A surface delay device which exhibits good precision in delay timing when it is ignited from the side output of a low-energy detonating cord (LEDC) trunkline and end-initiates an LEDC trunkline or downline has a percussion-sensitive ignition charge wedged between the integrally closed end of a metal shell and the end of a delay capsule, which houses the delay and priming charges. An orifice in the end of the delay capsule between the ignition and delay charges is kept free of the ignition charge, e.g., by providing an axial recess in the end of the shell extending at least as far as the orifice. In the field the end of a cord is fitted into a well which is seated in the main detonating charge, adapted to be initiated by the priming charge; and another cord is positioned transversely against the ignition end of the shell.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a nonelectric delay initiator for 
transmitting an explosion from a donor low-energy detonating cord to a 
receiver low-energy detonating cord, and to an assembly containing said 
initiator for the connection of said cords and initiation of the receiver 
cord. 
2. Description of the Prior Art 
The hazards associated with the use of electrical initiation systems for 
detonating explosive charges in mining operations, i.e., the hazards of 
premature initiation by stray or extraneous electricity from such sources 
as lightning, static, galvanic action, stray currents, radio transmitters, 
and transmission lines, are well-recognized. For this reason, nonelectric 
initiation through the use of a suitable detonating fuse or cord more and 
more has been capturing the interest of blasters. 
Low-energy detonating cords, usually those having an explosive core loading 
of up to about 2 grams per meter of cord length, are very useful 
detonation-transmitting means for nonelectric detonation systems because 
they are characterized by low brisance and the production of little noise, 
and therefore can be used as trunklines in cases where noise has to be 
kept to a minimum, and as downlines in systems in which the cord must not 
be so brisant as to detonate the borehole charge or an adjacent section of 
cord. A "trunkline" is a common surface line of detonating cord from which 
multiple "downlines" of detonating cord depend and extend to explosive 
charges emplaced in various boreholes. 
An improved low-energy detonating cord (LEDC) which is light-weight, 
flexible, and strong, detonates at high velocity, and is readily adapted 
to high-speed continuous manufacturing techniques is described in U.S. 
Pat. No. 4,232,606, issued Nov. 11, 1980, the disclosure of which is 
incorporated herein by reference. This cord can be initiated reliably by 
means of a coaxially abutted blasting cap, but not by the detonation of 
another length of detonating cord with which it is spliced or knotted. A 
field-connected explosive booster for propagating a detonation in 
connected detonating cord assemblies containing a cord such as that 
described in the aforementioned U.S. Pat. No. 4,232,606, e.g., an 
explosive starter for initiating a receiver low-energy detonating cord by 
means of a donor low-energy detonating cord, is described in co-pending 
U.S. Pat. No. 4,248,152, issued Feb. 3, 1981. One cord, usually the 
receiver, is inserted into an axial cavity of the booster in a manner such 
that an end-portion of the cord is surrounded by a granular explosive, and 
the other cord, usually the donor, is positioned transversely outside and 
adjacent to a closed end of the booster shell, preferably in a transverse 
slot in a tube which holds the booster. Detonation of the donor cord 
causes the instantaneous detonation of the receiver cord. 
A nonelectric delay detonator adapted for field-assembly with a cord such 
as that described in the aforementioned U.S. Pat. No. 4,232,606 for the 
purpose of actuating the detonator is described in co-pending U.S. patent 
application Ser. No. 177,210, which is a continuation-in-part of 
Application Ser. No. 015,288, filed Feb. 26, 1979, now abandoned. The 
cord, e.g., a downline, is inserted into a deformable expansion shell, and 
the pressure pulse resulting from the detonation of the cord causes the 
shell to expand and an ignition charge around the expansion shell to be 
actuated as a result of sudden compression between the expansion shell and 
a rigid capsule. This results in the ignition of the delay and priming 
charges and detonation of the base charge. 
In the art of nonelectric delay blasting there is need for a surface delay 
device adapted for field-assembly that will end-initiate a low-energy 
detonating cord (receiver cord), e.g., a trunkline or downline, from the 
side output of a low-energy detonating cord (donor cord), e.g., trunkline, 
transversely positioned outside a borehole, while providing a precise 
delay in the initiation of the receiver cord. The nonelectric delay 
detonator described in the aforementioned application Ser. No. 177,210 is 
adapted to be actuated by an axial cord (e.g., a downline cord) only, and 
thus is suited for use as an in-the-hole detonator to set off a blasting 
charge therein, directly or via a primer. The availability of a 
nonelectric delay initiator which could provide a precise delay between 
two trunklines, or between a trunkline and downline (as a delay starter) 
would provide the capability of delaying the firing of borehole charges at 
the surface as well as in the borehole. 
Other nonelectric delay initiators are known which, like the detonator of 
U.S. application Ser. No. 015,288, are adapted to be actuated by 
percussive force applied thereto by an axial detonating cord. For example, 
U.S. Pat. No. 3,106,892 shows a delay initiator which is actuated by the 
end-output of a low-energy detonating cord. This initiator contains the 
usual ignition-to-detonation train in a tubular shell, i.e., starting at 
the closed end, first a base charge of detonating explosive, then, in 
sequence, a priming charge, a charge of exothermic-burning delay 
composition, and a capsule housing a percussion-sensitive ignition 
composition and a spacing member, the ignition composition being 
positioned between the closed end of the capsule and one end of the 
spacing member which forms an anvil head, and the air gap provided by the 
spacing member extending from the ignition composition to the delay 
composition. A booster charge of detonating explosive abuts the closed end 
of the capsule, and a length of low-energy detonating cord closes the open 
extremity of the shell with the cord end abutting the booster charge. The 
end output of the cord, after being "boosted" or intensified by the 
booster charge, applies the necessary percussive force to the ignition 
capsule. 
Another delay detonator actuated by the percussion produced from a 
detonating cord adjacent a capsule containing a percussive-sensitive 
ignition composition is described in U.S. Pat. No. 3,709,149. In this 
detonator, as in the detonator described in U.S. Pat. No. 3,106,892, a 
spacing member provides an air gap between the percussion-sensitive 
ignition composition and the delay composition. Furthermore, in the 
detonator assembly shown in U.S. Pat. No. 3,709,149 any receiver 
detonating cord which may be present (e.g., downline 9 as a receiver cord 
with respect to detonator assembly 6') is positioned outside the detonator 
shell. 
U.S. Pat. No. 3,776,135 also describes a cord-actuated delay detonator, the 
cord in this case being separated from the ignition charge by a 
perforation to allow venting of gases. 
U.S. Pat. No. 3,205,818 does not describe a detonator, but it shows a 
connector for securing two detonating cords in perpendicular, operative 
relationship to one another. A capsule containing a booster charge of 
high-velocity detonating explosive is crimped to one end of a length of 
LEDC which abuts the booster charge. The bottom, closed end of the capsule 
is positioned adjacent to the side of a length of detonating fuse in a 
transverse slot in a tube which holds the capsule/LEDC assembly. 
In summary, none of the cord-actuated delay initiators known to the art are 
adapted to be ignited from the side output of a transversely positioned 
cord to bring about the detonation of an axial cord. Although the 
detonator described in the aforementioned U.S. Pat. No. 3,709,149 is 
adapted to be ignited from the side output of a cord transversely 
positioned outside the detonator capsule, the ignition-to-detonation train 
progresses in the direction of the base of the detonator capsule, and no 
provision is made to affix an axial detonating cord thereto for the 
detonation thereof. 
A detonator having an ignition-to-detonation train in a reversed direction 
is described in U.S. Pat. No. 2,652,775, but this detonator is not a delay 
detonator and no detonating cords are used therewith. The detonator, which 
is designed for firing a blasting charge in a well, comprises a tubular 
metal shell containing a thin layer of an impact-sensitive ignition charge 
pressed against a flat, thin closed end thereof, a metal anvil interposed 
between the ignition charge and an explosive priming charge, and a pressed 
main detonator charge adjacent to the priming charge. The anvil is either 
of slightly smaller diameter than the inside of the shell, or is provided 
with channels or perforations. A sealing plug closes the other end of the 
shell. To actuate this detonator, the ignition end of the shell is 
depressed by a firing pin moved by the impact of a dropping weight and a 
striker rod. The ignition charge is thereby squeezed between the shell and 
the anvil, and ignited. The resulting flash is transmitted to the priming 
charge, and the main charge detonates, thereby setting off a surrounding 
blasting charge. 
SUMMARY OF THE INVENTION 
The present invention provides a nonelectric delay initiator comprising a 
first tubular metal shell integrally closed at one end and containing, in 
sequence from the closed end: 
(a) a percussion-sensitive ignition charge, e.g., a granular mixture of red 
lead, boron, and lead azide; 
(b) a tubular metal capsule having one open extremity and a closure at the 
other extremity provided with an axial orifice therethrough, the capsule 
being nested within the first shell with its closed end innermost and 
seated against the ignition charge, substantially all of the ignition 
charge being wedged between the first shell and the capsule; 
(c) a delay charge of an exothermic-burning composition, e.g., a boron/red 
lead mixture, within the capsule at the orifice-containing closed end 
thereof; 
(d) a priming charge of a heat-sensitive detonating explosive composition, 
e.g., lead azide, within the capsule and adjacent to the delay charge; 
(e) a second tubular metal shell integrally closed at one end and 
positioned coaxially within the first shell in a manner such as to produce 
an annular spacing around the second shell; and 
(f) a main charge of a detonating explosive composition, e.g., granular 
pentaerythritol tetranitrate (PETN), in the annular spacing and between 
the closed end of the second shell and the priming charge; 
means being provided for sealing off the charges from the atmosphere and 
for preventing the venting of gases resulting from the burning of the 
ignition and delay charges, an open cavity extending from one end to the 
other of the second shell for receiving a low-energy detonating cord 
adapted to be detonated by the pressure pulse applied thereto by the 
detonation of the main charge adjacent to the second shell, and the cavity 
being provided with a cord-retention means for holding the cord coaxially 
therein. 
As will be explained more fully later, better precision in delay timing 
results when the ignition charge in the initiator is present essentially 
only between the capsule and shell surfaces, i.e., substantially absent 
from the orifice in the delay capsule. During loading, any part of the 
ignition charge that collects in the orifice can be removed prior to the 
loading of the delay charge. Moreover, in a preferred embodiment, the 
closed end of the first tubular metal shell is provided with an axial 
recess which extends at least as far as the axial orifice in the capsule. 
This recess forms an axial convex inner surface on the end of the shell 
which prevents the ignition charge from being deposited in the orifice and 
causes it to adopt an annular configuration.

DETAILED DESCRIPTION 
In the initiator depicted in FIG. 1, 1 is a first tubular metal shell, 
i.e., the outer shell of the initiator; and 2 is a second tubular metal 
shell positioned coaxially within shell 1. Both shell 1 and shell 2 are 
closed at one end and open at the opposite end, shell 2 being seated 
within shell 1 with its closed end the innermost end and in a manner such 
that an annulus separates the sidewalls of the two shells. 
Tubular metal capsule 3 is nested within shell 1. This capsule has one open 
extremity 4 and a closed extremity 5 provided with an axial orifice 6. 
Capsule 3 holds a delay charge 10 of an exothermic-burning composition, 
which is also present in orifice 6. Closed extremity 5 of capsule 3 is 
seated against adjacent percussion-sensitive ignition charge 7, orifice 6 
being coaxial with an axial recess 8 in the closed end of shell 1, and 
recess 8 extending into orifice 6. Convex inner surface 9 is a means of 
keeping ignition powder 7 from collecting in orifice 6 during the loading 
of the charges into shell 1. 
Capsule 3, which is a carrier for delay charge 10, also carries the priming 
charge 11 of heat-sensitive detonating explosive. This feature also 
assures better precision in timing owing, it is believed, to the 
inaccessibility of the priming charge to the gases evolved when ignition 
charge 7 burns. The main or output charge 12, 13 of detonating explosive 
composition has a pressed portion 13 adjacent to priming charge 11 and a 
loose-load portion 12 surrounding the closed end portion of shell 2. 
A deformable grommet or sleeve 14, e.g., one made of rubber or a plastic 
such as polyethylene, fits around shell 2 near the outer, open end 
thereof. A convenient way of making the initiator is to load the charges 
and capsule into shell 1, and then to seat shell 2, with grommet 14 
mounted thereon, within shell 1 while displacing some of charge 12 up into 
the spacing between the shells' walls. Grommet 14 is of such a length as 
to extend into the space between the walls about as far as charge 12. 
One of the functions of inner shell 2 is to provide a means of sealing the 
charges from the atmosphere, a feature which is essential if the initiator 
is to have a field-assembly capability. Another function of shell 2 is 
associated with the open cavity 15 therein that extends from one end of 
shell 2 to the other. This cavity acts as a well for the proper axial 
positioning therein of a detonating cord which is to be initiated by the 
pressure pulse applied thereto by the detonation of main charge 12. 
Located in cavity 15 is a cord-retention means in the form of an 
open-ended metal sleeve 16 that frictionally engages the inside wall of 
shell 2 and has cord-gripping means 17, i.e., a number of inwardly 
directed prongs, formed on its inner end. While a cord can be inserted 
into cavity 15 through prong-ended sleeve 16, the prongs prevent the 
motion of the cord in the opposite direction when tension is applied 
thereto. 
The outer end of metal sleeve 16 is provided with a lip portion 18 that 
extends over the outer ends of shell 2 and grommet 14. Crimp 19 locks 
shell 2 in place, keeping it from becoming dislodged by the internal 
pressure produced when charge 7 ignites. Grommet 14 and circumferential 
crimp 20 in the side of shell 1 seal charges 7, 10, 11, 13, and 12 off 
from the atmosphere. 
The initiator is a self-contained, sealed unit and can be stored, 
transported, and otherwise handled as required separated from the 
detonating cords with which it is designed to be used. At the time of use, 
the initiator can be assembled together with the cords using any suitable 
connection means. However, a preferred means for retaining the cords and 
initiator in their required positions for effecting the propagation of a 
detonation from a trunkline to another trunkline or to a downline is a 
connector of the type described in U.S. Pat. No. 3,204,818 and in the 
aforementioned U.S. Pat. No. 4,248,152, the disclosures of which are 
incorporated herein by reference. 
Referring to the initiator shown in FIG. 1 and the initiator-connector 
assembly shown in FIG. 2, an end-portion of a length of low-energy 
detonating cord trunkline or downline 21 is located in cavity 15 and has 
its end seated against the closed end of shell 2. Prongs 17 grip cord 21 
and thus prevent it from being pulled out of cavity 15. Cord 21 consists 
of a continuous solid core 22 of a deformable bonded detonating explosive 
composition, e.g., superfine PETN admixed with a binding agent such as 
plasticized nitrocellulose; core-reinforcement means (not shown) 
consisting of a mass of filaments derived from multi-filament yarns in 
contact with the periphery of core 22 parallel to the core's longitudinal 
axis; and a protective plastic sheath 23, which encloses core 22 and the 
core-reinforcing filaments. Cords of this type are described in the 
aforementioned U.S. Pat. No. 4,232,606. The explosive loading in the core 
of this cord preferably is about from 0.2 to 2 grams per meter of length. 
The connector shown in FIG. 2 comprises a tube 24 of preferably 
electrically nonconductive material, e.g., a plastic material, having open 
extremities A and B and a transverse slot 25 near extremity B and 
communicating with the bore 27 of the tube. Slot 25 has a recessed channel 
26 which is adapted to engage a trunkline perpendicular to the 
longitudinal axis of tube 24. The initiator is seated in the bore 27 of 
the tube with the closed end of shell 1 adjacent to slot 25 and the other 
end of shell 1 resting against shoulder projection 28, which prevents the 
initiator from being pulled out of tube 24 when a force is exerted on cord 
21. It is feasible to first insert the initiator into tube 24 through 
extremity B until it becomes seated against projection 28 (e.g., at the 
time of use, or at the place of manufacture or elsewhere prior to the time 
of use), and thereafter to insert cord 21 into cavity 15 until the end of 
cord 21 becomes seated against the closed end of shell 2. Likewise, cord 
21 can be positioned in cavity 15 first, and thereafter the initiator-cord 
assembly threaded through tube 24 from extremity B until the initiator 
becomes seated against projection 28 while cord 21 emerges from extremity 
A. Tube 24 has slotted locking means 29 adapted to form a closure with 
slot 25 to lock the trunkline in place. 
FIG. 3 shows a length of low-energy detonating cord trunkline 30, e.g., a 
cord having the same structure as cord 21 and a core explosive loading in 
the same range, positioned in recessed channel 26 in a manner such that a 
side-portion of the trunkline is adjacent to the closed end of shell 1. 
The use of the initiator and cord assembly of the invention will now be 
described by way of examples. 
EXAMPLE 1 
The initiator shown in FIG. 1 was made as follows: Shell 1 was a standard 
detonator shell, e.g., a shell made of Type 5052 aluminum alloy, 33 mm 
long and having an outer diameter of 7.1 mm and an internal diameter of 
6.6 mm. Its bottom, which was 0.9 mm thick, had an axial recess 1.0 mm 
deep. Shell 2 also was made of Type 5052 aluminum alloy, and had a wall 
and bottom thickness of 0.3 mm. The length of shell 2 was 3.3 mm in its 
smallest-internal-diameter section of 2.9 mm, and 5.1 mm in its 
largest-internal-diameter section of 5.0 mm. Its overall length was 16.5 
mm. The upper taper in the wall of shell 2 was 30.degree. off, and the 
lower taper 60.degree. off, the longitudinal axis. 
Ignition charge 7, which consisted of 0.5 gram of a 1.7/98.3/10 (by weight) 
boron/red lead/dextrinated lead azide mixture, was loosely loaded into 
shell 1, after which bronze capsule 3 was pressed into the shell at 1335 
Newtons until its extremity 5 was essentially in contact with the convex 
surface of recess 8. The thickness of ignition charge 7 was about 0.5 mm. 
After the placement of capsule 3, shell 1 was overturned and shaken to 
remove any grains of ignition charge 7 that may have been lodged in 
orifice 6. 
Capsule 3 was 11.1 mm long, and had an outer diameter of 6.5 mm and an 
inner diameter of 5.7 mm. Axial orifice 6 was 2.0 mm in diameter. Delay 
charge 10, which was pressed into capsule 3 at 1335 Newtons, was a 
2.5/97.5/20 mixture (by weight) of boron, red lead, and silicon, grained 
with polysulfide rubber, the weight of charge 10 (and therefore its 
length) varying depending on the delay period to be provided. Priming 
charge 11 was 0.2 gram of dextrinated lead azide, which had been loaded 
into capsule 3 and pressed therein at 1335 Newtons. Portion 13 of the main 
charge was 0.33 g of PETN pressed into capsule 3 and shell 1 at 1335 
Newtons. Portion 12 was 0.23 g of loose-loaded PETN. 
Grommet 14, made of low-density polyethylene and having a length of 9.0 mm, 
an outer diameter of 6.4 mm, and an inside diameter of 5.4 mm, was fitted 
onto shell 2 in a manner such that the edge surfaces of shell 2 and 
grommet 14 at the outer end were substantially coplanar. Bronze sleeve 16 
had an overall length of 12 mm, an outer diameter of 4.5 mm, an inner 
diameter of 4 mm, and a 2.5-mm tapered portion having four cord-gripping 
prongs 17, which reduced the diameter of the sleeve at the gripping end to 
2 mm. Sleeve 16 was fitted into shell 2 in a manner such that lip portion 
18 rested over the ends of shell 2 and grommet 14. The assembly of shell 
2, grommet 14, and sleeve 16 was pressed into shell 1 at 667 Newtons, 
thereby compacting charge 12 and displacing some of it into the annular 
space between the facing walls of shells 1 and 2. 
The initiator was positioned in the cord connector shown in FIG. 2 as 
follows: 
Trunkline cord 21 had an outer diameter of 2.5 mm, a 1.3-mm-diameter core 
(22), and an 0.6-mm-thick low-density polyethylene sheath (23). The core 
22 consisted of a mixture of 75% superfine PETN, 21% acetyl tributyl 
citrate, and 4% nitrocellulose prepared by the procedure described in U.S. 
Pat. No. 2,992,087. The superfine PETN had an average particle size less 
than 15 microns, with all particles smaller than 44 microns. The 
core-reinforcing filaments were derived from eight 1000-denier strands of 
polyethylene terephthalate yarn substantially uniformly distributed on the 
periphery of core 22. The PETN loading in core 22 was 1.49 grams per 
meter. 
One end of a length of trunkline cord 21 was inserted into cavity 15 of 
shell 2 of the initiator until it became seated against the closed end of 
shell 2. Prongs 17 gripped trunkline cord 21 and prevented it from being 
retracted from shell 2. The initiator had previously been positioned in 
tube 24 until it had become seated against projection 28 as shown in FIG. 
2. Tube 24 was made of low-density polyethylene. 
A length of trunkline cord 30 (the same as core 21) was positioned in 
recess channel 26 of slot 25 of connector tube 24 whereby the closed end 
of shell 1 of the initiator was butted against the side of trunkline cord 
30. Slotted locking means 29 was pushed into slot 25 and snapped into 
place, thereby locking trunkline cord 30 into its transverse position. 
Trunkline 30 was detonated by means of a No. 6 blasting cap having its end 
in coaxial abutment with the exposed end of the cord. The detonation was 
transmitted from trunkline 30 to the initiator (surface delay), and from 
the initiator to trunkline 21. 
The above-described initiator was made in different delay periods, each 
having a different weight (and length) of delay charge. The initiators 
were tested for delay time in the cord assembly described above. The 
results were as follows: 
______________________________________ 
Delay Charge Measured Delay Time, ms. 
Length Standard 
Wt., g. mm. Mean* Deviation 
Range 
______________________________________ 
0.18 2.0 10.8 1.0 3.9 
0.18 2.0 11.2 0.4 1.3 
0.23 2.54 14.1 0.7 2.2 
0.35 3.78 21.2 0.4 1.5 
______________________________________ 
*Based on 15 initiators tested 
EXAMPLE 2 
The same initiator described in Example 1 was made except that the closed 
end of shell 1 was substantially flat (i.e., there was no recess therein), 
as depicted in FIG. 4. After capsule 3 had been pressed into place, grains 
of ignition charge 7 present in orifice 6 were dislodged by overturning 
and shaking the assembly. Delay charge 10 entered orifice 6 as a result of 
being pressed into capsule 3. In this configuration the delay charge 10 
was initiated essentially circumferentially by the thin layer of ignition 
charge wedged between shell 1 and capsule 3. The delay timing of this 
initiator was tested as described in Example 1. 
______________________________________ 
Delay Charge Measured Delay Time, ms. 
Length Standard 
Wt., g. mm. Mean* Deviation 
Range 
______________________________________ 
0.25 2.72 15.9 1.4 2.8 
0.28 3.00 17.6 0.8 2.6 
0.30 3.25 19.8 1.1 2.8 
0.35 3.78 20.2 1.5 3.6 
0.40 4.32 24.0 0.5 1.8 
0.45 4.85 26.5 0.4 0.8 
0.50 5.38 28.0 0.9 2.2 
0.52 5.59 44.8 12.6 31.5 
0.35.sup.(a) 
3.78 29.8 0.8 2.6 
0.38.sup.(b) 
4.11 39.4 1.9 6.5 
0.35.sup.(c) 
3.78 59.0 1.4 3.9 
______________________________________ 
*Based on 10 initiators tested 
.sup.(a) Delay charge: 2.5/97.5 boron/red lead 
.sup.(b) Delay charge: 2.0/98 boron/red lead 
.sup.(c) Delay charge: 1.5/98.5 boron/red lead 
EXAMPLE 3 
The initiator shown in FIG. 1 with the end-modification shown in FIG. 4 was 
tested for delay timing and compared with the same initiator in which the 
grains of ignition charge 7 had not been removed from orifice 6. The 
ignition charge was 0.045 g of 1.7/98.3/10 boron-red lead-dextrinated lead 
azide, and the delay charge was 0.25 g of the composition used in Example 
1. The results were as follows: 
______________________________________ 
Measured Delay Time, ms. 
Powder Removed Standard 
from Orifice Mean* Deviation Range 
______________________________________ 
Yes 16.1 1.1 3.0 
No 12.1 2.3 7.7 
______________________________________ 
*Based on 10 initiators tested 
An important prerequisite to successful delay blasting is that the delay 
times of a number of initiators of stated delay rating be as uniform as 
possible from initiator to initiator. Without good uniformity, it is 
difficult to achieve a desired rock fragmentation, vibration reduction, 
etc. as expected from a given delay pattern. The foregoing examples show 
that the delay initiator of the invention exhibits good uniformity and 
predictability of delay time, and that this uniformity is related to the 
sharp interface or separation between the ignition and delay charges 
achieved by the absence of the ignition charge in the orifice in the delay 
capsule. 
Precision of delay timing also is dependent on controlling the size of the 
ignition and delay charges. Keeping the ignition charge to a minimum, 
e.g., about from 0.2 to 0.6 mm thick, permits a smooth ignition of the 
delay charge, thereby avoiding variations in timing caused by disturbance 
of the delay column. The composition selected to be used as the ignition 
charge is one which is ignitible by percussion, i.e., by the sudden impact 
of the bottom of the initiator shell from the detonation of the cord 
transversely adjacent thereto; reliably propagates the initiation stimulus 
from the detonating cord to the delay charge 10; and is substantially 
gasless when it decomposes, to prevent rupturing of the surrounding shell. 
Preferred ignition compositions consist essentially, by weight, of at 
least about 80% red lead (lead tetroxide), about from 1 to 5.0% boron, and 
up to about 15% lead azide, lead styphnate, or a mixture thereof. Certain 
of these compositions are described in U.S. Pat. No. 3,306,201, the 
disclosure of which is incorporated herein by reference. More-sensitive 
ignition compositions may be required in initiators to be used with 
detonating cords having smaller core loadings than in those used with 
cords having larger loadings. Generally, about a 0.02 to 0.06 gram 
ignition charge gives best results and is preferred. 
The exothermic-burning composition used as the delay charge can be any of 
the gasless exothermic-reacting mixtures of solid oxidizing and reducing 
agents that burn at a constant rate and that are commonly used in ventless 
delay detonators. Examples of such mixtures are boron-red lead, boron-red 
lead-dibasic lead phosphite, boron-red lead-silicon, silicon-red lead, 
aluminum-cupric oxide, magnesium-barium peroxide-selenium, etc. The charge 
should be pressed into the delay capsule with a force of at least about 
890 Newtons. The range of delay charge weights over which good precision 
is attained varies with different compositions. For example, as can be 
seen from Example 2, with boron-red lead compositions good precision is 
achieved in a delay load range of about from 0.30 to 0.40 gram; while a 
wider range, i.e., about from 0.25 to 0.50 gram, is operable with 
boron-red lead-silicon compositions. 
The priming charge can be any heat-sensitive detonating explosive 
composition which is readily initiated by the burning of the delay 
composition, e.g., lead azide, mercury fulminate, diazodinitrophenol, or a 
similar composition. 
The composition used for the main charge can be any of the charges 
conventionally used as base charges in detonators, e.g., PETN, 
cyclotrimethylenetrinitramine, cyclotetramethylenetetranitramine, lead 
azide, picryl sulfone, nitromannite, TNT, and the like. 
While the present initiator can be adapted to transmit an explosion from 
any low-energy detonating cord to another in the manner described herein, 
it is especially adapted to be actuated from the side output of detonating 
cord having an explosive loading of about from 0.2 to 2 grams per meter, 
and to end initiate a cord having an explosive loading of about from 0.2 
to 2 grams per meter.