US3421589A - Blade mountings and controls for road graders - Google Patents

Description

Jan. 14, 1969 T. RlVlNlUS 3,421,589

BLADE .MOUNTINGS AND CONTROLS FOR ROAD GRADERS Filed Sept. 16, 1965 Sheet of'4 FIE: 1

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T. RIVINIUS 3,421,589

BLADE MOUNTINGS AND CONTROLS FOR ROAD GRADERS Sheet 3 of 4 Jan. 14, 1969 Filed Sept. 16, 1965 f BY a AM, W

Jan. 14, 1969 3,421,589

BLADE MOUNTINGS AND CONTROLS FOR ROAD GRADERS T. RIVINIUS Filed Sept. 16, 1965 Sheet 1 of 4 WIEIIW I l V ENTOR. TA/Eobakt JP1400/04- lrrakans United States Patent 3,421,589 BLADE MOUNTINGS AND CONTROLS FOR ROAD GRADERS Theodore Rivinius, 1011 Ave. B West, Bismarck, N. Dak. 58501 Continuation-impart of application Ser. No. 362,740, Apr. 27, 1964. This application Sept. 16, 1965, Ser. No. 487,785 U.S. Cl. 1724.5 11 Claims Int. Cl. E02f 3/76; E02f 3/12 ABSTRACT OF THE DISCLOSURE A grading machine having a main frame and an earthworking blade mounted onto a circle frame which in turn is attached to the main frame. Linkages are positioned on opposite sides of the circle frame for controlling the depth of the earthworking blade and the transverse angle of the blade. The linkages hold the circle frame stable in fore and aft directions so that the circle flame moves up and down in a parallel relationship with respect to an axis extending in the direction of movement of the grading machine.

This application represents a continuation-in-part of my .co-pending application Ser. No. 362,740, filed Apr. 27, 1964, now Patent No. 3,303,589, and also certain improvements thereover.

This invention relates to controls for road graders and the like and more particularly to a unique mounting for the circle frame on which the earth working blade of the road grader is attached in order to give absolute control and precision cutting when the automatic controls are being used.

Many automatic controls have been advanced for use with road graders, but these are usually very complex or are inaccurate. The problem arises from the fact that the axis :of the circle frame, on which the earth working blade is mounted, and consequently the vertical axis about which the earth working blade will rotate in order to change the angle thereof, is not perpendicular to the lane which is cut by the blade, or in other words, the cutting plane of the blade. The plane of the mounting frame for the blade is not parallel to the plane cut by the blade. This is usually due to the fact that the circle frame is mounted through a drawbar that in turn is mounted with a ball joint adjacent the front axle of the working blade, and the drawbar then slopes downwardly to the circle frame causing the circle frame plane to be out of parallel with the plane cut by the earth working blade.

When the plane of the circle frame is not parallel to the plane which is cut by the earth working blade, in a fore and aft direction, each time the blade is rotated about its vertical axis to change the angle of the blade, the angle of the blade cutting plane in a transverse direction will also change.

In order to overcome this problem, the device of the present invention discloses a unique way of mounting the circle frame so that it can be adjusted to make the plane of the circle frame exactly parallel to the plane cut by the grader blade as the grader moves along over the earth. In doing so, the plane of the circle frame is held exactly parallel to the cutting plane of the blade, in both fore and aft directions and transverse direction. The linkage utilized comprises a four bar linkage which attaches between the controls for the raising and lowering of the circle frame and the frame itself so that the position of the circle frame is controlled by the raising and lowering linkage. The transverse angle of the circle frame "ice and the blade can be changed, as can the depth of cut, but the fore and aft angle does not change.

Also, as shown, a pendulum sensing unit is utilized for actuating the controls to maintain a desired transverse slope on the blade. Once the proper transverse slope of the cutting plane is reached, no matter where the blade is rotated about its vertical rotational axis, the same transverse slope will be held, because the plane of the circle frame is parallel to the cutting plane that is desired, and rotation of the blade in this plane will mean that the blade will remain parallel to the plane regardless of its angular position.

The device is used primarily in finish work where very shallow cuts are made. Thus the normal range of the blade in working position does not affect the setting of the circle frame plane.

It is an object of the present invention to present a new control device for graders comprising a unique method of mounting the circle frame on which the blade is mounted, and automatic controls for use in connection therewith.

In the drawings,

FIG. 1 is a side elevational view of a road grader having a circle frame mounted according to the teachings of the present invention installed thereon;

FIG. 2 is a fragmentary top plan view of the drawbar and front portions of the circle frame made according to the present invention and taken as on line 2--2 of FIG. 1;

FIG. 3 is a fragmentary sectional view taken as on line 33 in FIG. 1;

FIG. 4 is a fragmentary sectional view and part hydraulic schematic view taken as on line 4-4 in FIG. 1;

FIG. 5 is a fragmentary top plan view of the circle frame portion of the road grader of FIG. 1;

FIG. 6 is a sectional view of a pendulum sensing unit made according to the present invention and taken as on line 6-6 in FIG. 5;

FIG. 7 is a fragmentary sectional view of the device of FIG. 6 as viewed from the rear thereof;

FIG. 8 is a schematic representation of an electrical circuit utilized with the sensing unit of the present invention; and

FIG. 9 is a fragmentary front view of the slope indicator used with the present invention.

Referring to the drawings and numerals of reference thereon, a road grader 15, which is conventionally made, as shown, the type made by the Galion Iron Works & Mfg. Co. of Galion, Ohio, is utilized. The grader has an elongated frame 16 and is mounted on a plurality of wheels 17. The grader is powered from an engine 18 with suitable mechanism (not shown). A cab 19 is positioned on the main frame of the grader and houses the grader operational controls illustrated generally at 20.

An earth working blade 21 is mounted through suitable brackets 22 to a circle frame 23.

The circle frame itself is rotatably mounted on and with respect to a mounting frame assembly 24, which comprises, as shown, a front mounting member 25 and a rear mounting member 26 which are joined together rigidly with a longitudinally extending member or frame 27. This can perhaps best be seen in FIG. 5. The circle frame itself is slidably mounted to the mounting frame 24 on slider brackets that are bolted through the rear member 26 with suitable bolts 31. The circle frame has its inner peripheral edge notched to form teeth 32. The circle frame can be rotated on the slider brackets about its upright axis through the use, in this grader, of a hydraulic motor 33 that is controlled through suitable hydraulic controls, from the cab. The exact details of these controls are not shown because this is conventionally 'done. The hydraulic motor Bit-operates through a suitable gear reduction mechanism which engages the inner toothed edge of the circle frame to rotate the frame and attached blade.

The mounting assembly 24 is attached to the main frame of the grader througha drawbar linkage 34. The drawbar linkage 34 is attached to the mounting frame 24 at the front cross member 25, through a pair of ball joint assemblies 35. The ball joint assemblies 35, as shown, have ball members 36, 36 fixedly attached to a bracket 37 in transversely spaced apart relationship, and the ball members 36 are mounted in housings 38 which in turn are attached to the front cross member 25. As can be seen, the ball members are spaced quite widely apart and on opposite sides of the longitudinal axis of the drawbar linkage.

The ball joint assemblies 35 can be termed universal members and will pivot in all directions. As shown, however usage of the two ball joint assemblies will permit the mounting frame 24 and then thus the circle frame to pivot only about a transverse axis passing through the ball joint members. This axis is parallel to the plane of the circle frame and also perpendicular to the longitudinal axis of the drawbar.

The front end of the drawbar linkage 34 is mounted through a ball joint 39 to the frame 16 of the grader at the front axle thereof. This can be mounted in the usual preferred manner which will permit the drawbar linkage 34 to pivot from side to side, as well as up and down.

The height of the circle frame and mounting member 24 above the ground is controlled through the use of suitable linkage which is illustrated in FIG. 1, FIG. 3 and schematically in FIG. 4. As shown, a pair of rock shafts 41 and 42, respectively, are pivotally mounted on suitable brackets 43 that in turn are mounted to the main frame 16 of the grader. The rock shafts 41 and 42 have separated control levers 44 and 45, respectively, fixedly attached thereto adjacent the rear portions thereof. The control levers 44 and 45 are actuated through the use of a pair of hydraulic cylinders 46 and 47, respectively, which are attached to a frame member 48 of the grader and they have extendable cylinder rods 49 which in turn are pivotally attached to the control levers 44 and 45. As the cylinders 46 and 47 are extended or retracted, the control levers 44 and 45 will move, causing the rock shafts 41 and 42 to pivot as desired under their control. The hydraulic cylinders 46 and 47 are controlled through hydraulic control valves 52 and 53, respectively which have control handles 54 and 55. The hydraulic pump illustrated schematically at 56 is connected through suitable pressure lines 57 to the control valves 52 and 53. Return lines 58 are connected to a reservoir 59 to complete the hydraulic circuit to the valves. When the valve handles are operated, they will move a spool valve inside the respective valve assembly 52 and 53 to direct pressure either through the pressure line 60 or 61 which would cause the rods 49 and 50 to extend or through pressure line 62 or 63, respectively, which would cause the rod 49 or 50 to retract.

Each of the rock shafts 41 and 42 have two lift arms 64 and 65 respectively, attached at their forward ends thereof. As shown, the arm 64 is attached near the intermediate portion of the rock shaft and the arm 65 is attached at the forward end of the rock shaft. Thus, when the rock shafts rotate, the arms 64 and 65 will also rotate. It should be noted that the arms 64 and 65 extend outwardly from the rock shaft while the levers 44 and 45 extend inwardly. In the conventional situation the rock shafts have only one arm each, which corresponds to the intermediate arms shown. To convert standard units to devices of the present invention, the conventional rock shafts can be extended and the front lift arms 65 added.

The arms 64, which are attached to the rock shaft 41 and 42, are connected to the circle frame through adjustable lift links 66. The links 66 are connected to the arms 64 through ball or swivel j i or other suitable connections illustrated at 67 and are also connected to the outer ends rear cross frame member 26 through similar ball joints 68 or other connections. The links 66 are, as shown, adjustable in longitudinal length. They comprise an outer section and a telescoping inner section which can be pinned through suitable pins to the outer section. Thus the length of the links 66 can be adjusted.

The arms 65 have forward lift links 71 attached thereto with ball joints 72, and the lower link ends of the links 71 are attached to the outer ends of the front cross member 25 of the mounting frame 24 of the circle frame with suitable ball joints or connections 73.

The front links 71 are also longitudinally adjustable, comprising an outer member and a telescoping inner member at the lower end thereof. However, instead of merely pinning the inner and outer members of each link together, the lower member of each link 71 has suitable bolts 74 attached thereto at the ball joints 73 and which extend up through openings in ears 75 which in turn are welded to the outside of the outer member of the link. The bolts pass through provided openings in the cars 75 and suitable nuts 76 are threaded on opposite sides of the cars so that the nuts can be threaded to obtain a very precise adjustment in length of each of the links 71. The reason for making the precise adjustment of the forward links 71 will be apparent as the description proceeds. The links are adjusted to position wherein the plane of the circle frame is parallel to the cutting plane of the earth working blade, when the blade is at Working depth. The depth of the blade and also its transverse angle can be set manually be operating the valves 52 and 53. Normally, the cut is very shallow and is not adjusted very much when working.

The control valves 52 and 53, besides being manually operative, are also operated by solenoids, if desired. The solenoids are used when automatic leveling of the unit is to be changed. The controls for the solenoid will be subsequently explained, but it can be seen that the handle 54 has an actuating link which extends to engage the spool of the valve 52 and this actuating link in turn is connected as at 111 to a solenoid operated arm 112 that is actuated from a solenoid 113 which in turn is mounted to the base of the grader. The solenoid 113 is actually two solenoids in one, and will operate the arm 112 in either direction of movement along its longitudinal axis.

The lever or control handle 55 has an actuating link 115 attached thereto and the actuating link is connected as at 116 to a second solenoid arm 117 that is controlled by a second solenoid 118. The second solenoid 118 is also connected to the frame of the grader, and, as will be apparent as the description proceeds, actually contains two sol'e'noid coils so that the arm 117 can be actuated in either direction along its longitudinal axis. Each of the solenoids 113 and 118 are identical in construction, except that they are connected to control different valves.

The transverse angle of the circle frame and earth working blade, which is attached to the frame, also can be automatically controlled through the use of a horizon sensing case 80, which is mounted onto the mounting member 24 for the circle frame. A pendulum sensing unit is utilized, and when the circle frame tilts away from the normal operating position, the pendulum is used to actuate suitable controls (valve 52 or 53) to bring the circle frame back to its predetermined original position. The case 80 is pivotally mounted to a mounting bracket 81 through the use of a pin 82. The pin 82 is fixed to the case front wall and passes through an upright plate 86 of the bracket 81. The bracket 81, in turn, has a brace member 83 that is attached to the longitudinally extending member 27 of the mounting frame 24 for the circle frame.

The mounting bracket 81 is attached so that the axis of the pin 82 is parallel to the longitudinal axis of the grader, with the circle frame centered under the grader frame. The pivoting of the case 80 about its pivot 82 will permit an artificial plane to be established at which the circle frame will remain under control of the horizon sensing case 80.

In order to control the pivoting of the case 80 about its pin 82, a linkage 84 which is pivoted to the case at 85 is utilized. The operation of this linkage and the manner in which it fixes the angular relationship of the horizon sensing pendulum case 80 with respect to the support mounting plate 81 will be more fully explained later.

As perhaps best seen in FIGS. 6 and 7, inside the pendulum case or horizon sensing case 80 a pendulum 90 is mounted on a pendulum shaft 91 which in turn is rotatably mounted on suitable bearings 92, 92 in the case 80. The bearings 92, 92 are antifriction bearings and permit the shaft 91 to rotate very easily. The pendulum 90 is mountted for movement about the longitudinal axis of the shaft 91 (which is parallel to the axis of pin 82) but is restrained from movement longitudinally along the shaft. The pendulum has a pair of integral vanes 93, 93 positioned on the opposite side thereof. These vanes are spaced very slightly inwardly from the corresponding edges of the case 80. Two other side surfaces 94, 94 of the pendulum are spaced inwardly a relatively greater distance from the corresponding side edges of the case 80. This is to allow the pendulum to move from side to side within the pendulum case as it pivots about the axis of the shaft 91. A pair of stop bolts 95, 95 are threadably mounted as at 96 with respect to the side edges of the pendulum case 43. The bolts are aligned with side surfaces 94, 94 of the pendulum, and are adapted to engage these side surfaces to prevent the pendulum from swinging farther than necessary to operate the control system. The pendulum case 80 is filled with a highly refined oil indicated at 97 which dampens the movement of the pendulum as it swings about the axis of shaft 91. A small clearance between vanes 93 in the corresponding sides of the pendulum case constricts the flow of oil as the pendulum swings.

Pendulum shaft 91 has an end portion 101 which extends outwardly from the case 80 into a housing 99 which is fixed to the case. An actuating lug or ear 102 is fixedly attached to the shaft end portion 101. As best seen in FIG. 7, a first switch 103 is mounted on the housing 99 on one side of the lug 102 and a second switch 104 is mounted on the housing in the opposite side of the lug 102. Actuating buttons 108, 108 for these switches are positioned adjacent the lug.

As can be seen in FIG. 8, which is the electrical circuit diagram for the unit, a motor 105 is connected through a source of electromotive force 106 through a main power on-oif switch 107.

The motor 105, when the main switch 107 is closed, is energized and this in turn drives a cam member 121 which actuates a micro-switch 122, by opening and closing it intermittently. The micro-switch 122, when it is closed, connects the source of electromotive force 106 through each of the switches 103 and 104 to a reversing switch 123. This reversing switch can be a three position switch in which the center of disconnect position can serve as the off switch for the control apparatus. A separate power onotf switch 107 is also utilized if desired. The reversing switch, in turn, is connected to a double pole double throw switch 124, which will connect the switches 103 and 104 to solenoid 113 or to solenoid 118, whichever is to be used in operation of the unit. It should be explained that during the automatic operation of the unit, only one of the hydraulic control valves is automatically controlled. Thus, only one of the solenoids needs to be operated. The other hydraulic control valve can be manually actuated to set the depth of the blade and the automatic control will actuate the other valve to cause the blade to assume its predetermined slope or position at the new depth.

If the angle of the blade is reversed (as shown the left end of the blade is leading, if reversed the right end of the blade would lead), then the other solenoid will be used for operation. As shown, the solenoid 113 is connected for operation. It should be understood, again, that the solenoid 118 can also be connected, and will operate in the same manner as the solenoid 113, merely by throwing the double pole double throw switch 124 to its opposite position.

Assuming that the switch 124 is positioned as shown, connecting the solenoid 113 into the circuit, when the reversing switch 123 is thrown to the upward position as shown in FIG. 8, the power will flow from the micro switch 122 (intermittently) and switch 103 (when closed) to a relay 125 which will cause a first solenoid coil 126 to be energized. :Power will flow through the micro-switch 122 and the switch 104 (when closed) to a relay 127 which will power a second solenoid coil 128. With the reversing switch in this upward position, tilting of the pendulum case to cause the lug 102 to close switch 104 will cause the second solenoid coil 108 to be energized intermittently every time the micro-switch 122 closes to permit power to flow therethrough and the solenoid armature 129 will be moved to the left as seen in FIG. 8. Solenoid operating arm 117 is integral with the armature 129 and will also move to the left. When the micro-switch 122 is not passing the current, (the cam 121 permits the micro-switch to open) the springs 131 and 132 will center the armature 129 to the position as seen in FIG. 8.

Movement of the armature will actuate the handle of valve 52 in direction to cause the cylinder 46 to rotate rock shaft 41 and change the position of the circle frame in a manner to cause the lug 102 to mave away from switch 104.

When the sensing case moves so that the lug 102 under the urging of the pendulum 100 closes switch 103, current through the micro-switch 122 will cause current to flow through the first solenoid coil 126 and the solenoid arm 117 and armature 129 will move to the right as seen in FIG. 8. When the current stops flowing through the switch 122, because of the switch opening, the springs 131 and 132 will again center the armature.

The action described above results in a series of intermittent incremental movement on the arm 117 in direction determined by positioning of the reversing switch 123 and by the relationship of the pendulum 100 and the lug 102 with respect to the horizon sensing case 80 and the switches mounted with respect thereto. The controls are set so that the left links will be moved to set the transverse slope of the circle frame in a position wherein the pendulum will no longer actuate the switches 103 or 104.

The action will be exactly the same for the solenoid 118 (the internal construction is the same as the solenoid 113) when the double pole double throw switch 124 is reversed in position. In that case, the current will flow either to a relay 133 or to a relay 134, depending upon whether the switch 103 or 104 is closed. The relays in turn will control suitable solenoid coils inside the solenoid assembly 118 to move that solenoid arm 112 in the required position to obtain the proper movement of the cylinders, and their corresponding rock shafts to in turn adjust the circle frame and blade properly to center the pendulum.

With the parts in electrical circuitry positioned as shown in FIG. 8, so that the solenoid 113 is operated, movement of the solenoid operating arm 117 away from the main solenoid 118 will cause the lever 55 to be pivoted, actuating the valve 53 in the first direction, compressing the cylinder 50 which in turn will rotate lever 45 and rock shaft 42. This means that the arms 64 and 65 attached to rock shaft 42 will be raised thereby lifting the links 66 and 71 and raising that side of the circle frame assembly. This will change the angular relationship of the circle plane and consequently the work plane determined by the loci of movement of the lower working edge 135 of the grader blade 21. The solenoid operating arm is only in the activated position momentarily while the micro-switch 122 is passing current, the increment of angular displacement of the operating plane of the grader blade will be slight. If the incremental movement is not sufficient to cause the lug 62 to move into clearing relationship with respect to the go switch which originally chartered the movement (103 or 104) then when the micro-switch 122 next closes, a further incremental movement in the same direction will take place. As soon as this small movement is sufficient to cause the switch 103 or 104 moved to the open condition, no such further movement of the controls will be forthcoming. The pendulum controls the lug, and the pendulum always seeks a vertical position.

Should the grader operator want the earth working grader blade 21 to make a deeper or shallower cut while the solenoid 113 is in the operating position, he merely has to operate the second control handle 54 for the valve 52 to cause the opposite side of the circle frame mounting member 24 and consequently the circle frame itself to be raised or lowered as desired. As the pendulum in the case, which is mounted on the circle frame member, attempts to maintain its vertical relationship, it will then be tilted and will activate one of the switches 103 or 194- and the automatic control mechanism just described will operate to raise or lower the opposite side of the circle frame to maintain or re-establish the desired working plane.

The angle of the plane passing through the axis of the shaft 91 supporting the pendulum and the pin 82, will always seek to be-perpendicular to the horizontal when the actuating mechanism is in operation, because the pendulum will seek the vertical direction due to gravity and will actuate the switches 103 or 104 until it is at the vertical position and the lug 102 no longer contacts either of these switches. The angle of plane with respect to the plane of the circle frame can be mechanically changed through the linkage 84 in order to establish an angular relationship between the plane of the circle frame and the horizontal in a transverse direction. This is done by utilizing the connection 135 between the linkage 84 and the top portion of the case 80. A reversible motor 141 is mounted with respect to the mounting member 83 and operating through a gear box 142 can be made to extend or shorten the link 84 longitudinally in its own axis, thereby rotating the case 30 about the pivot pin 82. The reversible motor 141 can be of any suitable type which will drive suitable gearing that will extend or shorten the link 84. Usually the internal member of the link 84 will be tubular and have an internal nut that is threaded over a shaft which in turn is rotationally driven through the Worm gearing 142 by the motor 141. As the shaft rotates it will cause the nut and the inner portion of the link 84 to shorten or lengthen with respect to the outer portion of this link. The motor 141 itself is mounted on an arm 143 that is attached to the frame mounting member 83.

In order to indicate the extent of the rotation on the case 80 with respect to the frame plate 81, a link 144 can be attached to the case in any suitable manner and in turn can control (through a pivoting connection) an indicator rod 145 which is pivotally mounted as at 148 (see FIG. 9) to an upright bracket 146 that in turn is attached to an extension of arm 143 and operates in conjunction with an indicator plate 147, which will have suitable indicia thereon. When the case 86 is tilted, thereby establishing an inclined cutting plane for the blade, it will cause the link 144 to move, pivoting the indicator arm 145 with respect to the plate to show the angle of the case, and thus slope of the plane of the circle frame when the automatic control has made the necessary adjustments. Any suitable indicating mechanism can be used, but as shown, the plate 147 can be read from the cab of the grader to easily show what slope is being cut by the lower cutting edge 135 of the blade 21.

The circuit for operating the reversible motor 141 is, as seen in FIG. 8, wherein a reversible switch 150 will be normally positioned in the neutral or off condition (it is shown on) and can be manually manipulated to cause the motor to run frontward or backward thus to adjust the angular relationship of the case to the desired work plane in either direction of slope, by lengthening or shortening the link 84. The angular relationship of the case 80 to the circle frame plane will be indicated by the mechanism 145-147 which the operator will watch as he operates the motor 121. As soon as the automatic controls are activated the device of the invention will conform the Work plane of the grader blade to that indicated on the indicia plate by the indicator needle.

When the device is to be used, the lift links 66 and 71 are adjusted in length so that the plane of the circle frame is exactly parallel to the cutting plane. The adjustment is made when the blade is at its normal cutting depth. Because the circle frame is held at four points and is lifted at two spaced points on each side whenever a rock shaft is actuated the angular position of the circle frame in fore and aft direction does not change at all. While the transverse slope of the plane of the circle frame can be changed, the fore and aft slope cannot be changed. As the circle frame is raised or lowered, the ball joints 35 permit the circle frame to move up and down without changing the angle of its plane in fore and aft direction. The angle of the drawbar changes but the circle frame does not. The great advantage from operating the circle frame in this manner is that when the blade 21 is rotated (the circle frame and blade are rotated together through the gear case 30) the transverse angle of the plane cut by the cutting edge as the grader moves along the ground will not change no matter what the angular position of the grader blade about its upright axis is. Previous devices where the circle frame plane inclined in the fore and aft direction changing the angle of the grader blade about its upright axis of rotation would change the trans verse slope of the cutting plane of the blade as well.

Previously, attempts were made to compensate for this inclination of the circle frame in fore and aft direction, but it has now been found that by mounting the circle frame so that it is held parallel to the cutting plane the problems are eliminated. Once the desired slope has been set in transverse direction, rotation of the circle frame and the grader blade attached thereto will not change this transverse angle. The use of two lift links on each side of the circle frame which are on a common control means that the lifting of one side or the other does not change the fore and aft angle.

Further, the usual operation of the device will leave the circle frame centered underneath the grader frame so that the axis of shaft 92 will be parallel to the longitudinal axis of movement of the grader blade. The road graders presently being used have provisions thereon for shifting the blade from one side to the other with respect to its support members 22 so that the circle frame does not have to be shifted from side to side. This means that it is not necessary to compensate for changes in angle of the pivotal axis of the pendulum, because this pivotal axis will usually remain parallel to the direction of movement.

What is claimed is:

1. In a grading machine, the combination of a machine frame movable over the ground in a normal direction of travel, a mounting frame, a circle frame mounted on the mounting frame and rotatable with respect thereto about a substantially upright circle frame axis, a blade mounted on and carried by the circle frame with its working edge in a plane perpendicular to the circle frame axis and parallel to the plane of movement of the circle frame, means to support said mounting frame on said machine frame including linkage means for raising and lowering said mounting frame, said linkage means being positioned on opposite sides of the mounting frame to permit selectively lifting of one side or the other of said mounting frame, and including means to stabilize the mounting frame in fore and aft direction so that as the mounting frame is raised or lowered the plane of the circle frame does not change in angle with repsect to the cutting plane of the blade as the respective linkage means are moved up and down, said linkage means constituting the sole means to stabilize the mounting frame, and drawbar means pivotally attached to the forward portions of said machine frame and pivotally attached to the mounting frame about a pivot axis transverse to the machine frame and parallel to the plane of the circle frame to permit movement of the mounting frame without changing the angle of the circle frame in fore and aft direction.

2. The combination as specified in claim 1 wherein the linkage means between said machine frame and said mounting frame includes four upright links, two of said links being positioned adjacent each of the opposite sides of the mounting frame, and said two links on each side being spaced apart in fore and aft direction.

3. The combination as specified in claim 2 wherein said two links on each side of the machine are controlled by a separate common control shaft on each side of the machine frame, means to pivotally mount said control shafts on said machine frame above the mounting frame and power means to separately control movement of said shafts.

4. The combination as specified in claim 3 wherein at least one link on each side of the machine has means thereon for adjusting the length thereof to level the mounting frame.

5. The combination as specified in claim 1 and a pendulum mounted on said mounting frame and having a normal position and control means to restore said mounting frame to a predetermined position when said pendulum is moved from its normal position.

6. The combination as specified in claim 5 wherein said control means includes an interrupter means to pulsate the movement of said mounting frame to its predetermined position in incremental steps, said interrupter means comprising a mechanical cam operating to intermittently disable said control means.

7. In a grading machine, the combination of a machine frame movable over the ground in normal direction of travel, a mounting frame, a circle frame mounted to this mounting frame and rotatable with respect thereto about a circle axis, a blade mounted on the circle frame with its working edge in a plane substantially parallel to the plane of rotation of the circle axis, a drawbar member mounted to forward portions of said machine frame for pivotal movement and to the mounting frame so as to be pivotally movable about an axis parallel to the plane of the circle frame and perpendicular to the longitudinal axis of said drawbar member, selectively actuable lift link means mounted to said mounting member on opposite sides of said mounting frame, said lift link means independently supporting said mounting frame for up and down movement, and preventing said mounting frame from tilting about a transverse axis so that said mounting frame will be raised up and down 'without changing the angle of the plane of the circle frame in fore and aft directions, said lift link means constituting the sole means for preventing the mounting frame from tilting about a transverse axis, a pendulum control member, means to pivotally mount said pendulum on said mounting frame, and control means actuated by said pendulum for restoring the transverse angle of the plane of the circle frame whenever said pendulum is moved from a predetermined position.

8. The combination as specified in claim 7 'wherein said pendulum is mounted in a case and the case is pivotally mounted to the mounting frame, and means to tilt said pendulum case to cause said pendulum to ope-rate said control means to establish a predetermined slope in transverse direction of said circle frame.

9. The combination as specified in claim '8 wherein said lift link means are comprised as four separate links, two of said links being mounted adjacent each side of said mounting frame, each pair of links on each side of said mounting frame being raised by a common control member.

10. The combination as specified in claim 9 wherein said drawbar is attached to said mounting frame with two ball joint members which are transversely spaced apart an equal distance on opposite sides of the axis of pull of said drawbar, and are spaced a substantial distance apart to give stability to the mounting member.

11. The combination as specified in claim 7 wherein said control means includes power actuated lift mechanism and an electrical circuit controlling operation of said power actuated lift mechanism, said control means further including a cam member, means to rotate said cam member, a switch in said electrical circuit, and said cam member being operative to intermittently open and close said switch as it rotates.

References Cited UNITED STATES PATENTS 1,720,189 7/1929 Jackson 335-73 X 1,732,892 10/1929 Hinds 37-156 2,074,081 3/1937 Burns 37-1'57 2,497,778 2/ 1950 Lado 37-156 2,904,911 9/1959 Colee.

2,941,319 6/1960 Beemer et al 37-156 3,094,796 6/1963 Atchley 37-156 ABRAHAM G. STONE, Primary Examiner.

ALAN KOP'ECKI, Assistant Examiner.

US. Cl. X.R.

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