Patent Publication Number: US-2011067513-A1

Title: Gear box assembly for rotating turret system

Description:
The present invention relates to rotating turret systems, and in particular to gear boxes for rotating turret systems. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  shows the HMMWV M-1114 (also commonly referred to as a Humvee). The HMMWV has seen extensive use by the U.S. Military during the recent wars in Iraq and Afghanistan. The HMMWV is available from AM General, Inc. and can be purchased with varying degrees of armament. For example an unarmored HMMWV is more likely to be used by the military behind the front lines and out of danger of heavy combat. The behind the line vehicles retail for an approximate price of $65,000. A heavily armored HMMWV is built to operate during combat and retails for an approximate price of $400,000. 
     HMMWV  1  includes rotating turret assembly  2 . Rotating turret assembly  2  includes .50 cal machine gun  3 . To operate .50 cal machine gun  3 , soldier  4  stands up within HMMWV  1  and stands behind armored shield  5  as shown. The soldier can fire machine gun  3  and receive armored protection from the armament of HMMWV  1  and armored shield  5 . 
     During combat and during patrol it is important to be able to have the ability to aim machine gun  3  in a full 360 degree pattern so that the gunner can protect himself and the other soldiers in the HMMWV and nearby. Hence, turret assembly  2  is fully rotatable allowing 360 degree coverage. 
       FIGS. 2-4  illustrate the prior art method of rotating turret assembly  2 . Prior art gears  8  and  18  are housed in prior art gear box  25 . Prior art gear box  25  is fabricated from cast aluminum. The soldier manning machine gun  3  is responsible for also rotating the position of turret assembly  2 . The soldier controls the position of turret assembly  2  by turning hand crank  7  ( FIG. 2 ). This causes a turning of 2:1 reduction gear  8  and causes turning of sprocket  9 . Sprocket  9  is connected via chain  11  to sprocket  10 . The turning of sprocket  10  causes turning of sprocket  12 . The teeth of sprocket  12  are engaged with the teeth  15  of turret  2 . Hence, the rotation of sprocket  12  directly controls the rotation of turret assembly  2 . 
     Failure of Turret Assembly in the Prior Art 
     Unfortunately, there is a very high rate of failure of turret assembly  2  during combat and patrol. An armored turret assembly (including armored shield  5 ) can weigh over 500 pounds. During combat, the soldier operating hand crank  7  turns it quickly to get into the appropriate position. This puts tremendous strain on the teeth of meshing gears  8  and  18 . Such a situation is obviously hazardous when, for example, the operator is attempting to maneuver a turret mounted weapon into firing position, especially when HMMWV  1  is on an incline ( FIG. 1 ) that adds additional gravitational forces that must be overcome. Once gear  8  fails, machine gun  3  cannot be rotated and HMMWV  1  becomes extremely vulnerable. 
     Test of Prior art Prior Art Gear Box 
     To test prior art gear box  25  a new prior art gear box  25  was attached to turret assembly  2  as shown in  FIG. 2 . HMMWV  1  was parked at a 30 degree slant as shown in  FIG. 1 . Turret assembly  2  was loaded with 400 pounds operational simulated load. A soldier operated hand crank  7  to rotate the turret assembly vigorously as if in a combat situation. After only 3 minutes of turning hand crank  7  prior art gears  8  and  18  failed, thereby rendering turret assembly  2  essentially useless. 
     What is needed is a better gear box assembly for turret assemblies. 
     SUMMARY OF THE INVENTION 
     The present invention provides a gear assembly for retrofitting a rotatable turret assembly having pre-existing mounting brackets. A gear assembly housing is fabricated so that it fits onto the pre-existing housing mounting brackets. An operator controlled hand crank is connected to an input shaft. The input shaft extends through the gear assembly housing and includes an input shaft gear that meshes with a drive shaft gear. The size of the drive shaft gear has been maximized so that it fits within the gear housing that has been mounted on the pre-existing mounting brackets. A drive shaft is connected to the drive shaft gear and extends through the gear housing. A sprocket is connected to the end of the drive shaft gear. The sprocket is mechanically linked to the turret assembly for controlling the rotation of the turret assembly. In a preferred embodiment, the turret assembly is mounted to a HMMWV. Also, in a preferred embodiment the gear housing is fabricated from 6061 billet aluminum and includes cuts to allow for a maximum sized drive shaft gear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art HMMWV with prior art turret assembly. 
         FIGS. 2-4  show a prior art gear box assembly. 
         FIGS. 5-7  show a preferred embodiment of the present invention. 
         FIG. 8  shows a preferred gear box assembly. 
         FIG. 9  illustrates the utilization of a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred gear box assembly  50  is shown in  FIGS. 5-7 .  FIG. 5  is an exploded view and  FIG. 6  is a side view.  FIG. 7  shows a front view of gear box  50  mounted inside prior art mounting brackets  52 . Preferred gear box assembly  50  is extremely cost efficient because it is unnecessary to redesign and rebuild turret assembly  2  by modifying or redoing mounting brackets  52 . Gear box  50  fits within the space allowed by pre-existing mounting brackets  52 . The horizontal distance between mounting brackets  52  is approximately 2⅛ inches. 
     As explained in the Background section, prior art gears  8  and  18  fail during normal combat usage. To solve the problem of gear failure, the gear box assembly uses larger gears  55  and  60 . Housing unit  57 , and end caps  58  and  59  are fabricated from high quality aircraft grade 6061 billet aluminum. Also, the utilization of end caps  58  and  59  allows for gear box assembly  50  to be easily taken apart for routine maintenance. 
     Components of the Preferred Embodiment 
     Drive Gear 
     Drive gear  55  is a spiral bevel gear. In the prior art gear box, drive gear  8  suffers failure primarily because of its size. It is therefore the goal of the present invention to make drive gear  55  as large as possible within the confines set up by mounting brackets  52 . In a preferred embodiment of the present invention drive gear  55  is approximately 1.86 inches in diameter. 
     Table 1 summarizes a preferred drive gear  55 : 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Gear Type 
                 Spiral Bevel Gear 
               
               
                   
                   
               
             
            
               
                   
                 Number of Teeth 
                 26/13 
               
               
                   
                 Pitch Diameter 
                 1.86/.93  
               
               
                   
                 Face 
                 .31 
               
               
                   
                 Bore 
                  .750/.4375 
               
               
                   
                 Mounting Distance 
                 1.188/1.250 
               
               
                   
                 Hub Diameter 
                 1.38/.81  
               
               
                   
                   
               
            
           
         
       
     
     Input Gear 
     Input gear  60  meshes with drive gear. Input gear  60  is attached to input shaft  62 . 
     Input Shaft 
     Input shaft  62  is supported by bearings  63  and  64 . Bearings  63  and  64  are separated by approximately 1.5 inches to allow for optimum support. The distance of 1.5 inches reduces torsional stress on input shaft  62 . Snap ring  65  helps hold bearing  64  in place and seal  66  seals housing  57 . 
     Coupler and Adapter 
     Coupler  67  and adapter  68  fit on input shaft  62 . Adapter  68  attaches to prior art crank  7  ( FIG. 2 ) to receive rotational input from the soldier operator. 
     Drive Shaft 
     Drive shaft  70  extends through housing  57  and is supported by bearings  71  and  72 . Bearing  71  fits into end cap  58  and bearing  72  fits into end cap  59 . Seal  73  is adjacent bearing  72  and seals drive shaft  70  within housing  57 . Drive gear  55  is connected to drive shaft  57  as shown. 
     Gear Housing and End Caps 
     Gear housing  57  and end caps  58  and  59  are all fabricated from 6061 billet aluminum. 6061 billet aluminum provides the optimum balance of hardness and strength to reduce unnecessarily torsional stress and wear on the gears. End caps  58  and  59  are both bolted to gear housing  57  ( FIG. 8 ). Maintenance and repair can be easily performed on any of the components by merely removing end caps  58  and  59  to have access. This is in contrast to prior art gear box  25  which does not have end caps and cannot be taken apart without damaging the gear box. A failure of prior art gear box  25  requires a replacement of the entire gear box. 
     It should also be noted that the utilization of 6061 billet aluminum allows the utilization of very large drive gears. For example,  FIG. 8  shows a gear housing  57  with a cut-out view to see drive gear  55 . Housing  57  has been cut at  57   b  to allow for drive gear  55  to extend almost to the edge of mounting bracket  52  ( FIG. 7 ). For example, 6061 billet aluminum is cut so that it is approximately ⅛ inch thick at  57   c  (near the location of drive gear  55 ). This allows for a maximum size drive gear  55 . 
     Drive Sprocket 
     Drive sprocket  95  is connected to the end of drive shaft  70 . Drive sprocket  95  is further held in place by utilization of bolt and washer  96 . 
     Utilization of Preferred Embodiment 
       FIG. 9  shows a perspective view of a preferred embodiment of the present invention utilized in turret assembly  2 . Gear box assembly  50  is easily bolted into pre-existing mounting brackets  52 . The soldier operator turns hand crank  7  to cause sprocket  12  engage teeth  15  to rotate turret assembly  2 . 
     Test of Preferred Embodiment 
     To test the preferred embodiment, gear box assembly  50  was attached to turret assembly  2  as shown in  FIG. 9 . HMMWV  1  was parked at a 30 degree slant as shown in  FIG. 1 . Turret assembly  2  was loaded with 400 pounds operational simulated load. A soldier operated hand crank  7  to rotate the turret assembly vigorously as if in a combat situation. After fifteen minutes of rigorous rotation, there was no failure. The operation load was then increased to 700 pounds. Again, after fifteen minutes of rigorous rotation, there was still no failure. 
     In the preferred embodiment described above, gear box assembly  50  has a load rating of 148 inch-pounds. This is a 100% increase in strength over prior art gear box  25 . 
     Other Features of the Preferred Embodiment 
     A significant advantage of gear box assembly  50  is that it is very easy to repair existing HMMWV&#39;s currently in operation. There is no need to replace the entire turret assembly, only the gear box assemblies need replacement. Also, drive gear  55  is larger and will last much longer than the prior art drive gear. Finally, when it is determined that it is appropriate to replace drive gear  55 , it can be replaced easily by removing end caps  58  and  59  as discussed above. Drive gear  55  can be inspected and replaced if necessary, without having to replace the entire gear box assembly  50 . 
     Other Applications of Improved Gear Box Assembly The above discussion focused on the utilization of gear box assembly  50  for a HMMWV. However, it should be noted that other turret systems on other military vehicles could also utilize the improved gear box assembly discussed above. For example, there are other MATV (Multipurpose All Terrain Vehicles) that have a rotating turret assembly with confined or pre-existing mounting brackets. For example, the MRAP (Mine Resistant Ambush Protected) vehicle includes a rotating turret assembly with pre-existing mounting brackets. Gear Assembly  50  could be configured to fit within the mounting brackets while simultaneously maximizing the size of drive gear  55 . 
     Although the above-preferred embodiments have been described with specificity, persons skilled in this art will recognize that many changes to the specific embodiments disclosed above could be made without departing from the spirit of the invention. Therefore, the attached claims and their legal equivalents should determine the scope of the invention.