Abstract:
A front axle assembly for a tractor or similar motor vehicle is provided with a front axle and a connecting unit interposed between the front axle and the frame of the tractor. The front axle assembly has an axle casing closed by oil-tight closing device supporting a gear for receiving motion from a propeller shaft forming part of the connecting unit.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a front axle assembly for a tractor or similar motor vehicle. 
     Though specific reference is made herein to a tractor, it is firmly understood that the following description also applies to any other motor vehicle which may be provided with a front axle assembly of the type dealt with in the present invention. 
     Axle assemblies are commonly known components in tractor manufacturing. Substantially, they comprise a front axle, and a connecting unit interposed between the front axle and the tractor frame. The connecting unit may be fitted to the frame at one end by means of a spherical joint, and at the other end by means of a suspension device located close to the front axle. One type of suspension device commonly used in the tractor industry is a PANHARD system. 
     Currently marketed axle assemblies, however, have several drawbacks. Foremost of these is the fact that they are normally supplied to the tractor manufacturing facility fully assembled, i.e. with the front axle unitary fitted to the connecting unit forming an extremely bulky, substantially T-shaped structure. This makes transport of the axle assembly as a whole difficult, especially on account of the length of the connecting unit between the front axle and the frame. 
     An inventive solution has therefore been devised to disconnect the front axle structurally from the connecting unit, to enable the front axle and the connecting unit to be manufactured separately, even at two remote manufacturing plants, and assembled later. 
     Moreover, the front axle and the connecting unit have different lubricating systems: whereas the front axle requires oil lubrication considering that it houses a differential and axle shafts, the connecting unit simply needs the normal greasing of the two universal joints of the propeller shaft, of the spherical joint on the suspension arm, and of the suspension device (eventually of the Panhard type). The axle assembly according to the present invention therefore enables separate manufacture, even at two remote manufacturing plants, of a perfectly oil-tight, oil-lubricated front axle, and a connecting unit which is greased after assembly. Moreover, the novel closing device for closing the axle casing to define the front axle not only ensures a perfect sealing of the front axle, but also enables an easy and effective connection to the front axle of one end of the propeller shaft and one end of the suspension arm. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to overcome the prior art drawbacks by providing an axle assembly having considerable advantages in terms of production by enabling the two basic substructures of the axle assembly—the front axle and connecting unit—to be manufactured separately. 
     According to the present invention, there is provided a front axle assembly for a tractor or similar motor vehicle, comprising a front axle and a connecting unit interposed between the front axle and the frame of the tractor; the front axle assembly being characterized in that the front axle in turn comprises an axle casing closed by oil-tight closing means supporting a gear for receiving motion from a propeller shaft forming part of the connecting unit. 
     It is an advantage of this invention that the manufacturing of the front axle and connecting unit can be accomplished at two different locations, followed by assembly. 
     It is another advantage of this invention that the front axle can be manufactured as an oil lubricated part and the connecting unit can be manufactured as a grease-lubricated part. 
     It is still another advantage of this invention that the assembly and disassembly of connecting unit and front axle can be accomplished through the use of fasteners, such as screws, to provide a trouble-free operation. 
     It is yet another advantage of this invention that the suspension device can be located between the axle casing and the joint. 
     These and other objects, features and advantages are accomplished according to the instant invention in which a front axle assembly for a tractor or similar motor vehicle is provided with a front axle and a connecting unit interposed between the front axle and the frame of the tractor. The front axle assembly has an axle casing closed by oil-tight closing device supporting a gear for receiving motion from a propeller shaft forming part of the connecting unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 shows a longitudinal section of a tractor featuring a front axle assembly in accordance with the present invention; 
     FIG. 2 shows a cross section of the FIG. 1 tractor illustrating in particular the suspension members of the connecting unit and the front axle; 
     FIG. 3 shows a longitudinal section of the front axle assembly according to the present invention; 
     FIG. 4 shows an enlarged first detail of the FIG. 3 front axle assembly; and 
     FIG. 5 shows an enlarged second detail of the FIG. 3 front axle assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1 and 2, a tractor  1  incorporating the principles of the instant invention, including an axle assembly  2 , can best be seen. In the following description, only the particulars of tractor  1  essential to a clear understanding of the present invention will be described in detail, the remaining aspects of the tractor being conventional and well known to one of ordinary skill in the art. 
     With reference to FIGS. 1 to  5  as a whole, axle assembly  2  substantially comprises a front axle  3  extending crosswise with respect to a connecting unit  4 . The unit  4  is located rearwardly of the axle  3  and extends lengthwise of tractor  1  between the frame  5  of the tractor  1  and the front axle  3 . 
     Front axle  3  supports in a known manner two front wheels  6   a ,  6   b , and houses axle shafts  7  driven by a propeller shaft  8  via a differential  9 . More specifically, front axle  3  can easily be divided into an axle casing  13 , which in a way represents the main housing of axle shafts  7  and the differential  9 , and an oil-tight closing device  14  closing axle casing  13  by means of conventional fastening means (not shown). 
     Connecting unit  4  on the other hand comprises a suspension arm  10  for supporting front axle  3 , which would otherwise rotate under the weight of frame  5 . Suspension arm  10  is connected to the frame  5  by an articulated joint  11  described in detail hereafter with reference to FIGS. 3 and 5. The connecting unit  4  further comprises a propeller shaft  8 , which is provided at one end with a universal joint  12 . 
     Closing device  14  of front axle  3  plays a decisive role in the present invention. The closing device, in fact, may be pre-fitted to axle casing  13  to define a lubricated, oil-tight front axle  3 , which is easily connectable, by means of four screws  15  (of which only two are shown in FIGS.  3  and  4 ), to suspension arm  10  which, together with the other components of connecting unit  4 , defines the portion of axle assembly  2  not requiring oil lubrication. 
     The main advantage of such a solution lies in the possibility of manufacturing front axle  3 —which, as stated, defines the oil-lubricated portion of axle assembly  2 —at a different plant from that producing connecting unit  4 . 
     In other words, closing device  14  defines a sort of cover for axle casing  13 , so that casing  13  may be filled with lubricating oil and transported safely, with basically no leakage, to the assembly plant for assembly to connecting unit  4 . 
     Closing device  14  (FIG. 4) in turn comprises a sleeve  16  connectable to casing  13  by known means, such as bolts (not shown). These bolts have countersunk heads so as not to interfere with a mating surface of a first end  17   a  of the suspension arm  10 . The outer shape of the sleeve  16  substantially reproduces the inner shape of said first end  17   a  of the suspension arm  10  and basically consists of a cylindrical portion running out in an outwardly turned flange. Part of the cylindrical portion of the sleeve  16  represents a close fit with an internal cylindrical portion of said first end  17   a  of the suspension arm  10 . The outer surface of sleeve  16  may therefore be fitted easily to the inner surface of first end  17   a  of arm  10 . This first end  17   a , as stated, is connected to front axle  3  by means of four screws  15 , which run through four appropriate holes in sleeve  16 , these holes being offset from the bolts for connecting sleeve  16  to casing  13 . 
     The cylindrical portion of sleeve  16  comprises two inner seats  18   a ,  18   b  for housing respective roller bearings  19   a ,  19   b  supporting a shaft  19 , which acts as a connecting member between universal joint  12  and differential  9 . Motion is actually transmitted between propeller shaft  8  and differential  9  by means of a pinion  20  which meshes with the gears of differential  9  and is fitted to shaft  19  at the end opposite the end facing universal joint  12 . Shaft  19  and propeller shaft  8  are connected by known systems at universal joint  12 . 
     A seal  21 , made of plastic material and fitted to shaft  19  at the end opposite pinion  20 , is operable to seal casing  13  and prevent leakage of lubricating oil from axle casing  13 . 
     Connecting unit  4  and closing device  14  are supported in known manner by a Panhard suspension device  22  suspended from frame  5  of tractor  1 . As shown in FIG. 2, suspension device  22  is defined by a supporting member  23 , which comprises a seat  24  for first end  17   a  of arm  10  and is suspended from a main body member  25  connected by known means (not shown) to frame  5 . More specifically, supporting member  23  is connected at one end, by means of an articulated joint  26 , to a lug member  27  integral with main body member  25 , and at the other end, by means of an articulated joint  28 , to one end of a hydraulic shock-absorbing cylinder  29 , the other end of which is connected by an articulated joint  30  to main body member  25 . 
     As shown in FIGS. 1 and 3, suspension device  22  is located between front axle  3  and spherical joint  11 , which provides a second connection of arm  10  to frame  5 . In other words, arm  10  and, consequently, front axle  3  are suspended from frame  5  by means of suspension device  22  at one end and spherical joint  11  at the other. 
     With particular reference to FIGS. 3 and 5, spherical joint  11  comprises a box body  30  connected to frame  5  by four screws  31  and two locating pins  32  (only one shown) which are provided for withstanding the shear stress from suspension arm  10 . Spherical joint  11  also comprises a hinge pin  33  fitted to the box body by means of two adjacent seats  34 ,  35 , each formed in a respective wall  30   a ,  30   b  of box body  30 . To form a connection between the suspension arm  10  and the spherical joint  11 , a ball  36 , combined with a respective ball bearing  37  integral with arm  10 , is interposed between pin  33  and a second end  17   b  of suspension arm  10 . As a result, as best can be seen from FIG. 3, spherical joint  11  permits both pitching and rolling oscillations of front axle  3 . 
     Front axle assembly  2  according to the present invention provides for excellent performance in terms of both stress distribution and power transmission. 
     In particular, the following advantages are accomplished according to the instant invention: 
     manufacturing front axle  3  and connecting unit  4  at two different locations, followed by assembly; 
     manufacturing an oil-lubricated first part (front axle  3 ) and a grease-lubricated second part (connecting unit  4 ); 
     trouble-free assembly and disassembly of connecting unit  4  and front axle  3  by means of screws  15 ; and 
     locating suspension device  22  between axle casing  13  and joint  11 . 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.