Abstract:
A multiplicity of horizontal axis rotors are coaxially attached, at spaced intervals, to an elongate driveshaft. This driveshaft with attached rotors is aimed, not directly into the wind, but at a slightly offset angle, allowing each rotor to encounter a wind stream having fresh wind. That offset angle may be in the vertical plane, horizontal plane, or oblique. The shaft is held with rotational freedom at or near its midsection by a cantilevered bearing means, and drives a load, such as an electrical generator. This cantilevered bearing means, along with the rotor laden driveshaft which it supports, is allowed to pivot, as an entire unit, about the vertical axis of a supporting tower. The generator, brake, support frame, as well as a dedicated counterweight can also serve as a counterweight to help elevate the downwind section of the driveshaft, by pushing downward on the upwind section of the turbine.

Description:
[0001]     (This patent application is related to U.S. Pat. Nos. 6,616,402 and 6,692,230 issued to this inventor, and U.S. patent application Ser. No. 10/781213 by this inventor) 
     
    
     BACKGROUND  
       [0002]     This invention relates to wind turbines.  
       PRIOR ART  
       [0003]     In U.S. Pat. No. 6,616,402 I introduce a downwind-projecting, co-axial, multi-rotor, wind turbine that orients the driveshaft at an offset angle from the wind direction, allowing fresh wind to each rotor. The advantages include lighter total rotor weight for the swept area, and higher rpm for a given power rating. Shaft rotation at higher rpm delivers a given amount of power at less torque, and requires a smaller generator, and/or less gearing for the same power output.  
         [0004]     In U.S. Pat. No. 6,692,230 I introduce a balanced version of the co-axial, multi-rotor wind turbine, having an upwind section of the driveshaft that serves to some degree as a counterbalance to the downwind section of the driveshaft. This upwind section, like the downwind section, has rotors attached at spaced intervals, adding power to the system. In the second embodiment of this U.S. Pat. No. 6,692,230 illustrated in FIGS. 9 and 10 of that patent, a counterweight attached to the upwind section of the driveshaft serves to counterbalance against a much longer downwind section of the driveshaft. The extra length of the downwind section allows the attachment of additional rotors, providing even more power.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     The present invention uses the generator itself as a counterweight, to counterbalance the downwind section of the driveshaft and its attached rotors. This is accomplished by mounting the generator forward of a pivot point. Other heavy components, such as a disc brake, and a supporting frame, can also be advantageously placed as far forward, or upwind, as possible in relation to a pivot, to provide a ballast effect to push down on the upwind, or forward section of the driveshaft. Pushing down on the upwind section helps to lift the downwind section of the driveshaft, like a teeter-totter. Additional weight can be added. The weight of the generator, components such as a brake, and any additional weights mounted upwind of a pivot point, help to balance against the weight of an extended downwind section of the driveshaft. A longer downwind section of the driveshaft can support more rotors, producing more power.  
         [0006]     This counterweight effect may be accomplished in several ways: 
        The generator and other heavy components may be mounted toward the forward end of a teetering central frame that also supports the driveshaft.     The central support frame itself can be mounted largely forward of a pivot point     Alternatively, the generator may be mounted to, and supported by, the upwind section of the driveshaft itself. In this case the generator may be located near some midpoint of the front driveshaft, or may be located at or near the upwind, forward end of the front driveshaft.        
 
         [0010]     A spring or other lifting means, such as a lifting body may also be used to augment the forces that serve to elevate the downwind section of the driveshaft. A damping means such as a shock absorber may be applied to regulate the movement of the driveshaft.  
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0011]      FIG. 1  shows the first embodiment.  
         [0012]      FIG. 2  shows the second embodiment.  
         [0013]      FIG. 3  shows the third embodiment.  
         [0014]      FIG. 4  shows the fourth embodiment.  
         [0015]      FIG. 5  shows the fifth embodiment.  
         [0016]      FIG. 6  shows the sixth embodiment.  
         [0017]      FIG. 7  shows the seventh embodiment.  
         [0018]      FIG. 8  shows a close-up view of the seventh embodiment.  
         [0019]      FIG. 9  shows the eighth embodiment.  
         [0020]      FIG. 10  shows the ninth embodiment. 
     
    
     PART NUMBERS IN THE DRAWING FIGURES  
       [0021]      4  bearing support means (central support frame)  
         [0022]      5  cantilevered bearing means  
         [0023]      6  load  
         [0024]      10  elongate driveshaft  
         [0025]      11  bearing  
         [0026]      13  horizontal axis type rotor  
         [0027]      15  axle  
         [0028]      27  resilient spring means  
         [0029]      31  lifting body  
         [0030]      34  damping means (shock absorber)  
         [0031]      35  yaw bearing  
         [0032]      36  elevation angle control means  
         [0033]      37  lifting mechanism  
         [0034]      38  pivot means  
         [0035]      49  upwind section of the driveshaft  
         [0036]      50  downwind section of the driveshaft  
         [0037]      55  guy wire  
         [0038]      66  continuous power conduit means (electric cable)  
         [0039]      67  ballast counterweight means  
         [0040]      81  brake  
         [0041]      90  tower means  
         [0042]      122  tail  
         [0043]      170  truss structure  
         [0044]      172  boom  
         [0045]      174  secondary boom  
         [0046]      176  guy wire to lift downwind section  
         [0047]     α offset angle from wind direction, (becomes simply the elevation angle if the angular offset is solely from the horizontal)  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0048]     1. First Embodiment:  FIG. 1 : A co-axial, multi-rotor wind turbine, with the axis of rotation offset from the wind direction by angle α (alpha), in this case the offset angle α is in the vertical plane. A multiplicity of horizontal axis type rotors  13  are attached at spaced intervals to the upwind section  49 , and the downwind section  50  of the driveshaft  10 . The offset angle a combined with the spacing between rotors  13  allows fresh wind to each rotor, as explained in U.S. Pat. No. 6,692,230 issued to this inventor. The downwind section  50  of the driveshaft  10  is longer than the upwind section  49  and has more attached rotors  13 . The tail  122 , along with the higher number of rotors and extra length of the downwind section  50  help to keep the turbine headed into the wind, by presenting more total wind resistance than the upwind section, in relation to yaw bearing  35 , about which the entire turbine pivots directionally. A cantilevered bearing means  5  comprises bearings  11 , a rigid axle  15  which is part of driveshaft  10 , and a bearing support means that is in this case a central support frame  4 . Central support frame  4  has a counterweight  67  at the front. Load  6 , which is in this case a generator, is at the center. More rotors  13  are mounted to the downwind section  50  of the driveshaft  10  than to the upwind section  49 . The combined extra rotor weight on the downwind section of the driveshaft, and the extra weight of the additional length of the downwind section itself, as well as the extra leverage afforded by the extra length of this downwind section, are counterbalanced about pivot  38  by counterweight  67 , located forward, or upwind, of pivot  38 . Counterweight  67  exerts a downward force on the forward, or upwind part of the turbine, which translates to an upward force lifting the downwind section of the driveshaft. This upward force helps to elevate the downwind section  50 , allowing it to be longer, and to support more rotors  13 , which results in more power output from the turbine, as more rotors  13  capture more power. Also shown is a lifting mechanism  37  comprising a spring  27  that is disposed to help lift the downwind section  50  of the driveshaft  10 , and a damping means  34  that is illustrated as a simple shock absorber, that helps to regulate and slow the tilting movement fore and aft. The elevation angle control means  36  comprises in this case a rest  180  that determines the offset angle α of the driveshaft in the normal operating position. The geometry and forces are so chosen so that in excessively strong winds the turbine is allowed to be blown into a horizontal position, placing the driveshaft parallel to the wind, so that offset angle α is equal to zero and all rotors are directly in line with the wind, and with each other. This arrangement places all rotors except the first within the wake of upwind rotors, reducing total power output for protection from overspeed. This change in offset angle α may be abrupt, taking place at a certain wind speed, or may be progressive and gradual over a range of wind speeds. The effect is to flatten the upper end of the power curve.  
         [0049]     2. Second Embodiment:  FIG. 2 : Same as first embodiment except load  6 , a generator, is located forward of pivot  38 , about ⅓ of the way from the front, and a brake  81  is also located upwind of pivot  38 . Thus the weight of the generator itself, and the weight of the brake, also act as counterweights, pushing down on the forward (upwind) part of the turbine, so as to lift the downwind section  50  of the driveshaft and its attached rotors  13 . Note that since the generator is still located between the bearings  11 , the upwind section  49  of the driveshaft  10  may be supported in a projecting, cantilevered manner from the forward bearing and the generator, as the generator itself may be part of the cantilevered bearing means  5 .  
         [0050]     3. Third Embodiment:  FIG. 3 : The third embodiment is the same as the second embodiment, except that here the load  6  (generator) is located at the front of the central support frame. The generator  6  itself serves as the front bearing. So in this case the generator has 3 jobs: it is acting as a generator, as a counterweight, and as a bearing. More specifically, the at least one bearing of the generator serves as the upwind main bearing  11  of cantilevered bearing means  5  that support the driveshaft  10 . In this case the generator becomes a part of cantilevered bearing means  5 .  
         [0051]     4. Fourth Embodiment:  FIG. 4 : The fourth embodiment is the same as the first embodiment, except that in this fourth embodiment the generator  6  is actually supported by the upwind section of the driveshaft itself, being located just downwind of the second rotor. This gives the generator  6  more leverage about pivot  38  to better serve as a counterweight. A ballast counterweight  67  helps further in this regard, as before and in this case counterweight  67  is attached to the generator and also serves as a means for the stator of the generator to resist rotation. Power is channeled along the continuous power conduit means  66  (in this case an electric cable). As before, we may optionally include a spring  27  to help lift the rear of the support frame, and shock absorber  34  to damp movement.  
         [0052]     5. Fifth Embodiment:  FIG. 5 : This fifth embodiment is similar to the fourth embodiment except that in the fifth embodiment the load  6  (generator) and counterweight  67  are located at the far upwind end of the upwind section  49  of the driveshaft  10 , just behind the first (upwind) rotor. This far upwind placement enhances the counterweight behavior of the generator and counterweight by increasing the length of their lever arm in relation to the pivot  38 . The part of the driveshaft that goes through the generator can be of a smaller diameter, since it supports only a single rotor close to the generator.  
         [0053]     6. Sixth Embodiment:  FIG. 6 : The sixth embodiment is similar to the fifth embodiment except that here in the sixth embodiment, the load  6  (generator) is located at the far upwind end of the driveshaft, with all rotors  13  downwind of the generator  6 .  
         [0054]     7. Seventhth Embodiment:  FIGS. 7 and 8 : The seventh embodiment is similar to the third embodiment, with the generator  6  located at the upwind end of the support frame  4 , doing triple duty by serving as the generator and also as both the upwind bearing, and as a counterweight. In this embodiment, the support frame  4  itself is located mostly upwind of pivot  38 , so that this support frame  4  itself is also acting as a counterweight. This allows an even longer downwind section  50  of driveshaft  10 , with more rotors.  FIGS. 7 and 8  show that there is no dedicated tail  122 , as the extra length of downwind section  50  of driveshaft  10 , and the extra rotors  13  attached to the downwind section  50  provide enough wind resistance to keep the turbine directionally headed into the wind without the need for a dedicated tail. Brake  81  and counterweight  67  may optionally be included to also counterbalance against the extended downwind section  50  and its attached rotors. Resilient spring means  27  and damping means (shock absorber)  34  may alternatively be reconfigured to be properly located forward of pivot  34 , allowing support frame  4  to be located even further upwind, (not illustrated) for extra leverage. The resilient spring means  27  could in that case pull downward on the support frame  4  at a point upwind (forward) of the pivot  38 , which in effect pulls downward on the entire upwind section  49  of the driveshaft, to help raise the downwind section  50  of the driveshaft. This embodiment seeks to place as much of the apparatus as possible upwind of the pivot, so that as long a downwind section  50  of the driveshaft as possible can be counterbalanced thereby.  
         [0055]     8. Eighth Embodiment:  FIG. 9 : The eight embodiment is similar to the seventh embodiment, with the addition of one or more guy wires  176  to help stabilize the downwind section  50  of driveshaft  10 . In this case the guy wires  176  serve to lift this downwind section, in the manner of a crane or truss, so that it does not sag. The attachment point of the guy wires to the downwind section  50  of driveshaft  10  comprises at least one bearing  11  to allow free rotation of the driveshaft. The two guy wires shown will also have the effect of laterally stabilizing the structure. Many generally equivalent structures are possible, within the scope of this invention. In general the guy wires may serve to transmit the counterweight forces upwind of pivot  38  to the downwind section  50  of the driveshaft  10  to help lift it. Alternatively the guy wires may simply transfer the weight of the downwind section  50  and its attached rotors to the support frame  4 . The optional inclusion of at least one boom  172  attached to the support frame  4 , and optional inclusion of at least one secondary boom  174  may be utilized to form, along with the guy wires and the driveshaft itself, a sort of truss structure  170 , which can resist bending better than the driveshaft alone, and thereby allow for a longer downwind section  50  of the driveshaft  10 , which can reach higher into the sky, with more rotors, to capture more wind, and produce more power.  
         [0056]     9. Ninth Embodiment:  FIG. 10  This ninth embodiment is similar to the eighth embodiment, with the addition of at least one lifting body  31  attached to the downwind section  50  of driveshaft  10  the help elevate it. Such a lifting body may have aerodynamic lift, buoyant lift, or both. Buoyant lift may be obtained through the use of a buoyant gas, such as helium or hydrogen. The buoyant gas may be used to fill the lifting body. At least one bearing  11  attaching said driveshaft to said lifting body allows the driveshaft to rotate relative to the lifting body.  
         [0057]     10. Tenth Embodiment: If the driveshaft is hollow, a buoyant gas may be used to fill the driveshaft itself, making the driveshaft itself, or a part of the driveshaft itself, atmospherically buoyant.