Abstract:
A drop-in-module consisting of a mass produced engine coupled to a drive system by use of a common mid-section mounting platform. The module provides a single assembly that can be easily installed and removed from a vessel. The drive system is based on motors using a vertical crankshaft orientation joined to a 90 degree gearbox with a forward-neutral-reverse transmission. A speed sensitive clutch arrangement separates the engine from the gearbox. The heat created by the air cooled versions of these engines can be vented into the propeller wash through a passage formed in the mounting plate.

Description:
PRIORITY APPLICATION 
     This Application is based upon Provisional Patent Application No. 60/889,596 filed Feb. 13, 2007 and related to application Ser. No. 12/030,029 filed simultaneously with the instant application on Feb. 12, 2008, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention is directed to the field of watercraft, and in particular to a propulsion system that installs into the vessel as a single complete module, the propulsion system having an RPM sensitive clutch positioned between the engine and the propeller and integrated into the mounting plate, and a means for ducting engine cooling air out of the engine box. 
     BACKGROUND OF THE INVENTION 
     The cost of outboard motors has increased at an alarming rate. The average yearly price increase over the last ten years has been 6.5% with an 11.5% increase attributable to 2005 alone. An outboard motor can account for over 60% of the cost of a boat/motor/trailer package. This high cost has become a serious hindrance to attracting new customers to the recreational activity of boating. 
     It is well known in the field of marine propulsion that it is advantageous to use engines designed and manufactured for use in other, higher volume industries. For example, gasoline engines from the automotive industry are the predominant power source to the marine industry for small to mid-size vessels that rely upon stern drives and inboards. The primary power source for larger vessels is diesel engines adapted for use from the trucking industry. 
     While engines from the automotive and trucking industry provide cost advantages over custom built engines, such as outboard motors, the adaptation still requires the use of customized cooling systems and other modifications that can be most expensive. 
     Any time an engine designed for another industry is adapted for use in the Marine environment; there are design barriers which must be overcome. For instance, automobile engines corrode when exposed to salt water found in oceans. So closed cooling systems are often added to protect the iron engine blocks. 
     Further, since engines designed for other industries are not anticipated to be installed in a boat, one must find a way to make such installation simple and cost effective. 
     The lowest cost engines in the world, on a $/hp basis, come from the L&amp;G (Lawn and Garden) industry. Unfortunately these engines are not designed to be used in boats. 
     The idle rpm of L&amp;G engines are unacceptable for a marine application, often approaching 1,800 rpm when a conventional outboard motor would be expected to idle at less than 1,000 rpm. 
     Finally, L&amp;G engines that are the most cost effective are air cooled. So one must find ways to bring cool air into the lawn and garden engine and dispose of that hot air in a safe and cost effective manner. 
     U.S. Pat. No. 3,164,122 by Fageol discloses a transom mounted propulsion assembly. Fageol does not employ commonly available motors or rudder systems. 
     U.S. Pat. No. 2,976,836 by Fageol discloses a vertical shaft inboard marine power plant wherein the drive assembly is in combination with the rudder. The engine and drive assembly are secured by a ball and socket assembly wherein the propeller is moved to cause directional steering of the vessel. 
     U.S. Pat. No. 4,907,994 by Jones discloses a drive system for a vessel wherein the propeller is moved to cause directional steering of the vessel. 
     U.S. Pat. No. 5,108,325 by Livingston discloses a drive system for a vessel wherein the propeller is moved to cause directional steering of the vessel, and further allows elevated movement of the propeller. 
     U.S. Pat. No. 5,326,294 by Schoel discloses a stern drive system for a vessel wherein the propeller and rudder are moved to cause directional steering of the vessel. 
     One of the problems with the prior art is the movement of the propeller induces inefficiencies in operation by changing the flow characteristics as well as inducing unpredictable flow currents in relation to the hull. 
     Thus, what is needed in the marine industry is a low cost mass produced engine from the lawn and garden industry that provides the performance, installation ease, idle quality and reliability of an outboard motor, without the associated specialty motor expense. 
     SUMMARY OF THE INVENTION 
     The instant invention is a drop-in-module or “D.I.M.” consisting of a conventional vertical crankshaft mass produced motor coupled to a drive system by an interfacing mounting plate. The assembly provides a single module that can be placed in watercraft with minimal installation expense. The preferred power source for this module is an air cooled vertical crankshaft engine from the lawn and garden industry although water cooled engines could also be used. Such engines are mass produced in extremely high volumes and so have a very low cost. 
     An objective of the invention is to provide an engine that utilizes a vertical crankshaft orientation joined to a 90 degree gearbox with a forward-neutral-reverse transmission. The components are rigidly bolted together as a single assembly and available for placement into a generally horizontal opening in a vented tunnel system although this surface can be inclined as well. The engine may be bolted to the mounting plate rigidly or if desired, rubber isolators can be placed between the engine and the mounting plate to reduce vibration and noise. 
     Still another objective of the instant invention is to teach the use of air cooled engines from the lawn and garden industry to avoid the expensive cooling systems, wherein engine heat is drawn into the vented tunnel for mixing with prop wash. 
     Another objective of the invention is to teach the use of clutches to permit the use of engines with high idle rpms. Still another objective of the invention is to teach the use of stacking inexpensive centrifugal clutches together in parallel. 
     Yet still another objective of the invention is to employ a wet disk located inside the gear case on the vertical drive shaft. At low speeds the wet disk clutch can tolerate light slip loads indefinitely and the heat can be dissipated in the tunnel as it is almost fully wetted at the slip speeds. 
     Still another objective of the invention is to provide a drop in module for use in a tunnel created for surface piercing propellers. The rigid assembly is protected from impact by the tunnel shape effectively providing a zero draft vessel. 
     Still another objective of this invention is to teach ways to extract and remove hot air from the cooling fan of an air cooled engine and safely dispose of it in a vessel environment. 
     Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of the drop in module; 
         FIG. 2  is a perspective view of the drop in module; 
         FIG. 3  is a perspective view of a watercraft with the drop in module in the vessel&#39;s hull; 
         FIG. 4  is a top view of the watercraft&#39;s hull without the module installed; 
         FIG. 5  is a cross sectional side view of the propulsion module mounted within the vessel showing the engine hot air exhaust when the vessel is on plane; 
         FIG. 6  is a cross sectional side view of the propulsion module mounted within the vessel showing the engine hot air exhaust when the vessel is as rest with the engine in idle; 
         FIG. 7  is a top view of the module mounted within the vessel with the engine box cover removed; 
         FIG. 8  is a top view of the mounting plate within the vessel showing a plurality of hot air ducts located thereon; 
         FIG. 9  is a sectional view of the module showing the engine, the mounting plate, the clutches and the propeller casing; 
         FIGS. 10A ,  10 B,  10 C and  10 D are prospective views of alternate embodiments of the slip clutches; 
         FIG. 11  is a pictorial view of the drop in module within a vessel that has a tunnel extending the length of the vessel; and 
         FIG. 12  is a pictorial view of a larger vessel with the drop in module placed beneath an enclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment is to use vertical crankshaft engines from the Lawn and Garden industry which are considerably less expensive than the same horsepower horizontal crankshaft orientation engines. The engine is coupled to a fixed gear box. Unlike outboards the gear box does not rotate for purposes of steering. Further, the fixed gear box eliminates the need for the complex gimbal used in inboard/outboards. In the instant invention, conventional rudders are employed. Rudders are proven reliable and can be mounted independently to the hull or in combination with the engine mounting plate. 
       FIGS. 1 through 3  depict a general overview of the drop in module employing the air cooled engine ( 10 ) having a vertical shaft for securement to a mid-section mounting base ( 12 ). The mid-section mounting base operates as a securement platform with attachment fasteners to secure the engine and gear case ( 14 ) into a single assembly. The single assembly ( 16 ) can then be dropped in the vessel as a fully assembly module requiring connections only for the controls, fuel and electrical. The fasteners and seal, not shown, allow a fully tested assembly to be secured to a vessel hull with minimal effort. The result is a module that can be easily removed for repair or replacement. In addition, the use of a conventional rudder assembly ( 18 ) can be secured to the mid-section mounting plate and a conventional steering system or means, further simplifying the installation. This assembly ( 16 ) provides a bolt-on propulsion and steering system for a watercraft. 
       FIG. 4  depicts a vessel ( 24 ) having a full side wall tunnel ( 26 ) with an opening ( 28 ) available for securement of the drop in module assembly ( 16 ). The module ( 16 ) is bolted in place through use of the fastening holes. Once installed, the controls can be supplied for operation of the engine, gear case, and rudders. The electrical is attached and fuel lines thereby facilitating installation. It should be noted that the use of the tunnel allows the propeller ( 20 ) and gear case ( 14 ) to be located above the keel ( 22 ) of the vessel to prevent damage from impact. Further, the use of a tunnel has been found most beneficial when used with surface piercing propellers. Surface piercing propellers obtain optimum efficiency when operated under a vented condition wherein air is drawn into the tunnel. This has a unique effect of removing pressure from the roof of the tunnel thereby diminishing the possibility of a pressure induced lead around the mounting base. The propeller also provides a propeller fluid flow which in turn moves the watercraft forward. 
     The use of an internal combustion engine necessitates cooling due to engine inefficiencies. The use of an air cooled engine is properly cooled by ventilation of the engine, the heated air must be then drawn away from the engine. In the preferred embodiment, the hot engine air is drawn into the vented tunnel ( 26 ), as shown in pictorial of  FIG. 5 ; with air exiting through the primary air feed holes in the side wall of the tunnel  26 . 
     The tunnel shape for surface piercing propellers is disclosed in U.S. Pat. Nos. 4,689,026; 6,045,420; 6,193,573; and 6,213,824, all of which are incorporated herein by reference. Air drawn from around the engine exits the back of the boat with the prop wash. As shown in  FIGS. 5 ,  6 ,  7  and  8 , hot air from around the engine is drawn into hot air ducts  32  formed as a component of the mounting plate  12 . The hot air duct has an inlet in an area adjacent the engine and an outlet that communicates with a passageway  35 . Passageway  35  has a first opening  36  on the stern of the vessel and a second opening  38  into tunnel  26  at a location forward of gear case  14 . 
     As shown in  FIG. 5 , when the vessel is on plane with wide open throttle, air is drawn in from the first opening  36  on the stern as well as the inlet of the hot air duct  32  into passageway  35 . The combined flows are then induced to flow out of the second opening  38  in passageway  35  and into the tunnel  26  at a location ahead of the gear case  14 . 
       FIG. 6  is a view of the hot air flow when the vessel is at rest and the engine is idling. In this mode of operation the hot air from around the engine enters hot air duct  32  and passes into passageway  35 . This forms a venting means to cool the engine. As a result of the second opening  38  being filled with water, the hot air entering passageway  35  exits the vessel through first opening  36  and out the stern of the vessel. 
     The use of an air cooled engine requires that a high volume of hot air be managed. In one embodiment the engine can be left completely uncovered, like a riding lawn mower without the hood installed, but is unsightly for most installations. Covering the engine with an insulated box requires cold air to be drawn into the engine compartment and expelled. The expelled air is ducted from inside the box (around the engine) through a passage formed in the mounting plate that secures the engine and gear case to the vessel and into the air baffle system of the tunnel. Since the tunnel requires large amounts of air to properly ventilate the surface piercing propeller, the tunnel can be used to pull the hot air out of the engine box. The tunnel will cool the hot gases so they can be safely discarded and by mixing the gases with the water from the propeller any noise coming out of the engine box with the hot gases will be muffled and sound levels reduced. While this method of hot air extraction works well once the vessel is moving forward with sufficient speed to ventilate the tunnel this method does not work when the vessel is at rest and idling. Under this condition, hot air must be given a path to exit the engine box and escape into the air inlet passage above the static water line of the vessel and out the transom as shown in  FIG. 6 . 
       FIG. 7  shows a top view perspective of the installed engine with an engine cover box removed for clarity. A single hot air duct  32  is shown on mounting plate  12 .  FIG. 8  shows an alternative embodiment with two hot air ducts  32  on mounting plate  12 . 
       FIG. 9  illustrates the engine ( 10 ) bolted to the gear house ( 14 ) with mid-section mounting plate ( 12 ). A centrifugal and/or electric and/or wet disk clutch ( 50 ) isolates the engine from the propeller ( 32 ). A dog clutch ( 52 ) enacts for neutral or reverse propeller rotation. 
     Lawn and Garden engines have idle speeds (defined as the lower engine rpm that the engine will continue to run with some load on it), in the range of 1,400-2,000 rpm. Conventional outboards have idle speeds between 600 and 800 rpm or half to one-third of those found in Lawn and Garden type engines. In addition, the maximum operating speeds are routinely governed at 3,600 rpm whereas Outboard engines are in the range of 5,000 or 6,500 rpm. The ratio of maximum engine speed to minimum engine speed is a critical factor in determining how slow the boat will idle. Outboards idle at speeds from 2-3 mph while the use of a L&amp;G engine in this same application produces minimum idle speeds of 6-7 mph, far in excess of what is required for trolling and too fast for safe docking, especially by a novice boater. 
     The instant invention places another clutch, a clutch that can slip indefinitely at low levels of torque, between the engine and the dog clutch in the gear case. This clutch&#39;s purpose is two fold. First to disengage the engine from the propeller so that even it the dog clutch in the gear case is in gear (forward or reverse) the engine can idle at any idle speed and the boat does not move and second, to lock up at some point and transfer the full power of the engine to the propeller. As engine rpm is increased we begin to slowly increase propeller rpm. At a critical and predetermined boat speed or engine load, the clutch will lock up and engine speed and propeller speed will then be directly related in a ratio determined by the ratio in the gear case. 
     The problem is that very few clutches are able to slip indefinitely. Most, like centrifugal clutches, become hot when they slip and so they are not designed to slip for a long time. Electric clutches have the same problem; they will overheat if they slip for too long. 
     It has been determined that in order to overcome this design problem cost effectively the preferred embodiment is a stack of low cost centrifugal clutches normally found in use on Go-carts and other small vehicles. By stacking multiple low cost clutches one overcomes the overheating problem by having excess capacity in the clutching system. 
     In another embodiment, a hybrid clutch is employed. In this embodiment there are two clutches in parallel, one electric clutch and one centrifugal. Initially the centrifugal clutch operates to allow the engine to idle at any speed and not turn the prop at all. Once engine rpm is increased the centrifugal clutch begins to engage. As engine load (throttle) is increased the propeller turns faster and the clutch slips less. At some predetermined load (throttle opening) the electric clutch is switched on and the centrifugal clutch is taken out of the loop. This stops the centrifugal clutch from overheating. 
       FIG. 10   b  shows an embodiment of clutch  50  wherein the clutch includes a centrifugal clutch as well as an electromagnetic clutch. The motor drive shaft is connected to clutch  50  input shaft  152 . Clutch input shaft  152  includes friction shoes  151  mounted thereon. Friction shoes  151  are mounted to allow radial motion of shoes so as to contact the inner surface of outer hub  153  when sufficient centrifugal acceleration is generated due to the rotation speed of the motor drive shaft. Within a predetermined range of motor RPM the shoes  151  will intermittently contact the inner surface of the outer hub  153  and transmit rotation to the clutch output shaft  154  on outer hub  153 . Clutch input shaft  152  includes an electro mechanical clutch coil  155 . Outer hub  153  contains armature elements that will be selectively actuated. At a predetermined RPM the armature will be actuated thereby causing the drive shaft  152  to engage the inner surface of hub  153  via the clutching elements to lock against the inner surface of hub  153  and provide 1:1 rotational velocity of the input shaft  152  to the output shaft  154 . 
     In another embodiment, an increase to the clutch capacity is made by stacking multiple low cost high volume metallic shoe clutches together in parallel. In this embodiment, high capacity is obtained but because the clutch shoe material is less sensitive to heat.  FIG. 10   a  shows this embodiment of clutch  50 . The motor drive shaft is connected to clutch  50  input shaft  52 . Clutch input shaft  52  includes friction shoes  51  mounted thereon. Friction shoes  51  are mounted to allow radial motion of shoes so as to contact the inner surface of outer hub  53  when sufficient centrifugal acceleration is generated due to the rotation speed of the motor drive shaft. Within a predetermined range of motor RPM the shoes  51  will intermittently contact the inner surface of the outer hub  53  and transmit rotation to the clutch output shaft  54  on outer hub  53 . Under sufficient motor RPM, the centrifugal acceleration will be high enough to cause the shoes  51  to lock against the inner surface of hub  53  and provide 1:1 rotational velocity of the input shaft  52  to the output shaft  54 . While this embodiment as illustrated shows two stacks of four shoes, more shoes  51  could be used if the application requires. 
     In still another embodiment, a wet disk is located inside the gear case on the vertical drive shaft. Provided it can be cooled, the wet disk clutch can tolerate light slip loads indefinitely. At low speeds, the tunnel is almost fully wetted. This means that the clutch plates are surrounded by cooling water. water. As the clutch slips the heat is taken away by the water. This electro mechanical multi-disk wet or dry clutch is illustrated in  FIG. 10C . In this embodiment clutch  50  includes an electro magnetic coil  255  which is rotatably mounted on clutch input shaft  252 . The electro magnetic coil is selectively energized at a predetermined RPM of the clutch input shaft  252 . When voltage/current is applied to the electro magnetic coil  255  the coil produces magnetic lines of flux. This flux is then transferred through a small air gap between the field and a rotor  256 . The rotor portion  256  of the clutch becomes magnetized and sets up a magnetic loop, which attracts both the armature  257  and the friction disks  258 . The attraction of the armature compresses or squeezes the friction disks  258 , transferring the torque from the inner driver  252  to the outer disks  259 . 
       FIG. 10D  shows an alternate configuration of the electromagnetic clutch shown in  FIG. 10C . In this arrangement the clutch  50  includes an electro magnetic coil  355  which is rotatably mounted on clutch input shaft  352 . The electro magnetic coil is selectively energized at a predetermined RPM of the clutch input shaft  352 . When voltage/current is applied to the electro magnetic coil  355  the coil produces magnetic lines of flux. This flux is then transferred through a small air gap between the field and a rotor  356 . The rotor portion  356  of the clutch becomes magnetized and sets up a magnetic loop, which attracts both the armature  357  and the friction disks  358 . The attraction of the armature  357  compresses or squeezes the friction disks  358 , transferring the torque from the inner driver  352  to the rotor  356  and then to an annular plate which has a central aperture operatively connected to the clutch output shaft  354 . 
       FIG. 11  depicts a vessel ( 120 ) having a tunnel ( 122 ) extending the length of the vessel with controls ( 130 ) centrally located before the drop in module.  FIG. 12  depicts a larger vessel ( 100 ) with a drop in module placed beneath an enclosure ( 102 ). 
     The drop in module is most beneficial when placed in a tunnel such as those created for surface piercing propeller. The rigid assembly is protected from impact by the tunnel shape effectively providing a zero draft vessel. 
     It is to be understood that while I have illustrated and described certain forms of my invention, it is not to be limited to the specific forms or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.