Abstract:
The moldboard support assembly for a motor grader reinforces the rear face of the moldboard by a series of vertical ribs. Upper and lower slide rails are secured to the ribs at a position outwardly of the rear face of the moldboard. This produces a series of gaps between adjacent ribs and between the rear face of the moldboard and the slide rails. These gaps allow material to clear away from the slide rails and thereby reduce bearing contamination of the slide rails.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a moldboard assembly for a motor grader and in particular, to a slide arrangement for the moldboard of the motor grader.  
           [0002]    Motor graders are used to grade a base material such as gravel or sand to provide a generally planar or contoured surface. It can be used to provide a consistent grade to a surface such as a road bed or road shoulder. These operations are accomplished by the accurate positioning and control of a moldboard which is suspended beneath the grader frame. The moldboard is slidable relative to a drawbar used to secure the moldboard to the grader frame. The securement of the moldboard beneath the grader frame should be designed to avoid wobble or excess clearance in the support arrangement as poor tolerance variations can very significantly affect the control the operator has on the moldboard and the precision that is possible in a grading operation.  
           [0003]    Motor graders perform relatively precise grading operations, however, they are a type of construction equipment and therefore, must be rugged and able to withstand very significant forces. The equipment is fairly robust in construction, however, the slide support of a moldboard and the requirement to maintain tight tolerances remain a difficult design problem. A moldboard, when in use, moves stone, dirt or other particulate material and this material can pass over the face of the moldboard and contaminate the slide arrangement which is located behind the moldboard. Such contamination can increase the wear of the slide bearings used to support the moldboard. Given the environment in which the grader is used and the nature of grading the slide support arrangement behind the moldboard will be subject to this type of contamination.  
           [0004]    Most grader moldboards have two horizontal slide rails secured on longitudinal channel type members secured to the rear of the moldboard. These channel members are horizontal, reinforce the moldboard, and typically support the slide rails. With this arrangement, dirt or other material which passes over the moldboard can collect and remains in close proximity to the slide rail.  
           [0005]    U.S. Pat. No. 5,678,800 and U.S. Pat. No. 5,076,370 are typical of the designs described above.  
           [0006]    The present invention overcomes a number of disadvantages of these prior moldboard support arrangements.  
         SUMMARY OF THE INVENTION  
         [0007]    A moldboard assembly according to the present invention comprises a moldboard, upper and lower slide rails secured to the moldboard by a series of vertical ribs spaced in the length of the moldboard and secured thereto. The ribs are secured to the rails at positions intermediate the length of the rails leaving an upper portion of one of the slide rails and a lower portion of the other slide rail unobstructed thereby defining bearing slide surfaces which traverse said ribs.  
           [0008]    According to an aspect of the invention, the ribs are secured to a lower portion of the upper rail and an upper portion of the lower rail.  
           [0009]    According to further aspect of the invention, each rib is spaced from an adjacent rib by a distance of less than 12 inches.  
           [0010]    In a preferred aspect of the moldboard assembly, each rib spaces the slide rails outwardly of the moldboard defining a series of gaps between said ribs and between said slide rails and said moldboard.  
           [0011]    According to yet a further aspect of the invention, the ribs are located to define a gap between adjacent ribs of less than 7 inches. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Preferred embodiments of the invention are shown in the drawings, wherein:  
         [0013]    [0013]FIG. 1 is a side view of a motor grader with a moldboard supported beneath the grader;  
         [0014]    [0014]FIG. 2 is a side view of a drawbar of a motor grader with a support arrangement for the moldboard secured beneath the drawbar;  
         [0015]    [0015]FIG. 3 is a rear view of the grader moldboard;  
         [0016]    [0016]FIG. 4 is a top view of the grader moldboard; and  
         [0017]    [0017]FIG. 5 is a sectional view taken along line A-A of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The motor grader  2  shown in FIG. 1 has a drawbar  4  suspended beneath the grader and the moldboard assembly  10  is supported beneath the grader frame  8  by lift cylinders  11  and side shift cylinder  15 . These cylinders in combination with a moldboard shift cylinder accurately locate the moldboard and maintain the position thereof beneath the grader frame.  
         [0019]    Additional details of the moldboard assembly  10  are shown in FIG. 2. The moldboard  14  has on the back face  18 , a series of vertical ribs  16 . These vertical ribs are welded or otherwise secured to the back face of the moldboard and provide reinforcement of the moldboard.  
         [0020]    The vertical ribs support the upper slide rail  20  and the lower slide rail  22  in a manner to allow the inverted V-shaped upper surface of the top slide rail and the V-shaped lower surface of the lower slide rail to act as bearing slide surfaces. The slide rails  20  and  22  are welded to the ribs and also reinforce the moldboard  14 . The slide rails, in combination with the vertical ribs, oppose deformation about the vertical axis of the moldboard.  
         [0021]    The series of vertical ribs  16  are preferrably spaced approximately 7 inches apart such that the upper and lower rails are supported every 7 inches. The moldboard assembly  10  includes a central support arrangement  26  which has attached thereto the upper slide bearing support arm  32  which locates the upper slide bearing  30  against the inverted V-shaped bearing slide surface of the upper slide rail  20 . The lower slide bearing support arm  38  is secured to the central support arrangement  26  and locates and supports the lower slide bearing  36 . Basically the V-shaped bearing surface of the lower slide rail is located within the lower slide bearing  36  and the upper slide bearing  30  is adjusted to allow sliding of the moldboard horizontally while reducing play in the fore or aft direction or in the vertical plane. In this way, the moldboard  14  is slidable relative to the central support arrangement  26  while being maintained to reduce wobble of the moldboard.  
         [0022]    During grading, the moldboard  14  is subject to high loads and the moldboard support assembly must oppose these large forces. The vertical reinforcing by the series of ribs  16  welded to the moldboard assist in transmitting these loads to the drawbar  4 . In addition the upper slide rail  20  and the lower slide rail  22  are substantial structural members welded to the ribs. These slide rails are made of square steel bars of a cross section two inch by two inch, and therefore provide longitudinal stiffening of the moldboard. This stiffening is enhanced due to the spacing of the rails at an upper and lower position as well as the outward spacing of the rails away from the back face of the moldboard.  
         [0023]    Furthermore, the inclined surfaces of the slide rails encourage any dirt or particulate material which passes over the face of the moldboard and onto these rails to slide off the rails through a gap between the back face of the moldboard and the slide rails or off the free edge of the rails. The vertical ribs are preferrably located at approximately every 7 inches and only present a small surface on which material might tend to accumulate. It has been found that any such material quickly falls away. The top surface of the ribs could also be inclined to encourage material to fall away.  
         [0024]    This self clearing of the slide rails has found to significantly increases or improves the life of the bearing slide members. This improvement in life renders the adjustability of the bearings less important in that they will maintain a tight tolerance longer and generally require infrequent service.  
         [0025]    As shown in some of the drawings, there are five slide bearings. There are three upper slide bearings and two lower slide bearings. The extra upper slide bearing is centrally located. The purpose of the center, upper bearing in the illustrated embodiment, is to transmit forces from the blade tilt adjusting glide. This bearing is required in alternate embodiments where a different structure is used for implementing blade tilt adjustment. The bearings are approximately 10 inches in length and provide a large surface area to distribute the loads.  
         [0026]    It has been found that the moldboard assembly as described above, is advantageously reinforced by the slide arrangement and the vertical support ribs welded at a host of positions intermediate the length of the moldboard also stiffen the moldboard. This assembly increases the strength and rigidity of the moldboard or allows the moldboard itself to be of less strength given that it is now reinforced by the ribs and the slide bars. The number of ribs connected by the rails are believed to cooperate to distribute loads.  
         [0027]    The spacing of the ribs along the moldboard can vary as a function of the moldboard itself, the size of the slide rails, and the size of the ribs. Preferrably the ribs are positioned at least every 12 inches. If the ribs are spaced at a greater distance, the slide rails could be increased in size and/or the moldboard longitudinally stiffened. The sizing of the ribs, rails and bearings, and the number of ribs determine the stiffness and fatigue properties of the moldboard. It is preferred to over design the components to reduce deformation and fatigue and to provide a stiff, robust moldboard.  
         [0028]    Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.