determines the additional partial rotation of the blade 2 beyond the dead zone.

(27) At this point, as shown in FIG. 9, the main servomotor 5 is again activated and it is moved downwards to complete the inversion of the blade 2. After the complete rotation of the blade is carried out, the runner unit 30 may be again activated.

(28) While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.