Patent Publication Number: US-6210244-B1

Title: Split-bladed propulsion apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a propulsion apparatus for water sports, and more particularly to a rowing apparatus having a split blade and surface contours and adaptable for use as either an oar or a paddle. 
     2. Description of the Prior Art 
     The present invention represents a development from and an improvement on an earlier invention of the same inventor, entitled contoured paddle for water sports, and disclosed in U.S. Utility Patent Application filed Aug. 30, 1999. The prior design comprises, in part, a blade with surface topography for advantageously channeling water over the blade face when in use, and further has a crooked loom for increasing propulsive force. The surface topography comprises fluted channels formed in conjunction with a plurality of gently curving, raised channel ridges. The fluted channels direct water over the sweet spot (or center) of the blade, thereby increasing thrust, and thereafter conduct the water to the blade edges and outwardly in a fashion that evenly distributes water flow, thereby aiding blade stability and propulsion. The primary principle in operation is the Bernoulli effect, which describes local pressure differentials produced by varying velocities of fluid. These pressure differentials are exploited by the contoured paddle to increase efficiency while decreasing the strain on the user. 
     In certain applications and uses, it would be advantageous to further exploit the principles in effect in the contoured paddle. The present invention represents such an advance. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided an improved propulsion apparatus which may be embodied as either an oar or paddle, said oar or paddle being adapted to propel shallow draft watercraft, including kayaks, canoes, racing shells, rafts, skiffs, and the like. The oar or paddle comprises a handle portion, or loom, and at least one split blade, depending upon its use. The split blade comprises at least two working surfaces, preferably only two, having a front and a back blade section, each one of which has topography on its working surface. The topography comprises channel dividers and fluted channels defined thereby for channeling water across the front surfaces of the front and back blade sections of the blade when in use. 
     As a first preferred embodiment, the present invention may be either a single or double-bladed paddle, suitable, e.g., for canoeing or kayaking, respectively. A second embodiment of the present invention is adapted for use as an oar for rowing shells or white water rafts. In either embodiment, the front and back blade sections may be conjoined to form an opening between the two sections for further advantageous channeling of water. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first embodiment of the split blade paddle of the present invention showing the blade connected to a handle; 
     FIG. 2 is side elevation view of the left front face blade portion of the split blade paddle of FIG. 1, Showing the “composite” blade, which includes both the front and back blade sections as joined together; 
     FIG. 2A is a cross-sectional end view on the cutting plane shown in FIG. 2; 
     FIG. 2B is a cross-sectional end view on the cutting plane shown in FIG. 2; 
     FIG. 3A is a side elevation view of the back blade section of the split blade paddle; 
     FIG. 3B is a side elevation view of the front blade section of the split blade paddle; 
     FIG. 4 is side elevation cross-sectional view of the split blade paddle showing the regions of physical connection between the front and back blade sections; 
     FIG. 5 is a bottom cross-sectional view of the split blade paddle as viewed from the cutting plane shown in FIG. 4; 
     FIG. 6 is an end elevation cross-sectional view of the split blade paddle as viewed from the cutting plane shown in FIG. 4; 
     FIG. 7 is an end elevation cross-sectional view of the split blade paddle as viewed from the cutting plane shown in FIG. 4, showing the theoretical hydrodynamic water flow pattern between the front and back blade sections when in use; 
     FIG. 8 is a side elevation view of the theoretical hydrodynamic water flow across the working surface of the split blade paddle; 
     FIG. 9 is a perspective view of a second embodiment of the present invention, showing a split blade oar with a handle; 
     FIG. 10 is a side elevation view of the combined front and back blade sections of the “composite” split blade oar; 
     FIG. 11A is a side elevation view of the front blade section of the split blade oar; 
     FIG. 11B is a side elevation view of the back blade section of the split blade oar; 
     FIG. 12 is a side elevation cross-sectional view of the composite oar of FIG. 10, showing the regions of connection between the front and back blade sections; 
     FIG. 13 is a bottom cross-sectional view of the split blade oar as viewed from the cutting plane shown FIG. 12; and 
     FIG. 14 is an end elevation cross-sectional view of the oar as viewed from the cutting plane shown in FIG.  12 . 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     FIG. 1 is a perspective view of a first embodiment of the split blade propulsion apparatus of the present invention, showing the blade connected to a handle, and FIG. 2 is side elevation view of the left front face blade portion of the split blade paddle of FIG.  1 . This first embodiment is adapted for use as a paddle blade for propelling shallow draft watercraft such as canoes, kayaks, rafts, and the like. These views show that the split blade paddle, generally denominated  10 , has at least two working surfaces (also known as power faces), preferably including a front blade section  12 , and a back blade section  14 , each having a contoured working surface, that is, a surface topography, comprised of channel dividers  16 , and fluted channels  18 , for channeling water across the front surface of each of said front and back blade sections of the split blade when in use. (As used herein, “working surface” or “power face” refers to that surface of the blade that moves against the water during a productive stroke.) While it is possible for the front and back blade sections to remain physically unconnected, preferably the front and back blade sections are conjoined in a “split-blade” configuration having a proximal end  20  for connection to a handle (or loom)  22 , and a distal end  24 . In the preferred embodiment, the front blade section is offset in a position slightly below and overlapping the back blade section. 
     FIG. 2A is a cross-sectional end view along the cutting plane shown in FIG.  2 . This view shows that when viewed on end near the distal end the split blade paddle has a concave profile to its working surface  30 , and a convex profile to its non-working surface  32 . The back blade section  34  and front blade section are conjoined to form a region of overlap  38 . This view further shows the topography of the working surfaces, including channel ridges  40 , are shown to have a taper from base  42  to tip  44 . 
     FIG. 2B is a cross-sectional end view along the cutting plane shown in FIG.  2 . This view shows that when viewed on end near the proximal end, the split blade paddle has a substantially larger area of overlap between the front blade section  50  and the back blade section  52 , than at the distal end, such that the sections are effectively unified from the lowest point of overlap  54  to the upper edge  56  of the blade. 
     FIG. 3A is a side elevation view of the back blade section  60  of the split blade paddle, which section has an upper edge  62  and a lower edge  64 . This view shows that the back blade section has a first channel divider  66  and a second channel divider  68 , which are discontinuous with one another. FIG. 3B is a side elevation view of the front blade section  70  of the split blade paddle, showing that this blade section has an upper edge  72  and a lower edge  74 , and first and second channel dividers  76  and  78 , respectively 
     FIG. 4 is side elevation cross-sectional view of the split blade paddle showing the two general regions of physical connection between the front and back blade sections, including a distal region  80  and a proximal region  82 . The front and back blade sections need not be conjoined to provide certain hydrodynamic advantages when in use, but in the preferred embodiment the sections are conjoined so as to create an oblique opening  84 , or through channel, between the back of the front blade section and the front of the back blade section. The through channel has a water inlet opening  86  proximate the front blade section upper edge  88  for the inlet of water flowing along the front surface of the back blade section and an expanded water outlet  90  proximate the lower edge  92  of the back blade section for the dissipation of water outwardly and downwardly from the working surface of the back blade section. 
     Preferably the back blade section includes an upper curled edge  94 , which curls backwardly toward the working surface of the back blade section and effectively “grips” the water during a working stroke so as to increase the volume of water retained and channeled across the blade surface. Additionally, the front blade section preferably includes a proximal section of a beveled lower edge  96  having a ridge generally perpendicular to the plane of the working surface. 
     FIG. 5 is a bottom cross-sectional view of the split blade paddle as viewed from the cutting plane shown in FIG. 4 showing the water inlet opening  100  of the through channel  102  of the split blade between the front working surface of the back blade section and the rear surface of the front blade section. This shows that through channel  102  has a generally oblong cross section. The edge of the upper curled edge  104  of the back blade section is visible through the through channel. 
     FIG. 6 is an end elevation cross-sectional view of the split blade paddle as viewed from the cutting plane shown in FIG.  4 . This view provides another depiction of the through channel  110  formed by the combination of the front and back blade sections,  112  and  114 , respectively, and more particularly how through channel  110  narrows from the inlet opening  116  at its upper end to the discharge opening  118  at its lower end. 
     FIG. 7 is an end elevation cross-sectional view of the split blade paddle as viewed from the cutting plane shown in FIG. 4, showing the theoretical hydrodynamic water flow pattern, W, between the front and back blade sections,  120  and  122 , respectively, when in use. It will be appreciated that water entering water directed into inlet opening  124  is rapidly accelerated as it moves downwardly via through opening  126  toward the lower edge  128  of the front blade section. Preferably opening  126  includes a bulge region  125  where the opening profile widens from the inlet opening profile. At this stage in the opening the moving water decelerates and momentarily pools before being rapidly accelerated through outlet opening  127 , which is narrower than both inlet opening  124  and bulge region  125 . The actual size of the bulge region can be tailored to the desired characteristics of the blade, with a larger region providing more propulsive force. 
     FIG. 8 is a side elevation view of the theoretical hydrodynamic water flow across the entire working surface of the split blade paddle. This view shows that the front and back blade sections combine to conduct water across the working surfaces of the composite paddle. More specifically, the surface topography of the blade sections, including fluted channels  130 , channel dividers  132 , and upper curled edge  134 , conduct water longitudinally and transversely, and in combinations thereof, across the working surfaces of the blade&#39;s two sections, moving from the distal end  136  toward the proximal end  138 . Broken lines depict water flow via the through channel  140 , which generally defines the center of mass of the blade sections, individually and collectively. A paramount feature of the contoured blade surfaces is that the water moves generally across the center of mass and propulsive force, proximate to but not necessarily located at the geometrical center of the blade. This is the “sweet spot” of the blade, and by concentrating water at this locus, propulsive force is increased while torsional forces that cause blade flutter are reduced. After directing water across the sweet spot of the working surface of the paddle or oar, the channels then broadcast the water outwardly from the center and to and from the edges of the blade in a balanced fashion. While increasing the propulsive effect of the stroke, this pattern of water movement further decreases torsional forces at the edges of the blade. The blade therefore feels more stable to the user. 
     Each section of the split blade may be either substantially flat or gently curved when viewed from above in their profile aspect. Additionally, the sections, individually or in combination, may be symmetrical or asymmetrical, though the preferred design for a split blade paddle is asymmetrical, as illustrated by the drawings herein. 
     FIG. 9 is a perspective view of a second embodiment of the present invention, showing a split blade oar  150 . FIG. 10 is a side elevation view of the combined front and back blade sections of the “composite” split blade oar. FIG. 11A is a side elevation view of the front blade section of the split blade oar. FIG. 11B is a side elevation view of the back blade section of the split blade oar. These figures show that the split blade oar has elements and topographical features corresponding to those of the split blade paddle, but tailored to the fluid dynamics connected with rowing rather than paddling. Specifically, as shown in FIG. 9, the split blade oar comprises a front blade section  152  and a back blade section  154 , said front and back blade sections preferably conjoined to form an oblique through channel  156 . The oar has a generally straight distal end  158  and a proximal end  160  for connection to an oar handle  162 . 
     As shown in FIGS. 10 through 11B, the composite oar blade  170  comprises conjoined back blade section  172  and front blade section  174 . Front blade section  172  has a graduated curled upper edge  174  for gripping water during a productive stroke. The working surface of the front blade section has a sloping face  176  that slopes upwardly from the curled edge  174  to a channel ridge  178  sweeping generally longitudinally along the lower portion of the front blade section, and thereafter slopes downwardly from the channel ridge  178  to the lower border  180  of the front blade section, which in the preferred embodiment is contiguous with and joins the lower portion of the back blade section  182 . 
     The back blade section  174  of the split blade oar has an upper grooved channel  184  and a lower grooved channel  186 , each of which direct and rapidly accelerate water along the working surface and into the through channel. Additionally, the distal portion  188  of the split blade oar, comprising the distal portion of the back blade section, preferably includes a shallow fluted channel  190  near the distal edge  188 , which edge is preferably straight, and a deep fluted channel  192  more proximate the center of the blade. Preferably, back blade section  174  has a beveled section  194  of lower edge  182 , said beveled section commencing where the lower edge begins to taper and converge toward the upper edge to form the proximal end  196  where the oar is adapted for connection to a handle. 
     FIG. 12 is a side elevation cross-sectional view of the composite oar of FIG. 10, showing the distal and proximal regions of connection,  200  and  202 , respectively, between the front and back blade sections, and through channel  204  defined by a region between the regions of connection and the front and back oar blade sections. 
     FIG. 13 is a bottom cross-sectional view of the split blade oar as viewed from the cutting plane shown in FIG. 12, and FIG. 14 is an end elevation cross-sectional view of the oar as viewed from the cutting plane shown in FIG.  12 . 
     Referring now to FIG. 14, as with the split blade paddle, the water inlet to the through channel  204  of the split blade oar has a relatively broad opening. However, the sides of the through channel, defined by the back side  206  of front blade section  208  and the front side  210  of back blade section  212  quickly converge to choke the water into a narrow passage. This narrowing functions as a venturi to jet flowing water toward and through outlet  214 , located at the upper border  216  of the back blade section. From this drawing it will be apparent that the inventive apparatus as embodied in an oar contemplates having the front blade section positioned above the back blade section. This contrasts with the above-described paddle, wherein the orientation is reversed. 
     It may be appreciated that the general shape of the conjoined sections in this second embodiment may also be either flat or curved, symmetrical or asymmetrical. Preferably, the combined front and back blade sections form a generally symmetrical oar when viewed directly in front of the working surfaces. Curvature may be unidirectional or about a center located at the approximate geometric center of the blade sections. As is well known in the art, curvature may be introduced to accentuate the water trapping or “gripping” feature of the blade. This principle applies equally well to the present invention, though the surface topography relegates blade shaping to an optional characteristic for customization only. 
     Paddles and oars are employed for a variety of purposes. Accordingly, the size, shape, and precise surface topography of the composite split blade paddles and oars may be varied. Competitive racers, for example, may require a size, shape, and working surfaces designed to maximize thrust under a manageable and sustainable muscular exertion. Touring and other recreational users may prefer a configuration designed to provide optimum velocity under considerably more modest propulsive forces while also minimizing the strain and fatigue suffered by the user. This need for application-specific customization highlights one of the significant advantages of the present invention: namely, increased versatility. 
     It will further be appreciated that the present invention is adapted for connection to either paddle or oar handles, and in the former instance either to double-bladed paddles (e.g., kayak paddles) or single-bladed paddles (e.g., canoe paddles). Furthermore, when configured in a double-bladed paddle, the paddle may be either feathered or non-feathered. 
     When interpreting the drawings herein, it must be understood that when paddling, the power face is pulled toward the user; when rowing, the power face is “pulled” away from the rower via the radial motion of the oar due to its fixed axis in the oar lock. 
     While this invention has been described in connection with preferred embodiments thereof, it is obvious that modifications and changes therein may be made by those skilled in the art to which it pertains without departing from the spirit and scope of the invention. Accordingly, the scope of this invention is to be limited only by the appended claims.