CA1068550A - Electrically initiated fuse ignitor - Google Patents
Electrically initiated fuse ignitorInfo
- Publication number
- CA1068550A CA1068550A CA272,984A CA272984A CA1068550A CA 1068550 A CA1068550 A CA 1068550A CA 272984 A CA272984 A CA 272984A CA 1068550 A CA1068550 A CA 1068550A
- Authority
- CA
- Canada
- Prior art keywords
- pyro
- fuse
- detonation
- bridgewire
- cap assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Fuses (AREA)
- Air Bags (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A fuse or the like, for the ignition of a detonator, partially cut at an angle to its longitudinal axis to expose the ignition train, having an electrically actuated ignition device mounted in the cut in contact with the ignition train.
A fuse or the like, for the ignition of a detonator, partially cut at an angle to its longitudinal axis to expose the ignition train, having an electrically actuated ignition device mounted in the cut in contact with the ignition train.
Description
10~1 35SO
1Conventionally used commercial electric detonator caps have the disadvantage of an inherent hazard of premature ignition from extraneous electrical sources such as lightning stactic -electricity, R. F. transmissions (usually F M signals), galvanic cells, and the like. Such electrically actuated detonator caps regularly fire at about 0.25 amperes, with a safety reservation that 0.06 amperes, or more, represents a hazard of unintentional initiation.
In many instances where a plurality of electric caps are used, with a plurality of explosive charges, such as are used in construction work and mining, there is a reason ~o include delays between charges or series of charges to reduce seismic shock or to obtain particular types of rock breaks.
Concurrently, it is not always necessary that the initial cap detonation be instantanious, and a short delay of, for example a one or two second delay, for the initial cap detonation may be tolerated without creating any new problems.
The present invention provides a simple method of accomplishing fuse initiation electrically to gain most of the - 20 advantages of electrical initiation, yet reduce most of the hazards usually related to electrically actuated detonation caps.
The present method provides some inherent delay, a short delay of a second cjr so to predetermined longer times of delay, after imposing the initial current. ~riefly the invention involves the soldering of a short bridgewire, long enough to span the diameter of the fuse, about 1/4 inch, to two electric lead wires which in turn may be connected into a firing circuit. The ;~bridgewire is a pyro-alloying wire producing an exothermic re-. .
;'' '~
: ~a~sso :
1 action when initiated by a reasonably strong electric current.
The bridgewire is made of one of the platinum group of metals and aluminum. One commerc~ally available bridgewire is sold under the trademark of "Pyrofuse" manufactured by Sigmund Cohn Co. m e mounted bridgewire is pulled into a cut, made half way through the fuse, and it may be t~ped into proper position when - desired. Preferrably, the cut is made at an angle in the fuse, directed away from a cap mounted on the end of the fuse. The ; cut must be sufficiently deep to enter or expose the ignition train, but must be made only deep enoughtto maintain tensile strength to the assembly. When the leads to the bridgewire carry a sufficient current, the bridgewire shorting across the leads is heated, initiating the alloy reaction, which gives off a substantial amount of heat and sparks sufficient to ignite the ignition train of the fu~e, the fuse in turn detonates the cap. 3~g~;f~caRo~
The bridgewire may be used to ignite "~s~Hhr~s~}", a thermite cord, which may, also, be used in the detonating system.
Although Ignitacord is not recommended for use to initiate caps in a direct manner, it may be used. The bridgewire may be used to initiate a cap or a s~uib directly instead of a fuse, to avoid delay caused by the use of the fu~e. This method, however, - may introduce several safety considerations which are not found by putting the bridgewire in the slot of the fuse mentioned a-.
bove.
A series of timed spaced detonations may be arranged ;..
with a plurality of explosive charges by changing the length of the fuse to the variou~ caps from ~he bridgewires to provide for successive explosion~ in the series~ The length of the delay in-tervals is a simple function of the burning rate of the ignition ~-~` train of the fuse, and the length of the fuse is from the bridge-- wire to the cap determines the delay.
; 1 Included among the objects and advantages of thepresent invention is to proviae an electrically initiated de- `
tona~on of a cap.
Another object of the invention is to provide the ~-~
electrical detonation of a cap by system which requires a high current thereby producing a very safe system. -Another ob~ect of the invention is to provide a de-tonation sy~tem for a cap utilizing a safety fuse, and a pyro-alloying bridgewire which is initiated by a high current for igniting the ignition train of the fuse.
Still another object of the invention is to provide an electrically initiated detonation of a cap utilizing a fuse -~
which is electrically ignited to provide a predetermined time ~ -delay in the detonation of the cap from the activation of the -!' electrical circuit-Yet another ob~ect of the invention is to provide an electrically actuated cap detonation utilizing a simple, safe - system without the use of sensitive, electrically actuated caps.
These and other ob~ects and advantages of the invention may be readily ascertained by referring to the descr~ption and appended illustrations in which:
Fig. 1 ~s top plan view of a bridgewire ignitor for a fuseT
Fig. 2 is a side elevational view of the device of Fig. 1:
Fig. 3 i~ a side elavational view of a portion of a fuse and fuse lgnited, detonating cap attached thereto;
Fig. 4 is a side elevational view of a device similar to that of Fig. 3, having a slit cut at an angle to the longit-udinal axis of the fuse and into the ign~tion train of the fuse;and Fig. 5 is a side elevational view of the electrically :.
~ actuated fuse ignitor in place ready for the detonation of a cap.
.
: ` ` ` `
10~i~5S0 .. ~`:, 1 The fuse ignitor illustrated in Figs. 1 and 2 includes - --an electric lead wire 10 covered by insulation 12, and a lead wire 14 covered by insulation 16. The bare ends of lead wires lOa and 14a are ~o be attached to a two lead, electric circuit wire, and, of course, must be separated, to prevent shorting a-cross the lead~ of the electric ignitor. The insulated wires are necked down providing a short length 18 where the wires are close together, and are again expanded at point 20 so that ends lOb and 14b are spaced a distance, to effectively stradle a fuse, as explained below. A bridgewire 22 ~s soldered across the ends lOb and 14b providing an electrically connection acros~ the leads.
A plastic reinforcing member 24 is welded or otherwise secured to the ends of the leads, holding the ends apart and protecting the bridgewire 22. The pla~tic str~ngthing member may be a small sheet of a thermo-plastic reqin, for example polyethylene, poly-propylene, etc. Which provides some strength to the unit, and is easily secured to the wires by heating to melt the wires into the plastic. The plastic, of course, may be secured in the other means such as cement, or the like.
A~ shown in Fig. 2, the fuse ignitor i~ es~entially planar except for the end~ lOb and 14b of the electrical con-ductor~ which are bent at a slight angle to the plane of the , lead wire~. The angle is arranged to provide a secure fit of ; ~he fu~e ignitor in a fuse. As shown in Fig. 3, a lenyth of safety fuse 30, or the like, is secured by conventional means into a cap 32. The cap is a fuse ignited detonating cap com-monly used commerically for a fu~e having an ignition train.
- ; The leng~h of the fuse 30 is not critical, but should be su-fficiently long for the placement of the fuse ignitor therein, and to provide a structure for supporting the same. A slit 34 is cut into the fuse 30 sufficiently deep to expose the ignition train in the fuse. Preferably, the cut 34 is made at an angle ~`` 106~5S0 1 of about 20~ to 45 to the longitudinal axis through the fuse.
~he distance of the fuse from the cut to about the center of ;
the detonating cap is predetermined to give a ~ime delay from the actual firing of the ignition train of the fuse to the de-tonation of the cap. This distance may obviously extend ad- `
jacent the cap edge to a substantial distance from the cap to provide a long term delay, as determined by the rate of travel of the fire front in the ignition train in ~he fuse.
In using the ignitor of the inventio~ the unit is ,d~
placed in a fuse, with the legs, adjacent the brioJgowi~e, stradl-~ .
ing the fuse, which is normally about a 1/4 of an inch in dia-meter. m e bridgewire and it~ supporting strengthening member 24 is forced into the cut 34 so that the bridgewire 22 is in --`
close contact with the ignition train in the fuse. With the bridgewire in place, it may be secured therein by means of tape wrapped around the unit to hold the ignitor in the fuse. The bare ends 10a and 14a are attached to the two lead wires from an electric current source to provide current for the bridgewire.
When the electrical system is initiated with sufficient current, the pyro-alloying reaction is initiated, giving off a great deal ; , of heat and many sparkq are thrown, to ignite the core of the fuseO Once the ignition train is lit, it sets off the cap in the predetermined time interval.
The "Pyrofuse", mentioned above, may be obtained in different diame~ers, resistance and other physical and elect-rical characteristics. It is, however, of high tensile strength and it is easy to solder, so that making the assemblies of the ignitor is easy and inexpensive. Since the bridgewire does not exceed much over a 1/4 of an inch, the cost of the bridgewire 30 is low making an inexpensive assembly. In one tested assembly, a strand o~ Pyrofuse of 0.002 inches diameter was initiated by the generator of a blasting machine. The pyro-alloying wire '.`' ~ -6-1 used in the present invention is not a resistance wire of the type used in detonator cap bridgewire circuits, and it has good conductiv~y. The assembly may be made for quite innocuous circuits, yet be initiated with relatively low voltage. High voltage does not create a problem, as an electrical source, and it may, also, be readily used. The 0.002 inch Pyrofuse requires about 0.6 amperes to initiate the alloying reaction. With the relatively high current necessary for initiating the reaction, stray currents are not normally sufficient to ignite the bridge-wire and it, therefore, is very safe unit for detonating ex-plosive charges.
The plastic support across the electrical leads ad-~acent the bridgewire may be a high dielectric, low conductance and high resistance material. This provides support for and protection for the bridgewire prior to in~ertion into the cut in the fuse, and, also, after insertion in the cut. It must be of a material that is essentially non-conducting with suf-ficient strength to support the assembly. The polyethylene, etc. plastic is satisfactory, as are many other type of plastic, wood, glass, etc. The non-thermal plastic materials may be cemented or otherwise secured in the proper position across the leads.
. .
., .
' ~
. '
1Conventionally used commercial electric detonator caps have the disadvantage of an inherent hazard of premature ignition from extraneous electrical sources such as lightning stactic -electricity, R. F. transmissions (usually F M signals), galvanic cells, and the like. Such electrically actuated detonator caps regularly fire at about 0.25 amperes, with a safety reservation that 0.06 amperes, or more, represents a hazard of unintentional initiation.
In many instances where a plurality of electric caps are used, with a plurality of explosive charges, such as are used in construction work and mining, there is a reason ~o include delays between charges or series of charges to reduce seismic shock or to obtain particular types of rock breaks.
Concurrently, it is not always necessary that the initial cap detonation be instantanious, and a short delay of, for example a one or two second delay, for the initial cap detonation may be tolerated without creating any new problems.
The present invention provides a simple method of accomplishing fuse initiation electrically to gain most of the - 20 advantages of electrical initiation, yet reduce most of the hazards usually related to electrically actuated detonation caps.
The present method provides some inherent delay, a short delay of a second cjr so to predetermined longer times of delay, after imposing the initial current. ~riefly the invention involves the soldering of a short bridgewire, long enough to span the diameter of the fuse, about 1/4 inch, to two electric lead wires which in turn may be connected into a firing circuit. The ;~bridgewire is a pyro-alloying wire producing an exothermic re-. .
;'' '~
: ~a~sso :
1 action when initiated by a reasonably strong electric current.
The bridgewire is made of one of the platinum group of metals and aluminum. One commerc~ally available bridgewire is sold under the trademark of "Pyrofuse" manufactured by Sigmund Cohn Co. m e mounted bridgewire is pulled into a cut, made half way through the fuse, and it may be t~ped into proper position when - desired. Preferrably, the cut is made at an angle in the fuse, directed away from a cap mounted on the end of the fuse. The ; cut must be sufficiently deep to enter or expose the ignition train, but must be made only deep enoughtto maintain tensile strength to the assembly. When the leads to the bridgewire carry a sufficient current, the bridgewire shorting across the leads is heated, initiating the alloy reaction, which gives off a substantial amount of heat and sparks sufficient to ignite the ignition train of the fu~e, the fuse in turn detonates the cap. 3~g~;f~caRo~
The bridgewire may be used to ignite "~s~Hhr~s~}", a thermite cord, which may, also, be used in the detonating system.
Although Ignitacord is not recommended for use to initiate caps in a direct manner, it may be used. The bridgewire may be used to initiate a cap or a s~uib directly instead of a fuse, to avoid delay caused by the use of the fu~e. This method, however, - may introduce several safety considerations which are not found by putting the bridgewire in the slot of the fuse mentioned a-.
bove.
A series of timed spaced detonations may be arranged ;..
with a plurality of explosive charges by changing the length of the fuse to the variou~ caps from ~he bridgewires to provide for successive explosion~ in the series~ The length of the delay in-tervals is a simple function of the burning rate of the ignition ~-~` train of the fuse, and the length of the fuse is from the bridge-- wire to the cap determines the delay.
; 1 Included among the objects and advantages of thepresent invention is to proviae an electrically initiated de- `
tona~on of a cap.
Another object of the invention is to provide the ~-~
electrical detonation of a cap by system which requires a high current thereby producing a very safe system. -Another ob~ect of the invention is to provide a de-tonation sy~tem for a cap utilizing a safety fuse, and a pyro-alloying bridgewire which is initiated by a high current for igniting the ignition train of the fuse.
Still another object of the invention is to provide an electrically initiated detonation of a cap utilizing a fuse -~
which is electrically ignited to provide a predetermined time ~ -delay in the detonation of the cap from the activation of the -!' electrical circuit-Yet another ob~ect of the invention is to provide an electrically actuated cap detonation utilizing a simple, safe - system without the use of sensitive, electrically actuated caps.
These and other ob~ects and advantages of the invention may be readily ascertained by referring to the descr~ption and appended illustrations in which:
Fig. 1 ~s top plan view of a bridgewire ignitor for a fuseT
Fig. 2 is a side elevational view of the device of Fig. 1:
Fig. 3 i~ a side elavational view of a portion of a fuse and fuse lgnited, detonating cap attached thereto;
Fig. 4 is a side elevational view of a device similar to that of Fig. 3, having a slit cut at an angle to the longit-udinal axis of the fuse and into the ign~tion train of the fuse;and Fig. 5 is a side elevational view of the electrically :.
~ actuated fuse ignitor in place ready for the detonation of a cap.
.
: ` ` ` `
10~i~5S0 .. ~`:, 1 The fuse ignitor illustrated in Figs. 1 and 2 includes - --an electric lead wire 10 covered by insulation 12, and a lead wire 14 covered by insulation 16. The bare ends of lead wires lOa and 14a are ~o be attached to a two lead, electric circuit wire, and, of course, must be separated, to prevent shorting a-cross the lead~ of the electric ignitor. The insulated wires are necked down providing a short length 18 where the wires are close together, and are again expanded at point 20 so that ends lOb and 14b are spaced a distance, to effectively stradle a fuse, as explained below. A bridgewire 22 ~s soldered across the ends lOb and 14b providing an electrically connection acros~ the leads.
A plastic reinforcing member 24 is welded or otherwise secured to the ends of the leads, holding the ends apart and protecting the bridgewire 22. The pla~tic str~ngthing member may be a small sheet of a thermo-plastic reqin, for example polyethylene, poly-propylene, etc. Which provides some strength to the unit, and is easily secured to the wires by heating to melt the wires into the plastic. The plastic, of course, may be secured in the other means such as cement, or the like.
A~ shown in Fig. 2, the fuse ignitor i~ es~entially planar except for the end~ lOb and 14b of the electrical con-ductor~ which are bent at a slight angle to the plane of the , lead wire~. The angle is arranged to provide a secure fit of ; ~he fu~e ignitor in a fuse. As shown in Fig. 3, a lenyth of safety fuse 30, or the like, is secured by conventional means into a cap 32. The cap is a fuse ignited detonating cap com-monly used commerically for a fu~e having an ignition train.
- ; The leng~h of the fuse 30 is not critical, but should be su-fficiently long for the placement of the fuse ignitor therein, and to provide a structure for supporting the same. A slit 34 is cut into the fuse 30 sufficiently deep to expose the ignition train in the fuse. Preferably, the cut 34 is made at an angle ~`` 106~5S0 1 of about 20~ to 45 to the longitudinal axis through the fuse.
~he distance of the fuse from the cut to about the center of ;
the detonating cap is predetermined to give a ~ime delay from the actual firing of the ignition train of the fuse to the de-tonation of the cap. This distance may obviously extend ad- `
jacent the cap edge to a substantial distance from the cap to provide a long term delay, as determined by the rate of travel of the fire front in the ignition train in ~he fuse.
In using the ignitor of the inventio~ the unit is ,d~
placed in a fuse, with the legs, adjacent the brioJgowi~e, stradl-~ .
ing the fuse, which is normally about a 1/4 of an inch in dia-meter. m e bridgewire and it~ supporting strengthening member 24 is forced into the cut 34 so that the bridgewire 22 is in --`
close contact with the ignition train in the fuse. With the bridgewire in place, it may be secured therein by means of tape wrapped around the unit to hold the ignitor in the fuse. The bare ends 10a and 14a are attached to the two lead wires from an electric current source to provide current for the bridgewire.
When the electrical system is initiated with sufficient current, the pyro-alloying reaction is initiated, giving off a great deal ; , of heat and many sparkq are thrown, to ignite the core of the fuseO Once the ignition train is lit, it sets off the cap in the predetermined time interval.
The "Pyrofuse", mentioned above, may be obtained in different diame~ers, resistance and other physical and elect-rical characteristics. It is, however, of high tensile strength and it is easy to solder, so that making the assemblies of the ignitor is easy and inexpensive. Since the bridgewire does not exceed much over a 1/4 of an inch, the cost of the bridgewire 30 is low making an inexpensive assembly. In one tested assembly, a strand o~ Pyrofuse of 0.002 inches diameter was initiated by the generator of a blasting machine. The pyro-alloying wire '.`' ~ -6-1 used in the present invention is not a resistance wire of the type used in detonator cap bridgewire circuits, and it has good conductiv~y. The assembly may be made for quite innocuous circuits, yet be initiated with relatively low voltage. High voltage does not create a problem, as an electrical source, and it may, also, be readily used. The 0.002 inch Pyrofuse requires about 0.6 amperes to initiate the alloying reaction. With the relatively high current necessary for initiating the reaction, stray currents are not normally sufficient to ignite the bridge-wire and it, therefore, is very safe unit for detonating ex-plosive charges.
The plastic support across the electrical leads ad-~acent the bridgewire may be a high dielectric, low conductance and high resistance material. This provides support for and protection for the bridgewire prior to in~ertion into the cut in the fuse, and, also, after insertion in the cut. It must be of a material that is essentially non-conducting with suf-ficient strength to support the assembly. The polyethylene, etc. plastic is satisfactory, as are many other type of plastic, wood, glass, etc. The non-thermal plastic materials may be cemented or otherwise secured in the proper position across the leads.
. .
., .
' ~
. '
Claims (10)
1. An electrically initiated pyro-detonation cap assembly resistant to static electricity comprising:
(a) a length of fuse means of the ignition type having an ignition train;
(b) a pyro-detonation cap secured to an end of said fuse means;
(c) a cut in said length of fuse means exposing the igni-tion train therein;
(d) a pyro-alloying, conducting bridgewire mounted in said cut essentially in contact with said ignition train, said bridgewire comprising a pyro-alloying composition which is not a re-sistance wire, and (e) an electrical lead secured to and extending from each end of said bridgewire to an electric cur-rent source, arranged to activate the alloying reaction of said bridgewire and ignite said fuse ignition train.
(a) a length of fuse means of the ignition type having an ignition train;
(b) a pyro-detonation cap secured to an end of said fuse means;
(c) a cut in said length of fuse means exposing the igni-tion train therein;
(d) a pyro-alloying, conducting bridgewire mounted in said cut essentially in contact with said ignition train, said bridgewire comprising a pyro-alloying composition which is not a re-sistance wire, and (e) an electrical lead secured to and extending from each end of said bridgewire to an electric cur-rent source, arranged to activate the alloying reaction of said bridgewire and ignite said fuse ignition train.
2. An electrically initiated pyro-detonation cap assembly according to claim 1, wherein said pyro-alloying composition in-cludes a platinum group metal and aluminum.
3. An electrically initiated pyro-detonation cap assembly according to claim 1, wherein said cut is spaced from said cap at a predetermined distance, providing a predetermined time for ignition of the ignition train and a delay for detonation of said cap.
4. An electrically initiated pyro-detonation cap assembly according to claim 1 wherein said fuse means is a safety fuse.
5. An electrically initiated pyro-detonation cap assembly according to claim 1, wherein said cut in said fuse means is at an angle to the longitudinal axis of said fuse means directed away from said cap.
6. An electrically initiated pyro-detonation cap assembly according to claim 5, wherein said angle is from 20° to 45°.
7. An electrically initiated pyro-detonation cap assembly according to claim 1, wherein a non-conducting support member secured to the electrical leads adjacent said bridgewire rein-forces the same.
8. An electrically initiated pyro-detonation cap assembly according to claim 7, wherein said electrical leads extend be-yond said bridgewire and said non-conducting support member is secured to the extending ends.
9. An electrically initiated pyro-detonation cap assembly according to claim 8, wherein said non-conducting support member is a thermal plastic sheet.
10. An electrically initiated pyro-detonation cap assembly according to claim 9, wherein said thermal plastic sheet is poly-ethylene.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA272,984A CA1068550A (en) | 1977-03-02 | 1977-03-02 | Electrically initiated fuse ignitor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA272,984A CA1068550A (en) | 1977-03-02 | 1977-03-02 | Electrically initiated fuse ignitor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1068550A true CA1068550A (en) | 1979-12-25 |
Family
ID=4108055
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA272,984A Expired CA1068550A (en) | 1977-03-02 | 1977-03-02 | Electrically initiated fuse ignitor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1068550A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100465574C (en) * | 2007-04-13 | 2009-03-04 | 史凡 | Bridging fibril welding procedure of electric detonator firing device and joint structure thereof |
-
1977
- 1977-03-02 CA CA272,984A patent/CA1068550A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100465574C (en) * | 2007-04-13 | 2009-03-04 | 史凡 | Bridging fibril welding procedure of electric detonator firing device and joint structure thereof |
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