AU778043B2 - Method and apparatus for laying roadway materials - Google Patents

Description

-1-

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant/s: Actual Inventor/s: Address for Service: John Russell Sharpe and Alan Victor Sharpe and Ronald Douglas Sharpe John Russell Sharpe and Alan Victor Sharpe and Ronald Douglas Sharpe BALDWIN SHELSTON WATERS MARGARET STREET SYDNEY NSW 2000 'METHOD AND APPARATUS FOR LAYING ROADWAY

MATERIALS'

Invention Title: Details of Associated Provisional Application No. PQ0574 dated 26 May 1999 The following statement is a full description of this invention, including the best method of performing it known to me/us:- File: 28235AUP00 -2- FIELD OF THE INVENTION This invention relates to the laying of roadway materials, and in particular to the laying of sections of roadway materials, including road surface materials such as asphalt, by means of a road paving machine. The invention has particular applications in the laying of new sections of roadway and in the renewal of sections of damaged or deteriorated asphalt in an existing roadway.

BACKGROUND ART •Road paving machines are commonly employed when a new section of roadway is to be laid. Commercially available road paving machines, such as those marketed by BLAW-KNOX TM and INGERSOL RAND TM, are typically designed with a "floating" screed for levelling the deposited roadway material. The screed is connected to the road paving machine, usually by means of a pair of arms. As the screed is drawn forward by the machine, roadway material is metered under the screed and the screed is displaced vertically by the material flowing beneath it, thus establishing the depth or thickness of .i 15 the deposited layer. The screed is therefore free to "float" up or down, independent of the rest of the machine, as dictated by the flow of material. The thickness of the deposited layer, commonly known as the "mat depth", is established and maintained by controlling this rise and fall of the screed. As paving progresses, the free-floating action of the screed will compensate for irregularities in the grade or base surface over which paving is being performed.

However, even experienced road paving machine operators often encounter difficulty in achieving the desired level for a new roadway surface. For example, when using a road paving machine with a floating screed to lay a section of roadway, it is often A I -3difficult for the operator to match the level of the new section of roadway with the level of the existing road or pavement, particularly at the commencement or completion of the new section.

An additional problem is that it is not uncommon for the screed to come into contact with the roadway when a new section of roadway material is being laid. This leads to wear and/or damage to the screed and may result in the necessity to replace the screed.

OBJECT OF THE INVENTION It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

DISCLOSURE OF THE INVENTION To this end, a first aspect of the present invention provides a method of depositing a section of roadway material with a self propelled road paving machine, said road paving machine including: a hopper for storing roadway material; :a feed conveyor for transferring said roadway material from said hopper to a laterally extending spreading means comprising one or more rotatable augers; oooO 0a screed for levelling said roadway material, said screed located rearwardly of said one or more rotatable augers; and C. Cl o S 20 a height control means including an arm of variable length located on said screed for controlling the height of the screed above a surface on which said roadway o=oO So. material is to be laid; o 1 ~wherein said arm on said screed is extended to contact a surface adjacent where C C g the section of roadway material is to be laid so that the height of the screed above the •o 25 surface on which said roadway material is to be laid is determined with reference to said adjacent surface; said roadway material being held in the hopper of the machine and fed via said feed conveyor towards the rear of the machine whereupon it is deposited onto the roadway, the deposited material being spread laterally by means of said rotating augers, the screed of the paving machine acting to level the deposited material so that a layer of said roadway material of relatively uniform height is formed on the roadway as the road -4paving machine moves in a forward direction, the height of the screed above the road surface determining the thickness of the layer of roadway material.

Preferably the height control means is connected to the screed of the paving machine at a position outside the line of the screed.

Preferably the screed assembly is provided with a pair of height control means with one height control means positioned on each side of the screed.

Preferably the height control means includes a telescopic ram actuated by hydraulics or pneumatics so as to enable adjustment of the height of the screed relative to the road surface adjacent where the layer of roadway material is to be laid.

Preferably the height control means includes a member which, in use, contacts and moves over the existing road surface as the road paving machine traverses the section of roadway to be filled.

A second aspect of the present invention provides a self-propelled road paving machine including: a hopper for storing roadway material; a feed conveyor for transferring said roadway material from said hopper to a laterally extending spreading means comprising one or more rotatable augers; a screed for levelling said roadway material, said screed located rearwardly of said one or more rotatable augers; and a height control means including an arm of variable length located on said screed for controlling the height of the screed above a surface on which said roadway material is to be laid, wherein said arm is extendable to contact a surface adjacent where *the section of roadway material is to be laid so that the height of the screed above the surface on which said roadway material is to be laid is determined with reference to said 25 adjacent surface.

A third aspect of the present invention provides a method of depositing a section of roadway material with a road paving machine, said method including locating a source of laser light in the vicinity of the section so as to provide a reference level for the desired level of the roadway material, said road paving machine including a target upon which said laser light is directed so as to enable the level of the screed of the road paving machine to be adjusted to the desired level.

••co A fourth aspect of the present invention provides a method of depositing a section of roadway material with a road paving machine, said method including locating a source of laser light on said road paving machine and directing said laser light at a target located in the vicinity of the section so as to enable the level of the screed of the road paving machine to be adjusted to a desired level.

The present invention can be utilised in the deposition of a roadway material, such as a hot-mix asphalt.

Advantageously, the present invention provides an improved method for laying a section of roadway material, such as asphalt, which reduces the time and labour requirements of the present methods.

The method and apparatus of the present invention can be adapted to be used with most conventional road paving machines, including machines marketed by BLAW- KNOX TM and INGERSOL RAND TM The present invention may be employed to repair an existing section of roadway, or to widen a section of roadway.

Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

oeo e• -6- BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS The various aspects of the present invention will be better understood and appreciated from the following discussion of the features of preferred embodiments the invention may take. Reference is made to the accompanying drawings in which: Fig. 1 is a side elevation of a typical road paving machine employing the first aspect of the present invention and illustrating the flow of road material through the machine.

Fig. 2 is a simplified plan view of the road paving machine depicted in Fig. 1 illustrating the material flow path through the machine.

Fig. 3 is a simplified side elevation of the paving mechanism of a typical road paving machine, illustrating the relationship between the augers, the screed assembly of the paving mechanism, and the screed height control means.

Fig. 4 is a schematic transverse elevation view ofa screed assembly and screed height control assembly in accordance with the present invention during the process of 15I laying a course of roadway material.

Fig. 5 is a schematic transverse elevation view of a screed assembly and screed height control assembly in the process of laying a second course of roadway material.

Fig. 6 is a side elevation of a typical road paving machine and illustrating a second aspect of the present invention.

Fig. 7 is a schematic transverse elevation view of a screed assembly of a road paving machine and illustrating a third aspect of the present invention.

-7- DETAILED DESCRIPTION OF INVENTION Referring to Figs. I to 3, a typical commercially available road paving machine 1 is depicted. Hot mix asphalt 2 is held in a hopper section 3 of the machine and is fed via feed conveyors 4 towards the rear of the machine where it is deposited onto the roadway 5. The deposited material 6 is spread laterally by means of rotating augers 7 located forwardly of the screed section 8 of the paving machine. The screed 8 of the paving machine acts to level the deposited material 6 so that a layer of asphalt 9 of relatively uniform height is formed on the roadway 5 as the paving machine 1 traverses from right to left as illustrated. The height of the screed 8 above the road surface 5 determines the thickness (or "mat depth") of the layer of asphalt 9.

In accordance with a first aspect of the present invention a height control means is employed to control the height of the screed assembly 8 relative to the existing road surface 5. More particularly, the height control assembly 20 is connected to the screed .assembly 8 of the road paving machine so as to control the height of the screed relative to the surface adjacent where the new section of roadway material is being laid. The height control assembly 20 may be permanently attached to the screed assembly 8 or, alternatively, may be demountable from the screed assembly.

Fig. 2 depicts a plan view of the road paving machine of Fig. 1 and illustrates the preferred positioning of the height control assembly 20 of the screed 8. As illustrated, the screed height control assembly 20 is preferably connected to the screed assembly of the paving machine at a position outside the line of the screed. Preferably, and as depicted in Fig. 2, the screed assembly 8 is provided with a pair of height control -8assemblies 20a, 20b, with one height control assembly positioned on each side of the screed assembly.

Referring to Figs. 4 and 5, in one preferred form of this aspect of the invention the height control means 20 includes a telescopic ram 21 actuated by hydraulics or pneumatics so as to enable adjustment of the height of the screed relative to the road surface 23 adjacent where the layer of roadway material is to be laid. Alternatively, a mechanical arrangement such as a threaded shaft or the like may be used. In this way the height of the screed relative to the road surface 23 may be adjusted as desired.

The screed height control assembly 20 additionally includes a member 22 which, in use, contacts and moves over the existing road surface 23 as the road paving machine traverses the section of roadway to be filled. In the embodiment depicted, the member 22 takes the form of a plate which rides on the existing road surface 23 as the road paving machine progresses along the section. In an alternative embodiment, the plate member may include, or be replaced by, one or more wheels which, in use, roll over the existing road surface as the road paving machine traverses the section of roadway to be filled.

It should be noted that the method and apparatus of the present invention may be used to deposit a single layer of roadway material, or alternatively can be used when laying multiple layers of roadway material.

For example, referring to Fig. 4, a schematic transverse elevation view of a screed assembly and screed height control assembly is depicted. A trench 10 to be filled with roadway material is traversed by the road paving machine, with roadway material being deposited in the trench and spread laterally by means of the augers of the paving -9machine. The screed 8 acts to level the deposited roadway material and to control the height of the deposited layer 9. The height control means 20 contacts the roadway surface 23 adjacent the trench 10 so as to control the height of the screed 8.

Fig. 5 depicts a second layer 9b of roadway material being deposited over the s previously laid layer 9a. It will be noted that the second layer of roadway material is deposited in the trench to a height above that of the level of the existing roadway in order to allow for the subsequent compaction of the material. For example, hot mix asphalt material can typically experience a compaction ratio of approximately 20% to o.

25%. Therefore, for a trench depth of 25 mm the allowance for compaction is typically an additional 5 mm, whilst for a 150 mm depth of trench the allowance for compaction is typically a further 30 mm.

The abovementioned aspect of the present invention provides a number of S -advantages. Firstly, it enables a relatively inexperienced operator to be able to lay one or more layers of roadway material with a road paving machine which, allowing for .i 15 compaction, can closely match the level of the existing roadway surface. It also assists in training operators in how to control a floating screed paving machine. Additionally, the invention reduces the possibility of the screed coming into contact with the ground, thereby reducing the incidence of wear and/or damage to the screed.

Fig. 6 illustrates the second aspect of the present invention. This aspect of the invention involves the use of a source of laser light 30 to provide the operator of the road paving machine with a reference level in order to position the screed of the road paving machine at the desired level. The source of laser light 30 is positioned at one end of the section, whilst a target 31 is positioned at an appropriate location and height at the opposing end of the section of roadway, such that when the laser is directed onto the target 3 1 the beam 32 of laser light defines a level which is parallel to the desired level for the surface of roadway material to be laid. The beam 32 of laser light thereby defines a reference level in the longitudinal direction of the section (ie. the direction of the motion of the road paving machine as it traverses the section). The road paving machine includes a target or referencing means 33 which is connected to and movable with the screed assembly. Preferably the position of the target 33 is also adjustable with respect to the screed assembly so as to enable the vertical distance between the target 33 and the o lower surface of the screed to be varied. When the road paving machine is positioned to lay the new section, the target 33 on the screed assembly is positioned so as to intersect the beam 32. As mentioned, the position of the target 33 on the screed assembly is adjustable so that the operator can vary the vertical distance between the target 33 and the lower surface of the screed. By adjusting the vertical distance between the target 33 :o**oon the screed assembly and the lower surface of the screed, the operator is able to 15 determine the vertical distance between the beam 32 and the lower surface of the screed.

The beam 32 of laser light being directed onto the target 33 on the paver enables the operator to adjust the level of the screed to the desired level. In this way, the operator is provided with a continuous reference level in the longitudinal direction of the section by which to monitor and control the height of the screed as the paving machine traverses the section.

Referring to Fig. 7, a further aspect of the present invention is depicted. Fig. 7 depicts a transverse elevation of a roadway in which two adjacent sections of roadway material are to be laid. When laying sections of roadway material, it is often difficult to -11determine and maintain the correct level for the screed in the transverse direction. For example, when laying adjacent sections of roadway material it is often difficult to determine and maintain the correct level for the first section in the trench so that when the next, adjacent section of material is laid, the surfaces of the two sections will meet and lie in a common plane. Fig. 7 schematically illustrates a transverse cross-sectional view of a section of roadway upon which a new layer of roadway material is to be deposited. This aspect of the invention involves the use of a source of laser light :o located on the road paving machine, preferably the screed assembly 8, so as to provide the operator of the road paving machine with a means for referencing the positioning of the screed of the road paving machine at the desired level for the road surface to be laid.

One or more targets 31, such as a staff, reference markers, a string line, or the like is/are positioned at an appropriate location along the section of roadway. As the road paving machine traverses the section, the laser beam 32 is directed onto the target(s) 31 to provide an indication of the level of the screed and enable the operator to determine if 15 the screed is being maintained at the desired level in the transverse direction to the direction of movement of the paving machine. In this way, the operator is able to reference the level of the screed and make adjustments to the positioning of the screed as necessary as the road paving machine progressively traverses the section.

Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims (9)

1. A method of depositing a section of roadway material with a self propelled road paving machine, said road paving machine including: a hopper for storing roadway material; a feed conveyor for transferring said roadway material from said hopper to a laterally extending spreading means comprising one or more rotatable augers; a screed for levelling said roadway material, said screed located rearwardly of said one or more rotatable augers; and a height control means including an arm of variable length located on said screed for controlling the height of the screed above a surface on which said roadway material is to be laid; wherein said arm on said screed is extended to contact a surface adjacent where the section of roadway material is to be laid so that the height of the screed above the surface on which said roadway material is to be laid is determined with reference to said adjacent surface; said roadway material being held in the hopper of the machine and fed via said feed conveyor towards the rear of the machine whereupon it is deposited onto the roadway, the deposited material being spread laterally by means of said rotating augers, the screed of the paving machine acting to level the deposited material so that a layer of said roadway material of relatively uniform height is formed on the roadway as the road paving machine moves in a forward direction, the height of the screed above the road surface determining the thickness of the layer of roadway material.

2. The method of depositing a section of roadway material with a road paving machine as claimed in claim 1, wherein said height control means is connected to the 25 screed of the paving machine at a position outside the line of the screed.

3. The method of depositing a section of roadway material with a road paving machine as claimed in claim 1 or 2, wherein said screed is provided with a pair of height control means with one height control means positioned on each side of the screed.

4. The method of depositing a section of roadway material with a road paving oo.o 30 machine as claimed in any one of the preceding claims, wherein the height control means .:includes a telescopic ram actuated by hydraulics or pneumatics so as to enable 0*o o* -13- adjustment of the height of the screed relative to the road surface adjacent where the layer of roadway material is to be laid.

The method of depositing a section of roadway material with a road paving machine as claimed in any one of the preceding claims, wherein the height control means includes a member which, in use, contacts and moves over the existing road surface as the road paving machine traverses the section of roadway to be filled.

6. The method of depositing a section of roadway material with a road paving machine as claimed in any one of the preceding claims, wherein said roadway material is a hot-mix asphalt.

7. A self-propelled road paving machine including: a hopper for storing roadway material; a feed conveyor for transferring said roadway material from said hopper to a laterally extending spreading means comprising one or more rotatable augers; a screed for levelling said roadway material, said screed located rearwardly of said one or more rotatable augers; and a height control means including an arm of variable length located on said screed for controlling the height of the screed above a surface on which said roadway material is to be laid, wherein said arm is extendable to contact a surface adjacent where the section of roadway material is to be laid so that the height of the screed above the surface on which said roadway material is to be laid is determined with reference to said adjacent surface.

8. The road paving machine as claimed in claim 7, wherein said feed conveyor is a slat-type conveyor.

9. A method of depositing roadway material with a self-propelled road paving 25 machine substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. A self-propelled road paving machine substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. DATED this 14th Day of September, 2004 °oe° BALDWIN SHELSTON WATERS S°Attorneys for: John Russell Sharpe, Alan Victor Sharpe and Ronald Douglas Sharpe