FIELD OF THE INVENTION

This invention relates to a lance used to mix and deliver an explosives matrix.

BACKGROUND TO THE INVENTION

Explosives are widely used in underground mining operations. These mines extend to great depths and their work faces may be located at great distances from their shafts. This necessitates continuous transport of explosives from secure storage areas to mine 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 pumpable emulsion explosives, also called an explosives matrix, have been developed as an alternative or replacement for traditional packaged explosives. Such pumpable explosives are insensitive to initiation prior to sensitization they are classified as UN Class 5.1 , and as such are free from many of the regulations imposed on Class 1 explosives.

The explosives 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 explosives 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 an explosives matrix into a blast hole is equally important to the mixing of the components to it to form the matrix. The optimum performance of such explosives matrix depends on thorough mixing of the base emulsion and sensitizer. Malfunction of an explosives matrix may occur for a number of reasons, one of which is insufficient mixing of the matrix components. This leads to unpredictability of blasting results, and may contribute to problems such as fragmentation, overbreak and dilution, which impacts on mine profitability by influencing, at least, downstream processing of mined ore. Predictability is essential for blasting operations, and an explosives matrix that is delivered into a blasthole in less than optimally mixed condition negatively affects blasting predictability.

OBJECTIVE OF THE INVENTION

It is an objective of the invention to provide an explosives matrix lance which at least partly overcomes the abovementioned problems.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided an explosives matrix lance comprising a housing provided with - attachment means for an emulsion supply tube and attachment means for a sensitizer supply tube,

a receiving chamber for receiving emulsion and sensitizer from an emulsion supply tube and a sensitizer supply tube operatively connected to the housing, and a delivery tube extending from the receiving chamber;

with the sensitizer supply tube attachment means extending into a sensitizer inlet having an opening located in the receiving chamber, and

with the delivery tube including a plurality of baffles to form an inline mixer for mixing emulsion and sensitizer to form an explosives matrix in the delivery tube for delivery thereof into a blast hole.

There is further provided for the housing to comprise a cylindrical tube, for the receiving chamber to include an emulsion receiving chamber and a sensitizer receiving chamber; with the emulsion receiving chamber comprising a right circular cylindrical passage extending from the emulsion supply tube attachment means;

with the sensitizer receiving chamber comprising a circular cylindrical venturi chamber with - an emulsion inlet extending from the emulsion receiving chamber,

a sensitizer inlet extending from the sensitizer supply tube, and

an outlet extending into the delivery tube. There is still further provided for the sensitizer inlet to comprise a right circular cylindrical tube extending at a right angle to the longitudinal axis of the venturi chamber,

with the sensitizer inlet tube terminating in an outlet end that is cut to form an end-face orientated at an angle to the longitudinal axis of the sensitizer inlet tube.

There is also provided for the outlet end of the sensitizer inlet tube to be cut at an angle of about 45° to the longitudinal axis of the sensitizer inlet tube, and preferably for the centre of the sensitizer inlet opening end-face to be located at a position where it intersects the longitudinal axis of the venturi chamber, and more preferably for the sensitizer inlet opening end-face to be directed at the outlet of the venturi chamber.

There is still further provided for the emulsion supply tube attachment means to comprise a screw threaded tube extending from the operative rear end of the housing, enabling a complimentary coupling at an end of an emulsion supply tube to be secured to it.

There is also provided for the baffles to comprise a series of members extending from the inner wall of the delivery tube towards the centre of the delivery tube, and with each of the baffles having at least one edge at least directed to the venturi chamber, operatively for emulsion and sensitizer that move through the delivery tube over the baffle edges to be deflected and mixed by the baffles, ad preferably for each baffle to have a curved surface at least partly facing the venturi chamber.

There is still further provided for the explosives matrix lance to include a handle and for the sensitizer inlet tube to extend at a right angle through a side wall of the lance adjacent the handle into the venturi chamber, with the sensitizer inlet tube having an inlet end that terminates in an elbow fitted with a screw threaded end directed towards the operative rear end of the housing, enabling a complimentary coupling secured to the end of an sensitizer supply tube to be secured to it an axial alignment with an emulsion supply tube secured to the rear end of the housing.

There is also provided for the delivery tube to include a nozzle extending from it, with the nozzle comprising a flexible tube.

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 photograph of an explosives matrix lance according to the invention, secured to emulsion and sensitizer supply tubes;

Figure 2 is a cross sectional side view of part of the lance of Figure 1 ; and

Figure 3 is a sectional end view of the inside of the lance of Figure 1.

DETAILED DESCRIPTION OF THE INVENTION

An explosives matrix lance (1) according to the invention comprises a housing in the form of a cylindrical tube (2). The tube (2) includes, at an operative rear end thereof, attachment means (3) for an emulsion supply tube (4), a handle (5), and attachment means (6) for a sensitizer supply tube (7), and a delivery tube (8) at the operative front end of the lance (1).

The attachment means (3) for the emulsion supply tube (4) comprises a screw threaded end to the tube (2) which allows a complimentary screw threaded coupling (9) on the end of the emulsion supply tube (4) to be screwed onto the rear of the lance (1).

The handle (5) is secured to the operative bottom of the tube (2) with the attachment means (6) for the sensitizer supply tube (7) extending from the tube (2) to the operative rear of the handle (5). This attachment means (6) includes a screw threaded end which allows a complimentary screw threaded coupling (10) on the end of the sensitizer supply tube (7) to be screwed to the lance (1).

The delivery tube (8) includes at its opposing operative front end a flexible delivery nozzle (15) that is extendable into a drilled blasthole (not shown) to allow mixed and sensitised explosives matrix to be pumped directly into such a blast hole.

The tube (2) includes a receiving chamber which comprises an emulsion receiving chamber (11) and a sensitizer receiving chamber (12).

The emulsion receiving chamber (11) comprises a right circular cylindrical passage (16) extending from the emulsion supply tube attachment means (3). The sensitizer receiving chamber (12) comprises a circular cylindrical venturi chamber (17) extending from the emulsion receiving chamber (11) to the delivery tube (8). The venturi chamber (17) has an emulsion inlet (20) extending from the emulsion receiving chamber

(11), a sensitizer inlet opening (14) extending from a sensitizer supply tube (13), and an outlet (21) extending into the delivery tube (8).

The emulsion receiving chamber (11), sensitizer receiving chamber (12) and delivery tube (8) are all axially aligned. The emulsion receiving chamber (11) and delivery tube (8) have similar internal diameters. The sensitizer inlet opening (14) is located centrally in the sensitizer receiving chamber (12), i.e. centrally in the venturi chamber (17).

The sensitizer attachment means (6) includes a sensitizer supply tube (13) that extends to a sensitizer inlet opening (14) that is located centrally into the sensitizer receiving chamber

(12). The sensitizer inlet opening (14) is provided with an angled end-face (19), which directs the sensitizer inlet opening end-face (19) into the venturi chamber and longitudinally aligned with it. The end-face (19) is directed at the outlet of the venturi chamber, i.e. at the delivery tube (8).

The delivery tube (8) is provided with an in-line mixer (18) which includes a plurality of baffles inside the delivery tube (8).

In use, emulsion and sensitizer supply lines (4, 7) are connected to the emulsion attachment means (3) and the sensitizer attachment means (6) respectively. Emulsion and sensitizer are supplied in a predetermined ratio for the and sensitizer to correctly sensitize the emulsion.

Emulsion enters the lance (1) through the emulsion attachment means (3) and moves through the rear of the tube (2) into venturi chamber (12). Sensitizer enters the lance (1) through the sensitizer attachment means (6) and out of the sensitizer inlet opening (14) into the centre of the emulsion that fills the venturi chamber (12).

Due to the venturi effect an area of relative low pressure is created in the venturi chamber (12) which assists in drawing sensitizer into the centre of the stream of emulsion passing through the venturi chamber (12). If the opening (14) was directed in the opposite direction, i.e. at the inlet of the venturi chamber, a high pressure zone would be created at the opening (14) which would inhibit flow of sensitizer into the sensitizer receiving chamber (12). Since the sensitizer is delivered into the centre of the stream of emulsion and directed to be longitudinally aligned with the flow of the emulsion through the venturi chamber (17), the sensitizer is positioned centrally inside the stream of emulsion before it reaches the in-line mixer (18).

The combined emulsion and sensitizer stream, which creates an explosives matrix stream, is then mixed by the in-line mixer (18) with the shearing action that the baffles of the in-line mixer delivers onto the matrix stream. Through repeated passages over baffles the matrix stream is repeatedly separated and mixed. By the time the matrix stream reaches the front end of delivery tube (8) it is completely mixed. This means the sensitizer is uniformly distributed through the emulsion which enables the emulsion to provide reliable and predictable explosive performance. It will be appreciated that the embodiment described above 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 the embodiment without departing from the essence of the invention.