Abstract
A spool for use in a blasting system which carries a coiled signal-transmitting conductor which is connected at one end to a detonator and at an opposed end to a connector.
Claims
1. An apparatus for use in a blasting system which includes a spool with a hub, first and second discs which are mounted to the hub, an elongate flexible signal-transmitting conductor which has a first end and a second end and which is coiled on the hub between the discs, at least a first detonator which is connected to the signal-transmitting conductor at or near the first end, a connector device which is connected or exposed to the signal-transmitting conductor at or near the second end, wherein the signal-transmitting conductor includes spaced-apart markings or formations and wherein the spool includes a sensor, responsive to passage of a marking or formation past the sensor to produce a measure of a length of the signal-transmitting conductor which is uncoiled from the hub and a release mechanism which, in use, permits a degree of rotation of the spool or movement of the conductor when a tensile force exerted on the conductor increases above a predetermined level, thereby to reduce the level of the tensile force exerted on the conductor characterised in that the connector device includes, wholly located inside the hub, a transmitter/receiver module, a battery and a processor and, on one of the discs, connector formations which are adapted to establish communication with a control device.
2. An apparatus according to claim 1 wherein the signal-transmitting conductor is selected from the following: electrical leads, a fibre-optic cable, and a shock tube.
3. An apparatus according to claim 1 which includes at least one light emitting device which is used to indicate the physical location of the spool.
4. An apparatus according to claim 1 wherein the transmitter/receiver module communicates an identity which is uniquely associated with the detonator.
5. An apparatus according to claim 1 wherein the transmitter/receiver module is capable of receiving a signal and, in response to the reception of such signal, of transmitting a reply.
6. An apparatus according to claim 1 which includes at least one sensor which is responsive at least to environmental or operative conditions including temperature, vibration, a specific chemical or chemicals.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention is further described by way of examples with reference to the accompanying drawings in which:
(2) FIG. 1 is a side view of an apparatus according to a first form of the invention,
(3) FIG. 2 depicts in cross-section an apparatus according to a variation of the invention,
(4) FIG. 3 is a side view, partly sectioned, of an apparatus according to another form of the invention,
(5) FIG. 4 is similar to FIG. 3 illustrating an apparatus according to a different form of the invention, and
(6) FIG. 5 depicts a portion of a signal-transmitting conductor which can be used in the apparatus of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
(7) FIG. 1 of the accompanying drawings illustrates an apparatus 10 according to the invention. The apparatus includes a spool 12 on which is coiled an elongate, signal-transmitting conductor 14. By way of example the signal-transmitting conductor could be an electrical wire or a number of electrical wires, a shock tube, a fibre-optic cable or the like. A requirement in this respect is that the signal-transmitting conductor should be capable of transmitting a signal to a detonator 16 which is connected to the conductor at or close to a first end 18 of the conductor.
(8) The spool includes a hub 24 with a centrally positioned passage 26. Two discs 28 and 30 are spaced apart from each other and are fixed to the hub. The discs bound an annular space 34 within which the conductor 14 is coiled.
(9) Referring again to FIG. 1 a second end 38 of the conductor 14 is coupled to a connector 40 which, preferably, is of the type described in the specification of international application No. PCT/ZA2015/050022. This connector (see FIG. 2 as well) includes a power source 54, a radio transmitter/radio receiver module 52, a processor/logic unit 56 and terminals 68 which are mounted in or to a housing 44 which, preferably, is flush with an outer surface 46 of one of the discs 28, 30.
(10) In use of the apparatus 10 the spool which is preferably integrally moulded from a suitable inexpensive plastics material is transported to a site of use and the detonator 16, suspended from the conductor 14, is then lowered into a borehole (not shown) to a desired depth. Thereafter the borehole is charged with an explosive material.
(11) The connector 40 is coupled to a bus on the surface which is also connected to a control device, as is known in the art. Alternatively the connector 40 can be used to establish wireless communication, i.e. without physical conductive links, with the control device—again using techniques which are known in the art.
(12) An advantage of using the apparatus 10 is that the coiled conductor 14 is kept at all times in a neat and tidy configuration on the hub. The likelihood that winding of the conductor which is deployed from the hub upon rotation of the spool, can become entangled with one another, is much reduced.
(13) FIG. 2 illustrates an apparatus 10A, in cross-section, which comprises a variation of the arrangement shown in FIG. 1. A detonator, not shown, is connected to an end of a signal-transmitting conductor 14 which is coiled on the hub 24. The hub is enlarged in that it defines an annular cylindrical cavity 50 in which components, corresponding to those listed in connection with the connector 40, are mounted. Thus the tubular hub contains a transmitter/receiver module 52, a battery 54 and a processor 56. Two light emitting devices, e.g. LED's, 58 and 60 which are mounted to the discs 28 and 30 respectively can be powered under controlled conditions by energy drawn from the battery 54. Optionally, a photo-voltaic cell 64 which is mounted to one of the discs is used to recharge the battery 54, when the cell is exposed to sunlight conditions.
(14) Connector formations 68 are provided on one of the discs. These connector formations duplicate connector formations which are provided on the connector 40. In essence therefore the connector 40 which is shown in FIG. 1 is wholly mounted to the spool 12. Additionally the light-emitting diodes 58 and 60 mounted to the discs are coupled to the connector components.
(15) In a broad sense the apparatus 10A is used in the same way as the apparatus 10 in that the conductor 14 is deployed from the spool to a required length as may be necessary to position a detonator, which is attached to the connector, at a desired position inside a borehole. During this process a short axle (not shown) placed through the passage 26 allows the spool to be rotated thereby to facilitate uncoiling of the conductor. Connections in the blasting system are then made via the formations 68.
(16) If the apparatus 10A is interrogated from a remote control location then the light-emitting diodes 58 and 60 can be caused to pulse so that physical indications are given of the location of the spool. Alternatively or additionally a radio signal can be transmitted so that the spool can easily be located. This radio signal can also carry identity data pertaining at least to the detonator which is attached to the conductor.
(17) FIG. 3 illustrates a variation 10B of the apparatus of the invention. A spool 12A is mounted for rotation about an axle 70 which in turn is supported on a stand 74 which is fixed, using suitable fasteners 76, to the ground 80 adjacent a borehole 82. The conductor 14 passes through a guide 84 which is mounted to the stand 74. A further guide 86 is used to position the conductor correctly in relation to the borehole 82. When the detonator 16 is at a desired depth inside the borehole explosive material, not shown, is placed into the borehole to cover the detonator and that portion of the conductor 14 which is inside the borehole. As explained in the preamble hereof frictional and loading forces exerted by the explosive on the conductor and directly on the detonator can cause the conductor to elongate in a longitudinal direction of the borehole. The tensile forces can be so great that the tensile strength of the conductor is exceeded and, in this event, the conductor breaks. To reduce the likelihood of this unfortunate event occurring the apparatus 10B includes an annular, centrally located, cylindrical cavity 90 which has a number of inwardly directed formations 94 on an inner surface. The axle 70 has a number of flexible or resilient leaves 96 which are brought into contact with the various formations 94. The arrangement is such that the leaves prevent free rotation of the cavity 90 about the axle 26. However, when the explosive exerts a tensile force F on the conductor and detonator, and the magnitude of the force F approaches the ultimate tensile strength of the conductor, the flexible leaves are deflected, automatically, by the formations 94 and a degree of rotation of the spool takes place which causes the tensile force in the conductor to be reduced. If the tensile force increases then the release mechanism again functions and the spool can rotate, in the manner described, through a limited arc to reduce the magnitude of the tensile force prevailing in the conductor.
(18) FIG. 4 shows an apparatus 100 which bears a number of similarities to the apparatus 10B. However the release mechanism 88 is replaced by a movement-restricting device 100 which, in this example, is mounted on the ground at a mouth of the borehole 82. The device 100 can take on different forms and conveniently comprises a plate 106 with a compressible friction component 110 mounted to the plate. The conductor 14 passes through a hole in the component 110 and in the plate 106. If the component 110 is compressed in a radial direction, as is indicated by arrows 112, then a frictional force is exerted on an outer surface of the conductor which tends to lock the conductor to the plate. The force is such that free movement of the conductor through the plate is inhibited. However if a tensile force is exerted on the conductor by the explosive in the hole then, once a limiting tensile force is reached, the frictional braking action of the component is exceeded and the conductor can move into the hole thereby to reduce the tensile force prevailing in the conductor.
(19) The apparatus of the invention can also include a measuring device which facilitates a determination of a length of the conductor 14 which is placed into a borehole 82. Referring for example to FIG. 5 the conductor 14 can include a plurality of formations 116 at spaced apart and regular intervals. When the conductor is deployed from the spool (not shown) the formations pass a sensor 120 which detects, physically, the presence of the enlarged formations and a count is established of the number of formations which pass the sensor 120. The depth to which the detonator is placed into the borehole can then be assessed. In a variation of this idea the formations are replaced by markings on the conductor 14 and an optically based sensor 120 then detects the passage of the markings in a contactless manner which enables a count to be kept of the depth to which a detonator is placed in a borehole.
