Abstract:
A model vehicle, such as a model electric train, includes a force-isolating drive mechanism. The drive mechanism provides a mechanical linkage and speed reduction between an output shaft of a motor for a model locomotive and its drive wheels, via a gear train. The gear train includes a floating mechanism that permits the model locomotive drive wheels vertical freedom of movement, while still remaining mechanically linked to the gear train. The floating mechanism isolates the model locomotive from forces transmitted from the track bed through the drive wheels, thereby providing a more stable and vibration-free model performance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No. 60/575,591, filed May 28, 2004, which application is specifically incorporated herein, in its entirety, by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to electric-powered model vehicles, such as model trains, and more particularly, to an adaptive drive mechanism for a model train or other model vehicle. 
   2. Description of Related Art 
   Various model trains and vehicles are known in the art, which model an actual or imaginary train or vehicle at a reduced scale. In a typical model layout, a model train having an engine is provided. The model train engine includes an electrical motor that receives power from a voltage that is applied to model railway tracks. A transformer is used to apply the power to the tracks, while contacts (e.g., a roller) on the bottom of the train, or metallic wheels of the train, pick up the applied power for the train motor. In some model train layouts, the transformer controls the amplitude, and in a DC system, the polarity, of the voltage, thereby controlling the speed and direction of the train. In HO systems, the voltage is a DC voltage. In O-gauge systems, the track voltage is an AC voltage transformed by the transformer from a household line voltage provided by a standard wall socket, such 120 or 240 V, to a reduced AC voltage, such as 0-18 volts AC. 
   Model electric trains therefore include a drive train linking one or more pairs of powered drive wheels to an electric motor housed in a model locomotive. Many model locomotives make use of a direct gear drive, such as a spur gear set or other gear drive. Direct gear drives provide a direct mechanical link between the motor and the drive wheels, and are generally recognized as providing excellent responsiveness and low backlash for speed control and motion reversal. Properly designed gear drives are also reliable, have low maintenance requirements, and long service lives. These characteristics make gear drives prevalent in many model vehicles. 
   Notwithstanding their advantages, gear drive mechanisms may be subject to certain disadvantages. Conventional gear drives are used with a relatively rigid or stiff mechanical connection between the drive wheels and the motor. Consequently, displacement of the drive wheels from bumps or unevenness of a model track is transmitted to the model locomotive, which may visibly bounce up and down or sway side-to-side in a way that does not resemble a full-scale locomotive. Modern full-scale locomotives employ sophisticated drive trains and suspension systems, as well as being much more massive than reduced-scale model locomotives. Full-scale model locomotives therefore may exhibit a much smoother, stable response to vibration received from travel over the track bed, as compared to many prior-art model vehicles. Achieving a more realistic dynamic response in model vehicles is desirable, but only within certain economic constraints. For example, merely scaling down all the primary mechanical characteristics of actual locomotives, such as mass, moment of inertia, suspension and drive systems, is not economically feasible for model vehicles intended for consumer toy or hobbyist applications. 
   Accordingly, a need exists for a model train with a drive mechanism that overcomes these and other limitations of the prior art. 
   SUMMARY OF THE INVENTION 
   The invention provides a reduced-scale model vehicle with an adaptive drive mechanism for driving drive wheels of a model locomotive of the like. The drive mechanism transmits motive power through a direct gear drive, without sacrificing the ability to absorb bumps and other irregularities in a model track layout. A model locomotive equipped with the drive mechanism therefore reacts to the track bed in a way that more closely resembles, at a reduced scale, the performance of a full-scale locomotive. At the same time, the benefits of a gear drive, such as responsiveness, low backlash, reliability, and low maintenance, are preserved for the enjoyment of the model hobbyist. 
   In an embodiment of the invention, a gear drive mechanism provides a direct mechanical linkage to a model locomotive engine, while at the same time providing the drive wheels of the locomotive with a floating mechanism. The gear mechanism may be configured for translating speed and torque from the output shaft of the motor to the drive wheels of a model locomotive, in any suitable manner as known in the art. The floating mechanism permits the drive wheels to “float,” in the sense that the drive wheels are provided with freedom of movement relative to the drive mechanism, while still remaining in gear. Thus, when the drive wheels encounter a bump or other unevenness in the track, they are free to move independently of the gear train and of the locomotive. Forces from motion over the track are thereby at least partly isolated from the locomotive, which enjoys a more stable, vibration-free ride. This provides a more realistic effect and enjoyment to the model hobbyist. 
   In an embodiment of the invention, the gear drive and floating mechanism are provided in a “truck” assembly. The truck comprises a plurality of wheels, which in a full-scale locomotive are needed to bear the massive weight of the locomotive. A reduced-scale truck may be configured to resemble various types of full-scale locomotive trucks. For the convenience of the hobbyist, the model truck may comprise a modular unit that can readily be removed for maintenance, repair or for use with a compatible locomotive. 
   A more complete understanding of the model vehicle with an adaptive drive mechanism will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings which will first be described briefly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view of a model vehicle layout in accordance with the present invention. 
       FIG. 2  is a cross-sectional view showing an exemplary embodiment of a gear drive mechanism in accordance with the present invention, assembled to a model locomotive. 
       FIG. 3  is a schematic perspective diagram showing a portion of an exemplary drive mechanism in accordance with the present invention. 
       FIG. 4  is a cross-sectional view showing an exemplary embodiment of a gear drive mechanism in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The present invention provides a model locomotive with a force-isolating drive train, that overcomes the limitations of the prior art. In the detailed description that follows, like element numerals are used to indicate like elements appearing in one or more of the figures. 
     FIG. 1  shows a first exemplary embodiment of a model vehicle system  10 . Model vehicle system  10  includes a track  12 , a power supply  14 , and a model vehicle  16 . In an exemplary embodiment, track  12  may comprise a three rail track that is configured for travel thereon by model vehicle  16 . Power source  14  provides power to track  12  by way of connectors  20  and  22 . A power terminal of the power supply may be connected to the center or third rail of track  12  via connector  22 , and the neutral terminal may be connected to at least one of the two outer rails of track  12  via connector  20 . A locomotive of model vehicle  16  may be configured with contacts on the bottom thereof, or an arrangement of electrically conductive metallic wheels, to pick up the applied power and supply it to an electric motor of the locomotive. In the alternative, or in addition, train cars other than locomotive may be used to pick up the power from track  12 . The arrangement described above is for exemplary purposes only and is not meant to be limiting in nature. 
   Power source  14  may comprise a conventional AC or DC transformer, depending on the requirements of railroad layout  10 , and in particular, model vehicle  16 . Additionally, power source  14  may provide a fixed output, a variable output, or both. In an exemplary embodiment, railroad layout  10  comprises an O-gauge layout and power source  14  comprises an AC transformer which transforms typical AC line voltage (e.g., 120 VAC) to a reduced level (e.g., 0-18 VAC for a conventional O-gauge variable output model train transformer) and supplies the same to track  12 . 
   With reference to  FIG. 2 , a portion of model vehicle  16  is illustrated. Model vehicle  16  includes a main body  22 , a gear set frame  24  (also called truck  24 ), a first drive axle  26 , a second drive axle  28 , a gear set  30 , a first interior space  32 , and a second interior space  34  in frame  24 . Truck  24  may be coupled to main body  22  of model vehicle  16 . While only one truck is illustrated and discussed herein, model vehicle  16  may include more than one truck like truck  24  coupled thereto. In an exemplary embodiment, truck  24  is pivotally coupled to main body  22 , such as via a ball or pin joint. 
   With continued reference to  FIGS. 2-4 , first and second drive axles  26 ,  28  may be connected to a respective first and second drive wheels  36 , and  362 . Respective second wheels  38   1 ,  38   2  may likewise be connected to the drive axles on an opposite side of truck  24 . Each drive axle may be associated with a respective output gear  40   1 ,  40   2  operative to drive each respective drive axle. Each drive axle  26 ,  28  may be aligned with a respective horizontal longitudinal axis  42   1 ,  42   2 . In the illustrated embodiment, first and second drive axles  26 ,  28  are each configured to be mounted to truck frame  24 . It should be noted that while the above described arrangement includes a pair of drive axles, this embodiment is provided for exemplary purposes only and is not meant to be limiting in nature. Vehicles having more or less drive axles and associated output gears and wheels remain within the spirit and scope of the present invention. 
   Gear set  30 , also called a gear train, may be mounted to frame  24 , disposed between and engaged with first and second drive axles  26 ,  28 . Gear set  30  may comprise one or more gears, such as, for example, five gears  30   1 ,  30   2 ,  30   3 ,  30   4 ,  30   5 , each of which is in mesh with each adjacent gear of gear set  30 , and each of which has its own respective gear axle  44   1 ,  44   2 ,  44   3 ,  44   4 ,  44   5 , coupled to frame  24 . Two gears of gear set  30 , gears  30   1  and  30   5 , for example, are also in mesh with output gears  40   1 ,  40   2 , respectively, and accordingly, gear set  30  is operative to assist in the driving of output gears  40   1 ,  40   2 , and therefore, model vehicle  16 . As shown in  FIG. 4 , one of gear axles  44   1 ,  44   2 ,  44   3 ,  44   4 ,  44   5 , such as gear axle  44   4  for example, may be coupled to a second gear  46  that is configured and arranged to be in mesh with and driven by an input gear  48 . Input gear  48  may comprise a vertically-oriented worm gear, or other suitable gear, coupled to an output shaft  50  of a drive motor  52  that powers and causes model vehicle  16  to move. 
   When model vehicle  16  is commanded to move, motor  52  turns output shaft  50 . Worm gear  48  is attached to shaft  50  and rotates in either a clockwise or counterclockwise direction. This rotation is transferred to gear  46 , which then causes axle  44   4  and corresponding gear  304  to rotate, which then, through the arrangement of gears in gear set  30 , causes output gears  40   1 ,  40   2 , and therefore, drive axles  26 ,  28  and wheels  36   1 ,  36   2 ,  38   1 ,  38   2  to rotate, thereby causing model vehicle  16  to move. It should be noted, however, that this arrangement and configuration are provided for exemplary purposes only and is not meant to be limiting in nature. In alternate embodiments, gear  46  may be associated with any of gear axles  44   1 ,  44   2 ,  44   3 ,  44   4 ,  44   5 , or one of the gears of gear set  30  may be driven directly by output shaft  50 . Similarly, one of output gears  40   1 ,  40   2  may be driven by output shaft  50  with the gears of gear set  30  transferring the rotation of the driven output gear to the other output gear. 
   An interior space  32  may be provided in or adjacent to frame  24 , in which one of the output gears  40   1  may be disposed. Referring to  FIGS. 2 and 3 , space  32  and output gear  40   1  may be disposed on a first side  54  of model vehicle  16 , proximal to drive wheel  36   1 . Space  32  should permit a range of vertical movement of output gear  40   1 . In the illustrated embodiment, space  32  is oblong shaped. Any other suitable shape may also be used. A second space  34  may also be provided in or adjacent to frame  24 , in which a second moveable output gear  40   2  may be disposed. Space  34  likewise provides a range of vertical motion for output gear  40   2 . 
   First drive axle  26  is disposed at least partly within space  32 , while second drive axle  28  may be disposed at least partly within space  34 . In this arrangement, and with particular reference to  FIG. 3 , first drive axle  26  and second drive axle  28  may each be pivotally coupled by way of a coupling member  58  to axle  44  of an adjacent gear of gear set  30 . Members  58  comprise exemplary moveable links or floating mechanisms by which a portion of axles  26 ,  28  proximal to output gears  40   1 ,  40   2  may be provided with a range of vertical movement. At the same time, a portion of axles  26 ,  28  distal to output gears  40   1 ,  40   2  may be substantially fixed, but with a degree of elasticity that permits vertical movement of the moveable drive wheels  36   1 ,  36   2 . That is, drive wheels  38   1 ,  38   2  may be substantially fixed. In this arrangement, axles  26 ,  28  or frame  24  act as elastic elements, in essence providing an independent, spring loaded suspension to the drive wheels  36   1 ,  36   2  on one side  54  of the locomotive  16 . It is believed sufficient, for the purpose of providing improved stability to a model locomotive, to provide the depicted elastic suspension for drive wheels on one side of truck  24 . Such a system may be described as a partly independent or quasi-independent suspension. In the alternative, wheels  38   1 ,  38   2  may also be provided with an elastic suspension, permitting vertical movement on a second side  56 . Such a fully-independent suspension, however, would likely entail additional complexity and cost, which may make it less desirable for many model vehicle applications. 
   In the illustrated embodiment, drive axle  26  is pivotally coupled to fixed gear axle  44   1  of gear  30   1 , while drive axle  28  is pivotally coupled to fixed gear axle  44   5  of gear  30   5 . It should be noted, however, that illustrated mounting of drive axles  26 ,  28  to adjacent gear axles, while believed to be advantageous, is provided for exemplary purposes only. Drive axles  26 ,  28  may be movable coupled to any portion of track frame  24  that is similarly situated to gear axles  44 , and that will allow for the functionality described herein. More complex suspensions may be used, but are likely to entail considerably greater cost. For example, a spring-loaded wishbone suspension with universal joints, such as used for automobiles, may be used to permit vertical motion while transmitting torque to the drive wheels. Such an arrangement would likely be much more complex and expensive to implement. On the other hand, various simplified suspensions may be devised that may permit vertical movement of the drive wheels at an acceptable cost, and the invention is not limited to a pivoting coupling as shown in the exemplary embodiment. 
   In accordance with the illustrated embodiment, when model vehicle  16  traverses an uneven portion of track, axles  26 ,  28  pivot about adjacent gear axles  44 , thereby isolating the locomotive from vertical forces and absorbing energy from the vertical force input. While providing a partly independent suspension, truck  24  and gear train  30  also function as a transmission for transmitting torque to the drive wheels. A cost-effective force-isolating drive mechanism for stabilizing a model vehicle is thus provided, which retains all of the advantages of conventional gear drives. 
   Having thus described a preferred embodiment of a model vehicle with an force-isolating drive mechanism, it should be apparent to those skilled in the art that certain advantages of the within system have been achieved. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. For example, a particular drive mechanism has been illustrated, but it should be apparent that the inventive concepts described above would be equally applicable to other mechanisms, for example belt drives or chain drives, arranged according to the spirit and scope of the invention. The invention is defined by the following claims.