Abstract:
A tow bar adapted to be coupled to a steerable nose wheel assembly of an aircraft. The tow bar includes an arm assembly having a handle at a first end thereof and an oppositely-disposed second end. First and second arms are pivotally coupled at first ends thereof to the arm assembly to enable oppositely-disposed second ends of the first and second arms to pivot toward and away from each other. Engagement members are disposed at the second ends of the first and second arms, and each engagement member is adapted to engage a portion of the steerable nose wheel assembly. A mechanism is provided for locking the first and second arms to prevent their pivoting relative to each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to vehicle tow bars, and in particular to tow bars suitable for use with light aircraft equipped with a nose wheel assembly to which a tow bar may be attached. 
         [0002]    Light aircraft, and particularly single-engine aircraft, are often manually maneuvered while on the ground. For this purpose, tow bars have been developed that are adapted to engage the nose wheel assembly in some manner, as evidenced by U.S. Pat. Nos. 4,269,429, 4,470,564 and 7,464,974. A tow bar should be sufficiently rigid during use to provide the operator with greater control over the movement of the aircraft. Furthermore, a tow bar should be sufficiently long so that the operator can avoid the blades of the propeller and maneuver an airplane in a comfortable and safe manner while the operator is substantially upright. While various types of tow bars are commercially available, including those capable of use with a variety of different types of aircraft, tow bars that can be stored within an aircraft would be especially convenient to aircraft operators. However, to fit within an aircraft, a tow bar must typically be collapsible to a much smaller size, which includes its overall length. 
         [0003]    There is an ongoing need for a collapsible tow bar that is of minimal weight and can be collapsed to a convenient size for storage within a small aircraft, yet is simple to expand and when expanded is sufficiently rigid and long to perform effectively. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    The present invention provides a tow bar for maneuvering light aircraft, such as single-engine airplanes having a steerable nose wheel assembly to which a tow bar may be connected. 
         [0005]    According to a first aspect of the invention, the tow bar includes an arm assembly having a handle at a first end thereof and an oppositely-disposed second end. First and second arms are pivotally coupled at first ends thereof to the arm assembly so that the first ends of the first and second arms are spaced apart and separated by the arm assembly and oppositely-disposed second ends of the first and second arms are able to pivot toward and away from each other. First and second engagement members are disposed at the second ends of the first and second arms, respectively, and each of the first and second engagement members is adapted to engage a portion of the steerable nose wheel assembly. Means is provided for locking the first and second arms to prevent the first and second arms from pivoting relative to each other. The arm assembly is coupled to the first and second arms to enable the arm assembly to acquire a deployed configuration in which the first end of the arm assembly extends in an opposite direction relative to the first and second arms, and to also acquire a stowable configuration in which the arm assembly is between the first and second arms. 
         [0006]    A technical effect of the invention is the ability of the tow bar to be collapsed to a stowable configuration that is sufficiently small and light to enable the tow bar to be conveniently stowed on board a light aircraft, yet can also be easily expanded to a deployed configuration that is sufficiently rigid and long to maneuver the aircraft. 
         [0007]    Other aspects and advantages of this invention will be better appreciated from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a collapsible tow bar according to a first embodiment of the present invention, with the tow bar shown in a deployed configuration and coupled to a nose wheel strut of an aircraft. 
           [0009]      FIG. 2  is a plan view of the tow bar of  FIG. 1  after being collapsed to acquire a stowable configuration of the tow bar. 
           [0010]      FIG. 3  is a perspective view of the tow bar of  FIGS. 1 and 2  in the deployed configuration thereof. 
           [0011]      FIG. 4  is a cross-sectional view of the tow bar of  FIGS. 1 through 3  along section line  4 - 4  of  FIG. 2 . 
           [0012]      FIG. 5  is a perspective view of a collapsible tow bar according to a second embodiment of the present invention, with the tow bar shown in a deployed configuration for coupling to a nose wheel strut of an aircraft. 
           [0013]      FIG. 6  is a plan view of the tow bar of  FIG. 5  after being collapsed to acquire a stowable configuration of the tow bar. 
           [0014]      FIG. 7  is a cross-sectional view of the tow bar of  FIGS. 5 and 6  along section line  7 - 7  of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The present invention comprises a tow bar adapted for manually maneuvering an aircraft on the ground, and in particular light aircraft equipped with a steerable nose wheel assembly, as is often found on single-engine aircraft. Notable but nonlimiting examples of such aircraft include certain models manufactured by the Cessna Aircraft Company. 
         [0016]      FIGS. 1 through 7  represent two embodiments of collapsible tow bars  10  that can be extended to a deployed configuration ( FIGS. 1 ,  3  and  5 ) for towing and maneuvering an aircraft, and collapsed to a stowable configuration ( FIGS. 2 and 6 ) that has a sufficiently small profile or outline to be readily stowed within the cabin of a light aircraft. 
         [0017]    Referring to  FIGS. 1 through 4 , the tow bar  10  is represented as comprising engagement members  12  and  14  that oppose each other and are adapted to engage opposite sides of an aircraft steerable nose wheel assembly  16 , generally as shown in  FIG. 1 . For this purpose, the engagement members  12  and  14  are coaxially aligned and their opposing ends are preferably configured to engage the axle or hub of the wheel assembly  16 . For example, the engagement members  12  and  14  can be configured as sockets adapted to engage the ends of the wheel axle of the wheel assembly  16  or engage recesses defined in the ends of the wheel axle. The engagement members  12  and  14  are represented as having approximate equal axial lengths. As nonlimiting examples, the members  12  and  14  may have axial lengths of about three centimeters and approximately equal diameters of about two centimeters, though greater and lesser lengths and diameters are also within the scope of the invention. The engagement members  12  and  14  are mounted at distal ends of a corresponding pair of arms  18  and  20 , respectively. The members  12  and  14  can be mounted with, for example, screws, roll pins, rivets, welds, etc. The arms  18  and  20  have approximately equal axial lengths, for example, about fifty centimeters, and approximately equal outer dimensions, for example, diameters of about two centimeters, though again greater and lesser dimensions are also within the scope of the invention. The engagement members  12  and  14  and arms  18  and  20  are represented as having cylindrical outer shapes, though other cross-sectional shapes are possible, depending on the type of material used in their construction. In addition, the engagement members  12  and  14  and/or arms  18  and  20  may have tubular constructions, in other words, hollow along their entire lengths. According to a particular embodiment of the invention, the engagement members  12  and  14  and arms  18  and  20  are formed of an aluminum alloy, such as Al 6061. 
         [0018]    The arms  18  and  20  are pivotally attached to an extension arm assembly  22 , for example, with an annular-shaped coupling  24  mounted on a distal end  25  of the arm assembly  22 . The arms  18  and  20  is represented as pivotally connected to the coupling  24  with a pin or shaft  38  that extends through the coupling  24 , through the end  25  of the arm assembly  22 , and through the end of each arm  18  and  20 . As represented in more detail in  FIG. 4 , the shaft  38  is secured within the arms  18  and  20  with roll pins  40 , which allow the arms  18  and  20  to pivot toward and away from each other and, therefore, enables the distance between the engagement members  12  and  14  to be adjusted to allow the members  12  and  14  to engage and disengage the wheel assembly  16 . In addition, a cross pin  42  passes through the coupling  24 , through the end  25  of the arm assembly  22 , and through a diametrical hole  44  in the shaft  38  to releasably secure the shaft  38  to the arm assembly  22  and its coupling  24 . As represented in  FIG. 2 , the pin  42  can be secured with a split ring  46  that, when removed, allows the pin  42  to be withdrawn from the hole  44  in the shaft  38 . By removing or at least sufficiently retracting the cross pin  42  to disengage the shaft hole  44 , the arms  18  and  20  and shaft  38  are permitted to rotate relative to the arm assembly  22  about the axis of the shaft  38 , which is transverse and preferably perpendicular to the axis of the arm assembly  22 . In this manner, the arm assembly  22  and the arms  18  and  20  are able to be rotated relative to each other, and between the deployed configuration shown in  FIGS. 1 and 3  and the stowable configuration shown in  FIG. 2 . As evident from  FIGS. 1 and 3 , the arm assembly  22  extends away from the arms  18  and  20  in the deployed configuration, terminating with a handle  36  that is located at an opposite end of the tow bar  10  relative to the engagement members  12  and  14 . The handle  36  is shown as being configured as a T-handle, though other configurations are possible. As evident from  FIG. 2 , in the stowable configuration the arm assembly  22  is between the arms  18  and  20  and the handle  36  is adjacent the engagement members  12  and  14 , while the end  25  of the arm assembly  22  remains disposed between the ends of the arms  18  and  20  to which it is pivotally coupled with the shaft  38 . Notably, all but the handle  36  of the arm assembly  22  is disposed between the arms  18  and  20 , resulting in a very compact stowable configuration. 
         [0019]    The arm assembly  22  shown in  FIGS. 1 through 3  is represented as further comprising three extension arm sections  26 ,  28 , and  30  that are telescopically assembled together. While three arm sections  26 ,  28  and  30  are shown, two arm sections or more than three arm sections could be employed. The arm section  28  is larger in diameter than the arm section  30  to accommodate the latter, and the arm section  26  is largest in diameter to accommodate both of the remaining arm sections  28  and  30 . Consequently, at least the arm sections  26  and  28  have a tubular shape. For purposes of maximizing the strength-to-weight ratio of the tow bar  10 , the arm sections  26 ,  28  and  30  preferably have a tubular construction. Al 6061 is again a suitable material for the arm sections  26 ,  28  and  30 . The arm sections  26 ,  28 , and  30  can be equipped with any suitable features, for example, pins, screws, rivets or flanges that permit the arm assembly  22  to expand to its fully deployed configuration (shown in  FIGS. 1 and 3 ), while preventing the smaller arm sections  28  and  30  from being completely removed from their larger adjacent arm sections  26  and  28 , respectively. As represented in  FIG. 2 , to prevent unintended extension of the arm assembly  22 , the arm sections  26  and  30  can be secured to each other in their collapsed positions with a pin  32  that is mounted to the arm section  26  and adapted to engage one or more holes  34  provided in the arm section  30 . As evident from  FIGS. 1 and 3 , the pin  32  can also be used to secure the arm sections  26  and  28  together in their extended positions, for example, by passing through a complementary hole (not shown) in the arm section  28 . 
         [0020]    A locking mechanism  48  is attached to the arms  18  and  20  to allow for adjusting and fixing the distance between the arms  18  and  20  and their respective engagement members  12  and  14 . The locking mechanism  48  is represented as being a friction lock assembly comprising a bar  50  attached to the arm  18 , a collar (not shown) mounted to the arm  20  and in which the bar  50  is slidably received, and a knob  54  that is threaded into the collar in order to selectively engage and disengage the bar  50  within the collar in order to lock and release, respectively, the bar  50  relative to the collar and, therefore, the arms  18  and  20  relative to each other. Other locking assemblies are possible and within the scope of the invention. 
         [0021]    In view of the above, the tow bar  10  can be converted from the stowable configuration of  FIG. 2 , in which the arm assembly  22  is between the arms  18  and  20 , to the deployed configuration of  FIGS. 1 and 3 , in which the arm assembly  22  is not between the arms  18  and  20  and instead extends away from the arms  18  and  20 , by disengaging the pin  42  from the shaft  38  to allow the arms  18  and  20  to rotate relative to the arm assembly  22 . As evident from  FIG. 4 , rotating the arms  18  and  20  about 180 degrees relative to the arm assembly  22  enables the pin  42  to re-engage the diametrical hole  44  in the shaft  38  and lock the positions of the arms  18  and  20  in the deployed configuration. In addition, the arm assembly  22  is telescopically extended by disengaging the pin  32  located on the arm section  26  from the holes  34  located in the arm section  30 , and then engaging the pin  32  in a hole (not shown) located in the arm section  28  to lock the arm sections  26  and  28  in the deployed (extended) configuration. The engagement members  12  and  14  can then be coupled to the axle of the steerable nose wheel assembly  16  ( FIG. 1 ) by loosening the locking mechanism  48  to allow the arms  18  and  20  and their engagement members  12  and  14  to pivot toward each other and into engagement with the axle, after which the locking mechanism  48  can be tightened to lock the engagement members  12  and  14  in engagement with axle. An operator can then grasp the handle  36  to maneuver the aircraft by pushing, pulling and moving the tow bar  10  laterally from side to side. 
         [0022]    The embodiment of  FIGS. 5 through 7  is similar in may respects to the embodiment of  FIG. 1 through 4 , and therefore the same reference numbers will be used in  FIGS. 5 through 7  to designate components that are the same or functionally equivalent to components identified above for the embodiment of  FIGS. 1 through 4 . 
         [0023]    In one respect, the embodiment of  FIGS. 5 through 7  differs as a result of the arm assembly  22  comprising, in addition to the handle  36 , a single arm section  26 , which is slidably received in the collar  24  secured between the arms  18  and  20 . Instead of telescoping, the entire arm assembly  22  is able to slide through the collar  24  until its end  25  opposite the handle  36  is disposed between the engagement members  12  and  14 , the handle  36  is adjacent the collar  24 , and the arm assembly  22  is between the arms  18  and  20 , resulting in the stowable configuration of  FIG. 6 . 
         [0024]    In another respect, the embodiment of  FIGS. 5 through 7  differs as a result of the pin  32  being biased with a spring  58  disposed within a collar  56  with which the pin  32  is mounted to the collar  24  of the arm section  26 . The spring  58  biases the pin  32  into engagement with either of two holes  34 A ( FIG. 5) and 34B  ( FIG. 6 ) at opposite ends of the arm section  26 . The spring  58  permits the pin  32  to be sufficiently retracted to disengage the hole  34 A or  34 B with which it is engaged. In the deployed configuration of  FIG. 5 , the pin  32  is engaged with the hole  34 B, and by disengaging the pin  32  from the hole  34 B the arm assembly  22  is allowed to be retracted through the collar  24  until the pin  32  is able to engage the hole  34 A near the handle  36  of the arm assembly  22 , at which time the arm assembly  22  can be locked in its stowable configuration shown in  FIG. 6 . Notably, similar to the embodiment of  FIGS. 1 through 4 , all but the handle  36  of the arm assembly  22  is disposed between the arms  18  and  20 , resulting in a very compact stowable configuration. 
         [0025]    Another difference embodied in  FIGS. 5 through 7  is that the shaft  38  of  FIGS. 1 through 4  is replaced with pins or trunnions  38  projecting in opposite directions from the collar  24 . As represented in more detail in  FIG. 7 , the arms  18  and  20  are pivotally connected to the trunnions  38  with roll pins  40  or any other suitable fastener. The roll pins  40  allow the arms  18  and  20  to pivot toward and away from each other, similar to the arms  18  and  20  of the embodiment of  FIGS. 1 through 4 . Relative movement of the arms  18  and  20  is again restricted with a locking mechanism  48 , represented in  FIGS. 5 and 6  as being a friction lock assembly comprising a bar  50  attached to the arm  18  and slidably received in a channel  52  attached to the arm  20 , and a thumb screw or knob  54  that is threaded into the bar  50  for selective frictionally engagement with the channel  52  when sufficiently threaded into the bar  50 . Other locking assemblies are possible and within the scope of the invention. 
         [0026]    In view of the above, it can be appreciated that both embodiments of the invention provide a compact design that allows for convenient storage onboard a light aircraft, while also providing a sufficiently long and rigid tow bar  10  that can be readily deployed for use and the collapsed for stowing. The components of the tow bars  10  can be fabricated using various techniques and materials, such as wrought 6061 aluminum alloy or another relatively light and corrosion-resistant material. 
         [0027]    While the invention has been described in terms of particular embodiments, it is apparent that other forms could be adopted by one skilled in the art. In addition, components and features of either embodiment can be utilized in the other embodiment. For example, the pins  32  and  42  of the embodiment shown in  FIGS. 1 through 4  could be spring-biased similar to the pin  32  of the embodiment shown in  FIGS. 5 through 7 , and the arm assembly  22  of the embodiment shown in  FIGS. 5 through 7  could comprise two or more telescoping arm sections similar to the arm sections  26 ,  28  and/or  30  of  FIGS. 1 through 4 . Accordingly, the scope of our invention is to be limited only by the following claims.