Grade averaging apparatus

An improved portable grade averaging apparatus comprising an averaging bar assembly that serves as an elevation control reference for a track supported road working machine. One end of an averaging bar member is pivotally supported by a forward steering drive track assembly that serves as a forward walking beam, and the other end of the averaging bar member is pivotally supported by a rear track assembly that serves as a rear walking beam. A grade sensor assembly supported on one side by the road working machine contactingly engages the averaging bar member for directing the elevation of one side of the road working machine to establish the elevation of a working tool supported by the road working machine.

BACKGROUND OF INVENTION 
1. Field of Invention 
The present invention relates generally to road working machines and, more 
particularly but without limitation, to an improved apparatus for 
providing a portable elevation control reference. 
2. Prior Art 
When a road working machine having a work piece, such as a planing cutter, 
is utilized to perform a surfacing operation on a roadway, such as a 
surface planing operation, an elevation control reference may be disposed 
alongside the roadway when the finished surface is to have a predetermined 
elevation. One of the more common means for establishing an elevation 
control reference is a conventional stringline setup positioned alongside 
the roadway. Sensing means on the road working machine continuously sense 
the elevation of the stringline above grade and provides an elevation 
control signal to an elevation control assembly provided as a part of the 
road working machine. In turn, the elevation control assembly maintains 
the work piece at a predetermined working elevation, or cutting depth, in 
relation to the grade of the roadway surface. Thus a uniform finish grade 
can be formed which is substantially free of high or low spots. In some 
instances, an existing curb alongside the roadway may be utilized in place 
of a stringline as the elevation control reference, if the grade elevation 
of the curb is generally uniform in relation to that of the roadway. 
Stringline setups have proven to be very valuable as utilized to provide an 
elevation control reference for making an initial pass down a roadway 
surface. It is relatively simple to construct a stringline setup along a 
shoulder portion of the roadway in a manner convenient to the positioning 
of the elevation sensing device. However, as subsequent passes are made 
along the roadway, it becomes highly impractical to utilize the initial 
stringline setup, and it is not economical to construct a separate 
stringline setup for each pass made by the road working machine. This is 
particularly true when the roadway is relatively wide. 
There are also many occasions when a planing operation is utilized to 
remove a specified amount of material from an existing roadway. An example 
of such would be where a planing specification requires the removal of the 
surface of a roadway down to a specified depth measured in inches below an 
existing roadway surface. 
Whether the roadway working machine is to remove surface material by 
referring to a stringline or to the existing surface itself, it would be 
desirable to have an elevation control reference which is portable, or 
which more or less, is always carried with the road working machine, or 
which can be readily attached thereto. Although not meeting this 
description, walking beam assemblies connected alongside a road working 
machine have been utilized in some instances to provide an elevation 
control reference which is roughly indicative of the desired finish grade. 
A walking beam assembly of this latter type is disclosed in U.S. Pat. No. 
3,414,327, issued to Austin. 
In the Austin patent, a grade elevation sensor assembly is utilized for 
determining the average grade elevation of the roadway forward of the work 
piece. The grade elevation sensor assembly provides a control signal 
indicative of this average grade elevation, and the control signal does 
substantially maintain the work piece at a predetermined working depth. 
However, since the grade elevation sensor assembly senses the grade 
elevation of the roadway forwardly of the work piece, the work piece will 
generally be maintained at a working depth indicative of the average grade 
elevation forward of the work piece as opposed to the average grade 
elevation next to the work piece. Thus, the resulting finish grade formed 
via the work piece will not be as uniform as if the work piece had been 
positioned at a working depth indicative of the average grade elevation of 
the roadway in near proximity to the work piece. 
An additional problem with conventional portable walking beam assemblies is 
that they restrict the maneuverability of the road working machine. In use 
of a road working machine employing a planing cutter, by way of example, 
the machine frequently must take multiple cutting passes along the 
roadway. At the end of each pass, the machine must be maneuvered into 
position to make the next cutting pass. It is not unusual to find that the 
machine must be turned around and repositioned to travel in the opposite 
direction, and such turn around often must be performed in tight quarters 
having minimum clearance and maneuvering room. When a conventional 
portable control reference apparatus is attached to the road working 
machine, more turn around area must be provided in which the machine is 
repositioned, or the control reference apparatus must be removed before 
turning the machine, and remounted once the machine is repositioned. 
Summary of Invention 
The present invention is related to the above mentioned U.S. Patent 
Application No. 887,004, and the disclosure contained therein is 
incorporated by reference into the present disclosure. The present 
disclosure deals with a portable grade averaging apparatus that is 
supported along one side of the road working machine, and provides a 
portable grade averaging apparatus for providing an elevation control 
reference that is adjacent to a work piece carried beneath the frame of 
the road working machine. The grade averaging apparatus is continuously 
contacted by a grade sensor, the elevation control reference being 
indicative of the average grade of selected reference surfaces near the 
work piece. More particularly, the apparatus utilizes a front steering 
drive track assembly of the road working machine as a forward walking 
beam, and it utilizes a rear drive track assembly as a rear walking beam. 
The forward steering drive track assembly, serving as a track walking 
beam, provides a forward elevation reference indicative of the average 
grade elevation forwardly of the work piece, and the rear drive track 
assembly, serving as a track walking beam, provides a rear elevation 
reference indicative of the average grade elevation rearwardly of the work 
piece. An averaging bar member, pivotally supported by each of the forward 
steering drive track assembly and the rear drive track assembly provides 
the elevation control reference which is indicative of the average of the 
front elevation reference and the rear elevation reference. Since the 
front steering drive track assembly must be free to swivel relative to the 
frame of the road working machine in order to effect steering of the 
machine, a swivel plate assembly is supported by the front steering drive 
track assembly and bearingly supports the forward end of the averaging bar 
member in a manner that permits both pivotation and swiveling motion of 
the forward steering drive track assembly relative to the forward end of 
the averaging bar member. 
It is an object of the present invention to provide an improved grade 
averaging apparatus that is connectable to a road working machine such 
that the forward and rear track assemblies along one side of the machine 
serve as track walking beams to provide an elevation control reference 
indicative of the average of the grade elevations forwardly and rearwardly 
of a work piece connected to the frame of the road working machine. 
Another object of the present invention is to utilize the supporting drive 
track assemblies of one side of a road working machine as the grade 
averaging portions of the grade averaging apparatus, without further need 
of other grade averaging devices along that side of the road working 
machine. 
Yet another object of the present invention is to provide a self-storing 
portable grade averaging apparatus that affords greater maneuverability 
for the road working machine. 
A further object of the present invention is to provide an improved 
portable grade averaging apparatus that offers simplicity of construction, 
and which requires minimum upkeep and repair. 
Other objects, advantages and features of the present invention will become 
apparent from the following detailed description when read in conjunction 
with the accompanying drawings and appended claims.

Description of the Embodiment 
Referring to the figures in general, and to FIGS. 1 and 2 in particular, 
shown therein is a road working machine 10 assembled in combination with a 
grade averaging apparatus 12 constructed in accordance with the present 
invention. The road working machine 10 that is shown is a planar apparatus 
that is generally utilized to perform surfacing or resurfacing operations 
on an existing, or old grade 13 of a roadway 14. The grade averaging 
apparatus 12 is utilized to provide a first elevation control reference 
generally indicative of, or proportional to, a selected surface whereby a 
new surface, or finished grade 16, is formed, as will become more clear 
below. In the interest of simplifying the drawings included in the present 
disclosure, details such as hydraulic conduits, electrical lines, and 
machine controls have not been shown as such are conventional and need not 
be described for purposes of this disclosure. 
An illustrative example of a conventional road working apparatus such as 
the machine 10 is disclosed in U.S. Pat. No. 4,139,318, entitled "A Method 
and Apparatus for Planing a Paved Roadway", assigned to the assignee of 
the present invention. Even though the present invention is particularly 
applicable to the planing of a paved roadway, it should be noted that the 
present invention is also applicable to other roadway surfaces such as, 
for example, grading. Furthermore, as will be clear to one skilled in the 
art, even though the road working apparatus related to the above mentioned 
patent application as disclosed therein has been utilized for planing a 
paved roadway, it is contemplated that the basic form of such a road 
working apparatus could, with minor modifications, be used for other road 
surfacing operations such as, for example, grading. 
In a basic form, the road working machine 10 generally comprises a frame 
18; a prime mover, such as a diesel power plant 19A; a hydraulic pump 
assembly 19B; a work piece 20 supported by the frame 18; a drive assembly 
21 connected to and supporting the frame 18; a grade sensor assembly 22A 
connected to the frame 18 and supported adjacent the work piece 20 near a 
right side 23 of the frame 18; another grade sensor assembly 22B connected 
to the frame 18 and supported adjacent the work piece 20 near an opposite, 
or left, side 24 of the frame 18; and an elevational control assembly 25, 
connected to the frame 18 and having portions connected to the drive 
assembly tracks of the drive assembly 21, as will be described more fully 
below. 
The frame 18 substantially includes the chassis, body panels, and in 
general, all of the supportive and protective portions and components 
normally associated with a road working machine such as the machine 10. 
The work piece 20 is rigidly attached to the underside of the frame 18 and 
extends generally transversely to a medial portion of the frame 18, and 
therefore the work piece 20 also extends generally transversely to the 
roadway 14. The elevation of the work piece 20, which is the portion of 
the road working machine 10 that interacts with the roadway 14, is 
determined by the elevation of the frame 18. Of course, the type of 
surfacing operation performed on the roadway 14 by the road working 
machine 10 is determined by the kind of work piece utilized. 
In one embodiment of the present invention and as shown more clearly in 
FIG. 3, the work piece 20 is in the form of a drum type planer apparatus 
28, such as that disclosed in the above mentioned patent No. 4,139,318. A 
planer housing 30 is disposed about the planer apparatus 28 to contain 
road material cuttings produced by the planer apparatus 28 and to form a 
supportive means for other components of the present invention to be 
discussed below. 
As shown in FIGS. 1 and 2, the drive assembly 21, provided for moving the 
frame 18 in a forward direction 32 as powered by the conventional prime 
mover 19A and the hydraulic pump and transmission 19B (not detailed), 
comprises a right front steering drive track assembly 33A, a left front 
steering drive track assembly 33B, a right rear drive track assembly 34A, 
and a left rear drive track assembly 34B. The rear drive track assemblies 
34A and 34B are pivotally connected to the frame 18 so as to be pivotable 
about a rear control axis 36 disposed rearwardly of the work piece 20, and 
for convenience of description herein, the rear drive track assemblies 
34A, 34B will be referred to respectively as right and left rear drive 
track assemblies, said designations arbitrarily assigned from the 
perspective of an operator of the machine 10 who is facing in the forward 
direction 32. 
In like manner to that above described for the rear drive track assemblies 
34A and 34B, the front steering drive track assemblies 33A and 33B are 
pivotally connected to the frame 18 so as to be pivotable about a forward 
control axis 37 disposed forwardly of the work piece 20. Also each of the 
front steering drive track assemblies is connected via conventional 
steering means so as to swivel in the rotational directions 38A and 38B as 
shown by the respective arrows in FIG. 2. This permits the machine 10 to 
be steered by selectively directing the front steering drive track 
assemblies 33A and 33B to swivel in unison as the machine 10 is operated. 
Each of the rear drive track assemblies 34A and 34B has a ground contact 
portion 39 which is in continuous driving contact with a surface portion 
of the roadway 14 as the frame 18 is moved in the forward direction 32 by 
the drive assembly 21. The ground contact portion 39 of each rear drive 
track is further characterized as having a leading end 40 and a trailing 
end 42. The distance between the leading end 40 and the trailing end 42 
(that is, the length of the ground contact portion 39) defines the 
effective span of the respective rear drive track assemblies 34A and 34B. 
Furthermore, each of the rear drive track assemblies 34A and 34B is of 
such construction that the ground contact portion 39 extends in a planar 
fashion between the leading and trailing ends 40 and 42 thereof regardless 
of the contour of the supporting grade. Thus, the elevation above grade of 
the rear control axis 36 at each side of the frame 18 at any selected 
position relative to the roadway 14 will be indicative of, or proportional 
to, the average of the difference (if any difference exists) between the 
grade elevations of the leading and trailing ends 40 and 42 of the ground 
contact portions 38. 
In like manner to that described for the rear drive track assemblies 34A 
and 34B, each of the forward steering drive track assemblies 33A and 33B 
has a ground contact portion 43 which is in continuous driving contact 
with the roadway 14. The round contact portion 43 of each front steering 
drive track assembly has a leading end 44 and a trailing end 45, and the 
distance between these ends defines the effective span of the respective 
forward steering drive track assemblies 33A and 33B. Furthermore, each of 
the forward steering drive track assemblies 33A and 33B is of such 
construction that the ground contact portion 43 extends in a planar 
fashion between the leading and trailing ends 44 and 45 thereof regardless 
of the contour of the supporting grade. Thus, the elevation above grade of 
the front control axis 37 at each side of the frame 18 at any selected 
position relative to the roadway 14 will be indicative of, or proportional 
to, the average of the difference (if any difference exists) between the 
grade elevations of the leading and trailing ends 44 and 45 of the ground 
contact portions 43. 
The grade assembly 22A, shown more clearly in FIG. 3, is preferably 
connected to a portion of the frame 18 in near proximity to the work piece 
20 in a selectively positionable manner, and is utilized to sense the 
first elevation control reference provided by the grade averaging 
apparatus 12. In response to sensing the first elevational control 
reference, the grade sensor assembly 22A provides a first elevation 
control signal to a portion of the elevation control assembly 25 which is 
indicative of, or proportional to, a deviation of the right end of the 
work piece 20 from the first elevation control reference, as will become 
more clear below. The grade sensor assembly 22A has a sensor actuating 
portion which specifically senses the first elevation control reference 
and, in response thereto, causes the grade sensor assembly 22A to provide 
the first elevation control signal. In the preferred embodiment, the grade 
sensor assembly 22A is in the form of a hydraulic sensor 46A having a 
sensing wand 48A which generally defines the sensor actuating portion 
thereof. More particularly, in the preferred embodiment, the sensing wand 
48A is pivotally connected to the hydraulic sensor 46A and controls the 
positioning of a fluid valve (not shown) disposed therein, with the fluid 
valve controlling fluid flow to a portion of the elevation control 
assembly 25, as will become clear below. 
The grade sensor assembly 22B, located near the opposite side 24 of the 
frame 18, and viewable in FIG. 2, is similar in construction to that 
described for the grade sensor assembly 22A, and comprises a corresponding 
hydraulic sensor 46B and sensing wand 48B. In like manner to that 
described for the grade sensor assembly 22A, the grade sensor assembly 22B 
provides a second elevation control signal via the positioning of a fluid 
valve that controls fluid flow to a portion of the elevation control 
assembly 25. The grade sensor assembly 22B cooperates with other 
apparatus, described below, to sense the positioning of a second elevation 
control reference. 
The elevation control assembly 25 is utilized to vary the elevation of the 
frame 18, and consequently, the work piece 20 in response to the elevation 
control signals provided via the grade sensor assemblies 22A and 22B. 
Thus, the elevation and slope of the work piece 20 is determined relative 
to the first and second elevation control references. In other words, the 
work piece 20 is selectively positionable in a vertical manner by the 
operation of the elevation control assembly which determines the elevation 
of the frame 18. In the road working machine 10 herein described, the 
elevation control assembly 25 comprises hydraulic cylinder 34H and 35H 
that are connected respectively between the frame 18 and the right rear 
drive track assembly 34A and the left rear drive track assembly 34B. The 
hydraulic cylinders 34H and 35H, shown in broken line detail in FIGS. 1 
and 2, serve to position the frame 18 vertically relative to the 
supporting rear drive track assemblies 34A and 34B. Also, the elevation 
control assembly 25 comprises a pair of hydraulic cylinders 33H that are 
connected between the frame 18 and the front steering drive track 
assemblies 33A and 33B; the hydraulic cylinders 33H serve to vertically 
position the front portion of the frame 18 relative to the front steering 
drive track assemblies 33A and 33B. The grade sensor assemblies 22A and 
22B are in fluid communication with the elevation control assembly 25 by 
valves and conduits that are not shown in the drawings, but which are 
conventional in the prior art. 
With further reference to FIGS. 1 and 2, the grade averaging apparatus 12, 
which has been referred to above, generally comprises a bar member 50 
having a forward end 52, a mid portion 54 and a rear end 56. The rear end 
of the bar member 50 is pivotally connected to the right rear drive track 
assembly 34A via a bearing connection to a stationary arbor supported by 
the right rear drive track assembly 34A near the rear control axis 36 at a 
pivoting point defining the rear elevation reference. 
The forward end 52 of the bar member 50 is supported by a bar connecting 
assembly 60 as shown in FIG. 1, and as also shown in more detail in the 
partial views of FIGS. 5 and 6. Supported by the right forward steering 
track assembly 33A, the bar connecting assembly 60 is comprised of a 
swivel plate assembly 62 that includes a mounting base 64 shaped in the 
form of a pedestal and attached to the left forward steering drive track 
assembly 33A via bolting means. Attached to the upper portion of the 
mounting base 64 is a platform member 66 that is a planar member generally 
horizontally disposed and generally curvilinearly shaped (as best shown in 
the plan view of FIG. 6). The platform member 66 has an upper surface 68 
that serves as a bearing surface upon which the weight of the forward end 
52 of the bar member 50 is borne. 
The bar connecting assembly 60 also comprises a bearing assembly 70 that 
attaches to the forward end 52 of bar member 50 and which is interposed 
between bar member 50 and the swivel assembly 60. The bearing assembly 70 
is comprised of a block portion 72 having a bore (not shown) through which 
the bar forward end 52 extends. Locking means secure the block 72 in a 
determined position on the bar forward end 52. A swivel ball assembly 74 
is attached to the block 72 at the lower end of the bearing assembly 70. 
The swivel ball assembly 74 has a pair of swivel casters 76, retained in a 
race 78, that engage the bearing surface 68 of the swivel platform 66. 
The bar connecting assembly 60 supports parts of the weight of the bar 
member 50 and transfers that weight to the right front steering drive 
track assembly 33A in a manner that permits the swiveling movement of the 
track 33A beneath the bar member 50 without affecting the elevation of the 
bar member. This will be described in more detail below. 
The shape of the bar member 50 is not believed to be limiting in the 
present invention, and as drawn in the present disclosure, the forward end 
portion 52 and the rear end portion 56 are angularly attached to the mid 
portion 54 such that the mid portion 54 is positioned at a convenient 
elevation to meet the placement needs of the right grade assembly 22A. It 
will be recognized that other shapes could be assigned to the bar member 
50, but it is recommended that the shape be established such that the mid 
portion 54 is generally horizontally disposed when the road working 
machine 10 is on substantially level ground. In the drawings attached 
hereto, the bar member 50 is composed of hollow, square stock portions, 
and the mid portion 54 has an upper surface that is designated by the 
numeral 75. As shown in FIG. 4, an attaching member 80 is provided to 
connect the sensing wand 48A to the bar mid portion 54. 
The attaching member 80 comprises a bracket 82 having a bore through which 
the cross sectional shape of the bar member 50 is passable, and an 
extendable arm assembly 84. The bracket 82 has a socket 86 which secures 
to one end of the arm assembly 84 via locking means, while the other end 
of the arm assembly 84 has a loop portion 88 that is disposable over the 
sensing wand 48A. The arm assembly 84 has a hollow upper portion 90 into 
which the upper end of the lower portion 92 of the arm assembly 84 is 
received. A locking screw 94 secures these two portions together to 
determine the length of the arm assembly 84. This arrangement connects the 
wand 48A to the bar member 50, and the position of the upper surface 75 of 
the bar mid portion 54 determines the elevation of the wand 48A. 
Turning again to the rear track assembly 34A, it will be clear that the 
pivotal nature of the right rear drive track assembly 34A about the rear 
control axis 36 causes the right rear drive track assembly 34A to act as a 
track walking beam, and the rear elevation reference is therefore 
indicative of the average grade of the surface that supports the right 
rear drive track assembly 34A. The bar member 50 is connected at a pivot 
point on the track assembly 34A that is fixed in constant spatial 
relationship to the rear control axis 36; for this reason, a change in 
elevation of the rear control axis 36 will effect an exact elevational 
change to the rear elevation reference (defined as passing through the 
center of the arbor or pivot point to which the bar rear end 56 is 
connected). 
In like manner, the bar forward end 52 is supported via the bar connecting 
assembly 60 to provide a pivot point defined by the contacting area of the 
swivel ball 76 of the bearing assembly 70 that bearingly engage the 
bearing surface 68 of the swivel plate assembly 62. This arrangement 
provides for a pivotal support of the bar forward end 52 relative to the 
right forward steering drive track assembly 33A. The pivotal nature of the 
right forward steering drive track assembly 33A about the forward control 
axis 37 causes the track 33A to act as a track walking beam; consequently, 
the elevation of the forward control axis 37 is determined by the average 
grade of the surface supporting the right forward steering drive track 
assembly 33A. The forward elevation reference, defined as passing through 
the point of contact of the swivel ball 76 with the bearing surface 68, 
remains a fixed distance away from the forward control axis 37, even 
though this axis will turn with the swivel rotation of the track assembly 
33A. Of course, practical construction considerations bear upon these 
relationships, and it is recognized that the bearing surface of the swivel 
balls 76 is an area of contact and not that of a single point. However, 
one caster could be used in the present invention, or other means could be 
utilized which would more exactly define a point of pivotation that could 
then more accurately be referred to as a forward elevation reference, but 
for purposes of the present invention, the described arrangement of 
multiple swivel balls has proven to be satisfactory for providing 
sufficient operating sensitivity and for distributing the stress over a 
larger area of contact. Further, it is recognized that a swivel rotation 
of the track 33A varies somewhat the distance between the forward 
elevation reference and the forward control axis 37 (however, the distance 
between the vertical center of the track 33A and the forward elevation 
reference remains constant). As the right forward steering drive track 
assembly 33A swivels, the platform member 66 turns under the bearing 
assembly 70 such that the swivel casters 76 bear against the bearing 
surface 68 along a travel arc of contact. This arrangement permits 
steering rotation of the forward steering drive track assembly 33A without 
effect on the elevation of the forward elevation reference. A change of 
elevation of the forward control axis 37 as the forward steering drive 
track assembly 33A passes over surface irregularities will effect an 
identical change in elevation to the forward control reference to the bar 
forward end 50. 
From the above, it will be clear that if the bar 50 were to extend linearly 
between the rear elevation reference and the front elevation reference in 
parallel relationship to the roadway 14, the mid point therebetween as 
located on the bar 50 would substantially define an elevation above grade 
generally indicative of the average of the rear elevation reference and 
the front elevation reference. However, in a more practical situation, 
since the bar 50 is constructed to conform to requirements of the road 
working machine 10, the actual mid point between the rear and front 
elevation references, as located on the bar member 50, may not accurately 
define the elevation control reference as an average of the contour sensed 
by the forward and rearward track assemblies 33A and 34A. Accordingly, the 
bracket 82 of the attaching member 80 is adjustable along the mid portion 
84, within the other structural restraints above mentioned, in order to 
achieve optimum placement thereof corresponding to achieving indication of 
the average elevation between the forward and rear walking beams provided 
by the forward and rear track assemblies 33A and 34A. 
As mentioned above, the grade sensor assembly 22B, shown in FIG. 2, is 
located on the opposite side 24 of the frame 18, and serves in a similar 
manner to that described for the grade sensor assembly 22A that is located 
on side 23 of the frame 18. That is, the sensing wand 48B of the grade 
sensor assembly 22B serves to sense the location of an arm 84B that 
extends from a conventional skid assembly 100 that is supported by the 
planer housing 30 along the opposite side 24. Of course, another grade 
averaging apparatus constructed in accordance with the present invention 
and similar to the grade averaging apparatus 12 could be attached to the 
side 24, and if this were done, the wand 48B would be actuated by an 
attaching member similar to the attaching member 80. However, for the 
purpose of this disclosure, a conventional skid 100 is displayed in FIG. 
2, and since the construction of such skids is known, details need not be 
given herein except to comment that the skid 100 is constructed to slide 
along a surface adjacent the opposite side 24 as the road working machine 
10 moves along the roadway 14. 
It will be recognized that a stringline could be set up for sensing by the 
wand 48B, in which case the wand 48B would be oriented to extend generally 
normal to the side 24. As will be discussed below, the use of a stringline 
is an option that may be desirable for a cutting pass close to the edge of 
a roadway. Another option of controlling the elevation of a portion of the 
frame 18 is a conventional slope control that would position one portion 
of the frame 18 at a constant setting relative to another portion of the 
frame 18. Since slope controls are well known, further discussion need not 
be provided. 
Operation 
During a typical surfacing operation, such as a surface planing operation 
performed by the work piece 20, the road working machine 10 and the work 
piece 20 are initially aligned over the roadway 14 at a designated 
take-off area, with the work piece 20 being disposed generally 
transversely to the roadway 14. The take-off area generally defines the 
starting point of an initial pass to be made over the roadway 14 by the 
machine 10. 
Before the machine 10 begins the initial pass, an elevation control 
reference is normally established along the side 24 in order to maintain 
the working depth of the work piece 20 at a constant elevation relative to 
the roadway surface. For the initial pass, the second elevation control 
reference along the edge of the roadway 14 may be provided in a 
conventional manner such as by the use of a stringline along the edge, or 
if there should be a curbing surface or the like adjacent the roadway 14, 
the skid 100 (or a grade averaging assembly similar to the grade averaging 
assembly 12) may be utilized to provide the second elevation control 
reference for the initial pass. That is, the present grade averaging 
apparatus 12 can be used on either side or on both sides of the machine 
10; or the grade averaging apparatus can be used on one side of the 
machine 10 while the elevation of the opposite side of the machine 10 is 
controlled by a stringline, by a conventional skid apparatus, or by a 
cross slope control. In the interest of brevity herein, the present 
invention will be discussed with the machine 10 equipped with the skid 100 
on one side of the machine and with the grade averaging apparatus 12 on 
the other side. The assignment of the machine 10 for the purpose of this 
discussion will be to remove the top surface of the roadway 14 to a 
uniform depth of a determined number of inches measured from the top of 
the existing grade. 
In this mode of the machine 10, the elevation of the frame 18 would be 
controlled as follows. The first elevation control reference is provided 
by the grade averaging apparatus 12, and the grade sensor 22A provides the 
first elevation control signal to a portion of the elevation control 
assembly 25 as the sensing wand 48A is actuated as the machine 10 
progresses forward. The hydraulic cylinder 34H, connected between the 
frame 18 and the right rear drive track assembly 34A, is actuated and 
positioned in response to this first elevation control signal. 
Continuing the discussion of this mode of the machine 10, the second 
elevation control reference is provided by the skid apparatus 100, and the 
grade sensor 22B provides the second elevation control signal to a portion 
of the elevation control assembly 25 as the sensing wand 48B is actuated 
by the skid 100 as it moves along the surface adjacent to the side 24 of 
the frame 18. The hydraulic cylinders 33H connected between the frame 18 
and the front steering drive track assemblies 33A, 33B are hydraulically 
coupled and are actuated for extension or contraction in response to the 
second elevation control signal. 
In operation, the roadway machine 10 is positioned to make the initial 
pass. The skid 100 is supported on a curb apron or the like along the edge 
of the roadway 14, and the grade averaging apparatus 12 is supported 
alongside the machine 10 on the existing pavement surface of the roadway 
14. While in this position, the elevation of the frame 18 is altered by 
manually controlling the hydraulic cylinders 33H, 34H and 35H (by manual 
controls not shown) to position the work piece 20 in touching contact with 
the top of the roadway 14. That is, the axis of the work piece 20 will at 
this point have been placed in transverse and parallel relationship to the 
top surface of the roadway 14 since the slope of the axis of the work 
piece 20 will be the same as the transverse slope of the roadway 14. Once 
this has been achieved, the rotation of the work piece 20 is commenced, 
and the entire frame 18 is lowered by the required number of inches 
necessary to achieve the specified depth of cut. At this point, the 
machine 10 is advanced until the rear drive track assemblies are 
positioned on the finish grade 16, and the hydraulic cylinder 35H is 
locked in a fixed position to lock the left rear drive track assembly 34B 
to grade. This establishes the rear portion of the frame 18 on the side 24 
at a fixed elevation above the newly cut finish grade 16. The elevation 
control assembly is now set on its automatic mode to maintain the 
specified cutting depth as controlled by the grade sensor assemblies 22A 
and 22B that respectively control the elevation of the frame 18 by 
effecting the extension, respectively, of the hydraulic cylinders 34H and 
33H. At this point, the roadway machine 10 is prepared for cutting 
advancement along the roadway 14. 
As the machine 10 moves forward, a depression in the existing grade, were 
it not for the present invention, would cause the work piece 20 to deviate 
downwardly to an elevation below the desired cutting depth. However, the 
first elevation control signal provided by the grade averaging apparatus 
12 of the present invention will offset this tendency by signalling the 
elevation control assembly to change the elevation of the frame 18 (and 
consequently the elevation of the work piece 20) by an amount proportional 
to an average of forwardly and rearwardly sensed grade elevations. In this 
way, the work piece 20 will be maintained at a more uniform cutting depth 
in relation to the average grade elevation of the roadway 14 as indicated 
by the grade averaging apparatus 12. 
The work piece 20 forms a work path as the road working machine 10 makes it 
initial pass over the roadway 14, with the rear drive track assemblies 34A 
and 34B following the work path in the wake of the work piece 20 when the 
distance span of the rear drive track assemblies 34A and 34B is less than 
the transverse length of the work piece 20. When a planing operation is 
being performed by the machine 10, the work path represents that portion 
of the roadway 14 which has been planed, designated as the finish grade 
16. As mentioned above, the elevation controls must be adjusted once the 
rear drive tracks 34A and 34B are resting in the work path so as to obtain 
the desired cutting depth. 
After the initial pass has been completed, the road working machine 10 is 
usually positioned to make at least one, and generally several subsequent 
passes adjacent to the initial pass until the entire roadway 14 has been 
exposed to the planing operation. During all subsequent passes, as in the 
initial pass, the grade averaging apparatus 12 is again utilized to 
provide the first elevation control reference, and the skid apparatus 100 
again is repositioned to provide the second elevation control reference. 
However, during the subsequent passes, the skid 100 will slide along the 
cut work path of the previous pass, necessitating adjustment of the 
elevation of the frame 18 once again as described above for the 
commencement of the initial pass. 
More particularly, with respect to the operation of the grade apparatus 12 
of the present invention, it should be noted that a deviation in the 
surface of the roadway 14 will first be sensed by the forward walking 
beam, the forward steering drive track assembly 33A, and a deviation in 
the surface of the work path will be sensed by the rear walking beam, the 
rear drive track assembly 34A. The forward elevation reference sensed by 
the forward walking beam will be averaged with the rear elevation 
reference that is sensed by the rear walking beam, with the elevation of 
the averaging bar member 50 being effected thereby. Therefore, the first 
elevation control signal provided by the hydraulic sensor 46A will be 
indicative of, or proportional to, a twice-averaged deviation, as opposed 
to responding directly to any given deviation. Thus, the cutting depth of 
the work piece 20 will be varied as necessary to maintain a more uniform 
cutting depth with each pass. 
To further explain the averaging effect of the track walking beams, the 
operation of the right rear drive track 33A will be considered, by way of 
example. When the right rear drive track assembly 34A travels over a 
depression in the work path, the elevation of the rear control axis 36 of 
the rear drive track assembly 34A will be changed only if the distance 
across the depression is greater than half the distance from the leading 
end 40 to the trailing end 42, since the planar nature of the ground 
contact portion 38 of the rear drive track assembly 34A. Even if the 
depression, or surface irregularity, in the work path is of sufficient 
size to be sensed by the right rear drive track assembly 34A, will cause 
the track assembly to span any smaller depressions, the elevation of the 
rear control axis 36 will be averaged with the grade concurrently sensed 
by the forward walking beam 33A to determine the elevation of the 
averaging bar member 50. 
After the road working machine 10 finishes a pass and is being maneuvered 
to its next cutting position, the portability and simplicity of operation 
of the grade averaging assembly 12 will be appreciated. Since the grade 
averaging assembly 12 is completely self contained upon the road working 
machine 10, the machine 10 is simply operated in its manual mode during 
repositioning maneuvers without regard to the grade averaging assembly 12. 
As soon as the machine 10 is readied in its new position, the grade 
averaging apparatus 12 will be automatically positioned to continue 
operations in the manner discussed above. Once the machine is in position 
for the next pass, only minor elevation adjustment is usually necessary 
before the operator can place the elevation control assembly back into its 
automatic control mode. If the elevation of the frame 18 deviates from the 
required elevation in order to null the grade sensor assemblies 22A and 
22B, the elevation of the frame 18 will automatically be reset for the 
start of this pass because of the determined cutting depth having been 
before established. This demonstrates the ease of establishing an 
elevation control reference afforded by the portable grade averaging 
apparatus 12 of the present invention. 
As mentioned above, another grade averaging apparatus constructed in 
accordance with the present invention and which is similar to the grade 
averaging apparatus 12 can be utilized alongside the opposite side 24 of 
the frame 18 instead of using the skid apparatus 100. In practice, since 
the uniformity of the cutting depth achieved by using the grade averaging 
apparatus 12 is quite good, it has been determined that a conventional 
skid 100 may be used on one side of the machine 10 where the skid 100 is 
to slidingly contact a curb apron during the initial pass, and the skid 
100 is to slidingly contact the work path of the previous pass during 
subsequent passes of the roadway machine 10. 
It is believed that it will be clear from the above disclosure that the 
present invention is well adapted to carry out the objects and to attain 
the ends and advantages herein mentioned, as well as those which are 
inherent therein. While a presently preferred embodiment of the invention 
has been described for the purpose of this disclosure, numerous changes 
may be made which will readily suggest themselves to those skilled in the 
art and which are encompassed within the spirit of the invention disclosed 
and as defined in the appended claims.