Abstract:
A releasable latch for a marine instrument is provided for a transom mounted sensor on a marine vessel which enables the sensor to be rotated about a pivot point when an object is struck by the vessel.

Description:
RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/444,991, filed Feb. 4, 2003. The entire teachings of the above application are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention is in the field of marine instrumentation for providing information with respect to the speed of a marine vehicle through water, and optionally, with respect to the depth and temperature of the water.  
           [0003]    Instruments for measuring and displaying speed or velocity of a marine vessel through water have utilized a wide variety of sensors (See, for example, U.S. Pat. No. 4,206,637- paddlewheel interrupts photodetector; U.S. Pat. Nos. 3,496,770; 3,457,782—paddlewheel with magnet on each paddle or paddle made of magnetic field permeable material which is sensed by electromagnetic pick-up coil; and U.S. Pat. No. 3,706,224—paddlewheel with magnet on each paddle which interrupts current flow in a circuit).  
           [0004]    Similarly, numerous instruments exist for providing ultrasonic signals for depth sounding or fish locating. (See, for example, U.S. Pat. No. 4,110,727 and various references cited therein.)  
           [0005]    It has also been found helpful for marine navigation and fish finding to measure water temperature by various means.  
           [0006]    For the most part, prior art speedometers are mounted through the hull of the vessel requiring the drilling of a large hole in the hull and the attendant sealing problems (See the knotmeter of U.S. Pat. No. 3,531,988 referenced above). Additionally, with the exception of the transom mounted speedometer, it is customary to completely enclose the paddlewheel speed sensor except for a small portion in which the paddle extends into the water (See U.S. Pat. No. 3,457,782 above, for example). In such “closed cavity” devices, the speed sensor becomes non-linear at higher speeds of, for example, in excess of 35 miles per hour.  
           [0007]    U.S. Pat. No. 4,555,938 discloses a marine device which combines in one transom mounted housing the functions of speed sensing, water temperature sensing and depth or fish sounding. In the apparatus of U.S. Pat. No. 4,555,938, a sensor housing is provided for enclosing an ultrasonic transducer assembly, and a temperature sensor comprising a thermistor.  
           [0008]    In addition, a paddlewheel, or impeller, is attached to the housing. The paddlewheel is formed of amorphous magnetic material and the blades are magnetized to provide alternate North-South poles. As the marine vessel moves through water, the paddlewheel rotates at a rate proportional to the velocity of the vessel. A Hall-effect device mounted inside the housing adjacent the paddlewheel senses the change in electromagnetic field, as the polarized rotating paddlewheels pass by, and generates an electrical signal, the frequency of which is proportional to vessel speed.  
           [0009]    Electrical leads running from the ultrasonic transducer, Hall-effect device, and thermal sensor are coupled to appropriate interface circuitry and display devices on the vessel.  
           [0010]    Generally, the housing is rigidly attached to the vessel such that in the event the bottom of the vessel hits an obstacle, damage to the marine device is likely to occur.  
         SUMMARY OF THE INVENTION  
         [0011]    A rotatable mounting bracket is provided for a marine sensor device attached to a marine vessel and which enables the device to be freely pivoted about a pivot point by releasing a locking latch. The rotatable bracket couples a sensor housing to a fixed member on the marine vessel.  
           [0012]    In one embodiment, a speed sensor is contained in the housing; the speed sensor may be a rotatable magnetized paddlewheel disposed adjacent an electromagnetic sensor and extending aft of the vessel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0014]    [0014]FIG. 1 is partial perspective view of a first embodiment of the invention showing a transducer assembly  4  which attaches to a marine vessel (not shown).  
         [0015]    [0015]FIG. 2 is a partial plan top view of FIG. 1 in which the modular speed sensor sub-assembly  14  of FIG. 1 has been removed from the housing  10  and wherein the housing  10  is shown in a “latched” position in which the housing is latched onto fixed bracket  12 .  
         [0016]    [0016]FIG. 3A is a partial sectional side view along the lines B-B of FIG. 2.  
         [0017]    [0017]FIG. 3B is a partial side view of FIG. 1 showing the removable sub-assembly  14 .  
         [0018]    [0018]FIG. 4 is a partial plan top view as in FIG. 2 wherein the housing is “unlatched” from the fixed bracket  12 .  
         [0019]    [0019]FIG. 5A is a partial sectional side view along the lines C-C of FIG. 4.  
         [0020]    [0020]FIG. 5B is a side view of a cosmetic cover  90  of an alternate embodiment.  
         [0021]    [0021]FIG. 6 is a perspective view of the completed invention with certain internal items shown.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    A description of preferred embodiments of the invention follows.  
         [0023]    Referring to FIGS. 1-6, a transom mount transducer assembly  4  may be seen to comprise, in general, a housing  10 , a cover  70 , and a fixed bracket  12 . The housing comprises a rotatable bracket  30 , sensor housing  38 , and external mount  26 . The rotatable bracket  30  rotatably connects to the fixed bracket  12  which attaches by bolts  16  to a marine vessel (not shown). The fixed bracket comprises mounting slots  22  which enable the assembly to be adjustably mounted to the marine vessel (not shown) with bolts  16 .  
         [0024]    The sensor housing  38  is comprised of electromagnetically permeable material, such as polycarbonate. An ultrasonic transducer assembly  60  (FIG. 6) is centrally mounted within the walls of the housing  10 . The ultrasonic transducer assembly comprises a copper or other electrically conductive material forming an electromagnetic shield about a piezoelectric transducer. The piezoelectric transducer consists of a piezoelectric device which, upon being provided with an appropriate alternating electrical signal, produces a mechanical vibratory force which is transmitted into the water and, upon return of this signal, the transducer converts the mechanical vibratory signal into a corresponding electrical signal, which may be displayed on an appropriate meter provided on the vessel (not shown).  
         [0025]    A paddlewheel sub-assembly  14  or cosmetic cover  90  may be optionally attached to the external mount  26  of the housing  10 . As shown in FIG. 5B, the cosmetic cover  90  may be used in place of the paddlewheel sub-assembly  14  for users not interested in having a speed sensor function but still desirous of having a depth sounding capability.  
         [0026]    The paddlewheel sub-assembly  14  comprises a paddlewheel  8  rotatably mounted between a pair of struts  20  attached to a frame  24 .  
         [0027]    Preferably, an electromagnetic sensing (Hall-effect) device  18  (FIGS. 2,4) is mounted on the inner aft wall of sensor housing  10 . However, in other embodiments the Hall-effect device  18  may be mounted within the paddlewheel sub-assembly  14 .  
         [0028]    The paddlewheel  8  consists of a hub portion from which extends a plurality of paddles. The paddlewheel  8  is formed of amorphous magnetic material, such as barium ferrite. After formation of the paddlewheel  8 , the paddles may be electromagnetically polarized in a magnetic field, such that the polarity of the paddles at the tip alternates from north to south.  
         [0029]    As the paddles rotate about a shaft, the variation in electromagnetic field caused by the polarity changes, is sensed by the Hall-effect device  18  mounted on the interior aft wall to the sensor housing  10 . In operation, the paddlewheel  8  is adapted to be mounted on the transom of a vessel in a position such that the paddles pierce the surface of the water when the vessel is planing.  
         [0030]    As the paddles of the paddlewheel  8  rotate past the Hall-effect device  18 , an alternating voltage signal is generated. The frequency of the voltage signal is directly proportional to the rotational speed of the paddle-wheel and, therefore, to the velocity of the vessel.  
         [0031]    In accordance with the present invention, paddlewheel assembly  14  is adapted to be separably mounted onto sensor housing  10  for convenience of removal for replacement or cleaning purposes or where the end user does not require a speed sensor function. This separability is achieved by the interrelationship between the external mount  26  on the housing  10  and the locking tabs  28  on the struts  20  of the paddlewheel assembly  14 . Once assembly  14  is mounted, as shown by the dotted lines in FIG. 3B, screws  36  (FIG. 6) may be engaged to secure the sub-assembly in place.  
         [0032]    Oppositely disposed pivot holes  44  are formed, as by molding or drilling, the upper portion  46  of the rotatable bracket  30  of housing  10 , cover  70 , and fixed bracket  12 . Tightening screws  40  connect to each other through pivot holes  44  to provide for rotational motion about the axis A of FIG. 1.  
         [0033]    It should be noted that in the event the housing  10  is subjected to excessive forces, particularly in the rearward direction (for example, by striking an object in the water), the compressive forces formed by the tightening screws  40  together are adapted to be overcome before the plastic housing breaks in which case housing  10  is, thereby, enabled to rotate counterclockwise (as viewed in FIGS. 1-6), thereby releasing the assembly upward, for pivotal or rotational movement about the axis A.  
         [0034]    More importantly, referring now to FIG. 3A, it may be seen that housing  10  is more securely rotatably fastened to fixed bracket  12  (mounted on the vessel) by coupling a flexible leading edge member  32  of housing  10  to a lip  34  of the fixed bracket  12 .  
         [0035]    [0035]FIGS. 1 and 5A illustrates how housing  10  may be more readily disengaged from fixed bracket  12  by inserting a screwdriver or other suitable object into slot  50  to deflect the flexible leading edge member  32  downwardly to release the lip  34  of the fixed bracket  12 , thereby enabling the housing  10  to be freely rotated counterclockwise (as viewed in FIGS. 1-6) and released from the fixed bracket  12  for various reasons, such as inspection and cleaning or repair. This method of disengaging the housing allows a user to access the housing without having to exert the pivot release force necessary to pivot the housing when the vessel strikes an object under speed. Because the housing is made of plastic, many users are reluctant to use such force for fear of breaking the bracket.  
         [0036]    A cover  70  (FIGS. 1,6) may be affixed over the housing  10  to complete the assembly.  
         [0037]    While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.