Multi-speed worm gear reduction assembly

Abstract

A gearbox assembly including a housing supporting an input shaft to drive a first shaft that includes drive gears that correspond to driven gears on a second shaft. The driven gears are movable axially along the second shaft by shift levers such that a desired gear ratio can be selected. The second shaft also includes a worm shaft portion that drives a corresponding worm gear disposed on an output shaft. Another embodiment includes an input shaft driving gears that engage drive gears of the first or second shafts. A gear on the third shaft drives a gear of an output shaft. The clutch assemblies move one the driven gears into engagement with one of the first and second drive gears to selectively vary the speed of the output shaft.

What is claimed is:  
     
         1 . A worm drive gear box assembly comprising; 
 a housing;    an input shaft supported by said housing, and driven at a first speed;    a first intermediate shaft driven by said input shaft and including at least one drive gears;    a second intermediate shaft driven by said first intermediate shaft and including a worm shaft;    an output shaft including a worm gear driven by said worm shaft of said second intermediate shaft, and driven at a second speed; and    said second intermediate shaft including at least two driven gears selectively engageable to said drive gears of said first intermediate shaft to vary a speed of said output shaft relative to said input shaft.    
     
     
         2 . The assembly of  claim 1 , wherein said drive gears are movable axially along said second intermediate shaft.  
     
     
         3 . The assembly of  claim 1 , wherein said drive gears include first, second and third drive gears.  
     
     
         4 . The assembly of  claim 3 , wherein said second intermediate shaft includes first, second and third driven gears selectively engagable with said drive gears.  
     
     
         5 . The assembly of  claim 4 , further including at least one shift lever to move said driven gears axially along said second intermediate shaft to selectively engage said drive gears.  
     
     
         6 . The assembly of  claim 4 , wherein at least two of said driven gears are included in a common integral spur gear.  
     
     
         7 . The assembly of  claim 1 , wherein said input shaft includes a gear head to drive a shaft gear on said first intermediate shaft.  
     
     
         8 . The assembly of  claim 7 , wherein said shaft gear, and said first and second gears comprise a cluster spur gear.  
     
     
         9 . The assembly of  claim 1 , wherein said housing includes a plurality of bearings to support rotation of said input shaft.  
     
     
         10 . The assembly of  claim 1 , further including a thrust washer and bearings to support said second intermediate shaft for rotation.  
     
     
         11 . The assembly of  claim 1 , wherein said second intermediate shaft includes a first splined portion, and a second worm gear shaft portion.  
     
     
         12 . The assembly of  claim 11 , further including a pair of bearing assemblies disposed on either side of said worm gear shaft portion.  
     
     
         13 . The assembly of  claim 1 , further including shifter levers to move said driven gears into engagement with said drive gears, said shift levers slidably disposed on a shifter bar.  
     
     
         14 . A worm drive gearbox assembly comprising; 
 a housing;    an input shaft supported by said housing, and driven at a first speed;    a first intermediate shaft driven by said input shaft including a first drive gear;    a second intermediate shaft driven by said input shaft including a second drive gear;    a third intermediate shaft driven by one of said first or second intermediate shafts and including first and second driven gears and a final drive gear;    an output shaft including a final driven gear driven by said final drive gear of said third intermediate shaft at a second speed; and    at least one clutch assembly disposed on said third intermediate shaft for shifting one of said first and second driven gears into engagement with one of said first and second drive gears to selectively vary said second speed of said output shaft.    
     
     
         15 . The assembly of  claim 14 , wherein said first intermediate shaft is also said input shaft.  
     
     
         16 . The assembly of  claim 14 , wherein said input shaft includes a first spur gear and said first and second intermediate shafts include second and third spur gears driven by said first spur gear.  
     
     
         17 . The assembly of  claim 14 , wherein said first intermediate shaft includes a worm shaft portion and said second intermediate shaft includes a helical gear.  
     
     
         18 . The assembly of  claim 14 , wherein said third intermediate shaft includes first and second clutch assemblies to selectively engage one of said first and second driven gears.  
     
     
         19 . The assembly of  claim 18 , wherein said clutches are remotely actuated.