Abstract:
A coupling apparatus for adjusting and axially coupling first and second shafts about a feathering axis, comprising a collar having an end face having a plurality of axial notches, an insert having an extended portion and at least one radial pin and a cam ring circumscribing the collar. The collar is securable to a free end of a first. The insert is securable in a free end of a second shaft such that the extended portion extends axially from the second shaft and are receivable in the free end of the first shaft such that the pins engage upon the notches so as to axially couple the first and second shafts. The cam ring includes a plurality of radial flange segments and is rotatable to engage the pins so as to retain the pins in engagement with the notches.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. provisional application Ser. No. 60/673,055, filed Apr. 20, 2005, the content of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     This invention relates to a shaft coupling apparatus, and more particularly, to an apparatus for providing a repositionable paddle assembly for varying the relative pitch angle between oppositely disposed paddle blades.  
         [0004]     2. Description of Related Art  
         [0005]     The sport or activity of kayaking is rapidly growing in popularity as it provides a source of enjoyment/entertainment, rigorous exercise, and a unique connection with nature. One can analogize kayaking to the sport of cycling inasmuch as each involves individual effort, self-motivation, and self-propulsion.  
         [0006]     While kayaking has many similarities to cycling, there is a large disparity in the number of individuals who enjoy each activity. Aside from the obvious need for a body of water, the cost and convenience of kayaking is, perhaps, the largest deterrent to involvement in the sport. Fortunately, recent innovations in kayak and kayak paddle design and manufacture have made kayaking more affordable, easier to handle/maneuver, and less cumbersome to transport.  
         [0007]     Consequently, there is a constant evolution in kayak paddle design aimed at making kayaking more enjoyable. For example, Aqua-Bound Technology Ltd., one of the largest manufacturer&#39;s of kayak paddles and accessories, were one of the first to introduce gas assist injection molded kayak paddles which made paddles, previously one of the most expensive accessories required, much more affordable.  
         [0008]     Other advances in the area of kayak design and construction, to which the present invention is directed, relates to reconfiguring twin-bladed paddle assemblies to vary the pitch angle between opposing blades. Paddle blade assemblies are often constructed with a pair of paddle blades mounted at opposite ends of a central handle. While such paddle assemblies facilitate an ergonomically smooth motion i.e., as a paddler passes each paddle blade through the water to either side of a kayak, the paddle blade which rises above the water can produce significant aerodynamic drag especially in windy conditions. That is, when a paddler passes one paddle blade through the water, the opposing blade can, if disposed at a high angle of attack relative to the freestream airflow, produce significant profile drag. Such drag forces are, it will be appreciated, exacerbated by high wind speeds/gusts commonly produced on the water. To counteract such drag forces, it is typical for paddle assemblies to include a center coupling capable of varying the relative pitch angle of the paddle blades. That is, by disposing the blades at a relative pitch angle of, for example, 60 to 90 degrees, the paddle blade in the free stream airflow can be feathered to an angle close to a zero angle of attack. Furthermore, depending upon the direction of the wind relative to the watercraft, other pitch angles may be desired to minimize drag.  
         [0009]     U.S. Pat. No. 4,605,378 to Hamilton discloses a repositionable coupling which employs a spring biased pin disposed in telescoping segments of a paddle assembly. The pin, which is connected to one of the paddle segments, seats within an aperture of the other segment. By depressing the spring biased pin, the paddle assemblies may be rotated until the pin is reset into a second aperture, e.g., disposed 90 degrees apart from the first, to change the relative pitch angle of the paddle blades. While this paddle design addresses the difficulties associated with aerodynamic drag, the repositionable coupling has certain design deficiencies. For example, only a limited number of apertures can be employed without impacting the structural integrity of the paddle assembly. Hence, the relative rotational position of the paddle assemblies is limited to several choices, e.g., +/−90 degrees.  
         [0010]     Furthermore, after extended use, the coupling can fail or develop “play” due to fretting wear between the pin and aperture. That is, the aperture can become elongated or oval-shaped over time such that the coupled components become loose and prematurely fail.  
         [0011]     Yet other prior art coupling arrangements such as that illustrated in U.S. Pat. No. 6,881,111 to Bridge, et al. employ a combination of spring biased pins and a spline for accepting an elongate key. While this coupling design eliminates the structural deficiencies of the Hamilton &#39;378 patent, i.e., by separating the axial and torsional load paths, this arrangement employs a number of moving parts and/or high tolerance connections. As such salt water corrosion of the spring mechanism as well as debris from sand or salt deposits can jam or otherwise render the coupling inoperable.  
         [0012]     A need, therefore, exists for a reliable and secure repositionable coupling which enables greater flexibility in terms of paddle blade positioning.  
       SUMMARY OF THE INVENTION  
       [0013]     In accordance with one aspect of the present invention there is provided a coupling apparatus for adjustably and axially coupling first and second shafts about a feathering axis. The coupling apparatus comprises a collar having an end face. The end face has a plurality of axial notches and is securable to a free end of the first shaft. The coupling apparatus further includes an insert having an extended portion and at least one radial pin. The insert is securable in a free end of the second shaft such that the extended portion extends axially from the second shaft, whereby, the extended portion is receivable in the free end of the first shaft such that the pins engage upon the notches so as to axially couple the first and second shafts. The coupling apparatus further includes a cam ring circumscribing the collar. The cam ring has a plurality of radial flange segments having a cam surface facing said engagement plane. The cam ring is rotatable to engage the pins so as to retain the pins in engagement with the notches for fixing the relative position of the first and second shafts.  
         [0014]     In accordance with another aspect of the present invention, there is provided a twin-bladed paddle assembly comprising first and second paddle segments each having a handle portion for mounting a paddle blade at an outboard end. The handle portions define a feathering axis about which the paddle segments may independently rotate. The first handle portion has at least one radial pin. The second handle portion has at least one axial notch which accept and engage the radial pins along an engagement plane. The twin-bladed paddle assembly further includes a camming device adapted to retain the pins in engagement with the notches to rotationally fix the relative angular position of the paddle segments.  
         [0015]     Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     In drawings which illustrate embodiments of the invention,  
         [0017]      FIG. 1  is a perspective view of a twin-bladed paddle assembly having a repositionable coupling in accordance with an embodiment of the present invention;  
         [0018]      FIG. 2  is an exploded perspective view of the repositionable coupling including a plurality of radial pins, a ring cam, and a plurality of axial notches for accepting and engaging the radial pins;  
         [0019]      FIG. 3  is a broken away sectional view of the assembled repositionable coupling;  
         [0020]      FIG. 4  is a cross sectional view taken substantially along line  4 - 4  of  FIG. 3  showing an end view of the repositionable coupling upon being rotated in a direction which retains the radial pins in engagement with the axial notches;  
         [0021]      FIG. 5  is a cross sectional view taken substantially along line  5 - 5  of  FIG. 4  showing the operation of a camming device for engaging the radial pins with the axial notches;  
         [0022]      FIG. 6  is a partial longitudinal cross-sectional view of the repositioned coupling of  FIG. 1 , showing the radial pins aligned with the axial gaps to permit adjustment or separation of the paddle segments;  
         [0023]      FIG. 7  is a partial longitudinal cross-sectional view of the repositioned coupling of  FIG. 1 , showing the flange segments retaining the radial pins in engagement with the axial notches;  
         [0024]      FIG. 8  is an exploded perspective view of a coupler according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0025]     The following discussion is presented to enable one skilled in the art to make and use the invention. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the applicable art, and the teachings herein may be applied to other embodiments without departing from the spirit and scope of the invention as defined in the appended claims. Thus the present invention is not intended to be limited to the embodiments shown, but is to be afforded the broadest scope consistent with the principles and features disclosed herein.  
         [0026]     The invention described herein relates to a two bladed paddle to propel a watercraft along each side thereof. Furthermore, the two-bladed paddle is configured for use by a single paddler to maximize handling efficiency, i.e., use a smooth uninterrupted motion to manipulate the paddle blades through and over the water. Such paddles can generally be used on any boat having a sufficiently narrow beam so as to allow a single paddle to span its width such as a kayak, canoe, pontoon or inflatable boat. Therefore, as will be appreciated from the subsequent description and illustrations, the teachings are broadly applicable to a variety of watercraft applications.  
         [0027]     In  FIG. 1 , a perspective view of a kayak paddle assembly  10  is shown including paddle blades  12  disposed on opposite ends of a central handle  14 . The central handle  14  is segmented along its length to define first and second paddle segments  16   a ,  16   b , each of the paddle segments  16   a ,  16   b  including a portion,  18   a  or  18   b , of the central handle  14  and a single paddle blade  12 . Furthermore, each of the paddle segments  16   a ,  16   b  are joined by a repositionable coupling  20  disposed in combination with the handle portions  18   a ,  18   b , to permit axial separation and relative rotation of the paddle segments  16   a ,  16   b . That is, the paddle segments  16   a ,  16   b  may be separated to facilitate storage and transport. The paddle segments may also be rotationally repositioned about a feathering axis  10 A to facilitate blade angle variations desired during certain boating conditions.  
         [0028]     In  FIG. 2 , an enlarged isolated perspective view of the repositionable coupling  20  is shown. In the broadest sense of the invention, the coupling  20  includes at least one radial pin  22 , a plurality of axial notches  24  and a camming device  26 . The radial pins  22  are disposed at an end of one handle portion  18   a . The axial notches  24  are disposed on an end face  25  of the other handle portion  18   b , the axial notches accepting and engaging the radial pins  22 . The camming device  26  circumscribes and is disposed over an engagement plane defined by the radial pins  22  and axial notches  24 . Each of the principle elements of the coupling  20  will be described in greater detail below.  
         [0029]     In  FIGS. 1, 2  and  3 , an innermost end portion  28  of the first handle portion  18   a  is disposed axially inboard of the radial pins  22  to fit snuggly, i.e., telescopes, into a bore  30  defined by the second handle portion  18   b . Functionally, the telescoping sections  28  serve to align the handle portions  18   a ,  18   b  along the longitudinal axis  14 A of the central handle  14  (coincident with the feathering axis  10 A) and provide bending moment stability. Furthermore, the telescoping sections  28  permit independent rotational displacement of each paddle segment  16   a ,  16   b  about the feathering axis  10 A.  
         [0030]     The radial pins  22  preferably extend radially outboard of the face surface of the first handle portion  18   a  and are positioned circumferentially in equiangular increments thereabout. At a minimum, at least one (1) radial pin is used. Preferably, however, four (4) radial pins  22  disposed approximately ninety (90) degrees apart provides even greater load distribution and bending moment stability (i.e., about axes orthogonal to the longitudinal axis  14 A). In the preferred embodiment, the radial pins  22  have a substantially V-shaped profile configuration and include at least one substantially planar sidewall surface  32 . The significance of this configuration will become clear when describing the operation of the coupling  20  and elements which structurally interact with the sidewall surfaces  32  of the radial pins  22 .  
         [0031]     The axial notches  24  are formed along the end face  25  of the second handle portion  18   b  in combination or integrally with the face surface of the second handle portion  18   b . As such, the end face has a shape closely resembling a crown wherein the points  36  thereof project axially from the end of the second handle portion  18   b . However, it will be appreciated that the axial notches  24  may be formed integrally with the end portion of the handle portion  18   b . While the number of axial notches  24  can, at minimum, be as few as the number of radial pins  22 , preferably, the number of axial notches  24  is a multiple of the number of radial pins  22 . In the embodiment shown in FIGS.  1  to  3 , sixteen (16) axial notches are employed in varying increments about the end face of the second handle portion  18   b . Accordingly, the axial notches  24  are disposed at angles between fifteen (15) and thirty (30) degree increments from center to center. While, in the preferred embodiment, the axial notches  24  are arranged in varying increments, it will be appreciated that the notches may be disposed at other angular positions depending upon the desired relative pitch angle between the paddle segments.  
         [0032]     The shape of each axial notch  24  preferably compliments the shape of each radial pin  22 , and in the described embodiment, defines a substantially V-shaped profile complimenting the preferred shape of the radial pins  22 . Furthermore, the depth or axial length of each axial notch is preferably equal to or less than the axial length of the V-shaped notch. One skilled in the art will appreciate that the depth is designed as a function of the anticipated torsional loads, the angle of the V-shaped notch and the maximum shear strength of the materials used to fabricate the radial pins  22  and the axial notches  24 .  
         [0033]     The camming device  26  envelopes an engagement plane defined by the radial pins  22  and axial notches  24  and may rotate in either direction about the longitudinal axis  14 A of the central handle  14 . In the context used herein, the “engagement plane” is the plane where each radial pin  22  engages a respective axial notch  24  and is substantially normal to the longitudinal axis  14 A of the central handle  14 . In the broadest sense, the camming device  26  retains the radial pins  22  in engagement with the axial notches  24 . In addition, the camming device  26  may effect axial displacement of the radial pins  22  toward the axial notches  24  to engage/rotationally fix the position of the paddle segments  16   a ,  16   b . The camming device  26  enables axial displacement of the radial pins  22  away from the axial notches  24 , i.e., out of engagement therewith, to permit relative rotation of the paddle segments  16   a ,  16   b . And, the camming device  26  facilitates axial displacement of the radial pins  22  to detach and/or assemble the paddle segments  16   a ,  16   b , i.e., for transport or storage of the paddle assembly  10 . Consequently, the camming device  26  effects engagement, separation and indexing of the paddle segments  16   a ,  16   b.    
         [0034]     Specifically, and referring to  FIGS. 2 through 5 , the camming device  26  includes a cam ring  40  defining a plurality of flange segments  42  having first and second ends  45  and  47  respectively, which project radially inwardly toward the longitudinal axis  14 A of the central handle  14 . Each flange segment  42  includes a stopping portion  46  extending perpendicular from the second end  47  of the flange segments towards the axial notches  24  for engaging upon a side of the radial pins  22  to prevent over-rotation of the cam ring as well as providing extra structural support to the flange segments  42 . The flange segments also include a cam surface  44  along a sidewall surface thereof for engaging a sidewall surface  32  of each radial pin  22 . The cam surfaces  44  may be inclined relative to the engagement plane and positioned such that the radial pins interpose the flange segments  42  and the axial notches  24 . The inclined cam surfaces  44  preferably define a shallow angle θ between about one (1) degree to about ten degrees (10) degrees. More preferably the angle θ of inclination is between about five (5) degrees to ten (10) degrees.  
         [0035]     In the described embodiment, the cam ring  40  is mounted about one of the handle portions  18   b  by a low friction bearing assembly or collar  34  for retaining the axial position of the cam ring  40  and facilitating rotational displacement thereof about the longitudinal axis  14 A of the central handle  14 . The bearing assembly  34  comprises a pair of arcuate shoulders  34   a ,  34   b  disposed along the face surface of the handle portion  18   b , which shoulders  34   a ,  34   b  engage a cylindrical groove  54  formed internally of the cam ring  40 . More specifically, the arcuate shoulders  34   a ,  34   b  protrude through circumferential apertures  36   a ,  36   b  formed through the surface, and proximal to the end, of the handle portion  18   b . As a consequence, a circumferential abutment surface  50  is generated about the cylindrical face surface of the handle  18  to enable rotation of the cam ring  40  while retaining the axial position of the ring  40 .  
         [0036]     As such, rotation of the cam ring  40  in one direction i.e., in the direction of arrow  41  as shown in  FIGS. 4, 5  and  7 , causes the cam surfaces  44  to abut the linear sidewall surfaces  32  of the radial pins  22  and retain the radial pins  22  in engagement with the axial notches  24 . Furthermore, should the cam surfaces  44  be inclined as shown, the inclined cam surfaces  44  may urge the radial pins  22  axially in the direction of arrow  22 D, into abutting engagement with the axial notches  24 . During this rotational motion, the cam ring  40  is retained axially by the abutment surface  50 . When the flange segments  42  and cam surfaces  44  have fully engaged the radial pins  22  with the respective set of axial notches  24 , frictional forces fix the rotational position of the cam ring  40  relative to the central handle  14 . Accordingly, the paddle segments  16   a ,  16   b  are axially and rotationally secured. Rotation of the cam ring  40  in the opposite direction may produce an axial gap between the cam surfaces  44  and the radial pins  22 , i.e., sufficient to enable disengagement of the radial pins  22  relative to the axial notches  24 .  
         [0037]     In the arrangement shown in  FIG. 6 , the cam ring  40  has been rotated in the direction indicated at  39  such that the radial pins  22  are located within an axial gap  48  between adjacent flange segments  42 . This enables the operator/paddler to axially displace the handle portions  18   a  and  18   b  to uncouple or axially realign the first and second paddle segments  16   a  and  16   b . By aligning the radial pins  22  with the axial gap  48 , adequate axial clearance may be provided between the radial pins  22  and axial notches  24 , to clear the points  36  between the axial notches  24 . Accordingly, the radial pins  22  may be indexed/rotated in either direction for alignment with other axial notches  24  to vary the relative pitch angle of the paddle segments  16   a ,  16   b , and, consequently, the paddle blades  12 . The paddle segments may thereafter be locked together by rotating the cam ring  40  in the direction  41  as shown in  FIG. 7 .  
         [0038]     In addition to enabling axial displacement for indexing purposes, the axial gaps  48  enable detachment of the paddle segments  16   a ,  16   b  for transport and/or storage. That is, to fully separate the paddle segments  16   a ,  16   b , the radial pins  22  will pass through the axial gaps  48 , between the flange segments  42 , as the ends of each handle portion  18   a ,  18   b  are telescopically disengaged. It will be appreciated, of course, that the axial gaps  48  also enable attachment and assembly of the paddle segments  16   a ,  16   b , as the radial pins  22  are passed therethrough to engage the axial notches  24 .  
         [0039]     As shown in  FIG. 2 , the first paddle portion  18   a  may further includes a friction pad  33  disposed adjacent to the radial pins  22 . The friction pad  33  comprises a raised surface adapted to frictionally engage a corresponding engagement surface  43  on the flange segments  42 . As shown in  FIG. 2 , the friction pad are located adjacent to the radial pins  22  in the longitudinal direction of the paddle blade  12  of the first paddle portion. The friction pads  33  include a leading edge  35  which is longitudinally offset relative to a corresponding leading edge of the radial pin. When the cam ring  40  is rotated in the direction indicated by  41  in  FIG. 7 , the engagement surface  43  of the flange segments  42  will contact the leading edge  35  of the friction pads  33  before the cam surface  44  if longitudinally aligned with the corresponding leading edge of the radial pin. Further rotation of the cam ring  40  relative to the first handle portion  18   a  will cause the engagement surfaces  43  to frictionally traverse the friction pads  33 .  
         [0040]     According to the present embodiment, the friction pads  33  serve two purposes. When the coupling  20  is in the arrangement as shown in  FIG. 6 , the contact between the leading edge  35  of the friction pads  33  and the engagement surface will cause the first handle portion  18   a  to rotate with the cam ring  40  if the first handle portion  18   a  is not rotational secured relative to the cam ring  40 . This will enable the user to rotate the first handle portion  18   a  to a desired position relative to the second handle portion  18   b  by turning the cam ring  40  while holding the second handle portion  18   b . The user may then rotate the cam ring  40  relative to the first handle portion  18   a  to lock the coupling  20 .  
         [0041]     The second purpose of the friction pads  33  is to provide a more secure locking engagement between the first and second handle portions  18   a  and  18   b  when the coupling  20  is in the arrangement as shown in  FIG. 7 . Due to the angle of inclination of the flange segments  42  in some embodiments, should the cam ring  40  become loosened from it&#39;s locked position due to impacts, vibration or improper locking, the cam ring may then freely rotate out of the locked position shown in  FIG. 7  to the open position shown in  FIG. 6 . The friction pads  33  prevent this free rotation by providing an addition friction contact between the cam ring  40  and the first handle portion  18   a  that opposes free rotation of the cam ring relative to the first handle portion  18   a.    
         [0042]     In summary, the twin bladed paddle assembly and coupling kit provide a repositionable coupling to vary the relative pitch angle of opposing paddle blades. The repositionable coupling employ a ring cam to frictionally engage and secure the radial pins against the axial notches. Furthermore, the repositionable coupling enables greater flexibility in terms of the number of angular positions available for indexing the paddle segments. It will be recalled that the number apertures employed in prior art paddle assemblies was limited due to structural considerations.  
         [0043]     In addition, the apertures of prior solutions interposed the axial, torsional and bending moment load paths in the central handle of the prior art paddle assemblies. In contrast, axial and bending moment loads bridge the repositionable coupling without passing through the axial notches, thereby reducing the loads required to be supported by the notches and pins. Moreover, the repositionable coupling employs a minimum number of easily accessible moving parts for improving its overall reliability. That is, the opportunity for sand or salt to jam the coupling is minimized, as the moving parts and connections of the repositionable coupling may be readily accessed for cleaning when the paddle portions are separated. Finally, the paddle assembly and coupling of the present invention is elegantly simple and, as a consequence, fabrication costs are minimized.  
         [0044]     A further embodiment of the present invention is shown in  FIG. 8 . In the embodiment shown in  FIG. 8 , the coupling  100  comprises a kit that may be applied to a new pair of paddle portions  102  and  104  or retrofitted to existing paddle portions. The coupling  100  comprises an insert  110 , a collar  120  and a cam ring  130 . As shown in  FIG. 8 , the insert  110  comprises a cylindrical body  112  operable to be inserted into a free end  106  of a first paddle portion  102  and secured thereto. The insert  110  includes radial pins  114  and friction pads  116  as previously described. The insert  110  also includes an extended portion  118  which extends coaxial with and away from the first paddle portion  102  when the insert is inserted in the first paddle portion. The radial pins  114  may be spaced longitudinally a distance from the free end  106  of the first paddle portion when the insert is secured to the first paddle portion. The collar  120  comprises a tubular body  122  having a first end  124 . The first end  124  includes a plurality of axial notches  126  disposed radially around the first end as previously described. The collar may be applied to a free end  108  of the second paddle portion  104  such that the axial notches are longitudinally spaced a distance from the free end  108 . The collar includes shoulder inserts  128  adapted to be received within apertures  127  in the collar so as to form a circumferential ridge around the collar.  
         [0045]     The cam ring  130  coaxially and rotatably circumscribes the axial notches  126 . The cam ring comprises a tubular body  132  and includes a plurality of flange segments  134  longitudinally spaced apart from the axial notches and as previously described. The cam ring  130  includes a circumferential slot adapted to be received upon the ridge formed by shoulder inserts  128  of collar  120 .  
         [0046]     As set out above, the insert may be inserted into the free end of a first paddle portion while the collar surrounds the free end of a second paddle portion. The two paddle portions may then be connected by inserting the extended portion into a corresponding bore  105  in the free end  104  of the second pipe portion. The first and second paddle portions may then be pressed together until the radial pins  114  engage with the axial notches  126 . The first and second paddle portions may then be locked together by rotating the cam ring so as to cause said flange segments to retain the radial pins in the axial notches.  
         [0047]     While the invention has been described in terms of an exemplary embodiment, it will be appreciated that other changes, variations and omissions may be made within the spirit and scope of the invention. For example, while a V-Shaped radial pin and axial notch are shown in the described embodiment, the pins may be cylindrical or define another polygonal profile configuration. While the number of axial notches illustrated is sixteen, the number is at least equal to or a multiple of the number of radial pins.  
         [0048]     While the cam ring  40  is shown to define axial gaps  48  between the flange segments  42 , the cam ring  40  need only provide a recess or clearance for the radial pins  22  to disengage the axial notches  24 . As discussed supra, the axial gaps  48  facilitate separation of the paddle segments, however, such separation may be effected in a variety of other ways.  
         [0049]     While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.