Apparatus and method for spraying a mixture of a binder and a volatile liquid

Abstract

 An apparatus and a method for spraying a mixture of a binder and a volatile liquid.
One particular application ofthe invention is in spraying a foamed binder such as bitumen or tar onto a road surface.
As shown in Figure 2 the apparatus comprises a binder tank (22) and a pump (23). The binder is transferred using a pump (23) and passes to a spray bar (25) having a number of spaced branches (26).
Volatile liquid in a tank (27) passes through a pump (23A), and needle valves (42) to a manifold (31 ) which has a number of spaced branches (32).
The supply of binder, from spray bar (25), through a typical branch (26) passes through a control valve (33) to a mixing chamber (35). A series of mixi ng chambers (35) are equally spaced along the liquid manifold (₃1) and spray bar (25) which are close to each other.
The volatile liquid passes through the branches (32) to control valves (36) and non-retum valves (37) and then into the same mixing chambers (₃₅). Thus each mixing chamber (35) receives a controlled supply of binder from the tank (22) and a controlled supply of volatile liquid from the tank (27). The control valves (33 and 36) are synchronised either pneumatically or mechanicalty-

Description

[0001] This invention relates to an apparatus and a method for spraying a mixture of a binder and a volatile liquid.

[0002] One particular application of the invention is in spraying a foamed binder onto a road surface, usually followed by the application of chippings which are rolled into the surface.

[0003] Typical of the binders which may be used are bitumen, tar, blends of bitumen and tar, the aforementioned materials incorporating various modifiers including polymers, and certain proprietary materials, all of which may be foamed by use of a suitable volatile liquid such as an aqueous phase.

[0004] It is known to spray a film of binder onto a road surface by means of a spray bar mounted on a road tanker vehicle. The binder is circulated at controlled temperature and pressure through a spray bar and` is discharged onto the surface through jets positioned at regular intervals across the width of the bar.

[0005] In such a known single phase system the binder passes directly from the vehicle tank through the spraybar and jets onto the surface without admixture.

[0006] Using this technique the viscosity of the binder is adjusted by the use of flux oils or emulsification, and by controlling the temperature of application, so that the binder will initially wet and adhere to the original road surface and the chippings. The binder then stiffens and holds the chippings in position by an increase in viscosity caused by falling temperature and the loss of the more volatile oils contained in the flux.

[0007] The method described suffers from the fact that the relatively low viscosity of the binder which is needed in order to be able to spray the binder and initially wet the original surface and the chippings limits the final viscosity which is achieved following the changes referred to. This, in turn, limits the stability of the surface dressing in its early life whilst the binder is still progressively hardening by loss of the less volatile flux oils and by various environmental effects, and can furthermore lead to "blacking" of the surface if the binder is affected by hot weather conditions whilst in its relatively soft state. Such blacking of the surface is potentially dangerous in the case of road maintenance work in as much as it reduces the skid resistance of the new surface.

[0008] A further shortcoming of the method described is that the loss of the more volatile flux oils at the time of applying the binder on the surface causes environmental pollution and can be a fire risk.

[0009] The present invention is directed to a new technique for surface treatment in which the binder is applied as a foamed product. This involves a two phase system instead of the single phase system referred to..

[0010] An object of the invention is to provide a method and apparatus which enables a two phase system to be effectively used, and this is achieved by providing individual uniformly spaced mixer chambers fed with separate streams of volatile liquid and binder so that expansion of the mixture occurs immediately it leaves the apparatus.

[0011] From one aspect, the invention relates to a method of spraying a mixture of a binder and volatile liquid comprising heating a binder material and supplying it at controlled pressure, flow-rate, and temperature to a distributor producing a number of discrete spaced streams of binder, simultaneously supplying volatile liquid at a controlled flow rate and pressure to a manifold so as to produce a number of discrete spaced streams of volatile liquid, mixing the streams of volatile liquid and the binder in a plurality of spaced mixer chambers, each chamber being connected to receive one stream of binder and one of volatile liquid, each mixer chamber being connected to a spray jet terminating in a nozzle so as to produce a plurality of sprays of mixed binder and volatile liquid, preferably as a foamed mixture.

[0012] The mixer chamber may be connected to the spray nozzle via an expansion and swirl chamber.

[0013] The method involves, preferably, synchronising the flow rates of the binder and volatile liquid so as to automatically achieve an appropriate mixture in the mixing chambers.

[0014] The synchronisation may be effected by use of pneumatically controlled valves, a valve being provided for each stream of binder and a separate valve for each stream of volatile liquid, each pair of valves being under the control of a single source of pneumatic pressure so as to achieve synchronisation.

[0015] Alternatively the synchronisation may be effected by the use of mechanically controlled valves with again a valve being provided for each stream of binder and a separate valve for each stream of volatile liquid. Preferably the valve spindle of the binder valve is operable directly by the movement of a cam opearting handle and the valve spindle of the volatile liquid valve is operable indirectly by a bar attached to the valve spindle of the binder valve.

[0016] From another aspect the invention relates to apparatus for spraying a mixture of a binder and a volatile liquid, comprising a source of binder, a source of volatile liquid, means for heating and supplying the binder at controlled pressure, flow rate, and temperature from the source t6)a distributor producing a number of discrete spaced streams of binder, means for simultaneously supplying volatile liquid at controlled flow rate to a manifold so as to produce a number of discrete spaced streams of volatile liquid, the manifold and the distributor being optionally located adjacent each other, and a plurality of spaced mixer chambers, each chamber being connected to receive one stream of binder and one of volatile liquid respectively from the distributor and the manifold, each mixing chamber being equipped with jet producing means so as to produce a series of spaced sprays of mixed binder and volatile liquid.

[0017] Preferably the sprays are produced as a foamed mixture..

[0018] Optionally, each mixing chamber may have connected to it an expansion and swirl chamber in turn connected to a jet, such as a slotted jet or a cone jet, so as to produce, through a plurality of such jets, the spaced series of sprays.

[0019] The binder may be supplied from a tank which is lagged and heated via a pump and pressure reducing valve to a conventional spray bar which will act as said distributor, the spaced outlets of the spray bar being connected via the control valves to a spaced series of individual mixing chambers. The volatile liquid, contained in a separate tank, may be supplied via a ring main and flow-meter and a regulator to the volatile liquid manifold the outlets of which at spaced intervals are supplied through control valves and non-return valves to each of the mixing chambers separately, pressure in the ring main being controlled by a pressure relief valve.

[0020] The respective supplies of binder and volatile liquid may each pass through conventional flow-meters with needle valves for controlling flow rates. The whole apparatus may be mounted on a vehicle with the final spaced jets exiting from the mixing chambers being spaced across the vehicle so as to enable a road or other surface to be sprayed uniformly as the vehicle moves along.

[0021] The invention is not restricted to spraying of foamed bitumen and the like but might equally well be used for mixing components of other surface dressings or crop treatment liquids or for mixing selective weed killers with crop promoting nutrients. Other applications are spraying waterproofing coatings on bridge structures, swimming pools, and dispensing of binders for road and roofing materials etc.

[0022] In the accompanying drawings:-

Figure 1 shows diagrammatically an existing apparatus for spraying binder such as bitumen onto a road surface;

Figure 2 is a very diagrammatic outline in block form-af apparatus in accordance with this present invention showing only the bare essentials of the apparatus;

Figure 3 is the volatile liquid circuit diagram;

Figure 4 shows again somewhat diagrammatically apparatus embodying the invention which may be mounted on a vehicle so as to mix volatile liquid as an aqueous phase and binder and spray the binder in foamed form onto a road surface;

Figure 5 shows in outline form one of the mixing chambers and a way in which it is supplied with binder and aqueous phase and illustrates particularly pneumatic synchronisation of the control valve;

Figure 6 is a section through the mixing chamber shown in Figure 5, and the distributor for the binder, and also includes..the volatile liquid control valve;

Figure 7 is similar to Figure 5 but a modified type of mixing chamber is illustrated:

Figure 8 is an enlarged elevation partly in section of the modified mixing chamber of Figure 7 and also shows the adjacent non-return valve and air operated water valve; and

Figure 9 shows diagrammatically a manual or mechanical control system for synchronisation of the binder valve and volatile liquid valve.

[0023] In the known apparatus shown in Figure 1 there is shown, by way of example a 4,000 gallon bitumen tank 10 provided with heaters, not shown, and a pump 11 which supplies bitumen from the tank via pipe 12 and filter 13 and has a by-pass 14 with a bitumen relief valve 15.

[0024] The bitumen supplied along pipe 16 passes through a filter 17 with a manual by-pass system 18, and is then supplied to a spray bar 19 which has a number of discrete jets throughout its length. The whole apparatus is mounted on the rear of a vehicle so that it can be used to effect continuous spraying of a road surface as the vehicle moves along slowly.

[0025] The present invention involves using a similar apparatus to produce a series of discrete streams of the bitumen material and, as shown in Figure 2, incorporates a similar tank 22 for the binder, usually bitumen. The binder is transferred using a pump 23 and the pressure is regulated by a relief valve 24 and passes to a spray bar 25 having a number of spaced branches 26.

[0026] The volatile liquid is contained in a tank 2" (Figs. 2, 3 and 4) and passes through a pump 23A, ='low- meters 29 and regulators or needle valves 42 and a pipe 30 to a volatile liquid manifold 31. This manifol: 31 also has a number of spaced branches 32.

[0027] The supply of binder, from spray bar 25, through a typical branch 26 passes through a control valve 33 to a mixing chamber 35. It will be seen that there are a series of mixing chambers 35 equally spaced along the liquid manifold 31 and spray bar 25 and that the spray bar 25 and liquid manifold 31 are arranged close to each other.

[0028] The volatile liquid passes through the branches 32 to control valves 36 and non-return valves 37 and then into the same mixing chambers 35. Thus each mixing chamber 35 receives a controlled supply of binder from the tank 22 and a controlled supply of volatile liquid from the tank 27. The control valves 33 and 36 are synchronised either pneumatically or mechanically by apparatus which will be described hereafter.

[0029] Each mixing chamber 35 also has, in this instance, an expansion and swirl chamber 38 and cone jet 39 terminating in a nozzle 39A so that there are a series of spaced nozzles 39A across the width of the apparatus.

[0030] Figure 4 shows the apparatus in a somewhat more practical form. The binder tank 10 and its pump 11, by-pass 14 etc. are as described in connection with Figure 1 and supply a spray bar 25 mounted on the rear end of a vehicle.

[0031] The volatile liquid or aqueous phase is supplied from a tank 27 via a positive displacement pump 23A to a one inch ring main containing a pressure reducing valve 28. At each side of the ring main are flow meters 29 and manually controlled needle valves 42. Water is supplied to an aqueous phase manifold 31 having a number of branches 32.

[0032] A typical mixing chamber arrangement is shown at 35 in Figures 5 and 6. Aqueous phase from the manifold 31 is supplied via an air operated valve 36 and non-return valve 37 to the mixing chamber 35. Binder from the binder distributor or spray bar 25 is supplied via a valve 33 movement of which is controlled by a valve spindle 45.

[0033] Movements of the valves 33 and 36 are, in this instance, synchronised by using a common air operated control. A master valve 46 with a manually controlled lever 47 supplies air to an air motor 48 which operates the valve spindle 45 and also supplies air simultaneously to operate the valve 36. Thus simultaneous supplies of binder and aqueous phase to the mixing chamber 35 are achieved. The circuit includes a jet-cutting control 44 for controlling the width of the spray area and an exhaust valve 48A.

[0034] Alternatively the movement of valves 33 and 36 may be synchronised by mechanical means as illustrated in Figure 9. In this instance the movement of a cam operating handle 60, through a jet open/close cam 61, causes a raising or lowering of a bar 62 fixed to the valve spindle of the binder valve 33 and via a second bar 63 also fixed to the valve spindle of the binder valve causes a corresponding movement of the valve spindle of the volatile liquid valve 36. Thus, simultaneous supplies of binder and volatile liquid to the mixing chamber 35 are achieved. The arrangement includes a jet-cutting control in the form of a jet release handle 64 for the separate control of the individual jets.

[0035] Figure 6 shows part of Figure 5 in somewhat more detail but omits the air control lines and other features. In Figure 6 it will be seen that the valve spindle 45 moves a valve 49 up or down under control of the air motor 48 shown in Figure 4. This valve cup, when open, allows a flow of binder indicated by arrows 53, from the spray bar 25 into the two component mixing chamber 35. The aqueous phase valve 36, when opened by air pressure allows aqueous phase to flow to the valve 36 and non-return valve 37 to the mixing chamber 35 where preliminary mixing occurs. From the mixing chamber 35 the mixed components pass to the expansion and swirl chamber 38 and to jets 39 so as to produce a spray.

[0036] It will be appreciated that what is shown in Figures 5 and 6 is repeated at equal intervals right across the apparatus as illustrated diagrammatically in Figure 2.

[0037] In Figure 7 is shown a modified version of Figure 5 in which all components are the same except that the mixing chamber 35 of Figures 5 and 6 is replaced by a modified mixing chamber 65, shown in section in Figure 8. It will be seen, in Figure 8, that the separate offset expansion and swirl chamber of Figure 6 have been omitted and there is now a straight-through mixing chamber 66 terminating in a specially designed jet 67. The entry to the chamber 66 is restricted, as at 68. The remaining details of the mixing chamber and adjacent structure are as shown in Figure 6. The straight-through flow provided by this mixing chamber introduces less restriction to flow and therefore involves less loss of pressure than the arrangement shown in Figure 6.

[0038] The jets 67 may be cone jets, slotted jets or any other form of jets.

[0039] Returning now to the first aspect of the invention, in applying the method the heating of the binder is closely controlled so that a highly viscous grade of binder is pumped at controlled temperature and pressure through the spray bar into the mixing chambers positioned at regular intervals across the width of the spray bar. The aqueous phase is also pumped at controlled flow and pressure and simultaneously introduced into the mixing chambers where heat is transferred from the binder to the aqueous phase. ' The mixed two phase system may optionally pass under pressure into the expansion swirl chambers and be discharged from these through specially designed jets onto the road surface. The release of pressure combined with the heat transfer is sufficient to vapourise the aqueous phase causing the viscous binder to foam and expand to several times its normal volume.

[0040] By locating the final mixing and spray devices close to the area to be sprayed the necessary expansion takes place just as the mixture is emitted from the jet just before it goes out onto the surface which is the ideal to be aimed at in a system of this type. The jets being mounted at the exit from the expansion swirl chambers or mixing chambers create rapid release of the pressure of the two phase system at the point of discharge sufficient to ensure immediate vapourisation of the volatile liquid component and consequent frothing and expansion of the binder phase and furthermore are designed to ensure that each individual jet along the width of the spray bar delivers onto the surface, an application of foamed binder which overlaps with adjacent applications so as to provide a substantially uniform layer of foamed binder across the area sprayed.

[0041] The expansion and swirl chamber when used are fitted with a tangential entry to receive the two phases from the mixing chamber and are specially designed to ensure that the mixture of binder and aqueous phase is homogenous at the point of discharge the synchronisation of the actions of the control valves discharging binder from the spray bar and aqueous phase from the manifold ensure that the two systems open and close simultaneously.

[0042] The invention permits a two phase binder system to be prepared and sprayed on surfaces using a spraying mechanism of unique design which permits the two phases to be admixed immediately prior to application on the surface. Using this method it is possible to foam and expand to several times its normal volume a high viscosity binder which would otherwise be too viscous to spray with conventional spraying-equipment at a temperature which is safe and economic.

[0043] In its foamed and expanded condition the viscosity and surface tension of the binder are lowered sufficiently for the binder to wet and adhere to the surface and to the chippings which are subsequently applied as a part of the surface dressing treatment. Following the initial collapse of the foam the binder gradually looses its expanded state and during this interphase period still therefore displays good adhesive qualities which make the binder more tolerant of delay problems arising during surface dressing operations. Immediately the binder reverts to its normal pre-foamed state its highly viscous nature is restored and this results in a tenacious grip of the chippings. This ensures a'highly stable surface dressing and, compared with conventional treatments, permits early trafficking of the surface with comparative safety.

[0044] Due to the absence of flux oils the binder is sprayed in safety at a temperature substantially below its flash point which is not the case with many other hot applied binders.

[0045] The binder is much less prone to bleeding and/or fatting problems which can cause blacking of the road surface and relatively unsafe driving conditions due to reduced skid resistance. This improvement stems from the high viscosity of the binder, the practice of not adding flux oils, the reduced temperature susceptibility of the binder achieved by careful blending of base bituminous binder stocks and the use of various additives in the binder and volatile liquid phases to modify the rheological properties of the finished product.

[0046] Also arising from the reduced temperature susceptibility of the binder, it is not so prone to embrittlement problems in extreme cold weather conditions.

[0047] The volatile liquid should be capable of generating a high ratio of vapour to the original liquid and be substantially immiscible with the binder phase, and may contain special additives to modify the surface tension of the binder phase during the generation of the mixture.

[0048] The mechanism also enables the use of volatile liquids containing additives such as thermosetting resins, thermoplastic polymers or other additives selected to improve the mechanical properties of the binder when mixed with the binder as part of the foaming process described.

[0049] The binder should preferably be a specially blended base bituminous binder of high viscosity and may be modified by the addition of special additives to control and improve the stability of the foam (i.e. time during which the binder is expanded), the ratio of the expansion to the original binder volume, and the chemical polar adhesive properties of the binder to aggregate chippings and the surface.

[0050] It is also possible to modify the mechanical properties of the binder by the addition of thermoplastic polymers, resins or other additives, to improve the elasticity, cohesion, adhesion and strength, and further reduce temperature susceptibility of the binder so produced. These improved binders can also be expanded by foaming and spraying on the surface by the method and mechanism already described without detracting from the advantages described.

[0051] Another application of the invention is to the spraying of mixtures of binders and volatile liquids into aggregates such as sands and fine limestones in a mixing vessel for the purpose of manufacture of coated stone road, flooring, and roofing materials.

Claims

1. A method of spraying a mixture of a binder and volatile liquid comprising heating a binder material and supplying it at controlled pressure, flow-rate, and temperature to a distributor (25) producing a number of discrete spaced streams of binder, simultaneously supplying volatile liquid at a controlled flow rate and pressure to a manifold (31) so as to produce a number of discrete spaced streams of.volatile.liquid, mixing the streams of volatile liquid and the binder in a plurality of spaced mixer chambers (35), each chamber (35) being connected to receive one stream of binder and one of volatile liquid, each mixer chamber (35) being connected to a jet (39) terminating in a nozzle (39A) so as to produce a plurality of sprays of mixed binder and volatile liquid.

2. A method according to claim 1 and in which the sprays are produced as a foamed mixture.

3. A method according to claim 1 or claim 2 and in which the mixer chamber (35) is connected to the spray nozzle (39A) via an expansion and swirl chamber (38).

4. A method according to any preceding claim including synchronising the flow rates of the binder and volatile liquid so as to automatically achieve an appropriate mixture in the mixing chambers.

5. A method according to claim 4 in which the synchronisation is achievedpneumatically.

6. A method according to claim 4 and in which the synchronisation is achieved mechanically.

7. A method according to claim 5 in which the synchronisation is effected by use of pneumatically controlled valves, a valve (33) being provided for each stream of binder and a separate valve (36) for each stream of volatile liquid, each pair of valves being under the control of a single source of pneumatic pressure so as to achieve synchronisation.

8. A method according to claim 6 and in which the synchronisation is effected by the use of mechanically controlled valves, a valve (33) being provided for each stream of binder and a separate valve (36) for each stream of volatile liquid.

9. A method according to claim 8 and in which the valve spindle of the binder valve (33) is operable directly by the movement of a cam operating handle (60) and the valve spindle of the volatile liquid valve (36) is operable indirectly by a bar (63) attached to the valve spindle of the binder valve (33).

10. Apparatus for spraying a mixture of a binder and a volatile liquid, comprising a source (22) of binder, a source of volatile liquid (27), means for heating and supplying the binder at controlled pressure, flow rate, and temperature from the source to a distributor (19) producing a number of discrete spaced streams of binder, means-for simultaneously supplying volatile liquid at controlled flow rate to a manifold (31) so as to produce a number of discrete spaced streams of volatile liquid, the manifold and the distributor being optionally located adjacent each other, and a plurality of spaced mixer chambers (35), each chamber being connected to receive one stream of binder and one of volatile liquid respectively from the distributor and the manifold, each mixing chamber being equipped with jet producing means (38,39,39A) so as to produce a series of spaced sprays of mixed binder and volatile liquid.

11. Apparatus according to claim 10 including means (66) to produce the sprays as a foamed mixture.

12. Apparatus according to claim 10 or claim 11 and in which each mixing chamber (35) has connected to it an expansion and swirl chamber (38) in turn connected to a jet (39), so as to produce, through a plurality of such jets, the spaced series of sprays.

13. Apparatus according to claim 12 and in which said jets (39) are slotted jets or coned jets.

14. Apparatus according to any of claims 10 to 13 in which the binder supply tank (22) is lagged and heated and a pump (11) and pressure relief valve (24) through which a binder is conveyed from the tank to a conventional spray bar (25) which acts as said distributor, the spaced outlets of the spray bar being connected via the control valves (33) to a spaced series of individual mixing chambers (35).

15. Apparatus according to any of claims 10 to 14 and in which the volatile liquid, contained in a separate tank (27), is supplied via a ring main (31) and flow-meter (29) and a regulator (42) to the volatile liquid manifold (31), the outlets of which, at spaced intervals, are supplied through control valves (36) and non-return valves (37) to each of the mixing chambers (35) separately, pressure in the ring main being controlled by a pressure relief valve.

16. Apparatus according to any of claims 10 to 15 in which the respective supplies of binder and volatile liquid each pass through conventional flow-meters (29) with needle valves (47) for controlling flow rates.

17. Apparatus according to any of claims 10 to 16 and in which means are provided to synchronise the flows of binder and volatile liquid to the mixing chambers.

18. Apparatus according to claim 17 and in which said means is mechanical.

19. Apparatus according to claim 17 and in which said means is pneumatic.

20. Apparatus according to any of claims 10 to 19 mounted on a vehicle with the final spaced jets exiting from the mixing chambers spaced across the vehicle so as to enable a raod or other surface to be sprayed uniformly as the vehicle moves along.

21. Apparatus according to any of claims 10 to 20 when used for spraying of foamed bitumen.

22. Apparatus according to any of claims 10 to 20 when used for mixing components of surface dressings or crop treatment liquids or for mixing selective weed killers with crop promoting nutrients, or for spraying waterproofing coatings on bridge structures, swimming pools, or for dispensing of binders for road and roofing materials.

Drawing