GB2418155A

GB2418155A - Emulsion macadam mixing apparatus

Info

Publication number: GB2418155A
Application number: GB0420923A
Authority: GB
Inventors: B Beasley
Original assignee: BCB COATED STONE Ltd
Current assignee: BCB COATED STONE Ltd
Priority date: 2004-09-21
Filing date: 2004-09-21
Publication date: 2006-03-22
Anticipated expiration: 2024-09-21
Also published as: GB0420923D0; GB2418155B

Abstract

Emulsion macadam mixing apparatus (10), comprises aggregate supply means (12), water supply means (14), bitumen emulsion supply means (16), and mixing means (18) which, in use, receive material from the supply means (12, 14, 10) and are operable to mix the said received material, the apparatus (10). The apparatus further comprises control means (20) operable, in use, to provide volumetric control of the delivery of material to the mixing means (18) by the supply means (12, 14, 16). The apparatus is a road vehicle and the volumetric control of aggregate is achieved by a belt and gate arrangement (12) and of water and bitumen comprises a variable pump and flow meter. Delivery and mixing of the emulsion macadam is by a screw conveyer (18). The control means (20) is operable to receive a specification of the material to be mixed and controls the supply means to meet the specification. The control means further maintains a record of the specification mixed by the apparatus.

Description

Emulsion Macadam The present invention relates to emulsion macadam and

particularly, to the mixing thereof.

Emulsion macadam is a material used for highway surfaces and the like. The material includes an aggregate, such as stone or recycled asphalt, mixed into a water emulsion of bitumen. After mixing and evaporation of the water content, the strength of the resulting macadam is determined by the grade of aggregate used, and the viscosity of the bitumen.

The present invention provides emulsion macadam mixing apparatus, comprising: aggregate supply means; water supply means; bitumen emulsion supply means; and mixing means which, in use, receive material from the supply means and are operable to mix the said received material, the apparatus further comprising control means operable, in use, to provide volumetric control of the delivery of material to the mixing means by the supply means.

The control means may be operable to receive a specification for material to be mixed, and to control the supply means to meet the specification. The control means preferably maintains a record of the

specification of material mixed by the apparatus.

The mixing means may comprise a screw conveyor along which the material to be mixed is conveyed, to be mixed while being conveyed. The Ail control means is preferably operable to control the speed of the screw conveyor, whereby to control the rate of delivery of mixed material.

The aggregate supply may comprise a belt conveyor and an associated gate defining a maximum clearance above the belt, whereby the clearance and the belt speed together define the rate of delivery of material, by volume, and wherein at least one of the clearance and the speed is adjustable and controlled by the control means. Preferably both speed and clearance are adjustable. The aggregate supply may comprise at least one hopper for aggregate.

The water supply may comprise a flow meter operable to provide the control means with information relating to the volume of water being supplied to the mixer means. The water supply means may comprise variable pump means operable to control the water flow to the mixer means, and controlled by the control means. The water supply means may comprise a water tank.

The bitumen emulsion supply may comprise a flow meter operable to provide the control means with information relating to the volume of bitumen emulsion being supplied to the mixer means. The bitumen emulsion supply means may comprise variable pump means operable to control the bitumen emulsion flow to the mixer means, and controlled by the control means. The bitumen emulsion supply means may comprise a bitumen emulsion tank.

The apparatus may further comprise cement supply means operable to supply hydrophilic material, such as cement, to the mixing means and controlled by the control means to provide volumetric control of the delivery of hydrophilic material for control of the water content of the emulsion macadam.

The hydrophilic material supply means may comprise a variable speed screw conveyor.

Preferably, the apparatus is in the form of a road vehicle. The apparatus is preferably self-contained.

The invention also provides a method of mixing emulsion macadam, in which aggregate, water and bitumen emulsion are supplied for mixing, there being volumetric control of the delivery of material for mixing.

In a further aspect, the invention provides emulsion macadam mixing apparatus, comprising: aggregate supply means; water supply means; bitumen emulsion supply means; and mixing means which, in use, receive material from the supply means and are operable to mix the said received material, wherein the mixing means comprise a screw conveyor along which the material to be mixed is conveyed, to be mixed while being conveyed.

The apparatus may further comprise control means operable, in use, to provide volumetric control of the delivery of material to the mixing means by the supply means.

specification of material mixed by the apparatus.

The control means is preferably operable to control the speed of the screw conveyor, whereby to control the rate of delivery of mixed material.

The apparatus may further comprise cement supply means operable to supply cement to the mixing means and controlled by the control means to provide volumetric control of the delivery of cement. The cement supply means may comprise a variable speed screw conveyor.

The invention also provides a method of mixing emulsion macadam, in which aggregate, water and bitumen are supplied to a screw conveyor along which the material is conveyed, and is mixed while being conveyed.

An embodiment of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings, in which: Fig. 1 is a schematic diagram of one embodiment of apparatus according to the present invention; Fig. 2 is a simple, enlarged view of part of the apparatus of Fig. 1; and Fig. 3 is a partially schematic representation of a practical implementation of the apparatus of Figs. 1 and 2.

Fig. 1 illustrates emulsion macadam mixing apparatus 10. This includes aggregate supply means, generally at 12, water supply means, generally at 14, bitumen emulsion supply means, generally at 16 and mixing means, generally at 18. The mixing means 18 receive material from the supply means 12, 14, 16 and are operable to mix the received material.

Control means 20 control the supply means 12, 14, 16 to provide volumetric control of the delivery of material to the mixing means 18 by the supply means 12,14, 16.

The apparatus 10 may also include a supply for hydrophilic material, in this case cement. The supply is generally at 22 and also controlled by the control means 20 for volumetric control of the delivery of cement from the supply 22 to the mixing means 18. It is envisaged that cement (or another hydrophilic material, such as lime) will be used in small quantities, primarily to control water content of the final mix.

The mixing means 18 include a screw conveyor 24 illustrated schematically in Fig. 1 and in the form of a helical blade around a rotatable axial shaft, mounted within a passage 26. A variable speed motor 28 drives the screw conveyor 24 and is controlled by the control means 20 by means of a control connection 30.

In use, material is received at the inlet end 32 of the conveyor 24, as will be described, and is conveyed through the passage 26 to the outlet end 34. Material within the passage 26 is mixed as it is conveyed. The rotational speed of the screw conveyor 24 controls the rate of delivery of mixed material from the outlet 34 and is thus controlled by the control 20, by means of the motor 28. The speed of the screw conveyor 24 also affects how gentle the mixing process is. This should be sufficient to avoid the bitumen emulsion breaking down prematurely. The angle of the screw conveyor 24 from the horizontal determines the mixing time.

The aggregate supply 12 is provided, in this example, as two parallel supply arrangements supplying the mixer 18. Each arrangement is in the form of a hopper 36 for aggregate material, which may be the same in each hopper, or each hopper 36 may contain a different type or grade of material.

A conveyor 38 is provided beneath each hopper 36. Each conveyor 38 is in the form of a belt conveyor which may have a continuous or apertures surface, or be a chain conveyor, for example. Other forms of conveyor could be used, depending on the nature of the aggregate within the hopper 36.

Each conveyor 38 has a belt 40 which runs around rollers 42, one of which is driven by a motor 44. A gate 46 is provided above each belt 40, downstream of the corresponding hopper 36. This is illustrated on a larger scale in Fig. 2.

The gate 46 is located above the belt 40 to provide a maximum clearance at 48, between the belt 40 and the lower edge 50 of the gate 46. This limits the height of material which can be carried past the gate 46 by the belt 40. Thus, the clearance 48 and the speed of the belt 40 together define the rate of delivery of material, by volume, by the conveyor 38 to the mixer 18.

The aggregate supply 12 is controlled by the control means 20 by control connections 52, either to control the clearance 48 by movement of the gates 46, or to control the speeds of the belts, by controlling the speeds of the motors 44, or preferably, allowing all of these parameters to be controlled.

JO The water supply 14 comprises a water tank 54 from which water is pumped to the mixer 18 by a variable speed pump 56. A flow meter 58 is also provided, to determine the rate of supply of water, by volume, to the mixer 18.

The pump 56 is controlled by the control 20 by means of a connection 60, to allow the rate of supply of water to be changed by the control means 20.

The bitumen emulsion supply 16 comprises a bitumen emulsion tank 62 from which bitumen emulsion is pumped to the mixer 18 by a variable speed pump 64. A flow meter 66 is also provided, to determine the rate of supply of bitumen emulsion, by volume, to the mixer 18. The pump 64 is controlled by the control 20 by means of a connection 68, to allow the rate of supply of bitumen emulsion to be changed by the control means 20.

Pumps and flow meters suitable for use with bitumen are commercially available, e.g. for use in the oil industry. For example, direct displacement pumps may be used, in order to pump without breaking up the emulsion.

The cement supply 22, which may be optional, has a hopper 70 which feeds a screw conveyor 72 to deliver cement from the hopper 70 to the mixer 18. The screw conveyor 72 is controlled by a variable speed motor 74 which is in turn controlled by the control 20, through a control connection 76. This allows the rate of delivery of cement to the mixer 18 to be controlled by volume.

The control means 20 may be implemented as a computer operating I under appropriate software control, or as appropriate dedicated hardware or as a combination of these arrangements. A computer is preferred, for speed of processing and accuracy. The control 20 receives instructions from user controls 78 to define the required specification of emulsion macadam to be mixed. This specification will be defined in volumetric terms, or converted to volumetric terms by the control 20. That is, the specification defines the required rate, by volume, of delivery of the various materials to the mixer 18, in order to achieve the required specification. The specification will also determine the required delivery rate from the mixer 18 and the permitted severity of mixing, preferably by specifying a maximum and minimum rotation speed of the screw conveyor 24. Mixing time is controlled by adjusting the angle of the screw conveyor to the horizontal. When the apparatus 10 is in operation, the control 20 makes use of this specification, and calibration information to control the various supplies 12,14,16 and 22, and the mixer 18 in order to provide the required volumetric control of the delivery of material to the mixer 18 by the supplies. The control 20 preferably also maintains a record of the specification of material which has been mixed by the apparatus 10, to allow for subsequent monitoring as part of a quality control system, for

example.

Turning now to Fig. 3, there is shown a road vehicle 80 which carries the apparatus described. Thus, the vehicle 80 has a driver cab 82 and a rear load deck 84, carrying the various supplies. The mixer 18 is located at the rear of the vehicle. Aggregate supply hoppers 36 are located side by side, at the front of the load deck 84, with the conveyors 38 located underneath. A water tank 54 and emulsion tank 62 are located side by side and, in this example, behind the hoppers 36. A cement hopper 70 is located behind the tanks 54, 62. A control panel 86 incorporates the control means 20 and user controls 72. The vehicle 80 is thus fully self- contained. In particular, it can be driven to an appropriate location to be loaded with aggregate, water, bitumen / - emulsion and cement, and then driven to the location at which mixed emulsion macadam is required, then being operated to prepare the required emulsion macadam. It is envisaged that the self-contained nature of the vehicle will have various advantages. In particular, it is expected that the mobility of the vehicle 80 will enable aggregate material to be used at the location of its source, thus allowing recycled aggregate (e.g. from a roadway which is being resurfaced) to be re-used without requiring it to be transported to the location of a fixed mixing plant. This avoids transportation costs and l O also increases the speed with which aggregate can be recycled.

In alternative arrangements, the apparatus 10 may be provided in the form of a trailer which is not self-powered, but can be towed to an appropriate location to achieve the advantages just described.

In a further alternative, it may be possible to remove the tanks 54, 62 and hopper 70 from the apparatus 10, thus making the apparatus smaller and lighter, with material being drawn from an appropriate, locally available supply when needed, but mixed in a manner which remains controlled as described above. For example, water may be taken from a mains supply available locally, rather than being carried in a tank by the vehicle.

It will be apparent from the above description that the apparatus can be operated as a continuous process which can be started and stopped at any time, except that the mixer 18 must be emptied of all mixed material, to prevent jamming as the mixed material sets within the mixer 18. This is achieved by continuing to rotate the screw 24 after all other systems have stopped, in order to clear the screw mixer of residual material. Each time the apparatus is re-started, material can immediately be manufactured to a new specification, by appropriate control of the volumetric delivery of material to the mixer 18. \

Appropriate calibration of the arrangements for measuring or setting the rates of delivery, by volume of the materials, such as the motors, flow meters, gate settings etc., will initially be required and will require checking as part of routine maintenance. It may be necessary for the control 20 to take into account the water content of the aggregate being supplied, in order to determine the required flow rate from the water supply 14, in order to control the final water content of the mixed material. Thus, the moisture content of the aggregate may be monitored continuously by an appropriate sensor, or periodically sampled and the result provided to the control 20.

The emulsion tank 62 may be temperature controlled.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims 1. Emulsion macadam mixing apparatus, comprising: aggregate supply

means; water supply means; bitumen emulsion supply means; and mixing means which, in use, receive material from the supply means and are operable to mix the said received material, the apparatus further comprising control means operable, in use, to provide volumetric control of the delivery of material to the mixing means by the supply means. . -
2. Emulsion macadam mixing apparatus as claimed in claim 1 wherein ë the control means is operable to receive a specification for material to be .: mixed, and to control the supply means to meet the specification. :e
3. Emulsion macadam mixing apparatus as claimed in claim 2 wherein the control means maintains a record of the specification of material mixed by ë the apparatus.
4. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the mixing means comprises a screw conveyor along which the material to be mixed is conveyed, to be mixed while being conveyed.
5. Emulsion macadam mixing apparatus as claimed in claim 4 wherein the control means is operable to control the speed of the screw conveyor, whereby to control the rate of delivery of mixed material.
6. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the aggregate supply means comprises a belt conveyor and an associated gate defining a maximum clearance above the belt, whereby the clearance and the belt speed together define the rate of delivery of material, by volume, and wherein at least one of the clearance and the speed is adjustable and controlled by the control means.
7. Emulsion macadam mixing apparatus as claimed in claim 6 wherein both speed and clearance are adjustable.
8. Emulsion macadam mixing apparatus as claimed in any preceding l O claim wherein the aggregate supply means comprises at least one hopper for aggregate.
9. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the water supply means comprises a flow meter operable to .e provide the control means with information relating to the volume of water -e being supplied to the mixer means. . .
10. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the water supply means comprises variable pump means - 2.0 operable to control the water flow to the mixer means, and controlled by the control means.
11. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the water supply means comprises a water tank.
12. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the bitumen emulsion supply means comprises a flow meter operable to provide the control means with information relating to the volume of bitumen emulsion being supplied to the mixer means.
13. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the bitumen emulsion supply means comprises variable pump means operable to control the bitumen emulsion flow to the mixer means, and controlled by the control means.
14. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the bitumen emulsion supply means comprises a bitumen emulsion tank.
15. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the apparatus comprises cement supply means operable to l O supply hydrophilic material, such as cement, to the mixing means and controlled by the control means to provide volumetric control of the delivery of hydrophilic material for control of the water content of the emulsion macadam.
16. Emulsion macadam mixing apparatus as claimed in claim 15 wherein the hydrophilic material supply means comprises a variable speed screw conveyor. . . .

:
17. Emulsion macadam mixing apparatus as claimed in any preceding claim wherein the apparatus is in the form of a road vehicle. .
18. Emulsion macadam mixing apparatus as claimed in claim 17 wherein the apparatus is self-contained.
19. A method of mixing emulsion macadam, in which aggregate, water and bitumen emulsion are supplied for mixing, there being volumetric control of the delivery of material for mixing.
20. Emulsion macadam mixing apparatus, comprising: aggregate supply means; water supply means; bitumen emulsion supply means; and mixing means which, in use, receive material from the supply means and are operable to mix the said received material, wherein the mixing means comprise a screw conveyor along which the material to be mixed is conveyed, to be mixed while being conveyed.
21. Emulsion macadam mixing apparatus as claimed in claim 20 wherein the apparatus comprises control means operable, in use, to provide volumetric control of the delivery of material to the mixing means by the l O supply means.
22. Emulsion macadam mixing apparatus as claimed in claim 21 wherein the control means is operable to receive a specification for material to be : . . mixed, and to control the supply means to meet the specification. . .e
23. Emulsion macadam mixing apparatus as claimed in claim 22 wherein .

: the control means maintains a record of the specification of material mixed by : the apparatus. .
24. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 23 wherein the control means is operable to control the speed of the screw conveyor, whereby to control the rate of delivery of mixed material.
25. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 24 wherein the aggregate supply means comprises a belt conveyor and an associated gate defining a maximum clearance above the belt, whereby the clearance and the belt speed together define the rate of delivery of material, by volume, and wherein at least one of the clearance and the speed is adjustable and controlled by the control means.
26. Emulsion macadam mixing apparatus as claimed in claim 25 wherein both speed and clearance are adjustable.
27. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 26 wherein the aggregate supply comprises at least one hopper for aggregate.
28. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 27 wherein the water supply means comprises a flow meter operable to provide the control means with information relating to the volume of water being supplied to the mixer means.

l O
29. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 28 wherein the water supply means comprises variable pump means operable to control the water flow to the mixer means, and controlled by the control means.
30. Emulsion macadam mixing apparatus as claimed in any of claims 20 to . - 29 wherein the water supply means comprises a water tank. . .
31. Emulsion macadam mixing apparatus as claimed in any of claims 20 to . 30 wherein the bitumen emulsion supply comprises a flow meter operable to provide the control means with information relating to the volume of bitumen ë emulsion being supplied to the mixer means.
32. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 31 wherein the bitumen emulsion supply means comprises variable pump means operable to control the bitumen emulsion flow to the mixer means, and controlled by the control means.
33. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 32 the bitumen emulsion supply means comprises a bitumen emulsion tank.
34. Emulsion macadam mixing apparatus as claimed in any of claims 20 to 33 wherein the apparatus comprises cement supply means operable to supply cement to the mixing means and controlled by the control means to provide volumetric control of the delivery of cement.
35. Emulsion macadam mixing apparatus as claimed in claim 34 wherein the cement supply means comprises a variable speed screw conveyor.
36. Emulsion macadam mixing apparatus as claimed in any of claims 20 to wherein the apparatus is in the form of a road vehicle.
37. Emulsion macadam mixing apparatus as claimed in claim 36 wherein the apparatus is preferably self-contained.
38. A method of mixing emulsion macadam, in which aggregate, water and : . . bitumen are supplied to a screw conveyor along which the material is -e conveyed, and is mixed while being conveyed. ëee

a:
39. Emulsion macadam mixing apparatus substantially as hereinbefore : described with reference to and/or as shown in the accompanying drawings.
40. Any novel subject master or combination including novel subject master disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.