Patent Publication Number: US-6712653-B2

Title: Self-tensioning pedal drive mechanism for a human powered boat

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not applicable 
     BACKGROUND OF THE INVENTION 
     In inventing a propeller drive for a human powered boat, the initial impulse would be to use a rope or belt. Indeed, this approach has been picked up on in the development of human powered boat drive systems at least as far back as Victorian times as represented in 1869 with Ross (U.S. Pat. No. 98,302), 1889 with Frenzel (U.S. Pat. No. 397,282), as well as by others including Storms, (U.S. Pat. No. 621,465), Mosteller (U.S. Pat. No. 1,072,027), Szafka (U.S. Pat. No. 1,411,540), Avellino (U.S. Pat. No. 3,182,628), Shiraki (U.S. Pat. No. 5,194,024), Parant (U.S. Pat. No. 5,362,264), Avvocato (France 1,375,350), _Lackner (Germany 2,226,178) . The fact that even though a toothed belt may be used as in White (5,547,406 et el), Lekhtman (U.S. Pat. No. 6,231,408), Marinc (U.S. Pat. No. 5,580,288), et el, doesn&#39;t ease the condition of energy loss due to deforming soft material as it engages into and twists around a pulley. This type of system absorbs too much of the cyclist&#39;s energy to actuate it. Furthermore, in higher torque situations, ropes or belts will tend to slip. Toothed belts can be built large enough by those trained in the art to prevent slippage with medium-high torque propellers, but by the time this problem has been solved, he material deformation energy loss as the drive is actuated will have been way too high. This fact can be further proven in that although belts and toothed belts have been around for a long time, their use has still not caught on in bicycles. 
     In 1984, a pedal powered watercraft called the Flying Fish was the first known hydrofoil to achieve successful flight under human power (IHPVA, 1984). It had broken most national and international speed records from the 100 meter sprint to the 2000 meter (SCIENTIFIC AMERICAN, 1986). The strut and drive system consisted of a drive shaft in the plane of the pedal crank connected to a propeller shaft by a #25 or ¼ pitch chain twisted into a “mobius”, and engaged to a driven propeller shaft sprocket below and whose plane of rotation was twisted a quarter turn away. Examples are also to be found in Hoffman 1982 (U.S. Pat. No. 4,349,340), Eide 1991 (U.S. Pat. No. 5,011,441), Parant 1994 (U.S. Pat. No. 5,362,264), et el. 
     Due to the fact that the Flying Fish chain was operated near its breaking point, it spun easily, but could only be used in racing. Also the Flying Fish type setup used secondary shafting which means two or more chains. Other prior art which also includes the use of secondary shafts is exemplified in Marangoni (U.S. Pat. No. 1,701,381), Maranic (U.S. Pat. No. 5,580,288), White (U.S. Pat. No. 5,547,406, et el), Kasper (U.S. Pat. No. 5,651,706), Grundner (Swiss 23,067), (Germany 10,338) et el. Although this characteristic allows for easy pulley diameter/gear ratio change adaptation, it is heavier, more complex because of more moving parts, requires extra power to operate the extra shaft, chain/belt and bearings, and is extremely difficult to maintain the tension of both or more belts or chains. 
     Although Eide (U.S. Pat. No. 5,011,441), et el simplify the drive over those using secondary shafting to the use of just two shafts, reliability problems were present due to derailing and/or chain breakage. Although the drive unit of Eide et el would provide chain operation with low power loss in a twisted environment, it would often prematurely break due to the chain not being heavy duty enough as well as operating in a continually loosening or loosening and sometimes tightening situation. For those and other reasons, chains, and ultimately sprockets would wear out faster. 
     Attempts to solve the problem of chain tensioning included drive units with adjustable fixed idler systems that could be unbolted, relocated, then retightened. These attempts started in the human powered boat racing efforts of this inventor pre-1992; Bill Murphy, Paul Niedermann, Warren Beauchaump, Bob Buerger pre-1998, et el, and an example is to be found in Gauthier (U.S. Pat. No. 5,672,080) 
     In a non constantly tensioned system, if a single bolted idler or jack shaft were to get repositioned, or if the drive system was to experience a chain which lengthens, the system will jam, skip or undergo teething problems. Chains lengthen or ‘stretch ’ due to initial breaking in, temperature changes, wear, etc. A constant vigil must therefore be kept on anything other than self-tensioning drive in order for the system to work properly. 
     SUMMARY OF THE INVENTION INCLUDING OBJECTS OF THE INVENTION 
     Newer type bicycle chains (#43; ½ k pitch) are currently available on the market that lend themselves to being operated while twisted. There are now available full size bicycle chain types that can be twisted 90 degrees over a distance of some 18 inches or less. This development allows full size chain to be used in struts almost as narrow as they would need to be for the thinner lighter duty chain. Bicycle chain has 2 to 2.5 times larger tensile strength than #25 
     It is absolutely essential that the drive unit be able to provide the MOST TORQUE POSSIBLE with the LEAST OPERATIONAL DRAG POSSIBLE. 
     If propellers were analyzed for drag where they do the most lifting, (average=0.8×[propeller tip diameter]) it would be found that the faster the rotational velocity, the more drag there is. The extreme would be where there&#39;s infinite velocity, no advance, and therefore infinite surface drag. This is due to the increased surface friction of the higher revving propellers, and is arrived at by the equation:        Fd   =       Cd        (     1   2     )          ρ                   V   2        S                     
     where Fd=drag; Cd=drag coefficient [constant]; [½ ρ cancels out near the water surface] ρ is density (½ ρ cancels out near the water surface in English units); and note here: V=velocity and its squared!; S=surface area. 
     On blade angles, the formula that applies is          V        (   final   )       =       V        (   boat   )         sin        (   β   )                         
     where V(final)=blade velocity, V(boat)=boat velocity; B=blade angle at a particular diameter. Suffice it to say that the lesser angle B is, the faster the blade element has to go in order to get the same advance. 
     The full proof is very long, but the general idea is that when the velocity increases, drag force increases to the square! 
     Therefore, slower turning propellers with higher pitch to diameter ratios have less drag, but the bad news is that they have increased torque. The extreme is where there&#39;s zero velocity, infinite advance, and, of course, infinite torque. 
     My invention is the first hydrodynamically low drag daggerboard type drive that is intended for use with regular size bicycle chain. It can withstand two and a half times as much torque as those units that employ #45 ¼ inch pitch chain. 
     Concerning dependability, a user of a pedal powered drive unit will want to spend as little time as possible fixing, tinkering and adjusting the unit and the most time pedaling out on the water. My invention promotes this in that it is the first pedal powered drive that has a self-tensioner; in other words, as the length of the chain varies, the tensioner ADAPTS to it! The tensioner keeps the chain under tension regardless of its length. Chains will stretch due to eventual wear, but more likely because of factors like frictional heat, even temperature change. My invention solves the reliability problem by constantly tensioning the chain in a way somewhat similar to a regular rear-wheeled-tensioned multi speed bicycle, except in three dimensions instead of substantially two. 
     In order to prevent the chain from derailing (as well as have the lowest drag as possible), idlers must each be parallel to the pivot plane of the chain, perpendicular to path of the chain pin/roller axis. Therefore, in a twisted chain drive, they must be tilted the same degree as the twist. The leeward idlers in this invention are all matched up to the twist in three dimensions, and each idler and sprocket is surrounded by guide plates to further prevent derailing. 
     Therefore, It is the object of this invention to provide a rugged durable lightweight compact human powered boat drive system that lends itself to installation as a kick-up daggerboard, that lends itself to a multihull installation, an economical installation, a high performance installation, an integrated human powered hydrofoil strut installation, a high torque (large propeller pitch) installation, or any combination of the above. 
     It is another object of this invention to provide a self-tensioning drive system wherein it requires less adjustment, maintenance, 
     It is another object of this invention to provide a drive system that can be framed in as a one-piece jacket that supports the pedal crank bracket and hardware in an accessible fashion above the waterline, and houses the propeller shaft mount, chainpath, internally in a smooth faired streamlined case below the water. 
     It is further an object of this invention to provide a drive system that is entirely maintenance free, and wherein the entire drive system lends itself to being totally waterproof wherein the interior workings may be non-corrosion-resistant, and therefore of lesser expense. 
     It is another object of this invention to provide a drive with a narrower strut, and therefore faster speeds. 
     Other objects of this invention will become obvious upon further examination. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Moving now to the drawings, 
     FIG. 1 shows a forward view of the mechanism including a cut away view of the shaft and idler sprockets. 
     FIG. 2 shows a three-quarter aft view of the port side 
     FIG. 3 shows details of the driven shaft assembly 
     FIG. 4 shows the top three-quarter view of the whole drive unit 
     FIG. 5 shows the detail of the tensioner arm as assembled 
     FIG. 6 shows an exploded view of the tensioner arm 
     FIG. 7 shows the detail of the drive sprocket size-adjustment-sleeve 
     FIGS. 8 and 9 shows the two extreme positions of the adjustment 
     FIG. 10 shows the anti-derailment guide plates on the tensioner arm and upper stationary idlers 
     FIG. 11 shows the guide plates around the driven sprocket and idler 
     FIG. 12 shows a perspective view of a reversal/opposite twisting figure-8 mobius orientation of the chain roller centers as they progress through the three dimensional chain path 
     FIG. 13 shows a a perspective view of uniform twist where both axis of chain roller centers are the same as each other as they progress through the three dimensional chain path 
     FIG. 14 shows a top view of the orientation of lower and upper idlers as well as those idlers in the tensioner arm oriented with respect to the drive and driven sprockets 
     FIG. 15 shows an alternative embodiment of the tensioner arm assembly 
     FIG. 16 shows an alternative embodiment of the drive unit with the chain path entirely external, and coordinated with a long shaft 
     FIG. 17 shows an alternative embodiment wherein the chain and tensioning components are contained entirely within in a waterproof casing. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     The following preferred embodiment and alternative embodiments are put fourth to give an idea of the invention, but by no means do they represent the only form this invention would take. 
     A pedal-powered drive mechanism supported by frame and jacket  1  in [FIG.  1 ] has streamlined sections  2  in [FIG.  3  and  4 ] for the strut region below the waterline  3 . The drive sprocket  4  in [FIG.  2 ] is driven by pedals  5  which pulls tensioned chain  6  through a narrow tube/passageway  7  encased within said strut region  3  from driven sprocket  8 . The leeward non tensioned chain  9  is fed from said drive sprocket  4  through upper positioning idler  10  out again to upper tensioning arm idler  11 . Said leeward chain  9  proceeds through assembly of idler arm  12  in an outward protruding plane to lower tension arm idler  13 , then back to lower positioning idler  14 . Said chain  9  progressing through idlers  10 ,  11 ,  13 ,  14  is kept from derailing by washers and retaining plate means (not shown). 
     Said leeward non tensioned chain  9  then continues down through said narrow tube/passageway  7 . The driven sprocket positioning idler  15  in [FIGS.  1  and  3 ] receives said leeward chain  9  in a close proximity to said tension chain  6  and feeds it to the circumferential perimeter of driven sprocket  8 . The propeller shaft  16  supports the propeller  17 . Access to said propeller shaft  16 , propeller shaft keeper bearings  18  in [FIG.  3 ], and driven sprocket  8 , both sprocket  8  and idler  15  preventing derailment by washer and guide plate means  42  and  43  are covered by waterproof access cover  19 . Said propeller shaft  16  is kept waterproof by shaft—seal  20  in [FIG.  4 ]. 
     The said tensioner arm  12  in [FIGS.  2  and  4 ] is supported from said frame  1  by a boss  21  in [FIG.  5 ] supporting around tensioner arm pivot pin  22  in (FIGS.  5  and  6 ] so that said tensioner arm  12  can swivel up and down. Adjustments to said leeward chain  9  can be made by rotating chain adjustment cylinder  23  in [FIGS.  5  and  6 ] so the lower idler mounting bolt hole  24  in [FIG.  6 ] can be repositioned enough to compensate for at least  2  chain link lengths. Said position of chain adjustment cylinder  23  is held tightly by the chain adjusting cylinder mount clamp  25 . Said tensioner arm  12  is pulled towards said frame  1  by a spring means  26  bolted to said frame  1  by fastener  27  and hooked to said tensioner arm  12  through guide holes  28 . Chain skipping or “teething” caused by propeller reversal, stops, etc., can be compensated for by squeezing a hand brake (not shown) which actuates push cable  29 , pulling in said tensioner arm  12  by means of cable with swaging  31  secured to said arm  12 , thereby increasing tension. Said cable and swaging  31  is secured to said tensioner arm  12  by fastener means  32 . Push cable is secured to said frame  1  by means of fastener  33 . 
     In order to accommodate drive sprockets of different sizes, and thus change the gear ratio, the position of the pedal axis is changeable while not affecting the tangential relationship of said tensioned chain  6  with said drive sprocket  4  and said driven sprocket  8  proceeding through said narrow tube/passageway  7 . A cylindrical sleeve  35  in [FIG.  7 ] has outside diameter to match inside diameter of clamping ring  36  which integrates into said upper frame  1 , and has a single axial wall split  37 . Said cylindrical sleeve  35  has substantially eccentric (non concentric) inner and outer diameters while their center lines are parallel. The inner diameter of said sleeve  35  is the same as and accommodates the outer diameter of the pedal bracket shell  38  which supports a standard pedal bracket cartridge (not shown). 
     Adjustment for a small sprocket  4 a in [FIG.  8 ] has said cylinder  35  rotated such that said pedal bracket shell  38  is close to the centerline of said tensioned chain  6 , while for large sprocket  4   b  in [FIG.  9 ], said cylindrical sleeve  35  is rotated such that said bracket shell  38  is further away from said tensioned chain  6  centerline. Said leeward non tensioned chain  9  in [FIG.  10 ] is kept from derailing between said drive sprocket  4  and said tensioner arm  12 , as well as between said arm  12  and driven sprocket  8  in [FIG.  11 ] , by plate means  39  mounted over said upper and lower positioning idlers  10  and  14  to said frame  1 . Derailment of said chain  9  progressing through upper and lower tensioning arm idlers  11  and  13  on said tensioner arm  12 , is prevented by inner and outer plate means  40  and  41 . Derailment from said driven sprocket  8  and said driven sprocket positioning idler  15  in [FIGS.  3  and  11 ] is performed by washer means  42  and guide plate means  43 . 
     PREFERRED OPERATION 
     As tension in tensioned chain  6  is caused by applying torque to the drive sprocket  4 , the chain wraps around said drive sprocket  4  until it is fed to the leeward non tensioned region  9  in [FIG.  1  and  10 ]. Said leeward chain  9  is first fed through upper idler  10  and out to upper tension idler  11  in the same plane defined vertically by centerline  59  in [FIGS.  12  and  13 ] and said drive sprocket  4 . Although this first leeward section of chain  59  continues to said upper tension arm sprocket  11  in the same plane as said centerline  59 , and said drive sprocket  4 , it twists between said idlers  10  and  11 . After said chain  9  is fed through said upper tension arm idler  11 , it is fed into another plane defined by the chain centerline  59  at the upper bound, and chain centerline  60  at the lower bound. Said centerline  59  is between idlers  10  and  11 , and centerline  60  is between idlers  13  and  14 . Chain in said centerline portions  59  and  60  is twisted; Chain in portion  61  between idlers  11  and  13  is not. 
     Said idler  10  runs in the same plane as said drive sprocket  4 . The plane of said idler  14  is aimed outward while the fed chain is as close as possible to being tangent to a common origin vertex of centerlines of  60  and  61  in [FIG.  12  and  13 ]. The degree to which this plane is angled is defined by the following formula:        α   =       90      x     l                     
     whereα is the angle from said drive sprocket plane  62  in [FIG.  14 ] (or the driven sprocket plane  63  depending on which origin is referred to), x is the distance from said idler centers of  14 , and  15 , to the center of said drive sprocket  4  (or said driven sprocket  8 ), l is the distance between said drive and driven sprockets  4  and  8 . 
     The portion of chain centerline  60  is fed from said idler  13  to said idler  14 . Said portion  60  is along said centerline  64  in [FIG.  14 ] and twists so that the chain centerline portion  68  in [FIG.  12  and  13 ] is heading substantially vertical after it is fed through said idler  14 . Said leeward chain  9  twists as it travels through said center line portion  68  such that by the time it reaches said driven sprocket positioning idler  15 . After being fed through said driven sprocket positioning idler  15 , it is in a plane 90 degrees from plane of said drive sprocket  4 . In order for said driven sprocket positioning idler  15  to be placed most optimally, it is slightly out of plane from said plane of driven sprocket  8 , with its plane-twist-angle  65  in [FIG.  14 ] being defined by the above formula. After the chain follows around said driven sprocket  8 , it completes a cycle and again becomes said tension portion  6  twisting 90 degrees between centerlines of said driven and drive sprockets  8  and  4 . 
     ALTERNATIVE EMBODIMENT #1 
     An alternative Embodiment for the tensioner arm  12  in [FIG.  15 ] is where there is one large diameter idler  44  in lieu of idlers  11  and  13 , and said tensioner arm  12  has one lug on it&#39;s end to fit said chain adjusting means  45 . 
     ALTERNATIVE EMBODIMENT #2 
     Another alternative embodiment of this drive mechanism is where the frame  1  is a trunk in [FIG.  16 ] which supports the components entirely externally. Upper positioning idler  10  is supported by upper positioning idler boss  46 . Lower positioning idler  14  is supported by lower positioning idler boss  47 . Tensioner arm is supported by tensioner arm boss  48 . Drive sprocket adjustment sleeve  35  is supported by adjustment sleeve boss  49 . Driven sprocket positioning idler  15  is supported by driven sprocket positioning idler boss  50 . The propeller shaft  16  is substantially long, and is held in place by an also substantially long keeper tube  51  and supported by occasional bushings (not shown). Said shaft and keeper descends past the waterline  52  in a gradual manner wherein there is low water resistance and only slight angle from the horizontal. Said keeper tube  51  is connected to said trunk frame  1  by clamping collars  53 . 
     ALTERNATIVE EMBODIMENT #3 
     Still another alternative embodiment consists of the frame and jacket  1  in [FIG.  17 ] entirely encapsulating the components such that the drive mechanism is waterproof. A drive shaft  54  is driven by taper-pinned-pedals  55 , with the drive sprocket  4  affixed in center of said shaft  54 . Said shaft  54  is supported by water-sealed bearings  56  which rest in grooves  57 . A water sealed cap  66  mounts said bearings  56  in place while keeping the resulting parting line watertight. Access to the tensioner arm  12  and the rest of the upper components is kept watertight by waterproof access cover  58 . 
     ALTERNATIVE EMBODIMENT #4 
     An Alternative embodiment for said sleeve  35  in [FIG.  7 ] and/or water sealed bearings  56  and grooves  57  in [FIG.  17 ] is where the sleeve is graduated or mechanically indexed to mark the optimum sprocket positions, or the water sealed bearing package is faceted to insure bearing alignment of each side when different size sprocket/shaft assemblies are installed 
     ALTERNATIVE EMBODIMENT #5 
     To further prevent skipping or teething while coasting, or when the drive is pedaled in reverse, a ratchet and prawl-like freewheeling device can be installed in concert with or in lieu of the system with the handbrake, push cable  29 , and swaged cable  31  in [FIG.  6 ].