Abstract:
An engine to transmission coupler includes an isolator that dampens, reduces or eliminates torque spikes and vibrations transmitted to the transmission. The isolator is located between the flywheel and a flywheel adaptor plate mounted to the flywheel. A universal joint assembly extends through central openings in the flywheel adaptor plate and isolator.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to engine to transmission couplers for drive trains of small motor vehicles such as riding lawn mowers, all terrain vehicles and utility vehicles. More specifically, the invention relates to engine to transmission couplers that help isolate and dampen torque spikes and vibrations between a crankshaft and transmission of such vehicles. 
   BACKGROUND OF THE INVENTION 
   Small motor vehicle drive trains may include a crankshaft, a flywheel mounted to the crankshaft, and a transmission. The transmission may be coupled to the crankshaft through one or more universal joints to allow for angular misalignment of the crankshaft with respect to the transmission, especially during vehicle operation. 
   Forces of firing pistons in an internal combustion engine may be transmitted to the crankshaft. The flywheel, by its inertia, helps reduce torque spikes and vibrations that may be transmitted to the transmission. However, there also is a need for an isolator in a coupling between the crankshaft and transmission to dampen, reduce or eliminate torque spikes and vibrations to the transmission and prevent damage to transmission components. 
   An isolator may be placed in series with one or more universal joints in a coupling between a crankshaft and transmission. The isolator may include elastomeric material such as rubber that may yield resiliently in response to torque spikes, vibrations and similar loads. 
   In small motor vehicles, such as riding lawn mowers, all terrain vehicles and utility vehicles, it may be desirable to reduce the coupling length between the crankshaft and transmission, and thereby help reduce the length, size and/or weight of the vehicle drive train. An engine to transmission coupler is needed that will allow for angular misalignment of the engine crankshaft relative to the transmission. A shortened engine to transmission coupler is needed with an isolator to dampen, reduce or eliminate torque spikes and vibrations to the transmission. 
   SUMMARY OF THE INVENTION 
   A shortened engine to transmission coupler is provided that includes an isolator to dampen, reduce, or eliminate torque spikes and vibrations to the transmission. The coupler will allow for angular misalignment of the engine crankshaft relative to the transmission. The coupler helps reduce the length, size and weight of drive trains for small motor vehicles such as riding lawn mowers, all terrain vehicles and utility vehicles. 
   A ring-shaped isolator is positioned between the flywheel and a flywheel adaptor plate. The flywheel adaptor plate is mounted to the flywheel, and at least part of the flywheel adaptor plate is spaced from the flywheel. For example, the flywheel adaptor plate may have a central hub spaced from the flywheel, and the isolator may be located and enclosed in the central hub. A universal joint assembly including one or more universal joints may extend through central openings in the isolator and the flywheel adaptor plate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a small motor vehicle engine, transmission, and engine to transmission coupler according to one embodiment of the invention. 
       FIG. 2  is a rear perspective view of a first embodiment of an engine to transmission coupler. 
       FIG. 3  is an exploded perspective view of the engine to transmission coupler of  FIG. 2 . 
       FIG. 4  is a front perspective view of a second embodiment of an engine to transmission coupler. 
       FIG. 5  is an exploded perspective view of the engine to transmission coupler of  FIG. 4 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In one embodiment of the invention, as shown in  FIG. 1 , a small motor vehicle drive train may include engine  101 , transmission  102 , and engine to transmission coupler  103 . For example, the engine may be an internal combustion engine having a crankshaft with a first generally longitudinal axis, and a flywheel mounted to the crankshaft. The transmission may have a second generally longitudinal axis that may be angularly misaligned from the first longitudinal axis upon assembly and/or during operation. The transmission may be connected to one or more axles and/or drive wheels. The engine to transmission coupler may include one or more universal joints to allow for angular misalignment between the engine crankshaft and transmission. 
     FIGS. 1 ,  2  and  3  show engine to transmission coupler  103  in a first embodiment having one universal joint. Flywheel adaptor plate  105  may be mounted to engine flywheel  130 . In one embodiment, the flywheel adaptor plate may be mounted to a flywheel by threaded fasteners  131  inserted through mounting holes  104  through outer rim  109  of the flywheel adaptor plate and corresponding mounting holes near the perimeter of the flywheel. 
   When the flywheel adaptor plate is mounted to the flywheel, the flywheel adaptor plate may have a first surface spaced from the flywheel. In one embodiment, the first surface spaced from the flywheel may be central hub  110 . Additionally, central opening  113  may extend through the central hub. In one embodiment, the flywheel adaptor plate may have a thickness of about 4.55 mm. 
   In one embodiment, the first surface of the flywheel adaptor plate that is spaced from the flywheel may be a dish-shaped or concave central hub. Isolator  117  may be positioned and enclosed within the dish-shaped or concave central hub, so that the isolator is between the flywheel adaptor plate and flywheel. The isolator may be a generally ring-shaped member preferably made from rubber, or including a rubber or other resilient and/or elastomeric component capable of yielding elastically sufficiently to dampen, reduce or eliminate high torque spikes and vibrations that might otherwise damage transmission components. 
   To connect the isolator to the flywheel adaptor plate, according to one embodiment, central opening  113  may have one or more inwardly extending lobes  116 . Threaded fasteners  114  may be inserted through mounting holes  115  in lobes  116 , through corresponding holes  121  from the first face  118  through to the second face  119  of the isolator, and tightened onto nuts  122 . In one embodiment, threaded fasteners connecting the isolator to the flywheel adaptor plate may be inserted into three of the six holes through the isolator. 
   In one embodiment, sleeves  123  may be positioned in holes  121  through the isolator. The sleeves may be bonded to the holes in the isolator. Threaded fasteners may be inserted through the sleeves. The sleeves may be the same length, or slightly longer or shorter than holes  121 , if desired. For example, the sleeves may be 35 mm in length and the holes may be 31.75 mm in length. 
   To connect the isolator to the transmission, according to one embodiment, universal joint assembly  124  may have a flange  127  at a first end thereof. Threaded fasteners  125  may be inserted through mounting holes  128  in flange  127 , through corresponding holes  121  in the isolator, and tightened onto nuts  126 . In one embodiment, threaded fasteners  125  connecting the isolator to the universal joint assembly may be inserted through three of the six holes through the isolator. 
   The first surface of the flywheel adaptor plate should be spaced from the flywheel sufficiently to provide adequate clearance for angular displacement of isolator  117  and flange  127 , both of which may be positioned between the flywheel adaptor plate and the flywheel. 
   For example, in the first embodiment, the height of the isolator H l  (i.e., measured from first face  118  to second face  119 ) together with the flange may be less than the internal height of the central hub H CH . Additionally, the outer diameter of the isolator OD l  and flange may be less than the internal diameter D CH  of the central hub. In one embodiment, the height of the isolator H l  may be about 31 mm, the outer diameter OD l  may be about 132 mm, and the inner diameter ID l  may be about 70 mm. 
   The universal joint assembly may include one or more universal joints that may be interconnected in a manner known to those skilled in the art. When the isolator is connected to flange  127 , universal joint assembly  124  may extend through central opening  120  in the isolator and central opening  113  in the flywheel adaptor plate. Flange  127  also may include apertures  129  for adequate clearance of threaded fasteners  114  and nuts  122 . 
   The isolator has a first face  118  and a second face  119 . The first face of the isolator, facing transmission  102  and universal joint assembly  124 , abuts and may be connected to the inside of the central hub of the flywheel adaptor plate. The second face of the isolator, facing engine  101  and the engine flywheel, abuts and is connected to flange  127  of the universal joint assembly. 
   In  FIGS. 4 and 5 , a second embodiment is shown in which engine to transmission coupler  203  may include two universal joints. Flywheel adaptor plate  205  may be mounted to an engine flywheel by threaded fasteners (not shown) through the perimeter of the flywheel and through mounting holes in rim  209 . Isolator  217  may be positioned between the flywheel adaptor plate and the flywheel. For example, the isolator may be enclosed within central hub  210  of the flywheel adaptor plate. 
   Isolator  217  may have a first face  218 , a second face  219 , a central opening  220 , and holes  221  from the first face to the second face. The first face of the isolator may abut and be connected to the flywheel adaptor plate by threaded fasteners  214  inserted through mounting holes in lobes  216 , holes  221  through the isolator, and tightened onto nuts  222 . The second face of the isolator may abut and be connected to universal joint assembly  224  by threaded fasteners  225  inserted through mounting holes  228  in flange  227 , holes  221  through the isolator, and tightened onto nuts  226 . Preferably, holes  221  may be equally divided into those receiving threaded fasteners connecting the isolator to the flywheel adaptor plate, and those receiving threaded fasteners connecting the isolator to the flange of the universal joint assembly. Optionally, sleeves  223  may be positioned in and/or bonded to holes  221 . 
   When a second embodiment of the engine to transmission coupler is assembled, universal joint assembly  224  may extend through central opening  220  in the isolator and central opening  213  in the flywheel adaptor plate. Flange  227  may include openings sufficient to provide adequate clearance for threaded fasteners  214  and nuts  222 . 
   The central hub may be dimensioned to provide sufficient clearance for angular displacement of isolator  217  and flange  227 , both of which are positioned between the flywheel adaptor plate and the flywheel. Thus, in the second embodiment, the combined height and diameter of the isolator and flange may be less than the internal height and diameter of the central hub. 
   In a third embodiment, a flywheel adaptor plate may be a generally ring-shaped flat surface that is spaced from the flywheel. In this embodiment, the flywheel adaptor plate may be attached to the flywheel by threaded fasteners and spacers. The isolator may be positioned between the generally ring-shaped flat flywheel adaptor plate and the flywheel, but not enclosed. 
   Isolators of the type used in the described embodiments are available from Lord Corporation of Cary, N.C. For example, model nos. LCR 400-800-060A and LCR 300-600-028A may be used in these embodiments. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.