Title of Invention	A NOVEL DEVICE FOR BOTTOM HOLE NON-ELECTRIC INITIATION OF NON-CAP SENSITIVE EXPLOSIVE COLUMN AND A PROCESS THEREFOR
Abstract	A novel device for bottom hole non-electric initiation of non-cap sensitive explosive column, which comprises a length of conventional detonating fuse (2) so as to transmit shock wave and a length of non- metallic flexible rope (11), characterised in that the said fuse and rope lengths being joined at one end and kept parallel to each other by means of plurality of non-metallic spatial separation spacers (12), the said joint of fuse and rope being provided with a booster charge (3 ) and a dead weight (13), the said rope being provided along its length with a plurality of booster charges (3) fixed at intervals to provide a ratio of the order of 1 : 500 by weight between booster charges and non-cap sensitive explosive column.

Title of Invention

A NOVEL DEVICE FOR BOTTOM HOLE NON-ELECTRIC INITIATION OF NON-CAP SENSITIVE EXPLOSIVE COLUMN AND A PROCESS THEREFOR

Abstract

A novel device for bottom hole non-electric initiation of non-cap sensitive explosive column, which comprises a length of conventional detonating fuse (2) so as to transmit shock wave and a length of non- metallic flexible rope (11), characterised in that the said fuse and rope lengths being joined at one end and kept parallel to each other by means of plurality of non-metallic spatial separation spacers (12), the said joint of fuse and rope being provided with a booster charge (3 ) and a dead weight (13), the said rope being provided along its length with a plurality of booster charges (3) fixed at intervals to provide a ratio of the order of 1 : 500 by weight between booster charges and non-cap sensitive explosive column.

Full Text	The present invention relates to a novel device for bottom hole non-electric initiation of non-cap sensitive expldsive column and a process therefor. The present invention particularly relates to a novel device for bottom hole nonelectric Initiation of non-cap sensitive explosive column wherein the device of the present invention essentially consists of a conventional detonating fuse coupled with a nonmetallic flexible rope tied with a weight and provided with one or more number of nonmetallic spacers and having suitably spaced booster charges. The innin u.se of lite device ol'lhe present invention is l t > i n i l i n l e delonnUon from llie bottom of a non-cap sensitive explosive column filled in a drill hole. The explosives which are incapable of getting initiated by electric or non-electric detonation are called non-cap sensitive explosive. The initiation in such cases are made by a booster explosive /booster (high strength explosive) which is initiated first to subsequently initiate the noncap sensitive explosives. Generally several number of boosters, each of 100-250 grams weight, spaced at a regular interval are provided in an explosive column The number of boosters to be provided in an explosive column depends on the total explosive quantity and the ratio is maintained such that 100 gm of booster is used for every 50 kg of non-cap sensitive explosives which indicates that ratio of explosive weight to booster weight should be 500. Almost 99 per cent of the explosives used in open cast mining is of noncap sensitive type because of cost consideration. The cap-sensitive explosives are very costly and are not used in production blasting. Top initiation of any explosive column of diameter ranging from 75 to 310 mm by conventional technique is shown in Figure 1 of the drawings accompanying this specification. The legend to the Figure 1 is as under: Legend to the Figure 1: 1. Blast hole 2. Detonating fuse length 3. Cast booster (booster charge) 4. Detonating fuse initiated outside the blast hole 5. Point of initiation of explosive column 6. Direction of propagation of detonation front 7. Explosive coulumn 8. Stemming column It can be understood from Figure 1 that the inititaion of explosive column starts from the top of the blast hole as the top most booster is in connection with the detonating fuse. The top portion of the explosive column, which is initiated first in case of top initiation, is in direct contact of the stemming material placed at the top of the drill hole to provide a momentary resistance against the dissipation of explosive energy to the atmosphere. The drawbacks of the top hole initiation are as follows: 1) It leads to destabilisation or ejection of stemming material immediately as the top portion of the explosive column is detonated. The explosive energy utilisation becomes poor as a result. This may lead to poor fragmentation and more ground vibration. 2) Underbreak at the bottom of the drill hole may occur as the stemming column becomes less effective while the bottom portion of the explosive colurnn gets initiated. 3) Due to ejection or destabilisation of stemming material, the rock fragments produced by blasting at the top of the drill hole are frequently thrown to an abnormal distance which may cause damage to human life and property. l l IN evident Ihnl (he nbove disndvimlnueN due lo lop inil'mlion method am lie nvoided by initiating the explosives from the bottom of the hole, generally called as bottom hole initiation or bottom initiation. However, the top initiation method is followed in most of the opencast coal and metal mines in India in spite of the said disadvantages because of non-availability of a cost-effective device for bottom hole initiation. The bottom hole initiation can be complied by means of electric or non-electric detonating systems. The electric detonating systems are mainly used for small diameter (25-32 mm) shallow 0.75-3 m deep holes. Initiation of deeper holes by electric systems may be hazardous causing misfires. Hence, bottom hole initiation by non-electric method is recommended.! Non-electric bottom initiation by non-electric detonator (NONEL) is used in many opencast mines of India and abroad. The device is integrated with shock tube which is coated with thin layer of explosive inside for transmission of shock to the bottom of the explosive column without damaging the tube. A detonator, coupled at the bottom end of the shock tube and inserted in booster explosive charge detonates as soon as it receives the shock transmitted through the shock tube. The detonator in turn detonates the booster and this subsequently initiates the explosive column. The bottom hole initiation by NONIZL is explained in Figure 2 of the drawings. The legend to the Figure 2 is ns under: Legend to the Figure 2: 1. Blast hole 3. Cast booster (booster charge) 4. NONEL initiation outside the blast.hole 5. Point of initiation of explosive column 6. Direction of propagation of detonation front 7. Explosive column 8. Stemming column 9. NONEL shock tube 10. Detonator The advantage of the NONEL is that bottom hole initiation can be achieved both in cap-sensitive and non-cap sensitive explosives as the shock wave being carried through the shock tube is incapable of detonating any explosive material outside the tube. But, the NONEL device has not, been very popular as it is very expensive compared to the detonating fuse used for top initiation. Hence, the advantages of bottom initiation of explosive column have been overlooked in many cases to avoid additional mining cost. This calls for development of a novel but cheaper method of bottom initiation of explosive column. Reference may be made to US patent No.s: 3590739 and 4998478, wherein the bottom hole initiation of explosive by transmission of shock wave through tubes has been disclosed. The device is sold under the trade name NONEL (a trademark of Nitro- Nobel AB, Sweden). Such tubes are often referred to as "shock tube", typically has an inner diameter of 1.5 mm and an outer diameter of 3 mm and contains a small quantity of explosive material coated on the inner surface of a plastic tube. The explosive material is a mixture of an explosive called HMX and fine aluminium flakes in the mass ratio of 42:3. A shock wave will typically propagate at 2000 m/s in NONEL tubing and will be contained within the confines of the tube. The drawbacks in the use of NONEL is its high cost which prevents its mass application in spite of the advantages associated with its use. The main object of the present invention is to provide a novel device for bottom hole non-electric initiation of non-cap sensitive explosive column which obviates the drawbacks of the expensive NONEL. Another object is to provide a device which is cheap and, hence, should find mass application to derive the full advantages of bottom hole initiation. Yet another object is to provide a process for bottom hole non-electric initiation of non-cap sensitive explosive column. The device of present invention constitutes an assembly of detoning fuse, boosters, flexible rope of suitable material such as coir, jute, one or more spacers and a weight. Figure 3 of the drawings shows a schematic embodiment of the novel device of the present invention which enables bottom hole non-electric initiation of non-cap sensitive explosive column. The legend to the Figure 3 is as under: Legend to the Figure 3: 1. Blast hole 2. Detonating fuse length 3. Cast booster (booster charge) 4. Initiation of detonating fuse from outside the hole 5. Point of initiation of explosive column 6. Direction of propagation of detonation front 7. Explosive column 8. Stemming colurim 11. Non-metallic flelxible rope 12. Spacers 13. Weight The assembly of numbers 2, 3, 11, 12 and 13 above constitute the present invention. Accordingly, the present invention provides a novel device for bottom hole nonelectric initiation of non-cap sensitive explosive column, which comprises a length of conventional detonating fuse (2) so as to transmit shock wave and a length of non-metallic flexible rope (11), characterised in that the said fuse and rope lengths being joined at one end and kept parallel to each other by means of plurality of non-metallic spatial separation spacers (12), the said joint of fuse and rope being provided with a booster charge (3 ) and a dead weight (13), the said rope being provided along its length with a plurality of booster charges (3) fixed at intervals to provide a ratio of the order of 1 : 500 by weight between booster charges and non-cap sensitive explosive column. In an embodiment of the present invention the booster charge(s) used is of conventional type. In another embodiment of the present invention the non-metallic rope used IS of materials such as coir, jute. In yet another embodiment of the present invention non-metallic spacers used are made of materials like wood, bamboo pieces and are provided to maintain a separation of at least 100 mm between the detonating fuse and the rope. The spacers are fitted above and below the booster charge provided along the rope at certain interval to maintain a ratio of 1 :5 00 by weight between the booster and the explosive mass. The spacers should be about 30 rnm shorter than the standardised hole diameter to facilitate easy insertion in the blast hole of diameter such as 150 mm, 250 mm, 310 mm. In still another embodiment of the present invention a dead weight of around 2 kg is provided at the junction of fuse and the rope to create tension so that the rope and the detonating fuse are maintained in a parallel position to each other. The wooden spacer and weight are provided to ensure separation of the flexible rope and the detonating fuse throughout which is essential for achieving bottom initirtion of the explosive column. Accordingly, the present invention provides a process for bottom hole nonelectric initiation of non-cap sensitive explosive column using the novel device as described herein above which comprises lowering concentrically the dead weight end of the device in a conventional blast hole, packing the said blast hole with non-cap sensitive explosive mass of the order of about 500 times the weight of the booster charge of the above device, igniting the free end of the detonating fuse at the blast hole top. The process of the bottom hole initiation with the device of the present is explained below: The detonating fuse when ignited outside the hole carries the shock wave to the bottom of the hole filled with non-cap sensitive explosive column. As the explosive column is non-cap sensitive, it is not exploded by the detonating fuse but a small portion of it gets burnt due to initiation of the detonating fuse. The detonating fuse subsequently initiates the booster tied at the bottom of the fuse which in turn initiates the explosive column, which are tied along the rope and are separated by the spacers fixed one above and one below the booster enabling the separation of detonating fuse from the rope by atleast 100 mm so as the boosters donot get prematurely initiated by the detonating fuse before the bottom most one is initiated. The spacers, which must be of non-metallic materials like wood or bamboo pieces, should be at least 30 mm smaller than the blast hole diameter facilitating easy insertion of the assembly in the blast hole. The dead weight of 2 kg mass tied at the junction of detonating fuse and the rope provides tension so that the rope and the detonating fuse remain parallel throughout and never come in contact with each other. The 2 kg weight has been selected based on the experience and convenience of the user. The whole assembly of the present device can be standardised for various blast hole diameters like 150 mm, 250 mm and 310 mm. The parameters like the spacers dimensions, intervals of the boosters can be standardised according to various blast hole sizes. In the novel device of the present invention/resides in the parallel coupling of conventional detonating fuse and non-metallic ropes wherein the first booster charge is provided at the end of the detonating fuse which is joined to the non-metallic rope and subsequent booster charges are provided along the rope for explosive mass equal to 500 times the booster weight. The present invention introduces a novel way to initiate the explosive from the bottom of the explosive column while blasting with a detonating fuse and replaces the existing methods of less effective top initiation by detonating fuse and bottom initiation by expensive NONEL. The present invention provides an effective but cheaper method of initiation of the explosive from the bottom of the hole and provides better fragmentation, less underbreak, reduced ground vibration and fly rock. The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example- 1 Experiments in the field were conducted with the invention in western part of the 4th bench of Jayant opencast mine of Northern Coalfields Ltd.. A portion of front rows of holes in the blast was initiated with conventional top initiation by detonating fuse and the other portion in the same row was initiated with the device of the present invention to compare the performances of these two methods. The blast was monitored with high speed video camera. When the video photographs were analysed clip by clip, it was observed that the bottom was moved earlier than the rest of the column in case of bottom hole initiation by detonating fuse and the reverse was observed in case of top initiation by detonating fuse. Fly of rock fragments were also observed in case of top initiation by detonating fuse. Example-2 The following full scale blasts were conducted in the western part of the Jayant'mine of Northern Coalfields Ltd., and in PK OC-II mine of Singareni Collieries Company Ltd. (SCCL) using the novel device described under present invention. The main features of the blasts are listed in Table 1. In conclusion, the experiments demonstrated that the present invention yields a safe and good blast performance while providing a cost-effective substitute to the shock tube NONEL combination.. The main advantages of the invention are: 1. Provides considerably cheaper substitute to the NONEL, 2. Achieves bottom hole initiation of the non-cap sensitive explosive column, 3. Provides better fragmentation in comparison to top hole initiation, I 4. Controls flyrock (Unwanted rock trajectories), 5. Reduces ground vibration in comparison to top hole initiation, 6. Minimises throw in comparison to top hole initiation, and 7. Controls underbreak. We claim: 1. A novel device for bottom hole non-electric initiation of non-cap sensitive explosive column, which comprises a length of conventional detonating fuse (2) so as to transmit shock wave and a length of non- metallic flexible rope (11), characterised in that the said fuse and rope lengths being joined at one end and kept parallel to each other by means of plurality of non-metallic spatial separation spacers (12), the said joint of fuse and rope being provided with a booster charge (3 ) and a dead weight (13), the said rope being provided along its length with a plurality of booster charges (3) fixed at intervals to provide a ratio of the order of 1 : 500 by weight between booster charges and non-cap sensitive explosive column. 2. A novel device as claimed in claim 1 wherein the booster charge(s) used is of conventional type. 3. A novel device as claimed in claim 1 wherein the non-metallic rope used is of materials such as coir, jute. 4. A novel device as claimed in claims 1 wherein spacers of non-metallic material such as wood, bamboo are provided in between the detonating fuse and the rope lengths to maintain a separation of at least 100 mm between the detonating fuse and rope. 5. A novel device as claimed in claim 1 wherein the spacers are 30 mm shorter than the conventional blast hole diameter(s) and are fitted just above and below each booster charge . 6. A novel device as claimed in claim 1 wherein a dead weight of around 2 kg is provided at the junction of fuse and the rope. 7. A process for bottom hole non-electric initiation of non-cap sensitive explosive column using the novel device as claimed in claims 1 which comprises lowering concentrically the dead-weight end or the device in a conventional blast hole, packing the said blast hole with non-cap sensitive explosive mass of the order of 1:500 times the weight of booster charges of the device, igniting the free end of the detonating fuse at the blast hole top. 8. A novel device for bottom hole non-electric initiation of non-cap sensitive explosive column, substantially as herein described with reference to the examples and figure 3 of the drawings accompanying this specification.

Full Text

The present invention relates to a novel device for bottom hole non-electric initiation
of non-cap sensitive expldsive column and a process therefor.
The present invention particularly relates to a novel device for bottom hole nonelectric
Initiation of non-cap sensitive explosive column wherein the device of the present
invention essentially consists of a conventional detonating fuse coupled with a nonmetallic
flexible rope tied with a weight and provided with one or more number of nonmetallic
spacers and having suitably spaced booster charges.
The innin u.se of lite device ol'lhe present invention is l t > i n i l i n l e delonnUon from llie
bottom of a non-cap sensitive explosive column filled in a drill hole. The explosives
which are incapable of getting initiated by electric or non-electric detonation are called
non-cap sensitive explosive. The initiation in such cases are made by a booster explosive
/booster (high strength explosive) which is initiated first to subsequently initiate the noncap
sensitive explosives. Generally several number of boosters, each of 100-250 grams
weight, spaced at a regular interval are provided in an explosive column The number of
boosters to be provided in an explosive column depends on the total explosive quantity
and the ratio is maintained such that 100 gm of booster is used for every 50 kg of non-cap
sensitive explosives which indicates that ratio of explosive weight to booster weight
should be 500. Almost 99 per cent of the explosives used in open cast mining is of noncap
sensitive type because of cost consideration. The cap-sensitive explosives are very
costly and are not used in production blasting.
Top initiation of any explosive column of diameter ranging from 75 to 310 mm by
conventional technique is shown in Figure 1 of the drawings accompanying this
specification. The legend to the Figure 1 is as under:
Legend to the Figure 1:
1. Blast hole
2. Detonating fuse length
3. Cast booster (booster charge)
4. Detonating fuse initiated outside the blast hole
5. Point of initiation of explosive column
6. Direction of propagation of detonation front
7. Explosive coulumn
8. Stemming column
It can be understood from Figure 1 that the inititaion of explosive column starts from
the top of the blast hole as the top most booster is in connection with the detonating fuse.
The top portion of the explosive column, which is initiated first in case of top initiation, is
in direct contact of the stemming material placed at the top of the drill hole to provide a
momentary resistance against the dissipation of explosive energy to the atmosphere. The
drawbacks of the top hole initiation are as follows:
1) It leads to destabilisation or ejection of stemming material immediately as the top
portion of the explosive column is detonated. The explosive energy utilisation
becomes poor as a result. This may lead to poor fragmentation and more ground
vibration.
2) Underbreak at the bottom of the drill hole may occur as the stemming column
becomes less effective while the bottom portion of the explosive colurnn gets
initiated.
3) Due to ejection or destabilisation of stemming material, the rock fragments
produced by blasting at the top of the drill hole are frequently thrown to an
abnormal distance which may cause damage to human life and property.
l l IN evident Ihnl (he nbove disndvimlnueN due lo lop inil'mlion method am lie nvoided
by initiating the explosives from the bottom of the hole, generally called as bottom hole
initiation or bottom initiation. However, the top initiation method is followed in most of
the opencast coal and metal mines in India in spite of the said disadvantages because of
non-availability of a cost-effective device for bottom hole initiation.
The bottom hole initiation can be complied by means of electric or non-electric
detonating systems. The electric detonating systems are mainly used for small diameter
(25-32 mm) shallow 0.75-3 m deep holes. Initiation of deeper holes by electric systems
may be hazardous causing misfires. Hence, bottom hole initiation by non-electric
method is recommended.!
Non-electric bottom initiation by non-electric detonator (NONEL) is used in many
opencast mines of India and abroad. The device is integrated with shock tube which is
coated with thin layer of explosive inside for transmission of shock to the bottom of the
explosive column without damaging the tube. A detonator, coupled at the bottom end of
the shock tube and inserted in booster explosive charge detonates as soon as it receives
the shock transmitted through the shock tube. The detonator in turn detonates the booster
and this subsequently initiates the explosive column. The bottom hole initiation by
NONIZL is explained in Figure 2 of the drawings. The legend to the Figure 2 is ns under:
Legend to the Figure 2:
1. Blast hole
3. Cast booster (booster charge)
4. NONEL initiation outside the blast.hole
5. Point of initiation of explosive column
6. Direction of propagation of detonation front
7. Explosive column
8. Stemming column
9. NONEL shock tube
10. Detonator
The advantage of the NONEL is that bottom hole initiation can be achieved both in
cap-sensitive and non-cap sensitive explosives as the shock wave being carried through
the shock tube is incapable of detonating any explosive material outside the tube. But, the
NONEL device has not, been very popular as it is very expensive compared to the
detonating fuse used for top initiation. Hence, the advantages of bottom initiation of
explosive column have been overlooked in many cases to avoid additional mining cost.
This calls for development of a novel but cheaper method of bottom initiation of
explosive column.
Reference may be made to US patent No.s: 3590739 and 4998478, wherein the
bottom hole initiation of explosive by transmission of shock wave through tubes has
been disclosed. The device is sold under the trade name NONEL (a trademark of Nitro-
Nobel AB, Sweden). Such tubes are often referred to as "shock tube", typically has an
inner diameter of 1.5 mm and an outer diameter of 3 mm and contains a small quantity of
explosive material coated on the inner surface of a plastic tube. The explosive material is
a mixture of an explosive called HMX and fine aluminium flakes in the mass ratio of
42:3. A shock wave will typically propagate at 2000 m/s in NONEL tubing and will be
contained within the confines of the tube. The drawbacks in the use of NONEL is its
high cost which prevents its mass application in spite of the advantages associated with
its use.
The main object of the present invention is to provide a novel device for bottom hole non-electric initiation of non-cap sensitive explosive column which obviates the drawbacks of the expensive NONEL.
Another object is to provide a device which is cheap and, hence, should find mass application to derive the full advantages of bottom hole initiation.
Yet another object is to provide a process for bottom hole non-electric initiation of non-cap sensitive explosive column.
The device of present invention constitutes an assembly of detoning fuse, boosters, flexible rope of suitable material such as coir, jute, one or more spacers and a weight.
Figure 3 of the drawings shows a schematic embodiment of the novel device of the present invention which enables bottom hole non-electric initiation of non-cap sensitive explosive column. The legend to the Figure 3 is as under: Legend to the Figure 3:
1. Blast hole
2. Detonating fuse length
3. Cast booster (booster charge)
4. Initiation of detonating fuse from outside the hole
5. Point of initiation of explosive column
6. Direction of propagation of detonation front
7. Explosive column
8. Stemming colurim

11. Non-metallic flelxible rope
12. Spacers
13. Weight
The assembly of numbers 2, 3, 11, 12 and 13 above constitute the present invention.

Accordingly, the present invention provides a novel device for bottom hole nonelectric initiation of non-cap sensitive explosive column, which comprises a length of conventional detonating fuse (2) so as to transmit shock wave and a length of non-metallic flexible rope (11), characterised in that the said fuse and rope lengths being joined at one end and kept parallel to each other by means of plurality of non-metallic spatial separation spacers (12), the said joint of fuse and rope being provided with a booster charge (3 ) and a dead weight (13), the said rope being provided along its length with a plurality of booster charges (3) fixed at intervals to provide a ratio of the order of 1 : 500 by weight between booster charges and non-cap sensitive explosive column.
In an embodiment of the present invention the booster charge(s) used is of conventional type.
In another embodiment of the present invention the non-metallic rope used IS of materials such as coir, jute.
In yet another embodiment of the present invention non-metallic spacers used are made of materials like wood, bamboo pieces and are provided to maintain a separation of at least 100 mm between the detonating fuse and the rope. The spacers are fitted above and below the booster charge provided along the rope at certain interval to maintain a ratio of 1 :5 00 by weight between the booster and the explosive mass. The spacers should be about 30 rnm shorter than the standardised hole diameter to facilitate easy insertion in the blast hole of diameter such as 150 mm, 250 mm, 310 mm.
In still another embodiment of the present invention a dead weight of around 2 kg is provided at the junction of fuse and the rope to create tension so that the rope and the detonating fuse are maintained in a parallel position to each other.
The wooden spacer and weight are provided to ensure separation of the flexible rope and the detonating fuse throughout which is essential for achieving bottom initirtion of the explosive column.

Accordingly, the present invention provides a process for bottom hole nonelectric initiation of non-cap sensitive explosive column using the novel device as described herein above which comprises lowering concentrically the dead weight end of the device in a conventional blast hole, packing the said blast hole with non-cap sensitive explosive mass of the order of about 500 times the weight of the booster charge of the above device, igniting the free end of the detonating fuse at the blast hole top.
The process of the bottom hole initiation with the device of the present is explained below:
The detonating fuse when ignited outside the hole carries the shock wave to the bottom of the hole filled with non-cap sensitive explosive column. As the explosive column is non-cap sensitive, it is not exploded by the detonating fuse but a small portion of it gets burnt due to initiation of the detonating fuse. The detonating fuse subsequently initiates the booster tied at the bottom of the fuse which in turn initiates the explosive column, which are tied along the rope and are separated by the spacers fixed one above and one below the booster enabling the separation of detonating fuse from the rope by atleast 100 mm so as the boosters donot get prematurely initiated by the detonating fuse before the bottom most one is initiated. The spacers, which must be of non-metallic materials like wood or bamboo pieces, should be at least 30 mm smaller than the blast hole diameter facilitating easy insertion of the assembly in the blast hole. The dead weight of 2 kg mass tied at the junction of detonating fuse and the rope provides tension so that the rope and the detonating fuse remain parallel throughout and never come in contact with each other. The 2 kg weight has been selected based on the experience and convenience of the user. The whole assembly of the present device can be standardised

for various blast hole diameters like 150 mm, 250 mm and 310 mm. The parameters like
the spacers dimensions, intervals of the boosters can be standardised according to various
blast hole sizes.
In the novel device of the present invention/resides in the parallel coupling of
conventional detonating fuse and non-metallic ropes wherein the first booster charge is
provided at the end of the detonating fuse which is joined to the non-metallic rope and
subsequent booster charges are provided along the rope for explosive mass equal to 500
times the booster weight.
The present invention introduces a novel way to initiate the explosive from the
bottom of the explosive column while blasting with a detonating fuse and replaces the
existing methods of less effective top initiation by detonating fuse and bottom initiation
by expensive NONEL. The present invention provides an effective but cheaper method of
initiation of the explosive from the bottom of the hole and provides better fragmentation,
less underbreak, reduced ground vibration and fly rock.
The following example is given by way of illustration and therefore should not be
construed to limit the scope of the present invention.
Example- 1
Experiments in the field were conducted with the invention in western part of the 4th
bench of Jayant opencast mine of Northern Coalfields Ltd.. A portion of front rows of
holes in the blast was initiated with conventional top initiation by detonating fuse and the
other portion in the same row was initiated with the device of the present invention to
compare the performances of these two methods. The blast was monitored with high
speed video camera. When the video photographs were analysed clip by clip, it was
observed that the bottom was moved earlier than the rest of the column in case of bottom
hole initiation by detonating fuse and the reverse was observed in case of top initiation by
detonating fuse. Fly of rock fragments were also observed in case of top initiation by
detonating fuse.
Example-2
The following full scale blasts were conducted in the western part of the Jayant'mine
of Northern Coalfields Ltd., and in PK OC-II mine of Singareni Collieries Company Ltd.
(SCCL) using the novel device described under present invention. The main features of
the blasts are listed in Table 1.
In conclusion, the experiments demonstrated that the present invention yields a safe
and good blast performance while providing a cost-effective substitute to the shock tube
NONEL combination..
The main advantages of the invention are:
1. Provides considerably cheaper substitute to the NONEL,
2. Achieves bottom hole initiation of the non-cap sensitive explosive column,
3. Provides better fragmentation in comparison to top hole initiation,
I
4. Controls flyrock (Unwanted rock trajectories),
5. Reduces ground vibration in comparison to top hole initiation,
6. Minimises throw in comparison to top hole initiation, and
7. Controls underbreak.

We claim:
1. A novel device for bottom hole non-electric initiation of non-cap sensitive explosive column, which comprises a length of conventional detonating fuse (2) so as to transmit shock wave and a length of non- metallic flexible rope (11), characterised in that the said fuse and rope lengths being joined at one end and kept parallel to each other by means of plurality of non-metallic spatial separation spacers (12), the said joint of fuse and rope being provided with a booster charge (3 ) and a dead weight (13), the said rope being provided along its length with a plurality of booster charges (3) fixed at intervals to provide a ratio of the order of 1 : 500 by weight between booster charges and non-cap sensitive explosive column.
2. A novel device as claimed in claim 1 wherein the booster charge(s) used is of conventional type.
3. A novel device as claimed in claim 1 wherein the non-metallic rope used is of materials such as coir, jute.
4. A novel device as claimed in claims 1 wherein spacers of non-metallic material such as wood, bamboo are provided in between the detonating fuse and the rope lengths to maintain a separation of at least 100 mm between the detonating fuse and rope.
5. A novel device as claimed in claim 1 wherein the spacers are 30 mm shorter than the conventional blast hole diameter(s) and are fitted just above and below each booster charge .
6. A novel device as claimed in claim 1 wherein a dead weight of around 2 kg is provided at the junction of fuse and the rope.
7. A process for bottom hole non-electric initiation of non-cap sensitive explosive column using the novel device as claimed in claims 1 which comprises lowering concentrically the dead-weight end or the device in a conventional blast hole, packing the said blast hole with non-cap sensitive explosive mass of the order of 1:500 times the weight of booster charges of the device, igniting the free end of the detonating fuse at the blast hole top.
8. A novel device for bottom hole non-electric initiation of non-cap sensitive explosive
column, substantially as herein described with reference to the examples and figure 3 of the
drawings accompanying this specification.

Documents:

760-DEL-2001-Abstract-(08-12-2008).pdf

760-del-2001-abstract.pdf

760-DEL-2001-Claims-(08-12-2008).pdf

760-del-2001-claims.pdf

760-DEL-2001-Correspondence-Others-(08-12-2008).pdf

760-del-2001-correspondence-others.pdf

760-DEL-2001-Description (Complete)-(08-12-2008).pdf

760-del-2001-description (complete).pdf

760-del-2001-drawings.pdf

760-DEL-2001-Form-1-(08-12-2008).pdf

760-del-2001-form-1.pdf

760-del-2001-form-18.pdf

760-del-2001-form-2.pdf

760-DEL-2001-Form-3-(08-12-2008).pdf

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Patent Number

233361

Indian Patent Application Number

760/DEL/2001

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

29-Mar-2009

Date of Filing

11-Jul-2001

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INIDA.

Inventors:

#	Inventor's Name	Inventor's Address
1	ASHOKE KUMAR CHAKRABORTY	CENTRAL MINING RESEARCH INSTITUTE, REGIONAL CENTRE, 54-B, SHANKAR NAGAR, NAGPUR, MAHARASTRA STATE, INDIA-440 010
2	MORE RAMULU	CENTRAL MINING RESEARCH INSTITUTE, REGIONAL CENTRE, 54-B, SHANKAR NAGAR, NAGPUR, MAHARASTRA STATE, INDIA-440 010
3	PARTHO BISWAPATI CHOUDHAURY	CENTRAL MINING RESEARCH INSTITUTE, REGIONAL CENTRE, 54-B, SHANKAR NAGAR, NAGPUR, MAHARASTRA STATE, INDIA-440 010
4	ABHAY DUDHANKAR	CENTRAL MINING RESEARCH INSTITUTE, REGIONAL CENTRE, 54-B, SHANKAR NAGAR, NAGPUR, MAHARASTRA STATE, INDIA-440 010
5	JAYANTILAL JETHWA	CENTRAL MINING RESEARCH INSTITUTE, REGIONAL CENTRE, 54-B, SHANKAR NAGAR, NAGPUR, MAHARASTRA STATE, INDIA-440 010
6	AUTAR KRISHEN RAINA	CENTRAL MINING RESEARCH INSTITUTE, REGIONAL CENTRE, 54-B, SHANKAR NAGAR, NAGPUR, MAHARASTRA STATE, INDIA-440 010

PCT International Classification Number

F42D 3/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA