GB2043752A - Improvements relating to paving machines - Google Patents

Abstract

A modification for a paving machine when used to pave a narrow trench with a bituminous material comprises a material distribution device including a laterally restricted discharge opening (20) disposed forwardly of a screed (14), and conveying means in the form of augers rotated so as to converge the material into the discharge opening. The augers act against arcuate surfaces (27) on width control boxes (21) which are used to restrict the width of the discharge opening (20). The width control boxes (21) may be adjusted by hydraulic or worm driven means. Hydraulic or gear drive may be used to reverse the rotation of conventional augers. <IMAGE>

Description

SPECIFICATION Improvements relating to paving machines This invention relates to paving machines for laying bituminous paving material such as asphalt.

The invention is particularly concerned with a type of paving machine, hereinafter called a paving machine of the type specified, in which a hopper is provided for the bituminous paving material and is arranged to discharge the material at a suitable rate from an outlet to a distribution device which is then used to spread the material laterally of the front to back centreline of the paving machine away from the outlet, to a chosen width approximating to the width of the paving being laid. The material is then discharged from the machine, and levelled and compacted by a screed such as a tamper screed or vibratory screed to form the paving.

Typical paving machines have previously been constructed to pave a standard width equivalent to one-road carriageway (about two and a half metres) at a pass. Wider pavings have been constructed by the addition of extension pieces to the screed, these either being of fixed size and being secured onto the screed to extend its effective width or being extensible during use of the machine, for example by hydraulic means which are controlled by the operator.

Narrower pavings have been achieved by blocking off part of the available width into which the bituminous paving material can be spread, for example by the fitment of one or more shoes in the region of the distribution device.

However, very narrow widths of the Order of 150 to 1,000 millimetres are filled and compacted by hand, because conventional paving machines are not capable of achieving satisfactory filling and compaction of such narrowtrenches.Where major pipe laying or cable laying operations are carried out, narrow trenches which are sometimes many miles in length have to be dug and subsequently filled in so that it would greatly reduce the time and cost of such operations if a paving machine could be used to pave the filled-in trench.

It is an object of the invention to provide improvement in or relating to paving machines to perform satisfatorty paving of such narrow widths.

According to the invention there is provided, in or for fitment to a paving machine of the type specified, a material distribution device including means defining a laterally restricted discharge opening disposed forwardly of the screed and corresponding in width with a trench to be paved, and conveying means constructed and arranged to constrain and converge the material into said discharge opening.

The conveying means may comprise one or more rotary augers rotatably driven to move material towards said discharge opening.

The discharge opening may at least partly be defined by a control box associated with the, or with one of the augers and including an arcuate surface disposed adjacent the associated auger and adapted to constrain the material relative to the auger.

A pivoted flap may be mounted on the side of the auger remote from this arcuate surface.

In a preferred form, the distribution device may comprise two augers provided in line with each other and disposed perpendicularto the front to back centreline of the machine and the discharge opening may be disposed between the augers.

The or each control box may be movable in a direction laterally of the front to back centreline of the machine. For example, the control box may be movable by hydraulic means or by worm means.

Another aspect of the invention concerns the provision of conversion means for effecting a conversion of a paving machine of the type specified including one or more augers disposed at right angles to the front to back centreline of the machine, so that its material distribution device conforms to the present invention.

According to this aspect, the invention comprises conversion means for effecting the conversion of a paving machine of the type specified and including one or more augers disposed at right angles to the front to back centreline of the machine and arranged to receive bituminous paving material from the outlet of the hopper and to spread the material laterally of said centreline, said conversion means comprising, in combination, reversing means for fitment in the drive to the or each auger and adapted to cause reversal of the direction of rotation thereof and means adapted to define a laterally restricted discharge opening disposed forwardly of the screed and co-operable with the augers to constrain and converge material from the hopper into the discharge opening.

The reversing means may comprise a reverse gear train. Alternatively, when the drive to the auger or augers is hydraulic, the reversing means may comprise hydraulic valve means adapted to reverse the drive.

The means adapted to define a laterally restricted discharge opening may comprise a control box associated with the or each auger and including an arcuate surface disposed adjacent the associated auger and adapted to constrain the material relative to the auger.

A further object of the invention is to provide a method for paving a narrow trench using a paving machine of the type specified.

According to this aspect of the invention there is provided a method of paving a narrow trench using a paving machine of the type specified which includes one or more augers disposed at right an lestothefrontto back centreline of the machine and arranged to receive bituminous paving material from the outlet of the hopper and to spread the material laterally of the centreline and discharge it through a discharge opening; comprising the steps of restricting the lateral extent of the discharge opening to correspond to the width of the trench and rotatably driving the or each auger in a reversed direction, whereby the material from the outlet of the hopper is converged into said restricted discharge opening.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings in which FIGURE 1 is a diagrammatic perspective view of a pair of control boxes which may form part of the distribution device according to the invention shown in relation to certain parts of an existing paving machine; and FIGURE 2 shows a paving machine having a material distribution device embodying the invention.

It will be appreciated that the invention can be applied to different types of paving machine and that the outline shown in Figure 2 of the drawings is only indicative of a typical paving machine. In this particu lar machine, the body 10 is mounted for forward movement on a pair of caterpillar tracks 11 and carries a hopper 12 at its forward end, the hopper having road wheels 13. Alternatively, the paving machine may be provided with wheels or with a combination of tracks and wheels. A screed 14 is drawn behind the body 10 of the machine and is pivotally mounted on a pair of arms 15 so as to be self-levelling in use.

Bituminous paving material is deposited into the hopper 12, usually from the body of a tipper lorry, and is transferred through the machine to an outlet (not shown) where the material is gradually discharged into a distribution device generally indicated at 16.

In the conventional machine, the distribution device comprises a pair of rotatable augers, arranged to rotate in such a manner that material caught on the augers is spread laterally across the machine. The hopper outlet lies on the front to back centreline of the machine between the augers, which move the material laterally across the machine and away from the centreline in opposite directions, to pave a typical width. The horizontal screed plate is drawn over the material deposited on the ground where it has been spread by the distribution device, and acts to level and compress the material to form the paving.

In use, the apparatus can be driven by an operator seated on the seat 17 or riding on a platform adjacent the screed 14 (not shown).

We will now describe the modification of the conventional machine so that it becomes a machine having a distribution device according to the invention.

However, it will be appreciated that the features of the invention can be provided in a purpose-designed paving machine or can be provided by conversion of some other type of paving machine, which may or may not include one or more augers in the distribution device.

It will be seen that a the screed 14 comprises a generally L-shaped plate which is carried from the arms 15 by brackets 18. As seen in Figure 1 of the drawings, extension plates 19 are mounted on the screed, one at each side, and are conventionally used to extend the operative paving width of the machine when they are in fully extended position shown in full lines in Figure 1 of the drawings. The operative paving width is normally the width of the screed 14 but, when the extension plates 19 are used, the machine can pave up to the width of the screed plus the two extension plates. In normal use for paving wide areas, the extension plates 19 can be moved outwardly to the position shown in full lines by power operated means such as hydraulic rams or by a worm mechanism, and the extension plates 19 may be operated independently.In some alternative forms of machine, the extension plates may require to be bolted on.

It will be seen from the dotted lines in Figure 1 that the extension plates 19 can be withdrawn inwardly into the apparatus when not in use to extend the width of the paving formed. Conveniently, when bringing the present invention into operation, the extension plates are withdrawn inwardly so as to define a narrow gap 20 equivalent to the width of the trench to be paved.

Of course, were this the only modification made to the machine, paving up to the full width of the screed 14 would continue. However, a pair of control boxes generally indicated at 21 are fitted to the rear faces of the extension plates 19 by means of suitable fastenings such as a pair of brackets 22 held in placed by bolts 23 and pins 24. Conveniently, fitting of the control boxes takes place with the extension plates 19 in their outermost positions and then the extension plates 19 are withdrawn into the machine hydraulically to define the gap 20.

Each control box includes an inner end wall 25, an outer end wall 26 and an arcuate face 27. The arcuate face 27 faces forwardly as considered in the direction of movement of the machine during paving. The function of the arcuate face is to define a restricted region 28 between itself and the auger which is represented by the circle 29, the positioning of this restricted region being such that material can be squeezed along the restricted region by rotation of the auger in a reversed direction compared with its normal direction of rotation. Pivoted flaps 30 are provided~at the forward face of the auger 29 to prevent material from being forced the wrong way.

When the apparatus is being used to pave a narrow trench, the control boxes are firstly fitted as described above with the extension plates 19 of the machine extended. The extension plates 19 are then withdrawn into the machine to a sufficient extent to define the gap 20 which is aligned along the trench and is of an equivalent width to the trench. The augers are then rotated in the reverse direction to their normal direction of rotation, the normal direction being such that the material released from the outlet of the hopper is directed away from the front to back centreline of the machine. When the rotation has been reversed, the material is squeezed along the auger in the opposite direction within the restricted region 28 defined between the auger 29 and the arcuate face 27 until it reaches the gap 20 between the extension plates 19 and control boxes 21. The material is then in a state of compression and is forced downwardly into the trench to be filled.

As the machine moves forwardly, the screed 14 is drawn across the surface of the deposited material in the trench to level and compact it in the conventional manner.

A distinction is drawn between the operation of the machine according to the invention described above and the previous use of shoes to restrict the width of a paving within the region of the screed 14.

Such shoes only prevent material spread laterally by the augers from spreading beyond a certain width determined by the positioning of the shoes. However, this arrangement cannot be used to fill narrow trenches satisfactorily because firstly there is a limit to the positions available for the shoes and secondly the material is not under sufficient compression as it leaves the machine satisfactorily to fill a narrow trench ready for compaction by the screed.

In addition to the apparatus described, it is considered that the method by which the apparatus is used to pave a trench should be considered to be an aspect of the invention.

Claims (17)

1. In or for fitment to a paving machine of the type specified, a material distribution device including means defining a laterally restricted discharge opening disposed forwardly of the screed and corresponding in width with a trench to be paved, and conveying means constructed and arranged to constrain and converge the material into said discharge opening.

2. A device according to Claim 1 wherein the conveying means comprises one or more rotary augers rotatably driven to move material towards said discharge opening.

3. A device according to any preceding claim wherein the discharge opening is at least partly defined by a control box associated with the, or one of the augers and including an arcuate surface disposed adjacent the associated auger and adapted to constrain the material relative to the auger.

4. A device according to Claim 3 wherein a pivoted flap is mounted on the side of the auger remote from the arcuate surface.

5. A device according to any one of Claims 2 to 4 wherein two augers are provided in line with each other and disposed at right angles to the front to back centre-line of the machine and wherein the discharge opening is disposed between the augers.

6. A device according to any one of Claims 3 to 5 wherein the or each control box is movable in a direction laterally of the front to back centreline of the machine.

7. A device according to Claim 6 wherein hydraulic means are provided for moving the or each control box.

8. A device according to Claim 6 wherein worm means are provided for moving the or each control box.

9. Conversion means for effecting the conversion of a paving machine of the type specified and including one or more augers disposed at right angles to the front to back centreline of the machine and arranged to receive bituminous paving material from the outlet of the hopper and to spread the material laterally of said centreline; the conversion means comprising, in combinaton, reversing means for fitment in the drive to the or each auger and adapted to cause reversal of the direction of rotation thereof and means adapted to define a laterally restricted discharge opening disposed forward of the screed and co-operable with the auger or augers to constrain and converge material from the hopper into the discharge opening.

10. Conversion means according to Claim 9 wherein the reversing means comprise a reverse gear train.

11. Conversion means according to Claim 9 wherein the drive to the augers is hydraulic and wherein the reversing means comprise hydraulic valve means adapted to reverse said drive.

12. Conversion means according to any one of claims 9 to 11 wherein the means adapted to define a laterally restricted discharge opening comprise a control box associated with the or each auger and including an arcuate surface disposed adjacent the associated auger and adapted to constrain the material relative to the auger.

13. A method of paving a narrow trench using a paving machine of the type specified which includes one or more augers disposed at right angles to the front to back centreline of the machine and arranged to receive bituminous paving material from the outlet of the hopper and to spread the material laterally of said centreline and discharge it through a discharge opening; the method comprising the steps of restricting the lateral extent of the discharge opening to correspond to the width of the trench and rotatably driving the or each auger in a reversed direction, whereby the material from the outlet of the hopper is converged into said restricted discharge opening.

14. In or for fitment to a paving machine of the type specified, a material distribution device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

15. A paving machine of the type specified including a material distribution device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

16. Conversion means for a paving machine of the type specified, the conversion means being substantially as hereinbefore described with reference to and as illustrated in the accompnaying drawings.

17. A method of paving a trench according to Claim 13 and substantially as hereinbefore described.