Towed paver with thickness and leveling control

Abstract

A towed paver for use with a dump truck has a fixed hopper and screed and vertically adjustable support wheels and sensors engaging a supporting surface on which the wheels travel controlling devices moving said adjustable support wheels to control the thickness and level of an asphalt mat laid by the paver.

Parent Case Text

This application is a continuation-in-part of my co-pending patent application on PAVING MACHINE WITH THICKNESS AND LEVELING CONTROL, Ser. No. 391,882, filed Aug. 27, 1973.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to towed pavers which position, level and partially compact bituminous paving materials and provide regulation of the level and thickness of the material being laid.

2. Description of the Prior Art

The prior art paving machines of the towed type may be seen in U.S. Pat. Nos. 3,482,494 and 3,304,101 wherein manual adjustments are provided for varying the positioning of the screed and the hopper of the machine to achieve a desired thickness and level of the material being laid.

In U.S. Pat. No. 3,285,148 an automatic grade control system is illustrated in operative relation to a paver in which the screed is positioned on the ends of a pair of trailing arms and means is provided for moving the trailing arms and therefore the screed to maintain grade control.

This invention incorporates the advantages of a relatively inexpensive towed paver with directly mounted ground engaging support wheels and the automatic grade control heretofore found only in the complicated expensive self-propelled pavers.

SUMMARY OF THE INVENTION

A towed paver with thickness and leveling control incorporates a unitary hopper and screed with ground engaging supporting wheels beneath the hopper arranged to be vertically adjusted to vary the position of the hopper and the screed relative to paving material being laid thereby. Sensors carried on the hopper and engaging the surface over which the adjustable wheels travel actuate mechanisms varying the position of the wheels and therefore the angle of attack of the fixed screed relative to the paving material being laid.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of the towed paver with thickness and leveling controls;

FIG. 2 is a side elevation with parts broken away and parts in cross section illustrating the wheel adjusting devices of the towed paver. Broken lines in FIG. 2 illustrate optional locations of the wheel adjustment means;

FIG. 3 is a vertical elevation on line 3--3 of FIG. 2 with parts broken away, and

FIG. 4 is a diagrammatic view of the automatic sensing and leveling means.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In its simplest form the towed paver of this invention consists of a hopper 10 having a rearwardly extending fixed screed 11, the hopper 10 being open across its upper surface 12 and provided at its forward portion with detachable tow bars 13 by which it may be towed by a dump truck as seen in FIG. 1 of the drawings and wherein a dump body on the tow truck is indicated by the letter D.

Alternate means of towing the towed paver by the dump truck will occur to those skilled in the art, one of such means being illustrated in my aforesaid patent application Ser. No. 391,882.

In FIG. 1 of the drawings the hopper 10 with its fixed screed 11 is provided with supporting ground engaging wheels 14 located adjacent the sides and the forward portion of the hopper 10 and a pair of skis 15 are positioned one at each side of the hopper 10 and movably maintained in that position by telescopic supports 16 attached to the end walls of the hopper 10. A flexible cable 17 is attached to each of the skis 15 and extends substantially vertically from its point of attachment to a reel 18 on a sensor 19.

By referring now to FIG. 2 of the drawings it will be seen that the adjustable support wheels 14 at each side of the hopper 10 are carried on axles 20 which are in turn positioned on the free ends of arms 21 which are pivoted as at 22 to the bottom of the hopper 10. In order that the wheels 14 at each side of the hopper may be individually moved vertically relative thereto, piston and cylinder assemblies 23 are provided and may be located vertically above the axles 20 or horizontally rearwardly thereof. In FIG. 2 of the drawings solid lines show the vertical positioning of the piston and cylinder assemblies 23 and extensions of the piston rods 24 engage the axles 20. Broken lines in FIG. 2 show the alternate horizontal positioning of the piston and cylinder assemblies 23 and the alternate positioning of the extensions of the piston rods 24 and it will be observed that in either of the positions illustrated the piston and cylinder assemblies 23 will move the axles 20 so as to impart vertical movement on an arcuate path to the axles 20 and accordingly raise and lower the ground supporting wheels 14 relative to the hopper 10.

Means not shown is provided on the paver for providing fluid pressure to the piston and cylinder assemblies 23 and may comprise for example a quick detachable valved connection with suitable flexible hoses extending to the hydraulic system of the dump truck by which the paver is towed. Alternately compressed gas cylinders may be carried on the towed paver and utilized as a source of fluid pressure for actuating the piston and cylinder assemblies 23.

It will thus be seen that when the truck towing the paver moves forwardly, to the left as seen in FIGS. 1 and 2 of the drawings, the towed paver will move along with it and paving material deposited in the hopper 10 will be discharged through an opening in the rear portion thereof and leveled and partially compacted by the screed 11 passing thereover. The irregularities in the supporting surface traveled by the wheels 14 will be sensed by the skis 15 and the movement of the skis 15 relative to the hopper 10 will actuate the sensors 19, each of which controls the piston and cylinder assembly 23 adjustably positioning the wheel 14 on that side of the towed paver. The control is by way of valves in the pressure lines communicating with the piston and cylinder assembly and by providing for the individual actuation of the piston and cylinder assemblies 23 by the individual skis 15 the front corner portions of the towed paver may be adjusted vertically, individually or simultaneously to maintain a desired level and attack angle of the screed portion 11 of the towed paver.

It will occur to those skilled in the art that alternate means of moving the support wheels vertically relative to the bottom of the paver may be used and by referring to FIG. 3 of the drawings one such alternate proposal may be seen.

In FIG. 3 of the drawings a hopper 26 having a bottom 27 therein is illustrated as carrying a pair of vertically positioned guide channels 28 in spaced relation to one another with blocks 29 slidable vertically therein and in turn carrying an axle 30 on which ground engaging support wheels 31 are journeled. A vertically positioned piston and cylinder assembly 32 has the piston rod 33 thereof extended to engage the axle 30 whereby the support wheels 31 may be moved vertically again subject to the control of a sensor system including a sensor 34 and skis 35 which are the same as those illustrated in FIGS. 1 and 2 of the drawings heretofore described. Dual wheels and two pairs of piston and cylinder assemblies are used.

It will thus be seen that a simple relatively inexpensive towed paver with a unitary hopper and screed can be provided with individually adjustable supporting wheels adjacent its front corners and those wheels moved by automatic sensors and means controlled thereby as occasioned by irregularities in the supporting surface over which the towed paver is moved so that the towed paver is lowered or raised at its front corner portions to enable its unitary screed to overcome irregularities in the support surface and lay a substantially smooth and level mat of paving material.

By referring now to FIG. 4 of the drawings, the automatic leveling mechanism incorporated in the towed paver to translate the signals from the sensors 19 to the actuation of the hydraulic piston and cylinder assemblies 23 may be seen. By referring thereto the skis 15 are diagrammatically connected with the sensors 19 which are potentiometers in electric circuits 37 which are connected with a pair of solenoid actuated valves 38 each of which controls a fluid pressure line 39 in communication with one of the piston and cylinder assemblies 23 and with a pump 40. A relief valve 41 communicates with the pressure system and the solenoid valves 38 are so arranged that they will connect the piston and cylinder assemblies 23 with the fluid pressure line 39 so as to move the piston rods outwardly thereof as in elevating the respective ends of the hopper 10 of the towed paver.

Alternately the solenoid valves 38 will disconnect the piston and cylinder assemblies 23 from the fluid pressure supply lines communicating with the pump 40 and place the piston and cylinder assemblies 23 in communication with the fluid reservoir in the system.

Those skilled in the art will observe that there is an electric power source such as a battery in the control system to supply energy for the actuation of the solenoid valves. The sensors 19 which are potentiometers are arranged to vary the flow of current to the solenoid valves dependent upon their actuation by movement of the skis 15. The piston and cylinder assemblies 23 can be manually actuated as in initially setting the hopper 10 with its unitary screed 11 at a desired position to produce a paving mat of the desired thickness and/or slope and upon such setting being made the sensors 19 are adjusted to a zero position so that the resulting actuation by the skis 15 will increase or decrease the current flow controlled by the sensors 19 and thereby actuate the hydraulic valves 38 as desired to raise and/or lower the hopper 10 and its integral screed 11 thereby providing automatic control of the thickness and grade and level and the paving material being laid by the towed paver.

It will thus be seen that the towed paver disclosed herein is capable of operating automatically to maintain the desired grade and/or slope angle in a mat of paving material being laid thereby by the novel adjustment of the individually adjustable wheels 14 which result in the repositioning of the integral hopper and screed of the towed paver.

It will occur to those skilled in the art that the sensors hereinbefore described may be modified to comprise a simple mechanical arrangement with levers interconnecting the skis and the wheel carrying means so that movement of the skis will impart related movement to the wheels and thereby adjust the grade and level of the paver. Also it will be seen that mechanical devices such as jacks may be used for moving said wheels relative to said hopper and provided with motors for actuating said jacks which in turn are controlled by said sensors.

Although but one embodiment of the invention and a modification thereof have been illustrated and described it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention.

Claims

Having thus described my invention what I claim is:

1. The combination of a towed paver and grade sensing and control means therefor, the paver comprising a hopper having front and back walls with a material depositing opening therebetween, at least two vertically adjustable supporting wheels beneath said front wall, a screed attached to the back wall of said hopper in fixed relation thereto and extending rearwardly of said material depositing opening, extendible devices between said wheels and the front wall of said hopper and a power source for said extendible devices whereby said hopper and screed may be moved relative to said wheels as said paver is towed over a surface to be paved; said sensing and control means comprising skis movably supported on said hopper and engaging said surface to be paved, means on said hopper connected to said skis for emitting a signal, secondary means controlling said power source with respect to said extendible devices and acting responsive to said signal to move said extendible devices and the hopper and screed responsive to movement of the skis due to deviation in the grade of said surface to be paved so as to change the angle of attack of said screed.

2. The combination of claim 1 further characterized by the grade sensing means being mounted on both sides of said paver.

3. The combination of claim 1 further characterized by said extendible devices consisting of hydraulic piston and cylinder assemblies.

4. The combination of claim 1 further characterized by said grade sensing means consisting of a pair of elongated skis, support means on said hopper moveably holding said skis.

5. The combination of claim 1 further characterized by said extendible devices comprising a pair of piston and cylinder assemblies adjustably attaching the front wall of said hopper to said wheels and spaced with respect to one another so as to tilt said hopper and screed on a transverse axis.

6. In combination with a towed paver that is attached to a truck and towed thereby over a supporting surface to be paved and comprises a unitary hopper and screed with a material depositing opening therebetween and at least two vertically adjustable supporting wheels beneath said hopper and spaced forwardly of said screed, means for moving said wheels relative to said hopper whereby the hopper pivots on the screed and changes the angle of attack of said screed with respect to material moving through said opening, grade sensing means and mechanical devices interconnecting said grade sensing means and said adjustable wheels arranged so that movement of said grade sensing means imparts related movement to said adjustable wheels to adjust the position of the hopper and the angle of attack of said screed.