AU8934301A - Methods and apparatus for delivering binders for use with a ground stabilisation machine - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: 4. 44** Name of Applicant: Adelaide Brighton Limited Actual Inventor(s): Guy Kenneth Martin, Stephen Lester Benson, Richard William McAuley Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: METHODS AND APPARATUS FOR DELIVERING BINDERS FOR USE WITH A GROUND STABILISATION MACHINE Our Ref: 656331 POF Code: 356550/329771 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 0 6006q ~i ~i -"5ia- -2- METHODS AND APPARATUS FOR DELIVERING BINDERS FOR USE WITH A GROUND STABILISATION MACHINE Field of the Invention The present invention relates to methods and apparatus for delivering binders during ground stabilisation. Ground stabilisation is a part of the construction process for roads, paths, parking lots and runways and the like, and in particular is the process of preparing sub-grade, base and sub-base materials to provide a higher load bearing capacity such that they better withstand heavy traffic stresses.

Background of the Invention Ground stabilisation generally involves thoroughly milling and pulverising the sub-grade, base and sub-base material (often in-situ), and subsequently mixing the pulverised material with suitable binders, such that after proper compaction .o eo and curing the material is more dense (stable) and provides the desired stronger base. Stabilisation techniques are used for new construction as well as for the recycling of older, deteriorated roads and the like.

The stability and load bearing capacity of a base material generally depends on two factors the internal friction between particles and the cohesion of particles. In this respect, the higher the internal friction, the better the cohesion and the greater the load bearing capability of the base layer. It is recognised that the addition of a binder to the base material assists in allowing the particles to mneet the desired requirements for friction and cohesion.

Binders are typically provided using one of two techniques. Firstly, binders may be slurried or foamed and provided in fluid form to the milled and pulverised base material during milling and pulverising. Secondly, and most commonly, binders in dry form may be laid in-situ over a base material to provide a coating A ~F rj.-~rrli" A~~~rl;~ir -,i~r;i -3layer, such that a milling and pulverising machine may then pass over the coated base material to mill, pulverise and mix the binder into the base material in one action.

The existing wet techniques (namely, providing slurried or foamed binders such as bitumen foam or bitumen emulsions) present various difficulties, such as difficulties in cleaning the equipment after use and difficulties in disposing of unused slurry. Additionally, use in already wet areas generates unduly boggy conditions, and wet techniques are unable to process some popular binders (such as quicklime) due to problems caused by the hydration of the binder in the slurry mixer and pump.

Therefore, the dry techniques are often preferred, and have proven to be more popular. However, the existing dry techniques (such as laying binder before the ground stabilisation machines) generate significant amounts of dust that presents environmental and health problems. Whilst some attempts have been made to remove this problem by spraying water over the binder layer, this has merely served to again introduce similar problems to those mentioned above S°with the existing wet techniques, and has for instance caused hydration problems with certain binders.

a S It is thus an aim to provide a method and apparatus for incorporating binders during stabilisation which are not subject to the above difficulties.

a 25 Summary of the Invention According to the present invention there is provided a binder delivery means for use with a ground stabilisation machine having a ground breaking assembly, a mixing chamber and a binder reservoir under positive pressure, the binder delivery means including at least one delivery tube for delivering binder from the binder reservoir to the mixing chamber, each delivery tube being made of a flexible and resilient material and having an inlet and an outlet, and each h l~ rS~i -4delivery tube being associated with an inlet regulating means and an outlet regulating means for controlling the entry and exit of binder to and from the delivery tube, wherein each delivery tube may be filled to expand the tube against its natural resilience, and may be emptied with assistance from the natural resilience returning the tube to its at-rest position.

The present invention also provides a method for delivering binder from a binder reservoir to a mixing chamber of a ground stabilisation machine, the method including: continuously supplying binder to the binder reservoir under positive pressure; and operating a cycle of filling and then emptying at least one delivery tube made of a flexible and resilient material with binder from the binder reservoir, the emptying acting to deliver binder to the mixing chamber; wherein each delivery tube has an inlet regulating means for controlling the entry of binder thereto, and an outlet regulating means for controlling the outlet of binder therefrom, and the cycle of filling and emptying operates as follows: closing the outlet regulating means and opening the inlet regulating means of a delivery tube to allow the filling of the delivery tube S. with a predetermined volume whilst expanding the delivery tube against its natural resilience; oloo• closing the inlet regulating means and opening the outlet 25 regulating means, allowing the delivery tube to return to its at-rest position and thus emptying the binder in the delivery tube into the mixing chamber; and re-commencing the cycle at The inlet and outlet regulating means of the binder delivery means are preferably some type of valve, adapted so as to open and/or close the inlet and ~~wr;i s ii~N:l": i~ 5 ~y ba; in;i; T1Jw;i ~Eli~ Y*~i~S1~~i~-~Llf bi~i~iril*Y~iCT;~iiI."*.~:IYIWL*II~~"IU outlet of the delivery tube as desired. In a preferred form, each delivery tube will have its own inlet regulating means and its own outlet regulating means.

Due to the binder reservoir being under a positive pressure, when the inlet regulating means is open, binder is urged into the delivery tube. Preferably, the outlet regulating means remains closed whilst the delivery tube fills with binder.

Once full, the inlet regulating means will close, enclosing within the delivery tube an amount of binder. By knowing the volume of the delivery tube, the amount of binder about to be delivered to the mixing chamber will thus be known.

The outlet regulating means may then be opened, allowing binder to exit the delivery tube and be delivered to the mixing chamber.

In a preferred form, the delivery tube is made of a flexible and resilient material, for example a soft but tough rubber such as a natural blend of white rubber having a hardness of in the range of 30 to 40 Duro. In this form, upon filling of the delivery tube in the manner described above, the positive pressure of the .0.0 binder reservoir will force the tube to expand beyond its at-rest position. The binder in the tube when the inlet regulating means closes will then also be under positive pressure due to the natural resilience of the expanded tube.

Upon opening the outlet regulating means, the positive pressure on the binder in the delivery tube (caused by the natural resilience of the tube) will urge the binder out of the tube into the mixing chamber.

I* Preferably, the operation of the binder delivery means in the manner described above is such as to provide a cycle of filling and emptying each delivery tube.

In this way, a known volume of binder can be delivered to the mixing chamber from each delivery tube. By altering the speed of the cycle, the volume delivered may be increased or decreased, thus increasing or decreasing the spread rate and amount of binder. Of course, such a change in cycle speed -6may be used merely to maintain a spread rate, in accordance with variations in the speed of travel of the ground stabilisation machine.

In a preferred form of binder delivery means, the inlet and outlet regulating means may be pinch-type valves comprising pneumatically operated pinch bars configured on opposed sides of a delivery tube. The pinch bars are thus actuated to move together and pinch the delivery tube therebetween, causing the tube to be closed and sealed at that point. It will be appreciated that such pinch-type valves may alternatively comprise a fixed pinch bar and an opposed actuatable pinch bar. Furthermore, more than two pinch-type valves may be arranged along the length of each delivery tube. For instance, three such valves may be used, one at each end and one in the middle. Further still, one pinch-type valve may be configured so as to pinch more than one delivery tube.

In this form, one pinch-type valve may be configured to have an elongate pinch bar that is long enough to pinch two tubes.

Preferably, the binder reservoir is located above the mixing chamber, and S: delivery tubes are configured substantially vertically therebetween, with their inlet being the uppermost end in communication the binder reservoir, and their outlet being the lowermost end in communication with the mixing chamber.

S- In one form, the mixing chamber is an elongate chamber extending across the width of the ground stabilisation machine. In this form, the binder reservoir will also be elongate, similarly extending across the width of the ground stabilisation machine. A plurality of delivery tubes may then be provided, preferably configured closely adjacent to each other, extending across the width of the ground stabilisation machine. Thus, in operation, binder may be spread across the full width of the ground stabilisation machine.

Finally, the binder reservoir preferably includes an inlet for passage of binder from the binder handling system, and an outlet for return of excess binder to the binder handling system. The reservoir may also include internal baffle plates.

-7- The baffle plates assist in removing binder from suspension in the air stream from the binder handling system. They also assist in stabilising the binder to prevent surging within, or whilst exiting, the binder reservoir.

Brief Description of the Drawings The present invention will now be described in relation to a preferred embodiment as illustrated in the accompanying drawings. However, it is to be appreciated that the following description is not to limit the generality of the above description.

In the drawings: Figure 1 is a schematic side view of a conventional ground stabilisation machine; Figure 2 is an exploded view of a part of the machine of Figure 1; Figure 3 is a schematic flow-sheet of a binder handling system; Figures 4(a) and 4(b) are side schematic views (from opposite sides) of a S.vehicle adapted in accordance with the arrangement of Figure 3; Figure 5 is a perspective view of a preferred form of binder delivery means; S 0. Figure 6 is a section view through the binder delivery means of Figure 5; and Figures 7(a) to 7(d) are an illustration of the sequence of operation of the binder delivery means of Figures 5 and 6.

Detailed Description of the Preferred Embodiments WF 11 uuuuuuuuuuuu -8- In the following description reference is made to the adaptation of an existing ground stabilisation machine. This is described in the art as a 'retro-fit'.

However, it is to be appreciated that the scope of the present invention extends to cover the manufacture of new machines which utilise the inventive principles.

Indeed, such new machines are illustrated and described in relation to the apparatus illustrated in Figures 4 to 7.

Thus, a conventional ground stabilisation machine 10 is illustrated in Figures 1 and 2. The machine 10 is as described in international patent application PCT/EP96/00556, and generally includes a working vehicle 12 having a ground breaking assembly 14 mounted between drive axles (16 and 18). The ground breaking assembly 14 is better illustrated in Figure 2, and generally includes a cylindrical drum 20 having a plurality of outwardly projecting teeth 22 configured over its external surface 24.

The ground breaking assembly 14 includes a hood 26 mounted over the drum 20 to form a substantially enclosed mixing chamber 28.

°o In operation, the ground 30 over which the machine 10 passes (in direction of travel A) is dug up by the action of the rotating drum 20 (and its teeth 22). The ground is thus milled and pulverised to a predetermined size range, and re-laid behind the machine 10 as a stabilised layer 32. Thus, a typical prior art operation would see binder laid over the ground 30 in advance of the machine and the binder would interact and be blended with the milled and pulverised 25 particles to form the stablised layer 32.

However, the presently described arrangement introduces binder in a substantially dry form directly to a mixing chamber, such as the mixing chamber 28 shown in Figure 2. Indeed, further discussion of the arrangements illustrated in Figures 3 to 7 will refer to features of the prior art apparatus illustrated in Figures 1 and 2. Figure 2 shows a nozzle or aperture 34 in the hood 26 that is shown to illustrate the manner in which binder, in substantially dry form may be added to a mixing chamber.

Figure 3 illustrates a preferred binder handling system for delivering the binder to the hood 26 in a continuous manner. This system is a continuously alternating, pressurised, multi-chamber system having a primary supply chamber 36 and a secondary supply chamber 38 for supplying binder to a binder delivery means 42. Both the primary and secondary supply chambers (36 and 38) are connected via lines to a binder reservoir 40, which in turn communicates with the binder delivery means 42 (the preferred operation of which will be described below). Binder passes from the binder delivery means 42 to the mixing.chamber 28 via a delivery flap 44.

The preferred operation of the system of Figure 3 will now be described. The primary chamber 36 is filled with binder (ie cement powder etc) by loading through a filler hatch 46 or by pumping in through the return line 69 and valve :i 70. Valve 70 is automatically opened when the system is in fill mode.

00 "During filling by (for example) a pressure tanker, the filter 71 in the secondary chamber 38 is operated and connected via the vent line 49 and a valve 50. The valve 50 is operated automatically when the system is in fill mode, and serves S. to allow air to be expelled by the system (after being filtered) as the primary chamber 36 is filling.

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o99oo9 25 When the spreading operation commences, the primary chamber 36 is pressurised by a compressor 52. Valves 54 and 56 are opened to allow the pressurisation of the primary chamber 36 and the passage of binder therefrom to the binder reservoir 40 via the delivery line 59. The manner of fluidisation of the binder is described in more detail below.

Valves 58 and 60 are closed to prevent pressurisation of the secondary chamber 38 and to prevent binder being delivered from the secondary chamber 38. The secondary chamber 38 is put under suction by opening valve 55 and running the suction fan 57. Valve 48 is opened on the return line to allow overflow of binder from the binder reservoir 40 to return to the secondary chamber 38 via the return line 69.

The binder is then aerated or fluidised and flows to the binder reservoir 40. To aerate the binder in the primary chamber 36, compressed air is supplied by the compressor 52 via a line 51 to the underside of an aeration bed 53 in the primary chamber 36. The aeration bed 53 is constructed of a perforated metal base, supporting a layer of course woven cloth. The cloth allows the compressed air to pass into the load of binder in the primary chamber 36, while preventing the binder from entering the aeration bed 53 and possibly blocking the compressed air line 51.

The compressed air passing into the binder causes the binder to become fluidised in the vicinity of the aeration bed 53, allowing it to move down the :I delivery line 59 as the pressure in the primary chamber 36 increases. Of S:course, it will be appreciated that a similar mechanism is provided for the secondary chamber 38, illustrated as the aeration bed 63.

In the embodiment illustrated and described, the flow of binder commences when the internal pressure reaches approximately 30kPa. The compressed air percolates through the binder and accumulates in the primary chamber 36, raising the internal pressure in the primary chamber 36 to approximately 120 25 kPa. The maintenance of this internal pressure continually pushes the binder *down the delivery line 59 to the binder reservoir When the binder reservoir 40 is full, the overflow binder flows via the return line to the secondary chamber 38.

When the level of binder in the primary chamber 36 reaches the low level sensor 64, or the high level sensor 66 in the secondary chamber, the system -11 changes over. To affect this, valves 48, 54 and 56 remain open, valve 55 is closed and valves 50 and 70 are opened. The pressure in the two chambers is allowed to equalise, and then valves 48, 50, 54 and 56 are closed, valves 58 and 68 are opened and chamber 36 is vented. This is done to minimise the change over time by reducing the time required to pressurise the secondary chamber 38 and re-establish the binder flow to the binder reservoir The process is repeated until both of the low level probes (64 and 72) are activated together, indicating both chambers are empty.

The filters 71 and 73 are cleaned continuously by a pulse of pressurised air generated by a control air compressor 74 and regulated by a valve system (76 and 78). Each filter is cleaned individually in a sequence so as to minimise the loss in filter efficiency.

:A system such as that illustrated in Figure 3 is preferably built into a service tanker that would follow or precede a machine such as that illustrated in Figures 1 and 2. As can be seen, the binder handling system (illustrated in Figure 3) **allows for the continuous supply of binder to the mixing chamber of the stabilisation machine.

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Indeed, illustrated in Figures 4a and 4b is such a service tanker embodying the system illustrated schematically in Figure 3. The service tanker is in the form of *ooa truck 80*having a cab 82 and a chassis 84. The chassis 84 carries a pressure 25 vessel 86 partitioned so as to provide a primary chamber 36 and a secondary chamber 38. The service tanker is designed to move ahead of the machine of Figure 1 to provide a continuous supply of binder in the manner described above.

Various features of the service tanker are illustrated using the same reference numerals as used above in relation to the description of the flow diagram in Figure 3. Figure 4a generally illustrates the binder feed and flow system, and -12shows the return line 69, the delivery line 59, an aeration bed 53, the vent line 49, the main compressor 52, and the general location of the filters 71 and 73.

Figure 4b generally illustrates the filter system, showing the suction fans 57 and a control air compressor. The location of the aeration beds 53 and 63 is also well illustrated.

Figure 5 shows the general relationship of the parts of a binder delivery means 150, being a binder reservoir 152, delivery tubes 156, inlet and outlet regulating means (164, 166), and a mixing chamber 162, at least in the preferred embodiment illustrated.

The binder delivery means 150 is intended for use in conjunction with, for example, the ground breaking assembly 14 and the machine 10 illustrated in Figures 1 and 2. The binder delivery means 150 includes the binder reservoir .152 fed by a delivery line 154. The binder reservoir 152 is, in use, maintained under positive pressure by virtue of the pressurisation of the binder in the primary or secondary chambers (36,38) of the service tanker, to a level necessary to fluidise the binder with air.

It is envisaged that the binder reservoir 152 will operate under pressures in the order of 30 kPa to 80 kPa, with a pressure of about 50 kPa being preferred.

•The binder delivery means 150 also includes at least one delivery tube. In this embodiment, there is a plurality of delivery tubes 156 extending across the full width of the binder reservoir 152, and thus the full width of the machine carrying the ground breaking assembly 14 of Figures 1 and 2.

The delivery tubes 156 are configured substantially vertically between the binder reservoir 152 and the hood 158 surrounding the milling device 160 (shown in outline). The hood 158, together with the ground, defines the mixing chamber 162 therebetween.

-13- Figure 5 also shows each delivery tube 156 having its own inlet regulating means 164 and outlet regulating means 166. The operation of the regulating means will be described below in relation to Figures 6 and 7.

Illustrated in Figure 6 is a more detailed view of a single delivery tube 56 and its relationship with the binder reservoir 152 and the mixing chamber 162, particularly by virtue of the inlet regulating means 164 and the outlet regulating means 166.

The inlet regulating means 164 and the outlet regulating means 166 are both shown as pinch-type valves, each having a pneumatic actuator 168 and a pinch bar 170. The pneumatic actuators are each rigidly fixed such that opposed pinch bars both move towards and against the delivery tube 156 to close and seal. The retraction of opposed pinch bars then unseals and opens the delivery tube.

In operation, and referring to Figures 7(a) to 7(d) where the inlet regulating •means 164 is designated X and the outlet regulating means 166 is designated Y, both valves X and Y will be initially closed (Figure Valve X will open to allow binder to fill the delivery tube 156 while valve Y remains closed (Figure The tube 156 is flexible and resilient, and pressure of the binder reservoir 152 urges binder into the tube expanding it slightly against its inherent •resilience (Figure Valve X is then closed, valve Y is opened and the 9900..

25 resilience of the delivery tube 156, as it returns to its at-rest position, urges binder out into the mixing chamber 162 (Figure The operation cycles continuously in this manner. In this respect, and in this preferred embodiment, all of the delivery tubes 156 cycle in the same sequence at the same time. However, it will be appreciated that this need not always be desirable. It may be preferred to have some tubes filling while others are emptying. It may also be preferred to only have some of the delivery tubes -14functioning, perhaps only every second or third tube depending on flow-rates required. Alternatively, it may only be required to provide a thin internal band of binder within the mixing chamber, in which case perhaps only the central third of tubes would be used.

It will be appreciated that all such functions of the operations of all matters described herein may be controlled by suitable controllers and computers.

Figure 6 also illustrated baffles 172 provided within the binder reservoir 152, together with a manually of automatically operable flap 174 which may be configured to close off the outlet 176 of the delivery tubes 165.

In the particular embodiments illustrated in Figures 3 to 7, it will be understood that operating conditions may vary significantly depending on the use of the apparatus, and the desired results. However, in the embodiment illustrated and described herein, the following operating conditions have been found to be :I suitable. The primary and secondary chambers will preferably have an internal volume of about 20 m 3 and 10 m 3 respectively, while the binder reservoir will °•have an internal volume of about 300 litres. The compressor capacity is preferably about 320 cfm and the filter capacity is preferably about 500 cfm against 8' WG 20 0 C. The delivery and return lines for the binder are preferably of a diameter of about 100mm NB.

The internal diameter of the pinch-tubes is preferably about 50mm. With a typical depth of stabilised road base in the order of 100 to 500mm, a typical stabiliser speed of about 5 to 15 m/min, and a typical desired spread rate of 3 to 30 kg/m 2 the pinch-tube valves will typically cycle at rates in the order of 50 to 150 cycles/min.

Finally, it will be appreciated that there may be other modifications and alterations made to the configurations described herein that are also within the scope of the present invention.

Claims (3)

1. A binder delivery means for use with a ground stabilisation machine having a ground breaking assembly, a mixing chamber and a binder reservoir under positive pressure, the binder delivery means including at least one delivery tube for delivering binder from the binder reservoir to the mixing chamber, each delivery tube being made of a flexible and resilient material and having an inlet and an outlet, and each delivery tube being associated with an inlet regulating means and an outlet regulating means for controlling the entry and exit of binder to and from the delivery tube, wherein each delivery tube may be filled to expand the tube against its natural resilience, and may be emptied with assistance from the natural resilience returning the tube to its at-rest position.

2. A binder delivery means according to claim 1 wherein the binder reservoir is located above the mixing chamber and delivery tubes are configured substantially vertically therebetween. S. 55O o° S o S A binder delivery means according to claim 1 or claim 2 wherein the inlet S• 20 and outlet regulating means are pinch-type valves comprising pinch bars configured on opposed sides of a delivery tube, the pinch bars being actuatable to move together to pinch the delivery tube therebetween, to close and seal the tube at that point. @Se oO Sl 25 4. A method for delivering binder from a binder reservoir to a mixing chamber of a ground stabilisation machine, the method including: continuously supplying binder to the binder reservoir under positive pressure; and operating a cycle of filling and then emptying at least one delivery tube made of a flexible and resilient material with binder from the binder reservoir, the emptying acting to deliver binder to the mixing chamber; 111 M'1'1 Z -Yj'r .4 -16- wherein each delivery tube has an inlet regulating means for controlling the entry of binder thereto, and an outlet regulating means for controlling the outlet of binder therefrom, and the cycle of filling and emptying operates as follows: closing the outlet regulating means and opening the inlet regulating means of a delivery tube to allow the filling of the delivery tube with a predetermined volume whilst expanding the delivery tube against its natural resilience; closing the inlet regulating means and opening the outlet regulating means, allowing the delivery tube to return to its at-rest position and thus emptying the binder in the delivery tube into the mixing chamber; and re-commencing the cycle at A method according to claim 4 wherein the inlet regulating means and the outlet regulating means are pinch-type valves. 0

6. A binder delivery means substantially as hereinbefore described with 0@ S°reference to Figures 3 to 7(d) of the accompanying drawings. *0*S S 20 7. A method for delivering binder substantially as hereinbefore described with reference to the Figures 3 to 7(d) of the accompanying drawings. 0Bi 0550 o DATED: 8 November 2001 PHILLIPS ORMONDE FITZPATRICK Attorneys for: ADELAIDE BRIGHTON LIMITED