Power transmitting system through cables for airborne wind-type power generation applications

The present invention deals with a new system for transmitting energy through a cable and interconnected pulleys. The traditional power transmission through pulleys sizes the system of belts and friction surfaces depending on energy to be transmitted and is obtained through systems composed of a rotary element for every point of application and of a flexible element for the connection. In the proposed system, the flexible element is a high-resistance cable and friction on the rotary element is increased by using interconnected pulleys, which increase the cable friction surface allowing power transmissions without any sliding till the cable breaking point. The lightness of such system allows it to find optimum application in transmitting to ground all wind energy produced at an upper level. The system of interconnected pulleys is further applied to discontinuous tractions in the sailing field, replacing the traditionally used winches.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage of International Patent Application No. PCT/IT2008/000699, titled “Power Transmitting System Through Cables for Airborne Wind-Type Power Generation and Sail Winch-Driving Applications,” filed Nov. 10, 2008, which claims priority from Italian Patent Application No. TO2007A000833 filed Nov. 21, 2007, the contents of which are incorporated in this disclosure by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention refers to a power transmitting system through cables, in particular for wind-type power generation and sail winch-driving applications.

2. Background Art

The generation of energy at an upper level, where strong and constant winds blow, has always encountered a difficulty linked to the weight of systems designed for such purpose.

One of the most complete studies about this subject has been made for the Skywindpower system, for which a prototype has been built, which can operate only with a great wind intensity: in fact, it can transform into energy only a reduced percentage of the wind that bumps into it, using the remaining part as support for its structure.

The main components of a wind-type generating system by rotation are rotor and generator, this latter one generally placed next to the rotor and connected to an electrical cable for transmitting generated energy to the ground. Regarding the generator, so far its placement has been thought at an upper level due to the difficulties of transferring generated energy to the ground. The generator weight therefore has remained the main obstacle to the development of wind generation at an upper level.

SUMMARY OF THE INVENTION

Object of the present invention is solving the above prior art problems by providing a power transmitting system that allows having the generator placed on the ground, thereby allowing to develop an efficient wind generator at an upper level.

The present invention is an innovation to typical traditional pulley-type transmissions, where size and mass of pulleys and belts depend on friction to be obtained, that must be greater than the force to be transmitted.

The above and other objects of and advantages of the invention, as will appear from the following description, are obtained with a power transmitting system like the one disclosed herein. Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionalities) can be made to what is described, without departing from the scope of the invention as appears from the enclosed claim.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As stated above, the present invention uses the typical traditional pulley-type transmissions, where size and mass of pulleys and belts depend on friction to be obtained, that must be greater than the forces to be transmitted. The big winches used on sailing boats, coupled with fiber cables with an optimum weight/resistance ratio, are a good example of a discontinuous energy transmission, where the necessary friction on the drum is obtained with many cable windings.

In order to increase the friction surfaces between pulleys and cable, without needing many windings on the same rotary element, and in order to give continuity to energy transmission through cables, it is necessary to modify the system of winches by creating special, mutually mechanically interconnected pulleys (FIG. 1), with a high-resistance cable with pre-established length that is closed as a loop (like in the application inFIG. 2).

The principle of power transmission is similar to the one of a bicycle chain, with a traction cable2(FIG. 2). The number of mutually mechanically interconnected pulleys1,3,5and the number of connected force points change depending on performances to be obtained.

Regarding the application of the power transmitting system P of the present invention to a wind-type power generating application with rotation, referring toFIG. 2, a rotor6is shown with reduced weight (in order to allow its use in aeolian applications at an upper level) due to the use of tie-rods7that allows emulating the performances of a turbine8with reduced weight.

The transmitting system P described in the aeolian application operates differently from the bicycle example, since, in case of a bicycle, the energy transmission occurs between two fixed points, while in case of the aeolian generating system at an upper level, there is a moving point at an upper level, and therefore there is the need of having, on such moving point, a traction force in an opposite direction and with a force greater than the force to be transmitted.

When there is wind, the aerodynamic shape of the aeolian generator (and its possible integration with power wing profiles or kites that increase lift or the use of auxiliary supporting means that are lighter than air) can guarantee the prevalence of the traction force on force to be transmitted.

The rotation of the blades8of the wind-type generator9moves the pulley assembly10which exerts a traction on cable2. On the ground, the generator assembly11contains a generator13with variable energy absorption, that is rotated by the traction of cable2by means of its own power transmitting system P with pulleys1,3,5, generating a balanced system in which the wind-type generator9will keep its position at an upper level stable.

A suitable sensor15for sensing the cable2tension allows adjusting the energy absorption by the generator13. The block of ground system rotation will produce a recovery of the wind-type generator9by self-traction on the traction cable2. With no wind, the recovery of the wind-type generator9will be possible by shortening the cable2obtained with a suitable motor (not shown). The recovery will occur according to the same principle of an helicopter placed in self-traction.

The proposed system P can be equipped with one or more mechanically interconnected rotors6.

Regarding the application of the power transmitting system P to sail winches (FIG. 4), winding on a rotary winch of ropes2on which a traction has to be exerted, and handling of the winch with suitably, manually-operated demultipliers, is a complex operation, which is also dangerous when a rope under traction has to be put in force, or when the same rope has to be quickly released.

The present invention avoids the need of intervening on the ropes2, since they can be used in all required functions without modifying their path in the pulleys1,3,5. In fact, by using the system P of the invention as a winch, the system P itself allows operating by traction of the cable2, by keeping the traction or, by simply transforming the traction pulleys1,3,5into more or less braked free-rotating wheels, in order to more or less quickly free the cable2itself.

The complete removal of every danger will be obtained with the use of a system for collecting the free rope2through coils16,18or another technology, that avoids the risk of dangers with things or people. The same technology is valid for automatic mechanical drive, nowadays made with more complex and costly drum-type winches.

In summary, the above described invention relates to a power transmitting system P comprising at least one first pulley1adapted to operatively cooperate with at least one second pulley3,5, and a cable2adapted to pass in succession around a circumference of the first pulleys1, then around a circumference of the second pulley3,5in order to perform a path adapted to provide an extended friction surface for the cable2.

Obviously, the second pulleys3,5could be more than one (in the Figures, two second pulleys3,5are for example shown) and the respective diameters of the first pulley1and the second pulleys3,5could be identical, or different.

For example, according to the embodiment shown in the Figures, the power transmitting system P comprises at least one first pulley1having a first diameter and adapted to operatively cooperate with at least two second pulleys3,5, each having a second diameter, the first diameter being greater than the second diameter, and a cable2adapted to pass in succession around a circumference of one (3) of the two second pulleys3,5, then around a circumference of the first pulley1, and then around a circumference of another one (5) of the two second pulleys3,5in order to perform a path adapted to provide an extended friction surface for the cable2.

Moreover, the first pulley1is equipped on its surface with a plurality of teeth1′ and has a smooth circumferential part1″ onto which the cable2is wound, the second pulleys3,5are equipped on their surface with a respective plurality of teeth3′,5′ and have a smooth circumferential part3″,5″onto which the cable2is wound, the first pulley1being adapted to operatively cooperate with the second pulleys3,5through their respective teeth1′,3′,5′.

In the arrangement shown inFIG. 2, a first power transmitting system P is operatively connected with a generator13placed on a ground and adapted to generate energy coming from an aeolian generator9placed at an upper level and operatively connected to a second power transmitting system P, the first and second power transmitting systems P being also mutually operatively connected through the same cable2.

In the sail winch-driving arrangement shown inFIG. 4, instead, the power transmitting system P can also be adapted to be operatively coupled to at least one first coil16,18by passing the cable2exiting one of the second pulleys3,5around the first coil16,18. And moreover, the power transmitting system P can be adapted to be operatively coupled also to at least one second coil16,18by passing the cable2exiting one of the second pulleys3,5around the first coil16,18and by passing the cable2exiting another one of the second pulleys3,5around the second coil16,18.

With such arrangement and the related increase of friction surfaces, the transmission of power is enabled for applications that alternate traction steps with release steps, such as for example in case of sailboat winches.

Returning toFIG. 2, the wind-type power generating arrangement preferably comprises:at least one aeolian generator9placed at an upper level equipped with rotating blades8and operatively connected to a power transmitting system P of the invention;at least one power-generating assembly11placed on the ground and comprising a generator13and a power transmitting system P of the invention; anda cable2adapted to operatively connect the aeolian generator9and the power-generating assembly11.

The above wind-type power generating arrangement can further comprise at least one sensor15for sensing a tension on the cable2and adapted to regulate an energy absorption by the generator13.

With such arrangement and the related increase of friction surfaces, the transmission of power is enabled between an aerodynamic system for picking-up wind energy placed at an upper level and a system for transforming energy placed on the ground.