Title of Invention	A DETONATOR ASSEMBLY
Abstract	This invention relates to a detonator assembly. It consists of a housing provided with a hollow cup shaped body and a spacer member separating the cup from a hollow cylindrical body. The cup shaped body has terminals connected thereto and houses initiator charges and a secondary explosive in close contact with each other. The cylindrical body has two columns of charges. The transition charge column located near the spacer has a smaller diameter than the output charge next to it. The transition charge also is lower density than the output charge. A closure member seals the assembly.

Title of Invention

A DETONATOR ASSEMBLY

Abstract

This invention relates to a detonator assembly. It consists of a housing provided with a hollow cup shaped body and a spacer member separating the cup from a hollow cylindrical body. The cup shaped body has terminals connected thereto and houses initiator charges and a secondary explosive in close contact with each other. The cylindrical body has two columns of charges. The transition charge column located near the spacer has a smaller diameter than the output charge next to it. The transition charge also is lower density than the output charge. A closure member seals the assembly.

Full Text	This invention relates to a detonator assembly and is particularly but not exclusively related to a one ampere/one watt (lA/IW) deflagration to detonation transition (DDT) detonator. The detonator of the subject invention avoids the use of sensitive primary esq. losivos. Brief description of the invention. Detonators are extensively used for various military and civilian applications. Detonators with a no-fire current of one ampere and a bridge wire resistance of one ohm, popularly designated as lA/lW detonator, is being used as first fire element for the initiation of high explosive systems in launch vehicles. In its normal design a detonator contains a heat sensitive charge in contact with a bridge wire, followed by a primary and a secondary explosives. In the present design the primary explosive has been dispensed with and a pyrotechnic composition called the initiatory charge, acts as the hot-wire sensitive charge in contact with the bridge wire. Then the initiatory charge directly initiates the secondary explosive PETN. Various initiatory charges can be used for this application. However, selection of a particular charge is dictated by considerations Uke the operating environment and its ability to meet the specifications stipulated for his application. These include the electrical ratings, ground/high altitude ignitability, gas-to-solids ratio of the reaction products, flame temperature etc. For a no-fire (NF) rating of lA and an all-fur (AF) rating of 3 A, we have found zirconium/potassium perchlorate (ZPP) initiatory charge as well as boron/potassium nitrate/lead thiocyanate tricomponent system quite suitable. Normal detonators known in literature use an initiatory charge (pyrotechnic)/heat sensitive primary explosive in contact with a bridge wire as the initiation point. The main output charge is a secondary explosive like PETN/RDX which undergoes detonation by accepting the shock wave generated by a primary explosive like lead aide and lead Stephanie that precedes it. These primary explosives are very sensitive to shock and friction and hence is very risky in processing and handling. In the present design these sensitive primary explosives are dispensed with and the heat output from a pyrotechnic charge directly initiates the secondary explosive PETN. The heat output from the pyrotechnic charge deflagrates the secondary explosive PETN in contact with it and a deflagration-to-detonation transition (DDT) occurs within the PETN column before it is filly consumed. This DDT is brought about by suitably adjusting the loading density and column length of PETN charge. The output from the PETN charge detonates a second column of secondary explosive in front of it which acts as the output charge and the output from the detonator can be made to match the requirement by suitably controlling the quantity/column length of this charge. This output charge can be either PETN itself or any other secondary explosive like RDX, HNS etc. The advantage is that it is much safer, simple and easy to handle, compared to the conventional one, as it contains no primary explosive which is very sensitive to friction and impact. The object of this invention is to develop a detonator for various applications, including space, using a design philosophy of avoiding a primary explosive in the ejqilosive train of the detonator. Thus the stress is to go directly from a pyrotechnic charge to the secondary qjlosive, PETN. The principle of the development is that the current rating of the detonator is dictated by the rating of the initiatory charge and hence by choosing suitable compositions, detonators of appropriate rating can be obtained. The output from the pyrocharge deflagrates a column of PETN kept in immediate contact with the pyrocharge. The deflagration continues till it builds up sufficient pressure to shear an aluminium spacer kept separating this charge from a column of lower density PETN which acts as a transition column. When the high pressure gases from the deflagrating charge drive the sheared plate into the transition column, there transition from deflagration to detonation takes place. The shock generated by this transition ensures detonation of the output charge kept in front of the transition column. The output charge can be either PETN itself or any other secondary explosive. Since the detonator energy primarily depends on the output charge, the energy output can be varied by suitably adjusting the charge quantity. The detonator assembly according to lathis invention comprises a housing accommodating a hollow body provided with electrical contact means, and a bridge wire, said hollow body containing conventional initiatory charge and secondary explosives is juxtaposed with a hollow cylindrical member through a hearable spacer member, said cylindrical member housing conventional transition charge and output charge, said transition charge being in contact with said shearable spacer member and is of a smaller diva than that of said output charge. The detonator housing is made of any material possessing sufficient strength to withstand detonation shock. Stainless steel is found suitable for this purpose. The hollow body accommodated within this housing may be a ceramic cup and tike electrical contacts are terminal pins connectable to power supply. A one ohm bridge wire is preferred and is soldered to the terminal pins. Conventional initiatory and secondary explosive charges may be press loaded into this ceramic cup. Pentane Erythritol Tretra Nitrate PETN is a preferred secondary charge. Zirconium/potassium perchlorate or boron/potassium nitrate/lead thiocyanate tricomponent system may be used as an initiator. The pressed secondary charge must have a density of 1.5 to 1.6 g/cm . The shearable spacer may be made of aluminium or the like metals or alloys thereof and may preferably be 0.5 to 1mm thick. The cylinder located next to the ceramic cup above the spacer may be made of any hard material like stainless steel. The cylinder has a cylinderical cavity of 2 to 3 mm dia and 7 to 9 mm length at the end next to the spacer member followed by a cavity of 7 mm dia and 1 mm depth. The transition charge is loaded in the smaller dia area and at a preferred density of 1.1 to 1.3 g/cm . The output charge is processed into the wider cavity at a loading density of 1.5 to 1.6 g/cm^. The housing is also provided with a closure member which preferably is made of aluminium. The closure member is crimped to the housing at the outer end of the cylindrical body. The detonator assembly is assembled by positioning the hollow ceramic body in a glass sealed detonator housing containing terminal pins. The protruding ends of these pins are ground and made flush with the surface of the hollow body. The bridge wire is then soldered across the terminals. 20 to 30 mg of initiator charge is introduced into the hollow body at a load of 170 kg. Above this charge 70 to 80 mg PETN of >3500 cm^/g surface area is loaded to a density of 1.5 to 1.6 g/cm^. It is not necessary to provide a gap between the initiator charge and the secondary explosive. Aluminium or the Uke shearable spacer is bonded over this using epoxy bonding agents. The hollow cylindrical body is then introduced into the housing and the bottom column with smaller dia is filled with PETN. The density of this filling is between 1.1 to 1.3 g/cm^. Output charge is then filled at a density of 1.5 to 1.6 g/cm^ in the wider cavity. The closure member is then placed over this assembly and sealed by crimping to close the assembly. Initiatory charges: The initiator charge used in this study are zirconium/potassium perchlorate or boron/potassium nitrate/lead thiocyanate. Typical compositions are : 50-56% zirconium and 43-50% potassium perchlorate; 18-23% boron, 72-78% potassium nitrate, 3-8% lead thiocyanate. However, further variations in the above percentages based on particle size are possible. With the first composition 1.5-3% of a suitable binder like ethyl cellulose/Vito etc. is used to provide suitable adhesion during pressing. This invention will now be described with reference to the accompanying drawings wherein reference numeral 1 indicates the housing, and the numeral 2 represents the hollow ceramic body. Terminal pin is shown by numeral 3 and the bridge were by numeral 4. Initiator charge which is a pyrotechnic substance within the ceramic body is shown by numeral 5 and the secondary explosive charge by numeral 6. Method of Operation: When initiated, the output from the initiatory charge deflagrates the column of secondary explosive like PETN kept in immediate contact therewith. Deflagration continues till sufficient pressure is built to shear the spacer member which separates this from the transition charge kept in the small dia cylindrical cavity. The sheared member is driven to the transition charge to detonate it and the shock generated by the detonation of this charge ensures detonation of the output charge kept in front of the transition charge. ' The advantage of the new detonator assembly is that use of sensitive primary explosives are avoided thereby making it safe for operation. Further, the deflagration to detonation transition is smoother and safer than the existing system where primary explosives are used. Conventional explosives like cyclotrimethyk le trinitramine popularly known as RDX, Fetal Erythntol tetra nitrate (PETN), Hexane nitro stilbene (HNS) are in hiss detonator assembly. WE CLAIM: 1. A detonator assembly comprising a housing accommodating a hollow body provided with electrical contact means, and a bridge wire, said hollow body containing conventional initiatory charges and a secondary explosive is juxtaposed with a hollow cylindrical member through a sharable spacer member, said cylindrical member housing known transition charge and output charge, said transition charge being in contact with said spacer member, and is of a smaller dia than that of said output charge. 2. The detonator as claimed in claim 1, wherein said hollow body is a cup shaped ceramic body. 3. The detonator as claimed in claims 1 and 2 wherein the electrical contacts are terminal pins of round flush with the hollow body and has the bridge wire soldered across thereon. 4. The detonator as claimed in claims 1-3, wherein the sharable spacer member is made of aluminium. 5. The detonator as claimed in claims 1 to 4, wherein said initiator charge is selected from zirconium/potassium per chlorate and boron/potassium nitrate/lead thiocyanate tricomponent system. The detonator as claimed in claims 1 to 5, wherein the secondary explosive in contact with said initiator charge is Punta Erythriotol Tetra Nitrate (PETN). The detonator as claimed in claims 1 to 6, wherein said hollow cylindrical body has a column of low density transition charge of PETN, said column having a density of 1.1 to 1.3 g/cm^. The detonator as claimed in claims 1 to 7, wherein said output charge column has a density of 1.5 to 1.6 g/cm'. The detonator as claimed in claims 1 to 8, wherein the said output charge is selected from a secondary like PETN, RDX, HNS etc. The detonator as claimed in claims 1 to 8, wherein said cylindrical body is provided with a closure member. A detonator assembly substantially as herein described and illustrated.

Full Text

This invention relates to a detonator assembly and is particularly but not exclusively related to a one ampere/one watt (lA/IW) deflagration to detonation transition (DDT) detonator. The detonator of the subject invention avoids the use of sensitive primary esq. losivos.
Brief description of the invention.
Detonators are extensively used for various military and civilian applications. Detonators with a no-fire current of one ampere and a bridge wire resistance of one ohm, popularly designated as lA/lW detonator, is being used as first fire element for the initiation of high explosive systems in launch vehicles. In its normal design a detonator contains a heat sensitive charge in contact with a bridge wire, followed by a primary and a secondary explosives. In the present design the primary explosive has been dispensed with and a pyrotechnic composition called the initiatory charge, acts as the hot-wire sensitive charge in contact with the bridge wire. Then the initiatory charge directly initiates the secondary explosive PETN. Various initiatory charges can be used for this application. However, selection of a particular charge is dictated by considerations Uke the operating environment and its ability to meet the specifications stipulated for his application. These include the electrical ratings, ground/high altitude ignitability, gas-to-solids ratio of the reaction products, flame temperature etc. For a no-fire (NF) rating of lA and an all-fur (AF) rating of 3 A, we have found zirconium/potassium perchlorate (ZPP) initiatory charge as well as boron/potassium nitrate/lead thiocyanate tricomponent system quite suitable.

Normal detonators known in literature use an initiatory charge (pyrotechnic)/heat sensitive primary explosive in contact with a bridge wire as the initiation point. The main output charge is a secondary explosive like PETN/RDX which undergoes detonation by accepting the shock wave generated by a primary explosive like lead aide and lead Stephanie that precedes it. These primary explosives are very sensitive to shock and friction and hence is very risky in processing and handling. In the present design these sensitive primary explosives are dispensed with and the heat output from a pyrotechnic charge directly initiates the secondary explosive PETN. The heat output from the pyrotechnic charge deflagrates the secondary explosive PETN in contact with it and a deflagration-to-detonation transition (DDT) occurs within the PETN column before it is filly consumed. This DDT is brought about by suitably adjusting the loading density and column length of PETN charge. The output from the PETN charge detonates a second column of secondary explosive in front of it which acts as the output charge and the output from the detonator can be made to match the requirement by suitably controlling the quantity/column length of this charge. This output charge can be either PETN itself or any other secondary explosive like RDX, HNS etc. The advantage is that it is much safer, simple and easy to handle, compared to the conventional one, as it contains no primary explosive which is very sensitive to friction and impact.

The object of this invention is to develop a detonator for various applications, including space, using a design philosophy of avoiding a primary explosive in the ejqilosive train of the detonator. Thus the stress is to go directly from a pyrotechnic charge to the secondary qjlosive, PETN.
The principle of the development is that the current rating of the detonator is dictated by the rating of the initiatory charge and hence by choosing suitable compositions, detonators of appropriate rating can be obtained. The output from the pyrocharge deflagrates a column of PETN kept in immediate contact with the pyrocharge. The deflagration continues till it builds up sufficient pressure to shear an aluminium spacer kept separating this charge from a column of lower density PETN which acts as a transition column. When the high pressure gases from the deflagrating charge drive the sheared plate into the transition column, there transition from deflagration to detonation takes place. The shock generated by this transition ensures detonation of the output charge kept in front of the transition column. The output charge can be either PETN itself or any other secondary explosive. Since the detonator energy primarily depends on the output charge, the energy output can be varied by suitably adjusting the charge quantity.
The detonator assembly according to lathis invention comprises a housing accommodating a hollow body provided with electrical contact means, and a bridge wire, said hollow body containing conventional initiatory charge and secondary explosives is juxtaposed with a hollow cylindrical member through a hearable spacer member, said cylindrical member housing conventional transition charge and output charge, said

transition charge being in contact with said shearable spacer member and is of a smaller diva than that of said output charge.
The detonator housing is made of any material possessing sufficient strength to withstand detonation shock. Stainless steel is found suitable for this purpose. The hollow body accommodated within this housing may be a ceramic cup and tike electrical contacts are terminal pins connectable to power supply. A one ohm bridge wire is preferred and is soldered to the terminal pins. Conventional initiatory and secondary explosive charges may be press loaded into this ceramic cup. Pentane Erythritol Tretra Nitrate PETN is a preferred secondary charge. Zirconium/potassium perchlorate or boron/potassium nitrate/lead thiocyanate tricomponent system may be used as an initiator. The pressed secondary charge must have a density of 1.5 to 1.6 g/cm . The shearable spacer may be made of aluminium or the like metals or alloys thereof and may preferably be 0.5 to 1mm thick. The cylinder located next to the ceramic cup above the spacer may be made of any hard material like stainless steel. The cylinder has a cylinderical cavity of 2 to 3 mm dia and 7 to 9 mm length at the end next to the spacer member followed by a cavity of 7 mm dia and 1 mm depth. The transition charge is loaded in the smaller dia area and at a preferred density of 1.1 to 1.3 g/cm . The output charge is processed into the wider cavity at a loading density of 1.5 to 1.6 g/cm^. The housing is also provided with a closure member which preferably is made of aluminium. The closure member is crimped to the housing at the outer end of the cylindrical body.

The detonator assembly is assembled by positioning the hollow ceramic body in a glass sealed detonator housing containing terminal pins. The protruding ends of these pins are ground and made flush with the surface of the hollow body. The bridge wire is then soldered across the terminals. 20 to 30 mg of initiator charge is introduced into the hollow body at a load of 170 kg. Above this charge 70 to 80 mg PETN of >3500 cm^/g surface area is loaded to a density of 1.5 to 1.6 g/cm^. It is not necessary to provide a gap between the initiator charge and the secondary explosive. Aluminium or the Uke shearable spacer is bonded over this using epoxy bonding agents. The hollow cylindrical body is then introduced into the housing and the bottom column with smaller dia is filled with PETN. The density of this filling is between 1.1 to 1.3 g/cm^. Output charge is then filled at a density of 1.5 to 1.6 g/cm^ in the wider cavity. The closure member is then placed over this assembly and sealed by crimping to close the assembly.
Initiatory charges:
The initiator charge used in this study are zirconium/potassium perchlorate or boron/potassium nitrate/lead thiocyanate. Typical compositions are : 50-56% zirconium and 43-50% potassium perchlorate; 18-23% boron, 72-78% potassium nitrate, 3-8% lead thiocyanate. However, further variations in the above percentages based on particle size are possible. With the first composition 1.5-3% of a suitable binder like ethyl cellulose/Vito etc. is used to provide suitable adhesion during pressing.

This invention will now be described with reference to the accompanying drawings wherein reference numeral 1 indicates the housing, and the numeral 2 represents the hollow ceramic body. Terminal pin is shown by numeral 3 and the bridge were by numeral 4. Initiator charge which is a pyrotechnic substance within the ceramic body is shown by numeral 5 and the secondary explosive charge by numeral 6.
Method of Operation:
When initiated, the output from the initiatory charge deflagrates the column of secondary explosive like PETN kept in immediate contact therewith. Deflagration continues till sufficient pressure is built to shear the spacer member which separates this from the transition charge kept in the small dia cylindrical cavity. The sheared member is driven to the transition charge to detonate it and the shock generated by the detonation of this charge ensures detonation of the output charge kept in front of the transition charge.

'
The advantage of the new detonator assembly is that use of sensitive primary explosives are avoided thereby making it safe for operation. Further, the deflagration to detonation transition is smoother and safer than the existing system where primary explosives are used.
Conventional explosives like cyclotrimethyk le trinitramine popularly known as RDX, Fetal Erythntol tetra nitrate (PETN), Hexane nitro stilbene (HNS) are in hiss detonator assembly.

WE CLAIM:
1. A detonator assembly comprising a housing accommodating a hollow body provided with electrical contact means, and a bridge wire, said hollow body containing conventional initiatory charges and a secondary explosive is juxtaposed with a hollow cylindrical member through a sharable spacer member, said cylindrical member housing known transition charge and output charge, said transition charge being in contact with said spacer member, and is of a smaller dia than that of said output charge.
2. The detonator as claimed in claim 1, wherein said hollow body is a cup shaped ceramic body.
3. The detonator as claimed in claims 1 and 2 wherein the electrical contacts are terminal pins of round flush with the hollow body and has the bridge wire soldered across thereon.
4. The detonator as claimed in claims 1-3, wherein the sharable spacer member is made of aluminium.
5. The detonator as claimed in claims 1 to 4, wherein said initiator charge is selected from zirconium/potassium per chlorate and boron/potassium nitrate/lead thiocyanate tricomponent system.

The detonator as claimed in claims 1 to 5, wherein the secondary explosive in contact with said initiator charge is Punta Erythriotol Tetra Nitrate (PETN).
The detonator as claimed in claims 1 to 6, wherein said hollow cylindrical body has a column of low density transition charge of PETN, said column having a density of 1.1 to 1.3 g/cm^.
The detonator as claimed in claims 1 to 7, wherein said output charge column has a density of 1.5 to 1.6 g/cm'.
The detonator as claimed in claims 1 to 8, wherein the said output charge is selected from a secondary like PETN, RDX, HNS etc.
The detonator as claimed in claims 1 to 8, wherein said cylindrical body is provided with a closure member.
A detonator assembly substantially as herein described and illustrated.

Documents:

879-mas-2000 abstract duplicate.pdf

879-mas-2000 claims duplicate.pdf

879-mas-2000 description (complete) duplicate.pdf

879-mas-2000-abstract.pdf

879-mas-2000-claims.pdf

879-mas-2000-correspondnece-others.pdf

879-mas-2000-correspondnece-po.pdf

879-mas-2000-description(complete).pdf

879-mas-2000-drawings.pdf

879-mas-2000-form 1.pdf

879-mas-2000-form 19.pdf

879-mas-2000-form 26.pdf

879-mas-2000-form 3.pdf

« Previous Patent

Next Patent »

Patent Number

224638

Indian Patent Application Number

879/MAS/2000

PG Journal Number

49/2008

Publication Date

05-Dec-2008

Grant Date

21-Oct-2008

Date of Filing

16-Oct-2000

Name of Patentee

INDIAN SPACE RESEARCH ORGANISATION

Applicant Address

DEPARTMENT OF SPACE, ANTARIKSHA BHAVAN, NEW BEL ROAD, BANGALORE 560 094,

Inventors:

#	Inventor's Name	Inventor's Address
1	KANDATHIL SUKUMARAN CHANDRABHANU	SPACE ORDNANCE GROUP, VIKRAM SARABHAI SPACE CENTRE, THIRUVANANTHAPURAM - 695 022,
2	AROLICKAL GOPALAN RAJENDRAN	SPACE ORDNANCE GROUP, VIKRAM SARABHAI SPACE CENTRE, THIRUVANANTHAPURAM - 695 022,
3	MUTHUKUMARASAMY RAVINDRAN	SPACE ORDNANCE GROUP, VIKRAM SARABHAI SPACE CENTRE, THIRUVANANTHAPURAM - 695 022,
4	CHERANELLOOR BHASKARAN KARTHA	SPACE ORDNANCE GROUP, VIKRAM SARABHAI SPACE CENTRE, THIRUVANANTHAPURAM - 695 022,

PCT International Classification Number

F42B12/20

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA