Abstract:
A dolly for transporting a helicopter across the ground is herein disclosed. The dolly comprises a pair of steerable wheel assemblies that are affixed to the respective ends of an axle. The axle has coupled thereto a pair of clamping assemblies that secure the skids of a helicopter to the dolly. A tow bar is coupled to the axle and also to a linkage that is connected between the steering mechanisms of the two steerable wheel assemblies for steering the dolly. To move the helicopter, the dolly is inserted beneath the forward ends of the helicopter&#39;s skids and coupled thereto. The helicopter is then supported upon the dolly and upon the rear ends of the helicopter&#39;s skids which may also be provided with wheels. The dolly is adjustable to compensate for helicopters having skids spaced at various distances.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a steerable dolly for moving helicopters. 
     Unlike conventional fixed-wing aircraft, helicopters are capable of vertical take-off and landings, thereby obviating the need for landing gear or wheels. As a helicopter does not need wheels to fly, most helicopters, and especially small one- and two-man models, are supported on an undercarriage that includes a pair of parallel skids. However, once they have landed, helicopters can be difficult to move, as the skids upon which they are supported are not well adapted for moving the helicopters about. Skid mounted helicopters have traditionally been moved by either dragging them across the ground, landing them on a trailer which then may be used to move the helicopter, or by securing a single wheel to the rear-most portion of each of the helicopter skids. This latter mode of moving a helicopter has been useful only on smaller helicopters as only the smaller helicopters are small enough to be moved in this manner. Moving the helicopter using this method is accomplished by forcing the tail of a helicopter equipped with the skid mounted wheels towards the ground, thereby lifting the nose and tilting the weight of the helicopter onto the skid mounted wheels. The helicopter is then rolled on its wheels to its new location. The problem with this mode of moving a helicopter is that it is strenuous and quite difficult to move a helicopter in this manner over unpaved surfaces. The relatively small wheels are not able to negotiate grass, mud, or ruts that may be present in many airfields where helicopters are kept. 
     Therefore, it is object of the present invention to disclose a steerable dolly, which will permit a pilot or ground crewman to move a landed helicopter with ease over varying terrain. These and other objectives and advantages of the invention will appear more fully from the following description, made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views. 
     BRIEF SUMMARY OF THE INVENTION 
     A dolly which meets the objectives set forth above comprises a pair of steerable wheel assemblies affixed to the respective ends of an axle, a pair of clamping assemblies that are coupled to the axle and which secure the skids of the helicopter thereto, and a tow bar that is rotatively coupled to the axle and to the wheel assemblies for towing and steering the dolly. Preferably, the axis of the axle of the dolly will be vertically offset from an axis passing through the center of the tires of the wheel assemblies, i.e. the axle will be lower than the centers of the wheels. 
     The tow bar itself comprises an actuating link that is rotatively coupled to the axle and to a steering linkage that is coupled between the wheel assemblies. A tongue is hingedly coupled to the actuating link such that the tongue may pivot toward and away from the helicopter. The tongue of the tow bar typically has a connecting mechanism such as a D-ring for hitching the dolly to a towing vehicle and/or a handle. 
     Each of the clamping assemblies that secures one of a helicopter&#39;s skids to the dolly essentially comprises a pair of opposable clamping elements in which one of the clamping elements is rotatable between a first, open position and a second, closed position. The clamping elements are constructed and arranged to that when the clamping elements are in their second, closed position, they will be able to clamp therebetween a skid of the helicopter. A locking device is provided for maintaining the clamping elements in their second, closed position so that the skids of the helicopter will remain coupled to the dolly during transport. 
     Where the distance between the skids of a helicopter or helicopters may vary by make or model or through deformation of the undercarriage of the helicopter, the clamping assemblies may be adjustably coupled to the axle of the dolly. Alternatively or in addition to adjustably coupling the clamping assemblies to axle of the dolly, the axle can be provided with a telescoping joint that permits the length of the axle to be altered as needed. 
     The steerable wheel assemblies of the dolly include a tire mounted upon a rim that is coupled to a wheel axle that is itself secured to a vertical spindle. The vertical spindle is rotatable about a vertical axis such that the rotation of the vertical spindle causes the tire to be steered in the direction of the rotation of the spindle. The vertical spindle of each wheel assembly is actuated by a pitman arm that is coupled thereto. In order to steer the tires of the wheels assemblies in conjunction with one another, the respective pitman arms are coupled together by a linkage that is also coupled to the tow bar of the dolly. 
     An alternate embodiment of the present invention substitutes swivel wheels similar to those on an office chair for the steerable wheel assemblies described above. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a helicopter mounted upon a dolly of the present invention, the dolly having one of the wheels thereof removed for clarity; 
     FIG. 2 is a close-up cutaway view of the skid of a helicopter mounted upon the dolly of the present invention; 
     FIG. 3 is a top, plan view of the dolly of the present invention; 
     FIG. 4 is a front elevational view of a helicopter mounted upon a dolly constructed according to the present invention; 
     FIG. 5 is a front elevational view of a helicopter mounted in an alternate embodiment of the dolly of the present invention; and 
     FIG. 6 is a top, plan view of the dolly of FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     The steerable dolly  10  of the present invention is constructed and arranged to support a small helicopter  12  thereon so as to allow the helicopter  12  to be moved from place to place once it has landed as illustrated in FIG.  1 . The helicopter  12  in FIG. 1 is supported on an undercarriage comprising front and rear vertical struts  9  and right and left skids  13 . Smaller helicopter such as helicopter  12  of FIG. 1 are often provided with wheels  8  at the rearmost end of skids  13  for the purpose of moving the helicopter as described above. 
     As can best be seen in FIGS. 2 and 3, the dolly  10  is comprised of a pair of steerable wheel assemblies  14  mounted to the respective ends of an axle  16 . The wheel assemblies  14  are secured to the axle  16  by means of a plate  18  that is bolted or welded therebetween. It is possible to connect the axle  16  directly to the wheel assemblies  14 , however by using the plate  18 , the axle can be offset toward the ground so as to lower the center of gravity of the dolly  10 . This feature is important in that it provides a more stable platform for the helicopter  12  when it is mounted upon the dolly  10 . 
     Clamping assemblies  20  for clamping the skids  13  of the helicopter  12  to the dolly  10  are secured to the dolly adjacent the wheel assemblies  14 . The clamping assemblies  20  are preferably comprised of a pair of clamping elements  22   a  and  22   b  that are connected to one another by hinge  24 . Element  22   b  is preferably secured as by welding to the axle  16  and, if so desired, to the plate  18  as well. Alternatively, element  22   b  can be bolted or clamped to the axle  16  so as to allow the clamping assemblies  20  to be secured to the axle  16  in various positions. Hinge  24  is preferably capable of opening 180° in order to allow element  22   a  to be swung out of the way of a skid  13  that is to be placed in the clamping assembly  20 . However, the only requirement is that element  22   a  must allow a skid  13  to be placed in and removed from the clamping assemblies  20 . A locking device  26  is coupled to element  22   b  for the purpose of securely clamping a skid  13  between clamping elements  22   a  and  22   b.  It is preferred to utilize a quick-acting device such as a cam lock or other over-center type locking device, however, any mechanism capable of maintaining the clamping elements  22   a  and  22   b  in a closed position such as a screw device, a padlock, a chain, or a lock pin may be utilized. To improve the grip of the clamping assemblies  20  upon the skids  13  of the helicopter  12 , the clamping elements  22   a  and  22   b  may be lined with a resilient material such as rubber padding  23 . 
     As indicated above, the wheel assemblies  14  are steerable and are comprised of a tire  28  mounted on a rim  30 . Rim  30  is in turn secured to a wheel axle  32  that is secured to a vertical spindle  34 . Vertical spindle  34  is mounted in a pivot block  35  and is pivotable about a vertical axis and allows the tires  28  to be pivoted to the right and to the left. Pitman arm  36  is connected to vertical spindle  34  for steering the wheel assembly  14  and by rotating the pitman arm  36 , the tires  28  are pivoted either right or left, as desired. A linkage  38  connects the pitman arms  36  of each of the wheel assemblies  14  and thereby constrains the wheel assemblies  14  to steer the tires  28  in conjunction with one another. The linkage  38  is actuated by tow bar  40  which is also connected to the axle  16  as seen in FIG.  3 . It is advantageous to arrange the position of the pitman arms  36  upon the vertical spindles such that the linkage  38  will be parallel and adjacent the axle  16 . In this manner the axle  16  will prevent the linkage from becoming snagged on debris or on the terrain over which the dolly  10  is being moved. It is to be kept in mind that the specific structure of the wheel assemblies  14  described herein is but one of many equivalent structures for a wheel assembly that may be utilized with the present invention. 
     Tow bar  40  is comprised of an actuating link  42  that is rotatively pinned at  44  to the linkage  38  and to the axle  16  at  46 . The connection between the actuating link  42  and the axle  16  at  46  is a structural connection and is preferably made with a suitably large bolt or pin. The connection between the actuating link  42  and the linkage  38  is simply to actuate the wheel assemblies  14  for steering the tires  28  and is typically a smaller pin or bolt. Tongue  48  is hingedly secured to the actuating link  42  by a pin  50  that allows the tongue  48  to be pivoted toward and away from the fuselage of the helicopter  12 . While a hinged connection between the tongue  48  and actuating link  42  is not strictly necessary to the operation of the dolly  10 , allowing the tongue  48  to be pivoted with respect to the actuating link  42  will prevent the tongue  48  from striking the fuselage of the helicopter  12 , thereby avoiding damage and costly repairs to the body and windscreen of the helicopter  12 . 
     The tongue  48  is typically provided with a standard connecting mechanism  52 , such as a D-ring, that allows the dolly  10  to be coupled to a towing vehicle (not shown). In addition, the tongue  48  may be provided with a handle  54  that allows a person to pull the dolly  10  by hand. 
     As can be appreciated from FIG. 4, the clamping assemblies  20  must be aligned with the skids  13  of the helicopter in order to function properly. As the distance between the skids  13  may vary for different makes and models of helicopters  12 , it may be useful to secure the clamping assemblies  20  to the dolly  10  in a manner that allows the clamping assemblies  20  to be adjusted to accommodate the skids  13  of different makes and models of helicopters  12 . Alternate embodiments of the present invention that allow for adjusting the distance between the clamping assemblies  20  may be seen in FIGS. 5 and 6. In one embodiment, the clamping assemblies  20  may be slidingly mounted upon a track  56  that would allow the clamping assemblies to be adjusted to accommodate the skids  13  of a given helicopter  12 . One or both of the clamping assemblies  20  may be mounted in such a manner. Alternatively, the clamping assemblies  20  may be bolted to the axle  16  in a manner that would allow them to be moved in relation to one another. 
     In another embodiment, the axle  16  may be of a telescoping nature as illustrated at  58 . By varying the length of the axle  16 , the distance between the clamping assemblies  20  may be modified. It is to be noted that other means for modifying the distance between the clamping assemblies  20  may also be used without exceeding the scope of this specification. Furthermore, multiple means for modifying the distance between the clamping assemblies  20  may be used simultaneously. 
     In another embodiment of the present invention, wheel assemblies  14  may be replaced with large swivel wheels capable of swiveling a full 180°. In this alternate embodiment, the linkage  38  may be omitted. Rather than being steerable in the stricter sense, the swivel wheels will allow a helicopter  12  supported on the dolly  10  to be easily turned. While swivel wheels do not provide for as great a control of the dolly in towing, they will allow for much greater maneuverability of a helicopter  12  supported on the dolly. 
     In operation, a dolly  10  having clamping assemblies appropriately spaced to accommodate the skids  13  of a chosen helicopter  12  is positioned in front of the chosen helicopter  12 . Once the dolly  10  is suitably positioned, the helicopter  12  is rotated onto the back portion of its skids  13 . This can be accomplished by pushing down on the tail of the helicopter  12  as at  11   a  or by pushing up on the nose of the helicopter  12  as at  11   b.  Where the force required to rotate the helicopter  12  onto the rear portion of its skids  13  is too great for a single person, one or more additional persons or a mechanical assist device such as a winch may be used to rotate the helicopter  12  onto the rear of its skids  13 . Preferably, the rear portion of the skids  13  of the helicopter  12  will be provided with wheels  8 , though the present invention may be utilized with a somewhat lower degree of success with helicopters  12  that are not so equipped. 
     Once the helicopter  12  has been rotated onto its wheels  8  and clamping elements  22   a  of clamping assemblies  20  have been rotated to their open positions, the dolly  10  is moved into position beneath the skids  13  of the helicopter  12 . Once the dolly  10  has been appropriately positioned, the helicopter  12  is lowered onto clamping elements  22   b  of the clamping assemblies  20 . Clamping assemblies  22   a  are then rotated into their closed position as illustrated in FIGS. 2 and 4 and secured by actuating the respective locking devices  26 . The helicopter  12  is now supported upon the tires  28  of the dolly  10  and upon wheels  8  of the helicopter skids  13  or upon the rear of the skids  13  themselves. 
     It is preferred to locate the dolly  10  so that the clamping assemblies  20  may engage the skids  13  immediately forward the front struts  9  of the helicopter undercarriage. It is important to note that the dolly  10  may be positioned farther back along the skids if so desired. However, the dolly  10  should never be positioned at or behind the center of gravity of the helicopter  12  as the helicopter will be prone to tipping forward. In general the center of gravity of a helicopter is located along the axis of the main rotor of the helicopter, as illustrated in FIG. 1 at C. Locating the clamping assemblies  20  of the dolly  10  forward of the struts  9  of the helicopter  12  results in a longer and more stable wheelbase upon which the helicopter  12  may be transported. 
     Once the dolly  10  has been properly secured to the helicopter  12 , the tongue  48  may be connected to a towing vehicle with D-ring  52  or may be pulled by a ground crewman using the handle  54 . In either case, the helicopter  12  will move easily as the larger diameter of the tires  28  will span bumps or ruts in the surface over which the helicopter is being transported. In addition, the increased surface area of the tires  28  in contact with the ground will also move more easily across softer ground and mud than the smaller wheels  8  could alone. By applying lateral forces to the tow bar  40 , the actuating link  42  will cause the linkage  38  to move laterally in a direction opposite to the force applied to the tow bar  40 . The lateral movement of the linkage  38  is in turn transmitted to the pitman arms  36  of the wheel assemblies  14 , which cause the respective spindles  34  to rotate the tires  28  in the direction in which the lateral force was applied to the tow bar  40 . In this manner, the helicopter may be steered as it is towed or transported around the airfield. 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.