MXPA01007292A - Accumulated detonating cord explosive charge and method of making and of use of the same - Google Patents

Abstract

An initiator (14c) for a secondary explosive receptor charge is provided by forming a length of detonating cord (14) into a helical coil containing a plurality of windings with a cut-off barrier provided by e.g., a separating rib (46) between adjacent windings. The adjacent windings may be not more than about 0.5 inch (12, 7 mm) apart. The detonating cord (14) may be wound about a spindle (16) which may optionally provide the separating rib (46). The coil may be a tapered coil which may define a taper angle of e.g., from about 2 to 4 degrees. Alternatively, the coil may be a cylindrical coil, or the cord may be configured in a planar spiral. Optionally, the detonating cord in the helical coil may have a core of explosive material with a loading of less than 15 grains per foot of the cord, e.g., less than 12 grains per foot of the cord, or a loading in the range of from 8 to 12 grains per foot of the cord. The coil may consume about six inches of the cord. Conversely, the detonating cord in the spiral may have a core of explosive material with a loading of at least 2.5 grains per foot, optionally at least 15 grains per foot of the cord.

Description

ACCUMULATED EXPLOSIVE LOAD OF DETONATOR MINT AND METHOD TO MAKE AND USE THE SAME DESCRIPTION OF THE INVENTION This application claims the benefit of the provisional North American application serial number 60/116/493, filed on January 20, 1999, entitled "LOW-ENERGY DETONATING CORD ACCUMULATOR AND METHOD FOR INITIATION OF EXPLOSIVE CHARGES. "The present invention relates to a device and method for forming an explosive charge and an explosive of detonating fuse and for the initiation of receivers such as signal transmission lines and explosive charges. It is known that explosive initiation systems Prior to the prior art, an explosive for launch initiator charge descends into a borehole having a cover cavity into which an electric detonator has been inserted.The electric detonator is conditioned with electrically conductive detonator wires that are long enough To extend from the borehole to the blasting surface, the long detonator wires of such systems are expensive and tend to break when descending and place the initiating launching charges in the borehole. primary explosive of the detonators with the initiating charges Secondary explosive launching in the borehole increases handling risks in relation to starter loads that do not contain primary explosive materials. It is also known in the art to use, instead of electrically conductive detonator wires, high-energy, down-line detonator cords to initiate launch initiator charge explosives. Such high-energy detonator cords typically have explosive core charges of approximately 3.8 to 10.6 grains per linear meter of wick ("g / m"), equivalents of 18 to 50 grains per linear foot of wick ("gr / ft") of pentaerythritol tetranitrate ("PETN") or equivalent amounts, in terms of explosive power, of another secondary explosive. Such a high-energy detonating wick is used in the mining industry to initiate launch initiator charge explosives without the intervention of a detonator between the downline detonator wick and the initiating launch charge. In mining operations, however, the high-energy detonating wick tends to interrupt the voluminous (main) explosive charge and is expensive when compared to the low-energy detonating fuse. In seismic explosion operations, the use of the high-energy detonating wick is not satisfactory because the high-energy detonating wick releases significant energy along remote paths from the points at which the energy is released by the charges initiators, and therefore provides less accurate seismic data. It is also known to use a low energy detonating wick to directly initiate (without a detonator or the like) an explosive charge containing a sensitive explosive against which a low energy detonating wick is placed and which is in contact or near of an explosive charge comprising a less sensitive explosive, for example, a secondary one. This arrangement requires the use of a more sensitive explosive together with a less sensitive one, increasing the risk of accidental initiation of the explosive charge. The American Patent 5,714,712, issued to Ewick et al, describes an explosive initiation system that improves many of the above-mentioned problems directly by connecting a low-energy detonating wick to the initiating charge explosive. The system of US Patent 5,714,712 is especially useful for initiating a plurality of substantially simultaneous seismic detonations and includes an electric main line circuit placed on the surface of a trigger site containing boreholes, within which initiating charges are placed. The initiator charges 30a-30b (Figure 1 of U.S. Patent 5,714,712) are connected without detonators intervening to the ends located at the bottom of the drilling of equal size lengths of low energy fuse 28a-28d detonator, the surface ends of which are connected to the electric detonators contained within blocks 24a-24d connectors, which are connected in series in the trip circuit. Figure 2 of U.S. Patent 5,714,712 illustrates a way to connect the bottom end of the bore of the low energy detonating wick 28a to an initiating load 30a by embedding a knotted end of the low energy detonating wick within the load 30th launch initiator. The knot provides a wick in a non-planar, non-cylindrical configuration. The embodiment of Figure 2 requires a factory setting to empty the explosive around the low knotted energy detonating wick and prevents the on-site cutting of the detonating wick to selected lengths from a reel. In the embodiment illustrated in Figures 2a and 2b, a wick retention member 41 is used to retain a double length of the low energy detonating wick inside a wick cavity 39 formed in the upper portion 32x of the initiating charge 30x. of launch. The embodiment of Figures 2a and 2b may be assembled in the field but may expose only a limited amount of low energy detonating wick to the initiating charge explosive. As used herein, the term "detonating wick" has its usual meaning of flexible scroll wick having a high explosive core, the wick having a secondary explosive, usually PETN. The term "low energy detonating wick" or "LEDC", conventionally used to mean a detonating wick that will not reliably initiate itself when placed in contact with itself by rolling or crossing lengths of the wick, and which will not initiate , when in a non-assembled configuration, directly reliably a secondary or less sensitive explosive receiving charge, for example, those that may comprise secondary explosive materials (e.g., mixtures of PETN Pentolite and trinitrotoluene ("TNT") to the Substantial exclusion of the primary explosive materials Such non-assembled configurations include, for example, simple surface-to-surface contact between an unrolled LEDC and a receiving charge and the insertion of the end of a substantially straight length of LEDC into a well in the body. of a receiving load, for this reason, the LEDC is typically used to start an amp device Higher sensitive high energy lifier as a detonator that is sensitive to LEDC (usually by virtue of containing a primary explosive material) and that generates a sufficient output signal to initiate the less sensitive secondary explosive receiving charge. The present invention provides a method for forming an explosive charge, the method comprising forming a length of detonating cord within a substantially helical coil comprising a plurality of windings with a shear barrier between the adjacent windings. According to various aspects of the invention, the method may comprise adjacent windings spaced no more than about 12.7 mm (0.5 inches) apart from one another, eg, about 3.3 mm (0.13 inches), the method may comprise wrapping the detonating wick around a spindle that can optionally comprise the cutting barrier; the method may comprise forming the length of the detonating wick in a tapered coil which may optionally define an inclined angle from about 2 to 4 degrees; or the method may comprise forming the length of the detonating wick in a cylindrical coil. According to another aspect of the invention, the detonating wick may have a core of explosive material with a load of less than 15 grains per foot of the wick. For example, the detonating wick may have a core of explosive material with a load of 12 grains or less per foot of the wick, or a load in the range of 8 to 12 grains per foot of the wick. According to yet another embodiment of the invention, the coil may comprise about 6 inches of detonating wick. This invention also provides a method for forming an explosive charge comprising forming a length of detonating cord in a substantially planar spiral comprising a plurality of windings. Optionally the detonating wick in the spiral may have a core of explosive material with a load of at least 2.5 grains per foot of the wick. The invention also provides an explosive charge comprising a length of detonating wick as described above placed in a substantially helical coil or a planar spiral configuration by the above method or any other means. According to one aspect of this invention, the initiator may comprise a spindle around which the coil is placed. The spindle may optionally be configured to support a substantially helical coil defining an inclined angle of about 2 to 4 degrees. The spindle can optionally comprise the cutting barrier. Alternatively, the spindle may be configured to support a substantially flat coil. In such an embodiment, the detonating wick may have a core of explosive material with a charge of at least 2.5 grains per foot of the detonating wick, optionally at least 15 grains per foot. The spindle may comprise a pair of plates between which the substantially planar spiral is placed. This invention is also related to a method for initiating an explosive receiving charge. The method comprises inserting within an explosive charge an initiator comprising a length of detonating wick placed in a spiral or helical coil as described above, and initiating the detonating wick. Optionally, the detonator wick may comprise a low energy detonating wick and optionally, the receiving charge and the initiator may be substantially free of primary explosive materials. This invention is also related to an accumulator spindle comprising a spindle body carrying a spiral cut barrier, the barrier defining a helical groove in the spindle body; and an anchor opening. The spindle may also comprise a projecting jaw. The helical groove can define an inclined angle of approximately 2 to 4 degrees. Also optionally, the notch may have two ends and the anchoring opening may be at one end of the notch and the protruding jaw may be at the other end of the notch.

Alternatively, the present invention can provide an accumulator spindle comprising a spindle body comprising two separate parallel plates; an anchor opening; and a protruding jaw. This invention further pertains to a receiver-initiator assembly comprising a receiving charge comprising a body of explosive material having an initiating cavity therein; and a flat or helical coil for detonating the wick placed inside the starter cavity. There may be a receiving portion associated with the body of explosive material, the helical coil may be mounted on a spindle and the spindle may be secured to the receiving portion. For example, the spindle can be secured to the receiving portion by a detent and notch coupling therebetween. Optionally, the helical coil and the initiating cavity each define an inclined angle of approximately 2 to 4 degrees. In any of the above embodiments, one or both of the initiator and receiver charges may be substantially free of primary explosive materials. As used herein, the terms "large" and "small" when used to refer to the detonating wick, including the LEDC, refer to the relative charge of explosive material in the core of the wick, one more wick small having less explosive material per linear unit and, consequently, a less powerful result than a larger wick. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of an assembly of a launch initiator charge and an LEDC initiator according to an embodiment of the present invention; Figure 2 is a partial perspective view of the accumulator shown in Figure 1; Figure 3 is a perspective view of an LEDC initiator according to a second embodiment of the present invention; Figure 4 is a cross-sectional view, enlarged in relation to Figure 3, taken along the line IV-IV of Figure 3; Figure 5 is a schematic side elevational view of an accumulator according to another embodiment of the present invention; Figure 6 is a cross-sectional view taken along line VI-VI of Figure 5; and Figure 7 is a schematic view of an initiating launch charge explosive configured to receive an accumulator according to the present invention positioned therein. Generally, the present invention provides improved reliability in the use of detonating wick, including a low energy detonating wick, as an explosive charge for various functions where a linearly straight line wick will not provide adequate output power. One such use is for the direct initiation of receiving charges such as a signal transmission line (for example, another detonating cord) or major explosive charges (for example, "initiating" charges used in boreholes at blasting sites) that they are composed of relatively insensitive explosive materials, for example secondary explosive material. The present invention provides initiator charges for such receiver charges produced by a method comprising configuring or "accumulating" the detonator wick within a coil comprising a plurality of windings to increase the amount of explosive material of the wick in a starter charge or other receiving device in relation to a linear configuration of the wick, and further provides devices in which the detonating wick can also be configured in this way. The device comprises an accumulator spindle for supporting the detonating wick in a spiral or helical configuration. As a result of the coiled configurations described herein, the amount of energy released by the detonating wick in a given initiating charge or other receiving device is increased relative to the substantially straight detonating wick that passes therethrough and the reliability of the detonating wick in direct initiating receiving charges, especially those that consist essentially of secondary or less sensitive explosive materials. Consequently, where the prior practice requires a detonating wick for a particular core charge for the reliable initiation of, for example, an initiating charge, the present invention allows the use of a detonating wick of a lower core charge with a reliability equivalent. For example, the prior art practice required 50 PETN grains per foot of the detonating wick to initiate a 50/50 Pentolite starter charge (50% PETN, 50% TNT), the present invention allows the use of detonating wick having a core load of 25 grains per foot. Similarly, where the prior art requires 25 grains per foot to initiate a 60/40 Pentolite initiator, the present invention allows the use of LEDC having a core charge in the range of about 6 to 10 grains per foot. As will be appreciated by those of ordinary skill in the art, the Pentolite 60/40 is more sensitive to initiation than the Pentolite 50/50 and also allows the use of a smaller core charge detonator wick than is necessary for Pentolite 50/50.

It has been found in tests that a certain winding detonator wick will cross or self-start, between windings, that is, the result of a winding will reliably initiate an adjacent winding. It has been found that this occurs with core loads of more than 12 grains per foot of PETN. However, when the LEDC only has about 12 grains per foot or less and there is contact between adjacent windings of the wick, or when the coil windings are too close to each other, a portion of the wick may break or "cut", that is, tearing or damaging, for another that has been started, without initiating the cutting portion. As a result, the cut portion does not start when the initiation reaction proceeds from it to the portion that caused the cut. The entire potential result of the LEDC coil is therefore not released. If the windings are separated sufficiently to avoid cutting, the resulting energy released by the LEDC can be sufficiently concentrated to reliably initiate a secondary explosive receiving charge. One aspect of the present invention pertains to the formation of an LEDC coil having a core load of 12 g / ft or less where the windings are close enough to initiate a receiving device as a 60/40 Pentolite initiator and to avoid cutting by placing a barrier between the adjacent windings of the coil. The barrier protects the uninitiated windings from the result of the initiated windings and thus preserves the integrity of the coil as the initiation signal proceeds through it. The coil may or may not have a precisely defined configuration, that is, the propeller does not need to have a uniform height, angle or radius, for example, the windings may vary in terms of separation from one another. Accordingly, the coil is referred to herein as a substantially helical coil. A variety of spindle configurations as described above can be employed to support such a coil. One method of the present invention for directly initiating a secondary or less sensitive explosive with LEDC comprises winding the donor LEDC so that the multiple turns of the LEDC are close to one another and placing the coiled LEDC in contact with, or near a receiving device such as a signal transmission means or an explosive charge to start the receiving device. The preferred method also provides the confinement of the configured body of the LEDC to improve the focus of its explosive energy in the target receiving device. While the present invention was developed for use with LEDC, it has a wider application capability and thus can optionally be practiced using also a standard detonator wick.

The present invention makes possible the use of a detonating wick containing explosive in an amount less than about 5.3 grains per linear meter of wick ("g / m"), which is equivalent to 25 grains per linear foot of wick ("gr / foot ") of PETN or an equivalent material), such as a rolled explosive charge as described herein. For example, the preferred LEDC, especially for use with initiator charges of Pentolite 60/40 (comprising 60% PETN and 40% TNT (trinitrotoluene)) contains no more than about 2.55 g / m (12 g / ft) of PETN, for example, from approximately 1.7 to 2.55 g / n (8 to 12 g / ft) of PETN or the equivalent in explosive strength of some other suitable explosive. In one embodiment, the LEDC may contain a load of 10 grains per foot. By using the teachings of the present invention such LEDC, when properly accommodated in a configured LEDC body as described herein, will reliably initiate less sensitive or secondary explosives without the need for intermediates, such as primary explosives, to amplify the result LEDC. The invention, however, can optionally be used for the initiation of receiving charges containing primary explosive materials. The invention is not limited to the preferred embodiment and can be practiced with LEDC having a load of 10 g / ft, and loads of less than 8 grains per foot, for example, the invention has been practiced with LEDC having loads of 7, 6 and 4 gr / ft and can be practiced using even smaller LEDC. By allowing the use of a smaller detonator wick (of lower energy) than was previously necessary for the reliable initiation of a particular receiver device for example a particular initiator charge, the present invention provides an improvement in terms of safety and security. reliability of the explosion operation. Safety is improved because the smaller detonator wick presents less risk to the users and the reliability is improved because the smaller detonator wick causes less disruption at the blast site before the initiation of the receiving charge. This is particularly advantageous with respect to the use of a downstream detonating wick used to initiate a wellbore bursting charge because an excessively powerful detonating wick may interrupt the borehole explosive column (typically ANFO). Using a smaller detonator wick to initiate the initiating charge reduces the likelihood that such an interruption occurs. In addition, the use of a smaller detonating wick is advantageous in seismology because the seismic measurements are taken from the burst of an initiating charge implanted in the ground. The detonating wick used to initiate the initiating charge creates certain seismic vibrations that precede and interfere as "noise" in the seismic signals derived from the initiation of the initiating charge. By using a smaller detonating wick, the generated seismic noise is reduced when the initiating charge is initiated and thus leads to a more accurate and easier seismology. Figure 1 shows a schematic view of a receiver-initiator assembly A according to an embodiment of the present invention useful for mining operations. The assembly A comprises a receiving charge 22 and an initiating apparatus 10 comprising an accumulator spindle 16 around which a low energy detonating wick is wound according to a configuration of the present invention. The initiator apparatus 10 comprises a hollow body 12 having a storage spindle 16 at one end thereof and a coupling cylinder 18 at the other end thereof. The body 12 is generally cylindrical and may be composed of any suitably resistant and durable material such as a synthetic organic polymer (plastic). The body 12 of the initiating apparatus 10 also includes a pair of anchoring fins 32 diverging backwardly, longitudinally extending reinforcing ribs 34 and locking flanges 36. The coupling cylinder 18 has a hollow cup-like construction for receiving, for example, an extension rod used to push the assembly into place within a borehole, as will be described later. The anchoring fins 32 serve to contact, at their distant ends, the wall of a borehole to hold Assembly A in place in a borehole and prevent reverse movement (removal) of Assembly A as is pushed into the borehole (in the direction of the arrow and number in Figure 1) by an extension rod (not shown) received within the coupling cylinder 18. The receiving charge 22 comprises a cover 24 within which the body of the explosive charge 26 is placed. The explosive charge 26 substantially fills the cover 24 from its front end 24a to its portion 24b of reduced diameter. ("Frontal" and "rear" as used with respect to the receiving charge 22 and the initiating apparatus 10 refer to the direction of movement of Assembly A, indicated by the arrow without number in Figure 1, through a well of sounding for its placement within it). The explosive charge 26 has, formed therein, an initiating cavity 30. If desired, the explosive charge 26 may also have one or more cover cavities (not shown) formed therein and which open to the surface 26a. The inclusion of such conventional cover cavities provides a "universal" initiating charge which allows the receiving charge 22 to be used with either a conventional detonator cover system or with the LEDC system of the present invention. The explosive charge 26 may comprise any suitable secondary explosive such as a mixture of PETN and trinitrotoluene ("TNT") (commonly referred to as "Pentolite"), suitable for initiating an industrial borehole explosion as an ANFO (ammonium nitrate / fuel) of oil). In order to improve the reliability of the initiation of the receiving charge 22, a more sensitive secondary explosive or a primary explosive such as lead azide may be optionally employed, at least near the starter cavity. The cover 24 includes reinforcement ribs 25a, 25b, 25c and locking notches 38, an adjacent collar 39 which may be made of any suitable plastic material such as medium or high concentration polyethylene. The cover 24 has a hollow receiving portion 24c which is carried with the receiving load 22 and which is dimensioned and configured to receive therein that body portion 12 between the locking flanges 36 and the accumulator spindle 16, as will be better described. later. A length of the LEDC 14 is selected to be long enough to extend from the selected position of the Assemble Á into a borehole to an initiating device to which an LEDC 14 may be connected in any conventional manner. Such initiation devices are well known in the art. An example of such a connection is shown in U.S. Patent No. 5,714,712, the disclosure of which is incorporated herein by reference for background information. Of course, the LEDC 14 can be connected to any suitable circuit or trigger system, electric or non-electrical, or on the surface or inside the borehole. The LEDC 14 contains a solid explosive core such as PETN or a mixture of PETN and TNT, contained within a flexible liner or sleeve of a suitable protective and insulating material, such as plastic, which can optionally be reinforced with fibers. The accumulator spindle 16, which can best be seen in Figure 2, functions to provide a support for winding a length of the LEDC 14 in a helical coil to form an initiator 14c which is composed of approximately 4 wad wrappers. In such a configuration, the mass of the LEDC core 14 is accumulated within the space around the accumulator spindle 16 so that the explosive force of the LEDC 14 is concentrated or focused correspondingly in contact with the explosive charge 26 surrounding the starter cavity 30, as shown in FIG. describe later. The accumulator spindle 16 has a cylindrical shape so that the coil of the LEDC is cylindrical, that is, it conforms to a uniform radius. The storage spindle 16 can be composed of any suitable durable and durable material such as polyethylene of medium or high concentration and comprises a helical groove 40 and an axial opening 42. The helical groove 40 extends between the axial opening 42 and a portion 44 for releasing the accumulator spindle and is joined by helical spacing rib 46 which lies between the adjacent windings of the helical groove. The opening 42 is dimensioned to receive and retain the end 14b of the LEDC 14 thereby holding it in place while winding a length of the LEDC 14 (Figure 1) into the helical groove 40, thereby forming a helical coil with the rib 46 serving as a cut barrier between the adjacent windings. An optional protruding jaw 48 (Figure 2) is positioned opposite the opening 42 along the notch 40, adjacent to the release portion 44. The protruding jaw 48 cooperates with it to hold the LEDC 14 in the accumulator spindle 16 so that the LEDC 14 wound up can not easily unwind from the accumulator spindle 16, as best seen in Figure 1. This prevents unwinding of the initiator 14c and retain it in the form of the configured body desired in the accumulator. This strong retention of the LEDC 14 by the accumulator spindle 16 is also particularly advantageous in the case where the initiating apparatus 10 is lowered into the borehole by means of a low energy detonating wick 14 only. The coiled configuration provides an increased concentration of explosive material in a given volume of space near or within a receiving device as compared to a straight length of the LEDC. While not wishing to be bound by any particular theory, it is believed that by placing turns or windings of LEDC 14 (Figure 1) close to one another to form initiator 14c, the initiation of the LEDC will generate mutually reinforced cross explosive shock waves that improve the energy input within the receiving charge, that is, within the secondary explosive charge 26, or within a signal transmitting detonator wick or other receiving device. The spacing ribs 46 provide a barrier between the adjacent turns of the low energy detonating wick 14 to prevent cutting of a winding by the initiation of an adjacent winding. In this way, the rib 46 helps ensure that the entire coil of the LEDC starts and the total energy output of the coil is supplied to the receiving load. It should be understood that the spacing rib 46 of the accumulator spindle 16 may be omitted or reduced in size for use with a detonating wick containing relatively high core charges, for which cutting is not a problem. In such a case, shallow notches 40 may be employed to simply guide the position of each turn of the wound detonator wick without avoiding the coil-to-coil splice contact. The accumulator spindle 16 can be integrated with the body 12 or it can be a separate piece that is designed to be joined to the body 12 by any suitable means. It has been found that when using low energy detonating wick having a wick load of 1,702 to 2.55 grams of PETN per meter of length of wick (approximately 8 to 12 grains per foot), 3 to 4 turns of LEDC 14 around the spindle 16 accumulator having a generally cylindrical configuration with a cross-sectional diameter of approximately 1.59 cm (5/8 inch) and separated by a barrier having a thickness of 3.3 mm (0.13 inches), will produce an initiator 14c that will reliably initiate a receiving charge explosive secondary as a charge of Pentolite. This particular configuration results in a winding of a linear length of wick of about 15.24 cm (6 inches) around the accumulator spindle 16. A barrier of 3.3 mm (0.13 inches) was found to be adequate to avoid cutting at the LEDC having a core load of 12 grains per foot. A smaller barrier would be enough for a LEDC smaller but possibly not for the LEDC of 12 gr / ft or greater. Since the barrier that prevents the cutting of the wick is greater, it will also avoid cutting into smaller wicks, the same efficiency is achieved by producing a spindle with the barrier of 3.3 mm (0.13 inches) because this can be used to avoid cutting of the larger LEDC for which cutting is an interest and for many smaller LEDCs alike. Generally, four LEDC windings having a PETN core charge of approximately 4 * i grains per foot or more will provide a sufficient result to reliably start a 60/40 Pentolite initiator; 3 6g / ft LEDC casings have been found to be suitable and two 8g / ft LEDC casings have been found to be suitable for Pentolite 60/40. It will be appreciated that the LEDC with PETN loads lower than 4 ^ g / ft could be used taking into account that the lower load is displaced as necessary with more windings in the coil. After the LEDC 14 is wound around the notch of the accumulator spindle 16 as described above, the receiving charge 22 engages with the initiating apparatus 10 to provide Assembly A by inserting the initiating apparatus 10 into the receiving portion 24c of the cover 24 until the accumulator spindle 16, with the initiator 14 wound around it, is received within the initiating cavity 30 of the explosive charge 26. At this point, the locking tabs 36 in the body 12 of the initiating apparatus 10 engage, for example, snap-fit, in the locking notches 38 formed adjacent the collar 39 of the receiving portion 24c of the cover 24. The LEDC 14 passes through the annular space between the exterior of the body 12 and the interior of the receiving portion 24c of the cover 24. The annular separation is maintained by the ribs 34 that separate the central or core portion of the body 12 away from the wall inside the receiving portion 24c. The LEDC 14 can be extended from Assembly A resulting from the receiving load 22 through the length of the borehole and up to the surface of the explosion site with a sufficient surface length to facilitate connection to a firing system used to initiate the LEDC. Assembly A may be used in a conventional manner to initiate an explosive borehole well as described in the aforementioned U.S. Patent 5,714,712. It will also be appreciated that the initiating apparatus 10 can be used to initiate another length of low energy detonating wick or a length of detonating wick or a length of high energy detonating wick. According to another embodiment of this invention, the accumulator spindle and the detonating wick can also be formed with a diameter that is large enough to be placed around the charge itself. That is, one end of the explosive charge can be received within a hollow accumulator spindle that supports the LEDC wound. Optionally, the LEDC can be placed on the inner surface of a hollow accumulator spindle. The spindle may optionally have notches and ridges thereon to retain the LEDC in a coiled configuration. According to yet another embodiment of this invention, an initiator may comprise a LEDC wound in multiple capable around the accumulator spindle, taking into account that an adequate separation between the layers is maintained or that a barrier is provided between them, if necessary , to avoid cutting. Additionally, it will be appreciated that an accumulator spindle can have different configurations in cross section, such as oval, polygon, "etc., around which the helical coil of the detonating wick and the barrier for it are placed. it has to have a uniform transverse configuration Another possible configuration is in the form of a flat spindle wheel A similar conical or tapered configuration can also be advantageous where a shaped loading effect is desired.Also, the accumulator spindle can be used together with a liner metal placed, for example, within the starter cavity 30 to function as fin plates for increased initiation capability.

Figure 3 shows another embodiment of an LEDC initiator according to the present invention, the accumulator spindle 16 'which is shown in an enlarged cross-sectional view in Figure 4. In this embodiment, the spindle 16' accumulator includes an inclination having an angle A which is suitable for the creation of a tapered coil LEDC initiator thereon. The tapered configuration facilitates the resultant initiator intensification within an initiating cavity 30 while maintaining a tight fit between the explosive charge 26 and the coils of the LEDC 14 around the accumulator spindle 16 '. The tilt may also function to increase the interface pressure between the LEDC 14 and the explosive load 26. In a particular embodiment, the angle A can be from about 2 to 4 degrees, the diameter of the accumulator spindle 16 'decreases from its end near its distal end, ie, in the forward direction. In other embodiments, angle A may be larger than this; other suitable inclination angles can be selected without undue experimentation. The body 12 'is reinforced by a pattern of reinforcement ribs 20, Figure 3, and, at the end opposite the end on which the accumulation spindle 16' is fixed, comprises a hollow cup-shaped coupling cylinder 18 '. designed, as a coupling cylinder 18 of the embodiment of Figure 1, to receive, for example, an extension rod, which is used to push the body assembly 12 'and a suitable initiating charge coupled together with it into a well of sounding. The initiating apparatus 10 'is inserted into an initiating charge in a manner identical to that described with respect to the embodiment of Figure 1 with its coiled initiator 14c' received within an aperture cavity formed in the casting explosive of the initiating charge. . The locking tabs (not shown in Figure 3) or other suitable means may be employed to lock the LEDC initiator 10 'in place within the initiating charge associated therewith. The spindle 16"accumulator has a helically extending notch 40 'and spacing ribs 46' as well as a release portion 44 'and a protrusion 48' which serves as the same function as described above together with the embodiment of the accumulator spindle 16 of Figures 1 and 2. A tapered configuration as shown in Figure 3 is advantageous because it facilitates the insertion of the wound starter into the receiving charge and because it allows the wound detonator wick to be pressed against the body of the receiver. the receiving charge when it is inserted into it, thereby improving the efficiency of the energy transfer from the detonating wick to the receiving charge The coupling mechanism that holds the spindle in the receiving charge can be configured to do so and maintain the pressure between the rolled starter and the receiving load A tapered spindle, such as a non-tapered spindle, can have any configuration in cut t ransversal, for example, curve (round, oval, etc.) polygonal, etc. Generally, to initiate the receiver charge 22, an LEDC initiator, such as a coiled initiator 14c or 14c 'engages the receiving charge with the coiled initiator inserted into an initiating cavity congruently shaped as the initiating cavity 30, to provide a contact intimate between the configured body of the rolled LEDC and the explosive that defines the walls of the initiating cavity. By winding a detonating wick around an accumulator spindle as described above, the formation of the windings of the detonating cord and the arrangement of the barrier between the adjacent windings is facilitated. It also provides a guide for proper separation of the windings and helps the user to achieve and maintain the rolled configurations without creating a "crossover", that is, a portion of detonating wick that overlaps another. This is advantageous for the LEDC because the crosses can cause undesirable cuts. Referring now to Figures 5 and 6, another "one-spindle 16" accumulator mode having a pair of separate circular plates 17a, 17b is shown which are connected to each other by a central post or shaft 19 (Figure 6) .The central post 19 thus configured as a "axis" connects tandem "wheels" composed of plates 17a, 17b As can be seen in Figure 6, the post 19 has a slot 19a into which an end (without number) of the detonating wick 14 'can be inserted. The groove 19a thus performs a function analogous to the axial opening 42 in the embodiment of Figure 4. With one end of the detonating wick 1 'secured within the slot 19a, the detonating wick 14' it is wound in a substantially flat or planar spiral configuration between the circular plates 17a and 17b to form a flat coiled initiator 14b.The lower plate 17a has a nib 17c which allows the detonator wick 14 'to pass without exceeding the circular periphery of the hus or 16"and thus allows a receiving charge to have an initiating cavity configured to receive the plates 17a and 17b without taking into account the size or position of the detonating wick thereon. Optionally, the spindle 16"may comprise a nib and a protruding jaw 48 'to secure the free end of the detonating wick and help prevent the coil from unrolling between the plates 17a and 17b In this arrangement, the detonating wick 14' it must be chosen so that the self-initiating winding can be wound in. Once started, the explosive energy generated by the configured body of the coiled detonator wick 14 'is forced axially outward by the confining action of the circular plates 17a, 17b to provide a focused result of energy that will strike a receiver that is arranged to surround the space defined between the circular peripheries of the circular plates 17a, 17b For example, a spindle 16"accumulator and an initiator 14d can be inserted into a cast explosive having a starter cavity similar to the initiator cavity 30 of the receiving charge 22 of the embodiment of Figure 1. For the purpose of this invention However, any coil having a height of less than the diameter of the detonating wick, including a zero height, is substantially flat or planar. Optionally, the height of the substantially planar spiral may not be more than half the diameter of the wick. Referring now to Figure 7, there is shown schematically a cast starter explosive charge 26 'with a generally cylindrical configuration having a threaded port 58 extending therethrough and opening at opposite ends 26a' and 26b ' of load 26 'explosive receiver. An initiating cavity 30 'is formed within the receiving charge 26' and opens at the end 26b 'thereof. In this embodiment, one end of a length of detonating wick (not shown in Figure 7) can be inserted into threaded port 58 through an opening 58a thereof and threaded therethrough to emerge through an opening 58b in the other end of port 58 threaded. The threaded port 58 will have a dimension and configuration relative to the detonator wick (not shown) so that the detonator wick fits slidably but tightly within the threaded port 58 in a linear configuration, in which its initiation does not release sufficient energy to start the load 26 '. The detonating wick will be pulled through the threaded port 58 until a length thereof emerges from the opening 58b. The detonating wick is pulled until the emerging length is long enough to form a coiled initiator, for example, being wrapped around an accumulator spindle 16 of Figure 1 or an accumulator spindle 16 of Figure 5. The coiled starter then is inserted into the starter cavity 30 and the additional detonating wick is removed through the threaded port 58. The tight fit of the detonating wick inside the threaded port 58 securely holds the detonating wick in place.If the spindle 16"accumulator is used. with load 26"explosive starter pouring, the circular plate 17b will be seated against the bottom 30a 'of the starter cavity 30. The method of the present invention is easily used even in the field in adverse weather conditions and even when the operator is wearing gloves or mittens to protect his hands against cold weather. By inserting the LEDC end into a slot in the accumulator and over it by wrapping it around the accumulator and placing it in place it is easy to carry out even under adverse field conditions. As indicated above, the practice of the present invention need not be restricted to a low energy detonating wick. Optionally, the detonating wick which is not low energy may be formed in a coil as taught and claimed herein to form an initiating charge. In each case, a detonating wick may optionally be used in place of a conventional initiating charge. For example, a detonator wick formed in a coil as taught herein can be used to replace an initiating charge such as the charge 26 'shown in Figure 7. The coiled detonator wick can constitute an explosive charge which can then be used to directly initiate an explosive volume charge, for example, a column of borehole explosives such as ammonium nitrate / fuel oil (ANFO) or the like. Alternatively, a coiled detonator wick can be used directly to achieve results on non-explosive objects, for example, it can be used to break rocks. While the invention has been described in detail with reference to the particular embodiments thereof, numerous variations to the specific embodiments may be found within the scope of the present invention.

Claims (50)

1. CLAIMS 1. A method for forming an explosive charge, characterized in that it comprises forming a length of detonating wick in a substantially helical coil comprising a plurality of windings and a cut barrier between the adjacent windings. The method according to claim 1, characterized in that it comprises adjacent windings spaced no more than 12.7 mm (0.5 inches) apart from each other. 3. The method of compliance with the claim 1, characterized in that it comprises wrapping the detonating wick around a spindle. 4. The method according to claim 1, characterized in that it comprises forming the length of the detonating wick in a tapered bobbin. 5. The method according to claim 4, characterized in that it comprises forming a tapered coil that defines an inclination angle of approximately 2 to 4 degrees. 6. The method of compliance with the claim 1, characterized in that it comprises forming the length of the detonating wick in a cylindrical coil. The method according to claim 1, claim 2 or claim 3, characterized in that the detonating wick has a core of explosive material with a load of 12 grains or less per foot of the wick. The method according to claim 7, characterized in that it comprises two to four windings of the wick. 9. The method of compliance with the claim 7, characterized in that the detonating wick has a core of explosive material with a load in the range of 8 to 12 grains per foot of the wick. The method according to claim 7, characterized in that the coil comprises approximately 15. 24 cm (six inches) of detonating wick. 11. A method for forming an explosive charge characterized in that it comprises forming a length of detonating wick in a substantially planar spiral comprising a plurality of windings. The method according to claim 11, characterized in that the detonating wick has a core of explosive material with a load of at least 15 grains per foot of the wick. 13. An explosive charge characterized in that it comprises a length of detonating wick disposed in a substantially helical coil comprising a plurality of windings and a cut barrier between the adjacent windings. 14. The explosive charge according to claim 13, characterized in that it comprises adjacent windings spaced from one another by no more than about 12.7 mm (or 0.5 inches). 15. The explosive charge according to claim 13 or claim 14, characterized in that the detonating wick has a core of explosive material with a load of 12 grains or less per foot of the wick. 16. The explosive charge according to claim 15, characterized in that it comprises from 2 to 4 windings. 17. The explosive charge according to claim 15, characterized in that the detonating wick has a core of explosive material with a charge in the range of about 8 to 12 grains per foot of the wick. 18. The explosive charge according to claim 13 or claim 14, characterized in that it comprises a spindle around which the coil is dispersed. 19. The explosive charge according to claim 18, characterized in that the spindle is configured to produce a coil defining an inclined angle of about 2 to 4 degrees. An explosive charge characterized in that it comprises a length of detonating wick disposed in a flat coil comprising a plurality of windings 21. The explosive charge according to claim 20, characterized in that the detonating wick has a core of explosive material with a charge of at least 15 grains per foot of the detonating wick. 22. The explosive charge according to claim 20 or claim 21, characterized in that it comprises a spindle comprising a pair of plates between which a flat spiral is placed. 23. The explosive charge according to claim 22, characterized in that the spindle defines an anchoring opening and a projecting jaw. 24. A method for initiating an explosive receiving charge, the method is characterized in that it comprises inserting within the explosive receiving charge an initiating charge comprising a length of detonating wick placed in a substantially helical coil comprising a plurality of windings and a surge barrier. Cut between the adjacent windings, and start the detonating wick. 25. The method of compliance with the claim 24, characterized in that the initiator charge comprises adjacent windings spaced from one another by no more than about 12.7 mm (or 0.5 inches). 26. The method according to claim 24 or 25, characterized in that it comprises inserting a spindle around which the coil is dispersed within the explosive charge. 27. The method according to claim 24 or 25, characterized in that the detonating wick has a core of explosive material with a load of 12 grains or less per foot of the wick. 28. The method of compliance with the claim 27, characterized in that the receiving charge comprises Pentolite 60/40. 29. The method of compliance with the claim 28, characterized in that the detonating wick has a core of explosive material with a charge in the range of about 8 to 12 grains per foot of the wick 30. The method according to claim 29, characterized in that the spindle is configured for The method according to claim 24 or claim 25, characterized in that the receiving charge and the initiating charge are substantially free of primary explosive materials. method for initiating an explosive charge of secondary explosive material, the method is characterized in that it comprises inserting within the explosive charge an initiating charge comprising a length of detonating wick placed in a substantially flat spiral comprising a plurality of windings. according to claim 32, characterized in that it comprises a spindle around or from which the coil is dispersed. 34. The method according to claim 32 or 33, characterized in that the detonating wick has a core of explosive material with a load of at least 15 grains per foot of the wick. 35. An accumulator spindle characterized in that it comprises: a spindle body carrying a spiral cutting barrier; and an anchor opening. 36. The accumulator spindle according to claim 35, characterized in that it further comprises: a protruding jaw 37. The accumulator spindle according to claim 35, characterized in that the spindle body defines an inclination. 38. The accumulator spindle according to claim 36, characterized in that the barrier defines a substantially helical groove, wherein the groove has two ends, and wherein the anchor opening is at one end of the groove and the protruding jaw is the other end of the notch. 39. The accumulator spindle according to claim 37, characterized in that it has an inclined angle in the range of approximately 2 to 4 degrees. 40. An accumulator spindle characterized in that it comprises: a spindle body comprising two parallel parallel plates; an anchor opening; and a protruding jaw. A receiver-initiator assembly characterized in that it comprises: a receiving charge comprising a body of explosive material having an initiating cavity therein; and a substantially helical coil of detonator wick placed in the initiator cavity. 42. The assembly according to claim 41, characterized in that it comprises a receiving portion associated with the body of the explosive material, wherein the substantially helical coil is mounted on a spindle and the spindle is secured to the receiving portion. 43. The assembly according to claim 41 or claim 42, characterized in that the helical coil and the initiating cavity each define an inclined angle of approximately 2 to 4 degrees. 44. The assembly according to claim 41 or claim 42, characterized in that the receiving charge and the initiator are substantially free of primary explosive materials. 45. A receiver-initiator assembly characterized in that it comprises: a receiving charge comprising a body of explosive material having an initiating cavity therein.; and a substantially flat coil comprising a plurality of detonating wick windings placed in the initiating cavity. 46. The assembly according to claim 45, characterized in that it comprises a receiving portion associated with the body of the explosive material wherein the substantially flat coil is mounted on a spindle and the spindle is coupled to the receiving portion. 47. The assembly according to claim 45, characterized in that the receiving charge and the initiator are substantially free of primary explosive materials. 48. The method according to claim 1, characterized in that it comprises separating adjacent windings by approximately 3.3 mm (0.13 inches). 49. The explosive charge according to claim 14, characterized in that the windings are separated from each other by approximately 3.3 mm (0.13 inches). 50. The method according to claim 25, characterized in that the windings are separated from each other by approximately 3.3 mm (0.13 inches).