Abstract:
A smoke production system for a model locomotive capable of accurately simulating the exhaust characteristics of an actual locomotive. The present invention accomplishes this by monitoring the rotation to the flywheel of the electric motor used to drive the drive wheels of the model locomotive. Various devices may be used to monitor the rotation of the flywheel. For example, a magnet is employed on the flywheel and a magnetically-reactive element such as a reed switch or Hall effect sensor is positioned adjacent to the flywheel. Alternatively, an opticoupler or cam may be used to track the rotations of the flywheel. A controller counts the rotations of the flywheel and actuates a smoke production device to emit smoke four discrete times for every rotation of the model locomotive&#39;s drive wheel.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   Not Applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable 
   MICROFICHE APPENDIX 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to the field of model trains. More specifically, the present invention comprises a smoke production system for a model locomotive. 
   2. Description of the Related Art 
   Model train hobbyists spend a great deal of time and effort in constructing model train systems which accurately simulate reality. For example, many hobbyists enjoy building railroad sets which recreate the environment and scenery of popular railways. Likewise, many hobbyists purchase or develop elaborate controllers or soundcards for replicating traditional sounds heard around a railway including whistles, steam chuffs, and brakes. Model locomotives and rail cars are also recreated in exacting detail. 
   A lesser amount of attention has been directed towards simulating the appearance of steam emitted from an operating locomotive. Actual steam-powered locomotives use steam pressure to drive reciprocating pistons. The reciprocating pistons turn drive wheels on the railroad track to propel the locomotive forward or rearward on the track. The reciprocating pistons are attached to the drive wheels through connecting rods and linkages. Those that are familiar with the operation of steam locomotives know that four discrete exhaust pulses are emitted from the locomotive for every revolution of the drive wheel. Prior art steam exhaust simulation devices do a very poor job at replicating this feature. As such, it would be beneficial to provide a smoke production system for a model locomotive capable of accurately simulating the exhaust characteristics of an actual locomotive. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is a smoke production system for a model locomotive capable of accurately simulating the exhaust characteristics of an actual locomotive. The present invention accomplishes this by monitoring the rotation to the flywheel of the electric motor used to drive the drive wheels of the model locomotive. Various devices may be used to monitor the rotation of the flywheel. In the preferred embodiment, a magnet is employed on the flywheel and a magnetically-reactive element such as a reed switch or Hall effect sensor is positioned adjacent to the flywheel. Alternatively, an opticoupler or cam may be used to track the rotations of the flywheel. A controller counts the rotations of the flywheel and actuates a smoke production device to emit smoke four discrete times for every rotation of the model locomotive&#39;s drive wheel. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a perspective view, illustrating the present invention. 
       FIG. 2  is a plan view, illustrating components of the present invention. 
       FIG. 3A  is a detail view, illustrating components of the present invention. 
       FIG. 3B  is a detail view, illustrating components of the present invention. 
       FIG. 4A  is a detail view, illustrating a smoke production unit. 
       FIG. 4B  is a detail view, illustrating a smoke production unit. 
       FIG. 5  is a detail view, illustrating components of the present invention. 
       FIG. 6A  is a detail view, illustrating components of the present invention. 
       FIG. 6B  is a detail view, illustrating components of the present invention. 
       FIG. 7  is a schematic, illustrating operation of the present invention. 
       FIG. 8  is a schematic, illustrating operation of the present invention. 
   

   
     
       
             
           
             
             
             
             
           
         
             
                 
             
             
               REFERENCE NUMERALS IN THE DRAWINGS 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               10 
               model locomotive 
               12 
               motor 
             
             
               14 
               power transmission unit 
               16 
               worm gear 
             
             
               18 
               worm gear 
               20 
               spur gear 
             
             
               22 
               spur gear 
               24 
               smoke production device 
             
             
               26 
               conductor 
               28 
               drive shaft 
             
             
               30 
               power shaft 
               32 
               universal coupling joint 
             
             
               34 
               universal coupling joint 
               36 
               transmission 
             
             
               38 
               flywheel 
               40 
               magnet 
             
             
               42 
               reed switch 
               44 
               fixed contact 
             
             
               46 
               movable contact 
               48 
               heating element 
             
             
               50 
               smoking substance 
               52 
               fan motor 
             
             
               54 
               fan 
               56 
               stepper motor 
             
             
               58 
               shutter valve 
               60 
               smoke stack 
             
             
               62 
               smoke 
               64 
               drive wheel 
             
             
               66 
               support structure 
               68 
               reflective surface 
             
             
               70 
               nonreflective strips 
               72 
               light source 
             
             
               74 
               sensor 
               76 
               conductor 
             
             
               78 
               cam 
               80 
               switch 
             
             
               82 
               conductor 
               84 
               controller 
             
             
               86 
               comparator 
               88 
               reset command 
             
             
               90 
               power command 
               92 
               counter 
             
             
                 
             
           
        
       
     
   
   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention, a smoke production system for a model locomotive, is illustrated in  FIG. 1 . Model locomotive  10  includes motor  12 . Motor  12  is a DC motor which is powered by a voltage supplied to the model railroad track by a power unit. The speed of motor  12  may be adjusted by changing the track voltage. The power shaft of motor  12  supplies mechanical power to power transmission unit  14 . Power transmission unit  14  transfers the mechanical power to worm gears  16  and  18  which drive spur gears  22  and  20 , respectively. Spur gear  22  turns drive wheel  64  which propels model locomotive  10  forward or rearward along the railroad track. Power transmission unit  14 , worm gear  16 , and spur gear  22 , collectively act as a gear reduction to motor  12 . The standard gear reduction for model locomotives is 22:1. In other words, drive wheel  64  rotates one time for every 22 rotations of motor  12 . The direction of travel typically depends on the polarity of the track voltage. In most applications, the direction of travel may be reversed by reversing the polarity of the track voltage. 
   Model locomotive  10  also has smoke production device  24  for producing a “smoke effect.” Smoke production device  24  is electrically connected to a controller (not illustrated here) and a sensor attached to power transmission unit  14  by conductor  26 . It should be appreciated that these components may be provided to hobbyists independently of model locomotive  10  and sold as an “aftermarket” accessory. 
   Turning to  FIG. 2 , power transmission unit  14  is illustrated in greater detail. Power transmission unit  14  is mechanically linked to power shaft  30  of motor  12  via universal coupling joint  32 . Flywheel  38  is linked to universal coupling joint  32  and rotates at the same speed as motor  12 . Transmission  36  includes one or more reduction gears which reduce the rotational speed of drive shaft  28 . Drive shaft  28  is linked to power transmission unit  14  via universal coupling joint  34 . As shown in  FIG. 1 , drive shaft  28  rotates worm gears  16  and  18 . 
   Support structure  66  supports and maintains the alignment of flywheel  38  and transmission  36  with power shaft  30  and drive shaft  28 . A sensor (in this example, reed switch  42 ) is attached to support structure  66  adjacent to flywheel  38 . Magnet  40  is attached to flywheel  38  near the perimeter in one sector. Reed switch is electrically connected with a controller via conductor  26 . 
   Turning to  FIG. 3A , the reader will note that reed switch  42  includes magnetically-reactive, movable contact  46  and non-reactive, fixed contact  44 . When flywheel  38  rotates, magnet  40  repeatedly moves in and out of proximity with respect to reed switch  42 . When flywheel  38  is in the position shown in  FIG. 3A , the magnetic field produced by magnet  40  causes movable contact  46  to deflect into fixed contact  44 , closing the switch on conductor  26 . 
   Turning to  FIG. 3B , flywheel  38  is shown exactly one-half of a rotation (180 degrees) out of phase with the position depicted in  FIG. 3A . In this position, reed switch  42  is not affected by magnet  40  and movable contact  46  returns to its normal, undeflected position. This creates an open circuit condition on conductor  26 . 
   Although, reed switch  42  is illustrated in  FIGS. 3A and 3B , other magnetically reactive elements may be used in place of reed switch  42 . For example, a Hall effect sensor may be attached to support structure  66  in place of reed switch  42 . Those that are skilled in the art know that a Hall effect sensor is a solid state transducer which varies its output voltage based on its proximity to a magnetic field. 
   Alternatively, other devices may be used to sense the rotation of flywheel  38  in place of reed switch  42 . For example, as shown in  FIG. 5 , an opticoupler type photo sensor may be used. Those that are skilled in the art know that an opticoupler uses a light emitter and sensor to detect variations in light reflection on a moving surface. When employed on flywheel  38 , the rate of change of these variations corresponds to the rotational speed of flywheel  38 . In the embodiment illustrated in  FIG. 5 , flywheel  38  has reflective surface  68 . Nonreflective strips  70  are provide angularly near the perimeter of flywheel  38 . The opticoupler includes light source  72  which emits light against flywheel  38  near its perimeter. Sensor  74  detects light reflecting off of flywheel  38 . Thus, the opticoupler will detect the movement of flywheel  38  as nonreflective strips  70  pass through the focused light beam emitted by light source  72 . The opticoupler transmits a signal to the controller via conductor  76  when a change in reflectivity is detected. The controller can easily compute rotational speed or the quantity of rotations since the number of nonreflective strips  70  is known. 
     FIGS. 6A and 6B  illustrate yet another sensor configuration for detecting rotation of flywheel  38 . In this embodiment, cam  78  is provided on the perimeter of flywheel  38 . Contact switch  80  is attached to support structure  66  at a location where cam  78  will close switch  80  when flywheel  38  rotates.  FIG. 6A  shows the closure of switch  80  when cam  78  contacts switch  80 .  FIG. 6B  shows the opening of switch  80  when cam  78  rotates away from switch  80 . 
   For simplicity, the invention will be described as if a reed switch type sensor is used. As shown in  FIG. 7 , controller  84  receives its input from reed switch  42 . In response, controller  84  selectively supplies power to smoke production device  24 . Turning to  FIG. 8 , counter  92  of controller  84  registers every time reed switch  42  closes. The reader will recall that reed switch  42  closes once every time flywheel  38  makes a complete rotation. The reader will also recall that conventional steam locomotives produce four exhaust pulses for every rotation of the train&#39;s drive wheel. As such, controller  84  is preferably programmed to supply power to smoke production unit four times per rotation of the model locomotive&#39;s drive wheel. Because of the 22:1 gear reduction ratio, this corresponds to one exhaust pulse for every 5.5 rotations of the model locomotive&#39;s flywheel. 
   For simplicity of illustration, the reader will appreciate that emitting one exhaust pulse every 5 rotations of the locomotive&#39;s flywheel is a close approximation to the exhaust emission characteristics of a conventional steam-powered locomotive. In fact, the difference in exhaust timing corresponding to the additional delay of 0.5 rotations of the model locomotive&#39;s flywheel would be virtually imperceptible to most hobbyists. Nevertheless, the controller could easily be programmed to emit an exhaust pulse every 5.5 rotations of the flywheel. 
   Every time counter  92  registers a closure of reed switch  42 , comparator  86  compares the “count” of counter  92  to see if the count is equal to the value of “5.” If it is not, then the process is repeated the next time counter  92  registers a new closure of reed switch  42 . When comparator  86  determines that the count is equal to 5, power command  90  is generated and controller  84  supplies power to smoke production device  24 . The controller also generates reset command  88  which resets counter  92  to “zero.” 
     FIGS. 4A and 4B  illustrate a smoke production device. Smoke production device  24  includes heating element  48  which is in contact with smoking substance  50 . Smoking substance  50  may be an oil or any other substance which produces smoke when heated. Fan  54  having fan motor  52  is also positioned inside smoke production device  24 . Smoke production device  24  has smokestack  60  which may be opened or closed by the movement of shutter valve  58 .  FIG. 4A  illustrates smoke production device  24  in its normal, nonproducing state. 
   As shown in  FIG. 4B , when power is supplied to smoke production device  24 , heating element  48  heats smoking substance  50  causing smoke  62  to be produces inside smoke production device  24 . Stepper motor  56  turns causing rotation of shutter valve  58  which allows smoke  62  to exhaust through smoke stack  60 . Fan motor  52  rotates fan  54  to evacuate  62  more quickly through smoke stack  60 . Thus, the reader will appreciate the power supplied to smoke production device  24  powers heating element, fan motor  52  and stepper motor  56 . Although shown connected in series, these devices may also be connected in series or parallel. 
   The preceding description contains significant detail regarding the novel aspects of the present invention. It should not be construed, however, as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.