US3285148A

US3285148A - Grade control system on bituminous pavers

Info

Publication number: US3285148A
Application number: US262145A
Authority: US
Inventors: Munyon Julian Marland
Original assignee: Barber Greene Co
Current assignee: Barber Greene Co
Priority date: 1963-03-01
Filing date: 1963-03-01
Publication date: 1966-11-15
Anticipated expiration: 1983-11-15

Description

J. M. MUNYON 3,285,148

Nov. 15, 1966 GRADE CONTROL SYSTEM ON BITUMINOUS PAVERS 5 Sheets-Sheet 1 Filed March 1, 1963 --SIGNAL LIGHT RH. SOLENOID LEVELING VALVE COMMAND PANEL BATTERY LEVELING RAM L4H SOLENOID LEVELING VA LVE CONTROL ZUBICLE/ 35 7 RAM I RH. SOLENOID LH SOLENOID 70 LEVELING VALVE LEvELINO vALvE 70 I 36 L 0 V 66 I RAM I 5' 68 RAM FLOW REGULATOR TANK 60 73 FLOW REGULATOR HYD. OIL PUMP F] 2 INVENTOR.

JULIAN M. MUNYON ATTO NEYS Nov. 15, 1966 J. M. MUNYON GRADE CONTROL SYSTEM ON BITUMINOUS PAVERS Filed March 1, 1963 5 Sheets-Sheet 2 GEO mOmZmm WW 5053 Jo zou MN 52 021554 QozHom I dz 92228 km, Eukzm M J @2355 90258 Im INVENTOR.

JULIAN M. MUNVON AT TORNEYS INVENTOR.

J. M. MUNYON GRADE CONTROL SYSTEM ON BITUMINOUS PAVERS 5 Sheets-Sheet 3 kmn M VHNHI KN 4/1\| JNI Lb I mjgmDU JOKFZOU JuuAN M. MUNYON B ZKN AT ORN EYS Nov. 15, 1966 Filed March 1, 1963 3,285,148 GRADE CONTROL SYSTEM N BITUMINOUS PAVERS Julian Marland Munyon, Big Rock, Ill., assignor to Barber-Greene Company, Aurora, 111., a corporation of Illinois Filed Mar. 1, 1963, Ser. No. 262,145 14 Claims. (Cl. 94-46) The present invention relates to improvements in roadfinishing machines or pavers and more particularly to such machines which lay and finish bituminous or like paving materials along a roadway. More particularly, the instant invention is concerned with the location of a transverse level laying sensing device on bituminous road-finishing machines or pavers. According to my invention, I have located the transverse-sensing device near a leading edge of a screed on the paver to furnish an error or control signal to a control system. Draft arms are actuated in response to an amplified signal transmitted to the draft arms by the control system whereby a bituminous mat may be formed having a desired transverse slope.

In the past, it has been the practice to locate transverse leveling sensing means at the pull points of the draft arms. This system would be satisfactory if the Sensing means could reflect a fixed relationship between the sensor level and a predetermined screed level. In practice, however, this relationship exists only if the attack angle of the screed is the same across the full screed width. It has been found that the attack angle of the screed between its ends tends to change with some of the variables encountered in laying a bituminous mat. When the screed slope is thus changed, the transversesensing means located at the pull ends of the draft arms will not register this change and no correction is provided.

It has further been found that the sensing means could not exercise the desired control when located on the screed, for the controls when located on the screed go into oscillation producing an unstable control system. Analog computor studies indicate that the optimum position of the sensing means should be just ahead of the screed unit which still permits a signal to be registered on a change in base elevation, a grade line change, or a change due to screed-angle variations. Where the transverse leveling sensing means is disposed immediately in front of the screed and tamper unit, but rearwardly of the hopper, a mat surface having a transverse slope of any desired value may be conviently and accurately produced during operation of the paver.

Accordingly, an important object of this invention is to provide a new and improved automatic transverse leveling sensing means which is capable of reducing and minimizing errors in the slope of the mat surface produced by a paver.

Stated in other terms, the floating screed principle employed on a paver of the present type can reduce surface error. Variations of this type cause differential errors between the two outside edges of the screed. Where a transverse-sensing device is located on a beam between the pivot points of the leveling arms, the transversesensing device fails to sense any change in relative elevation of the screed and only senses changes of the pivot points. Due to the differential errors between two outside edges of a floating-type screed, a transverse-sensing device located between the pivot or tow points of the leveling arms is unable to correct the errors and the resulting mat surface produced by the machine contains a large percentage of error.

It has been found that where the sensor error signal is located immediately forward of the screed and tamper 3,285,148 Patented Nov. 15, race unit, but rearwardly of the hopper, the signal produced is the same as the error of the screed off its desired grade, and elimination of the sensor error places the screed back on the desired grade.

An important feature of this invention relates to the disposition of transverse leveling sensing means immediately in front of the screed and tamper unit and rearwardly of the hopper in order that a mat surface having a desired transverse slope may be conveniently and accurately produced during operation of the paver.

According to still other features of my invention, a transverse beam is supported on draft arms, which beam is located longitudinally between the hopper and the tamper and screed unit. The beam has a pendulum mounted between its ends and a grid sensor is mounted on one end of the beam at one side of the machine.

The pendulum and grid sensor are connected with a control means or cubicle for delivering electrical signals thereto. Amplified signals are transmitted from the control cubicle to solenoid valves and to hydraulic cylinders which vertically shift the transverse pivot axes of the draft arms in order'to produce a mat having a desired transverse slope with a minimum of error.

Another feature of this invention relates to the provision of an electric light on the machine which acts as a signal to indicate that the grid is functioning properly.

According to other features of this invention, a pair of lever arms are pivotally connected to the machine each at one end, and the lever arms are pivotally connected to the transverse pivot axes of the draft arms at opposite ends so that the rams may be connected with the lever arms to permit the transverse pivot axesof the draft arms to be vertically shifted to control the attack angle of the screed.

Other objects and features of this invention will more fully become apparent in view of the following detailed description taken in conjunction with the accompanying drawings illustrating a single embodiment and in which:

FIGURE 1 is a schematic view in dotted and full lines of a road paver with the illustrations in full lines illustrating a screed-control system;

FIGURE 2 is a schematic diagram representing an illustrative hydraulic system in accordance with my invention;

FIGURE 3 is a schematic diagram representing an illustrative electrical system in accordance with my invention; and

FIGURE 4 is a side view of a road paver illustrated in dotted and full lines with the screed-control system shown in full lines.

In the present illustrative embodiment, the invention is utilized for controlling a typical road-finishing machine or paver of a known type such as is shown in H. A. Barber et al. US. Patent 3,054,334

The reference numeral 9 indicates generally a paving machine or paver. The paving machine 9 includes a paver frame 10 which is mounted on crawlers or tracks 11. A hopper 12 is mounted at a forward end of the paver 9 on the paver frame 10 for receiving paving material from a dump truck in a conventional manner. The rollers 13 are adapted to engage with the rear wheels of the dump truck as the paving material is unloaded into the hopper 12.

Mounted behind the hopper 12 at a rear end of the paver 9 is a tamper and screed unit 14. The unit 14 includes a screed 14a and a tamper 1412 which are diagrammatically illustrated by the dotted lines in FIGURE 3. The tamper and screed unit may be of any suitable wellknown construction such as isshown in Harry A. Barber US. Patents Nos. 2,351,592 and 2,351,593.

Disposed between the hopper 12 and the tamper and screed unit 14 is a mechanism 15 such as a screw for unloading the paving material from the hopper and depositing the same upon the ground in front of the tamper and screed unit 14 such as is illustrated in FIGURE 1 of Harry A. Barber et al., US. Patent 2,796,8/11.

Mounted upon the frame 10 is a pair of leveling arms or draft arms with the left hand draft arm being designated by the reference numeral 16 and with the right hand leveling arm being designated by the numeral 16. The

arms

16 and 16 are provided with forward leveling or draft arm pivots 17 and 17'. Lever arms 18 and 18' are provided with

lever arm pivots

19 and 19 joining the lever arms with the frame. arms 18 and 18' are connected with the draft arm pivots 17 and 17'. It will thus be appreciated that the leveling arms or draft arms 16 and 1-6 are pivoted on their associated pivots 17 and 17' as the lever arms 18 and 18' are moved upwardly or downwardly in a manner which will be further described hereafter.

Mounted on the draft arms 16 and 16' rearwardly of the

pivots

17 and 17 is a transverse beam 20. The beam 20 is secured to the draft arms 16 and 16' by suitable clamps 21 and 21' shown in FIGURE 1. Mounted on the transverse beam is a slope sensor or pendulum 22. Also mounted on the transverse beam 20 at one side of the machine is a grade sensor or sens-r grid 23.

The pendulum 22 may be of any suitable type which is conventionally employed for road machinery. The pendulum may consist of a float with freedom of movement about one axis, suspended in a liquid in an'enclosed container. Normally, a pendulum of this type does not have any external moving parts. Any change of slope of the screed is sensed by the pendulum which notes the degree of change and relays the information to a control cubicle as will be further described herein. The tamper and screed unit 14 is secured with the draft arms in a conventional manner. During operation of the paver 9, the screed engages a top surface of the paving material as indicated at S in FIGURE 1. Forward side edges of the screed are supported by the draft arms.

The combination sensor and grid unit or slope sensor 23 includes a grid 24 and a sensor 25. The grid 24 rides upon a grade reference at an approximate 45 trailing altitude at a zero setting of a grade-control knob provided on a command panel such as is illustrated at 30 in FIG- UR-E 1. As the rear of the grid is raised or lowered, it rotates a shaft (not shown) the cylindrical sensor 25 that causes a signal to be set giving the degree and direction of deviation of the screed from the desired grade.

There are many means of obtaining a grade reference. The present application shows the paver 9 as being provided with the grid and sensor unit 23. Other commonly used systems include a ski riding on an existing surface, and a matching shoe riding on a previously laid mat. The grid 24, as herein shown, is adapted to be used with a string line L (FIGURE 1) and the grid 24 is engaged therewith.

A pair of leveling rams 26 and 26' is each pivotally joined at one end with the paver frame with the pivots being indicated at 27 and 27. Opposite ends of the level ing rams 26 and 26 are joined with the lever arms 18 and 18 at pivots 28 and 28'. The hydraulic rams are preferably of the double-acting type.

In FIGURE 4, it will be noted that a command panel 30 is provided having a grade-control dial 31 and a slopecontrol dial 32. Other suit-able controls are provided on the command panel for automatic and manual operation of the screed leveling system herein disclosed. Several of the components employed in my screed leveling system are manufactured by Minneapolis-Honeywell. The penduhim 22 is identified by the Minneapolis-Honeywell par-t No. SB95A1027, the command panel 30 is identified by part No. W675A1026 and a control cubicle 35, to be hereafter described, is identified by part No. W674A1045.

After the screed and tamper unit 14 has been set at a Opposite ends of the lever,

desired position, the pendulum 22 will generate a signal where a variation in the screed angle of attack occurs which signal is transmitted through electric line 33 and cable 34 to the control cubicle 35 as shown in FIGURE 3. The control cubicle 35 then delivers an amplified signal to either a RH. solenoid leveling valve 36 or to a L.H. solenoid leveling valve 36' depending on the type of variation that has occurred. The R.H. valve 36 is connected with the control cubicle 35 by means of a cable 37 containing

lines

38, 39, 40 and 41. The L.H. valve 36' is connected with the control cubicle 35 by means of a cable 37' containing lines 38', 39', 40 and 41'.

The electric power necessary to operate the system is provided by a 12-volt battery 45. The control cubicle 35 has a power supply module which converts the DC. battery power to isolate DC. at various voltage levels. The cubicle 35 further includes two identical preamplifier modules that amplify the signals from the sensor and the pendulum and send the signals on to the sensor or pendulum power amplifier modules. Two identical power amplifier modules (one for each leveling valve) are also provided inside the cubicle. These power amplifier modules operate the solenoids on the leveling valve to raise or lower the leveling rams. Also provided within the eubicle 35 is a pair of sensitivity potentiometers (one for the sensor and one for the pendulum) which are adjustable to determine the sensitivity at which the pendulum 22 and the sensor 25 operate.

The battery 45'has a power line 46 that is joined with a on-olf switch 47. A second line 48 isv joined at one end with the on-ofi' switch 47 and housed in cable 49 that is connected to the control cubicle 35. The battery 45 has a ground line 50 which is connected with the control cubicle 35 at its opposite end. It is essential that the limit switch 47 and the fuse 47 be installed in the hot line.

The electrical system further includes electric lines 51 and 52 which join a signal light 53 with the control cubicle 35. The signal light must be insulated from the paver frame 10 by any suitable means. The signal light is coordinated with the grid 24 and the light is generally on when the grid is operating normally. detached from the sensor 25, the light circuit is broken so that the light goes off giving the operator a signal that the screed-control system is incapable of functioning correctly until such time as when the grid is repaired.

The command panel 30 has a cable 54 which is joined with the control cubicle 35 for communicating signals to the cubicle as a result of the operation of the command panel dials 31 and 32 as well as such other controls that may be provided on the command panel.

The hydraulic system for operating the leveling rams 26 and 26 is illustrated in FIGURE 2. When the transverse slope angle sensing rneans or pendulum and the grade sensing means emits signals to the solenoid leveling valves 36 and 36', the hydraulic rams are activated in order to move the screed to its preset position in order to compensate for attack angle deviations of the screed. The hydraulic system includes a hydraulic oil pump 60 that has a fluid line 61 joining the pump with a flow regulator 62. The flow regulator has a fluid line 63 which is joined with uni-directional flow regulators 64 and 64'. The flow regulator 64 is associated with the L.H. leveling ram while the flow regulator 64' is associated with the RH. leveling ram 26. The flow regulators 64 and 64 have

fluid lines

65 and 65' joining them with L.H. solenoid leveling valve 36 and RH. solenoid leveling valve 36'. Fluid lines '66 and 66' join the valves 36 and 36' with flowco'n-trol valves '67 and 67. The valves 67 and 67' have fluid lines '68 and 68' joining the valves 36 and 36' with one side of the leveling rams 26 and 26'. The opposite sides of the leveling rams 26 and 26 are joined with the leveling valves 36 and 36' by means of fluid lines 69 and 69'. Thus, as an example, when the leveling ram 26 is to be actuated in one direction, fluid is caused to be flowed through the valve 36 into the fluid line 69' and returned When the grid is to the valve 36' through the fluid line 68'. The leveling ram 26' can be actuated in an opposite direction where a signal is relayed to the solenoid leveling valve causing fluid to flow through fluid line 68' into the ram 26 whereupon the fluid is returned to the valve 36' through the fluid line 69'.

I have found that it is desirable to employ a hydraulic system which has pressure in it at all times so that when corrective signals are emitted by the pendulum 22 and by the sensor grid unit 23, a corrective signal may be transmitted to the solenoid leveling valves 36 and 36' to cause the leveling rams 26 and 26' to be instantaneously moved to alter the screed angle of attack to correct such error. During normal operation, the fluid will flow from the pump through the fluid lines and components previously described and through the valves 36 and 36' into fluid lines 70 and 70 which are in communication with a fluid line 71 connected with a flow-control valve 72. The uni-directional flow control valve 72 has a fluid line 73 that communicates at one end 'with a relief valve 74 and at an opposite end with a oil tank 75.

The automatic grade-control system on the payer 9 can be placed in condition for operation by moving the paver onto a roadway to be paved. The screed is then blocked up to the desired thickness and/ or slope. Both thickness and control screws 14c and 140' are rotated to a neutral position and then turned so that the screed may be set at the desired angle of attack. The grade and slope dials 31 and 32 are rotated until a zero position is indicated. Switches on the command panel are then moved from a manual position to an automatic position to place the grade slope control system in condition for automatic operation.

In some instances, where it is desired to pave superelevated curves where a great degree of accuracy is desired, a pair of grid sensor units 23 are mounted on opposite ends of the transverse beam 20. These units are identical to one another and the additional grid sensor unit is connected with the control cubicle detaching the pendulum cable 33 from the pendulum and joining the pendulum cable 33 with the added sensor unit 23. Where a pair of grid sensor units are employed, it is preferable to use a pair of string lines also. It is in this way that the automatic grade-control system which has been described enables the screed on the paver 9 to be automatically held at the desired grade and slope. The desired grade and slope is maintained by raising or lowering the leveling anm pivot points 17 and 17' to control the screed angle of attack. The sensor and grid unit 23 is used with a string line, a previously laid mat, or a ski, to maintain the desired grade. The unit 23 may be mounted on either side or both sides of the paver. Any change in the attitude of the -paver in relation to the grade causes the leveling arm pivot to be raised or lowered the distance necessary to maintain the desired grade.

The enclosed pendulum 22 mounted on the transverse beam 20 between the

paver leveling arms

16 and 16 cooperate with the sensor unit 23 to maintain the screed at the desired grade level and at the desired sloped angle of attack. Any variation of the screed from the desired slope angle and from the desired grade causes the pendulum and the grade sensor unit to send signals which raises or lowers one or more of the leveling arm pivots to main tain the screed at the desired slope angle and at the desired grade.

Excellent results are obtainable where the

sensors

22 and 23 are positioned in front of the taper and screed unit 14 a distance of approximately to of the draft arm length from its transverse pivot axis 17. Stated otherwise, the

sensors

22 and 23 are desirably positioned forwardly of the unit 14 from 2" to 12".

According to further objects and features of my invention, I have provided an improved method of maintaining a screed at a desired grade level and/ or at a desired slope angle by employing sensors which are capable of generating electrical signals at transversely spaced points immediately in front of the screed, but rearwardly of a paving material hopper in response to movement of the screed from its desired preset position. These electrical signals are utilized for almost instantaneously returning the screed to its aforesaid preset grade level and angle of attack, in the event of any undesired change of position of the screed.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted here-on, all such modifications .as reasonably and pnoperly come within the scope of my contribution to the art.

I claim as my invention:

1. In combination with a paving machine that is moving forwardly over the ground and that comprises two draft arms pivotally mounted at opposite sides of the machine on transverse pivot axes and extending rearwardl; therefrom,

a screed and tamper unit with the screed having portions mounted on the respective draft arms adjacent their rearward ends,

means for depositing paving material adjacent a forward edge of said screed to form a mat surface on which the screed rides,

a transverse beam supported on said draft arms adjacent said unit, I

a transverse slope angle sensing means supported on said transverse beam immediately adjacent and forwardly of said screed and tamper unit for emitting an electrical signal to a control means,

grade sensing means supported on said transverse beam immediately adjacent and forwardly of said screed and tamper unit at one side of said machine for emitting an electrical signal to a control means,

control means for receiving electrical signals from said slope angle sensing means and from said grade sensing means and for emitting amplified electrical signals,

a pair of cylinders having leveling rams connected with and supporting said draft arms on said machine adjacent said transverse pivot axes for raising and lowering the pivot axes of said arms, and

electrically operated valves each operatively associated with one of said leveling rams and being operatively associated with said control means for receiving amplified electrical signals therefrom for causing independent controlled movement of said rams to move said transverse pivot axes and said screed to correct deviations from a grade line and/ or to correct deviations in the transverse slope angle to form a mat surface having a desired transverse slope.

2. The combination of claim 1 further characterized by said transverse slope angle sensing means including a pendulum mounted between opposite ends of said transverse beam.

3. The combination of claim 1 further characterized by said grade slope angle sensing means being mounted on an opposite side of said machine.

4. The combination of claim 1 further characterized by said pair of lever arms on opposite sides of said machine and each being pivotally joined at one end with the associate side, the lever arms being pivotally joined at opposite ends with the transverse pivot axes of said draft arms, and said rams being pivotally joined with said lever arms for pivoting said lever arms and said draft arms in response to signals from said control means.

5. In combination with a paving machine that is moving forwardly over the ground,

a pair of lever arms pivotally mounted at forward ends on opposite sides of the machine,

a pair of draft arms pivotally mounted at opposite sides of the machine on transverse pivot axes on rearward ends of said lever arms and extending rearwardly therefrom,

a transverse beam supported on said draft arms forwardly of said screed,

a pair of cylinders having leveling rams connected with said lever arms adjacent said transverse pivot axes and supporting said draft arms on said machine adjacent said transverse pivot axes for raising and lowering the pivot axes of said arms, and

electrically operated valves each operatively associated with one of said leveling rams and being operatively associated with said control means for receiving amplified electrical signals therefrom for causing independent controlled movement of said rams to move said transverse pivot. axes and said screed to correct deviations in the transverse slope angle to form a mat surface having a desired transverse slope.

6. The combination of claim further characterized by said transverse slope angle sensing means and said grade level sensing means being positioned forwardly of said tamper and screed unit from 2" to 12".

7. The combination of claim 5 further characterized by said transverse beam being spaced slightly in front of said unit at a distance of approximately /3 to W of the draft arm length from its transverse pivot axis.

, 8. The combination of claim 5 further characterized by said grade level sensing means including a grid and a light signal mounted on said machine and operatively connected with said grid for indicating that the grid is intact and in operative assembly with the transverse beam and for indicating when the grid is knocked free of operative assembly with the transverse beam.

9. In combination with a paving machine that is movable forwardly over the ground and that comprises two draft arms pivotally mounted at opposite sides of the machine on transverse pivot axes and extending rearwardly therefrom,

a screed having its end portions mounted on the respective draft arms adjacent their rearward ends,

a hopper from which paving material is moved and deposited adjacent a forward edge of the screed to form a mat on which the screed rides,

adjusting means operable to vary independently the angles of attack at which the respective screed end portions engage the deposited material,

-a transverse beam supported on said draft arms disposed between s-aid hopper and said screed,

a transverse slope angle sensing means supported on said transverse beam immediately adjacent and forwardly of said screed for emitting an electrical signal to a control means,

grade sensing means supported on said transverse beam immediately adjacent and forwardly of said screed at one side of said machine for emitting an electrical signal to a control means,

a pair of cylinders having leveling r-ams connected with and supporting said draft arms on said machine adjacent said transverse pivot axes for raising and lowering the pivot axes of said arms, and

electrically operated solenoid valves each operatively associated with one of said leveling rams and being operatively associated with said control means for receiving amplified electrical signals therefrom for causing independent controlled movement of said rams to maintain a desired transverse slope of the mat surface.

10. In combination with a paving machine having two draft arms pivotally mounted at opposite sides of the machine on transverse pivot axes and which draft arms extend rearwardly therefrom,

a screed being mounted on the respective draft arms adjacent their rearward ends,

a transverse beam supported on said draft arms disposed between said pivot axes and said screed,

a transverse slope sensing means supported on said transverse beam immediately adjacent and forwardly of said screed for emitting an electrical signal to a control means,

a hydraulic system including a pair of leveling rams connected with and supporting said draft arms on said machine adjacent said transverse pivot axes for raising and lowering the pivot axes of said arms, and

electrically operated valves each operatively associated with one of said leveling rams and being operatively associated with said control means for receiving amplified electrical signals therefrom for causing independent controlled movement of said rams to obtain a mat surface of -a desired transverse slope and/or of a desired grade.

11. The combination of claim 10 further characterized by said hydraulic system being continuously pressurized to minimize time lag from when a corrective signal is emitted by said control means to when the rams are actuated for returning the screed to a desired position.

12. In combination with :a paving machine having two draft arms pivotally mounted at opposite sides of the machine on transverse pivot axes and which draft arms extend rear-wandly therefrom,

a floating type screed being mounted on the respective draft arms adjacent their rearward ends,

.a transverse beam supported on said draft arms disposed between said pivot axes and said screed,

grade sensing means supported on said transverse beam immediately adjacent and forwardly of said screed at one side of the machine for emitting an electrical signal to a control means,

a first means connected with said draft arms adjacent said transverse pivot axes for raising and lowering the pivot axes of said arms, and

a second means operatively associated with said first means and being operatively associated with said control means for receiving amplified electrical signals therefrom for causing independent controlled movement of said arms to obtain a mat surface of a desired transverse slope and/ or of a desired grade.

13. In combination with a paving machine having two draft arms pivotally mounted at opposite sides of the machine on transverse pivot axes and which draft arms extend rearwardly therefrom,

a second means operatively associated with said first means and being operatively associated with said control means for receiving amplified electrical signals therefrom for causing independent controlled movement of said arms to obtain a mat surface of a desired transverse slope and/ or of a desired grade,

said transverse slope angle sensing means and said grade level sensing means being positioned forwardly of said screed from 2" to 12".

14. In combination with a paving machine having two draft arms pivotally mounted at opposite sides of the machine on transverse pivot axes and which draft arms extend rearwardly therefrom,

a floating type screed being mounted on the respective draft arm-s adjacent their rearward ends,

a second means operatively associated with said first means and being operatively associated with said control means for receiving amplified electrical signals therefrom for causing independent controlled movement of said arms to obtain a mat surface of a desired transverse slope and/or of a desired grade,

said transverse beam being spaced slightly in front of said unit at a distance of approximately 73 to V of the draft arm length from its transverse pivot axis.

References Cited by the Examiner UNITED STATES PATENTS 2,295,519 8/ 1942 Millikin 94-46 2,922,345 1/ 1960 Mentes.

3,029,715 4/ 1962 Bowen 94-46 3,029,716 4/ 1962 Shea 9446 3,054,334 9/1962 Barber 94--46 3,111,070 11/1963 Pollitz 94-46 CHARLES E. OCONNELL, Primary Examiner.

N. C. BYERS, Assistant Examiner.

Claims

1. IN COMBINATION WITH A PAVING MACHINE THAT IS MOVING FORWARDLY OVER THE GROUND AND THAT COMPRISES TWO DRAFT ARMS PIVOTALLY MOUNTED AT OPPOSITE SIDES OF THE MACHINE ON TRANSVERSE PIVOT AXES AND EXTENDING REARWARDLY THEREFROM, A SCREED AND TAMPER UNIT WITH THE SCREED HAVING PORTIONS MOUNTED ON THE RESPECTIVE DRAFT ARMS ADJACENT THEIR REARWARD ENDS, MEANS FOR DEPOSITING PAVING MATERIAL ADJACENT A FORWARD EDGE OF SAID SCREED TO FORM A MAT SURFACE ON WHICH THE SCREED RIDES, A TRANSVERSE BEAM SUPPORTED ON SAID DRAFT ARMS ADJACENT SAID UNIT, A TRANSVERSE SLOPE ANGLE SENSING MEANS SUPPORTED ON SAID TRANSVERSE BEAM IMMEDIATELY ADJACENT AND FORWARDLY OF SAID SCREED AND TAMPERED UNIT FOR EMITTING AN ELECTRICAL SIGNAL TO A CONTROL MEANS, GRADE SENSING MEANS SUPPORTED ON SAID TRANSVERSE BEAM IMMEDIATELY ADJACENT AND FORWARDLY OF SAID SCREED AND TAMPER UNIT AT ONE SIDE OF SAID MACHINE FOR EMITTING AN ELECTRICAL SIGNALS TO A CONTROL MEANS, CONTROL MEANS FOR RECEIVING ELECTRICAL SIGNALS FROM SAID SLOPE ANGLE SENSING MEANS AND FROM SAID GRADE SENSING MEANS FOR EMITTING AMPLIFIED ELECTRICASL SIGNALS, A PAIR OF CYLINDERS HAVING LEVELING RAMS CONNECTED WITH AND SUPPORTING SAID DRAFT ARMS ON SAID MACHINE ADJACENT SAID TRANSVERSE PIVOT AXES FOR RAISING AND LOWERING THE PIVOT AXES OF SAID ARMS, AND ELECTRICALLY OPERATED VALVES EACH OPERATIVELY ASSOCIATED WITH ONE OF SAID LEVELING RAMS AND BEING OPERATIVELY ASSOCIATED WITH SAID CONTROL MEANS FOR RECEIVING AMPLIFIED ELECTRICAL SIGNALS THEREFROM FOR CAUSING INDEPENDENT CONTROLLED MOVEMENT OF SAID RAMS TO MOVE SAID TRANSVERSE PIVOT AXES AND SAID SCREED TO CORRECT DEVIATIONS FROM A GRADE LINE AND/OR TO CORRECT DEVIATIONS IN THE TRANSVERSE SLOPE ANGLE TO FORM A MAT SURFACE HAVING A DESIRED TRANSVERSE SLOPE.