Abstract:
A tug device for moving small aircraft having front wheels. A portable drill is connected to a drive wheel and a frame is attached to the wheel. The device is compact and easily assembled for use and disassembled for storage. The device includes a pair of drive wheels and is steerable when a locking latch is released. The locking latch provides rigidity to the device under load.

Description:
This is a continuation-in-part of my prior application entitled STEERABLE POWER TUB FOR SMALL AIRCRAFT filed Aug. 23, 2002, now U.S. Pat. No. 6,604,787 having Ser. No. 10/226,574, which in turn is a continuation-in-part for my prior application entitled POWER TUB FOR SMALL AIRCRAFT filed Dec. 26, 2001, now U.S. Pat. No. 6,536,709, having Ser. No. 10/034,314. 

   FIELD OF THE INVENTION 
   The present invention relates to a power tug for moving aircraft at airports and the like. More particularly the present invention relates to a power tug using a commercially available portable electric drill to drive a gear and dual wheel assembly capable of rapid attachment to aircraft front wheel axles and nose struts. The present embodiment is steerable. 
   BACKGROUND OF THE INVENTION 
   Moving small aircraft on the ground is often necessary when the aircraft is serviced or taken to a hanger or brought out. In the past, the motor has been started and the aircraft&#39;s own power has moved it from one place to another. This, of course, presents a potential danger from the rotating propeller. It also produces unnecessary wear and stress on the motor when it is operated for just a short while. 
   As an alternative, aircraft tugs have been employed, much like the large tugs that move commercial jet aircraft and the like. However, this requires a significant investment in equipment costs for operating the tug. It also requires having someone available to operate the device and/or train small aircraft owners to use the machine. 
   It would be of great advantage if a simple, efficient device could be developed that would permit owners to move their own planes without worrying about safety concerns from the motor of the plane. 
   One such device has been proposed. Olson U.S. Pat. No. 4,915,185 discloses a portable aircraft moving device using a portable electric drill. The drill output shaft is linked to a worm gear to mount temporarily to the front wheel of the airplane above the airplane wheel. While the drawings of this patent are clearly not intended to be to scale, the size of the airplane and the operator distort the difficulties of moving aircraft that may weigh several thousand pounds. Olson requires a drive wheel in the device to engage the aircraft front wheel and use that wheel to push or pull the aircraft. One additional drawback of Olson is that it places frictional stress on the nose wheel. It is not adaptable to all aircraft, requiring a specific axle adapter for each make or model. 
   Other patents have also found use for portable electric drills. Hawgood U.S. Pat. No. 4,156,315 discloses a dolly for maneuvering trailers, again using a worm gear. 
   Perkins U.S. Pat. No. 4,280,578 teaches the use of an electric drill for a walker for the disabled, a far less substantial weight and effort than aircraft. Perkins also uses a worm gear arrangement. 
   Finally, Hurt U.S. Pat. No. 3,713,501 employs an electric drill to alternatively move a belt to elevate the hand truck up or down stairs or move the wheel axle of the hand truck on flat ground. None of these other devices suggest a simple, effective method for moving small aircraft without frictional engagement with the nose wheel of the aircraft, and without having separate fittings for each make or model of the plane being moved. 
   In my earlier continuation-in-part application, a solution to the problems of the prior are is described and claimed. In my newer copending application, the design was modified to make the device steerable, producing substantial advantages including the ability to move much heavier aircraft because of the steerable features. In this application, the tug design is improved to make it transportable without major assembly or the use of tool. It also has a much higher capacity and has an improved steering option. 
   Other advantages will appear hereinafter. 
   SUMMARY OF THE INVENTION 
   It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, the present invention provides a dual wheel tug for moving aircraft on the ground while the motor of the airplane is off. 
   The tug device is assembled at the factory and includes a simple configuration that permits the device to be unfolded from the carton and assembled without tools in minutes. Because the device has a pair of drive wheels, the weight capability is significantly improved over my other designs. The present design also permits alignment in two distinct orientations, so that it is able to attach and tow aircraft at either the axle of the front wheel or the front strut. Two separate angles of attachment are needed and the present invention permits simple election between the two forms of attachment. 
   The tug device includes a power transmission column having a battery powered drill having a variable output, mounted on the upper end of the column and a drive wheel at the other end. A drive shaft engages the drill and a speed reducing gear box to drive the unit. The unit is steered by movement of a handle on the column. In the present invention, the steering function can be locked out, to give more stability of the device under load. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the invention, reference is hereby made to the drawings, in which: 
       FIG. 1  is a side elevational view, partially cut away, showing the preferred embodiment in use with an aircraft shown in dot and dash lines; 
       FIG. 2  is a top view of the device of  FIG. 1 ; 
       FIG. 3  is a side elevational view of the device of  FIG. 1 , in use with an alternative type of aircraft wheel; 
       FIG. 4  is a top view of the device of  FIG. 3 ; 
       FIGS. 5A and 5B  are detail views of the method of attachment of the frame to the power column in two configurations; 
       FIG. 6  is detail view illustrating the attachment of the frame to the power column in one configuration; 
       FIG. 7  is a detail view of the operation of the engagement trunion of the invention, with some components illustrated in dot and dash lines; 
       FIG. 8  is a detail view of the locking engagement mechanism for the engaging trunion; 
       FIG. 9  is a side view illustrating the device shown in  FIG. 8 ; 
       FIG. 10  is a top view showing the trunions in position to engage an aircraft wheel; 
       FIG. 11  is an end view of the device on the right of  FIG. 10 ; 
       FIG. 12  is a side elevational view of the power element of the present invention; 
       FIGS. 13   a - 13   d  are side elevational views showing the device of the present invention being unfolded from the shipping container to full assembly; 
       FIG. 14  is a perspective view showing insertion of the pin as shown in  FIG. 13   d;    
       FIG. 15  is a plan view of the device showing two locations for insertion of the pin in  FIG. 14 ; 
       FIG. 16  is a side elevational view illustrating the step to be taken to insert the pin into the element shown in  FIG. 15 ; 
       FIG. 17  is a perspective view showing the second component being installed in the device of this invention; 
       FIG. 18  is a side elevational view of the device of this invention in use with one kind of aircraft; 
       FIG. 19  is a side elevational view of the device of this invention in use with another kind of aircraft; 
       FIG. 20  is a plan view of one embodiment of the present invention; 
       FIG. 21  is a perspective view showing the action of the lock as shown in  FIG. 20 ; 
       FIG. 22  is a plan view of details of the steering mechanism; and 
       FIG. 23  is a detail view of the lock and unlock mechanism of FIG.  22  and shown in place in the device of this invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As shown in the drawings, particularly  FIGS. 1 and 2 , the present invention provides a device  10  generally for use with an airplane  11  having a front wheel  13  supported on a front axle  15 . Aircraft of any make or model weight less than about 3,000 pounds are suitable for use with the power tug of this invention. The tug includes a battery powered conventional electric drill  17 , with rechargeable battery  19 , for providing a suitable variable speed power source. 
   The preferred electric drill is a cordless 18-volt battery operated drill, having a quick release battery that snaps in place. A spare battery can be carried on the device. 
   The device includes a handle  19  for directional control of the device which is attached to the tubular power column  23 . Column  23  includes a drive shaft  25 , shown in dashed lines in  FIG. 1 , which communicates with drive wheel  27  to allow the device to be positioned near airplane  11  while propeller  29  is not operating, allowing a safe movement of plane  11 . drive wheel is operated by drive shaft  25  and worm gear speed reducer  31 , allowing drive wheel  27  to rotate in either direction, to push or pull aircraft  11 . 
   A tubular frame  33  is attached to the drive shaft  25  and drive wheel  27  via simple connecting point, described below, which permits the unit to be separated into two major parts or components. Tubular frame  33  supports dolly wheels  35 , which permit free wheeling movement of the unit when it is not attached to an aircraft. 
   Tubular frame  33  also includes a rotating engaging tube  37  for locking the tug to the airplane. Engaging tube  37  includes an engaging trunion  39  which is used to engage the aircraft axle  15  after fixed position trunion  41  has engaged the other side of axle  15 . An aircraft engaging control lever  43  is foot operated to pivot engaging trunion  39  on to axle  15 . 
     FIGS. 3 and 4  illustrate an alternative use of the present invention with aircraft having enclosed front wheels  45  so that the engageable trunion  39  and fixed trunion  41  engage the airplane nose gear strut  47 . tubular frame  33  is attached to the power column  23  and drive wheel  27  at a different angle or position, shown in FIG.  3 . 
   Frame  33  and power column  23  are joined using the attachment means shown in  FIGS. 5A ,  5 B and FIG.  6 .  FIG. 5A  is a side view of the power column  23  and worm gear box  31 , also showing drive shaft  25 . In  FIG. 5B , drive wheel  27  includes a wheel to shaft attaching hub  49  and driven shaft  51 . Worm gear box  31  is mounted on driven shaft  51 , and the gear box  31  also includes bolts  53  for bracket  55  for attachment in the orientation shown in  FIGS. 1 and 2 , using lock washers  57  and hex nuts  59 . Alternatively, shown in dot and dash line in  FIG. 5B , bolts  54  are used with bracket  56 , lock washer  58  and hex nut  60  for attachment in the orientation shown in  FIGS. 3 and 4 . 
     FIGS. 7 ,  8  and  9  illustrate the preferred engagement mechanism for attachment to the axle  15  or aircraft strut  47 , depending on the particular airplane being towed by the tug device of this invention. Stationary tube  33  is enclosed by rotating engaging tube  37 , shown in  FIG. 7  as both are partially cut away. Engaging tube  37  includes a bracket  61  for holding link  63 , which moves engaging trunion  39  about the axis of rotating engaging tube  37  for engagement with the axle  15  or strut  47  as described below. 
     FIG. 8  illustrates the way aircraft engaging control lever  43  is rotated to cause trunion  39  to be pivoted about that axis.  FIG. 9  illustrates the control lever  43  in the engaged position, so that trunion  39  is, for example, engaged with axle  15 , not shown in this figure. Movement of control lever  43   a  to the position shown in dot and dash lines moves link  63 , and therefore trunion  39  away from the axle to the position shown, also seen as dot and dash lines in FIG.  7 . The arrows illustrate the direction of movement of the components shown in these figures. Engagement is easy and secure, and an operator can use his or her foot to move control lever between the two positions. 
     FIG. 10  illustrates sliding engaging trunion  39  in greater detail and shows additional details of fixed position trunion  41 , both of which are shown as square tubular stock  40  and  42  respectively. Adapters  65  are fitted on tubular stock  40  and  42 . The airplane is then put in position, such as that of  FIGS. 1 and 2 , for example, so that axle  15  is first engaged by adapter  65  on stock  42 , so that when sliding engaging trunion  39  is moved as described above, adapter  65  on tubular stock  40  also engages axle  15 .  FIG. 11  illustrates one end of adapter  65  mounted on stock  42 , taken along lines  11 — 11  of FIG.  10 . The unit is ready to move the aircraft. 
     FIG. 12  illustrates the attachment and/or removal and replacement of cordless electric drill  17 , if, for example, drill  17  should fail. In most commercially available drills, such as the ones shown here, battery  19  can be removed for recharging and, if desired, a spare battery could be used while charging the first such battery. It is important to note that the drill  17  may also be a corded drill connected to a power source. This feature permits movement of a large number of airplanes in a confined area where the tub does not have to go farther than a long extension or power cord. Drill  17  includes a drill chuck  65  which engages drive shaft  25 , shown in dot and dash line in  FIG. 12. A  split collar  67  is welded to tubular power column  23  and fitted with a clamping screw  69  to mount the drill  17  firmly to the column  23 . Pressure on trigger  71  causes shaft  25  to rotate in either direction, depending on the rotation direction  10  selected on drill  17 , so that shaft  25  rotates to drive wheel  27  through a conventional worm gear speed reducer  31 , seen in  FIG. 1 , for example. 
   Once the wheel  13  of an aircraft has been engaged, drill  17  moves drive wheel as desired, as fast or as slow as necessary, so that the aircraft can be brought to or from its parking location, or maintenance hanger. Handle  21  allows the device to be steered, providing excellent maneuverability. 
   The tug device of the present invention has been tested on a number of small aircraft. Tests have shown that the tug device is capable of moving a 3,000 pound airplane in and out of hangers with no strain or noticeable effort. One fully charged battery will continuously move an aircraft for at least ⅛ mile at two feet per second. There is no need to bend or stoop, since the control lever  43  is foot controlled, snapping from an engaged position to a disengaged position and back. 
   Since different airplane manufactures have different front wheel designs, the trunions are easily changed as desired in minutes. The cordless driver is intended to be a name brand drill that can be serviced at thousands of tool service centers, and can be removed and replaced in seconds. Since the drive wheel  27  is engaged with the gear box and drive shaft at all times, the drill acts as a positive brake for safe control on grades. Because there is full time engagement on the nose strut of the airplane, either on the nose wheel or the strut itself, there is no loss of control of the aircraft while in motion. The ability to attach and detach the frame to the power column allows for easier storage and for positioning the trunions for the two common forms of front airplane wheel assemblies gives the tug of this invention universal applicability. 
   Turning now to  FIGS. 13-23 , the improved steerable feature of the present invention is shown, in which like numbers identify the same elements as in  FIGS. 1-12  as described herein above. As noted above, the present invention comes in a carton in a folded condition as in  FIG. 13   a , and includes a handle  101  and an aircraft engaging member  103 , along with the gearbox, drive shaft in handle  101 . The wheels  102  and  104 , shown better in  FIG. 17 , support the device. Handle  101  is lifted as shown by the arrows in  FIGS. 13   b  and  13   c  to a final assembly position shown in  FIG. 13   d . Aircraft engaging member  103  is moved as shown in  FIG. 14  to align marks  105  on member  103 , and pin  107  is inserted into connecting box  108  into one of two pin holes,  111  and  112  in connecting box  108 , so that the angle that the engaging member  103  makes with respect to the handle  101  is defined on one of two positions, depending on which form of aircraft is of interest. The pin  107  fits in either pin hole  111  or  112  as desired.  FIG. 16  illustrates how the engaging member  103  is to be moved to permit alignment with either pin hole  111  or  112 . 
   Next the dolly wheel assembly  113 , which comprises an axle  115  and wheels  117  is positioned with mounting tube  119  in alignment with receiving tube  121  on gearbox  109 , and short pin  121  is inserted in the hole  123  on receiving tube  123 . The device is now ready for installation of the electric drill/drive motor  17  as described herein above. 
     FIGS. 18 and 19  illustrate the two towing positions for the device of this invention, where the aircraft engaging member  103  engages the axle of wheel  127  in  FIG. 18  or the strut  129  in FIG.  19 . In both cases, dolly wheels  117  remain about two inches or so above the ground. 
   Near the top of handle  101  and below electric drill  17  is a twist action steering release bar  131  which is rotated in one direction  133  (counterclockwise here) to lock the steering mechanism and in the other direction  135  (clockwise here) to release the lock and permit the device to be turned, as shown in  FIG. 20  to steer the aircraft. The handle grip bar  131  will hold its unlock or release position when the dot (preferably colored red)  137  is aligned with the line (again preferably colored red)  139  as illustrated in FIG.  21 . 
     FIG. 20  illustrates a situation when the engaging member  103  has engaged a wheel  127  of an aircraft and the release bar  131  has been moved to the unlocked position  135  and dot  137  is aligned with line  139 . It should be noted that wheels  117  are above ground by the aforementioned two inches or so, and this permits the wheels  102  and  104  can pivot about a shaft inside gearbox  109  from a far left to a far right angle, making a total angle of steering travel of 56° as shown by arrow  141 . 
     FIGS. 21-23  illustrate the steering unlock/lock mechanism that permits the present invention to operate in the steering mode. The handle  101  (which includes the same drive shaft  25  that is shown, inter alia, in FIG.  1  and engages the gears in the gearbox  109  in the same manner as shaft  25  engages gearbox  27  in  FIG. 5A ) also includes an additional rod  143 , abutting gear box  109  for stability. Rod  143  is attached to release bar  131  at its other end and is mounted off to the side of the center of handle  101  to avoid interference with the drive shaft  25 . When release bar is moved as described above, rod  143  rotates about its axis. Connecting cube  145  is mounted on the lower frame  147 , like lower frame  33  of FIG.  6 . Connecting cube  145  is adapted to pivot in the vertical axis about steering post  149  unless it is locked, and pivots in the horizontal axis on the iron member of lower frame  147  to which it is attached, to permit steering. 
   A latch  151  is mounted on the lower end of rod  143  and pivots about the axis of rod  143  when the release bar  131  is moved as described above. When latch  151  pivots, its outer end tilts in a vertical plane. Return spring  153  adds a biasing force on latch  151  so that the latch slides across the bottom face  155  of connecting cube  145 , shown in FIG.  21 . Lock pin  157  extends down from face  155 . Latch  151  includes a hole  159 , seen in  FIG. 22 , that engages lock pin  157  when the release bar  131  is twisted in the locking direction  133 . When release bar  131  is twisted in the other direction  135 , latch  151  tilts off the lock pin  157  and permits horizontal movement of the wheels (about the axis with respect to the frame, thus allowing the device to be steered. 
   In operation, the improved steerable power tug for small aircraft has shown significant advances in movement of such small planes on the ground. With the steerable feature, maneuvering is significantly improved. Moreover, it has been surprisingly discovered that heavier and larger aircraft can be moved with the tug of this invention. In one test, a Cesna Citation, a twin engine plane weighing about 4,000 pounds, was moved easily, whereas the non-steerable device was designed for aircraft up to about 3,000 pounds. 
   While particular embodiments of the present invention have been illustrated and described, it is not intended to limit the invention, except as defined by the following claims.