Abstract:
A self steering system for a sailboat has a rotatably and pendulously supported servo blade or “oar” member, which is suspended in the water behind the boat. A central body portion is attached to the transom of the boat. A pendulum body having two lever arms or “winglets” which extend generally in opposite directions is fixedly supported on a shaft suspended below the central body portion. A line is attached to each of the tips of the lever arms. Each of these lines runs upwardly and through separate blocks to the boat&#39;s steering control. A wind vane is installed on the top of the assembly and drives a push rod, which is coupled, to the servo blade. In operation, the wind vane provides a motional signal in accordance with changes in the heading of the boat from a preset heading, this motional signal operating to drive the servo blade, which controls the sailboat&#39;s main rudder, to bring the boat back to its preset heading.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to self steering systems for sailing craft and more particularly to such a system which employs a rotatably and pendulously supported oar member which is suspended in the water stream behind the craft which is used to control the sailing craft in response to a device such as a wind vane which senses and provides an output signal in accordance with changes in boat heading from a preset heading relative to the wind direction. 
     2. Descriptions of the Related Art 
     Self steering systems for sailboats are described in my prior U.S. Pat. No. 3,983,831 issued Oct. 5, 1976; U.S. Pat. No. 4,327,657 issued May 4, 1982; U.S. Pat. No. 4,766,833 issued August, 1988; and U.S. Pat. No. 5,309,858 issued May 10, 1994. Each of the systems described in the above patents employs a different implementation, which makes for some advantage in operation or fabrication. The present invention is most closely related to the device of U.S. Pat. No. 5,309,858 and will therefore be compared in its implementation to that of this patent. 
     The system of U.S. Pat. No. 5,309,858 employs a pendulum body rotating on a fixed pendulum shaft. The pendulum shaft is attached to a universal bracket, which is fixedly attached to the transom of the sailboat. The system has a major upright section, which includes a base and a tubular wind vane support extending upwardly from the base. This wind vane support is secured to the pendulum shaft and positioned aft of the pendulum body. An output “pull-pull” line attachment shoulder or rocker is positioned on the top of the pendulum body, above the pendulum shaft. Pull-pull output lines run to a set of blocks positioned on opposite sides of the attachment shoulder. 
     It has been found that the location of the pull-pull lines in prior art systems obstructs swim ladders and “walk-thru” features of the boat. In addition, it has been found to be difficult to correctly position the “pull-pull” line side blocks with double ended boat geometry, a strongly curved boat transom or with off center mountings of the main elements of the system. 
     Additionally, the pendulum shaft is subject to damage from high accidental mechanical loads from the upright wind vane support, requiring an extra large diameter for the shaft. 
     A still further disadvantage of this prior art system is that it employs a complex universal bracket which is capable of holding the extra-large pendulum shaft and adapting to a wide range of different transom angles. 
     SUMMARY OF THE INVENTION 
     The invention described herein provides an improved and more useful system. It is simpler to manufacture and can be built to have superior strength and lower weight. The system of the present invention, further, is simpler to install than the systems of the prior art and is more suitable for off-center mounting and walk through sailboat transom geometries, which is a desirable feature for most modern sailboats. In addition, in the system of the present invention, the main body of the device of the invention can be attached directly to the sailboat&#39;s transom using a simpler bracket which has a universal base. A pendulum body without a shoulder section is suspended with a small diameter pendulum, which is subject to less mechanical loads than prior art systems. 
     In addition, several of the components of the system can be fabricated from sheet metal rather than through castings. This approach can greatly reduce the cost of manufacture 
     A different pendulum body than that of the prior art is employed. This pendulum body incorporates two side mounted lever arms or “winglets” for pull-pull line attachments, permitting these lines to run upwardly to the blocks, which are secured, directly on the upright section of the system, thus avoiding having obstructing lines on the side of the device. These lever arms or winglets are positioned substantially aft of the pendulum shaft and will pivot or swing free and clear of the center body. A mast tube extension is employed permitting large pendulum swing angles (typically 120-170 degrees to each side). This permits the servo blade to be lifted out of the water and placed in a near upright position for stowage when the system is not in use. The pull-pull lines run substantially upward from the winglets, which keeps them free from interference with other elements of the system. Another significant feature is the provision of a central body, which is substantially flat and can readily be fabricated of sheet metal having substantially higher tensile strength than typical castings and of minimum expense. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded elevational view of a first embodiment of the invention; 
         FIG. 2  is a side plan view of the embodiment shown in  FIG. 1 . 
         FIG. 3  is a side elevational view of a second embodiment of the invention; 
         FIG. 4  is a rear elevational view of the first embodiment; 
         FIG. 5  is a side elevational view of a line circuit configuration for use in the system of the invention; 
         FIG. 6  is a rear elevational view of a third embodiment of the invention, which employs a fully or partially circular drum device rather than lever arms; 
         FIG. 7  is a side elevational exploded view illustrating a fourth embodiment of the invention; and 
         FIGS. 8 and 8A  are elevational drawings of a fifth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , a first embodiment of the invention is shown. 
     Central body  1  is a substantially vertical plate, which may be of metal and is substantially parallel to the longitudinal axis of the sailboat. The central body is attached to base member  2  at a desired angle by means of bolts and nuts  28  and the base member is attached to the transom  3  of the yacht in a symmetrical manner by means of four bolts  29  along with washers and nuts. The axis  6  of pendulum body  4  is slanted, as described in U.S. Pat. No. 5,309,858, which is incorporated herein by reference. This slant angle provides the desired stability for the servo blade. The slant angle of axis  6  is typically between 15 and 40 degrees relative to the water surface, which is horizontal. It is to be noted that larger angles provide more “toe-in” for the servo blade and greater stability. It is to be noted that the slant angle of linkage arm  15  to central body  1  does not have to be the sane as for the pendulum axis  6 . Often the slant angle of the linkage arm  15  relative to the horizontal is selected to be larger than the slant angle of pendulum axis  6 . The “toe-in” angle then becomes larger than dictated by the slant angle for the pendulum axis  6  alone. 
     The pendulum body  4  is suspended on the shaft  5  beneath the central body  1  and extends aft, a tubular section of the pendulum body having the servo blade shaft  16  installed therein. The pendulum body  4 , a lever arm  7  extending to the port side of the boat, and a lever arm  8  extending to the starboard side. 
     For normal operation of the system of the invention, the rocking motion of the pendulum body  4  is generally limited to 20-30 degrees to each side and thus, as shown in the Figures, the configurations of lever arms  8  and  9 , often referred to as “winglets” are simpler and more compact. This is as compared with a larger and heavier circular ring/drum configuration with a V groove device for the pull-pull lines, as is generally found in the prior art. 
     Mast tube  11  is fixedly secured to central body  1  by means of holders  30 . The pull-pull output lines  9  and  10  are attached to the compact lever arms  7  and  8 , respectively. The attachment points of the lines to the lever arms are located at substantially equal distances from a region near the interception point of the pendulum axis  6  and the axis  27  of servo blade  17 , this region normally being slightly above the interception point of the two axes to avoid both undesirable line slack or line tensioning with motion of the pendulum  4 . The output lines  9  and  10  run upwardly and over the blocks  20  and  19  respectively. The blocks are secured to the mast tube  11 . The lines then run to the boat&#39;s tiller or wheel as shown in  FIGS. 1 and 2 . 
     When the self-steering device is not in use, the lines can be disconnected and the line tension released, for example, by the use of cam cleats or stoppers (not shown). The pendulum device can then be allowed to swing up to the maximum possible side angle, which typically can be as high as 160-170 degrees. In the “parked” non-operative position and with the blade  17  or shaft  16  tied to the mast tube  11 . The mast tube  11  is secured to the central body  1  using mast tube holders  30 . 
     Push rod  12  runs inside mast tube  11  from the vane assembly  41 . The push rod  12  has a forked bottom end, which is connected to a front lever arm, which is connected to rocker shaft  13 . Rocker shaft  13  is connected to linkage arm  15  and thus guides the movement of this arm. Linkage arm  15  has a spherical end, which fits into a mating aperture forming a bearing in the hole formed in rocker  14 . 
     In the Figures, the servo blade  17  is shown rigidly attached to blade shaft  16 . In the alternative, such attachment can be achieved with a fork holding the shaft to the blade with a breakable shear pin, permitting the blade to fold up backwards or forwards in case of an accidental impact, thereby saving system components from mechanical overload and resultant damage. 
     The boat&#39;s main rudder is shown schematically. Lines  9  and  10  run to the wheel or tiller in a known prior art fashion and control the angle or quadrant of the rudder. The main rudder  18  is the principal steering device for the boat and holds a desired course in response to the wind vector  42  on command from the servo blade  17  and the system which responds thereto. 
     The servo blade is suspended on the servo blade shaft  16  and oscillates with low friction on bearings  21  and  22  shown in the FIGS as roller bearings. The pendulum shaft  5  is suspended on bearings  23  and  24 , which may comprise high load journal bearings. Rocker shaft  13  is suspended on bearings  25  and  26 . 
     The vane assembly, which includes air vane  41 , vane base turret  34 , vane rod  38 , and vane rocker  37 , is mounted on the circular top of mast tube  11 . The vane base turret  34  can rotate on the circular top of the mast tube. A handle  35  and a locking device  36  for locking the handle in place are employed for course selection and course locking. The vane rocker  37  pivots around the slanted vane pivot axis  44  with pivotal motion being generally restricted to 20-45 degrees to each side of the axis by restricting line  40 , which runs around mast tube  11 . 
     The lightweight air vane  41 , which is generally larger than servo blade  17 , is secured to vane rod  38 . Counter weight  39  is balanced and secured to the lower section of vane rod  38 . To get high sensitivity with light winds, the joint center of gravity for components  37 , 38 , 39 ,  40 , and  41  is placed only slightly below the vane pivot axis  44 . 
     The static waterline of the boat is shown by numeral  32  with a higher dynamic waterline being shown by numeral  33 . The water flow vector to the servo blade is shown by numeral  43 . The universal base  2  should be positioned and secured to the transom  3  of the boat at such a height that when sailing at full hull speed, the dynamic waterline does not reach the pendulum body  4  or the lower bearing  22  of the servo blade shaft 
     The air vane assembly is fully disclosed the cited prior art and is incorporated herein by reference. The air vane  41  is shown schematically in  FIG. 2 . The air vane assembly with this prior art configuration generates a downward motion to the pushrod  12  when the boat falls off course to port. When this occurs servo blade shaft  16  is rotated counter clockwise, as seen from above and the servo blade  17  is swung to port. Line  10  is thereby pulled to turn the boat&#39;s main rudder so that it generates a hydrodynamic force in the port direction. This causes the boat to make a steering correction to starboard to reach the correct course heading. 
     Referring particularly to  FIG. 4 , a rear view of the system of the first embodiment of the invention is illustrated. Holders for shaft bearings  23 , 24 , 25 , and  26 , shown in  FIG. 1  but not show in  FIG. 4 , are separate parts secured to the central body  1 . The mast tube  11  is positioned to the starboard side of plate  1  and held in place by mast tube holders  30 . The lever arms (winglets)  7  and  8  are shown as separate parts, which are typically made of sheet metal. Each of the lever arms  7  and  8  is bolted to the pendulum body  4 . Universal base  2  here is mounted on the starboard side of central body  1 . (See  FIG. 1 ). The rocker shaft  13  and supports for the rocker shaft bearings can be seen in  FIG. 1  but are only shown schematically in  FIG. 4 . 
     Pull-pull lines  9  and  10  and blocks  19  and  20  are shown in  FIG. 4  but reference is directed to  FIGS. 1 and 2  for a showing of the line circuits to the wheel and tiller of the boat. 
     As show in  FIG. 4 , blocks  19  and  20  are shown secured directly to mast tube  11 . It is also possible to secure these blocks directly to the top section of central body  1  or to a separate block holder component secured to the central body or mast tube. 
     Block positions as well as pull-line attachment positions on the lever arms  7  and  8  relative to the pendulum axis  6  are selected to give desired minimum stretch or slack in the line circuit for the useful pendulum range. Pendulum swing angles of 20 degrees to each side have been found to be suitable for sailboat steering purposes. Pendulum swing angles of 160-170 degrees to the port side and a swing to the starboard side of slightly less are mechanically possible and useful for blade “parking” when not in use and the line circuit is disconnected. 
     Referring now to  FIG. 3 , a second embodiment of the invention is illustrated. In this embodiment, the angle of the servo blade shaft  16  and the angle of attack of the servo blade  17  ( FIG. 1 ) is controlled with the help provided by a bevel gear assembly  46 . The input bevel gear  46   a  is oriented coaxially with the pendulum axis  6  and the output bevel gear  46   b  is oriented coaxially with the servo blade axis  27 . 
     The angle between the servo blade axis  27  and the pendulum axis  6  need not be 90 degrees. The pitch angles, which are the angles between the pitch cones and the bevel gear axes (half angles of the pitch cones), are normally unequal. The push rod  12  drives a lever  49  connected to the bevel gear shaft  48  thereby rotating the bevel gears. 
     In the device of  FIG. 3 , the central body  1  as for the embodiment of  FIGS. 1 and 2  can be envisioned as an essentially flat plate with pendulum axis  6 , the coaxial pendulum shaft  5  and the coaxial gear shaft  48  all positioned behind the flat plate to the port side, and the mast tube  11  on the front to starboard side. Lever  49  is positioned within an aperture  50  formed in the central body. 
     Axes  6  and  27  intersect so that the shaft  16  is mounted slightly to the side relative to central plate  1 , which can readily be accomplished. 
       FIG. 3  partially shows only the port side lever  7  and the pull line  9 , which runs from lever  7  to block  20 . Pull line  10  which runs from starboard side  8  lever  10  to block  19  are not shown in  FIG. 3  but can be seen in  FIG. 1 . 
     The trajectory of the lever arms  7  and  8  (not shown in  FIG. 3  but can be seen in  FIG. 1 ) when the pendulum body swings out are again well behind the central body  1 , permitting the desired large swing angles, for example (120-170 degrees to each side without obstruction. 
     The pull-pull lines  9  and  10  (see  FIG. 1  for line  10 ) are attached to the side sections of rings  47  at geometrically similar but opposite positions relative to the pendulum axis  6  for the side for the side lever configuration as can best be seen in  FIG. 1 . 
     With the air vane  41  (see  FIG. 2 ) and push rod  12  in a fixed positions, the oar shaft  16  will turn when the pendulum body  4  swings to the side, providing an angular “toe-in” for the servo blade  17  which assures the necessary hydrodynamic stability for the system. The amount of toe-in for the system shown in  FIG. 3  is controlled by selecting the right combination of pitch angles for the bevel gears and slant angle of pendulum axis  6  relative to the surface of the water. 
     Referring now to  FIG. 5  a practical line circuit configuration for use with the device of the invention is illustrated. This configuration allows for short lever arms arms (winglets) which is highly advantageous. A set of “doubling” blocks  51  and  53  are attached to the tips of the lever arms  7  and  8 . As in the previous embodiments, the first set of blocks  19  and  20  are secured to the mast tube  11  or central body  1  (See  FIG. 1 ). A pair of standard cam cleats or standard stoppers  54  and  55  and a pair of pad eyes  53  are employed. With the doubling blocks, the pull line motion is doubled thus allowing for shorter lever arms. The helm line tension or slack can be simply controlled by adjusting the individual line positions in the cam cleats  54  and  55 . Rapid release or rapid engagement of the line circuit to the boat&#39;s wheel or tiller is also possible using the cam cleats  54  and  55 , release being achieved by lifting lines out of the cam cleats and engagement being achieved by installing lines in the cam cleats. 
     Referring now to  FIG. 6 , a rear view of a third embodiment is illustrated, this embodiment is illustrated, this embodiment employing a partial or full circular drum  56  instead of the lever arms. (port and starboard levers shown in  FIG. 1 ). The drum axis is substantially coaxial with the pendulum axis  6 . Lines  9  and  10  are fitted into standard V-grooves in drum  56  and are secured in the bottom section of the drum. The drum is located behind central body  1 . The configuration of this embodiment is suitable for use with the linkage arm  15  device shown in  FIG. 1  and the bevel gear device  46  shown in  FIG. 3 . Double blocks (not shown) can be employed along the paths of lines  9  and  10 . 
     Referring now to  FIG. 7 , a fourth embodiment of the invention is illustrated. This system employs a linkage arm  15  and a rocker  14  in lieu of the beveled gears  46  shown in  FIG. 3 . The major parts of this embodiment can be manufactured simply and inexpensively from sheet metal and metal bars. A light metal alloy is favored but standard stainless steel can also be employed. Carbon fiber and plastic might also be used. 
     The central body  1  consists of a flat metal plate with two rectangular bars  58  and  59  attached thereto. The bars have circular holes formed therein for receiving pendulum shaft  5  and pendulum bearings  23  and  24 . Push rod  12  and the top of the vane assembly are not shown in this Figure. The pendulum shaft  57  has a rectangular center section, which is bolted to pendulum body  4 , and two coaxial end shaft sections  5 . The rectangular bars  58  and  59  are bolted to the lower end of central body  1 . The pendulum body consists of several parts, which are bolted together. These parts include the sheet metal units  4 , 7 , 8 , and  62  and the bar parts  60  and  61 . The bar parts have holes formed therein for receiving the servo blade shaft  16  with roller bearing elements  21  and  22  on the shaft in engagement with mating gear elements formed in the holes. 
     The lever arms  7  and  8  with support element  62  make for a stiff and lightweight configuration capable of handling the mechanical loads from the servo blade  17  and the pull lines  9  and  10 , Sheet metal element  62  is bolted to bar parts  60  and  61  thus transferring mechanical loads to and from the plate section  4  and from there to and from the pendulum shaft  5 . 
     The servo blade  17  is attached to servo blade shaft  16  employing simple sheet metal fork parts  63  and  64 . The fork parts are bolted to the shaft using the two upper bolt holes  17   a  and  17   b . Servo blade  17  is attached to the shaft between the forks  63  and  64  by means of bolts, the upper one of which can be a shear pin. 
     Referring now to  FIGS. 8 and 8A , a fifth embodiment of the invention is illustrated. In this embodiment, the pendulum body consists of two separate flat plates  4   a  and  4   b  of equal thickness bolted over elements  65  and  66  and  57 . This assembly has higher rigidity permitting the use of plates having smaller thickness. This contributes to weight waving as compared with the arrangement of the other embodiments, which employ a single plate. The servo blade shaft  67  is off center, being located behind axis  27 . The servo blade is suspended on two simple hinges without roller or ball bearings. For the side loads. The upper hinge  65  and huge portion  68  has a small diameter pin  70   a  positioned in a sleeve bearing attached to servo blade shaft  67 . The lower hinge  66  employs a hinge portion  69 , which is retained by means of pin  70   b  in a sleeve bearing attached to servo blade shaft  67 . 
     A counterweight  71  is employed for proper balancing and bringing the center of gravity of the entire assembly including off center shaft  67 , fork plates  63  and  64 , blade  17  and the counterweight near or ahead of axis  27 . This balancing is of importance, particularly in light wind sailing by assisting in the desired stabilizing blade “toe-in” for the pendulum. 
     The servo blade  17  is held by the two fork plates  63  and  64 . The blade is secured by a main holding bolt  65  and a shear pin  66 . Upon heavy impact or overload of the servo blade  17  from ahead, the shear pin will break and the blade is permitted to fold backward. The lever arms (winglets).  7  and  8  are bolted to the two pendulum body plates  4   a  and  4   b . Short sections of the pendulum body plates facing aft are here bent 70-90 degrees outwardly, away from the symmetry plane. Each of the lever arm winglets are bolted respectively to the pendulum bent body sections  4   a  and  4   b.    
     While the invention has been described and illustrated in detail, it is to be understood that this is intended by illustration and example only and not by way of limitation, the coverage of the patent being limited by the terms of the following claims.