GB1586496A - Explosives initiation assembly and system - Google Patents

Description

(54) EXPLOSIVES INITIATION ASSEMBLY AND SYSTEM (71) We, CXA LTD/CXA LTÉE, a corporation of Canada, of 630 Dorchester Boulevard West Montreal, Province of Quebec, Canada, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an assembly for the non-electric initiation of an explosive charge. More particularly, the invention involves an assembly whereby an initiating energy pulse may be transmitted from an energy generator or energy emitter to a blasting cap or other explosive device without resort to the use of any connecting detonating, or deflagrating or burning fuse.

The use of non-electric explosives initiation systems are now well known in the blasting art. Generally, these systems comprise the use of one or more lengths of detonating fuse cord each having attached at one end thereof an instantaneous or delay blasting cap. When the opposite end of the cord is initiated by means of an explosive initiator such as a cap or priming trunk line fuse cord, the detonating fuse is detonated and an explosive wave is transmitted along its length at high velocity to set off the attached blasting cap. The use of such a system is generally chosen where there may be hazards involved in using an electric initiation system and electric blasting caps.

In the recent past many improvements have been made in the quality and reliability of non-electric initiation systems and in detonating fuse cord. Typical of such improvement is that of Per-Anders Persson, shown in United States patent No. 3,590,739, granted July 6, 1971, which patent discloses a detonating fuse which comprises a tube having only a thin layer of a reactive substance coated on the inner area thereof. Such a fuse is marketed under the registered trade mark "Nonel". In United states patent No. 3,730,096, granted May 1, 1973, Josef Prior dicloses a very high detonation velocity cord wherein the reactive explosive substance is placed between inner and outer concentric tubes.While meritorious, these and similar improved cords nevertheless require the use of sensitive explosive material in their construction, the use of which sensitive material involves inherent hazard in manufacture and in use.

It has now been found that detonation energy adequate to initiate a conventional blasting cap or blasting relay can be transmitted from an energy generator to the cap to be initiated without the use of either conventional or modified detonating or deflagrating cord. It has been surprisingly discovered that the energy from the explosive or deflagrative initiation of a reactive substance can be transmitted through substantial lengths of hollow, small diameter tubing which is devoid of any explosive or reactive material content. The detonation of a reactive substance confined within a generator attached to one end of a length of, for example, small internal diameter polyethylene or other plastic tubing, permits the transmission through the tubing of sufficient explosive energy to set off a conventional blasting cap attached at the opposite end of the tubing.It is thus possible to initiate a non-electric blasting cap from a remote source without the use of any explosive-containing detonating cord or fuse.

According to the present invention therefore, there is provided a non-electric energy generating-transmitting-initiating assembly comprising in combination a source of detonation energy, a detonable explosive charge and a detonation energy transmitter connecting said generator and said charge in a detonable relationship, said energy transmitter comprising a length of hollow, flexible tubing devoid of any reactive material content and of an internal cross-sectional area sufficient to permit passage therethrough of detonation energy.

Also according to the present invention, there is provided a method of transmitting explosive detonation energy from a source to a detonable explosive charge to be detonated comprising the step of connecting together said energy source and said explosive charge in a detonable relationship by means of a hollow, flexible tube devoid of any reactive material content and of an internal cross-sectional area sufficient to permit passage therethrough of detonation energy.

In order to better understand the invention, reference is made to the drawing accompanying the Provisional Specification wherein, Figure 1 shows in cross-section a typical assembly according to the invention comprising a generator, connecting tubing and cap; and Figure 2 shows, also in cross-section, one means for attaching an initiating means to the energy generator of Figure 1.

The figures of the drawings are not to be construed as a limitation of the invention.

Referring to Figure 1, there is shown a typical non-electric delay blasting cap 1 containing in sequence from the closed end a base explosive charge 2, a priming charge 3 and an ignition or a delay element 4. A non-conductive channelled closure plug 5 is shown crimped in place in the open end of cap 1. The end of a length of hollow tubing 6 is held within the channel of closure plug 5, the end of which tubing abutts ignition or delay element 4. At the opposite end of tubing 6 is energy generator 7. In the embodiment depicted, generator 7 has the form of a blank ammunition cartridge and comprises a metal shell 8 with a closed rim end 9 and an open end 10. Within shell 8 at rim end 9 is a heat and impact sensitive composition 11. In contact with composition 11 is a high energy reactive substance 12. A destructable diaphragm or membrane 13 is shown over the surface of substance 12.A non-conductive channelled closure plug 14 is crimped in position in the open end of shell 8.

Closure plug 14 holds within the channel the end of hollow tube 6 tightly against membrane 13. Membrane 13 may be an integral part of closure plug 14.

Referring to Figure 2, there is shown the energy generator 7 of Figure 1 having around part of metal sheel 8 and close to closed rim end 9, a slip-on or molded-on, resilient connector 15. Connector 15 can comprise, for example, a hollow cylinder of plastic material adapted for tight fit over shell 8. A protruding sleeve portion 16 of connector 15 extends beyond rim end 9 and is notched in V-shaped fashion to receive therein a cord-like initiator such as, for example, a length of low energy detonating cord trunk line (not shown).

The impact and heat sensitive composition 11 within shell 8 can be any such composition known to the explosive art. For example, an ammunition primer composition comprising a mixture of tetracene, lead styphnate, barium nitrate and powdered glass has been found useful. Other suitable primer composition mixtures are, for example (a) styphnate, tetracene, barium nitrate, calcium silicide and lead peroxide; (b) lead styphnate, tetracene, barium nitrate, aluminium powder and antimony sulfide; (c) lead azide, antimony sulfide, potassium chlorate and lead thiocyanate. The high energy reactive substance 12, in contact with composition 11 may be any one of a number of single or mixed fast burning pyrotechnic or explosive substances known to the art. Useful substances include, for example smokeless powder, black powder, magnesium and PETN or mixtures of these.

In use in the field, an assembly comprising an energy generator, a blasting cap and an interconnecting hollow tube as shown in Figure 1, and preferably pre-assembled in the explosive factory, is selected wherein the length of the interconnecting tube is appropriate for the blasting operation to be undertaken. An initiating means for the energy generator, for example, the end of a length of low energy detonating cord, is secured or attached to the sensitive composition end of the energy generator unit 7. Attachment may be accomplished by, for example, use of the connector unit shown in Figure 2. The cap end 1 of the assembly is placed in contact with an explosive charge, for example, in a borehole or agnainst a boulder. Initiation of the low energy detonating cord from a remote location causes composition 11 and substance 12 within energy generator 7 to be ignited or detonated. Hot gases and flash from this detonation are transmitted via hollow tube 6 to initiate blasting cap 1 which, in turn, detonates the associated explosive charge. Where a series of charges are to be detonated, a series of assemblies may be connected at intervals along a single trunk line length of detonating cord which, upon ignition, sets off the attached energy generator and connected caps in a sequential manner.

The following Examples further illustrate the present invention.

Example 1 A series of tests were conducted wherein the energy generator comprised a standard ammunition primer composition and a reactive substance charge consisting of a 72 milligram intermixture of smokeless powder/magnesium metal powder (70 - 80 mesh) in the mass ratio 46/54. The energy generators were affixed to the ends of plastic tubes of various internal diameters. At the free end of each assembly, standard fuse blasting caps were attached. The blasting caps utilized had an ingnition charge of 60/40 lead - azide/lead styphnate. The maximum propagation distance, or the maximum tubing length through which the generators would initiate a fuse blasting cap, was measured. Results obtained are tabulated below in Table I.

TABLE 1 Tubing I.D. Maximum Propagation (inches) Distance (inches) 0.138 72 0.090 60 0.070 42 0.049 27 The results demonstrated that propagation distance is related to the internal diameter of the tubing with a constant size of charge of reactive substance in the energy generator.

Example 2 The effect of assembly length on delay time and average propagation velocity is demonstrated in Table II below. In these tests, an intermixture of 77 milligrams of smokeless powder and 65 milligrams of magnesium (70 - 80 mesh) served as the reactive substance charge. Each unit comprised a length of polypropylene/nylon tubing of dimensions I.D. 0.138", O.D. 0.188", having a fuse blasting cap affixed to one free end and a standard ammunition primer crimped to the remaining free end.

TABLE II Tubing Length Delay Time Average Propagation (feet) (milliseconds) Velocity (feet/second) 2 0.56 3571 4 1.02 3922 6 1.68 3571 8 2.29 3494 10 3.38 2959 Example 3 A reactive substance charge comprising a base layer of 16 milligrams of blackpowder and a top layer of 15 milligrams of PETN was utilized in the energy generator. The generator and fuse blasting caps were attached together by lengths of polypropylene/nylon tubing of dimensions I.D. 0.138", O.D. 0.188".

Delay times between ignition of the generator and detonation of the cap using 4 feet and 5 feet lengths of tubing were respectively 1.17 milliseconds and 1.58 milliseconds. thus indicating that a useful time-delay function can be achieved by varying the length of the connecting tubing.

Example 4 A reactive substance charge in the energy generator consisted of a 132 mg intermixture of 68% granulated black-powder and 32% magnesium metal powder, by weight. The generator and fuse blasting caps were attached together by lengths of "Surlyn" (Reg. Trade Mark) tubing of dimensions I.D. 0.090", O.D. 0.155".

Delay times between ignition of the generator and detonation of the cap using 4 and 5 feet lengths of tubing were respectively 1.48 and 1.89 milliseconds.

Example 5 A reactive substance charge in the energy generator consisted of a 94 milligram intermixture of 59% smokeless powder and 41% magnesium metal powder; by weight. The generators were crimped to 3 feet lengths of plastic tubing having dimensions I.D. 0.138" and O.D. 0.188". Fuse blasting caps were attached to the free end of each tubing assembly.

The delay times between ignition of the generator and detonation of the cap of five such assemblies were measured. The mean delay time and its associated standard deviation were 0.75 milliseconds and 0.12 milliseconds respectively.

Example 6 The tests described in Example 5 were repeated with identical energy generator assemblies but with delay detonators affixed to the tubing. The delay detonators utilized were of the short period variety, containing a Pb304/Si pyrotechnic delay element. The rated, or nominal, delay time and delay time tolerance of these detonators were respectively 800 milliseconds and 731 to 869 milliseconds. Measurements of the delay time between the ignition of the generator and detonation of the delay cap of ten assemblies, each 3 feet in length, yielded a mean value of 829.5 milliseconds and a delay time standard deviation of 8.1 milliseconds.

Example 7 The test described in Example 5 were repeated but with a reactive substance charge within the energy generator comprising an intimate mixture (83 mg) of smokeless powder and magnesium metal powder in the mass ratio 53%/47% (S.P./Mg). The delay times of five assemblies, each of length 3 feet, produced a mean value of 0.80 milliseconds and a delay time standard deviation of 0.07 milliseconds.

Example 8 The tests described in Example 7 were repeated with identical energy generators and type of tubing but in this case, 4 feet lengths of tubing in conjunction with delay detonators were utilized. The delay detonators employed were of the same type as described in Example 5. Measurements of the delay times of ten such assemblies yielded a mean delay time of 839.2 milliseconds and a delay time standard deviation of 9.0 milliseconds.

It will be appreciated by knowledgeable workers in the art that the components of the assembly will have to be compatibly matched in order to insure the utility of the system. For example, the means employed to initiate the energy generator must not be so powerful as to cause destruction of the generator rather than its initiation. The quantity and type of reactive substances employed in the generator will have to be selected to produce the necessary heat and flash effect to set off the attached blasting cap without rupturing the conductive tubing. Similarly, the material of construction, wall thickness, inside diameter and length of the tubing employed will be selected to retain the pressurized hot gases from the energy to ignite the attached detonator unit.Further, the blasting cap or other explosive device for detonation will necessarily be of a type susceptible to initiation by the generator.

Also, the means of connecting of both the generator and cap to the tubing will have to be secure enough to maintain a pressure tight system.

The non-electric ignition assembly of the invention provides important advantages over other non-electric systems known from the prior art.

Since the connecting tubing does not rupture during firing, an explosive column in a borehole adjacent the tubing cannot be prematurely detonated by lateral energy. In addition, the great strength of the tubing also implies that in the case of accidental initiation of hollow tube assemblies during handling or transportation, the immediate environment is exposed to minimum risk. The tubing does not contain any reactive or explosive substances and hence is insensitive to initiation by electro-magnetic effects such as stray electric currents or static electricity.

The connecting tubing which preferably comprises polyethylene, polypropylene, nylon, "Surlyn" (Reg. TM) or combinations of these materials being devoid of any explosive content results in a non-hazardous manufacturing operation in comparison to conventional products.

WHAT WE CLAIM IS: 1. A non-electric energy generating-transmitting-initiating assembly comprising in combination a source of detonation energy, a detonable explosive charge and a detonation energy transmitter connecting said generator and said charge in a detonable relationship, said energy transmitter comprising a length of hollow, flexible tubing devoid of any reactive material content and of an internal cross-sectional area sufficient to permit passage therethrough of detonation energy.

2. An assembly as claimed in claim 1 wherein the said energy source is an impact or heat sensitive explosive material.

3. An assembly as claimed in claim 1 or claim 2 wherein the said explosive charge is a non-electric blasting cap.

4. An assembly as claimed in any one of claims 1 to 3 wherein the said hollow tube is constructed from synthetic plastic material.

5. A method of transmitting explosive detonation energy from a source to a detonable explosive charge to be detonated comprising the step of connecting together said energy

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. 0.75 milliseconds and 0.12 milliseconds respectively. Example 6 The tests described in Example 5 were repeated with identical energy generator assemblies but with delay detonators affixed to the tubing. The delay detonators utilized were of the short period variety, containing a Pb304/Si pyrotechnic delay element. The rated, or nominal, delay time and delay time tolerance of these detonators were respectively 800 milliseconds and 731 to 869 milliseconds. Measurements of the delay time between the ignition of the generator and detonation of the delay cap of ten assemblies, each 3 feet in length, yielded a mean value of 829.5 milliseconds and a delay time standard deviation of 8.1 milliseconds. Example 7 The test described in Example 5 were repeated but with a reactive substance charge within the energy generator comprising an intimate mixture (83 mg) of smokeless powder and magnesium metal powder in the mass ratio 53%/47% (S.P./Mg). The delay times of five assemblies, each of length 3 feet, produced a mean value of 0.80 milliseconds and a delay time standard deviation of 0.07 milliseconds. Example 8 The tests described in Example 7 were repeated with identical energy generators and type of tubing but in this case, 4 feet lengths of tubing in conjunction with delay detonators were utilized. The delay detonators employed were of the same type as described in Example 5. Measurements of the delay times of ten such assemblies yielded a mean delay time of 839.2 milliseconds and a delay time standard deviation of 9.0 milliseconds. It will be appreciated by knowledgeable workers in the art that the components of the assembly will have to be compatibly matched in order to insure the utility of the system. For example, the means employed to initiate the energy generator must not be so powerful as to cause destruction of the generator rather than its initiation. The quantity and type of reactive substances employed in the generator will have to be selected to produce the necessary heat and flash effect to set off the attached blasting cap without rupturing the conductive tubing. Similarly, the material of construction, wall thickness, inside diameter and length of the tubing employed will be selected to retain the pressurized hot gases from the energy to ignite the attached detonator unit.Further, the blasting cap or other explosive device for detonation will necessarily be of a type susceptible to initiation by the generator. Also, the means of connecting of both the generator and cap to the tubing will have to be secure enough to maintain a pressure tight system. The non-electric ignition assembly of the invention provides important advantages over other non-electric systems known from the prior art. Since the connecting tubing does not rupture during firing, an explosive column in a borehole adjacent the tubing cannot be prematurely detonated by lateral energy. In addition, the great strength of the tubing also implies that in the case of accidental initiation of hollow tube assemblies during handling or transportation, the immediate environment is exposed to minimum risk. The tubing does not contain any reactive or explosive substances and hence is insensitive to initiation by electro-magnetic effects such as stray electric currents or static electricity. The connecting tubing which preferably comprises polyethylene, polypropylene, nylon, "Surlyn" (Reg. TM) or combinations of these materials being devoid of any explosive content results in a non-hazardous manufacturing operation in comparison to conventional products. WHAT WE CLAIM IS:

1. A non-electric energy generating-transmitting-initiating assembly comprising in combination a source of detonation energy, a detonable explosive charge and a detonation energy transmitter connecting said generator and said charge in a detonable relationship, said energy transmitter comprising a length of hollow, flexible tubing devoid of any reactive material content and of an internal cross-sectional area sufficient to permit passage therethrough of detonation energy.

2. An assembly as claimed in claim 1 wherein the said energy source is an impact or heat sensitive explosive material.

3. An assembly as claimed in claim 1 or claim 2 wherein the said explosive charge is a non-electric blasting cap.

4. An assembly as claimed in any one of claims 1 to 3 wherein the said hollow tube is constructed from synthetic plastic material.

5. A method of transmitting explosive detonation energy from a source to a detonable explosive charge to be detonated comprising the step of connecting together said energy

source and said explosive charge in a detonable relationship by means of a hollow, flexible tube devoid of any reactive material content and of an internal cross-sectional area sufficient to permit passage therethrough of detonation energy.

6. An assembly as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the drawings acompanying the Provisional Specification.

7. An assembly as claimed in claim 1, substantially as hereinbefore described in any one of Example 1 and 3 to 8.

8. An assembly as claimed in claim 1, substantially as hereinbefore described in Example 2.

9. A method as claimed in claim 5 and substantially as hereinbefore described in Example 1 and 3 to 8.

10. A method as claimed in claim 5 and substantially as hereinbefore described with reference to Example 2.

11. A method as claimed in claim 5, substantially as hereinbefore described with reference to and as illustrated in the drawings accompanying the Provisional Specification.