GB2083527A - Blasting - Google Patents

Abstract

The invention provides an apparatus and method for initiating an explosive which has been loaded into a hole or series of holes. The apparatus includes a holder for a detonator, alignment means for bringing the holder and detonator into register with the hole, and urging means for urging the detonator from the holder into the hole. The method involves, correspondingly, inserting a detonator into a hole by bringing the detonator in a holder into register with the hole, urging the detonator into the hole and initiating the detonator.

Description

SPECIFICATION Method and Apparatus for Initiating an Explosive This invention relates to an apparatus and method for initiating an explosive. In particular, the invention relates to an apparatus and method suitable for initiating a slurry-type explosive which has been loaded into a hole drilled in rock.

According to the invention an apparatus for intitiating an explosive which has been loaded into a hole includes a holder for a detonator, alignment means for bringing the holder and detonator into register with the hole, and urging means for urging the detonator from the holder into the hole.

The apparatus may include a plurality of the holders, arranged in series, the alignment means being adapted to bring the holders sequentially into alignment with th.e urging means to permit the urging means to act on the detonators held thereby, in sequence.

The holders may be provided on a belt mounted on alignment means in the form of a rotatable reel arrangement and the holders may extend substantially transversely to the length of belt, being evenly spaced along the belt, in the fashion of a cartridge belt.

Typically the holders will be arranged to hold elongated detonator or elongated detonator elements of which the detonators form part. Use of the elongated detonators or elements permits them to be thrust into explosive, such as a slurry explosive, of suitable consistancy loaded into the hole.

The urging means may be arranged so that operation thereof advances the belt along the reel arrangement, and the urging means may be a reciprocable plunger arranged to urge each detonator from its holder and into the loaded hole.

The apparatus may include detonating means for detonating each detonator after it has been urged into its hole and the apparatus may be adapted to initiate explosive in two (or more) holes simultaneously, the apparatus including e.g.

two holders or two series of holders, two alignment means and two urging means.

Further according to the invention a method of initiating an explosive which has been loaded into a hole, includes inserting a detonator into the hole by bringing the detonator in a holder into register with the hole, urging the detonator from the holder and into the hole, and initating the detonator.

Urging the detonator from the holder and into the hole may be by means of a reciprocable plunger.

The method may include successively bringing a plurality of detonators held in holders in series respectively into register with a series of loaded holes, successively urging them from their holders and into the holes, and successively initiating the detonators. Thus the holders may be mounted on a belt, bringing the holders successively into register with the loaded holes being by moving the belt over a rotatable reel arrangement.

The method may include moving an apparatus on which the holders are mounted along a series of loaded holes and by indexing the apparatus with regard to the holes. The apparatus as a whole may thus be mobile and indexable, or mountable on a mobile carriage which is indexable.

Each detonator may be detonated after it has been urged into its hole, and before a subsequent detonator is urged into its hole.

The method may include simultaneously bringing two or more detonators in separate holders into register with separate holes, urging the detonators simultaneously into the respective holes and initiating the detonators simultaneously.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows in side elevation an apparatus in accordance with the invention for initiating an explosive; Figure 2 shows a plan view of the apparatus of .Figure 1; Figure 3 shows a section in the direction of line Ill-Ill in Figure 1; Figure 4 shows a section in the direction of line IV--IV in Figure 1; Figure 5 shows a detail, in end elevation, of one of the reels of the apparatus of Figure 1; and Figure 6 shows a side elevation of the detail of Figure 5.

In Figures 1 to 4 of the drawings, reference numeral 10 generally designates apparatus in accordance with the invention for initiating an explosive and suitable for initiating a slurry-type explosive which has been loaded into a pair of holes drilled in rock. The apparatus in fact thus comprises two essentially similar units, one above the other, the upper one being for initiating explosive in the upper hole of the pair, and the lower one for initiating explosive in the lower hole. The apparatus is for use where the upper hole in the rock is substantially horizontal and the upper unit is thus horizontally aligned, while the lower hole in the rock will slope inwardly and downwardly away from the upper hole at an angle "A" to the horizontal.The lower unit is thus inclined at the angle "A" to the upper unit (see Figure 1) but the units are otherwise essentially similar in function and construction and are arranged to operate simultaneously. The apparatus comprises a frame 12 which, as described hereunder, will in general be mounted on a movable carriage, the frame being enclosed by a housing 13 and supporting said pair of units, each unit comprising a plurality of holders (described hereunder with reference to Figures 5 and 6) for detonators, alignment means, generally designated 14, for bringing the holders and detonators into register with a hole drilled in rock loaded with slurry explosive, and urging means, generally designated 16, for urging the detonators respectively into said loaded holes.

The urging means 16 comprises a reciprocable plunger 1 8 mounted on a carriage 20 which is movable lengthwise along a rotatable, externally screw-threaded shaft 22, the carriage 20 having a correspondingly screw-threaded passage therethrough engaging with the shaft 22.

The shaft 22 is provided with a pulley 24 driven by means of a V-belt 26 passing around the pulley of a high speed reversible and brakeable electric motor 28. The carriage 20 is slidable lengthwise along a guide rod 30 parallel to the shaft 22, which passes through a passage in the carriage 20 to prevent any rotation of the carriage as a whole around the shaft 22.

The alignment means 14 comprises a rotatable reel arrangement 32 and an indexing mechanism 34.

The reel arrangement 32 comprises two rotatable reels (described in more detail hereunder with reference also to Figures 5 and 6), namely a feed reel 36 and a takeup reel 38. The reels 36, 38 rotatably mounted about axes parallel to the shaft 22, and are replaceable by means of quick-release mechanisms 40.

The reel arrangement 32 further comprises an indexing drum 42, parallel to the reels 36, 38, and rotatable together with them.

The drum 42 and the reel 38 are driven by a toothed bolt 55 passing respectively over a pulley and overspeeding slipping clutch arrangement 46 on the reel 38, and a pulley 48 on the drum 42.

The reel 36 is in turn provided with a clutch dragging mechanism, and a tensioning pulley 49 acts on the belt 44 between the reel 38 and drum 42.

The indexing mechanism comprises a drum 50 having a pulley 52 engaging with the belt 44, the drum 50 being rotatable about an axis parallel to the reels 36, 38 and drum 42.

The drum 50 has a zig-zag slot (shown diagrammatically in broken lines by reference numeral 54 in Figures 1 and 2) along its outer curved surface. The slot 54 opens radially outwardly and is endless and extends circumferentially around the drum 50, zig-zagging from one end of the drum towards the other, and is shaped and profiled to provide, as described hereunder, for unidirectional rotation of the drum 50.

The indexing mechanism 34 further comprises a carriage 56 which is slidable lengthwise along guide rods 58, which are parallel to the shaft 22, and which pass through passages in the carriage 56. A pin 60, mounted on the carriage 56, engages the slot 54 on the drum 50, and the carriage 56 is resiiiently biassed by biassing means in the form of a coil spring (not shown) along the rods 58 towards the reel arrangement 32 (Figures 1 and 2). The carriage 20 has a stop member or abutment 62 which engages a stop member or abutment 64 (Figure 1) on the carriage 56. The biassing means biasses the abutment 64 against the abutment 62 when the carriage 20 is at the end of the shaft adjacent the motor 28.The carriage 20 being movable along the shaft 22 to move the abutment 62 away from the abutment 64, to enable the carriage 56 to move towards the reel arrangement 32 under the influence of its biassing means.

In Figures 5 and 6, one of the reels 36 is shown in more detail, having wound around it a belt 66 which carries, spaced along its length, a plurality of holders 68 for detonator elements 70. The belt 66 comprises a flexible backing member 72, and has mounted on the backing member 72 a series of the holders 68 extending along opposite edges thereof, as well as series of the holders 68 at a cental position across its width. Three series of the holders 68 are shown, but it will be appreciated that there may be more if desired, the series being spaced from one another across the width of the belt 66.

Each holder 68 comprises a bar which is roughlyT-shaped in transverse cross section, as seen in Figure 5, the upright or the limb of the T being fast with the backing member 72, and the arms of the T extending parallel to the length of the belt 66. The holders 68 are arranged in series extending normal to the belt and alongside one another, and the corners between the arms and limb of each member 68 are rounded to define spaces in which the detonator elements 70 are located and held by said arms against the backing member 72. When the belt 66 is flexed around a drum or pulley with the backing member 72 on the inside, for example when the belt is curved around the drum 42, the detonator elements 70 are axially slidable in the spaces defined between the backing member 72 and the limbs and arms of the adjacent holders 68 in which they are located.The belt 72 has, along its opposite side edges and mounted on its inside, a pair of toothed belts 71 engageable in use with toothed pulleys 73 at opposite ends of the drum 42.

In use, a belt 66 will be loaded with a plurality of detonator elements 70, each detonator element comprising an elongated plastics or metal tube 74 with a detonator 76 crimped to one end thereof as at 78. Lead wires (not shown) extend from the detonators 76 along the interiors of the tubes 74, to the ends of the tubes 74 remote from the detonators 76, where said lead wires are respectively connected to a pair of conductors 80 on the outsides of the respective tubes 74. In this regard, it will be noted from Figure 6 that the belt 66 has, adjacent its edge remote from the detonators 76, a conductive strip 82 which short-circuits the conductors 80 to guard against accidental detonation of the detonators 76.

In use, the detonator elements 70 will be loaded into position, as shown on the belt, and the belt will be wound around the reel in question, which will be the reel 36 shown in Figures 1 to 4.

The reel 36 is placed in position as shown in Figures 1 to 4, by operating its quick-release mechanism 40, and the belt 66 will be passed around the drum 42 and thence to an empty reel which, in use will be the reel 38 shown in Figures 1 to 4, to which it is connected. Rotation of the reel arrangement 32 in the direction of arrow 84 (Figure 3) will cause the belt 66 to pass from the reel 36, over the drum 42 and onto the reel 38, as described hereunder.

It will be appreciated that the description above has been directed principally at one of the units, but that their construction and function (described hereunder) is essentially similar.

In use, the apparatus 10 will be mounted, for example, on a carriage (not shown) movable along a rock fac,e in which pairs of vertically spaced holes have been drilled, and loaded with slurry explosive. The upper hole of each pair is horizontal, the lower sloping downwardly by the angle "a". In this regard, the apparatus 10 has a guard member in the form of a robust metal plate 86, and the belt 66 will be fitted so that the detonators 76 are at the ends of the reels 36, 38 and drum 42 adjacent the metal plate 86. The metal plate will have an opening axially in register with the plunger 18. The apparatus will further be protected by barricading or shielding, independently mounted between the plate 86 and the rock wall to be blasted, with access therethrough for detonators, in line with the plunger 1 8.

The carriage on which the apparatus 10 is mounted, will be accurately indexable so that each opening through the plate 86 and each plunger 1 8 are simultaneously aligned, successively, with the pairs of holes loaded with slurry explosive in the rock face to be blasted The toothed belt 44 and drum 50 with its slot 54 of each unit will be arranged in conjunction with the pin 60, and in conjunction with the belt 66 passing over the reels 36, 38 and drum 42, so that one of the detonator elements 70 is aligned directly in register with its opening through the plate 86, and axially aligned with its plunger 18, opposite the loaded hole in the rock face, when the carriages 20 and 56 have moved forward, as described hereunder, from their positions shown in Figures 1 and 2, and when the plunger 18 is closely approaching drum 42.

The electric motors 28 are then operated rapidly and simultaneously to rotate the shafts 22 to carry the carriages 20 towards the plate 86.

The plungers 18 then engage the ends of the detonator elements 70 remote from the detonators 76, and urge said elements 70 with their detonators 76 into the loaded holes in the rock face, to a desired depth. Each motor 28 is then braked to a standstill and a solenoid 87 actuated to bring a pair of electrical dontacts 88 into contact with the conductors 80. With contact between the contacts 88 and conductors 80 a firing pulse triggered as required through the contacts will cause initiation of the detonator 76 in question. This intitiates the explosive in the hole in the rock face.

In this regard, it will be appreciated that the plate 86 will be of robust construction, and the plunger 18 can be arranged so that it together with the adjacent end of the element 70 closes off the hole or passage through the plate 86, the plunger 1 8 being sufficiently robust together with the separate barricading used, to prevent any damaging effects of the blast from passing inwardly through said opening in the barricading 86 to the apparatus. Subsequent to the initiation, operation of each motor 28 in the forward direction causes the associated plunger 1 8 to move the stub of the spent element 70 (which has acted as a blast buffer) out of the hole through the plate 86. The motor 28 is then reversed to effect withdrawal of the carriage 20 and plunger 18, leaving said hole open.

As the carriage 20 moves towards the plate 86, it permits the carriage 56 likewise to move in the same direction under the influence of its biassing means. The slot 54 will be shaped and profiled so that it varies radially in depth and so that during said forward movement the drum 50 rotates about its axis in the direction of arrow 90 (Figure 3) by a desired amount. As the carriage 20 returns to its position shown in Figures 1 and 2, upon reverse operation of motor 28, the stop 62 will engage the stop 64. This moves the carriage 56 back to its position shown in Figures 1 and 2 against the bias of the biassing means, moving the pin 60 along the next or return limb of the zigzag of the slots 54.The shape of the slot 54 and the profile of the zig-zag is arranged so that upon such return movement, the drum 50 does not rotate (although for ease of illustration the zig-zag slot 54 is not shown, as it should be, with its return limb parallel to the axis of the drum 50).

Rotation of the drum 50 rotates the drum 42 via the belt 44 so that the next detonator element 70 is placed in register with the plunger 18 and the opening through the barricading 86. This is done by the toothed pulleys 73 on the drum 42 acting on the toothed belts 71 at the edges of the belt 66. The belt 44 also rotates the pulley and overspeeding clutch arrangement 46 on the reel 38 so that the belt 66 is taken up on to the reel 38 while tension is maintained in the belt 66. At the same time, the clutch dragging mechanism on the reel 36 maintains belt tension between the reel 36 and drum 42, as the belt 66 is wound off the reel 36.

The carriage on which the apparatus 10 is mounted is then or in the meanwhile indexed to the next pair of loaded holes in the rock face, and the above sequence is repeated.

When the belts 66 have all their detonators detonated, the reels 36, 38 will then appropriately be replaced by new reels, the take-up reels empty and the feed reels provided with new belts 66 loaded with detonators 70.

The present invention permits the use of a multitude of different types of electrically initiated detonators, and as the invention permits heavy electric currents to be supplied to the detonators, limitations to currents set by conventional circuit requirements are overcome.

Claims (14)

Claims

1. An apparatus for initiating an explosive which has been loaded into a hole, which apparatus includes a holder for a detonator, alignment means for bringing the holder and detonator into register with the hole, and urging means for urging the detonator from the holder into the hole.

2. An apparatus as claimed in claim 1, which includes a plurality of holders, arranged in series, the alignment means being adapted to bring the holders sequentially into alignment with the urging means to permit the urging means to act on the detonators held thereby, in sequence.

3. An apparatus as claimed in claim 2, wherein the holders are provided on a belt mounted on alignment means in the form of a rotatable reel arrangement.

4. An apparatus as claimed in claim 3, wherein the holders extend substantially transversely to the length of belt and are evenly spaced along the belt.

5. An apparatus as claimed in claim 3 or claim 4, in which the urging means is arranged so that operation thereof advances the belt along the reel arrangement.

6. An apparatus as claimed in any one of the preceding claims, wherein the urging means is a reciprocable plunger arranged to urge each detonator from its holder and into the loaded hole.

7. An apparatus as claimed in any one of the preceding claims, which includes detonating means for detonating each detonator after it has been urged into its hole.

8. An apparatus as claimed in any one of the preceding claims, which is adapted to initiate explosive in two holes at a time, the apparatus including two holders or two series of holders, two alignment means and two urging means.

9. An apparatus for initiating an explosive which has been loaded into a hole, substantially as herein described and illustrated.

1 0. A method of initiating an explosive which has been loaded into a hole, which includes inserting a detonator into the hole by bringing the detonator in a holder into register with the hple, urging the detonator from the holder and into the hole, and initiating the detonator.

11. A method as claimed in claim 10, which includes urging the detonator from the holder and into the hole by means of a reciprocable plunger.

12. A method as claimed in claim 10 or 11, which includes successively bringing a plurality of detonators held in holders in series respectively into register with a series of loaded holes, successively urging them from their holders and into the holes, and successively initiating the detonators.

13. A method as claimed in claim 12, in which the holders are mounted on a belt, bringing the holders successively into register with the loaded holes being by moving the belt over a rotatable reel arrangement.

14. A method as claimed in claim 12 or claim 13, which includes moving an apparatus on which the holders are mounted along a series of loaded holes by indexing the apparatus with regard to the holes.

1 5. A method as claimed in any one of claims 12 to 14, wherein each detonator is detonated after it has been urged into its hole, and before a subsequent detonator is urged into its hole.

1 6. A method as claimed in any one of claims 10 to 1 5 inclusive, which includes simultaneously bringing two or more detonators in separate holders into register with separate holes, urging the detonators simultaneously into the respective holes and initiating the detonators simultaneously.

1 7. A method of initiating an explosive which has been loaded into a hole, substantially as herein described and illustrated.