ZA200601773B - Explosive - Google Patents

Description

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THIS INVENTION relates, broadly, to the forming of charges of emulsion explosive from a base emulsion by mixing batches of base emulsion with corresponding batches of flowable sensitising agent. More particularly, the invention relates to a method of forming successive charges of emulsion explosive from a base emulsion and a flowable sensitising agent; to a device for use in the method; and to an assembly comprising the device.

According to one aspect of the invention there is provided a method of forming successive charges of emulsion explosive from respective sources of supply of a base emulsion and of a flowable sensitising agent, the method comprising the steps of: withdrawing a measured batch of the base emulsion from the source of supply thereof; simultaneously withdrawing a batch of the flowable sensitising agent from the source of supply thereof, the batch of sensitising agent being matched with the batch of base emulsion; and mixing the measured batch of the base emulsion with the matched batch of the sensitising agent to form a charge of emulsion explosive,

the withdrawing of the base emulsion from the source of supply thereof being against a biasing force which exerts a pressure on the withdrawn base emulsion, and the biasing force, after the completion of the withdrawal, acting to mix the batch of base emulsion with the batch of sensitising agent to form a charge of emulsion explosive, > the above steps, after completion of the mixing, being repeated cyclically in sequence to form successive charges of the emulsion explosive.

The withdrawing of the measured batch of the base emulsion may be from a said source of supply thereof which is under pressure, being by admitting it into a space in a container, such as the interior of a cylinder of a piston- and-cylinder assembly, pressure from the source of supply forcing the base emulsion under pressure into the container and acting to stress a resilient biasing arrangement which has a stressed state in which it provides the biasing force. While the pressure of the source of supply of the base emulsion can, in principle, arise from gravity, being in the form of a static head, the method conveniently includes pumping the source of supply of base emulsion, for example by means of an air-driven centrifugal pump, to provide it under pressure.

When the withdrawing of the base emulsion is into the cylinder of a piston-and-cylinder assembly as described above, so that the space in the container is the interior of the cylinder of a piston-and-cylinder assembly, the withdrawing of the base emulsion may act to admit it under pressure into the cylinder of the assembly, to urge the piston of the assembly to move along the interior of the cylinder in a direction which enlarges the space in the cylinder into which the emulsion is admitted, while simultaneously resiliently stressing a said biasing arrangement, which may be a spring such as a coil spring. In this case, e.g. if the source of supply of base emulsion is pumped to place it under pressure, movement of the piston along the interior of the cylinder may be used to stop the withdrawing of : the base emulsion, e.g. by stopping the pumping, when the cylinder has been filled with the measured batch of base emulsion, subsequent movement in the appropriate direction by the piston along the cylinder to empty the cylinder acting to permit said withdrawal to resume once the cylinder has subsequently been emptied, thereby to admit a succeeding batch of the base emulsion into the cylinder. This may be by periodically interrupting and then re-establishing a power supply, such a compressed air supply, to a pump used for said pumping.

The withdrawing of the matched batch of sensitising agent from its source of supply may be arranged, for example by means of a mechanical interlock, to take place simultaneously, i.e. in synchronisation with, the withdrawing of the base emulsion from its source of supply. Thus, when the base emulsion is withdrawn into the cylinder of a piston-and-cylinder assembly and acts to move the piston thereof, simultaneously withdrawing the sensitising agent may be into a cylinder of another piston-and-cylinder assembly, the two assemblies being mechanically interconnected so that withdrawal of base emulsion simultaneously results in movement of the associated piston along its oylinder to stress the associated biasing arrangement, and acts to move the piston of the other assembly along the other cylinder in a direction which enlarges a space in the other cylinder, into which space the sensitising agent is withdrawn.

The biasing force, e.g. of the biasing spring, may be used to expel the measured batch of base emulsion from the associated cylinder, said mechanical interconnection acting simultaneously and automatically to expel the matched batch of sensitising agent from the other cylinder, i.e. in synchronisation therewith, the batches being expelled together through a mixing device, such as a static mixer, to form a charge of sensitised emulsion explosive. In this regard, by matched is meant that the batches are of respective sizes or volumes, not necessarily equal, which are in a selected ratio such that sufficiently homogeneous mixing thereof provides a sensitised explosive having acceptable properties.

Withdrawing of the matched batch of sensitising agent may be from a source of supply thereof which is contained in a vessel, such as a portable tank, the vessel being associated with a controller, such as a float control, which automatically interrupts withdrawal of the base emulsion from its source of supply, for example by interrupting said power supply to the pump when the level of the sensitising agent in the vessel drops because of prior withdrawal of successive batches thereof, to a predetermined low value, to guard against of mixing of a full batch of base emulsion with a partial batch of sensitising agent. Naturally, when the pressure of the supply of base emulsion arises from a static head caused by gravity, there is no pump to shut down, but the control may instead act automatically to prevent withdrawal of the base emulsion from its source of supply when said level of sensitising agent in the vessel reaches said low value. Formation of further charges of explosive may thereafter be prevented until the sensitising agent in the vessel is replenished.

In accordance with the method, the mixing of the batches of emulsion and sensitising agent to form the charge of emulsion explosive may be by manually triggering, and then manually maintaining, outflow of the batches of base emulsion ) and sensitising agent from their respective cylinders into a common flow line leading to a mixing device, such as a static mixer, the mixing device being located at or near the end of a lance at the end of a hose connected to the cylinders, the hose and lance providing the common flow line. The outflow may be triggered and maintained by means of a spring-loaded trigger which automatically closes the flow line when the trigger is released after a charge of explosive has been formed, for example in a borehole into which the outlet of the lance has been inserted. The cylinders, which are emptied by said outflow therefrom, are then in a condition automatically to be re- filled with succeeding respective batches of base emulsion and sensitising agent.

In this regard it should be noted that, if the source of supply of base emulsion is under a static pressure head arising from gravity with no pump, the piston-and-cylinder assembly used for withdrawal of the base emulsion may, instead of being arranged to interrupt or stop the pumping as described above, be arranged automatically to isolate itself from the bulk supply as soon as it has been filled, and to resume communication with the bulk supply when it has been emptied, to provide for automatic withdrawing of successive batches of batch emulsion from the bulk supply thereof, in response to the forming of prior successive charges of explosive, in a similar fashion to the abovementioned periodic interruption and re-establishment of the air supply to the pump, for the same purpose, when a pump is used to pressurise the source of supply of base emulsion.

The method of the invention permits a user to form successive charges ) of explosive, for example in successive boreholes, simply by manually triggering and maintaining simultaneous outflow and mixing of batches of base emulsion and sensitising agent from their respective piston-and-cylinder assemblies, along the common flow line and through the mixing device. As long as base emulsion and sensitising agent are available from the sources of supply thereof, and as long as the source of supply of base emulsion is maintained under pressure, either by gravity or by pumping when needed, the piston-and-cylinder assemblies will automatically re- fill as soon as they have been emptied by formation of a prior charge of explosive, ready for formation of the succeeding charge. The method, as mentioned above, further provides for automatic interruption of withdrawal of base emulsion from its source of supply, for example by interrupting the power supply to the pump, when a pump is used to pressurise the source of supply of the base emulsion, as soon as the piston-and-cylinder assemblies have been filled, or as soon as the source of supply of the sensitising agent has been used up.

According to another aspect of the invention there is provided a charge-forming device for use in forming successive charges of emulsion explosive from a source of supply of base emulsion and from a flowable sensitising agent, the device comprising: a vessel for holding the source of supply of flowable sensitising agent;

a sensitiser container connected in flow communication with the vessel for receiving successive batches of sensitising agent from the vessel, an emulsion container for connection to the source of supply of base emulsion for receiving successive batches of base emulsion therefrom; a mixing device in flow communication with the containers for mixing together batches of base emulsion and sensitising agent received respectively from the containers; a controller for controlling flow into the emulsion container from a said source of supply of base emulsion to which it is connected; and a biasing arrangement for exerting a biasing force on batches of base emulsion admitted into the emulsion container, to place and maintain them under pressure, the containers respectively having interior spaces of variable volume defined therein for receiving said batches, and the containers being operatively interlocked for simultaneous variation of the volumes of said spaces for simultaneously receiving said batches and then simultaneously expelling them through the mixing device in response to the biasing force from the biasing arrangement.

The various components of the device may be mechanically connected together, for example by being mounted on a common base or framework, or housed in a common housing, so that the device is in the form of a unit which is preferably portable, or at least movable, by one or two persons. Thus, the vessel, the sensitiser container, the emulsion container, the mixing device, the controller and the biasing arrangement may be connected together so that the device is in the form of a unit which has a mass of at most 30kg with the vessel fully charged with sensitiser.

In a particular embodiment the emulsion container and the sensitiser ) container each comprise a cylinder of a piston-and-cylinder assembly, the cylinder in each case being associated with a piston having a piston head located in the interior of the associated cylinder and a piston rod projecting longitudinally out of an end of the cylinder, spaces respectively for receiving base emulsion or sensitising agent, as the case may be, being defined in the cylinders between the respective piston heads and the ends of the associated cylinders, for example their ends opposite the ends from which the piston rods project. In this embodiment the biasing arrangement may be a coil spring acting on the piston of the emulsion container, the coil spring for example being located around the piston rod, between the piston head and the end of the cylinder from which the piston rod projects, the coil spring being arranged to be stressed, e.g. by compression thereof, in response to admission of base emulsion into the space between the piston head and the end of the container, to maintain the base emulsion in said space under pressure. In this embodiment the piston rods of the two containers may be connected to each other, outside their respective cylinders, so that they are interlocked for simultaneous movement, i.e. simultaneous extension and retraction thereof relative to their cylinders, and so that movement of the piston of the emulsion container in response to a biasing force from the coil spring results in automatic movement of the piston rod of the sensitiser container.

When the emulsion container is for connection to a source of supply of base emulsion which is placed under pressure by pumping, for example by pumping by means of a centrifugal pump, the device may include a said controller which may be a switch for a power supply to the pump, the switch being operatively connected ’ to the piston of the emulsion container. Compressed air power supplies are preferred in an environment exposed to explosives, to avoid electrical sparks, in which case the switch may be a closure valve for insertion into a compressed air power supply to the pump. If, however, the emulsion container is for connection to a source of supply of base emulsion which is pressurised by gravity and is not pumped, the controller connected to the emulsion container piston rod may be a switch in the form of a closure valve for insertion into a flow line between the emulsion container and the source of supply of base emulsion.

The device of the invention may also include a further controller, which may be a float control, associated with the vessel, for preventing flow of base emulsion from the source of supply thereof to the emulsion container when the volume of sensitising agent in the vessel is below a predetermined threshold. This controller may likewise comprise a switch such as a closure valve which, similarly to the switch connected to the emulsion container piston, either is for connection into the power supply to a pump for pressurising the source of supply of base emulsion, or is for connection into a flow line from a source of supply of base emulsion pressurised by gravity, to the emulsion container.

The cylinder of the emulsion container may have an inlet for receiving base emulsion from the source of supply thereof, which inlet is associated with a non-return inlet valve for preventing reverse emulsion flow from the cylinder to said source of supply; and said cylinder may have an outlet communicating via a flow line with the mixing device and associated with a non-return valve for preventing reverse flow through the outlet into the cylinder.

Similarly, the cylinder of the sensitiser container may have an inlet for receiving sensitising agent from the vessel and associated with a non-return valve for preventing reverse flow of sensitising agent from said cylinder to the vessel; and said cylinder may have an outlet communicating via a flow line with the mixing device, also being associated with a non-return valve for preventing reverse flow of sensitising agent via the outlet into said cylinder.

In other words, the emulsion container may have an emulsion inlet for receiving base emulsion from the source of supply thereof, which emulsion inlet is associated with a non-return inlet valve for preventing reverse emulsion flow from the emulsion container to said source of supply, said emulsion container having an outlet communicating via a flow line with the mixing device, the outlet being associated with a non-return outlet valve for preventing reverse flow through the outlet into the emulsion container, the sensitiser container having a sensitiser inlet for receiving flowable sensitising agent from the vessel, the sensitiser inlet being associated with a non-return inlet valve for preventing reverse flow of sensitising agent from said sensitiser container to the vessel, and said sensitizer container having a sensitiser outlet communicating via a flow line with the mixing device, the sensitiser outlet being associated with a non-return outlet valve for preventing reverse flow of sensitising agent via the outlet into the sensitiser container.

The mixing device may comprise at least one static mixer, located at or near the outlet end or free end of a lance which is in turn connected to the free end or outlet end of a hose leading from the outlets of the emulsion container and the ’ sensitiser container, the lance being provided with a trigger for triggering, and thereafter maintaining, outflow from the lance.

The invention extends also to an assembly for forming successive charges of emulsion explosive, the assembly comprising a charge-forming device as described above, and a source of supply of base emulsion under pressure connected to the emulsion container of the device.

The source of supply of base emulsion may be under pressure.

The invention will now be described, by way of non-limiting illustrative example, with reference to the accompanying diagrammatic drawing, the single figure of which is a schematic flow diagram of an assembly in accordance with the present invention, for forming successive charges of emulsion explosive, for example underground in a mine, from a source of supply of base emulsion. in the drawing, reference numeral 10 generally designates an assembly in accordance with the invention, for forming successive charges of emulsion explosive, typically underground in a mine. The assembly 10 includes a source of supply 12 of base emulsion, shown connected by a flow line 14 containing a non-return valve 16, to a centrifugal air-driven emulsion pump 18. The pump 18 is connected by a drive shaft 20 to an air motor 22, which is in turn connected to a compressed air power supply line 24 and has a spent air exhaust line 26 issuing therefrom. The valve 16 is an inlet valve to an inlet 27 to the pump 18, which pump is connected to a hose forming an outlet flow line 28 provided with a non-return outlet valve 30, associated with and adjacent an outlet 32 from the pump 18.

Flow line 28 leads to a device 34, schematically shown by broken lines and comprising a portable framework which can be carried in the fashion of a suitcase by a user, on which framework the various constituent parts of the device 34, described hereunder, are mounted. The device 34 comprises a vessel 36 shown holding a source of supply of sensitising agent in the form of gassing solution 38, being in the form of a plastics bottle with a filling cap 40; and the device 34 further comprises a sensitiser container 42 and an emulsion container 44, each in the form of a cylinder of a piston-and-cylinder assembly.

The sensitising container 42 is associated with a piston having a piston head 46 located in the cylinder 42 and a piston rod 48 projecting from an end thereof; and the container 44 is associated with a piston having a piston head 50 located in the cylinder 44 and a piston rod 52 projecting from an end thereof. The cylinders 42 and 44 are arranged side-by-side, and their piston rods 48 and 52 are interconnected by a cross-member 54 to interlock them together for simultaneous movement of the pistons. A coil spring 56 is shown under compression in the cylinder 44, between the piston head 50 and the end of the cylinder 44 from which the rod 52 projects. The cylinder 44 has an emulsion inlet 58 connected to the flow line 28 and associated with a non-return inlet valve 60 in the flow line 28 adjacent the inlet 58. The cylinder 44 further has an outlet 62 into a flow line provided by a hose 64 and associated with a non-return outlet valve 66 in the hose 64 adjacent the outlet 62. The hose 64 leads to a lance 68 provided with a mixing device 70 formed by a plurality of static mixers 72 arranged in series, and is provided with a trigger 74 comprising a spring-loaded outlet valve.

The cylinder 42 in turn has an inlet 76 connected to the vessel 36 by a pipe forming a flow line 78, the pipe 78 being provided with a filter 80 adjacent the vessel 36 and with a non-return inlet valve 82 into the cylinder 42, adjacent the cylinder 42. The cylinder has an outlet 84 leading via a branch hose 86 into the hose 64 and provided with a non-return outlet valve 88 adjacent the outlet 84.

The device 34 further comprises a controller 90 in the form of a closure valve having a closure member 92 connected to the end of the piston rod 52 remote from the cylinder 44, the closure member being located in a housing 94 provided in the air supply line 24. The air supply line 24 passes, on the side of the controller remote from the motor 22, through the vessel 36 in which vessel is located a further controller in the form of a float control valve 96. The float control valve 96 comprises a housing 98 connected into the air supply line 24 and a closure member 100 connected by a rod 102 to a float 104, the housing being provided with openings 106 communicating with the vessel 36. The housing 98 is elongated and is vertically aligned in the vessel 36, so that the rod 102 extends upwardly from the float 104 to the closure member 100, which is above the float 104, the openings 106 being at the bottom of the housing 96 at a low level in the vessel 36.

In use, it is contemplated that the device 34 of the present invention will ) be used, for example underground in a mine, together with a bulk source of supply 12 of base emulsion, from which a plurality of charges of emulsion explosive can be made by mixing with a sensitising agent 38 in the form of a suitable sensitising solution. In the illustrated Example the source 12 is placed under pressure by the pump 18.

It is expected that the method, device 34 and assembly 10 of the invention will be used to form successive charges of emulsion explosive in a plurality of boreholes underground in the mine, most of the charges being substantially identical in size and nature, but with the option loading peripheral boreholes with charges of a different size.

Accordingly, a device 34 will be selected having matched capacities of its sensitiser container 42 and emulsion container 44, to provide explosive charges of an appropriate size or volume in a plurality of boreholes. The device 34, which is portable in the fashion of a suitcase, can be carried by a user to the pump 18, where the container 44 is connected to the pump 18 via the hose 28 at 108, the controller 90 being connected to the motor 22 via the air supply line 24 at 110, the air supply line 24, upstream of the vessel 36, being connected to a source of supply (not shown) of air under pressure.

As long as the container 44 is empty of base emulsion, the spring 56 will hold the closure member 92 of the controller 90 in its open position, shown in solid lines in the drawing; and with sufficient sensitising solution 38 in the vessel 36, ’ sensitising agent in the housing 98 of the controller 96 will permit the float 104 to hold the closure member 100 in its open position (also shown in solid lines in the drawing). This permits compressed air from the air supply to flow along air supply line 24 to the air motor 22 to drive the air motor, spent air exhausting from the air motor 22 via the exhaust line 26.

The air motor, via the shaft 20, drives the centrifugal pump 18, which pumps base emulsion along flow lines 14 and 28 from the source of supply 12 and through the non-return valves 16, 30 and 60 to the emulsion container 44, to charge the container 44 with base emulsion while compressing the spring 56 and pushing the piston rod 52 outwardly from the container 44 to cause the closure member 92 of the controller 90 eventually to close off the air supply line 24 (broken lines) when a full charge of base emulsion has entered the container 44.

Movement of the piston rod 48, via the cross member 54, moves the piston rod 48 upwardly out of the sensitiser container 42, thereby withdrawing sensitising solution 38 from the vessel 36 along the flow line provided by the pipe 78, through the filter 80 and non-return valve 82 into the container 42.

The cross-sectional areas of the containers 42 and 44 are matched so that the amount of sensitising solution withdrawn into the container 42 automatically matches the amount of base emulsion withdrawn into the container 44 in an appropriate ratio for mixing to provide the desired emulsion explosive. The positions ) of the respective piston heads 46 and 50 are shown in the drawing in broken lines when full charges of base emulsion and sensitising solution have respectively been withdrawn from the source 12 and vessel 36 into the emulsion container 44 and sensitiser container 42.

To load a charge of emulsion explosive into a borehole, a user manipulates the lance 68 to place its free end in a borehole, and then operates the trigger 74 to permit flow along the hoses 64 and 86 to the static mixers 72 in the lance 68. The coil spring 56 pushes the piston heads 46 and 50 respectively downwardly in the associated containers 44 and 42 to discharge base emulsion and sensitiser solution along said hoses 64 and 86 through the mixing device 70 where the static mixers 72 mix them together, before issuance thereof as a mixture from the lance 68 into the borehole where the mixture forms a sensitised charge of explosive.

As soon as the charge has been loaded in the borehole the trigger 74 is released and succeeding batches of base emulsion and sensitising solution respectively be withdrawn from the source of supply 12 and vessel 36 according to the above-described cycle of operations, into the containers 44 and 42 respectively, which, after filling, are ready for use in discharging the succeeding charge of explosive into the succeeding borehole.

As a safety precaution, bearing in mind that the vessel 36 is expected to be emptied before the source of supply 12 of base emulsion, the controller 96 acts, when the sensitising solution 38 has dropped to a sufficiently low level in the vessel 36, so that it no longer supports the float 104. The float 104 thus drops to place the closure member 100 in its closed condition, closing off the air supply along the line 24 to the air motor 22. This prevents the discharge into boreholes of charges of base emulsion or of explosive containing insufficient sensitising agent.

An advantage of the invention is that, for example for the charging of peripheral boreholes requiring charges of a different and usually reduced volume, the device 34 can be disconnected from the air motor 22 and pump 18, and can be replaced by a different device 34, with containers 42 and 44 of different and usually reduced volumes. Furthermore, the device 34 can be replaced whenever the vessel 36 runs out of sensitising solution, unless the device is constructed in a fashion which makes it more convenient simply to replace the vessel 36.

The invention thus provides a versatile method, device and assembly for charging boreholes, for example underground in mines, from a bulk source of supply of base emulsion.

Claims (21)

1. A method of forming successive charges of emulsion explosive from respective sources of supply of a base emulsion and of a flowable sensitising agent, ’ the method comprising the steps of: withdrawing a measured batch of the base emulsion from the source of supply thereof; simultaneously withdrawing a batch of the flowable sensitising agent from the source of supply thereof, the batch of sensitising agent being matched with the batch of base emulsion; and mixing the measured batch of the base emulsion with the matched batch of the sensitising agent to form a charge of emulsion explosive, the withdrawing of the base emulsion from the source of supply thereof being against a biasing force which exerts a pressure on the withdrawn base emulsion, and the biasing force, after the completion of the withdrawal, acting to mix the batch of base emulsion with the batch of sensitising agent to form a charge of emulsion explosive, the above steps, after completion of the mixing, being repeated cyclically in sequence to form successive charges of the emulsion explosive.

2. A method as claimed in Claim 1, in which the withdrawing of the measured batch of the base emulsion is from a said source of supply thereof which is under pressure, being by admitting it into a space in a container, pressure from the source of supply forcing the base emulsion under pressure into the container and acting to stress a resilient biasing arrangement which has a stressed state in which it provides the biasing force.

3. A method as claimed in Claim 2, in which the method includes pumping the ) source of supply of base emulsion, to place it under pressure.

4. A method as claimed in Claim 2 or Claim 3, in which the space in the container is the interior of the cylinder of a piston-and-cylinder assembly, the withdrawing of the base emulsion acting to admit it under pressure into the cylinder of the assembly, to urge the piston of the assembly to move along the interior of the cylinder in a direction which enlarges the space in the cylinder into which the emulsion is admitted, while simultaneously resiliently stressing a said biasing arrangement.

5. A method as claimed in Claim 4, in which movement of the piston along the interior of the cylinder is used to stop the withdrawing of the base emulsion when the cylinder has been filled with the measured batch of base emulsion, subsequent movement in the appropriate direction of the piston along the cylinder to empty the cylinder acting to permit said withdrawal to resume once the cylinder has been emptied, thereby to admit a succeeding batch of the base emulsion into the cylinder.

6. A method as claimed in Claim 4 or Claim 5, in which, when the base emulsion is withdrawn into the cylinder of the piston-and-cylinder assembly and acts to move the piston thereof, simultaneously withdrawing the sensitising agent is into a cylinder of another piston-and-cylinder assembly, the two assemblies being mechanically interconnected so that withdrawal of base emulsion simultaneously results in movement of the associated piston along its cylinder to stress the associated biasing arrangement, and acts to move the piston of the other assembly along the other ) cylinder in a direction which enlarges a space in the other cylinder, into which space the sensitising agent is withdrawn.

7. A method as claimed in Claim 6, in which the biasing force is used to expel the measured batch of base emulsion from the associated cylinder, said mechanical interconnection acting simultaneously and automatically to expel the matched batch of sensitising agent from the other cylinder, the batches being expelled together through a mixing device to form a charge of sensitised emulsion explosive.

8. A method as claimed in Claim 7, in which the mixing of the batches of emulsion and sensitising agent to form the charge of emulsion explosive is by manually triggering, and then manually maintaining, outflow of the batches of base emulsion and sensitising agent from their respective cylinders into a common flow line leading to the mixing device, the mixing device being located at or near the end of a lance at the end of a hose connected to the cylinders, the hose and lance providing the common flow line.

9. A method as claimed in Claim 8, in which the outflow is triggered and maintained by operating a spring-loaded trigger which automatically closes the flow line when the trigger is released.

10. A method as claimed in Claim 1, substantially as described and as illustrated herein.

11. A charge-forming device for use in forming successive charges of emulsion ) explosive from a source of supply of base emulsion and from a flowable sensitising agent, the device comprising: a vessel for holding the source of supply of flowable sensitising agent; a sensitiser container connected in flow communication with the vessel for receiving successive batches of sensitising agent from the vessel, an emulsion container for connection to the source of supply of base emulsion for receiving successive batches of base emulsion therefrom; a mixing device in flow communication with the containers for mixing together batches of base emulsion and sensitising agent received respectively from the containers; a controller for controlling flow into the emulsion container from a said source of supply of base emulsion to which it is connected; and a biasing arrangement for exerting a biasing force on batches of base emulsion admitted into the emulsion container, to place and maintain them under pressure, the containers respectively having interior spaces of variable volume defined therein for receiving said batches, and the containers being operatively interlocked for simultaneous variation of the volumes of said spaces for simultaneously receiving said batches and then simultaneously expelling them through the mixing device in response to the biasing force from the biasing arrangement.

12. A device as claimed in Claim 11, in which the vessel, the sensitiser container, . the emulsion container, the mixing device, the controller and the biasing arrangement are connected together, so that the device is in the form of a unit which ) has a mass of at most 30 kg with the vessel fully charged with sensitiser.

13. A device as claimed in Claim 11 or Claim 12, in which the emulsion container and the sensitiser container each comprise a cylinder of a piston-and-cylinder assembly, the cylinder in each case being associated with a piston having a piston head located in the interior of the associated cylinder and a piston rod projecting longitudinally out of an end of the cylinder, spaces respectively for receiving base emulsion and sensitising agent being defined in the cylinders between the respective piston heads and the ends of the associated cylinders.

14. A device as claimed in Claim 13, in which the biasing arrangement is a coil spring acting on the piston of the emulsion container, the coil spring being arranged to be stressed in response to admission of base emulsion into the space between the piston head and the end of the emulsion container, to maintain the base emulsion in said space under pressure.

15. A device as claimed in Claim 14, in which the piston rods of the two containers are connected to each other, outside their respective cylinders, so that they are interlocked for simultaneous extension and retraction thereof relative to their cylinders, and so that movement of the piston of the emulsion container in response to a biasing force from the coil spring results in automatic movement of the piston rod of the sensitiser container.

16. A device as claimed in any one of Claims 11 — 15 inclusive, which includes a i further controller, associated with the vessel, for preventing flow of base emulsion from the source of supply thereof to the emulsion container when the volume of sensitising agent in the vessel is below a predetermined threshold.

17. A device as claimed in any one of Claims 11 — 16 inclusive, in which the emulsion container has an emulsion inlet for receiving base emulsion from the source of supply thereof, which emulsion inlet is associated with a non-return inlet valve for preventing reverse emulsion flow from the emulsion container to said source of supply, said emulsion container having an outlet communicating via a flow line with the mixing device, the outlet being associated with a non-return outlet valve for preventing reverse flow through the outlet into the emulsion container, the sensitiser container having a sensitiser inlet for receiving flowable sensitising agent from the vessel, the sensitiser inlet being associated with a non-return inlet valve for preventing reverse flow of sensitising agent from said sensitiser container to the vessel, and said sensitizer container having a sensitiser outlet communicating via a flow line with the mixing device, the sensitiser outlet being associated with a non- return outlet valve for preventing reverse flow of sensitising agent via the outlet into the sensitiser container.

[2006/0117 73

18. A device as claimed in any one of Claims 11 — 17 inclusive, which comprises at least one static mixer, located at or near the outlet end or free end of a lance which is in turn connected to the free end or outlet end of a hose leading from the respective outlets of the emulsion container and the sensitiser container, the lance ’ being provided with a trigger for triggering, and thereafter maintaining, outflow from the lance.

19. A device as claimed in Claim 11, substantially as described and as illustrated herein.

20. An assembly for forming successive charges of emulsion explosive, the assembly comprising a charge-forming device as claimed in any one of Claims 11 — 19 inclusive, and a source of supply of base emulsion connected to the emulsion container of the device.

21. An assembly as claimed in Claim 20, substantially as described and as illustrated therein. DATED THIS 28" day of FEBRUARY 2006 fe JHW LMARANS ADAMS & ADAMS APPLICANT'S PATENT ATTORNEYS