Abstract:
A multiple wheel drive assembly including front and wheel axles and four independent gear boxes one for each wheel axle and two intermediate gear boxes each of which is connected to a pair of front and rear wheel axle gear boxes. Each of the gear boxes has a ring gear disposed therein and is capable of effectively reducing the inputted rpms up to eight times and also allows the user to easily adjust the wheel bases to any width and length without having to effect the gear boxes including the ring gears. Each pair of front and rear wheel axles are actuated independently of one another.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a multiple wheel drive assembly for a utility vehicle such as a skid steer. 
     Utility vehicles such as skid steers commonly have four wheel drive systems, wherein power is transferred to the front wheels independently of one another and is also transferred to the rear wheels independently of one another unlike passenger and transport vehicles such as automobiles and trucks. Currently, skid-steer types of utility vehicles have at least one elongate gear box extending substantially the length of the frame with a plurality of gears disposed in the oil-filled gear box. A drive shaft powered by the engine actuates the gears in the gear box, of which, in turn, actuates the axles to which the wheels are mounted at a gear reduction of up to fifty to one. This type of drive system is usually limited to a vehicle having just one wheel base length. Any changes to the length of the wheel base would involve changing the gear box and the number of gears therein, a problem not easily solved. In addition, because of the number of gears in the gear box and the oil contained therein, this type of drive system is exposed to many other problems, such as breakage of gears and the difficulty of repairing them and also leakage of oil from the large gear box. 
     Other types of utility vehicles commonly use chains and sprockets in their drive systems, wherein either the front or rear axles are driven by the drive shaft and the other of which is driven by an endless chain carried about sprockets mounted to the axles. This type of drive system has even more problems than the drive system having at least one large elongate gear box. Because of the herky-jerky motion typical of utility vehicles and the number of moving parts of the endless chains and sprockets, this type of drive system is more easily apt to break down, and the chains tend to stretch which commonly results in the chains slipping about the sprockets, all problems not encountered with by the present drive system. 
     SUMMARY OF THE INVENTION 
     The present invention includes a multiple wheel drive assembly which includes a plurality of conventional differential gears with a different differential gear being proximate to each wheel and also with a different differential gear being intermediate to each pair of front and rear wheels, and further includes a plurality of stub axles with one stub axle rotatably extending within each wheel differential gear, and also includes a plurality of drive shafts interconnecting each intermediate differential gear to each pair of respective front and rear wheel differential gears and interconnecting the intermediate differential gears, and further includes a plurality of support members one interconnecting the front wheel differential gears and one interconnecting the rear wheel differential gears for structural support and strength. Each differential gear includes a housing, a pinion gear and a ring gear disposed within the housing. 
     One objective of the present invention includes a multiple wheel drive assembly which can be quickly and conveniently adjusted to any wheel base size unlike the known prior art. 
     Another objective of the present invention includes a multiple wheel drive assembly which also strengthens the structural frame of the utility vehicle. 
     Also, another objective of the present invention includes a multiple wheel drive assembly which is operated essentially with drive shafts rather than gears thus substantially reducing the possibility of breakdowns commonly associated with gears which are more likely to wear out or be stripped than are drive shafts. 
     Yet, another objective of the present invention includes a multiple wheel drive assembly which costs substantially less than the known prior art and which is virtually maintenance free. 
     Further objectives and advantages of the present invention will become apparent as the description proceeds and when taken in conjunction with the accompanying drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective view of the multiple wheel drive assembly mounted upon the frame of a utility vehicle. 
     FIG. 2 is a top plan view of the multiple wheel drive assembly mounted upon the frame of a utility vehicle. 
     FIG. 3 is a detailed cross-sectional view of a differential gear of the multiple wheel drive assembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in FIGS. 1-3, in particular, the multiple wheel drive assembly comprises a plurality of conventional gear boxes  20 A-D, 22 A-B each of which includes a housing, a pair of opposed openings  20 B 1 -B 2  extending into the housing, a rotatable stub shaft  26 A journaled through a bearing (not shown) and extending into the housing through a third opening  20 B 3  therein at an approximately ninety degrees relative to the pair of opposed openings  20 B 1 -B 2  and having a first end disposed outside of the housing with an attachment member  26 A 1 ,B 1 ,C 1 ,D 1  disposed at the first end and including a conventional knuckle joint or a set of splines and further having a second end disposed inside the housing with a pinion gear  26 A 2  fixedly attached or welded to the second end. The pinion gear  26 A 2  is engaged to a ring gear  20 A 1  which is disposed inside the housing and which has an opening through the center thereof with the opening being defined by a plurality of keyways  20 A 2  spacedly disposed thereabout. Each wheel axle has its own gear box which operates independently of the other wheel gear boxes. Each wheel axle  30 A-D includes a stub axle, a portion of which extends to the outside of the frame  50  and the other portion of which extends inside the frame  50  and through a first one  20 B 2  of the pair of opposed openings in the respective housing. Each stub axle has a first end which extends inside the respective housing and which is engaged with the keyways  20 A 2  defining the opening in the ring gear  20 A 1  for rotation with the ring gear  20 A 1 . The front wheel gear boxes  20 C-D are structurally interconnected with a first and second support members  27 C-D with each having two ends. One of the ends  27 C 1  of the first support member  27 C is conventionally fastened to one of the ends  27 D 1  of the second support member  27 D with the other end of the first support member  27 C extending through the second one  20 B 1  of the pair of opposed openings in the housing of one of the front wheel gear boxes  20 C-D and being conventionally secured therein with fasteners, and with the other end of the second support member  27 D extending through the second one of the pair of opposed openings in the housing of the other of the front wheel gear boxes  20 D and being conventionally secured therein with fasteners. 
     The rear wheel gear boxes  20 A-B are structurally interconnected with third and fourth support members  27 A-B with each having two ends. One of the ends  27 A 1  of the third support member  27 A is conventionally fastened to one of the ends  27 B 1  of the fourth support member  27 B with the other end of the third support member extending through the second one of the pair of opposed openings in the housing of one of the rear wheel gear boxes  20 A and being conventionally secured therein with fasteners, and with the other end of the fourth support member  27 B extending through the second one of the pair of opposed openings in the housing of the other of the rear wheel gear boxes  20 B and being conventionally secured therein with fasteners. 
     As shown in FIGS. 1-2, in addition to each wheel axle  30 A-D having its own gear box  20 A-D, there are two additional gear boxes  22 A-B with one being disposed intermediate to one pair of front and rear wheel gear boxes and the other being disposed intermediate to the other pair of front and rear wheel gear boxes. Each intermediate gear box  22 A-B interconnects the respective front and rear wheel gear boxes  20 A-D with rotatable shafts  25 A-D, one of the rotatable shafts  25 A, 25 C extending through a first one of the openings in the respective intermediate gear box  22 A-B and being engaged in the keyways defining the opening through the ring gear and further having its other end coupled to the conventional attachment member  26 A 1 -D 1  of the stub shaft  26 A-D for one of the respective front or rear gear box  20 A-D, and another of the rotatable shafts  25 B, 25 D extending through a second one of the opposed openings in the respective intermediate gear box  22 A-B and being engaged in the opening through the ring gear and further having its other end coupled to the attachment member of the stub shaft for the other of the respective front or rear gear box  20 A-D. The ends of all the rotatable shafts which are coupled to the attachment members  26 A 1 -D 1  of all the stub shafts are essentially either sets of splines or knuckle joints, and all of the attachment members  25 A 1 -D 1  of the rotatable shafts  25 A-D are likewise essentially either sets of splines or knuckle joints. The ends of the rotatable shafts  25 A, 25 C which are securely coupled to the attachment members of the stub shafts  26 A, 26 C are essentially splined, and all of the attachment members of the stub shafts  26 A, 26 C are essentially splined also. The attachment members of the rotatable shafts  25 A, 25 C and the stub shafts  26 A, 26 C are coupled together with conventional coupling members which are essentially sleeves  28 A, 28 C having splined ends which are securely engaged to the attachment members  25 A 1 , 25 C 1 , 26 A 1 , 26 C 1  of rotatable shafts  25 A, 25 C and stub shafts  26 A, 26 C. The attachment members  25 B 1 , 25 D 1  of the rotatable shafts  25 B, 25 D and the attachment members  26 B 1 , 26 D 1  of the stub shafts  26 B, 26 D are coupled together with conventional knuckle pins  28 B, 28 D which are securely engaged to the attachment members  25 B 1 , 25 D 1 , 26 B 1 , 26 D 1  of rotatable shafts  25 B, 25 D and stub shafts  26 B, 26 D. Each intermediate gear box  22 A-B is attached to a motor  40 A-B such as a hydraulic motor which has a motor shaft  40 A 1 -B 1  with a pinion gear attached at the end thereof. The end of the motor shaft  40 A 1 -B 1  with the pinion gear is extended through the third one of the openings of the respective intermediate gear box  22 A-B, and the pinion gear is engaged to the ring gear disposed inside the respective intermediate gear box  22 A-B. The motors are capable of generating 3500 rpms with each gear box designed to reduce the inputted rpms anywhere up to eight times with the rpms at each axle being reduced to approximately 70 rpms. In operation, the motors actuate the ring gears in the gear boxes which, in turn, actuate the rotatable shafts at a substantial speed reduction with the rotatable shafts actuating the ring gears in the wheel axle gear boxes which actuate the wheel axles at another substantial speed reduction. This particular drive assembly allows the user to easily and conveniently change the width and length of the wheel base without having to redesign the drive assembly unlike the prior art by simply changing the length of the shafts interconnecting the gear boxes with the arrangement and number of gears remaining constant. 
     Various changes and departures may be made to the invention without departing from the spirit and scope thereof. Accordingly, it is not intended that the invention be limited to that specifically described in the specification or as illustrated in the drawings but only as set forth in the claims.