Apparatus for machining an earth grader blade support

An apparatus for simultaneously machining three circumferential surfaces of a circular workpiece. The device includes a frame having support for securing the workpiece thereto. A center tube rotatably supported by the frame extends into the interior of the circular workpiece and supports diametrically opposed spindle arms. One spindle arm supports a pair of rotatably grinding wheels disposed to grind parallel horizontal surfaces on the workpiece. The other spindle arm supports a rotatable grinding wheel for machining the interior radial surface of the workpiece. The position of the grinding wheels may be accurately controlled by dovetail slides and handwheels. The grinding wheels are rotated with respect to their spindle arms and the center tube is rotated so as to move the grinding wheels about the circumference of the workpiece to simultaneously machine each of the three surfaces of the workpiece.

BACKGROUND OF THE DISCLOSURE 
The present invention relates to a device for machining a large workpiece 
and, more particularly, to a device for machining the rotatable circle 
that supports the blade of an earth grader. 
Earth graders typically support a blade that may be raised and lowered to 
adjust the depth of cut of the grading edge, and may be rotated about a 
vertical axis to adjust the angle of the grader edge with respect to the 
direction of travel of the grader, thus adjusting the width of the cut. 
The blade is mounted on a removeable, internally-toothed "circle", the 
teeth on the circle meshing with teeth on a rotatable turntable carried by 
the grader. The circle is typically made of cast metal and is on the order 
of 40 inches in diameter. 
After a period of use, the teeth on the circle become worn and the circle, 
itself, worn outof round, permitting play of the circle with respect to 
the grader turntable, which greatly affects the accuracy with which the 
grader blade may be adjusted. Consequently, the teeth of the circle are 
periodically reconditioned to ensure a minimum of play and the greatest 
amount of grading accuracy. 
To recondition the grader circle, the worn tooth segments are removed and 
new teeth are welded to the interior of the circle. After such welding, 
the upper and lower surfaces of the new teeth must be ground parallel to 
one another, and the interior surface of the circle machined to be 
concentric with the crest of the teeth and perpendicular to the upper and 
lower surfaces thereof. The accuracy of machining the reconditioned circle 
is critical to insure that the circle will rotate freely, with minimal 
play, when it is replaced on the grader and to permit precise adjustment 
of the grader blade. 
While accurately machining large workpieces is typically a difficult 
procedure, the machining of the wear surfacs of the grader circle is 
further complicated because the welding of the teeth to the circle serves 
to further distort the geometry of the circle. Previously, grinding of the 
three wear surfaces has been a time consuming and difficult process 
because of both (1) the accuracy required, particularly to machine the 
parallel surfaces of the reconditioned teeth, and (2) the large size of 
the workpiece to be machined. 
Accordingly, it is the principal object of the present invention to provide 
an apparatus that accurately machines the reconditioned circle of an earth 
grader. 
A further object is to provide an apparatus that simultaneously machines 
the parallel surfaces of a circular workpiece. 
More particularly, it is an object to provide an apparatus that quickly and 
accurately machines each of the three wear surfaces of a reconditioned 
grader circle. 
It is an additional object to provide such a device that is simple to set 
up and operate. 
These objects, as well as others that will become apparent upon reference 
to the accompanying drawings and following detailed description, are 
provided by an apparatus for machining a circular workpiece including a 
frame having support means for securing the workpiece to the frame. A 
center tube is rotatably supported by the frame so as to extend into the 
interior of the circular workpiece at substantially the center thereof so 
that a central axis defined by the tube is substantially perpendicular to 
a horizontal plane defined by the workpiece. The center tube supports 
diametrically opposed spindle arms, one spindle arm supporting a pair of 
rotatable grinding wheels at its outer end so that the grinding surfaces 
of such grinding wheels define planes substantially parallel to the plane 
defined by the workpiece. The other spindle arm supports a rotatable 
grinding wheel at its outer end that has its grinding surface defining a 
plane substantially perpendicular to the plane defined by the workpiece. 
Adjustment means is provided for moving the parallel grinding wheels in 
unison in a direction perpendicular to the plane defined by the workpiece, 
with a second adjustment means provided for adjusting the position of one 
of the parallel grinding wheels in such a direction. Adjustment means is 
also associated with the third grinding wheel for controlling the radial 
position thereof. The three grinding wheels are rotated with respect to 
their spindle arms and the center tube is rotated so as to move the 
grinding wheels about the circumference of the workpiece to simultaneously 
machine each of the three wear surfaces thereof. In a preferred 
embodiment, the grinding wheels are rotated by a series of rotatable 
shafts connected by drive belts, certain of the shafts being mounted 
eccentrically within rotatable bearing housings so that the drive belts 
may be adjustably tensioned by rotating the bearing housings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning to the figures of the drawing, there is seen in FIG. 1 a device, 
generally indicated by 10, for machining a large, circular workpiece, such 
as a reconditioned earth grader circle 12. The device 10 includes a 
free-standing work table 14 having a generally-square table top 16 (best 
seen in FIG. 2) with a cross-frame 18 overlying the top thereof. 
The cross-frame 18 includes upright members 20 at the radially-outer end of 
each frame member for supporting the grader circle 12. The upright members 
20 may be carried by telescoping members (not shown) that are received 
within the individual members of the cross-frame 18 and may be adjusted 
outwardly to support workpieces of a larger diameter. Each upright member 
20 includes two thumbscrews 22, 24 disposed in the vertical and horizontal 
planes, respectively, to permit leveling and centering of the grader 
circle 12 and to secure the grader circle 12 to the cross-frame 18. 
As best seen in FIG. 3, a reconditioned grader circle 12 has replacement 
tooth segments 26 secured thereto by upper and lower welds 28, 30, the 
welding process resulting in weld deposits or beads on the upper and lower 
wear surfaces 32, 34 of the grader circle 12. After such replacement tooth 
segments 26 have been welded to the circle 12, the welds 28, 30 and the 
radial wear surface 36 of the grader circle 12 must be ground to permit 
the repositioning of the circle 12 on its associated earth grader. If the 
wear surfaces 32, 34, 36 of the circle are not true, i.e. with the 
surfaces 32 and 34 being parallel to each other and the surface 36 being 
concentric with the crests of the tooth segments 26 and perpendicular to 
the surfaces 32, 34, the accuracy with which the blade on the earth grader 
may be adjusted is reduced. 
In accordance with the present invention, the work table 14 supports a 
rotatable grinding assemblage, generally indicated by 38, mounted interior 
of and concentric with the grader circle 12 (when one is supported by the 
work table 14.). The grinding assemblage 38 includes parallelly-disposed 
rotatable grinding wheels 40, 42 for machining, respectively, the upper 
and lower wear surfaces 32, 34 of the grader circle 12 and a radial 
rotatable grinding wheel 44 for machining the radial wear surface 36. 
Means is provided for rotating the grinding assemblage 38 with respect to 
the grader circle 12. Additionally, in order to adjust the depth of cut of 
the grinding wheels 40, 42, 44, means is provided for adjusting both the 
radial and vertical positions of the grinding wheels 40, 42 and for 
adjusting the radial position of the grinding wheel 44. 
As best seen in FIG. 1, the grinding assemblage 38 is supported by a center 
tube 46 journaled in the work table 14 at the center thereof by tube 
bearings 48, with a thrust bearing 50 maintaining the vertical position of 
the center tube with respect to the work table 14 and cross frame 18. A 
two-part sleeve 52 is clamped to the upper end of the center tube 46 (the 
two halves, 52a, 52b, being best seen in FIG. 2), each half 52a, 52b 
having an I-beam section 54, 56 welded thereto and extending radially 
outward from the center tube 46. The parallel grinding wheels 40, 42 are 
supported by a spindle-arm structure 58 extending from the end of arm 54, 
while the radial grinding wheel 44 is supported by a spindle-arm structure 
60 extending from the end of the arm 56. 
To support its respective spindle-arm structure 58, 60, each I-beam section 
54, 56 terminates at its radially-outer end in a verticallyoriented 
cylindrical arm clamp 62, 64. Each cylindrical arm clamp 62, 64 supports a 
bearing housing 66, 68, respectively, that is rotatable with respect to 
its arm clamp. The bearing housing 68 carries a split bushing (not shown) 
and a single spindle arm 70 for rotatably supporting the radial grinding 
wheel 44, while bearing housing 66 carries two spindle-arms 72, 74 for 
rotatably supporting the upper and lower grinding wheels 40, 42, 
respectively. Each spindle-arm 70, 72, 74 terminates in a 
vertically-oriented tubular arm clamp 76, 78, 80 respectively, that 
supports a rotatable bearing housing 82, 84, 86, respectively. Journaled 
within the bearing housings 82, 84, 86, are spindles 88, 90, 92 which 
carry the grinding wheels 44, 40, 42, respectively. 
To rotate the spindles 80, 90, 92 (and thus the grinding wheels 44, 40, 42) 
the device 10 includes a motor 94 (in practice, a three-phase, five 
horsepower motor) mounted to the work table 14. The drive shaft 96 of the 
motor 94 carries a driving pulley 98 which, through a double drive belt 
100 and driven pulley 102, rotates a center shaft 104 journaled in the 
center tube 46. The upper end of the center shaft 104 supports a driving 
pulley 106 that carries a pair of double drive belts 108, 110. The drive 
belts 108, 110 rotate counter shafts 112, 114 journaled in the bearing 
housings 66, 68, and carrying driven pulleys 116, 118. The counter shaft 
112 carries driving pulleys 120, 122 on its upper and lower ends, 
respectively, while the counter shaft 114 carries a single driving pulley 
124. Drive belts 126, 128, 130 are carried by the pulleys 120, 122, 124 
and connect these pulleys to driven pulleys 132, 134, 136 mounted on the 
spindles 90, 92, 88, respectively, to rotate their respective grinding 
wheels 40, 42, 44. (In practice, the device 10 is provided with guards 
overlying the drive belts 108, 110, 126, 128, 130 to ensure the safety of 
the operator. Such guards have been omitted in the illustrated device for 
clarity.) In the preferred embodiment, the counter shafts 112, 114 and 
spindles 88, 90, 92 are eccentrically mounted in their respective bearing 
housings 66, 68, and 82, 84, 86. Consequently, tensioning of the drive 
belts 108, 110, 126, 128, 130 may be accomplished by rotating the bearing 
housings within their respective arm clamps. 
In keeping with another aspect of the invention, the positions of the 
grinding wheels 40, 42 are adjustable in their axial directions and the 
position of the grinding wheel 44 is adjustable in its radial direction to 
provide for precise machining of the wear surfaces 32, 34, 36 of the 
grader circle 12. To this end, the spindle arm structure 58 includes a 
pair of vertically-disposed dovetail slides 138, 140 operated by hand 
wheels 142, 144, respectively. As illustrated, the dovetail slide 138 is 
positioned on the I-beam section 54 between the center tube 46 and the 
cylindrical arm clamp 62 so that both grinding wheels 40, 42 can be moved 
in unison in a vertical direction by rotation of the hand wheel 142. The 
second tool slide 140 is positioned on the spindle arm 72 intermediate the 
bearing housing 66 and the tubular arm clamp 78 so that the distance 
between the grinding surfaces of the grinding wheels 40, 42 may be 
accurately adjusted. With this arrangement of the tool slides 138, 140, an 
equipment operator can first precisely position the lower grinding wheel 
42 for machining the lower wear surface 34 of the grader circle 12 by 
adjustment of the hand wheel 142, and then position the upper grinding 
wheel 40 by adjustment of the hand wheel 144 so that the upper wear 
surface 32 may be ground simultaneously with the lower wear surface 34. 
To adjust the radial position of the grinding wheel 44, a 
horizontally-oriented hand wheel 146 is threadably received in an upright 
post 148 which, in turn, is pivotably-supported on the upper surface of 
the I-beam 56. As best seen in FIG. 2, the threaded shaft 150 of the hand 
wheel 146 is received in a vertically-oriented rotatable pin 152 supported 
by an extension 154 of the spindle-arm 70. Accordingly, the sindle-arm 70 
may be rotated about its bearing housing 68--thus adjusting the radial 
position of the grinding wheel 44--by rotation of the hand wheel 146. 
In accordance with another aspect of the invention, the three wear surfaces 
32, 34, 36 may be simultaneously machined about their entire 
circumferential extent. To this end, the entire grinding assemblage 38 is 
rotated about a vertical axis coincident with the axes of the center tube 
46 and center shaft 104 by means of a motor 156 (in practice a one-quarter 
horsepower, variable-speed DC motor) mounted to the work table 14 and 
directly coupled to a worm-drive reduction unit 158. A roller chain 160 
operatively connects the worm-drive unit 158 to a sprocket 162 carried on 
the center tube 46 for rotating the same, and, consequently, rotating the 
entire grinding assemblage 38. In practice, the motor 156 is operated by a 
variable speed control 164, which has a separate 110V power supply, and is 
adjusted so that the grinding assemblage 38 will rotate at approximately 
6-8 revolutions per minute. Power is supplied to the entire device 10 
through a three-phase starter 166 and 220V power-supply cord 168. In 
operation, to facilitate placement of a reconditioned circle 12 on the 
upright support members 20 of the cross frame 18, the spindle arms 70, 72, 
74 are first pivoted toward the center tube 46. After a grader circle 12 
is placed on the work table 14, thumbscrews 22 are adjusted to level the 
circle, while thumbscrews 24 are adjusted to center the circle 12 with 
respect to the center tube 46. After proper location of the circle 12 on 
the work table 14, the spindle arms 70, 72, 74 are pivoted outwards toward 
their positions as shown in FIGS. 1, 2, and 3. 
The vertical positions of the grinding wheels 40, 42 and the radial 
position of the grinding wheel 44 may be precisely adjusted by the 
handwheels 142, 144, 146 (as described above) to position the grinding 
wheels to within approximately 1/16th inch from the highest points of the 
weld deposits on the reconditioned wear surfaces 32, 34, 36. The motor 94 
is then activated to rotate the grinding wheels 40, 42, 44 and the motor 
156 is activated to rotate the grinding assemblage 38 about the center 
tube 46. With the grinding wheels 40, 42, 44 and the assemblage 38 all in 
motion, the handwheels 142, 144, 146 may all be adjusted to simultaneously 
grind the three wear surfaces 32, 34, 36 of the grader circle 12. After 
grinding is complete, the above steps are reversed to remove the grader 
circle 12 from the work table 14. 
From the foregoing, it can be seen that a device for easily and accurately 
machining an earth grader circle has been provided that fully meets the 
objects of the instant invention. While the device has been described in 
terms of a preferred embodiment, there is no intent to limit the invention 
to the same. On the contrary, it is intended to cover all modifications 
and equivalents within the scope of the appended claims.