Abstract:
An aircraft tug hitch assembly includes deflectable guide plates providing a converging pocket for mechanically positioning a tow bar eyelet with the hitch lock pin. The hitch includes a lock assembly including a lock pin is mounted on a slidable piston for operator controlled movement between a detented raised unlocked position and a lower locked position capturing the tow bar eyelet. An indicator ball carried by the piston is observable by the tug operator when the lock assembly is in the unlocked position, but is not visible in the locked position thereby confirming hitch status without the need for verbal communication with ground personnel.

Description:
RELATED APPLICATION 
   This application claims the benefit under 35 USC 121 of U.S. Provisional Application No. 60/397,243 filed on Jul. 22, 2002 in the name of Thomas M. Williams, Jr. and entitled “Aircraft Tug Hitch Assembly”. 

   FIELD OF THE INVENTION 
   The present invention relates to coupling systems for releasably attaching a tow bar to an aircraft tug for transferring an aircraft between field locations. 
   BACKGROUND OF THE INVENTION 
   Aircraft tractors or tugs are used in combination with a tow bar attached to the nose wheel of an aircraft for transporting the aircraft on the ground, such as ramp and taxi positions. The tug typically has a hitch at the rear having upper and lower apertured plates. The tow bar frontally terminates with an apertured tow eyelet. For connecting, the tug operator maneuvers the hitch into proximity with the tow bar, while the eyelet is aligned with the hitch by an assistant on the ground. Inasmuch as the tug structure prevents direct visual observation, the tug operator is reliant on the assistant for movement instructions. When properly aligned the assistant inserts a latch pin through the plates and the eyelet to complete the coupling. The operation requires accurate and timely communication between the parties to accomplish a time efficient and safe connection. These requirements are often compromised by operating conditions resulting in a large incidence of personnel injuries.  
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides hitch assembly for coupling an aircraft tow bar with an aircraft tug having a hitch at the rear including vertically spaced upper and lower plates having coaxially aligned apertures with which an apertured eyelet is aligned for coupling. The hitch assembly includes: a locking assembly fixedly connected to said upper plate having a sliding locking bolt that is moveable between a lowered locked position extending through said plates and the eyelet, and a raised unlocked position. A lift handle raises the locking bolt between the lower and raised position including a detent notch for releasably maintaining said unlocked position. A pair of spring biased laterally spaced inwardly converging guide plates carried between the hitch plate provides a receiving pocket for aligning the toy bar eyelet with the lock pin. The guide plates resiliently deflect to permit tight radius turns. A signal rod on the locking bolt caries an indicator ball at top. The ball is visible to the tug operator to indicate the unlocked position, but is not visible in the locked position to thereby indicate coupled locked status between the aircraft and the tug. 
   Accordingly, it is an object of the invention to provide a hitch assembly for coupling an aircraft tug with an aircraft tow bar wherein coupling can be readily and safely accomplished. 
   Another object is to provide an aircraft hitch wherein the aircraft tug operator can visually determine the status of the hitch coupling. 
   A further object is to provide an aircraft tug hitch assembly wherein deflectable guide surfaces properly orient a tow bar eyelet for coupling. 
   Yet another object is to provide a locking aircraft towing hitch that may be aligned and locked by a single operator with reduced interaction with the aircraft tug operator.  

   
     DESCRIPTION OF THE DRAWINGS 
     The above and other features of the present invention will become apparent upon reading the following written description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a rear perspective view of an aircraft tug provided with the tug hitch assembly in the unlocked position prior to coupling with an aircraft tow bar; 
       FIG. 2  is a rear perspective view of the aircraft tug with the tug hitch assembly coupled in the locked position with the aircraft tow bar; 
       FIG. 3  is a side elevational view of the tug hitch assembly in the locked position with the aircraft tow bar; 
       FIG. 4  is a view showing the tow arm aligned at the hitch assembly in the locked position; 
       FIG. 5  is another view showing the hitch assembly in locked position with the tow bar; and 
       FIG. 6  is a top view of the tug hitch assembly; 
       FIG. 7  is a top view of the guide assembly of the tug hitch assembly taken along line  7 — 7  in  FIG. 5 ; and 
       FIG. 8  is a fragmentary view taken along line  8 — 8  in  FIG. 3  showing the lock assembly in the locked position. 
   

   DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1 and 2  for the purpose of describing a preferred embodiment of the present invention and not for limiting same, a self-aligning tug hitch assembly  10  is provided for coupling an aircraft tow bar  12  including a hitch eyelet  13  to the hitch  14  at the rear of an aircraft tractor or tug  16 . In  FIG. 1 , the tug hitch assembly  10  is in the unlocked position with the tow bar  12  proximate thereto. The tug hitch assembly  10  carries a  vertical indicating pole  18  having an indicator ball  19  at the top thereof. In the unlocked position, the indicator ball  19  is above the rear end of the tug  16  providing visual indication of the unlocked status. In  FIG. 2 , the tow bar  12  is coupled to the tug hitch assembly  10  in a locked position and the indicator ball  19  is below the rear of the tug and not visible to the operator thereby indicating the locked status. 
   Referring additionally to  FIG. 3 , the hitch  14  is of a type conventionally incorporated on commercial aircraft tugs. The hitch  14  comprises a pair of triangular, vertically spaced upper and lower plates  20 ,  21  defining therebetween a rearwardly opening horizontal slot for receiving the tow bar eyelet. As shown in  FIGS. 4 through 6 , the plates  20 ,  21  are attached at their base ends to the tug  16 . The plates  20 ,  21  have vertical coaxially aligned holes  22  at the forward end. In conventional use, a lock pin is inserted through the holes  22  for coupling the tow bar. The tow bar  12  is a conventional. In a coupling position as shown in  FIG. 4 , the opening in the eyelet  13  registers with the holes  22  in the plates  20 ,  21 . 
   The hitch assembly  10  includes a lock assembly  40  and a guide assembly  42 . The lock assembly  40  is fixedly connected above the upper plate  20  of the hitch  14 . The guide assembly  42  is fixedly connected in the horizontal slot between the upper and lower plates  20 ,  21  of the hitch  14 . 
   The lock assembly  40  includes a mounting plate  44 , a lock cylinder  46 , a lifting handle  48  and a release handle  49 . The mounting plate  44  and the guide assembly  42  are attached to the top surface of the upper plate  21  by pair of fasteners  50  in two longitudinally spaced transverse rows  52 ,  54 . The layout of the fastener holes conforms with existing hole patterns on many existing tugs.  
   The lock cylinder  46  is welded at a lower end to the top surface of the mounting plate  44  coaxial with the holes  22  in the hitch plates  20 ,  21  and a complementary hole in the mounting plate  44 . 
   Referring to  FIGS. 4 and 5 , a lock pin assembly  60  is slidably carried by the lock cylinder  46 . The lock pin assembly  60  includes a cylindrical piston  62  coaxially carrying at the lower end a downwardly depending lock pin  64 . A latch rod  66  is transversely connected to the piston  62 . As additionally shown in  FIG. 8 , the latch rod  66  extends outwardly through an upwardly opening vertical guide slot  68  formed in the rearward side of the cylinder  46 . A circumferential notch  69  is formed adjacent the slot  68  and provides a stop surface for the latch rod  66  in the unlocked position as described in greater detail below. 
   As shown in  FIGS. 1 and 5 , in a raised unlocked position, the piston  62  withdraws the lock pin  64  from the hitch slot. Thereafter the handle  49  is rotated to rotate the piston  62  to locate the latch pin  66  at the notch  69  to establish a detented locked position. In the locked position as shown in  FIGS. 2 and 4 , the handle  49  and piston  62  are rotated to align the latch rod  66  with the guide slot  68  allowing the piston to fall until the piston  62  engages the mounting plate  44  and the lock pin  64  slides into the openings  22  in the hitch plate  20 ,  21  thereby coupling the eyelet  30  of the tow bar  12  enabling towing of the aircraft by the tug  16 . If desired, a spring assist may be employed for biasing the piston after release. 
   Referring to  FIGS. 3 ,  6  and  8 , the lift handle  48  extends transversely to the mounting plate  44  rearward of the lock cylinder  46 . The inner end of the handle  48  is received between a pair of spaced transverse guide plates  70  attached to the mounting plate  44 . The lift handle  48  includes a horizontal leg  72  inwardly terminating with an upwardly inclined arm  74 . The outer  end of the arm  74  is connected at the upper and outer ends of the guide plates  70  by fastener  76  for pivotal movement about a longitudinal horizontal axis  78 . In the locked position the latch rod  66  is slightly above the arm  74  of the lift handle  48 . As an operator raises the leg  72  upwardly, the arm  74  engages the latch rod  66 , shifting the later and the latch pin assembly  60  upwardly in the guide slot  68 . The indicator pole  18  is carried at the top of the piston  62 . In the unlocked position, the ball  19  is above the top of the tug chassis and the ball is clearly visible by the tug operator  48  to denote an unlocked condition. In the locked condition, the ball  19  is below the chassis and not observable by the tug operator. Accordingly, the tug operator by virtue of the ball location can determine the locking status of the tug hitch. 
   Referring to  FIGS. 3 and 7 , the guide assembly  32  comprises a pair of laterally spaced, spring biased locating plate assemblies  80  pivotally attached at inner ends to the hitch  14 . The locating plate assemblies  80  are generally wedge shaped having triangular top and bottom plates, forwardly and inwardly converging front plates  82 ; and transverse rear plates  84 . The front plates  82  are normal to the vertical axis of the hitch opening  22  and defining a rearwardly opening triangular pocket of sufficient size for receiving and aligning the tow bar eyelet  13  with the locking pin  64  as the tug operator advances toward the tow bar. Preferably, the front plates  82  have an included angle of around 60° to 120°. Spring assemblies  86  bias the plate assemblies  80  to the illustrated normal position for receiving the tow bar eyelet. Each spring assembly  86  includes a compression spring  88  surrounding a threaded rod  90  having a hook end  92  captured by the shank of a fastener  50 . The front end of the rod  90  that extends through an aperture in the rear plate  84  and has a nut and washer assembly  94  adjustably connected thereto for establishing the inclination of the front plates  82  and preloading of the spring  88 . Access to the assemblies  94  is provided through apertures  86  in the top plate. As is apparent, in addition to guiding the tow bar into alignment for coupling, the plate assemblies  80  will absorb impacts during alignment. Further, each plate assembly  80  may pivot about the associated fastener  50  sufficiently to accommodate a tow bar orientation transverse to the tug  16 , thereby allowing tight radius turns in the towing of the aircraft.  
   In operation, a ground assistant aligns the tow bar  12  with the pocket of the guide assembly  42  as shown in  FIG. 1 . The tug operator has see the ball  19  to verify the unlocked condition. When the eyelet  13  is accurately aligned, the assistant rotates the release handle  49  to align with the slot  68  and the piston  62  and lock pin  64  to drop to the locked position shown in  FIG. 4 , thereby coupling the tow bar, whereat the ball  19  is no longer visible by the tug operator thus confirming the connection. 
   Unlatching is effected by raising the lifting lever  48 , as shown in  FIG. 5 , to raise the lock pin to the unlocked raised position. Thereafter, the release handle  49  is rotated to locate the latch rod  66  in the notch to establish the unlocked condition. 
   Having thus described a presently preferred embodiment of the present invention, it will now be appreciated that the objects of the invention have been fully achieved, and it will be understood by those skilled in the art that many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the sprit and scope of the present invention. The disclosures and description herein are intended to be illustrative and are not in any sense limiting of the invention, which is defined solely in accordance with the following claims.