Abstract:
A joint connecting a cylinder actuator of a trim tab to a watercraft includes a first part couplable to a wall of the watercraft, a second part couplable to the cylinder actuator, a pin coupled to one part and a pin seat formed in the other part. In one embodiment, the seat is defined by a portion of a circular cylindrical surface having an opening on one side. The surface portion has an angular extension larger than 180°, and the pin has a correspondingly cylindrical portion with a laterally flattened surface for introduction into the opening of the pin seat. The opening of the cylindrical pin seat and the flattened portion/s of the pin are in such reciprocal angular positions that the two joint parts are operably connectable and disconnectable by disposing them in a relative angular position, which cannot be attained in the mounted operating condition.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a joint for connecting a cylinder actuator of a trim tab to a watercraft, comprising a first part designed to be fixed to a wall of the watercraft, a second part designed to be fixed to one end of the cylinder actuator, at least one pin integral with one of said two parts and at least one pin seat formed in the other of said two parts which is adapted to receive said pin to form a hinge connection. 
     BACKGROUND OF THE INVENTION 
     Many watercrafts currently use trim tabs mounted to the transom for attitude control during navigation. Trim tabs, which are also known as “stabilizers”, “trim controls” or “flaps”, are movable plate-like extensions of the hull, usually made of metal, that are hinged to the transom flush with the keel and driven by one or more cylinder actuators to variously tilted positions relative to the keel. 
     Like in aircraft flaps, appropriate control of watercraft trim tabs provides control of the hydrodynamic force which tends to lift the stern, and consequently lower the bow, thereby ensuring the ideal pitch attitude for navigation in a variety of conditions, for instance according to load distribution, speed, weather and other variables. 
     Each trim tab is generally driven by a cylinder actuator having ends hinged to the transom and to the trim tab. Such cylinder actuators may be of a hydraulic or electric type and are well known in the art. For instance, U.S. Pat. No. 5,881,666 discloses an electrical cylinder actuator. The actuator disclosed in this document, like all currently available actuators, has slots at its ends for pins designed to secure it to corresponding fixing plates having a coaxial lug integral with the trim tab and with the transom to form hinge connections that allow oscillation of the trim tab according to the length of the piston rod. These connections are obtained by fastening the fixing plates to the corresponding surfaces of the trim tab and/or the transom, by transversely fitting the slots of the cylinder into alignment with the lugs and by axially mounting a pin into the slots/lugs so aligned. Otherwise, the cylinder may be equipped with a hinge already mounted to a fixing plate to be fastened to the corresponding surfaces of the trim tab and the transom. In both cases, the mounting/removal process is particularly laborious and generally requires highly skilled personnel. On the other hand, the cylinder actuator, like any materials designed to operate in contact with seawater, is subjected to wear and often requires maintenance, and hence repeated mounting/removal procedures. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a connection, which at least partially obviates the above drawback in a simple and reliable manner, so that cylinder actuators of watercraft trim tabs may be easily, practically and quickly mounted and removed even by unskilled personnel. 
     The invention fulfils the above object by providing a joint, in which the pin seat is defined by a portion of a circular cylindrical surface having an opening on one side for introduction and removal of the pin into and from the pin seat. The pin is displaced during introduction and removal into and from the seat, for example, may be displaced transversely, particularly perpendicularly, to the radial direction related to the axis of the pin and/or the cylindrical seat. Such portion of the cylindrical surface may have an angular extension of more than 180°. 
     The pin has a correspondingly cylindrical portion with a laterally flattened surface allowing introduction thereof into the opening of the pin seat. Such opening of the cylindrical pin seat for pin introduction and removal via the flattened portion/s of the pin are located in the cylindrical surface of the cylindrical seat and respectively on the outer cylindrical surface of the pin in such angular positions, with respect to the position in which the seat is fixed to a wall of the watercraft and to the position in which the cylinder actuator is fixed to the trim tab, that the two joint parts are operably connectable/disconnectable when they assume a relative angular position, which cannot otherwise be attained by the joint in the normal operating state. 
     Advantageously, the portion of the pin that is designed to cooperate with the pin seat has a circular segment cross section with an angular extension of more than 180° and a height smaller than the width of the seat opening, whereas the two joint parts preferably have perfectly mating shapes in the connected state to form a very compact connection device. 
     In practice, the joint of the invention provides a removable hinge, with practically and quickly connecting/disconnecting parts, which affords the same safety as prior art hinges, thanks to a coupling/uncoupling mechanism that cannot be actuated during normal operation of the trim tab. This type of operation is allowed by the lateral opening of the lug hole and the corresponding flattening portion of the pin, which allow the parts to mate only when they are in a given angular position. 
     In one embodiment, one of the two joint parts comprises a fixing plate having at least one pair of lugs with a coaxial cylindrical hole, within which the pin associated with the other joint part rotates freely. Each hole delimiting wall has a corresponding lateral, radial opening for the pin to be inserted therein in a direction transverse to the hole axis when the flattened surface of the pin is brought to alignment with the radial openings by rotation of one joint part relative to the other. The lugs also may be connected together at the side opposite to the opening of the respective holes, thereby providing a particularly firm support to pin insertion. Typically, the joint part integral with the pin includes a tab with two opposed flat surfaces. The lugs are longitudinally spaced for the tab to be interposed between the lugs substantially in the middle when the joint is in the connected state, thereby forming a hinge equivalent in all respects to those of the prior art. The tab has two coaxial pin stumps at its opposed surfaces, which are designed to engage with the hole of the corresponding lugs. In particular, each pin stump is disposed orthogonally to the corresponding surface of the tab and has a flattened portion of such size to allow passage thereof through the lateral opening of the hole of the corresponding lug when the flattened portion is brought to alignment with the lateral opening of the hole by rotation of the tab relative to the fixing plate or vice versa. The alignment positions of the flattened portions of the pin with the radial openings of the holes are a relative angular position of the opening of the holes with the flattened portions, which cannot be attained when the actuator is in the mounted and operating state. 
     The pin or pin stumps may be glued and/or welded and/or formed of one piece with the tab of the cylinder actuator, particularly by molding or casting, or the pin may be press fitted and locked into a hole of the tab to project by its two opposite ends from the two opposite faces of the tab. The same applies to the lugs, which may be glued and/or welded and/or formed of one piece with the fixing plate, particularly by molding or casting. 
     In view of the foregoing and as further shown hereinbelow, the two lugs that act as supports for the hinging pin ends or stumps have recesses for receiving the two pin ends or the two stumps and form a kind of fork for supporting the hinging pin. Such fork has openings for receiving the pin ends or the two stumps in that position and with a width smaller than the diameter of the pin or the two stumps, whereby the pin ends or stumps must have one or more diameter-reducing flattened portions, to be fitted into the seat. Conversely, the flattened portions and openings of the seat are in such a position relative to the angular operating position of the cylinder actuator that the flattened portions on the pin ends or stumps cannot be angularly aligned with the seat openings and slip off the respective seats through their openings. 
     In prior art systems, the power cable/duct to the cylinder actuator typically crosses the transom via a bulkhead feedthrough to reach the cylinder actuator, with which it is connected, via a cable sleeve that operates against the head of the cylinder actuator. Thus, the cable/duct has an external path that is designed to be in contact with water and that is subjected to wear. In a particularly advantageous embodiment of the joint of the invention, the cable/duct may be arranged to pass through a watertight seat which prevents contact with water for increased durability and reliability. For this purpose, the joint parts have an internal guide passage which actually consists of an essentially central, particularly axial hole or conduct formed in the tab, and a corresponding hole formed in the fixing plate which is designed to be aligned with the hole or conduit of the tab at a given angular position of the joint. This angular position corresponds, for instance, to the relative position that allows connection/disconnection of the joint parts. Advantageously, the end section of the internal guide passage is widened at the end of the joint part associated with the pin or pin stumps and facing toward the fixing plate, particularly in the tab associated with the cylinder actuator. This configuration allows the two joint parts to oscillate when the internal guide passage holds the power duct or cable, with the widened portion extending angularly about an axis parallel to the axis of oscillation of the two joint parts. These arrangements provide for a very compact joint with an integrated cable sleeve feature. 
     The joint advantageously has means for fastening the part related to the pin seats to the watercraft wall and also for fastening the part related to the pin/s to one end of the cylinder actuator. These means are typically associated respectively with the fixing plate and the tab. In particular, the fastening means associated with the tab include a terminal, which is designed to be press fitted or screwed into a corresponding element of the cylinder actuator. The terminal typically consists of or is integral with the head or cover of the cylinder actuator and has peripheral holes for receiving a fastener, for example, a screw fastener. 
     In one embodiment, the terminal has an outlet hole for the duct or cable received in the guide passage, and watertight fastening means are further provided between the duct or cable and the outlet hole. Advantageously, the watertight fastening means include a cable sleeve which operates against the head or cover of the cylinder actuator from the interior of the cylinder to the terminal of the joint, thereby forming a sealing mechanism that is completely different from prior art systems, in which the cable sleeve operates against the cylinder head from the exterior to the interior of the cylinder. Through this arrangement, cylinder actuators may have one open end, because the head or cover may be associated directly with the joint for higher flexibility and easier mounting/removal. 
     In another aspect, the invention relates to a watercraft comprising a trim tab hinged to the transom for attitude control, in which a trim tab is driven by a cylinder actuator connected to the transom via a joint as described above. 
     In yet another aspect, the invention relates to a control system for controlling the attitude of a watercraft that includes at least one trim tab hinged to the transom of the watercraft, a pneumatic or electric cylinder actuator hinged at one end to the trim tab and at the other end to the transom via a joint according to the invention, and a hydraulic or electric control device connected to the cylinder actuator through a pneumatic duct or an electric cable partially held in the internal guide passage of the joint. The piston rod has such a maximum length that, in operation, the angular position corresponding to the disengagement state of the joint parts is not attained. 
     Additional features and improvements provided by the invention are recited the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention and the advantages derived therefrom will be more apparent from the following detailed description of the enclosed drawings, in which: 
         FIGS. 1 ,  2  and  3  are side perspective views of one embodiment of the joint of the invention having three distinct steps of connection of the two parts thereof; 
         FIG. 4  is a top perspective view of the joint shown in  FIG. 3 ; 
         FIGS. 5 and 6  are sectional views of the joint shown in  FIGS. 2 and 3 ; 
         FIGS. 7 ,  8  are side perspective views of the two separate joint parts; 
         FIG. 9  is a side perspective view of the two decoupled parts of the joint of  FIGS. 2 and 3  with the power cable mounted thereto; 
         FIG. 10  is a sectional view of the joint of  FIG. 9 ; 
         FIG. 11A  is a perspective view of the joint as shown in the previous figures, when mounted to one end of a cylinder actuator of a watercraft trim tab system according to the invention; 
         FIG. 11B  is an enlarged detail of  FIG. 11A ; 
         FIGS. 12 and 13  are respectively a top perspective view and a side view of a trim tab or fin according to a preferred embodiment of the invention; 
         FIG. 14  shows a general block diagram of a control circuit for controlling the blade or trim tab actuator in a device as shown in the previous figures, in which a switch known as Neutral Safety Switch is associated with the neutral state of the motor and is automatically switched, when the motor is in neutral, to generate a signal of displacement of the trim tab/s to the neutral trim position; and 
         FIGS. 15 to 17  show three different alternative modes of connection of the neutral safety switch that drives the trim tabs to neutral as soon as the motor is put in neutral. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 to 3 , the joint is composed of two distinct parts  1 ,  2  comprising the pin seat and the hinge tab respectively. 
     The part  1  consists of a triangular fixing plate  101  having three peripheral holes  201  in the proximity of the vertices, allowing it to be fastened to the watercraft wall  4  by screws or bolts. Two lugs  301  are provided at the center, on the side away from the wall and orthogonal to the plate  101 , each having a coaxial hole  401 . The lugs  301  are preferably formed of one piece, particularly by casting or molding, with the plate  101  and are interconnected at the upper part by a stiffening rib  801 . 
     The holes in the lugs  401  have a lateral radial opening  601  for transversely receiving the two pin stumps  102  of the tab  202  of the joint part  2 . Each opening  601  has an angular extension of less than 180°, to ensure a sufficient guide surface to the corresponding pin stump during rotation and to prevent its disengagement during operation. Each pin stump  102  has a diameter slightly smaller than the diameter of the lug holes and has a lateral flattened portion  302  so that its cross section can form a circular segment having an angular extension of more than 180° and a height smaller than the width of the opening of the corresponding lug. 
     Connection of two joint parts is achieved by the following steps: 
     rotating the tab  202  relative to the lugs  301  until of the flattened portion  302  of each pin stump  102  is aligned with the lower delimiting surface  701  of the corresponding opening  601 , as shown in  FIG. 1 ; 
     translating the tab  202  for the pin stumps  102  to be transversely fitted into the corresponding openings  601  as shown in  FIG. 2 ; 
     rotating the tab  202  until each flattened portion  302  is no longer aligned with its respective opening  601 , as shown in  FIG. 3 , so that the part  402  of the pin stumps next to the opening  601  can interfere with the opening, thereby preventing the stumps  102  from disengaging from the hole of the lugs  301 . 
     The above steps relate to a configuration in which the second part  2  is designed to rotate and translate relative to the first part  1 , but it shall be understood that the connection/disconnection of the joint is caused by the motion of any part relative to the other. 
     The angular position of the opening  601  of the hole  401  of the lugs  301  relative to the fixing plate  101  and the position of the flattened portion  302  at the ends of the pin  102  relative to the axis of the cylinder actuator  2 , with whose tab  202  it is connected, defines the maximum possible oscillation of the joint before the latter reaches the disconnection position. The figures show, for example, a configuration in which the angle between the axis of the openings and the plane that passes through the surface of the plate is more than 90°, although different angles may be envisaged. 
     The joint part  2  that carries the tab  202  has a cap or cover element at the end portion, on the side away from the hinge, which is adapted to engage with one of the ends  103  of the cylinder actuator  3  ( FIG. 11A ) with the interposition of seals. The cap or cover  502  has peripheral holes  602 , through which it may be fastened by screw or bolt means to corresponding annular flange-like surfaces of the cylinder  3  and is advantageously formed of one piece with the tab  202 , particularly by molding or casting. The above mentioned end preferably forms a proper cover, which is sealably press fitted onto an open-ended cylinder, but may be easily modified for connection with a closed-ended actuator, such as by screw fastening onto a ring nut. 
     The joint of the invention is particularly advantageous, not only in that it forms a removable hinge that facilitates mounting/removal of the cylinder actuator  3  in a watercraft trim system, but also in that, by particular arrangements, it can also act as a cable sleeve between the cylinder actuator  3  and the watercraft wall  4 . For this purpose, an internal guide passage is provided, in a substantially central position, for holding a power duct or cable  5  of the cylinder actuator  3  as shown in  FIGS. 5 and 6  for two different angular positions of the joint. 
     The guide passage substantially consists of a hole or duct  702 , which axially crosses the second joint part  2  from the end  802  of the tab  202  facing toward the fixing plate  101  to the opposite end that carries the cover  502  of the cylinder actuator  3 . The fixing plate  101  has a corresponding hole  901 , which is aligned with the outlet hole or duct of the tab  202  in a given angular position of the joint parts  1 ,  2 , e.g. the connection/disconnection position. In order to prevent the cable or duct  5  from hindering joint oscillation during operation, the tab  202  has a widened portion  902  of the internal guide portion in the end  802  facing toward the fixing plate  101 . The widened portion  902  has a “delta” shaped angular extension about an axis parallel to the axis of oscillation of the two joint parts, particularly about the hinge axis. The radial extension of the widened portion  902  is related to the maximum oscillation of the joint and hence, in one embodiment, it substantially coincides or is slightly smaller than the angle that defines the axial position of the opening  601  of the hole  401  of the lugs  301  which, as mentioned above, defines the joint disconnection position. 
     The device finally includes the cable sleeve  112  that operates against the cover  502  of the cylinder actuator  3  or of the end of the joint part that is designed to be attached thereto, and a bulkhead feedthrough (not shown) which operates from the interior of the watercraft against the transom wall  4 , which has the plate  101  of the joint mounted thereto and has a hole therein for the passage of the power duct or cable  5 . 
       FIGS. 11A and 11B  provide a general view of an attitude control system for a watercraft having trim tabs that incorporate the joint of the invention. The trim tab  6  is connected on one side to the transom wall  4  through the hinge  204  and on the other side to one end  203  of the cylinder actuator  3  through the hinge  206  mounted to the support  306 . The hinge  206  is of a conventional type, although it may advantageously be of the type of the invention, for even easier mounting/removal. The opposite end  103  of the cylinder actuator  3  is connected to the wall  4  through a joint of the invention. 
     Mounting is performed as follows: a hole is formed in the wall  4  for the passage of the power cable or duct  5  of the cylinder  3 , then the plate  101  of the joint is mounted using a cable sleeve or a bulkhead feedthrough to ensure watertightness. The cable or duct  5  is introduced into the guide  702  of the second joint part  2 , led out of the hole  122  of the cover  502  and then sealed by the cable sleeve  112  before fixing the cover  502  to the upper end  103  of the cylinder  3 . Then, the joint is assembled by rotating the cylinder  3  until the flattened portion  302  of the pins  102  of the tab  202  is aligned with the openings  601  of the delimiting wall  501  of the holes  401  of the lugs  301  and by acting transverse thereto in the direction of insertion of the pins  102  into the holes  401 . Then, the other end  203  of the cylinder  3  is hinged to the trim tab  6 . The maximum stroke of the piston rod  303  of the cylinder  3  defines the maximum relative angular position of the two joint parts  1 ,  2  and is set to such a value that the disconnection position can never be attained during operation. Therefore, disconnection requires the end  203  of the cylinder  3  to be released in such a manner that the cylinder  3  can rotate to allow the joint parts to attain such position. The maximum elongation of the rod  303  may be electronically or electromechanically controlled by the control transmitted to the actuator or, with a higher reliability, using a mechanical stop member during mounting, or more simply by providing rods  303  of predetermined length according to the joint to be used, e.g. by providing trim tab and joint kits to be sold in a single package. 
     Referring to  FIGS. 12 and 13 , a trim tab  6  or fin is shown, which has a particularly advantageous fluid-dynamic trimming conformation. Namely, the trim tab  6  or fin has a rib or tooth, at the transverse edge opposite to the hinging end  106  of the trim tab, which projects downwards beyond the underside of the trim tab  6  or fin. In the figures, the rib or tooth are designated by numeral  406  and extend throughout the rear, transverse side of the trim tab  6  or fin. When, like in this particular embodiment, the trim tab  6  or fin has its longitudinal edge, i.e. the edge oriented longitudinally to the hull, equipped with a lateral fin  506  inclined in relation to the rest of the trim tab, particularly upwards, and when the lateral fin  506  terminates at its rear transverse edge to join the rear transverse edge of the rest of the trim tab, then the rib or tooth  406  only extends along the rear transverse edge of that part of the trim tab  606  that does not form the longitudinally inclined lateral fin  506 . 
     The end rib or tooth  406  may have various inclinations in relation to the part of the trim tab  606 , from whose transverse rear side it projects. In the embodiment of the figures, the rib or tooth  406  is oriented substantially perpendicular to the underside of the part of the trim tab  606  with which it is joined. 
     Concerning the length of the rib, i.e. the projection thereof from the underside of the part of the trim tab  606  with which it is joined, said length is from about 1/15 to 1/50 of the overall length of the trim tab  6  or fin from the transverse hinging side to the rear transverse side, with which said rib or tooth  406  is joined. Nevertheless, in the illustrated embodiment such projection can never fall out of a range from 0.5 mm to 50 mm. 
     According to yet another advantageous embodiment, the invention has automatic devices for moving the trim tabs  6  or fins into the neutral, i.e. rest position, in which they have no trimming action when the watercraft is put in neutral, i.e. when the inverter is controlled into the idle state, for instance by disconnecting the shaft for transmitting motion to the propeller from the drive shaft. 
     Manual control members, such as levers or the like, are typically provided to switch among neutral, forward and reverse gears, and operate by mechanical, electromechanical, power-assisted or electronic transmission on the inverter controlling actuators. A safety switch is further provided in combination with those control members to reset the operating units to neutral. Such switch is automatically actuated by the gear lever and, in a preferred embodiment, also acts to generate a signal for moving the trim tab/s  6  into the rest or neutral position. 
     Referring now to  FIG. 14 , the trim tab driving actuators  3  are controlled by a master unit  30 , which supplies power for the time required to set a predetermined angular position of the trim tabs  6 . Such master unit  30  has inputs for connection to a switch that is designed to generate a control for moving the trim tab/s  6  into said neutral position, which inputs are connected to the two contacts of the switch  31  known as Neutral Safety Switch. 
     As shown in  FIGS. 15 to 17 , the switch  31  may be used in various circuit configurations. 
     In the embodiment of  FIG. 15 , the switch only generates a short-circuit condition in two ports of the master unit  30 , designated as NS+ and NS−. In the closed state, the master board  30  drives the actuators  3  to move the trim tabs  6  into the above mentioned neutral position. 
     In the embodiment of  FIG. 15 , the Neutral Safety Switch  31  is a simple switch that is connected to no particular unit and that may be directly connected to the ports NS+ and NS− of the Master Unit  30 . These ports have no polarity, wherefore no connection problem arises. 
     In the embodiments of  FIGS. 16 and 17 , the Neutral Safety Switch  31  can control additional units, which are generally designated by numeral  32 . Here, in the circuit of  FIG. 16 , the Neutral Safety Switch  31  is again a simple switch, one having contacts connected to the positive pole of the battery, designated as +VBat, whereas the other contact of the switch is connected to the units  32  and to an input port NS+ of the master unit  30  that controls the actuator/s  3  of the trim tabs  6 , which also acts as a unit. 
     The embodiment of  FIG. 17  is a variant, in which the Neutral Safety Switch  31  is interposed between the port NS− of the master unit that is connected to one of the contacts of the switch and the ground pole that is connected to the other contact of the switch  31 . The same contact of the switch  31  is used to connect with the port NS− of the master unit  30  and the other units  32 . 
     The above variants show that the use of the Neutral Safety Switch  31 , which is generally supplied as part of the watercraft control equipment, may be extended to the control for moving the trim tab/s back into the neutral position, considering the trimming function and the above mentioned definition of neutral position. Regardless of the settings of the circuit that is already present on board and of the type of the additional units controlled by the Neutral Safety Switch  31 , such Neutral Safety Switch  31  may be also connected to the Master Unit  30  that controls the actuator/s  3 , so that, when the switch  31  is actuated by the inverter control lever to set the neutral gear, a control is generated for moving the trim tab/s into the neutral position. 
     The invention is not limited to the embodiments described and illustrated herein but may be greatly varied, especially as regards construction. For example, the joint may be used, still in marine applications, for connecting to the cylinder actuator of a hatch lifter, or in any other field that requires the use of a hinge connection with separable parts. All these applications and equivalents thereof are without departure from the guiding principle of the invention as disclosed above and claimed below.