Abstract:
A system for harnessing wind energy to charge the electric storage battery of an all-electric motor vehicle, whether the vehicle is parked or in motion. While the vehicle is being driven, a roof-mounted, internal wind turbine harnesses wind energy and causes rotation of the shaft of an electric generator mounted to an interior surface of the roof. For charging the battery while the vehicle is parked, an external wind turbine is storable in the vehicle when not in use and attaches to the internal wind turbine. Cups of the kind used in cup anemometers are attached to radial arms that extend from an external shaft of the external wind turbine and catch ambient wind currents while the vehicle is parked, causing the external shaft and the generator shaft to rotate.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY APPROVED RESEARCH OR DEVELOPMENT 
     None. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to devices for charging an electric battery of a motorized vehicle, and more particularly to devices for harnessing wind energy to charge an electric battery of an electric car. 
     2. Background Art 
     As used here, the term “all-electric vehicle” refers to any motor vehicle that is powered exclusively by an electric drive train. Hybrid motor vehicles with a drive train powered by an internal combustion engine in combination with one or more electric motors are now common on our streets and highways, but public acceptance of all-electric vehicles has been relatively slow. The slow acceptance of all-electric vehicles is largely due to the limited driving range such vehicles are currently capable of on a single charge of their electric storage batteries. In addition, currently, there are relatively few places accessible to the public for recharging the batteries of an all-electric vehicle compared to the number of gasoline and diesel refueling stations; and, in any case, the time required to recharge the batteries is significantly longer than the time required to fill the fuel tank of a vehicle that runs on gasoline or diesel fuel. Driving an all-electric vehicle beyond its rated driving range and to a location that lacks suitable battery charging facilities would likely mean incurring the time and expense for tow truck assistance before the driver could be underway again. To avoid that fate, and to promote public acceptance of all-electric cars, it would be desirable to harness wind energy to help maintain some of the charge in the electric storage battery of an all-electric vehicle while the vehicle is being driven, as well as to charge the battery by harnessing wind energy while the vehicle is parked. 
     U.S. Pat. No. 7,886,669 B2 disclosed a method for harnessing wind energy to charge a system battery that powered electronic components of a stationary locomotive after engine shut down or while the locomotive was coasting under gravity with its engine shut down, such components comprising lights and on-board monitoring and display systems of the locomotive. An electric device, such as a motor that could be run in generator mode, was coupled to an airflow device that was rotatable by ambient air flow, and a controller was provided to enable the airflow device and generator only when some minimum rotational speed of the airflow device was detected. For instance, the airflow device was fan blades that, in a first mode of operation, could be driven by the electric device to provide cooling and, in a second mode of operation, harness ambient wind energy to drive the electric device to generate electricity, which electricity was conducted to the electric power load and/or to the electric storage battery of the locomotive. 
     U.S. Pat. No. 7,828,091 B2 disclosed an all electric vehicle that used an internal wind turbine generator mounted in the nose of the vehicle, compressed air and a high voltage battery to generate electricity to power the DC motors that drove the vehicle. When available wind energy was inadequate, compressed air stored in one or more air tanks drove an air motor coupled to an electric generator to generate electricity to recharge the electric battery and/or to power the DC motors. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system for charging an electric storage battery of an all-electric motor vehicle. The system includes a first, internal wind turbine that mounts to the roof of the vehicle after a vertically-directed, through-hole has been created in a central portion of the roof. The term “internal” as applied to the first wind turbine is here intended to signify a wind turbine that, when mounted to the roof of an all-electric motor vehicle and ready for use, is substantially enclosed within a housing, described below, and covered by a lid. The internal wind turbine is intended to provide electric current charge to the vehicle&#39;s electric storage battery while the vehicle is in motion. The invention further includes a second, external wind turbine that also mounts to the roof exterior of an all-electric vehicle, but is intended to provide electric current charge to the vehicle&#39;s electric storage battery while the vehicle is parked. The term “external” here signifies that the second, external wind turbine, when mounted to an all-electric vehicle, is external not only to the vehicle itself, but also to the housing. 
     The internal wind turbine has a housing that includes a bottom panel that extends longitudinally from a front end to an opposite, rear end thereof, and extends laterally from a first side to an opposite, second side thereof. The bottom panel is dimensioned and contoured to overlie the vehicle roof that includes the through-hole. The bottom panel has a centrally-disposed, flat, upper surface and an opposite, lower surface. A vertically-directed, shaft opening extends from the flat upper surface of the bottom panel through the panel to its lower surface. The housing further includes an air inlet opening that overlies the front end of the bottom panel, an air outlet opening that overlies the rear end of the bottom panel, and an air flow corridor attached to the bottom panel that extends between, and joins, the air inlet and outlet openings. The air flow corridor comprises an entryway portion in communication with the air inlet opening, a discharge portion in communication with the air outlet opening, and a central portion that communicates with the entryway and discharge portions. The entryway portion is contoured to conduct air entering the inlet opening while the vehicle is in forward motion toward the second side of the bottom panel, the central portion is contoured to conduct air rotationally around the shaft opening, and the discharge portion is contoured to conduct air within the central portion to the air outlet opening. 
     The internal wind turbine further includes a turbine blade assembly disposed within the central portion of the air flow corridor. The turbine blade assembly includes a hub that extends axially along a turbine shaft axis from a first, lower end to a second, upper end thereof and is rotatable about said axis. A plurality of turbine blades are distributed about the periphery of the hub and extend radially away from the hub normal to the turbine shaft axis. Each turbine blade has a weighted, blade tip. 
     The internal wind turbine also includes electric generator means, comprising an electric generator; means for attaching the electric generator to an inside surface of the roof of the vehicle; and means for coupling the shaft of the electric generator to the hub of the turbine blade assembly. The first wind turbine further includes a lid that extends longitudinally from a front end to an opposite rear end thereof. The front end of the lid is pivotally attached to a front portion of the housing such that the lid is pivotable between a lowered, housing-covering position and a raised, open position. In its lowered position, the lid, in combination with the corridor, bottom panel and seal means, forms a closed compartment surrounding the turbine blade assembly, except for the air inlet and air outlet openings. The internal wind turbine further includes locking means attachable to a rear end of the lid and to a rear portion of the vehicle for alternately securing the lid in a lowered, closed position and releasing the lid to a raised position. The turbine blade assembly may be removed from the housing to replace damaged blades, clean the housing. To facilitate removal of the turbine blade assembly from the housing, the means for coupling the shaft of the electric generator to the hub of the turbine blade assembly preferably includes an adaptor with radially-directed splines that attaches to the shaft of the electric generator shaft by set screws, and a hub shaft that extends axially though the hub and has a lower, recess that is shaped and dimensioned to receive the adaptor splines in mating engagement. A removable pin inserts through aligned apertures in the hub and hub shaft to couple them for co-rotation. Accordingly, when so coupled by the adaptor and said pin, the generator shaft and the turbine blade assembly rotate as one about the turbine shaft axis. The blades are preferably attached to the hub by threaded fasteners, which facilitates replacement of damaged blades once the blade assembly has been lifted off the splined adaptor and removed from the vehicle. 
     The invention further includes an external wind turbine. The external wind turbine is intended for converting wind energy into electrical current to charge the battery of the vehicle while the vehicle is parked. To accommodate installation of the second wind turbine, the lid has an opening where the turbine shaft axis (A-A) passes through the lid when the lid is in a lowered position. Means to seal the housing against moisture and air leaks is optionally provided, which means includes a disk-shaped, hub grommet disposed above and covering an upper portion of the hub, which grommet has an upstanding neck that extends up through the opening in the lid; a washer mounted on the neck adjacent to an upper surface of said lid; and a cap seal that mounts on the neck over the washer. The external wind turbine includes an external shaft that extends from an upper end to an opposite, lower end along an external shaft axis, which shaft is rotatable about that axis. The external shaft is “external” in the sense that, when installed in operating mode on the parked vehicle, said shaft extends upward and externally from the housing and with only a lower end portion of the shaft extending into the housing. The external wind turbine further includes a plurality of radially-directed arms circumferentially spaced apart around the external shaft, wherein each arm has an inner end attached to the shaft and an opposite, outer end. For “catching” the movements of ambient wind, a cup is attached to an outer end of each arm. Each cup has a concave inner surface and a convex outer surface that meet at the opening of the cup. The opening of each cup is directed essentially along the tangent to the rotational path of the cups about the external shaft axis, and all cups are oriented in the same rotational sense about the external shaft axis. The number of arms and cups is optional, but three of each spaced at 120° intervals about the shaft rotary axis is the preferred number. Thus, the external wind turbine resembles a cup anemometer in appearance and mechanical function. 
     The invention further includes means to couple the lower end of the external shaft to the hub for co-rotation therewith while maintaining the external shaft in coaxial alignment with the turbine shaft axis. In a first embodiment, the means to couple the external shaft to the hub is accomplished as follows. An upper end portion of the hub shaft has a cylindrical, upper recess that extends downward along the turbine shaft axis from the upper end of the hub shaft to a bottom end of the recess. The upper recess is dimensioned to receive in surrounding engagement a lower end portion of the external shaft, thereby defining an upper recess wall. The upper recess wall has a pair of grooved pathways disposed at diametrically opposite locations on the recess wall. Each pathway comprises, sequentially, a first leg that extends from the upper end of the hub shaft toward the bottom end of the recess, a second leg that extends through a circumferential arc normal to the turbine shaft axis, and a third leg that extends reversely part way back toward the upper end of the hub shaft  70 , thereby forming a blind end of the pathway. A pair of oppositely-disposed, oppositely-directed ears are attached to, and extend away from the lower end portion of the external shaft, which ears are shaped and dimensioned to be received in sliding engagement within the grooved pathways. A disk-shaped buffer plate is disposed within the upper recess intermediate the bottom end and the grooved pathways thereof. The buffer plate is dimensioned for sliding engagement with an inner surface of the upper recess wall and along the turbine shaft axis, and a spring disposed intermediate the bottom wall of the upper recess and the buffer plate urges the buffer plate away from the bottom end of the recess and toward the grooved pathways. 
     To install the external wind turbine on a parked, all-electric, vehicle, the internal wind turbine remains in place mounted on the roof exterior and with the lid lowered and locked. A lower end of the external shaft is inserted down through the opening of the lid and aligned coaxial with the turbine shaft axis and with its ears aligned with the first legs of the grooves. The external shaft is pressed downward against the buffer plate as the ears slide down through the first legs of the grooves, thereby compressing the spring. The external shaft is then partially rotated about the turbine shaft axis to move the ears through the second legs of the grooves, and then partially retracted so that the ears slide up the third legs and lodge within the blind ends of the grooves. To dismount the external turbine from the vehicle, that process is reversed, and the external turbine can then be stored within the vehicle, available for future use. 
     In a second, alternative embodiment of the invention, the coupling of the external shaft to the hub is accomplished as follows. An upper end portion of the hub shaft has an upper recess that extends downward along the turbine shaft axis from the upper end of the hub shaft to a bottom end of the recess. The upper recess is shaped and dimensioned to receive in surrounding engagement a lower end portion of the external shaft, thereby defining an upper recess wall. One or more ball-and-spring assemblies are attached to an inner surface of the recess within an alcove thereof. Each ball-and-spring assembly comprises a spring having a first end attached to the upper recess wall and a second, opposite end to which is attached a ball, such that the ball is movable between an extended, recess-occluding position and a retracted, non-occluding position within an alcove. The lower end portion of the external shaft has at least one beveled indent that is shaped and dimensioned to receive in sliding engagement a ball, thereby causing, as the external shaft is moved into the upper recess, the following sequence of events: sliding engagement with the balls, progressive compression of the springs, retraction of the balls into its alcoves, and then capture of the balls within the beveled indent of the external shaft. Accordingly, downward movement of a lower end of the external shaft along the turbine shaft axis will seat the external shaft for co-rotation with the hub, whereas a forceful yank upwards on the external shaft will de-couple them and permit removal of the external wind turbine from the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front, perspective view of a 2-door, all-electric motor vehicle equipped with the present invention and configured for charging the electric storage battery of the vehicle while the vehicle is in motion; 
         FIG. 2  a top, perspective view thereof, with the lid removed; 
         FIG. 3  is a front, perspective view thereof showing the hinged lid angularly raised and showing the blades of the turbine blade assembly in phantom outline; 
         FIG. 4  is a rear, elevational view thereof with the lid in closed position; 
         FIG. 5  is a front, perspective view thereof with the external wind turbine of the invention mounted to the vehicle for charging the electric storage battery of the vehicle while the vehicle is parked; 
         FIG. 6  is an enlarged, exploded, perspective, side view of the internal wind turbine of the invention showing the vehicle to which it attaches depicted in fragmentary, phantom outline; 
         FIG. 7  is an exploded, perspective, side view of a turbine hub assembly and of an upper end portion of an electric generator shaft to which is attached a splined adaptor that is insertable into a mating, splined recess of a hub shaft portion of the hub assembly; 
         FIG. 8  is an enlarged, side elevational view of the hub assembly, showing a hub shaft that extends along the axis A-A of the hub and protrudes above the hub and turbine blades fitted into radially-directed collars that are spaced apart around the periphery of the hub and attached by hex-head bolts; 
         FIG. 9  is a vertical cross-section view taken along line  9 - 9  of  FIG. 8 ; 
         FIG. 10  is a perspective, side view of a single turbine blade, showing its insertion through a collar, a fragmentary view of a lower portion of the hub, and a pair of weights attached to an upstream, concave side of a blade at the tip end thereof; 
         FIG. 11  is an enlarged, perspective, side view of a hub shaft according to a first embodiment of the invention, wherein an upper end portion of the hub shaft has a cylindrical, upper recess dimensioned to receive a lower end portion of the external shaft of an external wind turbine, said shaft has a pair of oppositely-disposed, radially-directed ears that are insertable into an oppositely-disposed pair of grooves in the wall of the upper recess when the external turbine shaft is moved axially downward into the upper recess as indicated by arrow  240 A, rotated about the turbine shaft axis A-A as indicated by arrow  240 B, and axially retracted as indicated by arrow  240 C; 
         FIG. 12  is an enlarged, vertical, cross-sectional view of the lower end portion of the external turbine shaft of  FIG. 11  shown inserted through an opening in the lid and into the upper recess of the hub shaft and with an ear lodged within a blind end of a grooved pathway; 
         FIG. 13  is an enlarged, perspective, side view of a hub shaft according to a second embodiment of the invention, wherein an upper end portion the hub shaft has a cylindrical, upper recess for receiving a lower end portion of the external shaft of an external wind turbine, which shaft has oppositely-disposed, radially-directed, beveled recesses, an upper end portion of the hub shaft has an upper recess dimensioned to receive the lower end portion of the external shaft, and a pair of oppositely-disposed ball-and-spring assemblies attached to the inner wall of the upper recess; and 
         FIG. 14  is an enlarged, cross-section on a vertical plane that includes the ball-and-spring assemblies of  FIG. 13 , showing the balls thereof inserted into the beveled recesses of the external shaft, thereby coupling the external turbine shaft to the hub shaft for co-rotation therewith. 
         FIG. 15  is an enlarged, top plan view of the external wind turbine (the vehicle roof is omitted in this view). 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIGS. 1-4 , the internal wind turbine  10  of the present invention is shown mounted to the roof  14  of an all-electric, motor vehicle  12 . The motor vehicle depicted is a 2-door sedan, but the invention can be installed on the roof of other types of all-electric, motor vehicles, such as all-electric 4-door sedans, roadsters, vans, pickup trucks, etc. Although not depicted in the drawings, it will be understood that the vehicle  12  is equipped with one or more electric storage batteries that provide electric power to one or more drive motors that are in driving engagement with the wheels  18  of the vehicle when the vehicle is being driven. Prior to installation of the internal wind turbine  10  on the roof  14  of the vehicle  12 , a vertical through-hole  16  is drilled through the roof  14  as may be seen in  FIG. 6 . The internal wind turbine  10  has a housing  20 , comprising a bottom panel  22  that extends longitudinally from a front end  22 F to an opposite, rear end  22 R thereof, and extends laterally from a first side  26  to an opposite, second side  28  thereof. For the sake of appearance and to minimize wind resistance and noise when the vehicle is being driven, the bottom panel  22  is preferably dimensioned and contoured to closely overlie an exterior surface of at least the portion of the vehicle roof that includes the through-hole  16 . This means, for instance, that any gap between the bottom panel  22  and the exterior surface of the roof  14  preferably should be kept to less than 5 mm. Centrally disposed on the bottom panel  22  is an area of flat, upper surface  30 . A vertically-directed, shaft opening  32  in that flat upper surface  30  extends through the bottom panel  22  to an opposite, lower surface thereof. An air inlet opening  34  overlies the front end  22 F of the bottom panel  22  and permits air to enter the internal wind turbine  10  while the vehicle  12  is in forward motion. An air outlet opening  36  overlies the rear end  22 R of the bottom panel  22  and permits air to exit the internal wind turbine  10  when the vehicle  12  is in forward motion. An air flow corridor  38  attached to the bottom panel extends between, and joins, the air inlet  34  and outlet  36  openings. The air flow  38  corridor comprises an entryway portion  38 E in communication with said air inlet opening, a discharge portion  38 D in communication with said air outlet opening  36 , and a central portion  38 C that communicates with said entryway  38 E and discharge  38 D portions. The entryway portion  38 E is contoured to conduct air entering the inlet opening  34  toward the second side  28  of the bottom panel  22 . The central portion  38 C is contoured to conduct air from the entryway portion  38 C rotationally around the shaft opening  32  and is defined by first and second, upstanding, semicylindrical, interior walls that are laterally and symmetrically spaced apart on opposite sides of the turbine shaft axis A-A. Although the term “semicylindrical” generally refers to a bisected half of a cylinder, in the present context it will be understood that the term “semicylindrical” is being used loosely to include an arcuate sector that can be somewhat less than a full, 180° semicircular arc—for example, an arc anywhere in the range 120° to 180°. The discharge portion  38 D is contoured to conduct air from the central portion  38 C to the air outlet opening  36 . Accordingly, with the vehicle  12  in forward motion, as air rushes through the air flow corridor  38  a rotational moment is imparted to the air about the turbine shaft axis A-A in a counterclockwise direction as the corridor  38  is depicted in  FIG. 2 . The air flow corridor  38  further includes a tongue  38 T that extends laterally from the first pivot mount  82  part way across, and above, said front end  22 F of the bottom panel  22 , and, as such, helps define the air inlet opening  34 . While the vehicle  12  is in forward motion, the tongue  38 T deflects the oncoming flow of air away from the first side  26  and toward the second side  28  of the bottom panel  22 , the better to impart a rotational moment to the air about the turbine shaft axis A-A. 
     Referring now to  FIGS. 6-12 , the internal wind turbine  10  further includes a turbine blade assembly, denoted generally by the numeral  40 , disposed within the central portion  38 C of the air flow corridor  38 . The turbine blade assembly  40  includes a hub  42  that extends axially along the turbine shaft axis A-A from a first, lower end  42 L to a second, upper end  42 U thereof and is rotatable about said axis. A plurality of turbine blades  44  is distributed about the periphery of the hub and extend radially away from the hub  42  normal to the turbine shaft axis A-A. For each blade  44 , the hub  42  has a collar  41  within an opening in the hub, which collar may be welded or press fit therein. A first end of each blade  44  is attached by threaded fasteners  45  (e.g., hex-head bolts) to a collar  41  and has an opposite, tip end  46 . Preferably, each blade tip  46  is weighted as, for example, by two beads of metal  47  welded to an upstream, concave side of the blade tip; see  FIG. 10 . A damaged blade  44  may be removed for replacement by loosening its threaded fasteners  45  and pulling the blade out of its collar  41 . 
     Referring now to  FIG. 6 , it is seen that the internal wind turbine  10  further comprises electric generator means, which means include an electric generator  48 , means  50  for attaching the electric generator to an inside surface of the roof  14  of the vehicle  12 , and means  52  for coupling the shaft  54  of the electric generator to the hub  42 . The means  50  for attaching the electric generator  48  to the inside surface of the roof  14  can be any of various means known to persons of ordinary skill in the art of installation of motor vehicle electrical components, such as the pair of brackets  56  and the threaded fasteners  58  depicted in  FIG. 6 . To minimize reduction of headroom space inside the passenger compartment of the vehicle  12 , the electric generator  48  should be compact and have a narrow side profile. 
     The internal wind turbine  10  further includes a lid  80  that extends longitudinally from a front end  80 F to an opposite rear end  80 R thereof and is shaped and dimensioned to be able to cover the entirety of the housing  20 . The housing  20  has a pair of laterally spaced-apart, upstanding, apertured, pivot mounts  81  attached to the bottom panel  22 , at or near a front end  22 F of said panel. A front end  80 F of the lid  80  has a laterally-directed, pin-receiving aperture  85  and is pivotally attached to the pivot mounts  82  by a pair of pivot pins  83  that insert into said apertures, such that the lid is pivotable between a lowered, housing-covering position ( FIG. 1 ) and a raised, open position ( FIG. 3 ). To facilitate repair and maintenance of the internal wind turbine  10 , the pivot pins  83  can be withdrawn from the pivot mounts  82 , which permits removing the lid  80  entirely from the housing  20 . The lid  80  has an opening  82  aligned with the turbine shaft axis A-A when the lid is in the lowered position. In the lowered position, the lid  80 , in combination with the corridor  38 , bottom panel  22  and seal means  90 , forms a closed compartment surrounding said turbine blade assembly  40 , except for the air inlet  34  and air outlet  36  openings. Referring to  FIG. 6 , the seal means  90  for sealing the housing  20  against moisture and air leaks includes hub grommet  92  comprising a ring washer joined to an upstanding, hollow, cylindrical, neck or tube that extends up through the opening  82  in the lid  80 . The neck portion of the hub grommet  92  extends above the upper surface of the lid  80  by, for example, 3 to 10 mm, and a removable cap  96  having a downward-directed hollow, cylindrical neck or tube mounts on that upper, extended neck portion of the hub grommet  92  in surrounding engagement. Preferably, the seal means  90  further includes an annular washer  97  that also mounts on the neck portion of the hub grommet  92  intermediate the upper surface of the lid  80  and the cap  96 . The seal means  90  will ordinarily remain in place attached to the lid  80  while the lid is being pivoted up and down between its lowered and raised positions; but, when the vehicle  12  is parked with the lid in lowered position, and it is desired to use wind energy to charge the electric storage battery, the cap  96  is removed and the external shaft  202  of an external wind turbine  200  is inserted through the lid opening  82  and hub grommet  92 . Accordingly, the lid opening  82  and the hub grommet  92  are dimensioned to receive the external shaft  202 . The hub grommet  92 , cap  96  and annular washer  97  preferably comprise butyl rubber. 
     The internal wind turbine  10  also has lid locking means, denoted generally by the numeral  100 , comprising a laterally spaced apart pair of upper half clasps  102  that attach by hinges to the rear end  80 R of the lid  80  and a mating, laterally spaced apart pair of half clasps  104  that attach to a rear portion of the vehicle  12  by threaded fasteners  106 —for example, to a rear portion  14 R of the roof  14  thereof. As will be apparent to persons of ordinary skill, any of a variety of kinds of mating pairs of half clasps can be used for this purpose—for example, the mating pairs of half clasps on steamer trunks as well the mating pairs of half clasps on mechanics&#39; tool boxes. 
     The internal wind turbine  10  has means  52  for coupling the shaft  54  of the electric generator  48  to the hub  42  so that they will rotate as one about the turbine shaft axis A-A. The means  52  includes an adaptor  60  that is attachable to the generator shaft  54  by, for example, set screws  62  that screw into threaded apertures in the adaptor;  FIG. 7 . The adaptor  60  includes a plurality of radially-directed, splines or vanes  60 S circumferentially spaced apart about the adaptor and has a throughbore  60 B having a diameter dimensioned to receive in surrounding engagement the generator shaft  54 . Although the adaptor  60  depicted in  FIG. 7  has four splines  60 S, the number of splines may vary from one to 12. The hub  42  has an axial throughbore  42 B that extends from the lower end  42 L to the upper end  42 U thereof. A hub shaft  70  having an external diameter somewhat less than the internal diameter of the throughbore  42 B is slidably insertable into and out of the throughbore. Optionally, when fully inserted into the throughbore  42 B of the hub  42 , the hub shaft  70  may have an upper end portion  74  that protrudes above the upper end  42 U of the hub  42 , as depicted in  FIG. 6 , but such protrusion must not be so far as to interfere with lowering the lid  80  to a fully closed and locked position. 
     A lower end portion of the hub shaft  70  includes a lower recess  72  (phantom outline in  FIG. 7 ) that is shaped and dimensioned to receive in mating engagement the splines  60 S of the adaptor  60 . When the splines  60 S of the adaptor  60  are inserted within the lower recess  72  of the hub shaft  70 , the generator shaft  54  is coupled for co-rotation with the hub shaft  70 . A pin  76  is insertable through a horizontal aperture  78  in the hub shaft  70  as well as through a co-aligned aperture  73  in hub  42  near the upper end  42 U of the hub  42 . So long as the pin  76  is so inserted through both the hub  42  and the hub shaft  70 , the generator shaft  54 , adaptor  60 , hub shaft  70  and hub  42  are mechanically coupled and will rotate as one about the turbine shaft axis A-A. Moreover, in the event the vehicle  12  is jostled traversing uneven ground, the pin  76  prevents relative vertical movement between the hub  42  and the hub shaft  70 . By raising or removing the lid  80  and withdrawing the pin  76  from the hub  42  and hub shaft  70 , the hub  42  and attached blades  44  can be lifted up and away from the adaptor  60  and hub shaft  70 , which permits replacing a damaged blade  44  and/or cleaning the housing  20  of accumulated dirt and debris. To minimize the friction of rotation of the turbine blade assembly  40  and to support the axial load thereof, a concentric pair of ball bearing races  33  containing a plurality of ball bearings (not shown) are interposed between the lower end  42 L of the hub  42  and the upper surface  30  of the bottom plate  22 , centered on the turbine shaft axis A-A, with the ball bearing races attached to said upper surface and the lower end of the hub  42  resting on the ball bearings;  FIG. 6 . 
     For converting ambient wind energy into electrical current to charge the electric storage battery of an all-electric vehicle  12  while the vehicle is parked, the invention further includes an external wind turbine  200 . The external wind turbine  200  may be stored in the trunk  13  or other secure location within the vehicle  12  until it is needed. As may be seen in  FIGS. 5 and 15 , the external wind turbine  200  includes an external shaft  202  that extends from an upper end  202 U to an opposite, lower end  202 L along an external shaft axis, and is rotatable about that axis. The external wind turbine  200  further includes a plurality of radially-directed arms  204  circumferentially spaced apart around the upper end  202 U of the external shaft  202 . Each arm  204  has an inner end  2041  attached to the external shaft  202  and an opposite, outer end  2043 . For catching ambient wind currents, a cup  206  is attached to an outer end  2043  of each arm  204 . Each cup  206  has a concave inner surface  208  (dashed lines in  FIG. 15 ) and a convex outer surface  210  that meet at the opening  212  of the cup. The opening  212  of each cup  206  is directed essentially along the tangent to the rotational path (arrows,  232 ) of the cups about the external shaft axis, and all the cups are oriented in the same rotational sense about the external shaft axis, as illustrated, for example, in  FIG. 15 . The number of arms and cups is optional, but three of each spaced at 120° intervals about the external shaft axis is the preferred number. Thus, the external wind turbine  200  resembles a cup anemometer in appearance and mechanical function. Cups  204  are used in the external wind turbine instead of turbine blades as a better way to harness the energy in ambient, variable, low velocity winds while the vehicle  12  is parked. 
     The external wind turbine  200  includes means to couple a lower end portion  202 L of the external shaft  202  to the hub  42  while maintaining the external shaft in coaxial alignment with the turbine shaft axis A-A. To that end, an upper end portion  70 U of the hub shaft  70  has a cylindrical recess  230  that extends downward along the turbine shaft axis A-A from the upper end of the hub shaft to a bottom end  230 B of the recess, thereby defining a recess wall  230 W. The recess  230  is shaped and dimensioned to receive in close-fitting, surrounding engagement a cylindrical, lower end portion  202 L of the external shaft  202  when said shaft is inserted through the opening  82  of the lid  80 . In a first embodiment of the invention, the recess wall  230 W has a pair of grooved pathways  270  disposed at diametrically opposite locations on the recess wall. As depicted in  FIG. 11 , each pathway  270  comprises, sequentially, a first leg  270 A that extends from the upper end of the hub shaft  70  toward the bottom end  230 B of the recess  230 , a second leg  270 B that extends through a circumferential arc normal to the turbine shaft axis A-A, and a third leg  270 C that extends reversely part way back toward the upper end of the hub shaft  70 , thereby forming a blind end of the pathway. Attached to the lower end portion  202 L of the external shaft  202  are a pair of oppositely-disposed, oppositely-directed ears  220 . The ears  220  are shaped and dimensioned to be received in sliding engagement within the grooved pathways  270  when the lower end portion  202 L of the external shaft is inserted into the recess  230 . Preferably, the first embodiment means to couple a lower end portion  202 L of the external shaft  202  to the hub  42  further includes a disk-shaped, buffer plate  260  disposed near the bottom end  230 B of the recess  230 . The diameter of the buffer plate  260  is slightly less than the internal diameter of the recess  230  so that the buffer plate can slide axially up and down along the recess wall  230 W. Disposed intermediate the buffer plate  260  and the recess bottom  230 B is a spring  262  (e.g., a coil spring) that urges the buffer plate axially upwards towards the pathways  270 . 
     To couple the external shaft  202  to the hub shaft  70  according to the first embodiment of the invention, the lower end portion  202 L of the external shaft is passed through the opening  202  of lowered lid  80 , and the ears  220  are aligned with the first legs  270 A of the pathways  270 . The shaft  202  is then pressed down against the buffer plate  260  as the ears slide down along the first legs  270 A (arrow  240 A), thereby compressing the spring  262 . The external shaft  202  is then rotated about the turbine shaft axis A-A to slide the ears  220  through the circumferential legs  2706  (arrow  240 B). Lastly, the external shaft  202  is retracted axially to permit the ears  220  to slide along legs  270 C (arrow  240 C) and lodge in the blind ends of the pathways  270 . The spring  262  helps to keep the ears  220  firmly within the blind ends of the pathways  270 . For this to work properly, the distance H between the ears  220  and the lower end of the external shaft  202  needs to be about equal to the distance between the buffer plate  260  and the blind ends of the pathways  270  when the external shaft is coupled to the hub shaft—i.e., when the spring  262  is at least partially decompressed. To uncouple the external shaft  202  from the hub shaft  70 , that process is simply reversed. 
     In a second, alternative embodiment of the invention, the hub shaft  70  likewise has an axially-directed, cylindrical recess  230  that extends from the upper end of the hub shaft to a bottom end  230 B of the recess, and the recess is dimensioned to receive in surrounding engagement a lower end portion  202 L of the external shaft  202 . As depicted in  FIGS. 13 and 14 , an oppositely-disposed pair of ball-and-spring assemblies, denoted generally by the numeral  250 , is attached to the recess wall  230 W. Each such assembly  250  comprises a spring  254  having a first end attached to an alcove  256  in the recess wall  230 W and an opposite end attached to a ball  252 . For each assembly  250 , when its spring  254  is uncompressed, its ball  252  extends at least part way out of the alcove  256  and partially occludes the recess  230 . A lower end portion  202 L of the external shaft  202  has a pair of oppositely-disposed, notched, indents  258 . Each indent  258  comprises an upper, inwardly beveled edge surface that is joined to a lower, outwardly beveled edge surface. The distance H′ between the bottom  202 B of the external shaft  202  and the indents  258  corresponds to the distance H′ between the recess bottom  23 B and the ball-and-spring assemblies  250 . Accordingly, to couple the external shaft  202  to the hub shaft  70 , with the vehicle  12  parked and the lid  80  in lowered position, the cap  96  is removed and the lower end portion  202 L of the external shaft is passed through the lid opening  82  and into the hub shaft recess  230 . Initially, downward movement of the external shaft  202  forces the balls  252  into the alcoves  256  and the springs  254  are compressed; but, upon arrival of the indents  258  at the alcoves  256 , the balls, under the urging of the springs  254 , move into the indents. Thus, to operate properly, the alcoves  256  need to be large enough to accommodate both the balls  252  and the springs  254 . To uncouple the external shaft  202  from the hub shaft  70 , the external shaft is grasped and yanked upward, thereby sliding the lower beveled surfaces of the indents  258  past the balls  252 , forcing the balls back into the alcoves until the external shaft has been fully raised above them, after which the balls once again extend from the alcoves out into the recess. Although only a single pair of indents  258  and a single pair of ball-and-spring assemblies  250  have been illustrated and described, additional pairs of each for coupling the external shaft  202  to the hub shaft  70  are within the scope and intent of the present invention. 
     Thus, it should be evident that a system for harnessing wind energy to charge an electric storage battery of an all-electric motor vehicle according to the concepts of the present invention has been shown and described in sufficient detail to enable one of ordinary skill in the art to practice the invention. Although not illustrated and described above, it will be understood that practicing the invention requires routing electrical cables from electrical output terminals of the generator  48  through the vehicle  12  to its electrical storage battery. Since various modifications in detail, materials, arrangements of parts, and equivalents thereof, are within the spirit of the invention herein disclosed and described, the scope of the invention should be limited solely by the scope of the appended patent claims.