Abstract:
A propulsion system for miniature vehicles, such as model airplanes, having multiple direct-current motors arranged about a central axis of the propulsion system in a radial, opposed, in-line, or V-12 configuration. The motors drive a propeller system.

Description:
RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application Ser. No. 11/103,989, filed Apr. 12, 2005, now U.S. Pat. No. 7,377,466, the contents of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates to a propulsion system for miniature vehicles. More particularly, the invention relates to an electric-powered propulsion system for miniature vehicles such as aircraft. 
   BACKGROUND OF THE INVENTION 
   The popularity of the radio-control hobby, as it applies to miniature or model aircraft, cars, boats and miniature military vehicles, has seen dramatic growth in recent years. Advancements in electric power technology, such as the increase in power-to-weight ratio of electric motors and batteries, have encouraged interest in the hobby for all age groups. 
   Today&#39;s radio-controlled models are less expensive and can be purchased ready or almost ready-to-fly or launch. Aircraft models are typically made of molded foam in attractive colors with motors and control equipment pre-installed. 
   An important factor in the use of electric propulsion is the extreme quietness of the units. Noise pollution is almost non-existent so electric models, particularly aircraft, can be flown at almost any park, school ground or ball field. 
   Most recently the challenges of electric flight have diminished to the point that it has become a common form of propulsion for all types of miniature aircraft. 
   All electric, radio-controlled models are believed to utilize a single motor or multiple single motor configurations. 
   It is the intent of this invention to provide a propulsion system that can be used on model airplanes. 
   It is a further intent of this invention to provide a propulsion system that allows a scale-like, electric motor to power models of World War I and II vintage aircraft. There are many examples of these aircraft such as English Sopwith Camels, German Fokker Tri-planes and a vast selection of United States bi-plane trainers, fighter planes and civilian aircraft. All of the above examples sold to the public at this time use single motor configurations. 
   It is the intent of this invention to offer an electric propulsion system that is powerful and offers the additional advantage of scale-like appearance and sound. 
   It is a further intent of this invention to provide a multiple-cylinder, electric motor propulsion system, in a radial, opposed, in-line (i.e., vertical), or V-12 configuration, to power miniature model planes at a scale-like speed that is safe, quiet, durable and economical to operate and that enhances the appearance of any scale-type model by more closely duplicating in appearance the original, full-scale type of engine. 
   SUMMARY OF THE INVENTION 
   This invention is a propulsion system for use in a miniature vehicle, particularly a model airplane, having a motor assembly comprised of a plurality of direct current motors operating together and arranged either radially, opposed, in-line (i.e., vertically), or in a V-12 configuration from a central axis of the motor assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
       FIG. 1   a  is a frontal view of one embodiment of the propulsion system of the present invention, having five cylinders or electric motors in a radial configuration, as mounted on one type of a miniature aircraft, with the propeller cutaway. 
       FIG. 1   b  is a side view of the propulsion system of  FIG. 1   a  installed on a different type of a miniature aircraft, with the propeller in place. 
       FIG. 2  is a partially-exploded side view of the embodiment of the propulsion system of  FIG. 1   a  showing the propeller assembly, the motor assembly and the drive shaft of the present invention. 
       FIG. 3  is a front view of a five cylinder radially configured motor assembly of the present invention along lines A-A′ of  FIG. 2 . 
       FIG. 4  is a rear view of a five cylinder radially configured motor assembly of the present invention. 
       FIG. 5  is a front view of a three cylinder radially configured motor assembly of the present invention. 
       FIG. 6   a  is a side view of a five cylinder radially configured motor assembly of the present invention for a Rhone-type installation where the cylinders spin with the propeller of the aircraft. 
       FIG. 6   b  is a front view of the motor assembly of  FIG. 6   a.    
       FIG. 7  is a front view of a seven cylinder radially configured motor assembly of the present invention. 
       FIG. 8  is a front view of a nine cylinder radially configured motor assembly of the present invention. 
       FIG. 9  is a top view of a twin cylinder motor assembly of the present invention in an opposed configuration. 
       FIG. 10  is a top view of a four cylinder motor assembly of the present invention in an opposed configuration. 
       FIG. 11  is a top view of a six cylinder motor assembly of the present invention in an opposed configuration. 
       FIG. 12  is a top view of a four cylinder motor assembly of the present invention in an in-line or vertical configuration. 
       FIG. 13  is a side view of a four cylinder motor assembly of the present invention in an in-line or vertical configuration. 
       FIG. 14  is a front view of a four cylinder motor assembly of the present invention in an in-line or vertical configuration. 
       FIG. 15  is a front view of the rear mounting plate for the four cylinder inline motor assembly of  FIG. 14 , without the motor being shown. 
       FIG. 16  is a front view of the front mounting plate for the four cylinder inline motor assembly of  FIG. 14 , without the motor being shown. 
       FIG. 17  is a partially exploded parts view of a cylinder pair portion of a V-12 cylinder Merlin type motor assembly of the present invention. 
       FIG. 18  is a top view of a V-12 cylinder Merlin type motor assembly of the present invention. 
       FIG. 19  is a front view of a two engine portion of the V-12 cylinder Merlin type motor assembly of  FIG. 18 . 
       FIG. 20  is a front view of the mounting plate for the V-12 cylinder Merlin type motor assembly of the present invention, without the V-12 motor attached. 
       FIG. 21  is a front view of the V-12 cylinder Merlin type motor assembly of the present invention, showing the front and rear support or mounting plates. 
       FIG. 22  is a front view of the front support plate for the V-12 cylinder Merlin type motor assembly of  FIG. 21 . 
       FIG. 23  is a side view of the V-12 cylinder Merlin type motor assembly of the present invention. 
       FIG. 24  is a top view of the V-12 cylinder Merlin type motor assembly of the present invention. 
       FIG. 25  is a top or end view of one of the motors for the V-12 cylinder Merlin type motor assembly of  FIG. 24 . 
       FIG. 26  is a side view of one of the motors for the V-12 cylinder Merlin type motor assembly of  FIG. 24 . 
       FIG. 27  is a side view of a 6 cylinder inline motor assembly of the present invention. 
       FIG. 28   a  is a frontal view of another embodiment of the propulsion system of the present invention, having three cylinders or electric motors in a radial configuration, as mounted on one type of a miniature aircraft, with the propeller cutaway. 
       FIG. 28   b  is a side view of the propulsion system of  FIG. 28   a  installed on the same miniature aircraft, with the propeller in place. 
       FIG. 29   a  is a frontal view of another embodiment of the propulsion system of the present invention, having four cylinders or electric motors in an opposed configuration, as mounted on one type of a miniature aircraft, with the propeller cutaway. 
       FIG. 29   b  is a side view of the propulsion system of  FIG. 29   a  installed on the same miniature aircraft, with the propeller in place. 
       FIG. 29   c  is a top view of the motor assembly used in the miniature aircraft in  FIGS. 29   a  and  29   b.    
       FIG. 30   a  is a frontal view of another embodiment of the propulsion system of the present invention, having four cylinders or electric motors in an in-line configuration, as mounted on one type of a miniature aircraft, with the propeller cutaway. 
       FIG. 30   b  is a side view of the propulsion system of  FIG. 30   a  installed on the same miniature aircraft, with the propeller in place. 
       FIG. 31   a  is a frontal view of another embodiment of the propulsion system of the present invention, having twelve cylinders or electric motors in a V-12 configuration, as mounted on one type of a miniature aircraft, with the propeller cutaway. 
       FIG. 31   b  is a side view of the propulsion system of  FIG. 31   a  installed on the same miniature aircraft, with the propeller in place. 
       FIG. 31   c  is a top view of the motor assembly used in the miniature aircraft in  FIGS. 31   a  and  31   b.    
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, it is noted that like reference characters designate like or similar parts throughout the drawings. The figures, or drawings, are not intended to be to scale. For example, purely for the sake of greater clarity in the drawings, wall thicknesses and spacings are not dimensioned as they actually exist in the assembled embodiments. 
     FIGS. 1   a ,  28   a ,  29   a ,  30   a , and  31   a  are frontal views of some preferred embodiments of the propulsion system  100  mounted on a miniature aircraft  102   a  or  102   c .  FIGS. 1   b ,  28   b ,  29   b ,  30   b , and  31   b  are side views of some preferred embodiments of the propulsion system  100  mounted on the front of the aircraft  102   a  or  102   b  or  102   c  by attaching the propulsion system  100  to a firewall  104  in the aircraft  102   a ,  102   b  or  102   c , respectively. 
   The propulsion system  100  of the preferred embodiment includes the elements shown in  FIG. 2 , for example, and other figures discussed herein. The details of the preferred embodiment are discussed below and include a motor assembly  106  and a propeller assembly  108  connected together with a drive shaft  110 . 
   As shown in the front views in  FIGS. 3 ,  5 ,  7 , and  8 , the motor assembly  106  ( 106   a ,  106   b ,  106   c ,  106   d , respectively) of a preferred radial embodiment utilizes three, five, seven or nine small, approximately 3-7 volt direct current electric motors  112  configured in a symmetrical pattern that is radially disbursed from the drive shaft  110  which is the axis of the motor assembly  106 . The motors must be configured properly for the voltage, weight, torque and amperage specifications of the desired unit. The five-unit embodiment of  FIG. 1   a  is meant by way of example and is not intended to limit the scope of the invention. 
   The radial motor configuration emulates the advantage of the fly-wheel effect produced by a large propeller (not shown). This effect is what develops the maximum power of the motor assembly  106  and allows the aircraft  102   a  and  102   b  to fly. This phenomenon also is evident in full-scale aircraft designed with radial engines (not shown). Conversely, increasing the voltage and RPM has little effect on power output and only serves to use more energy. 
   The dimensions of the individual motors  112  in all of the preferred embodiments herein are approximately 1⅜″ long by 1″ wide with about a ⅜″ long by 2 mm diameter motor shaft  114 . The top and bottom of the individual motors  112 , which may also be referred to herein as “cylinders,” are approximately flat which makes the height of the motors  112  approximately ¾. Cylindrical motors (not shown) of approximately the same size and power requirements also can be used. All dimensions are meant by way of example and are not meant to limit the scope of the invention. 
   As shown in  FIGS. 2 ,  3 ,  4 ,  5 ,  6   a ,  6   b ,  7 ,  8 ,  9 ,  10 ,  11 ,  13 ,  14 ,  17 ,  18 ,  19 ,  21 ,  23 ,  24 ,  25 ,  26 , and  27 , each DC motor  112  has approximately a ½ inch diameter, 45-degree pinion gear  116  pressed onto the respective motor  112 . All of the pinion gears  116  mate to a main gear  118 . The main gear  118  is about 1½ inches in diameter. The final gear ratio (pinion to main gear) is preferably 3:1 and turns a 14-inch diameter by 10-inch pitch propeller  120  approximately 2300 RPM. This 3:1 ratio is critical to the proper rotational speed of the propeller  120 , which is targeted for optimum flight time and power. With the five motor radial configuration of the invention, for example, this 3:1 gear ratio produces about 12.9 ounces of thrust at a 3.9 ampere draw from a 12-volt flight battery (not shown). The thrust and ampere draw will vary, however, with the number of motors. For the nine motor radial configuration of  FIG. 8 , a 4:1 final gear ratio may be substituted for the 3:1 gear ratio to allow for a larger gear to accommodate the nine DC motors in the radial configuration. 
   The main gear  118  and the pinion gears  116  can be made of nylon, plastic or other light-weight, non-conductive material. Only a slight amount of lubricant (not shown) is required for the main gear  118  and the pinion gears  116 . Typically, one small drop is sufficient for every ten flights. 
   As illustrated in  FIGS. 2 ,  3 ,  4 ,  5 ,  6   a ,  6   b ,  7 , and  FIG. 8 , the 45-degree configuration of the main gear  118  and the pinion gears  116  allows the motors  112  to be mounted flat and in a radial arrangement around the main gear  118 , with the motor shafts  114  of the motors  112  positioned perpendicular to the drive shaft  110 . This mounting configuration replicates a full-scale aircraft engine (not shown). Additionally, having the main gear  118  mounted forward of the pinion gears  116  provides a way to easily adjust the pinion-to-main gear clearance. The clearance is set by simply sliding the propeller assembly  108  and the main gear  118  forward and off the pinion gears  116  and inserting a strip of material of known thickness, such as a common business card, to set the clearance at the desired depth of 0.005-0.008 inches. Proper gear spacing is important to reduce drag. 
   Similarly, in an alternative embodiment illustrated in  FIGS. 9 ,  10 ,  11  and  29   c , the 45-degree configuration of the main gear  118  and the pinion gears  116  allows the motors  112  to be mounted flat in an arrangement of opposed pairs of two, four, or six motors  112  around the main gear  118 , with the motor shafts  114  of the motors  112  positioned perpendicular to the drive shaft  110 . This mounting configuration replicates a different type full-scale aircraft engine (not shown) than the one with a radial engine arrangement. As with the radial arrangement, the main gear  118  is preferably mounted forward of the pinion gears  116  to provide a way to easily adjust the pinion-to-main gear clearance. The final gear ratio (pinion to main gear) is preferably 3:1. 
   In another alternative embodiment illustrated in  FIGS. 12 ,  13 ,  14 , and  30   b , the 45-degree configuration of the main gear  118  and the pinion gears  116  allows the motors  112  to be mounted flat in an in-line or vertical arrangement of four or six motors  112  around the main gear  118 , with the motor shafts  114  of the motors  112  positioned perpendicular to the drive shaft  110 . This mounting configuration replicates a different type full-scale aircraft engine (not shown) than the one with a radial engine arrangement. As with the radial arrangement, the main gear  118  is preferably mounted forward of the pinion gears  116  to provide a way to easily adjust the pinion-to-main gear clearance. 
   In still another embodiment, as illustrated in  FIGS. 18 ,  19 ,  21 ,  24  and  31   c , the 45-degree configuration of the main gear  118  and the pinion gears  116  allows the motors  112  to be mounted flat and in a V-12 arrangement around the main gear  118 , with the motor shafts  114  of the motors  112  positioned at an angle to the drive shaft  110 . That is, each of six pairs of motors  112  are positioned at 72° angles with respect to each other, when measuring between the motor shafts  114  as shown in  FIG. 19  and perpendicular with respect to the drive shaft  110 . This mounting configuration also replicates a full-scale aircraft engine popularly known as the Merlin (not shown). As with the other embodiments, the main gear  118  is preferably mounted forward of the pinion gears  116  to provide a way to easily adjust the pinion-to-main gear clearance. 
   In a further embodiment, as illustrated in  FIGS. 6   a  and  6   b , the 45-degree configuration of the main gear  118  and the pinion gears  116  allows the motors  112  to be mounted flat and in a radial arrangement around the main gear  118 , with the motor shafts  114  of the motors  112  positioned perpendicular to the drive shaft  110 , also as in  FIGS. 3 and 4 . However, in this alternative embodiment, the motors  112  are attached to the drive shaft  110   a  such that the motors  112  spin with the drive shaft  110   a  and with the propeller (not shown), instead of themselves remaining stationary while the drive shaft  110   a  spins the propeller. This mounting configuration replicates still another full-scale aircraft engine (not shown) popularly known as the Rhone. 
   In all of the arrangements or embodiments herein, the gear clearance is locked in place by a thrust collar  122  at the distal end  124  of the drive shaft  110 . The thrust collar  122  is pinned to the drive shaft  110  by a set screw  148  and rides on a thrust washer  126 . It serves to secure the drive shaft  110  to a front mounting plate  128  and a rear mounting plate  130 . The rear mounting plate  130  has equally-spaced mounting holes  140  ( FIGS. 4 ,  5 ,  6   b ,  7 ,  8 ,  19 , and  21 ) around the edge of the plate  130  to allow screws (not shown) to pass through the rear mounting plate  130  to mount the propulsion system  100  to the firewall  104  in the aircraft  102   a ,  102   b  or  102   c.    
   In preferred embodiments, the front mounting plate  128  ( FIGS. 3 ,  4 ,  15 ,  16 , and  21 ) is designed in a star configuration and allows airflow around the motors  112  to facilitate cooling. As shown in  FIG. 2 , the rear mounting plate  130  is separated from the front mounting plate  128  by ½ inch plate supports (spacers)  132 . This separation or clearance between the front mounting plate  128  and the rear mounting plate  130  increases cooling by providing additional airflow space around the motors  112  and provides space for the separation of drive shaft bearings  134 . This space between the front mounting plate  128  and the rear mounting plate  130  strengthens the entire motor assembly  106  and separates the drive shaft bearings  134  for precise alignment of the drive shaft  110 .  FIGS. 16 ,  19  and  21  show alternative shapes for the front mounting plates  128   a ,  128   b , and  128   c.    
   The front mounting plate  128  and the rear mounting plate  130  can be made of plywood or molded from plastic or other light-weight, non-conductive, rigid and durable material. 
   The dimensions of the drive shaft  110  are approximately ¼ inch by 3 inches. The drive shaft  110  can be made of nylon, plastic or other durable, light-weight, non-conductive material. The propeller  120  is mounted at the proximal end  136  of the drive shaft  110  and is secured to a propeller hub  144  by a spinner nut  138  (¼ inch by twenty-eight threads per inch). The spinner nut  138  can be made of plastic, aluminum or other similarly featured material. Propellers  120  are commonly available and are frequently made of wood or molded plastic. 
   The propeller hub  144  is positioned on the drive shaft  110  between the propeller  120  and the main gear  118  and rotates in synchronization with the propeller  120 . The propeller hub  144  is pinned to the drive shaft  110  by a pin  146 . 
   All wiring (not shown) is pre-installed to each motor terminal and can be color-coded for positive and negative polarity. An electrical connector can be soldered to the end of the motor wires for connecting to an electronic throttle control device (not shown) provided by the kit manufacturer or consumer. 
   The propulsion system  100  can be easily installed on many ready made and quick-assembly kits for miniature aircraft  102   a  and/or  102   b  and/or  102   c  for example as shown in  FIGS. 1   a ,  1   b ,  28   a ,  29   a ,  30   a , and  31   a . Short screws (not shown) are used to connect the propulsion system  100  to the aircraft firewall  104 . The flight transmitter (not shown) sends commands to the electronic throttle control device (not shown) that controls the throttle on/off and power setting of the propulsion system  100 . The Rhone-type embodiment of the present invention, as illustrated in  FIGS. 6   a  and  6   b , may not or will not necessarily have a throttle. 
   The flight batteries (not shown) are quick charged from a 12-volt field battery (not shown) or automobile batteries (not shown) on site. Many 800 milliamp flights can be made during the normal flying session. 
   Flight duration with a typical 30-inch span bi-plane ( FIGS. 1   a ,  28   a ,  29   a , and  30   a ) with 400-500 square inches of wing area, weighing 28 ounces, will typically last about 20-30 minutes. However, exact flying time depends on the amount of aerobatics performed and throttle setting, wind speeds and other factors. The motors  112  also can be wired in parallel (not shown) for more power but less flight time. 
   It is anticipated that those skilled in the art of motors will recognize various other ways of practicing the invention and other uses of the invention. While the invention has been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention, as set forth in the following claims.
       100  propulsion system ( 106 + 108 + 110 )     102   a  miniature aircraft     102   b  miniature aircraft     102   c  miniature aircraft     104  firewall in aircraft     106  motor assembly ( 112 + 128 + 130 + 116 + 118 )     108  propeller assembly ( 138 + 120 + 144 )     110  drive shaft     112  DC motors     114  motor shafts     116  pinion gears     118  main gear     120  propeller     122  thrust collar     124  distal end of the drive shaft     126  thrust washer/drive shaft bearings     128  front mounting plate     130  rear mounting plate     132  spacers/plate supports     134  flange/drive shaft bearings     136  proximal end of the drive shaft     138  spinner nut     140  mounting holes (in rear mounting plate)     142  screws     144  propeller hub     146  pin (propeller hub to drive shaft)     148  set screw (thrust collar to drive shaft)