FIELD OF THE INVENTION

This invention relates to a device for mixing and dispensing explosive matrix for use in blasting operations.

BACKGROUND TO THE INVENTION

Explosives are widely used in underground mining operations. These mines extend to great depths and the work faces to great distances from the mines shafts. This necessitates continuous transport of explosives from secure storage areas to work faces.

Due to the harsh conditions prevalent in underground mines and the ever-present requirement to assure the safety of mining personnel, the handling of explosives is strictly controlled. As part of this consideration emulsion explosives, also called an explosive matrix, have been developed as an alternative or replacement for traditional packaged explosives.

The explosive matrix comprises two separate components, namely a base emulsion or gel that forms the main component of the explosive and a secondary sensitizer or accelerator component.

The base emulsion and the sensitizer are both classified as non-detonable and non-explosive, respectively. The base emulsion comprises, typically, a mixture of two immiscible liquids and an emulsifier. The sensitizer is an aqueous or emulsified liquid, which, when added to the base emulsion and mixed, creates an explosive matrix in the blast hole.

The base emulsion and sensitizer are transported separately to the blast hole and mixed upon pumping it into the blast hole.

The safe delivery of explosive matrix into a blast hole is equally important to the mixing of the components to it to form the matrix. Current devices are cumbersome and require substantial effort in cleaning it from matrix after use, to prevent activated explosive (matrix) remaining in a system after use. Some of the passages through which the specialised delivery unit have to be manoeuvred have low heights and extend at inclines or declines, making the handling therefore very difficult. This specialised delivery unit is heavy and cumbersome to operate and are costly.

Even though safer the use of emulsion explosives instead of packaged explosives has been limited because of a capital requirements, ongoing maintenance, machinery and accessory equipment. In respect of the accessory equipment weight, ease of handling and cost remain significant factors.

The limitations of the presently available delivery units for the emulsion are limiting the use of the safer emulsion explosives.

OBJECT OF THE INVENTION

It is an object of the invention to provide an explosive matrix mixer and dispenser which at least partly overcomes the abovementioned problem.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided an explosive matrix mixer and dispenser which comprises a frame supporting an emulsion dispenser chamber and a sensitizer dispenser chamber, each chamber including a piston movable between a first end and second end thereof, and each chamber having an exit extending from its second end into a barrel that extends from the frame;

the frame supporting a base secured to the emulsion chamber piston and a base secured to the sensitizer chamber piston, with the emulsion chamber base and the sensitizer chamber base being simultaneously movable between a first and second position;

the mixer and dispenser further provided with drive means for the emulsion chamber base and the sensitizer chamber base, and a control for the drive means to enable simultaneous driving of the emulsion chamber base and the sensitizer chamber base from the first to the second position to simultaneously move the emulsion chamber piston and sensitizer chamber piston from their respective first ends to their respective second ends to simultaneously dispense emulsion and sensitizer contained within the chambers through the chamber exits into the barrel; with the barrel being provided with an array of spaced apart laminar flow disrupting members extending at least partly into barrel from its sidewalls operatively to mix the emulsion and sensitizer within the barrel to form an explosive matrix, and

with the barrel having a diameter sized to fit into a blast hole to enable dispending of the explosive matrix within the blast hole.

There is further provided for the emulsion chamber base and the sensitizer chamber base to comprise a main piston movable between a first and second position within a cylinder contained in the frame, and for the main piston to have an emulsion chamber stem extending from it into the emulsion chamber and being connected to the emulsion chamber piston, and for the main piston to have a sensitizer chamber stem extending from it into the sensitizer chamber and being connected to the sensitizer chamber piston.

There is further provided for the drive means to comprise a pressurised fluid supply, preferably a pressurised air supply, and for the control to comprise a handle, extending from the frame, with a resiliently biased trigger; operatively allowing the mixer and dispenser to be held by the handle and the trigger operated to open and close the valve.

There is also provided for the pressurised air supply to be connectable to two inlets into the frame cylinder containing the main piston, with a first inlet located proximate the first position of the main piston, and a second inlet located proximate the second position of the main piston, and for the valve actuator to be operable to direct pressurised air to either of the two inlets operatively to move the main piston from the first to the second position when air supply is directed to the first inlet, and from the second position to the first position when airflow is directed to the second inlet.

There is further provided for the emulsion to be provided in the form of an elongate flexible container shaped and sized to fit inside the emulsion chamber, with the flexible container including an outlet at one end shaped and sized to extend into the exit of the emulsion container; and for the flexible container to be provided in a range of predetermined volumes each corresponding to a desired explosive matrix volume for a blast hole.

There is still further provided for the emulsion chamber to have an adjustable size determined by the position of the emulsion chamber piston within the emulsion chamber relative to its second end, with the emulsion chamber piston having a plurality of indexed positions, with each position corresponding to a predetermined volume of the flexible container. There is still further provided for the flexible container to include a flexible plastics material shell, and for the outlet of the flexible container to comprise a tube extending from the flexible container having an outer diameter smaller than the inner diameter of the emulsion chamber exit, allowing the tube to be extended into the exit and to be located within it with the flexible container being contained within the emulsion chamber.

There is still further provided for the laminar flow disrupting members to comprise a plurality of spiral members located within the barrel, each comprising a spiralled strip extending across the inner surface of the barrel inside for a predetermined length and with the end of a first spiral member being aligned substantially at a right angle to the start of a spiral member following it in the barrel.

There is further provided for each spiral member to extend in excess of 120° in respect of the orientation of its end to its start, preferably for its end to be orientated about 140° with respect to its start.

According to an alternative aspect of the invention there is provided for at least some of the spiral strips to be provided with apertures to allow emulsion and sensitizer to pass from one side of the strip to the other within the barrel;

alternatively, for at least some of the spiral strips to be provided with slots extending at least partly into it towards the centre of the barrel from the side walls of the barrel;

further alternatively, for the strips to be provided with ribs extending across the flow path of the emulsion and sensitizer.

According to a yet further aspect of the invention there is provided for at least some of the spiral strips to include two or more of the apertures, slots and ribs as defined above.

These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a sectional side elevation of a mixer and dispenser according to the invention; Figure 2 is a sectional side view of the barrel showing the mixer members in the barrel;

Figure 3 is a front-end view of the mixer and dispenser of Figure 1 ;

Figure 4 is a sectional view of the barrel of the mixer and dispenser of Figure 1 ;

Figure 5 is sectional view showing detail of the operation of the base to dispense emulsion and sensitizer; and

Figure 6 is a perspective view of person operating the mixer and dispenser.

DETAILED DESCRIPTION OF THE INVENTION

An explosive matrix mixer and dispenser (1 ) is shown in the drawings. It comprises a frame (2) that supports an emulsion dispenser chamber (3) and sensitizer dispenser chamber (4).

Each chamber (3, 4) is provided with a piston (5, 6) that is movable between a first end (3A, 4A) and second end (3B, 4B) thereof. Each chamber (3, 4) has an exit (7, 8) extending from its second end (3B, 4B) into a barrel (9) that extends from the frame (2).

The frame (2) supports a main piston (10) that is secured to the pistons (5, 6) of both the emulsion chamber (3) and sensitizer chamber (4). The main piston (10) is movable between a first position (1 1 ) and a second position (12) to simultaneously move the pistons (5, 6) from the first end (3A, 4A) to the second end (3B, 4B) to dispense emulsion (13) and sensitizer (14) contained within the two chambers (3, 4) through their exits (7, 8) respectively into the barrel (9).

The matrix mixer and dispenser (1 ) also includes drive means (15) for the main piston (10) and a control (16) for the drive means (15) to enable driving the main piston (10) from the first end (3A, 4A) to the second end (3B, 4B). The main piston (10) is located within a sealed cylinder (20) housed by the frame (2). The drive means (15) for the main piston (10) comprises a pressurised air supply (15) that connects to a 2-way switch, from where two air lines (15A, 15B) run to opposite ends of the sealed cylinder, entering the cylinder on opposite sides of the main piston (10).

The emulsion (13) is provided in the form of an elongate flexible container (17) shaped and sized to fit inside the emulsion chamber (3). The emulsion container (17) includes an outlet (18) at one end that is shaped and sized to extend into the exit (7) of the emulsion chamber (3), into the barrel (9). The emulsion container (17) is formed from a flexible plastics material, similar to nylon material casings used to package processed meat. In use, the emulsion container’s outlet (17) is opened and inserted into the emulsion chamber’s exit (7), which leads into the barrel (9). To provide space for the emulsion container (17) in the emulsion chamber (3) the piston (5) is moved to the first end (3A) of the chamber (3). This effectively loads the chamber (3) with emulsion (13). Movement of the piston (5) from the first end (3A) to the second end (3B) compresses the flexible emulsion container (17) and forces emulsion (13) from the container (17) through the chamber’s exit (7) into the barrel (9).

The sensitizer is provided in a container (19) that clips to the side of the mixer dispenser (1 ). The sensitizer container (19) includes an outlet which is in fluid communication with an inlet into the sensitizer chamber (4).

In use, the 2-way switch (16) is turned to the‘load’ position to direct air supply to the front (10B) of the cylinder (20). This forces the main piston (10) to move from its second position (10B) to its first position (10A), to the rear (10A) of the cylinder (20) by pressuring the cylinder (20) in front of it and this simultaneously moves the pistons (5, 6) from their second ends (3B, 4B) to their first ends (3A, 4A) of their chambers (3, 4) through the actions of the main piston (10) via stems (21 A, 21 B) onto the pistons (5, 6). The movement of the sensitizer chamber piston (6) draws a vacuum in the sensitizer chamber (4) which draws sensitizer from the sensitizer container (19) into the sensitizer chamber (4).

The 2-way switch (16) is then turned to the other position which is the‘dispense’ position, to direct pressurised air flow to rear of the base (10) in the frame cylinder (20).

The emulsion chamber piston (5) acts to compress the emulsion container (17) as described above. The sensitizer chamber piston (6) forces sensitizer (15) from the sensitizer chamber (4) through its exit (8) and through a tube (8A) connected to it into the barrel (9).

In this manner, the contents of the emulsion chamber (3) and sensitizer chamber (4) are simultaneously dispensed into the barrel (9). The volumes of the emulsion (13) and sensitizer (14) dispensed are rationed to comply with the desired mixing ratio of the specific explosive matrix. This is controlled by the relative volumes of the emulsion container (17) to the sensitizer chamber (4). With the sensitizer chamber (4) volume predefined the ratio is controlled by the volume of the emulsion container (17), and more specifically its diameter. The instantaneous volumes of emulsion (13) and sensitizer (14) dispensed into the barrel (9) remain consistent with their predetermined ratio for the specific explosive matrix. The actual volume of matrix dispensed by the mixer and dispenser (1 ) depends on the position that the pistons (5, 6) are placed in at the outset of a mixing and dispensing stroke. This can be controlled by positioning the pistons (5, 6) into various indexed positions, each corresponding to a specific volume of explosive matrix. The emulsion may be provided in a range of predetermined volumes, each corresponding to a predetermined matrix volume.

Once the emulsion (13) and sensitizer (14) are expelled into the barrel these components of the matrix have not yet been mixed. Simply expelling them from their chambers (3, 4) or the barrel (9) won’t mix them properly into the expelled paste. As shown in Figure 4, to achieve mixing the barrel (9) is provided with a series of mixing members (22). These are effectively laminar flow disrupting members, designed to interfere with the laminar flow of a fluid flowing though the barrel (9).

The preferred embodiment of mixing members (22) comprises a spiralled strip (22A) extending across the inside of the barrel (9) for a predetermined length. The end of a first spiral member (23) is aligned substantially at a right angle to the start (24) of a spiral member following it in the barrel.

Each spiral member (22) extends in excess of 120° in respect of the orientation of its end to its start. In this embodiment the end is orientated about 140° with respect to its start. This mixes emulsion and sensitizer within the barrel to form an explosive matrix. The barrel (9), has a diameter sized to fit into a blast hole to enable dispending of the explosive matrix within the blast hole.

In use and as shown in Figure 6, an operator (25) clips a sensitizer container (19) onto the mixer and dispenser (1 ) and connects it to a pressurised fluid supply line (15), typically pressurised air.

The operator positions the actuator valve in the‘load’ position to dispense sensitizer from the sensitizer container (19) into the sensitizer chamber (4). This will push back the sensitizer chamber piston (6), which also moves the main piston (10) to its first position (10A), and the emulsion chamber piston to its first end (3A). This loads the sensitizer chamber (4) and opens the emulsion chamber (3) for loading. Once the sensitizer chamber (4) has been fully loaded the valve actuator/trigger (16) is released. An emulsion container (17) is opened at its outlet (18) and placed into the emulsion chamber (3), with the outlet (18) located inside the chamber exit (7).

The valve is now turned to the‘dispense’ position and the actuator/trigger (16) activated again. The pressurised air (15) is now directed to the rear of the main piston (10) in the cylinder chamber (20), which drives the main piston forward from its first position (10A) to its second position (10B). This moves the pistons (5, 6) forward to expel the emulsion and sensitizer into the barrel (9).

Once the emulsion and sensitizer have been expelled and mixed in the barrel (9) to form explosive matrix, it dispenses from the end of the barrel (9) into the blast hole. When the chambers (3, 4) are empty, the valve it turned to the‘load’ position again and actuated. This again loads sensitizer into the sensitizer chamber (4) and resets the emulsion chamber to accept a fresh emulsion container. Once a new emulsion container has been loaded the process can continue. With the barrel still full of mixed emulsion and sensitizer, explosive matrix will be dispensed from the barrel (9) immediately when the actuator/trigger (16) is depressed.

When a mixing and dispensing session is completed, the mixer and dispenser (1 ) may be cleaned by clipping a container with neutral fluid instead of sensitizer and loading a flexible container with neutral paste instead of emulsion, and processing that through the mixer and dispenser (1 ). That allows the operator to expel any residual explosive matrix safely in line with current operating procedures.

It will be appreciated that the above embodiment is given by way of example only and is not intended to limit the scope of the invention. It is possible to alter aspects of this embodiment without departing from the essence of the invention.

It is for example possible for the spiral strips in the barrel to be provided with apertures to allow emulsion and sensitizer to pass from one side of a strip to the other within the barrel. A further alternative is for the strip to include slots extending at least partly into it towards the centre of the barrel from the side walls of the barrel. Further alternatively the strips to may include ribs extending across the flow path of the emulsion and sensitizer. A combination of two or more of these options may also be used. It is envisaged that this will further improve mixing. It is also possible to split the pressurised air supply line which connects to the front of the cylinder to also feed into the sensitizer container. This will still create the vacuum in the sensitizer chamber to draw sensitizer from the sensitizer container into the sensitizer chamber as described above, and this will be assisted by the pressurisation of the sensitizer container to feed sensitizer into the sensitizer chamber.